Dual-Potential Ratiometric Electrochemiluminescent Immunosensor Modulated by the Single Luminophore Gd-Ru-MOFs

Multi-signal ratiometric electrochemiluminescence (ECL) sensors have attracted considerable attention owing to their remarkable sensitivity and precision. Here, a novel dual-potential ratiometric ECL sensor has been developed for the ultrasensitive detection of estriol (E3), employing Gd-Ru metal-organic frameworks (Gd-Ru-MOFs) as the single luminophore. The Gd-Ru-MOFs, synthesized with meso-tetra(4-carboxyphenyl)porphine (TCPP) and tris(4,4'-dicarboxylicacid-2,2'-bipyridyl)ruthenium(II) chloride (Ru(H₂dcbpy)₃·Cl₂) as the ligands, are capable of emitting stable cathodic and anodic ECL signals when potassium persulfate (K₂S₂O₈) and triethylamine (TPrA) are present. In order to improve the ECL sensor's sensitivity, Ce:CuCoO₂, which exhibits a broad ultraviolet absorption spectrum, is utilized as a quencher. This quencher effectively suppresses both cathodic and anodic ECL signals from Gd-Ru-MOFs through resonance energy transfer (RET). Under optimal experimental conditions, the developed ECL sensor demonstrated a linear detection range spanning from 10 fg/mL to 100 ng/mL, with a low detection limit of 3.26 fg/mL (S/N = 3). Finally, the dual-potential ratiometric ECL sensor was successfully applied to the detection of E3 in river. Thus, the proposed strategy has the potential to be extended to other ECL luminophores, offering a novel approach for the development of dual-potential ratiometric ECL sensors.