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Fluorescent lipid probes such as 1-palmitoyl-2-(6-[7-nitro-2-1,3-benzoxadiazol-4-yl]amino-hexanoyl)-sn-glycero-3-phosphocholine (C6 NBD-PC) have been used extensively to study the kinetics of lipid flip-flop. However, the efficacy of these probes as reliable reporters of native lipid translocation has never been tested. In this study, sum-frequency vibrational spectroscopy (SFVS) was used to measure the kinetics of C6 NBD-PC lipid flip-flop and the flip-flop of native lipids in planar supported lipid bilayers. C6 NBD-PC was investigated at concentrations of 1 and 3 mol. % in both chain-matched 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and chain-mismatched 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) to assess the ability of C6 NBD-PC to mimic the behavior of the surrounding matrix lipids. It was observed that C6 NBD-PC exhibited faster flip-flop kinetics compared to the native lipids in both DPPC and DSPC matrices, with notably accelerated rates in the chain-mismatched DSPC system. SFVS was also used to measure the acyl chain orientation and gauche content of C6 NBD-PC in both DPPC and DSPC membranes. In the DSPC matrix (chain mismatched), C6 NBD-PC was more disordered in terms of both gauche content and acyl tilt, whereas it maintained an orientation similar to that of the native lipids in the DPPC matrix (chain matched). In addition, the flip-flop kinetics of C6 NBD-PC were also measured using second-harmonic generation (SHG) spectroscopy, by probing the motion of the NBD chromophore directly. The flip-flop kinetics measured by SHG were consistent with those obtained from SFVS. This study also marks the first instance of phospholipid flip-flop kinetics being measured via SHG. The results of this study clearly demonstrate that C6 NBD-PC does not adequately mimic the behavior of native lipids within a membrane. These findings also highlight the significant impact of the lipid matrix on the flip-flop behavior of the fluorescently labeled lipid, C6 NBD-PC. [ABSTRACT FROM AUTHOR]

RNA methylation is a metabolic process validated for its association with various diseases, and thus, RNA methyltransferases (MTases) have become increasingly important in drug discovery. Yet, most frequently utilized RNA MTase assays are limited in their throughput and hamper this rapidly evolving field of medicinal chemistry. In this study, we describe a modular nanomole scale building block system that allowed the identification of tailored fluorescent MTase probes to unlock a broad selection of MTase drug targets for fluorescence‐based binding assays. Probe candidates were initially prepared on a 4 nanomole scale and could be tested directly from crude reaction mixtures to allow rapid probe identification and optimization. Using an alkyne‐azide click late‐stage functionalization strategy and in silico protein databank mining, we established a selection of fluorescent probes suitable for relevant drug targets from the METTL and NSUN families, as well as bacterial and viral MTases. Using this concept, a high‐throughput screening on the unexplored drug target METTL1 discovered three hit compounds with micromolar potency providing a (1H‐pyrazol‐4‐yl)pyridine‐based starting point for METTL1 drug discovery. [ABSTRACT FROM AUTHOR]

In this study, a new near-infrared (NIR) fluorescent turn-on probe featuring a large Stokes shift (198 nm) was developed for the detection of biothiols. The probe was based on a dicyanoisophorone derivative serving as the fluorophore and a 2,4-dinitrobenzenesulfonyl (DNBS) group functioning as both a recognition site and a fluorescence quencher. In the absence of biothiols, the fluorescence of the probe was low due to the photoinduced electron transfer (PET) effect between the fluorophore and DNBS. Upon the presence of biothiols, the DNBS group underwent a nucleophilic aromatic substitution reaction with the sulfhydryl group of biothiols, leading to the release of the fluorophore and a notable emission peak at 668 nm. This developed probe exhibited exceptional selectivity and sensitivity to biothiols in solution, with an impressive detection limit of 28 nM for cysteine (Cys), 22 nM for homocysteine (Hcy), and 24 nM for glutathione (GSH). Furthermore, the probe demonstrated its applicability by successfully visualizing both endogenous and exogenous biothiols in living systems. [ABSTRACT FROM AUTHOR]

Fe2+ plays a crucial role in biological systems as an essential trace element in the body. Iron is absorbed by the body through food and Fe2+ is also an important component of living cells; therefore, quantitative testing of Fe2+ in food and in living cells is of great importance. This paper presents the development of a novel π-bridge EDOT-based N-oxide turn-on fluorescent probe, designated as FeE, for the detection of Fe2+. The probe has been shown to exhibit excellent sensitivity, a favorable linear relationship between fluorescence signal intensity and Fe2+ concentration, and an effective immunity to interference. The probe has low cytotoxicity and has been successfully used to detect Fe2+ in cells using laser confocal fluorescence microscopy. It is also possible to determine the presence of Fe2+ in animal blood, spinach, apple juice, red wine, mineral water and metal cans. The Fe2+ responsive probe FeE can be prepared as a Fe2+ responsive test strip that can detect Fe2+ in food samples and exogenous and endogenous Fe2+ in cells. [ABSTRACT FROM AUTHOR]

Chromene as the efficient biothiol recognition site was widely used to develop fluorescent probes based on thiol-chromene click reaction. However, chromene-based fluorescent probes with the both properties of ratiometric measurement and mitochondria-targeted function have not been reported and remain challenging. In this paper, we skillfully designed and synthesized the first mitochondria-targeted ratiometric fluorescent probe (Probe 1) for biothiols based on chromene. Upon addition of biothiols (Cys, Hcy, and GSH), the absorption and fluorescence spectra of Probe 1 changed from 490 to 426 nm and from 567 to 498 nm respectively, accompanied by color changes from orange to pale yellow under natural light and from orange to blue under a 365-nm UV lamp, which can be attributed to the click reaction of biothiols with α,β-unsaturated ketone of chromene moiety, subsequent pyran ring-opening, and phenol formation as well as 1,6-elimination of p-hydroxybenzyl moiety. Probe 1 not only exhibited high sensitivity (LODs of 149 nM, 133 nM, and 116 nM for Cys, GSH, and Hcy respectively), rapid response, and excellent selectivity for biothiols (Cys, Hcy, and GSH), but also could target in mitochondria and ratiometrically image the fluctuation of intracellular biothiols. Moreover, the novel design strategy of modifying chromene to the N atom of pyridine was proposed for the first time. [ABSTRACT FROM AUTHOR]

