| dc.description.abstract | In this study, we would like to investigate if the combination cell penetrating peptides (CPPs) and polyethylenimine (PEI) may facilitate gene delivery. Polyethylenimine (PEI, 750 kDa & 25 kDa) were combined with cell-penet rating peptides(CPPs) as gene vectors. By electrostatic interaction, self- assemble nanoparticles using PEI, CPPs, and plasmid DNA were prepared in different amine/phosphate (N/P) ratios. The BCA assay was applied to evaluate the cytotoxicity of CPPs. Both R9 and SAP-10 were biocompatible compared to IL which may induced serious toxicity at high concentration. By combing PEI and CPPs as gene vehicles, transfection efficiencies can be highly improved over the pure PEI delivery, which was especially efficient to promote gene transfer of PEI with molecular weight of 750 kDa, a poor vector when it was solely administrated. Dynamics light scattering (DLS) assay and scanning electron microscopy (SEM) were performed to characterize PEI/CPPs/DNA complex. Complexed particle demonstrated sizes between the 200 nm to 400 nm and zeta potentials between +10 to +20 mV, suggesting that these nanoparticles should be suitable for gene delivery. The electrophoresis data indicated that the PEI and CPPs could complex DNA completely to form a stable particle. The experiment of changing complexation order revealed that only complexed CPPs may help DNA delivery. Finally, the delivery mechanism of CPPs was studied. It suggested that CPPs should not only increase cellular uptake, but also promote complexes escaping from endosome by route other than proton sponge effect. In addition, the competition experiment demonstrated that IL and SAP10 should interfere the interaction between PEI and DNA to increase the chance of dissociation when they were internalized. Through this study, the adjuvant effects of CPPs on facilitating gene delivery using cationic polymer were studied, which should be beneficial to development a safe and highly efficiency nonviral vector for gene therapy.
Key words：polyethylenimine, cell-penetrating peptides, gene delivery
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