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In the practice of in vivo imaging with carbon nanodots (CNDs) as probe, the volume of CNDs solution introduced into living body should be kept at minimum, and a higher concentration is needed to ensure sufficient quantity of the probe for obtaining bright image. Therefore, the improvement on biocompatibility of the CNDs is among the most important and critical issues. We report herein the improvement on the biocompatibility of CNDs with modification by ionic liquid. Amide group functionalization of carbon nanodots is first conducted through microwave irradiation, followed by coupling the ionic liquid 1-carboxymethyl-3-methyl imidazolium bromide on the surface of the Amide-CNDs via covalent conjunction to produce the modified carbon nanodots (IL-CNDs). This modification process significantly improved the biocompatibility of CNDs, as demonstrated by cell imaging at a higher concentration of CNDs. Both Amide-CNDs and IL-CNDs exhibit abundant surface functional groups, resulting in tunable fluorescent emission feature and potential applications in two-color cell imaging. [ABSTRACT FROM AUTHOR]

A simple naphthalene-based fluorescent probe ( AENO ) for formaldehyde (FA) was successfully synthesized, which exhibited a significant fluorescence turn-on response towards FA in aqueous solution. The probe could quantitatively determine the concentration of FA (0–1.0 mM) with excellent selectivity, high sensitivity and low limit of detection (0.57 µM). The sensing mechanism was proposed as 2-aza-Cope rearrangement for AENO after reaction with FA, which was confirmed by 1 H NMR, HR-MS, FT-IR, UV–vis and fluorescence spectra. The probe has been employed to determine the FA contents in several commercially available toffee samples with satisfactory performance. Thus, AENO might be used as a promising tool for quantitative detection of FA in food. Furthermore, fluorescence imaging of HeLa cells indicated that the probe was cell membrane permeable and could be used for visualizing/imaging the FA trace/transportation in cancer cells. [ABSTRACT FROM AUTHOR]

A bioorthogonal Raman reporter-embedded Au-core and polydopamine-shell nanoprobe was initially designed and synthesized for live cell surface-enhanced Raman scattering (SERS) imaging in Raman-silent region. The firstly synthetic bioorthogonal Raman reporter (E)-2- ((4-(phenylethynyl) benzylidene)amino)ethanethiol (PBAT) provided intense Raman signal at 2220cm-1 in Raman-silent region. And its synthetic method was environmentally benign, high yield and easy in operation. In addition, the hydrophobicity of PBAT led to slightly aggregation of gold nanoparticles, which enhance the SERS intensity of the nanoprobe through hot spots. Furthermore, owing to the remarkable biocompatibility of polydopamine (PDA), the SERS nanoprobe can be smoothly internalized into cancer cells to realize SERS imaging in Raman-silent region. Finally, the SERS mapping results confirmed that nanoprobe exhibited strong SERS signal intensity, excellent stability in complex biological environment and low toxicity inside live cancer cells. Therefore, the reporter-embedded core-shell nanoprobe has enormous potential of applications in biomedical diagnostics in the near future. Graphical abstractHighlights· One-step synthetic method of thiol and alkynyl contained bioorthogonal SERS reporter is environmentally benign, high yield and easy in operation. · Au@PBAT@PDA nanoparticles exhibit strong SERS signal intensity, excellent stability in complex biological environment. · Au@PBAT@PDA nanoparticles show good imaging results for live cancer cell SERS imaging in Raman-silent region. · The rich functional groups (i.e., catechol and amine) on PDA surface provide a broad platform for further modification in biomedical application. · A Raman-silent region nanoprobe was synthesized for live cell SERS imaging. [ABSTRACT FROM AUTHOR]

Metallothionein (MT) is a cysteine-rich, low-molecular-weight protein, which adopts a unique dumbbell-shaped structure with a stable C-terminal α -domain and a reactive N-terminal β -domain. The specific configuration serves as a unique scaffold for the synthesis of ultra-small fluorescent metal nanoclusters (NCs). For the first time, MT-templated Ag NCs (MT-Ag NCs) with excellent antioxidant capacity and superior biocompatibility were facilely synthesized. The NCs were thoroughly characterized by various techniques. Zn 2+ in the β -domain was preferentially replaced by Ag + , which was then reduced by NaBH 4 to yield Ag NCs, while Zn 2+ in the α -domain was intactly tetrahedrally-coordinated through thiolate ligands in MT. Fluorescent imaging of HeLa cells was achieved by attaching folic acid (FA) to MT-Ag NCs. Due to the strong binding capacity toward the thiolate ligands in the α -domain, Hg 2+ was assayed via quenching the fluorescence of Ag NCs by an energy transfer process. The methodology described herein may be extended to the synthesis of other metal NCs with potential applications in biosensing and cell imaging. [ABSTRACT FROM AUTHOR]

Since the content levels of biomarkers at the early stage of many diseases are generally lower than the detection threshold concentration, achieving ultrasensitive and accurate detection of these biomarkers is still one of the major goals in bio-analysis. To achieve ultrasensitive and reliable bioassay, it requires developing highly sensitive biosensors. Among all kinds of biosensors, electrogenerated chemiluminescence (ECL) based biosensors have attracted enormous attention due to their excellent properties. In order to improve the performance of ECL biosensors, gold nanoparticles (Au NPs) have been widely utilized as signal amplification tags. The introduction of Au NPs could dramatically enhance the performance of the constructed ECL biosensors via diverse ways such as electrode modification material, efficient energy acceptor in ECL resonant energy transfer (ECL-RET), reaction catalyst, surface plasmon resonance (SPR) enhancer, and as nanocarrier. Herein, we summarize recent developments and progress of ECL biosensors based on Au NPs signal amplification strategies. We will cover ECL applications of Au NPs as a signal amplification tag in the detection of proteins, metal ions, nucleic acids, small molecules, living cells, exosomes, and cell imaging. Finally, brief summary and future outlooks of this field will be presented. [Display omitted] • AuNPs played unique and irreplaceable roles in ECL sensors. • AuNPs based ECL sensors have been widely used in detection of various biomolecules, metal ions and even cells. • AuNPs based ECL signal amplification strategies and their bioassay applications has been systematically reviewed. [ABSTRACT FROM AUTHOR]

Pyridoxal-2-hydrazinopyridine Schiff-base ( 1 ) was prepared by one-step synthesis from commercially available materials of pyridoxal and 2-hydrazinopyridine. Compound 1 could be applied as a fluorescent chemosensor for Zn(II) in aqueous solution at pH 7.4. After binding to Zn(II) with a molar ratio of 1:1, 1 exhibited 17-fold fluorescence enhancement. In addition, 1 showed a good selectivity toward Zn(II) over other metal ions, which can especially distinguish Zn(II) from Cd(II). A linear range of 5.0–20.0 μmol L −1 and a detection limit of 70 nmol L −1 were also achieved. Moreover, the utility of chemosensor 1 in bioimaging of Zn(II) in living cells was demonstrated, which suggested that 1 could be used as a Zn(II)-selective chemosensor in biological samples. [ABSTRACT FROM AUTHOR]

