Electrochemical Immunosensor for Detection of H. pylori Secretory Protein VacA on g-C 3 N 4 /ZnO Nanocomposite-Modified Au Electrode.

A g-C 3 N 4 /ZnO (graphitic carbon nitride/zinc oxide) nanocomposite-decorated gold electrode was employed to design an antigen-antibody-based electrochemical biosensor to detect Helicobacter pylori specific toxin, vacuolating cytotoxin A (VacA). The thermal condensation method was used to synthesize the g-C 3 N 4 /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-C 3 N 4 /ZnO-modified gold electrode. This modified electrode was exploited for immunosensing of H. pylori -specific VacA antigen. The immunosensor was stable for up to 30 days and exhibited good sensitivity of 0.3 μA -1 ng mL -1 in a linear detection range of 0.1 to 12.8 ng mL -1 . Apart from this, the fabricated sensor showed unprecedented reproducibility and remarkable selectivity toward the H. pylori toxin VacA. Thus, the highly sensitive immunosensor is a desirable platform for H. pylori detection in practical applications and clinical diagnosis.