Investigation of zeolite systems: Focus on Fenton chemistry oxidative stress from asbestos like minerals and zeolite-based dissolved oxygen sensing

The research in this dissertation has focused on studying zeolite systems in two areas. The first goal of the research was to examine particle properties leading to hydroxyl radical related toxicity. The second goal was to create an efficient optical oxygen sensor for intracellular monitoring of oxygen. Asbestos is known to cause a variety of respiratory health problems; however, the exact mechanism leading to these problems is unknown. Typically, asbestos participates in Fenton chemistry producing hydroxyl radicals which lead to toxicity in vivo. During these times of oxidative stress in vivo, the intracellular oxygen is under flux. Being able to monitor the intracellular oxygen concentration can provide critical information related to the condition of the cell.;Initially, studies were performed focusing on Fenton chemistry and oxidative stress from asbestos like minerals. Researchers are striving to elucidate an exact mechanism of asbestos toxicity because it has led and is still leading to multiple respiratory health problems. The physicochemical characteristics of asbestos contributing to respiratory health problems are not fully defined. The goal of this research was to correlate particle toxicity with physicochemical characteristics to help eventually elucidate the mechanism of asbestos toxicity. After the asbestos is inhaled, the particles interact with lung lining fluid, which contains antioxidants. The antioxidants have the ability to reduce ferric iron on the asbestos particles. The particles are then phagocytosed by macrophages, and subsequently an oxidative burst is induced in an effort to remove the inhaled particles. During this oxidative burst, hydrogen peroxide is produced inducing Fenton chemistry with the ferrous iron. Mimicking the oxidative burst process with minerals having properties similar to that of asbestos, but different toxicities, can provide great insight as to the critical physicochemical characteristics related to toxicity. Mordenite, a benign aluminosilicate, and erionite, a highly carcinogenic aluminosilicate, were iron ion-exchanged, exposed to antioxidants, and then exposed to hydrogen peroxide to induce oxidative burst. Monitoring the production of hydroxyl radicals determined if differences between the physicochemical properties of the mineral aluminosilicates resulted in differing Fenton activity. The conclusion of this study was that the coordination of the iron on the mineral surface plays an important role in Fenton activity.;During the oxidative burst, a flux of oxygen within the cell occurs. Being able to monitor the hydroxyl radical production, along with the oxygen consumption, would be useful in understanding the full mechanism of what happens during particle inhalation. Furthermore, efficient monitoring of intracellular oxygen concentration is an important area of research that can provide insight as to cellular function and status. This leads into the second and main component of this research, creation of efficient optical oxygen with a novel matrix to prevent probe leaching and provide linear Stern-Volmer plots. The probe utilized is tris(2,2'-bipyridyl) ruthenium(II), and the matrix is siliceous zeolite-Y. The goal of this research was to improve the loading level of a sensor previously established in our research group then demonstrate the sensor's abilities in the following areas: (1) monitoring dissolved oxygen in solution via a glucose oxidase assay as an in situ measurement via emission quenching, (2) monitoring dissolved oxygen in macrophage cells during an oxidative burst via confocal microscopy, and (3) demonstrating the ability to immobilize the ruthenium loaded zeolite on the end of a fiber optic and discussing future optimization to improve the sensing parameters. The synthetic scheme utilized to load the tris(2,2'-bipyridyl) ruthenium(II) inside of the siliceous zeolite-Y supercages was altered by changing the ruthenium precursor and some of the experimental conditions to improve the loading level. The results showed an improved loading level of the ruthenium complex in the zeolite, which did not leach and gave linear Stern-Volmer plots during oxygen quenching experiments. In the realms of intracellular monitoring of dissolved oxygen as well as fiber optic sensing, parameters have been established demonstrating the working ability of the ruthenium loaded zeolite providing a basis for future optimization.