In the cryopreservation of biological materials, size, temperature and composition of a water droplet determine whether the droplet is vitrified or crystallized.
Online PR News – 11-March-2010 – – Boston, MA - Utkan Demirci, PhD, of the Center for Bioengineering in the Department of Medicine at BWH, and colleagues have used mathematical modeling to demonstrate that in the cryopreservation of biological materials, size, temperature and composition of a water droplet determine whether the droplet gets vitrified or crystallized. The findings could enable the development of high throughput automated methods of droplet-based cryopreservation of biological samples such as blood. These findings appear in the February 22 of issue of Proceedings of the 'National Academy of Science'.
Cryopreservation of biological materials depends on the rapid removal of water from the material to be preserved. Cells and tissues are preserved in a vitrified state by suspending them in cryoprotectant liquids before being immersed in liquid nitrogen. Vitrification protects cells by halting the metabolic process preventing the formation of ice crystals. To determine the factors that drive vitrification, the researchers studied the physical phenomena occurring when a droplet of the cryoprotectant plummets into liquid nitrogen. When ejected into liquid nitrogen the droplet rises to the surface buoyed by a vapor cloud generated around it by the evaporation of the surrounding liquid nitrogen. After skittering around on the surface, the droplet sinks when its temperature finally reaches that of liquid nitrogen. This process is comparable to the Leidenfrost effect observed when water is sprinkled on a hot skillet.
This new understanding has implications in a variety of settings, not only in preserving biological samples, like blood, but also in improving some fertility treatments. The researchers are currently applying this new droplet-based biopreservation technology to mouse oocytes as an initial step towards future clinical trials.
The study was funded by a grant provided by the National Institutes of Health.
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