Single solution hydrogels with covalent bonds formed in situ, composition designs and medical treatments using the same

Abstract

Compositions, methods, and uses for single-component systems for the formation of in situ hydrogels are described. The single-component systems are effective to form a stable single solution containing precursors that provide both electrophilic and nucleophilic groups that chemically crosslink upon contact with physiological fluids associated with physiological tissues of the living body. The single-component systems can be applied using a variety of delivery vehicles, such as injections, needle and needle-free catheters, sprayers, etc. The single-component systems can be useful to allow multiple injections from a single syringe through small gauge needles or other dispensers. Methods for transcervical placement of the in situ formed hydrogels into one or more fallopian tubes are described.

Description

[Technical field]

[0001] Aspects of the present invention relate to single-component compositions and methods of application for forming hydrogels in situ. The present invention further relates to stable hydrogel solutions that chemically crosslink upon contact with physiological fluids and / or tissues. [Background technology]

[0002] Hydrogels have found important applications in a wide range of medical applications, including as drug delivery platforms, adhesion inhibitors, sealants, space fillers, and organ spacers. Hydrogels based on certain chemistries have gained widespread acceptance based on their overall good tolerability and minimal side effects. Corresponding approved products are commercially available.

[0003] Implants that slowly deliver drugs in therapeutically effective doses are useful in many fields. In the context of drug delivery, hydrogels can provide large reservoir volumes while offering the ability to engineer release profiles within selected ranges. This advancement in technology allows for the delivery of a variety of drugs with different solubilities and stabilities. Hydrogel-based drug delivery systems offer the ability to engineer controlled drug releases suitable for a variety of applications.

[0004] Many in situ formed hydrogels use two-component systems to activate the in situ hydrogel forming reaction upon mixing. This can have the advantage of providing a discrete starting point, allowing for rapid and reliable formation of the hydrogel. However, for medical applications, specialized delivery catheters, sprayers, and other devices are typically required, and the two-component nature of these systems can make the design, development, and use of these delivery systems more complicated. To date, no single-component system has been developed that can achieve reproducible polymerization of hydrogel systems on time scales that are convenient and useful in medical or surgical situations. Summary of the Invention [Means for solving the problem]

[0005] Disclosed are biocompatible crosslinked polymers, methods for their preparation, and methods of use, in which a single solution system containing precursors providing both electrophilic and nucleophilic groups capable of reacting and crosslinking in situ is used to form a hydrogel, which is formed in the absence of a separate precursor solution. The crosslinking reaction can be performed in situ after deposition of the single mixture, but the solution forming the system remains an aqueous mixture containing a selected ratio of electrophilic and neutrophilic groups prior to placement in vivo. Applications of such biocompatible hydrogels include, for example, the formation of injectable depots, space or dermal fillers and tissue augmentation, augmentation and spacing applications, and extraluminal stenting of lumens, including blood vessels or hollow organs. Additional applications may be useful in primary or secondary controlled drug delivery applications, particularly for placement in difficult to access locations that are currently not possible with bulky two-part systems that are at risk of clogging.

[0006] Compositions, methods, and uses are provided for biocompatible hydrogels formed in situ in the absence of chemical or physical activators for use in medical devices and pharmaceutical applications. The invention is based on electrophilic and nucleophilic species being dissolved together in a single working system, where the electrophilic species is a macromer, such as a polymer, with suitable reactive functional groups to form an adduct with a suitable nucleophile, and the nucleophilic species can be a macromer, such as a polymer, in an acid complex form that can lower the pH when used in aqueous solutions that may be unbuffered. Unlike similar existing covalently crosslinked hydrogel systems known in the art, this composition does not require a separate activator or external activation event to function. Conventional technologies surrounding hydrogel single solution systems require the input of energy in the form of radiation or thermal energy to promote crosslinking for in situ hydrogel formation. Dual systems known in the art require mixing of two components and use of an activator in the form of a pH-based promoter or radical initiator for redox reactions. In contrast, the single solution system of the present invention does not require separation of reactive components, external input from an activation source, or immediate delivery after mixing to form the depot in situ. The electrophilic and acid complexing species are dissolved in an aqueous solution and remain unreacted until introduced into the body, where the acid complexing species are neutralized by diffusional exchange of fluids, raising the local pH at the site of the precursor and forming a gel in situ. The single solution system can include therapeutic agents to provide additional therapy in combination with the application of the hydrogel to a medical device, or can function alone as a drug depot capable of localized and / or some degree of systemic drug delivery. The therapeutic agent can be included as a low solubility slow eluting component or as a suspended drug delivery particle that is further encapsulated by the hydrogel. In some embodiments, the same or different type of hydrogel can be used for secondary hydrogel encapsulation, resulting in a suspension of hydrogel particles within the single solution system in situ forming hydrogel formulation.

[0007] The application method of the in situ forming system obtained from a single solution of both electrophilic and nucleophilic acid complex species includes introduction by conventional means using intraluminal delivery. Suitable delivery means include injections, needle and needleless catheters, sprayers, and the like, including tools known in the art. Advantages of the present invention include eliminating the need for mixing and specialized delivery systems, and allowing multiple injections from the same actuation system without strict time constraints. Unlike dual reservoir systems known in the art, this system allows for intraluminal delivery to be stopped and restarted without clogging the delivery device until the desired application is achieved or the system is depleted. The application method of the single system in situ hydrogel without external activating agents offers the possibility of integration with conventional delivery systems, while eliminating all of the associated problems of sophistication, ease of use, and accessibility seen in the prior art.

[0008] The application of a single solution system containing two reactive precursors that can form a gel without external activators or secondary activators required for depot formation in the body is ideal in clinical applications where the flow of the precursor solution may be restricted or where the diffusion area defined by the surrounding tissues / organs / anatomical features may be limited. Applications that are particularly suitable for the compositions of the present invention include procedures where the gel time can be extended and the need for rapid gelation, such as less than 20 seconds, is not critical and the system is not significantly diluted. These applications include injection into the eye for bulk augmentation, such as dermal fillers, or scleral bulking, or placement of a depot in the fornix of the eye. Additional clinical applications include reinforcing the luminal walls surrounding hollow blood vessels and / or organs to prevent luminal narrowing and occlusion. In other applications, the lumen can be opened with a standard balloon catheter and the single system can be injected into the wall without the use of external activators or specialized catheter delivery devices. This approach to widening the lumen may be useful, for example, in the treatment of benign prostatic hyperplasia (BPH), where urinary flow may be restricted by narrowing of the urethral lumen. Injection of a single-component hydrogel-forming precursor can be performed within the prostate body, and then as the precursor solidifies and "sets" in a compacted configuration within the prostate, an intraluminal balloon can be inflated to mold the urethra into an open, expanded position. Injection into the prostate can be performed intraurethrally or via a transrectal route, similar to that performed during a prostate biopsy.

[0009] Other applications may include cases where a single solution system is a therapeutic delivery depot, such as for vault insertions, intraocular injections into the anterior and posterior spaces of the eye, and intratumoral injections of chemotherapy delivery depots that are difficult or impossible to access with traditional catheter access. Multi-pronged needles that allow injections into tumors and even circumferentially around the lumen are useful delivery systems for such precursors. Other applications may focus on therapeutics where off-target drug application would result in side effects, which may be achieved with a start-stop hydrogel system by the ability to perform small repeated injections (i.e., tattoos, Botox® injections, or injections into the eyelash line). In tattoo applications, tattoos that last for a significant period of time, but only for a limited period of time, or tattoos that contain non-degradable hydrogels, may be provided. Other stop-start applications include multiple needle injections using a single solution prepared for administration to multiple patients. Other stop-start applications specific to single-solution systems containing acid complexes that cannot be achieved with two-solution systems requiring external application include nasal applications such as sprays, which require unblocked exposure of both nasal passages, or high-pressure needleless injections, where crosslinking is initiated prior to entry into the body, preventing penetration through the skin.

[0010] One particularly desirable application involves filling a patient's fallopian tubes for contraception or other medical purposes. The hydrogel system described herein is well suited for penetrating the complex structure of the fallopian tube wall. The hydrogel can be designed to last for an extended period of time, such as at least about 180 days, or perhaps the patient's lifetime, or can be designed to last for a shorter selected period of time.

[0011] In one aspect, the present invention relates to a medical hydrogel precursor solution that contains a mixture of an aqueous solvent having a pH of about 6 or less, a first precursor comprising a plurality of electrophilic functional groups and a first hydrophilic core, and a second precursor comprising a plurality of protonated amine groups. Typically, the precursor solution remains fluid for at least 10 minutes after formation and gels within 20 minutes after dilution with ⅓ volume of 37° C. phosphate buffered saline (PBS) (3 volumes of hydrogel precursor solution with 1 volume of PBS).

[0012] In a further aspect, the present invention relates to a medical hydrogel precursor solution comprising an aqueous solvent having a pH of about 6 or less, a mixture of a first precursor comprising a plurality of electrophilic functional groups and a first hydrophilic core, and a second precursor comprising a plurality of protonated amine groups and a second hydrophilic core.

[0013] In a further aspect, the present invention provides a method for delivering a medical hydrogel for in situ crosslinking, comprising: blending an electrophilic precursor and a nucleophilic precursor with an aqueous solvent having a pH of about 6 or less to form a precursor solution having storage stability to flow conditions at room temperature for at least about 10 minutes, said storage stability being determined by the ability to inject the precursor solution from a 5 ml syringe equipped with a 25 gauge needle; and delivering a quantity of a precursor solution to the patient, wherein the precursor solution contacts physiological fluids associated with physiological tissue of the body to induce crosslinking of the hydrogel, such that the hydrogel gels in vivo within about 5 minutes; The present invention relates to a method comprising the steps of:

[0014] In another aspect, the present invention provides a method for producing a composition comprising: 1. A method of injecting an in situ crosslinked hydrogel into a patient's fallopian tube, comprising: sequentially delivering a hydrogel precursor solution directly to a first fallopian tube of the patient using an applicator, and subsequently to a second fallopian tube of the patient; the applicator comprises a reservoir of hydrogel precursor solution connected to a catheter configured to transcervically place the hydrogel precursor in the fallopian tube; the hydrogel precursor solution comprises a mixture of a first compound having a plurality of electrophilic groups, a second compound having a plurality of nucleophilic groups, and an aqueous solvent having a pH of about 6 or less; the hydrogel precursor solution gels within about 3 minutes of contact with the tissue of the first fallopian tube and gels within about 3 minutes of contact with the tissue of the second fallopian tube; It concerns the method. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 illustrates the preparation of a single solution system. [Diagram 2] FIG. 1 shows an applicator with a single reservoir for delivering a single solution system. [Figure 3A] FIG. 1 is a side view of a delivery system for injecting crosslinkable precursors to seal a body cavity in a single solution system. [Figure 3B] FIG. 3B is a cross-sectional view taken along line AA in FIG. 3A. [Figure 4] FIG. 3B illustrates a method of occluding a fallopian tube using the device of FIG. 3A. [Diagram 5] 1 is a plot of gel time versus dilution as a function of pH for a buffered single solution system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] A medical hydrogel suitable for in situ formation by covalent crosslinking chemistry has been developed for delivery from a single stable solution. Delivery of the hydrogel precursor from a stable single solution offers great convenience to the physician in terms of delivering the composition without the need for strict planning around the time constraints set by the stability of the precursor, and in terms of enabling applications of hydrogels that were previously impractical. The system is designed to contact tissues such that the gelation process is achieved by pH changes induced by the natural physiological environment without the addition of additional energy sources or starting solutions. Thus, the treatment can be applied simply and efficiently without the need for manipulations other than the delivery of the composition. It would be advantageous to have a single component based formulation that can be delivered by conventional needle and fluid delivery systems already widely used in medicine. The composition can be effectively used for a variety of applications. Specific applications suitable for the hydrogel system described herein include delivery of hydrogels to fill the fallopian tubes in women. Other applications include, for example, ophthalmic applications for drug delivery, drug delivery for tumor treatment, treatment of BPH, and delivery of therapeutic agents around blood vessels, but a wide range of useful applications are described herein. A variety of applicator designs may be suitable, with some designs being effectively used with one hand.

[0017] Two-component hydrogel systems have been found to be widely applicable for medical applications involving in situ gelation. Commercially available products with in situ gelation include, for example, DuraSeal® Cranial Sealant (Integra Life Systems), DuraSeal® Exact Spine Sealant (Integra Life Systems), SpaceOAR™ (Boston Scientific), SpaceOAR™ Vue (Boston Scientific), and ReSure® Sealant (Ocular Therapeutix). Although two-component hydrogel systems work very well, the precursors are mixed in the catheter during delivery, and the catheter typically begins to clog in less than a minute. In some applications, the precursors can be mixed in a container for application in a predefined short time, such as less than 20 seconds. For appropriate applications, these are excellent conditions, and the hydrogel can gel correspondingly quickly, in some embodiments, within a few seconds. In other applications, this timing constraint may make it impractical, inconvenient, or excessively expensive due to the need to use the mixed material very quickly and the remaining material generally cannot be delivered to a second location, resulting in wasted material.

[0018] Some hydrogels can be initiated with radiation, such as UV or visible light, to mimic the radicals of the crosslinking process. See, for example, U.S. Pat. No. 5,410,016, entitled "Photopolymerizable Biodegradable Hydrogels as Tissue Contacting Materials and Controlled-Release Carriers," by Hubbell et al., and WO 2021 / 101983, entitled "Tough Tissue Sealants and Use Thereof," by Sheikhi et al., both of which are incorporated herein by reference. Embodiments involving delivery of UV light, such as with fiber optics or UV lamps, require additional time to perform crosslinking by irradiation and the expense of equipment to provide UV light or other radiation. For some applications, the use of radiation may be impractical due to the timing of crosslinking and the difficulty of irradiating the hydrogel precursor. The electrophilic-nucleophilic reactions involving the hydrogels described herein are controlled by pH.

[0019] To deliver a mixed electrophilic-nucleophilic precursor system with a single applicator, efforts have involved slowing down the gelation time sufficiently to allow the precursors to be mixed immediately prior to use. An embodiment of such a hydrogel is described in US Patent Application Publication No. 2016 / 0331738, entitled "Drug Delivery from Hydrogels" to Jarrett et al. (hereinafter the '738 application), which is incorporated herein by reference. The '738 application teaches a buffering agent that is added to each of the separate precursors that are then mixed. These hydrogels were specifically designed for injection into the eye where the hydrogel does not move significantly during the gel time (usually less than one minute, but may be up to five minutes). The delivery reservoir would have a pot life equivalent to the gel time. These systems would not have the advantages of the hydrogel systems described herein.

[0020] Applicant's co-pending application describes a mixture of nucleophilic and electrophilic precursors, which is then mixed with an activator solution during delivery. See Bassett et al., U.S. Patent Application Serial No. 17 / 494,752, entitled "Transcervical Access Systems For Intrauterine Fluid Exchange, Such As Placement of Hydrogels Formed In Situ" (hereinafter the '752 application), which is incorporated herein by reference. These systems provide excellent space-filling properties in moderate dilution situations and provide desirable short gel times. Further developed alternative hydrogel systems described herein can eliminate the use of an activation solution and provide a longer pot life for depositing hydrogels, but on the other hand, gel times may be somewhat longer and more susceptible to dilution effects. The present invention's developments in hydrogel systems and the embodiments of the '752 application together provide important features for corresponding appropriate applications.

