Cryonics: a new step

Americans have learned to defrost organs without damage

Vasily Sychev, N+1

Researchers at the American University of Minnesota have developed a new way to defrost organs without damaging them. The work of scientists has been published Science Translational Medicine (Manuchehrabadi et al., Improved tissue cryopreservation using inductive heating of magnetic nanoparticles), and a summary of it is given in the university's report (New technology rewarms large-scale tissues preserved at low temperatures). The method developed by the researchers makes it possible to evenly warm up a frozen organ at a rate of one hundred to two hundred degrees Celsius per minute. This is ten times faster than modern defrosting methods.

Cryogenic freezing, or cryopreservation, is considered the most promising way to preserve donor organs. For freezing, donor organs are placed in a special cryoprotector solution. It is usually made on the basis of glycerin or propylene glycol. This solution prevents the formation of ice crystals that can damage the cells of the organ and make it unsuitable for further use. Cryopreservation is performed at a temperature of -196 degrees Celsius in liquid nitrogen.

Cryopreservation is currently used to freeze sperm, cell cultures, or preimplantation embryos. Large organs or living organisms are frozen relatively rarely, since there is no reliable way to safely defrost them yet. The fact is that with slow defrosting, supercooled organs are covered with ice crystals that damage tissues. If the heating is accelerated, then the organs simply crack due to the temperature difference inside and outside.

A new method developed by American scientists involves adding iron oxide nanoparticles coated with porous silicon dioxide to the cryoprotector solution. This material is able to heat up quickly under the influence of electromagnetic radiation. Thanks to the uniform stirring of nanoparticles in the cryoprotector, it is possible to ensure their penetration into the donor organ and, during defrosting, quickly and evenly warm up the latter.

Comparison of fast convective and new inductive defrosting

During the experiments, the researchers used large heart valves and blood vessels of animals subjected to cryopreservation in VS55 solution with the addition of new nanoparticles. Subsequently, an installation with an induction coil was used for defrosting. The power of the installation ranged from one to 15 kilowatts and was changed by changing the induction coil. Kilowatt power was used to defrost samples in one-milliliter containers, and 15–kilowatt power was used in 80 milliliter containers.

During defrosting, the coil generated electromagnetic radiation with a frequency of one hundred to 400 kilohertz. During the experiment, cryopreserved samples were quickly thawed. Microscopy examination showed that the samples did not receive cellular damage. The control fast convective and slow defrosting showed the worst results, some of the samples were damaged.

After successful defrosting, the samples were washed and tested for the absence of iron oxide nanoparticles. Control by ultrasound and magnetic resonance imaging of nanoparticles after washing the samples was not detected.

In February last year, researchers from 21st Century Medicine managed to defrost the brains of a rabbit and a pig after cryopreservation, while maintaining neural connections. To freeze organs, scientists used a new method called aldehyde-stabilized cryopreservation. Before cryopreservation, a fixing solution based on glutaraldehyde and a cryoprotector with the addition of ethylene glycol were fed into the dead brains of animals. Then the animals' brains were cooled to -135 degrees Celsius.

The researchers then defrosted the animals' brains, removed the fixing solution and cryoprotector, and analyzed the state of the brain using electron microscopy. It turned out that freezing and subsequent defrosting did not affect the microstructure of synapses. They remained untouched. Researchers believe that in the future this will allow cryopreservation of the brain with preservation of long-term memory.

Portal "Eternal youth" http://vechnayamolodost.ru  02.03.2017