HYDROGEL COMPRISING A CROSS-LINKED AND SILYLATED POLYSACCHARIDE AND PROCESS FOR OBTAINING SAME

Abstract

The present invention relates to a process for preparing a hydrogel, comprising the following steps: a) provision of a polysaccharide or a salt thereof; b) crosslinking of the polysaccharide in the presence of 0.05 to 10 mol %, preferentially 0.1 to 2 mol %, of at least one crosslinking agent, or a salt thereof, per 1 mol of repeat units of the polysaccharide; c) functionalisation of the polysaccharide with at least one silylated molecule of formula Chem. I or a salt thereof; d) sol-gel reaction of at least one part of the Si—OR.sup.10 groups and optionally at least one part of the SiOR.sup.4 groups of the molecule of formula Chem. I or a salt thereof when they are present.

Claims

1. A process for preparing a hydrogel comprising the following steps: a) providing at least a polysaccharide or a salt thereof; b) cross-linking the polysaccharide in the presence of 0.05 to 10 mol % of at least a cross-linking agent, or a salt thereof, per 1 mole of repeat units of the polysaccharide, the cross-linking agent comprising at least two functional Z groups, which are identical or different, selected from the group consisting of isocyanate, amino, epoxide, carboxyl, N-succinimidyloxycarbonyl, N-sulfosuccinimidyloxycarbonyl, halogenocarbonyl, isothiocyanate, vinyl, formyl, hydroxyl, sulfhydryl, hydrazino, acylhydrazino, aminoxy, carbodiimide, and an acid anhydride residue; c) functionalizing the polysaccharide with at least a molecule of formula Chem. I: ##STR00006## or a salt thereof in which: T represents an isocyanate, amino, epoxide, carboxyl, N-succinimidyloxycarbonyl, N-sulfosuccinimidyloxycarbonyl, halogenocarbonyl, isothiocyanate, vinyl, formyl, hydroxyl, sulfhydryl, hydrazino, acylhydrazino, aminoxy, carbodiimide group, or an acid anhydride residue; A represents a chemical bond or a spacer group; R.sup.5 and R.sup.6, which are identical or different, represent a hydrogen atom; a halogen atom; an —OR.sup.4 group with R.sup.4 representing a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms; an aryl; or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms optionally substituted by one or more group(s) selected from the group consisting of a halogen atom, an aryl and a hydroxyl; R.sup.10 represents a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms; d) sol-gel reacting at least a part of the Si—OR.sup.10 groups and optionally at least a part of the SiOR.sup.4 groups when they are present; in which step b) is carried out before, or concomitantly with step c), or step b) is carried out consecutively to steps c) and d).

2. The process according to claim 1, wherein the polysaccharide is selected from the group consisting of pectin and pectic substances, chitosan, cellulose and derivatives thereof, agarose, glycosaminoglycans, heparosan, chondroitin sulfate, and mixtures thereof.

3. The process according to claim 1 wherein the polysaccharide is hyaluronic acid.

4. The process according to claim 1, wherein the cross-linking agent is a compound of formula Chem. II:
Y—(Z).sub.n in which the Z groups, which are identical or different, are selected from the group consisting of isocyanate, amino, epoxide, carboxyl, N-succinimidyloxycarbonyl, N-sulfosuccinimidyloxycarbonyl, halogenocarbonyl, isothiocyanate, vinyl, formyl, hydroxyl, sulfhydryl, hydrazino, acylhydrazino, aminoxy, carbodiimide, and an acid anhydride residue; n is an integer greater than or equal to 2; Y is a polyvalent hydrocarbon group having a valence of n and including from 1 to 50 carbon atoms: in which one or more units CH2 are optionally replaced by one or more divalent units selected from the group consisting of arylenes, —O—, —S—, —S(O)—, —C(═O)—, —SO.sub.2—, —N(R.sup.1)—, and —[SiR.sup.2R.sup.3O].sub.m—SiR.sup.2R.sup.3—, with R.sup.1 representing a hydrogen atom, an aliphatic hydrocarbon group including from 1 to 6 carbon atoms, or an aryl —(C1-C6)alkyl, m being an integer comprised between 1 and 20, and R.sup.2 and R.sup.3, which are identical or different, representing a hydrogen atom; a halogen atom; an —OR.sup.11 group with R.sup.11 representing a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms; an aryl; or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms optionally substituted by one or more groups selected from the group consisting of a halogen atom, an aryl and a hydroxyl; said polyvalent hydrocarbon group being unsubstituted or substituted by one or more monovalent groups selected from the group consisting of a halogen atom, a hydroxyl and an aryl-(C1-C6)alkyl.

5. The process according to claim 1, wherein the cross-linking agent is a compound of formula Chem. IIa:
Z.sup.1—Y.sup.1—Z.sup.2 in which Z.sup.1 and Z.sup.2, which are identical or different, are selected from the group consisting of isocyanate, amino, epoxide, carboxyl, N-succinimidyloxycarbonyl, N-sulfosuccinimidyloxycarbonyl, halogenocarbonyl, isothiocyanate, vinyl, formyl, hydroxyl, sulfhydryl, hydrazino, acylhydrazino, aminoxy, carbodiimide groups, and an acid anhydride residue, and Y.sup.1 represents a divalent aliphatic hydrocarbon chain including from 1 to 50 carbon atoms: in which one or more units CH2 are optionally replaced by one or more divalent units selected from the group consisting of —O—, —SO.sub.2—, —NH—, and —[SiR.sup.2R.sup.3O].sub.m—SiR.sup.2R.sup.3—, with m an integer comprised between 2 and 20, and R.sup.2 and R.sup.3, which are identical or different, representing a hydrogen atom; a halogen atom; an —OR.sup.11 group with R.sup.11 representing a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms; an aryl; or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms optionally substituted by one or more groups selected from the group consisting of a halogen atom, an aryl and a hydroxyl; said chain being unsubstituted or substituted by one or more monovalent groups selected from the group consisting of a halogen atom, a hydroxyl and an aryl-(C1-C6)alkyl.

6. The process according to claim 1 wherein the functional Z or Z.sup.1 and Z.sup.2 groups are identical and represent an epoxide group.

7. The process according to claim 1 wherein the cross-linking agent is selected from the group consisting of 1,4-butanediol diglycidyl ether (BDDE), 1,2,7,8-diepoxy-octane, poly(ethylene glycol) diglycidyl ether (PEGDGE), 1,2-bis(2,3-epoxypropoxy)ethane (EGDGE), and mixtures thereof.

8. The process according to claim 1, wherein the functional Z or Z.sup.1 and Z.sup.2 groups are identical and selected from the group consisting of amino, vinyl, formyl and carbodiimide groups.

9. The process according to claim 1 wherein A is a divalent aliphatic hydrocarbon chain including from 1 to 12 carbon atoms: in which are optionally interposed, between two carbon atoms of said chain, one or more divalent units selected from the group consisting of arylenes, —O—, —S—, —S(O)—, —C(═O)—, —SO.sub.2— and —N(R.sup.9)— with R.sup.9 representing a hydrogen atom, an aliphatic hydrocarbon group including from 1 to 6 carbon atoms, or an aryl-(C1-C6)alkyl; said chain being unsubstituted or substituted by one or more monovalent groups selected from the group consisting of a halogen atom, a hydroxyl and an aryl-(C1-C6)alkyl.

10. The process according to claim 1 wherein in the molecule of formula Chem. I: T is an isocyanate, amino, epoxide, carboxyl, N-succinimidyloxycarbonyl, N-sulfosuccinimidyloxycarbonyl, halogenocarbonyl, isothiocyanate, vinyl, formyl, hydroxyl, sulfhydryl, hydrazino, acylhydrazino, aminoxy, carbodiimide group, or an acid anhydride residue; A is a divalent chain —(C1-C6)alkylene-O—(C1-C6)alkylene; R.sup.5 and R.sup.6, which are identical or different, are each an —OR.sup.4 group with R.sup.4 representing a (C1-C6)alkyl group; or a (C1-C6)alkyl group and R.sup.10 is a (C1-C6)alkyl group.

11. The process according to claim 1, wherein in step c), the polysaccharide is functionalized in the presence of 5 to 50 mol % of molecule of formula Chem. I or a salt thereof per 1 mole repeat unit of the polysaccharide.

12. The process according to claim 1, wherein steps b) and c) are concomitant.

13. The process according to claim 1, that further comprises a step e) of adding a molecule of formula Chem. III:
R.sup.7O—[R.sup.12R.sup.13SiO].sub.p—R.sup.8 or a salt thereof in which: p is an integer from 1 to 20; R.sup.12 and R.sup.13, which are identical or different, represent a hydrogen atom; a halogen atom; an —OR.sup.14 group with R.sup.14 representing a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms; an aryl; or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms optionally substituted by one or more groups selected from the group consisting of a halogen atom, an aryl and a hydroxyl; and R.sup.7 and R.sup.8, which are identical or different, represent a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms.

14. The process according to claim 1, that further comprises a step f) of adding an additional component selected from the group consisting of anesthetics, antioxidants, amino acids, vitamins, minerals, nucleic acids and mixtures thereof.

15. A hydrogel obtainable according to the process of claim 1.

16. A hydrogel comprising at least a polysaccharide cross-linked with at least one cross-linking bond LR1 and at least one cross-linking bond LR2, the cross-linking bond LR1 comprising at least one unit Si—O—Si, the cross-linking bond LR2, different from the cross-linking bond LR1, being obtained by cross-linking a polysaccharide with at least a cross-linking agent comprising at least two functional Z groups, which are identical or different, selected from the group consisting of isocyanate, amino, epoxide, carboxyl, N-succinimidyloxycarbonyl, N-sulfo succinimidyloxycarbonyl, halogenocarbonyl, isothiocyanate, vinyl, formyl, hydroxyl, sulfhydryl, hydrazino, acylhydrazino, aminoxy, carbodiimide groups, and an acid anhydride residue; the hydrogel having a degree of modification by the cross-linking agent of 0.05 to 10.0%.

17. The hydrogel according to claim 16, wherein the polysaccharide(s) is selected from the group consisting of pectin and pectic substances, chitosan, cellulose and derivatives thereof, agarose, glycosaminoglycans, heparosan or chondroitin sulfate, and mixtures thereof.

18. The hydrogel according to claim 16, wherein the cross-linking agent is a compound of formula Chem. II:
Y—(Z).sub.n in which the Z groups, which are identical or different, are selected from the group consisting of isocyanate, amino, epoxide, carboxyl, N-succinimidyloxycarbonyl, N-sulfosuccinimidyloxycarbonyl, halogenocarbonyl, isothiocyanate, vinyl, formyl, hydroxyl, sulfhydryl, hydrazino, acylhydrazino, aminoxy, carbodiimide, and an acid anhydride residue; n is an integer greater than or equal to 2: Y is a polyvalent hydrocarbon group having a valence of n and including from 1 to 50 carbon atoms: in which one or more units CH.sub.2 are optionally replaced by one or more divalent units selected from the group consisting of arylenes, —O—, —S—, —S(O)—, —C(═O)—, —SO.sub.2—, —N(R.sup.1)—, and —[SiR.sup.2R.sup.3O].sub.m—SiR.sup.2R.sup.3—, with R.sup.1 representing a hydrogen atom, an aliphatic hydrocarbon group including from 1 to 6 carbon atoms, or an aryl —(C1-C6)alkyl, m an integer comprised between 1 and 20, and R.sup.2 and R.sup.3, which are identical or different, representing a hydrogen atom: a halogen atom: an —OR.sup.11 group with R.sup.11 representing a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms: an aryl: or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms optionally substituted by one or more groups selected from the group consisting of a halogen atom, an aryl and a hydroxyl; said polyvalent hydrocarbon group being unsubstituted or substituted by one or more monovalent groups selected from the group consisting of a halogen atom, a hydroxyl and an aryl-(C1-C6)alkyl.

