Book Description

Optical imaging and spectroscopy technologies offer the ability to provide structural and functional information in a fast, low-cost, ionizing radiation free, highly sensitive and high throughput fashion. The diverse contrast mechanisms and complementary imaging platforms form the foundation for the application of optical imaging in pre-clinical studies of pathophysiological development as well as direct clinical application as a tool for diagnosis and therapy. Fluorescence imaging techniques have been one of the most rapidly adopted methods in biology and biomedicine. Visualization of biological processes and pathologic conditions at the cellular and tissue levels largely relies on the use of exogenous fluorophores or their bioconjugates. Some fluorescent molecular probes provide usable contrast for disease diagnosis due to their responsiveness to interactions with other molecular species and/or immediate microenvironment. As a result, understanding exogenous fluorescent contrast mechanisms will allow the development of efficient strategies for biomedical fluorescence imaging. The present work focuses on exploring novel fluorescent molecular probe strategies for imaging cancer and cardiovascular diseases. We have developed a platform for synthesizing activatable fluorescent molecular probes using the fluorescence quenching properties of copper (II) ions. We used these activatable probes for rapid imaging of cancerous tissue in vivo in mice. While developing these molecular probes, we discovered an unexpected molecular interaction that yields stable dimeric molecules. This finding can potentially enable the development of new molecular entities for modifying the signaling properties of fluorescent dyes to minimize background fluorescence. Although planar fluorescence imaging methods using exogenous molecular probes provide rapid information about molecular processes in vivo, extraction of depth information require complex data acquisition and image analysis methods. By designing a dual emission fluorescent probe incorporating two spectrally different fluorophore systems, we developed a method to successfully estimate the depth of fluorescent inclusions from planar imaging data and demonstrated the potential of using this approach to locate a blood vessel and tumorous tissue in mouse in vivo. An important feature of fluorescence methods is the availability of various techniques that provide complementary information. Combining the fluorescence intensity and lifetime properties of a biologically targeted near infrared fluorescent probe, we demonstrate an effective way to distinguish specific from nonspecific uptake mechanisms in cancer cells, an approach that can be translated in vivo. Alternatively, dynamic fluorescence imaging technique expands the scope of applications to include detection and estimation of the size of circulating cancer cells and clusters. The approach developed in this work could allow longitudinal monitoring of these cells, which are implicated in cancer metastases. To circumvent the shallow penetration of light using optical methods, we developed multimodal imaging approaches by incorporating a radionuclide for nuclear imaging into a broad spectrum near infrared fluorescent tumor targeting agent. This molecular construct allows for noninvasive whole body nuclear imaging of tumors, followed by fluorescence image guided resection. In each of these areas, novel fluorescent molecular probes were developed, characterized and applied to solve critical biomedical problems.