Magnetic trapping has been employed in the development of analytical methods owing to its ease and simplicity in handling samples. Nevertheless, the generation of functional probes is usually time consuming. A new and simple affinity method that uses gadolinium ion (Gd3+), a magnetic ion, as affinity probe for magnetic tapping of pathogenic bacteria was demonstrated in the present study. Escherichia coli O157:H7, Staphylococcus aureus, and Acinetobacter baumannii were selected as model bacteria. The model bacteria were magnetically isolated after incubation in Tris buffer (pH 8) containing Gd3+ (0.1 M) under microwave heating (power: 180 W, 90 s × 3). The resultant Gd3+-bacterium conjugates possessed sufficient magnetism, resulting in magnetic aggregations by an external magnet (∼4,000 Gauss). For ease of magnetic isolation, the sample containing Gd3+-bacterium complexes was stirred by a small magnet. After 1 h, the magnet attached with precipitates, i.e., Gd3+-bacterium conjugates, was readily removed using a pair of tweezers. The bacteria in the resultant conjugates were characterized by matrix-assisted laser desorption/ionization mass spectrometry. The limits of detection of the current approach toward E. coli O157:H7, S. aureus, and A. baumannii in complex samples were ∼104-105 cells mL-1.

中文翻译：

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使用钆离子作为亲和探针从复杂样品中选择性地富集和磁性分离细菌

磁捕集因其易于处理样品而被用于开发分析方法。然而，功能探针的生成通常是耗时的。本研究展示了一种新的简单的亲和方法，它使用钆离子 (Gd3+)，一种磁性离子，作为对病原菌进行磁攻的亲和探针。选择大肠杆菌O157:H7、金黄色葡萄球菌和鲍曼不动杆菌作为模型菌。在微波加热（功率：180 W，90 s × 3）下，在含有 Gd3+（0.1 M）的 Tris 缓冲液（pH 8）中孵育后，模型细菌被磁性分离。所得的 Gd3+-细菌结合物具有足够的磁性，通过外部磁铁（~4,000 高斯）导致磁性聚集。为了便于磁隔离，用小磁铁搅拌含有 Gd3+-细菌复合物的样品。1 小时后，附着有沉淀物（即 Gd3+-细菌缀合物）的磁体可以使用一对镊子轻松去除。通过基质辅助激光解吸/电离质谱法表征所得缀合物中的细菌。当前方法对复杂样品中大肠杆菌 O157:H7、金黄色葡萄球菌和鲍曼不动杆菌的检测限为 ~104-105 个细胞 mL-1。