WO2025226214A1

WO2025226214A1 - A thermogel-drug composition suitable for use in the delivery of a therapeutic agent

Info

Publication number: WO2025226214A1
Application number: PCT/SG2025/050261
Authority: WO
Inventors: Hui Min Joey WONG; Belynn Leng Leng SIM; Cally OWH; Yuan Chong Jason Lim; Zhi Rong Rubayn GOH; Xian Jun Loh
Original assignee: Agency for Science Technology and Research Singapore
Current assignee: Agency for Science Technology and Research Singapore
Priority date: 2024-04-25
Filing date: 2025-04-15
Publication date: 2025-10-30
Anticipated expiration: 2026-10-25

Abstract

There is provided a thermogel-drug composition comprising: a thermogel polymer comprising one or more repeating units derived from a hydrophilic polymer, one or more repeating units derived from a thermoresponsive polymer, and one or more repeating units derived from a vinyl-containing diol monomer; and a drug or a drug analog encapsulated by said thermogel polymer.

Description

A THERMOGEL-DRUG COMPOSITION SUITABLE FOR USE IN THE DELIVERY OF A THERAPEUTIC AGENT

TECHNICAL FIELD

The present disclosure relates broadly to a thermogel-drug composition and related methods thereof.

BACKGROUND

With a globally aging population and hence an increasing life expectancy and chronic illnesses, medicine use is expected to increase dramatically and efforts must be made to sustain a high quality of life. Drug delivery systems are pivotal for achieving sustained and modulated drug delivery, which improves therapeutic outcomes by maintaining drug concentrations within an optimal therapeutic window as well as enhances patient compliance by minimizing administration frequencies. To address this, 3^rd generation drug delivery systems have been developed to enable sustained and modulated drug delivery. Among them, injectable hydrogels have emerged as promising materials for applications in drug delivery, tissue engineering, and wound healing as they provide a minimally invasive strategy for administering drug depots.

Particularly, hydrogels offer significant advantages, including excellent biocompatibility, adjustable physiochemical properties, porous structure, as well as capability to encapsulate therapeutic agents and cells. Furthermore, hydrogels undergo spontaneous gelation upon injection, making them well- suited for sustained drug release.

However, most traditional covalently crosslinked hydrogels require prefabrication and subsequent implantation through highly invasive surgical procedures. Moreover, the preformed covalent network may get disrupted after being extruded through a narrow bore needle, resulting in the weakening of the mechanical properties and structural integrity of the hydrogel.

In contrast to covalently crosslinked hydrogels, injectable thermoresponsive hydrogels (thermogels) offer a distinct advantage in their ability to form a mechanically stable hydrogel, conform to irregularly shaped defects, and provide a non-invasive administration to the body. Specifically, thermogels undergo spontaneous gelation upon injection and function by forming a percolating network of micellar crosslinks above the critical gelation temperature (CGC).

The gelation mechanism of thermogels relies on the hydrophilic-to- hydrophobic transition of thermo-responsive amphiphiles to form supramolecular micellar crosslinks. However, the applicability of known thermogels is limited by the lack of synthetic pathways for tailoring functional groups, highlighting the need for more versatile and customizable solutions in drug delivery.

Indeed, with the ever-changing landscape of drug discovery and development, the ballooning diversity of drugs calls for new approaches in designing drug-specific injectable depots for sustained release. Current approaches, which either focus on targeted development for a single drug or rely on a one-size-fits-all approach, can only accommodate a limited number of drugs, as the release kinetics are often drug-dependent due to intermolecular interactions between gels and drugs.

In view of the above, there is a need to address or at least ameliorate the above-mentioned problems. In particular, there is a need to provide a method to conveniently allow tailorable chemical functionalization of thermogelling polymers, thereby accommodating a wide range of drugs and enabling future tailored applications in the field of medicine. SUMMARY

In one aspect, there is provided a thermogel-drug composition comprising, a thermogel polymer comprising one or more repeating units derived from a hydrophilic polymer, one or more repeating units derived from a thermoresponsive polymer, and one or more repeating units derived from a vinylcontaining diol monomer; and a drug or a drug analog encapsulated by said thermogel polymer.

In one embodiment, the one or more repeating units derived from a hydrophilic polymer are represented by general formula (1 ), the one or more repeating units derived from a thermoresponsive polymer are represented by general formula (2), and the one or more repeating units derived from a vinylcontaining diol monomer are represented by general formula (3) or its functionalized derivative thereof: wherein

_R1 a _R1b _R2a _R2b _R3a _R3b _R4a _R4b _R5 _{tQ R}10 _R12 _{and R}13 _{are each} independently selected from H, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted alkylene oxide, and optionally substituted poly(alkylene oxide); m is from 1 to 400; and n is from 1 to 400. In one embodiment, the one or more repeating units represented by general formula (1 ) is different from the one or more repeating units represented by general formula (2) in the thermogel polymer.

In one embodiment, the hydrophilic polymer comprises poly(ethylene glycol) (PEG) and the thermoresponsive polymer comprises polypropylene glycol) (PPG).

In one embodiment, the one or more repeating units represented by general formula (3) is derived from a compound selected from the group consisting of 1 ,5-hexadiene-3,4-diol, 3-(allyloxy)propane-1 ,2-diol and 2,3- dihydroxypropylmethacrylate.

In one embodiment, the functionalized derivative of general formula (3) comprises functional groups selected from the group consisting of cationic and anionic groups, zwitterionic groups, hydroxyl groups, aromatic rings, and combinations thereof.

In one embodiment, the functionalized derivative of general formula (3) comprises a structure represented by general formula (4): wherein

R⁵ to R¹⁰, R¹², R¹³, R²⁰, and R²¹ are each independently selected from H, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted alkylene oxide, and optionally substituted poly(alkylene oxide); and

X¹ and X² are each independently a moiety comprising a carboxylic acid, a carboxylate, a sulfonic acid, an amine, an amino acid, a sulfonate, an alkylsulfonate, an aminehydrochloride, protonated amine, an alcohol, a diol, a benzene, an alkylbenzene, imidazole, or salts thereof.

In one embodiment, X¹ and X² are each independently selected from the group consisting of the following structures:

In one embodiment, the thermogel polymer comprises from 0.01 mmol/g to 7 mmol/g of vinyl groups.

In one embodiment, the thermogel polymer, has a functional group density of X¹ and/or X², of from 0.01 mmol/g to 7 mmol/g.

In one embodiment, the one or more repeating units represented by general formula (1), the one or more repeating units represented general formula (2), and the one or more repeating units represented by general formula (3) or its functionalized derivative thereof, are chemically coupled together by at least one of urethane, carbamate, carbonate, ester, urea, amide linkages, thiolated analogues thereof, or combinations thereof.

In one embodiment, the at least one of urethane, carbamate, carbonate, ester, urea, amide linkages, is represented by general formula (5): wherein

R¹¹ is optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted cycloalkyl, or optionally substituted aromatic aryl; and

R¹⁴ and R¹⁵ are each independently selected from H, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted cycloalkyl, or optionally substituted aromatic aryl;).

In one embodiment, the linkage represented by general formula (5) is derived from a compound selected from the group consisting of diisophorone diisocyanate, 4,4’-diphenylmethane diisocyanate, and hexamethylene diisocyanate.

In one embodiment, the one or more repeating units represented by general formula (1 ) is present in an amount of between more than 0 mass% to 90 mass% of the thermogel polymer; the one or more repeating units represented by general formula (2) is present in an amount of more than 0 mass% to 90 mass% of the thermogel polymer; and the one or more repeating units represented by general formula (3) or its derivative thereof is present in an amount of from 0.1 mass% to 40 mass% of the thermogel polymer.

In one embodiment, the thermogel polymer has one or more of the following properties: a polydensity index (PDI) falling in a range of from 1.0 to 2.0; a pH value falling in a range of from 1 to 10; a critical gelation temperature falling in a range of from 4°C to 60°C; a crossover modulus falling in a range of from 5 Pa to 1000 Pa; a storage modulus (G’) falling in a range of from 1 Pa to 5000 Pa; a complex viscosity falling in a range of from 1 Pa.s to 1000 Pa.s; a mesh size falling in a range of from 5 nm to 30 nm; and a water content of more than 60% to more than 99% by weight.

In one embodiment, the drug or drug analog has a high molecular weight of no less than about 10 kDa, has an intermediate molecular weight of from 1 kDa to 10 kDa, or has a low molecular weight of no more than about 1 kDa.

In one embodiment, the drug or drug analog is cationic, anionic, zwitterionic, or neutral.

In one embodiment, the drug or drug analog is selected from the group consisting of crystal violet, orange II, dextran, imipramine, amitriptyline, thioridazine, chlorpromazine, trazodone, imiglucerase, certolizumab pegol, etanercept, nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, naproxen, diclofenac, aspirin, indomethacin, and piroxicam.

In one embodiment, the thermogel polymer comprises one or more repeating units represented by general formula (1 ), one or more repeating units represented by general formula (2), and one or more repeating units represented by general formula (3) or its functionalized derivative thereof, wherein the functionalized derivative of general formula (3) is functionalized with one or more functional groups selected from a group consisting of -NH₃ ⁺, -COO-, -COO- :NH₃ ⁺, -(OH)2, and -Ph; and the drug or drug analog comprises a low molecular weight cationic hydrophobic molecular drug or drug analog that is < 1 kDa,

In one embodiment, the thermogel polymer comprises one or more repeating units represented by general formula (1 ), one or more repeating units represented by general formula (2), and one or more repeating units represented by general formula (3) or its functionalized derivative thereof, wherein the functionalized derivative of general formula (3) is functionalized with one or more functional groups selected from a group consisting of -NH₃ ⁺, -COO :NH₃ ⁺, - (OH)₂, and -Ph; and the drug or drug analog comprises a low molecular weight anionic hydrophobic molecular drug or drug analog that is < 1 kDa.

In one embodiment, the thermogel polymer comprises one or more repeating units represented by general formula (1 ), one or more repeating units represented by general formula (2), and one or more repeating units) represented by general formula (3) or its functionalized derivative thereof, wherein the functionalized derivative of general formula (3) is functionalized with one or more functional groups selected from a group consisting of -NH₃ ⁺, -(OH)2, and -Ph; and the drug or drug analog comprises a high molecular weight neutral hydrophobic molecular drug or drug analog that is > 10 kDa.

In one embodiment, the thermogel-drug composition is capable of providing sustained drug release or a delayed biphasic release of from at least 1 day to at least 365 days.

In one aspect, there is also provided a method of preparing a thermogel- drug composition, the method comprising encapsulating one or more drugs or drug analog with a thermogel polymer disclosed herein.

In one embodiment, the method comprises coupling one or more hydrophilic polymers, one or more thermoresponsive polymers, and one or more vinyl-containing diol monomers in the presence of a coupling agent to obtain the thermogel polymer.

In one embodiment, the one or more hydrophilic polymers are represented by general formula (6), the one or more thermoresponsive polymers are represented by general formula (7), and the one or more vinyl-containing diol monomers are represented by general formula (8) or its functionalized derivative thereof: wherein

R^{1 a}, R^1b, R^2a, R^2b, R^3a, R^3b, R^4a, R^4b, R⁵ to R¹⁰, and R¹² to R¹⁹ are each independently selected from H, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted alkylene oxide, and optionally substituted poly(alkylene oxide); m is from 1 to 400; and n is from 1 to 400.

In one embodiment, the one or more hydrophilic polymers, the one or more thermoresponsive polymers, and the one or more vinyl-containing diol monomers are mixed in a mass ratio of 1 -20 : 1-10 : 0.01 -3.

In one embodiment, the coupling step is carried out in the presence of a coupling agent such that the one or more hydrophilic polymers represented by general formula (6), the one or more thermoresponsive polymers represented by general formula (7), and the one or more vinyl-containing diol monomers represented by general formula (8) or its functionalized derivative thereof are chemically coupled together by at least one of urethane, carbamate, carbonate, ester linkages, or combinations thereof to form the thermogel polymer. In one embodiment, the at least one of urethane, carbamate, carbonate, ester linkages, or combinations thereof is represented by general formula (5): wherein

R¹¹ is optionally substituted alkyl, optionally substituted alkenyl, and optionally substituted alkynyl, optionally substituted cycloalkyl, or optionally substituted aromatic aryl; and

R¹⁴ and R¹⁶ are each independently selected from H, optionally substituted alkyl, optionally substituted alkenyl, and optionally substituted alkynyl, optionally substituted cycloalkyl, or optionally substituted aromatic aryl.

In one embodiment, the method further comprises functionalizing the thermogel polymer with one or more thiols to obtain a functionalized thermogel polymer with functional groups X¹— S and X²— S, wherein X¹ and X² are each independently a moiety comprising a carboxylic acid, a carboxylate, a sulfonic acid, an amine, an amino acid, a sulfonate, an alkylsulfonate, an aminehydrochloride, protonated amine, an alcohol, a diol, a benzene, an alkylbenzene, imidazole or salts thereof.

In one embodiment, the weight percentage of the total thermogel polymer that has been functionalized after the functionalizing step is of from 70 wt% to 100 wt%.

In one embodiment, the one or more hydrophilic polymers comprise polyethylene glycol) (PEG); the one or more thermoresponsive polymers comprise polypropylene glycol) (PPG); the one or more vinyl-containing diol monomers comprise 1 ,5-hexadiene- 3,4-diol (HDDO), 3-(allyloxy)propane-1 ,2-diol, or 2,3- dihydroxypropylmethacrylate; and the coupling agent comprises hexamethylene diisocyanate (HMDI).

DEFINITIONS

The term “drug analog” as used herein refers to a chemical compound that shares structural similarity with a known drug but may differ in certain components, such as functional groups, substituents, stereochemistry, or substructures, or has been modified to improve or alter its pharmacological properties. For example, drug analogs may include various chemical entities which are able to exhibit a comparable mechanism of action or therapeutic outcome as a corresponding known drug, such as isomers, tautomers, derivatives, salts, polymorphs, solvates, esters, amides, or conjugates of the parent drug. This includes but is not limited to both metabolized and unmetabolized forms of the drug, including active metabolites and prodrugs. A prodrug is a chemically modified precursor that undergoes metabolic transformation within the body to release the pharmacologically active compound. For purposes of the present disclosure, drug analogs also include bioisosteric replacements and compounds designed through rational drug design approaches to mimic the essential features of a reference drug.

The term “derivative” as used herein refers to compounds that are derived from another compound and generally maintain the same general structure as the compound from which they are derived. For example, derivatives may include functionalized, substituted, or ionized forms of the parent compound, as well as compounds wherein one or more atoms have been replaced with different atoms or groups while maintaining the essential structural characteristics. These derivatives can undergo the same types or substantially similar types of reactions as the parent compound, yielding substantially similar reaction products. For instance, a functionalized derivative of general formula (8) disclosed herein can undergo polymerization with the compounds represented by general formulae (6) and (7) disclosed herein through reactions such as etherification or urethane formation at its hydroxyl group positions, resulting in a thermogel polymer.

The term “functional group” as used herein refers to a group of atoms arranged in a way that determines the chemical properties of the group and the molecule to which it is attached. Examples of functional groups include but are not limited to carboxylic acid groups, amino acid groups, sulfonate groups, alkylsulfonate groups, aminehydrochloride groups, alcohol groups, diol groups, benzene groups, alkylbenzene groups, halogen atom containing groups, the like, and derivatives thereof.

The terms "coupled" or “linked” as used in this description are intended to cover both directly connected or connected through one or more intermediate means, unless otherwise stated.

The term "alkyl" as a group or part of a group refers to a straight or branched aliphatic hydrocarbon group having 1 to 20 carbon atoms, 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16, 17, 18, 19 or 20 carbon atoms. Examples of suitable straight and branched alkyl substituents include methyl, ethyl, n-propyl, 2-propyl, isopropyl, n- butyl, isobutyl, sec-butyl, t-butyl, hexyl, amyl, 1 ,2-dimethylpropyl, 1 ,1 - dimethylpropyl, pentyl, isopentyl, hexyl, 4-methylpentyl, 1 -methylpentyl, 2- methylpentyl, 3-methylpentyl, 2,2-dimethylbutyl, 3,3-dimethylbutyl, 1 ,2- dimethylbutyl, 1 ,3-dimethylbutyl, 1 ,2,2-trimethylpropyl, 1 , 1 ,2-trimethylpropyl, 2- ethylpentyl, 3-ethylpentyl, heptyl, 1 -methylhexyl, 2,2-dimethylpentyl, 3,3- dimethylpentyl, 4,4-dimethylpentyl, 1 ,2-dimethylpentyl, 1 ,3-dimethylpentyl, 1 ,4- dimethylpentyl, 1 ,2,3-trimethylbutyl, 1 ,1 ,2-trimethylbutyl, 1 ,1 ,3-trimethylbutyl, 5- methylheptyl, 1 -methylheptyl, octyl, nonyl, decyl and the like. The group may be a terminal group or a bridging group. The term “optionally substituted,” when used to describe a chemical structure or moiety, refers to the chemical structure or moiety wherein one or more of its hydrogen atoms is optionally substituted with a chemical moiety or functional group such as alcohol, alkoxy, alkanoyloxy, alkoxycarbonyl, alkenyl, alkyl (e g., methyl, ethyl, propyl, t-butyl), alkynyl, alkylcarbonyloxy (-OC(O)alkyl), amide (-C(O)NH-alkyl- or -alkylNHC(O)alkyl), amine (such as alkylamino, arylamino, arylalkylamino), aryl, arylalkyl, arylalkenyl, aryloxy, azo, carbamoyl (-NHC(O)O-alkyl- or -OC(O)NH-alkyl), carbamyl (e.g., CONH₂, as well as CONH-alkyl, CONH-aryl, and CONH-arylalkyl), carboxyl, carboxylic acid, cyano, ester, ether (e.g., methoxy, ethoxy), halo, haloalkyl (e g., -CCI3, -CF3, -C(CF3)s), heteroalkyl, heterocyclyl, heteroaryl, isocyanate, isothiocyanate, nitrile, nitro, phosphodiester, phosphate, phosphonate, phosphinate, sulfide, sulfonamido (e.g., SO2NH2), sulfone, sulfonyl (including alkyl sulfonyl, arylsulfonyl and arylalkylsulfonyl), sulfoxide, thiol (e.g., sulfhydryl, thioether) or urea (-NHCONH- alkyl- ).

The term "associated", used herein when referring to two elements refers to a broad relationship between the two elements. The relationship includes, but is not limited to a physical, a chemical or a biological relationship. For example, when element A is associated with element B, elements A and B may be directly or indirectly attached to each other or element A may contain element B or vice versa.

The term "adjacent" used herein when referring to two elements refers to one element being in close proximity to another element and may be but is not limited to the elements contacting each other or may further include the elements being separated by one or more further elements disposed therebetween.

The term "and/or", e.g., "X and/or Y" is understood to mean either "X and Y" or "X or Y" and should be taken to provide explicit support for both meanings or for either meaning. Further, in the description herein, the word “substantially” whenever used is understood to include, but not restricted to, "entirely" or “completely” and the like. In addition, terms such as "comprising", "comprise", and the like whenever used, are intended to be non-restricting descriptive language in that they broadly include elements/components recited after such terms, in addition to other components not explicitly recited. For example, when “comprising” is used, reference to a “one” feature is also intended to be a reference to “at least one” of that feature. Terms such as “consisting”, “consist”, and the like, may in the appropriate context, be considered as a subset of terms such as "comprising", "comprise", and the like. Therefore, in embodiments disclosed herein using the terms such as "comprising", "comprise", and the like, it will be appreciated that these embodiments provide teaching for corresponding embodiments using terms such as “consisting”, “consist", and the like. Further, terms such as "about", "approximately" and the like whenever used, typically means a reasonable variation, for example a variation of +/- 5% of the disclosed value, or a variance of 4% of the disclosed value, or a variance of 3% of the disclosed value, a variance of 2% of the disclosed value or a variance of 1 % of the disclosed value.

