Improving the crosslinking of collagen casing and glutaraldehyde by facilitating the formation of conjugate structure via pH

Authors: YU, ZHE - Jiangnan University; WU, JINGMING - Ghent University; ZHANG, TING - Jiangnan University; CHEN, CHI - Jiangnan University; MA, YUN - Jiangnan University; LIU, HONGXIANG - Israel Institute Of Technology; Chiou, Bor Sen; LIU, FEI - Jiangnan University; LI, JIAN - Jiangnan University

Submitted to: Collagen and Leather
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2024
Publication Date: 10/1/2024
Citation: Yu, Z., Wu, J., Zhang, T., Chen, C., Ma, Y., Liu, H., Chiou, B., Liu, F., Li, J. 2024. Improving the crosslinking of collagen casing and glutaraldehyde by facilitating the formation of conjugate structure via pH. Collagen and Leather. 6. Article 29. https://doi.org/10.1186/s42825-024-00172-8.
DOI: https://doi.org/10.1186/s42825-024-00172-8

Interpretive Summary: Collagen-based materials have been widely used in many fields, including tissue engineering, biochemistry, and food engineering. To improve the material's properties, glutaraldehyde can be used to cross-link collagen. However, the cross-linking reaction can be complex since glutaraldehyde exists in many forms in solution. In this study, we determined the forms of glutaraldehyde in solution and examined its reaction with collagen at different pH levels. We found that glutaraldehyde can exist in its polymerized form under basic conditions. Also, glutaraldehyde cross-linked collagen to a greater degree under basic conditions than acidic conditions. This resulted in collagen films that swelled and shrank less in water. These results can be used to optimize the production of collagen films for specific material properties. Collagen films produced from animal hides have been widely used as casings in the production of sausages. Collagen undergoes multiple treatments, including pulverization, acid swelling, neutralization, washing, and drying, during the entire production process. However, few studies have examined the effects of these treatments on the triple-helix structure and material properties of the collagen films. In this study, we examined the changes in the material properties of colllagen during each stage of production. We found that acid swelling destroyed some triple-helix structure of collagen and increased the size of the helix structure. Also, neutralization destroyed most of the collagen structure. However, the helix structures reformed during drying of the films, although these structures were less thermally stable than the original ones. These results can be used to optimize production of casings to improve their material properties.

Technical Abstract: Glutaraldehyde (GTA) crosslinking is widely used to improve collagen material properties. The aim of this research was to determine the optimal pH of the crosslinking between GTA and collagen as well as the crosslinking mechanisms at different pH values. An alkaline environment enhanced GTA polymerization through the rapid generation of -C=C-C=O and -C=N-C=C- conjugate structures and enhanced the crosslinking reaction of the GTA polymers with amino groups. At a pH>8, the fibril diameter and d-space value declined significantly in the self-assembled collagen fibril – GTA system. Also, GTA treated collagen films under alkaline conditions showed greater thermal stability and hydrophobicity. In addition, the crosslinking mechanism between GTA and collagen under alkaline conditions was proposed, which could provide guidance on the crosslinking reaction studies of GTA with other proteins.