An ultra-sensitive fluorescent biosensor based on CDs/QDs@ZIF-8 and microfluidic fluidized bed was developed for rapid and ultra-sensitive detection of multiple target bacteria. The zeolitic imidazolate frameworks (ZIF-8) act as the carrier to encapsulate three kinds of fluorescence signal molecules from the CDs/QDs@ZIF-8 signal amplification system. Besides, three kinds of target pathogenic bacteria were automatically, continuously, and circularly captured by the magnetic nanoparticles (MNPs) in the microfluidic fluidized bed. The neutral Na₂EDTA solution was the first time reported to not only dissolve the ZIF-8 frameworks from the MNPs-bacteria-CDs/QDs@ZIF-8 sandwich complexes, but also release the CDs/QDs from sandwich complexes with no loss of fluorescence signal. Due to the advantages of signal amplification and automated sample pretreatment, the proposed fluorescent biosensor can simultaneously detect Escherichia coli O157:H7, Salmonella paratyphi A, and Salmonella paratyphi B as low as 10¹ CFU/mL within 1.5 h, respectively. The mean recovery in spiked milk samples can reach 99.18%, verifying the applicability of this biosensor in detecting multiple bacteria in real samples.

Graphical Abstract

中文翻译：

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基于CDs/QDs@ZIF-8和微流化床的超灵敏多种细菌检测荧光生物传感器

开发了一种基于CDs/QDs@ZIF-8和微流化床的超灵敏荧光生物传感器，用于快速、超灵敏地检测多种目标细菌。沸石咪唑酯骨架（ZIF-8）作为载体封装来自CDs/QDs@ZIF-8信号放大系统的三种荧光信号分子。此外，微流化床中的磁性纳米粒子（MNP）自动、连续、循环地捕获三种目标病原菌。首次报道中性Na ₂ EDTA溶液不仅可以溶解MNPs-bacteria-CDs/QDs@ZIF-8夹心复合物中的ZIF-8框架，而且还可以从夹心复合物中释放CDs/QDs，并且不会损失荧光信号。由于信号放大和自动化样品预处理的优点，所提出的荧光生物传感器可以 在1.5小时内同时检测大肠杆菌O157:H7、甲型副伤寒沙门氏菌和乙型副伤寒沙门氏菌，分别低至10 ¹ CFU/mL。加标牛奶样品的平均回收率可达99.18%，验证了该生物传感器在检测实际样品中多种细菌的适用性。

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