19. The hydrogel according to claim 16 wherein the cross-linking bond LR1 is a divalent group having the following formula Chem. IV:
-G.sup.1-A.sup.1-Si(R.sup.51)(R.sup.61)—O—[SiR.sup.121R.sup.131O].sub.p1—Si(R.sup.52)(R.sup.62)-A.sup.2-G.sup.2- in which: p1 is an integer from 0 to 20, A.sup.1 and A.sup.2, which are identical or different, represent a chemical bond or a spacer group, R.sup.51, R.sup.52, R.sup.61 and R.sup.62, which are identical or different, represent a hydrogen atom; a halogen atom; an —OR.sup.41 group with R.sup.41 representing a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms; an aryl; or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms optionally substituted by one or more group(s) selected from the group consisting of a halogen atom, an aryl and a hydroxyl, R.sup.121 and R.sup.131, which are identical or different, represent a hydrogen atom; a halogen atom; an —OR.sup.141 group with R.sup.141 representing a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms; an aryl; or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms optionally substituted by one or more groups selected from the group consisting of a halogen atom, an aryl and a hydroxyl, and G.sup.1 and G.sup.2, which are identical or different, are binder groups bound to carbon atoms of the polysaccharide(s) and selected from the group consisting of *—O—CO—NH—**, *—NH—CO—NH—, *—CO—NH—**, *—O—CH.sub.2—CH(OH)—**, *—COO—CH.sub.2—CH(OH)—**, *—O—CO—**, *—NH—CO—**, *—O—CS—NH—**, *—NH—CS—NH—, *—O—CH.sub.2—CH.sub.2—**, *—O—CH(OH)—**, *—NH—CH(OH)—**, *—CO—O—**, *—CO—S—**, *═NH—NH—**, *═NH—NH—CO—**, *═NH—O—**, *—CO—NR.sup.a—CO—NH—**, *—O—CO—CH.sub.2—N(CH.sub.2—COOH)—**, *—NH—CO—CH.sub.2—N(CH.sub.2—COOH)—**, *—O—CO—CH.sub.2—CH(COOH)—**, *—NH—CO—CH.sub.2—CH(COOH)—**, *—O—CO—CH═C(COOH)—** and *—NH—CO—CH═C(COOH)—**, where R.sup.a represents an aliphatic hydrocarbon group including from 1 to 20 carbon atoms, one or more carbon atoms of which are optionally replaced by a heteroatom selected from the group consisting of O, S and N, * represents the point of attachment to a carbon atom of the polysaccharide, and ** represents the point of attachment to A.sup.1 for G.sup.1 and to A.sup.2 for G.sup.2.

20. The hydrogel according to claim 19, wherein A.sup.t and A.sup.2, which are identical or different, are each a divalent aliphatic hydrocarbon chain including from 1 to 12 carbon atoms: in which are optionally interposed, between two carbon atoms of said chain, one or more divalent units selected from the group consisting of arylenes, —O—, —S—, —S(O)—, —C(═O)—, —SO.sub.2— and —N(R.sup.9)— with R.sup.9 representing a hydrogen atom, an aliphatic hydrocarbon group including from 1 to 6 carbon atoms, or an aryl-(C1-C6)alkyl; said chain being unsubstituted or substituted by one or more monovalent groups selected from the group consisting of a halogen atom, a hydroxyl and; an aryl-(C1-C6)alkyl.

21. The hydrogel according to claim 19 wherein: G.sup.1 and G.sup.2, which are identical or different, are binder groups bound to carbon atoms of the polysaccharide(s) and selected from the group consisting of *—O—CO—NH—**, *—NH—CO—NH—, *—CO—NH—**, *—O—CH.sub.2—CH(OH)—**, *—COO—CH.sub.2—CH(OH)—**, *—O—CO—**, *—NH—CO—**, *—O—CS—NH—**, *—NH—CS—NH—, *—O—CH.sub.2—CH.sub.2—**, *—O—CH(OH)—**, *—NH—CH(OH)—**, *—CO—O—** *—CO—S—**, *═NH—NH—**, *═NH—NH—CO—**, *═NH—O—**, *—CO—NR.sup.a—CO—NH—**, *—O—CO—CH.sub.2—N(CH.sub.2—COOH)—**, *—NH—CO—CH.sub.2—N(CH.sub.2—COOH)—**, *—O—CO—CH.sub.2—CH(COOH)—**, *—NH—CO—CH.sub.2—CH(COOH)—**, *—O—CO—CH═C(COOH)—** and *—NH—CO—CH═C(COOH)—**, A.sup.1 and A.sup.2 represent, independently of each other, a divalent chain —(C1-C6)alkylene-O—(C1-C6)alkylene; and R.sup.51, R.sup.52, R.sup.61 and R.sup.62 represent, independently of each other, an —OR.sup.41 group with R.sup.41 representing H or a (C1-C6)alkyl group; or a (C1-C6)alkyl group.

22. The hydrogel according to claim 16, that further comprises an additional component selected from the group consisting of anesthetics, antioxidants, amino acids, vitamins, minerals, nucleic acids and mixtures thereof.

23. A cosmetic or pharmaceutical composition comprising a hydrogel according to claim 16.

24. (canceled)

25. An aesthetic method for preventing and/or treating the alteration of the viscoelastic or biomechanical properties of the skin; to fill volume defects of the skin, to reduce the appearance of fine lines and wrinkles; or to regenerate, hydrate, firm or restore the radiance of the skin, that comprises administering to a subject a hydrogel according to claim 16.

26. The hydrogel according to claim 16, wherein the polysaccharide(s) is hyaluronic acid.

27. An aesthetic method for preventing and/or treating the alteration of the viscoelastic or biomechanical properties of the skin; to fill volume defects of the skin, to reduce the appearance of fine lines and wrinkles; or to regenerate, hydrate, firm or restore the radiance of the skin, that comprises administering to a subject a composition according to claim 23.

Description

DETAILED DESCRIPTION

[0105] Process

[0106] The present invention relates to a process for preparing a hydrogel described above, comprising steps a), b), c) and d). This process is advantageously carried out in an aqueous medium.

[0107] In particular, the hydrogel is an injectable hydrogel.

[0108] Step a)

[0109] Step a) of the process according to the invention comprises providing at least a polysaccharide or a salt thereof.

[0110] Preferably, the polysaccharide is selected from pectin and pectic substances; chitosan; cellulose and derivatives thereof; agarose; glycosaminoglycans such as hyaluronic acid, heparosan and chondroitin sulfate; and mixtures thereof.

[0111] In particular, the cellulose derivatives are selected from methylcellulose, ethylcellulose, ethylmethylcellulose, hydroxypropylcellulose (HPC), hydroxypropylmethylcellulose (HPMC), hydroxyethylcellulose (HEC), and carboxymethylcellulose (CMC).

[0112] Advantageously, the polysaccharide is a glycosaminoglycan, preferably hyaluronic acid or a salt thereof, more preferably hyaluronic acid or one of its physiologically acceptable salts such as sodium salt, potassium salt, zinc salt, silver salt and mixtures thereof, even more preferably hyaluronic acid or its sodium salt.

[0113] Preferably, the polysaccharide has a weight-average molecular mass Mw comprised between 0.05 and 10 MDa, preferentially between 0.5 and 5 MDa, for example between 0.5 and 4 MDa or between 0.5 and 2 MDa.

[0114] In particular, in step a) the polysaccharide is supplied in hydrated form, totally or partially, or in dry form, such as in powder or fiber form. More particularly, in step a), the polysaccharide is provided in dry form such as in powder or fiber form.

[0115] When the polysaccharide is provided in hydrated form, it is in the form of a non-cross-linked gel or a solution.

[0116] In particular, when the polysaccharide is in hydrated form, it is an aqueous non-cross-linked gel or an aqueous solution. More particularly, the polysaccharide is mixed with water, optionally added with a phosphate buffer or with a supplemented phosphate buffer, that is to say possibly comprising additional components as defined in step f), or an alkaline medium adapted for step b).

[0117] Step b)

[0118] Step b) of the process according to the invention comprises the cross-linking of the polysaccharide provided in step a) in the presence of 0.05 to 10 mol % of at least a cross-linking agent per 1 mole of repeat unit of the polysaccharide, said cross-linking agent comprising at least two functional Z groups as described below.

[0119] When the polysaccharide is a glycosaminoglycan such as hyaluronic acid, the repeat unit is therefore a disaccharide unit.

[0120] The functional Z groups, which are identical or different, are selected from isocyanate, amino, epoxide, carboxyl, N-succinimidyloxycarbonyl, N-sulfosuccinimidyloxycarbonyl, halogenocarbonyl, isothiocyanate, vinyl, formyl, hydroxyl, sulfhydryl, hydrazino, acylhydrazino, aminoxy, carbodiimide groups, and an acid anhydride residue.

[0121] Advantageously, the functional Z groups are identical.

[0122] Preferably, the functional Z groups are identical and represent an epoxide or vinyl group, more preferably epoxide.

[0123] According to another advantageous embodiment, the functional Z groups are identical and selected from amino, vinyl, formyl and carbodiimide groups, preferably are amino groups.

[0124] In particular, the cross-linking agent is selected from hexamethylene diisocyanate, diphenylmethylene 4,4′-diisocyanate, 4-arm PEG20K-isocyanate, spermine (or 1,12-diamino-5,9-diazadodecane), spermidine (or 1,8-diamino-5-azaoctane), cadaverine (or 1,5-diaminopentane), putrescine (or 1,4-diaminobutane), poly(ethylene glycol) diamine, ethylenediamine, 1,4-butanediol diglycidyl ether (BDDE), 1,2,7,8-diepoxy-octane, poly(ethylene glycol) diglycidyl ether (PEGDGE), 1,2-bis(2,3-epoxypropoxy) ethane (EGDGE), 1,3-bis(3-glycidyloxypropyl) tetramethyldisiloxane, poly(dimethylsiloxane) terminated at each end with a diglycidyl ether (CAS number: 130167-23-6), poly(ethylene glycol) diacid, disuccinimidyl suberate, bis(sulfosuccinimidyl)suberate, sebacoyl chloride, 1,4-butane diisothiocyanate, divinylsulfone (DVS), glutaraldehyde, polyethylene glycol, 1,5-pentanedithiol, adipic acid dihydrazid, bis-aminooxy-poly(ethylene glycol), diethylenetriaminepentaacetic acid dianhydride, and mixtures thereof.

