The solvent exchange method: A novel microencapsulation technique

The purpose of the present study was to develop a new microencapsulation technique that could address traditional difficulties that have been encountered during the microencapsulation of protein drugs. Reservoir-type microcapsules were produced using a dual microdispenser system or a coaxial ultrasonic atomizer, based on midair collision between component materials followed by interfacial phase separation of a polymeric membrane. It was found that the reported process had no negative effect on functional integrity of the encapsulated model protein, lysozyme. Furthermore, the microcapsules released the encapsulated lysozyme at near zero-order for an extended period when tested without drying. The reported example demonstrated a complete release of intact lysozyme over 50 days. It is believed that these results are additive effects of following features of the new microencapsulation method. First, the method minimizes the exposure of encapsulated proteins to a large water/organic solvent interfacial area, in which the proteins can easily accumulate and be denatured. Second, the method utilizes only a minimal energy for producing microdrops and does not generate damagingly strong mechanical stresses. Third, the contact between the encapsulated drugs and the hydrophobic polymer and their degradation products is minimal in the reservoir-type microcapsules, which could otherwise cause extensive denaturation of the encapsulated proteins. The new method provides a simple and efficient way of making protein-loaded microcapsules, which will lead to commercially viable products in the near future. To this end, post-encapsulation processes such as collection and drying of microcapsules are yet to be improved