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Sample records for direct colorimetric detection

  1. Polymeric assay film for direct colorimetric detection

    DOEpatents

    Charych, Deborah; Nagy, Jon; Spevak, Wayne

    2002-01-01

    A lipid bilayer with affinity to an analyte, which directly signals binding by a changes in the light absorption spectra. This novel assay means and method has special applications in the drug development and medical testing fields. Using a spectrometer, the system is easily automated, and a multiple well embodiment allows inexpensive screening and sequential testing. This invention also has applications in industry for feedstock and effluent monitoring.

  2. Polymeric assay film for direct colorimetric detection

    DOEpatents

    Charych, Deborah; Nagy, Jon; Spevak, Wayne

    1999-01-01

    A lipid bilayer with affinity to an analyte, which directly signals binding by a changes in the light absorption spectra. This novel assay means and method has special applications in the drug development and medical testing fields. Using a spectrometer, the system is easily automated, and a multiple well embodiment allows inexpensive screening and sequential testing. This invention also has applications in industry for feedstock and effluent monitoring.

  3. Sol-gel matrices for direct colorimetric detection of analytes

    DOEpatents

    Charych, Deborah H. (Albany, CA); Sasaki, Darryl (Albuquerque, NM); Yamanaka, Stacey (Dallas, TX)

    2000-01-01

    The present invention relates to methods and compositions for the direct detection of analytes using color changes that occur in immobilized biopolymeric material in response to selective binding of analytes to their surface. In particular, the present invention provides methods and compositions related to the encapsulation of biopolymeric material into metal oxide glass using the sol-gel method.

  4. Sol-Gel Matrices For Direct Colorimetric Detection Of Analytes

    DOEpatents

    Charych, Deborah H. (Albany, CA); Sasaki, Darryl (Albuquerque, NM); Yamanaka, Stacey (Dallas, TX)

    2002-11-26

    The present invention relates to methods and compositions for the direct detection of analytes using color changes that occur in immobilized biopolymeric material in response to selective binding of analytes to their surface. In particular, the present invention provides methods and compositions related to the encapsulation of biopolymeric material into metal oxide glass using the sol-gel method.

  5. Gum kondagogu reduced/stabilized silver nanoparticles as direct colorimetric sensor for the sensitive detection of Hg? in aqueous system.

    PubMed

    Rastogi, Lori; Sashidhar, R B; Karunasagar, D; Arunachalam, J

    2014-01-01

    A highly sensitive and selective method is reported for the colorimetric detection of Hg(2+) in aqueous system by using label free silver nanoparticles (Ag NPs). Ag NPs used in this method were synthesized by gum kondagogu (GK) which acted as both reducing and stabilizing agent. The average size of the GK-Ag NPs was found to be 5.0 2.8 nm as revealed by transmission electron microscope (TEM) analysis and the nanoparticles were stable at various pH conditions (pH 4-11) and salt concentrations (5-100 mM). The GK reduced/stabilized Ag NPs (GK-Ag NPs) were directly used for the selective colorimetric reaction with Hg(2+) without any further modification. The bright yellow colour of Ag NPs was found to fade in a concentration dependent manner with the added Hg(+) ions. The fading response was directly correlated with increasing concentration of Hg(2+). More importantly, this response was found to be highly selective for Hg(2+) as the absorption spectra were found to be unaffected by the presence of other ions like; Na(+), K(+), Mg(2+), Ca(2+), Cu(2+), Ni(2+), Co(2+), As(3+), Fe(2+), Cd(2+), etc. The metal sensing mechanism is explained based on the turbidometric and X-ray diffraction (XRD) analysis of GK-Ag NPs with Hg(2+). The proposed method was successfully applied for the determination of Hg(2+) in various ground water samples. The reported method can be effectively used for the quantification of total Hg(2+) in samples, wherein the organic mercury is first oxidized to inorganic form by ultraviolet (UV) irradiation. The limit of quantification for Hg(2+) using the proposed method was as low as 4.9 10(-8) mol L(-1) (50 nM). The proposed method has potential application for on-field qualitative detection of Hg(2+) in aqueous environmental samples. PMID:24274277

  6. Label free colorimetric and fluorimetric direct detection of methylated DNA based on silver nanoclusters for cancer early diagnosis.

    PubMed

    Dadmehr, Mehdi; Hosseini, Morteza; Hosseinkhani, Saman; Ganjali, Mohammad Reza; Sheikhnejad, Reza

    2015-11-15

    Epigenetic changes such as DNA methylation of CpG islands located in the promoter region of some tumor suppressor genes are very common in human diseases such as cancer. Detection of aberrant methylation pattern could serve as an excellent diagnostic approach. Recently, the direct detection of methylated DNA sequences without using chemical and enzymatic treatments or antibodies has received great deal of attentions. In this study, we report a colorimetric and fluorimetric technique for direct detection of DNA methylation. Here, the DNA is being used as an effective template for fluorescent silver nanoclusters formation without any chemical modification or DNA labeling. The sensitivity test showed that upon the addition of target methylated DNA, the fluorescence intensity is decreased in a linear range when the concentration of methylated DNA has increased from 2.010(-9) to 6.3 10(-7) M with the detection limit of 9.410(-10) M. The optical and fluorescence spectral behaviors were highly reproducible and clearly discriminated between unmethylated, methylated and even partially methylated DNA in CpG rich sequences. The results were also reproducible when the human plasma was present in our assay system. PMID:26056954

  7. Emergency First Responders' Experience with Colorimetric Detection Methods

    SciTech Connect

    Sandra L. Fox; Keith A. Daum; Carla J. Miller; Marnie M. Cortez

    2007-10-01

    Nationwide, first responders from state and federal support teams respond to hazardous materials incidents, industrial chemical spills, and potential weapons of mass destruction (WMD) attacks. Although first responders have sophisticated chemical, biological, radiological, and explosive detectors available for assessment of the incident scene, simple colorimetric detectors have a role in response actions. The large number of colorimetric chemical detection methods available on the market can make the selection of the proper methods difficult. Although each detector has unique aspects to provide qualitative or quantitative data about the unknown chemicals present, not all detectors provide consistent, accurate, and reliable results. Included here, in a consumer-report-style format, we provide boots on the ground information directly from first responders about how well colorimetric chemical detection methods meet their needs in the field and how they procure these methods.

  8. Colorimetric silver detection of DNA microarrays.

    PubMed

    Alexandre, I; Hamels, S; Dufour, S; Collet, J; Zammatteo, N; De Longueville, F; Gala, J L; Remacle, J

    2001-08-01

    Development of microarrays has revolutionized gene expression analysis and molecular diagnosis through miniaturization and the multiparametric features. Critical factors affecting detection efficiency of targets hybridization on microarray are the design of capture probes, the way they are attached to the support, and the sensitivity of the detection method. Microarrays are currently detected in fluorescence using a sophisticated confocal laser-based scanner. In this work, we present a new colorimetric detection method which is intented to make the use of microarray a powerful procedure and a low-cost tool in research and clinical settings. The signal generated with this method results from the precipitation of silver onto nanogold particles bound to streptavidin, the latter being used for detecting biotinylated DNA. This colorimetric method has been compared to the Cy-3 fluorescence method. The detection limit of both methods was equivalent and corresponds to 1 amol of biotinylated DNA attached on an array. Scanning and data analysis of the array were obtained with a colorimetric-based workstation. PMID:11476538

  9. Colorimetric detection of acetylcholine with plasmonic nanomaterials signaling.

    PubMed

    Oh, Ju-Hwan; Kim, Byoung Chan; Lee, Jae-Seung

    2014-11-01

    We have developed a highly sensitive and selective colorimetric method for detection of acetylcholine (ACh), using a tandem enzymatic reaction for biological target recognition and silver nanoplates (AgNPLs) for optical signal generation. The ACh molecules are enzymatically hydrolyzed and oxidized into betaine and hydrogen peroxide, the latter of which chemically oxidizes the AgNPLs to generate the "turn-on" signal. To optimize detection sensitivity, the chemical and biological properties of the detection mixtures containing the enzymes, ACh, and AgNPLs were thoroughly investigated with respect to component concentrations and reaction temperatures; a maximum sensitivity of 500 nM for colorimetric detection of ACh was achieved. We further directly compared the signaling profiles of (1) novel nanostructured and (2) conventional molecular chromogens, improving our understanding of the factors that should be considered when designing a detection system. PMID:25258290

  10. Colorimetric Detection of the Adenylation Activity in Nonribosomal Peptide Synthetases.

    PubMed

    Maruyama, Chitose; Niikura, Haruka; Takakuwa, Masahiro; Katano, Hajime; Hamano, Yoshimitsu

    2016-01-01

    Nonribosomal peptide synthetases (NRPSs) are multifunctional enzymes consisting of catalytic domains. The substrate specificities of adenylation (A) domains determine the amino-acid building blocks to be incorporated during nonribosomal peptide biosynthesis. The A-domains mediate ATP-dependent activation of amino-acid substrates as aminoacyl-O-AMP with pyrophosphate (PPi) release. Traditionally, the enzymatic activity of the A-domains has been measured by radioactive ATP-[(32)P]-PPi exchange assays with the detection of (32)P-labeled ATP. Recently, we developed a colorimetric assay for the direct detection of PPi as a yellow 18-molybdopyrophosphate anion ([(P2O7)Mo18O54](4-)). [(P2O7)Mo18O54](4-) was further reduced by ascorbic acid to give a more readily distinguishable blue coloration. Here we demonstrate the lab protocols for the colorimetric assay of PPi released in A-domain reactions. PMID:26831702

  11. Colorimetric Method for Beryllium Surface Contamination Detection

    SciTech Connect

    MCWHORTER, CHRISTOPHER

    2004-03-11

    To address the need for real-time accurate total beryllium analyses, Savannah River Technology Center Analytical Development Section personnel evaluated and modified a colorimetric screening method developed at Los Alamos National Lab to measure beryllium on surfaces. This method was based on a color complex formed by beryllium and chromium azurol s . SRTC converted this visual method to a quantitative analysis method using spectrophotometric detection. The addition of a cationic surfactant (hexadecyltrimethylammonium bromide, CTAB) to the Be-CAS system shifted the complex absorbance away from the CAS absorbance and allowed for the detection. Assuming complete dissolution and a 10 mL rinse solution volume to remove the beryllium from the wipe, the detection limit was calculated comfortably below the free release limit. The spectrophotometric method was rugged and simple enough that it could be used as a field method.

  12. Optical fiber waveguide sensor for the colorimetric detection of ammonia

    NASA Astrophysics Data System (ADS)

    Schmitt, Katrin; Rist, Jonas; Peter, Carolin; Wllenstein, Jrgen

    2011-06-01

    We present the development and characterization of a fiber-optic colorimetric gas sensor combined with the electronic circuitry for measurement control and RFID communication. The gas sensor detects ammonia using a 300 ?m polyolefin fiber coated with a gas-sensitive polymer film. The spectral and time-dependent sensitivity of various polymer films was tested in transmission measurements. Light from a standard LED at ? = 590 nm was coupled into the polyolefin fiber through the front face. A prototype of the gas sensor with the direct coupling method was tested under realistic measurement conditions, i.e. battery-driven and in a completely autonomous mode. The sensor system showed good sensitivity to the ammonia concentrations and response times in the order of minutes. The achievable power consumption was below 100?W.The films contained the pH-sensitive dyes bromocresol purple or bromophenol blue embedded in either ethyl cellulose or polyvinyl butyral, and optionally tributyl phosphate as plasticizer. The bromophenol blue based films showed a strong reaction to ammonia, with saturation concentrations around 1000 ppm and response times of about 15 seconds to 100ppm. The colorimetric reaction was simulated using a simple kinetic model which was in good agreement with the experimental results.

  13. Colorimetric detection of uranium in water

    DOEpatents

    DeVol, Timothy A.; Hixon, Amy E.; DiPrete, David P.

    2012-03-13

    Disclosed are methods, materials and systems that can be used to determine qualitatively or quantitatively the level of uranium contamination in water samples. Beneficially, disclosed systems are relatively simple and cost-effective. For example, disclosed systems can be utilized by consumers having little or no training in chemical analysis techniques. Methods generally include a concentration step and a complexation step. Uranium concentration can be carried out according to an extraction chromatographic process and complexation can chemically bind uranium with a detectable substance such that the formed substance is visually detectable. Methods can detect uranium contamination down to levels even below the MCL as established by the EPA.

  14. Field evaluation of two colorimetric coliphage detection methods.

    PubMed

    Ijzerman, M M; Falkinham, J O; Reneau, R B; Hagedorn, C

    1994-03-01

    Two new methods for coliphage detection, a colorimetric agar-based (CAB) method and a liquid colorimetric presence-absence (LCPA) method, were compared to the coliphage method proposed by the American Public Health Association (APHA; Standard Methods for the Examination of Water and Wastewater, 18th ed., American Public Health Association, Washington, D.C., 1992). Both new methods are based on the induction of beta-galactosidase in Escherichia coli and the release of the enzyme through a lytic cell infection. The released enzyme then cleaves a chromogenic substrate which produces a colored reaction product. Ninety split water samples from four different sources were tested. A total of 52 samples were positive by the CAB method, 52 were positive by the LCPA method, and 53 were positive by the APHA method. Results indicated that (i) the CAB and LCPA methods were as sensitive in coliphage detection as the APHA method, (ii) both the CAB and LCPA methods were easier to read and interpret than the APHA method, and (iii) the CAB method detected more coliphages in a positive sample than the APHA method in two of the four types of water sources. Importantly, the rapid and simple LCPA method was as reliable and sensitive as either of the two agar-based methods in coliphage detection. PMID:16349215

  15. Method for colorimetric detection of double-stranded nucleic acid using leuco triphenylmethane dyes.

    PubMed

    Miyamoto, Shigehiko; Sano, Sotaro; Takahashi, Koji; Jikihara, Takaaki

    2015-03-15

    Because loop-mediated isothermal amplification (LAMP) can amplify substantial amounts of DNA under isothermal conditions, its applications for simple genetic testing have attracted considerable attention. A positive LAMP reaction is indicated by the turbidity caused by by-products or by the color change after adding a metallochromic indicator to the reaction solution, but these methods have certain limitations. Leuco crystal violet (LCV), a colorless dye obtained after sodium sulfite treatment of crystal violet (CV), was used as a new colorimetric method for detecting LAMP. LCV is reconverted into CV through contact with double-stranded DNA (dsDNA). Therefore, the positive reaction of LAMP is indicated by color change from colorless to violet. The assay is sensitive enough to detect LAMP products, with a detection limit of 7.1 ng/?l for dsDNA. It is also highly selective to dsDNA, and interference with single-stranded DNA and deoxynucleotide triphosphates (dNTPs) is not observed. LCV facilitates direct colorimetric detection of the main product rather than a by-product of the LAMP reaction; therefore, this method can be used under various reaction conditions such as those with added pyrophosphatase in solution. This colorimetric LAMP detection method using LCV is useful for point-of-care genetic testing given its simplicity. PMID:25575759

  16. A gold nanoparticle-based colorimetric probe for rapid detection of 1-hydroxypyrene in urine.

    PubMed

    Hu, Yaqi; Du, Chunyan; Li, Yunchao; Fan, Louzhen; Li, Xiaohong

    2015-07-01

    Direct and rapid detection of 1-hydroxypyrene (1-OHP) is of great importance owing to its high carcinogenicity, teratogenicity and toxicity. In this study, a simple colorimetric assay for rapid determination of 1-OHP is reported, which is based on non-crosslinking aggregation of gold nanoparticles (Au NPs) induced by 1-OHP in the presence of formic acid (FA). Initially, Au NPs were synthesized with citrate as the capping agent and exhibited red color. Subsequently, the addition of FA did not cause aggregation of Au NPs, but a proton transfer process occurred from FA to carboxylic anions on the surface of Au NPs with a decreased zeta potential. The subsequent addition of 1-OHP resulted in a further decreased zeta potential and an intensely hydrophobic environment, which led to a strong and rapid non-crosslinking aggregation of Au NPs within 5 min with the color changing from red to violet blue. Based on this principle, sensitive and selective detection of 1-OHP was achieved. The detection limit was 3.3 nM. Finally, the colorimetric assay was successfully applied to detect 1-OHP in a urine sample. This strategy provides new insights into developing colorimetric methods for on-site and real-time detection of polycyclic aromatic hydrocarbons. PMID:25988203

  17. Colorimetric/fluorogenic detection of thiols by N-fused porphyrin in water.

    PubMed

    Ikawa, Yoshiya; Touden, Satoshi; Katsumata, Sho; Furuta, Hiroyuki

    2013-11-01

    A water-soluble derivative of N-fused porphyrin (NFP) possessing four cationic side-arms (pPyNFP) serves as a unique class of colorimetric/fluorogenic reporters that selectively react with biothiols in aquaous media to afford N-confused porphyrin (NCP) derivatives, while other nucleophilic amino acids were inert under a wide range of pH conditions. Owing to the large difference of the optical properties between NCP and NFP, the transformation enabled selective detection of biothiols in colorimetric/fluorogenic manner, especially in the near-infrared region. To the best our knowledge, this is the first example of porphyrin-based thiol detection systems that use the direct attack of thiol group on the optical reporter. PMID:24051075

  18. Double-stem Hairpin Probe and Ultrasensitive Colorimetric Detection of Cancer-related Nucleic Acids

    PubMed Central

    Xu, Jianguo; Li, Hongling; Wu, Zai-Sheng; Qian, Jun; Xue, Chang; Jia, Lee

    2016-01-01

    The development of a versatile biosensing platform to screen specific DNA sequences is still an essential issue of molecular biology research and clinic diagnosis of genetic disease. In this work, we for the first time reported a double-stem hairpin probe (DHP) that was simultaneously engineered to incorporate a DNAzyme, DNAzyme's complementary fragment and nicking enzyme recognition site. The important aspect of this hairpin probe is that, although it is designed to have a long ds DNA fragment, no intermolecular interaction occurs, circumventing the sticky-end pairing-determined disadvantages encountered by classic molecular beacon. For the DHP-based colorimetric sensing system, as a model analyte, cancer-related DNA sequence can trigger a cascade polymerization/nicking cycle on only one oligonucleotide probe. This led to the dramatic accumulation of G-quadruplexes directly responsible for colorimetric signal conversion without any loss. As a result, the target DNA is capable of being detected to 1 fM (six to eight orders of magnitude lower than that of catalytic molecular beacons) and point mutations are distinguished by the naked eye. The described DHP as a-proof-of-concept would not only promote the design of colorimetric biosensors but also open a good way to promote the diagnosis and treatment of genetic diseases. PMID:26909108

  19. Colorimetric detection of catalytic reactivity of nanoparticles in complex matrices.

    PubMed

    Corredor, Charlie; Borysiak, Mark D; Wolfer, Jay; Westerhoff, Paul; Posner, Jonathan D

    2015-03-17

    There is a need for new methodologies to quickly assess the presence and reactivity of nanoparticles (NPs) in commercial, environmental, and biological samples since current detection techniques require expensive and complex analytical instrumentation. Here, we investigate a simple and portable colorimetric detection assay that assesses the surface reactivity of NPs, which can be used to detect the presence of NPs, in complex matrices (e.g., environmental waters, serum, urine, and in dissolved organic matter) at as low as part per billion (ppb) or ng/mL concentration levels. Surface redox reactivity is a key emerging property related to potential toxicity of NPs with living cells, and is used in our assays as a key surrogate for the presence of NPs and a first tier analytical strategy toward assessing NP exposures. We detect a wide range of metal (e.g., Ag and Au) and oxide (e.g., CeO2, SiO2, VO2) NPs with a diameter range of 5 to 400 nm and multiple capping agents (tannic acid (TA), polyvinylpyrrolidone (PVP), branched polyethylenimine (BPEI), polyethylene glycol (PEG)). This method is sufficiently sensitive (ppb levels) to measure concentrations typically used in toxicological studies, and uses inexpensive, commercially available reagents. PMID:25635807

  20. Point-of-care colorimetric detection with a smartphone.

    PubMed

    Shen, Li; Hagen, Joshua A; Papautsky, Ian

    2012-11-01

    Paper-based immunoassays are becoming powerful and low-cost diagnostic tools, especially in resource-limited settings. Inexpensive methods for quantifying these assays have been shown using desktop scanners, which lack portability, and cameras, which suffer from the ever changing ambient light conditions. In this work, we introduce a novel approach of quantifying colors of colorimetric diagnostic assays with a smartphone that allows high accuracy measurements in a wide range of ambient conditions, making it a truly portable system. Instead of directly using the red, green, and blue (RGB) intensities of the color images taken by a smartphone camera, we use chromaticity values to construct calibration curves of analyte concentrations. We demonstrate the high accuracy of this approach in pH measurements with linear response ranges of 1-12. These results are comparable to those reported using a desktop scanner or silicon photodetectors. To make the approach adoptable under different lighting conditions, we developed a calibration technique to compensate for measurement errors due to variability in ambient light. This technique is applicable to a number of common light sources, such as sun light, fluorescent light, or smartphone LED light. Ultimately, the entire approach can be integrated in an "app" to enable one-click reading, making our smartphone based approach operable without any professional training or complex instrumentation. PMID:22996728

  1. PAR immobilized colorimetric fiber for heavy metal ion detection and adsorption.

    PubMed

    Li, Guowei; Zhang, Lianhai; Li, Zhiwei; Zhang, Wenqin

    2010-05-15

    A new wearable colorimetric fiber for heavy metal ion detection and adsorption has been synthesized by first aminating a commercially available polyacrylonitrile fiber with ethylenediamine and then covalently immobilizing 4-(2-pyridylazo)-1,3-benzenediol (PAR) on the modified fiber through a Mannich reaction. The fiber was characterized by X-ray powder diffraction spectra (XRD), scanning electron microscope (SEM), FTIR and UV-vis spectroscopy, and its acid exchange capacity, colorimetric properties, response speed, selectivity, reusability, photostability and adsorption capacity were investigated. In neutral aqueous solutions, the PAR immobilized fiber responds selectively to heavy metal ions, such as Hg(2+), Pb(2+), Cd(2+), Zn(2+), Ni(2+) and Cu(2+) with a color change from red-orange to dark-brown. Its visual detection limit for Pb(2+) is 1 x 10(-6)mol/L. Moreover, the selectivity increases with a decrease in pH, i.e. at pH 3.0, it shows a color change only for Hg(2+) and Cu(2+). This fiber also shows excellent reusability (>50 times), high photostability (>30 days under direct exposure to sunlight) and high adsorption capacity for Hg(2+) (0.74 mmol/g). PMID:20096995

  2. Highly Sensitive Colorimetric Detection of Ochratoxin A by a Label-Free Aptamer and Gold Nanoparticles

    PubMed Central

    Luan, Yunxia; Chen, Jiayi; Li, Cheng; Xie, Gang; Fu, Hailong; Ma, Zhihong; Lu, Anxiang

    2015-01-01

    A label-free aptamer-based assay for the highly sensitive and specific detection of Ochratoxin A (OTA) was developed using a cationic polymer and gold nanoparticles (AuNPs). The OTA aptamer was used as a recognition element for the colorimetric detection of OTA based on the aggregation of AuNPs by the cationic polymer. By spectroscopic quantitative analysis, the colorimetric assay could detect OTA down to 0.009 ng/mL with high selectivity in the presence of other interfering toxins. This study offers a new alternative in visual detection methods that is rapid and sensitive for OTA detection. PMID:26690477

  3. Colorimetric detection of bisphenol A based on unmodified aptamer and cationic polymer aggregated gold nanoparticles.

    PubMed

    Zhang, Dongwei; Yang, Jiayi; Ye, Jing; Xu, Lurong; Xu, Hanchu; Zhan, Shenshan; Xia, Bing; Wang, Lumei

    2016-04-15

    In this study, a colorimetric method was exploited to detect bisphenol A (BPA) based on BPA-specific aptamer and cationic polymer-induced aggregation of gold nanoparticles (AuNPs). The principle of this assay is very classical. The aggregation of AuNPs was induced by the concentration of cationic polymer, which is controlled by specific recognition of aptamer with BPA and the reaction of aptamer and cationic polymer forming "duplex" structure. This method enables colorimetric detection of BPA with selectivity and a detection limit of 1.50 nM. In addition, this colorimetric method was successfully used to determine spiked BPA in tap water and river water samples. PMID:26820097

  4. Identification of Escherichia coli O157 by Using a Novel Colorimetric Detection Method with DNA Microarrays

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Shiga toxin-producing Escherichia coli O157:H7 is a leading cause of foodborne illness worldwide. To evaluate better methods to rapidly detect and genotype E. coli O157 strains, the present study evaluated the use of ampliPHOX, a novel colorimetric detection method based on photopolymerization, for...

  5. A colorimetric receptor combined with a microcantilever sensor for explosive vapor detection

    NASA Astrophysics Data System (ADS)

    Zhu, Weibin; Park, Jung Su; Sessler, Jonathan L.; Gaitas, Angelo

    2011-03-01

    Substantial effort has been devoted to the synthesis of molecular receptors that can function as chemosensors for nitroaromatic explosives. In spite of several advantages, these receptors suffer from low sensitivity and difficulties translating the response into the gas phase. We have combined tetrathiafulvalene-functionalized calix[4]pyrrole, a colorimetric receptor, with a polyimide microcantilever, that includes a mechanical stress sensing element. The resulting system is capable of detecting 10 ppb trinitrobenzene vapor. This represents a 30-fold improvement relative to the receptor in halogenated solvents, suggesting that this approach can provide a solution to translating the chemical response of colorimetric chemosensors into practical devices.

  6. Colorimetric Detection of Creatinine Based on Plasmonic Nanoparticles via Synergistic Coordination Chemistry.

    PubMed

    Du, Jianjun; Zhu, Bowen; Leow, Wan Ru; Chen, Shi; Sum, Tze Chien; Peng, Xiaojun; Chen, Xiaodong

    2015-09-01

    A simple and portable colorimetric assay for creatinine detection is fabricated based on the synergistic coordination of creatinine and uric acid with Hg(2+) on the surface of gold nanoparticles, which exhibits good selectivity and sensitivity. Point-of-care clinical creatinine monitoring can be supported for monitoring renal function and diagnosing corresponding renal diseases at home. PMID:26037022

  7. Colorimetric detection of trivalent chromium in aqueous solution using tartrate-capped silver nanoparticles as probe.

    PubMed

    Xu, Yunbo; Dong, Yangjun; Jiang, Xue; Zhu, Ningning

    2013-10-01

    This study describes a simple and highly selective method for the colorimetric detection of trivalent chromium (Cr3+) using tartrate-capped silver nanoparticles (AgNPs) as probe. The addition of tartrate to the initially prepared AgNPs gives tartrate-stabilized AgNPs ascribing to the electrostatic repulsion of the highly negatively charged tartrate ions covered on the surface of AgNPs. It is found that, in the presence of Cr3+ in aqueous solution, the aggregation of tartrate-stabilized AgNPs occurs. The color of AgNPs suspension changes from yellow to pink and the surface plasmon absorption band broadens and red shifts, which could be applied for the colorimetric detection of Cr3+ in aqueous solution. The utilization of tartrate-stabilized AgNPs as probe substantially increases the selectivity and sensitivity for colorimetric detection of Cr3+. Control experiments with the addition of over 14 other metal ions, such as Pb2+, Zn2+, Cr2O7(2-), Cd2+, Co2+, Cu2+, Al3+, Ni2+, Mn2+, Ba2+, Fe3+, Ca2+, Mg2+, Sr+ do not result in a distinct change in the color or in the spectrum of the suspension, indicating that these metal ions do not interfere with the colorimetric detection of Cr3+. Under the conditions employed here, A502/A393 (ratio of absorption value at 502 nm to 393 nm) is linear with the concentration of Cr3+ within a concentration range from 0.1 to 1.17 microM with a detection limit of 0.06 microM. This study may offer a simple, rapid and sensitive approach to colorimetric detection of Cr3+ in aqueous solution. PMID:24245149

  8. An organic indicator functionalized graphene oxide nanocomposite-based colorimetric assay for the detection of sarcosine.

