Naked and unmodified oligonucleotides are rarely used in gene regulation due to challenges in intracellular delivery and stability. Spherical nucleic acids (SNAs), which consist of oligonucleotides covalently attached to the surface of a rigid structure, typically gold nanoparticles, exhibit enhanced nuclease stability and increased cell uptake. Many side effects associated with traditional polycationic gene carriers, such as toxicity and immunogenicity, can thus be alleviated by utilizing this polyanionic structure. It has been shown that the beneficial properties of SNAs stem from the dense packing and orientation of oligonucleotides, and are unrelated to the core material of the SNA. Therefore, it is possible to synthesize molecular SNA-type structures based on a polymeric backbone via graft-through methodology, given that the densities of the DNA are sufficiently high in the brush form. To reach these high densities, we have attempted direct grafting-through polymerization of natural oligonucleotides, which are modified at the 5’ or 3’ with a polymerizable monomer. However, the negatively charged character and hydrophilicity of oligonucleotides make them impossible to become solubilized in any solvent other than water to a reasonable degree for polymerization. Furthermore, the electron-rich bases are incompatible with traditional living polymerization methods. Here, we have synthesized non-charged, protected oligonucleotide precursors as macromonomers, which are soluble in the organic phase. The protected strands also make the chemistry compatible with ring-opening metathesis polymerization (ROMP), which yields brush-type poly(oligonucleotides) that can then be deprotected after polymerization. These DNA brushes can be fractionated down to molecular purity, which allows us to study interactions between polyvalent DNA and cells and other living systems.

Synthesis of high-density molecular DNA brushes by direct grafting-through polymerization of oligonucleotides

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.