Data on medical applications of
cerium oxide nanoparticles CeO2 (CONP) are promising, yet information regarding their action in cells is incomplete and there are conflicting reports about in vitro toxicity. Herein, we have studied cytotoxic effect of CONP in several
cancer and normal cell lines and their potential to change intracellular redox status. The IC50 was achieved only in two of eight tested cell lines,
melanoma 518A2 and colorectal
adenocarcinoma HT-29. Self-propagating room temperature method was applied to produce CONP with an average crystalline size of 4 nm. The results confirmed presence of Ce(3+) and O(2-) vacancies. The induction of cell death by CONP and the production of
reactive oxygen species (ROS) were analyzed by flow-cytometry.
Free radicals related
antioxidant capacity of the cells was studied by the reduction of stable
free radical TEMPONE using electron spin resonance spectroscopy. CONP showed low or moderate cytotoxicity in
cancer cell lines:
adenocarcinoma DLD1 and multi-
drug resistant DLD1-TxR,
non-small cell lung carcinoma NCI-H460 and multi-
drug resistant NCI-H460/R, while normal cell lines (keratinocytes HaCaT, lung fetal fibroblasts MRC-5) were insensitive. The most sensitive were 518A2
melanoma and HT-29 colorectal
adenocarcinoma cell lines, with the IC50 values being between 100 and 200 μM. Decreased rate of
TEMPONE reduction and increased production of certain ROS species (
peroxynitrite and
hydrogen peroxide anion) indicates that
free radical metabolism, thus redox status was changed, and
antioxidant capacity damaged in the CONP treated 518A2 and HT-29 cells. In conclusion, changes in intracellular redox status induced by CONP are partly attributed to the prooxidant activity of the nanoparticles. Further, ROS induced cell damages might eventually lead to the cell death. However, low inhibitory potential of CONP in the other human cell lines tested indicates that CONP may be safe for human usage in industry and medicine.