| Summary: | Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, February 2010. === Vita. Cataloged from PDF version of thesis. === Includes bibliographical references. === In addition to cancer cells, solid tumors consist of a variety of cell types and tissues defining a complex microenvironment that influences disease progression and response to therapy. To fully characterize and probe the tumor microenvironment, new tools are needed to quantitatively assess microanatomical and physiological changes during tumor growth and treatment. Particularly important, is the metabolic microenvironment defined in tumors by hypoxia (low p02) and acidity (low pH). These parameters have been shown to influence response to radiation therapy and chemotherapy. However, very little is known about spatio-temporal changes in p02 and pH during tumor progression and therapy. By modifying the technique of intravital multiphoton microscopy (MPM) to perform phosphorescence quenching microscopy, I developed a non-invasive method to quantify oxygen tension (p02) in living tissue at high three-dimensional resolution. To probe functional changes in the metabolic microenvironment, I measured in vivo P02 during tumor growth and antiangiogenic (vascular targeted) treatment in preclinical tumor models. Nanotechnology is rapidly emerging as an important source of biocompatible tools that may shape the future of medical practice. Fluorescent semiconductor nanocrystals (NCs), also known as quantum dots, are a powerful tool for biological imaging, cellular targeting and molecular sensing. === (cont.) I adapted novel fluorescence resonance energy transfer (FRET) -based nanocrystal (NC) biosensors for use with MPM to qualitatively measure in vivo extracellular pH in tumors at high-resolution. While intravital multiphoton microscopy demonstrates utility and adaptability in the study of cancer and response to therapy, the requisite high numerical aperture and exogenous contrast agents result in a limited capacity to investigate substantial tissue volumes or probe dynamic changes repeatedly over prolonged periods. By applying optical frequency domain imaging (OFDI) as an intravital microscopic tool, the technical limitations of multiphoton microscopy can be circumvented providing unprecedented access to previously unexplored, critically important aspects of tumor biology. Using entirely intrinsic mechanisms of contrast within murine tumor models, OFDI is able to simultaneously, rapidly, and repeatedly probe the microvasculature, lymphatic vessels, and tissue microstructure and composition over large volumes. Using OFDI-based techniques, measurements of tumor angiogenesis, lymphangiogenesis, tissue viability and both vascular and cellular responses to therapy were demonstrated, thereby highlighting the potential of OFDI to facilitate the exploration of pathophysiological processes and the evaluation of treatment strategies. === by Ryan M. Lanning. === Ph.D.
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