Search

[Display omitted] • Herein we constructed and synthesized turn-on fluorescent probe NSP based on simple condensation reaction. • Probe on incubating with triphosgene in presence of 1 % Triethylamine (TEA) show maximum emission at 586 nm within ≤3 s. • The probe displayed both colorimetric and fluorescence response with phosgene (0.01 ppm). • The probe-loaded paper strips, allowed for the direct visualization of phosgene vapour from household bleaching powder. • The probe detect phosgene in living cells. Phosgene is a vital industrial gas that might substantially imperil public safety in the case of an accident or terrorist attack due to its extreme toxicity and history of use as a chemical warfare agent. Herein we built a simple photoinduced electron transfer-intramolecular charge transfer based turn-on fluorescent probe for ultrafast detection of phosgene within ≤ 3 s. The probe provides low detection limit (0.01 ppm) with distinct colour and fluorescence changes only in the presence of phosgene. With the help of a readily available colour smartphone app, the probe-loaded paper strips allowed for the direct visualization and quantitative measurement of phosgene vapour. Using the probe-coated strips to detect phosgene that evolved from common household bleach. Finally, the probe was utilized to detect phosgene in living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • The probe P-1 can selectively detect H 2 O 2 with colorimetric change. • the P-1 can be used for on-site and visual detection of H 2 O 2. • The P-1 can image H 2 O 2 in cells and distinguish cancer cells and normal cells. • The P-1 probe was applied to monitor H 2 O 2 of tumor in mice. We designed and developed the probe P-1 for detecting H 2 O 2. The probe can selectively detect H 2 O 2 with colorimetric change. In addition, the combination of portable test strips with a smartphone platform provided great convenience for on-site and visual detection of H 2 O 2 with satisfactory sensitivity and reliability. The P-1 can image exogenous and endogenous H 2 O 2 in cells and distinguish cancer cells and normal cells by fluorescence image of H 2 O 2 and flow cytometry. Meanwhile, the P-1 probe has been successfully applied to monitor H 2 O 2 levels of tumor in mice, and the results showed the level of H 2 O 2 in tumor tissue increased significantly. Therefore, P-1 provided a potential chemical tool to understand pathological and physiological mechanisms of diseases by imaging H 2 O 2. [ABSTRACT FROM AUTHOR]

[Display omitted] • The new probes with AIE characteristic for cell imaging. • The probe has high sensitivity in the presence of solvent shielding effects. • The probe has good reversibility for environmental testing and could be recycled. A new fluorescent probe TPA-DAP with aggregation-induced emission (AIE) characteristic based on 2,6-pyridinedicarboxylic acid was synthesized for the detection of paramagnetic ions (Cu2+, Co2+, Ni2+). In the DMF/PBS (5:95, v/v, pH = 7.40) solvent mixture, the fluorescence intensity exhibited a notable enhancement of over 3-fold when compared to DMF alone. Concurrently, fluorescence quenching phenomena were observed in the presence of Cu2+, Co2+, and Ni2+, with corresponding detection limits measured at 56.4 nM, 22.4 nM, and 26.5 nM, respectively. These detection limits were found to be lower than the prescribed thresholds for Cu2+ in Class I groundwater and Co2+, Ni2+ in Class III groundwater, multi-functional detection was possible. The coordination constants were 9.07 × 105, 3.63 × 105 and 5.69 × 105, respectively. However, in the DMSO system, the probe will be highly selective in the presence of solvent shielding effects. The probe showed more than 10-fold enhancement of fluorescence intensity in DMSO/Tris-HCl (5:95, v/v, pH = 7.00) compared to DMSO and specific detection of Cu2+ with a detection limit of 36.7 nM and a coordination constant of 4.35 × 105, and was cyclically detectable in the presence of EDTA. TPA-DAP was applied for the detection of Cu2+ in actual water samples and showed good biocompatibility and recyclability, making it suitable for water testing and test paper experiments, and also for a wide range of applications in the identification of Cu2+, Co2+, Ni2+ and other bioassays in cells and zebrafish. Solvents could be selected according to actual test requirements. [ABSTRACT FROM AUTHOR]

[Display omitted] • Characterization of cresyl violet fluorescence in plant cells. • Cresyl violet can be used to distinguish acidic endosomes and vacuoles. • Cresyl violet is more reliable to maps endosomes populations in plant leaf and root cells. • Cresyl violet in plant cells is highly photostable and is devoid of cytotoxic properties. The advent of fluorescent probes and the characterization of their photochemical properties in the past years allowed significant advances in the studies of spatiotemporal cellular processes within complex and crowded systems. Dyes are indeed extremely useful tools for the visualization of cellular and subcellular structures present in living cells, as well as to study their dynamic and molecular composition or physiological changes. There are some areas of plant cell biology that have been more challenging to explore due to the physiology and organization of certain endomembrane compartments. In this study we characterize the labeling properties of cresyl violet as quick and inexpensive imaging agent for tracking endosomes, vacuole compartments which are usually very differentiated and categorized as more acidic as well as acidic plant compartments. Its photobleaching, labelling and cytotoxic properties are compared with other well-known and currently most used synthetic and molecular probes. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new fluorescent chemosensor (SDAF) was developed for Al3+. • The SDAF has an ultralow detection limit (28 nM) and fast response time. • DFT studies were strongly confirmed the spectroscopy results. • The SDAF was successfully used to detect Al3+ in water samples, test-kits and living cells. A new fluorescent chemoprobe (SDAF) was successfully synthesized and utilized as a sensor for the recognition of Al3+ in EtOH:HEPES (3:2, v:v, pH: 7.0) media. The SDAF depicted a selective "turn–on" response at λ em = 467 nm to Al3+ over competitive cations, and the SDAF– Al3+ complex had a reversible response with F−. The limit of detection (LOD) was found about at nano–molar level (28.0 nM), demonstrating the sensitivity of the chemoprobe toward Al3+. The binding stoichiometry of SDAF –Al3+ was investigated by TOF–MS, Job's plot, 1H NMR and 13C NMR methods and found as 1:1. The recognition mechanisms of SDAF for the detection of Al3+ were the –C = N isomerization and photoinduced electron transfer (PET) mechanisms, and they were confirmed by density functional theory (DFT) computation. Furthermore, the SDAF was successfully employed in living–cell bioimaging and cytotoxicity, it was also utilized in Smartphone, test–kit and natural spring water (recovery values; 89.01 %– 96.33 %)applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • The crystal structure of π–π stacking of red carbon nanosheets, and enhance the fluorescence properties of red carbon in aggregation state. • The fluorescence of red carbon can be quenched by the Fe3+ and recovered by ethylene diamine tetraacetic acid. • The red carbon can detect the Fe3+ with highly sensitive, rapid response, and anti-interference and cellular imaging. The subcarboxylated carbon (C 3 O 2) is a unique molecule that spontaneously polymerizes into highly conjugated fluorescence structures p(C 3 O 2) n , named "red carbon". This unique property, combined with its role as aggregation-induced emission luminogens, has allowed for a deeper exploration of their emission mechanism. Herein, both density functional theory calculations and experimental approaches to elucidate the crystal structure of π–π stacking in red carbon, thereby enhancing the fluorescence properties of p(C 3 O 2) n polymer in its aggregated state. The time-dependent density functional theory calculations and experimental observations indicate that the fluorescence of red carbon can be quenched by ferric ions (Fe3+) and subsequently restored by ethylenediaminetetraaceticacid (EDTA). This quenching process follows first-order reaction kinetics. On the basis of the coordination to metal ions from abundant heteroatoms on red carbon, the high sensitivity, quick responsive (1 min), sensitive detection (the lowest detection limit is 0.97 μM) for the Fe3+ were realized in red carbon, which provides inspirations for the design of new turn-on probes with high stability in detecting the Fe3+ in aqueous solution. Crucially, the red carbon as a light-up fluorescence probe can be employed for the Fe3+ sensing in living cells, which enlighten a new perspective for designing non-conjugated fluorescent polymers. This innovative approach opens up new avenues for developing probes that can detect Fe3+ with high precision and reliability in complex biological environments. [ABSTRACT FROM AUTHOR]

