Skin absorption: Flow-through or static diffusion cells

Flow-through diffusion cells for the measurement of skin permeability in vitro are available commercially. We have designed a new system in our laboratory as an improvement on other cells. The CTL system is capable of running 15 cells simultaneously. In this study the flow-through diffusion system was compared with our well-validated and established static cell system, for ability to measure percutaneous absorption. Two hydrophilic chemicals-water and mannitol-were chosen as test penetrants. The permeability of whole skin, epidermis and dermatomed skin from humans, pigs, and rats was examined. The effect of tissue culture medium as receptor fluid was assessed in comparison with saline. Absorption data from the flow-through cells were similar to results from contemporary static cell. Thus, for each species and skin preparation there was good agreement in the permeability coefficients between the cell types. The absorption of the hydrophilic test penetrants into saline and tissue culture medium receptor fluid was also very similar. Further evaluation of this system, particularly for lipophilic molecules, is required.