Simple and Rapid Detection of Ibuprofen─A Typical Pharmaceuticals and Personal Care Products─by a Liquid Crystal Aptasensor

Abstract

This work established a liquid crystal (LC) aptasensor for simple and rapid detection of ibuprofen, a typical pharmaceuticals and personal care products (PPCPs) pollutant. A negatively charged DNA aptamer specific for ibuprofen and a positively charged amphiphilic surfactant, hexadecyltrimethylammonium bromide (CTAB), were incubated with the sample and then directly added onto the LC interface. In the presence of ibuprofen, the specific binding of ibuprofen with the DNA aptamer will release CTAB, which then adsorbed at the LC–aqueous interface and induced the orientational change of LCs to homeotropic orientation with a dark optical signal output. While in the absence of ibuprofen, the DNA aptamer binds with CTAB through hydrophobic and electrostatic interactions, LCs remained in the planar orientation with a bright optical signal output. This LC aptasensor also has good specificity for ibuprofen and can even detect ibuprofen drug in tap water. Moreover, the response time of the LC aptasensor is fast in minutes. Additionally, this LC aptasensor benefits in monitoring the water quality and inspires the exploration of a general platform for PPCPs detection.

State-of-the-Art Development in Liquid Crystal Biochemical Sensors

“…The aptamer-CTAB combination formed at the LC–aqueous surface, triggering planar orientation of LC. After introducing ibuprofen, the competitive binding of ibuprofen with the aptamer released CTAB, inducing homeotropic orientation [ 158 ]. Furthermore, Wu et al established a special LC-based assay for screening xanthine oxidase (XOD) inhibitors, which is essential in uric-acid-lowering therapy, as shown in Figure 12 a.…”

Design of a Super-Liquid Crystal-Phobic Coating for Immobilizing Liquid Crystal μ-Droplets─Without Affecting Their Sensitivity

“…The ordering transition of thermotropic liquid crystals (LC) appeared as an emerging tool for developing various functional and responsive soft materials. − In this context, the strategic use of highly sensitive micrometer-sized droplets of nematic LC (4-cyano-4′-pentylbiphenyl, 5CB) and their ordering transition from bipolar to radial configurations (Scheme −A−C) provided an elegant basis for monitoring different biological events, sensing various analytes, and modulating arrangement of nanoparticles. − The triggered and reversible ordering transition of nematic micrometer-sized LC (denoted as μ-LC) droplets due to the preferential surface anchoring of appropriate amphiphilic molecules resulted in a distinct optical appearance of LC droplets under a cross-polar microscope. − In the past, the microscopic characterizations of such ordering transition in optical appearance were often performed with randomly and freely translated/rotated μ-LC droplets in the aqueous phase before their sedimentation (Scheme D) to avoid the unfavorable influences of the droplet/solid surface interactions on their configuration. − However, the random translation of the μ-LC droplets in the aqueous phase with a speed higher than 1 μm s –1 , together with their rotation, makes the image acquiring process highly tedious and challenging as the dispersed μ-LC droplets hardly stay in the same plane of focus of the microscope during the analysis . In addition, tracking the ordering transition in a single LC droplet is nearly impossible to achieve with such continuously moving LC droplets under cross-polar microscope; eventually, a large number of LC droplets are characterized and analyzed to interpret an unambiguous result.…”