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(Hdcbpy)·Cl) as the ligands, are capable of emitting stable cathodic and anodic ECL signals when potassium persulfate (KSO) and triethylamine (TPrA) are present. In order to improve the ECL sensor's sensitivity, Ce:CuCoO, 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.