Liquid crystal based sensors for the detection of cholic acid

The concentration level of cholic acid is a biomarker for the early diagnosis of liver and intestinal diseases. We present a biosensor platform based on the anchoring transition of 4-cyano-4'-pentylbiphenyl (5CB) liquid crystals at surfactant-laden 5CB/aqueous interfaces for the detection of cholic acid (CA) in aqueous solution. In the biosensor platform, the competitive adsorption of CA at the surfactant-laden 5CB/aqueous interfaces can trigger a homeotropic-to-planar anchoring transition of the 5CB at the interface, which can be easily observed using a polarizing optical microscope. We find that the detection limit of the 5CB based biosensors for CA depends on the pH and ionic strength of the aqueous phase and the headgroup of the surfactants.