Optimization of spray-dried porous microparticles preparation for pulmonary delivery

Inhalation administration of dry powder particles is a common application route to achieve local and systemic drug effects. For pulmonary diseases, the deposition of drugs at the site of action is desirable. Thus, the parameters of the inhaled particles, especially their size, shape, or aerosolization, are essential for effective treatment. Suitable parameters can be achieved by choice of preparation method or excipients (carriers, porogens, or aerosolizing agents). This experiment aimed to prepare 11 batches of powder mixtures by spray drying, which differed in the carrier used and the amount of leucine or porogen. The aim was to optimize the formulation for drug binding concerning the requirements for pulmonary administration. The prepared particles were evaluated in terms of morphology, flow properties, porosity, and geometric and aerodynamic diameter. It was found that with increasing concentration of leucine, the bulk density of the particles decreased while the FPF value increased. Similarly, there was a decrease in MMAD. The batch containing 15% leucine was the most suitable. In determining the optimum porogen concentration for mannitol particles, the batch with its 1% gave the best results due to its adequate particle size compared to the other batches (MMAD 5.92 ± 1.32 μm), suitable porosity, and particle morphology. Thus, to formulate drug-loaded particles, it would be advisable to reduce the aerodynamic diameter of the particles, e.g., by spray drying process parameters.