Mediating high levels of gene transfer without cytotoxicity via hydrolytic cationic ester polymers

Cationic polymers are widely studied as gene-delivery vehicles, but are limited by low transfection due to inhibited release of DNA, and high cytotoxicity from the requisite positive charges. Here, we introduce a hydrolytic cationic ester polymer containing both tertiary and quaternary amines, which packages DNA into nanoparticles and then releases DNA upon hydrolysis. Cells were transfected with these nanoparticles. Luciferase expression from a polymer with the tertiary/quaternary ratio of 1:1 was equal to that obtained using branched polyethylenimine (PEI), and expression from an acidified polymer with the ratio of 3:1 was 20 times higher than branched PEI. These ratios best balance proton sponging from tertiary amines and packaging ability from cations. Importantly, no hydrolysed polymer exhibited cytotoxicity; the zwitterionic nature of the hydrolysed polymer ensured that the quaternary amines in this work do not cause cell death. Hydrolysis is critical for effective and safe gene therapy. (C) 2010 Elsevier Ltd. All rights reserved.