Massachusetts Institute of Technology , E17-504F, 77 Mass Avenue, Cambridge, Massachusetts 02139, United States.
Langmuir. 2017 Jul 18;33(28):7118-7123. doi: 10.1021/acs.langmuir.7b01104. Epub 2017 Jul 3.
The central dogma of nanoemulsion formation using low-energy methods at constant temperature-popularly known as the emulsion inversion point (EIP) method-is that to create O/W nanoemulsions, water should be added to a mixture of an oil and surfactant. Here, we demonstrate that the above order of mixing is not universal and a reverse order of mixing could be superior, depending on the choice of surfactant and liquid phases. We propose a more general methodology to make O/W as well as W/O nanoemulsions by studying the variation of droplet size with the surfactant hydrophilic-lypophilic balance for several model systems. Our analysis shows that surfactant migration from the initial phase to the interface is the critical step for successful nanoemulsion synthesis of both O/W and W/O nanoemulsions. On the basis of our understanding and experimental results, we utilize the reverse order of mixing for two applications: (1) crystallization and formulation of pharmaceutical drugs with faster dissolution rates and (2) synthesis of alginate-based nanogels. The general route provides insights into nanoemulsion formation through low-energy methods and also opens up possibilities that were previously overlooked in the field.
使用低能量方法在恒温下形成纳米乳的中心法则——俗称乳化反转点（EIP）方法——是，为了制备 O/W 纳米乳，应该将水添加到油和表面活性剂的混合物中。在这里，我们证明了上述混合顺序不是普遍适用的，并且根据表面活性剂和液相的选择，逆向混合可能更为优越。我们通过研究几个模型系统中液滴大小随表面活性剂亲水亲脂平衡的变化，提出了一种更通用的方法来制备 O/W 和 W/O 纳米乳。我们的分析表明，表面活性剂从初始相迁移到界面是成功合成 O/W 和 W/O 纳米乳的关键步骤。基于我们的理解和实验结果，我们将逆向混合顺序用于两个应用：（1）药物结晶和制剂，以获得更快的溶解速率；（2）海藻酸钠基纳米凝胶的合成。这条通用路线为通过低能量方法形成纳米乳提供了新的思路，并为该领域以前被忽视的可能性开辟了道路。
