Immunocytology of Fixed Cells
Karmella Haynes 2013
This procedure allows you to fix and stain cells in a 24-well culture plate without mounting slides. Image quality is limited, but processing larger sample numbers is easier.
- Adherent cells cultured in a 24-well plate
- Sterile 1xPBS (keep in the TC room)
- Paraformaldehyde 97% (dry) - Alfa Aesar A11313-22
- 20 mL aliquot of non-sterile 1xPBS to make fixing buffer
- 10M NaOH
- 50 mL aliquot of non-sterile 1xPBS for washes (keep at your bench)
- Permeabilization Solution - Cold methanol or 0.5% Triton-X100 in PBS
- Note: Different antibodies work better with different permeabilization. Try both and see which works best for your specific antibody.
- Make Fixing Buffer: Work under the fume hood. Add 1.0 g dry 97% Paraformaldehyde to the 20 mL aliquot of 1xPBS in a 50 mL conical tube. Add 25 μL 10M NaOH. Cap the tube, seal with parafilm, and heat at 50°C with occasional shaking until the paraformaldehyde dissolves. Cool the solution to room temperature (or chill in the refrigerator) before use.
- Do the following in the TC room in the biosafety cabinet: Remove medium from the cells. Add 1 mL warm Sterile 1x PBS to each well.
- Take the plate to your bench.
- Remove the 1xPBS from the cells.
- Work under the fume hood. Add 1 mL freshly made Fixing Buffer to each well. Incubate at Room Tmp./ 10 minutes.
- Remove Fixing Buffer. Add 0.5 mL Permeabilization Solution to each well and incubate at room temp. for 10 min.
- Remove Permeabilization Solution and rinse cells with 0.5 mL non-sterile 1xPBS.
Note: This is a stopping point. You can place a lid on the plate, seal it with parafilm, and store the cells +1xPBS at 4°C for several days. Or, proceed immediately to Antibody Staining.
- Block in 5% Normal Horse Serum in PBS (5% NHS) for at least one hour at Rm. Tmp. (can incubate overnight at 4°C if necessary).
7. Dilute primary antibody (according to supplier’s instructions) in 5% NHS. Add 15 μl to each cover slip and cover with a 1 cm2 piece of parafilm. Incubate at Room Tmp. for at least one hour in a humidified box (can incubate overnight at 4°C if necessary). 8. Wash 3 – 4 times/ 5 min. with PBS. 9. Dilute secondary antibody and Hoechst (DNA stain) in 5% NHS (see table). 10. Add diluted secondary to samples (same way as primary) and incubate at Room Tmp. for one hour. Protect the samples from light; fluorophores are light-sensitive. 11. Wash 3 – 4 times/ 5 min. with PBS.
Mounting and Storage 12. Place a small drop of Vinol Mounting Medium onto a clean slide. 13. Invert a cover slip, cell side down, onto the medium and press gently. 14. Blot excess mounting medium with a Kimwipe (be careful not to slide the cover slip out of place). 15. Rinse briefly with distilled water and blot dry. 16. Slides are best viewed after allowing the mounting medium to set overnight (at Room Tmp., protected from light); slides may be viewed immediately if handled carefully. 17. Slides may be stored indefinitely at Rm. Tmp. (morphology is preserved)
Secondary ab conjugate/ stain Color Dilution Cy2 1:200 Cy3 green (FITC) 1:2000 Alexafluor 488 green (FITC) 1:1000 Hoechst 33325 blue 1:1000 Images: For the Nikon scope, images using the 60X objective have a scale of 0.104167 μM per pixel. For the 20 x objective it’s 0.312501 μM/ pixel.