ABSTRACT
In vitro techniques are widely used in the assessment of percutaneous absorption of potentially toxic chemicals. Absorption measurements are much more easily obtained from diffusion cells than from analysis of biological specimens from clinical studies. Although many different designs have been used for diffusion cell studies, there are really only two basic cell types: the one-chambered and two-chambered cell. Studies comparing permeation through skin with Fickian diffusion through a membrane are performed in this fashion. A membrane used in an in vitro study should simulate the barrier layer in skin as closely as possible. The viability of skin can be maintained for 24 h in a flow-through diffusion cell using a physiological buffer as the receptor fluid. The selection of the receptor fluid has become an increasingly important decision as investigators strive to create in vitro conditions that can adequately duplicate the in vivo situation.
