UC Irvine

As a result of the COVID-19 pandemic, mRNA-based therapeutics have rapidly changed from being the “therapeutics of the future” to tangible FDA-approved medicines available for people of all ages and medical backgrounds. One advance that allowed these therapies to be so effective are lipid nanoparticle-based delivery vehicles. However, despite the tremendous advances in lipid nanoparticle technologies, there are some inherent disadvantages in using lipid nanoparticles in therapeutic designs. To circumvent these limitations, new biodegradable and biocompatible mRNA delivery vehicles are being pursued as tools that can accommodate roles where lipid nanoparticles prove insufficient, particularly in the field of RNA therapeutics and gene therapy. Chapter 1 of this thesis provides an extensive introduction on the background of gene therapy, RNA-based therapeutics, and current mRNA therapy delivery vehicles/ approaches along with relevant limitations. CRISPR-Cas9 gene editing will also be briefly explored, along with the different viral and synthetic vectors that are currently being explored for relevant CRISPR-Cas therapies. Chapter 2 explores a novel approach of generating multifunctional polydisulfide polymers using a post-polymerization functionalization scheme. The mRNA-delivery capability of these polymers is also detailed using two model mRNAs. Chapter 3 explores using multifunctional dendronized linear polymers to generate polymeric-RNA nanoparticles containing Cas9-encoding mRNA and gene-targeting sgRNA. CRISPR-Cas9 gene editing using these polymeric nanoparticles is discussed, and relevant nanoparticle in vivo distribution is examined. Chapter 4 discusses exploration into a facile cryopolymerization methodology to generate anionic and cationic polydisulfides for the purpose of mRNA delivery. With the works explored in Chapters 2 and 4, two new synthetic methodologies are outlined that greatly expand the use of lipoic acid-derived polydisulfides for mRNA delivery. From these new methodologies and the CRISPR-Cas9 gene editing obtained from the thiol-reducible polymers in chapter 3, the works described within this thesis should expand the utility of polydisulfide as biodegradable polymers for next-generation RNA delivery applications.