Cryobiology is the branch of

biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary i ...

that studies the effects of low

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

s on living things within Earth's

cryosphere ] The cryosphere (from the Ancient Greek, Greek ''kryos'', "cold", "frost" or "ice" and ''sphaira'', "globe, ball") is an all-encompassing term for those portions of Earth's surface where water is in solid form, including sea ice, lake ice, ri ...

or in science. The word cryobiology is derived from the Greek words κρῧος ryos "cold", βίος

ios iOS (formerly iPhone OS) is a mobile operating system created and developed by Apple Inc. exclusively for its hardware. It is the operating system that powers many of the company's mobile devices, including the iPhone; the term also includes ...

"life", and λόγος

ogos Ogo may refer to: Places * Ogo, Senegal (disambiguation) ** Ogo, Diourbel ** Ogo, Louga ** Ogo (arrondissement), Matam, Matam * Ogo Mountains, Somaliland, Somalia * Ōgo, Gunma, Japan; a town in Seta, Gunma ** Ōgo Station, Maebashi, Gunma, Japa ...

"word". In practice, cryobiology is the study of biological material or systems at temperatures below normal. Materials or systems studied may include

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...

, tissues,

organs In biology, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a fu ...

, or whole

organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...

s. Temperatures may range from moderately

hypothermic Hypothermia is defined as a body core temperature below in humans. Symptoms depend on the temperature. In mild hypothermia, there is shivering and mental confusion. In moderate hypothermia, shivering stops and confusion increases. In severe h ...

conditions to

cryogenic In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th IIR International Congress of Refrigeration (held in Washington DC in 1971) endorsed a universal definition of “cryogenics” and “cr ...

temperatures.

Areas of study

At least six major areas of cryobiology can be identified: 1) study of cold-adaptation of

microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

s, plants ( cold hardiness), and animals, both

invertebrates Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

and

vertebrates Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...

(including

hibernation Hibernation is a state of minimal activity and metabolic depression undergone by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It most ...

), 2)

cryopreservation Cryo-preservation or cryo-conservation is a process where Organism, organisms, organelles, cell (biology), cells, Biological tissue, tissues, extracellular matrix, Organ (anatomy), organs, or any other biological constructs susceptible to damage ...

of cells, tissues,

gamete A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce t ...

s, and

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...

s of animal and human origin for (medical) purposes of long-term storage by cooling to temperatures below the freezing point of water. This usually requires the addition of substances which protect the cells during

freezing Freezing is a phase transition where a liquid turns into a solid when its temperature is lowered below its freezing point. In accordance with the internationally established definition, freezing means the solidification phase change of a liquid o ...

and thawing (

cryoprotectant A cryoprotectant is a substance used to protect biological tissue from freezing damage (i.e. that due to ice formation). Arctic and Antarctic insects, fish and amphibians create cryoprotectants (antifreeze, antifreeze compounds and antifreeze prot ...

s), 3) preservation of organs under hypothermic conditions for transplantation, 4) lyophilization (

freeze-drying Freeze drying, also known as lyophilization or cryodesiccation, is a low temperature dehydration process that involves freezing the product and lowering pressure, removing the ice by sublimation. This is in contrast to dehydration by most conve ...

) of

pharmaceutical A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy (pharmacotherapy) is an important part of the medical field and re ...

s, 5)

cryosurgery Cryosurgery is the use of extreme cold in surgery to destroy abnormal or diseased tissue; thus, it is the surgical application of cryoablation. The term comes from the Greek words cryo (κρύο) ("icy cold") and surgery (''cheirourgiki'' – χ� ...

, a (minimally) invasive approach for the destruction of unhealthy tissue using cryogenic gases/fluids, and 6) physics of

supercooling Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid or a gas below its melting point without it becoming a solid. It achieves this in the absence of a seed crystal or nucleus around which a crystal ...

ice Ice is water frozen into a solid state, typically forming at or below temperatures of 0 degrees Celsius or Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaq ...

nucleation In thermodynamics, nucleation is the first step in the formation of either a new thermodynamic phase or structure via self-assembly or self-organization within a substance or mixture. Nucleation is typically defined to be the process that deter ...

/growth and mechanical engineering aspects of

heat transfer Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, ...

during cooling and warming, as applied to biological systems. Cryobiology would include

cryonics Cryonics (from el, κρύος ''kryos'' meaning 'cold') is the low-temperature freezing (usually at ) and storage of human remains, with the speculative hope that resurrection may be possible in the future. Cryonics is regarded with skepticis ...

