Modified Glass Beads as Model Carriers to Understand the Performance of Interactive Powder Blends

Niklas Renner, Zinaida Todorova, Regina Scherließ, Hartwig Steckel

In this study glass beads were used as model carriers for a systematic approach to investigate the effect of interparticle interactions on aerosolisation performance, thus deducing their impact on lung deposition. For this glass beads with a median particle size of 500 μm were treated with silanes differing in their functional groups to create carrier particles with varying surface hydrophobicity. The degree of hydrophobicity of the resulting product was determined via contact angle measurements. The beads were then blended with spray dried budesonide (BUD) to create interactive mixtures. To obtain different ratios of carrier to active pharmaceutical ingredient (API), blends with different quantities of API were prepared leading to theoretical carrier surface coverages from 25% to 100%. The aerodynamic performance was investigated using the Next Generation Pharmaceutical Impactor (NGI) and the Cyclohaler® was chosen as a reference dry powder inhaler (DPI) device. Results gained from evaluation of recovered doses showed that a true surface coverage of 100% could not be reached, regardless of the type of glass beads that were used. This can be attributed to an incomplete interaction between API and carrier leading to loss of API during blending and handling. Nevertheless, an almost linear relationship between true and calculated surface coverage was found. Data obtained from NGI experiments showed a significant increase in fine particle fraction for higher surface coverages, which might be due to the presence of more “active sites” on the carrier surface.

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