Tailoring the surface of liquid crystal droplets with chitosan/surfactant complexes for the selective detection of bile acids in biological fluids

We report an approach for tailoring the surface of 4-n-pentyl-4 '-cyanobiphenyl (5CB) droplets by the adsorption of chitosan (CHI) at the 5CB/aqueous interface, followed by the penetration of sodium tetradecyl sulfate (SC14S). The CHI/SC14S complex-coated 5CB droplets can be used as optical probes for the detection of cholic acid (CA) in phosphate-buffered saline and urine without dilution. We find that the CHI coating can significantly reduce the detection limit of 5CB droplets for CA. By controlling the number of CHI/SC14S complex-coated 5CB droplets, the detection limit for CA can be changed from similar to 75 mu M to similar to 0.5 mu M, which covers the concentration range of CA in individual urine with and without intestinal diseases.