Generation and characterization of electrostatically charged radiolabelled aerosols for lung scintigraphy

Abstract

Particles and droplets produced from pharmaceutical inhaler devices are naturally charged. Previous in silico and in vitro studies have shown that the levels of these electrostatic charges may potentially affect deposition in the airways but this has not been confirmed in vivo. Human lung scintigraphic studies using radiolabelled particles with controlled charges would provide crucial data on locating the deposition sites with respect to the particle charge level. An aerosol charging rig has been developed for this purpose. ^99mTc-radiolabelled droplets from an Aerogen® Solo vibrating mesh nebulizer were charged by induction and then dried to yield positively charged particles. Particles with near-neutral charges were produced at an induction voltage of −0.4 kV, while those with 10-4,000 elementary charges per particle were generated at −4.5 kV, depending on the particle size. The number of elementary charges per particle generally decreased with radioactivity, especially for solutions at 400 and 800 MBq/mL. This was attributed to the indirect ionizing effect of the gamma radiation in the air, which produced bipolar ions that neutralized the initially charged particles. Radioactivity at 100 MBq/mL was found to be optimal in generating the highest particle charges that could potentially affect in vivo deposition in the lungs. The aerosol charging rig is suitable for use in human scintigraphy studies which we will conduct in the near future.

Copyright © 2021 American Association for Aerosol Research

EDITOR:

• Yannis Drossinos

Acknowledgments

Dr Jim Fink of Aerogen Pharma Corporation is thanked for his helpful advice on the use of the Aerogen^® Solo vibrating mesh nebulisers.

Additional information

Funding

This work was financially supported by the Australian Research Council (Discovery Project 160102577).