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[Display omitted] • A dual-response fluorescent probe RPT for detecting SO 2 and HClO is synthesized. • The fluorescent probe can monitor SO 2 and HClO with a wavelength difference of 85 nm. • The fluorescent probe has simple synthetic method and is easy to be obtained. • Fluorescent probe can image SO 2 and HClO in living cells (HeLa and RAW 264.7 cells). • Fluorescent probe can detect SO 2 and HClO in various water and food samples. Hypochlorous acid (HClO) and sulfur dioxide (SO 2) play vital roles in various fields, including living organisms, water samples, food and so on. High doses of SO 2 and HClO are seriously harmful to human and are associated with a variety of diseases. Therefore, monitoring the level of SO 2 and HClO in various fields is significant for exploring their roles. In this work, a novel dual-response fluorescent probe RPT for detecting SO 2 and HClO is successfully designed and synthesized, which is composed by pyrylium moiety and thiazine part. The fluorescent probe RPT can respectively monitor SO 2 and HClO by two well-separated emission wavelength with an obvious difference of 85 nm. The fluorescent probe RPT also displays desired properties such as simple synthetic method, high sensitivity and selectivity. In addition, as a biocompatible molecule, RPT has been successfully used for monitoring SO 2 and HClO in HeLa cells and RAW 264.7 cells in two different channels (red channel and green channel). More importantly, SO 2 and HClO levels in various water and food samples have been detected with satisfactory results. [ABSTRACT FROM AUTHOR]

• A novel fluorescent probe DYH was fabricated and characterized. • In CH 3 CN/HEPES (7/3, v/v, HEPES 100 mM pH = 7.3), the probe DYH can continuously detect Cu2+ and S2−. • DYH has a wide linear range and low detection limit for Cu2+ (0.56 μM) and S2− (0.67 μM). • DYH was found useful for imaging of Cu2+ and S2− in living cells. In this paper, a fluorescent probe methyl(E)-2-(3-(benzo[ d ]thiazol-2-yl)-2‑hydroxy -5-methylbenzylidene) hydrazine-1-carboxylate (DYH) based on benzothiazole was designed and synthesized. The characterization involved NMR, HRMS, and crystal structure analysis. In case of the existence of other competing cations, the probe DYH showed high-affinity for Cu2+, and the resultant DYH Cu2+ showed exceptional capacity to recognize S2− in CH 3 CN/HEPES (7/3, v/v, HEPES 0.1 M, pH = 7.3). The detection limits of DYH for Cu2+ and DYH Cu2+ for S2− were 0.56 μM and 0.67 μM, respectively. It was determined that the binding stoichiometry between the DYH and Cu2+, as well as DYH Cu2+ and S2−, was 1:1 according to the job's curve. The pH of the probe and complex was stable between 4 and 10. Colorimetric experiments of the probe DYH were conducted using test paper as a carrier. Additionally, DYH was used for fluorescence imaging of Cu2+ and S2− in Hela cells with poor cellular toxicity and good cell permeability. [Display omitted] [ABSTRACT FROM AUTHOR]

Accurate detection of Cysteine (Cys) in cells is critical for clinical diagnosis and pathogen detection. It was of practical significance to develop fluorescent probes with specific recognition and rapid detection of Cys. Therefore, based on the nucleophile reaction and intramolecular cyclization reaction between biothiols and acrylates (AAS), a fluorescence probe, BTY-TPE-AAS , was designed and synthesized by combining the advantages of the Aggregation-Induced Emission (AIE) and Excited-State Intramolecular Proton Transfer (ESIPT) mechanisms. BTY-TPE-AAS could specifically detect Cys with a short detection time and strong anti-interference, which had important application value in the monitoring of Cys in the biomedical field. It provided some reference values for the design of a specific fluorescent probe for Cys detection. BTY-TPE-AAS was a chemical that combines tetraphenylethylene and benzothiazole via Suzuki coupling and employs acrylic ester (AAS) as the recognition site to detect Cys. The dual mechanism of "AIE + ESIPT" was discovered by examining BTY-TPE-AAS 's crystal structure, and BTY-TPE-AAS 's Stokes shift in pure DMF solution was higher than 200 nm, proving that the probe was not impacted by the self-fluorescence signal. The probe has high anti-interference properties, good Cys selectivity, and low toxicity, which allowed it to be used for cell imaging in HeLa cells. [Display omitted] • An "AIE-ESIPT" double-mechanism fluorescent crystals have been synthesized. • The relationship between BTY-TPE-AAS crystal and AIE properties is discussed. • BTY-TPE-AAS can identify and distinguish Cys in a short time and has a low detection limit. • BTY-TPE-AAS could detect Cys in 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]

