A dynamic topical hydrofluoroalkane foam to induce nanoparticle modification and drug release in situ.

Topical nanoparticles are usually applied using semi-solid formulations, but the delivery process is often inefficient due to the poor drug release from the particles. The aim of this study was to investigate the capability of a dynamic foam to break open nanoparticles upon application to the skin and enhance drug delivery efficiency. Vitamin E acetate (VEAc) was selected as a model drug and loaded into lipid nanoparticles (50-60 nm) prepared by phase inversion. The highest drug loading was 18.9+/-1.2 mg/ml and the corresponding encapsulation efficiency was 81.5+/-4.1%. Dynamic foams were generated by emulsifying VEAc-loaded nanoparticle suspensions with hydrofluoroalkane using pluronic L62D. An in vitro permeation study demonstrated that VEAc did not release from the nanoparticles when administered as an aqueous suspension, but attained a flux of 18.0+/-2.1 (microg cm(-2) h(-1)) when applied using the foam. Drug release from the foam was shown to be a consequence of nanoparticle modification after dose administration and this led to the foam delivering 0.7+/-0.3% VEAc into the stratum corneum (SC) when applied to human skin.