, the low temperature preservation of humans and mammals with the intention of future revival, although this is not part of mainstream cryobiology, depending heavily on speculative technology yet to be invented. Several of these areas of study rely on

cryogenics In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th IIR International Congress of Refrigeration (held in Washington DC in 1971) endorsed a universal definition of “cryogenics” and “cr ...

, the branch of

physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...

and

engineering Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad rang ...

that studies the production and use of very low

Cryopreservation in nature

Many living organisms are able to tolerate prolonged periods of time at temperatures below the freezing point of water. Most living organisms accumulate

s such as antinucleating proteins,

polyols In organic chemistry, a polyol is an organic compound containing multiple hydroxyl groups (). The term "polyol" can have slightly different meanings depending on whether it is used in food science or polymer chemistry. Polyols containing two, thre ...

, and

glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using ...

to protect themselves against frost damage by sharp ice crystals. Most plants, in particular, can safely reach temperatures of −4 °C to −12 °C.

Bacteria

Three species of bacteria, ''

Carnobacterium pleistocenium ''Carnobacterium pleistocenium'' is a recently discovered bacterium from the arctic part of Alaska. It was found in permafrost, seemingly frozen there for 32,000 years. Melting the ice, however, brought these extremophiles back to life. This i ...

'', ''

Chryseobacterium greenlandensis ''Chryseobacterium aquaticum'' is a Gram-negative, non- spore-forming and non-motile bacteria Non-motile bacteria are bacteria species that lack the ability and structures that would allow them to propel themselves, under their own power, thr ...

'', and '' Herminiimonas glaciei'', have reportedly been revived after surviving for thousands of years frozen in ice. Certain bacteria, notably ''

Pseudomonas syringae ''Pseudomonas syringae'' is a rod-shaped, Gram-negative bacterium with polar flagella. As a plant pathogen, it can infect a wide range of species, and exists as over 50 different pathovars, all of which are available to researchers from internat ...

'', produce specialized proteins that serve as potent ice nucleators, which they use to force ice formation on the surface of various fruits and plants at about −2 °C. The freezing causes injuries in the epithelia and makes the nutrients in the underlying plant tissues available to the bacteria. ''

Listeria ''Listeria'' is a genus of bacteria that acts as an intracellular parasite in mammals. Until 1992, 17 species were known, each containing two subspecies. By 2020, 21 species had been identified. The genus is named in honour of the British pi ...

'' grows slowly in temperatures as low as -1.5 °C and persists for some time in frozen foods.

Plants

Many plants undergo a process called hardening which allows them to survive temperatures below 0 °C for weeks to months.

Animals

Invertebrates

Nematodes The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-parasitic nematodes also known as eelworms. They are a diverse animal phylum inhabiting a broa ...

that survive below 0 °C include ''Trichostrongylus colubriformis'' and ''Panagrolaimus davidi''.

Cockroach Cockroaches (or roaches) are a paraphyletic group of insects belonging to Blattodea, containing all members of the group except termites. About 30 cockroach species out of 4,600 are associated with human habitats. Some species are well-known as ...

nymphs (''Periplaneta japonica'') survive short periods of freezing at -6 to -8 °C. The red flat bark beetle (''

Cucujus ''Cucujus'' is a genus of beetles in the family Cucujidae, the flat bark beetles. It contains 19 currently recognized species and subspecies. Description Species of ''Cucujus'' are of moderate size (6-25mm), greatly dorso-ventrally compressed, ...

clavipes'') can survive after being frozen to -150 °C. The

fungus gnat Fungus gnats are small, dark, short-lived gnats, of the families Sciaridae, Diadocidiidae, Ditomyiidae, Keroplatidae, Bolitophilidae, and Mycetophilidae (order Diptera); they comprise six of the seven families placed in the superfamily Sciaroide ...

''Exechia nugatoria'' can survive after being frozen to -50 °C, by a unique mechanism whereby ice crystals form in the body but not the head. Another freeze-tolerant beetle is ''

Upis ceramboides ''Upis ceramboides'' is a species of beetle, one of many wood-living insects that benefit from forest fires. It often occurs in quantities below the bark on the fire-damaged birches, but can sometimes be seen on other deciduous trees such as wil ...

