Diagnosis of tuberculosis using a liquid crystal-based optical sensor

Abstract

In this study, we developed an advanced liquid crystal (LC)-based biosensor using polymeric surfaces to detect anti-tuberculosis antibodies, specifically in solution. To manufacture the anisotropic nanostructures, poly (dimethylsiloxane) was stretched and subsequently relieved. Before the deposition of a gold film, the nanostructures were replicated on poly(urethane acrylate)-coated silica substrates. Then, tuberculous antigens (ESAT-6) were immobilized onto the surfaces previously treated via N-hydroxysuccinimide (NHS)/N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) chemistry. The LCs (4-cyano-4'-pentylbiphenyl, 5CB), which aligned in parallel with the plane of the antigen-immobilized surface, showed a uniform appearance. However, after incubation of the anti-tuberculosis antibody (anti-ESAT-6) on the antigen-immobilized surface, 5CB showed a random appearance that corresponded to its random orientation. In control experiments, the tuberculous antigen-immobilized surfaces retained a uniform appearance after incubation with another anti-tuberculosis antibody, human serum albumin, and phosphate-buffered saline. These results verified that the tuberculous antigen-antibody complexes on the surface masked the anisotropic surface topography, which led to the transition of 5CB from a uniform orientation to a random one. Consequently, LC sensing systems based on nanostructured polymeric surfaces could be used in the labelfree detection of anti-tuberculosis antibodies, and they could be expanded as a feasible application in the immunoassay of tuberculosis.