Sequence-selective G-quadruplex ligands are valuable for controlling gene expression. Here, we established a new fluorescence displacement assay using a NRAS G-quadruplex selective fluorescent probe to identify sequence-selective DNA G-quadruplex ligands. These sequence-selective NRAS G-quadruplex ligands retained their binding affinity even in the presence of excessive human telomeric DNA G-quadruplex and regulated enzymatic activities in a sequence-selective manner. [ABSTRACT FROM AUTHOR]

As one of the important components of active oxygen species, H2O2 (hydrogen peroxide) plays an important role in life activities. Many studies have shown that a high concentration of H2O2 can cause cell necrosis, resulting in oxidative stress and oxidative damage in the body, and then induce various diseases. The application of organic small molecule fluorescent probes in life sciences has attracted the attention of many researchers because of their advantages of being easy to obtain, high spatial and temporal resolution, little damage to biological samples and simple operation. In this study, a new hydrogen peroxide near infrared fluorescence probe JH was constructed using oxanthrene analogues as a molecular framework. The fluorescence emission wavelength of the probe is located in the near infrared region and has a large Stokes shift, which makes the probe less damaging to biological samples and gives lower background interference, which is conducive to improving the detection resolution. The probe can complete the response to H2O2 within 95 min with a low detection limit (4.72 μM), and the color of the solution changes from dark blue to light blue after the response, so H2O2 can be recognized by the naked eye without any tools. In addition, probe JH has been successfully used for the detection of H2O2 in cells, which is expected to become a tool for early diagnosis of diseases. [ABSTRACT FROM AUTHOR]

Fluorophores are essential tools for optical imaging and biomedical research. Their synthetic modification to incorporate new functions, however, remains a challenging task. Conventional strategies rely on linear synthesis in which a parent framework is gradually extended. We here designed and synthesized a versatile library of multi‐functional fluorophores via a scaffold‐based Ugi four‐component reaction (U‐4CR). The adaptability of the scaffold is achieved through modification of starting materials. This allows to use a small range of starting materials for the creation of fluorogenic probes that can detect reactive‐oxygen species and where the localization into subcellular organelles or membranes can be controlled. We present reaction yields ranging from 60 % to 90 % and discovered that some compounds can even function as imaging and therapeutic agents via Fenton chemistry inducing pyroptosis in living cancer cells. Our study underlines the potential of scaffold‐based synthesis for versatile creation of functional fluorophores and their applications. [ABSTRACT FROM AUTHOR]

Dipeptidyl peptidase 4 (DPP-4) is a promising biomarker for cancer and metabolic diseases. We demonstrate the design of novel fluorescent DPP-4 probes based on the protease's native substrates using a thioamide as a quencher for measuring in vitro kinetics, inhibition with sitagliptin, and DPP-4 activity in saliva samples. [ABSTRACT FROM AUTHOR]

Fluorofluorophores are a unique class of fluorophores that can be solubilized in perfluorocarbons (PFCs) and used to study biological systems. However, because of the low dielectric constant and high oxygen solubility in the fluorous phase, the brightness and photostability of the fluorofluorophores are significantly diminished. Here, we leveraged the tight ion pairing in the fluorous phase to improve the photophysical properties of a fluorous soluble pentamethine dye (FCy5) via counterion exchange. We found that larger, softer, fluorinated, aryl borate counterions promote the ideal polymethine state where charge delocalization across the polymethine chain increases the brightness (6‐fold) and photostability (55‐fold) of FCy5. [ABSTRACT FROM AUTHOR]

Octacalcium phosphate (OCP) is a fascinating calcium phosphate material with a layered structure that can incorporate various guest molecules, particularly dicarboxylate ions. However, the solution-phase synthesis of OCP fine particles is challenging. In this study, we developed a new precipitation method based on the LaMer model for synthesising fine particles of plain OCP and OCP with incorporated isophthalate and succinate ions. Highly concentrated aqueous solutions and appropriate reaction conditions yielded particle sizes of 100–200 nm for plain OCP and 200–300 nm for OCP with incorporated dicarboxylate ions. The obtained particle sizes were significantly smaller than those of OCPs synthesised using conventional methods. The incorporation of isophthalate and succinate ions into OCP was confirmed using various methods, particularly X-ray diffraction, which revealed expansion of the (100) interplanar spacing. During the synthesis of OCP with incorporated isophthalate ions, hydrolysis of the OCP phase was minimised when the initial pH range of the isophthalic acid solution was 5.2–5.3. Interestingly, OCP with incorporated isophthalate ions exhibited fluorescence (excitation and emission at 325 and 390 nm, respectively), demonstrating the potential of these fine particles as novel biofriendly fluorescent probes. This novel LaMer-model-based synthesis for preparing fine particles of OCP and OCP with incorporated functional carboxylate ions can contribute to the design and development of next-generation biofriendly imaging probes and other functional calcium phosphate materials, such as for use in biosensing and drug delivery applications. [ABSTRACT FROM AUTHOR]

Myeloperoxidase (MPO) plays an important role in the immune response of human neutrophils and has been implicated in autoimmune conditions, cardiovascular disorders, and neurodegeneration. Current methods to detect MPO activity rely on the detection of HOCl using activatable probes or require challenging experimental procedures. Therefore, these tools provide limited information about the dynamics and localization of MPO in complex molecular processes such as NETosis in real time. In this study, we report a ''turn-on" activity-based probe that fluoresces exclusively upon binding to MPO, exhibits minimal background fluorescence in buffered aqueous media, and is blocked by MPO inhibitors. Our probe facilitates real-time imaging of direct MPO activity in human neutrophils and HL-60-derived granulocytes during NETosis under wash-free conditions. Furthermore, it allows for the discrimination between different triggers of NETosis in human neutrophils. These findings hold promise for advancing our understanding of the role of MPO in immune responses and inflammatory conditions. Myeloperoxidase (MPO) plays an important role in the innate immune response of human neutrophils and has been implicated in various diseases, but current methods to detect MPO provide limited information about its dynamics and localization in complex molecular processes. Here, the authors develop an activity-based probe that fluoresces exclusively upon binding to MPO, enabling real-time imaging of direct intracellular MPO activity in human neutrophils and HL-60-derived granulocytes during NETosis under wash-free conditions. [ABSTRACT FROM AUTHOR]

