Cryopreservation is the science of using extremely low temperatures to preserve living cells and tissues to keep them structurally intact. This biological effect of cooling is carried out by the freezing of water – resulting in the dissolved solute concentration remaining in its liquid phase. 
However, alongside this cooling, the formation of ice crystals must be prevented to avert the destruction of cell organelles during the subsequent freezing process and cell death caused by dehydration. The destruction itself has been speculated to be the result of piercing the cell through direct mechanical action or by secondary effects in the form of changes in composition of the liquid phase. To prevent destruction of cells in either form, cryoprotective agents are utilised as they concurrently increase the total concentration of all solutes in the system, reduce the formation of ice, penetrate cells without causing harm and have low toxicity. Common cryoprotectants include glycerol (primarily to protect red blood cells) and dimethyl sulfoxide (to protect the majority of the remaining cells and tissues).
The majority of cryopreservation is executed in controlled-rate freezers that deliver liquid nitrogen into a chamber containing the cell/ tissue suspension; reaching temperatures of approximately -90 degrees Celsius. Another technique that can be used is vitrification; the process by which the cells enter a glassy state – behaving like a solid, but without the use of ice. 
Most commonly, cryopreservation is used in the freezing and storing of haematopoietic stem cells extracted from the patient prior to chemotherapy, after which the cells are then thawed and infused back into the body. This allows for high-dose chemotherapy to be carried out without damaging the vulnerable bone marrow. Another common application of cryopreservation is to freeze and store embryos and sperm for in-vitro fertilization.
Whilst cells can survive for more than a decade when frozen successfully, only specific tissues can do so as well. Despite this progress, no human organs have been preserved, then thawed for future use before and only the hopes of partial freezing have come close to becoming theoretically plausible. Subsequently, even long-term organ banking is currently part of a very unattainable future. Nevertheless, people still undergo cryonic preservation. It is hopes of better technological advancements in the future that motivate people to consider freezing their bodies for decades to come – waiting to be revived and continue to live out the rest of their lives. 
Due to the unpredictable nature of full-body cryopreservation, very few people sign up to have their bodies frozen and stored after death. Scepticism is due to a combination of factors, including: no prior successful animal trials (testing did occur on mammals, however, did not succeed) and the current impossibility to restore life into cells, blood vessels, organs and neurons. However, those with hopes to execute this manner of life after death, are dependent on the expectations that medical technology will evolve enough in the future to allow revival. 
There are many ethical considerations regarding the art of cryopreservation of full bodies. Despite fees being paid through trusts for the upkeep and maintenance of the cooling and storing facilities, there is always the risk of companies running out of money. This brings to question, what happens to the bodies after storage can no longer be maintained and is it the company that has a duty to still care for the bodies if the families are no longer alive or capable?
Another issue is whether it would be possible for brain function to be completely restored – would people even be conscious when awoken or remain in a vegetative state? It is difficult to believe that thawing of the body would not fundamentally alter the mind and body. Would one still have their prior knowledge and memories? Will revival still be wished for in a future where there are no family or friends waiting for them, in an unfamiliar time and place? Bioethicists also suggest the consequences of waking up in the unknown could include depression and other illnesses due to isolation. 
However, cryonics does not only affect the people themselves, but also the environment. The indirect effects of cryopreservation in the long-term would not only would it prevent the natural cycle of death as a means to control overpopulation but also substantially affect the amount of finite resources available. Should energy be used to store those that are already dead, and subsequently further harm the earth through global warming?
Despite being widely used around the world, ethical considerations question whether the cons are greater than the pros.
- David E. Pegg, ‘Principles of Cryopreservation’, National Library of Medicine, 2007, https://pubmed.ncbi.nlm.nih.gov/18080461/
- David H. Yawn, ‘Cryopreservation’, Britannica, Jul. 24, 2008, https://www.britannica.com/topic/Frostie
- Megan Scudellari, ‘Core Concept: Cryopreservation aims to engineer novel ways to freeze, store, and thaw organs’, PNAS, Dec. 12, 2017, https://www.pnas.org/content/114/50/13060
- Phillipa Roxby ‘What does cryopreservation do to human bodies?’, BBC, Nov. 18, 2016, https://www.bbc.co.uk/news/health-38019392
- Phillipa Roxby, ‘What are the ethics of cryonic preservation?’, BBC, Nov. 18, 2016, https://www.bbc.co.uk/news/health-38031428