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

TL;DR

This study develops highly swollen, mechanically tunable collagen hydrogels with preserved triple-helical structures, suitable for wound dressings and regenerative medicine, by covalent functionalization and multi-scale characterization.

Contribution

It introduces a multi-scale design approach for collagen hydrogels with adjustable mechanical and swelling properties while maintaining biofunctionality.

Findings

Achieved swelling ratios up to 1996 wt.-%

Tuned compressive modulus from 30 to 168 kPa

Maintained over 70% triple-helical structure

Abstract

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±12 &ndash 91±7 mol.-%) of introduced moieties governed the structure-property relationships in resulting collagen networks, so that the swelling ratio (<i>SR</i>: 707±51 &ndash 1996±182 wt.-%), bulk compressive modulus (<i>E_c</i>: 30±7 &ndash 168±40 kPa) and Atomic Force Microscopy elastic modulus (<i>E_AFM</i>: 16±2 &ndash 387±66 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.