Furthermore, in the description herein, certain values may be disclosed in a range. The values showing the end points of a range are intended to illustrate a preferred range. Whenever a range has been described, it is intended that the range covers and teaches all possible sub-ranges as well as individual numerical values within that range. That is, the end points of a range should not be interpreted as inflexible limitations. For example, a description of a range of 1 % to 5% is intended to have specifically disclosed sub-ranges 1 % to 2%, 1 % to 3%, 1 % to 4%, 2% to 3% etc., as well as individually, values within that range such as 1 %, 2%, 3%, 4% and 5%. It is to be appreciated that the individual numerical values within the range also include integers, fractions and decimals. Furthermore, whenever a range has been described, it is also intended that the range covers and teaches values of up to 2 additional decimal places or significant figures (where appropriate) from the shown numerical end points. For example, a description of a range of 1 % to 5% is intended to have specifically disclosed the ranges 1.00% to 5.00% and also 1.0% to 5.0% and all their intermediate values (such as 1.01 %, 1.02% ... 4.98%, 4.99%, 5.00% and 1.1 %, 1.2% ... 4.8%, 4.9%, 5.0% etc.,) spanning the ranges. The intention of the above specific disclosure is applicable to any depth/breadth of a range.

Additionally, when describing some embodiments, the disclosure may have disclosed a method and/or process as a particular sequence of steps. However, unless otherwise required, it will be appreciated that the method or process should not be limited to the particular sequence of steps disclosed. Other sequences of steps may be possible. The particular order of the steps disclosed herein should not be construed as undue limitations. Unless otherwise required, a method and/or process disclosed herein should not be limited to the steps being carried out in the order written. The sequence of steps may be varied and still remain within the scope of the disclosure.

Furthermore, it will be appreciated that while the present disclosure provides embodiments having one or more of the features/characteristics discussed herein, one or more of these features/characteristics may also be disclaimed in other alternative embodiments and the present disclosure provides support for such disclaimers and these associated alternative embodiments.

It will also be appreciated that where priority is claimed to an earlier application, the full contents of the earlier application is also taken to form part of the present disclosure and may serve as support for embodiments disclosed herein.

DESCRIPTION OF EMBODIMENTS

Exemplary, non-limiting embodiments of a thermogel-drug composition, a method of preparing the thermogel -drug composition, and a method of tailoring a thermogel-drug composition are disclosed hereinafter. In various embodiments, there is provided a thermogel-drug composition comprising, a thermogel polymer comprising one or more repeating units derived from a hydrophilic polymer, one or more repeating units derived from a thermoresponsive/thermosensitive polymer, and one or more repeating units derived from a vinyl-containing diol monomer; and a drug or a drug analog encapsulated by said thermogel.

In various embodiments, the thermogel polymer is optionally functionalized with one or more functional groups.

Advantageously, in various embodiments, the thermogel-drug composition is designed to be adjustable and/or customizable using the method developed in accordance with various embodiments disclosed herein, based on the properties/characteristics (e.g., molecular weight, charge, hydrophilicity/hydrophobicity, hydrogen-bonding capacity, and/or partition coefficient) of the drug or drug analog to be encapsulated. In various embodiments, functionalization (e.g., charge, hydrophilicity/hydrophobicity) of the thermogel may be customized to suit or to be compatible with the charge and/or molecular weight of the drug/drug analog, thereby optimizing loading efficiency, release kinetics, and therapeutic efficacy, depending on the application the thermogel-drug composition is to be used for. For example, when a cationic drug is to be used, then the thermogel may be functionalized with anionic group(s) to provide complementary ionic/coulombic interactions. Similarly, hydrophobic drugs may be paired with thermogels containing hydrophobic domains to enhance encapsulation and sustained release.

In various embodiments, the one or more repeating units derived from a hydrophilic polymer are represented by general formula (1 ), the one or more repeating units derived from a thermoresponsive/thermosensitive polymer are represented by general formula (2), and the one or more repeating units derived from a vinyl-containing diol monomer are represented by general formula (3) or its functionalized derivative thereof:

In various embodiments, the vinyl groups in general formula (3) may be further functionalized e g. , by click chemistry or click reactions, such as thiol-ene click reaction, or may be derivatized to introduce functional groups suitable for other orthogonal conjugation methods such as azide-alkyne cycloaddition or Diels-Alder reaction, thereby enabling the attachment of therapeutic agents, targeting moieties, or property-modifying groups.

In various embodiments, R^1a, R^{1 b}, R^2a, R^2b, R^3a, R^3b, R^4a, R^4b, R⁵ to R¹⁰, R¹², and R¹³are each independently selected from H, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted alkylene oxide (e.g., optionally substituted ethylene oxide), or optionally substituted poly(alkylene oxide) (e g., optionally substituted polyethylene oxide). For example, R^{1 a}, R^{1 b}, R^2a, R^2b, R^3a, R^3b, R^4a, R^4b, R⁵ to R¹⁰, R¹², and R¹³ may be selected from methyl, ethyl, n-propyl, 2-propyl, isopropyl, n-butyl, isobutyl, secbutyl, f-butyl, hexyl, amyl, 1 ,2-dimethylpropyl, 1 ,1 -dimethylpropyl, pentyl, isopentyl, hexyl, 4-methylpentyl, 1 -methylpentyl, 2-methylpentyl, 3-methylpentyl,

2.2-dimethylbutyl, 3,3-dimethylbutyl, 1 ,2-dimethylbutyl, 1 ,3-dimethylbutyl, 1 ,2,2- trimethylpropyl, 1 , 1 ,2-trimethylpropyl, 2-ethylpentyl, 3-ethylpentyl, heptyl, 1 - methylhexyl, 2,2-dimethylpentyl, 3,3-dimethylpentyl, 4,4-dimethylpentyl, 1 ,2- dimethylpentyl, 1 ,3-dimethylpentyl, 1 ,4-dimethylpentyl, 1 ,2,3-trimethylbutyl,

1 .1 .2-trimethylbutyl, 1 , 1 ,3-trimethylbutyl, 5-methylheptyl, 1 -methylheptyl, octyl, nonyl, decyl, the like, or combinations thereof. In various embodiments, at least one of R^1a and R^1b is H. In various embodiments, at least one of R^2a and R^2b is H. In various embodiments, at least one of R^3a and R^3b is H. In various embodiments, at least one of R^4a and R^4b is H. In various embodiments, at least one of R¹² and R¹³ is H. In various embodiments, R¹² and R¹³ are both H. For example, when one of the two (e.g., R^1a, R^2a, R^3a, R^4a, R¹²) is H, the other (e.g., R^{1 b}, R^2b, R^3b, R^4b, R¹³) is optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted alkylene oxide, and optionally substituted poly(alkylene oxide).

In various embodiments, m is from 1 to 400, from 5 to 395, from 10 to 390, from 15 to 385, from 20 to 80, from 25 to 375, from 30 to 370, from 35 to 365, from 40 to 360, from 45 to 355, from 50 to 350, from 60 to 340, from 70 to 330, from 80 to 320, from 90 to 310, from 100 to 300, from 1 10 to 290, from 120 to 280, from 130 to 270, from 140 to 260, from 150 to 250, from 160 to 240, from 170 to 230, from 180 to 220, from 190 to 210, or 200. In various embodiments, when m is approximately 340, the molecular weight of general formula (1 ) (e.g., PEG) is approximately 15 kDa.

In various embodiments, n is from 1 to 400, from 5 to 395, from 10 to 390, from 15 to 385, from 20 to 80, from 25 to 375, from 30 to 370, from 35 to 365, from 40 to 360, from 45 to 355, from 50 to 350, from 60 to 340, from 70 to 330, from 80 to 320, from 90 to 310, from 100 to 300, from 1 10 to 290, from 120 to 280, from 130 to 270, from 140 to 260, from 150 to 250, from 160 to 240, from 170 to 230, from 180 to 220, from 190 to 210, or 200.

In various embodiments, hydrophilicity, hydrophobicity, mechanical properties, effective pore sizes, temperature-responsiveness and/or drug releasee profile of the thermogel may be custom izable/adjustable by varying the value of m and/or n. In various embodiments, the one or more repeating units represented by general formula (1 ) is different from the one or more repeating units represented by general formula (2) in the thermogel polymer. For example, the one or more repeating units represented by general formula (1 ) may comprise a derivative of hydrophilic polymers such as polyethylene glycol (PEG) while the one or more repeating units represented by general formula (2) may comprise a derivative of thermal-responsive hydrophobic polymers such as polypropylene glycol (PPG) i.e., the one or more repeating units represented by general formulae (1 ) and (2) being derived from PEG and PPG respectively. In certain embodiments, a third polymer component such as, but not limited to, biodegradable polymers including poly(caprolactone) (PCL), poly(3-hydroxybutyrate) (PHB), and poly(lactic acid) (PLA), can also be incorporated into the thermogel structure to provide additional functionality such as controlled degradation profiles, modified mechanical properties, or enhanced drug release characteristics.

In various embodiments, general formula (3) may be functionalized with one or more functional groups. In various embodiments, the functionalized derivative of general formula (3) comprises functional groups selected from the group consisting of the likes of but not limited to cationic and anionic groups, zwitterionic groups, hydroxyl groups, aromatic rings, and combinations thereof. In various embodiments, the hydroxyl groups are capable of forming hydrogenbonding. In various embodiments, the aromatic rings can form TT-ir/pi-pi interactions and hydrophobic interactions.

In various embodiments, the functionalized derivative of general formula (3) comprises a structure represented by general formula (4):

wherein

R⁵ to R¹⁰, R¹², R¹³ are as defined above.

X¹— S and X²— S may be each independently derived from a thiol-containing functional group.

In various embodiments, R²⁰ and R²¹ are each independently selected from H, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted alkylene oxide (e.g., optionally substituted ethylene oxide), or optionally substituted poly(alkylene oxide) (e g., optionally substituted poly(ethylene oxide).. For example, R²⁰ and R²¹ may be selected from methyl, ethyl, n-propyl, 2-propyl, isopropyl, n-butyl, isobutyl, secbutyl, t-butyl, hexyl, amyl, 1 ,2-dimethylpropyl, 1 ,1 -dimethylpropyl, pentyl, isopentyl, hexyl, 4-methylpentyl, 1 -methylpentyl, 2-methylpentyl, 3-methylpentyl,

1 .1 .2-trimethylbutyl, 1 , 1 ,3-trimethylbutyl, 5-methylheptyl, 1 -methylheptyl, octyl, nonyl, decyl, the like, or combinations thereof. In various embodiments, R²⁰ and R²¹ are both H. In various embodiments, R¹² and R¹³ are both H. In various embodiments, X¹ and X² are each independently a moiety comprising a carboxylic acid, carboxylate (e.g., -COO- or -COO :NH₃ ⁺, etc), a sulfonic acid, an amine, an amino acid, a sulfonate (e.g., -SO₃-), an alkylsulfonate, an aminehydrochloride, protonated amine (e.g., -NH₃ ⁺ or -COO' :NH₃ ⁺, etc ), an alcohol, a diol (e.g., -(OH)2), a benzene (e.g., -Ph, a phenyl group having a structure of -C₆H₅), an alkylbenzene, imidazole, derivatives thereof, salts thereof, or the like.

In various embodiments, X¹ and X² may be each independently selected from the group consisting of the following structures or derivatives thereof:

For example, X¹ and X² may be independently derived from the group consisting of thioglycolic acid, 2-aminoethanethiol hydrochloride, thioglycerol, 2- phenylethanethiol, cysteine hydrochloride, His-SH (i.e., histidine-SH), and sodium 2-mercaptoethanesulfonate.

In various embodiments, the derivatives of the structures disclosed above include their ionized forms. It will be appreciated that other commercially available thiols such as mercaptoethanol, aromatic thiols (e.g., benzenethiol), the like, or derivatives thereof may also be used to obtain X¹-S and X²-S above.

In various embodiments, X¹ and/or X² have a functional group density falling in a range of from about 0.01 mmol/g to about 7 mmol/g, from about 0.01 mmol/g to about 6 mmol/g, from about 0.01 mmol/g to about 5 mmol/g, from about 0.01 mmol/g to about 4 mmol/g, from about 0.01 mmol/g to about 3 mmol/g, from about 0.01 mmol/g to about 2 mmol/g, from about 0.02 mmol/g to about 1.50 mmol/g, of from about 0.03 mmol/g to about 1 .40 mmol/g, from about 0.05 mmol/g to about 1 .35 mmol/g, from about 0.10 mmol/g to about 1 .30 mmol/g, from about 0.15 mmol/g to about 1 .25 mmol/g, from about 0.20 mmol/g to about 1 .20 mmol/g, from about 0.25 mmol/g to about 1.15 mmol/g, from about 0.30 mmol/g to about 1.10 mmol/g, from about 0.35 mmol/g to about 1.05 mmol/g, from about 0.40 mmol/g to about 1.00 mmol/g, from about 0.45 mmol/g to about 0.95 mmol/g, from about 0.50 mmol/g to about 0.90 mmol/g, from about 0.55 mmol/g to about 0.85 mmol/g, from about 0.60 mmol/g to about 0.80 mmol/g, from about 0.65 mmol/g to about 0.75 mmol/g, of about 0.70 mmol/g, of about 0.031 mmol/g, of about 0.032 mmol/g, of about 0.033 mmol/g, of about 0.034 mmol/g, of about 0.035 mmol/g, of about 0.036 mmol/g, of about 0.037 mmol/g, of about 0.038 mmol/g, of about 0.039 mmol/g, of about 1 .350 mmol/g, of about 1 .349 mmol/g, of about 1.348 mmol/g, of about 1.347 mmol/g, or of about 1.348 mmol/g. Advantageously, the functional group density achieved through providing midchain functionalizable vinyl groups is higher than that of the existing strategy of introducing functional groups through the end-domains. It will be appreciated that the functional group density may be tuned by changing the number of vinyl groups introduced into the thermogel polymer. In various embodiments, the functional group density may vary in accordance with functionalization of the vinylcontaining diol monomers (e.g., HDDO) with different hydrophobic/hydrophilic group. In various embodiments, the functional group density may vary in accordance with the ratio of the hydrophilic polymers to thermoresponsive/thermosensitive polymers in the functionalized thermogel polymer.

In various embodiments, the thermogel polymer comprises from about 0.01 mmol/g to about 7.0 mmol/g, from about 0.02 mmol/g to about 6.0 mmol/g, from about 0.03 mmol/g to about 5.0 mmol/g, from about 0.04 mmol/g to about 4.0 mmol/g, from about 0.05 mmol/g to about 3.0 mmol/g, from about 0.05 mmol/g to about 2.0 mmol/g, from about 0.05 mmol/g to about 1.5 mmol/g, from about 0.10 mmol/g to about 1 .45 mmol/g, from about 0.15 mmol/g to about 1 .40 mmol/g, from about 0.20 mmol/g to about 1.35 mmol/g, from about 0.25 mmol/g to about 1.30 mmol/g, from about 0.30 mmol/g to about 1.25 mmol/g, from about 0.35 mmol/g to about 1.20 mmol/g, from about 0.40 mmol/g to about 1.15 mmol/g, from about 0.45 mmol/g to about 1.10 mmol/g, from about 0.50 mmol/g to about 1.05 mmol/g, from about 0.55 mmol/g to about 1.00 mmol/g, from about 0.60 mmol/g to about 0.95 mmol/g, from about 0.65 mmol/g to about 0.90 mmol/g, from about 0.70 mmol/g to about 0.85 mmol/g, from about 0.75 mmol/g to about 0.80 mmol/g, about 0.06 mmol/g, about 0.07 mmol/g, about 0.08 mmol/g, about 0.09 mmol/g, about 0.1 mmol/g, about 1.35 mmol/g, about 1.34 mmol/g, about 1.33 mmol/g, about 1.32 mmol/g, or about 1.31 mmol/g of vinyl groups (i.e., - CH=CH2). Advantageously, in various embodiments, the vinyl groups allow for flexibility in the synthesis of a functionalized thermogel polymer. For example, the vinyl groups may serve as a reactive handle/functionality to enable the incorporation of chemical moieties that impart additional functional properties or mechanical enhancements to the thermogel polymer. In various embodiments, the weight percentage of vinyl groups incorporated into the thermogel polymer can be tailored by controlling the initial amount of general formula (3) (e.g., HDDO) used in the reaction. It will be appreciated that the general formula (3) comprises a derivative of a modified vinyl-containing diol monomer such as a modified HDDO. As modifying the vinyl-containing diol monomer allows tunable hydrophobic-hydrophilic balance, thermogel properties beyond the thermogel polymer stated in the examples disclosed herein may be achieved. For example, when general formula (3) comprises a derivative of HDDO, the HDDO may be tweaked to different polarities, such that the polymers subsequently obtained from these polymers may be capable of having higher vinyl content while retaining thermogel properties.

In various embodiments, general formula (3) may be a derivative of 1 ,5- hexadiene-3,4-diol (HDDO), a derivative of 3-(allyloxy)propane-1 ,2-diol, a derivative of 2,3-dihydroxypropylmethacrylate, or the like. In various embodiments, general formula (3) may be a compound that is proprietary/self- synthesized or one that is commercially available. In various embodiments, the thermogel polymer is a multi-block polymer.

In various embodiments, the multi-block polymer has at least one unit of the following structural sequence A-B-C, where A is a polymer block comprising at least one repeating unit represented by general formula (1 ), B is a polymer block comprising at least one repeating unit represented by general formula (2), and C is a polymer block comprising at least one repeating unit represented by general formula (3) or its functionalized derivative thereof.

In various embodiments, the positions of A, B, and C in the structural sequence A-B-C may be interchanged among themselves.

In various embodiments, the multi-block polymer may comprise a plurality of repeating units represented by general formula (1 ), a plurality of repeating units represented by general formula (2), and/or a plurality of repeating units represented by general formula (3) or its functionalized derivative thereof. In various embodiments, the multi-block copolymer comprises more than 3 polymeric blocks and the blocks may be randomly distributed/arranged within the polymer.

In various embodiments, the one or more repeating unit(s) derived from a hydrophilic polymer is/are part of a hydrophilic polymer block and the one or more repeating units derived from a thermoresponsive/thermosensitive polymer is/are part of a thermoresponsive/thermosensitive polymer block.

In various embodiments, the polymer block comprising at least one repeating unit of general formula (1 ), the polymer block comprising at least one repeating unit of general formula (2), and the polymer block comprising at least one repeating unit of general formula (3) or its functionalized derivative thereof are chemically coupled together by at least one of urethane, carbamate, carbonate, ester, urea, amide linkages, thiolated analogues thereof, or combinations thereof. For example, each of the polymer blocks are linked to their respective adjacent block by at least one of urethane, carbamate, carbonate, ester, urea, amide linkages, thiolated analogues thereof, or combinations thereof.