    PubMed

    Xue, Zhonghua; Yin, Bo; Wang, Hui; Li, Mengqian; Rao, Honghong; Liu, Xiuhui; Zhou, Xinbin; Lu, Xiaoquan

    2016-03-01

    Rapid detection of sarcosine is a key requirement for both diagnosis and treatment of disease. We report here a simple yet sensitive colorimetric nanocomposite platform for rapid detection of sarcosine in alkaline media. The approach exploited the benefits of a rapid color-producing reaction between an organic indicator, 1,2-naphthoquinone-4-sulphonic acid sodium salt (NQS), and the analyte of sarcosine species as well as the good catalytic ability of graphene oxide (GO) to the formation of highly colored products due to its good water dispersibility, extremely large surface area and facile surface modification. As a result, a NQS functionalized GO nanocomposite through π-π stacking has been demonstrated to be useful as a highly efficient catalyst system for the selective and sensitive colorimetric determination of sarcosine by providing a nanocomposite-amplified colorimetric response. Meanwhile, the strategy offered excellent selectivity toward sarcosine species against other amino acids as well as a satisfying detection limit of 0.73 μM. More importantly, by using an electrochemical method, a credible sensing mechanism of GO nanocomposite-based colorimetric platform for a special analyte determination can be easily verified and elucidated, which also provides an attractive alternative to conventional characterization strategies. PMID:26902537

  9. A colorimetric sensor based on anodized aluminum oxide (AAO) substrate for the detection of nitroaromatics.

    SciTech Connect

    Liu, Y.; Wang, H. H.; Indacochea, J. E.; Wang, M. L.

    2011-12-15

    Simple and low cost colorimetric sensors for explosives detection were explored and developed. Anodized aluminum oxide (AAO) with large surface area through its porous structure and light background color was utilized as the substrate for colorimetric sensors. Fabricated thin AAO films with thickness less than {approx} 500 nm allowed us to observe interference colors which were used as the background color for colorimetric detection. AAO thin films with various thickness and pore-to-pore distance were prepared through anodizing aluminum foils at different voltages and times in dilute sulfuric acid. Various interference colors were observed on these samples due to their difference in structures. Accordingly, suitable anodization conditions that produce AAO samples with desired light background colors for optical applications were obtained. Thin film interference model was applied to analyze the UV-vis reflectance spectra and to estimate the thickness of the AAO membranes. We found that the thickness of produced AAO films increased linearly with anodization time in sulfuric acid. In addition, the growth rate was higher for AAO anodized using higher voltages. The thin film interference formulism was further validated with a well established layer by layer deposition technique. Coating poly(styrene sulfonate) sodium salt (PSS) and poly(allylamine hydrochloride) (PAH) layer by layer on AAO thin film consistently shifted its surface color toward red due to the increase in thickness. The red shift of UV-vis reflectance was correlated quantitatively to the number of layers been assembled. This sensitive red shift due to molecular attachment (increase in thickness) on AAO substrate was applied toward nitroaromatics detection. Aminopropyltrimethoxysilane (APTS) which can be attached onto AAO nanowells covalently through silanization and attract TNT molecules was coated and applied for TNT detection. UV-vis spectra of AAO with APTS shifted to the longer wavelength side due to TNT attachment. This red shift implied AAO thickness increased and positive detection of TNT molecules. It was also observed that both APTS and polyethyleneimine (PEI) were electron rich polymers which formed Meisenheimer complexes with TNT in solution and changed its color abruptly. This strong color change due to chemical reaction was applied as another approach for direct TNT detection. Commercial AAO films with long pores (60 {mu}m) and white background color were coated with APTS or PEI and then exposed to TNT in solution. These membranes turned to pink rapidly and eventually became visibly orange after a few hours with a strong absorption around 500 nm that was consistent with the formation of Meisenheimer complexes. The visible color change can be observed by unaided eyes and is suitable for nitroaromatics detection at higher concentration while interference color red shift in AAO thin film is designed for nitroaromatics detection at monolayer (nm) level.

  10. Microfluidic chip-based silver nanoparticles aptasensor for colorimetric detection of thrombin.

    PubMed

    Zhao, Yaju; Liu, Xiaohui; Li, Jie; Qiang, Weibing; Sun, Liang; Li, Hui; Xu, Danke

    2016-04-01

    In this paper, a colorimetric silver nanoparticles aptasensor (aptamer-AgNPs) was developed for simple and straightforward detection of protein in microfluidic chip. Surface-functionalized microfluidic channels were employed as the capture platform. Then the mixture of target protein and aptamer-AgNPs were injected into the microfluidic channels for colorimetric detection. To demonstrate the performance of this detection platform, thrombin was chosen as a model target protein. Introduction of thrombin could form a sandwich-type complex involving immobilized AgNPs. The amount of aptamer-AgNPs on the complex augmented along with the increase of the thrombin concentration causing different color change that can be analyzed both by naked eyes and a flatbed scanner. This method is featured with low sample consumption, simple processes of microfluidic platform and straightforward colorimetric detection with aptamer-AgNPs. Thrombin at concentrations as low as 20pM can be detected using this aptasensor without signal amplification. This work demonstrated that it had good selectivity over other proteins and it could be a useful strategy to detect other targets with two affinity binding sites for ligands as well. PMID:26838384

  11. Colorimetric detection of hazardous gases using a remotely operated capturing and processing system.

    PubMed

    Montes-Robles, Roberto; Moragues, Mara Esperanza; Vivancos, Jos-Luis; Ibez, Javier; Fraile, Rubn; Martnez-Mez, Ramn; Garca-Breijo, Eduardo

    2015-11-01

    This paper presents an electronic system for the automatic detection of hazardous gases. The proposed system implements colorimetric sensing algorithms, thus providing a low-cost solution to the problem of gas sensing. It is remotely operated and it performs the tasks of image capturing and processing, hence obtaining colour measurements in RGB (Red-Green-Blue) space that are subsequently sent to a remote operator via the internet. A prototype of the system has been built to test its performance. Specifically, experiments have been carried out aimed at the detection of CO, CO2, NO, NO2, SO2 and formaldehyde at diverse concentrations by using a chromogenic array composed by 13 active and 2 inert compounds. Statistical analyses of the results reveal a good performance of the electronic system and the feasibility of remote hazardous gas detection using colorimetric sensor arrays. PMID:26434416

  12. Colorimetric detection of Shewanella oneidensis based on immunomagnetic capture and bacterial intrinsic peroxidase activity

    NASA Astrophysics Data System (ADS)

    Wen, Junlin; Zhou, Shungui; Chen, Junhua

    2014-06-01

    Rapid detection and enumeration of target microorganisms is considered as a powerful tool for monitoring bioremediation process that typically involves cleaning up polluted environments with functional microbes. A novel colorimetric assay is presented based on immunomagnetic capture and bacterial intrinsic peroxidase activity for rapidly detecting Shewanella oneidensis, an important model organism for environmental bioremediation because of its remarkably diverse respiratory abilities. Analyte bacteria captured on the immunomagnetic beads provided a bacterial out-membrane peroxidase-amplified colorimetric readout of the immunorecognition event by oxidizing 3, 3', 5, 5'-tetramethylbenzidine (TMB) in the present of hydrogen peroxide. The high-efficiency of immunomagnetic capture and signal amplification of peroxidase activity offers an excellent detection performance with a wide dynamic range between 5.0 103 and 5.0 106 CFU/mL toward target cells. Furthermore, this method was demonstrated to be feasible in detecting S. oneidensis cells spiked in environmental samples. The proposed colorimetric assay shows promising environmental applications for rapid detection of target microorganisms.

  13. Miniaturized 96-well ELISA chips for staphylococcal enterotoxin B detection using portable colorimetric detector.

    PubMed

    Sapsford, Kim E; Francis, Jesse; Sun, Steven; Kostov, Yordan; Rasooly, Avraham

    2009-05-01

    A previously developed fluorescence sensing platform, combining spatial illumination using electroluminescence (EL) semiconductor strips with charge coupled device (CCD)-based detection (EL-CCD), was adapted to a new 96-well chip for colorimetric immunological assays, enhancing the capabilities of the EL-CCD platform. The modified system was demonstrated using a colorimetric-based enzyme linked immunosorbent assay (ELISA) for detection of staphylococcal enterotoxin B (SEB). Limits of detection (LODs) of 3.9 ng/mL (+/-2.4 ng/mL) SEB were determined with the ELISA chip measured using the EL-CCD platform, following a standard 4-h ELISA protocol. The LODs were comparable to those obtained using standard 96-well ELISA plates measured using a standard laboratory 96-well plate reader. The miniature 96-well ELISA chip however required as little as 5-microL samples, representing a tenfold reduction in sample volume compared to a standard 96-well ELISA plates. The ELISA chip also demonstrated detection of SEB spiked into various food matrices (milk, mushrooms, and mayonnaise) using limited-to-no sample preparation, with LODs ranging from 3.9 to 18.5 ng/mL depending on the matrix. The EL-CCD platform is versatile, capable of multi-mode detection (e.g., fluorescent and colorimetric along with solution and solid phase assays), and could readily be applied to other field portable or point-of-care applications. PMID:19290511

  14. Colorimetric detection of Shewanella oneidensis based on immunomagnetic capture and bacterial intrinsic peroxidase activity

    PubMed Central

    Wen, Junlin; Zhou, Shungui; Chen, Junhua

    2014-01-01

    Rapid detection and enumeration of target microorganisms is considered as a powerful tool for monitoring bioremediation process that typically involves cleaning up polluted environments with functional microbes. A novel colorimetric assay is presented based on immunomagnetic capture and bacterial intrinsic peroxidase activity for rapidly detecting Shewanella oneidensis, an important model organism for environmental bioremediation because of its remarkably diverse respiratory abilities. Analyte bacteria captured on the immunomagnetic beads provided a bacterial out-membrane peroxidase-amplified colorimetric readout of the immunorecognition event by oxidizing 3, 3′, 5, 5′-tetramethylbenzidine (TMB) in the present of hydrogen peroxide. The high-efficiency of immunomagnetic capture and signal amplification of peroxidase activity offers an excellent detection performance with a wide dynamic range between 5.0 × 103 and 5.0 × 106 CFU/mL toward target cells. Furthermore, this method was demonstrated to be feasible in detecting S. oneidensis cells spiked in environmental samples. The proposed colorimetric assay shows promising environmental applications for rapid detection of target microorganisms. PMID:24898751

  15. Highly sensitive colorimetric detection of 17?-estradiol using split DNA aptamers immobilized on unmodified gold nanoparticles.

    PubMed

    Liu, Jinchuan; Bai, Wenhui; Niu, Shucao; Zhu, Chao; Yang, Shuming; Chen, Ailiang

    2014-01-01

    Gold nanoparticle (AuNP) based colorimetric aptasensor have been developed for many analytes recently largely because of the ease of detection, high sensitivity, and potential for high-throughput analysis. Most of the target aptamers for detection have short sequences. However, the approach shows poor performance in terms of detection sensitivity for most of the long-sequence aptamers. To address this problem, for the first time, we split the 76 mer aptamer of 17?-estradiol into two short pieces to improve the AuNP based colorimetric sensitivity. Our results showed that the split P1 + P2 still retained the original 76 mer aptamer's affinity and specificity but increased the detection limit by 10-fold, demonstrating that as low as 0.1 ng/mL 17?-estradiol could be detected. The increased sensitivity may be caused by lower aptamer adsorption concentration and a lower affinity to the AuNPs of a short single-strand DNA (ssDNA) sequence. Our study provided a new way to use long-sequence aptamers to develop a highly sensitive AuNP-based colorimetric aptasensor. PMID:25524368

  16. Gold nanoparticle aggregation-based colorimetric assay for ?-casein detection in bovine milk samples.

    PubMed

    Li, Y S; Zhou, Y; Meng, X Y; Zhang, Y Y; Song, F; Lu, S Y; Ren, H L; Hu, P; Liu, Z S; Zhang, J H

    2014-11-01

    Traditional Kjeldahl method, used for quality evaluation of bovine milk, has intrinsic defects of time-consuming sample preparation and two analyses to determine the difference between non-protein nitrogen content and total protein nitrogen content. Herein, based upon antibody functionalized gold nanoparticles (AuNPs), we described a colorimetric method for ?-casein (?-CN) detection in bovine milk samples. The linear dynamic range and the LOD were 0.08-250 ?g mL(-1), and 0.03 ?g mL(-1) respectively. In addition, the real content of ?-CN in bovine milk was measured by using the developed assay. The results are closely correlated with those from Kjeldahl method. The advantages of ?-CN triggered AuNP aggregation-based colorimetric assay are simple signal generation, the high sensitivity and specificity as well as no need of complicated sample preparation, which make it for on-site detection of ?-CN in bovine milk samples. PMID:24874352

  17. A simple ratiometric and colorimetric chemosensor for the selective detection of fluoride in DMSO buffered solution

    NASA Astrophysics Data System (ADS)

    Niu, Hu; Shu, Qinghai; Jin, Shaohua; Li, Bingjun; Zhu, Jiaping; Li, Lijie; Chen, Shusen

    2016-01-01

    A derivative of squaramide (cyclobuta[b]quinoxaline-1, 2(3H, 8H)-dione) has been synthesized for the ratiometric and colorimetric sensing of F- in aqueous solution in competitive fashion. With F-, probe 1 showed a highly selective naked-eye detectable color change along with a characteristic UV-Vis absorbance over other tested ions, which probably originates from the deprotonation occurred between 1 and F-, as proved by the 1H NMR titration experiments and DFT calculations.

  18. Simple colorimetric bacterial detection and high-throughput drug screening based on a graphene-enzyme complex

    NASA Astrophysics Data System (ADS)

    Li, Juan; Wu, Ling-Jie; Guo, Shan-Shan; Fu, Hua-E.; Chen, Guo-Nan; Yang, Huang-Hao

    2012-12-01

    A simple, colorimetric, sensitive, cost-effective and high-throughput system based on a positively charged graphene oxide-enzyme complex was developed for bacterial detection and drug screening.A simple, colorimetric, sensitive, cost-effective and high-throughput system based on a positively charged graphene oxide-enzyme complex was developed for bacterial detection and drug screening. Electronic supplementary information (ESI) available: Experimental details and supporting figures and procedures. See DOI: 10.1039/c2nr32704j

  19. A new rhodamine-based colorimetric chemosensor for naked-eye detection of Cu2 + in aqueous solution

    NASA Astrophysics Data System (ADS)

    Hu, Yang; Zhang, Jing; Lv, Yuan-Zheng; Huang, Xiao-Huan; Hu, Sheng-li

    2016-03-01

    A new colorimetric probe 1 based on rhodamine B lactam was developed for naked-eye detection of Cu2 +. The optical feature of 1 for Cu2 + was investigated by UV-vis absorption spectroscopy. Upon the addition of Cu2 +, the 1 displayed a distinct color change from colorless to pink, which can be directly detected by the naked eye. The stoichiometry of 1 to Cu2 + complex was found to be 1:1 and the naked-eye detection limit was determined as low as 2 μM. The results suggest that the probe 1 may provide a convenient method for visual detection of Cu2 + with high sensitivity.

  20. A new rhodamine-based colorimetric chemosensor for naked-eye detection of Cu(2+) in aqueous solution.

    PubMed

    Hu, Yang; Zhang, Jing; Lv, Yuan-Zheng; Huang, Xiao-Huan; Hu, Sheng-Li

    2016-03-15

    A new colorimetric probe 1 based on rhodamine B lactam was developed for naked-eye detection of Cu(2+). The optical feature of 1 for Cu(2+) was investigated by UV-vis absorption spectroscopy. Upon the addition of Cu(2+), the 1 displayed a distinct color change from colorless to pink, which can be directly detected by the naked eye. The stoichiometry of 1 to Cu(2+) complex was found to be 1:1 and the naked-eye detection limit was determined as low as 2μM. The results suggest that the probe 1 may provide a convenient method for visual detection of Cu(2+) with high sensitivity. PMID:26773260

  1. Colorimetric and Fluorescent Biosensors Based on Directed Assembly of Nanomaterials with Functional DNA

    NASA Astrophysics Data System (ADS)

    Liu, Juewen; Lu, Yi

    This chapter reviews recent progress in the interface between functional nucleic acids and nanoscale science and technology, and its analytical applications. In particular, the use of metallic nanoparticles as the color reporting groups for the action (binding, catalysis, or both) of aptamers, DNAzymes, and aptazymes is described in detail. Because metallic nanoparticles possess high extinction coefficients and distance-dependent optical properties, they allow highly sensitive detections with minimal consumption of materials. The combination of quantum dots (QDs) with functional nucleic acids as fluorescent sensors is also described. The chapter starts with the design of colorimetric and fluorescent sensors responsive to single analytes, followed by sensors responsive to multiple analytes with controllable cooperativity and multiplex detection using both colorimetric and fluorescent signals in one pot, and ends by transferring solution-based detections into litmus paper type of tests, making them generally applicable and usable for a wide range of on-site and real-time analytical applications such as household tests, environmental monitoring, and clinical diagnostics.

  2. An organic indicator functionalized graphene oxide nanocomposite-based colorimetric assay for the detection of sarcosine

    NASA Astrophysics Data System (ADS)

    Xue, Zhonghua; Yin, Bo; Wang, Hui; Li, Mengqian; Rao, Honghong; Liu, Xiuhui; Zhou, Xinbin; Lu, Xiaoquan

    2016-03-01

    Rapid detection of sarcosine is a key requirement for both diagnosis and treatment of disease. We report here a simple yet sensitive colorimetric nanocomposite platform for rapid detection of sarcosine in alkaline media. The approach exploited the benefits of a rapid color-producing reaction between an organic indicator, 1,2-naphthoquinone-4-sulphonic acid sodium salt (NQS), and the analyte of sarcosine species as well as the good catalytic ability of graphene oxide (GO) to the formation of highly colored products due to its good water dispersibility, extremely large surface area and facile surface modification. As a result, a NQS functionalized GO nanocomposite through π-π stacking has been demonstrated to be useful as a highly efficient catalyst system for the selective and sensitive colorimetric determination of sarcosine by providing a nanocomposite-amplified colorimetric response. Meanwhile, the strategy offered excellent selectivity toward sarcosine species against other amino acids as well as a satisfying detection limit of 0.73 μM. More importantly, by using an electrochemical method, a credible sensing mechanism of GO nanocomposite-based colorimetric platform for a special analyte determination can be easily verified and elucidated, which also provides an attractive alternative to conventional characterization strategies.Rapid detection of sarcosine is a key requirement for both diagnosis and treatment of disease. We report here a simple yet sensitive colorimetric nanocomposite platform for rapid detection of sarcosine in alkaline media. The approach exploited the benefits of a rapid color-producing reaction between an organic indicator, 1,2-naphthoquinone-4-sulphonic acid sodium salt (NQS), and the analyte of sarcosine species as well as the good catalytic ability of graphene oxide (GO) to the formation of highly colored products due to its good water dispersibility, extremely large surface area and facile surface modification. As a result, a NQS functionalized GO nanocomposite through π-π stacking has been demonstrated to be useful as a highly efficient catalyst system for the selective and sensitive colorimetric determination of sarcosine by providing a nanocomposite-amplified colorimetric response. Meanwhile, the strategy offered excellent selectivity toward sarcosine species against other amino acids as well as a satisfying detection limit of 0.73 μM. More importantly, by using an electrochemical method, a credible sensing mechanism of GO nanocomposite-based colorimetric platform for a special analyte determination can be easily verified and elucidated, which also provides an attractive alternative to conventional characterization strategies. Electronic supplementary information (ESI) available: Raman characterization of GO, SEM images of GO and NQS/GO modified GCE with and without addition of sarcosine. The proposed reaction scheme of amines with NQS, electrochemical parameters of redox probe on different electrodes and at NQS/GO GCE with addition of different amount sarcosine. The solution colors of NQS/GO with sarcosine at different pH values and the competition experiments. See DOI: 10.1039/c6nr00005c

  3. Highly Sensitive Colorimetric Cancer Cell Detection Based on Dual Signal Amplification.

    PubMed

    Yu, Tao; Dai, Pan-Pan; Xu, Jing-Juan; Chen, Hong-Yuan

    2016-02-24

    Facile and efficient detection of cancer cells at their preclinical stages is one of the central challenges in cancer diagnostics. A direct, rapid, highly sensitive and specific biosensor for detection of cancer biomarkers is desirable in early diagnosis and prognosis of cancer. In this work, we developed, for the first time, an easy and intuitive dispersion-dominated colorimetric strategy for cancer cell detection based on combining multi-DNA released from an aptamer scaffold with cyclic enzymatic amplification, which was triggered by aptamer DNA conformational switch and demonstrated by non-cross-linking gold nanoparticles (Au NPs) aggregation. First, five kinds of messenger DNAs (mDNAs) were aligned on the cancer cell aptamers modified on magnetic beads (MBs) to form mDNAs-Apt-MBs biocompatible nanosensors. In the presence of target cells, the aptamer would bind to the receptors on the cell membranes, and mDNAs would be released, resulting in the first amplification that one biological binding event would cause the release of multiple kinds of mDNAs simultaneously. After magnetic separation, the released mDNAs were introduced into the cyclic enzymatic amplification to cleave more single strand DNA (ssDNA) fragments. Instead of modification of Au NPs, these fragments and mDNAs could be adsorbed on the surface of Au NPs to prevent particle aggregation and ensure the stability and color of solution in high salt environments. The linear response for HL-60 cells in a concentration range from 10 to 10(4) cells was obtained with a detection limit of four cells in buffer solution. Moreover, the feasibility of the proposed strategy was demonstrated in a diluted serum sample. This dual signal amplification method can be extended to other types of cancer cells, which has potential application in point-of-care cancer diagnosis. PMID:26824724

  4. ``Red-to-blue'' colorimetric detection of cysteine via anti-etching of silver nanoprisms

    NASA Astrophysics Data System (ADS)

    Li, Yonglong; Li, Zihou; Gao, Yuexia; Gong, An; Zhang, Yujie; Hosmane, Narayan S.; Shen, Zheyu; Wu, Aiguo

    2014-08-01

    The reported strategies for cysteine (Cys) colorimetric detection based on noble metal nanomaterials include triggering aggregation, etching or fluorescence quenching of nanomaterials by Cys. In this study, we propose a new strategy for Cys colorimetric detection, i.e. anti-etching of silver nanoprisms (AgNPRs). In the absence of Cys, iodide ions (I-) could etch the corners and edges of AgNPRs and induce the morphology transition from nanoprism to nanodisk, which results in color change of the AgNPR dispersion from blue to red. In its presence, however, Cys can prevent the AgNPRs from I- attack. In that case, the color of the AgNPR dispersion containing I- and Cys remains blue. The mechanism is confirmed by using UV-vis spectra, TEM, DLS, Raman spectra and XPS spectra. According to the sensing effect of the Cys detection system, the concentration of I- incubated with AgNPRs, incubation time of AgNPRs and I-, and pH of AgNPR dispersions are optimized to 5.0 ?M, 10 min, and pH 6.2, respectively. Under the optimized conditions, the proposed Cys detection system has excellent selectivity and high sensitivity. The limit of detection (LOD) of our Cys detection system is 25 nM by the naked eye, which is much better than the reported lowest LOD by eye-vision (100 nM), and 10 nM by UV-vis spectroscopy. The results of Cys detection in rabbit urine or plasma samples reinforce that our Cys detection system is applicable for rapid colorimetric detection of Cys in real body fluid samples.The reported strategies for cysteine (Cys) colorimetric detection based on noble metal nanomaterials include triggering aggregation, etching or fluorescence quenching of nanomaterials by Cys. In this study, we propose a new strategy for Cys colorimetric detection, i.e. anti-etching of silver nanoprisms (AgNPRs). In the absence of Cys, iodide ions (I-) could etch the corners and edges of AgNPRs and induce the morphology transition from nanoprism to nanodisk, which results in color change of the AgNPR dispersion from blue to red. In its presence, however, Cys can prevent the AgNPRs from I- attack. In that case, the color of the AgNPR dispersion containing I- and Cys remains blue. The mechanism is confirmed by using UV-vis spectra, TEM, DLS, Raman spectra and XPS spectra. According to the sensing effect of the Cys detection system, the concentration of I- incubated with AgNPRs, incubation time of AgNPRs and I-, and pH of AgNPR dispersions are optimized to 5.0 ?M, 10 min, and pH 6.2, respectively. Under the optimized conditions, the proposed Cys detection system has excellent selectivity and high sensitivity. The limit of detection (LOD) of our Cys detection system is 25 nM by the naked eye, which is much better than the reported lowest LOD by eye-vision (100 nM), and 10 nM by UV-vis spectroscopy. The results of Cys detection in rabbit urine or plasma samples reinforce that our Cys detection system is applicable for rapid colorimetric detection of Cys in real body fluid samples. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03309d

  5. Ultrasensitive colorimetric detection of Cu2+ ion based on catalytic oxidation of L-cysteine.

    PubMed

    Yin, Kun; Li, Bowei; Wang, Xiaochun; Zhang, Weiwei; Chen, Lingxin

    2015-02-15

    As an essential element, copper ion (Cu(2+)) plays important roles in human beings for its participation in diverse metabolic processes as a cofactor and/or a structural component of enzymes. However, excessive uptake of Cu(2+) ion gives rise to the risk of certain diseases. So, it is important to develop simple ways to monitor and detect Cu(2+) ion. In this study, a simple, facile colorimetric sensor for the ultrasensitive determination of Cu(2+) ion was developed based on the following principle: L-cysteine and 1-chloro-2,4-dinitrobenzene (CDNB) could be conjugated to form the yellow product 2,4-dinitrophenylcysteine (DNPC), which was measurable at 355nm; however, upon addition of Cu(2+) ion, the absorbance of DNPC would be decreased owing to the Cu(2+) ion catalytic oxidation of L-cysteine to L-cystine in the presence of O2. Thus, the colorimetric detection of Cu(2+) ion could be achieved. The optimal pH, buffer, temperature and incubation time for the colorimetric sensor were obtained of pH 6.8 in 0.1M HEPES solution, 90 C and 50 min, respectively. A good linearity within the range of 0.8-10 nM (r = 0.996) was attained, with a high detectability up to 0.5nM. Analyses of Cu(2+) ion in drinking water, lake water, seawater and biological samples were carried out and the method performances were found to agree well with that obtained by ICP-MS. The developed simple colorimetric sensor proved applicable for Cu(2+) ion determination in real samples with high sensitivity and selectivity. PMID:25194800

  6. "Red-to-blue" colorimetric detection of cysteine via anti-etching of silver nanoprisms.

    PubMed

    Li, Yonglong; Li, Zihou; Gao, Yuexia; Gong, An; Zhang, Yujie; Hosmane, Narayan S; Shen, Zheyu; Wu, Aiguo

    2014-09-21

    The reported strategies for cysteine (Cys) colorimetric detection based on noble metal nanomaterials include triggering aggregation, etching or fluorescence quenching of nanomaterials by Cys. In this study, we propose a new strategy for Cys colorimetric detection, i.e. anti-etching of silver nanoprisms (AgNPRs). In the absence of Cys, iodide ions (I(-)) could etch the corners and edges of AgNPRs and induce the morphology transition from nanoprism to nanodisk, which results in color change of the AgNPR dispersion from blue to red. In its presence, however, Cys can prevent the AgNPRs from I(-) attack. In that case, the color of the AgNPR dispersion containing I(-) and Cys remains blue. The mechanism is confirmed by using UV-vis spectra, TEM, DLS, Raman spectra and XPS spectra. According to the sensing effect of the Cys detection system, the concentration of I(-) incubated with AgNPRs, incubation time of AgNPRs and I(-), and pH of AgNPR dispersions are optimized to 5.0 ?M, 10 min, and pH 6.2, respectively. Under the optimized conditions, the proposed Cys detection system has excellent selectivity and high sensitivity. The limit of detection (LOD) of our Cys detection system is 25 nM by the naked eye, which is much better than the reported lowest LOD by eye-vision (100 nM), and 10 nM by UV-vis spectroscopy. The results of Cys detection in rabbit urine or plasma samples reinforce that our Cys detection system is applicable for rapid colorimetric detection of Cys in real body fluid samples. PMID:25083798

  7. Colorimetric chemosensor for multi-signaling detection of metal ions using pyrrole based Schiff bases

    NASA Astrophysics Data System (ADS)

    Udhayakumari, Duraisamy; Velmathi, Sivan

    2014-03-01

    Pyrrole based Schiff bases act as a highly sensitive probe for metal ions in aqueous medium. Both receptors R1 and R2 are sensitive towards Fe3+, Cu2+, Hg2+ and Cr3+ among the other metal ions. The sensing ability of the receptors are investigated via colorimetric, optical and emission spectroscopic studies. The binding stoichiometries of R1 and R2 with metal ions have been determined as 2:1 by using Job's plot. The colorimetric receptors exhibited high sensitivity with a low detection limit of ?M levels. In the presence of metal ions both receptors shows fluorescence quenching. This might be due to the photo induced electron transfer mechanism. The quenching constant was further determined using Stern-Volmer plot.

