Construction of a novel NIR-emissive rhodamine derivative for monitoring mitochondrial viscosity in ferroptosis.

Ferroptosis, an iron-dependent programmed cell death mechanism, is mediated by distinct molecular pathways of lipid peroxidation caused by intracellular iron supplementation and glutathione synthesis inhibition that cause oxidative damage to the cell membrane. Monitoring viscosity changes of mitochondria is essential for a deeper understanding of ferroptosis, as mitochondria will be shrunk with increased membrane density and leading to drastic mitochondrial viscous changes during ferroptosis process. Thus, it is essential to explore novel and efficient fluorescent probes for monitoring viscosity in organisms.

A Mitochondria-Targeting Water-Soluble Fluorescent Probe for Selective Detection of Glyoxal in Living Cells.

Glyoxal (GL) is a physiological reactive α-oxoaldehyde metabolite, produced by lipid peroxidation and autoxidation of glucose. In this work, a specific mitochondria-targeting fluorescent probe Z-GL for glyoxal has been developed by an introducing isopropyl group on the recognition site to tune the selectivity toward glyoxal. The probe showed high selectivity and sensitivity for glyoxal in an aqueous system.

Selectively lighting up glyoxal in living cells using an -phenylenediamine fused hemicyanine.

Glyoxal (GL) is a reactive α-dicarbonyl compound generated from glycated proteins in the Maillard reaction. It has attracted particular attention over the past few years because of its possible clinical significance in chronic and age-related diseases. In this work, a reaction-based red emission fluorescent probe GL1 has been synthesized successfully by grafting an alkyl group onto an amino group to regulate its selectivity for GL.

A highly sensitive ratiometric fluorescence probe for sensing and imaging sulfite in food samples and living cells.

In this work, a ratiometric and chromogenic fluorescent probe 1 was synthesized for the detection of SO. The probe 1 at PBS (10 mM, pH = 7.4) presented a marked emission band at 661 nm.

A Biomimetic Upconversion Nanobait-Based Near Infrared Light Guided Photodynamic Therapy Alleviates Alzheimer's Disease by Inhibiting β-Amyloid Aggregation.

Aberrant β-amyloid (Aβ) fibrillation is the key event in Alzheimer's disease (AD), the inhibition and degradation of which are recognized as a promising therapeutic strategy to alleviate the nerve damage of AD. Photodynamic therapy (PDT) holds great potential for modulation of Aβ self-assembly, which is nevertheless limited by the inefficient utilization of reactive oxygen species (ROS). Herein, an erythrocyte membrane (EM)-modified core-shell upconversion nanoparticle (UCNP/Cur@EM) is designed and fabricated as a biomimetic nanobait to improve the PDT efficiency in AD.

A New Lysosome-Targeted NIR Fluorescent Probe for Specific Detection of Cysteine over Homocysteine and Glutathione.

In this paper, by modifying the thioxanthene-benzothiozolium fluorophore, BCy-Cys, a lysosome-targeted near-infrared (NIR) fluorescent probe was synthesized for the detection of cysteine (Cys) from homocysteine (Hcy)/glutathione (GSH). As expected, BCy-Cys exhibited high selectivity and high sensitivity for detection of Cys over Hcy/GSH, with an extremely low limit of detection at 0.31 μM, marked by obvious color changes.

Lysosomes-targeting near-infrared fluorescent probe for the detection of pH in living cells.

A new near-infrared fluorescent probe Qcy-OH with a turn-on mechanism based on a acceptor-donor-acceptor (ADA) π-electron system that can undergo an internal charge transfer to form new fluorochromes was developed for monitoring pH fluctuations in biological systems. With the pH value increases, Qcy-OH exhibited a strong pH-sensitive response from 1.1 to 9.

A New Phenylazo-Based Fluorescent Probe for Sensitive Detection of Hypochlorous Acid in Aqueous Solution.

In this paper, we designed and synthesized a novel phenylazo-based fluorescent probe (RHN) for the sensing and imaging of hypochlorous acid (HClO) in mitochondria in living cells. In this process, HClO promoted the oxidation of the phenylazo group to generate a free Rhodol fluorophore moiety, which in turn restored strong fluorescence and realized the detection of HClO. As expected, RHN exhibited high selectivity, high sensitivity and rapid response, with detection limits as low as 22 nM (1.

Mitochondria-targeted fluorescent probe for visualization of exogenous and endogenous methylglyoxal in living cells.

An activatable mitochondria-targeted fluorescent probe Hcy-OPD was synthesized for the detection of methylglyoxal (MGO). For the introduction of a preorganized isopropylamino group on the aromatic -diamine framework to regulate the hindrance effect, Hcy-OPD showed high selectivity and sensitivity (0.22 μM) for monitoring MGO.

