Method of preparing a crosslinked carboxymethyl cellulose or salt thereof, composition, and uses thereof

Abstract

Described herein is a method of preparing a crosslinked carboxymethyl cellulose and / or a salt thereof, compositions and uses of the crosslinked carboxymethyl cellulose. The method includes providing an aqueous solution comprising a salt of carboxymethyl cellulose and a linker compound, the linker compound comprising two or more terminal epoxides, incubating the aqueous solution for at least 4 hours at a temperature from 50 ºC to 100 ºC to react the salt of carboxymethyl cellulose with the two or more terminal epoxides to obtain the crosslinked carboxymethyl cellulose. The composition includes carboxymethylcellulose crosslinked with a plurality of linking moieties and / or a salt, each linking moiety join two glucopyranose monomer units of carboxymethylcellulose to form a crosslink, the linking moiety having two or more hydroxyl groups.

Description

METHOD OF PREPARING A CROSSLINKED CARBOXYMETHYL CELLULOSE OR SALT THEREOF, COMPOSITION, AND USES THEREOFREFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to Singapore patent application number 10202403442P with a filing date of 6 November 2024 and titled “Crosslinked Carboxymethylcellulose Hydrogel as an Ophthalmic Adjunct for Glaucoma Treatment” and is incorporated herein by reference.FIELD OF THE INVENTION

[0002] The present disclosure relates to a crosslinked carboxymethyl cellulose, a method of preparing the crosslinked carboxymethyl cellulose, and uses thereof.BACKGROUND OF THE INVENTION

[0003] Advanced Ophthalmic Innovations (AOI) has developed an implant to regulate intraocular pressure for glaucoma treatments, named PAUL®. This implant requires a surgical adjunct or viscous lubricant to be introduced as a spacer between the medical device and the conjunctiva of the eye to reduce tissue scarring from abrasion between the medical device and conjunctiva. For this purpose, hyaluronic acid (HA)-based commercial hydrogel products such as Healaflow® are typically used. EP 2737908 describes the product known commercially as Healaflow®, which is the current incumbent surgical adjunct used for glaucoma filtration surgery. This formulation contains HA chemically crosslinked with 1 ,4- BDDE, and is mixed together with auto crosslinked HA to achieve the targeted viscosity for ophthalmic applications. However, it has been found in actual clinical practice that the Healaflow® hydrogel is insufficiently cohesive, i.e. it spreads out to form a thin film, and therefore is suboptimal for usage. Further, hyaluronic acid is expensive, and the resulting hydrogels have limited viscosity, which limits the range of their applications. A biocompatible hydrogel formulation that is more viscous (i.e. cohesive) than Healaflow® is therefore required.

[0004] Carboxymethylcellulose (CMC) is a naturally-occurring biopolymer that has been widely used in the pharmaceutical industry due to its excellent biocompatibility. W02005089715 describes the use of sodiumcarboxymethylcellulose with minimal chemical modifications as a lubricant in artificial tear formulations for treating dry eyes. US9353191 describes CMC crosslinked with ester linkages using an anhydride-based chemical crosslinker derived from citric acid. The procedure for crosslinking involves first dissolving the CMC polymer in basic aqueous solution followed by addition of a crosslinker. Lawai et. al. (Microporous hydrogels of cellulose ether cross-linked with di- or polyfunctional glycidyl ether made for the delivery of bioactive substances, Colloid and Polymer Science, 2011 , 289, 1261 -1272 (DOI: 10.1007 / s00396-011 -2458-0)) describes CMC crosslinked with di- or polyfunctional glycidyl ethers containing PEG segments as spacers and were used to prepare hydrogels. The gels were used for sustained drug release of bovine serum albumin.

[0005] WO 2020 / 242420 describes the preparation of a hydrogel by mixing 7- 17% of carboxymethyl cellulose, 0.5-4% 1 ,4-butanediol diglycidyl ether, 1 % sodium hydroxide, and 80-95% deionised water. The mixture was subjected to a crosslinking reaction in a water bath for 4 hours at 40°C. The gel was subsequently cooled and neutralised to a pH of 6.8-7.4. The mixture was filtered with a sieve and new PBS solution added to allow the gel to swell more.

[0006] Della Sala et al (Gels 2024, 10, 67. https: / / doi.Org / 10.3390 / gels10010067) describes reacting 133.3 mg / mL of carboxymethyl cellulose, 8.33 pL / mL of ,4- butanediol diglycidyl ether and 1 % sodium hydroxide at 25°C for 24 hours or 50°C for 2 hours to prepare CMC hydrogels.SUMMARY OF THE INVENTION

[0007] In a first aspect, there is provided A method of preparing a crosslinked carboxymethyl cellulose and / or a salt thereof. The method comprises providing an aqueous solution comprising a salt of carboxymethyl cellulose and a linker compound, the linker compound comprising two or more terminal epoxides, incubating the aqueous solution for at least 4 hours at a temperature from 50 °C to 100 °C to react the salt of carboxymethyl cellulose with the two or more terminal epoxides to obtain the crosslinked carboxymethyl cellulose.

[0008] In an embodiment, incubating the aqueous solution is done without stirring or agitation.

[0009] In an embodiment, 1 weight percent (wt. %) of the salt of carboxymethyl cellulose in an aqueous solution has a viscosity of at least 1 .5 Pa*s in at 25 °C, preferably 1 weight percent (wt. %) of the salt of carboxymethyl cellulose in an aqueous solution has a viscosity of 1 .5 Pa*s to 4.5 Pa*s at 25 °C, more preferably the salt of carboxymethyl cellulose is a sodium salt of carboxymethyl cellulose.

[0010] In an embodiment, the linker compound is selected from the group consisting of a linear polyether, a branched polyether, a linear hydrocarbon, a branched hydrocarbon, a cyclic hydrocarbon, and combinations thereof, optionally with one or more functional groups within the hydrocarbon, the one or more functional groups selected from the group consisting of an ether, a thioether, an amine, an amide, a carbamide, a carbamate, and combinations thereof.

[0011] In an embodiment, the linker compound is a linear polyether with 2 terminal epoxides or a branched polyether with more than 2 terminal epoxides, the linear polyether or the branched polyether having a weight average molecular weight from 1 kDa to 50 kDa, preferably the weight average molecular weight is from 5 kDa to 40 kDa, more preferably the branched polyether has 3 to 10 terminal epoxides.

[0012] In an embodiment, the polyether has a polyethylene glycol backbone or a polypropylene glycol backbone.

