Abstract
The effect of the excipients used for the preparation of granules containing chitosan microspheres on the adsorption of the muco-polysaccharide mucin was studied. Adsorption isotherms at 37°C were obtained as one strategy for the in vitro evaluation of the muco-adhesive properties of granules carrying drugs. The microspheres were prepared via an ionotropic gelation technique using sodium tripolyphosphate as the cross-linking agent. The resulting microspheres were dried at 40°C until a water content of 75% was achieved and the subsequent extrusion/spherulation process carried out using different excipients, i.e. unmodified chitosan, pre-gelated starch or carboxymethylcellulose. The Langmuir adsorption equation gave a good fit to the experimental data. Mucin exhibited the best affinity to granules containing chitosan as the excipient. Such granules also appeared to have the best muco-adhesive properties.