Voltammetric immunosensing platform based on dual signal amplification using gold nanoparticle labels

Abstract An electrochemical immunosensing platform based on dual signal amplification strategy has been developed using gold nanoparticles. Human Immunoglobulin G was used as a model analyte in order to establish the immunosensing platform. The platform was fabricated using of 1,6-hexanedithiol self assembled on a gold disc electrode and was further modified by citrate capped gold nanoparticles. The direct immobilization of antibody was achieved through electrostatic interaction between negatively charged citrate capped gold nanoparticles and positively charged amino group of antibody. Each step of modification was analyzed using electroanalytical techniques like cyclic voltammetry and electrochemical impedance spectroscopy. The horseradish peroxidase (HRP)-labeled secondary antibodies conjugated on gold nanoparticles (AuNP-Ab 2 ) acted as nanolabels. Thus the sandwich immunocomplex formed on the electrode surface produced an electrocatalytic response through the reduction of hydrogen peroxide by HRP in the presence of thionine. Electrochemical studies were carried out to understand the role of citrate capped AuNP and AuNP-Ab 2 in dual signal amplification. The fabricated sensing platform can be used for the sensitive determination of various protein biomarkers by immobilizing specific antibody.