Angiopep targeting to the low-density lipoprotein receptor-related protein-1 (LRP1) was identified to exhibit high transcytosis capacity and parenchymal accumulation. In this study, it was exploited as a ligand for effective brain-targeting gene delivery. Polyamidoamine dendrimers (PAMAM) were modified with angiopep through bifunctional PEG, then complexed with DNA, yielding PAMAM-PEG-Angiopep/DNA nanoparticles (NPs). The angiopep-modified NPs were observed to be internalized by brain capillary endothelial cells (BCECs) through a clathrin- and caveolae-mediated energy-depending endocytosis, also partly through marcopinocytosis. Also, the cellular uptake of the angiopep-modified NPs were competed by angiopep-2, receptor-associated protein (RAP) and lactoferrin, indicating that LRP1-mediated endocytosis may be the main mechanism of cellular internalization of angiopep-modified NPs. And the angiopep-modified NPs showed higher efficiency in crossing blood-brain barrier (BBB) than unmodified NPs in an in vitro BBB model, and accumulated in brain more in vivo. The angiopep-modified NPs also showed higher efficiency in gene expressing in brain than the unmodified NPs. In conclusion, PAMAM-PEG-Angiopep showed great potential to be applied in designing brain-targeting drug delivery system. (C) 2009 Elsevier Ltd. All rights reserved.