Cryopreservation is a scientific process through which cells or tissues can be preserved by freezing them at extremely low temperatures of 77 Kelvin or -196 ˚ Celsius. It is an important area of science because of its numerous practical applications. Cryopreservation is used to freeze vital and useful tissues like blood, stem cells, samples of tumors and histological cross sections, human eggs (Oocytes), embryos, sperm, ovarian tissue and plant parts for study.
History of Cryopreservation
Freezing cells or tissues traditionally causes damage due to tears caused by the formation of ice crystals. However this concern was alleviated when it was found that glycerol protects cells from freezing damage. This discovery greatly broadened the scope of cryogenics, especially in the area of reproductive science and medicine. Intracellular freezing is more susceptible to damage that extra-cellular freezing; though it can be minimized by employing a slow cooling process.
How it works
At very low temperatures, the biological activity of a cell that will eventually lead to its death is stopped. Thus, cells like human eggs or sperm and stem cells can be preserved for later use. Chemicals known as Cryoprotectants are added in high concentrations to ensure minimal ice formation on cooling. Till 2005, vitrification (freezing) rates for transforming pure water to glassy surface were considered impossible to obtain. Cryogenic storage ensures that cells have an indefinite longevity. Extra cold and industrial strength deep freezers and refrigerators are sometimes used for this purpose; ultra cold liquid nitrogen at -196°C is most efficient for important and complex tissues. Machines using the SPF or Slow Programmable Freezing Technique are used worldwide to freeze biological samples using pre-programmed and slow steps. This preps them before immersion in liquid nitrogen.
Applications of Cryogenics
* Cancer Treatment: People diagnosed with chemotherapy or other chemical treatments no longer have to be denied a chance at motherhood or fatherhood. Often, after cancer treatment (particularly cervical and testicular cancer) fertility rates go down. They can bank or store their eggs and cells through cryopreservation. Those who are aware of this procedure can choose to get it done before treatment starts.
* Human embryos and sperm can be preserved for IVF or in vitro fertilization. Approximately 20% of all IVF babies are born through cryopreservation techniques.
* Cryopreservation is used to preserve plant seeds and tissue. Seeds of endangered or rare plants are preserved for research as well as regenerative purposes. In the event of a plant or crop disease, the preserved specimens will be useful for finding a cure.
* Special blood cells may be preserved for blood transfusions.
* Natural Cryopreservation occurs in multi cellular organisms known as Water Bears at a microscopic level. They can escape freezing temperatures by replacing their internal water with a sugar solution that acts as anti-freeze, much like chemical Cryoprotectants.
Vitrification of the brain is a hot topic in the area of Cryopreservation. Erstwhile thought to be impossible due to the many complications involved, it’s now on the cards. If successful, it could mean huge implications for mankind and the treatment of brain disorders. However, it is too new to discuss in detail. Thus, Cryopreservation is one of the most rewarding scientific and medical discoveries with a lot of future potential.
Akanksha Triguna Sharma
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