DNA walker-assisted aptasensor for highly sensitive determination of Ochratoxin A.

Ochratoxin A (OTA), a toxic secondary metabolite produced via various fungus, poses a serious threat to the health of human beings and animals. In this paper, an aptasensor for OTA detection based on gold nanoparticles decorated molybdenum oxide (AuNPs-MoO) nanocomposites, hybridization chain reaction (HCR) and a restriction endonuclease (Nb.BbvCI)-aided walker DNA machine was successfully constructed. In this electrochemical platform, the HCR was also used to embed more electrical signal molecules of methylene blue (MB) on silver nanoparticles (AgNPs) to achieve signal amplification. Under the optimum conditions, after adding OTA and Nb.BbvCI in turn and responding adequately under appropriate conditions, aptamer-DNA (6-DNA) carries the OTA away from the electrode surface, and walker DNA was hybridized autonomously with 5-DNA, releasing a large amount of 5'-DNA with the help of Nb.BBVCI. Finally, the electrochemical signal obtained by differential pulse voltammetry (DPV) was weakened. As an artificial and popular signal amplification technique, the DNA walking machine greatly improved the sensitivity. The proposed biosensor exhibited excellent analytical performance in the range of 0.01-10000 pg mL with a detection limit as low as 3.3 fg mL. Furthermore, direct comparison with ultraperformance liquid chromatography (UPLC) indicates excellent agreement to actual samples such as apple juice, orange juice, red wine and serum.