  8. Disassembly of a core-satellite nanoassembled substrate for colorimetric biomolecular detection.

    PubMed

    Waldeisen, John R; Wang, Tim; Ross, Benjamin M; Lee, Luke P

    2011-07-26

    The disassembly of a core-satellite nanostructured substrate is presented as a colorimetric biosensor observable under dark-field illumination. The fabrication method described herein utilizes thiol-mediated adsorption and streptavidin-biotin binding to self-assemble core-satellite nanostructures with a sacrificial linking peptide. Biosensing functionality is demonstrated with the protease trypsin, and the optical properties of the nanoassemblies are characterized. A figure of merit is presented to determine the optimal core and satellite size for visual detection. Nanoassemblies with 50 nm cores and 30 or 50 nm satellites are superior as these structures achieve an orange to green color shift greater than 70 nm that is easily discernible by the naked eye. This colorimetric substrate may prove to be a favorable alternative to liquid-based colloidal sensors and a useful visual readout mechanism for point-of-care microfluidic diagnostic assays. PMID:21667984

  9. A novel colorimetric assay for rapid detection of cysteine and Hg(2+) based on gold clusters.

    PubMed

    Wang, Yi-Wei; Tang, Shurong; Yang, Huang-Hao; Song, Hongbo

    2016-01-01

    Inhibition and recovery of the catalytic activity of bovine serum albumin-capped gold nanoclusters (BSA-AuNCs) is observed for the first time by introduction of cysteine and Hg(2+). The prepared BSA-AuNCs possess highly intrinsic peroxidase-like activity. It can catalyze the oxidation of 3, 3, 5, 5-tetramethylbenzidine by H2O2 to produce a blue colored product. Based on this phenomenon, a new colorimetric assay for rapid, selective and sensitive detection of cysteine and Hg(2+) in aqueous solution has been demonstrated. The interaction process between target molecule and BSA-AuNCs is very fast, so that the whole test can be completed within ten minutes. Moreover, the fabricated colorimetric sensor is simple and cost-effective, without the need of nucleic acid based recognition element and complicated washing, separation and labeling process, thus holds great promise for routine analysis of cysteine and Hg(2+) in real samples. PMID:26695236

  10. The Disassembly of a Core-Satellite Nanoassembled Substrate for Colorimetric Biomolecular Detection

    PubMed Central

    Waldeisen, John R.; Wang, Tim; Ross, Benjamin M.; Lee, Luke P.

    2012-01-01

    The disassembly of a core-satellite nanostructured substrate is presented as a colorimetric biosensor observable under dark field illumination. The fabrication method described herein utilizes thiol-mediated adsorption and streptavidin-biotin binding to self-assemble core-satellite nanostructures with a sacrificial linking peptide. Biosensing functionality is demonstrated with the protease trypsin and the optical properties of the nanoassemblies are characterized. A figure of merit is presented to determine the optimal core and satellite size for visual detection. Nanoassemblies with 50 nm cores and 30 nm or 50 nm satellites are superior as these structures achieve an orange to green color shift greater than 70 nm that is easily discernible by naked eye. This colorimetric substrate may prove to be a favorable alternative to liquid-based colloidal sensors and a useful visual readout mechanism for microfluidic diagnostic assays. PMID:21667984

  11. [Detection of viable metabolically active yeast cells using a colorimetric assay].

    PubMed

    Růzicka, F; Holá, V

    2008-02-01

    The increasing concern of yeasts able to form biofilm brings about the need for susceptibility testing of both planktonic and biofilm cells. Detection of viability or metabolic activity of yeast cells after exposure to antimicrobials plays a key role in the assessment of susceptibility testing results. Colorimetric assays based on the color change of the medium in the presence of metabolically active cells proved suitable for this purpose. In this study, the usability of a colorimetric assay with the resazurin redox indicator for monitoring the effect of yeast inoculum density on the reduction rate was tested. As correlation between the color change rate and inoculum density was observed, approximate quantification of viable cells was possible. The assay would be of relevance to antifungal susceptibility testing in both planktonic and biofilm yeasts. PMID:18318392

  12. A colorimetric indicator-displacement assay array for selective detection and identification of biological thiols.

    PubMed

    Qian, Sihua; Lin, Hengwei

    2014-03-01

    A simple, inexpensive yet highly selective colorimetric indicator-displacement assay array for the simultaneous detection and identification of three important biothiols at micromolar concentrations under physiological conditions and in real samples has been developed in this work. With use of an array composed of metal indicators and metal ions, clear differentiation among cysteine, homocysteine and glutathione was achieved. On the basis of the colour change of the array, quantification of each analyte was accomplished easily, and different biothiols were identified readily using standard chemometric approaches (hierarchical clustering analysis). Moreover, the colorimetric sensor array was not responsive to changes with 19 other natural amino acids, and it showed excellent reproducibility. Importantly, the sensor array developed was successfully applied to the determination and identification of the three biothiols in a real biological sample. PMID:24442012

  13. Highly sensitive and specific colorimetric detection of cancer cells via dual-aptamer target binding strategy.

    PubMed

    Wang, Kun; Fan, Daoqing; Liu, Yaqing; Wang, Erkang

    2015-11-15

    Simple, rapid, sensitive and specific detection of cancer cells is of great importance for early and accurate cancer diagnostics and therapy. By coupling nanotechnology and dual-aptamer target binding strategies, we developed a colorimetric assay for visually detecting cancer cells with high sensitivity and specificity. The nanotechnology including high catalytic activity of PtAuNP and magnetic separation & concentration plays a vital role on the signal amplification and improvement of detection sensitivity. The color change caused by small amount of target cancer cells (10 cells/mL) can be clearly distinguished by naked eyes. The dual-aptamer target binding strategy guarantees the detection specificity that large amount of non-cancer cells and different cancer cells (10(4) cells/mL) cannot cause obvious color change. A detection limit as low as 10 cells/mL with detection linear range from 10 to 10(5) cells/mL was reached according to the experimental detections in phosphate buffer solution as well as serum sample. The developed enzyme-free and cost effective colorimetric assay is simple and no need of instrument while still provides excellent sensitivity, specificity and repeatability, having potential application on point-of-care cancer diagnosis. PMID:26042871

  14. Colorimetric Detection Of Substances In Liquids And Gases

    NASA Technical Reports Server (NTRS)

    Harris, J. Milton; Mcgill, R. Andrew; Paley, Mark S.

    1992-01-01

    Thin polymer films containing solvatochromic dyes used as sensing elements to detect substances dissolved in liquids and gases. Dyes do not react with liquids in which dissolved, but do respond to changes in chemical compositions by changing color. Concentration determined visually by comparison of color with predetermined standard chart, or spectrophotometrically.

  15. Electrospun nanofiber based colorimetric probe for rapid detection of Fe2+ in water.

    PubMed

    Ondigo, D A; Tshentu, Z R; Torto, N

    2013-12-01

    An imidazole derivative, 2-(2'-pyridyl)imidazole (PIMH), was developed as a colorimetric probe for the qualitative analysis of Fe(2+) in aqueous solution. PIMH was then used to post-functionalize poly(vinylbenzyl chloride) (PVBC) nanofibers after electrospinning so as to afford a solid state colorimetric probe. Upon treatment with Fe(2+) the probe displayed a distinctive color change both in liquid and solid platforms. The linear dynamic range for the colorimetric determination of Fe(2+) was 0.0988-3.5 ?g mL(-1). The ligand showed a high chromogenic selectivity for Fe(2+) over other cations with a detection limit of 0.102 ?g mL(-1) in solution (lower than the WHO drinking water guideline limit of 2 mg L(-1)), and 2 ?g mL(-1) in the solid state. The concentration of Fe(2+) in a certified reference material (Iron, Ferrous, 1072) was found to be 2.390.01 mg L(-1), which was comparable with the certified value of 2.440.12 mg L(-1). Application of the probe to real samples spiked with Fe(2+) achieved recoveries of over 97% confirming accuracy of the method and its potential for on-site monitoring. PMID:24267086

  16. Optimization of Polydiacetylene-Coated Superparamagnetic Magnetite Biosensor for Colorimetric Detection of Biomarkers.

    PubMed

    Chan, Terence; Verma, Mohit S; Gu, Frank X

    2015-04-01

    Biosensors for point-of-care testing of critical illnesses are urgently needed, especially in many areas of poor healthcare infrastructure. Polydiacetylene-based sensors are ideal because of their unique colorimetric properties where blue to red color shifts can be observed with the naked eye. In this work, a colorimetric biosensor capable of simple, rapid magnetic separation is optimized, using horse IgG as a model antibody, to obtain higher sensitivity. Composed of a unique combination of polydiacetylene and superparamagnetic iron oxide, the biosensor is fabricated at varying ratios of polydiacetylene to demonstrate optimization of color responsiveness. At increasing polydiacetylene ratios, improved color responsiveness and aqueous dispersion are observed, but the magnetic separation efficiency starts to suffer. The optimal color response is obtained at 90 wt% polydiacetylene. In addition, a 50 times improved lower detection limit of 0.01 mg/mL horse IgG is achieved, a relevant biomarker concentration for diagnosing sepsis. This platform provides a promising colorimetric biosensor for point-of-care use. PMID:26353474

  17. Chloride accelerated Fenton chemistry for the ultrasensitive and selective colorimetric detection of copper.

    PubMed

    Shan, Zhi; Lu, Mingsheng; Wang, Li; MacDonald, Bruce; MacInnis, Judy; Mkandawire, Martin; Zhang, Xu; Oakes, Ken D

    2016-01-26

    A highly selective, ultrasensitive (visual and instrumental detection limits of 40 nM and 0.1 nM, respectively), environmentally-friendly, simple and rapid colorimetric sensor was developed for the detection of copper(ii) in water. This sensor is based on a novel signal-amplification mechanism involving reactive halide species (RHSs) including chlorides or bromides, which accelerate copper Fenton reactions oxidizing the chromogenic substrate to develop colour. The results of this study expand our understanding of copper-based Fenton chemistry. PMID:26685747

  18. Rapid microbial detection and enumeration using gel microdroplets and colorimetric or fluorescence indicator systems.

    PubMed Central

    Williams, G B; Weaver, J C; Demain, A L

    1990-01-01

    A new micromethod employing gel microdroplets (GMDs) and optical measurements can be used for rapid detection and enumeration of viable microorganisms (J. C. Weaver, G. B. Williams, A. M. Klibanov, and A. L. Demain, Bio/Technology 6:1084-1089, 1988) and has several potential applications in clinical microbiology. This method involves entrapping microorganisms in GMDs (10 to 100 microns in diameter) which are surrounded by a hydrophobic (low dielectric) fluid, subsequently distinguishing occupied and unoccupied GMDs with colorimetric or fluorescence indicators, counting both occupied and unoccupied GMDs, and applying Poisson statistical analysis. Acid-producing microorganisms were used to compare colorimetric and fluorescence pH indicator systems. Fluorescence systems were generally superior, particularly for detection before microbial growth occurred. Although colorimetric detection was reasonably fast for fast-growing microorganisms, significantly longer times were needed for slow-growing microorganisms. We investigated the dependence of the detection time on microbial division time, GMD size, and buffering capacity of the medium within GMDs. It was found possible to use a single preparation of GMDs, containing a range of GMD sizes, to simultaneously provide a viable enumeration of growing and nongrowing (e.g., stressed) cells. This was possible because small GMDs responded rapidly to both growing and nongrowing cells, while large GMDs, although slower, responded much more rapidly to growing cells than to nongrowing cells. Separate analysis of small and large GMDs in the same preparation yielded two enumerations, one of nongrowing cells and the other of growing cells. GMDs can also be used with conventional light microscopy to detect and enumerate fast-growing acid-producing bacteria much more quickly than conventional plating methods. PMID:2191001

  19. Prussian blue nanoparticles as peroxidase mimetics for sensitive colorimetric detection of hydrogen peroxide and glucose.

    PubMed

    Zhang, Weimin; Ma, Diao; Du, Jianxiu

    2014-03-01

    Prussian blue nanoparticles (PB NPs) exhibits an intrinsic peroxidase-like catalytic activity towards the hydrogen peroxide (H2O2)-mediated oxidation of classical peroxidase substrate 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt to produce a colored product. The catalysis follows Michaelis-Menen kinetics and shows strong affinity for H2O2. Using PB NPs as a peroxidase mimetics, a colorimetric method was developed for the detection of 0.05-50.0 ?M H2O2, with a detection limit of 0.031 ?M. When the catalytic reaction of PB NPs was coupled with the reaction of glucose oxidation catalyzed by glucose oxidase, a sensitive and selective colorimetric method for the detection of glucose was realized. The limit of detection for glucose was determined to be as low as 0.03 ?M and the linear range was from 0.1 ?M to 50.0 ?M. The method was successfully applied to the determination of glucose in human serum. Compared with other nanomaterials-based peroxidase mimetics, PB NPs provides 10-100 times higher sensitivity toward the detection of H2O2 and glucose. The detection platform developed showed great potential applications in varieties of physiological importance substances when merged with appropriate H2O2-producing oxidases. PMID:24468383

  20. Cationic Surfactant-Based Colorimetric Detection of Plasmodium Lactate Dehydrogenase, a Biomarker for Malaria, Using the Specific DNA Aptamer

    PubMed Central

    Lee, Seonghwan; Manjunatha, D H; Jeon, Weejeong; Ban, Changill

    2014-01-01

    A simple, sensitive, and selective colorimetric biosensor for the detection of the malarial biomarkers Plasmodium vivax lactate dehydrogenase (PvLDH) and Plasmodium falciparum LDH (PfLDH) was demonstrated using the pL1 aptamer as the recognition element and gold nanoparticles (AuNPs) as probes. The proposed method is based on the aggregation of AuNPs using hexadecyltrimethylammonium bromide (CTAB). The AuNPs exhibited a sensitive color change from red to blue, which could be seen directly with the naked eye and was monitored using UV-visible absorption spectroscopy and transmission electron microscopy (TEM). The reaction conditions were optimized to obtain the maximum color intensity. PvLDH and PfLDH were discernible with a detection limit of 1.25 pM and 2.94 pM, respectively. The applicability of the proposed biosensor was also examined in commercially available human serum. PMID:24992632

  1. Immunomagnetic capture and colorimetric detection of malarial biomarker Plasmodium falciparum lactate dehydrogenase.

    PubMed

    Markwalter, Christine F; Davis, Keersten M; Wright, David W

    2016-01-15

    We report a sensitive, magnetic bead-based colorimetric assay for Plasmodium falciparum lactate dehydrogenase (PfLDH) in which the biomarker is extracted from parasitized whole blood and purified based on antigen binding to antibody-functionalized magnetic particles. Antigen-bound particles are washed, and PfLDH activity is measured on-bead using an optimized colorimetric enzyme reaction (limit of detection [LOD]=21.10.4 parasites/?l). Enhanced analytical sensitivity is achieved by removal of PfLDH from the sample matrix before detection and elimination of nonspecific reductases and species that interfere with the optimal detection wavelength for measuring assay development. The optimized assay represents a simple and effective diagnostic strategy for P.falciparum malaria with time-to-result of 45min and detection limits similar to those of commercial enzyme-linked immunosorbent assay (ELISA) kits, which can take 4-6h. This method could be expanded to detect all species of malaria by switching the capture antibody on the magnetic particles to a pan-specific Plasmodium LDH antibody. PMID:26475567

  2. Centrifugal loop-mediated isothermal amplification microdevice for rapid, multiplex and colorimetric foodborne pathogen detection.

    PubMed

    Oh, Seung Jun; Park, Byung Hyun; Jung, Jae Hwan; Choi, Goro; Lee, Doh C; Kim, Do Hyun; Seo, Tae Seok

    2016-01-15

    We present a centrifugal microfluidic device which enables multiplex foodborne pathogen identification by loop-mediated isothermal amplification (LAMP) and colorimetric detection using Eriochrome Black T (EBT). Five identical structures were designed in the centrifugal microfluidic system to perform the genetic analysis of 25 pathogen samples in a high-throughput manner. The sequential loading and aliquoting of the LAMP cocktail, the primer mixtures, and the DNA sample solutions were accomplished by the optimized zigzag-shaped microchannels and RPM control. We targeted three kinds of pathogenic bacteria (Escherichia coli O157:H7, Salmonella typhimurium and Vibrio parahaemolyticus) and detected the amplicons of the LAMP reaction by the EBT-mediated colorimetric method. For the limit-of-detection (LOD) test, we carried out the LAMP reaction on a chip with serially diluted DNA templates of E. coli O157:H7, and could observe the color change with 380 copies. The used primer sets in the LAMP reaction were specific only to the genomic DNA of E. coli O157:H7, enabling the on-chip selective, sensitive, and high-throughput pathogen identification with the naked eyes. The entire process was completed in 60min. Since the proposed microsystem does not require any bulky and expensive instrumentation for end-point detection, our microdevice would be adequate for point-of-care (POC) testing with high simplicity and high speed, providing an advanced genetic analysis microsystem for foodborne pathogen detection. PMID:26322592

  3. A colorimetric and fluorescent probe for detecting intracellular GSH.

    PubMed

    Chen, Chunyang; Liu, Wei; Xu, Cong; Liu, Weisheng

    2015-09-15

    A new rapid and highly sensitive coumarin-based probe (probe 1) has been designed and synthesized for detecting intracellular GSH. Probe 1 was prepared from 4-methylumbelliferone using a 3-step procedure. It was converted into a latent fluorescence probe, which allowed it to achieve high sensitivity (LOD 122 nM) and fluorescence turn-on response (F/F0>15) toward GSH over other various natural amino acids in PBS buffer solution at pH 7.4. Owing to a specific Michael addition between thiols and the double bond of nitroolefin moiety, probe 1 displayed a high selectivity toward GSH. Afterwards, probe 1 was successfully used for fluorescence imaging of GSH in Hela and Hek-293a cells, and a rapid response was observed in the Hek-293a cells after incubating with probe 1 for 1 min. Simultaneously, a quantitative determination was achieved in Hela cells in the range of 8-48 μM. Specific fluorescence imaging of plants tissue was obtained for proving the permeability of probe 1. Finally, the viability was measured to be more than 80%, which shows probe 1 can serve as a rapid and biocompatible probe for GSH in cells. PMID:25889346

  4. Highly sensitive colorimetric sensor for Hg(2+) detection based on cationic polymer/DNA interaction.

    PubMed

    Zhu, Yingyue; Cai, Yilin; Zhu, Yibo; Zheng, Lixue; Ding, Jianying; Quan, Ying; Wang, Limei; Qi, Bin

    2015-07-15

    The detection of ultralow concentrations of mercury is a currently significant challenge. Here, a novel strategy is proposed: the colorimetric detection of Hg(2+) based on the aggregation of gold nanoparticles (AuNPs) driven by a cationic polymer. In this three-component system, DNA combines electrostatically with phthalic diglycol diacrylate (PDDA) in a solution of AuNPs. In the presence of Hg(2+), thymine (T)-Hg(2+)-T induced hairpin turns are formed in the DNA strands, which then do not interact with PDDA, enabling the freed PDDA to subsequently facilitate aggregation of the AuNPs. Thus, according to the change in color from wine-red to blue-purple upon AuNPs aggregation, a colorimetric sensor is established to detect Hg(2+). Under optimal conditions, the color change is clearly seen with the naked eye. A linear range of 0.25-500nM was obtained by absorption spectroscopy with a detection limit of approximately 0.15nM. Additionally, the proposed method shows high selectivity toward Hg(2+) in the presence of other heavy metal ions. Real sample analysis was evaluated with the use of lake water and the results suggest good potential for practical application. PMID:25727033

  5. Paper-based vapor detection of hydrogen peroxide: colorimetric sensing with tunable interface.

    PubMed

    Xu, Miao; Bunes, Benjamin R; Zang, Ling

    2011-03-01

    Vapor detection of hydrogen peroxide still remains challenging for conventional sensing techniques, though such vapor detection implies important applications in various practical areas, including locating IEDs. We report herein a new colorimetric sensor system that can detect hydrogen peroxide vapor down to parts per billion level. The sensory materials are based on the cellulose microfibril network of paper towels, which provide a tunable interface for modification with Ti(IV) oxo complexes for binding and reacting with H(2)O(2). The Ti(IV)-peroxide bond thus formed turns the complex from colorless to bright yellow with an absorption maximum around 400 nm. Such complexation-induced color change is exclusively selective for hydrogen peroxide, with no color change observed in the presence of water, oxygen, common organic reagents or other chelating reagents. This paper-based sensor material is disposable and one-time use, representing a cheap, simple approach to detect peroxide vapors. The reported sensor system also proves the technical feasibility of developing enhanced colorimetric sensing using nanofibril materials that will provide plenty of room to enlarge the surface area (by shrinking the fiber size), so as to enhance the surface interaction with gas phase. PMID:21355618

  6. A simple ratiometric and colorimetric chemosensor for the selective detection of fluoride in DMSO buffered solution.

    PubMed

    Niu, Hu; Shu, Qinghai; Jin, Shaohua; Li, Bingjun; Zhu, Jiaping; Li, Lijie; Chen, Shusen

    2016-01-15

    A derivative of squaramide (cyclobuta[b]quinoxaline-1, 2(3H, 8H)-dione) has been synthesized for the ratiometric and colorimetric sensing of F(-) in aqueous solution in competitive fashion. With F(-), probe 1 showed a highly selective naked-eye detectable color change along with a characteristic UV-Vis absorbance over other tested ions, which probably originates from the deprotonation occurred between 1 and F(-), as proved by the (1)H NMR titration experiments and DFT calculations. PMID:26311480

  7. Polydiacetylene-based colorimetric and fluorescent chemosensor for the detection of carbon dioxide.

    PubMed

    Xu, Qingling; Lee, Songyi; Cho, Yukyung; Kim, Myung Hwa; Bouffard, Jean; Yoon, Juyoung

    2013-11-27

    We developed a colorimetric and fluorescent turn-on carbon dioxide sensor that relies on a polydiacetylene, PDA-1, functionalized with amines and imidazolium groups. The pendant amines react with CO2 under basic conditions to form carbamoate anions, which partially neutralize the polymer's positive charges, inducing a phase transition. PDA-1 allows for the selective sensing of CO2 with high sensitivity, down to atmospheric concentrations. Naked-eye detection of CO2 is accomplished either in water solutions of PDA-1 or in the solid state with electrospun coatings of PDA-1 nanofibers. PMID:24195440

  8. Direct Quantification of Carotenoids in Low Fat Baby Foods Via Laser Photoacoustics and Colorimetric Index *

    NASA Astrophysics Data System (ADS)

    Dóka, O.; Ajtony, Zs.; Bicanic, D.; Valinger, D.; Végvári, Gy.

    2014-12-01

    Carotenoids are important antioxidants found in various foods including those for nutrition of infants. In this investigation, the total carotenoid content (TCC) of nine different commercially available baby foods was quantified using colorimetric index * obtained via reflectance colorimetry (RC) and by laser photoacoustic spectroscopy (LPAS) at 473 nm. The latter requires a minimum of sample preparation and only a one time calibration step which enables practically direct quantification of TCC. Results were verified versus UV-Vis spectrophotometry (SP) as the reference technique. It was shown that RC and LPAS (at 473 nm) provide satisfactory results for *, = 0.9925 and = 0.9972, respectively. Other color indices do not show a correlation with TCC. When determining the TCC in baby foods containing tomatoes, it is necessary to select a different analytical wavelength to compensate for the effect of lycopene's presence in the test samples.

  9. Direct colorimetric determination of formaldehyde in textile fabrics and other materials

    SciTech Connect

    Chrastil, J.; Reinhardt, R.M.

    1986-11-01

    A colorimetric method for direct determination of formaldehyde in textile fabrics and other materials is described. Color development and breaking formaldehyde bonds of the analyzed material occur simultaneously in the same reaction mixture without destruction of the material. The method is based on the color reaction of formaldehyde with indole-3-acetic acid or tryptophan. Common inorganic salts, higher aliphatic aldehydes, carbohydrates, amino acids (except tryptophan), and many other organic compounds do not react and do not interfere with the color reaction. Some interferences have been exhibited by acetaldehyde and glyoxal. The method was simple, accurate, and relatively insensitive to the reaction conditions. Only very small amounts of material are needed, and the reaction proceeds at room temperature. Different kinds of polymeric materials have been analyzed successfully (cotton, wool, plastics, collagen, wood, and furs). Most of the dyed fabrics or other materials could be analyzed in the same manner because under the reaction conditions the dyes were not extracted in the reaction mixture.

  10. Nucleic acid-coupled colorimetric analyte detectors

    DOEpatents

    Charych, Deborah H. (Albany, CA); Jonas, Ulrich (Mainz, DE)

    2001-01-01

    The present invention relates to methods and compositions for the direct detection of analytes and membrane conformational changes through the detection of color changes in biopolymeric materials. In particular, the present invention provide for the direct colorimetric detection of analytes using nucleic acid ligands at surfaces of polydiacetylene liposomes and related molecular layer systems.

  11. Single Gold Nanoparticle-Based Colorimetric Detection of Picomolar Mercury Ion with Dark-Field Microscopy.

    PubMed

    Liu, Xiaojun; Wu, Zhangjian; Zhang, Qingquan; Zhao, Wenfeng; Zong, Chenghua; Gai, Hongwei

    2016-02-16

    Mercury severely damages the environment and human health, particularly when it accumulates in the food chain. Methods for the colorimetric detection of Hg(2+) have increasingly been developed over the past decade because of the progress in nanotechnology. However, the limits of detection (LODs) of these methods are mostly either comparable to or higher than the allowable maximum level (10 nM) in drinking water set by the US Environmental Protection Agency. In this study, we report a single Au nanoparticle (AuNP)-based colorimetric assay for Hg(2+) detection in solution. AuNPs modified with oligonucleotides were fixed on the slide. The fixed AuNPs bound to free AuNPs in the solution in the presence of Hg(2+) because of oligonucleotide hybridization. This process was accompanied by a color change from green to yellow as observed under an optical microscope. The ratio of changed color spots corresponded with Hg(2+) concentration. The LOD was determined as 1.4 pM, which may help guard against mercury accumulation. The proposed approach was applied to environmental samples with recoveries of 98.3 7.7% and 110.0 8.8% for Yuquan River and industrial wastewater, respectively. PMID:26810926

  12. Simple colorimetric detection of doxycycline and oxytetracycline using unmodified gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Li, Jie; Fan, Shumin; Li, Zhigang; Xie, Yuanzhe; Wang, Rui; Ge, Baoyu; Wu, Jing; Wang, Ruiyong

    2014-08-01

    The interaction between tetracycline antibiotics and gold nanoparticles was studied. With citrate-coated gold nanoparticles as colorimetric probe, a simple and rapid detection method for doxycycline and oxytetracycline has been developed. This method relies on the distance-dependent optical properties of gold nanoparticles. In weakly acidic buffer medium, doxycycline and oxytetracycline could rapidly induce the aggregation of gold nanoparticles, resulting in red-to-blue (or purple) colour change. The experimental parameters were optimized with regard to pH, the concentration of the gold nanoparticles and the reaction time. Under optimal experimental conditions, the linear range of the colorimetric sensor for doxycycline/oxytetracycline was 0.06-0.66 and 0.59-8.85 ?g mL-1, respectively. The corresponding limit of detection for doxycycline and oxytetracycline was 0.0086 and 0.0838 ?g mL-1, respectively. This assay was sensitive, selective, simple and readily used to detect tetracycline antibiotics in food products.