[0013] In an embodiment, wherein the linker compound is selected from the group consisting of Formulaan integer from 1 to 4,Formula Ieach R1independently has a formula of Formula IIn, each R2is independently selected from the group consisting of Formula IIn , a C1-C3 alkyl, and hydrogen, wherein for Formula lb, Formula Ic, Formula Id and Formula le at least two of the R2is of Formula n,A is each independently selected from the group consisting of CH2, O, S,hydrogen or methyl, R5and R6is each independently hydrogen or a C1 toC3 alkyl, each n in Formula II is independently an integer from 0 to 6 except the n in R1of Formula la cannot both be zero, the value of m is such that the linker compound has a weight average molecular weight from 1 kDa to 50 kDa, preferably the weight average molecular weight is from 5 kDa to 40 kDa.

[0014] Preferably, A is each independently selected from the group consisting of

[0015] Preferably, the linker compound is of Formula HIA1and A2is each independently selected from the group consisting of CH2, O, S, NR5, CONR5, R5N(C=O)NR6, and O(C=O)NR5, R5and R6is each independently hydrogen or a C1 to C3 alkyl, ns is an integer from 2 to 13.

[0016] Preferably, A1and A2is each oxygen, and ns is an integer from 2 to 8, preferably ns is an integer from 3 to 5, more preferably ns is 4.

[0017] In an embodiment, at least 0.1 gram of the linker compound is added per gram of the salt of carboxymethyl cellulose or per gram of carboxymethyl cellulose or at least 0.5 mmol of the linker compound is added per gram of the salt of carboxymethyl cellulose or per gram of carboxymethyl cellulose.

[0018] Preferably, 0.1 gram to 4 grams of the linker compound is added per gram of the salt of carboxymethyl cellulose or per gram of carboxymethyl cellulose, more preferably 0.1 gram to 2 grams of the linker compound is added per gram of the salt of carboxymethyl cellulose or per gram of carboxymethyl cellulose, even more preferably 0.1 gram to 1 .5 grams of the linker compound is added per gram of the salt of carboxymethyl cellulose or per gram of carboxymethyl cellulose.

[0019] Preferably, 0.5 mmol to 20 mmol of the linker compound is added per gram of the salt of carboxymethyl cellulose or per gram of carboxymethyl cellulose, more preferably 0.5 mmol to 10 mmol of the linker compound is added per gram of the salt of carboxymethyl cellulose or per gram of carboxymethyl cellulose, even more preferably 0.5 mmol to 6 mmol of the linker compound is added per gram of the salt of carboxymethyl cellulose or per gram of carboxymethyl cellulose.

[0020] In an embodiment, providing the aqueous solution comprises dissolving carboxymethyl cellulose or the salt of carboxymethyl cellulose in a second aqueous solution of a base, preferably the base is an inorganic water-soluble base with a pKa of at least 12 in water at 25 °C, more preferably the base is sodium hydroxide or potassium hydroxide; and upon dissolution of the carboxymethyl cellulose or the salt of carboxymethyl cellulose, adding the linker compound with stirring to obtainthe aqueous solution, which is preferably incubated without delay at the temperature thereafter.

[0021] In an embodiment, the aqueous solution consists essentially of the salt of carboxymethyl cellulose and the linker compound, preferably the aqueous solution consists of the salt of carboxymethyl cellulose and the linker compound or according to claim 14 wherein the aqueous solution consists essentially of the base, the salt of carboxymethyl cellulose and the linker compound, preferably the aqueous solution consists of the base, the salt of carboxymethyl cellulose and the linker compound.

[0022] In an embodiment, incubating the aqueous solution is for at least 12 hours, preferably incubating the aqueous solution is for at least 16 hours, more preferably incubating the aqueous solution is for at least 18 hours.

[0023] In an embodiment, the method further comprises purifying the crosslinked carboxymethyl cellulose, preferably by dialysis, and lyophilising the purified crosslinked carboxymethyl cellulose, and preferably wherein the salt of the crosslinked carboxymethyl cellulose is not neutralised.

[0024] In a second aspect, there is provided a product obtained by any one of the methods according to the first aspect.

[0025] In a third aspect, there is provided a composition comprising carboxymethylcellulose crosslinked with a plurality of linking moieties and / or a salt thereof, wherein each linking moiety join two glucopyranose monomer units of carboxymethylcellulose to form a crosslink, the linking moiety comprising two or more hydroxyl groups, wherein 5 wt. % of the crosslinked carboxymethyl cellulose and / or salt thereof in an aqueous solution forms a hydrogel with an average peak viscosity of 10000 Pa*s or less at 37°C.

[0026] In an embodiment, 5 wt. % of the crosslinked carboxymethyl cellulose and / or salt thereof in an aqueous solution forms a hydrogel with an average peak viscosity from 500 Pa*s to 10000 Pa*S at 37°C, preferably the average peak viscosity is from 1000 Pa*s to 8000 Pa*, more preferably the average peak viscosity is from 1200 Pa*s to 6000 Pa*.

[0027] In an embodiment, the linking moiety is selected from the group consisting of a linear polyether, a branched polyether, a linear hydrocarbon, a branched hydrocarbon, a cyclic hydrocarbon, and combinations thereof, optionally with oneor more functional groups within the hydrocarbon, the one or more functional groups selected from the group consisting of an ether, a thioether, an amine, an amide, a carbamide, a carbamate, and combinations thereof.

[0028] In an embodiment, the linking moiety is a linear polyether with 2 hydroxyl groups or a branched polyether with more than 2 hydroxyl groups, the linear polyether or the branched polyether having a weight average molecular weight from 1 kDa to 50 kDa, preferably the weight average molecular weight is from 5 kDa to 40 kDa, more preferably the branched polyether has 3 to 10 hydroxyl groups.

[0029] In an embodiment, the polyether has a polyethylene glycol backbone or a polypropylene glycol backbone.

[0030] In an embodiment, each linking moiety is selected from the groupeach R8in Formula IVa independently has a formula ofnorOH ly selected from the group consisting of, a C1-C3 alkyl and hydrogen, wherein for Formula IVb, Formula IVc, Formula IVd and Formula IVe at least two of the R9has a formula ofA is each independently selected from the group consisting of CH2, O, S, NR5,each independently hydrogen or a C1 to C3 alkyl, each n is independently an integer from 0 to 6 except n in both R8of Formula IVa cannot both be zero, the value of m is such that the linker compound has a weight average molecular weight from 1 kDa to 50 kDa, preferably the weight average molecular weight is from 5 kDa to 40 kDa.

[0031] In an embodiment, A is each independently selected from the group consisting

[0032] In an embodiment, each linking moiety is independently selected from the group consisting of Formula Va, Formula Vb, Formula Vc and combinations thereof,_ .FormulaA1and A2is each independently selected from the group consisting of CH2, O, S, NRs, CONRs, R5N(C=O)NR6, and O(C=O)NR5, R5and R6is each independently hydrogen or a C1 to C3 alkyl, ns is an integer from 2 to 13.

[0033] In an embodiment, A1and A2is each oxygen, and ns is an integer from 2 to 8, preferably ns is an integer from 3 to 5, more preferably, ns is 4.

