Fluorescence polarization study of the interaction between phenothiazine and liposomes / Witinee Theeravit = การศึกษาทางฟลูออเรสเซนโพลาไรเซชั่นของปฏิกิริยาต่อกันระหว่างฟีโนไทอะซีนกับลิโปโซม / วิฒิณี ธีระวิทย์
The interaction between, phenothiazines tranquilizer and liposomes, a model membrane, was examined by using fluorescence polarization technique. Chlorpromazine (CPZ) and thioridazine (TRZ) were selected as drugs of choice and a fluorescent probe, 1-6-diphenyl-1, 3, 5-hexatriene (DPH) was used to monitor the order and dynamic within the acyl chain region of liposomal bilayer. These phenothiazines were found to lower and broaden thermotropic phase transition temperature (Tm) of liposomes reconstituted with dimyristoylphosphatidylcholine (DMPC) and also in distearoylphosphatidylcholine (DSPC). They increased membrane fluidity (fluidizing effect) at temperature below Tm and ordered the acyl chains of phospholipid (condensing effect) at temperature above Tm. For liposomes composed of natural phospholipid, egg yolk phosphatidylcholine (EPC), only condensing effect of phenothiazines was observed since EPC liposomes were in fluid phase overall the temperature studies. Same phenomena were also observed in phosphatidylcholine liposomes containing cholesterol but in a less extent due to an increase in lipid packing that might reduce penetration of drugs. Phenothiazines exhibited greatest effect on negatively charged liposomes, following by neutral and positively charge liposomes, respectively. These might explained by electrostatic attraction between positive charged on phenothiazines and negatively charged liposomes which enhanced more penetration of drugs into lipid bilayer while electrostatic repulsion was found in positively charged liposomes, thus the opposite effect was obtained. The activities of phenothiazines on all kinds of liposomes presented here were concentration dependence. The research suggested that the phenothiazines played their action on membrane and their effects depended on membrane composition.