Properties of bovine type I collagen hydrogelscross-linked with laccase-catalyzed gallic acid

Collagen hydrogels with a three-dimensional network structure were prepared through self-assembly of collagen molecules, and incubated in laccase-catalyzed gallic acid solutions (L-GA) with different concentrations (0.5–10%, w/v, calculated from the L-GA mother solution). UV-visible spectroscopy and Fourier transform infrared spectrometry suggested that quinones and cross-links between the quinones and the collagen molecules had formed. With an increase in L-GA concentration from 0.5 to 5%, the degree of cross-linking increased from 8.78% to 19.13%; when the L-GA concentration exceeded 5%, the degree of cross-linking increased slightly. At L-GA concentrations ≤ 5%, the thermal denaturation temperature (from 67.4to 74.7°C), the storage modulus (from 90 to 251.42 Pa) and the ABTS•+ free radical scavenging activity (from 4.89 to 98.92%) significantly increased, and a distinct decrease was observed in the degree of enzymatic degradation (from 81.48 to 49.34%). At L-GA concentrations >5%, only a slight improvement in these properties was observed. The gel strength of the modified collagen hydrogels reached a maximum value of 1346 g, which was more than twice that of the native collagen hydrogel (656 g) at 5%L-GA. Furthermore, afterthe concentration of L-GA exceeded 1%, the pore sizes observed by scanning electron microscopy began to diminish and showed denser network structures. These data indicated that the properties of collagen hydrogels can be substantially improved by modification with an appropriate concentration of L-GA.