Mitochondria-specific two-photon fluorogenic probe for simultaneously visualizing nitroreductase and viscosity in cancer cells

Rapid and accurate detection of early cancer biomarkers not only provides a scientific tool for cancer diagnosis, but also helps prevent further cancer progression. Herein, a mitochondrial-targeted two-photon fluorogenic probe (CQ-1) is designed to visualize the changes of nitroreductase (NTR) and viscosity in mitochondria of cancer cells. The CQ-1 consists of the N, N-dimethylnaphthalen-2-amine, pyridine salt and p-nitrobenzene. It shows the significant fluorescence enhancement of CQ-1 with the increase of viscosity due to the limited intramolecular rotation, and turn-on fluorescence signal after CQ-1 reacted with NTR since intramolecular charge transfer generation. Meanwhile, CQ-1 displays fascinating mitochondrial targeting ability. Due to the satisfactory detection capability of CQ-1, we further apply CQ-1 to monitor variations of mitochondrial viscosity and NTR in cancer cells by two-photon fluorescent microscope, as well as for specific imaging of NTR in zebrafish. We expect that this dual-response fluorogenic probe will provide a convenient and effective chemical tool for understanding the physiological functions of NTR and viscosity as well as for the diagnosis of important markers associated with cancer.