Comparison of the cell viability of HeLa cells treated with Cyt-c encapsulated in PLGA nanoparticles (NPs) vs. empty PLGA NPs after 72 (a) and 96 h (b) of incubation. The numbers 1–5 on the y-axis corresponds to 0.61, 1.21, 3.10, 6.19, and 12.38 μg/ml Cyt-c, respectively, in case of Cyt-c loaded PLGA NPs. Empty PLGA NPs were adjusted to the same PLGA concentrations as the corresponding Cyt-c-loaded PLGA NPs. Cyt-c-PLGA NPs induced a significant reduction in cell viability after 72 and 96 h of incubation for the 12.38 mg/ml protein concentration, whereas the PLGA NPs showed no significant cytotoxicity.