An injectable self-healing alginate hydrogel with desirable mechanical and degradation properties for enhancing osteochondral regeneration

Articular cartilage and subchondral bone defects have always been problematic because the osteochondral tissue plays a crucial role in the movement of the body and does not recover spontaneously. Here, an injectable hydrogel composed of oxidized sodium alginate/gelatin/chondroitin sulfate (OSAGC) was designed for the minimally invasive treatment and promotion of osteochondral regeneration. The OSAGC hydrogel had a double network based on dynamic covalent bonds, demonstrating commendable injectability and self-healing properties. Chondroitin sulfate was organically bound to the hydrogel network, retaining its own activity and gradually releasing during the degradation process as well as improving mechanical properties. The compressive strength could be increased up to 3 MPa by regulating the concentration of chondroitin sulphate and the oxidation level, and this mechanical stimulation could help repair injured tissue. The OSAGC hydrogel had a favourable affinity to articular cartilage and was able to release active ingredients in a sustained manner over 3 months. The OSAGC showed no cytotoxic effects. Results from animal studies demonstrated its capacity to regenerate new bone tissue in four weeks and new cartilage tissue in twelve weeks. The OSAGC hydrogel represented a promising approach to simplify bone surgery and repair damaged osteochondral tissue.