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]

[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]

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 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] • Probe FBC-DS performed sufficient selectivity, fast response time, high sensitivity and a large Stokes shift to HClO. • FBC-DS was applied for imaging of exogenous and endogenous HClO in living HeLa cells and zebrafish with satisfactory performances. • FBC-DS was applied for corroborating that HClO could be an efficient marker for APAP-induced hepatotoxicity in the mice liver injury models. Drug-induced liver injury (DILI), as a classic acute inflammation, has attracted widespread concern due to its unpredictability and severity. Among the various reactive oxygen species, HClO has been used as a marker for the detection of DILI process. Thus, we designed and synthesized a "turn-on" fluorescent probe FBC-DS by modifying 3'-formyl-4'-hydroxy-[1,1'-biphenyl]-4-carbonitrile (FBC-OH) with N, N-dimethylthiocarbamate group for sensitively sensing HClO. Probe FBC-DS showed a low detection limit (65 nM), fast response time (30 s), an enormous Stokes shift (183 nm) and 85-fold fluorescence enhancement at 508 nm in the detection of HClO. Probe FBC-DS could monitor exogenous and endogenous HClO in living HeLa cells, HepG2 cells and zebrafish. In addition, probe FBC-DS has been successfully utilized in biological vectors for imaging acetaminophen (APAP)-induced endogenous HClO. Moreover, DILI caused by APAP is evaluated by probe FBC-DS through imaging over-expression of endogenous HClO in the mice liver injury models. All in all, we have every reason to believe that probe FBC-DS can be a potential tool to study the complex biological relationship between HClO and drug-induced liver injury. [ABSTRACT FROM AUTHOR]

[Display omitted] • A fluorescent probe was synthesized based on benzopyran-chromone for detection of ONOO−. • The probe shows short response time for ONOO− (<30 s). • The probe shows specifically selectivity and a very low detection limit of 22.4 nM for ONOO−. • The probe can accurately identify endogenous and exogenous ONOO− in HeLa cells. Peroxynitrite is widely present in organisms and closely related to many pathophysiological functions. Therefore, it is of great physiological significance to develop capable probes for detecting ONOO−. In this work, a novel fluorescent probe B-Ch was designed based on the intramolecular charge transfer (ICT) effect. By means of molecular engineering, the replacement from diethylamine group to hydroxyl group has improved the detection sensitivity of the probe. After the addition of ONOO−, the solution color and fluorescence showed noticeable changes, which were visible to the naked eye. The probe showed excellent advantages: visualization, good selectivity, low sensitivity (22.4 nM), good stability and biocompatibility, exogenous and endogenous imaging of ONOO− in HeLa cells. [ABSTRACT FROM AUTHOR]

A probe TR-NOOO- was employed for tracking ONOO– level during Erastin-induced ferroptosis. [Display omitted] • A novel fluorescent probe TR-ONOO- based on tetraphenylene derivatives and rhodamine analogs was constructed. • Probe TR-ONOO– showed high selectivity and rapid sensing for ONOO–. • The probe could image ONOO– in living cells during erastin-induced ferroptosis. The reactive nitrogen species peroxynitrite (ONOO–) involve physiological and pathological processes as a significant factor. Develop a probe for monitoring the ONOO– during ferroptosis is very significant. Here, we designed and synthesized a probe TR-ONOO– based on tetraphenylene derivatives and rhodamine analogs for detection of ONOO– with fluorescence-on. Considering the strong oxidative properties of ONOO–, the carbon–carbon double bonds of bridged tetraphenylene derivatives and rhodamine analogs in the TR-ONOO– molecule are oxidized, so that the designed probe can realize fluorescence turn-on. When adding the ONOO– to the probe TR-ONOO– solution, the fluorescence intensity has increased about 40 folds and the color changed from purple to light yellow, enabling naked-eye detection of ONOO–. Furthermore, the probe TR-ONOO– can recognize ONOO– with high selectivity and fast response time. Combining with fluorescence imaging, TR-ONOO– was successfully employed for tracking endogenous ONOO– real-time and the over expression of ONOO– was effectively visualized during erastin-induced ferroptosis. [ABSTRACT FROM AUTHOR]

