I have several 24-well plates of CRISPR knockout human ES clones that I don't have time to screen for the next couple of weeks. I am hoping to freeze them down in the plates until I have time to screen them. They are growing feeder-free in TeSR-E8 medium at the moment. Does anyone have a good protocol to do in-plate freezing? I have found some protocols online but they all involve adding FBS to the freezing medium. My ES cells have not been exposed to FBS for many passages and I do not know how exposure to FBS again will affect them. Can KOSR be used as a substitute for FBS in the freezing medium?
Thank you for any suggestions or thoughts.