All-natural superhydrophobic coating for packaging and blood-repelling materials

The design of a bio-safe superhydrophobic coating to repel water adsorption, food and blood adherence is significantly important to attenuate food spoilage, food waste and thrombi. Herein, we synthesize an all-natural superhydrophobic interfacial material that has strong interfacial stability on a variety of substrates, and has good repellence towater, highly-viscous liquid foods and biofluids (blood, urine, etc.). The base material is simply prepared in an aqueous solution of lysozyme and cysteine, in which the rapid phase transition of lysozyme is triggered by a cysteine-induced thiol-disulfide exchange reaction. The resulting phase-transited lysozyme (PTL) aggregates into microparticles with a nanoscale roughness, which are further packed into a dense layer with a micro-/nano-topography. The PTL is composed of an inner amyloid-like structure and shows strong interfacial adhesion with the underlying substrate due to amyloid-inspired adhesion. The PTL layer is finally converted to a robust coating to effectively repel liquid foods and biofluids by being decorated with a natural hydrophobic carnauba wax. This coating noticeably enhances the water repellence of cellulose-based packaging materials, and the resulting superhydrophobic paper is completely non-wetted by water without weakening the mechanical stability and usability of the modified paper. The coating further resists the adhesion of milk, yogurt, honey and various other beverages and edible liquids, which leaves no residue on the coated surface. This coating also significantly resists wetting by blood and other human biofluids with a noticeable decrease in platelet adhesion on the surface. This work underlines the importance of an amyloid-like protein assembly in the preparation of an all-natural green interfacial coating towards the robust repellence of water, edible liquids and blood.