Membrane Structured Solid Nanoparticles – A Novel Nanotechnology for Delivery of Cosmetic Active Ingredients
Lipid nanoparticles have a structure similar to that of nanoemulsions. Their size ranges typically from 50 to 1000 nm. They differ from nanoemulsions in that the lipid core is a solid. The matrix consists of solid lipids or mixtures of lipids. Over the past years it has been demonstrated that solid lipid nanoparticles appear to be a promising drug carrier system for the future. Their occlusion properties reduce transepidermal water loss and can enhance penetration of active ingredients through the stratum corneum. As with all new technologies, some problems with the solid lipid nanoparticle technology need to be solved. One major problem is the homogeneous incorporation of amphiphilic active ingredients into the crystal matrix of the nanoparticles. Actives with an amphiphilic character like tocopherol or retinol cannot be kept homogeneously distributed in the wax structure during the emulsification process. Due to their hydrophilic head group they accumulate at the exterior layer of the nanoparticles together with the surfactant system used. Consequently, homogeneous release over time is not guaranteed and a burst release has to be expected. A second disadvantage is the manufacturing process. Solid lipid nanoparticles can be produced only under high pressure conditions. Also the concentration of the solid particles in the dispersion, which is added to an emulsion, is quite low. To overcome these problems membrane structured solid nanoparticles (MSSN) have been developed. These MSSN systems consist of liquid crystalline membrane systems with extremely low surfactant concentrations. The lateral movement of actives is controlled by amphiphilic solid actives such as ceramides and solid emollients. This guarantees maintenance of the advantageous properties of solid lipid nanoparticles such as retarded release of actives and their protection against chemical decomposition, but it also allows the homogeneous incorporation of amphiphilic actives. Membrane structured solid nanoparticles are produced using a continuous three-phase emulsification technique. This allows protection of heat-sensitive actives against decomposition. The concentration of nanoparticles in the MSSN dispersion can be kept higher than 60% (w/w). Even at these concentrations the nanodispersions keep their flow properties. As a result, they can be easily incorporated into the final formulation.
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Document Type: Research Article
Publication date: February 1, 2006