Griffin:Immunohistochemistry Paraffin

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(Immunohistochemistry Protocol 1)
Current revision (12:57, 8 October 2012) (view source)
 
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Line 1: Line 1:
-
==Immunohistochemistry Protocol 1==
+
==Immunohistochemistry Paraffin Section Protocol==
-
John M. Sanders B.S. Cardiovascular Research Center, University of Virginia Charlottesville, VA.
+
[[Image:IHCarteryCD68.jpg|thumb|right|Granular CD68 localization within macrophages of arterial athersclerotic plaque]]
 +
 
 +
[[Image:IHCimage1.jpg|thumb|right|Mature soluble MUC2 in human small intestine and colon in goblet cells]]
 +
 
 +
[[Image:IFimage2.jpg|thumb|right|Mouse pancreas tissue; Red: Amylase in zymogengranules of acinar cells, and secreted amylase in ducts, Blue: DAPI (nuclear)]]
 +
 
 +
Immunohistochemistry determines protein expression profiles in tissues using chromagenic substrate (3,3′-Diaminobenzidine (DAB), benzene derivative). Primary antibody binds to the protein in tissue following with a conjugated peroxidase enzyme. Addition of hydrogen peroxide + DAB, catalyzes DAB to its oxidized, brown precipitate form.
The procedure below has been proven to be effective for labeling of PECAM-1, ICAM and VCAM using validated antibodies.
The procedure below has been proven to be effective for labeling of PECAM-1, ICAM and VCAM using validated antibodies.
-
'''1.''' Deparaffinize and rehydrate
+
==Deparaffinize and rehydrate==
 +
 
5 min tray
5 min tray
Line 18: Line 25:
2 x milliQ H2O
2 x milliQ H2O
-
'''1.''' Quench endogenous peroxidase activity
+
==Quench endogenous peroxidase activity==
200 ml methanol + 3 ml (30% H2O2) in slide tub
200 ml methanol + 3 ml (30% H2O2) in slide tub
*make just before use, Incubate 30 minutes, RT
*make just before use, Incubate 30 minutes, RT
-
'''2a.''' wash H2O 5 min room temp.
+
*wash H2O 5 min room temp.
-
'''1.''' Make up antigen unmasking solution (Vector Labs; 4oC) OR [http://openwetware.org/wiki/Griffin:Antigen_Retrieval_Technique other antigen retrieval techniques]
+
==Antigen Retrieval==
 +
 
 +
Solution (Vector Labs; 4oC) OR [http://openwetware.org/wiki/Griffin:Antigen_Retrieval_Technique other antigen retrieval techniques]
*Shake well before measuring
*Shake well before measuring
Line 41: Line 50:
*1
*1
-
'''1.''' Cool slides in tub, covered, at room temp for 1 hour
+
==Blocking==
-
'''2.''' During 1 hour, make up 0.5% FSGO (fish skin gelatin oil) in PBS (1 500 ml bottle PBS + 2.5 ml FSGO; allow 15 min for FSGO to come out of pipet)
+
'''1.''' Cool slides in tub, covered, at room temp for 1 hour, then transfer to tub with plain room temperature PBS, 5 min
-
'''3.''' Transfer to tub with plain room temperature PBS, 5 min
+
*During 1 hour, make up 0.5% FSGO (fish skin gelatin oil) in PBS (1 500 ml bottle PBS + 2.5 ml FSGO; allow 15 min for FSGO to come out of pipet)
-
'''4.''' Make up avidin blocking solution:
+
'''2.''' Make up avidin blocking solution:
For 1 ml:
For 1 ml:
Line 57: Line 66:
*Invert tube to mix
*Invert tube to mix
-
'''5.''' Circle vessels with ‘pap pen’ ALWAYS KEEP SLIDES MOIST
+
'''3.''' Circle vessels with ‘pap pen’ ALWAYS KEEP SLIDES MOIST
-
'''6.''' Add blocking solution within circles; 1 hour in humidified chamber at room temperature
+
'''4.''' Add blocking solution within circles; 1 hour in humidified chamber at room temperature, then aspirate off blocking solution
-
'''7.''' Aspirate off blocking solution
+
==Primary Antibody==
-
'''8.''' Add primary antibody to vessels on slides.  
+
'''5.''' Add primary antibody @ 1:50 to vessels on slides.  
For 4 slides: antibody
For 4 slides: antibody
*PBS/FSGO 1 ml
*PBS/FSGO 1 ml
*normal serum 100 ul
*normal serum 100 ul
-
*biotin blocking solution (Vector Labs) 4 drops
+
*OPTIONAL : biotin blocking solution (Vector Labs) 4 drops
-
'''9.''' Incubate 4 oC overnight in humidified chamber.
+
'''6.''' Incubate 4 oC overnight in humidified chamber.
 +
 
