The relative contributions of electrorepulsion and electroosmosis to iontophoretic transport

摘要

Iontophoresis enhances transdermal delivery by electrorepulsion (ER) and electroosmosis (EO). The relative contribution of these two mechanisms depends on the electrical and physicochemical characteristics of the membrane and of the permeant. The isoelectric point of mammalian skin is about 4. At more basic pH, the membrane supports an increasing negative charge as ionisable groups (probably carboxylate moieties) deprotonate. The negative charge confers upon the skin its permselectivity to cations and consequently gives rise to an electroosmotic flow. Furthermore, pH affects the degree of ionisation of the permeant and will impact on its transport. Here we outline a theoretical approach to evaluate the effect of ionic mobility on iontophoretic transport and, in particular, on the balance between the ER and EO contributions.