Antibacterial effect and toxicity pathways of industrial and sunscreen ZnO nanoparticles on Escherichia coli

Abstract There has been an unprecedented increase in the production and consumption of metal oxide nanoparticles (NPs) due to their physicochemical properties. While NPs are advancing the frontiers of science, technology, medicine, and consumer products, their toxicity to human health and the environment remains an emerging concern. Since we are exposed to NPs largely through consumer products, this paper compares the toxicity of sunscreen lotion extracted ZnO NPs with industrial-grade ZnO NPs. E. coli was exposed to different concentrations of ZnO NPs for different durations. Our analysis suggests that E. coli growth and reactive oxygen species (ROS) varied according to type and size of particles, as well as level and duration of exposure to ZnO NPs. ROS generation was higher at the growth phase than at the stationary phase. Industrial ZnO NPs with smaller particle size were more toxic than those extracted from the sunscreen with larger particle size. The smaller particle size with homogenous distribution could be one of the underlying causes of their high toxicity. Our findings have implications for guiding policies to manage exposure to NPs in consumer products and the environment.