2.0 GPa Spider Silk by Ultrafine Nanofibril Creation for Powerful Actuation and Medical Applications

High-strength and tough fibers are essential in biological systems, such as ligaments and tendons, where they preserve tissue integrity under mechanical stress. Spider silk uniquely combines exceptional strength and toughness, arising through the hierarchical self-assembly of spidroin, while also offering excellent biocompatibility and inherent biodegradability, making it an ideal candidate for biomedical applications. Here, we demonstrate that rearranging spidroin peptide chains into ultrafine nanofibrils yields engineered natural spider silk fibers with markedly enhanced both mechanical and functional performance, achieving a breaking strength of 2.0 GPa, toughness of 480 MJ m^-3, and actuation stress of 92.6 MPa. Importantly, the contractile actuation enables these fibers to function as a self-adapting surgical suture: beyond passive wound closure, the fibers actively generate postoperative stress, improving tissue approximation and promoting repair. This work establishes a generalizable strategy for engineering natural fibers with integrated mechanical robustness, actuation, and biomedical utility, opening new avenues for intelligent biomaterials design.