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

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6. RFP Loaded PLGA Microspheres Prepared by Solvent Evaporation MethodPLGA microparticles size is normally affected by the presence of an emulsifier. In this casePVA was used to prevent aggregation of the emulsion droplets and polymer sticking duringstirring. 4% of PVA was able to stabilize particles also during their storage. This is confirmedby the polydispersity index tha was very low because aggregation did not occur and particlesmantained a narrow distribution, as confirmed also by SEM study.When working with microparticulate systems, it is often helpful to visualize particle shapesand surface characteristics in order to correlate other properties such as surface area and sizedistribution. RFP-loaded PLGA microspheres prepared using the solvent evaporation methodwere spherical in shape with a very smooth surface, as shown in Figures 6.1a and 1b. Theloading of the antimicrobial agent did not cause any significant change in morphology.SEM micrographs confirmed the narrow distribution of particles size found by PCSmeasurement, for each batch. As can be seen, no difference in particle morphology was foundas a consequence of the preparation method.abFigure 6.1: SEM Micrographs of PLGA Microspheres Obtained by Adding the Drug inthe Aqueosus Phase (a) or in the Organic Phase (b).6.2.3. Surface ChargeMicroparticle formulations were characterized also in term of zeta potential because, as wellknown, it can influence particle stability as well as particle mucoadhesion. In theory, morepronounced zeta potential values, being positive or negative, tend to stabilize particlesuspension. The electrostatic repulsion between particles with the same electric chargeprevents the aggregation of the spheres. The PLGA particles made by the solvent evaporationmethod were negatively chargedas can be seen in table 6.2 and, hence, were poorlymucoadhesive. At a neutral pH value the mucus layer is an anionic polyelectrolyte.Mucoadhesion is promoted by a positive zeta potential value and, thus, the presence of the92
6. RFP Loaded PLGA Microspheres Prepared by Solvent Evaporation Methodpositively charged groups on the particles could lead to electrical charge interactions betweenthe mucus and the particles. PLGA negatively charged microspheres were stable and dit notaggregate as confirmed also by SEM investigation, but this surface property make thempoorly mucoadhesive.6.2.4. Entrapment Efficiency (E%)Encapsulation efficiency (E%) is an important index to evaluate drug-loaded microspheres asit is more economical when high encapsulation efficiency can be obtained. An O/W emulsiontechnique is mostly used for the encapsulation of drugs. One objective of this study wastherefore to investigate the influence of drug solubility on the RFP entrapment in PLGAmicrospheres.Figure 6.2 shows E% of the prepared microspheres. As can be seen, no significant differencewas found between formulation 1 and 2. However, formulation 1, wich was obtained byadding the drug in the organic phase, showed a higher E% (72%) than formulation 2 (E% =65%). This small difference could be related to the higher affinity of RFP for the organicphase.Encapsulation efficiency was measured before and after freeze-drying in order to evaluate theeffect of this process on the drug retention. As can be seen in figure 6.2, freeze-drying did notcause any leakage of the drug encapsulated in chitosan microspheres. It was important toevaluate the effect of the freeze-drying process on this parameter because the aim of thisstudy, like for chitosan particles, was to obtain a stable product, in powder form, able to berapidly rehydrated just before its use.10080% RFP6040200PLGA 1 PLGA 2E% Before FD E% After FDFigure 6.2: Encapsulation Efficiency (E%) of PLGA Microspheres93
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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
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
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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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Page 120 and 121: 8. Final Discussion and Conclusions
Page 122 and 123: 9. References9. References1. Fred S
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Page 128 and 129: 1289. References135. Fukushima S.;
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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