 +
==Secondary Antibody==
Day 2:
Day 2:
'''1.''' Aspirate primary antibody solution and wash in FSGO/PBS in tub for 5 min at room temperature; agitate
'''1.''' Aspirate primary antibody solution and wash in FSGO/PBS in tub for 5 min at room temperature; agitate
-
'''2.''' Make up secondary antibody:
+
'''2.''' Make up secondary antibody at 1:100-1:500:
-
per ml:
+
(1:200) per ml:
*5 ul secondary antibody
*5 ul secondary antibody
*100 ul normal serum
*100 ul normal serum
Line 94: Line 105:
'''6.''' Blot slides and apply ABC; incubate 30 min at room temperature
'''6.''' Blot slides and apply ABC; incubate 30 min at room temperature
 +
 +
==Substrate==
'''7.''' Make up DAB solution:
'''7.''' Make up DAB solution:
 +
Approximately 30 min before using; add H2 O2 just before use
Approximately 30 min before using; add H2 O2 just before use
 +
*10 ml plain PBS
*10 ml plain PBS
*1 DAB tablet
*1 DAB tablet
-
*7.5 ul H2 O2 (30%)
+
*7.5 ul H2O2 (30%)
Test DAB and ABC by adding small amount of DAB to a small amount of left over ABC, should turn dark brown immediately.
Test DAB and ABC by adding small amount of DAB to a small amount of left over ABC, should turn dark brown immediately.
Line 109: Line 124:
'''10.''' Wash in dH20, 5 min room temperature
'''10.''' Wash in dH20, 5 min room temperature
-
'''11.''' Counterstain in filtered (#1 Whatman) Hematoxylin I (not Mayer’s); 4-5 min
+
==Counterstain==
-
'''12.''' Rinse in running tap water until clear, 4-5 min. Return hematoxylin to bottle for reuse
+
In filtered (#1 Whatman filter paper) Hematoxylin I (not Mayer’s); 4-5 min
-
'''13.''' Blueing if needed for 1 min; wash in tap water
+
'''12.''' Rinse in running tap water until clear, 4-5 min. Return hematoxylin to bottle for reuse.
 +
 
 +
==Blueing==
 +
 
 +
If needed for 1 min; wash in tap water
*Acid alcohol: 1% HCl in 50% EtOH
*Acid alcohol: 1% HCl in 50% EtOH
-
*Bluing reagent: commercially available (Fisher, VWR, Sigma, etc)
+
*Bluing reagent: commercially available (Fisher, VWR, Sigma (S5134), etc)
 +
 
 +
===Blueing Reagents===
Procedure: Dip slides quickly in acid alcohol and immediately wash with tap water (or squirt water on the slides) Dip slides briefly in Bluing Reagent. Wash slides with tap water and continue with the IHC staining procedure(i.e., dehydrate stained tissues and mount the slides).
Procedure: Dip slides quickly in acid alcohol and immediately wash with tap water (or squirt water on the slides) Dip slides briefly in Bluing Reagent. Wash slides with tap water and continue with the IHC staining procedure(i.e., dehydrate stained tissues and mount the slides).
-
'''14.''' Dehydrate, 5 minutes each:
+
====0.1% Sodium Bicarbonate====
 +
 
