Ultrasensitive ECL immunoassay for CA15-3 via self-enhanced L012-loaded ZnNi-MOF as an emitter and CeO₂-Pt as a co-reaction accelerator

Improvement in the sensitivity and accuracy of ECL-based biosensors, to a great extent, depends on the fabrication of high-performance electrochemiluminescence (ECL) sensors. Herein, polyethyleneimine (PEI)-grafted bimetallic ZnNi metal-organic framework (ZnNi-MOF/PEI) nanospheres were synthesized to prepare a L012-based ECL immunosensor for detecting carbohydrate antigen 15-3 (CA15-3). The introduced PEI was utilized not only as a bridging element for L012 luminophore and detection antibody (Ab₂) immobilization but also as a co-reactant for generating the self-enhanced ZnNi-MOF/PEI-L012@Ab₂ ECL signal probe. Furthermore, Pt nanoparticle-functionalized CeO₂ nanorods (CeO₂-Pt) featuring high-efficiency electrocatalytic properties, as a co-reaction accelerator, could catalyze H₂O₂ to generate abundant reactive oxygen species (ROS), further augmenting the ECL signal of ZnNi-MOF/PEI-L012@Ab₂. In the presence of CA15-3 antigen, the capture antibody (Ab₁)-conjugated CeO₂-Pt complex (CeO₂-Pt@Ab₁) and ZnNi-MOF/PEI-L012@Ab₂ would get closer to each other, with the formation of a "signal-on" sandwich-type ECL immunosensor. The ZnNi-MOF-assisted ECL biosensor achieved a detection limit of down to 5.75✕10^-5 U mL^-1. This work shows distinguished potential for measuring low levels of biomarkers that may help in the clinical diagnosis of breast cancer.