A dual-site multifunctional fluorescent probe for selective detection of endogenous H 2 O 2 and SO 2 derivatives based on ICT process and its bioimaging application. [Display omitted] • A dual-site multifunctional probe was designed for detection of endogenous H 2 O 2 and SO 3 2−. • The sensing mechanism was confirmed by 1H NMR and theoretical calculation data. • The probe was successfully used for bioimaging of endogenous H 2 O 2 and SO 3 2−. In this paper, we reported a coumarin-based fluorescent probe for selective detection of H 2 O 2 /SO 2 derivatives via ICT process. To the best of our knowledge, it was few reported with the same probe to enable visual detection of H 2 O 2 /SO 2 derivatives in vivo and in vitro. H 2 O 2 and SO 3 2− were selectively sensed over other analytes, and the probe displayed 20-fold and 220-fold relative fluorescence intensity respectively, as well as the good linear relationship and the excellent detection limits of 2.7 * 103 nM and 19.3 nM. Furthermore, the probe was successfully used for fluorescence imaging of the HeLa cells and the mice to monitor exogenous and endogenous H 2 O 2 and SO 3 2−, suggesting its potential biomedical application for investigation and detection the intermediate indicator of oxidative stress in vitro and in vivo. [ABSTRACT FROM AUTHOR]

In this study, a fluorescent probe-encapsulated reduction-sensitive smart nanohydrogel as a new nanosensor was fabricated. The nanohydrogel was prepared via distillation-precipitation polymerization by using N, N ′-bis(acryloyl) cystinamide both as the monomer and crosslinker. Besides, red fluorescent hydrophobic peroxyresorufin-1 (PR1) probe for H 2 O 2 was employed and encapsulated into the nanohydrogel. We found that the nanohydrogel not only can encapsulate a large number of hydrophobic fluorescent probes with high loading capacity, but also can avoid the aggregation of hydrophobic fluorescent probes. Confocal laser fluorescence imaging of H 2 O 2 in HeLa cells demonstrated that the PR1-encapsulated nanohydrogel allows efficient delivery of PR1 probe into living HeLa cells. In cytoplasm, the nanohydrogels reduced and degraded by glutathione, and the PR1 probes released from the nanohydrogel were enriched and concentrated in some local regions, resulting in enhanced imaging of endogenous H 2 O 2. This work provides a facile nanohydrogel-assisted probe-encapsulation strategy, which is also applicable to multiple fluorescent probes, thus enabling imaging of diverse endogenous bioactive molecules. [Display omitted] • A new fluorescent probe-encapsulated nanohydrogel (PR1@nanogel) was fabricated. • The nanohydrogel possess reduction-sensitivity. • The nanohydrogel can avoid the aggregation of fluorescent probes. • Imaging of endogenous H 2 O 2 in HeLa cells with the PR1@nanogel was achieved. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel dual-site fluorescent probe (MTRN) for HClO and H 2 S was constructed by combining naphthalimide fluorophore with rhodamine fluorophore. • The detection limits (LOD) for HClO and H 2 S were calculated to be 3.39 nM and 0.13 μM, respectively. • MTRN was successfully exploited for detecting HClO and H 2 S in cell imaging and test strip. HClO and H 2 S commonly coexist in organisms and act synergistically to maintain the redox dynamic balance in vivo; however, it is difficult to trace precisely and simultaneously HClO and H 2 S by single recognition-type fluorescent probes. In this paper, a novel probe (MTRN) was designed for detecting specifically HClO and H 2 S with dual-emission property by using an acrylate and a phenyl isothiocyanate as recognition sites. MTRN possessed outstanding performances including ultrasensitivity (LOD = 3.39 nM), high specificity and short response time (<2 min) for HClO under excitation of 530 nm with the fluorescence's color change from dark to red. Moreover, upon treating with H 2 S, the fluorescence peak centered at 488 nm of MTRN enhanced obviously within 1 min and color changed from colorless to blue, the LOD was found to be 0.13 µM. The possible reaction mechanism for HClO and H 2 S in CH 3 CN/PBS (9/1, v/v) was substantiated via 1H NMR and HRMS. Above all, MTRN was successfully used to detect HClO and H 2 S in HeLa cells and made into test strips to detect HClO and H 2 S. [ABSTRACT FROM AUTHOR]

