In Vitro Permeation Testing of Sunscreens using Reconstructed Human Skin versus Human Cadaver Skin Models

In vitro permeation testing (IVPT) is a method widely used to assess the skin permeation profiles of topical drug products for product development and regulatory evaluation. Various skin models serve as diffusion barriers in IVPT, including surgically excised human skin (EHS) and human cadaver skin (HCS). Limited EHS supply has led to the use of HCS in IVPT, but HCS shows variable skin permeation among donors, creating challenges in obtaining consistent results. To address these supply and variability issues, this study evaluated the potential of reconstructed human skin (RHS) as an alternative diffusion barrier for IVPT. Sunscreen (cream) permeation through four skin models were compared, including two HCS models and two RHS models with or without dermal layers. Among the tested skin models, EpiDermFT (RHS with dermal layers) exhibited consistent results for both intra-batch and inter-batch permeation. Additionally, EpiDermFT exhibited similar rank order of cumulative permeation compared to the HCS counterpart, whereas EpiDerm (RHS without dermal layers) exhibited greater sensitivity to pH changes in cream formulations than HCS models. These findings suggest that EpiDermFT has potential utility as a reliable alternative that provides comparable permeation results to HCS, whereas EpiDerm may serve as a sensitive tool to detect pH differences in topical formulations. However, to determine the broader applicability of RHS in IVPT, further investigations using diverse topical formulations across different dosage forms are necessary.