Covalent Functionalization of Metal-Oxide Surfaceswith Non-Traditional Ligands

Abstract

Herein detailed are the syntheses, properties, and applications of metal-oxide nanosubstrates covalently functionalized with two classes of materials, inorganic macrocycles called corroles, and genomic deoxyribonucleic acid (DNA). These products have found biomedical applications in tumor imaging and chemotherapeutic sequestration, respectively. Both classes of prepared materials are the first of their kind. Corroles are tetrapyrrolic macrocycles, which have found applications in tumor imaging and treatment, catalysis, solar fuels, and energy conversion. The direct functionalization of metal-oxides with inorganic macrocycles, including corroles, has largely revolved around the formation of hydrogen bonding type interactions between the substrate and the ligand. Hydrogen bonding motifs result in materials with only moderate stability due to solvent dissolution. In the first three chapters of this thesis, the scalable preparation of 5,10,15- (trispentafluorophenyl) corrole and its subsequent covalent functionalization of metal-oxide surfaces are discussed. Chapter 1 details mechanistic elements of the oligomerization and oxidative cyclization of 5,10,15-(trispentafluorophenyl) corrole from pentafluorobenzaldehyde and pyrrole. Prior to this work the synthesis of triperfluoroaryl corroles was dangerously exothermic and could only be carried out on milligram scale. Mechanistic insights led to a safe and scalable synthesis of the desired corrole species, achieving a 17.0 % yield (4.58 g). A detailed discussion of the covalent functionalization of the surface of TiO2 with chlorosulfonated derivatives of 5,10,15-tris(pentafluorophenyl) corrole is presented in Chapter 2. The chlorosulfonated species investigated include the freebase, gallium, and aluminum corroles. Hydroxyl groups on the metal-oxide react with the chlorosulfonyl groups of the corrole ring via nucleophilic attack, resulting in the formation of sulfonic ester linkages. The aluminum species was further investigated as a potential near-infrared optical contrast agent. The details of this study, described in Chapter 3, include imaging experiments with immortalized human cancer lines and harvested mouse hepatocytes. This nanoconjugate exhibited low toxicity and efficient cellular uptake. Conventional chemotherapy agents that target DNA are notorious for producing severe side-effects. Sequestering chemotherapeutics that enters systemic circulation, in a process deemed “ChemoFiltration,” is a strategy for reducing off-target toxicity. Materials capable of such activity have yet to be fully realized. Reported in Chapter 4 are the first methods covalent attachments of genomic DNA to surfaces, namely magnetite (Fe3O4) nanoparticles, via two separate strategies. These materials show efficacy in removing doxorubicin, cisplatin, and epirubicin from biologically relevant solutions. A device coated with this material demonstrated in vivo activity in a porcine model.