Cell Viability Assay Using MTT

Cell viability was determined using a 3(4,5 dimethylthiazol)-2,5 diphenyltetra-zolium (MTT) assay as previously described 31 (link). Cells were plated at an appropriate density depending on the growth rate (1000–3500 cells/well) in 96-well plates 5 h prior to the drug treatment. On the fourth day, cells were incubated with MTT solution (Roth, Karlsruhe, Germany) (5 mg/mL) for 4 h at 37°C, 5% CO₂. Cells were then lysed with 100 μL isopropanol + 0.1 N HCl. The optical density of each well was determined using the microplate reader Tecan SLT spectra (Crailsheim, Germany) set to 550 nm (wavelength correction set to 690 nm) using Tecan X Fluor4 software. Plates were normally read within 1 h of adding the isopropanol. The cells without drugs were used as control. The viability of the cells was expressed as the percentage of control. Assays were performed on at least three independent experiments.