A Dual-Functional Signal “On–Off–On” Biosensor Based on Coordination-Induced Enhancement and Interface Antifouling for Trace Analysis of Alpha-Fetoprotein in Serum

In electrochemiluminescence (ECL) analysis, strong output signals and anti-interference ability can improve the detection performance and service life of sensors, while the development of high-performance luminophores and antifouling interfaces is the key to achieving the above functions. Herein, a bimetallic organic framework (Zn/Ru-MOF) with the coordination-induced enhancement effect was prepared for ECL emissions using tris(4,4'-dicarboxylic acid-2,2'-bipyridine) ruthenium(II) [Ru(dcbpy)₃²⁺] as a ligand. Due to the effective aggregation of Ru(dcbpy)₃²⁺ and the suppression of nonradiative relaxation, as well as the energy transfer from Zn²⁺ to Ru(dcbpy)₃²⁺, the developed Zn/Ru-MOF exhibited high ECL efficiency and stable luminescence signals, thereby obtaining a strong "signal-on" state. Furthermore, 3-aminopropyldimethylamine oxide zwitterion was modified on Zn/Ru-MOF as the sensing substrate to resist the interface adsorption of interfering substances, realizing the integration of self-enhanced luminescence and interface antifouling. With the pairing of complementary chains and aptamer chains, a significant "signal-off" state was achieved through resonance energy transfer. According to the competition mechanism of targets, the quenched probes were released, leading to signal recovery. On this basis, the developed dual-functional "on-off-on" biosensor exhibited a low detection limit (4.7 fg/mL), indicating its huge potential for clinical monitoring of alpha-fetoprotein in complex serum media.