 +
*Sodium bicarbonate --------------------------- 1 g
 +
*Distilled water --------------------------------- 1000 ml
 +
 
 +
Mix to dissolve. The pH will be around 8.0 Store this solution at room temperature.
 +
 
 +
Note: this solution worked better than ammonia water solution according to testing result. Bluing for 30 seconds to 1 minute after hematoxylin staining and clearing/differentiation.
 +
 
 +
====0.2% Ammonia Water Solution (Bluing)====
 +
 
 +
*Ammonium hydroxide (concentrated) ------ 2 ml
 +
*Distilled water -------------------------------- 1000 ml
 +
 
 +
Mix well. The pH will be around 10.0 Store this solution at room temperature.
 +
 
 +
Note: this solution is not as good as sodium bicarbonate according to testing result. Bluing for 30 seconds to 1 minute after hematoxylin staining and clearing/differentiation.
 +
 
 +
====Lithium Carbonate Solution (Saturated)====
 +
 
 +
*Lithium carbonate ---------------------------- 1.54 g
 +
*Distilled water -------------------------------- 100 ml
 +
 
 +
Mix to dissolve and store at room temperature. Bluing for 30 seconds to 1 minute after hematoxylin staining and clearing/differentiation.
 +
 
 +
==Dehydrate==
 +
 
 +
5 minutes each:
*3 x absolute ETOH
*3 x absolute ETOH
*2 x xylene
*2 x xylene
-
'''15.''' Coverslip
+
==Coverslip==
 +
 
