Liquid Crystal‐Based Detection of Antigens with ELISA Sensitivity

Abstract

A highly sensitive label‐free liquid crystal (LC)‐based technique is presented for detecting Immunoglobulin G (IgG) antigens used to uncover viral infections. The effectiveness, sensitivity, and selectivity of this detection method is demonstrated with goat IgG antigen at concentrations as low as 100 pg ml−1, which is comparable to the sensitivity of the current enzyme‐linked immunosorbent assay (ELISA). The sensor is fabricated by decorating a transmission electron microscopy grid immobilized glass surfaces with antibodies; the target antigen is detected by a liquid crystal suspended onto the grid. This is different from previous methods where the antigen is detected either at the LC‐aqueous interface or in an LC sandwich cell with an antibody/antigen‐decorated substrate. This new approach has advantages such as easy sample preparation, higher sensitivity, and better storage capabilities. Binding the target antigen to the antibody results in a reorientation of the LC director that is detected optically. In addition to demonstrating the sensitivity, the physical principle of the detection is also discussed. This technique may apply to detect virtually any antigen of interest.

Heads or tails: investigating the effects of amphiphile features on the distortion of chiral nematic liquid crystal droplets

“…This is due to the high sensitivity of their alignment to the surroundings together with a clear optical feedback, 2,3 indicating the presence of analytes that induce an alignment and ordering change. [4][5][6][7][8][9][10][11][12][13][14] When chiral nematic (or cholesteric) liquid crystals (CLCs) -which have an additional helical modulation along with the long-range orientational order -are used, different textures can emerge. 15 By using CLC materials with a pitch on the same order as the wavelength of visible light, this response can manifest itself in the form of strongly reflected colors that can be seen by the unaided eye.…”

“…9,13,16,20 On the other hand, amphiphile sensing typically looks at a change in the alignment and orientation of the LC induced by the adsorption of a surface-active molecule at the interface. 5,18,[21][22][23][24] Other variants of amphiphile adsorption can also use binding events between antibodies and antigens which disrupt the orientation of the LC to detect macromolecules and proteins, 6,12,25,26 using a distortion or disruption in the texture to identify the presence or introduction of a target analyte.…”

“…Long known for their use in display applications 1 , liquid crystals (LCs) have become increasingly popular for biological sensing applications. This is due to the high sensitivity of their alignment to the surroundings together with a clear optical feedback 2,3 , indicating the presence of analytes that induce an alignment and ordering change [4][5][6][7][8][9][10][11][12][13][14] . When chiral nematic (or cholesteric) liquid crystals (CLCs) -which have an additional helical modulation along with the long-range orientational order -are used, different textures can emerge 15 .…”

“…A common question when using any LC-based sensors is how the output signal can be interpreted and translated into information about the system and what conditions can switch the LC alignment. Commonly, when using non-chiral nematic LCs, this is in the form of using the LC as a binary on-off switch, where a change in alignment 8,12,14,22,[25][26][27][28] or the loss of liquid crystalline ordering altogether 9,13,16,27 will indicate the presence or absence of an event. Some chiral nematic LC materials will additionally function as an on-off switch, most commonly in quickread temperature applications [29][30][31] .…”

A room temperature 9CB‐based chemical sensor

“…As a consequence, liquid crystals are deemed a fascinating class of functional and responsive materials, which can be used as probes to detect and translate events at the molecular level into measurable outputs and hence find use within a wide variety of technological applications, [ 1–9 ] namely in liquid crystal‐assisted chemical and biological sensing technologies. [ 6,10–23 ] The most commonly used liquid crystal sensor geometries include liquid crystal confinement in thin films with a free surface, [ 24–28 ] droplets, [ 29–36 ] and fibers. [ 37–41 ]…”