In various embodiments, the at least one of urethane, carbamate, carbonate, ester, urea, amide linkages, thiolated analogues thereof, or combinations thereof is represented by general formula (5):

In various embodiments, R¹¹ is selected from optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted cycloalkyl, or optionally substituted aromatic aryl. For example, R¹¹ may be selected from methyl, ethyl, n-propyl, 2-propyl, isopropyl, n-butyl, isobutyl, secbutyl, t-butyl, hexyl, amyl, 1 ,2-dimethylpropyl, 1 ,1 -dimethylpropyl, pentyl, isopentyl, hexyl, 4-methylpentyl, 1 -methylpentyl, 2-methylpentyl, 3-methylpentyl,

1 .1 .2-trimethylbutyl, 1 , 1 ,3-trimethylbutyl, 5-methylheptyl, 1 -methylheptyl, octyl, nonyl, decyl, the like, or combinations thereof. In various embodiments, when R¹¹ comprises optionally substituted cycloalkyl, general formula (5) may be derived from diisophorone diisocyanate. In various embodiments, when R¹¹ comprises optionally substituted aromatic aryl, general formula (5) may be derived from 4,4’- diphenylmethane diisocyanate. In various embodiments, when R¹¹ comprises optionally substituted alkyl (e g., hexyl), general formula (5) may be derived from hexamethylene diisocyanate (HMDI). In various embodiments, R¹⁴ and R¹⁵ are each independently selected from H, optionally substituted alkyl, optionally substituted alkenyl, and optionally substituted alkynyl, optionally substituted cycloalkyl, or optionally substituted aromatic aryl. For example, R¹⁴ and R¹⁶ may be selected from methyl, ethyl, n- propyl, 2-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, f-butyl, hexyl, amyl, 1 ,2- dimethylpropyl, 1 ,1 -dimethylpropyl, pentyl, isopentyl, hexyl, 4-methylpentyl, 1 - methylpentyl, 2-methylpentyl, 3-methylpentyl, 2,2-dimethylbutyl, 3,3- dimethylbutyl, 1 ,2-dimethylbutyl, 1 ,3-dimethylbutyl, 1 ,2,2-trimethylpropyl, 1 ,1 ,2- trimethylpropyl, 2-ethylpentyl, 3-ethylpentyl, heptyl, 1 -methylhexyl, 2,2- dimethylpentyl, 3,3-dimethylpentyl, 4,4-dimethylpentyl, 1 ,2-dimethylpentyl, 1 ,3- dimethylpentyl, 1 ,4-dimethylpentyl, 1 ,2,3-trimethylbutyl, 1 , 1 ,2-trimethylbutyl, 1 ,1 , 3-trimethylbutyl, 5-methylheptyl, 1 -methylheptyl, octyl, nonyl, decyl, the like, or combinations thereof. In various embodiments, R¹⁴ and R¹⁵ are both H.

In various embodiments, general formula (5) comprises urethanes or carbamates.

In various embodiments, the thermogel polymer comprises one or more repeating units represented by general formula (1 ); one or more repeating units represented by general formula (2); and one or more repeating units represented by general formula (4), wherein the repeating units are chemically coupled together by at least one of urethane/carbamate, carbonate, ester linkages or combinations thereof is/are represented by general formula (5): wherein _Ria _Rib _R2a _R2b _R3a _R3b _R5 _{to R}15 _R2o _R2i _{m n X} ¹ S, and X²-S are as defined above.

In various embodiments, the one or more repeating units represented by general formula (1 ) comprises a derivative of hydrophilic polymer such as PEG, the one or more repeating units represented by general formula (2) comprises a derivative of thermal-responsive hydrophobic polymer such as PPG, the one or more repeating units represented by general formula (3) or its functionalized derivative thereof comprises a derivative of HDDO, and general formula (5) comprises a derivative of hexamethylene diisocyanate (HMDI).

In various embodiments, polyurethane copolymers of poly(ethylene glycol) (PEG) and polypropylene glycol) (PPG) are particularly favoured as drug delivery systems or scaffolds for tissue regeneration due to their injectability, minimal invasiveness, low CGC, and biocompatibility. In various embodiments, these gels are able to determine the physical and local chemical environment of encapsulated drugs and cells - be it through specific interactions with drugs for sustained drug release, or through functional group- and modulus-dependent cell differentiation.

In various embodiments, the one or more repeating units represented by general formula (1 ) is present in an amount of falling in the range of between more than 0 mass% to about 90 mass%, from about 5 mass% to about 85 mass% from about 10 mass% to about 80 mass%, from about 15 mass% to about 75 mass%, from about 20 mass% to about 70 mass%, from about 25 mass% to about 65 mass%, from about 30 mass% to about 60 mass%, from about 35 mass% to about 55 mass%, from about 40 mass% to about 50 mass%, of about 41 mass%, of about 42 mass%, of about 43 mass%, of about 44 mass%, of about 45 mass%, of about 46 mass%, of about 47 mass%, of about 48 mass%, of about 49 mass%, of about 50 mass%, of about 51 mass%, of about 52 mass%, of about 53 mass%, of about 54 mass%, of about 55 mass%, of about 56 mass%, of about 57 mass%, of about 58 mass%, of about 59 mass%, of about 60 mass%, of about 61 mass%, of about 62 mass%, of about 63 mass%, of about 64 mass%, or of about 65 mass% of the thermogel polymer.

In various embodiments, the one or more repeating units represented by general formula (2) is present in an amount of between more than 0 mass% to about 90 mass%, from about 5 mass% to about 85 mass%, from about 10 mass% to about 80 mass%, from about 15 mass% to about 75 mass%, from about 20 mass% to about 70 mass%, from about 25 mass% to about 65 mass%, from about 30 mass% to about 60 mass%, from about 35 mass% to about 55 mass%, from about 40 mass% to about 50 mass%, from about 10 mass% to about 25 mass%, from about 11 mass% to about 24 mass%, from 12 mass% to about 23 mass%, from about 13 mass% to about 22 mass%, from about 14 mass% to about 21 mass%, from about 15 mass% to about 20 mass%, from about 16 mass% to about 19 mass%, from about 17 mass% to about 18 mass%, or about 17.5 mass% of the thermogel polymer.

In various embodiments, the one or more repeating units represented by general formula (3) or its functionalized derivative thereof is present in an amount of falling in the range of from about 0.1 mass% to about 40 mass%, from about 0.15 mass% to about 35 mass%, from about 0.2 mass% to about 30 mass%, from about 0.2 mass% to about 25 mass%, from about 0.2 mass% to about 20 mass%, from about 0.2 mass% to about 15 mass%, from about 0.2 mass% to about 10 mass%, from about 0.2 mass% to about 9.5 mass%, from about 0.2 mass% to about 9.0 mass%, from about 0.2 mass% to about 8.5 mass%, from about 0.2 mass% to about 8.0 %, from about 0.5 mass% to about 7.5 %, from about 1.0 mass% to about 7.0 %, from about 1.5 mass% to about 6.5 %, from about 2.0 mass% to about 6.0 %, from about 2.5 mass% to about 5.5 %, from about 3.0 mass% to about 5.0 %, from about 3.5 mass% to about 4.5 %, of about 4.0 mass%, of about 0.3 mass%, of about 0.31 mass%, of about 0.32 mass%, of about 0.33 mass%, of about 0.34 mass%, of about 0.35 mass%, of about 0.36 mass%, of about 0.37 mass%, of about 0.38 mass%, of about 0.39 mass%, of about 0.4 mass%, of about 8.0 mass%, of about 7.9 mass%, of about 7.8 mass%, of about 7.7 mass%, of about 7.6 mass%, of about 7.5 mass% of the thermogel polymer. It will be appreciated that the mass% of general formula (3) present in the thermogel polymer may vary with the molecular weight of the vinyl-containing diol monomer and the crosslinker used.

In various embodiments, the linkages represented by general formula (5) is present in an amount of from about 10 mass% to about 60 mass%, from about 12 mass% to about 55 mass%, from about 15 mass% to about 50 mass%, from about 15 mass% to about 45 mass%, from about 15 mass% to about 40 mass%, from about 16 mass% to about 39 mass%, from about 17 mass% to about 38 mass%, from about 18 mass% to about 37 mass%, from about 19 mass% to about 36 mass%, from about 20 mass% to about 35 mass%, from about 21 mass% to about 34 mass%, from about 22 mass% to about 33 mass%, from about 23 mass% to about 32 mass%, from about 24 mass% to about 31 mass%, from about 25 mass% to about 30 mass%, from about 26 mass% to about 29 mass%, from about 27 mass% to about 28 mass%, or about 27.5 mass% of the thermogel polymer. It will be appreciated that the mass% of general formula (5) present in the thermogel polymer may vary with the molecular weight of the monomers and the crosslinkers used.

In various embodiments, the thermogel polymer may further comprise other polymers and/or monomers that impart other desired properties to the thermogel polymer. For example, the thermogel polymer may comprise poly(caprolactone). Advantageously, in various embodiments, the poly(caprolactone) may provide biodegradability to the thermogel polymer.

In various embodiments, the thermogel polymer has one or more, two or more, three or more, four or more, five or more, six or more, seven or more, or all of the following properties: a polydensity index (PDI) falling in a range of from 1.0 to 2.0; a pH value falling in a range of from 1 to 10; a critical gelation temperature falling in a range of from 4°C to 60°C; a crossover modulus falling in a range of from 5 Pa to 1000 Pa; a storage modulus (G’) falling in a range of from 1 Pa to 5000 Pa; a complex viscosity falling in a range of from 1 Pa s to 1000 Pa.s; a mesh size falling in a range of from 5 nm to 30 nm; and a water content of more than 60% to more than 99% by weight.

In various embodiments, the thermogel polymer has a polydensity index (PDI) falling in a range of from about 1.0 to about 2, of from about 1.1 to about

1 .9, of from about 1 .2 to about 1 .8, from about 1 .3 to about 1 .7, from about 1 .4 to about 1.6, from about 1.45 to about 1.50, from about 1.31 to about 1.49, from about 1 .32 to about 1 .48, from about 1.33 to about 1 .47, from about 1 .34 to about 1.46, from about 1.35 to about 1.45, from about 1.36 to about 1.44, from about 1 .37 to about 1 .43, from about 1 .38 to about 1 .42, from about 1 .39 to about 1 .40, or about 1 .395. In various embodiments, the upper limit of the PDI is accordance with the Carother’s equation for polyaddition. Thus, due to nature of the type of polymerization that takes place, various embodiments of the presently disclosed polymer can result in a dispersity that is frequently large (e.g., up to a PDI of 2).

In various embodiments, the thermogel polymer has a pH value falling in a range of from about 1 to about 10, from about 1.5 to about 9.5, from about 2.0 to about 8.0, from about m2.5 to about 7.5, from about 3.0 to about 7.0, from about 3.5 to about 6.5, from about 4.0 to about 6.0, from about 4.5 to about 5.5, or about 5.0. in various embodiments, the thermogel polymer may have a pH value that is substantially similar to physiological pH value ranging from about 7 to about 8, from about 7.1 to about 7.9, from about 7.2 to about 7.8, from about 7.3 to about 7.7, from about 7.4 to about 7.6, or about 7.5. In various embodiments, advantageously, the thermogel polymer may be capable of demonstrating pH-responsive drug release. In various embodiments, the thermogel polymer may have a pH value that is substantially similar to physiological pH value ranging from about 7 to about 8, from about 7.1 to about

7.9, from about 7.2 to about 7.8, from about 7.3 to about 7.7, from about 7.4 to about 7.6, or about 7.5. In various embodiments, advantageously, the thermogel polymer may be capable of demonstrating pH -responsive drug release. For example, the thermogel polymer functionalized with anionic carboxylate, anionic sulfonates, cationic amines, zwitterionic amino acid (e.g., cysteine) may exhibit pH-dependent sustained drug release and antifouling properties.

In various embodiments, the thermogel polymer has a critical gelation temperature/thermo-reversible sol-gel transition temperature/converts from a liquid/flowable state to a non-flowable/gel-like state at a temperature falling in a range of from about 4 °C to about 60 °C, from about 5 °C to about 50 °C, from about 6 °C to about 45 °C, from about 7 °C to about 40 °C, from about 7.5 °C to about 39 °C, from about 8 °C to about 38 °C, from about 8.5 °C to about 37 °C, from about 9 °C to about 36 °C, from about 9.5 °C to about 35 °C, from about 10 °C to about 34 °C, from about 15 °C to about 33 °C, from about 20 °C to about 32 °C, from about 21 °C to about 31 °C, from about 22 °C to about 30 °C, from about 23 °C to about 29 °C, from about 24 °C to about 28 °C, from about 25 °C to about 27 °C, or of about 26 °C, or at a temperature that is substantially similar to living human body temperature ranging from about 36 °C to about 37 °C, or at about 37 °C. For example, the thermogel polymer may be in a liquid/flowable state at ambient room temperature (e.g., from about 20 °C to about 30 °C) and/or is in a non-flowable/gel-like state at living human body temperature (e.g., from about

36 °C to about 40 °C). Therefore, in some embodiments, the thermogel polymer is in a flowable state at a temperature falling in the range of 20 °C to 30 °C and is in a non-flowable gel-like state at a temperature falling in the range of 30 °C to

37 °C. Advantageously, in various embodiments, the thermogel polymer is deliverable/injectable/sprayable or capable of encapsulating temperaturesensitive therapeutics, drugs, proteins, or cells as a liquid at 25 °C and gel at about 37 °C (with a viscosity range of from about 10 Pa.s to about 200 Pa.s). Even more advantageously, the thermogel polymer may self-assemble into a supramolecular gel when the temperature is raised (i.e., upon contact with the human). In various embodiments, the thermogel polymer remains inert after the functionalization. In various embodiments, the functionalization of the thermogel polymer does not substantially affect its original gelation property. For example, the highly charged cationic and anionic polymers retain the capability to form gels at 37 °C. For example, while the hydrophobic aromatic phenyl group increases the storage modulus of the thermogels at 37 °C, they remain soluble at low temperatures. In various embodiments, when the functionalized thermogel polymer has a critical gelation temperature/thermo-reversible sol-gel transition temperature/converts from a liquid/flowable state to a non-flowable/gel-like state at a temperature falling beyond the range of a temperature that is substantially similar to living human body temperature, the functionalized thermogel polymer may be used in non-biological applications.

In various embodiments, the thermogel polymer has a crossover modulus falling in a range of from about 5 Pa to about 1000 Pa, from about 5 Pa to about 900 Pa, form about 5 Pa to about 800 Pa, from about 5 Pa to about 700 Pa, from about 5 Pa to about 600 Pa, from about 5 Pa to about 500 Pa, from about 5 Pa to about 400 Pa, from about 5 Pa to about 300 Pa, from about 5 Pa to about 200 Pa, from about 5 Pa to about 150 Pa, of from about 6 Pa to about 140 Pa, from about 7 Pa to about 130 Pa, from about 8 Pa to about 120 Pa, from about 9 Pa to about 115 Pa, from about 10 Pa to about 110 Pa, from about 20 Pa to about 100 Pa, from about 30 Pa to about 90 Pa, from about 40 Pa to about 80 Pa, from about 50 Pa to about 70 Pa, of about 11 Pa, of about 11.1 Pa, of about 11 .2 Pa, of about 11 .3 Pa, of about 11 .4 Pa, of about 11 .5 Pa, of about 11 .6 Pa, of about 11 .7 Pa, of about 11 .8 Pa, of about 11 .9 Pa, of about 12 Pa, of about 102 Pa, of about 101 .9 Pa, of about 101.8 Pa, of about 101.7 Pa, of about 101.6 Pa, of about 101.5 Pa, of about 101.4 Pa, of about 101.3 Pa, of about 101.2 Pa, of about 101.1 Pa, or of about 101 Pa. It will be appreciated that the crossover modulus of the thermogel polymer is dependent on its functional groups, catalyst, and polymer concentration. In various embodiments, the thermogel polymer has a storage modulus (G’) falling in a range of from about 1 Pa to about 5000 Pa, from about 1 Pa to about 4000 Pa, from about 1 Pa to about 3000 Pa, from about 1 Pa to about 2000 Pa, from about 1 Pa to about 1000 Pa, from about 2 Pa to about 900 Pa, from about 3 Pa to about 800 Pa, of from about 4 Pa to about 700 Pa, from about 50 Pa to about 650 Pa, from about 100 Pa to about 600 Pa, from about 150 Pa to about 550 Pa, from about 200 Pa to about 500 Pa, from about 250 Pa to about 450 Pa, from about 300 Pa to about 400 Pa, of about 4.1 Pa, of about 4.2 Pa, of about 4.3 Pa, of about 4.4 Pa, of about 4.5 Pa, of about 4.6 Pa, of about 4.7 Pa, of about 4.8 Pa, of about 690 Pa, of about 689 Pa, or of about 688 Pa, or of about 350 Pa at 37 °C. It will be appreciated that the storage modulus of the thermogel polymer is dependent on its functional groups, catalyst, and polymer concentration. In various embodiments, thermogel polymer functionalized with one or more hydrophobic aromatic phenyl groups may have an increased storage modulus at 37 °C while remaining soluble at low temperatures.

In various embodiments, the thermogel polymer has a complex viscosity falling in a range of from about 1 Pa.s to about 1000 Pa.s, from about 1 Pa.s to about 900 Pa.s, from about 1 Pa.s to about 800 Pa.s, from about 1 Pa.s to about 700 Pa.s, from about 1 Pa.s to about 600 Pa.s, from about 1 Pa.s to about 500 Pa.s, from about 1 Pa.s to about 400 Pa.s, from about 1 Pa.s to about 300 Pa.s, from about 1 Pa.s to about 200 Pa.s, from about 5 Pa.s to about 200 Pa.s, from about 10 Pa.s to about 200 Pa.s, from about 20 Pa.s to about 190 Pa.s, from about 20 Pa.s to 1 about 80 Pa.s, from about 30 Pa.s to about 170 Pa.s, from about 40 Pa.s to about 160 Pa.s, from about 50 Pa.s to about 150 Pa.s, from about 60 Pa.s to about 140 Pa.s, from about 70 Pa.s to about 130 Pa.s, from about 80 Pa.s to about 120 Pa.s, from about 90 Pa.s to about 110 Pa.s, of about 100 Pa.s, of about 1.5 Pa.s, of about 1.6 Pa.s, of about 1.7 Pa.s, of about 1.8 Pa.s, of about 119 Pa.s, of about 118 Pa.s, of about 117 Pa.s, of about 116 Pa.s, of about 115 Pa.s, or of about 114 Pa.s at 37 °C. It will be appreciated that the complex viscosity of the thermogel polymer is dependent on its functional groups, catalyst, and polymer concentration. In various embodiments, the thermogel polymer has a high water content of more than about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, about 90%, about 95%, about 96%, about 97%, about 98%, or about 99% by weight. Accordingly, the thermogel polymer may be a water-based polymer.

In various embodiments, the thermogel polymer has a mesh size of from about 5 nm to about 30 nm, from about 6 nm to about 30 nm, from about 7 nm to about 30 nm, from about 8 nm to about 30 nm, from about 9 nm to about 30 nm, from about 10 nm to about 30 nm, from about 11 nm to about 29 nm, from about 12 nm to about 28 nm, from about 13 nm to about 27 nm, from about 14 nm to about 26 nm, from about 15 nm to about 25 nm, from about 16 nm to about 24 nm, from about 17 nm to about 23 nm, from about 18 nm to about 22 nm, from about 19 nm to about 21 nm, or about 20 nm.

In various embodiments, the drug or drug analog is selected from a group consisting of a cationic drug or cationic drug analog, an anionic drug or anionic drug analog, a neutral drug or neutral drug analog (i.e., a drug or drug analog with no charges or no net electrical charges), a zwitterionic drug or drug analog, a high molecular weight drug or drug analog of no less than about 10 kDa, a low molecular weight drug or drug analog of no more than about 1 kDa, an intermediate molecular weight drug or drug analog ranging from about 1 kDa to about 10 kDa, or combinations thereof.

In various embodiments, the drug or drug analog is a cationic drug or cationic drug analog, an anionic drug or anionic drug analog or a neutral drug or neutral drug analog for e g., under physiological conditions.