[Display omitted] • A framework nucleic acids (FNAs) fluorescent nanoprobe was constructed. • The detection of multiple DNA repair enzymes in living cells was realized. • This method exhibits good selectivity and high sensitivity. • The FNAs enter the cell autonomously and image UDG and APE1. DNA repair enzymes play pivotal roles in DNA damage repair. Imaging multiple DNA repair enzymes in living cells is significant for DNA damage repair-related biological study and disease diagnosis. Here, we constructed a framework nucleic acids (FNAs) fluorescent nanoprobe for imaging multiple DNA repair enzymes in living cells. Uracil DNA glycosylase (UDG) and human apurinic/apyrimidinic endonuclease 1 (APE1) were used as the target analytes. Two double-stranded DNA probes (dsDNA1 and dsDNA2) were designed. dsDNA1 contained four uracil (U) bases for UDG recognition and was labeled with black hole quencher2 (BHQ2) /cyanine5 (Cy5). dsDNA2 contained one apurinic/apyrimidinic (AP) site for APE1 recognition and was labeled with black hole quencher1 (BHQ1) /fluorophore carboxyfluorescein (FAM). To obtain the FNAs fluorescent nanoprobe, dsDNA1 and dsDNA2 were attached to two vertices of a DNA tetrahedron (a type of FNAs). Under the action of UDG and APE1, dsDNA1 and dsDNA2 were both dissociated, generating fluorescence of Cy5 and FAM. Among them, Cy5 indicated the activity of UDG and FAM indicated the activity of APE1. This method had good sensitivity to UDG and APE1, and the detection limits were 0.0012 U/mL and 0.057 U/mL, respectively. This method also exhibited high selectivity for UDG and APE1. When the FNAs fluorescent nanoprobe was endocytosed, it had little toxicity to normal and cancer cells. Furthermore, this method successfully achieved multiple imaging UDG and APE1 in cancer cells. This study provides a novel strategy for imaging multiple DNA repair enzymes and holds great potential in biological applications and clinical diagnosis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cyanide exhibits a dual nature, serving as an industrial asset and causing an environmental threat. • The focus on cyanide detection increases as micromolar cyanide levels create fatal risks. • Colorimetric and fluorescent chemosensors offer quick, affordable, and portable detection of cyanide. • This review highlights colorimetric and fluorescent probes' significance in monitoring cyanide ions. • The survey was executed utilizing published reports from 2021 to 2023. Anions, specifically cyanide, occupy crucial roles in various biological, physiological, and industrial contexts. While cyanide is indispensable as a raw material in the synthesis of herbicides, resins, synthetic fibers, and the gold-extraction process, its widespread presence causes a significant threat to both environmental and social systems. Cyanide abundance in the environment arises not just from industrial effluents but also from the natural biological processes of fungi and algae. The dual nature of cyanide, serving both as a useful industrial component and a potential environmental hazard, highlights the importance of responsible management and regulation in its production and application. The detection of cyanide has become a matter of paramount importance due to its extreme toxicity and potential environmental contamination, where even micromolar levels can prove fatal to humans. In addressing this critical concern, researchers have focused on developing simple, inexpensive, and rapid detection methods, with chemosensors emerging as among the most promising solutions. These chemosensors rely on colorimetric and fluorometric responses, offering a synergistic combination that enhances the versatility of cyanide detection methodologies. Through novel design and synthesis, researchers have constructed a diverse range of chemosensors with tailored properties, such as high selectivity, low detection limits, and rapid response times. Especially, efforts have been directed towards making these detection systems portable and user-friendly, facilitating their practical implementation in real-world scenarios. This comprehensive review provides a focused examination of colorimetric and fluorescent probes designed for the specific and sensitive recognition of cyanide anions. Emphasizing their applicability in on-site portable strips and cellular imaging, the review aims to enhance readers' understanding of the critical need for monitoring cyanide ions in the context of human health and disease. The discussed probes are categorized into various classes, including small molecules, metal complexes, metal–organic frameworks (MOFs), macrocyclic compounds, nanomaterials, and polymer-based probes, each classified based on their structural properties and functional groups. Encompassing advancements made in the field from 2021 to 2023, the review underscores the progress achieved in developing these probes. Finally, the review addresses the potential future applications of colorimetric and fluorescent probes in detecting cyanide ions, pointing towards the evolving landscape of analytical techniques and their significance in advancing our ability to monitor cyanide levels effectively. [ABSTRACT FROM AUTHOR]

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

[Display omitted] • A phenothiazine coumarin based fluorescent probe (WX-Lyso) for the detection of ClO– was synthesized. • WX-Lyso displayed a low LOD (0.99 µm) and rapid responsive time to ClO– (<5 s). • WX-Lyso was proved successfully has good lysosomal-targeting and imaging abilities to ClO– in Hela cells. A new phenothiazine coumarin based probe WX-Lyso for detection of ClO– was developed. The probe showed obvious aggregation-induced emission (AIE) characteristic and exhibited a highly selective and sensitive turn-on fluorescence signal at 544 nm for ClO– with a large Stokes shift of 144 nm. The limit of detection (LOD) of ClO– was measured as low as 0.99 μM and a good line equation was obtained in the 0–50 μM concentration range. The detection mechanism was elucidated FT-IR, ESI-MS analysis and DFT. Furthermore, the probe had been demonstrated successfully has good lysosomal-targeting and high-contrast imaging abilities, which has the potential to become a new chemical tool and provide help for detecting ClO– in living systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis and Aggregation Induced Emission property of Dodecyl Carbazole Barbituric Acid. • Designed novel FRET light harvesting antenna in 90 % aqueous solution by coupling AIEgen-DCBA and ACQphore- Rhodamine 6G using steady state and time resolved fluorescence measurements. • Picomolar range detection limit toward Hg2+ was achieved via FRET. • The excellent pH stability of DCBA and DCBA-Rh6G FRET pair spans from pH 3 to pH 11, rendering them suitable as turn on–off chemosensor in water at both acidic and basic environmental conditions. • The fluorescent probe is utilized for sensitive and selective detection of Hg2+ in real water samples, paper strips and MCF 7 cells. Aggregation Induced Emission (AIE) is an intriguing photophysical phenomenon exhibited by certain chromophores that are non-emissive in dilute solutions but are induced to emit light upon aggregation. A "Turn-on" emission has been observed in Dodecyl Carbazole-Barbituric acid conjugate (DCBA) with the addition of poor solvent like water. FRET between an AIE luminogen- DCBA as donor and Rh6G as acceptor has been investigated using steady-state and time-resolved fluorescence studies. There is a significant spectral overlap between the AIE emission of DCBA and the absorption spectra of Rh6G in 9:1 water to THF binary solution. DCBA AIE emission quenching upon addition of Rh6G is identified as due to FRET. The energy transfer efficiency is found to increase linearly with acceptor concentration, reaching an optimum efficiency of 43 %. It holds the promise of being a multiple-donor single-acceptor artificial light harvesting antenna, with an antenna effect of 20.5 %. The proposed FRET system demonstrates excellent pH stability in pH range of 3 to 11. This FRET pair can serve as a turn off fluorescent probe in real water samples and live cells for sensing of Hg2+ ions with high sensitivity, selectivity, and low cytotoxicity. The sensor is also effective for paper strip based Hg2+ detection. [ABSTRACT FROM AUTHOR]

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

[Display omitted] • Water-soluble near-infrared QDs enable precise detection of intracellular copper ions with exceptional selectivity and sensitivity. • Low cytotoxicity and high biocompatibility of QDs ensure safe intracellular imaging applications. • Fluorescence bursts in response to changing copper ion content demonstrate QDs' excellent cellular imaging capabilities. • Synthesized QDs demonstrate stable and selective performance for precise quantification of copper content in biological systems. • This research contributes to understanding the physiological role of intracellular copper ions and advances biomedical imaging techniques. The detection and imaging of intracellular copper ions (Cu2+) play a crucial role in understanding their physiological implications and their involvement in various cellular processes. This study focuses on the synthesis and characterization of water-soluble near-infrared fluorescent CIS/ZnS core–shell quantum dots (QDs) with excellent biocompatibility and stability. The QDs exhibit exceptional selectivity and sensitivity for Cu2+ detection, allowing for precise quantification of Cu2+ content within biological systems. Furthermore, Co-incubation of the QDs with HeLa cells demonstrates their impressive cellular imaging capabilities, facilitated by fluorescence bursts in response to changing Cu2+ content. Overall, our proposed QDs are of great significance in advancing the research and application of near-infrared semiconductor quantum dots in biomedicine, and their near-infrared fluorescence properties and high fluorescence quantum yield (34.48 %) make them very advantageous for the precise detection of intracellular Cu2+ and cell fluorescence imaging. This research contributes to the understanding of copper ion dynamics within cells and opens avenues for further exploration of its role in cellular physiology. [ABSTRACT FROM AUTHOR]

