Simultaneous measurement of ochratoxin A and aflatoxin B1 using a duplexed-electrochemical aptasensor based on carbon nanodots decorated with gold nanoparticles and two redox probes hemin@HKUST-1 and ferrocene@HKUST-1

An electrochemical aptasensor was developed for the simultaneous determination of ochratoxin A (OTA) and aflatoxin B1 (AFB1). Two compounds hemin@HKUST-1 and ferrocene@HKUST-1 were synthesized by encapsulating hemin and ferrocene inside the MOF made by copper nodes and trimesic acid, known as HKUST-1 MOF, and then bind to complementary DNA sequences of OTA aptamer (cDNA1) and AFB1 aptamer (cDNA2), respectively. Then, the hemin@HKUST-1/cDNA1 and ferrocene@HKUST-1/cDNA2 bioconjugates were deposited on the glassy carbon electrode (GCE) modified with carbon nanodots decorated with gold nanoparticles (AuNPs-CNDs). In the absence of the two mycotoxins, the current response related to the electroactive labels of hemin and ferrocene in the discussed bioconjugates have been measured at two separate potentials simultaneously by the differential pulse voltammetry technique (DPV). Using the described aptasensor, it is possible to measure both OTA and AFB1 mycotoxins in the linear concentration range of 1.0 × 10-2 to 100.0 ng mL-1. Also, the detection limits of OTA and AFB1 were 4.3 × 10-3 ng mL-1 and 5.2 × 10-3 ng mL-1, respectively. Finally, the ability of the proposed duplex aptasensor for the simultaneous measurement of OTA and AFB1 in a corn flour sample was investigated and completely satisfactory results were achieved.

Development of an electrochemical aptasensor based on Au nanoparticles decorated on metal-organic framework nanosheets and p-biphenol electroactive label for the measurement of aflatoxin B1 in a rice flour sample

This study purposes designing a new aptasensor to detect aflatoxin B1 (AFB1). The AFB1 aptasensor was developed by growing gold nanoparticles on the surface of nickel-based metal-organic framework nanosheets (AuNPs/Ni-MOF) and an electroactive indicator (p-biphenol, PBP). The AFB1 aptamer was immobilized on the AuNPs/Ni-MOF and then hybridized with the complementary DNA (cDNA). PBP was intercalated within the double helix of the cDNA-aptamer. The difference between electrochemical responses of intercalated PBP before and after incubation of AFB1 with the immobilized aptamer was considered as an analytical response. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to monitor the construction processes of the aptasensor. By recording the differential pulse voltammograms of PBP in phosphate buffer (pH 7.0, 0.1 M), the linear range and the detection limit of AFB1 were found to be 5.0 × 10^-3-150.0 ng mL^-1 and 1.0 × 10^-3 ng mL^-1 (S/N = 3), respectively. Finally, the designed aptasensor has been successfully used to measure AFB1 in a rice flour sample with satisfying results. Schematic illustrated the different steps of constructing the electrochemical aptasensor based on Au nanoparticles decorated on Ni-metal-organic framework nanosheets and p-biphenol electroactive label for measuring aflatoxin B1 (AFB1).