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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]

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]

Ferroptosis is a distinctive iron-dependent and GSH-related cell death form, and has been demonstrated to closely relate with Golgi apparatus (GA). Exploring the fluctuations of GSH level in GA during ferroptosis is of great importance for the deep research of biological functions of GA in ferroptosis. Herein, we reported a novel GA-targeting probe (NA-G) for the detection of GSH in GA during ferroptosis. The probe NA-G utilized N-oxidized pyridine sulfonyl as a responsive site for GSH, with tetradecanoyl amide serving as GA-targeting moiety. NA-G exhibited remarkable sensitivity and selectivity, manifesting a heightened response to GSH and effectively visualizing GSH through bright green fluorescence under UV light. By fluorescence imaging of cellular GSH, NA-G was demonstrated to serve as a GA-targeting probe, and could successfully monitor the dynamic changes in intracellular GSH. Further experimentation revealed that NEM stimulation resulted in the removal of a significant amount of endogenous GSH in GA, and erastin-induced ferroptosis significantly reduced GSH levels in GA. Notably, we discovered that Fer-1 and VE effectively inhibited the substantial depletion of GSH in GA during ferroptosis. [Display omitted] • A Golgi apparatus-targeting probe (NA-G) for revealing the fluctuations of GSH during ferroptosis was developed. • The probe NA-G could be used to image endogenous GSH in Golgi apparatus of living cells. • Erastin-induced ferroptosis could decrease GSH level in Golgi apparatus of living cells. • Fer-1 and VE were demonstrated to efficiently inhibit the depletion of GSH during ferroptosis. [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]

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]

[Display omitted] • A new quinoxaline-based turn-on fluorescent probe for biothiols was developed. • Detecting biothiols with at least 69-fold fluorescence enhancement. • The probe exhibited outstanding sensitivity and selectivity towards biothiols. • A promising tool for detecting endogenous and exogenous biothiols in living cells. Maintaining biothiols homeostasis is extremely important for the health of organisms. In this work, a pair of fluorescent probes (Acr-QX8A and Acr-QX9A) was designed and synthesized to monitor biothiols. The two probes applied the same fused four ring quinoxaline as the skeleton, benzyl carbamate as the linker and acryloyl group as the recognition site, whose only difference was the amino group's position on the skeleton. By comparing the optical properties, Acr-QX9A exhibited superior performances than Acr-QX8A and chosen for further studies. Probe Acr-QX9A displayed 180-fold, 135-fold and 69-fold fluorescence intensity enhancements upon interactions with Cys, Hcy and GSH respectively, owing to the release of fluorophore QX9A and the restoration of intramolecular charge transfer (ICT) process. Acr-QX9A showed good selectivity and excellent anti-interference, which could be served as the naked-eye colorimetric probe for biothiols detection. More importantly, the probe exhibited high sensitivity towards biothiols with outstanding detection of limits (75.2 nM for Cys, 92.7 nM for Hcy and 370 nM for GSH). Encouraged by the appreciable results in solutions, probe Acr-QX9A was then successfully applied as a promising tool for monitoring both endogenous and exogenous biothiols in living cells. [ABSTRACT FROM AUTHOR]

Protein misfolding and aggregation are the leading cause of many diseases, including neuron degenerative diseases, cardiovascular diseases, and cancers. However, the inducing factors and mechanisms behind protein misfolding remain largely unrevealed, due to the lack of efficient analyzing and probing methods for the detection of inducing substrates and protein labelling. In this review, we investigated on the probing techniques and underlying mechanisms for various inducing factors of protein misfolding, including pH, ions, reactive oxygen species (ROS) and salinity. The mechanisms behind different inducing factors on triggering protein aggregation were discussed. We also compared existing methods for protein labelling and summarized their pros and cons, while also demonstrating their biochemical applications in live cells. In summary, this review provides readers a systematic understanding of protein aggregation inducing factors and disease-leading mechanisms, aiming to promote the development of specific therapeutic medicines for protein aggregation related diseases. • Description of various protein aggregation inducing factors and their inducing mechanism. • Summarizes the recent progress of novel analytical methods for protein aggregation inducing factors. • Comparison with different protein labelling methods. [ABSTRACT FROM AUTHOR]

Ratiometric probes are favored for their application in biological systems, and the signal ratio between two channels is a crucial indicator for evaluating the performance. Since changing the substituent group on the recognition group would significantly influence the response performance of a fluorescent probe, in this work, we modified the substituent group on the 7-position of a coumarin to give two Hg2+ probes based on through-bond energy transfer (TBET) strategy; the probes displayed a much higher detection capacity and emission ratio between the red and blue channels. The probes were successfully applied for Hg2+ imaging in cells and living mice and possess significant bacteriostatic activity, demonstrating potential application in biological science, but also present excellent stability and detection ability serving as solid-phase detection materials via fabricating into nanofiber using electrostatic spinning. [Display omitted] • TBET-based Hg2+ probes were constructed with LOD low to 2.7 nM. • Better response performance was achieved by modifying the recognition group. • Living cells and mice detection suggest good bioimaging ability. • The probes possess good bacteriostatic activity due to their lactam structure. • The probes were fabricated into nanofiber test strips via electrospinning. [ABSTRACT FROM AUTHOR]

