Specific detection of avidin–biotin binding using liquid crystal droplets

Abstract

Poly(acrylicacid-b-4-cynobiphenyl-4′-undecylacrylate) (PAA-b-LCP)-functionalized 4-cyano-4′-pentylbiphenyl (5CB) droplets were made by using microfluidic technique. The PAA chains on the 5CB droplets, were biotinylated, and used to specifically detect avidin–biotin binding at the 5CB/aqueous interface. The avidin–biotin binding was characterized by the configurational change (from radial to bipolar) of the 5CB droplets, as observed through a polarized optical microscope. The maximum biotinylation was obtained by injecting a >100μg/mL biotin aqueous solution, which enabled a limit of detection of 0.5μg/mL avidin. This droplet biosensor could specifically detect avidin against other proteins such as bovine serum albumin, lysozyme, hemoglobin, and chymotrypsinogen solutions. Avidin detection with 5CBPAA-biotin droplets having high sensitivity, specificity, and stability demonstrates new applications of the functionalized liquid crystal droplets that can detect specific proteins or other analytes through a ligand/receptor model.