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Sample records for simple fluorescence based

  1. A new simple Schiff base fluorescence "on" sensor for Al3+ and its living cell imaging.

    PubMed

    Kumar, Jutika; Sarma, Manas Jyoti; Phukan, Prodeep; Das, Diganta Kumar

    2015-03-14

    The simple Schiff base (Z)-N-benzylidenenaphthalen-1-amine (L) acts as an effective fluorescence sensor for Al(3+) by "off-on" mode, and ca. 42 times enhancement in fluorescence intensity is observed. The detection limit of L towards Al(3+) is observed to be 5 × 10(-5) M. UV/Visible and fluorescence data as well as DFT calculations confirm 1:3 coordination between Al(3+) and L through N atoms in a pyramidal shape. L is employed for imaging the Al(3+) ion in living biological cells and for the determination of the Al(3+) ion in bovine serum albumin.

  2. A simple fluorescent probe for sensing cysteine over homocysteine and glutathione based on PET

    NASA Astrophysics Data System (ADS)

    Fan, Wenlong; Huang, Ximing; Shi, Xiaomin; Wang, Zhuo; Lu, Zhengliang; Fan, Chunhua; Bo, Qibing

    2017-02-01

    A big challenge is the discrimination of sulfhydryl-containing amino acids due to their structural similarity. We designed and synthesized a simple fluorescent probe 3 for specific detection of cysteine based on photo-induced electron transfer (PET). The acrylate and BODIPY moieties in probe 3 act as a reaction site and reporter group, respectively. So the synergistic effect of the substituent groups endows probe 3 very strong green fluorescence at 525 nm (λex = 500 nm). The cleavage reaction induced by cysteine leads to acrylate hydrolysis, and thereby triggers PET on, which effectively quench the fluorescence of 3. Probe 3 exhibited a rapid response towards cysteine over homocysteine and glutathione. Probe 3 is successfully applied for sensing and imaging cysteine in vitro or in vivo cells with low cytotoxicity.

  3. Medically Relevant Assays with a Simple Smartphone and Tablet Based Fluorescence Detection System

    PubMed Central

    Wargocki, Piotr; Deng, Wei; Anwer, Ayad G.; Goldys, Ewa M.

    2015-01-01

    Cell phones and smart phones can be reconfigured as biomedical sensor devices but this requires specialized add-ons. In this paper we present a simple cell phone-based portable bioassay platform, which can be used with fluorescent assays in solution. The system consists of a tablet, a polarizer, a smart phone (camera) and a box that provides dark readout conditions. The assay in a well plate is placed on the tablet screen acting as an excitation source. A polarizer on top of the well plate separates excitation light from assay fluorescence emission enabling assay readout with a smartphone camera. The assay result is obtained by analysing the intensity of image pixels in an appropriate colour channel. With this device we carried out two assays, for collagenase and trypsin using fluorescein as the detected fluorophore. The results of collagenase assay with the lowest measured concentration of 3.75 µg/mL and 0.938 µg in total in the sample were comparable to those obtained by a microplate reader. The lowest measured amount of trypsin was 930 pg, which is comparable to the low detection limit of 400 pg for this assay obtained in a microplate reader. The device is sensitive enough to be used in point-of-care medical diagnostics of clinically relevant conditions, including arthritis, cystic fibrosis and acute pancreatitis. PMID:26007723

  4. Simple and rapid determination of hydrogen peroxide using phosphine-based fluorescent reagents with sodium tungstate dihydrate.

    PubMed

    Onoda, Maki; Uchiyama, Takefumi; Mawatari, Ken-Ichi; Kaneko, Kiyoko; Nakagomi, Kazuya

    2006-06-01

    A simple batch method for the fluorometric determination of hydrogen peroxide using phosphine-based fluorescent reagents has been developed. A rapid, mild and selective derivatization reaction was achieved by adding sodium tungstate dihydrate to the reaction mixture of hydrogen peroxide and a phosphine-based fluorescent reagent. When 4-diphenylphosphino-7-methylthio-2,1,3-benzoxadiazole was used as a reagent, the derivatization reaction was completed after 2 min at room temperature. The calibration curve was linear between 12.5 and 500 ng hydrogen peroxide in a 10 microL sample solution. This method is accurate and has potential for on-line applications.

  5. A MoS2 Nanosheet-Based Fluorescence Biosensor for Simple and Quantitative Analysis of DNA Methylation

    PubMed Central

    Xiao, Le; Xu, Li; Gao, Chuan; Zhang, Yulin; Yao, Qunfeng; Zhang, Guo-Jun

    2016-01-01

    MoS2 nanomaterial has unique properties, including innate affinity with ss-DNA and quenching ability for fluorescence dyes. Here, we present the development of a simple fluorescence biosensor based on water-soluble MoS2 nanosheets and restriction endonuclease BstUI for methylation analysis of p16 promoter. The biosensing platform exhibited excellent sensitivity in detecting DNA with a linear range of 100 pM~20 nM and a detection limit of 140 pM. More importantly, our method could distinguish as low as 1% difference in methylation level. Compared with previous methylation analysis, our design is both time saving and simple to operate, avoiding the limitations of PCR-based assays without compromising performance. PMID:27669248

  6. A simple and sensitive fluorescent sensor for methyl parathion based on L-tyrosine methyl ester functionalized carbon dots.

    PubMed

    Hou, Juying; Dong, Jing; Zhu, Haishuang; Teng, Xue; Ai, Shiyun; Mang, Minglin

    2015-06-15

    In this paper, a simple and sensitive fluorescent sensor for methyl parathion is developed based on L-tyrosine methyl ester functionalized carbon dots (Tyr-CDs) and tyrosinase system. The carbon dots are obtained by simple hydrothermal reaction using citric acid as carbon resource and L-tyrosine methyl ester as modification reagent. The carbon dots are characterized by transmission electron microscope, high resolution transmission electron microscopy, X-ray diffraction spectrum, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The carbon dots show strong and stable photoluminescence with a quantum yield of 3.8%. Tyrosinase can catalyze the oxidation of tyrosine methyl ester on the surface of carbon dots to corresponding quinone products, which can quench the fluorescence of carbon dots. When organophosphorus pesticides (OPs) are introduced in system, they can decrease the enzyme activity, thus decrease the fluorescence quenching rate. Methyl parathion, as a model of OPs, was detected. Experimental results show that the enzyme inhibition rate is proportional to the logarithm of the methyl parathion concentration in the range 1.0×10(-10)-1.0×10(-4) M with the detection limit (S/N=3) of 4.8×10(-11) M. This determination method shows a low detection limit, wide linear range, good selectivity and high reproducibility. This sensing system has been successfully used for the analysis of cabbage, milk and fruit juice samples.

  7. Simple boric acid-based fluorescent focusing for sensing of glucose and glycoprotein via multipath moving supramolecular boundary electrophoresis chip.

    PubMed

    Dong, Jingyu; Li, Si; Wang, Houyu; Meng, Qinghua; Fan, Liuyin; Xie, Haiyang; Cao, Chengxi; Zhang, Weibing

    2013-06-18

    Boric acid-based fluorescent complex probe of BBV-HPTS (boronic acid-based benzyl viologen (BBV) and hydroxypyrene trisulfonic acid trisodium salt (HPTS)) was rarely used for sensitive sensing of saccharide (especially glycoprotein) via electrophoresis. We proposed a novel model of moving supramolecular boundary (MSB) formed with monosaccharide or glycoprotein in microcolumn and the complex probe of BBV-HPTS in the cathodic injection tube, developed a method of MSB fluorescent focusing for sensitive recognition of monosaccharide and glycoprotein, and designed a special multipath capillary electrophoresis (CE) chip for relative experiments. As a proof of concept, glucose and hemoglobin A1c (HbA1c) were respectively used as the mode saccharide and glycoprotein for the relevant demonstration. The experiments revealed that (i) the complex of BBV-HPTS could interact with free glucose or bound one in glycoprotein; (ii) the fluorescent signal was a function of glucose or glycoprotein content approximately; and (iii) interestingly the fluorescent band motion was dependent on glucose content. The developed method had the following merits: (i) low cost; (ii) low limit of detection (down to 1.39 pg/mL for glucose and 2.0 pg per capillary HbA1c); and (iii) high throughput (up to 12 runs or more per patch) and speed (less than 5 min). The developed method has potential use for sensitive monitoring of monosaccharide and glycoprotein in biomedical samples.

  8. Simple and sensitive synchronous- fluorescence method for the determination of trace bisphenol S based on its inhibitory effect on the fluorescence quenching reaction of rhodamine B.

    PubMed

    Cao, Gui-ping; Chen, Ting; Zhuang, Ya-feng

    2013-07-01

    An inhibitory kinetic fluorimetric method is reported for the determination of trace bisphenol S (BPS). The proposed method is based on the inhibitory effect of BPS on the fluorescence quenching of rhodamine B (RhB) caused by potassium bromate in a dilute phosphoric acid medium. Under the optimal conditions of the experiment, the detection limit for BPS was 0.021 mg/L, and the linear range of determination was from 0.035 mg/L to 0.750 mg/L. The relative standard deviations of 11 measurements for 0.20 mg/L and 0.40 mg/L BPS solutions were 2.74 % and 1.87 %, respectively. The method was successfully applied to the determination of bisphenol S derived from commercially available plastic film samples in hot water. A possible reaction mechanism of the inhibitory effect of BPS on the fluorescence quenching of RhB was proposed.

  9. A novel recombinant cell fluorescence biosensor based on toxicity of pathway for rapid and simple evaluation of DON and ZEN

    PubMed Central

    Ji, Jian; Gu, Wenshu; Sun, Chao; Sun, Jiadi; Jiang, Hui; Zhang, Yinzhi; Sun, Xiulan

    2016-01-01

    During an exposure, humans and animals are most often exposed to a mixture rather than individual mycotoxins. In this study, a Human Embryonic Kidney 293 cell (HEK-293) fluorescence sensor was developed to detect and evaluate mycotoxins, deoxynivalenol (DON) and zearalenone (ZEN) compounds, produced by Fusarium culmorum that are common food contaminants. TRE-copGFP (green fluorescent protein) and ERE-TagRFP (red fluorescent protein) plasmids were constructed and cotransfected into HEK-293 cells through a highly efficient, lipid-mediated, DNA-transfection procedure. Results show that fluorescence intensity was proportional to DON and ZEN concentrations, ranging from 2 to 40 ng/mL and 10 to 100 ng/mL respectively, with a detection limit of 0.75 ng/mL and 3.2 ng/mL respectively. The EC50 of DON and ZEN are 30.13 ng/mL and 76.63 ng/mL respectively. Additionally, ZEN may have a synergistic effect on enhancing AP-1 activity of the toxicity pathway of DON. These data indicate the high sensitivity and effectiveness of our biosensor system in the evaluation of the combined toxicity of ZEN, DON and their derivatives. In addition, this approach is suitable for an early warning method for the detection of ZEN and DON family mycotoxins contamination without higher-priced, conventional analytical chemistry methods. PMID:27498557

  10. Selective fluorescence sensing of Cu(II) and Zn(II) using a simple Schiff base ligand: Naked eye detection and elucidation of photoinduced electron transfer (PET) mechanism

    NASA Astrophysics Data System (ADS)

    Ganguly, Aniruddha; Ghosh, Soumen; Kar, Samiran; Guchhait, Nikhil

    2015-05-01

    A simple Schiff base compound 2-((cyclohexylmethylimino)-methyl)-naphthalen-1-ol (2CMIMN1O) has been synthesized and characterized by 1H NMR, 13C NMR and FT-IR spectroscopic techniques. A significantly low emission yield of the compound has been rationalized in anticipation with photo-induced electron transfer (PET) from the imine receptor moiety to the naphthalene fluorophore unit. Consequently, an evaluation of the transition metal ion-induced modification of the fluorophore-receptor communication reveals the promising prospect of the title compound to function as a chemosensor for Cu2+ and Zn2+ ions selectively, through remarkable fluorescence enhancement as well as visual changes. While perturbation of the PET process has been argued to be the plausible mechanism behind the fluorescence enhancement, the selectivity for these two metal ions has been interpreted on the grounds of an appreciably strong binding interaction. Particularly notable aspects regarding the chemosensory activity of the compound is its ability to detect the aforesaid transition metal ions down to the level of micromolar concentration (detection limit being 2.74 and 2.27 ppm respectively), along with a simple and efficient synthetic procedure.

  11. A rapid and simple 8-quinolinol-based fluorescent stain of phosphoproteins in polyacrylamide gel after electrophoresis.

    PubMed

    Wang, Xu; Hwang, Sun-Young; Cong, Wei-Tao; Jin, Li-Tai; Choi, Jung-Kap

    2015-10-01

    In order to obtain an easy and rapid protocol to visualize phosphoproteins in SDS-PAGE, a fluorescent detection method named 8-Quinolinol (8-Q) stain is described. 8-Q can form ternary complexes in the gel matrix contributed by the affinity of aluminum ion (Al(3+) ) to the phosphate groups on the proteins and the metal chelating property of 8-Quinolinol, exhibiting strong fluorescence in ultraviolet light. It can visualize as little as 4∼8 ng of α-casein and β-casein, 16∼32 ng of ovalbumin and κ-casein which is more sensitive than Stains-All but less sensitive than Pro-Q Diamond. The protocol of 8-Q requires only 70 min in 0.75 mm mini-size or 1.0 mm large-size gels with five changes of solutions without destaining step; Pro-Q takes at least 250 min with 11 changes of solutions. In addition, the new method was confirmed by the study of dephosphorylation and LC-MS/MS, respectively. The approach to visualize phosphoprotein utilizing 8-Q could be an alternative to simplify the analytical operations for phosphoproteomics research.

  12. A simple and sensitive surface molecularly imprinted polymers based fluorescence sensor for detection of λ-Cyhalothrin.

    PubMed

    Liu, Chunbo; Song, Zhilong; Pan, Jianming; Yan, Yongsheng; Cao, Zhijing; Wei, Xiao; Gao, Lin; Wang, Juan; Dai, Jiangdong; Meng, Minjia; Yu, Ping

    2014-07-01

    In this study, surface molecularly imprinted YVO4:Eu(3+) nanoparticles with molecular recognitive optosensing activity were successfully prepared by precipitation polymerization using λ-Cyhalothrin (LC) as template molecules, methacrylic acid and ethylene glycol dimethacrylate as the polymerization precursors which could complex with template molecules, and the material has been characterized by SEM, TEM, FT-IR, XRD, TGA and so on. Meanwhile, the as-prepared core-shell structured nanocomposite (YVO4:Eu(3+)@MIPs), which was composed of lanthanide doped YVO4:Eu(3+) as fluorescent signal and surface molecular imprinted polymers as molecular selective recognition sites, could selectively and sensitively optosense the template molecules. After the experimental conditions were optimized, two linear relationship were obtained covering the concentration range of 2.0-10.0 μM and 10.0-90.0 μM, and the limit of detection (LOD) for LC was found to be 1.76 μM. Furthermore, a possible mechanism was put forward to explain the fluorescence quenching of YVO4:Eu(3+)@MIPs. More importantly, the obtained sensor was proven to be suitable for the detection of residues of LC in real examples. And the excellent performance of this sensor will facilitate future development of rapid and high-efficiency detection of LC.

  13. Rapid and simple quantitation of methamphetamine by using a homogeneous time-resolved fluoroimmunoassay based on fluorescence resonance energy transfer from europium to Cy5.

    PubMed

    Kimura, Hiroko; Matsumoto, Kazuko; Mukaida, Masahiro

    2005-01-01

    A rapid and simple homogeneous time-resolved fluoroimmunoassay based on fluorescence resonance energy transfer from europium (Eu) to cyanine dye (Cy5) has been developed for the quantitation of methamphetamine. In this assay, Eu chelate was labeled to a conjugate of methamphetamine and bovine serum albumin (MA-BSA), as an energy donor, and Cy5 was labeled to anti-MA as an energy acceptor. The close proximity between the two labels in the immunocomplex permits energy transfer from the excited Eu(3+) donor. Therefore, by measuring the sensitized emission of Cy5 with the time-resolved assay, immunocomplex of MA-BSA and anti-MA can be measured in the homogeneous solution without separation steps within 30 min. By a competitive immunoassay, MA could be assayed in the range 0.1-1,000 ng/mL. The intra-assay variations were 5.4-14.8% at 5 different concentrations. When urine or serum samples were examined, the quenching of Eu fluorescence was observed, but the acceptor-to-donor ratio constantly depended upon the dilution of samples. Twenty urine samples were assayed, and the data showed a good correlation to those obtained by gas chromatography (r = 0.94). The homogeneous assay using Eu-Cy5 energy transfer is time-saving without any washing procedures and is suitable for screening drugs that are commonly abused.

  14. Simple adaptive cubic spline interpolation of fluorescence decay functions

    NASA Astrophysics Data System (ADS)

    Kuśba, J.; Czuper, A.

    2007-05-01

    Simple method allowing for adaptive cubic spline interpolation of fluorescence decay functions is proposed. In the first step of the method, the interpolated function is integrated using the known adaptive algorithm based on Newton-Cotes quadratures. It is shown that, in this step, application of the Simpson's rule provides the smallest number of calls of the interpolated function. In the second step of the method, a typical cubic spline approximation is used to find values of the interpolated function between the points evaluated in the first step.

  15. A simple fluorescent probe for the determination of dissolved oxygen based on the catalytic activation of oxygen by iron(II) chelates.

    PubMed

    Luo, Wei; Abbas, M E; Zhu, Lihua; Zhou, Wenyi; Li, Kejing; Tang, Heqing; Liu, Shushen; Li, Weiying

    2009-04-27

    This work aims at establishing a simple fluorescent probe for the determination of dissolved oxygen. It is found that iron(II) ions activate oxygen to produce reactive species being capable of oxidizing non-fluorescent coumarin to fluorescent 7-hydroxycoumarin. However, this process is not effective because the yield of the reactive species is very low in the presence of simple iron(II) salts alone. The addition of organic ligands such as oxalate results in the formation of complexes between iron(II) ions, which leads to considerable increase in the yield of reactive species (such as hydroxyl radicals) and then increase in the fluorescence intensity of 7-hydroxycoumarin to a significant level. It has been observed that in the mixture solution of iron(II) ions, ligand, coumarin, and dissolved oxygen, there is an excellent linear response between the fluorescence and dissolved oxygen. Therefore, a new spectrofluorimetric method has been proposed for the determination of dissolved oxygen by using catalytic activation of O(2) by iron(II) chelates. Under optimized conditions, a linear correlation (r=0.995) has been observed between the fluorescence intensity of 7-hydroxycoumarin at 456 nm and the concentration of dissolved oxygen over the range of 0.96-9.22 mg L(-1). The limit of detection for dissolved oxygen at a signal-to-noise ratio of 3 has been estimated to be 0.35 mg L(-1). The proposed method has been applied to determine the concentration of dissolved oxygen in practical water samples with results as satisfactory as that obtained by the standard iodometric method.

  16. Genetic diversity analysis of sugarcane germplasm based on fluorescence-labeled simple sequence repeat markers and a capillary electrophoresis-based genotyping platform

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Genetic diversity analysis, which refers to the elaboration of total extent of genetic characteristics in the genetic makeup of a certain species, constitutes a classical strategy for the study of diversity, population genetic structure, and breeding practices. In this study, fluorescence-labeled se...

  17. A highly selective and simple fluorescent sensor for mercury (II) ion detection based on cysteamine-capped CdTe quantum dots synthesized by the reflux method.

    PubMed

    Ding, Xiaojie; Qu, Lingbo; Yang, Ran; Zhou, Yuchen; Li, Jianjun

    2015-06-01

    Cysteamine (CA)-capped CdTe quantum dots (QDs) (CA-CdTe QDs) were prepared by the reflux method and utilized as an efficient nano-sized fluorescent sensor to detect mercury (II) ions (Hg(2+) ). Under optimum conditions, the fluorescence quenching effect of CA-CdTe QDs was linear at Hg(2+) concentrations in the range of 6.0-450 nmol/L. The detection limit was calculated to be 4.0 nmol/L according to the 3σ IUPAC criteria. The influence of 10-fold Pb(2+) , Cu(2+) and Ag(+) on the determination of Hg(2+) was < 7% (superior to other reports based on crude QDs). Furthermore, the detection sensitivity and selectivity were much improved relative to a sensor based on the CA-CdTe QDs probe, which was prepared using a one-pot synthetic method. This CA-CdTe QDs sensor system represents a new feasibility to improve the detection performance of a QDs sensor by changing the synthesis method.

  18. A simple but efficient strategy to enhance hydrostability of intensely fluorescent Mg-based coordination polymer (CP) via forming a composite of CP with hydrophobic PVDF.

    PubMed

    Zhai, Lu; Zhang, Wen-Wei; Zuo, Jing-Lin; Ren, Xiao-Ming

    2016-02-28

    A coordination polymer (CP) of Mg(2+) with 1,3,5-benzenetricarboxylate (BTC(3-)) was synthesized using a solvothermal method. The Mg-CP, with a formula of Mg3(BTC)(HCOO)3(DMF)3, crystallizes in the trigonal space group P3[combining macron], with cell parameters of a = b = 13.972(5) Å, c = 8.090(5) Å and V = 1367.6(11) Å(3), and shows a lamella structure built from planar rosette-type hexanuclear architectures. The Mg-CP emits intense blue fluorescence arising from π* → π transition of intra-ligand of BTC(3-) with 21.69% quantum yield, yet it exhibits poor stability to water. The composites of Mg-CP with hydrophobic polyvinylidene fluoride (PVDF) were sequentially prepared by mechanically mixed, tableted and annealed processes, which showed good compatibility between Mg-CP and PVDF, high hydrostability, and intense blue emission. This study suggests a simple but efficient method to solve the drawbacks of some functional CPs unstable to water and to promote them as practical applications in the field of functional materials.

  19. Simple and cost-effective fluorescent labeling of 5-hydroxymethylcytosine

    NASA Astrophysics Data System (ADS)

    Shahal, Tamar; Green, Ori; Hananel, Uri; Michaeli, Yael; Shabat, Doron; Ebenstein, Yuval

    2016-12-01

    The nucleobase 5-hydroxymethylcytosine (5-hmC), a modified form of cytosine, is an important epigenetic mark related to regulation of gene expression. 5-hmC levels are highly dynamic during early development and are modulated during the progression of neurodegenerative disease and cancer. We describe a spectroscopic method for the global quantification of 5-hmC in genomic DNA. This method relies on the enzymatic glucosylation of 5-hmC, followed by a glucose oxidation step that results in the formation of aldehyde moieties that are covalently linked to a fluorescent reporter by oxime ligation. The fluorescence intensity of the labeled sample is directly proportional to its 5-hmC content. We show that this simple and cost-effective technique is suitable for quantification of 5-hmC content in different mouse tissues.

  20. (2-Naphthoxy)acetyl chloride, a simple fluorescent reagent.

    PubMed

    Duh, Tsai-Hui; Wu, Hsin-Lung; Kou, Hwang-Shang; Lu, Chi-Yu

    2003-02-14

    In continuing the search for fluorescent reagents for analytical derivatization in chromatography, we found a simple chemical, (2-naphthoxy)acetyl chloride, with potential fluorophore/chromophore characteristics for the highly sensitive detection of analytes with an amino function. The reagent has an auxochrome (a substituted alkoxy moiety) attached to the fluorophoric/chromophoric naphthalene system, resulting in favorable spectrophotometric properties. The reagent can be easily prepared from (2-naphthoxy)acetic acid and has been used in organic synthesis; it is initially introduced as a fluorescent reagent to derivatise amantadine and memantine (amino pharmaceuticals) as model analytes. The resulting naphthoxy derivatives of the drugs can be analyzed at sub-microM levels by HPLC with fluorimetric detection (excitation wavelength 227 nm, emission wavelength 348 nm). Application of the reagent to the fluorimetric derivatization of important biological amines for sensitive detection can be expected.

  1. A simple protocol for attenuating the auto-fluorescence of cyanobacteria for optimized fluorescence in situ hybridization (FISH) imaging.

    PubMed

    Zeller, Perrine; Ploux, Olivier; Méjean, Annick

    2016-03-01

    Cyanobacteria contain pigments, which generate auto-fluorescence that interferes with fluorescence in situ hybridization (FISH) imaging of cyanobacteria. We describe simple chemical treatments using CuSO4 or H2O2 that significantly reduce the auto-fluorescence of Microcystis strains. These protocols were successfully applied in FISH experiments using 16S rRNA specific probes and filamentous cyanobacteria.

  2. Fluorescence-Based Sensors

    NASA Astrophysics Data System (ADS)

    Orellana, Guillermo

    The natural luminescent phenomena (from the Latin words "lumen" and "essentia", i.e., "made of light") such as northern lights (aurora borealis), marine brightness, glow-worms, shining putrid fish scales, "bluish"- appearing water when contained in certain wooden cups (quinine fluorescence), some stones heated at high temperatures with reducing agents (BaS phosphorescence), or light emitted while crushing sugar (triboluminescence) already fascinated our ancestors. Nowadays we understand that ultraviolet and visible emission of light originates from a competitive deactivation pathway of the lowest electronic excited state of atoms and molecules that produces the so called luminescence (the sub-terms fluorescence and phosphorescence just designate whether the return of the excited to the ground state is an "allowed" or "forbidden" process, namely it is fast or slow, the loosely-defined border between them being a 1-μs-1 rate constant). Actually, luminescence is the only method to generate light in the known Universe regardless it is powered by the nuclear reactions in the stars, the ohmical heating in bulbs, an electric discharge, the absorption of light or a (bio)chemical reaction (chemiluminescence).

  3. A simple procedure to improve the surface passivation for single molecule fluorescence studies

    NASA Astrophysics Data System (ADS)

    Pan, Hai; Xia, Yifan; Qin, Meng; Cao, Yi; Wang, Wei

    2015-07-01

    The single-molecule fluorescence technique is becoming a general and mature tool to probe interactions and dynamics of biomolecules with ultra high precision and accuracy. However, nonspecific adsorption of biomolecules to the flow cells remains a major experimental riddle for the study of many complex biological systems, especially those exhibiting low binding affinity and presenting with weakly populated intermediates. Many novel surface passivation methods have been introduced to reduce nonspecific interactions. Here, we present an effective and inexpensive method to significantly reduce nonspecific binding of biomolecules in conventional poly (ethylene glycol) (PEG)-based surface passivation protocols, without additional exogenous effects. In particular, we propose a simple 10 min Tween-20 treatment for the PEG passivated surface, which could further increase the hydrophilicity of the surface and thus promote passivation efficacy by about 5 to 10 times. We anticipate that this new procedure will find broad practical applications and extend the current reaches of single-molecule fluorescence studies.

  4. A simple chlorophyll fluorescence parameter that correlates with the rate coefficient of photoinactivation of photosystem II.

    PubMed

    Hendrickson, Luke; Förster, Britta; Pogson, Barry J; Chow, Wah Soon

    2005-06-01

    A method of partitioning the energy in a mixed population of active and photoinactivated Photosystem II (PS II) complexes based on chlorophyll fluorescence measurements is presented. There are four energy fluxes, each with its quantum efficiency: a flux associated with photochemical electron flow in active PS II reaction centres (JPS II), thermal dissipation in photoinactivated, non-functional PS IIs (JNF), light-regulated thermal dissipation in active PS IIs (JNPQ) and a combined flux of fluorescence and constitutive, light-independent thermal dissipation (Jf,D). The four quantum efficiencies add up to 1.0, without the need to introduce an 'excess' term E, which in other studies has been claimed to be linearly correlated with the rate coefficient of photoinactivation of PS II (kpi). We examined the correlation of kpi with various fluxes, and found that the combined flux (JNPQ + Jf,D= Jpi) is as well correlated with kpi as is E. This combined flux arises from Fs/Fm ', the ratio of steady-state to maximum fluorescence during illumination, which represents the quantum efficiency of combined non-photochemical dissipation pathways in active PS IIs. Since Fs/Fm ' or its equivalent, Jpi, is a likely source of events leading to photoinactivation of PS II, we conclude that Fs/Fm ' is a simple predictor of kpi.

  5. Aptamer-Based Fluorescent Biosensors

    PubMed Central

    Wang, Rongsheng E.; Zhang, Yin; Cai, Jianfeng; Cai, Weibo; Gao, Ting

    2011-01-01

    Selected from random pools of DNA or RNA molecules through systematic evolution of ligands by exponential enrichment (SELEX), aptamers can bind to target molecules with high affinity and specificity, which makes them ideal recognition elements in the development of biosensors. To date, aptamer-based biosensors have used a wide variety of detection techniques, which are briefly summarized in this article. The focus of this review is on the development of aptamer-based fluorescent biosensors, with emphasis on their design as well as properties such as sensitivity and specificity. These biosensors can be broadly divided into two categories: those using fluorescently-labeled aptamers and others that employ label-free aptamers. Within each category, they can be further divided into “signal-on” and “signal-off” sensors. A number of these aptamer-based fluorescent biosensors have shown promising results in biological samples such as urine and serum, suggesting their potential applications in biomedical research and disease diagnostics. PMID:21838688

  6. A simple dental caries detection system using full spectrum of laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Rocha-Cabral, Renata Maciel; Mendes, Fausto Medeiros; Maldonado, Edison Puig; Zezell, Denise Maria

    2015-06-01

    Objectives: to develop an apparatus for the detection of early caries lesions in enamel using the full extent of the tooth fluorescence spectrum, through the integration of a laser diode, fiber optics, filters and one portable spectrometer connected to a computer, all commercially available; to evaluate the developed device in clinical and laboratory tests, and compare its performance with commercial equipment. Methods: clinical examinations were performed in patients with indication for exodontics of premolars. After examinations, the patients underwent surgery and the teeth were stored individually. The optical measurements were repeated approximately two months after extraction, on the same sites previously examined, then histological analysis was carried out. Results: the spectral detector has presented high specificity and moderate sensitivity when applied to differentiate between healthy and damaged tissues, with no significant differences from the performance of the commercial equipment. The developed device is able to detect initial damages in enamel, with depth of approximately 300 μm. Conclusions: we successfully demonstrated the development of a simple and portable system based in laser-induced fluorescence for caries detection, assembled from common commercial parts. As the spectral detector acquires a complete recording of the spectrum from each tissue, it is possible to use it for monitoring developments of caries lesions.

  7. A Simple Fluorescence Assay for Quantification of Canine Neutrophil Extracellular Trap Release.

    PubMed

    Jeffery, Unity; Gray, Robert D; LeVine, Dana N

    2016-11-21

    Neutrophil extracellular traps are networks of DNA, histones and neutrophil proteins released in response to infectious and inflammatory stimuli. Although a component of the innate immune response, NETs are implicated in a range of disease processes including autoimmunity and thrombosis. This protocol describes a simple method for canine neutrophil isolation and quantification of NETs using a microplate fluorescence assay. Blood is collected using conventional venipuncture techniques. Neutrophils are isolated using dextran sedimentation and a density gradient using conditions optimized for dog blood. After allowing time for attachment to the wells of a 96 well plate, neutrophils are treated with NET-inducing agonists such as phorbol-12-myristate-13-acetate or platelet activating factor. DNA release is measured by the fluorescence of a cell-impermeable nucleic acid dye. This assay is a simple, inexpensive method for quantifying NET release, but NET formation rather than other causes of cell death must be confirmed with alternative methods.

  8. A simple and general route for monofunctionalization of fluorescent and magnetic nanoparticles using peptides

    NASA Astrophysics Data System (ADS)

    Clarke, Samuel; Tamang, Sudarsan; Reiss, Peter; Dahan, Maxime

    2011-04-01

    Nanoparticles are now utilized in many diverse biological and medical applications. Despite this, it remains challenging to tailor their surface for specific molecular targeting while maintaining high biocompatibility. To address this problem, we evaluate a phytochelatin-related peptide surface coating to produce functional and biocompatible nanoparticles (NPs) based on fluorescent InP/ZnS and CdSe/ZnS or superparamagnetic FePt and Fe3O4. Using a combination of transmission electron microscopy, size-exclusion chromatography and gel electrophoresis (GE), we demonstrate the excellent colloidal properties of the peptide-coated NPs (pNPs) and the compact nature of the coating (~4 nm thickness). We develop a simple protocol for the monofunctionalization of the pNPs with targeting biomolecules, by combining covalent conjugation with GE purification. We then employ functionalized InP/ZnS pNPs in a live-cell, single-molecule imaging application to specifically target and detect individual proteins in the cell membrane. These findings showcase the versatility of the peptides for preparing compact NPs of various compositions and sizes, which are easily functionalized, and suitable for a broad range of biomedical applications.

  9. A simple and general route for monofunctionalization of fluorescent and magnetic nanoparticles using peptides.

    PubMed

    Clarke, Samuel; Tamang, Sudarsan; Reiss, Peter; Dahan, Maxime

    2011-04-29

    Nanoparticles are now utilized in many diverse biological and medical applications. Despite this, it remains challenging to tailor their surface for specific molecular targeting while maintaining high biocompatibility. To address this problem, we evaluate a phytochelatin-related peptide surface coating to produce functional and biocompatible nanoparticles (NPs) based on fluorescent InP/ZnS and CdSe/ZnS or superparamagnetic FePt and Fe(3)O(4). Using a combination of transmission electron microscopy, size-exclusion chromatography and gel electrophoresis (GE), we demonstrate the excellent colloidal properties of the peptide-coated NPs (pNPs) and the compact nature of the coating (∼4 nm thickness). We develop a simple protocol for the monofunctionalization of the pNPs with targeting biomolecules, by combining covalent conjugation with GE purification. We then employ functionalized InP/ZnS pNPs in a live-cell, single-molecule imaging application to specifically target and detect individual proteins in the cell membrane. These findings showcase the versatility of the peptides for preparing compact NPs of various compositions and sizes, which are easily functionalized, and suitable for a broad range of biomedical applications.

  10. A fluorescence high-temperature sensor based on fluorescence lifetime

    NASA Astrophysics Data System (ADS)

    Wu, Jinling; Wang, Yutian; Wang, Xinian

    2006-11-01

    A kind of fluorescence optic-fiber temperature sensor is devised based on the alexandrite crystal. In this system, a new optic- fiber probe fabrication techniques is proposed. This system is particularly adapted to the temperature measurement in the range of room temperature to 650°C. During the cause of experimentation, using the PLD-PMTR (termed the Pulse Modulated Phase-locked detection with Two References) signal processing scheme. This temperature measurement method is proved to be effective and useful for its highly resolution and precision. It ensured the detected fluorescence signal to noise ratio was high enough to be measurable when the temperature is raised to 650°C.

  11. Carbon Nanoparticle-based Fluorescent Bioimaging Probes

    PubMed Central

    Bhunia, Susanta Kumar; Saha, Arindam; Maity, Amit Ranjan; Ray, Sekhar C.; Jana, Nikhil R.

    2013-01-01

    Fluorescent nanoparticle-based imaging probes have advanced current labelling technology and are expected to generate new medical diagnostic tools based on their superior brightness and photostability compared with conventional molecular probes. Although significant progress has been made in fluorescent semiconductor nanocrystal-based biological labelling and imaging, the presence of heavy metals and the toxicity issues associated with heavy metals have severely limited the application potential of these nanocrystals. Here, we report a fluorescent carbon nanoparticle-based, alternative, nontoxic imaging probe that is suitable for biological staining and diagnostics. We have developed a chemical method to synthesise highly fluorescent carbon nanoparticles 1–10 nm in size; these particles exhibit size-dependent, tunable visible emission. These carbon nanoparticles have been transformed into various functionalised nanoprobes with hydrodynamic diameters of 5–15 nm and have been used as cell imaging probes. PMID:23502324

  12. A simple, fast and low-cost turn-on fluorescence method for dopamine detection using in situ reaction.

    PubMed

    Zhang, Xiulan; Zhu, Yonggang; Li, Xie; Guo, Xuhong; Zhang, Bo; Jia, Xin; Dai, Bin

    2016-11-09

    A simple, fast and low-cost method for dopamine (DA) detection based on turn-on fluorescence using resorcinol is developed. The rapid reaction between resorcinol and DA allows the detection to be performed within 5 min, and the reaction product (azamonardine) with high quantum yield generates strong fluorescence signal for sensitive optical detection. The detection exhibits a high sensitivity to DA with a wide linear range of 10 nM-20 μM and the limit of detection is estimated to be 1.8 nM (S/N = 3). This approach has been successfully applied to determine DA concentrations in human urine samples with satisfactory quantitative recovery of 97.84%-103.50%, which shows great potential in clinical diagnosis.

  13. Simple device for the direct visualization of oral-cavity tissue fluorescence

    NASA Astrophysics Data System (ADS)

    Lane, Pierre M.; Gilhuly, Terence; Whitehead, Peter D.; Zeng, Haishan; Poh, Catherine; Ng, Samson; Williams, Michelle; Zhang, Lewei; Rosin, Miriam; MacAulay, Calum E.

    2006-03-01

    Early identification of high-risk disease could greatly reduce both mortality and morbidity due to oral cancer. We describe a simple handheld device that facilitates the direct visualization of oral-cavity fluorescence for the detection of high-risk precancerous and early cancerous lesions. Blue excitation light (400 to 460 nm) is employed to excite green-red fluorescence from fluorophores in the oral tissues. Tissue fluorescence is viewed directly along an optical axis collinear with the axis of excitation to reduce inter- and intraoperator variability. This robust, field-of-view device enables the direct visualization of fluorescence in the context of surrounding normal tissue. Results from a pilot study of 44 patients are presented. Using histology as the gold standard, the device achieves a sensitivity of 98% and specificity of 100% when discriminating normal mucosa from severe dysplasia/carcinoma in situ (CIS) or invasive carcinoma. We envisage this device as a suitable adjunct for oral cancer screening, biopsy guidance, and margin delineation.

  14. a Simple, Cost Effective Raman-Fluorescence Spectrometer for Use in Laboratory and Field Experiments

    NASA Astrophysics Data System (ADS)

    Marshall, Frank E.; Pride, Michael A.; Rojo, Michellle; Brinker, Katelyn R.; Walker, Zachary; Storrie-Lombardi, Michael; Mormile, Melanie R.; Grubbs, G. S., II

    2015-06-01

    Research, design, construction, and operation of a portable mixed Raman and Fluorescence type spectrometer implemented by the Missouri University of Science and Technology's Mars Rover Design Team will be presented. This spectrometer has been built for the team's annual competition. The spectrometer, completely built by undergraduates, is designed to use a 50 mW, 532 nm constant waveform laser to probe a sample of soil to find bacteria or bio-markers. However, initial tests of the spectrometer were carried out in a laboratory environment making the spectrometer also suitable for simple undergraduate physical chemistry or chemical physics laboratory experiments. The final cost of the device is roughly 2100, weighs 1.4 kg, and is 22.9 cm x 22.6 cm in size. Integrating the spectrometer with a computer database, results from the competition, complications of fitting mixed Raman-Fluorescence spectra, and future ideas/improvements will also be discussed.

  15. Nucleic acid based fluorescent nanothermometers.

    PubMed

    Ebrahimi, Sara; Akhlaghi, Yousef; Kompany-Zareh, Mohsen; Rinnan, Asmund

    2014-10-28

    Accurate thermometry at micro- and nanoscales is essential in many nanobiotechnological applications. The nanothermometers introduced in this paper are composed of labeled molecular beacons (MBs) comprising gold nanoparticles (AuNPs) on which, depending on application, many MBs of one or more types are immobilized. In this design, three differently labeled MBs with different thermostabilities function as the sensing elements, and AuNPs act as carriers of the MBs and also quenchers of their fluorophores. This flexible design results in a number of nanothermometers with various temperature-sensing ranges. At the lowest temperature, the MBs are in the closed form, where they are quenched. By increasing the temperature, the MBs start to open with respect to their melting points (Tm), and as a result, the fluorescence emission will increase. The temperature resolution of the nanoprobes over a range of 15-60 °C is less than 0.50 °C, which indicates their high sensitivity. Such a good temperature resolution is a result of the specific design of the unusual less stable MBs and also presence of many MBs on AuNPs. The reproducibility and precision of the probes are also satisfactory. The multiplex MB nanoprobe is suitable for thermal imaging by fluorescence microscopy.

  16. Fluorescence-lifetime-based sensors for anions

    NASA Astrophysics Data System (ADS)

    Teichmann, Maria; Draxler, Sonja; Kieslinger, Dietmar; Lippitsch, Max E.

    1997-05-01

    Sensing of anions has been investigated using the fluorescence decaytime as the information carrier. The sensing mechanism is based on the coextraction of an anion and a proton, and the presence of a fluorophore with a rather long fluorescence decaytime inside the membrane to act as a pH indicator. The relevant theory is discussed shortly. As an example a sensor for nitrate is shown, and the influence of ionic additives on the working function has been investigated.

  17. A simple preparation of Ag@graphene nanocomposites for surface-enhanced Raman spectroscopy of fluorescent anticancer drug

    NASA Astrophysics Data System (ADS)

    Meng, Ying; Yan, Xueying; Wang, Yi

    2016-05-01

    A simple method was developed to synthesize Ag@graphene nanocomposites with rough Ag nanoparticles (AgNPs) conjugated with graphene nanosheets, and the nanocomposites could be used as substrates for effective surface-enhanced Raman spectroscopy (SERS) of fluorescent anticancer drug (Dox) since they could not only enhance the Raman signals but also suppress the fluorescent signals.

  18. Multiphoton excitation of fluorescent DNA base analogs.

    PubMed

    Katilius, Evaldas; Woodbury, Neal W

    2006-01-01

    Multiphoton excitation was used to investigate properties of the fluorescent DNA base analogs, 2-aminopurine (2AP) and 6-methylisoxanthopterin (6MI). 2-aminopurine, a fluorescent analog of adenine, was excited by three-photon absorption. Fluorescence correlation measurements were attempted to evaluate the feasibility of using three-photon excitation of 2AP for DNA-protein interaction studies. However, high excitation power and long integration times needed to acquire high signal-to-noise fluorescence correlation curves render three-photon excitation FCS of 2AP not very useful for studying DNA base dynamics. The fluorescence properties of 6-methylisoxanthopterin, a guanine analog, were investigated using two-photon excitation. The two-photon absorption cross-section of 6MI was estimated to be about 2.5 x 10(-50) cm(4)s (2.5 GM units) at 700 nm. The two-photon excitation spectrum was measured in the spectral region from 700 to 780 nm; in this region the shape of the two-photon excitation spectrum is very similar to the shape of single-photon excitation spectrum in the near-UV spectral region. Two-photon excitation of 6MI is suitable for fluorescence correlation measurements. Such measurements can be used to study DNA base dynamics and DNA-protein interactions over a broad range of time scales.

  19. A simple and effective strategy to increase the sensitivity of fluorescence probes in living cells.

    PubMed

    Izumi, Saki; Urano, Yasuteru; Hanaoka, Kenjiro; Terai, Takuya; Nagano, Tetsuo

    2009-07-29

    Noninvasive visualization and investigation of interactions among proteins, biomolecules, and enzymes in living cells is an important goal for biologists, and fluorescence probes are powerful tools for this purpose. Because many target molecules are present in only trace amounts, high sensitivity is very important, and it is common to improve the sensitivity of fluorescence probes by focusing on high reaction velocity, K(d). (Gee, K. R.; Archer, E. A.; Lapham, L. A.; Leonard, M. E.; Zhou, Z.; Bingham, J.; Diwu, Z. Bioorg. Med. Chem. Lett. 2000, 10, 1515-1518.) So far, we have designed and synthesized various highly sensitive fluorescence probes based on the above concepts. (Gabe, Y.; Urano, Y.; Kikuchi, K.; Kojima, H.; Nagano, T. J. Am. Chem. Soc. 2004, 126, 3357-3367. Komatsu, K.; Urano, Y.; Kojima, H.; Nagano, T. J. Am. Chem. Soc. 2007, 129, 13447-13454.) Nevertheless, they were sometimes insufficiently sensitive to detect biomolecules in living cells, despite high chemical sensitivity in cuvette. In this report, we suggest a new approach to increase the sensitivity of fluorescence probes, focusing on their intracellular retention. Since calcein is well-retained, we investigated its structural, chemical, and optical characteristics and found that the iminodiacetic acid group (IAG) is a key structure for the intracellular retention. We next designed and synthesized novel fluorescence probes containing IAGs. They showed superior intracellular retention, making it possible to visualize low concentrations of target molecules that would be difficult to observe with conventional probes and permitting long-term observation in living cells. Improvement of intracellular retention of fluorescence probes holds great promise as a strategy for developing a wide range of highly sensitive probes for studies on various biological phenomena.

  20. Ultrasensitive detection of potassium ions based on target induced DNA conformational switch enhanced fluorescence polarization.

    PubMed

    Hu, Kun; Huang, Yong; Zhao, Shulin; Tian, Jianniao; Wu, Qiang; Zhang, Guohai; Jiang, Jing

    2012-06-21

    We have developed a simple, highly sensitive and selective fluorescence polarization assay for the detection of potassium ions based on target induced DNA conformational switch from hairpin to G-quadruplex enhanced fluorescence polarization. The assay was applied in the detection of low nM concentrations of potassium ions and was highly selective over other cations.

  1. Quick and simple estimation of bacteria using a fluorescent paracetamol dimer-Au nanoparticle composite

    NASA Astrophysics Data System (ADS)

    Sahoo, Amaresh Kumar; Sharma, Shilpa; Chattopadhyay, Arun; Ghosh, Siddhartha Sankar

    2012-02-01

    Rapid, simple and sensitive detection of bacterial contamination is critical for safeguarding public health and the environment. Herein, we report an easy method of detection as well as enumeration of the bacterial cell number on the basis of fluorescence quenching of a non-antibacterial fluorescent nanocomposite, consisting of paracetamol dimer (PD) and Au nanoparticles (NPs), in the presence of bacteria. The composite was synthesized by reaction of paracetamol (p-hydroxyacetanilide) with HAuCl4. The Au NPs of the composite were characterized using UV-Vis spectroscopy, transmission electron microscopy (TEM), X-ray diffraction and selected area electron diffraction analysis. The paracetamol dimer in the composite showed emission peak at 435 nm when excited at 320 nm. The method successfully detected six bacterial strains with a sensitivity of 100 CFU mL-1. The Gram-positive and Gram-negative bacteria quenched the fluorescence of the composite differently, making it possible to distinguish between the two. The TEM analysis showed interaction of the composite with bacteria without any apparent damage to the bacteria. The chi-square test established the accuracy of the method. Quick, non-specific and highly sensitive detection of bacteria over a broad range of logarithmic dilutions within a short span of time demonstrates the potential of this method as an alternative to conventional methods.Rapid, simple and sensitive detection of bacterial contamination is critical for safeguarding public health and the environment. Herein, we report an easy method of detection as well as enumeration of the bacterial cell number on the basis of fluorescence quenching of a non-antibacterial fluorescent nanocomposite, consisting of paracetamol dimer (PD) and Au nanoparticles (NPs), in the presence of bacteria. The composite was synthesized by reaction of paracetamol (p-hydroxyacetanilide) with HAuCl4. The Au NPs of the composite were characterized using UV-Vis spectroscopy

  2. Nanoparticle fluorescence based technology for biological applications.

    PubMed

    Chen, Wei

    2008-03-01

    Fluorescence is widely used in biological detection and imaging. The emerging luminescent nanoparticles or quantum dots provide a new type of biological agents that can improve these applications. The advantages of luminescent nanoparticles for biological applications include their high quantum yield, color availability, good photo-stability, large surface-to-volume ratio, surface functionality, and small size. In this review article, we first introduce quantum size confinement, photoluminescence and upconversion luminescence of nanoparticles, then describe the preparation and conjugation of water soluble nanoparticles and introduce the applications of luminescence nanoparticles for in vitro and in vivo imaging, fluorescence resonance energy based detection, and the applications of luminescence nanoparticles for photodynamic activation.

  3. Simple, Script-Based Science Processing Archive

    NASA Technical Reports Server (NTRS)

    Lynnes, Christopher; Hegde, Mahabaleshwara; Barth, C. Wrandle

    2007-01-01

    The Simple, Scalable, Script-based Science Processing (S4P) Archive (S4PA) is a disk-based archival system for remote sensing data. It is based on the data-driven framework of S4P and is used for data transfer, data preprocessing, metadata generation, data archive, and data distribution. New data are automatically detected by the system. S4P provides services such as data access control, data subscription, metadata publication, data replication, and data recovery. It comprises scripts that control the data flow. The system detects the availability of data on an FTP (file transfer protocol) server, initiates data transfer, preprocesses data if necessary, and archives it on readily available disk drives with FTP and HTTP (Hypertext Transfer Protocol) access, allowing instantaneous data access. There are options for plug-ins for data preprocessing before storage. Publication of metadata to external applications such as the Earth Observing System Clearinghouse (ECHO) is also supported. S4PA includes a graphical user interface for monitoring the system operation and a tool for deploying the system. To ensure reliability, S4P continuously checks stored data for integrity, Further reliability is provided by tape backups of disks made once a disk partition is full and closed. The system is designed for low maintenance, requiring minimal operator oversight.

  4. A synthesis of fluorescent starch based on carbon nanoparticles for fingerprints detection

    NASA Astrophysics Data System (ADS)

    Li, Hongren; Guo, Xingjia; Liu, Jun; Li, Feng

    2016-10-01

    A pyrolysis method for synthesizing carbon nanoparticles (CNPs) were developed by using malic acid and ammonium oxalate as raw materials. The incorporation of a minor amount of carbon nanoparticles into starch powder imparts remarkable color-tunability. Based on this phenomenon, an environment friendly fluorescent starch powder for detecting latent fingerprints in non-porous surfaces was prepared. The fingerprints on different non-porous surfaces developed with this powder showed very good fluorescent images under ultraviolet excitation. The method using fluorescent starch powder as fluorescent marks is simple, rapid and green. Experimental results illustrated the effectiveness of proposed methods, enabling its practical applications in forensic sciences.

  5. Simple and sensitive determination of five quinolones in food by liquid chromatography with fluorescence detection.

    PubMed

    Ramos, Macarena; Aranda, Angela; Garcia, Elena; Reuvers, Thea; Hooghuis, Henny

    2003-06-15

    A simple and sensitive high-performance liquid chromatographic (HPLC) method has been developed for the determination of five different quinolones: enrofloxacin, ciprofloxacin, sarafloxacin, oxolinic acid and flumequine in pork and salmon muscle. The method includes one extraction and clean-up step for the five quinolones together which are detected in two separated HPLC runs by means of their fluorescence. The proposed analytical method involves homogenizing of the tissue sample with 0.05 M phosphate buffer, pH 7.4 and clean-up by Discovery DS-18 cartridges. For chromatographic separation a Symmetry C(18) column is used in two different runs: (1) ciprofloxacin, enrofloxacin and sarafloxacin with acetonitrile-0.02 M phosphate buffer pH 3.0 (18:82) as mobile phase and the detector at excitation wavelength: 280 nm and emission wavelength 450 nm; and (2) oxolinic acid and flumequine with acetonitrile-0.02 M phosphate buffer pH 3.0 (34:66) as mobile phase and excitation wavelength: 312 nm and emission wavelength: 366 nm. Detection limit was as low as 5 ng g(-1), except for sarafloxacin which had a limit of 10 ng g(-1). Standard curves using blank muscle tissues spiked at different levels showed a good linear correlation coefficient, r(2) higher than 0.999 for all quinolones.

  6. Simple Method for Fluorescence DNA In Situ Hybridization to Squashed Chromosomes

    PubMed Central

    Larracuente, Amanda M.; Ferree, Patrick M.

    2015-01-01

    DNA in situ hybridization (DNA ISH) is a commonly used method for mapping sequences to specific chromosome regions. This approach is particularly effective at mapping highly repetitive sequences to heterochromatic regions, where computational approaches face prohibitive challenges. Here we describe a streamlined protocol for DNA ISH that circumvents formamide washes that are standard steps in other DNA ISH protocols. Our protocol is optimized for hybridization with short single strand DNA probes that carry fluorescent dyes, which effectively mark repetitive DNA sequences within heterochromatic chromosomal regions across a number of different insect tissue types. However, applications may be extended to use with larger probes and visualization of single copy (non-repetitive) DNA sequences. We demonstrate this method by mapping several different repetitive sequences to squashed chromosomes from Drosophila melanogaster neural cells and Nasonia vitripennis spermatocytes. We show hybridization patterns for both small, commercially synthesized probes and for a larger probe for comparison. This procedure uses simple laboratory supplies and reagents, and is ideal for investigators who have little experience with performing DNA ISH. PMID:25591075

  7. Portable optical oxygen sensor based on time-resolved fluorescence.

    PubMed

    Chu, Cheng-Shane; Chu, Ssu-Wei

    2014-11-10

    A new, simple signal processing, low-cost technique for the fabrication of a portable oxygen sensor based on time-resolved fluorescence is described. The sensing film uses the oxygen sensing dye platinum meso-tetra (pentfluorophenyl) porphyrin (PtTFPP) embedded in a polymer matrix. The ratio τ0100 measures sensitivity of the sensing film, where τ0 and τ100 represent the detected fluorescence lifetimes from the sensing film exposed to 100% nitrogen and 100% oxygen, respectively. The experimental results reveal that the PtTFPP-doped oxygen sensor has a sensitivity of 2.2 in the 0%-100% range. A preparation procedure for coating the photodiodes with the oxygen sensor film that produces repetitive and reliable sensing devices is proposed. The developed time-resolved optical oxygen sensor is portable, low-cost, has simple signal processing, and lacks optical filter elements. It is a cost-effective alternative to traditional electrochemical-based oxygen sensors and provides a platform for other optical based sensors.

  8. Multispectral excitation based multiple fluorescent targets resolving in fluorescence molecular tomography

    NASA Astrophysics Data System (ADS)

    Zhou, Yuan; Guang, Huizhi; Pu, Huangsheng; Zhang, Jiulou; Bai, Jing; Luo, Jianwen

    2016-04-01

    Fluorescence molecular tomography (FMT) can visualize biological activities at cellular and molecular levels in vivo, and has been extensively used in drug delivery and tumor detection research of small animals. The ill-posedness of the FMT inverse problem makes it difficult to reconstruct and resolve multiple adjacent fluorescent targets that have different functional features but are labeled with the same fluorochrome. An algorithm based on independent component analysis (ICA) for multispectral excited FMT is proposed to resolve multiple fluorescent targets in this study. Fluorescent targets are excited by multispectral excitation, and the three-dimensional distribution of fluorescent yields under the excitation spectrum is reconstructed by an iterative Tikhonov regularization algorithm. Subsequently, multiple fluorescent targets are resolved from mixed fluorescence signals by employing ICA. Simulations were performed and the results demonstrate that multiple adjacent fluorescent targets can be resolved if the number of excitation wavelengths is not smaller than that of fluorescent targets with different concentrations. The algorithm obtains both independent components that provide spatial information of different fluorescent targets and spectral courses that reflect variation trends of fluorescent yields along with the excitation spectrum. By using this method, it is possible to visualize the metabolism status of drugs in different structure organs, and quantitatively depict the variation trends of fluorescent yields of each functional organ under the excitation spectrum. This method may provide a pattern for tumor detection, drug delivery and treatment monitoring in vivo.

  9. A capillary-based probe for in situ detection of enhanced fluorescence signals

    NASA Astrophysics Data System (ADS)

    Long, F.; Xiao, R.; Zhu, A. N.; Shi, H. C.; Wang, S. Q.

    2013-07-01

    A simple, compact, and high sensitivity capillary-based probe for the in situ detection of fluorescence signals with high sensitivity is demonstrated. A home-made single-multi-mode fiber coupler that is coaxially aligned with the capillary-based probe provides for the transmission of excitation light and the collection and transmission of fluorescence. We propose a conceptually straightforward theoretical model to optimize the factors affecting the fluorescence-capture capability of the capillary-based probe. The fluorescence signal detected by fiber-optic spectroscopy non-linearly increases with the length of the capillary-based probe. In addition, the thicker the capillary tube wall is, the less the fluorescence signals determined are. The performance of the proposed probe is evaluated experimentally by measuring the fluorescence spectra of Cy5.5 dye and blue-green algae. The experimental results show that the proposed probe provides more than a ten-fold increase in fluorescence signal compared with direct measurements by a flat-tipped multi-mode fiber probe. The advantages of the capillary-based probe, which include its simple and compact structure, excellent light collection efficiency, requirement of small sample volume, and recoverability of samples, allow its wide application to in situ detection in the medical, forensic, biological, geological, and environmental fields with high sensitivity.

  10. Highly fluorescent BF2 complexes of hydrazine-Schiff base linked bispyrrole.

    PubMed

    Yu, Changjiang; Jiao, Lijuan; Zhang, Ping; Feng, Zeya; Cheng, Chi; Wei, Yun; Mu, Xiaolong; Hao, Erhong

    2014-06-06

    A series of BF2 complexes of hydrazine-Schiff base linked bispyrrole have been prepared from a simple two-step reaction from commercially available substances and are highly fluorescent in solution, film, and solid states with larger Stokes shift and excellent photostabilities comparable or even super to those of their BODIPY analogues. These resultant fluorescent dyes are highly susceptible to the postfunctionalization, as demonstrated in this work via the Knoevenagel condensation to introducing functionalities or tether groups to the chromophore.

  11. Fluorescent Protein Based FRET Pairs with Improved Dynamic Range for Fluorescence Lifetime Measurements

    PubMed Central

    George Abraham, Bobin; Sarkisyan, Karen S.; Mishin, Alexander S.; Santala, Ville; Tkachenko, Nikolai V.; Karp, Matti

    2015-01-01

    Fluorescence Resonance Energy Transfer (FRET) using fluorescent protein variants is widely used to study biochemical processes in living cells. FRET detection by fluorescence lifetime measurements is the most direct and robust method to measure FRET. The traditional cyan-yellow fluorescent protein based FRET pairs are getting replaced by green-red fluorescent protein variants. The green-red pair enables excitation at a longer wavelength which reduces cellular autofluorescence and phototoxicity while monitoring FRET. Despite the advances in FRET based sensors, the low FRET efficiency and dynamic range still complicates their use in cell biology and high throughput screening. In this paper, we utilized the higher lifetime of NowGFP and screened red fluorescent protein variants to develop FRET pairs with high dynamic range and FRET efficiency. The FRET variations were analyzed by proteolytic activity and detected by steady-state and time-resolved measurements. Based on the results, NowGFP-tdTomato and NowGFP-mRuby2 have shown high potentials as FRET pairs with large fluorescence lifetime dynamic range. The in vitro measurements revealed that the NowGFP-tdTomato has the highest Förster radius for any fluorescent protein based FRET pairs yet used in biological studies. The developed FRET pairs will be useful for designing FRET based sensors and studies employing Fluorescence Lifetime Imaging Microscopy (FLIM). PMID:26237400

  12. Simple and rapid determination of homozygous transgenic mice via in vivo fluorescence imaging.

    PubMed

    Lin, Xiaolin; Jia, Junshuang; Qin, Yujuan; Lin, Xia; Li, Wei; Xiao, Gaofang; Li, Yanqing; Xie, Raoying; Huang, Hailu; Zhong, Lin; Wu, Qinghong; Wang, Wanshan; Huang, Wenhua; Yao, Kaitai; Xiao, Dong; Sun, Yan

    2015-11-17

    Setting up breeding programs for transgenic mouse strains require to distinguish homozygous from the heterozygous transgenic animals. The combinational use of the fluorescence reporter transgene and small animal in-vivo imaging system might allow us to rapidly and visually determine the transgenic mice homozygous for transgene(s) by the in vivo fluorescence imaging. RLG, RCLG or Rm17LG transgenic mice ubiquitously express red fluorescent protein (RFP). To identify homozygous RLG transgenic mice, whole-body fluorescence imaging for all of newborn F2-generation littermates produced by mating of RFP-positive heterozygous transgenic mice (F1-generation) derived from the same transgenic founder was performed. Subsequently, the immediate data analysis of the in vivo fluorescence imaging was carried out, which greatly facilitated us to rapidly and readily distinguish RLG transgenic individual(s) with strong fluorescence from the rest of F2-generation littermates, followed by further determining this/these RLG individual(s) showing strong fluorescence to be homozygous, as strongly confirmed by mouse mating. Additionally, homozygous RCLG or Rm17LG transgenic mice were also rapidly and precisely distinguished by the above-mentioned optical approach. This approach allowed us within the shortest time period to obtain 10, 8 and 2 transgenic mice homozygous for RLG, RCLG and Rm17LG transgene, respectively, as verified by mouse mating, indicating the practicality and reliability of this optical method. Taken together, our findings fully demonstrate that the in vivo fluorescence imaging offers a visual, rapid and reliable alternative method to the traditional approaches (i.e., mouse mating and real-time quantitative PCR) in identifying homozygous transgenic mice harboring fluorescence reporter transgene under the control of a ubiquitous promoter in the situation mentioned in this study.

  13. A novel and simple fluorescence probe for detecting main group magnesium ion in HeLa cells and Arabidopsis.

    PubMed

    Yu, Tingting; Sun, Ping; Hu, Yijie; Ji, Yinggang; Zhou, Hongping; Zhang, Baowei; Tian, Yupeng; Wu, Jieying

    2016-12-15

    A simple-molecule fluorescence probe L has been designed, synthesized and characterized, which shows high selectivity and sensitivity for the main group magnesium ion through fluorescence "turn-on" response in ethanol solution, and no interference from calcium ion in particular. Detection limit of probe L is 1.47×10(-6) M and the rapid response could reach about 15-20s. The recognition mechanism has been established by fluorescence spectra, (1)H NMR study. Moreover, probe L presents a great photostability, low toxicity and cellular permeability, then we have carried out fluorescent bio-imaging of the probe L for magnesium ions in HeLa cells, which showed that probe L could be utilized to detect the intracellular magnesium ion. Furthermore, it is successfully used as a magnesium ion developer in plant tissues, which shows that it not only can be well tracking the transport of magnesium ion but also make a corresponding fluorescence response to different concentrations magnesium ion. These results would make this probe a great potential application for detecting Mg(2+) in biological system.

  14. A FLUORESCENCE BASED ASSAY FOR DNA DAMAGE: INDUCED BY RADIATION, CHEMICALS AND ENZYMES

    EPA Science Inventory

    A simple and rapid assay to detect DNA damage is reported. This assay is based on the ability of certain dyes to fluoresce upon intercalation with dsDNA. Damage caused by ultraviolet (UV) radiation, chemicals or restriction enzymes is detected using this assay. UV radiation at...

  15. A FLUORESCENCE BASED ASSAY FOR DNA DAMAGE INDUCED BY RADIATION, CHEMICAL MUTAGENS AND ENZYMES

    EPA Science Inventory

    A simple and rapid assay to detect DNA damage is reported. This novel assay is based on changes in melting/annealing behavior and facilitated using certain dyes that increase their fluorescence upon association with double stranded (ds)DNA. Damage caused by ultraviolet (UV) ra...

  16. A FLUORESCENCE BASED ASSAY FOR DNA DAMAGE INDUCED BY STYRENE OXIDE

    EPA Science Inventory

    A rapid and simple assay to detect DNA damage to calf thymus DNA caused by styrene oxide (SO) is reported. This assay is based on changes observed in the melting and annealing behavior of the damaged DNA. The melting annealing process was monitored using a fluorescence indicat...

  17. Graphene-Based Biosensors: Going Simple.

    PubMed

    Morales-Narváez, Eden; Baptista-Pires, Luis; Zamora-Gálvez, Alejandro; Merkoçi, Arben

    2017-02-01

    The main properties of graphene derivatives facilitating optical and electrical biosensing platforms are discussed, along with how the integration of graphene derivatives, plastic, and paper can lead to innovative devices in order to simplify biosensing technology and manufacture easy-to-use, yet powerful electrical or optical biosensors. Some crucial issues to be overcome in order to bring graphene-based biosensors to the market are also underscored.

  18. A simple integrated microfluidic device for the multiplexed fluorescence-free detection of Salmonella enterica.

    PubMed

    Strachan, Briony C; Sloane, Hillary S; Houpt, Eric; Lee, Jacob C; Miranian, Daniel C; Li, Jingyi; Nelson, Daniel A; Landers, James P

    2016-02-07

    Rapid, inexpensive and simplistic nucleic acid testing (NAT) is pivotal in delivering biotechnology solutions at the point-of-care (POC). We present a poly(methylmethacrylate) (PMMA) microdevice where on-board infrared-mediated PCR amplification is seamlessly integrated with a particle-based, visual DNA detection for specific detection of bacterial targets in less than 35 minutes. Fluidic control is achieved using a capillary burst valve laser-ablated in a novel manner to confine the PCR reagents to a chamber during thermal cycling, and a manual torque-actuated pressure system to mobilize the fluid from the PCR chamber to the detection reservoir containing oligonucleotide-adducted magnetic particles. Interaction of amplified products specific to the target organism with the beads in a rotating magnetic field allows for near instantaneous (<30 s) detection based on hybridization-induced aggregation (HIA) of the particles and simple optical analysis. The integration of PCR with this rapid, sequence-specific DNA detection method on a single microdevice presents the possibility of creating POC NAT systems that are low cost, easy-to-use, and involve minimal external hardware.

  19. A simple DNA-based translation system.

    PubMed

    Garibotti, Alejandra V; Liao, Shiping; Seeman, Nadrian C

    2007-02-01

    We have used DNA double crossover (DX) molecules to produce a translation system that generates unique molecular products. The particular species of DX molecule used contains an even number of half-turns between crossover points, so there is a continuous strand on both sides of the molecule. One of these strands acts as the input strand containing the message, and a second strand acts as the product of translation. The crossover strands carry the "code" that connects the two sides of the molecule. This system is more robust, more extendable, and simpler than previous DNA-based translation systems that have been reported. It is designed to be useful in a variety of applications that utilize the concept of translating from one code to another.

  20. Green fluorescent protein with anionic tryptophan-based chromophore and long fluorescence lifetime.

    PubMed

    Sarkisyan, Karen S; Goryashchenko, Alexander S; Lidsky, Peter V; Gorbachev, Dmitry A; Bozhanova, Nina G; Gorokhovatsky, Andrey Yu; Pereverzeva, Alina R; Ryumina, Alina P; Zherdeva, Victoria V; Savitsky, Alexander P; Solntsev, Kyril M; Bommarius, Andreas S; Sharonov, George V; Lindquist, Jake R; Drobizhev, Mikhail; Hughes, Thomas E; Rebane, Aleksander; Lukyanov, Konstantin A; Mishin, Alexander S

    2015-07-21

    Spectral diversity of fluorescent proteins, crucial for multiparameter imaging, is based mainly on chemical diversity of their chromophores. Recently we have reported, to our knowledge, a new green fluorescent protein WasCFP-the first fluorescent protein with a tryptophan-based chromophore in the anionic state. However, only a small portion of WasCFP molecules exists in the anionic state at physiological conditions. In this study we report on an improved variant of WasCFP, named NowGFP, with the anionic form dominating at 37°C and neutral pH. It is 30% brighter than enhanced green fluorescent protein (EGFP) and exhibits a fluorescence lifetime of 5.1 ns. We demonstrated that signals of NowGFP and EGFP can be clearly distinguished by fluorescence lifetime in various models, including mammalian cells, mouse tumor xenograft, and Drosophila larvae. NowGFP thus provides an additional channel for multiparameter fluorescence lifetime imaging microscopy of green fluorescent proteins.

  1. Development of Highly Fluorescent Materials Based on Thiophenylimidazole Dyes

    NASA Technical Reports Server (NTRS)

    Santos, Javier; Bu, Xiu R.; Mintz, Eric A.; Meador, Michael A. (Technical Monitor)

    2000-01-01

    Organic fluorescent materials are expected to find many potential applications in optical devices and photo-functionalized materials. Although many investigations have been focused on heterocyclic compounds such as coumarins, bipyridines, rhodamines, and pyrrole derivatives, little is known for fluorescent imidazole materials. We discovered that one particular class of imidazole derivatives is highly fluorescent. A series of monomeric and polymeric based fluorescent dyes were prepared containing a thiophene unit at the second position of the imidazole ring. Dependence of fluorescence efficiency on parameters such as solvent polarity and substituent groups has been investigated. It was found that a formyl group at the 2-position of the thiophene ring dramatically enhance fluorescence properties. Ion recognition probes indicated their potential as sensor materials. These fluorophores have flexibility for introduction of versatile substituent groups that could improve the fluorescence efficiency and sensor properties.

  2. A Simple and Effective Ratiometric Fluorescent Probe for the Selective Detection of Cysteine and Homocysteine in Aqueous Media.

    PubMed

    Na, Risong; Zhu, Meiqing; Fan, Shisuo; Wang, Zhen; Wu, Xiangwei; Tang, Jun; Liu, Jia; Wang, Yi; Hua, Rimao

    2016-08-05

    Biothiols such as cysteine (Cys) and homocysteine (Hcy) are essential biomolecules participating in molecular and physiological processes in an organism. However, their selective detection remains challenging. In this study, ethyl 2-(3-formyl-4-hydroxyphenyl)-4-methylthiazole-5-carboxylate (NL) was synthesized as a ratiometric fluorescent probe for the rapid and selective detection of Cys and Hcy over glutathione (GSH) and other amino acids. The fluorescence intensity of the probe in the presence of Cys/Hcy increased about 3-fold at a concentration of 20 equiv. of the probe, compared with that in the absence of these chemicals in aqueous media. The limits of detection of the fluorescent assay were 0.911 μM and 0.828 μM of Cys and Hcy, respectively. ¹H-NMR and MS analyses indicated that an excited-state intramolecular proton transfer is the mechanism of fluorescence sensing. This ratiometric probe is structurally simple and highly selective. The results suggest that it has useful applications in analytical chemistry and diagnostics.

  3. Simple and sensitive high performance liquid chromatography method with fluorescence detection for therapeutic drug monitoring of topiramate.

    PubMed

    Milosheska, Daniela; Vovk, Tomaž; Grabnar, Iztok; Roškar, Robert

    2015-01-01

    A simple, sensitive, accurate, precise and inexpensive HPLC method with fluorescence detection, suitable for routine therapeutic drug monitoring (TDM) of an antiepileptic drug topiramate, was developed and validated. The determination of plasma topiramate concentration was carried out after precolumn derivatization, using 4-chloro-7-nitrobenzofurazan as a fluorescent labeling agent and bendroflumethiazide as an internal standard. The standard calibration curve was linear over the concentration range of 0.01-24 μg/mL (r² > 0.9998). The intra- and inter-day accuracies expressed as bias were from 1.4 to 9.9% and from 1.9 to 10.2%, respectively. The intra- and inter-day precisions were below 7.9% and 2.7%, respectively. The validated method was applied for the measurement of plasma topiramate concentrations in patients with epilepsy. The reported method is appropriate for TDM of topiramate as well as for pharmacokinetic and bioequivalence studies.

  4. Multiphoton, optical fiber-based fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Bereś-Pawlik, ElŻbieta; Stawska, Hanna; Popenda, Maciej; Pajewski, Łukasz; Malinowska, Natalia; Hossa, Robert

    2016-12-01

    This paper presents investigation of normal and cancerous tissue by the means of one and two photon fluorescence spectroscopy. A comparison those methods has been conducted, allowing for eventual determination of granting the best possible diagnostic results.

  5. Naphthoxazole-based singlet oxygen fluorescent probes.

    PubMed

    Ruiz-González, Rubén; Zanocco, Renzo; Gidi, Yasser; Zanocco, Antonio L; Nonell, Santi; Lemp, Else

    2013-01-01

    In this study, we report the synthesis and photochemical behavior of a new family of photoactive compounds to assess its potential as singlet oxygen ((1)O2) probes. The candidate dyads are composed by a (1)O2 trap plus a naphthoxazole moiety linked directly or through an unsaturated bond to the oxazole ring. In the native state, the inherent great fluorescence of the naphthoxazole moiety is quenched; but in the presence of (1)O2, generated by the addition and appropriate irradiation of an external photosensitizer, a photooxidation reaction occurs leading to the formation of a new chemical entity whose fluorescence is two orders of magnitude higher than that of the initial compound, at the optimal selected wavelength. The presented dyads outperform the commonly used indirect fluorescent (1)O2 probes in terms of fluorescence enhancement maintaining the required specificity for (1)O2 detection in solution.

  6. A quick and simple FISH protocol with hybridization-sensitive fluorescent linear oligodeoxynucleotide probes.

    PubMed

    Wang, Dan Ohtan; Matsuno, Hitomi; Ikeda, Shuji; Nakamura, Akiko; Yanagisawa, Hiroyuki; Hayashi, Yasunori; Okamoto, Akimitsu

    2012-01-01

    Fluorescence in situ hybridization (FISH) is a powerful tool used in karyotyping, cytogenotyping, cancer diagnosis, species specification, and gene-expression analysis. Although widely used, conventional FISH protocols are cumbersome and time consuming. We have now developed a FISH method using exciton-controlled hybridization-sensitive fluorescent oligodeoxynucleotide (ECHO) probes. ECHO-FISH uses a 25-min protocol from fixation to mounting that includes no stringency washing steps. We use ECHO-FISH to detect both specific DNA and RNA sequences with multicolor probes. ECHO-FISH is highly reproducible, stringent, and compatible with other fluorescent cellular labeling techniques. The resolution allows detection of intranuclear speckles of poly(A) RNA in HeLa cells and dissociated hippocampal primary cultures, and mRNAs in the distal dendrites of hippocampal neurons. We also demonstrate detection of telomeric and centromeric DNA on metaphase mouse chromosomes. The simplicity of the ECHO-FISH method will likely accelerate cytogenetic and gene-expression analysis with high resolution.

