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 TiO₂ NPs on Escherichia coli (E. coli) in the presence and absence of stabilizers (CMC, PVP, and SiO₂) commonly used in consumer products. Compared with uncoated TiO₂ 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 TiO₂ 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 TiO₂ and upon coating with SiO₂. This impact of SiO₂ can be related to the formation of a TiOSi chemical bond. The results of the present study emphasize the importance of nanoparticle coating to their anti-bacterial activity and toxicity.

Keywords: Antibacterial effect; Carboxymethyl cellulose (CMC); E. coli; Reactive oxygen species (ROS); TiO(2) nanoparticles; polyvinylpyrrolidone (PVP).