Investigation of the dynamic process during spray-drying to improve aerodynamic performance of inhalation particles.

Particle-tailoring technique requires significant improvement for wide use of pulmonary route for systemic drug delivery. In this study, the spray-dry method was used to prepare particles using maltose as a model component, with focus on interpretation of the dynamic process during the spray-drying. High-speed camera observation proved that the time required for particle formation was assumed to be on the millisecond scale. The surface tension at 10ms was found to correlate well with both the size of the droplet produced from the spray nozzle and that of the solid particles. The surfactant molecules accumulated spontaneously on the particle surface to improve surface characteristics, including dispersity and hygroscopicity. Addition of polymer molecules made the particle surface rough, which significantly improved particle dispersity. Good correlation was found between the surface roughness and the aerodynamic performance of the particles, which was determined by a cascade impactor. The particle morphology was interpreted in terms of the mass transport of each component during the drying process. This excipient approach seems to be a promising method to prepare fine drug particles of high dispersity for achieving an efficient pulmonary drug delivery.