ABSTRACT
Biodegradable polymers can be used in many different forms, depending on the application, with microspheres or microcapsules being the most popular form. Several techniques are available for microencapsulation, and the choice of a method depends on the physical and chemical properties of the polymer and antigen to be encapsulated, and the function and desired size of the microspheres. The method of microencapsulation significantly affects the characteristics of the microspheres. In general, porous, spherical particles, with a broad size distribution, that provide rapid release of incorporated active agent are obtained by the solvent extraction technique, whereas less porous microspheres are obtained by solvent evaporation and phase separation techniques. Placing the microspheres in a moisture-resistant container for reconstitution with a suitable vehicle before administration presents a suitable alternative. Potential oral delivery systems include tablets, capsules, and dry powder for reconstitution into a suspension.
