Electrostatic Charging in Pharmaceutical Aerosols for Inhalation

Abstract

While electrostatic effects are well known and can be observed all around us, it remains among the most poorly understood areas of physics. Pharmaceutical aerosols delivered by dry powder inhalers (DPIs) are known to carry bipolar charges that may influence lung deposition. Although the relationship between the magnitude and polarity of charges on total and regional lung deposition in human subjects is unclear, an important step towards understanding this relationship requires the accurate measurement of pharmaceutical aerosol charges. Hence, this thesis is focused on characterising electrostatic charge in pharmaceutical powder aerosols. Instruments such as the Electrical Low Pressure Impactor (ELPI™) and Bipolar Charge Analyzer (BOLAR™) were utilised to simultaneously measure charge and mass distributions of inhalable products. The first study examined the differences in net charge between amorphous and crystalline salbutamol sulfate (SS) using the ELPI™. Subsequent studies investigated bipolar charges using the BOLAR™. The capability of the BOLAR™ to characterise charge bipolarity and mass distributions was evaluated using spray-dried mannitol powder. Additionally, bipolar charges from commercial products such as Bricanyl® and Pulmicort® Turbuhalers® were characterised. The final study investigated the influence of modifying the design and material of Aerolizer® inhaler on bipolar charging of spray-dried mannitol powder. To this end, the findings in this thesis have provided insight into the effects of crystallinity and inhaler design on formulation electrostatic properties which could facilitate advances that may enhance pulmonary drug delivery in the near future.