Thermodynamics of fluoxetine partitioning into lipid bilayers: a comparative study between the solid - gel state lipid and liquid - crystalline state lipid

Abstract

The thermodynamics of partitioning of fluoxetine, a SSRI into 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) large unilamellar vesicles (LUVs) were studied. The partition coefficient, Kp values of fluoxetine between solid-gel phase lipid (DSPC) LUVs, liquid- crystalline phase lipid (DOPC) LUVs and water were determined at three different temperatures including: 25oC, 32oC and 37oC. As a result of increasing the temperature, the Kp had the trend of rising their values. The Van’t Hoff plot of the temperature dependence of Kp values was constructed and the free energies of transfer ΔG were calculated to be negative. Moreover, the positive ΔHwl and ΔSwl were also obtained from the Van’t Hoff plot. Those results prove that the processes of transfer of fluoxetine into both two lipids were spontaneous and the driving force for fluoxetine partitioning was the entropy compensation mechanism. Keywords Fluoxetine Thermodynamics Second – derivative spectrophotometry Liposome