Mollmann S H, Elofsson U, Bukrinsky J T, Frokjaer S
Department of Pharmaceutics, The Danish University of Pharmaceutical Sciences, DK-2100 Copenhagen, Denmark.
Pharm Res. 2005 Nov;22(11):1931-41. doi: 10.1007/s11095-005-7249-1. Epub 2005 Aug 16.
This study was conducted to investigate the mechanism of action in the displacement of adsorbed insulin from a hydrophobic surface by Tween 80 and of the competitive adsorption of the two species.
Total internal reflection fluorescence (TIRF) and ellipsometry were used as in situ methods to examine the processes taking place at hydrophobic model surfaces in the presence of insulin and Tween 80.
TIRF studies showed that the displacement of insulin by Tween 80 could be fitted to a sigmoidal function, indicating a nucleation-dependent process. Furthermore, a linear dependence between the apparent rate constant and the logarithm of the Tween 80 concentration was found. Competitive adsorption from solution mixtures of insulin and Tween 80 indicated that insulin was adsorbed first, but subsequently displaced by the surfactant. This displacement proved also to be dependent on the concentration of Tween 80 in the mixture.
The results indicate that Tween 80 at concentrations above critical micelle concentration can be used to protect insulin against surface adsorption. The presence of a lag phase in the displacement at low surfactant concentration indicates that the mechanism of action for Tween 80 to reduce adsorption of insulin may be by competing for sites at the surface.
本研究旨在探究吐温80使吸附在疏水表面的胰岛素发生位移的作用机制以及这两种物质的竞争性吸附机制。
采用全内反射荧光（TIRF）和椭偏仪作为原位方法，研究在胰岛素和吐温80存在的情况下，疏水模型表面发生的过程。
TIRF研究表明，吐温80使胰岛素发生位移的过程符合S形函数，表明这是一个依赖成核的过程。此外，还发现表观速率常数与吐温80浓度的对数呈线性关系。胰岛素和吐温80溶液混合物的竞争性吸附表明，胰岛素先被吸附，但随后被表面活性剂取代。这种取代也证明取决于混合物中吐温80的浓度。
结果表明，浓度高于临界胶束浓度的吐温80可用于保护胰岛素不被表面吸附。在低表面活性剂浓度下的位移过程中存在滞后阶段，这表明吐温80减少胰岛素吸附的作用机制可能是通过竞争表面位点。
