Hydrocortisone (HyC), a hydrophobic pharmaceutical active, was encapsulated in multi-lamellar liposomes (MLLs) composed of P100, a mixture of phospholipids, and Tween®80. Three different HyC-loaded formulations were designed to target the stratum corneum, the living epidermis and the hypodermis. The impact of encapsulation on their size, elasticity and zeta potential, the three key factors controlling MLLs skin penetration, was studied. Raman mapping of phospholipids and HyC allowed the localisation of both components inside an artificial skin, Strat-M®, demonstrating the efficiency of the targeting. Percutaneous permeation profiles through excised human skin were performed over 48 h, supporting results on artificial skin. Their modelling revealed that HyC encapsulated in MLLs, designed to target the stratum corneum and living epidermis, exhibited a non-Fickian diffusion process. In contrast, a Fickian diffusion was found for HyC administered in solution, in a pharmaceutical cream and in transdermal MLLs. These results allowed us to propose a mechanism of interaction between HyC-containing MLLs and the skin.
Keywords: Targeting; confocal Raman mapping; diffusion model; hydrocortisone; multi-lamellar liposomes; skin layers.