Aptamer based voltammetric patulin assay based on the use of ZnO nanorods

The authors describe an aptamer based assay for the mycotoxin patulin (PAT). A gold electrode was modified with a composite made from ZnO nanorods (ZnO-NRs) and chitosan. The ZnO-NRs was prepared by reaction with ammonia and subsequent hydrothermal growth. Its properties were characterized by X-ray diffraction, Raman spectroscopy and scanning electron microscopy. Subsequently, thiol-modified aptamers were self-assembled on AuNPs that had been electrodeposited on the surface of the modified electrode. The presence of ZnO-NRs on the electrode increases the loading with AuNPs and aptamers. It also warrants a relatively stable microenvironment for the aptamers. In the presence of PAT, it will form a complex with the aptamer on the electrode surface. This hinders electron transfer from the electrode to the redox probe hexacyanoferrate and results in reduced current, which is typically measured at 0.176 V (vs. Ag/AgCl). The concentration of PAT can be calculated from the differences in the peak current before and after incubation with PAT. The assay has a linear response in the 50 ng·mL-1 to 0.5 pg·mL-1 PAT concentration range and a 0.27 pg·mL-1 lower detection limit. The sensor is specific, reproducible, repeatable, and long-term stable. It was successfully applied to the determination of PAT in spiked juice samples. Graphical abstract Schematic representation of aptamer based detection of patulin (PAT). It is based on the fact that ZnO nanorods on the surface of the electrode increase the loading of the gold nanoparticles and the aptamers, thereby improving the electrode performance.