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To monitor the biological function of H2S in real time, this investigation demonstrated the design and synthesis of a novel fluorescent probe integrated with cyanine and 2,4-dinitrophenol for the qualitative and quantitative detection of H2S. An NIR sensitive sensor (FS-HS-1) was provided with a straightforward process. Spectroscopy experiments elucidated that FS-HS-1 could selectively detect H2S in a PBS solution (containing 40% acetonitrile) with a 111-fold fluorescence enhancement at 715 nm (ex. 605 nm). The response towards NaHS occurred in less than 2 min, and the detection limit was confirmed to be as low as 4.47 ± 0.11 nmol/L. Furthermore, the probe is capable of monitoring changes in exogenous H2S concentrations within living cells with confocal and 2P imaging. [ABSTRACT FROM AUTHOR]

Monitoring hydrogen sulfide (H2S) in living organisms is very important because H2S acts as a regulator in many physiological and pathological processes. Upregulation of endogenous H2S concentration has been shown to be closely related to the occurrence and development of tumors, atherosclerosis, neurodegenerative diseases and diabetes. Herin, a novel fluorescent probe HND with aggregation-induced emission was designed. Impressively, HND exhibited a high selectivity, fast response (1 min) and low detection limit (0.61 μM) for H2S in PBS buffer (10 mM, pH = 7.42). Moreover, the reaction mechanism between HND and H2S was conducted by Job's plot, HR-MS, and DFT. In particular, HND was successfully employed to detect H2S in HeLa cells. [ABSTRACT FROM AUTHOR]

This research centers on the development and synthesis of a longwave fluorescence probe, labeled as 60T, designed for the simultaneous detection of hydrogen sulfide, cysteine/homocysteine, and glutathione. The probe showcases a swift response, good linearity range, and heightened sensitivity, boasting that the detection limits of the probe for Cys, Hcy, GSH and H2S were 0.140, 0.202, 0.259 and 0.396 μM, respectively. Notably, its efficacy in monitoring thiol status changes in live MCF-7 cells is underscored by a substantial decrease in fluorescence intensity upon exposure to the thiol trapping reagent, N-ethyl maleimide (NEM). With an impressive red emission signal at 630 nm and a substantial Stokes shift of 80 nm, this probe exhibits remarkable sensitivity and selectivity for biothiols and H2S, indicating promising applications in the diagnosis and surgical navigation of relevant cancers. [ABSTRACT FROM AUTHOR]

A new structurally simple fluorescent CP probe based on chromone was designed and synthesized, and its structure was fully characterized using various analytical techniques. The CP probe displays a high selectivity and sensitivity for sensing Fe3+ with a "turn-off" fluorescence response over other metal ions in a DMSO/H2O (4:1, v/v) solution. The experiment results show that the CP probe is stable over a wide pH range of 2.0–12.0. The detection limit for Fe3+ was calculated to be 0.044 μmol•L−1. The molar ratio method indicated that the binding mode between the CP probe and Fe3+ is a 1:1 complex formation. HR-MS and density functional theory (DFT) calculations were also performed to further confirm the recognition mechanism. Both fluorescence imaging experiments and the MTT assay demonstrated that the CP probe was suitable for detecting intracellular Fe3+ and no significant cytotoxicity in living cells. [ABSTRACT FROM AUTHOR]

A series of functional glycopolymer nanoparticles with 1,8‐naphthalimide motif was designed, synthesized and applied for tumor cell imaging. With the pH‐sensitive and aggregation‐induced emission (AIE) effect of the 1,8‐naphthalimide fluorescent probe, the presence of glucose‐based glycopolymers enhanced its water‐solubility and biocompatibility. Owing to the dual tumor‐targeting effects of the dense glucose part and the boronic ester modification, the obtained glycopolymers showed high affinity to tumor cells, with a much faster staining rate than normal cells, indicating a great potential for diagnosis and treatments of cancers. [ABSTRACT FROM AUTHOR]

A novel coumarin-derived Schiff base fluorescent probe was reported to detect Cu2+ ions in human cells. It was synthesized by the reaction between 7-(diethylamino)coumarin-3-carbohydrazide and pyridoxal 5′-phosphate. The probe has good stability and it exhibited obviously decreasing fluorescent response at λ 490 nm upon addition of Cu(II) ions. The fluorescent probe showed high selectivity for Cu(II) ions compared to other metal ions. The probe has been successfully applied to detect Cu(II) ions in human cells. [ABSTRACT FROM AUTHOR]

A fluorescent probe Y((1,1'-([1,1'-biphenyl]-4,4'-diylbis(3-(2-hydroxyphenyl)-4,5-dihydro-1H-pyrazole-5,1-diyl)) bis(ethan-1-one))) was designed and synthesized, which could be used to Cu2+ and Fe3+ sensors. Through the study of optical properties, the probe Y shows good selectivity and sensitivity to Cu2+ and Fe3+ in aqueous tetrahydrofuran solution [10.0 mM HEPES, pH 7.4, THF-H2O = 9:1(v/v)] with has excellent anti-interference performance, and its detection limits were 0.931 uΜ for Cu2+ and 0.401uΜ for Fe3+. The coordination mechanism of probe Y with Cu2+ and Fe3+ was speculated and verified at DFT level and HRNM. By Hela cytotoxicity and imaging tests, probe Y not only has good biocompatibility, but also can be used for sensing Cu2+ in cells. [ABSTRACT FROM AUTHOR]

Although hydrazine (N2H4) is a versatile chemical used in many applications, it is toxic, and its leakage may pose a threat to both human health and environments. Consequently, the monitoring of N2H4 is significant. This study reports a one-step synthesis for coumarin-based ratiometric fluorescent probe (FP) CHAC, with acetyl as the recognition group. Selected deprotection of the acetyl group via N2H4 released the coumarin fluorophore, which recovered the intramolecular charge transfer process, which caused a prominent fluorescent, ratiometric response. CHAC demonstrated the advantages of high selectivity, a strong capacity for anti-interference, a low limit of detection (LOD) (0.16 μM), a large linear detection range (0–500 μM), and a wide effective pH interval (6–12) in N2H4 detection. Furthermore, the probe enabled quantitative N2H4 verifications in environmental water specimens in addition to qualitative detection of N2H4 in various soils and of gaseous N2H4. Finally, the probe ratiometrically monitored N2H4 in living cells having low cytotoxicity. [ABSTRACT FROM AUTHOR]

A novel dansyl-based fluorescent probe (DG) was designed via the introduction of a dipeptide, glycyl-L-glutamine. DG showed good selectivity and sensitivity towards Cu2+ in aqueous solutions in the pH span of ~ 6–12. The coordination of Cu2+ with the dipeptide moiety led to the fluorescent quenching of the dansyl fluorophore. The association constant value for Cu2+ was 0.78 × 104 M− 1 in a 1 to 1 stoichiometric ratio. The detection limit in HEPES buffer solution (10 mM, pH 7.4) was 1.52 µM. DG also showed strong anti-interference capability in the presence of other metal ions. It was worth noting that DG maintained the detection ability towards Cu2+ in real water samples and cell imaging, implying the potential application opportunities in complicated environments. [ABSTRACT FROM AUTHOR]

