Nanostructured Co3O4-CuO@MWCNTs functionalized platform for label-free immunosensing of microbial toxins

Abstract

α-Hemolysin, produced by Staphylococcus aureus, is one of the most potent secreted toxins. It directly destroys host cell membranes by forming transmembrane pores, ultimately leading to severe health complications. Accordingly, there is an urgent need to rapidly detect contaminated samples with such toxins. Here, disposable immunosensing system was designed using a selective anti-α-hemolysin antibody assembled onto nanostructured disposable sensor chips modified with AuNPs-Co3O4-CuO@MWCNTs nanocomposite. Bimetal oxides of cobalt and copper were chemically synthesized and integrated with the multiwalled carbon nanotubes and gold nanoparticles to yield the desired sensing platform that provides high electrocatalytic and high sensing performance. Consequently, the electrochemical assay was systematically optimized, with several analytical parameters evaluated, including the nanocomposite composition ratios, antibody loading concentration, incubation time between the exotoxin and its specific antibody, and the detectable concentration range of the target toxin. Furthermore, the nanostructured materials were comprehensively characterized through a combination of physical and chemical techniques, such as X-ray diffraction (XRD), Raman spectroscopy, electron microscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Eventually, a calibration curve with a wide dynamic range was obtained, demonstrating high sensitivity with a limit of detection of 0.01 ng/mL. The applicability of the newly designed immunosensors for real quantitative analysis in food samples was investigated, showing high recovery rates (from 96.0 to 107%) towards the target analyte.