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A new water-soluble fluorescent probe 1 based on hemicyanine dye is designed for selective detection of glutathione (GSH). Probe 1 shows a tremendous colorimetric and ratiometric fluorescence response toward GSH with high selectivity over cysteine/homocysteine. After nucleophilic aromatic substitution reaction with GSH, probe 1 undergoes an intramolecular aldimine condensation that leads to forming a ring, which is accompanied by 107 and 41 nm red-shifts in the absorption and fluorescence spectra, respectively. Subsequent experiments in living cells indicate that probe 1 has a good photostability and response to mitochondrial GSH level in a ratiometric manner. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H 2 O 2) as an important reactive oxygen species (ROS) is correlated in various oxidative stress and cell signaling processes. Thus, developing an effective method that can monitor H 2 O 2 in the Golgi apparatus is of great importance. Herein, a Golgi-targeting two-photon fluorescent probe (GT-H 2 O 2) that can be excited by a femto-second pulse (760 nm) is designed. GT-H 2 O 2 utilized aminoquinoline as a fluorophore / Golgi-targetable unit and borate ester as a H 2 O 2 -responsive unit with an intramolecular charge transfer strategy. The borate ester of GT-H 2 O 2 was oxidized by H 2 O 2 selectively to afford a new fluorescent molecule GT-NH 2 , thereby realizing a ratiometric detection of H 2 O 2. The probe exhibited a high sensitivity and selectivity to H 2 O 2 with a linear range from 5 to 60 μM. In addition, endogenous / exogenous H 2 O 2 could be directly visualized utilizing GT-H 2 O 2 in vitro and in vivo by one/two-photon microscopy. • A two-photon fluorescent probe (GT-H 2 O 2) is presented to sense H 2 O 2 levels. • GT-H 2 O 2 exhibited a rapid and notable ratiometric fluorescent response for H 2 O 2. • GT-H 2 O 2 can achieve Golgi localization. • GT-H 2 O 2 was visualized to monitor endogenous/exogenous H 2 O 2 by two-photon imaging. [ABSTRACT FROM AUTHOR]

The pH homeostasis of Golgi plays a vital role in maintaining normal cell functions. An effective near-infrared fluorescent probe that can sense pH changes in Golgi apparatus is of great significance. Here, a Golgi-targeting fluorescent probe (Golgi-hNR) based on a rhodamine derivative is presented to show a highly sensitive response to pH variations. Golgi-hNR displays a conspicuous pH-dependent behavior at 664 nm from pH 7.4–3.0 with a remarkable fluorescence off-on response. The pKa value of Golgi-hNR is measured to be 3.62. Confocal fluorescence imaging reveals that Golgi-hNR diffuses into Golgi with high selectivity. Using Golgi-hNR , we have successfully visualized real-time tracking of Golgi pH variations for medical therapy in living cells. • An effective near-infrared fluorescent probe (Golgi-hNR) based on rhodamine is presented to sense pH variations. • Golgi-hNR displays a conspicuous pH-dependent behavior with a remarkable fluorescence off-on response. • Golgi-hNR was successfully visualized for real-time tracking of Golgi pH variations for medical therapy in cells. [ABSTRACT FROM AUTHOR]