Cytotoxicity effects of single cell and bulk cell populations.

<p>(a) Cytotoxicity effects were analyzed by MTT. The data represents as the mean ±SD, and acquired from 3 independent tests. (b) The cytotoxicity effects of HeLa cells are shown by the overlay fluorescence images of GFP and PI as the MNP incubation time increased from 8 to 24 h. Green, live cells expressed green fluorescent protein (GFP); Red, dead cells stained by PI. The scale bar represents 40 µm. (c) Overlay fluorescence images of DAPI/PI stain distinguishing mechanisms of cell death (SKHep-1, HepG2 and HeLa) after treating with MNPs for 24 h. Control: cells were not treated with MNPs for 24 h in parallel to the treated groups. Apoptotic nuclei stained with DAPI showed intense blue fluorescence corresponding to chromatin condensation (indicated by arrow heads) and fragmentation (indicated by arrows). Defective cell membrane allowed PI to enter cytoplasm indicating that cells underwent late apoptosis or necrosis. Possible necrotic cell that correspond to those without clear nuclear fragment but stained with intense PI were circled. (d) Time course experiment of the DAPI/PI staining for the three kinds of cells.