[Display omitted] • The hydrogen sulfide NIR fluorescence probe (DCM-H 2 S) was designed and synthesized. • The probe DCM-H 2 S can specifically recognize H 2 S with a large emission wavelength (681 nm) and a large Stokes shift (121 nm). • The probe DHPC showed rapid response and high sensitivity (0.13 μM). • The probe DCM-H 2 S has been successfully applied to live cell imaging for real-time, dynamic tracking of exogenous and endogenous H 2 S. The signalling molecules of hydrogen sulphide (H 2 S) play an important role in a variety of physiological and pathological processes, and its abnormal concentration causes Down's syndrome, Alzheimer's disease and diabetes mellitus. Thus, the development of an effective detection tool is of vital importance and challenge. In this paper, we synthesized a new "turn-on" hydrogen sulfide near-infrared fluorescent probe (DCM-H 2 S). Remarkably, this probe demonstrated an unanticipated level of selectivity for hydrogen sulfide (H 2 S) over other analytes, rendering it suitable for the precise determination of H 2 S in both in vitro and in vivo settings. Expectedly, the probe exhibited unexpectedly heightened selectivity for H 2 S compared to other analytes, making it a viable option for the specific determination of H 2 S in both in vitro and in vivo applications. With the addition of H 2 S, the probe exhibited distinct turn-on near-infrared (NIR) fluorescence intensity alterations in the DMSO/H 2 O system, together with a high sensitivity (LOD = 0.13 μM) and large Stokes shift (121 nm). More importantly, the probe has been successfully applied to bioimaging for real-time, dynamic tracking of exogenous and endogenous H 2 S. The outcomes showed that the probe (DCM-H 2 S) provides a rapid and effective detection tool for monitoring H 2 S in vivo. [ABSTRACT FROM AUTHOR]

[Display omitted] • A single step of synthesis and assemble of lecithin-derived self-assemble carbon dots. • Enhanced photothermal and photoluminescence property. • Superior Theranostic efficiency after 24 h of incubation with enhanced retention. Photothermal therapy is a promising strategy for killing cancer cells, yet the use of carbon dots as a photothermal agent has limited its use due to the high excretion rate from the cancer cell due to its smaller size of less than 10 nm. In this study, we have developed a strategy for synthesizing self-assembled carbon dots with higher photothermal and lesser excretion from cells. Single-step synthesis of self-assembled carbon dots using thermal degradation method process using lecithin as carbon source. The self-assembly of lecithin-derived carbon dots is induced in the presence of water molecules. Excitingly, lecithin-derived self-assembly of carbon dots (LDSCD) shows superior photothermal efficacy even at low concentrations and fluorescence is red-shifted. Moreover, the LDSCD exhibits higher phototoxicity on incubation with cancer cells for two hours followed by near-infrared light exposure after twenty-four hours. The confocal images of the cells incubated with lecithin-derived self-assembly of carbon dots at two-time intervals (4 and 24 hrs) demonstrated higher retention of self-assembled quantum dots compared to the smaller-size carbon dots (<50 nm). [ABSTRACT FROM AUTHOR]

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

[Display omitted] • An AIE-active peptide-based fluorescent probe TPE-PGH was synthesized. • TPE-PGH exhibited high selectivity and good sensitivity (58.1 nM), rapid (within 50 s) response to Hg2+ ions. • TPE-PGH was successfully used for the detection of Hg2+ in food samples with good recovery. • TPE-PGH was successfully applied in imaging of Hg2+ in living cells based on good biocompatibility. • Smartphone-assisted test strips visual assays were successfully used to evaluate and monitor Hg2+ levels. A novel peptide-based fluorescent probe TPE-PGH was firstly developed based on aggregation-induced emission (AIE) effect. The fluorescence intensity of TPE-PGH was largely ignored in the low water fraction, whereas bright blue fluorescence was observed in the high water fraction. TPE-PGH achieved high selectivity and rapid detection of Hg2+, and has excellent sensitivity to detect Hg2+ with low LOD (58.1 nM). Interestingly, TPE-PGH provided a significant color changed from dark blue to bright cyan upon binding with Hg2+ ions under UV lamp (365 nm). In addition, TPE-PGH was able to simultaneously visualize Hg2+ in living cells with different fluorescence intensities based on excellent cells permeability and low toxicity. Further, TPE-PGH exhibited high precision (RSD < 4 %), and was successfully applied for detecting Hg2+ in real food samples, such as milk, soda drink, red wine, cucumber, tomato and carrot. Successful test strips responses also demonstrated that the potential of TPE-PGH for portable detection of Hg2+ in real samples. Especially, AIE based-test strips soaked in different Hg2+ concentrations was successfully utilized for semi-quantitative detection of Hg2+ using the RGB APP installed on a smartphone, which will provide a new approach for smart and portable detection of contaminated heavy metal ions in food samples. [ABSTRACT FROM AUTHOR]

A fluorescence and colorimetric bifunctional probe for recognition of Al3+ and Cu2+ was synthesized, which shows potential applicability in fluorescence test paper, cell fluorescence imaging, as well as practical environmental water samples. [Display omitted] • Probe 1 can simultaneously recognize Al3+ and Cu2+ in aqueous solution. • 1 has a high selectivity and a high sensitivity for Al3+ and Cu2+. • 1 shows a fluorescence visualizing probe in cells for Al3+. • 1 has excellent recyclability and anti-ion interference ability for Cu2+. • 1 shows excellent application in environmental water samples for Cu2+. A highly sensitive bifunctional probe (1) for Al3+ and Cu2+ by the reaction of 2-hydroxyl-1-naphthalene formaldehyde with indole-3-formyl hydrazine was synthesized. In THF-H 2 O (v/v = 3:7) solution, 1 only shows fluorescence enhanced recognition for Al3+ in 17 common metal ions, which shows that 1 can be used as a highly selective fluorescence enhancement probe for Al3+. When the concentration of Al3+ is 20.0 µM (1.0 equivalent), the fluorescence intensity of 1 is increased by 195 times, and the detection limit of 1 for Al3+ is calculated to be 3.8 nM, which shows that 1 is fluorescence probe for Al3+ with an ultra-high sensitivity. Trace Al3+ (For example, the WHO drinking water quality standard 7.4 μM) can be clearly observed by the fluorescence test paper covering 1 through the change of fluorescence color. In addition, the vivo-detection ability of 1 is verified by detected the Al3+ in living GS cells of epinephelus coioides. Furthermore, 1 can also be used as a high selective and sensitive colorimetric probe for Cu2+. In THF-H 2 O (v/v = 3:7) buffer solution (pH = 7.0), the addition of Cu2+ results in a 69 nm red shift in the UV–visible absorption spectrum of 1 solution, causing the color of 1 solution to change from colorless to yellow. In addition, 1 shows a low detection limit of 39.3 nM, a fast response time, excellent recyclability and anti-interference for Cu2+. Therefore, 1 can be used for fluorescence detection of Cu2+ in environmental water systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel probe BD-C based on the FRET-ICT mechanism was designed to detect cysteine. • Probe BD-C had superior selectivity without the interference of other biological thiols. • Probe BD-C had large Stokes shift and the energy transfer efficiency reached 98.8%. • Probe BD-C had superior endoplasmic reticulum-targeting. Cysteine is an important thiol amino acid that is abundantly present in cells and has an important function in various life processes of the human body. Therefore, it is of great significance to develop an accurate method for monitoring cysteine concentration in cells. We designed and synthesized a novel FRET-ICT-based ratiometric fluorescence and colorimetric probe (BD-C) for detecting cysteine. As cysteine was gradually added, the fluorescence intensity of probe BD-C in buffer solution decreased at 614 nm and increased at 428 nm. The logarithm of the fluorescence intensity ratio to cysteine exhibited favorable linearity in the concentration range of 0.5–14.0 μM, with a detection limit of 395 nM. The energy transfer efficiency of this FRET system is up to 98.8%. BD-C demonstrated preeminent selectivity for cysteine and could specifically react with cysteine, though other sulfhydryl amino acids, such as GSH and Hcy, were present. Furthermore, BD-C exhibited outstanding targeting ability to the endoplasmic reticulum (ER) and was successfully applied in cellular imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new lysosome-targeted fluorescent probe FAP1 for the recognition of FA was developed. • Probe FAP1 showed high sensitivity and selectivity for detecting FA with a large Stokes shift (130 nm). • Probe FAP1 exhibited good biocompatibility and could be used to image FA in lysosome. Formaldehyde (FA) is one of reactive carbonyl species (RCS), which is involved in various physiological and pathological processes of organisms. Herein, a novel fluorescent probe (FAP1) containing lysosomal localization group for the detection of FA was designed and synthesized. The probe exhibited good fluorescence recognition performances for FA, such as large Stokes shift (130 nm), specific selectivity, good anti-interference ability, and low minimum detection limit (16 nM). It is worth mentioning that the probe has good biocompatibility and could be applied to the imaging detection of FA in lysosome. [ABSTRACT FROM AUTHOR]

