Hydrogel capsules comprising covalently photocrosslinked polysaccharides and islet cells

Abstract

Described herein are hydrogel capsules (e g., alginate hydrogel capsules) comprising polysaccharide polymers capable of covalent crosslinking to another moiety, such as another polysaccharide polymer; and an islet cell; as well as related compositions and uses thereof.

Description

[0001] HYDROGEL CAPSULES COMPRISING COVALENTLY CROSSLINKED POLYSACCHARIDES AND ISLET CELLS CLAIM OF PRIORITY This application claims priority to U.S. Application No.63 / 452,127, filed March 14, 2023; the disclosure of the foregoing application is incorporated herein by reference in its entirety. BACKGROUND The function of implanted devices depends in large part on the biological immune response pathway of the recipient (Anderson et al., Semin. Immunol.20:86–100 (2008); Langer, Adv. Mater.21:3235–3236 (2009)). Modulation of the immune response may impart a beneficial effect on the fidelity and function of these devices. As such, there is a need in the art for new compounds, compositions, and devices that achieve this goal. SUMMARY Described herein are hydrogel capsules (e.g., alginate hydrogel capsules) comprising: (i) polysaccharide polymers capable of covalent crosslinking to another moiety, such as another polysaccharide polymer; and (ii) an islet cell; as well as related compositions and uses thereof. In an embodiment, the polysaccharide polymer comprises a photoactive crosslinking moiety, such as a compound of Formula (IV) or a pharmaceutically acceptable salt thereof. In an embodiment, the polysaccharide polymer comprises both a photoactive crosslinking moiety (e.g., a compound of Formula (IV)) and a compound of Formula (I) (e.g., an afibrotic compound), or a pharmaceutically acceptable salt thereof. These polysaccharide polymers can be present within a hydrogel capsule comprising one or more compartments, for example, in an outer compartment of a hydrogel capsule described herein or an inner compartment of a hydrogel capsule described herein, or both. In an embodiment, the polysaccharide polymer is capable of covalent and ionic crosslinking. The inclusion of a photoactive crosslinker into the polysaccharide polymers, and, in turn, the hydrogel capsules incorporating the polysaccharide polymers, may allow for tuning certain properties of the hydrogel capsules, including capsule diameter, stability, and integrity. The details of one or more embodiments of the disclosure are set forth herein. Other features, objects, and advantages of the invention will be apparent from the Detailed Description, the Figures, the Examples, and the Claims. BRIEF DESCRIPTION OF DRAWINGS FIG.1 shows a representative LC-UV chromatogram used to characterize components in the photoactive crosslinker reaction. FIGS.2A-2C show representative images of two-compartment alginate hydrogel capsules. FIG.2A is an image of alginate hydrogel capsules where both inner and outer compartments contain a blend of VLVG / SLG100 alginates. FIG 2B. is an image of alginate hydrogel capsules where both inner and outer compartments contain a blend of modified and unmodified alginate (VLVG / SLG100) and where the inner compartment contains dextrin beads to simulate mammalian cells. FIG.2C is an image of hydrogels where both inner and outer compartments contain a blend of methacrylamide-modified VLVG / SLG100 (70 / 30), and where the inner compartment contains dextrin beads to simulate mammalian cells. FIGS.3A-3C show representative images of the alginate hydrogel capsules from FIGS 2A-2C after one-month storage in buffer. FIGS.4A-4D show representative images that compare the size and stability of dual- crosslinked alginate hydrogels prepared with different concentrations of photoactive crosslinker, 7% photoactive crosslinker (FIG.4A), 5% photoactive crosslinker (FIG.4B), 3% photoactive crosslinker (FIG.4C), and 1.5% photoactive crosslinker (FIG.4D). FIG.4E is a chart showing the corresponding fracture strengths of the alginate hydrogels described in FIGS.4A-4D. FIG.5 compares the average fracture strength of an exemplary hydrogel capsule comprising a covalently cross-linked polymer comprising Compound 101 (2) to an ionically crosslinked alginate hydrogel (2) as described in Example 7. FIG.6 compares the average fracture strength of an exemplary hydrogel capsule comprising a covalently cross-linked polymer comprising Compound 111 (2) to an ionically crosslinked alginate hydrogel (2) as described in Example 7. FIGS.7A-7B show exemplary microscopy images of hydrogel capsule 1 (FIG.7A) and hydrogel capsule 2 (FIG.7B) as described in Table 8 FIGS.8A-8B show exemplary microscopy images of dual-crosslinked alginate hydrogel capsules comprising exemplary islet cells. FIG.9 is a bar plot comparing the fold change in macrophage adhesion for various modified alginate hydrogel capsules described herein; (1): empty spheres; (2)-(5) dual- crosslinked polymer hydrogels comprising exemplary islet cells. FIGS.10A-10B show the percent viability (FIG.10A) and total cell number (FIG.10B) of exemplary islet cells encapsulated in dual-crosslinked alginate hydrogel capsules; (1) and (3) were performed at room temperature; (2) and (4) were performed at 4 °C. FIGS.11A-11B show the effect of UV exposure time (FIG.11A) and UV intensity (FIG. 11B) on the fracture strength of exemplary modified alginate hydrogel capsules. FIGS.12A-12B shows the effect of UV exposure time (FIG.12A) and UV intensity (FIG.12B) on the viability of islet cells encapsulated in exemplary modified alginate hydrogel capsules. FIG.13 is plot showing the effect of UV exposure on the rate of release of encapsulated dextran polymers from exemplary modified alginate hydrogel capsules described herein. FIG.14A-14C shows the effect of in vivo residence time on compound retention (FIG. 14A), structural integrity (FIG.14B), and mechanical strength (FIG.14C) of exemplary modified alginate hydrogel capsules described herein; light gray represents dual-crosslinked alginate hydrogel capsules and dark gray represents ionically crosslinked alginate hydrogel capsules. FIG.15 is graph showing the relative PFO response on (1) empty spheres; (2) dual- crosslinked alginate hydrogel capsules comprising exemplary islet cells as described herein; and (3) polystyrene beads. FIGS.16A-16B are graphs showing the blood glucose levels of immune-deficient, diabetic mice upon administration of hydrogel capsules comprising a dual-crosslinked polymer and an islet cell as described herein. FIGS.17A-17C compare the effect of changing batch sizes on the size (FIG.17A), strength (FIG.17B), and IgG absorption (FIG.17C) of two compartment hydrogel capsules described herein. The hydrogel capsules comprise the same composition, which is described in Example 9 (hydrogel capsule #1). FIGS.18A-18B compare the effect of changing the density of a compound of Formula (IV) on the insulin diffusion (FIG.18A) and IgG absorption (FIG.18B) of two compartment hydrogel capsules prepared according to the method of Example 9 (hydrogel capsule #1). Sample (1) refers to an ionically crosslinked sphere with no covalent crosslinker present; sample (2) refers to a dual-crosslinked sphere wherein the inner and outer compartments comprise alginate modified with Compounds 101 and 205 (hydrogel capsule #2 from Example 9); and sample (3) refers to a dual-crosslinked sphere wherein the inner and outer compartments comprise alginate modified with Compounds 101 and 205 (hydrogel capsule #2 from Example 9) further comprising exemplary islet cells. FIGS.19A-19C show the effect of changing the density of a compound of Formula (IV) on the strength (FIG.19A), flexibility (FIG.19B), and size (FIG.19C) of two compartment hydrogel capsules, wherein (1; circles) refers to control hydrogel capsules, and (2; squares), (3; triangles), and (4; diamonds) refer to hydrogel capsules comprising 75%, 62%, and 50% reduction in Compound 205, respectively. The hydrogel capsules comprise the same composition, which is described in Example 9 (hydrogel capsule #1). FIGS.20A-20D show the effect of changing the density of a compound of Formula (IV) on the strength (FIG.20A), flexibility (FIG.20B), size (FIG.20C), and IgG absorption (FIG. 20D) of two compartment hydrogel capsules, wherein (1; circles) refers to control hydrogel capsules, and (2; squares), and (3; triangles), refer to hydrogel capsules comprising 62%, and 50% reduction in Compound 205, respectively. Sample (4) refers to an ionically crosslinked sphere with no covalent crosslinker present; sample (5) refers to a dual-crosslinked sphere wherein the inner and outer compartments comprise alginate modified with Compounds 101 and 205 (hydrogel capsule #2 from Example 9) and (6) refers to a dual-crosslinked sphere wherein the inner and outer compartments comprise alginate modified with Compounds 101 and 205 (hydrogel capsule #2 from Example 9) further comprising exemplary islet cells. FIGS.21A-21D shows the effect of changing UV-irradiation conditions on the size (FIG. 21A), strength (FIG.21B), flexibility (FIG.21C), and IgG absorption (FIG.21D) of two compartment hydrogel capsules. The hydrogel capsules tested are those described in Example 9 (hydrogel capsule #1). Sample (1) refers to an ionically crosslinked sphere with no covalent crosslinker present; sample (2) refers to a dual-crosslinked sphere wherein the inner and outer compartments comprise alginate modified with Compounds 101 and 205 (hydrogel capsule #2 from Example 9); sample (3) refers to a dual-crosslinked sphere wherein the inner and outer compartments comprise alginate modified with Compounds 101 and 205 (hydrogel capsule #2 from Example 9) further comprising exemplary islet cells; and sample (4) refers to an empty well control. FIG.22 shows the volumetric swelling ratio of exemplary two compartment hydrogel capsules described herein in different media. The hydrogel capsules tested are those described in Example 9 (hydrogel capsule #1). FIGS.23A-23D shows the effect of different alginate types in the inner compartment on the strength (FIG.23A), flexibility (FIG.23B), and encapsulated cell viability (FIG.23C) and IgG absorption (FIG.23D) of exemplary two compartment hydrogel capsules described herein. The hydrogel capsules tested are those described in Example 9 (hydrogel capsule #1) but with changing inner compartment alginate. Sample (1) refers to an ionically crosslinked sphere with no covalent crosslinker present; sample (2) refers to a dual-crosslinked sphere wherein the inner and outer compartments comprise alginate modified with Compounds 101 and 205 (hydrogel capsule #2 from Example 9); sample (3) refers to a dual-crosslinked sphere wherein the inner and outer compartments comprise alginate modified with Compounds 101 and 205 (hydrogel capsule #2 from Example 9) further comprising exemplary islet cells; and sample (4) refers to an empty well control. FIG.24 is a line graph showing the rate of barium release from exemplary alginate hydrogel capsules. Sample (1) refers to an ionically crosslinked sphere with no covalent crosslinker present that was washed 15X with buffer; sample (2) refers to hydrogel capsule #1 from Example 9 that was washed 8X with buffer; and sample (3) refers to hydrogel capsule #1 from Example 9 that was washed with EDTA. FIG.25 is a bar graph showing the residual barium in exemplary alginate hydrogel capsules (hydrogel capsule #1 from Example 9) following an increasing number of washes with CMRL or HPLM medium. FIG.26 is a schematic showing an overview of the indirect curing process. FIGS.27A-27C show the effect of an indirect covalent crosslinking method on the strength (FIG.27A), size (FIG.27B), and insulin diffusion (FIG.27C) of exemplary two compartment hydrogel capsules described herein. Samples (1), (2) and (3) refer to individual replicates wherein the hydrogel capsule is described in Example 9 (hydrogel capsule #1). Sample (1) refers to an ionically crosslinked sphere with no covalent crosslinker present; sample (2) refers to a dual-crosslinked sphere wherein the inner and outer compartments comprise alginate modified with Compounds 101 and 205 (hydrogel capsule #2 from Example 9); and sample (3) refers to a dual-crosslinked sphere wherein the inner and outer compartments comprise alginate modified with Compounds 101 and 205 (hydrogel capsule #2 from Example 9) further comprising exemplary islet cells. FIG.28 is a schematic depicting exemplary architecture of the polymers and related hydrogel capsules described herein. DETAILED DESCRIPTION The present disclosure provides hydrogel capsules (e.g., alginate hydrogel capsules) comprising (i) a polysaccharide polymer comprising a photoactive crosslinking moiety and a compound of Formula (I) and (ii) an islet cell; as well as related compositions, hydrogel capsules comprising the same, and methods of making and use thereof. Abbreviations and Definitions So that the disclosure may be more readily understood, certain technical and scientific terms are specifically defined below. Unless specifically defined elsewhere in this document, all other technical and scientific terms used herein have the meaning commonly understood by one of ordinary skill in the art to which this invention belongs. As used herein, including the appended claims, the singular forms of words such as "a," "an," and "the," include their corresponding plural references unless the context clearly dictates otherwise. “About" or “approximately” means when used herein to modify a numerically defined parameter (e.g., a physical description of a hydrogel capsule such as diameter, sphericity, number of cells encapsulated therein, the number of capsules in a preparation), means that the recited numerical value is within an acceptable functional range for the defined parameter as determined by one of ordinary skill in the art, which will depend in part on how the numerical value is measured or determined, e.g., the limitations of the measurement system, including the acceptable error range for that measurement system. For example, “about” can mean a range of 20% above and below the recited numerical value. As a non-limiting example, a hydrogel capsule defined as having a diameter of about 1.5 millimeters (mm) and encapsulating about 5 million (M) cells may have a diameter of 1.2 to 1.8 mm and may encapsulate 4 M to 6 M cells. As another non-limiting example, a preparation of about 100 devices (e.g., hydrogel capsules) includes preparations having 80 to 120 devices. In some embodiments, the term “about” means that the modified parameter may vary by as much as 15%, 10% or 5% above and below the stated numerical value for that parameter. Alternatively, particularly with respect to certain properties of the devices described herein, such as hydrogel capsule integrity of the afibrotic compound, the term “about” can mean within an order of magnitude above and below the recited value, e.g., within 5-fold, 4-fold, 3-fold, 2-fold or 1-fold. “Acquire” or “acquiring”, as used herein, refer to obtaining possession of a value, e.g., a numerical value, or image, or a physical entity (e.g., a sample), by “directly acquiring” or “indirectly acquiring” the value or physical entity. “Directly acquiring” means performing a process (e.g., performing an analytical method or protocol) to obtain the value or physical entity. “Indirectly acquiring” refers to receiving the value or physical entity from another party or source (e.g., a third-party laboratory that directly acquired the physical entity or value). Directly acquiring a value or physical entity includes performing a process that includes a physical change in a physical substance or the use of a machine or device. Examples of directly acquiring a value include obtaining a sample from a human subject. Directly acquiring a value includes performing a process that uses a machine or device, e.g., using a fluorescence microscope to acquire fluorescence microscopy data. “Administer”, “administering”, or “administration”, as used herein, refer to implanting, absorbing, ingesting, injecting or otherwise introducing into a subject, an entity described herein (e.g., a hydrogel capsule, a device or a preparation of hydrogel capsules or devices), or providing such an entity to a subject for administration. “Afibrotic”, as used herein, means a compound or material that mitigates the foreign body response (FBR). For example, the amount of FBR in a biological tissue that is induced by implant into that tissue of a device (e.g., hydrogel capsule) comprising an afibrotic compound (e.g., a hydrogel capsule comprising a polymer covalently modified with a compound listed in Table 3) is lower than the FBR induced by implantation of an afibrotic-null reference device, i.e., a device that lacks any afibrotic compound, but is of substantially the same composition (e.g., hydrogel of the same size, shape, number of compartments). In an embodiment, the degree of the FBR is assessed by the immunological response in the tissue containing the implanted device (e.g., hydrogel capsule), which may include, for example, protein adsorption, macrophages, multinucleated foreign body giant cells, fibroblasts, and angiogenesis, using assays known in the art, e.g., as described in WO 2017 / 075630, or using one or more of the assays / methods described in Vegas, A., et al., Nature Biotechnol (supra), (e.g., subcutaneous cathepsin measurement of implanted capsules), Masson’s trichrome (MT), hematoxylin or eosin staining of tissue sections, quantification of collagen density, cellular staining and confocal microscopy for macrophages (CD68 or F4 / 80), myofibroblasts (alpha-muscle actin, SMA) or general cellular deposition, quantification of 79 RNA sequences of known inflammation factors and immune cell markers, or FACS analysis for macrophage and neutrophil cells on retrieved devices (e.g., capsules) after 14 days in the intraperitoneal space of a suitable test subject, e.g., an immunocompetent mouse. In an embodiment, the FBR is assessed by measuring the levels in the tissue containing the implant of one or more biomarkers of immune response, e.g., cathepsin, TNF-α, IL-13, IL-6, G-CSF, GM-CSF, IL-4, CCL2, or CCL4. In some embodiments, the FBR induced by a device of the invention (e.g., a hydrogel capsule comprising an afibrotic compound disposed on its outer surface), is at least about 80%, about 85%, about 90%, about 95%, about 99%, or about 100% lower than the FBR induced by an FBR-null reference device, e.g., a device that is substantially identical to the test or claimed device except for lacking the means for mitigating the FBR (e.g., a hydrogel capsule that does not comprise an afibrotic compound but is otherwise substantially identical to the claimed capsule). In some embodiments, the FBR (e.g., level of a biomarker(s)) is measured after about 30 minutes, about 1 hour, about 6 hours, about 12 hours, about 1 day, about 2 days, about 3 days, about 4 days, about 1 week, about 2 weeks, about 1 month, about 2 months, about 3 months, about 6 months, or longer. “Cell,” as used herein, refers to an engineered cell or a cell that is not engineered. In an embodiment, a cell is an immortalized cell or an engineered cell derived from an immortalized cell. In an embodiment, the cell is a live cell, e.g., is viable as measured by any technique described herein or known in the art. “Cell-binding peptide (CBP)”, as used herein, means a linear or cyclic peptide that comprises an amino acid sequence that is derived from the cell binding domain of a ligand for a cell-adhesion molecule (CAM) (e.g., that mediates cell-matrix junctions or cell-cell junctions). The CBP is less than 50, 4030, 25, 20, 15 or 10 amino acids in length. In an embodiment, the CBP is between 3 and 12 amino acids in length, 4 and 10 amino acids in length, or is 3, 4, 5, 6, 7 8, 9 or 10 amino acids in length. The CBP amino acid sequence may be identical to the naturally occurring binding domain sequence or may be a conservatively substituted variant thereof. In an embodiment, the CAM ligand is a mammalian protein. In an embodiment, the CAM ligand is a human protein selected from the group of proteins listed in Table 1 below. In an embodiment, the CBP comprises a cell binding sequence listed in Table 1 below or a conservatively substituted variant thereof. In an embodiment, the CBP comprises at least one of the cell binding sequences listed in Table 1 below. In an embodiment, the CBP consists essentially of a cell binding sequence listed in Table 1 below. In an embodiment, the CBP is an RGD peptide, which means the peptide comprises the amino acid sequence RGD (SEQ ID NO: 43) and optionally comprises one or more additional amino acids located at one or both of the N-terminus and C- terminus. In an embodiment, the CBP is a cyclic peptide comprising RGD (SEQ ID NO: 43), e.g., one of the cyclic RGD peptides described in Vilaca, H. et al., Tetrahedron 70 (35):5420- 5427 (2014). In an embodiment, the CBP is a linear peptide comprising RGD (SEQ ID NO: 43) and is less than 6 amino acids in length. In an embodiment, the CBP is a linear peptide that consists essentially of RGD (SEQ ID NO: 43) or RGDSP (SEQ ID NO: 59). Table 1: Exemplary CAM Ligand Proteins and Cell Binding Sequences “CBP-polymer”, as used herein, means a polymer comprising at least one cell-binding peptide molecule covalently attached to the polymer via a linker. In an embodiment, the polymer is not a peptide or a polypeptide. In an embodiment, the polymer in a CBP-polymer does not contain any amino acids. In an embodiment, the polymer in a CBP-polymer is a synthetic or naturally occurring polysaccharide, e.g., an alginate, e.g., a sodium alginate. In an embodiment, the linker is an amino acid linker (i.e., consists essentially of a single amino acid, or a peptide of several identical or different amino acids), which is joined via a peptide bond to the N-terminus or C-terminus of the CBP. In an embodiment, the C-terminus of an amino acid linker is joined to the N-terminus of the CBP and the N-terminus of the amino acid linker is joined to at least one pendant carboxyl group in the polysaccharide via an amide bond. In an embodiment, the structure of the linker-CBP is expressed as G(1-4)-CBP, meaning that the linker has one, two, three or four glycine residues. In an embodiment, one or more of the monosaccharide moieties in a CBP-polysaccharide, e.g., a CBP-alginate is not modified with the CBP, e.g, the unmodified moiety has a free carboxyl group or lacks a modifiable pendant carboxyl group. In an embodiment, the number of polysaccharide moieties with a covalently attached CBP is less than any of the following values: 99%, 95%, 90%, 80%, 70%, 60%, 50%, 40% 30%, 20%, 10%, 5%, 1%. In an embodiment, the density of CBP modification in the CBP-polymer is estimated by combustion analysis for percent nitrogen. In an embodiment, the CBP-polymer is an RGD- polymer (e.g., an RGD-alginate), which is a polymer (e.g., an alginate) covalently modified with a linker-RGD molecule (e.g., a peptide consisting essentially of GRGD (SEQ ID NO: 62) or GRGDSP (SEQ ID NO: 60)) and the density of linker-RGD molecule modification (e.g., conjugation density) is about 0.05 % nitrogen (N) to 1.00 % N, about 0.10 % N to about 0.75 % N, about 0.20 % N to about 0.50% N, or about 0.30 % N to about 0.40 % N, as determined using an assay described herein. In an embodiment, the conjugation density of the linker-RGD modification in an RGD-alginate (e.g., a MMW alginate covalently modified with GRGDSP (SEQ ID NO: 60)) is 0.1 to 1.0, 0.2 to 0.8, 0.3 to 0.7, 0.3 to 0.6, 0.4 to 0.6 micromoles of the linker-RGD moiety per g of the RGD-polymer in solution (e.g., saline solution) with a viscosity of 80-120cP, as determined by any assay that is capable of quantitating the amount of a peptide conjugated to a polymer, e.g., a quantitative peptide conjugation assay described herein. Unless otherwise explicitly stated or readily apparent from the context, a specifically recited numerical concentration, concentration range, density or density range for a CBP in a CBP-polymer refers to the concentration or density of conjugated CBP molecules, i.e., it does not include any residual free (e.g., unconjugated) CBP that may be present in the CBP-polymer. “Conservatively modified variants” or conservative substitution”, as used herein, refers to a variant of a reference peptide or polypeptide that is identical to the reference molecule, except for having one or more conservative amino acid substitutions in its amino acid sequence. In an embodiment, a conservatively modified variant consists of an amino acid sequence that is at least 70%, 80%, 85%, 90%, 95%, 97%, 98% or 99% identical to the reference amino acid sequence. A conservative amino acid substitution refers to substitution of an amino acid with an amino acid having similar characteristics (e.g., charge, side-chain size, hydrophobicity / hydrophilicity, backbone conformation and rigidity, etc.) and which has minimal impact on the biological activity of the resulting substituted peptide or polypeptide. Conservative substitution tables of functionally similar amino acids are well known in the art, and exemplary substitutions grouped by functional features are set forth in Table 2 below. Table 2. Exemplary conservative amino acid substitution groups. “Crosslinked,” and variations thereof such as “crosslinking,” or “x-linked” as used herein, refers to at least one chemical bond (e.g., an ionic bond or a covalent bond) between two or more polymers. In some embodiments, when two or more chemical bonds are present, crosslinking refers to a mixture of both covalent and ionic bonds. In some embodiments, when two or more chemical bonds are present, crosslinking refers to different types of covalent bonds (e.g., covalent bonds comprising different or orthogonal functional groups). In some embodiments, when two or more chemical bonds are present, crosslinking refers to the same type of covalent bonds (e.g., covalent bonds comprising the same functional groups). In some embodiments, when two or more chemical bonds are present, crosslinking refers to the same type of ionic bonds (e.g., ionic bonds comprising the same ion, e.g., Ba2+). “Derived from”, as used herein with respect to cells, refers to cells obtained from tissue, cell lines, or cells, which optionally are then cultured, passaged, differentiated, induced, etc. to produce the derived cells. For example, mesenchymal stem cells can be derived from mesenchymal tissue and then differentiated into a variety of cell types. “Differential volume,” as used herein, refers to a volume of one compartment within a device described herein that excludes the space occupied by another compartment(s). For example, the differential volume of the second (e.g., outer) compartment in a two-compartment device with inner and outer compartments, refers to a volume within the second compartment that excludes space occupied by the first (inner) compartment. “Effective amount”, as used herein, refers to an amount of a device, a device composition, or a component of the device or device composition, e.g, a plurality of hydrogel capsules comprising an islet cell, e.g., an engineered islet cell, or an agent, e.g., a therapeutic agent, produced by a islet cell, sufficient to elicit a biological response. As will be appreciated by those of ordinary skill in this art, the effective amount may vary depending on such factors as the desired biological endpoint, the pharmacokinetics of the therapeutic agent, composition or device (e.g., a hydrogel capsule, particle), the condition being treated, the mode of administration, and the age and health of the subject. An effective amount encompasses therapeutic and prophylactic treatment. For example, to mitigate the FBR, an effective amount of a compound of Formula (I) may reduce the fibrosis or stop the growth or spread of fibrotic tissue on or near the implanted device. An “endogenous nucleic acid” as used herein, is a nucleic acid that occurs naturally in a subject cell. An “endogenous polypeptide,” as used herein, is a polypeptide that occurs naturally in a subject cell. “Engineered cell,” as used herein, is a cell having a non-naturally occurring alteration, and typically comprises a nucleic acid sequence (e.g., DNA or RNA) or a polypeptide not present (or present at a different level than) in an otherwise similar cell under similar conditions that is not engineered (an exogenous nucleic acid sequence). In an embodiment, an engineered cell comprises an exogenous nucleic acid (e.g., a vector or an altered chromosomal sequence). In an embodiment, an engineered cell comprises an exogenous polypeptide. In an embodiment, an engineered cell comprises an exogenous nucleic acid sequence, e.g., a sequence, e.g., DNA or RNA, not present in a similar cell that is not engineered. In an embodiment, the exogenous nucleic acid sequence is chromosomal, e.g., the exogenous nucleic acid sequence is an exogenous sequence disposed in endogenous chromosomal sequence. In an embodiment, the exogenous nucleic acid sequence is chromosomal or extra chromosomal, e.g., a non-integrated vector. In an embodiment, the exogenous nucleic acid sequence comprises an RNA sequence, e.g., an mRNA. In an embodiment, the exogenous nucleic acid sequence comprises a chromosomal or extra-chromosomal exogenous nucleic acid sequence that comprises a sequence which is expressed as RNA, e.g., mRNA or a regulatory RNA. In an embodiment, the exogenous nucleic acid sequence comprises a chromosomal or extra-chromosomal nucleic acid sequence, which comprises a sequence that encodes a polypeptide, or which is expressed as a polypeptide. In an embodiment, the exogenous nucleic acid sequence comprises a first chromosomal or extra-chromosomal exogenous nucleic acid sequence that modulates the conformation or expression of a second nucleic acid sequence, wherein the second amino acid sequence can be exogenous or endogenous. For example, an engineered cell can comprise an exogenous nucleic acid that controls the expression of an endogenous sequence. In an embodiment, an engineered cell comprises a polypeptide present at a level or distribution which differs from the level found in a similar cell that has not been engineered. In an embodiment, an engineered cell comprises an islet cell engineered to produce an RNA or a polypeptide. For example, an engineered cell may comprise an exogenous nucleic acid sequence comprising a chromosomal or extra-chromosomal exogenous nucleic acid sequence that comprises a sequence which is expressed as RNA, e.g., mRNA or a regulatory RNA. In an embodiment, an engineered cell (e.g., an islet cell) comprises an exogenous nucleic acid sequence that comprises a chromosomal or extra-chromosomal nucleic acid sequence comprising a sequence that encodes a polypeptide, or which is expressed as a polypeptide. In an embodiment, the polypeptide is encoded by a codon optimized sequence to achieve higher expression of the polypeptide than a naturally occurring coding sequence. The codon optimized sequence may be generated using a commercially available algorithm, e.g., GeneOptimizer (ThermoFisher Scientific), OptimumGeneTM(GenScript, Piscataway, NJ USA), GeneGPS® (ATUM, Newark, CA USA), or Java Codon Adaptation Tool (JCat, www.jcat.de, Grote, A. et al., Nucleic Acids Research, Vol 33, Issue suppl_2, pp. W526-W531 (2005). An “exogenous nucleic acid,” as used herein, is a nucleic acid that does not occur naturally in a subject cell. An “exogenous polypeptide,” as used herein, is a polypeptide that does not occur naturally in a subject cell, e.g., engineered cell. Reference to an amino acid position of a specific sequence means the position of said amino acid in a reference amino acid sequence, e.g., sequence of a full-length mature (after signal peptide cleavage) wild-type protein (unless otherwise stated), and does not exclude the presence of variations, e.g., deletions, insertions and / or substitutions at other positions in the reference amino acid sequence. “Islet cell” as used herein means a cell that comprises any naturally occurring or any synthetically created, or modified, cell that is intended to recapitulate, mimic or otherwise express, in part or in whole, the functions, in part or in whole, of the cells of the pancreatic islets of Langerhans. The term “islet cells” includes glucose-responsive, insulin producing cells derived from stem cells, e.g., from an induced pluripotent stem cell line. “Photoactive,” as used herein, refers to a compound or moiety capable of forming a reactive species after activation by light, e.g., light at a certain wavelength. In an embodiment, a photoactive compound is chemically inert in standard laboratory conditions, but becomes reactive upon activation by light. A “photoactive crosslinker” is a crosslinker compound that is activated for crosslinking upon activation by light. “Polymer composition”, as used herein, is a composition (e.g., a solution, mixture) comprising one or more polymers. As a class, “polymers’ includes homopolymers, heteropolymers, co-polymers, block polymers, block co-polymers and can be both natural and synthetic. Homopolymers contain one type of building block, or monomer, whereas co- polymers contain more than one type of monomer. “Polypeptide”, as used herein, refers to a polymer comprising amino acid residues linked through peptide bonds and having at least two, and in some embodiments, at least 10, 50, 75, 100, 150 or 200 amino acid residues. “Prevention,” “prevent,” and “preventing” as used herein refers to a treatment that comprises administering or applying a therapy, e.g., administering a composition of devices encapsulating cells (e.g., as described herein), prior to the onset of a disease, disorder, or condition (e.g., Type 1 diabetes) to preclude the physical manifestation of said disease, disorder, or condition (e.g., Type 1 diabetes). In some embodiments, “prevention,” “prevent,” and “preventing” require that signs or symptoms of the disease, disorder, or condition have not yet developed or have not yet been observed. In some embodiments, treatment comprises prevention and in other embodiments it does not. “Sequence identity” or “percent identical”, when used herein to refer to two nucleotide sequences or two amino acid sequences, means the two sequences are the same within a specified region, or have the same nucleotides or amino acids at a specified percentage of nucleotide or amino acid positions within the specified when the two sequences are compared and aligned for maximum correspondence over a comparison window or designated region. Sequence identity may be determined using standard techniques known in the art including, but not limited to, any of the algorithms described in US Patent Application Publication No. 2017 / 02334455. In an embodiment, the specified percentage of identical nucleotide or amino acid positions is at least about 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or higher. “Spherical” as used herein, means a device (e.g., a hydrogel capsule or other particle) having a curved surface that forms a sphere (e.g., a completely round ball) or sphere-like shape, which may have waves and undulations, e.g., on the surface. Spheres and sphere-like objects can be mathematically defined by rotation of circles, ellipses, or a combination around each of the three perpendicular axes, a, b, and c. For a sphere, the three axes are the same length. Generally, a sphere-like shape is an ellipsoid (for its averaged surface) with semi-principal axes within 10%, or 5%, or 2.5% of each other. The diameter of a sphere or sphere-like shape is the average diameter, such as the average of the semi-principal axes. “Spheroid”, as that term is used herein to refer to a device (e.g., a hydrogel capsule or other particle), means the device has (i) a perfect or classical oblate spheroid or prolate spheroid shape or (ii) has a surface that roughly forms a spheroid, e.g., may have waves and undulations and / or may be an ellipsoid (for its averaged surface) with semi-principal axes within 100% of each other. “Subject” as used herein refers to a human or non-human animal. In an embodiment, the subject is a human (i.e., a male or female), e.g., of any age group, a pediatric subject (e.g., infant, child, adolescent) or adult subject (e.g., young adult, middle–aged adult, or senior adult). In an embodiment, the subject is a non-human animal, for example, a mammal (e.g., a mouse, a dog, a primate (e.g., a cynomolgus monkey or a rhesus monkey)). In an embodiment, the subject is a commercially relevant mammal (e.g., a cattle, pig, horse, sheep, goat, cat, or dog) or a bird (e.g., a commercially relevant bird such as a chicken, duck, goose, or turkey). In certain embodiments, the animal is a mammal. The animal may be a male or female and at any stage of development. A non-human animal may be a transgenic animal. “Total volume,” as used herein, refers to a volume within one compartment of a multi- compartment device that includes the space occupied by another compartment. For example, the total volume of the second (e.g., outer) compartment of a two-compartment device refers to a volume within the second compartment that includes space occupied by the first compartment. “Treatment,” “treat,” and “treating” as used herein refers to one or more of reducing, reversing, alleviating, delaying the onset of, or inhibiting the progress of one or more of a symptom, manifestation, or underlying cause, of a disease, disorder, or condition (e.g., Type 1 diabetes). In an embodiment, treating comprises reducing, reversing, alleviating, delaying the onset of, or inhibiting the progress of a symptom of a disease, disorder, or condition. In an embodiment, treating comprises reducing, reversing, alleviating, delaying the onset of, or inhibiting the progress of a manifestation of a disease, disorder, or condition (e.g., Type 1 diabetes). In an embodiment, treating comprises reducing, reversing, alleviating, reducing, or delaying the onset of, an underlying cause of a disease, disorder, or condition (e.g., Type 1 diabetes). In some embodiments, “treatment,” “treat,” and “treating” require that signs or symptoms of the disease, disorder, or condition have developed or have been observed. In other embodiments, treatment may be administered in the absence of signs or symptoms of the disease or condition, e.g., in preventive treatment. For example, treatment may be administered to a susceptible individual prior to the onset of symptoms (e.g., considering a history of symptoms and / or in light of genetic or other susceptibility factors). Treatment may also be continued after symptoms have resolved, for example, to delay or prevent recurrence. In some embodiments, treatment comprises prevention and in other embodiments it does not. “VLVG” or “VLVG alginate” refers to a very low viscosity sodium alginate that has an average molecular weight of less than about 75 kDa and that comprises greater than 60% guluronate units (i.e., has a guluronate to mannuronate ratio of greater than or equal to 1.5). “SG100” or “SG100 alginate” refers to a sodium alginate that has an average molecular weight of about 150-250 kDa and that comprises greater than 60% guluronate units (i.e., has a guluronate to mannuronate ratio of greater than or equal to 1). Selected Chemical Definitions Definitions of specific functional groups and chemical terms are described in more detail below. The chemical elements are identified in accordance with the Periodic Table of the Elements, CAS version, Handbook of Chemistry and Physics, 75thEd., inside cover, and specific functional groups are generally defined as described therein. Additionally, general principles of organic chemistry, as well as specific functional moieties and reactivity, are described in Thomas Sorrell, Organic Chemistry, University Science Books, Sausalito, 1999; Smith and March, March’s Advanced Organic Chemistry, 5thEdition, John Wiley & Sons, Inc., New York, 2001; Larock, Comprehensive Organic Transformations, VCH Publishers, Inc., New York, 1989; and Carruthers, Some Modern Methods of Organic Synthesis, 3rdEdition, Cambridge University Press, Cambridge, 1987. The abbreviations used herein have their conventional meaning within the chemical and biological arts. The chemical structures and formulae set forth herein are constructed according to the standard rules of chemical valency known in the chemical arts. When a range of values is listed, it is intended to encompass each value and sub–range within the range. For example, “C1-C6alkyl” is intended to encompass, C1, C2, C3, C4, C5, C6, C1-C6, C1- C5, C1-C4, C1-C3, C1-C2, C2-C6, C2-C5, C2-C4, C2-C3, C3-C6, C3-C5, C3-C4, C4-C6, C4-C5, and C5- C6 alkyl. As used herein, “alkyl” refers to a radical of a straight–chain or branched saturated hydrocarbon group having from 1 to 24 carbon atoms (“C1-C24alkyl”). In some embodiments, an alkyl group has 1 to 12 carbon atoms (“C1-C12alkyl”), 1 to 10 carbon atoms (“C1-C12alkyl”), 1 to 8 carbon atoms (“C1-C8 alkyl”), 1 to 6 carbon atoms (“C1-C6 alkyl”), 1 to 5 carbon atoms (“C1-C5alkyl”), 1 to 4 carbon atoms (“C1-C4alkyl”), 1 to 3 carbon atoms (“C1-C3alkyl”), 1 to 2 carbon atoms (“C1-C2alkyl”), or 1 carbon atom (“C1alkyl”). In some embodiments, an alkyl group has 2 to 6 carbon atoms (“C2-C6alkyl”). Examples of C1-C6 alkyl groups include methyl(C1), ethyl (C2), n–propyl (C3), isopropyl (C3), n–butyl (C4), tert–butyl (C4), sec–butyl (C4), iso–butyl (C4), n–pentyl (C5), 3–pentanyl (C5), amyl (C5), neopentyl (C5), 3–methyl–2–butanyl (C5), tertiary amyl (C5), and n–hexyl (C6). Additional examples of alkyl groups include n–heptyl (C7), n–octyl (C8) and the like. Each instance of an alkyl group may be independently optionally substituted, i.e., unsubstituted (an “unsubstituted alkyl”) or substituted (a “substituted alkyl”) with one or more substituents; e.g., for instance from 1 to 5 substituents, 1 to 3 substituents, or 1 substituent. As used herein, “alkenyl” refers to a radical of a straight–chain or branched hydrocarbon group having from 2 to 24 carbon atoms, one or more carbon–carbon double bonds, and no triple bonds (“C2-C24 alkenyl”). In some embodiments, an alkenyl group has 2 to 10 carbon atoms (“C2-C10 alkenyl”), 2 to 8 carbon atoms (“C2-C8 alkenyl”), 2 to 6 carbon atoms (“C2-C6 alkenyl”), 2 to 5 carbon atoms (“C2-C5alkenyl”), 2 to 4 carbon atoms (“C2-C4alkenyl”), 2 to 3 carbon atoms (“C2-C3alkenyl”), or 2 carbon atoms (“C2alkenyl”). The one or more carbon– carbon double bonds can be internal (such as in 2–butenyl) or terminal (such as in 1–butenyl). Examples of C2-C4 alkenyl groups include ethenyl (C2), 1–propenyl (C3), 2–propenyl (C3), 1– butenyl (C4), 2–butenyl (C4), butadienyl (C4), and the like. Examples of C2-C6alkenyl groups include the aforementioned C2–4 alkenyl groups as well as pentenyl (C5), pentadienyl (C5), hexenyl (C6), and the like. Each instance of an alkenyl group may be independently optionally substituted, i.e., unsubstituted (an “unsubstituted alkenyl”) or substituted (a “substituted alkenyl”) with one or more substituents e.g., for instance from 1 to 5 substituents, 1 to 3 substituents, or 1 substituent. As used herein, the term “alkynyl” refers to a radical of a straight–chain or branched hydrocarbon group having from 2 to 24 carbon atoms, one or more carbon–carbon triple bonds (“C2-C24 alkenyl”). In some embodiments, an alkynyl group has 2 to 10 carbon atoms (“C2-C10 alkynyl”), 2 to 8 carbon atoms (“C2-C8 alkynyl”), 2 to 6 carbon atoms (“C2-C6 alkynyl”), 2 to 5 carbon atoms (“C2-C5alkynyl”), 2 to 4 carbon atoms (“C2-C4alkynyl”), 2 to 3 carbon atoms (“C2-C3alkynyl”), or 2 carbon atoms (“C2alkynyl”). The one or more carbon–carbon triple bonds can be internal (such as in 2–butynyl) or terminal (such as in 1–butynyl). Examples of C2- C4alkynyl groups include ethynyl (C2), 1–propynyl (C3), 2–propynyl (C3), 1–butynyl (C4), 2– butynyl (C4), and the like. Each instance of an alkynyl group may be independently optionally substituted, i.e., unsubstituted (an “unsubstituted alkynyl”) or substituted (a “substituted alkynyl”) with one or more substituents e.g., for instance from 1 to 5 substituents, 1 to 3 substituents, or 1 substituent. As used herein, the term "heteroalkyl," refers to a non-cyclic stable straight or branched chain, or combinations thereof, including at least one carbon atom and at least one heteroatom selected from the group consisting of O, N, P, Si, and S, and wherein the nitrogen and sulfur atoms may optionally be oxidized, and the nitrogen heteroatom may optionally be quaternized. The heteroatom(s) O, N, P, S, and Si may be placed at any position of the heteroalkyl group. Exemplary heteroalkyl groups include, but are not limited to: -CH2-CH2-O-CH3, -CH2-CH2-NH- CH3, -CH2-CH2-N(CH3)-CH3, -CH2-S-CH2-CH3, -CH2-CH2, -S(O)-CH3, -CH2-CH2-S(O)2-CH3, - CH=CH-O-CH3, -Si(CH3)3, -CH2-CH=N-OCH3, -CH=CH-N(CH3)-CH3, -O-CH3, and -O-CH2- CH3. Up to two or three heteroatoms may be consecutive, such as, for example, -CH2-NH-OCH3 and -CH2-O-Si(CH3)3. Where "heteroalkyl" is recited, followed by recitations of specific heteroalkyl groups, such as –CH2O, –NRCRD, or the like, it will be understood that the terms heteroalkyl and –CH2O or –NRCRDare not redundant or mutually exclusive. Rather, the specific heteroalkyl groups are recited to add clarity. Thus, the term "heteroalkyl" should not be interpreted herein as excluding specific heteroalkyl groups, such as –CH2O, –NRCRD, or the like. Each instance of a heteroalkyl group may be independently optionally substituted, i.e., unsubstituted (an “unsubstituted heteroalkyl”) or substituted (a “substituted heteroalkyl”) with one or more substituents e.g., for instance from 1 to 5 substituents, 1 to 3 substituents, or 1 substituent. The terms "alkylene," “alkenylene,” “alkynylene,” or “heteroalkylene,” alone or as part of another substituent, mean, unless otherwise stated, a divalent radical derived from an alkyl, alkenyl, alkynyl, or heteroalkyl, respectively. An alkylene, alkenylene, alkynylene, or heteroalkylene group may be described as, e.g., a C1-C6-membered alkylene, C2-C6-membered alkenylene, C2-C6-membered alkynylene, or C1-C6-membered heteroalkylene, wherein the term “membered” refers to the non-hydrogen atoms within the moiety. In the case of heteroalkylene groups, heteroatoms can also occupy either or both chain termini (e.g., alkyleneoxy, alkylenedioxy, alkyleneamino, alkylenediamino, and the like). Still further, for alkylene and heteroalkylene linking groups, no orientation of the linking group is implied by the direction in which the formula of the linking group is written. For example, the formula -C(O)2R’- may represent both -C(O)2R’- and –R’C(O)2-. As used herein, “aryl” refers to a radical of a monocyclic or polycyclic (e.g., bicyclic or tricyclic) 4n+2 aromatic ring system (e.g., having 6, 10, or 14 π electrons shared in a cyclic array) having 6–14 ring carbon atoms and zero heteroatoms provided in the aromatic ring system (“C6-C14 aryl”). In some embodiments, an aryl group has six ring carbon atoms (“C6 aryl”; e.g., phenyl). In some embodiments, an aryl group has ten ring carbon atoms (“C10 aryl”; e.g., naphthyl such as 1–naphthyl and 2–naphthyl). In some embodiments, an aryl group has fourteen ring carbon atoms (“C14 aryl”; e.g., anthracyl). An aryl group may be described as, e.g., a C6- C10-membered aryl, wherein the term “membered” refers to the non-hydrogen ring atoms within the moiety. Aryl groups include phenyl, naphthyl, indenyl, and tetrahydronaphthyl. Each instance of an aryl group may be independently optionally substituted, i.e., unsubstituted (an “unsubstituted aryl”) or substituted (a “substituted aryl”) with one or more substituents. As used herein, “heteroaryl” refers to a radical of a 5–10 membered monocyclic or bicyclic 4n+2 aromatic ring system (e.g., having 6 or 10 π electrons shared in a cyclic array) having ring carbon atoms and 1–4 ring heteroatoms provided in the aromatic ring system, wherein each heteroatom is independently selected from nitrogen, oxygen and sulfur (“5–10 membered heteroaryl”). In heteroaryl groups that contain one or more nitrogen atoms, the point of attachment can be a carbon or nitrogen atom, as valency permits. Heteroaryl bicyclic ring systems can include one or more heteroatoms in one or both rings. “Heteroaryl” also includes ring systems wherein the heteroaryl ring, as defined above, is fused with one or more aryl groups wherein the point of attachment is either on the aryl or heteroaryl ring, and in such instances, the number of ring members designates the number of ring members in the fused (aryl / heteroaryl) ring system. Bicyclic heteroaryl groups wherein one ring does not contain a heteroatom (e.g., indolyl, quinolinyl, carbazolyl, and the like) the point of attachment can be on either ring, i.e., either the ring bearing a heteroatom (e.g., 2–indolyl) or the ring that does not contain a heteroatom (e.g., 5–indolyl). A heteroaryl group may be described as, e.g., a 6-10-membered heteroaryl, wherein the term “membered” refers to the non-hydrogen ring atoms within the moiety. In some embodiments, a heteroaryl group is a 5–10 membered aromatic ring system having ring carbon atoms and 1–4 ring heteroatoms provided in the aromatic ring system, wherein each heteroatom is independently selected from nitrogen, oxygen, and sulfur (“5–10 membered heteroaryl”). In some embodiments, a heteroaryl group is a 5–8 membered aromatic ring system having ring carbon atoms and 1–4 ring heteroatoms provided in the aromatic ring system, wherein each heteroatom is independently selected from nitrogen, oxygen, and sulfur (“5–8 membered heteroaryl”). In some embodiments, a heteroaryl group is a 5–6 membered aromatic ring system having ring carbon atoms and 1–4 ring heteroatoms provided in the aromatic ring system, wherein each heteroatom is independently selected from nitrogen, oxygen, and sulfur (“5–6 membered heteroaryl”). In some embodiments, the 5–6 membered heteroaryl has 1–3 ring heteroatoms selected from nitrogen, oxygen, and sulfur. In some embodiments, the 5–6 membered heteroaryl has 1–2 ring heteroatoms selected from nitrogen, oxygen, and sulfur. In some embodiments, the 5–6 membered heteroaryl has 1 ring heteroatom selected from nitrogen, oxygen, and sulfur. Each instance of a heteroaryl group may be independently optionally substituted, i.e., unsubstituted (an “unsubstituted heteroaryl”) or substituted (a “substituted heteroaryl”) with one or more substituents. Exemplary 5–membered heteroaryl groups containing one heteroatom include, without limitation, pyrrolyl, furanyl and thiophenyl. Exemplary 5–membered heteroaryl groups containing two heteroatoms include, without limitation, imidazolyl, pyrazolyl, oxazolyl, isoxazolyl, thiazolyl, and isothiazolyl. Exemplary 5–membered heteroaryl groups containing three heteroatoms include, without limitation, triazolyl, oxadiazolyl, and thiadiazolyl. Exemplary 5–membered heteroaryl groups containing four heteroatoms include, without limitation, tetrazolyl. Exemplary 6–membered heteroaryl groups containing one heteroatom include, without limitation, pyridinyl. Exemplary 6–membered heteroaryl groups containing two heteroatoms include, without limitation, pyridazinyl, pyrimidinyl, and pyrazinyl. Exemplary 6– membered heteroaryl groups containing three or four heteroatoms include, without limitation, triazinyl and tetrazinyl, respectively. Exemplary 7–membered heteroaryl groups containing one heteroatom include, without limitation, azepinyl, oxepinyl, and thiepinyl. Exemplary 5,6– bicyclic heteroaryl groups include, without limitation, indolyl, isoindolyl, indazolyl, benzotriazolyl, benzothiophenyl, isobenzothiophenyl, benzofuranyl, benzoisofuranyl, benzimidazolyl, benzoxazolyl, benzisoxazolyl, benzoxadiazolyl, benzthiazolyl, benzisothiazolyl, benzthiadiazolyl, indolizinyl, and purinyl. Exemplary 6,6–bicyclic heteroaryl groups include, without limitation, naphthyridinyl, pteridinyl, quinolinyl, isoquinolinyl, cinnolinyl, quinoxalinyl, phthalazinyl, and quinazolinyl. Other exemplary heteroaryl groups include heme and heme derivatives. As used herein, the terms "arylene" and "heteroarylene," alone or as part of another substituent, mean a divalent radical derived from an aryl and heteroaryl, respectively. As used herein, “cycloalkyl” refers to a radical of a non–aromatic cyclic hydrocarbon group having from 3 to 10 ring carbon atoms (“C3-C10 cycloalkyl”) and zero heteroatoms in the non–aromatic ring system. In some embodiments, a cycloalkyl group has 3 to 8 ring carbon atoms (“C3-C8cycloalkyl”), 3 to 6 ring carbon atoms (“C3-C6cycloalkyl”), or 5 to 10 ring carbon atoms (“C5-C10 cycloalkyl”). A cycloalkyl group may be described as, e.g., a C4-C7-membered cycloalkyl, wherein the term “membered” refers to the non-hydrogen ring atoms within the moiety. Exemplary C3-C6cycloalkyl groups include, without limitation, cyclopropyl (C3), cyclopropenyl (C3), cyclobutyl (C4), cyclobutenyl (C4), cyclopentyl (C5), cyclopentenyl (C5), cyclohexyl (C6), cyclohexenyl (C6), cyclohexadienyl (C6), and the like. Exemplary C3-C8 cycloalkyl groups include, without limitation, the aforementioned C3-C6cycloalkyl groups as well as cycloheptyl (C7), cycloheptenyl (C7), cycloheptadienyl (C7), cycloheptatrienyl (C7), cyclooctyl (C8), cyclooctenyl (C8), cubanyl (C8), bicyclo[1.1.1]pentanyl (C5), bicyclo[2.2.2]octanyl (C8), bicyclo[2.1.1]hexanyl (C6), bicyclo[3.1.1]heptanyl (C7), and the like. Exemplary C3-C10cycloalkyl groups include, without limitation, the aforementioned C3-C8cycloalkyl groups as well as cyclononyl (C9), cyclononenyl (C9), cyclodecyl (C10), cyclodecenyl (C10), octahydro–1H–indenyl (C9), decahydronaphthalenyl (C10), spiro [4.5] decanyl (C10), and the like. As the foregoing examples illustrate, in certain embodiments, the cycloalkyl group is either monocyclic (“monocyclic cycloalkyl”) or contain a fused, bridged or spiro ring system such as a bicyclic system (“bicyclic cycloalkyl”) and can be saturated or can be partially unsaturated. “Cycloalkyl” also includes ring systems wherein the cycloalkyl ring, as defined above, is fused with one or more aryl groups wherein the point of attachment is on the cycloalkyl ring, and in such instances, the number of carbons continue to designate the number of carbons in the cycloalkyl ring system. Each instance of a cycloalkyl group may be independently optionally substituted, i.e., unsubstituted (an “unsubstituted cycloalkyl”) or substituted (a “substituted cycloalkyl”) with one or more substituents. “Heterocyclyl” as used herein refers to a radical of a 3– to 10–membered non–aromatic ring system having ring carbon atoms and 1 to 4 ring heteroatoms, wherein each heteroatom is independently selected from nitrogen, oxygen, sulfur, boron, phosphorus, and silicon (“3–10 membered heterocyclyl”). In heterocyclyl groups that contain one or more nitrogen atoms, the point of attachment can be a carbon or nitrogen atom, as valency permits. A heterocyclyl group can either be monocyclic (“monocyclic heterocyclyl”) or a fused, bridged or spiro ring system such as a bicyclic system (“bicyclic heterocyclyl”), and can be saturated or can be partially unsaturated. Heterocyclyl bicyclic ring systems can include one or more heteroatoms in one or both rings. “Heterocyclyl” also includes ring systems wherein the heterocyclyl ring, as defined above, is fused with one or more cycloalkyl groups wherein the point of attachment is either on the cycloalkyl or heterocyclyl ring, or ring systems wherein the heterocyclyl ring, as defined above, is fused with one or more aryl or heteroaryl groups, wherein the point of attachment is on the heterocyclyl ring, and in such instances, the number of ring members continue to designate the number of ring members in the heterocyclyl ring system. A heterocyclyl group may be described as, e.g., a 3-7-membered heterocyclyl, wherein the term “membered” refers to the non- hydrogen ring atoms, i.e., carbon, nitrogen, oxygen, sulfur, boron, phosphorus, and silicon, within the moiety. Each instance of heterocyclyl may be independently optionally substituted, i.e., unsubstituted (an “unsubstituted heterocyclyl”) or substituted (a “substituted heterocyclyl”) with one or more substituents. In certain embodiments, the heterocyclyl group is unsubstituted 3–10 membered heterocyclyl. In certain embodiments, the heterocyclyl group is substituted 3– 10 membered heterocyclyl. In some embodiments, a heterocyclyl group is a 5–10 membered non–aromatic ring system having ring carbon atoms and 1–4 ring heteroatoms, wherein each heteroatom is independently selected from nitrogen, oxygen, sulfur, boron, phosphorus, and silicon (“5–10 membered heterocyclyl”). In some embodiments, a heterocyclyl group is a 5–8 membered non– aromatic ring system having ring carbon atoms and 1–4 ring heteroatoms, wherein each heteroatom is independently selected from nitrogen, oxygen, and sulfur (“5–8 membered heterocyclyl”). In some embodiments, a heterocyclyl group is a 5–6 membered non–aromatic ring system having ring carbon atoms and 1–4 ring heteroatoms, wherein each heteroatom is independently selected from nitrogen, oxygen, and sulfur (“5–6 membered heterocyclyl”). In some embodiments, the 5–6 membered heterocyclyl has 1–3 ring heteroatoms selected from nitrogen, oxygen, and sulfur. In some embodiments, the 5–6 membered heterocyclyl has 1–2 ring heteroatoms selected from nitrogen, oxygen, and sulfur. In some embodiments, the 5–6 membered heterocyclyl has one ring heteroatom selected from nitrogen, oxygen, and sulfur. Exemplary 3–membered heterocyclyl groups containing one heteroatom include, without limitation, azirdinyl, oxiranyl, thiorenyl. Exemplary 4–membered heterocyclyl groups containing one heteroatom include, without limitation, azetidinyl, oxetanyl and thietanyl. Exemplary 5–membered heterocyclyl groups containing one heteroatom include, without limitation, tetrahydrofuranyl, dihydrofuranyl, tetrahydrothiophenyl, dihydrothiophenyl, pyrrolidinyl, dihydropyrrolyl and pyrrolyl–2,5–dione. Exemplary 5–membered heterocyclyl groups containing two heteroatoms include, without limitation, dioxolanyl, oxasulfuranyl, disulfuranyl, and oxazolidin–2–one. Exemplary 5–membered heterocyclyl groups containing three heteroatoms include, without limitation, triazolinyl, oxadiazolinyl, and thiadiazolinyl. Exemplary 6–membered heterocyclyl groups containing one heteroatom include, without limitation, piperidinyl, piperazinyl, tetrahydropyranyl, dihydropyridinyl, and thianyl. Exemplary 6–membered heterocyclyl groups containing two heteroatoms include, without limitation, piperazinyl, morpholinyl, dithianyl, dioxanyl. Exemplary 6–membered heterocyclyl groups containing two heteroatoms