A multipedal DNA walker with bidirectional walking mechanism for pesticide residue detection in food samples

Abstract

Given the detrimental effects of pesticide residues on human health and the ecological environment, it is crucial to sensitively and quantitatively detect these chemicals in food and environmental samples. This study presents a novel multipedal DNA walker that employs a bidirectional walking mechanism for detecting pesticide residues. The walking system is composed of four essential components: a lantern probe (LP) for target recognition, two ingeniously designed hairpin structures facilitating a hybridization chain reaction (HCR), and a spherical nucleic acid probe (SNP). When a specific pesticide residue is present, the HCR process leads to the assembly of an HCR thread, which functions as the walking orbit alongside the SNP. The walker operates by utilizing the SNP as the DNA orbit, enabling continuous and automated movement along the SNP, which is driven by Eb.BbvCI. This process results in the fluorescence signals emitted from the SNP. Conversely, when the HCR thread is utilized as the orbit, movement transpires along the HCR thread, powered by Et.BbvCI, which generates fluorescence signals from the HCR thread. This bidirectional walking mechanism enhances signal amplification and accumulation, enabling ultra-sensitive detection of pesticides, achieving detection limits of 6.8 aM for acetamiprid and 5.2 aM for malathion. The quantification of acetamiprid residues in real food samples demonstrates the practical applicability of this walker. Therefore, this approach presents a novel walking mechanism for walker development and offers a highly sensitive methodology for detecting pesticide residues in food, showing significant potential in food safety assessment, environmental pollution monitoring, and public health protection.