title: Chitosan-modified dry powder formulations for pulmonary gene delivery.
abstract: OBJECTIVE
  Spray-drying is an effective process for preparing micron-dimensioned particles for pulmonary delivery. Previously, we have demonstrated enhanced dispersibility and fine particle fraction of spray-dried nonviral gene delivery formulations using amino acids or absorption enhancers as dispersibility-enhancing excipients. In this study, we investigate the use of the cationic polymer chitosan as a readily available and biocompatible dispersibility enhancer.
  
  
  METHODS
  Lactose-lipid:polycation:pDNA (LPD) powders were prepared by spray-drying and post-mixed with chitosan or spray-dried chitosan. In addition, the water-soluble chitosan derivative, trimethyl chitosan, was added to the lactose-LPD formulation before spray-drying.
  
  
  RESULTS
  Spray-dried chitosan particles, displaying an irregular surface morphology and diameter of less than 2 microm, readily adsorbed to lactose-LPD particles following mixing. In contrast with the smooth spherical surface of lactose-LPD particles, spray-dried trimethyl chitosan-lactose-LPD particles demonstrated increased surface roughness and a unimodal particle size distribution (mean diameter 3.4 microm), compared with the multimodal distribution for unmodified lactose-LPD powders (mean diameter 23.7 microm). The emitted dose and in vitro deposition of chitosan-modified powders was significantly greater than that of unmodified powders. Moreover, the inclusion of chitosan mediated an enhanced level of reporter gene expression.
  
  
  CONCLUSIONS
  In summary, chitosan enhances the dispersibility and in vitro pulmonary deposition performance of spray-dried powders.
authors.affiliation: Gene Delivery Research Group, Welsh School of Pharmacy, Cardiff University, Redwood Building, King Edward VII Avenue, Cardiff CF10 3XF, UK.
authors.forename: Hao-Ying
authors.initials: HY
authors.lastname: Li
authors.forename: James
authors.initials: J
authors.lastname: Birchall
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D045744:Cell Line, Tumor; D048271:Chitosan / Q000031:analogs & derivatives / Q000737:chemistry*; D049452:Green Fluorescent Proteins / Q000235:genetics; D006801:Humans; D007785:Lactose / Q000737:chemistry; D008055:Lipids / Q000737:chemistry; D009330:Nebulizers and Vaporizers; D009690:Nucleic Acid Conformation; D010316:Particle Size; D010957:Plasmids / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011208:Powders; D020545:Respiratory Mucosa / Q000378:metabolism*; D012137:Respiratory System; D013499:Surface Properties; D013678:Technology, Pharmaceutical; D014162:Transfection
chemical_list: D001672:Biocompatible Materials; D008055:Lipids; D011208:Powders; D049452:Green Fluorescent Proteins; D048271:Chitosan; D007785:Lactose