[Show abstract][Hide abstract] ABSTRACT: Safe and effective gene delivery is essential to the success of gene therapy. We synthesized and characterized a novel nonviral gene delivery system in which folate (FA) molecules were functioned as blockers on cationic polyrotaxanes (PR) composed of poly(ethylenimine) (PEI)(600)-grafted α-cyclodextrin rings linearized on polyethylene glycol to form FA-terminated PR-PEI(600) (FPP). The FA terminal caps of FPP target cell surfaces abundant in FA receptor (FR), a common feature of tumor cells. The structure of FPP was characterized by using (1)H nuclear magnetic resonance ((1)H NMR). The delivery particle was composed of chemically bonded PEG (4000), α-cyclodextrins (CD), and PEI (600 Da) at a molar ratio of 1:17:86.7, and the particle size and zeta potential of FPP/pDNA polyplexes were measured using dynamic light scattering. FPP/pDNA exhibited a lower cytotoxicity, strong specificity to FR, and high efficiency of delivering DNA to target cells in vitro and in vivo with the reporter genes. Furthermore, the FPP/DNA complex showed an enhanced antitumor effect in the nude mice compared with other delivery systems, such as PEI-25K. Together, these results suggest that FPP may be useful for gene therapy.