Herein we developed a cascade detection mode for the detection of HS− and ClO− by the novel probe NM-Cl bearing a conjugating naphthalene-dicyanoisophorone unit. The probe displayed sensitive and remarkable fluorescent enhancement in response to HS−, but not to other analytes. The mixture of probe and HS− constructed a specific sensing system for ClO− by fluorescent quenching response. The mechanism studies indicated that the successive reacting of HS− substitution Cl atom in probe and then addition of ClO− facilitation a thiofuran ring-forming induced differentiated fluorescence emission. This study provides a novel mechanism for the detection of HS− and ClO−, the imaging of cell and living animal further indicating the good application prospects of the probe in biosensing and bioimaging. A highly specific and visible method for cascade detection HS− and ClO−. The substitution reaction of the Cl atom by SH group facilitates sensitive detection toward HS−. The responsiveness to ClO− is based on the thiofuran ring-forming reaction, which providing a brand-new mechanism for sensing ClO−. This cell and living animal imaging indicating the good application prospects of these probes in biosensing and bioimaging. [Display omitted] • A novel fluorescent probe for cascade detection of HS− and ClO− was developed. • The responsiveness to ClO− is based on the thiofuran ring-forming reaction, which provides a band-new mechanism for sensing ClO−. • The application of the probe in living cells and mice imaging reveal its potential for HS− and ClO− sensing. [ABSTRACT FROM AUTHOR]

The liver plays a crucial role in several important processes in the human body, including metabolism, detoxification, and immune function. When the liver experiences acute injury, it can cause significant harm and requires prompt detection. Traditional biomarkers lack specificity and cannot detect changes in real-time, making them unsuitable for monitoring pathological processes. Recent studies have shown that acute liver injury (ALI) is closely related to oxidative stress, with peroxynitrite (ONOO−) being a vital byproduct of liver metabolism and become a critical biomarker for detecting liver damage. As a result, this research developed an activatable near-infrared fluorescent probe W-3a that can be used to detect endogenous ONOO− in a mouse model of ALI induced by lipopolysaccharides (LPS). The probe has high selectivity and anti-interference ability, with a reaction time <10 min and a detection limit of 85 nM. It was successfully utilized in detecting endogenous ONOO− in cells and live imaging of ALI mice. This research developed an activatable near-infrared fluorescent probe W-3a that can be used to detect endogenous ONOO− in a mouse model of ALI induced by lipopolysaccharides (LPS). The probe has high selectivity and anti-interference ability, with a reaction time <10 min and a detection limit of 85 nM. It was successfully utilized in detecting endogenous ONOO− in cells and live imaging of ALI mice. [Display omitted] • Development of a near-infrared fluorescent probe W-3a. • W-3a has high sensitivity and selectivity for ONOO−. • Realized in vivo imaging of cells and liver-injured mice. [ABSTRACT FROM AUTHOR]

