Electrochemiluminescence immunoassays (ECLIA) have emerged as powerful tools for sensitive biomarker detection, with increasing interest in their adaptation to miniaturized point-of-care diagnostic platforms. Herein, we report the enhancement of the luminescent signals of a spatially resolved ECLIA (SR-ECLIA) for multiplex biomarker detection on screen-printed carbon electrodes through the incorporation of a water-soluble redox mediator, sulfonated tris(1-phenylpyrazolato)iridium(III) (Ir(sppz)33-). Introduction of the nonemissive Ir(sppz)33- complex enabled efficient amplification of ECL signals while preserving assay multiplexing capability and compatibility with microarray formats. Application to a duplex SR-ECLIA targeting heart-type fatty acid-binding protein (H-FABP) and glial fibrillary acidic protein (GFAP) demonstrated a marked improvement in assay performance. The redox mediator amplified the absolute ECL immunoassay signals by approximately six-fold and increased the analytical sensitivity (slope of the calibration curve) for both biomarkers five-fold. The enhancement was found to arise from electrocatalysis of coreactant oxidation, which generates more intermediate radicals for the reductive (TPrA•) excitation of the oxidized luminophore, in conjunction with the previously elucidated redox mediator-enhanced oxidative excitation pathways. Overall, this work highlights the promise of novel Ir(III)-based redox mediators in advancing SR-ECLIA toward highly sensitive, multiplexed, and point-of-care diagnostic platforms.
Jović et al. (Fri,) studied this question.
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