Ayu Lestari1, Philip Chi Lip Kwok1 & Hak-Kim Chan1
1Advanced Drug Delivery Group, Sydney Pharmacy School, Faculty of Medicine and Health, The University of Sydney, NSW 2006, Australia
Summary
Understanding the electrostatic charging of inhalable powders is relevant to dry powder inhalers formulation as particle charges may influence deposition. This study examined the triboelectric charging behaviour of spray-dried salbutamol sulfate formulated with L-leucine at fixed L-leucine concentrations in a range between 5–95% w/w. Electrostatic charge measurements were conducted using an Electrical Low-Pressure Impactor housed in a controlled environment cabinet maintained at 50% relative humidity. The incorporation of L-leucine markedly influenced both the magnitude and polarity of the net charge. A polarity reversal from positive to negative was observed at 5% L-leucine, with the highest charge magnitudes recorded between 5–30% L-leucine. At L-leucine concentrations ≥40%, a reduction in charge and reversion to positive polarity were observed. The presence of L-leucine was found to suppress charging, likely due to its surface enrichment and affecting charge transfer during dispersion. This finding offers valuable insights into the interplay between formulation composition and particle surface characteristics in governing electrostatic charging during aerosolization of dry powder inhaler formulations.