[0034] In an embodiment, at least 80% of the plurality of linking moieties is Formula Va, more preferably at least 90% of the plurality of linking moieties is Formula Va, even more preferably the plurality of linking moieties is Formula Va.

[0035] In an embodiment, the carboxymethylcellulose and / or a salt thereof crosslinked with the plurality of linking moieties is of Formula VIImoiety), and the linking moiety, preferably R10is each independently selected from the group consisting of H, CH2COOH, CH2COO and CH2COO(the linking moiety).

[0036] In an embodiment, the composition consists essentially of the carboxymethylcellulose crosslinked with the plurality of linking moieties and / or the salt thereof, preferably the composition consists of the carboxymethylcellulose crosslinked with the plurality of linking moieties and / or the salt thereof .

[0037] In an embodiment, the carboxymethylcellulose and / or the salt thereof crosslinked with a plurality of linking moieties is lyophilised.

[0038] In a fourth aspect, there is provided a hydrogel comprising 0.5 weight percent (wt. %) to 20 wt. % of the composition according to the third aspect; and water, preferably the hydrogel comprises 0.5 wt. % to 10 wt. % of the composition according to the third aspect; and water.

[0039] In an embodiment, the hydrogel further comprises a buffer solution, preferably the buffer solution is selected from the group consisting of an acetate buffer, a citrate buffer, a borate buffer, a Tris buffer, and a phosphate buffer.

[0040] In an embodiment, the hydrogel consist essentially of 0.5 wt. % to 20 wt. % of the composition according to the third aspect; and water or consist essentially of 0.5 wt. % to 20 wt. % of the composition according to the third aspect; water and the buffer solution, preferably the hydrogel consists of 0.5 wt. % to 20 wt. % of the composition according to the third aspect; and water or consists of 0.5 wt. % to 20 wt. % of the composition according to the third aspect; water and the buffer solution.

[0041] In an embodiment, the composition is present from 2 wt. % to 8 wt. %, preferably the composition is present from 5 wt. % to 7 wt. %.

[0042] In a fifth aspect, there is provided the hydrogel according to the fourth aspect for use as a medicament, in therapy and / or surgery.

[0043] In an embodiment, the hydrogel for use in the treatment and / or surgery of an eye disease or as an ophthalmic medicament.

[0044] In an embodiment, the hydrogel for use in therapy and / or surgery as a lubricant or a vitreous substitute to be administered in an eye.

[0045] In an embodiment, use of the hydrogel in the manufacture of a medicament for the treatment and / or prevention of an eye disease.

[0046] In an embodiment, a method of treating and / or preventing an eye condition, the method comprising administering an effective dose of the hydrogel to a subject’s eye. Preferably, the method comprises inserting a glaucoma implant into an eye of a subject; and administering an effective dose of the hydrogel comprises inserting the hydrogel in a subconjunctival space under a conjunctiva in the eye of the subject.

[0047] In a sixth aspect, there is provided a formulation comprising the hydrogel according to the fourth aspect; and an active pharmaceutical ingredient.

[0048] In a seventh aspect, there is provided a use of the hydrogel according to the fourth aspect as a rheological modifier and / or thickener in cosmetic applications.

[0049] The linker compounds to crosslink carboxymethyl cellulose may be any suitable molecule. An example of a suitable linker compound has two or more terminal epoxides of which 1 ,4-Butanediol Diglycidyl Ether is an example. Other similar bisglycidyl ethers that may be used include varying the length of the spacer unit between both terminal epoxides (or glycidyl ether units) to any lengths including PEG of different molecular weights. The identity of the spacer unit can be varied as well. The PEG backbone may be possibly replaced with polypropylene glycol), or even alkyl chains of different lengths. A linker compound with 3 or more terminal epoxides or glycidyl ether units may also be used. Glycidyl ethers from spacers with different extents of branching are possible as well, including but not limited to 4-, 6- or 8-arm PEG, with each arm terminated by a glycidyl ether unit. These linker compounds share similar chemistry as 1 ,4-butanediol Diglycidyl Ether (BDDE), and would result in crosslinked carboxymethyl cellulose polymers that are likely to form hydrogel with similar properties.BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure (FIG.) 1 shows a reaction scheme to prepare a crosslinked carboxymethyl cellulose.

[0051] FIG. 2A, FIG. 2B, FIG. 2C, and FIG. 2D show the characterisation of the gel by rheolology. FIG. 2A shows the storage modulus and loss modulus when the gel is subjected to a temperature ramp. FIG. 2B shows the viscosity of the gel. FIG. 2C and 2D respectively show the frequency sweep and amplitude sweep and the effect on the storage modulus and loss modulus.

[0052] FIG. 3 shows the effect on the viscosity of the gel due to the stirring rates in preparing the gel.

[0053] FIG. 4 shows the effect on the viscosity of the gel due to the different concentrations of BDDE with stirring during the reaction.

[0054] FIG. 5 shows the effect on the viscosity of the gel due to the different concentrations of BDDE without stirring during the reaction.

[0055] FIG. 6 shows the effect on the viscosity of the gel due to the different concentrations of carboxymethyl cellulose without stirring during the reaction.

[0056] FIG. 7 shows the effect on the viscosity of the gel due to the different reaction vessels.

[0057] FIG. 8 shows the effect on the viscosity of the gel due to the different scale of the reaction.

[0058] FIG. 9 shows the effect on the viscosity of the gel due to the different scale of the reaction.

[0059] FIG. 10 shows the effect on the viscosity of the gel due to the different storage conditions. FIG. 10A, FIG. 10B, and FIG. 10C are for storage at room temperature, 4 °C, and -20 °C respectively.

[0060] FIG. 11 shows the transparency of the gel formed.

[0061] FIG. 12A, FIG. 12B, FIG. 12C, and FIG. 12D respectively show the characterisation and comparison of an embodiment against the commercial Healaflow® on a temperature ramp, viscosity, angular frequency and amplitude sweep.

[0062] FIG. 13 shows a comparison of an embodiment produced on large scale against the commercial Healaflow® by rheology (viscosity).

[0063] FIG. 14 shows the viscosity of 0.5 wt. % of the gel.

[0064] FIG. 15 shows the viscosity of 10 wt. % of the gel.

[0065] FIG. 15 shows a storage stability study of the gel at room temperature with no obvious decrease in viscosity over 4 months.

[0066] FIG. 17 shows the rheological results of post stem sterilisation of the crosslinked CMC gels with Panel A and Panel B being for 5 wt. % and 7 wt. % of the gel respectively. Each parameter variables were conducted with a duplicated sample set-up using individually prepared samples.

[0067] FIG. 18 shows a comparison of various gels for subretinal use.DETAILED DESCRIPTION OF THE INVENTION

[0068] In the following description, numerous specific details are set forth in order to provide a thorough understanding of various illustrative embodiments of the invention. It will be understood, however, to one skilled in the art, that embodiments of the invention may be practiced without some or all of these specific details.Embodiments described in the context of one of the methods or products are analogously valid for the other methods or products. Similarly, embodiments described in the context of a method are analogously valid for a product, and vice versa.

