食源性单核细胞增生李斯特菌（单增李斯特菌）引发的食品安全问题日益严重，寻求快速灵敏的检测方法对保障人体健康、减少经济损失具有重要意义。该研究研发了一种过氧化氢（H2O2）介导的Au-Fe3O4磁探针组装策略，并基于此，构建了一种用于单增李斯特菌快速检测的磁弛豫免疫传感方法。H2O2能够将银离子还原为银单质，而银单质沉积到Au部分的表面，进而将分散的Au-Fe3O4磁探针组装为聚集状态，从而引起横向弛豫时间（T2）的变化。结合免疫反应，单增李斯特菌浓度决定辣根过氧化物酶（HRP）-抗体的含量，而HRP能够调控H2O2浓度，进而调控Au-Fe3O4磁探针组装程度，引起T2信号的改变，从而实现单增李斯特菌的定量检测。本方法检测单增李斯特菌的灵敏度为50 CFU/mL，线性范围为102 CFU/mL~106 CFU/mL，回收率为79.4%~105.9%，在火腿中单增李斯特菌的检测中与荧光定量PCR方法一致性良好。该研究所构建的Ag@Au-Fe3O4-MRS免疫传感器具有灵敏度高、稳定性好、方法简单、特异性强的优点，对食源性致病菌的快速检测提供了有力的工具。

With the food safety problems caused by foodborne Listeria monocytogenes becoming increasingly widespread and severe, the development of rapid and sensitive methods for detecting the pathogen will have great significance in ensuring the protection of human health and reducing economic losses. Here, we describe the development of a hydrogen peroxide-mediated Au-Fe3O4 magnetic nanoprobe assembly strategy to construct a magnetic relaxation switching (MRS) immunosensor for the rapid detection of foodborne L. monocytogenes. Hydrogen peroxide reduces the silver ions to elemental silver atoms, which then deposit on the surface of the gold atoms in the probe. This causes the assembly of the dispersed Au-Fe3O4 probes into an aggregated state, leading to a change in the transverse relaxation time (T2). During the immunoreaction, the content of horseradish peroxidase (HRP)-conjugated antibody is determined using the concentration of L. monocytogenes. Consequently, the HRP content regulates the hydrogen peroxide concentration, which in turn regulates the degree of Au-Fe3O4 probe assembly. Thus, the resultant change in the T2 signal based on the degree of nanoprobe assembly enables the quantitative detection of L. monocytogenes. This method achieved a sensitivity of 50 CFU/mL, a linear range of 102~106 CFU/mL, and a recovery rate range of 79.4%~105.9% in the detection of L. monocytogenes. When used to quantify the pathogen in ham, the nanoprobe assay returned results that were highly consistent with those obtained using quantitative PCR. Given its high sensitivity and specificity, good stability, and ease of use, this Ag@Au-Fe3O4-MRS immunosensor should be a powerful tool for the rapid detection of foodborne pathogens.

国家重点研发计划项目（2019YFC1605502）；岭南现代农业实验室自主科研项目（NZ2021036）