''. See

insect winter ecology Insect winter ecology describes the overwinter survival strategies of insects, which are in many respects more similar to those of plants than to many other animals, such as mammals and birds. Unlike those animals, which can generate their own hea ...

and

antifreeze protein Antifreeze proteins (AFPs) or ice structuring proteins refer to a class of polypeptides produced by certain animals, plants, fungi and bacteria that permit their survival in temperatures below the freezing point of water. AFPs bind to small i ...

. Another invertebrate that is briefly tolerant to temperatures down to -273 °C is the

tardigrade Tardigrades (), known colloquially as water bears or moss piglets, are a phylum of eight-legged segmented micro-animals. They were first described by the German zoologist Johann August Ephraim Goeze in 1773, who called them Kleiner Wasserbär ...

. The larvae of ''

Haemonchus contortus ''Haemonchus contortus'', also known as the barber's pole worm, is a very common parasite and one of the most pathogenic nematodes of ruminants. Adult worms attach to abomasal mucosa and feed on the blood. This parasite is responsible for anemia ...

'', a

nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...

, can survive 44 weeks frozen at -196 °C.

Vertebrates

For the

wood frog ''Lithobates sylvaticus'' or ''Rana sylvatica'', commonly known as the wood frog, is a frog species that has a broad distribution over North America, extending from the boreal forest of the north to the southern Appalachians, with several notab ...

(''Rana sylvatica''), in the winter, as much as 45% of its body may freeze and turn to ice. "Ice crystals form beneath the skin and become interspersed among the body's skeletal muscles. During the freeze, the frog's breathing, blood flow, and heartbeat cease. Freezing is made possible by specialized proteins and glucose, which prevent intracellular freezing and dehydration." The wood frog can survive up to 11 days frozen at -4 °C. Other vertebrates that survive at body temperatures below 0 °C include painted turtles (''

Chrysemys picta The painted turtle (''Chrysemys picta'') is the most widespread native turtle of North America. It lives in slow-moving fresh waters, from southern Canada to northern Mexico, and from the Atlantic to the Pacific. They have been shown to prefer l ...

''),

gray tree frog The gray treefrog (''Dryophytes versicolor'') is a species of small arboreal holarctic tree frog native to much of the eastern United States and southeastern Canada. It is sometimes referred to as the eastern gray treefrog, northern gray tree ...

s (''Hyla versicolor''), moor frogs (Rana arvalis),

box turtles Box turtle is the common name for several species of turtle. It may refer to those of the genus '' Cuora'' or ''Pyxidea'', which are the Asian box turtles, or more commonly to species of the genus '' Terrapene'', the North American box turtles. T ...

(''Terrapene carolina'' - 48 hours at -2 °C),

spring peeper The spring peeper (''Pseudacris crucifer'') is a small chorus frog widespread throughout the eastern United States and Canada. They prefer permanent ponds due to their advantage in avoiding predation; however, they are very adaptable with respect ...

(''Pseudacris crucifer''),

garter snakes Garter snake is a common name for generally harmless, small to medium-sized snakes belonging to the genus ''Thamnophis'' in the family Colubridae. Native to North and Central America, species in the genus ''Thamnophis'' can be found from the sub ...

(''

Thamnophis sirtalis The common garter snake (''Thamnophis sirtalis'') is a species of thamnophis snake, in the natricine subfamily, which is indigenous to North America and found widely across the continent. Most common garter snakes have a pattern of yellow stri ...

''- 24 hours at -1.5 °C), the

chorus frog ''Pseudacris'' (commonly known as the chorus frogs) is a genus of frogs in the family Hylidae found in North America ranging from the Pacific coastline to the Atlantic. The name of the genus comes from the Greek ''pseudes'' (false) and ''akris ...

(''Pseudacris triseriata''),

Siberian salamander ''Salamandrella keyserlingii'', the Siberian salamander, is a species of salamander found in Northeast Asia. It lives in wet woods and riparian groves. Distribution It is found primarily in Siberia east of the Sosva River and the Urals, in ...

(''Salamandrella keyserlingii'' - 24 hours at -15.3 °C), European common lizard ('' Lacerta vivipara'') and Antarctic fish such as ''

Pagothenia borchgrevinki The bald notothen (''Pagothenia borchgrevinki''), also known as the bald rockcod, is a species of marine ray-finned fish belonging to the family Nototheniidae, the notothens or cod icefishes. It is native to the Southern Ocean. Taxonomy The bald ...

