High-Sensitivity Immunohistochemistry Method Using a Combination of Fluorescent Nanoparticles and Tyramide Linker

Immunohistochemistry (IHC) is a useful method for visualizing antigens in tissues using target-specific antibodies in drug discovery and clinical research. Color reactions with horseradish peroxidase enzymatic activity have been used for IHC. This method has a long history and is highly reliable when applied to in vitro diagnostics. However, an IHC method with high sensitivity is required for low-expression target molecules in antibody-drug conjugates and immunotherapy. Therefore, many studies have been conducted in recent years to improve the sensitivity using highly brilliant and light-resistant phosphor-integrated dots (PIDs). In this method, streptavidin-coated PIDs are linked via biotinylated antibodies and the target molecules are visualized (PID-AbL). PID-AbL is more sensitive than IHC with chromophores. Hence, this study aimed to improve the sensitivity and quantitative results of IHC by combining PIDs with a biotinylated tyramide linker (PID-TL). PID-TL is able to detect ultralow human epidermal growth factor receptor 2-expressed cells. Moreover, PID-TL may be applied to human tissue samples as well as in vitro diagnostic kits. This new approach may help detect low-expression target molecules for clinical research.