Aerosol Dynamics on Inhalation at High Relative Humidity

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Pulmonary administration of medications has many advantages, including reduced side effects and faster onset of therapeutic effects. However, formulating for inhalable drugs can be difficult due to the complex physiology of the lungs. The particles have to be below 5 um to reach the bronchioles and even smaller to travel further into the alveoli. Currently, many predictions of the deposition pattern of inhalable medications are based on the size of the particles in theirs bulk phase, which may be inaccurate, as the relative humidity (RH) in the lungs is close to 100%, which is much higher than the ambient RH (~40%). Drug particles may take up water as they enter the respiratory system and grow in size, which may alter their deposition site. Therefore, the hygroscopicity of the particles can affect the therapeutic effect of that medication. Previous studies have looked into the hygroscopicity of various excipients and active pharmaceutical ingredients (APIs), however, due to limitations on the instruments, the hygroscopicity is mostly investigated under a low RH condition. This project aims to use novel techniques such as comparative kinetic electrodynamic balance (CK-EDB) and optical tweezers to interrogate the aerosol dynamics of excipients and APIs at close to 100% RH.