Injectable hydrogel for embolization

Abstract

A biomaterial includes a plurality of thioester functional group linkages and a polymer comprising a plurality of free thiol functional groups. The biomaterial may be configured to undergo shear-thinning when subjected to shear-forces.

Description

INJECTABLE HYDROGEL FOR EMBOLIZATION

[0001] This application is a PCT application claiming priority to, and the benefit of, U.S. Provisional Patent Application No.63 / 621,270, filed January 16, 2024, the entire contents of which is incorporated herein by reference. BACKGROUND

[0002] Therapeutic embolization is the intentional endovascular occlusion of an artery or vein. The embolic agent of choice depends on the desired clinical outcome, as well as the inherent properties and behavior of the agent. Suitable embolic agents may be temporary or permanent. Example embolic agents include solid vascular occlusion devices such as coils, plugs, balloons, solid particles made from biopolymers or synthetic polymers such as collagen, thrombin, gelatin foam and polyvinyl alcohol (PVA), and liquid glue type embolic agents such as cyanoacrylates, the liquid embolic system available under the trade designation ONYX from Medtronic, Inc., Minneapolis, MN, other liquid embolic agents such as Squid and PHIL, and the like. SUMMARY

[0003] This disclosure is directed to biomaterials including hydrogels configured for shear-thinning. A biomaterial may be include a plurality of thioester functional group linkages and a polymer comprising a plurality of free thiol functional groups. In some examples, the polymer may include keratin proteins crosslinked using crosslinkers containing thioester functional group linkages. The crosslinked keratin proteins may include free thiol functional groups that enable shear-thinning of the hydrogel. In some examples, these hydrogels containing free, or excess, thiols can be used in a wide variety of applications including, but not limited to, embolic agents to occlude vasculature of the human body, agents for drug delivery, or scaffolds for cell growth. In some examples, the thiol-reactive crosslinks are functional or multifunctional, and can include oligomeric or polymeric functional groups such as, for example, water soluble synthetic polymers and biopolymers including alkylene oxide oligomers such as poly(ethylene glycol) (PEG), which may itself optionally be functionalized, a functional or non-functional polysaccharide and polypeptide, and the like.

[0004] As described herein, the biomaterials may be used as embolic agents that are in a gel, solid, or semi-solid form under atmospheric pressure. When subjected to shear-forces, such as pressure causing shear stress on the biomaterial, the biomaterial may undergo shear-thinning that reduces the viscosity such that the biomaterial can flow as long as subjected to the shear-thinning forces. Upon exiting a catheter or otherwise no longer subjected to the shear-thinning forces, the biomaterial may increase in viscosity and reform into a gel, semi-solid, or solid form. The biomaterial may also be configured to be dissolved when no longer needed.

[0005] In some examples, the keratin proteins in the hydrogels of the present disclosure are obtained from human hair. When used as an embolic agent in the human body, the hydrogels have excellent biocompatibility and would be expected to have fewer issues ofimmunogenicity compared to embolic agents derived from synthetic or animal basedmaterials.

[0006] The hydrogels of the present disclosure form rapidly (e.g., less than 10 minutes, less than 1 minutes, or even less than 10 seconds) in aqueous solution, and no potentially toxic organic solvents such as DMSO are required for crosslinking. In various examples, the hydrogels form via thiol-maleimide addition reactions that may be conducted without catalysts or application of radiation (for example, ultraviolet light (UV)) over a wide range of temperatures, and react cleanly to produce little or no potentially harmful byproducts. Multiple linking groups from these reactions can enable the crosslinking to occur which results in example hydrogels herein. Once formed, the hydrogels may be readily degraded as needed. In some examples, as described herein, the hydrogels may be constructed to be dissolvable or rapidly dissolvable hydrogels that can act as keratin embolic agents. Generally the hydrogels described herein may be dissolved in less than 10 minutes. However, rapidly dissolvable hydrogels may be dissolvable in less than 5 minutes or less than 3 minutes, for example. In this manner, the hydrogel may be dissolved to revert the embolization without damaging tissue if needed.

[0007] In some examples, the hydrogels may be loaded with one or more biological or therapeutic agents such as, for example, drugs like small molecule drugs or protein drugs.

[0008] In one example, the present disclosure is directed to a biomaterial including a plurality of thioester functional group linkages, and a polymer comprising a plurality of free thiol functional groups.

[0009] In another example, a method includes reacting a first aqueous pre-gel solution comprising a water soluble keratein (or other polymer) with an aqueous solution comprising crosslinking compounds comprising the plurality of the thioester functionalgroup linkages, to create the biomaterial comprising the polymer crosslinked with the plurality of thioester functional group linkages.

[0010] In another example, a system includes a single catheter configured to be disposed within a blood vessel, and a syringe configured to be coupled to the single catheter and filled with a biomaterial, wherein compression of a plunger of the syringe causes shear- thinning of the biomaterial and movement of the biomaterial through the single catheter, and wherein the biomaterial includes a plurality of thioester functional group linkages and a polymer comprising a plurality of free thiol functional groups.

[0011] In another example, a kit for conducting an embolization procedure include: a first solution comprising a first polymer comprising a plurality of thioester functional group linkages; a second solution comprising a second polymer comprising a plurality of free thiol functional groups; saline; a 3-way connector; a catheter configured to couple to the 3-way connector; a first syringe configured to withdraw the first solution; a second syringe configured to withdraw the second solution, wherein the first and second syringes are configured to mix the first and second solutions via the 3-way connector and pressurize a resulting hydrogel from mixing the first and second polymers of the first and second solutions to cause shear-thinning of the hydrogel and movement of the hydrogel through a catheter, wherein the hydrogel is configured to thicken and form an occlusion upon exiting the catheter. The kit can thus be configured to create the occlusion for the embolization procedure when the hydrogel is no longer subjected to the shear-thinning forces within the catheter.

[0012] The details of one or more examples of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF DRAWINGS

[0013] FIG.1 is schematic representation of a reaction between an example multifunctional crosslinker and an example polymer to form an example crosslinked hydrogel biomaterial, as described herein in various examples.

[0014] FIG.2 is a schematic representation of an example reaction for hydrogel formation an example thioester-thiol exchange reaction.

[0015] FIGS.3A and 3B are graphs of example biomaterial behavior subject to different frequencies and stead shear rates.

[0016] FIGS.3C and 3D are graphs of example biomaterial moduli due to different strain.

[0017] FIGS.4A, 4B, 4C, and 4D are illustrations of an example system configured to deliver a biomaterial configured for shear-thinning as described herein.

[0018] FIG.5 is a graph of injection force vs. extension (moving distance of the plunger of a 1mL syringe) for an example biomaterial described herein.

[0019] FIG.6 includes images of example biomaterials with different liquids.

[0020] FIG.7 is a graph of the remaining mass of an example biomaterial over time.

