Bacterial contamination is a serious issue for public health and food safety. In this work, a simple and label-free fluorescence detection nanoplatform for Escherichia coli (E. coli) was established on the basis of the competitive relationship for the reduction of Cu²⁺ in CuS-BSA between E. coli and O-phenylenediamine (OPD). OPD could be directly oxidized by Cu²⁺ to produce 2,3-diaminophenazine (ox OPD) with fluorescence properties. When OPD was introduced into an aqueous solution containing CuS-BSA and E. coli, the oxidation of OPD was inhibited owing to the reduction of Cu²⁺ to Cu⁺/Cu⁰ by NADH-2 dehydrogenase in the bacterial copper homeostasis mechanism, thus decreasing the fluorescence response signal of the system. Meanwhile, our strategy exhibited a satisfactory performance with a broad linear response to E. coli ranging from 12 to 1.2 × 10⁷ CFU mL⁻¹, and the limit of detection was 9 CFU mL⁻¹. The practicability of the developed fluorescence biosensing platform in real samples was evaluated by successful determination of E. coli in drinking water and orange juice. These findings provide a new sensing strategy for analyzing other foodborne bacteria and ensuring food safety assessment.

中文翻译：

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基于 CuS-BSA 的大肠杆菌无标记荧光检测纳米生物传感平台


细菌污染是公共卫生和食品安全的一个严重问题。本工作基于大肠杆菌与邻苯二胺 （OPD） 之间还原 CuS-BSA 中 Cu²⁺ 的竞争关系，建立了一种简单且无标记的大肠杆菌 （E. coli） 荧光检测纳米平台。OPD 可被 Cu²⁺ 直接氧化，生成具有荧光特性的 2,3-二氨基吩嗪 （ox OPD）。当将 OPD 引入含有 CuS-BSA 和大肠杆菌的水溶液中时，由于细菌铜稳态机制中 NADH-2 脱氢酶将 Cu²⁺ 还原为 Cu⁺/Cu^0，OPD 的氧化受到抑制，从而降低了系统的荧光响应信号。同时，我们的策略表现出令人满意的性能，对大肠杆菌的广泛线性反应范围为 12 至 1.2 × 10⁷ CFU ^mL-1，检测限为 9 CFU ^mL-1。通过成功测定饮用水和橙汁中的大肠杆菌，评价了所开发的荧光生物传感平台在实际样品中的实用性。这些发现为分析其他食源性细菌和确保食品安全评估提供了一种新的传感策略。