[0021] A delivery catheter suitable for placement in the fallopian tube is described in U.S. Patent No. 6,152,943 to Sawhney, entitled "Methods and Apparatus for Intraluminal Deposition of Hydrogels" (hereinafter the '943 patent), which is incorporated herein by reference. Although other structures may be used, the basic structure of the catheter of the '943 patent and its modifications with appropriate adjustments for the precursor reservoir of the present invention will generally be desirable for delivery of hydrogel precursors to the fallopian tube. The '943 patent describes a hydrogel system of two precursor components that are mixed within the catheter during delivery.

[0022] Hydrogels are materials composed of insoluble hydrophilic polymers, and when fully hydrated, consist essentially of water within a matrix of insoluble hydrophilic polymers. Hydrogels can include materials that are absorbent or nonabsorbent when in contact with the patient's body fluids, and some hydrogels slowly hydrolyze and degrade when in contact with water or other aqueous solutions. Some hydrogel systems are able to control the crosslinking process by delaying crosslinking until delivery of the hydrogel. This is because, for example, a significant increase in the viscosity of the material flowing through the delivery device does not occur until the mass of hydrogel precursor is in place. Historically, these systems require the use of an external activation source that serves a dual purpose. First, it allows for the injection of hydrogel systems that only activate after they leave the application device to prevent catheter clogging. Second, it allows for working time before the act of injection. In these embodiments, activation has typically been achieved by the use of external radiation, such as light, to induce radical crosslinking or other energy input in thermally activated polymers, such as thermoreversible polymers and thermally induced radical polymerization. Single systems with external activation sources are cumbersome, limiting their use to certain clinical applications requiring one-handed application and manual dexterity, as well as lengthening procedure times. Furthermore, single-component thermoreversible polymers do not form hydrogels with the mechanical integrity and modulus suitable for many medical devices and longer-lasting drug delivery applications.

[0023] Dual-component systems involve mixing of two solutions that are fluid while the solutions pass through the applicator device and are configured to form a hydrogel in situ. Two-component systems suffer from the need for mixing and the "one and done" approach. These systems typically rely on mixing during deployment, which runs the risk of premature clogging of the device complicating placement of the hydrogel and the inability to reapply when multiple or reapplications are required, such as in two fallopian tubes. For suitable applications, two-component hydrogel systems based on a polyethylene glycol hydrophilic core have found commercial success, such as Duraseal® and Duraseal® Exact (Integra Lifesystems), Mynx® (Cordis), SpaceOAR™ and SpaceOAR VUE™ (Boston Scientific).

[0024] The hydrogels described herein can be delivered by less invasive means, typically a catheter for in situ gelation. Typically, the hydrogel can begin as a single liquid precursor solution capable of forming a gel upon contact with the patient's physiological fluid, which allows for the formation of the hydrogel by neutralizing the acidified amine groups, thereby equilibrating the pH at physiological pH and making it available for the crosslinking reaction. The exemplified NHS-amine crosslinking reaction does not occur significantly in unbuffered aqueous systems in which the amine-acid complex is present, nor in similar hydrogel systems. The unreacted co-dissolved product can be obtained by forming a single solution containing the acid complexes of the electrophilic and nucleophilic polymers in unbuffered or weakly acidic buffered solutions that naturally occur at low pH (typically pH 2-5). "Pot life" or storage stability is a term that refers to the amount of time that the single solution remains stable after co-dissolution.

[0025] The hydrogel precursors described herein surprisingly have a pot life of at least 1 hour, but can gel in less than 10 minutes, and in some embodiments, less than 1 minute, after delivery to a patient. Storage stability, as used herein, refers to the time from mixing the hydrogel precursors to form a precursor solution ready for delivery to a patient until the hydrogel becomes too viscous to be effective delivered due to effective transition to a non-flowable state. Effective delivery of the precursor solution may depend on the specific application, but to identify the storage stability of a precursor solution composition, this can be evaluated as injectability through a 24-gauge needle from a 5 ml syringe. These hydrogel precursors typically contain amines with a pH of 6 pH units or less prior to delivery, with acceptable buffer concentrations, or without added buffers. Dissolved carbon dioxide provides a small amount of carbonic acid, but this can be considered a baseline and is not an added buffer. Physiological fluids are naturally buffered due to the overlapping presence of dissolved carbon dioxide, and the presence of dissolved carbon dioxide does not interfere with the performance of the hydrogel. The design of these precursor solutions goes against the commonly held belief that buffers are important to control the behavior of the precursor. By formulating the precursor solutions with acceptable amounts of buffers or no additives, gel times can be desirably kept short by allowing for more rapid equilibration with the patient's physiological pH (usually around 7.1 and 7.6). The low pH of the precursor solutions prior to delivery inhibits significant crosslinking, resulting in a fairly long pot life. Pot life is essentially the time from preparation of the precursor solution until it becomes so viscous that it induces clogging of the delivery catheter.

[0026] The electrophilic precursor component may have a functional group suitable for crosslinking with an amine group to form a hydrogel. The crosslinking functional group is usually pendant on a hydrophilic core, which is usually a polymer, providing a moderate molecular weight. The precursor usually has three or more crosslinking groups, providing a highly crosslinked hydrogel. The precursor may or may not have a degradable functional group that can be degraded by hydrolysis by enzymes or other biodegradation pathways. The nucleophilic precursor usually contains three or more amine groups, which are usually pendant on a hydrophilic core. The hydrophilic core of the nucleophilic precursor may be a polymer. The amines in the precursor are usually substantially deprotonated under physiological conditions, making the amines available for crosslinking. The protonated amines are protected from crosslinking by acidification of the amines, stabilizing the precursor solution. The ability to rapidly deprotonate under physiological conditions allows for rapid crosslinking without basic buffers.

[0027] The single solution system described herein can be used to create a permanent or temporary blockage in the fallopian tube, such as for the purpose of preventing pregnancy. The single solution hydrogel system overcomes the limitations of other contraceptive methods targeted at the fallopian tube. One such method involves permanently implanting a metal coil device in the fallopian tube. After insertion, the device and associated scar tissue can block the fallopian tube, causing permanent infertility. One such device was sold under the brand name Essure®. Serious side effects have been reported with the Essure® device, including headaches, bleeding, allergic reactions, persistent pain, development of holes in the uterus or fallopian tube, and migration of the device from the fallopian tube to the pelvis or abdomen. According to a report from the U.S. FDA, sales of Essure® were discontinued in the United States in 2019. Other methods that have been attempted to sterilize women include forming silicone fallopian tube plugs by injecting liquid silicone into the fallopian tubes through a hysteroscope. This procedure requires a precise amount of catalyst to be mixed with the liquid silicone within a specific time period prior to injection. During administration, the hysteroscope must be carefully positioned and aligned before the catalyst is added. This procedure suffers from high failure rates of plug placement and retention, as well as problems with reactions to the silicone. One aspect of the high failure rate of silicone plug systems is believed to be due to a mismatch between the hydrophobic silicone and the hydrophilic tissue of the fallopian tube, which makes it impossible to access the folds and crevices present within the fallopian tube. Silicone in situ plugs have been clinically tested in the United States and marketed in Europe. Preformed silicone plugs were marketed for a short time under the trade name Adiana, but were discontinued after several years due to multiple problems. The single solution system disclosed herein is hydrophilic and forms a hydrophilic plug that is well retained. The use of a hydrogel polymer with a long history of successful implantation should avoid the problems seen with other polymer systems.

[0028] Antitumor drug delivery can be complicated with respect to delivering the desired dose to the tumor without inflicting toxic levels on the surrounding tissues, as antitumor drugs can be toxic to normal tissues. Studies using hydrogels as drug delivery matrices in tumor-implanted depots have suggested improved drug therapy. For example, 5-fluorouracil was loaded onto PEG-based polymers and tested in mice against induced tumors of human non-small cell lung adenocarcinoma with promising results. See Yi et al., “Pharmacokinetic properties and antitumor effect of the 5-fluorouracil loaded PEG-hydrogel,” BMC Cancer 2010,10:211, which is incorporated herein by reference. Similarly, to study the avoidance of drug washout in intratumoral drug delivery, the fluorescent dye BODIPY was loaded onto microspheres, which were then placed into a hydrogel matrix for delivery to tumors associated with glioblastoma multiforme (GBM), with promising results observed for drug delivery. See Brachi et al., “Intratumoral injection of hydrogel-embedded nanoparticles enhances retention in glioblastoma,” Nanoscale. 2020 Dec 14;12(46):23838-23850, which is incorporated herein by reference. The hydrogel systems described herein are highly suitable for drug delivery and offer the opportunity for in situ hydrogel formation that may facilitate delivery into tumors with higher permeability. Extensive experience in drug delivery based on two-component hydrogels can be adapted to the one-component system of the present invention with the ability to influence the drug release profile.

[0029] Hydrogels have been developed to be effective for ophthalmic applications. Hydrogels can be an effective alternative to eye drops for drug delivery with consistent results. The amount used is generally small, so two-component hydrogels with very short time windows of delivery can be cost prohibitive for routine use with low-cost ophthalmic drugs. Using the hydrogel system described herein for drug delivery, a single batch of prepared drug-loaded hydrogel can be used for multiple patients over the pot life of the sample, spreading the cost and providing improved, cost-effective treatment. The drug-loaded hydrogel applied to the patient's eye can spread and coat the ocular surface or other target ocular location where the hydrogel forms by crosslinking, providing sustained release of the drug to the eye. Drug delivery by hydrogels can generally provide a more uniform sustained release compared to delivery by eye drops, which may be particularly desirable for certain applications. For example, this can be effectively used to deliver, for example, steroids, antibiotics, glaucoma medications, other suitable ophthalmic drugs, or combinations thereof, during the completion of a patient's treatment after eye surgery. This model can be adapted to other situations where a hydrogel system can provide desirable results at low cost and in large volumes. Also, compared to other depots for drug delivery, such as preformed intraductal inserts, in situ single-component based depots can be placed through smaller canals, usually in larger volumes, without the need for predilatation of the punctal sphincter. These depots can also be placed in the fornix of the eye using a thin blunt cannula, resulting in the formation of a larger depot for delivery to the ocular surface. Such delivery systems, due to their larger volume, can use a broader range of drugs that may be less potent than preformed depot formulations.

[0030] The hydrogels described herein can be applied in aesthetic applications such as dermal fillers for wrinkle removal. Hydrogels containing suitable dyes can also be used to form tattoos. The resulting tattoos can last for long periods of time or can be designed to be absorbed and removed in a selected time window. The dyes can be bound to the hydrogel, allowing the visual effect to last for the same period of time as the hydrogel. In contrast to traditional tattoo pigments, the use of dyes allows for more flexibility in terms of visual effects. Thus, fluorescent dyes can be especially visible under certain lighting such as blue light, black light, or UV light. Typically, vivid images can be formed as images that are not permanent but can last for a significant amount of time, for example, months or more, or even shorter periods such as days.

[0031] Typically, the in situ hydrogels herein do not include a process of mixing a hydrophilic reactive precursor species having nucleophilic functional groups with a hydrophilic reactive precursor species having electrophilic functional groups at the time of delivery. Instead, the reactive precursor species, including the acid complex, are co-dissolved in an aqueous medicament at the appropriate pH, such that the acid complex of the amine provides sufficient pH lowering activity to limit reaction in the precursor solution. Upon introduction into the body, no mixing with an activator solution (e.g., a high pH promoter) or an external activator (e.g., light) is used to promote the in situ covalent crosslinking of the gel. In some embodiments, the molecular weight of the acid complexed nucleophilic precursor is not significantly smaller than the molecular weight of the electrophilic precursor, and can be the same Mw or larger. In embodiments where low molecular weight amines such as lysine or trilysine are used, the acid complex is typically slow or difficult to deprotonate without mixing with an external promoter, but these low molecular acid complexes can be used in some applications where slow gelation is acceptable. Also, acid complexes of small amines tend to have short pot lives, which poses another limitation on their usefulness.

[0032] The hydrogel systems described herein can provide improved delivery for certain applications compared to currently available hydrogels. These hydrogels can be effectively used for space filling, tissue protection, drug delivery, and other suitable medical applications. In general, hydrogels are convenient and easily deliverable.

[0033] Hydrogel Systems and Applicators Typically, at the start of a procedure or series of procedures, the electrophilic and nucleophilic precursors are mixed with a solvent and placed in a suitable dispenser / applicator, such as that shown in Figure 1. A variety of suitable procedures can be used to form this precursor solution, and the process selection can be based on the convenience of the user. If the solvent is mixed with the precursors directly in the applicator / dispenser, the transfer step can be eliminated, but in that case the applicator must be suitable for direct mixing in the applicator / dispenser accordingly.

[0034] The electrophilic precursor 102 and the nucleophilic precursor 104 are placed in the dispenser 108 to form a solution in the dispenser. The electrophilic precursor 102 and the nucleophilic precursor 104 are typically solids at room temperature, although in principle at least one precursor may be liquid at room temperature. The two precursors may be supplied as a dry powder blend, so that the formation of the precursor solution involves adding a solvent without a separate precursor blending step. To form the precursor solution 107, an aqueous solvent 106 may be added to the precursors in the dispenser 108, and the solution may be mixed until the electrophilic precursor 102 and the nucleophilic precursor 104 are dissolved. In some embodiments, the separate precursors may be shipped as aqueous solutions, but shipping the precursors without a solvent is generally more convenient, easier to package, and simplifies sterilization. In some embodiments, dissolution may be determined by the absence of particles visible to the naked eye. Usually, proper mixing can be achieved by shaking by hand. In some embodiments, dissolution occurs in less than 5 seconds, about 5-15 seconds, 20 seconds or less, 30 seconds or less, 1 minute or less, 5 minutes or less, or 15 minutes or less. A person of ordinary skill in the art will recognize that additional ranges of dissolution times within the explicit ranges above are contemplated and are within the scope of the present disclosure. If the electrophilic precursor 102 and / or the nucleophilic precursor 104 are solid at room temperature, a consistent low dissolution time can be obtained by adding the precursor to the dispenser as a powder, such as a fine flowable powder, since a larger surface area dissolves more easily. The dispenser 108 may be a syringe for use in delivery of a single solution system, or any other suitable device, such as a dropper or a catheter with a reservoir, for appropriate applications. Alternatively, the solutions can be mixed in a separate container and then the mixed solution can be drawn into the dispenser, such as by drawing the solution into a syringe.

[0035] In some embodiments, the syringe barrel can be pre-filled with the electrophilic precursor 102 and the nucleophilic precursor 104, and the aqueous solvent 106 can be drawn into the syringe with a needle or catheter. In further embodiments, the syringe barrel can have a volume larger than the volume of the solution to provide sufficient head space for mixing the solutions by shaking, swirling, tilting, etc. of the syringe barrel. In some embodiments, the volume of the syringe barrel can be about 1.25 to about 2.5 times the volume of the aqueous solvent 106, and in further embodiments, about 1.5 to about 2.25 times the volume of the aqueous solvent. A person of ordinary skill in the art will recognize that additional ranges of relative volumes within the explicit volumes above are contemplated and are within the scope of the present disclosure.