[0021] FIG.8 is a graph of swelling of an example biomaterial over time.

[0022] FIG.9 includes photographs of example blood clotting of a biomaterial in vitro.

[0023] FIG.10 is a graph of example degradation of a biomaterial in plasma by mass over time in vitro.

[0024] FIG.11 is a graph of hemolysis potential of example materials, including a biomaterial hydrogel as described herein.

[0025] FIG.12 includes images of example embolization using an example biomaterial hydrogel as described herein.

[0026] FIG.13 is a gel of electrophoresis of example samples of keratin in a non- reducing and a reducing conditions.

[0027] FIGS.14A and 14B are graphs of1H-nuclear magnetic resonance (NMR) spectroscopy for sample PEG crosslinker before and after reacting with cysteine methyl ester (CME, an example small thiol-containing molecule).

[0028] FIG.15 is a flow chart of a technique for delivering a shear-thinning biomaterial as described herein.

[0029] Like symbols in the drawings indicate like elements. DETAILED DESCRIPTION

[0030] This disclosure describes compounds, devices, systems, and techniques for providing delivery and dissolution of embolization compounds. Traditional solid embolic agents, including coils, particles, and microspheres, cannot fit all situations, and these solutions rely on thrombus formation to facilitate complete occlusion. Therefore, in clinic, many coils might be needed for one aneurysm or for one complex blood vessel anatomy, which increases the cost. The thrombi that filled the vessel may be lysed and cause undesired re-canalization that can require re-treatment. Liquid embolic agents typically do not provide an immediate occlusion and require extensive training to use.The traditional solidification mechanisms include precipitation from DMSO (Onyx, PHIL, SQUID) and rapid polymerization upon mixing with ions in blood (glue).

[0031] Biodegradable embolic agents, which can be resorbed once the occlusion role is complete, can be more desirable by patients and also have better clinical outcome than traditional permanent embolic agents, in terms of preventing chronic inflammation and eliminate healthy tissue ischemia. Biodegradable embolic agents can consist of compounds such as polysaccharide, PLA-PEG.

[0032] Additionally, most embolization procedures are irreversible in nature. Once the embolic agents are deployed, it can be difficult to remedy or correct any problems. Hydrogels are biocompatible materials that can be designed and synthesized to have a range of moduli. Catheter deliverable materials enable minimally invasive procedures which have advantages including less hospital time and less pain. Currently, endovascular injectable embolic materials are usually toxic and require extensive training and experience to use. Shear-thinning hydrogels can be advantageous over traditional solid embolic agents in order for the embolization to conform to the complex blood vessel anatomy. Shear-thinning hydrogels can be advantageous over two-catheter deliverable materials due to the elimination of multiple catheters and less risk of premature mixing and embolization. However, there is a lack of dissolvable materials that can be catheter deliverable, so there is less risk tolerance to these materials in use. In interventional radiology (IR) in particular, materials injected often result in unavoidable off-target delivery. In some examples, alginate allows for dissolving, but requires two catheters for delivery, and the dissolving agent, ethylenediaminetetraacetic acid (EDTA), is potentially toxic. There are some dissolvable would healing materials. However, none of these solutions provide the combination of easy of delivery, such as use of a single catheter, and ease of rapid dissolution once the embolism is no longer desired or needed.

[0033] As described herein, a biomaterial may be synthesized that is configured with shear-thinning properties. For example, the biomaterial, which may be a hydrogel, may include a plurality of thioester functional group linkages and a polymer comprising a plurality of free thiol functional groups. Segments of this polymer may be cross-linked together with other thiol-reactive crosslinkers that contain thioester functional groups linkages, while retaining the excess, or free, thiol functional groups. In one example, the biomaterial may include keratin to provide excess thiols on the polymer in order to allow shear-thinning (e.g., viscosity reducing under strain) and self-healing (e.g., reformation of broken bonds after strain is removed from the material). This biomaterial may also be ahydrogel that remains dissolvable. In this manner, the biomaterial may be a catheter deliverable hydrogel that is shear-thinning and dissolvable. In some examples, the biomaterial may be stored as a gel and reduced in viscosity to flow through a catheter to a target location. Removal of the pressure, and strain, from the biomaterial may immediately increase viscosity due to self-healing and reduce any extra flow of the biomaterial. This may be true within the catheter and after the biomaterial exits the catheter when shear stress is drastically reduced or removed. In this manner, the biomaterial may form an embolism after exiting the catheter. The biomaterial may be dissolved quickly when desired, either after a procedure is completed or the biomaterial is delivered to an undesired location.

[0034] FIG.1 is schematic representation of reaction 10 between an example multifunctional crosslinker 12 and an example polymer 14 to form an example crosslinked hydrogel biomaterial 16, as described herein in various examples. In general, a biomaterial, with crosslinked hydrogel biomaterial 16 being one example, may include a plurality of thioester functional group linkages (e.g., thioester groups 20) and a polymer comprising a plurality of free thiol functional groups (e.g., thiol functional groups 24). In some examples, the biomaterial is in the form of a hydrogel. As discussed in the example of FIG.1, the polymer comprises keratin. However, the polymer can include any base polymer compound that contains or is modified with free thiol pendent groups. The base polymers can be polyesters, polyethers, polyglycerols, polypeptides, polyether-esters, polyamino acids, polyester-amines, polyurethanes, polycarbonates, polyamino alcohols. In some examples, the plurality of free thiol groups are bonded directly to the polymer. These free thiol groups can be deprotonated to react with the thioester bonds to enable self-healing of the biomaterials after the biomaterial network is disrupted due to the applied shear stress or strain, which results in the shear-thinning properties and the injectability of the biomaterial.

[0035] In some examples, the polymer of the biomaterial 16 may be a first polymer comprising a plurality of polymer segments (such as multiple segments of keratin), and wherein the biomaterial comprises a plurality of second polymers crosslinked to the polymer segments to form a network containing at least some thioester functional group linkages of the plurality of thioester functional group linkages. These second polymers may be or include a crosslinker such as multifunctional crosslinker 12. In some examples, the plurality of second polymers include monomeric or copolymeric units chosen from poly(ethylene oxide) (PEO), poly(vinyl alcohol) (PVA), poly(acrylic acid)(PAA), polyacrylamide, poly(N-(2-hydroxypropyl) methacrylamide) (PHPMA), a polysaccharide, poly(ethylene glycol) (PEG), polyesters, polyethers, polyglycerols, polypeptides, polyether-esters, polyamino acids, polyester-amines, polyurethanes, polycarbonates, polyamino alcohols and combinations thereof. These second polymers may be water soluble and include PEG in some examples. In some examples, the plurality of second polymers include multi-arm polymers. As shown in FIG.1, the multi- arm polymer is PEG-4-SO-MI. In some of the examples, at least some of the plurality of thioester functional group linkages of the biomaterial are bonded directly to a respective maleimide group of a plurality of maleimide groups.

