Transfection of Airway Epithelium by Stable PEGylated Poly-L-lysine DNA Nanoparticles in Vivo

DNA can be compacted using polyethylene glycol-substituted poly-L-lysine into discrete unimolecular (with respect to DNA) nanoparticles with minor diameter <20 nm that are stable in normal saline for at least 23 months at 4°C. We compared the activity of firefly luciferase in lungs of C57BL/6 mice that received 100 g compacted plasmid in 25 l saline (shown to be the optimal dose) via intratracheal or intranasal instillation with levels in animals given 100 g naked plasmid or in untreated mice. Mice dosed with compacted DNA nanoparticles had peak activity of luciferase in lung at 2 days postinstil-lation, which declined in log-linear fashion with a half-life of 1.4 days. Luciferase activity in animals dosed with naked DNA was 200-fold less. Addition of polyethylene glycol to the complex was necessary for efficient gene transfer and animals that received DNA compacted with unmodified poly-L-lysine did not exhibit luciferase activity above background. Immunohistochemical staining for bacterial -galactosidase 2 days after administration of a compacted lacZ expression plasmid (n 8) revealed expression predominantly in the dependent portions of the right lungs of mice, in alveolar and airway epithelial cells, though macrophages and sometimes endothelial cells also were trans-fected. No staining for -galactosidase was observed in uninjected animals (n 4) or those dosed with naked lacZ plasmid (n 7). Tissue survey for transgene expression shows expression only in lung and trachea following intranasal administration. Stable compacted DNA nanoparticles transfer exog-enous genes to airway epithelium and show promise for lung gene therapy