[0036] In another embodiment, the aqueous solvent 106 is added to the dispenser 108 first, and then the electrophilic precursor 102 and the nucleophilic precursor 104 are added to the dispenser 108 and mixed to form a single solution system. For example, the electrophilic precursor 102 and the nucleophilic precursor 104 can be provided as a dry powder blend. Alternatively, a first portion of the aqueous solvent 106 is added to the electrophilic precursor 102 to form a first precursor solution in a first container, and a second portion of the aqueous solvent 106 is added to the nucleophilic precursor 104 to form a second solution in a second container. The first and second precursor solutions can be stored. Prior to use, the first and second precursor solutions can be mixed in the dispenser 108 to form a single solution system. In general, any reasonable mixing order can be used to form a solution for delivering the precursors to a patient. In some embodiments, the electrophilic precursor 102 and / or the nucleophilic precursor 104 are independently a mixture of precursors having different chemical compositions or structures. Differences may include the chemical composition of the core, the molecular weight of the core, the degree of branching of the core, the number of arms, the average molecular weight of the arms, the functional groups, the degree of functionalization of the arms, etc. The aqueous solvent 106 is preferably an unbuffered medium.

[0037] In some embodiments, the aqueous medium 106 is purified / sterile water (e.g., water for injection), unbuffered saline, or any physiologically acceptable aqueous solution with appropriate buffering capacity. Although the choice of fluid may be influenced by the specific application, sterile saline (normal saline) for intravenous use is generally readily available to medical personnel and is safe for most or all applications. In particular, intravenous sterile saline is typically expressed as about 0.9 weight percent NaCl per volume, or equivalently, 9.0 g NaCl per liter. The effects of buffering agents can be complex and dependent on both pKa and concentration. Additionally, many suitable physiological buffering agents may be polyprotic, which further complicates the effects. The issue of buffering agents is discussed further below, but for most applications, more desirable results can be achieved without the addition of buffering agents. The precursor solution typically has a polymer solids content of about 30% by weight or less, in further embodiments about 27% by weight or less, in additional embodiments about 1% to about 25% by weight, in other embodiments about 2.5% to about 23% by weight, and in some embodiments about 5% to about 22% by weight. The polymer solids content can be considered as the weight determined from the added components. Too little polymer solids content can cause undesirable dilution effects and slow gelation, and too much polymer solids content can cause slow gelation due to slower deprotonation of amines. The properties of the precursor can also influence the selection of the polymer solids content value. A person of ordinary skill in the art will recognize that additional ranges of polymer solids content within the explicit ranges above are contemplated and are within the scope of the present disclosure.

[0038] After the precursors are mixed into a single solution, a time can be noted to provide a time window for targeted delivery of the hydrogel before the precursor batch expires. The time window is related to storage stability, but practical considerations may dictate that the time window be set slightly shorter than the storage stability to provide an additional safety margin if the time window is not strictly adhered to. During this time window, one or more hydrogel delivery procedures can be performed. The actual time window may also be influenced by the delivery format for a specific application.

[0039] Storage stability can be evaluated in vitro as a property of the precursor solution. Specifically, storage stability can be the time that the precursor solution can be delivered using a given delivery approach for the application while gelling within an acceptable time after delivery in a physiological solution, unless otherwise specifically indicated. In some embodiments, some crosslinking may occur prior to the end of the storage stability period, but it can be expected to be significantly less than the crosslinking that occurs during gelation. In some embodiments, some hydrolysis may occur prior to delivery, and hydrolysis of electrophilic esters may occur during storage, and longer gel times may be observed after delivery because hydrolysis removes crosslinking groups. Typically, storage stability is at least about 10 minutes, in other embodiments at least about 15 minutes, in additional embodiments from about 20 minutes to about 2 days, in some embodiments from about 30 minutes to about 10 hours, in further embodiments from about 45 minutes to about 8 hours, and in other embodiments from about 1 hour to about 6 hours. Another time parameter is gel time, which is the time until the precursor is sufficiently crosslinked to no longer flow, and for convenience, gel time can be measured in vitro. Although complete crosslinking may take a significant amount of time, once gelation has occurred, the hydrogel is typically fixed in its deposited position. A short gel time is generally desirable. In some embodiments, the gel time is 10 minutes or less, in further embodiments, 5 minutes or less, in additional embodiments, 3 minutes or less, in some embodiments, about 2 minutes or less, in other embodiments, about 2 seconds to about 90 seconds, and in further embodiments, about 10 seconds to about 60 seconds, although typically an upper cutoff can be selected depending on the specific application, such as 5 or 10 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, 60 seconds, 70 seconds, 80 seconds, 90 seconds, 100 seconds, or 110 seconds. Gel times are measured in vitro by injecting a volume of precursor solution at room temperature into ⅓ volume of phosphate buffered saline (PBS) at 37° C., maintaining the combined volume at 37° C., and recording the time until a solid or semi-solid mass is formed, where the volume of precursor solution and the volume of PBS are equal. In other words, a volume of precursor solution is injected (combined) with PBS at 1 / 3 the volume of the precursor solution.The PBS is standard PBS having a pH of about 7.4, which for clarity is deemed to contain 1.37 millimolar (mM) NaCl, 2.7 mM KCl, 10(8) mM Na2HPO4, 1.8(2.0) mM KH2PO4. A person of ordinary skill in the art will recognize that additional ranges of gel time and storage stability time within the explicit ranges above are contemplated and are within the present disclosure.

[0040] With regard to buffers, hydrogel precursors are not considered buffers whether they change the pH or not, and in principle may provide some buffering function. Although dissolved carbon dioxide is usually present, this is not considered an additional buffering agent, and it has been observed that carbon dioxide acts as a baseline. The amine precursors are supplied in an acidified form, with the acidic protons acting as protective groups that prevent crosslinking. Naturally, the acidification is in equilibrium in the solution. Upon contact with body fluids at physiological pH, the acidified amines can be neutralized, so that they can crosslink with the electrophilic precursors at an appropriate rate. The precursor solution usually has no added buffering capacity or should have an adequate buffering capacity. Buffers are usually made up of anions (B) corresponding to weak acids (HB) and anions (B). - ) and can be considered as any Brønsted base in equilibrium with the corresponding weak acid. Anions corresponding to strong acids, such as halide anions, do not function as buffers. If the precursor solution has added buffering capacity, the pot life may be shortened and / or the gel time may be increased, but such effects may be within acceptable limits. The effect of the buffer depends on the pKa and the concentration. Although it is usually desirable to have no buffer added to the precursor solution other than the contribution of impurities and dissolved carbon dioxide, it will usually be acceptable for at least some applications to have a suitable buffer added at an appropriate concentration. Because of these complexities, the appropriate buffer and concentration can be evaluated based on storage stability and gel time. For many applications, a storage stability of at least about 10 minutes, and a gel time of 2 minutes or less provide a reasonable window for the evaluation of the buffer, although other limits within the general discussion of these parameters can be used as needed.

[0041] There are various procedures that can benefit from the use of the single solution system described herein. In general, the single solution system is particularly useful for delivery to locations that require some time for proper placement, such as where existing two-component hydrogels may clog the applicator / dispenser before delivery is complete, or where multiple delivery locations that are not suitable for a two-component system without multiple applicators require time for complete delivery, or where multiple deliveries are required to deliver prepared aliquots of the single solution system to multiple patients. Specific applications discussed below include tubal ligation and drug delivery. For tubal applications, the syringe of FIG. 2 can be attached to an appropriate catheter, which will be described below. With regard to drug delivery, specific applications may relate to antineoplastic agents or ophthalmic applications. For antineoplastic agent placement, proper placement may require significant time, and for ophthalmic drug delivery, a single applicator / dispenser can be used for multiple patients in appropriate circumstances, with appropriate consideration given to sterilizing or disposing of the necessary components between patients.

[0042] FIG. 2 illustrates a dispenser suitable for delivery of the single solution system described herein. In this embodiment, the dispenser 200 includes a syringe 202 with a connector 203, such as a standard Luer lock fitting. The connector 203 is connected to a conduit 204 having a distal end 206 and a delivery tip 208. The basic dispenser 200 also includes a plunger 210 attached to a plunger seal 212. The plunger seal 212 contacts the solution 214 in the syringe 202. Delivery of the solution 214 through the delivery tip 208 can be controlled by pressing the plunger 210. In some embodiments, the conduit 204 can be a needle or a catheter. In some embodiments, the delivery tip 208 has one or more side ports, an open-ended distal port, or a combination thereof. Dispensers for use with single solution systems are not particularly limited and include commercially available applicators. In some embodiments, applicators designed for more complex systems, such as dual solution systems, can be used if desired.

[0043] The applicator of FIG. 2 can be used effectively for a variety of applications. The conduit 204 can be a common catheter or needle, or it can be specially designed to facilitate a particular procedure. A special conduit for delivery to the fallopian tube or similar lumen in a patient is described next. The applicator for the hydrogel precursor can have another design that can be more suitable for a particular application, whether or not the dispenser of FIG. 2 can be used.

[0044] Within the basic formulation of the precursor solution, the nucleophilic and electrophilic precursors provide crosslinking functional groups and a hydrophilic core that imparts typical hydrogel properties, and optionally additional functional groups that allow the hydrogel to degrade after delivery. The details of the precursors control the specific properties of the resulting hydrogel, whose delivery is controlled by the basic features of the delivery system defined in this section. For some applications, a hydrogel that degrades over an appropriate period of time may be desired, and functional groups can be selected to provide some fine tuning of the degradation time, such as by using appropriately selected hydrolyzable functional groups. For other applications, it may be desirable to use a more permanent hydrogel that degrades only slowly or not at all. These long-lasting hydrogels may be desirable for delivery to the fallopian tube. Further details of the precursors are provided below.

[0045] Chemically crosslinked hydrogel systems The hydrogel systems described herein for providing a desired medical function are provided as a single solution formulated to provide a desired precursor solution over a time window. The hydrogel precursors can be designed to spontaneously crosslink upon contact with physiological solutions such as lymph, blood, tissue, other bodily fluids, or similar aqueous solutions based on nucleophilic-electrophilic reactions. By appropriately designing the hydrogel system, the precursors can be designed to crosslink rapidly after delivery while incorporating them into a solution that is stable over the time desired for the completion of a procedure or series of procedures.

[0046] Thus, the first aspect of the design of a polymer system is the formation of an appropriately stable initial blend of precursors. The polymer precursors must be adequately stable so as not to significantly crosslink prior to delivery, yet the solution must crosslink reasonably quickly upon contact with physiological conditions. The basic chemical structures of the hydrogels and precursors are described below in relation to their properties. The properties of hydrogels are described in more detail below.

[0047] The precursors typically contain at least two different polymerizable compounds as described above, although the precursor solution may contain two or more electrophilic precursors and / or two or more amine precursors. To form highly crosslinked hydrogels, the precursors typically each have more than two reactive functional groups for forming crosslinks. In some embodiments, each precursor compound typically has a moderate molecular weight and may contain polymeric moieties. Water-soluble polymerizable monomers that form hydrogels with functionality greater than 2 (i.e., that form a crosslinked network upon polymerization) may be referred to herein as macromers if they have at least a moderate molecular weight and / or polymeric moieties in the core. Molecular weight ranges are further discussed below. The precursor functional groups impart the characteristics of crosslinking reactions and, if present, biodegradability, as well as the overall properties of the precursor solution and the product hydrogel.

[0048] Typically, pH is used to control the crosslinking reaction. Thus, by not adding a buffer to the precursor solution, the pH can be adjusted more quickly upon contact with a fluid having physiological pH, and even if an accelerator solution is not used, the pH can be raised so that the crosslinking reaction can proceed at a typically fast rate. The addition of a small amount of a properly selected buffer to the solution can increase the gel time to some extent, which may be acceptable in certain circumstances and may be desirable in some embodiments, such as dermal fillers that may be repositioned after delivery before gelling. In either case, upon contact with a fluid at physiological pH, the pH of the precursor solution increases, the amine groups are deprotonated, and the crosslinking reaction proceeds. It is believed that long distance macromolecular diffusion is not required to form a highly crosslinked hydrogel, since diffusion to equilibrate the pH can occur quickly and the precursor molecules are mixed. The amine precursors are selected to be substantially deprotonated at physiological pH, and the macromer precursors described herein possess this characteristic. After the gel time has elapsed, further crosslinking occurs over an extended period of time.

[0049] Hydrogel systems may also advantageously employ suitable functional groups for crosslinking macromers to form tissue implants in situ, such as macromers containing electrophilic groups that are reactive toward amine functional groups. Thus, multicomponent hydrogel systems can be spontaneously crosslinked when the components are activated by contact with physiological fluids, but two or more components are suitably stable for a reasonable processing time before activation by physiological fluids. Such systems include, for example, a monomer (e.g., a macromer) that is a bifunctional or multifunctional amine in one component and a macromer with a bifunctional or multifunctional electrophilic group, such as an N-succinimidyl-containing moiety, in the other component. The succinimidyl functional group promotes the formation of amide bonds upon reaction with amines and has been used in other medical hydrogels, although other suitable electrophilic precursors are discussed below.

[0050] The hydrogel precursors can have crosslinks that are activated by physiological fluids that the precursors contact after delivery. The hydrogel precursors described herein can be designed to be dilution resistant when formed with sufficient solids content. The properties of the hydrogel and precursor solutions are further described below. Parameters that affect the properties include functional group chemistry, crosslink density / molecular weight of the monomers, monomer composition, percent solids in the hydrogel precursor, and ionic strength.

[0051] The crosslink density of the resulting biocompatible crosslinked polymer is controlled by the overall molecular weight of the macromer and the number of functional groups available per molecule. A low molecular weight between crosslinks, such as 600, will result in a much higher crosslink density compared to a higher molecular weight, such as 10,000. Higher molecular weight macromers provide desirable gel times, and in some embodiments, greater than 3000 Da, resulting in elastic gels. In certain embodiments, the molecular weight of the nucleophilic acid complexed form of the polymer is not significantly smaller than the molecular weight of the electrophilic polymer; in some embodiments, it is the same order of magnitude or greater.

[0052] Crosslink density can also be controlled by the overall solids percentage of the crosslinker and functional polymer solutions. In two-component hydrogel systems, increasing the solids percentage in the precursor formulation increases the probability that electrophilic functional groups will combine with nucleophilic functional groups before being deactivated by hydrolysis. Surprisingly, some embodiments of single-solution systems exhibit different behavior. In particular, without wishing to be limited by theory, it has been observed that a higher solids percentage can be inversely proportional to the probability of reaction between electrophilic and nucleophilic functional groups, possibly due to slower deprotonation of amines. Single-solution systems containing 25-30% solids can have significantly longer gel times than single-solution systems containing 10-15% solids. The range of solids concentrations is given above in the description of the precursor solutions. Without wishing to be limited by theory, it is believed that the longer gel times are related to slower diffusion of physiological fluids into and / or acid complex species out of the in situ placed solutions with higher solids percentages. Yet another method of controlling crosslink density is by adjusting the stoichiometry of nucleophilic to electrophilic functional groups. A 1:1 ratio results in the highest crosslink density.

