A novel electrochemical aptasensor for fumonisin B₁ determination using DNA and exonuclease-I as signal amplification...

In this work, using DNA and exonuclease-I (Exo-I) as signal amplification strategy, a novel and facile electrochemical aptasensor was constructed for fumonisin B₁ (FB₁) detection. The G-rich complementary DNA (cDNA) was immobilized onto the electrode surface. Then, aptamer of FB₁ was hybridized with cDNA to form double-stranded DNA. In the absence of FB₁, double-stranded DNA and G-rich cDNA on the electrode surface promoted effectively methylene blue (MB) enrichment and amplified the initial electrochemical response. In the presence of FB₁, the combination of aptamer and FB₁ led to the release of aptamer from the electrode surface and the expose of 3' end of single-stranded cDNA. When Exo-I was added onto the electrode surface, the single-stranded cDNA was degraded in the 3'-5' direction. The decrease of double-stranded DNA and G-rich cDNA resulted in the less access of MB to the electrode surface, which decreased the electrochemical signal. The experimental conditions including incubation time of FB₁, the amount of Exo-I and incubation time of Exo-I were optimized. Under the optimal conditions, the linear relationship between the change of peak current and the logarithmic concentration of FB₁ was observed in the range of 1.0 × 10^-3-1000 ng mL^-1 with a low limit of detection of 0.15 pg mL^-1. The experimental results showed that the prepared aptasensor had acceptable specificity, reproducibility, repeatability and stability. Therefore, this proposed aptasensor has a potential application in the food safety detection.