Synthesis of ROMP polymers for biological applications

Ring opening metathesis polymerisation (ROMP) is a living polymerisation which allows for the synthesis of polymers with controlled length and composition, as well as narrow distribution of the molecular weights. Thanks to the availability of metal alkylidene catalysts at a cheap price, ROMP has become a versatile method for the preparation of materials for different applications, including optics and electronics, energy storage and nanomedicine among others.

This project explored the use of ROMP for the realisation of biologically relevant polymers. In particular, ROMP has been used in two applications. The first application involved the preparation of amphiphilic block copolymers consisting of ibuprofen and PEG, which were covalently linked to the polymer backbone via a cleavable bond. Ibuprofen and PEG respectively constituted the hydrophobic and hydrophilic portions of the block copolymer. Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) which was selected in this study thanks to its potential role in chemoprevention and chemotherapy. The so synthesised amphiphilic block copolymer could self-assembled in aqueous environment to form nanoparticles with precise size and morphology, and that could entrap the drug within the hydrophobic core. This allowed for the studies of the drug release from the polymeric nanoparticles using both physiological and alkaline conditions. Our studies demonstrated a high stability of the synthesised nanoparticles under physiological environments, while slow drug release could be obtained under strong basic conditions. In the second application ROMP has been used for the preparation of amphiphilic cationic polymers for the development of antimicrobial materials. Homopolymers bearing pyridinium cations and SSA (self-associating amphiphilic salts) counterions were prepared. SSAs are a novel class of antimicrobial agents synthesised by the Hiscock group at the University of Kent. In this collaboration, the so synthesised homopolymers were studied for their antimicrobial activity against both Gram-negative and Gram-positive bacteria. The results demonstrated an antagonistic effect between the amphiphilic cationic ROMP polymer and the selected SSA.