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

Abstract

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.Viral and nonviral gene transfer systems have been under intense investigation, as interest in the potential of gene therapy for the treatment and prevention of disease is greater than ever (1). Nonviral systems potentially offer many advantages over viral systems, such as ease of manufacture, safety, stability, lack of vector size limitations, low immunogenicity, and the modular attachment of targeting ligands (2). Most nonviral gene delivery systems are based on cationic compounds-either cationic lipids (2) or cationic polymers (3)-that spontaneously complex with a plasmid DNA vector by means of electrostatic interactions, yielding a condensed form of DNA that shows increased stability toward nucleases. Although cationic lipids have been quite successful at delivering genes in vitro, the success of these compounds in vivo has been modest, often because of their high toxicity and low transduction efficiency.A wide variety of cationic polymers have been shown to mediate in vitro transfection, ranging from proteins [such as histones (4) and high mobility group (HMG) proteins (5)] and polypeptides [such as polylysine (3, 6), short synthetic peptides (7, 8), and helical amphiphilic peptides (9, 10)] to synthetic polymers [such as polyethyleneimine (11), cationic dendrimers (12, 13), and glucaramide polymers (14)]. Although the efficiencies of gene transfer vary with these systems, a large variety of cationic structures are effective. Unfortunately, it has been difficult to study systematically the effect of polycation structure on transfection activity.To understand more fully the structure-activity relationship of these cationic polymer delivery systems, we examined a set of cationic N-substituted glycine oligomers (NSG peptoids) of defined length and sequence. Peptoids are a large family of synthetic oligomers that were originally developed for the combinatorial synthesis of compound libraries for drug discovery (15). Recent optimization of the solid-phase coupling chemistry has allowed the synthesis of long oligomers...

Regulation of Cyclooxygenase-2 and Periostin by Wnt-3 in Mouse Mammary Epithelial Cells

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