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

Fluorometric determination of different biologically, industrially, and environmentally important analytes is a powerful technique because this technique has excellent selectivity, high sensitivity, rapid photoluminescence response, low cost, applicability to bioimaging, and low detection limit. Fluorescence imaging is a powerful technique for screening different analytes in the living system. Heterocyclic organic compounds have been extensively used as a fluorescence chemosensor for the determination of different biologically important cations like Co2+, Zn2+, Cu2+, Hg2+, Ag+, Ni2+, Cr3+, Al3+, Pd2+, Fe3+ Pt2+, Mn2+, Sn2+, Pd2+, Au3+, Pd2+, Cd2+, Pb2+ and other ions in biological and environmental systems. These compounds also showed significant biological applications such as anti-cancer, anti-ulcerogenic, antifungal, anti-inflammatory, anti neuropathic, antihistaminic, antihypertensive, analgesic, antitubercular, antioxidant, antimalarial, antiparasitic, antiglycation, antiviral anti-obesity, and antibacterial potency. In this review, we summarize the heterocyclic organic compounds based on fluorescent chemosensors and their applications in bioimaging studies for the recognition of different biologically important metal ions. [ABSTRACT FROM AUTHOR]

Detecting circulating tumor cells has exhibited great significance in treating cancers since its concentration is an index strongly associated with the development and transfer of the tumor. However, the present commercial method for CTC detection is still expensive, because special antibodies and complicated devices must be used for cell separation and imaging. Hence, it is quite necessary to apply alternative materials and methods to decrease the cost of CTC detection. In this article, we coated a cellulose acetate membrane with nanoparticles formed by the polymerization of melamine and furfural, creating a surface with nanoscale roughness for the highly efficient capture of the sparse CTCs in a blood sample. Subsequently, the CTCs on the surface can be quantitatively detected by colorimetry with the aid of a COF-based nanozyme. The detection limit (LOD) can be as low as 3 cells/mL, which is the lowest LOD among the colorimetric methods to our knowledge. Considering the low cost of fabricating the membrane for CTC capture and the robustness of nanozymes compared with natural enzymes, this CTC detection approach displays great potential to decrease the financial burden of commercial CTC detection. [ABSTRACT FROM AUTHOR]

Abstract Herein we have reported a fluorescent probe (MB-M) based on MB derivative for Cu2+ ions detection. The probe was well characterized by 1H NMR, 13C NMR and HR-MS spectrum. Probe MB-M showed naked-eyes recognition to Cu2+ as color change from colorless to indigo. The probe exhibited promising features such as high fluorescence and UV–vis selectivity, fast response (5 mint), workable at pH 2–7, and low limit of detection (LOD = 0.33 µM). Probe MB-M was also used for Cu2+ ions imaging in HepG-2 cells and detection in daily life (Test Strip and lake water). Moreover, non-covalent interaction (NCI) and quantum theory of atoms in molecules (QTAIM) analysis were used to study the interaction between MB-M and Cu2+ ions. By examining the electronic characteristics of the complex using natural bond orbital (NBO), electron density difference (EDD), and frontier molecular orbital (FMO) analysis, the sensitivity of MB-M towards Cu2+ ions were investigated. The results illustrated that the interactions between MB-M and Cu2+ ions involved chemisorption.

Herein we have reported a fluorescent probe (MB-M) based on MB derivative for Cu2+ ions detection. The probe was well characterized by 1H NMR, 13C NMR and HR-MS spectrum. Probe MB-M showed naked-eyes recognition to Cu2+ as color change from colorless to indigo. The probe exhibited promising features such as high fluorescence and UV–vis selectivity, fast response (5 mint), workable at pH 2–7, and low limit of detection (LOD = 0.33 µM). Probe MB-M was also used for Cu2+ ions imaging in HepG-2 cells and detection in daily life (Test Strip and lake water). Moreover, non-covalent interaction (NCI) and quantum theory of atoms in molecules (QTAIM) analysis were used to study the interaction between MB-M and Cu2+ ions. By examining the electronic characteristics of the complex using natural bond orbital (NBO), electron density difference (EDD), and frontier molecular orbital (FMO) analysis, the sensitivity of MB-M towards Cu2+ ions were investigated. The results illustrated that the interactions between MB-M and Cu2+ ions involved chemisorption. [ABSTRACT FROM AUTHOR]

Cuprous ions (Cu+) are essential for various biological activities. However, it is still a great challenge to detect Cu+ efficiently in cells in situ. As emerging 0‐D carbon photoluminescence nanomaterials, carbon dots (CDs) exhibit non‐toxicity and ultra stability, which shows great advantages in biosensing and bioimaging. In this work, CDs are prepared by a one‐step microwave‐assisted hydrothermal method. To enhance the selectivity and efficiency of the CDs‐based sensor, the NS4‐CDs are synthesized by surface modification of CDs using Cu+ chelating molecules. The NS4‐CDs, that carry specific detection molecules, exhibit remarkable selectivity and high sensitivity with an extraordinarily low detection limit (26 nmol L−1). It is noteworthy that the detection response is extremely fast, which only takes 20 s. The PL response mechanism of NS4‐CDs is also thoroughly investigated. In addition, the NS4‐CDs possess great biocompatibility and non‐cytotoxicity, which is vital for advanced cellular imaging applications. Finally, the NS4‐CDs are successfully applied to Cu+ detection in cells in situ. This work paves a new path for the design and efficient construction of CDs‐based biosensors for ion detection in cells, which expands the application area of carbon nanomaterials. [ABSTRACT FROM AUTHOR]

Hemicyanine dyes are an ideal structure for building near-infrared fluorescent probes due to their excellent emission wavelength properties and biocompatibility in biological imaging field. Developing a near-infrared fluorescent probe capable of detecting cysteine (Cys) was the aim of this study. A novel developed fluorescent probe P showed high selectivity and sensitivity to Cys in the presence of various analytes. The detection limit of P was found to be 0.329 μM. The MTT assay showed that the probe was essentially non-cytotoxic. Furthermore, the probe was successfully used as cysteine imaging in living cells and mice. [ABSTRACT FROM AUTHOR]