The article discusses the importance of calcium flux balance in the heart, focusing on the equilibrium between calcium entering and leaving cardiac cells to prevent calcium overload. It highlights the role of various proteins and organelles in maintaining this balance, such as SERCA, NCX, LTCC, and RyR. The text responds to criticisms regarding the effects of caffeine on calcium release and emphasizes the necessity of considering calcium flux balance when studying the impact of drugs on calcium handling in the heart. [Extracted from the article]

Biothiols, characterized by their unique sulfhydryl (-SH) groups, possess excellent antioxidant properties, effectively neutralizing the damage to cellular structures caused by reactive oxygen species (ROS) in living organisms. Additionally, lysosomes play a crucial role in decomposing damaged biomolecules through the action of their internal enzymes, regulating the cellular redox state, and mitigating oxidative stress. To facilitate rapid monitoring of intracellular biothiols, particularly within lysosomes, we constructed a lysosome-targeted biothiol fluorescent probe, PHL-DNP, in this study. PHL-DNP exhibited excellent photophysical properties in an aqueous test system, including strong fluorescence enhancement response, excellent selectivity, and low detection limits (Cys 16.5 nM, Hcy 16.8 nM, GSH 21.3 nM, Cap 26.6 nM). These attributes enabled easy and efficient qualification of Cys on test strips and accurate determination of the effective content of captopril tablets. Notably, PHL-DNP demonstrated low cytotoxicity and precise lysosomal targeting. Through bioimaging, PHL-DNP not only monitored changes in biothiol levels under oxidative stress but also assessed biothiols in complex biological systems such as live HeLa cells, zebrafish, tumor tissue sections, and radish roots. This provides a promising tool for quantitative analysis of biothiols, disease marker detection, and drug testing. [ABSTRACT FROM AUTHOR]

Enzymes play a significant role in mediating inflammatory and immune responses in periodontitis. Effective diagnosis, timely treatment, and continuous management of periodontal enzymes are essential to prevent undesirable consequences; however, this remains a significant challenge. Nanoparticles (NPs) have attracted significant attention in biomedicine because of their advantageous nanosized effects. NPs are conjugated with specific enzyme substrates at responsive sites that are triggered by periodontitis enzyme biomarkers, leading to functional or characteristic changes. In contrast, NPs with enzyme-mimetic activities exhibit catalytic activity, effectively destroying pathogenic biofilms and modulating the immune response in periodontitis. The unique properties of enzyme-targeting NPs have enabled the development of biosensors and fluorescent probes capable of identifying enzyme biomarkers associated with periodontitis. Enzyme-responsive and enzyme-mimetic NPs both exert therapeutic applications in the treatment of periodontitis. In this review, we provide a comprehensive overview of the enzymes associated with periodontitis, the mechanisms of enzyme-responsive and enzyme-mimetic NPs, recent advancements in the use of NPs for detecting these enzymes, and the therapeutic applications of NPs in targeting or mimicking enzyme functions. We also discuss the challenges and prospects of using NPs in the diagnosis and treatment of periodontitis. [ABSTRACT FROM AUTHOR]

Streptococcus suis serotypes 2 and 14 are the most common zoonotic strains, but previous identification methods made distinguish these two serotypes from other S. suis serotypes difficult. To effectively prevent and control them, there is an urgent need for a highly sensitive and specific method to identify these two serotypes. In this study, a fluorescent probe was designed for the single nucleotide polymorphism site at cpsK 483 of Streptococcus suis type 2 and type 14 compared with other serotypes, and an enzyme-activated probe quantitative PCR (EA-probe qPCR) method was established for the detection of Streptococcus suis type 2 and type 14 by combining with the specific hydrolysis characteristics of the RNase H2 enzyme. The results showed that the optimal probe concentration for this method was 0.5 µM and the optimal RNase H2 enzyme concentration was 25 mU.This method showed no reactivity with genomic DNA from Streptococcus suis strains 1/2, 5, 7, 9, 23, 28, 29, and 31, confirming its high specificity. And its sensitivity can reach 18.4 CFU. In addition, 19 clinical strains of Streptococcus suis type 2 or type 1/2 were tested. The results showed 100% agreement with the gene sequencing method. In conclusion, this method can meet the needs of accurate laboratory testing of Streptococcus suis serotypes 2 and 14 and has value for clinical prevention. [ABSTRACT FROM AUTHOR]

Synthetic molecular sensors are crucial for real-time monitoring in biological systems and biotechnological applications, where detecting targets amidst potential interferents is essential. This task is particularly challenging in competitive environments that lacking chemically reactive functional groups, common in agricultural, biological, and environmental contexts. Consequently, scientific efforts have focused on developing sensitive and rapid analytical techniques, with fluorescent sensors emerging as prominent tools. Among these, the albumin-based supramolecular fluorescent indicator displacement assay (AS-FIDA) represents a significant advancement. Our research group has extensively contributed to this field, demonstrating the practical utility of various AS-FIDAs. We pioneered the use of albumin (ALB) as a host molecule in these synthetic chemical sensors, marking a notable advancement. AS-FIDA employs ALB as a versatile host molecule with multiple flexible and asymmetrical binding pockets capable of forming complexes with guest dyes, resulting in ALB@dye ensembles tailored for specific analyte recognition. Recent advancements in AS-FIDA have significantly expanded its applications. This review explores recent advances in ALB-based supramolecular sensors and sensor arrays for detecting biologically and environmentally significant molecules, such as pesticides, hormones, biomarkers, reactive species, mycotoxins, drugs, and carcinogens. The versatility of AS-FIDA positions it as a valuable tool in diverse settings, from laboratory research to practical applications in portable devices, smartphone-assisted on-site monitoring, imaging of living cells, and real sample analysis. [ABSTRACT FROM AUTHOR]