[0053] monomer Crosslinkable monomers can be used to form biocompatible implants. As mentioned above, the monomers can be macromers, which may or may not be polymeric. As used herein, the term polymer refers to a molecule formed from at least three repeating groups. Generally, the term "reactive precursor species" refers to a polymer, functional polymer, macromolecule, or small molecule that can participate in a reaction to form a network of crosslinked molecules, such as a hydrogel. As mentioned above, to form a stable one-component hydrogel precursor system, the monomers are generally macromers, as defined below.

[0054] Monomers can include biodegradable, water-soluble macromers, such as those described in U.S. Pat. No. 7,332,566 to Pathak et al., entitled "Biocompatible Crosslinked Polymers With Visualization Agents" (hereinafter the '566 patent), which is incorporated herein by reference. These monomers are characterized by having at least two polymerizable groups, which may or may not be separated by at least one degradable region. When polymerized in aqueous solution, they form a coherent gel that lasts indefinitely or until removed by biodegradation. Typically, macromers are formed with a core of water-soluble, biocompatible polymers (e.g., polyalkylene oxides such as polyethylene glycol) flanked on either side by hydroxycarboxylic acids such as lactic acid to form degradable esters or non-degradable amides. In addition to being biocompatible and non-toxic, suitable monomers can also have at least some elasticity after crosslinking or curing, and in some embodiments are degradable. In the case of electrophilic compounds or compounds with amine groups, the core of the compound can have multiple arms or branches, each with a functional group suitable for crosslinking. As mentioned above, polyethylene glycol (PEG)-based monomers are well-established hydrogel precursors, and the precursor compounds are commercially available.

[0055] The nucleophilic functional group is usually an amine group. The amine group can be protonated as a protecting group or gate to control crosslinking. The nucleophilic amine group of the precursor can be designed to deprotonate significantly at physiological pH values, e.g., about 7.1 to about 7.6 pH units, while blood and tissues are usually in a narrower pH range in healthy individuals. In some embodiments, the polymer can have hydrolytically biodegradable moieties or bonds, e.g., esters, carbonates, or other suitable bonds. Some such bonds are known in the art and are derived from alpha-hydroxy acids, their cyclic dimers, or other chemical species used in the synthesis of biodegradable articles, e.g., glycolide, dl-lactide, l-lactide, caprolactone, dioxanone, trimethylene carbonate, or copolymers thereof.

[0056] Typically, the monomers providing electrophilic functional groups and the monomers providing amine groups are macromers. Macromers usually have a biologically inert and water-soluble core that contains pendant reactive functional groups for crosslinking. When the core is a water-soluble polymeric region, the polymers that can be used can be natural or synthetic polymers. Suitable polymers for the core can include, for example, polyethers such as polyalkylene oxides, for example, polyethylene glycol ("PEG"), polyethylene oxide ("PEO"), polyethylene oxide-co-polypropylene oxide ("PPO"), co-polyethylene oxide block or random copolymers, poloxamers, for example, Pluronic® F-127; and polyvinyl alcohol ("PVA"); poly(vinylpyrrolidinone) ("PVP"); polylactic acid ("PLA"); and polysaccharides, for example, hyaluronic acid, chitosan, dextran, cellulose, and derivatives thereof. Based on extensive experience with existing medical products, polyethers, more specifically polyethylene glycol (also known as poly(oxyalkylene) or poly(ethylene glycol)), are particularly suitable.

[0057] The use of low molecular weight polyamines has been successful in two-component polyethylene glycol-based hydrogels for medical applications. Trilysine in particular has been used. As seen in the examples below, trilysine can also be used in one-part format, but has a short pot life and long gel time. Nevertheless, for some embodiments, these embodiments may be useful, especially in buffer-free systems. Specific small molecule amines include, for example, lysine, dilysine, trilysine, tetralysine, pentalysine, and mixtures thereof. Low molecular weight polyamines can generally have a molecular weight of 200 to about 1800, in further embodiments from about 225 to about 1650, and in additional embodiments from about 250 to about 1500. One of ordinary skill in the art will recognize that additional ranges of molecular weights of low molecular weight polyamines within the above explicit ranges are contemplated and are within the scope of the present disclosure.

[0058] Hydrogels formed with macromers having longer distances between crosslinks have been found to be typically softer, more compliant, and more elastic. Thus, in the polymers of the '566 patent, increasing the length of the water-soluble segments, such as polyethylene glycol, tends to increase elasticity. The molecular weight of hydrophilic macromers used herein, such as macromers having a polyethylene glycol macromer core, is typically at least about 2,000, and in some embodiments from about 5,000 to about 500,000, in further embodiments from about 7500 to about 100,000, in additional embodiments from about 10,000 to about 50,000, and in other embodiments from about 15,000 to about 40,000. As used herein, molecular weight (mass) is in conventional units and may be interchangeably expressed as Daltons or molar mass-grams / mole (in both cases assuming the presence of natural isotopes), and for polymers, if there is a distribution of molecular weights, the molecular weight is generally reported as an average value. A person of ordinary skill in the art will recognize that additional ranges within the explicit ranges above are contemplated and are within the present disclosure.

[0059] The hydrogel precursors in the hydrogel precursor solution have a certain ratio of electrophilic functional groups to amine functional groups. The ratio of functional groups can change the crosslink density and properties of the resulting hydrogel. Typically, when the ratio of the number of electrophilic functional groups to the number of amines is 1:1, the hydrogel can be fully crosslinked, assuming sufficient time and no constraints. Typically, the ratio of electrophilic groups to nucleophilic groups can be about 0.8 to 1.2, in further embodiments about 0.9 to about 1.1, and in further embodiments about 0.95 to about 1.05, although the ratio can be approximately 1:1. A person of ordinary skill in the art will recognize that additional ranges of ratios within the explicit ranges above are contemplated and are within the scope of the present disclosure.

[0060] To achieve the desired ratio of functional groups, the functional groups can be distributed in various ways. The pendant functional groups extending from the core may be referred to as being associated with the arms of the precursor. The precursors usually have 2, 3, 4, 5, 6, 7, 8, 9, 10, or more arms. At least one precursor has at least three arms to obtain crosslinking, and precursors with 4, 6, or 8 arms may be advantageous to obtain the desired hydrogel properties. To obtain a 1:1 ratio of functional groups, equimolar amounts of precursors can be used if they have the same number of arms, or if different numbers of arms are present in each precursor, the molar ratio can be adjusted accordingly. Thus, a 4-arm precursor can be combined with an 8-arm precursor in twice the molar amount to obtain a 1:1 functional group ratio. For weight ratios, the molar ratios can be adjusted based on the relative weights. An 8-arm 10K MW (10,000 molecular weight) precursor would be combined with twice the mass of an 8-arm 20K MW precursor to obtain a 1:1 functional group ratio. One of ordinary skill in the art can adjust these calculations to obtain different ratios of functional group numbers.

[0061] Functional Groups and Crosslinking Reactions Crosslinking reactions are typically designed to occur in aqueous solutions in vivo surrounded by physiological conditions, while hydrogel reactions occur in a temporary local environment. Thus, the crosslinking reaction occurs "in situ", meaning that it occurs at a local site such as an organ or tissue in a living animal or human body. Due to the in situ nature of the reaction, the crosslinking reaction can be designed to not release undesirable amounts of heat of polymerization. The gelation times for the desired procedure are described above, and complete crosslinking can usually be completed after 15 minutes to 24 hours, although other times outside this range may be acceptable. Certain functional groups, such as alcohols and carboxylic acids, do not normally react with other functional groups, such as amines, at physiologically acceptable pH (e.g., pH 7.2-11.0, 37°C). However, such functional groups can be made more reactive by using an activating group such as N-hydroxysuccinimide or its derivatives. In general, several methods for activating such functional groups are known in the art. Suitable activating groups include, for example, carbonyldiimidazole, sulfonyl chloride, chlorocarbonate, aryl halides, sulfosuccinimidyl esters, N-hydroxysuccinimidyl esters (NHS), succinimidyl esters, succinimidyl amides, epoxides, aldehydes, maleimides, imidoesters, etc. The N-hydroxysuccinimide ester or N-hydroxysulfosuccinimide group is a desirable group for crosslinking amine-functionalized polymers such as amino-terminated polyethylene glycols ("APEGs") due to their acceptance in medical implants that have been used for a long time in approved products.

[0062] A suitable nucleophilic functional group is a polymer containing a primary amine complexed with an acid. Thus, the other functional group used for crosslinking is usually an amine. Amines are weak bases, and the pKa of the protonated amine depends on the molecule. In some embodiments, the acid complex is HCl, forming the PEG amine in the HCl salt form. The acid complex can be selected to match the molar concentration of the amine. The advantage of the NHS-amine reaction is that it gels quickly, usually within about 10 minutes, more usually within about 1 minute, and most usually within about 30 seconds, depending on the reaction kinetics. Ultra-fast gelling applications, such as those with gelation in 5 seconds or less, are usually not suitable for in situ reactions using the precursors described herein. Rather, applications in confined spaces, such as subcutaneous or along surfaces, generally produce desirable results.

[0063] Protonated amines are generally not suitable for nucleophilic substitution. Thus, the precursor solution can be prepared at an appropriate pH to maintain the amines substantially protonated before being delivered for contact with the physiological solution. This preparation can keep the precursor solution from premature crosslinking.

[0064] The crosslink density of the resulting biocompatible crosslinked hydrogel is controlled by the overall molecular weight of the monomers and the number of functional groups available per molecule. A lower molecular weight between crosslinks, such as 2000 Da, will result in a higher crosslink density compared to a higher molecular weight, such as 100,000 Da. Using higher molecular weight monomers will result in a hydrogel with higher elasticity, and similarly using lower molecular weight monomers will result in a hydrogel with lower elasticity. Different hydrogel properties can be proposed depending on the application.

[0065] Crosslink density can also be controlled to some extent by the percent solids of the total monomers in the precursor solution. Increasing the percent solids increases the probability that an electrophilic functional group can combine with a nucleophilic functional group before hydrolytic inactivation. Another way to control crosslink density is to adjust the stoichiometry of nucleophilic and electrophilic functional groups. A 1:1 ratio results in the highest crosslink density. Typically, over time, the hydrogel will complete curing and the available crosslinking sites will form crosslinks. If the electrophilic and nucleophilic precursors are provided in equal amounts, it can be expected that after full curing, nearly all of the functional groups will form crosslinks. The highest crosslink density will be with the same number (or reactive equivalents) of the two types of reagents. If different functional group ratios are used, the properties of the cured hydrogel may vary slightly accordingly. Crosslink density may depend on the number of functional groups on the precursor molecules and the ratio of precursor molecules. If desired, a non-stoichiometric ratio of electrophilic and nucleophilic groups can be used to modify the crosslink density. In some embodiments, the ratio of electrophilic functional groups to nucleophilic functional groups can be from 0.8:1.0 to 1.0:0.8. A person of ordinary skill in the art will recognize that additional ranges within these explicit ranges are contemplated and are within the present disclosure.

[0066] Degradable or non-degradable bonds Depending on the application, it may or may not be desirable for the hydrogel to be degradable, such as through hydrolysis or biodegradation by enzymatic activity. If it is desired that the biocompatible crosslinked hydrogel polymer is degradable or absorbable, one or more precursors may be used that have degradable bonds present between functional groups. As used in the art, absorbable polymers may be referred to as biodegradable if they are absorbed under physiological conditions, whether or not they degrade through biological action, such as enzymatic cleavage. The degradable bonds may optionally function as part of the water-soluble core of one or more precursors. Alternatively, or in addition, the functional groups of the precursors may be selected such that the reaction product between them results in a degradable bond. In each approach, the degradable bonds may be selected such that the resulting degradable biocompatible crosslinked hydrogel polymer is degraded or absorbed over a targeted time range. In another embodiment, the functional groups and bonds to the functional groups may be selected to resist degradation under physiological conditions, greatly reducing or eliminating degradation.

[0067] Typically, the degradable linkages are selected to degrade under physiological conditions into non-toxic products. The degradable linkages can be chemically or enzymatically hydrolyzable or absorbable. Exemplary enzymatically hydrolyzable biodegradable linkages include peptide bonds cleavable by metalloproteases or collagenases. Additional exemplary biodegradable linkages can be functional groups on the core polymers and copolymers, such as hydroxy carboxylic acid, orthocarbonate, anhydride, lactone, (amino acid, carbonate, phosphonate, or combinations thereof. In an exemplary embodiment, the degradable linkages are esters formed by hydroxy carboxylic acid moieties adjacent to electrophilic groups used for crosslinking. Esters can be slowly degraded by hydrolysis under physiological conditions, with degradation times depending on the specific structure. To obtain non-degradable hydrogels, the esters formed by hydroxy carboxylic acid moieties can be replaced with amide groups, which are generally not hydrolyzed under physiological conditions. Monomers having a PEG core can be prepared, for example, as described in Jenkem et al., in which N-succinimidyl electrophilic groups are attached by amide bonds or by ester bonds. PEG amines with various numbers of arms and molecular weights are also available from Jenkem. Desirable degradable electrophilic groups with ester bonds include, for example, N-hydroxysuccinimidyl succinate (SS), N-hydroxysulfosuccinimidyl succinate, N-hydroxysulfosuccinimidyl gluterate, succinimidyl glutarate (SG), succinimidyl adipate (SAP), succinimidyl azelate (SAZ), or mixtures thereof. There is usually a correlation between the hydrolysis time and the length of the ester-forming group attached to the PEG core. Thus, in an environment that allows hydrolysis, such as in vivo, SS degrades faster, other parameters being the same. Crosslink density, monomer size, and other parameters may also affect the degradation time in vivo.

[0068] Hydrogel properties Although not desirable for all applications, the one-component hydrogels described herein can be used in a variety of applications. Appropriate properties will generally depend on the specific application. As explained in some detail above, the desired degradation time may range from as short as a day or less to as moderate as days to months, with further embodiments not degrading or degrading over long periods of time, such as years. Due to the flexibility of the chemistry and experience with similar two-component hydrogels, the elastic modulus, density, swelling, and other properties of the hydrogels can be similarly engineered over a significant range. Measurements of elastic modulus and swelling are described in co-pending U.S. Patent Application Serial No. 17 / 522,727 to Bassett et al., entitled "Hydrogels Formed In Situ and Composition Design for Intrauterine Us," which is incorporated herein by reference.

[0069] Visualization Agent Where convenient, the biocompatible crosslinked hydrogel polymer may contain a visualization agent to improve visibility during medical procedures. As used herein, visualization agent may refer to optical visualization (colored) or visualization using diagnostic imaging such as X-ray or ultrasound. Visualization agents are particularly useful when used in minimally invasive surgical (MIS, e.g., laparoscopic) procedures, in part because of improved visibility, particularly on color monitors. It may be useful to impart color by adding a colored visualization agent to the single solution system prior to crosslinking.

[0070] The visualization agent (optical) can be selected from among any of a variety of non-toxic colored substances suitable for use in medical implant medical devices, such as FD&C BLUE dyes 1, 2, 3, and 6, indocyanine green, or colored dyes commonly found in synthetic surgical sutures. In some embodiments, green or blue colors are desirable because these colors are more visible in the presence of blood and on pink or white tissue backgrounds. Although visualization aids are generally utilized to aid in proper placement for medical procedures, visualization agents can also be selected based on aesthetic reasons. Thus, for tattoo applications, visualization agents can be selected to provide a desired color in terms of creating an aesthetic design.

