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An on-site bacterial detection strategy based on broad-spectrum antibacterial ε-polylysine functionalized magnetic nanoparticles combined with a portable fluorometer

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A sensitive on-site bacterial detection strategy is presented that integrates the broad-spectrum capturing feature of ε-polylysine-functionalized magnetic nanoparticles with an in-house built portable fluorometer. Based on the electrostatic interaction, the functionalized magnetic nanoparticles (ε-PL-MNPs) were prepared for Gram-positive and Gram-negative bacterial separation and subsequent viable release. ε-PL-MNPs show a broad reactivity towards bacteria with the high capture efficiency from real-world sample media. They also enable controlled viable bacterial release with pH adjustment. Detection of bacteria is based on a combination of broad-spectrum capture with colorimetric and fluorimetric immunoassays. A portable fluorometer is built to enhance the applicability for sensitive on-site detection. A limit of detection of 98 CFU·mL−1 is achieved that is comparable to that of a known spectrofluorometric method for E. coli DH5α.

Schematic presentation of bacterial capture using cationic polymer functionalized magnetic nanoparticles and general fluorometric immunoassay with portable fluorometer. The limit of detection is 98 CFU·mL−1 for E. coli DH5α.

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This work was supported by the National Natural Science Foundation of China (No. 21535006 and 21475004).

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Correspondence to Na Li.

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The characterizations of TEM and zeta potentials of MNPs, ε-PL-MNP and PEI-MNPs. The effect of pH, incubation times and ionic strength on capture efficiency of ε-PL-MNP and PEI-MNPs. The culture results of capture efficiency of ε-PL-MNPs and PEI-MNPs at low concentrations. The optimization of colorimetric and fluorescent immunoassay conditions. The calibration plot between fluorescence intensity versus the concentration of Shigella flexneri and Staphylococcus aureus, respectively. General protocol with an unknown sample. An overview on recently reported nanomaterial-based methods for determination of bacteria.


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Wu, X., Lai, T., Jiang, J. et al. An on-site bacterial detection strategy based on broad-spectrum antibacterial ε-polylysine functionalized magnetic nanoparticles combined with a portable fluorometer. Microchim Acta 186, 526 (2019).

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