Endosomal escape is a key step in nonviral cellular trafficking and thus the transfection efficiency of nonviral vehicles can be increased by targeting release of DNA from the endosome with EEPs.

The goal of this study was to develop a gene delivery vehicle that can specifically target cell surface receptors with low nonspecific protein adsorption and low cytotoxicity. Toward this goal, four-arm poly(ethylene glycol) vehicles were functionalized with DNA-binding peptides (DBPs) and integrin-binding (RGD) peptides. We have previously described a novel PEG-based gene delivery vehicle functionalized with DBPs that successfully transfected Chinese hamster ovary (CHO) cells with low toxicity and low protein adsorption. This work investigated whether incorporating RGD peptides onto PEG-DBP vehicles could target specific cell surface receptors and increase transfection efficiency of HEPG2 cells. DBP and RGD peptides were coupled onto PEG-tetraacrylate (PEG-TA) in three combinations (molar ratios of DBP:RGD of 1:3, 2:2, and 3:1) and characterized by measuring particle size, zeta potential, and transfection efficiency as a function of charge ratio (peptide amine groups:DNA phosphate). Nonspecific protein adsorption and cytotoxicity of PEG-DBP-RGD vehicles were also measured. Dynamic light scattering showed that PEG-DBP-RGD vehicles condensed DNA into particles having mean diameters of 250-300 nm and zeta potentials ranging from -10 to 7 mV. It was found that coupling two RGD peptides to the PEG-DBP 2 vehicle increased the transfection efficiency at a polymer/DNA charge ratio of 5:1 (+/-) and 6:1 (+/-) and that these vehicles had transfection efficiencies similar to those of polyethylenimine (PEI)/DNA particles. However, coupling one or three RGD peptides to PEG-DBP vehicles did not increase the transfection efficiency. Additionally, the PEG-DBP-RGD/DNA particles adsorbed less protein than PEI particles and were less toxic to HEPG2 cells.