Relation of Rigidity of Membrane and Stability of Dipalmitoylphosphatidylcholine Liposomes with Soybean-Derived Sterols Prepared by Reverse Phase Evaporation Vesicle Method

Abstract

A soybean-derived sterol mixture (SS) was used to stabilize liposomes prepared from dipalmitoylphosphatidylcholine (DPPC). The effect of SS on the stability and rigidity of liposomes entrapping calcein was investigated by measuring retentivity of calcein in liposomes in vitro and in vivo, and by fluorescence anisotropy, respectively. The entrapment efficiency is directly proportional to the total concentration of DPPC and SS. The presence of SS tends to increase the rigidity of the bilayer above its gel-liquid crystalline phase transition temperature of liposomes, and SS tends to fluidize the bilayer below its gel-liquid crystalline phase transition temperature. The relation between the stability of DPPC-liposomes with SS and the rigidity of liposomal membrane was discussed.