Norcyanine-Carbamates Are Versatile Near-Infrared Fluorogenic Probes

Fluorogenic probes in the near-infrared (NIR) region have the potential to provide stimuli-dependent information in living organisms. Here, we describe a new class of fluorogenic probes based on the heptamethine cyanine scaffold, the most broadly used NIR chromophore. These compounds result from modification of heptamethine norcyanines with stimuli-responsive carbamate linkers. The resulting cyanine carbamates (CyBams) exhibit exceptional turn-ON ratios (similar to 170x) due to dual requirements for NIR emission: carbamate cleavage through 1,6-elimination and chromophore protonation. Illustrating their utility in complex in vivo settings, a gamma-glutamate substituted CyBam was applied to imaging gamma-glutamyl transpeptidase (GGT) activity in a metastatic model of ovarian cancer. Overall, CyBams have significant potential to extend the reach of fluorogenic strategies to intact tissue and live animal imaging applications.

Automated summary

A new class of fluorogenic probes, CyBams, based on the heptamethine cyanine scaffold, exhibit exceptional turn-ON ratios due to dual requirements for NIR emission. These probes have the potential to extend the reach of fluorogenic strategies to intact tissue and live animal imaging applications.