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

5. RFP Loaded Chitosan Microspheres Prepared by Spray-Drying MethodAs can be seen in Figure 5.4, cross-linked formulations A-D showed better NE% thanuncrossed linked formulations: almost 80% of rifampicin was recovered after nebulizationfrom formulations A-C. On the contrary, NE% was quite low for the uncross-linkedformulations E-H, thus confirming their stability is lower than that of the corresponding GAcontaining formulations.10080% RFP6040200A B C D E F G HNebulizarion Efficiency (NE%)Figure 5.4: Nebulization Efficiency (NE%) of Spray-Dryed MicrospheresSince nebulization can lead to drug leakage, it is also important to evaluate how much of theaerosolized drug is still encapsulated after the nebulization (NEED%). Best results in terms ofNEED% were obtained from the cross-linked formulations A-D that were able to retain up to70% of the encapsulated drug. NEED values were affected by chitosan concentration: theydecreased as chitosan concentration increased. Once again, uncross-linked formulations E-Hshowed very poor nebulization properties since NEED values ranged from 5 to 20%. Resultsobtained in this analysis seem to point out that the most important factor affecting NEED ispolymer cross-linkage, as can be seen by the comparison of NEED values from formulationsobtained using the same amount of chitosan in Figure 5.5. Cross-linkage contributes toimprove chitosan microsphere stability by immobilizing the encapsulated drug80