Hybrid Cell-Penetrating Foldamer with Superior Intracellular Delivery Properties and Serum Stability

Sequence specific molecules with high folding ability (i.e., foldamers) can be used to precisely control the distribution and projection of side chains in space and have recently been introduced as tailored systems for delivering nucleic acids into cells. Designed oligourea sequences with an amphipathic distribution of Arg- and His-type residues were shown to form tight complexes with plasmid DNA, and to effectively promote the release of DNA from the endosomes. Herein, we report the synthesis of new cell-penetrating foldamer sequences in which the foldamer segment is conjugated via a reducible disulfide bond to a ligand that binds cell-surface expressed nucleoproteins with the idea that this system could facilitate both assemblies with nucleic acids and cell entry. This new system was evaluated for delivery of DNA in several cell lines and was found to compare favorably with all comparators tested (DOTAP and b-PEI as well as a number of known cell penetrating peptides) in various cell lines and particularly in culture medium containing up to 50% of serum. These results suggest that this dual molecular platform which is long lasting and noncytotoxic could be of practical use for in vivo applications.