In the presence of molecular oxygen, edible oils can be oxidized to form a multitude of α,β-unsaturated carbonyl products collectively called 'lipid-derived electrophiles'. These molecules affect the taste of fat-containing foods but also act as electrophiles by covalently binding to protein amines/thiols and DNA nucleotides. The chemical modification of proteins by lipid-derived electrophiles appears to play an important role in human health, but the quantification of this diverse class of compounds remains a challenge. In this study, we describe a method capable of measuring the relative content of α,β-unsaturated carbonyls in food containing edible oils by using a "turn-on" fluorescent probe. The detection of electrophiles is based on a pre-fluorescent probe, 7-mercapto-4-methyl-coumarin (C-SH). The fluorescence of C-SH increases after nucleophilic addition to electrophilic lipid oxidation products. Since different lipid-derived electrophiles will react at a different rate with our fluorescent probe, we expressed the probe's response against a standard electrophile: trans-2-nonenal. In this assay, electrophiles which react more quickly will have a more dominant weight in the measurements carried out. Using this analytical technique, we can compare electrophilic content in French fries from several restaurants, and find they have lower amounts of lipid-derived electrophiles versus frozen fries baked at home. We also demonstrate that potato chips sealed in a reduced oxygen atmosphere will have a low 'electrophilic content' that increases over time, whereas chips in oxygen-permeable packaging initially have a higher 'electrophilic content' that does not increase as much over time. The relative ease of fluorescence measurements using microplate readers coupled with a simple oil extraction protocol should allow this method to quantify 'electrophilic content' in several food sources. [ABSTRACT FROM AUTHOR]

The processes of apoptosis and inflammatory responses, which are defensive strategies used by cells to confront external substances, can give rise to diverse diseases when prolonged or disrupted, such as cancer, Alzheimer's disease, and Parkinson's disease. Here we engineered a live-cell imaging fluorescent probe for nitric oxide (NO) based on naphthalimide and o-phenylenediamine, enabling the sensitive detection of NO in cancer cells and thereby live-monitoring of the doxorubicin-induced apoptosis and lipopolysaccharide-triggered inflammation reactions. Importantly, we found that the level of released NO can sensitively indicate the early stages of both cellular inflammatory responses and apoptotic processes. This suggested that cellular NO in fact behaves as a new class of signaling molecule for inflammatory responses and apoptosis processes, providing a potent tool for live-monitoring cellular physiological reactions. [ABSTRACT FROM AUTHOR]

The scanning tunneling microscope (STM) provides access to atomic-scale properties of a conductive sample. While single-molecule tip functionalization has become a standard procedure, fluorescent molecular probes remained absent from the available tool set. Here, the plasmonic tip of an STM is functionalized with a single fluorescent molecule and is scanned on a plasmonic substrate. The tunneling current flowing through the tip-molecule-substrate junction generates a narrow-line emission of light corresponding to the fluorescence of the negatively charged molecule suspended at the apex of the tip, i.e., the emission of the excited molecular anion. The fluorescence of this molecular probe is recorded for tip-substrate nanocavities featuring different plasmonic resonances, for different tip-substrate distances and applied bias voltages, and on different substrates. We demonstrate that the width of the emission peak can be used as a probe of the exciton-plasmon coupling strength and that the energy of the emitted photons is governed by the molecule interactions with its environment. Additionally, we theoretically elucidate why the direct contact of the suspended molecule with the metallic tip does not totally quench the radiative emission of the molecule. Scanning tunneling microscopy (STM) gives access to the atomic-scale properties of matter. Here, the authors showcase the fluorescent functionalization of an STM tip using a single molecule in direct metal contact, permitting the local electrostatic and -dynamic environment to be probed. [ABSTRACT FROM AUTHOR]

A highly selective fluorescent "turn on" probe for Al3+ based on the conjugate of aminourea and pyrazolone was devised and synthesized. The fluorescence intensity of the probe solution was significantly enhanced by the addition of Al3+ to the probe solution. Other cations such as Cu2+, Ni2+, Fe3+, Co2+, Ag+, Mn2+, Sn2+, Sn4+, Mg2+, Li+, Zn2+, Zr4+, Ce3+, Ca2+, and Na+ did not interfere the detection of Al3+. The 1 : 1 complexation between Al3+ and the probe was confirmed by Job's plot curve. In addition, the solution of the complex formed by Al3+ and the probe can be used for the specific detection of Hg2+, appearing as fluorescence quenching. [ABSTRACT FROM AUTHOR]

ABSTRACT Antibiotic pollution in hydrophytic ecosystems has aroused widespread notice due to its adverse impact on both the ecological environment and human physical well‐being. Thus, the development of effective antibiotic detection materials is not only urgently needed but is also challenging. Herein, the luminescent metal–organic framework [Mn3/2(HBCTC)·5H2O] (1) was successfully synthesized based on [9,9′‐bicarbazole]‐3,3′,6,6′‐tetracarboxylic acid (H4BCTC) under solvothermal conditions. Compound 1 can be employed as a fluorescent probe to detect antibiotic difloxacin hydrochloride (DIF) in water, demonstrating a remarkable linear relationship between fluorescence intensity ratio I0/I and the concentration of DIF (0–40 μM), with Ksv of 79,405 M−1 and LOD of 114 nM. More importantly, 1 represents the first fluorescent sensing material based on MOF for the detection of DIF, exhibiting exceptional selectivity, sensitivity, and anti‐interference capability. Furthermore, the mechanism of fluorescence quenching was studied comprehensively. [ABSTRACT FROM AUTHOR]

A multifunctional fluorescent probe P based on a naphthalimide derivative for the detection of Ag+ and Hg2+ through a dual-signal was designed and characterized. P exhibited a large Stokes shift (107 nm), high selectivity, good sensitivity, and fast response time. By adjusting the testing medium and the order of reagent addition, multifunctional detection with P was achieved. The addition of Ag+ or Hg2+ to P solution in either ethanol or an ethanol–water mixture resulted in a significant quenching of fluorescence emission at 537 nm and caused a decrease in the absorbance at 440 nm accompanied by the appearance of a new absorption peak at around 340 nm, and there was an obvious color change from yellow to colorless. In contrast, the addition of other common metal ions and anions did not produce substantial spectral or color changes. The detection limit of probe P for Ag+ and Hg2+ was calculated to be 0.33 μM. The sensing mechanism was proposed and validated through MS and 1H NMR spectrometry methods. Additionally, P demonstrated the capability to recognize Ag+ and Hg2+ in living cells with satisfactory results. [ABSTRACT FROM AUTHOR]

