Abstract
Chitosan-pCMV-Luc complex powders as a pulmonary gene delivery system were prepared by dispersing aqueous pCMV-Luc/mannitol solutions with or without chitosan in a supercritical carbon dioxide (CO2) /ethanol admixture. The addition of chitosan suppressed the degradation of pCMV-Luc during the supercritical CO2 process. The chitosan-pCMV-Luc powders increased the luciferase activity in mouse lung compared with pCMV-Luc powders without chitosan or pCMV-Luc solutions with or without chitosan after pulmonary administration. The chitosan-pCMV-Luc powder of N/P ratio=5 increased the luciferase activity 27 times that of the pCMV-Luc solution. These results suggest that gene powder with chitosan is a useful pulmonary gene delivery system. Next, the obtained gene powders and gene solutions were placed in stability chambers at 25 or 40°C for 4 weeks. The integrity and transfection potency of the gene were examined by electrophoresis and in vivo pulmonary transfection study in mice. The decrease in the supercoiled and open circular DNA in the powders during storage was much slower than that in solutions. The powders had higher transfection potency than the solutions containing the same amount of DNA. Chitosan improved the stability of DNA in powders. Thus, a gene powder with a cationic vector is a promising ready-to-use formulation for inhalation therapy of pulmonary diseases.
