Label-free, rapid, and sensitive detection of carboxylesterase using surfactant-doped liquid crystal sensor

Abstract

Carboxylesterases (CES) has been regarded as a most effective biomarker candidate of the hepatoma cells and fruitfully used in the early detection. For this reason, establishing a reliable and simple system to detect CES has become attractive in the practical applications of medical diagnosis and treatment. In this study, a novel strategy for monitoring CES based on the aqueous/liquid crystals (LCs) interface was reported. A cleavable surfactant, N-octadecyloxycarbonylmethyl-N, N, N-trimethylammonium bromide (OTB) was synthesized and utilized to control the orientation of 4-cyano-4′-pentylbiphenyl (5CB) molecules on aqueous/LCs interface. The formation of OTB self-assembly monolayer promotes the alignment of the LCs, on average, normal to the surface (homotropic), whereas a corresponding black image was observed by polarized optical microscopy (POM). Subsequently, the doping of CES induces the hydrolysis of the OTB, resulting in the disruption of OTB monolayer and thereby an obvious dark-to-bright transition in the optical response. This optical transition provides a quick and easy way of detecting CES. OTB-decorated LC surfaces have been developed as a sensor, with a detection limit of 18 U/L for CES detection. As-made LCs-based sensor exhibits superior detection sensitivity and specificity towards the detection of CES, as well as the excellent long-term stability. The preliminary results shows success in sensing CES from the urine samples, which also suggests the promising detection performance of LCs sensor in practical situations. In summary, the as-prepared CES sensor, offers several advantages along with its cost-effective and easy fabrication procedure, demonstrates its potential for medically assisted therapy in human samples.