Preparation and characterization of magnetizable aerosols.

Magnetizable aerosols can be used for inhalative magnetic drug targeting in order to enhance the drug concentration at a certain target site within the lung. The aim of the present study was to clarify how a typical ferrofluid can be atomized in a reproducible way. The influence of the atomization principle, the concentration of magnetic nanoparticles within the carrier liquid and the addition of commonly used pharmaceutical excipients on the aerosol droplet size were investigated. Iron oxide (magnetite) nanoparticles were synthesized by alkaline precipitation of mixtures of iron(II)- and iron(III)-chloride and coated with citric acid. The resulting ferrofluid was characterized by photon correlation spectroscopy and vibrating sample magnetometry. Two different nebulizers (Pari Boy and eFlow) with different atomization principles were used to generate ferrofluid aerosols. A range of substances that influence the surface tension, viscosity, density or vapor pressure of the ferrofluid were added to investigate their impact on the generated aerosol droplets. The particle size was determined by laser diffraction. A stable ferrofluid with a magnetic core diameter of 10.7 ± 0.45 nm and a hydrodynamic diameter of 124 nm was nebulized by Pari Boy and eFlow. The aerosol droplet size of Pari Boy was approximately 2.5 μm and remained unaffected by the addition of substances that changed the physical properties of the solvent. The droplet size of aerosols generated by eFlow was approximately 5 μm. It was significantly reduced by the addition of Cremophor RH 40, glycerol, polyvinyl pyrrolidone and ethanol.