A highly sensitive sensor for colorimetric detection of palladium(II) in lysosomes and its applications.

Considering the scarcity of palladium ion probes with subcellular organelle targeting, especially probes with near-infrared (NIR) emission wavelength fluorophores, our group has been working to overcome this problem and looking forward to providing potential practical tools for exploring the toxicity of palladium ions at the subcellular level. In this paper, a novel colorimetric and NIR fluorescent probe, BHCy-Pd, for the specific detection of palladium ions (Pd) in lysosomes an internal charge-transfer (ICT) mechanism was designed and synthesized. As expected, BHCy-Pd exhibited a rapid, selective, and sensitive response for palladium with an ultralow limit of detection at 5.

Rational design of a large Stokes shift xanthene-benzothiozolium dyad for probing cysteine in mitochondria.

Xanthene-modified cyanine dyes are considered to be an effective means to extend the emission wavelength and improve the photo-stability of cyanine dyes. However, the fluorophores obtained by this strategy generally have narrow Stokes shifts, which severely limits their application in biological imaging. Herein, a reasonable design strategy is adopted to provide an effective strategy to commendably improve the Stokes shift of xanthene-benzothiozolium fluorophores the simultaneous expansion of a molecular π-conjugated system and heteroatomic substitution.

Novel near-infrared spectroscopic probe for visualizing hydrogen sulfide in lysosomes.

Considering the scarcity of hydrogen sulfide (HS) probes with subcellular organelle targeting, especially probes with near-infrared (NIR) emission wavelengths fluorophores, our group has been working to overcome this problem and looking forward to providing potential practical tools for exploring the relationship between the physiology and pathology of HS at subcellular level. In this paper, a novel colorimetric and NIR fluorescent probe SHCy-HS for the specific detection of HS in lysosome over other biological thiols was designed and synthesized. The xanthene-benzothiozolium fluorophore was chosen to provide fluorescence emission maxima over 735 nm, and 2,4-dinitrophenyl group was chosen as fluorescence quenching group and specific HS response site.

A new near-infrared fluorescent probe for sensing extreme acidity and bioimaging in lysosome.

Since the intracellular pH plays an important role in the physiological and pathological processes, however, the probes that can be used for monitoring pH fluctuation under extreme acidic conditions are currently rare, so it is necessary to construct fluorescent probes for sensing pH less than 4. In this work, we developed a new near-infrared (NIR) fluorescent probefor sensing pH fluctuation under extremely acidic conditions. For the preparation of this probe, benzothiozolium moiety was chosen as lysosomal targeting unit and NIR fluorophore, and barbituric acid moiety was fused in the polymethine chain of probe to introduce protonation center.

An NADH-selective and sensitive fluorescence probe to evaluate living cell hypoxic stress.

Cellular disease and senescence are often accompanied by an imbalance in the local oxygen supply. Under hypoxia, mitochondrial NADH and FADH cannot be oxidized by the mitochondrial electron transport chain, which leads to the accumulation of reducing equivalents and subsequent reduction stress. Detecting changes in intracellular NADH levels is expected to allow an assessment of stress.

Novel lysosome-targeted fluorescent molecular rotors based on a cyanine-like modular system and their application in living cells.

Two novel fluorescence molecular rotors DpIn and NaIn were designed and synthesized involving of indolium units linked with meta-diphenol or ortha-naphthalenediol moiety, respectively. They underwent intramolecular charge transfer to form a cyanine-like modular system at a physiological pH. In glycerol aqueous solutions, the probe DpIn exhibited NIR strong emission (3-fold) at ca.

Mitochondria-targeted fluorescent probe for imaging endogenous hydrogen sulfide in cellular antioxidant stress.

Hydrogen sulfide (HS) is believed to play an important role in maintaining cellular redox homeostasis and avoiding oxidative damage caused by abnormally raised ROS levels. Highly selective and sensitive fluorescent probes for the detection and imaging of endogenous HS in living cells over other biological thiols are desirable. Herein, we developed a mitochondria-targeted fluorescent probe L, a thioxanthene-benzo[e]indolium derivative, for the discrimination of HS from other chemically similar biothiols.

Novel rhodamine dye with large Stokes shifts by fusing the 1,4-diethylpiperazine moiety and its applications in fast detection of Cu.

