Nanoparticles for skin penetration enhancement--a comparison of a dendritic core-multishell-nanotransporter and solid lipid nanoparticles.

Nanosized particles are of growing interest for topical treatment of skin diseases to increase skin penetration of drugs and to reduce side effects. Effects of the particle structure and size were studied loading nile red to dendritic core-multishell (CMS) nanotransporters (20-30 nm) and solid lipid nanoparticles (SLNs, 150-170 nm). Interaction properties of CMS nanotransporters with the dye molecules--attachment to the carrier surface or incorporation in the carrier matrix--were studied by UV/Vis and parelectric spectroscopy. Pig skin penetration was studied ex vivo using a cream for reference. Interactions of SLN and skin were followed by scanning electron microscopy, internalisation of the particles by viable keratinocytes by laser scanning microscopy. Incorporating nile red into a stable dendritic nanoparticle matrix, dye amounts increased eightfold in the stratum corneum and 13-fold in the epidermis compared to the cream. Despite SLN degradation at the stratum corneum surface, SLN enhanced skin penetration less efficiently (3.8- and 6.3-fold). Viable human keratinocytes showed an internalisation of both nanocarriers. In conclusion, CMS nanotransporters can favour the penetration of a model dye into the skin even more than SLN which may reflect size effects.