Abstract A novel dansyl-tetrapeptide fluorescent probe (L) for the continuous fluorescent "off-on-off" response detection of Cd2+ ions and Cysteine (Cys) has been designed and synthesized. In our approach, L exhibited very high selectivity to Cd2+ ions over other common metal ions in buffer aqueous solution at natural pH. The resulting L -Cd binding motif system could continuously detect Cys among Glutathione (GSH), Homocysteine (HCy) and 20 natural amino acids. The excellent reversibility and cyclicity of L were also confirmed during the detection of Cd2+ ions and Cys. The detection limit of Cd2+ ions and Cys were obtained to be 93 nM and 35 nM, and lower than EPA and WHO guidelines. What's more, L showed low cytotoxicity and exciting cell infiltration toward living cells, which successfully fluorescent "off-on-off" biological imaged Cd2+ ions and Cys effectively in HeLa cells and renal tubule epithelium (HK2) cells by confocal fluorescence imaging. This study will promote the development of novel multifunctional peptide-based fluorescent probe for Cd2+ ions and Cys in environmental and biological systems. Graphical abstract Unlabelled Image Highlights • A novel peptide fluorescent probe L was synthesized. • L displayed high sensitivity for Cd(II) with a low detection limit of 93 nM. • L -Cd binding motif system could continuously detected Cys with detection limits of 35 nM, and cycle effect were very good. • As a potential probe, L could continuously detected Cd2+ ions and Cys in living HeLa cells. [ABSTRACT FROM AUTHOR]

Abstract In this study, sodium 2-Mercaptobenzimidazole-5-sulfonate (SMBD) was used as both a protecting ligand and a reducing agent to synthesize highly fluorescent gold nanoclusters (SMBD@AuNCs). When 360 nm was used as the excitation wavelength, the resultant AuNCs exhibited orange-yellow fluorescence with the maximum emission at 630 nm. In addition, it was found that the fluorescent SMBD@AuNCs could been significantly quenched by Hg2+ over other ions. The phenomenon was further used to design a SMBD@AuNCs-based fluorescence sensing method for the detection of Hg2+. Under the optimal conditions, the detection limit of the proposed method for Hg2+ was 0.5 nM, with a good linear range from 4.0 nM to 20.0 μM (R2 = 0.999). Then, it could be successfully utilized for determining trace amount of Hg2+ in real water samples. Furthermore, owing to the excellent biocompatibility, the as-prepared fluorescent AuNCs showed a great potential application in bioimaging fields. Cytotoxicity studies showed that the AuNCs exhibited negligible effects in altering cell proliferation or triggering apoptosis. The as-synthesized AuNCs have been successfully applied as a photoluminescent probe for human bladder cancer cellular imaging. Highlights • A facile, rapid "one-pot" synthesis of orange-yellow fluorescent SMBD@AuNCs at room temperature was proposed. • A new fluorescence sensing method for Hg2+ was designed based on the quenching phenomenon of SMBD@AuNCs. • The AuNCs have been successfully applied in human bladder cancer cellular imaging. [ABSTRACT FROM AUTHOR]

Abstract An oxadiazole-based chemosensor (sensor 1) for Fe3+/Fe2+ was successfully designed and synthesized. Sensor 1 displayed fluorescence quenching response towards both Fe3+ and Fe2+ in THF:H 2 O (4:1, v/v) solvent with high selectivity and sensitivity over all other competitive metal ions. Job's plot, mass spectra, DFT calculation and fluorescence titration disclosed that fluorescence quenching was caused by forming 1:1 complex between sensor 1 and iron ions. Sensor 1 presented high sensitive fluorescence response at the pH value of human body and its fluorescence intensity showed linear relationship with the concentration of iron ion. Sensor 1 also presented fast fluorescence response towards iron ions and the lower detection limit, 7.78 μM for Fe2+ ion and 6.95 μM for Fe3+ ion, respectively. Sensor 1 can be used as test strips to detect iron ions in water samples. Fluorescence cell imaging also demonstrated sensor 1 can recognize iron ions in living cells. Graphical abstract Unlabelled Image Highlights • A new fluorescent sensor 1 containing oxadiazole and picolinic acid was designed and synthesized. • Sensor 1 displayed selective fluorescence quenching response towards both Fe2+ and Fe3+. • Sensor 1 can recognize iron ions with high selectivity in a wide pH range of 3~10. • Sensor 1 can detect iron ions in water sample and recognize iron ions in the form of test strips. • Fluorescence imaging proved sensor 1 can sense both Fe2+ and Fe3+ in living cell. [ABSTRACT FROM AUTHOR]

Graphical abstract Unlabelled Image Highlights • Synthesis of a CDs using green, cost free spider silk as a carbon precursor • CDs have high sensitivity and selectivity for Hg2+ ions detection (LOD 5.3 nM). • Sensing mechanism was analysed by UV, FTIR, HRTEM, Zeta potential and FL life time. • The probe was applied with great potential to estimated Hg2+ ions in real samples. • Showed positive action in cell viability & cell imaging treatment with HepG2 cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dual-emission carbon dots were gotten from tetracycline by microwave method. • Carbon dots were developed as ratiometric sensors for detection of Co2+ and EDTA. • The smartphone imaging were established for visual quantification of Co2+ and EDTA. • Carbon dots-based sensors were applied for tracking Co2+ and EDTA in living cells. Ratiometric fluorescence analysis provides the feasibility for visual quantitative sensing by presenting continuous color changes. Herein, dual-emission carbon dots (D-CDs) have been developed for ratiometric recognition of Co2+ and EDTA, along with successive fluorescence variation of yellow, purplish-pink, purple, light blue, and dark blue. D-CDs have been synthesized by microwave-assisted heating of tetracycline and manifest dual emissions at 562 nm and 610 nm under 450 nm excitation. Intriguingly, the emissions at 562 nm and 610 nm are quenched while a ratio rising emission emerges at 482 nm upon introducing Co2+, which displays ratiometric fluorescence emission characteristics (I 482 /I 562) in the range of 0.25–400 µM with significant fluorescence varying from yellow, purplish-pink, purple, light blue, to dark blue. Subsequent addition of EDTA could ratiometric recover the fluorescence of D-CDs in the range of 50–130 µM with the fluorescence returning from dark blue, light blue, purple, purplish-pink, to yellow. More crucially, integrating continuous color changes and color recognizer APP in the smartphone, visual quantification of Co2+ and EDTA can be realized based on the ratio of blue value and red value (B/R) with linear ranges of 0–400 µM and 0–300 µM, respectively. Furthermore, proposed D-CDs could be extended as a visual biosensing platform for tracking Co2+ and EDTA in living cells, which have potential application prospect in biosystem. [ABSTRACT FROM AUTHOR]

[Display omitted] • Blue-luminescent CDs by hydrothermal method using CA and EDA for a growth time of only one hour. • Prepared biocompatible CDs were effectively used for cancer cell (N2a) imaging. • CDs as an ultrafast luminescence-based detector of folic acid (FA) with a limit of detection of 6 nM. • The mechanism of detection is the inner filter effect and static quenching due to the formation of a complex between CDs and FA. • The sensor is tested on plasma samples of albino mice and validated with more than 60% accuracy. The development of an ultrafast folic acid (FA) sensor (with no incubation time), having a detection limit and detection range in the nanomolar levels is of high importance in the field of biomedical FA sensing. For that, highly luminescent carbon dots (CDs) are synthesized by hydrothermal method with a lower growth duration of '1 h' using the precursors, anhydrous citric acid as the carbon source and ethylenediamine as the nitrogen dopant material. TEM images confirmed a spherical morphology for the prepared CDs with an average size of nearly 2.8 nm. A photoluminescence quenching-based technique is used for FA detection using the prepared CDs. The detection limit is 6 nM, the lowest reported for CDs made from these precursors and the detection range is 0–50 nM. The mode of quenching is found to be static, based on the lifetime measurements and UV–vis spectroscopy. The mechanism of static quenching due to the formation of a ground state complex between the synthesized CDs and FA is confirmed by Raman spectroscopy and dynamic light scattering (DLS) study, and the binding mechanism of CDs and FA is explained in detail using FTIR and Raman spectroscopy for the first time. The fabricated CDs are used as biocompatible probes to image the N2a cells. A quantitative reduction in fluorescence intensity was observed for CD + FA mixtures internalized into the cells with incremental addition of FA. Furthermore, the practicality of the CD probe as an FA sensor is evaluated by testing the amount of FA in spiked plasma samples from albino rats, and the results are validated using a clinical method. [ABSTRACT FROM AUTHOR]

