Department of Applied Physics, University of Granada, Campus de Fuentenueva, sn, 18071 Granada, Spain.
Division of Food Sciences, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, United Kingdom.
Adv Colloid Interface Sci. 2015 Aug;222:488-501. doi: 10.1016/j.cis.2014.08.002. Epub 2014 Aug 15.
The development of the coaxial double capillary 15 years ago opened up the possibility to undertake accurate desorption and penetration studies of interfacial layers in the pendant drop technique. Drop and bubble methods offer several advantages with respect to other interfacial techniques. They allow a more stringent control of the environmental conditions, use smaller amounts of material and provide a much higher interface/volume ratio than in conventional Langmuir Troughs.
The coaxial capillary was developed 15 years ago at the University of Granada as an accessory for the pendant drop surface film balance. It allows exchanging the subphase of the drop without disturbing the surface film and preserving the drop volume throughout the subphase exchange. Hence, this methodology enables one to carry out a great variety of interfacial studies well beyond the usual adsorption profiles. Penetration studies, sequential adsorption measurements, desorption kinetics, reversibility of adsorption and testing of enzymatic treatments on interfacial layers are amongst the principal applications. The coaxial capillary has been recently upgraded to a multi-exchange device which has boosted its applicability. It can be now used to address multilayer formation, create soft interfacial nano-composites such as membranes, polyelectrolyte assemblies and simulate in vitro digestion in a single droplet.
This review aims to compile the experimental work done, using the pendant drop subphase exchange in the last decade, and how its use has provided new insights into the surface/interfacial properties of many different materials. Special emphasis is placed on recent work regarding simulation of in vitro digestion in order to address issues relating to metabolism degradation profiles. The use of this methodology when dealing with interfacial studies allows setting the foundations of interfacial engineering technology. Based on subphase exchange experiments, we aim to develop models for competitive adsorption of different compounds at the interface and build up layer-by-layer interfacial structures. Future challenges comprise the design of finely adjusted nanoengineering systems, based on multilayer assemblies with tailored functionalities, to match the application demand.
15 年前同轴双毛细管的发展开辟了在吊片技术中进行界面层精确解吸和渗透研究的可能性。滴状和气泡方法相对于其他界面技术具有几个优势。它们允许更严格地控制环境条件，使用更少的材料，并提供比传统 Langmuir 槽高得多的界面/体积比。
同轴毛细管是 15 年前在格拉纳达大学开发的，作为吊片表面膜天平的附件。它允许在不干扰表面膜的情况下交换滴的亚相，并在整个亚相交换过程中保持滴的体积。因此，这种方法使人们能够进行各种各样的界面研究，远远超出通常的吸附曲线。渗透研究、顺序吸附测量、解吸动力学、吸附的可逆性以及对界面层的酶处理测试是主要应用之一。同轴毛细管最近已升级为多交换装置，从而提高了其适用性。现在可以使用它来解决多层形成问题，创建软界面纳米复合材料，如膜、聚电解质组装体，并在单个液滴中模拟体外消化。
本综述旨在汇编过去十年中使用吊片亚相交换进行的实验工作，以及它的使用如何为许多不同材料的表面/界面特性提供新的见解。特别强调了最近关于体外消化模拟的工作，以解决与代谢降解曲线相关的问题。当涉及到界面研究时，使用这种方法可以为界面工程技术奠定基础。基于亚相交换实验，我们旨在开发不同化合物在界面上竞争吸附的模型，并构建层状界面结构。未来的挑战包括设计基于具有定制功能的多层组装的精细调整的纳米工程系统，以满足应用需求。
