LAUSR

Abstract We report the surface modification of 4-n-pentyl-4’-cyanobiphenyl (5CB) droplets in aqueous solution by the adsorption of sulfated β-CD/tetradecyl sulfate sodium (SC14S) complexes at the 5CB-aqueous interface, followed by the coating of poly(diallyldimethylammonium chloride) (PDADMAC) through electrostatic interaction. The PDADMAC/sulfate β-CD/SC14S complex-coated 5CB droplets are highly stable in aqueous solution. We show that bile acids are able to penetrate into the PDADMAC coating and displace the SC14S from the cavity of the β-CD immobilized at the surface of the 5CB droplets through the competitive host-guest recognition, consequently inducing the radial-to-bipolar configuration transition of the 5CB droplets. The integration of PDADMAC/sulfate β-CD/SC14S complex-coated 5CB droplets in microfluidic channels allows the selective detection of bile acids in a small sample volume (1 μL) in the presence of ascorbic acid, uric acid, creatinine and urea by observing the configuration transition of the 5CB droplets. The detection limit of the miniaturized 5CB droplet-based sensor platform for bile acids can be tuned by the number density of 5CB droplets.