Electrochemically deposited nanocomposite of chitosan and carbon nanotubes for detection of human chorionic gonadotrophin

A new label-free amperometric immunosensor was developed for detection of human chorionic gonadotrophin (hCG) based on multiwall carbon nanotubes–chitosan (MWNTs–CS) complex film and three-dimensional AuNPs–TiO2 hybrid. Firstly, MWNTs–CS film was deposited on a glassy carbon electrode (GCE) by a simple and controllable electrodeposition method. Next, thionine (Thi), as a redox probe, was covalently bound onto the MWNTs–CS film with glutaraldehyde (GA) to obtain the Thi/MWNTs–CS film. The free amino groups of the composite membrane were used to adsorb AuNPs–TiO2 for immobilizing human chorionic gonadotrophin antibody (anti-hCG) because of its large surface area and satisfactory biocompatibility. At last, BSA was employed to block possible remaining active sites. Under optimized conditions, the immunosensor displayed high sensitivity, good reproducibility, and a low detection limit of 0.08 mIU/mL at 3 times the background noise. The ease of non-manual technique and the promising feature of biocomposite could serve as a versatile platform for constructing other biosensors.