Developing Inorganic Approaches to Polymerization and Bioconjugation
Multi-disciplinary approaches to problem solving are needed given the increasing complexity of fundamental scientific questions. This dissertation undertakes a holistic approach to research and tackles challenges spanning the biology, chemistry, and materials interface. The central theme for most projects involves applying inorganic and main group chemistry to develop new bioconjugation strategies or polymerization methodologies to access novel materials.
Chapter One describes efforts in understanding the effects of trehalose polymers towards protein stabilization. The stabilization capability of polymers made from a set of styrenyl-based trehalose monomer regioisomers were studied. Polymers of each trehalose monomer regioisomer and one polymer which contained all three isomers combined were synthesized. All polymer regioisomers stabilized insulin to a similar degree towards agitation and heat stress.
Chapter Two details the initial discovery that icosahedral boron-rich cluster compounds of the type B12(OR12)—where “R” can be any alkyl or aryl group— could be utilized as strong one-electron photooxidants thereby initiating the polymerization of olefins. The perfunctionalized clusters are able to initiate polymerization of a range of styrene substrates under blue LED irradiation. Also demonstrated, is the visible light initiated, metal free cationic polymerization of isobutylene into poly(isobutylene).
Chapter Three introduces a new class of carborane-based chain-transfer agents (CTA’s) to be used in reversible addition-fragmentation chain-transfer (RAFT) polymerization. The carborane-based CTA’s mediate the controlled polymerization of monomers such as styrene, N-isopropylacrylamide, and methyl acrylate to produce monodisperse carborane terminated polymers. The carborane-based scaffold, appended on the polymer chain end, serves as a general 1H NMR spectroscopic handle used to elucidate polymer molecular weight. Binding of carborane into the hydrophobic cavity of β-cyclodextrin was demonstrated by isothermal titration calorimetry thereby validating its potential use as an affinity label. The carborane RAFT agents also act as Raman active probes.
Chapter Four explores the reactivity of gold(III) organometallic complexes in the context of bioconjugation chemistry. The gold(III) organometallic complexes mediated the conjugation of small molecule substrates which included heterocycles, an anti-cancer drug, biotin, and low molecular weight PEG to cysteine residues on biomolecules. The bioconjugation reactions proceeded rapidly, with high efficiency, and in a broad pH range.