Bagworm Silk-Mimetic Protein Fibers with Extraordinary Stiffness via In Vivo Polymerization and Hierarchical Self-Assembly

Bagworm silk proteins, which contain crystalline structures with large β-nanocrystal sizes, are ideal candidates for biosynthetic high-performance fibers. However, the extremely high glycine content and greater molecular weight limit their heterologous expression efficiency and further application exploration. Here, a multi-module assembly strategy is developed to engineer novel chimeric structural proteins by incorporating the mechanical functional domains of bagworm silk proteins with the C-terminal self-assembly domains of spider silk proteins. By selecting a single repetitive unit of the functional region of bagworm silk proteins, the challenge of low heterologous expression efficiency is successfully addressed. Furthermore, the content and ordering of β-sheet structure are enhanced in the chimeric proteins through the alignment mediated by the spider silk C-terminal domain and ligation facilitated by split inteins, resulting in a remarkable Young's modulus of ≈15 GPa. This surpasses many artificial protein fibers, synthetic polymer fibers, and even natural spider silk. Notably, these protein fibers are drawn into surgical sutures and demonstrate superior wound healing effects compared to clinical suture in a skin wound model. This research presents a novel strategy for developing high-performance protein fibers, which will expand the scope of their mechanically demanding applications.