THE IMPORTANCE OF GASTROINTESTINAL UPTAKE OF PARTICLES IN THE DESIGN OF ORAL DELIVERY SYSTEMS

The oral delivery of drugs and vaccines is regarded as the optimal mea ns for achieving therapeutic and prophylactic effects for a number of conditions. For both drug and vaccine delivery the enteric route has t he advantages of increased patient compliance, relieves the need for i njection and does not require the presence of trained personnel. In th e case of vaccination, enteric delivery may result in the induction of a protective mucosal immune response against pathogens which colonise and invade the mucosae. Unfortunately, the oral delivery route is bes et with problems such as: gastrointestinal destruction of labile molec ules; low levels of macromolecular absorption; and poor immunity usual ly elicited to orally applied soluble vaccine antigens. To reduce the impact of gut secretions and to ensure the absorption of bioactive age nts in an unaltered form, molecules may be incorporated into biodegrad able microparticles. This oral delivery system therefore relies on the capacity of the gastrointestinal tract to absorb microparticulate mat erials, a function which has been demonstrated to be carried out by me mbranous/microfold (M) cells in the Peyer's patches of the mammalian g ut. This review examines the nature and extent of particulate absorpti on by the gut and considers the implications of this process for the o ral delivery of drugs and vaccines.