Figure 4: Quantification of cellular uptake using flow cytometry. Cells were treated with 15, 60 or 200 nm SiO2 NP at 20 μg/mL for either 2h (A) or 24h (B). Uptake was quantified using flow cytometry as mean fluorescence intensities of the cells. Data are presented as means ± SEM of at least three independent experiments.