Alginate-oligochitosan microcapsules. II. Control of mechanical resistance and permeability of the membrane

The simultaneous regulation of mechanical properties and permeability, for a new microcapsule based on the complexation of oligochitosan and alginate, is possible through control of the reaction conditions. Specifically, the results of mechanistic study have shown that the molar mass-of the polyanion influences primarily the capsule mechanical resistance, without changing its permeability. Furthermore, both a reduction in membrane permeability and an improvement in mechanical strength can be achieved by raising the polyanion concentration. Alginate coatings were also found to be an effective means to reduce the membrane permeability and cutoff without altering-the microcapsule's mechanical resistance. It has been shown that the size of the capsules does not effect the morphological characteristic of the capsule membrane. However, due to the differences in the membrane thickness, some changes in mechanical and permeability characteristic were observed. Additionally, a linear correlation between internal bursting pressure and the capsule wall thickness was found with a mechanical resistance of the alginate-chitosan membrane of approximately 360 MPa/ m. The high microcapsule strengths, and its tunable permeability, are ideally suited for, and have been tested in, applications such as microencapsulation of living cells and control delivery systems.