Rhodamine dyes were widely developed for designing probes due to their excellent photophysical properties and biocompatibility. However, traditional rhodamine dyes still bear major drawbacks of short emission wavelengths (<600 nm) and narrow Stokes shifts (<30 nm), which limit their biological imaging applications. Herein, we reported a novel mitochondria-targeted fluorescent dye JRQ with near-infrared (NIR) emission wavelength and improved Stokes shift (63 nm) by tuning the donor-acceptor-donor (D-A-D) character of the rhodamine skeleton.

A lysosome-targeting viscosity-sensitive fluorescent probe based on a novel functionalised near-infrared xanthene-indolium dye and its application in living cells.

The viscosity of lysosomes plays a significant role in modulating biological processes and reflects the status and function of this kind of organelle, e.g., locations, morphologies, and components.

A lysosome-targeted fluorescent probe for the specific detection and imaging of formaldehyde in living cells.

We presented herien the rational design, synthesis, and photophysical property studies of the lysosome-targeted fluorescence FA probe NP-Lyso, an isopropyl group modified ortho-diaminonaphthalimide derivative. After the reaction of FA and ortho-phenylenediamine modified with the isopropyl group in NP-Lyso, the probe exhibited favorable features such as a large fluorescence enhancement, specific selectivity and high sensitivity for the detection of FA. More importantly, NP-Lyso could be used to detect and image endogenous FA in lysosomes.

Novel near-infrared fluorescent probe with a large Stokes shift for sensing hypochlorous acid in mitochondria.

Hypochlorous acid (HOCl) plays a crucial role in various physiological and pathological processes. However, it is still a challenge to design a xanthene-based near-infrared (NIR) fluorescent probe with a large Stokes shift for sensing HOCl. In this work, a novel mitochondria-targeted fluorescent probe, MXS, with a large Stokes shift based on a xanthene-hemicyanine dyad structure, has been successfully designed and synthesized for the specific detection of HOCl.

A novel near-infrared fluorescent probe with large stokes shifts for sensing extreme acidity and its application in bioimaging.

In this work, we reported a novel near-infrared (NIR) fluorescent probe RQNN with large Stokes shift (98 nm) for monitoring pH under extremely acidic conditions. For the preparation of this probe, a 1,4-diethylpiperazine moiety was introduced in rhodamine scaffold to tune the electron-donating character, and an o-phenylenediamine was introduced in spironolactone to provide larger steric hindrance. The deprotonated-protonated equilibrium between RQNN, RQNN-H and RQNN-H were evaluated in different pH by absorption and emission spectra.

A deep-red fluorescent molecular rotor based on donor-two-acceptor modular system for imaging mitochondrial viscosity.

A new donor-two-acceptor modular fluorescence rotor DpCy7 involving a phenolate donor unit and two benzothiazolium acceptor moieties was designed and synthesized. The DpCy7 underwent an internal charge transfer to form a Cy7-like longer conjugated system fluorochrome at a physiological pH. The probe exhibited a strong turn-on (8.

A near-infrared fluorescent probe with an improved Stokes shift achieved by tuning the donor-acceptor-donor character of the rhodamine skeleton and its applications.

In this paper, we report a novel near-infrared (NIR) mitochondrion-targeted fluorescent probe, RQS, with an improved Stokes shift (96 nm) for the specific detection of mitochondrial mercury ion (Hg) because mitochondrion is one of the main targeted organelles of Hg. For the preparation of the probe, a novel asymmetrical fluorescent xanthene dye RQ was first synthesized by tuning the donor-acceptor-donor (D-A-D) character of the rhodamine skeleton, and then the probe RQS was constructed by the mechanism of mercury-promoted ring-opening reaction. As expected, RQS could be used for the specific detection of Hg with high selectivity, high sensitivity, and a detection limit down to the nanomolar range (2 nM).

A novel near-infrared fluorescent probe with an improved Stokes shift for specific detection of Hg in mitochondria.

The mercury ion (Hg2+), one of the most notorious heavy metal ions, not only causes environmental pollution, but also endangers human health. There is evidence that Hg2+ tends to accumulate in the mitochondria and to induce apoptosis. However, mitochondria-targeted near-infrared (NIR) fluorescent probes with large Stokes shifts are still scarcely described for the specific detection of Hg2+.

A near-infrared fluorescent probe based on a novel rectilinearly π-extended rhodamine derivative and its applications.

We designed and synthesized a novel near-infrared (NIR) mitochondria-targeted fluorescent probe RQNA for the specific detection of mitochondrial Cu2+ because mitochondria are important reservoirs of intracellular copper. For the preparation of this probe, a novel π-extended fluorescent xanthene dye RQN was firstly synthesized via an intramolecular nucleophilic substitution of aromatic hydrogen (SNArH) strategy. Then, probe RQNA was prepared by the reaction of RQN and hydrazine hydrate, followed by treatment with acetone.