食品农药残留是我国乃至世界上最突出的食品安全问题之一，而现有检测方法难以满足快速检测需求。核酸适配体和四链体DNAzyme等功能核酸，因稳定性高、修饰方便、易于转化为信号输出等优点，在检测领域得到广泛应用。但目前基于功能核酸的农药残留检测很少用到信号放大策略，且可用于信号放大的四链体DNAzyme局限于G-四链体DNAzyme，这为基于功能核酸的农药残留检测留下极大改进空间。项目从选择合适的i-motif形成序列及其配体入手，构建新型i-motif DNAzyme并探究其催化性能和机理，然后基于靶标农药分子分别与DNAzyme配体、i-motif结构及DNAzyme反应底物作用，引起i-motif DNAzyme催化性能发生的变化，建立果蔬中常用农药残留快速检测新方法。项目的实施，将研制一类高催化活性DNAzyme，赋予功能核酸更广的应用潜能，为我国食品农药残留检测提供理论依据和技术支撑。

Pesticide residue is one of the most prominent food safety problems in China and even in the world. The existing pesticide detection methods are difficult to meet the demand of rapid detection. Functional nucleic acids (FNAs) such as aptamer and quadruplex-based DNAzyme have been widely used in the field of analysis and detection, due to their advantages of high stability, convenient modification and easy conversion to signal output. However, currently the signal amplification strategy has been seldom used in the FNAs-based pesticide detection methods, and quadruplex-based DNAzyme which can be applied in signal amplification is still limited in G-quadruplex/hemin DNAzyme. These shortages leave great room for improvement of FNAs-based pesticide residue detection. In this project, novel i-motif DNAzyme will be constructed by selecting appropriate C-rich ssDNA sequences that can form into C-quadruplex (i.e. i-motif) and its ligands. After the catalytic performance and mechanism of the constructed i-motif DNAzyme been studied, applications of it in detection of pesticide residues in fruits and vegetables will be considered through utilizing its obviously changed catalytic performance that originated from the interactions between the target pesticides and the ligands, the i-motif structures or the DNAzyme substrates, respectively. With the implementation of the project, a class of DNAzyme with high catalytic activity will be developed, wider application potential of FNAs will be endowed, and theoretical basis as well as technical support for the detection of pesticide residues in food in China will be provided.