Oligobenzylethylenimine enriches linear polyethylenimine with a pH-sensitive membrane-disruptive property and leads to enhanced gene delivery activity.

We report here the synthesis of a diblock linear polymer of oligo(benzylethylenimine)-b-polyethylenimine (OBzEI-PEI) and investigate its gene delivery properties. The linear copolymer OBzEI-PEI was prepared in a straightforward manner by acidic hydrolysis of a diblock polyoxazoline, which had been made by sequential polymerization of 4-benzyl-2-ethyl-2-oxazoline followed by 2-ethyl-2-oxazoline. pH titration and DNA complexation profiles of the new polymer are similar to regular linear PEIs, but with higher gene transfection efficiencies in various cell lines despite a decreased cellular uptake of plasmid DNA. Further experiments suggest that the OBzEI tail complements the intrinsic proton-sponge endosomolytic activities of PEI with an acid pH-sensitive membrane-perturbing activity.