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Although the use of synthetic amorphous silica (SAS) is steady increasing, scarce information exists on its potential health risk. In particular few and conflictive data exist on its genotoxicity. To fill in this gap we have used Drosophila melanogaster as in vivo model test organism to detect the genotoxic activity of different SAS with different primary sizes (6, 15, 30 and 55 nm). The wing-spot assay and the comet assay in larvae haemocytes were used, and the obtained results were compared with those obtained with the microparticulated form (silicon dioxide). All compounds were administered to third instar larvae at concentrations ranging from 0.1 to 10 mM. No significant increases in the frequencies of mutant spots were observed in the wing-spot assay with any of the tested compounds. On the other hand, significant dose-dependent increases in the levels of primary DNA damage, measured by the comet assay, were observed for all the SAS evaluated but mainly when high doses (5 and 10 mM) were used. These in vivo results contribute to increase the database dealing with the potential genotoxic risk associated to SAS nanoparticles exposure. [ABSTRACT FROM AUTHOR]

The in vitro genotoxic and the soft-agar anchorage independent cell transformation ability of titanium dioxide nanoparticles (nano-TiO 2 ) and its microparticulated form has been evaluated in human embryonic kidney (HEK293) and in mouse embryonic fibroblast (NIH/3T3) cells. Nano-TiO 2 of two different sizes (21 and 50 nm) were used in this study. The comet assay, with and without the use of FPG enzyme, the micronucleus assay and the soft-agar colony assay were used. For both the comet assay and the frequency of micronuclei a statistically significant induction of DNA damage, was observed at the highest dose tested (1000 µg/mL). No oxidative DNA damage induction was observed when the comet assay was complemented with the use of FPG enzyme. Furthermore, long-term exposure to nano-TiO 2 has also proved to induce cell-transformation promoting cell-anchorage independent growth in soft-agar. Results were similar for the two nano-TiO 2 sizes. Negative results were obtained when the microparticulated form of TiO 2 was tested, indicating the existence of important differences between the microparticulated and nanoparticulated forms. As a conclusion it should be indicated that the observed genotoxic/tranforming effects were only detected at the higher dose tested (1000 µg/mL) what play down the real risk of environmental exposures to this nanomaterial. [ABSTRACT FROM AUTHOR]