Constant size, variable density aerosol particles by ultrasonic spray freeze drying

Area of Science:

• Pharmaceutical Technology
• Materials Science
• Aerosol Science

Background:

• Optimizing inhaled drug delivery requires precise control over aerosol particle characteristics.
• Ultrasonic spray freeze drying (USFD) is a promising technique for producing inhalation particles.
• Understanding process-structure relationships in USFD is crucial for reproducible particle engineering.

Purpose of the Study:

• To investigate the impact of solute concentration on the properties of inhalation aerosol particles produced by USFD.
• To establish precise control over particle size and aerodynamic properties.
• To experimentally validate the relationship between particle density and aerodynamic behavior.

Main Methods:

• Production of porous mannitol, lysozyme, and bovine serum albumin (BSA) particles using USFD.
• Systematic variation of solute concentration (1-5 wt%) in the liquid feed.
• Measurement of particle size, Fine Particle Fraction (FPF) using cascade impaction, and particle density.

Main Results:

• Particle size was independent of solute concentration, determined by atomization drop size.
• A linear relationship was observed between FPF and the square root of solute concentration for mannitol and lysozyme.
• FPF decreased with increasing solute concentration for mannitol and lysozyme, while BSA showed minimal change due to cohesion.

Conclusions:

• USFD allows independent control over particle size and aerodynamic properties.
• Solute concentration is a critical parameter influencing particle density and FPF.
• The study experimentally demonstrated the relationship between particle density and aerodynamic size for particles of constant geometric size.