A combinatorial approach to the discovery of efficient cationic peptoid reagents for gene delivery

A family of N-substituted glycine oligomers (peptoids) of defined length and sequence are shown to condense plasmid DNA into small particles, protect it from nuclease degradation, and efficiently mediate the transfection of several cell lines. The oligomers were discovered by screening a combinatorial library of cationic peptoids that varied in length, density of charge, side-chain shape, and hydrophobicity. Transfection activity and peptoid–DNA complex formation are shown to be highly dependent on the peptoid structure. The most active peptoid is a 36-mer that contains 12 cationic aminoethyl side chains. This molecule can be synthesized efficiently from readily available building blocks. The peptoid condenses plasmid DNA into uniform particles 50–100 nm in diameter and mediates the transfection of a number of cell lines with efficiencies greater than or comparable to DMRIE-C, Lipofectin, and Lipofectamine. Unlike many cationic lipids, peptoids are capable of working in the presence of serum.