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

4. RFP Loaded Chitosan Microspheres Prepared by Precipitation Methodthe table, did not vary significantly in size after the nebulization process thus confirming theirhigher stability. All samples were still monodispersed as shown by their low P.I. value.Table 4.3: Particle Size of Chitosan Microspheres Before and After Nebulization ProcessParticle Size (nm P.I ± SD Particle Size P.I ± SDFormulation ± SD)Before Nebulization(nm ± SD)After nebulizationForm. Ø NM NM NM NMForm. 1 2310 ± 106 0.160 ± 0.027 1697 ± 54,62 0,234 ± 0,046Form. 2 2470 ± 50.99 0.238 ± 0.011 2120 ± 72,11 0,232 ± 0,028Form. 3 2710 ± 77.88 0.252 ± 0.013 2440 ± 47,44 0,291 ± 0,017Form. ØG NM NM NM NMForm. 4 1470 ± 20.13 0.210 ± 0.089 1770 ± 18,16 0,213 ± 0,076Form. 5 1730 ± 26.30 0.290 ± 0.018 1693 ± 92,37 0,297 ± 0,022Form. 6 2190 ± 47.60 0.243 ± 0.092 2480 ± 44,22 0,364 ± 0,054Using the nebulization device described in the experimental section, we evaluated thenebulization ability of the different types of prepared microparticles. Since association of RFPwith particles is a prerequisite for achieving high RFP concentration in alveolar macrophages,the most important characteristic for these particles is their ability to retain the drug during thenebulization process, which was also evaluated.As can be seen in figure 4.5, the percentage of RFP collected in nebulized microparticlesamples (NE%) ranged from 34.35 to 53.0% although the different microparticle formulationsshowed different nebulization ability for RFP loaded particles. In fact, significant differenceswere measured for NE% among the different nebulized chitosan microparticles. Indeed, as thechitosan concentration in the particles decreased (which results in a decrease of the particledispersion viscosity), their NE% increased. A negative effect of viscosity on NE% wasdemonstrated previously during nebulization of liposomes (257).However, the cross-linked chitosan particles (with GA) always demonstrated slightly higherNE% compared to the non-cross-linked ones.63