| X-rays have been used for non-invasive high-resolution imaging of thick biological specimens since their discovery in 1895. They are widely used for structural imaging of bone, metal implants, and cavities in soft tissue. Recently, a number of new contrast methodologies have emerged which are expanding X-ray's biomedical applications to functional as well as structural imaging. However, traditional X-ray imaging provides high spatial resolution imaging through tissue but do not measure chemical concentrations. In this dissertation, we describe an X-ray excited optical luminescence (XEOL) technique which uses a scanning X-ray beam to irradiate Gd2O2S phosphors and detect the resulting visible luminescence through the tissue. The amount of light collected is modulated by optical absorption in close proximity to the luminescence source. The ability to specifically target biological processes in vivo makes nanophosphors promising molecular imaging agents for XEOL. We also describe versatile techniques to design and fabricate multifunctional X-ray nanophosphors. The addition of pH-triggred drug release on our X-ray nanophosphors make it possible to monitor pH-triggered drug release rate in real time. The iron oxide encapsulated X-ray nanosctintillators offer promising multimodal MRI/fluorescence/X-ray luminescence contrast agents. |
