Small sizes of TiO2-NPs exhibit adverse effects at predicted environmental relevant concentrations on nematodes in a modified chronic toxicity assay system.

In Caenorhabditis elegans, although acute toxicity of TiO(2) nanoparticles (TiO(2)-NPs) at high concentrations has been investigated, we still know little about chronic toxicity of TiO(2)-NPs. Our data here showed that acute TiO(2)-NPs exposure in the range of μg/L had no obviously adverse effects on nematodes, but the chronic toxicities of large sizes (60 nm and 90 nm) of TiO(2)-NPs in the range of μg/L were detected in nematodes in a modified chronic toxicity assay system. Moreover, chronic toxicities of small sizes (4 nm and 10nm) of TiO(2)-NPs in the range of ng/L were observed in nematodes with locomotion behavior and ROS production as endpoints. In nematodes chronically exposed to small sizes of TiO(2)-NPs at predicted environmental relevant concentrations, locomotion behavior was significantly (P<0.01) correlated with ROS production. Furthermore, treatment with antioxidants (ascorbate and N-acetyl-l-cysteine) inhibited both the induction of ROS production and the decrease of locomotion behaviors observed in nematodes chronically exposed to small sizes of TiO(2)-NPs at predicted environmental relevant concentrations. Therefore, chronic exposure to small sizes of TiO(2)-NPs at predicted environmental relevant concentrations can cause adverse effects on nematodes, and formation of such adverse effects may be largely due to the induction of oxidative stress.