Figure 8.

Washing cells after incubation with MTT removes extracellular formazan crystals: The effect of washing the cells’ supernatant on the OD levels. 20,000 PC-3 cells were seeded per well of 96-well plates and were allowed to grow in phenol red-free RPMI with or without FCS for 26 h. The cells were then incubated with 0.4 mg/mL MTT for 3 h. Wells were then divided into two groups: (i) Non-washed wells: 85 µL of supernatant in each well was removed before adding DMSO so that 25 µL was left in each well. (ii) Washed wells: Supernatant was totally removed. Then wells were washed two times with PBS and 25 µL of fresh media was added before adding DMSO. Data shown as mean OD of triplicate wells and error bars represent standard deviation. * One-tail t-test p-value = 0.025.