Detection of aflatoxin M1 in milk using electrochemical aptasensor based on screen printed electrode and cyclic voltammetry method

Milk, from its production to consumption, is exposed to a variety of microbial and chemical contaminants. Aflatoxin M1 (AFM1) is one of the most important contaminants in milk, which has always received attention due to its carcinogenic and destructive effects on the consumer. Accordingly, the rapid, sensitive, and cost-effective identification of AFM1 in milk is essential. In the present paper, an electrochemical aptasensor based on screen printed electrode (SPE) modified with magnetic nanoparticles (MNPs) and gold nanoparticles (AuNPs) was proposed to identify AFM1 in cow milk samples. SPE was activated by applying a potential within the range of -1.5 to +1 V versus the reference electrode at a scan rate of 200 mV/s for 5 continuous cycles in the 0.5 M sulfuric acid and 0.1 M potassium chloride solution. Changes of the electrode surface at different stages of preparation were assessed using cyclic voltammetry (CV) technique. Using CV in optimal conditions, it was found that the aptasensor presents a concentration range of 100-700 ng/l and a limit of detection (LOD) of 50 ng/l.  There was a linear relationship between changes of the current peak (∆I) and analyte concentration. This relationship follows the regression equation of ∆I=0.0209C+2.14 (R²=0.9897). Calculation of the relative standard deviation (RSD=3.2%) indicated the acceptable repeatability of the electrochemical aptasensor. The current peak was obtained to be 7.4% in the investigation of RSD reproducibility, indicating the good reproducibility of the electrochemical aptasensor. The obtained results showed that the aptasensor response after 8 days has only reduced by 7% compared to the first day, indicating the desirable stability of the aptasensor. The recovery percentage range for cow milk samples at concentrations of 100 and 200 ng/l was obtained to be 86.5 and 93%, respectively, showing the acceptable recovery percentage of the electrochemical aptasensor.