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

4. RFP Loaded Chitosan Microspheres Prepared by Precipitation Method4.2.2. Size and Morphological Characteristics of MicrospheresRFP-loaded chitosan microspheres were obtained in the size ranging from 1 to 3 µm. Allformulations were monodispersed as shown by the polidispersity index that was always in therange 0.16-0.29 (table 4.2). all particles in this study were also freeze-dried and tha influenceof this procedure on microspheres properties was evaluatedin order to design a freeze-driedformulation capable of being rapidly hydrated nad nebulized for the delivery of RFP to lungmacrophages. PCS analyses showed that lyophilization did not affect microsphere size (datanot shown).As can be seen from the table, microsphere size increased as chitosan concentration and,therefore, solution viscosity increased. As expected cross-linked microspheres were smallerthan the corresponding uncross-linked particles: these differences in size indicate that crosslinkedmicrospheres were more compact in structure because of the cross-linkage.Table 4.2: Particle Size and Zeta Potential of Chitosan MicrospheresFormulation Particle Size (nm ± SD) P.I ± SD Zeta Potential (mV ± SD)Form.Ø NM NM NMForm.1 2310 ± 106 0.160 ± 0.027 +32.5 ± 0.4Form.2 2470 ± 50.99 0.238 ± 0.011 +34.7 ± 0.1Form.3 2710 ± 77.88 0.252 ± 0.013 +37.0 ± 0.2Form.Ø G NM NM NMForm.4 1470 ± 20.13 0.210 ± 0.089 +23.7 ± 0.6Form.5 1730 ± 26.30 0.290 ± 0.018 +21.9 ± 0.2Form.6 2190 ± 47.60 0.243 ± 0.092 +15.6 ± 0.2Microsphere formation and particle morphology were studied with optical microscopy andSEM. Optical micrographs showed round particles, in a range of size that confirmed PCSmeasurements. SEM micrographs showed that uncross-linked microspheres were sphericaland more regular in shape than the cross-linked ones. As can be seen from figure 4.2, crosslinkingwith GA gave particles different in shape and with a rough surface.60