Background: The purpose of this study was to synthesize and evaluate hyperbranched cationic glycogen derivatives as an efficient nonviral gene-delivery vector.
Methods: A series of hyperbranched cationic glycogen derivatives conjugated with 3-(dimethylamino)-1-propylamine (DMAPA-Glyp) and 1-(2-aminoethyl) piperazine (AEPZ-Glyp) residues were synthesized and characterized by Fourier-transform infrared and hydrogen-1 nuclear magnetic resonance spectroscopy. Their buffer capacity was assessed by acid-base titration in aqueous NaCl solution. Plasmid deoxyribonucleic acid (pDNA) condensation ability and protection against DNase I degradation of the glycogen derivatives were assessed using agarose gel electrophoresis. The zeta potentials and particle sizes of the glycogen derivative/pDNA complexes were measured, and the images of the complexes were observed using atomic force microscopy. Blood compatibility and cytotoxicity were evaluated by hemolysis assay and MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay, respectively. pDNA transfection efficiency mediated by the cationic glycogen derivatives was evaluated by flow cytometry and fluorescence microscopy in the 293T (human embryonic kidney) and the CNE2 (human nasopharyngeal carcinoma) cell lines. In vivo delivery of pDNA in model animals (Sprague Dawley rats) was evaluated to identify the safety and transfection efficiency.
Results: The hyperbranched cationic glycogen derivatives conjugated with DMAPA and AEPZ residues were synthesized. They exhibited better blood compatibility and lower cytotoxicity when compared to branched polyethyleneimine (bPEI). They were able to bind and condense pDNA to form the complexes of 100-250 nm in size. The transfection efficiency of the DMAPA-Glyp/pDNA complexes was higher than those of the AEPZ-Glyp/pDNA complexes in both the 293T and CNE2 cells, and almost equal to those of bPEI. Furthermore, pDNA could be more safely delivered to the blood vessels in brain tissue of Sprague Dawley rats by the DMAPA-Glyp derivatives, and then expressed as green fluorescence protein, compared with the control group.
Conclusion: The hyperbranched cationic glycogen derivatives, especially the DMAPA-Glyp derivatives, showed high gene-transfection efficiency, good blood compatibility, and low cyto toxicity when transfected in vitro and in vivo, which are novel potential nonviral gene vectors.
Keywords: blood compatibility; cytotoxicity; gene delivery; glycogen.