Application of cationic liposomes containing surfactants to an enhancer in firefly 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 luciferin-luciferase reaction with adenosine 5'-triphosphate (ATP) and on the stability of liposomes were investigated by use of vesicles formed by extrusion technique. Stearyltrimethylammonium chloride (STAC) and distearyldimethylammonium chloride (DSDAC) were used as a surfactant having single and two alkyl chains, respectively. The BL intensity in the presence of liposomes containing DSDAC increased twice compared with those containing STAC. The detection limit for ATP upon using liposomes containing DSDAC was 0.5 pM in aqueous 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.