  7. Characterization of flavin-based fluorescent proteins: an emerging class of fluorescent reporters.

    PubMed

    Mukherjee, Arnab; Walker, Joshua; Weyant, Kevin B; Schroeder, Charles M

    2013-01-01

    Fluorescent reporter proteins based on flavin-binding photosensors were recently developed as a new class of genetically encoded probes characterized by small size and oxygen-independent maturation of fluorescence. Flavin-based fluorescent proteins (FbFPs) address two major limitations associated with existing fluorescent reporters derived from the green fluorescent protein (GFP)-namely, the overall large size and oxygen-dependent maturation of fluorescence of GFP. However, FbFPs are at a nascent stage of development and have been utilized in only a handful of biological studies. Importantly, a full understanding of the performance and properties of FbFPs as a practical set of biological probes is lacking. In this work, we extensively characterize three FbFPs isolated from Pseudomonas putida, Bacillus subtilis, and Arabidopsis thaliana, using in vitro studies to assess probe brightness, oligomeric state, maturation time, fraction of fluorescent holoprotein, pH tolerance, redox sensitivity, and thermal stability. Furthermore, we validate FbFPs as stable molecular tags using in vivo studies by constructing a series of FbFP-based transcriptional constructs to probe promoter activity in Escherichia coli. Overall, FbFPs show key advantages as broad-spectrum biological reporters including robust pH tolerance (4-11), thermal stability (up to 60°C), and rapid maturation of fluorescence (<3 min.). In addition, the FbFP derived from Arabidopsis thaliana (iLOV) emerged as a stable and nonperturbative reporter of promoter activity in Escherichia coli. Our results demonstrate that FbFP-based reporters have the potential to address key limitations associated with the use of GFP, such as pH-sensitive fluorescence and slow kinetics of fluorescence maturation (10-40 minutes for half maximal fluorescence recovery). From this view, FbFPs represent a useful new addition to the fluorescent reporter protein palette, and our results constitute an important framework to enable

  8. Phytoplankton photocompensation from space-based fluorescence measurements

    NASA Astrophysics Data System (ADS)

    Morrison, J. Ruairidh; Goodwin, Deborah S.

    2010-03-01

    Recent satellite-derived observations linked global scale phytoplankton fluorescence variability with iron stress and hinted at photophysiological responses associated with changing light levels. These photocompensation reactions, the sum of photoacclimation and photoadaptation, were examined with climatological data for the Gulf of Maine. Significant seasonal variability was observed in the fluorescence quantum yield that was unrelated to patterns of biomass. Up to 89% of the variability in the fluorescence quantum yield was explained by a physiology-based photocompensation model. Spatial variability in seasonal patterns was associated with differing hydrodynamic regimes. This variability in the quantum yield demonstrates that satellite-based fluorescence is inappropriate for phytoplankton biomass determinations. More importantly, the work presented here provides the modeling foundation for fluorescence-based investigations of temporal and spatial variability in phytoplankton physiology associated with growth irradiance. These space-based physiological observations have the potential to decrease uncertainties in future ocean color derived primary productivity estimates.

  9. Recent Advances in Silicon Nanomaterial-Based Fluorescent Sensors

    PubMed Central

    Wang, Houyu; He, Yao

    2017-01-01

    During the past decades, owing to silicon nanomaterials’ unique optical properties, benign biocompatibility, and abundant surface chemistry, different dimensional silicon nanostructures have been widely employed for rationally designing and fabricating high-performance fluorescent sensors for the detection of various chemical and biological species. Among of these, zero-dimensional silicon nanoparticles (SiNPs) and one-dimensional silicon nanowires (SiNWs) are of particular interest. Herein, we focus on reviewing recent advances in silicon nanomaterials-based fluorescent sensors from a broad perspective and discuss possible future directions. Firstly, we introduce the latest achievement of zero-dimensional SiNP-based fluorescent sensors. Next, we present recent advances of one-dimensional SiNW-based fluorescent sensors. Finally, we discuss the major challenges and prospects for the development of silicon-based fluorescent sensors. PMID:28165357

  10. Genetically encoded biosensors based on engineered fluorescent proteins.

    PubMed

    Frommer, Wolf B; Davidson, Michael W; Campbell, Robert E

    2009-10-01

    Fluorescent proteins have revolutionized cell biology by allowing researchers to non-invasively peer into the inner workings of cells and organisms. While the most common applications of fluorescent proteins are to image expression, localization, and dynamics of protein chimeras, there is a growing interest in using fluorescent proteins to create biosensors for minimally invasive imaging of concentrations of ions and small molecules, the activity of enzymes, and changes in the conformation of proteins in living cells. This tutorial review provides an overview of the progress made in the development of fluorescent protein-based biosensors to date.

  11. Mosaic-Detector-Based Fluorescence Spectral Imager

    NASA Technical Reports Server (NTRS)

    Son, Kyung-Ah; Moon, Jeong

    2007-01-01

    A battery-powered, pen-sized, portable instrument for measuring molecular fluorescence spectra of chemical and biological samples in the field has been proposed. Molecular fluorescence spectroscopy is among the techniques used most frequently in laboratories to analyze compositions of chemical and biological samples. Heretofore, it has been possible to measure fluorescence spectra of molecular species at relative concentrations as low as parts per billion (ppb), with a few nm spectral resolution. The proposed instrument would include a planar array (mosaic) of detectors, onto which a fluorescence spectrum would be spatially mapped. Unlike in the larger laboratory-type molecular fluorescence spectrometers, mapping of wavelengths to spatial positions would be accomplished without use of relatively bulky optical parts. The proposed instrument is expected to be sensitive enough to enable measurement of spectra of chemical species at relative concentrations <1 ppb, with spectral resolution that could be tailored by design to be comparable to a laboratory molecular fluorescence spectrometer. The proposed instrument (see figure) would include a button-cell battery and a laser diode, which would generate the monochromatic ultraviolet light needed to excite fluorescence in a sample. The sample would be held in a cell bounded by far-ultraviolet-transparent quartz or optical glass. The detector array would be, more specifically, a complementary metal oxide/ semiconductor or charge-coupled- device imaging photodetector array, the photodetectors of which would be tailored to respond to light in the wavelength range of the fluorescence spectrum to be measured. The light-input face of the photodetector array would be covered with a matching checkerboard array of multilayer thin film interference filters, such that each pixel in the array would be sensitive only to light in a spectral band narrow enough so as not to overlap significantly with the band of an adjacent pixel. The

  12. A simple fluorescence quenching method for berberine determination using water-soluble CdTe quantum dots as probes

    NASA Astrophysics Data System (ADS)

    Cao, Ming; Liu, Meigui; Cao, Chun; Xia, Yunsheng; Bao, Linjun; Jin, Yingqiong; Yang, Song; Zhu, Changqing

    2010-03-01

    A novel method for the determination of berberine has been developed based on quenching of the fluorescence of thioglycolic acid-capped CdTe quantum dots (TGA-CdTe QDs) by berberine in aqueous solutions. Under optimum conditions, the relative fluorescence intensity was linearly proportional to the concentration of berberine between 2.5 × 10 -8 and 8.0 × 10 -6 mol L -1 with a detection limit of 6.0 × 10 -9 mol L -1. The method has been applied to the determination of berberine in real samples, and satisfactory results were obtained. The mechanism of the proposed reaction was also discussed.

  13. Spectral properties of a simple azine Schiff base and its sensing ability towards protic environment through hydrogen bonding interaction.

    PubMed

    Ray, Debarati; Dalapati, Sasanka; Guchhait, Nikhil

    2013-11-01

    A simple azine linkage containing Schiff base p-N,N-diethylaminobenzaldazine (PDEAB) has been synthesized and its spectroscopic properties have been investigated using steady state absorption and fluorescence measurement. Both the absorption and emission studies indicate that the compound PDEAB forms intermolecular hydrogen bond with protic solvents. The formation of intermolecular hydrogen bond between PDEAB and protic solvents is further verified by Quantum chemical calculation using Density Functional Theory (DFT) (B3LYP/6-31++G(d,p)) and Natural Bond Orbital (NBO) analysis. The non-fluorescent nature (fluorescence off) of PDEAB in aprotic environment can be switched over to a fluorescent system (fluorescence on) in presence of protic solvents and hence this molecule can be used as highly sensitive fluorosensor for protic solvent in aprotic medium like ACN or DOX.

  14. Spectral properties of a simple azine Schiff base and its sensing ability towards protic environment through hydrogen bonding interaction

    NASA Astrophysics Data System (ADS)

    Ray, Debarati; Dalapati, Sasanka; Guchhait, Nikhil

    2013-11-01

    A simple azine linkage containing Schiff base p-N,N-diethylaminobenzaldazine (PDEAB) has been synthesized and its spectroscopic properties have been investigated using steady state absorption and fluorescence measurement. Both the absorption and emission studies indicate that the compound PDEAB forms intermolecular hydrogen bond with protic solvents. The formation of intermolecular hydrogen bond between PDEAB and protic solvents is further verified by Quantum chemical calculation using Density Functional Theory (DFT) (B3LYP/6-31++G(d,p)) and Natural Bond Orbital (NBO) analysis. The non-fluorescent nature (fluorescence off) of PDEAB in aprotic environment can be switched over to a fluorescent system (fluorescence on) in presence of protic solvents and hence this molecule can be used as highly sensitive fluorosensor for protic solvent in aprotic medium like ACN or DOX.

  15. A Simple Visualization of Double Bond Properties: Chemical Reactivity and UV Fluorescence

    ERIC Educational Resources Information Center

    Grayson, Scott M.

    2012-01-01

    A simple, easily visualized thin-layer chromatography (TLC) staining experiment is presented that highlights the difference in reactivity between aromatic double bonds and nonaromatic double bonds. Although the stability of aromatic systems is a major theme in organic chemistry, the concept is rarely reinforced "visually" in the undergraduate…

  16. Eco-friendly carbon-nanodot-based fluorescent paints for advanced photocatalytic systems

    NASA Astrophysics Data System (ADS)

    Young Park, So; Uk Lee, Hyun; Lee, Young-Chul; Choi, Saehae; Hyun Cho, Dae; Sik Kim, Hee; Bang, Sunghee; Seo, Soonjoo; Chang Lee, Soon; Won, Jonghan; Son, Byung-Chul; Yang, Mino; Lee, Jouhahn

    2015-07-01

    Fluorescent carbon nanomaterials, especially zero-dimensional (0D) carbon nanodots (CDs), are widely used in broad biological and optoelectronic applications. CDs have unique characteristics such as strong fluorescence, biocompatibility, sun-light response, and capability of mass-production. Beyond the previous green CD obtained from harmful natural substances, we report a new type of fluid-based fluorescent CD paints (C-paints) derived from polyethylene glycol (PEG; via simple ultrasound irradiation at room temperatures) and produced in quantum yields of up to ~14%. Additionally, C-paints possess a strong, UV- and visible-light-responsive photoluminescent (PL) property. Most especially, C-paints, by incorporation into a photocatalytic system, show additional roles in the emission of fluorescent light for activation of TiO2 nanoparticles (NPs) and the resultant detoxification of most organic dyes, thus further enabling embarkation in advanced water purification.

  17. Eco-friendly carbon-nanodot-based fluorescent paints for advanced photocatalytic systems

    PubMed Central

    Young Park, So; Uk Lee, Hyun; Lee, Young-Chul; Choi, Saehae; Hyun Cho, Dae; Sik Kim, Hee; Bang, Sunghee; Seo, Soonjoo; Chang Lee, Soon; Won, Jonghan; Son, Byung-Chul; Yang, Mino; Lee, Jouhahn

    2015-01-01

    Fluorescent carbon nanomaterials, especially zero-dimensional (0D) carbon nanodots (CDs), are widely used in broad biological and optoelectronic applications. CDs have unique characteristics such as strong fluorescence, biocompatibility, sun-light response, and capability of mass-production. Beyond the previous green CD obtained from harmful natural substances, we report a new type of fluid-based fluorescent CD paints (C-paints) derived from polyethylene glycol (PEG; via simple ultrasound irradiation at room temperatures) and produced in quantum yields of up to ~14%. Additionally, C-paints possess a strong, UV- and visible-light-responsive photoluminescent (PL) property. Most especially, C-paints, by incorporation into a photocatalytic system, show additional roles in the emission of fluorescent light for activation of TiO2 nanoparticles (NPs) and the resultant detoxification of most organic dyes, thus further enabling embarkation in advanced water purification. PMID:26201431

  18. Simple and rapid preparation of red fluorescence and red color S. aureus derived nanobioparticles for pathogen detection.

    PubMed

    Hu, Wei; Zhang, Yun; Yang, Hang; Yu, Junping; Wei, Hongping

    2015-08-01

    In this study, a simple and rapid method was developed to transform protein A producing Staphylococcus aureus cells into red color and red fluorescent nanobioparticles, which were homogeneous, dispersive and relatively stable with a uniform size of 800 nm. The method consists of reaction with a monotetrazolium redox dye at 25°C for 15 min and heat inactivation at 65°C for 30 min. This method provided the first S. aureus nanobioparticles with the dual property of red color and red fluorescence. Attributed to the IgG binding site known as protein A on their surface, the nanobioparticles could be used as vectors for immunoassays of many bacteria and viruses. Coagglutination test of Escherichia coli O157:H7 observed by naked eyes showed that the detection limitation of the nanobioprobes was 1∗10(6) CFU/ml, which was about 100 times more sensitive than the natural uncolored S. aureus bioprobes. Red fluorescence detection and analysis of the coagglutination product by a microplate reader lowered the detection limit to 2.5∗10(4) CFU/ml.

  19. Combination of DNA ligase reaction and gold nanoparticle-quenched fluorescent oligonucleotides: a simple and efficient approach for fluorescent assaying of single-nucleotide polymorphisms.

    PubMed

    Wang, Hao; Li, Jishan; Wang, Yongxiang; Jin, Jiangyu; Yang, Ronghua; Wang, Kemin; Tan, Weihong

    2010-09-15

    A new fluorescent sensing approach for detection of single-nucleotide polymorphisms (SNPs) is proposed based on the ligase reaction and gold nanoparticle (AuNPs)-quenched fluorescent oligonucleotides. The design exploits the strong fluorescence quenching of AuNPs for organic dyes and the difference in noncovalent interactions of the nanoparticles with single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA), where ssDNA can be adsorbed onto the surface of AuNPs while dsDNA cannot be. In the assay, two half primer DNA probes, one being labeled with a dye and the other being phosphorylated, were first incubated with a target DNA template. In the presence of DNA ligase, the two captured ssDNAs are linked for the perfectly matched DNA target to form a stable duplex, but the duplex could not be formed by the single-base mismatched DNA template. After addition of AuNPs, the fluorescence of dye-tagged DNA probe will be efficiently quenched unless the perfectly matched DNA target is present. To demonstrate the feasibility of this design, the performance of SNP detection using two different DNA ligases, T4 DNA ligase and Escherichia coli DNA ligase, were investigated. In the case of T4 DNA ligase, the signal enhancement of the dye-tagged DNA for perfectly matched DNA target is 4.6-fold higher than that for the single-base mismatched DNA. While in the presence of E. coli DNA ligase, the value raises to be 30.2, suggesting excellent capability for SNP discrimination.

  20. Fluorescence-based resource for semi-automated genomic analyses

    SciTech Connect

    Kiser, M.B.; Dragwa, C.; Jedlicka, A.E.

    1994-09-01

    To facilitate the practical application of highly efficient semi-automated methods for general application in genomic analyses, we have developed a fluorescence-based marker resource. Ninety highly polymorphic simple tandem repeat markers were combined to provide a rapid, accurate, and highly efficient initial genome-wide screening system. These markers are spaced on average every 33 recombination units, with a mean heterozygosity of 81% (range 65-94%), covering 22 autosomes and the X and Y chromosomes. Less than 3% of the genome lies beyond 30 cM of the nearest marker. Markers were placed in a vertical ladder that we have termed a SET according to the size of the PCR fragments they produce during electrophoresis. Each SET was designed to avoid overlap between loci during gel separations to assure accuracy when scoring genotypes. We have constructed 15 SETS of markers. Three SETS, each labelled with one of three fluors, were combined into what we have termed a GROUP, which is co-electrophoresed with internal size standards that are labelled with a fourth flour. Five GROUPS of markers were assembled that contain a total of 15 SETS of markers. Each GROUP cover 18 regions of the genome that can be detected simultaneously, since this genomic analysis system is fully compatible with automated fragment analyzers using simultaneous four-color fluorescence-based detection systems. This allows for multiplex detection and a throughput of 1,944 genotypes daily per instrument. This system will be highly beneficial in a number of clinical and research applications including: linkage, cancer genetics, forensics, and cytogenetics.

  1. Tomato seeds maturity detection system based on chlorophyll fluorescence

    NASA Astrophysics Data System (ADS)

    Li, Cuiling; Wang, Xiu; Meng, Zhijun

    2016-10-01

    Chlorophyll fluorescence intensity can be used as seed maturity and quality evaluation indicator. Chlorophyll fluorescence intensity of seed coats is tested to judge the level of chlorophyll content in seeds, and further to judge the maturity and quality of seeds. This research developed a detection system of tomato seeds maturity based on chlorophyll fluorescence spectrum technology, the system included an excitation light source unit, a fluorescent signal acquisition unit and a data processing unit. The excitation light source unit consisted of two high power LEDs, two radiators and two constant current power supplies, and it was designed to excite chlorophyll fluorescence of tomato seeds. The fluorescent signal acquisition unit was made up of a fluorescence spectrometer, an optical fiber, an optical fiber scaffolds and a narrowband filter. The data processing unit mainly included a computer. Tomato fruits of green ripe stage, discoloration stage, firm ripe stage and full ripe stage were harvested, and their seeds were collected directly. In this research, the developed tomato seeds maturity testing system was used to collect fluorescence spectrums of tomato seeds of different maturities. Principal component analysis (PCA) method was utilized to reduce the dimension of spectral data and extract principal components, and PCA was combined with linear discriminant analysis (LDA) to establish discriminant model of tomato seeds maturity, the discriminant accuracy was greater than 90%. Research results show that using chlorophyll fluorescence spectrum technology is feasible for seeds maturity detection, and the developed tomato seeds maturity testing system has high detection accuracy.

  2. A simple approach to spectrally resolved fluorescence and bright field microscopy over select regions of interest

    PubMed Central

    Dahlberg, Peter D.; Boughter, Christopher T.; Faruk, Nabil F.; Hong, Lu; Koh, Young Hoon; Reyer, Matthew A.; Sherani, Aiman; Hammond, Adam T.

    2016-01-01

    A standard wide field inverted microscope was converted to a spatially selective spectrally resolved microscope through the addition of a polarizing beam splitter, a pair of polarizers, an amplitude-mode liquid crystal-spatial light modulator, and a USB spectrometer. The instrument is capable of simultaneously imaging and acquiring spectra over user defined regions of interest. The microscope can also be operated in a bright-field mode to acquire absorption spectra of micron scale objects. The utility of the instrument is demonstrated on three different samples. First, the instrument is used to resolve three differently labeled fluorescent beads in vitro. Second, the instrument is used to recover time dependent bleaching dynamics that have distinct spectral changes in the cyanobacteria, Synechococcus leopoliensis UTEX 625. Lastly, the technique is used to acquire the absorption spectra of CH3NH3PbBr3 perovskites and measure differences between nanocrystal films and micron scale crystals. PMID:27910631

  3. A simple approach to spectrally resolved fluorescence and bright field microscopy over select regions of interest

    NASA Astrophysics Data System (ADS)

    Dahlberg, Peter D.; Boughter, Christopher T.; Faruk, Nabil F.; Hong, Lu; Koh, Young Hoon; Reyer, Matthew A.; Shaiber, Alon; Sherani, Aiman; Zhang, Jiacheng; Jureller, Justin E.; Hammond, Adam T.

    2016-11-01

    A standard wide field inverted microscope was converted to a spatially selective spectrally resolved microscope through the addition of a polarizing beam splitter, a pair of polarizers, an amplitude-mode liquid crystal-spatial light modulator, and a USB spectrometer. The instrument is capable of simultaneously imaging and acquiring spectra over user defined regions of interest. The microscope can also be operated in a bright-field mode to acquire absorption spectra of micron scale objects. The utility of the instrument is demonstrated on three different samples. First, the instrument is used to resolve three differently labeled fluorescent beads in vitro. Second, the instrument is used to recover time dependent bleaching dynamics that have distinct spectral changes in the cyanobacteria, Synechococcus leopoliensis UTEX 625. Lastly, the technique is used to acquire the absorption spectra of CH3NH3PbBr3 perovskites and measure differences between nanocrystal films and micron scale crystals.

  4. Simple replacement of violaxanthin by zeaxanthin in LHC-II does not cause chlorophyll fluorescence quenching.

    PubMed

    Dreuw, Andreas; Wormit, Michael

    2008-03-01

    Recently, a mechanism for the energy-dependent component (qE) of non-photochemical quenching (NPQ), the fundamental photo-protection mechanism in green plants, has been suggested. Replacement of violaxanthin by zeaxanthin in the binding pocket of the major light harvesting complex LHC-II may be sufficient to invoke efficient chlorophyll fluorescence quenching. Our quantum chemical calculations, however, show that the excited state energies of violaxanthin and zeaxanthin are practically identical when their geometry is constrained to the naturally observed structure of violaxanthin in LHC-II. Therefore, since violaxanthin does not quench LHC-II, zeaxanthin should not either. This theoretical finding is nicely in agreement with experimental results obtained by femtosecond spectroscopy on LHC-II complexes containing violaxanthin or zeaxanthin.

  5. Novel pyrazoline-based selective fluorescent probe for the detection of hydrazine.

    PubMed

    Zheng, Xiao-Xin; Wang, Sheng-Qing; Wang, Hao-Yan; Zhang, Rong-Rong; Liu, Jin-Ting; Zhao, Bao-Xiang

    2015-03-05

    A novel pyrazoline-based fluorescent probe, 2-[4-(3,5-diphenyl-4,5-dihydro-pyrazol-1-yl)-benzylidene]-malononitrile, with a simple structure and low detection limit (6.16×10(-6)M) for the detection of hydrazine is designed and synthesized. The probe responds selectively to hydrazine over other molecules with marked fluorescence enhancement. The probe can detect hydrazine effectively at pH 5.0-9.0 with a special emission wavelength at 520nm. Moreover, the probe can be used to detect hydrazine from variety of natural source water.

  6. Laser-induced fluorescence made simple: implications for the diagnosis and follow-up monitoring of basal cell carcinoma.

    PubMed

    Drakaki, Eleni; Dessinioti, Clio; Stratigos, Alexander J; Salavastru, Carmen; Antoniou, Christina

    2014-03-01

    Noninvasive treatments are increasingly being used for the management of basal cell carcinoma (BCC), the predominant type of nonmelanoma skin cancer, making the development of noninvasive diagnostic technologies highly relevant for clinical practice. Laser-induced fluorescence (LIF) spectroscopy emerges as an attractive diagnostic technique for the diagnosis and demarcation of BCC due to its noninvasiveness, high sensitivity, real-time measurements, and user-friendly methodology. LIF relies on the principle of differential fluorescence emission between abnormal and normal skin tissues (ex vivo and in vivo) in response to excitation by a specific wavelength of light. Fluorescence originates either from endogenous fluorophores (autofluorescence) or from exogenously administered fluorophores (photosensitizers). The measured optical properties and fluorophore contributions of normal skin and BCC are significantly different from each other and correlate well with tissue histology. Photodynamic diagnosis (PDD) is based on the visualization of a fluorophore, with the ability to accumulate in tumor tissue, by the use of fluorescence imaging. PDD may be used for detecting subclinical disease, determining surgical margins, and following-up patients for residual tumor or BCC relapse. In this review, we will present the basic principles of LIF and discuss its uses for the diagnosis, management, and follow-up of BCC.

  7. A simple and rapid fluorescence in situ hybridization microwave protocol for reliable dicentric chromosome analysis.

    PubMed

    Cartwright, Ian M; Genet, Matthew D; Kato, Takamitsu A

    2013-03-01

    Fluorescence in situhybridization (FISH) is an extremely effective and sensitive approach to analyzing chromosome aberrations. Until recently, this procedure has taken multiple days to complete. The introduction of telomeric and centromeric peptide nucleic acid (PNA) probes has reduced the procedure's duration to several hours, but the protocols still call for a high temperature (80-90°C) step followed by 1-3 h of hybridization. The newest method to speed up the FISH protocol is the use of a microwave to shorten the heating element to less than a minute; however this protocol still calls for a 1-h hybridization period. We have utilized PNA centromere/telomere probes in conjunction with a microwave oven to show telomere and centromere staining in as little as 30 s. We have optimized the hybridization conditions to increase the sensitivity and effectiveness of the new protocol and can effectively stain chromosomes in 2 min and 30 s of incubation. We have found that our new approach to FISH produces extremely clear and distinct signals. Radiation-induced dicentric formation in mouse and human fibroblast cells was analyzed by two individual scorers and the observed dicentrics matched very well.

  8. Toward quantitatively fluorescent carbon-based "quantum" dots.

    PubMed

    Anilkumar, Parambath; Wang, Xin; Cao, Li; Sahu, Sushant; Liu, Jia-Hui; Wang, Ping; Korch, Katerina; Tackett, Kenneth N; Parenzan, Alexander; Sun, Ya-Ping

    2011-05-01

    Carbon-based "quantum" dots (or "carbon dots") are generally defined as surface-passivated small carbon nanoparticles that are brightly fluorescent. Apparently, the carbon particle surface passivation in carbon dots is critical to their fluorescence performance. An effective way to improve the surface passivation is to dope the surface of the precursor carbon nanoparticles with an inorganic salt, followed by the typical functionalization with organic molecules. In this work we passivated small carbon nanoparticles by a combination of the surface-doping with nanoscale semiconductors and the organic functionalization, coupled with gel column fractionation to harvest the most fluorescent carbon dots, which exhibited fluorescence emission quantum yields of up to 78%. Experimental and mechanistic issues relevant to potentially further improve the performance of carbon dots toward their being quantitatively fluorescent are discussed.

  9. Aliphatic amine responsive organogel system based on a simple naphthalimide derivative.

    PubMed

    Cao, Xinhua; Zhang, Tingting; Gao, Aiping; Li, Keli; Cheng, Qiuli; Song, Lijuan; Zhang, Min

    2014-09-07

    A new gelator 1 based on a simple naphthalimide derivative was synthesized and fully characterized. It was found that the organogel 1 was formed only in a mixed solvent of methanol and H2O (1/1, v/v). The organogel was thoroughly characterized by using various microscopic techniques including field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and UV-vis, fluorescence and Fourier transform infrared (FTIR) spectroscopy. Hydrogen bonds were the main driving force for the organogel formation. Interestingly, the organogel 1 exhibited the ability to distinguish aliphatic amines from aromatic amines. The gel state and fluorescence emission intensity were both changed after two minutes after the addition of aliphatic amines. This organogel system could be applied in the detection of aliphatic amine pollutants.

  10. Seesawed fluorescence nano-aptasensor based on highly vertical ZnO nanorods and three-dimensional quantitative fluorescence imaging for enhanced detection accuracy of ATP.

    PubMed

    Shrivastava, Sajal; Triet, Nguyen Minh; Son, Young-Min; Lee, Won-Il; Lee, Nae-Eung

    2017-04-15

    Probe-mediated fluorescence biosensing methods based on spectrophotometry still have limitations such as detection inaccuracy caused by the occurrence of false signals and lack of simultaneous qualitative and quantitative read-outs with an ultra-low detection limit. Herein, we describe a novel seesawed fluorescence detection strategy based on dual-colour imaging-based quantitation in which the green fluorescence of the capture aptamer decreases and the red fluorescence of the detection aptamer increases simultaneously upon their respective interactions with the target biomolecule. This approach enhances detection accuracy through facilitating identification of probable false-positives in biological samples. Furthermore, combining the seesawed detection scheme with three-dimensional imaging of fluorescence signal enhanced by highly vertical ZnO nanorods increases signal-to-noise ratio, which addresses the limited performance of digital cameras and, in turn, enhances sensitivity and dynamic range. This simple, robust, scalable, imaging-based and label-free fluorescence method allows highly specific and sensitive quantification of biomolecules with excellent reliability.

  11. Peptide-based fluorescence biosensors for detection/measurement of nanoparticles.

    PubMed

    Akinloye, Oluyemi; Krishnamurthy, Ramanarayan; Wishart, David; Goss, Greg G

    2017-02-01

    The ability to detect and quantify nanoparticles is essential but there is currently no simple, sensitive, and rapid method for the detection of nanomaterials. We have developed a novel peptide-based fluorescence-based biosensor for detection and measurement of negatively charged engineered nanoparticles (ENPs). A peptide biosensor (seven lysine residues linked to a cysteine through a three glycine residue linker) with attached fluorescent probes-fluorescein-5-maleimide (F5M) and tetramethylrhodamine-5-maleimide (TMR5M)-was constructed. The fluorescent probes allow close monitoring of the molecular interaction of the labeled peptide with ENPs. The ENP-peptide interaction induces the formation of agglomerates that can be detected and measured by changes in the fluorescence intensities of the labeled peptides or/and by differential light scattering. The relative fluorescence intensities of F5M and TMR5M decreased in a concentration-dependent manner on interaction with various types of negatively charged ENPs (ZnO, Fe3O4, CeO, and single-walled carbon nanotubes). Differential light scattering measurements also showed increases in the hydrodynamic size of the complex. The interactions were not affected by the pH of aqueous media, where humic acid (1 μg/mL) quenched the fluorescence intensity of F5M by approximately 25 %, whereas that of TMR5M was completely quenched. Interference by humic acid at lower concentrations was less prevalent. This novel method is a simple, rapid, and inexpensive in situ assay that shows promise as a primary-level testing technique for detection of ENPs in environmental samples. Graphical Abstract Detection of nanomaterials in aqueous solutions using fluorescently-labeled designer peptides.

  12. A simple, rapid and low-cost staining method for gel-electrophoresis separated phosphoproteins via the fluorescent purpurin dye.

    PubMed

    Cong, Weitao; Shen, Jiayi; Xuan, Yuanhu; Zhu, Xinliang; Ni, Maowei; Zhu, Zhongxin; Hong, Guoying; Lu, Xianghong; Jin, Litai

    2014-12-07

    A novel fluorescence detection method for phosphoproteins in 1-D and 2-D SDS-PAGE by using purpurin is developed in this study. Phosphoproteins as low as 4-8 ng could be specifically detected by purpurin within 60 min, and the detection limit is similar to or better than that of Pro-Q Diamond staining. Only 2 steps (staining and destaining) are needed for purpurin staining without requiring excessive fixing and washing steps, and for single use, $0.8 is enough for purpurin staining. By comprehensively comparing with Pro-Q Diamond staining, it is concluded that purpurin staining is a simple, rapid and low-cost staining method for a broad application to the research of phosphoproteins.

  13. Towards a spectrum-based bar code for identification of weakly fluorescent microparticles

    NASA Astrophysics Data System (ADS)

    Petrášek, Zdeněk; Wiedemann, Jens; Schwille, Petra

    2014-03-01

    Spectrally resolved detection of fluorescent probes can be used to identify multiple labeled target molecules in an unknown mixture. We study how the spectral shape, the experimental noise, and the number of spectral detection channels affect the success of identification of weakly fluorescent beads on basis of their emission spectra. The proposed formalism allows to estimate the performance of the spectral identification procedure with a given set of spectral codes on the basis of the reference spectra only. We constructed a simple prism-based setup for spectral detection and demonstrate that seven distinct but overlapping spectral codes realized by combining up to three fluorescent dyes bound to a single bead in a barcode-based manner can be reliably identified. The procedure allows correct identification even in the presence of known autofluorescence background stronger than the actual signal.

  14. A simple turn on fluorescent sensor for the selective detection of thiamine using coconut water derived luminescent carbon dots.

    PubMed

    Purbia, Rahul; Paria, Santanu

    2016-05-15

    In this study microwave-assisted hydrothermal method was used to prepare highly luminescent carbon dots (1-6 nm size) within a minute from tender coconut (Cocos nucifera) water. The synthesized carbon dots (C-dots) exhibit emission of blue and green lights while excited at 390 and 450 nm wavelengths, respectively. As an application, these C-dots were tested for a simple "turn on" fluorescent sensor for rapid detection of thiamine (vitamin B1). The detection of thiamine in human body is very important to prevent various diseases such as beriberi, neurological disorders, optic neuropathy, etc. The fluorescence emission intensity of C-dots quenches after addition of Cu(2+) ion and then again increases selectively (turn on) after the addition of thiamine. The fluorescence emission intensity enhancement of Cu(2+) ion modified C-dots in the presence of thiamine exhibits a linear relationship within the thiamine concentration range of 10-50 μM. The limit of detection was found to be 280 nM from this study. The selectivity of the detection was also tested in the presence of different organic molecules and inorganic ions (Ca(2+), Mg(2+), Na(+), K(+), Cl(-), SO4(2-), and NO3(-)) which are present in blood serum and urine and found to be almost no interference in the detection. Finally, to see the applicability in real samples a commercial vitamin capsule was tested and found less than 3% error in the detected concentration. The C-dots were also used for bioimaging of fungus and the results show they are also suitable for this application too.

  15. Highly sensitive fluorescence and SERS detection of azide through a simple click reaction of 8-chloroquinoline and phenylacetylene.

    PubMed

    Zeng, Qing; Ye, Lingling; Ma, Lu; Yin, Wenqing; Li, Tingsheng; Liang, Aihui; Jiang, Zhiliang

    2015-05-01

    In 0.19 mol/L acetic acid (HAc), a click reaction of 8-chloroquinoline/azide/phenylacetylene take places in aqueous solution without Cu(I) as a catalyst. 8-Chloroquinoline (CQN) exhibited a strong fluorescence peak at 430 nm that was quenched linearly as the concentration of azide increased from 20 to 1000 ng/mL. This quenching was due to consumption of CQN in the click reaction and a decrease in the number of efficiently excited photons due to the presence of triazole-quinoline ramification molecules with strong hydrophobicity. Using blue nanosilver sol as the substrate, CQN absorbed onto the surface of nanosilver particles, showing a strong surface-enhanced Raman scattering (SERS) peak at 1585 cm(-1) that decreased linearly as the azide concentration increased from 8 to 500 ng/mL; the detection limit was 4 ng/mL. Thus, two new, simple and sensitive fluorescence and SERS methods have been developed for the determination of azide via the click reaction.

  16. A rapid-screening approach to detect and quantify microplastics based on fluorescent tagging with Nile Red

    NASA Astrophysics Data System (ADS)

    Maes, Thomas; Jessop, Rebecca; Wellner, Nikolaus; Haupt, Karsten; Mayes, Andrew G.

    2017-03-01

    A new approach is presented for analysis of microplastics in environmental samples, based on selective fluorescent staining using Nile Red (NR), followed by density-based extraction and filtration. The dye adsorbs onto plastic surfaces and renders them fluorescent when irradiated with blue light. Fluorescence emission is detected using simple photography through an orange filter. Image-analysis allows fluorescent particles to be identified and counted. Magnified images can be recorded and tiled to cover the whole filter area, allowing particles down to a few micrometres to be detected. The solvatochromic nature of Nile Red also offers the possibility of plastic categorisation based on surface polarity characteristics of identified particles. This article details the development of this staining method and its initial cross-validation by comparison with infrared (IR) microscopy. Microplastics of different sizes could be detected and counted in marine sediment samples. The fluorescence staining identified the same particles as those found by scanning a filter area with IR-microscopy.

  17. A rapid-screening approach to detect and quantify microplastics based on fluorescent tagging with Nile Red.

    PubMed

    Maes, Thomas; Jessop, Rebecca; Wellner, Nikolaus; Haupt, Karsten; Mayes, Andrew G

    2017-03-16

    A new approach is presented for analysis of microplastics in environmental samples, based on selective fluorescent staining using Nile Red (NR), followed by density-based extraction and filtration. The dye adsorbs onto plastic surfaces and renders them fluorescent when irradiated with blue light. Fluorescence emission is detected using simple photography through an orange filter. Image-analysis allows fluorescent particles to be identified and counted. Magnified images can be recorded and tiled to cover the whole filter area, allowing particles down to a few micrometres to be detected. The solvatochromic nature of Nile Red also offers the possibility of plastic categorisation based on surface polarity characteristics of identified particles. This article details the development of this staining method and its initial cross-validation by comparison with infrared (IR) microscopy. Microplastics of different sizes could be detected and counted in marine sediment samples. The fluorescence staining identified the same particles as those found by scanning a filter area with IR-microscopy.

  18. A Simple Inquiry-Based Lab for Teaching Osmosis

    ERIC Educational Resources Information Center

    Taylor, John R.

    2014-01-01

    This simple inquiry-based lab was designed to teach the principle of osmosis while also providing an experience for students to use the skills and practices commonly found in science. Students first design their own experiment using very basic equipment and supplies, which generally results in mixed, but mostly poor, outcomes. Classroom "talk…

  19. Simple method of DNA stretching on glass substrate for fluorescence image and spectroscopy

    NASA Astrophysics Data System (ADS)

    Neupane, Guru P.; Dhakal, Krishna P.; Lee, Hyunsoo; Guthold, Martin; Joseph, Vincent S.; Hong, Jong-Dal; Kim, Jeongyong

    2013-05-01

    Study of biological molecule DNA has contributed to developing many breaking thoughts and wide applications in multidisciplinary fields, such as genomic, medical, sensing and forensic fields. Stretching of DNA molecules is an important supportive tool for AFM or spectroscopic studies of DNA in a single molecular level. In this article, we established a simple method of DNA stretching (to its full length) that occurred on a rotating negatively-charged surface of glass substrate. The isolation of a single DNA molecule was attained by the two competitive forces on DNA molecules, that is, the electrostatic attraction developed between the positively charged YOYO-1 stained DNA and the negatively charged substrate, and the centrifugal force of the rotating substrate, which separates the DNA aggregates into the single molecule. Density of stretched DNA molecules was controlled by selecting the specific parameters such as spinning time and rates, loading volume of DNA-dye complex solution etc. The atomic force microscopy image exhibited a single DNA molecule on the negatively-charged substrate in an isolated state. Further, the photoluminescence spectra of a single DNA molecule stained with YOYO-1 were achieved using the method developed in the present study, which is strongly believed to effectively support the spectroscopic analysis of DNA in a single molecular level.

  20. Fluorescence quenching of Rhodamine B base by two amines

    NASA Astrophysics Data System (ADS)

    Bakkialakshmi, S.; Selvarani, P.; Chenthamarai, S.

    2013-03-01

    Fluorescence quenching of Rhodamine B base (RhB) in DMF solution has been studied at different concentrations of the amine Triethyl amine (TEA) and n-butyl amine (NBA) at room temperature. It has been observed that the fluorescence intensity of RhB decrease with increase in the concentration of the TEA and NBA. It has been observed that the quenching due to amines proceeds via dynamic quenching process. The rate constants for the quenching process have been calculated using Stern-Volmer equation. Time resolved fluorescence study and 1H NMR spectral study have also been carried out and discussed.

  1. Simple refractometer based on in-line fiber interferometers

    NASA Astrophysics Data System (ADS)

    Esteban, Ó.; Martínez Manuel, R.; Shlyagin, M. G.

    2015-09-01

    A very simple but accurate optical fiber refractometer based on the Fresnel reflection in the fiber tip and two in-line low-reflective mirrors for light intensity referencing is reported. Each mirror was generated by connecting together 2 fiber sections with FC/PC and FC/APC connectors using the standard FC/PC mating sleeve. For the sensor interrogation, a standard DFB diode laser pumped with a sawtooth-wave current was used. A resolution of 6 x 10-4 was experimentally demonstrated using different liquids. A simple sensor construction and the use of low cost components make the reported system interesting for many applications.

  2. Development of fluorescent lead II sensor based on an anthracene derived chalcone.

    PubMed

    Prabhu, J; Velmurugan, K; Nandhakumar, R

    2015-06-05

    A simple anthracene based chalcone as a fluorescent chemosensor 1, capable of detecting Pb(2+) in aqueous media, has been synthesized by the reaction between pyridine 2-carboxaldehyde and 9-acetyl anthracene. The Pb(2+) recognition processes follows a photo induced electron transfer (PET) mechanism and are scarcely influenced by other coexisting metal ions. In addition, determination of lead in a variety of samples was also determined.

  3. A competitive strategy based on cucurbit[7]uril supramolecular interaction for simple and sensitive detection of dibucaine.

    PubMed

    Li, Yan; Li, Chang-Feng; Du, Li-Ming; Feng, Jian-Xia; Liu, Hai-Long; Fu, Yun-Long

    2015-01-01

    In this work, the competitive interaction between dibucaine and three fluorescent probes (i.e., berberine, palmatine, and coptisine) for occupancy of the cucurbit[7]uril (CB[7]) cavity was studied by fluorescence spectra, UV-visible absorption spectra, (1)H NMR spectra, and theoretical calculations in acidic aqueous solution. Based on the fluorescence enhancement of berberine, palmatine, and coptisine upon binding with CB[7], respectively, a series of fluorescence detection methods for dibucaine were proposed. At the optimized conditions, the fluorescence intensity of berberine-CB[7], palmatine-CB[7], and coptisine-CB[7] complexes showed negative correlation to the concentration of dibucaine, which led to a series of simple and sensitive fluorescence methods for the determination of dibucaine for the first time. Linear ranges obtained in the detection of the dibucaine were 0.018-3.34 μmol L(-1), 0.032-4.47 μmol L(-1), and 0.079-4.42 μmol L(-1) with detection limits of 6.0 nmol L(-1), 12.0 nmol L(-1), and 25.0 nmol L(-1), respectively. Moreover, the proposed method was successfully applied for the determination of the drug in biological fluids. The competitive mode based on CB[7] superstructure provided a promising assay strategy for fluorescence detection in various potential applications.

  4. Highly sensitive turn-on fluorescence detection of thrombomodulin based on fluorescence resonance energy transfer

    NASA Astrophysics Data System (ADS)

    Kong, Liyan; Zhu, Jiaming; Wang, Wen; Jin, Lehe; Fu, Yanjiao; Duan, Bohui; Tan, Liang

    2017-02-01

    As an integral glycoprotein on the surface of endothelial cells, thrombomodulin (TM) has very high affinity for thrombin. TM has been regarded to be a marker of endothelial damage since it can be released during endothelial cell injury. In this work, a highly sensitive fluorescence method for the quantitative detection of TM was developed. TM antibody (Ab) and bovine serum albumin (BSA) were bound on gold nanoparticles (AuNPs) to construct BSA-AuNPs-Ab nanocomposites and they were characterized by transmission electron microscope and UV-vis spectrophotometry. The fluorescence of acridine orange (AO) was quenched by the prepared gold nanocomposites based on fluorescence resonance energy transfer (FRET). In the presence of TM, the fluorescence was turned on due to the effective separation of AO from the surface of gold nanocomposites. Under optimum conditions, the enhanced fluorescence intensity displayed a linear relationship with the logarithm of the TM concentration from 0.1 pg mL- 1 to 5 ng mL- 1 with a low detection limit of 12 fg mL- 1. The release of soluble thrombomodulin (sTM) by the injured HUVEC-C cells in the presence of H2O2 was investigated using the proposed method. The released sTM content in the growth medium was found to be increased with the enhancement of contact time of the cells with H2O2.

  5. Field portable mobile phone based fluorescence microscopy for detection of Giardia lamblia cysts in water samples

    NASA Astrophysics Data System (ADS)

    Ceylan Koydemir, Hatice; Gorocs, Zoltan; McLeod, Euan; Tseng, Derek; Ozcan, Aydogan

    2015-03-01

    Giardia lamblia is a waterborne parasite that causes an intestinal infection, known as giardiasis, and it is found not only in countries with inadequate sanitation and unsafe water but also streams and lakes of developed countries. Simple, sensitive, and rapid detection of this pathogen is important for monitoring of drinking water. Here we present a cost-effective and field portable mobile-phone based fluorescence microscopy platform designed for automated detection of Giardia lamblia cysts in large volume water samples (i.e., 10 ml) to be used in low-resource field settings. This fluorescence microscope is integrated with a disposable water-sampling cassette, which is based on a flow-through porous polycarbonate membrane and provides a wide surface area for fluorescence imaging and enumeration of the captured Giardia cysts on the membrane. Water sample of interest, containing fluorescently labeled Giardia cysts, is introduced into the absorbent pads that are in contact with the membrane in the cassette by capillary action, which eliminates the need for electrically driven flow for sample processing. Our fluorescence microscope weighs ~170 grams in total and has all the components of a regular microscope, capable of detecting individual fluorescently labeled cysts under light-emitting-diode (LED) based excitation. Including all the sample preparation, labeling and imaging steps, the entire measurement takes less than one hour for a sample volume of 10 ml. This mobile phone based compact and cost-effective fluorescent imaging platform together with its machine learning based cyst counting interface is easy to use and can even work in resource limited and field settings for spatio-temporal monitoring of water quality.

  6. A label-free amplified fluorescence DNA detection based on isothermal circular strand-displacement polymerization reaction and graphene oxide.

    PubMed

    Li, Zhen; Zhu, Wenping; Zhang, Jinwen; Jiang, Jianhui; Shen, Guoli; Yu, Ruqin

    2013-07-07

    A label-free fluorescent DNA biosensor has been presented based on isothermal circular strand-displacement polymerization reaction (ICSDPR) combined with graphene oxide (GO) binding. The proposed method is simple and cost-effective with a low detection limit of 4 pM, which compares favorably with other GO-based homogenous DNA detection methods.

  7. "Turn off-on" fluorescent sensor for platinum drugs-DNA interactions based on quantum dots.

    PubMed

    Zhao, Dan; Li, Jiaotian; Yang, Tianming; He, Zhike

    2014-02-15

    A "turn off-on" mode has been established by using the interaction between platinum anticancer drugs and DNA as input signal and the fluorescence reversible change of quantum dots (QDs) as output signal. The QDs fluorescence can be quenched by platinum anticancer drugs via photo-induced electron transfer process, rendering the system into "turn off" status, and the system can then be "turned on" when fluorescence is restored due to covalent conjugation between DNA and platinum anticancer drugs. This dual-directional fluorescence change realized the detection of cisplatin and DNA, overcoming the selectivity problem commonly existed in the traditional mono-directional fluorescence detection mode. The reversible fluorescent "turn off-on" mode has been further employed to study the interactions between DNA and different platinum anticancer drugs (cisplatin, oxaliplatin and carboplatin). Furthermore, the impacts of different types of DNAs (different in base sequence, chain length and ssDNA/dsDNA) on the mode are also explored. This simple, fast and convenient spectroscopic method owns promising applications in the study on interaction between medical molecules and DNA, and in biochemical detections.

  8. Radioiodine detector based on laser induced fluorescence

    DOEpatents

    McDonald, Jimmie R.; Baronavski, Andrew P.

    1980-01-01

    The invention involves the measurement of the concentration of the radioisotope .sup.129 I.sub.2 in the presence of a gas. The invention uses a laser to excite a sample of the .sup.129 I.sub.2 in a sample gas chamber and a reference sample of a known concentration of .sup.129 I.sub.2 in a reference gas chamber. The .sup.129 I.sub.2 in the sample and reference gas chamber each gives off fluorescence emissions which are received by photomultipliers which provide signals to a detector. The detector uses a ratioing technique to determine the concentration of .sup.129 I.sub.2 in the sample gas chamber.

  9. Flavin-based fluorescent proteins: emerging paradigms in biological imaging.

    PubMed

    Mukherjee, Arnab; Schroeder, Charles M

    2015-02-01

    Flavin-based fluorescent proteins (FbFPs) are an emerging class of fluorescent reporters characterized by oxygen-independent fluorescence and a small size - key advantages compared to the green fluorescent protein (GFP). FbFPs are at a nascent stage of development. However, they have already been used as versatile reporters for studying anaerobic biosystems and viral assemblies. Recently, FbFPs with improved brightness and photostability have been engineered. In addition, several FbFPs show high degrees of thermal and pH stability. For these reasons, FbFPs hold strong promise to extend bioimaging to clinically and industrially significant systems that have been challenging to study using GFPs. In this review, we highlight recent developments in the FbFP toolbox and explore further improvements necessary to maximize the potential of FbFPs.

  10. Doped semiconductor nanocrystal based fluorescent cellular imaging probes.

    PubMed

    Maity, Amit Ranjan; Palmal, Sharbari; Basiruddin, S K; Karan, Niladri Sekhar; Sarkar, Suresh; Pradhan, Narayan; Jana, Nikhil R

    2013-06-21

    Doped semiconductor nanocrystals such as Mn doped ZnS, Mn doped ZnSe and Cu doped InZnS, are considered as new classes of fluorescent biological probes with low toxicity. Although the synthesis in high quality of such nanomaterials is now well established, transforming them into functional fluorescent probes remains a challenge. Here we report a fluorescent cellular imaging probe made of high quality doped semiconductor nanocrystals. We have identified two different coating approaches suitable for transforming the as synthesized hydrophobic doped semiconductor nanocrystals into water-soluble functional nanoparticles. Following these approaches we have synthesized TAT-peptide- and folate-functionalized nanoparticles of 10-80 nm hydrodynamic diameter and used them as a fluorescent cell label. The results shows that doped semiconductor nanocrystals can be an attractive alternative for conventional cadmium based quantum dots with low toxicity.

  11. DNA-Based Self-Assembly of Fluorescent Nanodiamonds.

    PubMed

    Zhang, Tao; Neumann, Andre; Lindlau, Jessica; Wu, Yuzhou; Pramanik, Goutam; Naydenov, Boris; Jelezko, Fedor; Schüder, Florian; Huber, Sebastian; Huber, Marinus; Stehr, Florian; Högele, Alexander; Weil, Tanja; Liedl, Tim

    2015-08-12

    As a step toward deterministic and scalable assembly of ordered spin arrays we here demonstrate a bottom-up approach to position fluorescent nanodiamonds (NDs) with nanometer precision on DNA origami structures. We have realized a reliable and broadly applicable surface modification strategy that results in DNA-functionalized and perfectly dispersed NDs that were then self-assembled in predefined geometries. With optical studies we show that the fluorescence properties of the nitrogen-vacancy color centers in NDs are preserved during surface modification and DNA assembly. As this method allows the nanoscale arrangement of fluorescent NDs together with other optically active components in complex geometries, applications based on self-assembled spin lattices or plasmon-enhanced spin sensors as well as improved fluorescent labeling for bioimaging could be envisioned.

  12. Motor Oil Classification Based on Time-Resolved Fluorescence

    PubMed Central

    Mu, Taotao; Chen, Siying; Zhang, Yinchao; Guo, Pan; Chen, He; Meng, Fandong

    2014-01-01

    A time-resolved fluorescence (TRF) technique is presented for classifying motor oils. The system is constructed with a third harmonic Nd:YAG laser, a spectrometer, and an intensified charge coupled device (ICCD) camera. Steady-state and time-resolved fluorescence (TRF) measurements are reported for several motor oils. It is found that steady-state fluorescence is insufficient to distinguish the motor oil samples. Then contour diagrams of TRF intensities (CDTRFIs) are acquired to serve as unique fingerprints to identify motor oils by using the distinct TRF of motor oils. CDTRFIs are preferable to steady-state fluorescence spectra for classifying different motor oils, making CDTRFIs a particularly choice for the development of fluorescence-based methods for the discrimination and characterization of motor oils. The two-dimensional fluorescence contour diagrams contain more information, not only the changing shapes of the LIF spectra but also the relative intensity. The results indicate that motor oils can be differentiated based on the new proposed method, which provides reliable methods for analyzing and classifying motor oils. PMID:24988439

  13. Fluorescence-based temperature control for polymerase chain reaction.

    PubMed

    Sanford, Lindsay N; Wittwer, Carl T

    2014-03-01

    The ability to accurately monitor solution temperature is important for the polymerase chain reaction (PCR). Robust amplification during PCR is contingent on the solution reaching denaturation and annealing temperatures. By correlating temperature to the fluorescence of a passive dye, noninvasive monitoring of solution temperatures is possible. The temperature sensitivity of 22 fluorescent dyes was assessed. Emission spectra were monitored and the change in fluorescence between 45 and 95°C was quantified. Seven dyes decreased in intensity as the temperature increased, and 15 were variable depending on the excitation wavelength. Sulforhodamine B (monosodium salt) exhibited a fold change in fluorescence of 2.85. Faster PCR minimizes cycling times and improves turnaround time, throughput, and specificity. If temperature measurements are accurate, no holding period is required even at rapid speeds. A custom instrument using fluorescence-based temperature monitoring with dynamic feedback control for temperature cycling amplified a fragment surrounding rs917118 from genomic DNA in 3min and 45s using 35 cycles, allowing subsequent genotyping by high-resolution melting analysis. Gold-standard thermocouple readings and fluorescence-based temperature differences were 0.29±0.17 and 0.96±0.26°C at annealing and denaturation, respectively. This new method for temperature cycling may allow faster speeds for PCR than currently considered possible.

  14. Doped semiconductor nanocrystal based fluorescent cellular imaging probes

    NASA Astrophysics Data System (ADS)

    Maity, Amit Ranjan; Palmal, Sharbari; Basiruddin, Sk; Karan, Niladri Sekhar; Sarkar, Suresh; Pradhan, Narayan; Jana, Nikhil R.

    2013-05-01

    Doped semiconductor nanocrystals such as Mn doped ZnS, Mn doped ZnSe and Cu doped InZnS, are considered as new classes of fluorescent biological probes with low toxicity. Although the synthesis in high quality of such nanomaterials is now well established, transforming them into functional fluorescent probes remains a challenge. Here we report a fluorescent cellular imaging probe made of high quality doped semiconductor nanocrystals. We have identified two different coating approaches suitable for transforming the as synthesized hydrophobic doped semiconductor nanocrystals into water-soluble functional nanoparticles. Following these approaches we have synthesized TAT-peptide- and folate-functionalized nanoparticles of 10-80 nm hydrodynamic diameter and used them as a fluorescent cell label. The results shows that doped semiconductor nanocrystals can be an attractive alternative for conventional cadmium based quantum dots with low toxicity.Doped semiconductor nanocrystals such as Mn doped ZnS, Mn doped ZnSe and Cu doped InZnS, are considered as new classes of fluorescent biological probes with low toxicity. Although the synthesis in high quality of such nanomaterials is now well established, transforming them into functional fluorescent probes remains a challenge. Here we report a fluorescent cellular imaging probe made of high quality doped semiconductor nanocrystals. We have identified two different coating approaches suitable for transforming the as synthesized hydrophobic doped semiconductor nanocrystals into water-soluble functional nanoparticles. Following these approaches we have synthesized TAT-peptide- and folate-functionalized nanoparticles of 10-80 nm hydrodynamic diameter and used them as a fluorescent cell label. The results shows that doped semiconductor nanocrystals can be an attractive alternative for conventional cadmium based quantum dots with low toxicity. Electronic supplementary information available: Characterization details of coating and

  15. Endoscopic Excision of Symptomatic Simple Bone Cyst at Skull Base

    PubMed Central

    Gunawat, Prashant; Karmarkar, Vikram; Deopujari, Chandrashekhar; Shah, Nishit

    2016-01-01

    Seizure is a classical feature of intra axial brain parenchymal lesion. Simple bone cyst is an unusual bony pathology at skull base presenting with unexpected symptoms of complex partial seizures. Skull base neuro-endoscopy has managed such lesions more effectively with reduced post-operative morbidity as compared to transcranial approach. This case report discusses a 20-year-old male who presented with 3 episodes of seizure over a time period of 10 months. MRI brain revealed T1 hypo and T2 hyper intense cystic lesion in middle cranial fossa with no enhancement on contrast administration. CT scan showed cystic lesion involving greater wing and pterygoid plate of sphenoid on left side. CT cisternographic evaluation showed CSF outpouching in the sphenoid air sinus. Excision of the cystic lesion was carried out through endoscopic transmaxillary transpterygoid approach. Histopathological examination showed the lesion to be a simple bone cyst. PMID:27891396

  16. Photophysical properties of pyrrolocytosine, a cytosine fluorescent base analogue†

    PubMed Central

    Nguyen, Quynh L.; Spata, Vincent A.

    2016-01-01

    The photophysical behavior of pyrrolocytosine (PC), a fluorescent base analogue of cytosine, has been investigated using theoretical approaches. The similarities between the PC and cytosine structures allow PC to maintain the pseudo-Watson–Crick base-pairing arrangement with guanine. Cytosine, similar to the other natural nucleobases, is practically non-fluorescent, because of ultrafast radiationless decay occurring through conical intersections. PC displays a much higher fluorescence quantum yield than cytosine, making it an effective fluorescent marker to study the structure, function, and dynamics of DNA/RNA complexes. Similar to 2-aminopurine, a constitutional isomer of adenine that base-pairs with thymine, PC's fluorescence is quenched when it is incorporated into a dinucleotide or a trinucleotide. In this work we examine the photophysical properties of isolated PC, microhydrated PC, as well as, complexes where PC is either base-stacked or hydrogen-bonded with guanine. Our results indicate that hydration affects the radiationless decay pathways in PC by destabilizing conical intersections. The calculations of dimers and trimers show that the radiative decay is affected by π stacking, while the presence of charge transfer states between PC and guanine may contribute to radiationless decay. PMID:27251599

  17. Luminol as a fluorescent acid-base indicator.

    PubMed

    Erdey, L; Buzás, I; Vigh, K

    1966-03-01

    The acid and base dissociation constants of luminol are determined at various ionic strengths. The transition interval occurs at pH 7.7-9.0, therefore luminol is a fluorescent indicator for the titration of strong and weak acids and strong bases. Its value as an indicator is established by titrating milk, red wine and cherry juice.

  18. Direct detection of sulfide ions [S2-] in aqueous media based on fluorescence quenching of functionalized CdS QDs at trace levels: analytical applications to environmental analysis.

    PubMed

    Gore, Anil H; Vatre, Sandip B; Anbhule, Prashant V; Han, Sung-Hwan; Patil, Shivajirao R; Kolekar, Govind B

    2013-03-07

    A novel, simple but highly selective fluorescent probe is developed for the direct detection of sulfide ions [S(2-)] based on the fluorescence quenching of the functionalized CdS QDs in aqueous solution at trace levels and successfully applied for quantitation of S(2-) from water samples in a complex matrix exclusive of pretreatment by standard addition method.

  19. Fluorescence-based characterization of non-fluorescent transient states of tryptophan – prospects for protein conformation and interaction studies

    NASA Astrophysics Data System (ADS)

    Hevekerl, Heike; Tornmalm, Johan; Widengren, Jerker

    2016-10-01

    Tryptophan fluorescence is extensively used for label-free protein characterization. Here, we show that by analyzing how the average tryptophan fluorescence intensity varies with excitation modulation, kinetics of tryptophan dark transient states can be determined in a simple, robust and reliable manner. Thereby, highly environment-, protein conformation- and interaction-sensitive information can be recorded, inaccessible via traditional protein fluorescence readouts. For verification, tryptophan transient state kinetics were determined under different environmental conditions, and compared to literature data. Conformational changes in a spider silk protein were monitored via the triplet state kinetics of its tryptophan residues, reflecting their exposure to an air-saturated aqueous solution. Moreover, tryptophan fluorescence anti-bunching was discovered, reflecting local pH and buffer conditions, previously observed only by ultrasensitive measurements in highly fluorescent photo-acids. Taken together, the presented approach, broadly applicable under biologically relevant conditions, has the potential to become a standard biophysical approach for protein conformation, interaction and microenvironment studies.

  20. Red Fluorescent Carbon Nanoparticle-Based Cell Imaging Probe.

    PubMed

    Ali, Haydar; Bhunia, Susanta Kumar; Dalal, Chumki; Jana, Nikhil R

    2016-04-13

    Fluorescent carbon nanoparticle-based probes with tunable visible emission are biocompatible, environment friendly and most suitable for various biomedical applications. However, synthesis of red fluorescent carbon nanoparticles and their transformation into functional nanoparticles are very challenging. Here we report red fluorescent carbon nanoparticle-based nanobioconjugates of <25 nm hydrodynamic size and their application as fluorescent cell labels. Hydrophobic carbon nanoparticles are synthesized via high temperature colloid-chemical approach and transformed into water-soluble functional nanoparticles via coating with amphiphilic polymer followed by covalent linking with desired biomolecules. Following this approach, carbon nanoparticles are functionalized with polyethylene glycol, primary amine, glucose, arginine, histidine, biotin and folic acid. These functional nanoparticles can be excited with blue/green light (i.e., 400-550 nm) to capture their emission spanning from 550 to 750 nm. Arginine and folic acid functionalized nanoparticles have been demonstrated as fluorescent cell labels where blue and green excitation has been used for imaging of labeled cells. The presented method can be extended for the development of carbon nanoparticle-based other bioimaging probes.

  1. A selective fluorescence probe for mercury ion based on the fluorescence quenching of terbium(III)-doped cadmium sulfide composite nanoparticles.

    PubMed

    Fu, Jie; Wang, Lun; Chen, Hongqi; Bo, Ling; Zhou, Cailing; Chen, Jingguo

    2010-10-15

    A fluorescent probe for mercury(II) ions, based on the quenching of fluorescence of terbium(III) ions doped in CdS nanoparticles, has been developed. The terbium(III)-doped cadmium sulfide composite nanoparticles were successfully synthesized through a straightforward one-pot process, with the biomolecule glutathione (GSH) as a capping ligand. In addition, the terbium(III) ions were observed an enhancement of emission intensity, owing to fluorescence energy transfer from the excited CdS particles to the emitting terbium(III). Because of a specific interaction, the fluorescence intensity of terbium(III)-doped CdS particles is obviously reduced in the presence of mercury(II) ions. The fluorescence quenching phenomenon of terbium(III) can be attributed to the fact that the energy transfer system was destroyed by combining with mercury(II). Under the optimal conditions, the fluorescent intensity of terbium(III) ions at 491nm decreased linearly with the concentration of mercury(II) ions ranging from 4.5nmolL(-1) to 550nmolL(-1). The limit of detection for mercury(II) was 0.1nmolL(-1). This method is simple, practical, relatively free of interference from coexisting substances and can be successfully applied to the determination of mercury(II) ions in real water samples. In addition, the probable mechanism of reaction between terbium(III)-doped CdS composite nanoparticles and mercury(II) was also discussed.

  2. Simple super-resolution live-cell imaging based on diffusion-assisted Förster resonance energy transfer

    PubMed Central

    Cho, Sangyeon; Jang, Jaeduck; Song, Chaeyeon; Lee, Heeyoung; Ganesan, Prabhakar; Yoon, Tae-Young; Kim, Mahn Won; Choi, Myung Chul; Ihee, Hyotcherl; Heo, Won Do; Park, YongKeun

    2013-01-01

    Despite the recent development of several super-resolution fluorescence microscopic techniques, there are still few techniques that can be readily employed in conventional imaging systems. We present a very simple, rapid, general and cost-efficient super-resolution imaging method, which can be directly employed in a simple fluorescent imaging system with general fluorophores. Based on diffusion-assisted Förster resonance energy transfer (FRET), fluorescent donor molecules that label specific target structures can be stochastically quenched by diffusing acceptor molecules, thereby temporally separating otherwise spatially overlapped fluorescence signals and allowing super-resolution imaging. The proposed method provides two- to three-fold-enhancement in spatial resolution, a significant optical sectioning property, and favorable temporal resolution in live-cell imaging. We demonstrate super-resolution live-cell dynamic imaging using general fluorophores in a standard epi-fluorescence microscope with light-emitting diode (LED) illumination. Due to the simplicity of this approach, we expect that the proposed method will prove an attractive option for super-resolution imaging. PMID:23383376

  3. A simple, rapid, and high-throughput fluorescence polarization immunoassay for simultaneous detection of organophosphorus pesticides in vegetable and environmental water samples

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A simple, rapid, and high-throughput fluorescent polarization immunoassay (FPIA) for simultaneous determination of organophosphorus pesticides (OPs) was developed. Three haptens were labeled with a fluorescein probe and used as tracers to develop a homogenous FPIA using a broad-specificity monoclon...

  4. Fluorescent switch for fast and selective detection of mercury (II) ions in vitro and in living cells and a simple device for its removal.

    PubMed

    Yuan, Yue; Jiang, Shenlong; Miao, Qingqing; Zhang, Jia; Wang, Mengjing; An, Linna; Cao, Qinjingwen; Guan, Yafeng; Zhang, Qun; Liang, Gaolin

    2014-07-01

    A water-soluble, biocompatible, and fluorescent chemosensor (1) for label-free, simple, and fast detection of mercury ions (Hg(2+)) in aqueous solutions and in HepG2 cells with high selectivity is reported herein. Chelation of 1 with Hg(2+) results in the disappearance of its fluorescence emission at 350 nm and the appearance of a new emission at 405 nm. Selectivity and interference studies indicated that 1 could be selectively chelated by Hg(2+) 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 Hg(2+) in living cells and for removing Hg(2+) from river water. Moreover, we also constructed a simple device for fast and effective removal of Hg(2+) from contaminated liquid samples.

  5. A Rapid Fluorescence-based Assay for Soluble Methane Monooxgyenase

    SciTech Connect

    Miller, Amber Reese; Keener, William Kelvin; Roberto, Francisco Figueroa; Watwood, Maribeth E.

    2002-01-01

    A fluorescence-based assay was developed to estimate soluble methane monooxygenase (sMMO) activity in solution. Whole cells of Methylosinus trichosporium OB3b expressing sMMO were used to oxidize various compounds to screen for fluorescent products. Of the 12 compounds tested, only coumarin yielded a fluorescent product. The UV absorbance spectrum of the product matches that of 7-hydroxycoumarin, and this identification was confirmed by 13C-NMR spectroscopy. The dependence of the fluorescent reaction on sMMO activity was investigated by pre-incubation with acetylene, a known inhibitor of sMMO activity. Apparent kinetic parameters for whole cells were determined to be Km(app)=262 µM and Vmax(app)=821 nmol 7-hydroxycoumarin min–1 mg protein–1. The rate of coumarin oxidation by sMMO correlates well with those of trichloroethylene degradation and naphthalene oxidation. Advantages of the fluorescence-based coumarin oxidation assay over the naphthalene oxidation assay include a more stable product, direct detection of the product without additional reagents, and greater speed and convenience.

  6. Fluorescence lifetime-based glucose sensor using NADH

    NASA Astrophysics Data System (ADS)

    von Ketteler, A.; Siegberg, D.; Herten, D. P.; Horn, C.; Petrich, W.

    2012-03-01

    Fluorescence lifetime-based glucose sensing does not depend on fluctuations of the intensity of the light source, light scattering, or changes in the transmission of optical components. Here we demonstrate the sensing of glucose based on the fluorescence lifetime properties of dihydro nicotinamide adenine dinucleotide (NADH), which is reduced from NAD in the presence of glucose and glucose dehydrogenase. In particular we use the difference in the fluorescence properties of free and protein-bound NADH and calculate an average fluorescence lifetime, which arises from the two short lifetimes τ1=0.28ns and τ2=0.60ns (representing free NADH) and the longer lifetime of τ3=2.9ns (for the protein-bound NADH). While initial results were derived from measurements in aqueous solution, we also demonstrate the suitability of this method for determining the concentration of glucose in blood using test strips. We find that the average fluorescence lifetime changes linearly by a factor of 0.17 per 100mg/dl change in glucose concentration. As an alternative the ratio between free and protein-bound components Rs/l may also be used for quantification. Rs/l increases by a factor of 0.74 per 100mg/dl change in glucose concentration.

  7. A virus-MIPs fluorescent sensor based on FRET for highly sensitive detection of JEV.

    PubMed

    Liang, Caishuang; Wang, Huan; He, Kui; Chen, Chunyan; Chen, Xiaoming; Gong, Hang; Cai, Changqun

    2016-11-01

    Major stumbling blocks in the recognition and detection of virus are the unstable biological recognition element or the complex detection means. Here a fluorescent sensor based on virus-molecular imprinted polymers (virus-MIPs) was designed for specific recognition and highly sensitive detection of Japanese encephalitis virus (JEV). The virus-MIPs were anchored on the surface of silica microspheres modified by fluorescent dye, pyrene-1-carboxaldehyde (PC). The fluorescence intensity of PC can be enhanced by the principle of fluorescence resonance energy transfer (FRET), where virus acted as energy donor and PC acted as energy acceptor. The enhanced fluorescence intensity was proportional to the concentration of virus in the range of 24-960pM, with a limit of detection (LOD, 3σ) of 9.6pM, and the relative standard deviation was 1.99%. In additional, the specificity study confirmed the resultant MIPs has high-selectivity for JEV. This sensor would become a new key for the detection of virus because of its high sensitive, simple operation, high stability and low cost.

  8. Performance validation of EMCCD and ICCD based near-infrared fluorescence imaging systems on a fluorescence solid phantom

    NASA Astrophysics Data System (ADS)

    Zhu, Banghe; Sevick-Muraca, Eva M.

    2012-03-01

    Near infrared (NIR) fluorescence imaging has been successfully applied for non-invasive assessment of both lymphatic architecture and function as well as potential disease markers of lymphatic dysfunction in clinical studies with intradermal injection of indocyanine green (ICG). For new "first-in-humans" NIR fluorescence imaging agents that need to be employed at far lower quantities, NIR fluorescence imaging devices with high measurement sensitivity are most favorable. However, the measurement sensitivity of NIR fluorescence imaging devices is limited by various parameters, including quantum efficiency of CCD chip, noise sources in the CCD camera, and the leakage of excitation light through optical filters. In this contribution, we present a quantum dot-based fluorescence solid phantom and its use for characterization of excitation light leakage and measurement sensitivity in both the intensified CCD (ICCD) and Electron Multiplying CCD (EMCCD) based NIR fluorescence imaging devices. The stability of the constructed quantum dot-based fluorescence solid phantom was first demonstrated and used to demonstrate higher measurement sensitivity compared of the ICCD as opposed to the EMCCD based NIR fluorescence imaging device when integration time were maintained less than 1.0 s. The phantom was used to assess the calculated transmission ratio, R, to minimize noise owing to excitation light leakage and show optimized filtering capabilities. The constructed quantum dot based solid phantom and the methodology for measuring parameters of transmission ratio and SNR can be used as a standard and quantifiable metric for installation and operational qualification of all NIR fluorescence imaging devices.

  9. Fluorescence resonance energy transfer from sulfonated graphene to riboflavin: a simple way to detect vitamin B2.

    PubMed

    Kundu, Aniruddha; Nandi, Sudipta; Layek, Rama K; Nandi, Arun K

    2013-08-14

    We have prepared sulfonated graphene (SG) by diazonium coupling technique and it has been characterized by UV-vis absorption spectroscopy, Raman spectroscopy, electron microscopy, energy-dispersive spectroscopy (EDS), EDS elemental mapping, X-ray photoelectron spectroscopy (XPS), and FTIR spectroscopy. The photoluminescence (PL) property of SG at different pH (pH 4, 7, and 9.2) has been investigated and SG shows highest PL-intensity and quantum yield at pH 4 compared to those at higher pH and that of GO at pH 4. Due to the strong overlap between the emission spectrum of SG and absorption spectrum of riboflavin (RF, vitamin B2) at pH 4, it has been tactfully used as donor for the fluorescence resonance energy transfer (FRET) process. However, graphene oxide (GO) does not exhibit any FRET with RF at an identical condition due to its much lower quantum yield. We have demonstrated a selective detection of vitamin B2 in presence of nucleic acid (DNA, RNA), protein (BSA), amino acid (Lysine) and other water-soluble vitamins (Becosules, Zevit capsules) based on the spontaneous FRET from PL-active SG (donor) to RF (acceptor). The calibration curve indicates excellent affirmation to detect vitamin B2 using FRET and it is superior to the ordinary fluorescence method of detecting RF in presence of different biomolecules.

  10. Broccoli: rapid selection of an RNA mimic of green fluorescent protein by fluorescence-based selection and directed evolution.

    PubMed

    Filonov, Grigory S; Moon, Jared D; Svensen, Nina; Jaffrey, Samie R

    2014-11-19

    Genetically encoded fluorescent ribonucleic acids (RNAs) have diverse applications, including imaging RNA trafficking and as a component of RNA-based sensors that exhibit fluorescence upon binding small molecules in live cells. These RNAs include the Spinach and Spinach2 aptamers, which bind and activate the fluorescence of fluorophores similar to that found in green fluorescent protein. Although additional highly fluorescent RNA-fluorophore complexes would extend the utility of this technology, the identification of novel RNA-fluorophore complexes is difficult. Current approaches select aptamers on the basis of their ability to bind fluorophores, even though fluorophore binding alone is not sufficient to activate fluorescence. Additionally, aptamers require extensive mutagenesis to efficiently fold and exhibit fluorescence in living cells. Here we describe a platform for rapid generation of highly fluorescent RNA-fluorophore complexes that are optimized for function in cells. This procedure involves selection of aptamers on the basis of their binding to fluorophores, coupled with fluorescence-activated cell sorting (FACS) of millions of aptamers expressed in Escherichia coli. Promising aptamers are then further optimized using a FACS-based directed evolution approach. Using this approach, we identified several novel aptamers, including a 49-nt aptamer, Broccoli. Broccoli binds and activates the fluorescence of (Z)-4-(3,5-difluoro-4-hydroxybenzylidene)-1,2-dimethyl-1H-imidazol-5(4H)-one. Broccoli shows robust folding and green fluorescence in cells, and increased fluorescence relative to Spinach2. This reflects, in part, improved folding in the presence of low cytosolic magnesium concentrations. Thus, this novel fluorescence-based selection approach simplifies the generation of aptamers that are optimized for expression and performance in living cells.

  11. Homogeneous plate based antibody internalization assay using pH sensor fluorescent dye.

    PubMed

    Nath, Nidhi; Godat, Becky; Zimprich, Chad; Dwight, Stephen J; Corona, Cesear; McDougall, Mark; Urh, Marjeta

    2016-04-01

    Receptor-mediated antibody internalization is a key mechanism underlying several anti-cancer antibody therapeutics. Delivering highly toxic drugs to cancer cells, as in the case of antibody drug conjugates (ADCs), efficient removal of surface receptors from cancer cells and changing the pharmacokinetics profile of the antibody drugs are some of key ways that internalization impacts the therapeutic efficacy of the antibodies. Over the years, several techniques have been used to study antibody internalization including radiolabels, fluorescent microscopy, flow cytometry and cellular toxicity assays. While these methods allow analysis of internalization, they have limitations including a multistep process and limited throughput and are generally endpoint assays. Here, we present a new homogeneous method that enables time and concentration dependent measurements of antibody internalization. The method uses a new hydrophilic and bright pH sensor dye (pHAb dye), which is not fluorescent at neutral pH but becomes highly fluorescent at acidic pH. For receptor mediated antibody internalization studies, antibodies against receptors are conjugated with the pHAb dye and incubated with the cells expressing the receptors. Upon binding to the receptor, the dyes conjugated to the antibody are not fluorescent because of the neutral pH of the media, but upon internalization and trafficking into endosomal and lysosomal vesicles the pH drops and dyes become fluorescent. The enabling attributes of the pHAb dyes are the hydrophilic nature to minimize antibody aggregation and bright fluorescence at acidic pH which allows development of simple plate based assays using a fluorescent reader. Using two different therapeutic antibodies--Trastuzumab (anti-HER2) and Cetuximab (anti-EGFR)--we show labeling with pHAb dye using amine and thiol chemistries and impact of chemistry and dye to antibody ration on internalization. We finally present two new approaches using the pHAb dye, which will be

  12. VCSEL-based flexible opto-fluidic fluorescence sensors

    NASA Astrophysics Data System (ADS)

    Kang, Dongseok; Gai, Boju; Yoon, Jongseung

    2016-03-01

    Flexible opto-fluidic fluorescence sensors based on microscale vertical cavity surface emitting lasers (micro-VCSELs) and silicon photodiodes (Si-PDs) are demonstrated, where arrays of 850 nm micro-VCSELs and thin film Si-PDs are heterogeneously integrated on a polyethylene terephthalate (PET) substrate by transfer printing, in conjunction with elastomeric fluidic channel. Enabled with optical isolation trenches together with wavelength- and angle-selective spectral filters implemented to suppress the absorption of excitation light, the integrated flexible fluorescence sensors exhibited significantly enhanced signal-to-background ratio, resulting in a maximum sensitivity of 5 × 10-5 wt% of infrared-absorbing organic dyes.

