Cell viability assay

Cell viability was detected by the method of MTT [3-(4,5-dimethylthiazol-2-yl)-3,5-diphenyltetrazolium bromide), incubating 4 × 10⁴ cells/100 μl in a 96-well plate under different conditions. 1 h before the incubation end, 10 μl of MTT solution (5 mg/ml in PBS) was added to each well. Incubations were stopped by addition of 20 μl of a pH 4.7 solution containing 20% (w:v) SDS, 50% (v:v) N,N-dimethylformamide, 2 % (v:v) acetic acid and 25 mM HCl. Plates were read at λ 540 nm absorbance, in a Titertek Multiskan Plus plate reader (Flow Laboratories, Sutton, U.K.). DC₅₀ (concentration inducing 50% of cell death) values were calculated with Prism 4.0c software.