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What is Cryopreservation?
Cryopreservation is the storage of material below -135°C (-211°F) to provide longevity to biological samples. Around -135°C is referred to as the glass transition point (Tg) of polyol’s water. It is generally accepted that below Tg biological activity essentially ceases. At these temperatures, enzymatic activity slows to a stop while frozen water molecules no longer move and participate in chemical reactions. Current best practices recommend dry storage below -150°C (-328°F) in LN2 vapor for a significant safety margin and to reduce the risk of sample cross contamination.
Why is it Important?
Biological samples are needed for life science research, drug discovery, diagnostic testing, and therapies. Temperatures above Tg are typically not sufficient to preserve essential biological properties for long-term storage. Below Tg, samples can be stored for decades, retrieved, thawed, and be virtually the same physiologically as the day they were frozen. Advances in cell therapy and regenerative medicine with further necessitate quality samples and the cold chain solutions that make them possible.
Cryo Best Practices
Excerpts from ISBER Best Practices for Repositories:
- “The use of LN2 freezers for long-term specimen preservation is optimal for the storage of some types of biological material…”
- “When considering storing in LN2…vapor phase storage is preferred because it provides sufficiently low temperatures to maintain samples below Tg while avoiding the safety hazards inherent in liquid phase storage.”
- “Daily LN2 usage should be recorded…as excessive LN2 usage can indicate problems with the vacuum component of the freezer.”
- “A minimum three-day supply of LN2 at normal usage and replenishment intervals should be maintained, with the assumption that a re-supply is readily available.”
- “Face and eye protection is recommended…heavy gloves appropriate for LN2…normal laboratory personal protective equipment should be worn.”
- “Oxygen level sensors should always be employed when LN2 freezers are used…normal levels of oxygen in ambient air should be near 21%.”