Tough biodegradable chitosan-gelatin hydrogels via in situ precipitation for potential cartilage tissue engineering

Tough porous chitosan-gelatin (CG) hydrogels have been prepared through in situ precipitation with tunable porosity and degradation rates by adjusting the preparation formulations. Compression tests showed a Young's modulus of 3.25 MPa and a compressive strength of 2.15 MPa for the optimized C4G4 hydrogels, which are similar to or higher than those for human cartilage. Cyclic compression tests showed overlapping hysteresis loops for several cycles, with a compressive toughness of about 75.8 J m(-2). In vitro enzymatic degradation results showed a degradation of 65.9% in 70 days, comparable to the regeneration rate of engineered cartilage reported in literature. Moreover, in vitro cell culture experiments showed excellent adhesion and proliferation of human thyroid cartilage cells on these hydrogels, where the chondrocytes function to secrete ECM. These tough and biodegradable hydrogels may have potential applications for cartilage tissue engineering.