''. Antifreeze proteins cloned from such fish have been used to confer frost-resistance on

transgenic A transgene is a gene that has been transferred naturally, or by any of a number of genetic engineering techniques, from one organism to another. The introduction of a transgene, in a process known as transgenesis, has the potential to change the ...

plants. Hibernating

Arctic ground squirrel The Arctic ground squirrel (''Urocitellus parryii'') (Inuktitut: ''ᓯᒃᓯᒃ, siksik'') is a species of ground squirrel native to the Arctic and Subarctic of North America and Asia. People in Alaska, particularly around the Aleutians, refer to ...

s may have abdominal temperatures as low as −2.9 °C (26.8 °F), maintaining subzero abdominal temperatures for more than three weeks at a time, although the temperatures at the head and neck remain at 0 °C or above.

Applied cryobiology

Historical background

Cryobiology history can be traced back to antiquity. As early as in 2500 BC, low temperatures were used in Egypt in medicine. The use of cold was recommended by

Hippocrates Hippocrates of Kos (; grc-gre, Ἱπποκράτης ὁ Κῷος, Hippokrátēs ho Kôios; ), also known as Hippocrates II, was a Greek physician of the classical period who is considered one of the most outstanding figures in the history of ...

to stop bleeding and swelling. With the emergence of modern science,

Robert Boyle Robert Boyle (; 25 January 1627 – 31 December 1691) was an Anglo-Irish natural philosopher, chemist, physicist, alchemist and inventor. Boyle is largely regarded today as the first modern chemist, and therefore one of the founders of ...

studied the effects of low temperatures on animals. In 1949, bull

semen Semen, also known as seminal fluid, is an organic bodily fluid created to contain spermatozoa. It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphroditic animals and can fertilize the female ovum. Semen i ...

was

cryopreserved Cryo-preservation or cryo-conservation is a process where organisms, organelles, cells, tissues, extracellular matrix, organs, or any other biological constructs susceptible to damage caused by unregulated chemical kinetics are preserved by co ...

for the first time by a team of scientists led by

Christopher Polge Ernest John Christopher Polge (16 August 1926 – 17 August 2006) was an English biologist, most noted for his work in cryopreservation. The son of a Buckinghamshire farmer, he was educated at Bootham School in York, before going to the Univers ...

. This led to a much wider use of

today, with many

, tissues and

cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...

s routinely stored at low

s. Large organs such as

heart The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide t ...

s are usually stored and transported, for short times only, at cool but not freezing temperatures for transplantation. Cell suspensions (like blood and semen) and thin tissue sections can sometimes be stored almost indefinitely in

liquid nitrogen Liquid nitrogen—LN2—is nitrogen in a liquid state at low temperature. Liquid nitrogen has a boiling point of about . It is produced industrially by fractional distillation of liquid air. It is a colorless, low viscosity liquid that is wide ...

temperature (

). Human sperm, eggs, and

s are routinely stored in

fertility Fertility is the capability to produce offspring through reproduction following the onset of sexual maturity. The fertility rate is the average number of children born by a female during her lifetime and is quantified demographically. Fertili ...

research and treatments. Controlled-rate and slow freezing are well established techniques pioneered in the early 1970s which enabled the first human embryo frozen birth (Zoe Leyland) in 1984. Since then, machines that freeze biological samples using programmable steps, or controlled rates, have been used all over the world for human, animal, and cell biology – 'freezing down' a sample to better preserve it for eventual thawing, before it is deep frozen, or cryopreserved, in liquid nitrogen. Such machines are used for freezing oocytes, skin, blood products, embryo, sperm, stem cells, and general tissue preservation in hospitals, veterinary practices, and research labs. The number of live births from 'slow frozen' embryos is some 300,000 to 400,000 or 20% of the estimated 3 million ''in vitro'' fertilized births. Dr Christopher Chen, Australia, reported the world’s first pregnancy using slow-frozen oocytes from a British controlled-rate freezer in 1986.

Cryosurgery Cryosurgery is the use of extreme cold in surgery to destroy abnormal or diseased tissue; thus, it is the surgical application of cryoablation. The term comes from the Greek words cryo (κρύο) ("icy cold") and surgery (''cheirourgiki'' – χ� ...

