Surface area involved in transdermal transport of charged species due to skin electroporation

The electroporative effect on the stratum corneum (SC) is highly localized. However, the fractional area for the transport of small ions and larger ionic species differs considerably during and after high voltage (HV) application. Electroporation of SC creates new aqueous pathways, accessible for small ions, such as Cl− and Na+ ions. The pores are distributed across the skin surface yielding a fractional area for current flow during electroporation of up to 0.1%. An increased permeability after high voltage application persists within a fractional area on the order of 10−3%. The permeabilization of SC for larger, charged molecules (M>200 g/mol) involves Joule heating and a phase transition of the long chain sphingolipids within local transport regions (LTR). The transport area for these molecules (≈10−3%) changes only negligibly after high voltage application.