The cause and influence of sequentially assembling higher and lower deacetylated chitosans on the membrane formation...

Alginate-chitosan (AC) microcapsules with desired strength and biocompatibility are preferred in cell-based therapy. Sequential assembly of higher and lower deacetylated chitosans (C1 and C2 ) on alginate has produced AC1 C2 microcapsule with improved membrane strength and biocompatibility. In this article, the assembly and complexation processes of two cationic chitosans on anionic alginate were concerned, and the cause and influence of sequentially assembling chitosans on AC1 C2 microcapsules membrane formation were evaluated. It was found that C1 complexation was the key factor for deciding the membrane thickness of AC1 C2 microcapsule. Specifically, the binding amount of C2 positively related to the binding amount of C1 , which suggested the first layer by C1 complexation on alginate had no obvious resistance on the sequential cationic C2 complexation. Further analyses demonstrated that outward migration of alginate molecules and inward diffusion of both chitosans under electrostatic interaction contributed to the sequential coating of C2 on first C1 layer. Moreover, C2 complexation through the surface to inner layer of membrane helped smoothen the first layer by C1 complexation that displayed a synergy role on the formation of AC1 C2 microcapsule membrane. Therefore, the two chitosans played different roles and synergistically contributed to membrane properties that can be easily regulated with membrane complexation time.