Nanoconfined metal-organic frameworks encapsulating platinum(II) complexes with self-catalytic aggregation-induced electrochemiluminescence for ultrasensitive miRNA-21 biosensing

Abstract

Aggregation-induced electrochemiluminescence (AIECL) luminophores have garnered significant attention for biosensing applications owing to their enhanced electrochemiluminescence (ECL) emission in aggregated states. However, conventional AIECL systems often suffer from structural instability in physiological environments due to weak intermolecular force of their aggregation. Here, we have successfully constructed nanoconfined Zr-based metal-organic frameworks (PCN-777 MOFs) encapsulating platinum(II)-[4,2':6′,4″-terpyridine]-4′-carboxylic acid (Pt(tpyc)²⁺) complexes, in which Pt(tpyc)²⁺) complexes are immobilized into PCN-777 MOFs via Zr⁴⁺ and -COO^- coordination bond. The resulting Pt-PCN-777 MOFs achieved exceptional structural stability and high loading efficiency of Pt(tpyc)²⁺. Critically, the mesoporous structural of the PCN-777-MOFs efficiently proconcentrates of S₂O₈²⁻ co-reactant within its channels, significantly shortening electron-transfer pathway between immobilized Pt(tpyc)²⁺ emitters and coreactants. The synergistic effect of the Pt-PCN-777 MOFs accelerates K₂S₂O₈ decomposition, leading to enhanced ECL signal. Through integrating catalytic hairpin assembly and hemin-quenching strategies, the "Signal On-Off" ECL biosensor is constructed for ultra-sensitive detection of miRNA-21. The miRNA-21 biosensor exhibits superior analytical performance, such as high sensitivity (approximately 9.03 × 10¹⁷), wide linear range (10²–10⁹ aM), femtomolar-level detection limit (∼66 aM), exceptional selectivity and operational stability. This study addresses the limitations of instability of traditional AIECL systems and is hopeful to establish a versatile platform of Pt(II)-MOF composites for advanced ECL probes in clinical diagnosis.