I agree with the experts who have already replied that they should be
fine ... but it's not 100% ideal.
Unfortunately due to space we sometimes are forced to store blocks at
-20 deg C too and they work just fine - as long as the cut surface is
"sealed" and they are wrapped properly. I find at -20 deg C some
people's blocks sort of shrivel up which is a disaster but I suspect
this is because they weren't being stored wrapped in foil or in
airtight containers and the cut surface was exposed.
I would move to -80 deg C as soon as possible though. I store mine
wrapped in foil in bitran bags and have reactivity for years. If for
some reason the OCT seems gooey or dried out you can always cut away
the old OCT and "reembed", if you will, it works well in a pinch.
Note that if you were asking about cut sections it might be a whole
different matter. I find cut sections don't always survive the warmer
temp freezers so well. Antigenicity definitely gets lost over time.
>I would like some opinions on the storage of oct embedded tissues. These
>samples of animal tissues are embedded into 1 x 1cm pieces of oct and
>sit in a vial containing isopentane, and have been stored at -20 degrees
>for around 6 months. The freezer is only used for long term storage and
>so isn't opened very often (perhaps once per month). In the past I have
>stored my oct embedded tissues like this at -70 degrees. What would be
>your opinion of the antigenicity in these tissues if they were to be
>used for immunohistochemistry??
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