(intended and controlled tissue destruction by ice formation) was carried out by James Arnott in 1845 in an operation on a patient with cancer.

Preservation techniques

Cryobiology as an

applied science Applied science is the use of the scientific method and knowledge obtained via conclusions from the method to attain practical goals. It includes a broad range of disciplines such as engineering and medicine. Applied science is often contrasted ...

is primarily concerned with low-temperature preservation.

Hypothermic Hypothermia is defined as a body core temperature below in humans. Symptoms depend on the temperature. In mild hypothermia, there is shivering and mental confusion. In moderate hypothermia, shivering stops and confusion increases. In severe h ...

storage is typically above 0 °C but below normothermic (32 °C to 37 °C) mammalian temperatures. Storage by cryopreservation, on the other hand, will be in the −80 to −196 °C temperature range. Organs, and tissues are more frequently the objects of hypothermic storage, whereas single cells have been the most common objects cryopreserved. A rule of thumb in hypothermic storage is that every 10 °C reduction in temperature is accompanied by a 50% decrease in

oxygen consumption Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well as ...

. Although hibernating animals have adapted mechanisms to avoid metabolic imbalances associated with hypothermia, hypothermic organs, and tissues being maintained for transplantation require special preservation solutions to counter

acidosis Acidosis is a process causing increased acidity in the blood and other body tissues (i.e., an increase in hydrogen ion concentration). If not further qualified, it usually refers to acidity of the blood plasma. The term ''acidemia'' describes t ...

, depressed

sodium pump Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable isot ...

activity. and increased intracellular

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...

. Special organ preservation solutions such as

Viaspan Viaspan was the trademark under which the University of Wisconsin cold storage solution (also known as University of Wisconsin solution or UW solution) was sold. Currently, UW solution is sold under the Belzer UW trademark and others like Bel-Gen o ...

(University of Wisconsin solution), HTK, and Celsior have been designed for this purpose. These solutions also contain ingredients to minimize damage by

free radicals In chemistry, a radical, also known as a free radical, is an atom, molecule, or ion that has at least one unpaired valence electron. With some exceptions, these unpaired electrons make radicals highly chemically reactive. Many radicals spont ...

, prevent

edema Edema, also spelled oedema, and also known as fluid retention, dropsy, hydropsy and swelling, is the build-up of fluid in the body's Tissue (biology), tissue. Most commonly, the legs or arms are affected. Symptoms may include skin which feels t ...

, compensate for ATP loss, etc. Cryopreservation of cells is guided by the "two-factor hypothesis" of American cryobiologis
Peter Mazur
which states that excessively rapid cooling kills cells by intracellular ice formation and excessively slow cooling kills cells by either

electrolyte An electrolyte is a medium containing ions that is electrically conducting through the movement of those ions, but not conducting electrons. This includes most soluble salts, acids, and bases dissolved in a polar solvent, such as water. Upon dis ...

toxicity Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subst ...

or mechanical crushing. During slow cooling, ice forms extracellularly, causing water to osmotically leave cells, thereby

dehydrating In physiology, dehydration is a lack of total body water, with an accompanying disruption of Metabolism, metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental tempe ...

them. Intracellular ice can be much more damaging than extracellular ice. For

red blood cell Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...

s, the optimum cooling rate is very rapid (nearly 100 °C per second), whereas for

stem cell In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type o ...

s the optimum cooling rate is very slow (1 °C per minute). Cryoprotectants, such as

dimethyl sulfoxide Dimethyl sulfoxide (DMSO) is an organosulfur compound with the formula ( CH3)2. This colorless liquid is the sulfoxide most widely used commercially. It is an important polar aprotic solvent that dissolves both polar and nonpolar compounds a ...

and

glycerol Glycerol (), also called glycerine in British English and glycerin in American English, is a simple triol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids known ...

, are used to protect cells from freezing. A variety of cell types are protected by 10% dimethyl sulfoxide. Cryobiologists attempt to optimize cryoprotectant concentration (minimizing both ice formation and toxicity) and cooling rate. Cells may be cooled at an optimum rate to a temperature between −30 and −40 °C before being plunged into liquid nitrogen. Slow cooling methods rely on the fact that cells contain few nucleating agents, but contain naturally occurring vitrifying substances that can prevent ice formation in cells that have been moderately dehydrated. Some cryobiologists are seeking mixtures of cryoprotectants for full

vitrification Vitrification (from Latin ''vitreum'', "glass" via French ''vitrifier'') is the full or partial transformation of a substance into a glass, that is to say, a non-crystalline amorphous solid. Glasses differ from liquids structurally and glasses po ...

