The increasing number of nucleic acid-based therapeutics demonstrates the potential to treat diseases at the genetic level. Although oligonucleotides show clinical potential, challenges remain including nuclease degradation, rapid clearance when administered systemically, low cell permeability, and limited distribution to tissues of interest. This is largely imparted by the polyanionic phosphate backbone, which produces unfavourable electrostatic interactions at cell membranes. As a result, their clinical translation is dependent on delivery technologies that improve stability, facilitate cell entry, and increase target affinity. Spherical nucleic acids (SNAs) consist of radially orienting linear nucleic acids onto a nanoparticle core, conferring them a three-dimensional, spherical architecture. These structures enter cells readily and display distinct properties that are independent of their nanoparticle core. Accordingly, we decided to replace the intrinsically anionic phosphodiester linkage of DNA with a phosphoramidate linkage (P-N), allowing us to incorporate new functionality at the phosphate backbone. With this handle, we inserted cationic and hydrophobically modified functional groups that were compatible with nanoscale architectures, giving rise to new properties relevant in biological contexts. Specifically, amine and guanidinium derivatized functional groups provided SNAs with a ~10-fold increase in cell uptake at early incubation times compared with unmodified SNAs. This demonstrates that we can tune the behaviour of SNAs with phosphate backbone modifications in a highly controlled manner. We hypothesize that the stringent control over location and placement of functional groups within the SNA framework will afford them favourable interactions at cell membranes, not only increasing their cell uptake, but also access to alternative uptake mechanisms and potency as therapeutics. / Thesis / Master of Science (MSc) / Oligonucleotides are short synthetic sequences of DNA or RNA that have the capacity to treat diseases at the genetic level. However, they face challenges such as degradation, low cell uptake, and poor tissue distribution. To overcome this issue, we plan to incorporate chemical modifications at the phosphate backbone of oligonucleotides to make them more stable and facilitate more favourable interactions at cell membranes. Conferring oligonucleotides into a 3D arrangement further enhances their stability and cell uptake relative to linear oligonucleotides. By densely functionalizing them onto a nanoparticle core, we can create spherical nucleic acids (SNAs). We hypothesize that the modifications imparted onto the phosphate backbone of linear oligonucleotides will translate their properties into SNAs. The new properties afforded to the SNAs will provide increased cell uptake, alternative uptake mechanisms, and access to cytosolic and nuclear targets, highlighting their potency and therapeutic potential.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/28977 |
| Date | January 2023 |
| Creators | Maggisano, Joseph |
| Contributors | Bujold, Katherine, Chemistry and Chemical Biology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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