Abstract
Superparamagnetic iron oxide nanoparticles (SPIONs) are widely used for various biomedical applications, for example, magnetic resonance imaging, targeted delivery of drugs, and in hyperthermia. Because the materials is applied to human, the cytotoxicity of SPIONs is discussed by many research teams. However, they hold different opinions. SPIONs induce toxicity via the generation of hydroxyl radicals. SPIONs are dissociated iron ions with H+ ions, the free iron in the form of ferrous ions (Fe2+) can react with hydrogen peroxide produce highly reactive hydroxyl radicals via the Fenton reaction: Fe2++H2O2--> Fe3++OH_+OH. . We know the dissociation extent of SPIONs is related with pH value from Fe3O4 + 2H γFe2O3 + Fe2+ + H2O, therefore, we consider the dissociation of SPIONs is different at various organelle and lead to production of intracellular hydroxyl radicals and cytotoxicity are different. In order to check the SPIONs ‘s catalysis production of hydroxyl radicals at different pH organelle. we use the thermal-sensitive liposome system as carrier to encapsulate SPIONs and control SPIONs to different organelle, after that, we observe the variation of cytotoxicity. Our results had shown that release SPIONs in lysosome leads to more hydroxyl radicals and significant cytotoxicity. It is encouraging to conclude the pH value in lysosome is benefit to SPIONs catalysis and directly induce cell death.