A novel approach based on lipid nanoparticles (SLN) for topical delivery of alpha-lipoic acid.

This study describes the development, preparation and characterization of solid lipid nanoparticles (SLN) containing the novel anti-ageing substance alpha-lipoic acid. Lipoic acid is chemically labile, i.e. the degradation products possess an unpleasant odour. Therefore, the active was encapsulated in SLN. A lipid with low melting point (Softisan 601) was selected for preparation of active-loaded SLN after screening the solubility of alpha-lipoic acid in physicochemically different lipids. An entrapment efficiency of 90% (UV analysis) was obtained for all developed formulations using Miranol Ultra C32 as emulsifying agent. Particle size stability was monitored during 3 months storing the samples at 20 degrees C and at 4 degrees C. Results of DSC analysis confirm that these systems are characterized by a solid-like behaviour, although with a very low crystallinity index.