Label-Free Immunohistochemistry Imaging by Oblique-Incidence Reflectivity Difference

Immunohistochemistry (IHC) is a well-established method in tissue pathology and finds critical applications in both clinical and fundamental medical science. Generally, labeled antibodies are a requisite for IHC to visualize the spatial distribution of the biomarker (antigen) of interest in the tissue slices. In this work, a label-free IHC imaging strategy is reported for the first time by using an oblique-incidence reflectivity difference (OIRD) to obviate the need for labeled antibodies. The position-resolved relative abundance of biomarkers was successfully mapped by the differential OIRD image upon the binding of native antibody on the tissue slices. The dynamic binding kinetics of antibody on the tissue are also monitored. The efficacy of such a label-free IHC strategy is further verified with fluorescent IHC images. This work explores the application of the OIRD imaging technique in tissue slices and offers a label-free IHC imaging strategy for pathological analysis, disease diagnosis, and drug screening.