subject: Cryopreservation- Important Factors [print this page] Cryopreservation is a process that helps in the preservation of organs or tissues by freezing these tissues or organs at very low temperatures so that it can be used in the future. The freezing temperature for cryopreservation depends on the medium that is being cooled and is usually kept at the sub-zero levels.
This process has been chiefly used for the preservation of the small tissues, cells and fragments, embryos and the sperm cells involved in most fertility programs. However, the very concept of using the process of cryopreservation technique for the purpose of preserving human tissues, cells and fragments has long been an important subject for debate.
Cryopreservation Requirements
This process involves the use of special agents called the cryoprotectants that help in the technique of rapid freezing or vitrification. These agents help in the conversion of the cells or tissue fragments into glass like objects that remain free from being crystallized. Thus the main function of these cryoprotectants is to ensure the lowering of the freezing point. This helps in the prevention in the formation of the ice crystals. In most cases the agents or the cryoprotectants used are connected to the nature or the type of the cell, tissue or the organism that needs to be frozen. The agents used in this process are diluted in strength to suit the type of the object that requires to be cryopreserved. However, it requires extreme caution and precaution for selecting the right agent for a particular organism. This is because some of the agents used for the freezing get quickly absorbed by the body through the skin. These can then release chemicals into the body that can be extremely harmful. So, extreme care is required during the vitrification stage to lower any chances of harmful exposures.
Cryopreservation - Rate of Cooling
The rate of cooling is a very important factor in the process of cryopreservation as it can affect the ice crystal formations. Thus equipment that is programmable and allows the selection of different rates for the cell-freezing (cell cryopreservation) for the varying portions is required. In addition, to ensure a uniform rate of cooling for the varying portions, specially designed containers are used. These are capable of undertaking freezing at -60 degree C (both uncontrolled as well as semi controlled cooling), along with controlled cooling at -40 degrees C at the rate of 1 degree C every minute.
Apart from the rate of cooling, thawing also forms an important part of the cryopreservation technique.