  13. Fluorescence-based Broad Dynamic Range Viscosity Probes.

    PubMed

    Dragan, Anatoliy; Graham, August E; Geddes, Chris D

    2014-03-01

    We introduce two new fluorescent viscosity probes, SYBR Green (SG) and PicoGreen (PG), that we have studied over a broad range of viscosity and in collagen solutions. In water, both dyes have low quantum yields and excited state lifetimes, while in viscous solvents or in complex with DNA both parameters dramatically (300-1000-fold) increase. We show that in log-log scale the dependence of the dyes' quantum yield vs. viscosity is linear, the slope of which is sensitive to temperature. Application of SG and PG, as a fluorescence-based broad dynamic range viscosity probes, to the life sciences is discussed.

  14. Magnetite nanoparticles for biosensor model based on bacteria fluorescence

    NASA Astrophysics Data System (ADS)

    Poita, A.; Creanga, D.-E.; Airinei, A.; Tupu, P.; Goiceanu, C.; Avadanei, O.

    2009-06-01

    Fluorescence emission of pyoverdine - the siderophore synthesized by iron scavenger bacteria - was studied using in vitro cultures of Pseudomonas aeruginosa with the aim to design a biosensor system for liquid sample iron loading. Diluted suspensions of colloidal magnetite nanoparticles were supplied in the culture medium (10 microl/l and 100 microl/l) to simulate magnetic loading with iron oxides of either environmental waters or human body fluids. The electromagnetic exposure to radiofrequency waves of bacterial samples grown in the presence of magnetic nanoparticles was also carried out. Cell density diminution but fluorescence stimulation following 10 microl/l ferrofluid addition and simultaneous exposure to radiofrequency waves was evidenced. The inhibitory influence of 100 microl/l ferrofluid combined with RF exposure was evidenced by fluorescence data. Mathematical model was proposed to approach quantitatively the dynamics of cell density and fluorescence emission in relation with the consumption of magnetite nanoparticle supplied medium. The biosensor scheme was shaped based on the response to iron loading of bacterial sample fluorescence.

  15. Advanced Fluorescence Protein-Based Synapse-Detectors

    PubMed Central

    Lee, Hojin; Oh, Won Chan; Seong, Jihye; Kim, Jinhyun

    2016-01-01

    The complex information-processing capabilities of the central nervous system emerge from intricate patterns of synaptic input-output relationships among various neuronal circuit components. Understanding these capabilities thus requires a precise description of the individual synapses that comprise neural networks. Recent advances in fluorescent protein engineering, along with developments in light-favoring tissue clearing and optical imaging techniques, have rendered light microscopy (LM) a potent candidate for large-scale analyses of synapses, their properties, and their connectivity. Optically imaging newly engineered fluorescent proteins (FPs) tagged to synaptic proteins or microstructures enables the efficient, fine-resolution illumination of synaptic anatomy and function in large neural circuits. Here we review the latest progress in fluorescent protein-based molecular tools for imaging individual synapses and synaptic connectivity. We also identify associated technologies in gene delivery, tissue processing, and computational image analysis that will play a crucial role in bridging the gap between synapse- and system-level neuroscience. PMID:27445785

  16. Fluorescence lifetime based characterization of active and tunable plasmonic nanostructures.

    PubMed

    Ashry, Islam; Zhang, Baigang; Khalifa, Moataz B; Calderone, Joseph A; Santos, Webster L; Heflin, James R; Robinson, Hans D; Xu, Yong

    2014-08-25

    We report a non-contact method that utilizes fluorescence lifetime (FL) to characterize morphological changes of a tunable plasmonic nanostructure with nanoscale accuracy. The key component of the plasmonic nanostructure is pH-responsive polyelectrolyte multilayers (PEMs), which serve as a dynamically tunable "spacer" layer that separates the plasmonic structure and the fluorescent materials. The validity of our method is confirmed through direct comparison with ellipsometry and atomic force microscopy (AFM) measurements. Applying the FL-based approach, we find that a monolayer polycation film responds to pH changes with significantly less hysteresis than a thicker multilayer film with polyelectrolytes of both charges. Additionally, we characterize an active and tunable plasmonic nanostructure composed of self-assembled fluorescent dye (Texas Red), pH-sensitive PEMs, and gold nanospheres adsorbed on the PEM surface. Our results point towards the possibility of using stimulus-sensitive polymers to construct active and tunable plasmonic nanodevices.

  17. Optical carbon dioxide sensor based on fluorescent capillary array

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Wen, Zhihui; Yang, Bo; Yang, Xuefeng

    A novel carbon dioxide (CO2) gas sensor based on capillary array is presented. The capillary array is composed of 51 capillaries and modified by fluorescent dye 8-hydroxy-1,3,6-pyrenetrisulfonic acid trisodium salt (HPTS, PTS-) and tetraoctylammonium cation (TOA+) doped porous ethyl cellulose. A Y-fiber is used to transmit exciting light and fluorescence. A fiber optic pigtail-contained spectrophotometer is used to collect and deal with optical signals. Due to its structural features, each capillary has the two rolling-up layers of inner and outer sensing films, which make the 2 cm long capillary array has large sensing area about 12.81 cm2 and the fluorescence signal easily be collected. The sensing probe has advantages such as small volume, compact structure and large sensing area. The results demonstrate that the sensor has a linear response in the CO2 volume ratio range from 0 to 10%.

  18. Gaseous ammonia fluorescence probe based on cellulose acetate modified microstructured optical fiber

    NASA Astrophysics Data System (ADS)

    Peng, Lirong; Yang, Xinghua; Yuan, Libo; Wang, Lili; Zhao, Enming; Tian, Fengjun; Liu, Yanxin

    2011-09-01

    In this article, we report a novel fluorescent ammonia gas probe based on microstructured optical fiber (MOF) which is modified with eosin-doped cellulose acetate film. This probe was fabricated by liquid fluxion coating process. Polymer solution doped with eosin was directly inhaled into 18 array holes of MOF and then formed matrix film in them. The sensing properties of the optical fiber sensor to gaseous ammonia at room temperature were investigated. The sensing probe showed different fluorescence intensity at 576 nm to different concentrations of trace ammonia in carrier gas of nitrogen. The response range was 50-400 ppm, with short response time within 500 ms. Furthermore, the response range could be tailored through CTAB co-entrapment process in the sensing film. These test results demonstrated that low cost, simple structured fiber optic sensors for detecting ammonia gas samples could be developed based on MOF.

  19. Multiplex fluorescent immunoassay device based on magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Godjevargova, T. I.; Ivanov, Y. L.; Dinev, D. D.

    2017-02-01

    Immunofluorescent analyzer based compact disc for simultaneous detection of 3 antibiotics in the same milk sample is consisting of two parts: CD-based immunofluorescence kit and optoelectronic fluorometer. Kit consists of 2 parts: Lyophilized immobilized antibodies on supermagnetic nanoparticles in Eppendorf tubes and CD-based microfluidic disk, in which are formed five chamber systems for simultaneous detecting of 5 separate samples. Each system consists of 2 chambers connected by a special micro channel acting as a hydrophobic valve. In the first chamber lyophilised conjugates of 3 antibiotics with accordingly 3 different fluorescent dyes are placed. The second chamber is for detection of fluorescent signal. The optoelectronic fluorometer is comprising of: integrated thermostatic block; mechanical-detecting unit (fluorometer) and block with controlling and visualizing electronics.The disc gets into a second block of the analyzer, where centrifugation is performed and also reporting of the fluorescent signals. This unit comprises a rotor on which the disc is fixed, permanent electromagnet in the form of a ring inserted under the disc and module of 3 LED diodes with emission filters for the relevant wavelengths corresponding to the used fluorescent dyes and 1 integrated photodiode, in front of which is mounted filter with 3 spectral peaks.The signal from the photodiode is detected by the electronic unit which is sensitive "lock-in" amplifier, the engine rotor management, control of thermostatic device and management of periphery of the analyzer, consisting of display and communications with computer.

  20. Biosensors based on surface plasmon-enhanced fluorescence spectroscopy.

    PubMed

    Dostálek, Jakub; Knoll, Wolfgang

    2008-09-01

    The implementation of surface plasmon-enhanced fluorescence spectroscopy (SPFS) to surface plasmon resonance (SPR) biosensors enables increasing their sensitivity by several orders of magnitude. In SPR-based biosensors, surface plasmons probe the binding of target molecules contained in a liquid sample by their affinity partners attached to a metallic sensor surface. SPR biosensors relying on the detection of refractive index changes allow for direct observation of the binding of large and medium size molecules that produces sufficiently large refractive index changes. In SPR biosensors exploiting SPFS, the capture of fluorophore-labeled molecules to the sensor surface is observed by the detection of fluorescence light emitted from the surface. This technique takes advantage of the enhanced intensity of electromagnetic field accompanied with the resonant excitation of surface plasmons. The interaction with surface plasmons can greatly increase the measured fluorescence signal through enhancing the excitation rate of fluorophores and by more efficient collecting of fluorescence light. SPFS-based biosensors were shown to enable the analysis of samples with extremely low analyte concentrations and the detection of small molecules. In this review, we describe the fundamental principles, implementations, and current state of the art applications of SPFS biosensors. This review focuses on SPFS-based biosensors employing the excitation of surface plasmons on continuous metal-dielectric interfaces.

  1. Simple noise-reduction method based on nonlinear forecasting

    NASA Astrophysics Data System (ADS)

    Tan, James P. L.

    2017-03-01

    Nonparametric detrending or noise reduction methods are often employed to separate trends from noisy time series when no satisfactory models exist to fit the data. However, conventional noise reduction methods depend on subjective choices of smoothing parameters. Here we present a simple multivariate noise reduction method based on available nonlinear forecasting techniques. These are in turn based on state-space reconstruction for which a strong theoretical justification exists for their use in nonparametric forecasting. The noise reduction method presented here is conceptually similar to Schreiber's noise reduction method using state-space reconstruction. However, we show that Schreiber's method has a minor flaw that can be overcome with forecasting. Furthermore, our method contains a simple but nontrivial extension to multivariate time series. We apply the method to multivariate time series generated from the Van der Pol oscillator, the Lorenz equations, the Hindmarsh-Rose model of neuronal spiking activity, and to two other univariate real-world data sets. It is demonstrated that noise reduction heuristics can be objectively optimized with in-sample forecasting errors that correlate well with actual noise reduction errors.

  2. Simple and robust diagnosis of early, small and AFP-negative primary hepatic carcinomas: an integrative approach of serum fluorescence and conventional blood tests

    PubMed Central

    Wang, Ting; Zhang, Kun-He; Hu, Piao-Ping; Huang, Zeng-Yong; Zhang, Pan; Wan, Qin-Si; Huang, De-Qiang; Lv, Nong-Hua

    2016-01-01

    The diagnosis of early, small and alpha-fetoprotein (AFP)-negative primary hepatic carcinomas (PHCs) remains a significant challenge. We developed a simple and robust approach to noninvasively detect these PHCs. A rapid, high-throughput and single-tube method was firstly developed to measure serum autofluorescence and cell-free DNA (cfDNA)-related fluorescence using a real-time PCR system, and both types of serum fluorescence were measured and routine laboratory data were collected in 1229 subjects, including 353 PHC patients, 331 liver cirrhosis (LC) patients, 213 chronic hepatitis (CH) patients and 332 normal controls (NC). The results showed that fluorescence indicators of PHC differed from those of NC, CH and LC to various extents, and all of them were not associated with age, gender, or AFP level. The logistic regression models established with the fluorescence indicators alone and combined with AFP, hepatic function tests and blood cell analyses were valuable for distinguishing early, small, AFP-negative and all PHC from LC, CH, NC and all non-PHC, with areas under the receiver operating characteristic curves 0.857–0.993 and diagnostic accuracies 80.2–97.7%. Conclusively, serum autofluorescence and cfDNA-related fluorescence are able to be rapidly and simultaneously measured by our simple method and valuable for diagnosing early, small and AFP-negative PHCs, especially integrating with AFP and conventional blood tests. PMID:27590520

  3. Simple and robust diagnosis of early, small and AFP-negative primary hepatic carcinomas: an integrative approach of serum fluorescence and conventional blood tests.

    PubMed

    Wang, Ting; Zhang, Kun-He; Hu, Piao-Ping; Huang, Zeng-Yong; Zhang, Pan; Wan, Qin-Si; Huang, De-Qiang; Lv, Nong-Hua

    2016-09-27

    The diagnosis of early, small and alpha-fetoprotein (AFP)-negative primary hepatic carcinomas (PHCs) remains a significant challenge. We developed a simple and robust approach to noninvasively detect these PHCs. A rapid, high-throughput and single-tube method was firstly developed to measure serum autofluorescence and cell-free DNA (cfDNA)-related fluorescence using a real-time PCR system, and both types of serum fluorescence were measured and routine laboratory data were collected in 1229 subjects, including 353 PHC patients, 331 liver cirrhosis (LC) patients, 213 chronic hepatitis (CH) patients and 332 normal controls (NC). The results showed that fluorescence indicators of PHC differed from those of NC, CH and LC to various extents, and all of them were not associated with age, gender, or AFP level. The logistic regression models established with the fluorescence indicators alone and combined with AFP, hepatic function tests and blood cell analyses were valuable for distinguishing early, small, AFP-negative and all PHC from LC, CH, NC and all non-PHC, with areas under the receiver operating characteristic curves 0.857-0.993 and diagnostic accuracies 80.2-97.7%. Conclusively, serum autofluorescence and cfDNA-related fluorescence are able to be rapidly and simultaneously measured by our simple method and valuable for diagnosing early, small and AFP-negative PHCs, especially integrating with AFP and conventional blood tests.

  4. The Fluorescence Enhancement of Mercury Detected in Food Based on Rhodamine Derivatives.

    PubMed

    Fan, Cai-ling; Xie, Pu-hui; Cui, Shu-min; Yang, Li-na; Sun, Qing; Ai, Zhi-lu

    2015-05-01

    Recently, the problem of food security is more and more serious, and people pay attention to mercury because of the toxic of it. A new approach for the determination of mercury content in foodstuff is devised. In this paper, first, we design and synthesis a new kind of fluorescent probe whose matrix based on rhodamine B, hydrazine hydrate and hydroxy benzaldehyde. Through the analysis of H-NMR spectra of the synthesized product L1, we confirm that the synthetic substance is the adjacent carboxyl benzaldehyde hydrazone structure generation of rhodamine B. Then, we measure the fluorescence signal intensity of the probe with different concentrations of mercury ions fully upon complexation by fluorescence spectrometer and we can study the relationship between the mercury ion concentration and the fluorescence intensity and draw the standard working curve. Following, It's time to discuss the microwave digestion processing of tea, after digestion we use the synthetic probe Li for determination of mercury content in tea. The experimental results show that the maximum excitation wavelength of the probe and coordination compound are 568. 05 and 560. 00 nm, the maximum emission wavelength are 587. 94 and 580. 00 nm. Then we can find the best testing conditions to improve the degree of accuracy, that is: room temperature, 50% the methanol solution, 3. 0 mL pH 4. 0 buffer solution, in the extent of 30 min. The experimental results show that Na+, K+, Ca2+, Cu2+, Zn2+, Al3+ have little impact on the fluorescence intensity of the:probe. Fe3+, Mg2+, Ba2+ has a weak enhancement to the fluorescence intensity of the probe. While a low concentrations of Hg2+ have an obviously enhanced effect on the fluorescence intensity of the probe. In contrast to other metal ions, the probe for Hg2+ has a good selectivity. Linear relationship between the magnitude of increase in fluorescence intensity and concentration of mercury ion was in the range of 5~20 ng . L-1 with detection limit (3S/N) of

  5. Simple, Scalable, Script-Based Science Processor (S4P)

    NASA Technical Reports Server (NTRS)

    Lynnes, Christopher; Vollmer, Bruce; Berrick, Stephen; Mack, Robert; Pham, Long; Zhou, Bryan; Wharton, Stephen W. (Technical Monitor)

    2001-01-01

    The development and deployment of data processing systems to process Earth Observing System (EOS) data has proven to be costly and prone to technical and schedule risk. Integration of science algorithms into a robust operational system has been difficult. The core processing system, based on commercial tools, has demonstrated limitations at the rates needed to produce the several terabytes per day for EOS, primarily due to job management overhead. This has motivated an evolution in the EOS Data Information System toward a more distributed one incorporating Science Investigator-led Processing Systems (SIPS). As part of this evolution, the Goddard Earth Sciences Distributed Active Archive Center (GES DAAC) has developed a simplified processing system to accommodate the increased load expected with the advent of reprocessing and launch of a second satellite. This system, the Simple, Scalable, Script-based Science Processor (S42) may also serve as a resource for future SIPS. The current EOSDIS Core System was designed to be general, resulting in a large, complex mix of commercial and custom software. In contrast, many simpler systems, such as the EROS Data Center AVHRR IKM system, rely on a simple directory structure to drive processing, with directories representing different stages of production. The system passes input data to a directory, and the output data is placed in a "downstream" directory. The GES DAAC's Simple Scalable Script-based Science Processing System is based on the latter concept, but with modifications to allow varied science algorithms and improve portability. It uses a factory assembly-line paradigm: when work orders arrive at a station, an executable is run, and output work orders are sent to downstream stations. The stations are implemented as UNIX directories, while work orders are simple ASCII files. The core S4P infrastructure consists of a Perl program called stationmaster, which detects newly arrived work orders and forks a job to run the

  6. High efficient solar tracker based on a simple shutter structure

    NASA Astrophysics Data System (ADS)

    Chen, Jin-Jia; Liu, Te-Shu; Huang, Kuang-Lung; Lin, Po-Chih

    2013-09-01

    In many photovoltaic (PV) or sunlight-illumination systems, solar trackers are always essential to obtain high energy/flux concentration efficiency, and that would lead to increase cost and extra power consumption due to the complex structure and heavy weight of the trackers. To decrease the cost while without sacrificing efficiency, a Fresnellens concentrator incorporated with a simple and cheap shutter, which consists of high reflective mirrors instead of conventional trackers, is proposed in this paper to provide solar tracking during the daytime. Thus, the time-variant and slant-incident sunlight rays can be redirected to vertically incident upon the surface of the Fresnel lens by appropriately arranging mirrors and swinging them to the proper slant angles with respect to the orientation of sunlight. The computer simulation results show that power concentration efficiency over 90%, as compared with the efficiency of directly normal incident sunlight, can be achieved with the mirror reflectance of 0.97 and for any solar incident angle within +/-75 degrees to the normal of the Fresnel lens. To verify the feasibility and performance of the concentrator with the proposed shutter, a sunlight illumination system based on this novel structure is demonstrated. Both computer simulation and practical measurement results for the prototype of the sunlight illumination system are also given to compare with. The results prove the simple and high efficient shutter applicable to general PV or sunlight-illumination systems for solar tracking.

  7. Nanoparticle-based energy transfer for rapid and simple detection of protein glycosylation

    SciTech Connect

    Oh, Eunkeu; Lee, Dohoon; Kim, Young-Pil; Cha, Seung YOUP; Oh, Doo BEYONG; Kim, Jungbae; Kang, Hyun AH; Kim, Hak SUNG

    2006-12-04

    Glycan moiety of glycoproteins plays an essential role in its biological activity in vivo, and the analysis of glycosylation is of great importance in the development of protein therapeutics. In this study, we report a rapid and simple detection of protein glycosylation based on the fluorescence resonance energy transfer (FRET) between concanavalin A-conjugated gold nanoparticles (ConA-AuNPs) and dextran-conjugated quantum dots (Dex-QDs). The increased photoluminescence (PL) signals of Dex-QDs due to the competitive inhibition of glycoproteins were well correlated with the glycosylation chain length of glucose oxidases as well as the mannosylation degree of bovine serum albumin (BSA). The parallel analysis of the diversely mannosylated BSAs using an image analyzer further demonstrated the potential of this new technique in high-throughput screening of glycoprotein and carbohydrate therapeutics.

  8. Simple-random-sampling-based multiclass text classification algorithm.

    PubMed

    Liu, Wuying; Wang, Lin; Yi, Mianzhu

    2014-01-01

    Multiclass text classification (MTC) is a challenging issue and the corresponding MTC algorithms can be used in many applications. The space-time overhead of the algorithms must be concerned about the era of big data. Through the investigation of the token frequency distribution in a Chinese web document collection, this paper reexamines the power law and proposes a simple-random-sampling-based MTC (SRSMTC) algorithm. Supported by a token level memory to store labeled documents, the SRSMTC algorithm uses a text retrieval approach to solve text classification problems. The experimental results on the TanCorp data set show that SRSMTC algorithm can achieve the state-of-the-art performance at greatly reduced space-time requirements.

  9. Electrospun sol-gel fibers for fluorescence-based sensing

    NASA Astrophysics Data System (ADS)

    Memisevic, Jasenka; Riley, Lela; Grant, Sheila A.

    2009-05-01

    Fluorescence based biosensors have the ability to provide reliable pathogen detection. However, the performance could be improved by enhancing the effective surface area of the biosensor. We report on a new nanofibrous fluorescencebased biosensor, whereas a sol-gel platform mesh was constructed by utilizing electrospinning techniques. Furthermore, incorporating cetyltrimethylammonium bromide (CTAB) and conducting pore-forming techniques resulted in a high surface area material suitable for biosensor immobilization. The biosensor was designed to detect Helicobacter hepaticus bacterium by sandwiching the pathogen between two antibodies, one labeled with Alexa Fluor 546 fluorescent dye and the other with 20nm Au nanoparticles. In the presence of pathogen, the close proximity of Au nanoparticles quenched the Alexa Fluor fluorescence, suggesting that the electrospun fiber platforms are suitable for sensing H. Hepaticus. Additionally, sol-gel fibers used as biosensor platform have the added benefit of increased immobilization, as fluorescence intensity from immobilized biosensors is 8.5x106 cps higher on fibers than on a flat, non-porous substrate.

  10. A fluorescence biosensor for VEGF detection based on DNA assembly structure switching and isothermal amplification.

    PubMed

    Li, Junlong; Sun, Kexin; Chen, Zhongping; Shi, Jifei; Zhou, Dandan; Xie, Guoming

    2017-03-15

    Vascular endothelial growth factor (VEGF) is an important biomarker in cancer angiogenesis. Here, we develop a aptasensor method for VEGF detection based on DNA assembly structure switching and isothermal amplification. The design employs a DNA assembly made of a isothermal amplification template, a aptamer, a primer and a protector chain. The DNA assembly is unable to undergo isothermal amplification in the absence of target. The presence of the target, however, triggers a structure switching event that causes hybridization of primer with template to facilitate isothermal amplification. Whereafter, toehold-mediated DNA strand displacement reaction between the generated (single-stranded DNA) ssDNA and fluorescent/quencher labeled probe are performed. Then, the increase in fluorescence provides an analytical signal. This strategy opens up a sensitive, selective and simple sensing platform for detection of VEGF. The system was also implemented to analyze the VEGF in human serum samples with satisfactory results.

  11. A coumarin-indole based colorimetric and 'turn on' fluorescent probe for cyanide

    NASA Astrophysics Data System (ADS)

    Xu, Yu; Dai, Xi; Zhao, Bao-Xiang

    2015-03-01

    A novel coumarin-indole based chemodosimeter with a simple structure was designed and prepared via a condensation reaction in high yield. The probe exhibited very high selectivity towards cyanide on both fluorescence and UV-vis spectra, which allowed it to quantitatively detect and imaging cyanide ions in organic-aqueous solution by either fluorescence enhancement or colorimetric changes. Confirmed by 1H NMR and HRMS spectra, the detection mechanism was proved to be related with the Michael addition reaction induced by cyanide ions, which blocked the intramolecular charge transfer (ICT) of the probe. Moreover, the probe was able to be utilized efficiently in a wide pH range (7.5-10) with negligible interference from other anions and a low detection limit of 0.51 μM. Application in 5 kinds of natural water source and accurate detection of cyanide in tap water solvent system also indicated the high practical significance of the probe.

  12. A reliable and sensitive bead-based fluorescence assay for identification of nucleic acid sequences

    NASA Astrophysics Data System (ADS)

    Klamp, Tobias; Yahiatène, Idir; Lampe, André; Schüttpelz, Mark; Sauer, Markus

    2011-03-01

    The sensitive and rapid detection of pathogenic DNA is of tremendous importance in the field of diagnostics. We demonstrate the ability of detecting and quantifying single- and double-stranded pathogenic DNA with picomolar sensitivity in a bead-based fluorescence assay. Selecting appropriate capturing and detection sequences enables rapid (2 h) and reliable DNA quantification. We show that synthetic sequences of S. pneumoniae and M. luteus can be quantified in very small sample volumes (20 μL) across a linear detection range over four orders of magnitude from 1 nM to 1 pM, using a miniaturized wide-field fluorescence microscope without amplification steps. The method offers single molecule detection sensitivity without using complex setups and thus volunteers as simple, robust, and reliable method for the sensitive detection of DNA and RNA sequences.

  13. Paper-based upconversion fluorescence resonance energy transfer biosensor for sensitive detection of multiple cancer biomarkers

    PubMed Central

    Xu, Sai; Dong, Biao; Zhou, Donglei; Yin, Ze; Cui, Shaobo; Xu, Wen; Chen, Baojiu; Song, Hongwei

    2016-01-01

    A paper-based upconversion fluorescence resonance energy transfer assay device is proposed for sensitive detection of CEA. The device is fabricated on a normal filter paper with simple nano-printing method. Upconversion nanoparticles tagged with specific antibodies are printed to the test zones on the test paper, followed by the introduction of assay antigen. Upconversion fluorescence measurements are directly conducted on the test zones after the antigen-to-antibody reactions. Furthermore, a multi-channel test paper for simultaneous detection of multiple cancer biomarkers was established by the same method and obtained positive results. The device showed high anti-interfere, stability, reproducible and low detection limit (0.89 ng/mL), moreover it is very easy to fabricate and operate, which is a promising prospect for a clinical point-of-care test. PMID:27001460

  14. A coumarin-indole based colorimetric and "turn on" fluorescent probe for cyanide.

    PubMed

    Xu, Yu; Dai, Xi; Zhao, Bao-Xiang

    2015-03-05

    A novel coumarin-indole based chemodosimeter with a simple structure was designed and prepared via a condensation reaction in high yield. The probe exhibited very high selectivity towards cyanide on both fluorescence and UV-vis spectra, which allowed it to quantitatively detect and imaging cyanide ions in organic-aqueous solution by either fluorescence enhancement or colorimetric changes. Confirmed by (1)H NMR and HRMS spectra, the detection mechanism was proved to be related with the Michael addition reaction induced by cyanide ions, which blocked the intramolecular charge transfer (ICT) of the probe. Moreover, the probe was able to be utilized efficiently in a wide pH range (7.5-10) with negligible interference from other anions and a low detection limit of 0.51μM. Application in 5 kinds of natural water source and accurate detection of cyanide in tap water solvent system also indicated the high practical significance of the probe.

  15. Photon upconversion in homogeneous fluorescence-based bioanalytical assays.

    PubMed

    Soukka, Tero; Rantanen, Terhi; Kuningas, Katri

    2008-01-01

    Upconverting phosphors (UCPs) are very attractive reporters for fluorescence resonance energy transfer (FRET)-based bioanalytical assays. The large anti-Stokes shift and capability to convert near-infrared to visible light via sequential absorption of multiple photons enable complete elimination of autofluorescence, which commonly impairs the performance of fluorescence-based assays. UCPs are ideal donors for FRET, because their very narrow-banded emission allows measurement of the sensitized acceptor emission, in principle, without any crosstalk from the donor emission at a wavelength just tens of nanometers from the emission peak of the donor. In addition, acceptor dyes emitting at visible wavelengths are essentially not excited by near-infrared, which further emphasizes the unique potential of upconversion FRET (UC-FRET). These characteristics result in favorable assay performance using detection instrumentation based on epifluorometer configuration and laser diode excitation. Although UC-FRET is a recently emerged technology, it has already been applied in both immunoassays and nucleic acid hybridization assays. The technology is also compatible with optically difficult biological samples, such as whole blood. Significant advances in assay performance are expected using upconverting lanthanide-doped nanocrystals, which are currently under extensive research. UC-FRET, similarly to other fluorescence techniques based on resonance energy transfer, is strongly distance dependent and may have limited applicability, for example in sandwich-type assays for large biomolecules, such as viruses. In this article, we summarize the essentials of UC-FRET, describe its current applications, and outline the expectations for its future potential.

  16. Determination of adenine based on the fluorescence recovery of the L-Tryptophan-Cu2+ complex

    NASA Astrophysics Data System (ADS)

    Duan, Ruilin; Li, Chunyan; Liu, Shaopu; Liu, Zhongfang; Li, Yuanfang; Yuan, Yusheng; Hu, Xiaoli

    2016-01-01

    A simple and sensitive method for determination of adenine was developed based on fluorescence quenching and recovery of L-Tryptophan (L-Trp). The fluorescence of L-Trp could efficiently quenched by copper ion compared with other common metal ions. Upon addition of adenine (Ade) in L-Trp-Cu(II) system, the fluorescence was reoccurred. Under the optimum conditions, the recovery fluorescence intensity was linearly correlated with the concentration of adenine in the range from 0.34 to 25.0 μmol L-1, with a correlation coefficient (R2) of 0.9994. The detection limit (3σ/k) was 0.046 μmol L-1, indicating that this method could applied to detect trace adenine. In this study, amino acids including L-Trp, D-Trp, L-Tyr, D-Tyr, L-Phe, D-Phe were investigated and only L-Trp could well chelated copper ion. Additionally, the mechanism of quench and recovery also were discussed and the method was successfully applied to detect the adenine in DNA with satisfactory results.

  17. Determination of adenine based on the fluorescence recovery of the L-Tryptophan-Cu(2+) complex.

    PubMed

    Duan, Ruilin; Li, Chunyan; Liu, Shaopu; Liu, Zhongfang; Li, Yuanfang; Yuan, Yusheng; Hu, Xiaoli

    2016-01-05

    A simple and sensitive method for determination of adenine was developed based on fluorescence quenching and recovery of L-Tryptophan (L-Trp). The fluorescence of L-Trp could efficiently quenched by copper ion compared with other common metal ions. Upon addition of adenine (Ade) in L-Trp-Cu(II) system, the fluorescence was reoccurred. Under the optimum conditions, the recovery fluorescence intensity was linearly correlated with the concentration of adenine in the range from 0.34 to 25.0μmolL(-1), with a correlation coefficient (R(2)) of 0.9994. The detection limit (3σ/k) was 0.046μmolL(-1), indicating that this method could applied to detect trace adenine. In this study, amino acids including L-Trp, D-Trp, L-Tyr, D-Tyr, L-Phe, D-Phe were investigated and only L-Trp could well chelated copper ion. Additionally, the mechanism of quench and recovery also were discussed and the method was successfully applied to detect the adenine in DNA with satisfactory results.

  18. A Graphene Oxide-Based Fluorescent Method for the Detection of Human Chorionic Gonadotropin

    PubMed Central

    Xia, Ning; Wang, Xin; Liu, Lin

    2016-01-01

    Human chorionic gonadotropin (hCG) has been regarded as a biomarker for the diagnosis of pregnancy and some cancers. Because the currently used methods (e.g., disposable Point of Care Testing (POCT) device) for hCG detection require the use of many less stable antibodies, simple and cost-effective methods for the sensitive and selective detection of hCG have always been desired. In this work, we have developed a graphene oxide (GO)-based fluorescent platform for the detection of hCG using a fluorescein isothiocyanate (FITC)-labeled hCG-specific binding peptide aptamer (denoted as FITC-PPLRINRHILTR) as the probe, which can be manufactured cheaply and consistently. Specifically, FITC-PPLRINRHILTR adsorbed onto the surface of GO via electrostatic interaction showed a poor fluorescence signal. The specific binding of hCG to FITC-PPLRINRHILTR resulted in the release of the peptide from the GO surface. As a result, an enhanced fluorescence signal was observed. The fluorescence intensity was directly proportional to the hCG concentration in the range of 0.05–20 IU/mL. The detection limit was found to be 20 mIU/mL. The amenability of the strategy to hCG analysis in biological fluids was demonstrated by assaying hCG in the urine samples. PMID:27754379

  19. Knowledge-based vision and simple visual machines.

    PubMed Central

    Cliff, D; Noble, J

    1997-01-01

    The vast majority of work in machine vision emphasizes the representation of perceived objects and events: it is these internal representations that incorporate the 'knowledge' in knowledge-based vision or form the 'models' in model-based vision. In this paper, we discuss simple machine vision systems developed by artificial evolution rather than traditional engineering design techniques, and note that the task of identifying internal representations within such systems is made difficult by the lack of an operational definition of representation at the causal mechanistic level. Consequently, we question the nature and indeed the existence of representations posited to be used within natural vision systems (i.e. animals). We conclude that representations argued for on a priori grounds by external observers of a particular vision system may well be illusory, and are at best place-holders for yet-to-be-identified causal mechanistic interactions. That is, applying the knowledge-based vision approach in the understanding of evolved systems (machines or animals) may well lead to theories and models that are internally consistent, computationally plausible, and entirely wrong. PMID:9304684

  20. A simple microviscometric approach based on Brownian motion tracking

    NASA Astrophysics Data System (ADS)

    Hnyluchová, Zuzana; Bjalončíková, Petra; Karas, Pavel; Mravec, Filip; Halasová, Tereza; Pekař, Miloslav; Kubala, Lukáš; Víteček, Jan

    2015-02-01

    Viscosity—an integral property of a liquid—is traditionally determined by mechanical instruments. The most pronounced disadvantage of such an approach is the requirement of a large sample volume, which poses a serious obstacle, particularly in biology and biophysics when working with limited samples. Scaling down the required volume by means of microviscometry based on tracking the Brownian motion of particles can provide a reasonable alternative. In this paper, we report a simple microviscometric approach which can be conducted with common laboratory equipment. The core of this approach consists in a freely available standalone script to process particle trajectory data based on a Newtonian model. In our study, this setup allowed the sample to be scaled down to 10 μl. The utility of the approach was demonstrated using model solutions of glycerine, hyaluronate, and mouse blood plasma. Therefore, this microviscometric approach based on a newly developed freely available script can be suggested for determination of the viscosity of small biological samples (e.g., body fluids).

  1. Simple, distance-based measurement for paper analytical devices.

    PubMed

    Cate, David M; Dungchai, Wijitar; Cunningham, Josephine C; Volckens, John; Henry, Charles S

    2013-06-21

    Paper-based analytical devices (PADs) represent a growing class of elegant, yet inexpensive chemical sensor technologies designed for point-of-use applications. Most PADs, however, still utilize some form of instrumentation such as a camera for quantitative detection. We describe here a simple technique to render PAD measurements more quantitative and straightforward using the distance of colour development as a detection motif. The so-called distance-based detection enables PAD chemistries that are more portable and less resource intensive compared to classical approaches that rely on the use of peripheral equipment for quantitative measurement. We demonstrate the utility and broad applicability of this technique with measurements of glucose, nickel, and glutathione using three different detection chemistries: enzymatic reactions, metal complexation, and nanoparticle aggregation, respectively. The results show excellent quantitative agreement with certified standards in complex sample matrices. This work provides the first demonstration of distance-based PAD detection with broad application as a class of new, inexpensive sensor technologies designed for point-of-use applications.

  2. Validation of a simple and fast method to quantify in vitro mineralization with fluorescent probes used in molecular imaging of bone

    SciTech Connect

    Moester, Martiene J.C.; Schoeman, Monique A.E.; Oudshoorn, Ineke B.; Beusekom, Mara M. van; Mol, Isabel M.; Kaijzel, Eric L.; Löwik, Clemens W.G.M.; Rooij, Karien E. de

    2014-01-03

    Highlights: •We validate a simple and fast method of quantification of in vitro mineralization. •Fluorescently labeled agents can detect calcium deposits in the mineralized matrix of cell cultures. •Fluorescent signals of the probes correlated with Alizarin Red S staining. -- Abstract: Alizarin Red S staining is the standard method to indicate and quantify matrix mineralization during differentiation of osteoblast cultures. KS483 cells are multipotent mouse mesenchymal progenitor cells that can differentiate into chondrocytes, adipocytes and osteoblasts and are a well-characterized model for the study of bone formation. Matrix mineralization is the last step of differentiation of bone cells and is therefore a very important outcome measure in bone research. Fluorescently labelled calcium chelating agents, e.g. BoneTag and OsteoSense, are currently used for in vivo imaging of bone. The aim of the present study was to validate these probes for fast and simple detection and quantification of in vitro matrix mineralization by KS483 cells and thus enabling high-throughput screening experiments. KS483 cells were cultured under osteogenic conditions in the presence of compounds that either stimulate or inhibit osteoblast differentiation and thereby matrix mineralization. After 21 days of differentiation, fluorescence of stained cultures was quantified with a near-infrared imager and compared to Alizarin Red S quantification. Fluorescence of both probes closely correlated to Alizarin Red S staining in both inhibiting and stimulating conditions. In addition, both compounds displayed specificity for mineralized nodules. We therefore conclude that this method of quantification of bone mineralization using fluorescent compounds is a good alternative for the Alizarin Red S staining.

  3. A label-free, fluorescence based assay for microarray

    NASA Astrophysics Data System (ADS)

    Niu, Sanjun

    DNA chip technology has drawn tremendous attention since it emerged in the mid 90's as a method that expedites gene sequencing by over 100-fold. DNA chip, also called DNA microarray, is a combinatorial technology in which different single-stranded DNA (ssDNA) molecules of known sequences are immobilized at specific spots. The immobilized ssDNA strands are called probes. In application, the chip is exposed to a solution containing ssDNA of unknown sequence, called targets, which are labeled with fluorescent dyes. Due to specific molecular recognition among the base pairs in the DNA, the binding or hybridization occurs only when the probe and target sequences are complementary. The nucleotide sequence of the target is determined by imaging the fluorescence from the spots. The uncertainty of background in signal detection and statistical error in data analysis, primarily due to the error in the DNA amplification process and statistical distribution of the tags in the target DNA, have become the fundamental barriers in bringing the technology into application for clinical diagnostics. Furthermore, the dye and tagging process are expensive, making the cost of DNA chips inhibitive for clinical testing. These limitations and challenges make it difficult to implement DNA chip methods as a diagnostic tool in a pathology laboratory. The objective of this dissertation research is to provide an alternative approach that will address the above challenges. In this research, a label-free assay is designed and studied. Polystyrene (PS), a commonly used polymeric material, serves as the fluorescence agent. Probe ssDNA is covalently immobilized on polystyrene thin film that is supported by a reflecting substrate. When this chip is exposed to excitation light, fluorescence light intensity from PS is detected as the signal. Since the optical constants and conformations of ssDNA and dsDNA (double stranded DNA) are different, the measured fluorescence from PS changes for the same

  4. Isothermal amplification of DNA using quadruplex primers with fluorescent pteridine base analogue 3-methyl isoxanthopterin.

    PubMed

    Gogichaishvili, Shota; Johnson, John; Gvarjaladze, David; Lomidze, Levan; Kankia, Besik

    2014-06-01

    We previously developed a method, known as quadruplex priming amplification (QPA), which greatly simplifies DNA amplification and quantification assays. QPA employs specific primers based on GGGTGGGTGGGTGGG (G3T) sequence, which upon polymerase elongation spontaneously dissociates from the target and folds into a stable quadruplex. Fluorescent nucleotide analogs, when incorporated into these primers, emit light upon quadruplex formation and permit simple, specific, and sensitive quantification without the attachment of probe molecules. Here, we studied optical [fluorescence and circular dichroism (CD)] and thermodynamic properties of the G3T sequence and variants incorporating 3-methylisoxanthopterin (3MI), a highly fluorescent nucleotide analog suitable for QPA. CD studies demonstrate that the incorporation of 3MI does not change the overall tertiary structure of G3T; however, thermal unfolding experiments revealed that it significantly destabilizes the quadruplex. Enzymatic studies revealed that Taq and Bst are practically unable to incorporate any nucleotides opposite to template 3MI. Based on this knowledge, we designed QPA assays with truncated targets that demonstrate efficient amplification around 55°C. Overall, these studies suggest that 3MI-based QPA is a useful assay for DNA amplification and detection.

  5. Fluorescence encoded super resolution imaging based on a location estimation algorithm for high-density fluorescence probes

    NASA Astrophysics Data System (ADS)

    Nishimura, Takahiro; Kimura, Hitoshi; Ogura, Yusuke; Tanida, Jun

    2016-11-01

    In this paper, we propose a fluorescence encoded super resolution technique based on an estimation algorithm to determine locations of high-density fluorescence emitters. In our method, several types of fluorescence coded probes are employed to reduce densities of target molecules labeled with individual codes. By applying an estimation algorithm to each coded image, the locations of the high density probes can be determined. Due to multiplexed fluorescence imaging, this approach will provide fast super resolution microscopy. In experiments, we evaluated the performance of the method using probes with different fluorescence wavelengths. Numerical simulation results show that the locations of probes with the density of 200 μ m^{-2} , which is a typical membrane-receptor expression level, are determined with acquisition of 16 different coded images.

  6. Fluorescence-lifetime-based sensors using inhomogeneous waveguiding

    NASA Astrophysics Data System (ADS)

    Draxler, Sonja; Kieslinger, Dietmar; Trznadel, Karolina; Lippitsch, Max E.

    1996-12-01

    Most intrinsic fiberoptic sensors are based on the evanescent-wave scheme, where the evanescent field of modes guided in a fiber reaches out into a chemically sensitive coating. In the commonly used multimode waveguides, the evanescent field contains only a small part of the total energy, however, thus making evanescent-wave sensors rather insensitive. Combining a transparent substrate and a transparent sensing layer of rather similar refractive index into a common waveguiding structure produces an inhomogeneous waveguide, where a large portion of the total energy transverses the sensing layer. This yields much superior sensor performance. The transmission through a waveguide is subject to various disturbing influences. Thus it is advantageous to combine the inhomogeneous waveguiding approach with a measuring scheme that is not prone to those disturbances. Such a scheme is available with fluorescence lifetime-based sensors. The fluorescence lifetime of an indicator incorporated into the sensing layer is changed by the presence of the respective analyte. This lifetime is independent of the transmission through the waveguide. Thus inhomogeneous waveguiding together with fluorescence lifetime measurement paves the way for optical chemical sensors with high analyte sensitivity and immunity to external disturbances.

  7. Hybridization assay based on evanescent fluorescence excitation and collection

    NASA Astrophysics Data System (ADS)

    Sumner, James J.; Mmerole, Robert U.; Stratis-Cullum, Dimitra N.; Yi, Hyunmin; Bentley, William E.; Gillespie, James B.

    2003-08-01

    There is a great need for high throughput and sensitive sensors for genetic analysis. These sensors can be used for varied purposes from monitoring gene expression in organims to speciation of possible pathogens. Consequently, an instrument capable of these tasks would be a great benefit for food and water safety, medical diagnostics and defense of military and civilian populations from biological threats. This work examines the development of a hybridization-based biosensor using a novel tapered fiber optic rpobe. The immobilization of single-stranded, synthetic ologinucleotides utilizing aminoproplytriethoxysilane and glutaraldehyde was implemented on the fiber optic sensor. Hybridization takes place with a complementary analyte sequence followed by a fluorescent, labeled signaling probe to form a sandwich assay. Following hybridization, the fiber is interrogated with a diode laser source and the resulting fluorescence signal is detected using a miniature spectrometer.

  8. Fluorescence based fiber optic and planar waveguide biosensors. A review.

    PubMed

    Benito-Peña, Elena; Valdés, Mayra Granda; Glahn-Martínez, Bettina; Moreno-Bondi, Maria C

    2016-11-02

    The application of optical biosensors, specifically those that use optical fibers and planar waveguides, has escalated throughout the years in many fields, including environmental analysis, food safety and clinical diagnosis. Fluorescence is, without doubt, the most popular transducer signal used in these devices because of its higher selectivity and sensitivity, but most of all due to its wide versatility. This paper focuses on the working principles and configurations of fluorescence-based fiber optic and planar waveguide biosensors and will review biological recognition elements, sensing schemes, as well as some major and recent applications, published in the last ten years. The main goal is to provide the reader a general overview of a field that requires the joint collaboration of researchers of many different areas, including chemistry, physics, biology, engineering, and material science.

  9. A New Fluorescent Sensor Based on Bisindolizine Derivative.

    PubMed

    I, Anitha; M, Sheela Gopal; Thomas, Divya

    2016-03-01

    A fluorescent sensor based on 1,2,1',2'- Tetra(methoxycarbonyl)- 3,3'- bis(p-methylbenzoyl)- 7,7'-bisindolizine (MBI) showing excellent selectivity towards Fe(3+) ions was developed. Under optimized experimental conditions, the fluorescence intensity of 1,2,1',2'- Tetramethoxycarbonyl- 3,3'- bis(p-methylbenzoyl)- 7,7'-bisindolizine was quenched linearly by Fe(3+) ions in the range of 2.00 × 10(-2) to 4.76 × 10(-3) M. The limit of detection was found to be 3.17 × 10(-3) M. The mechanism for quenching was investigated. The developed sensor was applied for the determination of Fe(3+) in pharmaceutical samples.

  10. Modulating fluorescence anisotropy of terminally labeled double-stranded DNA via the interaction between dye and nucleotides for rational design of DNA recognition based applications.

    PubMed

    Huang, Hongduan; Wei, Hejia; Zou, Mingjian; Xu, Xiao; Xia, Bin; Liu, Feng; Li, Na

    2015-03-03

    Effective signal enhancement for fluorescence anisotropy in a simple manner is most desirable for fluorescence anisotropy method development. This work aimed to provide insights into the fluorescence anisotropy of terminally labeled double-stranded DNA (dsDNA) to facilitate a facile and universal design strategy for DNA recognition based applications. We demonstrated that fluorescence anisotropy of dsDNA could be regulated by the nature of dyes, the molecular volume, and the end structure of dsDNA. Fluorescence anisotropy ascended with the increased number of base pairs up to 18 bp and leveled off thereafter, indicating the molecular volume was not the only factor responsible for fluorescence anisotropy. By choosing dyes with the positively charged center, high fluorescence anisotropy signal was obtained due to the confinement of the segmental motion of dyes through the electrostatic interaction. By properly designing the end structure of dsDNA, fluorescence anisotropy could be further improved by enlarging the effective overall rotational volume, as supported by two-dimensional (2D) (1)H-(1)H nuclear Overhauser enhancement spectroscopy (NOESY). With the successful enhancement of the fluorescence anisotropy for terminally labeled dsDNA, simple and universal designs were demonstrated by sensing of major classes of analytes from macromolecules (DNA and protein) to small molecules (cocaine).

  11. CINCH (confocal incoherent correlation holography) super resolution fluorescence microscopy based upon FINCH (Fresnel incoherent correlation holography)

    PubMed Central

    Siegel, Nisan; Storrie, Brian; Bruce, Marc

    2016-01-01

    FINCH holographic fluorescence microscopy creates high resolution super-resolved images with enhanced depth of focus. The simple addition of a real-time Nipkow disk confocal image scanner in a conjugate plane of this incoherent holographic system is shown to reduce the depth of focus, and the combination of both techniques provides a simple way to enhance the axial resolution of FINCH in a combined method called “CINCH”. An important feature of the combined system allows for the simultaneous real-time image capture of widefield and holographic images or confocal and confocal holographic images for ready comparison of each method on the exact same field of view. Additional GPU based complex deconvolution processing of the images further enhances resolution. PMID:26839443

  12. A colorimetric and fluorescent cyanide chemosensor based on dicyanovinyl derivatives: Utilization of the mechanism of intramolecular charge transfer blocking

    NASA Astrophysics Data System (ADS)

    Li, Qiao; Cai, Yi; Yao, Hong; Lin, Qi; Zhu, Yuan-Rong; Li, Hui; Zhang, You-Ming; Wei, Tai-Bao

    2015-02-01

    Chemosensor (CS1) was designed and synthesized by simple green chemistry procedure. CS1 exhibited both colorimetric and fluorescence turn-off responses for cyanide (CN-) ion in aqueous solution. The probe showed an immediate visible color changes from yellow to colorless and green fluorescence disappearance when CN- was added. The mechanism of chemosensor reaction with CN- was studied using 1HH NMR and 13C NMR spectroscopies and mass spectrometry. Moreover, test strips based on the sensor were fabricated, which served as convenient and efficient CN- test kits.

  13. Cyanine-based probe\\tag-peptide pair fluorescence protein imaging and fluorescence protein imaging methods

    DOEpatents

    Mayer-Cumblidge, M. Uljana; Cao, Haishi

    2013-01-15

    A molecular probe comprises two arsenic atoms and at least one cyanine based moiety. A method of producing a molecular probe includes providing a molecule having a first formula, treating the molecule with HgOAc, and subsequently transmetallizing with AsCl.sub.3. The As is liganded to ethanedithiol to produce a probe having a second formula. A method of labeling a peptide includes providing a peptide comprising a tag sequence and contacting the peptide with a biarsenical molecular probe. A complex is formed comprising the tag sequence and the molecular probe. A method of studying a peptide includes providing a mixture containing a peptide comprising a peptide tag sequence, adding a biarsenical probe to the mixture, and monitoring the fluorescence of the mixture.

  14. A simple enzyme based biosensor on flexible plastic substrate

    NASA Astrophysics Data System (ADS)

    Kanakamedala, Senaka K.; Alshakhouri, Haidar T.; Agarwal, Mangilal; Fang, Ji; DeCoster, Mark A.

    2010-08-01

    An enzyme based biosensor was fabricated by employing a simple, inexpensive and rapid xurography fabrication process. The electrodes and channel were made from the conducting polymer poly(3,4-ethyelenedioxythiphene) poly(styrene sulfonate) (PEDOT:PSS). PEDOT:PSS was selectively deposited using a polyimide tape mask. The tape mask was peeled off from the substrate after annealing the polymer in vacuum. Polymer wells of defined dimensions were made and were attached to the device to accommodate the solutions. This sensor utilizes the change in current as a parameter to measure different analyte concentrations. Initial experiments were done by using the sensor for glucose detection. The sensor is able to detect the glucose concentrations approximately from 1 μM to 10 mM range covering glucose in human saliva (8-210 μM). The glucose oxidase activity was independently measured using colorimetric method and the results indicate that the sensor retains the enzyme activity and can be used as a biosensor to detect various analytes. The analyte of interest can be measured by preloading the corresponding enzyme into the wells.

  15. Soil moisture downscaling using a simple thermal based proxy

    NASA Astrophysics Data System (ADS)

    Peng, Jian; Loew, Alexander; Niesel, Jonathan

    2016-04-01

    Microwave remote sensing has been largely applied to retrieve soil moisture (SM) from active and passive sensors. The obvious advantage of microwave sensor is that SM can be obtained regardless of atmospheric conditions. However, existing global SM products only provide observations at coarse spatial resolutions, which often hamper their applications in regional hydrological studies. Therefore, various downscaling methods have been proposed to enhance the spatial resolution of satellite soil moisture products. The aim of this study is to investigate the validity and robustness of a simple Vegetation Temperature Condition Index (VTCI) downscaling scheme over different climates and regions. Both polar orbiting (MODIS) and geostationary (MSG SEVIRI) satellite data are used to improve the spatial resolution of the European Space Agency's Water Cycle Multi-mission Observation Strategy and Climate Change Initiative (ESA CCI) soil moisture, which is a merged product based on both active and passive microwave observations. The results from direct validation against soil moisture in-situ measurements, spatial pattern comparison, as well as seasonal and land use analyses show that the downscaling method can significantly improve the spatial details of CCI soil moisture while maintain the accuracy of CCI soil moisture. The application of the scheme with different satellite platforms and over different regions further demonstrate the robustness and effectiveness of the proposed method. Therefore, the VTCI downscaling method has the potential to facilitate relevant hydrological applications that require high spatial and temporal resolution soil moisture.

  16. Feasibility of a simple microsieve-based immunoassay platform.

    PubMed

    Zweitzig, Daniel R; Tibbe, Arjan G; Nguyen, Ai T; van Rijn, Cees J M; Kopnitsky, Mark J; Cichonski, Kathleen; Terstappen, Leon W M M

    2016-10-01

    The intrinsic properties of silicon microsieves, such as an optically flat surface, high overall porosity, and low flow resistance have led to an increasing number of biotechnology applications. In this report, the feasibility of creating a microsieve-based immunoassay platform was explored. Microsieves containing 5μm pores were coupled with poly-acrylic acid chains, and then mounted into a plastic holder to enable rapid reagent exchanges via a wicking mechanism. The mounted microsieves were coated with infectious disease-related antigens at [2.5 and 25μg/mL], [20 and 50μg/mL], and [20 and 100μg/mL] to facilitate detection of serum-derived human antibodies against Rubella (3-day measles), B. burgdorferi (Lyme disease), or T. pallidum (syphilis), respectively. The prototype microsieve-based immunoassay platform was able to distinguish positive control sera containing antibodies against Rubella, T. pallidum, and B. burgdorferi from negative control sera with similar qualitative results as FDA-approved ELISA tests. Testing of a WHO IgG syphilitic standard at 0.3, 0.15, 0.075, 0.0375, and 0.01875IU/mL demonstrated that the T. pallidum microsieve assay is able to distinguish disease-specific IgG signal from background signal at similar, and possibly lower, levels than the corresponding ELISA. The T. pallidum microsieve assay prototype also differentiated positive clinical serum samples from negative donor samples, and the results were in good agreement with ELISA (R(2)=0.9046). These feasibility studies demonstrate the potential for utilizing microsieves, along with a reagent wicking device, as a simple diagnostic immunoassay platform.

  17. A simple fluorescence labeling method to visualize the three-dimensional arrangement of collagen fibers in the equine periodontal ligament.

    PubMed

    Staszyk, Carsten; Gasse, Hagen

    2004-04-01

    In order to display the collagen-fiber arrangement in the equine periodontal ligament an inexpensive and easy staining procedure with fluorescein was applied to paraffin sections. After fluorescein labeling a section was suitable for successful examination with three special microscopical systems: a) fluorescence microscopy b) phase contrast microscopy and c) polarized light microscopy. Collagen fibers were clearly displayed as compact structures in the fluorescence microscope. This distinct feature of the fluorescent image generated an almost three-dimensional impression of the fiber arrangement. Phase contrast microscopy and polarized light microscopical investigations of the same section supplemented the findings with further structural details. This contributed to demonstration of the complex architecture of the PDL, i. e. the varying sizes of the fiber bundles, their specific spatial alignment, and the entheses to the dental cementum.

  18. Fluorescence-based characterization of non-fluorescent transient states of tryptophan – prospects for protein conformation and interaction studies

    PubMed Central

    Hevekerl, Heike; Tornmalm, Johan; Widengren, Jerker

    2016-01-01

    Tryptophan fluorescence is extensively used for label-free protein characterization. Here, we show that by analyzing how the average tryptophan fluorescence intensity varies with excitation modulation, kinetics of tryptophan dark transient states can be determined in a simple, robust and reliable manner. Thereby, highly environment-, protein conformation- and interaction-sensitive information can be recorded, inaccessible via traditional protein fluorescence readouts. For verification, tryptophan transient state kinetics were determined under different environmental conditions, and compared to literature data. Conformational changes in a spider silk protein were monitored via the triplet state kinetics of its tryptophan residues, reflecting their exposure to an air-saturated aqueous solution. Moreover, tryptophan fluorescence anti-bunching was discovered, reflecting local pH and buffer conditions, previously observed only by ultrasensitive measurements in highly fluorescent photo-acids. Taken together, the presented approach, broadly applicable under biologically relevant conditions, has the potential to become a standard biophysical approach for protein conformation, interaction and microenvironment studies. PMID:27748381

  19. Sensitive turn-on fluorescent detection of tartrazine based on fluorescence resonance energy transfer.

    PubMed

    Huang, Sheng Tian; Shi, Yan; Li, Nian Bing; Luo, Hong Qun

    2012-01-18

    We introduce a sensitive, rapid, label-free and general fluorescent method for the determination of tartrazine by competitive binding to reduced graphene oxide (rGO) against fluorescein, and the fluorescence recovery upon fluorescein desorption from rGO provides a quantitative readout for tartrazine, giving a detection limit of 0.53 ng mL(-1).

  20. Expression-Enhanced Fluorescent Proteins Based on Enhanced Green Fluorescent Protein for Super-resolution Microscopy.

    PubMed

    Duwé, Sam; De Zitter, Elke; Gielen, Vincent; Moeyaert, Benjamien; Vandenberg, Wim; Grotjohann, Tim; Clays, Koen; Jakobs, Stefan; Van Meervelt, Luc; Dedecker, Peter

    2015-10-27

    "Smart fluorophores", such as reversibly switchable fluorescent proteins, are crucial for advanced fluorescence imaging. However, only a limited number of such labels is available, and many display reduced biological performance compared to more classical variants. We present the development of robustly photoswitchable variants of enhanced green fluorescent protein (EGFP), named rsGreens, that display up to 30-fold higher fluorescence in E. coli colonies grown at 37 °C and more than 4-fold higher fluorescence when expressed in HEK293T cells compared to their ancestor protein rsEGFP. This enhancement is not due to an intrinsic increase in the fluorescence brightness of the probes, but rather due to enhanced expression levels that allow many more probe molecules to be functional at any given time. We developed rsGreens displaying a range of photoswitching kinetics and show how these can be used for multimodal diffraction-unlimited fluorescence imaging such as pcSOFI and RESOLFT, achieving a spatial resolution of ∼70 nm. By determining the first ever crystal structures of a negative reversibly switchable FP derived from Aequorea victoria in both the "on"- and "off"-conformation we were able to confirm the presence of a cis-trans isomerization and provide further insights into the mechanisms underlying the photochromism. Our work demonstrates that genetically encoded "smart fluorophores" can be readily optimized for biological performance and provides a practical strategy for developing maturation- and stability-enhanced photochromic fluorescent proteins.

  1. Hybrid Integrated Silicon Microfluidic Platform for Fluorescence Based Biodetection

    PubMed Central

    Chandrasekaran, Arvind; Acharya, Ashwin; You, Jian Liang; Soo, Kim Young; Packirisamy, Muthukumaran; Stiharu, Ion; Darveau, Andre

    2007-01-01

    The desideratum to develop a fully integrated Lab-on-a-chip device capable of rapid specimen detection for high throughput in-situ biomedical diagnoses and Point-of-Care testing applications has called for the integration of some of the novel technologies such as the microfluidics, microphotonics, immunoproteomics and Micro Electro Mechanical Systems (MEMS). In the present work, a silicon based microfluidic device has been developed for carrying out fluorescence based immunoassay. By hybrid attachment of the microfluidic device with a Spectrometer-on-chip, the feasibility of synthesizing an integrated Lab-on-a-chip type device for fluorescence based biosensing has been demonstrated. Biodetection using the microfluidic device has been carried out using antigen sheep IgG and Alexafluor-647 tagged antibody particles and the experimental results prove that silicon is a compatible material for the present application given the various advantages it offers such as cost-effectiveness, ease of bulk microfabrication, superior surface affinity to biomolecules, ease of disposability of the device etc., and is thus suitable for fabricating Lab-on-a-chip type devices.

  2. Folding coupled with assembly in split green fluorescent proteins studied by structure-based molecular simulations.

    PubMed

    Ito, Mashiho; Ozawa, Takeaki; Takada, Shoji

    2013-10-24

    Split green fluorescent protein (GFP) is a powerful tool for imaging of protein-protein interactions in living cells, but molecular mechanisms of the folding and the assembly of split GFPs are poorly understood. Here, using a simple Go model that is based on the energy landscape theory, we performed comprehensive folding simulations of six split GFPs with different split points. Of the six, the fluorescence recovery was reported in four but not in the other two. In the simulations, we found that when the complete folding and assembly were observed, the N-terminal fragment always folded earlier than the C-terminal fragment. The in silico folding rates of the split GFPs were larger for the four split GFPs that the fluorescence recovery was reported in literature. The stability of standalone N-terminal fragments were well-correlated with the folding rates of split GFPs. These suggest that the efficient folding and assembly of split GFPs are realized when the N-terminal fragment folds spontaneously with the central α-helix as a nucleation core and that the C-terminal fragment folding is coupled to the assembly to the preformed N-terminal fragment.

  3. DNA base-pair flipping with fluorescent perylenediimide pincers.

    PubMed

    Zeidan, Tarek A; Hariharan, Mahesh; Siegmund, Karsten; Lewis, Frederick D

    2010-07-30

    The synthesis, structure, and electronic spectra of a series of DNA hairpins possessing two perylenediimide (PDI) base pair surrogates are reported. The PDI chromophores are located in opposite strands of the hairpin base pair domain opposite abasic sites and are either adjacent to each other or separated by a variable number of AT or GC base pairs. Molecular modeling of the conjugate having adjacent PDI chromophores shows that they adopt a slipped, pi-stacked geometry with an angle of 40 degrees between the PDI long axes. The electronic absorption, fluorescence, and circular dichroism of this conjugate are consistent with a stacked PDI structure. Conjugates having one or two GC base pairs between the PDI chromophores display spectra that are consistent with isolated PDIs. Conjugates having 1-4 AT base pairs have more complex spectra, suggestive of an equilibrium between base paired and flipped structures having stacked PDIs. Heating of the conjugates possessing isolated PDI chromophores results in base pair flipping. The free energy for PDI stacking is greater than that for a single AT base pair and comparable to that for a single GC base pair or two AT base pairs.

  4. Introducing a fluorescence-based standard to quantify protein partitioning into membranes.

    PubMed

    Thomas, Franziska A; Visco, Ilaria; Petrášek, Zdeněk; Heinemann, Fabian; Schwille, Petra

    2015-11-01

    The affinity of peripheral membrane proteins for a lipid bilayer can be described using the partition coefficient (KP). Although several methods to determine KP are known, all possess limitations. To address some of these issues, we developed both: a versatile method based on single molecule detection and fluorescence imaging for determining KP, and a simple measurement standard employing hexahistidine-tagged enhanced green fluorescent protein (eGFP-His6) and free standing membranes of giant unilamellar vesicles (GUVs) functionalized with NTA(Ni) lipids as binding sites. To ensure intrinsic control, our method features two measurement modes. In the single molecule mode, fluorescence correlation spectroscopy (FCS) is applied to quantify free and membrane associated protein concentrations at equilibrium and calculate KP. In the imaging mode, confocal fluorescence images of GUVs are recorded and analyzed with semi-automated software to extract protein mean concentrations used to derive KP. Both modes were compared by determining the affinity of our standard, resulting in equivalent KP values. As observed in other systems, eGFP-His6 affinity for membranes containing increasing amounts of NTA(Ni) lipids rises in a stronger-than-linear fashion. We compared our dual approach with a FCS-based assay that uses large unilamellar vesicles (LUVs), which however fails to capture the stronger-than-linear trend for our NTA(Ni)-His6 standard. Hence, we determined the KP of the MARCKS effector domain with our FCS approach on GUVs, whose results are consistent with previously published data using LUVs. We finally provide a practical manual on how to measure KP and understand it in terms of molecules per lipid surface.

  5. Highly adaptable and sensitive protease assay based on fluorescence resonance energy transfer.

    PubMed

    Zauner, Thomas; Berger-Hoffmann, Renate; Müller, Katrin; Hoffmann, Ralf; Zuchner, Thole

    2011-10-01

    Proteases are widely used in analytical sciences and play a central role in several widespread diseases. Thus, there is an immense need for highly adaptable and sensitive assays for the detection and monitoring of various proteolytic enzymes. We established a simple protease fluorescence resonance energy transfer (pro-FRET) assay for the determination of protease activities, which could in principle be adapted for the detection of all proteases. As proof of principle, we demonstrated the potential of our method using trypsin and enteropeptidase in complex biological mixtures. Briefly, the assay is based on the cleavage of a FRET peptide substrate, which results in a dramatic increase of the donor fluorescence. The assay was highly sensitive and fast for both proteases. The detection limits for trypsin and enteropeptidase in Escherichia coli lysate were 100 and 10 amol, respectively. The improved sensitivity for enteropeptidase was due to the application of an enzyme cascade, which leads to signal amplification. The pro-FRET assay is highly specific as even high concentrations of other proteases did not result in significant background signals. In conclusion, this sensitive and simple assay can be performed in complex biological mixtures and can be easily adapted to act as a versatile tool for the sensitive detection of proteases.

  6. Synthesis of Functional Fluorescent BODIPY‐based Dyes through Electrophilic Aromatic Substitution: Straightforward Approach towards Customized Fluorescent Probes

    PubMed Central

    Schoenmakers, Daniël C.; Veranič, Peter; Muševič, Igor

    2016-01-01

    Abstract Fluorescent materials are widely used in biological and material applications as probes for imaging or sensing; however, their customization is usually complicated without the support of an organic chemistry laboratory. Here, we present a straightforward method for the customization of BODIPY cores, which are among the most commonly used fluorescent probes. The method is based on the formation of a new C−C bond through Friedel–Crafts electrophilic aromatic substitution carried out at room temperature. The method presented can be used to obtain completely customized fluorescent materials in one or two steps from commercially available compounds. Examples of the preparation of fluorescent materials for cell staining and functionalization of silica colloids are also presented. PMID:27777837

  7. Monitoring water supplies for weaponized bacteria and bacterial toxins using rapid fluorescence-based viability and affinity assays

    NASA Astrophysics Data System (ADS)

    Van Tassell, Roger L.; Evans, Mishell

    2004-03-01

    The rapid detection of weaponized bacteria and toxins is a major problem during a biological attack. Although sensitive detection formats exist for many biowarfare agents, they often require advanced training and complex procedures. Luna has developed simple, rapid means for determining the presence of pathogens and bacterial toxins in water supplies using fluorescence-based assays that can be adapted for field use. The batteries of rapid assays are designed for i) determining cell viability and bacterial loads by exploiting metabolic markers (e.g., acid-production, redox potentials, etc) and ii) detecting bacterial toxins using fluorescent, polymerized affinity liposomes (fluorosomes). The viability assays were characterized using E. coli, S. aureus and the anthrax simulant, B. globigii. The viability assays detected bacterial loads of ~ 104 CFU/ml and with simple filtration ~ 100CFU/ml could be detected. The affinity fluorosomes were characterized using cholera toxin (CT). Affinity liposomes displaying GM1 and anti-CT antibodies could detect CT at <μg/ml levels. Stability studies showed that affinity vesicles could be stored for weeks at 4°C or freeze-dried with no significant loss of binding capacity. Using an in-house fiber optic fluorescence system, Luna characterized the binding of affinity fluorosomes to respective targets and determined the responses of bacterial loads in the fluorescent viability assays. Using this two-tiered approach, Luna demonstrated that water susceptible to sabotage could be easily monitored and confirmed for specific agents using simple, general and specific fluorescence-based detection schemes based on metabolism and ligand-target interactions.

  8. Fluorescence turn-on sensing of protein based on mannose functionalized perylene bisimides and its fluorescence imaging.

    PubMed

    Wang, Ke-Rang; An, Hong-Wei; Rong, Rui-Xue; Cao, Zhi-Ran; Li, Xiao-Liu

    2014-08-15

    A new water-soluble glycocluster based on perylene bisimides PBI-12-Man has been designed and synthesized, and its specific and selective binding property with Concanavalin A (Con A) has been investigated by fluorescence spectroscopy and circular dichroism (CD) spectroscopy, which showed strong binding affinity for Con A with the binding constant of 8.2×10(5)M(-1) for monomeric mannose unit, two orders of magnitude higher than the corresponding monosaccharide ligand. Most interestingly, a fluorescence enhancement of PBI-12-Man was observed upon binding with Con A because of deaggregation of the self-assembly of PBI-12-Man induced by carbohydrate-protein interaction, and the further study of the fluorescence enhancement with macrophage cells showed that PBI-12-Man as a biocompatible agent had fluorescence imaging of the surface mannose receptor of the cells. Such fluorescence turn-on sensing of protein based on carbohydrate-protein interactions would facilitate the development of new protein-specific fluorescent probe for diagnosis and molecular imaging under live cell conditions.

  9. Miniature fiber optic sensor based on fluorescence energy transfer

    NASA Astrophysics Data System (ADS)

    Meadows, David L.; Schultz, Jerome S.

    1992-04-01

    Optical fiber biosensors based on fluorescence assays have several distinct advantages when measuring biological analytes such as metabolites, cofactors, toxins, etc. Not only are optical signals immune to electronic interferences, but the polychromatic nature of most fluorochemical assays provides more potentially useful data about the system being studied. One of the most common difficulties normally encountered with optical biosensors is the inability to routinely recalibrate the optical and electronic components of the system throughout the life of the sensor. With this in mind, we present an optical fiber assay system for glucose based on a homogeneous singlet/singlet energy transfer assay along with the electronic instrumentation built to support the sensor system. In the sensor probe, glucose concentrations are indirectly measured from the level of fluorescence quenching caused by the homogeneous competition assay between TRITC labeled concanavalin A (receptor) and FITC labeled Dextran (ligand). The FITC signal is used to indicate glucose concentrations and the TRITC signal is used for internal calibration. Data is also presented on a protein derivatization procedure that was used to prevent aggregation of the receptor protein in solution. Also, a molecular model is described for the singlet/singlet energy transfer interactions that can occur in a model system composed of a monovalent ligand (FITC labeled papain) and a monovalent receptor (TRITC labeled concanavalin A).

  10. Autojoin: A Simple Rule Based Query Service for Complex Databases

    NASA Astrophysics Data System (ADS)

    Gaffney, N. I.; Gardner, L.; Brandt, M.

    Most databases used today are no longer flat. While the power of using these more complex data stores is well known, construction of queries can be quite a complex task. Currently this often requires detailed knowledge of the database structure and schema. As we move towards a VO paradigm, users cannot be expected to know the structure of databases, but will need to query them. Databases will need to provide query engines to complete queries automatically given only what the user wants to have returned and any qualifications they place on the query. For years StarView, a database query and data retrieval tool for the Space Telescope Science Institute, relied on a complex third party LISP-based program (QUICK) to construct valid SQL queries for the one database it could query. This limited our ability to support StarView as we could not easily add new rules to the system without completely rebuilding the query engine. Furthermore, QUICK did not have the ability to create SQL that would join tables in different databases (but hosted on the same server). Finally, the cost of upgrading to a new version of QUICK was prohibitively high. Our solution was to develop a rather simple database table driven Perl CGI program which is able to take as its input a skeleton SQL program. This may come from a program or other web page. In the query only the SELECT and user qualified WHERE clause are specified; no FROM or WHERE clause join information is included. The service then returns a fully qualified and syntactically correct query for the host database SQL program that can be used to get the information the user needs. Thus, an additional layer of abstraction for dealing with databases is created, freeing the user from having to know how tables are related in the database. In this paper we discuss the design and algorithm used to make Autojoin work as well as discuss how, when combined with a robust and searchable description of all the fields that can be publicly queried in

  11. A simple method for the determination of glyphosate and aminomethylphosphonic acid in seawater matrix with high performance liquid chromatography and fluorescence detection.

    PubMed

    Wang, Shu; Liu, Baomin; Yuan, Dongxing; Ma, Jian

    2016-12-01

    Glyphosate (GLYP) is an important herbicide which is also used as the phosphorus source for marine organisms. The wide applications of GLYP can lead to its accumulation in oceans and coastal waters, thus creating environmental issues. However, there is limited methods for detection of GLYP and its degradation product, aminomethylphosphonic acid (AMPA) in saline samples. Therefore, a simple and fast method for the quantification of GLYP and AMPA in seawater matrix has been developed based on the derivatization with 9-fluorenylmethylchloroformate (FMOC-Cl), separation with high performance liquid chromatography (HPLC) and detection with fluorescence detector (FLD). In order to maximize sensitivity, the derivatization procedure was carefully optimized regarding concentration of FMOC-Cl, volume of borate buffer, pH of borate buffer, mixing and derivatization time. The derivatization reaction could be completed within 30min in seawater samples without any additional clean-up or desalting steps. Under the optimized conditions, the developed HPLC method showed a wide linear response (up to several mg/L, R(2)>0.99). The limits of detection were 0.60μg/L and 0.30μg/L for GLYP and AMPA in seawater matrix, respectively. The relative standard deviation was 14.0% for GLYP (1.00mg/L) and 3.1% for AMPA (100μg/L) in saline samples with three different operators (n=24). This method was applied to determine the concentration of GLYP and AMPA in seawater culture media and the recovery data indicated minimal matrix interference. Due to its simplicity, high reproducibility and successful application in seawater culture media analysis, this method is a potentially useful analytical technique for both marine research and environmental science.

  12. A rapid-screening approach to detect and quantify microplastics based on fluorescent tagging with Nile Red

    PubMed Central

    Maes, Thomas; Jessop, Rebecca; Wellner, Nikolaus; Haupt, Karsten; Mayes, Andrew G.

