Hello Petra Fodor

I have not worked with MM28 cell line. But generally, while freezing cells the main points to remember in order to get high cell viability on thawing are:

1. Freeze cells when they are 80% confluent.

2. Carry out gradual freezing of cells i.e., -1 degree C/minute before you place your cells in liquid nitrogen. You may use Mr. Frosty freezing container commercially available that will help in gradual cooling. Place the freezing vials in Mr. Frosty container in -70°C freezer for a minimum of 4 hours and then remove frozen tubes and place them in liquid nitrogen (vapor phase) for long-term storage. Always use pre-cooled freezing vials. Freeze approx. 2 million cells per ml per vial.

3. MM28 cells are frozen in 90% FBS and 10% DMSO as the freezing medium.

Best.