Regulating Protein Secondary Structures Enables Versatile Hydrogels with Tunable Mechanical Properties

Regulating the mechanical performance of a material, especially for protein hydrogels, in situ from elasticity to plasticity and vice versa would be difficult but highly anticipated due to the diversity of promising applications. Herein, we proposed a strategy to prepare versatile hydrogels with tunable mechanical properties. It was demonstrated that we could rapidly prepare regenerated silk fibroin/gelatin (RSF/Gel) copolymer hydrogels by chemically modifying RSF by glycidyl methacrylate (RSF-MA) and gelatin by methacrylic anhydride (Gel-MA) under UV light in 60 s. Furthermore, the RSF/Gel hydrogels showed tunable mechanical properties by controlling the β-sheet content of SF, which can realize reversible switch between elasticity and plasticity in situ. The significant alteration of tensile stress at break and tensile elastic modulus at 10% strain was achieved with 720 times and 2000 times improvement from an elastic to plastic hydrogel. The compressive elastic modulus at 50% strain of a plastic hydrogel was improved to 3.6 MPa, which was 62 times higher than that of an elastic hydrogel. In addition, the performance of drug release of RSF/Gel hydrogel microneedles could be modulated by controlling the β-sheet content of SF, which could be a drug carrier and also be other promising biomaterials for a variety of biological and clinical applications.