Pulmonary toxicity of Fe₂O₃, ZnFe₂O₄, NiFe₂O₄ and NiZnFe₄O₈ nanomaterials: Inflammation and DNA strand breaks

Abstract

<p>Exposure to metal oxide nanomaterials potentially occurs at the workplace. We investigated the toxicity of two Fe-oxides: Fe<sub>2</sub>O<sub>3</sub> nanoparticles and nanorods; and three MFe<sub>2</sub>O<sub>4</sub> spinels: NiZnFe<sub>4</sub>O<sub>8</sub>, ZnFe<sub>2</sub>O<sub>4</sub>, and NiFe<sub>2</sub>O<sub>4</sub> nanoparticles. Mice were dosed 14, 43 or 128 μg by intratracheal instillation. Recovery periods were 1, 3, or 28 days. Inflammation – neutrophil influx into bronchoalveolar lavage (BAL) fluid – occurred for Fe<sub>2</sub>O<sub>3</sub> rods (1 day), ZnFe<sub>2</sub>O<sub>4</sub> (1, 3 days), NiFe<sub>2</sub>O<sub>4</sub> (1, 3, 28 days), Fe<sub>2</sub>O<sub>3</sub> (28 days) and NiZnFe<sub>4</sub>O<sub>8</sub> (28 days). Conversion of mass-dose into specific surface-area-dose showed that inflammation correlated with deposited surface area and consequently, all these nanomaterials belong to the so-called low-solubility, low-toxicity class. Increased levels of DNA strand breaks were observed for both Fe<sub>2</sub>O<sub>3</sub> particles and rods, in BAL cells three days post-exposure. To our knowledge, this is, besides magnetite (Fe<sub>3</sub>O<sub>4</sub>), the first study of the pulmonary toxicity of MFe<sub>2</sub>O<sub>4</sub> spinel nanomaterials.</p>