An intelligent NIR fluorescent dye with dual response to pH and viscosity for investigating the interactions between LDs and mitochondria.

The interaction between lipid droplets and mitochondria plays a pivotal role in biological processes including cellular stress, metabolic homeostasis, cellular autophagy and apoptosis. Deciphering the complex interplay between lipid droplets and mitochondria is essential for gaining insights into the fundamental workings of the cell and can have broad implications for the development of therapeutic strategies for various diseases, including metabolic disorders, neurodegenerative diseases, and cancer. In this study, we develop a pH and viscosity-responsive near-infrared (NIR) fluorescent probe PTOH to investigate the interaction between lipid droplets and mitochondria. This probe demonstrates a significant enhancement in fluorescence intensity at 470 nm when the pH increases, while under acidic conditions, its fluorescence intensity at 730 nm intensifies by a factor of 35 with rising system viscosity. Cell imaging experiments revealed that PTOH can effectively discriminate between normal and cancerous cells, as well as detect intracellular pH and viscosity alterations induced by drugs. Additionally, PTOH is utilized to visualize the interaction between lipid droplets and mitochondria and to differentiate between cellular autophagy and apoptosis phenomena, providing a valuable tool for elucidating the mechanisms underlying lipid droplet-mitochondria interactions and their associated diseases.

Unveiling Cellular Microenvironments with a Near-Infrared Fluorescent Sensor: A Dual-Edge Tool for Cancer Detection and Drug Screening.

Mitochondria and lysosomes are pivotal intracellular organelles, and the injury or dysfunction of these organelles can trigger a range of pathological processes. Early diagnosis and treatment of cancer are of paramount importance due to cancer's status as a leading health threat. This study introduces a novel fluorescent probe, BDHV, for detecting mitochondrial and lysosomal viscosity and pH abnormalities in tumors, facilitating early cancer detection and screening of anticancer drugs. Under acidic conditions, the red fluorescence of the probe gradually increases with increasing viscosity. Conversely, in alkaline environments, an increase in viscosity leads to a decrease in green fluorescence and an increase in red fluorescence. The inclusion of a benzothiazole group endows BDHV with strong dual-targeting capability for mitochondria and lysosomes and without being affected by the mitochondrial membrane potential. Most notably, BDHV has potential applications for early cancer diagnosis and in effectively assessing the efficacy of various anticancer drugs.

A dual-responsive crimson fluorescent probe for real-time diagnosis of alcoholic acute liver injury.

The polarity and viscosity of the microenvironment are associated with the control of the onset and progression of pathological diseases, including inflammation, immuno-suppression and cancer. If appropriate treatment is neglected, alcoholic acute liver injury (AALI), the initial sign of alcoholic liver diseases, may transform into hepatic lesions. Therefore, it's crucial to create a particular probe to detect AALI swiftly and track its progression. Herein a polarity and viscosity dual-responsive crimson fluorescent probe (PPBI) was designed and developed, which can target mitochondria and lipid droplets. PPBI possesses aggregation-induced emission properties, good photostability and strong anti-interference ability against pH, metal ions, anions and biomolecules. This probe can distinguish cancer cells from normal ones using changes of green and red fluorescence, as well as identify changes in the cellular microenvironment associated with inflammatory and ferroptosis processes. In addition, changes in polarity and viscosity can be amplified by in vivo imaging in a mouse model to monitor alcohol-induced acute liver injury and to effectively detect the course of pharmacological intervention therapy. All the results suggest that PPBI could be a promising real-time fluorescence imaging tool for diagnosis and treatment of acute alcoholic liver injury.

NIR Mitochondrial Fluorescent Probe for Visualizing SO2/Polarity in Drug Induced Inflammatory Mice.

SO2 and polarity are important microenvironmental parameters in cells, which are closely related to physiological activities in organisms. The intracellular levels of SO2 and polarity are abnormal in inflammatory models. To this end, a novel near-infrared fluorescent probe BTHP that can simultaneously detect SO2 and polarity was studied. BTHP can sensitively detect polarity change with emission peak change from 677 to 818 nm. BTHP can also detect SO2 with fluorescence change from red to green. After addition of SO2, the fluorescence emission intensity ratio I517/I768 of the probe increased by about 33.6 times. BTHP can determine bisulfite in single crystal rock sugar with high recovery rate (99.2%-101.7%). Fluorescence imaging of cells showed that BTHP could better target mitochondria and monitor exogenous SO2 in A549 cells. More importantly, BTHP has been successfully used for dual channel monitoring SO2 and polarity in drug-induced inflammatory cells and mice. In particular, the probe showed increased green fluorescence with the generation of SO2 and increased red fluorescence with the decrease of polarity in inflammatory cells and mice.

