Amperometric immunosensors based on layer-by-layer assembly of gold nanoparticles and methylene blue on thiourea modified glassy carbon electrode for determination of human chorionic gonadotrophin.

Nano-Au and methylene blue (MB) were assembled layer-by-layer (LBL) into films on the glassy carbon electrode modified by thiourea for detection of human chorionic gonadotrophin (HCG). The electrode modification process was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron micrograph (SEM). The factors influencing the performance of the amperometric immunosensor were studied in detail. Tests performed with this immunosensor showed good linearity, the working range for the system was 1.0-100.0 mIU/mL with a detection limit of 0.3 mIU/mL at 3sigma. Moreover, the studied immunosensor exhibited high sensitivity and long-term stability. The present work supplied a promising test method for clinical immunoassay.