Gold Microbeads Enabled Proximity Electrochemiluminescence for Highly Sensitive and Size-Encoded Multiplex Immunoassays

Developing highly sensitive multipleximmunoassays isurgentlyneeded to guide medical research and improve clinical diagnosis. Here,we report the proximity electrochemiluminescence (ECL) generationenabled by gold microbeads (GMBs) for improving the detection sensitivityand multiplexing capacity of ECL immunoassays (ECLIAs). As demonstratedby microscopy and finite element simulation, GMBs can function asspherical ultramicroelectrodes for triggering ECL reactions in solutions.Employing GMBs as solid carriers in the bead-based ECLIA, the electrochemicaloxidation of a coreactant can occur at both the GMB surface and thesubstrate electrode, allowing the coreactant radicals to diffuse onlya short distance of & SIM;100 nm to react with ECL luminophoresthat are labeled on the GMB surface. The ECL generation via this proximitylow oxidation potential (LOP) route results in a 21.7-fold increasein the turnover frequency of ECL generation compared with the non-conductivemicrobeads that rely exclusively on the conventional LOP route. Moreover,the proximity ECL generation is not restricted by the diffusion distanceof short-lived coreactant radicals, which enables the simultaneousdetermination of multiple acute myocardial infarction biomarkers usingsize-encoded GMB-based multiplex ECLIAs. This work brings new insightinto the understanding of ECL mechanisms and may advance the practicaluse of multiplex ECLIAs.

Automated summary

Developing highly sensitive multipleximmunoassays is urgently needed to guide medical research and improve clinical diagnosis. In this study, proximity electrochemiluminescence (ECL) generation enabled by gold microbeads (GMBs) was used to enhance the sensitivity and multiplexing capacity of ECL immunoassays. By employing GMBs as solid carriers, the ECL generation through proximity low oxidation potential (LOP) route significantly increased the turnover frequency compared to conventional non-conductive microbeads. Moreover, the proximity ECL generation allowed for the simultaneous detection of multiple acute myocardial infarction biomarkers using size-encoded GMB-based multiplex ECLIAs. This work provides new insights into ECL mechanisms and advances the practical use of multiplex ECLIAs.