include, without limitation, triazinanyl or thiomorpholinyl-1,1- dioxide. Exemplary 7–membered heterocyclyl groups containing one heteroatom include, without limitation, azepanyl, oxepanyl and thiepanyl. Exemplary 8–membered heterocyclyl groups containing one heteroatom include, without limitation, azocanyl, oxecanyl and thiocanyl. Exemplary 5–membered heterocyclyl groups fused to a C6 aryl ring (also referred to herein as a 5,6–bicyclic heterocyclic ring) include, without limitation, indolinyl, isoindolinyl, dihydrobenzofuranyl, dihydrobenzothienyl, benzoxazolinonyl, and the like. Exemplary 6– membered heterocyclyl groups fused to an aryl ring (also referred to herein as a 6,6–bicyclic heterocyclic ring) include, without limitation, tetrahydroquinolinyl, tetrahydroisoquinolinyl, and the like. “Amino” as used herein refers to the radical –NR70R71, wherein R70and R71are each independently hydrogen, C1–C8 alkyl, C3–C10 cycloalkyl, C4–C10 heterocyclyl, C6–C10 aryl, and C5–C10 heteroaryl. In some embodiments, amino refers to NH2. As used herein, “cyano” refers to the radical –CN. As used herein, “halo” or “halogen,” independently or as part of another substituent, mean, unless otherwise stated, a fluorine (F), chlorine (Cl), bromine (Br), or iodine (I) atom. As used herein, “hydroxy” refers to the radical –OH. Alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, and heteroaryl groups, as defined herein, are optionally substituted (e.g., “substituted” or “unsubstituted” alkyl, “substituted” or “unsubstituted” alkenyl, “substituted” or “unsubstituted” alkynyl, “substituted” or “unsubstituted” heteroalkyl, “substituted” or “unsubstituted” cycloalkyl, “substituted” or “unsubstituted” heterocyclyl, “substituted” or “unsubstituted” aryl or “substituted” or “unsubstituted” heteroaryl group). In general, the term “substituted”, whether preceded by the term “optionally” or not, means that at least one hydrogen present on a group (e.g., a carbon or nitrogen atom) is replaced with a permissible substituent, e.g., a substituent which upon substitution results in a stable compound, e.g., a compound which does not spontaneously undergo transformation such as by rearrangement, cyclization, elimination, or other reaction. Unless otherwise indicated, a “substituted” group has a substituent at one or more substitutable positions of the group, and when more than one position in any given structure is substituted, the substituent is either the same or different at each position. The term “substituted” is contemplated to include substitution with all permissible substituents of organic compounds, such as any of the substituents described herein that result in the formation of a stable compound. The present disclosure contemplates any and all such combinations to arrive at a stable compound. For purposes of this disclosure, heteroatoms such as nitrogen may have hydrogen substituents and / or any suitable substituent as described herein which satisfy the valencies of the heteroatoms and results in the formation of a stable moiety. Two or more substituents may optionally be joined to form aryl, heteroaryl, cycloalkyl, or heterocyclyl groups. Such so-called ring-forming substituents are typically, though not necessarily, found attached to a cyclic base structure. In one embodiment, the ring-forming substituents are attached to adjacent members of the base structure. For example, two ring- forming substituents attached to adjacent members of a cyclic base structure create a fused ring structure. In another embodiment, the ring-forming substituents are attached to a single member of the base structure. For example, two ring-forming substituents attached to a single member of a cyclic base structure create a spirocyclic structure. In yet another embodiment, the ring- forming substituents are attached to non-adjacent members of the base structure. Compounds of Formula (I) described herein can comprise one or more asymmetric centers, and thus can exist in various isomeric forms, e.g., enantiomers and / or diastereomers. For example, the compounds described herein can be in the form of an individual enantiomer, diastereomer or geometric isomer, or can be in the form of a mixture of stereoisomers, including racemic mixtures and mixtures enriched in one or more stereoisomer. Isomers can be isolated from mixtures by methods known to those skilled in the art, including chiral high-pressure liquid chromatography (HPLC) and the formation and crystallization of chiral salts; or preferred isomers can be prepared by asymmetric syntheses. See, for example, Jacques et al., Enantiomers, Racemates and Resolutions (Wiley Interscience, New York, 1981); Wilen et al., Tetrahedron 33:2725 (1977); Eliel, Stereochemistry of Carbon Compounds (McGraw–Hill, NY, 1962); and Wilen, Tables of Resolving Agents and Optical Resolutions p.268 (E.L. Eliel, Ed., Univ. of Notre Dame Press, Notre Dame, IN 1972). The disclosure additionally encompasses compounds described herein as individual isomers substantially free of other isomers, and alternatively, as mixtures of various isomers. As used herein, a pure enantiomeric compound is substantially free from other enantiomers or stereoisomers of the compound (i.e., in enantiomeric excess). In other words, an “S” form of the compound is substantially free from the “R” form of the compound and is, thus, in enantiomeric excess of the “R” form. The term “enantiomerically pure” or “pure enantiomer” denotes that the compound comprises more than 75% by weight, more than 80% by weight, more than 85% by weight, more than 90% by weight, more than 91% by weight, more than 92% by weight, more than 93% by weight, more than 94% by weight, more than 95% by weight, more than 96% by weight, more than 97% by weight, more than 98% by weight, more than 99% by weight, more than 99.5% by weight, or more than 99.9% by weight, of the enantiomer. In certain embodiments, the weights are based upon total weight of all enantiomers or stereoisomers of the compound. Compounds of Formula (I) described herein may also comprise one or more isotopic substitutions. For example, H may be in any isotopic form, including1H,2H (D or deuterium), and3H (T or tritium); C may be in any isotopic form, including12C,13C, and14C; O may be in any isotopic form, including16O and18O; and the like. The term "pharmaceutically acceptable salt" is meant to include salts of the active compounds that are prepared with relatively nontoxic acids or bases, depending on the particular substituents found on the compounds described herein. When compounds of Formula (I) used to prepare devices of the present disclosure contain relatively acidic functionalities, base addition salts can be obtained by contacting the neutral form of such compounds with a sufficient amount of the desired base, either neat or in a suitable inert solvent. Examples of pharmaceutically acceptable base addition salts include sodium, potassium, calcium, ammonium, organic amino, or magnesium salt, or a similar salt. When compounds used in the present disclosure contain relatively basic functionalities, acid addition salts can be obtained by contacting the neutral form of such compounds with a sufficient amount of the desired acid, either neat or in a suitable inert solvent. Examples of pharmaceutically acceptable acid addition salts include those derived from inorganic acids like hydrochloric, hydrobromic, nitric, carbonic, monohydrogencarbonic, phosphoric, monohydrogenphosphoric, dihydrogenphosphoric, sulfuric, monohydrogensulfuric, hydriodic, or phosphorous acids and the like, as well as the salts derived from organic acids like acetic, propionic, isobutyric, maleic, malonic, benzoic, succinic, suberic, fumaric, lactic, mandelic, phthalic, benzenesulfonic, p-tolylsulfonic, citric, tartaric, methanesulfonic, and the like. Also included are salts of amino acids such as arginate and the like, and salts of organic acids like glucuronic or galacturonic acids and the like (see, e.g., Berge et al, Journal of Pharmaceutical Science 66: 1-19 (1977)). Certain specific compounds used in the devices of the present disclosure (e.g., a particle, a hydrogel capsule) contain both basic and acidic functionalities that allow the compounds to be converted into either base or acid addition salts. These salts may be prepared by methods known to those skilled in the art. Other pharmaceutically acceptable carriers known to those of skill in the art are suitable for use in the present disclosure. “Polysaccharide” as used herein, refers to a polymer of monosaccharide or disaccharide carbohydrates bound together by glycosidic linkages. Polysaccharides may be linear or branched. Exemplary monosaccharides include glucose, galactose, mannose, allose, altrose, talose, idose, gulose, fructose, ribose, arabinose, lyxose, xylose, rhamnose, glucuronic acid, galacturonic acid, uronic acid, mannuronic acid, and guluronic acid. Exemplary polysaccharides include alginate, agar, agarose, carrageenan, hyaluronate, amylopectin, glycogen, gelatin, cellulose, amylose, chitin, chitosan, or a derivative or variant thereof, e.g., as described in Laurienzo (2010), Mar Drugs 9:2435-65. Devices of the present disclosure may contain a compound of Formula (I) in a prodrug form. Prodrugs are those compounds that readily undergo chemical changes under physiological conditions to provide the compounds useful for preparing devices in the present disclosure. Additionally, prodrugs can be converted to useful compounds of Formula (I) by chemical or biochemical methods in an ex vivo environment. Certain compounds of Formula (I) described herein can exist in unsolvated forms as well as solvated forms, including hydrated forms. In general, the solvated forms are equivalent to unsolvated forms and are encompassed within the scope of the present disclosure. Certain compounds of Formula (I) described herein may exist in multiple crystalline or amorphous forms. In general, all physical forms are equivalent for the uses contemplated by the present disclosure and are intended to be within the scope of the present disclosure. The term “solvate” refers to forms of the compound that are associated with a solvent, usually by a solvolysis reaction. This physical association may include hydrogen bonding. Conventional solvents include water, methanol, ethanol, acetic acid, DMSO, THF, diethyl ether, and the like. The compounds described herein may be prepared, e.g., in crystalline form, and may be solvated. Suitable solvates include pharmaceutically acceptable solvates and further include both stoichiometric solvates and non-stoichiometric solvates. The term “hydrate” refers to a compound which is associated with water. Typically, the number of the water molecules contained in a hydrate of a compound is in a definite ratio to the number of the compound molecules in the hydrate. Therefore, a hydrate of a compound may be represented, for example, by the general formula R ^x H2O, wherein R is the compound and wherein x is a number greater than 0. The term “tautomer” as used herein refers to compounds that are interchangeable forms of a compound structure, and that vary in the displacement of hydrogen atoms and electrons. Thus, two structures may be in equilibrium through the movement of π electrons and an atom (usually H). For example, enols and ketones are tautomers because they are rapidly interconverted by treatment with either acid or base. Tautomeric forms may be relevant to the attainment of the optimal chemical reactivity and biological activity of a compound of interest. The symbol “ ” as used herein refers to a connection to an entity, e.g., a polymer (e.g., hydrogel-forming polymer such as alginate) or surface of an implantable device, e.g., a particle, a hydrogel capsule. The connection represented by “ ” may refer to direct attachment to the entity, e.g., a polymer (e.g., an alginate) or an implantable element, may refer to linkage to the entity through an attachment group. An “attachment group,” as described herein, refers to a moiety for linkage of a compound of Formulas (I)-(IV) to an entity (e.g., a hydrogel capsule or an implantable device) as described herein), and may comprise any attachment chemistry known in the art. A listing of exemplary attachment groups is outlined in Bioconjugate Techniques (3rded, Greg T. Hermanson, Waltham, MA: Elsevier, Inc, 2013), which is incorporated herein by reference in its entirety. In some embodiments, an attachment group comprises alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, – C(O)–, –OC(O)–, –N(RC)–, –N(RC)C(O)–, –C(O)N(RC)–, –N(RC)N(RD)–, –NCN–, – C(=N(RC)(RD))O–, –S–, –S(O)x–, –OS(O)x–, –N(RC)S(O)x–, –S(O)xN(RC)–, –P(RF)y–, – Si(ORA)2 –, –Si(RG)(ORA)–, –B(ORA)–, or a metal, wherein each of RA, RC, RD, RF, RG, x and y is independently as described herein. In some embodiments, an attachment group comprises an amine, ketone, ester, amide, alkyl, alkenyl, alkynyl, or thiol. In some embodiments, an attachment group is a cross-linker. In some embodiments, the attachment group is –C(O)(C1-C6- alkylene)–, wherein alkylene is substituted with R1, and R1is as described herein. In some embodiments, the attachment group is –C(O)(C1-C6-alkylene)–, wherein alkylene is substituted with 1-2 alkyl groups (e.g., 1-2 methyl groups). In some embodiments, the attachment group is – C(O)C(CH3)2-. In some embodiments, the attachment group is –C(O)(methylene)–, wherein alkylene is substituted with 1-2 alkyl groups (e.g., 1-2 methyl groups). In some embodiments, the attachment group is –C(O)CH(CH3)-. In some embodiments, the attachment group is – C(O)C(CH3)-. The terms “covalent,” “covalent bond,” and “covalent linkage” as used herein refer to a type of chemical bond that involves the sharing of electrons between two neighboring atoms. Examples of covalent bonds include those formed between carbon and hydrogen (C-H bond) , carbon atoms (C-C bond), carbon and oxygen atoms (C-O bond), and carbon and nitrogen (C-N bond). Depending on the identity of the atoms, a covalent bond may be a single, double, or triple bond, i.e., a covalent bond may involve the sharing of one, two, or three pairs of electrons. The terms “ionic,” “ionic bond,” and “ionic linkage” as used herein refer to a type of chemical bond that involves the Coulombic attraction between neighboring atoms (i.e., ions) of opposite charge. Modified Polysaccharide Polymers The polysaccharide polymers described herein are covalently modified with a covalent photoactive crosslinker moiety. In an embodiment, the polysaccharide polymer may be linear, branched, or cross-linked polysaccharide polymer, or a polysaccharide polymer of selected molecular weight ranges, degree of polymerization, viscosity or melt flow rate. A branched polysaccharide polymer can include one or more of the following types: star polymers, comb polymers, brush polymers, dendronized polymers, graft-co(polymers), ladders, and dendrimers. In some embodiments, the branched polysaccharide polymer is a star polymer. In some embodiments, the branched polysaccharide polymer is a comb polymer. In some embodiments, the branched polysaccharide polymer is a brush polymer. In some embodiments, the branched polysaccharide polymer is a dendronized polymer. In some embodiments, the branched polysaccharide polymer is a graft-(co)polymer. In some embodiments, the branched polysaccharide polymer is a ladder polymer. In some embodiments, the branched polysaccharide polymer is a dendrimer polymer. A polysaccharide polymer may be a thermoresponsive polymer, e.g., a gel (e.g., becomes a solid or liquid upon exposure to heat or a certain temperature) or a photocrosslinkable polymer. In some embodiments, the polysaccharide polymer is a photocrosslinkable polymer. In some embodiments, the polysaccharide polymers may be biodegradable, e.g., contain a labile bond, or may be dissociated by an enzyme, e.g., a lyase. In some embodiments, a polysaccharide polymer is made up of a single type of repeating monomeric unit. In other embodiments, a polysaccharide polymer is made up of different types of repeating monomeric units (e.g., two types of repeating monomeric units, three types of repeating monomeric units, e.g., a polymeric blend). In some embodiments, the polysaccharide polymer may be composed of mannuronic acid and guluronic acid monomers. In some embodiments, the polysaccharide polymer is a naturally occurring or synthetic polymer. In some embodiments, the polysaccharide polymer is a naturally occurring polysaccharide or a synthetic polysaccharide. In an embodiment, the polysaccharide polymer is a cellulose, e.g., carboxymethyl cellulose. In an embodiment, the polysaccharide polymer is a polylactide, a polyglycoside or a polycaprolactone. In an embodiment, the polysaccharide polymer is a hyaluronate, e.g., sodium hyaluronate. In an embodiment, the polysaccharide polymer is a collagen, elastin or gelatin. In an embodiment, the polysaccharide polymer is chitin. In some embodiments, the polysaccharide polymer is a hydrogel-forming polymer. Hydrogel-forming polymers comprise a hydrophilic structure that renders them capable of holding large amounts of water in a three-dimensional network. Hydrogel-forming polymers may include polymers which form homopolymeric hydrogels, copolymeric hydrogels, or multipolymer interpenetrating polymeric hydrogels, and may be amorphous, semicrystalline, or crystalline in nature, e.g., as described in Ahmed (2015) J Adv Res 6:105-121. Exemplary hydrogel-forming polymers include proteins (e.g., collagen), gelatin, polysaccharides (e.g., starch, alginate, hyaluronate, agarose), and synthetic polysaccharides. Exemplary polysaccharide polymers include alginate, agar, agarose, carrageenan, hyaluronate, amylopectin, glycogen, gelatin, cellulose, amylose, chitin, chitosan, or a derivative or variant thereof, e.g., as described in Laurienzo (2010), Mar Drugs 9:2435-65. A polysaccharide polymer may comprise heparin, chondoitin sulfate, dermatan, dextran, or carboxymethylcellulose. In some embodiments, a polysaccharide polymer is a cell-surface polysaccharide. In some embodiments, the polysaccharide polymer is an alginate. Alginate is a polysaccharide made up of β-D-mannuronic acid (M) and α-L-guluronic acid (G). In some embodiments, the alginate is a high guluronic acid (G) alginate, and comprises greater than about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or more guluronic acid (G). In some embodiments, the alginate is a high mannuronic acid (M) alginate, and comprises greater than about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or more mannuronic acid (M). In some embodiments, the ratio of M:G is about 1. In some embodiments, the ratio of M:G is less than 1. In some embodiments, the ratio of M:G is greater than 1. In some embodiments, the alginate has an approximate molecular weight of < 75 kDa, and optionally a G:M ratio of ≥ 1.5. In some embodiments, the alginate has an approximate molecular weight of 75 kDa to 150 kDa and optionally a G:M ratio of ≥ 1.5. In some embodiments, the alginate has an approximate molecular weight of 150 to 250 kDa and optionally a G:M ratio of ≥ 1.5. A polysaccharide polymer (e.g., any of the polymers described herein, for example, any of the alginates described herein) comprising a saccharide moiety having the structure of Formula (I) or a pharmaceutically acceptable salt thereof may be modified on one or more monomeric units. In some embodiments, at least 0.5 percent of the saccharide monomers of a polysaccharide polymer have the structure of Formula (I) (e.g., at least 1, 2.5, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 99 percent, or more of the saccharide monomers have the structure of Formula (I). In some embodiments, 0.5 to 50%, 10 to 90%, 10 to 50%, or 25-75%, of the saccharide monomers of a polysaccharide polymer have the structure of Formula (I). In some embodiments, 1 to 20% of the saccharide monomers of a polysaccharide polymer have the structure of Formula (I). In some embodiments, 1 to 10% of the saccharide monomers of a polysaccharide polymer have the structure of Formula (I). In some embodiments, 1 to 50% of the saccharide monomers have the structure of Formula (I). In some embodiments, the polysaccharide polymer (when comprising a saccharide monomer having the structure of Formula I) comprises an increase in % N (as compared with unmodified polymer) of at least 0.1, 0.2, 0.5, 1.0, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10% N by weight, where % N is determined by elemental analysis and corresponds to the amount of compound of Formula I in the modified polymer. In some embodiments, the polysaccharide polymer (when comprising a saccharide monomer having the structure of Formula I) comprises an increase in % N (as compared with unmodified polymer) of 0.1 to 10 % N by weight, where % N is determined by elemental analysis and corresponds to the amount of compound of Formula I in the modified polymer. In some embodiments, the polysaccharide polymer (when comprising a saccharide monomer having the structure of Formula (I) comprises an increase in % N (as compared with unmodified polymer) of 0.1 to 2 % N by weight, where % N is determined by elemental analysis and corresponds to the amount of compound of Formula I in the modified polymer. In some embodiments, the polysaccharide polymer (when comprising a saccharide monomer having the structure of Formula (I) comprises an increase in % N (as compared with unmodified polymer) of 2 to 4 % N by weight, where % N is determined by elemental analysis and corresponds to the amount of compound of Formula I in the modified polymer. In some embodiments, the polysaccharide polymer (when comprising a saccharide monomer having the structure of Formula (I) comprises an increase in % N (as compared with unmodified polymer) of 4 to 8 % N by weight, where % N is determined by elemental analysis and corresponds to the amount of compound of Formula I in the modified polymer. In some embodiments, any of the polysaccharide polymers described herein (e.g., an alginate) comprise a saccharide monomer having one or more of Formula (I-a), (I-b), (I-c), (I-d), (I-e), (I-f), or a pharmaceutically acceptable salt thereof. In some embodiments, the polysaccharide polymer comprises a saccharide monomer having the structure of Formula (II-a). In some embodiments, the polymer is modified with a compound of Formula (II-b). In some embodiments, the polysaccharide polymer comprises a saccharide monomer having the structure of Formula (II-c). In some embodiments, the polysaccharide polymer comprises a saccharide monomer having the structure of Formula (II-d). In some embodiments, the polysaccharide polymer comprises a saccharide monomer having the structure of Formula (II-e). In some embodiments, the polysaccharide polymer comprises a saccharide monomer having the structure of Formula (II-f). In some embodiments, the polysaccharide polymer (e.g., an alginate) is modified with a compound shown in Table 3. In some embodiments, a polymer (e.g., an alginate) modified with a compound of Formula (I) is not a modified polymer described in any one of WO2012 / 112982, WO2012 / 167223, WO2014 / 153126, WO2016 / 187225, WO2016 / 019391, WO2017 / 075630, WO 2017 / 075631, WO 2018 / 067615, WO 2019 / 169333, and US 2016-0030359. Afibrotic Compounds In some embodiments, the polysaccharide polymers described herein further comprise at least one afibrotic compound of Formula (I): or a pharmaceutically acceptable salt thereof, wherein: A is alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, –O–, – C(O)O–, –C(O)–, –OC(O)–, –N(RC)–, –N(RC)C(O)–, –C(O)N(RC)–, -N(RC)C(O)(C1-C6- alkylene)–, -N(RC)C(O)(C1-C6-alkenylene)–, –N(RC)N(RD)–, –NCN–, –C(=N(RC)(RD))O–, –S–, –S(O)x–, –OS(O)x–, –N(RC)S(O)x–, –S(O)xN(RC)–, –P(RF)y–, –Si(ORA)2–, –Si(RG)(ORA)–, – B(ORA)–, or a metal, each of which is optionally linked to an attachment group (e.g., an attachment group described herein) and is optionally substituted by one or more R1; each of L1and L3is independently a bond, alkyl, or heteroalkyl, wherein each alkyl and heteroalkyl is optionally substituted by one or more R2; L2is a bond; M is absent, alkyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, each of which is optionally substituted by one or more R3; P is absent, cycloalkyl, heterocyclyl, or heteroaryl, each of which is optionally substituted by one or more R4; Z is hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, –ORA, –C(O)RA, –C(O)ORA, – C(O)N(RC)(RD), –N(RC)C(O)RA, cycloalkyl, heterocyclyl, aryl, or heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, and heteroaryl is optionally substituted by one or more R5; each RA, RB, RC, RD, RE, RF, and RGis independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, azido, cycloalkyl, heterocyclyl, aryl, or heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, and heteroaryl is optionally substituted with one or more R6; or RCand RD, taken together with the nitrogen atom to which they are attached, form a ring (e.g., a 5-7 membered ring), optionally substituted with one or more R6; each R1, R2, R3, R4, R5, and R6is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, –N(RC1)(RD1), – N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, S(O)xRE1, –OS(O)xRE1, –N(RC1)S(O)xRE1, – S(O)xN(RC1)(RD1), –P(RF1)y, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, and heteroaryl is optionally substituted by one or more R7; each RA1, RB1, RC1, RD1, RE1, and RF1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted by one or more R7; each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl; x is 1 or 2; and y is 2, 3, or 4. In some embodiments, the compound of Formula (I) is a compound of Formula (I-a): or a pharmaceutically acceptable salt thereof, wherein: A is alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, –O–, –C(O)O–, –C(O)–, –OC(O)–, –N(RC)–, – N(RC)C(O)–, –C(O)N(RC)–, –N(RC)N(RD)–, N(RC)C(O)(C1-C6- alkylene)–, -N(RC)C(O)(C1-C6- alkenylene)–, –NCN–, –C(=N(RC)(RD))O–, –S–, –S(O)x–, –OS(O)x–, –N(RC)S(O)x–, – S(O)xN(RC)–, –P(RF)y–, –Si(ORA)2 –, –Si(RG)(ORA)–, –B(ORA)–, or a metal, each of which is optionally linked to an attachment group (e.g., an attachment group described herein) and optionally substituted by one or more R1; each of L1and L3is independently a bond, alkyl, or heteroalkyl, wherein each alkyl and heteroalkyl is optionally substituted by one or more R2; L2is a bond; M is absent, alkyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, each of which is optionally substituted by one or more R3; P is heteroaryl optionally substituted by one or more R4; Z is alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, each of which is optionally substituted by one or more R5; each RA, RB, RC, RD, RE, RF, and RGis independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, azido, cycloalkyl, heterocyclyl, aryl, or heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, and heteroaryl is optionally substituted with one or more R6; or RCand RD, taken together with the nitrogen atom to which they are attached, form a ring (e.g., a 5-7 membered ring), optionally substituted with one or more R6; each R1, R2, R3, R4, R5, and R6is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,– OC(O)RB1, –N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, S(O)xRE1, –OS(O)xRE1, – N(RC1)S(O)xRE1, – S(O)xN(RC1)(RD1), –P(RF1)y, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, and heteroaryl is optionally substituted by one or more R7; each RA1, RB1, RC1, RD1, RE1, and RF1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted by one or more R7; each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl; x is 1 or 2; and y is 2, 3, or 4. In some embodiments, for Formulas (I) and (I-a), A is alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, –O–, –C(O)O–, –C(O)–, –OC(O) –, –N(RC)C(O)-, – N(RC)C(O)(C1-C6-alkylene)–, –N(RC)C(O)(C1-C6-alkenylene)–, or –N(RC)–. In some embodiments, A is alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, –O–, –C(O)O–, –C(O)–, –OC(O) –, or –N(RC)–. In some embodiments, A is alkyl, alkenyl, alkynyl, heteroalkyl,–O–, –C(O)O–, –C(O)–,–OC(O) –, or –N(RC)–. In some embodiments, A is alkyl, –O–, –C(O)O–, –C(O)–, –OC(O), or –N(RC)–. In some embodiments, A is –N(RC)C(O)-, –N(RC)C(O)(C1-C6-alkylene)–, or –N(RC)C(O)(C1-C6-alkenylene)–. In some embodiments, A is –N(RC)–. In some embodiments, A is –N(RC) –, and RCan RDis independently hydrogen or alkyl. In some embodiments, A is –NH–. In some embodiments, A is –N(RC)C(O)(C1-C6-alkylene)–, wherein alkylene is substituted with R1. In some embodiments, A is –N(RC)C(O)(C1-C6- alkylene)–, and R1is alkyl (e.g., methyl). In some embodiments, A is –NHC(O)C(CH3)2-. In some embodiments, A is –N(RC)C(O)(methylene)–, and R1is alkyl (e.g., methyl). In some embodiments, A is –NHC(O)CH(CH3)-. In some embodiments, A is –NHC(O)C(CH3)-. In some embodiments, for Formulas (I) and (I-a), L1is a bond, alkyl, or heteroalkyl. In some embodiments, L1is a bond or alkyl. In some embodiments, L1is a bond. In some embodiments, L1is alkyl. In some embodiments, L1is C1-C6 alkyl. I n some embodiments, L1is –CH2–, – CH(CH3)–, –CH2CH2CH2, or –CH2CH2–. In some embodiments, L1is –CH2–or –CH2CH2–. In some embodiments, for Formulas (I) and (I-a), L3is a bond, alkyl, or heteroalkyl. In some embodiments, L3is a bond. In some embodiments, L3is alkyl. In some embodiments, L3is C1-C12alkyl. In some embodiments, L3 is C1-C6alkyl. In some embodiments, L3is –CH2–. In some embodiments, L3is heteroalkyl. In some embodiments, L3is C1-C12heteroalkyl, optionally substituted with one or more R2(e.g., oxo). In some embodiments, L3is C1-C6heteroalkyl, optionally substituted with one or more R2(e.g., oxo). In some embodiments, L3is –C(O)OCH2–, –CH2(OCH2CH2)2–, –CH2(OCH2CH2)3–, CH2CH2O–, or –CH2O–. In some embodiments, L3is –CH2O–. In some embodiments, for Formulas (I) and (I-a), M is absent, alkyl, heteroalkyl, aryl, or heteroaryl. In some embodiments, M is heteroalkyl, aryl, or heteroaryl. In some embodiments, M is absent. In some embodiments, M is alkyl (e.g., C1-C6alkyl). In some embodiments, M is - CH2–. In some embodiments, M is heteroalkyl (e.g., C1-C6 heteroalkyl). In some embodiments, M is (–OCH2CH2–)z, wherein z is an integer selected from 1 to 10. In some embodiments, z is an integer selected from 1 to 5. In some embodiments, M is –OCH2CH2–, (–OCH2CH2–)2, (–OCH2CH2–)3, (–OCH2CH2–)4, or (–OCH2CH2–)5. In some embodiments, M is –OCH2CH2–, (–OCH2CH2–)2, (–OCH2CH2–)3, or (–OCH2CH2–)4. In some embodiments, M is (–OCH2CH2–)3. In some embodiments, for Formulas (I) and (I-a), M is absent, alkyl, heteroalkyl, aryl, or heteroaryl. In some embodiments, M is heteroalkyl, aryl, or heteroaryl. In some embodiments, M is absent. In some embodiments, M is alkyl (e.g., C1-C6 alkyl). In some embodiments, M is - CH2–. In some embodiments, M is heteroalkyl (e.g., C1-C6 heteroalkyl). In some embodiments, M is (–OCH2CH2–)z, wherein z is an integer selected from 1 to 10. In some embodiments, z is an integer selected from 1 to 5. In some embodiments, M is –OCH2CH2–, (–OCH2CH2–)2, (–OCH2CH2–)3, (–OCH2CH2–)4, or (–OCH2CH2–)5. In some embodiments, M is –OCH2CH2–, (–OCH2CH2–)2, (–OCH2CH2–)3, or (–OCH2CH2–)4. In some embodiments, M is (–OCH2CH2–)3. In some embodiments, M is aryl. In some embodiments, M is phenyl. In some embodiments, M is unsubstituted phenyl. In some embodiments, M is . In some embodiments, M is phenyl substituted with R7(e.g., 1 R7). In some embodiments, M is . In some embodiments, R7is CF3. In some embodiments, for Formulas (I) and (I-a), P is absent, heterocyclyl, or heteroaryl. In some embodiments, P is absent. In some embodiments, for Formulas (I) and (I-a), P is a tricyclic, bicyclic, or monocyclic heteroaryl. In some embodiments, P is a monocyclic heteroaryl. In some embodiments, P is a nitrogen-containing heteroaryl. In some embodiments, P is a monocyclic, nitrogen-containing heteroaryl. In some embodiments, P is a 5-membered heteroaryl. In some embodiments, P is a 5-membered nitrogen-containing heteroaryl. In some embodiments, P is tetrazolyl, imidazolyl, pyrazolyl, or triazolyl, pyrrolyl, oxazolyl, or thiazolyl. In some embodiments, P is tetrazolyl, imidazolyl, pyrazolyl, or triazolyl, or pyrrolyl. In some embodiments, P is imidazolyl. In some embodiments, P is . In some embodiments, P is triazolyl. In some embodiments, P is 1,2,3-triazolyl. In some embodiments, P is . In some embodiments, P is heterocyclyl. In some embodiments, P is a 5-membered heterocyclyl or a 6-membered heterocyclyl. In some embodiments, P is imidazolidinonyl. In some embodiments, P is . In some embodiments, P is thiomorpholinyl-1,1-dioxidyl. In some embodiments, In some embodiments, for Formulas (I) and (I-a), Z is alkyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl. In some embodiments, Z is heterocyclyl. In some embodiments, Z is monocyclic or bicyclic heterocyclyl. In some embodiments, Z is an oxygen-containing heterocyclyl. In some embodiments, Z is a 4-membered heterocyclyl, 5-membered heterocyclyl, or 6-membered heterocyclyl. In some embodiments, Z is a 6-membered heterocyclyl. In some embodiments, Z is a 6-membered oxygen-containing heterocyclyl. In some embodiments, Z is tetrahydropyranyl. In some embodiments, Z is . In some embodiments, Z is a 4-membered oxygen-containing heterocyclyl. In some embodiments, Z is . In some embodiments, Z is a bicyclic oxygen-containing heterocyclyl. In some embodiments, Z is phthalic anhydridyl. In some embodiments, Z is a sulfur-containing heterocyclyl. In some embodiments, Z is a 6-membered sulfur-containing heterocyclyl. In some embodiments, Z is a 6- membered heterocyclyl containing a nitrogen atom and a sulfur atom. In some embodiments, Z is thiomorpholinyl-1,1-dioxidyl. In some embodiments, some embodiments, Z is a nitrogen-containing heterocyclyl. In some embodiments, Z is a 6-membered nitrogen- containing heterocyclyl. In some embodiments, Z is . In some embodiments, Z is a bicyclic heterocyclyl. In some embodiments, Z is a bicyclic nitrogen-containing heterocyclyl, optionally substituted with one or more R5. In some embodiments, Z is 2-oxa-7-azaspiro[3.5]nonanyl. In some embodiments, . In some embodiments, Z is 1-oxa-3,8-diazaspiro[4.5]decan-2-one. In some embodiments, Z is . In some embodiments, for Formulas (I) and (I-a), Z is aryl. In some embodiments, Z is monocyclic aryl. In some embodiments, Z is phenyl. In some embodiments, Z is monosubstituted phenyl (e.g., with 1 R5). In some embodiments, Z is monosubstituted phenyl, wherein the 1 R5is a nitrogen-containing group. In some embodiments, Z is monosubstituted phenyl, wherein the 1 R5is NH2. In some embodiments, Z is monosubstituted phenyl, wherein the 1 R5is an oxygen- containing group. In some embodiments, Z is monosubstituted phenyl, wherein the 1 R5is an oxygen-containing heteroalkyl. In some embodiments, Z is monosubstituted phenyl, wherein the 1 R5is OCH3. In some embodiments, Z is monosubstituted phenyl, wherein the 1 R5is in the ortho position. In some embodiments, Z is monosubstituted phenyl, wherein the 1 R5is in the meta position. In some embodiments, Z is monosubstituted phenyl, wherein the 1 R5is in the para position. In some embodiments, for Formulas (I) and (I-a), Z is alkyl. In some embodiments, Z is C1- C12alkyl. In some embodiments, Z is C1-C10alkyl. In some embodiments, Z is C1-C8alkyl. In some embodiments, Z is C1-C8alkyl substituted with 1-5 R5. In some embodiments, Z is C1-C8alkyl substituted with 1 R5. In some embodiments, Z is C1-C8 alkyl substituted with 1 R5, wherein R5is alkyl, heteroalkyl, halogen, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, or –N(RC1)(RD1). In some embodiments, Z is C1-C8alkyl substituted with 1 R5, wherein R5is –ORA1or –C(O)ORA1. In some embodiments, Z is C1-C8 alkyl substituted with 1 R5, wherein R5is –ORA1or –C(O)OH. In some embodiments, Z is -CH3. In some embodiments, for Formulas (I) and (I-a), Z is heteroalkyl. In some embodiments, Z is C1-C12 heteroalkyl. I n some embodiments, Z is C1-C10 heteroalkyl. In some embodiments, Z is C1-C8 heteroalkyl. I n some embodiments, Z is C1-C6 heteroalkyl. In some embodiments, Z is a nitrogen-containing heteroalkyl optionally substituted with one or more R5. I n some embodiments, Z is a nitrogen and sulfur-containing heteroalkyl substituted with 1-5 R5. In some embodiments, Z is N-methyl-2-(methylsulfonyl)ethan-1-aminyl. In some embodiments, Z is -ORAor -C(O)ORA. In some embodiments, Z is -ORA(e.g., -OH or –OCH3). In some embodiments, Z is –OCH3. In some embodiments, Z is -C(O)ORA(e.g., –C(O)OH). In some embodiments, Z is hydrogen. In some embodiments, L2is a bond and P and L3are independently absent. In some embodiments, L2is a bond, P is heteroaryl, L3is a bond, and Z is hydrogen. In some embodiments, P is heteroaryl, L3is heteroalkyl, and Z is alkyl. In some embodiments, the compound of Formula (I) is a compound of Formula (I-b): or a pharmaceutically acceptable salt thereof, wherein Ring M1is cycloalkyl, heterocyclyl, aryl, or heteroaryl, each of which is optionally substituted with 1-5 R3; Ring Z1is cycloalkyl, heterocyclyl, aryl or heteroaryl, optionally substituted with 1-5 R5; each of R2a, R2b, R2c, and R2dis independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halo, cyano, nitro, amino, cycloalkyl, heterocyclyl, aryl, or heteroaryl, or each of R2aand R2bor R2cand R2dis taken together to form an oxo group; X is absent, N(R10)(R11), O, or S; RCis hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl is optionally substituted with 1-6 R6; each R3, R5, and R6is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, – ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, –N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each of R10and R11is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, –C(O)N(RC1), cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl; each m and n is independently 1, 2, 3, 4, 5, or 6; and “ ” refers to a connection to an attachment group or a polymer described herein. In some embodiments, for each R3and R5, each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl is optionally and independently substituted with halogen, oxo, cyano, cycloalkyl, or heterocyclyl. In some embodiments, the compound of Formula (I-b) is a compound of Formula (I-b-i): or a pharmaceutically acceptable salt thereof, wherein Ring M2is aryl or heteroaryl optionally substituted with one or more R3; Ring Z2is cycloalkyl, heterocyclyl, aryl, or heteroaryl; each of R2a, R2b, R2c, and R2dis independently hydrogen, alkyl, or heteroalkyl, or each of R2aand R2bor R2cand R2dis taken together to form an oxo group; X is absent, O, or S; each R3and R5is independently alkyl, heteroalkyl, halogen, oxo, –ORA1, –C(O)ORA1, or –C(O)RB1, wherein each alkyl and heteroalkyl is optionally substituted with halogen; or two R5are taken together to form a 5-6 membered ring fused to Ring Z2; each RA1and RB1is independently hydrogen, alkyl, or heteroalkyl; m and n are each independently 1, 2, 3, 4, 5, or 6; p is 0, 1, 2, 3, 4, 5, or 6; and “ ” refers to a connection to an attachment group or a polymer described herein. In some embodiments, the compound of Formula (I-b-i) is a compound of Formula (I-b- ii): -ii), o r a pharmaceutically acceptable salt thereof, wherein Ring Z2is cycloalkyl, heterocyclyl, aryl or heteroaryl; each of R2cand R2dis independently hydrogen, alkyl, or heteroalkyl, or R2cand R2dand taken together to form an oxo group; each R3and R5is independently alkyl, heteroalkyl, halogen, oxo, –ORA1, –C(O)ORA1, or –C(O)RB1, wherein each alkyl and heteroalkyl is optionally substituted with halogen; each RA1and RB1is independently hydrogen, alkyl, or heteroalkyl; each of p and q is independently 0, 1, 2, 3, 4, 5, or 6; and “ ” refers to a connection to an attachment group or a polymer described herein. In some embodiments, the compound of Formula (I) is a compound of Formula (I-c): or a pharmaceutically acceptable salt thereof, wherein Ring Z2is cycloalkyl, heterocyclyl, aryl or heteroaryl; each of R2cand R2dis independently hydrogen, alkyl, or heteroalkyl, or R2cand R2dis taken together to form an oxo group; each R3and R5is independently alkyl, heteroalkyl, halogen, oxo, –ORA1, –C(O)ORA1, or –C(O)RB1, wherein each alkyl and heteroalkyl is optionally substituted with halogen; each RA1and RB1is independently hydrogen, alkyl, or heteroalkyl; m is 1, 2, 3, 4, 5, or 6; each of p and q is independently 0, 1, 2, 3, 4, 5, or 6; and “ ” refers to a connection to an attachment group or a polymer described herein. In some embodiments, the compound of Formula (I) is a compound of Formula (I-d): or a pharmaceutically acceptable salt thereof, wherein Ring Z2is cycloalkyl, heterocyclyl, aryl or heteroaryl; X is absent, O, or S; each of R2a, R2b, R2c, and R2dis independently hydrogen, alkyl, or heteroalkyl, or each of R2aand R2bor R2cand R2dis taken together to form an oxo group; each R5is independently alkyl, heteroalkyl, halogen, oxo, –ORA1, –C(O)ORA1, or –C(O)RB1, wherein each alkyl and heteroalkyl is optionally substituted with halogen; each RA1and RB1is independently hydrogen, alkyl, or heteroalkyl; each of m and n is independently 1, 2, 3, 4, 5, or 6; p is 0, 1, 2, 3, 4, 5, or 6; and “ ” refers to a connection to an attachment group or a polymer described herein. In some embodiments, the compound of Formula (I) is a compound of Formula (I-e): (I-e), or a pharmaceutically acceptable salt thereof, wherein Ring Z2is cycloalkyl, heterocyclyl, aryl or heteroaryl; X is absent, O, or S; each of R2a, R2b, R2c, and R2dis independently hydrogen, alkyl, or heteroalkyl, or each of R2aand R2bor R2cand R2dis taken together to form an oxo group; each R5is independently alkyl, heteroalkyl, halogen, oxo, –ORA1, –C(O)ORA1, or –C(O)RB1; each RA1and RB1is independently hydrogen, alkyl, or heteroalkyl; each of m and n is independently 1, 2, 3, 4, 5, or 6; p is 0, 1, 2, 3, 4, 5, or 6; and “ ” refers to a connection to an attachment group or a polymer described herein. In some embodiments, the compound of Formula (I) is a compound of Formula (I-f): or a pharmaceutically acceptable salt thereof, wherein M is alkyl optionally substituted with one or more R3; Ring P is heteroaryl optionally substituted with one or more R4; L3is alkyl or heteroalkyl optionally substituted with one or more R2; Z is alkyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, each of which is optionally substituted with one or more R5; each of R2aand R2bis independently hydrogen, alkyl, or heteroalkyl, or R2aand R2bis taken together to form an oxo group; each R2, R3, R4, and R5is independently alkyl, heteroalkyl, halogen, oxo, – ORA1, –C(O)ORA1, or –C(O)RB1; each RA1and RB1is independently hydrogen, alkyl, or heteroalkyl; n is independently 1, 2, 3, 4, 5, or 6; and “ ” refers to a connection to an attachment group or a polymer described herein. In some embodiments, the compound of Formula (I) is a compound of Formula (II): o r a p armaceutca y acceptab e salt thereof, wherein M is a bond, alkyl or aryl, wherein alkyl and aryl is optionally substituted with one or more R3; L3is alkyl or heteroalkyl optionally substituted with one or more R2; Z is hydrogen, alkyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl or –ORA, wherein alkyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, and heteroaryl is optionally substituted with one or more R5; RAis hydrogen; each of R2aand R2bis independently hydrogen, alkyl, or heteroalkyl, or R2aand R2bis taken together to form an oxo group; each R2, R3, and R5is independently alkyl, heteroalkyl, halogen, oxo, –ORA1, –C(O)ORA1, or –C(O)RB1; each RA1and RB1is independently hydrogen, alkyl, or heteroalkyl; n is independently 1, 2, 3, 4, 5, or 6; and “ ” refers to a connection to an attachment group or a polymer described herein. In some embodiments, the compound of Formula (II) is a compound of Formula (II-a): or a pharmaceutically acceptable salt thereof, wherein L3is alkyl or heteroalkyl, each of which is optionally substituted with one or more R2; Z is hydrogen, alkyl, heteroalkyl, or –ORA, wherein alkyl and heteroalkyl are optionally substituted with one or more R5; each of R2aand R2bis independently hydrogen, alkyl, or heteroalkyl, or R2aand R2bis taken together to form an oxo group; each R2, R3, and R5is independently alkyl, heteroalkyl, halogen, oxo, –ORA1, –C(O)ORA1, or –C(O)RB1; RAis hydrogen; each RA1and RB1is independently hydrogen, alkyl, or heteroalkyl; n is independently 1, 2, 3, 4, 5, or 6; and “ ” refers to a connection to an attachment group or a polymer described herein. In some embodiments, the compound of Formula (I) is a compound of Formula (III): or a pharmaceutically acceptable salt thereof, wherein Z1is alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, each of which is optionally substituted with 1-5 R5; each of R2a, R2b, R2c, and R2dis independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halo, cyano, nitro, amino, cycloalkyl, heterocyclyl, aryl, or heteroaryl; or R2aand R2bor R2cand R2dare taken together to form an oxo group; RCis hydrogen, alkyl, alkenyl, alkynyl, or heteroalkyl, wherein each of alkyl, alkenyl, alkynyl, or heteroalkyl is optionally substituted with 1-6 R6; each of R3, R5, and R6is independently alkyl, heteroalkyl, halogen, oxo, –ORA1, –C(O)ORA1, or – C(O)RB1; each RA1and RB1is independently hydrogen, alkyl, or heteroalkyl; m and n are each independently 1, 2, 3, 4, 5, or 6; q is an integer from 0 to 25; and “ ” refers to a connection to an attachment group or a polymer described herein. In some embodiments, the compound of Formula (III) is a compound of Formula (III-a): or a pharmaceutically acceptable salt thereof, wherein Ring Z2is cycloalkyl, heterocyclyl, aryl, or heteroaryl, each of which is optionally substituted with 1-5 R5; each of R2a, R2b, R2c, and R2dis independently hydrogen, alkyl, heteroalkyl, halo; or R2aand R2bor R2cand R2dare taken together to form an oxo group; each of R3and R5is independently alkyl, heteroalkyl, halogen, oxo, –ORA1, –C(O)ORA1, or –C(O)RB1; each RA1and RB1is independently hydrogen, alkyl, or heteroalkyl; m and n are each independently 1, 2, 3, 4, 5, or 6; o and p are each independently 0, 1, 2, 3, 4, or 5; q is an integer from 0 to 25; and “ ” refers to a connection to an attachment group or a polymer described herein. In some embodiments, the compound of Formula (III-a) is a compound of Formula (III- b): or a pharmaceutically acceptable salt thereof, wherein Ring Z2is cycloalkyl, heterocyclyl, aryl, or heteroaryl, each of which is optionally substituted with 1-5 R5; each of R2a, R2b, R2c, and R2dis independently hydrogen, alkyl, heteroalkyl, halo; or R2aand R2bor R2cand R2dare taken together to form an oxo group; each of R3and R5is independently alkyl, heteroalkyl, halogen, oxo, –ORA1, –C(O)ORA1, or –C(O)RB1; each RA1and RB1is independently hydrogen, alkyl, or heteroalkyl; m and n are each independently 1, 2, 3, 4, 5, or 6; o and p are each independently 0, 1, 2, 3, 4, or 5; q is an integer from 0 to 25; and “ ” refers to a connection to an attachment group or a polymer described herein. In some embodiments, the compound of Formula (III-a) is a compound of Formula (III-c): or a pharmaceutically acceptable salt thereof, wherein X is C(R’)(R”), N(R’), or S(O)x; each of R’ and R” is independently hydrogen, alkyl, halogen, or cycloalkyl; each of R2a, R2b, R2c, and R2dis independently hydrogen, alkyl, heteroalkyl, or halo; or R2aand R2bor R2cand R2dare taken together to form an oxo group; each of R3and R5is independently alkyl, heteroalkyl, halogen, oxo, –ORA1, –C(O)ORA1, or –C(O)RB1; each RA1and RB1is independently hydrogen, alkyl, or heteroalkyl; m and n are each independently 1, 2, 3, 4, 5, or 6; p is 0, 1, 2, 3, 4, or 5; q is an integer from 0 to 25; x is 0, 1, or 2; and “ ” refers to a connection to an attachment group or a polymer described herein. In some embodiments, the compound of Formula (III-c) is a compound of Formula (III-d): or a pharmaceutically acceptable salt thereof, wherein X is C(R’)(R”), N(R’), or S(O)x; each of R’ and R” is independently hydrogen, alkyl, halogen, or cycloalkyl; each of R2a, R2b, R2c, and R2disindependently hydrogen, alkyl, heteroalkyl, or halo; or R2a and R2b or R2c and R2d are taken togetherto form an oxo group; each of R3and R5is independently alkyl, heteroalkyl, halogen, oxo, –ORA1, –C(O)ORA1, or –C(O)RB1; each RA1and RB1is independently hydrogen, alkyl, or heteroalkyl; m and n are each independently 1, 2, 3, 4, 5, or 6; p is 0, 1, 2, 3, 4, or 5; q is an integer from 0 to 25; x is 0, 1, or 2; and “ ” refers to a connection to an attachment group or a polymer described herein. In some embodiments, the compound of Formula (I) is a compound of Formula (III-e): or a pharmaceutically acceptable salt thereof, wherein Z1is alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, each of which is optionally substituted with 1-5 R5;each of R2a, R2b, R2c, and R2dis independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halo, cyano, nitro, amino, cycloalkyl, heterocyclyl, aryl, or heteroaryl; or each of R2aand R2bor R2cand R2dis taken together to form an oxo group; RCis hydrogen, alkyl, alkenyl, alkynyl, or heteroalkyl, wherein each of alkyl, alkenyl, alkynyl, or heteroalkyl is optionally substituted with 1-6 R6; each of R3, R5, and R6is independently alkyl, heteroalkyl, halogen, oxo, –ORA1, –C(O)ORA1, or – C(O)RB1; each R12is independently deuterium, alkyl, heteroalkyl, haloalkyl, halo, cyano, nitro, or amino; each RA1and RB1is independently hydrogen, alkyl, or heteroalkyl; m and n are each independently 1, 2, 3, 4, 5, or 6; q is an integer from 0 to 25; w is 0 or 1; and “ ” refers to a connection to an attachment group or a polymer described herein. In some embodiments, the compound of Formula (I) is a compound of Formula (III-f): or a pharmaceutically acceptable salt thereof, wherein Ring Z1is cycloalkyl, heterocyclyl, aryl, or heteroaryl, each of which is optionally substituted with 1-5 R5; each of R2a, R2b, R2c, and R2dis independently hydrogen, alkyl, heteroalkyl, halo; or R2aand R2bor R2cand R2dare taken together to form an oxo group; RCis hydrogen, alkyl, alkenyl, alkynyl, or heteroalkyl, wherein each of alkyl, alkenyl, alkynyl, or heteroalkyl is optionally substituted with 1-6 R6; each of R3, R5, and R6is independently alkyl, heteroalkyl, halogen, oxo, –ORA1, –C(O)ORA1, or –C(O)RB1; each R12is independently deuterium, alkyl, heteroalkyl, haloalkyl, halo, cyano, nitro, or amino; each RA1and RB1is independently hydrogen, alkyl, or heteroalkyl; m and n are each independently 1, 2, 3, 4, 5, or 6; o and p are each independently 0, 1, 2, 3, 4, or 5; q is an integer from 0 to 25; w is 0 or 1; and “ ” refers to a connection to an attachment group or a polymer described herein. In some embodiments, the compound of Formula (I) is a compound of Formula (III-g): or a pharmaceutically acceptable salt thereof, wherein Ring Z1is cycloalkyl, heterocyclyl, aryl, or heteroaryl, each of which is optionally substituted with 1-5 R5; RCis hydrogen, alkyl, – N(RC)C(O)RB, –N(RC)C(O)(C1-C6-alkyl), or –N(RC)C(O)(C1-C6-alkenyl), wherein each of alkyl and alkenyl is optionally substituted with 1-6 R6; each of R2a, R2b, R2c, and R2dis independently hydrogen or alkyl; or R2aand R2bor R2cand R2dare taken together to form an oxo group; each of R3, R5, and R6is independently alkyl, heteroalkyl, halogen, oxo, –ORA1, –C(O)ORA1, or – C(O)RB1; R12is hydrogen, deuterium, alkyl, heteroalkyl, haloalkyl, halo, cyano, nitro, or amino; each RA1and RB1is independently hydrogen, alkyl, or heteroalkyl; m and n are each independently 1, 2, 3, 4, 5, or 6; q is an integer from 0 to 25; x is 0, 1, or 2; and “ ” refers to a connection to an attachment group or a polymer described herein. In some embodiments, the compound of Formula (I) is a compound of Formula (III-h): or a pharmaceutically acceptable salt thereof, wherein RCis hydrogen, alkyl, –N(RC)C(O)RB, – N(RC)C(O)(C1-C6-alkyl), or –N(RC)C(O)(C1-C6-alkenyl), wherein each of alkyl and alkenyl is optionally substituted with 1-6 R6; each of R2a, R2b, R2c, and R2dis independently hydrogen or alkyl; or R2aand R2bor R2cand R2dare taken together to form an oxo group; each of R3, R5, and R6is independently alkyl, heteroalkyl, halogen, oxo, –ORA1, –C(O)ORA1, or –C(O)RB1; R12is hydrogen, deuterium, alkyl, heteroalkyl, haloalkyl, halo, cyano, nitro, or amino; each RA1and RB1is independently hydrogen, alkyl, or heteroalkyl; m and n are each independently 1, 2, 3, 4, 5, or 6; q is an integer from 0 to 25; x is 0, 1, or 2; z is 0, 1, 2, 3, 4, 5, or 6, and “ ” refers to a connection to an attachment group or a polymer described herein. In some embodiments, the compound of Formula (I) is a compound of Formula (III-i): or a pharmaceutically acceptable salt thereof, wherein X is C(R’)(R”), N(R’), or S(O)x; each of R’ and R” is independently hydrogen, alkyl, or halogen; RCis hydrogen, alkyl, –N(RC)C(O)RB, – N(RC)C(O)(C1-C6-alkyl), or –N(RC)C(O)(C1-C6-alkenyl), wherein each of alkyl and alkenyl is optionally substituted with 1-6 R6; each of R2a, R2b, R2c, and R2dis independently hydrogen or alkyl; or R2aand R2bor R2cand R2dare taken together to form an oxo group; each of R3, R5, and R6is independently alkyl, heteroalkyl, halogen, oxo, –ORA1, –C(O)ORA1, or –C(O)RB1; R12is hydrogen, deuterium, alkyl, heteroalkyl, haloalkyl, halo, cyano, nitro, or amino; each RA1and RB1is independently hydrogen, alkyl, or heteroalkyl; m and n are each independently 1, 2, 3, 4, 5, or 6; q is an integer from 0 to 25; x is 0, 1, or 2; z is 0, 1, 2, 3, 4, 5, or 6, and “ ” refers to a connection to an attachment group or a polymer described herein. In some embodiments, the compound is a compound of Formula (I). In some embodiments, L2is a bond and P and L3are independently absent. In some embodiments, the compound is a compound of Formula (I-a). In some embodiments of Formula (II-a), L2is a bond, P is heteroaryl, L3is a bond, and Z is hydrogen. In some embodiments, P is heteroaryl, L3is heteroalkyl, and Z is alkyl. In some embodiments, L2is a bond and P and L3are independently absent. In some embodiments, L2is a bond, P is heteroaryl, L3is a bond, and Z is hydrogen. In some embodiments, P is heteroaryl, L3is heteroalkyl, and Z is alkyl. In some embodiments, the compound is a compound of Formula (I-b). In some embodiments, P is absent, L1is -NHCH2, L2is a bond, M is aryl (e.g., phenyl), L3is -CH2O, and Z is heterocyclyl (e.g., a nitrogen-containing heterocyclyl, e.g., thiomorpholinyl-1,1-dioxide). In some embodiments of Formula (I-b), P is absent, L1is -NHCH2, L2is a bond, M is absent, L3is a bond, and Z is heterocyclyl (e.g., an oxygen-containing heterocyclyl, e.g., tetrahydropyranyl, tetrahydrofuranyl, oxetanyl, or oxiranyl). In some embodiments, the compound is a compound of Formula (I-b-i). In some embodiments of Formula (I-b-i), each of R2aand R2bis independently hydrogen or CH3, each of R2cand R2dis independently hydrogen, m is 1 or 2, n is 1, X is O, p is 0, M2is phenyl optionally substituted with one or more R3, R3is -CF3, and Z2is heterocyclyl (e.g., an oxygen-containing heterocyclyl, e.g., tetrahydropyranyl, tetrahydrofuranyl, oxetanyl, or oxiranyl). In some embodiments, the compound is a compound of Formula (I-b-ii). In some embodiments of Formula (I-b-ii), each of R2a, R2b, R2c, and R2dis independently hydrogen, q is 0, p is 0, m is 1, and Z2is heterocyclyl (e.g., an oxygen-containing heterocyclyl, e.g., tetrahydropyranyl). In some embodiments, the compound is a compound of Formula (I-c). In some embodiments of Formula (I-c), each of R2cand R2dis independently hydrogen, m is 1, p is 1, q is 0, R5is –CH3, and Z is heterocyclyl (e.g., a nitrogen-containing heterocyclyl, e.g., piperazinyl). In some embodiments, the compound is a compound of Formula (I-d). In some embodiments of Formula (I-d), each of R2a, R2b, R2c, and R2dis independently hydrogen, m is 1, n is 3, X is O, p is 0, and Z is heterocyclyl (e.g., an oxygen-containing heterocyclyl, e.g., tetrahydropyranyl, tetrahydrofuranyl, oxetanyl, or oxiranyl). In some embodiments, the compound is a compound of Formula (I-f). In some embodiments of Formula (I-f), each of R2aand R2bis independently hydrogen, n is 1, M is -CH2-, P is a nitrogen-containing heteroaryl (e.g., imidazolyl), L3is -C(O)OCH2-, and Z is CH3. In some embodiments, the compound is a compound of Formula (II-a). In some embodiments of Formula (II-a), each of R2aand R2bis independently hydrogen, n is 1, q is 0, L3is –CH2(OCH2CH2)2, and Z is –OCH3In some embodiments of Formula (II-a), each of R2aand R2bis independently hydrogen, nis 1, L3 is a bond or –CH2,and Z is hydrogen or –OH. In some embodiments, the compound is a compound of Formula (III). In some embodiments of Formula (III), each of R2a, R2b, R2c, and R2dis independently hydrogen, m is 1, n is 2, q is 3, p is 0, RCis hydrogen, and Z1is heteroalkyl optionally substituted with R5(e.g., - N(CH3)(CH2CH2)S(O)2CH3). In some embodiments, the compound is a compound of Formula (III-b). In some embodiments of Formula (III-b), each of R2a, R2b, R2c, and R2dis independently hydrogen, m is 0, n is 2, q is 3, p is 0, and Z2is aryl (e.g., phenyl) substituted with 1 R5(e.g., -NH2). In some embodiments, the compound is a compound of Formula (III-b). In some embodiments of Formula (III-b), each of R2a, R2b, R2c, and R2dis independently hydrogen, m is 1, n is 2, q is 3, p is 0, RCis hydrogen, and Z2is heterocyclyl (e.g., a nitrogen-containing heterocyclyl, e.g., a nitrogen-containing spiro heterocyclyl, e.g., 2-oxa-7-azaspiro[3.5]nonanyl). In some embodiments, the compound is a compound of Formula (III-d). In some embodiments of Formula (III-d), each of R2a, R2b, R2c, and R2dis independently hydrogen, m is 1, n is 2, q is 1, 2, 3, or 4, p is 0, and X is S(O)2. In some embodiments of Formula (III-d), each of R2aand R2bis independently hydrogen, m is 1, n is 2, q is 1, 2, 3, or 4, p is 0, and X is S(O)2. In some embodiments, the compound is a compound of Formula (I-b), (I-d), or (I-e). In some embodiments, the compound is a compound of Formula (I-b), (I-d), or (II). In some embodiments, the compound is a compound of Formula (I-b), (I-d), or (I-f). In some embodiments, the compound is a compound of Formula (I-b), (I-d), or (III). In some embodiments, the compound of Formula (I) is not a compound disclosed in WO2012 / 112982, WO2012 / 167223, WO2014 / 153126, WO2016 / 019391, WO 2017 / 075630, US2012-0213708, US 2016-0030359 or US 2016-0030360. In some embodiments, the compound of Formula (I) comprises a compound shown in Table 3, or a pharmaceutically acceptable salt thereof. In some embodiments, the exterior surface and / or one or more compartments within a device described herein comprises a small molecule compound shown in Table 3, or a pharmaceutically acceptable salt thereof. Table 3: Exemplary Compounds of Formula (I)

