chitosan and plga microspheres as drug delivery ... - UniCA Eprints

5. RFP Loaded Chitosan Microspheres Prepared by Spray-Drying Methodformulation A is more capable of controlling the drug release than formulation E that releasedthe 90% of the drug in 48 hours at pH 1.2.1001008080% RFP6040% RFP6040202000 20 40 60Time (hours)00 20 40 60Time (hours)Form. AForm. EForm. AForm. EFigure 5.6: Release Studies pH 7.4 Figure 5.7: Release Studies pH 1.25.2.7. Mucoadhesive StudiesAerosol inhalation therapy via the respiratory tract is desirable for delivering drugs since ithas the following advantages over other routes: lung surface area is extremely large andmucosal permeation of drug is comparatively easy because the vascular system is welldeveloped and the walls of alveoli are extremely thin. Finally the intra-cellular or extracellularactivity of drug-metabolizing enzymes is relatively low.Since a strong interaction exists between mucin and chitosan, mucin should be spontaneouslyadsorbed to the surface of the chitosan microspheres. The mucoadhesive behaviour ofchitosan microspheres was assessed by their suspension in different amounts of mucin inaqueous solutions at room temperature. As can be seen in Figure 5.8 the amount of adsorbedmucin increased with increasing mucin concentration. These results confirm that chitosanmicrospheres have the ability to adsorb mucin. The amount of mucin adsorbed was affectedby the presence of the cross-linking agent. In fact cross-linked microspheres interacted with alower amount of mucin, probably because of the cross-linkage and the reduced positive82