Expression profile of plasmid DNA by spermine derivatives of pullulan with different extents of spermine introduced

The objective of this study is to prepare a novel gene carrier from pullulan, a polysaccharide with an inherent affinity for the liver, and evaluate the feasibility in gene transfection. Various amounts of spermine were chemically introduced into pullulan with molecular weights of 22,800, 47,300, and 112,000 to prepare cationized pullulan derivatives with different percentages of spermine introduced. Each cationized pullulan derivative was complexed with a plasmid DNA at various ratios and applied to HepG2 cells for in vitro gene transfection. The level of gene expression depended on the percent spermine introduced of cationized pullulan derivatives and the molecular weight of pullulan. However, when compared at the complexation molar ratio of pullulan derivative to the plasmid DNA, the expression level became maximum around the ratio of 10², irrespective of the pullulan molecular weight. Pre-treatment of cells with asialofetuin of asialoglycoprotein receptor ligand decreased the level of gene expression by the complexes. The cationized pullulan derivative with an appropriate physicochemical character is a promising non-viral carrier which promotes the receptor-mediated internalization of plasmid DNA and consequently enhances the expression level.