Efficient gene delivery targeted to the brain using a transferrin‐conjugated polyethyleneglycol‐modified polyamidoamine dendrimer

Abstract

The blood‐brain barrier (BBB) poses great difficulties for gene delivery to the brain. To circumvent the BBB, we investigated a novel brain‐targeting gene vector based on the nanoscopic high‐branching den‐drimer, polyamidoamine (PAMAM), in vitro and in vivo. Transferrin (Tf) was selected as a brain‐targeting ligand conjugated to PAMAM via bifunctional polyethylenegly‐col (PEG), yielding PAMAM‐PEG‐Tf. UV and nuclear magnetic resonance (NMR) spectroscopy were used to evaluate the synthesis of vectors. The characteristics and biodistribution of gene vectors were evaluated by fluorescent microscopy, flow cytometry, and a radiolabeling method. The transfection efficiency of vector/DNA complexes in brain capillary endothelial cells (BCECs) was evaluated by fluorescent microscopy and determination of luciferase activity. The potency of vector/DNA complexes was evaluated by using frozen sections and measuring tissue luciferase activity in Balb/c mice after i.v. administration. UV and NMR results demonstrated the successful synthesis of PAMAM‐PEG‐Tf. This vector showed a concentration‐dependent manner in cellular uptake study and a 2.25‐fold brain uptake compared with PAMAM and PAMAM‐PEG in vivo. Transfection efficiency of PAMAM‐PEG‐Tf/DNA complex was much higher than PAMAM/DNA and PAMAM‐PEG/DNA complexes in BCECs. Results of tissue expression experiments indicated the widespread expression of an exogenous gene in mouse brain after i.v. administration. With a PAMAM/DNA weight ratio of 10:1, the brain gene expression of the PAMAM‐PEG‐Tf/DNA complex was ~2‐fold higher than that of the PAMAM/DNA and PAMAM‐PEG/ DNA complexes. These results suggested that PAMAM‐PEG‐Tf can be exploited as a potential nonviral gene vector targeting to brain via noninvasive administration.—Huang, R‐Q., Qu, Y‐H., Ke, W‐L., Zhu, J‐H., Pei, Y‐Y., Jiang, C. Efficient gene delivery targeted to the brain using a transferrin‐conjugated polyethyleneglycol‐modified polyamidoamine dendrimer. FASEB J. 21, 1117–1125 (2007)