[0071] For dyes used as visualization agents, they are usually water-soluble. Water-soluble dyes can be expected to wash out of the hydrogel relatively quickly. If the dye has an appropriate functional group or is modified to have an appropriate functional group, the dye can be attached to the functional group of the hydrogel precursor, either before crosslinking the hydrogel or at the same time as crosslinking the hydrogel. Suitable functional groups include, for example, amine (-NH2), carboxylate (-COO-), thiol (-SH), or other suitable electrophilic or nucleophilic groups. Carboxylate can react with the precursor compound to form -NHS groups as well. A single functional group will not crosslink the dye, but a covalent bond is expected to allow the dye to persist until the hydrogel degrades and is absorbed by the patient. Fluorescein-NHS is commercially available as a fluorescent red / orange dye. A range of dyes can be used for imaging to cover primary colors, or alternative colors or shades, as needed.

[0072] A visualization agent may be present with the precursor solution prior to delivery. The colorant selected may or may not be chemically bound to the hydrogel. Additional visualization agents may be used, such as fluorescent (e.g., green or yellow fluorescent under visible light) compounds (e.g., fluorescein or eosin), X-ray contrast agents for visualization with X-ray imaging devices (e.g., iodinated compounds), ultrasound contrast agents (e.g., microbubbles), or MRI contrast agents (e.g., gadolinium-containing compounds). The biocompatible visualization agents FD&C BLUE#1 and Fluorescein-NHS may be particularly desirable for some applications. The visualization agent may be a biologically active agent suspended or dissolved within the hydrogel matrix, or a material used to encapsulate the biologically active agent, if present.

[0073] The visually observable visualization agents described above can be advantageously used for some embodiments. Wavelengths of light between about 400 and 750 nm are observable as colors by humans (RK Hobbie, Intermediate Physics for Medicine and Biology, 2006). nd Ed., pages 371-373). Blue is perceived when the eye is exposed to light with wavelengths of about 450-500 nm, and green is perceived at about 500-570 nm (ibid.). Furthermore, since the eye detects red or green or blue, combinations of these colors can be used to simulate any other color by simply exposing the eye to proportions of red, green, and blue that the human eye perceives as the desired color. Blue, as used herein, means the color perceived by the normal human eye stimulated by wavelengths of about 450-500 nm, and green, as used herein, means the color perceived by the normal human eye stimulated by wavelengths of about 500-570 nm.

[0074] One or more visualization agents can be present in the final electrophilic-nucleophilic precursor solution at concentrations greater than about 0.1 weight percent (wt %), in some embodiments in a concentration range of at least 0.001 to about 0.075 wt %, and in further embodiments in a range of 0.0025 to 0.05 wt %, although higher concentrations may be used up to the solubility limit of the visualization agent, and the selected concentration may be influenced by the specific visualization agent and the specific application. In some applications, these concentration ranges have been found to impart color to the desired hydrogel without interfering with the crosslinking time (measured by the time for the reactive precursor species to gel). The visualization agent is typically not covalently bonded to the hydrogel. One of ordinary skill in the art will recognize that additional ranges of visualization agent concentrations within the explicit ranges above are contemplated and are within the scope of the present disclosure.

[0075] In some embodiments, a method is used to form a hydrogel on the tissue until the color of the hydrogel indicates that a predetermined amount of hydrogel has been deposited on the tissue or within the space. The precursor is continually introduced into the space until the color of the material that enters the space and flows out is deemed to have reached the appropriate loading as indicated by observation of a visualization agent disposed in the flowing material.

[0076] A visualization agent can be useful in certain cases to visualize the injection of the hydrogel. For example, when injected into the fornix or subconjunctiva, the visualization agent can help distinguish the hydrogel from other fluids. Additionally, the hue of the colored hydrogel can provide information about the concentration of precursors in the hydrogel or the degree to which physiological fluids are mixed into the hydrogel. A darker colored hydrogel can indicate a higher concentration of precursors compared to a lighter colored hydrogel made from the same precursor solution. The colorant can be present in a premixed amount already selected for the application. In some embodiments, dyes can be attached to electrophilic or nucleophilic end groups and incorporated into the depot for visualization in direct correlation with persistence. In some cases, the dyes are fluorescent and can only be visualized under special lighting conditions, rendering the monolithic gel invisible under otherwise normal viewing conditions.

[0077] In some embodiments, a user can directly view the injectable depot by applying the monolithic hydrogel depot with a selected visualization agent to a tissue site. The visualization agent can be used by the user to view the hydrogel with the human eye or with the aid of an imaging device, such as a video camera, that detects the visually observable visualization agent. A visually observable visualization agent is an agent that has a color that is detectable by the human eye. A characteristic that provides an image to an x-ray or MRI machine is not a sufficient characteristic to establish the function as a visually observable visualization agent. Another embodiment is a visualization agent that is not normally visible to the human eye, but is detectable at a different wavelength, such as infrared or ultraviolet, when used in combination with an appropriate imaging device, such as a video camera. Hydrogels containing visualization agents for x-ray and / or ultrasound visualization are described in detail in U.S. Pat. No. 8,383,161 to Campbell et al., entitled "Radioopaque Covalently Crosslinked Hydrogel Particle Implants," which is incorporated herein by reference. Ultrasound visualization may be particularly desirable for fallopian tube procedures, and x-ray visualization may be particularly desirable for tumor delivery.

[0078] Delivery of therapeutic agents The crosslinked hydrogel material can be advantageously used for local or systemic treatment with therapeutic agents such as drugs. Biologically active agents or drug compounds that can be loaded and delivered from the crosslinked polymers or gels include proteins, glycosaminoglycans, carbohydrates, nucleic acids, inorganic and organic biologically active compounds, and specific biologically active agents include, but are not limited to, enzymes, anti-infective agents, anti-fungal agents, anti-inflammatory agents, anti-neoplastic agents, local anesthetic agents, hormones, angiogenic agents, anti-angiogenic agents, growth factors, antibodies, analgesics, anesthetic agents, steroids, neurotransmitters, psychotropic agents, anti-cancer agents, chemotherapeutic agents, anti-cancer agents, glaucoma agents, drugs that affect reproductive function, genes, oligonucleotides, glycosaminoglycans, antibiotics, non-steroidal anti-inflammatory agents, anti-neoplastic agents, intraocular pressure reducing agents, neurotransmitters, psychotropic agents, anti-cancer agents, cells, cell products, or combinations thereof. As used herein, therapeutic agent refers to a biologically active agent or drug. Various formulations have been developed to effectively deliver therapeutic agents at selective release rates from hydrogels.

[0079] To prepare such crosslinked compositions, the therapeutic agent can be mixed with the crosslinkable polymer precursor before, during, or after preparation of the aqueous precursor solution. This precursor-therapeutic agent mixture can then be injected as a single solution system for in situ polymerization at the targeted delivery site. The biodegradation rate of the polymer may or may not be selected to match the elution rate of the therapeutic agent, depending on the properties of the therapeutic agent and the hydrogel.

[0080] In some embodiments, when the crosslinkable polymer reacts to form a crosslinked polymer network or gel, the therapeutic agent is present in a separate phase. This phase separation can prevent the therapeutic agent from participating in chemical crosslinking reactions, such as the reaction of NHS esters with amine groups. Separate phases are also useful for controlling the release rate of active agents from crosslinked materials or gels. The "separate phase" in this case can be an oil (oil-in-water emulsion) or a biodegradable vehicle. Biodegradable vehicles in which the active agent may reside include encapsulation vehicles such as microparticles, microspheres, microbeads, micropellets, etc., in which the active agent is encapsulated within bioerodible or biodegradable polymers such as polymers and copolymers of poly(anhydrides), poly(hydroxy acids), poly(lactones), poly(trimethylene carbonate), poly(glycolic acid), poly(lactic acid), poly(glycolic acid)-co-poly(glycolic acid), poly(orthocarbonates), poly(caprolactones), crosslinked biodegradable hydrogel networks such as fibrin glues and fibrin sealants, caging and trapping molecules such as cyclodextrins, molecular sieves, etc. Microspheres made from poly(lactones) and poly(hydroxy acids) polymers and copolymers are of particular interest as biodegradable encapsulation vehicles.

[0081] Typically, the therapeutic agent or encapsulated therapeutic agent can be in the form of a solution or suspension in a single solution system. The chemical reaction between the nucleophile and the electrophile can easily occur to form a crosslinked gel, which acts as a depot for releasing the active agent to the host. Such a therapeutic agent delivery method can be used for systemic and / or local administration of the therapeutic agent.

[0082] When the crosslinked compositions are used for the delivery of therapeutic agents as described above, the amount of crosslinkable polymer, crosslinker, and administration agent introduced into the host is appropriately determined by the specific therapeutic agent and condition being treated. Administration for in situ gelation can be by any convenient means, such as syringe, cannula, trocar, catheter, etc. Once the depot is formed, the therapeutic agent can be released to provide localized treatment to the area. Depending on the location, the therapeutic agent can be distributed systemically via the bloodstream, or the therapeutic agent may be distributed throughout the organ.

[0083] Certain embodiments of therapeutic agent delivery hydrogels are realized by providing compositions and methods for controlling the release of relatively low molecular weight therapeutic species using hydrogels. In accordance with the principles herein, the therapeutic species is first dispersed or dissolved in one or more relatively hydrophobic rate control agents to form a mixture. The mixture can be formed into microparticles that are then entrapped within a bioabsorbable hydrogel matrix and release the water-soluble therapeutic agent in a controlled manner. Alternatively, the microparticles can be formed in situ during crosslinking of the hydrogel.

[0084] In one method of forming a therapeutic agent delivery hydrogel, hydrogel microspheres are formed from polymerizable macromers or monomers by dispersing a polymerizable phase in a second immiscible phase, where the polymerizable phase contains at least one component necessary to initiate polymerization resulting in crosslinking, and the immiscible bulk phase contains another component necessary to initiate crosslinking along with a phase transfer agent. Preformed microparticles containing a water-soluble therapeutic agent can be dispersed in the hydrogel precursor solution described above.

[0085] Embodiments of compositions and methods for forming composite hydrogel-based matrices and microspheres may have entrapped therapeutic compounds. In one embodiment, biologically active agents are entrapped in microparticles that have hydrophobic properties (referred to herein as "hydrophobic microdomains"), retarding leakage of the entrapped agent. In some embodiments, composites with two-phase dispersions have both phases that are absorbent but not miscible. For example, the continuous phase may be a hydrophilic network (such as a hydrogel, which may or may not be crosslinked), while the dispersed phase may be hydrophobic (such as an oil, fat, fatty acid, wax, fluorocarbon, or other synthetic or natural water-immiscible phase, collectively referred to herein as the "oil" or "hydrophobic" phase).

[0086] When an oil phase is used, it provides a barrier to release by trapping the drug and slowly distributing it into the hydrogel. The hydrogel phase protects the oil from digestion by enzymes such as lipases and from dissolution by naturally occurring lipids and surfactants. The latter are expected to only have limited penetration into the hydrogel, e.g., due to hydrophobicity, molecular weight, conformation, diffusion resistance, etc. For hydrophobic drugs with limited solubility in the hydrogel matrix, the particulate form of the drug can also act as a release rate modifier.

[0087] By themselves, hydrophobic microdomains may be degraded or rapidly excreted when administered in vivo, making it difficult to achieve direct long-term release using microdroplets or microparticles containing drugs entrapped in vivo. However, according to some embodiments, the hydrophobic microdomains are sequestered within a gel matrix. The gel matrix protects the hydrophobic microdomains from rapid excretion but does not impair the ability of the microdroplets or microparticles to slowly release their contents. A visualization agent may be included within the gel matrix or microdomain, for example.

[0088] In another embodiment of the composition, the active drug is hydrophobic and poorly water soluble, and is itself a hydrophobic domain. The insoluble drug particles may be essentially micronized to allow uniform suspension throughout the hydrogel and consistent application without clogging the delivery system. Upon formation of the in situ system, the hydrophobic poorly soluble drug particles remain trapped within the gel matrix, forming a concentrated environment that acts as a diffusion barrier to further dissolution of the drug, as the drug must dissolve and then diffuse out of the matrix for release. Poorly soluble hydrophobic drugs may exhibit zero-order or first-order release rates as a function of their solubility, the amount loaded into the gel, and the surface area of ​​the hydrogel to which they are applied. In more confined environments, such as the eye or subcutaneous, the release rate may be even longer as local tissues become saturated with the drug, further restricting the diffusion pathways from the hydrogel.

[0089] In another aspect of the composition, the hydrogel microspheres can be sized to selectively deposit the microspheres or can be linked with ligands that target specific areas or otherwise affect deposition of the microspheres within the patient.

[0090] Control of the rate of drug delivery can also be obtained in the system of the present invention by degradable covalent attachment of bioactive molecules to the crosslinked hydrogel network. The nature of the covalent attachment can be controlled to allow control of the release rate from hours to weeks or longer. By using composite materials made from attachments with different hydrolysis times, the controlled release profile can be extended for longer periods of time.

[0091] In certain embodiments, the addition of the therapeutic agent does not increase the existing pH of the unbuffered system and does not disrupt the acid complex. In another embodiment, the therapeutic agent is encapsulated or phase separated. The choice of therapeutic agent is usually influenced by the specific application. In this regard, some specific drugs / therapeutic agents are mentioned in the following discussion of specific applications.

[0092] Fallopian tube blockage Hydrogels can provide desirable functions with respect to occluding fallopian tubes as a means of contraception or for other medical reasons. The one-component hydrogel system described herein is particularly advantageous because it eliminates the significant time constraints of delivering hydrogel to both fallopian tubes. The hydrogel can be effective in conforming to the irregular surface shape of the fallopian tube, and the constrained space can accommodate fast but somewhat slower gelation times compared to two-component hydrogel systems. Although a specific applicator is described, other devices can be used as needed.

[0093] 3A and 3B show a delivery system applicator suitable for delivering a single solution as described herein to occlude a body cavity such as a fallopian tube. The delivery system 300 includes a multi-lumen catheter 302 having a proximal end 304 and a distal end 306. The proximal end 304 includes an inlet port 322 connected via a lumen 326 to outlet ports 312, 314, 330 located near the tip 316. A balloon expansion port 324 is connected to a balloon 332 via a balloon lumen 328. The two lumens 326, 328 can be seen in the cross-sectional view of FIG. 3B. In this embodiment, the lumen 326 functions as both a guidewire lumen and a lumen for hydrogel delivery. With the guidewire 334 in place, the outlet port 330 is substantially blocked to the exit of the hydrogel precursor solution. Alternatively, in operation, lumen 326 can be used to first position delivery system 300 at the desired location and then guidewire 334 is withdrawn. A single solution is then injected into lumen 326 through inlet port 322 and eventually exits through outlet port 330. Outlet ports 312, 314 may remain in use or may be removed.

[0094] A radiopaque marker band 333 is placed within the balloon 332 or elsewhere on the distal end 306 to aid in locating the distal end 306 of the delivery system 300 within the body cavity under fluoroscopic guidance. A guidewire 334 extends through the inlet port 322 and the outlet port 330 and can be used to intraluminally guide the tip 316 of the delivery system 300 to a treatment site, such as a fallopian tube, a peripheral vessel, an aneurysm, or other body cavity. The balloon 332 can be expanded to secure the catheter 302 in position within the body cavity during formation of the hydrogel implant, and can also occlude the lumen to prevent fluid flow from diluting the single solution system during gelation. The delivery system 300 can optionally include an outer sheath that surrounds the balloon 332 when the balloon is deflated.

