Chromogen enhancers increase the intensity of the color appearance of positive IHC staining reactions. 3,3’-diaminobenzidine (DAB) enhancers contain compounds that continue the DAB reaction or darken/change the color. An enhancer to the color can be heavy metals, such as copper, silver, nickel, gold, or cobalt. The most commonly used metal as an enhancer is nickel, which gives a blue-black color to the DAB. Gold is used for electron microscopy IHC procedures.
When using an enhancer for the first time, a control slide using the DAB without enhancers should be stained before adding the enhancer. The presence of the original unenhanced reaction validates that the enhancer is not turning a negative stain result into a (false) positive stain result.