 +
Mount
-
==Immunohistochemistry Protocol 2==
+
==Abbreviated Immunohistochemistry Protocol==
'''1.''' Deparaffinize and rehydrate
'''1.''' Deparaffinize and rehydrate
Line 161: Line 211:
==Controls==
==Controls==
-
*chromogen only; no primary or secondary antibody
+
*Chromogen only; no primary or secondary antibody
-
*conjugate and chromogen control; no primary
+
*Conjugate and chromogen control; no primary
-
*biotinylated antibody, conjugate, chromogen control
+
*Biotinylated antibody, conjugate, chromogen control
*Isotype control ( for monoclonal antibodies only)
*Isotype control ( for monoclonal antibodies only)
*Species control (ie. incubation with normal goat IgG)
*Species control (ie. incubation with normal goat IgG)
*Absorption control
*Absorption control
 +
 +
==DAB enhancement==
 +
 +
===Nickel===
 +
 +
DAB (0.5 mg/ml) with 0.08% nickel sulfate and 3% H2O2
 +
 +
*Volume total: 1 ml
 +
*2% nickel sulfate 40 ul
 +
*DAB Solution 1 ml
 +
*30% H2O2 10 ul
 +
 +
To make: 2% Nickel sulfate, NiSO4.6H2O: 0.9 g into 45 ml E-pure dd H2O = 2% solution. Keep in Fridge.
 +
(Dilute: 1/25 to give a 0.08% solution.)
 +
 +
'''NOTE:''' Time to stain will be more rapid. Nickel solution develops more precipitate. Blue-black ppt
 +
 +
===Copper===
 +
 +
*0.4% cupric sulfate (CuSO4 5H2O)In 0.9% NaCl
 +
 +
After DAB reaction has been completed and rinsed, immerse slides 5-20 mins, and then rinse with PBS. Darkens regular DAB color.Room temp cupric sulfate in a glass bottle is stable for many years.
 +
 +
==Trouble Shooting==
 +
 +
===Precipitate in DAB substrate preparation (or on tissue)===
 +
 +
'''DAB substrate preparation'''
 +
* 3,3'-Diaminobenzidine (DAB)
 +
*dH20
 +
*Substrate Buffer
 +
*Peroxidase Substrate (H2O2)
 +
 +
The DAB substrate preparation is not stable in solution for prolonged periods of time, and will precipitate in aqueous solution exposed to oxygen. A quick spin down of the DAB substrate preparation (3 minutes @ 10,000 g) prior to dropping on the slides will ensure only the aqueous fraction is used; in case there is any precipitate in the DAB substrate preparation, it will be pelleted by centrifugation. 
 +
 +
Desired staining can take 5-15 minutes. The DAB substrate produces a dark brown precipitate in the presence of horseradish peroxidase. Any suspended precipitate or sediments that form during this step may be removed after the desired color has been achieved by several washes with dH2O.
 +
 +
Peroxide-based chromogenic assays tend to have hydroperoxides and chromogenic electron donors to react before exposure to HRP catalytic enzyme. This oxidation "background" effect requires that the Peroxidase Substrate solution be used immediately (no later than few hours). One factor contributing to oxidation is contamination of chromogen solutions with trace amounts of oxidizing agents such as transition metals.
 +
 +
DAB has a molecular weight of 214.1 and yields a brown precipitate in the presence of HRP and peroxide. The brown, insoluble product can be readily chelated with osmium tetroxide. This property makes DAB ideal for electron microscopy. The color produced by DAB can be intensified with the addition of metals such as nickel, copper, silver and cobalt that form complexes. The color produced by the metal complexes is darker than the color produced by DAB alone, enhancing the sensitivity in staining applications. Peroxide must be added to a substrate for colorimetric detection with HRP.
 +
 +
===Preventing tissues from peeling off the slide===
 +
 +
*Insufficient fixation or unfixed tissues tend to come off slides more easily. Fix tissues longer to get completely fixation of tissues.
 +
*Formaldehyde fixed frozen sections are more prone to falling off slides. Try to dry slides for much longer time or use alternative fixation such as acetone or alcohol.
 +
*Tissue sections tend to come off slides more often on regular slides (uncharged or uncoated). Always use positively charged or coated slides for immunostaining.
 +
*You may just have had a bad batch of slides. Replace with a new batch of slides.
 +
*The disposable blades have oil on them. Clean disposable blades with xylene.
 +
*Wrinkles presented in the sections during the initial mounting. Try to spread the sections out and mount the sections on slides with wrinkle free.
 +
*Paraffin sections may not be dried completely before placing in the oven. Allow paraffin sections to air dry at least 30 minutes before placing in the oven at 56 C overnight.
 +
*Frozen sections may not be dried completely before fixation and immunostaining procedure. Allow frozen sections to air dry for at least 30 minutes before fixation and then air dry for another 30 minutes before immunostaining.
 +
*Antigen retrieval procedure can cause sections to come off slides, especially when EDTA (pH8.0) or Tris-EDTA (pH9.0) such high pH antigen retrieval solution is used. Use low pH solution such as citrate buffer (pH6.0) antigen retrieval Solution to replace EDTA (pH8.0) or Tris-EDTA (pH9.0) retrieval solution if it is possible.
 +
*Distilled water alone may make sections come off slides easy. Always use buffer solution to wash or rinse slides.
 +
*Bone (especially the cartilage) tends to fall off slides after heat treatment. Try other alternative retrieval methods such as enzyme digestion.
 +
*Antigen retrieval devices may be trouble. Try to use waterbath or steamer in stead of microwave or pressure cooker.
 +
*Plain water in waterbath for mounting paraffin sections. Add some gelatin in waterbath for mounting paraffin sections.
 +
*If you have tried everything above and the problem persists. Try gelatin coated slides and it has been working fairly well.
 +
 +
===Avidin versus Streptavidin===
 +
 +
[[Image:Avidin1.jpg|thumb|right|Avidin-Biotin]]
 +
 +
[[Image:Streptavidin1.jpg|thumb|right|Streptavidin-Biotin]]
 +
 +
Both Avidin and Streptavidin are suitable for binding to secondary biotin-conjugated antibodies. Streptavidin lacks carbohydrate modification and has a near-neutral pI, so it can produce lower nonspecific binding than avidin. However deglycosylated avidin (Neutravidin) is more comparable to the size, pI and specific binding of streptavidin.
 +
 +
*Avidin is a tetrameric protein originally isolated from chicken egg white with a MW of about 67K and an isoelectric point of about 10.
 +
*Streptavidin is a biotin binding protein isolated from cultures of ''Streptomyces avidinii'' with a MW of about 16K and an isoelectric point of 5-6.
 +
 +
One mole Avidin will bind four mole biotin. The high pI of Avidin may cause binding to acidic structures such as DNA. Biotin is a naturally occurring vitamin with a MW of 244.31 and an isoelectric point of 3.5. The Avidin-Biotin interaction is the strongest known non-covalent, biological interaction (Kd~10e-15 M). The bond formation is rapid and is unaffected over a wide range of pH.
==References==
==References==
 +
 +
John M. Sanders B.S. Cardiovascular Research Center, University of Virginia Charlottesville, VA.
<biblio>
<biblio>

