Electrochemiluminescence Resonance Energy Transfer Biosensor Based on Self-Enhanced Terbium-Based Metal–Organic Frameworks with Antenna Effect for Sensitive MicroRNA-155 Detection

The efficiency of electrochemiluminescence (ECL) emission relies heavily on the spatial proximity between luminophores and coreactant promoters. In conventional ternary systems, the diffusion-driven separation of components in solution often leads to energy loss and lower ECL efficiency. In this work, a self-enhanced lanthanide metal-organic framework (Ln-MOF) emitter, CuTb-BTC@AgNPs (CTBA), was constructed using Tb³⁺ as the luminophore, Cu²⁺ as the coreactant promoter, and Ag nanoparticles (AgNPs) as the electrical conductivity enhancer. An appropriate colocalization of these components significantly shortened the electron transfer distance between the luminescent group and the coreactant promoter, thereby enhancing the ECL efficiency. To modulate the signal, a Pd@Cu₂O quencher, which has a broad UV-Vis absorption range, was introduced for resonance energy transfer (RET)-based suppression. A dual-output toehold-mediated strand displacement (TMSD) strategy was employed to enable target recycling and "on-off" signal control. Using microRNA-155 (miR-155), a biomarker implicated in multiple cancers, as a model target, the biosensor exhibited a wide linear detection range from 10 aM to 1 nM and an ultralow detection limit of 4.7 aM. It also had excellent specificity and achieved high recovery rates when applied to detect human serum and cancer cell samples. Overall, this work describes a robust strategy for integrating Ln-MOF emission platforms with nucleic acid amplification, presenting a powerful tool for the ultrasensitive detection of clinically relevant miRNA.