Objectives To study the effects of nano silica (nm-SiO₂) and micro silica (μm-SiO₂) particles on the cytotoxicity and secretion of inflammatory factors in human lung adenocarcinoma cells (A549 cells).

Methods A549 cells were exposed to three sizes of nm-SiO₂ (20, 60 and 100nm) and μm-SiO₂ (0.1~5 μm) particles for 24 h at different doses (0, 12.5, 25, 50, 100 and 200 μg/mL) The cytotoxicity of nm-SiO₂ and μm-SiO₂ on A549 cells was measured by MTT method, the activity of LDH and the levels of IL-8 and TNF-α were measured by micro ELISA method

Results The viability of cells was inhibited and the activity of LDH was increased with a dose response relationship in all nm-SiO₂ groups The cytotoxicity of cells in 20-nm-SiO₂ group was most serious, even in a lower dose of 25μg/mL; the viability of cells in 20-nm-SiO₂ group was significantly lower than that of control group (P < 0.01) The activity of LDH in 20-nm-SiO₂ group was significantly higher than that of 60-nm-SiO₂ group, and the activity of LDH in 60-nm-SiO₂ group was higher than that of 100-nm-SiO₂ group (P < 0.05);but the viability of cells in μm-SiO₂ groups was reduced only in the highest dose group (P < 0.05 or P < 0.01) The secretion of IL-8 in cells was increased in 3-nm-SiO₂ groups, but no significant changes in the secretion of TNF-α from cells, the secretion of IL-8 from cells in 20-nm-SiO₂ group was significantly higher than that in 100-nm-SiO₂ group (P < 0.01) However, the secretion of IL-8 and TNF-α was not increased significantly in μm-SiO₂ groups

Conclusions Three nanometer sized SiO₂ particles could cause cytotoxicity and increase the secretion of IL-8 in A549 cells; and the smaller size of nm-SiO₂ particles were, the stronger of its toxic effects; but no significant change was observed in the secretion of TNF-α in the cell in nm-SiO₂ groups However, μm-SiO₂ particles could not cause significant cytotoxicity in A549 cells