Comparison of in vitro methods to determine nasal versus lung deposition of a protein formulation

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The aim of the study was to evaluate the deposition of a model protein formulation (representing a macromolecule for systemic delivery or an antigen used for vaccination) when administered as nasal dry powder spray or when inhaled orally. For this, the Next Generation Pharmaceutical Impactor (NGI) without or with the nasal adapter as well as a nasal cast model in different setups were used. The formulation consisted of the protein plus chitosan as mucoadhesive component facilitating prolonged contact time with the mucosa and decreased mucociliary clearance, and was produced by spray drying. To evaluate oral inhalation, the particles were delivered using the Aerolizer device. To evaluate nasal delivery, the particles were placed directly into the PowderJet, a nasal dry powder device. As the primary particle size was in the inhalable range, a considerable amount of particles may reach the lower respiratory tract when administered via the nose. The protein particles were easily dispersible resulting in an FPF in the NGI of almost 32% after application in the nasal cast (60% in the NGI from the Aerolizer). Interestingly, for distinguishing between the amount being deposited in the nose and the amount reaching the lungs, the simple nasal adapter for the NGI gave the same results as using a nasal cast model. Whereas the nasal cast allows a more profound description of the nasal deposition pattern, the NGI with nasal adapter incorporates an evaluation of lung deposition.