TEM image of Caco-2 cells exposed to 100 μg/mL of TiO2 STNPs. Caco-2 cells were cultured for 21 days and differentiated. The cells were exposed for 24 h at 100 μg/mL of TiO2 nanoparticles. The cells were washed, fixed, post-fixed, included, cut and stained before being examined by TEM. (Left) T-Lite. (Right) T-Lite DA.