X-Message-Number: 8418 Date: Thu, 24 Jul 1997 09:32:53 -0700 (PDT) From: Doug Skrecky <> Subject: "hot" cryonics In Message #8417 yvan Bozzonetti <> wrote: > That technology could be termed "hot" cryonics. In a first place we > would look at temperature near -130 deg. C, the next step would be to look > at dry ice temperature and so on until we have near room temperature > conservation. > Many cryoprotectants are stable at dry ice temperatures. These are "solid" cryoprotectants that do not melt at room temperature when dry. An example of one of these is sorbitol which melts at 110 C. However even completely dry sorbitol is not inert at room temperature. This only occurs when it hardens to a glass at what is called the glass transition temperature or "Tg". For sorbitol this is -9 C. As for stability of frozen tissue this occurs at the annealed glass transition temperature or Tg'. For sorbitol this is -64 C, so sorbitol treated frozen tissue can be expected to be inert at dry ice temperatures. However there is a price to be paid for this tremendous increase in stability & safety relative to "liquid" cryoprotectants like glycerol & DMSO, with Tg's below -100 C. As far as I am aware all potential cryoprotectants that could be used in conjunction with dry ice storage suffer from relatively slow permeation into tissue. So preparation of tissue with sorbitol and other "solid" cryoprotectants would be time consuming relative to current procedures, which use glycerol. One cryoprotectant that shows promise here is adonitol, which permeates cell membranes over 30 times as quickly as sorbitol yet still melts at a warm and toasty 102 C. For those concerned about safety or expense of cryonic storage, adonitol might be close to being the optimal choice of cryoprotectant for use in conjunction with dry ice storage. References: "Melting and Glass Transitions of Low Molecular Weight Carbohydrates" Carbohydrate Research 238: 39-48 1993 "Permeability Coefficients of Bull Speratozoa for water and polyhydric Alcohols" Experimental Cell Research 69: 212-216 1971 Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=8418