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Cryopreservation of plant shoots. Open tank of Liquid Nitrogen behind.
Cryopreservation of plant shoots. Open tank of Liquid Nitrogen behind.
A tank of liquid nitrogen, used to supply a cryogenic freezer (for storing laboratory samples at a temperature of about −150 degrees Celsius).
A tank of liquid nitrogen, used to supply a cryogenic freezer (for storing laboratory samples at a temperature of about −150 degrees Celsius). Liquid nitrogen (liquid density at the Triple point is 0707 g/mL is the liquid produced industrially in large quantities by Fractional distillation of

Cryopreservation is a process where cells or whole tissues are preserved by cooling to low sub-zero temperatures, such as (typically) 77 K or −196 °C (the boiling point of liquid nitrogen). The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called Tissue is a cellular organizational level intermediate between cells and a complete organism Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature Liquid nitrogen (liquid density at the Triple point is 0707 g/mL is the liquid produced industrially in large quantities by Fractional distillation of At these low temperatures, any biological activity, including the biochemical reactions that would lead to cell death, is effectively stopped. Programmed cell-death ( PCD) is death of a cell in any form mediated by an intracellular program However, when vitrification solutions are not used, the cells being preserved are often damaged due to freezing during the approach to low temperatures or warming to room temperature. Vitrification is a process of converting a material into a Glass -like Amorphous solid that is free from any Crystalline structure either by the quick removal The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called For freezing as a method of food preservation see Frozen food.

Contents

Risks

Phenomena which can cause damage to cells during cryopreservation are solution effects, extracellular ice formation, dehydration and intracellular ice formation. In Cell biology, Molecular biology and related fields the word extracellular (or sometimes extracellular space) means "outside the cell Not to be confused with Intercellular, meaning "between cells"

Solution effects

Solution effects caused by concentration of solutes in non-frozen solution during freezing as solutes are excluded from the crystal structure of the ice. High concentrations can be very damaging.

Extracellular ice formation

When tissues are cooled slowly, water migrates out of cells and ice forms in the extracellular space. The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called Ice is a Solid phase, usually crystalline, of a Non-metalic substance that is liquid or gas at Room temperature, such as Ammonia Too much extracellular ice can cause mechanical damage due to crushing

Dehydration

The migration of water causing extracellular ice formation can also cause cellular dehydration. The associated stresses on the cell can cause damage directly.

Intracellular ice formation

While some organisms and tissues can tolerate some extracellular ice, any appreciable intracellular ice is almost always fatal to cells. Tissue is a cellular organizational level intermediate between cells and a complete organism

Prevention of risks

Vitrification provides the benefits of cryopreservation without the damage due to ice crystal formation. Vitrification is a process of converting a material into a Glass -like Amorphous solid that is free from any Crystalline structure either by the quick removal In clinical cryropreservation, vitrification usually requires the addition of cryoprotectants prior to cooling. A cryoprotectant is a substance that is used to protect Biological tissue from Freezing damage (damage due to Ice formation The cryoprotectants act like antifreeze: they lower the freezing temperature. Antifreeze is a Cryoprotectant used in Internal combustion engines and for many other heat transfer applications such as electronics cooling and Chillers They also increase the viscosity. Instead of crystallizing, the syrupy solution turns into an amorphous ice—i. In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating Amorphous ice is an Amorphous solid form of water meaning it consists of Water molecules that are randomly arranged like the atoms of common Glass. e. it vitrifies. Vitrification of water is promoted by rapid cooling, and can be achieved without cryoprotectants by an extremely rapid drop in temperature (megakelvins per second). The rate that is required to attain glassy state in pure water was considered to be impossible until recently. [1]

Two conditions usually required to allow vitrification are an increase in the viscosity and a depression of the freezing temperature. Many solutes do both, but larger molecules generally have larger effect, particularly on viscosity. Rapid cooling also promotes vitrification.

In artificial cryopreservation, the solute must penetrate the cell membrane in order to achieve increased viscosity and depressed freezing temperature inside the cell. Sugars do not readily permeate through the membrane. Those solutes that do, such as dimethyl sulfoxide, a common cryoprotectant, are often toxic in high concentration. Dimethyl sulfoxide (DMSO is the Chemical compound with the formula (CH32SO One of the difficult compromises faced in artificial cryopreservation is limiting the damage produced by the cryoprotectant itself.

