The medium was then removed and replaced with ICB at various micromolar concentrations (N = 3) in the respective medium for 24 hours at 37 °C and 5% CO2 in a humidified incubator. After 24 hours, the dye was removed and replaced with growth medium containing [3-(4,5dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT, 1.1 mM). After a 4 hour incubation at 37 °C and 5% CO2, SDS-DMSO detergent solution was added to the cells. The samples were incubated overnight and the absorbance of each well was measured at 590 nm. The readings were normalized to untreated cells for each dye. All data are the average of triplicate measurements.