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Sulfur dioxide (SO2), as the fourth gas signal molecule, is closely related to many diseases including respiratory diseases, nervous system diseases, cardiovascular diseases and cancers. Herein, we present a novel mitochondria-targeted ratiometric fluorescent probe (CS) for the detection of SO2 in living cells and zebrafishes. The probe CS was constructed on the base of coumarin and benzopyranium fluorophores, and exhibited intense blue and red fluorescence simultaneously. After the response to SO2, the fluorescence at 433 nm enhanced significantly while the fluorescence at 683 nm decreased obviously. The probe CS has a high sensitivity and selectivity to SO2. Moreover, the probe CS has been successfully applied to the detection of mitochondrial SO2 in living cells and zebrafishes.

Sulfur dioxide (SO2) is an important signal molecule in living systems, and plays a wide range of physiological functions. Real-time and in situ detection of the dynamic balance of SO2 in mitochondria is of great significance to in-depth study its biological roles. Herein, we have developed a mitochondria-targeted fluorescent probe Nap-L based on the FRET mechanism to detect SO2 in living cells. The probe Nap-L employed naphthalimide and positively charged benzopyridine as the donor and acceptor in the FRET system, and emitted green and red fluorescence under excitation. In respond to SO2, the nucleophilic addition of bisulfite to benzopyridine and then interrupted the FRET process from naphthalimide to benzopyridine fluorophore, thereby triggering an obvious change in the fluorescence ratio. The probe Nap-L showed high selectivity to SO2 over the biothiols (Hcy, GSH, Cys) and other biologically related species. Biological experiments suggested that the probe Nap-L mainly distributed in mitochondria, and can be successfully used to detect mitochondrial endogenous SO2 in living cells.

1,4-Dithiothreitol (DTT) is an important small-molecular reducing agent and has extensive applications in biochemistry, peptide/protein chemistry and clinical medicine. The development of effective methods for monitoring DTT is of great importance for its safe use and studying its toxicity to human. In this work, we present a two-photon red-emissive probe for the imaging of DTT in living cells, tissues and animals. The probe employed a two-photon red-emissive xanthene dye as the fluorophore and selected 2,4-dinitrophenylate as the novel recognition site for DTT. In response to DTT, the probe displayed excellent sensitivity and selectivity. The probe was successfully applied to the two-photon imaging of DTT in living cells, and the imaging of DTT in living tissues and animals.

Monitoring copper level in cancer cells is important for the further understanding of its roles in the cell proliferation, and also could afford novel copper-based strategy for the cancer therapy. Herein, we have developed a novel cancer cell-specific fluorescent probe for the detecting Cu2+ in living cancer cells. The probe employed biotin as the cancer cell-specific group. Before the treatment of Cu2+, the probe showed nearly no fluorescence. However, the probe can display strong fluorescence at 581nm in response to Cu2+. The probe exhibited excellent sensitivity and high selectivity for Cu2+ over the other relative species. Under the guidance of biotin group, could be successfully used for detecting Cu2+ in living cancer cells. We expect that this design strategy could be further applied for detection of the other important biomolecules in living cancer cells.

The mitochondrial viscosity measurement with the amphiphilic copolymer fluorescent probe (PP) has been successfully revealed for the first time. PP was synthesized, starting from a hydrophobic rhodamine derivative fluorophore and hydrophilic 2-hydroxyethyl acrylate (HEA) by radical polymerization, which could be used to detect mitochondrial viscosity specifically. The systematic investigation demonstrated that the fluorescence emission of PP with a deep red emission increased about 9-fold when the medium is changed from methanol to 99% glycerol, indicating high viscosity dependence. Moreover, PP could self-assemble into nanospheres with the particle size of about 140 nm in water and the nano-structure enabled PP to enter living cells quickly. Cytotoxicity test showed that the cells survival rate remained above 70% at 70 μg·mL−1 of PP. Good biocompatibility and low cytotoxicity of PP are promising to provide a high contrast fluorescence imaging. Taken together, the results point the way to development of novel amphiphilic copolymer fluorescent probes-based the detection in solutions, physiology and pathology.