ABSTRACT
Immunization against infectious diseases has saved innumerable lives and contributed significantly to today’s increased life expectancy. In spite of these impressive results, there is still considerable potential for improved vaccines. Biodegradable delivery systems for vaccines that are administered by a parenteral application route may have the potential of overcoming some shortcomings of conventional vaccines. Copolymerization of lactic and glycolic acid is a very powerful method to manipulate biodegradation and antigen release of microspheres by controlling monomer stereochemistry, copolymer composition, and polymer molecular weight. The term microspheres, or microparticles, is sometime used rather liberally in the literature to describe particulate-delivery systems, irrespective of size, chemical composition, and manufacturing technique. Lipophilic injection vehicles, such as nonbiodegradable mineral oils or biodegradable oils are formulated into emulsions using surfactants. The biodegradable coating of the microcapsules would be impermeable for the protein, but water could slowly diffuse into the core, creating sufficient osmotic pressure for rupturing the membrane.
