Search

Lysosome pH is known to be acidic (4.5–5.5) and has emerged as a critical physiological factor for lysosome activities and functions. Herein, we designed a novel ratiometric lysosome-targeted fluorescence resonance energy transfer (FRET) pH probe, which was fabricated by integrating the coumarin moiety (donor) with the naphthalimide moiety (acceptor). The sensing mechanism was essentially an integration of ICT and FRET processes, leading to the simultaneous intensity enhancement of coumarin and naphthalimide with a pH increase. Furthermore, morpholine was introduced as a lysosome-targeted group. Moreover, the probe could respond to pH in a proportional relationship at very broad range from pH 4.5 to 11.0 and showed remarkable advantages, including rapid response, high sensitivity and selectivity, suitable pKa of 5.62, and good reversibility. Furthermore, the probe was successfully used as a ratiometric TP lysosome-targeted fluorescence probe, not only for imaging of lysosomal pH, but also for visualizing chloroquine-induced changes of intracellular pH in real time in living cells with low cytotoxicity and autofluorescence. These proof-of concept studies demonstrate the practical application of the probe in biological systems.

A novel ratiometric fluorescent chemodosimeter has been developed for reusable detection of Hg2+. The chemodosimeter responds to Hg2+ sensitively and selectively with a remarkable fluorescence change from green to blue through hampering the excited state intramolecular proton transfer (ESIPT) process. This recyclable chemodosimeter can remove Hg2+ from water by forming a unique mercury-containing compound, which could be reused in the presence of NaBH4. Moreover, the chemodosimeter exhibits a ratiometric fluorescence response to Hg2+ with a very low detection limit (1.0 ppb), and it can be used to detect Hg2+ in drinking water. Furthermore, the ratiometric chemodosimeter has been successfully used for imaging Hg2+ in living cells and tissues using two-photon fluorescence microscopy due to the remarkable emission change from green to blue. This provides a novel testing method for detecting Hg2+ in living cells and tissues with low cytotoxicity and autofluorescence.