A novel amperometric immunosensor based on layer-by-layer assembly of gold nanoparticles–multi-walled carbon nanotubes-thionine multilayer films on polyelectrolyte surface

A highly sensitive and label-free amperometric immunosensor has been developed for the detection of carcinoembryonic antigen (CEA) based on layer-by-layer (LBL) assembly of gold nanoparticles (GNPs), multi-walled carbon nanotubes-thionine (MWNTs-THI) and chitosan (CHIT) on 3-mercaptopropanesulfonic, sodium salt (MPS)-modified gold electrode surface by electrostatic adsorption. The stepwise LBL assembly process of electroactive species on electrode surface was characterized by means of cyclic voltammetry (CV) in PBS. The factors influencing the performance of the resulting immunosensor were studied in detail. The morphologies of MWNTs, MWNTs-THI and GNPs–MWNTs-THI–CHIT were further characterized by transmission electron microscopy (TEM). The immunosensor was highly sensitive to CEA with a detection limit of 0.01 ng mL−1 (signal/noise ratio of 3) and the linear range with two concentration intermittences was from 0.5 to 15.0 ng mL−1 and from 15.0 to 200.0 ng mL−1, respectively. In addition, the prepared immunosensor could be regenerated 10 times with 5 M urea solution. When the immunosensor was stored at 4 °C and measured intermittently (every 4–6 days), no apparent change was found over 3 months. The immunosensor system showed an excellent reproducibility and stability.