[0069] Where a combination is disclosed, each subcombination of the elements of that combination is also specifically disclosed and is within the scope of the invention. Conversely, where different elements or groups of elements are disclosed, combinations thereof are also disclosed. Where any element of an invention is disclosed as having a plurality of alternatives, examples of that invention in which each alternative is excluded singly or in any combination with the other alternatives are also hereby disclosed; more than one element of an invention can have such exclusions, and all combinations of elements having such exclusions are hereby disclosed.

[0070] Where a range of values is recited, it is to be understood that each intervening integer value, and each fraction thereof, between the recited upper and lower limits of that range is also specifically disclosed, along with each subrange between such values. The upper and lower limits of any range can independently be included in or excluded from the range, and each range where either, neither or both limits are included is also encompassed within the invention. Where a value being discussed has inherent limits, for example where a component can be present at a concentration of from 0 to 100%, or where the pH of an aqueous solution can range from 1 to 14, those inherent limits are specifically disclosed. Where a value is explicitly recited, it is to be understood that values which are about the same quantity or amount as the recited value are also within the scope of the invention, as are ranges based thereon.

[0071] The term "alkyl" as used herein is a branched or unbranched saturated monovalent hydrocarbon radical of 1 to 24 carbon atoms (C1 -C24), such as methyl, ethyl, n-propyl, isopropyl, nbutyl, isobutyl, s-butyl, f-butyl, n-pentyl, isopentyl, s- pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, eicosyl, tetracosyl, and the like. The alkyl group can be cyclic or acyclic. The alkyl group can be branched or unbranched. The alkyl group can also be substituted or unsubstituted. For example, the alkyl group can be substituted with one or moregroups including, but not limited to, alkyl, cycloalkyl, alkoxy, amino, ether, halide, hydroxy, nitro, silyl, sulfo-oxo, or thiol, as described herein.

[0072] Described herein is a highly-transparent hydrogel synthesised through the chemical crosslinking of high-viscosity Carboxymethyl Cellulose (CMC) using a bisepoxide chemical crosslinker. When the gel is described in wt. % herein, it refers to the wt. % of the crosslinked CMC. The hydrogel may be used as a surgical adjunct for glaucoma filtration surgery when used in conjunction with the PAUL® implant developed by Advanced Ophthalmic Innovations Pte. Ltd. CMC is an FDA approved polymer that has been widely used in the pharmaceutical industry, including for ophthalmology.

[0073] FIG. 1 shows a schematic of the preparation of a crosslinked CMC where a commercially available CMC is crosslinked with a linker. In an embodiment, the linker is 1 ,4-Butanediol diglycidyl ether (BDDE).

[0074] In an embodiment, the CMC hydrogel is formulated from a chemically-crosslinked CMC polymer The hydrogel may be synthesised at large scale (1 L batches) and purified by dialysis using deionised water to remove all unreacted crosslinkers and contaminants. Thereafter, lyophilisation affords the dry crosslinked polymer, which may be formulated into hydrogels of the appropriate concentration by mixing with deionised water.

[0075] Geneal procedure to synthesise crosslinked CMC

[0076] Small Scale Synthesis (100 millilitres (mL))

[0077] 1 gram (g) of NaOH pellets was dissolved in 100mL deionised (DI) Water.The solution was heated to 80°C and stirred with a cylindrical stirrer bar at 200 revolutions per minute (RPM). 2 g of high viscosity CMC powder was slowly added one spatula at a time to the solution. In an example, the viscosity of a 1 % solution of the high viscosity CMC in water at 25 °C is 1500 to 3000 centipoise (cps). The stirring was ramped up to 400 RPM, 500 RPM, 600 RPM, 700 RPM, and 800 RPM as CMC was added. The mixture was stirred vigorously until complete dissolution of the CMC. The solution was cooled down to 50°C. 1 mL of 1 ,4-butanediol diglycidyl ether (BDDE) was added with a long needle and syringe. The mixture was stirred vigorously at 800 RPM for 5 minutes (mins) to completely mix the reagent into the CMC solution to obtain a homogeneous solution. The stirring was stopped and the solution incubated overnight at 50°C for 20 hours (hr). A longer reaction time isunlikely to have an adverse effect on the crosslinked CMC. The crude reaction mixture was dialysed by pouring the whole reaction mixture into dialysis tubing of molecular weight cut-off (MWCO) of 3.5 kDa and dialysed against deionised (DI) water for 3 days. The purified sample was freeze dried. The 1 ,4-BDDE crosslinker is potentially toxic, and improper or incomplete removal from the final product can result in biocompatibility and biotoxicity. This may be overcome by thorough purification of the crosslinked polymer after synthesis through dialysis with distilled water over several days.

[0078] Large Scale Synthesis (1000 mL)

[0079] 1000 mL of 0.25M NaOH was prepared by dissolving 10g of NaOH pellets into l OOOmL of DI water. The solution was heated to 60°C and stirred with an overhead stirrer at 350 RPM (set at the 500mL mark). 20g of ultra-high viscosity CMC powder was added 5g at a time with the stirring speed increased with each addition (350 RPM to 500 RPM to 800 RPM to 1050 RPM). In an example, the viscosity of a 1 % solution of the ultra-high viscosity CMC in water at 25 °C is 1500 to 4500 centipoise (cps). The mixture was stirred at 1050 RPM for 3 hours to fully dissolve the ultra-high viscosity CMC. 10 mL 1 ,4-butanediol diglycidyl ether was added with a long needle and syringe at the reaction mid volume (500mL mark). The mixture was stirred vigorously (1200RPM) for 5 min to completely mix the reagent into the CMC solution to obtain a homogeneous solution. The stirring was stopped, and the solution was incubated overnight at 60°C for 20 hours in a pre-heated oven. The crude reaction mixture was dialysed by pouring the whole reaction into dialysis tubing of MWCO of 3.5 kDa and dialysed against DI water for 3 days. The purified sample was freeze dried.

[0080] Formulation of Gel (hydrogel)

[0081] The hydrogel may be formulated by mixing the lyophilised polymer with deionised water or aqueous buffer at the desired weight / volume ratios and centrifuged to remove any trapped air bubbles to obtain the clear, colourless and transparent gel.

[0082] The formulation of Gel was performed by the following procedures:

[0083] The lyophilised polymer was directly weighed into a glass vial and the appropriate quantity of DI Water was added to make up the desired concentration (e.g. 5 wt. % gel would require 50mg of the polymer in 1 mL of DI Water) to dissolvethe polymer in DI water for a day, then centrifuged at 5000 RPM for 7.5mins to remove all air bubbles. Different formulations may be prepared in individual glass vials. All vials were tightly sealed with Parafilm® to ensure a closed system. Instead of water, the hydrogel may be formed with any suitable aqueous buffer.

