In vivo Near-infrared Fluorescence Tumor Imaging Using DiR-loaded Nanocarriers

The hydrophobic long-chain dialkylcarbocyanine 1,1'-dioctadecyl-3,3,3',3'-tetramethylindotricarbocyanine iodide (DiR) is an important near infrared (NIR) fluorescent dye, which has a satisfactory photo stability for continuous excitation. During the past decade, it has been widely used for in vivo monitoring of cells. With the fast emergence of novel tumor-targeted nanocarriers, the applications of DiR in the development of fluorescent or multifunctional nano-probes for in vivo tumor imaging are also reported. In these studies, DiR-loaded nanocarriers have resulted in good fluorescence images, indicating the great potential of this dye. However, some important issues about DiR-loaded nanocarriers were often overlooked. These issues include the in vivo fluorescent properties, stability, toxicity, retention and metabolization of DiR-loaded nanocarriers. This review introduced the current use and the properties of DiR-loaded nanocarriers for in vivo tumor imaging. The perspective outlook at the last section highlights the future application of DiR-loaded nanocarriers.