Contrast Agents for Optical Imaging

Abstract

Optical imaging encompasses many different techniques which use light of the UV to the NIR spectral region to visualize tissue optical characteristics imparted through absorption and scattering of light, as well as emission of fluorescence. A variety of different probes for optical detection of diseases have been synthesized and characterized for their potential to engender disease-specific optical signals within the tissue. This review summarizes the essential literature in this research field, especially covering the chemistry of novel biocompatible probes from the cyanine dyes, tetrapyrroles, lanthanide chelates and some other entities. Different chemical, optical and pharmocological properties were exploited to provide extracellular dyes, target-specific conjugates, activatable probes or pro-drugs. In selected examples, the synthesis of such agents and their mode of action is described and accompanied with in vivo data demonstrating their diagnostic efficacy. Finally, a summary of medical applications is given with emphasis on the current and future role of optical contrast agents. Further progress in the design of designated dyes will be of great value for the establishment of novel optical diagnostic methods in routine clinical practice.