Nano-hydroxyapatite particles (Ca 10 (PO 4 ) 6 (OH) 2 , nano-HAp), the main inorganic components of human bone and teeth, has attracted much attentions as a kind of biocompatible carrier to construct dual/multi modal bioimaging probes in recent years. However, the currently developed HAp-based probes still have some shortcomings, such as poor mono-dispersion, potential toxicity and none near-infrared emission, which hinder their further applications in the field of bioimaging. In order to solve the above problems and to combine the high space resolution of CT and high sensitivity of fluorescence together, here we developed a novel dual-modal (CT/fluorescence) bioimaging probe based on nano-HAp. Ba 2 + as a CT contrast agent was doped into the lattice of nano-HAp, and Cu-doped quantum dots with near-infrared fluorescent emission and hyaluronic acid (HA) were conjugated with the HAp as a fluorescent agent and tumor-targeting ligand individually to realize its near-infrared imaging and tumor-targeting. The as-received Ba 2 + -doped HAp-QDs-HA conjugates not only well maintained the good dispersion of nano-HAp, but also possessed near-infrared emission at about 700 nm, good biocompatibility and photostability. Furthermore, the in-vitro CT and fluorescence cell imaging of the conjugates also exhibited good dual-modal bioimaging and tumor-targeting ability for potential applications in the field of early diagnosis and therapy of cancer. [ABSTRACT FROM AUTHOR]

[Display omitted] • A lysosome-targetable fluorescent probe for cysteine has been reported. • The probe displays high sensitivity and high selectivity for cysteine. • The probe can be utilized for determination of cysteine within the lysosomes of living cells. An essential sulfhydryl amino acid in the human body is cysteine (Cys). Its abnormal level is related to coronary heart disease, hypertension, growth retardation, sleepiness, liver injury and AIDS. At present, although many cysteine fluorescent probes have been synthesized, there are relatively few fluorescent probes for sensing cysteine in lysosomes. Therefore, based on a rhodamine derivative, we constructed a fluorescent probe with high selectivity for detecting cysteine in lysosome. The probe chose acrylate as the recognition group and morpholine as the positioning group. The probe was in spirolactone state and displayed very weak fluorescence when cysteine was absent. After adding cysteine, the conjugated xanthene structure was formed through the conversion of the closed spirolactone structure and strong green fluorescence appeared. Compared with glutathione (GSH) and homocysteine (Hcy), the probe had better selectivity to Cys. When the Cys concentration was altered from 1.0 × 10−7 to 6.0 × 10−6 mol·L−1, there was a good linear relationship between fluorescence intensity of the probe and Cys concentration. The detection limit had been evaluated to be 7.5 × 10−9 mol·L−1 for Cys. The probe can work under a wide pH range, including pH under physiological conditions. The probe also has a good effect in non-cytotoxic confocal imaging of endogenous and exogenous cysteine in A549 cells. These findings showed that the fluorescent probe synthesized in this study could be a useful tool for the detection of endogenic and exogenic cysteine. [ABSTRACT FROM AUTHOR]

[Display omitted] • The PbS nanoparticle cluster-loaded phospholipid micelles decorated with FA were used as a nanoprobe. • Electrochemical detection of folate receptor-positive CTCs based on CTC uptake of nanoprobes using the E-DNA sensor. • Electroless deposition was used to modify SPCE with Au nanostructures. Developing methods for the circulating tumor cells (CTCs) detection is important for noninvasive cancer diagnosis. A sensitive method for homogeneous electrochemical detection of CTCs was developed based on the affinity of folic acid (FA) for folate receptor (FR), which is overexpressed on the CTC surface. The PbS nanoparticle cluster-loaded phospholipid micelles decorated with FA were prepared and used as a nanoprobe. The specific binding of FA to FR-positive CTCs leads to the uptake of the nanoprobes into the CTCs. Cellular imaging assay showed the excellent biocompatibility and selectivity of nanoprobes. After separation of intracellular nanoprobes and the residual free nanoprobes in the solution by centrifugation, nanoprobes in the cell were dissolved using acid. The amount of the target cells was quantified by the electrochemical detection of Pd2+ using the electrochemical DNA (E-DNA) sensor, which was fabricated based on the self-assembly of probe DNA on the flowerlike gold nanostructures modified the screen-printed carbon electrode (SPCE). Because of the large quantities of detectable Pd2+ contained in the nanoprobes, the signal amplification effect was achieved. The developed electrochemical assay allows the detection of ∼5 cells from 1 mL of sample. Studies with both healthy individuals and cancer patient blood samples demonstrate that the assay is sensitive and FR-positive CTCs specific. [ABSTRACT FROM AUTHOR]

This study describes a facile strategy to synthesize nitrogen-doped carbon dots (N -CDs) through solid-phase thermal treatment of melamine and citric acid monohydrate (CA) as precursors. The N -CD-based fluorescence "on–off-on" sensing platform exhibited rapid, selective and sensitive detection of TCs (tetracycline hydrochloride and doxycycline) and Al3+. In addition, the N -CD probe can be used for cell imaging based on its low toxicity and good biocompatibility, implying the potential applications in the fields of biomarkers and bioanalysis in vivo imaging studies. [Display omitted] • Nitrogen-doped carbon dots (N -CDs) was designed through solid-phase thermal treatment method. • The N -CDs displayed a bright fluorescence emission with the fluorescence quantum yield of 24 %. • The bright fluorescence emission property allows the N -CDs to be utilized for cell imaging. • The fluorescence "on–off-on" sensing platform exhibited sensitive detection of TCs and Al3+. • The proposed sensing platform is utilized for detecting TCs and Al3+ in tap water and milk samples. Novel bifunctional nitrogen-doped carbon dots (N -CDs) were prepared through solid-phase thermal treatment of melamine and citric acid monohydrate (CA) as precursors. The N -CDs displayed uniform size distribution, excellent photostability and bright fluorescence emission with the fluorescence quantum yield of 24 %. The N -CD-based fluorescence "on–off-on" sensing platform exhibited rapid, selective and sensitive detection of TCs (tetracycline hydrochloride and doxycycline) and Al3+. The fluorescence at 472 nm can be quenched by TCs through the internal filtration effect (IFE) and can also be recovered with the addition of Al3+ by the stronger affinity between Al3+ and TCs than that of CDs. The fluorescent sensor exhibits excellent selectivity and high sensitivity toward TCs and Al3+ detection with low detection limits for tetracycline hydrochloride: 91.8 nM, doxycycline: 78 nM and Al3+: 163.5 nM. Moreover, the proposed sensing platform is utilized for detecting TCs and Al3+ in tap water and milk samples. In addition, the N -CD probe can be used for cell imaging based on its low toxicity and good biocompatibility, implying the potential applications in the fields of biomarkers and bioanalysis in vivo imaging studies. [ABSTRACT FROM AUTHOR]

