Fig. 2.

In vitro effects of 100- or 10-nm SiO₂ NPs on human PBMC viability. PBMCs (1 × 106/ml) were cultured with 100- (a; 500, 1,000, 2,000, or 4,000 ppm) or 10-nm NPs (b; 50, 100, 250, 500, 1,000, 2,000, or 4,000 ppm) for 24 and 48 h. Control PBMCs were cultured in absence of NPs. Cell viability was determined by propidium iodide permeability assessed by flow cytometry. Values shown are the mean ± SD from three separate experiments. Significant differences from control values are indicated by *ρ < 0.05