Electrochemiluminescence Mechanisms and Bioanalysis Based on Multishape Gold Nanoparticles and Visualized ATT-Au NCs

Herein, a visual electrochemiluminescence (ECL) luminophore, 6-azido-2-thioxanthine-coated gold nanoclusters (ATT-Au NCs), was prepared efficiently in a single step, followed by comprehensive characterization of their structural, optical, and ECL properties using diverse analytical methodologies. Concurrently, gold nanoparticles, gold dimers, gold nanorod (Au NR) dispersions, and gold nanorod dimers (parallel and perpendicular conformations) were synthesized via chemical reduction, DNA ligation, seed growth, and electrostatic adsorption of organic ligands, respectively. The finite difference time domain (FDTD) modeling was subsequently employed to analyze the electromagnetic field distribution surrounding these gold nanoparticles, revealing that parallel gold nanorod dimers notably enhanced the electromagnetic field intensity. Based on this, we constructed a novel ECL biosensor that harnessed surface-plasmon-coupled ECL (SPC-ECL) and resonance energy transfer (RET) between ATT-Au NCs and parallel Au NR dimers. The sensor incorporated Cu₂O nanoparticles (NPs) as quenching probes to precisely induce RET, leading to the ECL signal being switched "off". This dual enhancement and quenching strategy achieved a high signal-to-noise ratio, facilitating the sensitive detection of microRNA-21 (miRNA-21) with a linear range of 1 fM-100 nM and a low detection limit of 0.28 fM. This work not only extends our understanding of the SPC effect and the application of the RET mechanism in ECL, providing a theoretical foundation for further advancements in the ECL field, but also highlights its considerable potential for applications in biomedical research and clinical diagnostics.