Given the important role of carboxylesterase 2 (CES2) in the metabolism of various esters, it is of significance to develop a tool to determine endogenous CES2 activity in a rapid and highly selective manner. In this work, an "off-on" rhodamine-based fluorescent probe is reported as an effective tool for CES2 activity. Based on the substrate recognition preference of CES2 (large alcohol and small acyl groups), the probe with dimethyl carbamate as the recognition group performs well in terms of selectivity and sensitivity to CES2. The fluorescence switching control of the probe for CES2 was achieved by using the spirolactone structure of rhodamine. The probe shows the fast generation of a fluorescence signal at 634 nm upon hydrolysis of CES2 with excitation at 578 nm. The results showed a linear relationship between the fluorescence intensity at 634 nm and the CES2 activity from 0 to 4 μg/mL. The probe reacts rapidly with CES2, and the reaction is stable within 40 minutes. The probe is highly selective for CES2, with a detection limit as low as 0.303 μg/mL. In addition, the probe has currently been successfully utilized to evaluate CES2 activity in living cells. Hence, this probe is anticipated to be significant in identifying endogenous CES2 activity in intricate biological settings. [ABSTRACT FROM AUTHOR]

Picric acid (PA) is a powerful nitro-aromatic explosive that harms the environment and human health. Developing non-toxic and low-cost sensors for the rapid detection of PA is essential. An environment-friendly fluorescent probe for PA detection is designed based on carbon dots (CDs) directly separated from edible soy sauce by silica gel column chromatography. Neither organic reagents nor heating process was needed to prepare CDs. The obtained CDs exhibit bright blue fluorescence, good water solubility, and photostability. The fluorescent probe for PA was developed according to the CD's fluorescence can be significantly quenched via the inner filter effect between CDs and PA. The linear range was 0.2–24 µM with a limit of detection of 70 nM. This proposed method was successfully employed to detect PA in the real water samples with satisfactory recoveries between 98.0–104.0%. Moreover, the CDs were suitable for fluorescence imaging of HeLa cells owing to their low toxicity and good biocompatibility. [ABSTRACT FROM AUTHOR]

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. HRMS was conducted to confirm that the fluorescence intensity at 795 nm was significantly enhanced by the enhancement of intramolecular charge transfer (ICT). Importantly, BCy-Cys could be used to visualize both exogenous and endogenous lysosomal Cys, signifying its potential application in complex organismal systems. [ABSTRACT FROM AUTHOR]

Large accumulations of copper (Cu) ions in the human body may cause damage, including organ and brain damage. In recent years, studies have proven that a large accumulation of Cu ions can lead to Parkinson's disease and Alzheimer's disease; therefore, it is great important to develop novel strategies for detecting trace Cu in environmental and biological samples. In this work, we designed two new coumarin-based colorimetric and fluorescent probes, HQ1 and HQ2. These two probes could selectively respond to Cu2+ with obvious color and fluorescence changes, and the presence of other metal ions had no effect on these changes. The two probes also exhibited high sensitivity for Cu2+, with a detection limit as low as 1.81 x 10-8 M/1.57 x 10-8 M. Notably, the two probes showed potential practical applications and were successfully used for detecting Cu2+ in a test strip, A549 cells, and living zebrafish larvae. [ABSTRACT FROM AUTHOR]

As an important endogenous gasotransmitter, hydrogen sulfide (H2S) has been implicated with a variety of biological processes and has attracted more and more attention for its key role in a wide range of pathological processes. However, lacking tools for H2S-specific in situ detection, the changes of endogenous H2S levels in the pathological progression of diseases are still unclear. In this work, a turn-on fluorescent probe (BF2-DBS) has been designed and synthesized by two-step reactions using 4-diethylaminosalicylaldehyde and 1,4-dimethylpyridinium iodide as raw materials. Probe BF2-DBS displays high selectivity and sensitivity to H2S with a large Stokes shift and good anti-interference ability. The practical application of probe BF2-DBS to detect endogenous H2S was evaluated in living HeLa cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A lysosome-targetable fluorescent probe for H 2 O 2 has been reported. • The probe displays high sensitivity and high selectivity for H 2 O 2. • The probe can be utilized for determination of H 2 O 2 within the lysosomes of living cells. As an important member of reactive oxygen species, hydrogen peroxide (H 2 O 2) plays a key role in oxidative stress and cell signaling. Abnormal levels of H 2 O 2 in lysosomes can induce damage or even loss of lysosomal function, leading to certain diseases. Therefore, real-time monitoring of H 2 O 2 in lysosomes is very important. In this work, we designed and synthesized a novel lysosome-targeted fluorescent probe for H 2 O 2 -specific detection based on a benzothiazole derivative. A morpholine group was used as a lysosome-targeted unit and a boric acid ester was chosen as the reaction site. In the absence of H 2 O 2 , the probe exhibited very weak fluorescence. In the presence of H 2 O 2 , the probe showed an increased fluorescence emission. The fluorescence intensity of the probe for H 2 O 2 displayed a good linear relationship in the concentration range of H 2 O 2 from 8.0 × 10−7 to 2.0 × 10−4 mol·L−1. The detection limit was estimated to be 4.6 × 10−7 mol·L−1 for H 2 O 2. The probe possessed high selectivity, good sensitivity and short response time for the detection of H 2 O 2. Moreover, the probe had almost no cytotoxicity and had been successfully applied to confocal imaging of H 2 O 2 in lysosomes of A549 cells. These results illustrated that the developed fluorescent probe in this study could provide a good tool for the determination of H 2 O 2 in lysosomes. [ABSTRACT FROM AUTHOR]

Carboxylesterases (CEs) play important physiological roles in the human body and are involved in numerous cellular processes. Monitoring CEs activity has great potential for the rapid diagnosis of malignant tumors and multiple diseases. Herein, we developed a new phenazine-based "turn-on" fluorescent probe DBPpys by introducing 4-bromomethyl-phenyl acetate to DBPpy, which can selectively detect CEs with a low detection limit (9.38 × 10−5 U/mL) and a large Stokes shift (more than 250 nm) in vitro. In addition, DBPpys can also be converted into DBPpy by carboxylesterase in HeLa cells and localized in lipid droplets (LDs), emitting bright near-infrared fluorescence under the irradiation of white light. Moreover, we achieved the detection of cell health status by measuring the intensity of NIR fluorescence after co-incubation of DBPpys with H2O2-pretreated HeLa cells, indicating that DBPpys has great potential applications for assessing CEs activity and cellular health. [ABSTRACT FROM AUTHOR]

