The role of mechanical properties in DPI Carriers
Zeredescht Majid1, Constanze Mueller2, Ricarda Leister2 & Regina Scherließ1
1Department of Pharmaceutics and Biopharmaceutics, Kiel University, Gutenbergstrasse 76, 24118 Kiel, Germany
2Meggle GmbH & Co.KG, Megglestr. 6-12, 83512 Wasserburg am Inn, Germany
Summary
The aerodynamic performance of interactive blends is known to be influenced by mixing time and energy, but reasons remain poorly understood. The leading hypothesis as to explain why the fine particle fraction (FPF) decreases over increasing mixing time is based on the effect of so-called press-on forces. Plastic deformation of particles is seen a requirement for press-on forces to have an effect. If this hypothesis holds true, it follows that interactive powder mixtures comprising carriers with a higher propensity for plastic deformation would exhibit a higher sensitivity to these press-on forces compared to mixtures with carriers possessing a lower tendency for plastic deformation (brittle materials). Building upon this notion, we explored the idea by developing model carriers of different mechanical properties using Eudragit RL and varying amounts of PEG 4000 as a plasticiser. By adjusting plasticiser content, we were able to control the deformability of the carriers. To assess deformability, we fabricated films from these microspheres and determined their Young’s modulus under the assumption that the tensile deformation behaved similarly to the particles experiencing compressive stress. Utilising these model carriers, we created mixtures using a high shear mixer, took samples at different intervals of mixing time, and subsequently evaluated their aerodynamic performance. Through this systematic investigation, we successfully identified a correlation between the mechanical properties of the carrier and the maximum attainable FPF, as well as the decrease in FPF with mixing time.