Benzidine dihydrochloride as a chromogen for single- and double-label light and electron microscopic...

Area of Science:

• Immunocytochemistry
• Microscopy Techniques
• Biochemical Assays

Background:

• Sensitive chromogens are crucial for horseradish peroxidase localization in tracing studies.
• Existing chromogens have limitations in immunocytochemical applications.
• Need for improved chromogens for both light microscopy (LM) and electron microscopy (EM) immunocytochemistry.

Purpose of the Study:

• To introduce and validate benzidine dihydrochloride (BDHC) as a novel chromogen for LM and EM immunocytochemical studies.
• To demonstrate the advantages of BDHC over existing chromogens, such as DAB and tetramethylbenzidine.
• To establish a protocol for effective BDHC application in immunocytochemistry.

Main Methods:

• Developed a protocol using benzidine dihydrochloride (BDHC) as the chromogen for LM and EM immunocytochemistry.
• Adjusted reaction pH to be above 6.0 for BDHC.
• Optimized osmicating conditions (45°C in s-collidine buffer) for EM analysis of the BDHC reaction product.

Main Results:

• BDHC produces a bluish-green, crystalline reaction product at the LM level, distinct from the reddish-brown DAB product, enabling LM double-labeling.
• The BDHC protocol significantly increases immunoreaction sensitivity, allowing higher fixative concentrations, less detergent, and higher primary antibody dilutions.
• BDHC reaction product is preserved for EM analysis and its crystalline nature allows for clear detection and distinction from flocculent DAB product, facilitating EM double-labeling.

Conclusions:

• Benzidine dihydrochloride (BDHC) is a highly effective and sensitive chromogen for both LM and EM immunocytochemistry.
• The BDHC protocol offers superior sensitivity and enables double-labeling studies in both microscopy levels.
• This new method provides a valuable tool for enhanced immunocytochemical analysis and cell labeling.