Recombinant human collagen/chitosan-based soft hydrogels as biomaterials for soft tissue engineering.

Animal-derived collagen may contain viruses, and its impurity can cause immunological reactions. Chitosan, always required a neutralization step in fabricating it into the biocompatible tissue engineering scaffolds. To avoid these risks and simplify the production process, a series of recombinant human collagen/carboxylated chitosan (RHC-CHI) based soft hydrogel scaffolds were prepared by crosslinking-induced gelation and then investigated their feasibilities for use as soft tissue engineering scaffolds. The gelation time was optimized by modulating the biopolymer concentration or reaction temperature. The hydrogel swelling, degradation rate, and mechanical properties were also investigated. The results showed that these parameters could be tuned by adjusting either the RHC-to-chitosan ratio or the total polymer concentration. The mechanical properties of the hydrogels were improved by adding chitosan, but excess chitosan reduced the hydrogel mechanical strength and accelerated the degradation speed. Cytotoxicity tests showed that all fabricated soft hydrogels were biocompatible and displayed no cytotoxicity. Cytocompatibility tests and qRT-PCR studies indicated that the hydrogel system promoted the adhesion and proliferation of NIH-3T3 cells, and cellular activities were directly up-regulated by RHC. Finally, our in vivo study proved these hydrogels were able to accelerate the cell infiltration and wound closure. These results show that the soft RHC-CHI hydrogels show promise in soft-tissue engineering.