5 nm intense green emission NaYF 4 :Yb/Er upconversion nanoparticles (UCNPs) with pure β phase was synthesized with a simple “green” strategy for the first time. Traditional organic solvothermal method is often applied to prepare the high-quality and uniform UCNPs, but the preparation of lanthanide-oleate complexes is laborious as heating and multistep post-treatment for purification are often required. The water-alcohols solvothermal method is environmentally friendly, but the fabricated UCNPs have big size, poor biocompatibility and high cytotoxicity, which limited their application for cell imaging. Herein, NaYF 4 :Yb/Er UCNPs were prepared with rare-earth nitrates RE(NO 3 ) 3 (RE=Y 0.80 Yb 0.18 Er 0.02 ) as precursors and diethylene glycol (DEG)/ethylene glycol (EG)/water as the solvent. A facile green solvothermal method with the temperature being controlled at 300 °C was developed. The as-prepared NaYF 4 :Yb/Er UCNPs were characterized and were found to have enhanced UC emission and controllable particle size. The as-prepared UCNPs were further functionalized via folic acid coating for the targeted imaging and improved bio- compatibility. It was made the UCNPs potential for upconversion bioimaging of living cells by the strong upconversion luminescence, the excellent biocompatibility, and the super-small size. The good colloidal stability and low cell cytotoxicity of the as-prepared UCNPs and the developed synthesis protocol might advance both the fields of UCNPs and biomolecule-based nanotechnology for future studies. [ABSTRACT FROM AUTHOR]

Excessive amount of aluminum is detrimental to growing plants or animals and people are likely to suffer from various diseases upon long-term exposure to aluminum ions. Therefore, sensitive and selective detection of trace amounts of Al 3+ in real samples is of great importance. Herein, a ratiometric fluorescent probe for detecting aluminum ions based on pyrene-1-butyric acid (Py-L-COOH) was developed, which function via monomer/excimer conversion. In the presence of Al 3+ , the original monomer-state Py-L-COOH molecules coordinate with Al 3+ and form excimer, thus changing the emission wavelength from 350–400 nm to 450–500 nm and achieving the ratiometric detection for Al 3+ . The probe responds to Al 3+ quickly and can be operable in aqueous media with a very low detection limit of 0.29 µM. This system is capable of detecting Al 3+ in real samples and shows high selectivity. Furthermore, the probe exhibits low cytotoxicity and can be used in fluorescence imaging in Hela cell lines. The approach may provide an effective simple probe for aluminum ions determination with application to real samples, as well as offering insights for designing facile ratiometric fluorescent sensors. [ABSTRACT FROM AUTHOR]

We report a simple one-pot synthesis of highly fluorescent carbon dots (CDs) via modified hydrothermal (MHT) treatment of alkaline solution of dopamine and cysteine. These CDs ( λ ex =320 nm, λ em =390 nm, and quantum yield ∼5.1%) are of ∼2–3 nm in diameter. Further attempt of synthesizing CDs in some common water-miscible solvents ends up the fact that the MHT product from acetone medium is nonfluorescent. However, CDs, produced in aqueous medium, are so stable that they can be dried as a deliverable solid (WCD) without any alteration of fluorescing property if reversibly dispersed in water. Fluorescence of WCD is quenched selectively in acetone. Quenching occurs presumably due to the disruption of radiative recombination along with the hindrance in quantum confinement of the emissive energy traps to the particle surface. Successive quenching of fluorescence of WCD in different acetone concentration admixed in water paves the way to selective acetone sensing (LOD=8.75×10 −7 M). The synthesized CDs (in aqueous medium) are cytocompatible and are efficient fluorescent probe for cell imaging. Only living cells are recognized exclusively from fluorescence imaging leaving aside dead cells, while cells are treated with CDs. [ABSTRACT FROM AUTHOR]

A label-free electrochemiluminescence (ECL) cytosensor was developed for dynamically evaluating of epidermal growth factor receptor (EGFR) expression on MCF-7 cancer cells based on the specific recognition of epidermal growth factor (EGF) with its receptor (EGFR). EGF-cytosensor was fabricated by in-situ electro-polymerization of polyaniline as substrate, using CdS quantum dots (CdS QDs) as ECL probe and gold nanoparticles (AuNPs) as a carrier for loading of EGF. AuNPs and CdS QDs were jointly attached on polyaniline surface to provide a sensitive and stable sensing interface, as well as a simple and label-free mode for ECL assay. Electron microscopy, atomic force microscopy (AFM) and electrochemical methods were employed to characterize the multilayer construction process of the sensing interface. The proposed EGF-cytosensor exhibited excellent analytical performance for MCF-7 cancer cells, ranging from 12 to 1.2×10 6 cells mL −1 , with a low detection limit of 12 cells mL −1 . Also, it was successfully applied in evaluating EGFR expression of cells surface, which was stimulated by some inhibitors or activator, and the results were confirmed by using flow cytometry and laser scanning confocal microscopy analysis. The proposed ECL cytosensor has potential applications in monitoring the dynamic variation of receptor molecules expression on cell surfaces in response to external stimulation by drugs and screening anti-cancer therapeutic agents. [ABSTRACT FROM AUTHOR]

The real-time fluorescence tracking of gene delivery is very important as it helps to figure out how a vector enters a cell and also to follow its fate within the cell interior. Lanthanide-doped upconversion nanoparticles (UCNPs) have shown great potential in biomedical applications in virtue of their unique optical and biological properties. Herein, we report a simple and versatile strategy to fabricate a multifunctional nanocapsule for effective gene delivery and real-time luminescence tracking. The hydrophobic UCNPs were modified by positively charged amphiphilic polymer together with polyethylene glycol-poly(lactic-co-glycolic acid) (PEG–PLGA) polymer, affording biocompatible nanocapsules with high gene loading capacity and good stability. Red UC luminescence of UCNPs are able to track the delivery of nanocapsules in cells without background fluorescence interference, in the meantime, the green fluorescence of green fluorescence protein (GFP) expressed by the pDNA could subtly monitor the gene transfection efficacy. The results demonstrated that our nanocapsule has ideal biocompatibility, satisfactory gene loading capacity and great bioimaging ability, which is promising for imaging guided cell therapy and gene engineering. [ABSTRACT FROM AUTHOR]

Recently, carbon nanomaterials have received considerable attention as fluorescent probes owing to their low toxicity, water solubility and stable photochemical properties. However, the development of graphene quantum dots (GQDs) is still on its early stage. In this work, GQDs were successfully synthesized by one-step microwave assisted pyrolysis of aspartic acid (Asp) and NH 4 HCO 3 mixture. The as-prepared GQDs exhibited strongly blue fluorescence with high quantum yield up to 14%. Strong fluorescence quenching effect of Fe 3+ on GQDs can be used for its high selectivity detection among of general metal ions. The probe exhibited a wide linear response concentration range (0–50 μM) to Fe 3+ and the limit of detection (LOD) was calculated to be 0.26 μM. In addition, GQDs are also sensitive to the pH value in the range from 2 to 12 indicating a great potential as optical pH sensors. More importantly, the GQDs possess lower cellular toxicity and high photostability and can be directly used as fluorescent probes for cell imaging. [ABSTRACT FROM AUTHOR]

Surface-Enhanced Raman scattering (SERS) has been widely used for imaging and sensing. However, limited reports are currently available on SERS-based cancer cell targeting strategy due to the challenge of synthesizing highly sensitive, reproducible and biocompatible SERS probe. Herein, we developed novel SERS probes, based on BSA (Bull Serum Albumin) coated gold–silver core–shell nanorods modified with Raman reporter 5,5-dithiobis 2-nitrobenzoic acid (DTNB) (Au@AgNRs@BSA@Anti-MICA), for in vitro cancer cell detection. Our results demonstrate that the SERS probe is very robust for cancer cell ultrasensitive detection with good biocompatibility and strong SERS signal. [ABSTRACT FROM AUTHOR]