[0036] In some examples, the biomaterial includes a greater number of the free thiol functional groups (e.g., thiol functional groups 24) than the plurality of maleimide groups (e.g., maleimide group 22). In one example, the ratio may include a molar ratio of the free thiol functional groups to the plurality of maleimide groups of approximately 2:1, but smaller or greater ratios may be used in other examples. Although maleimide is described as one example compound that may be attached to thioester functional group linkages of a cross-linker, other compounds may be used in other examples. For example, instead of maleimide, another compound that provides a carbon-carbon double bond may be used. Example alternatives include methacrylate, norbornene, vinylsulfone, and other thiol- reactive functional groups, but other compounds, or combinations of any of these compounds may be attached to the crosslinker and used as a part of the biomaterial.

[0037] As shown in the example of FIG.1, a multifunctional crosslinker 12 (e.g., PEG-4- SO-MI, discussed below) can be used to crosslink segments of polymer 14 to form a biomaterial 16. Biomaterial 16 may be a hydrogel in some examples. In one example, multifunctional crosslinker 12 may include polyethylene glycol (PEG) attached to a thioester (SO) group 20 which is connected to a maleimide (MI) group 22. After reaction, the resulting biomaterial 16 may be a hydrogel that includes excess, or free, thiol functional groups 24 attached to the polymer segments of the hydrogel. Biomaterial 16 may be configured for shear-thinning and self-healing, to provide various advantages described herein.

[0038] In the example of FIG.1, various methods and materials may be used to produce biomaterial 16. In one example, materials include 4-arm PEG Succinimidyl Glutarate (PEG-4-SG, 10K) was purchased from Jenkem.

[0039] In one example, human hair was used for the keratin-SH preparation. Human hair was collected from volunteer donations. Human hair keratin was extracted according topreviously published reports with minor modification. Briefly, human hair was washed with detergent and then delipidized with methanol and chloroform (v : v = 1 : 2 ). The delipidized hair was air dried and then immersed in 0.5 M sodium sulfide solution (pH ~10) at 40° C for 24 hours. The resulting mixture was filtered, dialyzed against deionized water for 2 days, and lyophilized to afford a brown powder. The lyophilized keratin was reduced using 50 mM tris(2-carboxyethyl)phosphine (TCEP, 1 gram keratin in 20 mL TCEP solution) in water overnight at pH 6, centrifuged to remove insoluble residue and then the supernatant was filtered through 0.22 um membrane. The soluble keratin was further reduced using 50 mM TCEP overnight. After the second TCEP reduction, the keratin-SH was then dialyzed (MWCO 3.5kDa, Spectrum Laboratories) for 24 hours against deionized water (pH 6) to remove TCEP and preserve free thiol groups. Keratin- SH was lyophilized and collected as a slightly brown colored powder. Stock solutions of 20 wt% keratin-SH were made, and the final concentration of thiol was quantified by Ellman’s assay.

[0040] PEG-4-SO-MI (e.g., multifunctional crosslinker 12) was synthesized using a two- step synthesis method, such as described in International Patent Publication No. WO 2023 / 010115 A1, published February 2, 2023, which is incorporated herein by reference in its entirety.

[0041] For PEG-4-SO-COOH, PEG-4-SG (10K g / mol, 2 g, 0.2 mmol) was dissolved in anhydrous dichloromethane (DCM, 1mL) in a round-bottom flask. Thioglycolic acid (TGA, 90.7 L, 0.8 mmol) was added to the dissolved polymer solution followed by the addition of N,N-diisopropylehtylamine (DIPEA, 281.5 uL, 0.8 mmol). The reaction mixture was purged with argon for 5 minutes, followed by the addition of anhydrous DCM (1 mL) using a syringe. Then the mixture was stirred at room temperature for overnight. The reaction mixture was then washed with saturated citric acid solution, water, and brine. The solvent in the organic layer was evaporated under reduced pressure and the residue was purified by precipitation in diethyl ether to afford the PEG-4-SO- COOH as a white solid (~90% yield). 1H-NMR (D2O, 400 MHz): 4.20 (m, 8H), 3.90- 3.30 (overlap, ~900 H), 2.70 (t, 8H), 2.41 (t, 8H), 1.90 (tt, 8H).

[0042] For PEG-4-SO-MI, the PEG-4-SO-COOH (10k g / mol, 1 g, 0.1 mmol), benzotriazol-1-yloxytripyrrolidinophosphonium hexafluorophosphate (PyBOP, 410 mg, 0.8 mmol), N-(2-aminoethyl)maleimide (AEM, 141 mg, 0.8 mmol) and anhydrous DCM (2 mL) were added to a round-bottom flask equipped with a magnetic stir bar. Themixture was stirred and DIPEA (139 uL, 0.08 mmol) was added. The reaction mixture was purged with argon for 5 minutes, followed by the addition of anhydrous DCM (1 mL) using a syringe. Then the mixture was stirred at room temperature for overnight. The reaction mixture was then washed with saturated citric acid solution, water, and brine. The solvent in the organic layer was evaporated under reduced pressure and the residue was purified by precipitation in diethyl ether to afford a white solid. The white solid was dissolved in water and dialyzed against water at 4°C for 24 hours. The dialyzed aqueous solution was then lyophilized to afford PEG-4-SO-MI as a white solid (yield: ~70%). 1H-NMR (D2O, 400 MHz): 6.78 (s, 8H), 4.20 (m, 8H), 3.90-3.30 (overlap, ~900 H), 2.70 (m, 8H), 2.41 (t, 8H), 1.90 (m, 8H).

[0043] Hydrogel formulation development was then performed. Hydrogels were prepared using keratin-SH (3.3 wt%, ~36 mM SH, in saline) crosslinked with PEG-4-SO- MI (6.7 wt%, ~18mM MI, in saline). Gelation time was recorded as the initial time of the mixed polymer solutions (15 uL keratin-SH and 15 uL PEG-4-SO-MI) cannot be further mixed by hand with a pipet.

[0044] Hydrogels containing 20 wt% contrast were formed similarly to the abovementioned method and only replacing saline with 20:80 v:v mixture of Visipaque and saline.

[0045] In this example, hydrogels prepared for in vivo testing were made using pre-gel cursors that were filtered using Steriflip vacuum filtration system (0.22 um, from Merck KGaA). The two solutions were mixed through a 3-way stopcock (from Smiths Medical ASD, Inc) for ten times using aseptic technique. The in vivo formulations were all prepared on the same day of usage in capped sterile 1 mL syringes (from BD Medical).

