Development of a sandwich ECL aptamer sensor based on self-enhanced Ru(bpy)32+@ Zn-MOF luminophore and PoPD@Au NPs quencher for ultrasensitive EpCAM detection

Background Epithelial cell adhesion molecules (EpCAM) protein is one of the most frequently and intensely studied tumor-associated antigens because of its overexpression in most cancer cells. Thus, it is regarded as a tumor biomarker associated with a wide variety of carcinomas and reflects the existence and growth of tumors in the human body. It is highly required to detect low concentrations of EpCAM in early stage for ensuring human health. Results In this study, a novel sandwich electrochemiluminescence (ECL) aptasensor was developed for EpCAM detection. Wherein oxalate-based Zn-MOF supported tris(2,2′-bipyridyl)ruthenium (II) (Ru(bpy) 3 2+ @Zn-MOF) was used as luminophore and gold nanoparticle modified o-phenylenediamine (PoPD@Au NPs) as quencher. The 3D Ru(bpy) 3 2+ @Zn-MOF generated self-enhanced ECL without additional co-reactants. Furthermore, it remained stable and had short electron transfer distance, ensuring high and stable ECL signal. The ECL signal could be effectively quenched by PoPD@Au NPs through resonance energy transfer (RET) and electron transfer (ET), due to its absorption spectrum overlapping with the ECL emission spectrum of Ru(bpy) 3 2+ @Zn-MOF. In the presence of EpCAM, the aptamer acted as a linker between the luminophore and quencher, forming a sandwich structure that had reduced ECL intensity. Under optimal conditions, EpCAM could be sensitively detected over the range of 1 pg mL -1 -100 ng mL -1 , with a detection limit of 0.34 pg mL -1 . Significance This work developed a ECL aptasensor with self-enhanced Ru(bpy) 3 2+ @Zn-MOF luminophore for EpCAM detection. The ECL system was simple, but ultrasensitive for EpCAM monitoring, thanks to the ECL-RET and ET between Ru(bpy) 3 2+ @Zn-MOF and PoPD@Au NPs. It also could be applied to detect other biomolecules by replacing the aptamer, offering significant potential in disease diagnosis.