Abstract
The highly porous and lightweight microparticles were prepared by a novel spray freeze-drying technique (SFD) for applying dry powder inhalation (DPI). The aqueous latex dispersion of methacrylic acid - ethyl acrylate copolymer was used as a matrix former to obtain the porous but rigid spherical structure. Several types of SFD particles with preset particle density ranging in 0.04 to 0.15 g / cm3 could be successfully prepared by changing the solid concentration in the spray suspension. The methodology to measure the particle density accurately was newly established by using pseudo-SFD particles with mm-order in size. The SFD particles with around 10μm in geometric mean diameter exhibited the excellent in vitro aerosol performance due to their low density. The particles with around 0.11 g / cm3 of density had the highest fine particle fraction, which was defined as percentage less than 4.7μm in aerodynamic cut-off diameter. It was also suggested that the improvement of aerosol performance was attributed to cohesive behavior between particles in airflow.