[0046] For rheological characterization, the hydrogels were formed by mixing the precursor solutions in a 1.7 mL Eppendorf microtube, vortexed for 5 seconds, and then immediately transferred onto the 40 mm Peltier plate at room temperature. The upper geometry, a 40 mm 2° cone plate was lowered until a 0.25 N normal force was measured to prevent hydrogel slip. Strain sweeps were performed to determine the linear viscoelastic regime. Oscillatory frequency sweep tests were performed between 0.01 and 100 Hz with 0.2 % constant strain (linear viscoelastic regime). Flow rate measurements were conducted between 0.1 and 100 s-1. Step-strain oscillation measurements were conducted at 0.2% and 700% strain and an angular frequency of 10 rad / s. All rheology experiments were performed at room temperature (~23°C), except for one frequencysweep test at 37°C to check the hydrogel moduli change at room temperature and physiological temperature.

[0047] The biomaterial may have hemocompatibility with mammals, such as humans. In some examples, the biomaterial may be referred to as an injectable on-demand dissolvable material indicating the properties that it contains. In one examples, citrated whole ovine blood was used for all blood-related testing.

[0048] Hemolysis testing was performed according to published protocols. Briefly, citrated whole blood was diluted 50X into 0.9% (w / v) saline solutions. The biomaterial, such as biomaterial 16, was formed in 1.5-mL Eppendorf tubes and incubated for at least 20 minutes before the addition of diluted blood. Diluted blood (100 uL) was added into Eppendorf tubes containing biomaterial 16, saline (negative control), CME sucrose solution, or DI water (positive control) and the samples were incubated at 37°C for 2 hours with mild agitation. Post incubation, the samples were centrifuges and the supernatant (80 uL) was collected into wells of a 96-well plate and read at 545 nm. The percent of hemolysis was calculated as a function of [(AbsSample – AbsNegativeControl) / AbsPositiveControl].

[0049] Clotting time was evaluated. The blood clotting time were measured according to a published protocol. Briefly, blood was mixed with 10% (w / v) 0.1M CaCl2 in deionized (DI) water and pipetted into a 96-well plate. When testing the biomaterial 16 hydrogel, the hydrogel was formed in the well plates, ensuring the entire bottom was coated. The clotting time was recorded as the time that a uniform clot was formed without change in the subsequent wells.

[0050] Degradation in plasma was also studied. Ovine plasma was separated from citrated whole blood by centrifuge. Plasma was used to incubate weighed biomaterial 16 hydrogel in 1.5-mL Eppendorf tubes (VWR) at 37°C. At time points, the remaining biomaterial 16 hydrogel was weighed after removing the plasma. After weighing, fresh plasma was added. N=3.

[0051] Swelling and degradation characterization was also performed for biomaterial 16.

[0052] With regard to in vivo experiments, the feasibility of embolization and on-demand recanalization of the biomaterial 16 gel was evaluated in a rabbit renal model using a New Zealand white rabbit (male, approximately 4 kg). Protocols for the animal experiments were approved. The right common femoral artery was surgically exposed and a 4-F sheath was placed. Under the guidance of fluoroscopy, the renal artery was catheterized with a 4-F Cobra catheter (ID = 0.03800, length: 70 cm, Performa, MeritMedical) and was advanced into the main renal artery. In this example, biomaterial 16 gel containing 20wt% Visipaque was injected until total occlusion was achieved. Angiography was performed before, immediately after, and 10 minutes after the embolic procedure. The volume of the biomaterial 16 gel used was recorded. The 4-F catheter was then temporarily removed and the remaining biomaterial 16 gel was flushed out using saline and then placed back. Then a 2.4-F microcatheter (ID=0.022”, length: 140cm, Progreat, Terumo) was introduced and passed through the main renal artery to select a smaller vessel. 0.2 mL dissolving agent (0.3M CME, 10wt% sucrose, 20wt% Visipaque) was injected. Angiography was performed 5 minutes after the administration of the dissolving agent. Next, 0.2 mL dissolving agent was administered through the 4-F catheter to the main artery. Angiography was performed 5 minutes afterwards. Another two times administration of the dissolving agent was delivered through the microcatheter. The microcatheter was filled with the dissolving agent and then saline was used to inject it. Angiography was performed 5 minutes after each dissolving attempt. Finally, the microcatheter was advanced to the small top vessel and 0.4 mL dissolving agent was injected while the microcatheter was moved to the main artery. Angiography was performed 5 minutes after the administration. The microcatheter was then advanced to the main renal artery of the left kidney and 0.2 mL of biomaterial 16 gel was administered to embolize the kidney. Angiography was performed before and after the embolization.

[0053] For statistics for this example, the Kruskal-Wallis method with Dunn’s multiple comparisons test was used for 3 group data sets (the hemolysis data).

[0054] Various results were observed from these examples. Human hair keratin has been extracted using the oxidation or reduction methods. The reducing method was used to get thiol containing keratins. Chloroform and methanol delipidized the human hair and then Na2S reduced the disulfide. The non-dissolvable residue was removed, and the dissolvable part of reduced human hair keratin was lyophilized. Thiol contents from the reduced human hair keratin was very low (0.01 mmol per gram). Additional reduction could be used to achieve high enough thiol content for desired gelation. For the additional reducing steps, TCEP, a non-thiol containing reducing agent was selected. The keratin was treated with TCEP once, filtered through a 0.22 m filter, and then treated with TCEP again before the final dialysis and lyophilization steps to ensure sufficient thiol content. The collected thiol content of the keratin-SH (e.g., polymer 14) was determined using Ellman’s assay as 1.0-1.4 mmol per gram keratin, which was higherthan the ~0.55 mmol per gram reported by Khademhosseini et al. From SDS-PAGE, the keratin used in the biomaterial 16 gels of this example have molecular weight in the range of 10-15 kDa, as shown in the gel of FIG.13. Keratins from human hair may be keratin- associated proteins (KAPs) and can present high cysteine content comparing with the higher molecular weight type I (acidic; 40-50 kDa) and typo II (neutral / basic; 55-65 kDa) keratins. Additionally, thiols are known to be very reactive and can form disulfide in air. After storing at -20°C for a year, the free thiol content of biomaterial 16 decreased about 50%. Therefore, biomaterial 16, for example, may be generally stable and functional for months or years. However, the functionality of biomaterial 16 may reduce over time.

[0055] For the SDS-PAGE: 0.02g of sample was solubilized in 1 mL double-deionized water (DDW) for two hours. The material was diluted 1:4 with additional DDW to reduce smearing. A final dilution was done with 100 L of the sample and 100 L of Laemmli Buffer for the non-reducing sample (NR), and 100 L sample with 95 L Laemmli buffer + 5 L of beta-mercaptoethanol (BME) for the reducing sample (R). The samples were placed in a boiling water bath for five minutes, left to cool, and then run on a 4-20% gradient polyacrylamide gel in an SDS-PAGE buffer solution at 200 V for about 35 minutes. Gels were stained, destained, and imaged the next day. An example gel is provided in FIG.13, which is keratin for SDS-PAGE.

