Abstract
Titanium dioxide (TiO2) nanoparticles have a high surface-to-mass ratio and rapidly aggregate in water causing great difficulties for toxicity test exposed to aquatic organisms or other cell lines. This study uses a cell viability kit for routine toxicity test of TiO2 as well as other nanoparticles which accumulate in the aquatic environment. Tetrahymena immediately endocytoses TiO2 nanoparticles and stores them in food vacuoles until the particles undergo exocytosis as larger aggregates. However, during the process of endocytosis and exocytosis, TiO2 particles interfere with cell growth and consequently induce acute toxicity. It exerted high cell growth inhibition at 20 h incubation and induces significant cytotoxic effects. Surprisingly, the effect of TiO2 decreases at 40 h incubation, due to the recovery of cell growth and reduction of the cytotoxicity of the particles.
Acknowledgment
This research was supported and funded by Helmholtz Zentrum München-German Research Center for Environmental Health, Ingolstädter Landstrasse 1, D-85764 Neuherberg, Germany. The authors want to thank to Tetrahymena Stock Center, C5 155 Veterinary Medical Center, Cornell University, Ithaca, New York, for providing Tetrahymena thermophila cell line.