ENTROPY-DRIVEN BINDING PARTITION OF AMINO-ACIDS DIPEPTIDES TO STRATUM-CORNEUM LIPID VESICLES/

This study employed large unilamillar vesicles composed of purchased s tratum corneum lipids to investigate the binding/partition of amino ac ids/dipeptides to stratum corneum lipid vesicles. The partition coeffi cients of amino acids/dipeptides between the stratum corneum lipid ves icles and the acetate buffer were determined by HPLC. In addition, the binding/partition enthalpy of amino acids/dipeptides with the stratum corneum lipid vesicles was derived by directly measuring the binding/ partition heat with isothermal titration calorimetry. According to the binding/partition Gibbs free energy and the binding/partition enthalp y, all the binding/partition of amino acids/dipeptides with the stratu m corneum lipid vesicles is endothermic, implying an entropy-driven bi nding/partition. Also, the equilibrium binding/partition results demon strate that the partition coefficients of amino acids/dipeptides do no t correlate with the transdermal permeability. This finding suggests t hat either the interaction between the penetrants and the lipid bilaye r between corneocytes may not be a determining step or that the parace llular path is not a dominant route of transdermal penetration. (C) 19 98 Elsevier Science B.V.