School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA.
Department of Biomedical Engineering, Tufts University, 4 Colby St, Medford, MA, 02155, USA.
Macromol Biosci. 2019 Mar;19(3):e1800176. doi: 10.1002/mabi.201800176. Epub 2018 Aug 13.
Microencapsulation techniques represent a critical step in realizing highly controlled transport of functional materials in multiphase systems. The first demonstration of microcapsules prepared from minimally grafted silk ionomers (silk fibroin modified with cationic/anionic charge groups) are presented here. These tailored biomacromolecules have shown significantly increased biocompatibility over traditional polyelectrolytes and heavily grafted silk ionomers, but the low grafting density had previously limited attempts to fabricate stable microcapsules. In addition, the first microcapsules from polyethylene-glycol-grafted silk ionomers are fabricated and the corresponding impact on microcapsule behavior is demonstrated. The materials are shown to exhibit pH-responsive properties, with the microcapsules demonstrating an approx. tenfold decrease in stiffness and an approx. threefold change in diffusion coefficient when moving from acidic to basic buffer. Finally, the effect of assembly conditions of the microcapsules are shown to play a large role in determining final properties, with microcapsules prepared in acidic buffers showing lower roughness, stiffness, and an inversion in transport behavior (i.e., permeability decreases at higher pH).
微胶囊化技术是实现多相体系中功能材料高度可控传输的关键步骤。本文首次展示了由最小接枝丝离子体（带有阳离子/阴离子电荷基团的丝纤维蛋白改性）制备的微胶囊。这些经过精心设计的生物大分子在生物相容性方面明显优于传统的聚电解质和接枝密度高的丝离子体，但低接枝密度此前限制了制备稳定微胶囊的尝试。此外，首次制备了聚乙二醇接枝丝离子体的微胶囊，并证明了其对微胶囊行为的相应影响。这些材料表现出 pH 响应特性，当从酸性缓冲液移动到碱性缓冲液时，微胶囊的刚性约降低十倍，扩散系数约变化三倍。最后，显示出微胶囊的组装条件对最终性能起着重要作用，在酸性缓冲液中制备的微胶囊具有较低的粗糙度、刚性和传输行为的反转（即，在较高 pH 值时渗透率降低）。
