Injectable <i>in Situ</i> Cross-linked Oxidized Alginate-Gelatin-Based Hydrogels for Cartilage Tissue Engineering

The present study introduces an injectable oxidized alginate-gelatin hydrogel system for cartilage tissue engineering, employing a combination of covalent and noncovalent cross-linking mechanisms. Specifically, the network is formed through Schiff's Base reactions alongside enzymatic and ionic cross-linking. The hydrogels were investigated regarding their mechanical properties, swelling and degradation behavior, injectability, and cytocompatibility. The results indicated tailorable mechanical properties with an effective modulus ranging from 12 to 20 kPa, depending on the enzymatic cross-linker concentration, while demonstrating suitable injectability required for clinical applications with injection forces in the range of 3-5 N. Moreover, the syringe-mixing approach of <i>in situ</i> cross-linked hydrogels showed favorable cell-material interactions with chondrogenic ATDC5 cells.