What is cryopreservation?

Let's answer the question " What is cryopreservation ? ".

Cryopreservation is the act of preserving something by freezing it. Cryos means cold and derives from the Greek language.

The suffix cryo has become commonly used in words such as cryonics, cryosurgery, cryobiology, cryogenics. cryopreservation,

Cryogenics is the production of freezing cold. Permanent gases such has hydrogen, oxygen, air and others reach a boiling point at -180 degrees Celsius. This is the temperature where experts in cryogenics have chosen to mark the defining line as to where cryogenics begins. However storing tissue and organs is sometimes done at temperatures starting at -80 Celsius. Interest in the freezing of all types of building block materials started a very long time ago but modern science has taken the subject of cryopreservation to highly technical levels beginning back in the mid 1900's and involves all types of materials: biological and non biological.

Cryonics is the preservation of humans and animals through the process of freezing. The concept of preserving life in a suspended animation state wasn't new however. As early as 1773, Benjamin Franklyn was making notes on the subject. In 1845 James Arnott was testing surgery with the use of ice formation on a cancer patient in what we now call cryosurgery.  In 1949 Christopher Polge and his team of scientists managed to cryopresevere the first human sperm. the 1960's a physicist named Robert Ettinger wrote a book called " The Prospect of Immortality" in which he argued life and death and the prospect of a future where what seemed like certain death in his days could one day be reversible. Many other medical scientist expanded on this theory and entire groups came on the scene such as the Life Extension Society, the American Cryonics Institute and others.

But long before even Franklyn's concept there was mention of cryobiology. It may not have been mentioned under that title but as early as 2500 BC the Egyptian medical experts were recommending cold temperatures as medical treatments.

Hypothermic storage of tissue and organs is a type of temperature preservation much like cryopreservation is however with hypothermic preservation the temperature applied to the biological substance is much higher. Where cryopreservation uses the -80 and lower Celsius range, hypothermic commonly uses 0 to 32 degrees Celsius. This is sufficient to preserve tissue or organs that are stored temporarily or long enough to deliver them from one location to another.. The hypothermic storage method requires all types of preservation agents to make the transfer successful. This is important when considering that certain organisms and animals have intuitive methods of entering hypothermic states of suspended animation ( link to an alternate view on  cryogenics ) such as seen in the hybernating bear.

The history of cryopreservation is explained in the following manner on Wikipedia.

One of the most important early workers on the theory of cryopreservation was James Lovelock of Gaia theory fame. Dr. Lovelock's work suggested that damage to red blood cells during freezing was due to osmotic stresses. Lovelock in early 1950s had also suggested that increasing salt concentrations in a cell as it dehydrates to lose water to the external ice might cause damages to the cell. Cryopreservation of tissue in recent times started with the freezing of fowl sperm, which in 1949 was cryopreserved for the first time by a team of scientists in the UK led by Dr Christopher Polge. The process moved into the human world in the 1950s with pregnancies obtained after insemination of frozen sperm. However, the rapid immersion of the samples in liquid nitrogen did not, for certain of these samples–such as types of embryos, bone marrow and stem cells–produce the necessary viability to make them usable on thawing. Increased understanding of the mechanism of freezing injury to cells emphasised the importance of controlled or slow cooling to obtain maximum survival on thawing of the living cells. A controlled rate cooling process, allowing biological samples to equilibrate to optimal physical parameters osmotically in a cryoprotectant (a form of anti-freeze) before cooling in a predetermined, controlled way proved necessary. The ability of cryoprotectants, in the early cases glycerol, to protect cells from freezing injury was discovered accidentally. Freezing injury has two aspects–direct damage from the ice crystals and secondary damage caused by the increase in concentration of solutes as progressively more ice is formed. In 1963 Peter Mazur, at Oak Ridge National Laboratory in the USA, showed that lethal intracellular freezing could be avoided if cooling was slow enough to permit sufficient water to leave the cell during progressive freezing of the extracellular fluid. That rate differs between cells of differing size and water permeability: a typical cooling rate around 1°C/minute is appropriate for many mammalian cells after treatment with cryoprotectants such as glycerol or dimethyl sulphoxide, but the rate is not a universal optimum.