A benzothiazole-based derivative aggregation-induced emission (AIE) fluorescent 'turn-on' probe named 2-(2-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl)oxy)phenyl)benzo[d]thiazole (probe BT-BO) was developed and synthesized successfully for detecting hydrogen peroxide (H2O2) in living cells. The synthesis method of probe BT-BO is facile. Probe BT-BO demonstrates a well-resolved emission peak at 604 nm and the ability to prevent the interference of reactive oxygen species (ROS), various metal ions and anion ions, and good sensitivity. Additionally, the probe boasts impressive pH range versatility, a fast response time to H2O2 and low cytotoxicity. Finally, probe BT-BO was applied successfully to image A549 and Hep G2 cells to monitor both exogenous and endogenous H2O2. [ABSTRACT FROM AUTHOR]

Accurate water content detection is crucial for optimizing chemical reactions, ensuring product quality in pharmaceutical manufacturing, and maintaining food safety. In this study, nitrogen and sulfur co-doped graphene quantum dots (R-GQDs) were synthesized via a one-step hydrothermal method using o-phenylenediamine as the carbon source. The synthesis conditions, including reaction time, temperature, o-phenylenediamine concentration, and H2SO4/water ratio, were optimized using the Box-Behnken response surface methodology. The R-GQDs exhibited excellent fluorescence stability and distinct solvent-dependent characteristics, alongside a broad linear detection range and high sensitivity, making them highly suitable for dual-mode water content detection (colorimetric and fluorescent). To enhance the accuracy of visual detection, R-GQDs were incorporated into portable test strips with smartphone-assisted analysis, compensating for the human eye's limitations in distinguishing subtle color changes. The sensor's practical utility was validated through spiked recovery experiments in food samples, and the R-GQDs demonstrated good biocompatibility for in vivo imaging in shrimp. These findings highlight a novel strategy for developing portable, real-time water content sensors with potential applications in both portable detection systems and biological imaging. [ABSTRACT FROM AUTHOR]

Metal nanoclusters assembled using short peptides as templates exhibit significant potential for development and application in the fields of catalysis and biomedicine, owing to their distinctive electronic structure, favorable optical properties, and biocompatibility. Among them, tripeptides exhibit a simpler structure and greater flexibility, enabling them to readily co-assemble with other functional components to create novel materials with significant application value. They can be assembled with copper ions to synthesize highly efficient luminescent nanoclusters, which can serve as an effective fluorescent probe. Here, we report a method for the synthesis of copper nanoclusters (Cu NCs) using tripeptides as templates, which also act as stabilizers and reducing agents. The synthesis conditions and properties were explored and optimized. Under optimal conditions, the Cu NCs exhibit excellent stability and are strongly fluorescent. The Cu NCs can detect 0.1–1.0 μmol/L of ascorbic acid with a low detection limit of 0.075 μmol/L, demonstrating high sensitivity and offering significant application potential for the trace of ascorbic acid in various substances. It also provides new ideas for the assembly of metal nanoclusters and the construction of fluorescent probe sensing platforms. [ABSTRACT FROM AUTHOR]

Phosphate is widely used in industry and agriculture fields. However, excess accumulation of PO43− causes several adverse effects on the human body and ecological environment. Consequently, it is important to develop a simple method for the detection of PO43− concentration in the ecological environment and in vivo. Herein, two caffeic acid derivative-based fluorescence probes (BAM-HM and BAM-HH) were developed for the detection of phosphate. The BAM-HM probe could detect phosphate via fluorescence enhancement at 500 nm, with the detection limit being 0.612 µM. Meanwhile, the BAM-HH probe showed a significant turn-on signal at 450 nm after the addition of phosphate, and the detection limit was calculated to be 0.318 µM. The sensing mechanism was determined by 1H NMR and MS. Furthermore, the two probes (BAM-HM and BAM-HH) were applied for PO43−detection in living cells and water samples. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Inorganic Analytical Chemistry / Zhongguo Wuji Fenxi Huaxue is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Mercury is highly toxic, and appropriate amounts of the mercury‐selenium complex can protect plasma. However, when excessive mercury (II) ions (Hg2+) are exposed to human skin or ingested directly, it can lead to irreversible accumulation in the body. Therefore, detecting the presence of Hg2+ in cells is important. A novel fluorescent probe BTD‐Hg‐Lyso was designed and constructed based on the intramolecular charge transfer mechanism. Thiotaldehyde could specifically recognize Hg2+ so that the probe could produce a fluorescence enhancement effect. In addition, the fluorescent probe BTD‐Hg‐Lyso exhibited the advantages of large Stokes shift (210 nm) and good selectivity. More importantly, the probe BTD‐Hg‐Lyso could be used for the determination of Hg2+ in cellular lysosomes. BTD‐Hg‐Lyso was able to image Hg2+ in HeLa cells, zebrafish, and tobacco seedlings (rhizome and stem) successfully. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs), also known as nanoparticle-based fluorescent probes, are luminescent semiconductor particles with a size range of 2-20 nm. The unique optical and electronic capabilities of QDs have led to expanded applications in several fields such as optoelectronics, transistors, sensors, photodetection, catalysis, and medicine. The distinct quantum effects of nanocrystals can be controlled by changing their sizes and shapes using a variety of top-down and bottom-up tactics. QDs were traditionally fabricated using complex, expensive, toxic, and aggressive chemical techniques, which limited their application in a variety of disciplines. A unique approach for the biosynthesis of nanomaterials has been devised, which employs living organisms in the synthesis process and adheres to green chemistry principles. Biogenic QDs have favorable physicochemical features, biocompatibility, and fewer cytotoxic effects as a result of using natural biomolecules and enzymatic processes for mineralization, detoxification, and nucleation of metals and nonmetals to synthesize QDs. This is the first comprehensive review of its kind that highlights the synthesis of several doped and undoped QDs, including graphene QDs, carbon dots, silicon QDs, N/S-CDs, silver-CDs, cadmium-selenium QDs, and zinc oxide QDs, exclusively using photoautotrophic algae and plants. The different plausible mechanisms behind phyco- and phyto-fabrication of QDs are also discussed in detail along with their applications that include detection of organic and inorganic compounds, degradation of hazardous dyes, free radical scavenging, antimicrobial activity, cytotoxicity and bioimaging. Thus, this review aims to give valuable insights for the rational fabrication of photoluminescent nanomaterials with tunable structural and functional properties. [ABSTRACT FROM AUTHOR]

