Copper doping enhanced the oxidative stress-mediated cytotoxicity of TiO nanoparticles in A549 cells.

Physicochemical properties of titanium dioxide nanoparticles (TiO NPs) can be tuned by doping with metals or nonmetals. Copper (Cu) doping improved the photocatalytic behavior of TiO NPs that can be applied in various fields such as environmental remediation and nanomedicine. However, interaction of Cu-doped TiO NPs with human cells is scarce. This study was designed to explore the role of Cu doping in cytotoxic response of TiO NPs in human lung epithelial (A549) cells. Characterization data demonstrated the presence of both TiO and Cu in Cu-doped TiO NPs with high-quality lattice fringes without any distortion. The size of Cu-doped TiO NPs (24 nm) was lower than pure TiO NPs (30 nm). Biological results showed that both pure and Cu-doped TiO NPs induced cytotoxicity and oxidative stress in a dose-dependent manner. Low mitochondrial membrane potential and higher caspase-3 enzyme (apoptotic markers) activity were also observed in A549 cells exposed to pure and Cu-doped TiO NPs. We further observed that cytotoxicity caused by Cu-doped TiO NPs was higher than pure TiO NPs. Moreover, antioxidant N-acetyl cysteine effectively prevented the reactive oxygen species generation, glutathione depletion, and cell viability reduction caused by Cu-doped TiO NPs. This is the first report showing that Cu-doped TiO NPs induced cytotoxicity and oxidative stress in A549 cells. This study warranted further research to explore the role of Cu doping in toxicity mechanisms of TiO NPs.