Nicoli Sara, Cappellazzi Michela, Colombo Paolo, Santi Patrizia
Department of Pharmacy, Universită degli Studi di Parma, Parco Area delle Scienze, 43100 Parma, Italy.
J Pharm Sci. 2003 Jul;92(7):1482-8. doi: 10.1002/jps.10405.
The use of iontophoresis to enhance transdermal transport of drugs necessitates further investigations on the membrane used to simulate human skin because one of the transport mechanisms involved, electroosmosis, strictly depends on the properties of the skin (i.e., its isoelectric point, IP). The aim of this work was to characterize rabbit ear skin permselectivity by measuring the sodium transport number at different pH values. This method allowed us to estimate the skin IP. To confirm the validity of the method, mannitol flux was measured. In addition, the sodium transport number method was applied to the study of human skin and a model drug iontophoretic flux through rabbit and human skin was evaluated. The results indicate that rabbit ear skin behaves as a permselective membrane, with an IP between 2 and 3. The same result was obtained using human skin. The mannitol flux data confirm that the direction of electroosmotic flow at physiological pH is in the anode-to-cathode direction. Finally, permeation experiments performed with a model drug showed that the relative electroosmotic and electrorepulsive contributions to the total flux are the same for human and rabbit skin. It can be concluded that rabbit ear skin is a suitable model for the study of iontophoretic permeation of drugs.
利用离子电渗疗法增强药物的透皮转运，需要对用于模拟人体皮肤的膜进行进一步研究，因为其中涉及的一种转运机制——电渗，严格取决于皮肤的特性（即其等电点，IP）。这项工作的目的是通过测量不同pH值下的钠迁移数来表征兔耳皮肤的选择渗透性。这种方法使我们能够估算皮肤的等电点。为了证实该方法的有效性，测量了甘露醇通量。此外，将钠迁移数法应用于人体皮肤研究，并评估了一种模型药物通过兔皮和人皮的离子电渗通量。结果表明，兔耳皮肤表现为一种选择渗透膜，其等电点在2到3之间。用人皮也得到了相同的结果。甘露醇通量数据证实，在生理pH值下，电渗流的方向是从阳极到阴极。最后，用一种模型药物进行的渗透实验表明，电渗和电排斥对总通量的相对贡献在人皮和兔皮中是相同的。可以得出结论，兔耳皮肤是研究药物离子电渗渗透的合适模型。