  13. Colorimetric test-systems for creatinine detection based on composite molecularly imprinted polymer membranes.

    PubMed

    Sergeyeva, T A; Gorbach, L A; Piletska, E V; Piletsky, S A; Brovko, O O; Honcharova, L A; Lutsyk, O D; Sergeeva, L M; Zinchenko, O A; El'skaya, A V

    2013-04-01

    An easy-to-use colorimetric test-system for the efficient detection of creatinine in aqueous samples was developed. The test-system is based on composite molecularly imprinted polymer (MIP) membranes with artificial receptor sites capable of creatinine recognition. A thin MIP layer was created on the surface of microfiltration polyvinylidene fluoride (PVDF) membranes using method of photo-initiated grafting polymerization. The MIP layer was obtained by co-polymerization of a functional monomer (e.g. 2-acrylamido-2-methyl-1-propanesulfonic acid, itaconic acid or methacrylic acid) with N, N'-methylenebisacrylamide as a cross-linker. The choice of the functional monomer was based on the results of computational modeling. The creatinine-selective composite MIP membranes were used for measuring creatinine in aqueous samples. Creatinine molecules were selectively adsorbed by the MIP membranes and quantified using color reaction with picrates. The intensity of MIP membranes staining was proportional to creatinine concentration in an analyzed sample. The colorimetric test-system based on the composite MIP membranes was characterized with 0.25 mM detection limit and 0.25-2.5mM linear dynamic range. Storage stability of the MIP membranes was estimated as at least 1 year at room temperature. As compared to the traditional methods of creatinine detection the developed test-system is characterized by simplicity of operation, small size and low cost. PMID:23498699

  14. A novel colorimetric biosensor for monitoring and detecting acute toxicity in water.

    PubMed

    Zhai, Junfeng; Yong, Daming; Li, Jing; Dong, Shaojun

    2013-01-21

    This work presents a new colorimetric microorganism biosensor for monitoring and detecting acute toxicity in water, where prussian blue (PB) is used as the colorimetric indicator and E. coli as the model bacterial. In this biosensor, the electron mediator, ferricyanide, accepts electrons from E. coli during respiration to produce ferrocyanide, which subsequently reacts with ferric ions to yield PB, a famous material with a blue color. Since toxicants can inhibit the respiratory activity of E. coli and then reduce the ferrocyanide and consequent PB production, toxicity can be easily detected by measuring the decrease in the production of PB induced by toxicants. Three important toxicants, 3,5-dichlorophenol (DCP), As(3+), Cr(6+) are tested and the detection limits are 3.2, 25, and 3.2 ppm, respectively. Moreover, we could identify the yellow green to dark green color change by naked eye even at concentrations as low as 12.5 ppm for both DCP and Cr(6+). Subsequently, the acute toxicities of groundwater and south lake water are successfully determined by this sensor. This biosensor is rapid, sensitive and cost-effective, and can thus be regarded as a promising biosensor for giving an early warning of acute water toxicity. PMID:23187797

  15. Sensitive colorimetric detection of K(I) using catalytically active gold nanoparticles triggered signal amplification.

    PubMed

    Chen, Zhengbo; Tan, Lulu; Wang, Shaoxiong; Zhang, Yimeng; Li, Yonghui

    2016-05-15

    In this work, we report a simple, ultrasensitive, and feasible colorimetric assay for metal ion (K(+), used as a model) via inherent peroxidase-like enzymatic amplification strategy of gold nanoparticles (AuNPs). It is shown that peroxidase-like activity of AuNPs can be improved dramatically by its surface activation with target-specific aptamer molecules. Whereas when the target exists, the aptamers leave the surface of AuNPs in a target concentration-dependent manner, resulting in a decrease of the nanoenzymatic catalytic ability of AuNPs. Thus, K(+) can be quantified in the presence of AuNPs by using a colorimetric sensing probe (3,3',5,5'-tetramethylbenzidine). The color change of the solution is relevant to the dose of the target, and this can be achieved with the naked eyes and monitored by UV-vis spectrometry. A linear dependence between the absorbance and target K(+) concentration is obtained under optimal conditions in the range from 0. 1nM to 1μM with a detection limit (LOD) of 0.06nM estimated at the 3Sblank level. The sensitivity displays to be 2-9 orders of magnitude better than those of other K(+) detection methods. This sensing strategy may in principle be universally applicable for the detection of a range of environmental or biomedical molecules of interest. PMID:26774090

  16. A reversible competition colorimetric assay for the detection of biothiols based on ruthenium-containing complex.

    PubMed

    Hao, Yuanqiang; Xiong, Dandan; Wang, Liqiang; Chen, Wansong; Zhou, Binbin; Liu, You-Nian

    2013-10-15

    A novel reversible colorimetric sensor, which based on a competitive ligation of Hg(2+) by thiols, cysteine (Cys) or glutathione (GSH), and thiocyanate (SCN) on the N3 dye (bis(4,4'-dicarboxy-2,2'-bipyridine) dithiocyanato ruthenium (II)), was developed for the detection of biothiols. First, Hg(2+) ions coordinate to the sulfur atom of the dyes' SCN groups, and this interaction induces a change in color from red to yellow, owing to the formation of a complex of Hg(2+)-N3. Then, in the presence of biothiols, the red color of N3 is recovered concomitantly with the dissociation of the Hg(2+)-N3 complex, due to the extraction of Hg(2+) by biothiols. Thus the corresponding color variation in the process of the dissociation of the Hg(2+)-N3 complex can be employed for the quantitative detection of thiols using UV-vis spectroscopy. In particular, the transformation can be readily viewed with the naked eye. A good linear relationship between the change in absorbance (ΔAbs) of Hg(2+)-N3 at 461 nm and the thiol concentration was obtained in the range of 0.5-25 μM, and the detection limits are then calculated to be 57 and 52 nM for Cys and GSH, respectively. The proposed colorimetric assay displays a high selectivity for Cys over various other amino acids and GSSG (oxidized glutathione). PMID:24054588

  17. Ultra-rapid colorimetric assay for protease detection using magnetic nanoparticle-based biosensors.

    PubMed

    Suaifan, Ghadeer A R Y; Esseghaier, Chiheb; Ng, Andy; Zourob, Mohammed

    2013-07-01

    Sensitive protease detection methods often require time-consuming techniques and expensive instrumentation. To overcome this limitation, a novel, simple, sensitive and selective colorimetric detection approach was developed. This biosensing configuration was validated by the use of prostate specific antigen (PSA) protease as a model target. In this method, proteolytically active PSA capable of cleaving PSA substrates caused the release of black-colored magnetic carrier complexes, exposing the gold color sensor surface visible to the naked eye. The assay showed excellent sensitivity as well as specificity, capable of discriminating between different types of protease targets. The biosensor was able to quantitatively detect different PSA concentrations with a detection limit as low as 10 ng mL(-1). The sensor offers the possibility of developing a wash-less and cost-effective point-of-care device due to the simplicity of the probe immobilization process and the elimination of labeling and reporter molecules during the biosensing step. PMID:23676852

  18. Colorimetric detection of hepatitis B virus (HBV) DNA based on DNA-templated copper nanoclusters.

    PubMed

    Mao, Xiaoxia; Liu, Siyu; Yang, Chao; Liu, Fengzhen; Wang, Keming; Chen, Guifang

    2016-02-25

    DNA detection plays an important role in early diagnosis of genetic disease. The conventional detection methods of DNA are based on expensive equipment, which do not meet the demands of developing countries. Thus, we developed a colorimetric method, which could be observed with naked eye and used copper nanoclusters for cost-effective. Moreover, the target of this method is the DNA in Hepatitis B virus that is one of the most popular chronic viral infections in developing countries over the past years. Our method was sensitive and the limit of detection was 12 × 10(9) molecules. Three-base-pair mismatches target DNA was detected easily. These results revealed the favorable sensitivity and selectivity of this approach. Most importantly, our method may have potential applications in correct diagnosis of genetic disease and monitoring of gene therapy in the poverty-stricken areas. PMID:26851090

  19. Colorimetric detection of clinical DNA samples using an intercalator-conjugated polydiacetylene sensor.

    PubMed

    Jung, Yun Kyung; Park, Hyun Gyu

    2015-10-15

    We herein developed a novel colorimetric polydiacetylene (PDA) sensor for very convenient detection of clinical DNA samples based on the interaction between an intercalator and dsDNA. We modified the terminal carboxyl group of a diacetylene monomer (10,12-pentacosadiynoic acid; PCDA) with the intercalator 9-aminoacridine (9AA) and prepared 9AA-modified PDA liposomes containing PCDA-9AA/PCDA/phospholipid (1,2-dimyristoyl-rac-glycero-3-phosphocholine) at a molar ratio of 1.5:6.5:2.0. The PDA sensor underwent an obvious color transition from blue to red in the presence of dsDNA molecules that were PCR-amplified from genomic DNA due to the insertion of the 9AA head group of PDA into the dsDNA. DNA concentrations as low as 20 nM and relatively small molecules (around 100 base pairs) could be detected by the sensor within 1h without DNA electrophoresis. This novel colorimetric method is simple, does not require any instrument, and is therefore appropriate for POCT or portable molecular diagnostic kit. PMID:25978440

  20. Chemically-modified cellulose paper as smart sensor device for colorimetric and optical detection of hydrogen sulfate in water.

    PubMed

    Rull-Barrull, Jordi; d'Halluin, Martin; Le Grognec, Erwan; Felpin, Franois-Xavier

    2016-02-11

    A portable, recyclable and highly selective paper-based sensor device for the colorimetric and optical detection of hydrogen sulfate anions in water was developed. The detection system features a rhodamine-based sensor covalently grafted onto the highly hydrophilic surface of cellulose paper. PMID:26741398

  1. Nanomolar colorimetric quantitative detection of Fe(3+) and PPi with high selectivity.

    PubMed

    Li, Zhanxian; Li, Haixia; Shi, Caixia; Yu, Mingming; Wei, Liuhe; Ni, Zhonghai

    2016-04-15

    A novel rhodamine and 8-hydroxyquinoline-based derivative was synthesized, which is shown to act as a colorimetric chemosensor for Fe(3+) in aqueous solution with high selectivity over various environmentally and biologically relevant metal ions and anions with a distinct color change from colorless to pink in very fast response time (<1min). Fe(3+) can be detected quantitatively in the concentration range from 6.7 to 16μM and the detection limit (LOD) on UV-vis response of the sensor can be as low as 15nM. The 'in situ' prepared Fe(3+) complex (1⋅Fe) showed high selectivity toward PPi against many common anions, and sensitivity (the LOD can be as low as 71nM). In addition, both the chemosensor and the 'in situ' prepared Fe(3+) complex are reusable for the detection of Fe(3+) and PPi respectively. PMID:26878355

  2. Nanomolar colorimetric quantitative detection of Fe3 + and PPi with high selectivity

    NASA Astrophysics Data System (ADS)

    Li, Zhanxian; Li, Haixia; Shi, Caixia; Yu, Mingming; Wei, Liuhe; Ni, Zhonghai

    2016-04-01

    A novel rhodamine and 8-hydroxyquinoline-based derivative was synthesized, which is shown to act as a colorimetric chemosensor for Fe3 + in aqueous solution with high selectivity over various environmentally and biologically relevant metal ions and anions with a distinct color change from colorless to pink in very fast response time (< 1 min). Fe3 + can be detected quantitatively in the concentration range from 6.7 to 16 μM and the detection limit (LOD) on UV-vis response of the sensor can be as low as 15 nM. The 'in situ' prepared Fe3 + complex (1 ṡ Fe) showed high selectivity toward PPi against many common anions, and sensitivity (the LOD can be as low as 71 nM). In addition, both the chemosensor and the 'in situ' prepared Fe3 + complex are reusable for the detection of Fe3 + and PPi respectively.

  3. Colorimetric detection of DNA hybridization based on a dual platform of gold nanoparticles and graphene oxide.

    PubMed

    Thavanathan, Jeevan; Huang, Nay Ming; Thong, Kwai Lin

    2014-05-15

    The unique property of gold nanoparticles (Au NP) to induce colour change and the versatility of graphene oxides (GO) in surface modification makes them ideal in the application of colorimetric biosensor. Thus we developed a label free optical method to detect DNA hybridization through a visually observed colour change. The Au NP is conjugated to a DNA probe and is allowed to hybridize with the DNA target to the GO thus causing a change in colour from pinkish-red to purplish blue. Spectrophometry analysis gave a wavelength shift of 22 nm with 1 M of DNA target. Sensitivity testing using serially diluted DNA conjugated GO showed that the optimum detection was at 63 nM of DNA target with the limit at 8 nM. This proves the possibility for the detection of DNA hybridization through the use of dual nanoparticle system by visual observation. PMID:24368225

  4. Novel pyridyl based azo-derivative for the selective and colorimetric detection of nickel(II).

    PubMed

    Biswas, Sujan; Acharyya, Samik; Sarkar, Deblina; Gharami, Saswati; Mondal, Tapan Kumar

    2016-04-15

    A highly sensitive and selective pyridyl based colorimetric chemosensor (H2L) for the efficient detection of Ni(2+) has been reported. The synthesized chemosensor H2L is highly efficient in detecting Ni(2+) even in the presence of other metal ions that commonly co-exist with Ni(2+). H2L also shows distinct color change from green to deep red visible under naked eye due to specific binding with Ni(2+). This color change is due to formation of a new band at 510nm upon gradual addition of Ni(2+). The association constant has been found to be 1.27×10(5)M(-1) with limit of detection (LOD) of 8.3×10(-7)M. Electronic structure of the H2L-Ni(2+) complex and sensing mechanism have been interpreted theoretically by DFT and TDDFT calculations. PMID:26845582

  5. An Aptamer-Based Biosensor for Colorimetric Detection of Escherichia coli O157:H7

    PubMed Central

    Zhong, Yuhong; Yang, Jie; Zhao, Yuhong; Wu, Wenping; Ye, Wei; Wen, Jie; Wang, Qi; Lu, Jianxin

    2012-01-01

    Background An aptamer based biosensor (aptasensor) was developed and evaluated for rapid colorimetric detection of Escherichia coli (E. coli) O157:H7. Methodology/Principal Findings The aptasensor was assembled by modifying the truncated lipopolysaccharides (LPS)-binding aptamer on the surface of nanoscale polydiacetylene (PDA) vesicle using peptide bonding between the carboxyl group of the vesicle and the amine group of the aptamer. Molecular recognition between E. coli O157:H7 and aptamer at the interface of the vesicle lead to blue-red transition of PDA which was readily visible to the naked eyes and could be quantified by colorimetric responses (CR). Confocal laser scanning microscope (CLSM) and transmission electron microscopy (TEM) was used to confirm the specific interactions between the truncated aptamer and E. coli O157:H7. The aptasensor could detect cellular concentrations in a range of 104∼ 108 colony-forming units (CFU)/ml within 2 hours and its specificity was 100% for detection of E. coli O157:H7. Compared with the standard culture method, the correspondent rate was 98.5% for the detection of E. coli O157:H7 on 203 clinical fecal specimens with our aptasensor. Conclusions The new aptasensor represents a significant advancement in detection capabilities based on the combination of nucleic acid aptamer with PDA vesicle, and offers a specific and convenient screening method for the detection of pathogenic bacteria. This technic could also be applied in areas from clinical analysis to biological terrorism defense, especially in low-resource settings. PMID:23145045

  6. New function of exonuclease and highly sensitive label-free colorimetric DNA detection.

    PubMed

    Li, Hongbo; Wang, Suqin; Wu, Zaisheng; Xu, Jianguo; Shen, Guoli; Yu, Ruqin

    2016-03-15

    Enzymatic manipulation and modulation of nucleic acids are a central part of cellular function, protection, and reproduction, while rapid and accurate detection of ultralow amount of nucleic acids remains a major challenge in molecular biology research and clinic diagnosis of genetic diseases. Herein, we reported that exonuclease III can degrade the G-quadruplex structure, indicating the new exonuclease's function. Basing on the function of exonuclease III, a novel G-quadruplex-hemin DNAzyme-based colorimetric detection of tumor suppressor gene p53 was successfully developed. Although only one oligonucleotide probe was involved, the sensing strategy could suppress the optical background and achieve an efficient G-quadruplex-hemin DNAzyme-based signal amplification. Specifically, a label-free functional nucleic acid probe (called THzyme probe) was designed via introducing target DNA probe-contained hairpin structure into G-quadruplex DNAzyme. Even if this probe can fold into G-quadruplex structure in the presence of hemin very different from the double-stranded DNA, it is easily degraded by exonuclease III. Thus, no change in UV-vis absorption intensity is detected in the absence of target DNA. However, the hybridization of target DNA can protect the integrity and catalytic activity of THzyme probe, producing the DNAzyme-amplified colorimetric signal. As a result, the p53 gene was able to be detected down to 1.0 pM (final concentration in the signal-generating solution: 50.0 fM) and mismatched target DNAs were easily distinguished. It is expected that this simple sensing methodology for DNA detection can find its utility in point-of-care applications. PMID:26519729

  7. Ultrasensitive electrospun fluorescent nanofibrous membrane for rapid visual colorimetric detection of H2O2.

    PubMed

    Senthamizhan, Anitha; Balusamy, Brabu; Aytac, Zeynep; Uyar, Tamer

    2016-02-01

    We report herein a flexible fluorescent nanofibrous membrane (FNFM) prepared by decorating the gold nanocluster (AuNC) on electrospun polysulfone nanofibrous membrane for rapid visual colorimetric detection of H2O2. The provision of AuNC coupled to NFM has proven to be advantageous for facile and quick visualization of the obtained results, permitting instant, selective, and on-site detection. We strongly suggest that the fast response time is ascribed to the enhanced probabilities of interaction with AuNC located at the surface of NF. It has been observed that the color change from red to blue is dependent on the concentration, which is exclusively selective for hydrogen peroxide. The detection limit has been found to be 500 nM using confocal laser scanning microscope (CLSM), visually recognizable with good accuracy and stability. A systematic comparison was performed between the sensing performance of FNFM and AuNC solution. The underlying sensing mechanism is demonstrated using UV spectra, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The corresponding disappearance of the characteristic emissions of gold nanoclusters and the emergence of a localized surface plasmon resonance (LSPR) band, stressing this unique characteristic of gold nanoparticles. Hence, it is evident that the conversion of nanoparticles from nanoclusters has taken place in the presence of H2O2. Our work here has paved a new path for the detection of bioanalytes, highlighting the merits of rapid readout, sensitivity, and user-friendliness. Graphical Abstract Rapid visual colorimetric detection of H2O2. PMID:26637215

  8. Beetroot-Pigment-Derived Colorimetric Sensor for Detection of Calcium Dipicolinate in Bacterial Spores

    PubMed Central

    Gonalves, Letcia Christina Pires; Da Silva, Sandra Maria; DeRose, Paul C.; Ando, Rmulo Augusto; Bastos, Erick Leite

    2013-01-01

    In this proof-of-concept study, we describe the use of the main red beet pigment betanin for the quantification of calcium dipicolinate in bacterial spores, including Bacillus anthracis. In the presence of europium(III) ions, betanin is converted to a water-soluble, non-luminescent orange 1?1 complex with a stability constant of 1.4105 L mol1. The addition of calcium dipicolinate, largely found in bacterial spores, changes the color of the aqueous solution of [Eu(Bn)+] from orange to magenta. The limit of detection (LOD) of calcium dipicolinate is around 2.0106 mol L1 and the LOD determined for both spores, B. cereus and B. anthracis, is (1.10.3)106 spores mL1. This simple, green, fast and low cost colorimetric assay was selective for calcium dipicolinate when compared to several analogous compounds. The importance of this work relies on the potential use of betalains, raw natural pigments, as colorimetric sensors for biological applications. PMID:24019934

  9. A selectively fluorescein-based colorimetric probe for detecting copper(II) ion

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Zhang, Xianhong

    2014-12-01

    A novel fluorescein derivative 3-bromo-5-methylsalicylaldehyde fluorescein hydrazone (BMSFH) has been synthesized by reacting fluorescein hydrazide with 3-bromo-5-methylsalicylaldehyde and was developed as a new colorimetric probe for detection of Cu2+. In the presence of Cu2+ the BMSFH exhibits a rapid color change from colorless to yellow together with an obvious new band appeared at 502 nm in the UV-vis absorption spectra. However, other common alkali-, alkaline earth-, transition- and rare earth metal ions induced no or minimal spectral changes. This change is attributed to BMSFH via coordination with Cu2+ in a 1:1 stoichiometry and this binding to Cu2+ is reversible, as indicated by the bleaching of the color when the Cu2+ is extracted with EDTA. Experimental results indicate that the BMSFH can provide a rapid, selective and sensitive response to Cu2+ with a linear dynamic range 3.0-330 ?mol/L and can be used as a potential Cu2+ colorimetric probe in aqueous solution.

  10. Nylon 6-Gold Nanoparticle Composite Fibers for Colorimetric Detection of Urinary 1-Hydroxypyrene

    NASA Astrophysics Data System (ADS)

    Ifegwu, O. Clinton; Anyakora, C.; Torto, N.

    2015-05-01

    A one-step in situ synthesis of nylon 6 nanofibers filled with gold nanoparticles for the colorimetric probe of 1-hydroxypyrene, a biomarker associated with the largest class of cancer-causing chemical compounds polycyclic aromatic hydrocarbons (PAHs) is proposed in this study. The gold nanoparticles (AuNPs) were successfully embedded on the surface of the nylon 6 fibers where the gold particles were chemisorbed onto the amide groups in the nylon 6 backbones. By electrospinning the nylon 6/gold nanocomposite, the gold nanoparticles were uniformly dispersed on the polymer fibers to give a photostable reddish white fiber which turned purple/blue when brought in contact with a standard solution of the biomarker. The TEM revealed the formation of spherical AuNPs with an average diameter of 8 nm well arrayed within the nanofibers, but no significant change in the morphology of the nanofibers was observed. The thermal properties of the composite fibers were greatly improved compared to the electrospun nylon 6 fiber. The developed method described herein is simple, effective, requires no post-treatments, and is highly sensitive (100 ng/ml) hence the nanocomposite fibers can be employed as a test strip for the colorimetric detection of 1-hydroxypyrene in human urine or other diagnostic probe biosensors.

  11. A colorimetric and ratiometric fluorescent probe for selective detection and cellular imaging of glutathione.

    PubMed

    Xu, Chang; Li, Hongda; Yin, Bingzhu

    2015-10-15

    A new colorimetric and ratiometric fluorescent probe 1 based on a chlorinated coumarinyl aldehyde was developed for selective detection and cellular imaging of glutathione (GSH) over cysteine (Cys) and homocysteine (Hcy). Probe 1 exhibits a dramatic colorimetric and ratiometric fluorescence responses toward biothiols Cys, Hcy and GSH with high selectivity over other amino acids. Cys (or Hcy) induces a tandem SNAr-rearrangement reaction to form the corresponding amino-coumarins (2a or 2b), which result in about 75 nm and 35 nm blue-shifts in absorption and emission, respectively. By comparison, the thio-coumarin (3') derived from the SNAr reaction with GSH, which does not occur rearrangement because of steric hindrance, undergoes an intramolecular aldimine condensation lead to a cyclic iminium cation (3) with 47 nm and 39 nm red-shifts in absorption and emission, respectively. The significantly difference of photophysical properties enable excellent selectivity towards GSH over Cys and Hcy. Further application to cellular imaging indicates that the probe has appreciable cell permeability and is highly responsive to the changes of GSH level. As a result, it is applicable to monitor GSH level in living cells. PMID:25988996

  12. Colorimetric As (V) detection based on S-layer functionalized gold nanoparticles.

    PubMed

    Lakatos, Mathias; Matys, Sabine; Raff, Johannes; Pompe, Wolfgang

    2015-11-01

    Herein, we present simple and rapid colorimetric and UV/VIS spectroscopic methods for detecting anionic arsenic (V) complexes in aqueous media. The methods exploit the aggregation of S-layer-functionalized spherical gold nanoparticles of sizes between 20 and 50 nm in the presence of arsenic species. The gold nanoparticles were functionalized with oligomers of the S-layer protein of Lysinibacillus sphaericus JG-A12. The aggregation of the nanoparticles results in a color change from burgundy-red for widely dispersed nanoparticles to blue for aggregated nanoparticles. A detailed signal analysis was achieved by measuring the shift of the particle plasmon resonance signal with UV/VIS spectroscopy. To further improve signal sensitivity, the influence of larger nanoparticles was tested. In the case of 50 nm gold nanoparticles, a concentration of the anionic arsenic (V) complex lower than 24 ppb was detectable. PMID:26452816

  13. Colorimetric detection of melamine in milk by citrate-stabilized gold nanoparticles.

    PubMed

    Kumar, Naveen; Seth, Raman; Kumar, Harish

    2014-07-01

    Here, we report a simple and sensitive colorimetric method for detection of melamine in milk using gold nanoparticles (AuNPs). AuNPs of 21-nm size were synthesized by the citrate reduction method. The method is based on the principle that the melamine causes the aggregation of AuNPs and, hence, the wine red color of AuNPs changes to blue or purple. This change in color can be visualized with the naked eye or an ultraviolet-visible (UV-Vis) spectrometer. Under optimized conditions, AuNPs are highly specific for melamine and can detect melamine down to a concentration of 0.05 mg L(-1). PMID:24727351

  14. Naked-eye colorimetric and turn-on fluorometric chemosensors for reversible Hg2+ detection

    NASA Astrophysics Data System (ADS)

    Wanichacheva, Nantanit; Praikaew, Panida; Suwanich, Thanapat; Sukrat, Kanjarat

    2014-01-01

    Two new Hg2+-colorimetric and fluorescent sensors based on 2-[3-(2-aminoethylsulfanyl) propylsulfanyl]ethanamine covalently bound to one and two units of rhodamine-6G moieties, 1 and 2, were synthesised, and their sensing behaviors toward metal ions were investigated by UV/Vis and fluorescence spectroscopy. Upon the addition of Hg2+, the sensors exhibited highly sensitive turn-on fluorescence enhancement as well as a color change from colorless to pink, which was readily noticeable for naked eye detection. Especially, 1 exhibited the reversible behavior and revealed a very high selectivity in the presence of competitive ions, particularly Cu2+, Ag+, Pb2+, Ca2+, Cd2+, Co2+, Fe2+, Mn2+, Na+, Ni2+, K+, Ba2+, Li+ and Zn2+, with a low detection limit of 1.7 ppb toward Hg2+.

