Alginate-oligochitosan microcapsules. II. Control of mechanical resistanceand 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 polyanio n influences primarily the capsule mechanical resistance, without changing its permeability. Furthermore, both a reduction in membrane permeability an d an improvement in mechanical strength can be achieved by raising the poly anion concentration. Alginate coatings were also found to be an effective m eans to reduce the membrane permeability and cutoff without altering-the mi crocapsule's mechanical resistance. It has been shown that the size of the capsules does not effect the morphological characteristic of the capsule me mbrane. However, due to the differences in the membrane thickness, some cha nges in mechanical and permeability characteristic were observed. Additiona lly, a linear correlation between internal bursting pressure and the capsul e wall thickness was found with a mechanical resistance of the alginate-chi tosan membrane of approximately 360 MPa/ m. The high microcapsule strengths , and its tunable permeability, are ideally suited for, and have been teste d in, applications such as microencapsulation of living cells and control d elivery systems.