Cryobiology, << `kry` oh by OL uh jee, >> is the study of how extremely low temperatures affect living things. Cryobiologists use temperatures that range from 32 °F (0 °C), the freezing point of water, down to just above -459.67 °F (-273.15 °C), which is absolute zero (see Absolute zero). The word cryobiology comes from the Greek kryos (cold) and biology (science of living things).
Cryobiologists are chiefly concerned with freezing living matter to preserve it for future use. The freezing must be done to keep the cells alive. Cryobiologists use a liquid gas, usually nitrogen, to obtain temperatures far below normal freezing. Cells kept cold in the gas stop working. But they stay alive and unchanged in a state of “suspended animation.” They can remain in this state without harm for long periods. After thawing, the cells resume their normal work almost at once. Cryobiologists are experimenting with a technique called vitrification to preserve living cells that are normally damaged by other freezing techniques. Vitrification involves cooling specimens into glasslike solids using solutions that prevent ice crystals from forming.
The freezing of blood and tissues such as corneas and skin makes it possible to store these parts in “banks.” Doctors may use skin from such a bank to graft onto a badly burned patient. They use stored corneas to replace diseased or damaged ones. Frozen red blood cells can be stored for many years. Frozen sperm, eggs, and embryos are commonly used for animal breeding and sometimes for human in vitro fertilization.
In cryosurgery, surgeons use extreme cold to destroy diseased tissue. For example, surgeons can perform a “bloodless” operation using instruments equipped with freezing tips.
See also Cryogenics.
