Dual Site-Controlled and Lysosome-Targeted Intramolecular Charge Transfer–Photoinduced Electron Transfer–Fluorescence Resonance Energy Transfer Fluorescent Probe for Monitoring pH Changes in Living Cells

Abstract

Acidic pH is a critical physiological factor for controlling the activities and functions of lysosome. Herein, we report a novel dual site-controlled and lysosome-targeted intramolecular charge transfer-photoinduced electron transfer-Fluorescence resonance energy transfer (ICT-PET-FRET) fluorescent probe (CN-pH), which was essentially the combination of a turn-on pH probe (CN-1) and a turn-off pH probe (CN-2) by a nonconjugated linker. Coumarin and naphthalimide fluorophores were selected as donor and acceptor to construct the FRET platform. Hydroxyl group and morpholine were simultaneously employed as the two pH sensing sites and controlled the fluorescence of coumarin and naphthalimide units by ICT and PET, respectively. The sensing mechanism of CN-pH to pH was essentially an integration of ICT, PET, and FRET processes. Meanwhile, the morpholine also can serve as a lysosome-targeted group. By combining the two data analysis approaches of the ratios of the two emission intensities (R) and the reverse ratio R' (R' = 1/R), the fluorescent ratio of CN-pH can show proportional relationship to pH values in a very broad range from pH 4.0 to 8.0 with high sensitivity. The probe has been successfully applied for the fluorescence imaging of the lysosomal pH values, as well as ratiometrically visualizing chloroquine-stimulated changes of intracellular pH in living cells. These features demonstrate that the probe can afford practical application in biological systems.

Highly sensitive and fast responsive ratiometric fluorescent probe for Cu2+ based on a naphthalimide-rhodamine dyad and its application in living cell imaging

“…For a FRET system, a substantial spectral overlap which is necessary between the donor emission band and the acceptor absorption band is closely related to the energy transfer efficiency. The naphthalimide derivatives have broad absorption spectra (450-650 nm) [31][32][33], which covers a part of absorption of rhodamine (500-560 nm) and fulfills a favorable condition for FRET (Fig. S1).…”

Fluorescein‐Containing Superoxide Probes with a Modular Copper‐Based Trigger

“…By further attaching a morpholine containing moiety as a lysosome targeting group, [10] Lyso-SOP-green was obtained. Fluorescence studies showed that the superoxide selectivity of Lyso-SOP-green are very similar to those of SOP-green, demonstrating that this bond cleavage-based strategy could be versatilely applied to other superoxide-triggered release.…”

Recent progress in H2S activated diagnosis and treatment agents

“…Optical detection methods are attracting increasing research interest owing to their high sensitivity, short response time, non-invasive nature, capacity for real-time monitoring and easy sample preparation. [30][31][32][33] Based on the good nucleophilic and reducing chemistry of H 2 S, researchers have been developing optical probes with high sensitivity, selectivity and biocompatibility for the detection of H 2 S in biological systems. These probes are based primarily on specic H 2 S-induced reactions, including azide reduction, [34][35][36] nitro reduction, 37,38 removal of quenchers (such as copper(II)), [39][40][41] and nucleophilic reactions, [42][43][44] to allow uorescence to be turned on for H 2 S detection at different biological levels.…”