Neurotoxicity and biochemical responses in the earthworm Pheretima hawayana exposed to TiO2NPs

Serious concerns have been expressed about potential risks of manufactured TiO(2)NPs. In this research, toxicity of nanoparticulate and bulk TiO2 were examined to the earthworm Pheretima hawayana. The 24-h median lethal concentration (LC50) and sublethal endpoints were assessed. Both NPs and their bulk counterparts were toxic. The 24-h LC50 for TiO(2)NPs (145.36 mg kg(-1)) was highly toxic than that of bulk TiO2 (357.77 mg kg(-1)). The aim of the present work is to evaluate the suitability of P. hawayana and its biochemical responses to be used as a bioindicator organism and biomarkers of TiO2 toxicity. Earthworms were exposed to three sublethal concentrations of TiO(2)NPs (1, 10 and 100 jig kg(-1)) for 28 days to test acetylcholinesterase (AChE), antioxidant enzymes (superoxide dismutase: SOD and catalase: CAT) activities and MDA content. The response of the antioxidant enzymes combined with AChE inhibition and MDA accumulation indicated that TiO2NP5 could induce significant impairments to the earthworms at the actual environment tested concentrations. The results pointed out the high sensitivity of the antioxidant and oxidative stress related responses to TiO(2)NPs exposure, demonstrating their usefulness in environmental monitoring and risk assessment. The study highlights also the usefulness of earthworm P. hawayana as potential bioindicator species for assessing the risk of nanoparticles environmental contamination. (C) 2015 Elsevier Inc. All rights reserved.