In vitro gene delivery mediated by chitosan. Effect of pH, serum, and molecular mass of chitosan on the transfection efficiency

Aminopolysaccharides such as chitosan and polygalactosamine (pGalN) were used to transfer luciferase plasmid into tumor cells. Chitosan largely enhanced the transfection efficiency of luciferase plasmid (pGL3), while pGalN did not at all. Transfection efficiencies of the pGL3/chitosan complexes were dependent on pH of culture medium, stoicheometry of pGL3 : chitosan, serum, and molecular mass of chitosan. Transfection efficiency at pH 6.9 was higher than that at pH7.6. Optimum charge ratio of the pGL3 : chitosan was 1 : 5. Chitosan polymer of 15 and 52 kDa largely promoted luciferase activities. Transfection efficiency mediated by chitosan of >100 kDa was less than that by chitosan of 15 and 52 kDa. Heptamer (1.3 kDa) did not show any gene expression. Cationic liposome (lipofectin)-associated gene expression was inhibited by serum, while chitosan showed resistance to serum.