[0084] Characterisation of gel properties

[0085] All experiments were performed in duplicates.

[0086] Different formulations of the gel were prepared from 0.5 wt. % to 10 wt. %. The different gel formulations were characterised to determine their properties.

[0087] FIG. 2 shows the properties of the gel containing 5 wt.% of the crosslinked CMC polymer prepared from the small scale synthesis. FIG. 2A shows the effect of the temperature on the storage module and loss modulus. FIG. 2B shows a viscosity sweep of the gel. FIG. 2C and FIG. 2D respectively show a frequency sweep and an amplitude sweep of the gel which indicates the material is behaving more like a flowable liquid than a gel.

[0088] Variation of the synthetic process was conducted throughout the project to determine factors which may affect the CMC and the resultant hydrogel. The variations in the process described in the following paragraphs may be made by replacing the relevant part with the variation.

[0089] Reaction Stirring Speeds: An experiment was conducted comparing reactions at 300 RPM and at 500RPM. No significant differences were seen from the different reaction stirring speeds as shown in FIG. 3.

[0090] Different BDDE amounts: The amount of crosslinkers used for the reaction was lowered and no significant differences to the gel strength beyond 0.7 ml_ BDDE was observed as shown in FIG. 4. The procedure used is the same as the small scale synthesis procedure as described above except for the quantities for the BDDE used. For CMC2BDDE1 , 2 g of CMC and 1 mL (5.4 mmol) of BDDE is used. For CMC2BDDE0.7, 2 g of CMC and 0.7 mL of BDDE is used. For CMC2BDDE0.4, 2 g of CMC and 0.4 mL of BDDE is used. Each sample in FIG. 4 and other figures is identified by the quantities of CMC and BDDE used

[0091] Effects of stirring during reaction: The effects of stirring during the reaction process (after adding the crosslinker) and saw no differences between stirring and not stirring during reaction as seen from the viscosities in FIG. 5 with 2g of CMCand 0.4 mL of BDDE used, and for the following experiments no stirring was done during the reaction process (i.e. during the incubation).

[0092] In WO 2020 / 242420 and Della Sala et al., the mixtures are presumably stirred during the reaction. In the present experimental measurements, it was found that there were no significant differences in rheological measurements when the product was stirred during crosslinking or not. Thus, in further optimisation experiments, no stirring was used. The purpose of this is to reduce the batch-to- batch variability during potential GMP manufacturing, as stirring introduces variations in the form of reagent mass transfer that can possibly affect crosslinking efficiency, density and rheological properties of the eventual gel. Stirring of the reaction mixture changes the mass transfer of reagents in the reaction medium and thus produces a different crosslinked carboxymethyl cellulose product. Furthermore, the reaction time in both prior art is fairly short compared to the examples herein. Hence, the crosslinked carboxymethyl cellulose prepared in both prior art documents is believed to have considerably different rheological properties like viscosity from the hydrogel prepared from the crosslinked carboxymethyl cellulose described herein. Stirring of a reaction mixture in the synthesis of a compound is commonly practiced and it is counterintuitive and non-routine in synthesis procedure to not stir the reaction mixture.

[0093] Increasing CMC amounts: Higher concentrations of CMC were tested with 3g and 4g of CMC. The BDDE quantity was held constant at 2mL. The samples were identified by the quantities of CMC and BDDE used. The results showed higher concentrations of CMC resulted in higher viscosities as seen in FIG. 6. The viscosity of 3g and 4g of CMC was almost identical. However, the time required for the CMC to dissolve in 0.25M NaOH during the first step of the protocol was longer at higher CMC concentrations and may not be practical.

[0094] Reaction vessel: To prepare for upscaled productions, the effects of different reaction vessels were tested. It was found that between using a round bottom flask (RBF) and beaker for the reaction, a beaker would result in a much simpler set up for upscaling purposes. There were no difference in viscosities between using the RBF or beaker as shown in FIG. 7. The subsequent experiments were conducted with a beaker as its reaction vessel.

[0095] Upscaling: To test the effects of upscaling the production, FIG. 8 shows that upscaling the production did not affect the viscosities of the resultant gel.

[0096] Repeatability of upscaling: Repeatability of the upscaling production was conducted to test how well the production can be reproduced. FIG. 9 shows that similar viscosities between the gels were able to be maintained compared to small scale production (100mL). FIG. 14 and FIG. 15 shows the viscosity of the gel containing 0.5 wt. % and 10 wt. % of the crosslinked CMC polymer respectively prepared from the upscaling or large scale synthesis of the crosslinked CMC polymer, The 0.5 wt. % formulation had a maximum viscosity of 95 Pa s while the 10 wt. % formulation had a maximum viscosity of 46415 Pa.S.

[0097] Gel Stability

[0098] To study the stability of the gel at different storage conditions, 5 wt. % gel samples were stored at room temperature (in the shade, approximately 25 °C), 4 °C (normal fridge) and -20 °C (freezer) for appropriate durations. The changes in their viscosity were tracked for up to 4 months. Viscosity was measured with a rheometer at 37°C.

[0099] As observed in FIG. 10A (storage at room temperature), FIG. 10B (storage at 4 °C), and FIG. 10C (storage at -20 °C), although there were some fluctuations in the viscosity measured due to unavoidable experimental errors, the viscosity of the gels remained largely unchanged throughout the entire duration of monitoring. Considering these, the formulated gels can be stored at room temperature for at least 4 months (and potentially longer) without significant loss of mechanical integrity. FIG. 15 similarly shows the gel is stable at room temperature.

[0100] Transparency Tests

[0101] The refractive index (Rl) of a 5 wt.% gel formulation and DI water were measured and shown in Table 1 . The data shows the refractive index is almost the same for both. The transparency of the gel may be observed in FIG. 11 .Table 1 : Recorded Refractive Index (Rl) Measurements

[0102] Comparison between described gel and Healaflow®

[0103] A comparison of the rheology of the gel containing 5 wt. % of the crosslinked CMC prepared on a small scale as described herein (termed “initial gel”) and Healaflow was done. Stirring was initially done to mix all the reagents, after which the reaction was left to incubate overnight unstirred in the small scale synthesis of the crosslinked CMC. FIG. 12A shows the storage module and loss modulus at different temperatures of Healaflow on the left and the initial gel on the right. It may be observed that the gel has a substantially larger storage module and loss modulus. FIG. 12B shows the shear rate of the initial gel and Healaflow with the initial gel having a higher viscosity at all shear rates measured with a maximum viscosity double that of Healaflow.

[0104] FIG. 12C shows the angular frequency of Healaflow on the left and the initial gel on the right. The initial gel has a significantly higher storage modulus and loss modulus than Healaflow. The maximum loss modulus was only observed at the extreme end of measurement of the angular frequency while the maximum of the storage modulus is outside the range of the angular frequency measured. The angular frequency is a measure of the material’s time-dependent response to cyclic deformation as a parameter of the gel’s viscoelasticity.