    2017-01-01

    A new approach is presented for analysis of microplastics in environmental samples, based on selective fluorescent staining using Nile Red (NR), followed by density-based extraction and filtration. The dye adsorbs onto plastic surfaces and renders them fluorescent when irradiated with blue light. Fluorescence emission is detected using simple photography through an orange filter. Image-analysis allows fluorescent particles to be identified and counted. Magnified images can be recorded and tiled to cover the whole filter area, allowing particles down to a few micrometres to be detected. The solvatochromic nature of Nile Red also offers the possibility of plastic categorisation based on surface polarity characteristics of identified particles. This article details the development of this staining method and its initial cross-validation by comparison with infrared (IR) microscopy. Microplastics of different sizes could be detected and counted in marine sediment samples. The fluorescence staining identified the same particles as those found by scanning a filter area with IR-microscopy. PMID:28300146

  13. Physically-based in silico light sheet microscopy for visualizing fluorescent brain models

    PubMed Central

    2015-01-01

    Background We present a physically-based computational model of the light sheet fluorescence microscope (LSFM). Based on Monte Carlo ray tracing and geometric optics, our method simulates the operational aspects and image formation process of the LSFM. This simulated, in silico LSFM creates synthetic images of digital fluorescent specimens that can resemble those generated by a real LSFM, as opposed to established visualization methods producing visually-plausible images. We also propose an accurate fluorescence rendering model which takes into account the intrinsic characteristics of fluorescent dyes to simulate the light interaction with fluorescent biological specimen. Results We demonstrate first results of our visualization pipeline to a simplified brain tissue model reconstructed from the somatosensory cortex of a young rat. The modeling aspects of the LSFM units are qualitatively analysed, and the results of the fluorescence model were quantitatively validated against the fluorescence brightness equation and characteristic emission spectra of different fluorescent dyes. AMS subject classification Modelling and simulation PMID:26329404

  14. Carbon-dot-based dual-emission silica nanoparticles as a ratiometric fluorescent probe for Bisphenol A

    NASA Astrophysics Data System (ADS)

    Xiang, Guo-Qiang; Ren, Yue; Xia, Yin; Mao, Wenjie; Fan, Chao; Guo, Si-Yu; Wang, Pan-Pan; Yang, Deng-Hui; He, Lijun; Jiang, Xiuming

    2017-04-01

    A simple and effective strategy for designing a ratiometric fluorescent nanosensor is described in this work. A carbon dots (CDs) based dual-emission nanosensor for Bisphenol A (BPA) was prepared by coating CDs on the surface of dye-doped silica nanoparticles. The fluorescence of dual-emission silica nanoparticles was quenched in hydrochloric acid by potassium bromate (KBrO3) oxidation; BPA inhibited KBrO3 oxidation, resulting in the ratiometric fluorescence response of dual-emission silica nanoparticles. Several important parameters affecting the performance of the nanosensor were investigated and optimized. The detection limit of this nanosensor was 0.80 ng mL- 1 with a linear range from 10 to 500 ng mL- 1. This was applied successfully to determine BPA in the leached solution of different plastic products with satisfactory results.

  15. Simplified and optimized multispectral imaging for 5-ALA-based fluorescence diagnosis of malignant lesions

    PubMed Central

    Minamikawa, Takeo; Matsuo, Hisataka; Kato, Yoshiyuki; Harada, Yoshinori; Otsuji, Eigo; Yanagisawa, Akio; Tanaka, Hideo; Takamatsu, Tetsuro

    2016-01-01

    5-aminolevulinic acid (5-ALA)-based fluorescence diagnosis is now clinically applied for accurate and ultrarapid diagnosis of malignant lesions such as lymph node metastasis during surgery. 5-ALA-based diagnosis evaluates fluorescence intensity of a fluorescent metabolite of 5-ALA, protoporphyrin IX (PPIX); however, the fluorescence of PPIX is often affected by autofluorescence of tissue chromophores, such as collagen and flavins. In this study, we demonstrated PPIX fluorescence estimation with autofluorescence elimination for 5-ALA-based fluorescence diagnosis of malignant lesions by simplified and optimized multispectral imaging. We computationally optimized observation wavelength regions for the estimation of PPIX fluorescence in terms of minimizing prediction error of PPIX fluorescence intensity in the presence of typical chromophores, collagen and flavins. By using the fluorescence intensities of the optimized wavelength regions, we verified quantitative detection of PPIX fluorescence by using chemical mixtures of PPIX, flavins, and collagen. Furthermore, we demonstrated detection capability by using metastatic and non-metastatic lymph nodes of colorectal cancer patients. These results suggest the potential and usefulness of the background-free estimation method of PPIX fluorescence for 5-ALA-based fluorescence diagnosis of malignant lesions, and we expect this method to be beneficial for intraoperative and rapid cancer diagnosis. PMID:27149301

  16. Base motif recognition and design of DNA templates for fluorescent silver clusters by machine learning.

    PubMed

    Copp, Stacy M; Bogdanov, Petko; Debord, Mark; Singh, Ambuj; Gwinn, Elisabeth

    2014-09-03

    Discriminative base motifs within DNA templates for fluorescent silver clusters are identified using methods that combine large experimental data sets with machine learning tools for pattern recognition. Combining the discovery of certain multibase motifs important for determining fluorescence brightness with a generative algorithm, the probability of selecting DNA templates that stabilize fluorescent silver clusters is increased by a factor of >3.

  17. Glycol Chitosan-Based Fluorescent Theranostic Nanoagents for Cancer Therapy

    PubMed Central

    Rhee, Jin-Kyu; Park, Ok Kyu; Lee, Aeju; Yang, Dae Hyeok; Park, Kyeongsoon

    2014-01-01

    Theranostics is an integrated nanosystem that combines therapeutics with diagnostics in attempt to develop new personalized treatments with enhanced therapeutic efficacy and safety. As a promising therapeutic paradigm with cutting-edge technologies, theranostic agents are able to simultaneously deliver therapeutic drugs and diagnostic imaging agents and also monitor the response to therapy. Polymeric nanosystems have been intensively explored for biomedical applications to diagnose and treat various cancers. In recent years, glycol chitosan-based nanoagents have been developed as dual-purpose materials for simultaneous diagnosis and therapy. They have shown great potential in cancer therapies, such as chemotherapeutics and nucleic acid and photodynamic therapies. In this review, we summarize the recent progress and potential applications of glycol chitosan-based fluorescent theranostic nanoagents for cancer treatments and discuss their possible underlying mechanisms. PMID:25522316

  18. Highly Selective Fluorescent Sensing of Proteins Based on a Fluorescent Molecularly Imprinted Nanosensor

    PubMed Central

    Deng, Qiliang; Wu, Jianhua; Zhai, Xiaorui; Fang, Guozhen; Wang, Shuo

    2013-01-01

    A fluorescent molecularly imprinted nanosensor was obtained by grafting imprinted polymer onto the surface of multi-wall carbon nanotubes and post-imprinting treatment with fluorescein isothiocyanate (FITC). The fluorescence of lysozyme-imprinted polymer (Lys-MIP) was quenched more strongly by Lys than that of nonimprinted polymer (NIP), which indicated that the Lys-MIP could recognize Lys. The resulted imprinted material has the ability to selectively sense a target protein, and an imprinting factor of 3.34 was achieved. The Lys-MIP also showed selective detection for Lys among other proteins such as cytochrome C (Cyt C), hemoglobin (HB) and bovine serum albumin (BSA) due to the imprinted sites in the Lys-MIP. This approach combines the high selectivity of surface molecular imprinting technology and fluorescence, and converts binding events into detectable signals by monitoring fluorescence spectra. Therefore, it will have further applications for Lys sensing. PMID:24077318

  19. Frequency-domain flow cytometry: fluorescence-lifetime-based sensing technology for analyzing cells and chromosomes labeled with fluorescent probes

    NASA Astrophysics Data System (ADS)

    Steinkamp, John A.; Crissman, Harry A.; Lehnert, Bruce E.; Lehnert, Nancy M.; Deka, Chiranjit

    1997-05-01

    A flow cytometer has been developed that combines flow cytometry (FCM) and fluorescence lifetime spectroscopy measurement principles to provide unique capabilities for making frequency-domain, excited-state lifetime measurements on cells/chromosomes labeled with fluorescent probes, while preserving conventional FCM capabilities. Cells are analyzed as they intersect a high-frequency, intensity-modulated (sine-wave) laser excitation beam. Fluorescence signals are processed by (1) low-pass filtering to obtain conventional FCM dc-excited signals and (2) phase-sensitive detection electronics to resolve heterogeneous fluorescence based on differences in lifetimes expressed as phase-shifts and to quantify fluorescence lifetimes in real time. Processed signals are displayed as frequency distribution histograms and bivariate contour diagrams. Recent examples of biological applications include: (1) lifetime histograms recorded on autofluorescent human lung fibroblasts, murine thymus cells labeled with antibodies conjugated to fluorophores for studying fluorescence quenching as a function of antibody dilution and F/P ratio, and on cultured cells, nuclei, and chromosomes stained with DNA-binding fluorochromes and (2) phase-resolved, fluorescence signal- intensity histograms recorded on autofluorescent HLFs labeled with immunofluorescence markers and on murine thymus cells labeled with Red 613-antiThy 1.2 and propidium iodide (PI positive `dead' cells) to demonstrate the resolution of signals from highly overlapping emission spectra. This technology will increase the number of fluorescent markers usable in multilabeling studies and lifetimes can be used as spectroscopic probes to study the interaction of markers with their targets, each other, and the surrounding microenvironment.

  20. Simple, benign, aqueous-based amination of polycarbonate surfaces

    DOE PAGES

    VanDelinder, Virginia; Wheeler, David R.; Small, Leo J.; ...

    2015-03-18

    Here we report a simple, safe, environmentally-friendly aqueous method that uses diamines to functionalize a polycarbonate surface with amino groups. We demonstrate the ability of this facile method to serve as a foundation upon which other functionalities may be attached, including anti-fouling coatings and oriented membrane proteins. The use of water as the solvent for the functionalization ensures that solvent induced swelling does not affect the optical or mechanical properties of the polycarbonate.

  1. Optical biopsy fiber-based fluorescence spectroscopy instrumentation

    NASA Astrophysics Data System (ADS)

    Katz, Alvin; Ganesan, Singaravelu; Yang, Yuanlong; Tang, Gui C.; Budansky, Yury; Celmer, Edward J.; Savage, Howard E.; Schantz, Stimson P.; Alfano, Robert R.

    1996-04-01

    Native fluorescence spectroscopy of biomolecules has emerged as a new modality to the medical community in characterizing the various physiological conditions of tissues. In the past several years, many groups have been working to introduce the spectroscopic methods to diagnose cancer. Researchers have successfully used native fluorescence to distinguish cancerous from normal tissue samples in rat and human tissue. We have developed three generations of instruments, called the CD-scan, CD-ratiometer and CD-map, to allow the medical community to use optics for diagnosing tissue. Using ultraviolet excitation and emission spectral measurements on both normal and cancerous tissue of the breast, gynecology, colon, and aerodigestive tract can be separated. For example, from emission intensities at 340 nm to 440 nm (300 nm excitation), a statistically consistent difference between malignant tissue and normal or benign tissue is observed. In order to utilize optical biopsy techniques in a clinical setting, the CD-scan instrument was developed, which allows for rapid and reliable in-vitro and in-vivo florescence measurements of the aerodigestive tract with high accuracy. The instrumentation employs high sensitivity detection techniques which allows for lamp excitation, small diameter optical fiber probes; the higher spatial resolution afforded by the small diameter probes can increase the ability to detect smaller tumors. The fiber optic probes allow for usage in the aerodigestive tract, cervix and colon. Needle based fiber probes have been developed for in-vivo detection of breast cancer.

  2. Wafer-scale aluminum plasmonics for fluorescence based biodetection

    NASA Astrophysics Data System (ADS)

    Farhang, Arash; George, Matthew C.; Williamson, Brent; Black, Mike; Wangensteen, Ted; Fraser, James; Petrova, Rumyana; Prestgard, Kent

    2015-08-01

    Moxtek has leveraged existing capabilities in wafer-scale patterning of sub-wavelength wire grid polarizers into the fabrication of 1D and 2D periodic aluminum plasmonic structures. This work will discuss progress in 200 mm diameter wafer-scale fabrication, with detailed emphasis within the realm of microarray based fluorescence detection. Aluminum nanohole arrays in a hexagonal lattice are first numerically investigated. The nanohole array geometry and periodicity are specifically tuned to coincide both with the excitation of the fluorophore Cy3, and to provide a high field enhancement within the nanoholes where labeled biomolecules are captured. This is accomplished through numerical modelling, nanofabrication, SEM imaging, and optical characterization. A 200mm diameter wafer, patterned with the optically optimized nanohole array, is cut into standard 1x3 inch microscope slide pieces and then subsequently printed with various antigens at 9 different concentrations. A sandwich bioassay is then carried out, using the corresponding conjugate antibodies in order to demonstrate specificity. The nanohole array exhibit a 3-4 times total fluorescence enhancement of Cy3, when compared to a leading commercial microarray glass slide.

  3. A simple polyethylenimine-salicylaldehyde fluorescence probe: sensitive and selective detection of Zn2+ and Cd2+ in aqueous solution by adding S2- ion

    NASA Astrophysics Data System (ADS)

    Tan, Nai-Di; Yin, Jian-Hang; Pu, Guang; Yuan, Yaqing; Meng, Lei; Xu, Na

    2016-12-01

    A novel polyethylenimine (PEI)-salicylaldehyde (SA) fluorescence probe, simply prepared by stirring procedure, can sensitively detect Zn2+ (25 nM) and Cd2+ (10 nM) in aqueous solution. Formation of metal-to-ligand complexes (Zn2+@PEI-SA and Cd2+@PEI-SA) between ions and Schiff base generate a new emission at 454 nm, which increase with the concentration of the ions (turn-on). Furthermore, after adding S2- into the complexes, we can distinguish them due to the fluorescence quenching for Cd2+@PEI-SA (turn-off). Both response times for turning on and off the fluorescence are less than 1 min.

  4. Simple and sensitive detection method for Cobalt(II) in water using CePO4:Tb3+ nanocrystals as fluorescent probes.

    PubMed

    Chen, Hongqi; Yuan, Fei; Xu, Juan; Zhang, Yiyang; Wu, Yong; Wang, Lun

    2013-04-15

    A simple and sensitive method for detecting cobalt by synchronous fluorescence spectrometry technique with a novel fluorescence probe CePO4:Tb(3+) has been developed. CePO4:Tb(3+) nanocrystals were synthesized in aqueous solutions and characterized by transmission electron microscopy, electron diffraction pattern spectroscopy and spectrofluorometry. When Δλ=210 nm, the selected synchronous fluorescence is produced at 284 nm. CePO4:Tb(3+) nanocrystals were negatively charged under weakly basic conditions (pH=8.2), which can interact with Co(2+) via electrostatic interaction. Moreover, there is the spectrum overlap between the emission wavelength of CePO4:Tb(3+) NCs and the absorbance of Co(2+). So the energy transfer would occur, leading to the quenching phenomenon. The quenching equation of the system was agreed with the Stern-Volmer equation. The linear range and detection limit of Co(2+) were 5-1.8 μM and 3.5 nM, respectively. The method is successfully applied to the quantification of Co(2+) in water samples.

  5. A simple chip free-flow electrophoresis for monosaccharide sensing via supermolecule interaction of boronic acid functionalized quencher and fluorescent dye.

    PubMed

    Yin, Xiao-Yang; Dong, Jing-Yu; Wang, Hou-Yu; Li, Si; Fan, Liu-Yin; Cao, Cheng-Xi

    2013-08-01

    Here, a simple micro free-flow electrophoresis (μFFE) was developed for fluorescence sensing of monosaccharide via supermolecule interaction of synthesized boronic acid functionalized benzyl viologen (ο-BBV) and fluorescent dye. The μFFE contained two open electrode cavities and an ion-exchange membrane was sandwiched between two polymethylmethacrylate plates. The experiments demonstrated the following merits of developed μFFE: (i) up to 90.5% of voltage efficiency due to high conductivity of ion-exchange membrane; (ii) a strong ability against influence of bubble produced in two electrodes due to open design of electrode cavities; and (iii) reusable and washable separation chamber (45 mm × 17 mm × 100 μm, 77 μL) avoiding the discard of μFFE due to blockage of solute precipitation in chamber. Remarkably, the μFFE was first designed for the sensing of monosaccharide via the supermolecule interaction of synthesized ο-BBV, fluorescent dye, and monosaccharide. Under the optimized conditions, the minimum concentration of monosaccharide that could be detected was 1 × 10(-11) M. Finally, the developed device was used for the detection of 0.3 mM glucose spiked in human urine. All of the results demonstrated the feasibility of monosaccharide detection via the μFFE.

  6. Label-free fluorescent detection of thrombin activity based on a recombinant enhanced green fluorescence protein and nickel ions immobilized nitrilotriacetic acid-coated magnetic nanoparticles.

    PubMed

    Wang, Ming; Lei, Chunyang; Nie, Zhou; Guo, Manli; Huang, Yan; Yao, Shouzhuo

    2013-11-15

    Herein, a novel label-free fluorescent assay has been developed to detect the activity of thrombin and its inhibitor, based on a recombinant enhanced green fluorescence protein (EGFP) and Ni(2+) ions immobilized nitrilotriacetic acid-coated magnetic nanoparticles (Ni(2+)-NTA MNPs). The EGFP, containing a thrombin cleavage site and a hexahistidine sequence (His-tag) at its N-terminal, was adsorbed onto Ni(2+)-NTA MNPs through Ni(2+)-hexahistidine interaction, and dragged out of the solution by magnetic separation. Thrombin can selectively digest EGFP accompanied by His-tag peptide sequence leaving, and the resulting EGFP cannot be captured by Ni(2+)-NTA MNPs and kept in supernatant. Hence the fluorescence change of supernatant can clearly represent the activity of thrombin. Under optimized conditions, such assay showed a relatively low detection limit (3.0×10(-4) U mL(-1)), and was also used to detect the thrombin inhibitor, Hirudin, and further applied to detect thrombin activity in serum. Combined with the satisfactory reusability of Ni(2+)-NTA MNPs, our method presents a promising candidate for simple, sensitive, and cost-saving protease activity detecting and inhibitor screening.

  7. Unusual non-fluorescent broad spectrum siderophore activity (SID EGYII) by Pseudomonas aeruginosa strain EGYII DSM 101801 and a new insight towards simple siderophore bioassay.

    PubMed

    Embaby, Amira M; Heshmat, Yasmin; Hussein, Ahmed

    2016-03-01

    Present study highlights an unusual non-fluorescent hydroxamate broad spectrum siderophore (SID EGYII) activity from Pseudomonas aeruginosa strain EGYII DSM 101801, a soil bacterial isolate, along with simple low cost effective siderophore bioassay. Detection of SID EGYII activity qualitatively was proved by masking this activity against Erwinia amylovora strain EGY1 DSM 101800, an indicator strain, in well-cut diffusion assay containing 100 µM FeCl3. SID EGYII activity was expressed quantitatively as arbitrary units [Siderophore arbitrary units (SAU)] 380 SAU/mL against E. amylovora strain EGY1 DSM 101800. Maximal SID EGYII activity was achieved upon growing P. aeruginosa strain EGYII DSM 101801 in PYB broth at 180 rpm for 24 h. SID EGYII displayed a broad spectrum antimicrobial activity against some human pathogens (i.e., Gram-positive bacteria, Gram-negative bacteria and yeasts) and a fireblight plant pathogen. Interestingly, transformants of Escherichia coli JM109 (DE3)pSID/EGYII harboring P. aeruginosa strain EGYII DSM 101801 plasmid demonstrated a perceivable antimicrobial activity against E. amylovora strain EGY1 DSM 101800. The broad spectrum antimicrobial activity of the unusual non-fluorescent SID EGYII would underpin its high potential in targeting bacterial pathogens posing probable threats to human health and agricultural economy. The present simple low cost effective bioassay is a new insight towards an alternative to the expensive cumbersome siderophore Chrome Azurol S assay.

  8. ESIPT-Based Photoactivatable Fluorescent Probe for Ratiometric Spatiotemporal Bioimaging

    PubMed Central

    Zhou, Xiaohong; Jiang, Yuren; Zhao, Xiongjie; Guo, Dong

    2016-01-01

    Photoactivatable fluorophores have become an important technique for the high spatiotemporal resolution of biological imaging. Here, we developed a novel photoactivatable probe (PHBT), which is based on 2-(2-hydroxyphenyl)benzothiazole (HBT), a small organic fluorophore known for its classic luminescence mechanism through excited-state intramolecular proton transfer (ESIPT) with the keto form and the enol form. After photocleavage, PHBT released a ratiometric fluorophore HBT, which showed dual emission bands with more than 73-fold fluorescence enhancement at 512 nm in buffer and more than 69-fold enhancement at 452 nm in bovine serum. The probe displayed a high ratiometric imaging resolution and is believed to have a wide application in biological imaging. PMID:27754338

  9. Fluorescence based real time monitoring of fouling in process chromatography

    PubMed Central

    Pathak, Mili; Lintern, Katherine; Chopda, Viki; Bracewell, Daniel G.; Rathore, Anurag S.

    2017-01-01

    A real time monitoring of fouling in liquid chromatography has been presented. The versatility of the approach has been proven by successful implementation in three case studies with an error <1%. The first application demonstrates the monitoring of protein A ligand density and foulant concentration for assessing performance of protein A chromatography resin during purification of monoclonal antibodies. The observations have been supported from LC-MS/MS studies that were independently performed. The second application involves monitoring of foulant deposition during multimode cation exchange chromatography based purification of human serum albumin. Finally, in the third application, monitoring of foulants during multimodal hydrophobic interaction chromatography of recombinant human granulocyte colony stimulating factor is demonstrated. In all three cases, it is observed that the fluorescence intensity consistently increases with resin reuse as more foulants are deposited over time. The proposed approach can be readily used for real time monitoring of fouling and process control. PMID:28358349

  10. A facile label-free G-quadruplex based fluorescent aptasensor method for rapid detection of ATP

    NASA Astrophysics Data System (ADS)

    Liu, Haisheng; Ma, Changbei; Ning, Feng; Chen, Hanchun; He, Hailun; Wang, Kemin; Wang, Jun

    2017-03-01

    The present work demonstrates a simple, rapid and label-free ATP detection method using a fluorescent aptasensor that is based on G-quadruplex formation. In the absence of ATP, the Thioflavin T (ThT) dye binds to the G-rich ATP aptamer and forms an ATP aptamer/ThT G-quadruplex complex, which results in high fluorescence intensity. Upon addition of ATP, the ATP aptamer/ThT complex will be replaced by the formation of an ATP aptamer/ATP complex. During this process, separation of the ThT dye from the ATP aptamer/ThT complex decreases the fluorescence intensity of the reaction mixture dramatically. This fluorescence aptasensor is highly sensitive and rapid, with a detection limit of 18 nM and a total reaction time of only 10 min. Furthermore, this method is cost-effective and simple, removing the requirement for labeling the detection reagents with a fluorophore-quencher pair.

  11. Rapid, simple and inexpensive production of custom 3D printed equipment for large-volume fluorescence microscopy

    PubMed Central

    Tyson, Adam L.; Hilton, Stephen T.; Andreae, Laura C.

    2015-01-01

    The cost of 3D printing has reduced dramatically over the last few years and is now within reach of many scientific laboratories. This work presents an example of how 3D printing can be applied to the development of custom laboratory equipment that is specifically adapted for use with the novel brain tissue clearing technique, CLARITY. A simple, freely available online software tool was used, along with consumer-grade equipment, to produce a brain slicing chamber and a combined antibody staining and imaging chamber. Using standard 3D printers we were able to produce research-grade parts in an iterative manner at a fraction of the cost of commercial equipment. 3D printing provides a reproducible, flexible, simple and cost-effective method for researchers to produce the equipment needed to quickly adopt new methods. PMID:25797056

  12. Fluorescence-based visualization of autophagic activity predicts mouse embryo viability

    PubMed Central

    Tsukamoto, Satoshi; Hara, Taichi; Yamamoto, Atsushi; Kito, Seiji; Minami, Naojiro; Kubota, Toshiro; Sato, Ken; Kokubo, Toshiaki

    2014-01-01

    Embryo quality is a critical parameter in assisted reproductive technologies. Although embryo quality can be evaluated morphologically, embryo morphology does not correlate perfectly with embryo viability. To improve this, it is important to understand which molecular mechanisms are involved in embryo quality control. Autophagy is an evolutionarily conserved catabolic process in which cytoplasmic materials sequestered by autophagosomes are degraded in lysosomes. We previously demonstrated that autophagy is highly activated after fertilization and is essential for further embryonic development. Here, we developed a simple fluorescence-based method for visualizing autophagic activity in live mouse embryos. Our method is based on imaging of the fluorescence intensity of GFP-LC3, a versatile marker for autophagy, which is microinjected into the embryos. Using this method, we show that embryonic autophagic activity declines with advancing maternal age, probably due to a decline in the activity of lysosomal hydrolases. We also demonstrate that embryonic autophagic activity is associated with the developmental viability of the embryo. Our results suggest that embryonic autophagic activity can be utilized as a novel indicator of embryo quality. PMID:24681842

  13. Fluorescence-based visualization of autophagic activity predicts mouse embryo viability

    NASA Astrophysics Data System (ADS)

    Tsukamoto, Satoshi; Hara, Taichi; Yamamoto, Atsushi; Kito, Seiji; Minami, Naojiro; Kubota, Toshiro; Sato, Ken; Kokubo, Toshiaki

    2014-03-01

    Embryo quality is a critical parameter in assisted reproductive technologies. Although embryo quality can be evaluated morphologically, embryo morphology does not correlate perfectly with embryo viability. To improve this, it is important to understand which molecular mechanisms are involved in embryo quality control. Autophagy is an evolutionarily conserved catabolic process in which cytoplasmic materials sequestered by autophagosomes are degraded in lysosomes. We previously demonstrated that autophagy is highly activated after fertilization and is essential for further embryonic development. Here, we developed a simple fluorescence-based method for visualizing autophagic activity in live mouse embryos. Our method is based on imaging of the fluorescence intensity of GFP-LC3, a versatile marker for autophagy, which is microinjected into the embryos. Using this method, we show that embryonic autophagic activity declines with advancing maternal age, probably due to a decline in the activity of lysosomal hydrolases. We also demonstrate that embryonic autophagic activity is associated with the developmental viability of the embryo. Our results suggest that embryonic autophagic activity can be utilized as a novel indicator of embryo quality.

  14. Non-enzymatic Fluorescent Biosensor for Glucose Sensing Based on ZnO Nanorods

    NASA Astrophysics Data System (ADS)

    Mai, Hong Hanh; Pham, Van Thanh; Nguyen, Viet Tuyen; Sai, Cong Doanh; Hoang, Chi Hieu; Nguyen, The Binh

    2017-02-01

    We have developed a non-enzymatic fluorescent biosensor for glucose sensing based on ZnO nanorods. ZnO nanorods of high density, high crystallinity, and good alignment were grown on low-cost industrial copper substrates at low temperature. To grow them directly on the substrates without using a seed layer, we utilized a simple one-step seedless hydrothermal method, which is based on galvanic cell structure. Herein, the glucose-treated ZnO nanorods together with the ultraviolet (UV) irradiation of the sample during the photoluminescent measurement played the role of a catalyst. They decomposed glucose into hydrogen peroxide (H2O2) and gluconic acid, which is similar to the glucose oxidase enzyme (GOx) used in enzymatic sensors. Due to the formation of H2O2, the photoluminescence intensity of the UV emission peak of ZnO nanorods decreased as the glucose concentration increased from 1 mM to 100 mM. In comparison with glucose concentration of a normal human serum, which is in the range of 4.4-6.6 mM, the obtained results show potential of non-enzymatic fluorescent biosensors in medical applications.

  15. Direct Georeferencing of Uav Data Based on Simple Building Structures

    NASA Astrophysics Data System (ADS)

    Tampubolon, W.; Reinhardt, W.

    2016-06-01

    Unmanned Aerial Vehicle (UAV) data acquisition is more flexible compared with the more complex traditional airborne data acquisition. This advantage puts UAV platforms in a position as an alternative acquisition method in many applications including Large Scale Topographical Mapping (LSTM). LSTM, i.e. larger or equal than 1:10.000 map scale, is one of a number of prominent priority tasks to be solved in an accelerated way especially in third world developing countries such as Indonesia. As one component of fundamental geospatial data sets, large scale topographical maps are mandatory in order to enable detailed spatial planning. However, the accuracy of the products derived from the UAV data are normally not sufficient for LSTM as it needs robust georeferencing, which requires additional costly efforts such as the incorporation of sophisticated GPS Inertial Navigation System (INS) or Inertial Measurement Unit (IMU) on the platform and/or Ground Control Point (GCP) data on the ground. To reduce the costs and the weight on the UAV alternative solutions have to be found. This paper outlines a direct georeferencing method of UAV data by providing image orientation parameters derived from simple building structures and presents results of an investigation on the achievable results in a LSTM application. In this case, the image orientation determination has been performed through sequential images without any input from INS/IMU equipment. The simple building structures play a significant role in such a way that geometrical characteristics have been considered. Some instances are the orthogonality of the building's wall/rooftop and the local knowledge of the building orientation in the field. In addition, we want to include the Structure from Motion (SfM) approach in order to reduce the number of required GCPs especially for the absolute orientation purpose. The SfM technique applied to the UAV data and simple building structures additionally presents an effective tool

  16. Upconversion Nanoparticles and Monodispersed Magnetic Polystyrene Microsphere Based Fluorescence Immunoassay for the Detection of Sulfaquinoxaline in Animal-Derived Foods.

    PubMed

    Hu, Gaoshuang; Sheng, Wei; Zhang, Yan; Wang, Junping; Wu, Xuening; Wang, Shuo

    2016-05-18

    A novel fluorescence immunoassay for detecting sulfaquinoxaline (SQX) in animal-derived foods was developed using NaYF4:Yb/Tm upconversion nanoparticles (UCNPs) conjugated with antibodies as fluorescence signal probes, and monodisperse magnetic polystyrene microspheres (MMPMs) modified with coating antigen as immune-sensing capture probes for trapping and separating the signal probes. Based on a competitive immunoassay format, the detection limit of the proposed method for detecting SQX was 0.1 μg L(-1) in buffer and 0.5 μg kg(-1) in food samples. The recoveries of SQX in spiked samples ranged from 69.80 to 133.00%, with coefficients of variation of 0.24-25.06%. The extraction procedure was fast, simple, and environmentally friendly, requiring no organic solvents. In particular, milk samples can be analyzed directly after simple dilution. This method has appealing properties, such as sensitive fluorescence response, a simple and fast extraction procedure, and environmental friendliness, and could be applied to detecting SQX in animal-derived foods.

  17. Fluorogen-based reporters for fluorescence imaging: a review

    NASA Astrophysics Data System (ADS)

    Jullien, Ludovic; Gautier, Arnaud

    2015-12-01

    Fluorescence bioimaging has recently jumped into a new area of spatiotemporal resolution and sensitivity thanks to synergistic advances in both optical physics and probe/biosensor design. This review focuses on the recent development of genetically encodable fluorescent reporters that bind endogenously present or exogenously applied fluorogenic chromophores (so-called fluorogens) and activate their fluorescence. We highlight the innovative engineering and design that gave rise to these new natural and synthetic fluorescent reporters, and describe some of the emerging applications in imaging and biosensing.

  18. Simple, benign, aqueous-based amination of polycarbonate surfaces.

    PubMed

    VanDelinder, Virginia; Wheeler, David R; Small, Leo J; Brumbach, Michael T; Spoerke, Erik D; Henderson, Ian; Bachand, George D

    2015-03-18

    Polycarbonate is a desirable material for many applications due to its favorable mechanical and optical properties. Here, we report a simple, safe, environmentally friendly aqueous method that uses diamines to functionalize a polycarbonate surface with amino groups. The use of water as the solvent for the functionalization ensures that solvent induced swelling does not affect the optical or mechanical properties of the polycarbonate. We characterize the efficacy of the surface amination using X-ray photo spectroscopy, Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), and contact angle measurements. Furthermore, we demonstrate the ability of this facile method to serve as a foundation upon which other functionalities may be attached, including antifouling coatings and oriented membrane proteins.

  19. Rapid and quantitative detection of 4(5)-methylimidazole in caramel colours: A novel fluorescent-based immunochromatographic assay.

    PubMed

    Wu, Xinlan; Huang, Minghui; Yu, Shujuan; Kong, Fansheng

    2016-01-01

    A novel fluorescence-based immunochromatographic assay (ICA) for rapid detecting 4(5)-methylimidazole (4-MI) is presented in this study. In our work, the conjugates of fluorescent microspheres (FMs) and 4-MI monoclonal antibody were used as probe for ICA. Under optimal conditions, a standard curve of ICA-based detection of 4-MI was developed, linear detection ranged from 0.50 to 32.0 mg/L. The cross-reactivities were observed less than 3.93% by detecting 6 selected structural analogues of 4-MI. The recoveries of 4-MI in caramels detection were ranged from 82.85% to 102.31%, with the coefficient of variation (n = 3) below 9.06%. Quantitative comparison of the established fluorescence-based ICA with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) and indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) analysis of real caramel colour samples indicated a good correlation among the methods. Therefore, our developed fluorescence-based ICA method shows great potential for simple, rapid, sensitive, and cost-effective quantitative detection of 4-MI in food safety control.

  20. Gold nanoparticle based surface enhanced fluorescence for detection of organophosphorus agents

    NASA Astrophysics Data System (ADS)

    Dasary, Samuel S. R.; Rai, Uma S.; Yu, Hongtao; Anjaneyulu, Yerramilli; Dubey, Madan; Ray, Paresh Chandra

    2008-07-01

    Organophosphorus agents (OPA) represent a serious concern to public safety as nerve agents and pesticides. Here we report the development of gold nanoparticle based surface enhanced fluorescence (NSEF) spectroscopy for rapid and sensitive screening of organophosphorus agents. Fluorescent from Eu 3+ ions that are bound within the electromagnetic field of gold nanoparticles exhibit a strong enhancement. In the presence of OPA, Eu 3+ ions are released from the gold nanoparticle surface and thus a very distinct fluorescence signal change was observed. We discussed the mechanism of fluorescence enhancement and the role of OPA for fluorescence intensity change in the presence of gold nanoparticles.

  1. RNA containing pyrrolocytidine base analogs: good binding affinity and fluorescence that responds to hybridization.

    PubMed

    Wahba, Alexander S; Damha, Masad J; Hudson, Robert H E

    2008-01-01

    6-Phenylpyrrolocytidine and 6-methoxymethylene-pyrrolocytidine are base-modified nucleosides with remarkable fluorescence properties. When incorporated into RNA, these analogs enhance binding affinity towards RNA and DNA targets with a concomitant change in their fluorescence upon duplex formation. The fluorescence response depends on the nature of the 6-substituent and the sequence position of the modified nucleoside. The fluorescence response of these structurally conservative, well-tolerated fluorescent nucleosides may be exploited as probes in the study of nucleic acid processing enzymes.

  2. Fluorescence intensity, lifetime, and anisotropy screening of living cells based on total internal reflection techniques

    NASA Astrophysics Data System (ADS)

    Bruns, Thomas; Angres, Brigitte; Steuer, Heiko; Strauss, Wolfgang S. L.; Schneckenburger, Herbert

    2009-02-01

    A setup for fluorescence measurements of surfaces of biological samples, in particular the plasma membrane of living cells, is described. The method is based on splitting of a laser beam and multiple total internal reflections (TIR) within the bottom of a microtiter plate, such that up to 96 individual samples are illuminated simultaneously by an evanescent electromagnetic field. Two different screening procedures for the detection of fluorescence arising from the plasma membrane of living cells by High Throughput Screening (HTS) and High Content Screening (HCS), are distinguished. In the first case a rapid measurement of large sample numbers based on fluorescence intensity, and in the second case a high content of information from a single sample based on the parameters fluorescence lifetime (Fluorescence Lifetime Screening, FLiS) and fluorescence anisotropy (Fluorescence Lifetime Polarization Screening, FLiPS) is achieved. Both screening systems were validated using cultivated cells incubated with different fluorescent markers (e. g. NBD-cholesterol) as well as stably transfected cells expressing a fluorescent membrane-associating protein. In addition, particularly with regard of potential pharmaceutical applications, the kinetics of the intracellular translocation of a fluorescent protein kinase c fusion protein upon stimulation of the cells was determined. Further, a caspase sensor based on Förster Resonance Energy Transfer (FRET) between fluorescent proteins was tested. Enhanced cyan fluorescent protein (ECFP) anchored to the inner leaflet of the plasma membrane of living cells transfers its excitation energy via a spacer (DEVD) to an enhanced yellow fluorescent protein (EYFP). Upon apoptosis DEVD is cleaved, and energy transfer is disrupted, as proven by changes in fluorescence intensity and decay times.

  3. A label-free fluorescence DNA probe based on ligation reaction with quadruplex formation for highly sensitive and selective detection of nicotinamide adenine dinucleotide.

    PubMed

    Zhao, Jingjin; Zhang, Liangliang; Jiang, Jianhui; Shen, Guoli; Yu, Ruqin

    2012-05-11

    A simple label-free fluorescent sensing scheme for sensitive and selective detection of nicotinamide adenine dinucleotide (NAD(+)) has been developed based on DNA ligation reaction with ligand-responsive quadruplex formation. This approach can detect 0.5 nM NAD(+) with high selectivity against other NAD(+) analogs.

  4. Sensitive arginine sensing based on inner filter effect of Au nanoparticles on the fluorescence of CdTe quantum dots

    NASA Astrophysics Data System (ADS)

    Liu, Haijian; Li, Ming; Jiang, Linye; Shen, Feng; Hu, Yufeng; Ren, Xueqin

    2017-02-01

    Arginine plays an important role in many biological functions, whose detection is very significant. Herein, a sensitive, simple and cost-effective fluorescent method for the detection of arginine has been developed based on the inner filter effect (IFE) of citrate-stabilized gold nanoparticles (AuNPs) on the fluorescence of thioglycolic acid-capped CdTe quantum dots (QDs). When citrate-stabilized AuNPs were mixed with thioglycolic acid-capped CdTe QDs, the fluorescence of CdTe QDs was significantly quenched by AuNPs via the IFE. With the presence of arginine, arginine could induce the aggregation and corresponding absorption spectra change of AuNPs, which then IFE-decreased fluorescence could gradually recover with increasing amounts of arginine, achieving fluorescence "turn on" sensing for arginine. The detection mechanism is clearly illustrated and various experimental conditions were also optimized. Under the optimum conditions, a decent linear relationship was obtained in the range from 16 to 121 μg L- 1 and the limit of detection was 5.6 μg L- 1. And satisfactory results were achieved in arginine analysis using arginine injection, compound amino acid injection, even blood plasma as samples. Therefore, the present assay showed various merits, such as simplicity, low cost, high sensitivity and selectivity, making it promising for sensing arginine in biological samples.

  5. A mixed alkanethiol based immunosensor for surface plasmon field-enhanced fluorescence spectroscopy in serum.

    PubMed

    Scholten, Andreas; Menges, Bernhard; Juebner, Martin; Rothschild, Markus A; Bender, Katja

    2013-03-21

    This paper describes a simple and sensitive immuno-based biosensor for interference-reduced detection of C-reactive protein (CRP) in serum. The detection was performed by using a non-competitive sandwich immunoassay in combination with surface plasmon field-enhanced fluorescence spectroscopy (SPFS). CRP is an important marker for the diagnosis of inflammatory processes and cardiovascular diseases (CVD). It is nowadays detected by high-sensitivity enzyme-linked immunosorbent assays (ELISA) in blood serum. CRP was used as a model analyte in this work because it is well-characterized. However, interfering effects of matrix components affect the limit of detection (LOD) and quantification (LOQ) in general. Therefore, the availability of fast, sensitive and robust analytical methods is of major interest. A number of biosensor approaches have been described already, but only a few have demonstrated their usefulness in authentic samples such as serum. Thus our aim was to develop a simple and sensitive immunoassay-based biosensor for an interference-reduced detection of CRP in serum with surface plasmon enhanced fluorescence spectroscopy (SPFS). LODs and LOQs were experimentally determined both for CRP spiked buffer and serum. SPFS in combination with our biosensor allows sensitive analysis of CRP, achieving in buffer a LOD of 0.016 μg mL(-1) and a LOQ of 0.049 μg mL(-1). In serum the accomplished LOD was 0.026 μg mL(-1) and the LOQ was found to be 0.08 μg mL(-1). These low LODs and LOQs demonstrate the applicability of the designed biosensor for qualitative and semi-quantitative analysis of trace amounts of substances in very small sample volumes of body fluids.

  6. Magnetic quantum tunneling: insights from simple molecule-based magnets.

    PubMed

    Hill, Stephen; Datta, Saiti; Liu, Junjie; Inglis, Ross; Milios, Constantinos J; Feng, Patrick L; Henderson, John J; del Barco, Enrique; Brechin, Euan K; Hendrickson, David N

    2010-05-28

    This perspectives article takes a broad view of the current understanding of magnetic bistability and magnetic quantum tunneling in single-molecule magnets (SMMs), focusing on three families of relatively simple, low-nuclearity transition metal clusters: spin S = 4 Ni(II)(4), Mn(III)(3) (S = 2 and 6) and Mn(III)(6) (S = 4 and 12). The Mn(III) complexes are related by the fact that they contain triangular Mn(III)(3) units in which the exchange may be switched from antiferromagnetic to ferromagnetic without significantly altering the coordination around the Mn(III) centers, thereby leaving the single-ion physics more-or-less unaltered. This allows for a detailed and systematic study of the way in which the individual-ion anisotropies project onto the molecular spin ground state in otherwise identical low- and high-spin molecules, thus providing unique insights into the key factors that control the quantum dynamics of SMMs, namely: (i) the height of the kinetic barrier to magnetization relaxation; and (ii) the transverse interactions that cause tunneling through this barrier. Numerical calculations are supported by an unprecedented experimental data set (17 different compounds), including very detailed spectroscopic information obtained from high-frequency electron paramagnetic resonance and low-temperature hysteresis measurements. Comparisons are made between the giant spin and multi-spin phenomenologies. The giant spin approach assumes the ground state spin, S, to be exact, enabling implementation of simple anisotropy projection techniques. This methodology provides a basic understanding of the concept of anisotropy dilution whereby the cluster anisotropy decreases as the total spin increases, resulting in a barrier that depends weakly on S. This partly explains why the record barrier for a SMM (86 K for Mn(6)) has barely increased in the 15 years since the first studies of Mn(12)-acetate, and why the tiny Mn(3) molecule can have a barrier approaching 60% of this

  7. A new boronic acid based fluorescent reporter for catechol.

    PubMed

    Wu, Zhongyu; Li, Minyong; Fang, Hao; Wang, Binghe

    2012-12-01

    Catechol skeleton widely exists in natural products and bioactive substances. Fluorescent reporters which could recognize catechol are very promising for the construction of chemosensors to detect catechol and its derivatives in biological environment. Herein, we reported a novel catechol reporter, 2-(4-boronophenyl)quinoline-4-carboxylic acid, which exhibits significant fluorescent property changes upon binding catechol containing molecules in an aqueous solution.

  8. Latest methods of fluorescence-based protein crystal identification

    SciTech Connect

    Meyer, Arne; Betzel, Christian

    2015-01-28

    Fluorescence, whether intrinsic or by using trace fluorescent labeling, can be a powerful aid in macromolecule crystallization. Its use in screening for crystals is discussed here. Successful protein crystallization screening experiments are dependent upon the experimenter being able to identify positive outcomes. The introduction of fluorescence techniques has brought a powerful and versatile tool to the aid of the crystal grower. Trace fluorescent labeling, in which a fluorescent probe is covalently bound to a subpopulation (<0.5%) of the protein, enables the use of visible fluorescence. Alternatively, one can avoid covalent modification and use UV fluorescence, exploiting the intrinsic fluorescent amino acids present in most proteins. By the use of these techniques, crystals that had previously been obscured in the crystallization drop can readily be identified and distinguished from amorphous precipitate or salt crystals. Additionally, lead conditions that may not have been obvious as such under white-light illumination can be identified. In all cases review of the screening plate is considerably accelerated, as the eye can quickly note objects of increased intensity.

  9. Novel Chalcone-Based Fluorescent Human Histamine H3 Receptor Ligands as Pharmacological Tools

    PubMed Central

    Tomasch, Miriam; Schwed, J. Stephan; Weizel, Lilia; Stark, Holger

    2012-01-01

    Novel fluorescent chalcone-based ligands at human histamine H3 receptors (hH3R) have been designed, synthesized, and characterized. Compounds described are non-imidazole analogs of ciproxifan with a tetralone motif. Tetralones as chemical precursors and related fluorescent chalcones exhibit affinities at hH3R in the same concentration range like the reference antagonist ciproxifan (hH3R pKi value of 7.2). Fluorescence characterization of our novel ligands shows emission maxima about 570 nm for yellow fluorescent chalcones and ≥600 nm for the red fluorescent derivatives. Interferences to cellular autofluorescence could be excluded. All synthesized chalcone compounds could be used to visualize hH3R proteins in stably transfected HEK-293 cells using confocal laser scanning fluorescence microscopy. These novel fluorescent ligands possess high potential to be used as pharmacological tools for hH3R visualization in different tissues. PMID:22470321

  10. A novel device based on a fluorescent cross-responsive sensor array for detecting pesticide residue

    NASA Astrophysics Data System (ADS)

    Huang, Jing; Hou, Changjun; Lei, Jincan; Huo, Danqun; Luo, Xiaogang; Dong, Liang

    2016-11-01

    In this paper, a novel, simple, rapid, and low-cost detection device for pesticide residue was constructed. A sensor array based on a cross-responsive mechanism was designed. The data collection and processing system was used to detect fluorescent signal of the sensor arrays, and to extract unique patterns of the tested pesticide residue. Four selected pesticides, carbendazim, diazine, fenvalerate, and pentachloronitrobenzene, were detected by the proposed device. Unsupervised pattern recognition methods, hierarchical cluster analysis and principal component analysis, were used to analyze the data. The results showed that the methods could 100% discriminate the four pesticide residues. According to the standard regression linear curve of the fluorescence intensity and the concentration of pesticide, the quantitative value of the pesticide was detected, and the device obtained responses at concentrations below 8 ppb, and it has a good linear relationship in the range of 0.01-1 ppm. According to the results, the proposed detection device showed excellent selectivity and discrimination ability for the pesticide residues. However, our preliminary study demonstrated that the proposed detection device has excellent potential application for the safety inspection of food.

  11. A direct, continuous, sensitive assay for protein disulphide-isomerase based on fluorescence self-quenching.

    PubMed

    Raturi, Arun; Vacratsis, Panayiotis O; Seslija, Dana; Lee, Lana; Mutus, Bulent

    2005-10-15

    PDI (protein disulphide-isomerase) activity is generally monitored by insulin turbidity assay or scrambled RNase assay, both of which are performed by UV-visible spectroscopy. In this paper, we present a sensitive fluorimetric assay for continuous determination of disulphide reduction activity of PDI. This assay utilizes the pseudo-substrate diabz-GSSG [where diabz stands for di-(o-aminobenzoyl)], which is formed by the reaction of isatoic anhydride with the two free N-terminal amino groups of GSSG. The proximity of two benzoyl groups leads to quenching of the diabz-GSSG fluorescence by approx. 50% in comparison with its non-disulphide-linked form, abz-GSH (where abz stands for o-aminobenzoyl). Therefore the PDI-dependent disulphide reduction can be monitored by the increase in fluorescence accompanying the loss of proximity-quenching upon conversion of diabz-GSSG into abz-GSH. The apparent K(m) of PDI for diabz-GSSG was estimated to be approx. 15 muM. Unlike the insulin turbidity assay and scrambled RNase assay, the diabz-GSSG-based assay was shown to be effective in determining a single turnover of enzyme in the absence of reducing agents with no appreciable blank rates. The assay is simple to perform and very sensitive, with an estimated detection limit of approx. 2.5 nM PDI, enabling its use for the determination of platelet surface PDI activity in crude sample preparations.

  12. Simple membrane-based model of the Min oscillator

    NASA Astrophysics Data System (ADS)

    Petrášek, Zdeněk; Schwille, Petra

    2015-04-01

    Min proteins in E. coli bacteria organize into a dynamic pattern oscillating between the two cell poles. This process identifies the middle of the cell and enables symmetric cell division. In an experimental model system consisting of a flat membrane with effectively infinite supply of proteins and energy source, the Min proteins assemble into travelling waves. Here we propose a simple one-dimensional model of the Min dynamics that, unlike the existing models, reproduces the sharp decrease of Min concentration when the majority of protein detaches from the membrane, and even the narrow MinE maximum immediately preceding the detachment. The proposed model thus provides a possible mechanism for the formation of the MinE ring known from cells. The model is restricted to one dimension, with protein interactions described by chemical kinetics allowing at most bimolecular reactions, and explicitly considering only three, membrane-bound, species. The bulk solution above the membrane is approximated as being well-mixed, with constant concentrations of all species. Unlike other models, our proposal does not require autocatalytic binding of MinD to the membrane. Instead, it is assumed that two MinE molecules are necessary to induce the dissociation of the MinD dimer and its subsequent detachment from the membrane. We investigate which reaction schemes lead to unstable homogeneous steady states and limit cycle oscillations, and how diffusion affects their stability. The suggested model qualitatively describes the shape of the Min waves observed on flat membranes, and agrees with the experimental dependence of the wave period on the MinE concentration. These results highlight the importance of MinE presence on the membrane without being bound to MinD, and of the reactions of Min proteins on the membrane.

  13. Simple method of determination of copper, mercury and lead in potable water with preliminary pre-concentration by total reflection X-ray fluorescence spectrometry

    NASA Astrophysics Data System (ADS)

    Hołyńska, B.; Ostachowicz, B.; Wȩgrzynek, D.

    1996-06-01

    Total reflection X-ray fluorescence spectrometry and chemical pre-concentration procedures have been applied for the analysis of trace concentrations of copper, mercury, and lead in drinking water samples. A simple total reflection module has been used in X-ray measurements. The elements under investigation were pre-concentrated by complexation using a mixture of carbamates followed by solvent extraction with methyl isobutyl ketone. The preconcentration procedure was tested with the use of twice-distilled water samples and samples of mineral and tap water spiked with known additions of copper, mercury, and lead. The obtained recovery and precision values are presented. The minimum detection limits for the determination of these elements in mineral and tap water samples were found to be 40 ng l -1, 60 ng l -1, and 60 ng l -1, respectively.

  14. Neoplasm diagnostics based on fluorescence of polymethine dyes

    NASA Astrophysics Data System (ADS)

    Samtsov, Michael P.; Voropay, Eugene S.; Chalov, Vadim N.; Zhavrid, Edvard A.

    2002-05-01

    Investigated polymethine dye TICS has near IR bands of fluorescence and absorption within the transparency region of biological tissues. It can be detected up to 1.5 cm from the surface of the skin. The intensity of a fluorescence signal of TICS is linear for doses up to 2 mg/kg in both tumor and muscle tissue. The ratio of an intensity of light induced fluorescence in tumor tissue to one in muscle tissue is up to 3.6 for rapidly growing tumors. The retention time of TICS is 7 days in all tissues. TICS can be used in the detection of tumor boundaries and tumor internal structure.

  15. Fluorescent zinc and copper complexes for detection of adrafinil in paper-based microfluidic devices.

    PubMed

    Caglayan, Mehmet Gokhan; Sheykhi, Sara; Mosca, Lorenzo; Anzenbacher, Pavel

    2016-07-07

    Recognition of electroneutral Lewis bases and anions in aqueous media is extremely difficult. We show that fluorescent coordinatively unsaturated metal complexes can recognize various Lewis bases while providing an easy-to-detect fluorescence response. This approach is applied to the detection of adrafinil, a banned performance-enhancing drug.

  16. Simple and sensitive HPLC method with fluorescence detection for the measurement of ibuprofen in rat plasma: application to a long-lasting dosage form.

    PubMed

    Hassan, Ahmed Sheikh; Sapin, Anne; Ubrich, Nathalie; Maincent, Philippe; Bolzan, Claire; Leroy, Pierre

    2008-10-01

    A simple and sensitive high-performance liquid chromatography (HPLC) assay applied to the measurement of ibuprofen in rat plasma has been developed. Two parameters have been investigated to improve ibuprofen detectability using fluorescence detection: variation of mobile phase pH and the use of beta-cyclodextrin (beta-CD). Increasing the pH value from 2.5 to 6.5 and adding 5 mM beta-CD enhanced the fluorescence signal (lambda(exc) = 224 nm; lambda(em) = 290 nm) by 2.5 and 1.3-fold, respectively, when using standards. In the case of plasma samples, only pH variation significantly lowered detection and quantification limits, down to 10 and 35 ng/mL, respectively. Full selectivity was obtained with a single step for plasma treatment, that is, protein precipitation with acidified acetonitrile. The validated method was applied to a pharmacokinetic study of ibuprofen encapsulated in microspheres and subcutaneously administered to rats.

  17. Indocyanine green-based fluorescent angiography in breast reconstruction

    PubMed Central

    Chae, Michael P.; Rozen, Warren Matthew

    2016-01-01

    Background Fluorescent angiography (FA) has been useful for assessing blood flow and assessing tissue perfusion in ophthalmology and other surgical disciplines for decades. In plastic surgery, indocyanine green (ICG) dye-based FA is a relatively novel imaging technology with high potential in various applications. We review the various FA detector systems currently available and critically appraise its utility in breast reconstruction. Methods A review of the published English literature dating from 1950 to 2015 using databases, such as PubMed, Medline, Web of Science, and EMBASE was undertaken. Results In comparison to the old fluorescein dye, ICG has a superior side effect profile and can be accurately detected by various commercial devices, such as SPY Elite (Novadaq, Canada), FLARE (Curadel LLC, USA), PDE-Neo (Hamamatsu Photonics, Japan), Fluobeam 800 (Fluoptics, France), and IC-View (Pulsion Medical Systems AG, Germany). In breast reconstruction, ICG has established as a safer, more accurate tracer agent, in lieu of the traditional blue dyes, for detection of sentinel lymph nodes with radioactive isotopes (99m-Technetium). In prosthesis-based breast reconstruction, intraoperative assessment of the mastectomy skin flap to guide excision of hypoperfused areas translates to improved clinical outcomes. Similarly, in autologous breast reconstructions, FA can be utilized to detect poorly perfused areas of the free flap, evaluate microvascular anastomosis for patency, and assess SIEA vascular territory for use as an alternative free flap with minimal donor site morbidity. Conclusions ICG-based FA is a novel, useful tool for various applications in breast reconstruction. More studies with higher level of evidence are currently lacking to validate this technology. PMID:27047782

  18. Label-free fluorescent sensor for lead ion detection based on lead(II)-stabilized G-quadruplex formation.

    PubMed

    Zhan, Shenshan; Wu, Yuangen; Luo, Yanfang; Liu, Le; He, Lan; Xing, Haibo; Zhou, Pei

    2014-10-01

    A label-free fluorescent DNA sensor for the detection of lead ions (Pb(2+)) based on lead(II)-stabilized G-quadruplex formation is proposed in this article. A guanine (G)-rich oligonucleotide, T30695, was used as a recognition probe, and a DNA intercalator, SYBR Green I (SG), was used as a signal reporter. In the absence of Pb(2+), the SG intercalated with the single-stranded random-coil T30695 and emitted strong fluorescence. While in the presence of Pb(2+), the random-coil T30695 would fold into a G-quadruplex structure and the SG could barely show weak fluorescence, and the fluorescence intensity was inversely proportional to the involving amount of Pb(2+). Based on this, a selective lead ion sensor with a limit of detection of 3.79 ppb (parts per billion) and a detection range from 0 to 600 ppb was constructed. Because detection for real samples was also demonstrated to be reliable, this simple, low-cost, sensitive, and selective sensor holds good potential for Pb(2+) detection in real environmental samples.

  19. Development of a quantitative fluorescence-based ligand-binding assay

    PubMed Central

    Breen, Conor J.; Raverdeau, Mathilde; Voorheis, H. Paul

    2016-01-01

    A major goal of biology is to develop a quantitative ligand-binding assay that does not involve the use of radioactivity. Existing fluorescence-based assays have a serious drawback due to fluorescence quenching that accompanies the binding of fluorescently-labeled ligands to their receptors. This limitation of existing fluorescence-based assays prevents the number of cellular receptors under investigation from being accurately measured. We have developed a method where FITC-labeled proteins bound to a cell surface are proteolyzed extensively to eliminate fluorescence quenching and then the fluorescence of the resulting sample is compared to that of a known concentration of the proteolyzed FITC-protein employed. This step enables the number of cellular receptors to be measured quantitatively. We expect that this method will provide researchers with a viable alternative to the use of radioactivity in ligand binding assays. PMID:27161290

  20. Characterisation of fluorescent Schiff bases formed during oxidation of pig myofibrils.

    PubMed

    Chelh, Ilham; Gatellier, Philippe; Santé-Lhoutellier, Véronique

    2007-06-01

    The aim of this study was to investigate the formation of fluorescent Schiff bases between proteins and lipid oxidation products in myofibrils. Myofibrils were prepared from pig M. longissimus dorsi and oxidized by hydroxyl (OH()) and superoxide (O(2)(-)) radical generating systems. Protein oxidation was measured by the carbonyl content and lipid oxidation was estimated by measurement of thiobarbituric acid reactive substances (TBARS). To avoid any bias due to their low solubility, fluorescent pigments were estimated directly in the solid state by a front-face fluorescence technique. Hydroxyl radicals generated high levels of lipid and protein oxidation as well as fluorescent pigments, whereas only fluorescence was affected by superoxide radicals. The formation of fluorescent pigments was linked not only to aldehyde production, but also to the availability of the amino groups of the myofibrillar protein side chains. Schiff bases could be implicated in protein aggregation with deleterious effect on meat quality.

  1. Determination of flumioxazin residue in food samples through a sensitive fluorescent sensor based on click chemistry.

    PubMed

    Lu, Lijun; Yang, Linlin; Cai, Huijian; Zhang, Lan; Lin, Zhenyu; Guo, Longhua; Qiu, Bin; Chen, Guonan

    2014-11-01

    A sensitive and selective fluorescent sensor for flumioxazin was designed based on the formation of strong fluorescence compound (1,2,3-triazole compounds) via the reaction of the alkynyl group in flumioxazin with 3-azido-7-hydroxycoumarin, a weak-fluorescent compound, through the Cu(+)-catalysed azide-alkyne cycloaddition (CuAAC) reaction. The fluorescence increase factor (represented by F/F0) of the system exhibited a good linear relationship with the concentrations of flumioxazin in the range of 0.25-6.0 μg/L with a detection limit of 0.18 μg/L (S/N=3). Also, the proposed fluorescent sensor demonstrated good selectivity for flumioxazin assay even in the presence of high concentration of other pesticides. Based on such high sensitivity and selectivity, the proposed fluorescent sensor has been applied to test the flumioxazin residue in some vegetable and water samples with satisfied results.

  2. A sensitive quantum dots-based "OFF-ON" fluorescent sensor for ruthenium anticancer drugs and ctDNA.

    PubMed

    Huang, Shan; Zhu, Fawei; Qiu, Hangna; Xiao, Qi; Zhou, Quan; Su, Wei; Hu, Baoqing

    2014-05-01

    In this contribution, a simple and sensitive fluorescent sensor for the determination of both the three ruthenium anticancer drugs (1 to 3) and calf thymus DNA (ctDNA) was established based on the CdTe quantum dots (QDs) fluorescence "OFF-ON" mode. Under the experimental conditions, the fluorescence of CdTe QDs can be effectively quenched by ruthenium anticancer drugs because of the surface binding of these drugs on CdTe QDs and the subsequent photoinduced electron transfer (PET) process from CdTe QDs to ruthenium anticancer drugs, which render the system into fluorescence "OFF" status. The system can then be "ON" after the addition of ctDNA which brought the restoration of CdTe QDs fluorescence intensity, since ruthenium anticancer drugs broke away from the surface of CdTe QDs and inserted into double helix structure of ctDNA. The fluorescence quenching effect of the CdTe QDs-ruthenium anticancer drugs systems was mainly concentration dependent, which could be used to detect three ruthenium anticancer drugs. The limits of detection were 5.5 × 10(-8) M for ruthenium anticancer drug 1, 7.0 × 10(-8) M for ruthenium anticancer drug 2, and 7.9× 10(-8) M for ruthenium anticancer drug 3, respectively. The relative restored fluorescence intensity was directly proportional to the concentration of ctDNA in the range of 1.0 × 10(-8) M ∼ 3.0 × 10(-7) M, with a correlation coefficient (R) of 0.9983 and a limit of detection of 1.1 × 10(-9) M. The relative standard deviation (RSD) for 1.5 × 10(-7) M ctDNA was 1.5% (n = 5). There was almost no interference to some common chemical compounds, nucleotides, amino acids, and proteins. The proposed method was applied to the determination of ctDNA in three synthetic samples with satisfactory results. The possible reaction mechanism of CdTe QDs fluorescence "OFF-ON" was further investigated. This simple and sensitive approach possessed some potential applications in the investigation of interaction between drug molecules and DNA.

  3. A simple data base for identification of risk profiles

    SciTech Connect

    Munganahalli, D.

    1996-12-31

    Sedco Forex is a drilling contractor that operates approximately 80 rigs on land and offshore worldwide. The HSE management system developed by Sedco Forex is an effort to prevent accidents and minimize losses. An integral part of the HSE management system is establishing risk profiles and thereby minimizing risk and reducing loss exposures. Risk profiles are established based on accident reports, potential accident reports and other risk identification reports (RIR) like the Du Pont STOP system. A rig could fill in as many as 30 accident reports, 30 potential accident reports and 500 STOP cards each year. Statistics are important for an HSE management system, since they are indicators of success or failure of HSE systems. It is however difficult to establish risk profiles based on statistical information, unless tools are available at the rig site to aid with the analysis. Risk profiles are then used to identify important areas in the operation that may require specific attention to minimize the loss exposure. Programs to address the loss exposure can then be identified and implemented with either a local or corporate approach. In January 1995, Sedco Forex implemented a uniform HSE Database on all the rigs worldwide. In one year companywide, the HSE database would contain information on approximately 500 accident and potential accident reports, and 10,000 STOP cards. This paper demonstrates the salient features of the database and describes how it has helped in establishing key risk profiles. It also shows a recent example of how risk profiles have been established at the corporate level and used to identify the key contributing factors to hands and finger injuries. Based on this information, a campaign was launched to minimize the frequency of occurrence and associated loss attributed to hands and fingers accidents.

  4. RNA containing pyrrolocytidine base analogs: increased binding affinity and fluorescence that responds to hybridization.

    PubMed

    Wahba, Alexander S; Damha, Masad J; Hudson, Robert H E

    2008-01-01

    6-Phenylpyrrolocytidine and 6-methoxymethylene-pyrrolocytidine are base-modified nucleosides with remarkable fluorescence properties. These analogs produce increased binding affinity to both RNA and DNA targets when incorporated into oligoribonucleotides. The fluorescence observed for the single-stranded oligomers is quenched upon duplex formation with either RNA or DNA targets. The fluorescence response depends on the nature of the 6-substituent and the sequence position of the modified nucleoside.

  5. A simple optical fiber interferometer based breathing sensor

    NASA Astrophysics Data System (ADS)

    Li, Xixi; Liu, Dejun; Kumar, Rahul; Ng, Wai Pang; Fu, Yong-qing; Yuan, Jinhui; Yu, Chongxiu; Wu, Yufeng; Zhou, Guorui; Farrell, Gerald; Semenova, Yuliya; Wu, Qiang

    2017-03-01

    A breathing sensor has been experimentally demonstrated based on a singlemode–multimode–singlemode (SMS) fiber structure which is attached to a thin plastic film in an oxygen mask. By detecting power variations due to the macro bending applied to the SMS section by each inhalation and exhalation process, the breath state can be monitored. The proposed sensor is capable of distinguishing different types of breathing conditions including regular and irregular breath state. The sensor can be used in a strong electric/magnetic field and radioactive testing systems such as magnetic resonance imaging (MRI) systems and computed tomography (CT) examinations where electrical sensors are restricted.

  6. Reaction analysis on Yb(3+) and DNA based on quantum dots: The design of a fluorescent reversible off-on mode.

    PubMed

    Wang, Linlin; Song, Jing; Liu, Shaopu; Hao, Chenxia; Kuang, Nianxi; He, Youqiu

    2015-11-01

    Even though various strategies have reported for DNA detection, development of a simple, time-saving and specific fluorescent sensing platform still remains a desired goal. In this work, a quantum dots (QDs) based fluorescent reversible "off-on" mode was developed for sensitively recognition of herring sperm DNA (hsDNA). Firstly, in the "turn off" stage, the fluorescence of glutathione (GSH) capped CdTe QDs could be effectively quenched by ytterbium ion (Yb(3+)) was due to the occurrence of the electron transfer between Yb(3+) and the photoexcited QDs. And then, in the following "turn on" stage, with the effective binding reaction of Yb(3+) to hsDNA, the fluorescence intensity of GSH-capped CdTe QDs enhanced. Under the optimal conditions, the linear range of fluorescence versus the concentration of hsDNA was 0.010-12 μg/mL, and the detection limit was 3.033 ng/mL. In addition, the reaction mechanism among GSH-capped CdTe QDs, Yb(3+) and hsDNA were investigated by fluorescence spectroscopy, UV-vis spectrophotometry, fluorescence lifetime measurement and viscosity measurements. This analytical fluorescent reversible "off-on" pattern offered a way with good sensitivity and selectivity for the detection of hsDNA.

  7. Simple laser-based pipeline corrosion assessment system

    SciTech Connect

    Bruce, W.A.; Yapp, D.; Barborak, D.M.; Fingerhut, M.P.; Kania, R.

    1997-03-01

    The article focuses on development and use of a simpler laser-based system for accurately and efficiently measuring and assessing corrosion damage on the external surface of an exposed pipeline. The system uses a laser-based range sensor, which relies on optical spray, sensor movement, and the principal of triangulation to construct a three-dimensional measurement. Baseline subtraction, where a polynomial curve-fit is used to approximate the ideal pipe profile above the corroded area, is used. Future profiles are subtracted from the ideal profile, and when differences are significant, corrosion depth measurements are made by constructing normal vectors at points along the ideal profile. The use of such a system for accurately mapping corrosion damage allows more accurate assessments, thereby reducing the number of unnecessary repairs and cut outs, and reduces the risk of non-conservative assessments. The use of this system also results in reduced labor costs associated with mapping corrosion damage and allows the assessment process to be carried out over a much shorter period of time. The system can also be used to develop an accurate correlation between inline inspection (ILI) results and corrosion geometry during the first few excavations following ILI, resulting in the need to excavate fewer areas.

  8. A nanostructured aluminum oxide-based microfluidic device for enhancing immunoassay's fluorescence and detection sensitivity.

    PubMed

    Li, Xiang; Yin, Haocheng; Que, Long

    2014-10-01

    A nanostructured aluminum oxide (NAO)-based fluorescence biosensing platform with a programmable sample delivery microfluidic interface is reported. The NAO-based fluorescence sensor can tremendously enhance the fluorescence signals, typically up to 100 × or more, over the glass substrate. The programmable sample delivery microfluidic interface, which is integrated with the NAO-based sensors, can automatically generate and deliver a series of different concentrations of the biological samples to each individual sensor. Hence it can facilitate the fluorescence-based biodetection and analysis for high throughput applications. Using Protein A and fluorophore-labeled Immunoglobulin G (IgG) as models, the binding between them on this platform have been demonstrated. It has been shown that the IgG of programmable concentrations can be delivered to individual sensor using the microfluidic interface and confirmed by the fluorescence images. Using current NAO-based fluorescence sensors without any optimization, the detectable concentration of IgG can be as low as 20 pg/mm(2) using a conventional fluorescence microscope. Due to its inexpensive fabrication process, this technology could provide a disposable technical platform for fluorescence-based sensing and analysis.

  9. Recent progress in design of protein-based fluorescent biosensors and their cellular applications.

    PubMed

    Tamura, Tomonori; Hamachi, Itaru

    2014-12-19

    Protein-based fluorescent biosensors have emerged as key bioanalytical tools to visualize and quantify a wide range of biological substances and events in vitro, in cells, and even in vivo. On the basis of the construction method, the protein-based fluorescent biosensors can be principally classified into two classes: (1) genetically encoded fluorescent biosensors harnessing fluorescent proteins (FPs) and (2) semisynthetic biosensors comprised of protein scaffolds and synthetic fluorophores. Recent advances in protein engineering and chemical biology not only allowed the further optimization of conventional biosensors but also facilitated the creation of novel biosensors based on unique strategies. In this review, we survey the recent studies in the development and improvement of protein-based fluorescent biosensors and highlight the successful applications to live cell and in vivo imaging. Furthermore, we provide perspectives on possible future directions of the technique.

  10. Fast-Response Turn-on Fluorescent Probes Based on Thiolysis of NBD Amine for H2 S Bioimaging.

    PubMed

    Wang, Runyu; Li, Zhifei; Zhang, Changyu; Li, Yanyan; Xu, Guoce; Zhang, Qiang-Zhe; Li, Lu-Yuan; Yi, Long; Xi, Zhen

    2016-05-17

    Hydrogen sulfide (H2 S) is an important endogenous signaling molecule with multiple biological functions. New selective fluorescent turn-on probes based on fast thiolyling of NBD (7-nitro-1,2,3-benzoxadiazole) amine were explored for sensing H2 S in aqueous buffer and in living cells. The syntheses of both probes are simple and quite straightforward. The probes are highly sensitive and selective toward H2 S over other biologically relevant species. The fluorescein-NBD-based probe showed 65-fold green fluorescent increase upon H2 S activation. The rhodamine-NBD-based probe reacted rapidly with H2 S (t1/2 ≈1 min) to give a 4.5-fold increase in red fluorescence. Moreover, both probes were successfully used for monitoring H2 S in living cells and in mice. Based on such probe-based tools, we could observe H2 O2 -induced H2 S biogenesis in a concentration-dependent and time-dependent fashion in living cells.

  11. An improved bimolecular fluorescence complementation tool based on superfolder green fluorescent protein.

    PubMed

    Zhou, Jun; Lin, Jian; Zhou, Cuihong; Deng, Xiaoyan; Xia, Bin

    2011-03-01

    Bimolecular fluorescence complementation (BiFC) has been widely used in the analysis of protein-protein interactions (PPIs) in recent years. There are many notable advantages of BiFC such as convenience and direct visualization of PPI in cells. However, BiFC has one common limitation: the separated non-fluorescent fragments can be spontaneously self-assembled into an intact protein, which leads to false-positive results. In this study, a pair of complementary fragments (sfGFPN and sfGFPC) was constructed by splitting superfolder GFP (sfGFP) between the 214 and 215 amino acid residue, and sfGFPC was mutated by site-directed gene mutagenesis to decrease the signal of negative control. Our results showed that mutations in sfGFPC (sfGFPC(m12)) can effectively decrease the signal of negative control. Thus, we provide an improved BiFC tool for the analysis of PPI. Further, since the self-assembly problem is a common shortcoming for application of BiFC, our research provides a feasible strategy for other BiFC candidate proteins with the same problem.

  12. Photo-Physical Behavior and Fluorescence of Thermo Switchable Nanocomposite Based on Methyl Methacrylate -Spirobenzopyran.

    PubMed

    Rouhani, Shohre; Pishvaei, Malihe

    2017-03-01

    Nanocomposites with thermo and photo-switchable fluorescent properties were synthesized via mini-emulsion polymerization based on spiropyran and methyl methacrylate monomer. The photophysical behavior of fluorescence nanocomposites was investigated by fluorescence spectrophotometry in different temperature, UV-light and time of exposure. It was found that methyl methacrylate polymer is capable of acting as a protective layer and play a critical role in improving the photostability of colorants. The nanocomposites exhibited excellent fluorescent thermo-switching action with respect to the free spiro molecule. Graphical Abstract ᅟ.

  13. Fluorescent probe based on heteroatom containing styrylcyanine: pH-sensitive properties and bioimaging in vivo.

    PubMed

    Yang, Xiaodong; Gao, Ya; Huang, Zhibing; Chen, Xiaohui; Ke, Zhiyong; Zhao, Peiliang; Yan, Yichen; Liu, Ruiyuan; Qu, Jinqing

    2015-01-01

    A novel fluorescent probe based on heteroatom containing styrylcyanine is synthesized. The fluorescence of probe is bright green in basic and neutral media but dark orange in strong acidic environments, which could be reversibly switched. Such behavior enables it to work as a fluorescent pH sensor in the solution state and a chemosensor for detecting acidic and basic volatile organic compounds. Analyses by NMR spectroscopy confirm that the protonation or deprotonation of pyridinyl moiety is responsible for the sensing process. In addition, the fluorescent microscopic images of probe in live cells and zebrafish are achieved successfully, suggesting that the probe has good cell membrane permeability and low cytotoxicity.

  14. An 'activatable' aptamer-based fluorescence probe for the detection of HepG2 cells.

    PubMed

    Lai, Zongqiang; Tan, Juntao; Wan, Ruirong; Tan, Jie; Zhang, Zhenghua; Hu, Zixi; Li, Jieping; Yang, Wei; Wang, Yiwei; Jiang, Yafeng; He, Jian; Yang, Nuo; Lu, Xiaoling; Zhao, Yongxiang

    2017-05-01

    It is significant to develop a probe with sensitivity and specificity for the detection of cancer cells. The present study aimed to develop an 'activatable' aptamer-based fluorescence probe (AAFP) to detect cancer cells and frozen cancer tissue. This AAFP consisted of two fragments: aptamer TLS11a that targets HepG2 cells, and two short extending complementary DNA sequences with a 5'- and 3'-terminus that make the aptamer in hairpin structure a capable quencher to fluorophore. The ability of the AAFP to bind specifically to cancer cells was assessed using flow cytometry, fluorescence spectroscopy and fluorescence microscopy. Its ability to bind to frozen cancer tissue was assessed using fluorescence microscopy. As a result, in the absence of cancer cells, AAFP showed minimal fluorescence, reflecting auto-quenching. In the presence of cancer cells, however, AAFP showed a strong fluorescent signal. Therefore, this AAFP may be a promising tool for sensitive and specific detection of cancer.

  15. Selective recognition of Pr3+ based on fluorescence enhancement sensor.

    PubMed

    Ganjali, M R; Hosseini, M; Ghafarloo, A; Khoobi, M; Faridbod, F; Shafiee, A; Norouzi, P

    2013-10-01

    (E)-2-(1-(4-hydroxy-2-oxo-2H-chromen-3-yl)ethylidene)hydrazinecarbothioamide (L) has been used to detect trace amounts of praseodymium ion in acetonitrile-water solution (MeCN/H2O) by fluorescence spectroscopy. The fluorescent probe undergoes fluorescent emission intensity enhancement upon binding to Pr(3+) ions in MeCN/H2O (9/1:v/v) solution. The fluorescence enhancement of L is attributed to a 1:1 complex formation between L and Pr(3+), which has been utilized as the basis for selective detection of Pr(3+). The sensor can be applied to the quantification of praseodymium ion with a linear range of 1.6×10(-7) to 1.0×10(-5) M. The limit of detection was 8.3×10(-8) M. The sensor exhibits high selectivity toward praseodymium ions in comparison with common metal ions. The proposed fluorescent sensor was successfully used for determination of Pr(3+) in water samples.