  15. Detection of meat-borne trimethylamine based on nanoporous colorimetric sensor arrays.

    PubMed

    Huang, Xiao-wei; Li, Zhi-hua; Zou, Xiao-bo; Shi, Ji-yong; Mao, Han-ping; Zhao, Jie-wen; Hao, Li-min; Holmes, Mel

    2016-04-15

    Trimethylamine (TMA) is a key measurement indicator for meat spoilage. In order to develop simple, cheap, and sensitive sensors for TMA detection, a nanoporous colorimetric sensor array (NCSA) was developed. A sol-gel method has been used to obtain TiO2 nanoporous film as substrate material to improve the sensitivity and stability of the CSA. The sensor enabled the visual detection of TMA gas from the permissible exposure limits (PEL) 10 ppm to 60 ppb concentrations with significant response. Principal component analysis (PCA) was used to characterize the functional relationship between the color difference data and TMA concentrations. Furthermore, the NCSA was used to predict the presence of TMA in Yao-meat. A partial least square (PLS) prediction model was obtained with the correlation coefficients of 0.896 and 0.837 in calibration and prediction sets, respectively. This research suggested that the NCSA offers a useful technology for quality evaluation of TMA in meat. PMID:26617036

  16. Sensitive and selective detection of cysteine using gold nanoparticles as colorimetric probes.

    PubMed

    Li, Li; Li, Baoxin

    2009-07-01

    We report herein the development of a highly sensitive and selective colorimetric detection method for cysteine using gold nanoparticles probes. This assay relies upon the distance-dependent optical properties of gold nanoparticles, the self-assembly of cysteine on gold nanoparticles, and the interaction of a 2:1 cysteine/Cu2+ complex. In the presence of Cu2+, cysteine could rapidly induce the aggregation of gold nanoparticles, thereby resulting in red-to-blue (or purple) color change. The concentration of cysteine can be determined by monitoring with the naked eye or a UV-vis spectrometer. The present limit of detection for cysteine is 10 nM. This method exhibits excellent selectivity for cysteine over other alpha-amino acids, glutathione, thioglycolic acid and mercaptoethyl alcohol. PMID:19562202

  17. Highly sensitive colorimetric detection of lead using maleic acid functionalized gold nanoparticles.

    PubMed

    Ratnarathorn, Nalin; Chailapakul, Orawon; Dungchai, Wijitar

    2015-01-01

    Highly sensitive colorimetric detection for Pb(2+) has been developed using maleic acid (MA) functionalized GNP. The -COOH on MA was used to modify GNP surface whereas the other -COOH functional group have strong affinity to coordination behavior of Pb(2+) allowing the selective formation more than other ions. MA-GNPs solution changed from red to blue color after the addition of Pb(2+) due to nanoparticle aggregation. The different optical absorption and discriminate of particle size between the MA-GNPs solution with and without Pb(2+) were characterized by UV-visible spectroscopy and transmission electron microscopy (TEM), respectively. The color intensity as a function of Pb(2+) concentration gave a linear response in the range of 0.0-10.0 g L(-1) (R(2)=0.990). The detection limit was found at 0.5 g L(-1) by naked eye and can be completed the analysis within 15 min. The MA-GNPs aggregated with Pb(2+) showed high selectivity when was compared to other metal ions (As(3+), Ca(2+), Cd(2+), Co(2+), Cu(2+), Fe(3+), Hg(2+), Mg(2+), Mn(2+), Ni(2+), Pb(2+) and Zn(2+)) and anions (Cl(-), NO3(-) and SO4(2-)). Our proposed method was also applied for the determination of Pb(2+) in real drinking water samples from 5 sources. The result of real water samples were not statistically significant different from the standard methods at the 95% confidence level (pair t-test method). Moreover, we evaluated our proposed method for the determination of trace Pb(2+) concentration in real breast milk samples. The recoveries were acceptable and ranged from 101 to 104% for spiked Pb(2+) in real breast milk samples. Thus, MA-GNP colorimetric sensing provides a simple, rapid, sensitive, easy-to-use, inexpensive and low detection limit for the monitoring of Pb(2+). PMID:25476352

  18. A fast, sensitive and easy colorimetric assay for chitinase and cellulase activity detection

    PubMed Central

    2014-01-01

    Background Most of the current colorimetric methods for detection of chitinase or cellulase activities on the insoluble natural polymers chitin and cellulose depend on a chemical redox reaction. The reaction involves the reducing ends of the hydrolytic products. The Schales procedure and the 3,5-dinitrosalicylic acid (DNS) method are two examples that are commonly used. However, these methods lack sensitivity and present practical difficulties of usage in high-throughput screening assays as they require boiling or heating steps for color development. Results We report a novel method for colorimetric detection of chitinase and cellulase activity. The assay is based on the use of two oxidases: wild-type chito-oligosaccharide oxidase, ChitO, and a mutant thereof, ChitO-Q268R. ChitO was used for chitinase, while ChitO-Q268R was used for cellulase activity detection. These oxidases release hydrogen peroxide upon the oxidation of chitinase- or cellulase-produced hydrolytic products. The hydrogen peroxide produced can be monitored using a second enzyme, horseradish peroxidase (HRP), and a chromogenic peroxidase substrate. The developed ChitO-based assay can detect chitinase activity as low as 10 ?U within 15minutes of assay time. Similarly, cellulase activity can be detected in the range of 6 to 375mU. A linear response was observed when applying the ChitO-based assay for detecting individual chito-oligosaccharides and cello-oligosaccharides. The detection limits for these compounds ranged from 5 to 25?M. In contrast to the other commonly used methods, the Schales procedure and the DNS method, no boiling or heating is needed in the ChitO-based assays. The method was also evaluated for detecting hydrolytic activity on biomass-derived substrates, that is, wheat straw as a source of cellulose and shrimp shells as a source of chitin. Conclusion The ChitO-based assay has clear advantages for the detection of chitinase and cellulase activity over the conventional Schales procedure and DNS method. The detection limit is lower and there is no requirement for harsh conditions for the development of the signal. The assay also involves fewer and easier handling steps. There is no need for boiling to develop the color and results are available within 15minutes. These aforementioned features render this newly developed assay method highly suitable for applications in biorefinery-related research. PMID:24612932

  19. New colorimetric screening assays for the directed evolution of fungal laccases to improve the conversion of plant biomass

    PubMed Central

    2013-01-01

    Background Fungal laccases are multicopper oxidases with huge applicability in different sectors. Here, we describe the development of a set of high-throughput colorimetric assays for screening laccase libraries in directed evolution studies. Results Firstly, we designed three colorimetric assays based on the oxidation of sinapic acid, acetosyringone and syringaldehyde with λmax of 512, 520 and 370 nm, respectively. These syringyl-type phenolic compounds are released during the degradation of lignocellulose and can act as laccase redox mediators. The oxidation of the three compounds by low and high-redox potential laccases evolved in Saccharomyces cerevisiae produced quantifiable and linear responses, with detection limits around 1 mU/mL and CV values below 16%. The phenolic substrates were also suitable for pre-screening mutant libraries on solid phase format. Intense colored-halos were developed around the yeast colonies secreting laccase. Furthermore, the oxidation of violuric acid to its iminoxyl radical (λmax of 515 nm and CV below 15%) was devised as reporter assay for laccase redox potential during the screening of mutant libraries from high-redox potential laccases. Finally, we developed three dye-decolorizing assays based on the enzymatic oxidation of Methyl Orange (470 nm), Evans Blue (605 nm) and Remazol Brilliant Blue (640 nm) giving up to 40% decolorization yields and CV values below 18%. The assays were reliable for direct measurement of laccase activity or to indirectly explore the oxidation of mediators that do not render colored products (but promote dye decolorization). Every single assay reported in this work was tested by exploring mutant libraries created by error prone PCR of fungal laccases secreted by yeast. Conclusions The high-throughput screening methods reported in this work could be useful for engineering laccases for different purposes. The assays based on the oxidation of syringyl-compounds might be valuable tools for tailoring laccases precisely enhanced to aid biomass conversion processes. The violuric assay might be useful to preserve the redox potential of laccase whilst evolving towards new functions. The dye-decolorizing assays are useful for engineering ad hoc laccases for detoxification of textile wastewaters, or as indirect assays to explore laccase activity on other natural mediators. PMID:24159930

  20. A novel polymeric chemosensor: dual colorimetric detection of metal ions through click synthesis.

    PubMed

    Li, Yongrong; Ashizawa, Minoru; Uchida, Satoshi; Michinobu, Tsuyoshi

    2011-11-15

    A highly colored polystyrene derivative bearing side chain chromophores composed of dialkylanilino donor and cyano-based acceptor groups, prepared by atom-economic click postfunctionalization, displays the dual colorimetric detection behavior of several metal ions based on the specific interactions with different nitrogen atoms. Hard to borderline metal ions, such as Fe(3+) , Fe(2+) , and Sn(2+) , are always recognized by the dialkylanilino nitrogen atom, resulting in a decrease in the charge-transfer (CT) band intensity of the donor-acceptor chromophores. On the other hand, the recognition site of a soft metal ion of Ag(+) is the cyano nitrogen atom due to the readily formed multivalent coordination, which produces a bathochromic shift of the CT band. PMID:21905148

  1. Bio-functionalized silver nanoparticles: a novel colorimetric probe for cysteine detection.

    PubMed

    Borase, Hemant P; Patil, Chandrashekhar D; Salunkhe, Rahul B; Suryawanshi, Rahul K; Kim, Beom S; Bapat, Vishwas A; Patil, Satish V

    2015-04-01

    Chemical interactions between nanoparticles and biomolecules are vital for applying nanoparticles in medicine and life science. Development of sensitive, rapid, low-cost, and eco-friendly sensors for the detection of molecules acting as disease indicator is need of an hour. In the present investigation, a green trend for silver nanoparticle synthesis was followed using leaf extract of Calotropis procera. Silver nanoparticles exhibited surface plasmon absorption peak at 421 nm, spherical shape with average size of 10 nm, and zeta potential of -22.4 mV. The as-synthesized silver nanoparticles were used for selective and sensitive detection of cysteine. Cysteine induces aggregation in stable silver nanoparticles owing to selective and strong interaction of -SH group of cysteine with silver nanoparticle surface. Cysteine-induced silver nanoparticle aggregation can be observed visually by change in color of silver nanoparticles from yellow to pink. Cysteine concentration was estimated colorimetrically by measuring absorption at surface plasmon wavelength. Limit of detection for cysteine using silver nanoparticles is ultralow, i.e., 100 nM. The mechanistic insight into cysteine detection by silver nanoparticles was investigated using FT-IR, TEM, DLS, and TLC analysis. Proposed method can be applied for the detection of cysteine in blood plasma and may give rise to a new insight into development of eco-friendly fabricated nanodiagnostic device in future. PMID:25637511

  2. Colorimetric detection of melamine based on methanobactin-mediated synthesis of gold nanoparticles.

    PubMed

    Xin, Jia-ying; Zhang, Lan-xuan; Chen, Dan-dan; Lin, Kai; Fan, Hong-chen; Wang, Yan; Xia, Chun-gu

    2015-05-01

    A simple and rapid field-portable colorimetric method for the detection of melamine in liquid milk was reported. Methanobactin (Mb) could reduce Au (III) to Au (0) and mediate the synthesis of gold nanoparticles (Au-NPs). Upon the addition of melamine, melamine interacted with oxazolone ring of Mb, which interrupted the formation of Au-NPs. Melamine could also stimulate the aggregation of formed Au-NPs. In this paper, these characteristics have been used to detect melamine in liquid milk by naked eyes observation with a detection limit of 5.56 10(-6)M (0.7 mg/kg). Further, the plasmon absorbance of the formed Au-NPs allowed the quantitative detection of melamine by UV-vis spectrometer. A linear correlation was existed between the absorbance and the melamine concentration ranging from 3.90 10(-7)M to 3.97 10(-6)M with a correlation coefficient of 0.9685. The detection limit (3?) obtained by UV-vis spectrum was as low as 2.38 10(-7)M (i.e., 0.03 mg/kg). PMID:25529708

  3. Detection of mercury(II) ions using colorimetric gold nanoparticles on paper-based analytical devices.

    PubMed

    Chen, Guan-Hua; Chen, Wei-Yu; Yen, Yu-Chun; Wang, Chia-Wei; Chang, Huan-Tsung; Chen, Chien-Fu

    2014-07-15

    An on-field colorimetric sensing strategy employing gold nanoparticles (AuNPs) and a paper-based analytical platform was investigated for mercury ion (Hg(2+)) detection at water sources. By utilizing thymine-Hg(2+)-thymine (T-Hg(2+)-T) coordination chemistry, label-free detection oligonucleotide sequences were attached to unmodified gold nanoparticles to provide rapid mercury ion sensing without complicated and time-consuming thiolated or other costly labeled probe preparation processes. Not only is this strategy's sensing mechanism specific toward Hg(2+), rather than other metal ions, but also the conformational change in the detection oligonucleotide sequences introduces different degrees of AuNP aggregation that causes the color of AuNPs to exhibit a mixture variance. To eliminate the use of sophisticated equipment and minimize the power requirement for data analysis and transmission, the color variance of multiple detection results were transferred and concentrated on cellulose-based paper analytical devices, and the data were subsequently transmitted for the readout and storage of results using cloud computing via a smartphone. As a result, a detection limit of 50 nM for Hg(2+) spiked pond and river water could be achieved. Furthermore, multiple tests could be performed simultaneously with a 40 min turnaround time. These results suggest that the proposed platform possesses the capability for sensitive and high-throughput on-site mercury pollution monitoring in resource-constrained settings. PMID:24932699

  4. Colorimetric-based detection of TNT explosives using functionalized silica nanoparticles.

    PubMed

    Idros, Noorhayati; Ho, Man Yi; Pivnenko, Mike; Qasim, Malik M; Xu, Hua; Gu, Zhongze; Chu, Daping

    2015-01-01

    This proof-of-concept study proposes a novel sensing mechanism for selective and label-free detection of 2,4,6-trinitrotoluene (TNT). It is realized by surface chemistry functionalization of silica nanoparticles (NPs) with 3-aminopropyl-triethoxysilane (APTES). The primary amine anchored to the surface of the silica nanoparticles (SiO2-NH2) acts as a capturing probe for TNT target binding to form Meisenheimer amine-TNT complexes. A colorimetric change of the self-assembled (SAM) NP samples from the initial green of a SiO2-NH2 nanoparticle film towards red was observed after successful attachment of TNT, which was confirmed as a result of the increased separation between the nanoparticles. The shift in the peak wavelength of the reflected light normal to the film surface and the associated change of the peak width were measured, and a merit function taking into account their combined effect was proposed for the detection of TNT concentrations from 10-12 to 10-4 molar. The selectivity of our sensing approach is confirmed by using TNT-bound nanoparticles incubated in AptamerX, with 2,4-dinitrotoluene (DNT) and toluene used as control and baseline, respectively. Our results show the repeatable systematic color change with the TNT concentration and the possibility to develop a robust, easy-to-use, and low-cost TNT detection method for performing a sensitive, reliable, and semi-quantitative detection in a wide detection range. PMID:26046595

  5. G-quadruplex based two-stage isothermal exponential amplification reaction for label-free DNA colorimetric detection.

    PubMed

    Nie, Ji; Zhang, De-Wen; Tie, Cai; Zhou, Ying-Lin; Zhang, Xin-Xiang

    2014-06-15

    A novel G-quadruplex based two-stage isothermal exponential amplification reaction (GQ-EXPAR) was developed for label-free DNA colorimetric detection in this work. The exponential amplified trigger DNA in the first stage can convert into G-quadruplex sequence EAD2 by a linear amplification circuit in the second stage. Created EAD2 can form G-quadruplex/hemin DNAzyme to act as a direct signal readout element. The GQ-EXPAR combines the exponential amplification of DNA sequence and the peroxidase-mimicking DNAzyme induced signal amplification, which achieves tandem dual-amplification. Taking advantages of isothermal incubation, this label-free homogeneous assay obviates the need of thermal cycling . As no complex synthesis or extra downstream operation is needed, the whole easy handling procedure can be finished in no more than 1h. This assay allows the sensing of the model DNA with the limit of detection to be 2.5pM. Moreover, it demonstrates good discrimination of mismatched sequences. The strategy has also been successfully implemented to sensitively detect Tay-Sachs genetic disorder mutant. PMID:24508547

  6. Fenton reaction-based colorimetric immunoassay for sensitive detection of brevetoxin B.

    PubMed

    Lai, Wenqiang; Wei, Qiaohua; Zhuang, Junyang; Lu, Minghua; Tang, Dianping

    2016-06-15

    We designed a new colorimetric immunoassay for sensitive monitoring of brevetoxin B (BTB) using enzyme-controlled Fenton reaction with a high-resolution 3,3',5,5'-tetramethylbenzidine (TMB)-based visual colored system. Upon addition of hydrogen peroxide (H2O2), the equivalent iron(II) could be first converted into iron(III) and free hydroxyl radical (•OH) via the classical Fenton reaction. Then the as-produced iron(III) and •OH could cause a perceptible change from colorless to blue with the increasing H2O2 concentration in the presence of TMB. Based on Fenton reaction-triggered visual colored system, a novel competitive-type colorimetric enzyme immunoassay was developed for the quantitative screening of target BTB on the bovine serum albumin-BTB-modified magnetic bead using glucose oxidase/anti-BTB antibody-labeled gold nanoparticle as the signal-transduction tag. Upon target BTB introduction, the analyte competed with the conjugated BTB on the magnetic bead for anti-BTB antibody on gold nanoparticle. The carried glucose oxidase with the gold nanoparticle could implement the oxidation of glucose to produce H2O2, and the generated H2O2 promoted the above-mentioned Fenton reaction for color development. Under the optimal conditions, the absorbance decreased with the increasing target BTB in the range from 0.1 to 150ngkg(-1) with a low detection limit (LOD) of 0.076ngkg(-1). The LOD was 500-fold lower than that of commercialized Abraxis BTB ELISA kit. Non-specific adsorption was not observed. The precision, reproducibility and specificity were acceptable. Finally, the method accuracy was also validated for monitoring spiked seafood samples, giving results well matched with the referenced brevetoxin ELISA kit. PMID:26851583

  7. Colorimetric Assay for the Detection of Typical Biomarkers for Periodontitis Using a Magnetic Nanoparticle Biosensor.

    PubMed

    Wignarajah, Shayalini; Suaifan, Ghadeer A R Y; Bizzarro, Sergio; Bikker, Floris J; Kaman, Wendy E; Zourob, Mohammed

    2015-12-15

    Periodontitis is a chronic disease which affects at least 10% of the population. If untreated, periodontitis can lead to teeth loss. Unfortunately, current diagnostic tests are limited in their sensitivity and specificity. In this study, a novel multiplex hand-held colorimetric diagnostic biosensor, using two typical inflammatory salivary biomarkers, Human Neutrophil Elastase (HNE) and Cathepsin-G, was constructed as proof of concept to potentially detect periodontitis. The biosensing method was based on the measurement of proteolytic activity using specific proteases probes. These probes consist of specific proteases substrates covalently bound to a magnetic bead from one end and to the gold sensor surface by the other end. When intact, this renders the golden sensor black. Upon proteolysis, the cleaved magnetic beads will be attracted by an external magnet revealing the golden color of the sensor surface observable by the naked eye. The biosensor was capable of specific and quantitative detection of HNE and Cathepsin-G in solution and in spiked saliva samples with a lower detection limit of 1 pg/mL and 100 fg/mL for HNE and Cathepsin-G, respectively. Examination of periodontitis patients' sample and a healthy control showed the potential of the multiplex biosensor to detect the presence of HNE and Cathepsin-G activity in situ. This approach is anticipated to be a useful biochip array amenable to low-cost point-of-care devices. PMID:26631371

  8. Gold nanoparticle-based colorimetric aptasensor for rapid detection of six organophosphorous pesticides.

    PubMed

    Bai, Wenhui; Zhu, Chao; Liu, Jinchuan; Yan, Mengmeng; Yang, Shuming; Chen, Ailiang

    2015-10-01

    Fast immunoassay-based screening methods are unavailable for most small-molecule pesticides because of a lack of immunogenicity and the difficulty in obtaining antibodies by animal immunization. Aptamers are single-stranded DNA molecules selected through an in vitro process, which can bind to any target including nonimmunogenic small molecules with high affinity and specificity. Although various aptamer-based sensing methods have been developed for antibiotics, microorganisms, heavy metal ions, and biotoxins, there are few reports on aptamer-based methods for quick detection of organophosphorous pesticides. The gold (Au) nanoparticle (AuNP) colorimetric assay is a widely utilized rapid detection method because of properties such as easy operation and visualized results. In the present study, organophosphorous pesticide aptamers were adsorbed on the surface of AuNPs to stabilize the AuNP solution against high concentrations of salt to prevent AuNP aggregation. After the addition of targets, the aptamers binding to the targets are detached from the AuNPs, resulting in aggregation of AuNPs and a color change from red to purple-blue. The proposed method can detect 6 organophosphorous pesticides with good recoveries from 72% to 135% in environmental river water samples. The present study provides a new way for simple, rapid, and multiplex detection of organophosphorous pesticides. PMID:26031388

  9. A novel colorimetric triple-helix molecular switch aptasensor for ultrasensitive detection of tetracycline.

    PubMed

    Ramezani, Mohammad; Mohammad Danesh, Noor; Lavaee, Parirokh; Abnous, Khalil; Mohammad Taghdisi, Seyed

    2015-08-15

    Detection methods of antibiotic residues in blood serum and animal derived foods are of great interest. In this study a colorimetric aptasensor was designed for sensitive, selective and fast detection of tetracycline based on triple-helix molecular switch (THMS) and gold nanoparticles (AuNPs). As a biosensor, THMS shows distinct advantages including high stability, sensitivity and preserving the selectivity and affinity of the original aptamer. In the absence of tetracycline, THMS is stable, leading to the aggregation of AuNPs by salt and an obvious color change from red to blue. In the presence of tetracycline, aptamer binds to its target, signal transduction probe (STP) leaves the THMS and adsorbs on the surface of AuNPs. So the well-dispersed AuNPs remain stable against salt-induced aggregation with a red color. The presented aptasensor showed high selectivity toward tetracyclines with a limit of detection as low as 266 pM for tetracycline. The designed aptasensor was successfully applied to detect tetracycline in serum and milk. PMID:25814407

  10. Novel core etching technique of gold nanoparticles for colorimetric dopamine detection.

    PubMed

    Lee, Ho-Cheng; Chen, Tzu-Heng; Tseng, Wei-Lung; Lin, Che-Hsin

    2012-11-21

    This study develops a novel and high performance colorimetric probe for dopamine (DA) detection. Aqueous-phase gold nanoparticles (AuNPs) extracted with 4-(dimethylamino)pyridine (DMAP) from toluene solvent are used as the reaction probes. The original AuNPs of diameter around 13 nm separate into 2-5 nm sizes when dopamine (DA) is added, resulting in the color change of the AuNP solution from red to blackish green. Transmission electron microscopy (TEM) observations and dynamic light scattering (DLS) tests show that the AuNPs break into their smaller sizes right after addition of DA. The results confirm that the DMAP capped AuNPs are etched by the DA molecules due to the strong affinity between DA and AuNPs, thus causing a blue shift in the absorption spectrum. The concentration of DA is quantitatively monitored by using a UV-Vis spectrometer with a limit of detection (LOD) as low as 5 nM. In addition, the results also show that the methods developed appear to have no significant problems in detecting DA in the sample even with the presence of (10 mM) common interferents such as ascorbic acid (AA), homovanillic acid (HVA), catechol (CA) and glutathione (GSH). The developed AuNP etching protocol for dopamine detection provides a novel and versatile approach for rapid biosensing applications. PMID:23016153

  11. Aptamer-based Colorimetric and Chemiluminescence Detection of Aflatoxin B1 in Foods Samples.

    PubMed

    Hosseini, Morteza; Khabbaz, Hossein; Dadmehr, Mehdi; Ganjali, Mohammad Reza; Mohamadnejad, Javad

    2015-01-01

    We developed a new biosensor for the detection of aflatoxin B1(AFB1) based on the interaction of gold nanoparticles (AuNPs) with the aptamer. Aggregation of AuNPs was induced by desorption of the AFB1 binding aptamer from the surface of AuNPs as a result of the aptamer target interaction leading to the color change of AuNPs from red to purple. The linear range of the colorimetric aptasensor covered a large variation of AFB1 concentrations from 80 to 270 nM and the detection limit of 7 nM was obtained. Also, the catalytic activity of the aggregated AuNPs greatly enhanced the chemiluminescence (CL) reaction, where the detection limit was determined at 0.5 nM with a regression coefficient of R(2) = 0.9921. We have also shown that the sensitivity of detection was increased by employing CL and using the catalytic activity of aggregated AuNPs, during luminol-hydrogen peroxide reaction. Therefore the proposed nanobiosensor was demonstrated to be sensitive, selective, and simple, introducing a viable alternative for rapid screening of toxin in foods. PMID:26466094

  12. Colorimetric Detection of Some Highly Hydrophobic Flavonoids Using Polydiacetylene Liposomes Containing Pentacosa-10,12-diynoyl Succinoglycan Monomers

    PubMed Central

    Yun, Deokgyu; Jeong, Daham; Cho, Eunae; Jung, Seunho

    2015-01-01

    Flavonoids are a group of plant secondary metabolites including polyphenolic molecules, and they are well known for antioxidant, anti-allergic, anti-inflammatory and anti-viral propertied. In general, flavonoids are detected with various non-colorimetric detection methods such as column liquid chromatography, thin-layer chromatography, and electrochemical analysis. For the first time, we developed a straightforward colorimetric detection system allowing recognition of some highly hydrophobic flavonoids such as alpha-naphthoflavone and beta-naphthoflavone, visually using 10,12-pentacosadiynoic acid (PCDA) derivatized with succinoglycan monomers isolated from Sinorhizobium meliloti. Besides changes in visible spectrum, we also demonstrate fluorescence changes using our detection system in the presence of those flavonoids. The succinoglycan monomers attached to PCDA molecules may function as an unstructured molecular capturer for some highly hydrophobic flavonoids by hydrophobic interactions, and transmit their molecular interactions as a color change throughout the PCDA liposome. PMID:26600071

  13. Field-deployable colorimetric biosensor system for the rapid detection of pathogenic organisms

    NASA Astrophysics Data System (ADS)

    Duy, Janice

    The rapid identification of pathogenic organisms is necessary for recognizing and managing human and environmental health risks. Numerous detection schemes are available, but most are difficult to employ in non-laboratory settings due to their need for bulky, specialized equipment, multiple reagents, or highly trained personnel. To address this problem, a rapid, field-compatible biosensor system based on the colorimetric detection of nucleic acid hybrids was developed. Peptide nucleic acid (PNA) probes were used to capture ribosomal RNA sequences from environmental samples. Non-target nucleic acids, including single-base mismatches flanked by adenines and uracils, were removed with a micrococcal nuclease digestion step. Matched PNA-RNA hybrids remained intact and were indicated by the cyanine dye DiSC2(5). PNA-containing duplexes function as templates for the aggregation of DiSC2(5), visualized as a change in solution color from blue to purple. This transition can be measured as an increase in the solution absorbance at 540 nm (dye aggregate) at the expense of the dye monomer peak at 650 nm. These concomitant spectral changes were used to calculate a "hybridization signal" using the ratio A aggregate/Amonomer ≈ A540/A650. Testing with pathogenic environmental samples was accomplished using two model organisms: the harmful algal bloom-causing dinoflagellate Alexandrium species, and the potato wart disease-causing fungus Synchytrium endobioticum. In both cases, the colorimetric approach was able to distinguish the targets with sensitivities rivaling those of established techniques, but with the advantages of decreased hands-on time and cost. Assay fieldability was tested with a portable colorimeter designed to quantify the dye-indicated hybridization signal and assembled from commercially available components. Side-by-side testing revealed no difference in the sensing performance of the colorimeter compared to a laboratory spectrophotometer (Pearson's r=0.99935). Assay results were obtained within 15 minutes, with a limit of detection down to 10--17 mole. This quick, inexpensive and robust system has the potential to replace laborious pathogen identification schemes in field environments, and is easily adapted for the detection of different organisms.

  14. Colorimetric detection of Al3+ ions using triazole-ether functionalized gold nanoparticles.

    PubMed

    Chen, Yu-Ching; Lee, I-Lin; Sung, Yi-Ming; Wu, Shu-Pao

    2013-12-15

    A sensitive, selective colorimetric Al(3+) detection method has been developed by using triazole-ether functionalized gold nanoparticles (TTP-AuNPs). Gold nanoparticles were prepared by reducing HAuCl4 with sodium borohydride in the presence of 5-(1,2-dithiolan-3-yl)-N-(prop-2-yn-1-yl)pentanamide (TP). The azide part of 2-[2-(2-azidoethoxy)ethoxy]ethanol and the acetylene part of TP were combined to form a triazole structure through a click reaction. Aggregation of TTP-AuNPs was induced immediately in the presence of Al(3+) ions, yielding a color change from red to blue. This Al(3+)-induced aggregation of TTP-AuNPs was monitored first with the naked eye and then UV-vis spectroscopy with a detection limit of 18.0 nM. The TTP-AuNPs showed excellent selectivity for Al(3+), compared to other metal ions (Ag(+), Ca(2+), Cd(2+), Co(2+), Cu(2+), Cr(3+), Fe(2+), Fe(3+), Hg(2+), Mg(2+), Mn(2+), Ni(2+), Pb(2+), and Zn(2+)). In addition, TTP-AuNPs were used to detect Al(3+) in sea water samples, with low interference. PMID:24209312

  15. Identification of Escherichia coli O157 by Using a Novel Colorimetric Detection Method with DNA Microarrays

    PubMed Central

    Swimley, Michelle S.; Taylor, Amber W.; Dawson, Erica D.

    2011-01-01

    Abstract Shiga toxinproducing Escherichia coli O157 is a leading cause of foodborne illness worldwide. To evaluate better methods to rapidly detect and genotype E. coli O157 strains, the present study evaluated the use of ampliPHOX, a novel colorimetric detection method based on photopolymerization, for pathogen identification with DNA microarrays. A low-density DNA oligonucleotide microarray was designed to target stx1 and stx2 genes encoding Shiga toxin production, the eae gene coding for adherence membrane protein, and the per gene encoding the O157-antigen perosamine synthetase. Results from the validation experiments demonstrated that the use of ampliPHOX allowed the accurate genotyping of the tested E. coli strains, and positive hybridization signals were observed for only probes targeting virulence genes present in the reference strains. Quantification showed that the average signal-to-noise ratio values ranged from 47.73??7.12 to 76.71??8.33, whereas average signal-to-noise ratio values below 2.5 were determined for probes where no polymer was formed due to lack of specific hybridization. Sensitivity tests demonstrated that the sensitivity threshold for E. coli O157 detection was 1001000 CFU/mL. Thus, the use of DNA microarrays in combination with photopolymerization allowed the rapid and accurate genotyping of E. coli O157 strains. PMID:21288130

  16. Detection of Mycoplasma mycoides subspecies mycoides SC in clinical material by a rapid colorimetric PCR.

    PubMed

    Bashiruddin, J B; De Santis, P; Vacciana, A; Santini, F G

    1999-02-01

    A colorimetric polymerase chain reaction (PCR) test for the detection of Mycoplasma mycoides subsp. mycoides SC (Mmm SC), the cause of contagious bovine pleuropneumonia (CBPP), was used to test clinical samples from suspect and known cases of the disease. A commercially available detection kit, pleuro TRAP from AMRAD, Australia, which captures amplified double stranded DNA in the wells of a microtitre plate was used. Tissues tested from animals ranging from a variety of anatomical locations included lung, lymph node, kidney, spleen, pleural fluid and nasal swabs. Polymerase chain reaction was conducted on DNA extracted from tissues as well as on culture-derived mycoplasmas. Positive results could be seen by the development of a yellow colour in microtitre wells after the enzymatic detection procedure indicating the presence of specifically amplified products. Spectrophotometric values of OD450for positive samples ranged from 0.211 to 1.409 compared to negative values of around 0.020 which reduced the subjectivity in the interpretation of results. Mmm SC was successfully identified from cultures of reference and field strains, nasal swabs and excised tissue by amplification with primers supplied in the kit. The system is suitable for automation and may be a cost effective alternative to gel electrophoresis for the screening of moderately large sample numbers as is the case in surveillance programmes. PMID:10024429

  17. Colorimetric detection of copper in water using a Schiff base derivative

    NASA Astrophysics Data System (ADS)

    Peralta Domnguez, D.; Ramos-Ortiz, G.; Maldonado, J. L.; Rodriguez, M.; Meneses-Nava, M. A.; Barbosa-Garcia, O.; Santillan, R.; Farfn, N.

