| Summary: | <p>Abstract</p> <p>Background</p> <p>Little is known of how the toxicity of nanoparticles is affected by the incorporation in complex matrices. We compared the toxic effects of the titanium dioxide nanoparticle UV-Titan L181 (NanoTiO<sub>2</sub>), pure or embedded in a paint matrix. We also compared the effects of the same paint with and without NanoTiO<sub>2</sub>.</p> <p>Methods</p> <p>Mice received a single intratracheal instillation of 18, 54 and 162 μg of NanoTiO<sub>2 </sub>or 54, 162 and 486 μg of the sanding dust from paint with and without NanoTiO<sub>2</sub>. DNA damage in broncheoalveolar lavage cells and liver, lung inflammation and liver histology were evaluated 1, 3 and 28 days after intratracheal instillation. Printex 90 was included as positive control.</p> <p>Results</p> <p>There was no additive effect of adding NanoTiO<sub>2 </sub>to paints: Therefore the toxicity of NanoTiO<sub>2 </sub>was reduced by inclusion into a paint matrix. NanoTiO<sub>2 </sub>induced inflammation in mice with severity similar to Printex 90. The inflammatory response of NanoTiO<sub>2 </sub>and Printex 90 correlated with the instilled surface area. None of the materials, except of Printex 90, induced DNA damage in lung lining fluid cells. The highest dose of NanoTiO<sub>2 </sub>caused DNA damage in hepatic tissue 1 day after intratracheal instillation. Exposure of mice to the dust from paints with and without TiO<sub>2 </sub>was not associated with hepatic histopathological changes. Exposure to NanoTiO<sub>2 </sub>or to Printex 90 caused slight histopathological changes in the liver in some of the mice at different time points.</p> <p>Conclusions</p> <p>Pulmonary inflammation and DNA damage and hepatic histopathology were not changed in mice instilled with sanding dust from NanoTiO<sub>2 </sub>paint compared to paint without NanoTiO<sub>2</sub>. However, pure NanoTiO<sub>2 </sub>caused greater inflammation than NanoTiO<sub>2 </sub>embedded in the paint matrix.</p>
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