Generally it is going to come down to how well your sample is sealed. Oxidation is the biggest killer of fluorescence in fluorescent samples. If you are working with tissue sections then mouting them in histo mount, DPX, or somethign similar will kep the fluorescence for years (i have looked at slides that were 5 years old and they were still good). If mounted this way they wont even need to be kept in the fridge.

For samples mounting in vecta shield, prolong etc if the coverslip is sealed well with nail polish you can keep them in the fridge for a year or more without any problems. he biggist issue i have had with storing glycerol type mounted slides is that if you store them on their edge (i.e in a normal slide box) you can find that the coverslip slides off over time.

Cameron - thanks, I agree on oxidation, but I would dispute use of DPX on a fluorescent dye, - the result is unpredictable; it's whole another question which dye can survive organic solvents.

We routinely use DAPI, hoechst, alexas, tritc phalloidin and cellmask without a problem.

Hi, I checked my slides which were stained with DAPI Vectashield and sealed with nail polish - they are still OK. Today these slides are 2 years old and they are stored in the fridge. All the best, Anna

Hi, the durability of the fluorescence in your sample will depend on the quality of the prepared slide, the photo-bleaching conditions of the dyes which invariably will inform how to prepare the slides for long storage. I use Alexa dyes and they prove to stay long with the signal when tightly wrapped in aluminium foil and stored in -20 C.

I used a 4 year old sample stained with Alexa, DAPI and rhodamine for training purposes on confocal microscopy. It was mounted in mowiol and stored in the fridge. I could still observe it under the micorscope except for the rhodamine that had almost vanished.

If you use an alexa dye and a stabilising mountant such as vectashield, 6-9 months

I had DAPI and Cy3 staining. I kept the slides at 4°C, without Mowiol, just in PBS to avoid dehydration. The staining was fine even after 2 months.

Also antibodies may tend to disociate from the epitop if samples are stored in freeze. The repetitive freezing and defreezing may be a big killer of specific signal. So if you prepare a sample and want to observe in weeks, it may be better to store them in 4°C. I saw a yesterday fresh imunucytochemistry samples stored in freezer overnight badly affected and unreliable.

we are regularly revisiting samples stored under -20 for over one year. Our mounting/antifading medium is 0,01% paraphenylene diamine in 90% v/v glycerol with 100 mM Tris-Cl pH 8,4. Paraphenylene diamine is tricky to prepare, quite unstable if you are not too careful and highly toxic, but it maintains fluorescence like nothing else in the market.

one can do a quick FA or PFA postfix after staining with secondary abs, if the epitop "moves" after embedding. sometimes it helps.

For the correct preservation of the slides, several criteria are important. The fluorochrome coupled to the antibody, the mounting medium, the storage temperature.

We use the Alexa Fluor, Vectashield + DAPI, 4 ° C in the fridge for two months of storage in a humid chamber with PBS.