Distribution and immunotoxicity by intravenous injection of iron nanoparticles in a murine model

With the increased application of iron oxide nanoparticles (FeNPs) for biomedical imaging purposes, concerns regarding the onset of the unexpected adverse health effects following exposure have been rapidly raised. In this study, we investigated the tissue distribution and immunotoxicity of FeNPs (2 and 4 mg kg^-1) over time (2, 4 and 13 weeks) after single intravenous injection. At 13 weeks after a single injection, the iron levels increased in all measured tissues compared to the control, and iron accumulation was notable in the liver, spleen and thymus. These changes were accompanied by changes in levels of redox reaction-related elements, including copper, manganese, zinc and cobalt. In addition, as compared to the control, the number of white blood cells and percentage of neutrophils significantly increased in the treated groups, and the interleukin-8 secretion and lactate dehydrogenase release were clearly elevated in the treated groups along with enhanced expressions of chemotaxis-related proteins. However, expression of antigen presenting related proteins attenuated following accumulation of FeNPs. Taken together, we suggest that FeNPs may primarily induce toxicity in the liver and immune system, and immunotoxicological evaluation should be considered to predict adverse health effects following exposure to NPs.