Frozen fish, anyone? A new method of flash-heating frozen fish embryos makes it possible to preserve zebrafish in the earliest stages of development. The method may eventually make it possible to tuck away embryos in “fish banks” that could be used to restore biodiversity in oceans and freshwater.
The technique involves the use of nanoparticles injected inside the embryos prior to freezing. When the frozen embryos need to be rewarmed, they are targeted with a laser, which causes the particles to act as tiny heaters. The rewarmed embryos can survive for up to five days after thawing, although more work is needed to produce fish that grow to maturity.
Cryopreservation has long been the key to assisted reproduction in a variety of species, including humans. But it is not as simple as tossing some cells in the freezer; normal freezing causes ice crystals to form in cells, damaging membranes and rendering the cells nonviable. Chemicals called cryoprotectants — combined with rapid chilling and reheating — can protect sperm, eggs, and embryos from this fate. The goal, says John Bischof, the Carl and Janet Kuhrmeyer Chair of Mechanical Engineering and...
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