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

Ferric ion (Fe3+) serves as an essential and indispensable inorganic element in various biological process. Excess Fe3+ is harmful for biological systems and human health. Herein, highly sensitive carbon quantum dots (Fe-CQDs) for ferric ions were synthesized by a high-efficiency, one-step hydrothermal route utilizing L-arginine and citric acid. The prepared Fe-CQDs exhibited good water solubility, high photostability, and bright blue florescence with relatively high quantum yields (QYs) over 21.33% and a Stokes shift exceeding 100 nm. The functionalized Fe-CQDs offer rapid, sensitive, and selective recognition of Fe3+ with a linear relationship from 0.6 to 80 μM and a low detection limit of 0.2 μM. Moreover, the synthesized Fe-CQDs illustrated strong anti-interference properties in samples and buffer solutions. The developed sensor demonstrated high biocompatibility and was successfully applied for intracellular Fe3+ determination in SHSY5Y and HT22 cells, illustrating excellent imaging application. The present work provides a promising platform for the early clinical diagnosis of Fe3+-associated diseases. [ABSTRACT FROM AUTHOR]

Hypochlorite is a kind of endogenously produced reactive oxygen species (ROS) in the human immune system and plays a crucial role in many pathophysiological processes. In this work a novel fluorescent probe derived from 6‐methylthio coumarin was designed and synthesised for detection of hypochlorite in acetonitrile/phosphate‐buffered saline (MeCN/PBS) (1:1, v/v, pH 7.4) medium. The probe displayed high specificity toward hypochlorite over other ROS analytes, rapid response to hypochlorite within 30 s, and a broad applicable range of pH 3–8. The detection limit was calculated to be 1.48 μM. Application of this probe for in vitro Hecat cell imaging to detect hypochlorite ions was confirmed. A sensing mechanism based on thioether to sulfoxide oxidation by hypochlorite was proposed and demonstrated. The study presented an effective approach for construction of highly efficient hypochlorite chemosensors from hydrophilic methylthio‐substituted coumarins considering their facile access. [ABSTRACT FROM AUTHOR]

This article presents the distinctive butyrylcholinesterase (BChE) fluorescent probe P5, designed via a targeting-site method. This method was proposed to enhance the affinity of the probe for BChE by targeting the peripheral anionic site (PAS) of BChE. By mimicking the natural substrate butyrylcholine, the structure of the probe was optimized by introducing a positive charge. Fluorescent probe P5, selected from a series of designed fluorescent probes P1–P6, exhibited excellent affinity and specificity towards BChE, enabling rapid detection within 5 min with a low detection limit of 16.7 ng/mL. Furthermore, this probe can distinguish between normal cells and Alzheimer's disease (AD) model cells, and demonstrated good imaging results in a P12 cell AD model. The results of this study indicate that this novel fluorescent probe could serve as a promising tool for the rapid detection of BChE and accurate AD diagnosis. [ABSTRACT FROM AUTHOR]

A fluorogenic aptamer (FA)-based hybridization chain reaction (HCR) could provide a sensitive and label-free signal amplification method for imaging molecules in living cells. However, existing FA-HCR methods usually face some problems, such as a complicated design and significant background leakage, which greatly limit their application. Herein, we developed an FA-centered HCR (FAC-HCR) method based on a remote toehold-mediated strand displacement reaction. Compared to traditional HCRs mediated by four hairpin probes (HPs) and two HPs, the FAC-HCR displayed significantly decreased background leakage and improved sensitivity. Furthermore, the FAC-HCR was used to test a non-nucleic acid target, apurinic/apyrimidinic endonuclease 1 (APE1), an important BER-involved endonuclease. The fluorescence analysis results confirmed that FAC-HCR can reach a detection limit of 0.1174 U/mL. By using the two HPs for FAC-HCR with polyetherimide-based nanoparticles, the activity of APE1 in living cells can be imaged. In summary, this study could provide a new idea to design an FA-based HCR and improve the performance of HCRs in live cell imaging. [ABSTRACT FROM AUTHOR]

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

A water‐soluble polymeric pyrene‐based polythioacetal (PTA‐Py) with thioacetal units in the main chain is simply synthesized by direct polycondensation of 3, 6‐dioxa‐1, 8‐octanedithiol, 1‐pyrene formaldehyde, and mPEG2k‐SH. The probe PTA‐Py shows a good fluorescence response to Hg2+ ions due to the Hg2+‐promoted deprotection reaction of thioacetal groups to regenerate the original 1‐pyrene formaldehyde compound. After adding Hg2+ to the PTA‐Py solution, the fluorescence intensity (FI) gradually increases with increasing concentrations of Hg2+. Compared with other metal ions, the probe exhibits high sensitivity, good selectivity, and rapid response to Hg2+. The low detection limits are 12.3 nm in ethanol‐PBS buffer and 13.3 nm in water, respectively. The results imply that the simply synthesized water‐soluble polymeric probe had potential applications in the rapid detection of Hg2+ ions in aqueous solutions. Moreover, the polymeric PTA‐Py shows high sensitivity for CH3Hg+ with detection limits of 26.5 nm in ethanol/PBS buffer. In addition, PTA‐Py can efficiently detect Hg2+ ions in HeLa cells. The results demonstrate that a valuable method is developed for biocompatible polymeric sensors for Hg2+ ions in biological and environmental samples. [ABSTRACT FROM AUTHOR]

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

This work presents a coumarin-anthracene-based chemodosimeter L for the selective detection of Arginine (Arg) via hydrolysis of the imine bond of the Schiff base L. Significant changes in the emission and absorption spectra of L were observed during the detection of Arg. Chemodosimeter L displayed an impressive detection limit of 0.46 μM for Arg by the emission spectral titrations. A combination of UV-Vis, emission, and mass spectral studies, as well as excited-state lifetime measurements, and quantum yield calculations illustrated Arg-assisted dosimetry of L. The sensing of Arg by L was employed in cell imaging and for the colorimetric detection and paper test strip-based practical detection methods. This work presents a chemodosimeter L based on a coumarin-anthracene platform for the selective detection of amino acid arginine. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S) is a toxic gas derived from the sulfur industry and trace H2S in the environment can cause serious ecological damage while inhalation can cause serious damage and lead to disease. Therefore, the real-time and accurate detection of trace sulfur ions is of great significance for environmental protection and early disease detection. Considering the shortcoming of current H2S probes in terms of stability and sensitivity, the development of novel probes is necessary. Herein, a novel metal-organic frameworks (MOF)-based material, UiO-66-NH2@BDC, was designed and prepared for the visual detection of H2S with rapid response (< 6 s) and low detection limit of S2− (0.13 µM) by hydrogen bonding. Based on its good optical performance, the UiO-66-NH2@BDC probe can detect S2− in various water environments. More importantly, UiO-66-NH2@BDC probe realize imaging S2− in cells and live zebrafish. [ABSTRACT FROM AUTHOR]

