MICROCAPSULE DRUG DELIVERY SYSTEMS.

Abstract

Microencapsulation is a process designed to reproducibly apply thin polymeric coatings to small particles of solids, droplets of liquid (pure or solutions), or dispersions. For the purposes of this discussion, microencapsulation is arbitrarily differentiated from macrocoating techniques in that the former involves the coating of particles ranging dimensionally from several tenths of a micron to 5,000 microns in size. A unique feature of this micropackaging technique is in the minuteness of the coated particles and their subsequent potential usefulness in handling physiologically active materials in a variety of dose forms. A number of microencapsulation processes are described in the literature, and these have been referred to as mechanical, electrostatic or vacuum deposition and polymerization. The processes reviewed in this paper are primarily those utilizing phase separation or coacervation techniques. The coating material, which is basically a film-forming polymeric material, can be selected from a wide variety of natural and synthetic polymers, depending on the material to be coated and the characteristics desired in the final microcapsules. Effective control of release properties can be achieved with materials having diverse water solubilities. Judicious selection of an appropriate coating material and variation of the coating thickness allow a spectrum of patterns to be achieved.