Peptide nucleic acid conjugates: Synthesis, properties and applications

Artificial control of gene expression has great potential in the treatment of many human diseases, and peptide nucleic acids (PNAs) offer several potential advantages for silencing gene expression in mammalian cells. The pseudopeptide backbone of the PNA makes it resistant to enzymatic degradation, and PNAs bind complementary DNA and RNA with high affinity and specificity. PNAs are potentially leading agents for antigene and antisense therapeutics, but the application of PNAs in the in vivo setting is hampered by their poor intracellular delivery. This problem has been addressed by PNA conjugation to lipophilic moieties, peptides, and cell-specific receptor ligands. The biological activity of PNAs can also benefit from conjugation to DNA interactive compounds like intercalators and alkylators. Here we review the most interesting literature concerning PNA conjugation with small molecules, emphasizing synthetic approaches, properties and applications of the PNA conjugates.