Multiple organelle-targeted near-infrared fluorescent probes toward pH and viscosity.

Organelles, including mitochondria (mito), lysosomes (lyso), endoplasmic reticulum (ER), Golgi apparatus (Golgi), and ribosome et al., play a vital role in maintaining the regular work of the cell. Viscosity is an essential parameter in the cellular microenvironment. Herein, four viscosity-sensitive near-infrared fluorescent probes DMPC, DEPC, DHDM and DHDV that can simultaneously target multiple organelles were synthesized. As the viscosity increased, the fluorescence intensity of the probes gradually increased due to the hindrance of the rotation of the carbon-carbon single bond. The fluorescence intensity of DHDV increased by about 453 times, and the fluorescence quantum yield also increased from 0.051 to 0.681. Cell experiments indicated the probes could simultaneously target four kinds of organelles, and the four probes could also track mitochondria with no dependence on membrane potential. Further experiments showed that the probes could detect viscosity changes in lyso and mito. In addition, the probes also demonstrated the advantages of low cytotoxicity, good anti-interference and stability, providing a simple and effective tool for studying the activity of organelles with changing viscosity signals.

Coumarin-based fluorescent probes toward viscosity in mitochondrion/lysosome.

Viscosity is an important microenvironmental indicator that plays an important role in the process of information transmission in various regions. Herein, two coumarin-based viscosity-sensitive fluorescent probes (CHB, CHN) were synthesized and the photophysical properties of the two probes were studied. The fluorescence quantum yields of CHB and CHN in glycerol can be as high as 25.2% and 18.3% respectively. The two probes can linearly detect viscosity in the viscosity logarithm range of 0.83-2.07, which is not interfered with pH, metal ions, anions and biomolecules. Fluorescent confocal cell experiments show CHB and CHN have good targeting ability to mitochondrion, lysosome, Endoplasmic reticulum and Golgi apparatus, and can be used to detect viscosity in mitochondrion/lysosome.

Er-Based Luminescent Nanothermometer to Explore the Real-Time Temperature of Cells under External Stimuli.

Temperature as a typical parameter, which influences the status of living creatures, is essential to life activities and indicates the initial cellular activities. In recent years, the rapid development of nanotechnology provides a new tool for studying temperature variation at the micro- or nano-scales. In this study, an important phenomenon is observed at the cell level using luminescent probes to explore intracellular temperature changes, based on Yb-Er doping nanoparticles with special upconversion readout mode and intensity ratio signals (I525 and I545 ). Further optimization of this four-layer core-shell ratio nanothermometer endows it with remarkable characteristics: super photostability, sensitivity, and protection owing to the shell. Thus this kind of thermal probe has the property of anti-interference to the complex chemical environment, responding exclusively to temperature, when it is used in liquid and cells to reflect external temperature changes at the nanoscale. The intracellular temperature of living RAW and CAOV3 cells are observed to have a resistance mechanism to external stimuli and approach a more favorable temperature, especially for CAOV3 cells with good heat resistance, with the intracellular temperature 4.8 °C higher than incubated medium under 5 °C environment, and 4.4 °C lower than the medium under 60 °C environment.

Imaging of intracellular bisulfate based on sensitive ratiometric fluorescent probes.

Sulfur dioxide (SO2) is an environmental pollutant in the atmosphere which is easily absorbed by the human body. After being inhaled in the body, SO2 is quickly converted into bisulfite (HSO3-), forming a balance in which SO2 and HSO3- coexist in the body status. A large number of epidemiological studies have shown that abnormal levels of sulfite and bisulfite are related to the appearance of numerous diseases such as atherosclerosis, essential hypertension, and lung tissue fibrosis. Therefore, it is essential to develop an effective method to detect bisulfite. In this work, starting from 4-bromonaphthalene-1-carbonitrile, three uncomplicated but efficient HSO3- sensitive ratiometric fluorescent probes HNIC, CIVP and HVIC were designed and synthesized through ICT mechanism and the Michael-type addition reaction. The probes can image HSO3- in living cells. The probes not only have good fluorescence stability and strong anti-interference ability, but also display mitochondrial targeting ability.

A mitochondrial and lysosomal targeted ratiometric probe for detecting intracellular H2S.

Based on coumarin and benzopyran derivatives, a dual-wavelength excitation ratiometric fluorescent probe, HABA, was prepared to detect H2S. The HABA probe showed good selectivity and anti-interference abilities during H2S detection. Fluorescence co-localization experiments showed that HABA had excellent localization abilities toward mitochondria and lysosomes. More importantly, HABA can not only detect exogenous H2S, but it can also detect endogenous H2S, indicating that HABA has high application potential and value in the biological field.

