Combrinck Johann, Otto Anja, du Plessis Jeanetta
Centre of Excellence for Pharmaceutical Sciences, North-West University, Potchefstroom Campus, Private Bag X6001, Potchefstroom, 2520, South Africa.
AAPS PharmSciTech. 2014 Jun;15(3):588-600. doi: 10.1208/s12249-014-0081-3. Epub 2014 Feb 19.
Emulsions are widely used as topical formulations in the pharmaceutical and cosmetic industries. They are thermodynamically unstable and require emulsifiers for stabilization. Studies have indicated that emulsifiers could affect topical delivery of actives, and this study was therefore designed to investigate the effects of different polymers, applied as emulsifiers, as well as the effects of pH on the release and topical delivery of the active. O/w emulsions were prepared by the layer-by-layer technique, with whey protein forming the first layer around the oil droplets, while either chitosan or carrageenan was subsequently adsorbed to the protein at the interface. Additionally, the emulsions were prepared at three different pH values to introduce different charges to the polymers. The active ingredient, salicylic acid, was incorporated into the oil phase of the emulsions. Physical characterization of the resulting formulations, i.e., droplet size, zeta potential, stability, and turbidity in the water phase, was performed. Release studies were conducted, after which skin absorption studies were performed on the five most stable emulsions, by using Franz type diffusion cells and utilizing human, abdominal skin membranes. It was found that an increase in emulsion droplet charge could negatively affect the release of salicylic acid from these formulations. Contrary, positively charged emulsion droplets were found to enhance dermal and transdermal delivery of salicylic acid from emulsions. It was hypothesized that electrostatic complex formation between the emulsifier and salicylic acid could affect its release, whereas electrostatic interaction between the emulsion droplets and skin could influence dermal/transdermal delivery of the active.
乳液在制药和化妆品行业中广泛用作局部用制剂。它们在热力学上不稳定，需要乳化剂来稳定。研究表明，乳化剂会影响活性成分的局部递送，因此本研究旨在研究用作乳化剂的不同聚合物的影响，以及pH对活性成分释放和局部递送的影响。采用层层技术制备水包油乳液，乳清蛋白在油滴周围形成第一层，随后壳聚糖或角叉菜胶在界面处吸附到蛋白质上。此外，在三种不同的pH值下制备乳液，以使聚合物带有不同的电荷。将活性成分水杨酸掺入乳液的油相中。对所得制剂进行物理表征，即液滴大小、zeta电位、稳定性和水相中的浊度。进行释放研究，之后使用Franz型扩散池并利用人体腹部皮肤膜对五种最稳定的乳液进行皮肤吸收研究。发现乳液液滴电荷的增加会对水杨酸从这些制剂中的释放产生负面影响。相反，发现带正电荷的乳液液滴可增强乳液中水杨酸的真皮和透皮递送。据推测，乳化剂与水杨酸之间形成的静电复合物会影响其释放，而乳液液滴与皮肤之间的静电相互作用会影响活性成分的真皮/透皮递送。