[0105] FIG. 12D shows the amplitude sweep of Healaflow on the left and the initial gel on the right. It may be observed that the initial gel has a significantly higher storage modulus and loss modulus at the measured oscillation strain. The amplitude sweep is a measure of how the material responds to oscillatory deformation (e g. wiggling back and forth) of different size. At certain amplitudes the solid-like gel structure collapses into a flowable liquid. Fig 12D shows that Healaflow retains its gel-like structure up to very high strains (1000%), but the described gel of the embodiments herein transits to a more liquid-like behaviour at lower strains (~100%). Further, the gel if the embodiments herein is much more viscous than Healaflow at biologically-relevant low strains, which may be useful for certain applications, like as a surgical adjunct or viscous lubricant.

[0106] FIG. 13 shows a comparison of the Healaflow and the gel produced on a large scale (beaker of 1000 mL). It may be observed that the gel had a higher viscosity than Healaflow across the shear rates measured. The maximum viscosity of the gel prepared from the crosslinked CMC prepared on a large scale was 3.75times higher than that of Healaflow and almost double that of the gel prepared from the crosslinked CMC prepared on a small scale (see FIG. 12B).

[0107] Animal Studies

[0108] Methodology

[0109] Subconjunctival gel injection procedure:

[0110] (i) A loop thread was used to lift and expose the rabbit’s eyeball. A small opening is made at the conjunctival area to create a pocket.

[0111] (ii) Gels were injected into the subconjunctiva pocket using a 19-G or 27- G needle.

[0112] (iii) The pocket was closed using 7-0 Vicryl suture.

[0113] (iv) Tobradex ointment was subsequently applied into the eyes twice per day for 1 week to prevent eye infections.

[0114] A total of n=6 rabbit eyes were operated with the same procedure. Details are listed in Table 2. The crosslinked CMC gel in Table 2 is prepared as described above.Table 2: Observations After Subconjunctiva Injection In Rabbit Eye

[0115] The gels were injected through either 19G or27G needle / cannula into the subconjunctival pocket in the eye of 6 rabbits. In physical observation, 5 wt. % of the gel was comparable to 1.6 wt. % sodium hyaluronate (Amvisc Plus) which serves as the control, while 7 wt. % of the gel formulation was a bit more viscous. Both 5 wt. % and 7 wt. % formulations can be injected through 27G needle. The 7 wt. % formulation was observed to be a bit harder to push, but can still be injected through. The blebs formed by the 27G cannula were relatively larger than 19G needle on Day 0. The majority of the cases’ blebs (5 of 6) got flatten by Day 1 . The possible reason might be due to the thin conjunctiva in rabbits and the gel within the bleb expanded to other non-injected conjunctiva area when the rabbits were blinking. The only case with a huge bleb (almost detached % of conjunctiva during injection) last for three more days and then became flat. During the entire observation period (2 weeks), there was no inflammation or infection observed in all six cases.

[0116] Subretinal gel injection procedure:

[0117] (i) A loop thread was used to lift and expose the rabbit’s eyeball, followed by a standard three-port pars plana vitrectomy to remove the vitreous.

[0118] (ii) Gels were injected into the subretinal space using a 38-G PolyTip® cannula.

[0119] (iii) The sclerotomy sites were closed using 7-0 Vicryl sutures.

[0120] (iv) Tobradex ointment was subsequently applied into the eyes twice per day for 1 week to prevent infections.

[0121] FIG. 18 shows the use of various gels for subretinal use. The white arrows indicate the bleb region. The retina exhibited thinning relative to the adjacent healthy tissue for the 0.75 wt. % gelatine gel tested. The use of the gel containing 0.5 wt. % of the crosslinked CMC described herein was able to fully reattach the retina at 2 months and the retinal layers were well preserved. Full-field electroretinograms were well preserved in all cases, which was expected as the bleb region is too small to contribute a significant drop or effect on the amplitude of the a-wave and b-wave.

[0122] Sterilisation by steam sterilization

[0123] Sterilisation of the final product cannot be performed during hydrogel formulation using the crosslinked CMC polymer. This necessitates a separate step of steam sterilisation under autoclave conditions, which may add to the productioncosts. However, autoclave sterilisation is a common procedure for GMP manufacture of biomedical products.

[0124] Steam Sterilisation Protocol:

[0125] The sterilisation was done by first removing the Parafilm® and loosening the cap ajar. The vials are then placed in a Tyvek Pouch before placing the pouch into the autoclave. The autoclave parameters were set at the following: 115°C, 15 PSI, 45 mins; 115°C, 15 PSI, 30 mins; 121 °C, 15 PSI, 30mins; and 121°C, 15 PSI, 15mins.

[0126] To investigate the degradability of the gel after the steam sterilisation, a rheological test was conducted on all the samples. In the rheology runs, a flow study from shear rates of 0.01 s-1to 0.1 s-1was conducted at 25°C, and the max viscosity was recorded per sample. Sterilisation for 45 mins at either 115 °C or 121 °C was found to be feasible, with a small decrease in the viscosity of the gel material at both 5 wt. % (left chart of FIG. 17) and 7 wt. % (right chart of FIG. 17) of the crosslinked CMC as shown in FIG. 17.

[0127] A crosslinked CMC polymer concentration of 5 wt. % (i.e. 50 mg polymer in 1 .0 mL deionised water) was been found to be the optimal formulation for PAUL®.

[0128] When formulated at 5 wt. % polymer concentration, the hydrogel has the following desirable characteristics:(a) more viscous and cohesiveness than the incumbent Healaflow® hydrogel and forms a bleb without spreading out when aspirated through needles;(b) optically transparent;(c) injectable through surgically-relevant 27G needles, and therefore suited for surgical application during implantation of PAUL®;(d) amenable to steam sterilisation in an autoclave, which is a common procedure for Good Manufacturing Practice (GMP) manufacturing and thus facilitates manufacturing;(e) stable for at least 4 months when stored at room temperature without any noticeable loss of viscosity as determined by rheology;(f) biocompatible and does not cause inflammation or infection upon subconjunctiva injection on rabbit models.

[0129] Advantages of the hydrogel include the hydrogel may be synthesised in one step in water without the use of organic solvents at any stage, of the processwhich enables greater safety and convenience. This protocol is amenable to upscaling to litre-scales and requires little technical expertise to perform. The ease of synthesis facilitates scaled-up production. The ester linkages formed from epoxide ring-opening enable the polymer hydrogel to be biodegradable and naturally broken down through hydrolysis or through enzymes (esterases), potentially enabling natural removal from the body after implantation that does not require additional removal surgery. The hydrogel may be easily formulated by simply mixing the lyophilised (dry) polymer with water or a suitable aqueous buffer at different weight / volume ratios. The hydrogels formed are highly transparent and aesthetically-pleasing, making them especially suited for ophthalmic applications where optical transparency is highly desired. The formulated hydrogels are injectable through 19G and surgically-relevant 27G needles. The formulated hydrogels are stable for at least 4 months with no appreciable difference in viscosity when stored at room temperature, enabling ease of storage without cold-chain technology.