Colorimetric and Ratiometric Fluorescence Detection of HSO3- With a NIR Fluorescent Dye.

Bisulfite (HSO3-) has been widely used in food and industry, which has brought convenience to human life, but also seriously endangered human health. In this work, the probe PBI was designed and synthesized to detect bisulfite (HSO3-) through nucleophilic addition reaction. The probe PBI showed a selective reaction to HSO3- and can quantitatively detect HSO3-. At the same time, the color of the probe PBI changed significantly, which provided a simple method for the naked eye to identify HSO3-. Finally, it was successfully applied to the fluorescence imaging of HSO3- in living cells.

Preparation of Yellow Fluorescent N,O-CDs and its Application in Detection of ClO.

Accurate and efficient detection of ClO- was extremely important due to the harm of ROS in the environment and organism. In this paper, yellow fluorescent N,O-CDs were successfully prepared by the solvothermal method. The microscopic size of the N,O-CDs was approximately spherical with an average particle size of 4.8 ± 0.8 nm. The fluorescence quantum yield in ethanol solution was calculated as 10.5 % using fluorescein as the standard reference. The as-fabricated N,O-CDs had high sensitivity and low detection limit (7.5 µM) for quantitatively detecting ClO- with a linear range from 0.07 mM to 0.16 mM. The probe not only shows good selectivity and anti-interference to metal ions, anions and amino acids but also has excellent light stability and thermal stability. Also, a wide selection range for pH was demonstrated.

Measurement of Temperature Distribution at the Nanoscale with Luminescent Probes Based on Lanthanide Nanoparticles and Quantum Dots.

It is very challenging to probe the temperature in a nanoscale because of the lack of detection technique. Temperature-sensitive luminescent probes at a nanoscale provide the possibility to solve this problem. Herein, we fabricated a model, which combined two kinds of temperature sensitive nanoprobes and gold nanoparticle heater within mesoporous silica nanoparticles. Upconverting nanoparticles and quantum dots located at different positions inside 110 nm nanoparticles reported different temperatures when the gold nanoparticles generated heat by 532 nm laser irradiation. The temperature difference between two probes with an average distance of 55 nm can reach about 30 °C. Our results prove that the temperature distribution at a nanoscale can be measured, and it will be noteworthy if a nano-heater is applied.

One-step synthesis of mitochondrion-targeted fluorescent carbon dots and fluorescence detection of silver ions.

Silver ions (Ag+) are the most representative harmful ions found in polluted water and widely used in many industries; excessive ingestion of Ag+ in the human body may result in interaction with different metabolites in the human body and in aquatic microorganisms, leading to many diseases. Therefore, there is a great desire to develop good fluorescent probes for Ag+. Herein, a kind of mitochondrion-targeted fluorescent carbon dot was developed. These carbon dots exhibit 29.5% fluorescence quantum yield in water, good photostability and thermal stability. The as-fabricated carbon dots can quickly detect Ag+ in 100% water solution with good selectivity and anti-interference ability. Further, the carbon dots have been successfully applied to monitor Ag+ in living cells via the dual-channel method.

A mitochondrion-targeting fluorescent probe for hypochlorite anion in living cells.

As momentous reactive oxygen species (ROS), it is necessary to develop high-sensitivity and high-specificity fluorescent probes for tracking hypochlorite anion (ClO-) in environmental and biological systems. Herein, a kind of red luminescent carbon dots (NS-dots) was synthesized by one-step solvothermal method to detect ClO- in PBS buffer solution (VPBS:VEtOH = 100:1, pH = 7.4). The NS-dots has high sensitivity and low detection limit (13.3 µmol/L) for detecting ClO- with linear range from 6.7 × 10-5 mol/L to 26.7 × 10-5 mol/L. Using Rhodamine B (31% at 520 nm in water) as a reference, the NS-dots have a fluorescence quantum yield of 7.2%. Intracellular photostability, mitochondrial targeting properties and the fluorescence imaging towards intracellular ClO- were demonstrated.

Carbon-dot-based ratiometric fluorescent probe of intracellular zinc ion and persulfate ion with low dark toxicity.

