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Controlling the adhesion of mammalian cells at the interface between materials and biological environments is a real challenge when designing materials for tissue engineering applications. The surface properties of implanted materials are known to have a significant impact on cell adhesion. Herein, two types of polyelectrolyte multilayers (PEMs) hydrogel membrane based on marine-derived polysaccharides of chitosan (CHI) and alginate (ALG) biopolymers were fabricated by the layer-by-layer (LbL) technique using simple approach involving the change in assemble sequence of chitosan with different degree of deacetylation (DD). The effect of PEMs formation on the surface properties and their effects on the adhesion of mouse fibroblast cell (L929) of the two membranes were studied. The results showed that the formations of ALG/CHI membranes were related to the rigidity and conformations of chitosan molecules. The adhesion of L929 cell was strongly depended on the surface roughness rather than stiffness. The surface of PEMs can be strongly cytophilic (cell adhesive, terminated with chitosan (C1)) or strongly cytophobic (cell resistant, terminated with chitosan (C2)). The results obtained indicate that ALG/CHI PEMs with different surface morphology and roughness could be used in vitro to manipulate cell behaviors to improve upon the design of tissue-engineered membranes.

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.

Cell encapsulation technology holds promise for the cell-based therapy. But poor mechanical strength and biocompatibility of microcapsule membrane are still obstacles for the clinical applications. A novel strategy is presented to prepare AC(1)C(2)A microcapsules with bifunctional membrane (that is, both desirable biocompatibility and membrane stability) by sequentially complexing chitosans with higher deacetylation degree (C-1) and lower deacetylation degree (C-2) on alginate (A) gel beads. Both in vitro and in vivo evaluation of AC(1)C(2)A microcapsules demonstrate higher membrane stability and less cell adhesion, because the introduction of C-2 increases membrane strength and decreases surface roughness. Moreover, diffusion test of AC(1)C(2)A microcapsules displays no inward permeation of IgG protein suggesting good immunoisolation function. The results demonstrate that AC(1)C(2)A microcapsules with bi-functional membrane could be a promising candidate for microencapsulated cell implantation with cost effective usage of naturally biocompatible polysaccharides.

Alginate-chitosan (AC) microcapsule with polyelectrolyte complex (PEC) membrane has been attractive in biotechnological area such as cell immobilization fermentation. The PEC membrane has been known important to control microcapsule performance, but the knowledge was mainly obtained with empty or drug-loaded microcapsules. In this paper, the emphasis was to explore the influence of cell growth on PEC membrane characteristics, that is, to study the membrane characteristics in dynamic process. AC microcapsule entrapping yeast cells (Saccharomyces cerevisiae BY4741) was used as model, and the PEC membrane characteristics including membrane thickness, swelling behavior, permeability, and component were studied during cell culture process. It was found that both the membrane thickness and volume swelling degree of AC microcapsule increased, however, membrane permeability decreased with the growth of entrapped yeast cells. Fluorescence-labeling studies suggested the concentrated alginate layer squeezed by the proliferated cells and macromolecular metabolites layer secreted by proliferated cells contributed to above increment. The former PEC membrane, together with the new layers, constituted the 'apparent membrane', which increased the diffusion resistance of substances. (C) 2011 Elsevier B.V. All rights reserved.

In this study, an improved indirect cell coculture system was constructed by using a polyelectrolyte complex membrane generated by alginate (A) and chitosan (C). Methodologies of characterizing thickness and permeability of flat AC membrane were first established due to the importance of these two parameters in determining intercellular distance and degree of contact between cocultured cells. Compared to reaction time, both alginate concentration and molecular weight (Mw) of chitosan play more dominant roles in determining the membrane thickness and diffusion coefficients. Moreover, cells in the alginate gel and on the AC membrane could maintain high cell viability. Thus, an improved indirect cell coculture system constructed by flat AC membrane was fabricated and characterized, which provides a robust tool to study the effect of intercellular distance and degree of contact between cocultured cells on cell–cell interactions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43100.