[0002] Conjugation of any of the compounds in Table 3 to a polymer (e.g., an alginate) may be performed as described in Example 2 of WO 2019 / 195055 or any other suitable chemical reaction. In some embodiments, the compound is a compound of Formula (I) (e.g., Formulas (I-a), (I-b), (I-c), (I-d), (I-e), (I-f), (II), (II-a), (III), (III-a), (III-b), (III-c), (III-d), (III-e), (III-f), (III-g), (III-h), or (III-i)), or a pharmaceutically acceptable salt thereof and is selected from: pharmaceutically acceptable salt thereof. In some embodiments, the device described herein comprises the compound of pharmaceutically acceptable salt of either compound. In some embodiments, the device described herein comprises the compound of , pharmaceutically acceptable salt of either compound. In some embodiments, the device described herein comprises the compound of , compounds. In some embodiments, a compound of Formula (I) (e.g., Compound 101 in Table 3) is covalently attached to an alginate (e.g., an alginate with approximate MW < 75 kDa, G:M ratio ≥ 1.5) at a conjugation density of at least 2.0 % and less than 9.0 %, or 3.0 % to 8.0 %, 4.0-7.0, 5.0 to 7.0, or 6.0 to 7.0 or about 6.8 as determined by combustion analysis for percent nitrogen as described in WO 2020 / 069429. Photoactive Crosslinkers and Photoinitiators Described herein are hydrogel capsules comprising polysaccharide polymers covalently bound to photoactive crosslinkers, as well as compositions and methods of use thereof. Photoactive crosslinkers comprise a moiety that is activated upon exposure to light. The light may comprise any wavelength of light, from infrared to x-ray energy. In some embodiments, the light comprises ultraviolet light (e.g., between 360 nm to 400 nm, e.g., 370 nm to 390 nm, e.g., 380 nm to 400 nm, e.g., 390 nm to 400 nm). In some embodiments, the light comprises visible light (e.g., between 400 nm to 700 nm). Photoactive crosslinkers often include at least one unsaturated functional group capable of undergoing free radical polymerization. In some embodiments, a photoactive crosslinker comprises an alkenyl group (e.g, C2-C12 alkenyl, C2-C8 alkenyl). In some embodiments, a photoactive crosslinker comprises an alkynyl group (e.g,, C2- C12alkynyl, C2-C8alkynyl). Moieties that may be activated upon exposure to irradiation include aromatic groups, alkenyl groups, alkynyl groups, and azide groups. Exemplary alkenyl compounds that may act as photoactive crosslinkers include alkenoic acids such as acrylate, methacrylate, acrylamide, and methacrylamide and their corresponding acid chlorides and anhydrides. In some embodiments, the photoactive crosslinker comprises an acrylate group. In some embodiments, the photoactive crosslinker comprises an methacrylate group. In some embodiments, the photoactive crosslinker comprises an acrylamide group. In some embodiments, the photoactive crosslinker comprises an methacrylamide group. Other exemplary alkenyl compounds include enols (e.g., 2-propen-1-ol), alkenyl halides (such as allyl chloride, and the like), organometallic alkenyl compounds (such as vinyl magnesium bromide), aryl compounds (e.g., styrene). Exemplary photoactive crosslinkers include acrylate, methacrylate, ethylene glycol dimethylacrylate, divinylbenzene, 1,3-diisopropyl benzene, and N,N’-methylenebisacrylamide. In an embodiment, the photoactive crosslinker is a bifunctional crosslinker, i.e., has two reactive functional groups. In an embodiment, the photoactive covalent crosslinker has both alkenyl and amide functional groups. In an embodiment, the photoactive crosslinker has both alkenyl and carboxylate functional groups. In an embodiment, the photoactive crosslinker has both alkenyl and amide functional groups. In an embodiment, the photoactive crosslinker has the structure of Formula (IV): pharmaceutically acceptable salt or tautomer thereof, wherein X1is absent, O, NR33, or C(R34a)(R34b); each of R30a, R30b, R31, R32, R33, R34a, and R34bis independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, –N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl. In an embodiment, X1is O, each of R30a, R30b, R31, and R32is hydrogen, and R32is heteroalkyl (e.g., propylamine, e.g., -CH2CH2CH2NH2). In an embodiment, X1is O, each of R30a, R30b, R31, and R32is hydrogen, and R32is heteroalkyl (e.g., ethylamine, e.g., -CH2CH2NH2). In an embodiment, the photoactive crosslinker of Formula (IV) is methacrylate. In an embodiment X1is absent; R32is halo (e.g., chloro); and each of R30a, R30band R31is hydrogen. In an embodiment, the photoactive crosslinker of Formula (IV) is acryloyl chloride. In an embodiment, X1is NR33(e.g., NH), and each of R30a, R30b, R31, and R32is hydrogen. In an embodiment, the photoactive crosslinker of Formula (IV) is acrylamide. In an embodiment, the photoactive crosslinker of Formula (IV) has the structure of Formula (IV-a): pharmaceutically acceptable salt or tautomer thereof, wherein each of R30a, R30b, R31, R32and R35is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, – N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl. In an embodiment, the photoactive crosslinker of Formula (IV) has the structure of Formula (IV-b): pharmaceutically acceptable salt or tautomer thereof, wherein each of R30a, R30b, R31, R32, R36a, and R36bis independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, – N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl; R35is hydrogen, alkyl, heteroalkyl, halo, cyano, nitro, amino, cycloalkyl, heterocyclyl, aryl, or heteroaryl; and n is 1, 2, 3, 4, 5, or 6. In an embodiment, the photoactive crosslinker of Formula (IV) has the structure of Formula (IV-c): e halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, –N(RC1)(RD1), – N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; R32is alkyl, alkenyl, alkynyl, heteroalkyl,–C(O)ORA1, –C(O)RB1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl. In an embodiment, the photoactive crosslinker of Formula (IV) has the structure of Formula (IV-d): pharmaceutically acceptable salt or tautomer thereof,wherein each of R30a, R30b, R31, R32, R36a, and R36b is independently hydrogen, alkyl, alkenyl,alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, – N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; R32is alkyl, alkenyl, alkynyl, heteroalkyl,–C(O)ORA1, –C(O)RB1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl; and n is 1, 2, 3, 4, 5, or 6. In some embodiments, the photoactive crosslinker is a compound of Table 4. Table 4. Exemplary photoactive crosslinkers of Formula (IV) Compound No Structure Photoactive crosslinkers may be used alone or, preferably in the presence of a photoinitiator. A “photoinitiator,” as used herein, refers to a molecule capable of absorbing radiation e.g., light e.g., photons, and forming a reactive species in an excited state. A variety of free radical initiators, as can readily be identified by those of skill in the art, can be employed in the practice of the present invention. In an embodiment, a photoinitiator is an ultraviolet (UV) photoinitiator. Exemplary UV photoinitiators include lithium phenyl-2,4,6- trimethylbenzoylphopshinate (LAP), camphorquinone, benzoin methyl ether, 1-hydroxy- cyclohexyl-phenyl-ketone (i.e., Irgacure 184), 2-hydroxy-2-methyl-1-phenyl-1-propanone (i.e., Darocur 1173) 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methylpropan-1-one (i.e., Irgacure 2959), 2-benzyl-2-(dimethylamino)-1-(4-morpholin-4-ylphenyl)butan-1-one (i.e., Irgacure 369), 2-methyl-1-(4-methylsulfanylphenyl)-2-morpholin-4-ylpropan-1-one (i.e., Irgacure 907) diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (e.g., Darocur TPO), benzoin ethyl ether, benzophenone, 9,10-anthraquinone, ethyl-4-N,N-dimethylaminobenzoate, diphenyliodonium chloride, and water soluble derivatives thereof. In some embodiments, the photoinitiator is LAP. In some embodiments, the photoinitiator is camphorquinone. In some embodiments, the photoinitiator is benzoin methyl ether. In some embodiments, the photoinitiator is Irgacure 2959. For visible light polymerization, a system of dye and cocatalyst may be used. Exemplary visible light photoinitiators include 2-(2,4,5,7-tetrabromo-3-hydroxy-6-oxoxanthen-9-yl)benzoic acid (i.e., Eosin Y), erythrosine, riboflavin, rose Bengal, methylene blue, and thionine. In some embodiments, the visible light photoinitiator is Eosin Y. In some embodiments, the visible light photoinitiator is erythrosine. In some embodiments, the visible light photoinitiator is riboflavin. In some embodiments, the visible light photoinitiator is rose Bengal. In some embodiments, the visible light photoinitiator is methylene blue. In some embodiments, the visible light photoinitiator is thionine. A small amount of a comonomer can optionally be added to the crosslinking reaction to increase the polymerization rates. Examples of suitable comonomers include vinyl pyrrolidinone, acrylamide, methacrylamide, acrylic acid, methacrylic acid, sodium acrylate, sodium methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate (HEMA), ethylene glycol diacrylate, ethylene glycol dimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, trimethylol propane triacrylate, trimethylol propane trimethacrylate, tripropylene glycol diacrylate, tripropylene glycol dimethacrylate, glyceryl acrylate, glyceryl methacrylate, and the like. In some embodiments, the photoinitiator is a thermally activated photoinitiator. A photoactive crosslinker may be used in the presence of a single photoinitiator or a plurality of photoinitiators. The plurality of photoinitiators may include 2, 3, 4, 5, 6, 7, 8, or more photoinitiators. In an embodiment, the covalent crosslinking moiety is present on the polysaccharide polymer at a density of at least 1%, e.g., 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20% or more, e.g., as determined by LC-UV assay. In an embodiment, the covalent crosslinking moiety is present on the polysaccharide polymer at a density of less than 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20% or more, e.g., as determined by LC-UV assay. In an embodiment, the covalent crosslinking moiety is present on the polysaccharide polymer at a density of greater than 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20% or more, e.g., as determined by LC-UV assay. Modified polysaccharides may comprise a photoactive crosslinker moiety. The photoactive crosslinker (e.g., a compound of Formulas (IV)-(IV-d)) may be covalently bound to a polysaccharide, e.g., an alginate. The modified polysaccharide polymer, e.g., modified alginate polymer, may be capable of being crosslinked to another polymer. In an embodiment, the polysaccharide polymer is modified with more than one type of photoactive crosslinker. In an embodiment, the polysaccharide is modified with a group capable of undergoing free radical polymerization. In an embodiment, the polysaccharide is modified with a compound of Formulas (IV), (IV-a), (IV-b), (IV-c), or (IV-d). In an embodiment, the modified polysaccharide is modified with a compound selected from Table 4. In an embodiment, the polysaccharide is modified with . In an embodiment, the modified polysaccharide is a compound of Formula (V): pharmaceutically acceptable salt or tautomer thereof, wherein each of T and U is independently C(R40)(R41), O, or N(R42); each of R38a, R38b, R39a, R39b, R40, R41,and R42is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, – N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each of R32and R35is hydrogen, alkyl, heteroalkyl, halo, cyano, nitro, amino, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl; and the photoactive crosslinker has the structure of Formula (IV), (IV-a), (IV-b), (IV-c), or (IV-d). In an embodiment, the modified polysaccharide polymer of Formula (V) has the structure of Formula (V-a): pharmaceutically acceptable salt or tautomer thereof, wherein each of T and U is independently C(R40)(R41), O, or N(R42); each of R30a, R30b, R31, R32, R38a, R38b, R39a, R39b, R40, R41, and R42is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, – N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl. In an embodiment, the modified polysaccharide polymer of Formula (V) has the structure of Formula (V-b): pharmaceutically acceptable salt or tautomer thereof, wherein each of U and T is independently C(R40)(R41), O, or N(R42); each of R30a, R30b, R31, R35, R38a, R38b, R39a, R39b, R40, R41, R42, R43a, and R43bis independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,– OC(O)RB1, –N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl; and n is 1, 2, 3, 4, 5, or 6. In an embodiment, the modified polysaccharide polymer of Formula (V) has the structure of Formula (V-c): pharmaceutically acceptable salt or tautomer thereof, wherein U is C(R40)(R41), O, or N(R42); each of R30a, R30b, R31, R35, R38a, R38b, R39a, R39b, R40, R41, R42, R43a, R43band R44is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, –N(RC1)(RD1), – N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl; and n is 1, 2, 3, 4, 5, or 6. In an embodiment, the modified polysaccharide polymer of Formula (V) has the structure of Formula (V-d): pharmaceutically acceptable salt or tautomer thereof, wherein U is C(R40)(R41), O, or N(R42); each of R30a, R30b, R31, R38a, R38b, R39a, R39b, R40, R41, R42, R43a, and R43bis independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, –N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl; and n is 1, 2, 3, 4, 5, or 6. In an embodiment, the modified polysaccharide polymer comprises the structure of Formula (VI): or a p harmaceutically acceptable salt or tautomer thereof, wherein each of W, T1, T2, U1, and U2is independently C(R40)(R41), O, or N(R42); each of R38a, R38b, R38c, R38dR39a, R39b, R39a, R39b, R40, R41, and R42is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, –N(RC1)(RD1), –N(RC1)C(O)RB1, – C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl; p is an integer from 1-100; the afibrotic compound has the structure of Formulas (I), (I-a), (I-b), (I-b-i), (I-b-ii), (I-c), (I-d), (I-e), (I-f), (II), (II-a), (III), (III-a), (III-b), (III-c), (III-d), (III-e), (III-f), (III-g), (III-h) or (III-i); and the photoactive crosslinker has the structure of Formulas (IV), (IV-a), (IV-b), (IV- c), (IV-d) or (IV-e). In an embodiment, the modified polysaccharide polymer comprises the structure of Formula (VI-a-i):

