Abstract: In order to investigate the effects of high-pressure homogenization and cholesterol on vesicle characteristics and stability of liposomes, liposomes were prepared by the traditional thin film hydration method combined with high-pressure homogenization. The vesicle size, polydispersity index, zeta potential and centrifugal stability of liposomes were determined as a function of homogenization pressure and cycles and cholesterol content, and a fluorescence probe and a transmission electron microscope were applied to explore the effect of cholesterol content on the membrane characteristics and morphology. The results indicated that increased homogenization pressure and cycles could significantly reduce the vesicle size and improve the centrifugal stability of liposomes. However, excessive pressure and cycles had no effect in further reducing the vesicle size and changing the zeta potential of liposomes. The lower the cholesterol content, the smaller the vesicle size and the denser the membrane structure of liposomes. Besides, cholesterol significantly decreased the micropolarity and surface hydrophobicity, and it reduced the membrane fluidity of liposomes as evidenced by increased degree of polarization. The centrifugal stability of liposomes decreased dramatically with the incorporation of too much cholesterol (soybean lecithin:cholesterol = 2:1, m/m) (P < 0.05). In conclusion, liposomes loading an appropriate amount of cholesterol (soybean lecithin:cholesterol = 3:1, m/m) have good centrifugal stability due to the stable microstructure of liposomal vesicles, which provides useful information for the encapsulation of bioactive compounds in the future.

Key words: liposomes, high pressure homogenization, cholesterol, stability