Continuous Detection of Cobalt Ions and Pyrophosphates by NAC-CdTe Quantum Dots Fluorescence Probes.

In this work, a simple and sensitive N-acetyl-L-cysteine (NAC)-covered CdTe quantum dots (NAC-CdTe QDs) fluorescence probe for continuous detection of Co2+ and pyrophosphate ions (PPi, P2O74-) was synthesized. The fluorescence of the quantum dots was significantly quenched by Co2+ through the coordination of Co2+ and the carboxyl groups on the NAC-CdTe quantum dots. Interestingly, the combination of NAC-CdTe quantum dots with Co2+ yields a new fluorescence probe of Co2+-modified NAC-CdTe QDs (Co2+@NAC-CdTe). The addition of PPi restored the fluorescence due to the competition between PPi and carboxyl groups with Co2+ causing Co2+ to detach from the surface of Co2+@NAC-CdTe quantum dots. Thus, a sensitive and reversible detection of Co2+ and PPi had been successfully established. The Co2+@NAC-CdTe quantum dots fluorescence probe exhibits excellent selectivity and high sensitivity toward PPi detection with low detection limit of 0.28 µM. In addition, the novel fluorescence probe was successfully applied to detect the concentration of PPi in environmental water samples and in-vitro cells imaging.

A Novel DNBS-based Fluorescent Probe for the Detection of H2S in Cells and on Test Strips.

Hydrogen sulfide (H2S) plays a key role in the physiology and pathology of organisms, and H2S in the environment is easily absorbed and harmful to health. It is of great significance to develop a probe with good selectivity, high sensitivity and good stability that can detect hydrogen sulfide inside and outside organisms. In this work, we designed a novel "turn-on" fluorescent probe CIM-SDB for the detection of H2S. The probe CIM-SDB used indene-carbazole as the fluorophore and 2,4-dinitrobenzenesulfonyl as the recognition site. The probe CIM-SDB exhibited high selectivity and sensitivity to H2S (detection limit as low as 123 nM). Moreover, the probe CIM-SDB was successfully applied to the detection of intracellular exogenous and endogenous H2S, and the test strips prepared by the probe CIM-SDB could realize the convenient and rapid detection of H2S.

A novel fluorescent probe based on carbazole-thiophene for the recognition of hypochlorite and its applications.

A carbazole thiophene-aldehyde and 4-methylbenzenesulfonhydrazide conjugate CSH was synthesized by introducing 5-thiophene aldehyde at the 3-position of the carbazole group as the precursor and then condensing it with 4-methylbenzenesulfonhydrazide. CSH has high selectivity and sensitivity towards ClO-, which can specifically identify ClO- by UV-Vis and fluorescence spectroscopy. CSH can rapidly respond to ClO- in the physiological pH range through a fluorescence quenching pattern, accompanied by the color of CSH changing markedly from turquoise to yellowish green under the 365 nm UV light. Probe CSH exhibits a quantitative response to ClO- (0-11 µM) with a low detection limit (1.16 × 10-6 M). Cell imaging experiments have shown that CSH can capture fluorescent signals in the cyan and yellow channels of HeLa cells through fluorescence confocal microscopy, and can successfully identify exogenous ClO- in HeLa cells. In addition, probe CSH can also be used to detect ClO- in environmental water samples. These results indicate that CSH has potential application prospects in the environmental analysis and biological aspects.

A Novel L-Arginine Functionalized CdTe Quantum Dots Fluorescence Probe for Pyrophosphate Anion Detection.

In this paper, a novel amino acid surface-functionalized semiconductor CdTe quantum dot fluorescent probe amidated by carboxyl and amide groups was synthesized to detect pyrophosphate ions (P2O74-, PPi). L-Arginine (L-Arg) was grafted onto cysteine modified CdTe quantum dots (Mea-CdTe QDs) to form a new L-Arginine-functionalized quantum dot fluorescent probe (L-Arg@Mea-CdTe). The prepared probe has good optical properties with multiple grafted functional groups on the surface. The guanidine group of the L-Arg@Mea-CdTe fluorescent probe is strongly basic and will be fully protonated under physiological conditions. The resulting hydrogen bonds bound to pyrophosphate lead to significant changes in the fluorescence of CdTe quantum dots. IR and XPS characterization were performed to confirm it. The addition of PPi induces a significant fluorescence quenching of L-Arg@Mea-CdTe in aqueous solution. The fluorescent QDs probe can also detect pyrophosphate with good sensitivity and anti-interference performance. The detection limit of the L-Arg@Mea-CdTe fluorescence probe for PPi is as low as 0.30 µM. In addition, the novel nano-fluorescent probe was successfully applied to detect PPi in water and in cell imaging.