A novel sulfur and nitrogen binary doped carbon dots (S,N-CDs) was synthesized by one-step manner through the hydrothermal treatment of citric acid (CA) and ammonium thiocyanate, and the procedures for biomedical applications, including probing doxycycline in living cells and multicolor cell imaging were developed. The obtained S,N-CDs are stable in aqueous solution, possess a very high quantum yield (QY, 74.15%) and good photostability. The fluorescence of S,N-CDs can be specifically quenched by doxycycline, providing a convenient turn-off assay of doxycycline. This assay shows a wide linear detection range from 0.08 to 60 μM with a low detection limit of 20 nM. The present method also displays a good selectivity. More importantly, the S,N-CDs have an excellent biocompatibility and low cytotoxicity, allowing the multicolor cell imaging and doxycycline detection in living cells. Consequently, the developed doxycycline methods is facile, low-cost, biocompatible, sensitive and selective, which may hold the potential applications in the fields of food safety and environmental monitoring, as well as cancer therapy and related mechanism research. [ABSTRACT FROM AUTHOR]

The chemosensor 2,3-bis((E)-((2-hydroxynaphthalen-1-yl)methylene)amino)maleonitrile ( 1 ) has been synthesized using 2-hydroxy-1-napthaldehyde and 2,3-diaminomaleonitrile and characterized. Sensor 1 exhibits selective binding with CN − in dimethyl sulfoxide (DMSO)/H 2 O (7:3 v/v) and DMSO/aqueous Tris (Tris(hydroxymethyl)aminomethane) buffer (7:3 v/v, 10 mM, pH 7.2) media with significant changes in its UV–visible and fluorescence spectra. Titration of 1 -Zn(II) complex with CN − ion in DMSO/aqueous Tris buffer (7:3 v/v, 10 mM, pH 7.2) regenerates the free sensor 1 , as supported by UV–visible spectra. 1 H NMR titration of 1 with CN ‒ in (CD 3 ) 2 SO confirms the hydrogen-bonding interaction between the two OH groups of the former and the latter in bidentate manner. Sensor 1 impregnated on silica gel thin layer chromatography (TLC) strip followed by dipping in anion solutions in DMSO/H 2 O (7:3 v/v) generates yellow to red spectacular colour change with CN − ion selectively which can be exploited as potential tool for ready-made detection of toxic CN − ion in environmental and analytical chemistry. Similar visual change in colour for 1 is observed selectively with CN − also when both of them are taken in DMSO/H 2 O (7:3 v/v) solution. Sensor 1 is used as an imaging reagent for detection of the cellular uptake of CN − ion in Baby Hamster Kidney (BHK-21) cells. [ABSTRACT FROM AUTHOR]

Most of the proteins locate more than one organelle in a cell. Unmixing the localization patterns of proteins is critical for understanding the protein functions and other vital cellular processes. Herein, non-linear machine learning technique is proposed for the first time upon protein pattern unmixing. Variable-weighted support vector machine (VW-SVM) is a demonstrated robust modeling technique with flexible and rational variable selection. As optimized by a global stochastic optimization technique, particle swarm optimization (PSO) algorithm, it makes VW-SVM to be an adaptive parameter-free method for automated unmixing of protein subcellular patterns. Results obtained by pattern unmixing of a set of fluorescence microscope images of cells indicate VW-SVM as optimized by PSO is able to extract useful pattern features by optimally rescaling each variable for non-linear SVM modeling, consequently leading to improved performances in multiplex protein pattern unmixing compared with conventional SVM and other exiting pattern unmixing methods. [ABSTRACT FROM AUTHOR]

Most of the near-infrared (NIR) fluorescent copper ion probes are coordination-based, and the fluorescence enhancement is between 10 and 20 folds. Herein, a novel NIR fluorescent dye named CSCN with excellent photostability and a reaction-based Cu 2+ NIR probe named CSCN–Cu were reported. CSCN exhibited good photostability toward photo irradiation. CSCN–Cu showed lower background fluorescent interference and over 40-fold fluorescence enhancement in NIR region, it also exhibited good selectivity toward Cu 2+ in Hepes solution. Biotic experiments demonstrated that CSCN–Cu possessed low toxicity and successfully imaged Cu 2+ in living cells under the conditions performed. [ABSTRACT FROM AUTHOR]

In this study, Cu(II)-mediated differential alteration of cysteine (Cys) reactivity is reported by using a Cys-specific fluorescent probe. The probe could react with Cys to give out strong fluorescence. When Cys was preincubated with Cu(II), the fluorescence of the probe was decreased due to the inhibition of Cys's reactivity by Cu(II). Remarkably, experimental results reveal that the probe could detect Cu(II) at subnanomolar concentrations. In contrast, Cu(II) could only partially inhibit the reaction between Cys and Ellman's reagent (DTNB). Furthermore, selectivity experiments show that Cu(II) is a much more potent inhibitor for Cys compared to other metal ions. Cell imaging experiments also confirm the inhibitory effects of Cu(II) on Cys's reactivity in living cells. We envision that the probe could add a useful tool for sensitive and selective detection of Cu(II) for biomedical research. [ABSTRACT FROM AUTHOR]

A molecular probe of DibOH (2,6-bis(4-hydroxybenzylidene)cyclohexanone) designed as the ameliorant to the curcumin was prepared in which one enol unit was removed to avoid the intramolecular hydrogen bond and thus more rigidity and better coplanarity were achieved. Deprotonation of the phenolic hydroxyl group led to the negative charge and the intramolecular charge transfer (ICT) functioned accordingly. The DibOH probe in basic conditions exhibited the absorption peak at 468 nm, which indicated a red shift of 183 nm relative to that in acid conditions and was visible as a brown color to naked eyes. The ratio of fluorescence intensity at 612 nm to that at 520 nm ( I 612 / I 520 ) was calculated and a clear correlation with the pH value was obtained. The density functional theory (DFT) was performed on theoretical investigation of the acidic and basic forms of DibOH. The DibOH probe was evaluated in fluorescent imaging of human breast cancer cells (MCF-7) wherein the heterogeneous distribution of the intracellular pH microenvironment was observed [ABSTRACT FROM AUTHOR]

In this study, double shelled NIR CdSeTe/CdS/C quantum dots (QDs) were synthesized by a liquid phase method. The as-prepared QDs showed low cytotoxicity and good biocompatibility due to the formation of carbon shell. The imaging of targeted Human cervical carcinoma cells (HeLa cells) indicates that the CdSeTe/CdS/C QDs have excellent optical properties and cell viability. These results clearly shows that the CdSeTe/CdS/C QDs can be a good candidate for bioapplications. [ABSTRACT FROM AUTHOR]

