4.2. Cell Viability Assay

Cell viability was determined using the CellTiter 96 Aqueous One Solution Cell Proliferation Assay Kit MTS (Promega, Madison, WI, USA). The MTS assay is based on the conversion of a tetrazolium salt into a colored, aqueous soluble formazan product by dehydrogenase enzymes in metabolically active cells. The amount of formazan produced is directly proportional to the number of living cells in culture. Two hundred fifty thousand cells per two hundred milliliter were seeded in triplicate in 96-well plates and were treated with cal14.1a (27 μM) and C+ (5 μM) for 24 h. Twenty microliters (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS)) were added, and the amount of formazan converted by viable cells was determined by measuring absorbance at 490 nm on a 96-well microplate reader EPOCH (BioTek, Winooski, VT, USA). Results are expressed as the percentage of treated to untreated cells.