Figure 6.

Effect of SiO₂NPs on cell proliferation and death. (A,B) Cellular assessment of apoptosis induction by SiO₂NPs. Following 24 h in 25 nM SiO₂NPs, polyps were macerated and the percentage of apoptotic cells was determined by counting the DAPI-stained fragmented nuclei [arrow in (A)]. Scale bar: 50 μm. Inset in (A): phase contrast–DAPI merged of the same image. The arrow in the inset shows a pyknotic nucleus. The graph in (B) shows the percentage of total pyknotic nuclei and phagocytic moiety in normal and treated conditions. Cell cycling activity of interstitial stem cells (i-cells) (C) and of epithelial cells (EPI) (D) were estimated in untreated and 25 nM SiO₂NPs treated animals by continuous incubation with BrdU, followed by maceration of 10 animals at the indicated time points followed by colorimetric immunostaining. SiO₂NPs impaired the proliferating activity of epithelial, as shown by the lower percentage of BrdU labeled nuclei. In (B–D) data represent mean ± SD of three independent experiments; 100 cells were counted for each experiment.