Modular Protein Fibers with Outstanding High‐Strength and Acid‐Resistance Performance Mediated by Copper Ion Binding and Imine Networking

Abstract Engineered protein fibers are promising biomaterials with diverse applications due to their tunable protein structure and outstanding mechanical properties. However, it remains challenging at the molecular level to achieve satisfied mechanical properties and environmental tolerance simultaneously, especially under extreme acid conditions. Herein, the construction of artificial fibers comprising chimeric proteins made of rigid amyloid peptide and flexible cationic elastin‐like protein (ELP) module is reported. The amyloid peptide readily assembles into highly organized β ‐sheet structures that can be further strengthened by the coordination of Cu 2+ , while the flexible ELP module allows the formation of imine‐based crosslinking networks. These double networks synergistically enhance the mechanical properties of the fibers, leading to a high tensile strength and toughness, overwhelming many reported recombinant spidroin fibers. Notably, the coordination of Cu 2+ with serine residues could stabilize β ‐sheet structures in the fibers under acidic conditions, which makes the fibers robust against acid, thus enabling their successful utilization in gastric perforation suturing. This work highlights the customization of double networks at the molecular level to create tailored high‐performance protein fibers for various application scenarios.