In this study, we developed organelle-specific blue-emitting two-photon (TP) probes for Ca2+ (BCa-1 , BCa-2 mito , and BCa-3 mem), with absorption maxima (λ max) at 350–358 nm, emission maxima (λ fl) at 464–466 nm, and TP action cross-section (Φδ max) values of 55–70 × 10−50 cm4s/photon, in the presence of excess Ca2+ at 750 nm. Moreover, the probes had dissociation constants of 0.18, 2.7, and 100 μM, respectively, which are appropriate values for sensing Ca2+ in the cytoplasm, mitochondria, and plasma membrane, respectively. The measurements were conducted using a calcium calibration buffer (10 mM 3-[ N -morpholino]propanesulfonic acid and 100 mM KCl) at pH 7.2. The TP microscopy results revealed that the probes could facilitate the real-time detection of Ca2+ in the cytoplasm, mitochondria, and plasma membranes of live cells and tissues. Additionally, we developed a green-emitting TP probe for H+ (FHEt-1 lyso) with λ max = 359 nm, λ fl = 571 nm, and Φδ max = 70 × 10−50 cm4s/photon at pH 4.3 in a universal buffer (0.1 M citric acid, 0.1 M KH 2 PO 4 , 0.1 M Na 2 B 4 O 7 , 0.1 M tris[hydroxymethyl]aminomethane, and 0.1 M KCl); this probe could detect H+ in the lysosomes. Using BCa-1 and FHEt-1 lyso , it was possible to simultaneously monitor the changes in cytosolic Ca2+ and lysosomal H+ concentrations in live cells and tissues using dual-color TP microscopy in real time. When used with TP probes emitting wavelengths of green light or longer, these blue-emitting Ca2+ probes can be used to investigate the physiological role of Ca2+ in cellular organelles as well as the crosstalk between Ca2+ and other metal ions in specific organelles. [Display omitted] • We developed organelle-specific blue-emitting two-photon Ca2+ probes. • They can detect Ca2+ in organelles of living cells and tissues in real-time. • They have appropriate K d values for Ca2+ for each organelle. • They show high sensitivity, low pH dependency, and negligible cytotoxicity. • They can monitor the crosstalk among metal ions using multicolor TPM imaging. [ABSTRACT FROM AUTHOR]

The facile and noninjurious image of cells with high resolution and low toxicity is essential since imaging can offer rich and direct information and insights into metabolic activities, clinical diagnosis, drug delivery and cancer therapy. In this contribution, a smart imaging probe was employed as a contrast agent for dark-field cell imaging. Au core/Ag shell nanorods (Au@Ag NRs) that characterized by X-ray diffraction and X-ray photoelectron spectroscopy, formed Au@Ag@AgI NRs when exposed to iodine, which greatly enhanced the light scattering of nanorods. Herein, the silver shell acted as the response element for iodine as well as the protective agent for Au core. When conjugated with folate, the nanorods can be used to image human cervical cancer cells (HeLa cells) under a dark-field microscope. Nanorods were demonstrated with excellent tumor cellular uptake ability without obvious cytotoxicity, making them ideal candidates in biosensing and bioimaging applications. Nanorods were restructured with iodine to enhance the light scattering for cell imaging, making them ideal candidates in bioimaging applications. [Display omitted] • The light scattering of AuNRs has been greatly enhanced for cell imaging. • The iodine-induced restructuring of Au@Ag NRs is highly specific among inorganic ions and biological macromolecules. • Nanorods with strong light scattering can enter cells readily, making them potentially useful as contrast agents. • Silver coating acted as the response element for iodine as well as the protective agent for AuNRs to avoid exposure to iodine. [ABSTRACT FROM AUTHOR]

The fluorescent probe, GXY-ADP-2, with xanthene structure as the fluorescent core was designed and prepared for the selective detection of peroxynitrite (ONOO−). ONOO− can be produced endogenously and exogenously and is a strong oxidant with a short half-life. Oxidative modifications of biomolecules, that can be attributed to the formation of ONOO−, occur in the reactions of biomolecules with secondary ONOO−-derived radical oxidants. Therefore, it is very important to develop a specific fluorescent probe for detecting ONOO− to monitor oxidative stress state. The excitation wavelength and emission wavelength of the probe are 689 nm and 739 nm respectively. In the process of co-incubation with ONOO−, generate a new substance with two internal conjugated structures through a special reaction mechanism, one giving the fluorescence with the excitation wavelength of 347 nm and the emission wavelength of 484 nm with the detection limit of 0.12 μM, and the other that with the excitation wavelength of 433 nm and the emission wavelength of 583 nm with the detection limit of 0.077 μM. The linear dynamic range of the probe is 0–5 μM. Its response is not affected by the other reactive oxygen species, thus can sensitively detect ONOO−. In bioimaging experiments with HepG2 cells, the green and blue cell fluorescence signals (583 nm and 433 nm, respectively) were increased, while the red one (739 nm) was significantly reduced, under lipopolysaccharide (LPS) induced oxidative stress, proving that the probe could sensitively detect ONOO− in living cells. This work provides a new tool for the dynamic changes of ONOO− and oxidative stress processes in biological systems. [Display omitted] • A new fluorescent probe, GXY-ADP-2, was developed for detection of ONOO−. • GXY-ADP-2 exhibited high specificity and sensitivity to ONOO−. • GXY-ADP-2 is a ratiometric fluorescent probe with three-channel fluorescence signal changed. • GXY-ADP-2 can detect the dynamic change of ONOO− in living cells. [ABSTRACT FROM AUTHOR]

Recently, using nanomaterials to enhance the endocytosis capability and sensitivity of probes for RNA imaging in living cells has gotten the attention of many researchers. Nanomaterials, as a reliable alternative to transfection reagents, could prevent nucleic acid probes from being degraded by DNase, and bring them into sub-cellular locations for efficient internalization. Therefore, nanomaterial-based fluorescent probes (NFPs) provide a promising sensing platform to realize in situ RNA detection and imaging, which can reveal the expression of RNA at single cell level and provide large amount of information about RNA spatial localization. Meanwhile, many RNAs are in low abundance in living cells, resulting in difficulty in sensitive detection. Thus, the incorporation of NFPs and signal amplification strategy offers a broader prospect for the detection of RNAs, that have been proven as predominant therapeutic targets or diagnostic biomarkers. Herein, the purpose of our review is to first introduce the general procedure of NFPs used for in situ RNA imaging and how nanomaterials deliver these probes into living cells. Further, we focused on different kinds of nanomaterials that are mainly used for sensitive detection of RNAs and those in low abundance, through different signal read-out modes. Nanomaterial-based fluorescent probe (NFP) provides a promising sensing platform to realize effectively cellular endocytosis and intracellular RNA Imaging in situ. In our review, we try to basically introduce the whole progress of NFPs used for in situ RNA imaging, particularly focusing on the endocytic pathways that nanomaterials deliver these probes into living cells, as well as different kinds of nanomaterials that are mainly used for sensitive signal detection of RNAs, especially for those in low abundance. [Display omitted] • Monitoring the level of RNA expression, can assist our understanding of the progression, diagnosis and further treatment of tumor. • NFPs has high internalization efficiency and excellent biocompatibility to achieve cellular uptake and RNA imaging in situ. • Different kinds of nanomaterials for detection of RNAs, especially for those in low abundance, are summarized. [ABSTRACT FROM AUTHOR]