Logic gate-based fluorescent probes are powerful tools for the discriminative sensing of multiple signaling molecules that are expressed in concert during the progression of many diseases such as inflammation, cancer, aging, and other disorders. To achieve logical sensing, multiple functional groups are introduced to the different substitution sites of a single fluorescent dye, which increases the complexity of chemical synthesis. Herein, we report a simple strategy that incorporates just one responsive unit into a hemicyanine dye achieving the logic gate-based sensing of two independent analytes. We introduce boronic acid to hemicyanine to quench the fluorescence, and in the presence of hydrogen peroxide (H 2 O 2), the fluorescence is recovered due to removal of the boronate. Interestingly, the subsequent decrease in pH turned the red fluorescence of hemicyanine to green emissive because of protonation of the phenolic alcohol. This unique feature of the probe enables us to construct "INHIBIT" and "AND" logical gates for the accurate measuring of intracellular H 2 O 2 and acidic pH in tandem. This study offers insight into the simple construction of logic-gate based fluorescent probes for the tandem sensing of multiple analytes that are correlatively produced during disease progression. Logical probes HCyBA for tandem sensing of H 2 O 2 and pH by using of just one reactive unit and the construction of logic gates for diagnosis of H 2 O 2 and acid related pathological cells are reported. [Display omitted] • A general strategy to develop logic gate-based fluorescent probes for tandem sensing of H 2 O 2 and acidic pH. • Red fluorescence of the probe is activated in the presence of H 2 O 2 , and then turned green when pH decreases. • Construction of "INHIBIT" and "AND" logic gates for precise sensing of H 2 O 2 and acidic pH in cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • Developed FDCM-BChE, a near-infrared probe, for accurate BChE quantification in serum. • The probe features rapid response and high selectivity, enhancing fluorescence-based BChE assays. • Employed FDCM-BChE in cellular imaging to reveal BChE downregulation in liver cancer and hepatic injury. • Demonstrated the probe's utility in identifying elevated BChE levels in diabetic subjects. Butyrylcholinesterase (BChE) is a crucial hydrolytic enzyme predominantly synthesized in the liver, playing a significant role in conditions like liver disorders, diabetes, Alzheimer's disease, and fat metabolism regulation. This study aims to address the current limitations in visualizing BChE activity in diseases at various states by introducing an ultra-sensitive near-infrared fluorescent probe, FDCM-BChE. The probe was engineered to have several properties, such as a large Stokes shift, rapid response time, high stability, excellent selectivity, and low detection limits. We validated the efficacy of FDCM-BChE in quantifying BChE activity in human serum and leveraged its low cytotoxicity for cellular imaging. The study revealed the downregulation of BChE activity in liver cancer and hepatic injury and the upregulation in diabetes. Thus, FDCM-BChE shows promise as a tool for specific applications, providing insights into diseases associated with BChE activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Successful synthesis and characterization of a new fluorescent probe, NR-ClO, for ClO– detection in biological systems. • NR-ClO demonstrated low cytotoxicity, high selectivity, and sensitivity to ClO–. • Confirmed applicability of NR-ClO in both in vitro HepG2 cell studies and in vivo mouse model of rheumatoid arthritis. This study presents the synthesis and application of a novel fluorescent probe, NR-ClO, for the detection of hypochlorite ion (ClO–) in biological systems. The probe was synthesized through a nucleophilic substitution reaction between Nile red and dimethylcarbamothioic chloride. The synthesized probe had high sensitivity and selectivity towards ClO–, with a detection limit of 75 nM and a linear range of 0.1–200 μM. The probe's efficacy was validated through in vitro studies using HepG2 cells and in vivo experiments using a mouse model of rheumatoid arthritis. The findings demonstrate that the NR-ClO probe is a promisingly reliable tool for real-time monitoring of ClO– in complex biological environments. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel Al3+ Schiff base probe JHK was designed and synthesized. • JHK has high selectivity, high fluorescence quantum yield and low detection limit for Al3+. • JHK was successfully applied to living cells and zebrafish. A novel fluorescent probe N'-(2-hydroxybenzylidene)-indole-3-formylhydrazine (JHK) was designed and synthesized based on the condensation reaction of indole-3-formylhydrazine and salicylaldehyde. The probe JHK solution could highly selectively recognize Al3+ by the obvious fluorescence enhancement (288-fold) after adding Al3+. And the probe solution with Al3+ had a very high fluorescence quantum yield (89.29 %). The detection limit was calculated to be 1.135 nM, which was significantly lower than many reported detection limits, indicating that the probe JHK had pretty good sensitivity. The ratio of JHK to Al3+ (1:1) and the sensing mechanism were determined by Job's plot, 1H NMR spectra, FTIR spectra, ESI-MS and Gaussian calculation. The probe solution and medium-speed filter paper were successfully used to make test papers for more convenient detection of Al3+. Furthermore, the probe JHK had been successfully applied to the detection of Al3+ in real water, zebrafish and living cells. [ABSTRACT FROM AUTHOR]

Ferroptosis is a non-apoptotic form of cell death characterized by iron-dependent lipid peroxidation and glutathione (GSH) depletion. Despite recent advances, challenges remain in understanding the bidirectional interactions or interplay between organelles during ferroptosis. In this study, we aimed to understand the interplay between mitochondria (Mito) and lysosomes (Lyso) in cell homeostasis and ferroptosis. For this purpose, we designed a single fluorescent probe that marks GSH in Mito and hypochlorous acid (HOCl) in Lyso with two distinct emissions. Using this dual-targeted single fluorescent probe (9-morphorino pyronine), we detected Mito-Lyso interplay in ferroptosis. We disclosed differences in Mito-Lyso interplay depending on the induction of ferroptosis. Although erastin treatment decreased GSH, RSL3 triggered a HOCl burst, and FIN56- and FINO2-induced ferroptosis increased GSH and HOCl. Additionally, we showed that only extracellular vesicles generated during erastin-induced ferroptosis could spontaneously move and dock to neighboring cells, resulting in accelerated cell death. [Display omitted] • Simultaneous tracking of the GSH level in mitochondria (Mito) and the HOCl level in lysosomes (Lyso), respectively • Detected distinct Mito-Lyso interplay dynamics and GSH-HOCl crosstalk in ferroptosis • Diverse extracellular vesicle (EV) dynamics in different ferroptosis pathways • Spontaneous movement and docking of the EV accelerate neighboring cell death Wang et al. show the different dynamics of mitochondria-lysosome interplay in the four ferroptosis pathways. They identify diverse extracellular vesicles (EVs) in ferroptosis, of which only erastin-induced EVs can spontaneously move and dock to neighboring cells, resulting in accelerated cell death. [ABSTRACT FROM AUTHOR]

