Investigation on the Structure and Mechanical Properties of Highly Tunable Elastomeric Silk Fibroin Hydrogels Cross-Linked by Gamma-Ray Radiation

Silk fibroin (SF) is a natural polymer with low immunogenicity and good biocompatibility. However, most silk-based hydrogels formed through chemical or physical cross-linking are brittle, the preparation of which also inevitably introduce the cytotoxic cross-linking agents. Herein, a simple strategy is presented for synthesizing SF hydrogels with tunable mechanical properties by combining gamma-ray radiation with ethanol treatment. Neither toxic initiators nor chemical agents are utilized during the whole preparation procedure. For “soft” hydrogels, the compressive modulus are less than 29 kPa (SF-S hydrogels), while for “tough” hydrogels, the compressive modulus are between 1.21 and 2.41 MPa (SF-D hydrogels). Specifically, gamma-ray radiation makes SF form uniform and stable chemical cross-linking sites within and between molecular chains, resulting in "soft" and highly elastic SF hydrogels. The physical cross-linking via ethanol treatment leads to the self-assembly of fibroin chains, transforming those ...