ABSTRACT
Recently, various uorescent probes have been developed for noninvasive imaging in living mice. Among them, near-infrared (NIR) organic uorescent dyes have been shown to exhibit fewer eects on viability than have uorescent quantum dots, which can be cytotoxic (Yong et al. 2013). Indocyanine green is a clinically approved dye for diagnostic purposes. NIR light can penetrate fairly deep into tissue, because light absorption, light scattering, and autouorescence in tissues are minimal in the NIR window (660-900 nm) (Weissleder 2001; Weissleder and Ntziachristos 2003). In addition to the appropriate emitting light wavelength, there are other characteristics for imaging probes, such as high aqueous solubility, high quantum yield, high photostability, and optimal clearance. Furthermore, probe delivery into target cells or tissues should be the most important factor for in vivo imaging. For this type of imaging, the
13.1 Introduction 335 13.2 Self-Quenched Fluorescent Probes 336 13.3 Activity-Based Probes 339 13.4 Activatable Cell-Penetrating Peptides 341 13.5 Hydroxyapatite-Targeting Fluorescent Probes 343 13.6 Activatable Probes for Monitoring Reactive Oxygen Species 347 13.7 NIR Fluorescent Probes for Tumor Hypoxia 349 13.8 Conclusions 350 References 350
target cells are required to express the characteristic molecules, enzymes, or receptors.