Excessive production of potent biological oxidants such as HOCl has been implicated in numerous diseases. Thus, it is crucial to develop highly specific and precise methods to detect HOCl in living systems, preferably with molecules that can show a distinct therapeutic effect. Our study introduces the synthesis and application of a highly sensitive fluorescence "turn-on" probe, Myco-OCl, based on the mycophenolic acid scaffold with exceptional water solubility. The ESIPT-driven mechanism enables Myco-OCl to specifically and rapidly detect (<5 s) HOCl with an impressive Stokes shift of 105 nm (λex = 417 nm, λem = 522 nm) and a sub-nanomolar (97.3 nM) detection limit with the detection range of 0 to 50 μM. The potential of Myco-OCl as an excellent biosensor is evident from its successful application for live cell imaging of exogenous and endogenous HOCl. In addition, Myco-OCl enabled us to detect HOCl in a zebrafish inflammatory animal model. These underscore the great potential of Myco-OCl for detecting HOCl in diverse physiological systems. Our findings thus offer a highly promising tool for detecting HOCl in living organisms. [ABSTRACT FROM AUTHOR]

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

A diformylphenol Schiff base of triazole‐amine, 4‐methyl‐2, 6‐bis‐[(1H‐[1,2,4] triazol‐3‐ylimino)‐methyl]‐phenol (PTR) has been synthesised and characterised by spectroscopic data (ESI‐MS, UV‐vis, FT‐IR, NMR spectra). The probe, PTR, emits at 610 nm upon excitation at 380 nm and the emission is strongly intensified on interacting with Zn2+ ion in DMSO‐water (99:1, v/v; HEPES buffer, pH, 7.2) solution even in the presence of 15 other cations (Cu2+, Mn2+, Co2+, Ni2+, Pd2+, Cd2+, Pb2+, Hg2+, Fe3+, Cr3+, Al3+, Na+, K+, Ba2+, Ca2+) and the emission band has been shifted to 530 nm. The limit of detection of Zn2+, 0.30 μM is much lower than WHO recommended value (76 μM). The binding constant (Kd) is 4.2585 × 104 M−1. Selective and sensitive chemosensing behaviour of PTR to Zn2+ has been explained by switching off ESIPT quenching of the keto‐enol tautomerisation of the probe along with the chelation enhancement of fluorescence (CHEF) by binding with Zn2+. The Job's plot and NMR titration have been extended to measure the 1:1 M composition [PTR + Zn2+]. The energy calculation by the DFT computation of keto and enol isomers supports easy tautomerisation and helps ESIPT quenching by proton transfer. Intracellular Zn2+ ions in living cells of HEK293 (PBS: phosphate buffer saline; pH, 7.2) have also been identified by the probe, PTR, using fluorescence microscopic imaging technique. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S) produced and metabolized by mitochondria is closely associated to human physiological function, but its mechanism is not fully revealed due to the difficulty in determining the dose of hydrogen sulfide. Therefore, fluorescent probes with both excellent mitochondrial targeting ability and rapid H2S detection are urgently needed. In this work, a novel fluorescent probe, TPAS-TN, was developed to detect H2S in mitochondria. TPAS-TN with a D–π–A structure had a large Stokes shift (213 nm), and possessed low background interference in cell imaging. By introducing a twisted triphenylamine group as the donor, TPAS-TN was endowed with AIE properties, and the positively charged pyridium unit was the acceptor, so that TPAS-TN exhibited good mitochondrial targeting ability and biocompatibility. Meanwhile, the π-bridge was composed of phenyl and dinitrophenyl (DNP) ether to make TPAS-TN exhibit "off–on" properties, low detection limit (69.5 nM), and high sensitivity and selectivity. Besides, TPAS-TN with the above characteristics was successfully applied to high-contrast H2S imaging in mitochondria. [ABSTRACT FROM AUTHOR]

[Display omitted] Carbon dots (CDs) have been extensively employed in biomolecule imaging. However, the imaging of biological enzymes with CDs has not been reported, which greatly limits their application in biological imaging. Herein, for the first time, a new type of fluorescent CDs is elaborately designed to realize the direct mapping of alkaline phosphatase (ALP) in cells. The obtained phosphorus and nitrogen co-doped CDs (P, N-CDs) generate specific structures including xanthene oxide and phosphate ester, thereby enabling P, N-CDs to be exclusively cleaved by ALP without auxiliary media. The fluorescence intensity of P, N-CDs can be specifically turned on in the presence of ALP, making them powerful probes for sensitive sensing of ALP activity with a detection limit of 1.27 U·L−1. Meanwhile, P, N-CDs possessing electron deficiency structure fulfill sensitive responding to polarity variations. The excellent photo-bleaching resistance and biocompatibility of the P, N-CDs are taken for directly mapping the intracellular endogenous ALP via turned-on fluorescence imaging, as well as real-time monitoring the polarity fluctuation in cells through ratiometric fluorescence imaging. The present work offers a new way to design and synthesize functional CDs for direct imaging of intracellular enzymes. [ABSTRACT FROM AUTHOR]

Nitrogen-doped carbon dots (NCDs) have been constructed in which coal washing wastewater is used as carbon precursor, tryptophan is added for nitrogen doping and surface functional together with polyethylene glycol. The nitrogen doping and surface functional with electron rich groups resulted in excellent fluorescent properties regarding stability, reversibility, printability with high quantum yield which not only enable the NCDs as fluorescent ink for advanced message encryption, but also realize specific on-off-on fluorescent sensing of Hg2+ and GSH as solution, hydrogel and filter paper sensors. The NCDs had a linear range of 0.01-100 μM and a detection limit of 6.27 nM (RSD 0.33%) for Hg2+ and the NCDs@Hg2+ had a linear range of 0.01–60 μM and a detection limit of 3.53 nM (RSD 1.53%) for GSH in sensing studies with aqueous solutions. In addition, with the low cytotoxicity and good biocompatibility NCDs have been successfully used for imaging Hg2+ and GSH in living MG-63 cells. The presented NCDs recycle waste coal washing water into worthwhile material which can be implemented as promising anti-counterfeiting and message encryption candidates as well as effective Hg2+ and GSH sensing, tracking and removing tools in complicated environmental and biological systems. [ABSTRACT FROM AUTHOR]

