Development and in vitro evaluation of lipid nanoparticle-based dressings for topical treatment of chronic wounds

This research addresses the development and in vitro evaluation of lipid nanoparticle (NP)-based dressings to optimize the delivery of human recombinant epidermal growth factor (rhEGF) for the topical treatment of chronic wounds. The systems investigated were rhEGF-loaded solid lipid nanoparticles (rhEGF-SLN) and rhEGF-loaded nanostructured lipid carriers (rhEGF-NLC) formulated in wound dressings comprising either semi-solid hydrogels or fibrin-based solid scaffolds. Following detailed characterisation of the NP, in vitro diffusion cell experiments (coupled with dermatopharmacokinetic measurements), together with confocal microscopic imaging, conducted on both intact skin samples, and those from which the barrier (the stratum corneum) had been removed, revealed that (a) the particles remained essentially superficially located for at least up to 48 h post-application, (b) rhEGF released on the surface of intact skin was unable to penetrate to the deeper, viable layers, and (c) sustained release of growth factor from the NP "drug reservoirs" into barrier-compromised skin was observed. There were no significant differences between the in vitro performance of rhEGF-SLN and rhEGF-NLC, irrespective of the formulation employed. It is concluded that, because of their potentially longer-term stability, the fibrin-based scaffolds may be the most suitable approach to formulate rhEGF-loaded lipid nanoparticles.