A COMPARATIVE-STUDY ON THE ROLE PLAYED BY MUCUS GLYCOPROTEINS IN THE RHEOLOGICAL BEHAVIOR OF THE MUCOADHESIVE MUCOSAL INTERFACE

One proposed mechanism of mucoadhesion involves the interpenetration o f the mucus/mucoadhesive molecules followed by the formation of non-co valent interactions. Mucus glycoproteins are believed to be the major structure forming component of mucus, giving rise to the cohesive and the viscoelastic nature of the mucus gel. The addition of a known muco adhesive, the polyacrylic acid Carbopol 934P (paa), to purified mucus glycoprotein resulted in the formation of a strengthened gel network. This was indicated on visual examination, and also on rheological exam ination using mechanical spectroscopy. A large mean G' (the storage mo dulus, found between 10 and 0.1 HZ) was obtained for the glycoprotein/ paa mix in comparison to when the glycoprotein and paa gels were teste d separately at the same concentration. Similar results were obtained with crude and homogenised mucus samples. This gel strengthening pheno mena was optimum at pH values around the pK(a) of paa. It was conclude d that it is the glycoprotein component of mucus which interacts with paa to produce gel strengthening, and this may increase the cohesive n ature of the weakest component of a mucoadhesive joint, thus allowing prolonged mucosal adhesion. A rheological investigation of a pH 6.2 gl ycoprotein/paa mix between 10 and 0.002 Hz indicated that this gel str engthening effect resulted from both chain entanglement and the format ion of secondary chemical bonds.