Metal cations such as Zn2+, Al3+, Hg2+, Cd2+, Sn2+, Fe2+, Fe3+ and Cu2+ play important roles in biology, medicine, and the environment. However, when these are not maintained in proper concentration, they can be lethal to life. Therefore, selective sensing of metal cations is of great importance in understanding various metabolic processes, disease diagnosis, checking the purity of environmental samples, and detecting toxic analytes. Schiff base probes have been largely used in designing fluorescent sensors for sensing metal ions because of their easy processing, availability, fast response time, and low detection limit. Herein, an in-depth report on metal ions recognition by some Schiff base fluorescent sensors, their sensing mechanism, their practical applicability in cell imaging, building logic gates, and analysis of real-life samples has been presented. The metal ions having biological, industrial, and environmental significance are targeted. The compiled information is expected to prove beneficial in designing and synthesis of the related Schiff base fluorescent sensors. [ABSTRACT FROM AUTHOR]

Mercury ion (Hg2+) contamination is very hazardous and harmful to the natural environment and human health. The development of small molecule fluorescent probes for the rapid detection of Hg2+ is of great significance. In the present work, an "AIE + ESIPT" mechanism-based benzothiazole derived fluorescent probe was applied to Hg2+ detection and displayed excellent selectivity, good anti-interference ability, low detection limit (2.85 × 10−9 M), and a large Stokes shift (170 nm) in the DMF/H2O mixture solution with fw = 60% H2O volume fraction. The fluorescence response mechanism, involving the desulfurization reaction of O-(2-(benzo[d]thiazol-2-yl)-6-formyl-4-methylphenyl)dimethylcarbamothioate (probe L) with Hg2+ to release the "AIE + ESIPT" fluorophore, was well established based on the UV-vis, 1H NMR, and HRMS spectral analyses. The practical application evaluation indicates that probe L could be used to precisely determine Hg2+ in live cell imaging, natural water, and seafood samples. [ABSTRACT FROM AUTHOR]

A new bis-spirocyclic rhodamine B derivative was developed as a near-infrared colorimetric and "turn-on" fluorometric chemodosimeter (1) with a large Stokes shift (70 nm) for Cu2+. In response to Cu2+, the solution of 1 displayed major absorption at 700 nm, from colorless to blue within ten seconds. At the same time, emissions at 580 nm (excitation at 520 nm) and at 770 nm (excitation at 650 nm) were turned on. Good linear relationships between absorbance at 700 nm, fluorescence at 580 and 770 nm and concentration of Cu2+ in wide ranges were obtained in both colorimetric and fluorometric analyses, with the detection limits of 0.57 μM, 9 nM and 28 nM, respectively. Irreversible ring-opening processes of 1 coordinated with Cu2+, followed by hydrolysis as well as acylated reaction were proposed. Furthermore, 1 was applied to image Cu2+ in HepG2 living cells and within the mitochondria of the cells in the roots of paulownia sprouts. [ABSTRACT FROM AUTHOR]

Qualitative and quantitative analysis of mercury at concentration levels as low as parts per billion (ppb) is a basic and practical concern. The vast majority of research in this field has centered on the development of potent chemosensor to monitor mercuric (Hg2+) ions. Mercury exists in three oxidation states, + 2, + 1 and 0, all of which are highly poisonous. In this study, (N1E,N2E)-N1,N2-bis(pyrene-1-ylmethylene)benzene-1,2-diamine (PAPM), a novel photoluminescent sensor based on pyrene platform was synthesized. Over the tested metal ions (Cd2+, Co2+, Cu2+, Mg2+, Mn2+, Ni2+, K+, Na+, Zn2+, Sr2+, Pb2+, Al3+, Cr3+ and Fe3+) the sensor responds only to Hg2+ by showing high selectivity and sensitivity. After treatment with mercuric ions at room temperature, the luminescence intensity of probe was quenched at 456 nm. The quenching of fluorescence intensity of probe upon addition of mercury is due to the effect of "turn-off" chelation enhanced quenching (CHEQ) by the formation of 1:1 complex. The ESI–MS spectrum and the Job's experimental results confirm the formation of 1:1 complex between PAPM and Hg2+. The detection limit and association constant of sensor for mercury is computed using fluorescence titration data and were found to be 9.0 × 10–8 M and 1.29 × 105 M−1 respectively. The practical application of sensor towards recognition of mercury(II) ions was explored through economically viable test strips and also using cell imaging studies. [ABSTRACT FROM AUTHOR]

