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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]

A one-pot, three-component reaction between isatoic anhydride, 1,3-diketones, and amines/arylhydrazines catalyzed by a combination of molecular I2 and Et3N in open-air affords a series of quinazolin-4(3H)-one derivatives in good yield. The protocol offers an operationally simple, facile, and cost-effective pathway utilizing easily accessible reagents under mild reaction conditions with significant substrate scope. The results of steady state and time-resolved absorption and emission spectroscopy indicate the potential of quinazolin-4(3H)-one derivatives as a fluorescence probe. They exhibit unique photophysical responses in different solvent environments. In addition, they can also act as FRET acceptors during interaction with protein lysozyme. Preliminary biological studies indicate that quinazolin-4(3H)-ones are cell permeable and can be used as a fluorescent probe for bio-imaging of human cervical cancer (HeLa) cells. [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]

An endoplasmic reticulum (ER) targetable two-photon fluorescent probe termed ER-N3 is presented for the determination of hydrogen sulfide (H2S) in living cells and mice. The results demonstrate that ER-N3 was highly selective and sensitive to H2S. Confocal fluorescence imaging in living cells indicated that ER-N3 was accumulated in the endoplasmic reticulum and visualized exogenous and endogenous H2S production. Moreover, a burst of H2S upregulated by the nitric oxide donor sodium nitroprusside was monitored. Meanwhile, the increase of H2S ended following the addition of DL-propargylglycine, an inhibitor for cystathionine β-synthase and cystathionine γ-lyase that are the main sources of H2S. Importantly, the exogenous H2S was visualized in abdominal tissue of mice by utilizing two-photon fluorescence microscopy. The ER-N3 fluorescent probe may be an excellent tool to image H2S fluctuations in the endoplasmic reticulum and characterize the relationship between H2S and disease in vivo. [ABSTRACT FROM AUTHOR]

Photo-sensitive probes based on coumarin deserve extensive attention because of their high biocompatibility, quantum yield, and stability. The synthesis of coumarin and its derivatives is mainly based on four classical methods: Perkin synthesis, Knoevenagel synthesis, Wittig synthesis, and Pechmann synthesis. As everyone knows, fluorescent probes consist of a recognition group, a bridging group, and a luminescent group. Mechanism of fluorescent probes can be roughly summarized into four models: Chelation-induced enhanced fluorescence (CHEF), intramolecular charge transfer (ICT), photoinduced electron transfer (PET), and aggregation-induced luminescence (AIE), which can instruct the design of coumarin-based photo-sensitive probes. Since the fluorescence-based probe was first reported, probes based on coumarin have found widespread application in analytical chemistry, proving to be a selective, efficient, and convenient tool in ion monitoring, molecular monitoring, cell imaging, drug delivery, and many other fields. In this critical review, the synthetic routes of these compounds and the design for fluorescent probes were reported. Furthermore, the recent researches on the employment of coumarin in analytical chemistry were also introduced. Finally, the future research trends and application foreground of coumarin derivatives were forecasted herein. [ABSTRACT FROM AUTHOR]

A commercially available probe (RS) has been reported for instantaneous selective colorimetric detection of Cu(II) and fluorescent detection of Al(III) ions in H2O:DMSO (90:10% v/v) medium. The probe displays a color change from pale yellow (kab 352 nm) to yellowish-green (kab 411 nm) with Cu(II) and a change in emission from green (tex 340nm; tem 522 nm) to bluish-green (tem 489nm) with Al(III) ions. The optical detection of these metal ions by RS is via the formation of tetragonally distorted octahedral RS-Cu(II) and tetrahedral RS-Al(III) complexes as evidenced from the results of UV-Vis, 27Al & ¹H NMR, HRMS, EPR and thermal analysis studies. Job's method indicates that the stoichiometry of both these complexes is 1:1. The probe's corresponding optical changes are particular for Cu(II) and Al(III) ions in the presence of other metal ions. RS displays high selectivity to these ions in a wide pH range. The limits of the detection of Cu(II) and Al(III) are as low as 66nM and 0.83 mM, respectively. Further, RS could be applied as a fluorescent probe for observing Al(III) ions in living HeLa cells by carrying out cell image studies.A commercially available probe (RS) has been reported for instantaneous selective colorimetric detection of Cu(II) and fluorescent detection of Al(III) ions in H2O:DMSO (90:10% v/v) medium. The probe displays a color change from pale yellow (kab 352 nm) to yellowish-green (kab 411 nm) with Cu(II) and a change in emission from green (kex 340nm; kem 522 nm) to bluish-green (kem 489nm) with Al(III) ions. The optical detection of these metal ions by RS is via the formation of tetragonally distorted octahedral RS-Cu(II) and tetrahedral RS-Al(III) complexes as evidenced from the results of UV-Vis, 27Al & 1H NMR, HRMS, EPR and thermal analysis studies. Job's method indicates that the stoichiometry of both these complexes is 1:1. The probe's corresponding optical changes are particular for Cu(II) and Al(III) ions in the presence of other metal ions. RS displays high selectivity to these ions in a wide pH range. The limits of the detection of Cu(II) and Al(III) are as low as 66nM and 0.83 mM, respectively. Further, RS could be applied as a fluorescent probe for observing Al(III) ions in living HeLa cells by carrying out cell image studies. [ABSTRACT FROM AUTHOR]