In various embodiments, the drug or drug analog is a low molecular weight drug or drug analog of no more than about 1 kDa. In various embodiments, the low molecular weight drug or drug analog is selected from peptidomimetic, inorganic, chemotherapeutics, gastro-intestinal drugs, antiepileptic drugs, the like, or combinations thereof.

In various embodiments, the drug or drug analog is an intermediate molecular weight drug or drug analog of from about 1 kDa to about 10 kDa, from about 2 kDa to about 9 kDa, from about 3 kDa to about 8 kDa, from about 4 kDa to about 7 kDa, from about 5 kDa to about 6 kDa, or about 5.5 kDa.

In various embodiments, the drug or drug analog is a high molecular weight drug or drug analog of no less than about 10 kDa. In various embodiments, the high molecular weight drug or drug analog is selected from proteins, DNA, RNA, vaccines, insulin, ocular therapy drugs, the like, or combination thereof.

In various embodiments, the drug is a small molecule cationic hydrophobic drug with TT-TT interactions and poor water solubility, a small molecule monovalent anionic drug, and/or a macromolecular drug.

In various embodiments, the drug or drug analog is selected from the group consisting of crystal violet, orange II, dextran (30-100 kDa), imipramine, amitriptyline, thioridazine, chlorpromazine, trazodone, imiglucerase, certolizumab pegol, etanercept, nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, naproxen, diclofenac, aspirin, indomethacin, piroxicam, derivatives thereof, or the like.

In various embodiments, the drug analog is selected from the group consisting of a small molecule cationic hydrophobic drug analog, a small molecule monovalent anionic drug analog, and a macromolecular drug analog. In various embodiments, the molecular weight of the macromolecular drug is more than about 50 kDa.

In various embodiments, the thermogel-drug composition is capable of providing sustained drug release or a delayed biphasic release of at least about 1 day, at least about 2 days, at least about 3 days, at least about 4 days, at least about 5 days, at least about 6 days, at least about 7 days, at least about 8 days, at least about 9 days, at least about 10 days, at least about 15 days, at least about 20 days, at least about 30 days, at least about 40 days, at least about 50 days, at least about 60 days, at least about 70 days, at least about 80 days, at least about 90 days, at least about 100 days, at least about 110 days, at least about 120 days, at least about 130 days, at least about 140 days, at least about 150 days, at least about 160 days, at least about 170 days, or at least about 180 days, at least about 190 days, at least about 200 days, at least about 210 days, at least about 220 days, at least about 230 days, at least about 240 days, at least about 250 days, at least about 260 days, at least about 270 days, at least about 280 days, at least about 290 days, at least about 300 days, at least about 310 days, at least about 320 days, at least about 330 days, at least about 340 days, at least about 350 days, at least about 360 days, at least about 365 days, at least about 1 week to at least about 52 weeks, or at least about 1 month to at least about 12 months. It will be appreciated that as drug release can depend on multiple factors (such as gel concentration) and the release timeframe can be tailored based on this. Advantageously, the various embodiment as disclosed herein provide the chemical versatility that allows one to modulate these factors (to tailor the chemical interactions between the gel and drug). In various embodiments, the composition may be used for sustained and stimuli-responsive delivery of both low and high molecular weight drugs.

In various embodiments, the drug or drug analog is a low molecular weight cationic hydrophobic molecular drug or drug analog that is < 1 kDa (e.g., crystal violet as analog, imipramine, amitriptyline, thioridazine, chlorpromazine, and trazodone) and optionally the thermogel polymer is functionalized with none or one or more functional groups selected from a group consisting of -NH₃ ⁺, -COO- , -COO':NH3⁺, -(OH)₂, and -Ph. In various embodiments, the thermogel-drug composition has a sustained release that is more than 6 months when the functional group is -(OH)2, -Ph, or absent. In various embodiments, the drug or drug analog is low molecular weight anionic hydrophobic molecular drug or drug analog that is < 1 kDa (e.g., e.g., orange II as analog, nonsteroidal anti-inflammatory drug (NSAID) such as ibuprofen, naproxen, diclofenac, aspirin, indomethacin, and piroxicam) and optionally the thermogel polymer is functionalized with none or one or more functional groups selected from a group consisting of -NH₃ ⁺, -COO :NH3⁺, - (OH)₂, and -Ph. In various embodiments, the thermogel-drug composition has a sustained release that is more than 5 months when the functional group is -NH3⁺.

In various embodiments, the drug or drug analog is high molecular weight neutral hydrophobic molecular drug or drug analog that is > 10 kDa (e.g., e.g., orange II as analog, nonsteroidal anti-inflammatory drug (NSAID) such as ibuprofen, naproxen, diclofenac, aspirin, indomethacin, and piroxicam) and optionally the thermogel polymer is functionalized with none or one or more functional groups selected from a group consisting of -NH3⁺, -(OH)2, and -Ph.

In various embodiments, the thermogel-drug composition has a sustained release that is more than 2 months when the functional group is -NH₃ ⁺, -(OH)2, -Ph, or absent.

In various embodiments, the thermogel-drug composition comprises: a thermogel polymer comprising one or more repeating unit(s) represented by general formula (1 ), one or more repeating unit(s) represented by general formula (2), and one or more repeating unit(s) represented by general formula (3) or its functionalized derivative thereof, wherein the functionalized derivative of general formula (3) is optionally functionalized with one or more functional groups selected from a group consisting of -NH₃ ⁺, -COO-, -COO':NH₃ ⁺, -(OH)2, and - Ph; and a drug or drug analog comprising a low molecular weight cationic hydrophobic molecular drug or drug analog that is < 1 kDa.

In various embodiments, the thermogel-drug composition comprises: a thermogel polymer comprising one or more repeating unit(s) represented by general formula (1 ), one or more repeating unit(s) represented by general formula (2), and one or more repeating unit(s) represented by general formula (3) or its functionalized derivative thereof, wherein the functionalized derivative of general formula (3) is optionally functionalized with one or more functional groups selected from a group consisting of -NH₃ ⁺, -COO':NH₃ ⁺, -(OH)2, and -Ph; and a drug or drug analog comprising a low molecular weight anionic hydrophobic molecular drug or drug analog that is < 1 kDa.

In various embodiments, the thermogel-drug composition comprises: a thermogel polymer comprising one or more repeating unit(s) represented by general formula (1 ), one or more repeating unit(s) represented by general formula (2), and represented by general formula (3) or its functionalized derivative thereof, wherein the functionalized derivative of general formula (3) is optionally functionalized with one or more functional groups selected from a group consisting of -NH₃ ⁺, -(OH)2, and -Ph; and a drug or drug analog comprising a high molecular weight neutral hydrophobic molecular drug or drug analog that is > 10 kDa.

In various embodiments, the thermogel comprises a plurality of micellar crosslinks. In various embodiments, the thermogel comprises one or more micelles that are crosslinked. In various embodiments, the thermogel comprises hydrophobic micellar core and hydrophilic micellar shell. Advantageously, core of micellar crosslinks allows encapsulation and subsequent release of the drug.

In various embodiments, the method of synthesis and purification of the thermogel polymer (i.e., EPV) disclosed herein may follow the general steps disclosed in PCT application no. PCT/SG2024/050074, the contents of which are fully incorporated herein.

In various embodiments, there is provided a method of preparing a thermogel-drug composition in accordance with various embodiments as disclosed herein, the method comprising encapsulating one or more drugs or drug analog with a thermogel polymer in accordance with various embodiments disclosed herein.

In various embodiments, the method may comprise coupling one or more hydrophilic polymers, one or more thermoresponsive/thermosensitive polymers, and one or more vinyl-containing diol monomers in the presence of a coupling agent to obtain a thermogel polymer.

In various embodiments, the one or more hydrophilic polymers are represented by general formula (6), the one or more thermoresponsive/thermosensitive polymers are represented by general formula (7), and the one or more vinyl-containing diol monomers are represented by general formula (8) or its functionalized derivative thereof:

(6) (7) (8) wherein

_R1 a _R1b _R2a _R2b _R3a _R3b _R4a _R4b _R5 fo _R10 _R12 _R13 _{m and n are as} defined above.

In various embodiments, R¹⁴ to R¹⁹ are each independently selected from H, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted alkylene oxide (e.g., optionally substituted ethylene oxide), or optionally substituted poly(alkylene oxide) (e.g., optionally substituted polyethylene oxide). For example, R¹⁴ to R¹⁹ may be selected from methyl, ethyl, n-propyl, 2-propyl, isopropyl, n-butyl, isobutyl, sec- butyl, t-butyl, hexyl, amyl, 1 ,2-dimethylpropyl, 1 ,1 -dimethylpropyl, pentyl, isopentyl, hexyl, 4-methylpentyl, 1 -methylpentyl, 2-methylpentyl, 3-methylpentyl,

1.1.2-trimethylbutyl, 1 , 1 ,3-trimethylbutyl, 5-methylheptyl, 1 -methylheptyl, octyl, nonyl, decyl, the like, or combinations thereof.

In various embodiments, the coupling step is carried out in the presence of a coupling agent such that the one or more hydrophilic polymers represented by general formula (6), the one or more thermoresponsive polymers represented by general formula (7), and the one or more vinyl-containing diol monomers represented by general formula (8) or its functionalized derivative thereof are chemically coupled together by at least one of urethane, carbamate, carbonate, ester linkages, or combinations thereof to form the thermogel polymer.

In various embodiments, the coupling agent comprises a urethane/carbamate forming agent, carbonate forming agent, ester forming agent, or combinations thereof. In various embodiments, the coupling agent comprises an isocyanate monomer that contains at least two (e.g. two or more) isocyanate functional groups. The coupling agent may be a diisocyanate selected from the group consisting of hexamethylene diisocyanate (HMDI), tetramethylene diisocyanate, cyclohexane diisocyanate, tetramethylxylene diisocyanate, dodecylene diisocyanate, tolylene 2,4-diisocyanate, tolylene 2,6-diisocyanate, or the like and combinations thereof. In various embodiments, the coupling agent may be a compound comprising a diisocyanate that is proprietary/self- synthesized or one that is commercially available. In various embodiments, the coupling agent may be devoid of an isocyanate such as precursors for nonisocyanate polyurethanes. In various embodiments, the coupling agent is added in a ratio of about 1 - 2 : about 1 -2, about 1 :1 , about 1 :1.01 , about 1 :1.02, about 1 :1.03, about 1 :1.04, about 1 :1.05, about 1 :1.06, about 1 :1.07, about 1 :1.08, about 1 :1.09, about 1 :1.10, about 1 :1.2, about 1 :1.3, about 1 :1.4, about 1 :1.5, about 1 :1.6, about 1 :1.7, about 1 :1.8, about 1 :1.9, about 1 :2, about 1.10:1 , about 1.2:1 , about 1.3:1 , about 1.4:1 , about 1.5:1 , about 1.6:1 , about 1.7:1 , about 1.8:1 , about 1.9:1 , about 2:1 relative to one or more polymers or monomers represented by general formulae (6), (7), and/or (8) or its functionalized derivative thereof.

In various embodiments, the at least one of urethane, carbamate, carbonate, ester linkages, or combinations thereof is represented by general formula (5): wherein

R¹¹, R¹⁴, and R¹⁶ are as defined above.

In various embodiments, the one or more hydrophilic polymers represented by general formula (6) is different from the one or more thermoresponsive/thermosensitive polymers represented by general formula (7) in the thermogel polymer. For example, the one or more hydrophilic polymers represented by general formula (6) comprises PEG while the one or more thermoresponsive/thermosensitive polymers represented by general formula (7) comprises PPG. In various embodiments, the at least one of urethane, carbamate, carbonate, ester linkages, or combinations thereof represented by general formula (5) comprises urethanes/carbamates. Thus, in various embodiments, the one or more hydrophilic polymers represented by general formula (6) comprises polyethylene glycol) (PEG), the one or more thermoresponsive/thermosensitive polymers represented by general formula (7) comprises polypropylene glycol) (PPG), and the one or more vinyl-containing diol monomers represented by general formula (8) comprises 1 ,5-hexadiene-3,4- diol (HDDO).

In various embodiments, the one or more hydrophilic polymers represented by general formula (6), the one or more thermoresponsive/thermosensitive polymers represented by general formula (7), and the one or more vinyl-containing diol monomers represented by general formula (8) are mixed in a mass ratio of about 1 -20 : 1 -10 : 0.01 -3. For example, the mass ratio of the one or more hydrophilic polymers represented by general formula (6), the one or more thermoresponsive/thermosensitive polymers represented by general formula (7), and the one or more vinyl-containing diol monomers represented by general formula (8) may be about 3:1 :0.01 , about

3:1 :0.10, about 3:1 :0.20, about 3:1 :0.30, about 3:1 :0.40, about 3:1 :0.50, about

3:1 :0.51 , about 3:1 :0.52, about 3:1 :0.53, about 3:1 :0.54, about 3:1 :0.55, about

3:1 :0.56, about 3:1 :0.57, about 3:1 :0.58, about 3:1 :1 , about 3:1 :2, about 3:1 :3, about 3:1 :4, or about 3:1 :5. In various embodiments, the mass ratio of the one or more hydrophilic polymers represented by general formula (6) to the one or more thermoresponsive/thermosensitive polymers represented by general formula (7) is about 3:1 , about 3:2, about 3:3, about 3:4, about 3:5, about 15:1 , about 15:2, about 15:3, or about 15:4. It will be appreciated that functionalizing the vinylcontaining diol monomer (e.g., HDDO) with different mass ratios of hydrophobic and hydrophilic groups may affect the hydrophilic/hydrophobic balance and the thermogel ability of the functionalized thermogel polymer. For example, tailoring the ratio of PEG:PPG may allow a functionalized thermogel polymer with a high HDDO content to be obtained.

In various embodiments, the coupling and/or mixing step is performed at an elevated temperature of from about 60 °C to about 150°C, from about 70 °C to about 150°C, from about 80 °C to about 150°C, from about 90 °C to about 150°C, from about 100 °C to about 150 °C, from about 102 °C to about 148 °C, 104 °C to about 146 °C, from about 106 °C to about 144 °C, from about 108 °C to about 142 °C, from about 110 °C to about 140 °C, from about 112 °C to about 138 °C, from about 1 14 °C to about 136 °C, from about 1 16 °C to about 134 °C, from about 1 18 °C to about 132 °C, from about 120 °C to about 130 °C, from about 122 °C to about 128 °C, from about 124 °C to about 126 °C, or about 123 °C. It will be appreciated that the temperature may vary according to the reaction time and catalysts used.

In various embodiments, the coupling and/or mixing step is carried out for up to about 36 hours, up to about 35 hours, up to about 30 hours, up to about 24 hours, up to about 20 hours, up to about 15 hours, up to about 10 hours, at least about 2 hours, at least about 3 hours, at least about 4 hours, or at least about 5 hours.

In various embodiments, the coupling and/or mixing step is performed in the absence of air and/or water/moisture and/or in the presence of a drying agent such as molecular sieves. Accordingly, in various embodiments, the absence of air and/or water/moisture may reduce or prevent occurrence of undesired side reactions. For example, the absence of air and/or water/moisture may reduce or prevent occurrence of premature termination of polymerization and allow thermogel polymers of sufficient molecular weight to be obtained.

In various embodiments, the coupling and/or mixing step is carried out in the presence of a solvent. In various embodiments, the solvent may comprise an anhydrous solvent selected from the group consisting of toluene, benzene, xylene, the like, or combinations thereof.

In various embodiments, the coupling and/or mixing step is carried out in the presence of a metal-containing or non-metal containing catalyst that is capable of catalysing formation of urethane, carbamate, carbonate, ester linkages, or combinations thereof e.g. from alcohols and a suitable isocyanate precursor or derivatives thereof. In various embodiments, the metal-containing catalyst may comprise Lewis acid metals such as Bi³⁺, Fe³⁺, Zn²⁺, Sc³⁺, La³⁺, Ti⁴⁺, and Sn⁴⁺. In various embodiments, the metal-containing catalyst comprising Sn(IV) complexes is preferred. In various embodiments, the Lewis acid metals may be in any oxidation state. In various embodiments, the metal-containing catalyst may comprise a tin-based or zinc-based catalyst selected from the group consisting of alkyltin compounds, aryltin compounds, and dialkyltin diesters such as dibutyltin dilaurate (DBTL), dibutyltin diacetate, dibutyltin dioctanoate, dibutyltin distearate, zinc diethyldithiocarbamate, the like, or combinations thereof. In various embodiments, the non-metal containing catalyst may be an organocatalyst.

In various embodiments, the method comprises functionalizing the thermogel polymer. The vinyl groups in general formula (3) may be further functionalized e.g. by click chemistry or click reactions, such as thiol-ene click reaction. Thus, in various embodiments, the method may comprise functionalizing the thermogel polymer with one or more thiols to obtain a functionalized thermogel polymer with functional groups X¹— S and X²— S, where X¹— S and X²— S are as defined above.

In various embodiments, the thermogel polymer may be functionalized with multiple functional groups that are different or the same. For example, the vinyl groups of the thermogel polymer may be functionalized with two or more of the structures for X¹ and X² described above.

In various embodiments, the step of functionalizing the thermogel polymer is carried out in the presence of a radical initiator, a photoinitiator, and/or an irradiation source such as ultraviolet (UV) light or the like.

In various embodiments, the functionalizing step is carried out for at least about 30 minutes, at least about 1 hour, at least about 2 hours, at least about 3 hours, at least about 4 hours, at least about 5 hours, at least about 6 hours, at least about 7 hours, at least about 8 hours, at least about 9 hours, at least about 10 hours, at least about 11 hours, or at least about 12 hours, optionally in the presence of a radical initiator, a photoinitiator, and/or an irradiation source such as ultraviolet (UV) light or the like.

In various embodiments, the radical initiator and/or photoinitiator is added in a molar ratio of at least 1 -3 : 3-1 relative to the vinyl groups in the functionalized thermogel polymer. For example, the molar ratio of the radical initiator and/or photoinitiator to the vinyl groups in the thermogel polymer may be about 3: 1 , about 2: 1 , about 1 : 1 , about 1 :2, or about 1 :3.

In various embodiments, the radical initiator comprises a photoinitiator, 2-hydroxy-4’-(2-hydroxyethoxy)-2 -methylpropiophenone.

In various embodiments, the step of functionalizing the thermogel polymer with one or more thiols is carried out in the presence of an anhydrous solvent. In various embodiments, the anhydrous solvent may be selected from the group of anhydrous tetrahydrofuran (THF), anhydrous methanol, or the like and combinations thereof. It will be appreciated that the choice of the anhydrous solvent depends on the solubility of the one or more thiols used. For example, thiols such as sodium 2-mercaptoethanesulfonate, 2-aminoethanethiol hydrochloride, cysteine hydrochloride, and histamine-1 -thiol (His-SH) may be dissolved in anhydrous methanol while thiols such as thioglycolic acid, thioglycerol, and 2-phenylethanethiol may be dissolved in anhydrous THF.

In various embodiments, the one or more thiols is added in a molar ratio of 20-1 : 1 -20 relative to the vinyl groups in the thermogel polymer. For example, the molar ratio of the one or more thiols added to the vinyl groups in the thermogel polymer may be about 20: 1 , about 15: 1 , about 10:1 , about 5:1 , about 4:1 , about 3:1 , about 2:1 , about 1 :1 , about 1 :2, about 1 :3, about 1 :4, about 1 :5, about 1 : 10, about 1 :15, or about 1 :20. Advantageously, in some embodiments, it was found that when the one or more thiols is added in 20 times excess, the functionalization step may reach completion, achieving a functionalization efficiency of 100%. In various embodiments where the ratio of the thiols to the vinyl groups is low, a partial completion of thiol-ene click reaction may be leveraged to produce a thermogel polymer comprising both vinyl groups and ionized form of Xi and X2 (e g., cations).

