Mitochondrion-Targeting, Environment-Sensitive Red Fluorescent Probe for Highly Sensitive Detection and Imaging of Vicinal Dithiol-Containing Proteins.

Mitochondrial vicinal dithiol-containing proteins (VDPs) are key regulators in cellular redox homeostasis and useful markers for diagnostics of redox-dependent diseases. Current probes fail to target mitochondrial VDPs and show limited sensitivity and response rate. We develop a novel fluorescent probe using an engineered benzoxadiazole fluorophore that allows selective targeting of mitochondria and exhibits highly sensitive environment responsiveness. This probe is almost nonfluorescent in aqueous media, while delivering intense fluorescence upon binding to VDPs via a cyclic dithiaarsane ligand. The fluorescence probe is shown to have rapid response within 30 s and high sensitivity for detecting reduced bovine serum albumin (rBSA) in the concentration range from 0 to 0.1 μM with a detection limit of 2 nM. To our knowledge, this is the first fluorescence probe for VDPs which exhibits deep red emission, instantaneous response, high turn-on fluorescence ratio, and specific mitochondrial localization. It may provide a new tool for in situ monitoring mitochondrial VDPs.