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

6. RFP Loaded PLGA Microspheres Prepared by Solvent Evaporation Methoddiffuses into the aqueous medium and finally evaporates into the air. In the solventevaporation method, poly(vinyl alcohol) (PVA) is widely used as an emulsifier in the externalaqueous phase and dichloromethane is the most commonly used solvent to dissolve thepolymer. The o/w emulsion method was varied in our laboratory in order to make particles byadding the drug not only in the organic phase but also in the aqueous phase.In fact two types of particles were prepared: the first ones were obtained by dissolving RFP inthe organic phase (1) and the second ones were obtained by dissolving RFP in the aqueousphase (2). These different samples were prepared in order to evaluate the influence of drugsolubility on different parameters (E%, NE% and NEED%) and on particle characteristics.Composition of RFP-loaded PLGA microspheres is reported in table 6.1.Table 6.1: RFP-loaded PLGA Microspheres CompositionRFP PLGA PVAForm. 1 2 mg/ml 2 mg/ml 4%Form. 2 2 mg/ml 2 mg/ml 4%6.2.2. Size and Morphological Properties of PLGA MicrospheresRFP-loaded PLGA microspheres were obtained in the size range around 2 µm and goodpolidispersity index as shown in table 6.2. The size distribution of PLGA microspheres wasevaluated before and after freeze-drying process. Lyophilized microspheres were mixed withwater, vortexed for few minutes and than measured. No change in average particle sizeappeared after lyophilization and resuspension (data not shown).Table 6.2: Particle Size and Zeta Potential of PLGA MicrospheresFormulationParticle Size (nm ±SD)P.I ± SD Zeta Potential (mV ±SD)PLGA 1 2563 ± 49.32 0.192 ± 0.030 -4.60 ± 0.2PLGA 2 2606 ± 61.10 0.203 ± 0.049 -4.80 ± 0.1As can be seen in table 6.2 the addition of the drug in the organic or in the aqueous phase didnot affect particle size and this is probably because RFP is an amphipatic drug and it can bedissolved in both organic and aqueous phases, although it is more lipophilic.91