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

7. RFP Loaded PLGA Coated Chitosan Microspheres Obtained by WSD Method100100909080807070% RFP released60504030% RFP released605040302020101000 20 40 60 8000 20 40 60 80Time (hours)Time (hours)No Chit.0,1% ChitNo Chit.0,1% Chit.0,25% Chit 0,5% Chit0,25% Chit. 0,5% Chit.0,75% Chit0,75% Chit.Figure 7.5: Release Studies pH 7.4 Figure 7.6: Release Studies pH 4.4This behaviour is more evident at pH 7.4. In fact, at pH 4.4 release from the coated particles isfaster even if there is, also in this case, a reduction of the initial burst. Therefore, resultsconfirm the capacity of chitosan on the particle surface to prevent drug leakage in the initialphase of the release. The increased release at pH 4.4 can be explained as a consequence of theionization of D-glucosamine residues that resulted in extensive swelling and faster drugrelease.However, as can be seen in figures 7.5 and 7.6, pH of the release medium does not affect drugrelease7.2.7. Mucoadhesive StudiesIt has been reported that chitosan has preferable properties for improving drug absorption,such as protection of the drug against enzymatic degradation (274), by opening theintercellular tight junction of the lung epithelium and absorption-enhancing effects in thenasal/pulmonary mucosa (275, 276, 277). However, whether or not chitosan enhances drugabsorption in the lungs remains to be determined. For this reason the mucoadhesive propertiesofRFP-loaded PLGA coated chitosan microspheres were evaluated by measuring theadsorption/association of mucin with the microspheres.114