Lipid droplets (LDs) and lysosomes serve as important subcellular organelles, which plays an important role in a variety of physiological processes. The components in lipid droplets can be degraded by lysosomes, so it is of great value to study the relationship between LDs and lysosomes. However, simultaneous targeting of lipid droplets and lysosomal polymer fluorescent probes has hardly been reported. Therefore, we developed a novel polyethylene glycol fluorescent probe PEG-Nap-Lyso that could be applied to simultaneously track lysosomes and lipid droplets. PEG-Nap-Lyso was able to not only track cells in different physiological environments, but also differentiate live cells from dead cells by changes in the polarity of the intracellular microenvironment. In addition, the probe had the advantages of amphiphilicity, pH resistance, high selectivity, good stability (3600s), low biotoxicity and large Stokes shift (167 nm). These excellent properties made the fluorescent probe PEG-Nap-Lyso provided an effective way to study the relationship between LDs and lysosomes. [Display omitted] • A unique amphipathic PEG-based fluorescent probe PEG-Nap-Lyso was designed with a large Stokes shift (167 nm). • The novel fluorescent probe could target lipid droplets and lysosomes in living cells. • The novel fluorescent probe had been successfully used for dual-channel imaging to discriminate living and dead cells. • The novel fluorescent probe could tracking LDs in cells under different physiological conditions. Lipid droplets (LDs) and lysosomes serve as important subcellular organelles, which plays an important role in a variety of physiological processes. The components in lipid droplets can be degraded by lysosomes, so it is of great value to study the relationship between LDs and lysosomes. However, few polymer fluorescent probes targeting both lipid droplets and lysosomes have been reported. Therefore, we developed a novel polyethylene glycol fluorescent probe PEG-Nap-Lyso that could be applied to simultaneously track lysosomes and lipid droplets. PEG-Nap-Lyso was able to not only track cells in different physiological environments, but also differentiate live cells from dead cells by changes in the polarity of the intracellular microenvironment. In addition, the probe showed the advantages of amphiphilicity, pH resistance, high selectivity, good stability (3600 s), low biotoxicity and large Stokes shift (167 nm). These excellent properties made the fluorescent probe PEG-Nap-Lyso provided an effective way to study the relationship between LDs and lysosomes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carbon dots and gold nanoclusters were used combinedly for determination α-glucosidase in human serum. • Ratiometric fluorometry was designed based on aggregation-induced emission enhancement of gold nanoclusters and steady emission of carbon dots. • Good cell membrane permeability of the probe facilitates its application in cellular imaging. A fluorescence probe was designed based on carbon dots (CDs) and glutathione-capped gold nanoclusters (GSH-AuNCs) for detecting α-glucosidase in human serum. By employing l -ascorbic acid-2-O-α- d -glucopyranosyl (AAG) as substrate for the α-glucosidase catalyzed hydrolysis reaction, ascorbic acid (AA) was generated, and subsequently reduced cerium (IV) ion (Ce4+) to Ce3+. Since Ce3+ would selectively improve the aggregation of GSH-AuNCs, the consequent aggregation-induced emission enhancement (AIEE) of aggregated GSH-AuNCs was measured for indicating the activity of α-glucosidase involved in the hydrolysis process. To furtherly improve the precision of spectral response, ratiometric fluorometry was realized by taking the fluorescence emission of CDs, which was affected insignificantly during the above process, as the fluorescence reference. The developed probe exhibited a linear response to α-glucosidase activity in the range of 0.01 ∼ 0.1 U‧mL−1, with a limit of detection (LOD) of 0.0055 U‧mL−1. Results of serum sample examination and cellular imaging reveal the promising potential of the developed probe for clinical diagnosis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Coumarin-based fluorescence turn-on probes CMONOO1 and CMONOO2 were constructed for ONOO– detecting. • CMONOO1 and CMONOO2 have excellent detection limits as low as 23.3 nM and 21.4 nM, respectively. • CMONOO2 was applied for ONOO– image in living cells, inflammatory tissues, and mice with satisfactory results. Peroxynitrite anion (ONOO–), a type of reactive nitrogen species (RNS), profoundly implicated in the physiological and pathological processes of a series of oxidative stress-related diseases. Thus, construction of reliable tools to track peroxynitrite (ONOO–) in biosystems is urgently desired. In this work, based-on D-π- d -structure of coumarin derivative and 2-(4-nitrophenyl)-2-oxoacetamide (also served as the fluorescence quencher) as flourophore and response group, respectively, two fluorescence turn-on probes CMONOO1 and CMONOO2 were constructed for rapidly detection and imaging of ONOO– in living cells, and inflammatory tissues and mice. These two probes had fast response time for ONOO– (∼60 s), and exhibited highly selectivity and sensitivity detection performance for ONOO– over other ROS and RNS. Also they had excellent detection limits in the ranges of 0–1.0 μM as low as 23.3 nM and 21.4 nM respectively. In addition, both probes have markedly biocompatibility, which could be beneficial to the imaging analysis of ONOO– in living biosystems. Therefore, CMONOO2 was selected as a representative for ONOO– imaging analysis in living cells, and inflammatory tissues and mice with satisfactory results, demonstrating these two robust probes have great potential to further elucidate ONOO–-related diseases. [ABSTRACT FROM AUTHOR]

[Display omitted] • A ratiometric fluorogenic nanoprobe for detecting ClO− was rationally designed and prepared. • The probe could ratiometricly detect ClO− within 5 s in an ultrafast and highly selective manner. • The probe has been utilized to realize the ratiometric ClO− imaging in living cells and zebrafish. In this paper, we report the design and preparation of a new fluorescent nanoprobe (HC-NP 420/565) that could ratiometricly detect ClO− within five seconds by fluorescence imaging in an ultrafast and highly selective manner. The ratiometric response of the probe was facilely achieved by integrating 2-oxime-coumarin as a ClO− receptor, and a 1,8-naphthimide derivative as the internal reference into a Pluronic F-127 matrix. The probe showed highly sensitive and specific responsibility towards ClO− at physiological conditions with the detection limit of 105.16 μM. Notably, the probe displayed excellent ClO− ratiometric imaging performance in living cells and zebrafish larvae, demonstrating the potential application in ClO−-related chemical biology studies. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel aggregation-induced emission active chemosensor has been developed. • The sensor could detect Cu2+ and S2− with low detection limit (34.6 nM and 1.15 μM, respectively) in an almost neat aqueous solution. • The sensor has been successfully applied to imaging of Cu2+ and S2− in living cells and zebrafish. A simple reversible fluorescent chemosensor 1 was constructed using a coumarin backbone, which displayed notable aggregation-induced emission. Particularly, Cu2+ could selectively and sensitively induce fluorescence quenching of sensor 1 in an almost neat aqueous solution. Furthermore, addition of S2− to 1 -Cu2+ system could specifically restore the fluorescence emission of 1 by snatching Cu2+ ion from its complex. The detection limits of sensor 1 towards Cu2+ and S2− were 34.6 nM and 1.15 μM, respectively. Notably, sensor 1 was successfully applied to detect Cu2+ and S2− in living cells and zebrafish owing to its remarkable fluorescence behavior and low cytotoxicity. [ABSTRACT FROM AUTHOR]

[Display omitted] • A "turn-on" chalcone-based fluorescence probe with lysosome-targeting has been developed. • The probe can monitor hydrogen sulfide (H 2 S) with a short response time (within 20 s), low detection limit (120 nM), and a wide pH range (2.0–9.0). • The probe has been successfully applied to the imaging of endogenous and exogenous H 2 S in living cells and zebrafish. A chalcone-based probe was designed to hydrogen sulfide (H 2 S) detection by employing 2,4-dinitrophenyl either as a recognition group. This probe can rapidly and specifically detect H 2 S in semi-aqueous solutions with the detection limit of 120 nM and a wide pH range from 2.0 to 9.0. The sensing mechanism was determined by UV–Vis, fluorescence spectra, mass spectra, 1H NMR studies and density functional theory calculations, respectively. Additionally, the probe can target lysosomes and monitor H 2 S in living cells and zebrafish by fluorescence imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • Acid-mediated synthesis with liquid–liquid extraction assisted separation strategy was built. • The developed strategy was successfully used to obtain double-color long wavelengths CDs. • R-CDs with acid-sensitivity can be applied as sensing platform for pH and cell-imaging. • O-CDs with dual emissions can be used to water content detection in various organic solvents. Owing to their various advantages, such as low photodamage and high tissue penetration, carbon dots (CDs) with long emission wavelength have gained much attention, and are used to compensate for blue to green fluorescent CDs. However, their synthesis has been challenging. In the present study, an acid-mediated synthesis method was developed for the preparation of long-wavelength CDs by using N -phenyl-o-phenylenediamine as a precursor, phosphoric acid as an acidity regulator. According to the principle of similarity compatibility, liquid–liquid extraction was further adopted to separate red CDs (R-CDs) and orange double-color CDs (O-CDs) from long-wavelength CDs mixture for the first time. By optimizing the factors that affect quantum yield (QY), R-CDs with a QY of 4.16% and O-CDs with a QY of 60.80% were obtained. Structural analysis revealed that both types of CDs had a graphite-like structure with an abundance of various groups on their surface. Their fluorescence colors were quite different because of differences in the nature of these functional groups (e.g. contents of N and P). To explore the application value of two kinds of CDs, the potential use of R-CDs, for pH sensing and O-CDs for water content detection in organic solvents was studied systematically. The results revealed that R-CDs was acid sensitive and can be used to detect different pH values. While O-CDs can be used for the detection of various water content in different organic solvents including ethyl acetate, ethanol, methanol, DMSO, DMF and acetone. Finally, due to the low toxicity and good biocompatibility, the potential of R-CDs as probe for cell imaging was explored preliminarily. Co-localization experiments with commercial dye Lyso-tracker Red showed that R-CDs was localized in lysozyme and can be used for lysosomal imaging, further proving that R-CDs is a potential lysosomal probe. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new fluorescent probe DAHK was synthesized based on copper peptide backbone. • DAHK could detect Cu2+ in 100 % aqueous medium with obvious fluorescence quenching. • DAHK-Cu2+ ensemble exhibited fluorescent "off–on" response with H 2 S. • DAHK was successfully used to selectively detect Cu2+ and H 2 S in living cells. • DAHK was successfully applied to sensitively detect Cu2+ and H 2 S in test strips. Copper ions (Cu2+) and hydrogen sulfide (H 2 S) detection is of great significance in environmental monitoring and disease screening. Herein, a novel fluorescent probe (DAHK) was rationally designed and easily synthesized based on a copper peptide backbone labelled a dansyl fluorophore. DAHK exhibited large Stokes shift (210 nm), high sensitivity (38.9 nM) and high selectivity response to Cu2+ ions based on obvious fluorescence quenching in HEPES buffer (10.0 mM, pH 7.4) solutions. In addition, the in situ formed DAHK -Cu2+ ensemble was successfully used as a secondary probe for rapidly and sequentially detected H 2 S via fluorescence "off–on" response, and without interference by a range of other anions. The limit of detection (LOD) for 47.3 nM was determined, which was a much lower value than WHO and EPA guidelines (H 2 S) for drinking water. The reversibility of interaction of DAHK with Cu2+ and H 2 S was monitored using fluorescence emission spectra. Cells imaging experiments exhibited that DAHK had good membrane permeability and excellent low toxicity. Moreover, DAHK was successfully made into fluorescent test strips for visual detection and rapid analysis based on the exciting stability and excellent water solubility. [ABSTRACT FROM AUTHOR]

