Properties of collagen gels cross-linked by N-hydroxysuccinimide activated adipic acid deriviate

In order to improve the properties of collagen gel, N-hydroxysuccinimide activated adipic acid derivative (NHS-AA) was introduced into the formation of collagen fibrils. NHS-AA with different [NHS-AA]/[NH2] ratios (0.1–1.5, calculated by [ester group] of NHS-AA and [NH2] of lysine and hydroxylysine residues of collagen) was added after, simultaneously with or before the formation of collagen fibrils (abbreviated CAF, CSF and CBF, respectively) to obtain different collagen gels. With the same dose of NHS-AA, the cross-linking degree for CAF was lower than those for CSF and CBF. The formation of collagen fibrils was restrained by NHS-AA for CSF and CBF while that for CAF was unaffected. When the dose of NHS-AA increased from 0.1 to 1.5, the water contents of CSF and CBF increased while that of CAF had no obvious change. With lower dose of NHS-AA (0.1), CAF possessed higher value of G′ (87.3 Pa) and the best thermal stability (47.6 °C). As the ratio of [NHS-AA]/[NH2] increased to 1.5, CSF had the maximum value of G′ (288.8 Pa) and CAF had the best thermal stability (52.9 °C). These results showed collagen gels with different properties could be prepared by adding NHS-AA with different adding sequence and dose.