[0003] pharmaceutically a cceptable salt or tautomer thereof, wherein each of W, T , U , and U is independently C(R40)(R41), O, or N(R42); each of R38a, R38b, R38c, R38d, R39a, R39b, R39c, R39d, R40, R41, and R42is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, –N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl; variables M1, Z1, R2a, R2b, R2c, R2d, X, RC, m, and n are as defined in Formula (I-b); p is an integer from 1-100; and the photoactive crosslinker has the structure of Formulas (IV), (IV-a), (IV-b), (IV-c), (IV-d) or (IV- e). In an embodiment, the modified polysaccharide polymer comprises the structure of Formula (VI-a-ii): pharmaceutically acceptable salt or tautomer thereof, wherein each of W, T1, U1, and U2is independently C(R40)(R41), O, or N(R42); each of R38a, R38b, R38c, R38d, R39a, R39b, R39c, R39d, R40, R41, and R42is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, –N(RC1)(RD1), –N(RC1)C(O)RB1, – C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl; variables Z1, R2a, R2b, R2c, R2d, RC, m, n, and q are as defined in Formula (III-f); p is an integer from 1-100; and the photoactive crosslinker has the structure of Formulas (IV), (IV-a), (IV-b), (IV-c), (IV-d), or (IV-e). In an embodiment, the modified polysaccharide polymer comprises the structure of Formula (VI-b-i): pharmaceutically acceptable salt or tautomer thereof, wherein each of W, X1, T2, U1and U2is independently C(R40)(R41), O, or N(R42); each of R30a, R30b, R31, R32, R38a, R38b, R38c, R38d, R39a, R39b, R39c, R39d, R40, R41, R42, and R44is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, –N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl; and the afibrotic compound has the structure of Formulas (I), (I-a), (I-b), (I-b-i), (I-b-ii), (I-c), (I-d), (I-e), (I-f), (II), (II-a), (III), (III-a), (III-b), (III-c), (III-d), (III-e), (III-f), (III-g), (III-h) or (III-i). In an embodiment, the polysaccharide polymer comprises the structure of Formula (VI-c- i): pharmaceutically acceptable salt or tautomer thereof, wherein each of X1, U1,U2, and W is independently C(R40)(R41), O, or N(R42); each of R30a, R30b, R31, R32, R38a, R38b, R38c, R38d, R39a, R39b, R39c, R39d, R40, R41, R42, and R44is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, – N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl; variables M1, Z1, R2a, R2b, R2c, R2d, X, RC, m, and n are as defined in Formula (I-b); and p is an integer from 1-100. In an embodiment, the polysaccharide polymer comprises the structure of Formula (VI-c- ii): 73

[0004] ii), or a pharmaceutically acceptable salt or tautomer thereof, wherein each of W, X1, Y1, and Y2is independently C(R40)(R41), O, or N(R42); each of R30a, R30b, R31, R32, R38a, R38b, R38c, R38d, R39a, R39b, R39c, R39d, R40, R41, R42, and R44is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, –N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl; variables Z1, R2a, R2b, R2c, R2d, RC, m, n, and q are as defined in Formula (III-f); and p is an integer from 1-100. In an embodiment, the modified polysaccharide polymer of Formula (VI) is a compound selected from Table 5: Table 5. Exemplary Compounds of Formula (VI) or a pharmaceutically acceptable salt thereof.

