Injectable and self-crosslinkable hydrogels based on collagen type II and activated chondroitin sulfate for cell delivery

Injectable hydrogels are attractive and alternative scaffolds for cell delivery because they could form in situ, simulate natural tissue and fill any shape of defect. This study aimed at fabricating injectable, self-crosslinkable and biomimetic hydrogels based on collagen type II (Col II) and activated chondroitin sulfate (CS-sNHS) under physiological conditions without the addition of any catalysts or crosslinking agents. The inner morphology of hydrogels was detected by scanning electron microscopy, and it showed that fibrous structure formed in the hydrogels. The gelation time, water absorption capacity and the mechanical property of hydrogels were closely related to the weight ratio of Col II and CS-sNHS in hydrogels. Chondrocytes were encapsulated into these hydrogels, and the effect of hydrogels on survival, proliferation, morphology of cells and remolding of extracellular matrix was investigated. The results demonstrated that chondrocytes survived well and showed round or oval morphology in these hydrogels, in addition, the matrix in hydrogels had been remolded and the collagen fibers displayed periodic alternation of light and shade. These results implied that the injectable and self-crosslinkable hydrogels were alternative carriers for chondrocyte delivery.