Genotoxic effects of nanosized and fine TiO2.

The in-vitro genotoxicity of nanosized TiO(2) rutile and anatase was assessed in comparison with fine TiO(2) rutile in human bronchial epithelial BEAS 2B cells using the single-cell gel electrophoresis (comet) assay and the cytokinesis-block micronucleus test. BEAS 2B cells were exposed to eight doses (1-100 microg/cm(2)) of titanium(IV) oxide nanosized rutile (>95%, <5% amorphous SiO(2) coating; 10 x 40 nm), nanosized anatase (99.7%; <25 nm), or fine rutile (99.9%; <5 microm) for 24, 48, and 72 h. Fine rutile reduced cell viability at lower doses than nanosized anatase, which was more cytotoxic than nanosized rutile. In the comet assay, nanosized anatase and fine rutile induced DNA damage at several doses with all treatment times. Dose-dependent effects were seen after the 48- and 72-h treatments with nanosized anatase and after the 24-, 48- (in one out of two experiments), and 72-h treatments (one experiment) with fine rutile. The lowest doses inducing DNA damage were 1 microg/cm(2) for fine rutile and 10 microg/cm( 2) for nanosized anatase. Nanosized rutile showed a significant induction in DNA damage only at 80 microg/cm(2) in the 24-h treatment and at 80 and 100 microg/ cm(2) in the 72-h treatment (with a dose-dependent effect). Only nanosized anatase could elevate the frequency of micronucleated BEAS 2B cells, producing a significant increase at 10 and 60 microg/cm( 2) after the 72-h treatment (no dose-dependency). At increasing doses of all the particles, MN analysis became difficult due to the presence of TiO(2) on the microscopic slides. In conclusion, our studies in human bronchial epithelial BEAS 2B cells showed that uncoated nanosized anatase TiO(2) and fine rutile TiO(2) are more efficient than SiO( 2)-coated nanosized rutile TiO(2) in inducing DNA damage, whereas only nanosized anatase is able to slightly induce micronuclei.

Preparation of nanoparticle dispersions for in-vitro toxicity testing.

Studies on potential toxicity of engineered nanoparticle (ENP) in biological systems require a proper and accurate particle characterization to ensure the reproducibility of the results and to understand biological effects of ENP. A full characterization of ENP should include various measurements such as particle size and size distribution, shape and morphology, crystallinity, composition, surface chemistry, and surface area of ENP. It is also important to characterize the state of ENP dispersions. In this study, four different ENPs, rutile and anatase titanium dioxides and short single- and multi-walled carbon nanotubes, were characterized in two dispersion media: bronchial epithelial growth medium, used for bronchial epithelial BEAS cells, and RPMI-1640 culture media with 10% of fetal calf serum (FCS) for human mesothelial (MeT-5A) cells. The purpose of this study was to determine the characteristics of ENPs and their dispersions as well as to compare dispersion additives suitable for toxicity tests and thus establish an appropriate way to prepare dispersions that performs well with the selected ENP. Dispersion additives studied in the media were bovine serum albumin (BSA) as a protein resource, dipalmitoyl phosphatidylcholine (DPPC) as a model lung surfactant, and combination of BSA and DPPC. Dispersions were characterized using optical microscopy and transmission electron microscopy. Our results showed that protein addition, BSA or FCS, in cell culture media generated small agglomerates of primary particles with narrow size variations and improved the stability of the dispersions and thus also the relevance of the in-vitro genotoxicity tests to be done.