Oxidative stress plays significant roles in the development of various diseases. H 2 O 2 acts as a signaling molecule physiologically or harmful substance pathologically and the mitochondria are one of the most active places for the generation of H 2 O 2. Thus, a new mitochondria-targeted probe 1 for H 2 O 2 detection was synthesized herein, based on D-π-A structure with a large Stokes shift (150 nm) due to its ICT process. To improve its water solubility and sensitivity, probe 2 with PEG chain and probe 3 with two responsive boronated groups were then designed based on the structure of probe 1. As a result, the fluorescence intensity of probe 2 was far higher than that of probe 1 and probe 3 not only in vitro experiment but in cell imaging study with a larger linear range and signal-to-noise ratio, rendering it the best probe for further exogenous and endogenous H 2 O 2 detection in Hela cells. [Display omitted] • Based on the principle of donor-π-acceptor and p -pinacolborylbenzyl group as recognition part, three novel probes for H 2 O 2 were designed. • These near-infrared probes with a large Stokes shift (150 nm) had good selectivity and sensitivity toward H 2 O 2. • The fluorescence intensity of the PEGylated probe was far higher than those of other probes not only in vitro experiment but in cell imaging study. • The probes had good mitochondria-targeting capacities. [ABSTRACT FROM AUTHOR]

A rhodamine-based fluorescent probe (Rho-GSH) was rationally designed and synthesized, using nitrobenzene as recognition group for monitoring and imaging GSH in vitro and in vivo. In the presence of GSH, Rho-GSH undergoes sequential nucleophilic substitution and spiro-ring-opening reaction, resulting the fluorescence increase of probe, which enables quantitative detection of GSH with "off-on" fluorescence. The cascade reaction also enables Rho-GSH to rapidly detect GSH (3 s). In addition, Rho-GSH exhibited outstanding selectivity in detecting GSH vs cysteine (Cys) and homocysteine (Hcy). Based on the outstanding detection performance and superior biocompatibility of Rho-GSH , it was used to visualize GSH in vitro and in vivo , demonstrating its highly selectivity for GSH detection (with respect to Cys and Hcy). Rho-GSH can help visually distinguishing cancer cells from normal cells by fluorescence imaging, demonstrating the overexpression of GSH in cancer cells. Because of the outstanding analytical capabilities of Rho-GSH for GSH detection, Rho-GSH may be useful for cancer diagnosis and clinical evaluation. [Display omitted] • Rho-GSH is a rhodamine-based fluorescent probe based on cascade reactions. • Rho-GSH can quantitatively detect GSH with high selectivity and rapidity (3 s). • Rho-GSH can visualize GSH in vitro and in vivo. • Rho-GSH distinguishes cancer cells from normal cells. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S) has recently been identified as the third gaseous signaling molecule that is involved in regulating many important cellular processes. We report herein a novel fluorescent probe for detecting H 2 S based on iminocoumarin benzothiazole scaffold. The probe displayed high sensitivity and around 80-fold increment in fluorescence signal after reacting with H 2 S under physiological condition. The fluorescent intensity of the probe was linearly related to H 2 S concentration in the range of 0–100 μM with a detection limit of 0.15 μM (3σ/slope). The probe also showed excellent selectivity towards H 2 S over other biologically relevant species, including ROS, RSS and RNS. Its selectivity for H 2 S is 32 folds higher than other reactive sulfur species. Furthermore, the probe has been applied for imaging H 2 S in living cells. Cell imaging experiments demonstrated that the probe is cell-permeable and can be used to monitor the alteration of H 2 S concentrations in living cells. We envisage that this probe can provide useful tools to further elucidate the biological roles of H 2 S. [ABSTRACT FROM AUTHOR]

By retaining the quadrapyridyl receptor of polypyridylhexaazatriphenylene (a Cd2+ sensor reported by us) and extending its chromophoric group with pyrene, a chemical sensor (1) was designed and synthesized in this work. This sensor exhibit selective off-on fluorescence response to Cd2+ over other metal ions, and the detection limit is as low as 0.02 μM. The Cd2+ sensing of 1 has high water toleration and can be carried out in the media with the water content up to 70%. Additionally, 1 was successfully applied to the in vivo imaging of intracellular Cd2+ in living HaLa cells, and showed low cytotoxicity and cell membrane permeability in these experiments. These results suggest that 1 has potential application in the Cd2+ analysis of environmental and biological samples. [ABSTRACT FROM AUTHOR]

Mucin 1 (MUC1) overexpression in tumor cells is related to various cancers, including breast, stomach, and lung cancer. MUC1 detection and imaging are important for cancer localization in tissue sections to support histopathological diagnosis. In this study, we developed a simple, enzyme-free MUC1 detection and in situ imaging method. Three hairpin probes, Apt-trigger, HP1-FAM, and HP2, were designed for MUC1 recognition and hybridization chain reaction (HCR). The Apt-trigger probe was composed of two sequences: the MUC1 aptamer and HCR trigger sequence. The 5' end of the HP1-FAM probe was modified with a FAM signal molecule. In the presence of MUC1, the aptamer sequence is activated and bound to MUC1, which opens the hairpin structure. Then, the trigger sequence gets exposed and, complementary to HP1-FAM, triggers a continuous HCR process. This method was successfully used to detect MUC1 of 200 pM–25 nM and MUC1 in situ imaging in specific cells, such as human breast carcinoma (MCF-7) and human colon cancer (HT-29) cells. A simple, enzyme-free detection and in situ imaging method for MUC1 was developed. This method was not only successfully used for MUC1 detection, but also its in situ imaging in specific cells. [Display omitted] • A simple, enzyme-free detection and in situ imaging method for MUC1 was developed. • An aptamer conformational switch was used for MUC1 recognition. • The hybridization chain reaction (HCR) was used for signal amplification. • This approach has potential applications in the detection and in situ imaging of various proteins. [ABSTRACT FROM AUTHOR]

Abstract: A malonohydrazide derivative bearing an imine and phenolic group was synthesized and had a high affinity and selectivity towards Zn2+. The recognition properties of receptor 1 were evaluated using absorbance and fluorescence spectroscopy. The 1:1 stoichiometry of 1.Zn2+ was confirmed from job׳s plot, mass spectra and density functional theory (DFT). The detection of Zn2+ in intracellular environment of HeLa cell through confocal microscopy was successfully applied for live cell imaging. [Copyright &y& Elsevier]

Abstract: A water-soluble, biocompatible, and fluorescent chemosensor (1) for label-free, simple, and fast detection of mercury ions (Hg2+) in aqueous solutions and in HepG2 cells with high selectivity is reported herein. Chelation of 1 with Hg2+ results in the disappearance of its fluorescence emission at 350nm and the appearance of a new emission at 405nm. Selectivity and interference studies indicated that 1 could be selectively chelated by Hg2+ without interference from other metal ions. Insight into the mechanisms responsible for its fluorescence effect was gained from ultrafast transient absorption spectroscopy. With these properties, 1 was successfully applied for imaging Hg2+ in living cells and for removing Hg2+ from river water. Moreover, we also constructed a simple device for fast and effective removal of Hg2+ from contaminated liquid samples. [Copyright &y& Elsevier]

Abstract: A novel coumarin-based fluorescent probe L ((4E)-4-((7-hydroxy-4-methyl-2-oxo-2H-chromen-8-yl) methyleneamino)-1,2-dihyydro-2,3-dimethyl-1-phenylpyrazol-5-one) has been developed as a simple and efficient chemosensor which exhibits a significant fluorescence reduction in the presence of metal cations. This sensor exhibits high selectivity and sensitivity toward Cu2+ over other common cations. The mechanism for detecting copper was evaluated by time-dependent density functional theory (TD-DFT) calculations and the coordination mode was also confirmed by density functional theory (DFT) calculations. Furthermore, results of cell imaging in this study indicate that this new probe may be useful for detection and monitoring of Cu2+ in biological applications. [Copyright &y& Elsevier]

