Ultrasensitive Detection of Carcinoembryonic Antigen by Chitosan/Polythiophene/CdTe Electrochemical Biosensor

[Image: see text] A facile method for the in situ fabrication of chitosan/polythiophene/CdTe (CS/PTh/CdTe) nanocomposite has been developed. It was then connected with anti-CEA (Ab), which was evoked for the electrochemical detection of carcinoembryonic antigen (CEA, Ag) within K(4)Fe(CN)(6). The results indicate that CS/PTh/CdTe/GCE has a high selectivity for the detection of CEA with a wide linear range of 0.0001–10000 ng/mL and excellent sensitivity with a low detection limit of 40 fg/mL. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and in situ FT-IR spectra are evoked to study the mechanism of detection of CEA via CS/PTh/CdTe/GCE. The high sensitivity of the electrochemical sensor is due to the fact that the electrochemical oxidation products of K(4)Fe(CN)(6) can directly oxidize CdTe from a low energy state to a high energy state (CdTe)*, making CdTe more prone to be oxidized and facilitate electron transfer. The developed electrochemical biosensor can be used for the detection of real samples, providing a precise method for the detection of CEA with potential application in the clinical detection of tumors.