Abstract

Gene therapy with nucleic acid-based therapeutic agents has emerged as a promising strategy to treat various human diseases. However, the efficient delivery of nucleic acids faces a critical challenge as they are susceptible to hydrolytic and enzymatic degradation during blood circulation and in the body. The conventional delivery strategy for nucleic acids involves cationic polymers which bind with the anionic phosphate groups of the nucleic acid by ionic interaction to form polyplexes. These polyplexes are designed for effective endosomal escape of the nucleic acids through the proton-sponge effect, leading to release of their cargos, resulting in excellent gene transfection. However, the polyplex-based nanocarriers present critical drawbacks including cytotoxicity of cationic polymers, the degradation of nucleic acids in polyplexes, and the propensity to aggregate with serum proteins during blood circulation.
My MSc thesis focuses on the exploration of a new paradigm for nucleic acid delivery which explores the design of reactive, but neutral hydrophilic copolymers and the use of nucleic acids as therapeutics and cross-linkers. A poly(phosphonic acid) with terminal thiol groups to mimic oligonucleotides is synthesized by reversible addition fragmentation chain-transfer polymerization. Consequently, the poly(phosphonic acid) is covalently conjugated with a water-soluble random copolymer bearing pendant pyridyl-disulfide functional groups through a thiol-disulfide exchange reaction in aqueous solution, resulting in the formation of cross-linked nanogels through the formation of new disulfide bonds. Consequently, the reductive cleavage of the disulfide linkages in the fabricated nanogels has the potential to prompt the detachment of therapeutic nucleic acids from the nanogel cores. The enhanced release of nucleic acids through degradation (or destabilization) of nanogel cores can occur in the presence of glutathione inside cells.