  16. Memory-Based Simple Heuristics as Attribute Substitution: Competitive Tests of Binary Choice Inference Models.

    PubMed

    Honda, Hidehito; Matsuka, Toshihiko; Ueda, Kazuhiro

    2016-07-20

    Some researchers on binary choice inference have argued that people make inferences based on simple heuristics, such as recognition, fluency, or familiarity. Others have argued that people make inferences based on available knowledge. To examine the boundary between heuristic and knowledge usage, we examine binary choice inference processes in terms of attribute substitution in heuristic use (Kahneman & Frederick, 2005). In this framework, it is predicted that people will rely on heuristic or knowledge-based inference depending on the subjective difficulty of the inference task. We conducted competitive tests of binary choice inference models representing simple heuristics (fluency and familiarity heuristics) and knowledge-based inference models. We found that a simple heuristic model (especially a familiarity heuristic model) explained inference patterns for subjectively difficult inference tasks, and that a knowledge-based inference model explained subjectively easy inference tasks. These results were consistent with the predictions of the attribute substitution framework. Issues on usage of simple heuristics and psychological processes are discussed.

  17. A base-modified PNA-graphene oxide platform as a turn-on fluorescence sensor for the detection of human telomeric repeats

    NASA Astrophysics Data System (ADS)

    Sabale, Pramod M.; George, Jerrin Thomas; Srivatsan, Seergazhi G.

    2014-08-01

    Given the biological and therapeutic significance of telomeres and other G-quadruplex forming sequences in human genome, it is highly desirable to develop simple methods to study these structures, which can also be implemented in screening formats for the discovery of G-quadruplex binders. The majority of telomere detection methods developed so far are laborious and use elaborate assay and instrumental setups, and hence, are not amenable to discovery platforms. Here, we describe the development of a simple homogeneous fluorescence turn-on method, which uses a unique combination of an environment-sensitive fluorescent nucleobase analogue, the superior base pairing property of PNA, and DNA-binding and fluorescence quenching properties of graphene oxide, to detect human telomeric DNA repeats of varying lengths. Our results demonstrate that this method, which does not involve a rigorous assay setup, would provide new opportunities to study G-quadruplex structures.Given the biological and therapeutic significance of telomeres and other G-quadruplex forming sequences in human genome, it is highly desirable to develop simple methods to study these structures, which can also be implemented in screening formats for the discovery of G-quadruplex binders. The majority of telomere detection methods developed so far are laborious and use elaborate assay and instrumental setups, and hence, are not amenable to discovery platforms. Here, we describe the development of a simple homogeneous fluorescence turn-on method, which uses a unique combination of an environment-sensitive fluorescent nucleobase analogue, the superior base pairing property of PNA, and DNA-binding and fluorescence quenching properties of graphene oxide, to detect human telomeric DNA repeats of varying lengths. Our results demonstrate that this method, which does not involve a rigorous assay setup, would provide new opportunities to study G-quadruplex structures. Electronic supplementary information (ESI

  18. Plasmon-enhanced fluorescence imaging with silicon-based silver chips for protein and nucleic acid assay.

    PubMed

    Yuan, Bing; Jiang, Xiangxu; Yao, Chu; Bao, Meimei; Liu, Jiaojiao; Dou, Yujiang; Xu, Yinze; He, Yao; Yang, Kai; Ma, Yuqiang

    2017-02-22

    Metal-enhanced fluorescence shows great potential for improving the sensitivity of fluoroscopy, which has been widely used in protein and nucleic acid detection for biosensor and bioassay applications. In comparison with the traditional glass-supported metal nanoparticles (MNPs), the introduction of a silicon substrate has been shown to provide an increased surface-enhanced Raman scattering (SERS) effect due to the coupling between the MNPs and the semiconducting silicon substrate. In this work, we further study the fluorescence-enhanced effect of the silicon-supported silver-island (Ag@Si) plasmonic chips. In particular, we investigate their practical application of improving the traditional immunoassay such as the biotin-streptavidin-based protein assay and the protein-/nucleic acid-labeled cell and tissue samples. The protein assay shows a wavelength-dependent enhancement effect of the Ag@Si chip, with an enhancement factor ranging from 1.2 (at 532 nm) to 57.3 (at 800 nm). Moreover, for the protein- and nucleic acid-labeled cell and tissue samples, the Ag@Si chip provides a fluorescence enhancement factor of 3.0-4.1 (at 800 nm) and a significant improvement in the signal/background ratio for the microscopy images. Such a ready accommodation of the fluorescence-enhanced effect for the immunoassay samples with simple manipulations indicates broad potential for applications of the Ag@Si chip not only in biological studies but also in the clinical field.

  19. Development and characterization of the NanoOrange protein quantitation assay: a fluorescence-based assay of proteins in solution.

    PubMed

    Jones, Laurie J; Haugland, Richard P; Singer, Victoria L

    2003-04-01

    We developed a sensitive fluorescence assay for the quantitation of proteins in solution using the NanoOrange reagent, a merocyanine dye that produces a large increase in fluorescence quantum yield upon interaction with detergent-coated proteins. The NanoOrange assay allowed for the detection of 10 ng/mL to 10 micrograms/mL protein with a standard fluorometer, offering a broad, dynamic quantitation range and improved sensitivity relative to absorption-based protein solution assays. The protein-to-protein variability of the NanoOrange assay was comparable to those of standard assays, including Lowry, bicinchoninic acid, and Bradford procedures. We also found that the NanoOrange assay is useful for detecting relatively small proteins or large peptides, such as aprotinin and insulin. The assay was somewhat sensitive to the presence of several common contaminants found in protein preparations such as salts and detergents; however, it was insensitive to the presence of reducing agents, nucleic acids, and free amino acids. The simple assay protocol is suitable for automation. Samples are briefly heated in the presence of dye in a detergent-containing diluent, allowed to cool to room temperature, and fluorescence is measured using 485-nm excitation and 590-nm emission wavelengths. Therefore, the NanoOrange assay is well suited for use with standard fluorescence microplate readers, fluorometers, and some laser scanners.

  20. Generation of circularly permuted fluorescent-protein-based indicators for in vitro and in vivo detection of citrate.

    PubMed

    Honda, Yuki; Kirimura, Kohtaro

    2013-01-01

    Indicators for citrate, particularly those applicable to its in vivo detection and quantitation, have attracted much interest in both biochemical studies and industrial applications since citrate is a key metabolic intermediate playing important roles in living cells. We generated novel fluorescence indicators for citrate by fusing the circularly permuted fluorescent protein (cpFP) and the periplasmic domain of the bacterial histidine kinase CitA, which can bind to citrate with high specificity. The ratiometric fluorescent signal change was observed with one of these cpFP-based indicators, named CF98: upon addition of citrate, the excitation peak at 504 nm increased proportionally to the decrease in the peak at 413 nm, suitable for build-in quantitative estimation of the binding compound. We confirmed that CF98 can be used for detecting citrate in vitro at millimolar levels in the range of 0.1 to 50 mM with high selectivity; even in the presence of other organic acids such as isocitrate and malate, the fluorescence intensity of CF98 remains unaffected. We finally demonstrated the in vivo applicability of CF98 to estimation of the intracellular citrate concentration in Escherichia coli co-expressing the genes encoding CF98 and the citrate carrier CitT. The novel indicator CF98 can be a specific and simple detection tool for citrate in vitro and a non-invasive tool for real-time estimation of intracellular concentrations of the compound in vivo.

  1. When Simple Harmonic Motion is not That Simple: Managing Epistemological Complexity by Using Computer-based Representations

    NASA Astrophysics Data System (ADS)

    Parnafes, Orit

    2010-12-01

    Many real-world phenomena, even "simple" physical phenomena such as natural harmonic motion, are complex in the sense that they require coordinating multiple subtle foci of attention to get the required information when experiencing them. Moreover, for students to develop sound understanding of a concept or a phenomenon, they need to learn to get the same type of information across different contexts and situations (diSessa and Sherin 1998; diSessa and Wagner 2005). Rather than simplifying complex situations, or creating a linear instructional sequence in which students move from one context to another, this paper demonstrates the use of computer-based representations to facilitate developing understanding of complex physical phenomena. The data is collected from 8 studies in which pairs of students are engaged in an exploratory activity, trying to understand the dynamic behavior of a simulation and, at the same time, to attribute meaning to it in terms of the physical phenomenon it represents. The analysis focuses on three episodes. The first two episodes demonstrate the epistemological complexity involved in attempting to make sense of natural harmonic oscillation. A third episode demonstrates the process by which students develop understanding in this complex perceptual and conceptual territory, through the mediation (Vygotsky 1978) of computer-based representations designed to facilitate understanding in this topic.

  2. Rational Design of a Fluorescent Hydrogen Peroxide Probe Based on the Umbelliferone Fluorophore

    PubMed Central

    Du, Lupei; Li, Minyong; Zheng, Shilong; Wang, Binghe

    2008-01-01

    In this study, we report a novel water-soluble umbelliferone-based fluorescent probe for hydrogen peroxide. This probe shows very large increases (up to 100 fold) in fluorescent intensity upon reaction with hydrogen peroxide, and good selectivity over other reactive oxygen species (ROS). PMID:19081820

  3. Fluorescence in complexes based on quinolines-derivatives: a search for better fluorescent probes.

    PubMed

    Mecca, Carolina Z P; Fonseca, Fernando L A; Bagatin, Izilda A

    2016-11-05

    Quinoline-derived fluorescent complexes were designed; synthesized by the reaction of 5-nitro-8-hydroxyquinoline and 5-chloro-8-hydroxyquinoline with Al(3+), Mg(2+), Zn(2+), and Cd(2+) salts (1-8); and characterized. The (1)H NMR spectra of complexes 1 and 5, containing Al(3+), were consistent with an octahedral structure having approximate D3 symmetry, and the results supported the favored facial isomer (fac). Data for complexes 2-4 and 6-8 supported the formation of tetrahedral structures. Intense luminescence was detected for complexes 5-8, even with the naked eye, as indicated by quantum yield values of 0.087, 0.094, 0.051, and 0.021, respectively. Furthermore, in contrast to 5-nitro-8-hydroxyquinoline, the 5-chloro-8-hydroxyquinoline ligand exhibited bands at different energies depending on the coordinated metal, which supported its potential application in ionic and biological probes, as well as in cell imaging.

  4. Fluorescence in complexes based on quinolines-derivatives: a search for better fluorescent probes

    NASA Astrophysics Data System (ADS)

    Mecca, Carolina Z. P.; Fonseca, Fernando L. A.; Bagatin, Izilda A.

    2016-11-01

    Quinoline-derived fluorescent complexes were designed; synthesized by the reaction of 5-nitro-8-hydroxyquinoline and 5-chloro-8-hydroxyquinoline with Al3+, Mg2+, Zn2+, and Cd2+ salts (1-8); and characterized. The 1H NMR spectra of complexes 1 and 5, containing Al3+, were consistent with an octahedral structure having approximate D3 symmetry, and the results supported the favored facial isomer (fac). Data for complexes 2-4 and 6-8 supported the formation of tetrahedral structures. Intense luminescence was detected for complexes 5-8, even with the naked eye, as indicated by quantum yield values of 0.087, 0.094, 0.051, and 0.021, respectively. Furthermore, in contrast to 5-nitro-8-hydroxyquinoline, the 5-chloro-8-hydroxyquinoline ligand exhibited bands at different energies depending on the coordinated metal, which supported its potential application in ionic and biological probes, as well as in cell imaging.

  5. Fluorescence-based microendoscopes for breast cancer ductoscopy

    NASA Astrophysics Data System (ADS)

    Zeylikovich, Iosif; Tang, Guichen C.; Katz, A.; Budansky, Yury; Alfano, R. R.

    2006-02-01

    Recently microendoscopes are being developed as a tool to detection cancer or pre-cancerous lesions in the milk ducts of the human breast. The microendoscope can be inserted into the duct through the nipple. Integration of fluorescence spectroscopy into microendoscopy can provide an improved platform for real-time cancer detection followed by immediate intervention. Typically, the optical fibers employed by existing microendoscope systems transmit in the 450 to 900 nm range. A prototype system combining fluorescence spectroscopy with visible imaging by microendoscopy is described and preliminary measurements on ex vivo human breast tissues are presented. Image resolution and distortion are discussed.

  6. Fluorescence-Based Sensor for Monitoring Activation of Lunar Dust

    NASA Technical Reports Server (NTRS)

    Wallace, William T.; Jeevarajan, Antony S.

    2012-01-01

    This sensor unit is designed to determine the level of activation of lunar dust or simulant particles using a fluorescent technique. Activation of the surface of a lunar soil sample (for instance, through grinding) should produce a freshly fractured surface. When these reactive surfaces interact with oxygen and water, they produce hydroxyl radicals. These radicals will react with a terephthalate diluted in the aqueous medium to form 2-hydroxyterephthalate. The fluorescence produced by 2-hydroxyterephthalate provides qualitative proof of the activation of the sample. Using a calibration curve produced by synthesized 2-hydroxyterephthalate, the amount of hydroxyl radicals produced as a function of sample concentration can also be determined.

  7. Use of the Brucella melitensis native hapten to diagnose brucellosis in goats by a rapid, simple, and specific fluorescence polarization assay.

    PubMed

    Ramírez-Pfeiffer, Carlos; Díaz-Aparicio, Efrén; Gomez-Flores, Ricardo; Rodríguez-Padilla, Cristina; Morales-Loredo, Alberto; Alvarez-Ojeda, Genoveva

    2008-06-01

    The performance of the fluorescence polarization assay (FPA) using the recently described Brucella melitensis native hapten and the Brucella abortus O-polysaccharide tracer was evaluated and compared with those of The World Organization for Animal Health tests related to indirect and competitive enzyme-linked immunosorbent assays as classification variables for goat sera obtained from a high-prevalence area where vaccination was performed; test series were also evaluated to increase the final specificity of the tests. Our results showed that the respective relative sensitivity and specificity were 99.7% and 32.5% for the rose Bengal test with a 3% cell concentration (RBT3), 92.8% and 68.8% for the rose Bengal test with 8% cell concentration (RBT8), 98.4% and 84.9% for the Canadian complement fixation test (CFT), 83.7% and 65.5% for the Mexican CFT, 98.4% and 81.0% for the buffered plate agglutination test (BPAT), and 78.1% and 89.3% for the fluorescence polarization assay (FPA). The use of the FPA as the secondary test significantly increased the final specificities of test combinations; the screening tests BPAT, RBT3, and RBT8 plus FPA resulted in 90%, 91.2%, and 91.3% final specificities, respectively, whereas for the combinations RBT3 plus Mexican CFT, RBT8 plus Mexican CFT, and BPAT plus Canadian CFT, the specificities were 65.5%, 63.2%, and 91.7%, respectively. The results suggested that the FPA may be routinely applied as an adaptable screening test for diagnosis of goat brucellosis, since its cutoff can be adjusted to improve its sensitivity or specificity, it is a rapid and simple test, it can be the test of choice when specificity is relevant or when an alternative confirmatory test is not available, and it is not affected by vaccination, thus reducing the number of goats wrongly slaughtered due to misdiagnosis.

  8. A starting point for fluorescence-based single-molecule measurements in biomolecular research.

    PubMed

    Gust, Alexander; Zander, Adrian; Gietl, Andreas; Holzmeister, Phil; Schulz, Sarah; Lalkens, Birka; Tinnefeld, Philip; Grohmann, Dina

    2014-09-30

    Single-molecule fluorescence techniques are ideally suited to provide information about the structure-function-dynamics relationship of a biomolecule as static and dynamic heterogeneity can be easily detected. However, what type of single-molecule fluorescence technique is suited for which kind of biological question and what are the obstacles on the way to a successful single-molecule microscopy experiment? In this review, we provide practical insights into fluorescence-based single-molecule experiments aiming for scientists who wish to take their experiments to the single-molecule level. We especially focus on fluorescence resonance energy transfer (FRET) experiments as these are a widely employed tool for the investigation of biomolecular mechanisms. We will guide the reader through the most critical steps that determine the success and quality of diffusion-based confocal and immobilization-based total internal reflection fluorescence microscopy. We discuss the specific chemical and photophysical requirements that make fluorescent dyes suitable for single-molecule fluorescence experiments. Most importantly, we review recently emerged photoprotection systems as well as passivation and immobilization strategies that enable the observation of fluorescently labeled molecules under biocompatible conditions. Moreover, we discuss how the optical single-molecule toolkit has been extended in recent years to capture the physiological complexity of a cell making it even more relevant for biological research.

  9. The Statistical Value of Raw Fluorescence Signal in Luminex xMAP Based Multiplex Immunoassays

    PubMed Central

    Breen, Edmond J.; Tan, Woei; Khan, Alamgir

    2016-01-01

    Tissue samples (plasma, saliva, serum or urine) from 169 patients classified as either normal or having one of seven possible diseases are analysed across three 96-well plates for the presences of 37 analytes using cytokine inflammation multiplexed immunoassay panels. Censoring for concentration data caused problems for analysis of the low abundant analytes. Using fluorescence analysis over concentration based analysis allowed analysis of these low abundant analytes. Mixed-effects analysis on the resulting fluorescence and concentration responses reveals a combination of censoring and mapping the fluorescence responses to concentration values, through a 5PL curve, changed observed analyte concentrations. Simulation verifies this, by showing a dependence on the mean florescence response and its distribution on the observed analyte concentration levels. Differences from normality, in the fluorescence responses, can lead to differences in concentration estimates and unreliable probabilities for treatment effects. It is seen that when fluorescence responses are normally distributed, probabilities of treatment effects for fluorescence based t-tests has greater statistical power than the same probabilities from concentration based t-tests. We add evidence that the fluorescence response, unlike concentration values, doesn’t require censoring and we show with respect to differential analysis on the fluorescence responses that background correction is not required. PMID:27243383

  10. Fluorescent nitrile-based inhibitors of cysteine cathepsins.

    PubMed

    Frizler, Maxim; Mertens, Matthias D; Gütschow, Michael

    2012-12-15

    Cysteine cathepsins play an important role in many (patho)physiological conditions. Among them, cathepsins L, S, K and B are subjects of several drug discovery programs. Besides their role as drug targets, cysteine cathepsins are additionally considered to be possible biomarkers for inflammation and cancer. Herein, we describe the design, synthesis, biological evaluation and spectral properties of fluorescently labeled dipeptide- and azadipeptide nitriles.

  11. Fluorescence based spectral assessment of pork meat freshness

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Development of sensitive, nondestructive measurement methods for meat freshness is necessary to ensure safe distribution of meat products in the continually growing meat market. Fluorescence spectral technology has been shown to be a promising measurement method for quality and safety evaluation of ...

  12. Development of a Green Fluorescent Protein-Based Laboratory Curriculum

    ERIC Educational Resources Information Center

    Larkin, Patrick D.; Hartberg, Yasha

    2005-01-01

    A laboratory curriculum has been designed for an undergraduate biochemistry course that focuses on the investigation of the green fluorescent protein (GFP). The sequence of procedures extends from analysis of the DNA sequence through PCR amplification, recombinant plasmid DNA synthesis, bacterial transformation, expression, isolation, and…

  13. Integrated microspectrometer for fluorescence based analysis in a microfluidic format.

    PubMed

    Hu, Zhixiong; Glidle, Andrew; Ironside, Charles N; Sorel, Marc; Strain, Michael J; Cooper, Jon; Yin, Huabing

    2012-08-21

    We have demonstrated a monolithic integrated arrayed waveguide grating (AWG) microspectrometer microfluidic platform capable of fluorescence spectroscopic analysis. The microspectrometer in this proof of concept study has a small (1 cm × 1 cm) footprint and 8 output channels centred on different wavelengths. We show that the signals from the output channels detected on a camera chip can be used to recreate the complete fluorescence spectrum of an analyte. By making fluorescence measurements of (i) mixed quantum dot solutions, (ii) an organic fluorophore (Cy5) and (iii) the propidium iodide (PI)-DNA assay, we illustrate the unique advantages of the AWG platform for simultaneous, quantitative multiplex detection and its capability to detect small spectroscopic shifts. Although the current system is designed for fluorescence spectroscopic analysis, in principle, it can be implemented for other types of analysis, such as Raman spectroscopy. Fabricated using established semiconductor industry methods, this miniaturised platform holds great potential to create a handheld, low cost biosensor with versatile detection capability.

  14. The Mechanisms and Biomedical Applications of an NIR BODIPY-Based Switchable Fluorescent Probe

    PubMed Central

    Cheng, Bingbing; Bandi, Venugopal; Yu, Shuai; D’Souza, Francis; Nguyen, Kytai T.; Hong, Yi; Tang, Liping; Yuan, Baohong

    2017-01-01

    Highly environment-sensitive fluorophores have been desired for many biomedical applications. Because of the noninvasive operation, high sensitivity, and high specificity to the microenvironment change, they can be used as excellent probes for fluorescence sensing/imaging, cell tracking/imaging, molecular imaging for cancer, and so on (i.e., polarity, viscosity, temperature, or pH measurement). In this work, investigations of the switching mechanism of a recently reported near-infrared environment-sensitive fluorophore, ADP(CA)2, were conducted. Besides, multiple potential biomedical applications of this switchable fluorescent probe have been demonstrated, including wash-free live-cell fluorescence imaging, in vivo tissue fluorescence imaging, temperature sensing, and ultrasound-switchable fluorescence (USF) imaging. The fluorescence of the ADP(CA)2 is extremely sensitive to the microenvironment, especially polarity and viscosity. Our investigations showed that the fluorescence of ADP(CA)2 can be switched on by low polarity, high viscosity, or the presence of protein and surfactants. In wash-free live-cell imaging, the fluorescence of ADP(CA)2 inside cells was found much brighter than the dye-containing medium and was retained for at least two days. In all of the fluorescence imaging applications conducted in this study, high target-to-noise (>5-fold) was achieved. In addition, a high temperature sensitivity (73-fold per Celsius degree) of ADP(CA)2-based temperature probes was found in temperature sensing. PMID:28208666

  15. The Mechanisms and Biomedical Applications of an NIR BODIPY-Based Switchable Fluorescent Probe.

    PubMed

    Cheng, Bingbing; Bandi, Venugopal; Yu, Shuai; D'Souza, Francis; Nguyen, Kytai T; Hong, Yi; Tang, Liping; Yuan, Baohong

    2017-02-11

    Highly environment-sensitive fluorophores have been desired for many biomedical applications. Because of the noninvasive operation, high sensitivity, and high specificity to the microenvironment change, they can be used as excellent probes for fluorescence sensing/imaging, cell tracking/imaging, molecular imaging for cancer, and so on (i.e., polarity, viscosity, temperature, or pH measurement). In this work, investigations of the switching mechanism of a recently reported near-infrared environment-sensitive fluorophore, ADP(CA)₂, were conducted. Besides, multiple potential biomedical applications of this switchable fluorescent probe have been demonstrated, including wash-free live-cell fluorescence imaging, in vivo tissue fluorescence imaging, temperature sensing, and ultrasound-switchable fluorescence (USF) imaging. The fluorescence of the ADP(CA)₂ is extremely sensitive to the microenvironment, especially polarity and viscosity. Our investigations showed that the fluorescence of ADP(CA)₂ can be switched on by low polarity, high viscosity, or the presence of protein and surfactants. In wash-free live-cell imaging, the fluorescence of ADP(CA)₂ inside cells was found much brighter than the dye-containing medium and was retained for at least two days. In all of the fluorescence imaging applications conducted in this study, high target-to-noise (>5-fold) was achieved. In addition, a high temperature sensitivity (73-fold per Celsius degree) of ADP(CA)₂-based temperature probes was found in temperature sensing.

  16. Fluorescent detection of single nucleotide polymorphism utilizing a hairpin DNA containing a nucleotide base analog pyrrolo-deoxycytidine as a fluorescent probe.

    PubMed

    Zhang, Hongge; Wang, Minjuan; Gao, Qiang; Qi, Honglan; Zhang, Chengxiao

    2011-05-15

    A novel fluorescent method for the detection of single nucleotide polymorphism (SNP) was developed using a hairpin DNA containing nucleotide base analog pyrrolo-deoxycytidine (P-dC) as a fluorescent probe. This fluorescent probe was designed by incorporating a fluorescent P-dC into a stem of the hairpin DNA, whose sequence of the loop moiety complemented the target single strand DNA (ss-DNA). In the absence of the target ss-DNA, the fluorescent probe stays a closed configuration in which the P-dC is located in the double strand stem of the fluorescent probe, such that there is weak fluorescence, attributed to a more efficient stacking and collisional quenching of neighboring bases. In the presence of target ss-DNA, upon hybridizing the ss-DNA to the loop moiety, a stem-loop of the fluorescent probe is opened and the P-dC is located in the ss-DNA, thus resulting in strong fluorescence. The effective discrimination of the SNP, including single base mismatch ss-DNA (A, T, G) and double mismatch DNA (C, C), against perfect complementary ss-DNA was achieved by increased fluorescence intensity, and verified by thermal denaturation and circular dichroism spectroscopy. Relative fluorescence intensity had a linear relationship with the concentration of perfect complementary ss-DNA and ranged from 50 nM to 3.0 μM. The linear regression equation was F/F(0)=2.73 C (μM)+1.14 (R=0.9961) and the detection limit of perfect complementary ss-DNA was 16 nM (S/N=3). This study demonstrates that a hairpin DNA containing nucleotide base analog P-dC is a promising fluorescent probe for the effective discrimination of SNP and for highly sensitive detection of perfect complementary DNA.

  17. Evaluation of path-history-based fluorescence Monte Carlo method for photon migration in heterogeneous media.

    PubMed

    Jiang, Xu; Deng, Yong; Luo, Zhaoyang; Wang, Kan; Lian, Lichao; Yang, Xiaoquan; Meglinski, Igor; Luo, Qingming

    2014-12-29

    The path-history-based fluorescence Monte Carlo method used for fluorescence tomography imaging reconstruction has attracted increasing attention. In this paper, we first validate the standard fluorescence Monte Carlo (sfMC) method by experimenting with a cylindrical phantom. Then, we describe a path-history-based decoupled fluorescence Monte Carlo (dfMC) method, analyze different perturbation fluorescence Monte Carlo (pfMC) methods, and compare the calculation accuracy and computational efficiency of the dfMC and pfMC methods using the sfMC method as a reference. The results show that the dfMC method is more accurate and efficient than the pfMC method in heterogeneous medium.

  18. Exciton energy transfer-based quantum dot fluorescence sensing array: "chemical noses" for discrimination of different nucleobases.

    PubMed

    Liu, Jianbo; Li, Gui; Yang, Xiaohai; Wang, Kemin; Li, Li; Liu, Wei; Shi, Xing; Guo, Yali

    2015-01-20

    A novel exciton energy transfer-based fluorescence sensing array for the discrimination of different nucleobases was developed through target nucleobase-triggered self-assembly of quantum dots (QDs). Four QD nanoprobes with different ligand receptors, including mercaptoethylamine, N-acetyl-l-cysteine, 2-dimethyl-aminethanethiol, and thioglycolic acid, were created to detect and identify nucleobase targets. These QDs served as both selective recognition scaffolds and signal transduction elements for a biomolecule target. The extent of particle assembly, induced by the analyte-triggered self-assembly of QDs, led to an exciton energy transfer effect between interparticles that gave a readily detectable fluorescence quenching and distinct fluorescence response patterns. These patterns are characteristic for each nucleobase and can be quantitatively differentiated by linear discriminate analysis. Furthermore, a fingerprint-based barcode was established to conveniently discriminate the nucleobases. This pattern sensing was successfully used to identify nucleobase samples at unknown concentrations and five rare bases. In this "chemical noses" strategy, the robust characteristics of QD nanoprobes, coupled with the diversity of surface functionality that can be readily obtained using nanoparticles, provides a simple and label-free biosensing approach that shows great promise for biomedical applications.

  19. The development of chlorophyll-based markers in poultry diets to aid detection of fluorescent fecal contamination.

    PubMed

    Lee, M R F; Leemans, D; Theobald, V J; Fleming, H R; Gay, A P

    2013-12-01

    Incidents of foodborne illness associated with consuming undercooked or raw chicken are often linked to 2 causative pathogens: Campylobacter spp. or Salmonella spp. Numerous studies have shown that contamination of carcasses results when pathogens are transferred from the intestinal tract or fecal material on feet and feathers to the dressed carcass. Ultraviolet spectral imaging to detect surface fecal and ingesta contamination on poultry carcasses may provide a solution to aid detection. However, poultry diets do not provide sufficiently high levels of natural fluorophores for this system to be reliable. This study investigated the potential of chlorophyll-based feed additives to improve fluorescence of the feces and narrow the excitation and emission wavelengths to aid in the development of a simple visualization system. Twenty-four hens (Gallus gallus domesticus) were allocated at random to 1 of 4 treatments: control (C, no marker), Zn chlorophyllin, Mg chlorophyllin, or Fe chlorophyllin. All markers were incorporated into mash before pelleting at a rate of 1 g/kg of DM. The experiment consisted of two 4 × 4 Latin squares with each period consisting of 2 wk. Feces were collected and extracted in acetone:water (50:50; vol/vol) with fecal fluorescence emission spectra determined using a Jasco FP-6200 Spectrofluorometer with excitation at 382 nm. A main peak evolved at wavelength 670 nm with the total area under the peak used as fluorescence intensity. Following 7 d of marker supplementation, the 3 markers improved the fluorescence intensity by ×14.8, 12.8, and 6.9 for Fe, Mg, and Zn chlorophyllin, respectively, compared with the control. The addition of feces containing Mg chlorophyllin to chicken carcass increased detection of the feces compared with feces with no marker. Also, due to the plain background of chicken skin, a simple image at 675 nm with appropriate thresholds would allow detection of contaminated carcasses at the current slaughter line speed

  20. A graphitic carbon nitride based fluorescence resonance energy transfer detection of riboflavin.

    PubMed

    Han, Jing; Zou, Hong Yan; Gao, Ming Xuan; Huang, Cheng Zhi

    2016-01-01

    Fluorescence resonance energy transfer (FRET), which occurs between two luminescent chromophores, can greatly improve the selectivity and sensitivity of a fluorescent assay when a ratiometric signaling with the fluorescence enhancement of the acceptor at the expense of the donor is adopted. In this study, a fluorescence ratiometric detection (FRD) of riboflavin (RF) has been made based on FRET, as the strong overlap occurred between the emission spectrum of graphitic carbon nitride (g-C3N4) and absorption spectrum of RF, in which g-C3N4 acts as the energy donor and RF as the energy acceptor. With increasing concentration of RF, the fluorescence intensity of g-C3N4 emission at 444 nm decreased and the fluorescence peak at 523 nm for RF increased regularly, making the fluorescence intensity ratio of 523 nm to 444 nm linearly dependent on the concentration of RF in the range from 0.4 μM to 10 μM, giving a limit of the detection of 170 nM. This method can be used to quantify RF in complex systems such as milk and drink, showing that the novel FRET-based fluorescence ratiometric detection can enable an attractive assay platform for analytes of interest.

  1. Lanthanide based dual-emission fluorescent probe for detection of mercury (II) in milk.

    PubMed

    Tan, Hongliang; Li, Qian; Ma, Chanjiao; Song, Yonghai; Xu, Fugang; Chen, Shouhui; Wang, Li

    2015-01-15

    It is highly desirable to develop a simple and sensitive method for Hg(2+) detection because of the dangerous nature of Hg(2+). In this work, we prepared a dual-emission fluorescent probe for Hg(2+) detection by combining two lanthanide chelates with different emission wavelengths. Green-emitting terbium (Tb(3+)) chelates as reference signals were embedded into SiO2 nanoparticles and red-emitting europium (Eu(3+)) chelates as response units were covalently linked to the surface of silica shell. Upon the addition of Hg(2+), the fluorescence of Eu(3+) chelates can be selectively quenched, while the fluorescence of Tb(3+) chelates remained unchanged. As a kind of Hg(2+) nanosensor, the dual-emission fluorescent probe exhibited excellent selectivity to Hg(2+) and high sensitivity up to 7.07 nM detection limit. The Hg(2+) levels in drinking water and milk samples were determined by using the dual-emission fluorescent probe with satisfied recovery. Additionally, our probe has a long enough fluorescence lifetime, which can avoid the interference from autofluorescence of the biological samples. We envision that the proposed probe could find great potential applications for ultrasensitive time-resolved fluorometric assays and biomedical imaging in the future.

  2. Time-domain imaging with quench-based fluorescent contrast agents

    NASA Astrophysics Data System (ADS)

    Akers, Walter J.; Solomon, Metasebya; Sudlow, Gail P.; Berezin, Mikhail; Achilefu, Samuel

    2012-03-01

    Quench-based probes utilize unique characteristics of fluorescence resonance energy transfer (FRET) to enhance contrast upon de-quenching. This mechanism has been used in a variety of molecular probes for imaging of cancer related enzyme activity such as matrix metalloproteinases, cathepsins and caspases. While non-fluorescent upon administration, fluorescence can be restored by separation of donor and acceptor, resulting in higher intensity in the presence of activator. Along with decreased quantum yield, FRET also results in altered fluorescence lifetime. Time-domain imaging can further enhance contrast and information yield from quench-based probes. We present in vivo time-domain imaging for detecting activation of quench-based probes. Quench-based probes utilize unique characteristics of fluorescence resonance energy transfer (FRET) to enhance contrast upon de-quenching. This mechanism has been used in a variety of molecular probes for imaging of cancer related enzyme activity such as matrix metalloproteinases, cathepsins and caspases. While non-fluorescent upon administration, fluorescence can be restored by separation of donor and acceptor, resulting in higher intensity in the presence of activator. Along with decreased quantum yield, FRET also results in altered fluorescence lifetime. Time-domain imaging can further enhance contrast and information yield from quench-based probes. We present in vivo time-domain imaging for detecting activation of quench-based probes. Time-domain diffuse optical imaging was performed to assess the FRET and quenching in living mice with orthotopic breast cancer. Tumor contrast enhancement was accompanied by increased fluorescence lifetime after administration of quenched probes selective for matrix metalloproteinases while no significant change was observed for non-quenched probes for integrin receptors. These results demonstrate the utility of timedomain imaging for detection of cancer-related enzyme activity in vivo.

  3. Fluorescent acridine-based receptors for H2PO4(-).

    PubMed

    Martí-Centelles, Vicente; Burguete, M Isabel; Galindo, Francisco; Izquierdo, M Angeles; Kumar, D Krishna; White, Andrew J P; Luis, Santiago V; Vilar, Ramón

    2012-01-06

    Two new pseudopeptidic molecules (one macrocyclic and one open chain) containing an acridine unit have been prepared. The fluorescence response of these receptors to a series of acids was measured in CHCl(3). Receptors are selective to H(2)PO(4)(-) versus HSO(4)(-), and an even higher selectivity is found over other anions such as Cl(-), Br(-), CH(3)COO(-), and CF(3)COO(-). We show that the macrocyclic receptor is more selective for H(2)PO(4)(-) than the related open chain receptor. The supramolecular interactions of triprotonated receptors with different anions have been modeled in silico and have been studied by different experimental techniques. Optimized geometries obtained by computational calculations agree well with experimental data, in particular fluorescence experiments, suggesting that the selective supramolecular interaction takes places through coordination of the anions to the triprotonated form of the receptor.

  4. Fluorescence-based video profile beam diagnostics: Theory and experience

    SciTech Connect

    Sandoval, D.; Gilpatrick, D.; Shinas, M.; Garcia, R.; Yuan, V.; Zander, M.

    1994-05-01

    Inelastic collisions between accelerated particles and residual gas in the accelerator vessel can cause the residual gas to fluoresce. The gas fluorescence intensity is proportional to the current density of the particle beam. This process provides the foundation for a video diagnostic system to measure the profile and position of accelerated particle beams. This, in fact, has proven to be a useful diagnostic at several installations. This paper describes the light production process resulting from beam -- residual gas interactions and gives formulas for estimating the beam radiance for various conditions. Ground Test Accelerator (GTA) radiance calculations will be used as an example. In addition, measurement experiences with the GTA video diagnostics system will be discussed.

  5. Fluorescence-based video profile beam diagnostics: Theory and experience

    SciTech Connect

    Sandoval, D.P.; Garcia, R.C.; Gilpatrick, J.D.; Shinas, M.A.; Wright, R.; Yuan, V.; Zander, M.E. )

    1994-10-10

    Inelastic collisions between accelerated particles and residual gas in the accelerator vessel can cause the residual gas to fluoresce. The gas fluorescence intensity is proportional to the current density of the particle beam. This process provides the foundation for a video diagnostics system to measure the profile and position of accelerated particle beams. This, in fact, has proven to be a useful diagnostic at several installations. This paper describes the light production process resulting from beam-residual gas interactions and gives formulas for estimating the beam radiance for various conditions. Ground Test Accelerator (GTA) radiance calculations will be used as an example. In addition, measurement experiences with the GTA video diagnostics system will be discussed.

  6. Tetraphenylethene-based aggregation-induced emission fluorescent organic nanoparticles: facile preparation and cell imaging application.

    PubMed

    Zhang, Xiqi; Liu, Meiying; Yang, Bin; Zhang, Xiaoyong; Wei, Yen

    2013-12-01

    Tetraphenylethene-based (TPE) aggregation-induced emission fluorescent organic nanoparticles (FONs) were facilely prepared via Schiff base condensation with ɛ-polylysine (Ply) and subsequent reduction to form stable CN covalent bond. Thus obtained TPE-Ply FONs were characterized by a series of techniques including fluorescent spectroscopy, Fourier transform infrared spectroscopy and transmission electron microscopy. Biocompatibility evaluation and cell uptake behavior of TPE-Ply FONs were further investigated to explore their potential biomedical application. We demonstrated that such FONs showed high water dispersibility, intense fluorescence, uniform morphology (100-200nm) and excellent biocompatibility, making them promising for cell imaging application.

  7. Quantitative and qualitative 5-aminolevulinic acid–induced protoporphyrin IX fluorescence in skull base meningiomas

    PubMed Central

    Bekelis, Kimon; Valdés, Pablo A.; Erkmen, Kadir; Leblond, Frederic; Kim, Anthony; Wilson, Brian C.; Harris, Brent T.; Paulsen, Keith D.; Roberts, David W.

    2011-01-01

    Object Complete resection of skull base meningiomas provides patients with the best chance for a cure; however, surgery is frequently difficult given the proximity of lesions to vital structures, such as cranial nerves, major vessels, and venous sinuses. Accurate discrimination between tumor and normal tissue is crucial for optimal tumor resection. Qualitative assessment of protoporphyrin IX (PpIX) fluorescence following the exogenous administration of 5-aminolevulinic acid (ALA) has demonstrated utility in malignant glioma resection but limited use in meningiomas. Here the authors demonstrate the use of ALA-induced PpIX fluorescence guidance in resecting a skull base meningioma and elaborate on the advantages and disadvantages provided by both quantitative and qualitative fluorescence methodologies in skull base meningioma resection. Methods A 52-year-old patient with a sphenoid wing WHO Grade I meningioma underwent tumor resection as part of an institutional review board–approved prospective study of fluorescence-guided resection. A surgical microscope modified for fluorescence imaging was used for the qualitative assessment of visible fluorescence, and an intraoperative probe for in situ fluorescence detection was utilized for quantitative measurements of PpIX. The authors assessed the detection capabilities of both the qualitative and quantitative fluorescence approaches. Results The patient harboring a sphenoid wing meningioma with intraorbital extension underwent radical resection of the tumor with both visibly and nonvisibly fluorescent regions. The patient underwent a complete resection without any complications. Some areas of the tumor demonstrated visible fluorescence. The quantitative probe detected neoplastic tissue better than the qualitative modified surgical microscope. The intraoperative probe was particularly useful in areas that did not reveal visible fluorescence, and tissue from these areas was confirmed as tumor following histopathological

  8. A simple method for the multi-elemental analysis of organic fertilizer by slurry sampling and total reflection X-ray fluorescence.

    PubMed

    Resende, Luciene V; Nascentes, Clésia C

    2016-01-15

    A simple and fast method for the multi-elemental determination of 18 inorganic constituents (P, S, Cl, K, Ca, Ti, Cr, V, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, Ba and Pb) in organic fertilizers employing slurry sampling and total reflection X-ray fluorescence (TXRF) is presented. A 2(3) factorial design with a central point was employed to optimize the slurry sampling procedure. The internal standard and instrumental conditions were optimized by univariate studies. The selectivity of the method to determining Se, As, Pb, Cr, Ni and Cd was assessed. The accuracy was evaluated by the analysis of four standard reference materials (SRM). The recoveries varied from 72% to 114%. For most of the elements, good agreement was achieved between the certified value and the value measured in the SRM. The relative standard deviation (RSD %) ranged from 0.5% to 14%. The evaluated method was applied to the determination of analytes in the press cake of palm, castor, curcas, sunflower, fodder turnip, white lupin, rapeseed and pequi, and their potential to be used as organic fertilizer was evaluated in accordance with Brazilian legislation.

  9. A simple high-throughput method for determination of antiepileptic analogues of γ-aminobutyric acid in pharmaceutical dosage forms using microplate fluorescence reader.

    PubMed

    Martinc, Boštjan; Vovk, Tomaž

    2013-01-01

    Pregabalin (PGB), gabapentin (GBP), and vigabatrin (VGB) are structural analogues of γ-aminobutyric acid used for the treatment of different forms of epilepsy. Their analytical determination is challenging since these molecules have no significant UV or visible absorption. Several derivatization methods have been developed and used for their determination in bulk or pharmaceutical dosage forms. We aimed to develop a high- throughput method using a microplate reader with fluorescence detection and simple derivatization with fluorescamine. Obtained method involves derivatization step of only 5 min at room temperature and simultaneous measurements of 96 samples (λex 395, λem 476 nm) thus rendering excellent high-throughput analysis. The method was found to be linear with r²>0.998 across investigated analytical ranges of 0.75 to 30.0 µg/mL for PGB, 2.00 to 80.0 µg/mL for GBP, and 1.50 to 60.0 µg/mL for VGB. Intraday and interday precision values did not exceed 4.93%. The accuracy was ranging between 96.6 to 103.5%. The method was also found to be specific since used excipients did not interfere with the method. The robustness study showed that derivatization procedure is more robust than spectrofluorimetric conditions. The developed high-throughput method was successfully applied for determination of drug content and dissolution profiles in pharmaceutical dosage forms of studied antiepileptic drugs.

  10. Molecular dynamics study of the structure and performance of simple and double bases propellants.

    PubMed

    Ma, Xiufang; Zhu, Weihua; Xiao, Jijun; Xiao, Heming

    2008-08-15

    To investigate the structure and performance of simple and double bases propellants, the nitrocellulose (NC), nitroglycerin (NG), and double mixed system (NC+NG) have been simulated by using the molecular dynamics (MD) method with the COMPASS force field. The interactions between NC and NG have been analyzed by means of pair correlation functions. The mechanical properties of the three model systems, i.e. elastic coefficients, modulus, Cauchy pressure, and Poisson's ratio, etc., have been obtained. It is found that the rigidity, ductibility, and tenacity of the double bases propellants (NC+NG) are stronger than those of simple base propellants (NC), which attributes to the effect of NG and the strong interactions between NC and NG. The detonation properties of the three systems have also been calculated and the results show that compared with the simple base propellant (NC), the detonation heat and detonation velocity of the double base propellants (NC+NG) are increased.

  11. A benzothiazole-based fluorescent probe for distinguishing and bioimaging of Hg(2+) and Cu(2).

    PubMed

    Gu, Biao; Huang, Liyan; Su, Wei; Duan, Xiaoli; Li, Haitao; Yao, Shouzhuo

    2017-02-15

    A new benzothiazole-based fluorescent probe 2-(benzo[d]thiazol-2-yl)-4-(1,3- dithian-2-yl)phenol (BT) with two different reaction sites, a thioacetal group (site 1 for Hg(2+)), and O and N atoms of the benzothiazole dye (site 2 for Cu(2+)), was designed and synthesized. The probe BT showed ratiometric fluorescent response to Hg(2+) and fluorescence quenching behavior to Cu(2+), which induces naked-eye fluorescent color changes from green to blue and colorless, respectively. Moreover, it displayed highly sensitivity and selectivity toward Hg(2+) and Cu(2+) without interference from other metal ions. The sensing mechanisms were also confirmed by (1)H NMR titration, mass spectrum and Job's plot analyses. Finally, probe BT was successfully used for fluorescent imaging of Hg(2+) and Cu(2+) in living cells, demonstrating its potential applications in biological science.

  12. Angular shaping of fluorescence from synthetic opal-based photonic crystal

    NASA Astrophysics Data System (ADS)

    Boiko, Vitalii; Dovbeshko, Galyna; Dolgov, Leonid; Kiisk, Valter; Sildos, Ilmo; Loot, Ardi; Gorelik, Vladimir

    2015-02-01

    Spectral, angular, and temporal distributions of fluorescence as well as specular reflection were investigated for silica-based artificial opals. Periodic arrangement of nanosized silica globules in the opal causes a specific dip in the defect-related fluorescence spectra and a peak in the reflectance spectrum. The spectral position of the dip coincides with the photonic stop band. The latter is dependent on the size of silica globules and the angle of observation. The spectral shape and intensity of defect-related fluorescence can be controlled by variation of detection angle. Fluorescence intensity increases up to two times at the edges of the spectral dip. Partial photobleaching of fluorescence was observed. Photonic origin of the observed effects is discussed.

  13. A multi-state fluorescent switch based on a diarylethene with an acridine unit

    NASA Astrophysics Data System (ADS)

    Tian, Zhaoyan; Cui, Shiqiang; Zheng, Chunhong; Pu, Shouzhi

    2017-02-01

    A new asymmetrical fluorescent diarylethene derivative with an acridine unit was synthesized by Schiff base condensation. The derivative was sensitive to lights and special metal ions. Stimulated by UV/vis lights and Zn2 +, distinct changes were observed in UV-vis and fluorescent spectra. Upon addition of Zn2 +, the derivative emission peak was blue-shifted by 34 nm and the emission intensity was enhanced by 16 fold, accompanied by the fluorescent color changed from red to light yellow, due to the formation of a 1:1 metal/ligand complex. The complex exhibited excellent fluorescence switching upon irradiation with UV light. Taking advantage of the lights and Zn2 + stimuli (inputs), and fluorescence intensity at 580 nm (output), a molecular logic gate was constructed. Moreover, a new absorption band centered at 420-450 nm emerged upon exposure to Zn2 +. The dramatic color change of the solution made the 'naked-eyes' detection of Zn2 + possible.

  14. Angular shaping of fluorescence from synthetic opal-based photonic crystal.

    PubMed

    Boiko, Vitalii; Dovbeshko, Galyna; Dolgov, Leonid; Kiisk, Valter; Sildos, Ilmo; Loot, Ardi; Gorelik, Vladimir

    2015-01-01

    Spectral, angular, and temporal distributions of fluorescence as well as specular reflection were investigated for silica-based artificial opals. Periodic arrangement of nanosized silica globules in the opal causes a specific dip in the defect-related fluorescence spectra and a peak in the reflectance spectrum. The spectral position of the dip coincides with the photonic stop band. The latter is dependent on the size of silica globules and the angle of observation. The spectral shape and intensity of defect-related fluorescence can be controlled by variation of detection angle. Fluorescence intensity increases up to two times at the edges of the spectral dip. Partial photobleaching of fluorescence was observed. Photonic origin of the observed effects is discussed.

  15. [Photosynthetic Parameters Inversion Algorithm Study Based on Chlorophyll Fluorescence Induction Kinetics Curve].

    PubMed

    Qiu, Xiao-han; Zhang, Yu-jun; Yin, Gao-fang; Shi, Chao-yi; Yu, Xiao-ya; Zhao, Nan-jing; Liu, Wen-qing

    2015-08-01

    The fast chlorophyll fluorescence induction curve contains rich information of photosynthesis. It can reflect various information of vegetation, such as, the survival status, the pathological condition and the physiology trends under the stress state. Through the acquisition of algae fluorescence and induced optical signal, the fast phase of chlorophyll fluorescence kinetics curve was fitted. Based on least square fitting method, we introduced adaptive minimum error approaching method for fast multivariate nonlinear regression fitting toward chlorophyll fluorescence kinetics curve. We realized Fo (fixedfluorescent), Fm (maximum fluorescence yield), σPSII (PSII functional absorption cross section) details parameters inversion and the photosynthetic parameters inversion of Chlorella pyrenoidosa. And we also studied physiological variation of Chlorella pyrenoidosa under the stress of Cu(2+).

  16. A new boronic acid fluorescent sensor based on fluorene for monosaccharides at physiological pH

    NASA Astrophysics Data System (ADS)

    Hosseinzadeh, Rahman; Mohadjerani, Maryam; Pooryousef, Mona; Eslami, Abbas; Emami, Saeed

    2015-06-01

    Fluorescent boronic acids are very useful fluorescent sensor for detection of biologically important saccharides. Herein we synthesized a new fluorene-based fluorescent boronic acid that shows significant fluorescence changes upon addition of saccharides at physiological pH. Upon addition of fructose, sorbitol, glucose, galactose, ribose, and maltose at different concentration to the solution of 7-(dimethylamino)-9,9-dimethyl-9H-fluoren-2-yl-2-boronic acid (7-DMAFBA, 1), significant decreases in fluorescent intensity were observed. It was found that this boronic acid has high affinity (Ka = 3582.88 M-1) and selectivity for fructose over glucose at pH = 7.4. The sensor 1 showed a linear response toward D-fructose in the concentrations ranging from 2.5 × 10-5 to 4 × 10-4 mol L-1 with the detection limit of 1.3 × 10-5 mol L-1.

  17. Visualizing BPA by molecularly imprinted ratiometric fluorescence sensor based on dual emission nanoparticles.

    PubMed

    Lu, Hongzhi; Xu, Shoufang

    2017-06-15

    Construction of ratiometric fluorescent probe often involved in tedious multistep preparation or complicated coupling or chemical modification process. The emergence of dual emission fluorescent nanoparticles would simplify the construction process and avoids the tedious chemical coupling. Herein, we reported a facile strategy to prepare ratiometric fluorescence molecularly imprinted sensor based on dual emission nanoparticles (d-NPs) which comprised of carbon dots and gold nanoclusters for detection of Bisphenol A (BPA). D-NPs emission at 460nm and 580nm were first prepared by seed growth co-microwave method using gold nanoparticles as seeds and glucose as precursor for carbon dots. When they were applied to propose ratiometric fluorescence molecularly imprinted sensor, the preparation process was simplified, and the sensitivity of sensor was improved with detection limit of 29nM, and visualizing BPA was feasible based on the distinguish fluorescence color change. The feasibility of the developed method in real samples was successfully evaluated through the analysis of BPA in water samples with satisfactory recoveries of 95.9-98.9% and recoveries ranging from 92.6% to 98.6% in canned food samples. When detection BPA in positive feeding bottles, the results agree well with those obtained by accredited method. The developed method proposed in this work to prepare ratiometric fluorescence molecularly imprinted sensor based on dual emission nanoparticles proved to be a convenient, reliable and practical way to prepared high sensitive and selective fluorescence sensors.

  18. A fluorescence-based assay for indoleamine 2,3-dioxygenase.

    PubMed

    Matin, Azadeh; Streete, Isla M; Jamie, Ian M; Truscott, Roger J W; Jamie, Joanne F

    2006-02-01

    A rapid and sensitive fluorescence-based bioassay for determination of indoleamine 2,3-dioxygenase (IDO) activity has been developed. This assay relies on the quantification of the amount of kynurenine produced in the assay medium by fluorescence and complements the standard absorbance and high-performance liquid chromatography (HPLC) assay methods. The fluorescence method has limits of detection similar to those of the standard assay methods. Measured activities of IDO, including in the presence of tryptophan-based inhibitors, were in statistical agreement with the absorbance and HPLC assay methods. The fluorescence-based assay was also suitable for assessment of IDO inhibition by compounds that are incompatible with the absorbance method.

  19. A fluorescence-based assay for measuring the redox potential of 5-lipoxygenase inhibitors.

    PubMed

    Lee, Sangchul; Park, Youngsam; Kim, Junghwan; Han, Sung-Jun

    2014-01-01

    The activities and side effects of 5-lipoxygenase (5-LO) inhibitors can be predicted by identifying their redox mechanisms. In this study, we developed a fluorescence-based method to measure the redox potential of 5-LO inhibitors and compared it to the conventional, absorbance-based method. After the pseudo-peroxidase reaction, the amount of remaining lipid peroxide was quantified using the H2DCFDA (2',7'-dichlorodihydrofluorescein diacetate) fluorescence dye. Our method showed large signal windows and provided comparable redox potential values. Importantly, the redox mechanisms of known inhibitors were accurately measured with the fluorescence assay, whereas the conventional, absorbance-based method showed contradictory results. Our findings suggest that our developed method is a better alternative for classifying the redox potential of 5-LO inhibitors, and the fluorescence assay can be effectively used to study the mechanisms of action that are related to redox cycling.

  20. [Synthesis and theoretical study on fluorescence property of 4- (2-hydroxybenzylideneamino) phenyl ethanone schiff base].

    PubMed

    Liang, Xiao-Rui; Wang, Gang; Jiang, Yan-Lan; Qu, Cheng-Li; Wang, Xiu-Juan; Zhao, Bo

    2013-12-01

    Using salicylaldehyde and 4-aminophenyl ethanone as raw material, a Schiff base derivative 4-(2-hydroxybenzylidene-amino) phenyl ethanone was synthesized by the solid phase reaction method at room temperature. The structure of the product was characterized by elemental analysis and 1 HNMR The UV spectra, fluorescence emission spectra and fluorescence quantum yield of the title Schiff base derivative were investigated. The results showed that this Schiff base displayed superior fluorescence property. The ground state configuration of the title Schiff base was optimized by density functional theory (DFT) method at the B3LYP/6-311G level. After vibrational analysis, there is no imaginary frequency, which indicates that the structure is stable. Then the ground state configuration was optimized to the excited state configuration by the method of single excited interactions CIS. Based on the optimized structure for the ground state and excited state time-dependent density functional theory (TD-DFT) calculations were carried out at the B3LYP/6-31G level to predict the absorption spectra and the fluorescence spectra. The results show that the computed spectra were comparable with the spectra from the experiments. The relationship between the molecular structure and the fluorescence property of 4-(2-hydroxybenzylideneamino) phenyl ethanone was also discussed. The results obtained may provide some theoretical guidance for the design of new fluorescence compounds.

  1. Label free selective detection of estriol using graphene oxide-based fluorescence sensor

    NASA Astrophysics Data System (ADS)

    Kushwaha, H. S.; Sao, Reshma; Vaish, Rahul

    2014-07-01

    Water-soluble and fluorescent Graphene oxide (GO) is biocompatible, easy, and economical to synthesize. Interestingly, GO is also capable of quenching fluorescence. On the basis of its fluorescence and quenching abilities, GO has been reported to serve as an energy acceptor in a fluorescence resonance energy transfer (FRET) sensor. GO-based FRET biosensors have been widely reported for sensing of proteins, nucleic acid, ATP (Adenosine triphosphate), etc. GO complexes with fluorescent dyes and enzymes have been used to sense metal ions. Graphene derivatives have been used for sensing endocrine-disrupting chemicals like bisphenols and chlorophenols with high sensitivity and good reproducibility. On this basis, a novel GO based fluorescent sensor has been successfully designed to detect estriol with remarkable selectivity and sensitivity. Estriol is one of the three estrogens in women and is considered to be medically important. Estriol content of maternal urine or plasma acts as an important screening marker for estimating foetal growth and development. In addition, estriol is also used as diagnostic marker for diseases like breast cancer, osteoporosis, neurodegenerative and cardiovascular diseases, insulin resistance, lupus erythematosus, endometriosis, etc. In this present study, we report for the first time a rapid, sensitive with detection limit of 1.3 nM, selective and highly biocompatible method for label free detection of estriol under physiological conditions using fluorescence assay.

  2. Probes for biomolecules detection based on RET-enhanced fluorescence polarization.

    PubMed

    Ren, Dahai; Wang, Jun; Wang, Bin; You, Zheng

    2016-05-15

    Fluorescent probes based on the principle of resonance energy transfer (RET) or the principle of fluorescence polarization (FP) are already used to detect biomolecules independently. However, there were no in-depth studies about the impact of RET on FP. Also, very few studies gave a comprehensive analysis on how to effectively design such a fluorescent probe. Based on the principle of resonance energy transfer (RET), we constructed fluorescent probes (SA-488-sub-nanogold) using streptavidin labeled Alexa488 (SA-488), nanogold and biotinylated substrate peptide (biotin-subpeptide). The influence of the structure and the ingredients of the substrate peptide were discussed. After SA-488 was combined with the biotin-subpeptide and the nanogold, its fluorescence intensity (FI) would be suppressed due to the energy transfer, leading to an increase in its volume and mass. The suppression of the FI led to a decrease in SA-488's effective concentration, and the increase in the volume or mass prolonged the SA-488's rotational relaxation time. Both changes increased SA-488's polarization in the solution. Therefore, the FP performance of the probe is enhanced by the RET. Using the probe, trypsin and biotin were detected by the change in both fluorescence intensity and fluorescence polarization, showing higher reliability, higher sensitivity, and a lower detection limit.

  3. When Simple Harmonic Motion Is Not that Simple: Managing Epistemological Complexity by Using Computer-Based Representations

    ERIC Educational Resources Information Center

    Parnafes, Orit

    2010-01-01

    Many real-world phenomena, even "simple" physical phenomena such as natural harmonic motion, are complex in the sense that they require coordinating multiple subtle foci of attention to get the required information when experiencing them. Moreover, for students to develop sound understanding of a concept or a phenomenon, they need to learn to get…

  4. A resorufin-based colorimetric and fluorescent probe for live-cell monitoring of hydrazine.

    PubMed

    Qian, Yong; Lin, Jie; Han, Lujing; Lin, Lin; Zhu, Hailiang

    2014-08-15

    We report a novel colorimetric and red-emitting fluorescent probe for hydrazine detection based on resorufin platform. This OFF-ON fluorescent probe shows a large (117nm) red-shifted absorption spectrum and the color changes from colorless to red upon addition of hydrazine in the aqueous solution, which can serve as a "naked-eye" probe for hydrazine. Moreover, this probe also shows a significant fluorescence increase (~16 folds) and excellent linear relationship at physiological pH. Utilizing this sensitive and selective probe, we have successfully detected hydrazine in living cells.

  5. Novel fluorescent biosensor for α-glucosidase inhibitor screening based on cationic conjugated polymers.

    PubMed

    Cao, Ali; Tang, Yanli; Liu, Yue

    2012-08-01

    A new fluorescent biosensor has been designed to screen α-glucosidase inhibitors (AGIs) sensitively by utilizing signal amplification effect of conjugated polymers. The fluorescence of cationic poly(fluorenylene phenylene) (PFP) was quenched in the presence of para-nitrophenyl-α-d-glucopyranoside and α-glucosidase, and turned on upon addition of AGIs. Thus, a new method was developed for AGIs screening based on the fluorescence turn-off/turn-on. The IC(50) values obtained for inhibitors were compared with that reported using absorption spectroscopy. All results present the new method is more sensitive and promising in screening AGIs and inhibitors of other enzymes whose hydrolysis product is 4-nitrophenol.

  6. Highly fluorescent gold nanoclusters based sensor for the detection of quercetin

    NASA Astrophysics Data System (ADS)

    Chen, Zhanguang; Qian, Sihua; Chen, Junhui; Chen, Xi

    2012-12-01

    In this contribution, novel luminescent gold nanoclusters were synthesized by utilizing bovine serum albumin as templates with a simple, rapid, and one-pot procedure. The as-prepared gold nanoclusters were highly dispersed in aqueous solution and emitted an intense red fluorescence under UV light (365 nm). They exhibited strong fluorescence and the maximum excitation and emission wavelengths were 480 and 613.5 nm. In addition, the bovine serum albumin-stabilized gold nanoclusters were successfully utilized as novel fluorescent probes for the detection of quercetin for the first time. It was found that the addition of quercetin induced the strong fluorescence intensity of the gold nanoclusters to decrease. The decrease in fluorescence intensity of the gold nanoclusters caused by quercetin allowed the sensitive detection of quercetin in the range of 8.9 × 10-8-1.8 × 10-4 mol L-1. The detection limit for quercetin is 1.8 × 10-8 mol L-1 at a signal-to-noise ratio of 3. The present sensor for quercetin detection possessed a low detection limit and wide linear range. In addition, the real samples were analyzed with satisfactory results.

  7. "Turn-off" fluorescent data array sensor based on double quantum dots coupled with chemometrics for highly sensitive and selective detection of multicomponent pesticides.

    PubMed

    Fan, Yao; Liu, Li; Sun, Donglei; Lan, Hanyue; Fu, Haiyan; Yang, Tianming; She, Yuanbin; Ni, Chuang

    2016-04-15

    As a popular detection model, the fluorescence "turn-off" sensor based on quantum dots (QDs) has already been successfully employed in the detections of many materials, especially in the researches on the interactions between pesticides. However, the previous studies are mainly focused on simple single track or the comparison based on similar concentration of drugs. In this work, a new detection method based on the fluorescence "turn-off" model with water-soluble ZnCdSe and CdSe QDs simultaneously as the fluorescent probes is established to detect various pesticides. The fluorescence of the two QDs can be quenched by different pesticides with varying degrees, which leads to the differences in positions and intensities of two peaks. By combining with chemometrics methods, all the pesticides can be qualitative and quantitative respectively even in real samples with the limit of detection was 2 × 10(-8) mol L(-1) and a recognition rate of 100%. This work is, to the best of our knowledge, the first report on the detection of pesticides based on the fluorescence quenching phenomenon of double quantum dots combined with chemometrics methods. What's more, the excellent selectivity of the system has been verified in different mediums such as mixed ion disruption, waste water, tea and water extraction liquid drugs.

  8. Tissue viability assessment via laser-based fluorescence monitor

    NASA Astrophysics Data System (ADS)

    Curtis, Craig H.; Peyghambarian, Nasser; Dereniak, Eustace L.; Frink, Edward

    1996-04-01

    A preliminary study of the degree to which recently introduced inhalation anesthetics influence the intracellular energetic metabolism of isolated perfused rat livers is undertaken via NADH fluorometry. During liver transplantation, anesthesiologists desire to maintain a high level of metabolic energy status in newly transplanted liver tissue. Ischemic storage of donor liver tissue prior to transplantation is known to inhibit mitochondrial electron transfer, which results in decreased levels of ATP and increased levels of NADH in the stored tissue. The ability of transplanted liver tissue to regenerate ATP at normal levels is desirable for early post- operative recovery of liver function. Previous studies have examined the differential effects inhalation anesthetics have on the energetic metabolism of tissue at the cellular level; the trend of such agents is to induce a dose-dependent increase in NADH fluorescence in accordance with their strengths as general anesthetics. The present study evaluates the differential effects exhibited by new inhalation anesthetics on the return of function of energetic metabolism in liver tissue. The third-harmonic (355 nm) output of a Nd:YAG laser is spatially filtered and used as the excitation source for surface fluorometric measurements of isolated buffer-perfused rat livers. Lastly, maximum fluorescence emission versus spot-size are measured.

  9. Benzothiazole-Based Neutral Ratiometric Fluorescence Sensor for Amyloid Fibrils.

    PubMed

    Mora, Aruna K; Murudkar, Sushant; Alamelu, A; Singh, Prabhat K; Chattopadhyay, Subrata; Nath, Sukhendu

    2016-11-07

    Early detection of amyloid fibrils is very important for the timely diagnosis of several neurological diseases. Thioflavin-T (ThT) is a gold standard fluorescent probe for amyloid fibrils and has been used for the last few decades. However, due to its positive charge, ThT is incapable of crossing the blood-brain barrier and cannot be used for in vivo imaging of fibrils. In the present work, we synthesized a neutral ThT derivative, 2-[2'-Me,4'-(dimethylamino)phenyl]benzothiazole (2Me-DABT), which showed a strong affinity towards the amyloid fibrils. On association with the amyloid fibrils, 2Me-DABT not only showed a large increase in its emission intensity, but also, unlike ThT, a large blueshift in its emission spectrum was observed. Thus, unlike ThT, 2Me-DABT is a potential candidate for the ratiometric sensor of the amyloid fibrils. Detailed photophysical properties of 2Me-DABT in amyloid fibrils and different solvent media were studied to understand its sensory activity. Fluorescence resonance energy transfer (FRET) studies suggested that the sites of localization for ThT and 2Me-DABT in amyloid fibrils are not same and their average distance of separation in amyloid fibrils was determined. The experimental data was nicely supported by molecular docking studies, which confirmed the binding of 2Me-DABT in the inner core of the amyloid fibrils.

  10. Phenylboronic acid functionalized reduced graphene oxide based fluorescence nano sensor for glucose sensing.

    PubMed

    Basiruddin, S K; Swain, Sarat K

    2016-01-01

    Reduced graphene has emerged as promising tools for detection based application of biomolecules as it has high surface area with strong fluorescence quenching property. We have used the concept of fluorescent quenching property of reduced graphene oxide to the fluorescent probes which are close vicinity of its surface. In present work, we have synthesized fluorescent based nano-sensor consist of phenylboronic acid functionalized reduced graphene oxide (rGO-PBA) and di-ol modified fluorescent probe for detection of biologically important glucose molecules. This fluorescent graphene based nano-probe has been characterized by high resolution transmission electron microscope (HRTEM), Atomic force microscope (AFM), UV-visible, Photo-luminescence (PL) and Fourier transformed infrared (FT-IR) spectroscopy. Finally, using this PBA functionalized reduced GO based nano-sensor, we were able to detect glucose molecule in the range of 2 mg/mL to 75 mg/mL in aqueous solution of pH7.4.

  11. Conjugated poly(fluorene-quinoxaline) for fluorescence imaging and chemical detection of nerve agents with its paper-based strip.

    PubMed

    Jo, Seonyoung; Kim, Daigeun; Son, Sang-Ho; Kim, Yongkyun; Lee, Taek Seung

    2014-01-22

    Conjugated polymer of poly(fluorene-co-quinoxaline) was synthesized via Suzuki coupling polymerization. The emission color of the polymer can be tuned depending on the concentration of the polymer in solution. A low-energy bandgap is observed both in the concentrated solution and in the solid state, caused by aggregation of the polymer chains, resulting in long wavelength emission from the quinoxaline moiety, while short wavelength emission can be seen in diluted, well-dissolved solution. The presence of quinoxaline units enables us to demonstrate fluorescence switching and imaging. Paper-based strips containing the polymer are prepared via simple immersion of filter paper in the polymer solution for practical use in the detection of nerve agents. The emission of the paper-based strip is quenched upon exposure to diethyl chlorophosphate (DCP), a nerve agent simulant, and the initial emission intensity can be almost restored by treatment with aqueous sodium hydroxide solution, making a possible reversible paper-based sensor.

  12. Fluorescence Based Turn-on Probe for the Determination of Caffeine Using Europium-Tetracycline as Energy Transfer Complex.

    PubMed

    Nanjundaiah, Shwetha; Krishna, Honnur; Bhatt, Praveena

    2016-05-01

    The study describes a simple and sensitive fluorometric sensor based on the enhancement of fluorescence intensity of Europium ion (Eu(3+)) - tetracycline (TC) charge transfer complex on addition of caffeine. The Eu(3+)-TC ternary complex has a characteristic emission peak at 615 nm (λex = 375 nm), the intensity of which increases with increase in concentration of caffeine. The caffeine sensor assay was found to be linear in the range of 0.0515 mM to 51.5 mM. The limit of detection and quantification were found to be 0.0515 mM and 0.382 mM, respectively. A caffeine recovery of 90 to 110 % in biological samples (serum and urine) indicated minimal interference by commonly present excipients in the samples. Rosenthal plots to calculate the binding capacity of caffeine with the Eu(3+)- TC complex revealed an association constant (K) of 238 x 10(3) L/mol and binding number (N) of 1.9. Bland-Altman plot comparing the developed assay and HPLC showed good agreement between values obtained by both the methods. The proposed fluorescent chemical sensor is a rapid and convenient method to determine caffeine with excellent recovery and low detection limit. The probable reaction mechanism for the formation of the turn on fluorescent probe enhancer is discussed.

  13. A fluorescent biosensing platform based on the polydopamine nanospheres intergrating with Exonuclease III-assisted target recycling amplification.

    PubMed

    Qiang, Weibing; Wang, Xi; Li, Wei; Chen, Xiang; Li, Hui; Xu, Danke

    2015-09-15

    Rapid, cost-effective, sensitive and specific analysis of biomolecules is important in the modern healthcare system. Here, a fluorescent biosensing platform based on the polydopamine nanospheres (PDANS) intergrating with Exonuclease III (Exo III) was developed. Due to the interaction between the ssDNA and the PDANS, the fluorescence of 6-carboxyfluorescein (FAM) labelled in the probe would been quenched by PDANS through FRET. While, in the present of the target DNA, the probe DNA would hybridize with the target DNA to form the double-strand DNA complex. Thus, Exo III could catalyze the stepwise removal of mononucleotides from 3'-terminus in the probe DNA, releasing the target DNA. As the FAM was released from the probe DNA, the fluorescence would no longer been quenched, led to the signal on. As one target DNA molecule could undergo a number of cycles to trigger the degradation of abundant probe DNA, Exo III-assisted target recycling would led to the amplification of the signal. The detection limit for DNA was 5 pM, which was 20 times lower than that without Exo III. And the assay time was largely shortened due to the faster signal recovery kinetics. What is more, this target recycling strategy was also applied to conduct an aptamer-based biosensing platform. The fluorescence intensity was also enhanced for the assay of adenosine triphosphate (ATP). For the Exo III-assisted target recycling amplification, DNA and ATP were fast detected with high sensitivity and selectivity. This work provides opportunities to develop simple, rapid, economical, and sensitive biosensing platforms for biomedical diagnostics.

  14. A fluorescence-based hydrolytic enzyme activity assay for quantifying toxic effects of Roundup® to Daphnia magna.

    PubMed

    Ørsted, Michael; Roslev, Peter

    2015-08-01

    Daphnia magna is a widely used model organism for aquatic toxicity testing. In the present study, the authors investigated the hydrolytic enzyme activity of D. magna after exposure to toxicant stress. In vivo enzyme activity was quantified using 15 fluorogenic enzyme probes based on 4-methylumbelliferyl or 7-amino-4-methylcoumarin. Probing D. magna enzyme activity was evaluated using short-term exposure (24-48 h) to the reference chemical K2 Cr2 O7 or the herbicide formulation Roundup®. Toxicant-induced changes in hydrolytic enzyme activity were compared with changes in mobility (International Organization for Standardization standard 6341). The results showed that hydrolytic enzyme activity was quantifiable as a combination of whole body fluorescence of D. magna and the fluorescence of the surrounding water. Exposure of D. magna to lethal and sublethal concentrations of Roundup resulted in loss of whole body enzyme activity and release of cell constituents, including enzymes and DNA. Roundup caused comparable inhibition of mobility and alkaline phosphatase activity with median effective concentration values at 20 °C of 8.7 mg active ingredient (a.i.)/L to 11.7 mg a.i./L. Inhibition of alkaline phosphatase activity by Roundup was lowest at 14 °C and greater at 20 °C and 26 °C. The results suggest that the fluorescence-based hydrolytic enzyme activity assay (FLEA assay) can be used as an index of D. magna stress. Combining enzyme activity with fluorescence measurements may be applied as a simple and quantitative supplement for toxicity testing with D. magna.

  15. Fluorescence Assay Based on Aptamer-Quantum Dot Binding to Bacillus thuringiensis Spores

    DTIC Science & Technology

    2007-01-01

    Binding to Bacillus thuringiensis 5a. CONTRACT NUMBER N/A Spores 5b. GRANT NUMBER N/A 5c. PROGRAM ELEMENT NUMBER 62202F 6. AUTHOR(S) Milada...assay was developed for the detection of Bacillus thuringiensis (BT) spores. The assay is based on the fluorescence observed after binding an aptamer...units/ml. 15. SUBJECT TERMS Bacillus thuringiensis , Aptamer, Quantum dots, SELEX, Fluorescence 16. SECURITY CLASSIFICATION OF: Unclassified U

  16. An ESIPT-based fluorescent probe for sensitive detection of hydrazine in aqueous solution.

    PubMed

    Zhou, Ji; Shi, Ruiyan; Liu, Jianxu; Wang, Rui; Xu, Yufang; Qian, Xuhong

    2015-05-21

    A fluorescent probe for sensitive detection of hydrazine based on an ESIPT mechanism and a substitution-cyclization-elimination cascade was developed. After the addition of hydrazine, an approximately 50-fold enhancement in fluorescence intensity at 465 nm was observed and the subsequent decrease at 375 nm was observed in 10 min with a detection limit of 0.147 μM. We also detected hydrazine in HeLa cells successfully.

  17. Fabry-Perot-based Fourier-transform hyperspectral imaging allows multi-labeled fluorescence analysis.

    PubMed

    Pisani, Marco; Zucco, Massimo

    2014-05-10

    We demonstrate the ability of our hyperspectral imaging device, based on a scanning Fabry-Perot interferometer, to obtain a single hyper-image of a sample marked with different fluorescent molecules, and to unambiguously discriminate them by observing their spectral fingerprints. An experiment carried out with cyanines, fluorescein, and quantum dots emitting in the yellow-orange region, demonstrates the feasibility of multi-labeled fluorescence microscopy without the use of multiple filter sets or dispersive means.

  18. High-contrast fluorescence imaging based on the polarization dependence of the fluorescence enhancement using an optical interference mirror slide.

    PubMed

    Yasuda, Mitsuru; Akimoto, Takuo

    2015-01-01

    High-contrast fluorescence imaging using an optical interference mirror (OIM) slide that enhances the fluorescence from a fluorophore located on top of the OIM surface is reported. To enhance the fluorescence and reduce the background light of the OIM, transverse-electric-polarized excitation light was used as incident light, and the transverse-magnetic-polarized fluorescence signal was detected. As a result, an approximate 100-fold improvement in the signal-to-noise ratio was achieved through a 13-fold enhancement of the fluorescence signal and an 8-fold reduction of the background light.

