A quenching electrochemiluminescence energy resonance transfer system based on CdS and COFs for the ultrasensitive detection of CA242

Abstract

Carbohydrate antigen 24-2 (CA242) as a biomarker played critical roles in the early diagnosis of colorectal cancer. Herein, a quenching-typed electrochemiluminescence immunosensor based on resonance energy transfer strategy was proposed for ultrasensitive CA242 detection. CdS NCs exhibited good electrochemiluminescence performance, which was used as an ECL energy donor, while COFs with a porous structure presenting UV-vis light absorption was used as an energy acceptor, which could significantly quench the ECL signal of CdS NCs. The sandwich-type immunosensor was constructed with thiolated CdS NCs as substrates for primary antibody (Ab₁) immobilization and functionalized COFs as the carrier to immobilize secondary antibody (Ab₂). With CA242 antigen captured, the distance between CdS NCs and COFs was closed and the electron transfer path shortened, leading to the quenching of the ECL signal of CdS NCs. Under optimal conditions, the proposed immunosensor represented wide linearity, and the detection limit was in the range from 0.001 U mL⁻¹ to 1000 U mL⁻¹. At the same time, the detection limit of CA242 antigen was 0.000183 U mL⁻¹ (S/N = 3). The immunosensor exhibited its feasibility for the detection of CA242 and lays a good foundation for the high sensitivity sensing of other disease biomarkers in clinical diagnosis in the future.