Effects of coating materials on antibacterial properties of industrial and sunscreen-derived titanium-dioxide nanoparticles on Escherichia coli

Abstract Organic or inorganic stabilizers are often used for coating nanoparticles (NPs) in consumer products. However, upon release of stabilized NPs into the environment, uncertainty exists as to the antimicrobial properties of NPs due to stabilizers and the resultant bioaccumulation in organisms. This study investigates antibacterial effects and subsequent mechanisms of TiO 2 NPs on Escherichia coli ( E. coli) in the presence and absence of stabilizers (CMC, PVP, and SiO 2 ) commonly used in consumer products. Compared with uncoated TiO 2 NPs, the presence of any stabilizers tested in this study increased toxicity of NPs and enhanced growth inhibition in E. coli . While the particle sizes of TiO 2 were smaller as the result of coating with PVP or CMC and appeared to contribute to E. coli cell damage, the generation of reactive oxygen species (ROS) was independent of stabilizer type. In fact, coating with PVP and CMC exerted ROS scavenging properties. In contrast, increased ROS production was observed at higher concentrations of TiO 2 and upon coating with SiO 2 . This impact of SiO 2 can be related to the formation of a Ti O Si chemical bond. The results of the present study emphasize the importance of nanoparticle coating to their anti-bacterial activity and toxicity.