Lysine-functionalized chondroitin sulfate improves the biological properties of collagen/chitosan-based injectable hydrogels

Abstract

Novel bioactive collagen/chitosan/lysine-functionalized chondroitin sulfate (CSmod) injectable hydrogels are presented. The modification of CS with amine groups introduced with lysine moieties (the degree of substitution about 21%) guarantees its covalent binding with the hydrogel network while genipin crosslinking. Both the physicochemical and biological features of developed hydrogels might be adjusted by playing with CSmod and crosslinking agent concentrations. It was revealed that materials became more hydrophobic with increased CSmod content, while crosslinking degree and enzymatic degradation studies established the influence of CSmod concentration and Ch:CSmod ratio on the crosslinking process. In situ rheological experiments verified the injectability of resulted systems. The biological in vitro evaluation demonstrated that all designed materials are biocompatible as they supported proliferation and adhesion of MG-63 cell line. In vitro biomineralization study employing simulated body fluid model revealed CSmod-content dependent bioactivity of obtained hydrogels. Importantly for pristine collagen/chitosan materials, the formation of apatite-like structures was not observed. Our findings demonstrate that developed injectable ColChCSmod hydrogels particularly system with the greatest CSmod concentration exhibits high bioactive potential, without the need of applying additional inducers what renders them promising materials within tissue engineering applications.