Investigating the effect of macromolecular cross-linking and increasing fiber density on the diffusion and viscoelastic properties of extracellular matrix materials using multiparametric MRI

Synthetic polymer polyvinylpyrrolidone and fibrous protein collagen were used to investigate the effect of macromolecular cross-linking and increasing fiber density on the physicochemical properties of extracellular matrix models using clinical MRI parameters and torsional rheometry. T1 and T2 decreased with increasing viscoelastic moduli of both materials. Covalent cross-linking of macromolecules by irradiation affected stiffness, but had a smaller effect than polymer concentration on T1, T2 and ADC. Collagen at increasing concentrations sufficient to substantially affect tissue stiffness (reflecting increasing fiber density) affected the structure of water within tissue, (changes in T1 and T2), but did not hinder water diffusion.