In various embodiments, the step of functionalizing the thermogel polymer with one or more thiols has a functionalization efficiency/ degree of conversion falling in a range of from about 5 % to about 100 %, from about 10 % to about 95 %, from about 15 % to about 90 %, from about 20 % to about 85 %, from about 25 % to about 80 %, from about 30 % to about 75 %, from about 35 % to about 70 %, from about 40 % to about 65 %, from about 45 % to about 60 %, from about 50 % to about 55 %, of at least about 20 %, of at least about 21 %, of at least about 22 %, of at least about 23 %, of at least about 24 %, of at least about 25 %, of at least about 26 %, of at least about 27 %, or of at least about 28 %. It will be appreciated that, in various embodiments, quantitative functionalization may be improved through greater excess use of thiols.

In various embodiments, the wt% of the total thermogel polymer that has been functionalized after the functionalizing step (e.g., click efficiency) falls in the range of from about 1 wt% to about 100 wt%, of at least about 5 wt%, of at least about 10 wt%, of at least about 15 wt%, of at least about 20 wt%, of at least about 25 wt%, of at least about 30 wt%, of at least about 35 wt%, of at least about 40 wt%, of about at least 45 wt%, of at least about 50 wt%, of at least about 55 wt%, of at least about 60 wt%, at least about 65 wt%, at least about 70 wt%, at least about 75 wt%, at least about 80 wt%, at least about 85 wt%, at least about 90 wt%, or at least about 95 wt%.

In various embodiments, the method further comprises the step of quenching the coupling reaction using a quenching agent (e g., alcohols and its derivatives).

In various embodiments, the quenching agent comprises ethanol. In various embodiments, the quenching step may be carried out for at least about 10 minutes, at least about 20 minutes, at least about 30 minutes, at least about 40 minutes, at least about 50 minutes, or at least about 1 hour.

In various embodiments, the quenching step may be performed at an elevated temperature of no less than about 80°C, of no less than about 85°C, of no less than about 90°C, of no less than about 95°C, of from about 100 °C to about 150 °C, from about 102 °C to about 148 °C, 104 °C to about 146 °C, from about 106 °C to about 144 °C, from about 108 °C to about 142 °C, from about 1 10 °C to about 140 °C, from about 112 °C to about 138 °C, from about 114 °C to about 136 °C, from about 116 °C to about 134 °C, from about 118 °C to about 132 °C, from about 120 °C to about 130 °C, from about 122 °C to about 128 °C, from about 124 °C to about 126 °C, or about 125 °C.

In various embodiments, the method further comprises removing/purifying the synthesized thermogel polymer and/or synthesized functionalized thermogel polymer of/from contaminants via precipitation, filtering using a metal sieve, and/or drying overnight in the absence of air and/or water/moisture and/or in the presence of an inert gas such as nitrogen to remove unreacted reactants, solvents, and catalyst. In various embodiments, dialysis may be carried out at least about 3 times, at least about 4 times, or at least about 5 times with intervals of at least about 4 hours, at least about 5 hours, or at least about 6 hours before each change of dialysis buffer.

In various embodiments, there is provided a method of tailoring a thermogel-drug composition in accordance with various embodiments disclosed herein to achieve a predetermined drug release profile, the method comprising, profiling the hydrophobicity/hydrophilicity, the electrochemical charge and/or the molecular weight of the drug (e g., Orange II, Crystal Violet, dextran); coupling one or more hydrophilic polymers, one or more thermoresponsive/thermosensitive polymers, and one or more vinyl-containing diol monomers in the presence of a coupling agent at predetermined amounts based on the profiling carried out above to obtain a thermogel polymer in accordance with various embodiments disclosed herein; and optionally functionalizing the one or more vinyl-containing diol monomers with one or more specific functional groups (e.g., carboxylic acids (-COOH), amino acids (e.g., cysteine, histidine), sulfonates (-SO3H), alkylsulfonates (e.g., sodium ethanesulfonate), aminehydrochlorides (-NH3CI), alcohols (-OH), diols, benzenes, alkybenzenes) that is/are capable of interacting with the drug based on the profiling carried out above to obtain the predetermined drug release profile.

In various embodiments, the one or more functional groups are selected from a group consisting of a carboxylic acid, carboxylate (e.g., -COO-, or -COO- :NH3⁺, etc ), a sulfonic acid, an amine, an amino acid, a sulfonate (e.g., -SO3), an alkylsulfonate, an aminehydrochloride, protonated amine (e.g., -NH₃ ⁺, or - COO':NH3⁺, etc ), an alcohol, a diol (e.g., -(OH)2), a benzene (e.g., -Ph, a phenyl group having a structure of -CeHs), an alkylbenzene, imidazole, or salts thereof.

In various embodiments, the coupling of PEG, PPG, and HDDO is carried out in the presence of hexamethylene diisocyanate (HMDI) and dibutyltin dilaurate (DBTL). In various embodiments, the coupling comprises incorporating one or more drug molecules in the thermogel formulation.

In various embodiments, the optional functionalizing step may be based on establishing intermolecular complementary charges between the drug and polymer (e.g., attractive forces between the -NH³⁺ functional group in the polymer and orange II), which may contribute to the sustained release of the drug. In various embodiments, the optional functionalizing step may be based on establishing drug partitioning into micelles to achieve biphasic release instead of monophasic release (e.g., crystal violet drug partitioning into micelles) which may contribute to the sustained release of the drug. In various embodiments, the optional functionalizing step may be based on adjusting the ratio of the mesh size of the thermogel polymer to the hydrodynamic size of the drug to regulate steric hindrance which can influence the release rate and (e.g., release kinetics of dextran is mesh-size dependent) may contribute to the sustained release of the drug. In various embodiments, the resulting sustained release and the influence of thermogels’ functional groups and drugs on release profile (mono-, bi- or delayed biphasic) and release mechanisms is non-obvious from prior arts, cannot be predicted a priori, and adds another functional dimensionality to the thermoresponsive gel. For example, the charged anionic drug analog (e.g., orange II) demonstrates strong dependence on complementary ionic interactions leading to biphasic sustained release for more than 6 months. For example, the cationic drug analog (e.g., crystal violet) demonstrates no dependence on ionic interactions due to the diffused nature of the charge groups. For example, the less water-soluble crystal violet shows a delayed biphasic release with a strong dependence on the hydrophobicity of the functionalized groups. Therefore, it will be appreciated that without the benefit of the present disclosure, the specific combination of functional groups and drug-types for sustained release, as well as the possible mechanisms elucidated, cannot be easily extrapolated from existing PEG-based thermogels due to wide-ranging properties, hydrophobicity, and influence of the appended functional groups. It will also be appreciated that due to the supramolecular nature of thermogels, the influence of functional groups and drugs on the physical properties and the consequent release profiles of drugs cannot be easily extrapolated from presently known functionalized chemically crosslinked hydrogels as well without the benefit of the present disclosure.

In various embodiments, the method further comprises identifying release mechanisms of the drug from the thermogel polymer through fitting curves of drug release profiles using established models (e.g., Korsmeyer- Peppas (Power Law), First Order, Zero Order, and Higuchi models). Advantageously, the parameters derived from fitting, such as rate constant (k) and release exponent (n) may be useful for understanding drug release mechanisms.

In various embodiments, the one or more hydrophilic polymers comprise one or more poly(ethylene glycol) (PEG), the one or more thermoresponsive/thermosensitive polymers comprises one or more polypropylene glycol) (PPG), one or more vinyl-containing diol monomers comprise one or more 1 ,5-hexadiene-3,4-diol (HDDO), and the coupling agent comprises one or more hexamethylene diisocyanate (HMDI).

In various embodiments, the thermogel-drug composition is an injectable, syringeable, and/or topically spreadable composition.

In various embodiments, the thermogel-drug composition is syringeable and enables injectable, in situ gelation with sustained drug release for extended durations, wherein the release rate and profile are tunable based on polymer composition and formulation parameters.

In various embodiments, there is provided a method of treating a patient, the method comprising identifying a medical condition of the patient; identifying a drug that the patient requires for treating the medical condition; identifying a dosage release profile of the drug that patient requires for treating the medical condition; tailoring a thermogel-drug formulation in accordance with various embodiments as disclosed herein based on the dosage release profile of the drug; and administering the thermogel-drug formulation to the patient. In various embodiments, there is provided a carrier or delivery system/vehicle comprising the thermogel-drug composition in accordance with various embodiments as disclosed herein.

In various embodiments, there is provided a pharmaceutical composition comprising the composition/compound/thermogel-drug composition in accordance with various embodiments as disclosed herein.

In various embodiments, there is provided a method of delivering a therapeutic and/or prophylactic agent and/or biological agent to a cell or organ (e.g., a mammalian cell or organ), the method comprising the step of administering to a subject (e g., a mammal, such as a human) a thermogel-drug composition in accordance with various embodiments as disclosed herein.

In various embodiments, there is provided a method of treatment or prophylaxis of a disease, disorder, or condition in a subject, the method comprising the step of administering to a subject a therapeutically effective amount of a thermogel-drug composition in accordance with various embodiments as disclosed herein. In various embodiments,, the term "subject" refers to a biological entity that may benefit from the administration of the thermogel-drug composition. The subject can be a human or a non-human animal, including mammals such as primates, rodents, canines, felines, livestock (e.g., cattle, sheep, pigs, and horses), or other vertebrates.

In various embodiments, there is provided a thermogel-drug composition in accordance with various embodiments as disclosed herein for use in medicine. In various embodiments, the use of the composition may be applicable to vaccines, chemotherapy, immunotherapy, drug treatment of ocular diseases from localised depot, sustained drug and gene delivery, wound-healing, biomedical adhesives as well as antibacterial and anticorrosion coatings, 3D cell culture, and regenerative medicine. In various embodiments, the use of the composition may also be applicable to thermal stabilization of therapeutics (e.g., as an excipient during storage).

In various embodiments, there is provided a thermogel-drug composition in accordance with various embodiments as disclosed herein for use in delivering a therapeutic and/or prophylactic agent and/or biological agent to a cell or tissue or organ, wherein said thermogel-drug composition is to be administered to the subject.

In various embodiments, there is provided a thermogel-drug composition in accordance with various embodiments as disclosed herein for use in the treatment or prophylaxis of a disease, disorder or condition in a subject, wherein said thermogel-drug composition is to be administered to the subject.

In various embodiments, there is provided use of a thermogel-drug composition in accordance with various embodiments as disclosed herein in the manufacture of a medicament for the treatment or prophylaxis of a disease, disorder, or condition in a subject.

In various embodiments, there is provided use of a thermogel-drig composition in accordance with various embodiments as disclosed herein in biomedical applications such as drug delivery, tissue engineering, and ocular applications. Advanateously, tailorability of the composition enables prolonged and pH-triggered drug delivery, antibacterial, improved bioactivity, and applications where mechanical resilience is desired (e.g., cartilage repair).

In various embodiments, there is provided use of a thermogel-drig composition in accordance with various embodiments as disclosed herein in multifunctional applications such as structural batteries and conformable electrodes for plant sensors. In various embodiments, there is provided a thermogel-drug composition in accordance with various embodiments as disclosed herein, and related methods in accordance with various embodiments as disclosed herein.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 shows the ¹H NMR spectrum (in CDsOD) of representative thermogelling polyurethanes, including EP2V, EP2V-COO EP2V-NH3⁺, EP2V- (OH)₂, EP2V-COO :NH3⁺, EP2V-Ph, EP2V-SO3", synthesized in accordance with various embodiments disclosed herein. The presence of peaks corresponding to -OCONH- and -CH2OCONH- indicate the successful formation of urethane bonds. The spectrum shows the successful syntheses of the thermogelling polymer and its functionalized derivatives.

FIG. 2 shows the percentage polar surface area (PPSA) of each functional group that are introduced in the thermogels synthesized in accordance with various embodiments disclosed herein, including -COOiNH₃*, -SO3; -COO - (OH)₂, -NHS⁺, vinyl, and -Ph, where PPSA is determined by the fraction of their solvent-accessible surface area that is polar.

FIG. 3A shows the in vitro release profile (until day 30) of orange II dye from EP2V, EP2V-COO' and EP2V-NH₃ ⁺ hydrogels (7 wt%) at 37 °C, the hydrogels as synthesized in accordance with various embodiments disclosed herein. The phase transition in the biphasic release of orange II from EP2V-NH₃ ⁺ is also indicated in the diagram. FIGS. 3B and 3C show the in vitro release profiles (until day 200 and day 14 respectively) of orange II dye from EP2V-COO EP2V-COO-:NH₃ ⁺, EP2V, EP2V-(OH)₂, EP1V-Ph, and EP2V-NH₃ ⁺ hydrogels (7 wt%) at 37 °C, the hydrogels as synthesized in accordance with various embodiments disclosed herein. The onset of second regime in the biphasic release of orange II from EP2V-NH₃ ⁺ is also indicated in FIG. 3B. In FIGS. 3A to 3C, averages of triplicates are plotted as solid markers, with standard deviations of measurements represented by shaded regions. FIG. 4A shows the stacked ¹H NMR spectra (in D2O) of orange II dye (0.375 mg/mL) with and without EP2V-NH₃ ⁺ synthesized in accordance with various embodiments disclosed herein. The perturbance and broadening of peaks in the spectrum of orange II with EP2V-NH₃ ⁺ compared to the one without suggests a strong interaction between the drug and the thermogel. FIG. 4B shows the ¹H-¹H Two-Dimensional Nuclear Overhauser Effect Spectroscopy (2D NOESY) spectrum of orange II dye with EP2V-NH3⁺ synthesized in accordance with various embodiments disclosed herein. The presence of well-resolved crosspeaks on the spectrum indicates through-space correlations and interactions between the drug and the thermogel. FIG. 40 is a schematic diagram of a micelle formed by self-assembly of amphiphilic copolymer blocks (i.e., PEG blocks and PPG blocks) in a thermogel synthesized in accordance with various embodiments disclosed herein. The hydrophilic PEG micellar corona with high dielectric constant (s ~ 80) and hydrophobic PPG micellar core with low dielectric constant (s ~ 5) are illustrated.

FIGS. 5A and 5B respectively show the stacked ¹H NMR spectra (in D2O) of orange II dye (0.375 mg/mL) with and without EP2V or EP2V-COO synthesized in accordance with various embodiments disclosed herein. The lack of significant changes in the peak positions or broadening in the spectra of orange II when mixed with the respective thermogels, compared to its spectrum alone, suggests a weak interaction between the drug and these thermogels.

FIG. 6 shows the ¹H-¹H 2D NOESY spectrum of orange II dye with EP2V synthesized in accordance with various embodiments disclosed herein. The absence of cross-peaks on the spectrum indicates minimal interactions between the drug and the thermogel.

FIG. 7 shows the ¹H-¹H 2D NOESY spectrum of orange II dye with EP2V- COO' synthesized in accordance with various embodiments disclosed herein. The absence of cross-peaks on the spectrum indicates minimal interactions between the drug and the thermogel.

FIGS. 8A and 8B show the in vitro release profiles (until day 175 and day 70 respectively) of crystal violet from EP2V-COO-, EP2V-COO :NH3⁺, EP2V, EP2V-(OH)₂, EP1V-Ph, and EP2V-NH₃ ⁺ hydrogels (7 wt%) at 37 °C, the hydrogels as synthesized in accordance with various embodiments disclosed herein. The onsets of the lag phase or intermediate regime as well as of the secondary regime in the biphasic release of orange II from the aforementioned thermogels are also indicated in FIG. 8A. In FIGS. 8A and 8B, averages of triplicates are plotted as solid markers, with standard deviations of measurements represented by shaded regions.

FIG. 9A is a schematic diagram illustrating the partitioning of hydrophobic crystal violet dye into the hydrophobic micellar core and hydrophilic micellar shell in a thermogel synthesized in accordance with various embodiments disclosed herein. FIG. 9B shows the ¹H NMR spectra (in D2O) of crystal violet (0.375 mg/mL) as well as crystal violet with EP2V-COO; EP2V-COO':NH3⁺, EP2V, EP2 -(OH)2, and EP1V-Ph hydrogels synthesized in accordance with various embodiments disclosed herein. The downfield shift and broadening of peaks in the spectra of crystal violet and the aforementioned thermogels compared to the one without suggest a strong interaction between the drug and the thermogels. The assigned Ar’ and Ar” peaks correspond to overlapping signals from the aromatic rings of EP1V-Ph in the spectrum of crystal violet with EP1V-Ph.

FIG. 10 shows the stacked ¹H NMR spectra (in D2O) of crystal violet (CV) at different concentrations at 0.125 mg/mL and 0.063 mg/mL (without any polymers), referenced to the solvent residual signal. The downfield shift of the peaks upon a two-time dilution suggests a likely disruption of hydrophobic TT-TT stacking interactions, indicating that crystal violet undergoes selfassociation in water, which weakens as the concentration decreases. FIG. 11 shows the ¹H-¹H 2D NOESY spectrum (in D2O) of crystal violet (CV) with EP2V synthesized in accordance with various embodiments disclosed herein. The lack of cross-peaks between crystal violet and the hydrophilic PEG segments strongly suggests preferential partitioning of crystal violet into the hydrophobic PPG micelle segments.

FIG. 12A shows the in vitro release profile (until day 6) of dextran from EP2V-COO-, EP2V-COO :NH₃ ⁺, EP2V, and EP1V-Ph hydrogels (7 wt%) in PBS at 37 °C, the hydrogels as synthesized in accordance with various embodiments disclosed herein. FIG. 12B shows the in vitro release profile (until day 60) of dextran from EP2V-COO-, EP2V, and EP2V-(OH)₂ hydrogels (7 wt%) in PBS at 37 °C, the hydrogels as synthesized in accordance with various embodiments disclosed herein. The onset of the secondary regime or phase transition in the biphasic release of crystal violet from EP2V-(OH)₂ is also indicated. FIGS. 12C and 12D show the in vitro release profiles (until day 70 and day 5 respectively) of dextran from EP2V-COO-, EP2V-COO :NH₃ ⁺, EP2V, EP2V-(OH)₂, EP1V-Ph, and EP2V-NH₃ ⁺ hydrogels (7 wt%) in PBS at 37 °C, the hydrogels as synthesized in accordance with various embodiments disclosed herein. In FIGS. 12A to 12D, averages of triplicates are plotted as solid markers, with standard deviations of measurements represented by shaded regions.

FIG. 13A shows a plot of the estimated mesh size ( ) (nm) at 37 °C for various polyurethane copolymers synthesized in accordance with various embodiments disclosed herein, including EP2V-COO; EP2V-COO :NH₃ ⁺, EP2V, EP2V-(OH)₂, EP1 V-Ph, and EP2V-NH₃ ⁺, as a function of the rate constant (k) of the copolymers. Generally, the rate constant increases with increasing mesh size. FIG. 13B is a schematic diagram illustrating the mesh size in a micellar crosslinked thermogel comprising dextran synthesized in accordance with various embodiments disclosed herein.

FIG. 14A shows an overview of various drug release mechanisms and profiles that can be achieved by adopting a molecular engineering and formulation approach that leverages interactions between the thermogel scaffold, functional groups, and drugs. Specifically, different functional groups can influence the ionicity, hydrophilicity, and hydrophobicity of the copolymer, leading to various mechanisms as demonstrated in the in vitro studies, including (1 ) hydrophobic compartmentalization, (2) specific interactions, and (3) mesh-size- dependent release, resulting in different release profiles such as monophasic or biphasic. FIG. 14B is an Ashby plot showing a range of release kinetics observed in monophasic release (burst release) and the initial phase of biphasic releases (sustained release) of various drugs (orange II, crystal violet, and dextran) in different thermogels (EP2V-COO-, EP2V-COO-:NH₃ ⁺, EP2V, EP2V-(OH)₂, EP1V- Ph, and EP2V-NH₃ ⁺) in accordance with various embodiments disclosed herein. The plot illustrates the relationship between the rate constant (k) and the power law exponent or release exponent (n) values in the equation Q = kt^r, where Q represents the cumulative drug released and t is the release duration. Empirically, n describes the shape of the release profile while k reveals the rate of increase. The plot guidelines how various k and n values will influence tioo% based on the extrapolated Korsmeyer-Peppas release profile. The Korsmeyer-Peppas model (Q = ktⁿ) describes drug release from dynamically swelling polymers through the coupling of relaxation and diffusion.

