Bismuth oxide nanoparticles induce oxidative stress and apoptosis in human breast cancer cells

Metal nanomaterials such as bismuth oxide nanoparticles (Bi₂O₃NPs) have been extensively used in cosmetics, dental materials, pulp capping, and biomedical imaging. There is little knowledge about the health risk of Bi₂O₃NPs in humans, which warrants a thorough toxicity investigation of Bi₂O₃NPs at the cellular level. In this experiment, we investigated the cytotoxic effect of Bi₂O₃NPs on human breast cancer (MCF-7) cells over 24 and 48 h. MCF-7 cells were exposed to Bi₂O₃NPs at varying doses (0.1, 0.5, 1.0, 5, 10, 20, 40 μg/mL) for 24 and 48 h. We assessed the toxicity of Bi₂O₃NPs by measuring its effect on the viability and oxidative stress biomarkers, e.g., GSH, SOD, and catalase in MCF-7 cells. The pro-apoptotic effects of Bi₂O₃NPs on MCF-7 cells were determined via evaluating dysfunction of mitochondrial membrane potential (MMP), caspase-3 activity, externalization of phosphatidylserine, and chromosome condensation. Furthermore, apoptotic cells were evaluated using 7-AAD fluorescence stain and Annexin V-FITC. Bi₂O₃NPs induced oxidative stress in MCF-7 cells in a time- and dose-dependent manner. Bi₂O₃NPs increased the rate of both necrotic cells and apoptotic cells. In addition, the blue fluorescence of MCF-7 cells with condensed chromatin was increased in a time- and dose-dependent manner. In conclusion, the present study highlights the potential toxic effects of Bi₂O₃NPs at the cellular level and suggests further investigation of Bi₂O₃NPs before any medical purposes.