Abstract: A novel cell-permeable urea-linked dipodal naphthalene-based fluorescent receptor 1 (1,1׳-(1,5,5-trimethyl-3-oxocyclohexane-1,2-diyl)bis(3-(naphthalen-2-yl)urea) was designed and synthesized. The cation recognition ability of 1 was evaluated with a library of metal ions in DMSO/H2O (9:1, v/v). The receptor showed a selective chromogenic and fluorescent turn-off response towards Hg2+ among the surveyed metal ions. The developed sensor was successfully applied to image intracellular Hg2+ in living cells and also for the determination of Hg2+ content in real water samples. Moreover, the DFT calculations were performed to complement the experimental evidences. [Copyright &y& Elsevier]

Abstract: We have prepared enzyme-mimic Au–Pt nanocomposites (NCs) for catalyzing the decomposition of reactive oxygen species. After surface modification, the Au–Pt NCs can be readily internalized and retained by human skin cells and also can effectively reduce cellular oxidative stress. We have demonstrated that the active and biocompatible Au–Pt nanocomposites can be applied for preventing cell damages by scavenging cellular reactive oxygen species induced by ultraviolet irradiation, indicating potential uses for the prevention and therapy of ROS-mediated diseases. [Copyright &y& Elsevier]

Abstract: Modern biosensors require high sensitivity, great signal enhancement and extensive applicability for detection and diagnostic purposes. Traditional molecular beacons (MBs) do not meet these requirements because of the lack of signal amplification. The current amplification pathways using enzymes, DNAzymes and nanoparticles are usually quite sophisticated and are limited to specific applications. Herein, we developed simple biosensors based on the structure of kissing-hairpin. Through hybridization amplification of these nanomachines, the evolved MBs could greatly enhance the detected signals (approximately 10-fold higher than the signals generated by traditional molecular beacons), reduce the sensing limits for targets and, remarkably, distinguish single-base mismatches specifically for nucleic acid detection. In addition, these new MBs can be directly applied in living cells. By introducing aptamer sequences, these novel sensors can also detect proteins and small molecules. These properties were exemplified by the detection of both the β-actin gene and thrombin. The simplicity, sensitivity and flexibility of these devices make them appropriate for more expansive applications. [Copyright &y& Elsevier]

Abstract: We construct a novel fluorescent, surface enhanced Raman scattering (SERS) encoded and magnetic nanoprobe for live cell imaging. To fabricate this nanoprobe, single walled carbon nanotube (SWNT) is used as the building scaffold while gold nanoparticles (Au NPs), superparamagnetic iron oxide nanoparticles (SPIONs) and quantum dots (QDs) are employed as the building blocks. Here, Au NPs serve as the SERS substrate and QDs act as the fluorescent agent. Au NPs and SPIONs are first adsorbed on the SWNT via electrostatic interactions. Then a silica layer is coated on the SWNT. Finally, QDs are attached on the silica shell. With such a structure, various optical signals can be readily encoded to the nanoprobe simply by using different Raman molecules and QDs with different emission wavelengths. Experimental results show that the as-prepared nanoprobe exhibits well fluorescence and SERS performance. Furthermore, in vitro experiments demonstrate that the nanoprobe can fulfill magnetic field guided fluorescence and SERS dual mode imaging of live cells. As a fascinating optical encoding material and a multifunctional nanoplatform, the presented nanoprobe holds genuine potential in future biosensing applications. [Copyright &y& Elsevier]

Abstract: Herein, one multifunctional AS1411-functionalized fluorescent gold nanoparticles (named NAANPs) is synthesized and successfully applied for both targeted cancer cell imaging and efficient photodynamic therapy (PDT). The NAANPs are obtained by functionalizing the gold nanoparticles with AS1411 aptamer and then bound with one porphyrin derivative N-methylmesoporphyrin IX (NMM). Using HeLa cells over expressing nucleolin as representative cancer cells, the formed NAANPs can target to the cell surface via the specific AS1411-nucleolin interaction, which can discriminate the cancer cells from normal ones (e.g. HEK293) unambiguously. That the fluorescence intensity of NMM increased significantly upon binding to AS1411 G-quadruplex makes the NAANPs appropriate fluorescence reagent for cell imaging. Meanwhile, NMM can also be used as a photosensitizer, thus irradiation of the NAANPs by the white light from a common electric torch can lead to efficient production of cytotoxic reactive oxygen species for establishing a new type of PDT to cancer cells. Gold nanoparticles play the roles of both carrier and enhancer of the functional groups onto the cells. In addition, they not only possess inherently certain cytotoxicity to the cancer cells, but also boost the cellular uptake of the fluorescent groups. As a result, the efficiency of both the targeted cell imaging and PDT could be ensured. [Copyright &y& Elsevier]

Abstract: A magnetically controllable dual-mode optical probe is demonstrated for cellular imaging with an onion-liked structure, which can exhibit both surface enhanced Raman scattering (SERS) and fluorescence signals. For obtaining such a nanoprobe, Fe3O4 nanoparticles were first encapsulated into an inner layer of silica, which were then coated with a second layer of gold nanoshell (designated as Fe3O4@SiO2@Au). By adjusting the thickness of the gold shell, the surface plasmon resonance (SPR) of Fe3O4@SiO2@Au nanoparticles can be easily tuned from visible to near-infrared (NIR) region. Afterwards, the prepared Fe3O4@SiO2@Au nanoparticles were tagged with a third layer of Raman reporters to exhibit SERS signals and further coated with an outmost layer of dye-doped silica to generate fluorescence. When being excited at different wavelengths as 515nm and 633nm, the distinct fluorescence and SERS signals can be separately observed. More interestingly, an enhanced cellular uptake of the presented nanoprobes was observed in the presence of a magnetic field, which was proved by both fluorescence and SERS images. This onion-liked multi-modal nanoplatform has great potential in bio-imaging, targeted delivery applications and biological separations. [Copyright &y& Elsevier]

Abstract: Multifunctional fluorescent silica nanoparticles with phenylboronic acid tags were developed for labeling sialic acid on the surface of living cancer cells. In this paper, fluorescent silica nanoparticles (FSNPs) with strong and stable emission at 515nm were firstly prepared through a reverse microemulsion process, and then modified with highly selective phenylboronic acid (PBA) tags on their surface via an aqueous ‘thiol-ene’ click reaction. These nanoparticles had a hydrodynamic diameter of 92.6±9.1nm, and a bright fluorescence signal, which is 366 times higher than that of a single dye molecule. Meanwhile, these PBA-tagged FSNPs were found very stable in aqueous solution as well as in cell culture medium, verified by transmission electron microscopy, X-ray photoelectron spectroscopy and zeta potential analysis. The over-expressed sialic acid (SA) on the membrane of living HeLa cells was visualized in situ by a confocal laser scanning microscopy, ascribed to the specific interaction between PBA and SA. Thus, the PBA-FSBPs showed a great potential in probing SA expressed on living cells with high selectivity and sensitivity. [Copyright &y& Elsevier]

