Fraunhofer Institute for Applied Polymer Research, Geiselbergstr. 69, 14476, Potsdam-Golm, Germany.
Top Curr Chem (Cham). 2017 Jun;375(3):64. doi: 10.1007/s41061-017-0152-5. Epub 2017 May 31.
Microencapsulation is the generic term for numerous technologies, which are often used when the release rate of an active substance in a medium has to be controlled and/or contact between the active substance and the medium has to be prevented. This is achieved by wrapping the tiny particles or droplets of the active substance (capsule core) with a thin layer, or membrane, of another material (capsule shell). The permeability of the membrane determines whether, how fast and under which conditions the active material will be released and/or the components of the medium will enter the inner part of the capsule. Insofar as application is concerned, premature release of an active substance from microcapsules during storage is a very common problem. Prevention of diffusion of an active component or components of the outer medium through the capsule membrane is a complex challenge, which so far cannot be considered as solved. This review briefly covers the theoretical aspects of release kinetics from microcapsules and discusses how such parameters as capsule average size, capsule shell thickness as well as the chemical composition of active material and medium can influence the release profiles. All theoretical considerations are based on the dissolution-diffusion mechanism classically used for the explanation of diffusion trough flat membranes/films. In the second part of the manuscript it is discussed, which strategies have been used for the improvement of the barrier properties of microcapsules up to date and to which extent those strategies were successful.
微胶囊化是许多技术的通用术语，当需要控制活性物质在介质中的释放速率和/或防止活性物质与介质接触时，通常会使用这些技术。这是通过用另一层薄薄的材料（胶囊壳）包裹活性物质的微小颗粒或液滴（胶囊芯）来实现的。膜的渗透性决定了活性物质将以何种速度和条件释放，以及介质的成分将进入胶囊的内部。就应用而言，在储存过程中微胶囊中活性物质过早释放是一个非常常见的问题。防止活性成分或外部介质的成分通过胶囊膜扩散是一个复杂的挑战，到目前为止，还不能认为这个问题已经解决。本文简要介绍了从微胶囊中释放动力学的理论方面，并讨论了胶囊平均粒径、胶囊壳厚度以及活性物质和介质的化学组成等参数如何影响释放曲线。所有理论考虑都是基于经典的溶解-扩散机制，用于解释通过平膜/薄膜的扩散。在本文稿的第二部分，讨论了迄今为止用于提高微胶囊的阻隔性能的策略，以及这些策略在多大程度上取得了成功。
