Enhancement of firefly bioluminescence using liposomes containing cationic components

The effect of cationic components in liposome on the bioluminescence (BL) intensity from the firefly luciferin-luciferase reaction with ATP was investigated by use of vesicles formed by the extrusion technique (VET). Stearyltrimethyl-ammonium chloride (STAC), stearylamine (SA) and tetracaine (TC) were used as cationic components. The VET containing STAC and SA enhanced the maximum BL intensity. In contrast, a lowering of the maximum BL intensity was observed in the presence of the VET containing TC. The sensitivity for ATP in the presence of the VET containing STAC was improved by a factor of 2 and 10 times compared to that in the presence of the VET containing SA and that in water alone, respectively. The differences in the BL enhancement between cationic components could be explained in terms of different membrane surface potentials of the VET containing these cationc components.