Dual metal–organic-frameworks mediated resonance energy transfer for ultrasensitive electrochemiluminescence immunosensing

An electrochemiluminescence (ECL) biosensor for carcinoembryonic antigen (CEA) based on electrochemiluminescence resonance energy transfer (ECL-RET) was designed. Tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy)₃²⁺) was used as an energy donor for ECL-RET, and an Au nanoparticle-modified MOF framework (AuCoFe MOF) was used as an energy receptor for ECL-RET. The ECL emission spectra of Ru(bpy)₃²⁺ were in the range 550 to 680 nm, and a zinc oxalate MOF encapsulating Ru(bpy)₃²⁺ (Ru@ Zn oxalate MOF) was prepared. The UV–vis absorption spectrum of AuCoFe MOF ranges from 280 to 700 nm and overlaps with emission spectra of Ru@Zn oxalate MOF, which is critical for RET. The AuCoFe MOF-Ab₂ bioconjugate, target CEA antigen, and the Ru@Zn oxalate MOF-Ab₁ bioconjugate together form a sandwich structure, resulting in quenching of the ECL signal of Ru@Zn oxalate MOF by AuCoFe MOF. Under the optimized experimental conditions, the ECL-RET sensor exhibited excellent analytical performance in CEA detection with a linear range of 1.0 × 10⁻¹³ to 1.0 × 10⁻⁸ mg mL⁻¹; the minimum limit of detection is 1.4 × 10⁻¹⁴ mg mL⁻¹ (S/N = 3); and its recoveries of spiked samples ranging from 99.1 to 100.7%. The developed sensor has excellent stability, reproducibility, and specificity and is suitable for the detection of CEA in human serum and has the potential to provide sensitive detection of other biomarkers of diseases.

Graphical Abstract