An enhanced centrifuge-based approach to powder characterization: The interaction between particle roughness and particle-scale surface topography described by a size-dependent ‘effective’ Hamaker constant

Time dependent attachment properties of pollen grains in anemophilous plants tested by the mass centrifugation method

The process of pollen release, transfer and capture is the most critical step in reproduction of higher plants and requires several steps of detachment and reattachment of pollen grains to different surfaces. As a response to their specific biotic or abiotic factors, pollen grains have developed a huge variability of size, shape and surface structure, which affects their adhesion properties in a specific manner and contributes to the pollination syndrome of a plant. However, despite decades of research and a great public awareness, these adhesion forces have rarely been measured directly. In the present paper, we used a mass centrifugation setup with glass as a standard substrate, to characterize time dependent adhesion properties of pollen grains from four anemophilous species and compared them to the results of previous studies. Our results show strong differences in adhesion between species studied in fresh and aged state, which can be related to their respective pollination ecology. We discuss the species-specific adhesive properties of pollen grains and highlight methodological aspects, to establish centrifugation method as a standard approach, in order to collect a broad set of quantitative data about adhesion properties of pollen grains and to understand their role in the process of pollination.

Understanding the role of magnesium stearate in lowering punch sticking propensity of drugs during compression

The sticking of active pharmaceutical ingredient (API) to the surfaces of compaction tooling, frequently referred to as punch sticking, causes costly downtime or product failures in commercial tablet manufacturing. Magnesium stearate (MgSt) is a common tablet lubricant known to ameliorate the sticking problem, even though there exist exceptions. The mechanism by which MgSt lowers punch sticking propensity (PSP) by covering API surface is sensible but not yet experimentally proven. This work was aimed at elucidating the link between PSP and surface area coverage (SAC) of tablets by MgSt, in relation to some key formulation properties and process parameters, namely MgSt concentration, API loading, API particle size, and mixing conditions. The study was conducted using two model APIs with known high PSPs, tafamidis (TAF) and ertugliflozin-pyroglutamic acid (ERT). Results showed that PSP decreases exponentially with increasing SAC by MgSt. The composition of material stuck to punch face was also explored to better understand the onset of punch sticking and the impact of possible MgSt-effected punch conditioning event.