Investigation of the Cytotoxicity of Aluminum Oxide Nanoparticles and Nanowires and Their Localization in L929 Fibroblasts and RAW264 Macrophages

The biological responses of aluminum oxide (Al2 O3 ) nanoparticles (NPs) and nanowires (NWs) in cultured fibroblasts (L929) and macrophages (RAW264) were evaluated from their cytotoxicities and micromorphologic properties. Cultured cells were exposed to Al2 O3 NPs (13 nm diameter) and Al2 O3 NWs (2-6 × 200-400 nm). Cytotoxicity and genotoxicity were examined by immunostaining with fluorescence microscopy, and nanomaterial localization was studied by using scanning electron microscopy and transmission electron microscopy. The NPs were cytotoxic and genotoxic, whereas the NWs were not. The scanning electron microscopy images showed that the NPs aggregate more on the cell surface than do the NWs. The transmission electron microscopy images showed that the NPs were internalized into the vesicle and nuclei, for both cell types. In contrast, numerous solid NWs were observed as large aggregates in vesicles, but not in nuclei. Nuclear damage was confirmed by measuring cell viability and by immunostaining for NPs. The chemical changes induced by the NPs in the vesicles or cells may cause cell damage because of their large surface area per volume. The extent of NW entrapment was not sufficient to lower the viability of either cell type.