X-Message-Number: 10012 Date: Wed, 8 Jul 1998 03:10:09 -0700 (PDT) From: Doug Skrecky <> Subject: Is Erythritol a Superior Cryoprotectant? Using glycerol to preserve entire organs has certain drawbacks. Glycerol is actively metabolised to formaldehyde, and in addition at high enough concentrations it can destroy cell membranes. Erythritol appears not to suffer from any of these side effects. Unlike glycerol, erythritol is not actively metabolised. (1) Like sorbitol, erthyritol appears to stabilise membranes. Adding 5% erthyritol to bacteria cultures, which are freeze-dried preserves them well at 22 C for one month, whereas 5% glycerol is harmful. (2) Unfortuately, unlike glycerol very little work has been done with testing erythritol as a cryoprotectant. However in one test it proved to be superior to glycerol. Survival of rat embryos exposed to 0.3 M glycerol was 16%, while with 0.3 M erythritol it was 56%. At 1.0 M survival with glycerol 52%, and with erythritol it was 79%. (3) In addition to being less toxic, and yielding better results in at least one test, erythritol also offers the possibility of eliminating liquid nitrogen as a storage medium and replacing this with less expensive dry ice. Excellent stability of slowly cooled cryoprotectant solutions is known to occur at temperatures below the annealed glass transition temperature (Tg'), where the unfrozen phase of a solution hardens to a glass. This is known to correlate with the melting temperature of the cryoprotectant. The melting point of erythritol at 122 C is actually higher than for sorbitol, and since the Tg' of sorbitol is above dry ice temperatures, then one can predict that this would also probably be the case for erythritol. All of these advantages would be of little avail if erythritol did not penetrate tissue. Fortunately the membrane permeability in bull spermatozoa of erythritol is about 40 times that of sorbitol, so this would not appear to be a serious problem. (4) This is still slower than for glycerol, but in the case of erythritol the results may make it well worth the wait. (1) "Erythritol: A Review of Biological and Toxicological Studies" Regulatory Toxicology and Pharmacology 24: S191-S197 1996 (2) "Effect of Carbohydrates and Related Compounds on the Long-Term Preservation of Freeze-dried Bacteria" Cryobiology 11: 73-79 1974 (3) "Cryoprotective Effect of Polyols on Rat Embryos During Two-Step Freezing" Cryobiology 29: 332-341 1992 (4) "Permeability Coefficients of Bull Spermatozoa for Water and Polyhydric Alcohols" Experimental Cell Research 69: 212-216 1971 Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=10012