  19. A Novel Chromone Schiff-Base Fluorescent Chemosensor for Cd(II) Based on C=N Isomerization.

    PubMed

    Yan, Jun; Fan, Long; Qin, Jing-Can; Li, Chao-Rui; Yang, Zheng-Yin

    2016-05-01

    A new chromone Schiff-base fluorescent probe 7'-methoxychromone-3'-methylidene-1,2,4-triazole-3-imine (L) was designed and synthesized for selective recognition Cd(2+). With the fluorescence titration and the ESI-MS data, we reach the conclusion that the binding mode of the ligand-metal (L-Cd (2+) ) complex is 1:1. The sensor showed a strong fluorescence enhancement in ethanol system of Cd(2+) (excitation 409 nm and emission 462 nm) and the sensing mechanism based on the fact that C=N isomerization can be used to explain this phenomenon.

  20. A new Schiff base based on vanillin and naphthalimide as a fluorescent probe for Ag+ in aqueous solution

    NASA Astrophysics Data System (ADS)

    Zhou, Yanmei; Zhou, Hua; Ma, Tongsen; Zhang, Junli; Niu, Jingyang

    2012-03-01

    A new Schiff base based on vanillin and naphthalimide was designed and synthesized as fluorescent probe. The probe showed high selectivity for Ag+ over other metal ions such as Pb2+, Na+, K+, Cd2+, Ba2+, Cr3+, Zn2+, Cu2+, Ni2+, Ca2+, Al3+ and Mg2+ in aqueous solution. A new fluorescence emission was observed at 682 nm in the presence of Ag+ ion. The fluorescence intensity quenched with increasing the concentration of Ag+ at 682 nm. The method of job's plot confirmed the 1:2 complex between Ag+ and probe, and the mechanism was proposed.

  1. A sensitive method based on fluorescence-detected circular dichroism for protein local structure analysis.

    PubMed

    Nehira, Tatsuo; Ishihara, Kaoru; Matsuo, Koichi; Izumi, Shunsuke; Yamazaki, Takeshi; Ishida, Atsuhiko

    2012-11-15

    We report an improved fluorescence-detected circular dichroism (FDCD)-based analytical method that is useful for probing protein three-dimensional structures. The method uses a novel FDCD device with an ellipsoidal mirror that functions on a standard circular dichroism (CD) spectrometer and eliminates all artifacts. Our experiments demonstrated three important findings. First, the method is applicable to any proteins either by using intrinsic fluorescence derived from tryptophan residues or by introducing a fluorescent label onto nonfluorescent proteins. Second, by using intrinsic fluorescence, FDCD spectroscopy can detect a structural change in the tertiary structure of metmyoglobin due to stepwise denaturation on a change in pH. Such changes could not be detected by conventional CD spectroscopy. Third, based on the typical advantages of fluorescence-based analyses, FDCD measurements enable observation of only the target proteins in a solution even in the presence of other peptides. Using our ellipsoidal mirror FDCD device, we could observe structural changes of fluorescently labeled calmodulin on binding with Ca(2+) and/or interacting with binding peptides. Because FDCD appears to reflect the protein's local structure around the fluorophore, it may provide a useful means for "pinpoint analysis" of protein structures.

  2. Fluorescence detection in capillary arrays based on galvanometer step scanning.

    PubMed

    Xue, G; Yeung, E S

    2001-10-01

    A computer-controlled galvanometer scanner is adapted for scanning a focused laser beam across a 96-capillary array for laser-induced fluorescence detection. The signal at a single photomultiplier tube is temporally sorted to distinguish among the capillaries. The limit of detection for fluoresceins is 3 x 10(-11) M (S/N = 3) for 5 mW of total laser power scanned at 4 Hz. The observed cross-talk among capillaries is 0.2%. Advantages include the efficient utilization of light due to the high duty-cycle of step scan, good detection performance due to the reduction of stray light, ruggedness due to the small mass of the galvanometer mirror, low cost due to the simplicity of components, and flexibility due to the independent paths for excitation and emission.

  3. A simple interfacial pH detection method for cationic amphiphilic self-assemblies utilizing a Schiff-base molecule.

    PubMed

    Sarkar, Yeasmin; Das, Sanju; Ray, Ambarish; Jewrajka, Suresh K; Hirota, Shun; Parui, Partha Pratim

    2016-03-21

    A simple pH-sensing method for cationic micelle and vesicle interfaces is introduced, utilizing a Schiff-base molecule, 2-((4H-1,2,4-triazol-4-ylimino)methyl)-6-(hydroxymethyl)-4-methylphenol (AH). AH containing a phenolic moiety was obtained by the reaction between 4-amino-4H-1,2,4-triazole containing polar O- and N-centres with opposite polarity to the cationic interface and 2-hydroxy-3-(hydroxymethyl)-5-methylbenzaldehyde. The acid/base equilibrium of AH was investigated at the interfaces of cetrimonium bromide (CTAB) micelles, tri-block-copolymeric micelles (TBPs) and large unilamellar vesicles (LUVs) of different lipid compositions using steady state UV-Vis absorption spectroscopy. AH interacted strongly with the micelle and vesicle interfaces, according to the binding studies with LUV. A larger amount of AH proton dissociation was observed when localized at the interface of micelles and vesicles compared to that in the bulk phase, indicating that the pH values at the cationic interfaces are higher than in the bulk phase. The pH values were about 2.2 and 1.6 units higher at the CTAB and TBP micelle interfaces, respectively, than the bulk pH. The pH variation decreased from 2.4 to 1.5 units by increasing the neutral 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) lipid content from 0 to 50% in the cationic dimethyldioctadecylammonium (DDAB) LUV, indicating that the interfacial positive charges are responsible for the higher interfacial pH. Detailed structural and absorption characteristics of neutral AH and its anionic A(-) forms were investigated by fluorescence spectroscopic measurements and DFT based theoretical calculations. The present simple pH detection method may be applied to various biological micelle and vesicle interfaces.

  4. A ratiometric fluorescent probe for oxalate based on alkyne-conjugated carboxamidoquinolines in aqueous solution and imaging in living cells.

    PubMed

    He, Chunsheng; Qian, Xuhong; Xu, Yufang; Yang, Chunmei; Yin, Liyan; Zhu, Weiping

    2011-02-07

    A novel ratiometric fluorescent probe for oxalic acid was designed and synthesized, based on the zinc-containing [DAQZ@2Zn(2+)] complex. It shows highly selective "on-off" fluorescence changes with a more than 20 nm blue shift in wavelength for oxalic acids in aqueous solution. Moreover, it can fluorescently respond to oxalic acid in living cells.

  5. Graphene oxide-based fluorescent sensor for sensitive turn-on detection of sinapine

    NASA Astrophysics Data System (ADS)

    Xiang, Xia; Han, Ling; Zhang, Zhen; Huang, Fenghong

    2017-03-01

    Sinapine (SP) has attracted extensive attention in food and medical field because it is a crucial component in many plants with unique physiological activities. Here, we reported a fluorescent sensor based on the unique properties of graphene oxide (GO) for rapid, sensitive detection of SP concentration. In this strategy, GO has stronger affinity toward SP and can be also served as a quencher for DNA fluorescence probe. The fluorescence can make a recovery by the addition of SP, which can competitively desorb probe from the surface of GO, and the SP can thus be monitored by recording the fluorescence change. Because of the low background assays and high quenching ability offered by GO, the developed method provides a great potential for plant-derived molecules research.

  6. Assay of ceftazidime and cefepime based on fluorescence quenching of carbon quantum dots.

    PubMed

    Huang, Yu; Zhang, Ying; Yan, Zhengyu; Liao, Shenghua

    2015-11-01

    A novel and sensitive method for the determination of ceftazidime and cefepime in an active pharmaceutical ingredient (API) has been developed based on the fluorescence quenching of poly(ethylene glycol) (PEG)2000-capped carbon quantum dots (CQDs) prepared using a chemical oxidation method. The quenching of fluorescence intensity is proportional to the concentration of ceftazidime and cefepime over the range of 0.33-3.30 and 0.24-2.40 µg/mL, respectively. The mode of interaction between PEG2000-capped CQDs and ceftazidime/cefepime in aqueous solutions was investigated using a fluorescence, UV/Vis and Fourier transform infrared spectrometry (FTIR) at physiological pH. UV/Vis and FTIR spectra demonstrated that ground state compounds were formed through hydrophobic interaction the fluorescence quenching of CQDs caused by ceftazidime and cefepime. The quenching constants decreased with increases in temperature, which was consistent with static quenching.

  7. Development of optical phantoms for use in fluorescence-based imaging

    NASA Astrophysics Data System (ADS)

    Noiseux, Isabelle; Fortin, Michel; Leclair, Sébastien; Osouf, Jocelyne; Mermut, Ozzy

    2010-02-01

    We fabricated permanent solid polyurethane-based phantoms in which fluorophores were homogeneously incorporated. For this study, fluorophores of three different families were used: Cyanines, Alexa Fluor and Quantum Dots. The goal of this study was to evaluate the impact of casting the fluorophores in a polyurethane matrix on their optical properties, more specifically the absorbance, molecular extinction coefficient, emission of fluorescence and the resultant fluorescence intensity. All measurements were carried out with 5 concentrations of each fluorophores embedded in polyurethane and in solution. Stability over time was also monitored for a three months period. The casting of fluorophores affects the optical properties of the three dyes under study. The max absorbance, the fluorescence emission and intensity along with the molar extinction coefficient were all affected. Quantum dots behave differently to the cyanine and Alexa Fluor dyes. It was also observed that the incorporation of dyes enables long-term stability of the fluorescence signal.

  8. Synthesis of biocompatible glycodendrimer based on fluorescent perylene bisimides and its bioimaging.

    PubMed

    Wang, Ke-Rang; An, Hong-Wei; Rong, Rui-Xue; Cao, Zhi-Ran; Li, Xiao-Liu

    2014-04-01

    A novel water-soluble fluorescent glycodendrimer based on perylene bisimides is synthesized, which exhibits high fluorescence quantum yield of 54%. While the binding interactions of PBI-Man with Concanavalin A (Con A) are studied by fluorescence spectra and CD spectra, which show strong binding affinity for Con A with the binding constant of 3.8 × 10(7) m(-1) for monomeric mannose, nearly four orders of magnitude higher affinity than the monovalent mannose ligand. Furthermore, the fluorescence imaging of macrophage cell with PBI-Man is investigated, and shows selectively binding interaction with the mannose receptor-medicated cell entry. Moreover, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) activities of PBI-Man show that PBI-Man as a biocompatible agent is noncytotoxic to living cells.

  9. Tunable fluorescence enhancement based on bandgap-adjustable 3D Fe3O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Hu, Fei; Gao, Suning; Zhu, Lili; Liao, Fan; Yang, Lulu; Shao, Mingwang

    2016-06-01

    Great progress has been made in fluorescence-based detection utilizing solid state enhanced substrates in recent years. However, it is still difficult to achieve reliable substrates with tunable enhancement factors. The present work shows liquid fluorescence enhanced substrates consisting of suspensions of Fe3O4 nanoparticles (NPs), which can assemble 3D photonic crystal under the external magnetic field. The photonic bandgap induced by the equilibrium of attractive magnetic force and repulsive electrostatic force between adjacent Fe3O4 NPs is utilized to enhance fluorescence intensity of dye molecules (including R6G, RB, Cy5, DMTPS-DCV) in a reversible and controllable manner. The results show that a maximum of 12.3-fold fluorescence enhancement is realized in the 3D Fe3O4 NP substrates without the utilization of metal particles for PCs/DMTPS-DCV (1.0 × 10-7 M, water fraction (f w) = 90%).

  10. Cyanine-based probe\\tag-peptide pair for fluorescence protein imaging and fluorescence protein imaging methods

    DOEpatents

    Mayer-Cumblidge, M. Uljana; Cao, Haishi

    2010-08-17

    A molecular probe comprises two arsenic atoms and at least one cyanine based moiety. A method of producing a molecular probe includes providing a molecule having a first formula, treating the molecule with HgOAc, and subsequently transmetallizing with AsCl.sub.3. The As is liganded to ethanedithiol to produce a probe having a second formula. A method of labeling a peptide includes providing a peptide comprising a tag sequence and contacting the peptide with a biarsenical molecular probe. A complex is formed comprising the tag sequence and the molecular probe. A method of studying a peptide includes providing a mixture containing a peptide comprising a peptide tag sequence, adding a biarsenical probe to the mixture, and monitoring the fluorescence of the mixture.

  11. Two Simple Classes of Mastery Scores Based On the Beta-Binomial Model

    ERIC Educational Resources Information Center

    Huynh, Huynh

    1977-01-01

    A model for the setting of mastery cut scores is presented. The model, based on the beta-binomial test distribution, allows for hand calculation of cut scores. The model provides a simple way to explore the consequences of selecting a particular cut score. (Author/JKS)

  12. Two Simple Classroom Demonstrations for Scanning Probe Microscopy Based on a Macroscopic Analogy

    ERIC Educational Resources Information Center

    Hajkova, Zdenka; Fejfar, Antonin; Smejkal, Petr

    2013-01-01

    This article describes two simple classroom demonstrations that illustrate the principles of scanning probe microscopy (SPM) based on a macroscopic analogy. The analogy features the bumps in an egg carton to represent the atoms on a chemical surface and a probe that can be represented by a dwarf statue (illustrating an origin of the prefix…

  13. Effects of Toy Crane Design-Based Learning on Simple Machines

    ERIC Educational Resources Information Center

    Korur, Fikret; Efe, Gülfem; Erdogan, Fisun; Tunç, Berna

    2017-01-01

    The aim of this 2-group study was to investigate the following question: Are there significant differences between scaffolded design-based learning controlled using 7 forms and teacher-directed instruction methods for the toy crane project on grade 7 students' posttest scores on the simple machines achievement test, attitude toward simple…

  14. A Simple System for Observing Dynamic Phase Equilibrium via an Inquiry-Based Laboratory or Demonstration

    ERIC Educational Resources Information Center

    Cloonan, Carrie A.; Andrew, Julie A.; Nichol, Carolyn A.; Hutchinson, John S.

    2011-01-01

    This article describes an activity that can be used as an inquiry-based laboratory or demonstration for either high school or undergraduate chemistry students to provide a basis for understanding both vapor pressure and the concept of dynamic phase equilibrium. The activity includes a simple setup to create a closed system of only water liquid and…

  15. Real-time label-free quantitative fluorescence microscopy-based detection of ATP using a tunable fluorescent nano-aptasensor platform

    NASA Astrophysics Data System (ADS)

    Shrivastava, Sajal; Sohn, Il-Yung; Son, Young-Min; Lee, Won-Il; Lee, Nae-Eung

    2015-11-01

    Although real-time label-free fluorescent aptasensors based on nanomaterials are increasingly recognized as a useful strategy for the detection of target biomolecules with high fidelity, the lack of an imaging-based quantitative measurement platform limits their implementation with biological samples. Here we introduce an ensemble strategy for a real-time label-free fluorescent graphene (Gr) aptasensor platform. This platform employs aptamer length-dependent tunability, thus enabling the reagentless quantitative detection of biomolecules through computational processing coupled with real-time fluorescence imaging data. We demonstrate that this strategy effectively delivers dose-dependent quantitative readouts of adenosine triphosphate (ATP) concentration on chemical vapor deposited (CVD) Gr and reduced graphene oxide (rGO) surfaces, thereby providing cytotoxicity assessment. Compared with conventional fluorescence spectrometry methods, our highly efficient, universally applicable, and rational approach will facilitate broader implementation of imaging-based biosensing platforms for the quantitative evaluation of a range of target molecules.Although real-time label-free fluorescent aptasensors based on nanomaterials are increasingly recognized as a useful strategy for the detection of target biomolecules with high fidelity, the lack of an imaging-based quantitative measurement platform limits their implementation with biological samples. Here we introduce an ensemble strategy for a real-time label-free fluorescent graphene (Gr) aptasensor platform. This platform employs aptamer length-dependent tunability, thus enabling the reagentless quantitative detection of biomolecules through computational processing coupled with real-time fluorescence imaging data. We demonstrate that this strategy effectively delivers dose-dependent quantitative readouts of adenosine triphosphate (ATP) concentration on chemical vapor deposited (CVD) Gr and reduced graphene oxide (r

  16. Highly sensitive colorimetric and fluorescent sensor for cyanazine based on the inner filter effect of gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Dong, Liang; Hou, Changjun; Yang, Mei; Fa, Huanbao; Wu, Huixiang; Shen, Caihong; Huo, Danqun

    2016-06-01

    Cyanazine residue poses a great threat to human health and its derivatives would remain in soils, natural waters, and other environmental domains for a long time. Herein, a simple, rapid, and ultra-sensitive analytical method for the determination of cyanazine (CZ) based on inner filter effect (IFE) of Au nanoparticles (AuNPs) on the fluorescence of CdTe quantum dots (QDs) is first described in this study. With the presence of citrate-stabilized AuNPs, the fluorescence of GSH-capped CdTe QDs was remarkably quenched by AuNPs via IFE. The fluorescence of the AuNP-CdTe QD system was recovered upon addition of CZ. CZ can adsorb on to the surface of AuNPs due to its cyano group that has good affinity with gold, which could induce the aggregation of AuNPs accompanying color change from red to blue. Thus, the IFE of AuNPs on CdTe QDs was weakened, and the fluorescence intensity of CdTe QDs was recovered accordingly. A good linear correlation for detection of CZ was exhibited from 0.05 to 9 μM, and the detection limit reached 0.1568 μM, which was much lower than the safety limit required by the USA, the UK, and China. In order to probe into the selectivity of AuNPs towards CZ over other pesticides, various frequently used pesticides were mixed with AuNPs. AuNP composite solution shows good selectivity towards CZ among other pesticides. This method was successfully carried out for the assessment of CZ in real samples with satisfactory results, which revealed many advantages such as high sensitivity, low cost, and non-time-consuming compared with traditional methods.

  17. Synthesis and validation of novel cholesterol-based fluorescent lipids designed to observe the cellular trafficking of cationic liposomes.

    PubMed

    Kim, Bieong-Kil; Seu, Young-Bae; Choi, Jong-Soo; Park, Jong-Won; Doh, Kyung-Oh

    2015-09-15

    Cholesterol-based fluorescent lipids with ether linker were synthesized using NBD (Chol-E-NBD) or Rhodamine B (Chol-E-Rh), and the usefulnesses as fluorescent probes for tracing cholesterol-based liposomes were validated. The fluorescent intensities of liposomes containing these modified lipids were measured and observed under a microscope. Neither compound interfered with the expression of GFP plasmid, and live cell images were obtained without interferences. Changes in the fluorescent intensity of liposomes containing Chol-E-NBD were followed by flow cytometry for up to 24h. These fluorescent lipids could be useful probes for trafficking of cationic liposome-mediated gene delivery.

  18. [The X-Ray Fluorescence Spectrometer Based on Pyroelectric Effect].

    PubMed

    Dong, Yi-fan; Fan, Rui-rui; Guo, Dong-ya; Zhang, Chun-lei; Gao, Min; Wang, Jin-zhou; Liu, Ya-qing; Zhou, Da-wei; Wang, Huan-yu

    2016-02-01

    Pyroelectric X-ray generator is implemented, and an X-ray fluorescence spectrometer is accomplished by combining the pyroelectric X-ray generator with a high energy resolution silicon drift detector. Firstly, the parameters of the X-ray generator are decided by analyzing and calculating the influence of the thickness of the pyroelectriccrystal and the thickness of the target on emitted X-ray. Secondly, the emitted X-ray is measured. The energy of emitted X-ray is from 1 to 27 keV, containing the characteristic X-ray of Cu and Ta, and the max counting rate is more than 3 000 per second. The measurement also proves that the detector of the spectrometer has a high energy resolution which the FWMH is 210 eV at 8. 05 keV. Lastly, samples of Fe, Ti, Cr and high-Ti basalt are analyzed using the spectrometer, and the results are agreed with the elements of the samples. It shows that the spectrometer consisting of a pyroelectric X-ray generator and a silicon drift detector is effective for element analysis. Additionally, because each part of the spectrometer has a small volume, it can be easily modified to a portable one which is suitable for non-destructive, on-site and quick element analysis.

  19. Fluorescent properties of DNA base analogue tC upon incorporation into DNA — negligible influence of neighbouring bases on fluorescence quantum yield

    PubMed Central

    Sandin, Peter; Wilhelmsson, L. Marcus; Lincoln, Per; Powers, Vicki E. C.; Brown, Tom; Albinsson, Bo

    2005-01-01

    The quantum yield of the fluorescent tricyclic cytosine analogue, 1,3-diaza-2-oxophenothiazine, tC, is high and virtually unaffected by incorporation into both single- and double-stranded DNA irrespective of neighbouring bases (0.17–0.24 and 0.16–0.21, respectively) and the corresponding fluorescence decay curves are all mono-exponential, properties that are unmatched by any base analogue so far. The fluorescence lifetimes increase when going from tC free in solution (3.2 ns) to single- and double-stranded DNA (on average 5.7 and 6.3 ns, respectively). The mono-exponential decays further support previous NMR results where it was found that tC has a well-defined position and geometry within the DNA helix. Furthermore, we find that the oxidation potential of tC is 0.4 V lower than for deoxyguanosine, the natural base with the lowest oxidation potential. This suggests that tC may be of interest in charge transfer studies in DNA as an electron hole acceptor. We also present a novel synthetic route to the phosphoramidite form of tC. The results presented here together with previous work show that tC is a very good C-analogue that induces minimal perturbation to the native structure of DNA. This makes tC unique as a fluorescent base analogue and is thus highly interesting in a range of applications for studying e.g. structure, dynamics and kinetics in nucleic acid systems. PMID:16147985

  20. Silver Nanoparticle-Based Fluorescence-Quenching Lateral Flow Immunoassay for Sensitive Detection of Ochratoxin A in Grape Juice and Wine

    PubMed Central

    Jiang, Hu; Li, Xiangmin; Xiong, Ying; Pei, Ke; Nie, Lijuan; Xiong, Yonghua

    2017-01-01

    A silver nanoparticle (AgNP)-based fluorescence-quenching lateral flow immunoassay with competitive format (cLFIA) was developed for sensitive detection of ochratoxin A (OTA) in grape juice and wine samples in the present study. The Ru(phen)32+-doped silica nanoparticles (RuNPs) were sprayed on the test and control line zones as background fluorescence signals. The AgNPs were designed as the fluorescence quenchers of RuNPs because they can block the exciting light transferring to the RuNP molecules. The proposed method exhibited high sensitivity for OTA detection, with a detection limit of 0.06 µg/L under optimized conditions. The method also exhibited a good linear range for OTA quantitative analysis from 0.08 µg/L to 5.0 µg/L. The reliability of the fluorescence-quenching cLFIA method was evaluated through analysis of the OTA-spiked red grape wine and juice samples. The average recoveries ranged from 88.0% to 110.0% in red grape wine and from 92.0% to 110.0% in grape juice. Meanwhile, less than a 10% coefficient variation indicated an acceptable precision of the cLFIA method. In summary, the new AgNP-based fluorescence-quenching cLFIA is a simple, rapid, sensitive, and accurate method for quantitative detection of OTA in grape juice and wine or other foodstuffs. PMID:28264472

  1. Silver Nanoparticle-Based Fluorescence-Quenching Lateral Flow Immunoassay for Sensitive Detection of Ochratoxin A in Grape Juice and Wine.

    PubMed

    Jiang, Hu; Li, Xiangmin; Xiong, Ying; Pei, Ke; Nie, Lijuan; Xiong, Yonghua

    2017-02-28

    A silver nanoparticle (AgNP)-based fluorescence-quenching lateral flow immunoassay with competitive format (cLFIA) was developed for sensitive detection of ochratoxin A (OTA) in grape juice and wine samples in the present study. The Ru(phen) 3 2 + -doped silica nanoparticles (RuNPs) were sprayed on the test and control line zones as background fluorescence signals. The AgNPs were designed as the fluorescence quenchers of RuNPs because they can block the exciting light transferring to the RuNP molecules. The proposed method exhibited high sensitivity for OTA detection, with a detection limit of 0.06 µg/L under optimized conditions. The method also exhibited a good linear range for OTA quantitative analysis from 0.08 µg/L to 5.0 µg/L. The reliability of the fluorescence-quenching cLFIA method was evaluated through analysis of the OTA-spiked red grape wine and juice samples. The average recoveries ranged from 88.0% to 110.0% in red grape wine and from 92.0% to 110.0% in grape juice. Meanwhile, less than a 10% coefficient variation indicated an acceptable precision of the cLFIA method. In summary, the new AgNP-based fluorescence-quenching cLFIA is a simple, rapid, sensitive, and accurate method for quantitative detection of OTA in grape juice and wine or other foodstuffs.

  2. Local SIMPLE multi-atlas-based segmentation applied to lung lobe detection on chest CT

    NASA Astrophysics Data System (ADS)

    Agarwal, M.; Hendriks, E. A.; Stoel, B. C.; Bakker, M. E.; Reiber, J. H. C.; Staring, M.

    2012-02-01

    For multi atlas-based segmentation approaches, a segmentation fusion scheme which considers local performance measures may be more accurate than a method which uses a global performance measure. We improve upon an existing segmentation fusion method called SIMPLE and extend it to be localized and suitable for multi-labeled segmentations. We demonstrate the algorithm performance on 23 CT scans of COPD patients using a leave-one- out experiment. Our algorithm performs significantly better (p < 0.01) than majority voting, STAPLE, and SIMPLE, with a median overlap of the fissure of 0.45, 0.48, 0.55 and 0.6 for majority voting, STAPLE, SIMPLE, and the proposed algorithm, respectively.

  3. Solution based synthesis of simple fcc Si nano-crystals under ambient conditions.

    PubMed

    Balcı, Mustafa H; Sæterli, Ragnhild; Maria, Jerome; Lindgren, Mikael; Holmestad, Randi; Grande, Tor; Einarsrud, Mari-Ann

    2013-02-28

    We demonstrate for the first time that simple face-centered cubic (fcc) silicon nano-crystals can be produced by a solution based bottom-up synthesis route under ambient conditions. Simple fcc Si nano-crystals (2-7 nm) were prepared at room temperature by using sodium cyclopentadienide as a reducing agent for silicon tetrachloride. Photoluminescence emission at 550 nm was observed for the fcc silicon nano-crystals upon excitation at 340 nm, indicating that fcc Si nano-crystals were exhibiting direct bandgap like semiconductor properties with very fast radiative recombination rates. The new synthesis route makes possible the production and study of simple fcc polymorphs of Si nano-crystals with an easy alteration of surface termination groups.

  4. 10 CFR 429.35 - Bare or covered (no reflector) medium base compact fluorescent lamps.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 3 2012-01-01 2012-01-01 false Bare or covered (no reflector) medium base compact....35 Bare or covered (no reflector) medium base compact fluorescent lamps. (a) Sampling plan for selection of units for testing. (1) The requirements of § 429.11 are applicable to bare or covered...

  5. 10 CFR 429.35 - Bare or covered (no reflector) medium base compact fluorescent lamps.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 3 2013-01-01 2013-01-01 false Bare or covered (no reflector) medium base compact....35 Bare or covered (no reflector) medium base compact fluorescent lamps. (a) Sampling plan for selection of units for testing. (1) The requirements of § 429.11 are applicable to bare or covered...

  6. 10 CFR 429.35 - Bare or covered (no reflector) medium base compact fluorescent lamps.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 3 2014-01-01 2014-01-01 false Bare or covered (no reflector) medium base compact....35 Bare or covered (no reflector) medium base compact fluorescent lamps. (a) Sampling plan for selection of units for testing. (1) The requirements of § 429.11 are applicable to bare or covered...

  7. SimpleSynteny: a web-based tool for visualization of microsynteny across multiple species

    PubMed Central

    Veltri, Daniel; Wight, Martha Malapi; Crouch, Jo Anne

    2016-01-01

    Defining syntenic relationships among orthologous gene clusters is a frequent undertaking of biologists studying organismal evolution through comparative genomic approaches. With the increasing availability of genome data made possible through next-generation sequencing technology, there is a growing need for user-friendly tools capable of assessing synteny. Here we present SimpleSynteny, a new web-based platform capable of directly interrogating collinearity of local genomic neighbors across multiple species in a targeted manner. SimpleSynteny provides a pipeline for evaluating the synteny of a preselected set of gene targets across multiple organismal genomes. An emphasis has been placed on ease-of-use, and users are only required to submit FASTA files for their genomes and genes of interest. SimpleSynteny then guides the user through an iterative process of exploring and customizing genomes individually before combining them into a final high-resolution figure. Because the process is iterative, it allows the user to customize the organization of multiple contigs and incorporate knowledge from additional sources, rather than forcing complete dependence on the computational predictions. Additional tools are provided to help the user identify which contigs in a genome assembly contain gene targets and to optimize analyses of circular genomes. SimpleSynteny is freely available at: http://www.SimpleSynteny.com. PMID:27141960

  8. A synthetic amino acid residue containing a new oligopeptide-based photosensitive fluorescent organogel.

    PubMed

    Maiti, Dibakar Kumar; Banerjee, Arindam

    2013-01-01

    A synthetic amino acid (with a stilbene residue in the main chain) containing a tripeptide-based organogelator has been discovered. This peptide-based synthetic molecule 1 self-assembles in various organic solvents to form an organogel. The gel has been thoroughly characterized by using various microscopic techniques including field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), X-ray diffraction (XRD), UV-visible and fluorescence spectroscopy, and rheology. Morphological investigations using FESEM and AFM show a nanofibrillar network structure. Interestingly, the organogel is photoresponsive and a gel-sol transition occurred by irradiating the gel with UV light of 365 nm for 2 h as shown by the UV and fluorescence study. This photoresponsive fluorescent gel holds promise for new peptide-based soft materials with interesting applications.

  9. Two fluorescent Schiff base sensors for Zn(2+): the Zn(2+)/Cu(2+) ion interference.

    PubMed

    Jiménez-Sánchez, Arturo; Ortíz, Benjamín; Ortiz Navarrete, Vianney; Farfán, Norberto; Santillan, Rosa

    2015-09-07

    Two simple and low cost 2,4-di-tert-butyl-6-[(1-hydroxycyclohexylmethylimino)methyl]phenol (L1) and 2-[{(1-hydroxycyclohexyl)methylimino}methyl]phenol (L2) Schiff base sensors exhibiting selectivity for Zn(2+) in water:methanol (95:5, v/v, 10 mM HEPES) are described. L1 and L2 display an "off-on" fluorescence effect forming the L1·Zn and L2·Zn complexes, respectively. In the case of L1·Zn, the emission response is quenched by the addition of Cu(2+) forming the respective L1·Cu complex; in spite of that, the fluorescence signal can be completely restored only by the addition of tartrate anions (C4H4O6(2-)) forming again L1·Znvia the "off-on" displacement approach. However, in the case of L2·Zn no Cu(2+) interference is observed, which is a typical problem for Zn(2+) sensors. Here we describe that a very subtle structural change in the ligand during transition from the enol-imine tautomer in L1 to the keto-enamine tautomer in L2 is enough to modulate the Zn(2+)/Cu(2+) selectivity. Also, the Zn(2+)vs. Cd(2+) discrimination for L1 and L2 is proved. Moreover, we found that the interaction between both L·Zn complexes and tartrate anions completely restored the free ligands by the ligand substitution mechanism even in a more efficient association than phosphate anions. Further, a second colorimetric response channel upon addition of Fe(2+) was observed for L1 and L2. Then, TD-DFT theoretical calculations were conducted in order to study the efficiency of the sensors to give different responses in the presence of such metal ions. Finally, the L2 sensor successfully detects Zn(2+) in Jurkat cells cultured with and without Zn(2+) enriched medium.

  10. AlGaN-based deep-UV LEDs for fluorescence sensing

    NASA Astrophysics Data System (ADS)

    Vitta, Pranciskus; Kurilcik, Natalija; Novickovas, Algirdas; Jursenas, Saulius; Calkauskas, Henrikas; Zukauskas, Arturas; Gaska, Remis

    2004-12-01

    Recent progress in wide-bandgap semiconductor optoelectronics resulted in an appearance of deep-UV light-emitting diodes (LEDs), which can be used for fluorescence excitation in a variety of chemical and biological compounds. We used two generations of AlGaN-based UVTOP series deep ultraviolet LEDs developed by Sensor Electronic Technology, Inc. The peak wavelength of these fully packaged devices is 340 nm and 280 nm, line width at half maximum approximately 10 nm, wall-plug efficiency up to 0.9% and output power in the milliwatt range. The second-generation emitters are shown to have an extremely low level of unwanted long-wavelength emission what is important for fluorescence measurements. The UV LEDs were tested for fluorescence excitation in standard fluorophores (organic dyes), autofluorescent biological compounds (riboflavin, NADH, tryptophan, and tyrosine) and medical specimens (fluid secreted by prostate gland). Fluorescence lifetime measurements in the frequency domain were demonstrated using UVTOP-340 and -280 devices. The output of the LEDs was modulated at frequencies up to 200 MHz by high-frequency current drivers and the phase angle of the fluorescence signal was resolved using a radio-frequency lock-in amplifier. Nanosecond-scaled measurements of fluorescence lifetimes, which are the "fingerprints" of chemical and biological compounds, were demonstrated.

  11. Wideband fluorescence-based thermometry by neural network recognition: Photothermal application with 10 ns time resolution

    NASA Astrophysics Data System (ADS)

    Liu, Liwang; Zhong, Kuo; Munro, Troy; Alvarado, Salvador; Côte, Renaud; Creten, Sebastiaan; Fron, Eduard; Ban, Heng; Van der Auweraer, Mark; Roozen, N. B.; Matsuda, Osamu; Glorieux, Christ

    2015-11-01

    Neural network recognition of features of the fluorescence spectrum of a thermosensitive probe is exploited in order to achieve fluorescence-based thermometry with an accuracy of 200 mK with 100 MHz bandwidth, and with high robustness against fluctuations of the probe laser intensity used. The concept is implemented on a rhodamine B dyed mixture of copper chloride and glycerol, and the temperature dependent fluorescence is investigated in the temperature range between 234 K and 311 K. The spatial dependence of the calibrated amplitude and phase of photothermally induced temperature oscillations along the axis of the excitation laser are determined at different modulation frequencies. The spatial and frequency dependence of the extracted temperature signals is well fitted by a 1D multi-layer thermal diffusion model. In a time domain implementation of the approach, the gradual temperature rise due to the accumulation of the DC component of the heat flux supplied by repetitive laser pulses as well the immediate transient temperature evolution after each single pulse is extracted from acquired temporal sequences of fluorescence spectra induced by a CW green laser. A stroboscopic implementation of fluorescence thermometry, using a pulsed fluorescence evoking probe laser, is shown to achieve remote detection of temperature changes with a time resolution of 10 ns.

  12. Use of Time-Resolved Fluorescence to Monitor Bioactive Compounds in Plant Based Foodstuffs.

    PubMed

    Lemos, M Adília; Sárniková, Katarína; Bot, Francesca; Anese, Monica; Hungerford, Graham

    2015-06-26

    The study of compounds that exhibit antioxidant activity has recently received much interest in the food industry because of their potential health benefits. Most of these compounds are plant based, such as polyphenolics and carotenoids, and there is a need to monitor them from the field through processing and into the body. Ideally, a monitoring technique should be non-invasive with the potential for remote capabilities. The application of the phenomenon of fluorescence has proved to be well suited, as many plant associated compounds exhibit fluorescence. The photophysical behaviour of fluorescent molecules is also highly dependent on their microenvironment, making them suitable probes to monitor changes in pH, viscosity and polarity, for example. Time-resolved fluorescence techniques have recently come to the fore, as they offer the ability to obtain more information, coupled with the fact that the fluorescence lifetime is an absolute measure, while steady state just provides relative and average information. In this work, we will present illustrative time-resolved measurements, rather than a comprehensive review, to show the potential of time-resolved fluorescence applied to the study of bioactive substances. The aim is to help assess if any changes occur in their form, going from extraction via storage and cooking to the interaction with serum albumin, a principal blood transport protein.

  13. Use of Time-Resolved Fluorescence to Monitor Bioactive Compounds in Plant Based Foodstuffs

    PubMed Central

    Lemos, M. Adília; Sárniková, Katarína; Bot, Francesca; Anese, Monica; Hungerford, Graham

    2015-01-01

    The study of compounds that exhibit antioxidant activity has recently received much interest in the food industry because of their potential health benefits. Most of these compounds are plant based, such as polyphenolics and carotenoids, and there is a need to monitor them from the field through processing and into the body. Ideally, a monitoring technique should be non-invasive with the potential for remote capabilities. The application of the phenomenon of fluorescence has proved to be well suited, as many plant associated compounds exhibit fluorescence. The photophysical behaviour of fluorescent molecules is also highly dependent on their microenvironment, making them suitable probes to monitor changes in pH, viscosity and polarity, for example. Time-resolved fluorescence techniques have recently come to the fore, as they offer the ability to obtain more information, coupled with the fact that the fluorescence lifetime is an absolute measure, while steady state just provides relative and average information. In this work, we will present illustrative time-resolved measurements, rather than a comprehensive review, to show the potential of time-resolved fluorescence applied to the study of bioactive substances. The aim is to help assess if any changes occur in their form, going from extraction via storage and cooking to the interaction with serum albumin, a principal blood transport protein. PMID:26132136

  14. [Lake algae chemotaxonomy technology based on fluorescence excitation emission matrix and parallel factor analysis].

    PubMed

    Chen, Xiao-Na; Han, Xiu-Rong; Su, Rong-Guo; Shi, Xiao-Yong

    2014-03-01

    An in vivo three-dimensional fluorescence method for the determination of algae community structure was developed by parallel factor (PARAFAC) analysis and CHEMTAX. The PARAFAC model was applied to fluorescence excitation-emission matrix (EEM) of 23 algae species and 12 fluorescent components were identified according to the residual sum of squares and specificity of the composition profiles of fluorescent. Based on the 12 fluorescent components, the algae species at different growth stages were correctly classified at the division level using Bayesian discriminant analysis (BDA). Then the reference fluorescent component ratio matrix was constructed for CHEMTAX, and the EEM-PARAFAC-CHEMTAX method was developed to differentiate taxonomic groups of algae. When the fluorometric method was used for 531 single-species samples, the average correct discrimination ratio (CDR) was 99.1% and the correct discrimination ratios (CDRs) were 100% at the division level except Chlorophyta, the CDR of which was 97.5%. The CDRs for 95 mixtures were above 98.5% for the dominant algae species and above 90.5% for the subdominant algae species, with average relative contents of 69.7% and 26.4%, respectively. This technique would be of great aid when low-cost and rapid analysis is needed for samples in a large batch.

  15. A PDMS-Based Cylindrical Hybrid Lens for Enhanced Fluorescence Detection in Microfluidic Systems

    PubMed Central

    Lin, Bor-Shyh; Yang, Yu-Ching; Ho, Chong-Yi; Yang, Han-Yu; Wang, Hsiang-Yu

    2014-01-01

    Microfluidic systems based on fluorescence detection have been developed and applied for many biological and chemical applications. Because of the tiny amount of sample in the system; the induced fluorescence can be weak. Therefore, most microfluidic systems deploy multiple optical components or sophisticated equipment to enhance the efficiency of fluorescence detection. However, these strategies encounter common issues of complex manufacturing processes and high costs. In this study; a miniature, cylindrical and hybrid lens made of polydimethylsiloxane (PDMS) to improve the fluorescence detection in microfluidic systems is proposed. The hybrid lens integrates a laser focusing lens and a fluorescence collecting lens to achieve dual functions and simplify optical setup. Moreover, PDMS has advantages of low-cost and straightforward fabrication compared with conventional optical components. The performance of the proposed lens is first examined with two fluorescent dyes and the results show that the lens provides satisfactory enhancement for fluorescence detection of Rhodamine 6G and Nile Red. The overall increments in collected fluorescence signal and detection sensitivity are more than 220% of those without lens, and the detection limits of Rhodamine 6G and Nile red are lowered to 0.01 μg/mL and 0.05 μg/mL, respectively. The hybrid lens is further applied to the detection of Nile red-labeled Chlorella vulgaris cells and it increases both signal intensity and detection sensitivity by more than 520%. The proposed hybrid lens also dramatically reduces the variation in detected signal caused by the deviation in incident angle of excitation light. PMID:24531300

  16. Fluorescent directed heteroduplex analysis enhances PCR-based DQA1 and DQB1 genotyping

    SciTech Connect

    Zimmerman, P.A.; Mansfield, E.S.; Miyasaki, T.

    1994-09-01

    We previously showed how directed heteroduplex analysis (DHDA) simplifies DQA1 and DQB1 genotyping and have used the technique to identify a new DQA1 allele (DQA{sup *}0502, which has a single nucleotide difference from DQA1{sup *}0501). In DHDA, labeled probes are mixed with unlabeled PCR products amplified from patient genomic DNA. After controlled re-annealing, allelic heteroduplexes are resolved on polyacrylamide gels (5%, 2.7 M urea). To utilize fluorescence imaging for detecting the heteroduplexes in HLA-typing, probes are labeled by PCR amplification using locus-specific generic primers and gels scanned using the Fluorimager{trademark} 575 (Molecular Dynamics, Inc.). We generate 2-color DHDA probes using locus-specific PCR primers 5{prime}-end labeled with the fluorochromes FAM (positive-strand primer) and JOE (negative-strand primer) (Perkin-Elmer). Genotypic analysis within families obtained from the CEPH repository have been performed by fluorescence-based DHDA. Results to date show 100% concordance between DHDA and sequence-specific oligonucleotide probe (SSOP) genotyping. Fluorescence-based DHDA is performed with fewer probes than SSOP (1 set of locus-specific probes for DHDA and 10 SSOP probes for DQA1 typing or 13 SSOP probes for DQB1 typing). In addition, fluorescent DHDA allows rapid assessment of genotype, aproximately four hours from receipt of sample to typing result. These results suggest that fluorescent DHDA may facilitate DNA-based HLA-typing within the time constraints required for solid organ transplantation.

  17. Sandwich Immunoassays of Multicomponent Subtrace Pathogenic DNA Based on Magnetic Fluorescent Encoded Nanoparticles

    PubMed Central

    Liu, Yaxu; Zhang, Xuanjun; E, Yifeng; Fang, Fang; Kuang, Guangkai; Wang, Guannan

    2016-01-01

    A novel magnetic fluorescent encoded nanoimmunoassay system for multicomponent detection and separation of the subtrace pathogenic DNA (hepatitis B virus surface gene, HBV; hepatitis A virus poly the protein gene, HAV) was established based on new type of magnetic fluorescent encoded nanoparticles and sandwich immunoassay principle. This method combines multifunctional nanoparticles, immunoassay technique, fluorescence labeling, and magnetic separation of multicomponent technology. It has many advantages such as high sensitivity, low detection limit, easy operation, and great potential for development. The results of this work show that, based on nanoimmunoassay system, it could quantitatively detect the multicomponent trace pathogenic HAV and HBV DNA, as well as detection limit up to 0.1 pM and 0.12 pM. Furthermore, with the improvement of the performances of magnetic fluorescent encoded nanoparticles, the sensitivity will be further improved. In this experiment, a new nanoimmunoassay system based on magnetic fluorescent encoded nanoparticles was established, which will provide a new way for the immunoassay and separation of multicomponent biomolecules. PMID:26881227

  18. Optical sensor instrumentation using absorption- and fluorescence-based capillary waveguide optrodes

    NASA Astrophysics Data System (ADS)

    Weigl, Bernhard H.; Draxler, Sonja; Kieslinger, Dietmar; Lehmann, H.; Trettnak, Wolfgang; Wolfbeis, Otto S.; Lippitsch, Max E.

    1995-09-01

    An analytical instrument comprising absorption- and fluorescence-based capillary waveguide optrodes (CWOs) is described. Glass capillaries with a chemically sensitive coating on the inner surface are used for optical chemical sensing in gaseous and liquid samples. In case of absorption-based CWOs, light from a LED is coupled into and out of the capillary under a defined angle via a rigid waveguide and an immersion coupler. The coated glass capillary forms an inhomogeneous waveguide, in which the light is guided in both the glass and the coating. The portion of the light which is absorbed in the chemically sensitive coating is proportional to a chemcial concentration or activity. This principle is demonstrated with a pCO2-sensitive inner coating. Typical relative light intensity signal changes with this type of optical interrogation are 98%, with an active capillary length of 10 mm. For fluorescence- based CWOs, the excitation light from an LED is coupled diffusely into the glass capillary and the optical sensor layer. A major portion of the excited fluorescence light is then collected within the coated capillary, and guided to the photodiode, which is located on the distal end of the capillary waveguide. Hereby, the excitation light is separated very efficiently from the fluorescent light. As an example, a CWO for pO2 is described. By applying this optical geometry, it was possible to utilize fluorescence decay time of the sensor layer as the transducer signal even when using solid state components (LEDs and photodiodes).

  19. Fluorescence-Based Bioassays for the Detection and Evaluation of Food Materials

    PubMed Central

    Nishi, Kentaro; Isobe, Shin-Ichiro; Zhu, Yun; Kiyama, Ryoiti

    2015-01-01

    We summarize here the recent progress in fluorescence-based bioassays for the detection and evaluation of food materials by focusing on fluorescent dyes used in bioassays and applications of these assays for food safety, quality and efficacy. Fluorescent dyes have been used in various bioassays, such as biosensing, cell assay, energy transfer-based assay, probing, protein/immunological assay and microarray/biochip assay. Among the arrays used in microarray/biochip assay, fluorescence-based microarrays/biochips, such as antibody/protein microarrays, bead/suspension arrays, capillary/sensor arrays, DNA microarrays/polymerase chain reaction (PCR)-based arrays, glycan/lectin arrays, immunoassay/enzyme-linked immunosorbent assay (ELISA)-based arrays, microfluidic chips and tissue arrays, have been developed and used for the assessment of allergy/poisoning/toxicity, contamination and efficacy/mechanism, and quality control/safety. DNA microarray assays have been used widely for food safety and quality as well as searches for active components. DNA microarray-based gene expression profiling may be useful for such purposes due to its advantages in the evaluation of pathway-based intracellular signaling in response to food materials. PMID:26473869

  20. Fluorescence-based bioassays for the detection and evaluation of food materials.

    PubMed

    Nishi, Kentaro; Isobe, Shin-Ichiro; Zhu, Yun; Kiyama, Ryoiti

    2015-10-13

    We summarize here the recent progress in fluorescence-based bioassays for the detection and evaluation of food materials by focusing on fluorescent dyes used in bioassays and applications of these assays for food safety, quality and efficacy. Fluorescent dyes have been used in various bioassays, such as biosensing, cell assay, energy transfer-based assay, probing, protein/immunological assay and microarray/biochip assay. Among the arrays used in microarray/biochip assay, fluorescence-based microarrays/biochips, such as antibody/protein microarrays, bead/suspension arrays, capillary/sensor arrays, DNA microarrays/polymerase chain reaction (PCR)-based arrays, glycan/lectin arrays, immunoassay/enzyme-linked immunosorbent assay (ELISA)-based arrays, microfluidic chips and tissue arrays, have been developed and used for the assessment of allergy/poisoning/toxicity, contamination and efficacy/mechanism, and quality control/safety. DNA microarray assays have been used widely for food safety and quality as well as searches for active components. DNA microarray-based gene expression profiling may be useful for such purposes due to its advantages in the evaluation of pathway-based intracellular signaling in response to food materials.

  1. Selective fluorescence sensors for detection of nitroaniline and metal Ions based on ligand-based luminescent metal-organic frameworks

    SciTech Connect

    Yu, Zongchao; Wang, Fengqin; Lin, Xiangyi; Wang, Chengmiao; Fu, Yiyuan; Wang, Xiaojun; Zhao, Yongnan; Li, Guodong

    2015-12-15

    Metal-organic frameworks (MOFs) are porous crystalline materials with high potential for applications in fluorescence sensors. In this work, two solvent-induced Zn(II)–based metal-organic frameworks, Zn{sub 3}L{sub 3}(DMF){sub 2} (1) and Zn{sub 3}L{sub 3}(DMA){sub 2}(H{sub 2}O){sub 3} (2) (L=4,4′-stilbenedicarboxylic acid), were investigated as selective sensing materials for detection of nitroaromatic compounds and metal ions. The sensing experiments show that 1 and 2 both exhibit selective fluorescence quenching toward nitroaniline with a low detection limit. In addition, 1 exhibits high selectivity for detection of Fe{sup 3+} and Al{sup 3+} by significant fluorescence quenching or enhancement effect. While for 2, it only exhibits significant fluorescence quenching effect for Fe{sup 3+}. The results indicate that 1 and 2 are both promising fluorescence sensors for detecting and recognizing nitroaniline and metal ions with high sensitivity and selectivity. - Graphical abstract: Two MOFs have been selected as the fluorescence sensing materials for selectively sensing mitroaromatic compounds and metal ions. The high selectivity makes them promising fluorescence sensors for detecting and recognizing nitroaniline and Fe{sup 3+} or Al{sup 3+}.

  2. Conventional and photonic crystal fiber based two-photon fluorescence biosensing

    NASA Astrophysics Data System (ADS)

    Myaing, Mon Thiri

    Optical fiber probes are widely used in the biomedical field for applications such as optical microscopy, endoscopy, and optical biopsy. Due to their flexibility and small size, optical fibers offer a minimally invasive light interface for imaging and spectroscopic analysis of internal tissue. The development of fluorescent probes for studies of biological processes has increased the importance of developing optical methods for quantitative, in vivo diagnosis. In this dissertation, we discuss the development of a novel two-photon optical fiber fluorescence (TPOFF) probe for real time, in vivo, quantitative fluorescence measurements in biological samples. In order to understand and optimize two-photon excitation through an optical fiber, pulse propagation effects must be considered. We found a simple phenomenological scaling behavior for the energy dependence of the pulse width for negatively pre-chirped pulses propagating in a normally dispersive fiber. As a consequence of this scaling behavior, the dependence of two-photon fluorescence (TPF) on the pulse intensity becomes sub-quadratic. The TPOFF probe employs a scheme where the same single-mode fiber (SMF) is used for both the excitation and collection of TPF. Using this fiber probe, we show quantification of tumor fluorescence both ex vivo and in vivo. In ex vivo measurements of tumors developed from cells expressing the green fluorescence protein (GFP), the TPOFF probe detected fluorescence from tumors with as little as 0.3% GFP cells. These results were similar to flow cytometry analysis of isolated cells from the tumors. The TPOFF measurements of GFP tumors in live, anesthetized mice showed a linear relationship between the measured fluorescence and the percentage of GFP expressing cells. The TPOFF probe was also used in targeted binding experiments of Herceptin antibody and folic acid-dendrimer nanoparticle conjugates. To improve the sensitivity of the TPOFF probe, a double-clad photonic crystal fiber (DCF

  3. A coumarin based Schiff base probe for selective fluorescence detection of Al3 + and its application in live cell imaging

    NASA Astrophysics Data System (ADS)

    Sen, Bhaskar; Sheet, Sanjoy Kumar; Thounaojam, Romita; Jamatia, Ramen; Pal, Amarta Kumar; Aguan, Kripamoy; Khatua, Snehadrinarayan

    2017-02-01

    A new coumarin based Schiff base compound, CSB-1 has been synthesized to detect metal ion based on the chelation enhanced fluorescence (CHEF). The cation binding properties of CSB-1 was thoroughly examined in UV-vis and fluorescence spectroscopy. In fluorescence spectroscopy the compound showed high selectivity toward Al3 + ion and the Al3 + can be quantified in mixed aqueous buffer solution (MeOH: 0.01 M HEPES Buffer; 9:1; v/v) at pH 7.4 as well as in BSA media. The fluorescence intensity of CSB-1 was enhanced by 24 fold after addition of only five equivalents of Al3 +. The fluorescence titration of CSB-1 with Al3 + in mixed aqueous buffer afforded a binding constant, Ka = (1.06 ± 0.2) × 104 M- 1. The colour change from light yellow to colourless and the appearance of blue fluorescence, which can be observed by the naked eye, provides a real-time method for Al3 + sensing. Further the live cell imaging study indicated that the detection of intracellular Al3 + ions are also readily possible in living cell.

  4. Fluorescence assay based on aptamer-quantum dot binding to Bacillus thuringiensis spores.

    PubMed

    Ikanovic, Milada; Rudzinski, Walter E; Bruno, John G; Allman, Amity; Carrillo, Maria P; Dwarakanath, Sulatha; Bhahdigadi, Suneetha; Rao, Poornima; Kiel, Johnathan L; Andrews, Carrie J

    2007-03-01

    A novel assay was developed for the detection of Bacillus thuringiensis (BT) spores. The assay is based on the fluorescence observed after binding an aptamer-quantum dot conjugate to BT spores. The in vitro selection and amplification technique called SELEX (Systematic Evolution of Ligands by EXponential enrichment) was used in order to identify the DNA aptamer sequence specific for BT. The 60 base aptamer was then coupled to fluorescent zinc sulfide-capped, cadmium selenide quantum dots (QD). The assay is semi-quantitative, specific and can detect BT at concentrations of about 1,000 colony forming units/ml.

  5. "Turn-off-on" fluorescent sensor for (N-methyl-4-pyridyl) porphyrin -DNA and G-quadruplex interactions based on ZnCdSe quantum dots.

    PubMed

    Zhao, Dan; Fan, Yao; Gao, Fang; Yang, Tian-ming

    2015-08-12

    As a new detection model, the reversible fluorescence "turn-off-on" sensor based on quantum dots (QDs) has already been successfully employed in the detections of many biochemical materials, especially in the researches on the interactions between anticancer drugs. The previous studies, however, mainly focused on simple-structured oligonucleotides and Calf thymus DNA. G-quadruplex, an important target for anti-cancer drug with special secondary structure, has been stimulating increasing research interests. In this paper, we report a new detection method based on the fluorescence "turn-off-on" model with water-soluble ZnCdSe QDs as the fluorescent probe, to analyze the interactions between anticancer drug (N-methyl-4-pyridyl) porphyrin (TMPyP) and nucleic acid, especially the G-quadruplex. The fluorescence of QDs can be quenched by TMPyP via photo-induced electron transfer and fluorescence resonance energy transfer, while on the other hand, the combination between TMPyP and G-quadruplex releases QDs from their quenchers and thus recovers the fluorescence. Most importantly, the fluorescence "turn-off-on" model has been employed, for the first time, to analyze the impacts of special factors on the interaction between TMPyP and G-quadruplex. The excellent selectivity of the system has been verified in the studies of the interactions between TMPyP and different DNAs (double-stranded DNA, single-stranded G-quadruplex, and different types of G-quadruplexes) in Na(+) or K(+)-containing buffer.

  6. Quantitative generalized ratiometric fluorescence spectroscopy for turbid media based on probe encapsulated by biologically localized embedding.

    PubMed

    Yan, Xiu-Fang; Chen, Zeng-Ping; Cui, Yin-Yin; Hu, Yuan-Liang; Yu, Ru-Qin

    2016-05-19

    PEBBLE (probe encapsulated by biologically localized embedding) nanosensor encapsulating an intensity-based fluorescence indicator and an inert reference fluorescence dye inside the pores of stable matrix can be used as a generalized wavelength-ratiometric probe. However, the lack of an efficient quantitative model render the choices of inert reference dyes and intensity-based fluorescence indicators used in PEBBLEs based generalized wavelength-ratiometric probes rather limited. In this contribution, an extended quantitative fluorescence model was derived specifically for generalized wavelength-ratiometric probes based on PEBBLE technique (QFMGRP) with a view to simplify the design of PEBBLEs and hence further extend their application potentials. The effectiveness of QFMGRP has been tested on the quantitative determination of free Ca(2+) in both simulated and real turbid media using a Ca(2+) sensitive PEBBLE nanosensor encapsulating Rhod-2 and eosin B inside the micropores of stable polyacrylamide matrix. Experimental results demonstrated that QFMGRP could realize precise and accurate quantification of free Ca(2+) in turbid samples, even though there is serious overlapping between the fluorescence excitation peaks of eosin B and Ca(2+) bound Rhod-2. The average relative predictive error value of QFMGRP for the test simulated turbid samples was 5.9%, about 2-4 times lower than the corresponding values of partial least squares calibration model and the empirical ratiometric model based on the ratio of fluorescence intensities at the excitation peaks of Ca(2+) bound Rhod-2 and eosin B. The recovery rates of QFMGRP for the real and spiked turbid samples varied from 93.1% to 101%, comparable to the corresponding results of atomic absorption spectrometry.

  7. Synchrotron-radiation study of weak fluorescence from neat liquids of simple alkenes: Anomalous excitation spectra as evidence for wavelength-dependent photochemistry

    SciTech Connect

    Inoue, Yoshihisa; Daino, Yoshihiko; Tai, Akira; Hakushi, Tadao ); Okada, Tadashi )

    1989-07-19

    Fluorescence excitation spectra of trans-2-octene, trans-cyclooctene, 2-methyl-2-butene, and 2,3-dimethyl-2-butene were measured by using synchrotron radiation as a tunable light source in the vacuum UV and UV region. The wavelength dependence of the fluorescence yields provides direct evidence for the long-proposed assignment that the emissive state is the {pi},R(3s) Rydberg state, which in turn gives the carbene-derived photoproducts.

  8. Fluorescent Aptamer Sensors

    NASA Astrophysics Data System (ADS)

    Chen, Hui William; Kim, Youngmi; Meng, Ling; Mallikaratchy, Prabodhika; Martin, Jennifer; Tang, Zhiwen; Shangguan, Dihua; O'Donoghue, Meghan; Tan, Weihong

    Aptamers are single-stranded nucleic acid probes that can be evolved to have high specificity and affinity for different targets. These targets include biomar-ker proteins, small molecules, and even whole live cells that express a variety of surface proteins of interest. Aptamers offer several advantages over protein-based molecular probes such as low immunogenic activity, flexible modification, and in vitro synthesis. In addition, aptamers used as molecular probes can be made with easy signaling for binding with their corresponding targets. There are a few different fluorescence-based signal transduction mechanisms, such as direct fluorophore labeling, fluorescence resonance energy transfer (FRET), fluorescence quenching, fluorescence anisotropy, and light-switching excimers. These signaling processes in combination with various labeling strategies of nucleic acid aptamers contribute to simple, rapid, sensitive, and selective biological assays. In this chapter, we discuss the optical signaling of aptamers for single proteins such as α-thrombin and platelet-derived growth factor (PDGF). We also present detailed discussion about fluorescent aptamers developed from cell-based systematic evolution of ligands by exponential enrichment (SELEX) for the recognition of different target tumor cells.

  9. New solutions for standardization, monitoring and quality management of fluorescence-based imaging systems (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Royon, Arnaud; Papon, Gautier

    2016-03-01

    Fluorescence microscopes have become ubiquitous in life sciences laboratories, including those focused on pharmaceuticals, diagnosis, and forensics. For the past few years, the need for both performance guarantees and quantifiable results has driven development in this area. However, the lack of appropriate standards and reference materials makes it difficult or impossible to compare the results of two fluorescence microscopes, or to measure performance fluctuations of one microscope over time. Therefore, the operation of fluorescence microscopes is not monitored as often as their use warrants - an issue that is recognized by both systems manufacturers and national metrology institutes. We have developed a new process that enables the etching of long-term stable fluorescent patterns with sub-micrometer sizes in three dimensions inside glass. In this paper, we present, based on this new process, a fluorescent multi-dimensional ruler and a dedicated software that are suitable for monitoring and quality management of fluorescence-based imaging systems (wide-field, confocal, multiphoton, high content machines). In addition to fluorescence, the same patterns exhibit bright- and dark-field contrast, DIC, and phase contrast, which make them also relevant to monitor these types of microscopes. Non-exhaustively, this new solution enables the measurement of: The stage repositioning accuracy; The illumination and detection homogeneities; The field flatness; The detectors' characteristics; The lateral and axial spatial resolutions; The spectral response (spectrum, intensity and lifetime) of the system. Thanks to the stability of the patterns, microscope performance assessment can be carried out as well in a daily basis as in the long term.

  10. A fluorescence enhancement probe based on BODIPY for the discrimination of cysteine from homocysteine and glutathione.

    PubMed

    Gong, Deyan; Tian, Yuejun; Yang, Chengduan; Iqbal, Anam; Wang, Zhiping; Liu, Weisheng; Qin, Wenwu; Zhu, Xiangtao; Guo, Huichen

    2016-11-15

    Herein, a fluorescent probe BODIPY-based glyoxal hydrazone (BODIPY-GH) (1) for cysteine based on inhibiting of intramolecular charge transfer (ICT) quenching process upon reaction with the unsaturated aldehyde has been synthesized, which exhibits longer excitation wavelength, selective and sensitive colorimetric and fluorimetric response toward cysteine in natural media. The probe shows highly selectivity towards cysteine over homocysteine and glutathione as well as other amino acids with a significant fluorescence enhancement response within 15min In the presence of 50 equiv. of homocysteine, the emission increased slightly within 15min and completed in 2.5h to reach its maximum intensity. Therefore, the discrimination of cysteine from homocysteine and glutathione can be achieved through detection of probe 1. It shows low cytotoxicity and excellent membrane permeability toward living cells, which was successfully applied to detect and image intracellular cysteine effectively by confocal fluorescence imaging.

  11. A fluorescence turn-on chemosensor for hydrogen sulfate anion based on quinoline and naphthalimide

    NASA Astrophysics Data System (ADS)

    Luo, Zaoli; Yin, Kai; Yu, Zhu; Chen, Mengxue; Li, Yan; Ren, Jun

    2016-12-01

    A new fluorescence turn-on chemosensor 1 based on quinoline and naphthalimide was prepared and its anion sensing toward various anions behavior was explored in this paper. Sensor 1 exhibited a highly selective fluorescent response toward HSO4- with an 8-fold fluorescence intensity enhancement in the presence of 10 equiv. of HSO4- in DMSO-H2O (1/1, v/v) solution. The sensor also displayed high sensitivity to hydrogen sulfate and the detection limit was calculated to be 7.79 × 10- 7 M. The sensing mechanism has been suggested to proceed via a hydrolysis process of the Schiff base group. The hydrolysis product has been isolated and further identified by 1H NMR and MS.

  12. Applications of indocyanine green based near-infrared fluorescence imaging in thoracic surgery

    PubMed Central

    Zhou, Jian; Jiang, Guanchao; Wang, Jun

    2016-01-01

    Near-infrared (NIR) fluorescence guided surgery is an emerging technique. This technique uses the combination of dyes and NIR imaging devices to expand the visible spectrum. Thus it can provide more anatomic and functional information, and may facilitate a more complete resection of cancer, or better protection of important normal structures. Recently, significant progress has been made in the field of NIR fluorescence guided thoracic surgery. This may lead to better prognosis and health-economic outcomes. In this article, the current studies of indocyanine green (ICG) based NIR fluorescence guided thoracic surgeries are reviewed. The applications are classified into four categories, which are applications based on blood supply, lymphatic drainage, the enhanced permeability and retention (EPR) effect, and the other mechanisms. PMID:28066677

  13. The impact of fluorescent dyes on the performances of polystyrene-based plastic scintillators

    NASA Astrophysics Data System (ADS)

    Zhu, Jun; Deng, Cheng; Jiang, Huimin; Zheng, Zhanlong; Gong, Rui; Bi, Yutie; Zhang, Lin; Lin, Runxiong

    2016-11-01

    To investigate the influence of both the first luminescent additive and the wavelength-shifter on the performance of plastic scintillator, a series of polystyrene-based scintillator had been prepared by thermal polymerization. Three first luminescent additives (PPO, p-TP and b-PBD) and four wavelength-shifters (POPOP, Bis-MSB, Me-MSB and DPA) were added to the scintillators respectively. The comparison results showed that PPO and POPOP were the most adequate fluorescent dyes for the polystyrene-based plastic scintillator. Moreover, with the increase of the concentration of PPO and POPOP, the fluorescence intensity and light yield were increased firstly and then decreased. The plastic scintillator containing 2% PPO and 0.02% POPOP had the highest fluorescence intensity and light yield.

  14. Highly selectively monitoring heavy and transition metal ions by a fluorescent sensor based on dipeptide.

    PubMed

    Neupane, Lok Nath; Thirupathi, Ponnaboina; Jang, Sujung; Jang, Min Jung; Kim, Jung Hwa; Lee, Keun-Hyeung

    2011-09-15

    Fluorescent sensor (DMH) based on dipeptide was efficiently synthesized in solid phase synthesis. The dipeptide sensor shows sensitive response to Ag(I), Hg(II), and Cu(II) among 14 metal ions in 100% aqueous solution. The fluorescent sensor differentiates three heavy metal ions by response type; turn on response to Ag(I), ratiometric response to Hg(II), and turn off detection of Cu(II). The detection limits of the sensor for Ag(I) and Cu(II) were much lower than the EPA's drinking water maximum contaminant levels (MCL). Specially, DMH penetrated live cells and detected intracellular Ag(+) by turn on response. We described the fluorescent change, binding affinity, detection limit for the metal ions. The study of a heavy metal-responsive sensor based on dipeptide demonstrates its potential utility in the environment field.

  15. Live imaging of Tribolium castaneum embryonic development using light-sheet-based fluorescence microscopy.

    PubMed

    Strobl, Frederic; Schmitz, Alexander; Stelzer, Ernst H K

    2015-10-01

    Tribolium castaneum has become an important insect model organism for evolutionary developmental biology, genetics and biotechnology. However, few protocols for live fluorescence imaging of Tribolium have been reported, and little image data is available. Here we provide a protocol for recording the development of Tribolium embryos with light-sheet-based fluorescence microscopy. The protocol can be completed in 4-7 d and provides procedural details for: embryo collection, microscope configuration, embryo preparation and mounting, noninvasive live imaging for up to 120 h along multiple directions, retrieval of the live embryo once imaging is completed, and image data processing, for which exemplary data is provided. Stringent quality control criteria for developmental biology studies are also discussed. Light-sheet-based fluorescence microscopy complements existing toolkits used to study Tribolium development, can be adapted to other insect species, and requires no advanced imaging or sample preparation skills.

  16. Fluorescence-based enhanced reality (FLER) for real-time estimation of bowel perfusion in minimally invasive surgery

    NASA Astrophysics Data System (ADS)

    Diana, Michele

    2016-03-01

    Pre-anastomotic bowel perfusion is a key factor for a successful healing process. Clinical judgment has limited accuracy to evaluate intestinal microperfusion. Fluorescence videography is a promising tool for image-guided intraoperative assessment of the bowel perfusion at the future anastomotic site in the setting of minimally invasive procedures. The standard configuration for fluorescence videography includes a Near-Infrared endoscope able to detect the signal emitted by a fluorescent dye, more frequently Indocyanine Green (ICG), which is administered by intravenous injection. Fluorescence intensity is proportional to the amount of fluorescent dye diffusing in the tissue and consequently is a surrogate marker of tissue perfusion. However, fluorescence intensity alone remains a subjective approach and an integrated computer-based analysis of the over-time evolution of the fluorescence signal is required to obtain quantitative data. We have developed a solution integrating computer-based analysis for intra-operative evaluation of the optimal resection site, based on the bowel perfusion as determined by the dynamic fluorescence intensity. The software can generate a "virtual perfusion cartography", based on the "fluorescence time-to-peak". The virtual perfusion cartography can be overlapped onto real-time laparoscopic images to obtain the Enhanced Reality effect. We have defined this approach FLuorescence-based Enhanced Reality (FLER). This manuscript describes the stepwise development of the FLER concept.

  17. A dual analyte fluorescent chemosensor based on a furan-pyrene conjugate for Al3 + & HSO3-

    NASA Astrophysics Data System (ADS)

    Don, Derin; Velmurugan, K.; Prabhu, J.; Bhuvanesh, N.; Thamilselvan, A.; Nandhakumar, R.

    2017-03-01

    A simple chalcone based dual analyte fluorescent probe FPC for Al3 + and HSO3- ions was developed. FPC detects both the analytes through a "turn off-on" approach and by the PET and ICT mechanism. FPC showed high selectivity and sensitivity for Al3 + and HSO3- ions detection over other interfering and competing metal ions. In addition, the LOD of FPC for sensing Al3 + and HSO3- ions was found to be 1.60 × 10- 7 M and 0.17 × 10- 6 M respectively. An electrochemical desalination technique was employed for the complete removal of Al3 + ions from the environmental water samples by using the probe FPC.

  18. Fluorescence enhancement of the conjugated polymer films based on well-ordered Au nanoparticle arrays

    NASA Astrophysics Data System (ADS)

    Zhong, Benbin; Zu, Xihong; Yi, Guobin; Huang, Hailiang; Zhang, Minghai; Luo, Hongsheng

    2016-09-01

    In this paper, well-ordered Au nanoparticle arrays on silicon substrates were employed as efficient metal-enhanced fluorescence (MEF) substrates for investigating the fluorescence properties of the conjugated polymer poly(3-hexylthiophene) (P3HT). The ordered Au nanoparticle arrays were fabricated by block copolymer self-assembly technology, and the particle sizes were controlled by adjusting the molar ratios of HAuCl4 precursor to vinyl pyridine units. The approach is economical and suitable to fabricate large-area MEF substrates. The results about fluorescence properties of P3HT showed that the fluorescence intensities of the P3HT films were improved on ordered Au nanoparticle arrays compared to those on bare silicon substrate and were significantly enhanced with the Au nanoparticle sizes increasing. The mechanism is based on localized surface plasmon resonances, coupling and propagating surface plasmons, and the emission enhancement mainly resulted from the increase of the excitation rate. This work provides a new way to prepare efficient MEF substrates for high-performance fluorescence-based devices.

  19. The photoinduced transformation of fluorescent DNA base analogue tC triggers DNA melting.

    PubMed

    Preus, Søren; Jønck, Søren; Pittelkow, Michael; Dierckx, Anke; Karpkird, Thitinun; Albinsson, Bo; Wilhelmsson, L Marcus

    2013-08-01

    While fluorescent analogues of the canonical nucleobases have proven to be highly valuable in a large number of applications, up until today, fluorescent DNA base analogues remain virtually inapplicable for single-molecule fluorescence experiments which require extremely bright and photostable dyes. Insight into the photodegradation processes of these fluorophores is thus a key step in the continuous development towards dyes with improved performances. Here, we show that the commercially available fluorescent nucleobase analogue tC under intense long-term illumination and in the presence of O2 is degraded to form a single photoreaction product which we suggest to be the sulfoxide form of tC. The photoproduct is characterized by a blue-shifted absorption and a less intense fluorescence compared to that of tC. Interestingly, when tC is positioned inside double-stranded DNA this photodriven conversion of tC to its photoproduct greatly reduces the duplex stability of the overall double helix in which the probe is positioned. Since tC can be excited selectively at 400 nm, well outside the absorption band of the natural DNA bases, this observation points towards the application of tC as a general light-triggered switch of DNA duplex stability.

  20. Single-molecule analysis of fluorescent carbon dots towards localization-based super-resolution microscopy

    NASA Astrophysics Data System (ADS)

    Verma, Navneet C.; Khan, Syamantak; Nandi, Chayan K.

    2016-12-01

    The advancement of high-resolution bioimaging has always been dependent on the discovery of bright and easily available fluorescent probes. Fluorescent carbon nanodots, an interesting class of relatively new nanomaterials, have emerged as a versatile alternative due to their superior optical properties, non-toxicity, cell penetrability and easy routes to synthesis. Although a plethora of reports is available on bioimaging using carbon dots, single-molecule-based super-resolution imaging is rare in the literature. In this study, we have systematically characterized the single-molecule fluorescence of three carbon dots and compared them with a standard fluorescent probe. Each of these carbon dots showed a long-lived dark state in the presence of an electron acceptor. The electron transfer mechanism was investigated in single-molecule as well as in ensemble experiments. The average on-off rate between the fluorescent bright and dark states, which is one of the important parameters for single-molecule localization-based super-resolution microscopy, was measured by changing the laser power. We report that the photon budget and on-off rate of these carbon dots were good enough to achieve single-molecule localization with a precision of ~35 nm.

  1. Single-molecule analysis of fluorescent carbon dots towards localization-based super-resolution microscopy.

    PubMed

    Verma, Navneet C; Khan, Syamantak; Nandi, Chayan K

    2016-10-11

    The advancement of high-resolution bioimaging has always been dependent on the discovery of bright and easily available fluorescent probes. Fluorescent carbon nanodots, an interesting class of relatively new nanomaterials, have emerged as a versatile alternative due to their superior optical properties, non-toxicity, cell penetrability and easy routes to synthesis. Although a plethora of reports is available on bioimaging using carbon dots, single-molecule-based super-resolution imaging is rare in the literature. In this study, we have systematically characterized the single-molecule fluorescence of three carbon dots and compared them with a standard fluorescent probe. Each of these carbon dots showed a long-lived dark state in the presence of an electron acceptor. The electron transfer mechanism was investigated in single-molecule as well as in ensemble experiments. The average on-off rate between the fluorescent bright and dark states, which is one of the important parameters for single-molecule localization-based super-resolution microscopy, was measured by changing the laser power. We report that the photon budget and on-off rate of these carbon dots were good enough to achieve single-molecule localization with a precision of ~35 nm.

  2. Highly selective and sensitive nanoprobes for cyanide based on gold nanoclusters with red fluorescence emission

    NASA Astrophysics Data System (ADS)

    Zhang, Guomei; Qiao, Yunyun; Xu, Ting; Zhang, Caihong; Zhang, Yan; Shi, Lihong; Shuang, Shaomin; Dong, Chuan

    2015-07-01

    We report a novel and environmentally friendly fluorescent probe for detecting the cyanide ion (CN-) using l-amino acid oxidase (LAAOx)-protected Au nanoclusters (LAAOx@AuNCs) with red emission. The fluorescence-based sensing behaviour of LAAOx@AuNCs towards anions was investigated in buffered aqueous media. Among the anions studied, CN- was found to effectively quench the fluorescence emission of AuNCs based on CN- induced Au core decomposition. Excellent sensitivity and selectivity toward the detection of CN- in aqueous solution were observed. The CN- detection limit was determined to be approximately 180 nM, which is 15 times lower than the maximum level (2700 nM) of CN- in drinking water permitted by the World Health Organization (WHO). A linear relationship between the fluorescence intensity and CN- concentration was observed in two ranges of CN- concentration, including 3.2 × 10-6 to 3.4 × 10-5 mol L-1 and 3.81 × 10-5 to 1.04 × 10-4 mol L-1. The high sensitivity and selectivity to CN- among the 17 types of anions make the AuNCs good candidates for use in fluorescent nanoprobes of CN-.