[Display omitted] • Most recent development of fluorescence sensing for biochemical molecules are presented. • Biochemical assays based on fluorescence technique are classified to "turn-off" and "turn-on". • Probable mechanisms of fluorescence are summarized and discussed how to differentiate the quenching/enhancement mechanisms. Fluorescence materials have received much attention in scientific studies because of their potential uses in cell imaging, photonic devices, and sensors. Sensors based on the combination of fluorescence techniques with various luminescent nanomaterials have recently been developed for the selective and sensitive sensing of biochemical molecules with these nanoparticles. This review provides a summary of the most recent applications of fluorescence-based analytical techniques. Downshifting and upconversion procedures are discussed to briefly introduce the principles underlying the luminescence of a material. Following that, the most recent findings (2019–2022) on the applications of fluorescence techniques for analytical assays are presented, along with a classification of "turn-off" and "turn-on" approaches. In addition, we discussed how to differentiate the fluorescence quenching/enhancement mechanisms using unique spectroscopy techniques. [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]

[Display omitted] • Near-infrared carbon dots are synthesized using an eco-friendly and facile approach with narrow FWHM. • A Near-infrared nanoprobe exhibits high selectivity and stability for the detection of palladium ions in aqueous solution with a detection limit of 85.3 nM. • This nanoprobe shows high biocompatibility and is employed to monitor Pd2+ in Li-7 living cells. In this work, an eco-friendly unique approach was used to synthesize near-infrared carbon dots (NIR-CDs) from Magnolia denudata leaves. The as-prepared NIR-CDs showed a stable near-infrared emission with peak at about 678 nm and narrow full width at half maximum (FWHM), which was utilized as a fluorophore in a fluorescent nanoprobe after modification with Pluronic F-127 for detection of palladium ion (Pd2+). The resulting nanoprobe diaplayed admirable performances for detecting Pd2+ including high selectivity, excellent water solubility, and stability. The fluorescence intensity of the nanoprobe was selectivity quenched by Pd2+ within the scope of 0–200 μM. In addition, the limit of detection (LOD) was 85.3 nM. Moreover, the constructed nanoprobe had an approving assay performance in real water samples. Finally, the nanoprobe demonstrated low toxicity and could be utilized to monitor Pd2+ in Li-7 cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new dye was synthesized and the spectral properties were studied. • The dye showed good spectral properties and was used to detect SO 2 derivatives. • The reactivity of the probe could be regulated by the thiomorpholine group. A new coumarin-hemicyanine dye was synthesized and used as a ratiometric fluorescent probe for SO 2 derivatives (HSO 3 -/SO 3 2-). The probe showed deep-red fluorescence, ratiometric response, good selectivity, low detection limit and well-separated emission bands. Moreover, the probe was mitochondria-targeted, and was applied to image SO 2 derivatives in living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two new probes A and B were designed to detect thiophenols. • The probes had superior properties in sensitivity, selectivity and response time. • The probes responded to thiophenols with a good range of linearity and low detection limit. • The probes were used to detect thiophenol in water samples with good recovery. • Probe B was applied to visualize thiophenol in living cells. Thiophenol is known as a class of highly toxic pollutant that can damage to the environment and biological health. It is great significant to detect thiophenol rapidly and sensitively in living cells and environment samples. Hence, we designed and developed two reliable and efficient fluorescent probes that can monitor thiophenol rapidly. The two probes had superior properties in sensitivity and selectivity in the solvent system of pH = 7.4, which had high reactivity to thiophenol, and basically had no response to other sulfur compounds. These probes had a superior range of linearity and low limit of detection for thiophenols. The limits of detection for probe A and probe B (calculated by 3σ/k) are 63.9 nM and 24.7 nM, respectively. These probes have been applied to detect thiophenol in environmental water with good recovery. Moreover, probe B has been used to visualize thiophenol in living cells. Therefore, the fluorescent probes can provide an effective way to monitor thiophenols in environmental water and in cell imaging. [ABSTRACT FROM AUTHOR]

An efficient and green approach for the synthesis of N-CDs with Galli Gigerii Endothelium Corneum, a waste from chicken, as precursor was reported for the first time. The obtained N-CDs with outstanding blue fluorescence and can be acted as a sensitive and selective sensing platform for nitroimidazoles including MNZ, TNZ, ONZ and SNZ. Furthermore, the N-CDs were also successfully applied to the detection of nitroimidazoles in the real samples (e.g. tablets, chicken and plasma). The cytotoxicity and bio-imaging applications of N-CDs were conducted and the results confirmed the potential application of it in biological field. [Display omitted] • An efficient and green approach for N-CDs preparation with GGEC as precursor was reported. • The N-CDs showed outstanding blue fluorescence with high quantum yield of 19.45%. • The N-CDs can be acted as a sensitive and selective sensing platform for four nitroimidazoles. • The sensing platform can be applied to analyze real samples such as tablets, chicken and plasma. The reuse of waste from agriculture or food is of great significance. Herein, an efficient and green approach for the synthesis of N-CDs with GGEC, a waste from chicken, as precursor was reported for the first time. The obtained N-CDs with outstanding blue fluorescence demonstrated high quantum yield (QY) of 19.45%. Further, the optical and physicochemical properties of N-CDs were characterized through UV–vis, FL spectroscopy, TEM, FT-IR and XPS. Interestingly, the N-CDs can be acted as a sensitive and selective sensing platform for nitroimidazoles including MNZ, TNZ, ONZ and SNZ with the fluorescent quenching mechanisms of IFE and static quenching. The LODs of them were separately determined as 0.267 μM, 0.067 μM, 0.133 μM, 0.067 μM, which were satisfying in comparison with the reported fluorescence detection method. Furthermore, the N-CDs were also successfully applied to the detection of nitroimidazoles in the real samples (e.g. tablets, chicken and plasma) with satisfactory results. Eventually, the cytotoxicity and bio-imaging applications of N-CDs were conducted and the results confirmed the potential application of it in biological field. [ABSTRACT FROM AUTHOR]

