If you’ve processed and isolated your cell type of interest and suddenly realize that you can’t analyze your purified cells immediately by flow cytometry, we can recommend the following solutions:

• Refrigerate cells: Store your purified, unstained cells in the refrigerator at 2 - 8°C until the next morning. For some cell types, the cell viability may decrease following refrigeration, but your analysis can still proceed. To improve viability, resuspend your purified cells in the recommended buffer (e.g. D-PBS with 2% FBS, EasySep™ Buffer, or RoboSep™ Buffer), which contains proteins to help maintain cell viability.
• Fix cells: Depending on the experimental endpoint, you can fix your cells prior to analysis. If you are not planning to use the cells in downstream assays, such as in vitro culture, try fixing the cells to extend the time between purification and analysis by flow cytometry. Fix the cells in 4% formaldehyde (Catalog #100-1450) for 30 minutes, then wash and resuspend the sample in the recommended buffer before storing the cells in the refrigerator at 2 - 8°C. Long-term cell storage in 4% formaldehyde is not recommended. NOTE: It is important to determine whether the antibodies used for analysis can still bind to formaldehyde-fixed cells. It may be preferable to stain your cells first, then fix and store at 2 - 8°C (in the dark) until you are ready to analyze your cells.
• Freeze cells: For long-term storage, freeze an aliquot of your cells for analysis at a later date. A lab-made formulation containing 10% dimethyl sulfoxide (DMSO) and 90% fetal bovine serum (FBS) is a commonly used cryopreservation medium for maintaining the viability of specialized cell types. However, the use of FBS raises concerns about lot-to-lot variation and the risk of transmitting potentially infectious agents. Consequently, FBS is usually not recommended for commercial or clinical applications, such as the production of biologicals. Commercially available freezing media such as mFreSR™ (Catalog #05854) or CryoStor™ CS10 (Catalog #07930), which are ready-to-use and serum-free, can also be used for freezing applicable cell types, without the concerns associated with FBS. For controlled-rate freezing, use Corning® CoolCell® LX Cell Freezing Container (Catalog #200-0642) for reproducible freezing profiles in an alcohol-free polyethylene foam freezing environment.

Cell Freezing and Storage Media

If you are preparing to pause your research, choose reliable freezing and storage media to cryopreserve your cells and save on time and resources when you return to the lab.