  3. On-chip integrated lensless fluorescence microscopy/spectroscopy module for cell-based sensors

    NASA Astrophysics Data System (ADS)

    Li, Wei; Knoll, Thorsten; Sossalla, Adam; Bueth, Heiko; Thielecke, Hagen

    2011-03-01

    The integration of a fluorescence microscopy/spectroscopy module in cell-based lab-on-a-chip systems is of high interest for applications in cell-based diagnostics and substance evaluation in situ. We present an on-chip integrated lensless fluorescence imaging module applying the principle of contact/proximate optical lithography. The pixel resolution is comparable with a 4 x objective microscope. The module can be used for morphology and fluorescence imaging of mammalian cells (15 - 20 μm) as well as for testing the concentration of a fluorescent substance. The biological samples or solutions are sustained in disposable sterilized microfluidic chips with 1 μm thick silicon nitride (Si3N4) membranes. These chips are assembled on the surface of a 5 megapixel colored CMOS image sensor array with 1.75 μm pixel size, which is coated with an additional interference filter. Each culturing chip consists of a MEMS cavity chip and a PDMS microfluidic interface. The surface of the CMOS image sensor is smoothened using SU-8 photoresist spin-coating for a commercial grade interference filter (optical density >= 5) coating by Plasma-Ion Assisted Deposition thereafter. The function is demonstrated by primary imaging results of the non-/fluorescent mammalian cells/microspheres as well as by differentiating different concentrations of FITC solutions.

  4. Computer-assisted sperm morphometry fluorescence-based analysis has potential to determine progeny sex

    PubMed Central

    Santolaria, Pilar; Pauciullo, Alfredo; Silvestre, Miguel A; Vicente-Fiel, Sandra; Villanova, Leyre; Pinton, Alain; Viruel, Juan; Sales, Ester; Yániz, Jesús L

    2016-01-01

    This study was designed to determine the ability of computer-assisted sperm morphometry analysis (CASA-Morph) with fluorescence to discriminate between spermatozoa carrying different sex chromosomes from the nuclear morphometrics generated and different statistical procedures in the bovine species. The study was divided into two experiments. The first was to study the morphometric differences between X- and Y-chromosome-bearing spermatozoa (SX and SY, respectively). Spermatozoa from eight bulls were processed to assess simultaneously the sex chromosome by FISH and sperm morphometry by fluorescence-based CASA-Morph. SX cells were larger than SY cells on average (P < 0.001) although with important differences between bulls. A simultaneous evaluation of all the measured features by discriminant analysis revealed that nuclear area and average fluorescence intensity were the variables selected by stepwise discriminant function analysis as the best discriminators between SX and SY. In the second experiment, the sperm nuclear morphometric results from CASA-Morph in nonsexed (mixed SX and SY) and sexed (SX) semen samples from four bulls were compared. FISH allowed a successful classification of spermatozoa according to their sex chromosome content. X-sexed spermatozoa displayed a larger size and fluorescence intensity than nonsexed spermatozoa (P < 0.05). We conclude that the CASA-Morph fluorescence-based method has the potential to find differences between X- and Y-chromosome-bearing spermatozoa in bovine species although more studies are needed to increase the precision of sex determination by this technique. PMID:27624989

  5. Development of Ultrasound-switchable Fluorescence Imaging Contrast Agents based on Thermosensitive Polymers and Nanoparticles

    PubMed Central

    Cheng, Bingbing; Wei, Ming-Yuan; Liu, Yuan; Pitta, Harish; Xie, Zhiwei; Hong, Yi; Nguyen, Kytai T.; Yuan, Baohong

    2015-01-01

    In this work we first introduced a recently developed high-resolution, deep-tissue imaging technique, ultrasound-switchable fluorescence (USF). The imaging principles based on two types of USF contrast agents were reviewed. To improve USF imaging techniques further, excellent USF contrast agents were developed based on high-performance thermoresponsive polymers and environment-sensitive fluorophores. Herein, such contrast agents were synthesized and characterized with five key parameters: (1) peak excitation and emission wavelengths (λex and λem), (2) the fluorescence intensity ratio between on and off states (IOn/IOff), (3) the fluorescence lifetime ratio between on and off states (τOn/τOff), (4) the temperature threshold to switch on fluorophores (Tth), and (5) the temperature transition bandwidth (TBW). We mainly investigated fluorescence intensity and lifetime changes of four environment-sensitive dyes [7-(2-Aminoethylamino)-N,N-dimethyl-4-benzofurazansulfonamide (DBD-ED), St633, Sq660, and St700] as a function of temperature, while the dye was attached to poly(N-isopropylacrylamide) linear polymers or encapsulated in nanoparticles. Six fluorescence resonance energy transfer systems were invented in which both the donor (DBD-ED or ST425) and the acceptor (Sq660) were adopted. Our results indicate that three Förster resonance energy transfer systems, where both IOn/IOff and τOn/τOff are larger than 2.5, are promising for application in future surface tissue bioimaging by USF technique. PMID:26052192

  6. Synthesis of polymeric fluorescent brightener based on coumarin and its performances on paper as light stabilizer, fluorescent brightener and surface sizing agent

    NASA Astrophysics Data System (ADS)

    Zhang, Guanghua; Zheng, Hua; Guo, Mingyuan; Du, Lun; Liu, Guojun; Wang, Peng

    2016-03-01

    In this work, a novel polymeric fluorescent brightener based on coumarin (PFBC) was synthesized, using three-step synthetic route, from 7-amino-4-methylcoumarin, coumarin monomer (FBC), Acrylamide (AM) and methacrylatoethyl trimethyl ammonium chloride (DMC). The structure of PFBC was characterized by FT-IR, 1HNMR and GPC. PFBC was applied to paper fiber as light stabilizer, fluorescent brightener and surface sizing agent and its performances were evaluated by measuring the UV-vis, fluorescence, thermal stability, the cationic degree, surface strength and smoothness of paper, the brightness degree of paper and the PC value of paper. Results showed that PFBC had better solubility in water than that of FBC, by measuring the optical properties. Through the surface sizing experiment and UV aging experiment, PFBC not only enhanced the surface strength and smoothness of paper as a surface sizing agent, but also had better effect on anti-UV aging than that of FBC as light stabilizer and fluorescent brightener.

  7. Development of Fluorescence Sensing Material Based on CdSe/ZnS Quantum Dots and Molecularly Imprinted Polymer for the Detection of Carbaryl in Rice and Chinese Cabbage.

    PubMed

    Zhang, Can; Cui, Hanyu; Cai, Jianrong; Duan, Yuqing; Liu, Yuan

    2015-05-27

    A fluorescence sensing material based on quantum dots with excellent optical properties and molecularly imprinted polymer (QDs@MIP) with specific recognition has been developed. First the surface of CdSe/ZnS QDs was modified with ionic liquids (ILs) by electrostatic interaction. The fluorescence sensing material was constructed from anchoring the MIP layer on IL modified CdSe/ZnS QDs by copolymerization, which had been developed for the detection of carbaryl in rice and Chinese cabbage. The MIP fluorescence was more strongly quenched by carbaryl than the non-imprinted polymer (NIP) fluorescence, which indicated that the QDs@MIP could selectively recognize the corresponding carbaryl. Furthermore, the developed QDs@MIP method was validated by HPLC and ELISA respectively, and the results of these methods were well correlated (R(2) = 0.98). The fluorescence sensing material had obvious advantages, such as being easily prepared and having specific recognition and photostability. The developed method was simple and effective for the detection of carbaryl. And, it could also provide the technical support for the rapid detection in food safety fields.

  8. Development of a fluorescence-based microplate method for the determination of volatile fatty acids in anaerobically digested and sewage sludges.

    PubMed

    Robert-Peillard, F; Palacio-Barco, E; Coulomb, B; Boudenne, J L

    2012-01-15

    This paper presents a simple, accurate and multi-sample method for the determination of volatile fatty acids (VFAs) thanks to a 96-well microplate technique. A procedure using an activating reagent of the carboxylic function (water-soluble carbodiimide EDC) and a fluorescent amino labeling reagent (N-(1-naphthyl)ethylenediamine, EDAN) allows the formation of an isoindole derivative that needs to be separated from initial fluorescent amine for efficient VFAs determination. Isolation of these fluorescent VFA-derivatives was carried out by use of the fluorescent quenching of EDAN with o-phthaldialdehyde (OPA). Quenching was most efficient at pH around 7 and by heating at 40°C within the microplate reader. This optimized procedure has been applied to various carboxylic acids and other organic compounds, demonstrating that VFA exhibit the highest fluorescence responses with homogeneous results for the main ones (acetic, propionic and butyric acid, all mass concentration expressed as acetic acid equivalents). This protocol was calibrated against acetic acid and determination of VFA was thus possible in the range 3.9-2,000 mg L(-1) (acetic acid equivalents). Subsequent application to real samples (sewage sludges or anaerobically digested samples) and comparison to gas chromatography analyses gave accurate results, proving the great potential of our high-throughput microplate-based technique for the analysis of VFA.

  9. A turn-off fluorescent biosensor for the rapid and sensitive detection of uranyl ion based on molybdenum disulfide nanosheets and specific DNAzyme

    NASA Astrophysics Data System (ADS)

    Zhang, HongYan; Ruan, YaJuan; Lin, Ling; Lin, Minggui; Zeng, Xiaoxue; Xi, Zhiming; Fu, FengFu

    2015-07-01

    A novel fluorescent biosensor for detecting uranyl ion (UO22+) in aqueous environment has been developed based on the specific recognition of DNAzyme and the fluorescence quenching ability of molybdenum disulfide (MoS2) nanosheets. The DNAzyme contains a DNA enzyme strand and a 6-carboxylfluorescein (FAM)-labeled DNA substrate strand. We demonstrated that MoS2 nanosheets have low affinity to the substrate-enzyme complex DNAzyme. Whereas, in the presence of UO22+, UO22+ can specifically cleave DNAzyme to release FAM-labeled single-strand DNA and the released FAM-labeled single-strand DNA can be firmly adsorbed on the surface of MoS2 nanosheets, which resulted in an obvious decrease of fluorescence intensity. This provided a sensing platform for the rapid, simple and sensitive fluorescent detection of UO22+. By using the sensing platform, a sensitive and selective fluorescent method for the rapid detection of UO22+ has been developed. In comparison with previous biosensor, the proposed method has obvious analytical advantage such as relatively high sensitivity and good stability, short analytical time and low cost. It can be used to detect as low as 2.14 nM of UO22+ in aqueous environment with a recovery of 96-102% and a RSD < 5% (n = 6). The success of this study provides a promising alternative for the rapid and on-site detection of UO22+ in environmental monitoring.

  10. Label-free fluorescence turn-on detection of microRNA based on duplex-specific nuclease and a perylene probe.

    PubMed

    Hu, Zhenzhen; Chen, Jian; Li, Wenying; Wang, Yan; Li, Yongxin; Sang, Lijia; Li, Juanmin; Zhang, Qingfeng; Ibupoto, Zafar Hussain; Yu, Cong

    2015-10-01

    A novel fluorescence turn-on microRNA (miRNA) detection method based on duplex-specific nuclease (DSN) and a perylene probe is presented in this study. A positively charged perylene derivative (compound 1) was used as the fluorescent probe. Compound 1 exhibits strong monomer fluorescence in an aqueous buffer solution. It is well known that single-stranded DNA is a polyanion in nature. Thus, it can induce the aggregation of compound 1 through strong electrostatic, hydrophobic and π-π stacking interactions. As a result, the fluorescence of compound 1 was efficiently quenched. When the target miRNA was added, the formation of DNA-RNA hybridized duplex initiated the cleavage of the DNA strand by DSN cycle reaction, which resulted in disaggregation of compound 1. A fluorescence turn-on signal was detected, and a novel miRNA sensing method was therefore established. The presented method is label-free, simple, cost effective, sensitive and selective.

  11. Simple BOTDA temperature sensor based on distributed Brillouin phase-shift measurements within a Sagnac interferometer

    NASA Astrophysics Data System (ADS)

    López-Gil, Alexia; Angulo-Vinuesa, Xabier; Dominguez-López, Alejandro; Martín-López, Sonia; González-Herráez, Miguel

    2015-09-01

    In this work we demonstrate an extremely simple BOTDA scheme capable of delivering distributed Brillouin Phase Shift measurements along an optical fiber. It is based on exploiting the non-reciprocity of the Stimulated Brillouin Scattering effect. This non-reciprocity is easily characterized by means of a suitably tuned Sagnac Interferometer. The technique is advantageous as, in comparison with previous methods, no complex modulation, no sharp filtering and no highbandwidth detection is needed. Theoretical and experimental proofs of the concept are given.

  12. A universal cloning method based on yeast homologous recombination that is simple, efficient, and versatile

    PubMed Central

    Joska, Tammy M.; Mashruwala, Ameya; Boyd, Jeffrey M.; Belden, William J.

    2014-01-01

    Cloning by homologous recombination (HR) in Saccharomyces cerevisiae is an extremely efficient and cost-effective alternative to other methods of recombinant DNA technologies. Unfortunately, it is incompatible with all the various specialized plasmids currently used in microbiology and biomedical research laboratories, and is therefore, not widely adopted. In an effort to dramatically improve the versatility of yeast gap-repair cloning and make it compatible with any DNA plasmid, we demonstrate that by simply including a yeast-cloning cassette (YCC) that contains the 2-micron origin of replication (2 μm ori) and the ura3 gene for selection, multiple DNA fragments can be assembled into any DNA vector. We show this has almost unlimited potential by building a variety of plasmid for different uses including: recombinant protein production, epitope tagging, site-directed mutagenesis, and expression of fluorescent fusion proteins. We demonstrate the use in a variety of plasmids for use in microbial systems and even demonstrate it can be used in a vertebrate model. This method is remarkably simple and extremely efficient, plus it provides a significant cost saving over commercially available kits. PMID:24418681

  13. A universal cloning method based on yeast homologous recombination that is simple, efficient, and versatile.

    PubMed

    Joska, Tammy M; Mashruwala, Ameya; Boyd, Jeffrey M; Belden, William J

    2014-05-01

    Cloning by homologous recombination (HR) in Saccharomyces cerevisiae is an extremely efficient and cost-effective alternative to other methods of recombinant DNA technologies. Unfortunately, it is incompatible with all the various specialized plasmids currently used in microbiology and biomedical research laboratories, and is therefore, not widely adopted. In an effort to dramatically improve the versatility of yeast gap-repair cloning and make it compatible with any DNA plasmid, we demonstrate that by simply including a yeast-cloning cassette (YCC) that contains the 2-micron origin of replication (2μm ori) and the ura3 gene for selection, multiple DNA fragments can be assembled into any DNA vector. We show this has almost unlimited potential by building a variety of plasmid for different uses including: recombinant protein production, epitope tagging, site-directed mutagenesis, and expression of fluorescent fusion proteins. We demonstrate the use in a variety of plasmids for use in microbial systems and even demonstrate it can be used in a vertebrate model. This method is remarkably simple and extremely efficient, plus it provides a significant cost saving over commercially available kits.

  14. A simple modern correctness condition for a space-based high-performance multiprocessor

    NASA Technical Reports Server (NTRS)

    Probst, David K.; Li, Hon F.

    1992-01-01

    A number of U.S. national programs, including space-based detection of ballistic missile launches, envisage putting significant computing power into space. Given sufficient progress in low-power VLSI, multichip-module packaging and liquid-cooling technologies, we will see design of high-performance multiprocessors for individual satellites. In very high speed implementations, performance depends critically on tolerating large latencies in interprocessor communication; without latency tolerance, performance is limited by the vastly differing time scales in processor and data-memory modules, including interconnect times. The modern approach to tolerating remote-communication cost in scalable, shared-memory multiprocessors is to use a multithreaded architecture, and alter the semantics of shared memory slightly, at the price of forcing the programmer either to reason about program correctness in a relaxed consistency model or to agree to program in a constrained style. The literature on multiprocessor correctness conditions has become increasingly complex, and sometimes confusing, which may hinder its practical application. We propose a simple modern correctness condition for a high-performance, shared-memory multiprocessor; the correctness condition is based on a simple interface between the multiprocessor architecture and a high-performance, shared-memory multiprocessor; the correctness condition is based on a simple interface between the multiprocessor architecture and the parallel programming system.

  15. Fluorescence-based strategies to investigate the structure and dynamics of aptamer-ligand complexes

    NASA Astrophysics Data System (ADS)

    Perez-Gonzalez, Cibran; Lafontaine, Daniel; Penedo, J.

    2016-08-01

    In addition to the helical nature of double-stranded DNA and RNA, single-stranded oligonucleotides can arrange themselves into tridimensional structures containing loops, bulges, internal hairpins and many other motifs. This ability has been used for more than two decades to generate oligonucleotide sequences, so-called aptamers, that can recognize certain metabolites with high affinity and specificity. More recently, this library of artificially-generated nucleic acid aptamers has been expanded by the discovery that naturally occurring RNA sequences control bacterial gene expression in response to cellular concentration of a given metabolite. The application of fluorescence methods has been pivotal to characterize in detail the structure and dynamics of these aptamer-ligand complexes in solution. This is mostly due to the intrinsic high sensitivity of fluorescence methods and also to significant improvements in solid-phase synthesis, post-synthetic labelling strategies and optical instrumentation that took place during the last decade. In this work, we provide an overview of the most widely employed fluorescence methods to investigate aptamer structure and function by describing the use of aptamers labelled with a single dye in fluorescence quenching and anisotropy assays. The use of 2-aminopurine as a fluorescent analog of adenine to monitor local changes in structure and fluorescence resonance energy transfer (FRET) to follow long-range conformational changes is also covered in detail. The last part of the review is dedicated to the application of fluorescence techniques based on single-molecule microscopy, a technique that has revolutionized our understanding of nucleic acid structure and dynamics. We finally describe the advantages of monitoring ligand-binding and conformational changes, one molecule at a time, to decipher the complexity of regulatory aptamers and summarize the emerging folding and ligand-binding models arising from the application of these

  16. A distance-dependent metal-enhanced fluorescence sensing platform based on molecular beacon design.

    PubMed

    Zhou, Zhenpeng; Huang, Hongduan; Chen, Yang; Liu, Feng; Huang, Cheng Zhi; Li, Na

    2014-02-15

    A new metal-enhanced fluorescence (MEF) based platform was developed on the basis of distance-dependent fluorescence quenching-enhancement effect, which combined the easiness of Ag-thiol chemistry with the MEF property of noble-metal structures as well as the molecular beacon design. For the given sized AgNPs, the fluorescence enhancement factor was found to increase with a d(6) dependency in agreement with fluorescence resonance energy transfer mechanism at shorter distance and decrease with a d(-3) dependency in agreement with plasmonic enhancement mechanism at longer distance between the fluorophore and the AgNP surface. As a proof of concept, the platform was demonstrated by a sensitive detection of mercuric ions, using thymine-containing molecular beacon to tune silver nanoparticle (AgNP)-enhanced fluorescence. Mercuric ions were detected via formation of a thymine-mercuric-thymine structure to open the hairpin, facilitating fluorescence recovery and AgNP enhancement to yield a limit of detection of 1 nM, which is well below the U.S. Environmental Protection Agency regulation of the Maximum Contaminant Level Goal (10nM) in drinking water. Since the AgNP functioned as not only a quencher to reduce the reagent blank signal but also an enhancement substrate to increase fluorescence of the open hairpin when target mercuric ions were present, the quenching-enhancement strategy can greatly improve the detection sensitivity and can in principle be a universal approach for various targets when combined with molecular beacon design.

  17. Fluorescence-Based Strategies to Investigate the Structure and Dynamics of Aptamer-Ligand Complexes

    PubMed Central

    Perez-Gonzalez, Cibran; Lafontaine, Daniel A.; Penedo, J. Carlos

    2016-01-01

    In addition to the helical nature of double-stranded DNA and RNA, single-stranded oligonucleotides can arrange themselves into tridimensional structures containing loops, bulges, internal hairpins and many other motifs. This ability has been used for more than two decades to generate oligonucleotide sequences, so-called aptamers, that can recognize certain metabolites with high affinity and specificity. More recently, this library of artificially-generated nucleic acid aptamers has been expanded by the discovery that naturally occurring RNA sequences control bacterial gene expression in response to cellular concentration of a given metabolite. The application of fluorescence methods has been pivotal to characterize in detail the structure and dynamics of these aptamer-ligand complexes in solution. This is mostly due to the intrinsic high sensitivity of fluorescence methods and also to significant improvements in solid-phase synthesis, post-synthetic labeling strategies and optical instrumentation that took place during the last decade. In this work, we provide an overview of the most widely employed fluorescence methods to investigate aptamer structure and function by describing the use of aptamers labeled with a single dye in fluorescence quenching and anisotropy assays. The use of 2-aminopurine as a fluorescent analog of adenine to monitor local changes in structure and fluorescence resonance energy transfer (FRET) to follow long-range conformational changes is also covered in detail. The last part of the review is dedicated to the application of fluorescence techniques based on single-molecule microscopy, a technique that has revolutionized our understanding of nucleic acid structure and dynamics. We finally describe the advantages of monitoring ligand-binding and conformational changes, one molecule at a time, to decipher the complexity of regulatory aptamers and summarize the emerging folding and ligand-binding models arising from the application of these

  18. Copper ion-selective fluorescent sensor based on the inner filter effect using a spiropyran derivative.

    PubMed

    Shao, Na; Zhang, Ying; Cheung, Sinman; Yang, Ronghua; Chan, Winghong; Mo, Tain; Li, Kean; Liu, Feng

    2005-11-15

    A highly selective copper(II) ion fluorescent sensor has been designed based on the UV-visible absorption of a spiropyran derivative coupled with the use of a metal porphyrin operative on the fluorescence inner filter effect. Spiropyrans, which combine the characteristics of metal binding and signal transduction, have been widely utilized in cationic ion recognition by UV-visible spectroscopy. In the present work, the viability of converting the absorption signal of the spiropyran molecule into a fluorescence signal was explored. On account of overlap of the absorption band of the spiropyran (lambda(abs) = 547 nm) in the presence of copper ion with the Q-band of an added fluorophore, zinc meso-tetraphenylporphyrin (lambda(abs) = 556 nm), the effective light absorbed by the porphyrin and concomitantly the emitted light intensity vary as a result of varying absorption of the spiropyran via fluorescence inner filter effect. The metal binding characteristic of the spiropyran presents an excellent selectivity for copper ion in comparison with several other heavy or transition metal ions. Since the changes in the absorbance of the absorber translate into exponential changes in fluorescence of the fluorophore, the novelty of the present device is that the analytical signal is more sensitive over that of the absorptiometry or that of the fluorometry using one single dye. To realize a practical fluorescent sensor, both the absorber and fluorophore were immobilized in a plasticized poly(vinyl chloride) membrane, and the sensing characteristics of the membrane for copper ion were investigated. The sensor is useful for measuring Cu2+ at concentrations ranging from 7.5 x 10(-7) to 3.6 x 10(-5) M with a detection limit of 1.5 x 10(-7) M. The sensor is chemically reversible, the fluorescence was switched off by immersing the membrane in copper ion solution and switched on by washing it with EDTA solution.

  19. Activatable iRGD-based peptide monolith: Targeting, internalization, and fluorescence activation for precise tumor imaging.

    PubMed

    Cho, Hong-Jun; Lee, Sung-Jin; Park, Sung-Jun; Paik, Chang H; Lee, Sang-Myung; Kim, Sehoon; Lee, Yoon-Sik

    2016-09-10

    A disulfide-bridged cyclic RGD peptide, named iRGD (internalizing RGD, c(CRGDK/RGPD/EC)), is known to facilitate tumor targeting as well as tissue penetration. After the RGD motif-induced targeting on αv integrins expressed near tumor tissue, iRGD encounters proteolytic cleavage to expose the CendR motif that promotes penetration into cancer cells via the interaction with neuropilin-1. Based on these proteolytic cleavage and internalization mechanism, we designed an iRGD-based monolithic imaging probe that integrates multiple functions (cancer-specific targeting, internalization and fluorescence activation) within a small peptide framework. To provide the capability of activatable fluorescence signaling, we conjugated a fluorescent dye to the N-terminal of iRGD, which was linked to the internalizing sequence (CendR motif), and a quencher to the opposite C-terminal. It turned out that fluorescence activation of the dye/quencher-conjugated monolithic peptide probe requires dual (reductive and proteolytic) cleavages on both disulfide and amide bond of iRGD peptide. Furthermore, the cleavage of the iRGD peptide leading to fluorescence recovery was indeed operative depending on the tumor-related angiogenic receptors (αvβ3 integrin and neuropilin-1) in vitro as well as in vivo. Compared to an 'always fluorescent' iRGD control probe without quencher conjugation, the dye/quencher-conjugated activatable monolithic peptide probe visualized tumor regions more precisely with lower background noise after intravenous injection, owing to the multifunctional responses specific to tumor microenvironment. All these results, along with minimal in vitro and in vivo toxicity profiles, suggest potential of the iRGD-based activatable monolithic peptide probe as a promising imaging agent for precise tumor diagnosis.

  20. Anion recognition by simple chromogenic and chromo-fluorogenic salicylidene Schiff base or reduced-Schiff base receptors

    NASA Astrophysics Data System (ADS)

    Dalapati, Sasanka; Jana, Sankar; Guchhait, Nikhil

    2014-08-01

    This review contains extensive application of anion sensing ability of salicylidene type Schiff bases and their reduced forms having various substituents with respect to phenolic sbnd OH group. Some of these molecular systems behave as receptor for recognition or sensing of various anions in organic or aqueous-organic binary solvent mixture as well as in the solid supported test kits. Development of Schiff base or reduced Schiff base receptors for anion recognition event is commonly based on the theory of hydrogen bonding interaction or deprotonation of phenolic -OH group. The process of charge transfer (CT) or inhibition of excited proton transfer (ESIPT) or followed by photo-induced electron transfer (PET) lead to naked-eye color change, UV-vis spectral change, chemical shift in the NMR spectra and fluorescence spectral modifications. In this review we have tried to discuss about the anion sensing properties of Schiff base or reduced Schiff base receptors.

  1. Label-free detection of kanamycin based on a G-quadruplex DNA aptamer-based fluorescent intercalator displacement assay

    NASA Astrophysics Data System (ADS)

    Xing, Yun-Peng; Liu, Chun; Zhou, Xiao-Hong; Shi, Han-Chang

    2015-01-01

    This work was the first to report that the kanamycin-binding DNA aptamer (5'-TGG GGG TTG AGG CTA AGC CGA-3') can form stable parallel G-quadruplex DNA (G4-DNA) structures by themselves and that this phenomenon can be verified by nondenaturing polyacrylamide gel electrophoresis and circular dichroism spectroscopy. Based on these findings, we developed a novel label-free strategy for kanamycin detection based on the G4-DNA aptamer-based fluorescent intercalator displacement assay with thiazole orange (TO) as the fluorescence probe. In the proposed strategy, TO became strongly fluorescent upon binding to kanamycin-binding G4-DNA. However, the addition of kanamycin caused the displacement of TO from the G4-DNA-TO conjugate, thereby resulting in decreased fluorescent signal, which was inversely related to the kanamycin concentration. The detection limit of the proposed assay decreased to 59 nM with a linear working range of 0.1 μM to 20 μM for kanamycin. The cross-reactivity against six other antibiotics was negligible compared with the response to kanamycin. A satisfactory recovery of kanamycin in milk samples ranged from 80.1% to 98.0%, confirming the potential of this bioassay in the measurement of kanamycin in various applications. Our results also served as a good reference for developing similar fluorescent G4-DNA-based bioassays in the future.

  2. Label-free detection of kanamycin based on a G-quadruplex DNA aptamer-based fluorescent intercalator displacement assay.

    PubMed

    Xing, Yun-Peng; Liu, Chun; Zhou, Xiao-Hong; Shi, Han-Chang

    2015-01-30

    This work was the first to report that the kanamycin-binding DNA aptamer (5'-TGG GGG TTG AGG CTA AGC CGA-3') can form stable parallel G-quadruplex DNA (G4-DNA) structures by themselves and that this phenomenon can be verified by nondenaturing polyacrylamide gel electrophoresis and circular dichroism spectroscopy. Based on these findings, we developed a novel label-free strategy for kanamycin detection based on the G4-DNA aptamer-based fluorescent intercalator displacement assay with thiazole orange (TO) as the fluorescence probe. In the proposed strategy, TO became strongly fluorescent upon binding to kanamycin-binding G4-DNA. However, the addition of kanamycin caused the displacement of TO from the G4-DNA-TO conjugate, thereby resulting in decreased fluorescent signal, which was inversely related to the kanamycin concentration. The detection limit of the proposed assay decreased to 59 nM with a linear working range of 0.1 μM to 20 μM for kanamycin. The cross-reactivity against six other antibiotics was negligible compared with the response to kanamycin. A satisfactory recovery of kanamycin in milk samples ranged from 80.1% to 98.0%, confirming the potential of this bioassay in the measurement of kanamycin in various applications. Our results also served as a good reference for developing similar fluorescent G4-DNA-based bioassays in the future.

  3. Nucleic acid based fluorescent sensor for mercury detection

    DOEpatents

    Lu, Yi; Liu, Juewen

    2013-02-05

    A nucleic acid enzyme comprises an oligonucleotide containing thymine bases. The nucleic acid enzyme is dependent on both Hg.sup.2+and a second ion as cofactors, to produce a product from a substrate. The substrate comprises a ribonucleotide, a deoxyribonucleotide, or both.

  4. A fluorescent, photochromic and thermochromic trifunctional material based on a layered metal-viologen complex.

    PubMed

    Wan, Fang; Qiu, Li-Xia; Zhou, Liang-Liang; Sun, Yan-Qiong; You, Yi

    2015-11-14

    The azide anion as an energy acceptor and an electron donor has been introduced into a metal-viologen compound to form a 2D layered viologen-based trifunctional material, which exhibits the rare discolored function of reversible photochromism and thermochromism. Interestingly, its fluorescence can be switched by visible light irradiation and heating in air.

  5. A Fluorescent, Reagentless Biosensor for ATP, Based on Malonyl-Coenzyme A Synthetase

    PubMed Central

    2015-01-01

    A fluorescent reagentless biosensor for ATP has been developed, based on malonyl-coenzyme A synthetase from Rhodopseudomonas palustris as the protein scaffold and recognition element. Two 5-iodoacetamidotetramethylrhodamines were covalently bound to this protein to provide the readout. This adduct couples ATP binding to a 3.7-fold increase in fluorescence intensity with excitation at 553 nm and emission at 575 nm. It measures ATP concentrations with micromolar sensitivity and is highly selective for ATP relative to ADP. Its ability to monitor enzymatic ATP production or depletion was demonstrated in steady-state kinetic assays in which ATP is a product or substrate, respectively. PMID:26355992

  6. New approach to breast tumor detection based on fluorescence x-ray analysis

    PubMed Central

    Hayashi, Yasuhiko; Okuyama, Fumio

    2010-01-01

    A new technical approach to breast-tumor detection is proposed. The technique is based on fluorescence x-ray analysis, and can identify a miniature malignant tumor within the breast. The primary beam intensity needed in fluorescence x-ray analysis is on a lower order of magnitude than that used in mammography. Thus, the newly-proposed technique would enable detection of a still tiny breast cancer while dramatically lowering the radiation dose. Field-emission x-ray sources might be a key for translating this concept into a medical technique. PMID:20930932

  7. Speckle-based volume holographic microscopy for optically sectioned multi-plane fluorescent imaging.

    PubMed

    Chen, Hsi-Hsun; Singh, Vijay Raj; Luo, Yuan

    2015-03-23

    Structured illumination microscopy has been widely used to reconstruct optically sectioned fluorescence images in wide-field fashion; however, it still requires axial scanning to obtain multiple depth information of a volumetric sample. In this paper, a new imaging scheme, called speckle-based volume holographic microscopy system, is presented. The proposed system incorporates volumetric speckle illumination and multiplexed volume holographic gratings to acquire multi-plane images with optical sectioning capability, without any axial scanning. We present the design, implementation, and experimental image data demonstrating the proposed system's ability to simultaneously obtain wide-field, optically sectioned, and multi-depth resolved images of fluorescently labeled microspheres and tissue structures.

  8. Fluorescence pH probe based on microstructured polymer optical fiber.

    PubMed

    Yang, X H; Wang, L L

    2007-12-10

    A kind of optical pH sensor was demonstrated that is based on a pH-sensitive fluorescence dye-doped (eosin) cellulose acetate (CA) thin-film modified microstructured polymer optical fiber (MPOF). It was obtained by directly inhaling an eosin-CA-acetic acid mixed solution into array holes in a MPOF and then removing the solvent (acetic acid). The sensing film showed different fluorescence intensities to different pH solutions in a pH range of 2.5-4.5. Furthermore, the pH response range could be tailored through doping a surfactant, hexadecyl trimethyl ammonium bromide (CTAB), in the sensing film.

  9. Characterization of the regulatory region of the dopa decarboxylase gene in Medaka: an in vivo green fluorescent protein reporter assay combined with a simple TA-cloning method.

    PubMed

    Fujimori, Kazuhiro E

    2009-03-01

    The mechanism by which differentiated cells cooperatively express specific sets of genes in multicellular organisms is a fundamental question for biologists. Currently, the mechanism is primarily attributed to complex regulation of transcriptional machinery. Here, I provide a method for studying spatiotemporal characteristics of promoters in vivo by rapid construction of reporter gene-expression vectors based on simple TA-cloning using an in vivo eGFP reporter assay in Medaka (Oryzias latipes). As an application of this method, I focused on the dopa decarboxylase (Ddc) gene, an essential enzyme for production of neurotransmitters, dopamine, and serotonin. Based on the known structure of the Medaka genome, I predicted and cloned the approximately 3 kbp fragment flanking the Ddc gene. Using an eGFP reporter assay in vivo, I showed that it functions as a promoter, directing reporter gene expression in the brain, retina, epiphysis, and gut, but not in sympathetic ganglia, kidney, or liver. Thus, the procedure presented here provides a useful tool for rapid screening of possible promoter regions and for establishing germ line-transmitted transgenic lines of Medaka.

  10. Quantum dots based mesoporous structured imprinting microspheres for the sensitive fluorescent detection of phycocyanin.

    PubMed

    Zhang, Zhong; Li, Jinhua; Wang, Xiaoyan; Shen, Dazhong; Chen, Lingxin

    2015-05-06

    Phycocyanin with important physiological/environmental significance has attracted increasing attention; versatile molecularly imprinted polymers (MIPs) have been applied to diverse species, but protein imprinting is still quite difficult. Herein, using phycocyanin as template via a sol-gel process, we developed a novel fluorescent probe for specific recognition and sensitive detection of phycocyanin by quantum dots (QDs) based mesoporous structured imprinting microspheres (SiO2@QDs@ms-MIPs), obeying electron-transfer-induced fluorescence quenching mechanism. When phycocyanin was present, a Meisenheimer complex would be produced between phycocyanin and primary amino groups of QDs surface, and then the photoluminescent energy of QDs would be transferred to the complex, leading to the fluorescence quenching of QDs. As a result, the fluorescent intensity of the SiO2@QDs@ms-MIPs was significantly decreased within 8 min, and accordingly a favorable linearity within 0.02-0.8 μM and a high detectability of 5.9 nM were presented. Excellent recognition specificity for phycocyanin over its analogues was displayed, with a high imprinting factor of 4.72. Furthermore, the validated probe strategy was successfully applied to seawater and lake water sample analysis, and high recoveries in the range of 94.0-105.0% were attained at three spiking levels of phycocyanin, with precisions below 5.3%. The study provided promising perspectives to develop fluorescent probes for convenient, rapid recognition and sensitive detection of trace proteins from complex matrices, and further pushed forward protein imprinting research.

  11. A fluorescence-based method for rapid and direct determination of polybrominated diphenyl ethers in water

    SciTech Connect

    Shan, Huimei; Liu, Chongxuan; Wang, Zheming; Ma, Teng; Shang, Jianying; Pan, Duoqiang

    2015-01-01

    A new method was developed for rapid and direct measurement of polybrominated diphenyl ethers (PBDEs) in aqueous samples using fluorescence spectroscopy. The fluorescence spectra of tri- to deca-BDE (BDE 28, 47, 99, 153, 190, and 209) commonly found in environment were measured at variable emission and excitation wavelengths. The results revealed that the PBDEs have distinct fluorescence spectral profiles and peak positions that can be exploited to identify these species and determine their concentrations in aqueous solutions. The detection limits as determined in deionized water spiked with PBDEs are 1.71-5.82 ng/L for BDE 28, BDE 47, BDE 190, and BDE 209 and 45.55–69.95 ng/L for BDE 99 and BDE 153. The effects of environmental variables including pH, humic substance, and groundwater chemical composition on PBDEs measurements were also investigated. These environmental variables affected fluorescence intensity, but their effect can be corrected through linear additivity and separation of spectral signal contribution. Compared with conventional GC-based analytical methods, the fluorescence spectroscopy method is more efficient as it only uses a small amount of samples (2-4 mL), avoids lengthy complicated concentration and extraction steps, and has a low detection limit of a few ng/L.

  12. A fluorescence-based method for rapid and direct determination of polybrominated diphenyl ethers in water

    DOE PAGES

    Shan, Huimei; Liu, Chongxuan; Wang, Zheming; ...

    2015-01-01

    A new method was developed for rapid and direct measurement of polybrominated diphenyl ethers (PBDEs) in aqueous samples using fluorescence spectroscopy. The fluorescence spectra of tri- to deca-BDE (BDE 28, 47, 99, 153, 190, and 209) commonly found in environment were measured at variable emission and excitation wavelengths. The results revealed that the PBDEs have distinct fluorescence spectral profiles and peak positions that can be exploited to identify these species and determine their concentrations in aqueous solutions. The detection limits as determined in deionized water spiked with PBDEs are 1.71-5.82 ng/L for BDE 28, BDE 47, BDE 190, and BDEmore » 209 and 45.55–69.95 ng/L for BDE 99 and BDE 153. The effects of environmental variables including pH, humic substance, and groundwater chemical composition on PBDEs measurements were also investigated. These environmental variables affected fluorescence intensity, but their effect can be corrected through linear additivity and separation of spectral signal contribution. Compared with conventional GC-based analytical methods, the fluorescence spectroscopy method is more efficient as it only uses a small amount of samples (2-4 mL), avoids lengthy complicated concentration and extraction steps, and has a low detection limit of a few ng/L.« less

  13. Detection of pretreated fingerprint fluorescence using an LED-based excitation system.

    PubMed

    Takatsu, Masahisa; Shimoda, Osamu; Onishi, Kyoko; Onishi, Akira; Oguri, Naoki

    2008-07-01

    Optimization of a light emitting diode (LED)-based excitation system for the detection of pretreated fingerprint fluorescence is described. Fluorescent ridges can usually be excited by irradiation with forensic light sources such as xenon arc lamps or quartz-halogen lamps with high-power output and suitable filters. However, they are too expensive for many crime laboratories in smaller organizations. We concentrated on LEDs which have advantages over conventional light sources in that they are simpler and of lower cost, but the power output and quality of each individual LED unit is not sufficient for the detection of weak fluorescent ridges. To resolve this subject, blue and green LED arrays composed of ninety LED units were adopted and suitable low pass filters for them were designed. An experimental system, consisting of blue and green LED arrays with the suitable low pass filters for illumination, high pass filters for viewing, a digital camera and a computer, was tested. The fluorescent images of cyanoacrylate ester fumed/rhodamine 6G stained fingerprint on white polyethylene sheet and weak fluorescent ridges of ninhydrin/indium chloride treated fingerprint on white paper were successfully detected and photographed. It was shown that the improvement of LED beam in intensity and quality can compensate the disadvantages, resulting in well-contrasted images.

  14. Substrate Engineering Enabling Fluorescence Droplet Entrapment for IVC-FACS-Based Ultrahigh-Throughput Screening.

    PubMed

    Ma, Fuqiang; Fischer, Michael; Han, Yunbin; Withers, Stephen G; Feng, Yan; Yang, Guang-Yu

    2016-09-06

    In vitro compartmentalization-based fluorescence-activated cell sorting (IVC-FACS) is a powerful screening tool for directed evolution of enzymes. However, the efficiency of IVC-FACS is limited by the tendency of the fluorescent reporter to diffuse out of the droplets, which decouples the genotype and phenotype of the target gene. Herein we present a new strategy called fluorescence droplet entrapment (FDE) to solve this problem. The substrate is designed with a polarity that enables it to pass through the oil phase, react with the enzyme and generate an oil-impermeable and fluorescent product that remains entrapped inside the droplet. Several FDE substrates were designed, using two distinct substrate engineering strategies, for the detection of phosphotriesterases, carboxylesterases, and glycosidases activities. Model screening assays in which rare phosphotriesterase-active cells were enriched from large excesses of inactive cells showed that the enrichment efficiency achievable using an FDE substrate was as high as 900-fold: the highest yet reported in such an IVC-FACS system. Thus, FDE provides a means to tightly control the onset of the enzymatic reaction, minimize droplet cross-talk, and lower the background fluorescence. It therefore may serve as a useful strategy for the IVC-FACS screening of enzymes, antibodies, and other proteins.

  15. 2D fluorescence spectroscopy for monitoring ion-exchange membrane based technologies - Reverse electrodialysis (RED).

    PubMed

    Pawlowski, Sylwin; Galinha, Claudia F; Crespo, João G; Velizarov, Svetlozar

    2016-01-01

    Reverse electrodialysis (RED) is one of the emerging, membrane-based technologies for harvesting salinity gradient energy. In RED process, fouling is an undesirable operation constraint since it leads to a decrease of the obtainable net power density due to increasing stack electric resistance and pressure drop. Therefore, early fouling detection is one of the main challenges for successful RED technology implementation. In the present study, two-dimensional (2D) fluorescence spectroscopy was used, for the first time, as a tool for fouling monitoring in RED. Fluorescence excitation-emission matrices (EEMs) of ion-exchange membrane surfaces and of natural aqueous streams were acquired during one month of a RED stack operation. Fouling evolvement on the ion-exchange membrane surfaces was successfully followed by 2D fluorescence spectroscopy and quantified using principal components analysis (PCA). Additionally, the efficiency of cleaning strategy was assessed by measuring the membrane fluorescence emission intensity before and after cleaning. The anion-exchange membrane (AEM) surface in contact with river water showed to be significantly affected due to fouling by humic compounds, which were found to cross through the membrane from the lower salinity (river water) to higher salinity (sea water) stream. The results obtained show that the combined approach of using 2D fluorescence spectroscopy and PCA has a high potential for studying fouling development and membrane cleaning efficiency in ion exchange membrane processes.

  16. A fluorescence ratiometric sensor for hypochlorite based on a novel dual-fluorophore response approach.

    PubMed

    Long, Lingliang; Zhang, Dongdong; Li, Xiufen; Zhang, Jinfang; Zhang, Chi; Zhou, Liping

    2013-05-02

    A fluorescence ratiometric sensor for OCl(-) has been developed based on a novel dual fluorophore response approach. The sensor molecule contains a coumarin fluorophore and a rhodamine fluorophore, and the two fluorophores are directly linked to an OCl(-) recognition group. The structure of the sensor was characterized by ESI-MS, NMR, and X-ray crystallographic analysis. Upon treatment with OCl(-), both fluorophores in the sensor responded simultaneously at two separate optical windows, with large enhancement of the fluorescence ratio (I578/I501) from 0.01 to 39.55. The fluorescence ratios for the sensor showed a good linearity with the concentration of OCl(-) in the range of 0.2-40 μM and the detection limits is 0.024 μM (SN(-1)=3). Investigation of reaction products indicated that the sensor reaction with OCl(-) produced two new fluorescent molecules, which were responsible for the fluorescence changes in two optical windows. In addition, the sensor showed high selectivity to OCl(-) over other reactive oxygen species, reactive nitrogen species, cations, and anions. The sensor has also been successfully applied to detection of OCl(-) in natural water samples with satisfactory recovery.

  17. Color-Tunable Solid-State Fluorescence Emission from Carbazole-Based BODIPYs.

    PubMed

    Maeda, Chihiro; Todaka, Takumi; Ueda, Tomomi; Ema, Tadashi

    2016-05-23

    Several carbazole-based boron dipyrromethene (BODIPY) dyes were synthesized by organometallic approaches. Thiazole, benzothiazole, imidazole, benzimidazole, triazole, and indolone substituents were introduced at the 1-position of the carbazole moiety, and boron complexation of each dipyrrin generated the corresponding compounds 1, 2 a, and 3-6. The properties of these products were investigated by UV/Vis and fluorescence spectroscopy, cyclic voltammetry, X-ray crystallography, and DFT calculations. These compounds exhibited large Stokes shifts, and compounds 1, 2 a, and 3-5 fluoresced both in solution and in the solid state. Complex 2 a showed the highest fluorescence quantum yield (ΦF ) in the solid state, therefore boron complexes of the carbazole-benzothiazole hybrids 2 b-f, which had several different substituents, were prepared and the effects of the substituents on the photophysical properties of the compounds were examined. The fluorescence properties showed good correlation with the results of crystal-packing analyses, and the dyes exhibited color-tunable solid-state fluorescence.

  18. Development of fluorescence based handheld imaging devices for food safety inspection

    NASA Astrophysics Data System (ADS)

    Lee, Hoyoung; Kim, Moon S.; Chao, Kuanglin; Lefcourt, Alan M.; Chan, Diane E.

    2013-05-01

    For sanitation inspection in food processing environment, fluorescence imaging can be a very useful method because many organic materials reveal unique fluorescence emissions when excited by UV or violet radiation. Although some fluorescence-based automated inspection instrumentation has been developed for food products, there remains a need for devices that can assist on-site inspectors performing visual sanitation inspection of the surfaces of food processing/handling equipment. This paper reports the development of an inexpensive handheld imaging device designed to visualize fluorescence emissions and intended to help detect the presence of fecal contaminants, organic residues, and bacterial biofilms at multispectral fluorescence emission bands. The device consists of a miniature camera, multispectral (interference) filters, and high power LED illumination. With WiFi communication, live inspection images from the device can be displayed on smartphone or tablet devices. This imaging device could be a useful tool for assessing the effectiveness of sanitation procedures and for helping processors to minimize food safety risks or determine potential problem areas. This paper presents the design and development including evaluation and optimization of the hardware components of the imaging devices.

  19. Fluorescence suppression using wavelength modulated Raman spectroscopy in fiber-probe-based tissue analysis.

    PubMed

    Praveen, Bavishna B; Ashok, Praveen C; Mazilu, Michael; Riches, Andrew; Herrington, Simon; Dholakia, Kishan

    2012-07-01

    In the field of biomedical optics, Raman spectroscopy is a powerful tool for probing the chemical composition of biological samples. In particular, fiber Raman probes play a crucial role for in vivo and ex vivo tissue analysis. However, the high-fluorescence background typically contributed by the auto fluorescence from both a tissue sample and the fiber-probe interferes strongly with the relatively weak Raman signal. Here we demonstrate the implementation of wavelength-modulated Raman spectroscopy (WMRS) to suppress the fluorescence background while analyzing tissues using fiber Raman probes. We have observed a significant signal-to-noise ratio enhancement in the Raman bands of bone tissue, which have a relatively high fluorescence background. Implementation of WMRS in fiber-probe-based bone tissue study yielded usable Raman spectra in a relatively short acquisition time (∼30  s), notably without any special sample preparation stage. Finally, we have validated its capability to suppress fluorescence on other tissue samples such as adipose tissue derived from four different species.

  20. Enzymatic cascade based fluorescent DNAzyme machines for the ultrasensitive detection of Cu(II) ions.

    PubMed

    He, Jing-Lin; Zhu, Shuang-Li; Wu, Ping; Li, Pan-Pan; Li, Ting; Cao, Zhong

    2014-10-15

    A novel enzymatic cascade based fluorescent DNAzyme machine has been developed for the amplified detection of copper (Cu(2+)) ions. This is the first attempt to carry out the combination of the self-cleaving DNAzyme and the polymerase/endonuclease reaction cycles involving cleaved substrate extension. In the presence of Cu(2+) ions, the enzyme strand carries out catalytic reactions to hydrolytic cleavage of the substrate strand. The cleaved DNAzyme substrates act as primers and trigger the Klenow Fragment polymerization. Nb.BbvCI endonuclease cuts the double-stranded niking site and thus opens a new site for a new replication. The replication regenerates the complete dsDNA to initiate another cycle of nicking, polymerization and displacement. Finally the fluorescence dye, SG, inserts into the DNA double helix to generate a distinguishable fluorescence enhancement. The Cu(2+) ions act as the activator for enzymatic cascade amplification generating multiple duplex structures in the nascent product. An increasing fluorescence is observed with increasing Cu(2+) ions concentration. A good nonlinear correlation (R=0.9997) was obtained between fluorescence intensity and the cubic logarithm of the Cu(2+) ions concentration over the range 0.50-200 nM. This nonlinear response phenomenon results in an efficient improvement of the sensitivity of our current proposed assay. The activation of such enzymatic cascades through analyte-DNAzyme interactions is not only valuable to activate the cooperation of enzyme networks, but also has a substantial impact on the development of amplified DNAzyme sensors.

  1. Highly sensitive detection of superoxide dismutase based on an immunoassay with surface-enhanced fluorescence.

    PubMed

    Yang, Xiaoming; Dou, Yao; Zhu, Shanshan

    2013-06-07

    Herein, a novel highly sensitive enhanced-fluorescence immunoassay for detection of superoxide dismutase (SOD) is established by combining surface-enhanced fluorescence (SEF) with immuno-magnetic separation. Based on a sandwich-type immunoassay, analytes in samples are first captured by magnetic beads coated with a monoclonal antibody and then "sandwiched" by another monoclonal antibody on silver nanoparticles labeled with fluorescein-labeled oligonucleotides in the presence of a magnet. Subsequently, the immune complex is enriched by exposure to a magnetic field. Lastly, the fluorescence intensity is measured according to the number of dissociated fluoresceins. The increased fluorescence intensity permits highly sensitive detection of SOD in a linear range of 10-8 × 10(5) pg mL(-1), with a detection limit of 4 pg mL(-1) at a signal-to-noise ratio of 3. Significantly, this method was validated for detection of SOD in human serum, human urine, and cosmetic samples. Moreover, the reliability and accuracy of results obtained by the enhanced-fluorescence method was confirmed by the analysis of high performance liquid chromatography (HPLC).

  2. Multicolor-based discrimination of 21 short tandem repeats and amelogenin using four fluorescent universal primers.

    PubMed

    Asari, Masaru; Okuda, Katsuhiro; Hoshina, Chisato; Omura, Tomohiro; Tasaki, Yoshikazu; Shiono, Hiroshi; Matsubara, Kazuo; Shimizu, Keiko

    2016-02-01

    The aim of this study was to develop a cost-effective genotyping method using high-quality DNA for human identification. A total of 21 short tandem repeats (STRs) and amelogenin were selected, and fluorescent fragments at 22 loci were simultaneously amplified in a single-tube reaction using locus-specific primers with 24-base universal tails and four fluorescent universal primers. Several nucleotide substitutions in universal tails and fluorescent universal primers enabled the detection of specific fluorescent fragments from the 22 loci. Multiplex polymerase chain reaction (PCR) produced intense FAM-, VIC-, NED-, and PET-labeled fragments ranging from 90 to 400 bp, and these fragments were discriminated using standard capillary electrophoretic analysis. The selected 22 loci were also analyzed using two commercial kits (the AmpFLSTR Identifiler Kit and the PowerPlex ESX 17 System), and results for two loci (D19S433 and D16S539) were discordant between these kits due to mutations at the primer binding sites. All genotypes from the 100 samples were determined using 2.5 ng of DNA by our method, and the expected alleles were completely recovered. Multiplex 22-locus genotyping using four fluorescent universal primers effectively reduces the costs to less than 20% of genotyping using commercial kits, and our method would be useful to detect silent alleles from commercial kit analysis.

  3. Fluorescent reversible regulation based on the interactions of topotecan hydrochloride, neutral red and quantum dots.

    PubMed

    Wang, Linlin; Shen, Yizhong; Liu, Shaopu; Yang, Jidong; Liang, Wanjun; Li, Dan; He, Youqiu

    2015-02-05

    The interactions of topotecan hydrochloride (THC), neutral red (NR) and thioglycolic acid (TGA) capped CdTe/CdS quantum dots (QDs) built a solid base for the controlling of the fluorescent reversible regulation of the system. This study was developed by means of ultraviolet-visible (UV-vis) absorption, fluorescence (FL), resonance Rayleigh scattering (RRS) spectroscopy and transmission electron microscopy (TEM). Corresponding experimental results revealed that the fluorescence of TGA-CdTe/CdS QDs could be effectively quenched by NR, while the RRS of the QDs enhanced gradually with the each increment of NR concentration. After the addition of THC, the strong covalent conjugation between NR and THC which was in carboxylate state enabled NR to be dissociated from the surface of TGA-CdTe/CdS QDs to form more stable complex with THC, thereby enhancing the fluorescence of the TGA-CdTe/CdS QDs-NR system. What is more, through analyzing the optical properties and experimental data of the reaction between TGA-CdTe/CdS QDs and NR, the possible reaction mechanism of the whole system was discussed. This combination of multiple spectroscopic techniques could contribute to the investigation for the fluorescent reversible regulation of QDs and a method could also be established to research the interactions between camptothecin drugs and dyes.

  4. Fluorescent reversible regulation based on the interactions of topotecan hydrochloride, neutral red and quantum dots

    NASA Astrophysics Data System (ADS)

    Wang, Linlin; Shen, Yizhong; Liu, Shaopu; Yang, Jidong; Liang, Wanjun; Li, Dan; He, Youqiu

    2015-02-01

    The interactions of topotecan hydrochloride (THC), neutral red (NR) and thioglycolic acid (TGA) capped CdTe/CdS quantum dots (QDs) built a solid base for the controlling of the fluorescent reversible regulation of the system. This study was developed by means of ultraviolet-visible (UV-vis) absorption, fluorescence (FL), resonance Rayleigh scattering (RRS) spectroscopy and transmission electron microscopy (TEM). Corresponding experimental results revealed that the fluorescence of TGA-CdTe/CdS QDs could be effectively quenched by NR, while the RRS of the QDs enhanced gradually with the each increment of NR concentration. After the addition of THC, the strong covalent conjugation between NR and THC which was in carboxylate state enabled NR to be dissociated from the surface of TGA-CdTe/CdS QDs to form more stable complex with THC, thereby enhancing the fluorescence of the TGA-CdTe/CdS QDs-NR system. What is more, through analyzing the optical properties and experimental data of the reaction between TGA-CdTe/CdS QDs and NR, the possible reaction mechanism of the whole system was discussed. This combination of multiple spectroscopic techniques could contribute to the investigation for the fluorescent reversible regulation of QDs and a method could also be established to research the interactions between camptothecin drugs and dyes.

  5. Impact of background on color, transmittance, and fluorescence of leucite based ceramics.

    PubMed

    Rafael, Caroline Freitas; Güth, Jan-Frederik; Kauling, Ana Elisa Colle; Cesar, Paulo Francisco; Volpato, Claudia Angelo Mazieiro; Liebermann, Anja

    2017-03-29

    This study evaluated the impact of tooth shade on differences in color (∆E), lightness (∆L), chromaticity coordinates a*/b* (∆a and ∆b), transmittance and the degree of fluorescence of CAD/CAM leucite based ceramic (LBC). Ten disks were fabricated of LBC; Empress CAD, A2, thickness of 1.5 mm and eight disks of resin-nano-ceramic (RNC; Lava Ultimate) in different colors to simulate variations in substrate shade. The associations of LBC disks with different color substrates were analyzed with a spectrophotometer; ∆E, ∆L*, ∆a*, ∆b*, and transmittance were measured and calculated. Fluorescence was evaluated with a fluorescence system (Fluorescence System, Biopdi). All substrate shades influenced the optical properties of LBC, with regard to color, luminosity, coordinate a* and b*, transmittance, and fluorescence (p<0.001). Substrate colors with high saturation (A3.5 and C2) presented highest impact, whereas colors with lowest saturations (BL, B1) showed less impact. Substrate color influenced the optical properties of ceramic restorations.

  6. [Fluorescence spectrum analysis system for protoporphyrin IX in serum based on wavelet transform].

    PubMed

    Zhu, Dian-ming; Yang, Hong-peng; Luo, Xiao-sen; Liu, Ying; Shen, Zhong-hua; Lu, Jian; Ni, Xiao-wu

    2007-12-01

    Protoporphyrin IX is an important kind of organic compound for vital movement, and can be used as the sign of tumour blood. Human protoporphyrin IX content in serum is very low, and affected by various factors. The serum fluorescence spectrum analysis system based on wavelet transform was used to discriminated the protoporphyrin IX weak signals. The protoporphyrin IX fluorescence spectrum was obtained by a multi-function spectrum measuring system, and decomposed several times by wavelet transform to distinguish the noise and spectrum signals. The fluorescence spectrum can be divided into corresponding discrete approximations signals (a1-a6) and discrete details signals (d1-d6) by six times of decomposition, showing the signal frequency decreasing with decomposition times increasing and the protoporphyrin IX fluorescence character peak appears here. The weak signals were discriminated and the exactly component and quantity can be acquired for further analysis. So it can be analysed quantitatively. The researches in the present paper provide the potential application in the diagnosis of incipient tumous using the serum fluorescence spectrum

  7. Determination of the drug-DNA binding modes using fluorescence-based assays.

    PubMed

    Williams, Alicia K; Dasilva, Sofia Cheliout; Bhatta, Ankit; Rawal, Baibhav; Liu, Melinda; Korobkova, Ekaterina A

    2012-03-15

    Therapeutic drugs and environmental pollutants may exhibit high reactivity toward DNA bases and backbone. Understanding the mechanisms of drug-DNA binding is crucial for predicting their potential genotoxicity. We developed a fluorescence analytical method for the determination of the preferential binding mode for drug-DNA interactions. Two nucleic acid dyes were employed in the method: TO-PRO-3 iodide (TP3) and 4',6-diamidino-2-phenylindole (DAPI). TP3 binds DNA by intercalation, whereas DAPI exhibits minor groove binding. Both dyes exhibit significant fluorescence magnification on binding to DNA. We evaluated the DNA binding constant, K(b), for each dye. We also performed fluorescence quenching experiments with 11 molecules of various structures and measured a C(50) value for each compound. We determined preferential binding modes for the aforementioned molecules and found that they bound to DNA consistently, as indicated by other studies. The values of the likelihood of DNA intercalation were correlated with the partition coefficients of the molecules. In addition, we performed nuclear magnetic resonance (NMR) studies of the interactions with calf thymus DNA for the three molecules. The results were consistent with the fluorescence method described above. Thus, we conclude that the fluorescence method we developed provides a reliable determination of the likelihoods of the two different DNA binding modes.

  8. A Fluorescence-Based Method for Rapid and Direct Determination of Polybrominated Diphenyl Ethers in Water

    PubMed Central

    Shan, Huimei; Ma, Teng; Shang, Jianying; Pan, Duoqiang

    2015-01-01

    A new method was developed for rapid and direct measurement of polybrominated diphenyl ethers (PBDEs) in aqueous samples using fluorescence spectroscopy. The fluorescence spectra of tri- to deca-BDE (BDE 28, 47, 99, 153, 190, and 209) commonly found in environment were measured at variable emission and excitation wavelengths. The results revealed that the PBDEs have distinct fluorescence spectral profiles and peak positions that can be exploited to identify these species and determine their concentrations in aqueous solutions. The detection limits as determined in deionized water spiked with PBDEs are 1.71–5.82 ng/L for BDE 28, BDE 47, BDE 190, and BDE 209 and 45.55–69.95 ng/L for BDE 99 and BDE 153. The effects of environmental variables including pH, humic substance, and groundwater chemical composition on PBDEs measurements were also investigated. These environmental variables affected fluorescence intensity, but their effect can be corrected through linear additivity and separation of spectral signal contribution. Compared with conventional GC-based analytical methods, the fluorescence spectroscopy method is more efficient as it only uses a small amount of samples (2–4 mL), avoids lengthy complicated concentration and extraction steps, and has a low detection limit of a few ng/L. PMID:25705548

  9. A FRET-based fluorescent probe for mercury ions in water and living cells

    NASA Astrophysics Data System (ADS)

    Zhang, Bo; Ma, Pinyi; Gao, Dejiang; Wang, Xinghua; Sun, Ying; Song, Daqian; Li, Xuwen

    2016-08-01

    On the basis of fluorescence resonance energy transfer (FRET), a new rhodamine derivative (DRh) was synthesized as a ratiometric fluorescent probe for detecting Hg2 + in water and living cells samples. The recognition properties of the probe DRh with metal ions had been investigated in H2O/CH3CN (9:1, v/v; Tris-HCl 50 mmol L- 1; pH = 7.0) solution by the UV-Vis spectrophotometry and the fluorescence spectrophotometry. The results showed that the probe DRh exhibited the selective recognition of Hg2 +. Upon the addition of Hg2 +, the spirolactam ring of probe DRh was opened. The 1:1 stoichiometric structure between DRh and Hg2 + were supported by Job's plot, MS and DFT theoretical calculations. The linearly fluorescence intensity ratio (I582/I538) is proportional to the concentration of Hg2 + in the range 0-30 μmol L- 1. The limit of detection (LOD) of Hg2 + is 0.008 μmol L- 1 (base on S/N = 3). The present probe was applied to the determination of Hg2 + in neutral water samples and gave recoveries ranging from 104.5 to 107.9%. Furthermore, the fluorescent probe also can be applied as a bioimaging reagent for Hg2 + detection in HeLa cells.

  10. Synthesis and characterisation of highly fluorescent core-shell nanoparticles based on Alexa dyes

    NASA Astrophysics Data System (ADS)

    Natte, Kishore; Behnke, Thomas; Orts-Gil, Guillermo; Würth, Christian; Friedrich, Jörg F.; Österle, Werner; Resch-Genger, Ute

    2012-02-01

    Current and future developments in the emerging field of nanobiotechnology are closely linked to the rational design of novel fluorescent nanomaterials, e.g. for biosensing and imaging applications. Here, the synthesis of bright near infrared (NIR)-emissive nanoparticles based on the grafting of silica nanoparticles (SNPs) with 3-aminopropyl triethoxysilane (APTES) followed by covalent attachment of Alexa dyes and their subsequent shielding by an additional silica shell are presented. These nanoparticles were investigated by dynamic light scattering (DLS), transmission electron microscopy (TEM) and fluorescence spectroscopy. TEM studies revealed the monodispersity of the initially prepared and fluorophore-labelled silica particles and the subsequent formation of raspberry-like structures after addition of a silica precursor. Measurements of absolute fluorescence quantum yields of these scattering particle suspensions with an integrating sphere setup demonstrated the influence of dye labelling density-dependent fluorophore aggregation on the signaling behaviour of such nanoparticles.

  11. A single-wavelength-emitting ratiometric probe based on phototriggered fluorescence switching of graphene quantum dots.

    PubMed

    Qu, Zhi-bei; Zhang, Min; Zhou, Tianshu; Shi, Guoyue

    2014-10-13

    Ratiometric fluorescent probes are of great importance in research, because a built-in correction for environmental effects can be provided to reduce background interference. However, the traditional ratiometric fluorescent probes require two luminescent materials with different emission bands. Herein a novel ratiometric probe based on a single-wavelength-emitting material is reported. The probe works by regulating the luminescent property of graphene quantum dots with UV illumination as activator. The ratiometric sensor shows high sensitivity and specificity for iron ions. Moreover, the ratiometric sensor was successfully employed to monitor ferritin levels in Sprague Dawley rats with chemical-induced acute liver damage. The proposed single-wavelength ratiometric fluorescent probe may greatly broaden the applicability of ratiometric sensors in diagnostic devices, medical applications, and analytical chemistry.

  12. Chromophore Structure of Photochromic Fluorescent Protein Dronpa: Acid-Base Equilibrium of Two Cis Configurations.

    PubMed

    Higashino, Asuka; Mizuno, Misao; Mizutani, Yasuhisa

    2016-04-07

    Dronpa is a novel photochromic fluorescent protein that exhibits fast response to light. The present article is the first report of the resonance and preresonance Raman spectra of Dronpa. We used the intensity and frequency of Raman bands to determine the structure of the Dronpa chromophore in two thermally stable photochromic states. The acid-base equilibrium in one photochromic state was observed by spectroscopic pH titration. The Raman spectra revealed that the chromophore in this state shows a protonation/deprotonation transition with a pKa of 5.2 ± 0.3 and maintains the cis configuration. The observed resonance Raman bands showed that the other photochromic state of the chromophore is in a trans configuration. The results demonstrate that Raman bands selectively enhanced for the chromophore yield valuable information on the molecular structure of the chromophore in photochromic fluorescent proteins after careful elimination of the fluorescence background.

  13. A fluorescent thermometer based on a pyrene-labeled thermoresponsive polymer.

    PubMed

    Pietsch, Christian; Vollrath, Antje; Hoogenboom, Richard; Schubert, Ulrich S

    2010-01-01

    Thermoresponsive polymers that undergo a solubility transition by variation of the temperature are important materials for the development of 'smart' materials. In this contribution we exploit the solubility phase transition of poly(methoxy diethylene glycol methacrylate), which is accompanied by a transition from hydrophilic to hydrophobic, for the development of a fluorescent thermometer. To translate the polymer phase transition into a fluorescent response, the polymer was functionalized with pyrene resulting in a change of the emission based on the microenvironment. This approach led to a soluble polymeric fluorescent thermometer with a temperature range from 11 °C to 21 °C. The polymer phase transition that occurs during sensing is studied in detail by dynamic light scattering.

  14. Enhancement of Fluorescence-Based Sandwich Immunoassay Using Multilayered Microplates Modified with Plasma-Polymerized Films.

    PubMed

    Yano, Kazuyoshi; Iwasaki, Akira

    2016-12-25

    A functional modification of the surface of a 96-well microplate coupled with a thin layer deposition technique is demonstrated for enhanced fluorescence-based sandwich immunoassays. The plasma polymerization technique enabling the deposition of organic thin films was employed for the modification of the well surface of a microplate. A silver layer and a plasma-polymerized film were consecutively deposited on the microplate as a metal mirror and the optical interference layer, respectively. When Cy3-labeled antibody was applied to the wells of the resulting multilayered microplate without any immobilization step, greatly enhanced fluorescence was observed compared with that obtained with the unmodified one. The same effect could be also exhibited for an immunoassay targeting antigen directly adsorbed on the multilayered microplate. Furthermore, a sandwich immunoassay for the detection of interleukin 2 (IL-2) was performed with the multilayered microplates, resulting in specific and 88-fold-enhanced fluorescence detection.

  15. Charge-transfer-based terbium MOF nanoparticles as fluorescent pH sensor for extreme acidity.

    PubMed

    Qi, Zewan; Chen, Yang

    2017-01-15

    Newly emerged metal organic frameworks (MOFs) have aroused the great interest in designing functional materials by means of its flexible structure and component. In this study, we used lanthanide Tb(3+) ions and small molecular ligands to design and assemble a kind of pH-sensitive MOF nanoparticle based on intramolecular-charge-transfer effect. This kind of made-to-order MOF nanoparticle for H(+) is highly specific and sensitive and could be used to fluorescently indicate pH value of strong acidic solution via preset mechanism through luminescence of Tb(3+). The long luminescence lifetime of Tb(3+) allows eliminating concomitant non-specific fluorescence by time-revised fluorescence techniques, processing an advantage in sensing H(+) in biological media with strong autofluorescence. Our method showed a great potential of MOF structures in designing and constructing sensitive sensing materials for specific analytes directly via the assembly of functional ions/ligands.

  16. A novel fiber optic biosensor for nitric oxide determination based on vicinal diaminobenzozcridine fluorescent probe

    NASA Astrophysics Data System (ADS)

    Ding, Liyun; Huang, Lanfen; Huang, Jun; Zhong, Yunming; Fan, Dian

    2010-04-01

    A novel fiber optic biosensor for the determination of nitric oxide based on vicinal diaminobenzozcridine (VDABA) fluorescent probe was designed and fabricated. The reaction conditions between VDABA and NO, which include concentration of VDABA, temperature and pH, were studied in-depth. The sensitivity of VDABA for NO detection under the optimum conditions and its optical properties were also investigated. The fluorescence responses were concentration-dependent and a good linear relationship (R2=0.9863) was observed over the range 1.8×10-6 to 9×10-6 mol/L NO, the regression equation was F = 3.8889[NO] (mol/L)+217.2. Besides, a complex sensitive film embedding VDABA in cellulose acetate (CA) was prepared, and a fiber optic NO biosensor was fabricated using this film. Then the change of fluorescence phase shift of this biosensor was studied preliminarily by means of the lock-in technology.

  17. Enhancement of Fluorescence-Based Sandwich Immunoassay Using Multilayered Microplates Modified with Plasma-Polymerized Films

    PubMed Central

    Yano, Kazuyoshi; Iwasaki, Akira

    2016-01-01

    A functional modification of the surface of a 96-well microplate coupled with a thin layer deposition technique is demonstrated for enhanced fluorescence-based sandwich immunoassays. The plasma polymerization technique enabling the deposition of organic thin films was employed for the modification of the well surface of a microplate. A silver layer and a plasma-polymerized film were consecutively deposited on the microplate as a metal mirror and the optical interference layer, respectively. When Cy3-labeled antibody was applied to the wells of the resulting multilayered microplate without any immobilization step, greatly enhanced fluorescence was observed compared with that obtained with the unmodified one. The same effect could be also exhibited for an immunoassay targeting antigen directly adsorbed on the multilayered microplate. Furthermore, a sandwich immunoassay for the detection of interleukin 2 (IL-2) was performed with the multilayered microplates, resulting in specific and 88-fold–enhanced fluorescence detection. PMID:28029144

  18. A fluorescence detection of D-penicillamine based on Cu2+-induced fluorescence quenching system of protein-stabilized gold nanoclusters

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Li, Bang Lin; Li, Nian Bing; Luo, Hong Qun

    2015-01-01

    In this contribution, a luminescent gold nanoclusters which were synthesized by bovine serum albumin as novel fluorescent probes were successfully utilized for the determination of D-penicillamine for the first time. Cupric ion was employed to quench the strong fluorescence of the gold nanoclusters, whereas the addition of D-penicillamine caused obvious restoration of fluorescence intensity of the Cu2+-gold nanoclusters system. Under optimum conditions, the increment in fluorescence intensity of Cu2+-gold nanoclusters system caused by D-penicillamine was linearly proportional to the concentration of D-penicillamine in the range of 2.0 × 10-5-2.39 × 10-4 M. The detection limit for D-penicillamine was 5.4 × 10-6 M. With the off-on fluorescence signal at 650 nm approaching the near-infrared region, the present sensor for D-penicillamine detection had high sensitivity and low spectral interference. Furthermore, the novel gold nanoclusters-based fluorescent sensor has been applied to the determination of D-penicillamine in real biological samples with satisfactory results.

  19. A fluorescence detection of D-penicillamine based on Cu(2+)-induced fluorescence quenching system of protein-stabilized gold nanoclusters.

    PubMed

    Wang, Peng; Li, Bang Lin; Li, Nian Bing; Luo, Hong Qun

    2015-01-25

    In this contribution, a luminescent gold nanoclusters which were synthesized by bovine serum albumin as novel fluorescent probes were successfully utilized for the determination of D-penicillamine for the first time. Cupric ion was employed to quench the strong fluorescence of the gold nanoclusters, whereas the addition of D-penicillamine caused obvious restoration of fluorescence intensity of the Cu(2+)-gold nanoclusters system. Under optimum conditions, the increment in fluorescence intensity of Cu(2+)-gold nanoclusters system caused by D-penicillamine was linearly proportional to the concentration of D-penicillamine in the range of 2.0×10(-5)-2.39×10(-4) M. The detection limit for D-penicillamine was 5.4×10(-6) M. With the off-on fluorescence signal at 650 nm approaching the near-infrared region, the present sensor for D-penicillamine detection had high sensitivity and low spectral interference. Furthermore, the novel gold nanoclusters-based fluorescent sensor has been applied to the determination of D-penicillamine in real biological samples with satisfactory results.

  20. Structural Determinants of Improved Fluorescence in a Family of Bacteriophytochrome-Based Infrared Fluorescent Proteins: Insights from Continuum Electrostatic Calculations and Molecular Dynamics Simulations.

    PubMed

    Feliks, Mikolaj; Lafaye, Céline; Shu, Xiaokun; Royant, Antoine; Field, Martin

    2016-08-09

    Using X-ray crystallography, continuum electrostatic calculations, and molecular dynamics simulations, we have studied the structure, protonation behavior, and dynamics of the biliverdin chromophore and its molecular environment in a series of genetically engineered infrared fluorescent proteins (IFPs) based on the chromophore-binding domain of the Deinococcus radiodurans bacteriophytochrome. Our study suggests that the experimentally observed enhancement of fluorescent properties results from the improved rigidity and planarity of the biliverdin chromophore, in particular of the first two pyrrole rings neighboring the covalent linkage to the protein. We propose that the increases in the levels of both motion and bending of the chromophore out of planarity favor the decrease in fluorescence. The chromophore-binding pocket in some of the studied proteins, in particular the weakly fluorescent parent protein, is shown to be readily accessible to water molecules from the solvent. These waters entering the chromophore region form hydrogen bond networks that affect the otherwise planar conformation of the first three rings of the chromophore. On the basis of our simulations, the enhancement of fluorescence in IFPs can be achieved either by reducing the mobility of water molecules in the vicinity of the chromophore or by limiting the interactions of the nearby protein residues with the chromophore. Finally, simulations performed at both low and neutral pH values highlight differences in the dynamics of the chromophore and shed light on the mechanism of fluorescence loss at low pH.

  1. Fluorescence-based quantitative scratch wound healing assay demonstrating the role of MAPKAPK-2/3 in fibroblast migration.

    PubMed

    Menon, Manoj B; Ronkina, Natalia; Schwermann, Jessica; Kotlyarov, Alexey; Gaestel, Matthias

    2009-12-01

    The scratch wound healing assay is a sensitive method to characterize cell proliferation and migration, but it is difficult to be quantitatively evaluated. Therefore, we developed an infrared fluorescence detection-based real-time assay for sensitive and accurate quantification of cell migration in vitro. The method offers sensitivity, simplicity, and the potential for integration into automated large-scale screening studies. A live cell staining lipophilic tracer-1,1'-dioctadecyl-3,3,3',3'-tetramethyl indotricarbocyanine iodide (DiR)-is used for accurate imaging of wound closure in a simple 96-well scratch assay. Scratches are made on prestained confluent cell monolayers using a pipette tip and scanned at different time intervals using a fluorescent scanner. Images are analyzed using Image J software and the migration index is calculated. Effect of cell number, time after scratch and software settings are analyzed. The method is validated by showing concentration- and time-dependent effects of cytochalasin-D on fibroblast migration. Using this assay, we quantitatively evaluate the role of the MAPK-activated protein kinases MK2 and MK3 in fibroblast migration. First, the migratory phenotype of MK2-deficient MEFs is analyzed in a retroviral rescue model. In addition, migration of MK2/3-double-deficient cells is determined and the ability of MK3 to rescue cell migration in MK2/3-double-deficient fibroblasts is demonstrated.

