I have adherent cell line samples in multi well plates that I want to isolate RNA and DNA from in about 6 months to a year time. The plates are stored at -80 degrees now. Is it better to store it as it is or add lysis buffer and store it ? Or Will both result bad quality RNA and DNA if it is stored for long?
Storing cells frozen in plates for more than a few days is generally a bad idea because TC plates don't seal, so you are risking dessication and contamination of your samples. A much better option is to scrape your adherent cells into cold PBS, transfer to Eppendorf tubes and pellet by centrifugation at 4C. Then you can remove the PBS and freeze the cell pellets. As long as you work quickly and snap-freeze the pellets, you should be able to get good quality DNA and RNA this way.
Since your cells have already been frozen in plates, I don't think you could collect them in PBS at this stage. I think your best option is to either process the samples now, or else to thaw the cells by dropping lysis buffer onto them, and then immediately collect the lysis buffer into Eppendorf tubes and freeze them down again. Keep in mind that you will lose some potential DNA/RNA quality by doing this extra freeze/thaw. I have had good results freezing cell and tissue samples homogenised in Nucleozol (good quality RNA isolated 6-12 months later) but I am not sure if this reagent is suitable for extracting high quality DNA, I have only ever used it for RNA.
Hope this helps :)
You can store cells in plate for the purposes of DNa and RNA extraction at -80C but I take the point of the above correspondent as well. Seals do tend to come loose so that might incur contamination
You also asked about freezing cells versus lysates
Lysates ARE ALWAYS better: DNA but particularly RNA are more stable. That is because both types of lysis buffer contain guanidinium salts which are designed to stabilise nucleic acid
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