Principles of Genetics and Breeding

9.1.11 Vitrification

• Researchers who have developed a new technique, vitrification, in 2000 claim to provide the benefits of cryopreservation without damage due to ice crystal formation.
• In clinical cryopreservation, vitrification usually requires the addition of cryoprotectants prior to cooling.
• The cryoprotectants act like antifreeze: they lower the freezing temperature. They also increase the viscosity. Instead of crystallizing, the syrupy solution turns into an amorphous ice —i.e.,it vitrifies.
• Vitrification of water is promoted by rapid cooling, and can be achieved without cryoprotectants by an extremely rapid drop in temperature. Two conditions usually required to allow vitrification are an increase in the viscosity and a depression of the freezing temperature. Many solutes do both, but larger molecules generally have large reffect, particularly on viscosity. Rapid cooling also promotes vitrification.

In established methods of cryopreservation, the solute must penetrate the cell membrane in order to achieve increased viscosity and depress freezing temperature inside the cell. Sugars do not readily permeate through the membrane. Those solutes that do, such as dimethylsulfoxide, a common cryoprotectant, are often toxic in high concentration. One of the difficult compromises faced in vitrifying cryopreservation is limiting the damage produced by the cryoprotectant itself.