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

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]

• 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]

Biothiols, including cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), play key roles in biological processes, and detecting such thiols selectively is critical for understanding functions of biothiols. In this work, a pyridazine annelated perylene–based fluorescent probe PAPC is synthesized for highly selective detection of Cys. PAPC exhibits strong blue emission in PBS, while the red emission at 605 nm can be observed in the presence of Cys. The probe PAPC shows ratiometric fluorescence (I605/I460) detection of Cys with wide linear range of 1–120 μM and low detection limit of 0.19 μM. Super large Stokes shift (170 nm) and ratiometric fluorescence endow the probe low background signal. The discrimination of Cys over Hcy and GSH can be achieved through the difference of the ratiometric fluorescence. In addition, the probe has been proven to track Cys in real samples such as urine and HeLa cells. Therefore, PAPC probe is a promising candidate for detecting Cys in practical application. [ABSTRACT FROM AUTHOR]

Abnormal levels of Cys, Hcy and GSH are associated with various diseases, thus monitoring biothiols is of great significance. In this work, a dual-emission responsive near-infrared fluorescent probe NIR-NBD for detecting Hcy and Cys/GSH was developed based on the conjugation of a dicyanoisophorone based fluorophore (NIR-OH) and 7-nitrobenzofurazan (NBD). To our surprise, the addition of Hcy induced significant fluorescence enhancement at both 549 and 697 nm; while Cys/GSH resulted in major fluorescence emission at 697 nm. The detection limit was determined to be 33.2 nM for Cys, 33.5 nM for Hcy, and 34.4 nM for GSH. Therefore, the probe can be used for discriminative detection of Hcy and Cys/GSH. Moreover, fluorescence imaging of HeLa cells indicated that the probe was cell membrane permeable and could be used for visualizing Hcy and Cys/GSH in living cells. Image 1 • A novel NIR fluorescent probe for discriminative sensing of Hcy and Cys/GSH in dual channel was developed. • The probe can measure Hcy level in serum samples. • The probe could sense intracellular Hcy and Cys/GSH in living HeLa cells. [ABSTRACT FROM AUTHOR]

• A dicyanoisophorone-based fluorescent probe was developed for sensing H 2 S with a large Stokes shift (155 nm). • The probe showed faster time response and high sensitivity for H 2 S. • The probe can be used to detect exdogenous and endogenous H 2 S in living HeLa cells. Due to the importance of hydrogen sulfide (H 2 S) in physiology and pathology, the development of fluorescence probes for the detection of H 2 S has attracted extensive attention of researchers. We developed a H 2 S fluorescence probe (DCN-S) based on dicyanoisopentanone using dithioether and ester groups as the reaction sites. Under the nucleophilic substitution of H 2 S, disulfide bond of DCN-S was broken. Then the probe changed into dicyanoisophorone derivative and emitted an orange fluorescence band from 530 nm to 700 nm (centred 580 nm). Upon response for H 2 S, DCN-S exhibited high sensitivity (88 nM detection limit) and large stokes shift (155 nm). Importantly, the probe also was successfully used for endogenous and exogenous imaging of living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two novel near-infrared fluorescent probes DHX-1 and DHX-2 were designed and synthesized for SO 2 detection and bioimaging. • Fluorescent probes DHX-1 and DHX-2 showed great selectivities, good sensitivities and low cytotoxicities. • Fluorescent probe DHX-2 with a thiazole salt structure exhibited good mitochondria targeting ability. • Fluorescent probe DHX-2 has been successfully applied to the detection of SO 2 in situ imaging of mice. SO 2 and its derivatives play an important role in the antioxidation and anticorrosion of food and medicine. In biological systems, abnormal levels of SO 2 lead to the occurrence of many biological diseases. Hence, the development of suitable tools for monitoring SO 2 in mitochondria is beneficial for studying the biological effect of SO 2 in subcellular organelles. In this research, DHX-1 and DHX-2 are fluorescent probes designed on the basis of dihydroxanthene skeletons. Importantly, DHX-1 (650 nm) and DHX-2 (748 nm) show near-infrared fluorescence response toward endogenous and exogenous SO 2 , which showed advantages of great selectivity, good sensitivity and low cytotoxicity, and the detection limit is 5.6 μM and 4.08 μM of SO 2 , respectively. Moreover, DHX-1 and DHX-2 realized SO 2 sensing in HeLa cells and zebrafish. Moreover, cell imaging demonstrated that DHX-2 with a thiazole salt structure possesses good mitochondria-targeting ability. Additionally, DHX-2 was perfectly achieved by in situ imaging of SO 2 in mice. [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]