[0095] Alternatively, the catheter 302 can be configured with three lumens, for example a hydrogel precursor lumen, a guidewire lumen, and a balloon lumen, and thus separate guidewire and hydrogel precursor lumens are provided such that the outlet port 330 is not connected to the outlet ports 312 and 314. In this case, the hydrogel precursor lumen connects the hydrogel precursor inlet port to the outlet ports 312 and 314, the guidewire lumen connects the inlet port 322 to the outlet port 330, and the balloon lumen 328 connects the balloon expansion port 324 to the interior of the balloon 332. In operation, the guidewire lumen is used to position the delivery system 300 at the desired location, and then a single solution is injected through the hydrogel precursor inlet port. The solution crosslinks after being placed in the body cavity. As a further alternative to the embodiment of Figures 3A and 3B, the guidewire lumen need not extend the length of the catheter to form a so-called "over the wire" catheter. Alternatively, the guidewire lumen may be configured as a short lumen that exits catheter 302 through a skive immediately adjacent balloon 332 to form a so-called "rapid exchange" catheter, such as that described in U.S. Pat. No. 4,762,127 to Bonzel.

[0096] 4, a method of using the delivery system 300 of FIG. 3A to deliver a single solution system into the fallopian tube lumen to form a hydrophilic hydrogel occlusion is described. The fallopian tube F1 is accessed by passing a catheter 302 through the cervix C under fluoroscopic guidance. The proximal end 304 of the delivery system 300 is coupled to a single syringe-type device 340 that contains the single solution system 341 and has an actuator 342 that allows for controllable injection of the single solution system 341. The balloon 332 can be inflated with a liquid containing a contrast agent to confirm placement of the tip 316.

[0097] If desired, expansion of balloon 332 may be followed by filling or flushing the treatment space with a solution, such as an inert saline solution, to remove blood and other physiological fluids from the treatment space. Delivery system 300 may optionally include an additional lumen or use an existing lumen, such as lumen 326, to allow such flushing liquid to exit the treatment space. Alternatively, a non-inert solution, such as a solution containing a pharmaceutical agent, may be injected into the treatment space.

[0098] The actuator 342 is then depressed, resulting in the delivery of the single solution system 341 into the fallopian tube through one or more exit ports distal to the balloon 332. The rate of delivery and total delivery time of the single solution system 341 is not particularly limited. In some embodiments, the delivery time is about 30 seconds, about 1 minute, about 5 minutes, or about 10 minutes. In some embodiments, the initial delivery of the single solution system 341 may be followed by a pause of a few seconds or minutes. The single solution crosslinks about 30 seconds to about 5 minutes after contacting the fallopian tube tissue, resulting in the formation of a plug 344 that occludes the fallopian tube F1. The balloon 332 is then deflated and the catheter 302 is partially withdrawn. Use of the delivery system 300 continues, and then the fallopian tube F2 is accessed under fluoroscopic guidance, and the above procedure is repeated to form a plug 346.

[0099] In some embodiments, the tubal occlusion method can be made controllably reversible by using a single solution system 341 that forms degradable plugs 344 and 346 after a selected period of time. Selection of nucleophilic and electrophilic functional groups can be used to tailor the degradation time of the hydrogel plug. In another embodiment, the tubal occlusion method can be made permanent by using nucleophilic and electrophilic functional groups that react to form bonds, such as amide bonds, that are resistant to hydrolysis. To test the effectiveness of the plugs 344 and 346 in occluding the fallopian tubes F1 and F2, tubal patency tests can be performed immediately after insertion of the plugs 344 and 346, at regular intervals, and / or after a selected reversal period.

[0100] For these applications, the hydrogels can be loaded with a number of selected drugs. Suitable drugs can include, for example, anti-infective or anti-fungal agents for the treatment of uterine infections, where the drug's effectiveness is enhanced due to the proximity of the local target. For example, the following antibacterial drugs may be suitable: antivirals, broad-spectrum antibiotics (such as penicillins and cephalosporins), metronidazole (for bacterial vaginosis and trichomoniasis), fluconazole (for anti-fungal-yeast infections), doxycycline, or azithromycin. In some cases, it may be necessary to use anti-infective agents prophylactically. Anti-inflammatory agents, such as NSAIDs and steroids, are another class of drugs that can be used to treat conditions such as endometriosis without the systemic side effects associated with the long-term intake of these drugs.

[0101] Drugs such as hormones are available for local intrauterine delivery, from the treatment of endometriosis to hormone replacement therapy (HRT) in postmenopausal women. The use of oral contraceptives has been associated with an increased risk of thromboembolism and an increased incidence of breast cancer. Milder side effects of oral contraceptive use, such as mood changes, weight gain, intermenstrual vaginal and light bleeding, and decreased libido, can lead to irregular administration or cessation of oral contraceptive use, resulting in failure rates of oral contraceptives as high as 5% during the first year of use. At the other end of the life cycle, oral administration of HRT in postmenopausal women has been associated with an increased risk of coronary heart disease, stroke, and venous thromboembolism, as well as an increased risk of breast cancer with prolonged treatment.

[0102] Antitumor Drug Delivery The hydrogel system described herein provides an important tool in the context of drug delivery for the treatment of tumors. The use of the single solution system described herein offers the advantage of being able to efficiently inject into multiple locations within a tumor without clogging the applicator. Thus, a more uniform delivery of anti-tumor agents can be achieved. As will be appreciated by those skilled in the art, tumors can be accessed using medical techniques appropriate to the specific tumor location.

[0103] The specific drug can be selected based on the specific tumor type, and the drug is usually approved by the relevant medical regulatory agency. Hydrogel delivery approaches can be effective for the delivery of drugs that may not have an effective delivery approach using non-targeted approaches, such as systemic delivery approaches, for example, due to toxicity or solubility constraints. Thus, these hydrogel systems can be used to deliver cytotoxins, and the elution rate of the drug can be designed accordingly.

[0104] The above-cited paper by Yi et al. describes hydrogel delivery of the anticancer drug 5-fluorouracil, which can be similarly delivered using the single solution in situ hydrogels described herein. 5-Fluorouracil is commonly used to treat colorectal, esophageal, gastric, pancreatic, breast, cervical, actinic keratosis, and basal cell carcinoma. Other classes of anticancer drugs include, for example, monoclonal antibodies and cytokines. A review of the potential use of hydrogel delivery of anticancer drugs can be found in Zhang et al., “Locally Injectable Hydrogels for Tumor Immunotherapy,” Gels, 2021, 7, 224, which is incorporated herein by reference.

[0105] Further embodiment options In some embodiments, the hydrogel can include a polymer comprising the group -(CH2CHO)-. The hydrogel can further include a therapeutic agent. In some embodiments, the hydrogel can be biodegradable. For example, the hydrogel can be degradable by hydrolysis. The hydrogel can be biodegradable within 5 days, 8 days, 15 days, or in other embodiments, the hydrogel can be non-biodegradable. The hydrogel can be biodegradable within more than about half a day to about 770 days. Generally, the degradation time can be appropriately selected depending on the particular application. A person of ordinary skill in the art will recognize that additional ranges of degradation times within the above ranges are contemplated and are within the present disclosure.

[0106] The method of applying the hydrogel may include applying a single solution system containing two reactive precursors capable of forming a hydrogel without external or secondary activating agents. The method may include applying two or more reactive precursor components to an aqueous system to form an in situ gel without external activating agents such as irradiation, pH enhancers, redox reactions, or thermal activation. The hydrogel precursor solution may be applied through an intraluminal pathway such as a catheter, needle, port, etc. using standard fluid application methods related to single system injection without the need for mixing. The application method may incorporate a visualization agent. In some embodiments, the agent is a water-soluble biocompatible dye such as FD&C Blue#1 to provide contrast with tissue and / or blood. In another embodiment, the dye may be attached to an electrophilic or nucleophilic group and premixed with the reactive precursors in the same single aqueous solution. In certain embodiments, the dye is a fluorescein-NHS conjugate that can attach to the hydrogel network to render the gel observable by fluorescence through tissue.

[0107] The use of a single solution system containing two reactive precursors capable of forming a gel can be done without the need for external or secondary activating agents for depot formation in the body. For use of a single solution system in clinical applications where the flow of the precursor solution may be limited or where the diffusion area is limited as defined by the surrounding tissue / organ / anatomical features, the need for rapid gelation is not critical. In more specific applications, the gel time may range from 10 seconds to 10 minutes, in further embodiments from 15 seconds to 5 minutes, and in other embodiments from 20 seconds to 2 minutes. A desirable feature of the hydrogel systems described herein is that they do not require a unique or custom delivery system for delivery of the system and can be started and stopped repeatedly throughout use, although for some applications a specific applicator may be desirable. Applications may have a suitable delivery location for crosslinking to occur after entry into the body without the addition of a secondary activation source such as radiation. Some specific applications include, for example, tattooing and high pressure needleless injections where even a slight initiation of crosslinking prior to passing through the dermis can greatly reduce penetration efficiency and / or cause clogging. Another application is in relation to nasal locations where multiple injections may be desired due to the presence of multiple orifices.

[0108] In certain applications, the delivered depot can function as a bulking agent for tissue augmentation. Augmentation can include dermal filling, or intraluminal dilation, such as augmentation of hollow tubes or organ walls to prevent luminal narrowing. Bulking applications can include systemic sphincter augmentation, or cervical filling to prevent premature birth. Conversely, the use of a single solution system in the presence of a dilated conventional balloon catheter dilates and opens hollow tubes further. This can include dilating the urethra in cases of prostate swelling to reduce regular catheterization to relieve bladder strain. Augmentation can also have aesthetic applications, such as those related to smoothing, wrinkles, and the like. Augmentation can be done with shorter or longer residence times, such as non-degradable hydrogels. Other aesthetic applications include the application of tattoos. Conventional tattoos are permanent in nature and their removal can require painful procedures. The use of dyes to form tattoos has been described above, and binding the dye to a hydrogel allows the dye to last for the duration of the hydrogel and to be removed with the degradation of the hydrogel. Temporary tattoos are usually short-lived and have a different appearance than traditional tattoos. Hydrogel-based tattoos can last longer, have the potential to achieve a similar appearance, and can be medically safe. The composition can be delivered using medical needles or standard tattooing equipment. See, i.e., U.S. Patent Application Publication No. 2021 / 0386988 to Kim et al., entitled "Tattoo Needle Unit," and U.S. Patent Application Publication No. 2021 / 0386987 to Azdoud et al., entitled "Robotic Tattooing Systems and Related Technologies," both of which are incorporated herein by reference.

[0109] In some embodiments, any clinical application in which an active therapeutic agent may be added to provide localized therapy may be suitable. In some embodiments, the addition of a therapeutic agent is a complementary effect to the action of the device, such as adding an anesthetic to a booster injection to reduce pain during injection. In other embodiments, more traditional therapeutic agents may be required. Applications using a single precursor solution are distinguished from embodiments using a dual solution precursor system because they do not require specialized equipment and reduce the manual dexterity that may be required. Other desirable applications may include those in which delicacy is required for adjustable amounts and start-stop applicability is desired. One such application is the transtympanic application of a therapeutic agent depot to the ear, where injection without the risk of clogging is more effective to prevent unwanted injection side effects.

[0110] In certain embodiments, the application is purely for the formation of depots for therapeutic release, such as direct intratumoral injection containing a therapeutic agent for chemotherapy delivery to locations not traditionally accessible, including intravascular. Another embodiment includes delivery of chemotherapy agents for the treatment of cancers requiring 4-6 months of treatment. Delivery of therapeutic agents can be achieved by high loading of low solubility compounds, secondary encapsulation, or methods known in the art. Delivery of therapeutic agents can also be achieved by incorporating a secondary hydrogel particulate system containing the therapeutic agent and suspending it within the primary system.

[0111] Another therapeutic clinical embodiment includes the formation of depots on the ocular surface, such as fornix-based depots for delivery of therapeutic agents, including treatment of infections, allergies, inflammation, and glaucoma. Additional embodiments include intraocular injection for sustained release of therapeutics for delivery of anti-inflammatory agents, anti-infective agents, biologics, prostaglandins, beta-blockers, and the like, into the anterior and / or posterior chambers of the eye.

[0112] Other suitable applications may include those requiring repeated minute-by-minute administration of a single system depot where off-target application results in undesirable side effects. An example of such an application is tattooing the eyelid margin with a single system of long-acting prostaglandin depot to enhance eyelash thickening without browning the non-target crow's feet or possibly the iris. Latisse (Allegan) is an FDA-approved product that contains the prostaglandin bimatoprost and can be applied along the eyelid margin to thicken or otherwise enhance eyelashes. The dual hydrogel precursor system, like Latisse, must be applied to the outside of the eyelid to cover the surface area without clogging, and the hydrogel depot becomes dry and brittle when applied. Other injections include prostaglandins under the eye for sustained ablation of fat and reduction of "lid bag." In this case, a single system with an acid complex and no activator can be spread over multiple injections, whereas a dual system known in the art results in a single large bolus injection that is undesirable. XAF5 (developed by Topokine Therapeutics) is a topical eye ointment containing prostaglandins used to reduce eyelid sagging and is in clinical trials. EXAMPLES

[0113] Example 1: In Vitro Performance Testing In this example, the performance of a single component system is demonstrated in an in vitro model of a physiological fluid reservoir.

[0114] The single component system was prepared by mixing the first and second precursors (both dry powders), unbuffered water for injection (WFI, pH 5.5), and a trace amount of FD&C Blue #1 (less than about 0.011 wt%) to form a solution with a precursor concentration of 10 wt%. The solution was blue in color. The first precursor was an 8-arm polyethylene glycol-based precursor with a molecular weight of 15,000 Da and succinimidyl glutarate (SG) functional end groups (8A15k PEG SG, Jenkem USA). The second hydrogel precursor was an 8-arm polyethylene glycol-based precursor with a molecular weight of 20,000 Da and amine functional end groups in the HCl salt form (8A20k PEG amine-HCl, Jenkem USA). (USA). The first and second precursors were used in a 3:4 weight ratio to ensure approximately equal numbers of SG and amine functional end groups in the solution. The precursors dissolved rapidly in WFI as judged by the absence of particles on visual inspection. Once dissolved, the prepared solution was drawn up into a 5 ml syringe and fitted with a 27G gauge needle. Over a period of 30 minutes, 200 μl of the room temperature solution was injected intermittently through the 27G gauge needle into 200 μl aliquots of phosphate buffered saline (PBS) at 37° C. The solution remained flowable and injectable through the ** gauge needle throughout the observation time frame of the 30 minute working window. Each injection resulted in the formation of a blue solid to semi-solid mass in the PBS solution due to the precursors crosslinking to form a gel. This study demonstrated that the single component system has stability for more than 30 minutes after preparation.

[0115] Example 2: In Vitro Performance Test (with Comparative Example) This example illustrates the time-dependent performance of the single-component system of Example 1 and a single-component system including trilysine as the second hydrogel precursor. Comparisons were made to a single solution composition similar to the system of Example 1, except that the amine-functional end groups of the second precursor were not made into the HCl salt form.