[0056] FIGS.14A and 14B are graphs of nuclear magnetic resonance (NMR) spectroscopy for samples before and after reaction. In FIG.14A, the NMR of PEG-4-SO- MI is shown which includes a single peak 202 on the far left side of the graph. The thiol- conjugated PEG-4-SO-MI after reacting PEG-4-SO-MI with stoichiometric amount of CME is shown in FIG.14B. The single peak 202 on the left of FIG.14A indicates maleimide, which is not present in FIG.14B. This indicates that the free thiol groups react with maleimide before touching the thioester.

[0057] PEG-4-SO-MI synthesis and characterization was also performed. The PEG-4- SO-MI crosslinker containing four thioester (SO) and four maleimide (MI) end caps (e.g., multifunctional crosslinker 12) was designed and synthesized. First, the Succinimidyl Glutarate (SG) was reacted with thioglycolic acid in the presence of N,N- diisopropylethylamine (DIPEA) to introduce four thioester moieties. Next, the carboxylic acid end caps reacted with MAL moieties using (benzotriazol-1- yloxy)tripyrrolidinophosphonium hexafluorophosphate (PyBOP) as the coupling agent in the presence of DIPEA. The thioester (SO)-linked and maleimide(MI)-capped 4-arm PEG(PEG-4-SO-MI) was synthesized according to published reports with minor modifications. The two-step overall yield of the reaction is about 60%. The degree of modification was between 60 and 75%, indicating that on average at least two arms out of the four were modified with thioester and maleimide groups. Therefore, all the modified PEG crosslinkers can be integrated into the dynamic network.

[0058] The example biomaterial 16 gel was formed via the Michael type addition of MI on PEG-4-SO-MI (10k g / mol, 6.7 wt%, ~16 mM MI) and thiols on keratin-SH (3.3 wt%, ~33 mM -SH). The two aqueous solutions of PEG-4-SO-MI and keratin-SH (1:1 v:v) were mixed vigorously immediately upon mixing under ambient conditions and the gels formed rapidly. The molar ratio of MI, SH and thioester was approximately 1:2:1, with the assumption that thiol-maleimide reaction is faster than thiol-thioester. However, other ratios may be used in other examples. And, the excess thiol motifs after the consumption of thiol-maleimide reaction can provide for the shear-thinning properties, as they have thiol-thioester exchange with the network to provide self-healing as shear forces breaks the network of biomaterial 16. Other example biomaterials may be formed in similar methods consistent with the description herein.

[0059] The selectivity of thiol reacting with maleimide over thioester was investigated by treatment of the PEG-SO-MI with CME at stoichiometric equivalent amount. The proton resonance at 6.7 ppm corresponding to the vinylic protons on the maleimide ring completely disappeared, indicating that the thiol on CME selectively reacted with maleimide first (as shown in FIGS.14A and 14B). This suggests that there should be excess thiol functional groups as the biomaterial includes a 2:1:1 ratio of thiol:maleimide: thioester in the biomaterial 16 hydrogels. The pKa of cysteine is 8.5, which indicates that at physiological conditions the thiols remain deprotonated and will react with maleimide first. Thiol-maleimide reaction is known to be very rapid even at low pH conditions (within seconds of mixing), which corresponds to the observed rapid gelation. Therefore, in this formula, there should be approximately 1:1 ratio of thiol and thioester available for the thiol-thioester exchange reactions. In other examples, the ratio can be strategically manipulated for thiol, maleimide, and thioester to control the amount of free thiols in the hydrogel network and therefore control the dynamics of the biomaterial 16 hydrogel network. In some examples, changes of pH may also provide another handle on adjusting the hydrogel properties, because thiol functional groups can deprotonate more at higher pH conditions. As shown in the example of FIG.1, biomaterial 16 can be a hydrogel formed from PEG-4-SO-MI and keratin-SH. Indeed the schematic representation showsforming of biomaterial 16 network utilizing the maleimide on PEG-4-SO-MI (crosslinker 12) and the thiols on keratin-SH (polymer 14).

[0060] FIG.2 is a schematic representation of an example reaction for hydrogel formation an example thioester-thiol exchange reaction. In the top reaction 26 for gelation, the hydrogel formation via the Michael type addition between -MI and –SH. In the bottom thioester-thiol exchange reaction 28, the excess thiols on keratin-SH resulted in the shear-thinning properties and the addition of small molecule containing thiols caused hydrogel dissolution.

[0061] FIGS.3A and 3B are graphs of example biomaterial behavior subject to different frequencies and stead shear rates. FIGS.3C and 3D are graphs of example biomaterial moduli due to different strain. Specifically, the example of FIG.3A shows representative frequency sweep result of biomaterial 16 hydrogel at 0.2% strain representing the solid- like behavior of the IODD hydrogel. The example of FIG.3B shows viscosity versus steady shear rate for IODD hydrogel. FIG.3C shows representative oscillatory strain sweep result of Storage modulus (G’) and loss modulus (G”) of biomaterial 16 hydrogel at 10 hz frequency. FIG.3D shows storage modulus (G’) and loss modulus (G”) recovery of biomaterial 16 hydrogel at low (0.1%) and high (700%) oscillatory strain at a constant 10 rad / s frequency.

[0062] Hydrogel mechanical properties were determined for example biomaterial 16. The viscoelastic properties of the hydrogel were studied using a rheometer. First, the oscillatory strain sweep test was done to determine the linear viscoelastic region of the material. The storage (G’) and loss (G’’) moduli were independent of imposed stress or strain level in the range of 0.01 to 100%, indicating the linear viscoelastic region (FIG. 3C). Then, the frequency sweep was run at a constant 0.2% strain (value chosen from the linear viscoelastic region). The G’ and G’’ values were ~1000 and 10 Pa, respectively, which corresponded to an elastic hydrogel (FIG.3A).

[0063] Hydrogel Shear-Thinning and Self-Healing behavior were also tested. The shear- thinning behavior of the network was investigated on the composition that contains 1:1 ratio of thioester and excess thiol groups. A significant decrease in viscosity was observed in the shear-rate sweep test from low (0.1 S-1) to high shear rate (100 S-1) (FIG. 3B).

[0064] Step-shear measurements were performed to evaluate the recovery of the hydrogel. FIG.3D shows five cycles of high (700%) to low (0.2%) oscillatory strain amplitudes and the resulting DTS gel moduli. At low shear strain, the DTS gel exhibitedelastic solid properties and a storage modulus of 1000 Pa. At high shear strain (700%), the hydrogel structure was disrupted, demonstrated by an increase in G’’ and decrease in G’. The dominating G’’ indicated injectable liquid-like characteristics. The elastic strength of the gel was recovered instantaneously when the shear strain was reduced to low (0.2%), exhibiting the rapid self-healing which indicated that the material will not flow after the administration to the targeted site.

