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Magnetic ionic liquids: interactions with bacterial cells, behavior in aqueous suspension, and broader applications


Previously, we demonstrated capture and concentration of Salmonella enterica subspecies enterica ser. Typhimurium using magnetic ionic liquids (MILs), followed by rapid isothermal detection of captured cells via recombinase polymerase amplification (RPA). Here, we report work intended to explore the broader potential of MILs as novel pre-analytical capture reagents in food safety and related applications. Specifically, we evaluated the capacity of the ([P66614+][Ni(hfacac)3]) (“Ni(II)”) MIL to bind a wider range of human pathogens using a panel of Salmonella and Escherichia coli O157:H7 isolates, including a “deep rough” strain of S. Minnesota. We extended this exploration further to include other members of the family Enterobacteriaceae of food safety and clinical or agricultural significance. Both the Ni(II) MIL and the ([P66614+][Dy(hfacac)4]) (“Dy(III)”) MIL were evaluated for their effects on cell viability and structure-function relationships behind observed antimicrobial activities of the Dy(III) MIL were determined. Next, we used flow imaging microscopy (FIM) of Ni(II) MIL dispersions made in model liquid media to examine the impact of increasing ionic complexity on MIL droplet properties as a first step towards understanding the impact of suspension medium properties on MIL dispersion behavior. Finally, we used FIM to examine interactions between the Ni(II) MIL and Serratia marcescens, providing insights into how the MIL may act to capture and concentrate Gram-negative bacteria in aqueous samples, including food suspensions. Together, our results provide further characterization of bacteria-MIL interactions and support the broader utility of the Ni(II) MIL as a cell-friendly capture reagent for sample preparation prior to cultural or molecular analyses.

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BFBS acknowledges financial support from the Midwest Dairy Association (MDA) and Iowa Agriculture and Home Economics Experiment Station Project No. IOW03902, sponsored by Hatch Act and State of Iowa funds. JLA acknowledges funding from the Chemical Measurement and Imaging Program at the National Science Foundation (CHE-1709372). We thank Dr. Gwynn Beattie, Iowa State University Department of Plant Pathology, for supervision of work with plant pathogens and Fluid Imaging Technologies, Inc., for collecting data on MIL droplets and VisualSpreadsheet® analysis advice.

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Correspondence to Byron F. Brehm-Stecher.

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Hice, S.A., Varona, M., Brost, A. et al. Magnetic ionic liquids: interactions with bacterial cells, behavior in aqueous suspension, and broader applications. Anal Bioanal Chem 412, 1741–1755 (2020).

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  • Magnetic ionic liquids
  • Cell capture
  • Cell concentration
  • Gram-negative bacteria
  • Enterobacteriaceae
  • Flow imaging microscopy