A stable liquid crystals sensing platform decorated with cationic surfactant for detecting thrombin

Abstract

A liquid crystals (LCs) sensing platform to detect thrombin was demonstrated based on high specificity of aptamer recognition. Initially, LCs doped with a cationic surfactant, octadecyl-trimethylammonium bromide (OTAB), adopted homeotropic alignment corresponding to dark optical image. Upon introduction of thrombin aptamer, the orientational transition of LCs from homeotropic to tilted state occurred due to the electrostatic interaction between it and OTAB. And accordingly a visual dark-to-bright alteration was observed for the polarized light microscope (POM) image of LCs. In the presence of thrombin with which the aptamer preferred to bind, OTAB released could induce the vertical arrangement of LCs and a dark optical image was regained. Therefore, by observing the changes of bright and dark optical appearances for LCs, thrombin could be analyzed with a detection limit of ~ 136 nM. The LCs sensing system, assisted with the specific combination of target molecule and its corresponding aptamer, reveals a simple and effective way to achieve label-free and low-cost detection of biomolecules in related clinic diagnosis.