核酸适体是能对其靶标进行高亲和力和强特异性结合的分子识别元件，其传感技术的关键是如何将适体的识别机理转变为可检测信号。本项目针对动物性食品中常见抗生素残留，结合适体特异性识别和量子点-金属纳米粒子荧光共振能量转移（FRET）的优势，设计核酸适体结构开关。用磁性纳米粒子/量子点和金属纳米粒子分别修饰互补核酸片段，适体与靶标的特异性结合打开适体-互补核酸双链从而改变FRET效率，结合磁性纳米粒子的分离富集和Exo III酶切循环信号放大，建立“turn-on”荧光法检测抗生素；探索利用光谱性质显著差异的量子点-金属纳米粒子构建多重FRET，实现抗生素多残留分析；研究目标物识别过程中适体开关的结构转换，探索核酸适体特异性识别抗生素靶分子的作用机理及构象变化。本研究阐明小分子核酸适体结构开关的设计和工作机制，对拓展设计策略的通用性有重要意义，为将适体传感器用于检测复杂食品基质中的危害因子奠定基础。

Aptamer is a kind of molecular recognition element which can combine with its target with high affinity and specificity. The key technology in aptamer-based biosensors lies in how to translate the recognition mechanism into a detectable signal. In this project, structure-switching aptamers would be designed aiming at the analysis of common antibiotic residues in animal derived food, which utilizes the specific recognition of aptamers and the advantages of fluorescence resonance energy transfer (FRET) between quantum dots and metal nanoparticles. Magnetic nanoparticles/quantum dots and metal nanoparticles are respectively used to modify the complementary DNA fragments. The specific binding of the target to the aptamer could open the aptamer-complementary DNA double strands to alter the FRET efficiency. Thus, in combination with the separation and enrichment of magnetic nanoparticles and Exo III enzymatic circulation signal amplification technology, the “turn-on” fluorescence detection of antibiotic residues would be established. The multiple FRET will be explored to bulid using quantum dots - metal nanoparticles with significantly different optical properties, in order to realize simultaneous detection of many kinds of antibiotic residues. Moreover, researches will be focused on the structure transformation of structure-switching aptamers in the process of target recognition, and the different mechanism and conformational changes involved in the specific recognition of aptamers with the antibiotic targets. This project would be helpful to clarify the design and working mechanism of structure-switching aptamers for small molecules. It has important significance for the the versatility extension of the design strategy of structure-switching aptamers, and will contribute to the application of aptasensors in the detection of hazard factors in complex food.