A new Bi₂MoO₆ nano-tremella-based electrochemical immunosensor for the sensitive detection of a carcinoembryonic antigen

By doping molybdenum (Mo) into bismuth oxide (Bi₂O₃), we synthesized novel Bi₂MoO₆ nanohybrids with a unique tremella-like crystal structure via a one-pot hydrothermal method. Such a porous tremella structure of Bi₂MoO₆ possesses a significantly larger surface area than the spherical structure of Bi₂O₃, which is favorable for the special functionalization and effective immobilization of molecules such as antibodies on the surface of the tremella flaps. As expected, Au nanoparticles grew easily and uniformly outside the surface of the flaps of the as-prepared Bi₂MoO₆ NTs (Au@Bi₂MoO₆ NTs), showing preferable conductivity and biocompatibility, and the anti-carcinoembryonic antigen (anti-CEA) was effectively immobilized outside the obtained Au@Bi₂MoO₆ NTs. Acting as a novel label-free immunosensing platform, the anti-CEA-immobilized Au@Bi₂MoO₆ NTs were used to fabricate an electrochemical immunosensor for the quantitative detection of CEA. The as-prepared Au@Bi₂MoO₆-based immunosensor linearly responded to CEA in a wide concentration range from 1 pg mL^-1 to 1 μg mL^-1 with a detection limit calculated to be 0.3 pg mL^-1 (S/N = 3), significantly comparable to numerous existing immunosensors. Moreover, the minimum detection concentration of the designed immunosensor was about ten times smaller than that of many Bi and Mo-based sensors toward CEA detection, and the detection limit was lower, revealing higher sensitivity. The satisfactory selectivity and stability made the immunosensor potentially applicable for CEA detection in real samples.