Protein functionalized Pt nanoparticles-conducting polymer nanocomposite film: Characterization and immunosensor application

We report an electrochemically prepared 3-mercaptopropionic acid (MPA) capped Pt nanoparticles-Polypyrrole (PPy) nanocomposite film based bioelectrode for the detection of human C-reactive protein (αCRP). The electrochemical deposition provides homogeneous distribution of ultrafine Pt(MPA)-NPs within the uniform and adherent PPy film with high degree of geometrical conformity and controllable film thickness. Protein antibody, Ab-αCRP, was covalently immobilized through the site specific carboxyl groups of Pt(MPA)-NPs within the polymer nanocomposite film by carbodiimide coupling reaction. The bioelectrode interfacial surface electron transport study towards protein antigen, Ag-αCRP, was carried out by electrochemical impedance spectroscopy (EIS). The value of ‘n’, a Constant Phase Element exponent used as a gauge of the heterogeneity, for Pt(MPA)-PPy nanocomposite film was found to be 0.88∼1 which is indicative of a homogeneous morphology of the composite film with minimal defects. The EIS of the bioelectrode exhibited significant changes in charge transfer resistance (Ret) component at a low ac frequency of <20 Hz towards Ag-αCRP detection over a linear range of 10 ng mL−1–10 μg mL−1 in PBS with a sensitivity of 109.74 Ωcm2 per decade.