Dual defect g-C3N4 Faraday cage-type electrochemiluminescence immunosensors for ultrasensitive “turn on” detection of carcinoembryonic antigen

Abstract

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 Ab₁ onto the functionalized magnetic Fe₃O₄ nanoparticles, while the detection unit consisted of modified g-C₃N₄ labeled with antibody Ab₂. 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 hybridization with the detection unit; ultimately forming the Faraday-cage 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⁻¹, with a detection limit of 0.35 pg mL⁻¹. 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.