LAUSR

The aim of the work was to exploit a methodology based on contact angle measurements for the purpose of membrane transport studies. Special attention has been paid to a model system of pharmacological relevance, consisting of the drug dithranol (from semisolid Vaseline suspension) in contact with an artificial skin barrier. The drug permeation has been monitored by the surface wettability evolution during the drug transport process. The surface wettability parameters, such as: surface free energy, 2D film pressure, contact angle hysteresis (CAH) and surface excess for long and short adsorption time intervals, have been derived from dynamic contact angle measurements of the probe liquid drops deposited on the outermost membrane layer. The analysis has allowed the apparent Arrhenius-type energy barrier for the drug surface adsorption (Ea/RgT = -8.04 ± 0.84 at 295 K), the characteristic lag-time of the transport process (tlag = 20 ± 1.9 min) and the diffusion coefficient of the drug through the membrane (D = 1.25 ± 0.24·10-9 cm2 s-1) to be determined. The latter one remains in a good agreement with literature data for the same system investigated by means of spectroscopic methods.