    2013-09-01

    Organic molecular sensors have the advantage of being used through an easy, fast, economical and reliable optical method for detecting toxic metal ions in our environment. In this work, we present a simple but highly specific organic ligand compound 5-Chloro-2-((E)-((E)-3-(4-(dimethylamino)phenyl)allylidene)amino)phenol (L1) that acts as a colorimetric sensor for ions in a mixture of acetonitrile/water (ratio 10:1, v:v). Binding interaction between L1 and various metal-ions has been established by ultraviolet-visible spectroscopic measurements that indicate favorable coordination of the ligand with selective metal ions, particularly, with copper. These results showed that the electronic transition band shape of L1 change after binding with copper in aqueous solution. L1 exhibited binding-induced color changes from yellow to pink one detected by the naked eye. This new sensor presented 2.5 10-6 M as limit detection, even under the presence of other metal ions.

  18. Analyte-induced photoreduction method for visual and colorimetric detection of tyrosine.

    PubMed

    Satheeshkumar, Elumalai; Yang, Jyisy

    2015-06-16

    A new method based on photochemical formation of silver nanoparticles (AgNPs) was developed for detection of tyrosine (Tyr). To selectively detect Tyr and to simplify the detection procedure, the photoactivity of Tyr was utilized to trigger the photochemical reduction in production of AgNPs. The drastic change of solution color caused by the surface plasmon resonance (SPR) absorption band of the formed AgNPs was used to extract the quantitative information of Tyr. This developed method is simple in detection, while both the sensitivity and selectivity are significant improved. Meanwhile, the solution color was changed from colorless to dark yellow after the formation of AgNPs, which allows a much higher sensitivity in visual identification when compared with the SPR band shifting technique commonly, used in conventional colorimetric methods. To optimize the detection system and to understand the mechanism in this proposed method, parameters such as irradiation time, intensity of light source, and the concentration of Tyr were systematically examined. Results indicated that these factors mainly affected the reaction rate of photoreduction. The morphologies of the formed AgNPs were similar, but with small differences in particle sizes. In the examination of selectivity, sixteen other amino acids were examined. Results indicated that only amino acids of tryptophan, cysteine and histidine are photoactive and possess potential interferences in analysis of Tyr. Quantitative studies indicated that a linear response up to 10 μM with a detection limit of 100 nM could be obtained. For visually detection, color change could be observed with a concentration as low as 500 nM of Tyr. PMID:26002485

  19. [Rapid Detection of Trace Dimethoate Pesticide Residues Based on Colorimetric Spectroscopy].

    PubMed

    Li, Wen; Sun, Ming; Li, Min-zan; Sun, Hong

    2015-07-01

    In order to detect dimethoate pesticide residues rapidly and safely, a feasible method based on colorimetric spectroscopy was developed. Because dimethoate is one of organophosphorus pesticides containing sulfur, its sulfenyl can react with Pd2+ to produce a yellow complex named palladium sulfide. PdCl2 was used as the color agent, which was dissolved in acetic acid instead of the common concentrated hydrochloric acid. The dimethoate solution was prepared by dissolving the commercial pesticides into distilled water at different concentrations. The pesticide samples were reacted with the same amount of PdC2 solution respectively. The absorbance spectra of the samples after coloring reaction were measured in the region of 300-900 nm by a spectrophotometer. The result showed that the effect of using acetic acid instead of concentrated hydrochloric acid was not only safe but also preferable, and 0.5 mg x kg(-1) was the minimum concentration of the pesticide that could be distinguished in the spectra. The result met the pesticide residue detecting requirements of part fruits and vegetables in the national standard GB2763-2012 regulations. Further studies on random 40 dimethoate samples from 0.5 to 88 mg x kg(-1) were carried out. Thirty samples were randomly selected to establish the training model and remaining 10 samples were used to test the model. The preprocessing methods were carried on the spectrum data such as normalization and smoothing to get a better effect through comparison their prediction results with the correlation coefficient (r) and the root mean square error of cross-validation (RMSEP). The principal component analysis (PCA) method and partial least squares (PLS) method were used to establish prediction models respectively in the different wave ranges. By calculating the correlation coefficient of dimethoate samples in 350-900 nm the maximum of 0.9572 was obtained at wavelength 458 nm, so 453-463 and 400-600 nm were selected as feather regions. Experiments showed that the effect of SG preprocessing on the absorbance spectra in the region of 350-900 and 400-600 nm was obvious, and PLS method were better than PCA method. The optimum model was obtained in the region of 400-600 nm, when principal component number was 4, the training set r=0.9941, RMSEP=2.7703 and the validation set r=0.9933, RMSEP = 2.2148. This method was safe in operation and the colorimetric reaction time was 2 min, which provided theoretical and technical support for further studying on development of rapid, safe organophosphorus pesticide detection instrument. PMID:26717773

  20. Folic acid functionalized silver nanoparticles with sensitivity and selectivity colorimetric and fluorescent detection for Hg2+ and efficient catalysis

    NASA Astrophysics Data System (ADS)

    Su, Dongyue; Yang, Xin; Xia, Qingdong; Zhang, Qi; Chai, Fang; Wang, Chungang; Qu, Fengyu

    2014-09-01

    In this research, folic acid functionalized silver nanoparticles (FA-AgNPs) were selected as a colorimetric and a ‘turn on’ fluorescent sensor for detecting Hg2+. After being added into Hg2+, AgNPs can emit stable fluorescence at 440 nm when the excitation wavelength is selected at 275 nm. The absorbance and fluorescence of the FA-AgNPs could reflect the concentration of the Hg2+ ions. Thus, we developed a simple, sensitive analytical method to detect Hg2+ based on the colorimetric and fluorescence enhancement of FA-AgNPs. The sensor exhibits two linear response ranges between absorbance and fluorescence intensity with Hg2+ concentration, respectively. Meanwhile, a detection limit of 1 nM is estimated based on the linear relationship between responses with a concentration of Hg2+. The high specificity of Hg2+ with FA-AgNPs interactions provided the excellent selectivity towards detecting Hg2+ over other metal ions (Pb2+, Mg2+, Zn2+, Ni2+, Cu2+, Co2+, Ca2+, Mn2+, Fe2+, Cd2+, Ba2+, Cr6+ and Cr3+). This will provide a simple, effective and multifunctional colorimetric and fluorescent sensor for on-site and real-time Hg2+ ion detection. The proposed method can be applied to the analysis of trace Hg2+ in lake water. Additionally, the FA-AgNPs can be used as efficient catalyst for the reduction of 4-nitrophenol and potassium hexacyanoferrate (III).

  1. Colorimetric sensor array for detection and identification of organophosphorus and carbamate pesticides.

    PubMed

    Qian, Sihua; Lin, Hengwei

    2015-01-01

    Due to relatively low persistence and high effectiveness for insect and pest eradication, organophosphates (OPs) and carbamates are the two major classes of pesticides that broadly used in agriculture. Hence, the sensitive and selective detection of OPs and carbamates is highly significant. In this current study, a colorimetric sensor array comprising five inexpensive and commercially available thiocholine and H2O2 sensitive indicators for the simultaneous detection and identification of OPs and carbamates is developed. The sensing mechanism of this array is based on the irreversible inhibition capability of OPs and carbamates to the activity of acetylcholinesterase (AChE), preventing production of thiocholine and H2O2 from S-acetylthiocholine and acetylcholine and thus resulting in decreased or no color reactions to thiocholine and H2O2 sensitive indicators. Through recognition patterns and standard statistical methods (i.e., hierarchical clustering analysis and principal component analysis), the as-developed array demonstrates not only discrimination of OPs and carbamates from other kinds of pesticides but, more interestingly, identification of them exactly from each other. Moreover, this array is experimentally confirmed to have high selectivity and sensitivity, good anti-interference capability, and potential applications in real samples for OPs and carbamates. PMID:25913282

  2. Colorimetric Aptasensor Based on Enzyme for the Detection of Vibrio parahemolyticus.

    PubMed

    Wu, Shijia; Wang, Yinqiu; Duan, Nuo; Ma, Haile; Wang, Zhouping

    2015-09-01

    A simple colorimetric aptasensor system has been developed to detect Vibrio parahemolyticus. Magnetic nanoparticles (MNPs) are synthesized and conjugated with specific aptamers against target and used as capture probes. In addition, this method employs gold nanoparticles (AuNPs) as carriers of horseradish peroxidase (HRP) and aptamers, which served as signal probes. In the presence of target, a "sandwich-type" complex of AuNPs-HRP-aptamer-target-aptamer-MNPs is formed through specific recognition of aptamers and corresponding target. As a result, HRP molecules confined at the surface of the "sandwich" complexes catalyze the enzyme substrate, 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2 and generate an optical signal. Under optimal conditions, the signals are linearly dependent on V. parahemolyticus concentrations from 10 to 10(6) colony-forming units (cfu)/mL in a logarithmic plot, with a limit of detection of 10 cfu/mL. Owing to AuNPs, a large amount of HRP could be loaded, resulting in an amplified signal, and the sensitivity would be improved. This strategy has the potential of being extended to the construction of simple monitor systems for a variety of biomolecules related to food safety. PMID:26302256

  3. Simple, colorimetric detection of microRNA based on target amplification and DNAzyme.

    PubMed

    Yan, Chunyan; Jiang, Cheng; Jiang, Jianhui; Yu, Ruqin

    2013-01-01

    Considering the crucial role played by microRNAs (miRNAs) in biological processes, we developed a novel strategy for simple and colorimetric detection of miRNA by combining target amplification with DNAzyme. Throughout the work, a 22-nt oligonucleotide sequence was used as a model analyte. A label-free hairpin probe (HP) was used as a simple platform for sensing the target. In the presence of the target, the HP was opened, and then the isothermal circular strand-displacement process occurred with the help of a primer, deoxynucleotide solution mixture (dNTPs), Klenow fragment exo(-) polymerase, and Nb.BbvCI nicking enzyme. As a result, the target was recycled and multicopies of target analogues were generated that function in the same manner as the target, accompanied by the accumulation of signal elements. In this work, as low as 0.5 fM nucleic acid target was detected by horseradish peroxidase-mimicking DNAzyme catalyzing the oxidation of ABTS(2-) to colored ABTS(-). PMID:23749125

  4. Colorimetric detection of Hg2+ ions in aqueous media using CA-Au NPs

    NASA Astrophysics Data System (ADS)

    Liu, Zening; Hu, Jiao; Tong, Sijia; Cao, Qihua; Yuan, Hong

    2012-11-01

    Based on the selective interaction between Hg2+ ions and cyanuric acid (CA) and the anti-aggregation of CA stabilized gold nanoparticles (CA-Au NPs), a simple colorimetric method was developed for detecting Hg2+ ions. In a medium of pH 7.4 tris-HCl buffer containing 8 10-3 M NaCl, the CA-Au NPs solution was red, which was due to CA adsorbed onto the surface of Au NPs, stabilizing Au NPs against aggregation. When CA-HgII-CA complex was formed in the presence of Hg2+, the stability of CA-Au NPs reduced, and then aggregation of Au NPs occurred. Consequently, the color of the solution changed from red to blue and could easily be measured with a common spectrophotometer. The aggregation of Au NPs was also validated using transmission electron microscopy (TEM). The controlled experiment showed that other ions including Ba2+, Ca2+, Zn2+, Cd2+, Co2+, Mn2+, Cu2+, Mg2+, and Ni2+ ions did not induce any distinct spectral changes, which constituted a Hg2+-selective sensor. A dynamic range of 1.6-16 10-6 M Hg2+ ions was observed at the optimized reaction condition. This method provides a potentially useful tool for Hg2+ detection.

  5. An Amidochlorin-Based Colorimetric Fluorescent Probe for Selective Cu(2+) Detection.

    PubMed

    Li, Wenting; Zhu, Guohua; Li, Jinghua; Wang, Zhiqiang; Jin, Yingxue

    2016-01-01

    The design and synthesis of selective and sensitive chemosensors for the quantification of environmentally and biologically important ionic species has attracted widespread attention. Amidochlorin p6 (ACP); an effective colorimetric and fluorescent probe for copper ions (Cu(2+)) in aqueous solution derived from methyl pheophorbide-a (MPa) was designed and synthesized. A remarkable color change from pale yellow to blue was easily observed by the naked eye upon addition of Cu(2+); and a fluorescence quenching was also determined. The research of fluorescent quenching of ACP-Cu(2+) complexation showed the detection limit was 7.5 10(-8) mol/L; which suggested that ACP can act as a high sensitive probe for Cu(2+) and can be used to quantitatively detect low levels of Cu(2+) in aqueous solution. In aqueous solution the probe exhibits excellent selectivity and sensitivity toward Cu(2+) ions over other metal ions (M = Zn(2+); Ni(2+); Ba(2+); Ag?; Co(2+); Na?; K?; Mg(2+); Cd(2+); Pb(2+); Mn(2+); Fe(3+); and Ca(2+)). The obvious change from pale yellow to blue upon the addition of Cu(2+) could make it a suitable "naked eye" indicator for Cu(2+). PMID:26797591

  6. Colorimetric detection of DNA damage by using hemin-graphene nanocomposites

    NASA Astrophysics Data System (ADS)

    Wei, W.; Zhang, D. M.; Yin, L. H.; Pu, Y. P.; Liu, S. Q.

    2013-04-01

    A colorimetric method for detection of DNA damage was developed by using hemin-graphene nanosheets (H-GNs). H-GNs were skillfully synthesized by adsorping of hemin on graphene through ?-? interactions. The as-prepared H-GNs possessed both the ability of graphene to differentiate the damage DNA from intact DNA and the catalytic action of hemin. The damaged DNA made H-GNs coagulated to different degrees from the intact DNA because there were different amount of negative charge exposed on their surface, which made a great impact on the solubility of H-GNs. As a result, the corresponding centrifugal supernatant of H-GNs solution showed different color in the presence of 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2, which could be discriminated by naked eyes or by ultraviolet (UV)-visible spectrometer. Based on this, the damaged effects of styrene oxide (SO), NaAsO2 and UV radiation on DNA were studied. Results showed that SO exerted most serious damage effect on DNA although all of them damaged DNA seriously. The new method for detection of DNA damage showed good prospect in the evaluation of genotoxicity of new compounds, the maximum limit of pesticide residue, food additives, and so on, which is important in the fields of food science, pharmaceutical science and pesticide science.

  7. Simple and sensitive colorimetric detection of cysteine based on ssDNA-stabilized gold nanoparticles.

    PubMed

    Chen, Zhang; Luo, Shenglian; Liu, Chengbin; Cai, Qingyun

    2009-09-01

    In this paper, we demonstrate a simple and sensitive colorimetric detection of cysteine based on the cysteine-mediated color change of ssDNA-stabilized gold nanoparticles (AuNPs). Cysteine is capable of absorbing onto AuNPs surfaces via the strong interaction between its thiol group and gold. ssDNA molecules which stabilize AuNPs against salt-induced aggregation are removed away by cysteine encapsulation on the AuNPs surfaces, resulting in a characteristic color change of AuNPs from red to blue as soon as salt is added. The ratio of absorptions at 640 to 525 nm (A(640)/A(525)) is linear dependent on the cysteine concentration in the range from 0.1 to 5 microM. Furthermore, amino acids other than cysteine cannot mediate the color change under the identical conditions due to the absence of thiol groups, suggesting the selectivity of the proposed method toward cysteine. The employment of complicated protocols and sophisticated processes such as the preparation of modified AuNPs are successfully avoided in design to realize the simple and low-cost cysteine detection; and the high sensitivity and low cost of the method is favorable for practical applications. PMID:19641904

  8. Colorimetric-Based Detection of TNT Explosives Using Functionalized Silica Nanoparticles

    PubMed Central

    Idros, Noorhayati; Ho, Man Yi; Pivnenko, Mike; Qasim, Malik M.; Xu, Hua; Gu, Zhongze; Chu, Daping

    2015-01-01

    This proof-of-concept study proposes a novel sensing mechanism for selective and label-free detection of 2,4,6-trinitrotoluene (TNT). It is realized by surface chemistry functionalization of silica nanoparticles (NPs) with 3-aminopropyl-triethoxysilane (APTES). The primary amine anchored to the surface of the silica nanoparticles (SiO2-NH2) acts as a capturing probe for TNT target binding to form Meisenheimer amine–TNT complexes. A colorimetric change of the self-assembled (SAM) NP samples from the initial green of a SiO2-NH2 nanoparticle film towards red was observed after successful attachment of TNT, which was confirmed as a result of the increased separation between the nanoparticles. The shift in the peak wavelength of the reflected light normal to the film surface (λpeak) and the associated change of the peak width were measured, and a merit function taking into account their combined effect was proposed for the detection of TNT concentrations from 10−12 to 10−4 molar. The selectivity of our sensing approach is confirmed by using TNT-bound nanoparticles incubated in AptamerX, with 2,4-dinitrotoluene (DNT) and toluene used as control and baseline, respectively. Our results show the repeatable systematic color change with the TNT concentration and the possibility to develop a robust, easy-to-use, and low-cost TNT detection method for performing a sensitive, reliable, and semi-quantitative detection in a wide detection range. PMID:26046595

  9. Colorimetric Sensor Array Allows Fast Detection and Simultaneous Identification of Sepsis-Causing Bacteria in Spiked Blood Culture

    PubMed Central

    Mix, Samantha; Xu, Zeyu; Taba, Brian; Budvytiene, Indre; Berliner, Anders N.; Queralto, Nuria; Churi, Yair S.; Huang, Richard S.; Eiden, Michael; Martino, Raymond A.; Rhodes, Paul

    2014-01-01

    Sepsis is a medical emergency demanding early diagnosis and tailored antimicrobial therapy. Every hour of delay in initiating effective therapy measurably increases patient mortality. Blood culture is currently the reference standard for detecting bloodstream infection, a multistep process which may take one to several days. Here, we report a novel paradigm for earlier detection and the simultaneous identification of pathogens in spiked blood cultures by means of a metabolomic fingerprint of the volatile mixture outgassed by the organisms. The colorimetric sensor array provided significantly faster detection of positive blood cultures than a conventional blood culture system (12.1 h versus 14.9 h, P < 0.001) while allowing for the identification of 18 bacterial species with 91.9% overall accuracy within 2 h of growth detection. The colorimetric sensor array also allowed for discrimination between unrelated strains of methicillin-resistant Staphylococcus aureus, indicating that the metabolomic fingerprint has the potential to track nosocomial transmissions. Altogether, the colorimetric sensor array is a promising tool that offers a new paradigm for diagnosing bloodstream infections. PMID:24478493

  10. A novel colorimetric sandwich aptasensor based on an indirect competitive enzyme-free method for ultrasensitive detection of chloramphenicol.

    PubMed

    Abnous, Khalil; Danesh, Noor Mohammad; Ramezani, Mohammad; Emrani, Ahmad Sarreshtehdar; Taghdisi, Seyed Mohammad

    2016-04-15

    Analytical methods for detection and quantitation of chloramphenicol in blood serum and foodstuffs arse highly in demand. In this study, a colorimetric sandwich aptamer-based sensor (aptasensor) was fabricated for sensitive and selective detection of chloramphenicol, based on an indirect competitive enzyme-free assay using gold nanoparticles (AuNPs), biotin and streptavidin. The designed aptasensor acquires characteristics of AuNPs, including large surface area and unique optical properties, and strong interaction of biotin with streptavidin. In the absence of chloramphenicol, the sandwich structure of aptasensor forms, leading to the observation of sharp red color. In the presence of target, functionalized AuNPs could not bind to 96-well plates, resulting in a faint red color. The fabricated colorimetric aptasensor exhibited high selectivity toward chloramphenicol with a limit of detection as low as 451pM. Moreover, the developed colorimetric aptasensor was successfully used to detect chloramphenicol in milk and serum with LODs of 697 and 601pM, respectively. PMID:26599477

  11. Colorimetric sensor array allows fast detection and simultaneous identification of sepsis-causing bacteria in spiked blood culture.

    PubMed

    Lim, Sung H; Mix, Samantha; Xu, Zeyu; Taba, Brian; Budvytiene, Indre; Berliner, Anders N; Queralto, Nuria; Churi, Yair S; Huang, Richard S; Eiden, Michael; Martino, Raymond A; Rhodes, Paul; Banaei, Niaz

    2014-02-01

    Sepsis is a medical emergency demanding early diagnosis and tailored antimicrobial therapy. Every hour of delay in initiating effective therapy measurably increases patient mortality. Blood culture is currently the reference standard for detecting bloodstream infection, a multistep process which may take one to several days. Here, we report a novel paradigm for earlier detection and the simultaneous identification of pathogens in spiked blood cultures by means of a metabolomic "fingerprint" of the volatile mixture outgassed by the organisms. The colorimetric sensor array provided significantly faster detection of positive blood cultures than a conventional blood culture system (12.1 h versus 14.9 h, P < 0.001) while allowing for the identification of 18 bacterial species with 91.9% overall accuracy within 2 h of growth detection. The colorimetric sensor array also allowed for discrimination between unrelated strains of methicillin-resistant Staphylococcus aureus, indicating that the metabolomic fingerprint has the potential to track nosocomial transmissions. Altogether, the colorimetric sensor array is a promising tool that offers a new paradigm for diagnosing bloodstream infections. PMID:24478493

  12. A portable lab-on-a-chip system for gold-nanoparticle-based colorimetric detection of metal ions in water

    PubMed Central

    Zhao, Chen; Zhong, Guowei; Kim, Da-Eun; Liu, Jinxia; Liu, Xinyu

    2014-01-01

    Heavy metal ions released into various water systems have a severe impact on the environment and human beings, and excess exposure to toxic metal ions through drinking water poses high risks to human health and causes life-threatening diseases. Thus, there is high demand for the development of a rapid, low-cost, and sensitive method for detection of metal ions in water. We present a portable analytical system for colorimetric detection of lead (Pb2+) and aluminum (Al3+) ions in water based on gold nanoparticle probes and lab-on-a-chip instrumentation. The colorimetric detection of metal ions is conducted via single-step assays with low limits of detection (LODs) and high selectivity. We design a custom-made microwell plate and a handheld colorimetric reader for implementing the assays and quantifying the signal readout. The calibration experiments demonstrate that this portable system provides LODs of 30 ppb for Pb2+ and 89 ppb for Al3+, both comparable to bench-top analytical spectrometers. It promises an effective platform for metal ion analysis in a more economical and convenient way, which is particularly useful for water quality monitoring in field and resource-poor settings. PMID:25332734

  13. Correction: An integrated slidable and valveless microdevice with solid phase extraction, polymerase chain reaction, and immunochromatographic strip parts for multiplex colorimetric pathogen detection.

    PubMed

    Kim, Yong Tae; Lee, Dohwan; Heo, Hyun Young; Kim, Do Hyun; Seo, Tae Seok

    2015-12-01

    Correction for 'An integrated slidable and valveless microdevice with solid phase extraction, polymerase chain reaction, and immunochromatographic strip parts for multiplex colorimetric pathogen detection' by Yong Tae Kim et al., Lab Chip, 2015, 15, 4148-4155. PMID:26502177

  14. A high-throughput colorimetric assay for glucose detection based on glucose oxidase-catalyzed enlargement of gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Xiong, Yanmei; Zhang, Yuyan; Rong, Pengfei; Yang, Jie; Wang, Wei; Liu, Dingbin

    2015-09-01

    We developed a simple high-throughput colorimetric assay to detect glucose based on the glucose oxidase (GOx)-catalysed enlargement of gold nanoparticles (AuNPs). Compared with the currently available glucose kit method, the AuNP-based assay provides higher clinical sensitivity at lower cost, indicating its great potential to be a powerful tool for clinical screening of glucose.We developed a simple high-throughput colorimetric assay to detect glucose based on the glucose oxidase (GOx)-catalysed enlargement of gold nanoparticles (AuNPs). Compared with the currently available glucose kit method, the AuNP-based assay provides higher clinical sensitivity at lower cost, indicating its great potential to be a powerful tool for clinical screening of glucose. Electronic supplementary information (ESI) available: Experimental section and additional figures. See DOI: 10.1039/c5nr03758a

  15. Colorimetric detection of influenza A virus using antibody-functionalized gold nanoparticles.

    PubMed

    Liu, Yuanjian; Zhang, Linqun; Wei, Wei; Zhao, Hongyu; Zhou, Zhenxian; Zhang, Yuanjian; Liu, Songqin

    2015-06-21

    Early and accurate diagnosis is considered the key issue to prevent the further spread of viruses and facilitate influenza therapy. Herein, we report a colorimetric immunosensor for influenza A virus (IAV) based on gold nanoparticles (AuNPs) modified with monoclonal anti-hemagglutinin antibody (mAb). The immunosensor allows for a fast, simple, and selective detection of IAV. In this assay, influenza-specific antibodies are conjugated to AuNPs to create mAb-AuNP probes. Since IAV has multiple recognition sites for probes on the surface, the mAb-AuNP probes can be specifically arranged on the virus surface due to their very specific antigen recognition. In this case, this aggregation of the mAb-AuNP probes produces a red shift in the absorption spectrum due to plasmon coupling between adjacent AuNPs, and it can be detected with the naked eye as a color change from red to purple and quantified with the absorption spectral measurements. The aggregate formation is also confirmed with transmission electron microscopy (TEM) imaging and dynamic light scattering (DLS). Under the optimal conditions, the present immunoassay can sensitively measure H3N2 IAV (A/Brisbane/10/2007) with a detection limit of 7.8 hemagglutination units (HAU). This proposed immunosensor revealed high specificity, accuracy, and good stability. Notably, it is a single-step detection using AuNP probes and UV-vis spectrophotometer for readout, and no additional amplification, e.g., enzymatic, is needed to read the result. This assay depends on an ordered AuNP structure covering the virus surface and can be applied to any virus pathogen by incorporating the appropriate pathogen-specific antibody. PMID:25899840

  16. Colorimetric DNA detection of transgenic plants using gold nanoparticles functionalized with L-shaped DNA probes

    NASA Astrophysics Data System (ADS)

    Nourisaeid, Elham; Mousavi, Amir; Arpanaei, Ayyoob

    2016-01-01

    In this study, a DNA colorimetric detection system based on gold nanoparticles functionalized with L-shaped DNA probes was prepared and evaluated. We investigated the hybridization efficiency of the L-shaped probes and studied the effect of nanoparticle size and the L-shaped DNA probe length on the performance of the as-prepared system. Probes were attached to the surface of gold nanoparticles using an adenine sequence. An optimal sequence of 35S rRNA gene promoter from the cauliflower mosaic virus, which is frequently used in the development of transgenic plants, and the two complementary ends of this gene were employed as model target strands and probe molecules, respectively. The spectrophotometric properties of the as-prepared systems indicated that the large NPs show better changes in the absorption spectrum and consequently present a better performance. The results of this study revealed that the probe/Au-NPs prepared using a vertical spacer containing 5 thymine oligonucleotides exhibited a stronger spectrophotometric response in comparison to that of larger probes. These results in general indicate the suitable performance of the L-shaped DNA probe-functionalized Au-NPs, and in particular emphasize the important role of the gold nanoparticle size and length of the DNA probes in enhancing the performance of such a system.

  17. A colorimetric sensor array for detection and discrimination of biothiols based on aggregation of gold nanoparticles.