Endogenous sulfur dioxide (SO2), as a gas signal molecule, has a certain physiological functions. Understanding the role of endogenous SO2 in human physiology and pathology is of great significance to the biological characteristics of SO2,which bring challenges to develop fluorescent probes with excellent performance. Herein, we rationally designed and constructed a novel near-infrared bioprobe benzaldehyde-benzopyrylium (BBp) by employing the nucleophilic addition benzopyrylium perchlorate fluorophore and benzaldehyde moiety by means of C = C/C = O group that serves as both fluorescence reporting unit. Probe BBp exhibit excellent sensing performance with fluorescent "On − Off"rapid response (100 s) and long-wavelength emission (670 nm). With the treatment of HSO3−, the color of BBp solution obviously varies from purple to colorless, and the fluorescent color varies from red to colorless. By the fluorescence and colorimetric changes, probe BBp was capable of sensitive determination HSO3− with low limits of detection (LOD) of 0.43 μM, realizing visual quantitative monitoring SO2 derivative levels. Due to the low phototoxicity and good biocompatibility, it was successfully applied to monitor SO2 derivatives and fluorescence imaging in HepG2 and HeLa living cells. Hopefully, this work supplies a new strategy for designing NIR fluorescent probes for quantitative determination SO2 derivatives in biological samples. [ABSTRACT FROM AUTHOR]

RNA imaging is of great importance for understanding its complex spatiotemporal dynamics and cellular functions. Considerable effort has been devoted to the development of small-molecule fluorescent probes for RNA imaging. However, most of the reported studies have mainly focused on improving the photostability, permeability, long emission wavelength, and compatibility with live-cell imaging of RNA probes. Less attention has been paid to the selectivity and detection limit of this class of probes. Highly selective and sensitive RNA probes are still rarely available. In this study, a new set of styryl probes were designed and synthesized, with the aim of upgrading the detection limit and maintaining the selectivity of a lead probe QUID−1 for RNA. Among these newly synthesized compounds, QUID−2 was the most promising candidate. The limit of detection (LOD) value of QUID−2 for the RNA was up to 1.8 ng/mL in solution. This property was significantly improved in comparison with that of QUID−1. Further spectroscopy and cell imaging studies demonstrated the advantages of QUID−2 over a commercially available RNA staining probe, SYTO RNASelect, for highly selective and sensitive RNA imaging. In addition, QUID−2 exhibited excellent photostability and low cytotoxicity. Using QUID−2, the global dynamics of RNA were revealed in live cells. More importantly, QUID−2 was found to be potentially applicable for detecting RNA granules in live cells. Collectively, our work provides an ideal probe for RNA imaging. We anticipate that this powerful tool may create new opportunities to investigate the underlying roles of RNA and RNA granules in live cells. [ABSTRACT FROM AUTHOR]

Biothiols, such as cysteine(Cys), homocysteine (Hcy) and glutathione (GSH) play a central role in intracellular regulation of redox homeostasis and maintenance of cell functions.In this work, a fluorescent probe based on TTCNPy nanoparticles was been synthesized for the detection of biothiols.This probe had a near-infrared (NIR) fluorescence (λem=727 nm) and a large Stokes shift (260 nm) .It can sensitively detect biothiols in buffer solution.The detection limits of Hcy, Cys and GSH were calculated to be 0.479,0.429,0.480 μmol, respectively.Moreover, this probe had high selectivity and anti-interference ability due to the strong nucleophilic attack ability of the sulfhydryl group in biothiols which can destroy the conjugated structure and subsequently quench the fluorescence of probe.This probe had the advantages of simple synthesis, high sensitivity, high selectivity and low cytotoxicity, and can be used to detect biothiols in solution and living cells. [ABSTRACT FROM AUTHOR]

Native broken-rice starch was used to create starch nanoparticles (StNPs) with particle sizes ranging from 100 nm to 800 nm. The fluorescent isothiocyanate poly- l -lysine StNPs (FITC-PLL-StNPs) were created in two steps. First, the StNPs were electrostatically modified by poly- l -lysine (PLL) molecules rich in amino acids. Second, fluorescein isothiocyanate reacted with some amino groups on PLL molecules (FITC). Fluorescence spectrophotometry was used to determine the degree of substitution (DS) and fluorescent properties of fluorescent starches. The study found that FITC-PLL-StNP-200 has higher fluorescence stability, more phagocytic cells, and a better and clearer fluorescence detecting effect than FITC-PLL-St, FITC-PLL-StNP-100, FITC-PLL-StNP-400, and FITC-PLL-StNP-800. The biological evaluation results showed that FITC-PLL-StNP-200 did not affect the viability of HeLa cells at the lysosome labeling concentration. These findings suggest that FITC-PLL-StNP-200 has strong and stable fluorescence, indicating that FITC-PLL-StNP-200 can be used as a fluorescent probe and lysosome marker in a variety of applications, particularly in biomedicine. [Display omitted] • Fluorecent starch nanoparticles (StNP) were synthesized. • FITC-PLL-StNP-200 has clearer fluorescence detecting effect. • FITC-PLL-StNP-200 has higher phagocytic amount of Hela cells. • FITC-PLL-StNP-200 is safe and possesses excellent biocompatibility. [ABSTRACT FROM AUTHOR]

An intramolecular charge transfer (ICT)–based fluorescent probe P-ONOO− was synthesized to detect ONOO−. After responding to peroxynitrite, the dicyano-vinyl group of P-ONOO− generates the aldehyde group, emitting strong green fluorescence accompanied by quenching of the yellow fluorescence. According to the calculated Fukui function, the modification of the alkoxy group can enhance the f+ of P-ONOO−, which can enhance the probe's nucleophilic addition reactivity with ONOO−. It has been experimentally verified that P-ONOO− shows fast response (within 30 s), excellent sensitivity (the detection limit = 10.4 nM), and good selectivity towards ONOO−. Additionally, the probe P-ONOO− has high membrane permeability and good biocompatibility, which can image endogenous ONOO− and exogenous ONOO− in HeLa cells. [ABSTRACT FROM AUTHOR]

A new polarity sensitive fluorescent probe CO‐DBD with deep‐red to near‐infrared emission was designed and synthesized. CO‐DBD consists of β‐diketone‐boron difluoride and coumarin moieties, showing higher fluorescence intensity and shorter emission wavelength in low‐polarity solvent. Notably, CO‐DBD gives high absolute fluorescence quantum yield of 0.631 in toluene. Theoretical calculation results verify that the polarity response is attributed to intramolecular charge transfer and twisted intramolecular charge transfer process. Further experimental data demonstrate that CO‐DBD displays high selectivity, sensitivity and excellent stability. The precise polarity of binary mixture can be quantified by ratio fluorescence intensity of CO‐DBD. Moreover, this probe is successfully applied for live cell imaging with high contrast. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide is a biologically important molecule and developing chemical tools that enable further investigations into the functions of H2S is essential. Fluorescent turn‐on H2S probes have been developed for use in cellulo and in vivo, but the membrane permeability of these probes can lead to probe leakage and signal attenuation over time. Here we report a cell trappable fluorescent probe for H2S, CT‐MeRhoAz, which is based on a methylrhodolazide scaffold derivatized with an acetoxymethyl ester group. Prior to ester cleavage, the CT‐MeRhoAz probe generates a 2500‐fold turn‐on response to H2S, which is enhanced to a 3000‐fold response for the carboxylic acid form of the probe. Additionally, the probe is highly selective for H2S over other biologically relevant sulfur, oxygen, and nitrogen‐based analytes. Live cell imaging experiments confirmed the biocompatibility of CT‐MeRhoAz and also that it is cell trappable, unlike the parent MeRhoAz scaffold. [ABSTRACT FROM AUTHOR]