Three fluorescent probes (NAP-a , NAP-b and NAP-c) of oxime compounds were synthesized for specific labeling of lipid droplets, which have the advantages of low background and high photostability. [Display omitted] • 1,8-naphthalimide fluorescent probes NAP-a NAP-b and NAP-c were used for LDs imaging. • Oxime fluorescent probe was successfully used to label LDs. • The probes were successfully used for lipid droplet imaging in cells and zebrafish. • This work achieved the first specific labeling of lipid droplets with oxime compounds. Fluorescent probes can facilitate our further comprehension of the functional and physiological roles of LDs and thus promote the development of effective therapeutic approaches. Oxime compounds are widely used due to their good crystallinity and high reactivity. However, the majority oximes fluorescent probes are usually employed for the detection of HCIO, and the application of oximes in fluorescently labeled LD S is poorly reported. In this paper, three kinds of LDs fluorescent probes (NAP-a , NAP-b and NAP-c) with D-π-A structure were synthesized by simple synthesis method with 1,8-naphthalimide as fluorescent matrix and oxime group as electron donor. These probes were highly sensitive to polarity, and possessed good photostability and low cytotoxicity. Co-staining experiments showed that these probes could target LDs and the fluorescence image was green. These probes NAP-a , NAP-b and NAP-c possessed high Pearson coefficient (HeLa cells: 0.91, 0.95, 0.86) and Manders coefficient (HeLa cells: 0.91, 0.96, 0.86) with Nile Red. Interestingly, the dynamic variations in their size, shape and distribution could be clearly observed in the oleic acid-treated cell model of LDs. Imaging of zebrafish was performed and green fluorescence was collected in zebrafish. These excellent properties make oxime compound fluorescent probes a promising fluorescent probes for studying LDs and metabolic diseases. This study opens up a new way for the preparation of LDs fluorescent probe. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel fluorescent probe, COZ-DNB , for sensitive detection of H 2 S was developed. • Probe COZ-DNB performed sufficient selectivity, rapid detection, high sensitivity and a large Stokes to H 2 S. • COZ-DNB was applied for imaging of exogenous and endogenous H 2 S in living HeLa cells and zebrafish with satisfactory performances. Recent medical studies have confirmed that endogenous H 2 S serves as the third gas-messenger besides nitric oxide (NO) and carbon monoxide (CO), which is produced by enzyme-catalyzed metabolism of cysteine and takes part in multiple physiological processes. The abnormal levels induced by H 2 S overproduction in mammals can destroy tissues and organ systems, which lead to certain serious diseases, such as neurodegenerative diseases, cardiovascular diseases, and various cancers. In this work, we developed a novel coumarin-carbazole fluorescent probe COZ-DNB with yellow emission and a large Stokes shift for H 2 S detection. In probe COZ-DNB , the newly dye COZ-OH as a luminophore and the 2,4-dinitrophenyl ether moiety was chosen as a trigger group for H 2 S. Probe COZ-DNB itself displayed nearly non-fluorescent. However, COZ-DNB gave the remarkable fluorescence with an 83-fold enhancement in the yellow region after interaction with H 2 S. The sensing mechanism of COZ-DNB toward H 2 S was checked by means of UHPLC, HRMS and DFT/TD-DFT calculations. What's more, probe COZ-DNB also exhibited fast response (2.0 min), high sensitivity (65.0 nM), a large Stokes shift (161.0 nm), high stability and excellent selectivity. Furthermore, COZ-DNB was applied for imaging of exogenous and endogenous H 2 S in living HeLa cells and zebrafish with satisfactory performances. We anticipate COZ-DNB would be served as a potential tool for investigating the biological functions of H 2 S in pathological processes. [ABSTRACT FROM AUTHOR]

