Sterilization of biodegradable hydrogels

1. A method for sterilizing a biodegradable poly(ethylene glycol) based insoluble hydrogel comprising backbone moieties which are interconnected by hydrolytically degradable bonds, the method comprising the steps of:

(a) providing the hydrogel;

(b) solvating the hydrogel in a protective solvent, or in a mixture of the protective solvent with another protective solvent, or in an aqueous solution thereof; and

(c) subjecting the solvated hydrogel, in the presence of the protective solvent, to gamma radiation;

wherein the protective solvent comprises at least one component selected from the group consisting of NMP, DMA, DME and DMI; and

wherein the protective solvent optionally contains one or more protecting agents.

2. The method of claim 1 ;

wherein the protective solvent comprises NMP.

3. The method of claim 1 ;

wherein sterilization is obtained with gamma radiation with a dose of from 5 to 100 kGy.

4. The method of claim 1 ;

wherein sterilization is obtained with gamma radiation with a dose of from 8 to 50 kGy.

5. The method of claim 1 ;

wherein the hydrogel is loaded with small molecule biologically active moieties.

6. The method of claim 1 ;

wherein the backbone moieties of the hydrogel have each a molecular weight in the range of from 1 kDa to 20 kDa.

7. The method of claim 1 ;

wherein the backbone moieties of the hydrogel are interconnected by hydrolytically degradable bonds; and

wherein the backbone moieties are linked together through crosslinker moieties, each crosslinker moiety being terminated by at least two of the hydrolytically degradable bonds.

8. The method of claim 1 ;

wherein the hydrolytically degradable bonds are carboxylic esters, carbonates, phosphoesters, or sulfonic acid esters.

9. The method of claim 7 ;

wherein the crosslinker moieties have a molecular weight in the range of from 60 Da to 5 kDa.

10. The method of claim 1 ;

wherein the backbone moieties of the biodegradable PEG based insoluble hydrogel comprise a branching core of the following formula:

wherein the dashed line indicates attachment to the remainder of the backbone moiety.

11. The method of claim 1 ;

wherein the backbone moieties of the biodegradable PEG based insoluble hydrogel comprise a structure of the following formula:

wherein n is an integer of from 5 to 50, and the dashed line indicates attachment to the rest of the molecule.

12. The method of claim 1 ;

wherein the backbone moieties of the biodegradable PEG based insoluble hydrogel comprise a hyperbranched moiety Hyp.

13. The method of claim 12 ;

wherein the backbone moieties of the biodegradable PEG based insoluble hydrogel comprise a hyperbranched moiety Hyp of the following formula:

wherein the dashed lines indicate attachment to the rest of the molecule and carbon atoms marked with asterisks indicate S-configuration.

14. The method of claim 12 ;

wherein the backbone moieties are attached to at least one spacer of the following formula:

wherein one of the dashed lines indicates attachment to the hyperbranched moiety Hyp, and the second dashed line indicates attachment to the rest of the molecule; and

wherein m is an integer of from 2 to 4.

15. The method of claim 1 ;

wherein the backbone moieties are linked together through crosslinker moieties comprising the following structure:

wherein q is an integer from 3 to 100.

16. The method of Claim 1 ;

wherein the protecting agents are selected from propylamine, butylamine, pentylamine, Sec, butylamine, ethanolamine, diethanolamine, serinol, trishydroxymethyl-aminomethane, acetic acid, formic acid, ascorbic acid, glycineamide, pivalic acid, propanoic acid, succinic acid, glutaric acid, adipic acid, thioglycerin, dithiothreitol, mercaptoethanol, and reduced glutathione.