Effects of cross‐linking with EDC/NHS and genipin on characterizations of self‐assembled fibrillar gel prepared from tilapia collagen and alginate

Chemical cross-linking is prevalent for precise control of the properties of collagen-based materials. However, there is little information about detailed comparisons of cross-linking characteristics of collagen-based fibrillar gel with different cross-linkers. In this study, a fibrillar gel was prepared from tilapia collagen and alginate, and cross-linking conditions with EDC/NHS and genipin were discussed. By curve-fitting with Langmuir and pseudo-second-order model, the cross-linking process was controlled by monolayer chemisorption, and genipin showed much higher cross-linking degree at saturation compared with EDC/NHS. ATR-FTIR and XPS suggested that although hydrogen bonds were weakened by cross-linking, EDC/NHS offered short-range cross-linking formed by amino and carboxyl groups in fibrils, while genipin induced long-range cross-linking by interactions of amino groups in fibrils and ester groups in genipin. XRD and SEM revealed that the structural integrity was strengthened after cross-linking, however, fibril bundles were present in SA/PSC/EDC/NHS, and genipin induced disaggregation of fibrils. Both swelling properties and enzymatic resistance were improved by cross-linking, while thermal stability was unenhanced significantly. All fibrillar gels showed good biocompatibility, but cross-linking degree affected appearance and migration of cells. The results revealed that genipin-cross-linked fibrillar gel had greater potential application in biomaterials on the premise of tuning cross-linking degree than EDC/NHS-cross-linked one.