Fluorescence contrast agents and spectroscopy for the early detection of oral cancer
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Despite advancements in treatment techniques, the five-year survival rate for oral cancer has not increased significantly over the past 40 years. This is likely due to the fact that oral cancer is generally not diagnosed until it has reached advanced stages when treatment is more difficult and debilitating and the five-year survival rate for patients is poor. Currently, diagnosis of oral cancer is achieved through visual identification and recognition, which relies on the expertise of the treating clinician. Optical techniques could potentially improve diagnosis and detection of oral cancer by allowing objective assessment of the molecular and biochemical changes in neoplastic tissue relative to normal tissue. Successful application and validation of these techniques will lead to better screening and early detection of premalignant lesions, reducing the incidence of cancer in high-risk individuals. The work presented in this dissertation demonstrates the development of a molecular-specific fluorescent contrast agent in combination with fluorescence spectroscopy and confocal microscopy that could potentially be used as a diagnostic or screening technique in the oral cavity. The specificity of the contrast agent for epidermal growth factor receptor, a molecular marker overexpressed in oral cancer, was demonstrated using in vitro biological models, along with the ability to penetrate into multiple layers of epithelial cells using permeability-enhancing agents. The contrast agent was also evaluated in ex vivo biopsy samples, using fresh tissue slices from paired clinically abnormal and clinically normal biopsy samples. These experiments revealed that it may be possible to use the ratio of the mean fluorescence intensity from an abnormal to normal site or the surface mean fluorescence intensity as a diagnostic criteria to separate normal tissue from moderate dysplasia and cancer. The use of a simple spectroscopy system in conjunction with the contrast agent was also demonstrated, which would be ideal as an inexpensive diagnostic tool that could be used without specialized training. Finally, issues which must be considered for in vivo use of the contrast agent were explored. Together, the research presented in this dissertation lays the groundwork for the development of a tool that could be used in diagnosis of oral cancer.