Heptamethine cyanines in bioorthogonal chemistry

Due to their excellent fluorescence properties and biological function, cyanine dyes have been widely applied in biological imaging. Heptamethine cyanine(Cy7) dyes, as a type of classic near-infrared(NIR) fluorescent dyes, are considered as one of the effective fluorescent tools in the living organisms due to their good biocompatibility and very low background interference. Bioorthogonal reactions performed in living cells and tissues have developed by leaps and bounds in recent years. The NIR fluorescent labeling technique involving cyanine has attracted widespread attention. This review summarizes their recent application in the field of bioorthogonal imaging, mainly concluding Cy7-type dyes, labeling strategy, bioimaging application, etc. We expect this work can provide some helps for the studies of NIR bioorthogonal reaction in vivo.