Development of a Targeted Nucleic Acid Vector by Ring-Opening Metathesis Polymerisation of Norbornene-Ethidium Bromide Adducts and Supramolecular Self-Assembly of the Polymer into Fluorescent Nanoparticles

Vectors are microscopic vehicles that can transport foreign nucleic acid sequences into a host cell, which is essential for genetic engineering processes such as molecular cloning and genome editing, with medical applications including gene therapy and vaccine development. Modifying the chemistry of the vector's exterior, so that it targets only specific cell types, is important for many applications. Most vectors are derived from biological sources, a well-known example being modified viruses, but this can cause adverse immune responses, so there is a need for entirely synthetic vectors.

Intercalation is the insertion of planar, aromatic small molecules between the base pairs of a DNA double helix. Many of these molecules fluoresce under ultraviolet light, enabling their use as nucleic acid stains in research, one of the most widely used being ethidium bromide (EthBr). This project aimed to develop an artificial vector consisting of polymeric nanoparticles, with specific exterior chemistry appropriate for cell targeting, and EthBr bonded to the interior: to intercalate DNA and trap it inside the nanoparticles, so that it can be transported and visualised.

Using cheap, commercially available materials, and standard, microwave and dry reaction conditions, the syntheses were conducted of a norbornene derivative and of various EthBr analogues-until one was found that was coupled successfully with the norbornene derivative. Compounds produced (some of them novel) were analysed extensively by melting point, infrared spectroscopy, gas and liquid chromatography-mass spectrometry and various nuclear magnetic resonance experiments.