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  • Streptavidin is a 60,000 molecular weight with an extraordinarily high affinity for the small molecular weight vitamin, biotin. Because this affinity is over one million times higher than that of antibody for most antigens, the binding of Streptavidin to biotin (unlike antibody-antigen interactions) is essentially irreversible. In addition to this high affinity, the Biotin/ Streptavidin System can be effectively exploited because Streptavidin has four binding sites for biotin and most proteins (including antibodies and enzymes) can be conjugated with several molecules of biotin. These aspects provide the potential for macromolecular complexes to be formed between Streptavidin and biotinylated enzymes.


  • An immunoperoxidase procedure based on these properties was devised for localizing a variety of histologically significant antigens and other markers. (Hsu SM, Raine L, Fanger H: Am. J. Clin. Pathol. 7 5, 734-738, 1981; Hsu SM, Raine L, Fanger H: J . Histochem. Cytochem. 2 9, 577-580, 1981.) This technique employs unlabeled primary antibody, followed by biotinylated secondary antibody and then a preformed Avidin and Biotinylated horseradish peroxidase macromolecular Complex.


  • SABC kit contains Streptavidin and biotinylated horseradish peroxidase reagents, which have been specially prepared to form ideal complexes for immunoperoxidase staining. Although the structure of the Streptavidin: biotinylated horseradish peroxidase complex is still undefined, evidence suggests that it consists of many biotinylated horseradish peroxidase molecules crosslinked by Streptavidin into a three dimensional array. The complex apparently has few exposed biotin residues but retains at least one biotin binding site. Formation of the complex is achieved by mixing Streptavidin and biotinylated horseradish peroxidase in dilute solution and in defined amounts prior to use. After the initial incubation there appears to be little change in the complex as judged by only a marginal increase in immune peroxidase staining sensitivity and the complex remains stable for several hours after formation. The high sensitivity and shorter incubation times reported for the Medico SABC system are likely due to the number of active horseradish peroxidase molecules associated with the complex and the rapid, irreversible interaction of the complex with biotinylated antibody. The low background staining obtainable with the SABC Kits is probably due to the high dilutions of primary antisera and other reagents employed in the method, the quality of our affinity-purified biotinylated secondary antibodies, and the specially prepared Streptavidin and biotinylated horseradish peroxidase.


  • Reagents supplied (for 250 sections)
Blocking Serum20ml*2Store at 4°C for 1year
Biotinylated,Affinity-purified Anti-Rabbit IgG500ulStore at 4°C for 1year
Reagent A (Streptavidin)500ulStore at 4°C for 1year
Reagent B (Biotinylated Horseradish Peroxidase)500ulStore at 4°C for 1year
  • NOTE: reagents not supplied (Primary Antibody, Buffer, Hydrogen Peroxide, Oxidizable Peroxidase Substrate)


  • A number of different buffers can be used in the SABC system. One of the most common is 10 mM sodium phosphate, pH 7.4, 0.9% saIine (PBS). The SABC working solutions are prepared as follows:
  • Blocking Serum working solution: add 2ml of stock Blocking Serum to 10 ml of PBS. The preferred serum for blocking is prepared from the same species in which the biotinylated secondary antibody is made.
  • Biotinylated Antibody working solution: add 100ul Biotinylated Antibody to 10 ml of Blocking Serum working solution (PBS contain Blocking Serum).
  • SABC Reagent working solution: Mix 100ul of Reagent A and 100ul Reagent B in a EP tube, immediately. Then place it on 37°C for 30 Minutes, add the mixture into 10 ml of Blocking Serum working solution(PBS contain Blocking Serum)for using. It is best to use SABC Reagent working solution within 12 hours.
  • The configuration table
 Blocking Serum Working solutionBiotinylated Antibody Working solutionSABC Reagent Working solution
1 section200ul-400ul200ul200ul
10 sections2ml-4ml2ml2ml
100 sections20ml-40ml20ml20ml
250 sections50ml-100ml50ml50ml


  • Deparaffinize and hydrate tissue sections through xylenes or other clearing agents and graded alcohol series.
  • Rinse for 5 minutes in tap water.
  • If quenching of endogenous peroxidase activity is required, incubate the sections for 30 minutes in 0.3% H2O2 in methanol or water. Incubation times may be shortened by using higher concentrations of H2O2. If endogenous peroxidase activity does not present a problem, step 3 may be deleted.
  • Wash in buffer for 5 minutes.
  • Incubate sections for 60 minutes with diluted Blocking Serum working solution from the species in which the secondary antibody is made. (In cases where non-specific staining is not a problem, Steps 5 and 6 may be deleted).
  • Blot excess Blocking Serum working solution from sections.
  • Incubate sections for 60 minutes with primary antiserum diluted in buffer. (If background staining occurs, dilutions of the primary and secondary antibodies may be made in buffer containing 1-2% of the appropriate blocking serum.)
  • Wash slides for 5 minutes in buffer.
  • Incubate sections for 60 minutes with diluted biotinylated secondary antibody solution.
  • Wash slides for 5 minutes in buffer.
  • Incubate sections for 30 minutes with SABC Reagent working solution
  • Wash slides for 5 minutes in buffer.
  • Incubate sections in peroxidase substrate solution until desired stain intensity develops. (See Note 1)
  • Rinse sections in tap water. 15. Counterstain, clear and mount.


SABC Kit (Mouse)

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