An Electrochemical Aptasensor for Detection of Aflatoxin M₁ Based on Reduced Graphene Oxide

In this study, a fast and sensitive electrochemical aptasensor for sensitive determination of AFM₁ was successfully established based on reduced graphene oxide (RGO). RGO was prepared by reducing graphene oxide with jujube juice. The synthesized RGO was dropped onto the surface of GCE. AuNPs was modified on the surface of the RGO/GCE via electrodepositio. The thiolated aptamer (SH-Apt) of the AFM₁ was immobilized on the surface of the AuNPs/RGO/GCE through strong Au-S bond. When AFM₁ was present, AFM₁ bound specifically to the aptamer forming Apt-AFM₁ conjugates. The conjugates hindered electron transfer, causing a decrease of current signal. Differential pulse voltammetry (DPV) was used to monitor electrochemical signal. This electrochemical aptasensor was used to test aflatoxin B₁ (AFB₁), aflatoxin B₂ (AFB₂), ochratoxin A (OTA) and fumonisin B₁ (FB₁) to ensure the electrochemical aptasensor’s specificity. This electrochemical aptasensor was used to detect 1×10⁻⁷~5×10⁻⁴ ng/mL AFM₁ to ensure the electrochemical aptasensor’s sensitivity. And this electrochemical aptasensor was used to detect goat milk to evaluate the practical use of electrochemical aptasensor. The results showed that RGO had the strongest conductivity when GO to jujube juice was 2:1 (V:V) and pH value was about 11. There was a good linear relationship between electrochemical signal and logarithm of AFM₁ concentration in the range of 1×10⁻⁷~5×10⁻⁴ ng/mL with a low detection limit of 3.3×10⁻⁵ pg/mL. What’s more, the developed aptasensor was specific to AFM₁ and did not respond to interfering mycotoxins, which suggested that the electrochemical aptasensor possessed an excellent selectivity for AFM₁ detection. AFM₁ electrochemical aptamer sensor was used to determine the content of AFM₁ in goat milk. It was found that the sensor had high sensitivity and good selectivity, and it was expected to be applied to the rapid and accurate detection of mycotoxins in food industry.