Application of cationic liposomes containing surfactants to an enhancer infirefly bioluminescent assay of adenosine 5 '-triphosphate

The effects of surfactant having single and two alkyl chains as a component of liposomes on the intensity of bioluminescence (BL) from firefly lucifer in-luciferase reaction with adenosine 5'-triphosphate (ATP) and on the stab ility of liposomes were investigated by use of vesicles formed by extrusion technique. Stearyltrimethylammonium chloride (STAC) and distearyldimethyla mmonium chloride (DSDAC) were used as a surfactant having single and two al kyl chains, respectively. The BL intensity in the presence of liposomes con taining DSDAC increased twice compared with those containing STAC. The dete ction limit for ATP upon using liposomes containing DSDAC was 0.5 pM in aqu eous ATP standard solution, and was improved by a factor of 10 compared to that in water alone. Liposomes containing DSDAC were more stable than those containing STAC, and were superior to those containing STAC as an enhancer for the firefly BL assay of ATP. (C) 2000 Elsevier Science B.V. All rights reserved.