Optical imaging of cholylglycine by using liquid crystal droplet patterns on solid surfaces

Determining cholylglycine (CG) levels is of great importance in the detection of liver abnormalities. In this study, we present a novel liquid–crystal (LC)-based method assisted with cholylglycine hydrolase (CGH) for the optical detection of CG levels. The detection method is based on the disruption of the orientations of a nematic LC, 4-cyano-4′-pentylbiphenyl (5CB), doped with dodecyl aldehyde. Aldehyde-doped 5CB droplets were placed on pre-treated glass slides and patterned with solutions of interest. When in contact with a small drop of a CG aqueous solution, bright fan-shaped LC droplet patterns were observed under polarizing optical microscopy, indicating a planar orientation of LC at the aqueous/LC interface. However, aldehyde with short-alkyl chain couples with glycine released from the enzymatic reaction between CG and CGH forming amphiphilic Schiff bases, which display dark cross patterns of LC, suggesting a homeotropic orientation of the LC. This system may offer a highly sensitive and methodologically simple approach to determine CG levels for clinical diagnostics and commercial applications.