Efficient preparation of a permanent chitosan/gelatin hydrogel using an acid-tolerant tyrosinase

An acid-tolerant tyrosinase, tyrosinase-CNK, was used to form chitosan/gelatin hydrogels without any additional crosslinking materials at pH 4, where appropriate chitosan/gelatin blends were efficiently prepared based on the solubility of chitosan only under acidic conditions. The in vitro gelation degree and rheological studies revealed that the gelation of the chitosan/gelatin solution was successfully achieved within 12 min by the tyrosinase-CNK reaction at pH 4, and the glycol chitosan/gelatin blends were similarly crosslinked within 7 min at pH 6 (the optimum pH of tyrosinase-CNK). Remarkably, tyrosinase-CNK catalyzed the formation of permanent and stable chitosan/gelatin and glycol chitosan/gelatin gels, unlike the previous results of tyrosinase-mediated chitosan/gelatin gelation in which commercially available mushroom tyrosinase only catalyzed transient gel formation. In addition, the pore size distribution was greater than 100 μm in the morphological structure, and the high swelling ratio and enhanced mechanical properties are expected to be suitable for tissue engineering applications. These results demonstrate that the acid-tolerant tyrosinase-CNK can efficiently mediate the in vitro formation of chitosan/gelatin conjugates, and the obtained hydrogels have the potential to be used as a promising scaffold.