Molecular characterization of biological samples by ambient ionization mass spectrometry to advance clinical assessment of human disease

Ambient ionization mass spectrometry (MS) approaches have revolutionized the way diagnostic molecular information can be obtained from biological and clinical samples, requiring minimal to no sample pretreatment, being operationally simple, and most importantly, providing near real time assessment of molecular information directly from biospecimens. Ambient ionization approaches have been widely applied to various clinical applications including screening of inborn errors of metabolism, therapeutic drug monitoring, and disease diagnosis and subtyping, with the goal of evaluating their use for addressing complex challenges in human health. Desorption electrospray ionization (DESI) MS is the most extensively used ambient ionization method for the investigation of molecular changes in tissue biospecimens, showing great potential for providing complimentary information to routine histopathology. Since its inception, a variety of other ambient ionization MS methods have been developed, with newer techniques, such as the MasSpec Pen, envisioned for the intraoperative analysis of in vivo and ex vivo tissue specimen during surgery. This dissertation describes the development and application of ambient ionization MS methods for the investigation of various human diseases. Chapter 2 provides discussion on the robustness of DESI-MS for breast cancer tissue section evaluation and receptor status determination in a multi-center study, providing evidence of its potential use to compliment routine histopathological assessment. Chapter 3 describes the optimization of DESI-MS to expand the molecular information obtained from a single tissue section, demonstrating for the first time the detection of proteins directly from tissue sections by DESI-MS. Chapters 4 and 5 discuss the clinical translation of the MasSpec Pen into an operating room for feasibility testing as well as the evaluation of the technology for improving intraoperative surgical margin evaluation during breast cancer surgeries. Lastly, Chapter 6 discusses the modification of the MasSpec Pen to better analyze clinical nasal swabs and its application toward screening of COVID-19 disease using lipid information.