Figure 8: AgNPs induce apoptosis in MDA-MB-231 cells by caspase-3 activation. MDA-MB-231 cells were treated with AgNPs, purified caspase-3, and caspase-3 inhibitor for 24 h. The assay was performed as described in Materials and Methods Section. The caspase-3 activity is based on the hydrolysis of caspase-3 substrate (acetyl-Asp-Glu-Val-Asp p-nitroanilide (Ac-DEVD-pNA) by caspase-3, resulting in the release of the p-nitroaniline (pNA) moiety. The concentration of the pNA released from the substrate is calculated from the absorbance values at 405 nm. The assay was carried out in the presence of purified caspase-3 and caspase-3 inhibitor (Ac-DEVD-CHO) for a comparative analysis. The results represent the means of three separate experiments, and error bars represent the standard error of the mean. Treated groups showed statistically significant differences from the control group by the Student’s t-test ( ).