title: Enhanced dispersibility and deposition of spray-dried powders for pulmonary gene therapy.
abstract: Spray-drying represents a viable alternative to freeze-drying for preparing dry powder dispersions for delivering macromolecules to the lung. The dispersibility of spray-dried powders is limited however, and needs to be enhanced to improve lung deposition and subsequent biological activity. In this study, we investigate the utility of leucine as a dry powder dispersibility enhancer when added prior to spray-drying a model non-viral gene therapy formulation (lipid:polycation:pDNA, LPD). Freeze-dried lactose-LPD, spray-dried lactose-LPD and spray-dried leucine-lactose-LPD powders were prepared. Scanning electron microscopy showed that leucine increased the surface roughness of spray-dried lactose particles. Particle size analysis revealed that leucine-containing spray-dried powders were unimodally dispersed with a mean particle diameter of 3.12 microm. Both gel electrophoresis and in vitro cell (A549) transfection showed that leucine may compromise the integrity and biological functionality of the gene therapy vector. The deposition of the leucine containing powder was however significantly enhanced as evidenced by an increase in gene expression mediated by dry powder collected at lower stages of a multistage liquid impinger (MSLI). Further studies are required to determine the potential of leucine as a ubiquitous dispersibility enhancer for a variety of pulmonary formulations.
authors.affiliation: Gene Delivery Research Group, Welsh School of Pharmacy, Cardiff University, Cardiff, CF10 3XF, UK.
authors.forename: Hao-Ying
authors.initials: HY
authors.lastname: Li
authors.forename: Helen
authors.initials: H
authors.lastname: Neill
authors.forename: Rebecca
authors.initials: R
authors.lastname: Innocent
authors.forename: Peter
authors.initials: P
authors.lastname: Seville
authors.forename: Ian
authors.initials: I
authors.lastname: Williamson
authors.forename: James C
authors.initials: JC
authors.lastname: Birchall
mesh_terms: D045744:Cell Line, Tumor; D002626:Chemistry, Pharmaceutical; D004247:DNA / Q000008:administration & dosage / Q000493:pharmacokinetics; D004339:Drug Compounding; D004587:Electrophoresis, Agar Gel; D005079:Excipients; D005434:Flow Cytometry; D005612:Freeze Drying; D015870:Gene Expression / Q000235:genetics; D015316:Genetic Therapy / Q000379:methods*; D006801:Humans; D007785:Lactose / Q000737:chemistry; D007930:Leucine / Q000737:chemistry / Q000494:pharmacology; D008168:Lung / Q000378:metabolism*; D008171:Lung Diseases / Q000628:therapy*; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D011208:Powders; D013499:Surface Properties; D014162:Transfection
chemical_list: D005079:Excipients; D011208:Powders; D004247:DNA; D007930:Leucine; D007785:Lactose