Construction of label-free electrochemical aptasensor and logic circuit based on triple-stranded DNA molecular switch.

Background: Pesticide residues can cause chronic toxicity to the human body and lead to a series of diseases that damage the liver. Therefore, developing a highly sensitive, selective, and low-cost pesticide residues detection method is of great significance for protecting human health and safety. Nowadays, commonly used methods for pesticide residue detection include gas chromatography, high-performance liquid chromatography, and fluorescence sensing. These methods have some typical shortcomings, such as long sample pretreatment time, expensive instruments, and poor controllability. It was thought that a sensing platform based on electrochemical analysis method and functional DNA molecules can eliminate the above drawbacks.

Results: Herein, this study developed a simple and label-free electrochemical aptasensor based on a triple-stranded DNA molecular switch. Acetamiprid (ACE) was served as the analytical model, and its binding with the aptamer opened the triple-stranded DNA molecular switch, resulting in the in-situ formation of G-quadruplex/hemin complexes on the electrode surface, obtaining a significantly enhanced electrochemical signal and achieving high specificity and label-free detection of ACE, with a detection limit as low as 4.67 × 10 nM (S/N = 3). In addition, due to the specific recognition between the aptamer and the target, the aptasensor effectively avoided the interference of other pesticides and exhibited good specificity. Moreover, benefiting from the pH-switchable of the triple-stranded DNA molecular switch and the programmability of DNA molecules, "OR" logic gate and "OR-INHIBIT" cascade logic circuit were successfully implemented.

Significance: The proposed electrochemical aptasensor exhibited good accuracy and sensitivity in detecting acetamiprid in vegetable soil sample, indicating its practicality in the detection of pesticide residues in actual samples. Furthermore, the sensing system was reasonably programmed and successfully operated an "OR" logic gate and an "OR-INHIBIT" cascade logic circuit, demonstrating its potential application in intelligent sensing.