[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]

[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]

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]

Biothiols such as cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) play important roles in various physiological and pathological processes. However, it is still a great challenge to selectively detect Cys/Hcy and GSH in biological samples due to the similarity of structures and re-activities of these biothiols. In this paper, a new dual-channel near infrared-7-nitro-1,2,3-benzoxadiazole (NIR-NBD) fluorescent probe has been developed for the discriminative detection of Cys/Hcy and GSH. The probe is composed of two functional parts: a near-infrared dye of dicyanoisophorone, as fluorophore precursor, and NBD as both fluorophore precursor and sensing group. It was observed that NIR-NBD probe displayed two different fluorescent signals in response to biothiols, green-red for Cys/Hcy and red for GSH. It also showed a near infrared emission (756 nm), low detection limit, fast response, high stability, selectivity and sensitivity. Furthermore, NIR-NBD was effectively applied for the discriminative detection of Cys/Hcy and GSH in HeLa cells. Image 1 • A novel dye of dicyanoisophorone derivative was designed and synthesized. • A dual-channel fluorescent NIR-NBD probe was developed for the discriminative detection of Cys/Hcy and GSH. • The NIR-NBD probe was successfully used for imaging Hcy/Cys and GSH in living cells. [ABSTRACT FROM AUTHOR]

A new colorimetric and fluorescence probe NRSH based on Nile-red chromophore for the detection of biothiols has been developed, exhibiting high selectivity towards biothiols over other interfering species. NRSH shows a blue shift in absorption peak upon reacting with biothiols, from 587 nm to 567 nm, which induces an obvious color change from blue to pink and exhibits a 35-fold fluorescence enhancement at 645 nm in red emission range. NRSH displays rapid (<1 min) response for H2S, which is faster than other biothiols (>5 min). The detection limits of probe NRSH towards biothiols are very low (22.05 nM for H2S, 34.04 nM for Cys, 107.28 nM for GSH and 113.65 nM for Hcy). Furthermore, NRSH is low cytotoxic and can be successfully applied as a bioimaging tool for real-time monitoring biothiols in HeLa cells. In addition, fluorescence mechanism of probe NRSH is further understood by theoretical calculations. [ABSTRACT FROM AUTHOR]

A fast-responsive fluorescent probe PI-Py was designed and synthesized for sensitive and selective detecting hypochlorite (ClO−). The probe PI-Py was intrinsically non-fluorescent due to the PET effect of the phenothiazine moiety. After reacting with ClO−, the PET effect was blocked, and a strong green emission of the BODIPY unit was recovered. The probe PI-Py showed an excellent selectivity towards ClO− in comparison of other ROS. The limit of detection for ClO− was calculated to be 1.7 nM, proving the probe's high sensitivity. Moreover, the probe PI-Py has been proved to be effective in visualizing the variations of exogenous ClO− in living HeLa cells. A co-localization study employing Mito Tracker red reveals that the PI-Py is specifically located in the mitochondria. A new BODIPY-based fluorescent probe for ClO− was developed successfully. This probe can be used in visualizing the changes of exogenous ClO− in the mitochondria. Image 1 • A novel BODIPY-based fluorescent probe PI-Py was synthesized. • The probe PI-Py showed an excellent selectivity and sensitivity towards ClO−. • Fluorescent titrations, MS spectra support a PET OFF-ON mechanism. • Living cells imaging for exogenous ClO− located in the mitochondria was observed. [ABSTRACT FROM AUTHOR]

In this study, a mitochondria-specific fluorescent probe for efficient ratiometric detection of Cys was designed and investigated. Probe 1 is composed of a xanthylene skeleton and a benzyl group containing an acryloyl moiety. The probe showed excellent water solubility, good selectivity and sensitivity toward Cys over other analytes, and afforded an extremely low detection limit of 33.7 nM. The possible detection mechanism was ascertained by HRMS analysis. Moreover, probe 1 had excellent mitochondrial-targeting ability (the Pearson's correlation coefficient was 0.96), and was capable of monitoring endogenous Cys in living HeLa cells by dual channel ratiometric bioimaging, demonstrating its significant potential in biological applications. Image 1 • A novel ratiometric and mitochondria-targetability fluorescent probe 1 with a xanthylene skeleton for Cys was developed. • Probe 1 showed excellent water solubility, high selectivity and sensitivity (detection limit of 33.7 nM) towards Cys. • Probe 1 could be successfully used for imaging cellular exogenous and endogenous Cys. [ABSTRACT FROM AUTHOR]

