Polymeric carriers for oral uptake of microparticulates.
Delivery of vaccine antigens by the oral route is plagued with challenges. Much of the research has focused on the development of microparticles as antigen carriers to the gastrointestinal (GIT) mucosa. Polymers, either natural or synthetic, have been the class of compounds most often investigated for their ability to form microparticles containing antigen. A great deal of research has been performed using model microparticles composed of polystyrene. From this work it has become clear that microparticles are taken up and translocated across the GIT epithelium. Antigen carrying microparticles generated from both hydrophobic and hydrophilic polymers are able to induce significant immune responses after oral immunization. Although very little systematic work on the effects of the physicochemical properties of the polymer composing the microparticles has been done, enough is known to conclude that the surface of the polymeric microparticle can be decisive in determining the overall uptake of the microparticles. Charge and the hydrophobic/hydrophilic balance of the polymer are important physicochemical characteristics that determine the value of the polymer as a microparticulate carrier. This review examines the properties of polymeric matrices that make them viable candidates as oral vaccine delivery vehicles.