A label-free aptasensor based on electrodeposition of gold nanoparticles on silver-based metal–organic frameworks for measuring ochratoxin A in black and red pepper

Abstract

Since ochratoxin A (OTA) is immunotoxic, teratogenic and carcinogenic, it is very important to monitor this compound in food samples. In the present work, the development and fabrication of a label-free electrochemical aptasensor based on the gold nanoparticles/silver-based metal–organic framework (AuNPs/Ag-MOF) for the determination of ochratoxin A (OTA) is introduced. The aptasensor was fabricated by electrodeposition of AuNPs on a glassy carbon electrode modified with Ag-MOF. The characteristics of the synthesized Ag-MOF were determined by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and UV-Visible spectroscopy. The aptamer was immobilized on the modified electrode and then OTA was incubated on it. The process of different stages of the aptasensor construction has been confirmed by two methods of electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) and using [Fe(CN)₆]^3−/4− as a redox probe. The EIS method has also been used for the OTA quantitative determination. The difference in charge transfer resistance (R_ct) before and after the interaction of OTA with the immobilized aptamer was considered as the analytical response of the aptasensor. Using the developed aptasensor, it is possible to measure OTA in the concentration range of 1.0 × 10⁻³ to 200.0 ng mL⁻¹ with a detection limit of 2.2 × 10⁻⁴ ng mL⁻¹. Finally, the ability of the aptasensor to measure OTA in red and black pepper was investigated and completely satisfactory results were obtained.