Fig. 4. (A) Quantitative uptake of CPP functionalized silica particles (50, 150 and 300 nm diameter) into HeLa cells. Uptake was measured after 30 min of incubation using flow cytometry. For comparison, the significance between the internalization efficacies was determined by students t-test (*p < 0.05; **p < 0.005; ***p < 0.0005). (B) Confocal microscopy studies after incubating HeLa cells for 24 h with 50 nm CPP-coated silica nanoparticles. Cell nuclei were stained with Hoechst stain before imaging. Scale bar corresponds to 10 μm.