A novel technology coats stainless steel (SS) with antibacterial polyelectrolyte micelles that results in steel that disinfects itself.

Researchers at the University of Liège (Belgium) succeeded in developing the silver-based nanoparticle antimicrobial coatings for SS by alternating the deposition of aqueous solutions of positively charged polyelectrolyte micelles, formed by electrostatic interaction between two oppositely charged polymers: a polycation bearing 3,4-dihydroxyphenylalanine units (DOPA, a major component of natural adhesives) solution with a polyanion, poly(styrene sulfonate), (PSS).

The antimicrobial coating is built in only five dipping steps; the SS surface is first dipped into a solution of positively charged micelles bearing DOPA groups on their surfaces used as an adhesion promoter; the second layer is formed by dipping the surface into an aqueous solution of the PSS. The third layer is deposited from an aqueous solution of positively charged micelles containing ammonium groups and silver-based nanoparticles, providing high antibacterial properties over a broad spectrum of bacterial strains commonly found in daily life. The last two steps are repeated once again.

The DOPA units are exploited for their well-known ability to anchor to stainless steel and to form and stabilize biocidal silver nanoparticles (Ag0). The chlorine counter-anion of the polycation forms and stabilizes biocidal silver chloride nanoparticles (AgCl). Additionally, the micelles, which serve as reservoirs of biocidal silver (Ag+), can be easily reactivated after depletion by dipping the SS into a 0.1 M silver nitrate (AgNO3) solution for one hour, followed by extensive rinsing with deionized water. The study was published in the May 2012 issue of Langmuir.

“This novel water-based approach is convenient, simple, and attractive for industrial applications,” concluded senior author Christophe Detrembleur, PhD, and colleagues of the Center for Education and Research on Macromolecules (CERM). “The film can also be reloaded with silver-based particles by simply dipping it in a silver nitrate aqueous solution, which again boosts the antibacterial activity.”

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