A novel d‐gluconamide‐functionalized water‐soluble pillar[5]arene (GWP5) was synthesized through a simple synthetic route. GWP5 showed a remarkable aggregation‐induced emission (AIE) with increasing concentration. This feature served as the basis for the construction of an AIE‐based sensor for fluorescence detection of Fe3+ with high sensitivity and selectivity, with a linear relationship between luminescence quenching and Fe3+ concentration observed from 0 to 20 µM, and a limit of detection of 7.84 × 10−9 M. This fluorescent probe could be applied to the detection of Fe3+ ions in real environmental water samples and in serum samples. [ABSTRACT FROM AUTHOR]

This study aimed to enhance the surface defects and fluorescence properties of GdPO₄·H₂O:Tb³⁺ nanophosphors and develop a nanoscale dual-layer core-shell structured fluorescent probe, GdPO₄·H₂O:20%Tb³⁺@GdPO₄@PEG. Hydrothermal and microwave synthesis methods were employed. The former controlled the ratio of GdPO₄·H₂O:Tb³⁺ to GdPO₄, forming core-shell structured nanophosphors GdPO₄·H₂O:20%Tb³⁺@GdPO₄ with varying shell thicknesses. The latter involved Polyethylene Glycol (PEG) as a surface modification agent, resulting in a high-performance dual-layer fluorescent nanomaterial, GdPO₄·H₂O:20%Tb³⁺@GdPO₄@PEG. We characterized the modified and unmodified fluorescent powders for their structural, morphological, optical, and magnetic properties using XRD, SEM, TEM, FTIR, TG, FL, and VSM techniques. Both pre- and post-coated nanophosphors exhibited a singular hexagonal crystal structure with an ellipsoidal morphology, average particle sizes of approximately 40–50 nm, and coating layer thicknesses of about 5–15 nm. The excitation and emission peak positions remained relatively constant before and after the coating process. The dual-layer core-shell nano-fluorescent probe demonstrated significantly enhanced fluorescence intensity due to reduced non-radiative transition rates. Moreover, both pre- and post-coated nanophosphors exhibited excellent paramagnetic properties. This research successfully improved the hydrophilicity and biocompatibility of GdPO₄·H₂O:Tb³⁺ nanophosphors while concurrently enhancing their luminescent and magnetic performance. [ABSTRACT FROM AUTHOR]

Genetically encoded fluorescent biosensors became indispensable tools for biological research, enabling real-time observation of physiological processes in live cells. Recent protein engineering efforts have resulted in the generation of a large variety of fluorescent biosensors for a wide range of biologically relevant processes, from small ions to enzymatic activity and signaling pathways. However, biosensors for imaging sulfate ions, the fourth most abundant physiological anion, in mammalian cells are still lacking. Here, we report the development and characterization of a green fluorescent biosensor for sulfate named Thyone. Thyone, derived through structure-guided design from bright green fluorescent protein mNeonGreen, exhibited a large negative fluorescence response upon subsecond association with sulfate anion with an affinity of 11 mM in mammalian cells. By integrating mutagenesis analyses with molecular dynamics simulations, we elucidated the molecular mechanism of sulfate binding and revealed key amino acid residues responsible for sulfate sensitivity. High anion selectivity and sensitivity of Thyone allowed for imaging of sulfate anion transients mediated by sulfate transporter heterologously expressed in cultured mammalian cells. We believe that Thyone will find a broad application for assaying the sulfate transport in mammalian cells via anion transporters and exchangers. A genetically encoded green fluorescent sensor, Thyone, enables real-time imaging of sulfate anion dynamics in mammalian cells to probe the sulfate transport activity of the SLC26A2 protein. [ABSTRACT FROM AUTHOR]

Various techniques using fluorescent reporter probes have been developed, such as GFP transgenic mouse lines that are used to detect spatial–temporal expression levels of genes. Although GFP expression is largely considered non-toxic, recent reports have indicated that under certain conditions GFP can display cellular toxicity. We hereby report the nuclear toxicity of H2B-GFP using a K14 specific Tet-on reporter mouse system. Using this system, GFP accumulates in the nucleus of all K14 expressing cells, such as the ocular surface epithelia and ocular adnexa. Expression of high levels of nuclear GFP during embryonic stages led to an eye open-at-birth (EOB) phenotype and abnormal ocular adnexa development and during adult and aging stages showed notable toxicity to ocular tissues. Other tissues, such as skin, also presented multiple defects associated with H2B-GFP expression. This toxicity was found to be concentration dependent, with homozygous mice presenting extremely high toxicity, while heterozygous mice presented limited toxicity. Upon induction, the accumulation of H2B-GFP in the nucleus of homozygous mice led to apoptosis within 2 weeks. This study therefore shows that although the use of nuclear GFP reporter mice is a valuable tool, at high levels, nuclear GFP can be toxic, leading to cell death and affecting tissue function. [ABSTRACT FROM AUTHOR]

Substituted maleimides are customisable fluorescent linkers and probes with adaptable reactivity and optical properties. Their compact nature and tunability has led to their use in various applications. For example, their solvatochromic properties offer real‐time feedback on linking chemistry and environmental changes, essential for applications in material labelling, drug delivery, and nanoparticle functionalisation. This review focusses on developing, synthesising, and modifying substituted maleimides as environment‐sensitive fluorescent linkers and probes. It delves into their photophysical dynamics and strategic applications, highlighting their significant contributions to macromolecule conjugation and the development of self‐reporting materials. [ABSTRACT FROM AUTHOR]

By exploiting the programmability of DNA, dual-color DNA-templated silver nanoclusters have been synthesized to serve as a label-free fluorescent probe with a G5-linker at the 3′ end. This advancement facilitates the modular design of universal FRET-based aptasensors using aptamers with a C5-linker at the 3′ end for multiplexed detection, making them easily switch their applications. [ABSTRACT FROM AUTHOR]