[0005]

[0006]

[0007]

[0008]

[0009] In an embodiment, the modified polysaccharide polymer is selected from

[0010] pharmaceutically acceptable salt thereof. The polysaccharide polymers described herein may be modified on any suitable functional group (e.g., carboxyl or hydroxyl group). In an embodiment, the polysaccharide polymers are modified on a single type of functional group. In an embodiment, the polysaccharide polymers are modified on more than one type of functional group. In an embodiment, the polysaccharide polymers are modified on carboxyl groups. In an embodiment, the polysaccharide polymers are modified on carboxyl and hydroxyl groups. In an embodiment, the polysaccharide polymers described herein may be modified on one or more functional groups by a compound of Formula (I) and / or a compound of Formula (IV). In an embodiment, the degree of modification (i.e., percent of functional groups of the polymer modified with a photoactive crosslinker) is about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%or 99%. In an embodiment, the degree of modification (i.e., percent of functional groups of the polymer modified with a photoactive crosslinker) is greater than about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 99%. In an embodiment, the degree of modification (i.e., percent of functional groups of the polymer modified with a photoactive crosslinker) is less than about 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 99%. In some embodiments, the polysaccharide polymers described herein retain sufficient unreacted carboxylic acid groups to allow for ionic crosslinking, e.g., when the polymer is used to prepare hydrogel capsules with dual cross-linking. In some embodiments, the polysaccharide polymers described herein do not comprise a degree of modification of more than 10% of the carboxylic acid groups. In some embodiments, the polysaccharide polymers described herein do not comprise a degree of modification of more than 5% of the carboxylic acid groups. In some embodiments, the polysaccharide polymers described herein do not comprise a degree of modification of more than 5%, 6%, 7%, 8%, 9%, or 10% of the carboxylic acid groups. In an embodiment, the polysaccharide polymers described herein are modified with one, two, three, or more unique compounds. In an embodiment, the polysaccharide polymers described herein are modified with a photoactive crosslinker (e.g. a compound of Formula (IV)) and a compound of Formula (I). In an embodiment, the polysaccharide polymers described herein are modified with a photoactive crosslinker. In an embodiment, the polysaccharide polymers described herein are modified with compound of Formula (I). In a preferred embodiment, the polysaccharide polymers described herein are modified with both a photoactive crosslinker and a compound of Formula (I). In an embodiment, a polysaccharide polymer described herein is modified with both a photoactive crosslinker (e.g., Compound 201 and a compound of Formula (I) (e.g., a compound from Table 3). In an embodiment, a polysaccharide polymer described herein is modified with and a compound from Table 3. In an embodiment, a polysaccharide polymer described herein is modified with and a compound from Table 3. In an embodiment, a polysaccharide polymer described herein is modified with and a compound from Table 3. In an embodiment, a polysaccharide polymer described herein is modified with a compound from Table 3. In an embodiment, a polysaccharide polymer described herein is modified with and a compound from Table 3. In an embodiment, a polysaccharide polymer described herein is modified with and a compound from Table 3. In an embodiment, a polysaccharide polymer described herein is modified with and a compound from Table 3. In an embodiment, a polysaccharide polymer described herein is modified with and a compound from Table 3. In an embodiment, the polysaccharide polymer described herein is an alginate modified embodiment, the polysaccharide polymer described herein is an alginate modified with both and a compound of . In some embodiments, the polysaccharide polymers described herein alginates, e.g VLVG alginate or SLG-100 alginate, e.g., a low viscosity alginate, e.g., a high G:M ratio alginate, and are modified with a photoactive crosslinker and a compound of Formula (I) (e.g., from Table 3). In some embodiments, the polysaccharide polymers described herein are modified with a compound of Formula (I) and a compound of Formula (IV). In some embodiments, the polysaccharide polymers described herein are modified with a compound of Formula (I), a compound of Formula (IV), and do not comprise heparin. In some embodiments, the polysaccharide polymers described herein are modified with a compound of Formula (I), a compound of Formula (IV), and do not comprise an anti-CD3 antibody. In some embodiments, the polysaccharide polymers described herein are modified with a compound of Formula (I), a compound of Formula (IV), and do not comprise an anti-CD28 antibody. In some embodiments, the polysaccharide polymers described herein are modified with a compound of Formula (I), a compound of Formula (IV), and do not comprise a major histocompatibility peptide. In some embodiments, the polysaccharide polymers described herein are modified with a compound of Formula (I), a compound of Formula (IV), and do not comprise heparin, an anti-CD3 antibody, an anti-CD28 antibody, or a major histocompatibility peptide. Polysaccharides (e.g., alginate) may be modified on the hydroxyl groups to improve one or more physical properties. The polysaccharide polymers of the present invention may or may not be sulfonated (i.e., should not comprise a sulfate group). Features of Hydrogels and Hydrogel Capsules The present disclosure further features hydrogels and hydrogel capsules comprising both (i) a polysaccharide polymers described herein and (ii) an islet cell (e.g., a plurality of islet cells). The hydrogels and hydrogel capsules may be produced by crosslinking the photoactive crosslinking groups (i.e., covalent crosslinking) or by ionically crosslinking, e.g., in the presence of a divalent cation (e.g., Ba2+). In an embodiment, a hydrogel or hydrogel capsule described herein is produced by photoactive crosslinking. In an embodiment, a hydrogel or hydrogel capsule described herein is produced by photoactive crosslinking and ionic crosslinking, which is also referred to herein as dual crosslinking. A person skilled in the art will recognize that other methods of initiating polymerization are possible including thermal, ultrasonic, and gamma radiation in the presence of appropriate initiators. The polysaccharide polymers described herein comprising a photoactive crosslinker moiety may be able to undergo further polymerization, e.g., may react with compatible functional groups on the same or different polymer. In an embodiment, a polymer modified to include a thiol group and a second polymer modified to include an alkene group such that a crosslinked polymer may be formed by reacting the first and second polymers. In some embodiments, a hydrogel capsule is formed through the covalent crosslinking of unsaturated functional groups by a chain-growth polymerization process. In an embodiment, a hydrogel capsule is formed through the covalent crosslinking of an unsaturated functional group on a first polymer with an unsaturated functional group on a second polymer. In a preferred embodiment, a hydrogel capsule is formed through the covalent crosslinking of an alkenyl functional group on a first polymer with an alkenyl functional group on a second polymer. In other embodiments, a hydrogel capsule is formed by covalent crosslinking of unsaturated functional groups by a step- growth polymerization process. In an embodiment, the step-growth polymerization process comprises a reaction between one or more unsaturated functional groups (e.g., alkenyl groups) of one polysaccharide chain and thiolated functional groups of another polymer chain. The hydrogel capsules described herein are formed by the crosslinking of one or more types of polysaccharide polymers. In an embodiment, the hydrogel capsule comprises only polysaccharide polymers. In an embodiment, the hydrogel capsule comprises polysaccharide polymers of the same type, e.g., alginate polymers. In an embodiment, the hydrogel capsules is formed by the polymerization of two identical polysaccharides. In an embodiment, the hydrogel capsules is formed by the polymerization of two different polysaccharides. In an embodiment, the hydrogel capsule comprises a plurality of polymers, e.g., a plurality of polysaccharide polymers. In an embodiment, the hydrogel capsule comprises one polysaccharide polymer and a non-polysaccharide polymer. The hydrogel capsules described herein are formed by the crosslinking of one or more types of polysaccharide polymers. In an embodiment, the hydrogel capsule comprises only polysaccharide polymers. In an embodiment, the hydrogel capsule comprises polysaccharide polymers of the same type, e.g., alginate polymers. In an embodiment, the hydrogel capsule is formed by the polymerization of two identical polysaccharides. In an embodiment, the hydrogel capsule is formed by the polymerization of two different polysaccharides. In an embodiment, the hydrogel capsule comprises a plurality of polymers, e.g., a plurality of polysaccharide polymers. In an embodiment, the hydrogel capsule comprises one polysaccharide polymer and a non- polysacchairde polymer. The hydrogel capsules described herein may be homogenous, i.e., may not comprise a non-polysaccharide polymer. In an embodiment, the hydrogel capsule described herein does not comprise a polymer selected from polyacrylamide, poly(vinyl alcohol), poly(ethylene oxide), polyethylene glycol (PEG), and polyphosphazene. In an embodiment, the hydrogel capsule does not comprise poly(vinyl alcohol). In an embodiment, the hydrogel capsule does not comprise poly(ethylene oxide). In an embodiment, the hydrogel capsule does not comprise polyethylene glycol (PEG). In an embodiment, the hydrogel capsule does not comprise a polyphosphazene. In an embodiment, the hydrogel capsules are two-compartment hydrogel capsules. In an embodiment, the hydrogel capsules comprise an inner compartment and an outer compartment. In an embodiment, the two compartments are formed from the same type of modified polysaccharides. In an embodiment, the two compartments are formed from different types of modified polysaccharides. In an embodiment, the inner compartment is formed from a polysaccharide of Formula (V-b) and the outer compartment is formed from a polysaccharide of Formula (V-b). In an embodiment, the inner compartment is formed from a polysaccharide of Formula (V-d) and the outer compartment is formed from a polysaccharide of Formula (V-d). In an embodiment, the inner compartment is formed from a polysaccharide of Formula (VI-c-i) and the outer compartment is formed from a polysaccharide of Formula (VI-c-i). In some embodiments, the inner compartment is formed from an unmodified polysaccharide and the outer compartment is formed from a polysaccharide modified with a compound of Formula (V-b), (V-d), or (VI-c-i). In some embodiments, the outer compartment is formed from an unmodified polysaccharide and the inner compartment is formed from a polysaccharide modified with a compound of Formula (V-b), (V-d), or (VI-c-i). In some embodiments, the inner compartment is formed from a polysaccharide modified with a cell binding substance (e.g., a compound of Table 1) and the outer compartment is formed from a polysaccharide modified with a compound of Formula (V-b), (V-d), or (VI-c-i). In some embodiments, the inner compartment is formed from a polysaccharide modified with a compound of Table 1 and the outer compartment is formed from a polysaccharide modified with a compound of Formula (V-b), (V-d), or (VI-c-i). The present disclosure features a hydrogel capsule comprising a dual-crosslinked polysaccharide for encapsulating an islet cell, such as an engineered islet cell, a cadaveric islet cell, or a stem cell-derived islet cell. The islet cells are capable of expressing a therapeutic agent (e.g., insulin) upon implant of the hydrogel in a subject, e.g., a human or other mammalian subject. In addition, the hydrogel capsule further comprises at least one means for mitigating the FBR (as defined herein). In an embodiment, the means for mitigating the FBR comprises an afibrotic compound, as defined herein. In an embodiment, the dual-crosslinked polysaccharide polymer may further comprise at least one cell binding peptide (CBP) (as defined herein). The cells are capable of expressing a therapeutic agent upon implant of a device comprising the dual-crosslinked polysaccharide polymer (e.g., a hydrogel capsule), in a subject, e.g., a human or other mammalian subject. In addition, the device comprises at least one means for mitigating the FBR (as defined herein). In an embodiment, the means for mitigating the FBR comprises an afibrotic compound, as defined herein. In an embodiment, the afibrotic compound is covalently bound to the dual- crosslinked polysaccharide polymer. In some embodiments, the device (e.g., hydrogel capsule) further comprises an unmodified polysaccharide polymer. In some embodiments, the unmodified polysaccharide polymer is an unmodified alginate. In some embodiments, the alginate is a high guluronic acid (G) alginate, and comprises greater than about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or more guluronic acid (G). In some embodiments, the alginate is a high mannuronic acid (M) alginate, and comprises greater than about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or more mannuronic acid (M). In some embodiments, the ratio of M:G is about 1. In some embodiments, the ratio of M:G is less than 1. In some embodiments, the ratio of M:G is greater than 1. In an embodiment, the unmodified alginate has a molecular weight of 150 kDa – 250 kDa and a G:M ratio of ≥ 1.5. In some embodiments, the device (e.g., hydrogel capsule) modified polysaccharide polymer is an afibrotic polymer, e.g., an afibrotic alginate which comprises an alginate chemically modified with a Compound of Formula (I). The alginate in the afibrotic alginate polymer may be the same or different than any unmodified alginate that is present in the device. In an embodiment, the density of the Compound of Formula (I) in the afibrotic alginate (e.g., amount of conjugation) is between about 4.0% and about 8.0%, between about 5.0% and about 7.0 %, or between about 6.0% and about 7.0 % nitrogen (e.g., as determined by combustion analysis for percent nitrogen). In an embodiment, the amount of Compound 101 produces an increase in % N (as compared with the unmodified alginate) of about 0.5% to 2% 2% to 4% N, about 4% to 6% N, about 6% to 8%, or about 8% to 10% N), where % N is determined by combustion analysis and corresponds to the amount of Compound 101 in the modified alginate. The hydrogel capsules described herein may be porous or non-porous. The pores in a polysaccharide hydrogel capsule (e.g., formed from an alginate hydrogel) function as a selectively permeable membrane to small proteins and molecules while preventing larger, unwanted molecules such as immunoglobins access to encapsulated cells. In a preferred embodiment, the hydrogels and hydrogel capsules described herein are porous. In some embodiments, the average pore diameter is about 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, or 20 nm. In some embodiments, the average pore diameter is greater than about 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, or 20 nm. In some embodiments, the average pore diameter is less than about 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, or 20 nm. In some embodiments, the mean pore size of the first compartment and the second compartment of the particle (e.g., hydrogel capsule) is substantially the same. In some embodiments, the mean pore size of the first compartment and the second compartment of the particle differ by about 1.5%, 2%, 5%, 7.5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or more. In some embodiments, the mean pore size of the particle (e.g., mean pore size of the first compartment and / or mean pore size of the second compartment) is dependent on a number of factors, such as the material(s) within each compartment, the presence and density of the photoactive crosslinker, the presence and density of a compound of Formula (I). The hydrogel capsules described herein should not have pores of a sufficient diameter to allow for the movement of cells (e.g., immune cells, e.g., dendritic cells) through the hydrogel. In some embodiments, the diameters of the pores are small enough to prevent the movement of antibodies through the hydrogel. In some embodiments, the hydrogel capsules described herein do not have pore sizes greater than 75 µm. In some embodiments, the hydrogel capsules described herein do not have pore sizes greater than 1 µm, 2 µm, 3 µm, 4 µm, 5 µm, 6 µm, 7 µm, 8 µm, 9 µm, 10 µm, 15 µm, 20 µm, 25 µm, 30 µm, 35 µm, 40 µm, 45 µm, 50 µm, 55 µm, 60 µm, 65 µm, 70 µm or 75 µm. The physical properties of the hydrogel capsules described herein (e.g., as described in the Examples) control the release of encapsulated molecules and / or limit the uptake or penetration of undesired molecules external to the capsules (e.g., as determined by a dextran permeability assay). In some embodiments, the average molecular weight permeability is from about 1 kDa to about 150 kDa. In some embodiments, the average molecular weight permeability is about 1 kda, 5 kDa, 10 kDa, 15 kDa, 20 kDa, 25 kDa, 30 kDa, 35 kDa, 40 kDa, 45 kDa, 50 kDa, 55 kDa, 60 kDa, 65 kDa, 70 kDa, 75 kDa, 80 kDa, 85 kDa, 90 kDa, 95 kDa, 100 kDa, 105 kDa, 110 kDa, 115 kDa, 120 kDa, 125 kDa, 130 kDa, 135 kDa, 140 kDa, 145 kDa, or 150 kDa. In some embodiments, the average molecular weight permeability is greater than about 1 kda, 5 kDa, 10 kDa, 15 kDa, 20 kDa, 25 kDa, 30 kDa, 35 kDa, 40 kDa, 45 kDa, 50 kDa, 55 kDa, 60 kDa, 65 kDa, 70 kDa, 75 kDa, 80 kDa, 85 kDa, 90 kDa, 95 kDa, 100 kDa, 105 kDa, 110 kDa, 115 kDa, 120 kDa, 125 kDa, 130 kDa, 135 kDa, 140 kDa, 145 kDa, or 150 kDa. In some embodiments, the average molecular weight permeability is less than about 1 kda, 5 kDa, 10 kDa, 15 kDa, 20 kDa, 25 kDa, 30 kDa, 35 kDa, 40 kDa, 45 kDa, 50 kDa, 55 kDa, 60 kDa, 65 kDa, 70 kDa, 75 kDa, 80 kDa, 85 kDa, 90 kDa, 95 kDa, 100 kDa, 105 kDa, 110 kDa, 115 kDa, 120 kDa, 125 kDa, 130 kDa, 135 kDa, 140 kDa, 145 kDa, or 150 kDa. In some embodiments, the hydrogel capsules described herein may be characterized by their absolute fracture strength (e.g., crush strength) as determined by using a texture analyzer. In some embodiments, the absolute fracture strength is between 50 and 800 g. In some embodiments, the hydrogel capsules described herein have an absolute strength of about 50 g, 60 g, 70 g, 80 g, 90 g, 100 g, 110 g, 120 g, 130 g, 140 g, 150 g, 160 g, 170 g, 180 g, 190 g, 200 g, 210 g, 220 g, 230 g,240 g, 250 g, 260 g, 270 g, 280 g, 290 g, 300 g, 310 g, 320 g, 330 g, 340 g, 350 g, 360 g, 370 g, 380 g, 390 g, 400 g, 410 g, 420 g, 430 g, 440 g, 450 g, 460 g, 470 g, 480 g, 490 g, 500 g, 510 g, 520 g, 530 g, 540 g, 550 g, 560 g, 570 g, 580 g, 590 g, 600 g, 610 g, 620 g, 630 g, 640 g, 650 g, 660 g, 670 g, 680 g, 690 g, 700 g, 710 g, 720 g, 730 g, 740 g, 750 g, 760 g, 770 g, 780 g, 790 g, or 800 g. In some embodiments, the hydrogel capsules described herein have an absolute strength of greater than about 50 g, 60 g, 70 g, 80 g, 90 g, 100 g, 110 g, 120 g, 130 g, 140 g, 150 g, 160 g, 170 g, 180 g, 190 g, 200 g, 210 g, 220 g, 230 g,240 g, 250 g, 260 g, 270 g, 280 g, 290 g, 300 g, 310 g, 320 g, 330 g, 340 g, 350 g, 360 g, 370 g, 380 g, 390 g, 400 g, 410 g, 420 g, 430 g, 440 g, 450 g, 460 g, 470 g, 480 g, 490 g, 500 g, 510 g, 520 g, 530 g, 540 g, 550 g, 560 g, 570 g, 580 g, 590 g, 600 g, 610 g, 620 g, 630 g, 640 g, 650 g, 660 g, 670 g, 680 g, 690 g, 700 g, 710 g, 720 g, 730 g, 740 g, 750 g, 760 g, 770 g, 780 g, 790 g, or 800 g. In some embodiments, the hydrogel capsules described herein have an absolute strength of less than about 50 g, 60 g, 70 g, 80 g, 90 g, 100 g, 110 g, 120 g, 130 g, 140 g, 150 g, 160 g, 170 g, 180 g, 190 g, 200 g, 210 g, 220 g, 230 g,240 g, 250 g, 260 g, 270 g, 280 g, 290 g, 300 g, 310 g, 320 g, 330 g, 340 g, 350 g, 360 g, 370 g, 380 g, 390 g, 400 g, 410 g, 420 g, 430 g, 440 g, 450 g, 460 g, 470 g, 480 g, 490 g, 500 g, 510 g, 520 g, 530 g, 540 g, 550 g, 560 g, 570 g, 580 g, 590 g, 600 g, 610 g, 620 g, 630 g, 640 g, 650 g, 660 g, 670 g, 680 g, 690 g, 700 g, 710 g, 720 g, 730 g, 740 g, 750 g, 760 g, 770 g, 780 g, 790 g, or 800 g. The present disclosure features particles (e.g., hydrogel capsules) comprising a first compartment, a second compartment, a photoactive crosslinking moiety as described herein (e.g., a compound of Formula (IV, V or VI) and optionally a compound of Formula (I), e.g., a described herein. The photoactive crosslinking moiety is covalently bound to a polysaccharide polymer present in the first and / or second compartments. The particle (e.g., hydrogel capsule) may be spherical or have any other shape. The particle (e.g., hydrogel capsule) may comprise materials such as metals, metallic alloys, ceramics, polymers, fibers, inert materials, and combinations thereof. A particle (e.g., hydrogel capsule) may be completely made up of one type of material, or may comprise numerous other materials within the second (outer) compartment and first (inner) compartment. In an embodiment, the present disclosure features a hydrogel capsule comprising a first compartment, a second compartment, and a compound of Formula (I), e.g., a described herein. In some embodiments, the first compartment is modified with a compound of Formula (I). In some embodiments, the second compartment is modified with a compound of Formula (I). In some embodiments, both the first compartment and the second compartment are independently modified with a compound of Formula (I). In some embodiments, a particle (e.g., a hydrogel capsule) has a largest linear dimension (LLD), e.g., mean diameter, or size that is greater than 1 millimeter (mm), preferably 1.5 mm or greater. In some embodiments, the particle (e.g. hydrogel capsule) can be as large as 10 mm in diameter or size. For example, the hydrogel capsule described herein is in a size range of 0.5 mm to 10 mm, 1 mm to 10 mm, 1 mm to 8 mm, 1 mm to 6 mm, 1 mm to 5 mm, 1 mm to 4 mm, 1 mm to 3 mm, 1 mm to 2 mm, 1 mm to 1.5 mm, 1.5 mm to 8 mm, 1.5 mm to 6 mm, 1.5 mm to 5 mm, 1.5 mm to 4 mm, 1.5 mm to 3 mm, 1.5 mm to 2 mm, 2 mm to 8 mm, 2 mm to 7 mm, 2 mm to 6 mm, 2 mm to 5 mm, 2 mm to 4 mm, 2 mm to 3 mm, 2.5 mm to 8 mm, 2.5 mm to 7 mm, 2.5 mm to 6 mm, 2.5 mm to 5 mm, 2.5 mm to 4 mm, 2.5 mm to 3 mm, 3 mm to 8 mm, 3 mm to 7 mm, 3 mm to 6 mm, 3 mm to 5 mm, 3 mm to 4 mm, 3.5 mm to 8 mm, 3.5 mm to 7 mm, 3.5 mm to 6 mm, 3.5 mm to 5 mm, 3.5 mm to 4 mm, 4 mm to 8 mm, 4 mm to 7 mm, 4 mm to 6 mm, 4 mm to 5 mm, 4.5 mm to 8 mm, 4.5 mm to 7 mm, 4.5 mm to 6 mm, 4.5 mm to 5 mm, 5 mm to 8 mm, 5 mm to 7 mm, 5 mm to 6 mm, 5.5 mm to 8 mm, 5.5 mm to 7 mm, 5.5 mm to 6 mm, 6 mm to 8 mm, 6 mm to 7 mm, 6.5 mm to 8 mm, 6.5 mm to 7 mm, 7 mm to 8 mm, or 7.5 mm to 8 mm. In some embodiments, the particle (e.g., hydrogel capsule) has a mean diameter or size between 1 mm to 8 mm. In some embodiments, the particle (e.g.,hydrogel) capsule has a mean diameter or size between 1 mm to 4 mm. In some embodiments, the particle (e.g.,hydrogel capsule) has a mean diameter or size between 1 mm to 2 mm. In some embodiments, the particle (e.g.,hydrogel capsule) has a mean diameter or size between 1.5 mm to 2 mm. In some embodiments, the particle (e.g.,hydrogel capsule) has a largest linear dimension (LLD), e.g., mean diameter, or size that is 1 millimeter (mm) or smaller. In some embodiments, the particle (e.g.,hydrogel capsule) is in a size range of 0.3 mm to 1 mm, 0.4 mm to 1 mm, 0.5 mm to 1 mm, 0.6 mm to 1 mm, 0.7 mm to 1 mm, 0.8 mm to 1 mm or 0.9 mm to 1 mm. In some embodiments, the second (outer) compartment completely surrounds the first (inner) compartment, and the inner boundary of the second compartment forms an interface with the outer boundary of the first compartment. In such embodiments, the thickness of the second (outer) compartment means the average distance between the outer boundary of the second compartment and the interface between the two compartments. In some embodiments, the thickness of the outer compartment is greater than about 10 nanometers (nm), preferably 100 nm or greater and can be as large as 1 mm. For example, the thickness of the outer compartment in a particle described herein may be 10 nanometers to 1 millimeter, 100 nanometers to 1 millimeter, 500 nanometers to 1 millimeter, 1 micrometer (µm) to 1 millimeter, 1 µm to 1 mm, 1 µm to 500 µm, 1 µm to 250 µm, 1 µm to 1 mm, 5 µm to 500 µm, 5 µm to 250 µm, 10 µm to 1 mm, 10 µm to 500 µm, or 10 µm to 250 µm. In some embodiments, the thickness of the outer compartment is 100 nanometers to 1 millimeters, between 1 µm and 1 mm, between 1 µm and 500 µm or between 5 µm and 1 mm. In some embodiments, the particle (e.g.,hydrogel capsule) comprises at least one pore or opening, e.g., to allow for the free flow of materials. In some embodiments, the mean pore size of the hydrogel capsule is between about 0.1 µm to about 10 µm. For example, the mean pore size may be between 0.1 µm to 10 µm, 0.1 µm to 5 µm, 0.1 µm to 2 µm, 0.15 µm to 10 µm, 0.15 µm to 5 µm, 0.15 µm to 2 µm, 0.2 µm to 10 µm, 0.2 µm to 5 µm, 0.25 µm to 10 µm, 0.25 µm to 5 µm, 0.5 µm to 10 µm, 0.75 µm to 10 µm, 1 µm to 10 µm, 1 µm to 5 µm, 1 µm to 2 µm, 2 µm to 10 µm, 2 µm to 5 µm, or 5 µm to 10 µm. In some embodiments, the mean pore size of the hydrogel capsule is between about 0.1 µm to 10 µm. In some embodiments, the mean pore size of the hydrogel capsule is between about 0.1 µm to 5 µm. In some embodiments, the mean pore size of the hydrogel capsule is between about 0.1 µm to 1 µm. In some embodiments, the mean pore size of the first compartment and the second compartment of the particle is substantially the same. In some embodiments, the mean pore size of the first compartment and the second compartment of the particle differ by about 1.5%, 2%, 5%, 7.5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or more. In some embodiments, the mean pore size of the hydrogel capsule (e.g., mean pore size of the first compartment and / or mean pore size of the second compartment) is dependent on a number of factors, such as the material(s) within each compartment and the presence and density of a compound of Formula (I). In some embodiments, the hydrogel capsule comprises an alginate. Alginate is a polysaccharide made up of β-D-mannuronic acid (M) and α-L-guluronic acid (G). In some embodiments, the alginate is a high guluronic acid (G) alginate, and comprises greater than about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or more guluronic acid (G). In some embodiments, the alginate is a high mannuronic acid (M) alginate, and comprises greater than about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or more mannuronic acid (M). In some embodiments, the ratio of M:G is about 1. In some embodiments, the ratio of M:G is less than 1. In some embodiments, the ratio of M:G is greater than 1. In alginate-containing particles, the amount of alginate (e.g., by % weight of the particle, actual weight of the alginate) can be at least 5%, e.g., at least 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 99%, or more, e.g., w / w; less than 20%, e.g., less than 20%, 15%, 10%, 5%, 1%, 0.5%, 0.1%, or less. In some embodiments, both the first compartment and the second compartment comprise the same polymer. In some embodiments, the first compartment and the second compartment comprise different polymers. In some embodiments, the first compartment comprises an alginate. In some embodiments, the second compartment comprises an alginate. In some embodiments, both the first compartment and the second compartment comprise an alginate. In some embodiments, the alginate in the first compartment is different than the alginate in the second compartment. In some embodiments, the first compartment comprises an alginate and the second compartment comprises a different polymer (e.g., a polysaccharide, e.g., hyaluronate or chitosan). In some embodiments, the second compartment comprises an alginate and the first compartment comprises a different polymer (e.g., a polysaccharide, e.g., hyaluronate or chitosan). Both the first compartment and the second compartment may include a single component (e.g., one polymer) or more than one component (e.g., a blend of polymers). In some embodiments, the first compartment comprises only alginate (e.g., chemically modified alginate, or a blend of an unmodified alginate and a chemically modified alginate). In some embodiments, the second compartment comprises only alginate (e.g., chemically modified alginate or a blend of an unmodified alginate and a chemically modified alginate). In some embodiments, both the first and the second compartment independently comprise only alginate (e.g., chemically modified alginate or blend of an unmodified alginate and a chemically modified alginate). In some embodiments, the first and second compartments comprise a blend of polymers (i.e., a mixture of polymers). In some embodiments, the first (inner) compartment comprises a blend of polymers. In some embodiments, the second (outer) compartment comprises a blend of polymers. In some embodiments, the first and second compartments comprise the same blend of polymers. In some embodiments, the first and second compartments comprise different blends of polymers. In some embodiments, at least one polymer in the blend comprising the outer compartment is covalently modified with a photoactive crosslinker described herein (e.g., a compound of Formula (IV), (V) or (VI). In some embodiments, at least one polymer in the blend comprising the second (outer) compartment is covalently modified with an afibrotic compound described herein, e.g., a compound of Formula (I). In some embodiments, at least one polymer in the blend comprising the second (outer) compartment is covalently modified with both a photoactive crosslinker and an afibrotic compound. In some embodiments, the first compartment comprises a blend of 2, 3, 4, 5, 6, 7, 8, 9, 10 or more polymers. In some embodiments, the first compartment comprises a blend of 2 polymers. In some embodiments, the first compartment comprises a blend of 3 polymers. In some embodiments, the first compartment comprises a blend of 4 polymers. In some embodiments, the first compartment comprises a blend of 5 polymers. In some embodiments, the first compartment comprises a blend of 6 polymers. In some embodiments, the first (inner) compartment comprises a blend of 7 polymers. In some embodiments, the first (inner) compartment comprises a blend of 8 polymers. In some embodiments, the first (inner) compartment comprises a blend of 9 polymers. In some embodiments, the first (inner) compartment comprises a blend of 10 polymers. In some embodiments, the second (outer) compartment comprises a blend of 2, 3, 4, 5, 6, 7, 8, 9, 10 or more polymers. In some embodiments, the second (outer) compartment comprises a blend of 2 polymers. In some embodiments, the second (outer) compartment comprises a blend of 3 polymers. In some embodiments, the second (outer) compartment comprises a blend of 4 polymers. In some embodiments, the second (outer) compartment comprises a blend of 5 polymers. In some embodiments, the second (outer) compartment comprises a blend of 6 polymers. In some embodiments, the second (outer) compartment comprises a blend of 7 polymers. In some embodiments, the second (outer) compartment comprises a blend of 8 polymers. In some embodiments, the second (outer) compartment comprises a blend of 9 polymers. In some embodiments, the second (outer) compartment comprises a blend of 10 polymers. In some embodiments, the first compartment comprises a blend of polymers and the second compartment does not comprise a blend of polymers. In some embodiments, the first compartment comprises a blend of polymers and the second compartment comprises a single type of polymer. In some embodiments, the first compartment does not comprise a blend of polymers and the second compartment comprises a blend of polymers. In some embodiments, the first compartment comprises a single type of polymer and the second compartment comprises a blend of polymers. In some embodiments, the first and second compartments comprise a blend of polymers and the polymers of the blend are any two miscible polymers. In some embodiments, the first and second compartments comprise a blend of polymers and the polymers are selected from the group consisting of: alginate, hyaluronate, and chitosan. In some embodiments, the first and second compartments comprise a blend of polymers and the polymers are selected from the group consisting of: alginate, hyaluronate, and chitosan. In some embodiments, the first compartment comprises a blend of polymers and the polymers are selected from the group consisting of: alginate, hyaluronate, and chitosan. In some embodiments, the second compartment comprises a blend of polymers and the polymers are selected from the group consisting of: alginate, hyaluronate, and chitosan. In some embodiments, the first and second compartments comprise a blend of alginate polymers. In some embodiments, the first compartment comprises a blend of alginate polymers. In some embodiments, the second compartment comprises a blend of alginate polymers. In some embodiments, the first and second compartments comprise a blend of alginate polymers and the alginate polymers are selected from high-guluronic acid alginate and high- mannuronic acid alginate. In some embodiments, the first compartment comprises a blend of alginate polymers and the alginate polymers are selected from high-guluronic acid alginate and high-mannuronic acid alginate. In some embodiments, the second compartment comprises a blend of alginate polymers and the alginate polymers are selected from high-guluronic acid alginate and high-mannuronic acid alginate. In some embodiments, the first and second compartments comprise a blend of alginate polymers and the alginate polymers are selected from low molecular weight alginate, medium molecular weight alginate, high molecular weight alginate, and ultra-high molecular weight alginate. In some embodiments, the first compartment comprises a blend of alginate polymers and the alginate polymers are selected from low molecular weight alginate, medium molecular weight alginate, high molecular weight alginate, and ultra-high molecular weight alginate. In some embodiments, the second compartment comprises a blend of alginate polymers and the alginate polymers are selected from low molecular weight alginate, medium molecular weight alginate, high molecular weight alginate, and ultra-high molecular weight alginate. In some embodiments, the first and second compartments comprise a blend of alginate polymers and the alginate polymers are selected from Kimica Algin IL-2, Kimica Algin IL-6, Kimica Algin I-1, Kimica Algin I-3, Kimica Algin I-5, Kimica Algin I-8, Kimica Algin LZ-2, Kimica Algin ULV-L3, Kimica Algin ULV-L5, Kimica Algin ULV-1G, Kimica Algin ULV-5G, Kimica Algin ULV IL-6G, Pronova UP VLVM, Pronova UP LVM, Pronova UP MVM, Pronova UP VLVG, Pronova UP MVG, Pronova UP LVG, Pronova SLM20, Pronova SLM100, Pronova SLG20, and Pronova SLG100. In some embodiments, the first compartment comprises a blend of alginate polymers and the alginate polymers are selected from Kimica Algin IL-2, Kimica Algin IL-6, Kimica Algin I-1, Kimica Algin I-3, Kimica Algin I-5, Kimica Algin I-8, Kimica Algin LZ- 2, Kimica Algin ULV-L3, Kimica Algin ULV-L5, Kimica Algin ULV-1G, Kimica Algin ULV- 5G, Kimica Algin ULV IL-6G, Pronova UP VLVM, Pronova UP LVM, Pronova UP MVM, Pronova UP VLVG, Pronova UP MVG, Pronova UP LVG, Pronova SLM20, Pronova SLM100, Pronova SLG20, and Pronova SLG100. In some embodiments, the second compartment comprises a blend of alginate polymers and the alginate polymers are selected from Kimica Algin IL-2, Kimica Algin IL-6, Kimica Algin I-1, Kimica Algin I-3, Kimica Algin I-5, Kimica Algin I-8, Kimica Algin LZ-2, Kimica Algin ULV-L3, Kimica Algin ULV-L5, Kimica Algin ULV-1G, Kimica Algin ULV-5G, Kimica Algin ULV IL-6G, Pronova UP VLVM, Pronova UP LVM, Pronova UP MVM, Pronova UP VLVG, Pronova UP MVG, Pronova UP LVG, Pronova SLM20, Pronova SLM100, Pronova SLG20, and Pronova SLG100. In some embodiments, the first and second compartments comprise a blend of two alginate polymers at any ratio. In some embodiments, the ratio of the two alginate polymers in the blend is about 99:1, 95:5, 90:10, 85:15, 80:20, 75:25, 70:30, 65:35, 60:40, 55:45, or 50:50. In some embodiments, the ratio of the two alginate polymers in the blend is about 99:1. In some embodiments, the ratio of the two alginate polymers in the blend is about 95:5. In some embodiments, the ratio of the two alginate polymers in the blend is about 90:10. In some embodiments, the ratio of the two alginate polymers in the blend is about 85:15. In some embodiments, the ratio of the two alginate polymers in the blend is about 80:20. In some embodiments, the ratio of the two alginate polymers in the blend is about 75:25. In some embodiments, the ratio of the two alginate polymers in the blend is about 70:30. In some embodiments, the ratio of the two alginate polymers in the blend is about 65:35. In some embodiments, the ratio of the two alginate polymers in the blend is about 60:40. In some embodiments, the ratio of the two alginate polymers in the blend is about 55:45. In some embodiments, the ratio of the two alginate polymers in the blend is about 50:50. In some embodiments, the first and second compartments comprise a blend of two alginate polymers at any ratio. In some embodiments, the ratio of the two alginate polymers in the blend is greater than about 99:1, 95:5, 90:10, 85:15, 80:20, 75:25, 70:30, 65:35, 60:40, 55:45, or 50:50. In some embodiments, the ratio of the two alginate polymers in the blend is greater than about 99:1. In some embodiments, the ratio of the two alginate polymers in the blend is greater than about 95:5. In some embodiments, the ratio of the two alginate polymers in the blend is greater than about 90:10. In some embodiments, the ratio of the two alginate polymers in the blend is greater than about 85:15. In some embodiments, the ratio of the two alginate polymers in the blend is greater than about 80:20. In some embodiments, the ratio of the two alginate polymers in the blend is greater than about 75:25. In some embodiments, the ratio of the two alginate polymers in the blend is greater than about 70:30. In some embodiments, the ratio of the two alginate polymers in the blend is greater than about 65:35. In some embodiments, the ratio of the two alginate polymers in the blend is greater than about 60:40. In some embodiments, the ratio of the two alginate polymers in the blend is greater than about 55:45. In some embodiments, the ratio of the two alginate polymers in the blend is greater than about 50:50. In some embodiments of the invention, the first and second compartments comprise a blend of VLVG alginate and SLG100 alginate. In some embodiments of the invention, the first compartment comprises a blend of VLVG alginate and SLG100 alginate. In some embodiments of the invention, the second compartment comprises a blend of VLVG alginate and SLG100 alginate. In some embodiments of the invention, the first and second compartments comprise a blend of VLVG alginate and SLG100 alginate. In some embodiments of the invention, the first compartment comprises a blend of VLVG alginate and SLG100 alginate. In some embodiments of the invention, the second compartment comprises a blend of VLVG alginate and SLG100 alginate. In some embodiments, the polymer in one or both of the first and second compartments is (i) a low-molecular weight alginate, e.g., has an approximate MW < 75 kDa and G:M ratio ≥ 1.5, (ii) a medium molecular weight alginate, e.g., has approximate molecular weight of 75-150 kDa and G:M ratio ≥ 1.5, (iii) a high molecular weight alginate, e.g., has an approximate MW of 150 kDa – 250 kDa and G:M ratio ≥ 1.5, (iv) or a blend of two or more of these alginates. In an embodiment, the polymer in the first (inner) compartment is an unmodified, high molecular weight alginate or an unmodified, medium molecular weight alginate and the polymer in the second (outer) compartment is a blend of a chemically-modified alginate (e.g., alginate modified with Compound 101 shown in Table 3) and an unmodified alginate, e.g, a 70:30 blend or a 60:40 blend of CM-LMW-Alg-101:U-HMW-Alg, which may be prepared as described in the Examples below. In some embodiments, the particle (e.g., hydrogel capsule) comprises alginate, and the compound of Formula (I) is covalently attached to some or all the monomers in the alginate. In some embodiments, some or all the monomers in the alginate are modified with the same compound of Formula (I). In some embodiments, some or all the monomers in the alginate are modified with different compounds of Formula (I). In some embodiments, a polymer of the first compartment of the particle (e.g., hydrogel capsule) is modified with one compound of Formula (I), and a polymer of the second compartment of the particle (e.g., hydrogel capsule) is modified with a different compound of Formula (I). In some embodiments, the particle (e.g., hydrogel capsule) comprises a mixture of polymers modified with a compound of Formula (I) and unmodified polymers (e.g., polymers not modified with a compound of Formula (I)). In some embodiments, the first compartment comprises a mixture of polymers modified with a compound of Formula (I) and unmodified polymers (e.g., polymers not modified with a compound of Formula (I)). In some embodiments, the second compartment comprises a mixture of polymers modified with a compound of Formula (I) and unmodified polymers (e.g., polymers not modified with a compound of Formula (I)). A polymer of the particle (e.g., hydrogel capsule) described herein may be modified with a compound of Formula (I) or a pharmaceutically acceptable salt thereof on one or more monomers of the polymer. The modified polymer of the particle may be present in the first (inner) compartment of the particle (e.g., hydrogel capsule), the second (outer) compartment of the particle (e.g., hydrogel capsule), or both the first (inner) and second (outer) compartments of the particle (e.g., hydrogel capsule). In some embodiments, the modified polymer is present only in the second compartment (which includes the exterior particle surface). In some embodiments, at least 0.5% of the monomers of a polymer are modified with a compound of Formula (I) (e.g., at least 1%, 2.5%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%, or more of the monomers of a polymer are modified with a compound of Formula (I)). In some embodiments, 0.5% to 50%, 10% to 90%, 10% to 50%, or 25-75%, of the monomers of a polymer are modified with a compound of Formula (I). In some embodiments, 1% to 20% of the monomers of a polymer are modified with a compound of Formula (I). In some embodiments, 1% to 10% of the monomers of a polymer are modified with a compound of Formula (I). In some embodiments, the polymer (e.g., alginate) (when modified with a compound of Formula (I), e.g., Compound 101 of Table 3) comprises an increase in % N (as compared with unmodified polymer, e.g., alginate) of any of the following values: (i) at least 0.1%, 0.2%, 0.5%, 1.0%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, or 10% N by weight; (ii) 0.1% to 10% by weight, (iii) 0.1% to 2% N by weight; (iv) 2% to 4% N by weight; (v) 4% to 8% N by weight; (vi) 5% to 9% N by weight; (vii) 6% to 9% N by weight, (viii) 6% to 8% N by weight; (ix) 7% to 9% N by weight; and (x) 8% to 9% N by weight where, in each case, % N is determined by combustion analysis (e.g., as described in Example 2 herein) and corresponds to the amount of compound of Formula (I) in the modified polymer. The particle (e.g., hydrogel capsule) (e.g., a first compartment or second compartment therein) may comprise a compound of Formula (I) in an amount that confers a specific feature to the particle. For example, the hydrogel capsule surface (e.g., the exterior of the outer compartment) may comprise a concentration or density of a compound of Formula (I) such that the hydrogel capsule is afibrotic (i.e., mitigates the foreign body response) in a subject. In an embodiment, the hydrogel capsule surface comprises an alginate chemically modified with an afibrotic-effective amount of Compound 101. In an embodiment, the afibrotic-effective amount of Compound 101 produces an increase in % N (as compared with the unmodified alginate) of about 0.5% to 2% 2% to 4% N, about 4% to 6% N, about 6% to 8%, or about 8% to 10% N), where % N is determined by combustion analysis (e.g., as described in Example 2 herein) and corresponds to the amount of Compound 101 in the modified alginate. In an embodiment, mechanical testing of hydrogel capsules is performed on a TA.XT plus Texture Analyzer (Stable Micro Systems, Surrey, United Kingdom) using a 5mm probe attached to a 5kg load cell. Individual capsules are placed on a platform and are compressed from above by the probe at a fixed rate of 0.5mm / sec. Contact between the probe and capsule is detected when a repulsive force of 1g is measured. The probe continues to travel 90% of the distance between the contact height of the probe and the platform, compressing the capsule to the point of bursting. The resistance to the compressive force of the probe is measured and can be plotted as a function of probe travel (force v. displacement curve). Typically, before a capsule bursts completely it will fracture slightly and the force exerted against the probe will decrease a small amount. An analysis macro can be programmed to detect the first time a decrease of 0.25-0.5g occurs in the force v. displacement curve. The force applied by the probe when this occurs is termed the initial fracture force. In an embodiment, the desired mechanical strength of a particle described herein (e.g., a two-compartment hydrogel capsule) has an initial fracture force of greater than 1, 1.5, 2, 2.5 or 3 grams or at least 2 grams. In an embodiment, the desired mechanical strength of the hydrogel capsule is the ability to remain intact at a desired timepoint after implantation in a subject, e.g., both the outer and inner compartments of a particle (e.g., hydrogel capsule) removed from a subject are visibly intact after retrieval from an immune competent mouse when observed by optical microscopy, e.g., by brightfield imaging as described in the Examples herein. In an embodiment, the hydrogel capsule surface comprises an alginate chemically modified with Compound 101 in an amount that provides the particle with both an afibrotic property and a desired mechanical strength, e.g., a concentration or density of Compound 101 in the modified alginate that produces an increase in %N (as compared with the unmodified alginate) of any of the following values: (i) 1% to 3% by weight, (ii) 2% to 4% N by weight; (iii) 4% to 8% N by weight; (iv) 5% to 9% N by weight; (v) 6% to 9% N by weight, (vi) 6% to 8% N by weight; (vii) 7% to 9% N by weight; and (ix) 8% to 9% N by weight; where, in each case, % N is determined by combustion analysis (e.g., as described in Example 2 herein) and corresponds to the amount of compound of Formula (I) in the modified alginate. When the hydrogel capsule (e.g., a first compartment or second compartment therein) comprises alginate, the alginate can be chemically modified with a compound of Formula (I) using any suitable method known in the art. For example, the alginate carboxylic acid moiety can be activated for coupling to one or more amine-functionalized compounds to achieve an alginate modified with a compound of Formula (I). The alginate polymer may be dissolved in water (30 mL / gram polymer) and treated with 2-chloro-4,6-dimethoxy-1,3,5-triazine (0.5 eq) and N- methylmorpholine (1 eq). To this mixture may be added a solution of the compound of Formula (I) dissolved in a buffer or solvent, such as acetonitrile (0.3 M). The reaction may be warmed, e.g., to 55 oC for 16h, then cooled to room temperature and concentrated via rotary evaporation. The residue may then be dissolved in a buffer or solvent, e.g., water. The mixture may then be filtered, e.g., through a bed of cyano-modified silica gel (Silicycle) and the filter cake washed with water. The resulting solution may then be dialyzed (10,000 MWCO membrane) against a buffer or water for 24 hours, e.g., replacing the buffer or water at least one time, at least two times, at least three times, or more. The resulting solution can be concentrated, e.g., via lyophilization, to afford the desired chemically modified alginate. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising a blend of VLVG and SLG100 alginate, wherein the VLVG alginate comprises compound 101 and the SLG100 alginate is unmodified; and, (ii) an outer compartment comprising a blend of VLVG and SLG100 alginate, wherein the VLVG alginate comprises compound 101 and the SLG100 alginate is unmodified. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising a blend of VLVG and SLG100 alginate, wherein the VLVG alginate comprises compound 101 and the SLG100 alginate comprises compound 205; and, (ii) an outer compartment comprising a blend of VLVG and SLG100 alginate, wherein the VLVG alginate comprises compound 101 and the SLG100 alginate comprises compound 205. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 200. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 201. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 202. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 203. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 204. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 205. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 214. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 215. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 216. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 217. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 218. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 219. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 200. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 201. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 202. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 203. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 204. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 205. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 214. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 215. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 216. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 217. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 218. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 219. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100 comprising compound 101 and compound 201. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100 comprising compound 101 and compound 202. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100 comprising compound 101 and compound 203. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100 comprising compound 101 and compound 204. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100 comprising compound 101 and compound 205. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100 comprising compound 101 and compound 214. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100 comprising compound 101 and compound 215. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100 comprising compound 101 and compound 216. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100 comprising compound 101 and compound 217. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100comprising compound 101 and compound 218. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100 comprising compound 101 and compound 219. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 200. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 201. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 202. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 203. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 204. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 205. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114and compound 214. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 215. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 216. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 217. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 218. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 219. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 200. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 201. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 202. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 203. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 204. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 205. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 214. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 215. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 216. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 217. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 218. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 comprising compound 114 and compound 219. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100 comprising compound 114 and compound 201. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100 comprising compound 114 and compound 202. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100 comprising compound 114 and compound 203. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100 comprising compound 114 and compound 204. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100 comprising compound 114 and compound 205. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100 comprising compound 114and compound 214. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100 comprising compound 114 and compound 215. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100 comprising compound 114 and compound 216. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100 comprising compound 114 and compound 217. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100 comprising compound 114 and compound 218. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate; and, (ii) an outer compartment comprising SLG100 comprising compound 114 and compound 219. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG20 alginate; and (ii) an outer compartment comprising LG20 alginate modified with compound 101 and compound 205. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG20 alginate; and (ii) an outer compartment comprising LG20 alginate modified with compound 101 and compound 200. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG20 alginate; and (ii) an outer compartment comprising LG20 alginate modified with compound 101 and compound 201. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG20 alginate; and (ii) an outer compartment comprising LG20 alginate modified with compound 101 and compound 202. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG20 alginate; and (ii) an outer compartment comprising LG20 alginate modified with compound 101 and compound 203. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG20 alginate; and (ii) an outer compartment comprising LG20 alginate modified with compound 101 and compound 204. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG20 alginate; and (ii) an outer compartment comprising LG20 alginate modified with compound 101 and compound 206. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG20 alginate; and (ii) an outer compartment comprising LG20 alginate modified with compound 114 and compound 205. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG20 alginate; and (ii) an outer compartment comprising LG20 alginate modified with compound 114 and compound 200. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG20 alginate; and (ii) an outer compartment comprising LG20 alginate modified with compound 114 and compound 201. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG20 alginate; and (ii) an outer compartment comprising LG20 alginate modified with compound 114 and compound 202. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG20 alginate; and (ii) an outer compartment comprising LG20 alginate modified with compound 114 and compound 203. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG20 alginate; and (ii) an outer compartment comprising LG20 alginate modified with compound 114 and compound 204. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG20 alginate; and (ii) an outer compartment comprising LG20 alginate modified with compound 114 and compound 206. Cells and Therapeutic Agents The particles (e.g., hydrogel capsules) described herein comprises an islet cell. In some embodiments, the islet cell produces insulin. In some embodiments, the islet cell is engineered to produce insulin. In some embodiments, the islet cell is engineered to produce another therapeutic agent (e.g., a protein or polypeptide, e.g., an antibody, protein, enzyme, or growth factor). In some embodiments, the islet cell is disposed with the first compartment. In some embodiments, the islet cell is disposed within the second compartment. In some embodiments, the islet cell is disposed in the first compartment and the second compartment does not comprise an islet cell. The particle (e.g., hydrogel capsule) described herein may be configured to release a therapeutic agent described herein (e.g., insulin). In some embodiments, the therapeutic agent is a biological material. In some embodiments, the therapeutic agent is insulin. The particle (e.g., hydrogel capsule) (e.g., as described herein) may be provided as a preparation or composition for implantation or administration to a subject. In some embodiments, at least 20%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100% of the hydrogel capsules in a preparation or composition have a characteristic as described herein, e.g., mean diameter or mean pore size. In an embodiment, the particle (e.g., hydrogel capsules) described herein comprise a plurality of islet cells. In an embodiment, the plurality of islet cells is in the form of a cell suspension prior to being encapsulated within a hydrogel capsule described herein. The cells in the suspension may take the form of single cells (e.g., from a monolayer cell culture), or provided in another form, e.g., disposed on a microcarrier (e.g., a bead or matrix) or as a three- dimensional aggregate of cells (e.g., a cell cluster or spheroid). The cell suspension can comprise multiple cell clusters (e.g., as spheroids) or microcarriers. In some embodiments, the particle (e.g., hydrogel capsules) of the present disclosure decrease immune cell adhesion compared to an untreated control, e.g., a substantially identical particle (e.g., hydrogel capsule) lacking a compound of Formula (I). In an embodiment, the particle (e.g., hydrogel capsules) decrease macrophage adhesion compared to an untreated control. In an embodiment, the decrease in macrophage adhesion is between about 1 fold and 10 fold less than an untreated control. In an embodiment, the decrease in macrophage adhesion is between about 1-fold and 8 fold less than an untreated control. In an embodiment, the decrease in macrophage adhesion is between about 1-fold and 7 fold less than an untreated control. In an embodiment, the decrease in macrophage adhesion is between about 1-fold and 6 fold less than an untreated control. In an embodiment, the decrease in macrophage adhesion is between about 1-fold and 5 fold less than an untreated control. The hydrogels or particles (e.g., hydrogel capsules) of the present disclosure allow encapsulated islet cells (e.g., engineered cells) to retain viability (e.g., as determined by a cell viability assay). In some embodiments, the hydrogel capsule allows encapsulated islet cells to retain viability for at least seven days, at least one month, or at least one year. The present disclosure features particle (e.g., hydrogel capsules) comprising (i) a polysaccharide polymer described herein and (ii) an islet cell that produces or is capable of producing a therapeutic agent (e.g., insulin) for the prevention or treatment of a disease, disorder, or condition (e.g., Type 1 diabetes). In an embodiment, the islet cell is a naturally occurring islet cell, e.g., is not engineered. In an embodiment, the islet cell is an engineered islet cell. In an embodiment, the islet cell is engineered to sense a stimulus, e.g., a chemical signal, and express the therapeutic agent in response to the stimulus. In an embodiment, the islet cell is differentiated from a stem cell, e.g., an induced pluripotent stem cell, and the differentiated cell is capable of producing the therapeutic agent (e.g., insulin), either continuously or in response to a stimulus. In some embodiments, the therapeutic agent is insulin (e.g., insulin A-chain, insulin B-chain, or proinsulin). In some embodiments, the islet cell described herein produces insulin. In some embodiments, the therapeutic agent secreted or released from the islet cell (e.g., insulin) in an active form. In some embodiments, the therapeutic agent (e.g., insulin) is secreted or released from a cell in an inactive form, e.g., as a prodrug. In some embodiments, the hydrogel capsules described herein comprise mammalian cells at a concentration of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, or 50 M mL-1. In some embodiments, the hydrogel capsules described herein comprise mammalian cells at a concentration of about 1 M mL-1. In some embodiments, the hydrogel capsules described herein comprise mammalian cells at a concentration of about 2 M mL-1. In some embodiments, the hydrogel capsules described herein comprise mammalian cells at a concentration of about 3 M mL-1. In some embodiments, the hydrogel capsules described herein comprise mammalian cells at a concentration of about 4 M mL-1. In some embodiments, the hydrogel capsules described herein comprise mammalian cells at a concentration of about 5 M mL-1. In some embodiments, the hydrogel capsules described herein comprise mammalian cells at a concentration of about 6 M mL-1. In some embodiments, the hydrogel capsules described herein comprise mammalian cells at a concentration of about 7 M mL-1. In some embodiments, the hydrogel capsules described herein comprise mammalian cells at a concentration of about 8 M mL-1. In some embodiments, the hydrogel capsules described herein comprise mammalian cells at a concentration of about 9 M mL-1. In some embodiments, the hydrogel capsules described herein comprise mammalian cells at a concentration of about 10 M mL-1. In some embodiments, the hydrogel capsules described herein comprise mammalian cells at a concentration of about 15 M mL-1. In some embodiments, the hydrogel capsules described herein comprise mammalian cells at a concentration of about 20 M mL-1. In some embodiments, the hydrogel capsules described herein comprise mammalian cells at a concentration of about 25 M mL-1. In some embodiments, the hydrogel capsules described herein comprise mammalian cells at a concentration of about 30M mL-1. In some embodiments, the hydrogel capsules described herein comprise mammaliancells at a concentration of about 35 M mL-1. In some embodiments, the hydrogel capsules described herein comprise mammalian cells at a concentration of about 40 M mL-1. In some embodiments, the hydrogel capsules described herein comprise mammalian cells at a concentration of about 45 M mL-1.In some embodiments, the hydrogel capsules described herein comprise mammalian cells at a concentration of about 50 M mL-1. In some embodiments, the hydrogel capsules described herein comprise mammalian cells at a concentration between about 1-50 M mL-1, 1-45 M mL-1, 1-40 M mL-1, 1-35 M mL-1, 1-30 M mL-1, 1-25 M mL-1, 1-20 M mL-1, 1-15 M mL-1, 1-10 M mL-1, 1-5 M mL-1, 5-50 M mL-1, 5-45 M mL-1, 5-40 M mL-1, 5-35 M mL-1, 5-30 M mL-1, 5-25 M mL-1, 5-20 M mL-1, 5-15 M mL-1, 5- 10 M mL-1, 10-50 M mL-1, 10-45 M mL-1, 10-40 M mL-1, 10-35 M mL-1, 10-30 M mL-1, 10-25 M mL-1, 10-20 M mL-1, 10-15 M mL-1, 15-50 M mL-1, 15-45 M mL-1, 15-40 M mL-1, 15-35 M mL-1, 15-30 M mL-1, 15-25 M mL-1, 15-20 M mL-1, 20-50 M mL-1, 20-45 M mL-1, 20-40 M mL-1, 20-35 M mL-1, 20-30 M mL-1, or 20-25 M mL-1. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising a blend of VLVG and SLG100 alginate, wherein the VLVG alginate comprises compound 101 and the SLG100 alginate is unmodified, and mammalian cells at a concentration between 5-25 M mL-1; and, (ii) an outer compartment comprising a blend of VLVG and SLG100 alginate, wherein the VLVG alginate comprises compound 101 and the SLG100 alginate is unmodified. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising a blend of VLVG and SLG100 alginate, wherein the VLVG alginate comprises compound 101 and the SLG100 alginate comprises compound 205, and mammalian cells at a concentration between 5-25 M mL-1; and, (ii) an outer compartment comprising a blend of VLVG and SLG100 alginate, wherein the VLVG alginate comprises compound 101 and the SLG100 alginate comprises compound 205. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG100 alginate and mammalian cells at a concentration between 5-25 M mL-1; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 205. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified SLG20 alginate and mammalian cells at a concentration between 5-25 M mL-1; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 205. In some embodiments, the hydrogel capsule comprises: (i) an inner compartment comprising unmodified LG20 alginate and mammalian cells at a concentration between 5-25 M mL-1; and, (ii) an outer compartment comprising LG20 comprising compound 101 and compound 205. Methods of Treatment Described herein are methods for preventing or treating a disease, disorder, or condition in a subject through administration or implantation of a hydrogel capsule comprising (i) a polysaccharide polymer described herein and (ii) an islet cell. In some embodiments, the methods described herein directly or indirectly reduce or alleviate at least one symptom of a disease, disorder, or condition (e.g., Type 1 diabetes). In some embodiments, the methods described herein prevent or slow the onset of a disease, disorder, or condition (e.g., Type 1 diabetes). In some embodiments, the subject is a human. In some embodiments, the disease, disorder, or condition affects a system of the body, e.g. the nervous system (e.g., peripheral or central nervous system), vascular system, skeletal system, respiratory system, endocrine system, lymph system, reproductive system, or gastrointestinal tract. In some embodiments, the disease, disorder, or condition affects a part of the body, e.g., blood, eye, brain, skin, lung, stomach, mouth, ear, leg, foot, hand, liver, heart, kidney, bone, pancreas, spleen, large intestine, small intestine, spinal cord, muscle, ovary, uterus, vagina, or penis. In some embodiments, the disease, disorder or condition is an autoimmune disease. In some embodiments, the disease, disorder, or condition is diabetes (Type 1 or Type 2). The present disclosure further comprises methods for identifying a subject having or suspected of having a disease, disorder, or condition described herein (e.g., Type 1 diabetes), and upon such identification, administering to the subject an a hydrogel capsule comprising (i) a polysaccharide polymer described herein and (ii) an islet cell, e.g., wherein the hydrogel capsule is optionally modified with a compound of Formula (I), or a composition thereof. In an embodiment, the subject has or is diagnosed with having diabetes (e.g., Type 1 diabetes). The subject may have any biomarker or other diagnostic criteria associated with diabetes, such as a high blood glucose level (e.g., greater than 300 mg / dL, greater than 400 mg / dL) or a high hemoglobin A1C level (e.g., a hemoglobin A1C level greater than 5.9%, a hemoglobin A1C level greater than 6.5%, a hemoglobin A1C level greater than 7%). In an embodiment, the subject is a human. In an embodiment, the subject is an adult. In an embodiment, the subject is a child (e.g., a subject less than 21 years of age, less than 18 years of age, less than 15 years of age, less than 12 years of age, less than 10 years of age, or less than 6 years of age). Methods of Making Particles The present disclosure further comprises methods for making a hydrogel capsule described herein, e.g., a hydrogel capsule comprising a polysaccharide polymer comprising a first compartment, a second compartment, a photoactive crosslinking moiety, and a compound of Formula (I). In some embodiments, the method of making the hydrogel capsule comprises contacting a plurality of droplets comprising first and second polymer solutions (e.g., each comprising a hydrogel-forming polymer) with an aqueous cross-linking solution. In an embodiment, the aqueous cross-linking solution comprises an ionic cross-linking agent, e.g., a divalent cation such as calcium, barium and magnesium. The droplets can be formed using any technique known in the art. In further embodiments where the particle is a hydrogel capsule, the method of making the hydrogel capsule comprises an irradiation step, in which a solution comprising a polysaccharide polymer is exposed to ultraviolet light to initiate the photocrosslinking reaction. In an embodiment, one or both of the first and second polymer solutions may further contain a photoinitiator. Each compartment of a hydrogel capsule described herein may comprise any one or more of the following: an unmodified polymer, a polymer modified with one or both of a compound of Formula (I) and a photoactive crosslinking moiety, or a blend of the unmodified and modified polymers. Briefly, in performing a method of preparing a hydrogel capsule configured as a two- compartment hydrogel capsule, a volume of a first polymer solution (e.g., comprising an unmodified polymer, a polymer modified with a compound of Formula (I), a photoactive crosslinking moiety, or a blend thereof, and optionally containing cells,) is loaded into a first syringe connected to the inner lumen of a coaxial needle. The first syringe may then be connected to a syringe pump oriented vertically above a vessel containing an aqueous cross- linking solution which comprises a cross-linking agent, a buffer, and an osmolarity-adjusting agent. A volume of the second polymer solution (e.g., comprising an unmodified polymer, a polymer modified with a compound of Formula (I), a photoactive crosslinking moiety, or a blend thereof, and optionally containing cells) is loaded into a second syringe connected to the outer lumen of the coaxial needle. The second syringe may then be connected to a syringe pump oriented horizontally with respect to the vessel containing the cross-linking solution. A high voltage power generator may then be connected to the top and bottom of the needle. The syringe pumps and power generator can then be used to extrude the first and second polymer solutions through the syringes with settings determined to achieve a desired droplet rate of polymer solution into the cross-linking solution. The skilled artisan may readily determine various combinations of needle lumen sizes, voltage range, flow rates, droplet rate and drop distance to create 2-compartment hydrogel capsule compositions in which the majority (e.g., at least 80%, 85%, 90% or more) of the capsules are within 10% of the target size and have a sphere-like shape. After exhausting the first and second volumes of polymer solution, the droplets may be allowed to crosslink in the crosslinking solution for certain amount of time, e.g., about five minutes. Crosslinking may entail ionic crosslinking (e.g., by contacting the droplets with an ionic crosslinking agent, e.g., a divalent cation) and / or covalent crosslinking (e.g., by irradiating the droplets to activatea photoactive crosslinking agent, e.g., methacrylate or methacrylamide). Exemplary process parameters for preparing a composition of millicapsules (e.g., 1.5 mm diameter millicapsules) include the following. A coaxial needle is disposed above the surface of the cross-linking solution at a distance sufficient to provide a drop distance from the needle tip to the solution surface. In an embodiment, the distance between the needle tip and the solution surface is between 1 to 5 cm. In an embodiment, the first and second polymer solutions are extruded through the needle with a total flow rate of between 0.05 mL / min to 5 mL / min, or 0.05 mL / min to 2.5 mL / min, or 0.05 mL / min to about 1 mL / min, or 0.05 mL / min to 0.5 mL / min, or 0.1 mL / min to 0.5 mL / min. In an embodiment, the first and second polymer solutions are extruded through the needle with a total flow rate of about 0.05 mL / min, 0.1 mL / min, 0.15 mL / min, 0.2 mL / min, 0.25 mL / min, 0.3 mL / min, 0.35 mL / min, 0.4 mL / min, 0.45 mL / min, or 0.5 mL / min. In an embodiment, the flow rate of the first and second polymer solutions through the needle are substantially the same. In an embodiment, the flow rate of the first and second polymer solutions through the needle are different. In an embodiment, the voltage of the instrument is between 1 kV to 20kV, or 1 to 15 kV, or 1 kV to 10 kV, or 5 kV to 10 kV. The voltage may be adjusted until a desired droplet rate is reached. In an embodiment, the droplet rate of the instrument is between 1 droplet / 10 seconds to 50 droplets / 10 seconds, or 1 droplet / 10 seconds to 25 droplets / 10 seconds. In an embodiment, the number of non-particle debris on the surface of the cross-linking solution is determined. Hydrogel capsules that have fallen to the bottom of the cross-linking vessel may then be collected, e.g., by transferring cross-linking solution containing the hydrogel capsule to a separate container, leaving behind any non-particle debris on the solution surface in the original cross-linking vessel. The removed hydrogel capsule may then be allowed to settle, the cross-linking solution can be removed, and the hydrogel capsule may then be washed one or more times with a buffer (e.g., a HEPES buffer). In an embodiment, one or more aliquots of the resulting hydrogel capsule composition (e.g., preparation of hydrogel capsule) is inspected by microscopy to assess the quality of the composition, e.g., the number of hydrogel capsule defects and satellite hydrogel capsule. In some embodiments, the cross-linking solution further comprises a process additive (e.g., a hydrophilic, non-ionic surfactant). A process additive may reduce surface tension of the cross-linking solution. Agents useful as the process additive in the present disclosure include polysorbate-type surfactants, copolymer of polyethyleneoxide (PEO) and polypropyleneoxide (PPO), poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers, and non-ionic surfactants, such as Tween®20, Tween®80, TritonTMX-100, IGEPAL® CA-630, poloxamer 188, or poloxamer 407, or surfactants with substantially the same chemical and physical properties listed in the Exemplary Surfactant Table immediately below.a hydrophilic-lipophilic balancebChemical names and synonyms: polyethylene glycol sorbitan monolaurate, polyoxyethylene (20) sorbitan monolaurate, polysorbate 20, polyoxyethylene 20 sorbitan monododecanoatecChemical names and synonyms: polyethylene glycol sorbitan monooleate, polyoxyethylene (20) sorbitan monooleate, polysorbate 80, (x)-sorbitan mono-9-octadecenoate poly(oxy-1,2-ethanediyl)dChemical names and synonyms: 4-(1,1,3,3-Tetramethylbutyl)phenyl-polyethylene glycol, t-octylphenoxypolyethoxyethanol, polyethylene glycol tert-octylphenyl ether; octylphenol ethoxylate, octylphenol ethylene oxide condensateeChemical names and synonyms: octylphenoxypolyethoxyethanol, octylphenoxy poly(ethyleneoxy)ethanol, branchedfChemical name: Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol)gChemical name: Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) In some embodiments, the process additive is a non-ionic surfactant. In an embodiment, the process additive comprises more than one surfactant, e.g., more than one hydrophilic surfactant. In some embodiments, the process additive does not contain Tween® 20 (polysorbate 20) or TritonTMX-100. In an embodiment, the process additive is IGEPAL® CA-630 (polyethylene glycol sorbitan monooleate). In some embodiments, the process additive is poloxamer 188. In some embodiments, the process additive (e.g., surfactant) is present in the cross- linking solution at a concentration of at least 0.0001% or more. In some embodiments, the cross- linking solution comprises at least 0.001%, 0.01%, or 0.1% of the process additive. In some embodiments, the process additive is present at a concentration selected from about 0.001% to about 0.1%, about 0.005% to about 0.05%, about 0.005% to about 0.01%, and about 0.01% to about 0.5%. In an embodiment, the process additive is a surfactant and is present at a concentration that is below the critical micelle concentration for the surfactant. In some embodiments, the ionic crosslinking agent comprises divalent cations of a single type or a mixture of different types, e.g., one or more of Ba2+, Ca2+, Sr2+. In some embodiments, the ionic crosslinking agent is BaCl2, e.g., at a concentration of 1 mM to 100 mM or 7.5 mM to 20 mM. In some embodiments, the ionic crosslinking agent is CaCl2, e.g., at a concentration of 50 mM to 100 mM. In some embodiments, the ionic crosslinking agent is SrCl2, e.g., at a concentration of 37.5 mM to 100 mM. In some embodiments, the ionic crosslinking agent is a mixture of BaCl2 (e.g., 5 mM to 20 mM) and CaCl2 (e.g., 37.5 mM to 12.5 mM) or a mixture of BaCl2 (e.g., 5 mM to 20 mM) and SrCl2 (e.g., 37.5 mM to 12.5 mM). In some embodiments, the ionic crosslinking agent is SrCl2, and the process additive is Tween®80 (or a surfactant with substantially the same chemical and physical properties listed in the Exemplary Surfactant Table) at a concentration of less than 0.1%, e.g., about 0.005% to 0.05%, about 0.005% to about 0.01%. In some embodiments, the concentration of SrCl2 is about 50 mM. In some embodiments, the ionic crosslinking agent is SrCl2and the process additive is poloxamer 188 at a concentration of 1%. The type and concentration of buffer in the aqueous cross-linking solution is selected to maintain the solution pH at approximately neutral, e.g., from about 6.5 to about 7.5, about 7.0 to about 7.5, or about 7.0. In an embodiment, the buffer is compatible with a biological material to be encapsulated in the particle, e.g., cells. In some embodiments, the buffer in the aqueous cross-linking solution comprises HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid). The osmolarity-adjusting agent in the aqueous cross-linking solution is selected to maintain the solution osmolarity at a value similar to the osmolarity of the polymer solution (which in some embodiments comprises a suspension of cells), e.g., an osmolarity that has a higher or lower variance of up to 20%, 10% or 5%. In some embodiments, the osmolarity agent is mannitol at a concentration of 0.1 M to 0.3 M. In some embodiments, the cross-linking solution comprises 25 mM HEPES buffer, 20 mM BaCl2, 0.2 M mannitol and 0.01% poloxamer 188. In some embodiments, the cross-linking solution comprises 50 mM strontium chloride hexahydrate, 0.165 M mannitol, 25 mM HEPES and 0.01% of a surfactant with substantially the same chemical and physical properties listed in the Exemplary Surfactant Table for Tween 80. In an embodiment, the process additive is poloxamer 188, which is present in the particle composition (e.g., preparation of particles) in a detectable amount after the wash steps. Poloxamer 188 may be detected by any technique known in the art, e.g., by partially or completely dissolving the particles in an aliquot of the composition by sodium sulfate precipitation and analyzing the supernatant by LC / MS. Reduction in the surface tension of the cross-linking solution may be assessed by any method known in the art, for example, through the use of a contact angle goniometer or a tensiometer, e.g., via the du Nouy ring method (see, e.g., Davarci et al (2017) Food Hydrocolloids 62:119-127). EXEMPLARY ENUMERATED EMBODIMENTS 1. A polysaccharide polymer comprising: (i) a photoactive crosslinking moiety; and (ii) a compound of Formula (I): or a pharmaceutically ac ceptab e sa t t ereo , w ere n: A is alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, –O–, –C(O)O–, –C(O)–, –OC(O)–, –N(RC)–, –N(RC)C(O)–, –C(O)N(RC)–, –N(RC)N(RD)–, –NCN–, – N(RC)C(O)(C1-C6- alkylene)–, -N(RC)C(O)(C2-C6-alkenylene)–, –C(=N(RC)(RD))O–, –S–, –S(O)x–, –OS(O)x–, –N(RC)S(O)x–, –S(O)xN(RC)–, –P(RF)y–, –Si(ORA)2–, –Si(RG)(ORA)–, –B(ORA)–, or a metal, each of which is optionally linked to an attachment group (e.g., an attachment group described herein) and optionally substituted by one or more R1; each of L1and L3is independently a bond, alkyl, or heteroalkyl, wherein each alkyl and heteroalkyl is optionally substituted by one or more R2; L2is a bond; M is absent, alkyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, each of which is optionally substituted by one or more R3; P is heteroaryl optionally substituted by one or more R4; Z is alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, each of which is optionally substituted by one or more R5; each RA, RB, RC, RD, RE, RF, and RGis independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, azido, cycloalkyl, heterocyclyl, aryl, or heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, and heteroaryl is optionally substituted with one or more R6; or RCand RD, taken together with the nitrogen atom to which they are attached, form a ring (e.g., a 5-7 membered ring), optionally substituted with one or more R6; each R1, R2, R3, R4, R5, and R6is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, –N(RC1)(RD1), – N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, S(O)xRE1, –OS(O)xRE1, –N(RC1)S(O)xRE1, – S(O)xN(RC1)(RD1), –P(RF1)y, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, and heteroaryl is optionally substituted by one or more R7; each RA1, RB1, RC1, RD1, RE1, and RF1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted by one or more R7; each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl; x is 1 or 2; and y is 2, 3, or 4. 2. The polysaccharide polymer of embodiment 1, wherein the photoactive crosslinking moiety is covalently bound to a saccharide monomer within the polysaccharide polymer. 3. The polysaccharide polymer of embodiment 2, wherein the photoactive crosslinking moiety is bound to a carboxylate moiety within the saccharide monomer. 4. The polysaccharide polymer of any one of embodiments 1-3, wherein the photoactive crosslinking moiety comprises an alkyl, alkenyl, alkynyl, ester, ketone, amine, or amide group. 5. The polysaccharide polymer of any one of embodiments 1-3, wherein the photoactive crosslinking moiety comprises an alkyl group. 6. The polysaccharide polymer of any one of embodiments 1-3, wherein the photoactive crosslinking moiety comprises an alkenyl group. 7. The polysaccharide polymer of any one of embodiments 1-3, wherein the photoactive crosslinking moiety comprises an alkynyl group. 8. The polysaccharide polymer of any one of embodiments 1-3, wherein the photoactive crosslinking moiety comprises an ester group. 9. The polysaccharide polymer of any one of embodiments 1-3, wherein the photoactive crosslinking moiety comprises an ketone group. 10. The polysaccharide polymer of any one of embodiments 1-3, wherein the photoactive crosslinking moiety comprises an amine group. 11. The polysaccharide polymer of any one of embodiments 1-3, wherein the photoactive crosslinking moiety comprises an amide group. 12. The polysaccharide polymer of any one of embodiments 1-11, wherein the photoactive crosslinking moiety is capable of reacting with a second photoactive crosslinking moiety upon activation with light (e.g., ultraviolet light). 13. The polysaccharide polymer of any one of embodiments 1-12, wherein the photoactive crosslinking moiety is present on the polysaccharide polymer at a density of at least about 1%, e.g., 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or more, e.g., as determined (e.g., by an LC-MS assay) by comparison to a reference standard. 14. The polysaccharide polymer of any one of embodiments 1-13, wherein the photoactive crosslinking moiety is present on the polysaccharide polymer at a density of between 1%-10%, e.g., 1%-8%, 1%-6%, or 1%-4%, e.g., as determined by comparison to a reference standard. 15. The polysaccharide polymer of any one of embodiments 1-14, wherein the photoactive crosslinking moiety is present on the polysaccharide polymer at a density of between 1%-8%, e.g., as determined by comparison to a reference standard. 16. The polysaccharide polymer of any one of embodiments 1-15, wherein the photoactive crosslinking moiety is present on the polysaccharide polymer at a density of between 1%-6%, e.g., as determined by comparison to a reference standard. 17. The polysaccharide polymer of any one of embodiments 1-16, wherein the photoactive crosslinking moiety is present on the polysaccharide polymer at a density of between 1%-4%, e.g., as determined by comparison to a reference standard. 18. The polysaccharide polymer of any one of embodiments 1-17, wherein the polysaccharide polymer is selected from agarose, alginate, amylose, amylopectin, arabinogalactan, cellulose, chitin, chitosan, dextran, fructan, fucoidan, galactan, galactomannan, glycogen, gellan gum, hyaluronic acid, hyaluronate, inulin, laminarin, maltodextrin, pectin, pullulan, xanthan gum, xylan, carrageenan, and raffinose. 19. The polysaccharide polymer of any one of embodiments 1-18, wherein the polysaccharide polymer is not agarose, amylose, amylopectin, arabinogalactan, cellulose, chitin, chitosan, dextran, fructan, fucoidan, galactan, galactomannan, glycogen, gellan gum, hyaluronic acid, hyaluronate, inulin, laminarin, maltodextrin, pectin, pullulan, xanthan gum, xylan, carrageenan, and raffinose. 20. The polysaccharide polymer of any one of embodiments 1-19, wherein the polysaccharide polymer is selected from alginate, hyaluronate, and chitosan. 21. The polysaccharide polymer of any one of embodiments 1-20, wherein the polysaccharide polymer is alginate. 22. The polysaccharide polymer of any one of embodiments 1-21, wherein the polysaccharide polymer is hyaluronate. 23. The polysaccharide polymer of any one of embodiments 1-22, wherein the polysaccharide polymer is chitosan. 24. The polysaccharide polymer of embodiment 21, wherein the alginate is a high guluronic acid (G) alginate or a high mannuronic acid (M) alginate. 25. The polysaccharide polymer of embodiments 21 or 24, wherein the alginate is a high guluronic acid (G) alginate. 26. The polysaccharide polymer of embodiment 21 or 24-25, wherein the alginate is a high mannuronic acid (G) alginate. 27. The polysaccharide polymer of any of embodiments 21 or 24-26, wherein the alginate is not a high mannuronic acid (M) alginate. 28. The polysaccharide polymer of any of embodiments 21 or 24-27, wherein the alginate is selected from low molecular weight alginate, medium molecular weight alginate, high molecular weight alginate, and ultra-high molecular weight alginate. 29. The polysaccharide polymer of any of embodiments 21 or 24-28, wherein the alginate is low molecular weight alginate. 30. The polysaccharide polymer of any of embodiments 21 or 24-29, wherein the alginate is medium molecular weight alginate. 31. The polysaccharide polymer of any of embodiments 21 or 24-30, wherein the alginate is high molecular weight alginate. 32. The polysaccharide polymer of any of embodiments 21 or 24-31, wherein the alginate is ultra-high molecular weight alginate. 33. The polysaccharide polymer of any of embodiments 21 or 24-32, wherein the alginate is selected from low viscosity alginate, medium viscosity alginate, high viscosity alginate, and very high viscosity alginate. 34. The polysaccharide polymer of any of embodiments 21 or 24-33, wherein the alginate is low viscosity alginate. 35. The polysaccharide polymer of any of embodiments 21 or 24-34, wherein the alginate is medium viscosity alginate. 36. The polysaccharide polymer of any of embodiments 21 or 24-35, wherein the alginate is high viscosity alginate. 37. The polysaccharide polymer of any of embodiments 21 or 24-36, wherein the alginate is very high viscosity alginate. 38. The polysaccharide polymer of any of embodiments 21 or 24-37, wherein the alginate has a purity of greater than 90%, e.g., greater than 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, or 99.9% (e.g., as determined by high-performance liquid chromatography). 39. The polysaccharide polymer of any of embodiments 21 or 24-38, wherein the alginate has a purity greater than 95%. 40. The polysaccharide polymer of any of embodiments 21 or 24-39, wherein the alginate has a purity greater than 98%. 41. The polysaccharide polymer of any of embodiments 21 or 24-40, wherein the alginate has a purity greater than 99%. 42. The polysaccharide polymer of any of embodiments 21 or 24-41, wherein the alginate has a purity greater than 99.5%. 43. The polysaccharide polymer of any of embodiments 21 or 24-42, wherein the alginate has an endotoxin level below 50 EU / g. 44. The polysaccharide polymer of any of embodiments 21 or 24-43, wherein the alginate has a total viable bacterial count (TVC) below 100 colony forming units (CFU) per gram. 45. The polysaccharide polymer of any one of embodiments 21 or 24-44, wherein the alginate is selected from one of: Kimica Algin IL-2, Kimica Algin IL-6, Kimica Algin I-1, Kimica Algin I-3, Kimica Algin I-5, Kimica Algin I-8, Kimica Algin LZ-2, Kimica Algin ULV- L3, Kimica Algin ULV-L5, Kimica Algin ULV-1G, Kimica Algin ULV-5G, Kimica Algin ULV IL-6G, Pronova UP VLVM, Pronova UP LVM, Pronova UP MVM, Pronova UP VLVG, Pronova UP MVG, Pronova UP LVG, Pronova SLM20, Pronova SLM100, Pronova SLG20, Pronova UP LG 20, Pronova LG 100, and Pronova SLG100. 46. The polysaccharide polymer of any one of embodiments 21 or 24-45, wherein the alginate is selected from one of: Pronova UP VLVM, Pronova UP LVM, Pronova UP MVM, Pronova UP VLVG, Pronova UP MVG, Pronova UP LVG, Pronova SLM20, Pronova SLM100, Pronova SLG20, and Pronova SLG100. 47. The polysaccharide polymer of any one of embodiments 21 or 24-46, wherein the alginate is Pronova UP VLVG. 48. The polysaccharide polymer of any one of embodiments 21 or 24-46, wherein the alginate is Pronova SLG100. 49. The polysaccharide polymer of any one of embodiments 21 or 24-46 wherein the alginate is Pronova SLG20. 50. The polysaccharide polymer of any one of embodiments 21 or 24-46, wherein the alginate is Pronova LG 20. 51. The polysaccharide polymer of any one of embodiments 1-50, wherein the photoactive crosslinking moiety has a structure of Formula (IV): pharmaceutically acceptable salt or tautomer thereof, wherein X1is absent, O, NR33, or C(R34a)(R34b); each of R30a, R30b, R31, R32, R33, R34a, and R34bis independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, – N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl. 52. The polysaccharide polymer of embodiment 51, wherein X1is NR33(e.g., NH). 53. The polysaccharide polymer of any one of embodiments 51-52, wherein each of R30a, R30b, R31, and R32is hydrogen. 54. The polysaccharide polymer of any one of embodiments 51-53, wherein X1is NR33, each of R30a, R30b, R31and R33is hydrogen and R32is heteroalkyl (e.g., a nitrogen-containing heteroalkyl). 55. The polysaccharide polymer of embodiment 51, wherein X1is NR33, each of R30a, R30band R33is hydrogen, R31is alkyl, and R32is heteroalkyl (e.g., a nitrogen-containing heteroalkyl). 56. The polysaccharide polymer of embodiment 51, wherein X1is NR33, each of R30a, R30band R33is hydrogen, R31is C1-C12 alkyl, and R32is 2-12 membered heteroalkyl (e.g., a 2-12 membered nitrogen-containing heteroalkyl). 57. The polysaccharide polymer of embodiment 48, wherein X1is O, each of R30a, R30b, R31and R33is hydrogen and R32is heteroalkyl (e.g., a nitrogen-containing heteroalkyl). 58. The polysaccharide polymer of embodiment 51, wherein X1is O, each of R30aand R30bishydrogen, R31 is alkyl, and R32 is heteroalkyl (e.g., a nitrogen-containing heteroalkyl). 59. The polysaccharide polymer of embodiment 51, wherein X1is O, each of R30aand R30bis hydrogen, R31is C1-C12 alkyl, and R32is 2-12 membered heteroalkyl (e.g., a 2-12 membered nitrogen-containing heteroalkyl). 60. The polysaccharide polymer of embodiment 51, wherein X1is C(R34a)(R34b), each of R30a, R30b, R31, R33, R34a, and R34bis hydrogen and R32is heteroalkyl (e.g., a nitrogen-containing heteroalkyl). 61. The polysaccharide polymer of embodiment 51, wherein X1is C(R34a)(R34b), each of R30a, R30b, R31, R33, R34a, and R34bis hydrogen, R31is alkyl, and R32is heteroalkyl (e.g., a nitrogen- containing heteroalkyl). 62. The polysaccharide polymer of embodiment 51, wherein X1is C(R34a)(R34b), each of R30a, R30b, R31, R33, R34a, and R34bis hydrogen, R31is C1-C12alkyl, and R32is 2-12 membered heteroalkyl (e.g., a 2-12 membered nitrogen-containing heteroalkyl). 63. The polysaccharide polymer of embodiment 51, wherein X1is not O. 64. The polysaccharide polymer of embodiment 51, wherein X1is O, R32is a 2, 4, 5, 6, 7, 8, 9, 10, 11, or 12-membered heteroalkyl. 65. The polysaccharide polymer of embodiment 51, wherein X1is NR33, R32is a 2, 4, 5, 6, 7, 8, 9, 10, 11, or 12-membered heteroalkyl. 66. The polysaccharide polymer of embodiment 48, wherein X1is O and R32is not a 3- membered heteroalkyl. 67. The polysaccharide polymer of any of embodiments 48-66, wherein the photoactive crosslinking moiety is selected from: , , ,