[0130] The hydrogel may be used as surgical devices for ophthalmic applications such as surgical adjuncts as lubricants, as well as a potential vitreous substitute. Its transparency and injectability may allow it to be used as vitreous substitutes or other ophthalmic applications. Due to its injectability, it is potentially suitable to be used as a drug delivery vehicle and depot for drug release. The hydrogel may also be used as a rheological modifier or thickener in food or cosmetic applications.

Claims

Claims1. A method of preparing a crosslinked carboxymethyl cellulose and / or a salt thereof, the method comprising providing an aqueous solution comprising a salt of carboxymethyl cellulose and a linker compound, the linker compound comprising two or more terminal epoxides, incubating the aqueous solution for at least 4 hours at a temperature from 50 °C to 100 °C to react the salt of carboxymethyl cellulose with the two or more terminal epoxides to obtain the crosslinked carboxymethyl cellulose.

2. The method according to claim 1 , wherein incubating the aqueous solution is done without stirring or agitation.

3. The method according to claim 1 or claim 2, wherein 1 weight percent (wt. %) of the salt of carboxymethyl cellulose in an aqueous solution has a viscosity of at least 1 .5 Pa*s in at 25 °C, preferably 1 weight percent (wt. %) of the salt of carboxymethyl cellulose in an aqueous solution has a viscosity of 1.5 Pa*s to 4.5 Pa*s at 25 °C, more preferably the salt of carboxymethyl cellulose is a sodium salt of carboxymethyl cellulose.

4. The method according to any one of claims 1 to 3, wherein the linker compound is selected from the group consisting of a linear polyether, a branched polyether, a linear hydrocarbon, a branched hydrocarbon, a cyclic hydrocarbon, and combinations thereof, optionally with one or more functional groups within the hydrocarbon, the one or more functional groups selected from the group consisting of an ether, a thioether, an amine, an amide, a carbamide, a carbamate, and combinations thereof.

5. The method according to claim 4, wherein the linker compound is a linear polyether with 2 terminal epoxides or a branched polyether with more than 2 terminal epoxides, the linear polyether or the branched polyether having a weight average molecular weight from 1 kDa to 50 kDa, preferably the weightaverage molecular weight is from 5 kDa to 40 kDa, more preferably the branched polyether has 3 to 10 terminal epoxides.

6. The method according to claim 5, wherein the polyether has a polyethylene glycol backbone or a polypropylene glycol backbone.

7. The method according to any one of claims 1 to 4, wherein the linker compound is selected from the group consisting of Formulaeach R1independently has a formula of Formula IIn, each R2is independently selected from the group consisting of Formula IIa C1-C3 alkyl, and hydrogen, wherein for Formula lb,Formula Ic, Formula Id and Formula le at least two of the R2is of Formula n,A is each independently selected from the group consisting of CH2, 0, S,hydrogen or methyl, R5and R6is each independently hydrogen or a C1 to C3 alkyl, each n in Formula II is independently an integer from 0 to 6 except the n in R1of Formula la cannot both be zero, the value of m is such that the linker compound has a weight average molecular weight from 1 kDa to 50 kDa, preferably the weight average molecular weight is from 5 kDa to 40 kDa.

8. The method according to claim 7, wherein A is each independently selected from the group consisting of CH2, O,preferably A9. The method according to claim 7, wherein the linker compound is of FormulaIIIn3 , A1and A2is each independently selected from the group consisting of CH2, 0, S, NR5, CONR5, R5N(C=O)NR6, and O(C=O)NR5, R5and R6is each independently hydrogen or a C1 to C3 alkyl, ns is an integer from 2 to 13.

10. The method according to claim 9, wherein A1and A2is each oxygen, and ns is an integer from 2 to 8, preferably ns is an integer from 3 to 5, more preferably ns is 4.11 . The method according to any one of claims 1 to 10, wherein at least 0.1 gram of the linker compound is added per gram of the salt of carboxymethyl cellulose or per gram of carboxymethyl cellulose or at least 0.5 mmol of the linker compound is added per gram of the salt of carboxymethyl cellulose or per gram of carboxymethyl cellulose.

12. The method according to claim 11 , wherein 0.1 gram to 4 grams of the linker compound is added per gram of the salt of carboxymethyl cellulose or per gram of carboxy methyl cellulose, preferably 0.1 gram to 2 grams of the linker compound is added per gram of the salt of carboxymethyl cellulose or per gram of carboxymethyl cellulose, more preferably 0.1 gram to 1.5 grams of the linker compound is added per gram of the salt of carboxymethyl cellulose or per gram of carboxymethyl cellulose.

13. The method according to claim 11 , wherein 0.5 mmol to 20 mmol of the linker compound is added per gram of the salt of carboxymethyl cellulose or per gram of carboxymethyl cellulose, preferably 0.5 mmol to 10 mmol of the linker compound is added per gram of the salt of carboxymethyl cellulose or per gram of carboxymethyl cellulose, more preferably 0.5 mmol to 6 mmol of the linker compound is added per gram of the salt of carboxymethyl cellulose or per gram of carboxymethyl cellulose.

14. The method according to any one of claims 1 to 13, wherein providing the aqueous solution comprises dissolving carboxymethyl cellulose or the salt of carboxymethyl cellulose in a second aqueous solution of a base, preferably the base is an inorganic water-soluble base with a pKa of at least 12 in water at 25 °C, more preferably the base is sodium hydroxide or potassium hydroxide; and upon dissolution of the carboxymethyl cellulose or the salt ofcarboxymethyl cellulose, adding the linker compound with stirring to obtain the aqueous solution, which is preferably incubated without delay at the temperature thereafter.

15. The method according to any one of claims 1 to 13, wherein the aqueous solution consists essentially of the salt of carboxymethyl cellulose and the linker compound, preferably the aqueous solution consists of the salt of carboxymethyl cellulose and the linker compound or according to claim 14 wherein the aqueous solution consists essentially of the base, the salt of carboxymethyl cellulose and the linker compound, preferably the aqueous solution consists of the base, the salt of carboxymethyl cellulose and the linker compound.

16. The method according to any one of claims 1 to 15, wherein incubating the aqueous solution is for at least 12 hours, preferably incubating the aqueous solution is for at least 16 hours, more preferably incubating the aqueous solution is for at least 18 hours.

