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7. RFP Loaded PLGA Coated Chitosan Microspheres Obtained by WSD MethodFor all microsphere formulations nebulization efficiency and drug leakage after nebulizationwere evaluated. Both of these parameters depend on the stability of particles.As can be seen in figure 7.3 all coated formulations showed a good nebulization efficiencythat increased as chitosan concentration increaed. This is probably because chitosan on thesurface can reduce the drug leakage during the nebulization process.Similarly to chitosan particles described previously (chapter 4 and 5), chitosan coated PLGAmicrosphere dispersions showed a viscosity that increased as the chitosan concentrationincreased. However, in this case particles showed good aerodinamic propertiesas they couldbe easily nebulized (figure 7.4).A similar trend was observed when NEED% was calculated. As shown in figure 7.5, theamount of RFP still encapsulated after the nebulization was improved by coating the PLGAparticles with the hydrophilic polymer.once again, results demonstrated that nebulizationproperties of the prepared microspheres improved as chitosan concentration increased. Inparticular formulation 0,75% was able to retain 63,51% of the entrapped drug10080% RFP6040200No chit 0,1% chit 0,25% chit 0,5% chit 0,75% chitNE% before FDNE% after FDFigure 7.3: Nebulization Efficiency (NE%) of RFP-Loaded Plga Coated ChitosanMicrosferes112
7. RFP Loaded PLGA Coated Chitosan Microspheres Obtained by WSD Method10080% RFP6040200No chit 0,1% chit 0,25% chit 0,5% chit 0,75% chitNEED% before FDNEED% after FDFigure 7.4: Nebulization Efficiency of the Encapsulated Drug (NEED%) of Rfp-LoadedPlga Coated Chitosan MicrosferesFreeze-dried microspheres were re-suspended in water and also in this case all the parameterswere evaluated. As can be seen in figures 7.3 and 7.4 NE% and NEED% remained almost thesame after freeze-drying and these results suggested that the stability of PLGA coatedchitosan microspheres was not affected after liophilization and redispersion process.7.2.6. Release/Stability StudiesRelease studies were carried out by using two different release medium, phosphate buffer atpH 7.4 and acetic acid buffer at pH 4.4, in order to have the same pH values present insidephagosomes and lysosomes and to evaluate the effect of pH on RFP release from chitosanmicrospheres. In Figures 7.5 and 7.6, RFP release profiles from chitosan coated RFP-loadedPLGA microspheres at pH 7.4 and 4.4 buffer solutions respectively, are shown. At both pHvalues, about 25% of the drug is immediately released (2 hour) from the uncoatedmicrospheres. This finding indicates that some of the drug is localized on the surface of themicrospheres due to the partition of the drug into the surface-active agent layer adsorbed atthe surface of the emulsion droplets. After this initial burst, drug release is almost constant,and after 72h 55% of the drug is released from the microspheres. For uncoated PLGAparticles the fastest release was observed at pH 7.4 although no difference in the initial burstcould be noticed. However, as can be seen drug release from uncoated particles was notaffected by the medium pH. On the contrary, coating the microspheres with chitosan alteredthe drug release pattern: the initial burst was reduced and the reduction increased as chitosanamount increased, from 24 to 7% for uncoated and coated particles respectively.113
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European Union Ministero dell’Uni
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Table Of Contents1. GENERAL INTRODU
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7.1.4. Release Studies/Stability St
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1. General Introduction1.1. Pulmona
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1. General Introductionmucosa, and
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1. General Introductionis the fact
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1.3. Lung Anatomy1. General Introdu
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1. General Introductionhighly vascu
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201. General Introductionliquid (84
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1. General IntroductionAerosol size
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1. General Introductionof numerous
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1. General Introductionintermittent
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1. General Introductionsphere prepa
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1. General Introductionit, respecti
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1. General Introductionthe subject
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1. General IntroductionA. zahoor et
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2. Chitosan And PLGA2.1. Chitosan a
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2. Chitosan And PLGAfor the prepara
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2. Chitosan And PLGAmainly controll
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2. Chitosan And PLGAAt present, a n
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2. Chitosan And PLGAneed to be a go
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2. Chitosan And PLGAdichloromethane
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3. Aim of the Work49
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3. Aim of the WorkBiodegradable mic
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4. RFP Loaded Chitosan Microspheres
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Page 71 and 72: 5. Rifampicin Loaded ChitosanMicros
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Page 120 and 121: 8. Final Discussion and Conclusions
Page 122 and 123: 9. References9. References1. Fred S
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Page 130 and 131: 9. References173. Zeng X.M., Martin
Page 132 and 133: 9. References219. Berthold A., Crem
Page 134: 9. Referencesmediates target gene e
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