ABSTRACT
The ability of glycerol to protect cells from freezing injury was discovered accidentally.
The subsequent development of cryopreservation techniques has had a huge impact in
many fields, most notably in reproductive medicine. Freezing injury has been shown
to have two components, direct damage from the ice crystals and secondary damage caused
by the increase in concentration of solutes as progressively more ice is formed. Intracellular
freezing is generally lethal but can be avoided by sufficiently slow cooling, and
under usual conditions solute damage dominates. However, extracellular ice plays a
major role in tissues. Cryoprotectants act primarily by reducing the amount of ice
that is formed at any given subzero temperature. If sufficient cryoprotectant could
be introduced, freezing would be avoided altogether and a glassy or vitreous state
could be produced, but osmotic and toxic damage caused by the high concentrations
of cryoprotectant that are required then become critical problems. The transport of
cryoprotectants into and out of cells and tissues is sufficiently well understood
to make optimization by calculation a practical possibility but direct experiment
remains crucial to the development of other aspects of the cryopreservation process.
KEYWORD
Cryopreservation - cryoprotectant - freezing
