Bromley Keith M, MacPhee Cait E
School of Physics and Astronomy, University of Edinburgh, James Clerk Maxwell Building, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK.
Interface Focus. 2017 Aug 6;7(4):20160124. doi: 10.1098/rsfs.2016.0124. Epub 2017 Jun 16.
Emulsions are a central component of many modern formulations in food, pharmaceuticals, agrichemicals and personal care products. The droplets in these formulations are limited to being spherical as a consequence of the interfacial tension between the dispersed phase and continuous phase. The ability to control emulsion droplet morphology and stabilize non-spherical droplets would enable the modification of emulsion properties such as stability, substrate binding, delivery rate and rheology. One way of controlling droplet microstructure is to apply an elastic film around the droplet to prevent it from relaxing into a sphere. We have previously shown that BslA, an interfacial protein produced by the bacterial genus , forms an elastic film when exposed to an oil- or air-water interface. Here, we highlight BslA's ability to stabilize anisotropic emulsion droplets. First, we show that BslA is capable of arresting dynamic emulsification processes leading to emulsions with variable morphologies depending on the conditions and emulsification technique applied. We then show that frozen emulsion droplets can be manipulated to induce partial coalescence. The structure of the partially coalesced droplets is retained after melting, but only when there is sufficient free BslA in the continuous phase. That the fidelity of replication can be tuned by adjusting the amount of free BslA in solution suggests that freezing BslA-stabilized droplets disrupts the BslA film. Finally, we use BslA's ability to preserve emulsion droplet structural integrity throughout the melting process to design emulsion droplets with a chosen shape and size.
乳液是食品、药品、农用化学品和个人护理产品中许多现代配方的核心成分。由于分散相和连续相之间的界面张力，这些配方中的液滴只能是球形的。控制乳液液滴形态并稳定非球形液滴的能力将能够改变乳液的性质，如稳定性、底物结合、释放速率和流变学。控制液滴微观结构的一种方法是在液滴周围施加一层弹性膜，以防止其松弛成球形。我们之前已经表明，由芽孢杆菌属产生的一种界面蛋白BslA，在暴露于油-水或气-水界面时会形成一层弹性膜。在这里，我们突出展示了BslA稳定各向异性乳液液滴的能力。首先，我们表明BslA能够阻止动态乳化过程，从而形成取决于条件和应用的乳化技术的具有可变形态的乳液。然后我们表明，冷冻的乳液液滴可以被操控以诱导部分聚结。部分聚结的液滴在融化后结构得以保留，但前提是连续相中要有足够的游离BslA。通过调节溶液中游离BslA的量可以调节复制的保真度，这表明冷冻BslA稳定的液滴会破坏BslA膜。最后，我们利用BslA在整个融化过程中保持乳液液滴结构完整性的能力来设计具有选定形状和尺寸的乳液液滴。
