The effect of endosomal escape peptides on in vitro gene delivery of polyethylene glycol-based vehicles.

BACKGROUND: With recent progress in gene therapy clinical trials, there is an even greater demand to advance the development of nonviral gene delivery vehicles. We have previously developed poly(ethylene glycol) (PEG)-based vehicles with transfection efficiency similar to polyethyleneimine and low cytotoxicity. It was hypothesized that conjugating endosomal escape peptides (EEPs) to PEG-based vehicles would further increase their transfection efficiency. The present study aimed to determine how two different EEPs, INF7 and H5WYG, which destabilize the endosomal membrane at different pHs, affect the efficiency of PEG-based vehicles.
METHODS: INF7 and H5WYG were conjugated to PEG-tetraacrylate (PEG-TA) via a Michael-type addition at the desired molar ratios. The pH-dependent membrane lytic activity, transfection efficiency, particle size, zeta potential, and endosomal escape kinetic rate constants were determined.
RESULTS: Fusogenic peptides, INF7 and H5WYG, showed pH-dependent membrane lytic activity when conjugated to PEG-TA. The highest membrane lytic activity of PEG-INF7 and PEG-H5WYG conjugates occurred at pH 5 and 5.5, respectively. Coupling one INF7 peptide to PEG-DNA binding peptide (DBP) vehicles increased the transfection efficiency ten-fold and showed greater transfection efficiency than PEG-DBP vehicles coupled with H5WYG peptide. Fitting a first-order kinetic model to the average intracellular pH of the vehicle/DNA particles over time determined that coupling EEPs to PEG-DBP vehicles increased the endosomal escape rate constant by two orders of magnitude.
CONCLUSIONS: 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. Copyright (c) 2008 John Wiley & Sons, Ltd.