20 September 2013

Success of vitrification

"Glazed" donor organs are stored longer

ABC Magazine based on New Scientist: Heart of glass could be key to banking organsAt the sixth conference of the Scientific Society Strategies for Engineered Negligible Senescence (SENS), held at Queens College, Cambridge, UK (Queens’

College, Cambridge, UK) Dr. Stephen van Sickle from the Amrican company Arigos Biomedical presented a report on the use of vitrification technology (turning into glass) for the preservation of donor organs: storage of donor organs frozen in this way is possible for years or even decades, which will create real organ banks, increase their availability and reduce queues. The limitations of the method include thermomechanical damage ("glass" organs can crack) and biochemical toxicity of solutions used during freezing. Thanks to the developed technology, cracking can be eliminated and the toxicity of cryoprotectors for vitrification can be reduced. In preliminary experiments with pig kidneys, it was possible to achieve the absence of damage and a high cooling rate, which reduces the time of exposure to cryoprotectors.

When freezing living cells, the crystallization of extracellular and intracellular water occurs, which damages the most important structures, since the volume of crystals is greater than the volume of the original liquid. In addition, crystallization implies the influence of other factors of importance. Firstly, osmotic equilibrium is disturbed (the amount of water in which proteins and salts are dissolved decreases). Secondly, heat will be released (due to a decrease in entropy, freezing is an exothermic process) and cell structures are damaged from overheating.

During vitrification, the supercooled solution turns into a solid state, remaining amorphous (there is no crystalline structure of the substance), this can be achieved by very rapid cooling. However, even for one living cell, the required cooling rate is unattainable, and cryoprotectors solve this problem. Cryoprotectors form hydrogen bonds with water molecules and disrupt the formation of ice crystals, their use reduces the freezing rate. Despite the fact that cryoprotectors are toxic to cells by their nature, vitrification technology has been developed and is successfully used for the preservation of human embryos and oocytes in the treatment of infertility.

When vitrifying large organs, the question arises of the need to use more cryoprotectors and the fragility of the "glazed" organ. According to Dr. van Sickle, these problems are solved by using persufflation (replacing blood with gas) with helium. Thus, the organ cools faster, and less cryoprotectant is required, and the spaces between the tissues remain separated by gas, without sticking together.

Other companies have similar developments – for example, 21st Century Medicine reported successful vitrification, defrosting and transplantation of rabbit kidneys (smaller in size than pork ones). The largest organization in the field of cryobiology, the Alcor Life Extension Foundation, has been preserving human bodies in liquid nitrogen since 1976. In 2001, Alcor announced the possibility of "neurovitrification" – the preservation of the human brain in a state without damage by ice crystals, thanks to cryoprotectors created by the company.

Portal "Eternal youth" http://vechnayamolodost.ru20.09.2013

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