Annexin 5 fluorescein isothiocyanate fitc

Following co-culture for 24 or 48 h, the culture medium was discarded. Cells were washed with PBS and digested with 0.25% trypsin (excluding EDTA). Cells were resuspended in PBS and centrifuged for 5 min at 800 × g. The supernatant was discarded and the cells were divided evenly. A total of 5 µl annexin V-fluorescein isothiocyanate (FITC) (Beckman Coulter, Inc., Brea, CA, USA) was added into each tube, which were then vortexed prior to incubation in the dark at room temperature for 15 min. A total of 5 µl propidium iodide (PI) dye was added to each tube prior to detection for 5 min. Prior to detection, 200 µl 1X binding buffer was added into the tubes.