Effect of host particle size on the modification of powder flow behaviours for lactose monohydrate following dry coating

Abstract

-Our previous work demonstrated that the powder flowability of a cohesive lactose sample can be improved substantially using a dry coating technique. Our study reported here aims to investigate the influence of host particle size on the modification of powder flowability following dry coating process. Four commercial lactose monohydrate powders with different particle sizes were coated by an intensive mechanical process or mixed using a conventional tumbling process, both with magnesium stearate. All four untreated lactose samples showed a relatively poor powder flow. After dry coating, poured and tapped densities of all the lactose samples increased, while Carr indices and Hausner ratios decreased substantially. The angle of repose values were reduced to a notable extent only for particles with a median size larger than about 7 μm after dry coating. Both specific energy (SE) and cohesion values of lactose samples, measured by a powder rheometer system, decreased substantially after coating. In contrast, no apparent changes in powder flow were evident for conventionally mixed batches, except that in the dynamic powder rheometry measurement, a relatively small change in SE was observed. This study demonstrated that for the finer particles examined, cohesive forces were more influential in the powder bed after the surface treatment and resulted in a relatively poor flow. However, for the larger powders studied, the cohesive inter-particle forces could be overcome after this dry coating, whereby satisfactory flow could be obtained. This study indicated that the host particle size was a critical factor in influencing the modification of cohesive powder flowability.lactose monohydrate / dry coating / powder flow / particle size / powder rheometry Article published by EDP SciencesRésumé -Effet de la taille des particules de poudre de lactose monohydraté sur son enrobage à sec et sur son écoulement. Quatre poudres commerciales de lactose monohydraté ont été enrobées à sec par mécanofusion et mélangées avec du stéarate de magnésium de façon conventionnelle dans un tambour. Avant traitement, les quatre échantillons de lactose non traité présentaient des propriétés d'écoulement relativement faibles. Après enrobage à sec, les masses volumiques, apparente et tassée, de tous les échantillons de lactose augmentaient tandis que les indices de Carr et les ratios d'Hausner diminuaient nettement. Les plus grands changements de masse volumique étaient trouvés pour les échantillons de lactose ayant une taille de particules médiane entre 7 et 20 μm. L'angle de repos était réduit de façon beaucoup plus importante pour les particules ayant une taille médiane supérieure 7 μm. L'énergie spécifique et les valeurs de cohésion des échantillons de lactose mesurées à l'aide d'un rhéomètre à poudres diminuaient substantiellement après enrobage. Au contraire, aucun changement apparent dans l'écoulement de la poudre n'était évident pour les lots mélangés en tambour, si ce n'est que, dans les mesures dynamiques de rhéométrie de la poudr...

Characterisation and surface-profiling techniques for composite particles produced by dry powder coating in pharmaceutical drug delivery

“…Dry powder coating has been extensively employed to improve various functionalities with a focus on enhancement of flowability, fluidisation, aerosolization and dispersion properties [11,12,14,16,17,23,24,43,44]. Inclusion of sub-micron fine guest particles on to the surface of micro-sized cohesive host particles resulted in the formation of surface asperities that reduce surface contact between cohesive particles thereby enhancing flowability, dispersibility or fluidisability [11,17,19,45,46].…”

“…Dry powder coating or hybrid mixing is a process where fine guest particles are adsorbed on to the surface of host particles under high impaction and shear forces [6][7][8][9][10][11][12][13][14][15] and Beach, L., PhD Thesis, New Jersey Institute of Technology, 2011]. The process generates forces of attraction between guest and host particles that are stronger than the weight of an individual fine guest particle resulting in deposition of the fine particles and synthesis of composite particles with improved functionalities or new properties.…”

“…The forces of attraction range between van der Waals, electrostatic, hydrogen bonding and capillary forces (only generated in blends with some moisture content) [16][17][18][19][20]. Several applications in the pharmaceutical industry have been reported for dry coated particles and include enhancement of flowability and dispersibility of cohesive actives [10,12,16,21], improvement in content uniformity and modified drug dissolution [22][23][24]. These applications can produce significant advantages for enhancing process and manufacture of pharmaceuticals as well as address clinical challenges encountered in drug delivery [22][23][24].…”

Functionalised particles using dry powder coating in pharmaceutical drug delivery: promises and challenges

“…It can be concluded that surface coverage of guest particles is dictated by particle characteristics including size and density [38]. Zhou et al [41,42] investigated the effect of host particle size on flow properties using lactose as a model host that was dry coated with magnesium stearate (MgSt) as a guest material using mechanofusion. The results indicated that the host particle size has a crucial effect on improving the flowability.…”

“…Good flowability of dry powder is vital in various pharmaceutical operations like blending, die filling, tableting, capsule filling, re-suspending of powder in inhalers as well as cost reduction during handling, transportation and storage [42,55,[64][65][66][67]. Additionally, good flow property is necessary to achieve satisfactory fine-host interactive formulation properties in terms of metering, fluidisation, deagglomeration and dispersion [68].…”