Electrochemical sensing of fipronil in fruit and vegetable based on gold nanocrystal and target-induced DNA cycle signal amplification

Development of a high-performance electrochemical aptasensor that can detect fipronil in fruits and vegetables is important for human health improvement. This paper presents a method for synthesising Rubus Corchorifolius–like gold (RC-Au) nano-crystals using a type of 21 peptide as a shape inducer. The synthesis process involves the concurrent growth of nano-crystals and their asymmetric development, resulting in the formation of RC-Au nano-particles with increased exposure of their high-index facets, which enhances their catalytic activity. The RC-Au nano-crystals were then combined with an aptamer/auxiliary DNA hybrid to fabricate an electrochemical aptasensor that can sense fipronil via the release of the free auxiliary DNA strand, triggering target-induced DNA cycling. One fipronil molecule was found to transfer many RC-Au–thionine probes to the aptasensor surface, with the resulting oxidation and reduction of the probes leading to signal amplification. Increasing the concentration of fipronil from 1 × 10−17 to 1 × 10−12 M led to a linear increase in the amperometric current. A limit of detection of 3.7 × 10−18 M (S/N = 3) was obtained. The developed sensor exhibits higher sensitivity than other electrochemical fipronil sensors and was satisfactorily used to detect fipronil in fruits and vegetables. [Display omitted] •We reported synthesis of gold nanocrystals using chiral peptide containing multiple thiol groups.•The strategy enhances the exposure of high-index faces and lead to an improved catalytic activity.•Combination of gold nanocrystal wit DNA cycle realize high sensivity and selectivity for fipronil.•The study offers one way for synthesis of gold nanomaterial with good catalytic activity in sensing.