Overoxidized Polypyrrole Incorporated with Gold Nanoparticles as Platform for Impedimetric Anti-Transglutaminase Immunosensor

Abstract

Overoxidized polypyrrole (OvoxPpy) doped with gold-nanoparticles (GNP) on a glassy carbon electrode (GCE) was used as a platform to construct a novel label-free impedimetric immunosensor for anti-transglutaminase (anti-tTG). Field emission scanning electron microscopy results confirmed the deposition of GNP with good surface coverage across the OvoxPpy substrate. The average diameter of the nanocomposite was 100 nm. The platform (GNP|OvoxPpy||GCE) was conductive and exhibited reversible electrochemistry (E°’ = 395 mV) in (pH 7.4) PBS. The electrochemical characterization of the platform was studied by cyclic voltammetry (CV) and square wave voltammetry (SWV). OvoxPpy||GCE had a peak separation, ΔE p , value of −80 mV. The GNP|OvoxPpy||GCE showed enhanced interfacial charge transfer with ΔE p , being −30 mV. The SWV results corroborated CV findings which show enhanced peak current through GNP. The immunosensor was prepared by immobilizing 40 μL tTG (0.3 mg mL−1) onto the platform by drop coating. Electrochemical impedance spectroscopy (EIS) measurements indicated that the immunosensor system (BSA|tTG|GNP|OvoxPpy||GCE) markedly improved the conductivity and response of the anti-tTG immunosensor. The impedimetric immunosensor exhibited a charge transfer resistance (Rct)-dependent dynamic linearity of 10−6 to 10−4 M for target anti-tTG (r = 0.9808), and detection limit of 5.22 × 10−6 M.