Current revision

Contents

Immunohistochemistry Paraffin Section Protocol

Granular CD68 localization within macrophages of arterial athersclerotic plaque
Granular CD68 localization within macrophages of arterial athersclerotic plaque
Mature soluble MUC2 in human small intestine and colon in goblet cells
Mature soluble MUC2 in human small intestine and colon in goblet cells
Mouse pancreas tissue; Red: Amylase in zymogengranules of acinar cells, and secreted amylase in ducts, Blue: DAPI (nuclear)
Mouse pancreas tissue; Red: Amylase in zymogengranules of acinar cells, and secreted amylase in ducts, Blue: DAPI (nuclear)

Immunohistochemistry determines protein expression profiles in tissues using chromagenic substrate (3,3′-Diaminobenzidine (DAB), benzene derivative). Primary antibody binds to the protein in tissue following with a conjugated peroxidase enzyme. Addition of hydrogen peroxide + DAB, catalyzes DAB to its oxidized, brown precipitate form.

The procedure below has been proven to be effective for labeling of PECAM-1, ICAM and VCAM using validated antibodies.

Deparaffinize and rehydrate

5 min tray

2 x xylene

2 x absolute ETOH

2 x 95 % ETOH

2 x 70 % ETOH

2 x milliQ H2O

Quench endogenous peroxidase activity

200 ml methanol + 3 ml (30% H2O2) in slide tub

  • make just before use, Incubate 30 minutes, RT
  • wash H2O 5 min room temp.

Antigen Retrieval

Solution (Vector Labs; 4oC) OR other antigen retrieval techniques

  • Shake well before measuring
  • 320 milliQ H2O + 3 ml unmasking solution
  • Mix by inversion

1. Rinse in milliQ H2O in tub

2. In slide tub with “fill” mark, fill all 24 slots in slide holder with “blank slides” if necessary, add unmasking solution to fill line, COVER and microwave for 20 minutes Replenish with dH20 at:

  • 15 minutes remaining
  • 11
  • 7
  • 3
  • 1

Blocking

1. Cool slides in tub, covered, at room temp for 1 hour, then transfer to tub with plain room temperature PBS, 5 min

  • During 1 hour, make up 0.5% FSGO (fish skin gelatin oil) in PBS (1 500 ml bottle PBS + 2.5 ml FSGO; allow 15 min for FSGO to come out of pipet)

2. Make up avidin blocking solution:

For 1 ml:

  • 1 ml PBS/FSGO
  • 100 ul normal serum of same species as secondary antibody

4 drops avidin blocking solution (Vector Labs)

