The aim of this study was to elucidate the influence of the edge activator structure on the
properties of novel deformable liposomes, Penetration Enhancer-containing Vesicles (PEVs), capable
of delivering drugs to the skin. The PEVs were prepared by testing five different amphiphilic penetration
enhancers as edge activators in the bilayer composition, together with soy phosphatidylcholine and oleic acid. The
penetration enhancers contained the same lipophilic tail (one or more C8-C10 carbon chains) and different hydrophilic
heads. Conventional phospholipid liposomes were prepared and used as a control. Lidocaine was chosen as a model drug.
Liquid and gelified PEVs were obtained, depending on the penetration enhancer used. The vesicular systems were characterized
by measuring size distribution, zeta potential, incorporation efficiency, and monitoring these parameters over 90
days. Accelerated ageing tests were also performed to check the stability of the dispersions. The effects of the different
nature of the edge activator on the features of the obtained PEVs were assessed by TEM, SAXS and WAXS, rheological
and deformability studies. Higher interactions of the most lipophilic penetration enhancers with the lipid bilayers
and a consequent higher stability and elasticity of the obtained PEVs were observed. In vitro experiments
through pig skin confirmed the superior potential as carriers for lidocaine of the PEVs prepared with the most lipophilic
penetration enhancers, even in comparison with commercial EMLA cream.
Keywords: Liposome, penetration enhancer, lidocaine, rheology, skin penetration, EMLA cream.
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