Evaluation of cellular effects of silicon dioxide nanoparticles.

Silica nanoparticles (nSiO₂s) are an important type of manufactured nanoparticles. Although there are some reports about the cytotoxicity of nSiO₂, the association between physical and chemical properties of nSiO₂s and their cellular effects is still unclear. In this study, we examined the correlation between the physiochemical properties and cellular effects of three kinds of amorphous nSiO₂s; sub-micro-scale amorphous SiO₂, and micro-scale amorphous and crystalline SiO₂ particles. The SiO₂ particles were dispersed in culture medium and applied to HaCaT human keratinocytes and A549 human lung carcinoma cells. nSiO₂s showed stronger protein adsorption than larger SiO₂ particles. Moreover, the cellular effects of SiO₂ particles were independent of the particle size and crystalline phase. The extent of cell membrane damage and intracellular ROS levels were different among nSiO₂s. Upon exposure to nSiO₂s, some cells released lactate dehydrogenase (LDH), whereas another nSiO₂ did not induce LDH release. nSiO₂s caused a slight increase in intracellular ROS levels. These cellular effects were independent of the specific surface area and primary particle size of the nSiO₂s. Additionally, association of solubility and protein adsorption ability of nSiO₂ to its cellular effects seemed to be small. Taken together, our data suggest that nSiO₂s do not exert potent cytotoxic effects on cells in culture, especially compared to the effects of micro-scale SiO₂ particles. Further studies are needed to address the role of surface properties of nSiO₂s on cellular processes and cytotoxicity. [ABSTRACT FROM AUTHOR]