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

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8. Final Discussion and ConclusionsIn this thesis we described the preparation of RIF-loaded microparticles, designed for use asfreeze-dried formulations for rapid re-hydration-nebulization and RFP delivery to lungmacrophages. During this study we evaluated particles made with synthetic or naturalpolymers, (PLGA and chitosan) as well as mixtures of the two polymers (PLGA/chitosan),under identical conditions in order to compare the different cases. Particles were evaluated interms of RFP loading and stability during freeze-drying and nebulization.Comparison of the results obtained from the three different particle types, let us to concludethat RFP loading is generally higher in the order PLGA/chitosan > PLGA>chitosan (althoughthis does not apply for all the different samples evaluated in each group). Within the chitosangroup,RFP E% is affected by the chitosan concentration used during chitosan particleformation, but in all cases RFP-loading is considerably lower in chitosan microspherescompared to PLGA. For the PLGA microparticles it seems that RFP loading is higher whenRFP is initially added in the system through the organic phase (during microspherepreparation) a fact that is in line with the lipophilic nature of this drug.Considering the important characteristics of nebulization ability (NE%) and stability(NEED%), the order for particles is again (as for E%) PLGA/chitosan > PLGA > chitosan,while significant differences between the different particle compositions within the groupswere observed. For chitosan microparticles NE% increases significantly with decreasingchitosan concentration, due to the easier nebulization of dispersion with lower viscosity(Bridges et al, 2000). The microspheres that exhibited the highest stability during nebulization(PLGA 1 and 2, and PLGA/chitosan 0,75%), were those with a higher compact and stablestructure (compared to chitosan particles), as proven by their morphological assessment. ThePLGA-based particles showing the highest stability during nebulization were also found tohave constant mean diameter before and after the process.The high stability demonstrated for PLGA-based particles, during nebulization, may berelated to the possibility of reaction between the amino groups of RFP and the terminalcarboxyl groups of PLGA (278). This also explains the higher E% found for thesemicroparticles than those of chitosan particles. Nevertheless, the fact that chitosan-coatedPLGA particles are even better in terms of RFP E%, NE% and NEED% compared touncoated PLGA particles suggests that chitosan acts as a stabilizer for the particles, possiblyby interacting with PLGA (the amino groups of chitosan with the terminal carboxyl groups ofPLGA). This explains the almost linear dependence of particle stability on their chitosancontent.120
8. Final Discussion and ConclusionsRecently, it was proposed that for improved product shelf-life, particles intended for alveolardelivery of drugs could be prepared as freeze dried formulations that will be re-hydrated onlyprior to nebulization (279). All particles prepared herein were found to be very stable afterfreeze-drying and the freeze-drying/re-hydration cycle did not affect their NE% and NEED%.Additionally, the quality of the powder produced was always good since it could be easily rehydrated).Summarizing the results of this study, we may conclude that the PLGA polymer is better thatchitosan, for the formation of particles that could deliver RFP to alveolar macrophages bynebulization. However, the combination of the two polymers at proper quantities results in theformation of very stable microspheres with high loading capacity for RFP.121
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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 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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