# Self-Assembled MoS2/ssDNA Nanostructures for the Capacitive Aptasensing of Acetamiprid Insecticide
## 1 Introduction  
Neonicotinoid acetamiprid is considered as one of the most efficient neuro-active insecticides, so large amounts of acetamiprid are routinely used in agriculture for treatment of numerous pests. Due to its abuse of use, the threat of pesticide residues to human health and environmental pollution are a real public concern [1]. For instance, it has been reported that acetamiprid could affect human peripheral blood lymphocytes and cause DNA damages [2] and its accumulation in agricultural products is a serious threat for human beings [3]. Thus, the detection and monitoring of acetamiprid levels in foodstuffs are of great interest for public health safety. The United States Environmental Protection Agency (EPA) and the European Food Safety Authority have set the maximum residue level (MRL) of acetamiprid from 0.01 to 3 ppm depending on the nature of the vegetables and the legislation is regularly revised regarding this MRL [4]. However, detecting pesticides at these levels is still challenging. Therefore, the development of reliable, sensitive, direct, and fast analytical methods for the acetamiprid analysis in fresh products is of paramount importance. For this purpose, various analytical methods are available such as enzyme-linked immunosorbent assays [5], gas chromatography [6], high-performance liquid chromatography [7], and gas chromatography-mass spectrometry [8]. Nevertheless, these techniqueshave some limitations like high equipment costs, suitable only for laboratory analysis, time-consuming due to sample preparation and require trained technicians to operate them. Hence, the development of simple, cost-effective, sensitive, and portable alternatives is necessary for the fast detection of acetamiprid in environment and agricultural field to reduce the risk of public health. Over the last decade, electrochemical biosensors have gained increasing interest in the field of food monitoring due to their excellent properties and remarkable analytical performances [9]. Especially, oligonucleotide-based electrochemical biosensors are increasingly applied for sensitive detection of pesticide residues [10]. Aptamers are single-stranded oligonucleotides considered as excellent molecular probes, which are endowed with high affinity for various target substances, including small molecules [11], viruses [12] proteins [13], and cells [14]. In an attempt to develop electrochemical aptasensors, several acetamiprid sensing approaches based on the aptamer-target affinity have been developed. For instance, [PERSON] et al. [15] recently reported a dual signal amplification strategy for the aptasensing of acetamiprid using reduced graphene oxide and silver nanoparticles. The electrical signal recorded by cyclic voltammetry was significantly improved after the immobilization of Prussian blue-gold nanoparticles as a catalyst for the redox reaction. In another competition-based strategy, silica nanoparticles modified dsDNA formed by the perfect match of the aptamer and a complementary sequence intercalated with methylene blue (MB) as a redox probe are used. In the presence of acetamiprid, the high affinity of aptamer toward the target induced the release of MB that is detected electrochemically using an unmodified gold electrode [16]. In the other work, [PERSON] et al. [17] did not use a redox probe and proposed a label free impedimetric aptasensor based on complex composites of gold nanoparticles (AuNPs) decorated MWCNTs and reduced graphene oxide nanoribbons to detect femtomolar levels of the target. The aforementioned studies showed the use of conventional electrochemical techniques such as cyclic voltammetry and electrochemical impedance spectroscopy. Recent efforts focused to optimize and to enhance the signal sensitivity of these techniques and particularly of electrochemical impedance spectroscopy that needs theoretical modeling by an equivalent circuit. Accordingly, [PERSON] et al.