2.5. Crystal Violet (CV) Cell Viability Assay

Cell culture supernatants were replaced with 50μL of crystal violet stain (0.5%). The cells were stained and fixed for 10min at room temperature. Excess stain was rinsed away with demineralised water, and cells were left to air-dry overnight. 50μL of destaining solution was added for 10min. The optical density was read at 570nm with correction at 630nm [65]. A crystal violet standard plot was produced in each replicate experiment in which MCF-7 cell densities ranged from 0 to 80,000 and KGN cell densities from 0 to 100,000 cells per well in replicates of 6 for each cell density. Absorbance readings were plotted against cell densities with an average linear correlation of R² = 0.99 (n=3) replicate experiments for MCF-7 cells and R² = 0.97 (n=3) replicate experiments for KGN cells. Numbers of viable cells after exposure to chemotherapeutics and/or tocopherols were determined by comparison with the CV standard curve for the same experimental replicate.