Editing Cryonics (section)

=== Preservation damage ===
Medical laboratories have long used cryopreservation to maintain animal cells, human embryos, and even some organized tissues, for periods as long as three decades.<ref>{{cite journal|vauthors=Crippen DW, Reis RJ, Risco R, Vita N|date=October 2015|title=The Science Surrounding Cryonics |url=https://www.technologyreview.com/2015/10/19/109714/the-science-surrounding-cryonics/|journal=MIT Technology Review}}</ref> But recovering large animals and organs from a frozen state is not considered possible now.<ref>{{cite journal|author=Smith Audrey U |year=1957 |title=Problems in the Resuscitation of Mammals from Body Temperatures Below 0&nbsp;°C|journal=Proceedings of the Royal Society of London. Series B, Biological Sciences|volume=147|issue=929|pages=533–44|bibcode=1957RSPSB.147..533S|doi=10.1098/rspb.1957.0077|jstor=83173|pmid=13494469|s2cid=40568140}}</ref><ref name="Fahy GM, Wowk B, Pagotan R 167–75" /><ref>{{cite journal|vauthors=Fahy GM, Wowk B, Wu J|year=2006|title=Cryopreservation of complex systems: the missing link in the regenerative medicine supply chain|url=http://www.21cm.com/articles/Missing_Link.pdf|journal=Rejuvenation Research |volume=9 |issue=2 |pages=279–291 |citeseerx=10.1.1.539.7419|doi=10.1089/rej.2006.9.279|pmid=16706656|access-date=2017-10-24|archive-date=2017-10-25|archive-url=https://web.archive.org/web/20171025022108/http://www.21cm.com/articles/Missing_Link.pdf|url-status=live}}</ref> Large vitrified organs tend to develop fractures during cooling,<ref>{{cite journal |vauthors=Fahy GM, Saur J, Williams RJ |title=Physical problems with the vitrification of large biological systems|journal=Cryobiology |volume=27 |issue=5 |pages=492–510 |date=October 1990 |pmid=2249453 |doi=10.1016/0011-2240(90)90038-6}}</ref> a problem worsened by the large tissue masses and very low temperatures of cryonics.<ref>{{cite magazine |author=Wowk B |title=Systems for Intermediate Temperature Storage for Fracture Reduction and Avoidance| magazine =Cryonics| pages = 7–13| year=2011| volume =2011| issue =3| publisher = Alcor Life Extension Foundation| issn=1054-4305}}</ref> Without cryoprotectants, cell shrinkage and high salt concentrations during freezing usually prevent frozen cells from functioning again after thawing. Ice crystals can also disrupt connections between cells that are necessary for organs to function.<ref>{{cite journal|vauthors=Fahy GM, Levy DI, Ali SE|date=June 1987|title=Some Emerging Principles Underlying the Physical Properties, Biological Actions, and Utility of Vitrification Solutions|journal=Cryobiology|volume=24|issue=3|pages=196–213|doi=10.1016/0011-2240(87)90023-X|pmid=3595164}}</ref>

Some cryonics organizations use vitrification without a [[fixation (histology)|chemical fixation]] step,<ref>{{cite web |title=Alcor Position Statement on Brain Preservation Prize |publisher=Alcor Life Extension Foundation |date=2016-02-12 |url=http://www.alcor.org/blog/alcor-position-statement-on-brain-preservation-foundation-prize/ |access-date=2016-03-20 |archive-date=2016-02-15 |archive-url=https://web.archive.org/web/20160215230517/http://www.alcor.org/blog/alcor-position-statement-on-brain-preservation-foundation-prize/ |url-status=live}}</ref> sacrificing some structural preservation quality for less damage at the molecular level. Some scientists, like João Pedro Magalhães, have questioned whether using a deadly chemical for fixation eliminates the possibility of biological revival, making chemical fixation unsuitable for cryonics.<ref>{{cite web |title=Mammal brain frozen and thawed out perfectly for first time |url=https://www.newscientist.com/article/2077140-mammal-brain-frozen-and-thawed-out-perfectly-for-first-time/ |access-date=2016-06-06 |work=[[New Scientist]] |archive-date=2016-06-16 |archive-url=https://web.archive.org/web/20160616185949/https://www.newscientist.com/article/2077140-mammal-brain-frozen-and-thawed-out-perfectly-for-first-time/ |url-status=live}}</ref>

Outside of cryonics firms and cryonics-linked interest groups, many scientists are very skeptical about cryonics methods. [[Cryobiologist]] Dayong Gao has said, "we simply don't know if [subjects have] been damaged to the point where they've 'died' during vitrification because the subjects are now inside liquid nitrogen canisters." Based on experience with organ transplants, biochemist Ken Storey argues that "even if you only wanted to preserve the brain, it has dozens of different areas which would need to be cryopreserved using different protocols".<ref name="bbc frozen" />