Evaluation of cellular effects of silicon dioxide nanoparticles

Silica nanoparticles (nSiO(2)s) are an important type of manufactured nanoparticles. Although there are some reports about the cytotoxicity of nSiO(2), the association between physical and chemical properties of nSiO(2)s 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 nSiO(2)s; 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. nSiO(2)s 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 nSiO(2)s. Upon exposure to nSiO(2)s, some cells released lactate dehydrogenase (LDH), whereas another nSiO(2) did not induce LDH release. nSiO(2)s caused a slight increase in intracellular ROS levels. These cellular effects were independent of the specific surface area and primary particle size of the nSiO(2)s. Additionally, association of solubility and protein adsorption ability of nSiO(2) to its cellular effects seemed to be small. Taken together, our data suggest that nSiO(2)s 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 nSiO(2)s on cellular processes and cytotoxicity.