(zero ice formation) in preservation of cells, tissues, and organs. Vitrification methods pose a challenge in the requirement to search for cryoprotectant mixtures that can minimize toxicity.

In humans

Human

gametes A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce t ...

and two-, four- and eight-cell

embryos An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sper ...

can survive

at -196 °C for 10 years under well-controlled laboratory conditions. Cryopreservation in humans with regards to infertility involves preservation of embryos, sperm, or oocytes via freezing. Conception, ''in vitro'', is attempted when the sperm is thawed and introduced to the 'fresh' eggs, the frozen eggs are thawed and sperm is placed with the eggs and together they are placed back into the uterus or a frozen embryo is introduced to the uterus. Vitrification has flaws and is not as reliable or proven as freezing fertilized sperm, eggs, or embryos as traditional slow freezing methods because eggs alone are extremely sensitive to temperature. Many researchers are also freezing ovarian tissue in conjunction with the eggs in hopes that the ovarian tissue can be transplanted back into the uterus, stimulating normal ovulation cycles. In 2004, Donnez of Louvain in Belgium reported the first successful ovarian birth from frozen ovarian tissue. In 1997, samples of ovarian cortex were taken from a woman with Hodgkin's lymphoma and cryopreserved in a (Planer, UK) controlled-rate freezer and then stored in liquid nitrogen. Chemotherapy was initiated after the patient had premature ovarian failure. In 2003, after freeze-thawing, orthotopic autotransplantation of ovarian cortical tissue was done by laparoscopy and after five months, reimplantation signs indicated recovery of regular ovulatory cycles. Eleven months after reimplantation, a viable intrauterine pregnancy was confirmed, which resulted in the first such live birth – a girl named Tamara.

Therapeutic hypothermia Targeted temperature management (TTM) previously known as therapeutic hypothermia or protective hypothermia is an active treatment that tries to achieve and maintain a specific body temperature in a person for a specific duration of time in an e ...

, e.g. during

heart surgery Cardiac surgery, or cardiovascular surgery, is surgery on the heart or great vessels performed by cardiac surgeons. It is often used to treat complications of ischemic heart disease (for example, with coronary artery bypass grafting); to corr ...

on a "cold" heart (generated by cold perfusion without any ice formation) allows for much longer operations and improves recovery rates for patients.

Scientific societies

The

Society for Cryobiology The Society for Cryobiology is an international scientific society that was founded in 1964. Its objectives are to promote research in low temperature biology, to improve scientific understanding in this field, and to disseminate and aid in the app ...

was founded in 1964 to bring together those from the biological, medical, and physical sciences who have a common interest in the effects of low temperatures on

biological systems A biological system is a complex network which connects several biologically relevant entities. Biological organization spans several scales and are determined based different structures depending on what the system is. Examples of biological syst ...

. As of 2007, the Society for Cryobiology had about 280 members from around the world, and one-half of them are US-based. The purpose of the Society is to promote scientific research in low temperature biology, to improve scientific understanding in this field, and to disseminate and apply this knowledge to the benefit of mankind. The Society requires of all its members the highest ethical and scientific standards in the performance of their professional activities. According to the Society's

bylaw A by-law (bye-law, by(e)law, by(e) law), or as it is most commonly known in the United States bylaws, is a set of rules or law established by an organization or community so as to regulate itself, as allowed or provided for by some higher authorit ...

s, membership may be refused to applicants whose conduct is deemed detrimental to the Society; in 1982, the bylaws were amended explicitly to exclude "any practice or application of freezing deceased persons in the anticipation of their reanimation", over the objections of some members who were cryonicists, such as

Jerry Leaf Jerry Donnell Leaf (April 4, 1941 – July 10, 1991) was Vice President and Director of the cryonics organization Alcor Life Extension Foundation, and President of the cryonics service firm Cryovita, Inc. until his death in 1991. He was s ...

