Highly-sensitive label-free immunosensor for tumor necrosis factor α based on Ag@Pt core–shell nanoparticles supported on MWCNTs as an efficient electrocatalyst nanocomposite

Abstract

We have developed a novel and label-free electrochemical immunosensor for detection of tumor necrosis factor-alpha (TNF-α) based on bimetallic silver@platinum (Ag@Pt) core–shell nanoparticles supported on MWCNTs and chitosan (Ag@Pt-CNTs–CS) as a desirable sensor platform. The redox reaction of catechol on the graphite screen-printed electrodes modified with Ag@Pt-CNTs–CS applied as a probe for studying the immobilization and determination processes in immunosensor, due to enhanced electrocatalytic activity of Ag@Pt-CNTs for catechol. The results showed that this nanocomposite exhibited attractive electrocatalytic activity and also yielded a large capacity for antibody loading, which improved the amount of immobilized antibody. A decrease in differential pulse voltammetry (DPV) responses was observed with increasing concentrations of TNF-α in standard and real samples due to its obstruction to the electrocatalytic oxidation of catechol by Ag@Pt-CNTs after binding to the surface of the electrode through interaction with the antibody. The detection limit for TNF-α was found to be 1.6 pg mL⁻¹ and the detection concentrations were in the range between 6.0 and 60 pg mL⁻¹. The proposed electrochemical immunosensor showed high sensitivity, specificity, good reproducibility and stability as well as acceptable accuracy for TNF-α detection in human serum samples and this strategy might also be applied to detect other antigens.