Bioconcentration, depuration and toxicity of Pb in the presence of titanium dioxide nanoparticles in zebrafish larvae.

The interactions between nanoparticles (NPs) and metals in aquatic environments may modify the bioavailability and toxicity of metals to organisms. In this study, we investigated the effects of titanium dioxide NPs (n-TiO) on the bioconcentration, depuration, and neurotoxic effects of lead (Pb) in zebrafish larvae. Transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy showed that Pb was adsorbed by n-TiO to form NP-Pb complexes in suspension, and these complexes were observed in larval tissues. The bioconcentration of Pb in larvae along with the depuration rates of Pb were higher in the presence of n-TiO compared to when n-TiO was absent. Exposure to Pb alone induced the expression of the biomarker metallothionein, downregulated neurodevelopment-related genes, and reduced swimming activity of larvae. However, the addition of n-TiO to the exposure solution alleviated these effects. The results suggest that n-TiO can act as a carrier of Pb to increase its bioconcentration; however, the formation of NP-Pb complexes likely reduces the amount of free Pb, thereby reducing toxicity to larvae.