Controlling the size of nebulised droplets by pinning surface waves for precise delivery of aerosolised medicine
Elijah Nazarzadeh1, Nikita Lomis2, Xi King1, Rab Wilson1, Manlio Tassieri1, Julien Reboud1, Jon Cooper1, Satya Prakash2
1Division of Biomedical Engineering, University of Glasgow, Rankine Building, Glasgow G12 8LT, UK
2Biomedical Technology and Cell Therapy Research Laboratory, Department of Biomedical Engineering, 3775 University Street, Montreal H3A 2B4, Canada
The effective delivery of medication to the lungs via the inhalation of aerosols is strongly dependent upon the droplet size distribution; i.e., optimum pulmonary drug delivery occurs when the size falls between 1 and 5 μm in diameter.
In this study, we investigated the formation of aerosols by means of surface acoustic waves (SAWs) and developed a new solution to control the droplet size distribution within the required range. The acoustic waves were coupled into a microfabricated array of microconfinements of the liquid sample to be nebulised. The therapeutic suspension also advantageously act as the acoustic coupling agent. SAWs were generated on the surface of a piezoelectric substrate and the nebulisation process was monitored by a high-speed camera (100,000 fps) and the particles size distribution measured by a Spraytec (Malvern Panalytical).
We show that the physical confinement within the microstructures controls the wavelength of the deformation of the liquid, which allows us to precisely tailor the droplet size distribution of the aerosols to the optimum range for drug delivery (1 to 5μm). We also validated the applicability of the technique, by nebulising drug-loaded nanoparticles. Importantly, the control of the acoustic energy into the microstructures enables the direct formulation of encapsulated compounds from base materials (i.e. the compound and the shell). This new capability offers the possibility of nebulising formulations that have a short shelf-life when encapsulated. As a proof-of-concept, we demonstrate this by forming and nebulising the cancer drug Paclitaxel, encapsulated in ca. 250 nm human serum albumin particles.