In this manuscript, we designed and synthesized a fluorescent probe HBA based on caffeic acid for detecting Al3+ and HPO 4 2− by the mode of "off-on-off". The probe HBA can be utilized as a powerful method for the sequential recognition of Al3+ and HPO 4 2– in biological samples. [Display omitted] • A new dual-functioned fluorescent probe HBA based on caffeic acid was synthesized. • The new fluorescent probe HBA can sequential detect Al3+ and HPO 4 2–− with good selectivity and excellent sensitivity. • The probe HBA has good performance for detection of Al3+/HPO 4 2– in HeLa cells. In this work, we focused on synthesizing a new fluorescent probe HBA based on caffeic acid for detecting Al3+/HPO 4 2− by the mode of "off-on-off". HBA alone exhibited a weak fluorescence emission in aqueous solution. When Al3+ was added into the HBA solution, a significant green fluorescence was found at 498 nm. However, the introduction of HPO 4 2− to the solution of [ HBA -Al3+] complex induced the disappearance of green fluorescence. The detection limit of HBA was calculated as low as 41.7 nM for Al3+ and 62.1 nM for HPO 4 2−, respectively. Probe HBA exhibited good cell-membrane penetrability and had the potential to trace Al3+/HPO 4 2− in biological systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • A mitochondria-targetable fluorescent probe for cysteine has been reported. • The probe displays high sensitivity and high selectivity for cysteine. • The probe can be utilized for determination of cysteine within the mitochondria of living cells. Cysteine (Cys) is of great significance in biological systems and in the process of mitochondrial function. Highly selective and specificity recognizable probes for mitochondrial Cys are still in demand. In this work, a new fluorescent probe for detecting mitochondrial Cys was developed based on a rhodamine derivative. In this probe, acrylate unit was selected as group of Cys recognition and quaternized pyridinium moiety was utilized as mitochondrial targeting group. The probe showed colorless in daylight and extremely weak fluorescence in 365 nm due to its spirolactone structure when Cys did not exist. In the presence of Cys, the probe exhibited orange in daylight and produced intensely green fluorescence in 365 nm owing to the formation of the conjugated xanthene structure. The probe exhibited specific recognition for Cys. There was an excellent linear relationship between fluorescence intensity at 540 nm of the probe and the Cys concentration from 4.0 × 10-8 to 1.0 × 10-5 mol⋅L-1. And the detection limit was estimated to be 1.57 × 10-8 mol/L. Moreover, the probe was almost non-cytotoxic, possessed targeting-mitochondria ability and could sense Cys at the cellular level. The good bioimaging ability makes the probe a potential tool for studying mitochondrial Cys in biological samples. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S) is a multifunctional gaseous signaling molecule that plays a vital role in several biological processes. In the present study, a BODIPY-based fluorescent probe called 8-[4-((1,4,7,10-tetraazacyclododecane)methyl)phenyl]-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a, 4a-diaza- s -indacene (BA–Cyclen)–Cu was designed and synthesized; this probe is a Cu(Ⅱ) complex that uses Cu(Ⅱ) decomplexation to achieve the sensitive and rapid detection of aqueous H 2 S via the "turn-on" mode. We observed that BA–Cyclen–Cu exhibited good membrane permeability, low toxicity, and lysosome-targeting ability, facilitating H 2 S detection in living cells. Furthermore, we demonstrated the potential biological applications of the probe by measuring exogenous H 2 S originating from Na 2 S and GYY4137, a slow-release donor, and endogenous H 2 S generated via the catalysis of cystathionine- β -synthase in both normal (H9c2) and cancerous (U87) cells. Moreover, BA–Cyclen–Cu was successfully used to detect exogenous H 2 S by the external standard method in fetal bovine serum, the serum of a healthy person, and the serum of a patient with liver cancer. [Display omitted] • BA-Cyclen-Cu displayed high selectivity, sensitivity and fast response toward H 2 S with "turn-on" mode. • BA-Cyclen-Cu have a good performance on exogenous/endogenous H 2 S sensing in cancer cells and normal cells. • BA-Cyclen-Cu was successfully used to detect H 2 S in serum samples. [ABSTRACT FROM AUTHOR]

Hydrogen polysulfide (H 2 S n , n > 1) is an important component of reactive sulfur species (RSS), which is an important substance for maintaining the redox balance in cells. However, limited recognition moieties are available for hydrogen polysulfide probe design. In this study, we have constructed a small library containing several organic molecules to explore a new specific recognition moiety for H 2 S n fluorescent probe design. To validate the discovery, two fluorescent probes, 7 and BCC, were further developed based on coumarin and its derivative. The probes exhibited desirable specificity for H 2 S n monitoring, which can be used for detecting H 2 S n in solution and cells. The new specific recognition moiety for H 2 S n fluorescent probe design discovered in this work has certain guiding significance for development of H 2 S n probes exploring biological roles in the future. [Display omitted] • Constructed a small library to explore recognition moiety for H 2 S n probe design. • Two fluorescent probes were further developed to validate the discovery. • Probe 7 and BCC exhibited desirable application in H 2 S n monitor and cells imaging. [ABSTRACT FROM AUTHOR]

Fluorescent imaging of cellular superoxide anion radical (O 2 •-) is of great significance to investigate reactive oxygen species-related pathophysiological processes and drug metabolism. However, the application of this technique is far away from maximum partially due to the lack of suitable probes. In this work, we propose a new strategy for design of near-infrared (NIR) O 2 •- fluorescent probes in which p -cresol is used as a self-immolative linker to conjugate the NIR fluorophore DDAO (9H-1,3-Dichloro-7-hydroxy-9,9-dimethylacridine-2-one) with the O 2 •--sensing group (i.e., trifluoromethanesulfonate). The introduction of self-immolative linker effectively increases the self-stability of these probes under physiological conditions. Importantly, the electron-withdrawing halogen substituents on the linker greatly enhance the sensitivity of the probes to O 2 •-. As such, the representative probe DLS4 exhibits high self-stability over a broad range of pHs (5.0–8.5), high selectivity as well as excellent sensitivity to O 2 •- with a detection limit (LOD) of 7.3 nM and 720-fold fluorescence enhancement upon reaction with O 2 •-. Moreover, DLS4 enables imaging of O 2 •- generation in PMA-stimulated RAW 264.7 cells and HeLa cells, and the fluorescence intensities are proportional to the PMA concentrations. In addition, the doxorubicin-induced cytotoxicity of H9c2 cells was also evaluated using DLS4. The present study provides a novel strategy for molecular design of small-molecule O 2 •- fluorescent probes and the resulting probes show great potential as reliable tools to study the development and progression of O 2 •--related diseases and drug metabolism in various systems. [Display omitted] • Near-infrared fluorescent O 2.•- probes with self-immolative linkers were synthesized. • The self-immolative linker enhances self-stability and sensitivity of the probes. • The probe DLS4 exhibits excellent sensitivity and specificity to O 2.•-. • Cellular imaging of endogenous O 2.•- from two cell lines has been achieved using DLS4. • Doxorubicin-induced cytotoxicity of H9c2 cells was reasonably evaluated using DLS4. [ABSTRACT FROM AUTHOR]

