Many of the IHC detection systems offered today are the newer, advanced polymer systems where specific secondary antibodies and enzymes, such as horseradish peroxidase (HRP) and alkaline phosphatase (AP), are attached to dextran polymers or micro polymeric enzymes. The use of polymer technology offers:
- Biotin free system
- Increased sensitivity
- Shortened reaction times
- Background free (typically) staining
Previous technologies used biotin labeled secondary antibodies and enzyme labeled streptavidin or an avidin-biotin complex (ABC). While these systems still work quite well and have a place in specific applications, possibilities do exist for endogenous biotin to be exposed as a result of heat-induced epitope retrieval (HIER) or enzyme-induced epitope retrieval (EIER). Streptavidin or ABC complexes could nonspecifically bind to endogenous biotin and then react with the chromogenic substrate. To counter this potential pitfall, one must implement an avidin-biotin blocking step. While simple to perform, overall procedural time and steps are increased. The use of a non-biotin polymer technology overcomes this technical drawback.