Aerodynamic characterisation of PLGA nanoparticulate dry powder formulation for vaccine delivery via the respiratory tract

J Janke, R Scherließ

Polymeric nanoparticles offer a possibility as particulate carrier system for vaccines which can be administered to the respiratory tract. Nanoparticles were produced from PLGA by double emulsion technique and spray dried after solvent evaporation. The antigen, in this case ovalbumin as model antigen, was encapsulated inside the nanoparticles. PVA was used in order to stabilise the produced nanoparticles. Furthermore PVA acts as a bulking agent during spray drying; hence no further additives were necessary. Before spray-drying the particles have a size of 250 nm and a narrow size distribution. The spray-drying process embeds the antigen-carrying nanoparticles into
PVA microparticles which can easily be redispersed to nanoparticles. Laser diffraction measurements of the spray dried powder showed an average particle size of 2.3 μm.
The obtained dry powder was filled into HPMC capsules and the aerodynamic properties were determined with Next Generation Pharmaceutical Impactor (NGI) using the Unihaler, a novel capsule-based inhaler. The samples were analysed for ovalbumin content by BCA assay and fine particle fraction (FPF) as well as MMAD were calculated. FPF was about 50% of the loaded dose and mass median aerodynamic diameter (MMAD) was 3.1 μm. Furthermore the emitted dose was investigated with a dose unit sampling apparatus for DPIs according to USP Apparatus B and was
found to be 75% for the tested formulation utilising the Unihaler. The investigations of the spray dried powder produced by double emulsion technique showed that the powder is suitable for an administration via the respiratory tract. Moreover, the Unihaler can disperse the powder very well, but emitted dose may be capable of further optimisation.

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