I have been trying to get MTT working for the past one month, but i am unable to. Intially the worm used to die within 10 mins after i add MTT (But the worms survived in medium without PBS). But now the worms are alive after i add the dye but there is no change in color. What could be the reason for this? Also i wanted to know if MTT (10mg/ml) is completely soluble in PBS pH 7.4???