Liquid Crystal Emulsions as the Basis of Biological Sensors for the Optical Detection of Bacteria and Viruses

Authors

  • Sri Sivakumar,

    1. Centre for Nanoscience and Nanotechnology Department of Chemical and Biomolecular Engineering The University of Melbourne Melbourne 3010 (Australia)
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  • Kim L. Wark,

    1. CSIRO Molecular and Health Technologies, CSIRO Parkville, Victoria 3052 (Australia)
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  • Jugal K. Gupta,

    1. Department of Chemical and Biological Engineering University of Wisconsin-Madison Madison, WI 53706 (USA)
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  • Nicholas L. Abbott,

    Corresponding author
    1. Department of Chemical and Biological Engineering University of Wisconsin-Madison Madison, WI 53706 (USA)
    • Department of Chemical and Biological Engineering University of Wisconsin-Madison Madison, WI 53706 (USA).
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  • Frank Caruso

    Corresponding author
    1. Centre for Nanoscience and Nanotechnology Department of Chemical and Biomolecular Engineering The University of Melbourne Melbourne 3010 (Australia)
    • Centre for Nanoscience and Nanotechnology Department of Chemical and Biomolecular Engineering The University of Melbourne Melbourne 3010 (Australia).
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Abstract

A versatile sensing method based on monodisperse liquid crystal (LC) emulsion droplets detects and distinguishes between different types of bacteria (Gram +ve and −ve) and viruses (enveloped and non-enveloped). LCs of 4-cyano-4'-pentylbiphenyl transition from a bipolar to radial configuration when in contact with Gram −ve bacteria (E. coli) and lipid-enveloped viruses (A/NWS/Tokyo/67). This transition is consistent with the transfer of lipid from the organisms to the interfaces of the micrometer-sized LC droplets. In contrast, a transition to the radial configuration is not observed in the presence of Gram +ve bacteria (Bacillus subtilis and Micrococcus luteus) and non-enveloped viruses (M13 helper phage). The LC droplets can detect small numbers of E. coli bacteria (1–5) and low concentrations (104 pfu mL−1) of A/NWS/Tokyo/67 virus. Monodisperse LC emulsions incubated with phosholipid liposomes (similar to the E. coli cell wall lipid) reveal that the orientational change is triggered at an area per lipid molecule of ∼46 Å2 on an LC droplet (∼1.6 × 108 lipid molecules per droplet). This approach represents a novel means to sense and differentiate between types of bacteria and viruses based on their cell-wall/envelope structure, paving the way for the development of a new class of LC microdroplet-based biological sensors.

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