EDC cross-linking improves skin substitute strength and stability

Collagen-based scaffolds are extensively utilized as an analog for the extracellular matrix in cultured skin substitutes (CSS). To improve the mechanical properties and degradation rates of collagen scaffolds, chemical cross-linking is commonly employed. In this study, freeze-dried collagen-GAG sponges were crosslinked with increasing concentrations of 1-ethyl-3-3-dimethylaminopropylcarbodiimide hydrochloride (EDC; 0, 1, 5, 10, 50 mm). Cross-linking with EDC at concentrations >1 mm was shown to greatly decrease degradation by collagenase up to 21 days. Ultimate tensile strength (UTS) of acellular collagen sponges scaled positively with EDC concentration up to 10 mm. At 50 mm EDC, the UTS decreased dramatically likely due to the brittle nature of the highly crosslinked material. Co-culture of human fibroblasts (HF) and keratinocytes (HK) on these substrates reveals an apparent cytotoxicty of the EDC at high concentrations with reduced cell viability and poor cellular organization in CSS fabricated with scaffolds crosslinked with 10 or 50 mm EDC. From the data gathered in this study, intermediate concentrations of EDC, specifically 5 mm, increase collagen sponge stability and strength while providing an environment in which HF and HK can attach, proliferate and organize in a manner conducive to dermal and epidermal regeneration.