  2. Using fluorescence immunochromatographic test strips based on quantum dots for the rapid and sensitive determination of microcystin-LR.

    PubMed

    Sun, Jiadi; Li, Ying; Pi, Fuwei; Ji, Jian; Zhang, Yinzhi; Sun, Xiulan

    2017-03-01

    A novel immunosensor for the detection of microcystin-LR (MC-LR) was constructed with use of immunochromatographic test strips (ICTS). Quantum dots were chosen to be the fluorescent labels for the immune sensor in ICTS because of their excellent optical and electronic properties with a relatively narrow emission spectrum. The detection sensitivity of the ICTS was related to the concentration of the fluorescent probe and the amount of the MC-LR standards. Under optimal conditions, with MC-LR as the target, the ICTS sensor had a linear range from 0.25 to 5 μg/L, with a correlation coefficient of 0.9901 and a detection limit of 0.1 μg/L. Furthermore, the repeatability of the ICTS was good, and the coefficient of variation was 10%. The ICTS immunosensor allows the reliable detection of MC-LR in water, and has potential in simple, sensitive detection applications. Graphical Abstract A novel method was developed to detect MC-LR using QDs based immunochromatographic test strip.

  3. On Development of a Problem Based Learning System for Linear Algebra with Simple Input Method

    NASA Astrophysics Data System (ADS)

    Yokota, Hisashi

    2011-08-01

    Learning how to express a matrix using a keyboard inputs requires a lot of time for most of college students. Therefore, for a problem based learning system for linear algebra to be accessible for college students, it is inevitable to develop a simple method for expressing matrices. Studying the two most widely used input methods for expressing matrices, a simpler input method for expressing matrices is obtained. Furthermore, using this input method and educator's knowledge structure as a concept map, a problem based learning system for linear algebra which is capable of assessing students' knowledge structure and skill is developed.

  4. Fifth Graders' Learning About Simple Machines Through Engineering Design-Based Instruction Using LEGO™ Materials

    NASA Astrophysics Data System (ADS)

    Marulcu, Ismail; Barnett, Mike

    2012-12-01

    This study is part of a 5-year National Science Foundation-funded project, Transforming Elementary Science Learning Through LEGO™ Engineering Design. In this study, we report on the successes and challenges of implementing an engineering design-based and LEGO™-oriented unit in an urban classroom setting and we focus on the impact of the unit on students' content understanding of simple machines. The LEGO™ engineering-based simple machines module, which was developed for fifth graders by our research team, was implemented in an urban school in a large city in the Northeastern region of the USA. Thirty-three fifth grade students participated in the study, and they showed significant growth in content understanding. We measured students' content knowledge by using identical paper tests and semistructured interviews before and after instruction. Our paired t test analysis results showed that students significantly improved their test and interview scores (t = -3.62, p < 0.001 for multiple-choice items and t = -9.06, p < 0.000 for the open-ended items in the test and t = -12.11, p < 0.000 for the items in interviews). We also identified several alternative conceptions that are held by students on simple machines.

  5. A "turn-on" and label-free fluorescent assay for the rapid detection of exonuclease III activity based on Tb(3+)-induced G-quadruplex conjugates.

    PubMed

    Yang, WeiJuan; Ruan, YaJuan; Wu, WeiHua; Chen, PingPing; Xu, LiangJun; Fu, FengFu

    2014-07-01

    A "turn-on" and label-free fluorescent assay for the specific, rapid, and sensitive detection of 3' → 5' exonuclease III activity is reported in this study. The assay is based on the Tb(3+)-promoted G-quadruplex, which lead to the enhancement of Tb(3+) fluorescence due to the energy transfer from guanines. The proposed assay is highly simple, rapid, and cost-effective, and does not require sophisticated experimental techniques such as gel-based equipment or radioactive labels. It can be used for the rapid detection of exonuclease III activity with a detection limit of 0.8 U and a RSD (n = 6) <5 %. Notably, no dye was covalently conjugated to the DNA strands, which offers the advantages of low-cost and being interference-free.

  6. Paper-based fluorescence resonance energy transfer assay for directly detecting nucleic acids and proteins.

    PubMed

    Li, Hua; Fang, Xueen; Cao, Hongmei; Kong, Jilie

    2016-06-15

    Paper-based fluorescence resonance energy transfer assay (FRET) is gaining great interest in detecting macro-biological molecule. It is difficult to achieve conveniently and fast detection for macro-biological molecule. Herein, a graphene oxide (GO)-based paper chip (glass fiber) integrated with fluorescence labeled single-stranded DNA (ssDNA) for fast, inexpensive and direct detection of biological macromolecules (proteins and nucleic acids) has been developed. In this paper, we employed the Cy3/FAM-labeled ssDNA as the reporter and the GO as quencher and the original glass fiber paper as data acquisition substrates. The chip which was designed and fabricated by a cutting machine is a miniature biosensor that monitors fluorescence recovery from resonance energy transfer. The hybridization assays and fluorescence detection were all simplified, and the surface of the chip did not require immobilization or washing. A Nikon Eclipse was employed as excited resource and a commercial digital camera was employed for capturing digital images. This paper-based microfluidics chip has been applied in the detection of proteins and nucleic acids. The biosensing capability meets many potential requirements for disease diagnosis and biological analysis.

  7. A novel method for image denoising of fluorescence molecular imaging based on fuzzy C-Means clustering

    NASA Astrophysics Data System (ADS)

    An, Yu; Liu, Jie; Ye, Jinzuo; Mao, Yamin; Yang, Xin; Jiang, Shixin; Chi, Chongwei; Tian, Jie

    2015-03-01

    As an important molecular imaging modality, fluorescence molecular imaging (FMI) has the advantages of high sensitivity, low cost and ease of use. By labeling the regions of interest with fluorophore, FMI can noninvasively obtain the distribution of fluorophore in-vivo. However, due to the fact that the spectrum of fluorescence is in the section of the visible light range, there are mass of autofluorescence on the surface of the bio-tissues, which is a major disturbing factor in FMI. Meanwhile, the high-level of dark current for charge-coupled device (CCD) camera and other influencing factor can also produce a lot of background noise. In this paper, a novel method for image denoising of FMI based on fuzzy C-Means clustering (FCM) is proposed, because the fluorescent signal is the major component of the fluorescence images, and the intensity of autofluorescence and other background signals is relatively lower than the fluorescence signal. First, the fluorescence image is smoothed by sliding-neighborhood operations to initially eliminate the noise. Then, the wavelet transform (WLT) is performed on the fluorescence images to obtain the major component of the fluorescent signals. After that, the FCM method is adopt to separate the major component and background of the fluorescence images. Finally, the proposed method was validated using the original data obtained by in vivo implanted fluorophore experiment, and the results show that our proposed method can effectively obtain the fluorescence signal while eliminate the background noise, which could increase the quality of fluorescence images.

  8. Dynamics of a Cortical Neural Network Based on a Simple Model

    NASA Astrophysics Data System (ADS)

    Qu, Jing-Yi; Wang, Ru-Bin

    2012-08-01

    The collective dynamics of a randomly connected neuronal network motivated by the anatomy of a mammalian cortex based on a simple model are studied. This simple model can not only reproduce the rich behaviors of biological neurons but also has only two equations and one nonlinear term. By varying some key parameters, such as the connection weights of neurons, the external current injection and the noise of intensity, this neuronal network will exhibit various collective behaviors. It is demonstrated that the synchronization status of the neuronal network has a strong relationship with the key parameters and the external current has more influence on the spiking of inhibitory neurons than that of excitatory neurons. These results may be instructive in understanding the collective dynamics of a mammalian cortex.

  9. Platinum(II)-Oligonucleotide Coordination Based Aptasensor for Simple and Selective Detection of Platinum Compounds.

    PubMed

    Cai, Sheng; Tian, Xueke; Sun, Lianli; Hu, Haihong; Zheng, Shirui; Jiang, Huidi; Yu, Lushan; Zeng, Su

    2015-10-20

    Wide use of platinum-based chemotherapeutic regimens for the treatment for carcinoma calls for a simple and selective detection of platinum compound in biological samples. On the basis of the platinum(II)-base pair coordination, a novel type of aptameric platform for platinum detection has been introduced. This chemiluminescence (CL) aptasensor consists of a designed streptavidin (SA) aptamer sequence in which several base pairs were replaced by G-G mismatches. Only in the presence of platinum, coordination occurs between the platinum and G-G base pairs as opposed to the hydrogen-bonded G-C base pairs, which leads to SA aptamer sequence activation, resulting in their binding to SA coated magnetic beads. These Pt-DNA coordination events were monitored by a simple and direct luminol-peroxide CL reaction through horseradish peroxidase (HRP) catalysis with a strong chemiluminescence emission. The validated ranges of quantification were 0.12-240 μM with a limit of detection of 60 nM and selectivity over other metal ions. This assay was also successfully used in urine sample determination. It will be a promising candidate for the detection of platinum in biomedical and environmental samples.

  10. Comparison of bond strength between simple foil mesh and laser-structured base retention brackets.

    PubMed

    Sorel, Olivier; El Alam, Rafeh; Chagneau, Francis; Cathelineau, Guy

    2002-09-01

    The aims of the current study were to evaluate the bond strength of a new metallic orthodontic bracket with a laser structured base (Discovery, Dentaurum, Ispringen, Germany), and its effects on the site of bond failure and on the behavior of the enamel after debonding. One hundred and twenty recently extracted human premolars were bonded with 1 of 2 types of mechanical interlock base metal brackets: a standard system with a simple foil mesh pad (Minitrim, Dentaurum) and the Discovery bracket. A resin-based, chemically activated bonding system, No-mix (Dentaurum), was used as the adhesive system in this trial. The teeth were immersed in normal saline solution at 37 degrees C for 7 days before debonding and were randomly assigned to different subgroups. A testing machine was used to evaluate tensile and fatigue bond strengths for both brackets. After debonding, the amount of residual adhesive on the bracket and enamel detachment were assessed according to the adhesive remnant index (ARI) and the enamel detachment index (EDI) with a scanning electron microscope and an energy dispersive X-ray spectrometer. The scores obtained from the ARI and the EDI showed that the laser structured base brackets had a significantly higher bond strength (mean +/- SD: 17.1 +/- 0.7 MPa) that was 2 times higher than that observed with the simple foil mesh brackets (mean +/- SD: 8.7 +/- 1.4 MPa) (P <.001). Bond failure with the laser structured base was at the enamel-adhesive interface with an ARI score of 3 in 80% of the teeth, and bond failure with the simple foil mesh base was at the bracket-adhesive interface with an ARI score of 0 in 75% of the teeth. A small area, with less than 10% of the enamel damaged (1 on the EDI) and 1.5 microm in thickness, was observed for both brackets. The laser structured base bracket's bond strength was double that of the simple foil mesh bracket but was equally safe and did not induce significant enamel detachment.

  11. Simple Machines Made Simple.

    ERIC Educational Resources Information Center

    St. Andre, Ralph E.

    Simple machines have become a lost point of study in elementary schools as teachers continue to have more material to cover. This manual provides hands-on, cooperative learning activities for grades three through eight concerning the six simple machines: wheel and axle, inclined plane, screw, pulley, wedge, and lever. Most activities can be…

  12. Monitoring translocation of multisubunit RNA polymerase along the DNA with fluorescent base analogues.

    PubMed

    Malinen, Anssi M; Turtola, Matti; Belogurov, Georgiy A

    2015-01-01

    Here we describe a direct fluorescence method that reports real-time occupancies of the pre- and post-translocated state of multisubunit RNA polymerase. In a stopped-flow setup, this method is capable of resolving a single base-pair translocation motion of RNA polymerase in real time. In a conventional spectrofluorometer, this method can be employed for studies of the time-averaged distribution of RNA polymerase on the DNA template. This method utilizes commercially available base analogue fluorophores integrated into template DNA strand in place of natural bases. We describe two template DNA strand designs where translocation of RNA polymerase from a pre-translocation to a post-translocation state results in disruption of stacking interactions of fluorophore with neighboring bases, with a concomitant large increase in fluorescence intensity.

  13. A New Fluorescent "Turn-Off" Coumarin-Based Chemosensor: Synthesis, Structure and Cu-Selective Fluorescent Sensing in Water Samples.

    PubMed

    Karaoglu, Kaan; Yilmaz, Fatih; Menteşe, Emre

    2017-03-10

    We report the synthesis and characterization two coumarin-based fluorescence probes, N'-{[7-(diethylamino)-2-oxo-2H-chromen-3-yl]carbonyl}pyridine-3-carbohydrazide (3) and N'-benzoyl-7-(diethylamino)-2-oxo-2H-chromene-3-carbohydrazide (4), proposed as a novel fluorescent chemosensor. The two probes designed showed an instant turn-off fluorescence response to Cu(2+) over other metal ions in ethanol-water mixture based on intramolecular charge transfer (ICT). It was found that pyridine-analogue coumarin is highly selective and sensitive sensor for Cu(2+). The 3 sensor coordinates Cu(2+) in 1:1 stoichiometry with a binding constant, Ka = 5.22 M(-1) and the detection limit was calculated 1.97 × 10(-9) M.

  14. Highly Efficient Sky-Blue Fluorescent Organic Light Emitting Diode Based on Mixed Cohost System for Thermally Activated Delayed Fluorescence Emitter (2CzPN).

    PubMed

    Sun, Jin Won; Kim, Kwon-Hyeon; Moon, Chang-Ki; Lee, Jeong-Hwan; Kim, Jang-Joo

    2016-04-20

    The mixed cohosts of 1,3-bis(N-carbazolyl)benzene and 2,8-bis(diphenylphosphoryl)dibenzothiophene have been developed for a highly efficient blue fluorescent oragnic light emitting diode (OLED) doped with a thermally activated delayed fluorescence (TADF) emitter [4,5-di (9H-carbazol-9-yl) phthalonitrile (2CzPN)]. We have demonstrated one of the highest external quantum efficiency of 21.8% in blue fluorescent OLEDs, which is identical to the theoretically achievable maximum electroluminescence efficiency using the emitter. Interestingly, the efficiency roll-off is large even under the excellent charge balance in the device and almost the same as the single host based devices, indicating that the efficiency roll-off in 2CzPN based TADF host is related to the material characteristics, such as low reverse intesystem crossing rate rather than charge imbalance.

  15. MATtrack: A MATLAB-Based Quantitative Image Analysis Platform for Investigating Real-Time Photo-Converted Fluorescent Signals in Live Cells.

    PubMed

    Courtney, Jane; Woods, Elena; Scholz, Dimitri; Hall, William W; Gautier, Virginie W

    2015-01-01

    We introduce here MATtrack, an open source MATLAB-based computational platform developed to process multi-Tiff files produced by a photo-conversion time lapse protocol for live cell fluorescent microscopy. MATtrack automatically performs a series of steps required for image processing, including extraction and import of numerical values from Multi-Tiff files, red/green image classification using gating parameters, noise filtering, background extraction, contrast stretching and temporal smoothing. MATtrack also integrates a series of algorithms for quantitative image analysis enabling the construction of mean and standard deviation images, clustering and classification of subcellular regions and injection point approximation. In addition, MATtrack features a simple user interface, which enables monitoring of Fluorescent Signal Intensity in multiple Regions of Interest, over time. The latter encapsulates a region growing method to automatically delineate the contours of Regions of Interest selected by the user, and performs background and regional Average Fluorescence Tracking, and automatic plotting. Finally, MATtrack computes convenient visualization and exploration tools including a migration map, which provides an overview of the protein intracellular trajectories and accumulation areas. In conclusion, MATtrack is an open source MATLAB-based software package tailored to facilitate the analysis and visualization of large data files derived from real-time live cell fluorescent microscopy using photoconvertible proteins. It is flexible, user friendly, compatible with Windows, Mac, and Linux, and a wide range of data acquisition software. MATtrack is freely available for download at eleceng.dit.ie/courtney/MATtrack.zip.

  16. Design and Elementary Evaluation of a Highly-Automated Fluorescence-Based Instrument System for On-Site Detection of Food-Borne Pathogens

    PubMed Central

    Lu, Zhan; Zhang, Jianyi; Xu, Lizhou; Li, Yanbin; Chen, Siyu; Ye, Zunzhong; Wang, Jianping

    2017-01-01

    A simple, highly-automated instrument system used for on-site detection of foodborne pathogens based on fluorescence was designed, fabricated, and preliminarily tested in this paper. A corresponding method has been proved effective in our previous studies. This system utilizes a light-emitting diode (LED) to excite fluorescent labels and a spectrometer to record the fluorescence signal from samples. A rotation stage for positioning and switching samples was innovatively designed for high-throughput detection, ten at most in one single run. We also developed software based on LabVIEW for data receiving, processing, and the control of the whole system. In the test of using a pure quantum dot (QD) solution as a standard sample, detection results from this home-made system were highly-relevant with that from a well-commercialized product and even slightly better reproducibility was found. And in the test of three typical kinds of food-borne pathogens, fluorescence signals recorded by this system are highly proportional to the variation of the sample concentration, with a satisfied limit of detection (LOD) (nearly 102–103 CFU·mL−1 in food samples). Additionally, this instrument system is low-cost and easy-to-use, showing a promising potential for on-site rapid detection of food-borne pathogens. PMID:28241478

  17. Design and Elementary Evaluation of a Highly-Automated Fluorescence-Based Instrument System for On-Site Detection of Food-Borne Pathogens.

    PubMed

    Lu, Zhan; Zhang, Jianyi; Xu, Lizhou; Li, Yanbin; Chen, Siyu; Ye, Zunzhong; Wang, Jianping

    2017-02-23

    A simple, highly-automated instrument system used for on-site detection of foodborne pathogens based on fluorescence was designed, fabricated, and preliminarily tested in this paper. A corresponding method has been proved effective in our previous studies. This system utilizes a light-emitting diode (LED) to excite fluorescent labels and a spectrometer to record the fluorescence signal from samples. A rotation stage for positioning and switching samples was innovatively designed for high-throughput detection, ten at most in one single run. We also developed software based on LabVIEW for data receiving, processing, and the control of the whole system. In the test of using a pure quantum dot (QD) solution as a standard sample, detection results from this home-made system were highly-relevant with that from a well-commercialized product and even slightly better reproducibility was found. And in the test of three typical kinds of food-borne pathogens, fluorescence signals recorded by this system are highly proportional to the variation of the sample concentration, with a satisfied limit of detection (LOD) (nearly 10²-10³ CFU·mL(-1) in food samples). Additionally, this instrument system is low-cost and easy-to-use, showing a promising potential for on-site rapid detection of food-borne pathogens.

  18. MATtrack: A MATLAB-Based Quantitative Image Analysis Platform for Investigating Real-Time Photo-Converted Fluorescent Signals in Live Cells

    PubMed Central

    Courtney, Jane; Woods, Elena; Scholz, Dimitri; Hall, William W.; Gautier, Virginie W.

    2015-01-01

    We introduce here MATtrack, an open source MATLAB-based computational platform developed to process multi-Tiff files produced by a photo-conversion time lapse protocol for live cell fluorescent microscopy. MATtrack automatically performs a series of steps required for image processing, including extraction and import of numerical values from Multi-Tiff files, red/green image classification using gating parameters, noise filtering, background extraction, contrast stretching and temporal smoothing. MATtrack also integrates a series of algorithms for quantitative image analysis enabling the construction of mean and standard deviation images, clustering and classification of subcellular regions and injection point approximation. In addition, MATtrack features a simple user interface, which enables monitoring of Fluorescent Signal Intensity in multiple Regions of Interest, over time. The latter encapsulates a region growing method to automatically delineate the contours of Regions of Interest selected by the user, and performs background and regional Average Fluorescence Tracking, and automatic plotting. Finally, MATtrack computes convenient visualization and exploration tools including a migration map, which provides an overview of the protein intracellular trajectories and accumulation areas. In conclusion, MATtrack is an open source MATLAB-based software package tailored to facilitate the analysis and visualization of large data files derived from real-time live cell fluorescent microscopy using photoconvertible proteins. It is flexible, user friendly, compatible with Windows, Mac, and Linux, and a wide range of data acquisition software. MATtrack is freely available for download at eleceng.dit.ie/courtney/MATtrack.zip. PMID:26485569

  19. An efficient ratiometric fluorescence sensor based on metal-organic frameworks and quantum dots for highly selective detection of 6-mercaptopurine.

    PubMed

    Jin, Meng; Mou, Zhao-Li; Zhang, Rui-Ling; Liang, Si-Si; Zhang, Zhi-Qi

    2017-05-15

    The development of a simple and accurate quantitative method for the determination of 6-mercaptopurine (6-MP) is of great importance because of its serious side effects. Ratiometric fluorescence (RF) sensors are not subject to interference from environmental factors, and exhibit enhanced precision and accuracy. Therefore, a novel RF sensor for the selective detection of 6-MP was developed based on a dual-emission nanosensor. The nanosensor was fabricated by combining a blue-emission metal-organic framework (MOF) NH2-MIL-53(Al) (λem=425nm) with green-emission 3-mercaptopropionic acid-capped CdTe quantum dots (MPA-CdTe QDs) (λem=528nm) under a single excitation wavelength (335nm). Upon addition of 6-MP, the fluorescence of NH2-MIL-53(Al) in the nanohybrid was selectively quenched due to strong inner filter effects, while the fluorescence of the MPA-CdTe QDs was enhanced. The novel RF sensor exhibited higher selectivity towards 6-MP than CdTe QDs alone, and higher sensitivity than MOFs alone. 6-MP could be detected in the range of 0-50μM with a detection limit of 0.15μM (S/N=3). The developed sensor was applied for the determination of 6-MP in human urine samples and satisfactory results were obtained. Overall, a novel and efficient fluorescence-based method was developed for the detection of 6-MP in biosamples.

  20. Current transformer based on optical fiber fluorescent thermometry

    NASA Astrophysics Data System (ADS)

    Jia, Danping; Jia, Ting; He, Liang; Lin, Yingwen

    2008-12-01

    In the paper a review on the potential advantages of optical current transformers points out that it is the technology trend on the development of current transformer. But there are many more difficulties to be resolved, innovative ideas of developing optical current transformers must be strengthened. A high voltage current transformer project based on current thermal effect was introduced, which combined the current thermal effects and the optical fiber thermometry technology. Fiber optic temperature sensor was the earlier and mature product among fiber optic sensors in commercial, current thermal effects technology is more general applied, so the new project has the advantages over other current transformer projects which are now meeting the difficulties hardly to resolve. The relationship between the instantaneous value of measured current and the temperature rise was deduced, and the mathematical model of the current transformer was established. By use of the mathematical model, in theory, the instantaneous value of current can be tracked by the temperature output of sensor accurately, so that it can be used to measure instantaneous value of current. The technical data and features required of the main devices and components can be provided by use of the mathematical model for technical design of the project, simulation method and experiment tests were used to prove the availability.

  1. Fluorescence-based sensing of glucose using engineered glucose/galactose-binding protein: A comparison of fluorescence resonance energy transfer and environmentally sensitive dye labelling strategies

    SciTech Connect

    Khan, Faaizah; Gnudi, Luigi; Pickup, John C.

    2008-01-04

    Fluorescence-based glucose sensors using glucose-binding protein (GBP) as the receptor have employed fluorescence resonance energy transfer (FRET) and environmentally sensitive dyes, but with widely varying sensitivity. We therefore compared signal changes in (a) a FRET system constructed by transglutaminase-mediated N-terminal attachment of Alexa Fluor 488/555 as donor and QSY 7 as acceptor at Cys 152 or 182 mutations with (b) GBP labelled with the environmentally sensitive dye badan at C152 or 182. Both FRET systems had a small maximal fluorescence change at saturating glucose (7% and 16%), badan attached at C152 was associated with a 300% maximal fluorescence increase with glucose, though with badan at C182 there was no change. We conclude that glucose sensing based on GBP and FRET does not produce a larger enough signal change for clinical use; both the nature of the environmentally sensitive dye and its site of conjugation seem important for maximum signal change; badan-GBP152C has a large glucose-induced fluorescence change, suitable for development as a glucose sensor.

  2. Winter wheat GPC estimation with fluorescence-based sensor measurements of canopy

    NASA Astrophysics Data System (ADS)

    Song, Xiaoyu; Wang, Jihua; Gu, Xiaohe; Xu, Xingang

    2015-10-01

    This study focused on the wheat grain protein content (GPC) estimation based on wheat canopy chlorophyll parameters which acquired by hand-held instrument, Multiplex 3. Nine fluorescence spectral indices from Multiplex sensor were used in this study. The wheat GPC estimation experiment was conducted in 2012 at the National Experiment Station for Precision Agriculture in Changping district, Beijing. A square with area of 1.1 ha was selected and divided to 110 small plots by 10×10m in this study. In each plot, four 1-m2 area distributed in the square were selected for canopy fluorescence spectral measurements, physiological and biochemical analyses. Measurements were performed five times at wheat raising, jointing, heading stage, milking and ripening stage, respectively. The wheat plant samples for each plot were then collected after the measurement and sent to Lab for leaf N concentration (LNC) and canopy nitrogen density (CND) analyzed. GPC sampling for each plot was collected manually during the harvested season. Then, statistical analysis were performed to detect the correlation between fluorescence spectral indices and wheat CND for each growth stage, as well as GPC. The results indicate that two Nitrogen Balance Indices, NBI_G and NBI_R were more sensitive to wheat GPC than other fluorescence spectral indices at milking stage and ripening stage. Five linear regression models with GPC and fluorescence indices at different winter wheat growth stages were then established. The R2 of GPC estimated model increased form 0.312 at raising stage to 0.686 at ripening stage. The study reveals that canopy-level fluorescence spectral parameters were better indicators for the wheat group activity and could be demonstrated to be good indicators for winter wheat GPC estimation.

  3. A novel acidic pH fluorescent probe based on a benzothiazole derivative.

    PubMed

    Ma, Qiujuan; Li, Xian; Feng, Suxiang; Liang, Beibei; Zhou, Tiqiang; Xu, Min; Ma, Zhuoyi

    2017-04-15

    A novel acidic pH fluorescent probe 1 based on a benzothiazole derivative has been designed, synthesized and developed. The linear response range covers the acidic pH range from 3.44 to 6.46, which is valuable for pH researches in acidic environment. The evaluated pKa value of the probe 1 is 4.23. The fluorescence enhancement of the studied probe 1 with an increase in hydrogen ions concentration is based on the hindering of enhanced photo-induced electron transfer (PET) process. Moreover, the pH sensor possesses a highly selective response to H(+) in the presence of metal ions, anions and other bioactive small molecules which would be interfere with its fluorescent pH response. Furthermore, the probe 1 responds to acidic pH with short response time that was less than 1min. The probe 1 has been successfully applied to confocal fluorescence imaging in live HeLa cells and can selectively stain lysosomes. All of such good properties prove it can be used to monitoring pH fluctuations in acidic environment with high sensitivity, pH dependence and short response time.

  4. Green fluorescent protein-based monitoring of endoplasmic reticulum redox poise

    PubMed Central

    Birk, Julia; Ramming, Thomas; Odermatt, Alex; Appenzeller-Herzog, Christian

    2013-01-01

    Pathological endoplasmic reticulum (ER) stress is tightly linked to the accumulation of reactive oxidants, which can be both upstream and downstream of ER stress. Accordingly, detrimental intracellular stress signals are amplified through establishment of a vicious cycle. An increasing number of human diseases are characterized by tissue atrophy in response to ER stress and oxidative injury. Experimental monitoring of stress-induced, time-resolved changes in ER reduction-oxidation (redox) states is therefore important. Organelle-specific examination of redox changes has been facilitated by the advent of genetically encoded, fluorescent probes, which can be targeted to different subcellular locations by means of specific amino acid extensions. These probes include redox-sensitive green fluorescent proteins (roGFPs) and the yellow fluorescent protein-based redox biosensor HyPer. In the case of roGFPs, variants with known specificity toward defined redox couples are now available. Here, we review the experimental framework to measure ER redox changes using ER-targeted fluorescent biosensors. Advantages and drawbacks of plate-reader and microscopy-based measurements are discussed, and the power of these techniques demonstrated in the context of selected cell culture models for ER stress. PMID:23781233

  5. Real-time micro-scale temperature imaging at low cost based on fluorescent intensity ratio

    PubMed Central

    Xiong, Jianghao; Zhao, Mingshu; Han, Xiaotian; Cao, Zhongmin; Wei, Xiantao; Chen, Yonghu; Duan, Changkui; Yin, Min

    2017-01-01

    Real-time temperature imaging with high spatial resolution has been a challenging task but also one with wide potential applications. To achieve this task, temperature sensor is critical. Fluorescent materials stand out to be promising candidates due to their quick response and strong temperature dependence. However, former reported temperature imaging techniques with fluorescent materials are mainly based on point by point scanning, which cannot fulfill the requirement of real-time monitoring. Based on fluorescent intensity ratio (FIR) of two emission bands of SrB4O7:Sm2+, whose spatial distributions were simultaneously recorded by two cameras with special filters separately, real-time temperature imaging with high spatial resolution has been realized with low cost. The temperature resolution can reach about 2 °C in the temperature range from 120 to 280 °C; the spatial resolution is about 2.4 μm and the imaging time is as fast as one second. Adopting this system, we observed the dynamic change of a micro-scale thermal distribution on a printed circuit board (PCB). Different applications and better performance could also be achieved on this system with appropriate fluorescent materials and high sensitive CCD detectors according to the experimental environment. PMID:28145482

  6. A novel acidic pH fluorescent probe based on a benzothiazole derivative

    NASA Astrophysics Data System (ADS)

    Ma, Qiujuan; Li, Xian; Feng, Suxiang; Liang, Beibei; Zhou, Tiqiang; Xu, Min; Ma, Zhuoyi

    2017-04-01

    A novel acidic pH fluorescent probe 1 based on a benzothiazole derivative has been designed, synthesized and developed. The linear response range covers the acidic pH range from 3.44 to 6.46, which is valuable for pH researches in acidic environment. The evaluated pKa value of the probe 1 is 4.23. The fluorescence enhancement of the studied probe 1 with an increase in hydrogen ions concentration is based on the hindering of enhanced photo-induced electron transfer (PET) process. Moreover, the pH sensor possesses a highly selective response to H+ in the presence of metal ions, anions and other bioactive small molecules which would be interfere with its fluorescent pH response. Furthermore, the probe 1 responds to acidic pH with short response time that was less than 1 min. The probe 1 has been successfully applied to confocal fluorescence imaging in live HeLa cells and can selectively stain lysosomes. All of such good properties prove it can be used to monitoring pH fluctuations in acidic environment with high sensitivity, pH dependence and short response time.

  7. Fiber based in-vivo imaging of epithelial FAD fluorescence: experiments and simulations

    NASA Astrophysics Data System (ADS)

    Kanakaraj, Bala Nivetha; Narayanan Unni, Sujatha

    2015-03-01

    Fluorescence from endogenous fluorophores has been emerging as a promising biomarker for tissue discrimination resulting a noninvasive screening methodology to understand the biochemical and morphological variations in tissues associated with cancer development. We have developed a scan based fiber optic probe system to image increased flavin adenine dinucleotide (FAD) fluorescence from epithelial tissues under conditions mimicking dysplasia surrounded by normal tissues. Experiments were conducted on optical phantoms mimicking epithelial tissues excited by 450nm LED source. The spectral emission from the sample is collected via optical fibers and the imaging is performed by scanning the sample using a translation stage at desired resolution. Monte Carlo simulations were also performed by devising an optical model corresponding to epithelial tissue and the results were correlated with experimental fluorescence measurements. This whole field imaging approach could be useful for in vivo assessment of tissue pathologies based on auto fluorescence and can give a better quantitative approach for estimation of tissue properties by correlating the experimental and simulated data.

  8. Image overlay solution based on threshold detection for a compact near infrared fluorescence goggle system

    PubMed Central

    Gao, Shengkui; Mondal, Suman B.; Zhu, Nan; Liang, RongGuang; Achilefu, Samuel; Gruev, Viktor

    2015-01-01

    Abstract. Near infrared (NIR) fluorescence imaging has shown great potential for various clinical procedures, including intraoperative image guidance. However, existing NIR fluorescence imaging systems either have a large footprint or are handheld, which limits their usage in intraoperative applications. We present a compact NIR fluorescence imaging system (NFIS) with an image overlay solution based on threshold detection, which can be easily integrated with a goggle display system for intraoperative guidance. The proposed NFIS achieves compactness, light weight, hands-free operation, high-precision superimposition, and a real-time frame rate. In addition, the miniature and ultra-lightweight light-emitting diode tracking pod is easy to incorporate with NIR fluorescence imaging. Based on experimental evaluation, the proposed NFIS solution has a lower detection limit of 25 nM of indocyanine green at 27 fps and realizes a highly precise image overlay of NIR and visible images of mice in vivo. The overlay error is limited within a 2-mm scale at a 65-cm working distance, which is highly reliable for clinical study and surgical use. PMID:25607724

  9. Structural effects of naphthalimide-based fluorescent sensor for hydrogen sulfide and imaging in live zebrafish

    PubMed Central

    Choi, Seon-Ae; Park, Chul Soon; Kwon, Oh Seok; Giong, Hoi-Khoanh; Lee, Jeong-Soo; Ha, Tai Hwan; Lee, Chang-Soo

    2016-01-01

    Hydrogen sulfide (H2S) is an important biological messenger, but few biologically-compatible methods are available for its detection in aqueous solution. Herein, we report a highly water-soluble naphthalimide-based fluorescent probe (L1), which is a highly versatile building unit that absorbs and emits at long wavelengths and is selective for hydrogen sulfide over cysteine, glutathione, and other reactive sulfur, nitrogen, and oxygen species in aqueous solution. We describe turn-on fluorescent probes based on azide group reduction on the fluorogenic ‘naphthalene’ moiety to fluorescent amines and intracellular hydrogen sulfide detection without the use of an organic solvent. L1 and L2 were synthetically modified to functional groups with comparable solubility on the N-imide site, showing a marked change in turn-on fluorescent intensity in response to hydrogen sulfide in both PBS buffer and living cells. The probes were readily employed to assess intracellular hydrogen sulfide level changes by imaging endogenous hydrogen sulfide signal in RAW264.7 cells incubated with L1 and L2. Expanding the use of L1 to complex and heterogeneous biological settings, we successfully visualized hydrogen sulfide detection in the yolk, brain and spinal cord of living zebrafish embryos, thereby providing a powerful approach for live imaging for investigating chemical signaling in complex multicellular systems. PMID:27188400

  10. Fluorescence-based determination of the copper concentration in drinking water

    NASA Astrophysics Data System (ADS)

    Hötzer, Benjamin; Scheu, Timo; Jung, Gregor; Castritius, Stefan

    2013-05-01

    Copper is a heavy metal, which is used in heat and electrical conductors and in a multitude of alloys in the technical context. Moreover, it is a trace element that is essential for the life of organisms but can cause toxic effects in elevated concentrations. Maximum limits in water and beverages exist. Here, the decrease of the fluorescence lifetime of green fluorescent protein (GFP) by Förster resonance energy transfer is used to measure the copper ion concentration in drinking water. Therefore, a system is developed that is based on a GFP sample in a predefined concentration. The GFP mutant can be excited with blue light. For binding of copper ions, a His-tag is included in the GFP. After measuring the fluorescence lifetime of pure GFP, the copper determination of the sample is performed by lifetime measurement. Therefore, the lifetime can be assigned to the copper concentration of the GFP-doped drinking water sample. In summary, a method for the quantification of copper ions based on changes of the fluorescence lifetime of GFP is developed, and the measurement of the copper concentration in water samples is performed.

  11. Naphthol-based fluorescent sensors for aluminium ion and application to bioimaging

    NASA Astrophysics Data System (ADS)

    Liu, Bin; Wang, Pan-feng; Chai, Jie; Hu, Xiang-quan; Gao, Tingting; Chao, Jian-bin; Chen, Ting-gui; Yang, Bin-sheng

    2016-11-01

    Three naphthol Schiff base-type fluorescent sensors, 1,3-Bis(2-hydroxy-1-naphthylideneamino)propane (L1), 1,3-Bis(1-naphthylideneamino)-2-hydroxypropane (L2) and 1,3-Bis(2-hydroxy-1-naphthylideneamino)-2-hydroxypropane (L3), have been synthesized. Their recognition abilities for Al3 + are studied by fluorescence spectra. Coordination with Al3 + inhibited the Cdbnd N isomerization of Schiff base which intensely increase the fluorescence of L1-L3. Possessing a suitable space coordination structure, L3 is a best selective probe for Al3 + over other metal ions in MeOH-HEPES buffer (3/7, V/V, pH = 6.6, 25 °C, λem = 435 nm). A turn-on ratio over 140-fold is triggered with the addition of 1.0 equiv. Al3 + to L3. The binding constant Ka of L3-Al3 + is found to be 1.01 × 106.5 M- 1 in a 1:1 complex mode. The detection limit for Al3 + is 0.05 μM. Theoretical calculations have also been included in support of the configuration of the L3-Al3 + complex. Importantly, the probe L3 has been successfully used for fluorescence imaging in colon cancer SW480 cells.

  12. Structural effects of naphthalimide-based fluorescent sensor for hydrogen sulfide and imaging in live zebrafish

    NASA Astrophysics Data System (ADS)

    Choi, Seon-Ae; Park, Chul Soon; Kwon, Oh Seok; Giong, Hoi-Khoanh; Lee, Jeong-Soo; Ha, Tai Hwan; Lee, Chang-Soo

    2016-05-01

    Hydrogen sulfide (H2S) is an important biological messenger, but few biologically-compatible methods are available for its detection in aqueous solution. Herein, we report a highly water-soluble naphthalimide-based fluorescent probe (L1), which is a highly versatile building unit that absorbs and emits at long wavelengths and is selective for hydrogen sulfide over cysteine, glutathione, and other reactive sulfur, nitrogen, and oxygen species in aqueous solution. We describe turn-on fluorescent probes based on azide group reduction on the fluorogenic ‘naphthalene’ moiety to fluorescent amines and intracellular hydrogen sulfide detection without the use of an organic solvent. L1 and L2 were synthetically modified to functional groups with comparable solubility on the N-imide site, showing a marked change in turn-on fluorescent intensity in response to hydrogen sulfide in both PBS buffer and living cells. The probes were readily employed to assess intracellular hydrogen sulfide level changes by imaging endogenous hydrogen sulfide signal in RAW264.7 cells incubated with L1 and L2. Expanding the use of L1 to complex and heterogeneous biological settings, we successfully visualized hydrogen sulfide detection in the yolk, brain and spinal cord of living zebrafish embryos, thereby providing a powerful approach for live imaging for investigating chemical signaling in complex multicellular systems.

  13. Real-time micro-scale temperature imaging at low cost based on fluorescent intensity ratio

    NASA Astrophysics Data System (ADS)

    Xiong, Jianghao; Zhao, Mingshu; Han, Xiaotian; Cao, Zhongmin; Wei, Xiantao; Chen, Yonghu; Duan, Changkui; Yin, Min

    2017-02-01

    Real-time temperature imaging with high spatial resolution has been a challenging task but also one with wide potential applications. To achieve this task, temperature sensor is critical. Fluorescent materials stand out to be promising candidates due to their quick response and strong temperature dependence. However, former reported temperature imaging techniques with fluorescent materials are mainly based on point by point scanning, which cannot fulfill the requirement of real-time monitoring. Based on fluorescent intensity ratio (FIR) of two emission bands of SrB4O7:Sm2+, whose spatial distributions were simultaneously recorded by two cameras with special filters separately, real-time temperature imaging with high spatial resolution has been realized with low cost. The temperature resolution can reach about 2 °C in the temperature range from 120 to 280 °C the spatial resolution is about 2.4 μm and the imaging time is as fast as one second. Adopting this system, we observed the dynamic change of a micro-scale thermal distribution on a printed circuit board (PCB). Different applications and better performance could also be achieved on this system with appropriate fluorescent materials and high sensitive CCD detectors according to the experimental environment.

  14. Nicking enzyme-assisted biosensor for Salmonella enteritidis detection based on fluorescence resonance energy transfer.

    PubMed

    Song, Yang; Li, Wenkai; Duan, Yingfen; Li, Zhongjie; Deng, Le

    2014-05-15

    Salmonella enteritidis (S. enteritidis) outbreaks continue to occur, and have increased public awareness of this pathogen. Nicking endonuclease Nb.BbvC I is widely used for the detection of biomolecules and displays activity for specific double-stranded DNA (dsDNA). In this study, we developed a biosensor to detect S. enteritidis based on fluorescence resonance energy transfer (FRET) using nicking enzyme and carbon nanoparticles (CNPs). Because of the quenching effect of black hole quencher 1 (BHQ 1), the CNPs do not fluoresce in the reaction system. When the target bacteria are added, the nicking enzyme recognizes and cleaves the dsDNA fabricated by the interaction between probe and target. As a result, the CNPs dissociate from BHQ 1 and emit strong fluorescence. Using the nicking enzyme, the fluorescence signals of the biosensor are greatly amplified. The biosensor exhibited a linear relationship with the concentration of S. enteritidis ranging from 10(2) to 3 × 10(3)CFU/mL in water and from 1.5 × 10(2) to 3 × 10(3)CFU/mL in milk. The present results indicate that our FRET-based detection system can be widely employed for the effective detection of pathogens.

  15. Fluorescent Biosensor for Phosphate Determination Based on Immobilized Polyfluorene-Liposomal Nanoparticles Coupled with Alkaline Phosphatase.

    PubMed

    Kahveci, Zehra; Martínez-Tomé, Maria José; Mallavia, Ricardo; Mateo, C Reyes

    2017-01-11

    This work describes the development of a novel fluorescent biosensor based on the inhibition of alkaline phosphatase (ALP). The biosensor is composed of the enzyme ALP and the conjugated cationic polyfluorene HTMA-PFP. The working principle of the biosensor is based on the fluorescence quenching of this polyelectrolyte by p-nitrophenol (PNP), a product of the hydrolysis reaction of p-nitrophenyl phosphate (PNPP) catalyzed by ALP. Because HTMA-PFP forms unstable aggregates in buffer, with low fluorescence efficiency, previous stabilization of the polyelectrolyte was required before the development of the biosensor. HTMA-PFP was stabilized through its interaction with lipid vesicles to obtain stable blue-emitting nanoparticles (NPs). Fluorescent NPs were characterized, and the ability to be quenched by PNP was evaluated. These nanoparticles were coupled to ALP and entrapped in a sol-gel matrix to produce a biosensor that can serve as a screening platform to identify ALP inhibitors. The components of the biosensor were examined before and after sol-gel entrapment, and the biosensor was optimized to allow the determination of phosphate ion in aqueous medium.

  16. Fluoromodule-based reporter/probes designed for in vivo fluorescence imaging

    PubMed Central

    Zhang, Ming; Chakraborty, Subhasish K.; Sampath, Padma; Rojas, Juan J.; Hou, Weizhou; Saurabh, Saumya; Thorne, Steve H.; Bruchez, Marcel P.; Waggoner, Alan S.

    2015-01-01

    Optical imaging of whole, living animals has proven to be a powerful tool in multiple areas of preclinical research and has allowed noninvasive monitoring of immune responses, tumor and pathogen growth, and treatment responses in longitudinal studies. However, fluorescence-based studies in animals are challenging because tissue absorbs and autofluoresces strongly in the visible light spectrum. These optical properties drive development and use of fluorescent labels that absorb and emit at longer wavelengths. Here, we present a far-red absorbing fluoromodule–based reporter/probe system and show that this system can be used for imaging in living mice. The probe we developed is a fluorogenic dye called SC1 that is dark in solution but highly fluorescent when bound to its cognate reporter, Mars1. The reporter/probe complex, or fluoromodule, produced peak emission near 730 nm. Mars1 was able to bind a variety of structurally similar probes that differ in color and membrane permeability. We demonstrated that a tool kit of multiple probes can be used to label extracellular and intracellular reporter–tagged receptor pools with 2 colors. Imaging studies may benefit from this far-red excited reporter/probe system, which features tight coupling between probe fluorescence and reporter binding and offers the option of using an expandable family of fluorogenic probes with a single reporter gene. PMID:26348895

  17. Using quantum mechanics to investigate the photophysical properties of the DNA and RNA bases and their fluorescent analogs

    NASA Astrophysics Data System (ADS)

    Kistler, Kurt A.

    The ability of the nucleic acids to absorb ultraviolet light and remain relatively photostable is a property upon which life depends. The nucleobases, which are the primary chromophores, when irradiated display rapid radiationless decay back to the ground state, in general faster than is needed for photoreaction. Fluorescent analogs of these bases have structures similar to the nucleic acid bases, but display much longer excited state lifetimes. Theoretical investigations using quantum mechanical methods can provide insight into the precise mechanisms of these decay processes, and to the molecular specifics that contribute to them. The results of multi-reference configuration interaction (MRCI) ab initio investigations into these mechanisms are presented, with emphasis on cytosine and its fluorescent analog 5-methyl-2-pyrimidinone (5M2P). A comprehensive picture of the potential energy surfaces of these two bases is given, including stationary points and conical intersections, where radiationless transisitons are promoted, between up to three state surfaces, as well as pathways connecting these points for each base. Cytosine is shown to have two different energetically accessible radiationless decay channels. The fluorescence of 5M2P is also demonstrated theoretically, with mechanism proposed. The potential energy surfaces of the two bases have many close similarities, with the different photophysical properties being attributed to subtle energetic differences between the two bases. Nonadiabatic coupling and the geometric phase effect are analyzed in detail near conical intersections in cytosine, including in a region close to a three-state conical intersection. A substituent effect study on the 2-pyrimidinone ring system shows that the presence, position and orientation of the amino group in cytosine is central to its photophysical properties, particulary its high absorption energy, and can be explained with a simple Frontier Molecular Orbital model. The effects

  18. A Simple Metallothionein-Based Biosensor for Enhanced Detection of Arsenic and Mercury

    PubMed Central

    Irvine, Gordon W.; Tan, Swee Ngin; Stillman, Martin J.

    2017-01-01

    Metallothioneins (MTs) are a family of cysteine-rich proteins whose biological roles include the regulation of essential metal ions and protection against the harmful effects of toxic metals. Due to its high affinity for many toxic, soft metals, recombinant human MT isoform 1a was incorporated into an electrochemical-based biosensor for the detection of As3+ and Hg2+. A simple design was chosen to maximize its potential in environmental monitoring and MT was physically adsorbed onto paper discs placed on screen-printed carbon electrodes (SPCEs). This system was tested with concentrations of arsenic and mercury typical of contaminated water sources ranging from 5 to 1000 ppb. The analytical performance of the MT-adsorbed paper discs on SPCEs demonstrated a greater than three-fold signal enhancement and a lower detection limit compared to blank SPCEs, 13 ppb for As3+ and 45 ppb for Hg2+. While not being as low as some of the recommended drinking water limits, the sensitivity of the simple MT-biosensor would be potentially useful in monitoring of areas of concern with a known contamination problem. This paper describes the ability of the metal binding protein metallothionein to enhance the effectiveness of a simple, low-cost electrochemical sensor. PMID:28335390

  19. A Simple Metallothionein-Based Biosensor for Enhanced Detection of Arsenic and Mercury.

    PubMed

    Irvine, Gordon W; Tan, Swee Ngin; Stillman, Martin J

    2017-03-13

    Metallothioneins (MTs) are a family of cysteine-rich proteins whose biological roles include the regulation of essential metal ions and protection against the harmful effects of toxic metals. Due to its high affinity for many toxic, soft metals, recombinant human MT isoform 1a was incorporated into an electrochemical-based biosensor for the detection of As(3+) and Hg(2+). A simple design was chosen to maximize its potential in environmental monitoring and MT was physically adsorbed onto paper discs placed on screen-printed carbon electrodes (SPCEs). This system was tested with concentrations of arsenic and mercury typical of contaminated water sources ranging from 5 to 1000 ppb. The analytical performance of the MT-adsorbed paper discs on SPCEs demonstrated a greater than three-fold signal enhancement and a lower detection limit compared to blank SPCEs, 13 ppb for As(3+) and 45 ppb for Hg(2+). While not being as low as some of the recommended drinking water limits, the sensitivity of the simple MT-biosensor would be potentially useful in monitoring of areas of concern with a known contamination problem. This paper describes the ability of the metal binding protein metallothionein to enhance the effectiveness of a simple, low-cost electrochemical sensor.

  20. All-plastic miniature fluorescence microscope for point-of-care readout of bead-based bioassays

    NASA Astrophysics Data System (ADS)

    Forcucci, Alessandra; Pawlowski, Michal Emanuel; Crannell, Zachary; Pavlova, Ina; Richards-Kortum, Rebecca; Tkaczyk, Tomasz S.

    2015-10-01

    A number of new platforms have been developed for multiplexed bioassays that rely on imaging targeted fluorescent beads labeled with different fluorescent dyes. We developed a compact, low-cost three-dimensional printed fluorescence microscope that can be used as a detector for mutiplexed, bead-based assays to support point-of-care applications. Images obtained with the microscope were analyzed to differentiate multiple analytes in a single sample with a comparable limit of detection to commercially available macroscopic assay platforms.

  1. Quick and simple sample treatment for multiresidue analysis of bisphenols, bisphenol diglycidyl ethers and their derivatives in canned food prior to liquid chromatography and fluorescence detection.

    PubMed

    Alabi, A; Caballero-Casero, N; Rubio, S

    2014-04-04

    We report herein a multiresidue method for canned food determination of 12 bisphenols [bisphenol A (BPA), bisphenol B (BPB), bisphenol F (BPF), bisphenol E (BPE)], bisphenol diglycidyl ethers [bisphenol F diglycidyl ether (BFDGE), bisphenol A diglycidyl ether (BADGE)] and their derivatives [BADGE·2H2O, BADGE·H2O, BADGE·HCl·H2O, BADGE·HCl, BADGE·2HCl and BFDGE·2HCl]. The method was based on the microextraction of the target contaminants in 200mg food sample with 600 μL of a supramolecular solvent made up of inverse aggregates of tetradecanol, followed by analysis of the extract by liquid chromatography/fluorescence detection using external calibration. Chromatographic separation of all target compounds, including the ortho-ortho, ortho-para and para-para isomers of BFDGE and BFDGE·2HCl, was achieved with baseline separation (Resolution ≥ 1.52). No concentration of the extracts was required, the microextraction took about 30 min and several samples could be simultaneous treated. Method validation was carried out according to the recommendations of the European Commission Decision 2002/657/EC. Quantitation limits for the different analytes ranged between 0.9 and 3.5 μg kg(-1). Repeatability and reproducibility, expressed as relative standard deviation, were in the ranges 1.8-6.8% and 4.4-8.1%. The method was applied to the analysis of the target compounds in different food categories including vegetables, legumes, fruits, fish and seafood, meat product and grain. Recoveries in samples were within the range 80-110%. Only BPF and BPE were undetected in the canned food analyzed. The concentration found for the rest of bisphenols, diglycidyl ethers and derivatives was in the range 7.1-959 μg kg(-1). The study of the isomeric distribution of BFDGE and BFDGE·2HCl in food showed that they are preferentially present as one of the isomeric forms, that highlighting for further studies. The analytical and operational characteristics of this multiresidue method make

  2. Real-time fluorescence assays of alkaline phosphatase and ATP sulfurylase activities based on a novel PPi fluorescent probe.

    PubMed

    Wang, Xiaobo; Zhang, Zhiyang; Ma, Xiaoyan; Wen, Jinghan; Geng, Zhirong; Wang, Zhilin

    2015-05-01

    An anthracene-armed tetraaza macrocyclic fluorescent probe 3-(9-anthrylmethyl)-3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene(l) for detecting Zn(2+) in aqueous medium was synthesized. L-Zn(2+) complex, showed selectivity toward pyrophosphate ion (PPi) by quenching the fluorescence in aqueous HEPES buffer (pH 7.4). Furthermore, L-Zn(2+) was also used to set up a real-time fluorescence assay for monitoring enzyme activities of alkaline phosphatase (ALP) and adenosine triphosphate sulfurylase (ATPS). In the presence of ALP inhibitor Na3VO4 and ATPS inhibitor chlorate, two enzymes activities decreased obviously, respectively.

  3. Conditionally fluorescent molecular probes for detecting single base changes in double-stranded DNA.

    PubMed

    Chen, Sherry Xi; Zhang, David Yu; Seelig, Georg

    2013-09-01

    Small variations in nucleic acid sequences can have far-reaching phenotypic consequences. Reliably distinguishing closely related sequences is therefore important for research and clinical applications. Here, we demonstrate that conditionally fluorescent DNA probes are capable of distinguishing variations of a single base in a stretch of target DNA. These probes use a novel programmable mechanism in which each single nucleotide polymorphism generates two thermodynamically destabilizing mismatch bubbles rather than the single mismatch formed during typical hybridization-based assays. Up to a 12,000-fold excess of a target that contains a single nucleotide polymorphism is required to generate the same fluorescence as one equivalent of the intended target, and detection works reliably over a wide range of conditions. Using these probes we detected point mutations in a 198 base-pair subsequence of the Escherichia coli rpoB gene. That our probes are constructed from multiple oligonucleotides circumvents synthesis limitations and enables long continuous DNA sequences to be probed.

  4. Conditionally fluorescent molecular probes for detecting single base changes in double-stranded DNA

    NASA Astrophysics Data System (ADS)

    Chen, Sherry Xi; Zhang, David Yu; Seelig, Georg

    2013-09-01

    Small variations in nucleic acid sequences can have far-reaching phenotypic consequences. Reliably distinguishing closely related sequences is therefore important for research and clinical applications. Here, we demonstrate that conditionally fluorescent DNA probes are capable of distinguishing variations of a single base in a stretch of target DNA. These probes use a novel programmable mechanism in which each single nucleotide polymorphism generates two thermodynamically destabilizing mismatch bubbles rather than the single mismatch formed during typical hybridization-based assays. Up to a 12,000-fold excess of a target that contains a single nucleotide polymorphism is required to generate the same fluorescence as one equivalent of the intended target, and detection works reliably over a wide range of conditions. Using these probes we detected point mutations in a 198 base-pair subsequence of the Escherichia coli rpoB gene. That our probes are constructed from multiple oligonucleotides circumvents synthesis limitations and enables long continuous DNA sequences to be probed.

  5. Ultra-sensitive detection of kanamycin for food safety using a reduced graphene oxide-based fluorescent aptasensor

    NASA Astrophysics Data System (ADS)

    Ha, Na-Reum; Jung, In-Pil; La, Im-Joung; Jung, Ho-Sup; Yoon, Moon-Young

    2017-01-01

    Overuse of antibiotics has caused serious problems, such as appearance of super bacteria, whose accumulation in the human body through the food chain is a concern. Kanamycin is a common antibiotic used to treat diverse infections; however, residual kanamycin can cause many side effects in humans. Thus, development of an ultra-sensitive, precise, and simple detection system for residual kanamycin in food products is urgently needed for food safety. In this study, we identified kanamycin-binding aptamers via a new screening method, and truncated variants were analyzed for optimization of the minimal sequence required for target binding. We found various aptamers with high binding affinity from 34.7 to 669 nanomolar Kdapp values with good specificity against kanamycin. Furthermore, we developed a reduced graphene oxide (RGO)-based fluorescent aptasensor for kanamycin detection. In this system, kanamycin was detected at a concentration as low as 1 pM (582.6 fg/mL). In addition, this method could detect kanamycin accurately in kanamycin-spiked blood serum and milk samples. Consequently, this simple, rapid, and sensitive kanamycin detection system with newly structural and functional analysis aptamer exhibits outstanding detection compared to previous methods and provides a new possibility for point of care testing and food safety.

  6. Ultra-sensitive detection of kanamycin for food safety using a reduced graphene oxide-based fluorescent aptasensor

    PubMed Central

    Ha, Na-Reum; Jung, In-Pil; La, Im-Joung; Jung, Ho-Sup; Yoon, Moon-Young

    2017-01-01

    Overuse of antibiotics has caused serious problems, such as appearance of super bacteria, whose accumulation in the human body through the food chain is a concern. Kanamycin is a common antibiotic used to treat diverse infections; however, residual kanamycin can cause many side effects in humans. Thus, development of an ultra-sensitive, precise, and simple detection system for residual kanamycin in food products is urgently needed for food safety. In this study, we identified kanamycin-binding aptamers via a new screening method, and truncated variants were analyzed for optimization of the minimal sequence required for target binding. We found various aptamers with high binding affinity from 34.7 to 669 nanomolar Kdapp values with good specificity against kanamycin. Furthermore, we developed a reduced graphene oxide (RGO)-based fluorescent aptasensor for kanamycin detection. In this system, kanamycin was detected at a concentration as low as 1 pM (582.6 fg/mL). In addition, this method could detect kanamycin accurately in kanamycin-spiked blood serum and milk samples. Consequently, this simple, rapid, and sensitive kanamycin detection system with newly structural and functional analysis aptamer exhibits outstanding detection compared to previous methods and provides a new possibility for point of care testing and food safety. PMID:28054670

  7. Analysis of the THz response of a simple periodic graphite-based structure.

    PubMed

    Colleoni, M P M; Vidal, B

    2014-12-01

    We report the observation of the dichroism effect in simple wire grid structures made of graphite on a paper substrate, i.e. we investigate the feasibility of drawing polarizers for the THz band using conventional graphite-based lead pencils. The displacement of the maximum frequency of the selective absorption phenomenon by varying the wire pitch hints at a polarizing behavior. Measurements of the maximum and minimum of transmission efficiency, extinction ratio and degree of polarization are carried out with a transmission fiber THz-TDS setup. Experimental results show a 9 dB extinction ratio for an inexpensive (<1$) home-made component.

  8. A Simple Quality Assessment Index for Stereoscopic Images Based on 3D Gradient Magnitude

    PubMed Central

    Wang, Shanshan; Shao, Feng; Li, Fucui; Yu, Mei; Jiang, Gangyi

    2014-01-01

    We present a simple quality assessment index for stereoscopic images based on 3D gradient magnitude. To be more specific, we construct 3D volume from the stereoscopic images across different disparity spaces and calculate pointwise 3D gradient magnitude similarity (3D-GMS) along three horizontal, vertical, and viewpoint directions. Then, the quality score is obtained by averaging the 3D-GMS scores of all points in the 3D volume. Experimental results on four publicly available 3D image quality assessment databases demonstrate that, in comparison with the most related existing methods, the devised algorithm achieves high consistency alignment with subjective assessment. PMID:25133265

  9. Hydrogen sulfide deactivates common nitrobenzofurazan-based fluorescent thiol labeling reagents.

    PubMed

    Montoya, Leticia A; Pluth, Michael D

    2014-06-17

    Sulfhydryl-containing compounds, including thiols and hydrogen sulfide (H2S), play important but differential roles in biological structure and function. One major challenge in separating the biological roles of thiols and H2S is developing tools to effectively separate the reactivity of these sulfhydryl-containing compounds. To address this challenge, we report the differential responses of common electrophilic fluorescent thiol labeling reagents, including nitrobenzofurazan-based scaffolds, maleimides, alkylating agents, and electrophilic aldehydes, toward cysteine and H2S. Although H2S reacted with all of the investigated scaffolds, the photophysical response to each scaffold was significantly different. Maleimide-based, alkylating, and aldehydic thiol labeling reagents provided a diminished fluorescence response when treated with H2S. By contrast, nitrobenzofurazan-based labeling reagents were deactivated by H2S addition. Furthermore, the addition of H2S to thiol-activated nitrobenzofurazan-based reagents reduced the fluorescence signal, thus establishing the incompatibility of nitrobenzofurazan-based thiol labeling reagents in the presence of H2S. Taken together, these studies highlight the differential reactivity of thiols and H2S toward common thiol-labeling reagents and suggest that sufficient care must be taken when labeling or measuring thiols in cellular environments that produce H2S due to the potential for both false-positive and eroded responses.

  10. A simple representation of energy matrix elements in terms of symmetry-invariant bases.

    PubMed

    Cui, Peng; Wu, Jian; Zhang, Guiqing; Boyd, Russell J

    2010-02-01

    When a system under consideration has some symmetry, usually its Hamiltonian space can be parallel partitioned into a set of subspaces, which is invariant under symmetry operations. The bases that span these invariant subspaces are also invariant under the symmetry operations, and they are the symmetry-invariant bases. A standard methodology is available to construct a series of generator functions (GFs) and corresponding symmetry-adapted basis (SAB) functions from these symmetry-invariant bases. Elements of the factorized Hamiltonian and overlap matrix can be expressed in terms of these SAB functions, and their simple representations can be deduced in terms of GFs. The application of this method to the Heisenberg spin Hamiltonian is demonstrated.

  11. Sensitive signal-on fluorescent sensing for copper ions based on the polyethyleneimine-capped silver nanoclusters-cysteine system.

    PubMed

    Zhang, Na; Qu, Fei; Luo, Hong Qun; Li, Nian Bing

    2013-08-12

    In this work, we present a label-free sensor for copper ions. This sensor is composed of silver nanoclusters and cysteine. The fluorescence of the silver nanoclusters was quenched by cysteine, which was recovered in the presence of copper ions. This binding of silver nanoclusters to cysteine promoted agglomeration of silver nanoclusters to yield larger non-fluorescent silver nanoparticles. The presence of copper ions resulted in the oxidation of cysteine to form a disulfide compound, leading to recovery of fluorescence of the silver nanoclusters. The fluorescence of the silver nanoclusters in the presence of cysteine increased with increasing concentration of copper ions in the range of 10-200 nM. The detection limit of this sensor for copper ions was 2.3 nM. The silver nanoclusters-cysteine sensor provides a simple, cost-effective, and sensitive platform for the detection of copper ions.

  12. Colourimetric and fluorescent detection of oxalate in water by a new macrocycle-based dinuclear nickel complex: a remarkable red shift of the fluorescence band.

    PubMed

    Rhaman, Md Mhahabubur; Fronczek, Frank R; Powell, Douglas R; Hossain, Md Alamgir

    2014-03-28

    A new macrocycle-based dinuclear nickel chemosensor selectively binds oxalate anions both in solution and the solid state, displaying a remarkable red shift of the fluorescence band with a visible colour change in water at physiological pH in the presence of an external dye.

  13. Relay recognition of Cu2+ and S2- in water by a simple 2-(2'-aminophenyl)benzimidazole derivatized fluorescent sensor through modulating ESIPT.

    PubMed

    Tang, Lijun; Dai, Xin; Cai, Mingjun; Zhao, Jia; Zhou, Pei; Huang, Zhenlong

    2014-03-25

    A new 2-(2'-aminophenyl)benzimidazole (2-APBI) derivatized fluorescent sensor (L) that behaves relay recognition of Cu(2+) and S(2-) in water solution (pH 7.4) has been developed. Sensor L displays excited-state intramolecular proton transfer (ESIPT) featured two emission bands and performs highly selective and sensitive recognition to Cu(2+) through two emissions simultaneous quenching. The on-site formed L-Cu(2+) complex exhibits excellent selectivity to S(2-) with fluorescence "off-on" response via Cu(2+) displacement approach, which exerts ESIPT recovery. Thus, through modulation the ESIPT state of sensor L, relay recognition of Cu(2+) and S(2-) in water has been achieved.

  14. Conventional and fluorescent based semen quality assessment in Karan Fries bulls

    PubMed Central

    Panmei, A.; Gupta, A. K.; Shivahre, P. R.; Bhakat, M.; Upadhyay, A.

    2015-01-01

    Aim: The present study was carried out on semen ejaculates of 15 Karan Fries (KF) bulls maintained at Artificial Breeding Research Centre, National Dairy Research Institute, Karnal, India with an objective to evaluate the relationship between the conventional and fluorescent based semen quality analysis of the bulls. Materials and Methods: A total of 96 ejaculates were collected from 15 KF (Holstein Friesian [HF] crossbred) bulls. Semen were evaluated for color, volume, mass activity (MA) and percentage of individual motility (IM), sperm concentration, percent live spermatozoa, hypo-osmotic swelling test and acrosome integrity, chromatin integrity, sperm viability, and membrane integrity. Data were analyzed using SPSS software package for descriptive analysis. The correlation between rankings of sires based on conventional and fluorescent semen parameters were calculated by Spearman’s rank correlation coefficient. Results: The average ejaculates volume (ml), sperm concentration (106/ml), MA, IM (%), live (%), morphological abnormalities (%), host (%), acrosome integrity (%), chromomycin A3 (CMA3) (%), SYBR-PI (%), and fluorescent isothiocyanate-peanut agglutinin (FITC-PNA) (%) were 4.57±0.36, 1162.98±97.93, 2.95±0.09, 60.8±1.22, 71.41±2.10, 9.31±1.15, 65.5±1.81, 86.6±1.59, 3.53±0.43, 65.39±2.23 and 74.47±2.53, respectively. Rank correlations were found to be significant for SYBR-PI and FITC-PNA with most of the parameters evaluated by conventional methods. Overall, among conventional criteria, IM revealed ranking of bulls almost similar to that of fluorescent criteria. Conclusion: Overview of our results indicated that, among conventional criteria, MA and IM revealed ranking of bulls almost similar to that of fluorescent criteria. PMID:27047025

  15. Molecularly imprinted polymers as biomimetic receptors for fluorescence-based optical sensors

    NASA Astrophysics Data System (ADS)

    Moreno-Bondi, María C.; Urraca, Javier L.; Benito-Peña, Elena; Navarro-Villoslada, Fernando; Martins, Sofía A.; Orellana, Guillermo; Sellergren, Börje

    2007-07-01

    Molecularly imprinted polymers (MIPs), human-made polymers capable of recognizing a particular molecule in the presence of others due to the selective cavities of the material, have been successfully applied to the development of chromatographic and solid phase extraction methods. They have also been applied to the development of electrochemical, piezoelectrical and optical sensors. In parallel with the classification of biosensors, MIP-based devices can work according to two different detection schemes: (1) affinity sensors ("plastic-bodies") and, (2) catalytic sensors ("plastic-enzymes"). In the first case the change in a characteristic optical property, most frequently fluorescence, of the analyte or of the polymer is monitored, upon their mutual interaction. Alternatively, a fluorescent analogue of the target analyte can also be used to develop sensors based on competitive assays (MIAs). Optimization of the polymer composition and, in particular, a proper choice of the nature of the functional monomers involved in the polymerization process, is critical to prepare materials able to selectively interact with the analyte in aqueous media and with the fast kinetics required for analytical applications. Moreover, a rational design of fluorescent analogues of non-naturally fluorescent templates or of fluorescent monomers able to change its property upon interaction with the analyte, is also a bottle neck for wide application of this recognition elements in optical sensing. In this paper we present several approaches to address these issues namely the optimization of MIP composition and the design and synthesis of novel fluorophores for the analysis of antibiotics and mycotoxins in real samples.

  16. A fluorescent carbon-dots-based mitochondria-targetable nanoprobe for peroxynitrite sensing in living cells.

    PubMed

    Wu, Xiaoxue; Sun, Shan; Wang, Yuhui; Zhu, Jiali; Jiang, Kai; Leng, Yumin; Shu, Qinghai; Lin, Hengwei

    2017-04-15

    Mitochondria, the power generators in cell, are a primary organelle of oxygen consumption and a main source of reactive oxygen/nitrogen species (ROS/RNS). Peroxynitrite (ONOO(-)), known as a kind of RNS, has been considered to be a significant factor in many cell-related biological processes, and there is great desire to develop fluorescent probes that can sensitively and selectively detect peroxynitrite in living cells. Herein, we developed a fluorescent carbon-dots (C-dots) based mitochondria-targetable nanoprobe with high sensitivity and selectivity for peroxynitrite sensing in living cells. The C-dots with its surface rich in amino groups was synthesized using o-phenylenediamine as carbon precursor, and it could be covalently conjugated with a mitochondria-targeting moiety, i.e. triphenylphosphonium (TPP). In the presence of peroxynitrite, the fluorescence of the constructed nanoprobe (C-dots-TPP) was efficiently quenched via a mechanism of photoinduced electron transfer (PET). The nanoprobe exhibited relatively high sensitivity (limit of detection: 13.5nM) and selectivity towards peroxynitrite in aqueous buffer. The performance of the nanoprobe for fluorescence imaging of peroxynitrite in mitochondria was investigated. The results demonstrated that the nanoprobe showed fine mitochondria-targeting ability and imaging contrast towards peroxynitrite in living cells. We anticipate that the proposed nanoprobe will provide a facile tool to explore the role played by peroxynitrite in cytobiology.

  17. Ratiometric fluorescence, electrochemiluminescence, and photoelectrochemical chemo/biosensing based on semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Wu, Peng; Hou, Xiandeng; Xu, Jing-Juan; Chen, Hong-Yuan

    2016-04-01

    Ratiometric fluorescent sensors, which can provide built-in self-calibration for correction of a variety of analyte-independent factors, have attracted particular attention for analytical sensing and optical imaging with the potential to provide a precise and quantitative analysis. A wide variety of ratiometric sensing probes using small fluorescent molecules have been developed. Compared with organic dyes, exploiting semiconductor quantum dots (QDs) in ratiometric fluorescence sensing is even more intriguing, owing to their unique optical and photophysical properties that offer significant advantages over organic dyes. In this review, the main photophysical mechanism for generating dual-emission from QDs for ratiometry is discussed and categorized in detail. Typically, dual-emission can be obtained either with energy transfer from QDs to dyes or with independent dual fluorophores of QDs and dye/QDs. The recent discovery of intrinsic dual-emission from Mn-doped QDs offers new opportunities for ratiometric sensing. Particularly, the signal transduction of QDs is not restricted to fluorescence, and electrochemiluminescence and photoelectrochemistry from QDs are also promising for sensing, which can be made ratiometric for correction of interferences typically encountered in electrochemistry. All these unique photophysical properties of QDs lead to a new avenue of ratiometry, and the recent progress in this area is addressed and summarized here. Several interesting applications of QD-based ratiometry are presented for the determination of metal ions, temperature, and biomolecules, with specific emphasis on the design principles and photophysical mechanisms of these probes.

  18. Gold nanoparticles-based fluorescence resonance energy transfer for competitive immunoassay of biomolecules.

    PubMed

    Chen, Jia; Huang, Yong; Zhao, Shulin; Lu, Xin; Tian, Jianniao

    2012-12-21

    A novel platform for competitive immunoassay of biomolecules was designed based on fluorescence resonance energy transfer (FRET) between fluorescein isothiocyanate (FITC) and gold nanoparticles (AuNPs). The antigen was first labeled with FITC, and the FITC labeled antigen was then reacted with AuNPs functionalized with a relative antibody to obtain the nanometer-sized sensor. The FRET between FITC and AuNPs led to the fluorescent quenching of FITC. Upon the recognition of the target antigen, the FICT labeled antigen was released from the AuNPs surface because of competitive immunoreaction, the distance between the FITC and AuNPs increased, and the interaction between FITC and AuNPs became weaker, which significantly hindered the FRET and, thus, increased the fluorescence of FITC. The change in fluorescence intensity produced a novel method for detection of the target. By using immunoglobulin M (IgM) as a model analyte, the competitive immunoassay had a limit of detection of 42 pM. The present method was applied for the determination of IgM in human serum with satisfactory results. The proposed method exhibits several advantages such as high quenching efficiency and sensitivity, and good specificity toward target versus other analogues. Moreover, this strategy could be conveniently extended for the detection of other biomolecules by using the corresponding antigens and respective antibodies.

  19. Wireless fluorescence capsule for endoscopy using single photon-based detection

    PubMed Central

    Al-Rawhani, Mohammed A.; Beeley, James; Cumming, David R. S.

    2015-01-01

    Fluorescence Imaging (FI) is a powerful technique in biological science and clinical medicine. Current FI devices that are used either for in-vivo or in-vitro studies are expensive, bulky and consume substantial power, confining the technique to laboratories and hospital examination rooms. Here we present a miniaturised wireless fluorescence endoscope capsule with low power consumption that will pave the way for future FI systems and applications. With enhanced sensitivity compared to existing technology we have demonstrated that the capsule can be successfully used to image tissue autofluorescence and targeted fluorescence via fluorophore labelling of tissues. The capsule incorporates a state-of-the-art complementary metal oxide semiconductor single photon avalanche detector imaging array, miniaturised optical isolation, wireless technology and low power design. When in use the capsule consumes only 30.9 mW, and deploys very low-level 468 nm illumination. The device has the potential to replace highly power-hungry intrusive optical fibre based endoscopes and to extend the range of clinical examination below the duodenum. To demonstrate the performance of our capsule, we imaged fluorescence phantoms incorporating principal tissue fluorophores (flavins) and absorbers (haemoglobin). We also demonstrated the utility of marker identification by imaging a 20 μM fluorescein isothiocyanate (FITC) labelling solution on mammalian tissue. PMID:26678456

  20. Fluorescent sensors for selective detection of thiols: expanding the intramolecular displacement based mechanism to new chromophores.

    PubMed

    Niu, Li-Ya; Zheng, Hai-Rong; Chen, Yu-Zhe; Wu, Li-Zhu; Tung, Chen-Ho; Yang, Qing-Zheng

    2014-03-21

    Biological thiols, including cysteine (Cys), homocystein (Hcy) and glutathione (GSH), play crucial roles in maintaining the appropriate redox status of biological systems. An abnormal level of biothiols is associated with different diseases, therefore, the discrimination between them is of great importance. Herein, we present two fluorescent sensors for selective detection of biothiols based on our recently reported intramolecular displacement mechanism. We expanded this mechanism to commercially available chromophores, 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD-Cl) and heptamethine cyanine dye IR-780. The sensors operate by undergoing displacement of chloride by thiolate. The amino groups of Cys/Hcy further replace the thiolate to form amino-substituted products, which exhibit dramatically different photophysical properties compared to sulfur-substituted products from the reaction with GSH. NBD-Cl is highly selective towards Cys/Hcy and exhibits significant fluorescence enhancement. IR-780 showed a variation in its fluorescence ratio towards Cys over other thiols. Both of the sensors can be used for live-cell imaging of Cys. The wide applicability of the mechanism may provide a powerful tool for developing novel fluorescent sensors for selective detection of biothiols.