The multi-modal imaging contrast agent has been attracted an increased interest to the tumor detecting and diagnosis in these recent years since the multi-modal imaging technology combines the advantages of several medical imaging modalities. A water-soluble fullerenol probe containing glypican-3 monoclonal antibody (GPC3-mAb) group mAb-GPC3-C60(OH)10-(TMIO)3-(NI)3 was synthesized by the incorporation of 5-formyl-1,1,3,3-tetramethylisoindolin-2-yloxyl (FTMIO), naphthalimide (NI) and GPC3-mAb as a tumor-targeting group into fullerenol C60(OH)11. This nanomaterial was further characterized by FTIR, UV, MS, fluorescence, etc., and then its properties including electron paramagnetic resonance (EPR), particle size, electrophoresis, electrochemical assay, cell cytotoxicity, cell uptake and fluorescent imaging of HeLa tumor cells in vitro were also evaluated. Experiment results indicated that mAb-GPC3-C60(OH)10-(TMIO)3-(NI)3 had similar fluorescent properties as NI and similar electrochemical and redox properties as 5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl (CTMIO). Moreover, mAb-GPC3-C60(OH)10-(TMIO)3-(NI)3 possessed low cell cytotoxicity, good fluorescence and good tumor-targeting property. Meanwhile, mAb-GPC3-C60(OH)10-(TMIO)3-(NI)3 can be taken up highly by HeLa tumor cells, achieve good green fluorescent imaging in tumor cells and highly enhance the contrast of fluorescent images. Therefore, mAb-GPC3-C60(OH)10-(TMIO)3-(NI)3 can disperse homogeneously in aqueous solution and be used as a potential tumor-targeting dual-modal contrast agent for EPR imaging/fluorescence imaging (EPRI/FI). [ABSTRACT FROM AUTHOR]

In this work, we synthesized a simple fluorescent probe, which can selectively detect cysteine. With addition of cysteine, the probe solution showed marked color change from pale yellow to orange color by naked eye. There was an excellent linear relationship between fluorescence intensity of probe and cysteine concentration. Moreover, the probe displayed satisfactory detection limit. Low toxicity and cellular imaging offered the important conditions for detecting cysteine in biological system. [ABSTRACT FROM AUTHOR]

A new fluorescence probe 1 for sulfur dioxide derivatives has been developed which acts through nucleophilic addition of the derivatives and shows high stability, specificity, and sensitivity. In the presence of SO2 derivatives, the fluorescence intensity of probe 1 significantly decreases within a short time period of 40 s, along with a low detection limit of 0.32 µM. Fluorescence imaging capability of probe 1 was also investigated, showing clear detection of SO2 derivatives in living cells. The results indicate that this probe has a great potential for the detection of SO2 derivatives in broad biological and relevant samples. [ABSTRACT FROM AUTHOR]

In recent years, carbon dots have shown great potential in biological imaging, drug delivery, and other fields. In this study, red fluorescent carbon dots with carboxyl functional groups on the surface were designed and prepared, and the fluorescence properties were studied. At the same time, the carbon dot was combined with dendritic macromolecules, and the aggregate particle size was about 25nm. This combination has good dispersion and stability in both water and methanol, and the DOX-loaded is about 6.72%. The small particle size makes it easy to enter the cells, so as to achieve the function of tumor treatment and cell imaging. [ABSTRACT FROM AUTHOR]

In this article, a novel dual-color quantum dot–encoded fluorescent nanoprobe was prepared by the reverse microemulsion method and layer-by-layer assembly method. First, red fluorescence–emitting CdTe quantum dots were encapsulated in silica nanoparticles by the reverse microemulsion method. Yellow fluorescence–emitting quantum dots were deposited on the surface of silica nanoparticles to form a dual-color quantum dot@silica beads/quantum dot nanoprobe. Then capture DNA was linked to a QSQ nanoprobe via covalent bonding. We utilized the quantum dot@silica beads/quantum dot nanoprobe to capture and detect the mutant BRAF DNA sequence through the competitive immunoassay method. The resulting quantum dot@silica beads/quantum dot nanoprobe-capture DNA conjugates showed sequence-specific hybridization with target DNA. Furthermore, a multispectral imaging system was utilized to distinguish the quantum dot optical code in the quantum dot@silica beads/quantum dot nanoprobe. The quantum dot@silica beads/quantum dot nanoprobe was used in human osteoblast-like HepG2 cell imaging. The proposed quantum dot@silica beads/quantum dot nanoprobe and decoding analysis method could be used for targeting imaging, biological assays, and early detection of cancer. [ABSTRACT FROM PUBLISHER]

A synthetic fluorescent sensor (sensor1) is developed using boron-dipyrromethene as a fluorophore and phenoxo-bridged dipicolylamine as a receptor. Sensor1shows a significant enhancement of fluorescent intensity and a high selectivity for Zn2+over various metal cations. The electrochemical study provides a rationale for the fluorescence turn-on of sensor1upon complexation with Zn2+by the blocking of the photo-induced electron transfer mechanism. Sensor1can be used to image Zn2+in A549 cells. [ABSTRACT FROM PUBLISHER]