Hi, I have frozen two 96-well plates with cells that I need to stain using the CyQuant Cell Proliferation Assay from ThermoFisher (C7026). However, I didn't realize that we only have some very old "left overs" available in our lab (most likely at least 2 years old, stored at -20oC). The manufacturer says that the kit is stable for 6 months. However, everybody that has worked in the lab for a while knows that for some compounds the stability is very much longer than the label indicates. But for others it is not... anyone here that has tested some old CyQuant Prolif. kit?
Best regards, Sonja :)
Sonja, as the principle is a dye that is changing its fluorescence behaviour by binding to DNA and thus enables quantification DNA measured as fluorescence, it should be hard to destroy the functionality of the reagent, if it has been stored halfway properly. 6 months is usually what is guaranteed, but most chemicals won't drop dead from one month to the other.
Maybe test the reagents with a few samples of no value to assure the reagent is ok, check if your signal is similar to past experiments.
It seems to go much like the famous H33258 intercalating dye or even propidium iodide/ethidium bromide/cybr green might do the job (maybe the MSDS is giving you some clues), so you might be inclined to homebrew your own for a fraction of the cost (a nice job for a student intern, maybe). You may record UV/Vis and fluorescence spectra or just look at the recommended wavelength to identify the dye that is used.
Sonja Andersen two years is quite a while! It is true that the stability of some compound is longer than the manufacturers say and I have used this kit after 1 year which worked fine.
Possibly you could test the old kit with a new one and see if the results are comparable.
Thank you, Jack Hopkins and Wolfgang Schechinger ! I agree that it rarely is a clear cut "drop dead" loss of functionality, but then again 2 years is quite a while... Since my Seahorse plates in the freezer are quite precious, I have ordered a new kit just to be sure. But I might test it on something to compare new and old - and if I do, I will post the results in case someone else might be interested :)
Sonja Andersen that's probably the best way forward - I would be very interested to know the results!
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