Protonatable ionenes for nucleic acid complexation.

Novel tboc-protected ionenes with M(w) exceeding 30 kDa were prepared from the step-growth polymerization of tert-butyl bis[3-(dimethylamino)propyl]carbamate and 1,12-dibromododecane. The protected ionenes yielded pH-sensitive, protonatable ionenes with pK(a) approximately 6.6 for the conjugate acid of the protonated secondary amine. Polyplexes of the protected and deprotected ionenes, whose cytotoxicity for endothelial cells was analyzed using the MTT assay, efficiently complex plasmid DNA. Polyplexes destabilized cellular membranes as revealed using the lactate dehydrogenase assay at high concentrations. The polyplexes were successfully transfected into HBMECs at mass ratios 2, 4, 8, 12, and 16 (polymer/DNA) at polyplex concentrations less than 10 microg . mL(-1).