[0011] acceptable salt thereof. 68. The polysaccharide polymer of any of embodiments 48-66, wherein the photoactive c or a pharmaceutically acceptable salt thereof. 69. The polysaccharide polymer of any of embodiments 48-66, wherein the photoactive or a pharmaceutically acceptable salt thereof. 70. The polysaccharide polymer of any one ofembodiments 1-69, wherein the photoactive crosslinking moiety has a structure of Formula (IV-a): pharmaceutically acceptable salt or tautomer thereof, wherein: each of R30a, R30b, R31, R32and R35is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, – N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl. 71. The polysaccharide polymer of embodiment 70, wherein each of R30a, R30b, R31, R32, and R35is hydrogen. 72. The polysaccharide polymer of embodiment 70 or 71, wherein each of R30a, R30b, R31, and R35is hydrogen, and R32is heteroalkyl (e.g., nitrogen-containing heteroalkyl). 73. The polysaccharide polymer of any one of embodiments 70-72, wherein each of R30a, R30b, R31, and R35is hydrogen, and R32is a 2-4 membered heteroalkyl (e.g., 2-4 membered nitrogen-containing heteroalkyl). 74. The polysaccharide polymer of any of embodiments 70-73, wherein each of R30a, R30b, and R35is hydrogen, R31is C1-C6 alkyl, and R32is a 2-4 membered heteroalkyl (e.g., 2-4 membered nitrogen-containing heteroalkyl). 75. The polysaccharide polymer of any of embodiments 70-74, wherein the photoactive crosslinking moiety is selected from: , or a pharmaceutically acceptable salt thereof. 76. The polysaccharide polymer of any one of embodiments 1-69, wherein the photoactive crosslinking moiety has a structure of Formula (IV-c): pharmaceutically acceptable salt or tautomer thereof, wherein: each of R30a, R30b, and R31is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, – N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; R32is hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl,–C(O)ORA1, –C(O)RB1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl. 77. The polysaccharide polymer of embodiment 76, wherein each of R30a, R30b, R31, and R32is hydrogen. 78. The polysaccharide polymer of embodiment 76, wherein each of R30a, R30b, and R31is hydrogen, and R32is heteroalkyl (e.g., nitrogen-containing heteroalkyl). 79. The polysaccharide polymer of embodiment 76, wherein each of R30a, R30b, and R31is hydrogen, and R32is a 2-4 membered heteroalkyl (e.g., 2-4 membered nitrogen-containing heteroalkyl). 80. The polysaccharide polymer of any of embodiments 76-79, wherein each of R30aand R30bis hydrogen, R31is C1-C6 alkyl, and R32is a 2-4 membered heteroalkyl (e.g., 2-4 membered nitrogen-containing heteroalkyl). 81. The polysaccharide polymer of any one of embodiments 1-70, wherein the photoactive crosslinking moiety has a structure selected from Table 4, or a pharmaceutically acceptable salt thereof. 82. The polysaccharide polymer of any one of embodiments 1-81, wherein the photoactive crosslinking moiety is selected from acrylate, methacrylate, acrylamide, and methacrylamide, or a corresponding acid chloride and anhydride thereof. 83. The polysaccharide polymer of any one of embodiments 1-82, wherein the photoactive crosslinking moiety is acrylate or a corresponding acid chloride and anhydride thereof. 84. The polysaccharide polymer of any one of embodiments 1-82, wherein the photoactive crosslinking moiety is methacrylate or a corresponding acid chloride and anhydride thereof. 85. The polysaccharide polymer of any one of embodiments 1-82, wherein the photoactive crosslinking moiety is acrylamide or a corresponding acid chloride and anhydride thereof. 86. The polysaccharide polymer of any one of embodiments 1-82, wherein the photoactive crosslinking moiety is methacrylamide or a corresponding acid chloride and anhydride thereof. 87. The polysaccharide polymer of any one of embodiments 1-86, wherein the photoactive crosslinking moiety is selected from Compound 205 or Compound 217, or a pharmaceutically acceptable salt thereof. 88. The polysaccharide polymer of any one of embodiments 1-87, wherein the compound of Formula (I) is a compound of Formula (I-a). 89. The polysaccharide polymer of any one of embodiments 1-87, wherein the compound of Formula (I) is a compound of Formula (I-b). 90. The polysaccharide polymer of any one of embodiments 1-87, wherein the compound of Formula (I) is a compound of Formula (I-b-i). 91. The polysaccharide polymer of any one of embodiments 1-87, wherein the compound of Formula (I) is a compound of Formula (I-b-ii). 92. The polysaccharide polymer of any one of embodiments 1-87, wherein the compound of Formula (I) is a compound of Formula (I-c). 93. The polysaccharide polymer of any one of embodiments 1-87, wherein the compound of Formula (I) is a compound of Formula (I-d). 94. The polysaccharide polymer of any one of embodiments 1-87, wherein the compound of Formula (I) is a compound of Formula (I-e). 95. The polysaccharide polymer of any one of embodiments 1-87, wherein the compound of Formula (I) is a compound of Formula (I-f). 96. The polysaccharide polymer of any one of embodiments 1-87, wherein the compound of Formula (I) is a compound of Formula (II). 97. The polysaccharide polymer of any one of embodiments 1-87, wherein the compound of Formula (I) is a compound of Formula (II-a). 98. The polysaccharide polymer of any one of embodiments 1-87, wherein the compound of Formula (I) is a compound of Formula (III). 99. The polysaccharide polymer of any one of embodiments 1-87, wherein the compound of Formula (I) is a compound of Formula (III-a). 100. The polysaccharide polymer of any one of embodiments 1-87, wherein the compound of Formula (I) is a compound of Formula (III-b). 101. The polysaccharide polymer of any one of embodiments 1-87, wherein the compound of Formula (I) is a compound of Formula (III-c). 102. The polysaccharide polymer of any one of embodiments 1-87, wherein the compound of Formula (I) is a compound of Formula (III-d). 103. The polysaccharide polymer of any one of embodiments 1-87, wherein the compound of Formula (I) is a compound of Formula (III-e). 104. The polysaccharide polymer of any one of embodiments 1-87, wherein the compound of Formula (I) is a compound of Formula (III-f). 105. The polysaccharide polymer of any one of embodiments 1-87, wherein the compound of Formula (I) is a compound of Formula (III-g). 106. The polysaccharide polymer of any one of embodiments 1-87, wherein the compound of Formula (I) is a compound of Formula (III-h). 107. The polysaccharide polymer of any one of embodiments 1-87, wherein the compound of Formula (I) is a compound of Formula (III-i). 108. The polysaccharide polymer of any one of embodiments 1-107, wherein the compound of Formula (I) has a structure selected from Table 3, or a pharmaceutically acceptable salt thereof. 109. The polysaccharide polymer of any one of embodiments 1-108, wherein the compound of Formula (I) is selected from Compound 100, Compound 101, Compound 110, Compound 112, Compound 113, Compound 114, Compound 122, and Compound 123, or a pharmaceutically acceptable salt thereof. 110. The polysaccharide polymer of any one of embodiments 1-109, wherein the compound of Formula (I) is Compound 101 or a pharmaceutically acceptable salt thereof. 111. The polysaccharide polymer of any one of embodiments 1-109, wherein the compound of Formula (I) is Compound 111 or a pharmaceutically acceptable salt thereof. 112. The polysaccharide polymer of any one of embodiments 1-111, wherein the polysaccharide polymer is alginate, the photoactive crosslinking moiety is selected from Compound 205 and Compound 217 or a pharmaceutically acceptable salt thereof, and the compound of Formula (I) is Compound 101 or a pharmaceutically acceptable salt thereof. 113. The polysaccharide polymer of any one of embodiments 1-111, wherein the polysaccharide polymer is alginate, the photoactive crosslinking moiety is selected from Compound 205 and Compound 217 or a pharmaceutically acceptable salt thereof, and the compound of Formula (I) is Compound 111 or a pharmaceutically acceptable salt thereof. 114. A composition comprising a polysaccharide polymer of any one of embodiments 1-113. 115. A hydrogel capsule comprising a polysaccharide polymer of any one of embodiments 1- 113. 116. The hydrogel capsule of embodiment 115, wherein the hydrogel capsule comprises a single compartment comprising the polysaccharide polymer (e.g., a polysaccharide polymer described herein). 117. The hydrogel capsule of embodiment 115, wherein the hydrogel capsule does not comprise a single compartment comprising the polysaccharide polymer. 118. The hydrogel capsule of embodiments 115 or 117, wherein the hydrogel capsule comprises a plurality of compartments, wherein one of the compartments comprises the polysaccharide polymer (e.g., a polysaccharide polymer described herein). 119. The hydrogel capsule of any one of embodiments 115, or 117-118, herein the hydrogel capsule comprises a plurality of compartments, wherein more than one of the compartments comprises the polysaccharide polymer (e.g., a polysaccharide polymer described herein). 120. The hydrogel capsule of any one of embodiments 115 to 119, wherein the hydrogel capsule comprises an inner compartment and an outer compartment. 121. The hydrogel capsule of any one of embodiments 115-120 wherein: the inner compartment comprises a first polysaccharide polymer comprising the photoactive crosslinking moiety; the outer compartment comprises a second polysaccharide polymer comprising the photoactive crosslinking moiety. 122. The hydrogel capsule of any of embodiments 115-121, wherein: the inner compartment comprises a first an unmodified polysaccharide polymer; the outer compartment comprises a second polysaccharide polymer comprising the photoactive crosslinking moiety. 123. The hydrogel capsule of any of embodiments 115-122, wherein: the inner compartment comprises a first polysaccharide polymer modified with a cell binding substance; the outer compartment comprises a second polysaccharide polymer comprising the photoactive crosslinking moiety. 124. A hydrogel capsule comprising: (i) an inner compartment comprising a first polysaccharide polymer comprising a compound of Formula (I): Formula (I): or a pharmaceutically acceptable salt thereof, wherein: A is alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, –O–, –C(O)O–, –C(O)–, –OC(O)–, –N(RC)–, –N(RC)C(O)–, –C(O)N(RC)–, –N(RC)N(RD)–, –NCN–, – N(RC)C(O)(C1-C6- alkylene)–, -N(RC)C(O)(C2-C6-alkenylene)–, –C(=N(RC)(RD))O–, –S–, – S(O)x–, –OS(O)x–, –N(RC)S(O)x–, –S(O)xN(RC)–, –P(RF)y–, –Si(ORA)2 –, –Si(RG)(ORA)–, – B(ORA)–, or a metal, each of which is optionally linked to an attachment group (e.g., an attachment group described herein) and optionally substituted by one or more R1; each of L1and L3is independently a bond, alkyl, or heteroalkyl, wherein each alkyl and heteroalkyl is optionally substituted by one or more R2; L2is a bond; M is absent, alkyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, each of which is optionally substituted by one or more R3; P is heteroaryl optionally substituted by one or more R4; Z is alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, each of which is optionally substituted by one or more R5; each RA, RB, RC, RD, RE, RF, and RGis independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, azido, cycloalkyl, heterocyclyl, aryl, or heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, and heteroaryl is optionally substituted with one or more R6; or RCand RD, taken together with the nitrogen atom to which they are attached, form a ring (e.g., a 5-7 membered ring), optionally substituted with one or more R6; each R1, R2, R3, R4, R5, and R6is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, –N(RC1)(RD1), – N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, S(O)xRE1, –OS(O)xRE1, –N(RC1)S(O)xRE1, – S(O)xN(RC1)(RD1), –P(RF1)y, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, and heteroaryl is optionally substituted by one or more R7; each RA1, RB1, RC1, RD1, RE1, and RF1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted by one or more R7; each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl; x is 1 or 2; and y is 2, 3, or 4; and (ii) an outer compartment comprising a second polysaccharide polymer comprising a photoactive crosslinking moiety. 125. A hydrogel capsule comprising: (i) an inner compartment comprising a first unmodified polysaccharide polymer; and, (ii) an outer compartment comprising a second polysaccharide polymer comprising a photoactive crosslinking moiety and a compound of Formula (I). 126. A hydrogel capsule comprising: (i) an inner compartment comprising a first polysaccharide polymer modified with a cell binding substance; and (ii) an outer compartment comprising a second polysaccharide polymer comprising a photoactive crosslinking moiety and a compound of Formula (I). 127. A hydrogel capsule comprising: (i) an inner compartment comprising a first polysaccharide polymer modified with a photoactive crosslinking moiety; and, (ii) an outer compartment comprising a second polysaccharide polymer comprising a photoactive crosslinking moiety; wherein both the inner and outer compartments comprise a compound of Formula (I). 128. A hydrogel capsule comprising: (i) an inner compartment comprising a blend (e.g., mixture) of a first unmodified polysaccharide polymer and a second unmodified polysaccharide polymer; and, (ii) an outer compartment comprising a blend of a third polysaccharide polymer and a fourth polysaccharide polymer, wherein the third polysaccharide polymer comprises a compound of Formula (I) and the fourth polysaccharide polymer comprises a photoactive crosslinking moiety. 129. A hydrogel capsule comprising: (i) an inner compartment comprising a blend (e.g., mixture) of a first polysaccharide polymer and a second polysaccharide polymer, wherein the first polysaccharide polymer comprises a compound of Formula (I) and the second polysaccharide polymer comprises a photoactive crosslinking moiety; and, (ii) an outer compartment comprising a blend of a third polysaccharide polymer and a fourth polysaccharide polymer, wherein the third polysaccharide polymer comprises a compound of Formula (I) and the fourth polysaccharide polymer comprises a photoactive crosslinking moiety. 130. A hydrogel capsule comprising: (i) an inner compartment comprising at least one unmodified polysaccharide polymer; and, (ii) an outer compartment comprising a blend of a second polysaccharide polymer and a third polysaccharide polymer, wherein the second polysaccharide polymer comprises a compound of Formula (I) and the third polysaccharide polymer comprises a photoactive crosslinking moiety. 131. The hydrogel capsule of any one of embodiments 115-130, wherein the polysaccharide polymer (e.g., the first polysaccharide polymer, the second polysaccharide polymer, the third polysaccharide polymer, and / or the fourth polysaccharide polymer) is selected from alginate, hyaluronate, and chitosan. 132. The hydrogel capsule of any one of embodiments 115-131, wherein the polysaccharide polymer (e.g., the first polysaccharide polymer, the second polysaccharide polymer, the third polysaccharide polymer, and / or the fourth polysaccharide polymer) is alginate. 133. The hydrogel capsule of any one of embodiments 115-132, wherein the first polysaccharide polymer is alginate. 134. The hydrogel capsule of any one of embodiments 115-133, wherein the second polysaccharide polymer is alginate. 135. The hydrogel capsule of any one of embodiments 115-134, wherein the third polysaccharide polymer is alginate. 136. The hydrogel capsule of any one of embodiments 115-135, wherein the fourth polysaccharide polymer is alginate. 137. The hydrogel capsule of any one of embodiments 132-136, wherein the alginate is a high guluronic acid (G) alginate or a high mannuronic acid (M) alginate. 138. The hydrogel capsule of any one of embodiments 132-137, wherein the alginate is a high guluronic acid (G) alginate. 139. The hydrogel capsule of any one of embodiments 132-138, wherein the alginate is a high mannuronic acid (M) alginate. 140. The hydrogel capsule of any one of embodiments 132-138, wherein the alginate is not a high mannuronic acid (M) alginate. 141. The hydrogel capsule of any one of embodiments 132-140, wherein the alginate is selected from low molecular weight alginate, medium molecular weight alginate, high molecular weight alginate, and ultra-high molecular weight alginate. 142. The hydrogel capsule of any one of embodiments 132-141, wherein the alginate is low molecular weight alginate. 143. The hydrogel capsule of any one of embodiments 132-141, wherein the alginate is medium molecular weight alginate. 144. The hydrogel capsule of any one of embodiments 132-141, wherein the alginate is high molecular weight alginate. 145. The hydrogel capsule of any one of embodiments 132-141, wherein the alginate is ultra- high molecular weight alginate. 146. The hydrogel capsule of any one of embodiments 132-145, wherein the alginate is selected from low viscosity alginate, medium viscosity alginate, high viscosity alginate, and very high viscosity alginate. 147. The hydrogel capsule of any one of embodiments 132-146, wherein the alginate is low viscosity alginate. 148. The hydrogel capsule of any one of embodiments 132-146, wherein the alginate is medium viscosity alginate. 149. The hydrogel capsule of any one of embodiments 132-146, wherein the alginate is high viscosity alginate. 150. The hydrogel capsule of any one of embodiments 132-146, wherein the alginate is very high viscosity alginate. 151. The hydrogel capsule of any one of embodiments 132-150, wherein the alginate has a purity of greater than 90%, e.g., greater than 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, or 99.9% (e.g., as determined by high-performance liquid chromatography). 152. The hydrogel capsule of any one of embodiments 132-151, wherein the alginate has a purity greater than 95%. 153. The hydrogel capsule of any one of embodiments 132-152, wherein the alginate has a purity greater than 98%. 154. The hydrogel capsule of any one of embodiments 132-153, wherein the alginate has a purity greater than 99%. 155. The hydrogel capsule of any one of embodiments 132-154, wherein the alginate has a purity greater than 99.5%. 156. The hydrogel capsule of any one of embodiments 132-155, wherein the alginate has an endotoxin level below 50 EU / g. 157. The hydrogel capsule of any one of embodiments 132-156, wherein the alginate has a total viable bacterial count (TVC) below 100 colony forming units (CFU) per gram. 158. The hydrogel capsule of any one of embodiments 132-157, wherein the alginate is selected from one of: Kimica Algin IL-2, Kimica Algin IL-6, Kimica Algin I-1, Kimica Algin I- 3, Kimica Algin I-5, Kimica Algin I-8, Kimica Algin LZ-2, Kimica Algin ULV-L3, Kimica Algin ULV-L5, Kimica Algin ULV-1G, Kimica Algin ULV-5G, Kimica Algin ULV IL-6G, Pronova UP VLVM, Pronova UP LVM, Pronova UP MVM, Pronova UP VLVG, Pronova UP MVG, Pronova UP LVG, Pronova SLM20, Pronova SLM100, Pronova SLG20, and Pronova SLG100. 159. The hydrogel capsule of any one of embodiments 132-159, wherein the alginate is selected from one of: Pronova UP VLVM, Pronova UP LVM, Pronova UP MVM, Pronova UP VLVG, Pronova UP MVG, Pronova UP LVG, Pronova SLM20, Pronova SLM100, Pronova SLG20, and Pronova SLG100. 160. The hydrogel capsule of any one of embodiments 132-159, wherein the alginate is Pronova UP VLVG. 161. The hydrogel capsule of any one of embodiments 132-159, wherein the alginate is Pronova SLG100. 162. The hydrogel capsule of any one of embodiments 132-159, wherein the alginate is Pronova SLG20. 163. The hydrogel capsule of any one of embodiments 132-162, wherein the photoactive crosslinking moiety has a structure of Formula (IV): pharmaceutically acceptable salt or tautomer thereof, wherein X1is absent, O, NR33, or C(R34a)(R34b); each of R30a, R30b, R31, R32, R33, R34a, and R34bis independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, – N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl. 164. The hydrogel capsule of embodiment 163, wherein X1is NR33(e.g., NH). 165. The hydrogel capsule of any one of embodiments 163-164, wherein each of R30a, R30b, R31, and R32is hydrogen. 166. The hydrogel capsule of any one of embodiments 163-165, wherein X1is NR33, each of R30a, R30b, R31and R33is hydrogen and R32is heteroalkyl (e.g., a nitrogen-containing heteroalkyl). 167. The hydrogel capsule of any one of embodiments 163-166, wherein X1is NR33, each of R30a, R30band R33is hydrogen, R31is alkyl, and R32is heteroalkyl (e.g., a nitrogen-containing heteroalkyl). 168. The hydrogel capsule of any one of embodiments 163-167, wherein X1is NR33, each of R30a, R30band R33is hydrogen, R31is C1-C12alkyl, and R32is 2-12 membered heteroalkyl (e.g., a 2-12 membered nitrogen-containing heteroalkyl). 169. The hydrogel capsule of embodiment 163, wherein X1is O, each of R30a, R30b, R31and R33is hydrogen and R32is heteroalkyl (e.g., a nitrogen-containing heteroalkyl).170. The hydrogel capsule of embodiment 163 or 169, wherein X1 is O, each of R30a and R30bis hydrogen, R31is alkyl, and R32is heteroalkyl (e.g., a nitrogen-containing heteroalkyl). 171. The hydrogel capsule of any one of embodiments 163 or 169-170, wherein X1is O, each of R30aand R30bis hydrogen, R31is C1-C12 alkyl, and R32is 2-12 membered heteroalkyl (e.g., a 2- 12 membered nitrogen-containing heteroalkyl). 172. The hydrogel capsule of embodiment 163, wherein X1is C(R34a)(R34b), each of R30a, R30b, R31, R33, R34a, and R34bis hydrogen and R32is heteroalkyl (e.g., a nitrogen-containing heteroalkyl). 173. The hydrogel capsule of embodiment 163 or 172, wherein X1is C(R34a)(R34b), each of R30a, R30b, R31, R33, R34a, and R34bis hydrogen, R31is alkyl, and R32is heteroalkyl (e.g., a nitrogen-containing heteroalkyl). 174. The hydrogel capsule of any one of embodiments 163 or 172-173, wherein X1is C(R34a)(R34b), each of R30a, R30b, R31, R33, R34a, and R34bis hydrogen, R31is C1-C12 alkyl, and R32is 2-12 membered heteroalkyl (e.g., a 2-12 membered nitrogen-containing heteroalkyl). 175. The hydrogel capsule of any one of embodiments 163-168 or 172-174, wherein X1is not O. 176. The hydrogel capsule of any one of embodiments 163 or 169-171, wherein X1is O, R32is a 2, 4, 5, 6, 7, 8, 9, 10, 11, or 12-membered heteroalkyl. 177. The hydrogel capsule of embodiment 163, wherein X1is NR33, R32is a 2, 4, 5, 6, 7, 8, 9, 10, 11, or 12-membered heteroalkyl. 178. The hydrogel capsule of embodiment 163, wherein X1is O and R32is not a 3-membered heteroalkyl. 179. The hydrogel capsule of any of embodiments 163-178, wherein the photoactive crosslinking moiety is selected from: , acceptable salt thereof. 180. The hydrogel capsule of any of embodiments 163-179, wherein the photoactive crosslinking moiety is selected from: , or a pharmaceutically acceptable salt thereof. 181. The hydrogel capsule of any of embodiments 163-180, wherein the photoactive crosslinking or a pharmaceutically acceptable salt thereof. 182. The hydrogel capsule of any one of embodiments 163-168, or 179-181, wherein the photoactive crosslinking moiety has a structure of Formula (IV-a): pharmaceutically acceptable salt or tautomer thereof, wherein: each of R30a, R30b, R31, R32and R35is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, – N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl. 183. The hydrogel capsule of embodiment 182, wherein each of R30a, R30b, R31, R32, and R35is hydrogen. 184. The polysaccharide polymer of embodiment 182 or 183, wherein each of R30a, R30b, R31, and R35is hydrogen, and R32is heteroalkyl (e.g., nitrogen-containing heteroalkyl). 185. The polysaccharide polymer of any of embodiments 182-184, wherein each of R30a, R30b, R31, and R35is hydrogen, and R32is a 2-4 membered heteroalkyl (e.g., 2-4 membered nitrogen- containing heteroalkyl). 186. The polysaccharide polymer of any of embodiment 182-185, wherein each of R30a, R30b, and R35is hydrogen, R31is C1-C6 alkyl, and R32is a 2-4 membered heteroalkyl (e.g., 2-4 membered nitrogen-containing heteroalkyl). 187. The polysaccharide polymer of any of embodiments 182-186, wherein the photoactive crosslinking moiety is selected from: , or a pharmaceutically acceptable salt thereof. 188. The hydrogel capsule of any one of embodiments 163 or 169-171 or 179-181, wherein the photoactive crosslinking moiety has a structure of Formula (IV-c): pharmaceutically acceptable salt or tautomer thereof, wherein: each of R30a, R30b, and R31is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, – N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; R32is hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl,–C(O)ORA1, –C(O)RB1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl. 189. The hydrogel capsule of embodiment 188, wherein each of R30a, R30b, R31, and R32is hydrogen. 190. The polysaccharide polymer of embodiment 188 or 189, wherein each of R30a, R30b, and R31is hydrogen, and R32is heteroalkyl (e.g., nitrogen-containing heteroalkyl). 191. The polysaccharide polymer of any one of embodiments 188-190, wherein each of R30a, R30b, and R31is hydrogen, and R32is a 2-4 membered heteroalkyl (e.g., 2-4 membered nitrogen- containing heteroalkyl). 192. The polysaccharide polymer of any of embodiments 188-191, wherein each of R30aand R30bis hydrogen, R31is C1-C6alkyl, and R32is a 2-4 membered heteroalkyl (e.g., 2-4 membered nitrogen-containing heteroalkyl). 193. The hydrogel capsule of any one of embodiments 115-192, wherein the photoactive crosslinking moiety has a structure selected from Table 4, or a pharmaceutically acceptable salt thereof. 194. The hydrogel capsule of any one of embodiments 115-193, wherein the photoactive crosslinking moiety is selected from acrylate, methacrylate, acrylamide, and methacrylamide, or a corresponding acid chloride and anhydride thereof. 195. The hydrogel capsule of any one of embodiments 115-194, wherein the photoactive crosslinking moiety is acrylate or a corresponding acid chloride and anhydride thereof. 196. The hydrogel capsule of any one of embodiments 115-194, wherein the photoactive crosslinking moiety is methacrylate or a corresponding acid chloride and anhydride thereof. 197. The hydrogel capsule of any one of embodiments 115-194, wherein the photoactive crosslinking moiety is acrylamide or a corresponding acid chloride and anhydride thereof. 198. The hydrogel capsule of any one of embodiments 115-194, wherein the photoactive crosslinking moiety is methacrylamide or a corresponding acid chloride and anhydride thereof. 199. The hydrogel capsule of any one of embodiments 115-198, wherein the photoactive crosslinking moiety is selected from Compound 205 or Compound 217, or a pharmaceutically acceptable salt thereof. 200. The hydrogel capsule of any one of embodiments 115-199, wherein the compound of Formula (I) has a structure selected from Table 3, or a pharmaceutically acceptable salt thereof. 201. The hydrogel capsule of any one of embodiments 115-200, wherein the compound of Formula (I) is selected from Compound 100, Compound 101, Compound 110, Compound 112, Compound 113, Compound 114, Compound 122, and Compound 123, or a pharmaceutically acceptable salt thereof. 202. The hydrogel capsule of any one of claims 115-201, wherein the compound of Formula (I) is Compound 101 or a pharmaceutically acceptable salt thereof. 203. The hydrogel capsule of any one of embodiments 115-202, further comprising a divalent metal cation (e.g., Ba2+). 204. The hydrogel capsule of any one of embodiments 115-203, wherein the divalent metal cation is present at a concentration of 1.0 uM to 0.05 uM. 205. The hydrogel capsule of any one of embodiments 115-204, wherein the hydrogel capsule has a diameter of between 0.1 mm to 5 mm 206. The hydrogel capsule of any one of embodiments 115-205, wherein the hydrogel capsule has a diameter of between 1 mm to 5 mm. 207. The hydrogel capsule of any one of embodiments 115-206, wherein the hydrogel capsule has a diameter of between 1 mm to 2.5 mm. 208. The hydrogel capsule of any one of embodiments 115-207, wherein the hydrogel capsule has an average molecular weight permeability (e.g., as determined by a dextran permeability assay) of less than about 175 kDa. 209. The hydrogel capsule of any one of embodiments 115-208, wherein the hydrogel capsule has an average molecular weight permeability (e.g., as determined by a dextran permeability assay) of less than about 125 kDa. 210. The hydrogel capsule of any one of embodiments 115-209, wherein the hydrogel capsule has an average fracture strength of greater than about 200 g. 211. The hydrogel capsule of any one of embodiments 115-210, wherein the hydrogel capsule has an average fracture strength greater than about 100 g. 212. The hydrogel capsule of any one of embodiments 115-211, wherein the rate of release of a divalent cation (e.g., Ba2+) is less than 2 ug. 213. The hydrogel capsule of any one of embodiments 115-212, wherein the release of a divalent cation (e.g., Ba2+) is less than 2 µg per sphere. 214. The hydrogel capsule of any one of embodiments 115-213, wherein the hydrogel capsule is characterized by a swellability ratio of greater than 0.075 in cell culture medium. 215. The hydrogel capsule of any one of embodiments 115-214, wherein the hydrogel capsule is characterized by a swellability ratio of greater than 0.075 in a cell culture medium selected from: DMEM, HPLM, and CMRL. 216. The hydrogel capsule of any one of embodiments 115-215, wherein the hydrogel capsule is characterized by a swellability ratio of greater than 0.100 in cell culture medium selected from: DMEM, HPLM, and CMRL. 217. The hydrogel capsule of any one of embodiments 115-216, wherein the hydrogel capsule comprises an islet cell. 218. The hydrogel capsule of embodiment 217, wherein the islet cell is derived from a stem cell, e.g., from an induced pluripotent stem cell line. 219. The hydrogel capsule of embodiment 217 or 218, wherein the islet cell is from a subject (e.g., cadaveric islet cell). 220. The hydrogel capsule of any one of embodiments 217-219, wherein the islet cell produces a therapeutic agent. 221. The hydrogel capsule of any one of embodiments 217-220, wherein the hydrogel capsules comprise a plurality of islet cells. 222. The hydrogel capsule of any one of embodiments 217-221, wherein the islet cells are present at a concentration of greater than about 5 M / mL. 223. The hydrogel capsule of any one of embodiments 217-222, wherein the islet cells are present at a concentration of greater than about 20 M / mL. 224. The hydrogel capsule of any one of embodiments 217-223, wherein the therapeutic agent is a protein, e.g., insulin. 225. The hydrogel capsule of any one of embodiments 217-224, wherein the hydrogel capsule is formulated for implantation into a subject (e.g., into the intraperitoneal (IP) space, the peritoneal cavity, the omentum, the lesser sac, the subcutaneous fat). 226. The hydrogel capsule of any one of embodiments 115-225, wherein the hydrogel capsule is formulated for implantation into the IP space of a subject. 227. A composition comprising a hydrogel capsule of any one of embodiments 115-226. 228. A method of producing a hydrogel capsule comprising a polysaccharide polymer of any one of embodiments 1-114. 229. A method of increasing the stability of a hydrogel capsule comprising polysaccharide polymers, wherein the method comprises providing a means of both ionically crosslinking the polysaccharide polymers and covalently crosslinking the polysaccharide polymers. 230. The method of embodiment 229, wherein the means of ionically crosslinking the polysaccharide polymers comprises use of a divalent cation (e.g., Ba2+,Ca2+, Sr2+). 231. The method of any one of embodiments 229-230, wherein the means of covalently crosslinking the polysaccharide polymers comprises use of a photoactive crosslinking moiety (e.g., a vinyl crosslinker, e.g., methacrylate, methacrylamide, or a pharmaceutically acceptable salt thereof). 232. A hydrogel capsule comprising: (i) an inner compartment comprising a polysaccharide polymer comprising a cell- binding peptide and optionally a photoactive crosslinker compound; and (ii) an outer compartment comprising a photoactive crosslinker and a compound of formula (I) described herein. 233. A hydrogel capsule comprising inner and outer compartments comprising a polysaccharide polymer comprising a photoactive crosslinker compound and a compound of Formula (I), wherein the inner compartment comprises cells. 234. A hydrogel capsule comprising: (i) an inner compartment comprising a cell and a first polysaccharide polymer, optionally wherein the first polysaccharide polymer comprises a cell-binding peptide; and (ii) an outer compartment comprising a second polymer polysaccharide polymer comprising a photoactive crosslinker and a compound of formula (I). 235. A hydrogel capsule comprising: (i) an inner compartment comprising a cell and a first polysaccharide polymer, wherein the first polysaccharide polymer is covalently modified with one or both of a photoactive crosslinker and a compound of formula (I); and (ii) an outer compartment comprising a second polymer polysaccharide polymer, wherein the second polysaccharide polymer is covalently modified with both a photoactive crosslinker and a compound of formula (I). 236. The hydrogel capsule of any of embodiments 232-235, wherein the polymer in the first and second polysaccharide polymers is the same or different. 237. The hydrogel capsule of any one of embodiments 232-236, wherein the first and second polysaccharide polymers are the same. 238. The hydrogel capsule of any one of embodiments 232-237, wherein one or both of the inner compartments further comprises an unmodified polysaccharide. 239. The hydrogel capsule of any one of embodiments 232-228, wherein the inner compartment further comprises a third polysaccharide polymer covalently modified with a cell-binding peptide. 240. The hydrogel capsule of embodiment 239, wherein the polymer in the third polysaccharide polymer is an alginate. 241. A hydrogel capsule comprising: (i) an inner compartment comprising a blend (i.e., mixture) of 5% by weight VLVG alginate modified with compound 101 and 3% by weight unmodified SLG100 alginate; and, (ii) an outer compartment comprising an inner compartment comprising a blend (i.e., mixture) of 5% by weight VLVG alginate modified with compound 101 and 3% by weight unmodified SLG100 alginate. 242. A hydrogel capsule comprising: (i) an inner compartment comprising a blend (i.e., mixture) of 5% by weight VLVG alginate modified with compound 101 and 3% by weight SLG100 alginate modified with compound 204; and, (ii) an outer compartment comprising an inner compartment comprising a blend (i.e., mixture) of 5% by weight VLVG alginate modified with compound 101 and 3% by weight SLG100 alginate modified with compound 204. 243. A hydrogel capsule comprising: (i) an inner compartment comprising a blend (i.e., mixture) of 5% by weight VLVG alginate modified with both compound 101 and compound 204 and 3% by weight SLG100 alginate modified with compound 204; and, (ii) an outer compartment comprising a blend (i.e., mixture) of 5% by weight VLVG alginate modified with both compound 101 and compound 204 and 3% by weight SLG100 alginate modified with compound 204. 244. A hydrogel capsule comprising: (i) an inner compartment comprising LG20 alginate modified with both compound 101 and compound 227; and, (ii) an outer compartment comprising LG20 alginate modified with both compound 101 and compound 227. 245. A hydrogel capsule comprising: (i) an inner compartment comprising LG20 alginate modified with both compound 114 and compound 205; and, (ii) an outer compartment comprising LG20 alginate modified with both compound 114 and compound 205. 246. A hydrogel capsule comprising: (i) an inner compartment comprising unmodified LG20 alginate; and, (ii) an outer compartment comprising LG20 alginate modified with both compound 101 and compound 205. 247. A hydrogel capsule comprising: (i) an inner compartment comprising LG20 alginate modified with both compound 101 and compound 205; and, (ii) an outer compartment comprising LG20 alginate modified with both compound 101 and compound 205. 248. The hydrogel capsule of any one of embodiments 241-243, wherein the ratio of VLVG alginate to SLG100 alginate in the inner compartment is 70:30. 249. The hydrogel capsule of any one of embodiments 232-248, wherein the inner compartment further comprises an islet cell. 250. The hydrogel capsule of any one of embodiments 232-249, wherein the islet cell is derived from a stem cell, e.g., from an induced pluripotent stem cell line. 251. The hydrogel capsule of embodiment 249 or 250, wherein the islet cell is from a subject (e.g., cadaveric islet cell). 252. The hydrogel capsule of any one of embodiments 249-251, wherein the islet cell produces a therapeutic agent. 253. The hydrogel capsule of any one of embodiments 249-252, wherein the hydrogel capsules comprise a plurality of islet cells. 254. A method of treating a disease, disorder or condition in a subject, wherein the method comprises administering to the subject a hydrogel capsule of any one of embodiments 115-254. 255. The method of embodiment 254, wherein the disease, disorder, or condition is diabetes (e.g., Type 1 diabetes). EXAMPLES In order that the invention described herein may be more fully understood, the following examples are set forth. The synthetic and biological examples described in this application are offered to illustrate the compounds, compositions, devices, and methods provided herein and are not to be construed in any way as limiting their scope. The compounds, modified polysaccharide polymers, hydrogel capsules, and compositions thereof provided herein can be prepared from readily available starting materials using modifications to the specific synthesis protocols set forth below that would be well known to those of skill in the art. It will be appreciated that where typical or preferred process conditions (i.e., reaction temperatures, times, mole ratios of reactants, solvents, pressures, etc.) are given, other process conditions can also be used unless otherwise stated. Optimum reaction conditions may vary with the particular reactants or solvents used, but such conditions can be determined by those skilled in the art by routine optimization procedures. Additionally, as will be apparent to those skilled in the art, conventional protecting groups may be necessary to prevent certain functional groups from undergoing undesired reactions. The choice of a suitable protecting group for a particular functional group as well as suitable conditions for protection and deprotection are well known in the art. For example, numerous protecting groups, and their introduction and removal, are described in Greene et al., Protecting Groups in Organic Synthesis, Second Edition, Wiley, New York, 1991, and references cited therein. Exemplary compounds, modified polymers, implantable elements (e.g., hydrogel capsules), and compositions of the invention may be prepared using any of the strategies described below. Example 1: Synthesis of sodium alginate with a photoactive crosslinker and a compound of Formula (I) In this example, alginate hydrogels comprising both a photoactive crosslinker (methacrylamide) and an exemplary compound of Formula (I) are synthesized. Nova Matrix PRONOVATMUP LG20 (300 g; 1.25% w / w in water, 3.75 g sodium alginate) was weighed into a 400 mL EasyMax reactor (Mettler Toledo)equipped with overhead stirring. In a separate 150 mL sterile container was massed 4-((1-(2-(2-(2-(2-aminoethoxy)ethoxy)ethoxy)ethyl)-1H-1,2,3- triazol-4-yl)methyl)thiomorpholine 1,1-dioxide (5.77 g, 14.74 mmol) along with endotoxin free water (20 g) and mixed on a shaker at 300 rpm until fully dissolved. Once dissolved, the pH was adjusted to pH 7.0 with 6N and 1N hydrochloric acid and charged to the EasyMax reactor. Agitation was set at 300 rpm, and the batch temperature adjusted to 25˚C. In a separate 150 mL container was massed 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (3.88 g, 14.02 mmol) along with endotoxin free water (45 g) and mixed by hand until fully dissolved. The solution was then added to the EasyMax reactor over a period of two minutes. Once the addition was complete, the batch was heated to 35˚C in 1 hour, held at 35˚C for 15 hours before being cooled back down to 25 ˚C. Once the reaction was complete, the batch was filtered through a pad of cyano-silica prior to purification via tangential flow filtration (10 kDa molecular weight cutoff). The solution was first purified against 10 volume exchanges with normal saline followed by 10 volume exchanges with endotoxin free water. After purification, the solution was concentrated to a refractive index value of 1.3360 and charged back into the 400 mL EasyMax reactor. Agitation was set to 300 rpm and the batch temperature was adjusted to 25 ˚C. In a separate sterile container, N-(3-aminopropryl)- methacrylamide hydrochloride (0.943 g, 5.28 mmol) was weighed and dissolved in 1M MES pH 7.0 buffer (7.5 mL) and then charged to the reactor.4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4- methylmorpholinium chloride (1.61 g, 5.82 mmol) was weighed in a sterile container and dissolved in 1M MES pH 7.0 buffer (10 mL) and then added to the reactor over two minutes. Once the charge was complete, the reaction mixture was heated to 35 °C in 1 hour, held at 35 °C for 15 hours before being cooled back to 25 °C. The reaction mixture was purified via tangential flow filtration (10 kDa molecular weight cutoff) against 10 volumes exchanges with saline. After purification, the solution was concentrated to a refractive index value of 1.3380. A 0.5 mL sample was placed into a glass scintillation vial, along with ~1-2 milligrams of lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) initiator. The LAP was dissolved and then the solution was exposed to 390 nm light for 1 minute to result in the formation of a hydrogel to confirm the presence of the methacrylamide functionality on the polymer. Example 2: Synthesis of sodium alginate with a photoactive crosslinker and a compound of Formula (I) In this example, alginate hydrogels comprising both a photoactive crosslinker (methacrylate) and an exemplary compound of Formula (I) are synthesized.302 grams of Nova Matrix PRONOVATMUP LG20 (1.25% w / w in water, 3.75 g sodium alginate, ~18.8mmol - COOH) was weighed into a 400 mL EasyMax reactor equipped with overhead stirring. In a separate 150 mL sterile container was massed 4-((1-(2-(2-(2-(2-aminoethoxy)ethoxy)ethoxy)- ethyl)-1H-1,2,3-triazol-4-yl)methyl)thiomorpholine-1,1-dioxide (5.76 g, 14.74 mmol) along with endotoxin free water (20 g) and mixed on a shaker at 300 rpm until fully dissolved. Once dissolved, the pH was adjusted to pH 7.0 with 6N and 1N hydrochloric acid and charged to the EasyMax reactor. Agitation was set at 300 rpm, and the batch temperature adjusted to 25 ˚C. In a separate 150 mL container was massed 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4- methylmorpholinium chloride (3.90 g, 14.09 mmol) along with endotoxin free water (45 g) and mixed by hand until fully dissolved. The solution was then added to the EasyMax reactor over a period of two minutes. Once the addition was complete, the batch was heated to 35 ˚C in 1 hour, held at 35 ˚C for 15 hours before being cooled back down to 25 ˚C. Once the reaction was complete, the batch was filtered through a pad of cyano-silica prior to purification via tangential flow filtration (10 kDa molecular weight cutoff). The solution was first purified against 10 volume exchanges with normal saline followed by 10 volume exchanges with endotoxin free water. After purification, the solution was concentrated to a refractive index value of 1.3356 and charged back into the 400 mL EasyMax reactor. Agitation was set to 300 rpm and the batch temperature was adjusted to 25˚C.4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (1.61 g, 5.8 mmol) was weighed in a sterile container and dissolved in 0.5M sodium phosphate pH 7.0 buffer (20 mL) and then added to the reactor over two minutes. In a separate sterile container, 2-aminoethyl methacrylate hydrochloride (0.89 g, 5.4 mmol) was weighed and dissolved in 0.5M sodium phosphate pH 7.0 buffer (20 mL) and then charged to the reactor. Once the charge was complete, the reaction mixture was heated to 35°C in 1 hour, held at 35 °C for 15 hours...

