Branched chitosans: Effects of branching parameters on rheological and mechanical properties

Abstract

Chitosan continues to be studied as a promising biomaterial for tissue repair and regeneration applications. However, chitosan structures show a large reduction in tensile strength in the wet state. Methods for improving the wet strength of chitosan materials may broaden its applicability as a tissue scaffold for applications requiring significant load bearing capacity. In this study, the role of molecular architecture in defining the mechanical properties of hydrated chitosan membranes was examined. Specifically, branched chitosan molecules were synthesized with a range of branch lengths and branch densities. Physical and mechanical properties were characterized using viscometry, FTIR spectroscopy, and tensile testing measurements, and the results were correlated with the postulated architecture of the linear and branched chitosan materials. Both branch density and branch length were found to influence the mechanical properties of chitosan membranes. For example, high-molecular-weight (600 kDa) chitosans grafted with 80 kDa branches exhibited up to twofold increases in both tensile strength and extensibility. FTIR results indicated that these increases correlated with enhanced levels of hydrogen bonding in the branched materials. Vascular smooth muscle cells cultured on cast membranes of the branched chitosans exhibited no differences in adhesion or spreading as compared to the linear polymer. The results indicate that the mechanical properties of chitosan materials can be improved by the induction of a branched molecular architecture.