EXAMPLES

Example embodiments of the disclosure will be better understood and readily apparent to one of ordinary skill in the art from the following discussions and if applicable, in conjunction with the figures. It should be appreciated that other modifications related to structural, chemical and biological changes may be made without deviating from the scope of the invention. Example embodiments are not necessarily mutually exclusive as some may be combined with one or more embodiments to form new exemplary embodiments. The example embodiments should not be construed as limiting the scope of the disclosure. In examples below, an adaptable formulation strategy that harnesses the physicochemical properties of these drugs rather than being hindered by them is described. Thermogels with differing chemical properties were used to accommodate the wide range of drugs, enabling future tailored applications in precision medicine, gene therapies, and targeted therapies.

The examples demonstrate the formulation of injectable drug delivery systems comprising polyurethane thermogels functionalized with cationic (- NH₃ ⁺), anionic (-COO ), zwitterionic (-NH3⁺:COO ), hydrogen-bonding (- (OH)₂), and hydrophobic (-Ph) groups. These formulations were tested for compatibility across three analogs from three representative classes of drugs. The individual release kinetics were then quantified. The representative analogs were (1 ) crystal violet, a hydrophobic low molecular weight drug analog with diffused cationic charge, (2) orange II, a hydrophilic low molecular weight drug analog with anionic charge, and (3) dextran, a hydrophilic high molecular weight (~70 kDa) drug analog capable of forming hydrogen bonds. The examples below also demonstrate the approach's adaptability in creating sustained injectable drug delivery systems for drugs with diverse physicochemical properties.

The examples below have shown that formulations with releases ranging from days to months may be achieved. Formulation dependent release of ~6 months of low molecular weight analogs, and ~2 months for high molecular weight dextran have been demonstrated. Depending on the compatibility between thermogel functional groups and the physicochemical properties of drugs, the release profile varied between mono or multiphasic, with diverse release kinetics and release mechanisms. Additionally, by leveraging the synergy between bottom-up molecular engineering, mechanical characterization, in-vitro drug release, and two dimensional (2D) nuclear magnetic resonance (NMR), the impact of the three-way interactions involving the scaffold, functional groups, and drugs was elucidated. Embodiments of the method of the present disclosure enable the development of drug-specific injectable depots, and this strategy may be readily applicable to existing widely used therapeutics, particularly in therapies for targeted chemotherapy and gene delivery.

Example 1 : Formulation and characterization of thermogelling drug depots

1.1. Synthesis of polyurethane thermogel and its functionalized derivatives

As illustrated in Schemes 1 and 2, a series of injectable depots composed of polyurethane thermogels with both pH-dependent anions (COO ) and pH-independent anions (SOs-), pH-dependent cations (NH₃ ⁺), and zwitterions (COO :NH3⁺) were formulated. Additionally, injectable depots featuring enhanced hydrogen-bonding ((OH)2), aromatic TT-TT interactions (Ph), and hydrophobic vinyl groups (V) derived from 1 ,5-hexadiene-3,4-diol (HDDO) were also formulated. The backbone of these thermogelling polyurethanes are composed of poly(ethylene glycol) (PEG), denoted as “E” in the thermogel naming, and temperature-responsive poly(proplene glycol) (PPG), denoted as “P”, copolymerized in the presence of hexamethylene diisocyanate (HMDI). The number prefix of V, e.g., in EP1V, EP2V, etc., is indicative of the functional group densities. The functional group densities of these thermogelling polyurethanes listed in Table 1 were quantified by ¹H NMR, as shown in FIG. 1 . All formulations tested for drug release demonstrated sol-gel reversibility and thermogelling abilities in the range 4 °C to 30 °C.

Scheme 1 . Different thermogelling polyurethane copolymers with a PEG/PPG ratio of 3:1 used in the drug release study, where x represents the number of ethylene glycol repeating units and y denotes the number of propylene glycol repeating units in the polymer.

Scheme 2. EPV polymers with thiolated functional groups, including charged or neutral functional groups (-COO-, -NH₃ ⁺, -(OH)₂, -COO“:NH₃ ⁺, -Ph, and -SO₃“) are functionalized through thiol-ene click reactions via the 5- hexadiene-3,4-diol (HDDO) moiety in the polymer. The reaction is carried out under UV irradiation (A = 365 nm) in the presence of a photoinitiator. The general steps for functionalizing a thermogelling polymer in accordance with various embodiments disclosed herein include: functionalizing the thermogelling polymer with one or more thiols in the presence of a photoinitiator and/or ultraviolet (UV) light as shown in Scheme 3 below to obtain a functionalized thermogelling polymer with functional moieties X¹ — S and X² — S, where X¹ and X² are each independently a moiety comprising a carboxylic acid, an amino acid, a sulfonate, an alkylsulfonate, an aminehydrochloride, an alcohol, a diol, a benzene, an alkylbenzene or derivatives thereof and X¹ and X² correspond to R in Scheme 3.

Scheme 3. Chemical structure and functionalization procedure of an exemplary

EPV thermogelling polymer with various functional groups via thiol-ene click synthesis.

The general steps for preparing a thermogelling polymer in accordance with various embodiments disclosed herein include: coupling one or more polymers represented by general formula (6) (in the example below, PEG was used); one or more polymers represented by general formula (7) (in the example below, PPG was used); and one or more monomers represented by general formula (8) (in the example below, HDDO was used) in the presence of a coupling agent (in the example below, HMDI was used), a suitable catalyst (in the example below, DBTL was used), and a suitable solvent (in the example below, anhydrous toluene was used), as shown in Scheme 4 to obtain a thermogelling polymer.

Specifically, in this example, 37.5 g PEG and 12.5 g PPG were added to a round bottom flask and dried azeotropical ly with toluene on a rotary evaporator followed by drying under high vacuum at 110°C for 1 hour. The polymer mixture was then redissolved in 250ml anhydrous toluene under argon atmosphere. Subsequently, 0.6 g of HDDO was added to the polymer mixture for EP1V, and 1.5 g of HDDO was added for EP2V. The polymerization was then initiated with the addition of hexamethylene diisocyanate (HMDI) in a 1 diol : 1.01 HMDI ratio and allowed to proceed at 110 °C for 2.5 hours. EP1V and EP2V are subsequently functionalized in the presence of the respective thiol-containing functional groups and photoinitiator, 2-Hydroxy-4-(2-hydroxyethoxy)-2- methylpropiophenone and irradiated with UV at 365 nm for 3 hours.

Scheme 4. Chemical structure and polymerisation procedure of an exemplary EPV thermogelling polymer.

Table 1. Composition details of the functionalised polyurethanes obtained via Thiol-ene click reaction and their respective degree of conversion. Degree of conversion (%) was obtained from the disappearance of the resonance peak that corresponds to HDDO at 3 = 5.75 ppm by ¹H NMR.

1.2. Molecular characterisation synthesized polyurethane thermogel and its functionalized derivatives

1.2.1. Nuclear magnetic resonance (NMR) spectroscopy

To confirm the successful synthesis of the EPV copolymer and their functionalized products, ¹H and ¹³C nuclear magnetic resonance (NMR) spectra were obtained using a JEOL 500 MHz NMR spectrometer (Tokyo, Japan) at room temperature. Samples were either dissolved in deuterated methanol (CD3OD) or acetone (CD3COCD3). Chemical shifts were referenced to the solvent peak of CDsOD at 5 = 4.78 ppm for the ¹H NMR spectra and 6 = 49.3 ppm for the ¹³C spectra. Meanwhile, chemical shifts were referenced to the solvent peak of CD3COCD3 at 5 = 2.04 ppm for the ¹H NMR spectra and 5 = 29.8 ppm for the ¹³C spectra.

1.2.2. Gel Permeation Chromatography

The number average and weight average molecular weights (M_n and M_w) of the polyurethanes were determined via Gel Permeation Chromatography (GPC) using Agilent 1260 Infinity II. The GPC machine was equipped with a refractive index detector (RID) and calibrated with monodispersed polystyrene standards. To prepare the samples, 5 mg of the EPV copolymer was dissolved in 1 .67 mL of THF (HPLC grade) and filtered into a GPC glass test vial using a 0.2 pm polytetrafluoroethylene (PTFE) filter tip. For each GPC measurement, the prepared samples were injected at 5 mg mL'¹ and 20 pL.

1.2.3. Calculation of solvent accessible surface area

The percentage polar solvent accessible surface area of the major microspecies at pH 7.4 was calculated using the Molecular Surface Area plugin on MarvinSketch with a solvent radius of 1.4 A. The representative functional groups used in this calculation are listed in Table 2 below, while the percentage polar surface area (PPSA) of each functional group, determined by the fraction of the solvent accessible surface area that is polar, is shown in FIG. 2.

Table 2. Representative functional groups used in the calculation of solvent accessible surface area for each thermogelling polymer, including EPV, EPV- COO; EPV-SO3; EPV-NH₃ ⁺, EPV-COO-:NH₃ ⁺, EPV-(OH)₂, and EPV-Ph in accordance with embodiments disclosed herein. Example 2: Drug analogs and overview of tailoring of functionalized thermogels for sustained and controlled drug release

In this example, a brief overview of the results of the release of three drug analogs from their respective thermogel-drug compositions is provided.

The diverse range of drugs requires an equally adaptable approach to take advantage of gel-drug intermolecular interactions for sustained release. This disclosure details injectable depots composed of varying functional groups to allow for precise and sustained release. The approach has demonstrated its broad applicability across various drug classes. Therefore, this strategy is expected to be readily translatable to prevalent therapeutics for use in areas like targeted pain management, chemotherapy, and gene delivery.

As detailed in Table 3, crystal violet, orange II, and dextran are each representative of small molecular monovalent anionic drugs with charge delocalised over a small area, small molecular cationic monovalent hydrophobic drugs with n- n stacking, and macromolecular therapeutic agents respectively. The chemical features of these drug analogs are representative of drugs with similar physicochemical properties, examples are cited in Table 3.

Specifically, the release of anionic orange II drug analog from cationic thermogels with amine groups (EP2V-NH₃ ⁺) can lead to sustained release for more than 6 months. On the other hand, the release of less water-soluble, cationic drug analog, crystal violet from thermogels containing hydrophobic phenyl groups (EP1V-Ph) showed a delayed biphasic release of up to 5.8 months. The release of crystal violet from other thermogels also followed a monophasic profile, with the duration varying over a range of days. Lastly, release kinetics of macromolecular dextran involved a monophasic or biphasic profile with the release duration varied from ~1 day to ~2 months. The release kinetics of dextran correlated with gel strength and mesh size, with the higher gel strength and smaller mesh sizes providing more sustained release. In particular, the higher gel strength, smaller mesh size, and hydrogen bonding of EP2V-(OH)2 can lead to a biphasic sustained release of up to 2 months. By tailoring functional groups, the release profile, kinetics, and mechanisms for these drug analogs can thus be determined.

Table 3. Overview of drug analogs stemming from model drugs, Crystal Violet, Orange II, and Dextran.

Example 3: Fabrication of drug-loaded thermogels

The procedures below describe the methodology in preparing thermogels with various drug compositions to achieve sustained release or tailored release kinetics.

3.1. Materials

Table 4. Materials as well as their respective amounts and final concentrations for the preparation of drug-loaded thermogels with a total volume of 2 mL.

The polymer or gel weight percent indicated above can be tuned from 2-30 wt%. An appropriate amount can be selected within gel weight percent.

3.2. Preparation of Orange Il-loaded thermogel

The steps below outline the preparation of orange Il-loaded thermogel based on the materials and amounts listed in Table 4 above.

1 . Orange II stock solution was prepared by dissolving 10 mg of Orange II in 20 ml. of 1x PBS solution.

2. 0.14 g of polymer was added to 1.2 mL of the orange II stock solution and dissolved overnight at 4 °C. The polymer or gel weight percent indicated above can be tuned from 2-30 wt%. An appropriate amount can be selected within gel weight percent.

3. Orange Il-loaded thermogels were maintained at 4° C while being adjusted to a final pH of 7.4 using sodium hydroxide and/or hydrochloric acid.

4. 1x PBS was added to the thermogels to make up a final volume of 2 mL.

3.3. Preparation of dextran -loaded thermogel

The steps below outline the preparation of dextran-loaded thermogel based on the materials and amounts listed in Table 4 above. The preparation was performed under dark conditions.

1 . Dextran stock solution was prepared by dissolving 20 mg of dextran in 1 mL of 1x PBS solution in an opaque vial.

2. 0.14 g of polymer was added to 1 mL of the dextran stock solution and dissolved overnight at 4 °C in an opaque vial. The polymer or gel weight percent indicated above can be tuned from 2-30 wt%. An appropriate amount can be selected within gel weight percent.

3. Dextran-loaded thermogels were maintained at 4 °C while being adjusted to a final pH of 7.4 using sodium hydroxide and/or hydrochloric acid. 4. 1x PBS was added to the thermogels to make up a final volume of 2 mL.

3.4. Preparation of crystal violet-loaded thermogel

The steps below outline the preparation of crystal violet-loaded thermogel based on the materials and amounts listed in Table 4 above.

1. Crystal violet stock solution was prepared by dissolving 10 mg of crystal violet in 80 mL of 1x PBS solution.

2. 0.14 g of polymer was added to 1 .8 mL of the crystal violet stock solution and dissolved overnight at 4 °C. The polymer or gel weight percent indicated above can be tuned from 2-30 wt%. An appropriate amount can be selected within gel weight percent.

3. Crystal violet-loaded thermogels were maintained at 4° C while being adjusted to a final pH of 7.4 using sodium hydroxide and/or hydrochloric acid.

4. 1x PBS was added to the thermogels to make up a final volume of 2 mL.

Example 4: Methods for studying drug release from synthesized drug- loaded thermogels

4.1. In vitro drug release study

Each of the drug incorporated thermogels were loaded in triplicates of 150 pl into the transwells and incubated in the oven at 37 °C for 30 minutes for hydrogel formation. The drug loaded thermogels were immersed in 1.5 ml of fresh 1x PBS buffer solution at 37 °C with shaking at 35 rpm. At regular time intervals, the release medium was collected and replaced with an equal volume of 37 °C prewarmed 1x PBS buffer solution. The collected supernatant was kept frozen at -20 °C for future quantification. Drugs released were analysed using microplate reader (Infinite M200, TECAN, Switzerland). The absorbance wavelength were 485 nm and 590 nm for orange II and crystal violet respectively. The excitation and emission wavelength of dextran were 490 nm and 520 nm respectively.

4.2. NMR characterization for drug-polymer interactions

To investigate drug-polymer interactions, ¹H NMR and Nuclear Overhauser Effect Spectroscopy (NOESY) spectra were obtained using a JEOL 500 MHz NMR spectrometer (Tokyo, Japan) at room temperature. Samples of copolymers were dissolved in deuterated water (D2O) along with drug analogs. pH of the samples was tuned to pH 7.4 and the final concentration of copolymer was maintained at 15 mg/mL. Orange II concentration (final) was maintained at 0.375 mg/mL, whereas crystal violet concentration (final) was maintained at 0.125 mg/mL.

4.3. Drug release kinetics

The experimentally obtained release profiles were fitted to four established drug release models: Zero Order, First Order, Higuchi and the Korsmeyer Peppas (Power Law) model. All results were normalized to 100 % upon completion of release. With the exception of the First Order model, all profiles were modelled to 60 % of the release. For the First Order model, the entire release profile was modelled.

Biphasic release profiles were observed in some cases. In these situations, the transition points between the two phases were manually estimated based on the generated R-squared values of the second phase. Similarly, with the exception of the First Order model, all profiles were modelled to 60 % of the release of each phase. For the First Order model, the entire release phases were modelled. The different kinetic model equations for drug release are shown below: 1. Zero Order

Q_t = Q₀ + k_ot

Where Qt is the amount of drug released over time t, Q₀ is the initial amount of drug released (often, Q₀ = 0) and ko is the zero order release constant, and is usually expressed in units of concentration/time.

2. First Order

Where Co is the concentration of drug loaded initially, k is the first order rate constant, and t is the time.

3. Higuchi

Where Qt is the amount of drug released over time t and k_H is the release rate constant for the Higuchi model.

4. Korsmeyer Peppas (Power Law)

Where is fraction of drug released at time t, k is the rate constant and n is the release exponent.

4.4. Interactions Between Two Point Charges

The energy potential, ω (r), between two point charges with radius, r, is given by:

Whereby Qi and Q2 are the respective valency of the ions, EO the permittivity of vacuum, s_r the dielectric constant of the material, and r is the sum of the ionic radii.

In the case of interactions between Orange II and EP2V-NH₃ ⁺, the effective ionic radii can be roughly approximated to be that of a sulphate and ammonium with ~2.42 A, and ~1 .67 A.

Therefore,

Whereby k is the Boltzmann constant, and T is temperature.

Hence the predicted ionic interactions between Orange II and EP2V-NH3⁺, in both PEG and PPG domains are <J)PEG ~ 13.18 kT and MPPG ~ 26.36 kT.

According to Bell Theory, which states that the binding lifetime, T, scales exponentially with the interaction energy.

As the value of increases from 13 kT to 26 kT, complexes within the hydrophobic domain of PPG exhibit a binding lifetime approximately ~10⁵ times longer than those in PEG.

Example 5. Results and discussion on drug release

The release kinetics of drug delivery systems play a pivotal role in maintaining drug concentrations within the therapeutic window and the eventual efficacy of therapies. Furthermore, the intricate interactions between drugs, polymer scaffolds, and functional groups add to the challenge of tailoring precise drug release profiles. This complexity is exacerbated by the rapidly expanding range of therapeutics which encompasses hydrophobic compounds, charged molecules, and high molecular weight biologies. Thermogels with drug-specific and profile-targeted designs that incorporate controlled variations in hydrophobicity, specific interactions, and adjustable mesh sizes would vastly improve the approach towards drug release.

5.1. In vitro release studies of orange II, crystal violet, and dextran from thermogel-drug compositions comprising EP2V, EP2V-NH3⁺, EP2V- COO , EP2V-COO :NH₃ ⁺, EP2V-(OH)_2J and EP1V-Ph

The resulting sol-state viscosity and structural integrity of the thermogels depend on the density and type of functional groups. As a balance between processability, gel stability, and functional group density, the study on the in vitro release of three drug analogs was restricted to be from 7 wt% thermogels in phosphate-buffered saline (PBS) containing anionic (-COO-), cationic (-NH₃ ⁺), zwitterionic (-COO :NH₃ ⁺), hydrogen-bonding (-(OH)2) and (-Ph) groups, namely EP1V-Ph, EP2V-NH₃ ⁺, EP2V-COO; EP2V-COQ-:NH₃ ⁺, EP2V-(OH)₂, and EP2V. As shown in Table 1 above, the functional groups densities were 0.391 mmol/g for EP2V-NH₃ ⁺, 0.406 mmol/g for EP2V-COO; 0.341 mmol/g for EP2V- COO :NH₃ ⁺, 0.396 mmol/g for EP2V-(OH)₂, and 0.080 mmol/g for EP1V-Ph. To study the diverse possible drug-gel interactions, crystal violet was used as a cationic drug analog, orange II as an anionic drug analog, and dextran as a macromolecular drug analog. The study was conducted following the procedures outlined in Example 4.1 .