Development of noninvasive bioimaging fluorescent probes for detecting particular enzyme activity is greatly recommendable for preclinical diagnosis of cancer. Given that the elevated β-gal activity is positively correlated with several tumors, developing a fluorescent probe for the sensing of β-gal is therefore highly desirable for cancer diagnosis. Herein, a new enzyme-activatable near-infrared (NIR) turn-on fluorescent probe (DMC-βgal) was developed for accurately detecting β-gal activity characterized by excellent selectivity, high sensitivity (LOD = 0.298 U/L), and low toxicity. More importantly, DMC-βgal qualifies remarkable NIR excitation (725 nm) and emission wavelength (770 nm), an ideal tool for restrained photodamage and suppressed autofluorescence. The above excellent performance of DMC-β-gal allowed for the accurate monitoring of endogenous β-gal in living cells. Moreover, the probe was successfully applied to detect intracellular β-gal activity in different types of cancer cells, verifying that SKOV-3 cells had a higher level of β-gal activity than those of A549, HCT-116, MCF-7, and HepG2 cells. Furthermore, DMC-βgal could real-time visualize endogenously β-gal in tumor-bearing nude mice with low auto-fluorescence interference. All results fully demonstrated that DMC-βgal has potential value as a promising strategy for diagnosis of β-gal-related diseases. [Display omitted] • A new near-infrared excited and emitted β-galactosidase (β-gal) fluorescent probe DMC-βgal was synthesized. • The probe DMC-βgal is characterized by excellent selectivity and high sensitivity (LOD = 0.298 U/L). • The probe is applied to prove that the β-gal activity in SKOV-3 cells is higher than HepG2, A549, HCT-116, MCF-7 cells. • DMC-βgal can real-time visualize the β-gal activity in tumor-bearing nude mice with low photodamage and autofluorescence. [ABSTRACT FROM AUTHOR]

Here, a dual lock-and-key fluorescence probe was developed for visualizing the inflammatory process in myocardial H9C2 cells. The probe possessed two-photon properties, viscosity sensitivity, and hydrogen peroxide (H 2 O 2) responsiveness. A thiocarbamate spacer between fluorophore and H 2 O 2 responsive unit enabled the release of carbonyl sulfide (COS). This rapidly converts to the anti-inflammatory hydrogen sulfide (H 2 S) by the ubiquitous enzyme carbon anhydrase. The probe displayed a dual response towards hydrogen peroxide and viscosity in vitro. No obvious fluorescence changes were observed towards either hydrogen peroxide or viscosity alone. In cellular experiments, the probe demonstrated good biocompatibility, low toxicity, and was shown responses towards exogenous and endogenous hydrogen peroxide under viscosity conditions. LPS induced cell inflammation showed it was able to effectively alleviate the inflammation-caused damage by releasing H 2 S and eliminating H 2 O 2. The new protocol demonstrates its promising to achieve diagnosis and treatment of cellular inflammatory process. [Display omitted] • A dual response fluorescence probe possessing viscosity sensitivity, and hydrogen peroxide responsiveness was developed. • Hydrogen sulfide was generated from self-immolation of carbonyl sulfide, catalysed under carbon anhydrase. • The probe showed turn on fluorescence responses towards hydrogen peroxide and viscosity in vitro. • The probe was able to effectively alleviate the inflammation-caused damage through releasing H 2 S and eliminating H 2 O 2. [ABSTRACT FROM AUTHOR]

Ascorbic acid (AA) and glutathione (GSH), the most abundant intracellular reductive substances, have been widely used as biomarkers for cancer cells identification. The current methods relying on imaging of AA or GSH alone to identify cancer cells may cause systematic errors, since a mutual conversion relationship exists between AA and GSH. In this work, we propose a fluorescent nanosensor for the simultaneous imaging of intracellular reductive substances including AA and GSH. Biocompatible fluorescent silicon nanoparticles (SiNPs) with rich surface amine and carboxyl groups were synthesized. The fluorescence of the SiNP was initially quenched by chelation of Fe3+ ions, forming SiNP/Fe3+ complex as the fluorescent nanosensor. Upon the redox reaction with reductive substances, the nanosensor showed sensitively fluorescent recovery. Moreover, benefited from the efficient cellular uptake of the SiNP/Fe3+ and the overexpressed intracellular reductive substances in cancer cells, the fluorescent nanosensor was used to accurately identify the human breast carcinoma (MCF-7) cells from normal mammary epithelial (MCF-10A) cells by imaging of intracellular AA and GSH simultaneously. This strategy would be promising in imaging-guided precision cancer diagnosis. [Display omitted] • A SiNPs-based response to reductive substances fluorescent nanosensor was developed. • The good sensitivity and selectivity were obtained. • The nanosensor was utilized to image reductive substances in cell with satisfactory results. • Cancer cell identification was completed by the facile fluorescent nanosensor. [ABSTRACT FROM AUTHOR]

Cyanide detection methods are urgently needed due to the highly lethal to human beings. Herein, we report two fluorescence probes (Probe 1 and Probe 2) based on cyanoethylene group for cyanide anion (CN−) detection. The selective recognition for CN− was confirmed by the completely opposite green fluorescence of Probe 1 and red fluorescence of Probe 2 observed by fluorescence spectra and naked eyes. The probes take advantages of the large Stokes shift (~160 nm), rapid response (30 s), anti-interference performance and low detection limit (Probe 1 : 12.4 nM, Probe 2 : 101 nM). The sensing mechanism is certificated to the nucleophilic attack of CN− to electron-deficient cyanoethylene group of probes, which was demonstrated by 1H NMR titration, HR-MS, Job's plot and IR spectroscopy. Density functional theory (DFT) calculations were carried out to analyze the mechanism in theory. Further, practical applications were studied. Easy-to-use test strips treated with Probe 1 or Probe 2 are capable of CN− detection in pure drinking water. The good biocompatibility and membrane penetrability have achieved the bioimaging capability of Probe 1 and Probe 2 in living HepG-2 cells, making the probes promising for use in real lives. [Display omitted] • Probes show high selectivity towards cyanide (CN−) and good anti-interference ability against other competing anions. • Probes show high reactivity in aqueous media, making them can be used in actual environment and biological system. • Probes are capable of CN− detection by easy-to-use test in pure drinking water. • Probes have large Stokes shifts and low cytotoxicity so that they can be utilized as CN− sensors in living cells. [ABSTRACT FROM AUTHOR]

Mercury and sulfur dioxide (SO 2) are common pollutants in the ecological environment, which are important factors causing many diseases of organisms. The lack of appropriate analytical tools has limited the further understanding of the relationship between ionic mercury (Hg2+) and SO 2. Herein, a bifunctional fluorescent probe LJ was designed and explored to simultaneously detect Hg2+ and SO 2 via desulfurization reaction and Michael addition reaction, respectively. Probe LJ showed distinct fluorescence responses which a large near-infrared fluorescence enhancement towards Hg2+ at λ em = 713 nm and a blue shift at λ em = 450 nm towards SO 2 without any spectral cross interferences. To the best of our knowledge, this is the first fluorescent probe with dual fluorescent emission channels to detect Hg2+ and SO 2 with the detection limit of 187 nM and 354 nM, respectively. Moreover, cell fluorescent imaging experiments indicated that the probe was mitochondria targetable and provided evidence that SO 2 could be used as an antidote to attenuate the toxicity of Hg2+ in living cells. [Display omitted] • The first fluorescent probe LJ which can detect Hg2+ and SO 2 simultaneously was constructed. • LJ is mitochondria targetable, and can image Hg2+ and HSO 3 − in living cells. • The study presented the first evidence that HSO 3 − could be used as an antidote for Hg2+-induced toxicity in living cells. [ABSTRACT FROM AUTHOR]

