I presume the cold room means +4C, not a -4C. You can leave specimens in the PBS but protect them from the light. Usually, within 1 week, you will have no issue with your chromophores degrading, it can probably stay this way longer. You can dramatically increase your specimen's lifetime if you put them on the slides and protect them with an anti-fade reagents such as Dimondantiphade or any other relevant you use for prevention of the photobleaching in your imaging. I was able to pick up decent signals from the tissues on slides about 12 months old (DAPI had to be restained) due to DAPI degrading within a month or two.

Dear Cat, storing them in a fridge at 4C should be sufficient to store your samples for a short period of time in PBS. I've also used TBS-t previously, and have not observed any washout or significant fading of fluorophores (as using antifade mounting solutions was often not useable with the format of my setup)

Cat J Hershey A similar situation happened to me once and this is what I did.

I would say, do not submerge the scaffolds in PBS completely , as it may wash/weaken some amount of antibodies (depending on how long you store), instead add a small amount of PBS in the 6-well plate or enclosed dish (where you are storing ) enough to maintain it as a humidifying chamber in the fridge/cold room (4C) wrapped in an aluminium/tin foil. You may need to check that the chamber doesn't get dry, so you may need to add some more PBS from time to time.