A novel lipid droplets/lysosomes-targeting colorimetric and ratiometric fluorescent probe for Cu2+ and its application.

A novel multifunctional fluorescent probe LL2 was prepared via a one-step condensation reaction between 3-formyl-N-butylcarbazole and 2-Hydroxy-1-naphthylhydrazone. LL2 can work as a colorimetric probe for Cu2+, and can also selectively recognize Cu2+ via ratiometric fluorescence signal. After the addition of Cu2+, the probe LL2 responded rapidly within 5 s and reached stability within 30 s. In natural light, when Cu2+ were added to the solution, the color of probe LL2 changed from yellowish to colorless, while there was a discernible fluorescence changed from green to blue under a 365 nm UV lamp. The ratiometric fluorescence intensity (F449/F510) showed a good linear relationship (R2 = 0.9902) with Cu2+ concentration in the concentration range of 0-5 µmol/L, and the minimum detection limit was 1.96 µM. Cell imaging experiments showed that LL2 could capture fluorescence signals in the green and blue channels of HepG2 cells through fluorescence confocal microscope, and successfully recognize exogenous Cu2+ in HepG2 cells. In addition, fluorescence co-localization experiments showed that LL2 could target both lipid droplets and lysosomes. Meanwhile, LL2 could be applied to filter paper strip assay and detection of Cu2+ in actual water samples. These results indicated that probe LL2 has a good capability for monitoring Cu2+ in environment and living cells.

A fluorescent probe based on triphenylamine with AIE and ICT characteristics for hydrazine detection.

A fluorescent probe MAM based on triphenylamine scaffold was synthesized. The electron donating group 4-methoxyphenyl and the electron acceptor dicyanoethylene were introduced on the triphenylamine scaffold to form a D-π-A fluorescent probe. The probe MAM exhibited the typical aggregation-induced emission (AIE) and intramolecular charge transfer (ICT) characteristics with the bright orange-red fluorescent emission in high water fraction (fw ≥ 50%) and negligible emission in low water fraction. The probe MAM could detect hydrazine (N2H4) in DMSO-tris-HCl (10 mM, pH7.4, v/v, 3:1) with high selectivity and sensitivity. The specific reaction between MAM and hydrazine and the formation of the hydrazone blocked the ICT process, and the system emitted the cyan fluorescence which could be easily observed by naked eyes. The limit of detection (LOD) was 0.196 µM (6.25 ppb), which is lower than the US Environmental Protection Agency standard (10 ppb). The test strips prepared by the probe MAM could realize the convenient and rapid detection of N2H4 solution and vapor. The application of MAM in actual water samples and cells was investigated, and the results showed that MAM could sense N2H4 in environmental and biological aspects with potential application prospects.

Construction of continuously enhanced fluorescent sensor for detection of glutathione in normal and cancer cells.

In this paper, water-soluble cysteamine (CA)-capping CdSe quantum dots (CA-CdSe) could be used as a continuous fluorescent sensor. The CA-CdSe QDs can respond to Ag+ with a detection limit of 54.1 nM. Interestingly, CA-CdSe quantum dots combined with Ag+ to generate a new nano-fluorescence sensor-Ag+ modified CA-CdSe QDs (Ag+@CA-CdSe). Ag+@CA-CdSe can detect glutathione (GSH) with good sensitivity and anti-interference performance. The detection limit of Ag+@CA-CdSe fluorescenct sensor for GSH is as low as 0.74 µM. In addition, the novel nano-fluorescent sensor Ag+@CA-CdSe exhibited good cell permeability and was successfully applied to detect exogenous and endogenous GSH concentrations in cells. It could distinguish cancerous and normal cells by in vitro cell fluorescence imaging.

Using an affinity analysis to identify phytoplankton associations.

Phytoplankton functional traits can represent particular environmental conditions in complex aquatic ecosystems. Categorizing phytoplankton species into functional groups is challenging and time-consuming, and requires high-level expertise in species autecology. In this study, we introduced an affinity analysis to aid the identification of candidate associations of phytoplankton from two data sets comprised of phytoplankton and environmental information. In the Huaihe River Basin with a drainage area of 270,000 km2 in China, samples were collected from 217 selected sites during the low-water period in May 2013; monthly samples were collected during 2006-2011 in a man-made pond, Dishui Lake. Our results indicated that the affinity analysis can be used to define some meaningful functional groups. The identified phytoplankton associations reflect the ecological preferences of phytoplankton in terms of light and nutrient acquisition. Advantages and disadvantages of applying the affinity analysis to identify phytoplankton associations are discussed with perspectives on their utility in ecological assessment.

