Cytotoxicity of zinc oxide nanoparticles and silver nanoparticles in human epithelial colorectal adenocarcinoma cells

• The characterization of ZnO nanoparticles and Ag nanoparticles.
• The various morphologies of Caco-2 cells stained with double staining.
• The dose and time dependent cytotoxicity on Caco-2 cells by WST-1 assay.
• The comparison of oxidative stress damage between ZnO NPs and Ag NPs.

Safety concerns related to nanoparticles have stimulated research in this area. Therefore, the objective of this study was to compare the cytotoxicity of ZnO NPs with Ag NPs to human epithelial colorectal adenocarcinoma (Caco-2) cells. Nanoparticles were firstly characterized by size in transmission electron microscope. The WST-1 assay displayed cells exposed to higher nanoparticles concentrations and for longer time showed more serious cytotoxic changes. The acridine orange and ethidium bromide (AO/EB) double staining characterized the morphology of viable cells, apoptotic cells and necrotic cells. Both ZnO and Ag NPs cytotoxicity exhibited a significant depletion of superoxide dismutase (SOD) level with an increase in reactive oxygen species (ROS) level. Our conclusion suggested that ZnO NPs may exert higher cytotoxicity than Ag NPs in the same concentrations range. For ZnO NPs, cytotoxicity exhibited a dose- and time-dependent effects. In contrast with low concentrations Ag NPs, cells showed the subsequence of hormesis. There is still little knowledge about how nanoparticles in food packing materials interact with the cell membrane, and the consequence of these interactions.