Abstract: By using a visible-light-excited ternary Eu3+ complex, BHHBCB-Eu3+-BPT (BHHBCB: 1,2-bis[4′-(1“,1“,1“,2“,2“,3“,3“-heptafluoro-4″,6″-hexanedion-6″-yl)-benzyl]-4-chlorosulfobenzene; BPT: 2-(N,N-diethylanilin-4-yl)-4,6-bis(pyrazol-1-yl)-1,3,5-triazine), as a luminophore, two kinds of novel visible-light-excited europium materials, the silica-encapsulated BHHBCB-Eu3+-BPT (Eu@SiO2) nanoparticles and BHHBCB-Eu3+-BPT-conjugated bovine serum albumin (BSA–BHHBCB-Eu3+-BPT), were prepared for biolabeling and time-resolved luminescence cell imaging applications. The Eu@SiO2 nanoparticles, prepared by the copolymerization of 3-aminopropyl(triethoxy)silane–BHHBCB-Eu3+-BPT conjugate, free 3-aminopropyl(triethoxy) silane and tetraethyl orthosilicate in a water-in-oil reverse microemulsion, are monodispersed, spherical and uniform in size, and strongly luminescent with an excitation peak at ∼400nm and a long luminescence lifetime of 346μs. The BSA–BHHBCB-Eu3+-BPT, prepared by covalent binding of BHHBCB-Eu3+-BPT to BSA, shows also strong visible-light-excited luminescence with a excitation peak at ∼400nm and a long luminescence lifetime of 402μs. The two materials were used for labeling transferrin and folic acid. Using the time-resolved luminescence imaging of living HeLa cells, the cell-surface receptors of transferrin and folic acid were successfully visualized by the prepared biolabels based on the ligand–receptor affinity binding interaction. The results demonstrated the feasibility of the new materials as visible-light-excited biolabels for the time-resolved luminescence cell imaging. [Copyright &y& Elsevier]

Abstract: Nitric oxide (NO) is a signaling molecule, and plays an important role in some human neuroses. In this work, a novel europium(III) complex, [4′-(3-methylamino-4-aminophenoxy)-2,2′:6′,2′′-terpyridine-6,6′′-diyl] bis(methylenenitrilo) tetrakis(acetate)-Eu3+ (MATTA-Eu3+), has been designed and synthesized as a luminescent probe for the time-resolved luminescence detection of NO. The complex itself is weakly luminescent, but can specifically react with NO under the aerobic conditions to form its triazole derivative, [4′-(3-methyl-4-benzotriazol-6-yl-oxy)-2,2′:6′,2′′-terpyridine-6,6′′-diyl] bis(methylenenitrilo) tetrakis(acetate)-Eu3+ (MBTTA-Eu3+), accompanied by a remarkable luminescence enhancement with a long luminescence lifetime. The luminescence response of the complex to NO is rapid, highly selective and sensitive, and pH-insensitive in aqueous solutions. These properties enable MATTA-Eu3+ to be used as a turn-on luminescent probe for the selective recognition and sensitive time-resolved luminescence detection of NO in a wider pH range. The probe-loaded PC12 cells were prepared, and used for the time-resolved luminescence imaging detection of the glutamate-induced NO production in the cells. The result demonstrated the practical utility of the probe for imaging the NO production in neuron cells. [Copyright &y& Elsevier]

Abstract: A thiophene–coumarin hybrid molecule, (6E)-6-((thiophen-2-yl)methyleneamino)-2H-chromen-2-one (TMC) has been prepared and its single crystal X-ray structure is reported. TMC can selectively detect Cr3+ in presence of other common cations. Both TMC and its Cr3+ complex are well characterized by different spectroscopic techniques like 1H NMR, QTOF-MS ES+, FTIR and elemental analysis as well. TMC exhibits fluorescence enhancement upon binding Cr3+ in CH3CN–HEPES buffer (0.02M, pH 7.4) (4:6, v/v) medium. Detection limit of the method is 1×10−6 M. Binding constant is estimated with the Benesi–Hildebrand method and the value 8×104 indicates a fairly strong interaction between TMC and Cr3+. Speciation studies have been performed in a fast and environment friendly way using least sample volume, less hazardous chemicals and solvents. Cr3+ assisted restricted rotation around the imine bond and inhibited photo-induced electron transfer from the N,S-donor sites to the coumarin unit are responsible for fluorescence enhancement. TMC is capable to detect intracellular Cr3+ in living cells. [Copyright &y& Elsevier]

Abstract: The anticancer drug doxorubicin (DOX) appeared to adsorb efficiently on TiO2 nanoparticles (NPs) as evidenced by visible absorption and diffuse reflectance infrared spectroscopy data. The adsorbed drugs were found released in a controlled way by external glutathione (GSH). Fluorescence of DOX appeared to be quenched substantially by TiO2 NPs. The fabrication and release of DOX on TiO2 NPs were checked by monitoring the fluorescence. We could monitor real-time drug release in the live cell using fluorescence imaging techniques. By these methods, we were able to monitor up to a nanomolar amount of DOX release in vitro from TiO2 NPs triggered by external GSH. In vivo fluorescence images of DOX were obtained from the subcutaneous site in living mice after GSH treatment. On the basis of label-free fluorescence quenching measurements, a real-time release of DOX on TiO2 NPs can be monitored in vitro and in vivo after an external trigger of GSH. [Copyright &y& Elsevier]

Abstract: Time-resolved (or time-gated) luminescence detection technique using lanthanide chelates as luminescent probes is a widely used and highly sensitive method for the biological applications. The developments of various functional lanthanide probes that can selectively recognize the biological targets are the essential objective of the technique. In this work, a unique Tb3+ chelate-based luminescent probe, N,N,N 1 ,N 1 -[2,6-bis(3′-aminomethyl-1′-pyrazolyl)-4-(p-aminophenoxy)methylene-pyridine] tetrakis(acetate)-Tb3+(BMPTA-Tb3+), has been designed and synthesized for highly selective and sensitive time-resolved luminescence detection of one highly reactive oxygen species (ROS), hydroxyl radical (probe is almost non-luminescent, and can selectively react with hydroxyl radical to afford a highly luminescent Tb3+ chelate, N,N,N 1 ,N 1 -[2,6-bis(3′-aminomethyl-1′-pyrazolyl)-4-hydroxymethyl-pyridine] tetrakis(acetate)-Tb3+ (BHTA-Tb3+), accompanied by a 49-fold increase in luminescence quantum yield with a long luminescence lifetime (2.76ms). The luminescence response of the probe to hydroxyl radical is highly selective and insensitive to pH in the physiological pH range. For loading the probe into the living cells, the acetoxymethyl ester of BMPTA-Tb3+ was synthesized and used for the HeLa cell loading. Based on this probe, a background-free time-resolved luminescence imaging method for detecting hydroxyl radical in living cells was successfully established. [Copyright &y& Elsevier]

Abstract: In this paper, different sizes of glutathione-capped CdTe (GSH/CdTe) quantum dots (QDs) have been prepared directly in aqueous solution. The QDs have tunable fluorescence in the range of 510–670nm, and they also have high photoluminescence quantum yield (PLQY) without any postpreparative treatment. Furthermore, the QDs have strong resistance to photobleaching, and they also have to be considered as cytocompatible. In addition, for the first time, folic acid was covalently conjugated to the GSH/CdTe QDs for imaging of cancer cells, demonstrating their potentially broad application as biolabels. [ABSTRACT FROM AUTHOR]