Physicochemical properties of gelatin gels prepared using citric acid derivative

We have developed a novel cross-linking reagent, citric acid derivative (CAD) in order to prepare gelatin gels. CAD was prepared by the modification of three carboxyl groups of citric acid with N-hydroxysuccinimide in the presence of 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide hydrochloride. Gelatin gels were successfully obtained in the presence of CAD. Using the gelatin gels, residual amino group content, swelling ratio and enzymatic degradability were evaluated. Residual amino groups in gelatin gels decreased with increasing CAD concentration. On the other hand, swelling ratio of gelatin gels decreased with increasing CAD concentration up to 70 mM, then increased at elevated CAD concentration. Enzymatic degradation behavior was also correlated to the swelling ratio of gelatin gels. These results suggested that gelatin gels prepared at CAD concentration of 70 mM had minimum cross-linking density.