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

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)3 2+ 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)3 2+. 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.