[0065] FIGS.4A, 4B, 4C, and 4D are illustrations of an example system configured to deliver a biomaterial configured for shear-thinning as described herein. In the example of FIG.4A, biomaterial 16 gel is injectable through a 65 cm long 4F catheter. A representative image of the formed biomaterial 16 gel in a 1 mL luer-lock syringe connected with a 4F catheter. In the example of FIG.4B, the biomaterial 16 gel containing 20 wt% Visipaque was visible under the fluoroscope. The biomaterial 16 gel containing 20 wt% Visipaque was injected through a 4F catheter to air (as shown in FIG. 4C) and to saline (as shown in FIG.4D).

[0066] Needle and catheter injectability is possible. FIG.4C shows that the biomaterial 16 gel can be injected through a 4F catheter as a continuous hydrogel strand. In addition, FIG.4D shows that the hydrogel strand of biomaterial 16 injected in saline remained its shape (e.g., it self-healed) after shear stress was removed after leaving the catheter.

[0067] FIG.5 is a graph of injection force vs. extension for an example biomaterial described herein. As shown in the example of FIG.5, the injection force required to pass biomaterial 16 gel through a catheter changes as the plunger of the syringe moves. The injection force was defined as the force value of the plateau. The injection force was quantified and had a max injection force of 12.5 N and the force plateaued at the average of 8.5 N in FIG.5. Typical injectable does not mean catheter injectable: Hagen Poiseuille's Law. P is proportional to catheter length and inversely dependent on 4th power of the diameter. Many injectable hydrogels are injectable through needles. However, few hydrogels are reported to be catheter injectable.

[0068] FIG.6 includes images of example biomaterials with different liquids. Generally, biomaterial 16 is dissolvable and degradable in thiol-containing environment. As shown in the example of FIG.6, the biomaterial 16 gel can undergo in vitro on-demand dissolution in 0.3M CME dissolving agent solution.

[0069] On-demand dissolution and in vitro degradation may be a useful property. Thioester containing hydrogels can have on-demand dissolution properties. In this example, an aqueous solution of 0.3M CME at pH 8.5 and 10wt% sucrose was used asthe dissolving agent. The dissolution was observed in the presence of the dissolving agent in less than three minutes while the biomaterial 16 gel in saline remained the hydrogel status, as shown in FIG.6. The use of 0.3M CME has shown rapid dissolution with good biocompatibility in the application of wound healing and hemostatic sealant. The addition of 10 wt% sucrose was chosen to regulate the osmotic pressure between cells and their external environment. The slightly higher pH at 8.5 deprotonate the thiol functional groups in CME to achieve rapid dissolution.

[0070] FIG.7 is a graph of the remaining mass of an example biomaterial over time, and FIG.8 is a graph of swelling of an example biomaterial over time. Glutathione (GSH) is a cysteine-containing tripeptide that is found in tissues. As shown in FIG.7, the biomaterial 16 gel was degradable in GSH solutions (pH ~7). The degradation rate is higher at higher GSH concentration. In saline (line 100), the hydrogel maintained a relatively stable mass indicating the covalent bonds in the network was not subjected to hydrolysis. At 10 mM GSH condition (line 104), the biomaterial 16 hydrogel was completely dissolved at 6 hours. At 0.01 mM GSH condition (line 102), the hydrogel was slowly degrading.

[0071] In the example of FIG.8, biomaterial 16 gel is swelling in GSH solutions (pH ~7). In saline (line 110), the biomaterial 16 hydrogel stayed at about 120% of their original size. In the 10 mM GSH (line 114), the biomaterial 16 gel quickly degraded within 6 hours. The increased volume in 0.01 mM (line 112) indicated the breakage of the biomaterial 16 hydrogel network by GSH.

[0072] The concentration of GSH is higher than carcinoma tissue than in healthy tissues due to the abnormal proliferative activities of cancer cells. The stability of biomaterial 16 gel in saline and the tunable degradation based on GSH concentrations were shown in FIGS.7 and 8. In saline, the biomaterial 16 gel was stable at least for 144 hours (6 days) without significant change. In 0.01 mM GSH, biomaterial 16 gel started to swell and the swelling became significantly faster after 24 hours, indicating the breakage of the IODD gel network. In 10 mM GSH, the biomaterial 16 gel dissolved within 6 hours.

[0073] FIG.9 includes photographs of example clotting of a biomaterial in vitro, showing that biomaterial 16 gel is hemocompatible and hemostable in vitro. Representative photographs of the clotting time assay in vitro of the biomaterial 16 gel, with TCP as a control, in a 96 well-plate are provided. FIG.10 is a graph of example degradation of a biomaterial by mass over time in vitro, such as degradation of biomaterial 16 gel in plasma at 37°C. FIG.11 is a graph of hemolysis potential of example materials,including a biomaterial hydrogel as described herein. Hemolysis potential of biomaterial 16 gel is indicated, with saline as the negative control and DI water was the positive control. Hemostatic activity and hemocompatibility was assessed as shown in these figures.

[0074] In these examples, the hemostatic activity and hemocompatibility of biomaterial 16 gel were assessed using ovine blood. The clotting time when blood is in contact was observed at 10 minutes, whereas the clotting time without the biomaterial 16 was 11 minutes, as shown in FIG.9. Keratin has been reported to contribute to hemostasis. The potential of biomaterial 16 degradation in plasma was evaluated by incubation of biomaterial 16 with ovine blood plasma. In the 24 hours experimental time, no degradation was observed, as shown in the example of FIG.10. As the embolic agents involves the direct contact with blood, their hemolytic effect needs to be evaluated in which quantification of hemoglobin released from the ruptured red blood cells was investigated. The hemolysis percentage values of biomaterial 16 and the dissolving agent CME sucrose solution were 5.96 ± 4.93 % and 0.19 ± 1.15 % respectively. Both values indicated low hemolysis that were nonsignificant when compared with saline, as shown in FIG.11.

[0075] FIG.12 includes images of example embolization using an example biomaterial hydrogel as described herein. Images A and B show transcatheter arterial embolization (TAE) of renal arteries using biomaterial 16 in rabbits using 4F catheter. Images C and D use a 2.4 F microcatheter. TAE and on-demand recanalization using rabbit kidney as are shown in images E-H and in liver is shown in images I-K. Images A and C show that pre-embolization angiography showing patency of renal arteries. Images B and D indicate that 15 minutes post-embolization DSA confirms complete occlusion of the renal arteries. Black arrow heads indicate the radiopaque contract stopped at the location where biomaterial 16 was present.

[0076] In this example of in vivo rabbit model embolization and on-demand recanalization, the rabbit model was chosen to demonstrate the feasibility and applicability of biomaterial 16 gel for clinical use in embolization and on-demand recanalization for non-targeted embolization. In all the studies, a male New Zealand white rabbit was anesthetized, intubated using V-gel, and monitored throughout the procedure. The right femoral artery was accessed using a 4F sheath. The main renal artery was then catheterized with a 4F catheter.

