Figure 7: Transmission electron microscope of NCI-H441 cells after 12 days of cocultures treated with NPs. (a) NCI-H441 cells treated with CuO (25 μg/mL). (b) NCI-H441 cells treated with TiO2 (25 μg/mL). The presence of CuO NPs free in the cytoplasm can be related to the oxidative potential of these particles which determines the rupture of endosomal vesicles as well as to a different route of entry into the cells.