Bioadhesive potential of gliadin nanoparticulate systems.

The objective of this work was to prepare, characterise and evaluate the adhesive potential of gliadin nanoparticulate carriers. Firstly, lectin-nanoparticle conjugates were obtained by the carbodiimide (CDI) covalent binding of Dolichos biflorus lectin (DBA) to the surface of gliadin nanoparticles (NP) containing carbazole (as a model lipophilic drug). The DBA binding efficiency was favoured in mild acidic conditions. Similarly, a CDI concentration of about 0.63 mg/mg nanoparticles, acting during at least 1 h, provided binding efficiencies of about 50% bulk lectin. Under optimised experimental conditions, the DBA conjugates showed a size of around 500 nm and the amount of loaded carbazole and the DBA content were calculated to be around 15 and 23.5 microg/mg, respectively. The bioadhesive activity of NP and DBA conjugates was determined in samples of small and large rat intestinal mucosa. The amount of adsorbed NP was calculated to be around 8 and 4 g/m(2) in the small and large intestine, respectively. This high capacity to interact with the mucosa may be explained by gliadin composition. In fact, gliadin is rich in neutral and lipophilic residues. Neutral amino acids can promote hydrogen bonding interactions with the mucosa, while the lipophilic components can interact with the biological tissue by hydrophobic interactions. The bioadhesive activity of DBA conjugates was calculated to be about 2 g/m(2) in the small intestine and greater than 4 g/m(2) in the caecum and distal colon. These degrees of interaction were always significantly higher than those obtained with controls. Finally, DBA did not provide the specificity for interaction with Peyer's patches. In summary, gliadin nanoparticles show a high capacity of non-specific interaction with the intestine, whereas DBA binding to the surface of these carriers provided a greater specificity for colonic mucosa.