Fix perm and block protocol

This protocol provides general instructions for fixation, permeabilization, and blocking to prepare your cells for immunolabeling. Fixing and permeabilizing cells generally locks them in place and makes it possible for larger molecules such as antibodies to access the interior of the cell.

Download this protocol

Planning on using a mountant during your experiment? See vessel considerations and mounting coverslips
Protocol tip
If you are running short on time and have a robust system, you can block for 30 minutes instead
of 60
What you need
  • Live cells
  • Phosphate-buffered saline (PBS)
  • 4% Paraformaldehyde
  • 0.5% Triton® X-100
  • 3% w/v bovine serum albumin in PBS

General fix, perm & block protocol

The volumes given in this protocol are good for a single well of adherent cells grown in a 6-well plate or a 35 mm dish.

1Remove the medium from your cells (tip the vessel and pipet from the side).
2Add 1 mL of 4% (w/v) formaldehyde solution in phosphate-buffered saline (PBS).
3Incubate for 15 minutes at room temperature for most targets.
4Remove the fixative solution and wash by pipetting PBS (a volume that will just cover the cells) against the side of the vessel, gently swishing the solution from side to side, and then tilting the vessel and removing the PBS; repeat 3 times. The fixed sample can be stored for several days at 5°C if needed. Learn how to wash 
5Add 1 mL of 0.5% Triton® X-100 (v/v) in PBS.
6Incubate for 15 minutes at room temperature.
7Remove the permeabilization solution and wash 3 times with PBS as in step 4. 
Learn how to wash 
8Add 2 mL of 3% bovine serum albumin in PBS (or a different  blocking solution if required).
9Incubate for at least 60 minutes (up to overnight) at room temperature.
10Go to cell staining or immunolabeling.

For Research Use Only. Not for use in diagnostic procedures.