Hi all- I work with artificial insemination and have recently wondered how sperm/ eggs/ embryos be frozen in liquid nitrogen (for years!) and then later thawed (in about 60 seconds) where it’s then back to functioning like normal, but you can’t freeze a living person and then unfreeze them again? At what developmental point can you stop freezing biological material before it won’t work again? (No political motive here, just questioning the science behind it, please please no arguing)
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Well the biggest problem is water. Our cells contain it. It is a material that expands and forms ice crystals when frozen. These ice crystals will rupture the cell membrane, so that after the cell is thawed, its insides are all spilled out.
This is still a problem with egg/embryos. But the material is small enough that sometimes it’s enough to use a rapid freezing process, whereby the temperature is dropped quickly enough not to allow ice crystals to form. This is called vitrification.
If this began working on a larger scale, then we might see some realistic cryopreservation.
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