Deposition of ¹¹C-radiolabeled nicotine-containing aerosol in an airway cast model using positron emission tomography (PET)

We recently developed an in vitro system for quantification of deposited mass of labeled aerosol constituents in the human airway under realistic inhalation conditions including temperature and humidity control. The in vitro system consists of the upper respiratory airway cast with separate flow controls within distinct branches of the cast. The complete workflow including generation of the labeled aerosol particles, flow setup, and scanning deposited labeled constituent using positron emission tomography is presented. The system was used for evaluating deposition of ¹¹C-radiolabeled nicotine from pH-modified liquid formulations generated by a typical tank electronic nicotine delivery system. The airway deposition patterns were modulated by adjusted liquid pH-value, suggesting modified gas-liquid aerosol partitioning. This can be visually assessed in a qualitative manner, but more importantly measured in a quantitative manner by evaluating the total administered dose. The effects of temperature and humidity were separately assessed, showing significant influence of realistic inhalation conditions (temperature of 37 °C and nearly 100% relative humidity) on total nicotine deposition in the airway cast. Developed capabilities allow their future applications in generating validation data for modeling purposes as well as for conducting further studies concerning understanding of challenges in aerosol delivery and dosimetry assessments.