Dual-crosslinked silk fibroin hydrogels with elasticity and cytocompatibility for the regeneration of articular cartilage

Water-soluble conjugates of silk fibroin (SF) and butyl glycidyl ether (BGE) were synthesized via the ring-opening reaction of BGE of the epoxide group of BGE with the side chains of SF (-COOH, ?OH, and ?NH2 groups). The degree of substitution of the SF-BGE conjugates was calculated by 1H NMR spectroscopy and amino acid analysis. The color of the SF-BGE solution gradually changed from transparent to pale yellow with the increase in the amount of BGE, and its pH also changed from acidic to a weakly basic one. The photocrosslinking efficiency of the SF-BGE solution according to the polymer concentration, photoinitiator content, and irradiation time were investigated to achieve optimal chemical crosslinking. In addition, the mechanical strength of the photocrosslinked SF-BGE hydrogels was increased by treating with an aqueous ethanol solution to generate a dualcrosslinked structure. The crystalline structure, mechanical strength, crosslinking density, swelling, and biodegradation behavior of the SF-BGE hydrogels were analyzed. Finally, the in vitro cytocompatibility of the SFBGE hydrogels was evaluated as a preliminary study toward its application in articular cartilage.