Acute Phase Pulmonary Responses to a Single Intratracheal Spray Instillation of Magnetite (Fe3O4) Nanoparticles in Fischer 344 Rats

Iron nanomaterials are of considerable interest for application tonanotechnology-related fields including environmental catalysis, biomedical imaging, drugdelivery and hyperthermia, because of their superparamagnetic characteristics and highcatalytic abilities. However, information about potential risks of iron nanomaterials islimited. The present study assessed pulmonary responses to a single intratracheal sprayinstillation of triiron tetraoxide nanoparticles (magnetite) in rats. Ten-week-old maleand female Fischer 344 rats (n=5/group) were exposed to a single intratracheal sprayinstillation of 0 (vehicle), 5.0, 15.0 or 45.0 mg/kg body weight (BW) of magnetite. After14 days, the rats were sacrificed, and biological consequences were investigated. The lungweights of the 15.0 and 45.0 mg/kg BW male and female groups were significantly higherthan those of the control groups. The lungs of treated rats showed enlargement and blackpatches originating from the color of magnetite. The typical histopathological changes inthe lungs of the treated rats included infiltration of macrophages phagocytosingmagnetite, inflammatory cell infiltration, granuloma formation and an increase of gobletcells in the bronchial epithelium. The results clearly show that instilled magnetitecauses foreign body inflammatory and granulating lesions in the lung. These pulmonaryresponses occur in a dose-dependent manner in association with the increase in lungweight.