Particle engineering via spray drying is a very useful tool for tuning particles’ size, distribution, shape, density, and cohesiveness. Following this concept, dry powders for inhalation comprising large porous particles can be prepared. This is especially useful for pulmonary delivery, where particle size and density of a formulation play major role in delivery efficacy. However, to achieve large geometric size and low density, suitable spray drying additives have to be selected. Spray drying can be advantageously employed to formulate composite nanoparticles-containing microparticles. Embedding nanoparticles into microparticles preserves nanoparticles’ benefits, such as improved bioavailability and dose uniformity, and allows their delivery into lungs.
In our work we prepared composite microparticles by spray drying of a drug nanosuspension at two atomising gas settings. Five additives (ammonium carbonate, albumin, glycine, leucine, or trileucine) were used during the spray drying in order to form porous/hollow particles. The effect of these additives on particle size and morphology, surface area, and aerodynamic behaviour was studied. At lower atomising gas setting, the fine particle fraction (FPF) for all excipients except trileucine ranged between 18.9 and 28.5%. Trileucine composite particles reached FPF of 53.0 ± 2.7%; the mass median aerodynamic diameter (MMAD) was 2.0 ± 0.2 μm. Even better results were reached at higher atomising gas setting: all powders except for ammonium carbonate had FPF above 55%, trileucine having the highest FPF of 68.7 ± 2.0%.