Preserving RNA Before Isolation
Appropriate storage of cells or tissue samples prior to RNA isolation is critical for preservation of intact RNA within those samples. RNAlater is an aqueous solution designed specifically to maintain RNA integrity during storage of fresh tissue and cell samples. Below are some commonly asked questions regarding RNAlater® |
1) How do I use RNAlater to store my tissue/cell sample?
- For fresh tissue, simply cut samples to a maximum thickness of 0.5 cm in any one dimension and submerge in 5 volumes of RNAlater.
- Cultured cells should be pelleted, resuspended in a small volume of PBS, then mixed with 5-10 volumes of RNAlater.
- Once in RNAlater, samples can be stored for up to 1 day at 37°C, 1 week at 25°C, 1 month or more at 4°C, and long-term at -20°C or -80°.
2) Does storing samples in RNAlater have advantages over freezing samples on dry ice or in liquid nitrogen?
Using samples that were stored in RNAlater is much easier than using frozen samples. Frozen samples must be ground to a powder and then the frozen powder must be transferred to a tube for homogenization. This procedure is laborious, messy, risks loss of sample, and perhaps most importantly, may lead to sample thawing, which can compromise RNA integrity. Samples stored in RNAlater are protected from RNases as long as the tissue remains in the solution, and they can typically be disrupted using the simpler methods appropriate for freshly collected samples (grinding in liquid nitrogen is only required for extremely hard or tough tissues such as bone or tumor tissue). Thus, in addition to making sample disruption easier, storage in RNAlater eliminates the risks of sample loss and mess due to transferring or thawing frozen powdered tissue.
3) Has RNAlater been tested with my tissue or with blood samples?
RNAlater has been successfully tested with many different tissues, (including brain, heart, kidney, liver, skeletal muscle, fat, lung) and cell types (E. coli, Drosophila, cultured mammalian cells, and some plant cells). RNAlater can also be used to store anticoagulated whole blood or the white blood cell fraction of whole blood. Ambion's RiboPure™-Blood RNA Isolation Kit incorporates RNAlater and provides instructions on how best to use RNAlater with blood.
4) Which downstream applications can be used with tissue stored in RNAlater?
Tissue stored in RNAlater is compatible with all commonly used RNA isolation methods, including single reagent isolation products like Trizol®, and all of Ambion's RNA isolation kits. It is also possible to extract both genomic DNA and total protein from samples stored in RNAlater. RNAlater will denature proteins, so it is only compatible with routine protein analyses such as Western blotting and 2D gel electrophoresis that do not require native protein.
Note: RNAlater is not recommended for use with tissues that will be sectioned using a cryostat.
Note: RNAlater is not recommended for use with tissues that will be sectioned using a cryostat.
5) How can I ship my sample in RNAlater?
Samples in RNAlater can safely be shipped on wet ice for several days. For longer shipping times use dry ice
6) Can I add RNAlater to samples that are already frozen?
- A different product, RNAlater®-ICE, is used with samples that are already frozen. RNAlater-ICE transitions tissue from a frozen to a non-frozen state. The frozen tissue is simply placed in RNAlater-ICE and left at -20°C overnight. Treated tissues can then be used directly in standard homogenization and isolation protocols and processed like fresh tissue.
- RNAlater and RNAlater-ICE provide flexibility for sample collection and storage, and help ensure that high quality RNA is preserved in samples. Both are available in a variety of convenient sizes.
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