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 x 10-3 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.

Acetamiprid (ACT) has been detected in several water sources in Latin America. The presence of its degradation products in the environment is not negligible and transformation products (TPs) significantly contribute to environmental health risks. Although advanced oxidative processes are promising for the treatment of this neocotinoid, effects of these are still unknown. In this context, the effects of a mixture of photocatalytic degradation products resulting from an ACT treatment for 90 min employing TiO2/UV on cytotoxicity and oxidative stress parameters in Eisenia andrei earthworms in acute and chronic experiments using typical Latin American soil were assessed. Acute contact tests were performed (72 h) using a filter paper moistened with an ACT solution and a chronic test was performed using Oxisoil (200 g) moistened with an ACT solution for 45 days. Catalase (CAT) and glutathione-S-transferase (GST) activities, reduced glutathione (GSH) levels and cytotoxicity (cellular eleocyte and amoebocyte assessments) were investigated. Over 75 % of ACT was degraded within the first 15 min of treatment, with levels below the limit of detection after 60 min. The acute test revealed greater cytotoxic effects associated with the effluents treated for T0 and T15 min, with decreased cell density noted after 48 h of exposure, in addition to CAT induction (in all treatments) and GST induction following T0, T15 and T90 min exposures. Concerning the chronic assay, decreases in cell density (T0, T15, T60 and T90 min) and viability (T0, T60 and T90 min) were observed after 45 days, in addition to induced CAT activity following T0, T15 and T60 exposures and GST induction following the T60 min exposure. Reduced glutathione levels were unaltered, comprising the least sensitive biomarker among the investigated parameters to the treated effluent exposures. The mixture of ACT degradation products can cause toxic effects to non-target organisms, despite parent compound degradation, alerting for the need for ecotoxicological tests to prove decreased effluent toxicity, in addition to the improvement of degradation techniques.