Specific and non-specific bioadhesive particulate systems for oral delivery to the gastrointestinal tract.

The oral route constitutes the preferred route for drug delivery. However, numerous drugs remain poorly available when administered by this route. In order to circumvent this problem, it has been proposed, successfully for several of them, to associate drugs to polymeric nanoparticulate systems (or small particles in the range of the micrometre in size) because of their propensity to interact with the mucosal surface. The present review focuses on the gastrointestinal bioadhesion of micro- and nanoparticles. Bioadhesion can be obtained by the building of either non-specific interactions with the mucosal surface, which are driven by the physicochemical properties of the particles and the surfaces, or specific interactions when a ligand attached to the particle is used for the recognition and attachment to a specific site at the mucosal surface. The relative merits of those systems are discussed. Their fate in the gastrointestinal tract, including at least three different pathways: (i) bioadhesion, (ii) translocation through the mucosa and (iii) transit and direct faecal elimination, is also presented.