Cryopreservation is a commonly used method for long-term storage of cells, including human peripheral blood mononuclear cells (PBMCs) isolated from whole blood or leukopaks. To cryopreserve PBMCs, the cells are resuspended in cryopreservation medium, cooled to extremely low temperatures, then stored at liquid nitrogen temperatures (below -135°C) until needed. Once the cells are required, the cryopreserved PBMCs can be thawed and then used in downstream applications, such as further cell subset isolation using EasySep™.
A lab-made formulation of cryopreservation medium often contains fetal bovine serum (FBS), a nutrient-rich ingredient that protects cells and helps them recover after thawing. However, the use of FBS raises concerns about lot-to-lot variability and the risk of transmitting potentially infectious agents. FBS is usually not recommended for commercial or clinical applications, such as the production of biologicals. Dimethyl sulfoxide (DMSO), another additive that helps protect cells against osmotic lysis, is also a widely used cryoprotectant in cryopreservation media.
Using the appropriate cryopreservation medium, cell concentration, and freezing rate ensures that PBMCs maintain optimal viability and functionality upon thaw. The following protocol outlines two options for successful cryopreservation of purified PBMCs:
- Using a serum-free cryopreservation medium: CryoStor® CS10 (Catalog #07930), a serum- and animal component-free cryopreservation medium containing 10% DMSO, provides a safe, protective environment for cells and tissues during the freezing, storage, and thawing processes.
- Using a serum-containing formulation: A lab-made formulation containing 10% DMSO with 90% FBS solution is a commonly used, inexpensive, and effective cryopreservation medium.