    PubMed

    Ghasemi, Forough; Hormozi-Nezhad, M Reza; Mahmoudi, Morteza

    2015-07-01

    Developments of sensitive, rapid, and cheap systems for identification of a wide range of biomolecules have been recognized as a critical need in the biology field. Here, we introduce a simple colorimetric sensor array for detection of biological thiols, based on aggregation of three types of surface engineered gold nanoparticles (AuNPs). The low-molecular-weight biological thiols show high affinity to the surface of AuNPs; this causes replacement of AuNPs' shells with thiol containing target molecules leading to the aggregation of the AuNPs through intermolecular electrostatic interaction or hydrogen-bonding. As a result of the predetermined aggregation, color and UV-vis spectra of AuNPs are changed. We employed the digital mapping approach to analyze the spectral variations with statistical and chemometric methods, including hierarchical cluster analysis (HCA) and principal component analysis (PCA). The proposed array could successfully differentiate biological molecules (e.g., cysteine, glutathione and glutathione disulfide) from other potential interferences such as amino acids in the concentration range of 10-800 μmol L(-1). PMID:26043092

  18. Intelligent DNA machine for the ultrasensitive colorimetric detection of nucleic acids.

    PubMed

    Xu, Jianguo; Qian, Jun; Li, Hongling; Wu, Zai-Sheng; Shen, Weiyu; Jia, Lee

    2016-01-15

    As DNA is employed to serve as a smart building block, an increasing interest has been devoted to the development of different DNA-based machines for the specific purpose, for example, the exploration of inter- or intramolecular interaction. In the current contribution, we developed an intelligent DNA machine and its operation can be designed to execute the ultrasensitive colorimetric detection of target nucleic acids. The DNA machine consists of a hairpin probe (HP) and an assistant template (AT). Using p53 gene as the target model to trigger the molecular machine operation, cyclic nucleic acid strand displacement polymerization (CNDP) was specifically induced, leading to the DNAzyme mediated catalytic reaction for signal readout. Specifically, with the help of polymerase and nickase, one target molecule was able to drive DNA nano-mechanical devices one-by-one through the hybridization/polymerization displacement cycles, and every initiated machine continued to operate, causing the dramatic accumulation of G-quadruplex-contained products. The G-quadruplex structure after binding to hemin could act as a horseradish peroxidase (HRP)-mimicking DNAzyme and catalyzed the oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) by H2O2. As a result, an enhanced color change could be detected because of the generation of oxidation product ABTS(+). In this way, the DNA machine has no any signal loss and enables the quantitative measurement of p53 DNA with a detection limit of 10fM, indicating great promise for unique application in biomedical research and early clinical diagnosis. PMID:26291961

  19. Colorimetric Sensor for Label Free Detection of Porcine PCR Product (ID: 18)

    NASA Astrophysics Data System (ADS)

    Ali, M. E.; Hashim, U.; Bari, M. F.; Dhahi, Th. S.

    2011-05-01

    This report described the use of 40±5 nm in diameter citrate-coated gold nanoparticles (GNPs) as colorimetric sensor to visually detect the presence of a 17-base swine specific conserved sequence and nucleotide mismatch in the mixed PCR products of pig, deer and shad cytochrome b genes. The size of these PCR amplicons was 109 base-pair and was amplified with a pair of common primers. Colloidal GNPs changed color from pinkish- red to purple-gray in 2 mM PBS buffer by losing its characteristic surface plasmon resonance peak at 530 nm and gaining new features between 620 and 800 nm in the absorption spectrum indicating strong aggregation. The particles were stabilized against salt induced aggregation, retained spectral features and characteristic color upon adsorption of single-stranded DNA. The PCR products without any additional processing were hybridized with a 17-nucleotide swine probe prior to exposure to GNPs. At a critical annealing temperature (55° C) that differentiated between the match and mismatch pairing, the probe was hybridized with the pig PCR product and dehybridized from the deer's and shad's. The interaction of dehybridized probe to GNPs prevented them from salt-induced aggregation, retaining their characteristic red color. The assay did not need any surface modification chemistry or labeling steps. The results were determined visually and validated by absorption spectroscopy. The entire assay (hybridization plus visual detection) was performed in less than 10 min. The assay obviated the need of complex RFLP, sequencing or blotting to differentiate the same size PCR products. We find the application of the assay for species assignment in food analysis, mismatch detection in genetic screening and homology study among closely related species.

  20. A colorimetric aptamer biosensor based on cationic polymer and gold nanoparticles for the ultrasensitive detection of thrombin.

    PubMed

    Chen, Zhengbo; Tan, Yuan; Zhang, Chenmeng; Yin, Lu; Ma, He; Ye, Nengsheng; Qiang, Hong; Lin, Yuqing

    2014-06-15

    A colorimetric assay for the ultrasensitive determination of thrombin based on cationic polymer and gold nanoparticles was presented, in which unmodified gold nanoparticles (AuNPs) was used as probes and 21-mer thrombin-binding aptamer (TBA) as sensing elements. Upon the addition of thrombin, TBA interacted specifically with thrombin to form a G-quadruplex structure. As a result, the conformation change facilitated the cationic polymer, poly(diallyldimethylammonium chloride) (PDDA)-induced AuNP aggregation. Thus, the visible change in color from wine-red to blue-purple was readily seen by the naked eye. The colorimetric sensor could detect thrombin down to 1 pM with high selectivity in the presence of other interferring proteins. Furthermore, the assay was successfully employed to determine thrombin in human serum sample, which suggested its great potential for diagnostic purposes. PMID:24463195

  1. Synthesis of pyrazolylbisindoles over mesoporous Lewis acidic ZrTUD-1: Potential application in selective Cu(2+) colorimetric detection.

    PubMed

    Kandasamy, Karthikeyan; Ganesabaskaran, Sivaprasad; Pachamuthu, Muthusamy Poomalai; Maheswari, Rajamanickam; Ramanathan, Anand

    2015-11-01

    A series of pyrazolylbisindole (PBI) derivatives were prepared by simple condensation of indole and pyrazole aldehyde utilizing amorphous mesoporous ZrTUD-1 having predominant Lewis acid sites. The applicability of pyrazolylbisindolyl derivate as a colorimetric chemosensor with high selectivity toward Cu(2+) over other cations were tested. Among heavy and transition metal (HTM) ions in CH3CN solution, the probe only sensed Cu(2+) detectable by naked eye. The sensor exhibited a new absorption band at 488 nm (a red shift of 206 nm from 282 nm) with a large colorimetric response and affinity to Cu(2+) over other cations tested (Al(3+), Pb(2+), Cd(2+), Mg(2+), Mn(2+), Zn(2+), K(+), Fe(2+), Ca(2+), Cu(2+) and Hg(2+)). PMID:26023054

  2. Dual-channel detection of Cu2+ and F- with a simple Schiff-based colorimetric and fluorescent sensor

    NASA Astrophysics Data System (ADS)

    Na, Yu Jeong; Choi, Ye Won; Yun, Jin Yeong; Park, Kyung-Min; Chang, Pahn-Shick; Kim, Cheal

    2015-02-01

    A simple and easily synthesized colorimetric and fluorescent receptor 1, based on 4-diethylaminosalicylaldehyde moieties as a binding and signaling unit, has been synthesized and characterized. The receptor 1 has a selective colorimetric sensing ability for copper (II) ion by changing color from colorless to yellow in aqueous solution, and could be utilized to monitor Cu(II) over a wide pH range of 4-11. In addition, the detection limit (12 ?M) of 1 for Cu2+ is much lower than that (30 ?M) recommended by WHO in drinking water, and its copper complex could be reversible simply through treatment with a proper reagent such as EDTA. Moreover, receptor 1 exhibited both a color change from colorless to yellow and fluorescence enhancement with a red shift upon addition to F- in DMSO. The recognition mechanism was attributed to the intermolecular proton transfer between the hydroxyl group of the receptor and the fluoride.

  3. Simple, field portable colorimetric detection device for organic peroxides and hydrogen peroxide

    DOEpatents

    Pagoria, Philip F.; Mitchell, Alexander R.; Whipple, Richard E.; Carman, M. Leslie; Reynolds, John G.; Nunes, Peter; Shields, Sharon J.

    2010-11-09

    A simple and effective system for the colorimetric determination of organic peroxides and hydrogen peroxide. A peroxide pen utilizing a swipe material attached to a polyethylene tube contains two crushable vials. The two crushable vials contain a colorimetric reagent separated into dry ingredients and liquid ingredients. After swiping a suspected substance or surface the vials are broken, the reagent is mixed thoroughly and the reagent is allowed to wick into the swipe material. The presence of organic peroxides or hydrogen peroxide is confirmed by a deep blue color.

  4. Synthetic multivalent DNAzymes for enhanced hydrogen peroxide catalysis and sensitive colorimetric glucose detection.

    PubMed

    Yang, Deng-Kai; Kuo, Chia-Jung; Chen, Lin-Chi

    2015-01-26

    A peroxidase-mimic DNAzyme is a G-quadruplex (G4) DNA-hemin complex, in which the G4-DNA resembles an apoenzyme, and hemin is the cofactor for hydrogen peroxide (H2O2) catalysis. Twenty-one-mer CatG4 is a well-proven G4-DNA as well as a hemin-binding aptamer for constituting a DNAzyme. This work studied if a multivalent DNAzyme with accelerated catalysis could be constructed using a multimeric CatG4 with hemin. We compared CatG4 monomer, dimer, trimer, and tetramer, which were prepared by custom oligo synthesis, for G4 structure formation. According to circular dichroism (CD) analysis, we found that a CatG4 multimer exhibited more active G4 conformation than the sum effect of equal-number CatG4 monomers. However, the DNAzyme kinetics was not improved monotonically along with the subunit number of a multimeric CatG4. It was the trivalent DNAzyme, trimeric CatG4:hemin, resulting in the rapidest H2O2 catalysis instead of a tetravalent one. We discovered that the trivalent DNAzyme's highest catalytic rate was correlated to its most stable hemin-binding G4 structure, evidenced by CD melting temperature analysis. Finally, a trivalent DNAzyme-based colorimetric glucose assay with a detection limit as low as 10 μM was demonstrated, and this assay did not need adenosine 5'-tri-phosphate disodium salt hydrate (ATP) as a DNAzyme boosting agent. PMID:25542363

  5. Luminol functionalized gold nanoparticles as colorimetric and chemiluminescent probes for visual, label free, highly sensitive and selective detection of minocycline

    NASA Astrophysics Data System (ADS)

    He, Yi; Peng, Rufang

    2014-11-01

    In this work, luminol functionalized gold nanoparticles (LuAuNPs) were used as colorimetric and chemiluminescent probes for visual, label free, sensitive and selective detection of minocycline (MC). The LuAuNPs were prepared by simple one-pot reduction of HAuCl4 with luminol, which exhibited a good chemiluminescence (CL) activity owing to the presence of luminol molecules on their surface and surface plasmon resonance absorption. In the absence of MC, the color of LuAuNPs was wine red and their size was relatively small (˜25 nm), which could react with silver nitrate, producing a strong CL emission. Upon the addition of MC at acidic buffer solutions, the electrostatic interaction between positively charged MC and negatively charged LuAuNPs caused the aggregation of LuAuNPs, generating a purple or blue color. Simultaneously, the aggregated LuAuNPs did not effectively react with silver nitrate, producing a weak CL emission. The signal change was linearly dependent on the logarithm of MC concentration in the range from 30 ng to 1.0 μg for colorimetric detection and from 10 ng to 1.0 μg for CL detection. With colorimetry, a detection limit of 22 ng was achieved, while the detection limit for CL detection modality was 9.7 ng.

  6. Colorimetric Detection of Small Molecules in Complex Matrixes via Target-Mediated Growth of Aptamer-Functionalized Gold Nanoparticles.

    PubMed

    Soh, Jun Hui; Lin, Yiyang; Rana, Subinoy; Ying, Jackie Y; Stevens, Molly M

    2015-08-01

    A versatile and sensitive colorimetric assay that allows the rapid detection of small-molecule targets using the naked eye is demonstrated. The working principle of the assay integrates aptamer-target recognition and the aptamer-controlled growth of gold nanoparticles (Au NPs). Aptamer-target interactions modulate the amount of aptamer strands adsorbed on the surface of aptamer-functionalized Au NPs via desorption of the aptamer strands when target molecules bind with the aptamer. Depending on the resulting aptamer coverage, Au NPs grow into morphologically varied nanostructures, which give rise to different colored solutions. Au NPs with low aptamer coverage grow into spherical NPs, which produce red-colored solutions, whereas Au NPs with high aptamer coverage grow into branched NPs, which produce blue-colored solutions. We achieved visible colorimetric response and nanomolar detection limits for the detection of ochratoxin A (1 nM) in red wine samples, as well as cocaine (1 nM) and 17?-estradiol (0.2 nM) in spiked synthetic urine and saliva, respectively. The detection limits were well within clinically and physiologically relevant ranges, and below the maximum food safety limits. The assay is highly sensitive, specific, and able to detect an array of analytes rapidly without requiring sophisticated equipment, making it relevant for many applications, such as high-throughput drug and clinical screening, food sampling, and diagnostics. Furthermore, the assay is easily adapted as a chip-based platform for rapid and portable target detection. PMID:26197040

  7. Direct examination of the dietary preference of the copepod calanus helgolandicus using the colorimetric approach

    NASA Astrophysics Data System (ADS)

    Kang, Hyung-Ku; Poulet, Serge; Ju, Se-Jong

    2007-09-01

    The food selectivity of tethered females of the copepod Calanus helgolandicus was examined by using the colorimetric approach. First, feeding behavior of the copepod did not show any differences between the red-color stained with neutral red and non-stained diets using the diatom Coscinodiscus curvatulus. Then, the copepods were fed a mixtures of two diets, the diatom C. curvatulus, stained with neutral red, and the dinoflagellate Gymnodinium sanguineum for 14~60 minutes of feeding duration. The foregut colors of females were examined using a stereo-microscope and a video monitor. The foreguts of animals fed with a high density of diatoms in mixed diets showed a dark red color, whereas those fed with a high density of dinoflagellate in mixed diets were a dark yellow. The results suggest that this species of copepod may not selectively feed either one of the diets used for this study. Their feeding activity may be more likely related to the density of available prey in their environment. Therefore, this quick and easy colorimetric approach could provide very useful information, like the pre-screening procedure before designing and conducting the time-consuming and complex feeding experiments to understand the feeding ecology of copepods.

  8. Potassium sorbate residue levels and persistence in citrus fruit as detected by a simple colorimetric method

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Postharvest applications of potassium sorbate (PS) to fresh citrus fruit control fungal decay pathogens, such as Penicillium digitatum, cause of green mold. Although PS effectiveness has been examined repeatedly, little is known about PS residues. A colorimetric method that employed extraction of th...

  9. Visual detection of cancer cells by colorimetric aptasensor based on aggregation of gold nanoparticles induced by DNA hybridization.

    PubMed

    Borghei, Yasaman-Sadat; Hosseini, Morteza; Dadmehr, Mehdi; Hosseinkhani, Saman; Ganjali, Mohammad Reza; Sheikhnejad, Reza

    2016-01-21

    A simple but highly sensitive colorimetric method was developed to detect cancer cells based on aptamer-cell interaction. Cancer cells were able to capture nucleolin aptamers (AS 1411) through affinity interaction between AS 1411 and nucleolin receptors that are over expressed in cancer cells, The specific binding of AS 1411 to the target cells triggered the removal of aptamers from the solution. Therefore no aptamer remained in the solution to hybridize with complementary ssDNA-AuNP probes as a result the solution color is red. In the absence of target cells or the presence of normal cells, ssDNA-AuNP probes and aptamers were coexisted in solution and the aptamers assembled DNA-AuNPs, produced a purple solution. UV-vis spectrometry demonstrated that this hybridization-based method exhibited selective colorimetric responses to the presence or absence of target cells, which is detectable with naked eye. The linear response for MCF-7 cells in a concentration range from 10 to 10(5)cells was obtained with a detection limit of 10cells. The proposed method could be extended to detect other cells and showed potential applications in cancer cell detection and early cancer diagnosis. PMID:26724767

  10. Colorimetric assay for protein detection based on "nano-pumpkin" induced aggregation of peptide-decorated gold nanoparticles.

    PubMed

    Wei, Luming; Wang, Xiaoying; Li, Chao; Li, Xiaoxi; Yin, Yongmei; Li, Genxi

    2015-09-15

    Small peptide can be used as an effective biological recognition element and provide an alternative tool for protein detection. However, the development of peptide-based detecting strategy still remains elusive due to the difficulty of signal transduction. Herein, we report a peptide-based colorimetric strategy for the detection of disease biomarker by using vascular endothelial growth factor receptor 1 (Flt-1) as an example. In this strategy, N-terminal aromatic residue-containing peptide modified gold nanoparticles (GNPs) can form bulky aggregate by the introduction of cucurbit[8]uril (CB[8]) that can selectively accommodate two N-terminal aromatic residue of peptides simultaneously regardless of their sequences. However, in the presence of Flt-1, the peptide can specifically bind to the protein molecule and the N-terminal aromatic residue will be occupied, resulting in little aggregation of GNPs. By taking advantage of the highly affinitive peptide and efficiency cross-linking effect of CB[8] to GNPs, colorimetric assay for protein detection can be achieved with a detection limit of 0.2 nM, which is comparable with traditional methods. The feasibility of our method has also been demonstrated in spiked serum sample, indicating potential application in the future. PMID:25932793

  11. Aptamer-based colorimetric detection of proteins using a branched DNA cascade amplification strategy and unmodified gold nanoparticles.

    PubMed

    Chang, Chia-Chen; Chen, Chen-Yu; Chuang, Tsung-Liang; Wu, Tzu-Heng; Wei, Shu-Chen; Liao, Hongen; Lin, Chii-Wann

    2016-04-15

    A branched DNA amplification strategy was employed to design a colorimetric aptameric biosensor using unmodified gold nanoparticles (AuNPs). First, a programmed DNA dendritic nanostructure was formed using two double-stranded substrate DNAs and two single-stranded auxiliary DNAs as assembly components via a target-assisted cascade amplification reaction, and it was then captured by DNA sensing probe-stabilized AuNPs. The release of sensing probes from AuNPs led to the formation of unstable AuNPs, promoting salt-induced aggregation. By integrating the signal amplification capacity of the branched DNA cascade reaction and unmodified AuNPs as a sensing indicator, this amplified colorimetric sensing strategy allows protein detection with high sensitivity (at the femtomole level) and selectivity. The limit of detection of this approach for VEGF was lower than those of other aptamer-based detection methods. Moreover, this assay provides modification-free and enzyme-free protein detection without sophisticated instrumentation and might be generally applicable to the detection of other protein targets in the future. PMID:26609945

  12. A colorimetric detection of acrylamide in potato chips based on nucleophile-initiated thiol-ene Michael addition.

    PubMed

    Hu, Qinqin; Fu, Yingchun; Xu, Xiahong; Qiao, Zhaohui; Wang, Ronghui; Zhang, Ying; Li, Yanbin

    2016-02-01

    Acrylamide (AA), a neurotoxin and a potential carcinogen, has been found in various thermally processed foods such as potato chips, biscuits, and coffee. Simple, cost-effective, and sensitive methods for the rapid detection of AA are needed to ensure food safety. Herein, a novel colorimetric method was proposed for the visual detection of AA based on a nucleophile-initiated thiol-ene Michael addition reaction. Gold nanoparticles (AuNPs) were aggregated by glutathione (GSH) because of a ligand-replacement, accompanied by a color change from red to purple. In the presence of AA, after the thiol-ene Michael addition reaction between GSH and AA with the catalysis of a nucleophile, the sulfhydryl group of GSH was consumed by AA, which hindered the subsequent ligand-replacement and the aggregation of AuNPs. Therefore, the concentration of AA could be determined by the visible color change caused by dispersion/aggregation of AuNPs. This new method showed high sensitivity with a linear range from 0.1 μmol L(-1) to 80 μmol L(-1) and a detection limit of 28.6 nmol L(-1), and especially revealed better selectivity than the fluorescence sensing method reported previously. Moreover, this new method was used to detect AA in potato chips with a satisfactory result in comparison with the standard methods based on chromatography, which indicated that the colorimetric method can be expanded for the rapid detection of AA in thermally processed foods. PMID:26699696

  13. Colorimetric detection of Escherichia coli O157:H7 using functionalized Au@Pt nanoparticles as peroxidase mimetics.

    PubMed

    Su, Haichao; Zhao, Han; Qiao, Fengmin; Chen, Lijian; Duan, Ruihuan; Ai, Shiyun

    2013-05-21

    The presence of Escherichia coli (E. coli) in food and drinking water is a chronic problem worldwide. Protecting food against bacterial contamination and rapid diagnosis of infection require simple and rapid assays for detection of bacterial pathogens, including E. coli O157:H7. Here we report a rapid and novel colorimetric method for detecting E. coli O157:H7. This colorimetric method is based on the catalytic oxidation of the peroxidase substrate 3,3,5,5-tetramethylbenzidine by hydrogen peroxide using 4-mercaptophenylboronic acid-functioned Au@Pt nanoparticles adsorbed on the surface of E. coli O157:H7. The assay showed excellent sensitivity both with the naked eye and based on absorbance measurements. The absorbance at 652 nm was proportional to the concentration of E. coli O157:H7 ranging from 7 to 6 × 10(6) cfu mL(-1) with a limit of detection of 7 cfu mL(-1). The total detection time was less than 40 min. PMID:23577341

  14. Study on a colorimetric sensor with color switching: Naked-eye detection for Cu(II) ion

    NASA Astrophysics Data System (ADS)

    Gao, Yang; Ma, Wenzhong

    2012-12-01

    In this paper, we synthesize and report a Cu(II)-sensing probe of N'1,N'2-bis(4-(diethylamino)-2-hydroxybenzylidene)oxalohydrazide (BDHO) with two detection channels. Its colorimetric and fluorescence spectrophotometric responses towards Cu(II) ion are fully investigated. It is found that the absorption and emission spectra of BDHO are both sensitive towards Cu(II) ion with high sensitivity as well as excellent selectivity. In addition, the recognition of BDHO towards Cu(II) ion is also very quick and can be accomplished within less than 1 min. The actual sensing performance of BDHO towards Cu(II) ion is also tentatively explored.

  15. Highly-sensitive colorimetric detection of H2O2 based on the Pt@Te nanorods

    NASA Astrophysics Data System (ADS)

    Wan, Li-Juan; Huang, Xing-Jiu; Liu, Jin-Huai; Zhang, Zhong-Xiang; Hou, Shi-Li; Liu, Wei-Jing

    2015-05-01

    Te nanorods (NRs) were prepared from TeO2 in the presence of hydrazine hydrate without using any surfactants under ambient conditions. Te NRs were then used as sacrificial templates to prepare Pt@Te NRs by spontaneous redox galvanic replacement between Te and Pt ions. The as-synthesized Pt@Te NRs exhibit a strong catalytic activity for the colorimetric detection of H2O2 using 2, 2?-azino-bis (3-ethylbenzo-thiazoline-6-sulfonic acid) diammonium salt (ABTS) as an indicator.

  16. A colorimetric sensor array for the detection of the date-rape drug ?-hydroxybutyric acid (GHB): a supramolecular approach.

    PubMed

    Baumes, Laurent A; Buaki Sogo, Mireia; Montes-Navajas, Pedro; Corma, Avelino; Garcia, Hermenegildo

    2010-04-19

    ?-Hydroxybutyric acid (GHB), a colourless, odourless and tasteless chemical, has become one of the most dangerous illicit drugs of abuse today. At low doses, this drug is a central nervous system depressant that reduces anxiety and produces euphoria and relaxation, sedating the recipient. There is an urgent need for simple, easy-to-use sensors for GHB in solution. Here, we present a colorimetric sensor array based on supramolecular host-guest complexes of fluorescent dyes with organic capsules (cucurbiturils) for the detection of GHB. PMID:20309968

  17. Colorimetric sensing of alpha-amino acids and its application for the "label-free" detection of protease.

    PubMed

    Lou, Xiaoding; Zhang, Liyao; Qin, Jingui; Li, Zhen

    2010-02-01

    A new indirect approach to explore sensitive colorimetric sensors toward alpha-amino acids is proposed: the pink solution of 1 and copper ions changed to colorless immediately upon the addition of alpha-amino acids. As the hydrolysis of bovine serum albumin (BSA) with the aid of trypsin produces alpha-amino acids, the complex of 1/Cu(2+)/BSA could act as a label-free, sensitive, selective sensor toward trypsin. The detection process could be visually observed by naked eyes. PMID:20047345

  18. Directional Antineutrino Detection

    NASA Astrophysics Data System (ADS)

    Safdi, Benjamin R.; Suerfu, Burkhant

    2015-02-01

    We propose the first event-by-event directional antineutrino detector using inverse beta decay (IBD) interactions on hydrogen, with potential applications including monitoring for nuclear nonproliferation, spatially mapping geoneutrinos, characterizing the diffuse supernova neutrino background and searching for new physics in the neutrino sector. The detector consists of adjacent and separated target and capture scintillator planes. IBD events take place in the target layers, which are thin enough to allow the neutrons to escape without scattering elastically. The neutrons are detected in the thicker boron-loaded capture layers. The location of the IBD event and the momentum of the positron are determined by tracking the positron's trajectory through the detector. Our design is a straightforward modification of existing antineutrino detectors; a prototype could be built with existing technology.

  19. Directional antineutrino detection.

    PubMed

    Safdi, Benjamin R; Suerfu, Burkhant

    2015-02-20

    We propose the first event-by-event directional antineutrino detector using inverse beta decay (IBD) interactions on hydrogen, with potential applications including monitoring for nuclear nonproliferation, spatially mapping geoneutrinos, characterizing the diffuse supernova neutrino background and searching for new physics in the neutrino sector. The detector consists of adjacent and separated target and capture scintillator planes. IBD events take place in the target layers, which are thin enough to allow the neutrons to escape without scattering elastically. The neutrons are detected in the thicker boron-loaded capture layers. The location of the IBD event and the momentum of the positron are determined by tracking the positron's trajectory through the detector. Our design is a straightforward modification of existing antineutrino detectors; a prototype could be built with existing technology. PMID:25763953

  20. Multiplexed Colorimetric Solid-Phase Extraction

    NASA Technical Reports Server (NTRS)

    Gazda, Daniel B.; Fritz, James S.; Porter, Marc D.

    2009-01-01

    Multiplexed colorimetric solid-phase extraction (MC-SPE) is an extension of colorimetric solid-phase extraction (C-SPE) an analytical platform that combines colorimetric reagents, solid phase extraction, and diffuse reflectance spectroscopy to quantify trace analytes in water. In CSPE, analytes are extracted and complexed on the surface of an extraction membrane impregnated with a colorimetric reagent. The analytes are then quantified directly on the membrane surface using a handheld diffuse reflectance spectrophotometer. Importantly, the use of solid-phase extraction membranes as the matrix for impregnation of the colorimetric reagents creates a concentration factor that enables the detection of low concentrations of analytes in small sample volumes. In extending C-SPE to a multiplexed format, a filter holder that incorporates discrete analysis channels and a jig that facilitates the concurrent operation of multiple sample syringes have been designed, enabling the simultaneous determination of multiple analytes. Separate, single analyte membranes, placed in a readout cartridge create unique, analyte-specific addresses at the exit of each channel. Following sample exposure, the diffuse reflectance spectrum of each address is collected serially and the Kubelka-Munk function is used to quantify each water quality parameter via calibration curves. In a demonstration, MC-SPE was used to measure the pH of a sample and quantitate Ag(I) and Ni(II).

  1. Colorimetric detection of mercury ion based on unmodified gold nanoparticles and target-triggered hybridization chain reaction amplification

    NASA Astrophysics Data System (ADS)

    Wang, Qing; Yang, Xiaohan; Yang, Xiaohai; Liu, Pei; Wang, Kemin; Huang, Jin; Liu, Jianbo; Song, Chunxia; Wang, Jingjing

    2015-02-01

    A novel unmodified gold nanoparticles (AuNPs)-based colorimetric strategy for label-free, specific and sensitive mercury ion (Hg2+) detection was demonstrated by using thymine-Hg2+-thymine (T-Hg2+-T) recognition mechanism and hybridization chain reaction (HCR) amplification strategy. In this protocol, a structure-switching probe (H0) was designed to recognize Hg2+ and then propagated a chain reaction of hybridization events between two other hairpin probes (H1 and H2). In the absence of Hg2+, all hairpin probes could stably coexist in solution, the exposed sticky ends of hairpin probes were capable of stabilizing AuNPs. As a result, salt-induced AuNPs aggregation could be effectively prevented. In the presence of Hg2+, thymine bases of H0 could specifically interact with Hg2+ to form stable T-Hg2+-T complex. Consequently, the hairpin structure of H0 probe was changed. As H1/H2 probes were added, the HCR process could be triggered and nicked double-helixes were formed. Since it was difficult for the formed nicked double-helixes to inhibit salt-induced AuNPs aggregation, a red-to-blue color change was observed in the colloid solution as the salt concentration increased. With the elegant amplification effect of HCR, a detection limit of around 30 nM was achieved (S/N = 3), which was about 1-2 orders of magnitudes lower than that of previous unmodified AuNPs-based colorimetric methods. By using the T-Hg2+-T recognition mechanism, high selectivity was also obtained. As an unmodified AuNPs-based colorimetric strategy, the system was simple in design, convenient in operation, and eliminated the requirements of separation processes, chemical modifications, and sophisticated instrumentations.

