New nanovesicles for dermal drug delivery
Conventional liposomes obtained by incorporation of phospholipids and cholesterol in the lipid bilayer do not penetrate efficiently across the skin. In order to overcome the main obstacle of drug penetration, the stratum corneum (SC), the next generations of flexible liposomes exhibiting higher skin penetrability was developed by many researchers. The lipid bilayer of flexible liposomes is composed of unsaturated phospholipids and penetration enhancer, which destabilizes the bilayer structure and generates the elasticity of lipid bilayer. Hitherto, among the characteristics of liposome, e.g. particle size, surface charge, flexibility of lipid bilayer, it was and still is not completely clear which characteristic(s) should be more intensively considered in order to improve the drug penetrability, and what should be the ideal characteristic of surfactant (which serves as our interested group of penetration enhancer in this study). This study revealed that the modification by emulsifiers (especially DSPG negatively charged donors being used in our experiment) could enhance biological performance. Polymeric headgroup enhanced liposomes can penetrate the stratum corneum efficiently, however, the performance gain is restricted to a certain size and does not apply across the entire possible size range. Emulsifying agents are key components which improve native liposome attributes for skin penetration. Fundamentally, there are two important characteristics of preferable liposomes: 1). Lipid membrane should be flexible, allowing it to squeeze easily through skin and 2). Emulsifier to be incorporated into vesicle membrane should be constructed with small hydrophilic headgroup and long chain unsaturated fatty acid. These liposomes show potential promise in dermal drug delivery and commercial cosmetic applications.