Photoactivatable Platinum(IV) Pro-Drugs as Novel Delivery Vehicles for Chemotherapeutics. Part II: Pyridinium-Catalyzed Photoelectrochemical Reduction of CO2 to Multi-Carbon Products on p-Gallium Arsenide

Abstract

This thesis is divided into two parts. The first part of this thesis describes the photochemistry and cytotoxicity of six platinum(IV) trinuclear charge transfer pro-drugs. These complexes are reduced to the potent platinum(II) chemotherapeutics cisplatin, carboplatin, or oxaliplatin upon absorption of visible light, which results in a two electron transfer. Platinum(IV) photoactivatable pro-drugs have several advantages over platinum(II) drugs. Primarily, they are useful for targeted, localized treatment of tumors in combination with high-energy light sources. Treatments of this nature increase the therapeutic ratio, allowing for higher doses to be administered to patients, since the active drug is not disseminated to healthy tissues. Evidence for the reformation of the parent platinum(II) complex was obtained by incubation of the trinuclear pro-drugs with plasmid DNA. Irradiation of the mixture resulted in a shift of the migration of the plasmid through agarose during electrophoresis, indicating platinum was binding to the helix. Accumulation and cytotoxicity of the complexes was determined with A549 and MCF-7 cancer cell lines.

The second part extends the study of CO2 reduction to a p-GaAs electrode in the presence of the pyridinum electrocatalyst. Modification of the p-GaAs electrode surface with a discontinuous platinum layer minimized photocorrosion. Multi-carbon products were observed such as 2-propanol and acetone, with Faradaic yields of 56% and 36% respectively. Electrolysis in a closed system altered the product distribution with the primary products becoming 2-butanol and methanol. Mass spectral analysis of bulk electrolysis run with 13C labeled CO2 confirmed the observed products were in fact reduced from CO2.