| The purpose of this study is to evaluate the cytotoxicity and study the oxidative stress mechanism induced by SiO2 (15, 46 nm), CeO2 (20 nm), and ZnO (70, 420 nm) particles in cultured human bronchoalveolar carcinoma-derived cells (A549). After exposure to different dosages of particle suspension, the cell viability was measured by using sulforhodamine B (SRB) assay. In the oxidative stress mechanism study, biomarkers including total reactive oxygen species (ROS), glutathione (GSH), malondialdehyde (MDA), alpha-tocopherol, and lactate dehydrogenase (LDH), were quantitatively assessed. In addition, single cell gel electrophoresis (comet assay) was used to determine the oxidative DNA damage induced by ZnO particles. Our study showed all these particles induced significant cytotoxicity and oxidative stress at certain dosages, which were reflected by the significant (p < 0.05) decreased GSH levels, increased cellular ROS levels, MDA levels and LDH. The cytotoxic order of these particles was: ZnO > CeO2 > SiO2. Both ZnO particles induced significant but similar DNA damage at 10-14 mug/ml dosage range after 24 h exposure. The completely preventive effect of 5 mM NAC on 14 mug/ml ZnO (70 nm, 420 nm) induced cytotoxicity also supported the oxidative stress mechanism. Different sizes of SiO2 (15, 46 nm) and ZnO (70, 420 nm) did not show size-dependent cytotoxicity, probably due to the aggregation of nanoparticles and the subsequent similar hydrodynamic sizes in cell culture medium. |
