Survival of Erythrocytes After Cooling Into Liquid Nitrogen : Relation With Glass-Forming Tendency on Cooling and the Transition From Cubic Into Hexagonal Ice on Rewarming

If the survival rate of red blood cells cooled down to liquid nitrogen temperature is plotted versus cooling rate, it increases, decreases, then increases again at the highest cooling rates if the cryoprotectant concentration is sufficient, when subsequent rewarming is fast. This last increase coincides with the decrease of the quantity of ice crystallized in the solution, in the presence of various concentrations of 1,3- butanediol or 1,2-propanediol. The high survival at the highest cooling rates corresponds to total vitrification. On rewarming, if the solution was wholly amorphous, cubic ice first crystallizes. It transforms afterwards into hexagonal ice. Freezing damage parallels or follows immediately after this transition.