Peroxynitrite (ONOO−), as an important reactive oxygen species (ROS), holds great potential to react with a variety of biologically active substances, leading to the occurrence of various diseases such as cancer and neurodegenerative diseases. In this work, we developed a novel mitochondria-localized fluorescent probe, HDBT-ONOO−, which was designed as a mitochondria-targeting two-photon fluorescence probe based on 1,8-naphthylimide fluorophore and the reactive group of 4-(bromomethyl)-benzene boronic acid pinacol ester. More importantly, the probe exhibited good biocompatibility, sensitivity, and selectivity, enabling its successful application in imaging the generation of intracellular and extracellular ONOO−. Furthermore, exogenous and endogenous ONOO− products in live zebrafish were visualized. It is greatly expected that the designed probe can serve as a useful imaging tool for clarifying the distribution and pathophysiological functions of ONOO− in cells and zebrafish. [ABSTRACT FROM AUTHOR]

Hypochlorous acid (HClO), the core bactericidal substance of the human immune system, plays a vital role in many physiological and pathological processes in the human body. In this work, we designed and synthesized a novel deep-red fluorescent probe TCF-ClO for the determination of hypochlorous acid through theoretical analysis. The results showed that probe TCF-ClO exhibited excellent characteristics of long-wavelength emission (635 nm), fast response (< 1 min), and low detection limit (24 nM). In addition, it had been successfully used for imaging of HClO in living HeLa cells. More importantly, the TCF-ClO composited paper-based sensing material was successfully constructed. The RGB/gray value was obtained from a mobile phone and computer, which could achieve the quantitative detection of HClO, with a linear detection range of 0–50 μM and a detection limit of 1.09 μM (RGB mode)/3.38 μM (gray mode). The function of the paper-based sensor extended from qualitative to quantitative detection of HClO, and it is expected to become a portable device widely used in the environmental area. [ABSTRACT FROM AUTHOR]

The selective detection of hydrogen sulfide in physiological and pathological processes has gained substantial attention in recent years. However, the real-time detection of hydrogen sulfide remains an elusive goal. In this work, a new type of hemicyanidin-based fluorescent "turn-on" probe NTR-HS (Ex = 680 nm, Em = 760 nm) was developed to detected H2S in a very short time (3 min). The fluorescence quantum yield is 0.15 and accompanied with a noticeable color change from violet to blue that can be used to detect H2S in the range 1.04 × 10−7–4 × 10−5 M with a limit of detection of 1.04 x 10-7 M. The NTR-HS probe was also used for imaging of endogenous hydrogen sulfide and mitochondrial localization in HCT116 and HeLa cells. The detection mechanism was studied through fluorescence, UV–Vis, NMR, and mass analysis. Notably, the probe was successfully used to imaging H2S in mice and locating hydrogen sulfide in the large intestine of mice. [ABSTRACT FROM AUTHOR]

The first difunctional probe H-1 for detecting ONOO− and Zn2+ at the same time showed high selectivity, good anti-interference capability, lower detect limit and short response time to them. [Display omitted] • · A new difuctional probe H-1 for ONOO− and Zn2+ detection at the same time was obtained firstly. • ·H-1 showed good selectivity and strong anti-interference ability for detecting ONOO− and Zn2+. • ·H-1 could fast response to ONOO− and Zn2+ in 15 s. • ·H-1 was used to monitor the ONOO− and Zn2+ level in living cells. Peroxynitrite (ONOO−) is one of the most significant reactive oxygen species (ROS) in living cells. Zn2+ in living cells plays an essential part in different physiological processes. The abnormal concentration of ONOO− and Zn2+ in living cells are related to many kinds of diseases, such as anemia, epilepsy, diarrhea, Alzheimer's disease, and so on. The relationship of ONOO− and Zn2+ in living cells when the relative disease occurs remains unknown. So we develop the first probe H-1 for detecting ONOO− and Zn2+ at the same time. The probe H-1 shows high selectivity, good anti-interference capability, low detection limit and short response time to ONOO− and Zn2+. When the probe was applied to detect ONOO− and Zn2+ in HeLa cells, we could observe the fluorescence changing in the green and blue channels separately without interference in real time. It has the potential to employ the relation of ONOO− and Zn2+ in some disease mechanism research. [ABSTRACT FROM AUTHOR]

Nitroreductase (NTR) is overexpressed in hypoxic tumor cells, which is closely related to inflammation, tumorigenesis, tumor invasion and metastasis. Therefore, developing fluorescence probes for detecting intracellular NTR sensitivity has great significance for diagnosis and treatment of tumors. Therefore, we designed a novel fluorescent probe (Pro-CN) based on julolidine skeleton for the detection of NTR. The probe could discriminate rapidly NTR from other biological species like sulfhydryl compounds and some ions. Meanwhile, a fine linear relationship between fluorescence intensity of the probe and NTR consistence has been observed with a very low detection limit of 4.4 ng/mL. In addition, Pro-CN was successfully applied in imaging endogenous NTR in Hela cells and living zebrafish. The excellent performance of the probe makes it have great potential for monitoring NTR in complex biological systems, and it also provides the possibility of its application in human health, disease diagnosis and treatment. [Display omitted] • Probe Pro-CN exhibits a turn-on fluorescence for sensing NTR. • Pro-CN is highly sensitive to sense NTR with a very low detection limit of 4.4 ng/mL. • Pro-CN was successfully applied for imaging endogenous NTR in living Hela cells and zebrafish. [ABSTRACT FROM AUTHOR]

Emerging studies demonstrates that mitochondrial G-quadruplex (G4) may be a prospective diagnostic and therapeutic target for cancer. Fluorescent probes targeting mitochondrial G4 are crucial for in-depth research on G4 function and mechanism and developing new diagnostic techniques. Here, we report a benzothiazole derivative named ThT-E, which can be prepared with high yield through only one step of reaction. ThT-E exhibits superior detection sensitivity compared to existing probes, and also demonstrates reliable performance for in situ characterization of mitochondrial G4 in living cells. Interestingly, ThT-E has been used to differentiate tumor cells from normal cells by quantifying the formation of mitochondrial G4s, implicating that ThT-E may have wide applications in tumor diagnosis. • A benzothiazole derivative for monitoring mitochondrial G-quadruplexes. • More pronounced fluorescence enhancement in tumor cells than normal cells. • More G-quadruplex formation in tumor mitochondria. • Mitochondrial G-quadruplex as a potential cancer biomarker. • New probe tool for tumor diagnosis. [ABSTRACT FROM AUTHOR]