[0125] When the functional Z groups are epoxide groups, the cross-linking agent is preferably selected from 1,4-butanediol diglycidyl ether (BDDE), 1,2,7,8-diepoxy-octane, poly (ethylene glycol) diglycidyl ether (PEGDGE), 1,2-bis(2,3-epoxypropoxy)ethane (EGDGE), 1,3-bis(3-glycidyloxypropyl)tetramethyldisiloxane, poly(dimethylsiloxane) terminated at each end with a diglycidyl ether (CAS number: 130167-23-6), hydroxyapatite beads modified to carry epoxy groups and mixtures thereof.

[0126] More preferably, the cross-linking agent is selected from 1,4-butanediol diglycidyl ether (BDDE), 1,2,7,8-diepoxy-octane, poly(ethylene glycol) diglycidyl ether (PEGDGE), 1,2-bis(2,3-epoxypropoxy)ethane (EGDGE), and mixtures thereof.

[0127] When the functional Z groups are amino groups, the cross-linking agent is preferably a polyamine selected from spermine (or 1,12-diamino-5,9-diazadodecane), spermidine (or 1,8-diamino-5-azaoctane), cadaverine (or 1,5-diaminopentane), putrescine (or 1,4-diaminobutane), salts thereof or a mixture thereof, more preferably the cross-linking agent is a polyamine selected from spermine, spermidine, salts thereof and mixtures thereof.

[0128] When the functional Z groups are amino groups, the cross-linking reaction with the polysaccharide is advantageously carried out in the presence of at least an activator, and where appropriate combined with at least a coupling auxiliary.

[0129] In this regard, the activator can be selected from water-soluble carbodiimides such as 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), 1-ethyl-3-[3-(trimethylamino) propyl]carbodiimide hydrochloride (ETC), 1-cyclohexyl-3-(2-morphilinoethyl)carbodiimide (CMC), salts thereof and mixtures thereof, preferably is represented by EDC.

[0130] As regards the coupling auxiliary, when present, it can be selected from N-hydroxy succinimide (NHS), N-hydroxybenzotriazole (HOBt), 3,4-dihydro-3-hydroxy-4-oxo-1,2,3-benzotriazole (HOOBt), 1-hydroxy-7-7azabenzotriazole (HAt) and N-hydroxysylfosuccinimide (sulfo NHS), and mixtures thereof, preferably is represented by HOBt.

[0131] The cross-linking agent can be selected from hydroxyapatite beads modified to carry epoxy groups, a compound of formula Chem. II as described below, and mixtures thereof.

[0132] Preferably, the cross-linking agent is a compound of formula Chem. II:

Y—(Z).sub.n

in which the Z groups, which are identical or different, are as defined above, n is an integer greater than or equal to 2, in particular ranging from 2 to 8, preferably equal to 2,
Y is a polyvalent hydrocarbon group, in particular aliphatic, having a valence of n and including from 1 to 150 carbon atoms: [0133] in which one or more (for example 1 to 150, or else 1 to 50 or else 1 to 15 or else 1 or 2) units CH.sub.2 are optionally replaced by one or more divalent units selected from arylenes; —O—; —S—; —S(O)—; —C(═O)—; —SO.sub.2—; —N(R.sup.1)—; and —[SiR.sup.2R.sup.3O].sub.m—SiR.sup.2R.sup.3— with: [0134] R.sup.1 representing a hydrogen atom, an aliphatic hydrocarbon group including from 1 to 6 carbon atoms, or an aryl-(C1-C6)alkyl; [0135] m an integer comprised between 1 and 20 and [0136] the R.sup.2 and the R.sup.3, which are identical or different, representing a hydrogen atom; a halogen atom; an —OR.sup.11 group with R.sup.11 representing a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms; an aryl; or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms optionally substituted by one or more groups selected from a halogen atom, an aryl or a hydroxyl, [0137] said polyvalent group being unsubstituted or substituted by one or more monovalent groups selected from a halogen atom, a hydroxyl, and an aryl- (C1-C6)alkyl, preferably unsubstituted.

[0138] In particular n is an integer ranging from 2 to 8, preferably n represents 2, 3 or 4, even more preferably n is equal to 2.

[0139] Advantageously, R.sup.1 represents a hydrogen atom or a (C1-C6)alkyl group.

[0140] In particular, R.sup.2 and R.sup.3, which are identical or different, represent an aliphatic hydrocarbon group including from 1 to 6 carbon atoms, more particularly a (C1-C6)alkyl group.

[0141] Preferably, in the definition of Y, the hydrocarbon polyvalent group may be an aliphatic or aromatic hydrocarbon polyvalent group, preferably aliphatic and in particular saturated, having a valence of n and including from 1 to 150 carbon atoms, preferentially from 1 to 50 carbon atoms, more preferably from 1 to 20 carbon atoms, even more preferably from 2 to 20 carbon atoms.

[0142] In particular, in the definition of Y, the hydrocarbon polyvalent group is a linear, saturated, aliphatic hydrocarbon polyvalent group.

[0143] Preferably, Y is a hydrocarbon polyvalent group as described above in which one or more units CH.sub.2 are optionally replaced by one or more divalent units selected from —O—, —SO.sub.2, —[SiR.sup.2R.sub.3O].sub.m—SiR.sup.2R.sup.3— and —NH—, with R.sup.2, R.sup.3 and m as described above.

[0144] In particular, Y is a hydrocarbon polyvalent group as described above, preferably aliphatic and saturated, and in particular linear, branched, or starred, and optionally in which: [0145] at least two units CH.sub.2 are replaced by —O—, particularly between 1 and 50 units CH.sub.2, more particularly between 1 and 15 units CH.sub.2, or [0146] at least one, preferably one or two, units CH.sub.2 is replaced by a unit —NH—, or [0147] at least one, preferably one, unit CH.sub.2 is replaced by a unit —SO.sub.2—, or [0148] at least two, preferably two, units CH.sub.2 are replaced by —O— and at least one, preferably one, unit CH.sub.2 is replaced by a unit —[SiR.sup.2R.sup.3O].sub.m—SiR.sup.2R.sup.3— with R.sup.2, R.sup.3 and m as described above.

[0149] More particularly, when one or more units CH.sub.2 are replaced by —O—, the replaced unit(s) are such that Y comprises one or more —CH.sub.2—CH.sub.2—O— units. In particular, Y comprises from 1 to 50 units —CH.sub.2—CH.sub.2—O—, advantageously from 2 to 25 units —CH.sub.2—CH.sub.2—O—, more advantageously from 2 to 15 units —CH.sub.2—CH.sub.2—O—. Y can comprise only units —CH.sub.2—CH.sub.2—O—. More preferably, Y is an alkyl group comprising 1 to 150, in particular 1 to 50, in particular 1 to 20, for example 1 to 12, in particular 1 to 6 carbon atoms, preferably linear, in which optionally one or more units CH.sub.2 are replaced by one or more divalent units selected from —O— and —NH—, more particularly between 1 and 50, in particular between 1 and 15, for example 1 or 2, divalent units selected from —O— and —NH—.

[0150] According to a first embodiment, the R.sup.2 and the R.sup.3, which are identical or different, represent an —OR.sup.11 group with R.sup.11 as described above. In particular, R.sup.11 represents an aliphatic hydrocarbon group including from 1 to 6 carbon atoms, more particularly a (C1-C6)alkyl group.

[0151] According to a second embodiment, the R.sup.2 and the R.sup.3, which are identical or different, represent an aliphatic hydrocarbon group including from 1 to 6 carbon atoms optionally substituted (preferably unsubstituted) by one or more groups selected from a halogen atom, an aryl or a hydroxyl, more preferably an unsubstituted (C1-C6)alkyl group such as methyl or ethyl.

[0152] Advantageously, the cross-linking agent is a compound having the following formula Chem. IIa:

Z.sup.1—Y.sup.1—Z.sup.2

[0153] in which the Z.sup.1 and Z.sup.2 groups, which are identical or different, are selected from isocyanate, amino, epoxide, carboxyl, N-succinimidyloxycarbonyl, N-sulfosuccinimidyloxycarbonyl, halogenocarbonyl, isothiocyanate, vinyl, formyl, hydroxyl, sulfhydryl, hydrazino, acylhydrazino, aminoxy, carbodiimide groups, and an acid anhydride residue,

[0154] and Y.sup.1 represents a divalent hydrocarbon chain, in particular aliphatic, including from 1 to 50 carbon atoms: [0155] in which one or more (for example 1 to 15 or else 1 or 2) units CH.sub.2 are optionally replaced by one or more divalent units selected from arylenes, —O—, —S—, —S(O)—, —C(═O)—, —SO.sub.2—, —N(R.sup.1)—, and —[SiR.sup.2R.sup.3O].sub.m—SiR.sup.2R.sup.3— with [0156] R.sup.1 representing a hydrogen atom, an aliphatic hydrocarbon group including from 1 to 6 carbon atoms, or an aryl-(C1-C6)alkyl, [0157] m an integer comprised between 2 and 20, and [0158] the R.sup.2 and the R.sup.3, which are identical or different, representing a hydrogen atom; a halogen atom; a —OR.sup.11 group with R.sup.11 representing a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms; an aryl; or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms optionally substituted by one or more groups selected from a halogen atom, an aryl or a hydroxyl, [0159] said chain being unsubstituted or substituted by one or more monovalent groups selected from a halogen atom, a hydroxyl, an aryl-(C1-C6)alkyl.

[0160] The Z.sup.1 and Z.sup.2 groups have the same definition as the Z group defined above.

[0161] Y.sup.1 has the same definition as Y defined above with a valence n being equal to 2.

[0162] In particular, Y.sup.1 can only comprise units —CH.sub.2—CH.sub.2—O—, as defined previously.

[0163] Preferably, the cross-linking agent of formula Chem. II or Chem. IIa does not comprise units —[SiR.sup.2R.sup.3O].sub.m—SiR.sup.2R.sup.3—.

[0164] The cross-linking of the polysaccharide provided in step a) takes place in the presence of 0.05 to 10 mol %, in particular from 0.05 to 7 mol %, more advantageously from 0.05 to 5 mol %, even more advantageously from 0.1 to 2 mol % and in particular from 0.1 to 1 mol %, of at least a cross-linking agent per 1 mole of repeat unit of the polysaccharide.

[0165] The mass concentration of polysaccharide in the cross-linking medium is advantageously comprised between 50 and 300 mg/g of cross-linking medium, preferably between 100 and 200 mg/g.

[0166] In particular, the cross-linking takes place in an aqueous reaction medium. However, if necessary, an organic solvent such as an alcohol, in particular ethanol, or DMSO can be used to solubilize the cross-linking agent, for example when it comes to the poly(dimethylsiloxane) terminated at each end with a diglycidyl ether (CAS number: 130167-23-6) before addition to the aqueous reaction medium.

[0167] Advantageously, and in particular when the Z groups, such as Z.sup.1 or Z.sup.2, represent an epoxy group or a vinyl group, the cross-linking takes place at a pH greater than or equal to 10, more advantageously greater than or equal to 12.

[0168] For this purpose, the reaction medium preferably comprises a Bronsted base, more preferably a hydroxide salt, such as sodium or potassium hydroxide.

