Author ORCID Identifier
Semester
Fall
Date of Graduation
2024
Document Type
Dissertation
Degree Type
PhD
College
School of Medicine
Department
Not Listed
Committee Chair
Benoit Driesschaert
Committee Member
Timothy D. Eubank
Committee Member
Margaret Bennewitz
Committee Member
Brian Boone
Committee Member
Stephen S. Leonard
Abstract
Low-frequency Electron Paramagnetic Resonance (EPR) spectroscopy and imaging with biocompatible spin probes is an emerging technique that allows us to measure and map important biomarkers in vitro, ex-vivo, and in vivo. EPR is being assessed in clinical trials to measure reactive oxygen species ex-vivo and oxygen partial pressure in cancer patients. The bottleneck for the broader adoption of the technique in clinical settings is the availability of biocompatible probes sensitive to biomarkers of interest. This dissertation aimed to develop advanced EPR probes for measuring and mapping oxygen and reactive oxygen and nitrogen species (RONS) for future clinical and pre-clinical applications. In Chapter 2, we describe the development of a triarylmethyl radical (TAM-PPh2) that allows for ratiometric measurement of RONS. The sensitivity arises from the ~6-fold increase in 31P hyperfine splitting (ap) upon oxidation of TAM-PPh2 to TAM-POPh2. The probe is highly biocompatible and successfully detects RONS in cellular systems and a murine sepsis model. TAM-PPh2 shows a high reaction rate constant with the highly biologically relevant superoxide radical anion (O2 •-, k = 1.1 ± 0.5 x 106 M-1s-1). TAM-PPh2 overcomes the limitations of other EPR probes and trapping agents (hydroxylamine and nitrones), such as the instability of the products or the slow rate of reactions; however, it lacks selectivity toward a particular RONS. Chapter 3 delineates the development of a triarylmethyl radical for in vivo pO2 mapping (SOX71). The previous gold standard EPR probe for oxygen mapping (Ox071) suffers from self relaxation/line broadening at high probe concentration, causing overestimation of pO2. We showed that SOX71 has a lower dependence on concentration and, therefore, reports pO2 more accurately. SOX71 has an ideal pharmacokinetic profile and showed no toxicity upon systemic delivery, even at twice the dose required for pO2 imaging. Chapter 4 characterizes the interaction between triarylmethyl (TAM) radical spin probes and mesoporous silica nanoparticles (MSNs). MSNs have been proposed as nano-carriers of TAM radicals for in vivo oximetric applications. Thanks to our isotopically labeled 13C1 TAMs, we showed that loading TAM radicals inside MSNs could lead to a drastic decrease in probe mobility. The decrease in tumbling rate could affect the sensing property of the probe. This effect should be considered when using MSNs as carriers of EPR spin probes. With the ongoing development of the human EPR imaging system, if successful, these novel TAM radical spin probes hold great potential as a clinical diagnostic tool to detect RONS and pO2 in vivo, which are critical in understanding disease progression.
Recommended Citation
Shaw, Misa A., "Development of Triarylmethyl (TAM) Radical Spin Probes for Biomedical Electron Paramagnetic Resonance (EPR) Applications" (2024). Graduate Theses, Dissertations, and Problem Reports. 12677.
https://researchrepository.wvu.edu/etd/12677
Included in
Organic Chemicals Commons, Other Analytical, Diagnostic and Therapeutic Techniques and Equipment Commons
