Ice-Free Cryopreservation by Vitrification

Ice-free vitrification of biospecimens is an alternative cryopreservation strategy to conventional preservation by freezing. Vitrification is the amorphous solidification of a supercooled liquid. This state is achievable by adjusting the cryoprotectant concentration and cooling rate to minimize nucleation and growth of ice crystals. The cooled liquid is then converted to a glassy state, notice. Without ice crystal formation, the biospecimens’ extracellular matrix and cell viability is often better preserved. The decision to utilize an ice-free versus a freezing method for different types of biospecimens depends on which method is easiest for the product, whether the biospecimen will be washed before use, and whether an optimized method is already available. Generally, cells and tissues can be preserved using ice-free vitrification but isolated cells are easier to preserve using freezing methods because the cells are exposed to less risk of cryoprotectant-induced cytotoxicity and the cryoprotectant solutions are less viscous making the cells easier to handle. Samples such as tissue biopsies, Islets of Langerhans and encapsulated cells can also be preserved using either strategy, however the formation of ice during freezing may disrupt the tissues and distort or break capsules. Ice-free vitrification has major advantages for preservation of ovaries, heart valves, articular cartilage, and both natural and tissue engineered blood vessels, protecting the extracellular matrix and cells. In the extreme case of articular cartilage freezing results in less than 20% cell viability in contrast with ?80% after ice-free vitrification.