Post-Fixation Buffer Solutions, Storage and Timing
Recommended time to remain in fix after perfusion is 12-16 hours.
- Antibody staining: for formalin sensitive antibody staining 4 hours post perfusion is sufficient
Following fixation, transfer tissue into Phosphate-Buffered Saline (PBS) storage buffer, which is acceptable for all stains.
- Amino CuAg (degeneration staining): wait at least 24 hours before extracting brain to allow tissue to fully harden, preventing the induction of artifacts during staining
Protocol for making PBS buffer solution:
Na2HPO4 • 2H2O, M. wt. 178.05; 0.2M -solution contains 35.61 g/l.
Na2HPO4 • 12H2O, M. wt. 358.22; 0.2M -solution contains 71.64 g/l.
NaH2PO4 • H2O, M. wt. 138.01; 0.2M-solution contains 27.6 g/l.
NaH2PO4 • 2H2O, M. wt. 156.03; 0.2M-solution contains 31.21 g/l.
Depending on how many hydrogens are on each of the sodium phosphates you have to pick the one you have from the two choices for each of the monobasic and dibasic.
Make a stock solution for each by mixing the number of grams per liter as shown above.
Monobasic Sodium Phosphate 140ml 280ml
Dibasic Sodium Phosphate 360ml 720ml
Saline; NaCl 4.5g 9g
pH 7.2 7.2
Concentrated PBS is also commercially available from Sigma-Aldrich, Catalog# 79383-1L.
Phosphate-Buffered Saline (PBS) with 0.01% sodium azide should be used for tissue stored over three (3) weeks. Storage for this time period should take place in a refrigerator (4 degrees C).
Also see: Use of Cryroprotectant to Maintain Longterm Peptide Immunoreactivity and Tissue Morphology by Hoffman and Le.
For more information:
Consult with NSA to confirm the appropriate buffer and fixation time for your study via this form or call 865.675.2245.