The Ultrasensitive Detection of Aflatoxin M₁ Using Gold Nanoparticles Modified Electrode with Fe³⁺ as a Probe

The increasing incidence of diseases caused by highly carcinogenic aflatoxin M₁ (AFM₁) in food demands a simple, fast, and cost-effective detection technique capable of sensitively monitoring AFM₁. Recent works predominantly focus on the electrochemical aptamer-based biosensor, which still faces challenges and high costs in experimentally identifying an efficient candidate aptamer. However, the direct electrochemical detection of AFM₁ has been scarcely reported thus far. In this study, we observed a significant influence on the electrochemical signals of ferric ions at a gold nanoparticle-modified glassy carbon electrode (AuNPs/GCE) by adding varying amounts of AFM₁. Utilizing ferricyanide as a sensitive indicator of AFM₁, we have introduced a novel approach for detecting AFM₁, achieving an unprecedentedly low detection limit of 1.6 × 10^-21 g/L. Through monitoring the fluorescence quenching of AFM₁ with Fe³⁺ addition, the interaction between them has been identified at a ratio of 1:936. Transient fluorescence analysis reveals that the fluorescence quenching process is predominantly static. It is interesting that the application of iron chelator diethylenetriaminepentaacetic acid (DTPA) cannot prevent the interaction between AFM₁ and Fe³⁺. With a particle size distribution analysis, it is suggested that a combination of AFM₁ and Fe³⁺ occurs and forms a polymer-like aggregate. Nonetheless, the mutual reaction mechanism between AFM₁ and Fe³⁺ remains unexplained and urgently necessitates unveiling. Finally, the developed sensor is successfully applied for the AFM₁ test in real samples, fully meeting the detection requirements for milk.