Effect of SiO
NP on ATF-2 translocation in A549 cells. A549 cells were exposed to 0.5 mg/ml SiO2NP (30 nm) or anisomycin (positive control) for 24 h and fixed in 3% paraformaldehyde. Cells were labelled with the Cellomics® HCS reagent kit for ATF-2 activation (green). Nuclei were stained with Hoechst (blue). Cellular images were acquired by an IN Cell Analyzer 1000 automated microscope using 10 X objective (Image size: 0.897 mm × 0.671 mm). Red arrows indicate representative cells with activated ATF-2.