Cytotoxicity of copper (II) oxide nanoparticles in rat and human intestinal cell models

Copper (II) oxide nanoparticles (CuO NPs) have a variety of commercial applications ranging from catalysts to semiconductors. There is a potential for human oral exposure to CuO NPs following accidental or intentional ingestion, hand-to-mouth activity, or mucociliary transport following inhalation. CuO NPs are toxic to aquatic organisms but their mammalian toxicity is less well known. The objective of this study was to assess the cytotoxic effects of CuO NPs (size <50 nm) in rat and human intestinal cells. The rat cells are a 2-dimensional model (IEC-6) while the human cells are a 3-dimensional highly differentiated intestinal model. Three-dimensional cell culture systems offer greater predictability of in vivo toxicity than comparable 2-dimensional cell culture systems because of their complexity and their overall functions are more similar to native tissues. The effect of dose (0.1 – 100 μg/ml rat; 1-100 μg/ml, human) and time (4 and 24 hr) were evaluated. Cytotoxicity was assessed using a colorimetric method that measures mitochondrial activity (MTS, rat; MTT, human). Media with 10% fetal bovine serum was used as the negative control and triton X-100 (0.3%) was the positive control. CuSO₄ (0.1 – 100 μg/ml) was also tested in the rat cells for 24 h to assess Cu ion toxicity. Nano-particles were suspended in media and probe sonicated before dosing. Following incubation, the cells were washed with saline. In the rat cells, a significant dose-dependent (p<0.0001) decrease in cell viability was observed after 4- and 24-hr incubation of the CuO NPs. At both time points, a significant decrease was detected at ≥ 5 μg/ml CuO NPs in the rat cells. In the human cells, a significant dose-dependent (p<0.0001) decrease in cell viability was observed only after a 24-hr incubation of the CuO NPs; a significant decrease was detected at ≥ 50 μg/ml CuO NPs. Comparison of CuO NPs vs. CuSO₄ in rat cells showed greater cytotoxicity of the NPs, suggesting toxicity of the NPs is not due to release of Cu ions alone. In summary, CuO NPs are cytotoxic to rat and human intestinal cells in a dose- and time-dependent manner, although the rat model appears to be more sensitive. The 3-dimensional human model may be able to limit absorption of the CuO NPs or is better able to repair damage induced by these particles.

nanoparticles, EpiIntestinal (SMI-100), MTT

Cu (II) oxide, Dicopper oxide