Metal ions and anions play significant roles in biological systems and industrial processes, therefore it is important to develop good fluorescent probes to detect metal ions and anions. Here, N,O-co-doped carbon quantum dots (CDs) that could detect Zn2+ via a ratiometric fluorescence method were fabricated. The reaction between the as-prepared CDs and zinc acetate gave the composite CDs-Zn, in which fluorescence changed ratiometrically upon addition of S2 O8 2- . With change in excitation light, the emission peaks of the CDs and CDs-Zn were kept fixed while intensity changed. CDs and CDs-Zn exhibited good photostability, thermal stability, selectivity, and strong anti-interference ability. In addition, CDs and CDs-Zn displayed low dark toxicity under physiological temperatures. Ratiometric fluorescence imaging of intracellular Zn2+ and S2 O8 2- was carried out in living HeLa cells for both of these probes. Compared with reported ratiometric fluorescent hybrid nanosensors based on organic dyes and inorganic nanomaterials, the as-prepared CDs and CDs-Zn had low toxicity, and were easy to synthesize.

Colorimetric and fluorescent detection of hydrazine with high sensitivity and excellent selectivity.

It is critical to develop probes for rapid, selective, and sensitive detection of the highly toxic hydrazine in both environmental and biological science. In this work, under mild condition, a novel colorimetric and off-on fluorescent probe was synthesized for rapid recognition of hydrazine with excellent selectivity over other various species including some biological species, metal ions and anions. The limit of quantification (LOQ) value was 1.5×10-4M-3.2×10-3M (colorimetric method) and 1.5×10-4M-3.2×10-3M (fluorescent method) with as low as detection limit of 46.2µM.

NIR Ratiometric Luminescence Detection of pH Fluctuation in Living Cells with Hemicyanine Derivative-Assembled Upconversion Nanophosphors.

It is crucial for cell physiology to keep the homeostasis of pH, and it is highly demanded yet challenging to develop luminescence resonance energy transfer (LRET)-based near-infrared (NIR) ratiometric luminescent sensor for the detection of pH fluctuation with NIR excitation. As promising energy donors for LRET, upconversion nanoparticles (UCNPs) have been widely used to fabricate nanosensors, but the relatively low LRET efficiency limits their application in bioassay. To improve the LRET efficiency, core/shell/shell structured ß-NaGdF4@NaYF4:Yb,Tm@NaYF4 UCNPs were prepared and decorated with hemicyanine dyes as an LRET-based NIR ratiometric luminescent pH fluctuation-nanosensor for the first time. The as-developed nanosensor not only exhibits good antidisturbance ability, but it also can reversibly sense pH and linearly sense pH in a range of 6.0-9.0 and 6.8-9.0 from absorption and upconversion emission spectra, respectively. In addition, the nanosensor displays low dark toxicity under physiological temperature, indicating good biocompatibility. Furthermore, live cell imaging results revealed that the sensor can selectively monitor pH fluctuation via ratiometric upconversion luminescence behavior.

Near-infrared ratiometric fluorescent detection of arginine in lysosome with a new hemicyanine derivative.

A Near-Infrared (NIR) ratiometric and on-off fluorescent probe 1 was synthesized, which exhibited high sensitivity and excellent selectivity in arginine (Arg) recognition. 1 can quantitatively detect Arg in concentration range from 0 to 150µM with the LOD of 138nM. Further, it displayed excellent selectivity and anti-interference over many biological species, metal ions and anions. Due to its ability to target lysosome, the response of Arg to this probe in a living cell was successfully tracked in a ratiometric manner via fluorescence imaging.

Nanomolar colorimetric quantitative detection of Fe³âº and PPi with high selectivity.

A novel rhodamine and 8-hydroxyquinoline-based derivative was synthesized, which is shown to act as a colorimetric chemosensor for Fe(3+) in aqueous solution with high selectivity over various environmentally and biologically relevant metal ions and anions with a distinct color change from colorless to pink in very fast response time (<1 min). Fe(3+) can be detected quantitatively in the concentration range from 6.7 to 16 µM and the detection limit (LOD) on UV-vis response of the sensor can be as low as 15 nM. The 'in situ' prepared Fe(3+) complex (1⋅Fe) showed high selectivity toward PPi against many common anions, and sensitivity (the LOD can be as low as 71 nM). In addition, both the chemosensor and the 'in situ' prepared Fe(3+) complex are reusable for the detection of Fe(3+) and PPi respectively.

Note: Stability control of intermediate frequencies of a three laser far-infrared polarimeter-interferometer system.

Stability of the intermediate frequency (IF) in the far-infrared polarimeter-interferometer diagnostic system is critically important for the long pulse discharge experiments on the EAST tokamak. In this note, a real-time remote/local IF stability control system is described. The measured plasma parameters, including the Faraday rotation angle, electron density, lower hybrid wave, and plasma current, are obtained with the aid of this newly developed IF stability control system.