Microscopic Behavior of Ice Crystals and Biological Cells during Directional Solidification of Solutions with Cells

Abstract

This study aims at grasping the microscopic structure during slow freezing of human red blood cells, in relation to the mechanism of slow-freezing injury of cells. The process of directional solidification of suspensions with human red blood cells was observed for various cooling rates using a light microscope with a directional solidification stage, and a video system. Two kinds of solutions for suspension were used : physiological saline and physiological saline with 20% v/v glycerol, a common cryoprotectant. While the ice crystal growing in physiological saline had a cellular structure after a transition of a flat freezing interface into a cellular interface, the ice crystal in physiological saline with glycerol had a dendritic structure. It was found that the manners of interaction between the ice crystal and the cells are considerably different in two solutions. The possibility of a mechanical action of the ice crystal on the cells was discussed, and a classification of the patterns of interaction was proposed.