Surface forces and stratification in foam films formed with bile salts
Surface forces and stratification in foam films formed with bile salts
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DOI：
10.1039/d0me00024h
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发表时间：
2021-05-28
影响因子：
3.6
通讯作者：
Sharma, Vivek
中科院分区：
文献类型：
--
作者：
Kemal, Subinur Ilshat;Uribe Ortiz, Camila Alexandra;Sharma, Vivek
胆盐，特别是以其聚集或胶束形式，通过增溶胆固醇、脂溶性维生素和药物在健康和医学中发挥关键作用。然而，与头-尾（HT）表面活性剂如十二烷基硫酸钠（SDS）相比，两亲性胆汁盐具有不寻常的类固醇结构，并显示出较小的聚集数（< 20 molecules per micelle vs. N-agg >SDS的N-agg 50）。典型的表面活性剂如SDS的胶束溶液形成的泡沫膜表现出分层表现为逐步变薄和共存的平坦的厚薄区域，不同的步长成比例的胶束间的距离。我们认为排水通过分层研究作为一个有效的和有见地的探测胶束间相互作用的强度和幅度，并产生超分子振荡结构（SOS）的表面力贡献分离压力。然而，既没有先前的报告，在泡沫膜形成的胆盐溶液或SOS表面力的测量分层。在这里，我们报告的发现和表征的泡沫膜的水溶液形成的胆酸钠（NaC），牛磺胆酸钠（NaTC），脱氧胆酸钠（NaDC），和甘氨脱氧胆酸钠（NaGDC）-具有类似的类固醇核，但不同的共轭位点和羟基的数量（3为NaC和NaTC，2为NaDC和NaGC）。使用IDIOM（干涉数字成像光学显微镜）协议，我们最近开发的特征和分析的厚度变化和过渡，我们发现，与胆汁盐制成的泡沫膜表现出更少的逐步过渡和更小的步长比SDS解决方案。此外，我们测量了较低的表面张力下降和较低的幅度的厚度依赖的分离压力相比，SDS的解决方案。我们发现，胆汁盐与匹配数量的羟基表现出类似的性质，在张力和泡沫膜的研究。我们表明，分层研究可以表征化学结构的影响的大小和范围的胶束间的相互作用，以及它们对泡沫膜的排水和稳定性的影响。
Bile salts, especially in their aggregated or micellar form, play a critical role in health and medicine by solubilizing cholesterol, fat-soluble vitamins, and drugs. However, in contrast to the head-tail (HT) surfactants like sodium dodecyl sulfate (SDS), amphiphilic bile salts have an unusual steroid structure and exhibit a smaller aggregation number (N-agg < 20 molecules per micelle vs. N-agg > 50 for SDS). Foam films formed by micellar solutions of typical surfactants like SDS exhibit stratification manifested as stepwise thinning and coexistence of flat thick-thin regions that differ by a step-size proportional to the intermicellar distance. We consider drainage via stratification studies as an effective and insightful probe of the strength and magnitude of intermicellar interactions and resulting supramolecular oscillatory structural (SOS) surface force contribution to disjoining pressure. However, there are neither prior reports of stratification in foam films formed with bile salt solutions nor measurements of SOS surface forces. Here we report the discovery and characterization of stratification in foam films formed by aqueous solutions of four bile salts - sodium cholate (NaC), sodium taurocholate (NaTC), sodium deoxycholate (NaDC), and sodium glycodeoxycholate (NaGDC) - that have a similar steroid nucleus, but difference in conjugation sites and the number of hydroxyl groups (3 for NaC and NaTC, 2 for NaDC and NaGC). Using IDIOM (interferometry digital imaging optical microscopy) protocols we developed recently to characterize and analyze thickness variations and transitions, we find that foam films made with bile salts exhibit fewer stepwise transitions and smaller step-size than SDS solutions. Also, we measured a lower drop in surface tension and lower magnitude of thickness-dependent disjoining pressure compared to SDS solutions. We find that the bile salts with a matched number of hydroxyl groups exhibit similar properties in tensiometry and foam film studies. We show that the stratification studies can characterize the influence of chemical structure on the magnitude and range of intermicellar interactions as well their influence on drainage and stability of foam films.