When designing a new protocol for biosample storage, a fundamental point to consider is the temperature at which the collection will be maintained. Optimal storage temperatures depend on a variety of factors, such as sample type, container design, expected storage time, and planned future assays, and essentially, biobank storage temperature options fall into five main categories:
- room temperature (+20°C),
- refrigeration (+4°C),
- frozen (-20°C),
- ultra-low (-80°C) and
- cryogenic (-196°C).
Given that samples stored at lower temperatures are typically better preserved, it may come as somewhat of a surprise that some biosamples are best stored at temperatures above the freezing point of water. What’s more, freezing is sometimes unnecessary –and could even be detrimental for certain samples.
To illustrate my point, here’s a short list of sample types that can be stored at temperatures above the freezing point of water:
Formalin-fixed paraffin-embedded (FFPE) tissue. Formalin-fixed paraffin-embedded (FFPE) tissue can also be stored above freezing. If the samples will only be used for histology in the future, they can be stored indefinitely at room temperature. However, if you intend to extract DNA or RNA from the samples, it’s much better to store them at 4°C.
Purified DNA and RNA. Thanks to newly-developed chemical stabilizers (PDF), purified DNA and RNA can both be stored at room temperature. Studies have shown genetic material can be stored for years this way without any loss in quality.