Inhaled fluorescent magnetic nanoparticles induced extramedullary hematopoiesis in the spleen of mice.

OBJECTIVES Nanomaterials are used in a wide variety of industrial materials such as semiconductors, magnetic resonance imaging, gene delivery carriers for gene therapy and many others; thus, human seems to be frequently exposed to them. Such diverse applications of nanoparticles elicit the need to identify the positive aspects of nanomaterials while avoiding the potential toxic effects. In this study, inhalation toxicity of manufactured nanomaterials using fluorescent magnetic nanoparticles (FMNPs) was assessed to address the issue of potential nanoparticle toxicity. METHODS Biological samples from a previous mouse FMNP exposure experiment were analyzed for potential FMNP toxicity. Mice inhaled FMNPs for 4 wk through a nose-only exposure chamber developed by our group for 4 wk and the potential toxicity of FMNPs was analyzed. RESULTS The nanoparticle distribution by scanning mobility particle sizer (SMPS) analysis showed that the mean values of number concentration (mass concentrations) in the nose-only exposure chamber were maintained at 4.89 x 10(5)/cm3 (approximately 159.4 microg/m3) for the low concentration and 9.34 x 10(5)/cm3 (approximately 319.5 microg/m3) for the high concentration, respectively. Inhalation of FMNPs caused a decrease of body weight and significant changes of white blood cells (WBCs) levels in whole blood. The FMNPs induced extramedullary hematopoiesis in the spleen without having a pulmonary effect. CONCLUSIONS Our results support the proposition that extensive toxicity evaluation is needed for practical applications of anthropogenic nanomaterials and suggest that careful regulation of nanoparticle applications may be necessary to maintain a high quality of life as well as for facilitating the development of nanotechnology.