The feasibility and mechanism of gene delivery by pullulan-spermine, a recently developed cationic polysaccharide, were investigated. Pullulan-spermine-mediated transfection of plasmid DNA resulted in greatly reduced cytotoxicity and a 10-fold increase in the level of gene expression when compared to Lipofectamine 2000, a commercially available cationic lipid. Additionally, after transfection of p53-expressing plasmid DNA by pullulan-spermine but not Lipofectamine 2000, the in vitro proliferation of T24 cells was significantly reduced. Pullulan-spermine-mediated gene expression was inhibited by both chlorpromazine of clathrin-mediated endocytosis inhibitor and methyl-β-cyclodextrin and filipin of raft/caveolae inhibitors. We conclude that pullulan-spermine is a promising carrier for gene transfection, and that cellular uptake of pullulan-spermine-plasmid DNA complexes is mediated by clathrin- and raft/caveolae-dependent endocytotic pathways.
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