Label-Free Detection of Ochratoxin A Using Aptamer as Recognition Probe at Liquid Crystal-Aqueous Interface

Abstract

Aqueous interfaces of stimuli-responsive, thermotropic nematic liquid crystals (LC) have been utilized in the design of biosensing platforms for a range of analytes. Owing to the orientational changes in LC, these interfaces can easily report aptamer-target binding events at the LC-aqueous interface. We demonstrate a label-free, simple and robust technique for the detection of Ochratoxin A (OTA) using aptamer as the recognition probe. The self-assembly of CTAB (cetyltrimethylammonium bromide; cationic surfactant) at aqueous-LC interface gives a homeotropic orientation of LC. In presence of negatively charged OTA specific aptamer, aptamer forms a complex with CTAB. Formation of aptamer-CTAB complex results in ordering transition of LCs to planar/tilted. In presence of OTA, OTA forms a strong and stable G-quadruplex structure of aptamer that results in the redistribution of CTAB at LC-aqueous interface and leads to homeotropic orientation of LC. The designed LC aptasensor exhibits a detection limit of 0.1 nM. We observed that the sensitivity of LC aptasensor was affected by the pH and ionic strength. In addition, we demonstrated the applicability of the designed LC aptasensor for the detection of OTA in tap water and apple juice. This approach offers advantages over the conventional detection methods in terms of fabrication, ease of operation, and analysis.

Dynamic Microparticle Assembly at the Interface of Chemoresponsive Liquid Crystal Droplets

“…LCs are stimuli-responsive materials that can be confined within films, shells, and spherical microdroplets. , The ordering of LC molecules at the interface of the surrounding aqueous phase is sensitive to the presence of interfacial adsorbates. − For the first time, Lavrentovich et al showed that nematic drops show spontaneous transitions between different topological states . The equilibrium states are defined by the presence of topological defects that are formed as a result of the spherical confinement and anchoring conditions .…”