A Protocol for the Production of Gliadin-cyanoacrylate Nanoparticles for Hydrophilic Coating

This article presents a protocol for the production of protein-based nanoparticles that changes the hydrophobic surface to hydrophilic by a simple spray coating. These nanoparticles are produced by the polymerization reaction of alkyl cyanoacrylate on the surface of cereal protein (gliadin) molecules. Alkyl cyanoacrylate is a monomer that instantly polymerizes at RT when it is applied to the surface of materials. Its polymerization reaction is initiated by the trace amounts of weakly basic or nucleophilic species on the surface, including moisture. Once polymerized, the polymerized alkyl cyanoacrylates show a strong affinity with the object materials because nitrile groups are in the backbone of poly (alkyl cyanoacrylate). Proteins also work as initiator for this polymerization because they contain amine groups that can initiate the polymerization of cyanoacrylate. If aggregated protein is used as an initiator, protein aggregate is surrounded by the hydrophobic poly(alkyl cyanoacrylate) chains after the polymerization reaction of alkyl cyanoacrylate. By controlling the experimental condition, particles in the nanometer range are produced. The produced nanoparticles readily adsorb to the surface of most materials including glass, metals, plastics, wood, leather, and fabrics. When the surface of a material is sprayed with the produced nanoparticle suspension and rinsed with water, the micellar structure of nanoparticle changes its conformation, and the hydrophilic proteins are exposed to the air. As a result, the nanoparticle-coated surface changes to hydrophilic.