Subsequent curve fittings of the drug release profiles were conducted using four popular models: the Korsmeyer-Peppas (Power Law), First Order, Zero Order, and Higuchi models. These model equations are listed under Examples 4.3 and 4.4. The best-fit results based on the models are reported in Tables 7, 10, and 13 below. Comparison of the R-squared values showed that the Korsmeyer-Peppas model had a demonstrably improved fit over the other models (Tables 7, 10, and 13), which was in line with how the model was originally developed for use with polymeric systems. Additionally, fitting performed with the Korsmeyer-Peppas model allowed for the determination of the rate constant, k, as well as the elucidation of release mechanisms through the examination and the release exponent, n, described in the equation

Founded on the superimposition of two independent mechanisms of drug release from a polymeric system, Fickian diffusion and polymer relaxation (Case II transport), the Korsmeyer-Peppas model describes drug release from dynamically swelling polymers through the coupling of relaxation and diffusion. While empirically, n describes the shape of the release profile, it also elucidates the release mechanism at the molecular level (Tables 7, 10, and 13). For release exponents between Fickian diffusion and Case II transport, 0.5 < n < 1 , the release is ascribed to non-Fickian kinetics (anomalous transport), which is driven by the coupling of diffusional and relaxational mechanisms. At n > 1 , Super Case II transport occurs, and polymer relaxation is thought to occur at a much faster rate than diffusion. The release exponent, n, thus warrants greater examination to provide fundamental insights into the release kinetics of these systems. In vitro release of orange II, crystal violet, and dextran, from thermogels containing different functional groups are reported in FIGS. 3B, 3C, 8A, 8B, 12C, and 12D, and Korsmeyer-Peppas fitting parameters are reported in Table 5 below.

Table 5. Korsmeyer-Peppas fits of in vitro drug release.

5.2. Sustained release of Orange II based on ionic interactions

In vitro release studies were performed using orange II as a model anionic drug to investigate the effect of charge interactions on the release profiles of the thermogels containing varying functional groups (FIGS. 3A, 3B, and 3C). Unlike crystal violet, orange II has a less diffused charge that contributes to stronger ionic interactions and a comparatively higher polarity and water solubility (FIG. 4A). Water-soluble drugs do not partition into hydrophobic micelles as readily, and this is reflected in the release of orange II. The release of orange II from EP2V reaches completion in < 15 days in contrast to the ~5 months seen in the release of crystal violet, a less water-soluble drug analog (Table 5).

However, in the presence of complementary cations, the release of orange II from EP2V-NH3* was shown to be more sustained and biphasic in nature compared to the monophasic release in EP2V and EP2V-COO' (FIG. 3A). Orange II was fully released from EP2V-COO within 3 days, whereas EP2V-NH₃ ⁺ had a significantly lower cumulative release of 17.5% over the same duration and time to complete release (tioo%) of 188 days. Rapid burst release could have been caused by the weaker gel structure and repulsive forces in EP2V-COO-, while attractive forces in EP2V-NH₃ ⁺ would have contributed to the sustained release of orange II. This is further corroborated by the examination of the release exponent for the two hydrogels. While EP2V-NH3⁺ exhibited diffusion-dominated transport with a release exponent of ~0.5 for both phases, EP2V-COO- exhibited a super case II transport of its loaded cargo, with an exponent of ~1 .2 (Tables 5 and 7). EP2V-COO' hence demonstrates release that is rate-controlled by polymer relaxation, whereby the rate of diffusion is much greater than the rate of polymer relaxation. This increased diffusivity, coupled with the low gel strength (low storage modulus of 270 Pa) and empirically observed rapid erosion of the hydrogel matrix contributed to the burst release of orange II from the EP2V-COO' hydrogels. Such findings are consistent with previously published studies that have reported the association of polymer-drug electrostatic interactions with changes in their diffusivities in charged hydrogels. In the presence of EP2V-NH₃ ⁺, considerable linewidth broadening of orange H’s ¹H NMR spectrum was observed (FIG. 4A), which was not observed with EP2V and EP2V-COO- (FIGS. 5A and 5B). In addition, distinct perturbations to the ¹H NMR resonance peaks of orange II resulted with EP2V-NH₃ ⁺, but not EP2V and EP2V-COO’ (see FIGS. 5A and 5B). This is because binding of small molecules to macromolecules solution can significantly alter their translation and rotational motion rates compared to their free states in solution, leading to considerable changes in the molecular relaxation time and result in spectral broadening. The distinct linewidth broadening of orange II observed with EP2V-NH3⁺, but not EP2V and EP2V- COO' supports that the unique electrostatic interactions between their opposite charges result in strong association with the polymer, resulting in the exceptional slow release observed in FIG. 9A. In the presence of EP2V and EP2V-COO increased deshielding of most of orange Il’s NMR resonances was observed. These changes match those seen upon dilution of orange II in water, possibly resulting from disruption of intermolecular TT-TT stacking interactions that brings about dye disaggregation. It is thus possible that these polymers, by virtue of their inherent amphiphilic nature, may interfere with the TT-TT stacking interactions that cause dye aggregation at [0.5 mg/mL], Comparatively, different perturbations to the observed for proton f instead. This strongly suggests that the electrostatic binding of orange II to EP2V-NH₃ ⁺ could lead to unique aggregated structures between individual dye molecules distinct from EP2V and EP2V-COO'. These indicated that stronger interactions were occurring between orange II and EP2V- NH₃ ⁺ than EP2V and EP2V-COO-, likely mediated by their complementary charges. Shifts to the NMR resonance of the aromatic protons and significant broadening suggest the presence of interactions between orange II and EP2V- NH₃ ⁺ (FIG. 4A). Two-dimension (2D) ¹H-¹H Nuclear Overhauser Effect Spectroscopy (NOESY) complements one-dimension ¹H NMR and drug release kinetics by establishing molecular proximities and validating intermolecular interactions between orange II and EP2V-NH₃ ⁺. The ¹H-¹H NOESY spectrum of orange II shows well-resolved correlations between both PEG and PPG domains of EP2V-NH₃ ⁺ that arise from through-space interactions that is within a close proximity of < 5 A. The through-space correlations observed support the observation that intermolecular ionic interactions occur throughout both domains within the polymer and agree with the randomly incorporated cations across both PEG and PPG domains (FIGS. 4B and 4C). In contrast, these correlations were not observed for EP2V and EP2V-COO- (FIGS. 6 and 7), further ascertaining the strong binding between orange II and EP2V-NH3⁺. This is reflected in the difference in the rate constants of 0.095 and 0.069 for the initial and second phases respectively.

It is posited that the initial phase corresponds with the release of adsorbed orange II within the hydrophilic matrix of PEG while the secondary phase originates from orange II partitioned into the hydrophobic PPG micelle core. Since the impediment of ionic species diffusion in polyelectrolyte hydrogels depends on the strength of ionic complexes, and ionic interaction scales inversely to the dielectric constant, s, of the medium (electrostatic forces ex 1 /E). the difference in dielectric constant between PEG (s - 10) and PPG (s ~ 5) can effectively lead to an estimated two-fold increase in bond strength. According to Bell Theory, binding lifetime scales exponentially with bond energy, PPG associated ionic complexes can be predicted to have a lifetime that is significantly longer, up to -105 times, than PEG-associated complexes (Example 4.4). The difference in diffusivity of orange II between both phases may be lessened as not all orange II ions are associated and permeated water and other competitive ions are present as well. Comparatively, specific complementary interactions provided between 5 to 60 times sustaining effect in the release of orange II when comparing tioo% of -3 days in EP2V-COO' and -34 days in EP2V to -6.7 months in EP2V-NH₃ ⁺ (Tables 5 and 6). This demonstrated the capability of injectable thermogelling drug depots to sustain the biphasic release of hydrophilic ionic drugs through specific interactions and hydrophobic compartmentalization of ionic complexes. In summary, orange II is an anionic dye with a sulfonate point charge and a high water solubility of 116 mg/mL at room temperature. Comparing across all thermogel formulations, the time to complete release (tioo%) of orange II ranges from 3 days to ~6 months (Table 6). In the case of sustained release, EP2V-NH₃ ⁺ hydrogel bearing complementary cationic amine functional groups supersedes the release of all the other gel by 62 folds (FIG. 3A). Utilising cationic EP2V-NH₃ ⁺, a sustained release of small molecular anionic drug for up to 6 months can be achieved. Using 2D NMR, it was showed that partitioning of orange II into PPG happens. Hence, a biphasic release corresponding to different degrees of interactions of orange II with PEG and PPG was observed.

Table 6. Time taken for complete orange II release from all formulations. tioo% represents time required for 100% of the drug to be released.

Table 7. Fitting results of orange II drug release data with different kinetic models, k and R² represent rate constant and correlation coefficient respectively, n represents diffusion exponent.

5.3. Biphasic release of crystal violet due to drug partitioning in micellar system

Crystal violet as a cationic drug analog, despite its charged nature, is nonpolar and has poor water solubility due to its diffused charge. Amphiphilic thermogels have been used as drug delivery vehicles because the core of their micellar crosslinks allows the encapsulation and compartmentalization of hydrophobic drugs. The encapsulation efficacy is dependent on the compatibility between the drug and the hydrophobic domain, a factor that can be assessed by metrics like the Flory-Huggins interaction parameters or the Hansen solubility parameter. In the simplest sense, the premise of this is that like-dissolves-like. Hence, polymers bearing different functional groups will exhibit varying degree of hydrophobicity, encapsulation efficacy and release kinetics for various hydrophobic drugs. In vitro release studies of hydrophobic crystal violet dye from thermogels containing different functional groups were conducted at 37 °C to study the relationship between the hydrophobic compartmentalization of drugs in these thermogels and their release profiles (FIGS. 8A and 8B). Comparatively, EP2V-COO' experienced the fastest release rates of crystal violet with a monophasic burst release profile. On the other hand, slower release rates of crystal violet from EP2V-COO :NH₃ ⁺, followed by EP2V, EP2V-(OH)₂, and EP1V- Ph were observed (FIG. 8A). EPV-COO — had a tioo% 13 days, followed by 90 days for EP2V-COQ-:NH₃ ⁺, and 174 days for EP2V, EP2V-(OH)₂, and EP1V-Ph (Tables 5 and 9). In this case, the release of crystal violet was not determined by the complementary ionic character between EP2V-COO' and crystal violet. The presence of repulsive cations on EP2V-NH₃ ⁺ did not exacerbate the quick release of crystal violet, possibly due to a more diffused charge, and a short Debye screening length of ~0.5 nm in PBS. Furthermore, a plateau in the release of crystal violet from EP2V-COO :NH₃ ⁺, EP2V, EP2V-(OH)₂, and EP1V-Ph was observed beyond the 13^th day, followed by a sharp increase in the release of crystal violet representing the second phase. The biphasic release profile with an intermediate lag phase is reminiscent of an initial release of drugs that did not partition into the hydrophobic micelles, followed by a plateau corresponding to polymer relaxation and swelling and an erosion-driven secondary phase (FIG. 9A). The release rates of the initial phases as well as the release plateaus from the various gels generally mirror the trend observed in the storage modulus (G’) values of the gels. The G’ of EP2V- COO :NH₃ ⁺, EP2V, EP2V-(OH)₂, and EP1V-Ph were 389 Pa, 601 Pa, 829 Pa, and 713 Pa respectively. As G’ generally increases with decreasing polarity and increasing hydrophobicity, the release rates of the initial phases can thus also be correlated with the hydrophobicity of the copolymers. The solvent-accessible polar surface area of each functional groups is shown in FIG. 2. To explain the observed plateau, it is hypothesized that these gels encapsulate crystal violet within micelles with variable efficiency. This efficiency depends on the polymer’s hydrophobicity as well as the ease of micelle-formation. The release exponent for the first phase suggests a primarily diffusive mechanism with n values ranging from 0.55 to 0.84 (Table 5) and release rates corresponding to the impeded diffusivity arising from improved adsorption of crystal violet in the increasingly hydrophobic non-micellized domain. The release exponents of > 1 in the second phases is representative of a type II release involving polymer relaxation and erosion. Additionally, the onset of the second phase coincides with the increasing trend of G’ of these gels, which is indicative of the dependence of the onset on the structural integrity of these gels (Table 8).

Further validation by ¹H NMR indicated by the broadening and downfield shift of the crystal violet peaks in the presence of the copolymers at the same dye concentration, suggesting possible interactions between crystal violet and the copolymers (FIG. 9B). As these peaks are deshielded to a greater extent in the presence of EP2V, EP2V-(OH)2, and EP1V-Ph in comparison to EP2V-COO-, it can be inferred that crystal violet molecules interact more strongly with EP2V, EP2V-(OH)2, and EP1V-Ph and contribute to their slower release. Plausibly, crystal violet-polymer hydrophobic associations may disrupt the intermolecular interactions between individual crystal violet molecules in aqueous solution, resulting in downfield ¹H NMR peak perturbations (FIG. 10). Furthermore, significant and preferential partitioning of crystal violet into the hydrophobic micelle domains of EP2V is evident from 2D NOESY experiments, which showed cross peaks between crystal violet and the hydrophobic PPG polymer segments, but not the hydrophilic PEG units (FIG. 11 ). All in, these results further reinforce the importance of tailoring hydrophobicity for sustained drug release of hydrophobic drugs. Although the exact contribution between hydrophobic partitioning and gel integrity is inextricable due to the co-dependency from the hierarchical assembly, hydrogel formulations with differing properties provides an opportunity for empirical observation and optimization of release profiles.

In summary, crystal violet is a cationic dye with a delocalized charge and poorer water solubility of 16 mg/mL. A distinct delayed biphasic, which in some cases can also be deemed as triphasic, release was observed across four (i.e. , EP2V-COO-:NH₃ ⁺, EP2V, EP2V-(OH)₂, and EP1 V-Ph) of the six thermogels, with the remaining two formulations (i.e., EP2V-COO- and EP2V-NH₃ ⁺) being monophasic (FIG. 3A). For the release of crystal violet, tioo% ranged from 5 days to ~5.8 months (Table 9). The biphasic release profile can be rationalized as the ability of the thermogelling amphiphiles to encapsulate hydrophobic molecules. The initial release coincides with the diffusion of drugs in the hydrated domains, while the delayed secondary phase correlates with the micelle-encapsulated drugs. The release rate and the onset of the secondary phase correlate with the hydrophobicity of the substituents, with the more hydrophobic substituents leading to slower release and a more delayed onset of the second phase. Furthermore, phenyl-containing EP1V-Ph thermogels have shown the potential to achieve delayed biphasic release of less water-soluble, small molecular cationic drug for up to 5.8 months.

Table 8. Determined values of the drug released at the onset of the intermediate plateau and the duration to the onset of the 2^nd regime.

Table 9. Time taken for complete crystal violet release from all formulations. two% represents time required for 100% of the drug to be released.

Table 10. Fitting results of crystal violet drug release data with different kinetic models, k and R² represent rate constant and correlation coefficient respectively, n represents diffusion exponent.

5.4. Mesh size-dependent release kinetics of dextran

Due to steric hindrance, mesh sizes of hydrogels greatly influence the release rates and profiles of high molecular weight drugs. Dependent on formulation parameters such as polymer type and concentration, as well as external conditions like temperature and pH, this property can range from 5 - 100 nm in hydrogels and is of profound importance especially when examined in relation to drug size. Herein, fluorescein-labelled dextran with a molecular weight of ~70 kDa was used as a high molecular weight model drug. The ratio between the drug’s hydrodynamic size to the mesh size of the hydrogel can affect both the diffusional rates and the release mechanisms of the drug through the hydrogel matrix. When the mesh size is smaller than the hydrodynamic size of the drug, drugs are physically entrapped within the hydrogel and the release is primarily governed by the degradation, swelling, and deformation of the hydrogel matrix. On the contrary, when the mesh size is greater than the hydrodynamic size of the drug, the release depends on the frictional drag on the drug during simple diffusive transport. As the mesh size approaches the hydrodynamic size of the drug, drug diffusion is inhibited due to the increased frictional drag and prominence of the steric hindrance effect. In contrast to the charged small molecules in the earlier studies, dextran is neutral, with a molecular weight of ~70 kDa, and a larger hydrodynamic size of ~17 nm.

The effective mesh size of a hydrogel can be approximated with the rubber elasticity theory. The theory of rubber elasticity relates the storage modulus G’ to the mesh size ( , nm) by the following equation:

Where NA is Avogadro’s constant, R is the gas constant and T is temperature.

Therefore, hydrogels with higher G’ are expected to have lower mesh sizes, and consequently reduced release rates driven either through lower diffusional rates or through network relaxation and degradation. The storage modulus of EP2V, EP2V-COO :NH₃ ⁺, EP2V-(OH)₂, EP1V-Ph, EP2V-COO; and EP2V-NH₃ ⁺ were 601 Pa, 389 Pa, 829 Pa, 713 Pa, 270 Pa, and 318 Pa respectively. From the equation above, the mesh sizes of 7 wt% EP2V, EP2V- COO :NH₃ ⁺, EP2V-(OH)₂, EP1V-Ph, EP2V-COO; and EP2V-NH₃ ⁺ hydrogels were determined to range from 17.3 nm to 25.1 nm at 37 °C (Table 12). When examined in relation to dextran, the range of estimated mesh sizes was close to, but not smaller than the approximate 17 nm hydrodynamic size of the model drug. Therefore, substantial size exclusion is expected in addition to solute-chain interactions. With the exception of EP2V-COO' and EP2V-COO':NH₃ ⁺, the reduction of mesh sizes influenced the rate of release but did not alter the dominant release mechanism from diffusion to network relaxation (FIG. 12A). This was reflected in the release exponent derived from the curve-fitting of the release profiles to the Korsmeyer-Peppas model (Table 5). In these systems, the thermogels generally showed lower release constants with decreasing mesh sizes (FIGS. 13A and 13B). In the case of EP2V-COO- and EP2V-COO :NH₃ ⁺, the release was observed to be quick, with a tioo% of six and nine days respectively (Tables 5 and 11 ). It is thus theorized that the low storage moduli and large mesh sizes of the gels contributed to a burst release through a combination of rapid relaxation, erosion, and diffusion of the loaded drugs. This is supported by a release exponent of 0.94 in EP2V-COO :NH₃ ⁺, and 0.71 in EP2V-COO and a rate constant of 0.57 and 1.26 respectively.

Notably, the release of dextran from EP2V-(OH)2 exhibited biphasic behaviour that is distinct from the monophasic releases observed with EP2V and EP2V-COO- (FIG. 12B). EP2V-(OH)₂ first showed a release of 65 % within the first nine days, followed by a phase of sustained release whereby the remaining 35 % of dextran was released across the next 67 days - a ~20-fold decrease in the release rate constant from 0.23 to 0.01 while transitioning from diffusive release to anomalous release with exponents 0.54 in the initial phase and 0.81 in the second phase. A possible reason for a sustained release of dextran from EP2V-(OH)2 could be the co-encapsulation of dextran within the micelles due to the hydrogen bonding between the hydroxyls on dextran and EP2V-(OH)2 - these encapsulated dextrans are then released during erosion of the gel. Hydrogel formulations with distinct properties can lead to a complex landscape for tailoring suitable drug release depots. Fundamentally, the release of dextran in these gels is dominated by the influence of the mesh size while tailoring specific interactions in hydrogels has been suggested by EP2V-(OH)2 release profile to be a possibly adaptable solution for the sustained release of high molecular weight therapeutics.

