Cryopreservation is a method of freezing tissues or cells in order to preserve for use afterwards. Normally, cells are stored at ultra-low temperatures i.e. below – 1960C or 77K which is the boiling point of liquid nitrogen. As at this low temperature, any biological activities, which include the biochemical reactions that would lead to cell death, are successfully stopped. Therefore the tissues could be stored for quite a few years. This preservation is made possible by the using cryoprotectants.
In general the cryoprotectants are used for protection of the biological tissues from freezing and being spoiled from ice formation. They function like antifreeze by decreasing the freezing temperature and increasing the viscosity of the cell. Cryoprotectants are primarily divided into two wide classes. They are Penetrating cryoprotectants and non-penetrating cryoprotectants.
Storage of the tissue or the cell
The tissues are stored in two phases which includes in vapor phase and in liquid phase. The storage in the vapors phase helps to eliminate the risk of explosion with sealed ampoules. The tissues that are to be conserved are mostly biological materials, for the most part, cell suspensions or thin tissue samples. For example semen that can be used effectively after cryopreservation, tissue samples like tumors, blood i.e. special cells for transfusion or stem cells and histological cross sections and lastly eggs also known as oocytes.
Mostly, rapid thawing should be done in order to avoid any kind of harm from ice crystal growth and the tissues should be at once immersed in water bath and then should be transferred to re-warmed media. Surplus alkalinity should be avoided. Dish should be placed in the incubator in order to allow the saturation with CO2. Now, the thawed cells must be washed of cryoprotectants inside 24 hours and nursed back to standard growth. Ultimately, the materials should be diluted gradually.
Advantages of cryopreservation
The cryopreservation technique can sustain the preserved materials, even though not including it with any constant care and therefore it saves the time as well as the reagents. It helps to reduce the risk of microbial contamination and also the cross contamination with various other cell lines is very uncommon. It has the ability to decrease the rate of genetic drift and morphology. The tissues which are stored are greatly useful for research purposes and it has resulted as a boon for endangered species.
Role of cryopreservation in biodiversity conservation
In the current scenario, wild life is experiencing the threat of extinction as a result of habitat destruction. For that reason, conservation of habitat as well as germplasm is the current task for the scientists. Since 1980s, the idea of Frozen Zoo has proved to be a boon for ex-situ conservation. The plants and microbes as well as the germplasm of endangered species can be preserved by cryopreservation for future production. For a few examples: in the year 1972, the first mammal (mouse) was born from frozen embryo and then in the year 1984; the first human baby was born from frozen embryo transfer.