Enhanced firefly bioluminescent assay of adenosine 5′-triphosphate using liposomes containing cationic cholesterols

Cationic liposomes composed of phosphatidylcholine and cationic cholesterols were prepared by extrusion technique. Dimethylaminoethyl-carbamoyl cholesterol (DMAE-chol) and diethylaminoethyl-carbamoyl cholesterol (DEAE-chol) were synthesized as a cationic cholesterol. Cationic liposomes containing DMAE-chol and DEAE-chol enhanced the intensity of maximum light emission from the firefly bioluminescent (BL) reaction. The sensitivity for ATP in the presence of cationic liposomes containing DMAE-chol and DEAE-chol was improved by a factor of 10 times compared to that in water alone. The detection limit for ATP upon using cationic liposomes was 1.0 pmol/L in an aqueous standard solution. The BL enhancement in the presence of cationic liposomes could be explained in terms of BL emitters and electrostatic interaction between the liposomes surface and BL reactants. Copyright (C) 2001 John Wiley & Sons, Ltd.