Microneedle mediated delivery of nanoparticles into human skin.

The development of novel cutaneous delivery technologies that can produce micron-sized channels within the outermost skin layers has stimulated interest in the skin as an interface for localised and systemic delivery of macromolecular and nanoparticulate therapeutics. This investigation assesses the contribution of physicochemical factors to the rate and extent of nanoparticle delivery through microchannels created in a biological tissue, the skin, by novel delivery technologies such as the microneedle array. The hydrodynamic diameter, zeta potential and surface morphology of a representative fluorescent nanoparticle formulation were characterised. Permeation studies using static Franz-type diffusion cells assessed (i) the diffusion of nanoparticle formulations through a model membrane containing uniform cylindrical microchannels of variable diameter and (ii) nanoparticle penetration across microneedle treated human skin. Wet-etch microneedle array devices can be used to significantly enhance the intra/transdermal delivery of nanoparticle formulations. However the physicochemical factors, microchannel size and particle surface charge, have a significant influence on the permeation and subsequent distribution of a nanoparticle formulation within the skin. Further work is required to understand the behaviour of nanoparticle formulations within the biological environment and their interaction with the skin layers following disruption of the skin barrier with novel delivery devices such as the microneedle array.