Multi-scale Mechanical Characterization of Highly Swollen Photo-activated Collagen Hydrogels

Biological hydrogels have been increasingly sought after as e.g. wound dressings or scaffolds for regenerative medicine, due to their inherent biofunctionality in biological environments. Especially in moist wound healing, the ideal material should absorb large amounts of wound exudate whilst remaining mechanically competent in-situ. Despite their large hydration, however, current biological hydrogels still leave much to be desired in terms of mechanical properties in physiological conditions. To address this challenge, a multi-scale approach is presented for the synthetic design of cyto-compatible collagen hydrogels with tunable mechanical properties (from nano- up to the macro-scale), uniquely high swelling ratios and retained (>70%) triple-helical features. Type I collagen was covalently functionalized with three different monomers, i.e. 4 vinylbenzyl chloride, glycidyl methacrylate and methacrylic anhydride, respectively. Backbone rigidity, hydrogen-bonding capability and degree of functionalization (<i>F</i>: 16&plusmn12 &ndash 91&plusmn7 mol.-%) of introduced moieties governed the structure-property relationships in resulting collagen networks, so that the swelling ratio (<i>SR</i>: 707&plusmn51 &ndash 1996&plusmn182 wt.-%), bulk compressive modulus (<i>E_c</i>: 30&plusmn7 &ndash 168&plusmn40 kPa) and Atomic Force Microscopy elastic modulus (<i>E_AFM</i>: 16&plusmn2 &ndash 387&plusmn66 kPa) were readily adjusted. In light of their remarkably high swelling and mechanical properties, these tunable collagen hydrogels may be further exploited for the design of advanced dressings for chronic wound care.