Toxicity of CuO nanoparticles and Cu ions to tight epithelial cells from Xenopus laevis (A6): Effects on proliferation, cell cycle progression and cell death

Nanoparticles (NPs) have unique chemical and physical properties caused by their small size (1–100 nm) and high surface to volume ratio. This means that the NPs are potentially more toxic than their bulk counterparts. In the present study a cultured epithelial cell line from Xenopus laevis (A6) was used to investigate toxicity of copper (Cu) in 3 different forms; Cu ions (Cu2+), CuO NPs (6 nm) and poly-dispersed CuO NPs (100 nm, poly-CuO). Continuous exposures at concentrations of 143–200 lM demonstrated that cytotoxicity differed among the 3 Cu forms tested and that the effects depend on cell state (dividing or differentiated). Dividing cells treated with poly-CuO, CuO NPs (6 nm) or Cu2+ showed cell cycle arrest and caused significant increase in cell death via apoptosis after 48 h, 6 and 7 days of treatment, respectively.
Treatment with either CuO NPs (6 nm) or Cu2+ caused significant decrease in cell proliferation. Treatments of differentiated cells, revealed the same patterns of toxicity for Cu forms tested, but after shorter exposure periods.