Cathodic electrochemiluminescence immunosensor based on nanocomposites of semiconductor carboxylated g-C3N4 and graphene for the ultrasensitive detection of squamous cell carcinoma antigen

• ECL behavior of semiconductor carboxylated g-C3N4 was investigated.
• Graphene could enhance the ECL intensity of g-C3N4.
• The g-C3N4-graphene was prepared based on the electrostatic adsorption.
• Squamous cell carcinoma antigen was ultrasensitivly detected.

A novel label-free electrochemiluminescence (ECL) immunosensor was developed for the detection of squamous cell carcinoma antigen (SCCA) based on nanocomposites of semiconductor carboxylated graphitic carbon nitride (g-C3N4) and graphene (g-C3N4-graphene). The ECL intensity of carboxylated g-C3N4 was much enhanced after being combined with graphene which had excellent electron-transfer ability. The sensing platform was constructed by depositing g-C3N4-graphene on electrodes and immobilizing antibodies on the surface of carboxylated g-C3N4 through amidation. The specific immunoreaction between SCCA and antibody resulted in the decrease of ECL intensity and the intensity decreased linearly with the logarithm of SCCA concentration in the range of 0.025–10 ng mL−1 with a detection limit of 8.53 pg mL−1. The developed ECL immunosensor exhibited high sensitivity, good reproducibility and long-term stability, which possessed great potential for cancer detection in clinical laboratory diagnosis.