Toxic effects of prolonged exposure to [C₁₄mim]Br on Caenorhabditis elegans

Ionic liquids (ILs) are gradually concerned due to their potential environmental and health risks. In this work, the chronic effects of imidazolium-based ILs, using [C₁₄mim]Br as a representative, were evaluated using model animal Caenorhabditis elegans. Our results show that prolonged exposure (72 h) of ILs to the nematodes at concentrations of 5 and 10 mg/L induced adverse effects on the growth, locomotive behaviors and development. To explore the toxicity mechanism, lipofuscin content, ROS level and the expressions of five superoxide dismutase (SOD) genes were determined after the prolonged exposure. The lipofuscin content, ROS level and expressions of SOD genes did not show significant changes except that the expression of sod-5 was reduced by 2.7-fold following the treatment of 10 mg/L of [C₁₄mim]Br. These results suggest that oxidative stress may not be responsible for the adverse physiological effects induced by relatively low concentrations of imidazolium-based ILs. We further determined the gene expressions of phase I detoxification enzyme cytochrome P450 (CYP), phase II detoxification enzyme UDP-glucuronosyltransferase (UGT) and ATP-binding cassette (ABC) transporter P-glycoprotein (PGP). The results demonstrate that CYP, UGT and PGP may be involved in the detoxification of ILs. Our findings will aid in understanding the mechanisms of both toxicity and detoxification of imidazolium-based ILs in animals.