Multivalent Redox Reversible Conversion-Enhanced Electrochemiluminescence Strategy for Progesterone Detection

The performance of electrochemiluminescence (ECL) sensing platforms, especially the sensitivity, relies on an efficient signal enhancement mechanism and presents a critical challenge in developing novel strategies simultaneously. In this work, we reported a multivalent redox reversible conversion-enhanced ECL strategy based on the redox reactions of two pairs of multivalent metal elements on the electrode surface. TiO₂-loaded Eu(OH)₃ (Eu(OH)₃@TiO₂) was introduced as a dual-enhanced coreactant accelerator to catalyze the oxidation process of tripropylamine (TPrA), thus improving the reaction rate at the sensing interface and the ECL strength of the luminophore. Moreover, gadolinium hydroxide (Gd(OH)₃) served as the ECL emitter for the sensing platform. The stable luminescence property of Gd(OH)₃ was observed, laying the foundation for its application in ECL sensing. To construct the immunosensor, a heptapeptide affinity ligand (HWRGWVC, HGC) was introduced to oriented immobilize antibodies. HGC effectively maintained the biological activity, thus improving the incubation efficiency and detection performance of the immunosensor. In this study, a competitive ECL immunoassay model was designed for the sensitive detection of progesterone (P4). The competitive immunosensor exhibited a broad range of 0.001–200 ng·mL^–1 and a low detection limit of 0.38 pg·mL^–1. The competitive sensing model based on the dual-enhanced strategy is expected to offer a prospective approach to precise detection.