Cryopreservation

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Preservation of plant samples
Liquid nitrogen tank

Under cryopreservation (from Greek  κρύος , kryos "cold" and Latin conservare "obtained preserve") refers to the storage of cells or tissue by freezing in liquid nitrogen . With the help of this process it is possible to maintain the vitality of the cells almost indefinitely, although the biological system changes into the aggregate state of a solid . Cryopreservation can be applied to both plant cells and animal cells, for example blood, sperm , egg cells and embryos in humans . The storage takes place in so-called cryobanks .

The conserved cells can thus be preserved over a very long period of time in a kind of cold rigidity in which all metabolic processes almost come to a standstill. After thawing, the cells can resume their normal physiological processes. Embryos can then be transferred to the uterine cavity, for example .

Individual cells can be frozen so quickly that the water only forms small ice crystals . In larger, multicellular organisms, however, when the temperature drops too low, ice crystals form in the core when they freeze. These become so large that they break through the cell walls and thus irreparably destroy them. Freezing strawberries in the freezer clearly illustrates the cell damage caused by freezing: After thawing, the strawberries look mushy - they have lost water that has leaked from the damaged cells.

Nowadays, cryopreservation works with cell samples right through to small organs if, after preparing the samples beforehand with properly coordinated anti-freeze agents to prevent the growth of ice crystals, they are then frozen very quickly, for example with liquid nitrogen to 77  K (−196  ° C ) ( glazed ).

Various mosses can be cryopreserved at −135 ° C for several years without losing their ability to regenerate. However, larger organs and organisms suffer damage during cryopreservation that cannot be repaired with today's means. A success or failure of cryonics can therefore only be assessed in retrospect.

In cell biology, cells for cryopreservation are usually frozen in a freezing medium from the culture medium with dimethyl sulfoxide , e.g. B. in culture medium with 20% (V / V) FCS and 10% (V / V) DMSO. In some cases, ethylene glycol is also used instead of DMSO . In the case of vitrification , on the other hand, an attempt is made to avoid the formation of ice crystals during cooling entirely B. with concentrated glycerol solutions (17 mol per kilogram of water).

There are frogs like the wood frog or insects like the gall mosquito that survive freezing in winter up to a certain critical temperature due to the body's own antifreeze ( urea ).

In Siberia, nematodes have been found that had been preserved in the permafrost soil since the Pleistocene around 42,000 years ago . Despite the fact that they had been frozen for tens of thousands of years, two types of these worms have been successfully revived.

See also

literature

  • HM Schumacher: Completely solidified, but not dead: Cryogenic storage of plants at ultra-low temperatures. In Nicole C. Karafyllis : Theories of Living Collection. Plants, microbes and animals as biofacts in gene banks . Karl Alber, Freiburg 2018, pp. 137–168, ISBN 978-3-495-48975-8 .
  • R. Frankham, JD Ballou, DA Briscoe: Introduction to Conservation Genetics . Cambridge University Press, 2002, ISBN 0-521-63985-9 .
  • S. Schmitz: The experimenter : cell culture . Spectrum Academic Publishing House, 2007, ISBN 978-3-8274-1564-6 .

Individual evidence

  1. J. Schulte, R. Reski : High-throughput cryopreservation of 140000 Physcomitrella patens mutants. In: Plant Biol. 6, 2004, pp. 119-127. PMID 15045662 .
  2. Z. Shu, S. Heimfeld, D. Gao: Hematopoietic SCT with cryopreserved grafts: adverse reactions after transplantation and cryoprotectant removal before infusion. In: Bone Marrow Transplant. Volume 49, number 4, April 2014, pp. 469–476, doi: 10.1038 / bmt.2013.152 . PMID 24076548 , PMC 4420483 (free full text).
  3. Y. Agca, J. Liu, AT Peter, ES Critser, JK Critser: Effect of developmental stage on bovine oocyte plasma membrane water and cryoprotectant permeability characteristics. In: Molecular reproduction and development. Volume 49, Number 4, April 1998, pp. 408-415, doi : 10.1002 / (SICI) 1098-2795 (199804) 49: 4 <408 :: AID-MRD8> 3.0.CO; 2-R . PMID 9508092 .
  4. JA Bautista, H. Kanagawa: Current status of vitrification of embryos and oocytes in domestic animals: ethylene glycol as an emerging cryoprotectant of choice. In: The Japanese journal of veterinary research. Volume 45, Number 4, February 1998, pp. 183-191. PMID 9553322 .
  5. ^ AF Davidson, C. Glasscock, DR McClanahan, JD Benson, AZ Higgins: Toxicity Minimized Cryoprotectant Addition and Removal Procedures for Adherent Endothelial Cells. In: PloS one. Volume 10, number 11, 2015, p. E0142828, doi: 10.1371 / journal.pone.0142828 . PMID 26605546 , PMC 4659675 (free full text).
  6. AV Shatilovich, AV Tchesunov, TV Neretina, IP Grabarnik, SV Gubin, TA Vishnivetskaya, TC Onstott, EM Rivkina: Viable Nematodes from Late Pleistocene Permafrost of the Kolyma River Lowland. In: Doklady Biological Sciences. 480, 2018, p. 100, doi : 10.1134 / S0012496618030079 .