title: Optimized pulmonary gene transfection in mice by spray-freeze dried powder inhalation.
abstract: Spray-freeze drying (SFD) is an attractive technique to prepare highly porous dry powders for inhalation. However, there have been few reports of its application to dry powder inhalers (DPIs). Therefore, in this study, we prepared dry plasmid DNA (pDNA) powders with different molecular ratios of chitosan to pDNA (N/P ratios) by SFD. All the pDNA powders were spherical and highly porous, with particles approximately 20-40microm in geometric diameter. The morphology changed little with the alteration of the N/P ratio. On electrophoresis, a band of linear pDNA was detected in the preparation without chitosan, suggesting the destabilization of pDNA through SFD. However, the addition of chitosan protected pDNA from destabilization. Moreover, the pDNA powders were evaluated for pulmonary gene transfection efficiency using an in vivo dual imaging technique for gene DPIs developed previously. Maximum gene expression was observed at 9-12h following pulmonary administration of the powders into mice. The powder with the N/P ratio of 10 had the highest gene transfection efficiency. A higher affinity of chitosan for pDNA and a smaller (approximately 100nm) pDNA/chitosan complex (N/Pf10) were found at pH 6.5 (in lung) than at pH 7.4 (in physiological conditions), suggesting that the effective compaction of pDNA by chitosan at the N/P ratio of 10 at pH 6.5 contributes to the gene transfection efficiency in the lung. These results suggest inhalable dry pDNA powders with chitosan prepared by SFD to be a suitable formulation for pulmonary gene therapy.
authors.affiliation: Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya 468-8503, Japan.
authors.forename: Kohta
authors.initials: K
authors.lastname: Mohri
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Okuda
authors.forename: Asami
authors.initials: A
authors.lastname: Mori
authors.forename: Kazumi
authors.initials: K
authors.lastname: Danjo
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Okamoto
mesh_terms: D000280:Administration, Inhalation; D000818:Animals; D002626:Chemistry, Pharmaceutical; D048271:Chitosan / Q000737:chemistry / Q000378:metabolism; D004247:DNA / Q000008:administration & dosage / Q000235:genetics / Q000378:metabolism; D004304:Dosage Forms; D005260:Female; D005612:Freeze Drying; D005796:Genes; D015316:Genetic Therapy / Q000379:methods; D008168:Lung / Q000378:metabolism*; D051379:Mice; D008813:Mice, Inbred ICR; D010957:Plasmids; D011208:Powders / Q000008:administration & dosage / Q000737:chemistry / Q000378:metabolism; D014162:Transfection
chemical_list: D004304:Dosage Forms; D011208:Powders; D004247:DNA; D048271:Chitosan