Fiber Reinforcement of Soft Spider Silk Hydrogels.

Recombinant spider silk-based biomaterials show high application potential due to their biocompatibility, biodegradability, and low immunogenicity. Self-assembly of monomeric proteins into nanofibrils is necessary toward hydrogel formation and yields a dense physically entangled network, in which cells show high viability but so far low proliferative activity. To facilitate enhanced cell activity and growth, in this study low-concentration spider silk hydrogels were fabricated, resulting in higher cell proliferation but suffering from poor mechanical stability. Thus, electrospun fiber meshes also made from spider silk proteins were integrated into the soft hydrogels using a layer-by-layer approach. The composite structure significantly improved the mechanical properties and shape fidelity, including an increase in Young's modulus by an order of magnitude, while preserving the hydrogels' biocompatibility. This work provides a promising strategy for developing mechanically reinforced, cell-friendly spider silk-based hydrogels suitable for soft tissue engineering applications.