Gold nanoparticle aerosols for rodent inhalation and translocation studies

Abstract

The intensive use of nano-sized particles in many different applications necessitates studies on their risk assessment as there are still open questions on their safe handling and utilisation. For reliable risk assessment, the interaction of nanoparticles (NP) with biological systems after various routes of exposure needs to be investigated using well-characterized NP. We report here on the generation of gold-NP (Au-NP) aerosols with the spark ignition technique, and their characterization in terms of chemical composition, physical structure, morphology and specific surface area, and on interaction with lung tissues and lung cells after one hour inhalation by mice. The originally generated agglomerated Au-NP were converted into compact spherical Au-NP by thermal annealing at 600°C. Since there are currently no data available on inhaled Au-NP in the 10-50 nm diameter range the emphasis was to generate NP as small as 20 nm for inhalation in rodents. For anticipated in vivo systemic translocation and dosimetry analyses, radio-labeled Au-NP were created by proton irradiating the gold electrodes of the spark generator, thus forming gamma ray emitting 195Au with 186 days half-life, allowing long-term biokinetic studies. The dissolution rate of 195Au from the NP was below detection limits. The highly concentrated, polydisperse Au-NP aerosol (1-2×107 NP/cm3) proved to be constant over several hours in terms of its count median mobility diameter, its geometric standard deviation and number concentration.