[Histonet] PFA Fixed tissue not sticking to slides?

Hobbs, Carl carl.hobbs at kcl.ac.uk
Sat Jul 30 13:04:34 CDT 2016

Hi Jenny.
Can you use Pwax embedding as an alternative?
H&E will always be better on Pwax sections. 
IHC will also be in many instances.
What abs are you probing with?

Yes....you are fixing for too long ( for frozen sectioning....for Pwax you can fix your specimens for a week and still not suffer IHC-problems: after HIER they will or will never work, depending upon ab)
PFA( Formalin) fixed sections are well-known for not being as adherent as unfixed frozen material.

Why not freeze unfixed?
No sucrose required ( all that does is allow for slow freezing without, in most cases, formation of ice-crystals: good snap freezing does not need sucrose pretreatment)

If you are after good morphology then Pwax is the way to go, imho.
If you have to cut PFA-fixed then frozen tissues, after mounting on slides stick them in a 50C oven for 2hrs.
Use Superfrost Plus slides.
Then use or, store at 4C for a week or freeze.
For the latter 2, ALWAYS take out of fridge/freezer and immediately place under a fan/operating fume hood.
Do not allow condensation to form.
Or....place them immediately into that same 50C oven for an hour.
Do not do this to unfixed frozen sections!

Sure, check out EC's excellent advice ( as always)  re slides.


Carl Hobbs FIBMS
Histology and Imaging Manager
Wolfson CARD
Guys Campus, London Bridge 
Kings College London
020 7848 6813      

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