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As a class of highly dynamic organelles, lipid droplets (LDs) are involved in numerous physiological functions, and the changes in polarity of LDs are closely related to a variety of diseases. In this work, we developed two polarity-sensitive fluorescent probes (CC-CH and CC-Cl) based on curcumin analogs. CC-CH and CC-Cl with a donor–acceptor–donor (D–A–D) structure exhibited the property of intramolecular charge transfer (ICT); thus, their fluorescence emissions were significantly attenuated with increasing ambient polarity. Cell experiments indicated that CC-CH and CC-Cl showed excellent photostability, a low cytotoxicity, and a superior targeting ability regarding LDs. After treatment with oleic acid (OA) and methyl-β-cyclodextrin (M-β-CD), the polarity changes of LDs in living cells could be visualized by using CC-CH and CC-Cl. In addition, CC-CH and CC-Cl could monitor polarity changes of LDs in different pathological processes, including inflammatory responses, nutrient deprivation, and H2O2-induced oxidative stress. Therefore, CC-CH and CC-Cl are promising potential fluorescent probes for tracking intracellular LD polarity changes. [ABSTRACT FROM AUTHOR]

Crosstalk between the lysosome and the endoplasmic reticulum (ER) is essential for maintaining intracellular homeostasis and normal physiological activities. However, simultaneously visualizing the lysosome and ER by using a single fluorescent probe is of considerable significance and challenge. In this work, we developed a near-infrared (NIR) pH probe (F–CCOH) by introducing 7-hydroxycoumarin into the curcumin difluoroboron skeleton. The F–CCOH probe presented strong red emission (630 nm) under acidic conditions and NIR emission (755 nm) under basic conditions, which was attributed to the deprotonation of the hydroxyl group on coumarin. Moreover, by monitoring changes in the fluorescent intensity of F–CCOH in two channels, the pH variety of the lysosomes and ER in living cells can be visualized simultaneously. The experimental results showed that pH changes in the lysosome and ER were opposite during dexamethasone-induced apoptosis. This finding is extremely valuable for revealing the crosstalk between lysosome and ER in physiological activities. • F–CCOH exhibits red emission (630 nm) and near-infrared emission (755 nm) under different pH. • F–CCOH can simultaneously target lysosome and endoplasmic reticulum (ER) in living cells. • The pH changes in the lysosome and ER were opposite during dexamethasone-induced apoptosis. [ABSTRACT FROM AUTHOR]

SO 2 and its derivatives (HSO 3 −, SO 3 2−) play a significant important role in many industries and organisms. Based on coumarin and benzopyranose, a promising NIR ratiometric fluorescent probe BAOA (11-oxo-2,2′,3,3′,6,7,7′,8′-octahydro -1H,1′H,5H,6′H,11H- [10,12′-bipyrano [2,3-f] pyrido [3,2,1-ij] quinolin]-13′-ium perchlorate) was designed and developed to detect HSO 3 − rapidly and sensitively. The sensing mechanism was Michael addition reaction, in which, strongly nucleophilic HSO 3 − attacked carbon-carbon double bonds and BAOA-HSO 3 was formed. A superior linear calibration curve between the fluorescence ratio I 490 /I 722 and concentrations of HSO 3 − was obtained in the range of 1.25–8.75 μmol/L and the LOD was figured out as 63.0 nmol/L. Cell experiments showed that BAOA could not only locate mitochondria, lysosomes, ER and Golgi but also detect exogenous HSO 3 − in living cells. A promising NIR ratiometric fluorescent probe for HSO 3 − was designed, which sensing mechanism was nucleophilic HSO 3 − attacking carbon-carbon double bonds resulting from Michael addition reaction. [Display omitted] [ABSTRACT FROM AUTHOR]

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]

Real-time monitoring vascular responses is crucial for evaluating the therapeutic effects of vascular-targeted photodynamic therapy (V-PDT). Herein, we developed a highly-stable and bright aggregation induced emission (AIE) fluorophore (PTPE3 NP) for dynamic fluorescence (FL) imaging of vascular dysfunction beyond 1300 nm window during V-PDT. The superior brightness (ϵ max Φ f>1000 nm ≈ 180.05 M−1 cm−1) and high resolution of PTPE3 NP affords not only high-clarity images of whole-body and local vasculature (hindlimbs, mesentery, and tumor) but also high-speed video imaging for tracking blood circulation process. By virtue of the NPs' prolonged blood circulation time (t 1/2 ≈ 86.5 min) and excellent photo/chemical (pH, RONS) stability, mesenteric and tumor vascular dysfunction (thrombosis formation, vessel occlusion, and hemorrhage) can be successfully visualized during V-PDT by FL imaging for the first time. Furthermore, the reduction of blood flow velocity (BFV) can be monitored in real time for precisely evaluating efficacy of V-PDT. These provide a powerful approach for assessing vascular responses during V-PDT and promote the development of advanced fluorophores for biological imaging. [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]

[Display omitted] • A ratiometric fluorescent probe (Probe 1) was designed for GGT detection. • Probe 1 can sensitively and selectively detect GGT in complex biological systems. • Probe 1 can be successfully applied for ratiometric imaging of GGT in living cells. γ-Glutamyl transpeptidase (GGT) is one of the biomarker of cancer, hepatitis, and numerous other diseases. The accurate analysis of GGT is useful for the early diagnosis of these diseases. In this work, Probe 1 , a ratiometric fluorescent probe based on 2,3,5,6-tetrafluoroterephthalonitrile, was designed for GGT detection. The results indicated that Probe 1 can sensitively and selectively detect GGT in phosphate buffered solution and complex biological systems (e.g., blood serum). Furthermore, Probe 1 has been successfully applied for ratiometric imaging of GGT in cancer cells and normal cells. [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]

Solvents exhibit different color reactions via regulation of the structure, kinetics, and charge distribution of organic compound molecules. In recent years, solvatochromic probes have good application prospects in the fields of chemistry and biology. In this work, we synthesized three fluorescent probes (PBIC–C, PAIC-C, PPIC-C) sensitive to solvent polarity. We have studied the photophysical properties (spectra, quantum yield, and fluorescence lifetime under different solvents) of these probes. The isomerization nature was verified by nuclear magnetic titration. In order to further confirm our guess, we also performed theoretical calculations, and the results were roughly the same as the experimental results. In addition, cell imaging tests revealed that the designed probes could be used as dual intracellular mitochondria/lysosome-targeting fluorescent probes for biological applications. [Display omitted] • The probes exhibit sharp color changes in different polar solvents. • The probes show relatively high fluorescence quantum yields. • The probes achieve dual targeting of mitochondrials and lysosomes. [ABSTRACT FROM AUTHOR]