[Display omitted] • SEMA-1 is the first benzoselenazolium-based hemicyanine for G-quadruplex detection. • SEMA-1 has potential to detect nucleolar and mitochondrial G-quadruplexes in cells. • Benzoselenazolium-based hemicyanine is a valuable scaffold for probe design. Benzothiazolium and benzoxazolium are common groups for the construction of hemicyanine dyes; however, their isosteric analogue benzoselenazolium have rarely been studied. Here, we report the development of the first benzoselenazolium-based hemicyanine dye for the selective detection of G-quadruplexes. This molecule, SEMA-1 , was validated as a red-emitting and activatable fluorescent probe whose fluorescence would only be activated in the presence of G-quadruplexes in buffer solution. Consistent with this, SEMA-1 was found to accumulate in nucleoli and could be used to detect the high abundance of nucleolar rDNA and rRNA G-quadruplexes in fixed HeLa cells. On the other hand, due to the retained mitochondrial membrane potential in live HeLa cells, SEMA-1 was captured by mitochondria and had the potential to detect the mitochondrial G-quadruplexes. Collectively, this work demonstrates the value of developing G-quadruplex-specific fluorescent probes from novel benzoselenazolium-based hemicyanine scaffold. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two monothiosquaraine based fluorescent probes of Hg2+ have been constructed. • Hydrogen bonding assisted Hg2+-specific desulfurization has been used in Hg2+ sensing. • The fluorescent probes show excellent selectivity and high sensitivity. • They have been applied in environmental samples and high contrast living cell imaging. • The sensing mechanism has been discussed. Mercury (Hg) is an exceedingly toxic heavy metal which leads to grievous nonbiodegradable contamination and human health threat. Thus, developing a practical, quick, effective and labor-saving method for detecting Hg2+ is of great significance. In this study, we rationally design two novel near-infrared (NIR) monothiosquaraine-based probes MTSQ-1 and MTSQ-2 for tracking and bioimaging of Hg2+ with the mercury-desulfurization strategy. MTSQ-1 and MTSQ-2 show ultrahigh sensitivity, superb selectivity and rapid response for spotting of Hg2+ in vitro. We find that it is the intramolecular hydrogen bond between the carbonyl oxygen of the squaraine core and the ortho -hydroxyl substituent of the anilinyl moiety that promotes the desulfurization of the probes, inducing enhanced fluorescence emission. Related sensing mechanism has been fully discussed through experimental methods and theoretical calculations. Meanwhile, MTSQ-1 has been used in detection of Hg2+ in river samples, and MTSQ-2 encapsulated in β-CD possesses good ability for imaging of Hg2+ in HeLa cells with high signal-to-background ratio. [ABSTRACT FROM AUTHOR]

Acrolein is a highly toxic agent that can be generated exogenously and endogenously. Therefore, a highly specific and sensitive probe for acrolein with potential applications in acrolein detection must be developed. In this research, a novel fluorescent probe named "probe for acrolein detection" (Pr-ACR) was designed and synthesized based on a naphthalimide fluorophore skeleton, and a thiol group (-SH) was introduced into its structure for acrolein recognition. The -SH traps acrolein via Michael addition and the resultant interaction product of the probe inhibits the photoinduced electron transfer process and produce a strong fluorescence at 510 nm. The probe showed high sensitivity and specificity for acrolein. HPLC-MS/MS analysis verified that it can be used to quantify acrolein in foods, such as soda crackers, red wine, and baijiu, with a fluorescence spectrophotometer. After methyl esterification, the methyl esterified probe (mPr-ACR) successfully visualised acrolein in Hela cells under a laser scanning confocal microscope. This finding proved that Pr-ACR and mPr-ACR are potential tools for the detection and visualisation of acrolein from different sources. [Display omitted] • A napthalimide-based fluorescent probe was developed for sensitive detection of acrolein. • It recognized acrolein through thiol participation in Michael addition. • It was used to quantitatively determine acrolein in different foods. • It successfully tracked acrolein in Hela cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel developed fluorescent probe was synthesized for subsequen detection of Al3+and PPi. • The fluorescent sensing properties can be achieved in almost 100% aqueous medium. • The detection limits of the probe 1 for Al3+ and PPi were 35.7 and 76.0 nM, respectively. • Probe 1 was successfully applied to the detection of Al3+ and PPi in lysosomes of HeLa cells. A simple hydrazone probe (1) was designed and synthesized for the successive detection of Al3+ and pyrophosphate (PPi) in almost 100% buffer environment. The probe provided O 2 N donor set for chelation with Al3+, leading to a distinct fluorescence boost at 510 nm. The in-situ formed 1 -Al3+ complex detected PPi with an "on-off" behavior. The detection limits for Al3+ and PPi were 35.7 nM and 76 nM, respectively. Benefiting from the existence of morpholine as lysosome-targeting group, probe 1 was successfully applied to the detection of Al3+ and PPi in lysosomes. [ABSTRACT FROM AUTHOR]

