Biosynthesized Silk-Amyloid-Mussel Proteins as Dissolution Recyclable Materials With Tunable Supercontraction

Dissolution recycling represents a promising and potentially cost-effective strategy for material regeneration and greenhouse gas reduction. Yet, very few polymers are practically recyclable by dissolution because strong intermolecular interactions, essential for mechanical performance, are typically incompatible with solvent disruption during dissolution. Here, we present a rational material engineering approach that balances these competing requirements to create high-performance, dissolution-recyclable protein-based materials (PBMs). Using protein engineering and synthetic biology, we designed silk-amyloid-mussel (SAM) protein hybrids whose amorphous domains control solvent ingress, while crystalline domains maintain load-bearing intermolecular interactions. The engineered SAM fibers, SAM_HY, exhibited exceptional tensile strength (401 ± 40 MPa), toughness (124 ± 38 MJ/m^-3), and minimal supercontraction (2.2% ± 1.9%) under high humidity (>90%), alongside full recyclability through a rapid (<1 h), energy-efficient dissolution process using aqueous formic acid. Recycled fibers retained both structural integrity and mechanical performance over multiple recycling cycles. Moreover, the recycled SAM_HY protein was reprocessed into hydrogels with strong underwater adhesion and mechanical robustness even after further recycling. These findings establish fundamental design principles for recyclable PBMs and demonstrate the feasibility of producing versatile, high-performance, sustainable, and recyclable protein materials for a broad range of applications.