[Display omitted] • A triphenylamine based molecular probe (TPOH) is synthesized. • TPOH exhibits an extremely low toxic to HeLa cell. • TPOH has good prospects for biological and practical applications. • TPOH has the advantages of sensitive, rapidly response and low detection limit to the detection of Zn2+. A triphenylamine-based Schiff base (TPOH) was synthesized as a good fluorescent sensor for recognizing of Zn2+. The fluorescence intensity of the probe TPOH was significantly enhanced after coordination with Zn2+ with a yellow fluorescence at the excitation wavelength of 525 nm. In MeOH-H 2 O (3:7 in v/v) solution, the probe showed excellent selectively for Zn2+ over most other competing ions, which exhibited an Intramolecular Charge Transfer (ICT) mechanism in the recognition procedure. The reaction stoichiometry of 1:1 between TPOH and Zn2+ was determined based on the Job's plot and 1H NMR spectra, respectively. The HeLa cells maintained over 95 % of viability after 24 h exposure to TPOH, which identified the extremely low toxic of TPOH and can be used for in vivo cell imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • A near-infrared fluorescence probe based on dicyanomethylene-4H-pyrans was designed and synthesized. • The probe exhibited high sensitivity and selectivity to Hg2+ in ultrafast response time. • The probe can visualize Hg2+ in living HepG2 cells. Mercury ions (Hg2+) are a class of heavy metal ions that can cause serious harm to the human body due to their toxicity, fluidity, and bioaccumulation. Direct contact with Hg2+ can cause adverse effects on the human body. In addition, long-term exposure to Hg2+ can lead to extreme toxicity of enzymes and proteins in the body, disrupting the cell cycle and thus endangering human life. It is becoming increasingly important to develop a method that is reliable, stable, and sensitive for detecting Hg2+. In this study, a near-infrared "turn-on" fluorescent probe based on dicyanomethylene-4 H -pyran, DCM-Hg, was designed and synthesized to determine Hg2+ over other metal ions. Probe DCM-Hg had a detection limit (LOD) of 3.35 μM when used to detect Hg2+. The Hg2+ concentrations and the fluorescence intensities at 695 nm showed a good linear correlation. Additionally, Hg2+ in HepG2 cells was successfully visualized using the current probe. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new benzobodipy based fluorescent probe for HOCl has been designed and developed. • The probe has excellent sensitivity with a fast response to HOCl. • The probe was applied to the fluorescence imaging of HOCl in HeLa cells and zebrafish. Hypochlorous acid (HOCl) is a significant reactive oxygen species within biological systems, and its anomalous metabolism has been linked to a range of diseases. Therefore, it is crucial to track and monitor the concentration of HOCl in living organisms to understand its biological functions and study its pathogenic mechanisms. In this study, we developed a photoinduced electron transfer (PeT) mechanism-based benzo-fused bodipy fluorescence probe, named BBy-Se , for highly sensitive and selective detection of HOCl in aqueous solutions. BBy-Se demonstrated a good turn-on fluorescence response to HOCl by specifically oxidizing the selenium atom. It exhibited significant Stokes shift (82 nm), low detection limit (10.9 nM) and rapid response (less than 10 s). Furthermore, the probe was successfully employed for real-time fluorescence imaging of HOCl in living HeLa cells and zebrafish, as demonstrated by the bioimaging results. The development of BBy-Se presents a new approach to explore the biological roles of HOCl and offers a valuable tool for studying its function in diseases. [ABSTRACT FROM AUTHOR]

[Display omitted] • A fluorescent probe based on 1,3,5-Triazine was designed and synthesized to detect Hg(Ⅱ). • The novel fluorescent probe exhibited high selectivity, good stability, large Stokes shift (100 nm). • The novel fluorescent probe has been successfully used for cell and zebrafish imaging. • The novel fluorescent probe has successfully detected Hg(II) in tobacco. Non-biodegradable, bioaccumulative, and highly toxic, mercury(II) poses a significant threat to both ecosystems and human health. Extensive data indicates that even extremely low levels of Hg(II) can cause significant harm to human health. In this paper, the thiocarbonate specific recognition site was used for the detection of Hg(II), which was successfully synthesized by the hydroxyl group of 1,3,5-Triazine with phenyl chlorothiocarbonate. The probe exhibited advantages of high sensitivity (0.253 μM), good selectivity, large Stokes shift (100 nm), and good biocompatibility. The probe TzAr-Nap-Hg successfully fluorescently imaged Hg(II) in cells, zebrafish and tobacco, making it possible to detect the content of Hg(II) in agricultural and sideline products. [ABSTRACT FROM AUTHOR]

