A reversible frequency upconversion probe for real-time intracellular lysosome-pH detection and subcellular imaging.

Lysosomal pH is known to be acidic, which plays a vital role in various processes in living organisms. Frequency upconversion luminescence exhibits the unique ability to convert low energy photons into high energy photons, which can be used in live samples due to its deep penetration, low tissue damage, etc. The development of sensitive frequency upconversion probes with a low pKa, high sensitivity, and specific selectivity for lysosomal pH detection is of great importance. Herein, we report a novel frequency upconversion luminescence probe, NRH-Lyso, by conjugating the rhodamine derivative NRH and the lysosome targeting functional group 4-(2-aminoethyl)morpholine. NRH-Lyso shows a sensitive response to acidic pH and excellent selectivity in the presence of metal ions, anions, and small molecules. Due to the structural transformation of lactam ring opening and closing of NRH-Lyso, the probe shows an almost 80-fold enhancement in emission intensity when the pH changes from 7.0 to 4.0 under 808 nm laser excitation. The living cell imaging data reveals that NRH-Lyso can selectively detect lysosomal pH changes with excellent photostability and low cytotoxicity. All these features make NRH-Lyso a good candidate to investigate the lysosomal pH-associated physiological and pathological processes.

Self-Assembly of Luminescent Lanthanide Mesocates as Efficient Catalysts for Transforming Carbon Dioxide into Cyclic Carbonates.

Four dinuclear lanthanide mesocates were fabricated through a spontaneous self-assembly method, and the formation of these complexes was well studied by their absorption and emission spectra. These stable complexes were also found to exhibit superior performance in catalyzing the coupling reaction between epoxides and CO2 with excellent recyclability. Moreover, the catalysts could be prepared on large scale. Moreover, the Yb and Lu complexes featured emissions in the near-infrared and visible regions, respectively, and their intensities and lifetimes could be used for identification purposes. Thus, this new approach can be used to construct promising lanthanide complexes as efficient catalysts and it identifies the possibility to better study a catalytic reaction with a luminescent catalyst.

Highly Selective and Sensitive One- and Two-Photon Ratiometric Fluorescent Probe for Intracellular Hydrogen Polysulfide Sensing.

Hydrogen polysulfide (H2Sn) has attracted increasing attention due to the fact that it is actually the key signaling molecule rather than hydrogen sulfide (H2S). Therefore, developing a sensitive and accurate assay to investigate the biosynthetic pathways of H2Sn is of physiological and pathological significance. In this work, based on the commonly used two-photon fluorophore, 1,8-naphthalimide, a new probe, NRT-HP, has been designed and synthesized that displayed both one- and two-photon ratiometric fluorescence changes toward H2Sn via H2Sn-mediated benzodithiolone formation. NRT-HP exhibits excellent pH stability, high selectivity and low detection limit (0.1 µM) in aqueous media. Furthermore, two-photon fluorescence microscopy experiments have demonstrated that NRT-HP could be used for the H2Sn detection in live cells as well as tissue slices.

A colorimetric and ratiometric fluorescent probe for distinguishing cysteine from biothiols in water and living cells.

A merocyanine-based highly selective colorimetric and ratiometric fluorescent probe is described for Cys detection in water and diluted deproteinized human serum. Upon reaction with Cys in aqueous buffer solution, the probe showed a dramatic color change from faint yellow to pink and remarkable ratiometric fluorescence enhancement signals were also observed, which are ascribed to an intramolecular charge transfer (ICT) process. This strategy was based on modulating the merocyanine π-electron system by conjugation and removal of the acrylate group to release the chromophore group, resulting in a specific colorimetry and fluorescence response. The probe has low cytotoxicity and good cell permeability. It is readily employed for assessing the change of the intracellular Cys level.