Electrochemiluminescence immunosensor for cancer antigen 125 detection based on novel resonance energy transfer between graphitic carbon nitride and NIR CdTe/CdS QDs

Resonance energy transfer (RET), as an efficient strategy, has been widely used for exploring a variety of biological processes and achieving sensitive bioanalysis. In this work, fluorescence and electrochemiluminescence (ECL) RET between graphitic carbon nitride (g-C3N4) and NIR CdTe/CdS QDs was reported firstly. Based on this novel RET system, a sensitive sandwich-type ECL immunosensor was constructed to detect cancer antigen 125 (CA125). In this strategy, the ECL of Au NPs-functionalized graphitic carbon nitride nanohybrids (Au-gC3N4 NHs) was efficiently quenched by near-infrared CdTe/CdS quantum dots (NIR CdTe/CdS QDs), where NIR CdTe/CdS QDs acts as acceptors, and Au-g-C3N4 NHs acts as donors. Au NPs improved the intensity and stability of ECL and provided sites to immobilize the antibody. Silica nanospheres carried abundant NIR CdTe/CdS QDs (QDs-SiO2) labeling secondary antibodies, further enhancing the quenching effect. Under the optimum conditions, the constructed immunosensor showed excellent analytical performance with a linear concentration of CA125 from 0.0001 U mL?1 to 10 U mL?1 and the limit of detection reached 0.034 mU mL?1 (S/N = 3). Meanwhile, the immunosensor also revealed great stability, reproducibility, and selectivity and it could be applied in human serum samples successfully. This strategy provided a useful analytical method for the sensitive detection of biomarkers in the early stages of the disease and an innovative reference for developing more efficient and sensitive RET bioanalysis.