  • Invert tube to mix

3. Circle vessels with ‘pap pen’ ALWAYS KEEP SLIDES MOIST

4. Add blocking solution within circles; 1 hour in humidified chamber at room temperature, then aspirate off blocking solution

Primary Antibody

5. Add primary antibody @ 1:50 to vessels on slides.

For 4 slides: antibody

  • PBS/FSGO 1 ml
  • normal serum 100 ul
  • OPTIONAL : biotin blocking solution (Vector Labs) 4 drops

6. Incubate 4 oC overnight in humidified chamber.

Secondary Antibody

Day 2:

1. Aspirate primary antibody solution and wash in FSGO/PBS in tub for 5 min at room temperature; agitate 2. Make up secondary antibody at 1:100-1:500:

(1:200) per ml:

  • 5 ul secondary antibody
  • 100 ul normal serum
  • 1 ml FSGO/PBS

3. Blot slides with kimwipe and apply secondary antibody; incubate in humidified chamber 1 hour, room temperature

4. During incubation, make up ABC solution from kit: per ml:

  • 1 ml plain PBS
  • 20 ul A solution
  • 20 ul B solution

Allow to rock at room temperature for at least 30 min in order to form complex

5. Aspirate secondary antibody solution and wash in FSGO/PBS in tub for 5 min at room temperature; agitate

6. Blot slides and apply ABC; incubate 30 min at room temperature

Substrate

7. Make up DAB solution:

Approximately 30 min before using; add H2 O2 just before use

  • 10 ml plain PBS
  • 1 DAB tablet
  • 7.5 ul H2O2 (30%)

Test DAB and ABC by adding small amount of DAB to a small amount of left over ABC, should turn dark brown immediately.

8. Wash with agitation in plain PBS, 5 min room temperature

9. Blot slides and apply DAB solution, incubate 5 min room temperature

10. Wash in dH20, 5 min room temperature

Counterstain

In filtered (#1 Whatman filter paper) Hematoxylin I (not Mayer’s); 4-5 min

12. Rinse in running tap water until clear, 4-5 min. Return hematoxylin to bottle for reuse.

Blueing

If needed for 1 min; wash in tap water

  • Acid alcohol: 1% HCl in 50% EtOH
  • Bluing reagent: commercially available (Fisher, VWR, Sigma (S5134), etc)

Blueing Reagents

Procedure: Dip slides quickly in acid alcohol and immediately wash with tap water (or squirt water on the slides) Dip slides briefly in Bluing Reagent. Wash slides with tap water and continue with the IHC staining procedure(i.e., dehydrate stained tissues and mount the slides).

0.1% Sodium Bicarbonate

  • Sodium bicarbonate --------------------------- 1 g
  • Distilled water --------------------------------- 1000 ml

Mix to dissolve. The pH will be around 8.0 Store this solution at room temperature.

Note: this solution worked better than ammonia water solution according to testing result. Bluing for 30 seconds to 1 minute after hematoxylin staining and clearing/differentiation.

0.2% Ammonia Water Solution (Bluing)

  • Ammonium hydroxide (concentrated) ------ 2 ml
  • Distilled water -------------------------------- 1000 ml

Mix well. The pH will be around 10.0 Store this solution at room temperature.

Note: this solution is not as good as sodium bicarbonate according to testing result. Bluing for 30 seconds to 1 minute after hematoxylin staining and clearing/differentiation.

Lithium Carbonate Solution (Saturated)

  • Lithium carbonate ---------------------------- 1.54 g
  • Distilled water -------------------------------- 100 ml

Mix to dissolve and store at room temperature. Bluing for 30 seconds to 1 minute after hematoxylin staining and clearing/differentiation.

