Tough biohydrogels with interpenetrating network structure by bienzymatic crosslinking approach

Enzymatically crosslinked biohydrogels have increasingly attracted attention mainly due to the mildness of this type of reaction. However, their mechanical strength is usually so weak that their applications are limited in the field of medicine. In order to improve their mechanical properties and degradation resistance, bienzymatic crosslinking approach was utilized to prepare biohydrogels of gelatin and chitosan with an interpenetrating polymer network (IPN) structure in this report. First of all, chitosan was grafted with phloretic acid (chitosan-PA) used as a substrate of horseradish peroxidase (HRP). After that, the gelation process of gelatin/chitosan-PA IPN hydrogels was monitored by a rheometer. The results indicated the formation of dual networks: one gelatin network crosslinked by transglutaminase (TG) and another chitosan-PA network crosslinked by HRP in the presence of a low concentration of H2O2. In addition, the mechanical performances of the hydrogels were measured by a universal testing machine. It was found that the mechanical properties of the IPN gels were significantly improved compared with gelatin hydrogel crosslinked by TG. Moreover, the swelling ratio, degradation behavior, and cytocompatibility of the IPN hydrogels were investigated in detail. The preliminary biological evaluation indicated that the IPN hydrogels can support L929 cell adhesion and proliferation. Overall, the gelatin/chitosan IPN hydrogels prepared by bienzymatic crosslinking approach have excellent biocompatibility and mechanical properties. Therefore, dual enzyme-mediated crosslinking of natural polymer hydrogels is promising for the development of tissue engineering scaffolds and wound dressing. (C) 2015 Elsevier Ltd. All rights reserved.