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

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5. RFP Loaded Chitosan Microspheres Prepared by Spray-Drying Methodof microspheres was determined by first extracting the RFP and quantifying the amount ofdrug spectrophotometrically.The drug encapsulation efficiency was calculated as the percentage of drug entrapped inmicrospheres compared with the initial amount of drug recovered in unpurified samples. Theconcentration of rifampin contained in each sample was determined by measuring theabsorbance on a spectrophotometer at 485 nm.5.1.3.6 Nebulization of MicrospheresRFP-loaded chitosan microspheres aerosols were generated using an efficient high-outputcontinuous-flow Markos Mefar MB2 nebulizer, driven by a Nebula compressor (MarkosMefar) operated at 7l/min. A volume of 3 ml of sample was used for the nebulization. Theaerosols containing RFP-loaded chitosan microspheres were collected in a water solutionusing a modified 3 stages glass impinger. The impinger device was used with the collectingflask containing 3 ml of water to which the aerosol was introduced through a calibrated glasstube and critical orifice delivering the jet of aerosol 5 mm above the bottom of the flask.After aerosolization (10 minutes), the impinger contents were assayed in order to evaluate theeffect of nebulization on drug leakage of microspheres. The secondary aim of this experimentwas also to determine the total amount of formulation nebulised into the apparatus. Thenebulization efficiency (N.E%) of microsphere formulations is defined as the total output ofdrug collected on the impinger as a percentage of the total submitted to nebulization.NE% = (Aerosolised drug /Total drug placed in nebuliser) x 100Because nebulization can lead to drug leakage, it is important to also determine thenebulization efficiency of the encapsulated drug (N.E.E.D%). This parameter is defined as thepercentage of aerosolised drug that remains encapsulated after nebulization. A portion ofnebulised sample was purified by centrifugation and the amount of drug in the sample afterand before centrifugation was assayed.5.1.4. Release Studies/Stability StudiesIn vitro release of RFP from chitosan microspheres was determined using as the releasemedia, phosphate buffer pH 7.4 in order to simulate some of the conditions in the lungs, andpH 1.2 in order to evaluate the stability of chitosan microspheres in acidic medium. Freezedriedformulations were suspended in 500 ml of the dissolution medium, and the amount ofmicrospheres was varied in order to kept constant the amount of drug (25 mg). The74
5. RFP Loaded Chitosan Microspheres Prepared by Spray-Drying Methodexperiments were carried out at 37 ± 0.3°C at a rotation speed of 100 ± 2 rpm. A measure of 1ml samples were withdrawn at appropriate time intervals and centrifuged at 10000 rpm.Supernatants were diluted suitably with acetonitrile and absorbance of the resulting solutionwas measured at 485 nm. The residue (after centrifugation) was redispersed in 1 ml of thefresh dissolution medium and replaced back into the dissolution apparatus. The cumulativeamount of RFP was obtained from the calibration curves of RFP in acetonitrile. The stockstandard solution of RFP (2 mg/ml) was prepared by dissolving the drug in acetonitrile andstoring at 4°C. A standard calibration curve was built up by using standard solutions preparedby dilution of the stock standard solution with acetonitrile.5.1.5. Mucoadhesive Studies5.1.5.1. Adsorption of Mucin on Chitosan MicrospheresStandard calibration curves were prepared from 2 mL of mucin standard solutions (0.25, 0.5,0.75, and 1 mg/2 mL) and then, the absorbance of the solutions was recorded at 500 nm in aUV spectrophotometer. Triplicate samples were run.Mucin aqueous solution with different concentrations (0.025, 0.05, 0.1, 0.2, and 0.5 mg/mL)were prepared. Chitosan microspheres (20 mg) prepared by spray-drying method weredispersed in the above mucin solutions, vortexed, and shaken at room temperature. Then, thedispersions were centrifuged at 4000 rpm for 2 minutes, and the supernatant was used for themeasurement of the free mucin content. The mucin content was calculated from the standardcalibration curve.5.1.6. Statistical AnalysesAll experiments were repeated at least three times. Results are expressed as means ± standarddeviation. A difference between means was considered significant if the p value was less thanor equal to 0.05.5.2. Result And Discussion5.2.1. Preparation of RFP-Loaded Chitosan MicrospheresIn order to find the best microsphere formulations for the delivery of effective doses of RFPto macrophages after aerosol therapy, we also prepared and characterized chitosanmicrospheres of by using an alternative preparation method that is spray drying.Also in this case uncross- and crosslinked (GA) microparticles were prepared and theinfluence of different parameters was studied..75
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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
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 73: 5. RFP Loaded Chitosan Microspheres
Page 83: 5. RFP Loaded Chitosan Microspheres
Page 86 and 87: 6. RFP Loaded PLGA Microspheres Pre
Page 100 and 101: 100
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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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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