title: Evidence for the existence of powder sub-populations in micronized materials: aerodynamic size-fractions of aerosolized powders possess distinct physicochemical properties.
abstract: OBJECTIVE
  To investigate the agglomeration behaviour of the fine (<5.0 μm) and coarse (>12.8 μm) particle fractions of salmeterol xinafoate (SX) and fluticasone propionate (FP) by isolating aerodynamic size fractions and characterising their physicochemical and re-dispersal properties.
  
  
  METHODS
  Aerodynamic fractionation was conducted using the Next Generation Impactor (NGI). Re-crystallized control particles, unfractionated and fractionated materials were characterized for particle size, morphology, crystallinity and surface energy. Re-dispersal of the particles was assessed using dry dispersion laser diffraction and NGI analysis.
  
  
  RESULTS
  Aerosolized SX and FP particles deposited in the NGI as agglomerates of consistent particle/agglomerate morphology. SX particles depositing on Stages 3 and 5 had higher total surface energy than unfractionated SX, with Stage 5 particles showing the greatest surface energy heterogeneity. FP fractions had comparable surface energy distributions and bulk crystallinity but differences in surface chemistry. SX fractions demonstrated higher bulk disorder than unfractionated and re-crystallized particles. Upon aerosolization, the fractions differed in their intrinsic emission and dispersion into a fine particle fraction (<5.0 μm).
  
  
  CONCLUSIONS
  Micronized powders consisted of sub-populations of particles displaying distinct physicochemical and powder dispersal properties compared to the unfractionated bulk material. This may have implications for the efficiency of inhaled drug delivery.
authors.forename: Sara
authors.initials: S
authors.lastname: Jaffari
authors.forename: Ben
authors.initials: B
authors.lastname: Forbes
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Collins
authors.forename: Jiyi
authors.initials: J
authors.lastname: Khoo
authors.forename: Gary P
authors.initials: GP
authors.lastname: Martin
authors.forename: Darragh
authors.initials: D
authors.lastname: Murnane
mesh_terms: D000336:Aerosols; D000420:Albuterol / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000737:chemistry; D000730:Androstadienes / Q000008:administration & dosage / Q000737:chemistry; D001993:Bronchodilator Agents / Q000008:administration & dosage / Q000737:chemistry; D002626:Chemistry, Pharmaceutical; D003460:Crystallization; D000068298:Fluticasone; D010316:Particle Size; D011208:Powders; D000068299:Salmeterol Xinafoate; D013499:Surface Properties
chemical_list: D000336:Aerosols; D000730:Androstadienes; D001993:Bronchodilator Agents; D011208:Powders; D000068299:Salmeterol Xinafoate; D000068298:Fluticasone; D000420:Albuterol