The electrochemiluminescence immunosensor based on the Ce(III,IV)-MOF dual-function platform is used for the ultra-sensitive detection of AFP.

To address the challenges of unstable immobilization of tris(2,2'-bipyridine) ruthenium(II) (Ru(bpy)32+) and inefficient generation of the tri-n-propylamine radical (TPrA˙) in the Ru(bpy)32+/TPrA electrochemiluminescence (ECL) system, a novel dual-function strategy using a mixed-valence cerium metal-organic framework (Ce(III,IV)-MOF) was introduced in this study. The Ce(III,IV)-MOF was employed both as a scaffold for Ru(bpy)32+ and as a co-reaction catalyst. The three-dimensional structure of the Ce(III,IV)-MOF provides a stable environment for Ru(bpy)32+, while the Ce(III)/Ce(IV) redox pair within the framework facilitates TPrA oxidation through reversible single-electron transfer, thereby enhancing TPrA˙ generation. This design co-localizes the luminophore and catalytic centers within a single framework, reducing shortening the electron-transfer distance between Ru(bpy)32+ and the TPrA˙ site, and consequently enhancing the ECL performance of the Ru(bpy)32+/TPrA system. Compared with single-valence MOFs and their physically mixed MOF composites, the ECL performance of the Ru@Ce (III,IV)-MOF/TPrA system is significantly improved, with the maximum ECL signal amplification factor reaching up to 2.7 times. The sensor developed using this strategy showed a broad linear range (1 × 10-4 ng mL-1-100 ng mL-1) and a low detection limit (0.036 pg mL-1), together with excellent selectivity, stability, and reproducibility. This strategy provides a promising route for constructing multifunctional MOF-based ECL sensors for sensitive tumor biomarker detection.