subject: Cell Line Cryopreservation [print this page] Cell lines have important applications in the production of vaccines and several other biological products. Thus, preservation of cell lines is an important part of cell culture. Currently, the only effective method of preserving animal cells is freezing by using either using liquid nitrogen or cryogenic freezers.
The temperature of prepared cell lines is slowly reduced to -30c to -60c and then, they are transferred to an environment with temperature less than -130c. At such low temperatures, the cells suspend their biological activity and become inert. This way, they can be preserved for several years and used whenever required by thawing. The process of thawing is rapid, unlike freezing.
Cell line cryopreservation is different from preservation of bacteria and fungi because cultured cells require maintenance of higher viability. Survival rates as low as 1% is acceptable for microbial cultures but not for cell lines. The cell line cryopreservation methods must have viability of more than 90%. That means over 90% of the cells should survive the cryopreservation process.
The factors that affect viability of cryopreserved cell lines are:
1.Growth conditions before harvesting
2.Cell density
3.Physiological state of the cells
4.Type of cryoprotectant used
5.Handling technique
Glycerol and DMSO are good cryoprotectants as they prevent cells from undergoing dehydration during the process of cryopreservation. During cryopreservation, the concentration of cell suspension is kept at double of what is required for freezing so that a 2X cryoprotectant can be used in the same volume.
To further improve the viability of cells, you should handle the cell culture gently during the concentration and harvest stage. You should avoid subjecting the cell culture to activities such as vigorous pipetting, excessive enzymatic treatment and high speed centrifugation. In addition, you must observe the protocol for freezing and thawing to achieve cell line cryopreservation with high viability.
