A liquid crystal-based sensor for the simple and sensitive detection of cellulase and cysteine

A liquid crystal (LC)-based sensor, which is capable of monitoring enzymatic activity at the aqueous/LC interface and detecting cellulase and cysteine (Cys), was herein reported. When functionalized with a surfactant, dodecyl beta-D-glucopyranosicie, the 4-cyano-4'-pentylbiphenyl (5CB) displays a dark-to-bright transition in the optical appearance for cellulase. We attribute this change to the orientational transition of LCs, as a result of enzymatic hydrolysis between cellulase and surfactant. Furthermore, by adding cellulase and Cu2+, our surfactant-LCs system performs an interesting ability to detect Cys, even though Cys could not interact with surfactant or LC directly. Alternatively, through the strong binding between Cys and Cu2+, cellulase was able to hydrolyze surfactant in the presence of Cu2+, leading to the transition of LCs from dark to bright. The detection limit of the LC sensor was around 1 x 10(-5) mg/mL and 82.5 mu M for cellulase and Cys, respectively. The LC-based sensor may contribute to the development of low-cost, expedient, and label-free detection for cellulase and Cys and the design strategy may also provide a novel way for detecting multiple analytes. (C) 2016 Elsevier B.V. All rights reserved.