[Display omitted] • An efficient dual-function fluorescent probe SN-F for SO 2 derivatives and H 2 S. • SN-F had a swift response (2 min), strong selectivity and anti-interference capability for SO 2 derivatives. • Probe SN-F had a wide linear range for H 2 S. • Probe SN-F had superior endoplasmic reticulum-targeting. As gas signaling molecules in organisms, SO 2 derivatives and H 2 S play crucial regulating roles in a series of physiological processes. Therefore, developing an assay that can accurately monitor the concentration of SO 2 derivatives and H 2 S in cells is extremely important for the research and treatment of related illnesses. A bifunctional probe SN-F based on FRET mechanism for SO 2 derivatives and H 2 S was designed. SN-F had a short response time to SO 2 (2 min), excellent anti-interference capability and selectivity in the non-organic solvent system (pH = 7.4), which was suitable for the determination of SO 2 derivatives in cells. SN-F had a wide linear range for H 2 S. Moreover, SN-F was applied in cell imaging successfully with high targeting ability to endoplasmic reticulum (ER) and could monitor endogenous and exogenous H 2 S in cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • The probe 3-STF is first designed based on 3-thiolflavone. • The probe 3-STF exhibited a specific "turn-on" fluorescence response towards biothiols (Cys, Hcy, and GSH) with a large stokes shift of 140.6 nm. • The detection of biothiols did not suffer from the interference of other amino acids. • The detection mechanism was discussed in detail. • The probe 3-STF can be successfully applied to monitor endogenous and exogenous biothiols in HepG-2 cells. Abnormal levels of intracellular biothiol species, including glutathione (GSH), homocysteine (Hcy), and cysteine (Cys), are closely relevant to a variety of diseases. In this study, we first report the design and synthesis of a 3-thiolflavone-based probe 3-STF with an S–S linkage both as the fluorescence quenching agent and the recognition site. Upon treatment with biothiols, the S–S linkage was cleaved by nucleophilic attack of RS-, and 3 -STF exhibited a specific "turn-on" fluorescence response at 543.8 nm upon 390 nm excitation. Meanwhile, 3 -STF was proved to be highly sensitive and selective for the detection of biothiols over other nucleophiles such as amino acids and H 2 S. The sensing mechanism was further verified by 1H NMR and ESI-MS analysis. In addition, 3-STF with low cytotoxicity can be successfully applied to detect endogenous and exogenous biothiols in HepG-2 cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A fluorescent probe NBPI, utilizing cyanine phenothiazine and 7-nitro-1,2,3-benzoxadiazole (NBD), was developed for selective detection of Cys-SO 2 components. • The phenothiazine structure increased the bond energy of sulfonamide, thus the probe NBPI achieved a selective response to Cys. • The probe NBPI was successfully employed for the imaging of endogenous and exogenous Cys and SO 2 in HepG2 cells. A fluorescent probe has been designed using cyanine phenothiazine and 7-nitro-1,2,3-benzoxadiazole (NBD) for selective detection of Cys-SO 2 components. The probe utilizes the NBD structure to achieve specificity towards Cys and employs a reaction mechanism between the double bond of cyanine and phenothiazine with SO 3 2− to achieve selectivity towards SO 2. Importantly, the NBPI phenothiazine structure incorporates a large C-O bond energy attached to NBD, effectively eliminating interference from Hcy and ensuring highly selective response to Cys. The optimized design of the probe enables excellent linearity and extremely low detection limits for Cys-SO 2 components in vitro experiments. The probe NBPI allows separate detection of Cys-SO 2 in the presence of both components. Furthermore, the probe NBPI demonstrated successful imaging of endogenous and exogenous Cys and SO 2 in cell studies. [ABSTRACT FROM AUTHOR]

[Display omitted] • A naphthalimide-based fluorescent probe for relay recognition of Cu2+ and S2− has been designed and synthesized. • The sensor has lower detection limit for Cu2+ and S2−. • Fluorescence behavior in the presence of Cu2+ and S2− could be manufactured to IMPLICATION type logic gate. • Intracellular fluorescence imaging in living cells were developed. A fluorescent chemosensor based on naphthalimide derivative (HL) was prepared and characterized. HL exhibited strong fluorescence emission at 528 nm, which was attributed to naphthalimide moiety, while the addition of Cu2+ almost completely quenched the fluorescence emission. However, with the addition of S2−, the fluorescence at 528 nm reoccurred remarkably. The detection limits for Cu2+ and S2− were measured to be 1.72 × 10−7 M and 2.66 × 10−7 M, respectively. As determined, the fluorescence behavior of HL in the presence of Cu2+ and S2− could be manufactured to IMPLICATION type logic gate. Moreover, confocal fluorescence imaging in HepG2 cells indicated that the HL could act as a useful fluorescent probe for intracellular Cu2+ and S2− detection with negligible cytotoxicity. [ABSTRACT FROM AUTHOR]

