Vitrification, also known as “ultra-fast freezing”
Vitrification has been used increasingly in human medicine over the past 10 years or so. Vitrification is an ultra-fast freezing process.
During the vitrification process, water within the cells is removed by adding certain solutions. This prevents the formation of the ice crystals that destroy cells. Mechanical damage to parts of the cells is a very rare occurrence.
However, there is in principle some risk of toxicity to the cells due to the relatively high concentration of cryoprotective agents (freezing protection agents) used.
A major advantage of this method is the “thaw rate” of 98 % and the fact that vitrification permits the risk-free cryopreservation not only of inseminated egg cells, but also of non-inseminated egg cells and embryos.
However, the huge advantage of vitrification is that it can be used, for example, to preserve non-inseminated egg cells of women who are about to undergo chemotherapy or radiotherapy, which pose a risk to fertility (Fertility preservation). This approach can also be used to treat the egg cells of women aged between 25 and 35 who would like to make arrangements for Fertility preservation so that they can have an improved chance of pregnancy later on (for example, when they are 40 – 45 years old). This is also known as social freezing.
Embryo freezing is useful, particularly in countries in which embryo selection is permitted, if there are more embryos in the blastocyst stage on culture day 5 than are to be transferred.
The disadvantage of the method for the laboratory performing the freezing is that only individual cells (and not groups of egg cells) can be vitrified at once. AFurthermore, the use of this method requires a longer learning curve and a lot more manual dexterity than slow freezing.