Detection of pathogens present in food and water is essential to help ensure food safety. Among the popular methods for pathogen detection are those based on culture and colony-counting and polymerase chain reaction (PCR). However, the time-consuming nature and/or the need for sophisticated instrumentation of those methods limit their on-site applications. We have developed a rapid and highly sensitive immunosensing method for visible detection of bacteria in real matrices based on the aggregation of AuNPs without requiring any readout device. We use biotinylated anti-bacteria antibodies as bifunctional linkers (BLs) to mediate the aggregation of streptavidin-functionalized gold nanoparticles (st-AuNPs) to produce visually recognizable color change, due to surface plasmon resonance (SPR), which occurs in about 30 min of total assay time when the sample is mildly agitated or within three hours in quiescent conditions. The aggregation of st-AuNPs, which produces the indication signal, is achieved very differently than in visual detection methods reported previously and hence affords ultrahigh sensitivity. While BLs can both bind to the target and crosslink st-AuNPs, their latter function is essentially disabled when they bind to the target bacteria. By varying the amount of st-AuNPs used, we can tailor the assay effectiveness improving limit of detection (LOD) down to 10 CFU mL⁻¹ of E. coli and Salmonella. Test results obtained with tap water, lake water and milk samples show that assay performance is unaffected by matrix effects. Further, in a mixture of live and autoclaved E. coli cells our assay could detect only live cells. Therefore, our BL-based immunosensor is suitable for highly sensitive, rapid, and on-site detection of bacteria in real matrices.

检测食物和水中存在的病原体对于确保食品安全至关重要。流行的病原体检测方法包括基于培养和菌落计数以及聚合酶链反应（PCR）的方法。然而，这些方法的费时性质和/或对这些方法的精密仪器的需求限制了它们的现场应用。我们已经开发了一种快速且高度灵敏的免疫传感方法，基于AuNPs的聚集，可以在可见的矩阵中可视检测细菌，而无需任何读出设备。由于表面等离振子共振（SPR），我们使用生物素化的抗菌素抗体作为双功能接头（BLs）来介导链霉亲和素功能化的金纳米颗粒（st-AuNPs）的聚集，以产生视觉上可识别的颜色变化，当样品被轻度搅动或在静态条件下的三个小时内，大约在总测定时间的30分钟内发生。与先前报道的视觉检测方法相比，产生指示信号的st-AuNP的聚集非常不同，因此具有超高的灵敏度。虽然BLs既可以与靶标st-AuNP结合，也可以与它们交联，但是当它们与靶标细菌结合时，它们的后一种功能基本上被禁用。通过改变使用的st-AuNPs的数量，我们可以调整分析效率，从而将检测限（LOD）降低至10 CFU mL 虽然BLs既可以与靶标st-AuNP结合，也可以与它们交联，但是当它们与靶标细菌结合时，它们的后一种功能基本上被禁用。通过改变使用的st-AuNPs的数量，我们可以调整分析效率，从而将检测限（LOD）降低至10 CFU mL 虽然BLs既可以与靶标st-AuNP结合，也可以与它们交联，但是当它们与靶标细菌结合时，它们的后一种功能基本上被禁用。通过改变使用的st-AuNPs的数量，我们可以调整分析效率，从而将检测限（LOD）降低至10 CFU mL^-1的大肠杆菌和沙门氏菌。用自来水，湖水和牛奶样品获得的测试结果表明，测定性能不受基质效应的影响。此外，在活的和高压灭菌的大肠杆菌细胞的混合物中，我们的测定法只能检测到活细胞。因此，我们的基于BL的免疫传感器适用于高灵敏度，快速和现场检测真实基质中的细菌。