Boron and nitrogen co-doped carbon dots (B,N-CDs) with high quantum yield (25.3%) and strong fluorescence performance is used for Cu2+ determination and multicolor cell imaging. It exhibits wide linear range, low detection limit, satisfactory stability, selectivity and low cytotoxicity performance. [Display omitted] • B, N-CDs with high quantum yield and excellent stability were successfully synthesized by one-step hydrothermal method. • High quantum yield results from the synergistic effect of B, N co-doping and surface functional groups. • B, N-CDs were selective to Cu2+ with low detection limit, wide linear range and good immunity. • B, N-CDs were successfully applied to detect Cu2+ in real sample, which showed an outstanding detection performance. • Low toxicity, biocompatible B, N-CDs as the fluorescent marker could label Hela cells with two different color fluorescence. Boron and nitrogen co-doped carbon dots (B,N-CDs) with a high quantum yield (QY, 25.3%) and strong fluorescence (FL) performance is prepared through one-pot hydrothermal method using folic acid as the source of nitrogen and carbon, glycerol as the source of carbon, and borax as the source of boron. B,N-CDs has uniform dispersion with the average size of 5.1 ± 0.8 nm. The fluorescence of B,N-CDs is gradually quenched upon sequential addition of copper ion (Cu2+). And a linear relationship is observed in the range of 0.005–5 μM with a detection limit of 1.6 nM. The unique quenching of fluorescence (measured at excitation/emission wavelengths of 365/442 nm) is attributed to the selective capture of Cu2+ by the amino and amide groups on the surface of B,N-CDs. The amino group on the surface of B,N-CDs complex with Cu2+ to split the d orbital of Cu2+. This causes the excited state electrons from B,N-CDs transfer to the d orbital of Cu2+ and quenched the fluorescence. B,N-CDs display satisfactory stability, anti-interference performance and low cytotoxicity performance. It is successfully applied to the determination of Cu2+ in actual water samples. B,N-CDs treated cells display distinguished blue and green colors under a confocal microscope. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel Near-infrared Turn-on Fluorescent probe has been synthesized. • Fast response to Selenocysteine with a large turn-on Near-infrared fluorescence signal. • Low detection limit, high selectivity and sensitivity. • Capability for identification of Sec in living cells and mice. Selenocysteine (Sec) plays critical roles in many physiological and pathological processes of human beings, thus it is of great significance to develop accurate methods for detecting and visualizing Sec. Herein, a new anthracene derivative (YZ-M5) as a near-infrared (NIR) fluorescent probe for sensing Sec was designed. Based on the target-induced modulation of the intramolecular charge transfer (ICT) process of the probe, YZ-M5 can display a rapid strong NIR fluorescence enhancement at 660 nm for Sec within 5 min. The quantitative detection range for Sec is 0–40 μM with a low detection limit of 18.5 nM. YZ-M5 also showed high selectivity and sensitivity, as well as the capability for identification of Sec in living cells and mice. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple colorimetric and fluorescent sensor for cyanide based on phenolic substituted dicyanoisophorone derivative (2) has been synthesized. • The absorption spectra of chemosensor 2 showed large bathochromic shift (ca. 240 nm) upon titration with CN− while the solution color changed from yellow to green. • The detection limitation had been calculated to be 0.15 μM. • Meanwhile, the fluorescence intensity of 2 can be quenched upon reacting with CN− over other anions. • More importantly, chemosensor 2 can react instantaneously with cyanide in aqueous solution. A simple colorimetric and fluorescent sensor for cyanide based on phenolic substituted dicyanoisophorone derivative (2) has been synthesized. The absorption spectra of chemosensor 2 showed large bathochromic shift (ca. 240 nm) upon titration with CN− while the solution color changed from yellow to green. The absorption ratios (A 685 /A 446) responses of chemosensor 2 showed a favorable linear relationship with the CN− concentration and the detection limitation had been calculated to be 0.15 μM. Meanwhile, the fluorescence intensity of 2 can be quenched upon reacting with CN− over other anions. More importantly, chemosensor 2 can react instantaneously with cyanide in aqueous solution, and to visualize CN− in living HeLa cells by means of dramatic decrease of fluorescence intensity. Thus, the present sensor could be applicable in detecting cyanide ion both in natural water samples and biological systems conveniently. [ABSTRACT FROM AUTHOR]

[Display omitted] • Single-pot large-scale synthesis of C-dots from peptic digest of animal-tissue. • Emission of strong blue fluorescence at 350 nm comparable to synthetic organic dyes. • Prospective fluorescent probe for specific metal ions detection. • Excellent chelating agent for metal-ion toxicity for fast complexation & exocytosis. • Potential application in bioimaging due to quick uptake with minimal cytotoxicity. In recent years, there has been an increased interest in the use of fluorescent carbon dots (C-dots) as an alternative to toxic synthetic organic dyes in live cell imaging, medical diagnostics and other diverse biomedical applications. In the present work, highly fluorescent C-dots have been prepared from commercially available peptic digest of animal tissue, without using any additional chemical reagent for surface functionalization. The synthesized C-dots are monodispersed nanomaterials with hydroxyl, carboxyl and amino surface functionalities and remain stable in high ionic strength media and over a wide range of pH. They exhibit a strong blue fluorescence upon excitation at 350 nm with a high quantum yield of 61%. The potential use of these C-dots as fluorescent nanoprobe for specific metal ions (Cu2+ and Hg2+) detection through chelation, radical scavenging and cellular imaging has been investigated. These highly fluorescent labels show rapid cellular internalization without hampering cellular integrity. Cell proliferation assay demonstrates that these C-dots have minimal cell toxicity even at a high concentration of 3 mg/mL. They show significant quenching on incubation with cells pretreated with Cu2+ and Hg2+ ions. They also show rapid exocytosis from cells showcasing their high potential for chelation therapy. Thus, this study offers a scalable synthesis approach for highly fluorescent and bio-compatible C-dots from a cost-effective precursor, which can be used for specific metal ions detection and their removal from cells through chelation via exocytosis. They can also be used as an alternate to synthetic organic dyes for fluorescence-based cell-imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel peptide fluorescent probe DGGH was synthesized. • DGGH -Cu2+ system showed highly selective and "turn-on" response to S2−. • The detection limit of DGGH -Cu2+ for sensing S2− was calculated to be 13.7 nM. • DGGH -Cu2+ was successfully applied to monitor Cu2+ and S2− in real samples and living cells. We report a new fluorescent probe named DGGH with dansyl-labeled tripeptide (Dan-Gly-Gly-His-NH 2). DGGH showed obvious fluorescence quenching after the addition of Cu2+ ions and a 1:1 ensemble system (DGGH -Cu2+) was formed, the limit of detection was 37.9 nM. As expected, DGGH -Cu2+ ensemble system exhibited high selectivity and rapid response for S2− in 100% aqueous solutions, as a result of the addition of S2− immediately replaced Cu2+ from the DGGH -Cu2+ ensemble system. The limit of detection of the DGGH -Cu2+ ensemble for S2− was determined to be 13.7 nM. In addition, DGGH -Cu2+ has excellent detection performance within a wide pH range of 6 to 12, and its outstanding response time of less than 50s. Furthermore, we demonstrated the usability of the present approach for detecting Cu2+ and S2− in two water samples. What's more, DGGH was successfully applied to monitor Cu2+ and S2− in living LNcap cells based on good cells permeability and low toxicity. [ABSTRACT FROM AUTHOR]

• YG-CQDs was synthesized via a simple one-step hydrothermal method. • YG-CQDs can be used as an effective fluorescence sensor for congo red detection. • YG-CQDs was successfully applied to determination of congo red in real samples. • The YG-CQDs was also successfully used as an effective agent for cellular imaging. Herein, an innovative label-free fluorescent sensor based on yellow-green emissive carbon quantum dots (YG-CQDs) was first constructed to determine congo red with high speed and sensitivity. The YG-CQDs were simply and quickly prepared using p-phenylenediamine and citric acid as precursors via a hydrothermal method. The prepared YG-CQDs exhibits favorable water solubility and excellent photoluminescence. The YG-CQDs showed an obvious fluorescence quenching behavior as the congo red content increase duo to an inner filter effect (IFE). YG-CQDs served as an effective fluorescent sensor in detecting congo red with high selectivity and sensitivity in a fast and direct manner under optimal conditions. Two good linear relationships were obtained for congo red detection over the concentration ranges of 0.5–50 and 50–170 μg mL−1, corresponding to two lower detection limits of 0.04 and 0.03 μg mL−1, respectively. Meanwhile, the constructed fluorescent sensor was successfully adopted to determine congo red in tap and lake water samples where the accuracy was high. In addition, due to low toxicity and superior biocompatibility, YG-CQDs was also found to be an effective agent for cellular imaging with satisfactory results. The results reveal the good potential of the prepared YG-CQDs for congo red sensing and cellular imaging. [ABSTRACT FROM AUTHOR]