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

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.

Tuning the defect configurations in nematic and smectic liquid crystalline shells

“…This stabilizes the interface and prevents shell rupture, but, owing to the disordered polymer chain, it does not necessarily have a strong impact on the LC alignment. The resulting planar alignment is instead probably a result of the contact with the polar water phase, which is known to induce planar alignment [20]. The Pluronics F-127 surfactant has turned out to be compatible with planar as well as homeotropic alignment, and we found opposite results for nematic and smectic phases [19].…”

A new era for liquid crystal research: Applications of liquid crystals in soft matter nano-, bio- and microtechnology

“…The liquid crystal amplifies the binding event such that it becomes easily visible on a microscopic scale. The concept is most often applied to planar liquid crystal samples but also liquid crystal droplets were successfully used for detecting bacteria and viruses [309]. While most biodetectors require fluorescent tagging or labeling of key molecules, this is unnecessary with the liquid crystal-based detection technique.…”

Determination of Concentrations of Surface-Active Materials in Aqueous Solutions at Different pH Values Using Liquid Crystals

“…It was demonstrated that LC sensors are capable of determining chemicals that can be present as gases [1], identifying biological molecules (proteins, oligopeptides, immunoglobulins and nucleic acids) [2,3,4] sensing low concentrations of surfactants, lipids and charged molecules [5,6], single and double stranded DNA fragments on solid surfaces [7]. LC sensors were used for identification of viruses, bacteria and mammalian cells [8,9] and so on.…”