Tocopheryl acetate disposition in porcine and human skin when administered using lipid nanocarriers

Assessing the delivery of a drug into the skin when it has been formulated within a nanocarrier is a complex process that does not conform to the conventions of traditional semi-solid formulations. The aim of this study was to gain a fundamental understanding of drug disposition in both human and porcine skin when applied using a lipidic nanocarrier.

A model system was generated by loading tocopheryl acetate into a well-characterised solid lipid nanoparticle and formulating this system as a traditional aqueous hyaluronic acid gel. Franz diffusion cells fitted with a silicone or nylon membrane were used to assess drug and particle transport independently whilst human and pig skin were employed to determine skin delivery.

The tocopheryl acetate, when loaded into the solid lipid nanoparticles, did not release from the particle. However, 1.65 +/- 0.90% of an infinite dose of tocopheryl acetate penetrated into the stratum corneum of pig skin when delivered using a nanoparticle-containing gel.

These results suggest that hydration of the stratum corneum in pig skin could lead to the opening of hydrophilic pores big enough for 50 nm-sized particles to pass into the superficial layers of the skin, a phenomenon that was not repeated in human skin.