Ecotoxicological investigation of CeO(2) and TiO(2) nanoparticles on the soil nematode Caenorhabditis elegans using gene expression, growth, fertility, and survival as endpoints.

In this study, the potential harmful effect of cerium dioxide (CeO(2)), and titanium dioxide (TiO(2)) nanoparticles on the environment was investigated using Caenorhabditis elegans ecotoxicity tests. Multiple toxic endpoints, such as stress-response gene expression, growth, fertility, and survival, were analyzed in C. elegans, in response to the CeO(2) and TiO(2) exposure. To investigate relationship between sizes of nanoparticles and toxicity, C. elegans were exposed to nanoparticles to the different sizes of nanoparticles (15, 45nm for CeO(2) and 7, 20nm for TiO(2)). An increase in the expression of the cyp35a2 gene, decrease in fertility and survival parameters were observed in the 15 and 45nm of CeO(2) and in the 7nm of TiO(2) nanoparticles exposed to C. elegans. Gene knock-down experiment using RNA interference (RNAi) suggested that physiological level disturbances may be related with the cyp35a2 gene expression. Smaller sized nanoparticles (7nm of TiO(2) and 15nm of CeO(2)) seemed to be more toxic than larger sized ones (20nm of TiO(2) and 45nm of CeO(2)) on the observed toxicity. The size-dependent effect in CeO(2) and TiO(2) nanoparticles-induced toxicity needs to be investigated under more detailed experimental settings with the various sizes of nanoparticles. Further studies on the mechanism by which CeO(2) and TiO(2) nanoparticles affect cyp35a2 gene expression, fertility, and survival are warranted to better understand the CeO(2) and TiO(2) nanoparticles-induced ecotoxicity in C. elegans, as are studies with the causal relationships between these parameters. Overall results suggest that CeO(2) and TiO(2) nanoparticles have a potential for provoking ecotoxicity on C. elegans and the data obtained from this study can comprise a contribution to knowledge of the ecotoxicology of nanoparticles in C. elegans, about which little data are available.