[Display omitted] • The high sensitivity of the probe with a detection limit of 58 nM. • Successful detection of endogenous and exogenous CO in living cells. • Capable of detecting CO in zebrafish. • NIR probe with a high signal-to-noise ratio for imaging CO in biological samples. Carbon monoxide (CO) is a highly emitted atmospheric pollutant that can pose a serious health risk when its concentration is too high. However, endogenous CO plays an important role in maintaining human health. The development of tools capable of detecting CO in environmental samples and biological samples is therefore essential. Although CO fluorescent probes have been reported, their further applications are limited by factors such as low sensitivity and emission wavelength. Here, we have constructed a CO probe with simple structure, high sensitivity, good selectivity and near-infrared (NIR) emission characteristics. The probe uses the dicyanoisophorone derivative as fluorophore and connects allyl moiety as the reaction site. After the response, the intramolecular charge transfer (ICT) process turns on and releases strong near-infrared fluorescence at 675 nm. The linear range of fluorescence intensity of the probe for CO concentration is 1–10 μM and the detection limit is as low as 58 nM. The high sensitivity and NIR emission give the probe excellent imaging of cellular exogenous and endogenous CO. Moreover, the probe can also be used to image CO in zebrafish. There is reason to believe that the probe can be a powerful tool for detecting CO concentrations in environmental samples and for analyzing the biological role of CO in organisms. [ABSTRACT FROM AUTHOR]

Ammonia is a common toxic gas in industrial and agricultural production, which will cause harm to the environment and human health in certain extent. Here, a novel fluorescent probe (R)- 1 based on 1,1′-binaphthol (BINOL) was synthesized for real-time, on-site and quantitative detection of ammonia. The mechanism study shows that the functional groups of –CHO and –OH on (R)- 1 interact with ammonia, which changes the electronic state of the probe molecule and excites strong fluorescence. A test strip for rapid detection of ammonia was developed, which changed from light yellow to reddish brown under natural light after interacting with ammonia, thus realizing the rapid detection and easy visualization of ammonia. Meanwhile, bioimaging experiments shows that probe (R)- 1 can detect exogenous ammonia in cells. [Display omitted] • Specific selective fluorescence recognition of ammonia. • Fast response time (300 s) and high sensitivity (0.96 ppm). • A test strip for real-time and visual detection of ammonia. • Exogenous ammonia fluorescence imaging of cells. [ABSTRACT FROM AUTHOR]

Scheme 1 Illustration of the synthetic procedure of Br-CDs-AM and the application in sensing HClO in food matrices and lysosomal imaging. [Display omitted] • Br-CDs with excellent photostability were synthesized by self-doping strategy. • Br-CDs-AM as a probe was made of Br-CD and N -aminomorpholine by substitution reaction. • HClO in milk, yogurt and meat samples were detected accurately (96.5 %–108 %). • • Br-CDs-AM can be used to locate lysosome and visualize HClO in live cells. Hypochlorous acid (HClO) is used in food preservation. However, excessive HClO can deteriorate nutritional composition of food, compromise its quality, and potentially induce various diseases. Consequently, the development of multifunctional fluorescent probes for the sensitive and selective detection of HClO is highly anticipated for food safety. In this work, we designed a nanoprobe using N -aminomorpholine (AM)-functionalized bromine-doped carbon dots (Br-CDs-AM) for sensing HClO. This nanoprobe exhibits pH stability, strong resistance to photobleaching, superior long-term photostability (12 weeks), high sensitivity (19.3 nM), and an ultrarapid response (8 s) for detecting HClO residues in food matrices with percentage recovery (96.5 %–108 %) and RSDs less than 5.34 %. In addition, extremely low cytotoxicity and outstanding biocompatibility enable the nanoprobe to be used primarily for lysosome tracking and rapidly visualizing HClO in live cells. Thus, this study provides a new pathway to design unconventional nanoprobes for food safety assessment and subcellular organelle-specific imaging HClO. [ABSTRACT FROM AUTHOR]

Sulfur dioxide (SO 2) is a significant gas signaling molecule in organisms, and viscosity is a crucial parameter of the cellular microenvironment. They are both involved in regulating many physiological processes in the human body. However, abnormalities in SO 2 and viscosity levels are associated with various diseases, such as cardiovascular disease, lung cancer, respiratory diseases, neurological disorders, diabetes and Alzheimer's disease. Hence, it is essential to explore novel and efficient fluorescent probes for simultaneously monitoring SO 2 and viscosity in organisms. We selected quinolinium salt with good stability, high fluorescence intensity, good solubility and low cytotoxicity as the fluorophore and developed a highly sensitive ratiometric probe QQD to identify SO 2 and viscosity changes based on Förster resonance energy transfer/twisted intramolecular charge transfer (FRET/TICT) mechanism. Excitingly, compared with other probes for SO 2 detection, QQD not only identified HSO 3 −/SO 3 2− with a large Stokes shift (218 nm), low detection limit (1.87 μM), good selectivity, high energy transfer efficiency (92 %) and wide recognition range (1.87–200 μM), but also identified viscosity with a 26-fold fluorescence enhancement and good linearity. Crucially, QQD was applied to detect HSO 3 −/SO 3 2− and viscosity in actual water and food samples. In addition, QQD had low toxicity and good photostability for imaging HSO 3 −/SO 3 2− and viscosity in cells. These results confirmed the feasibility and reliability of QQD for HSO 3 −/SO 3 2− and viscosity imaging and environmental detection. We reported a unique ratiometric probe QQD for detecting HSO 3 −/SO 3 2− and viscosity based on the quinolinium skeleton. In addition to detecting HSO 3 −/SO 3 2− and viscosity change in actual water and food samples, QQD could also monitor the variations of HSO 3 −/SO 3 2− and viscosity in cells, which provided an experimental basis for further exploration of the role of SO 2 derivatives and viscosity in biological systems. [Display omitted] • A dual-function fluorescent probe was designed for detecting SO 2 and viscosity. • QQD had large Stokes shift of 218 nm and wide detection rang of 1.87–200 μM. • QQD showed high sensitivity and selectivity. • QQD achieved the dual colorimetric and ratiometric fluorescent strategy. • QQD achieved the application of foods, water samples and living cells. [ABSTRACT FROM AUTHOR]