• A novel fluorescent probe TZ-NBD was designed and synthesized for detection of Glutathione (GSH). • The probe TZ-NBD was rapid and sensitive for GSH. • The detection limit was 0.207 μM. • The probe TZ-NBD was demonstrated imaging of GSH in HepG2 cells. Biothiols are significant biomarkers for many diseases. The selective identification of biothiols is very crucial. Herein, we combined phenothiazine and 7-nitrobenzofurazan to form a new fluorescent probe TZ-NBD, due to the difference in response of reactive sulfur species to two fluorophores for distinguishing biothiols specifically. The specificity of TZ-NBD towards biothiols was high and sensitive. Moreover, its detection limit was 0.207 μM for Glutathione (GSH). Finally, TZ-NBD was successfully applied to GSH imaging in HepG2 cells. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • An "off–on" long-wavelength fluorescent probe is synthesized for Cys detection. • The probe has a large Stokes shift (211 nm) and reacted with Cys specifically. • The probe can monitor Cys fluctuations caused by redox imbalance in HepG2 cells. • The probe can be used for fluorescence imaging in cells and mice. In this research, an "off–on" long-wavelength fluorescent probe (DCMN-Cl) based on (E)-2-(3-(2-(6-hydroxynaphthalen-2-yl)vinyl)-5,5-dimethylcyclohex-2-en-1-ylidene) malononitrile (DCMN) is designed and synthesized for cysteine (Cys) detection. DCMN-Cl exhibits a large Stokes shift (211 nm) and shows rapid response and high specificity to Cys. The fluorescence initensity at 635 nm reveals a good linear relationship with Cys concentration in the 0 to 50 μM range, and the detection limit is as low as 159 nM. The probe is also used for fluorescence imaging of Cys in cells and mice. Moreover, the probe provided visual evidence of Cu2+ and curcumin-induced intracellular Cys fluctuations. [ABSTRACT FROM AUTHOR]

[Display omitted] • A fluorescent probe ( CyNa-N 3 ) based on naphthalimide and cyanine dyes was synthesized. • CyNa-N 3 can detect HClO and H 2 S with different fluorescence signals. • The sensing mechanism of CyNa-N 3 to HClO and H 2 S was confirmed by ESI–MS and 1H NMR. • CyNa-N 3 was adapted to visualize HClO and H 2 S in cell imaging. Hypochlorous acid (HClO) and hydrogen sulfide (H 2 S) play very important roles in both physiological and pathological processes, however, the methods for simultaneously detecting HClO and H 2 S were rarely reported. Here, a dual–responsive fluorescent probe ( CyNa-N 3 ) based on cyanine and naphthalimide dyes was synthesized and investigated. The fluorescence probe showed better sensitivity, high selectivity response to HClO and H 2 S by red emission and green emission bands, and the limits of detection were 0.17 µM and 0.15 µM respectively. MS (Mass Spectrum) and 1H NMR (Nuclear Magnetic Resonance) confirmed the sensing mechanism of CyNa-N 3 detected HClO and H 2 S, the calculation of density functional theory (DFT) further explained the internal mechanism of spectral change of CyNa-N 3 . Moreover, CyNa-N 3 was successfully applied to image HClO and H 2 S in living cells, which is beneficial for more efficient application in biological imaging. [ABSTRACT FROM AUTHOR]

As a class of heterocyclic compounds, 1,3,5-Triazines have a wide range of applications in degradable materials, drug synthesis, fluorescent dyes, etc. In this paper, donor-acceptor, π-conjugated 1,3,5-triazine dyes (TzAr-R) were successfully synthesized from 1,3,5-triazine and benzaldehyde derivatives, and their photophysical properties were studied. On this basis, two typical probes (TzAr-OH and TzAr-NapOH) were selected for in-depth study, and found to have the advantages of pH resistance, high selectivity, good viscosity response and low cytotoxicity. Furthermore, TzAr-OH and TzAr-NapOH exhibited excellent performance in cell viscosity detection and monitoring liquid food spoilage, indicating that the probes could be used as powerful imaging tools in the fields of biomedicine and food safety detection. [Display omitted] • A class of 1,3,5-Triazines based fluorescent dyes were constructed and their photophysical properties were studied. • Two typical probes (TzAr-OH and TzAr-NapOH) exhibited good advantages of pH resistance, high selectivity, good viscosity response and low cytotoxicity with large Stokes shifts. • TzAr-OH and TzAr-NapOH showed excellent performance in cell viscosity detection and monitoring liquid food spoilage. [ABSTRACT FROM AUTHOR]

A new hemicyanine-based near-infrared "off-on" recognition Cu2+ fluorescent probe NRh-NP was designed and successfully synthesized. The structure of NRh-NP was characterized by NMR, ESI-HRMS and single crystal X-ray diffraction analysis. NRh-NP has high sensitivity, selectivity and a low limit of detection (33 nM as fluorescence sensor and 35 nM as UV sensor) to Cu2+. According to Job's plot and ESI-HRMS, the coordination ratio of NRh-NP to Cu2+ was 1:1. DFT theoretical calculations proved that the sensor mechanism was photo-induced electron transfer (PET). More importantly, NRh-NP has excellent membrane permeability and low cytotoxicity, which could be used not only for the detection of Cu2+ in human breast cancer cells (MCF-7), but also for imaging Cu2+ in living mice. [Display omitted] • The structure of NRh-NP was characterized by NMR, ESI-HRMS and single crystal X-ray diffraction analysis. • The responses of NRh-NP toward Cu2+ were fully proved by Job's plot, ESI-HRMS and DFT theoretical calculations. • NRh-NP has high sensitivity and selectivity with detection limit as low as 33 nM. • NRh-NP can be used for Cu2+ imaging in living cells and in vivo. [ABSTRACT FROM AUTHOR]

