Experimental modelling of drug membrane permeability by capillary electrophoresis using liposomes, micelles and microemulsions

Capillary electrophoresis (CE) was evaluated as an in-vitro format for experimental modelling of membrane permeability using only nanogram quantities of drug compounds. The rationale for the CE technique emanates from emulation of a lipid-like pseudo-stationary phase that governs separations mainly as a result of differences in molecular size, lipophilicity, hydrogen bonding and charge, all of which also have a strong influence on in-vivo drug absorption. By means of micellar, microemulsion and liposome electrolytes, the migration behaviour was studied at 37 degrees C for 22 model drug compounds. The generated CE retention factor data were then compared with membrane permeability reference data. Both simple log D and more common Caco-2 cell parameters were evaluated. In addition, permeation through intestinal segments of rat ileum and rat colon was included. An improved correlation was obtained in the order: micellar < microemulsion < liposome systems. Although the correlation for the best liposome CE system was only R-2 = 0.77, the evaluation results for all emphasized the strength and flexibility of CE for assessing specific drug-membrane interaction through tailor-made lipophilic media.