Robust Protein Hydrogels from Silkworm Silk

Silk protein is a promising natural material applied in various fields, but the application of silk protein-based hydrogel is quite limited because of its long gelation time and poor mechanical properties. Here, we present a facile way to prepare strong silk protein hydrogels simply by adding surfactant into silk fibroin aqueous solution and incubating at 60 degrees C. The resulting silk protein hydrogels demonstrate fairly good mechanical properties; for example, the silk protein hydrogel made by adding sodium dodecyl sulfate (SDS) has the compressive and tensile moduli of 3.0 and 3.3 MPa, respectively, which are close to some tissues in the body, such as cartilages, tendons, and ligaments. The effect of different types of surfactant on the formation of strong silk protein hydrogel, and the possible reason for the improvement of the mechanical properties of the hydrogel are also discussed. In addition, we show that such a strong silk protein hydrogel maintains good biocompatibility when adding a proper amount of surfactant. Finally, we use a Fe3O4-loaded silk protein hydrogel as an example to demonstrate its application in the catalytic field. All these results imply that such a natural, sustainable, strong, and biocompatible protein-based hydrogel holds great promise as a multifunctional material in various applications.