MECHANISM OF ELECTROINDUCED IONIC SPECIES TRANSPORT THROUGH A MULTILAMELLAR LIPID SYSTEM

A theoretical model for electroporation of multilamellar lipid system due to a series of large electrical pulses is presented and then used to predict the functional dependence of the transport of charged molec ules. Previously, electroporation has been considered only for single bilayer systems such as artificial planar bilayer membranes and cell m embranes. The former have been extensively studied with respect to ele ctrical and mechanical behavior, and the latter with respect to molecu lar transport. Recent experimental results for both molecular transpor t and electrical resistance changes in the stratum corneum (SC) sugges t that electroporation also occurs in the multilamellar lipid membrane s of the SC. In addition, there is the possibility that other skin str uctures (the ''appendages'') also experience electroporation. A compar tment model is introduced to describe the transport of charged species across the SC, and the predicted dependence is compared with availabl e data. in this model, the SC is assumed to contain many hydrophilic c ompartments in series separated by boundary bilayers, so that these co mpartments become connected only upon electroporation. Two limiting ca ses for the transport of charged molecules are considered: (1) transpo rt along tortuous inter-bilayer pathways in each compartment, followed by transport across individual boundary bilayers due to electroporati on, and (2) transport along straight-through pathways in the boundary bilayers with fast mixing in each compartment, which includes the inte rior space of corneocytes. Both models were fitted to the experimental data. The large electropore radius (r(t) similar to 200 Angstrom) and porated fractional area (f(t) similar to 10(-3)) obtained from the fi tting for the tortuous model relative to the more reasonable values ob tained for the straight-through model (r(s) similar to 4 Angstrom, f(s ) similar to 10(-6)) suggest that the latter is a more realistic descr iption of electroinduced transport of ionized species through the skin .