Investigation of the Interaction between Epoxides and Collagen in Epoxy Tanning based on BDDGE Cross-linked Collagen Solution

Abstract

To investigate further the interaction between epoxides and collagen in epoxy tanning, collagen solutions (3 mg/ml) cross-linked with various concentrations (0.5–4-wt%) of 1,4-butanediol diglycidyl ether (BDDGE) at low temperature (4ºC), alkaline conditions (pH = 10) were prepared. The sodium dodecyl sulfate–polyacrylamide gel electrophoresis and Fourier transform infrared spectroscopy confirmed the intact triple-helix structure of the cross-linked collagen. With the increasing concentration of BDDGE, the denaturation temperature measured using VP-DSC increased from 42.56 ºC to 44.25ºC and thermogravimetric analysis showed that the decomposition temperature increased from 333.0ºC to 351.8ºC. In addition, the rheology properties such as G¢, G² and ?* were measured with a rotary rheometer using dynamic frequency scanning. The trinitrobenzensulfonic acid method and atomic force microscopy were used to investigate the interaction between collagen and BDDGE. The results indicated that the changes in cross-linked collagen performance were attributed to the transition of collagen aggregation caused by cross-linking. In addition, the transition point of 2-wt% BDDGE was the key node for the formation of a mature cross-linked network and the cross-linking barely increased above that. It is hoped that these findings deepen the understanding of epoxy tanning and provide guidance for the practical use of epoxides in tanning and biomaterials.