Recyclable thermo-responsive elastin-based adhesives with tough underwater adhesion and rapid hemostasis ability

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Protein-based underwater adhesives have attracted tremendous attention due to their excellent biocompatibility compared to adhesives prepared with synthetic polymers. However, the fabrication of protein-based adhesives always requires multiple successive steps, and their underwater adhesion is quite limited. Inspired by the human elastic fibers, bone matrix, and marine adhesive proteins, a thermo-responsive underwater adhesive was fabricated through a facial one-step complexation of elastin (ELN), hydroxyapatite (HAP), and tannic acid (TA) based on multiple non-covalent molecular interactions. During underwater adhesion, the adhesive can perform sufficient flowability to adhere seamlessly and strongly to the substrates upon heating at 37 ℃ and then significantly increase its cohesion through cooling down to 25 ℃ to sustain adhesion. The regulation of the balance between adhesion and cohesion in response to temperature change enables the adhesive to exhibit a robust underwater adhesion ranging from 0.3 to 1.1 MPa to the substrates with low, medium, or high surface energy, outperforming most protein-based adhesives. Importantly, the adhesive can be further processed into powders with well-maintained underwater adhesion by a simple drying and grinding method, facilitating adhesion onto irregular-shaped target sites, reusability, and closed-loop recycling. The adhesive powder also possesses a rapid in vivo hemostatic property, suggesting a potential biomedical application.