General Liquid-crystal droplets produced by microfluidics for urea detection

pH-sensitive 4-cyano-4′-pentylbiphenyl (5CB) droplets were produced for urea detection by coating with poly(acrylicacid-b-4-cyanobiphenyl-4-oxyundecylacrylate) (PAA-b-LCP) and covalently immobilizing urease on the PAA chains on the 5CB droplets using microfluidics. The functionalized 5CB droplets detected urea based on a bipolar-to-radial orientational change of the droplets observed by polarized optical microscopy using crossed polarizers. The detection limit was as low as 3 mM with a response time of 180 s. Urine was evaluated as a real sample for urea prescreening. This new and sensitive liquid crystal droplet-based urea biosensor has the merits of facile visual detection and is prospectively useful for urea prescreening for human subjects.