Dual-ligand engineering of amino-functionalized Eu-MOF for enhanced electrochemiluminescence

Efficient and highly sensitive detection of environmental estrogens at trace levels is critically important for accurate risk assessment and the mitigation of their potential carcinogenic effects. In this study, a dual-ligand europium-based metal-organic framework (Eu-MOF) was designed and synthesized as the luminophore for an electrochemiluminescence (ECL) immunosensor, utilizing 1,3,5-benzenetricarboxylic acid (BTC) and 2-aminoterephthalic acid (BDC-NH₂) as ligands and Eu³⁺ as the central metal ion. The introduction of dual ligands not only enhanced the antenna effect and improved the energy transfer efficiency, but also allowed the functional group (-NH₂) on the auxiliary ligand to modulate the local coordination environment, thereby amplifying the ECL signal of the Eu³⁺ centers. Through the incorporation of the ECL resonance energy transfer (ECL-RET) mechanism, a competitive ECL immunosensor for estriol (E3) detection was successfully developed, employing Eu-BTC-BDC-NH₂ as the energy donor and MIL-88A(Fe)@Au NPs as the energy acceptor. The immunosensor enabled ultrasensitive quantification of E3 across a broad concentration range of 10 fg mL^-1 to 500 ng mL^-1, with the lowest detectable concentration reaching 3.44 fg mL^-1. This work offers a promising approach for designing lanthanide metal MOFs in ECL sensing, enabling ultrasensitive and selective detection of environmental estrogens.