Preparation of monodispersed polyelectrolyte microcapsules with high encapsulation efficiency by an electrospray technique

The preparation of polyelectrolyte microcapsules by electrospray was investigated. When a polyanionic or polycationic aqueous solution was electrosprayed into an aqueous solution containing a polyelectrolyte with the opposite charge, a spherical interface consisting of a polyelectrolyte complex was formed by electrostatic interaction to produce a microcapsule. Alginate/chitosan microcapsules (∼100 μm) were successfully produced with a narrow diameter distribution (coefficient of variation 4.4%). The diameters of microcapsules were controlled in the range of 80–230 μm by varying the operating conditions, such as feed rate, working voltage, the distance from needle-to-collector, needle diameter and polyelectrolyte concentrations. We also succeeded in the encapsulation of protein, dextran and a polymeric microsphere within the polyelectrolyte microcapsules with high encapsulation efficiencies (more than 99%). The study of yeast encapsulation reveals that the electrospray technique can encapsulate a physiologically active substrate in the polyelectrolyte microcapsule and maintain its activity.