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

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4. RFP Loaded Chitosan Microspheres Prepared by Precipitation Method8060% RFP40200Form.0Form.1Form.2Form.3Form.0GForm.4Form.5Form.6NE%NE% After FDFigure 4.5: Nebulization Efficiency (NE%) Before and After Freeze-DryingThe retention of the drug in the nebulized particles (NEED%) is maybe the most importantparameter when a formulation is studied for nebulization delivery. This parameter, in fact,gives important information on the capability of the produced microparticles to retain theencapsulated drug in high amount during the nebulization procedure. Cross-linking chitosanparticles with GA definitely resulted in an increased stability during nebulization as it can beconcluded by comparing the NEED% values measured for the corresponding uncross-linkedchitosan formulations (figure 4.6). In fact, as we said before, GA is able to stabilize chitosanmicrospheres by immobilizing also the drug encapsulated. NEED% was also affected by thechitosan concentration: it increased as the chitosan concentration decreased.Freeze-dried microspheres were re-suspended in water and also in this case all the parameterswere evaluated. As can be seen in figures 4.5 and 4.6, NE% and NEED% remained almost thesame after freeze-drying, and these results suggested that the stability of chitosanmicrospheres was not affected after liophilization and redispersion process.64
4. RFP Loaded Chitosan Microspheres Prepared by Precipitation Method5040% RFP3020100Form.0Form.1Form.2Form.3Form.0GForm.4Form.5Form.6NEED%NEED% After FDFigure 4.6: Nebulization Efficiency of The Encapsulated Drug (NEED%) Before andAfter Freeze-Drying4.2.6. Release/Stability StudiesRelease studies were carried out by using three different release media. Phosphate buffer atpH 7.4 and acetic acid buffer at pH 4.4 were used in order to evaluate the influence of the pHinside phagosome and lysosome on RFP release from chitosan microspheres. In Figure 4.7and 4.8, RFP release profiles from RFP-loaded chitosan microspheres at pH 4.4 and 7.4 buffersolutions respectively, are shown.As can be seen from the figures, an initial burst effect was observed from all chitosanmicroparticles (between 19 and 30% of loaded RFP). After this initial burst, all studiedmicrospheres released RFP at a lower rate. RFP release from the was pH dependent (fasterrelease at pH 4.4 than at pH 7,4). This is attributed to the higher solubility of the polymer atlower pH. In fact, as proposed earlier (258), chitosan microspheres can also provide pHresponsiverelease profile by swelling in acidic environment of the gastric fluid. Whencomparing the release profiles from cross-linked (with GA) and uncross-linked chitosanmicrospheres, we see that at pH 7.40 the release of RIF is substantially decreased in the crosslinkedparticles. It has been proposed before that GA addition in chitosan particles can beused as a method to modulate release kinetics of drugs, as demonstrated for theophylline(259). However, the difference between the release kinetics of RFP from the two types ofchitosan particles is more or less diminished (or is a lot smaller) at pH 4.40, possibly due tothe rapid swelling and increased solubility of this polymer at low pH, which results in a veryfast release of particle- loaded RFP from all chitosan microspheres during the first 8 hours ofincubation.65
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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
Page 14 and 15: 1. General Introductionis the fact
Page 16 and 17: 1.3. Lung Anatomy1. General Introdu
Page 18 and 19: 1. General Introductionhighly vascu
Page 20 and 21: 201. General Introductionliquid (84
Page 22 and 23: 1. General IntroductionAerosol size
Page 24 and 25: 1. General Introductionof numerous
Page 26 and 27: 1. General Introductionintermittent
Page 28 and 29: 1. General Introductionsphere prepa
Page 30 and 31: 1. General Introductionit, respecti
Page 32 and 33: 1. General Introductionthe subject
Page 34 and 35: 1. General IntroductionA. zahoor et
Page 36 and 37: 2. Chitosan And PLGA2.1. Chitosan a
Page 38 and 39: 2. Chitosan And PLGAfor the prepara
Page 40 and 41: 2. Chitosan And PLGAmainly controll
Page 42 and 43: 2. Chitosan And PLGAAt present, a n
Page 44 and 45: 2. Chitosan And PLGAneed to be a go
Page 46 and 47: 2. Chitosan And PLGAdichloromethane
Page 49 and 50: 3. Aim of the Work49
Page 51: 3. Aim of the WorkBiodegradable mic
Page 54 and 55: 4. RFP Loaded Chitosan Microspheres
Page 71 and 72: 5. Rifampicin Loaded ChitosanMicros
Page 83: 5. RFP Loaded Chitosan Microspheres
Page 86 and 87: 6. RFP Loaded PLGA Microspheres Pre
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Page 102 and 103: 7. RFP Loaded PLGA Coated Chitosan
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7. RFP Loaded PLGA Coated Chitosan
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7. RFP Loaded PLGA Coated Chitosan
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8. Final Discussion and Conclusions
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9. References9. References1. Fred S
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9. References40. Wayne L.G., Good R
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1269. References88. Carpenter R.L.
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1289. References135. Fukushima S.;
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9. References173. Zeng X.M., Martin
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9. References219. Berthold A., Crem
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9. Referencesmediates target gene e
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