[0116] Two single component systems ("Test System 1" and "Test System 2") and a comparative system (CS-1) were prepared from the first precursor, the second precursor, and unbuffered water for injection (WFI) according to Table 1. CS-1 was prepared from the same precursors as Test System 1, except that the second precursor of CS-1 was not made into the form of an HCl salt. The precursor in dry powder form was mixed with WFI and a trace amount of FD&C Blue #1 (less than about 0.011% by weight) to form a solution having a precursor concentration of 10% by weight. The first and second precursors were used in a weight ratio such that each solution had approximately the same number of SG and amine functional end groups. The initial pH of Test System 1 was 2.91, and the initial pH of Test System 2 was 5.21. The precursors of the test systems dissolved rapidly in WFI, as judged by the absence of particles upon visual inspection. Rapid gelation occurred upon formation of solution CS-1. The pH of the comparative system could not be measured prior to gelation.

[0117] [Table 1]

[0118] Immediately after dissolution, a 150 μl aliquot of Test System 1 was pipetted into a 50 μl aliquot of phosphate buffered saline (PBS) at 37° C. This process was repeated two more times to obtain a total of three samples. Gelation was assessed visually based on observing the formation of cohesive bubbles around the rotating micro stir bar. The time to gelation for each sample at 0 minutes after dissolution was recorded as shown in Table 2. The average gel time was 23.11 seconds. This procedure was repeated at 30, 60, and 90 minutes after dissolution. Similarly, immediately after dissolution, a 150 μl aliquot of Test System 2 was pipetted into a 50 μl aliquot of phosphate buffered saline (PBS) at 37° C. This process was repeated for the second sample. As shown in Table 2, the time to gelation was 101.75 seconds for sample 1 and 101.44 seconds for sample 2. The average gel time for Test System 2 at 0 min after dissolution was 101.60 s (approximately 1.7 min), which is significantly longer than the average gel time of Test System 1, 23.11 s. The first sample of Test System 2 was tested at 30 min after preparation, but the gel time result is questionable due to the presence of gel in the solution during pipetting. Pipetting of a second 150 μl aliquot of Test System 2 was not possible due to the presence of gel. Therefore, samples could not be taken at 60 and 90 min, as shown in Table 2. Pipetting of a 150 μl aliquot of CS-1 was also not possible due to the presence of gel.

[0119] [Table 2]

[0120] Comparison of Test System 1 with CS-1 shows that when the second precursor is replaced with a non-salt version, a gel is formed immediately after preparation. CS-1 showed no storage stability. Comparison of Test System 1 with Test System 2 shows that when the second precursor is replaced with trilysine, the storage stability is less than 30 minutes when tested immediately after dissolution, and the gel time is significantly increased. This study shows that only Test System 1 has a storage stability of more than 30 minutes after preparation. Furthermore, the gel time of Test System 1 is less than 30 seconds. This study further shows that Test System 1 has a storage stability of more than 90 minutes, with the gel time not exceeding 50 seconds throughout this storage period.

[0121] Example 3: In Vitro Performance Testing of Systems Containing Buffers This example illustrates the effect of buffering on the performance of a single component system.

[0122] A single component system (Test System 1B) was prepared from the first and second precursors of Test System 1 of Example 2. For Test System 1B, the precursors were dissolved in 0.01M sodium phosphate monobasic buffer at pH 4.01 instead of WFI, as shown in Table 3. The precursors in dry powder form were mixed with the buffer and a trace amount of FD&C Blue#1 (less than about 0.011% by weight) to form a solution with a precursor concentration of 10% by weight. The first and second precursors were used in a weight ratio such that each solution had approximately the same number of SG and amine functional end groups. The initial pH of Test System 1 was 2.91, and the initial pH of Test System 1B was 2.09. In each solution, the precursors dissolved rapidly as judged by the absence of particles upon visual inspection.

[0123] [Table 3]

[0124] Immediately after dissolution, a 150 μl aliquot of Test System 1B was pipetted into a 50 μl aliquot of 37° C. phosphate buffered saline (PBS). This process was repeated two more times, resulting in a total of three samples. The time to gelation for each sample at 0 minutes after dissolution was recorded as shown in Table 4. The average gel time was 48.14 seconds. This is more than double the gel time of Test System 1. This result directly illustrates the effect of using a buffer as a precursor solvent compared to using (unbuffered) WFI. This procedure was repeated 30, 60, and 90 minutes after dissolution of Test System 1B. At each time tested, Test System 1B showed an increase in average gel time of at least 45%.

[0125] [Table 4]

[0126] This study showed that test system 1B had storage stability for more than 90 minutes after preparation, with an average gel time not exceeding 70 seconds throughout this storage period. The results indicate that a buffer can be used in the systems described in this invention, but the addition of a buffer does not appear to provide better or even comparable results to the system prepared with WFI.

[0127] Example 4: Effect of Buffer Concentration on In Vitro Performance This example illustrates the effect of buffer concentration and system pH on the performance of a single component system.

[0128] A single component system (Test System 1C) was prepared from the first and second precursors of Test System 1 of Example 2. For Test System 1C, the precursors were dissolved in 0.01M sodium phosphate monobasic buffer at pH 4.01 as shown in Table 5. The precursors in dry powder form were combined with the buffer and a trace amount of FD&C Blue#1 (less than about 0.011% by weight) to form a solution with a precursor concentration of 10% by weight. The first and second precursors were used in a weight ratio such that each solution had approximately equal numbers of SG and amine functional end groups. The precursors dissolved quickly as judged by the absence of particles upon visual inspection. The initial pH of Test System C was 2.92.

[0129] [Table 5]

[0130] Immediately after dissolution, a 150 μL aliquot of Test System 1C was pipetted into a 50 μL aliquot of 37° C. phosphate buffered saline (PBS). This process was repeated with a second sample. The pH of Test System 1C and the time to gelation for each sample after dissolution were recorded as shown in Table 6. A 250 μL aliquot of high concentration monobasic phosphate (0.0121 g monobasic / mL; pH 4.30) was added to the vial containing Test System 1C. The pH was measured. The gel time of the resulting solution was measured as described above. Additional aliquots of high concentration monobasic phosphate were added as shown in Table 6. The pH and gel time were measured after each addition. The results shown in Table 6 are plotted in FIG. 5 as gel time (left axis) and amount of high concentration monobasic added ("dilution amount", right axis) as a function of system pH.

[0131] [Table 6]

[0132] FIG. 5 shows that gel time increases nonlinearly with pH. At an initial pH of 2.92, the average gel time was about 51.88 seconds. At pH 3.16, the average gel time was 114.97 seconds, more than twice as long. At pH 3.35, the average gel time was 269.16 seconds (about 4.5 minutes), more than five times longer than the gel time of the test system 1C solution. This result suggests that the gel time is more affected by the presence of the buffer as the solution approaches the pH buffer range of the buffer. Importantly, the single solution system of this example did not exhibit storage stability limitations over the pH range investigated.

[0133] This testing showed that while a variety of buffer concentrations and pH can be used with the precursors described in this invention, the addition of buffer (and associated change in pH) has the effect of lengthening gel times, especially as one approaches the pH range of the buffer. These results account well for the buffer effect, since gelation requires an increase in pH to deprotonate the amines, but gelation is significantly slower in buffer systems with a high initial pH.

[0134] Example 5: Subcutaneous Performance Test In this example, an in vivo model was used to evaluate the effect of precursor concentration on the performance of the single-component system, as well as its efficacy for repeated subcutaneous injection along tissue.

[0135] Three concentrations of the single component system described in Example 1 were prepared to form 10 wt. %, 20 wt. %, and 30 wt. % solutions. In each solution, the precursor dissolved rapidly in WFI as judged by visual inspection. Once dissolved, each prepared solution was drawn up into a separate 5 ml syringe and fitted with a separate 25 gauge needle. Approximately 500 μl of each of the three solutions were injected subcutaneously into separate but similar sites along the abdomen of a sedated pig (weight 65 kg). The 10% and 20% solutions were observed to form distinct gel pockets that were felt as firm subcutaneous masses approximately 10-30 seconds after injection. One minute after injection, each injection site was dissected. The injection sites of the 10% and 20% solutions showed the presence of a blue gel. Dissection of the injection site of the 30% solution confirmed blue fluid oozing from the subcutaneous placement site, indicating that no gel had formed. The 30% solution was observed to gel within the dissected placement site after 2 minutes, suggesting an upper concentration limit for achieving gel formation with a single component system.

[0136] Following the initial trial, a series of closely spaced subcutaneous injections were made into the pig urethra using the original 10% solution (using the original syringe and needle). Each injection delivered a volume of approximately 250 μl. Injections continued for 5 minutes, during which no evidence of needle clogging was observed. The presence of gel at the injection site after 10-30 seconds was confirmed by pressing / kneading the tissue. A series of firm subcutaneous mass beads were felt, suggesting the formation of an interconnected gel with repeated injections.

[0137] This study demonstrated that the single component system is concentration-dependent and can be used efficiently with small gauge needles for repeated subcutaneous injections that form a gel within 10-30 seconds.

[0138] Example 6: Multi-site performance testing In this example, a single component system used sequentially at multiple sites in an in vivo model was evaluated.

[0139] A 10 wt% solution was prepared according to Example 1 with the modification of adding a small amount (<0.001%) of Fluorescein-NHS to the solution. Immediately after dissolution, the prepared solution was drawn up into a 5 ml syringe and fitted with a 30 gauge needle.

[0140] Part A: Subcutaneous injection site Approximately 500 μl of the solution was injected subcutaneously into the subcutaneous tissue of a freshly euthanized pig (body weight 65 kg). The gel felt firm and intact beneath the dermis within 10 seconds. One minute after injection, the injection site was dissected and evaluated under blue light. The presence of the gel resulted in the formation of a raised lump on the surface of the outer epidermis. The gel was visible through the outer epidermis and was shown to be a slightly elliptical flattened sphere with a radius of approximately 15 mm. Dissection confirmed the presence of the gel as well as its size and shape.

[0141] Part B: Subconjunctival injection site Using the same solution, syringe, and needle as in Part A, approximately 200 μl of solution was injected subconjunctivally into the pig eye of Part A. After injection, the injection site was visualized with blue light. The gel felt firm and intact beneath the dermis within 10 seconds.

[0142] Part C: Periodontal injection sites Using the same solution, syringe, and needle as in Parts A and B, approximately 250 μl aliquots of solution were injected multiple times under the gums of the pigs in Parts A and B. After injection, the injection sites were visualized with blue light, which showed the presence of multiple small gel depots. The gel felt firm and whole beneath the dermis within 10 seconds.

[0143] The study demonstrated that a single solution, syringe, and needle could be used to deliver hydrogel depots to multiple locations in the body over a period of approximately one hour. The time to gelation remained at approximately 10-30 seconds during this period. The study also demonstrated that contrast agents could be used to visualize the size and location of the hydrogel through the dermis in various tissues.

[0144] Example 7: Performance testing of multiple sites on the eye In this example, a single component system used sequentially at multiple ocular locations in an in vivo model was evaluated.

[0145] A 10 wt % solution was prepared according to Example 6. Once dissolved, the prepared solution was drawn up into a 5 ml syringe and fitted with a 30 gauge needle.

[0146] Part A: Eyelid injection site Separate 50 μl aliquots of the solution were injected into each of five locations on the eyelid margin of a freshly euthanized pig (body weight 65 kg). Visualization of the injection sites under blue light with a yellow filter showed the presence of multiple small gel depots throughout the eyelid. The gel felt firm and intact beneath the dermis within 10 seconds.

[0147] Part B: Anterior chamber injection site Using the same solution, syringe, and needle as in Part A, approximately 100 μl of solution was injected into the anterior chamber of the pig eye in Part A. The injection site was visualized under blue light with a yellow filter. The gel was determined to be solid within 10 seconds as the fluorescein-NHS dye did not dissipate or migrate through the aqueous humor.

[0148] This study demonstrated that a single solution, syringe, and needle could be used to deliver hydrogel depots through a small gauge needle to multiple locations in the eye, including repeated injections along the lash line and injections into the anterior chamber, without clogging the needle. In this study, the solution was used to successfully inject over a period of approximately 1 hour, with gelation times remaining at approximately 10-30 seconds throughout this period.

[0149] Example 8: Multiple-site skin injection study In this example, a single component system was evaluated for sequential use at multiple skin locations in an in vivo model.

[0150] A 10 wt% solution was prepared according to Example 6. Once dissolved, the prepared solution was drawn up into the 5 ml reservoir of a commercial tattoo device (i.e., gun).

[0151] Part A: Subcutaneous injection The solution was injected into the internal abdomen of a freshly euthanized pig (body weight 65 kg) in a continuous line across the internal abdomen. The injection site was visualized under blue light with a yellow filter, which showed the presence of a continuous line of gel depot across the skin of the pig's abdomen. The gel was clear and non-migratory and could be visualized under fluorescent lighting.