17. The method according to any one of claims 1 to 16, further comprising purifying the crosslinked carboxymethyl cellulose, preferably by dialysis, and lyophilising the purified crosslinked carboxymethyl cellulose, and preferably wherein the salt of the crosslinked carboxymethyl cellulose is not neutralised.

18. A product obtained by any one of the methods according to claims 1 to 17.

19. A composition comprising carboxymethylcellulose crosslinked with a plurality of linking moieties and / or a salt thereof, wherein each linking moiety join two glucopyranose monomer units of carboxymethylcellulose to form a crosslink, the linking moiety comprising two or more hydroxyl groups, wherein 5 wt. % of the crosslinked carboxymethyl cellulose and / or salt thereof in an aqueous solution forms a hydrogel with an average peak viscosity of 10000 Pa*s or less at 37°C.

20. The composition according to claim 19, wherein 5 wt. % of the crosslinked carboxymethyl cellulose and / or salt thereof in an aqueous solution forms a hydrogel with an average peak viscosity from 500 Pa*s to 10000 Pa*S at 37°C, preferably the average peak viscosity is from 1000 Pa*s to 8000 Pa* more preferably the average peak viscosity is from 1200 Pa*s to 6000 Pa*.

21. The composition according to claim 19 or 20, wherein the linking moiety is selected from the group consisting of a linear polyether, a branched polyether, a linear hydrocarbon, a branched hydrocarbon, a cyclic hydrocarbon, and combinations thereof, optionally with one or more functional groups within the hydrocarbon, the one or more functional groups selected from the group consisting of an ether, a thioether, an amine, an amide, a carbamide, a carbamate, and combinations thereof.

22. The composition according to claim 21 , wherein the linking moiety is a linear polyether with 2 hydroxyl groups or a branched polyether with more than 2 hydroxyl groups, the linear polyether or the branched polyether having a weight average molecular weight from 1 kDa to 50 kDa, preferably the weight average molecular weight is from 5 kDa to 40 kDa, more preferably the branched polyether has 3 to 10 hydroxyl groups.

23. The composition according to claim 22, wherein the polyether has a polyethylene glycol backbone or a polypropylene glycol backbone.

24. The composition according to any one of claims 19 to 21 , wherein each linking moiety is selected from the group consisting of Formula I, Formula Iinteger from 1 to 4,each R8in Formula IVa independently has a formula ofneach R9is independently selected from the group consisting ofhydrogen, wherein for Formula IVb, Formula IVc, Formula IVd and Formula IVe atOHleast two of the R9has a formula of n orA is each independently selected from the group consisting of CH2, O, S,R6is each independently hydrogen or a C1 to C3 alkyl, each n is independently an integer from 0 to 6 except n in both R8of Formula IVa cannot both be zero, the value of m is such that the linker compound has a weight average molecular weight from 1 kDa to 50 kDa, preferably the weight average molecular weight is from 5 kDa to 40 kDa.

25. The composition according to claim 24, wherein A is each independently selected from the group consisting of CH2 , O,26. The composition according to claim 24, wherein each linking moiety is independently selected from the group consisting of Formula Va, FormulaVb, Formula Vc and combinations thereof,FormulaA1and A2is each independently selected from the group consisting of CH2, O, S, NR5, CONRs, R5N(C=O)NR6, and O(C=O)NR5, R5and R6is each independently hydrogen or a C1 to C3 alkyl, ns is an integer from 2 to 13.

27. The composition according to claim 26, wherein A1and A2is each oxygen, and ns is an integer from 2 to 8, preferably ns is an integer from 3 to 5, more preferably, ns is 4.

28. The composition according to claim 26 or claim 27, wherein at least 80% of the plurality of linking moieties is Formula Va, more preferably at least 90% of the plurality of linking moieties is Formula Va, even more preferably the plurality of linking moieties is Formula Va.

29. The composition according to any one of claims 19 to 28, wherein the carboxymethylcellulose and / or a salt thereof crosslinked with the plurality of linking moieties is of Formula VII, wherein R10is each independently selected from the group consisting of H, CH2COOH, CH2COO CH2COO-(the linking moiety), and the linking moiety, preferably R10is each independently selected from the group consisting of H, CH2COOH, CH2C00- , and CH2COO(the linking moiety).

30. The composition according to any one of claims 19 to 29 consists essentially of the carboxymethylcellulose crosslinked with the plurality of linking moieties and / or the salt thereof, preferably the composition consists of the carboxymethylcellulose crosslinked with the plurality of linking moieties and / or the salt thereof .

31. The composition according to any one of claims 19 to 30, wherein the carboxymethylcellulose and / or the salt thereof crosslinked with a plurality of linking moieties is lyophilised.

32. A hydrogel comprising 0.5 weight percent (wt. %) to 20 wt. % of the composition according to any one of claims 19 to 31 ; and water, preferably the hydrogel comprises 0.5 wt. % to 10 wt. % of the composition according to any one of claims 19 to 31 ; and water.

33. The hydrogel according to claim 32 comprising a buffer solution, preferably the buffer solution is selected from the group consisting of an acetate buffer, a citrate buffer, a borate buffer, a Tris buffer, and a phosphate buffer.

34. The hydrogel according to claim 32 consist essentially of 0.5 wt. % to 20 wt. % of the composition according to any one of claims 19 to 30; and water or according to claim 33 consist essentially of 0.5 wt. % to 20 wt. % of the composition according to any one of claims 19 to 30; water and the buffer solution, preferably the hydrogel consists of 0.5 wt. % to 20 wt. % of the composition according to any one of claims 19 to 30; and water or according to claim 33 consists of 0.5 wt. % to 20 wt. % of the composition according to any one of claims 19 to 30; water and the buffer solution.

35. The hydrogel according to any one of claims 32 to 34, wherein the composition is present from 2 wt. % to 8 wt. %, preferably the composition is present from 5 wt. % to 7 wt. %.

36. The hydrogel according any one of claims 32 to 35 for use as a medicament, in therapy and / or surgery.

37. The hydrogel according to claim 36 for use in the treatment and / or surgery of an eye disease or as an ophthalmic medicament.

38. The hydrogel according to claim 36 or claim 37 for use in therapy and / or surgery as a lubricant or a vitreous substitute to be administered in an eye.

39. Use of the hydrogel according to any one of claims 32 to 35 in the manufacture of a medicament for the treatment and / or prevention of an eye disease.

40. A method of treating and / or preventing an eye condition, the method comprising administering an effective dose of the hydrogel according any one of claims 32 to 35 to a subject’s eye.

41. The method according to claim 40 comprising inserting a glaucoma implant into an eye of a subject; and administering an effective dose of the hydrogel comprises inserting the hydrogel in a subconjunctival space under a conjunctiva in the eye of the subject.

42. A formulation comprising the hydrogel according to any one of claims 32 to 35; and an active pharmaceutical ingredient.

43. Use of the hydrogel according to any one of claims 32 to 35 as a rheological modifier and / or thickener in cosmetic applications.

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