Polymeric Microcapsules: Introduction and Background by Sasha Bakhru
The following are short articles relevant to polymeric microencapsulation of stem cells to provide control over the ambient cellular microenvironment during in vitro culture.
Microcapsules are heterostructures composed of a core or lumen containing an active material surrounded by a wall or membrane. Conventionally, the core of a microcapsule serves to contain the active material, while the capsule wall protects it or mediates its egress. The practical applications of microencapsulation technologies encompass the scratch-and-sni? pages found in magazines, laundry detergents, drug and gene delivery systems, and carbonless copy paper.
Figure 1.1: Diagram of microcapsule structure.
Figure 1.2: Hollow alginate/chitosan micro?bers (unpublished data).
Microcapsule size and shape are principally dictated by function, spanning uniandmultilamellar spherical shells, cylindrical ?bers (Fig. 1.2), teardrops, and toroids with dimensions ranging from fractions of a micron to several millimeters, all achievable through established microencapsulation processes.
The microcapsule wall may serve a host of functions, most usually to provide a semipermeable barrier to isolate, at least in part, the active material from the local, ambient microenvironment. For the purpose of drug delivery, the limited, selective permeability of the wall allows the designer to tune the posological properties of the structure to achieve release pro?les of variable shape in time. In the case of cellular microencapsulation, irrespective of the particular application, the wall serves a dual purpose: ?rst, to provide a microenvironment conducive to the maintenance of cell viability and second, to mediate the exchange of nutrients, wastes, gasses, and signaling molecules with the ambient media.
Other Sites or Articles by Sasha Bakhru:
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Sasha Bakhru: Cellular Microencapsulation
