Physicochemical characterization of the human nail: I. Pressure sealed apparatus for measuring nail plate permeabilities.

Diffusion characteristics of the nail plate are necessary in providing the baselines for rational topical management of nail infections. In order to develop such baselines a unique stainless steel diffusion cell has been designed. The cell permits the exposure of 0.38 cm2 of nail plate to a bathing medium which is stirred by small motors mounted above the cell. The diffusion of water, methanol and ethanol at constant temperature (37 degrees C), has been examined over periods up to 4 h. Average permeability coefficients of water, methanol and ethanol were determined as 16.5 +/- 5.9 X 10(-3) cm hr-1, 5.6 X 10(-3) cm hr-1 and 5.8 +/- 3.1 X 10(-3) cm hr-1 respectively. Moreover rates of diffusion across the nail were inversely proportional to nail thickness. Based on methanol data, nail plate barrier property appears stable for long periods of aqueous immersion.