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3,4-Dihydroxybenzaldehyde, a derivative of catechol and an agent with an extensive pharmacological and biological activities, was used to modify collagen and prepared hydrogels. The aldehyde group of 3,4-dihydroxybenzaldehyde interacted with the ɛ-amino group of collagen, and then the catechol group of 3,4-dihydroxybenzaldehyde was oxidized and self-polymerized. The chemical network formed due to the cross-linking bridges of polymerized catechol groups among collagen molecules, resulting in the transformation from solution to hydrogel. The results of the Fourier-transform infrared measurement indicated that the triple helix structure of collagen was integrated after cross-linking. The appearance of hydrogels changed from golden to dark brown with the increasing 3,4-dihydroxybenzaldehyde dose. When the weight ratio of 3,4-dihydroxybenzaldehyde and collagen increased from 0 to 2:1, the thermal denaturation temperature of collagen increased from 40.2 to 77.6℃ while the elastic modulus of collagen increased from 13.6 to 1061.4 Pa. The addition of 3,4-dihydroxybenzaldehyde also caused more compact morphologies and a dramatic enhancement in the enzymatic resistance of hydrogels. Moreover, the results of cell proliferation assay demonstrated the favorable biocompatibility of collagen hydrogels with 3,4-dihydroxybenzaldehyde. These promising data indicate that the novel hydrogels had significant potential for applications.

Abstract 3,4-dihydroxybenzaldehyde (DB), a derivative of catechol, were applied to improve the physicochemical properties of collagen fibrils, prepared via the self-assembly of collagen molecules. The aldehyde group of DB interacted with ε-amino group of collagen, and then the catechol group of DB was oxidized and self-polymerized, resulting in the formation of cross-links among collagen. The results of spectral experiment showed that the triple helix structure of collagen were integrated and the Tyr residues of collagen might react after cross-linking. Collagen fibrils became dark brown and the yellowness (Δb*) ascended from 0 to 3.24 when the [CHO]/[NH 2 ] ratio rose from 0:1 to 40:1. Due to the effects of DB, the adjacent collagen fibrils agglomerated without particular orientation and the pore size of collagen fibril network decreased. The thermal stability of collagen fibrils had been improved about 15 °C while the elastic modulus obviously increased from 19 to 834 Pa after cross-linking. Moreover, the presence of DB also caused the dramatically enhancement in the enzymatic resistance of collagen fibrils while the biocompatibility of collagen fibrils was still desirable. These promising data suggested biomedical materials based on collagen fibrils with requisite properties can be obtained via adjusting the dose of DB. Highlights • Oxidized and self-assembled 3,4-dihydroxybenzaldehyde (DB) is applied to improve the stability of collagen fibrils. • The triple helix structure of collagen is integrated after cross-linked by DB. • Effects of DB are close to glutaraldehyde and superior to EDC and NHS derivative in reinforcements of collagen fibril. • The biocompatibility of DB is desirable and more favorable than that of glutaraldehyde. [ABSTRACT FROM AUTHOR]