4.4. Cell Viability and Apoptosis Assay by Flow Cytometry

Cell viability was assessed by dual staining with annexin V conjugated to fluorescein isothiocyanate (FITC) and propidium iodide (PI) [17]. Cells (0.5 × 10⁶) were stained by annexin V-FITC (BD Pharmingen, San Diego, CA, USA) and PI (BD Pharmingen) according to the manufacturer’s instructions. Cells were analyzed by a flow cytometer BD FACSCanto II (BD, Franklin Lakes, NJ, USA). Viable cells were those with both annexin V-FITC negative and PI negative staining. The viable cells in each sample were expressed as % by normalizing annexin V-/PI- cells to control. Annexin V-FITC positive cells were identified as apoptotic cells [18].