title: Investigation of the extent of surface coating via mechanofusion with varying additive levels and the influences on bulk powder flow properties.
abstract: The objective of this study was to investigate if the coating extent created by a mechanofusion process corresponded with observed changes in bulk powder properties. A fine lactose powder (approximate median diameter 20 μm) was dry coated with magnesium stearate using from 0.1 to 5% (w/w) content. An ultra-thin coating layer of magnesium stearate was anticipated, but previous attempts to determine such thin layers on these fine particles have had limited success, with poor resolution. In this study, the surface coating was examined using the state-of-the-art XPS and ToF-SIMS systems. The powder flow was characterized by Carr index and shear cell testing. XPS was successfully applied to demonstrate variations in surface coverage, as a function of additive levels, and indicated near complete coating coverage at additive levels of 1% (w/w) and above. ToF-SIMS results supported such coating coverage assessment, and indicated coating uniformly across the fine particle surfaces. The flow metrics employed could then be related to the coating coverage metrics. The mechanofusion process also modified the apparent surface roughness observed by SEM and BET. It was suggested that the changes in the surface chemical composition exerted a more evident and direct impact on the powder cohesion and flow characteristics than the changes in the surface morphological properties after the mechanofusion in this study.
authors.affiliation: Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia.
authors.forename: Qi Tony
authors.initials: QT
authors.lastname: Zhou
authors.forename: Li
authors.initials: L
authors.lastname: Qu
authors.forename: Thomas
authors.initials: T
authors.lastname: Gengenbach
authors.forename: John A
authors.initials: JA
authors.lastname: Denman
authors.forename: Ian
authors.initials: I
authors.lastname: Larson
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Stewart
authors.forename: David A V
authors.initials: DA
authors.lastname: Morton
mesh_terms: D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D004339:Drug Compounding; D016503:Drug Delivery Systems; D005079:Excipients / Q000737:chemistry*; D007785:Lactose / Q000737:chemistry; D008855:Microscopy, Electron, Scanning / Q000379:methods; D010316:Particle Size; D056951:Photoelectron Spectroscopy / Q000379:methods; D011208:Powders / Q000737:chemistry*; D018629:Spectrometry, Mass, Secondary Ion / Q000379:methods; D013229:Stearic Acids / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D020099:Coated Materials, Biocompatible; D005079:Excipients; D011208:Powders; D013229:Stearic Acids; C031183:stearic acid; D007785:Lactose