One-step preparation of disposable multi-functionalized g-C3N4 based electrochemiluminescence immunosensor for the detection of CA125

A novel, disposable and label-free electrochemiluminescence (ECL) immunosensor, based on multi-functionalized graphitic carbon nitride (g-C 3 N 4 ) coated on the one-off screen-printed carbon electrodes (SPCEs), for the detection of tumor marker carbohydrate antigen 125 (CA125) was developed. The multi-functionalized g-C 3 N 4 was prepared with amino-coated Fe 3 O 4 nanoparticles and CA125 antibody (anti-CA125) chemically bound to the surface of carboxylated g-C 3 N 4 simultaneously. The Fe 3 O 4 nanoparticles ensured the presence of multi-functionalized g-C 3 N 4 in the outer Helmholtz plane (OHP) of the ECL immunosensor and even becoming part of the electrode surface. This assembly promoted the electron transfer between g-C 3 N 4 and the electrode resulting in greatly enhanced ECL intensity. The CA125 was selectively captured by anti-CA125 leading to effective inhibition of the ECL signal. Under optimal conditions, this disposable ECL immunosensor exhibited a wide dynamic linear detection range for CA125 (0.001–5   U/mL) with a lower detection limit of 0.4   mU/mL, providing high sensitivity. In addition, the immunosensor also exhibited high specificity, good reproducibility and long-term stability. All these properties offer great promise for rapid, simple, selective and effective detection of CA125 in clinical applications.