Theory of biomolecular interactions at phospholipid-decorated surfaces of liquid crystals

Rapid, label-free and low-cost diagnostic kit for COVID-19 based on liquid crystals and machine learning

We report a label-free method for detection of the SARS-CoV-2 virus in nasopharyngeal swab samples without purification steps and multiplication of the target which simplifies and expedites the analysis process. The kit consists of a textile grid on which liquid crystals (LC) are deposited and the grid is placed in a crossed polarized microscopy. The swab samples are subsequently placed on the LCs. In the presence of a particular biomolecule, the direction of LCs changes locally based on the properties of the biomolecule and forms a particular pattern. As the swab samples are not perfectly purified, image processing and machine learning techniques are employed to detect the presence of specific molecules or quantify their concentrations in the medium. The method can differentiate negative and positive COVID-19 samples with an accuracy of 96% and also differentiate COVID-19 from influenza types A and B with an accuracy of 93%. The kit is portable, simple to manufacture, convenient to operate, cost effective, rapid and sensitive. The simplicity of the specimen processing, the speed of image acquisition, and fast diagnostic operations enable the deployment of the proposed technique for performing extensive on-spot screening of COVID-19 in public places.

Applications of liquid crystals in biosensing

Liquid crystals (LCs), as a promising branch of highly-sensitive, quick-response, and low-cost materials, are widely applied to the detection of weak external stimuli and have attracted significant attention. Over the past decade, many research groups have been devoted to developing LC-based biosensors due to their self-assembly potential and functional diversity. In this paper, recent investigations on the design and application of LC-based biosensors are reviewed, based on the phenomenon that the orientation of LCs can be directly influenced by the interactions between biomolecules and LC molecules. The sensing principle of LC-based biosensors, as well as their signal detection by probing interfacial interactions, is described to convert, amplify, and quantify the information from targets into optical and electrical parameters. Furthermore, commonly-used LC biosensing targets are introduced, including glucose, proteins, enzymes, nucleic acids, cells, microorganisms, ions, and other micromolecules that are critical to human health. Due to their self-assembly potential, chemical diversity, and high sensitivity, it has been reported that tunable stimuli-responsive LC biosensors show bright perspectives and high superiorities in biological applications. Finally, challenges and future prospects are discussed for the fabrication and application of LC biosensors to both enhance their performance and to realize their promise in the biosensing industry.

Construction and Biocompatibility of Three-Dimensional Composite Polyurethane Scaffolds in Liquid Crystal State

Liquid crystal (LC), a characteristic substance of biofilms, has been reported to positively affect cell affinity. To better combine and utilize the properties of an LC and the advantages of polyurethane (PU) elastomers, the three-dimensional printing (3DP) molding technology and the simple soaking-swelling blending technology were used to construct PU/LC 3D composite scaffolds, and the compressive strength, porosity, hydrophilicity, and in vitro cell experiments of the scaffolds were initially discussed. The results indicated that the newly developed PU/LC 3D composite scaffolds exhibited an LC state; the addition of an LC did not change the porosity after swelling while maintaining a high porosity; the compressive strength of the composite scaffolds decreased while still maintaining high mechanical properties and enhancing hydrophilicity. At the same time, it could improve the cell affinity on the surface of the material, which was beneficial to increase the cell adhesion rate and cell activity, promote the osteogenic differentiation of human mesenchymal stem cells grown on the materials, and improve the alkaline phosphatase activity, calcium nodules, and the expression of related osteogenic genes and proteins. These results demonstrated potential applications of PU/LC composite scaffolds in repairing or regeneration of bone tissue engineering.