Department of Chemistry, Jamanaben Narottambhai Motiram Patel Science College, Bharthana (Vesu), Surat, 395017, India.
Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai, 400085, India.
Colloids Surf B Biointerfaces. 2018 Jun 1;166:119-126. doi: 10.1016/j.colsurfb.2018.03.001. Epub 2018 Mar 2.
The present study was aimed to examine the interaction of two bile salts viz. sodium cholate (NaC) and sodium deoxycholate (NaDC) with three ethylene polyoxide-polypropylene polyoxide (PEO-PPO-PEO) triblock copolymers with similar PPO but varying PEO micelles with a focus on the effect of pH on mixed micelles. Mixed micelles of moderately hydrophobic Pluronic P123 were examined in the presence of two bile salts and compared with those from very hydrophobic L121 and very hydrophilic F127. Both the bile salts increase the cloud point (CP) of copolymer solution and decreased apparent micelle hydrodynamic diameter (D). SANS study revealed that P123 forms small spherical micelles showing a decrease in size on progressive addition of bile salts. The negatively charged mixed micelles contained fewer P123 molecules but progressively rich in bile salt. NaDC being more hydrophobic displays more pronounced effect than NaC. Interestingly, NaC shows micellar growth in acidic media which has been attributed to the formation of bile acids by protonation of carboxylate ion and subsequent solubilization. In contrast, NaDC showed phase separation at higher concentration. Nuclear Overhauser effect spectroscopy (NOESY) experiments provided information on interaction and location of bile salts in micelles. Results are discussed in terms of hydrophobicity of bile salts and Pluronics and the site of bile salt in polymer micelles. Proposed molecular interactions are useful to understand more about bile salts which play important role in physiological processes.
本研究旨在考察两种胆汁盐（即胆酸钠（NaC）和脱氧胆酸钠（NaDC））与三种具有相似 PPO 但具有不同 PEO 胶束的乙烯聚氧-丙烯聚氧（PEO-PPO-PEO）三嵌段共聚物的相互作用，重点关注 pH 对混合胶束的影响。在两种胆汁盐存在的情况下，研究了中等疏水性 Pluronic P123 的混合胶束，并将其与疏水性非常强的 L121 和亲水性非常强的 F127 的混合胶束进行了比较。两种胆汁盐均增加了共聚物溶液的浊点（CP）并降低了表观胶束水动力直径（D）。小角中子散射（SANS）研究表明，P123 形成小的球形胶束，随着胆汁盐的逐渐加入，胶束尺寸减小。带负电荷的混合胶束中含有较少的 P123 分子，但逐渐富含胆汁盐。由于羧酸根离子的质子化形成胆汁酸，随后的增溶作用，疏水性更强的 NaDC 比 NaC 显示出更明显的效果。有趣的是，NaC 在酸性介质中显示出胶束生长，这归因于羧酸盐离子的质子化和随后的增溶作用形成了胆汁酸。相比之下，NaDC 在较高浓度下表现出相分离。核 Overhauser 效应光谱（NOESY）实验提供了关于胆汁盐在胶束中相互作用和位置的信息。结果根据胆汁盐和 Pluronics 的疏水性以及胆汁盐在聚合物胶束中的位置进行了讨论。所提出的分子相互作用有助于更好地了解在生理过程中起重要作用的胆汁盐。