Construction of Hybrid Fluorescent Sensor for Cu2+ Detection Using Fluorescein-functionalized CdS Quantum Dots Via FRET.

A new hybrid fluorescent nanosensor (Flu@Mea-CdS) for the Cu2+ detection in aqueous solution was constructed through fluorescence resonance energy transfer (FRET). The Flu@Mea-CdS was fabricated by amide linkage between CdS quantum dots capped with cysteamine (Mea-CdS) and fluorescein. With the formation of FRET process from Mea-CdS quantum dots to fluorescein, the fluorescence intensity of fluorescein at 520 nm was significantly enhanced. In addition, the sensor based on FRET has high selectivity for Cu2+ ions detection. With the presence of Cu2+ ions, Cu2+ ions were transferred to Cu2S by the reaction with Flu@Mea-CdS, which caused the inhibition of FRET process and quenched the fluorescence signal of 520 nm. Compared with Mea-CdS quantum dots, the Flu@Mea-CdS sensor has a lower detection limit for Cu2+. The linear range is 4-14 µM, and the detection limit is 0.17 µM. The sensor has been successfully applied to the detection of Cu2+ ions in practical samples, which shows its potential application value in environmental monitoring.

MPA-CdTe quantum dots as "on-off-on" sensitive fluorescence probe to detect ascorbic acid via redox reaction.

Mercaptopropionic acid (MPA) capped CdTe quantum dots (MPA-CdTe QDs) were synthesized in aqueous medium by hydrothermal method, which modified by Fe3+ could be used as a fluorescent probe to detect ascorbic acid (AA). MPA-CdTe QDs fluorescence probe could be used as successive sensor for metal ions and AA with "on-off-on" process. The fluorescence of QDs was quenched after adding Fe3+ to MPA-CdTe QDs. Then, the fluorescence of the Fe3+@MPA-CdTe QDs can be sensitively turned on by AA to give an "on-off-on" fluorescence response according to the oxidation-reduction between Fe3+ and AA. There was a linear relationship between fluorescence intensity quenching value and the concentration of Fe3+ in the range of 2-10 µM since Fe3+ sensitively reacted with CdTe QDs. The linear detection range for AA was 0.1-1 µM with a limit of detection of 6.6 nM. The principle is proved by fluorescence emission spectroscopy, nuclear magnetic resonance spectroscopy. The proposed method is successfully used to detect the AA in human plasma sample.

A MADS-box transcription factor FoRlm1 regulates aerial hyphal growth, oxidative stress, cell wall biosynthesis and virulence in Fusarium oxysporum f. sp. cubense.

The fungal pathogen Fusarium oxysporum f. sp. cubense (Foc) causes Fusarium wilt that affects banana plants. However, the detailed molecular mechanisms of Foc virulence determinants have not been elucidated. In this study, we identified the MADS-box transcription factor FoRlm1 that is conserved among mitogen-activated protein kinases. Our data revealed that FoRlm1 is essential for aerial hyphal growth and virulence. Transcriptional analysis revealed that FoRlm1 deletion altered the expression of anti-oxidant enzymes, chitin synthases, fusaric acid (FA), and beauvericin biosynthesis genes. Furthermore, FoRlm1 deletion promoted tolerance to Congo red and increased sensitivity to hydrogen peroxide. Transcriptome analysis of ΔFoRlm1 mutant and wild-type strain indicated that the expression of many genes associated with fungal physiology and virulence was up- or down-regulated. Overall, these results suggested that FoRlm1 plays a critical role in the regulation of hyphal growth, anti-oxidation mechanisms, cell wall biosynthesis, transcription of mycotoxin biosynthetic genes encoding FA and beauvericin, and virulence in Foc.

AIE-active fluorescent polymeric nanoparticles about dextran derivative: preparation and bioimaging application.