[0169] Preferably, the cross-linking takes place between 4° C. and 60° C., more preferably between 10° C. and 50° C.

[0170] In particular, the cross-linking takes place between 1 hour and 2 weeks, more particularly between 3 hours and 1 week.

[0171] In the presence of several cross-linking agents, the cross-linking agents can be added simultaneously or separately over time. Step b) can thus comprise repeated cross-linking steps. The total cross-linking rate in cross-linking agents varies from 0.05 to 10% molar as defined previously.

[0172] This step allows to cross-link the polysaccharide chains with each other. The functional groups of the cross-linking agent react with functional groups present on the polysaccharides so as to bond the polysaccharide chains with each other and to cross-link them by forming intermolecular bonds. The cross-linking agent can also react with functional groups present on the same polysaccharide molecule so as to form intramolecular bonds. In particular, the functional groups of the cross-linking agent react with the —OH or —COOH, or else —CHO groups, present on the polysaccharides such as hyaluronic acid. Cross-linked polysaccharides comprising at least one cross-linking bond between two polysaccharide chains are thus obtained, said cross-linking bond being the residue of the cross-linking agent from step b).

[0173] In particular, following step b), the cross-linked polysaccharides comprise at least one cross-linking bond between two polysaccharide chains, said cross-linking bond comprising more particularly the polyvalent Y group as described above, preferably the divalent Y.sup.1 group as described above.

[0174] Some functional Z (such as Z.sup.1 and Z.sup.2) groups of the cross-linking agent may however not react with a polysaccharide chain.

[0175] In particular, when the cross-linking agent includes two functional Z.sup.1 and Z.sup.2 groups, one of the functional Z.sup.1 groups can react with a polysaccharide while the other functional Z.sup.2 group does not react with any polysaccharide. A dangling bond is then formed.

[0176] Step c)

[0177] Step c) of the process according to the invention comprises the functionalization of the polysaccharide with at least a molecule having the following formula Chem. I:

##STR00005##

or a salt thereof,
in which: [0178] T represents an isocyanate, amino, epoxide, carboxyl, N-succinimidyloxycarbonyl, N-sulfosuccinimidyloxycarbonyl, halogenocarbonyl, isothiocyanate, vinyl, formyl, hydroxyl, sulfhydryl, acylhydrazino, aminoxy, carbodiimide group, or an acid anhydride residue; [0179] A represents a chemical bond or a spacer group; [0180] R.sup.5 and R.sup.6, which are identical or different, represent a hydrogen atom; a halogen atom; an —OR.sup.4 group with R.sup.4 representing a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms; an aryl; or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms optionally substituted by one or more groups selected from a halogen atom, an aryl and a hydroxyl; [0181] R.sup.10 represents a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms.

[0182] Advantageously, T represents an isocyanate, sulfhydryl, amino, epoxide, vinyl, formyl or carbodiimide group, more advantageously, T represents an epoxide or amino group, even more advantageously T represents an epoxide group.

[0183] In particular, the T group of the molecule of formula Chem. I and the Z or Z.sup.1 and Z.sup.2 groups of the molecule of formula Chem. II/Chem. IIa are identical.

[0184] Preferably, A represents a spacer group, more preferably a divalent aliphatic hydrocarbon chain, in particular linear or branched and saturated, including from 1 to 12 carbon atoms: [0185] in which are optionally interposed, between two carbon atoms of said chain, one or more (in particular 1, 2, 3 or 4) divalent units selected from arylenes, —O—, —S—, —S(O)—, —C(═O)—, —SO.sub.2— and —N(R.sup.9)— with R.sup.9 representing a hydrogen atom, an aliphatic hydrocarbon group including from 1 to 6 carbon atoms, or an aryl-(C1-C6)alkyl, [0186] said chain being unsubstituted or substituted by one or more monovalent groups selected from a halogen atom, a hydroxyl, an aryl-(C1-C6)alkyl.

[0187] Advantageously, A is a divalent aliphatic hydrocarbon chain, in particular linear or branched and saturated, in which are optionally interposed, between two carbon atoms of said chain, one or more divalent units —O—, more advantageously from 1 to 4 divalent units —O—, even more preferably one divalent unit O.

[0188] Preferably, A is a (C1-C12)alkylene chain in which are optionally interposed, between two carbon atoms of said chain, one or more divalent units —O—, more preferably from 1 to 4 divalent units —O—, even more preferably one divalent unit —O—.

[0189] In particular, A represents a divalent chain —(C1-C6)alkylene-O—(C1-C6)alkylene-, in particular —(C1-C4)alkylene-O—(C1-C4)alkylene-, more particularly a divalent chain —CH.sub.2—O—(CH.sub.2).sub.3—, the CH.sub.2 group being bonded to T and the (CH.sub.2).sub.3 group being bonded to Si in the molecule of formula Chem. I.

[0190] Advantageously, R.sup.5 and R.sup.6, which are identical or different, represent an —OR.sup.4 group with R.sup.4 representing a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms; or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms optionally substituted by one or more groups selected from a halogen atom, an aryl and a hydroxyl.

[0191] In particular, R.sup.5 and R.sup.6, which are identical or different, represent an —OR.sup.4 group with R.sup.4 representing a (C1-C6)alkyl group; or a (C1-C6)alkyl group.

[0192] Advantageously, R.sup.5 and R.sup.6, which are identical or different, represent an —OR.sup.4 group with R.sup.4 representing a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms, preferably with R.sup.4 representing an aliphatic hydrocarbon group including from 1 to 6 carbon atoms, such as a (C1-C6)alkyl group.

[0193] Advantageously, R.sup.10 represents a hydrogen atom or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms such as a (C1-C6)alkyl group, more advantageously R.sup.10 represents an aliphatic hydrocarbon group including from 1 to 6 carbon atoms such as a (C1-C6)alkyl group.

[0194] Preferably, the molecule of formula Chem. I is such that: [0195] T is as defined above and advantageously represents an amino or epoxide group, preferably an epoxide group; [0196] A is a divalent chain —(C1-C6)alkylene-O—((C1-C6)alkylene-, in particular —(C1-C4)alkylene-O—(C1-C4)alkylene-, such as —CH.sub.2—O—(CH.sub.2).sub.3—, the CH.sub.2 group preferably being bonded to T and the (CH.sub.2).sub.3 group being bonded to Si in the molecule of formula Chem. I; [0197] R.sup.5 and R.sup.6, which are identical or different, are each an —OR.sup.4 group with R.sup.4 representing a (C1-C6)alkyl group, preferably a methyl or an ethyl; or a (C1-C6)alkyl group, preferably a methyl or an ethyl; and [0198] R.sup.10 is a (C1-C6)alkyl group, preferably methyl or ethyl; [0199] the R.sup.5, R.sup.6 and OR.sup.10 groups possibly being identical.

[0200] In particular, the molecule of formula Chem. I is selected from (3-glycidyloxypropyl)trimethoxysilane (GPTMS), 3-Glycidoxypropyldimethoxymethylsilane, 3-Glycidoxypropyldimethylethoxysilane, (3-glycidyloxypropyl)ethoxydimethoxysilane, (3-glycidyloxypropyl)triethoxysilane, diethoxy(3-glycidyloxypropyl)methylsilane, and mixtures thereof; preferably from (3-glycidyloxypropyl)trimethoxysilane (GPTMS), (3-glycidyloxypropyl)ethoxydimethoxysilane, (3-glycidyloxypropyl)triethoxysilane, diethoxy(3-glycidyloxypropyl)methylsilane, and mixtures thereof.

[0201] Preferably, in step c), the polysaccharide is functionalized in the presence of 5 to 50 mol %, preferentially of 10 to 45 mol %, in particular of 20 to 45 mol %, for example of 30 mol % to 45 mol %, or else in the presence of 5 to 25 mol %, in particular of 10 to 25 mol %, for example of 15 mol % to 25 mol %, of molecule of formula Chem. I or a salt thereof per 1 mole repeat unit of the polysaccharide.

[0202] The mass concentration of polysaccharide in the functionalization medium is advantageously comprised between 50 and 300 mg/g of functionalization medium, preferably between 100 and 200 mg/g.

[0203] In general, the amount of functionalizing agent increases when the amount of cross-linking agent is reduced, and vice versa.

[0204] Advantageously, the cross-linking of the polysaccharide takes place in step b) in the presence of 0.05 to 2 mol % or 0.05 to 1 mol % of at least a cross-linking agent per 1 mole of repeat unit of the polysaccharide, and the functionalization of the polysaccharide takes place in step c) in the presence of 10 mol % to 50 mol %, in particular from 10 mol % to 45 mol %, preferably from 30 mol % to 45 mol %, or else in the presence of 5 mol % to 50 mol %, in particular from 10 mol % to 25 mol %, preferably from 15 mol % to 25 mol %, of molecule of formula Chem. I or a salt thereof per 1 mole repeat unit of the polysaccharide.

[0205] Advantageously, the cross-linking of the polysaccharide takes place in step b) in the presence of 2 mol % to 10 mol % or 1 to 10 mol % of at least a cross-linking agent per 1 mole of repeat unit of the polysaccharide, and the functionalization of the polysaccharide takes place in step c) in the presence of 5 mol % to 50 mol %, in particular from 10 mol % to 45 mol %, preferably from 5 mol % to 25 mol % or 20 mol % or 45 mol % of molecule of formula Chem. I or a salt thereof per 1 mole repeat unit of the polysaccharide.

[0206] In particular, the functionalization takes place in an aqueous reaction medium.

[0207] Advantageously, and in particular when T is an epoxide, the functionalization takes place at a pH greater than or equal to 10, more advantageously greater than or equal to 12.

[0208] For this purpose, the reaction medium preferably comprises a Bronsted base, more preferably a hydroxide, even more preferably a sodium or potassium hydroxide.

[0209] Preferably, the functionalization takes place between 4° C. and 60° C., more preferably between 10° C. and 50° C.

[0210] In particular, the functionalization takes place between 1 hour and 2 weeks, more particularly between 3 hours and 1 week.

[0211] Step c) allows to functionalize the polysaccharide chains. The functional group T of the molecule of formula Chem. I thus reacts with a functional group present on the polysaccharides so as to functionalize the polysaccharide chains. In particular, the T functional group of the molecule Chem. I thus reacts with an —OH or —COOH group, or else a CHO function, present on polysaccharides such as hyaluronic acid.

[0212] Functionalized polysaccharides comprising dangling bonds on a polysaccharide chain are thus obtained, said dangling bonds comprising an -A-Si(R.sup.5)(R.sup.6)OR.sup.10 group, the -A-Si(R.sup.5)(R.sup.6)OR.sup.10 group from the molecule of formula Chem. I of step c) which can provide biological properties to the hydrogel.

[0213] Advantageously, steps b) and c) are concomitant.

[0214] Step d)

[0215] Step d) of the process according to the invention comprises a sol-gel reaction of at least part of the Si—OR.sup.10 groups and optionally of at least part of the SiOR.sup.4 groups when they are present.

