Impedimetric Polyaniline-Based Aptasensor for Aflatoxin B₁ Determination in Agricultural Products

An impedimetric aptasensor based on a polyaniline (PAni) support matrix is developed through the surface modification of a screen-printed carbon electrode (SPE) for aflatoxin B₁ (AFB₁) detection in foodstuffs and feedstuffs for food safety. The PAni is synthesized with the chemical oxidation method and characterized with potentiostat/galvanostat, FTIR, and UV-vis spectroscopy techniques. The stepwise fabrication procedure of the PAni-based aptasensor is characterized by means of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods. The impedimetric aptasensor is optimized using the EIS technique, and its feasibility of detecting AFB₁ in real sample matrices is evaluated via a recovery study in spiked foodstuffs and feedstuffs, such as pistachio nuts, cinnamons, cloves, corn, and soybeans, with a good recovery percentage, ranging from 87.9% to 94.7%. The charge transfer resistance (R_CT) at the aptasensor interface increases linearly with the AFB₁ concentration in the range of 3 × 10^-2 nM to 8 × 10^-2 nM, with a regression coefficient (R²) value of 0.9991 and detection limit of 0.01 nM. The proposed aptasensor is highly selective towards AFB₁ and partially selective to AFB₂ and ochratoxin A (OTA) due to their similar structures that differ only at the carbon-carbon double bond located at C₈ and C₉ and the large molecule size of OTA.