In this study, two types of biodegradable polycation (PAsp(DET) homopolymer\nand PEG-PAsp(DET) copolymer) were applied as vectors for inhalable dry gene powders\nprepared by spray freeze drying (SFD). The prepared dry gene powders had spherical and\nporous structures with a 5~10-m diameter, and the integrity of plasmid DNA could be\nmaintained during powder production. Furthermore, it was clarified that PEG-PAsp(DET)-\nbased dry gene powder could more sufficiently maintain both the physicochemical\nproperties and in vitro gene transfection efficiencies of polyplexes reconstituted after powder\nproduction than PAsp(DET)-based dry gene powder. From an in vitro inhalation study\nusing an Andersen cascade impactor, it was demonstrated that the addition of L-leucine\ncould markedly improve the inhalation performance of dry powders prepared by SFD.\nFollowing pulmonary delivery to mice, both PAsp(DET)- and PEG-PAsp(DET)-based dry\ngene powders could achieve higher gene transfection efficiencies in the lungs compared\nwith a chitosan-based dry gene powder previously reported by us.
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