In situ injectable poly(γ-glutamic acid) based biohydrogel formed by enzymatic crosslinking

Enzymatic crosslinking was developed to prepare in situ forming poly(c-glutamic acid) (c-PGA) based hydrogel in this study. First, the precursor of poly(c-glutamic acid)-tyramine (c-PGA-Ty) was synthesized through the reaction of carboxyl groups from a c-PGA backbone with tyramine. The structure of the grafted precursor was confirmed by 1 H-NMR and Fourier transform infrared spectroscopy. After that, the crosslinking of the phenol-containing c-PGA-Ty precursor was triggered by horseradish peroxi- dase in the presence of H2O2; this resulted in the formation of the c-PGA-Ty hydrogels. The equilibrium water content, morphology, enzymatic degradation rate, and mechanical properties of the hydrogels were characterized in detail. The data revealed that the well-interconnected hydrogels had tunable water contents, mechanical properties, and degradability through adjustments of the com- position. Furthermore, cell experiments proved the biocompatibility of the hydrogels by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylte- trazolium bromide assay. These characteristics provide an opportunity for the in situ formation of injectable biohydrogels as potential candidates in cell encapsulation and drug delivery. V C 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42301.