Double Magnetic Separation-assisted Fluorescence Method for Sensitive Detection of Ochratoxin A

A double magnetic separation-assisted fluorescence method was developed to rapidly detect ochratoxin A(OTA). The OTA aptamer functionalized magnetic nanomaterial(Fe₃O₄-Aptamer) and complementary DNA conjugated nitrogen-doped graphene quantum dots(NGQDs-cDNA) were used in this assay. Aptamer could hybridize with cDNA, which induced the NGQDs-cDNA to bind onto Fe₃O₄-Aptamer, and resulted in the fluorescence quenching of NGQDs. After the addition of OTA, the NGQDs-cDNA could release into the solution, and resulted in the recovery of fluorescence signal of NGQDs consequently. By utilizing the magnetic separation, the unbonded NGQDs-cDNA and residual Fe₃O₄-Aptamer were removed, which significantly increased the fluorescence signal intensity. OTA could be detected in the linear range of 10 nmol/L to 2000 nmol/L, with a limit of detection as 0.66 nmol/L. The advantages of this method include simple operation, good selectivity and high sensitivity, and this method can be used for the rapid detection of ochratoxin A in wheat and corn.