Electrochemical Immunosensor for Detection of Secretory Protein VacA on G-CN/ZnO Nanocomposite-Modified Au Electrode

A g-CN/ZnO (graphitic carbon nitride/zinc oxide) nanocomposite-decorated gold electrode was employed to design an antigen-antibody-based electrochemical biosensor to detect specific toxin, vacuolating cytotoxin A (VacA). The thermal condensation method was used to synthesize the g-CN/ZnO nanocomposite, and the nanocomposite was deposited electrochemically on a gold electrode. The morphology as well as the structure of the synthesized nanocomposite were confirmed by scanning electron microscopy, energy-dispersive X-ray analysis, X-ray diffraction, and Fourier transform infrared techniques. The nanocomposite efficiently increased the sensor performance by amplifying the signals. EDC-NHS chemistry was exploited for attachment of VacA antibodies covalently with the g-CN/ZnO-modified gold electrode. This modified electrode was exploited for immunosensing of -specific VacA antigen. The immunosensor was stable for up to 30 days and exhibited good sensitivity of 0.3 μA ng mL in a linear detection range of 0.1 to 12.8 ng mL. Apart from this, the fabricated sensor showed unprecedented reproducibility and remarkable selectivity toward the toxin VacA. Thus, the highly sensitive immunosensor is a desirable platform for detection in practical applications and clinical diagnosis.