BACKGROUND: Reductively reversible and hydrolytically degradable cationic polymers have been used as gene delivery systems. The present study aimed to enhance the low transfection efficiency caused by PEGylation by taking advantage of a nonviral vector containing a disulfide linkage. METHODS: The novel reducible targeted gene vector c(RGDyK)-poly(ethylene glycol)-SS-polyethylenimine (RGD-PEG-SS-PEI), representing a combination of RGD-PEG with PEI through a disulfide linkage, was synthesized and its reduction-sensitivity was tested in the presence of glutathione. The RGD-PEG-SS-PEI/pDNA complexes were formed and their stability was evaluated by agarose gel electrophoresis in both phosphate-buffered saline and Dulbecco's modified Eagle's medium with 10% serum. In vitro transfection efficiency and cell viability assay of the different polymers was performed for U87 cells using pEGFP-N2 and pGL4.2 reporter gene systems. RGD-PEG-SS-PEI/pDsRED-N1 and RGD-PEG-PEI/pDsRED-N1 complexes were injected intravenously into the U87 cell-bearing nude mice via their tail vein to investigate in vivo gene expression. RESULTS: RGD-PEG-SS-PEI has been synthesized successfully and its reduction-sensitivity was confirmed in the presence of glutathione. The RGD-PEG-SS-PEI/pDNA complexes demonstrated good stability in both conditions. In comparison with mPEG-PEI/pDNA for gene delivery, the RGD-PEG-SS-PEI/pDNA complex provided improved levels of transfection efficiency and reduced cytotoxicity when tested in U87 cells in vitro, and also enhanced levels of gene expression in the brains of intracranial U87 glioblastoma-bearing mice as demonstrated using dsRed gene transfer and bioimaging in vivo. CONCLUSIONS: The results of the present study suggest that RGD-PEG-SS-PEI represents a promising candidate for further study in glioblastoma and combined gene therapies.
BACKGROUND: Reductively reversible and hydrolytically degradable cationic polymers have been used as gene delivery systems. The present study aimed to enhance the low transfection efficiency caused by PEGylation by taking advantage of a nonviral vector containing a disulfide linkage. METHODS: The novel reducible targeted gene vector c(RGDyK)-poly(ethylene glycol)-SS-polyethylenimine (RGD-PEG-SS-PEI), representing a combination of RGD-PEG with PEI through a disulfide linkage, was synthesized and its reduction-sensitivity was tested in the presence of glutathione. The RGD-PEG-SS-PEI/pDNA complexes were formed and their stability was evaluated by agarose gel electrophoresis in both phosphate-buffered saline and Dulbecco's modified Eagle's medium with 10% serum. In vitro transfection efficiency and cell viability assay of the different polymers was performed for U87 cells using pEGFP-N2 and pGL4.2 reporter gene systems. RGD-PEG-SS-PEI/pDsRED-N1 and RGD-PEG-PEI/pDsRED-N1 complexes were injected intravenously into the U87 cell-bearing nude mice via their tail vein to investigate in vivo gene expression. RESULTS:RGD-PEG-SS-PEI has been synthesized successfully and its reduction-sensitivity was confirmed in the presence of glutathione. The RGD-PEG-SS-PEI/pDNA complexes demonstrated good stability in both conditions. In comparison with mPEG-PEI/pDNA for gene delivery, the RGD-PEG-SS-PEI/pDNA complex provided improved levels of transfection efficiency and reduced cytotoxicity when tested in U87 cells in vitro, and also enhanced levels of gene expression in the brains of intracranial U87 glioblastoma-bearing mice as demonstrated using dsRed gene transfer and bioimaging in vivo. CONCLUSIONS: The results of the present study suggest that RGD-PEG-SS-PEI represents a promising candidate for further study in glioblastoma and combined gene therapies.