Highly sensitive gold-overoxidized polypyrrole nanocomposite immunosensor for antitransglutaminase antibody

Patients with coeliac disease, a gluten intolerance autoimmune disorder, have elevated levels of antitransglutaminase antibody in their human sera. In this study, an immunosensor for the electrochemical determination of antitransglutaminase antibody was constructed. The immunosensor architecture was based on the electrostatic deposition of transglutaminase antigen on a glassy carbon electrode modified with electrosynthetic overoxidized polypyrrole and gold nanoparticles and capped the transglutaminase layer with bovine serum albumin. As a result, good surface coverage of the gold nanoparticles (~100 nm) was achieved across the overoxidized polypyrrole film. Electrochemical impedance spectroscopy parameters of the gold nanoparticle–overoxidized polypyrrole electrode include time constant, exchange current density, and heterogeneous rate constant. The impedimetric immunosensor exhibited a charge transfer resistance-dependent linear range with a correlation coefficient value of 0.98 and a dynamic linear range of 10−6–10−4 mg mL−1. The synergistic effect of the gold nanoparticles on the overoxidized polypyrrole formed the electronic insulator platform as a selective accumulator for the analytes surrounding the nanoelectrode. This biosensor characteristic enabled detection of antitransglutaminase antibodies at very low concentrations without the aid of a secondary label.

Determination of anthracene on Ag-Au alloy nanoparticles/overoxidized-polypyrrole composite modified glassy carbon electrodes

A novel electrochemical sensor for the detection of anthracene was prepared by modifying a glassy carbon electrode (GCE) with over-oxidized polypyrrole (PPyox) and Ag-Au (1:3) bimetallic nanoparticles (Ag-AuNPs). The composite electrode (PPyox/Ag-AuNPs/GCE) was prepared by potentiodynamic polymerization of pyrrole on GCE followed by its overoxidation in 0.1 M NaOH. Ag-Au bimetallic nanoparticles were chemically prepared by the reduction of AgNO₃ and HAuCl₄ using C₆H₅O₇Na₃ as the reducing agent as well as the capping agent and then immobilized on the surface of the PPyox/GCE. The nanoparticles were characterized by UV-visible spectroscopy technique which confirmed the homogeneous formation of the bimetallic alloy nanoparticles. Transmission electron microscopy showed that the synthesized bimetallic nanoparticles were in the range of 20–50 nm. The electrochemical behaviour of anthracene at the PPyox/Ag-AuNPs/GCE with Ag: Au atomic ratio 25:75 (1:3) exhibited a higher electrocatalytic effect compared to that observed when GCE was modified with each constituent of the composite (i.e., PPyox, Ag-AuNPs) and bare GCE. A linear relationship between anodic current and anthracene concentration was attained over the range of 3.0 × 10⁻⁶ to 3.56 × 10⁻⁴ M with a detection limit of 1.69 × 10⁻⁷ M. The proposed method was simple, less time consuming and showed a high sensitivity.