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

A highly sensitive, reversible, reusable and fluorogenic "turn-on" probe (HBTC) is fabricated for the sole detection of Al3+. On incremental addition of Al3+ in a solution of HBTC in ACN : H2O (4 : 1), a sharp "turn-on" emission enhancement is observed at 480 nm. The reversibility of the probe (HBTC) was displayed on the addition of F− solution. The detection limit is found to be of the order of 10−9 M which suggests that HBTC can detect Al3+ at a very minute level. The mechanism for Al3+ detection in ACN : H2O (4 : 1) is attributed to forbidding C＝N isomerization and ESIPT process simultaneously turning on the chelation-enhanced fluorescence process. The reusability and real-time application of the probe are also studied. Bioimaging study reveals that HBTC can detect Al3+ in human breast cancer cells (MDA-MB-231). Electronic structure of the probe is explained by density functional theory. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) are pivotal in regulating biological processes such as cell proliferation and disease progression. Traditional miRNA detection methods like qRT-PCR and Northern blotting do not allow for monitoring dynamic changes in living cells and typically require invasive sample collection. This research presents a robust, non-enzymatic technique known as the Localized Hybridization Chain Reaction Amplifier (LHCRA), designed for real-time, in vivo miRNA imaging. This method addresses these limitations by providing rapid and sensitive detection of miRNAs, crucial for progressing clinical diagnostics and research. The LHCRA utilizes hairpin chain reaction probes embedded within self-assembled DNA micelles (DM), significantly amplifying miRNA signals. LHCRA demonstrated exceptional performance, with a detection limit of 100 pM and a response time of 10 min. Importantly, it effectively differentiated between cancerous and normal cells using clinical peripheral blood samples, showcasing high specificity and stability under physiological conditions. Additionally, LHCRA maintained consistent performance in complex biological media, including 10 % serum and 2 U/mL DNase I, confirming its broad applicability in various diagnostic scenarios. This performance highlights LHCRA's potential as a transformative tool in miRNA-based diagnostics. The introduction of LHCRA marks a significant advancement in miRNA detection technology. By enabling accurate, non-invasive, and real-time monitoring of miRNA dynamics within living cells, this method offers substantial potential to enhance diagnostic accuracy and deepen our understanding of disease mechanisms, particularly in cancer. Thus, it could greatly improve therapeutic strategies and patient outcomes in clinical environment. [Display omitted] • LHCRA amplifies miRNA signals with high specificity and low detection limit. • Simple one-step synthesis with high reaction efficiency (10 min total time). • High stability and low toxicity in biological environments. • Successfully distinguishes cancerous from normal cells in clinical samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • An optical and dual NIR-channel fluorescent sensor for ONOO− was prepared. • The sensor showed a dual-emission fluorescent response (660 and 800 nm) upon the addition of ONOO−. • The dual-channels imaging of exogenous and endogenous ONOO− in live cells and zebrafish was successfully performed. As one of endogenous reactive oxygen species (ROS), peroxynitrite (ONOO−) performs various functions in both pathological and physiological mechanisms. In this work, an optical and near-infrared (NIR) fluorescent probe (NX), which based on 3-dihydro-1H-xanthene and 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) group was designed and prepared to detect ONOO−. This probe revealed an obvious optical and a fluorescent response when ONOO− was present and it exhibited higher selectivity over other ROS. Especially, the dual NIR fluorescence changes at 660 and 800 nm allowed quantitative detection of ONOO− in the range of 15–40 μM, and the detection limit was 82 nM. Finally, the probe was effectively employed to visualize exogenous and endogenous ONOO− in HepG2 cells and zebrafish, respectively. All the results indicated the dual NIR-channel probe could serve as a potent detecting tools in studying ONOO− in vitro and in vivo. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new dual-response probe with ESIPT and AIE features was fabricated. • It can sequentially sense PhSH and HClO in two well-separated channels. • It showed rapid response to PhSH and HClO with good selectivity and sensitivity. • It was capable of monitoring PhSH and PhSH-induced HClO generation in cells. As a valuable industrial chemical, thiophenol (PhSH) is poisonous, which can be easily absorbed by the human body, leading to many serious health issues. In addition, PhSH-triggered oxidative stress is considered to be related with the pathogenesis and toxicity of PhSH. Therefore, efficient methods for monitoring PhSH and ROS production induced by PhSH in living systems are very meaningful and desired. Herein, we reasonably developed a facile dual-response fluorescent probe (HDB-DNP) by incorporating the dinitrophenyl (DNP) group into a novel methylthio-substituted salicylaldehyde azine (HDB) with AIE and ESIPT features. The probe itself was non-fluorescent owing to the strong quenching effect of DNP group. In the presence of PhSH, HDB-DNP gave an intense red fluorescence (610 nm), which can rapidly switch to green fluorescence (510 nm) upon further addition of HClO, allowing the successive detection of PhSH and HClO in two well-separated channels. HDB-DNP proved to be a very promising dual-functional probe for rapid (PhSH: < 17 min; HClO: 10 s) and selective detection of PhSH and HClO in physiological conditions with low detection limit (PhSH: 13.8 nM; HClO: 88.6 nM). Inspired by its excellent recognition properties and low cytotoxicity, HDB-DNP was successfully applied for monitoring PhSH and PhSH-induced HClO generation in living cells with satisfactory results, which may help to better understand the pathogenesis of PhSH-related diseases. [ABSTRACT FROM AUTHOR]

[Display omitted] • The fluorescence response of the new biscarbazole sensor to Cu2+ (turn off) was examined using fluorescence methods. • The detection mechanism of sensor for Cu2+ was determined with Job's plot, 1H NMR titration, and theoretical calculation. • Anticancer investigation and fluorescence cell imaging analysis of sensor against PC-3 cell. Biscarbazole derivative probe (6) (Z)-2-(3-(((9-heptyl-9H-carbazol-3-yl)methylene)amino)-9H-carbazol-9-yl)ethan-1-ol containing an imine group, which is a sensitive and selective fluorescence chemosensor, was designed and synthesized for the effective evaluation of Cu2+ metal ion levels. The synthesized compounds were characterized using 1H NMR, 13C NMR, FT-IR, and MALDI-TOF MS (for compound 6) spectroscopic data. The interaction model between probe 6 and Cu2+ was determined by combining fluorescence methods, 1H NMR titration, Job's plot, and theoretical calculations. For probe 6 , the fluorogenic recognition of Cu2+ was investigated by fluorescence spectroscopy, and the optical changes caused by Cu2+ ions were carried out in ACN/H 2 O (50:50) solution at pH 7.0. Fluorescence probe 6 was found to " turn-off " its fluorescence in the presence of paramagnetic Cu2+ ions. Probe 6 was determined to have a rapid response within 40s and showed a fluorescence response to Cu2+ with a low detection limit of 0.16 μM. Additionally, in vitro anticancer activity and cell imaging studies of probe 6 against the prostate cell line (PC-3) were performed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A red-emitting fluorescent probe for biothiols has been designed and synthesized. • DIcou-DNBS can be used for the screening of drug inhibitors. • DIcou-DNBS exhibits large Stokes shift in detecting Cys/Hcy/GSH. Biothiols, comprising cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), play a pivotal role in maintaining the delicate redox balance essential for life processes, intricately intertwined with the well-being of living organisms. Deviations in their concentrations can precipitate a range of diseases. Herein, we presented a novel fluorescent probe, DIcou-DNBS , derived from coumarin, which possessed red emission and a substantial Stokes shift (122 nm), tailored for biothiol detection. DIcou-DNBS demonstrated rapid-responsiveness (6 min) towards Cys, Hcy and GSH with detection limits of 0.015 µM, 0.032 µM and 0.059 µM, respectively. Furthermore, its excellent biocompatibility enabled successful applications in biothiol fluorescence imaging of living cells and zebrafish. Beyond biothiol sensing, DIcou-DNBS leveraged its unique property to indirectly detect β-lactamases, making it a valuable tool in inhibitor screening and susceptibility testing of both sensitive (Staphylococcus aureus ATCC 29213) and resistant (Enterobacter cloacae ATCC 13047) bacterial strains. This assay system anticipates to furnish a potent instrument for visualization studies across biological and medical domains. [ABSTRACT FROM AUTHOR]

