Adhesive, Chemically Resistant and Antibacterial Protein Films by Coacervating Mineralization of Noble Metal-Binding Elastin-Like Polypeptides

Protein films (PFs) provide a sustainable, biocompatible platform for food packaging, biomedical, and advanced technological applications. However, chemical resistance and the incorporation of desirable characteristics imparted by nanoparticles are often difficult to achieve and require multi-step processing. Here, we describe a one-pot strategy for fabricating chemically-resistant PFs using fusion proteins that combine the noble-metal mineralization activity of Au/Ag-binding peptides with the thermally controlled liquid-liquid phase separation of elastin-like polypeptides (ELPs). While protein-aided mineralization of an Au3+ precursor solution at room temperature yields monodisperse gold nanoparticles capped by a thermoresponsive corona that drives the reversible assembly of approximately 100 nm plasmonic clusters, immediate transfer of the mixture to 45 °C produces a continuous composite film that conformally adheres to glass, polystyrene, and curved substrates. These PFs withstand prolonged exposure to ethanol, toluene and nitric acid, and can be activated with water and heat to bond to glass, supporting loads of up to 2 kg. The films are stabilized by metallic nanoparticle cross-links. Spectroscopic measurements suggest that they are formed in a three-step mineralization-phase separation pathway involving metal nucleation, coacervation-driven sedimentation, and interfacial reconstruction. We extend the approach to silver to produce PFs exhibiting antimicrobial activity against E. coli.