Sustainable Protein to Generate High-Strength and Durable All-Underwater Adhesive via Physical Condensation Boosting Chemical Cross-linking

Designing high-performance protein adhesives for hard tissue applications remains challenging. Here, we present a physical condensation boosting chemical cross-linking strategy to produce a high-performance all-underwater adhesive composed of corn-derived zein, genipin, and poly(l-lysine). Physical condensation between anionic zein colloids and cationic poly(l-lysine) generates a soft adhesive. Dehydration of the ionic moieties enables powdery genipin to be pre-encapsulated into the dried bulk of the physical condensate. After experiencing reversible hydration, the genipin-encapsulated adhesive can be injected and bonded to various surfaces under the waterline. Crucially, the condensed adhesive creates confined microenvironments for genipin-bridged slow chemical cross-linking, achieving sequential adhesion and curing, and in situ self-reinforcement. The protein adhesive exhibits an adhesion strength of 2.0 MPa on bovine bone and excellent friction resistance (μ ∼ 0.15). Moreover, the adhesive shows long-term stability in various complex aqueous environments. These properties coupled with excellent biocompatibility, sustainability, and scalable production indicate significant potential in bone adhesion and device coatings.