Abstract
In a nonviral gene delivery system, localization of a plasmid DNA in the nucleus is a prerequisite for expression of a desired therapeutic protein encoded in the plasmid DNA. In this study, a reducible polymer-based gene delivery system for improved intracellular trafficking and nuclear translocation of plasmid DNA is introduced. The system is consisted of two components, a plasmid DNA having repeated binding sequence for a karyophilic protein, NFkappaB, and a reducible polymer. A reducible poly(amido ethylenimine), poly(TETA-CBA), was synthesized by a Michael-type addition polymerization between cystamine bisacrylamide and triethyl tetramine. The polymer forming tight complexes with plasmid DNA could be degraded in the reductive cytosol to release the plasmid DNA. The triggered release mechanism in the cytosol could facilitate the interaction between cytosolic NFkappaB and the plasmid DNA having repeated NFkappaB biding motif. Upon activation of NFkappaB by interleukin-1beta (IL-1beta), most of the plasmid distributed in the cytoplasm was localized within the nucleus, resulting in significantly higher gene transfection efficiency than controls with nondegradable PEI. The current study suggests an alternative way of improving transfection efficiency by taking advantage of endogenous transport machinery for intracellular trafficking and nuclear translocation of a plasmid DNA.