Institute of Theoretical and Experimental Biophysics Russian Academy of Science, Institutskaya St., 3, 142290 Puschino, Moscow Region, Russia.
Int J Mol Sci. 2022 Aug 31;23(17):9917. doi: 10.3390/ijms23179917.
Polyelectrolyte microcapsules are used in the development of new forms of targeted delivery systems, self-healing materials, sensors, and smart materials. Nevertheless, their buffer capacity has not been practically studied, although that characteristic makes it possible to estimate the change in the state of protonation of the entire polyelectrolyte system. This is necessary both for creating a buffer barrier system for pH-sensitive compounds (metals, enzymes, polyelectrolytes, drugs) and for the correct interpretation of the results of research and studying of the PMC structure. The buffer capacity of a PMC can be affected by the concentration of microcapsules in solution and the number of shell layers since the listed parameters affect other physicochemical properties of the PMC shell. This includes, for example, the electrical conductivity, permeability (of ions), osmotic pressure, charge density, etc. In this regard, we studied the change in the buffer capacity of polyelectrolyte microcapsules depending on their concentration and the number of shell layers. As a result, it was found that with an increasing concentration of microcapsules, the buffering capacity of the PMC increases, but at the same time, in the pH range from 4 to 5.5, the calculated buffering capacity of 1 billion capsules decreases with increasing their concentration. This effect may be associated with a decrease in the available -NH groups of the PMC's shell. In addition, it was found that the main contribution to the buffer capacity of a PMC is made by the entire shell of the microcapsule and not just its surface. At the same time, the buffer capacity of the capsules has non-linear growth with an increase in the number of PMC shell layers. It is presumably associated either with a decrease in the polyelectrolyte layer with an increase in their number or with a decrease in the permeability of hydrogen protons.
聚电解质微胶囊用于开发新型靶向递药系统、自修复材料、传感器和智能材料。然而，尽管该特性可用于估计整个聚电解质系统质子化状态的变化，但它们的缓冲容量尚未得到实际研究。这对于创建 pH 敏感化合物（金属、酶、聚电解质、药物）的缓冲屏障系统以及正确解释研究结果和研究 PMC 结构都是必要的。聚电解质微胶囊的缓冲容量可能会受到溶液中微胶囊浓度和壳层数的影响，因为列出的参数会影响 PMC 壳的其他物理化学性质。这包括例如电导率、渗透性（离子）、渗透压、电荷密度等。因此，我们研究了聚电解质微胶囊的缓冲容量随其浓度和壳层数的变化。结果发现，随着微胶囊浓度的增加，PMC 的缓冲容量增加，但同时，在 pH 值为 4 至 5.5 的范围内，计算出的 10 亿个微胶囊的缓冲容量随着浓度的增加而降低。这种效应可能与 PMC 壳的可用-NH 基团减少有关。此外，还发现聚电解质微胶囊的缓冲容量主要由微胶囊的整个壳层贡献，而不仅仅是其表面。同时，随着 PMC 壳层数的增加，胶囊的缓冲容量呈非线性增长。这可能与随着数量的增加，聚电解质层减少或氢质子渗透率降低有关。
