(71g) Cross-Linking of Thiolated Chitosan Films: Effects On the Cell Adhesion, Degradation and Cyclic Mechanical Properties

Cross-linking of Thiolated Chitosan Films: Effects on the Cell Adhesion, Degradation and Cyclic Mechanical Properties

Rebecca Ball, Kevin Miles and Howard W.T. Matthew

Department of Chemical Engineering and Materials Science, Wayne State University

Chitosan is a linear polysaccharide composed of glucosamine with randomly distributed N-acetyl glucosamines. The biopolymer is widely studied for applications in tissue engineering because of its biocompatibility, biodegradability, and availability. Chitosan has been shown to have a low immune response and is able to degrade in vivo. However, chitosan on its own does not have adequate mechanical or cell adhesion properties required for many tissue engineering applications. One way to alter the properties of chitosan is to add sulfhydryl groups to the chitosan polymer chains. The addition of sulfhydryl groups promotes spontaneous cross-linking via disulfide bond formation that alters several properties of the polymer. In order to add sulfhydryl groups, N-acetyl-cysteine (NAC) was grafted onto the chitosan amino groups using carbodiimide chemistry. In this project, the chitosan was thiolated to degrees of substitution ranging from 6% to 20%, and the properties of the resultant polymer were subsequently evaluated.  Results show that thiolation created a stronger and more ductile polymer with the 20% thiolated chitosan able to withstand a maximum stress of 10 Mpa compared to the unmodified chitosan at 5.54 Mpa. As well, the highest substituted chitosan could withstand a maximum strain of 1.3% more than the unmodified chitosan. The degradation properties of thiolated chitosan films was evaluated by exposure to lysozyme solutions. Thiolation increased the rate of dry mass loss for chitosan films, in proportion to the degree of substitution. The effects of cyclic loading on the mechanical properties of the thiolated chitosan are being studied and the results will be reported. Current results of cyclic testing suggest that higher substituted chitosan may be more elastic; however, the data is being studied and correct assumptions will be made. Preliminary results also indicate improved vascular smooth muscle cell adhesion on thiolated chitosans. Results to date indicate that unlike several other crosslinking chemistries, thiol-mediated crosslinking of chitosan improves several biomaterial performance parameters including: strength, elasticity and cell adhesion and proliferation.