Photoinduced Electrochemiluminescence Immunoassays

Optimization of electrochemiluminescence (ECL) immunoassays is highly beneficial for enhancing clinical diagnostics. A major challenge is the improvement of the operation conditions required for the bead-based immunoassays using the typical [Ru(bpy)₃]²⁺/tri-n-propylamine (TPrA) system. In this study, we report a heterogeneous immunoassay based on near-infrared photoinduced ECL, which facilitates the imaging and quantitative analysis of [Ru(bpy)₃]²⁺-modified immunobeads at low anodic potential. The photovoltage generated by the photoanode under near-infrared light promotes oxidation processes at the electrode/electrolyte interface, thus considerably lowering the onset potential for both TPrA oxidation and ECL emission. The anti-Stokes shift between the excitation light (invisible to the human eyes) and the visible emitted light results in a clear and stable signal from the immunobeads. In addition, it offers the possibility of site-selective photoexcitation of the ECL process. This approach not only meets the performance of traditional ECL immunoassays in accuracy but also offers the additional benefits of lower potential requirements and enhanced stability, providing a new perspective for the optimization of commercial immunoassays.