[0216] This step also allows to cross-link the polysaccharide chains with one another when they are functionalized with molecules of formula Chem. I. Indeed, during this step, at least part of the Si—OR.sup.10 groups and optionally at least part of the SiOR.sup.4 groups will react in pairs, possibly after hydrolysis of these groups, to form Si—O—Si bonds. This implies that two molecules with the formula Chem. I grafted onto polysaccharide chains will react together via their terminal Si—OR.sup.10 (or even SiOR.sup.4 if necessary) groups and bind covalently via the formation of Si—O—Si bonds, thus allowing to bind the polysaccharide chains together and further cross-link them.

[0217] Cross-linked polysaccharides are thus obtained comprising cross-linking bonds between two polysaccharide chains, said cross-linking bonds comprising a divalent —Si—O—Si— group.

[0218] Therefore, step d) cannot take place before step c). It is in particular at least partly concomitant with step c).

[0219] As defined previously, the sol-gel reaction comprises one or two sub-steps, namely a hydrolysis sub-step d1) carried out only when R.sup.10 (or R.sup.4) is not a hydrogen atom and a condensation sub-step d2).

[0220] Advantageously, the hydrolysis step d1) takes place at a pH greater than 9, preferably greater than 10, more preferably greater than 12.

[0221] For this purpose, the reaction medium preferably comprises a Bronsted base, more preferably a hydroxide, even more preferably a sodium or potassium hydroxide.

[0222] Preferably, the hydrolysis takes place between 4° C. and 60° C., more preferably between 10° C. and 50° C.

[0223] In particular, the hydrolysis takes place between 1 hour and 2 weeks, more particularly between 3 hours and 1 week.

[0224] Step c) and step d1), when the latter takes place, are therefore preferably concomitant since they can be carried out under the same reaction conditions.

[0225] The condensation step d2) can take place at a pH greater than 9 but with slow kinetics.

[0226] This is why it is preferable to use other reaction conditions to promote this condensation, such as in particular lowering the pH to a value for example ranging from 6.8 to 7.8 or partially or completely drying (in particular dehydrating when the reaction medium is aqueous) the reaction medium (for example by heating (for example at 40-60° C.) optionally under vacuum, by placement under vacuum at room temperature (for example 20-25° C.), by freeze-drying).

[0227] Thus, the condensation step d2) will generally comprise: [0228] a pre-condensation step d21) concomitant with the functionalization step c) and with the hydrolysis step d1) if necessary, during which part of the Si—OR.sup.10 groups and optionally of the SiOR.sup.4 groups will condense with one another; and [0229] an advanced condensation step d22) after the functionalization step c) and the hydrolysis step d1) if necessary, during which more Si—OR.sup.10 groups and optionally SiOR.sup.4 groups will condense with one another.

[0230] During the advanced condensation step d22), the reaction medium is preferably dried or the pH is comprised between 6.8 and 7.8.

[0231] Thus, step d) is preferably carried out partly concomitantly with step c) then is favored by changing the reaction conditions as described above.

[0232] Step e)

[0233] Preferably, the process according to the invention further comprises a step e) of adding a molecule having the following formula Chem. III:

R.sup.7O—[R.sup.12R.sup.13SiO].sub.p—R.sup.8

or a salt thereof
in which: [0234] p is an integer from 1 to 20; [0235] R.sup.12 and R.sup.13, which are identical or different, represent a hydrogen atom; a halogen atom; an —OR.sup.14 group with R.sup.14 representing a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms; an aryl; or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms optionally substituted by one or more groups selected from a halogen atom, an aryl or a hydroxyl; and [0236] R.sup.7 and R.sup.8, which are identical or different, represent a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms.

[0237] Preferably, R.sup.12 and R.sup.13, which are identical or different, represent an —OR.sup.14 group with R.sup.14 representing a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms; an aryl; or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms optionally substituted by one or more groups selected from a halogen atom, an aryl or a hydroxyl.

[0238] In particular, R.sup.12 and R.sup.13, which are identical or different, represent an —OR.sup.14 group with R.sup.14 representing a hydrogen atom, an aliphatic hydrocarbon group including from 1 to 6 carbon atoms, preferably a (C1-C6)alkyl group; or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms, preferably a (C1-C6)alkyl group.

[0239] Advantageously, R.sup.7 and R.sup.8, which are identical or different, represent a hydrogen atom, or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms, preferably a (C1-C6)alkyl group.

[0240] This molecule of formula Chem. III includes Si—OR groups (Si—OR.sup.7, Si—OR.sup.8 and optionally Si—OR.sup.14) capable of reacting with the Si—OR (Si—OR.sup.10 and optionally Si—OR.sup.4) groups of the molecule of formula Chem. I. Thus, during the sol-gel reaction allowing the formation of Si—O—Si bonds, a molecule of formula Chem. III can bind to two molecules of formula Chem. I grafted onto polysaccharide chains so as to form cross-linking bonds resulting from the coupling of a molecule of formula Chem. III with two molecules of formula Chem. I.

[0241] For example, the molecule of formula Chem. III is orthosilicic acid, tetraethyl orthosilicate (TEOS), polydimethylsiloxane (PDMS), oligomerized TEOS/orthosilicic acid, or methyl silanetriol (preferably used in the form of its sodium salt called sodium methyl siliconate—NaMS).

[0242] This step e) can be carried out after step d).

[0243] Preferably, step e) is carried out before or concomitantly with step d), in particular during step d21).

[0244] Step f)

[0245] Advantageously, the process according to the invention further comprises a step f) of adding an additional component selected from anesthetics, antioxidants, amino acids, vitamins, minerals, nucleic acids and mixtures thereof as described below.

[0246] Step g) Preferably, the process further comprises a purification step g), in particular by dialysis.

[0247] According to a particular embodiment, the purification is carried out after steps b) and c).

[0248] Preferably, the purification is carried out after steps b), c) and d).

[0249] More preferably, the purification is carried out after steps b), c), d1) and d21) and before step d22).

[0250] Step h)

[0251] Advantageously, the process further comprises a sterilization step h), in particular a heat sterilization step carried out at a plateau temperature comprised between 121° C. and 135° C., preferably for a plateau duration comprised between 1 minute and 20 minutes with FO 15, or a sterilization step by UV radiation. Preferably, the sterilization step is carried out after steps a) to d) and the optional steps e), f) and g).

[0252] Hydrogel

[0253] The present invention also relates to a hydrogel capable of being obtained by the process according to the present invention.

[0254] This hydrogel is preferably an injectable hydrogel. It is preferably sterile, in particular heat sterilized at a plateau temperature comprised between 121° C. and 135° C., preferably for a plateau duration comprised between 1 minute and 20 minutes with F0≥15.

[0255] This hydrogel is preferably homogeneous. This hydrogel is preferably stringy, with in particular a phase angle δ comprised between 20° and 45°. This hydrogel can also comprise an additional component selected from anesthetics, antioxidants, amino acids, vitamins, minerals, nucleic acids and mixtures thereof as described below.

[0256] The polysaccharide of this hydrogel is preferably as defined above, in the context of the description of step a) of the process according to the invention.

[0257] The cross-linking agent used to cross-link the polysaccharide of this hydrogel is preferably as defined above, in the context of the description of step b) of the process according to the invention. Preferably, it does not comprise units Si—O—Si, and in particular it does not comprise —[SiR.sup.2R.sup.3O].sub.m—SiR.sup.2R.sup.3— units.

[0258] The molecule Chem. I used to functionalize the polysaccharide of this hydrogel is preferably as defined above, in the context of the description of step c) of the process according to the invention.

[0259] The present invention also relates to a hydrogel comprising at least a polysaccharide cross-linked with at least one cross-linking bond LR1 and at least one cross-linking bond LR2, [0260] the cross-linking bond LR1 comprising at least one unit Si—O—Si, [0261] the cross-linking bond LR2, different from the cross-linking bond LR1, being obtained by cross-linking said polysaccharide with at least a cross-linking agent comprising at least two functional Z groups, which are identical or different, selected from isocyanate, amino, epoxide, carboxyl, N-succinimidyloxycarbonyl, N-sulfo succinimidyloxycarbonyl, halogenocarbonyl, isothiocyanate, vinyl, formyl, hydroxyl, sulfhydryl, hydrazino, acylhydrazino, aminoxy, carbodiimide groups, and an acid anhydride residue, said hydrogel having a degree of modification by said at least a cross-linking agent of 0.05 to 10.0%, in particular from 0.05 to 5.0%, preferably from 0.1 to 1.0%.

[0262] This hydrogel is preferably an injectable hydrogel. It is preferably sterile, in particular sterilized by heat at a plateau temperature comprised between 121° C. and 135° C., preferably for a plateau duration comprised between 1 minute and 20 minutes with F0≥15. This hydrogel is preferably homogeneous. This hydrogel is preferably stringy, with in particular a phase angle δ comprised between 20° and 45°. This hydrogel can also comprise an additional component selected from anesthetics, antioxidants, amino acids, vitamins, minerals, nucleic acids and mixtures thereof as described below.

[0263] The polysaccharide of this hydrogel is preferably as defined above, in the context of the description of step a) of the process according to the invention.

[0264] The cross-linking agent used to cross-link the polysaccharide of this hydrogel is preferably as defined above, in the context of the description of step b) of the process according to the invention. Preferably, it does not comprise units Si—O—Si, and in particular it does not comprise —[SiR.sup.2R.sup.3O].sub.m—SiR.sup.2R.sup.3— units.

[0265] Thus, for example, when the cross-linking agent has the formula Chem. IIa above, the cross-linking bond LR2, obtained by cross-linking the polysaccharide with the cross-linking agent of formula Chem. IIa, will have the following formula Chem. V:

-G.sup.3-Y.sup.1-G.sup.4-

[0266] in which:

[0267] Y.sup.1 is as defined above, and

[0268] G.sup.3 and G.sup.4, which are identical or different, are binder groups bound to carbon atoms of the polysaccharide and resulting from the coupling of one of the functional Z.sup.1 and Z.sup.2 groups of the cross-linking agent of formula Chem. IIa with a functional group present on the polysaccharide (for example OH or COOH or else CHO for example when the polysaccharide is hyaluronic acid). G.sup.3 and G.sup.4, which are identical or different, are therefore for example selected from the following groups:

[0269] *—O—CO—NH—** (coupling of OH with an isocyanate), *—NH—CO—NH— (coupling of NH.sub.2 with an isocyanate), *—CO—NH—** (coupling of COOH with an amino), *—O—CH.sub.2—CH(OH)—** (coupling of OH with an epoxide), *—COO—CH.sub.2—CH(OH)—** (coupling of COOH with an epoxide), *—O—CO—** (coupling of OH with a carboxyl, N-succinimidyloxycarbonyl, N-sulfosuccinimidyloxycarbonyl, or halogenocarbonyl), *—NH—CO—** (coupling of NH.sub.2 with a carboxyl, N-succinimidyloxycarbonyl, N-sulfosuccinimidyloxycarbonyl, or halogenocarbonyl), *—O—CS—NH—** (coupling of OH with an isothiocyanate), *—NH—CS—NH— (coupling of NH.sub.2 with an isothiocyanate), *—O—CH.sub.2—CH.sub.2—** (coupling of OH with a vinyl), *—O—CH(OH)—** (coupling of OH with a formyl), *—NH—CH(OH)—** (coupling of NH.sub.2 with a formyl), *—CO—O—** (coupling of COOH with a hydroxyl), *—CO—S—** (coupling of COOH with a sulfhydryl), *═NH—NH—** (coupling of CHO with a hydrazino), *═NH—NH—CO—** (coupling of CHO with an acylhydrazino), *═NH—O—** (coupling of CHO with an aminoxy), *—CO—NR.sup.a—CO—NH—** with R.sup.a as defined above (coupling of COOH with a carbodiimide), *—O—CO—CH.sub.2N(CH.sub.2COOH)— (coupling of OH with the acid anhydride residue of formula Chem. GR3), *—NH—CO—CH.sub.2N(CH.sub.2COOH)— (coupling of NH.sub.2 with the acid anhydride residue of formula Chem. GR3), *—O—CO—CH.sub.2CH(COOH)—** (coupling of OH with the succinic anhydride residue), *—NH—CO—CH.sub.2—CH(COOH)—** (coupling of NH.sub.2 with the succinic anhydride residue), *—O—CO—CH═C(COOH)—** (coupling of OH with the maleic anhydride residue), *—NH—CO—CH═C(COOH)—** (coupling of NH.sub.2 with the maleic anhydride residue), in which:

[0270] * represents the point of attachment to a carbon atom of the polysaccharide, and

[0271] ** represents the point of attachment to Y.sup.1.

