Dual defected g-C 3 N 4 Faraday cage-type electrochemiluminescence immunosensor for ultrasensitive ' turn on ' detection of carcinoembryonic antigen

In this work, a novel Faraday cage-type electrochemiluminescence (ECL) biosensor was constructed for the ultrasensitive "turn on" detection of CEA. The capture unit was prepared by immobilizing the Carcinoembryonic antibody Ab 1 onto the functionalized magnetic Fe 3 O 4 nanoparticles, while the detection unit consisted of modified g-C 3 N 4 labeled with antibody Ab 2 . The recognition scaffold was assembled as follows: the capture unit was first fixed onto the magnetic electrode surface; the target CEA was then captured; followed by further hybridized with the detection unit; ultimately forming the Faradaycage biosensor structure. In this configuration, the signal unit became part of the electrode surface, enabling all electrochemiluminophores in the signal unit to participate in the electrode reaction, thereby significantly enhancing the detection sensitivity. Utilizing the proposed Faraday-cage cascade, the ECL intensity increased with the rising CEA concentration. The linear range was from 0.01 to 100 ng/mL, with a detection limit of 0.35 pg/mL. The sensor was validated for its selectivity, stability, reproducibility, precision, and application potential. This Faraday cage-type ECL biosensor shows promising prospects for clinical CEA detection.