Overview of Liquid Crystal Biosensors: From Basic Theory to Advanced Applications

Abstract

Liquid crystals (LCs), as the remarkable optical materials possessing stimuli-responsive property and optical modulation property simultaneously, have been utilized to fabricate a wide variety of optical devices. Integrating the LCs and receptors together, LC biosensors aimed at detecting various biomolecules have been extensively explored. Compared with the traditional biosensing technologies, the LC biosensors are simple, visualized, and efficient. Owning to the irreplaceable superiorities, the research enthusiasm for the LC biosensors is rapidly rising. As a result, it is necessary to overview the development of the LC biosensors to guide future work. This article reviews the basic theory and advanced applications of LC biosensors. We first discuss different mesophases and geometries employed to fabricate LC biosensors, after which we introduce various detecting mechanisms involved in biomolecular detection. We then focus on diverse detection targets such as proteins, enzymes, nucleic acids, glucose, cholesterol, bile acids, and lipopolysaccharides. For each of these targets, the development history and state-of-the-art work are exhibited in detail. Finally, the current challenges and potential development directions of the LC biosensors are introduced briefly.

Keywords: active optical components; biosensor; liquid crystal; optical sensing.

Figure 2

Different liquid crystal biosensors used for detecting enzymes: (a) detecting carboxylesterase using surfactant-doped liquid crystal biosensor [127]; reproduced with permission from Elsevier; (b) the sensing mechanism of the CLC/PAA IPN with urease detection property [129]; reproduced with permission from Wiley; (c) the fabrication and detection processes of the liquid crystal thrombin sensor based on Au nanoparticles [120]; reproduced with permission from the American Chemical Society; (d) schematic diagram of the experimental platform that measuring the LC penicillinase sensor by the WGM lasing [132]; reproduced with permission from Elsevier.

Figure 3

Different liquid crystal biosensors used for detecting nucleic acids: (a) schematic illustration of the liquid crystal nucleic acid sensor before and after detecting DNA [121]; reproduced with permission from Royal Society of Chemistry; (b) two strategies of introducing streptavidin to the liquid crystal nucleic sensor to increasing the contrast [136]; reproduced with permission from the American Chemical Society; (c) DNA hybridization-mediated liposome fusion at the aqueous–liquid crystal interface [137]; reproduced with permission from Wiley; (d) liquid crystal-based naked-eye home detection kit for detecting RNA of the SARS-CoV-2 [141]; reproduced with permission from Elsevier.

Figure 4

Different liquid crystal biosensors used for detecting proteins: (a) imaging the protein-induced phospholipid disruption using a liquid crystal protein sensor [142]; reproduced with permission from Elsevier; (b,c) the fabrication process and reversible detection property of the liquid crystal protein sensor based on the thermal responsive PNIPAAm [147]; reproduced with permission from Royal Society of Chemistry; (d) schematic representation of liquid crystal immunosensor sensor based on the ionic liquid crystals [150]; reproduced with permission from Elsevier; (e) schematic illustration of the dye liquid crystal-based biosensing platform [154]; reproduced with permission from Elsevier.

Figure 5

Advanced applications of liquid crystal protein sensors: (a) liquid crystal biosensor enabled identification of secondary structure of proteins [158]; reproduced with permission from the American Chemical Society; (b,c) the clinical diagnosis using the liquid crystal tuberculosis sensor [159]; reproduced with permission from the American Chemical Society; (d) molecular dynamics simulation study of protein binding at the liquid crystal–aqueous interfaces [160]; reproduced with permission from the American Chemical Society; (e) unveiling the lipid–protein interactions that drive the reorientation at the LC–droplet interface using the atomistic simulations [161]; reproduced with permission from the American Chemical Society.

Figure 6

Different liquid crystal biosensors used for detecting glucose, cholesterol, Lipopolysaccharides, and bile acids: (a) pH responsive liquid crystal droplets used for detecting glucose and cholesterol [163]; reproduced with permission from the American Chemical Society; (b) liquid crystal lipopolysaccharides sensor based on the interaction of lipopolysaccharides with peptidoglycan and lipoteichoic acid [171]; reproduced with permission from Elsevier; (c) the LC biosensor for rapid and precise recognition of the interaction of LPS with PG and LTA [174]; reproduced with permission from Royal Society of Chemistry.

Figure 1

Schematic showing the overall outline of this review, including the mesophases, mechanisms, geometries and detection targets of the LC biosensor.