An electrochemical impedimetric arrayed immunosensor based on indium tin oxide electrodes and silver-enhanced gold nanoparticles

A novel sensitive electrochemical impedance immunoassay based on metal nanoparticle labels and ITO electrodes has been developed. First, 2-aminobenzoic acid (2-ABA) was electropolymerized onto an indium tin oxide (ITO) electrode. The coupling reagents 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysulfosuccinimide were then used to activate the electroconductive polymer to form an active ester layer which could react with amino groups of antigen. Subsequently, immunoreaction was carried out between antigen and antibody labeled with gold nanoparticles, followed by the addition of the silver enhancer solution. The charge transfer processes of [Fe(CN)6]4−/[Fe(CN)6]3− on the ITO surface were affected due to the formation of silver precipitation on the gold nanoparticles, which was determined by electrochemical impedance spectroscopy. The surface was characterized by scanning electron microscopy. Finally, a multiplexed arrayed immunosensor was is described and the samples of antibody and antibody mixture were assayed specifically. The experimental conditions such as the number of electropolymerization cycles and the time of silver enhancement were examined and optimized. The detection range of antibody labeled with gold nanoparticles was between 10.0 ng mL−1 and 10.0 µg mL−1.