Deposition of 0.1 μm Aggregate and Near Spherical ⁶⁷Ga₂O₃ Particles Inhaled by Beagle Dogs

Abstract

Respiratory tract deposition of inhaled ⁶⁷Ga₂O₃ particles, both aggregate and near spherical, was studied in one group of 10 Beagle dogs using nose-only exposures to both aerosols. Aggregate particles were produced by vaporization of ⁶⁷Ga tetramethylheptanedione followed by heat treatment at 1100°C. Near spherical particles were produced by introducing steam at an intermediate temperature (500°C) to allow solubilization of the particles in a droplet before complete oxidation and drying at 1100°C. Particle sizes were 0.10 ± 0.02 μm (σ_g = 1.6) and 0.11 ± 0.02 μm (σ_g = 1.8) activity median diffusion diameter for the aggregate and near-spherical particles, respectively. The shape factors were 1.76 and 1.01 for aggregate and near-spherical particles, respectively. Whole body counting and gamma camera imaging techniques were used to determine deposition as a percentage of the inhaled particles. Percentage deposition values for the aggregate and near-spherical particles were, respectively: total respiratory tract, 39 ± 19% and 42 ± 16%; pulmonary, 25 ± 12% and 30 ± 10%. This similarity in deposition patterns shows that deposition data from aggregate particles can be generalized to other ultrafine particles when diffusion diameter is used to characterize particle size.