Enhanced asiaticoside skin permeation by Centella asiatica-loaded lipid nanoparticles: Effects of extract type and study of stratum corneum lipid dynamics

Asiaticoside (AS), the major active constituent of Centella asiatica extract, has numerous uses including the treatment of cutaneous diseases. In the present study, dried (D) and glycolic (G) extract were encapsulated in nanostructured lipid carriers (NLC) (NLC-D and NLC-G) for skin delivery. In vitro release and skin permeation studies were performed. Electron paramagnetic resonance (EPR) was performed to elucidate the lipid dynamics of NLC matrices and their influence on stratum corneum (SC) membrane fluidity. AS release from NLC-D was approximately 23.7%. NLC-G provided a 2-fold increase of AS release during the same period. EPR data demonstrated that NLC were able to enhance SC membrane fluidity, and a more pronounced effect was achieved with NLC-G. NLC-G allowed AS to penetrate into the deeper skin layers, with measurable quantification in the epidermis/dermis (9.14 +/- 0.54 mu g/cm(2)) in 24 h. Similar AS permeation was achieved from NLC-D only after 48 h (10.42 +/- 1.41 mu g/cm(2)). The faster release of the AS from NLC-G is responsible for enhanced skin permeation and the increase of SC fluidity produced by NLC-G also seems to increase AS skin permeation to deeper skin layers. Thus, NLC-G seems to be a promising formulation for the treatment of scleroderma.