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.