Aggregation-induced emission (AIE), as a special phenomenon of fluorescence, can elegantly overcome the fluorescence quenching caused by common fluorescent materials under high concentration conditions and has attracted interest of researchers in many fields. Particularly AIE-active polymer nanoparticles have been widely utilized in a modern biomedical research. In this work, we prepared a novel kind of AIE-active fluorescent polymeric nanoparticals (Dex-OH-CHO) through a facile esterification between a new hydrophobic AIE-active 1, 8-naphthalimide derivative and the hydrophilic dextran. The structure and optical properties of Dex-OH-CHO were characterized in detail by FTIR, 1H NMR, XPS, TEM and fluorescence spectra. The results showed that Dex-OH-CHO emitted light-blue fluorescence in aqueous solution with high fluorescent quantum yield (Φ = 24.43%, concentration is 20 µg/mL), low CMC (5 µg/mL), good photostability, high water solubility and well dispersivity. Moreover, good biocompatibility and ideal cell uptake made Dex-OH-CHO had a great application potential in biological imaging.

Genome-Wide Identification of Calcium-Dependent Protein Kinases in Chlamydomonas reinhardtii and Functional Analyses in Nitrogen Deficiency-Induced Oil Accumulation.

Calcium-dependent protein kinases (CDPKs) are recognized as important calcium (Ca2+) sensors in signal transduction and play multiple roles in plant growth and developmental processes, as well as in response to various environmental stresses. However, little information is available about the CDPK family in the green microalga Chlamydomonas reinhardtii. In this study, 15 CrCDPK genes were identified in C. reinhardtii genome, and their functions in nitrogen (N) deficiency-induced oil accumulation were analyzed. Our results showed that all CrCDPK proteins harbored the typical elongation factor (EF)-hand Ca2+-binding and protein kinase domains. Phylogenetic analysis revealed that these CrCDPKs were clustered into one group together with a subclade of several CPKs from Arabidopsis and rice, clearly separating from the remaining AtCPKs and OsCPKs. These genes were located in 10 chromosomes and one scaffold of C. reinhardtii and contained 6-17 exons. RNA sequencing and quantitative reverse transcription (qRT)-PCR assays indicated that most of these CrCDPKs were significantly induced by N deficiency and salt stress. Lanthanum chloride (LaCl3), a plasma membrane Ca2+ channel blocker, limited oil accumulation in C. reinhardtii under N-deficient conditions, suggesting that Ca2+ was involved in N deficiency-induced oil accumulation. Furthermore, RNA interference (RNAi) silencing analyses demonstrated that six CrCDPKs played positive roles and three CrCDPKs played negative roles in N deficiency-induced oil accumulation in C. reinhardtii.

A RNA-Targeted Two-Photon Bioprobe with High Selective Permeability into Nuclear Pore Complexes for Dynamically Tracking the Autophagy Process among Multi-Organelles.

Dynamic tracking of the spatiotemporal coordination among various organelles to in-depth understanding of the mechanism of autophagy have attracted considerable attention. However, the monitor of nucleoli participation in autophagy was somehow neglected. Herein, we report a RNA-targeted bioprobe (ADAP) with high selective permeability into nuclear pore complexes, which induced a two-photon (TP) fluorescence "off-on" response by groove combination with RNA, dynamically monitoring the autophagy process among multiorganelles (nucleoli, mitochondria, and mitochondria-containing lysosomes). This work provides a simple and convenient way to observe the dynamic behavior of multiorganelles during the autophagy process, which benefits the understanding of cellular metabolism.

A lipid droplet-targeted fluorescence probe for visualizing exogenous copper (II) based on LLCT and LMCT.

A simple and sensitive probe, pyridine-based Schiff base (PBSB), is prepared based on the previous studies, which shows a rapid response to copper (II) through a fluorescence enhancement process. On association with copper (II), PBSB immediately presents a large red-shift (130 nm) in emission spectrum simultaneously accompanying with increasing emission intensity. The mechanism and binding sites of PBSB detecting copper (II) have been established by theoretical calculations and 1HNMR study, respectively. More importantly, in the complex biological system, PBSB having an excellent membrane permeability and a great photostability can visualize copper (II) in lipid droplet by bio-imaging, which display so great promising advantages in the issues causing by disorder of copper ions that could be convenient for prevention and control problems with human health and complex bio-system.

Exploration research on synthesis and application of a new dye containing di-2-picolyamine.

A newly designed fluorescence dye L based on di-2-picolyamine (DPA) moiety as a chelator was obtained under the protection of N2 at 120°C, and KI as catalyst with relatively better yield. More interestingly, L not only could selectively and sensitively detect Cu2+ ions in aqueous medium but also examine the Cu2+ ions of the actual water samples. Nevertheless, L could be visual in Hela cells with excellent cell permeability, viz, monitoring exogenous Cu2+ ions as well as realizing an "on-off-on" process.