Three 5 H -benzo[a]phenoxazin-5-one-based (benzoresorufin and nile-red) Cysteine (Cys) detection probes have been comparatively designed and synthesized in this paper. The optical experiments exhibit probe 1b with a crotonoyl group has no response toward Cys; while probes 1a and 1c have the same reaction site (acryloyl group), their optical responses to Cys are quite different. The benzoresorufin-based-probe 1a shows a turn-on fluorescence response (118-fold) to Cys at 631 nm and affords a very low detection limit (DL = 19.8 nM). Compared with probe 1a , the nile-red-based probe 1c displays gradually diminishing fluorescence intensity with increased Cys concentration at 665 nm. And the notable different fluorescence response mechanisms of probes 1a and 1c toward Cys can be interpreted by HRMS and time-dependent density functional theorety (TDDFT) calculations. Furthermore, both of the two probes indicate high sensitivity and selectivity toward Cys over other similar structured amino acids including homocysteine (Hcy) and glutathione (GSH). Further cellular applications of the two probes have been successfully performed in HeLa cells. Image 1 • Three Cys probes 1a − c based on benzoxazine (benzoresorufin and nile-red) were comparatively designed, synthesized and investigated, and the mechanism was proposed. • Their different responses to Cys could indicate that the same fluorophore with different auxochrome groups and detection groups have different properties. • Probes 1a and 1c exhibited high selectivity for Cys, and 1a had a low detection limit of 19.8 nM. • Off-on and attenuation response; long emission wavelength; cell imaging. [ABSTRACT FROM AUTHOR]

Detection of glutathione in human serum is of great importance for clinical diagnosis of various diseases, such as AIDS, diabetes mellitus, Alzheimer disease and cancer. In this work, a new water-soluble bismacrocyclic polyamine-derived compound, namely L, which contains two molecules of 4-nitro-1,2,3-benzoxa-diazole as the fluorophores, was designed and prepared. The experiments of selectivity of L toward metal ions showed it could rapidly and sensitively detect Hg2+ with a detection limit of 27 nM. Furthermore, the cell imaging and co-staining experiments in HeLa cells demonstrated that the L-Hg2+ probe had selectivity for the Golgi apparatus to a certain degree. Moreover, it had excellent selectivity for biothiols, especially for glutathione. Finally, the probe was successfully applied to sensitively detect glutathione (GSH) in human serum and fetal bovine serum. We designed and synthesized a novel bimacrocyclic polyamine-based fluorescent probe for sensitive detection of Hg2+ with the LOD of 27 nM. Furthermore, the L -Hg2+ complex was successfully applied to detect GSH in human serum employing standard addition method. Image 1 • A new Hg2+ fluorescent probe L was synthesized and the LOD determined to be 27 nM. • L is a potential subcellular localization probe on Golgi apparatus. • The L -Hg2+ complex was successfully applied to detect glutathione in human serum. [ABSTRACT FROM AUTHOR]

A colorimetric and ratiometric fluorescent probe DTF for HSO 3 − was synthesized from natural and renewable nopinone. The fluorescent probe DTF can quantitatively detect HSO 3 − with high selectivity, sensitivity and fast response time (60 s). The detection process was accompanied with the visible color change from yellow to colorless and the fluorescent color change from green to blue. The fluorescence intensity ratio (F 430 /F 520) was linear with the concentration of HSO 3 − in the range of 0–80 μM, with a limit detection of 79.2 nM. The sensing mechanism was confirmed by 1H NMR and HRMS spectra. Above all, the novel fluorescent probe DTF was successfully applied to determine the concentration of HSO 3 − in food samples and HeLa cells. In this manuscript, we designed and synthesized a novel nopinone-based fluorescence probe for colorimetric and ratiometric detection of HSO 3 −, with high sensitivity, good selectivity and fast response time. The novel probe DTF was successfully applied for detection of the concentration of HSO 3 − in food samples and living HeLa cells. Image 1 • This is the first report that the synthesis of HSO 3 −-specific fluorescence probe based on nopinone. • The colorimetric and ratiometric fluorescent probe DTF can quantitatively detect HSO 3 − with high selectivity, sensitivity and fast response time. • Probe DTF was successfully applied for detection of the concentration of HSO 3 − in food samples and living HeLa cells. [ABSTRACT FROM AUTHOR]