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 x 10-2 to 100.0 ng mL-1. Also, the detection limits of OTA and AFB1 were 4.3 x 10-3 ng mL-1 and 5.2 x 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.