A Metal–Organic Framework-Based Electrochemiluminescence Immunosensor with Dual Quenching via Resonance Energy Transfer and Radical Scavenging

Abstract

This study reports a novel electrochemiluminescence (ECL) immunosensor designed for the highly sensitive detection of alpha-fetoprotein (AFP) via a dual quenching strategy. The sensor architecture employs an aluminum-based metal–organic framework (MIL RuMOF@Pt) as the ECL donor, with signal enhancement achieved through a two-step process. Encapsulation of Ru(bpy)32+ within the MIL-NH2-MOF framework significantly amplifies the ECL signal, which is further enhanced by the catalytic activity of Pt nanoparticles (Pt NPs). At equivalent concentrations, the ECL intensity of MIL RuMOF@Pt is 1.08 times that of MIL RuMOF and 1.61 times that of free Ru(bpy)32+. ZnO@PDA serves as the ECL-resonance energy transfer (ECL-RET) acceptor. Dual quenching of the ECL signal from RuMOF@Pt is achieved through two mechanisms: spectral overlap between the UV–vis absorption of ZnO@PDA and the fluorescence emission of MIL RuMOF@Pt, combined with the •O2– radical scavenging effect of polydopamine (PDA). The immunosensor was thus constructed on the basis of dual signal enhancement and dual quenching mechanisms. The fabricated immunosensor exhibits excellent linearity over a wide concentration range from 3.2 × 10–9 to 3.2 × 10–4 mg·mL–1, with a detection limit as low as 5.1 × 10–10 mg·mL–1. Recovery rates in spiked samples ranged from 99.1% to 112.3%. Unlike previous ECL sensors that mainly employed direct quenching or signal amplification, this work constructs a quenching-based sensor using ZnO@PDA, which integrates two distinct quenching mechanisms.