Whey protein is a natural polymer recently used as an excipient in buccoadhesive tablets but its mucoadhesive properties were barely studied. In this work, we characterize mucoadhesion of whey protein in order to determine the mechanisms and optimal conditions for use as excipient in oral drug delivery. Thus, native and denatured whey protein (NWP and DWP) were investigated and the effect of concentration and pH were also studied. Many methods of characterization were selected to allow the study of chemical and physical interactions with mucin and then the results were bound with an ex vivo experiments. Turbidity of WP-mucin mixture increased at acidic pH 1.2 till 4.5 indicating interaction with mucin but not at pH 6.8. No interaction with mucin was also found by ITC method at pH 6.8 for native and denatured whey protein used at 1% (w/w). Forces of bioadhesion evaluated by viscosity measurements were the best for high concentrated (10.8%) DWP solutions at pH 6.8 and were low at pH 1.2 for NWP and DWP solutions. Addition of chemical blockers indicated that hydrogen bondings and disulfide bridges were the main mechanisms of interactions with mucin. Reticulation of DWP with calcium ions to obtain microparticles (MP) did not influence the ability of interaction with mucin as shown by FTIR analysis. These results correlated with ex vivo study on rat tissue demonstrating important adhesion (75%) of WP MP on the intestine and null on the stomach after 2h of deposit.
Keywords: Gastro-intestinal mucoadhesion; Oral drug delivery system; Polymer; Whey proteins.
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