The effect of physical barriers and properties on the oral absorption of particulates.

This paper provides an in-depth review of the biological, immunological, and physicochemical barriers to the oral absorption of microparticles. The roles of the mucus and mucosal cell layers are discussed along with technologies and strategies that may be used to improve uptake, including attempts to determine the mechanisms of microparticulate uptake into enterocytes and membranous epithelial (M) cells. Considerations unique to the absorption of microparticles, such as particle size, surface characteristics, cell surface interactions, and the driving force for absorption of microparticles, are also addressed. Although the extent of absorption of microparticles is severely limited, this review provides insight into potential methods and technologies that have been and could be used to improve the oral absorption of microparticles.