Cellular Toxicity of Various Inhalable Metal Nanoparticles on Human Alveolar Epithelial Cells

Abstract

Nanoparticles (NPs) have a greater potential to travel through an organism via inhalation than any other larger particles, and could be more toxic due to their larger surface area and specific structural/chemical properties. The aim of this study was to evaluate in vitro biological effects of various inhalable metallic NPs (TiO₂, Ag, Al, Zn, Ni). Human alveolar epithelial cells (A549) were exposed to various concentrations of NPs for 24 h. The extent of morphological damage was in the order of m-TiO₂ > n-TiO₂ > m-silica ≫ n-Ni ≈ n-Zn ≈ n-Ag ≈ n-Al and was affected in a dose-dependent manner. The extent of apoptotic damage measured with two-color flow cytometry was in the order of n-Zn > n- Ni > m-silica ≫ n- TiO₂ > m- TiO₂ > n-Al > n-Ag. The extent of apoptotic damage measured with DNA fragmentation was in the order of n-Zn ≈ m-silica > n- Ni ≫ m- TiO₂ ≈ n- TiO₂ ≈ n-Al > n-Ag, indicating no significant difference in the damages by both m-TiO₂ and n-TiO₂. The extents of apoptotic damages were also affected in a dose-dependent manner. Uptake of no other NPs but n-TiO₂ and m-TiO₂ into the cells was observed after 24 h exposure. The intracellular generation of ROS was significant with n-Zn but not with the other particles. These results demonstrated that various inhalable metallic NPs (TiO₂, Ag, Al, Zn, Ni) could cause cell damages directly or indirectly. More detailed studies on the influence of size, structure, and composition of the NPs are needed to better understand their toxic mechanisms.