title: How much particle surface corrugation is sufficient to improve aerosol performance of powders?
abstract: OBJECTIVE
  The current study aimed to quantify the different degree of particle surface corrugation and correlate it to the aerosol performance of powders.
  
  
  METHODS
  Powders of different degree of surface corrugation were prepared by spray drying under varying conditions. The solid-state properties of the powders including particle size, morphology, crystal form, true density, and moisture content were characterized. The degree of surface corrugation was quantified by the surface fractal dimension (Ds) obtained by light scattering. The aerosol performance was studied by dispersing the powders using the Rotahaler at 60 L/min into a multi-stage liquid impinger. Fine particle fraction (FPF) was expressed as the wt% of BSA particles of size < or =5 microm in the aerosol.
  
  
  RESULTS
  Four powders of increasing degree of particle surface corrugation were prepared, with Ds ranging from 2.06 for the least corrugated to 2.41 for the most corrugated. The powders had a similar size distribution (VMD 3 microm, span 1.4-1.5) and solid-state properties. Increasing the surface corrugation, Ds, slightly from 2.06 to 2.18 enhanced the FPF significantly from 27% to 41%. This was explained by the reduced area of contacts and increased separation distance between the particles. Further increase of corrugation (Ds > or = 2.18) did not improve FPF.
  
  
  CONCLUSIONS
  Powders with varying degrees of corrugation were successfully obtained by spray drying with their surface roughness quantified by fractal analysis. It was shown that only a relatively small degree of surface corrugation was sufficient to accomplish a considerable improvement in the aerosol performance of the powder.
authors.affiliation: Faculty of Pharmacy, University of Sydney, NSW 2006, Australia.
authors.forename: Nora Y K
authors.initials: NY
authors.lastname: Chew
authors.forename: Patricia
authors.initials: P
authors.lastname: Tang
authors.forename: Hak-Kim
authors.initials: HK
authors.lastname: Chan
authors.forename: Judy A
authors.initials: JA
authors.lastname: Raper
mesh_terms: D000336:Aerosols / Q000737:chemistry*; D000818:Animals; D002417:Cattle; D010316:Particle Size; D011208:Powders / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000737:chemistry; D013499:Surface Properties
chemical_list: D000336:Aerosols; D011208:Powders; D012710:Serum Albumin, Bovine