Characterization of Spray-Dried Powders Using a Coated Alberta Idealized Nasal Inlet.

Dry powders offer the potential to increase stability and reduce cold-chain requirements associated with the distribution of vaccines and other thermally sensitive products. The Alberta Idealized Nasal Inlet (AINI) is a representative geometry for characterization of nasal products that may prove useful in examining intranasal delivery of powders. Spray-dried trehalose powders were loaded at 10, 20, and 40 mg doses into active single-dose devices. Primary particle sizes (∼50 = 10 µm for powder A and 25 µm for powder B), and sizes dispersed by devices, were evaluated using laser diffraction. The interior of the AINI was coated with a glycerol-surfactant mixture to mitigate particle bounce, and flow rates of 7.5 or 15 L/min were drawn through the AINI. Deposition of trehalose powder was determined in the four regions of the AINI (vestibule, turbinates, olfactory, and nasopharynx), a downstream preseparator, and an absolute filter (representing lung deposition) using liquid chromatography coupled with mass spectrometry. Coating the AINI was effective in mitigating particle bounce for both trehalose powders. No difference in regional nasal deposition was observed when testing at a flow rate of 7.5 versus 15 L/min. A high fraction of both powders penetrated past the vestibule and deposited in the turbinates and nasopharynx for all loaded doses. For powder A, a non-negligible fraction of the recovered dose (up to 7%) is deposited on the filter, representing potential lung exposure. Conversely, a negligible fraction of the total recovered dose was deposited on the filter for powder B. Powders with a larger primary particle size showed reduced penetration through the nasal airways while maintaining high turbinate deposition. Optimized spray-dried powders offer the potential to target delivery to the peripheral nasal airways based on powder particle size while reducing lung exposure.