Freezable tissues

In general, cryopreservation is easier for thin samples and small clumps of individual cells, because these can be cooled more quickly and so require lower doses of toxic cryoprotectants. Toxicity is the degree to which a substance is able to damage an exposed organism Therefore, the goal of cryopreserving human livers and hearts for storage and transplant is still some distance away. The liver is a vital organ in the human body and is present in Vertebrates and some other animals The heart is a muscular organ in all Vertebrates responsible for pumping Blood through the Blood vessels by repeated rhythmic

Nevertheless, suitable combinations of cryoprotectants and regimes of rapid cooling and rinsing during warming often allow the successful cryopreservation of biological materials, particularly cell suspensions or thin tissue samples. Examples include:

In addition, efforts are underway to preserve humans cryogenically, known as cryonics. Cryonics is the low-temperature Preservation of Humans and other Animals that can no longer be sustained by contemporary Medicine until In such efforts either the brain within the head or the entire body may undergo the above process. Cryonics is in a different category from the aforementioned examples, however, for while many cryopreserved cell suspensions, thin tissue samples, and some small organs have been warmed and successfully used, this has not yet been the case for cryopreserved brains or bodies. At issue are the criteria for defining "success". Proponents of cryonics make a case that cryopreservation using present technology, particularly vitrification of the brain, may be sufficient to preserve people in an "information theoretic" sense so that they could be revived and made whole by vastly advanced future technology. Information-theoretic death is the destruction of the human brain and information within it to such an extent that recovery of the original mind and person that occupied the brain is

Natural cryopreservation

Water bears (or tardigrada), microscopic multicellular organisms, can survive freezing at low temperatures by replacing most of their internal water with the sugar trehalose. Tardigrades (commonly known as water bears) form the Phylum Tardigrada, part of the superphylum Ecdysozoa. Tardigrades (commonly known as water bears) form the Phylum Tardigrada, part of the superphylum Ecdysozoa. For freezing as a method of food preservation see Frozen food. Sugar is a class of edible Crystalline substances mainly Sucrose, Lactose, and Fructose. Trehalose, also known as mycose, is a natural alpha-linked Disaccharide formed by an α α-1 1-glucoside bond between two α-glucose units Sugars and other solutes that do not easily crystallize have the effect of limiting the stresses that damage cell membranes. The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called MembraneA biological membrane or biomembrane is an enclosing or separating Amphipathic layer that acts as a barrier within or around a cell. Trehalose is a sugar that does not readily crystallize. Mixtures of solutes can achieve similar effects. Some solutes, including salts, have the disadvantage that they may be toxic at high concentrations.

History

One of the most important early workers on the theory of cryopreservation was James Lovelock of Gaia theory fame. Dr James Ephraim Lovelock, CH, CBE, FRS (born 26 July 1919) is an independent scientist author researcher environmentalist and The Gaia hypothesis is an ecological Hypothesis proposing that the Biosphere and the physical components of the Earth ( Atmosphere Dr. Lovelock's work suggested that damage to red blood cells during freezing was due to osmotic stresses. Blood is a specialized Bodily fluid that delivers necessary substances to the body's cells such as nutrients and oxygen—and transports Waste products Osmosis is the Diffusion of a solvent (frequently water through a semi-permeable membrane, from a solution of low solute concentration (high water potential 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. [2]

See also

References

  1. ^ Bhat SN, Sharma A, Bhat SV (2005). Cryobiology is the branch of Biology that studies the effects of low Temperatures on living things Cryonics is the low-temperature Preservation of Humans and other Animals that can no longer be sustained by contemporary Medicine until A frozen zoo is a Cryogenic facility for the long term storage of animal and plant genetic material such as DNA, Sperm, eggs, and Embryos Ex-situ conservation means literally "off-site conservation " "Vitrification and glass transition of water: insights from spin probe ESR". Phys Rev Lett 95 (23): 235702. PMID 16384318.  
  2. ^ Mazur P (1970). "Cryobiology: the freezing of biological systems". Science 168 (934): 939-49. PMID 5462399.  

3. Engelmann, F. , M. E. Dulloo, C. Astorga, S. Dussert and F. Anthony, editors (2007). Conserving coffee genetic resources. Bioversity International, CATIE, IRD.   61 p.

4. Panis, B and Tien Thinh, N. (2001). Cryopreservation of Musa germplasm. INIBAP (now Bioversity International).   45 p.


External links

Dictionary

cryopreservation

-noun

  1. the preservation of biological tissue at cryogenic temperatures, typically at -80°C (dry ice temperature) or -196°C (the boiling point of liquid nitrogen).
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