The limitations associated with avidin-biotin IHC staining methods led to the development of additional indirect staining methods with higher sensitivity and specificity that use polymer-based staining components in the mid-1990s. With polymer-based IHC staining, primary and secondary antibodies are conjugated to an enzyme-labeled dextran (polymer) chain. The polymer chain itself provides for multiple binding sites that essentially contribute to extreme sensitivity and specificity, especially when compared to ABC and LSAB methods. Additionally, polymer-based IHC has a reduced number of steps than other indirect IHC staining methods.
The mechanism of polymer-based IHC methods follows these steps:
- Unconjugated primary antibody
- Secondary antibody conjugated to an enzyme-labeled polymer
- Chromogenic substrate to visualize antigen site
Since polymer-based IHC methods are biotin-free, there is no concern for reaction with endogenous biotin. This is a significant advantage over ABC and LSAB staining methods.
