Electrochemical immunosensor for human chorionic gonadotropin based on horseradish peroxidase-functionalized Prussian blue-carbon nanotubes/gold nanocomposites as labels for signal amplification

A new strategy for the sensitive detection of biomarker using Prussian blue-carbon nanotubes/gold nanocomposites (GNPs-PB-CNTs) as labels and horseradish peroxidase (HRP) as an enhancer is presented herein. Chitosan hydrogel and TiO2 nanocomposites were first coated onto a glassy carbon electrode (GCE) surface, which provided a biocompatible interface with abundant -NH2 groups for the immobilization of primary antibodies (Ab(1)). The detectable signal was recorded and amplified based on a sandwich-type immunoassay by the employment of HRP-labeled secondary antibodies (HRP-Ab(2)) and GNPs-PB-CNTs bioconjugates according to the electrocatalytic reduction of H2O2 by bound HRP in the presence of PB. Using human chorionic gonadotropin (HCG) as a model analyte, experimental results showed that the prepared HRP-Ab(2)-GNPs-PB-CNTs bioconjugates exhibited satisfactory redox activity and high efficiency of enzyme catalysis. Under optimized conditions, the immunosensor showed a low detection limit of 0.023 mIU/mL HCG, with a linear range from 0.05 to 150 mIU/mL. The proposed method exhibited high sensitivity, acceptable stability and reproducibility, and could be extended to detect other protein targets. (C) 2010 Elsevier Ltd. All rights reserved.