Glyoxal is not good for which applications?

• A. Immunohistochemistry
• B. PAS
• C. Routine H&E
• D. Gram staining

Answer: (A)

Glyoxal fixes tissues by creating cross-links between proteins in a way that can alter or mask the epitopes that antibodies need to recognize in immunohistochemistry. Because IHC depends on antibodies binding to specific antigens, any change that hides or changes those epitopes reduces staining quality, leading to weak, uneven, or nonspecific results. Some epitopes that react well in formalin-fixed samples may not be as accessible after glyoxal fixation, and standard antigen retrieval methods tuned for formalin may not work as effectively with glyoxal. That makes glyoxal-fixation less reliable for IHC unless highly specialized retrieval protocols are used. In contrast, PAS and routine H&E rely on chemical reactions with carbohydrates and general tissue morphology, and Gram staining is compatible with fixed tissues, so they’re not as adversely affected by glyoxal fixation. Therefore, glyoxal is not ideal for immunohistochemistry.