Cryopreservation

Cryopreservation, also called cryo-conservation, is the process of preserving biological material - protoplasts, cells, tissues, organelles, organs, extracellular matrix, enzymes, or virtually any other biological sample - by cooling it to an extremely low temperature, around -196 degC, using liquid nitrogen (Figure 5.16). At this temperature essentially all enzymatic and chemical activity inside the material stops completely, which halts ageing, decay and metabolic change and leaves the material preserved in a stable, dormant state; it can later be revived for experimental use simply by warming it back to room temperature slowly and carefully. Because ice-crystal formation during freezing and thawing can physically rupture cell membranes, protective agents called cryoprotectants - commonly dimethyl sulphoxide, glycerol or sucrose - are added to the material before it is cooled, specifically to protect cells and tissues from the mechanical and osmotic stress of freezing. Cryopreservation is one of the m …