Cisplatin (DDP) is a potent chemotherapeutic drug, which can regulate tumor cell apoptosis by up-regulating caspase-3 activity. Thus, monitoring caspase-3 activity in breast cancer cells can directly illustrate the efficiency of DDP treatment. In this study, by using reduced graphene oxide (rGO) as a quencher of a fluorescence labeled peptide, we developed an "off to on" method to monitor the effect of DDP on caspase-3 in breast cancer cells. In this method, the rGO quenched fluorescence with an ultra-high level of efficiency. Caspase-3 hydrolyzed the polypeptide probe, generating two segments of different lengths. The release of a short segment marked with fluorophores led to the recovery of the fluorescence signal (Ex/Em = 450/521 nm). Under the optimal conditions, the linear range of caspase-3 was 0.4–7 U mL−1 and the limit of detection was 0.33 U mL−1. The upregulating effect of DDP on intracellular caspase-3 activity was visualized with the "off to on" method and flow cytometry assay showed that caspase-3 activity increased along with the apoptosis rate of tumor cells. The above results show the practical application of the method for evaluating the efficacy of drugs against cancer cells. [ABSTRACT FROM AUTHOR]

As an important cellular signaling molecule, carbon monoxide (CO) is of great significance in maintaining the physiological activities of biological systems. Exploring techniques for detecting CO at the subcellular fraction is crucial for understanding its various cellular functions. In this work, a simple and effective fluorescence probe (MNP-CO) with mitochondria-targeting ability was reported for detecting CO in mitochondria. The nitro group was chosen as the recognizing moiety, triphenylphosphine as the mitochondrial target unit and naphthalimide as a fluorescent group. This probe displays high selectivity, high sensitivity and excellent photo-stability. Moreover, biological imaging experiments have shown that MNP-CO has excellent fluorescence imaging ability for CO in cells and zebrafish and has mitochondrial targeting ability. [ABSTRACT FROM AUTHOR]

Optical imaging is a powerful tool for early disease detection and effective treatment planning, but its accuracy is often compromised by the uptake of imaging materials by the mononuclear phagocyte system (MPS). Herein, we leverage multivalent host-guest interactions between cyanine dyes and ß-cyclodextrin polymers to develop supramolecular probes with enhanced stability, optical, and transport profiles for accurate in vivo imaging. These multivalent interactions not only ensure the stability of the probes but also enhance fluorescence efficiency by minimizing nonradiative decay. Our self-assembly approach effectively modulates probe size and surface properties, enabling evasion of MPS clearance and promoting prolonged bloodstream circulation, thereby improving the signal-to-background ratio for imaging. The effectiveness of our design is demonstrated by substantial advancements in the early diagnosis of acute kidney injury and by providing high-contrast imaging and precise surgical navigation across various tumor models. Our strategy not only advances optical imaging materials toward clinical translation but also establishes a versatile platform applicable to multiple imaging modalities. [ABSTRACT FROM AUTHOR]

Fluorescence lifetime imaging microscopy is sensitive to molecular interactions and environments. In homo-dyne frequency-domain fluorescence lifetime imaging microscopy, images of fluorescence objects are acquired at different phase settings of the detector. The detected intensity as a function of detector phase is a sinusoidal function that is sensitive to the lifetime of the fluorescent species. In this paper, the theory of phase-sensitive fluorescence image correlation spectroscopy is described. In this version of lifetime imaging, image correlation spectroscopy analysis (i.e., spatial autocorrelation) is applied to successive fluorescence images acquired at different phase settings of the detector. Simulations of different types of lifetime distributions reveal that the phase-dependent density of fluorescent objects is dependent on the heterogeneity of lifetimes present in the objects. We provide an example of this analysis workflow to a cervical cancer cell stained with a fluorescent membrane probe. [ABSTRACT FROM AUTHOR]

Excessive sulfur dioxide (SO₂) disturbs physiology of lysosomes causing diseases and threatening human health. A fluorescent probe has been regarded as one of the most attractive approaches, which is compatible with living cells and possesses high sensitivity. However, most of fluorescent probes' reaction sites are activated before they reach the destination. In this work, an acid‐activatable fluorescent probe PT1 was synthesized, characterized, and used for SO2 detection. The introduction of oxazolines in PT1 enables the intelligent response of probe to release the activation stie for SO2 derivatives through Michael addition upon exposure to acid. In vitro studies showed a remarkable selectivity of PT1 to SO₂ derivatives than other biothiols with a limit of detection as low as 62 nM. By using this acidic pH‐controlled fluorescence responsiveness to SO₂, precise spatiotemporal identification of lysosomal SO2 fluctuations has been successfully performed. Furthermore, probe PT1 can be applied for monitoring SO₂ derivatives in traditional Chinese medicines. [ABSTRACT FROM AUTHOR]

In this investigation, the fluorescent poly(N‐hydroxyethyl morpholine acrylate) (PHEMA) and poly(N‐hydroxypropyl morpholine acrylate) (PHPMA) are prepared and applied as fluorescent probes for the specific detection of Cu2+ ions. Far different from the non‐fluorescent monomer, PHEMA and PHPMA emit a strong fluorescence at 410 nm due to the intramolecular aggregation of morpholine structures along macromolecular chains in the polymerization, indicating polymerization‐induced emission (PIE). The fluorescent emission of PHPMA shows the dependence on external factors including solution concentration, excitation wavelength, solvent, and pH value. PHPMA specifically detects Cu2+ ions even in the presence of 16 common metal ions and 6 anions, with an LOD of 0.077 µM. In the fluorescent quenching, the O atom from ─C═O and N atom from morpholine moiety on the PHPMA chain participate in the complexation with Cu2+ ions with the ratio of the structural unit and Cu2+ ion of 2:1, leading to the dynamic quenching of PHPMA solution. As for the application, PIE‐active PHPMA is easily made into a portable semi‐quantitative filter paper with recyclability. In brief, the PIE‐active PHPMA synthesized in this study can be used as a promising material for the specific detection of Cu2+ ions in industry, agriculture, and medicine fields. [ABSTRACT FROM AUTHOR]