The near-infrared (NIR) fluorescence sensor for sensitive, selective, and high tissue penetration detection of hydrogen peroxide (H 2 O 2) is quite significant in the localization and surgical removal of tumors. Herein, we reported a novel tumor-target NIR fluorescence probe BCy-Biotin for H 2 O 2 detection in tumors. The probe showed high selectivity and sensitivity toward H 2 O 2 with the calculated detection limit of 1.82 × 10−7 M. And it was applied in the detection of exogenous and endogenous H 2 O 2 levels in 4T1 cells with low cytotoxicity. In the subcutaneous 4T1 tumor model of mice, probe BCy-Biotin exhibited satisfactory tumor-target fluorescence imaging after the tail vein. Significance: Importantly, this probe was successfully employed in fluorescence image-guided surgical resection of tumors in mice. These results demonstrated that this probe had the potential for clinical diagnosis and surgical navigation of cancers. • A novel H 2 O 2 -activated fluorescent probe BCy-Biotin with tumor-targeting was developed. • The probe BCy-Biotin showed excellent sensitivity to H 2 O 2 with a calculated limit detection of 1.82 × 10−7 M. • The probe BCy-Biotin displayed high selectivity towards H 2 O 2 over other analytes. • The probe BCy-Biotin was employed in the imaging of endogenous H 2 O 2 in 4T1 cells. • The probe BCy-Biotin was used in the fluorescence-guided tumor resection in the 4T1 subcutaneous tumor mice model. [ABSTRACT FROM AUTHOR]

Existing studies have implied that H 2 S, SO 2 , and viscosity have potential interrelationships in diseases such as inflammation in the body. Developing fluorescent probes that can simultaneously distinguish and detect the three will be beneficial for relevant workers to explore their potential interrelationships in physiology and pathology. Due to the similar chemical properties of HS− and SO 3 2− (both possessing strong nucleophilic properties), it presents a task with certain challenges that demand careful consideration to detect and differentiate between them using a single probe capable of simultaneously monitoring viscosity changes. In this study, we have designed and prepared a near-infrared fluorescent probe capable of distinguishing and detecting HS−, SO 3 2−, and viscosity, as well as targeting mitochondria. The response of this probe to HS− and SO 3 2− is quenching type and ratio type, respectively, with extremely low detection limits (LOD 1 = 0.60 nM for HS−, LOD 2 = 1.28 μM for SO 3 2−), fast response time (T 1 = 1 min for HS−, T 2 = 2 min for SO 3 2−), good selectivity and outstanding anti-interference performance. The monitoring of the viscosity of the probe also shows superior performance. As the viscosity enhances from 0.89 cP to 1412 cP, the fluorescence signal value increases by 52 times, and the trend of fluorescence intensity with viscosity well complies with the Förster-Hoffmann equation. To better understand the response mechanism of the probe to viscosity, we conduct a more in-depth exploration using Gaussian calculations, whose results are in excellent agreement with experimental phenomena. In addition, the probe has successfully achieved monitoring and imaging of HS−, SO 3 2−, and viscosity in Hela cells and 97H cells. [Display omitted] A novel near infrared fluorescent probe for monitoring HS-, SO 3 2-, and viscosity in mitochondria was developed. The probe response to HS- is quenching type with an extremely low detection limit (LOD = 0.59 nM). The probe response to SO 3 2- is ratio type (LOD = 1.08 μM) with an effectively anti-interference. In addition, the probe is highly sensitive to viscosity, with a 52-fold increase in fluorescence signal from pure water to glycerol. Eventually, the probe has been successfully applied in live cell imaging. We believe that probe can be used as a convenient tool to explore the pathological and physiological effects of HS-, SO 3 2-, and viscosity in promoting related biological, pharmacological, and toxicological research. • A near-infrared fluorescent probe for distinguishing and detecting HS-, SO 3 2-, and viscosity was designed and prepared. • The probe response to HS- and SO 3 2- with low detection limits, fast response time, good selectivity. • The monitoring of viscosity of the probe also shows superior performance. • The probe has successfully achieved monitoring and imaging of HS-, SO 3 2-, and viscosity in Hela cells. [ABSTRACT FROM AUTHOR]

Hydrogen polysulfide (H 2 S n , n≥2), as a kind of active sulfur species (RSS), has become a hot topic in RSS. It can regulate the biological activity of many proteins through S-sulfhydrylation of cysteine residues (protein Cys-SSH), and has a protective effect on cells. Although there have been some studies on hydrogen polysulfide, its production, degradation pathway and regulation mechanism still need further be researched. In presented study, an original lysosome-localized fluorescent probe for determining H 2 S n was developed utilizing rhodamine as the fluorogen. The probe used morpholine as the locating unit of lysosomes and chose 2-fluoro-5-nitrobenzoate as the recognizing group. Before adding H 2 S n , the proposed probe displayed a spironolactone structure and emitted very weak fluorescence. After adding H 2 S n , a conjugated xanthene was formed and the probe demonstrated green fluorescence. When the H 2 S n concentration was varied from 6.0×10−7 mol·L−1 to 10.0×10−5 mol·L−1, the fluorescence intensity of the probe was linearly dependent on the H 2 S n concentration. And the detection limit was 1.5×10−7 mol·L−1. The presented probe owned a fast response speed, good selectivity, excellent sensitivity and broad pH work scope. In addition, the probe had been well utilized to sense endogenic and exogenic H 2 S n in lysosomes. [Display omitted] • A lysosome-targetable fluorescent probe for H 2 S n has been reported. • The probe displays high sensitivity and high selectivity for H 2 S n. • The probe can be utilized for determination of H 2 S n within the lysosomes. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S) is traditionally considered as an ecologically toxic gas, has been proven to be the third endogenous signalling gasotransmitter and plays important roles in physiological and pathophysiological conditions. Herein, we designed and synthesized a novel "turn off" fluorescent probe for the detection of hydrogen sulfide(H 2 S) in vitro. Probe A could detect H 2 S in CH 3 CN/PBS system with significant fluorescence quenching. Probe A also showed obviously aggregation-induced emission (AIE) effects. Fluorescence titration experiments revealed probe A combine with H 2 S in a 1: 1 ratio with a detection limit of 6.54 μM. Cell imaging results demonstrated the potential applicability of probe A for H 2 S detection in living cells. The supramolecular assembly of probe A and β-cyclodextrin further revealed the interaction with H 2 S. Recognition of H 2 S by a fluorescent probe regulated by AIE and its application in cell imaging. [Display omitted] • A novel chemosensor (p robe A ) based on Fluorescein was rationally designed and synthesized. • Probe A could sense H 2 S in CH 3 CN/PBS (pH = 7.42, v: v = 1: 4) without interference of other anions, metal ions and amino acid. • Sensing mechanism of H 2 S sensing was confirmed by HR-MS. • The practical applicability of p robe A for H 2 S detection in cell imaging have been achieved. [ABSTRACT FROM AUTHOR]