[0272] The cross-linking bond LR1 will more particularly comprise a unit having the following formula Chem. IVa:

—Si(R.sup.51)(R.sup.61)—O—[SiR.sup.121R.sup.131O].sub.p1—Si(R.sup.52)(R.sup.62)—

and more particularly will be a divalent group having the following formula Chem. IV:

-G′A.sup.1-Si(R.sup.51)(R.sup.61)—O—[SiR.sup.121R.sup.131O].sub.p1—Si(R.sup.52)(R.sup.62)-A.sup.2-G.sup.2-

in which: [0273] p1 is an integer from 0 to 20, preferably equal to 0, A.sup.1 and A.sup.2, which are identical or different, represent a chemical bond or a spacer group, each corresponding in particular to a group A as defined above, within the context of the description of step c) of the process according to the invention, [0274] R.sup.51, R.sup.52, R.sup.61 and R.sup.62, which are identical or different, represent a hydrogen atom; a halogen atom; an —OR.sup.41 group with R.sup.41 representing a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms; an aryl; or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms optionally substituted by one or more group(s) selected from a halogen atom, an aryl and a hydroxyl, R.sup.121 and R.sup.131, which are identical or different, represent a hydrogen atom; a halogen atom; an —OR.sup.141 group with R.sup.141 representing a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms; an aryl; or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms optionally substituted by one or more groups selected from a halogen atom, an aryl or a hydroxyl, and [0275] G.sup.1 and G.sup.2, which are identical or different, are binder groups bound to carbon atoms of the polysaccharide and selected from *—O—CO—NH—**. *—NH—CO—NH—. *—CO—NH—**. *—O—CH.sub.2—CH(OH)—**, *—COO—CH.sub.2—CH(OH)—**, *—O—CO—**, *—NH—CO—**, *—O—CS—NH—**, *—NH—CS—NH—, *—O—CH.sub.2—CH.sub.2—**, *—O—CH(OH)—**, *—NH—CH(OH)—**, *—CO—O—**, *—CO—S—**, *═NH—NH—**, *═NH—NH—CO—**, *═NH—O—**, *—CO—NR.sup.a—CO—NH—** with R.sup.a as defined above, *—O—CO—CH.sub.2—N(CH.sub.2—COOH)—**, *—NH—CO—CH.sub.2N(CH.sub.2—COOH)—**, *—O—CO—CH.sub.2—CH(COOH)—**, *—NH—CO—CH.sub.2—CH(COOH)—**, *—O—CO—CH═C(COOH)—** and *—NH—CO—CH═C(COOH)—**, [0276] where * represents the point of attachment to a carbon atom of the polysaccharide, and [0277] ** represents the point of attachment to A.sup.1 for G.sup.1 and to A.sup.2 for G.sup.2.

[0278] Advantageously, R.sup.51, R.sup.52, R.sup.61 and R.sup.62, which are identical or different, represent an —OR.sup.41 group with R.sup.41 representing a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms; or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms optionally substituted by one or more groups selected from a halogen atom, an aryl and a hydroxyl.

[0279] Advantageously, R.sup.51, R.sup.52, R.sup.61 and R.sup.62, which are identical or different, represent an —OR.sup.41 group with R.sup.41 representing a hydrogen atom, an aryl group or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms, preferably with R.sup.41 representing H or an aliphatic hydrocarbon group including from 1 to 6 carbon atoms, such as a (C1-C6)alkyl group.

[0280] Preferably: [0281] p1 is as defined above and advantageously represents 0; [0282] G.sup.1 and G.sup.2, which are identical or different, preferably identical, are as defined above and advantageously represent a *—CO—NH—** or *—O—CH.sub.2—CH(OH)—** group, preferably an *—O—CH.sub.2—CH(OH)—** group; [0283] A.sup.1 and A.sup.2, which are identical or different, preferably identical, are each a divalent chain —(C1-C6)alkylene-O—((C1-C6)alkylene-, in particular —(C1-C4)alkylene-O—(C1-C4)alkylene-, such as —CH.sub.2—O—(CH.sub.2).sub.3—, the CH.sub.2 group being preferably bound to G.sup.1 or G.sup.2 respectively and the (CH.sub.2).sub.3 group being bound to Si; and [0284] R.sup.51, R.sup.52, R.sup.61 and R.sup.62, which are identical or different, are each an —OR.sup.41 group with R.sup.41 representing H or a (C1-C6)alkyl group, preferably H, a methyl or an ethyl; or a (C1-C6)alkyl group, preferably a methyl or an ethyl; preferably R.sup.51, R.sup.52, R.sup.61 and R.sup.62, which are identical or different, are each an —OR.sup.41 group with R.sup.41 representing H or a (C1-C6)alkyl group, preferably H, a methyl or an ethyl.

[0285] The cross-linking bond LR1 advantageously results from the functionalization of the polysaccharide with a molecule of formula Chem. I as defined above and a sol-gel reaction allowing additional cross-linking, optionally in the presence of a molecule of formula Chem. III. Thus, in this case, the binder groups G.sup.1 and G.sup.2 result from the coupling of a functional group T of the molecule of formula Chem. I with a functional group present on the polysaccharide (for example OH or COOH or else CHO).

[0286] In particular, the hydrogel has a degree of modification by the molecule of formula Chem. I from 5 to 50%, preferably from 10 to 45%, in particular from 5 to 25%.

[0287] Composition

[0288] The present invention also relates to a composition comprising the hydrogel according to the present invention. It is preferably a cosmetic or pharmaceutical composition. It may also comprise physiologically acceptable excipients.

[0289] The hydrogel according to the invention comprises a cross-linked polysaccharide (for example, hyaluronic acid). The composition may also comprise a non-cross-linked polysaccharide (for example, hyaluronic acid).

[0290] The composition according to the present invention may thus comprise from 0.1 to 5% by weight, preferably from 1 to 3% by weight of polysaccharide (for example, hyaluronic acid), relative to the total weight of said composition, the polysaccharide (for example, hyaluronic acid) being present in cross-linked and optionally non-cross-linked form. In particular, the non-cross-linked polysaccharide (for example, hyaluronic acid) content varies from 0 to 40% by weight, preferably from 1 to 40% by weight, more preferably from 5 to 30% by weight, relative to the total weight of polysaccharide (for example, hyaluronic acid) present in the composition.

[0291] The polysaccharide of the hydrogel is preferably as defined above, in the context of the description of step a) of the process according to the invention, in particular hyaluronic acid.

[0292] The composition according to the present invention is preferably a sterile composition, in particular heat sterilized at a plateau temperature comprised between 121° C. and 135° C., preferably with a shelf life comprised between 1 minute and 20 minutes with F0≥15. It is preferably an injectable composition. The composition according to the invention then preferably comprises a physiologically acceptable medium, preferably a physiologically acceptable aqueous medium.

[0293] The physiologically acceptable aqueous medium can comprise a solvent or a mixture of physiologically acceptable solvents and preferably comprises water.

[0294] The physiologically acceptable medium can also comprise isotonic agents such as monosaccharides, sodium chloride and a mixture thereof.

[0295] The physiologically acceptable medium may further comprise at least one isotonic and physiologically acceptable saline solution.

[0296] Preferably, said balanced saline solution is a phosphate-buffered saline solution, and particularly a KH.sub.2PO.sub.4/K.sub.2HPO.sub.4 saline solution buffer. The composition according to the invention may further comprise at least an additional compound selected from anesthetics, antioxidants, amino acids, vitamins, minerals, nucleic acids, co-enzymes, adrenaline derivatives, and mixtures thereof.

[0297] As anesthetics mention may be made of Ambucaine, Amoxecaine, Amyleine, Aprindine, Aptocaine, Articaine, Benzocaine, Betoxycaine, Bupivacaine, Butacaine, Butamben, Butanilicaine, Chlorobutanol, Chloroprocaine, Cinchocaine, Clodacaine, Cocaine, Cryofluorane, Cyclomethycaine, Dexivacaine, Diamocaine, Diperodon, Dyclonine, Etidocaine, Euprocine, Febuverine, Fomocaine, Guafecainol, Heptacaine, Hexylcaine, Hydroxyprocaine, Hydroxytetracaine, Isobutamben, Leucinocaine, Levobupivacaine, Levoxadrol, Lidamidine, Lidocaine, Lotucaine, Menglytate, Mepivacaine, Meprylcaine, Myrtecaine, Octacaine, Octodrine, Oxetacaine, Oxybuprocaine, Parethoxycaine, Paridocaine, Phenacaine, Piperocaine, Piridocaine, Polidocanol, Pramocaine, Prilocaine, Procaine, Propanocaine, Propipocaine, Propoxycaine, Proxymetacaine, Pyrrocaine, Quatacaine, Quinisocaine, Risocaine, Rodocaine, Ropivacaine, Tetracaine, Tolycaine, Trimecaine or a salt thereof, in particular a hydrochloride thereof, and a mixture thereof.

[0298] As antioxidants, mention may be made of glutathione, reduced glutathione, ellagic acid, spermine, resveratrol, retinol, L-carnitine, polyols, polyphenols, flavonols, theaflavins, catechins, caffeine, ubiquinol, ubiquinone, alpha-lipoic acid and their derivatives, and a mixture thereof.

[0299] As amino acids, mention may be made of arginine (for example, L-arginine), isoleucine (for example, L-isoleucine), leucine (for example, L-leucine), lysine (for example, L-lysine or L-lysine monohydrate), glycine, valine (for example, L-valine), threonine (for example, L-threonine), proline (for example, L-proline), methionine, histidine, phenylalanine, tryptophan, cysteine, their derivatives (for example, N-acetyl derivatives such as N-acetyl-L-cysteine) and a mixture thereof.

