A) Study of DAPI and propidium iodine (PI) co-localization for the detection of apoptotic cells. Selective induction of apoptosis observed in HeLa cells incubated with the FA-PEG-PLGA-S-S-Cyt c NPs. No cellular or minimal apoptosis observed in untreated HeLa cells or when incubated with controls: FA-PEG-PLGA-SH conjugate, FA-PEG-PLGA-S-S-LA NPs, and PEG-PLGA-Cyt c NPs. B) Comparison of folate decorated and folate-free Cyt c-based NP cyto-toxicity in HeLa cells (all groups were statistical significance even at 0.125 mg/ml where the error bars overlap). HeLa cell incubated with polymers alone (control) had no effect on the cell viability. Asterisks (***) and (*) indicate statistical significance at p<0.0001 and p<0.05, respectively. The error bars are the calculated SD. C) Confocal fluorescence images of HeLa cells after incubation for 6h with FM4-64 (labeling endosomes), FITC labeled Cyt c-based NPs, and the merged view of A and B. Yellow color indicates localization of the NPs in the endosomes.