Recognition of H 2 S by a fluorescent probe regulated by AIE and its application in cell imaging. [Display omitted] • One AIE active probe for H 2 S was synthesized. • HMP exhibited high selectivity with the detection limit as low as 0.82 μM for H 2 S. • The C = N of probe were nucleophilic addition by H 2 S in aqueous solution. • Supramolecular assembly with β-CD to further elucidate the mechanism. • This probe has been successfully applied for imaging of H 2 S in live cells. Hydrogen sulfide (H 2 S) is a crucial endogenous gas transmitter, maintaining the redox homeostasis in biological systems. Thus, a real-time and specific H 2 S detection approach is urgently necessary to study the attack and management of disorders linked to H 2 S. In this paper, a novel fluorescent probe HMP based on AIE property for the detection of H 2 S was elaborately conducted. In PBS buffer solution HMP exhibited high photostability, low detection limit (0.82 μM), significant anti-interference ability and fast response time and specificity to H 2 S. What's more, it could be employed for the monitoring and luminescent imaging of H 2 S with Hela cells, thereby broadening the prospective capacity for diagnosing associated diseases. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel peptide-based fluorescent probe DNC for sequential detection of Hg2+ and S2− was synthesized. • The detection limits of Hg2+ (8.4 nM) and S2− (5.5 nM) were significantly low. • DNC were successfully applied for sequential detection of Hg2+ and S2− in living cells and zebrafish. • DNC achieved selective and sensitive sensing toward Hg2+ and S2− on test strips. • Smartphone with RGB Color Picker was employed to analyze the different Hg2+ and S2− concentrations. Mercury ions (Hg2+) and sulfur ions (S2−), have caused serious harm to the ecological environment and human health as two kinds of highly toxic pollutants widely used. Therefore, the visual quantitative determination of Hg2+ and S2− is of great significance in the field of environmental monitoring and medical therapy. In this study, a novel fluorescent "on–off-on" peptide-based probe DNC was designed and synthesized using dipeptide (Asn-Cys-NH 2) as the raw material via solid phase peptide synthesis (SPPS) technology with Fmoc chemistry. DNC displayed high selectivity in the recognition of Hg2+, and formed non-fluorescence complex (DNC- Hg2+) through 2:1 binding mode. Notably, DNC- Hg2+ complex generated in situ was used as relay response probe for highly selective sequential detection of S2− through reversible formation-separation. DNC achieved highly sensitive detection of Hg2+ and S2− with the detection limits (LODs) of 8.4 nM and 5.5 nM, respectively. Meanwhile, DNC demonstrated feasibility for Hg2+ and S2− detections in two water samples, and the considerable recovery rate was obtained. More importantly, DNC showed excellent water solubility and low toxicity, and was successfully used for consecutive discerning Hg2+ and S2− in test strips, living cells and zebrafish larvae. As an effective visual analysis method in the field, smartphone RGB Color Picker APP realized semi-quantitative detections of Hg2+ and S2− without the need for complicated device. [ABSTRACT FROM AUTHOR]

[Display omitted] • A solvent-dependent six-membered spirorhodamine probe has been firstly reported. • It exhibited dual channel responses for Cu2+ in CH 3 CN/H 2 O and ClO- in C 2 H 5 OH/H 2 O. • Detection limits were 36 nM for Cu2+ and 129 nM for ClO- in above two solvent systems. • The probe can be used to detect the concentration of Cu2+ in grape peel and A549 cells in vitro. To reveal the solvent dependence of six-membered rhodamine spirocycles (SMRS), a new probe SM-RB has been synthesized and investigated the spectral properties in different solvents upon the addition of various metal ions and anions. SM-RB exhibited high selectivity for Cu2+ in CH 3 CN/HEPES and ClO- in C 2 H 5 OH/HEPES solutions, respectively. The spectral changes of SM-RB in the presence of ClO- in C 2 H 5 OH/HEPES solution were much less than that of Cu2+ in CH 3 CN/HEPES. The detection limit of Cu2+ was as low as 36 nM (fl) in CH 3 CN/HEPES. The kinetic equilibration time (8 s) indicated that the two solvent systems did not delay the spectral response speed to Cu2+ and ClO-. Solvent systems influenced the pKa value of SM-RB in CH 3 CN/HEPES and C 2 H 5 OH/HEPES. The pKa value of SM-RB was 4.34 (±0.7) (Abs) and 4.75 (±0.14) (Fl) in CH 3 CN/H 2 O, but can't be exactly calculated by pH titration in C 2 H 5 OH/H 2 O. The reversibility and Job plot of SM-RB were investigated to propose the response mechanism of SM-RB with Cu2+ and ClO- in the two solvent systems. Finally, SM-RB not only can be used for the quantitative detection of copper ions in grape peel, but also can real-time monitor the fluctuation of Cu2+ in lysosomal pools. [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]