[0300] As vitamins, and salts thereof, mention may be made of vitamins E, A, C, B, especially vitamins B6, B8, B4, B5, B9, B7, B12, and better still pyridoxine and derivatives and/or salts thereof, preferably pyridoxine hydrochloride.

[0301] As minerals, mention may in particular be made of zinc salts (for example, zinc acetate, which is in particular dehydrated), magnesium salts, calcium salts, potassium salts, manganese salts, sodium salts, copper salts (for example, copper sulfate, which is in particular pentahydrate), optionally in a hydrated form, and mixtures thereof.

[0302] As nucleic acids, particular mention may be made of adenosine, cytidine, guanosine, thymidine, cytodine, their derivatives and a mixture thereof.

[0303] As co-enzymes, mention may be made of coenzyme Q10, CoA, NAD, NADP, and mixtures thereof.

[0304] As adrenaline derivatives, mention may be made of adrenaline, noradrenaline and a mixture thereof.

[0305] The amounts of additional compounds of course depend on the nature of the compound in question, on the desired effect, and on the destination of the composition as described here.

[0306] Applications

[0307] The hydrogel or the composition according to the invention can have therapeutic, cosmetic and/or aesthetic applications.

[0308] The present invention therefore also relates to a hydrogel or a composition according to the invention for its use in filling and/or replacing tissues, in particular soft tissues, in particular by injecting the hydrogel or the composition into the tissue.

[0309] In particular, the hydrogel or the composition according to the invention is used in oral care and more particularly in the treatment of gingival recession, or to fill periodontal pockets. More particularly, the hydrogel or the composition according to the invention is used to treat the defects of the gingival architecture which can occur with tooth loss, with aging, with periodontal diseases and disorders, or after the installation of tooth implants, crowns or bridges.

[0310] The hydrogel or the composition according to the invention can also be used in ophthalmology, more particularly to protect the ocular structures during eye surgery such as for example ophthalmic surgery of the anterior or posterior segment, the extraction of the cataract possibly with implantation of an intraocular lens, corneal transplant surgery, filtering surgery for glaucoma, or implantation of a secondary lens.

[0311] In this case, the hydrogel or the composition according to the invention will be more particularly injected into the eye.

[0312] The hydrogel or the composition according to the invention can also be used in orthopedics or rheumatology, for example by injection into the synovial cavity. The hydrogel or the composition according to the invention is then used as viscosupplementation.

[0313] The hydrogel or the composition according to the invention can also be used in the treatment of lipodystrophy.

[0314] The hydrogel or the composition according to the invention can be used in cosmetic surgery, in particular for gynecoplasties and/or penoplasties.

[0315] The hydrogel or the composition according to the invention is administered more particularly by injection.

[0316] The present invention also relates to a process for treating the pathologies indicated above which comprises the administration, to an individual in need thereof, of an effective dose of the hydrogel or of the composition.

[0317] The effective dose of the hydrogel or of the composition varies according to many parameters such as, for example, the route of administration chosen, the weight, the age, the sex, the state of progress of the pathology to be treated and the sensitivity of the individual to be treated.

[0318] The present invention preferably relates to the aesthetic, and therefore non-therapeutic, use of a hydrogel or of a composition according to the invention for preventing and/or treating the alteration of the viscoelastic or biomechanical properties of the skin, and in particular for regenerating, moisturizing, firming or restoring the radiance of the skin, in particular by mesotherapy; to fill volume defects of the skin, and in particular to fill wrinkles, fine lines or scars (in particular hollow scars); or to reduce the appearance of fine lines and wrinkles.

[0319] For example, the present invention relates to the aesthetic use of a hydrogel or of a composition according to the invention for attenuating the nasolabial folds and bitterness folds; to increase the volume of the cheekbones, chin or lips; to restore the volumes of the face, in particular of the cheeks, the temples, the oval of the face, and around the eye; or to regenerate, hydrate, firm or restore the radiance of the skin, in particular by mesotherapy.

[0320] In particular, the hydrogel or the composition according to the invention is a hydrogel or an anti-aging composition. The hydrogel or the composition according to the invention is administered more particularly by injection.

[0321] The present invention also relates to a process for the cosmetic, preferably anti-aging, treatment of keratin materials, in particular the skin, comprising at least a step of administering a hydrogel or a composition according to the invention on or through said keratin materials, more particularly by injection.

[0322] The administration can be an injection, in particular an intraepidermal and/or intradermal and/or subcutaneous injection. Administration by intraepidermal and/or intradermal and/or subcutaneous injection according to the invention aims at injecting a hydrogel or a composition of the invention into an epidermal, dermo-epidermal and/or dermal region. The hydrogel or the composition according to the invention can also be administered by a supraperiosteal injection.

[0323] The hydrogel or the composition according to the invention can be injected using any of the processes known to the person skilled in the art. In particular, a hydrogel or a composition according to the invention can be administered by means of an injection device adapted for intraepidermal and/or intradermal and/or subcutaneous and/or supraperiosteal injection. The injection device can in particular be selected from a syringe, a set of microsyringes, a laser or hydraulic device, an injection gun, a needleless injection device, or a microneedle roller.

[0324] The injection device may include any injection means usually used suitable for intraepidermal and/or intradermal and/or subcutaneous and/or supraperiosteal injection. Preferably, such a means may be a hypodermic needle or a cannula.

[0325] A needle or cannula according to the invention may have a diameter varying from 18 to 34 G, preferably between 25 and 32 G, and a length varying from 4 to 70 mm, and preferably from 4 to 25 mm. The needle or cannula is advantageously disposable.

[0326] Advantageously, the needle or cannula is associated with a syringe or any other device allowing to deliver said hydrogel or said injectable composition through the needle or the cannula.

[0327] According to a variant embodiment, a catheter can be inserted between the needle/cannula and the syringe. In a known manner, the syringe can be actuated manually by the practitioner or else by a syringe support such as guns.

[0328] Preferably, the injection device can be selected from a syringe or a set of microsyringes.

[0329] In a variant embodiment, the injection device can be adapted to the mesotherapy technique.

[0330] Mesotherapy is a treatment technique by intraepidermal and/or intradermal and/or subcutaneous injection of a composition or a hydrogel. The composition or the hydrogel is administered according to this technique by injection in the form of multiple small droplets at the epidermis, the dermo-epidermal junction and/or the dermis in order, in particular, to produce a subcutaneous coating. The mesotherapy technique is described in particular in the work “Traité de mésothérapie” by Jacques LE COZ, Masson edition, 2004. Mesotherapy performed on the face is also called mesolift, or also under the term “mesoglow”.

[0331] The administration can also be topical.

[0332] Preferably, it is a topical application on the surface of the skin, more particularly on the epidermis, even more particularly on the facial epidermis.

[0333] The present invention is illustrated by the non-limiting examples below.

EXAMPLES

[0334] Material [0335] GPTMS: (3-Glycidyloxypropyl)trimethoxy-silane (Sigma 440167), [0336] NaHA: non-cross-linked sodium hyaluronate 1.5 MDa and 4 MDa (HTL), [0337] 0.25M and 0.2M NaOH, [0338] 1M HCl (Chem Lab), [0339] PBS Phosphate Buffer (Braun), [0340] Lidocaine Hydrochloride, [0341] Lyophilizer, [0342] Three-Dimensional Shaker Turbula®, [0343] Rheometer DHR-2, [0344] Dynamometer Mecmesin AFG 100N, [0345] Test Bench Mecmesin 2.5-dV, [0346] Paddle homogenizer mill, [0347] Sterile bag for paddle homogenizer mill.

[0348] Measurement of Viscoelastic Properties

[0349] The viscoelastic properties of the hydrogels obtained were measured using a rheometer (DHR-2) having a stainless steel cone (1°- 40 mm) with cone-plane geometry and an anodized aluminum peltier plate (42 mm) (air gap 24 μm). 0.5 g of sterilized hydrogel is deposited between the peltier plate and said cone. Then a stress scan is performed at 1 Hz and 25° C. The elastic modulus G′, the viscous modulus G″ and the phase angle δ are reported for a stress of 5 Pa.

[0350] The stress at the intersection of G′ and G″ τ is determined at the intersection of the curves of the modules G′ and G″ and is expressed in Pascal.

[0351] Cohesiveness Measurement

[0352] For the measurement of cohesiveness (or mechanical resistance, expressed in Newtons), the gel is deposited on the peltier plate with an initial air gap of 2.60 mm then left to rest for 60 seconds. The gel is then compressed at a constant speed of 100 μm/s up to 70% of the initial air gap, at 25° C. The cohesiveness of the gel is measured at the end of the compression stroke.

[0353] Measurement of the Extrusion Force

[0354] The extrusion forces (in Newtons) of the gels packaged in syringes were conducted through a test bench equipped with a dynamometer at a constant speed of 12.5 mm/min, through a 27 G ½″ needle and at room temperature. The extrusion force results correspond to the average of the average extrusion forces on at least 2 samples.

Example 1: Preparation and Analyzes of Samples Based on BDDE and/or GPTMS-Modified Hyaluronic Acid

[0355] Prototypes no 1 to 12 are prepared as follows with the contents of NaOH, NaHA 1.5 MDa, BDDE, GPTMS described in Table 1: [0356] Sodium hyaluronate (120 mg of NaHA per gram of reaction medium) and the BDDE are dissolved in a sodium hydroxide solution with a concentration according to Table 1 in a sterile bag; [0357] The mixture is homogenized in a paddle mill for 2 cycles of 15 min at 210 rpm; [0358] The GPTMS is added to the sterile bag; [0359] The mixture is homogenized in a paddle mill for 2 cycles of 15 min at 210 rpm; [0360] The mixture is maintained at 21° C. for 72 hours, the pH of the mixture is approximately 13; [0361] A 1N HCl solution is added to the sterile bag until a pH of 7±0.5 is obtained; [0362] The mixture is diluted to a concentration of 23 mg of HA/g of product with PBS phosphate buffer; [0363] The mixture is homogenized for 24 hours using a three-dimensional shaker; [0364] The mixture is dialyzed; [0365] A sodium hyaluronate NaHA 4 MDa is added as a lubricant; [0366] The aqueous solution of lidocaine hydrochloride is added to obtain 0.3% by weight of lidocaine hydrochloride relative to the weight of the resulting product; [0367] The product thus obtained is sieved (710 μm sieve); [0368] In the case of prototypes n° 11 and 12, the product is at this stage dried by lyophilization (freezing at −80° C. for 6 hours followed by vacuum drying for 48 hours) then rehydrated in 24 hours at a concentration of 23 mg/mL using deionized water; [0369] The product thus obtained is packaged in a syringe; [0370] Finally, the product is sterilized in an autoclave (plateau temperature comprised between 121° C. and 135° C. with FO 15).

[0371] Prototypes n° 2 and 12 are comparative.

[0372] Prototypes n° 1 and 3-11 are hydrogels according to the present invention.

[0373] The results are reported in Table 1 below.