Background and Purpose: Pulmonary hypertension (PH) results from pulmonary vasculopathy, initially leading to a compensatory right ventricular (RV) hypertrophy, and eventually to RV failure. Hypoxia can trigger both pulmonary vasculopathy and RV failure. Therefore, we tested if myo‐inositol trispyrophosphate (ITPP), which facilitates oxygen dissociation from haemoglobin, can relieve pulmonary vasculopathy and RV hypoxia, and eventually prevent RV failure and mortality in the rat model of monocrotaline‐induced PH. Experimental approach: Rats were injected with monocrotaline (PH) or saline (control) and received ITPP or placebo for 5 weeks. Serial echocardiograms were obtained to monitor the disease, pressure‐volume loops were recorded and evaluated, myocardial pO2 was measured using a fluorescent probe, and histological and molecular analyses were conducted at the conclusion of the experiment. Key Results and Conclusions: ITPP reduced PH‐related mortality. It had no effect on progressive increase in pulmonary vascular resistance, yet significantly relieved intramyocardial RV hypoxia, which was associated with improvement of RV function and reduction of RV wall stress. ITPP also tended to prevent increased hypoxia inducible factor‐1α expression in RV cardiac myocytes but did not affect RV capillary density. Implications: Our study suggests that strategies aimed at increasing oxygen delivery to hypoxic RV in PH could potentially be used as adjuncts to other therapies that target pulmonary vessels, thus increasing the ability of the RV to withstand increased afterload and reducing mortality. ITPP may be one such potential therapy. [ABSTRACT FROM AUTHOR]

Lipid droplets (LDs) represent highly dynamic organelles found in almost all organisms and play a pivotal role in regulating the balance of intracellular lipid homeostasis. Viscosity directly affects the metabolism of lipid droplets, and the abnormal change of viscosity will lead to a series of related diseases. Therefore, developing a tool that can monitor changes in intracellular lipid droplet viscosity in real-time is of great significance for disease prevention, diagnosis, and treatment. In this study, a viscosity-sensitive fluorescent probe CA-LD based on an intramolecular twisted charge transfer (TICT) mechanism was developed. The CA-LD probe exhibited strong fluorescence emission at approximately 640 nm and showed a 161-fold increase in fluorescence intensity in 99% glycerol compared to water. Additionally, the probe CA-LD demonstrated the advantages of good anti-interference, excellent biocompatibility and good photostability. Significantly, because of the probe's sensitivity to viscosity, the probe CA-LD successfully distinguished normal cells from cancer cells and has been able to visualize changes in lipid droplets' viscosity induced by oleic acid. In addition, the probe CA-LD was effectively employed to monitor changes in the viscosity of cells and zebrafish induced by different drugs. Therefore, the probe CA-LD can provide an effective means for the detection of lipid droplet viscosity changes and is of great value for physiological diagnosis, pathological analysis and medical research on related diseases. [ABSTRACT FROM AUTHOR]

ABSTRACT A novel salamo‐Co (II) coordination polymer probe CP was synthesized firstly, and its crystal structure, [Co3(L)2(PTA)(H2O)2]n·4nDMF, was determined by X‐ray diffraction analysis. The probe has a rare aggregation‐induced luminescence enhancement (AIEE) effect. When applied to amino acid detection, it was found to have a high selective recognition of tyrosine. With the increase of tyrosine, the fluorescent strength of the probe was enhanced in a short period of time. In addition, the binding ratio of probe to Tyr was determined by fluorescence titration experiment, and the detection limit LOD of probe CP for Tyr was calculated to be 2.57 × 10−9 M, and the binding constant Ka was 2.96 × 105 M−1. According to UV absorption spectrum, FT‐IR spectra, ESI mass spectrometry, and DFT calculation, it was speculated that Tyr can bind to the probe after adding Tyr into the probe solution, triggering FRET and ICT effects, resulting in increased fluorescence intensity and blue shift, and finally achieving the specific recognition of tyrosine by probe CP. Finally, the practical application of probe CP was studied. Through strip test and real water sample test, it was found that the probe can be used for qualitative and quantitative analysis of tyrosine. [ABSTRACT FROM AUTHOR]

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This article reports the synthesis, along with structural and photophysical characterization of 2‐(2'‐hydroxyphenyl)benzazole derivatives functionalized with various azaheterocycles (pyridine, pyrimidine, terpyridine). These compounds show dual‐state emission properties, that is intense fluorescence both in solution and in the solid‐state with a range of fluorescent color going from blue to orange. Moreover, the nature of their excited state can be tuned by the presence of external stimuli such as protons or metal cations. In the absence of stimuli, these dyes show emission stemming from anionic species obtained after deprotonation (D* transition), whereas upon protonation or metal chelation, ESIPT process occurs leading to a stabilized and highly emissive K* transition. With the help of extensive ab initio calculations, we confirm that external stimuli can switch the nature of the transitions, making this series of dyes attractive candidates for the development of stimuli‐responsive fluorescent ratiometric probes. [ABSTRACT FROM AUTHOR]

Sensory stimulations at 40 Hz gamma (but not any other frequency), have shown promise in reversing Alzheimer's disease (AD)-related pathologies. What distinguishes 40 Hz? We hypothesized that stimuli at 40 Hz might summate more efficiently (temporal summation) or propagate more efficiently between cortical layers (vertically), or along cortical laminas (horizontally), compared to inputs at 20 or 83 Hz. To investigate these hypotheses, we used brain slices from AD mouse model animals (5xFAD). Extracellular (synaptic) stimuli were delivered in cortical layer 4 (L4). Leveraging a fluorescent voltage indicator (VSFP) expressed in cortical pyramidal neurons, we simultaneously monitored evoked cortical depolarizations at multiple sites, at 1 kHz sampling frequency. Experimental groups (AD-Female, CTRL-Female, AD-Male, and CTRL-Male) were tested at three stimulation frequencies (20, 40, and 83 Hz). Despite our initial hypothesis, two parameters—temporal summation of voltage waveforms and the strength of propagation through the cortical neuropil—did not reveal any distinct advantage of 40 Hz stimulation. Significant physiological differences between AD and Control mice were found at all stimulation frequencies tested, while the 40 Hz stimulation frequency was not remarkable. [ABSTRACT FROM AUTHOR]