[Display omitted] • BTCMN is constructed by coupling of 2-(2́-hydroxyphenyl) benzothiazole (HBT) scaffold to dicyanoisophorone through a C C bond bridge based on ESIPT mechanism. • BTCMN showed super-fast response to H 2 S as compared to other current probes. • BTCMN displayed specific selection and low detection limit towards to H 2 S. • BTCMN has been successfully used for visualizing endogenous and exogenous H 2 S in the HepG2 cells with low cytotoxicity. Hydrogen sulfide (H 2 S) plays a crucial role in various physiological processes and is implicated in the pathogenesis of several diseases. The fluorescent probe (E)-2-(3-(3-(benzo[d]thiazol-2-yl)-2-hydroxy-5-methylstyryl)-5,5-dimethylcyclohex-2-en-1-ylidene) malononitrile (BTCMN) has been designed to image H 2 S in living cells using the excited-state intramolecular proton transfer (ESIPT) mechanism. This probe is developed by coupling 2-(2′-hydroxyphenyl) benzothiazole (HBT) with dicyanoisophorone through a H 2 S-responsive C C bond. Upon interaction with H 2 S, BTCMN exhibits a remarkable fluorescent change from red to green. BTCMN , which has shown exceptional performance in detecting hydrogen sulfide (H 2 S) with super-fast response times, large Stokes shifts (252 nm), specific selection towards H 2 S, and low detection limits. Importantly, BTCMN has been successfully used for visualizing endogenous and exogenous H 2 S in HepG2 cells with low cytotoxicity. These features collectively contribute to its effectiveness as a fluorescent probe for detecting H 2 S in living cells. [ABSTRACT FROM AUTHOR]

The reactive nitrogen species (RNS) in lysosomes play a major role during the regulation of lysosomal microenvironment. Nitroxyl (HNO) belongs to active nitrogen species (RNS) and is becoming a potential diagnostic and therapeutic biomarker. However, the complex synthesis routes of HNO in biosystem always hinder the exact determination of HNO in living cells. Here, a rhodamine-based fluorescent probe used to determine nitroxyl (HNO) in lysosomes was constructed and synthesized. 2-(Diphenylphosphino)benzoate was utilized as the sensing unit for HNO and morpholine was chose as the targeting group for lysosome. Before the addition of HNO, the probe displayed a spirolactone structure and almost no fluorescence was found. After the addition of HNO, the probe existed as a conjugated xanthene form and an intense green fluorescence was observed. The fluorescent probe possessed fast response (3 min) and high selectivity for HNO. Furthermore, fluorescence intensity of the probe linearly related with the HNO concentration in the range of 6.0 × 10−8 to 6.0 × 10−5 mol L−1. The detection limit was found to be 1.87 × 10−8 mol L−1 for HNO. Moreover, the probe could selectively targeted lysosome with excellent biocompatibility and had been effectually utilized to recognize exogenous HNO in A549 cells. [Display omitted] • A lysosome-targetable fluorescent probe for HNO has been reported. • The probe displays high sensitivity and high selectivity for HNO. • The probe can be utilized for determination of HNO within the lysosomes of living cells. [ABSTRACT FROM AUTHOR]

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

High-quality fluorescent probes based on carbon dots (CDs) have promising applications in many fields owing to their good stability, low toxicity, high quantum yield, and low raw material price. The fluorine- and nitrogen-doped fluorescent CDs (NFCDs) with blue fluorescence was successfully synthesized using 3-aminophenol and 2,4-difluorobenzoic acid as the raw material by the hydrothermal method. The NFCDs as probe can be used to directly and indirectly detect Fe3+ (detection range: 0.1–150 μM and detection limit: 0.14 μM) and ascorbic acid (AA) (detection range: 10–80 μM and detection limit: 0.11 μM). The NFCDs-based probe shows exceptional selectivity and strong anti-interference for Fe3+ and ascorbic acid (AA). In addition, we examined the response of NFCDs to Fe3+ and AA in living cells, which showed that the timely use of AA can reduce the effects of iron poisoning. This has important biological significance. This means that using NFCDs as fluorescent probes is beneficial for Fe3+ and AA detection and observing their dynamic changes in living cells. Thus, this work may contribute to the study of Fe3+- and AA-related diseases. [ABSTRACT FROM AUTHOR]

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

Hypochlorite plays a vital role in biological systems and our daily life. The rapid and convenient detection of hypochlorite is imperative and significant for disease treatment and human health. In this work, EY/UiO-66-NH2 (EY = eosin Y) was prepared through a hydrothermal process and could be applied to the detection and bioimaging of hypochlorite as a self-calibrating sensing nanoprobe. EY/UiO-66-NH2 features two emissions at 432 nm and 533 nm, and the emission intensity of 533 nm is enhanced with increasing ClO− concentration. EY/UiO-66-NH2 could be utilized as a ratiometric fluorescence sensor of ClO−. The linear range of EY/UiO-66-NH2 towards ClO− is 0.1–200 μM and its detection limit is 46.4 nM. In comparison with previously reported probes for ClO−, EY/UiO-66-NH2 has the advantages of a wide linear range, low detection limit, turn-on fluorescence and ratiometric response. This work provides a new method for ClO− detection in living cells. [ABSTRACT FROM AUTHOR]

In this paper, the carbon dots (CDs) with strong blue fluorescence were synthesized through hydrothermal method, which using folic acid, ammonium citrate and ethylenediamine as precursors. The prepared CDs with a high absolute quantum yield of 81.94% and showed excellent stability in high concentration salt solution and different pH conditions. With the addition of Hg2+, the signal of CDs was selectively quenched. At the same time, the CDs-Hg2+ system could be recovered after the introduction of biothiols. Moreover, the fluorescence of CDs showed a good linear relationship with Hg2+ (1–15 µM), and the detection limit as low as 0.08 µM. In addition, the prepared CDs with low toxicity could be used to detect Hg2+ in living cells and actual water samples. [ABSTRACT FROM AUTHOR]

A novel near-infrared fluorescent probe SWJT-5 based on dicyanoisophorone was synthesized. It achieved the rapid (within 40 s) and discriminative detection of Cys over Hcy and GSH with a large Stokes shift (205 nm). It showed high selectivity and sensitivity for Cys, and had an obvious enhancement of fluorescence emission. The detection limit was 0.43 μM. This probe also had low background interference and little damage to biological samples. Therefore, SWJT-5 had been applied to bioimaging in living cells successfully. [ABSTRACT FROM AUTHOR]