. The Society organizes an annual scientific meeting dedicated to all aspects of low-temperature biology. This international meeting offers opportunities for presentation and discussion of the most up-to-date research in cryobiology, as well as reviewing specific aspects through symposia and workshops. Members are also kept informed of news and forthcoming meetings through the Society newsletter, ''News Notes''. The 2011–2012 president of the Society for Cryobiology was John H. Crowe. The Society for Low Temperature Biology was founded in 1964 and became a

registered charity A charitable organization or charity is an organization whose primary objectives are philanthropy and social well-being (e.g. educational, religious or other activities serving the public interest or common good). The legal definition of a ch ...

in 2003 with the purpose of promoting research into the effects of low temperatures on all types of organisms and their constituent cells, tissues, and organs. As of 2006, the society had around 130 (mostly British and European) members and holds at least one annual general meeting. The program usually includes both a

symposium In ancient Greece, the symposium ( grc-gre, συμπόσιον ''symposion'' or ''symposio'', from συμπίνειν ''sympinein'', "to drink together") was a part of a banquet that took place after the meal, when drinking for pleasure was acc ...

on a topical subject and a session of free communications on any aspect of low-temperature biology. Recent symposia have included long-term stability, preservation of aquatic organisms, cryopreservation of embryos and

s, preservation of plants, low-temperature

microscopy Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye (objects that are not within the resolution range of the normal eye). There are three well-known branches of micr ...

(glass formation of aqueous systems during cooling),

freeze drying Freeze drying, also known as lyophilization or cryodesiccation, is a low temperature dehydration process that involves freezing the product and lowering pressure, removing the ice by sublimation. This is in contrast to dehydration by most conve ...

and tissue banking. Members are informed through the Society Newsletter, which is presently published three times a year.

Journals

''Cryobiology'' (publisher:

Elsevier Elsevier () is a Dutch academic publishing company specializing in scientific, technical, and medical content. Its products include journals such as ''The Lancet'', ''Cell'', the ScienceDirect collection of electronic journals, '' Trends'', th ...

) is the foremost scientific publication in this area, with about 60 refereed contributions published each year. Articles concern any aspect of low-temperature biology and medicine (e.g. freezing,

, hibernation, cold tolerance and adaptation, cryoprotective compounds, medical applications of reduced temperature, cryosurgery,

hypothermia Hypothermia is defined as a body core temperature below in humans. Symptoms depend on the temperature. In mild hypothermia, there is shivering and mental confusion. In moderate hypothermia, shivering stops and confusion increases. In severe h ...

, and perfusion of organs). ''Cryo Letters'' is an independent UK-based rapid communication journal which publishes papers on the effects produced by low temperatures on a wide variety of biophysical and

biological processes Biological processes are those processes that are vital for an organism to live, and that shape its capacities for interacting with its environment. Biological processes are made of many chemical reactions or other events that are involved in the ...

, or studies involving low-temperature techniques in the investigation of biological and ecological topics. ''Biopreservation and Biobanking'' (formerly Cell Preservation Technology) is a

peer-reviewed Peer review is the evaluation of work by one or more people with similar competencies as the producers of the work (peers). It functions as a form of self-regulation by qualified members of a profession within the relevant field. Peer review ...

quarterly

scientific journal In academic publishing, a scientific journal is a periodical publication intended to further the progress of science, usually by reporting new research. Content Articles in scientific journals are mostly written by active scientists such as s ...

published by Mary Ann Liebert, Inc. dedicated to the diverse spectrum of preservation technologies including

, dry-state (

anhydrobiosis Cryptobiosis or anabiosis is a metabolic state of life entered by an organism in response to adverse environmental conditions such as desiccation, freezing, and oxygen deficiency. In the cryptobiotic state, all measurable metabolic processes sto ...

), and glassy-state and hypothermic maintenance. ''Cell Preservation Technology'' has been renamed ''Biopreservation and Biobanking'' and is the official journal of International Society for Biological and Environmental Repositories. ''Problems of Cryobiology and Cryomedicine '' (formerly 'Kriobiologiya' (1985-1990) and 'Problems of Cryobiology'(1991-2012) ) published by Institute for Problems of Cryobiology and Cryomedicine. The journal covers all topics related to low temperature biology, medicine and engineering.

References

External links

Cell Preservation TechnologyCellular cryobiology and anhydrobiologyAn overview of the science behind cryobiology at the Science Creative Quarterly
{{Authority control Phase transitions Cryogenics Cryonics