Gene Delivery by PAMAM Dendrimer Conjugated with the Nuclear Localization Signal Peptide Derived from Influenza B Virus Nucleoprotein

Polyamidoamine (PAMAM) dendrimer is one of the cationic polymers widely used in nonviral vector-based gene therapy. As PAMAM comprises biodegradable peptide bonds, it shows biocompatibility and relatively low cytotoxicity. In comparison with polyethylenimine (PEI, 25 kDa) that shows high transfection efficiency, the native PAMAM dendrimer has limitations as a gene carrier. To improve the gene expression efficiency, we introduced KRTR peptides derived from the influenza B virus nucleoprotein, known as a nuclear localization signal (NLS), to PAMAM generation 3. We synthesized PAMAM-RTRK and PAMAM-HRTRK and evaluated the effects of the histidine residue on cytotoxicity. The transfection efficiency of PAMAM-RTRK and PAMAM-HRTRK was similar to that of PEI in HepG2 cells, while their gene expression capacities were much higher than capacity of PEI in A549 cells. PAMAM-HRTRK showed relatively lower cytotoxicity than PAMAM-RTRK in the two cell lines, but the transfection capacity was similar for the two polymers. These results imply that the combination of histidine and KRTR peptide may potentially result in a novel PAMAM-based vector that could be used for prolonged gene therapy through the reduction in cytotoxicity and enhancement of gene expression.