Giving the fact that mercury ions (Hg2+) is highly toxic, migratory and bioaccumulative and even very small quantities of mercury can cause serious damage to health problems, resulting in many diseases, such as abdominal pain, renal failure, nervous system damage. The content of mercury in drinking water quality standard of our country has been strictly limited, and the maximum allowable concentration should not exceed 0.001 mg/L. (EPA) of the United States Environmental Protection Agency defines the maximum allowable limit of inorganic mercury in drinking water as 10 nM. In this study, a novel fluorescent probe based on isophoronitriles scaffold, DNC-Hg , was designed and synthesized for monitoring mercury ion in living HeLa cells. The probe exhibited good selectivity and stability, large Stokes shift(174 nm) and low cytotoxicity. Furthermore, this stable probe DNC-Hg could be used for cellular imaging. [Display omitted] • A novel and stable fluorescent probe based on isophoronitriles scaffold was designed and synthesized for monitoring mercury ion. • The probe exhibited good selectivity and stability, large Stokes shift (174 nm) and low cytotoxicity. • The stable probe DNC-Hg could be used for cell imaging. Giving the fact that mercury ions (Hg2+) is highly toxic, migratory and bioaccumulative and even very small amounts of mercury can cause serious damage to health, resulting in many diseases, such as abdominal pain, renal failure, nervous system damage. The content of mercury in drinking water quality standard of our country has been strictly limited. Therefore, it is of good research interest to develop a stable fluorescent probe capable of detecting the presence of mercury in biological cells. In this study, a novel fluorescent probe based on isophoronitriles scaffold, DNC-Hg , was designed and synthesized for monitoring mercury ion in living HeLa cells. The good properties of the probe may be attributed to the unique strong electron-absorbing group in the structural design, the good conjugation effect, and the mature Hg2+ recognition site. The probe exhibited good selectivity and stability, large Stokes shift(174 nm) and low cytotoxicity. Furthermore, this stable probe DNC-Hg could be used for cellular imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of 1,1′-((1E,1′E)-((4,5-dimethyl-1,2-phenylene)bis(azaneylylidene))bis(methaneylylidene))bis(naphthalen-2-ol) (PAMN). • Spectroscopic and photochemical investigations of PAMN. • PAMN exhibited a high sensitivity and selectivity toward Al3+ in DMSO-H 2 O (1:1 v/v, pH = 7.20) by forming a 1:1 complex with Al3+ ion. • PAMN was valid for fluorescence imaging of Al3+ in the Hela cell lines. A novel efficient fluorescent probe 1,1′-((1E,1′E)-((4,5-dimethyl-1,2-phenylene)bis(azaneylylidene))bis(methaneylylidene))bis(naphthalen-2-ol) (PAMN) for the recognition of Al3+ was synthesized and extensively characterized using various physicochemical techniques. Free PAMN fluoresced weakly, but when aluminium added, it fluoresced dramatically against various metal ions. The recognition process was relied mainly on the chelation-controlled C=N isomerization combined with an inhibition of the excited-state intramolecular proton transfer (ESIPT). The energies of both HOMO and LUMO for PAMN and PAMN-Al3+ complex were estimated by DFT calculations to elucidate the configuration of the complex. PAMN coordinated with Al3+ in [1:1] stoichiometry with an association-constant of 2.18 × 105 M−1. Upon coordination with Al3+ ions , PAMN displayed a good linear relationship in extremely low concentrations with a limit of detection of 7.05 × 10−9 M. The living-HeLa-cell imaging displayed that the probe had excellent cell membrane permeability, with great potential for intracellular Al3+ ion tracing via the fluorescence imaging technique. [ABSTRACT FROM AUTHOR]

