Fig. 5

The panel of cell images of live HeLa cells stained with calcein AM without (a) the Au nanoparticle and (b) in the presence of 3 nM of Au nanoparticles. The images of calcein stained cells (a) and (b) were acquired after 24 h of nanoparticle treatments upon excitation with a 443 laser diode and at bandpass filter 514/30 nm. The images of c and d represent the autofluorescence of cells without (a) the Au nanoparticle and (b) in the presence of 3 nM of Au nanoparticles after 24 h. The autofluorescence images of cells were collected upon an excitation at 640 nm and with a longpass filter of 655 nm. Cells with brighter autofluorescence in c and d are classified as dead. e represents rates of viable cells in the presence of 0.3 and 3 nM in the cell medium as well as in the absence of Au nanoparticle as the control at time interval = 0.5, 2, 12, 24 h