Claims

CLAIMS 1. A hydrogel capsule comprising: (i) a polysaccharide polymer comprising: (a) photoactive crosslinking moiety; and (b) a compound of Formula (I):or a pharmaceutically acceptable salt thereof, wherein: A is alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, –O–, –C(O)O–, –C(O)–, –OC(O)–, –N(RC)–, –N(RC)C(O)–, –C(O)N(RC)–, –N(RC)N(RD)–, –NCN–, – N(RC)C(O)(C1-C6- alkylene)–, -N(RC)C(O)(C2-C6-alkenylene)–, –C(=N(RC)(RD))O–, –S–, – S(O)x–, –OS(O)x–, –N(RC)S(O)x–, –S(O)xN(RC)–, –P(RF)y–, –Si(ORA)2 –, –Si(RG)(ORA)–, – B(ORA)–, or a metal, each of which is optionally linked to an attachment group (e.g., an attachment group described herein) and optionally substituted by one or more R1; each of L1and L3is independently a bond, alkyl, or heteroalkyl, wherein each alkyl and heteroalkyl is optionally substituted by one or more R2; L2is a bond; M is absent, alkyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, each of which is optionally substituted by one or more R3; P is heteroaryl optionally substituted by one or more R4; Z is alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, each of which is optionally substituted by one or more R5; each RA, RB, RC, RD, RE, RF, and RGis independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, azido, cycloalkyl, heterocyclyl, aryl, or heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, and heteroaryl is optionally substituted with one or more R6; or RCand RD, taken together with the nitrogen atom to which they are attached, form a ring (e.g., a 5-7 membered ring), optionally substituted with one or more R6; each R1, R2, R3, R4, R5, and R6is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, –N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, S(O)xRE1, –OS(O)xRE1, –N(RC1)S(O)xRE1, – S(O)xN(RC1)(RD1), –P(RF1)y, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, and heteroaryl is optionally substituted by one or more R7; each RA1, RB1, RC1, RD1, RE1, and RF1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted by one or more R7; each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl; x is 1 or 2; and y is 2, 3, or 4; and (ii) an islet cell.

2. The hydrogel capsule of claim 1, wherein the photoactive crosslinking moiety is covalently bound to a saccharide monomer within the polysaccharide polymer.

3. The hydrogel capsule of claim 2, wherein the photoactive crosslinking moiety is bound to a carboxylate moiety within the saccharide monomer.

4. The hydrogel capsule of any one of claims 1-3, wherein the photoactive crosslinking moiety comprises an alkyl, alkenyl, alkynyl, ester, ketone, amine, or amide group.

5. The hydrogel capsule of any one of claims 1-4, wherein the photoactive crosslinking moiety is capable of reacting with a second photoactive crosslinking moiety upon activation with light (e.g., ultraviolet light).

6. The hydrogel capsule of any one of claims 1-5, wherein the photoactive crosslinking moiety is present on the polysaccharide polymer at a density of at least about 1%, e.g., 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or more, e.g., as determined by comparison to a reference standard.

7. The hydrogel capsule of any one of claims 1-6, wherein the photoactive crosslinking moiety is present on the polysaccharide polymer at a density of between 1%-10%, e.g., 1%-8%, 1%-6%, or 1%-4%, e.g., as determined by comparison to a reference standard.

8. The hydrogel capsule of any one of claims 1-7, wherein the polysaccharide polymer is selected from alginate, hyaluronate, and chitosan.

9. The hydrogel capsule of any one of claims 1-8, wherein the polysaccharide polymer is alginate.

10. The hydrogel capsule of claim 9, wherein the alginate is a high guluronic acid (G) alginate or a high mannuronic acid (M) alginate.

11. The hydrogel capsule of any one of claims 1-8, wherein the photoactive crosslinking moiety has a structure of Formula (IV): pharmaceutically acceptable salt or tautomer thereof,wherein X1is absent, O, NR33, or C(R34a)(R34b); each of R30a, R30b, R31, R32, R33, R34a, and R34bis independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, – N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl.

12. The hydrogel capsule of claim 11, wherein X1is NR33(e.g., NH).

13. The hydrogel capsule of any one of claims 11-12, wherein each of R30a, R30b, R31, and R32is hydrogen.

14. The hydrogel capsule of any one of claims 1-13, wherein the photoactive crosslinking moiety has a structure of Formula (IV-a): pharmaceutically acceptable salt or tautomer thereof, wherein:each of R30a, R30b, R31, R32and R35is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, – N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl.

15. The hydrogel capsule of claim 14, wherein each of R30a, R30b, R31, R32, and R35is hydrogen.

16. The hydrogel capsule of any one of claims 1-13, wherein the photoactive crosslinking moiety has a structure of Formula (IV-c):pharmaceutically acceptable salt or tautomer thereof, wherein: each of R30a, R30b, and R31is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, – N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; R32is hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl,–C(O)ORA1, –C(O)RB1, cycloalkyl, heterocyclyl, aryl, or heteroaryl;each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl.

17. The hydrogel capsule of claim 16, wherein each of R30a, R30b, R31, and R32is hydrogen.

18. The hydrogel capsule of any one of claims 1-17, wherein the photoactive crosslinking moiety has a structure selected from Table 4, or a pharmaceutically acceptable salt thereof.

19. The hydrogel capsule of any one of claims 1-18, wherein the photoactive crosslinking moiety is selected from acrylate, methacrylate, acrylamide, and methacrylamide, or a corresponding acid chloride and anhydride thereof.

20. The hydrogel capsule of any one of claims 1-19, wherein the photoactive crosslinking moiety is selected from Compound 205 or Compound 217, or a pharmaceutically acceptable salt thereof.

21. The hydrogel capsule of any one of claims 1-20, wherein the compound of Formula (I) has a structure selected from Table 3, or a pharmaceutically acceptable salt thereof.

22. The hydrogel capsule of any one of claims 1-21, wherein the compound of Formula (I) is selected from Compound 100, Compound 101, Compound 110, Compound 112, Compound 113, Compound 114, Compound 122, and Compound 123, or a pharmaceutically acceptable salt thereof.

23. The hydrogel capsule of any one of claims 1-22, wherein the compound of Formula (I) is Compound 101 or a pharmaceutically acceptable salt thereof.

24. The hydrogel capsule of any one of claims 1-23, wherein the polysaccharide polymer is alginate, the photoactive crosslinking moiety is selected from Compound 205 and Compound 217 or a pharmaceutically acceptable salt thereof, and the compound of Formula (I) is Compound 101 or a pharmaceutically acceptable salt thereof.

25. A composition comprising a hydrogel capsule of any one of claims 1-24.

26. The composition of claim 25, further comprising an excipient (e.g., a pharmaceutically acceptable excipient).

27. The hydrogel capsule of any one of the preceding claims, wherein the hydrogel capsule comprises a single compartment comprising the polysaccharide polymer (e.g., a polysaccharide polymer described herein).

28. The hydrogel capsule of any one of the preceding claims, wherein the hydrogel capsule comprises a plurality of compartments, wherein one of the compartments comprises the polysaccharide polymer (e.g., a polysaccharide polymer described herein).

29. The hydrogel capsule of any one of the preceding claims, wherein the hydrogel capsule comprises an inner compartment and an outer compartment.

30. The hydrogel capsule of claim 29, wherein: the inner compartment comprises a first polysaccharide polymer comprising the photoactive crosslinking moiety; the outer compartment comprises a second polysaccharide polymer comprising the photoactive crosslinking moiety.

31. A hydrogel capsule comprising: (i) an inner compartment comprising a first polysaccharide polymer comprising a compound of Formula (I):Formula (I): or a pharmaceutically acceptable salt thereof, wherein: A is alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, –O–, –C(O)O–, –C(O)–, –OC(O)–, –N(RC)–, –N(RC)C(O)–, –C(O)N(RC)–, –N(RC)N(RD)–, –NCN–, –N(RC)C(O)(C1-C6- alkylene)–, -N(RC)C(O)(C2-C6-alkenylene)–, –C(=N(RC)(RD))O–, –S–, –S(O)x–, –OS(O)x–, –N(RC)S(O)x–, –S(O)xN(RC)–, –P(RF)y–, –Si(ORA)2–, –Si(RG)(ORA)–, – B(ORA)–, or a metal, each of which is optionally linked to an attachment group (e.g., an attachment group described herein) and optionally substituted by one or more R1; each of L1and L3is independently a bond, alkyl, or heteroalkyl, wherein each alkyl and heteroalkyl is optionally substituted by one or more R2; L2is a bond; M is absent, alkyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, each of which is optionally substituted by one or more R3; P is heteroaryl optionally substituted by one or more R4; Z is alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, each of which is optionally substituted by one or more R5; each RA, RB, RC, RD, RE, RF, and RGis independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, azido, cycloalkyl, heterocyclyl, aryl, or heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, and heteroaryl is optionally substituted with one or more R6; or RCand RD, taken together with the nitrogen atom to which they are attached, form a ring (e.g., a 5-7 membered ring), optionally substituted with one or more R6; each R1, R2, R3, R4, R5, and R6is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, –N(RC1)(RD1), – N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, S(O)xRE1, –OS(O)xRE1, –N(RC1)S(O)xRE1, – S(O)xN(RC1)(RD1), –P(RF1)y, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, and heteroaryl is optionally substituted by one or more R7;each RA1, RB1, RC1, RD1, RE1, and RF1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted by one or more R7; each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl; x is 1 or 2; and y is 2, 3, or 4; and (ii) an outer compartment comprising a second polysaccharide polymer comprising a photoactive crosslinking moiety; (iii) an islet cell.

32. The hydrogel capsule of any one of claims 26-31, wherein the polysaccharide polymer (e.g., the first polysaccharide polymer and / or the second polysaccharide polymer) is selected from alginate, hyaluronate, and chitosan.

33. The hydrogel capsule of any one of claims 26-32, wherein the polysaccharide polymer (e.g., the first polysaccharide polymer and / or the second polysaccharide polymer) is alginate.

34. The hydrogel capsule of any one of claims 31-33, wherein the first polysaccharide polymer is alginate.

35. The hydrogel capsule of any one of claims 31-34, wherein the second polysaccharide polymer is alginate.

36. The hydrogel capsule of any one of claims 33-35, wherein the alginate is a high guluronic acid (G) alginate or a high mannuronic acid (M) alginate.

37. The hydrogel capsule of any one of claims 31-36, wherein the photoactive crosslinking moiety has a structure of Formula (IV):pharmaceutically acceptable salt or tautomer thereof, wherein X1is absent, O, NR33, or C(R34a)(R34b); each of R30a, R30b, R31, R32, R33, R34a, and R34bis independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, – N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl.

38. The hydrogel capsule of claim 37, wherein X1is NR33(e.g., NH).

39. The hydrogel capsule of any one of claims 37-38, wherein each of R30a, R30b, R31, and R32is hydrogen.

40. The hydrogel capsule of any one of claims 31-39, wherein the photoactive crosslinking moiety has a structure of Formula (IV-a):pharmaceutically acceptable salt or tautomer thereof, wherein: each of R30a, R30b, R31, R32and R35is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, – N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; andeach R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl.

41. The hydrogel capsule of claim 40, wherein each of R30a, R30b, R31, R32, and R35is hydrogen.

42. The hydrogel capsule of any one of claims 37-39, wherein the photoactive crosslinking moiety has a structure of Formula (IV-c): pharmaceutically acceptable salt or tautomer thereof, wherein:each of R30a, R30b, and R31is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, azido, oxo, –ORA1, –C(O)ORA1, –C(O)RB1,–OC(O)RB1, – N(RC1)(RD1), –N(RC1)C(O)RB1, –C(O)N(RC1), SRE1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; R32is hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl,–C(O)ORA1, –C(O)RB1, cycloalkyl, heterocyclyl, aryl, or heteroaryl; each RA1, RB1, RC1, RD1, and RE1is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, wherein each of alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl is optionally substituted with 1-6 R7; and each R7is independently alkyl, alkenyl, alkynyl, heteroalkyl, halogen, cyano, oxo, hydroxyl, cycloalkyl, or heterocyclyl.

43. The hydrogel capsule of claim 42, wherein each of R30a, R30b, R31, and R32is hydrogen.

44. The hydrogel capsule of any one of claims 31-43, wherein the photoactive crosslinking moiety has a structure selected from Table 4, or a pharmaceutically acceptable salt thereof.

45. The hydrogel capsule of any one of claims 31-44, wherein the photoactive crosslinking moiety is selected from acrylate, methacrylate, acrylamide, and methacrylamide, or a corresponding acid chloride and anhydride thereof.

46. The hydrogel capsule of any one of claims 31-45, wherein the photoactive crosslinking moiety is selected from Compound 205 or Compound 217, or a pharmaceutically acceptable salt thereof.

47. The hydrogel capsule of any one of claims 31-46, wherein the compound of Formula (I) has a structure selected from Table 3, or a pharmaceutically acceptable salt thereof.

48. The hydrogel capsule of any one of claims 31-46, wherein the compound of Formula (I) is selected from Compound 100, Compound 101, Compound 110, Compound 112, Compound 113, Compound 114, Compound 122, and Compound 123, or a pharmaceutically acceptable salt thereof.

49. The hydrogel capsule of any one of claims 31-48, wherein the compound of Formula (I) is Compound 101 or a pharmaceutically acceptable salt thereof.

50. The hydrogel capsule of any one of claims 31-49, wherein the hydrogel capsule has a diameter of between 0.1 mm to 5 mm 51. The hydrogel capsule of any one of claims 31-50, wherein the hydrogel capsule has a diameter of between 1 mm to 5 mm.

52. The hydrogel capsule of any one of claims 31-51, wherein the hydrogel capsule has a diameter of between 1 mm to 2.5 mm.

53. The hydrogel capsule of any one of claims 31-52, wherein the hydrogel capsule encapsulates the islet cell.

54. The hydrogel capsule of claim 53, wherein the islet cell produces a therapeutic agent.

55. The hydrogel capsule of claim 54, wherein the therapeutic agent is insulin.

56. The hydrogel capsule of any one of claims 31-55, wherein the hydrogel capsule is formulated for implantation into a subject (e.g., into the intraperitoneal (IP) space, the peritoneal cavity, the omentum, the lesser sac, the subcutaneous fat).

57. The hydrogel capsule of any one of claims 31-56, wherein the hydrogel capsule is formulated for implantation into the IP space of a subject.

58. A composition comprising a hydrogel capsule of any one of claims 1-57.

59. A method of producing a hydrogel capsule comprising a polysaccharide polymer of any one of claims 1-57.

60. A method of increasing the stability of a hydrogel capsule comprising a plurality of polysaccharide polymers, wherein the method comprises providing a means of both ionically crosslinking the polysaccharide polymers and covalently crosslinking the polysaccharide polymers.

61. The method of claim 60, wherein the means of ionically crosslinking the polysaccharide polymers comprises use of a divalent cation (e.g., Ba2+,Ca2+, Sr2+).

62. The method of any one of claims 60-61, wherein the means of covalently crosslinking the polysaccharide polymers comprises use of a photoactive crosslinking moiety (e.g., a vinyl crosslinker, e.g., methacrylate, methacrylamide, or a pharmaceutically acceptable salt thereof).

63. A composition for use in treating a subject with a disease, disorder, or condition comprising hydrogel capsule of any one of claims 1-57.

64. The composition for use of claim 63, wherein the disease, disorder, or condition is diabetes (e.g., Type 1 diabetes).

65. The composition for use of any one of claims 63-64, wherein the subject is a human.

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