Enzymatically crosslinked dextran-tyramine hydrogels as injectable scaffolds for cartilage tissue engineering.

Enzymatic crosslinking of dextran-tyramine (Dex-TA) conjugates in the presence of horseradish peroxidase and hydrogen peroxide was successively applied in the preparation of hydrogels. Depending on the molecular weight of the dextran (M(n,) (GPC) of 14000 or 31000 g/mol) and the degree of substitution (of 5, 10, or 15) with TA groups, the gelation times ranged from 20 s to 1 min. Hydrogels prepared from Dex31k-TA with a degree of substitution of 10 had storage moduli up to 60 kPa. Similar values were found when chondrocytes were incorporated into the hydrogels. Chondrocyte-seeded Dex-TA hydrogels were prepared at a molar ratio of hydrogen peroxide/TA of 0.2 and cultured in a chondrocyte medium. A live-dead assay and a methylthiazol tetrazolium assay revealed that almost all chondrocytes retained their viability after 2 weeks. Scanning electron microscopy analysis showed that the encapsulated chondrocytes were capable of maintaining their round shape. Histology and immunofluorescent staining demonstrated the production of glycosaminoglycans (GAGs) and collagen type II after culturing for 14 and 21 days. Biochemical analysis showed that GAG accumulation increased with time inside Dex-TA hydrogels. Besides, GAG/DNA for Dex-TA hydrogels was higher than that for agarose at day 28. These results indicate that Dex-TA hydrogels are promising 3D scaffolds for cartilage tissue engineering applications.