[0077] The right kidney was used on the first rabbit to assess the embolization feasibility. Before the embolization, the renal arteries were patent, allowing the perfusion of radiopaque Visipaque (FIG.12, image A). After the injection of about 0.3 mL biomaterial 16 gel, the renal arteries were completely occluded (FIG.12, image B), indicated by the reflux of Visipaque.

[0078] The catheter deliverability of the biomaterial 16 gel through was also demonstrated using a 2.4-F microcatheter in the left kidney of the first rabbit, as shown in FIG.12, images C and D.

[0079] The second rabbit was used to assess the embolization and on-demand recanalization. FIG.12, image A shows a patent artery before the embolization, indicated by the perfusion of Visipaque. The renal artery was then successfully embolized within seconds after injection of about 0.3 mL biomaterial 16 gel. The biomaterial 16 gel remained in place, persisting the vessel occlusion for at least 10 minutes without migrating (FIG.12, image B). Next, a microcatheter was advanced to the smaller vessel and administered 0.2 mL dissolving agent. After 5 minutes, Visipaque was injected and demonstrated the re-opening of the small area where the biomaterial 16 gel was dissolved by the dissolving agent solution. This result demonstrated the super-selectivity of the on- demand dissolution. Because the dissolving rate is dependent on the concentration of CME and the pH of the solution, at current formula, only the areas adjacent to the dissolving agent administration site, where the microcatheter tip was located, can be re- opened (FIG.12, image C). Hepatic artery catheterization, embolization and subsequent recanalization was performed in the third rabbit model.

[0080] FIG.15 is a flow chart of a technique for delivering a shear-thinning biomaterial as described herein. The example technique will be described with respect to biomaterial 16, but any biomaterial according to this disclosure that is configured to have shear- thinning and self-healing properties may be used in this example,

[0081] As shown in the example of FIG.15, a user may fill a syringe with hydrogel, such as biomaterial 16 (30). In some examples, the syringe or other pressure-producing reservoir may be pre-filled with biomaterial 16 by a company, clinic, or in any way prior to use by the user. The user may insert a catheter attached to the syringe to the delivery site, which may be a blood vessel in some examples (32). In other examples, the user may insert the catheter first, and the syringe later attached. In some examples, the syringe may be filled with biomaterial 16 prior to insertion into the patient.

[0082] In some examples, the product may be two different polymers that are stored as separate dried powders. Each dry powder can be made into a solution in separate vials to form separate solutions, and then a user or machine can place those separate polymer solutions into separate 1 mL syringes. These two syringes can then be connected through a 3-way connector that leads into a single catheter. When the syringes are depressed, the separate solutions can flow through the 3-way connector and mix the aqueous polymer solutions in the 3-way connector and catheter to cause gelation of the mixing two polymers and into the hydrogel.

[0083] Once the catheter distal end is at the target location, the user can depress the syringe plunger (or multiple plungers or respective syringes) to cause shear-thinning of the hydrogel and delivery of the hydrogel out of the syringe and catheter (38). The user can then stop depressing the plunger to stop delivery of biomaterial 16, which may cause the biomaterial 16 to increase in viscosity once again (40). When the user is finished delivering biomaterial 16, the user can remove the catheter from the patient (42). As described herein, the user may dissolve biomaterial 16 in the patient when desired, either by flushing the area with dissolution fluid or reinserting a catheter to the embolized area containing biomaterial 16.

[0084] As described herein, the examples illustrate the development and proof-of-concept demonstration of a biomaterial, such as a gel, as safe and endovascularly injectable hydrogel, capable of blood vessel occlusion and on-demand re-opening. The biomaterial gel can be rapidly prepared by mixing aqueous solutions of biocompatible human hair keratin and PEG. The pre-gel cursors were two low-viscosity aqueous solutions and the addition of contrast (Visipaque) did not change its properties. The formed gel can be injected through 20 and 30 gauge needles as well as 4F and 2.8 F clinically relevant catheters. The biomaterial gel and the dissolving agents had low toxicity and no significant blood vessel damage.

[0085] In some examples, the biomaterial gel we reported herein present 1) shear- thinning properties and endovascularly injectable capability; 2) vessel occlusion and on- demand dissolution feature. A biomaterial gel as described herein may provide advantages such as a single-catheter injectable hydrogel that allows for rapid dissolution. The unique properties of biomaterial gel make it an improved embolic agent that has the potential to eliminate or reduce life-threatening and unavoidable off-target embolization. This biomaterial gel and its derivative hydrogels can serve as a promising hydrogelplatform for broad application including endovascular luminal repairing, drug / cell delivery, and tissue engineering.

[0086] The following examples are described herein,

[0087] Example 1. A biomaterial comprising: a plurality of thioester functional groups linkages; and a polymer comprising a plurality of free thiol functional groups.

[0088] Example 2. The biomaterial of example 1, wherein the biomaterial is in the form of a hydrogel.

[0089] Example 3. The biomaterial of any of examples 1 or 2, wherein the polymer comprises keratin.

[0090] Example 4. The biomaterial of any of examples 1 through 3, wherein the plurality of free thiol groups are bonded directly to the polymer.

[0091] Example 5. The biomaterial of any of examples 1 through 4, wherein the polymer is a first polymer comprising a plurality of polymer segments, and wherein the biomaterial comprises a plurality of second polymers crosslinked to the polymer segments via at least some thioester functional group linkages of the plurality of thioester functional group linkages.

[0092] Example 6. The biomaterial of example 5, wherein the plurality of second polymers comprises monomeric or copolymeric units chosen from poly(ethylene oxide) (PEO), poly(vinyl alcohol) (PVA), poly(acrylic acid) (PAA), polyacrylamide, poly(N-(2- hydroxypropyl) methacrylamide) (PHPMA), a polysaccharide, poly(ethylene glycol) (PEG), polyesters, polyethers, polyglycerols, polypeptides, polyether-esters, polyamino acids, polyester-amines, polyurethanes, polycarbonates, polyamino alcohols and combinations thereof.

[0093] Example 7. The biomaterial of example 6, wherein the plurality of second polymers are water soluble and comprise PEG.

[0094] Example 8. The biomaterial of any of examples 5 through 7, wherein the plurality of second polymers comprise multi-arm polymers.

[0095] Example 9. The biomaterial of any of examples 5 through 8, wherein at least some of the plurality of thioester functional group linkages are bonded directly to a respective maleimide group of a plurality of maleimide groups.

[0096] Example 10. The biomaterial of example 9, wherein biomaterial comprises a greater number of the free thiol functional groups than the plurality of maleimide groups.

[0097] Example 11. The biomaterial of example 10, wherein the molar ratio of the free thiol functional groups to the plurality of maleimide groups is approximately 2:1.