A reversible and highly selective fluorescence "on-off-on" probe for detecting nickel ion in the mitochondria of living cells.

A simple molecular fluorescent probe L has been designed, synthesized and characterized. The probe upon interaction with different metals ions show high selectivity and sensitivity for Ni(2+) through fluorescence "turn-off" response in acetonitrile, and the fluorescence could be recovered when chelating agent TPEN is added in this system, viz an "on-off-on" process. Its recognition mechanism has been established by fluorescence spectra, (1)H NMR study. Moreover, to further explore its utility in biological system, L is selected as a probe for Ni(2+) indicator in live cells and shows sensitivity on Ni(2+) intracellular distribution. Fluorescence co-localization studies demonstrate that L is a specific mitochondria-targeted fluorescent probe with excellent cell membrane permeability. Furthermore, a rapidly reversible fluorescence imaging of probe L detecting Ni(2+) in the mitochondria is successfully achieved. These facts would make this probe a great potential for detecting Ni(2+) in biology.

Rationally designed two-photon absorption compounds based on benzoxazole derivatives: structure-property relationships and bio-imaging applications.

A new series of benzoxazole-based two-photon absorption (2PA) chromophores (T1-5) were synthesized and fully characterized. Among them, T1-3 are linear donor (D)-π-acceptor (A) type fluorophores with various electron-donating groups, while T4 and T5 are multi-branched compounds stemming from T3. Their photophysical properties have been systematically investigated, and the two-photon absorption properties indicate that the highest 2PA cross-section (σ2PA) is 2702 GM for T5 (in DMF). Structure-property relationships of the chromophores are comprehensively discussed based on their optical properties, crystal structures and density functional theory (DFT) calculations. In addition, a two-photon fluorescence cell imaging experiment demonstrates the potential bio-application of T1-5 with good photostability and low cytotoxicity.

Application and recognition behaviors of TPA-cored probes with subtle structural change.

Two new triphenylamine-cored probes (L1, L2) with different receptor units have been synthesized and fully characterized by IR, NMR and MS spectra. Their photophysical properties have been investigated in detail. The recognition abilities of two probes were evaluated by a series of metal ions, which showed that L1 could recognize Cu(2+) over other metal ions. L2 could respond to Cu(2+), Hg(2+) in a short time, which interferes with a little each other. The Job's plot and (1)H NMR titration of L1 with Cu(2+) and L2 with Cu(2+) (Hg(2+)) in CD3CN verified the coordination mode of complexes L1-Cu(2+), L2-Cu(2+) and L2-Hg(2+), respectively. The limit of detection of L2 for Cu(2+) was lower than that of L1 towards Cu(2+). The results demonstrated that the receptor units in the probes had remarkable effect on recognizing metal ions. Meanwhile, L1 and L2 showed potential application in bio-imaging after mixing with Cu(2+).

Synthesis, photophysical and electrochemical properties of two novel carbazole-based dye molecules.

Two carbazole-based dye molecules: 3-(6-benzothiazol-2-yl-9H-hexylcarbazole-3-yl)-2-cyano-acylic acid (D3) and 3-[5-(6-benzothiazol-2-yl-9H-hexylcarbazole-3-yl)-thiophen-2-yl]-2-cyan-acylic acid (D4) were synthesized by an approach from carbazole derivate using Vilsmeier-Haack, Suzuki cross-coupling and Knoevenagel reactions. Their physical and electrochemical properties were investigated. D3 and D4 exhibit different optical properties, such as UV absorption, photoluminescence, fluorescence quantum yield and fluorescence lifetime in different solvents. Compared with D3 without a thiophene unit, the maximum absorption wavelength of D4 red-shift obviously and its fluorescence intensity is also enhanced. A shift of the EHOMO and ELUMO is observed for D3 (EHOMO=2.06 V, ELUMO=-1.39 V vs. NHE) and D4 (EHOMO=1.73 V, ELUMO=-1.33 V vs. NHE). D3 and D4 can be used as dyes for dye-sensitized solar cells (DSSCs) with TiO2 nanomaterial because their EHOMO are lower than the conduction band edge of TiO2 [-0.5 V (vs. NHE)] and their ELUMO are higher than the I(3-)/I(-) redox potential [0.42 V (vs. NHE)].