Viscoelasticity Can Be Tuned Through Covalent Incorporation of Chondroitin Sulphate in Allylated Gelatin Hydrogels

Cartilage is a slow-remodeling tissue with limited healing capacity. This has led to decades of tissue engineering efforts where the goal is biomaterials with regenerative capacity to restore functional integrity. Achieving full functional and mechanical integrity has proven difficult as cartilage has distinct mechanical properties. Glycosaminoglycans (GAGs) play a crucial role in cartilage mechanics due to their swelling behavior, contributing to viscoelasticity. The aims of this study are to covalently incorporate thiolated chondroitin sulphate (CSSH) in allylated gelatin (gelAGE) hydrogels at different concentrations to mimic GAG-rich regions in cartilage and create platforms to study subsequent cellular behavior. Hydrogels are evaluated for soluble fraction, swelling ratio, chondroitin sulphate (CS) retention, mechanical and viscoelastic properties, and cytocompatibility. ≈80% of CSSH is retained, and samples containing CSSH has an increased swelling ratio, indicating the incorporation of GAGs. Samples containing CSSH has an increased relaxation amplitude compared to gelAGE controls with a more elastic response. The addition of CSSH has no adverse effects on cytocompatibility. In conclusion, this study demonstrates the incorporation of thiolated CS in gelAGE hydrogels at different concentrations with no adverse effects on cytocompatibility. This allows for viscoelastic tuning which is important to consider when engineering new biomaterials.