• Two thiazole-fused fluoran-based fluorescent probes for copper ions have been prepared. • The two probes show high selectivity and sensitivity for copper ions. • MTFH achieves red emission (632 nm) towards copper ions due to the methyl functionalization. • The two probes can be utilized for tracing intracellular copper ions. In this work, two thiazole-fused fluoran-based fluorescent probes 8′-(diethylamino)-2-((2-hydroxyethyl) amino)spiro[isoindoline-1,11′-xantheno[2, 1- d ]thiazol]-3-one (TFH) and (8′-(diethylamino)-2-((2-hydroxyethyl)amino)-3′-methyl-3-oxospiro[isoindoline-1,11′-xantheno[2,1- d ]thiazol]-3′-ium).BF 4 (MTFH) have been prepared for copper ions. It should be noted that MTFH achieves red emission (632 nm) compared with TFH in the presence of copper ion, which mainly can be attributed to the methylation of molecule MTFH that induced more stronger ICT effect. The two probes show selective fluorescence off-on signal changes towards copper ions with detection limits of 8.8 and 60.8 nM. Copper ion detection can be conducted in a wide pH range including the physiological pH environment. Both TFH and MTFH exhibit suitable cytotoxicity and have been used for copper ion tracing in living cells. However, no other significant improvements of MTFH in sensing performance can be observed when compared with TFH. Two thiazole-fused fluoran-based fluorescent probes have been prepared for selectively and sensitively sensing copper ions, in particular, the methyl functionalization probe achieves red emission mainly due to a stronger ICT effect. [Display omitted] [ABSTRACT FROM AUTHOR]

To study the collaboration between lipid droplets (LDs) and lysosomes, and the lipid change in nonalcoholic fatty liver disease (NAFLD), herein two pH-triggered hydrophility-adjustable fluorescent probes (LD-Lyso and LD-Lyso 1) are designed. The mechanism is based on cyclization and ring-opening with thorough consideration of pH and hydrophilic differences between LDs and lysosomes. Both of the two probes exist in ring-opening form and emit red fluorescence in acidic environment, while they exist in cyclized form and the emission is blueshifted in alkaline environment due to reduced conjugate planes. Moreover, LD-Lyso exhibits near infrared fluorescence at 740 nm under ring-opening form, which facilitates further cell, tissue, and in vivo imaging. The cell imaging results show that LD-Lyso can simultaneously target LDs and lysosomes by two different colors. Impressively, LD-Lyso cannot only detect NAFLD tissues from the normal tissue, but also distinguish different degrees of NAFLD tissues and mice, which provides a very promising tool for timely diagnosis of early NAFLD. [Display omitted] [ABSTRACT FROM AUTHOR]

Mitophagy is a critical cellular self-protective mechanism involving the degradation and recycling of damaged or excessive mitochondria, which has been implicated in various diseases. In our study, we designed and synthesized two phenothiazine-based fluorescent probes, DPTZ and CMDP , specifically targeting mitochondria and lysosomes, respectively, to investigate mitophagy. H 2 S, a cell-protective agent, was chosen as the target molecule for both probes. Our findings demonstrate the selective localization of DPTZ to mitochondria and CMDP to lysosomes. Both probes exhibited rapid, selective, and highly sensitive recognition of H 2 S, enabling imaging of exogenous and endogenous H 2 S. By employing split-targeting and simultaneous detection, we were able to monitor changes in H 2 S levels in mitochondria and lysosomes, providing dynamic and visual imaging of the mitophagy processes. Upregulation of mitochondrial and lysosomal H 2 S was observed during mitochondrial autophagy. This work introduces valuable research methods and tools for investigating mitophagy, thereby enhancing our understanding of the molecular mechanisms underlying this process. [Display omitted] • Phenothiazine-based probes DPTZ and CMDP detect hydrogen sulfide. • DPTZ and CMDP target mitochondria and lysosomes for imaging in A549 cells. • Split-targeting and detection strategy reveals hydrogen sulfide fluctuations in autophagy. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new pH-sensitive fluorescent probe 1 based on hemicyanine fluorophore is developed. • The probe can respond to pH with high selectivity and sensitivity. • The probe can solely illumine the lysosomes and detect the exogenous pH difference in live cells. • The probe can successfully monitor the pH changes during food spoilage. pH as an important parameter is closely related to many pathological processes and food freshness. In this paper, a new pH-sensitive fluorescent probe 1 based on hemicyanine dye was synthesized and used for the detection of pH in live cells and food spoilage. Under neutral and alkaline conditions, the phenolic hydroxyl group of the probe deprotonates, forming a closed spirocyclic structure and resulting in fluorescence quenching. Under acidic conditions, the probe maintains an open-loop structure and has intense fluorescence. The probe possessing good selectivity and stability can target lysosomes and visualize the exogenous pH in live cells. Furthermore, by using this probe, we successfully achieved the monitoring of pH in metamorphic process of shrimp and pork. This probe is expected to provide a good imaging tool for real-time detection of pH in live cells and food monitoring. [ABSTRACT FROM AUTHOR]

Determining the activity of lysosomal β-hexosaminidase in cells is of great importance for understanding the roles that these enzymes play in pathophysiological events. Herein, we designed the new fluorescent probe, βGalNAc-Rhod-CM(NEt 2), which consisted of a βGalNAc-linked rhodol unit serving as a β-hexosaminidase reactive fluorogenic moiety and a N,N′ -diethylaminocoumarin (CM(NEt 2)) group acting as a fluorescence marker for determining the degree of cell permeabilization. Treatment of βGalNAc-Rhod-CM(NEt 2) with β-hexosaminidase promoted generation of Rhod-CM(NEt 2), thereby leading to an increase in the intensity of fluorescence of Rhod. However, this probe did not respond to the functionally related glycosidase, O-GlcNAcase. The detection limit of βGalNAc-Rhod-CM(NEt 2) for β-hexosaminidase was determined to be 0.52 nM, indicating that it has high sensitivity for this enzyme. Furthermore, the probe functioned as an excellent fluorogenic substrate for β-hexosaminidase with k cat and K m values of 17 sec−1 and 22 μM, respectively. The results of cell studies using βGalNAc-Rhod-CM(NEt 2) showed that levels of β-hexosaminidase activity in cells can be determined by measuring the intensity of fluorescence arising from Rhod and that the intensity of fluorescence of CM(NEt 2) can be employed to determine the degree of cell permeabilization of the probe. Utilizing the new probe, we assessed β-hexosaminidase activities in several types of cells and evaluated the effect of glucose concentrations in culture media on the activity of this enzyme. [Display omitted] • Development of the sensitive and selective fluorescent probe for β-hexosaminidase. • Determination of levels of β-hexosaminidase activities in several types of cells. • Evaluation of effect of glucose concentrations in media on β-hexosaminidase activity. [ABSTRACT FROM AUTHOR]

