Effect of polyol type on the structure and properties of lecithin liposomes prepared using the polyol dilution method

Abstract

The polyol dilution (PD) method is an approach for preparing liposomes by pre-mixing a lipid/polyol binary mixture, followed by hydration, and is widely used in the cosmetics industry. In this method, polyols play an important role in the formulation design and application, however, the effect of the polyol type on liposomes (PD-liposomes) is yet to be understood. In this study, we investigated the effect of three types of polyols—glycerol (Gly), propylene glycol (PG), and 1,3-butylene glycol (BG)—on the physicochemical properties of PD-liposomes composed of hydrogenated egg yolk lecithin (EL). The particle size of PD-liposomes was controlled by adjusting the type and concentration of the polyols. Furthermore, the addition of polyols improved the dispersion stability, indicating that PD-liposomes are suitable for industrial applications. The morphology of lipid/polyol binary mixture was the determining factor of the liposome structure, and the formation region of unilamellar vesicles (ULVs) and multilamellar vesicles (MLVs) was closely related to the dielectric constant of the dispersion medium. ULVs were formed using a high dielectric constant dispersion medium, such as Gly, and MLVs were formed using a low dielectric constant dispersion medium, such as PG and BG at high concentrations. This study showed that the addition of polyols improves the phase homogeneity of the bilayer and that PG or BG is more effective than Gly. The control of the homogeneity of the bilayer phase is an effective technique to prevent leakage and control the sustained release of the active ingredient; thus, this method enhances the efficacy of the active ingredient. This study is the first to systematically elucidate the control mechanisms of the physicochemical properties of PD-liposomes, including the particle size, dispersion stability, shape, and phase state of the bilayer. Our findings will contribute to the wide range of applications of PD-liposomes.