Selective toxicity of ZnO nanoparticles toward Gram-positive bacteria and cancer cells by apoptosis through lipid peroxidation.

Nanoparticles are increasingly recognized for their utility in biological applications including nanomedicine. The present study investigated the toxicity of zinc oxide (ZnO) nanoparticles toward prokaryotic and eukaryotic cells. Cytotoxicity of ZnO to mammalian cells was studied using human myeloblastic leukemia cells (HL60) and normal peripheral blood mononuclear cells (PBMCs). Antibacterial activity of ZnO was also tested against the Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa, as well as the Gram-positive bacterium Staphylococcus aureus, and the effect was more pronounced with the Gram-positive than the Gram-negative bacteria. ZnO nanoparticles exhibited a preferential ability to kill cancerous HL60 cells as compared with normal PBMCs. The nanoparticles enhanced ultrasound-induced lipid peroxidation in the liposomal membrane. The work suggested two mechanisms underlying the toxicity of ZnO: (i) involvement of the generation of reactive oxygen species (ROS) and (ii) induction of apoptosis. The work also revealed potential utility of ZnO nanoparticles in the treatment of cancer, for their selective toxicity to cancer cells. FROM THE CLINICAL EDITOR: The toxicity of zinc oxide to bacteria was related to the generation of reactive oxygen species and to the induction of apoptosis. Interestingly, these effects were differentially greater in human myeloblastic leukemia cells (HL60) than normal peripheral blood mononuclear cells.