A two-photon mitochondria-targeting azo reductase probe for imaging in tumor cells and mice

Abstract

Herein, a two-photon mitochondria-targeting fluorescent probe (TPNP) which can be activated by the azo reductase (AzoR) has been developed for imaging the hypoxic microenvironment of tumors in vivo. The probe TPNP showed a low detection limit (LOD = 1.85 eq), high selectivity, and considerable steadiness in different pH conditions (3.0–11.0). In living cells, it could co-locate with the commercial dye in the mitochondria (co-localization coefficient: 0.92) and indicate hypoxia in both one-photon and two-photon fluorescence imaging. Its AzoR-activation mechanism was further verified by the docking simulation as well as the experiments of adding AzoR or electron transporter inhibitors. Moreover, the in vivo real-time fluorescence imaging proved that TPNP could monitor hypoxia and the tumor progression in mouse tumor models. Overall, this designed probe exhibited high sensitivity, synthetic ease, and excellent fluorescent properties, which might therefore enlighten new ideas for the diagnosis of tumors in future studies.