Nanoporous Stainless Steel Surfaces for Anti-Bacterial Adhesion Performances

Abstract

Abstract. Stainless steel is one of the most widely used metals for food industry applications. Cavities and crevices on its surface are able to accommodate bacteria that can evade bactericidal activity. Therefore, the evaluation of electropolishing and anodizing treatments for anti-biofouling performance on stainless steel surfaces was carried out in this study. Plates of 316L stainless steel were electropolished to make nanosmooth surfaces in a mixture solution of phosphoric acid and sulfuric acid at 3.5 V at 80°C for 10 min. These samples were anodized in an anhydrous ethylene glycol solution containing perchloric acid to achieve nanoporous surfaces with diameters of 50 and 80 nm after being treated with 40 V for 10 min and 50 V for 35 min, respectively. Field emission scanning electron microscope and atomic force microscope images showed that the surface topographies of the stainless steel were strongly manipulated by the surface treatments. The populations of bacterial cells adhered to the nanosmooth, 50 nm nanoporous, and 80 nm nanoporous surfaces of stainless steel were 3.7, 1.7, and 1.5 log CFU cm-2, respectively. Nanoporous surfaces on stainless steel showed a significant repellency of as compared to nanosmooth stainless steel (p < 0.05). The results suggest that nanoporous characteristics on stainless steel surface have a great potential for biofilm prevention in food industries. Keywords: Anodization, Listeria monocytogenes, Nanoengineered surface, Stainless steel.