Multiwalled Carbon Nanotube-Graphene Nanosheet-Chitosan-1-Butyl-3-Methylimidazolium Hexafluorophosphate Nanocomposites and Gold Nanoparticle-Thionine for Electrochemical Detection of Cytomegalovirus Phosphoprotein

Abstract

We describe a sensitive and selective electrochemical immunosensor for the determination of the PP65 phosphoprotein antigen. A screen-printed carbon electrode was modified with a nanocomposite made from multiwalled carbon nanotubes, graphene nanosheets, chitosan and 1-butyl-3-methylimidazolium hexafluorophosphate. Gold nanoparticles were immobilized on the modified electrode and incorporated into layers of the polymeric redox mediator thionine. Next, monoclonal antibodies against PP65 were immobilized on the surface via an amine-gold interaction. Finally, horseradish peroxidase was used to block the remaining active sites on the gold nanoparticles and to act as an enzyme in the immunoassay. The decreased electrocatalytic reduction of hydrogen peroxide by horseradish peroxidase was monitored by differential pulse voltammetry. Under optimized conditions, the differential pulse voltammetry signal at a typical working voltage of 0.5 V decreased with increasing concentration of PP65 from 0.12 to 300 pg mL −1 , with a detection limit as low as 30 fg mL −1 (at a signal to noise ratio of 3). The immunosensor is highly specific with acceptable precision, and good stability and repeatability.