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

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6. RFP Loaded PLGA Microspheres Prepared by Solvent Evaporation Method6.2.5. Nebulization Studies of PLGA MicrospheresNebulization studies were carried out in order to evaluate the stability and the suitability ofPLGA particles for pulmonary/nasal administration. All these studies were performed byusing both freshly prepared and freeze-dried microspheres. Different analyses were performedon the nebulized samples. As for chitosan microspheres, only the sample trapped in water wasassayed, while the material deposited on the impinger walls was not included.Size of particles was evaluated after the nebulization process and, as can be seen in table 6.3,there was an important decrease of mean particle size and also a significant increase ofpolidispersity index. The decrease on mean size during nebulization can be explained takinginto account that during this process small particles can be nebulized easily. Nebulizationproved that PLGA microspheres, prepared during this work, were multidimensional as it isshown by the high P.I. value. In fact, three different microsphere populations were obtained inthe three different impinger stages. The increase in P.I. could also be related to the fact thatsize analysis was carried out by DLLS, whose sensitivity is not really appropriate for particlesin the micron range.Table 6.3:Particle Size of Spray-Dried Microspheres Before and After NebulizationProcessParticle Size (nmParticle SizeFormulation± SD)P.I ± SD(nm ± SD)P.I ± SDBefore nebulizationAfter nebulizationPLGA 1 2563 ± 49.32 0.192 ± 0.030 1073 ± 35.11 0.778 ± 0.053PLGA 2 2606 ± 61.10 0.203 ± 0.049 1166 ± 32.61 0.857 ± 0.013For all microsphere formulations nebulization efficiency and drug leakage after nebulizationwere evaluated. Both these parameters depend on the stability of particles.As can be seen in figure 6.3 all formulations showed a good nebulization efficiency (NE%)from 72% for PLGA 1 obtained by adding RFP in the organic phase, to 65% for PLGA 2obtained by adding RFP in the aqueous phase. During the nebulization process, part of thedrug can be lost as a consequence of different processes. In fact, some particles, which are toobig, can not be nebulized while others can be disrupted during the process. The little lowerNE% of PLGA 2 formulation is probably connected to the preparation method. In fact, byadding RFP in the aqueous phase it is possible to have some drug on the particle surface, fromwhich can be lose easily during the nebulization process.94
6. RFP Loaded PLGA Microspheres Prepared by Solvent Evaporation Method10080% RFP6040200PLGA 1 PLGA 2NE% Before FDNE% After FDFigure 6.3: Nebulization Efficiency (NE%) of PLGA MicrospheresThis behaviour was also confirmed by studing the drug leakage after nebulization. PLGA 1showed the highest medium NEED% value, (figure 6.4), although no significant differencecan be observed between the two formulations. Freeze-dried microspheres were rapidly rehydratedand also in this case all the parameters (NE% and NEED%) were evaluated. As canbe seen in figures 6.3 and 6.4, NE% and NEED% remained almost the same after freezedryingand these results suggest that the stability of PLGA microspheres was not affected bythe liophilization and redispersion process.10080% RFP6040200PLGA 1 PLGA 2NEED% Before FDNEED% After FDFigure 6.4: Nebulization Efficiency of the Encapsulated Drug (NEED%) of PLGAMicrospheres95
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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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Page 46 and 47: 2. Chitosan And PLGAdichloromethane
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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
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Page 102 and 103: 7. RFP Loaded PLGA Coated Chitosan
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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
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