Carbohydrate crosslinker
The invention relates to a hydrogel product comprising glycosaminoglycan molecules as the swellable polymer, wherein the glycosaminoglycan molecules are covalently crosslinked via crosslinks comprising a spacer group selected from the group consisting of di-, tri-, tetra-, and oligosaccharides.
1. A process of preparing a hydrogel product comprising crosslinked hyaluronic acid (HA) molecules, the process comprising:
(a) crosslinking activated carboxyl groups of HA molecules using diaminotrehalose (DATH) to obtain crosslinked HA molecules; and
(b) hydrolyzing ester bonds in the crosslinked HA molecules via alkaline hydrolysis to obtain a hydrogel product having less than 50% non-crosslinked HA molecules by weight of the hydrogel product.
2. The process according to claim 1 , further comprising activating carboxyl groups of the HA molecules with a coupling agent to produce the activated carboxyl groups.
3. The process according to claim 2 , wherein the coupling agent is a triazine-based coupling reagent.
4. The process according to claim 3 , wherein the coupling agent is 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM).
5. The process according to claim 2 , wherein the activating and the crosslinking occur simultaneously.
6. The process according to claim 1 , wherein the crosslinking provides amide bonds between the HA molecules and the DATH.
7. The process according to claim 6 , wherein after (b) at least 90% of bonds between the HA molecules and the DATH are amide bonds.
8. The process according to claim 1 , wherein after (b) less than 5% of bonds between the HA molecules and DATH are ester bonds.
9. The process according to claim 1 , wherein hydrolyzing the ester bonds comprises swelling the crosslinked HA molecules in an alkaline solution for at least 1 hour.
10. The process according to claim 9 , wherein the alkaline solution comprises a hydroxide.
11. The process according to claim 1 , wherein less than 20% by weight of the hydrogel product obtained in (b) comprises HA molecules that are not crosslinked.
12. The process according to claim 1 , wherein the crosslinked HA molecules are in the form of gel particles.
13. The process according to claim 12 , wherein the gel particles are 0.01 mm to 5 mm in size.
14. The process according to claim 1 , wherein the HA molecules, prior to crosslinking, have a molecular weight of about 10 kDa to 10 MDa.
15. The process according to claim 14 , wherein the HA molecules, prior to crosslinking, have a molecular weight of about 100 kDa to 1 MDa.
16. The process according to claim 1 , wherein the hydrogel product has an effective crosslinking ratio (CrR) of at least 0.43.
17. The process according to claim 1 , wherein the hydrogel product has an effective crosslinking ratio (CrR) of at least 0.63.
18. The process according to claim 1 , wherein the molar ratio of DATH to HA in (a) is 0.03 to 0.79 mol %.
19. The process according to claim 1 , further comprising:
(c) neutralizing the crosslinked HA molecules to a neutral pH;
(d) precipitating the neutralized crosslinked HA molecules;
(e) drying the precipitated crosslinked HA molecules; and
(f) swelling the dried crosslinked HA molecules in a phosphate buffer.
20. The process according to claim 1 , wherein the crosslinked HA molecules are free from synthetic non-carbohydrate structures and synthetic non-carbohydrate crosslinkers.