Toxicity assessment of synthesized titanium dioxide nanoparticles in fresh water algae Chlorella pyrenoidosa and a zebrafish liver cell line

This study aims to assess the toxicity of the commonly-spread titanium dioxide nanoparticles (TiO2 NPs) by evaluating the exposure impact of the particles on both freshwater algae Chlorella pyrenoidosa and zebrafish liver cell line (ZFL), the two common in vitro models in toxicological studies. To compare the toxic effects of TiO2 NPs with different physiochemical properties, three types of manufactured TiO2 were used: bulk TiO2, Degussa P25 TiO2, and ultrafine TiO2 NPs. Both short and long-term biological responses of green algae, such as the effect on the cell growth rate, pigment autofluorescence, and esterase activity were investigated. The dosage, physical property of TiO2 particles, and their interactions with algal cells affect cellular growth, especially after short-term exposure. The hydrodynamic size plays a critical role in determining the acute toxicity to C. pyrenoidosa in terms of autofluorescence and esterase activity, while all types of TiO2 NPs show toxic effects after exposure for 14 days. However, this observation is not seen when studying the effect of introduced particles in ZFL, for the precipitated Degussa P25 TiO2 showed the highest cellular inhibition. Interestingly, despite the obvious overall toxicity toward C. pyrenoidosa, the photocatalytical properties of TiO2 NPs may contribute to the enhanced photosynthesis in the low concentration range (< 40 mu g mL(-1)). Overall, we found that the physical interactions between TiO2 particles and the cells, particles' size and dispersibility play critical role in the cytotoxic effect for both algal and ZFL cells, while the photocatalytical properties of TiO2 particles may produce mixed effects on the cytotoxicity of green algae.

Automated summary

This study evaluates the toxicity of titanium dioxide nanoparticles on freshwater algae and zebrafish liver cells. Different types of TiO2 NPs showed varying toxic effects on the cells, with short-term exposure affecting cell growth and long-term exposure leading to more significant toxicity. Cell growth was influenced by the dosage, physical properties, and interactions of TiO2 particles with the cells, highlighting the importance of particle size and dispersibility in cytotoxicity. Despite overall toxicity towards algae, the photocatalytical properties of TiO2 NPs may enhance photosynthesis at low concentrations.