[0152] Additional Inventive Concepts 1. A method of injecting an in situ crosslinked hydrogel into a patient's fallopian tubes, comprising: sequentially delivering a hydrogel precursor solution directly to a first fallopian tube of the patient using an applicator, and subsequently to a second fallopian tube of the patient; the applicator comprising a reservoir of the hydrogel precursor solution connected to a catheter configured to transcervically place the hydrogel precursor in the fallopian tube; the hydrogel precursor solution comprises a mixture of a first compound having a plurality of electrophilic groups, a second compound having a plurality of nucleophilic groups, and an aqueous solvent having a pH of about 6 or less; the hydrogel precursor solution gels within about 3 minutes of contacting the first fallopian tube tissue and gels within about 3 minutes of contacting the second fallopian tube tissue; method. 2. The method of inventive concept 1, wherein said delivery is guided by x-ray, ultrasound, or other medical imaging. 3. The method according to inventive concept 1 or 2, wherein the catheter configured for transcervical placement comprises a balloon, and the balloon can be expanded after placing the catheter at the ostium of the fallopian tube and before delivering the hydrogel precursor solution. 4. The method according to any one of inventive concepts 1-3, wherein said first compound comprises a multi-arm polyethylene glycol having a succinimidyl functionality and said second compound comprises a multi-arm polyethylene glycol having a protonated amine functionality. 5. The method according to any one of inventive concepts 1-4, wherein the hydrogel precursor solution gels to form a first occlusion in the first fallopian tube and a second occlusion in the second fallopian tube. 6. The method of inventive concept 5, wherein said first occlusion and said second occlusion result in reversible or permanent female sterilization. 7. The method of any one of inventive concepts 1-6, further comprising performing a tubal patency test after a selected period of time. 8. A method for delivering a medical hydrogel for in situ crosslinking, comprising: blending an electrophilic precursor and a nucleophilic precursor with an aqueous solvent having a pH of about 6 or less to form a precursor solution having storage stability to flow conditions at room temperature for at least about 10 minutes, said storage stability being determined by being able to inject said precursor solution from a 5 ml syringe equipped with a 25 gauge needle; and delivering a quantity of a precursor solution to a patient, wherein the precursor solution contacts physiological fluids associated with physiological tissue of a living body to induce crosslinking of the hydrogel, such that the hydrogel gels in vivo within about 5 minutes; The method includes: 9. The method of inventive concept 8, wherein said electrophilic precursor and said nucleophilic precursor are powders. 10. The method of inventive concept 8 or 9, wherein said electrophilic precursor comprises a first hydrophilic polymer core and a plurality of electrophilic functional groups, said nucleophilic precursor comprises a second hydrophilic polymer core and a plurality of protonated amine groups, and said electrophilic precursor and said nucleophilic precursor are water soluble. 11. The method of any one of inventive concepts 8 to 10, wherein the electrophilic precursor and the nucleophilic precursor independently have a molecular weight of about 2 KDa to about 50 KDa and 4 to 8 arms. 12. The method of inventive concept 11, wherein said plurality of electrophilic functional groups comprises reactive esters. 13. The method of inventive concept 11, wherein said first hydrophilic polymer core and / or said second hydrophilic polymer core comprises polyethylene glycol, polyvinyl alcohol, polylactic acid, polyoxazoline, copolymers thereof, or mixtures thereof. 14. The method of any one of inventive concepts 8-13, further comprising an additional electrophilic precursor and / or an additional nucleophilic precursor. 15. The method of any one of inventive concepts 8-14, wherein the precursor solution further comprises a therapeutic and / or visualization agent comprising a colorant, a fluorescent molecule, an ultrasound contrast agent, an X-ray contrast agent, an MRI contrast agent, or a combination thereof. 16. The method of any one of inventive concepts 8-15, wherein the precursor solution has a storage stability to flowable conditions at room temperature for at least about 2 hours, said storage stability being measured by the ability to inject the precursor solution from a 5 ml syringe equipped with a 25 gauge needle. 17. The method of any one of inventive concepts 8-16, further comprising delivering a quantity of precursor solution to one or more additional patients to form one or more additional hydrogels, wherein the one or more additional hydrogels individually gel within about 3 minutes. 18. The method of any one of inventive concepts 8-17, wherein said delivering comprises injection through a needle, high pressure needleless injection, delivery through a catheter, delivery through a dropper, or spraying. 19. The method of any one of inventive concepts 8-18, wherein the delivery comprises multiple injections from a single barrel syringe, with the same needle being used for each injection, or the needle being replaced, or a combination thereof. 20. The method of any one of inventive concepts 8-19, further comprising determining an expiration date after blending and discarding the product after the expiration date has expired. 21. The method of any one of inventive concepts 8 to 20, wherein the physiological tissue of the living body comprises an immune-prone space, a subcutaneous location, an ocular location, an intramural location, a body cavity, an abnormal tissue, a target tissue, or a combination thereof. 22. The method of any one of inventive concepts 8-21, wherein said delivery is to a tumor, fallopian tube, uterus, urethra, blood vessel, a location within a muscle, a location between a muscle and a nerve, the eyelash line, or in and around the eye. 23. The method of any one of inventive concepts 8 to 22, wherein said delivery is monitored using a visualization agent. 24. The method according to any one of inventive concepts 8 to 23, wherein the hydrogel gels within 30 seconds. 25. The method of any one of inventive concepts 8 to 24, wherein the hydrogel degrades within about 14 days. 26. The method of any one of inventive concepts 8-25, wherein the hydrogel releases a therapeutic amount of a therapeutic agent. 27. The method of inventive concept 26, wherein said therapeutic agent comprises an analgesic, an anesthetic, a steroid, a chemotherapeutic agent, a glycosaminoglycan, a carbohydrate, a nucleic acid, a protein, an anti-tumor agent, a glaucoma agent, an antibiotic, an enzyme, an anti-infective agent, an anti-fungal agent, an anti-inflammatory agent, a non-steroidal anti-inflammatory agent, an anti-neoplastic agent, a hormone, an angiogenic agent, an anti-angiogenic agent, a growth factor, an intraocular pressure reducing agent, an antibody, a neurotransmitter, a psychoactive agent, an anti-cancer agent, an agent affecting fertility, a gene, a cell, a cell product, an oligonucleotide, or a combination thereof. 28. The method of any one of inventive concepts 8-27, wherein the hydrogel releases a therapeutic amount of the therapeutic agent for up to about 14 days. 29. The method of any one of inventive concepts 8-27, wherein the hydrogel releases a therapeutic amount of the therapeutic agent for up to about 180 days. 30. The method of any one of inventive concepts 8-27, wherein the hydrogel releases a therapeutic amount of the therapeutic agent for at least about 180 days. 31. The method of any one of inventive concepts 8-28, wherein the hydrogel degrades within about 14 days. 32. The method of any one of inventive concepts 8-29, wherein the hydrogel degrades within about 180 days. 33. The method of any one of inventive concepts 8-30, wherein the hydrogel persists for at least about 180 days. 34. The method according to any one of inventive concepts 8 to 33, wherein the multiple injections are performed to form a tattoo based on an aesthetic design. 35. The method of inventive concept 34, wherein the hydrogel comprises a covalently attached dye. 36. The method of inventive concept 34, wherein the hydrogel lasts for about 180 days or less.

[0153] The above embodiments are intended to be illustrative and not limiting. Additional embodiments are within the scope of the claims. Moreover, although the present invention has been described with reference to specific embodiments, those skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the present invention. Any incorporation by reference of the above documents is limited to not incorporating subject matter contrary to the express disclosure herein. To the extent that a particular structure, composition, and / or method is disclosed herein with components, elements, ingredients, or other categories, the disclosure herein should be understood to cover the specific embodiments, as well as embodiments that include the specific components, elements, ingredients, other categories, or combinations thereof, and embodiments that consist essentially of such specific components, ingredients, other categories, or combinations thereof, which may include additional features that do not alter the basic nature of the subject matter suggested in the discussion unless expressly indicated otherwise.

Claims

1. A medical hydrogel precursor solution comprising an aqueous solvent with a pH of approximately 6 or less, a mixture of a first precursor containing multiple electrophilic functional groups and a first hydrophilic core, and a second precursor containing multiple protonated amine groups, wherein the solution is fluid for at least 10 minutes after formation and gels within 20 minutes after dilution with 1 / 3 volume of 37°C phosphate-buffered saline (PBS) (3 volumes of hydrogel precursor solution containing 1 volume of PBS).

2. A medical hydrogel precursor solution according to claim 1, wherein the gel time is approximately 3 minutes or less, and the gel time is measured in vitro by injecting a fixed volume of the precursor solution at room temperature into a fixed volume of PBS at 37°C, maintaining the combined volume at 37°C, and recording the time until a solid or semi-solid mass is formed, and the volume of the precursor solution is the same as the volume of the PBS.

3. A medical hydrogel precursor solution according to claim 1, wherein the gel time is approximately 10 to 40 seconds, and the gel time is measured in vitro by injecting a fixed volume of the precursor solution at room temperature into a fixed volume of PBS at 37°C, maintaining the combined volume at 37°C, and recording the time until a solid or semi-solid mass is formed, wherein the volume of the precursor solution and the volume of the PBS are the same.

4. The medical hydrogel precursor solution according to claim 1, having storage stability under fluid conditions at room temperature for at least about 10 minutes, the storage stability being determined by the fact that the precursor solution can be injected from a 5 ml syringe equipped with a 27 gauge needle.

5. A medical hydrogel precursor solution according to claim 1, which does not contain added buffering agents exceeding approximately 0.025 M, and has storage stability under fluid conditions at room temperature for at least approximately 2 hours, the storage stability being determined by the fact that the precursor solution can be injected from a 5 ml syringe equipped with a 25 gauge needle.

6. The medical hydrogel precursor solution according to claim 1, which does not contain the buffer to which the aqueous solvent is added.

7. The medical hydrogel precursor solution according to claim 1, wherein the aqueous solvent essentially consists of unbuffered physiological saline or water for injection.

8. The medical hydrogel precursor solution according to claim 1, wherein the first hydrophilic core and / or the second hydrophilic core comprises a polymer.

9. The medical hydrogel precursor solution according to claim 1, wherein the first hydrophilic core and / or the second hydrophilic core comprises polyethylene glycol, polyvinyl alcohol, polyoxazoline, copolymers thereof, or mixtures thereof.

10. The medical hydrogel precursor solution according to claim 1, wherein the first hydrophilic core has a plurality of arms having electrophilic functional groups, or the second hydrophilic core has a plurality of arms having protonated amine groups, or a combination thereof.

11. The medical hydrogel precursor solution according to claim 10, wherein the plurality of arms number 3 to 8.

12. The medical hydrogel precursor solution according to claim 1, wherein the molecular weight of the second precursor is equal to or greater than the molecular weight of the first precursor.

13. The medical hydrogel precursor solution according to claim 1, wherein the first precursor and the second precursor independently have a molecular weight of about 2 kDa to about 50 kDa and 3 to 8 arms.

14. The medical hydrogel precursor solution according to claim 1, wherein the electrophilic functional group comprises a reactive ester.

15. The medical hydrogel precursor solution according to claim 1, wherein the electrophilic functional group comprises succinimidyl succinate, succinimidyl succinamide, succinimidyl glutarate, succinimidyl glutaramide, succinimidyl adipate, succinimidyl azelate, or a combination thereof.

16. The medical hydrogel precursor solution according to claim 1, wherein the electrophilic functional group has a degradable ester bond to the first hydrophilic core or a non-degradable amide bond to the first hydrophilic core.

17. The medical hydrogel precursor solution according to claim 1, wherein the precursor solution has a solid content concentration of at least about 1% by weight.

18. The medical hydrogel precursor solution according to claim 1, wherein the precursor solution has a solid content concentration of about 30% by weight or less.

19. The medical hydrogel precursor solution according to claim 1, wherein the precursor solution has a solid content concentration of about 8% to about 17% by weight.

20. A medical hydrogel precursor solution according to any one of claims 1 to 19, further comprising a therapeutic agent.

21. The medical hydrogel precursor solution according to claim 20, wherein the therapeutic agent comprises an analgesic, an anesthetic, steroid, chemotherapeutic agent, glycosaminoglycan, carbohydrate, nucleic acid, protein, antitumor agent, glaucoma agent, antibiotic, steroid, enzyme, antiinfective agent, antifungal agent, anti-inflammatory agent, nonsteroidal anti-inflammatory agent, antineoplastic agent, hormone, angiogenic agent, anti-angiogenic agent, growth factor, intraocular pressure lowering agent, antibody, neurotransmitter, psychoactive agent, anticancer agent, agent affecting reproductive capacity, gene, cell, oligonucleotide, or a combination thereof.

22. The aforementioned therapeutic agents include travoprost, prostaglandin analogs, low-soluble prostaglandin analogs, mydriatics, anti-VEGF drugs, anti-VEGFR1 drugs, anti-VEGFR2 drugs, anti-VEGFR3 drugs, anti-PDGF drugs, anti-PDGF-R drugs, anti-PDGFRβ drugs, sunitinib, E7080, takeda-6d, tivozanib, regorafenib, sorafenib, pazopanib, axitinib, nintedanib, cediranib, batalanib, motesanib, macrolides, sirolimus, everolimus, and tyrosine kinase inhibitors. A medical hydrogel solution according to claim 20, comprising imatinib, gefitinib, toceranib, erlotinib, lapatinib, nilotinib, bosutinib, neratinib, lapatinib, batalanib, dexamethasone, moxifloxacin, nepafenac, macrolides, rapamycin, sirolimus, tacrolimus, lipoic acid and its derivatives, sterols, oxysterols, mRNA, chimeric antigen receptor cells, T cells, NK cells, recombinant T cells, stem cells, pancreatic cells, or a combination thereof.

23. The medical hydrogel solution according to claim 20, wherein the therapeutic agent comprises mRNA, chimeric antigen receptor cells, T cells, NK cells, recombinant T cells, stem cells, pancreatic cells, or a combination thereof.

24. A medical hydrogel precursor solution according to claim 1, further comprising a visualization agent.

25. The medical hydrogel precursor solution according to claim 24, wherein the visualization agent is biocompatible and comprises a colorant, a fluorescent molecule, a contrast agent, or a combination thereof.

26. The medical hydrogel precursor solution according to claim 25, wherein the visualization agent is covalently bonded to the first precursor, the second precursor, or a combination thereof.

27. The medical hydrogel precursor solution according to claim 25, wherein the visualization agent comprises a reactive functional group that can react with the nucleophilic functional group of the second precursor at an appropriate pH.

28. The medical hydrogel precursor solution according to claim 1, further comprising a third precursor comprising a third hydrophilic core and a plurality of functional groups, wherein the plurality of functional groups comprises electrophilic functional groups or protonated amine groups.

29. The hydrogel precursor solution for medical use according to claim 1, wherein the hydrogel formed from the precursor solution has a decomposition time of approximately 14 days or less, and the decomposition time was measured in vitro by injecting a fixed volume of the precursor solution into a fixed volume of PBS at 37°C at room temperature, maintaining the combined volume at 37°C, and recording the time from the formation of a solid or semi-solid mass until the solid or semi-solid mass disappears, wherein the volume of the precursor solution and the volume of the PBS are the same.

30. The hydrogel precursor solution for medical use according to claim 1, wherein the hydrogel formed from the precursor solution has a decomposition time of approximately 180 days or less, and the decomposition time was measured in vitro by injecting a fixed volume of the precursor solution into a fixed volume of PBS at 37°C at room temperature, maintaining the combined volume at 37°C, and recording the time from the formation of a solid or semi-solid mass until the solid or semi-solid mass disappears, wherein the volume of the precursor solution and the volume of the PBS are the same.

31. The medical hydrogel precursor solution according to claim 29, wherein the visualization agent is covalently bonded to the first precursor, the second precursor, or a combination thereof.

32. The hydrogel precursor solution for medical use according to claim 1, wherein the hydrogel formed from the precursor solution has a decomposition time of at least about 180 days, the decomposition time being measured in vitro by injecting a fixed volume of the precursor solution into a fixed volume of PBS at 37°C at room temperature, maintaining the combined volume at 37°C, and recording the time from the formation of a solid or semi-solid mass until the solid or semi-solid mass disappears, wherein the volume of the precursor solution and the volume of the PBS are the same.

33. A dispenser containing the medical hydrogel precursor solution described in claim 1.

34. The dispenser according to claim 33, wherein the dispenser includes a needle and a syringe.

35. The dispenser according to claim 33, wherein the dispenser includes a dropper.

36. The dispenser according to claim 33, wherein the dispenser includes a catheter.

37. The dispenser according to claim 33, wherein the dispenser includes a tattooing device.

38. A hydrogel precursor solution for medical use, comprising an aqueous solvent with a pH of approximately 6 or less, a mixture of a first precursor containing multiple electrophilic functional groups and a first hydrophilic core, and a second precursor containing multiple protonated amine groups and a second hydrophilic core.

39. A method for delivering medical hydrogels for in situ crosslinking, Blending electrophilic precursors and nucleophilic precursors with an aqueous solvent having a pH of approximately 6 or less to form a precursor solution having storage stability under fluid conditions for at least approximately 10 minutes at room temperature, wherein the storage stability is determined by the fact that the precursor solution can be injected from a 5 ml syringe equipped with a 25 gauge needle; and The method involves delivering a certain amount of precursor solution to a patient, wherein the precursor solution comes into contact with physiological fluids related to the physiological tissues of the body, inducing crosslinking of the hydrogel, and the hydrogel gels in the body within approximately 5 minutes; A method that includes this.

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