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

7. RFP Loaded PLGA Coated Chitosan Microspheres Obtained by WSD Method7.1.3. Characterization of RFP-Loaded PLGA Coated Chitosan Microspheres7.1.3.1. Particle Sizing and MorphologyThe microspheres were analysed for their size and polydispersity index on Zetasizer Nano ZS,Malvern instruments, based on Photon Correlation Spectroscopy, at a scattering angle of 90°and temperature of 25°.Measurements were carried out both for fresh and freeze-dried samples. Before counting, thesamples were diluted with a 0.05% (w/v) tween 80 water solution in order to preventprecipitation during the measurements. Results are the means of triplicate experiments.7.1.3.2. Surface Charge (Zeta-Potential)The surface charge of the microspheres was determined with Zetasizer Nano ZS, Malverninstruments. The measurements were carried out in an aqueous solution of KCl 0,1N.Immediately before the determinations microspheres were diluted with KCl solution. Themeasured values were corrected to a standard reference at temperature of 20°. Results are themeans of triplicate experiments.7.1.3.3. Particle MorphologyIn preparation for scanning electron microscopy (SEM) several drops of the microspheresuspension were placed on an aluminum stub having previously been coated with adhesive.The samples were evaporated at ambient temperature until completely dried, leaving only athin layer of particles on the stub. All samples were sputter coated with gold-palladium(Polaron 5200,VG Microtech,West Sussex, UK) for 90 seconds (2.2 kV; 20 mA; 150–200A°)under an argon atmosphere. The SEM (Model 6300, JEOL, Peabody, NY) was operated usingan acceleration voltage of 10 kV.7.1.3.4. Measurement of Loading Efficiency of RFP in PLGA Coated ChitosanMicrospheresThe rifampin content of each lot of microspheres was determined by first extracting therifampin and quantifying the amount of drug spectrophotometrically. A series of rifampinsolutions of known concentrations in acetonitril were prepared, and absorbances weremeasured in order to generate a standard curve.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.104