Fluorescent microscopic images of L-132 cells stained with Cyto-dye and propidium iodide. Cells were exposed at TC-50 concentrations of ZnO and SiO₂ particles for 24 h. Live cells appeared green and dead cells were seen red in colour. Cells were cultured with (a) DMEM only (control); (b) nano ZnO; (c) micro ZnO; (d) nano SiO₂; and (e) TC-20 (i.e., 485 μg/mL) of micro SiO₂. The magnification was 400x.