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

Background: 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 in vitro characterization of nasal products that may prove useful in examining intranasal delivery of powders. Methods: Spray-dried trehalose powders were loaded at 10, 20, and 40 mg doses into active single-dose devices. Primary particle sizes (∼D_v50 = 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 in vitro lung deposition) using liquid chromatography coupled with mass spectrometry. Results: 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. Conclusion: 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.