Near-Infrared Dyes and Their Use in Medical Science

Abstract

Targeted imaging (diagnosis) and therapy using near-infrared (NIR) dyes can be accomplished with the help of the data obtained from fluorescence emission of the fluorophores and play an important role particularly in deep tissue imaging. The area NIR dyes absorb and emit light is defined as NIR spectroscopy (NIRS, 650–850 nm). Although NIR dyes are widely used for imagining purposes, they also find application in photodynamic therapy. In preclinical studies, phthalocyanine (Pc), chlorine, porphyrin, bacteriochlorin, cyanine, Alexa-fluor, and various BODIPY dye series are used as NIR fluorescent dyes/agents. When compared to other dyes, one of the most promising NIR dye is Pc because of their photophysical and chemical properties particularly for the imaging applications. Although NIR dyes have several advantages, their toxicity limits their usage in clinics. Indocyanine green, having negligible side effects, is the only FDA approved NIR dye used in clinics. It is used for controlling of cardiac function, liver output, and retinal angiography. In conclusion, the development of new generation NIR dyes with improved chemical, photophysical, and photochemical properties that are more appropriate for the aforementioned applications is inevitable. Nevertheless, the NIR dyes that have been developed and will be developed should be combined with the nanoparticular systems and/or targeting moieties to make them more advantageous for NIRS and therapy.