Collagen-collagen interactions mediated by plant-derived proanthocyanidins: A spectroscopic and atomic force microscopy study

Collagen cross-linkings are determinant of biological tissue stability and function. Plant-derived proanthocyanidins (PACs) mimic different hierarchical levels of collagen cross-links by non-enzymatic interactions resulting in the enhancement to the biomechanics and biostability of collagen-rich tissues such as dentin. This study investigated the interaction of PACs from Vitis vinifera grape seed extract with type I collagen in solubilized form and in the demineralized dentin matrix (DDM) by fluorescence spectral analysis; collagen-collagen binding forces in presence of cross-linking solutions by atomic force microscopy (AFM); and spectroscopic analysis of the DDM using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Glutaraldehyde (GA) and carbodiimide hydrochloride (EDC) with known cross-linking mechanisms were selected for comparative analyses. Changes in fluorescence upon interaction of solubilized type I collagen with PACs, EDC and GA reflected pronounced modifications in collagen conformation. PACs also promoted stronger collagen-collagen fibrils interaction than EDC and GA. A new feature was observed using ATR-FTIR spectroscopic analysis in PACs-treated collagen and DDM. The findings suggest covalent interactions between collagen and PACs. The mechanisms of interaction between PACs-collagen hold attractive and promising tissue-tailored biomedical applications and the binding forces that potentially drive such interaction were characterized.