Evaluation of environmental stress by comet assay on freshwater snail Lymnea luteola L. exposed to titanium dioxide nanoparticles

Abstract

The use of aquatic organisms to monitor for contamination is well-established. Therefore, this study was designed to assess the adverse effects of titanium dioxide nanoparticles (TiO2NP) in freshwater snail Lymnea luteola L. (L. luteola). For TiO2NPs ecotoxicity tests, snails were exposed for seven days. A dose and time-response relationship was observed for TiO2NP-induced genotoxicity. Induction of oxidative stress in digestive gland was observed by a decrease in glutathione and gluthathions-S-transferase levels accompanied by elevated malondialdehyde levels at TiO2NP (9 and 28 µg/mL). Superoxide dismutase activities were markedly reduced at TiO2NP (9 and 28 µg/mL) at days 1 and 3, but not at day 7. Catalase activities were decreased at days 1 and 3 but increased at higher concentration of TiO2NP at day 7. DNA fragmentation occurring in L. luteola due to ecotoxic impact TiO2NP was further substantiated by alkaline single-cell gel electrophoresis assay and expressed in terms of percent tail DNA and olive tail moment. The results indicate that the interaction of these TiO2NP with snail influences the toxicity, which is mediated by oxidative stress in a dose- and time-dependent manner. The measurement of DNA integrity in L. luteola thus provides an early warning signal of contamination of the aquatic ecosystem by TiO2NP. Data suggest the freshwater snail L. luteola is a potential biomonitor organism.