In summary, for the release of dextran, besides EP2 -(OH)2, the monophasic release of high molecular weight dextran seemed largely dependent on the mechanical stability and corresponding mesh size. For EP2V-(OH)2, a biphasic sustained release of ~2 months was seen (Table 11 ), and it suggests the sustaining effect of hydrogen bonding between the hydroxyls found in EP2V- (OH)₂ and dextran (FIGS. 12A and 12B).

Table 11. Time taken for complete dextran release from all formulations. two% represents time required for 100% of the drug to be released.

Table 12. Mesh sizes of EPV and their functionalised copolymers.

Table 13. Fitting results of dextran drug release data with different kinetic models, k and R² represent rate constant and correlation coefficient respectively, n represents diffusion exponent.

5.5. Summary of drug release profiles of orange II, crystal violet, and dextran form thermogels EP2V, EP2V-COO-, EP2V-NH₃ ⁺, EP2V- COO-:NH₃ ⁺, EP2V-(OH)₂, EP1V-Ph

(a) Vinyl-containing polyurethane thermogels (EP2V) were individually mixed with drug analogs - orange II, crystal violet, and dextran - in phosphate buffered saline at 7 wt%.

• Formulations of EP2V and low molecular weight anionic drug analog, orange II, achieved a monophasic release of 34 days.

• Formulations of EP2V and low molecular weight cationic drug analog with low water solubility, crystal violet, achieved a delayed biphasic release of 188 days.

• Formulations of EP2V and high molecular weight neutral drug analog, dextran, achieved a monophasic release of 76 days.

(b) Cationic amine-containing polyurethane thermogels (EP2V-NH₃ ⁺) were individually mixed with drug analogs - orange II, crystal violet, and dextran

- in phosphate buffered saline at 7 wt%.

• Formulations of EP2V-NH₃ ⁺ and low molecularweight anionic drug analog, orange II, achieved a biphasic release of 188 days.

• Formulations of EP2V-NH₃ ⁺ and low molecularweight cationic drug analog with low water solubility, crystal violet, achieved a monophasic release of 10 days.

• Formulations of EP2V-NH₃ ⁺ and high molecular weight neutral drug analog, dextran, achieved a monophasic release of 62 days.

(c) Formulations were prepared as described in 1 , wherein anionic carboxylate-containing polyurethane thermogels (EP2V-COO-) were individually mixed with drug analogs - orange II, crystal violet, and dextran

- in phosphate buffered saline at 7 wt%.

• Formulations of EP2V-COO- and low molecular weight anionic drug analog, orange II, achieved a monophasic release of 3 days. • Formulations of EP2V-COO- and low molecular weight cationic drug analog with low water solubility, crystal violet, achieved a monophasic release of 13 days.

• Formulations of EP2V-COO' and high molecular weight neutral drug analog, dextran, achieved a monophasic release of 6 days.

(d) Formulations were prepared as described in 1 , wherein zwitterionic ammonium- and carboxylate-containing polyurethane thermogels (EP2V- COO':NH3⁺) were individually mixed with drug analogs - orange II, crystal violet, and dextran - in phosphate buffered saline at 7 wt%.

• Formulations of EP2V-COO :NH₃ ⁺ and low molecular weight anionic drug analog, orange II, achieved a monophasic release of 83 days.

• Formulations of EP2V-COO :NH₃ ⁺ and low molecular weight cationic drug analog with low water solubility, crystal violet, achieved a delayed biphasic release of 90 days.

• Formulations of EP2V-COO :NH₃ ⁺ and high molecular weight neutral drug analog, dextran, achieved a monophasic release of 9 days.

(e) Hydrogen-bonding hydroxyl containing polyurethane thermogels (EP2V- (OH)₂) were individually mixed with drug analogs - orange II, crystal violet, and dextran - in phosphate buffered saline at 7 wt%.

• Formulations of EP2V-(OH)2 and low molecular weight anionic drug analog, orange II, achieved a monophasic release of 90 days.

• Formulations of EP2 -(OH)2 and low molecular weight cationic drug analog with low water solubility, crystal violet, achieved a delayed biphasic release of 188 days.

• Formulations of EP2V-(OH)2 and high molecular weight neutral drug analog, dextran, achieved a biphasic release of 76 days.

(f) Aromatic phenyl-containing polyurethane thermogels (EP1V-Ph) were individually mixed with drug analogs - orange II, crystal violet, and dextran - in phosphate buffered saline at 7 wt%. • Formulations of EP1 V-Ph and low molecular weight anionic drug analog, orange II, achieved a monophasic release of 20 days.

• Formulations of EP1V-Ph and low molecular weight cationic drug analog with low water solubility, crystal violet, achieved a delayed biphasic release of 188 days.

• Formulations of EP1 V-Ph and high molecular weight neutral drug analog, dextran, achieved a monophasic release of 62 days.

5.6. Conclusion

Thermogels comprising phenyl, ammonium, carboxylate, zwitterionic, and hydroxyl functional groups were utilized to confer hydrophobicity, ionicity, and enhanced hydrogen bonding. Consequently, the various functional groups can influence the physical properties of the hydrogel scaffold and interactions between polymer and therapeutics, resulting in different encapsulation and release mechanisms (FIG. 14A). The in vitro release studies demonstrated three primary mechanisms towards sustained release in these multifunctional thermogels (1) hydrophobic compartmentalization, (2) specific interactions, and (3) mesh-size dependent release (FIG. 14A). By utilizing hydrogels containing different functional groups, hydrophobicity was successfully fine-tuned for optimal compartmentalization. These gels were able to be adapted for complementary specific interactions and control the mesh-sizes of these gels. These modifications directly influenced the release kinetics and profiles, leading to drugs being released within days or over a period exceeding 6 months, with profiles between monophasic and biphasic (FIG. 14B).

These gel depots provide a local chemical environment for drug interactions and the intricacies between the structural properties of the gel scaffold, gel functional groups, and the drugs will determine the release profile and kinetics. The complex nature of the drug landscape makes it challenging to achieve sustained and modulated release from injectable gel depots. However, these intricate interactions also provide a unique opportunity in tuning drug- specific release kinetics. Herein, by leveraging the synergy between bottom - up molecular engineering, mechanical characterization, in vitro drug release, and 2D NMR, the impact of the three-way interactions involving the scaffold, functional groups, and drugs was elucidated. Subsequently, by tailoring drug formulations with polyurethane thermogels composed of poly(ethylene glycol), polypropylene glycol), and varying functional groups, an approach was established for formulating injectable, sustained release depots capable of adapting to an expansive range of drugs - ranging from low to high molecular weight drugs, whether charged or neutral, hydrophilic or hydrophobic. This technology holds promise as a drug delivery system for precision medicine due to its injectability and capability to achieve a diverse range of drug-specific release rates and profiles not seen in its predecessors. In conclusion, the present disclosure has provided a versatile formulation strategy for customizing injectable depots, enabling future tailored applications in precision medicine, gene therapies, and targeted treatments.

APPLICATIONS

Embodiments of the present disclosure provides a sustained injectable drug delivery system that is distinguished from and possesses certain advantages over those of the art at least in the unique design and composition. Advantageously, embodiments of the present disclosure can achieve sustained release of the drug for at least 1 day to more than 6 months with tailorable drug-specific release profiles. Even more advantageously, embodiments of the present disclosure may be used for the sustained release of drugs with varying release kinetics and release profiles (i.e., monophasic or biphasic).

Embodiments of the present disclosure provides a versatile and highly adaptable synthetic platform for developing drug-specific sustained injectable drug delivery systems for the diverse range of therapeutics. Advantageous, embodiments of the present disclosure enable functionalizable thermogel formulations of at least 7 functional groups and across 3 different drug types/categories. Even more advantageously, embodiments of the present disclosure provide the first injectable hydrogel platform with accessible and tailorable functional groups for tunable release rates, release profiles, and release mechanisms.

Embodiments of the present disclosure provides a thermogel polymer that is different from those in the art which have a different composition such as PEG/PPG without HDDO, PEG/PPG/PCL (polycaprolactone). Advantageously, embodiments of the present disclosure show that hydrogel formulations with distinct characteristics can be translated to a range of therapeutic drugs through insightful formations and high throughput screening. It will also be appreciated that it is not readily predictable how the release profiles of different drug classes would be when combined with the specific thermogels of the embodiments provided in the present disclosure due to the highly complex nature of the tripartite interactions among the scaffold, functional groups, and drugs.

Embodiments of the present disclosure provides an injectable depot that is different from those in the art that use swollen polymer film. Advantageously, besides sustained release, embodiments of the present technology also emphasize on injectability and tailorability of drug-specific release profiles.

Embodiments of the present disclosure provides an adaptable formulation method/approach for engineering sustained release or precise release kinetics for specific drugs from functionalized thermogels. Advantageously, embodiments of the present disclosure are applicable to a broad range of drugs, including but not limited to, ionic hydrophilic drugs, hydrophobic drugs, and high molecular weight drugs. It will be appreciated that the embodiments of the method/approach provided are different from those control mechanisms in the art in which rely on the molar ratio of the polymer components rather than the interaction of thermogel’s characteristics with different drug classes.

Embodiments of the present disclosure provides an easy synthesis of a thermogel polymer from readily available starting materials that potentially allows easy translation to outsource manufacturing at good manufacturing practice (GMP) facilities for scale-up and practical in-field applications. For example, embodiments of the present disclosure provide easy customisation of thermogel properties by changing number of vinyls on the polymer backbone and the identity of functional groups attached.

It will be appreciated by a person skilled in the art that other variations and/or modifications may be made to the embodiments disclosed herein without departing from the spirit or scope of the disclosure as broadly described. For example, in the description herein, features of different exemplary embodiments may be mixed, combined, interchanged, incorporated, adopted, modified, included etc. or the like across different exemplary embodiments. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.

Claims

1 . A thermogel-drug composition comprising, a thermogel polymer comprising one or more repeating units derived from a hydrophilic polymer, one or more repeating units derived from a thermoresponsive polymer, and one or more repeating units derived from a vinyl-containing diol monomer; and a drug or a drug analog encapsulated by said thermogel polymer.

2. The thermogel-drug composition according to claim 1 , wherein the one or more repeating units derived from a hydrophilic polymer are represented by general formula (1 ), the one or more repeating units derived from a thermoresponsive polymer are represented by general formula (2), and the one or more repeating units derived from a vinyl-containing diol monomer are represented by general formula (3) or its functionalized derivative thereof: wherein

R^{1 a}, R^1b, R^2a, R^2b, R^3a, R^3b, R^4a, R^4b, R⁵ to R¹⁰, R¹², and R¹³ are each independently selected from H, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted alkylene oxide, and optionally substituted poly(alkylene oxide); m is from 1 to 400; and n is from 1 to 400.

3. The thermogel-drug composition according to claim 2, wherein the one or more repeating units represented by general formula (1 ) is different from the one or more repeating units represented by general formula (2) in the thermogel polymer.

4. The thermogel-drug composition according to any one of claims 1 to 3, wherein the hydrophilic polymer comprises poly(ethylene glycol) (PEG) and the thermoresponsive polymer comprises polypropylene glycol) (PPG).

5. The thermogel-drug composition according to any one of claims 2 to 4, wherein the one or more repeating units represented by general formula (3) is derived from a compound selected from the group consisting of 1 ,5- hexadiene-3,4-diol, 3-(allyloxy)propane-1 ,2-diol and 2,3- dihydroxypropylmethacrylate.

6. The thermogel-drug composition according to any one of claims 2 to 5, wherein the functionalized derivative of general formula (3) comprises functional groups selected from the group consisting of cationic and anionic groups, zwitterionic groups, hydroxyl groups, aromatic rings, and combinations thereof.

7. The thermogel-drug composition according to any one of claims 2 to 6, wherein the functionalized derivative of general formula (3) comprises a structure represented by general formula (4):

wherein

R5 to R¹⁰ R¹² R¹³ R²⁰ and R²¹ are each independently selected from H, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted alkylene oxide, and optionally substituted poly(alkylene oxide); and

8. The thermogel-drug composition according to claim 7, wherein X¹ and X² are each independently selected from the group consisting of the following structures:

9. The thermogel-drug composition according to any one of claims 1 to 8, wherein the thermogel polymer comprises from 0.01 mmol/g to 7 mmol/g of vinyl groups.

10. The thermogel-drug composition according to any one of claims 7 to 9, wherein the thermogel polymer, has a functional group density of X¹ and/or X², of from 0.01 mmol/g to 7 mmol/g.

11. The thermogel-drug composition according to any one of claims 2 to 10, wherein the one or more repeating units represented by general formula (1 ), the one or more repeating units represented general formula (2), and the one or more repeating units represented by general formula (3) or its functionalized derivative thereof, are chemically coupled together by at least one of urethane, carbamate, carbonate, ester, urea, amide linkages, thiolated analogues thereof, or combinations thereof.

12. The thermogel-drug composition according to claim 11 , wherein the at least one of urethane, carbamate, carbonate, ester, urea, amide linkages, is represented by general formula (5): wherein

R¹⁴ and R¹⁵ are each independently selected from H, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted cycloalkyl, or optionally substituted aromatic aryl).

13. The thermogel-drug composition according to claim 12, wherein the linkage represented by general formula (5) is derived from a compound selected from the group consisting of diisophorone diisocyanate, 4,4’- diphenylmethane diisocyanate, and hexamethylene diisocyanate.

14. The thermogel-drug composition according to any one of claims 2 to 13, wherein the one or more repeating units represented by general formula (1 ) is present in an amount of between more than 0 mass% to 90 mass% of the thermogel polymer; the one or more repeating units represented by general formula (2) is present in an amount of more than 0 mass% to 90 mass% of the thermogel polymer; and the one or more repeating units represented by general formula (3) or its derivative thereof is present in an amount of from 0.1 mass% to 40 mass% of the thermogel polymer.

15. The thermogel-drug composition according to any one of claims 1 to 14, wherein the thermogel polymer has one or more of the following properties: a polydensity index (PDI) falling in a range of from 1 .0 to 2.0; a pH value falling in a range of from 1 to 10; a critical gelation temperature falling in a range of from 4°C to 60°C; a crossover modulus falling in a range of from 5 Pa to 1000 Pa; a storage modulus (G’) falling in a range of from 1 Pa to 5000 Pa; a complex viscosity falling in a range of from 1 Pa s to 1000 Pa.s; a mesh size falling in a range of from 5 nm to 30 nm; and a water content of more than 60% to more than 99% by weight.

16. The thermogel-drug composition according to any one of claims 1 to 15, wherein the drug or drug analog has a high molecular weight of no less than about 10 kDa, has an intermediate molecular weight of from 1 kDa to 10 kDa, or has a low molecular weight of no more than about 1 kDa.

17. The thermogel-drug composition according to any one of claims 1 to 16, wherein the drug or drug analog is cationic, anionic, zwitterionic, or neutral.

18. The thermogel-drug composition according to any one of claims 1 to 17, wherein the drug or drug analog is selected from the group consisting of crystal violet, orange II, dextran, imipramine, amitriptyline, thioridazine, chlorpromazine, trazodone, imiglucerase, certolizumab pegol, etanercept, nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, naproxen, diclofenac, aspirin, indomethacin, and piroxicam.

19. The thermogel-drug composition according to any one of claims 1 to 18, wherein the thermogel polymer comprises one or more repeating units represented by general formula (1 ), one or more repeating units represented by general formula (2), and one or more repeating units represented by general formula (3) or its functionalized derivative thereof, wherein the functionalized derivative of general formula (3) is functionalized with one or more functional groups selected from a group consisting of -NH3⁺, -COO-, -COO :NH3⁺, -(OH)2, and -Ph; and the drug or drug analog comprises a low molecular weight cationic hydrophobic molecular drug or drug analog that is < 1 kDa,

20. The thermogel-drug composition according to any one of claims 1 to 18, wherein the thermogel polymer comprises one or more repeating units represented by general formula (1 ), one or more repeating units represented by general formula (2), and one or more repeating units represented by general formula (3) or its functionalized derivative thereof, wherein the functionalized derivative of general formula (3) is functionalized with one or more functional groups selected from a group consisting of -NH₃ ⁺, -COOiNH₃*, -(OH)2, and -Ph; and the drug or drug analog comprises a low molecular weight anionic hydrophobic molecular drug or drug analog that is < 1 kDa.

21. The thermogel-drug composition according to any one of claims 1 to 18, wherein the thermogel polymer comprises one or more repeating units represented by general formula (1 ), one or more repeating units represented by general formula (2), and one or more repeating units) represented by general formula (3) or its functionalized derivative thereof, wherein the functionalized derivative of general formula (3) is functionalized with one or more functional groups selected from a group consisting of -NH₃ ⁺, -(OH)2, and -Ph; and the drug or drug analog comprises a high molecular weight neutral hydrophobic molecular drug or drug analog that is > 10 kDa.

22. The thermogel-drug composition according to any one of claims 1 to 21 , wherein the thermogel-drug composition is capable of providing sustained drug release or a delayed biphasic release of from at least 1 day to at least 365 days.

23. A method of preparing a thermogel-drug composition, the method comprising encapsulating one or more drugs or drug analog with a thermogel polymer according to any one of claims 1 to 22.

24. The method according to claim 23, wherein the method comprises coupling one or more hydrophilic polymers, one or more thermoresponsive polymers, and one or more vinyl-containing diol monomers in the presence of a coupling agent to obtain the thermogel polymer.

25. The method according to claim 24, wherein the one or more hydrophilic polymers are represented by general formula (6), the one or more thermoresponsive polymers are represented by general formula (7), and the one or more vinyl-containing diol monomers are represented by general formula (8) or its functionalized derivative thereof: wherein

26. The method of claim 24 or 25, wherein the one or more hydrophilic polymers, the one or more thermoresponsive polymers, and the one or more vinyl-containing diol monomers are mixed in a mass ratio of 1 -20 : 1 -10 : 0.01 -3.

27. The method according to any one of claims 24 to 26, wherein the coupling step is carried out in the presence of a coupling agent such that the one or more hydrophilic polymers represented by general formula (6), the one or more thermoresponsive polymers represented by general formula (7), and the one or more vinyl-containing diol monomers represented by general formula (8) or its functionalized derivative thereof are chemically coupled together by at least one of urethane, carbamate, carbonate, ester linkages, or combinations thereof to form the thermogel polymer.

28. The method according to claim 27, wherein the at least one of urethane, carbamate, carbonate, ester linkages, or combinations thereof is represented by general formula (5): wherein

R¹⁴ and R¹⁵ are each independently selected from H, optionally substituted alkyl, optionally substituted alkenyl, and optionally substituted alkynyl, optionally substituted cycloalkyl, or optionally substituted aromatic aryl.

29. The method according to any one of claims 23 to 28, wherein the method further comprises functionalizing the thermogel polymer with one or more thiols to obtain a functionalized thermogel polymer with functional groups X¹— S and X²— S, wherein X¹ and X² are each independently a moiety comprising a carboxylic acid, a carboxylate, a sulfonic acid, an amine, an amino acid, a sulfonate, an alkylsulfonate, an aminehydrochloride, protonated amine, an alcohol, a diol, a benzene, an alkylbenzene, imidazole or salts thereof.

30. The method according to claim 29, wherein the weight percentage of the total thermogel polymer that has been functionalized after the functionalizing step is of from 70 wt% to 100 wt%.

31. The method of preparing a thermogel-drug composition according to any one of claims 25 to 30, wherein the one or more hydrophilic polymers comprise poly(ethylene glycol) (PEG); the one or more thermoresponsive polymers comprise polypropylene glycol) (PPG); the one or more vinyl-containing diol monomers comprise 1 ,5- hexadiene-3,4-diol (HDDO), 3-(allyloxy)propane-1 ,2-diol, or 2,3- dihydroxypropylmethacrylate; and the coupling agent comprises hexamethylene diisocyanate (HMDI).