Evaluation of the Physico-mechanical Properties and Electrostatic Charging Behavior of Different Capsule Types for Inhalation Under Distinct Environmental Conditions

Joana T. Pinto, Thomas Wutscher, Milica Stankovic-Brandl, Sarah Zellnitz, Stefano Biserni, Alberto Mercandelli, Mirjam Kobler, Francesca Buttini, Laura Andrade, Veronica Daza, Susana Ecenarro, Laura Canalejas, Amrit Paudel*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Capsule-based dry powder inhaler (DPI) products can be influenced by a multitude of interacting factors, including electrostatic charging. Tribo-charging is a process of charge transfer impacted by various factors, i.e., material surface characteristics, mechanical properties, processing parameters and environmental conditions. Consequently, this work aimed to assess how the charging behavior of capsules intended for inhalation might be influenced by environmental conditions. Capsules having different chemical compositions (gelatin and hydroxypropyl methylcellulose (HPMC)) and distinct inherent characteristics from manufacturing (thermally and cold-gelled) were exposed to various environmental conditions (11%, 22% and 51% RH). Their resulting properties were characterized and tribo-charging behavior was measured against stainless steel and PVC. It was observed that all capsule materials tended to charge to a higher extent when in contact with PVC. The tribo-charging of the thermally gelled HPMC capsules (Vcaps® Plus) was more similar to the gelatin capsules (Quali-G™-I) than to their HPMC cold-gelled counterparts (Quali-V®-I). The sorption of water by the capsules at different relative humidities notably impacted their properties and tribo-charging behavior. Different interactions between the tested materials and water molecules were identified and are proposed to be the driver of distinct charging behaviors. Finally, we showed that depending on the capsule types, distinct environmental conditions are necessary to mitigate charging and assure optimal behavior of the capsules.

Original languageEnglish
Article number128
JournalAAPS PharmSciTech
Issue number4
Publication statusPublished - 1 May 2020


  • dry powder inhaler (DPI)
  • gelatin
  • hydroxypropyl methylcellulose (HPMC)
  • tribo-charging
  • water

ASJC Scopus subject areas

  • Pharmaceutical Science

Cite this