[0098] Example 12. The biomaterial of any of examples 1 through 11, wherein the biomaterial is configured to undergo shear-thinning when subject to shear-forces.

[0099] Example 13. A method for making the biomaterial of any of examples 1 through 12, wherein the method comprises reacting a first aqueous pre-gel solution comprising a water soluble keratein with an aqueous solution comprising crosslinking compounds comprising the plurality of the thioester functional group linkages, to create the biomaterial comprising the polymer crosslinked with the plurality of thioester functional group linkages.

[0100] Example 14. A system for delivering the biomaterial of any of examples 1 through 12, wherein the system comprises: a single catheter configured to be disposed within a blood vessel; and a syringe configured to be coupled to the single catheter and filled with the biomaterial, wherein compression of a plunger of the syringe causes shear-thinning of the biomaterial and movement of the biomaterial through the single catheter.

[0101] Example 15. A kit for conducting an embolization procedure using the biomaterial of any of examples 1 through 12, the kit comprising: a first solution comprising a first polymer comprising the plurality of thioester functional group linkages; a second solution comprising a second polymer comprising the plurality of free thiol functional groups; saline; a 3-way connector; a catheter configured to couple to the 3-way connector; a first syringe configured to withdraw the first solution; a second syringe configured to withdraw the second solution, wherein the first and second syringes are configured to mix the first and second solutions via the 3-way connector and pressurize a resulting hydrogel from mixing the first and second polymers of the first and second solutions to cause shear-thinning of the hydrogel and movement of the hydrogel through a catheter, wherein the hydrogel is configured to thicken and form an occlusion upon exiting the catheter.

[0102] Example 16. A method for making a biomaterial, wherein the method comprises: reacting a first aqueous pre-gel solution comprising a water soluble keratein with an aqueous solution comprising crosslinking compounds comprising a plurality of thioester functional group linkages, to create the biomaterial comprising a polymer crosslinked with the plurality of thioester functional group linkages.

[0103] Example 17. The method of example 16, wherein the biomaterial comprises a plurality of free thiol functional groups.

[0104] Example 18. A system for delivering a biomaterial, wherein the system comprises a biomaterial comprising a plurality of thioester functional groups linkages and a polymer comprising a plurality of free thiol functional groups; a single catheter configured to bedisposed within a blood vessel; and a syringe configured to be coupled to the single catheter and filled with the biomaterial, wherein compression of a plunger of the syringe causes shear-thinning of the biomaterial and movement of the biomaterial through the single catheter.

[0105] Example 19. A kit for conducting an embolization procedure, the kit comprising: a first solution comprising a first polymer comprising a plurality of thioester functional group linkages; a second solution comprising a second polymer comprising a plurality of free thiol functional groups; saline; a 3-way connector; a catheter configured to couple to the 3-way connector; a first syringe configured to withdraw the first solution; a second syringe configured to withdraw the second solution, wherein the first and second syringes are configured to mix the first and second solutions via the 3-way connector and pressurize a resulting hydrogel from mixing the first and second polymers of the first and second solutions to cause shear-thinning of the hydrogel and movement of the hydrogel through a catheter, wherein the hydrogel is configured to thicken and form an occlusion upon exiting the catheter.

[0106] Various examples of the invention have been described. These and other examples are within the scope of the following claims.

Claims

WHAT IS CLAIMED IS:

1. A biomaterial comprising: a plurality of thioester functional groups linkages; and a polymer comprising a plurality of free thiol functional groups.

2. The biomaterial of claim 1, wherein the biomaterial is in the form of a hydrogel.

3. The biomaterial of any of claims 1 or 2, wherein the polymer comprises keratin.

4. The biomaterial of any of claims 1 through 3, wherein the plurality of free thiol groups are bonded directly to the polymer.

5. The biomaterial of any of claims 1 through 4, wherein the polymer is a first polymer comprising a plurality of polymer segments, and wherein the biomaterial comprises a plurality of second polymers crosslinked to the polymer segments via at least some thioester functional group linkages of the plurality of thioester functional group linkages.

6. The biomaterial of claim 5, wherein the plurality of second polymers comprises monomeric or copolymeric units chosen from poly(ethylene oxide) (PEO), poly(vinyl alcohol) (PVA), poly(acrylic acid) (PAA), polyacrylamide, poly(N-(2-hydroxypropyl) methacrylamide) (PHPMA), a polysaccharide, poly(ethylene glycol) (PEG), polyesters, polyethers, polyglycerols, polypeptides, polyether-esters, polyamino acids, polyester- amines, polyurethanes, polycarbonates, polyamino alcohols and combinations thereof.

7. The biomaterial of claim 6, wherein the plurality of second polymers are water soluble and comprise PEG.

8. The biomaterial of any of claims 5 through 7, wherein the plurality of second polymers comprise multi-arm polymers.

9. The biomaterial of any of claims 5 through 8, wherein at least some of the plurality of thioester functional group linkages are bonded directly to a respective maleimide group of a plurality of maleimide groups.

10. The biomaterial of claim 9, wherein biomaterial comprises a greater number of the free thiol functional groups than the plurality of maleimide groups.

11. The biomaterial of claim 10, wherein the molar ratio of the free thiol functional groups to the plurality of maleimide groups is approximately 2:

1.

12. The biomaterial of any of claims 1 through 11, wherein the biomaterial is configured to undergo shear-thinning when subject to shear-forces.

13. A method for making the biomaterial of any of claims 1 through 12, wherein the method comprises reacting a first aqueous pre-gel solution comprising a water soluble keratein with an aqueous solution comprising crosslinking compounds comprising the plurality of the thioester functional group linkages, to create the biomaterial comprising the polymer crosslinked with the plurality of thioester functional group linkages.

14. A system for delivering the biomaterial of any of claims 1 through 12, wherein the system comprises: a single catheter configured to be disposed within a blood vessel; and a syringe configured to be coupled to the single catheter and filled with the biomaterial, wherein compression of a plunger of the syringe causes shear-thinning of the biomaterial and movement of the biomaterial through the single catheter.

15. A kit for conducting an embolization procedure using the biomaterial of any of claims 1 through 12, the kit comprising: a first solution comprising a first polymer comprising the plurality of thioester functional group linkages; a second solution comprising a second polymer comprising the plurality of free thiol functional groups; saline; a 3-way connector;a catheter configured to couple to the 3-way connector; a first syringe configured to withdraw the first solution; a second syringe configured to withdraw the second solution, wherein the first and second syringes are configured to mix the first and second solutions via the 3-way connector and pressurize a resulting hydrogel from mixing the first and second polymers of the first and second solutions to cause shear-thinning of the hydrogel and movement of the hydrogel through a catheter, wherein the hydrogel is configured to thicken and form an occlusion upon exiting the catheter.

Images