Dehydrate

5 minutes each:

  • 3 x absolute ETOH
  • 2 x xylene

Coverslip

Mount

Abbreviated Immunohistochemistry Protocol

1. Deparaffinize and rehydrate 5 min tray

2 x xylene

2 x absolute ETOH

2 x 95 % ETOH

2 x 70 % ETOH

2 x milliQ H2O

2. Antigen Retrieval

3. Rinse sections in 2 changes of PBS washing buffer in separate beakers, 2 minutes each.

4. Serum Blocking: incubate sections with 10% normal serum blocking solution for 30 minutes to block non-specific binding of immunoglobulin.

5. Primary Antibody: incubate sections with Primary antisera diluted 1:50 in 3% serum PBS, for 1 hour at room temperature to overnight 4C.

6. Rinse in PBS washing buffer for 2 x 2 min.

7. Secondary Antibody: incubate sections with conjugated secondary antibody 1:100-500 in 3% serum PBS, for 1 hour at room temperature.

8. Rinse in PBS washing buffer for 3 x 2 min.

9. Counter-stain in Gill´s formulation #2 hematoxylin for 5–10 seconds. Immediately wash with several changes of deionized H2O.

10. Dehydrate: Soak in 95% ethanol 2x10 seconds, then 100% ethanol 2x10 seconds, then xylenes 3x10 seconds. Pipet 1–2 (5ul) drops of permanent mounting medium, cover with a glass coverslip and observe by light microscopy.

Controls

  • Chromogen only; no primary or secondary antibody
  • Conjugate and chromogen control; no primary
  • Biotinylated antibody, conjugate, chromogen control
  • Isotype control ( for monoclonal antibodies only)
  • Species control (ie. incubation with normal goat IgG)
  • Absorption control

DAB enhancement

Nickel

DAB (0.5 mg/ml) with 0.08% nickel sulfate and 3% H2O2

  • Volume total: 1 ml
  • 2% nickel sulfate 40 ul
  • DAB Solution 1 ml
  • 30% H2O2 10 ul

To make: 2% Nickel sulfate, NiSO4.6H2O: 0.9 g into 45 ml E-pure dd H2O = 2% solution. Keep in Fridge. (Dilute: 1/25 to give a 0.08% solution.)

NOTE: Time to stain will be more rapid. Nickel solution develops more precipitate. Blue-black ppt

Copper

  • 0.4% cupric sulfate (CuSO4 5H2O)In 0.9% NaCl

After DAB reaction has been completed and rinsed, immerse slides 5-20 mins, and then rinse with PBS. Darkens regular DAB color.Room temp cupric sulfate in a glass bottle is stable for many years.

Trouble Shooting

Precipitate in DAB substrate preparation (or on tissue)

DAB substrate preparation

  • 3,3'-Diaminobenzidine (DAB)
  • dH20
  • Substrate Buffer
  • Peroxidase Substrate (H2O2)

The DAB substrate preparation is not stable in solution for prolonged periods of time, and will precipitate in aqueous solution exposed to oxygen. A quick spin down of the DAB substrate preparation (3 minutes @ 10,000 g) prior to dropping on the slides will ensure only the aqueous fraction is used; in case there is any precipitate in the DAB substrate preparation, it will be pelleted by centrifugation.

Desired staining can take 5-15 minutes. The DAB substrate produces a dark brown precipitate in the presence of horseradish peroxidase. Any suspended precipitate or sediments that form during this step may be removed after the desired color has been achieved by several washes with dH2O.

Peroxide-based chromogenic assays tend to have hydroperoxides and chromogenic electron donors to react before exposure to HRP catalytic enzyme. This oxidation "background" effect requires that the Peroxidase Substrate solution be used immediately (no later than few hours). One factor contributing to oxidation is contamination of chromogen solutions with trace amounts of oxidizing agents such as transition metals.

DAB has a molecular weight of 214.1 and yields a brown precipitate in the presence of HRP and peroxide. The brown, insoluble product can be readily chelated with osmium tetroxide. This property makes DAB ideal for electron microscopy. The color produced by DAB can be intensified with the addition of metals such as nickel, copper, silver and cobalt that form complexes. The color produced by the metal complexes is darker than the color produced by DAB alone, enhancing the sensitivity in staining applications. Peroxide must be added to a substrate for colorimetric detection with HRP.

