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Fig. 8 CPZ-loaded PLGA/PLGA-PEG show quick but limited burst release at physiological pH and delayed cell death kinetics. Freshly prepared batches of CPZ-loaded PLGA (A) and PLGA-PEG (B) were resuspended in pH 7.4 PBS and stirred at 400 RPM and at 37 °C. Aliquots were sampled at given time-points and analysed for CPZ-content by HPLC as described in the Methods section. The release data represents the ratio of CPZ found in the pellet (nanoparticles) and supernatant (free form), after separation by centrifugation. (C, D): MOLM-13 cells were incubated for up to 12 h with 10% v/v concentration of either empty or CPZ-loaded PLGA (C) or PLGA-PEG (D) nanoparticles, or free CPZ of equivalent drug concentrations. At given time points aliquots were transferred to 2% buffered formaldehyde (in pH 7.4 PBS containing Hoechst 33342). Nuclei-stained cells were imaged with an Axiovert 200 M fluorescence microscopy and normal and apoptotic nuclei were counted. Data are from a triplicate experiment.