[Display omitted] • A colorimetric and ratiometric fluorescent probe TPA-Y with AIE characteristic has been developed; • TPA-Y exhibits a large emission peak separation up to 185 nm and gives low LOD (47.1 nM) for bisulfite; • Quantitative detection of bisulfite in food samples (sugar and red wine) was achieved; • TPA-Y can reversible response to HSO 3 -/H 2 O 2 cycles and cell imaging. Reversible detection of bisulfite (HSO 3 -) and hydrogen peroxide (H 2 O 2) is highly desirable in biology and food safety owing to their redox pair function in biological systems and their utilization in food industry. In this work, a ratiometric fluorescent probe (TPA-Y) with aggregation-induced emission (AIE) properties based on triphenylamine fluorophore was designed and synthesized for reversibly monitoring of HSO 3 -/H 2 O 2. Reaction of HSO 3 - with TPA-Y can result in ratiometric fluorescence changes (I 444 / I 629), and the emission spectrum blue shift reaches 185 nm, which can effectively avoid spectral overlap. Meanwhile, the solution color changed obviously from orange to colorless, enabling naked eye detection of HSO 3 -. TPA-Y was capable of quantitatively detect HSO 3 - in sugar and wine samples with the recovery rates ranging from 94.52 to 102.18%. In addition, TPA-Y is suitable to prepare paper strips and anti-counterfeiting ink for HSO 3 - detection. In addition, the original TPA-Y can be released after the addition product (TPA-Y-HSO 3 -) is oxidized by H 2 O 2 , and the HSO 3 -/H 2 O 2 redox cycle can repeat for at least six times. The probe TPA-Y can be applied to fluorescence imaging of reversible and dynamic interconversion between HSO 3 - and H 2 O 2 in living MCF-7 cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A robust probe Bptp-RD was developed to identify DNA and RNA. • Bptp-RD was successfully applied to image DNA and RNA in cells. • Bptp-RD was successfully used to detect different types of DNA. • Recognition rule of probes to different types of DNA was revealed with Bptp-RD. The roles of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) in cells are closely related. However, the absence of molecular tools for simultaneous imaging of the two nucleic acids has prevented scientists from elucidating the regulatory mechanisms of nucleic acid interaction. The nucleic acid probes developed in recent years have ignored the regulatory relationship between DNA and RNA. Simultaneously imaging RNA and DNA in cells through a single small-molecule fluorescent probe is important. In this study, we propose a strategy for developing fluorescent probes localized to DNA and RNA to investigate their detection and imaging characteristics. The novel probe Bptp-RD has been successfully used for DNA and RNA imaging in cells. We investigated the detection and imaging characteristics of this nucleic acid probe and discovered the following: 1) the differences in the detection results of this nucleic acid probe for DNA and RNA come from the structural differences of the nucleic acids rather than chemical composition differences; 2) through using small-molecule probes to image a nucleic acid in cells, another nucleic acid can be visualized by reducing the fluorescence signal caused by DNA or RNA; 3) the order of response of the small-molecule fluorescent probe with intercalation and binding mechanisms to the type of nucleic acid structure is single chain, double chain, and ring. This work will help improve the understanding of RNA and DNA probes, and the novel probe has high potential to explore the interaction between RNA and DNA in cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel mitochondria-targeted red-emitting fluorescent probe (VP) was synthesized. • The probe VP was used to detect viscosity with high selectivity and sensitivity. • The probe VP could visualize the mitochondrial viscosity change in living cells. • The probe VP was a potential tool for monitoring viscosity and phagocytosis. Mitochondrial viscosity is a critical factor affecting numerous physiological processes, including phagocytosis. Abnormal viscosity in mitochondria is related to some pathological activities and diseases. Evaluating and detecting the changes in mitochondrial viscosity in vivo is crucial. Thus, a mitochondria-targeted red-emitting fluorescent probe (VP) was prepared, and can be used to detect viscosity with high selectivity and sensitivity. The synthesis of probe VP was as simple as two steps and the cost was low. In addition, the fluorescence intensity (log I 615) exhibited an excellent relationship with viscosity (log η) in the range of 0.5 – 2.5 (R2 = 0.9985) in water/glycerol mixture. It is noteworthy that the probe VP displayed the highest signal-to-noise ratio (about 50-fold) for viscosity in water and glycerol system. The probe VP can visualize the mitochondrial viscosity change in living cells. More importantly, phagocytic test for BV2 cells further demonstrated that phagocytosis decreased with increased viscosity. Furthermore, VP was successfully used for monitoring the mitophagy process induced by starvation, and mitochondrial viscosity exhibited enhancement during mitophagy. The probe was a potential tool for studying viscosity and phagocytosis. [ABSTRACT FROM AUTHOR]