Effect of particle morphology on the triboelectrification in dry powder inhalers.

Abstract Electrostatic charge of lactoses of different particle morphology and amorphous contents were measured during actuation from two different dry powder inhalers (DPIs). Triboelectric studies may give important information when new inhaler devices, materials and formulations are designed in order to improve the drug deposition. Two inhalers, Taifun™ (Focus Inhalation Oy, Finland) and Clickhaler™ (Innovata Biomed Ltd., UK) were filled with lactose powders which were spray dried from different solutions or suspensions of lactose, ethanol and water. Differences in the amorphous contents were determined with isothermal microcalorimetry (IMC) and X-ray diffraction (XRD) and the particle morphology was examined with laser diffraction and electron microscopy (SEM). Samples were actuated from the inhalers at given intervals into the Faraday pail and the generated charges were recorded. Increase in the water concentration of the feed suspension had negligible effect on the charging until it exceeded 70%. Reproducibility of the measurement was found to be better with samples of homogenous particles and higher crystallinity while more amorphous samples with different morphology and wide particle size distribution showed change in the sign of the charge in addition to higher variations of the magnitude. In this study we show that different inhalers, as well as the morphology of the lactose powder, has noticeable effects on the generated charge which has previously been shown to affect the deposition of the drug and the function of an inhaler.