(516al) Understanding The Effects Of Hydration For Improved Vaccine Antigen Delivery Through The Stratum Corneum

In the significant literature dealing with transport through the skin, hydration is considered a significant factor in facilitating permeation but its role is often not clearly understood. Studies on penetration using Franz cell techniques frequently involve extended contact of the skin with aqueous solutions. Many of these studies treat the skin as a static medium in describing the role of penetrants and penetration enhancers. Using porcine skin as a model, and using the tools of cryo-electron microscopy and confocal microscopy, we clearly show that the stratum corneum is a dynamic structure, where extended hydration (6-8 hours) swells corneocytes, creates intercorneocyte ruptures, and causes microstructural changes in lipid self-assembly. The implications to biomacromolecule penetration are significant, since these disruptions allow penetration through the barrier of the stratum corneum. The disruptions caused by extended hydration are reversible, as removing the hydration source easily restores the barrier. From a technological perspective, our results clearly indicate the viability of using a ?wet patch? to facilitate vaccine antigen penetration through the stratum corneum and presentation to the underlying dendritic cells of the immune system.