Alginate-oligochitosan microcapsules: A mechanistic study relating membrane and capsule properties to reaction conditions

A new generation of microcapsules was prepared by utilizing a polyelectroly te complexation reaction between two oppositely charged polysaccharides, on e of which is oligomeric. This capsule combines extremely high deformabilit y (>80%) and elasticity with permeability control and can be applied in var ious bioencapsulation technologies. The relative number of interchain ionic bonds, which determine the cross-linking density and membrane properties, can be controlled by either pH or ionic strength. Specific binding with res pect to the molar mass of chitosan occurs during capsule formation. With in creasing ionic strength and pH, a shift toward higher molar masses involved in membrane formation was observed. The preparation of capsules under phys iological conditions (pH 7.0, 0.9% NaCl) was demonstrated, overcoming the l imitation of all other microcapsules based on chitosan which must be prepar ed at pH below 6.5. It has been shown that the parameters such as reaction time, chitosan molar mass, and concentration primarily influence the mechan ical properties, whereas alginate concentration effects both mechanical and porosity characteristic of the capsule membrane.