快速检测沙门氏菌对保障食品安全具有重要意义，样本前处理是制约快速检测发展的瓶颈问题之一。适配体磁分离是极具发展前景的快速分离技术，但在食品基质中分离效果不佳。调控多价适配体与其靶点精准匹配可显著提高复杂基质中目标物的分离效率，但对分离食品基质中沙门氏菌的增强效果及机理尚未明晰。本项目拟结合DNA的可编程性，构建DNA精准调控的四面体多价单元和线性多价适配体，从亲和力、动力学及热力学等多方面考察多价适配体结构的靶点匹配程度与多价作用的关系，评估食品基质成分对多价适配体与靶点匹配程度的影响，阐明DNA精准调控的多价适配体高效分离食品中沙门氏菌的机理，结合磁分离技术，实现食品中沙门氏菌的高效分离。本项目将为食品中沙门氏菌快速检测提供新的样本处理方法，也为复杂食品基质中目标物的高效分离提供理论指导和技术参考。

Sensitive and rapid detection of Salmonella plays a vital role in food safety. Sample pretreatment is one of the greatest challenges for rapid detection of Salmonella. Aptamer based magnetic separation is a promising food sample pretreatment method, but the separation efficiency is poor in food sample. It is reported that the precisely match of multivalent aptamers with their binding sites can significantly enhance the separation efficiency in complex background. However, there are few studies on magnetic separation of foodborne pathogens based on the precisely controlled multivalent aptamers. The enhancement in separation efficiency and their mechanism are still unclear. This project intends to develop a DNA tetrahedron based trivalent aptamers and assemble them into line multivalent aptamers nanostructures (LMANs), which are spatially and precisely controlled to match the target protein units on the surface of Salmonella. All factors precisely control LMANs are evaluated to clarify relationship between their avidities and the match degrees of LMANs and their binding sites. The influences of different food components on the avidities of LMANs are also studied to elucidate mechanism of the separation efficiency improvement by LMANs in food matrix. According to the enhancement mechanism, magnetic separation based on LMAN is developed to separate Salmonella in food with a high separation efficiency. This study can provide a useful theoretical basis and promising strategy for separation of Salmonella in food sample.