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

5. RFP Loaded Chitosan Microspheres Prepared by Spray-Drying MethodComposition of RFP-loaded chitosan microspheres, prepared by the spray drying method, isreported in table 5.1.Table 5.1: Spray-Dried Chitosan Microspheres CompositionRFP CTS Acetic Acid GA 4 % (w/w)Form.A 2mg/ml 0.25% 2% +Form.B 2mg/ml 0.50% 2% +Form.C 2mg/ml 0.75% 2% +Form.D 2mg/ml 1% 2% +Form.E 2mg/ml 0.25% 2% -Form.F 2mg/ml 0.50% 2% -Form.G 2mg/ml 0.75% 2% -Form.H 2mg/ml 1% 2% -5.2.2. Size and Morphological Characteristics of MicrospheresSpray-dried chitosan microparticles showed a mean particle size ranging from 0.6 to 1.5 µm.As can be seen in table 5.2, microsphere size and polidispersity increased as chitosanconcentration and, therefore, solution viscosity increased. This result was probably due to theeffect of the solution viscosity on the droplet size during the atomization step. In general, themean size of droplets formed by atomization is proportional to liquid viscosity and surfacetension and it indirectly affects the spray-dried powder size, being an important processingvariable.The cross-linking degree controls chitosan microspheres properties and Table 5.2 shows alittle increase in the mean size of cross-linked mcirospheres.Morphology of microparticles was verified with optical microscopy (OM) and SEM. OMimages showed round particles, with size in the same range found by PCS analysis. (Figure5.2a and 5.2b). SEM images showed that microspheres obtained by the spray-drying methodwere of good morphological characteristics, spherical shape and smooth surface. Figures 5.3aand 5.3b show a sample of both cross-linked and uncross-linked chitosan microspheres (batchA and E respectively). No morphological difference was highlighted for these two differentmicrospheres. Therefore results seem to indicate that GA does not affect the morphologicalcharacteristics of cross-linked microspheres obtained by the spray-drying method.76