mitomycin c going into solution - (Nov/20/2009 )

Hello-

I am using mitomycin c to make my MEF feeder layers for iPS cells. I ordered a 2mg vial from Sigma and resuspended in 2ml of water. I vortexed the vial to make sure the powder went into suspension completely. I aliquoted them out at 100ul each. However, after freezing I noticed that some of the vials contained blue-gray suspensions while others looked like the mitomycin had fallen out of suspension (there were blue flecks in clear solution).

Has anyone else experienced this? I have read that suspending in PBS is also done. Can I still use the aliquots with the blue flecks and hope they dissolve in the culture media? I'm trying to avoid irradiating the cells so any advice for preparing the mitomycin c would be greatly appreciated. Thanks!!

It is very common for this to happen in our lab's experience. We get 10mg powder from ag scientific and dissolve it first in 1 ml dmso and add 9ml pbs prior to filtering. We store this 100x solution in amber tubes at 4 degrees. We still use mmc even if it has some drug that came out of solution, as long as the vial is mixed well to not alter the concentration. Most of the time, the pieces will go back into solution when you put them on your feeder plate. I think this may have something to do with the storage temperature. Just be sure that your stock solution does not turn brown because it probably won't work.