Understanding the complex relationship between active small molecules is of great significance in various physiological processes. Herein, we present the design and synthesis of a sequential responsive Lysosome-Naphthalene imide-Azido (lyso-NP-N 3) reporter for probing the H 2 S and HOBr within organelle (lysosome) in living cells. Probe lyso-NP-N 3 exhibited high selectivity and sensitivity towards H 2 S (LOD = 23.5 nM) and HOBr (LOD = 254 nM). Additionally, lyso-NP-N 3 possessed an excellent lysosome targeting ability and was utilized to visualize the exogenous/endogenous H 2 S and HOBr in RAW 264.7, Hela and HepG2 cells. Facilitated by this sequentially activated mechanism, the probe was successfully applied to confirm that the reported scavenger of HOBr, N-acetyl-L-cysteine (NAC) mainly relied on its metabolite H 2 S to eliminate excess HOBr, thereby playing the role of cell regulation and protection. These results establish the crosstalk between H 2 S and HOBr in lysosome and provide a promising tool to study metabolite interactions. [Display omitted] • A lysosome-targetable fluorescent probe lyso-NP-N 3 was developed for sensitive detection of H 2 S and HOBr sequentially. • The lyso-NP-N 3 was utilized to visualize the exogenous/endogenous H 2 S and HOBr in RAW 264.7, Hela and HepG2 cells. • It verified that N-acetyl-L-cysteine mainly relied on its metabolite H 2 S to eliminate excess HOBr. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fluorescent probe VA for the detection of esterase in living cells was synthesized. • Probe VA has good biocompatibility and high resolution. • Probe VA can judge the unhealthy state of H 2 O 2 -induced living cells. Esterase activity is often used as an index to evaluate the health status of cells and plays an important role in cell metabolism and apoptosis. Herein, we develop two fluorescent probes for visual biosensing of esterase activity and imaging in living cells. In vitro, after the introduction of esterase, enzymolysis destroys the ester bond of the probe, causing the fluorescent color of probe changes from yellow to red, thus realizing the visual strategy for determination of esterase activity, with high sensitivity and selectivity. Especially, probe VA, 2-(4-acetoxystyryl)-3-ethyl-1,1-dimethyl- 1H-benzo[e]indol-3-ium, exhibits higher sensitivity with a lower detection limit (up to 7.15 × 10-6 U/mL). In the cell experiment, the fluorescent probe VA also shows good biocompatibility and high spatial resolution, and is successfully applied to the intracellular fluorescent imaging and biosensing of esterase in living cells. More importantly, the probe VA can judge the unhealthy state of H 2 O 2 -induced HeLa cells using dual-fluorescence signals. The results confirm that the fluorescence method is a reliable tool for detecting endogenous esterase in living biological system. [ABSTRACT FROM AUTHOR]

A fluoran-phenothiazine hybrid fluorescent probe for selective sensing of Fe3+ and ClO− has been rationally designed and prepared with application in fluorescence imaging. [Display omitted] • A fluoran-phenothiazine hybrid fluorescent probe FP has been designed and prepared. • FP shows high selectivity and sensitivity towards Fe3+ and ClO− by dual emission. • The low cytotoxicity allows FP to trace intracellular Fe3+ by cell imaging. Bifunctional fluorescent probes with dual-emission response attract extensive attention. A novel fluorescent probe FP , a hybrid of fluoran and phenothiazine, has been designed and synthesized for selective sensing of Fe3+ and ClO− with dual-emission changes, which involes mechanisms of Fe3+-promoted spirolactone ring opening and ClO−-induced oxidation of phenothiazine moiety, respectively. In addition, the detection limits for Fe3+ and ClO− were estimated to be 49.1 and 35.9 nM, respectively. Significantly, FP can be employed as an tracer for the detection of Fe3+ ions within living HeLa cells by fluorescence imaging. [ABSTRACT FROM AUTHOR]