Quantitative and sensitive detection of lipase using a liquid crystal microfiber biosensor based on the whispering-gallery mode

In this study, we demonstrate a quantitative and sensitive strategy for monitoring the lipase concentration using a liquid crystal (LC) microfiber biosensor based on the whispering-gallery mode (WGM). An LC 4-cyano-4′-pentylbiphenyl (5CB) microfiber was doped with glycerol trioleate (GT) and used as both an optical microcavity and a sensing element. The self-assembled monolayer of a surfactant was formed at the LC/aqueous solution interface by the enzymatic reaction between lipase and GT, which resulted in the reorientation of the 5CB molecules from a planar to a homeotropic configuration. Interestingly, the structural change of the 5CB microfiber can be sensitively captured by the WGMs and quantitatively characterized by the wavelength shift. With this method, lipase with concentrations as low as 0.01 μg mL−1 in aqueous solution can be detected within 200 seconds, which is lower than the optimal value based on LC materials reported so far. In addition, our biodetection system is highly selective for lipase. We believe that the proposed biosensor has high potential for the detection of biochemical molecules.