Melzer Eva, Kreuter Jörg, Daniels Rolf
Institut für Pharmazeutische Technologie, Technische Universität Carolo-Wilhelmina zu Braunschweig, Braunschweig, Germany.
Eur J Pharm Biopharm. 2003 Jul;56(1):23-7. doi: 10.1016/s0939-6411(03)00025-0.
Cellulose ethers, in particular hypromellose, represent an interesting alternative when emulsions have to be stabilized avoiding conventional low molecular weight surfactants. So far this option has been only described for the formulation of oil-in-water (o/w) emulsions. Since surfactant-free water-in-oil (w/o) emulsions seem to be also attractive as drug carriers, ethyl cellulose, an oil-soluble cellulose derivative, was studied for its ability to stabilize w/o emulsions. Measurements of the interfacial tension confirmed that ethylcellulose was positively adsorbed at the water/oil interface with diverse lipids. Appearance of model emulsions was dependent on the processing temperature. At low temperatures (15 degrees C) cream-like o/w emulsions were obtained. Processing at 30 degrees C yielded fluid w/o-lotions. Investigation of the microstructure showed that the surface of the emulsion droplets was covered with particles which formed a mechanical barrier. These colloidal particles were shown to be a precipitate of ethylcellulose which forms when the polymer which was dissolved in the lipid phase comes into contact with water. Thus, ethylcellulose was demonstrated to represent a new type of particulate polymeric emulsifier.
当必须避免使用传统的低分子量表面活性剂来稳定乳液时，纤维素醚，特别是羟丙甲纤维素，是一种有趣的替代选择。到目前为止，这种选择仅在水包油（o/w）乳液的配方中有所描述。由于无表面活性剂的油包水（w/o）乳液作为药物载体似乎也很有吸引力，因此研究了油溶性纤维素衍生物乙基纤维素稳定w/o乳液的能力。界面张力的测量证实，乙基纤维素在水/油界面与多种脂质发生正吸附。模型乳液的外观取决于加工温度。在低温（15摄氏度）下可获得乳膏状的o/w乳液。在30摄氏度下加工可得到流动性的w/o洗剂。微观结构研究表明，乳液滴的表面覆盖着形成机械屏障的颗粒。这些胶体颗粒被证明是乙基纤维素的沉淀物，当溶解在脂质相中的聚合物与水接触时就会形成。因此，乙基纤维素被证明是一种新型的颗粒状聚合物乳化剂。