TABLE-US-00001 Content Cross-linking agent BDDE Functionalizing agent GPTMS NaOH in HA Cross-linking rate Functionalization rate concentration (mol %/ Mass Molar Mass Molar (mol/L) NaOH) rate (%) rate (%) rate (%) rate (%) Prototype 1 0.25 12 3.0 6.2 20.1 42.8 No 2 0.25 12 0.0 0.0 6.7 12.2 3 0.25 12 0.5 1.0 20.6 44.1 4 0.25 12 1.1 2.2 6.7 12.3 5 0.25 12 2.0 4.1 6.8 12.4 6 0.25 12 3.0 6.2 6.7 12.3 7 0.25 12 0.2 0.4 20.6 44.2 8 0.20 15 0.2 0.4 15.9 32.1 9 0.25 12 5.0 10.4 5.6 10.1 10 0.25 12 0.2 0.4 20.6 44.2 11 0.25 12 5.0 10.4 5.6 10.1 12 0.25 12 1.1 2.1 0.0 0.0

[0374] After sterilization, the prototypes are analyzed, the elastic modulus G′, the phase angle δ and the stress at the intersection of G′ and G″ are determined. The results are reported in Table 2 below.

TABLE-US-00002 Stress at the intersection MOD MOD Prototype of G′ and Extrusion Cohesiveness BDDE GPTMS No G′ (Pa) Delta (°) G″ (Pa) force (N) (N) (% .sup.(2)) (% .sup.(1)) 1 594 ± 20  8.2 ± 0.3 270 ± 13 9.3 ± 0.2 Not 3.0 12.5 measured 2  1 ± 0 76.1 ± 2.4 ND 5.0 ± 0.2 Not 0 5 measured 3 424 ± 18  8.5 ± 0.5 404 ± 20 11.0 ± 0.4  Not 1.3 27.0 measured 4 51 ± 2 34.3 ± 0.6 79 ± 3 11.4 ± 0.4  4.7 1.5 6 5 175 ± 9  15.8 ± 0.5 419 ± 3  11.4 ± 0.4  7.7 2.5 7 6 251 ± 17 10.1 ± 0.7 450 ± 9  9.6 ± 0.4 Not 5.3 5.5 measured 7 319 ± 17 10.0 ± 0.5 418 ± 21 13.5 ± 0.7  Not 0.2 18 measured 8 151 ± 8  22.4 ± 0.0 287 ± 3  15.9 ± 0.6  9.8 Undetectable 9 9 582 ± 28  6.0 ± 0.5 325 ± 50 9.2 ± 0.3 Not 8.5 5 measured 10 1153 ± 96   9.0 ± 0.0 26 ± 0 6.4 ± 0.3 Not 0.2 18.0 measured 11 1675 ± 147 11.2 ± 1.1 41 ± 4 6.5 ± 0.1 Not 8.5 5.0 measured 12 15 ± 2 49.6 ± 6.7 ND 7.9 ± 0.4 Not 1.8 0.0 measured ND: Not Determinable .sup.(1) % mol of GPTMS/100 moles of repeat units of HA .sup.(2) % mol of BDDE/100 moles of repeat units of HA

[0375] The control prototypes 2 and 12 without GPTMS or without BDDE do not allow to obtain gels with acceptable mechanical properties for the therapeutic, cosmetic and/or aesthetic applications targeted by the present invention. It is indeed the combination of BDDE and GPTMS which allows to obtain injectable elastic gels having the desired mechanical properties.

[0376] With mass contents of 1% BDDE and 6% GPTMS (prototype n° 4) (molar contents of 2% BDDE and 12% GPTMS), the prepared gel has desirable mechanical properties for the applications targeted in the scope of the present invention. Gels prepared with 0.2% by weight of BDDE (0.4% molar) and 15% or 20% by weight of GPTMS (32 and 44% molar) (respectively prototypes 8 and 7) have good rheological and injectability properties.

[0377] It should be noted that the prototype 8 is a gel with particularly advantageous, stringy sensory properties.

[0378] The effect of drying by freeze-drying then rehydration allows to exacerbate the elastic properties of the gels. Thus, the prototype 11, freeze-dried and rehydrated, shows a higher G′ than prototype 9 prepared with the same BDDE and GPTMS contents.

[0379] The same is observed when comparing prototypes 10 and 7.

Example 2: Study of the Effect of NaMS

[0380] Prototype n° 10 is prepared as described in Example 1. Prototype 13 is prepared in the same way with, at the time of addition of GPTMS, the addition of NaMS in a ratio of 1:6 (mole of NaMS: mole of disaccharide unit of NaHA).

[0381] The NaOH, NaHA (1.5 MDa), BDDE and GPTMS contents are described in Table 3 below.

TABLE-US-00003 Cross-linking agent BDDE Functionalizing agent GPTMS NaOH HA content Cross-linking rate Functionalization rate Prototype concentration (mol %/ Mass Molar Mass Molar No (mol/L) NaOH) rate (%) rate (%) rate (%) rate (%) 10 0.25 12 0.2 0.4 20.6 44.2 13 0.25 12 0.2 0.4 20.6 44.0

[0382] After sterilization, the prototypes are analyzed, the elastic modulus G′, the phase angle δ and the stress at the intersection of G′ and G″ are determined. The results are reported in Table 4 below.

TABLE-US-00004 Stress at the Prototype intersection of Extrusion No G′(Pa) δ (°) G′ and G″ (Pa) force (N) 10 1153 ± 96  9.0 ± 0.0 26 ± 0 6.4 ± 0.3 13 1843 ± 14 10.0 ± 0.4 64 ± 9 7.5 ± 0.8

[0383] The above results show that a product prepared in the presence of NaMS (prototype 13) has improved mechanical properties compared to a product prepared identically but without NaMS (prototype 10).

Example 3: Preparation and Analyzes of Samples Based on DVS and/or GPTMS Modified-Hyaluronic Acid

[0384] Prototypes n° 14 and 15 are prepared as follows with the contents of NaOH, NaHA (1.5 MDa), DVS and GPTMS described in Table 5: [0385] GPTMS, then NaOH then sodium hyaluronate NaHA (120 mg of NaHA per gram of reaction medium) are added to a sterile bag; [0386] The mixture is homogenized in a paddle mill for 3 cycles of 15 min at 210 rpm and by manual palpation of the bag between each cycle; [0387] The DVS is added in the bag; [0388] The mixture is homogenized in a paddle mill for 15 min at 210 rpm; [0389] The mixture is maintained at 21° C. for 48 hours, the pH of the mixture is approximately 13; [0390] A 1M HCl solution is added to the sterile bag until a pH of 7±0.5 is obtained; [0391] The mixture is diluted to a concentration of 23 mg of HA/g of product with PBS phosphate buffer; [0392] The mixture is homogenized for 24 hours using a three-dimensional shaker, [0393] The mixture is dialyzed; [0394] A sodium hyaluronate NaHA 4 MDa is added as a lubricant; [0395] The aqueous solution of lidocaine hydrochloride is added to the sterile bag to obtain 0.3% by weight of lidocaine hydrochloride relative to the weight of the resulting product; [0396] The product thus obtained is sieved then packaged in a syringe; [0397] Finally, the product is sterilized in an autoclave (plateau temperature comprised between 121° C. and 135° C. with FO 15).

[0398] The results are reported in Table 5 below.

TABLE-US-00005 Cross-linking agent Functionalizing agent DVS GPTMS Cross-linking rate Functionalization rate Prototype Mass rate Molar rate Mass rate Molar rate No (%) (%) (%) (%) 14 0.4 1.4 0.0 0.0 15 0.3 1.0 20.6 44.2

[0399] After sterilization, the prototypes are analyzed, the elastic modulus G′, the phase angle δ and the stress at the intersection of G′ and G″ are determined. The results are reported in Table 6 below.

TABLE-US-00006 Stress at the Prototype intersection of Extrusion No G′(Pa) δ (°) G′ and G″ (Pa) force (N) 14 10 ± 4 55.6 ± 2.6 ND* 5.6 ± 0.2 15 615 ± 40 11.3 ± 0.5 242 ± 7 9.5 ± 0.2

[0400] *ND: Not Determinable: prototype 14 has a viscous predominance with a modulus G″ greater than the modulus G′ including for low stresses (confirmed by its value of δ greater than 45°); there is therefore no intersection of the curves of G′ and G″.

[0401] The small amount of DVS used for the modification of the hyaluronic acid for preparing the prototype 14 does not allow to lead to the formation of a gel with acceptable mechanical properties for the therapeutic, cosmetic and/or aesthetic applications targeted by the present invention.

[0402] In contrast, in the case of prototype 15, with the additional use of GPTMS, even with such a low amount of DVS, a desirable gel is formed.

Example 4: Preparation and Analyzes of Samples Based on BDDE and APTES-Modified Hyaluronic Acid

[0403] Prototype n° 16 is prepared as follows with the NaOH, NaHA (1.5 MDa), BDDE, APTES, EDC and NHS contents described in Table 5: [0404] NaOH then sodium hyaluronate (50 mg/g) are added to a pot; [0405] The mixture is placed in the refrigerator (4±1° C.) and homogenized with a spatula for 5 minutes every hour for 4 hours; [0406] The BDDE and the mixture is homogenized with a spatula for 5 minutes; [0407] The mixture is maintained at 21° C. for 72 hours, the pH of the mixture is approximately 13; [0408] A 1M HCl solution is added to the pot until an acid pH between 4.5 and 6.5 is obtained; [0409] The EDC and the NHS are added to the pot and the mixture is homogenized for 5 minutes with a spatula then left to react at 21° C. for 30 minutes; [0410] The APTES is then added drop by drop and the mixture is homogenized with a spatula then left for 15 hours at 21° C.; [0411] The mixture is diluted to a concentration of 23 mg of HA/g of product with PBS phosphate buffer; [0412] The mixture is homogenized for 24 hours using a three-dimensional shaker; [0413] The mixture is dialyzed; [0414] A sodium hyaluronate NaHA 4 MDa is added as a lubricant; [0415] The aqueous solution of lidocaine hydrochloride is added to the sterile bag to obtain 0.3% by weight of lidocaine hydrochloride relative to the weight of the resulting product; [0416] The product thus obtained is sieved then packaged in a syringe; [0417] Finally, the product is sterilized in an autoclave (plateau temperature comprised between 121° C. and 135° C. with FO 15).

[0418] The results are reported in Table 7 below.

TABLE-US-00007 Cross-linking agent BDDE Functionalizing agent FIT Cross-linking rate Functionalization rate Prototype EDC/HA NHS/HA Mass Molar Mass Molar No molar ratio molar ration ratio (%) ratio (%) ratio (%) ratio (%) 16 1.5 1 0.7 1.5 35.7 101.0

[0419] After sterilization, the prototypes are analyzed, the elastic modulus G′, the phase angle δ and the stress at the intersection of G′ and G″ are determined. The results are reported in Table 8 below.

TABLE-US-00008 Stress at the Prototype intersection of Extrusion No G′(Pa) δ (°) G′ and G″ (Pa) force (N) 16 1707 ± 44 7.2 ± 0.1 136 ± 11 8.2 ± 0.4

[0420] Despite the use of a small amount of BDDE, thanks to the additional use of APTES for the modification of hyaluronic acid according to the present invention, the prototype 16 is a gel with acceptable mechanical properties for the therapeutic, cosmetic and/or aesthetic applications covered by the present invention.