Upconversion nanoparticles, Yb,Tm,Fe-doped NaYF4 nanoparticles, are synthesized and modified with polymyxin B for the selective detection of Gram-negative bacteria. Polymyxin B, a cyclic cationic antimicrobial peptide which can specifically bind to the lipopolysaccharides of cell wall of Gram-negative bacteria, such as Escherichia coli, is used to target and bind Gram-negative bacteria. The bacteria are then quantified by measuring the fluorescence intensity of the upconversion nanoparticle–bacteria complexes at 801 nm under 980 nm excitation. A limit of detection of 36 CFU/mL is achieved in the detection of Escherichia coli, and Escherichia coli in soybean milk is successfully detected. The limited autofluorescence and photobleaching properties of the upconversion nanoparticles make the proposed method useful for in vivo fluorescence imaging of Gram-negative bacteria.

中文翻译：

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多粘菌素 B 修饰的上转换纳米粒子用于选择性检测革兰氏阴性菌，如大肠杆菌

上转换纳米粒子 Yb、Tm、Fe 掺杂的 NaYF4 纳米粒子合成并用多粘菌素 B 修饰，用于选择性检测革兰氏阴性菌。多粘菌素 B 是一种环状阳离子抗菌肽，可与革兰氏阴性菌（如大肠杆菌）细胞壁的脂多糖特异性结合，用于靶向结合革兰氏阴性菌。然后通过在 980 nm 激发下测量 801 nm 上转换纳米颗粒 - 细菌复合物的荧光强度来量化细菌。大肠杆菌检测达到36 CFU/mL的检出限，成功检出豆奶中的大肠杆菌。