Characterization and Evaluation of Skin Permeation of Tocopheryl Phosphoric Acid-loaded Phospholipid Nanoparticles

Tocopheryl phosphoric acid (TPA, a hydrophilic vitamin E derivative) loaded liposome and glycerin containing phospholipid nanoparticles (GPLNP) were prepared using the film rehydration and extrusion method. Nanoparticle formulations were evaluated for size, zeta potential, and in vitro permeation across hairless mouse skin, and ³¹P NMR spectral analysis was performed. The prepared formulations were stable for 2 weeks, and their mean nanoparticle size varied between 90 and 140 nm. Although glycerin did not affect the particle size of the empty (no TPA) system, TPA-loading resulted in the reduction of particle size and conferred a negative charge. The ³¹P NMR spectral analysis showed that the presence of glycerin in the formulation changed the nanoparticle structure from a bilayer to a nonbilayer. Moreover, it was suggested that TPA molecules interacted with phospholipid by entrapping nanoparticles in the formulations. TPA did not permeate across the hairless mouse skin after 48 h. However, the TPA concentration in the hairless mouse skin after permeation study increased in the nanoparticle systems and the 30% GPLNP formulation was the best formulation for the accelerated TPA permeation in the hairless mouse skin. These results demonstrate that 30% GPLNP improved TPA permeation in the hairless mouse skin model. And it was strongly suggested that glycerin has an important role for changing the structure of nanoparticles and enhancing the skin permeation of TPA.