Preventing tissues from peeling off the slide

  • Insufficient fixation or unfixed tissues tend to come off slides more easily. Fix tissues longer to get completely fixation of tissues.
  • Formaldehyde fixed frozen sections are more prone to falling off slides. Try to dry slides for much longer time or use alternative fixation such as acetone or alcohol.
  • Tissue sections tend to come off slides more often on regular slides (uncharged or uncoated). Always use positively charged or coated slides for immunostaining.
  • You may just have had a bad batch of slides. Replace with a new batch of slides.
  • The disposable blades have oil on them. Clean disposable blades with xylene.
  • Wrinkles presented in the sections during the initial mounting. Try to spread the sections out and mount the sections on slides with wrinkle free.
  • Paraffin sections may not be dried completely before placing in the oven. Allow paraffin sections to air dry at least 30 minutes before placing in the oven at 56 C overnight.
  • Frozen sections may not be dried completely before fixation and immunostaining procedure. Allow frozen sections to air dry for at least 30 minutes before fixation and then air dry for another 30 minutes before immunostaining.
  • Antigen retrieval procedure can cause sections to come off slides, especially when EDTA (pH8.0) or Tris-EDTA (pH9.0) such high pH antigen retrieval solution is used. Use low pH solution such as citrate buffer (pH6.0) antigen retrieval Solution to replace EDTA (pH8.0) or Tris-EDTA (pH9.0) retrieval solution if it is possible.
  • Distilled water alone may make sections come off slides easy. Always use buffer solution to wash or rinse slides.
  • Bone (especially the cartilage) tends to fall off slides after heat treatment. Try other alternative retrieval methods such as enzyme digestion.
  • Antigen retrieval devices may be trouble. Try to use waterbath or steamer in stead of microwave or pressure cooker.
  • Plain water in waterbath for mounting paraffin sections. Add some gelatin in waterbath for mounting paraffin sections.
  • If you have tried everything above and the problem persists. Try gelatin coated slides and it has been working fairly well.

Avidin versus Streptavidin

Avidin-Biotin
Avidin-Biotin
Streptavidin-Biotin
Streptavidin-Biotin

Both Avidin and Streptavidin are suitable for binding to secondary biotin-conjugated antibodies. Streptavidin lacks carbohydrate modification and has a near-neutral pI, so it can produce lower nonspecific binding than avidin. However deglycosylated avidin (Neutravidin) is more comparable to the size, pI and specific binding of streptavidin.

  • Avidin is a tetrameric protein originally isolated from chicken egg white with a MW of about 67K and an isoelectric point of about 10.
  • Streptavidin is a biotin binding protein isolated from cultures of Streptomyces avidinii with a MW of about 16K and an isoelectric point of 5-6.

One mole Avidin will bind four mole biotin. The high pI of Avidin may cause binding to acidic structures such as DNA. Biotin is a naturally occurring vitamin with a MW of 244.31 and an isoelectric point of 3.5. The Avidin-Biotin interaction is the strongest known non-covalent, biological interaction (Kd~10e-15 M). The bond formation is rapid and is unaffected over a wide range of pH.

References

John M. Sanders B.S. Cardiovascular Research Center, University of Virginia Charlottesville, VA.

  1. Barringhaus KG, Phillips JW, Thatte JS, Sanders JM, Czarnik AC, Bennett DK, Ley KF, and Sarembock IJ. . pmid:15153775. PubMed HubMed [Paper1]
  2. Manka D, Forlow SB, Sanders JM, Hurwitz D, Bennett DK, Green SA, Ley K, and Sarembock IJ. . pmid:15072990. PubMed HubMed [Paper2]
All Medline abstracts: PubMed HubMed
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