ROS-tolerant and mitochondria-targeted fluorescent probe for accurate decipherment of viscosity change in mitochondria

Accurate and real-time deciphering of mitochondrial viscosity is of utmost importance owing to its crucial role in the diffusion-mediated processes. Fluorescence sensing relies on the detection of fluorophore changes when it interacts with a specific analyte. However, existing mitochondria-targeted fluorescent probes are susceptible to molecular backbone de-conjugation caused by oxidation of highly reactive oxygen species, leading to false signals. Herein, we introduce a modified dicyanoisophorone-based fluorescent probe DCN-C, which bearing a super antioxidant donor-it-acceptor skeleton via weakening the electron-donating capacity of the donator in the molecular architecture. DCN-C enables viscosity-sensitive response while fulfilling immunity towards various reactive oxygen species (hydroxyl radical, superoxide anion, peroxynitrite anion, hydrogen peroxide, hypochlorite and singlet oxygen) and other biological molecules in vitro. In cell studies, DCN-C achieves a high affinity to mitochondria and further confirmed its resistance towards reactive oxygen species (hydrogen peroxide and peroxynitrite anion) even at a high level of 30 mu M. Besides, DCN-C is capable of effectively detecting viscosity change in various dysfunctional intracellular environment. This work therefore provided a new tool to precisely monitor mitochondrial viscosity under the interference of reactive oxygen species, and further could be used as a reference probe to inform the development of diagnostic for mitochondrial viscosity related disease.