This work presented a FRET-ICT based fluorescent probe (named NTC) composed of coumarin-benzothiazole as the acceptor and 4-nitrobenzo[ c ][1,2,5] oxadiazole (NBD) as the donor for the detection of SO 2 derivatives in NIR. Probe NTC possessed superior performance including selectivity, quickly response toward SO 3 2−/HSO 3 − and high energy transfer efficiency (94 %). The test strips provided a simple and effective tool in detecting the presence of bisulfite. Besides, NTC was applied to test the sulfur dioxide derivatives in food samples and cells. [Display omitted] • A NIR ratiometric fluorescent probe NTC was developed to detect sulfur dioxide derivatives. • NTC had a large Stokes shift of 150 nm and 94 % energy transfer efficiency. • NTC possessed good selectivity and sensitivity toward sulfur dioxide derivatives. • NTC was applied to detect sulfur dioxide derivatives in test strips, food samples and cell imaging. [ABSTRACT FROM AUTHOR]

A convenient tool for detecting iron ions in subcellular structures is desired for better understanding its roles in biological systems. In this work, a new Fe3+ sensor, 2-(2-((1-(6-acetylpyridin-2-yl)ethylidene)amino)ethyl)-3',6'-bis(diethylamino)spiro[isoindoline-1,9'-xanthen]-3-one (RhPK), which operates across the entire cellular pH range and is capable of unambiguously detecting Fe3+ ion in live human cells at subcellular resolution, is reported. The sensor exhibits high selectivity and sensitivity toward Fe3+ with a rapid fluorescence response and a 12-fold increase in intensity upon the addition of 1 equivalent Fe3+ at pH 7.3. RhPK forms a 1:1 complex with Fe3+ with an apparent binding constant 1.54 × 107 M−1 and a detection limit of 50 nM. The sensor is stable between pH 4.2 and 9.0 and operates across the whole cellular pH range. Cell imaging demonstrates the ability of the sensor to unambiguously detect basal level Fe3+ as well as its dynamic changes in real-time in live cells at subcellular resolution, with one labile Fe3+ pool identified in mitochondria in human primary fibroblast (ws1) cells for the first time and two Fe3+ pools confirmed in mitochondria and endo/lysosomes in human SH-SY5Y neuroblastoma cells, suggesting different cell types have distinctive Fe3+ storage in subcellular compartments. The RhPK probe is powerful for rapid and sensitive bioimaging of Fe3+ at subcellular level, enabling the unambiguous detection of labile Fe3+ pools at the entire cellular pH range, which is of great significance to understand the biological chemistry of Fe3+ and its roles in physiological processes and diseases. [ABSTRACT FROM AUTHOR]

In this work, dual-emissive ratiometric fluorescent system was constructed by the introduction of an ideal internal reference. By virtue of its unique alkalinity, N2H4 could undergo a hydrazinolysis reaction with the ester group of F1, inducing remarkable fluorescence enhancement while the blue fluorescence of the internal reference DPA remained constant. Consequently, the fluorescence intensity ratios (I540/I440) were proportional to the concentrations of N2H4, which was beneficial for the exactly quantitative detection. The skillful strategy granted the sensing system advantages such as relative good solubility in aqueous media, easy-to-design, simple synthesis, large emission shift, good ratiometric response, as well as the successful application in real water samples and cell imaging. [ABSTRACT FROM AUTHOR]

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 (1.155 ng/mL). Importantly, the results of the cell imaging experiments indicated that RHN has the ability to image and sense HClO in mitochondria, which is of great significance for exploration of the specific role of HClO in both the immune system and diseases. [ABSTRACT FROM AUTHOR]

As one of the main ingredients in the traditional Chinese medicine Gastrodia elata, p-hydroxybenzaldehyde (PHBA) has many pharmacological effects. Therefore, the monitoring of PHBA level is of great significance to exact valuation of the pharmacokinetics and toxic effect of PHBA in body fluids. In order to achieve the sensitive detection of PHBA, nitrogen-doped carbon dots (NCDs) have been designed. NCDs were successfully prepared through a hydrothermal strategy with chrysanthemum as the precursor. The transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction pattern were used for the characterization of NCDs. The as-prepared NCDs showed bright fluorescence with excitation/emission maxima of 290/421 nm and exhibited a fluorescence quenching response to PHBA under the optimal conditions. A good linear response was constructed at the PHBA concentration, ranging 10.0–150.0 μM with a detection limit of 63 nM based on the mechanisms of static quenching and inner filter effect. The proposed probe has been successfully applied to the detection of PHBA in blood and urine samples. In addition, the as-prepared NCDs with good biocompatibility were utilized for cell imaging. These results suggested that NCDs were promising probes for biosensing and bioimaging. [ABSTRACT FROM AUTHOR]

In this paper, a new pyrroloquinoline-derivative-based fluorescent probe, PQP-1, was prepared for the selective detection of Lys in living cells and natural mineral water for drinking. PQP-1 exhibited high selectivity, low limit of detection, and a wide pH range. PQP-1 could be successfully applied for imaging Lys in living cells and in natural mineral water for drinking. We expect that PQP-1 will expand the detection reaction mechanism and the practical biological applications of Lys. [ABSTRACT FROM AUTHOR]

The selective detection of glutathione (GSH) in vitro and in vivo has attracted great attentions, credited to its important role in life activities and association with a series of diseases. Among all kinds of analytical techniques, the fluorescent probe for GSH detection become prevalent recently because of its ease of operation, high temporal-spatial resolution, visualization and noninvasiveness, etc. The special structural features of GSH, such as the nucleophilicity of sulfhydryl group, the concerted reaction ability of amino group, the negative charged nature, the latent hydrogen bonding ability along with its flexible molecular chain, are all potent factors to be employed to design the specific fluorescent probe for GSH and discriminate it from other bio-species including its analogues cysteine (Cys) and homocysteine (Hcy). This paper reviewed the studies in the last 3 years and was organized based on the reaction mechanism of each probe. According to the reactivity of GSH, various recognition mechanisms including Michael addition, nucleophilic aromatic substitution, ordinary nucleophilic substitution, multi-site reaction, and other unique reactions have been utilized to construct the GSH specific fluorescent probes, and the molecular design strategy, photophysical property, recognition mechanism, and bioimaging application of each reported probe were all discussed here systematically. Great progress has been made in this area, and we believe the analyses and summarization of these excellent studies would provide valuable message and inspiration to researchers to advance the research toward clinic applications. [ABSTRACT FROM AUTHOR]

Because cancer cells grow at an extremely fast rate,their internal oxygen demand far exceeds the blood supply, resulting in hypoxia in the tissues. In solid tumors, hypoxia leads to over-expression of some enzymes, among which the concentrations of nitroreductase, azo red uctase and diaphorase change the most. In this study, we took diaphorase as the detection target and synthesized a novel fluorescent probe Milla 1,with the benzoquinone as a recognition group.With nicotinamide adenine dinuclectide,it underwent a reduction reaction to generate hydroquinone (or semiquinone) and released the fluorophore through a bond-breaking reaction,achieving the optical detection effects towards diaphorase.In the specific recognition reaction,the diaphorase content fluctuation was directly detected by the changes of fluorescence values at 635 nm,and then the hypoxia degree in the relevant hypoxic area was deduced.Because probe Milla 1 has the advantages of high selectivity, good photostability, and low toxicity, it was successfully used in detection and optical imaging experiments of endogenous and exogenous diaphorase in HeLa cells and Caenorhabditis elegans. [ABSTRACT FROM AUTHOR]

