Development of a novel human stratum corneum model, as a tool in the optimization of drug formulations

Transdermal delivery represents a very attractive administration route that provides various advantages over other methods of administration, including enhanced patient compliance via non-invasive, painless and simple application and reduced side effects. Thereby, the research on suitable drugs for this route continues to increase. However, most of drug candidates face the challenges of low drug permeability across the skin's biologically active barrier - the stratum corneum (SC). In this context, a low cost, simple screening tool to evaluate penetration of drug candidates in a human SC barrier model was developed. The in vitro model is based on a modified phospholipid vesicle-based permeation assay (PVPA) with a lipid composition close to human SC layer. The new SC PVPA model can be stored up to 2 weeks at -20 °C, withstand a pH range from 2.0 to 8.0 and the presence of co-solvents (DMSO, oleic acid and cremophor®) without losing their integrity. The human mimicking SC PVPA model was able to detect calcein permeability differences when different drugs, applied in the therapy of skin-related diseases, were present. The obtained data correlated well with the well accepted pig ear model, which highlights the potential of this new human SC model.