Defect site and intraluminophore sensitization integrated Gd/Tb-MOF for electrochemiluminescent biosensing

In electrochemiluminescence (ECL) systems, luminophore design plays a critical role in signal enhancement. Herein, a self-enhanced Gd/Tb-MOF luminophore integrating defect sites and intraluminophore sensitization was developed for ECL biosensing. Defect sites promoted SO₄^•- generation through coreactant S₂O₈^2- activation, favoring excited-state Gd/Tb-MOF* formation. After Gd/Tb-MOF* formation, the Gd³⁺→H₃BTB→Tb³⁺ intraluminophore sensitization pathway promoted stepwise energy migration toward Tb³⁺ emissive centers, thereby favoring radiative relaxation and improving radiative output. These processes contributed to the amplified cathodic ECL intensity. Zn/Cu(OH)₂@Au was further introduced as a secondary antibody label to regulate the ECL intensity through resonance energy transfer (RET). Besides ECL/UV-vis spectral overlap and HOMO/LUMO energy level matching, the shortened fluorescence lifetime further confirmed the RET process. Finally, the constructed ECL biosensor enabled sensitive cytokeratin 19 fragment (Cyfra21-1) detection over a linear range from 100 fg mL^-1 to 100 ng mL^-1 with a limit of detection of 63.6 fg mL^-1 and exhibited good analytical performance in real serum samples. This work offers a design strategy for Ln-MOF ECL systems integrating defect sites and intraluminophore sensitization.