Al exists naturally in the environment and is an important component in acidic soils, which harm almost all plants. Furthermore, Al is widely used in food additives, cosmetics, and medicines, resulting in living organisms ingesting traces of Al orally or dermally every day. Accordingly, Al accumulates in the body, which can cause negative bioeffects and diseases, and this concern is gaining increasing attention. Therefore, to detect and track Al in the environment and in living organisms, the development of novel Al-selective probes that are water-soluble and exhibit fluorescence at long wavelengths is necessary. In this study, an Al3+-selective fluorescent probe PSP based on a novel pyrone molecule was synthesized and characterized to detect and track Al in biological systems. PSP exhibited fluorescence enhancement at 580 nm in the presence of Al3+ in aqueous media. Binding analysis using Job's plot and structural analysis using 1H NMR showed that PSP formed a 1:1 complex with Al3+ at the two carbonyl groups of the dimethyl malonate of the pyrone ring. Upon testing in biological systems, PSP showed good cell membrane permeability, detected intracellular Al3+ in human breast cancer cells (MDA-MB-231), and successfully imaged accumulated Al3+ in Microcystis aeruginosa and the larvae of Rheocricotopus species. The novel Al3+-selective fluorescent probe PSP is highly effective and is expected to aid in elucidating the role of Al3+ in the environment and living organisms. [Display omitted] • Water-soluble fluorescent Al3+ probe PSP developed based on phenylsulfonyl-2-pyrone • PSP exhibited fluorescence enhancement toward Al3+ at 580 nm in aqueous media • PSP successfully detected accumulated Al3+ in breast cells and small aquatic organisms [ABSTRACT FROM AUTHOR]

The investigation of cell membrane polarity is critical to determining cell physiological states and related disease for diagnosis and treatment. Herein, a ratiometric NIR cell membrane-targeted fluorescent probe, Cy-C 12 -MpN , was designed and synthesized to assess cell membrane polarity, which has an amphiphilic structure consisting of a dodecyl unit and a quaternary ammonium unit. It exhibited changes in emission wavelength and fluorescence intensity with the changes in polarity of the solution. It can use the ratio signal of the two peaks to report the polarity difference in its environment. The self-tuning of the probe internal system ensures the reliability of the test results and can be a semi-quantitative detection method. Indeed, in vitro polarity test, the ratio signal reported by Cy-C 12 -MpN had an optimal linear range with respect to polarity. Cell imaging illustrated the excellent cell membrane-targeted ability of Cy-C 12 -MpN , as it can rapidly target the cell membrane within 30 s and still anchor at it well after 1 hr. Moreover, Cy-C 12 -MpN showed that cell membrane polarity decreases after cells become cancerous, and observed the changes in cell membrane polarity caused by homeostatic membrane response stimulated by polyunsaturated fatty acids firstly. Imaging in vivo demonstrated the ability of Cy-C 12 -MpN to distinguish between tumor cells and normal cells, and further demonstrated that tumor cells have lower cell membrane polarity. In summary, the accuracy of the ratio detection of the probe Cy-C 12 -MpN and its excellent cell membrane targeting ability reveal reliable results that can provide very useful insights for cancer research. [Display omitted] • A novel NIR fluorescent probe for ratiometric detection of cell membrane polarity. • The degree of electron-hole transfer of the probe is calculated by Multiwfn to evaluate its polarity sensitivity. • The changes of cell membrane polarity in cell membrane homeostasis response stimulated by DHA were revealed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel turn-on near-infrared fluorescent probe TQ-AChE was developed to detect endogenous AChE. • The probe had high selectivity and sensitivity to AChE (LOD = 0.02 U/mL) and a fast response time (30 min). • In vivo studies in mouse models validate the potential of the probe in real-time monitoring of AChE expression in liver injury. Acetylcholinesterase (AChE) is a key enzyme in the cholinergic pathway of the nervous systems, with its aberrant expression linked to various diseases. In this study, we have developed a novel Turn-On near-infrared fluorescent probe, TQ-AChE, for the sensitive and selective detection of AChE activity. Characterized by its near-infrared emission at 740 nm, TQ-AChE effectively overcomes the limitations of traditional fluorescent probes, such as short excitation wavelengths and limited tissue penetration, crucial for both in vitro and in vivo applications. The probe's low limit of detection (LOD) of 0.02 U/mL for AChE makes it highly sensitive, enabling rapid quantification of AChE activity in serum effectively. Cell imaging studies demonstrate that TQ-AChE can confirm higher AChE activity expression in normal liver cells compared to liver cancer cells. TQ-AChE can also monitor AChE fluctuations in APAP-induced acute effectively, facilitating the evaluation of the efficacy of liver detoxifying agents. Additionally, in vivo studies in mouse models validate the potential of the probe in real-time monitoring of AChE expression in liver injury. The ability of TQ-AChE to visualize AChE expression signifies its potential as a promising tool for early liver disease diagnosis and therapeutic monitoring, opening new possibilities in hepatological research and clinical diagnostics. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new fluorescent probe CSH based on carbazole-thiophene was synthesized for the detection of ClO−. • CSH exhibits specific recognition of ClO− in the UV and fluorescence spectra, with detection limits as low as 3.61 × 10−6 mol/L and 1.16 × 10−6 mol/L. • Probe CSH can not only realize the detection of real water samples, but also can be applied to the detection of exogenous ClO− in HeLa cells. A carbazole thiophene-aldehyde and 4-methylbenzenesulfonhydrazide conjugate CSH was synthesized by introducing 5-thiophene aldehyde at the 3-position of the carbazole group as the precursor and then condensing it with 4-methylbenzenesulfonhydrazide. CSH has high selectivity and sensitivity towards ClO−, which can specifically identify ClO− by UV–Vis and fluorescence spectroscopy. CSH can rapidly respond to ClO− in the physiological pH range through a fluorescence quenching pattern, accompanied by the color of CSH changing markedly from turquoise to yellowish green under the 365 nm UV light. Probe CSH exhibits a quantitative response to ClO− (0–11 μM) with a low detection limit (1.16 × 10−6 M). Cell imaging experiments have shown that CSH can capture fluorescent signals in the cyan and yellow channels of HeLa cells through fluorescence confocal microscopy, and can successfully identify exogenous ClO− in HeLa cells. In addition, probe CSH can also be used to detect ClO− in environmental water samples. These results indicate that CSH has potential application prospects in the environmental analysis and biological aspects. [ABSTRACT FROM AUTHOR]