Physicochemical characterization and in vitro release studies of ascorbyl palmitate-loaded semi-solid nanostructured lipid carriers (NLC gels)

Abstract

The aim of this study was to characterize the physicochemical properties and to study in vitro release of ascorbyl palmitate from semi-solid lipid nanoparticles based on nanostructured lipid carriers (NLC gels) systems with the desired viscosity for dermal delivery. NLC gels were obtained by a one-step production procedure employing a high pressure homogenization technique using different solid lipid matrices. Ascorbyl palmitate (AP) was selected as a lipophilic active ingredient due to its range of cosmetic applications. After the production, particles within the size range 170-250 nm having polydispersity index lower than 0.3 were obtained from all formulations. After the AP incorporation into the NLC gels, the zeta potential increased to values higher than 30 mV . Almost 100% encapsulation efficiency was observed. The obtained SEM and AFM data revealed non-spherical shaped nanoparticles. From DSC and X-ray diffraction studies, it was shown that the lipid recrystallized in the solid state possessing a less ordered structure as compared to the bulk material. The release study of active-loaded NLC gel formulations using Franz diffusion cells revealed that the type of lipid matrix affects both the rate and the release pattern. The viscoelastic measurements revealed a more elastic than viscous behaviour of NLC formulations indicating a typical gel-like structure.