Liquid Crystal Chemical Sensors That Cells Can Wear

Abstract

Micrometer-scale droplets of thermotropic liquid crystals (LCs) suspended in aqueous media can act as exquisitely sensitive reporters of environmental analytes. [1][2][3][4][5][6][7][8] Aqueous emulsions of the nematic LC 4-cyano-4'-pentylbiphenyl (5CB), for example, can quantify exposure to bacterial endotoxin (a key component of the outer membranes of Gram-negative bacteria and a major cause of disease and contamination) at pg mL À1 concentrations. [4] The interaction of amphiphilic species with LC droplets promotes changes in orientational order that can be detected as changes in optical appearance [2,8] that reflect both the concentration and structure of the analyte. [2,4] The speed and sensitivity with which these changes occur, combined with the ease with which they can be detected using optical methods (e.g., polarized light microscopy), provide new principles for the design of dispersed, droplet-based sensors that can report on the presence of chemical and biological agents in aqueous solutions. [1][2][3][4][5][6][7][8] Here, we report the design of droplet-based LC sensors that can be immobilized directly on the surfaces of cells. We demonstrate that cells decorated with encapsulated LC droplets can report-in real-time and at the level of single droplets and individual cells-on the presence of toxic agents in surrounding media. This approach provides principles for the design of droplet-based LC sensors and methods for the local (mm scale) detection of agents in cellular environments in ways that are difficult to achieve in situ using free-floating LC droplets or other analytical methods. Our approach is based on the confinement of small droplets of nematic LC within covalently crosslinked, cell-adhesive polymer microcapsules.Our design incorporates several features important for the manipulation and immobilization of LC droplets in cellular environments: 1) encapsulation of LCs in polymeric microcapsules provides means to control LC droplet size, 2) sequestration of LC in a protective membrane prevents LC droplets from coalescing or wetting other surfaces (e.g., culture dishes) and can insulate cells from direct contact with the LC, 3) polymer capsules can be decorated with functionality that can interact with cell membranes to anchor droplets in specific locations, and 4) the use of capsules with semipermeable walls can protect the LC from contact with macromolecular components of culture media, while allowing smaller analytes to pass through unhindered. The work reported here demonstrates proof of concept and underscores the utility of these design features in the context of cell-based sensing using several different well-defined model systems.We selected the thermotropic LC known as E7 (Figure 1 A) here because it exhibits a nematic/isotropic transition temperature (ca. 60 8C) well above that used for mammalian Figure 1. A) Structures of E7 and HTAB. B, C) Schematic showing a SiO 2 particle coated with PEI/PVDMA multilayers (B) and reaction of azlactones to yield amine-functionalized coatings (C). E...

Broadband Circular Polarizing Film Based on Chiral Nematic Liquid Crystals

“…Magnified SEM images (Figure c 2 ) show that CNCs in the layers rotate with the helical axis parallel to the layer plane. This result may be attributed to an anchoring effect of surfactants on CNCs at the air–water interface . Because the helical axis is often perpendicular to the domain planes, the curved stacking direction in the distorted domains implies that the orientations of the helical axis (also the angle of the helical axis with respect to the normal of the film surface β) are also changed (illustrated in Figure S6a, Supporting Information).…”

Applications of metal ions and liquid crystals for multiplex detection of DNA

“…In the past, many chemical and biomolecular sensors based on the unique properties of LCs have been developed. For example, Abbott's group reported LC sensors for detecting peptides, lipids and other chemical compounds [2][3][4][5][6][7]. Other groups also developed a series of LC sensors for the detection of DNA, proteins and small molecules including thiol, amines and metal ions [8][9][10][11].…”

Theoretically informed Monte Carlo simulation of liquid crystals by sampling of alignment-tensor fields

“…[3][4][5] For many of these applications, it is essential to generate detailed theoretical and computational predictions of the system's structure and properties as a function of material characteristics, including any interfaces that may be used to control or manipulate the material's behavior. [6][7][8] Liquid crystals exhibit intriguing structural features at multiple lengths scales.…”