Rheological Characterization of Bioadhesive Nasal Gels

Bioadhesive gels improve both effectiveness and efficiency of the product due to intimate contact between a delivery device and the absorbing cell layer.  The interaction at the functional group level often results in the formation of mixtures capable of exhibiting rheological synergy.  Rheological synergy is the demonstration of greatly excess of viscosity and gel like properties when mixed with mucin than if the mucin and gels were examined separately.  This rheological synergism between gels and mucin could be used as an in vitro parameter to determine the mucoadhesive properties. In this study a simple rheological method is used to quantitatively determine various parameters like viscosity enhancement (ηenhance), relative viscosity enhancement of the combination system (ηrel), force of mucoadhesion (F) and viscosity component of bioadhesion (ηb). This is used to quantitatively compare different bioadhesive nasal gels prepared using carbopol which contain cyclodextrin as absorption enhancer. Composition of a gel can strongly influence its rheological properties and even one different constituent can lead to significantly different rheological behavior. The influence of the presence of cyclodextrin and different methods of addition of cyclodextrin was studied. The pattern noticed in this study was that the gels without the cyclodextrin showed the highest force of bioadhesion which was followed by the gels with cyclodextrin as inclusion complex and then by the gels with cyclodextrin as a physical mixture.  These gels were also subjected to Texture Profile Analysis.