  2. Lab-on-paper with dual electrochemical/colorimetric detection for simultaneous determination of gold and iron.

    PubMed

    Apilux, Amara; Dungchai, Wijitar; Siangproh, Weena; Praphairaksit, Narong; Henry, Charles S; Chailapakul, Orawon

    2010-03-01

    A novel lab-on-paper device combining electrochemical and colorimetric detection for the rapid screening of Au(III) in the presence of a common interference, Fe(III), in industrial waste solutions is presented here. With dilute aqua regia (0.1 M HCl + 0.05 M HNO(3)) as the supporting electrolyte, square wave voltammetry on paper provided a well-defined reduction peak for Au(III) at approximately 287 +/- 12 mV vs Ag/AgCl. Under the optimized working conditions, the calibration curve showed good linearity in the concentration range of 1-200 ppm of Au(III) with a correlation coefficient of 0.997. The limit of detection (LOD) of the proposed method is 1 ppm. Interferences from various cations were also studied. Fe(III) is the only metal that affects the electrochemical determination of Au(III) when present above a 2.5-fold excess concentration of that of the Au(III). To overcome this limitation, a colorimetric method was used to simultaneously detect Fe(III) as a screening tool. The procedure was then successfully applied to determine Au(III) in gold-refining waste solutions. The results are in agreement with those obtained from inductively coupled plasma-atomic emission spectrometry (ICP-AES). PMID:20121066

  3. Gold nanoparticles for the colorimetric and fluorescent detection of ions and small organic molecules

    NASA Astrophysics Data System (ADS)

    Liu, Dingbin; Wang, Zhuo; Jiang, Xingyu

    2011-04-01

    In recent years, gold nanoparticles (AuNPs) have drawn considerable research attention in the fields of catalysis, drug delivery, imaging, diagnostics, therapy and biosensors due to their unique optical and electronic properties. In this review, we summarized recent advances in the development of AuNP-based colorimetric and fluorescent assays for ions including cations (such as Hg2+, Cu2+, Pb2+, As3+, Ca2+, Al3+, etc) and anions (such as NO2-, CN-, PF6-, F-, I-, oxoanions), and small organic molecules (such as cysteine, homocysteine, trinitrotoluene, melamine and cocaine, ATP, glucose, dopamine and so forth). Many of these species adversely affect human health and the environment. Moreover, we paid particular attention to AuNP-based colorimetric and fluorescent assays in practical applications.

  4. Colorimetric detection of trace water in tetrahydrofuran using N,N'-substituted oxoporphyrinogens.

    PubMed

    Ishihara, Shinsuke; Labuta, Jan; ikorsk, Tom; Burda, Jaroslav V; Okamoto, Naoko; Abe, Hideki; Ariga, Katsuhiko; Hill, Jonathan P

    2012-04-25

    Oxoporphyrinogens (OxPs) bind water molecules at pyrrolic NH and quinonoid carbonyl groups leading to visible colour changes due to variation in the ?-electronic structure of OxPs. Introduction of hydrophilic substituents at two pyrrole NH groups improves sensitivity to H(2)O, and one OxP derivative is a colorimetric indicator of trace H(2)O (~50 ppm) in THF. PMID:22422278

  5. Virgin silver nanoparticles as colorimetric nanoprobe for simultaneous detection of iodide and bromide ion in aqueous medium.

    PubMed

    Bothra, Shilpa; Kumar, Rajender; Pati, Ranjan K; Kuwar, Anil; Choi, Heung-Jin; Sahoo, Suban K

    2015-10-01

    A simple colorimetric nanoprobe based on virgin silver nanoparticles (AgNPs) was developed for the selective detection of iodide and bromide ions via aggregation and anti-aggregation mechanism. With addition of I(-) ions, virgin AgNPs, in presence of Fe(3+), showed perceptible color change from yellow to colorless along with disappearance of surface plasmon resonance (SPR) band of AgNPs at 400 nm. But in presence of Cr(3+), AgNPs turned yellow upon addition of I(-)and Br(-) anions. The developed virgin AgNPs probe showed high specificity and selectivity with the detection limits down to 0.32 ?M and 1.32 ?M for I(-) ions via two different mechanistic routes. Also, the designed probe detects Br(-) with a detection limit down to 1.67 ?M. PMID:25950637

  6. Virgin silver nanoparticles as colorimetric nanoprobe for simultaneous detection of iodide and bromide ion in aqueous medium

    NASA Astrophysics Data System (ADS)

    Bothra, Shilpa; Kumar, Rajender; Pati, Ranjan K.; Kuwar, Anil; Choi, Heung-Jin; Sahoo, Suban K.

    2015-10-01

    A simple colorimetric nanoprobe based on virgin silver nanoparticles (AgNPs) was developed for the selective detection of iodide and bromide ions via aggregation and anti-aggregation mechanism. With addition of I- ions, virgin AgNPs, in presence of Fe3+, showed perceptible color change from yellow to colorless along with disappearance of surface plasmon resonance (SPR) band of AgNPs at 400 nm. But in presence of Cr3+, AgNPs turned yellow upon addition of I-and Br- anions. The developed virgin AgNPs probe showed high specificity and selectivity with the detection limits down to 0.32 ?M and 1.32 ?M for I- ions via two different mechanistic routes. Also, the designed probe detects Br- with a detection limit down to 1.67 ?M.

  7. A sensitive aptasensor for colorimetric detection of adenosine triphosphate based on the protective effect of ATP-aptamer complexes on unmodified gold nanoparticles.

    PubMed

    Huo, Yuan; Qi, Liang; Lv, Xiao-Jun; Lai, Ting; Zhang, Jing; Zhang, Zhi-Qi

    2016-04-15

    Adenosine triphosphate (ATP) is the most direct source of energy in organisms. This study is the first to demonstrate that ATP-aptamer complexes provide greater protection for unmodified gold nanoparticles (AuNPs) against salt-induced aggregation than either aptamer or ATP alone. This protective effect was confirmed using transmission electron microscopy, dynamic light scattering, Zeta potential measurement, and fluorescence polarization techniques. Utilizing controlled particle aggregation/dispersion as a gauge, a sensitive and selective aptasensor for colorimetric detection of ATP was developed using ATP-binding aptamers as the identification element and unmodified AuNPs as the probe. This aptasensor exhibited a good linear relationship between the absorbance and the logarithm concentration of ATP within a 50-1000nM range. ATP analogs such as guanosine triphosphate, uridine triphosphate and cytidine triphosphate resulted in little or no interference in the determination of ATP. PMID:26638040

  8. A colorimetric method for highly sensitive and accurate detection of iodide by finding the critical color in a color change process using silver triangular nanoplates.

    PubMed

    Yang, Xiu-Hua; Ling, Jian; Peng, Jun; Cao, Qiu-E; Ding, Zhong-Tao; Bian, Long-Chun

    2013-10-10

    In this contribution, we demonstrated a novel colorimetric method for highly sensitive and accurate detection of iodide using citrate-stabilized silver triangular nanoplates (silver TNPs). Very lower concentration of iodide can induce an appreciable color change of silver TNPs solution from blue to yellow by fusing of silver TNPs to nanoparticles, as confirmed by UV-vis absorption spectroscopy and transmission electron microscopy (TEM). The principle of this colorimetric assay is not an ordinary colorimetry, but a new colorimetric strategy by finding the critical color in a color change process. With this strategy, 0.1 ?M of iodide can be recognized within 30 min by naked-eyes observation, and lower concentration of iodide down to 8.8 nM can be detected using a spectrophotometer. Furthermore, this high sensitive colorimetric assay has good accuracy, stability and reproducibility comparing with other ordinary colorimetry. We believe this new colorimetric method will open up a fresh insight of simple, rapid and reliable detection of iodide and can find its future application in the biochemical analysis or clinical diagnosis. PMID:24070486

  9. Multifunctional Janus hematite-silica nanoparticles: mimicking peroxidase-like activity and sensitive colorimetric detection of glucose.

    PubMed

    Lu, Chang; Liu, Xiangjiang; Li, Yunfeng; Yu, Fang; Tang, Longhua; Hu, Yanjie; Ying, Yibin

    2015-07-22

    The design and engineering of multifunctional nanostructures with multiple components and synergistic properties are in urgent demand for variety of acceptable biosensing platforms, enabling users to fulfill multiple tasks in a single nanosystem. Herein, we report using an asymmetric hematite-silica hybrid of Janus γ-Fe2O3/SiO2 nanoparticles (JFSNs) as a multifunctional biosensing platform for sensitive colorimetric detection of H2O2 and glucose. It was demonstrated that JFSNs exhibit an intrinsic peroxidase-like catalytic activity. Compared with natural enzyme, JFSNs nanoenzymes could be used over a wider range of pH and temperatures and were more stable over time. Importantly, besides its excellent catalytic activity, the asymmetric properties of the Janus nanoparticle enable it to form the multiple functional utilities for various biosensing applications, including the ease of surface modification without deactivation of catalytic activity and recoverable use by magnetic separation. Thus, we utilized JFSNs with glucose oxidase (GOx) immobilization for glucose-sensitive colorimetric detection, which exhibited both catalytic activity of glucose oxidase and peroxidase with high selectivity and acceptable reproducibility. By combining these two analysis systems into Janus particles, an all-in-one and reusable sensor for blood glucose was formed and has the capability for determination of glucose in complex samples such as serum. These results suggest that such Janus nanosystems have the potential to construct robust nanoarchitecture with multiple functionalities for various biosensing applications. PMID:26110779

  10. Continuous colorimetric screening assay for detection of d-amino acid aminotransferase mutants displaying altered substrate specificity.

    PubMed

    Barber, Janet E B; Damry, Adam M; Calderini, Guido F; Walton, Curtis J W; Chica, Roberto A

    2014-10-15

    D-Amino acid aminotransferase (DAAT) catalyzes the synthesis of numerous d-amino acids, making it an attractive biocatalyst for the production of enantiopure d-amino acids. To bolster its biocatalytic applicability, improved variants displaying increased activity toward non-native substrates are desired. Here, we report the development of a high-throughput, colorimetric, continuous coupled enzyme assay for the screening of DAAT mutant libraries that is based on the use of d-amino acid oxidase (DAAO). In this assay, the d-amino acid product of DAAT is oxidized by DAAO with concomitant release of hydrogen peroxide, which is detected colorimetrically by the addition of horseradish peroxidase and o-dianisidine. Using this assay, we measured apparent KM and kcat values for DAAT and identified mutants displaying altered substrate specificity via the screening of cell lysates in 96-well plates. The DAAO coupled assay is sensitive in that it allowed the detection of a DAAT mutant displaying an approximately 2000-fold decrease in kcat/KM relative to wild type. In addition, the DAAO assay enabled the identification of two DAAT mutants (V33Y and V33G) that are more efficient than wild type at transaminating the non-native acceptor phenylpyruvate. We expect that this assay will be useful for the engineering of additional mutants displaying increased activity toward non-native substrates. PMID:24949900

  11. Enhanced peroxidase-like activity of porphyrin functionalized ceria nanorods for sensitive and selective colorimetric detection of glucose.

    PubMed

    Liu, Qingyun; Ding, Yanyuan; Yang, Yanting; Zhang, Leyou; Sun, Lifang; Chen, Pengpeng; Gao, Chun

    2016-02-01

    Ceria nanorods modified with 5,10,15,20-tetrakis(4-carboxyl phenyl)-porphyrin (H2TCPP) were prepared. These nanocomposites (H2TCPP-CeO2) exhibited the intrinsic peroxidase-like activity and could catalyze the oxidation of classical peroxidase substrate 3,3',5,5'-tetramethylbiphenyl dihydrochloride (TMB2HCl) in the presence of H2O2 to produce a typical color reaction from colorless to blue. Our results demonstrated that both the H2TCPP-CeO2 nanocomposites and CeO2 nanorods exhibited higher thermal durance than that of HRP. The affinity of The H2TCPP-CeO2 nanocomposites toward H2O2 and TMB is similar to that of HRP. Fluorescent results indicated that the catalytic mechanism of the H2TCPP-CeO2 nanocomposites were from the decomposition of H2O2 into hydroxyl radicals. Based on these studies, a simple, sensitive, and selective visual and colorimetric method using TMB as the substrate was designed to detect glucose when combined with glucose oxidase. The proposed colorimetric method can detect H2O2 at a low detection limit of 6.110(-6)M and a dynamic range of 10(-5)-10(-4)molL(-1). This method can also detect glucose at a low detection limit of 3.310(-5)molL(-1) and a dynamic range of 5.010(-5)-1.010(-4)molL(-1). PMID:26652395

  12. Recent progress in fluorescent and colorimetric chemosensors for detection of amino acids.

    PubMed

    Zhou, Ying; Yoon, Juyoung

    2012-01-01

    Due to the biological importance of amino acids, the development of optical probes for these molecules has been an active research area in recent years. This tutorial review focuses on recent contributions since the year 2000 concerning the fluorescent or colorimetric sensors for amino acids, and is organized according to their structural classification and reaction types. For reaction based chemosensors, the works are classified according to the mechanisms between sensors and amino acids, including imine formation, Michael addition, thiazinane or thiazolidine formation, cleavage of a sulfonate ester, cleavage of disulfide, metal complexes-displace coordination and others. PMID:21799954

  13. A colorimetric biosensor for detection of attomolar microRNA with a functional nucleic acid-based amplification machine.

    PubMed

    Li, Dandan; Cheng, Wei; Yan, Yurong; Zhang, Ye; Yin, Yibing; Ju, Huangxian; Ding, Shijia

    2016-01-01

    A functional nucleic acid-based amplification machine was designed for simple and label-free ultrasensitive colorimetric biosensing of microRNA (miRNA). The amplification machine was composed of a complex of trigger template and C-rich DNA modified molecular beacon (MB) and G-rich DNA (GDNA) as the probe, polymerase and nicking enzyme, and a dumbbell-shaped amplification template. The presence of target miRNA triggered MB mediated strand displacement to cyclically release nicking triggers, which led to a toehold initiated rolling circle amplification to produce large amounts of GDNAs. The formed GDNAs could stack with hemin to form G-quadruplex/hemin DNAzyme, a well-known horseradish peroxidase (HRP) mimic, for catalyzing a colorimetric reaction. The modified MB improved the stringent target recognition and reduced background signal. The proposed sensing strategy showed very high sensitivity and selectivity with a wide dynamic range from 10aM to 1.0nM, and enabled successful visual analysis of trace amount of miRNA in real sample by the naked eye. This rapid and highly efficient signal amplification strategy provided a simple and sensitive platform for miRNA detection. It would be a versatile and powerful tool for clinical molecular diagnostics. PMID:26695292

  14. Colorimetric detection of urea, urease, and urease inhibitor based on the peroxidase-like activity of gold nanoparticles.

    PubMed

    Deng, Hao-Hua; Hong, Guo-Lin; Lin, Feng-Lin; Liu, Ai-Lin; Xia, Xing-Hua; Chen, Wei

    2016-04-01

    Herein, we reported for the first time that gold nanoparticles-catalyzed 3,3',5,5'-tetramethylbenzidine-H2O2 system can serve as an ultrasensitive colorimetric pH indicator. Gold nanoparticles acted as a catalyst and imitated the function of horseradish peroxidase. The absorbance at 450 nm of the yellow-color product in the catalytic reaction exhibited a linear fashion over the pH range of 6.40-6.60. On the basis of this property, we constructed a novel sensing platform for the determination of urea, urease, and urease inhibitor. The limit of detection for urea and urease was 5 μM and 1.8 U/L, respectively. The half-maximal inhibition value IC50 of acetohydroxamic acid was found to be 0.05 mM. Urea in human urine and urease in soil were detected with satisfied results. PMID:26995642

  15. Colorimetric detection of fluoride ions by anthraimidazoledione based sensors in the presence of Cu(ii) ions.

    PubMed

    Sarkar, Amrita; Bhattacharyya, Sudipta; Mukherjee, Arindam

    2016-01-01

    Anthraquinone based anion receptors have gained importance due to their colorimetric response on sensing a specific anion and the possibility of tuning this property by varying the conjugated moiety (the donor) to the diamine. In this work, we have synthesized and characterized four anthraimidazoledione compounds having 2,5-dihydroxy benzene, 4-(bis(2-chloroethyl)amino)benzene, imidazole and 4-methylthiazole moieties respectively (). All of them were probed for their potential as anion sensors to study the effect of changes in the hydrogen bond donor-acceptor. The p-hydroquinone bound anthraimidazoledione () and thioimidazole bound anthraimidazoledione () were able to detect both F(-) and CN(-) in the presence of other anions Cl(-), Br(-), I(-), H2PO4(-), OAc(-), NO3(-) and ClO4(-). Both and could not differentiate F(-) from CN(-) and provided a similar response to both. The (1)H NMR studies of and with F(-), showed the formation of [HF2](-) at 16.3 ppm and the (19)F NMR showed a sharp peak at -145 ppm in both cases. However, although there may be NMR evidence of [HF2](-) formation F(-) may not be detected colorimetrically if the CT band remains almost unchanged, as found for . The results emphasize that the change of a hetero atom in the donor moiety of an anthraimidazoledione may render a large difference in sensitivity. In the case of selective detection of F(-) was possible in the presence of 0.5 equivalent of Cu(2+) with the exhibition of a distinct green colour with a Δλ shift of ca. 50 nm in contrast to CN(-) which showed orange colouration with a Δλ shift of only 15 nm. In the presence of Cu(2+) the F(-) detection limit was 0.038(5) ppm (below the WHO specified level) at a receptor concentration of 25 μM. PMID:26659520

  16. A Simple and Green Route for Room-Temperature Synthesis of Gold Nanoparticles and Selective Colorimetric Detection of Cysteine.

    PubMed

    Bagci, Pelin Onsekizoglu; Wang, Yi-Cheng; Gunasekaran, Sundaram

    2015-09-01

    Gold nanoparticles (AuNPs) were synthesized at room temperature following a simple, rapid, and green route using fresh-squeezed apple juice as a reducing reagent. The optimal AuNPs, based on the particle color, stability, and color change suitable for colorimetric detection of cysteine (Cys), are synthesized using 5 mL of 10% apple juice, 1 mL of 10 mM gold precursor solution, and 1 mL of 0.1 M NaOH. Under this set of parameters, the AuNPs are synthesized within 30 min at room temperature. The average size (11.1 3.2 nm) and ? potential (-36.5 mV) of the AuNPs synthesized were similar to those of AuNPs prepared via the conventional citrate-reduction method. In the presence of Cys, unlike with any other amino acid, the AuNPs aggregated, possibly due to the gold-sulfur covalent interaction, yielding red-to-purple color change of the sample solution. The red-shift of the localized surface plasmon resonance peak of the AuNPs responsible for the color change was recorded by UV-vis spectrometer. The effect of other potential interferents such as glucose, ascorbic acid, K(+) , Na(+) , Ca(2+) , Zn(2+) , Ag(+) , Ni(2+) , Cu(2+) , Co(2+) , and Hg(2+) were also examined. The results show that AuNPs can be used to selectively detect and measure Cys with a linear dependency in the range of 2 to 100 ?M and a limit of detection (signal-to-noise ratio > 3) of 50 nM. The results suggest that the green-synthesized AuNPs are useful for simple, rapid, and sensitive colorimetric detection of Cys, which is an essential amino acid in food and biological systems. PMID:26239641

  17. Architecture based on the integration of intermolecular G-quadruplex structure with sticky-end pairing and colorimetric detection of DNA hybridization

    NASA Astrophysics Data System (ADS)

    Li, Hongbo; Wu, Zai-Sheng; Shen, Zhifa; Shen, Guoli; Yu, Ruqin

    2014-01-01

    An interesting discovery is reported in that G-rich hairpin-based recognition probes can self-assemble into a nano-architecture based on the integration of an intermolecular G-quadruplex structure with the sticky-end pairing effect in the presence of target DNAs. Moreover, GNPs modified with partly complementary DNAs can intensively aggregate by hybridization-based intercalation between intermolecular G-quadruplexes, indicating an inspiring assembly mechanism and a powerful colorimetric DNA detection. The proposed intermolecular G-quadruplex-integrated sticky-end pairing assembly (called GISA)-based colorimetric system allows a specific and quantitative assay of p53 DNA with a linear range of more than two orders of magnitude and a detection limit of 0.2 nM, suggesting a considerably improved analytical performance. And more to the point, the discrimination of single-base mismatched target DNAs can be easily conducted via visual observation. The successful development of the present colorimetric system, especially the GISA-based aggregation mechanism of GNPs is different from traditional approaches, and offers a critical insight into the dependence of the GNP aggregation on the structural properties of oligonucleotides, opening a good way to design colorimetric sensing probes and DNA nanostructure. An interesting discovery is reported in that G-rich hairpin-based recognition probes can self-assemble into a nano-architecture based on the integration of an intermolecular G-quadruplex structure with the sticky-end pairing effect in the presence of target DNAs. Moreover, GNPs modified with partly complementary DNAs can intensively aggregate by hybridization-based intercalation between intermolecular G-quadruplexes, indicating an inspiring assembly mechanism and a powerful colorimetric DNA detection. The proposed intermolecular G-quadruplex-integrated sticky-end pairing assembly (called GISA)-based colorimetric system allows a specific and quantitative assay of p53 DNA with a linear range of more than two orders of magnitude and a detection limit of 0.2 nM, suggesting a considerably improved analytical performance. And more to the point, the discrimination of single-base mismatched target DNAs can be easily conducted via visual observation. The successful development of the present colorimetric system, especially the GISA-based aggregation mechanism of GNPs is different from traditional approaches, and offers a critical insight into the dependence of the GNP aggregation on the structural properties of oligonucleotides, opening a good way to design colorimetric sensing probes and DNA nanostructure. Electronic supplementary information (ESI) available: Experimental section, supplementary Figures and perspectives. See DOI: 10.1039/c3nr03547f

  18. [Colorimetric detection of human influenza A H1N1 virus by reverse transcription loop mediated isothermal amplification].

    PubMed

    Nie, Kai; Wang, Da-Yan; Qin, Meng; Gao, Rong-Bao; Wang, Miao; Zou, Shu-Mei; Han, Feng; Zhao, Xiang; Li, Xi-Yan; Shu, Yue-Long; Ma, Xue-Jun

    2010-03-01

    A simple, rapid and sensitive colorimetric Reverse Transcription Loop Mediated Isothermal Amplification (RT-LAMP) method was established to detect human influenza A H1N1 virus. The method employed a set of six specially designed primers that recognized eight distinct sequences of the HA gene for amplification of nucleic acid under isothermal conditions at 65 degrees C for one and half hour. The amplification process of RT-LAMP was monitored by the addition of HNB (Hydroxy naphthol blue) dye prior to amplification. A positive reaction was indicated by a color change from violet to sky blue and confirmed by agarose electrophoresis. The specificity of the RT-LAMP assay was validated by cross-reaction with different swine and human influenza virus including human seasonal influenza A /H1N1 A /H3N2, influenza B and swine A /H1N1. The sensitivity of this assay was evaluated by serial dilutions of RNA molecules from in vitro transcription of human influenza A H1N1 HA gene. The assay was further evaluated with 30 clinical specimens with suspected pandemic influenza A H1N1 virus infection in parallel with RT-PCR detection and 26 clinical specimens with seasonal influenza virus infection. Our results showed that the RT-LAMP was able to achieve a sensitivity of 60 RNA copies with high specificity, and detection rate was comparable to that of the RT-PCR with the clinical samples of pandemic influenza A H1N1 infection. The RT-LAMP reaction with HNB could also be measured at 650nm in a microplate reader for quantitative analysis. Thus, we concluded that this colorimetric RT-LAMP assay had potential for the rapid screening of the human influenza A H1N1 virus infection in National influenza monitoring network laboratories and sentinel hospitals of provincial and municipal region in China. PMID:20480635

  19. Directional Detection of Dark Matter

    NASA Astrophysics Data System (ADS)

    Mayet, F.; Billard, J.; Santos, D.

    2012-02-01

    Directional detection is a promising Dark Matter search strategy. Taking advantage on the rotation of the Solar system around the galactic center through the Dark Matter halo, it allows to show a direction dependence of WIMP events. It requires the simultaneous measurement of the energy and the 3D track of low energy recoils, which is a common challenge for all current projects of directional detectors. The third CYGNUS workshop on directional dark matter detection has brought together the scientific community working on both theoretical and experimental aspects of the subject. In this paper, we give an introductory revue of directional detection of Dark Matter, focusing on the main recent progresses.

  20. Detection of two different mRNAs in a single section by dual in situ hybridization: a comparison between colorimetric and fluorescent detection.

    PubMed

    Barroso-Chinea, Pedro; Aymerich, Mara S; Castle, Mara M; Prez-Manso, Mnica; Tun, Teresa; Erro, Elena; Lanciego, Jos L

    2007-05-15

    We have compared the performance of two methods designed to simultaneously detect two different mRNAs within a single brain section by dual ISH. Specific mRNA riboprobes labeled with biotin and digoxigenin were simultaneously hybridized and visualized using either brightfield or fluorescence microscopy. For brightfield visualization, the biotin-labeled riboprobe was detected with a peroxidase chromogen, whereas, an alkaline phosphatase substrate was used for the detection of the digoxigenin-labeled riboprobe. Dual fluorescent ISH involved the detection of the biotin-labeled riboprobe with an Alexa((R))488-conjugated streptavidin followed by the visualization of the digoxigenin-labeled riboprobe with the red fluorescent substrate HNPP. The dual ISH protocols presented here offer sensitive methods to detect the expression of two mRNAs of interest, with both colorimetric and fluorescent ISH each having its strengths and limitations. For example, dual colorimetric ISH has proven to be particularly useful to study the distribution of two mRNAs in different brain nuclei, whereas, dual fluorescent ISH has provided better results when studying the co-localization of two different mRNAs in single neurons. The comprehensive step-by-step procedure is presented, together with a troubleshooting section in which the advantages and limitations of these procedures are reviewed in depth. Moreover, alternative protocols for dual ISH were also compared to those presented here. PMID:17306886

  1. Microgel coating of magnetic nanoparticles via bienzyme-mediated free-radical polymerization for colorimetric detection of glucose.

    PubMed

    Wu, Qing; Wang, Xia; Liao, Chuanan; Wei, Qingcong; Wang, Qigang

    2015-10-28

    This study describes a new strategy for the fabrication of magnetic core-shell microgels by free-radical polymerization triggered by the cascade reaction of glucose oxidase (GOx) and horseradish peroxidase (HRP). The mild polymerization around the interface of the magnetic nanoparticles permits the mild coating of the microgel layer with excellent characteristics for various applications in biocatalysis and medical diagnostics, as well as in clinical fields. The immobilized bienzyme within the microgel has a largely retained activity relative to the non-immobilized one. The confining effect of the microgel and the well designed distance between the two enzymes can benefit the diffusion of intermediates to the HRP active site. The final microgels can be incontestably employed as sensitive biosensors for colorimetric glucose detection. PMID:26412343

  2. Microgel coating of magnetic nanoparticles via bienzyme-mediated free-radical polymerization for colorimetric detection of glucose

    NASA Astrophysics Data System (ADS)

    Wu, Qing; Wang, Xia; Liao, Chuanan; Wei, Qingcong; Wang, Qigang

    2015-10-01

    This study describes a new strategy for the fabrication of magnetic core-shell microgels by free-radical polymerization triggered by the cascade reaction of glucose oxidase (GOx) and horseradish peroxidase (HRP). The mild polymerization around the interface of the magnetic nanoparticles permits the mild coating of the microgel layer with excellent characteristics for various applications in biocatalysis and medical diagnostics, as well as in clinical fields. The immobilized bienzyme within the microgel has a largely retained activity relative to the non-immobilized one. The confining effect of the microgel and the well designed distance between the two enzymes can benefit the diffusion of intermediates to the HRP active site. The final microgels can be incontestably employed as sensitive biosensors for colorimetric glucose detection.This study describes a new strategy for the fabrication of magnetic core-shell microgels by free-radical polymerization triggered by the cascade reaction of glucose oxidase (GOx) and horseradish peroxidase (HRP). The mild polymerization around the interface of the magnetic nanoparticles permits the mild coating of the microgel layer with excellent characteristics for various applications in biocatalysis and medical diagnostics, as well as in clinical fields. The immobilized bienzyme within the microgel has a largely retained activity relative to the non-immobilized one. The confining effect of the microgel and the well designed distance between the two enzymes can benefit the diffusion of intermediates to the HRP active site. The final microgels can be incontestably employed as sensitive biosensors for colorimetric glucose detection. Electronic supplementary information (ESI) available: Experimental details and ESI figures. See DOI: 10.1039/c5nr05716g

  3. Dark Matter: Direct Detection

    SciTech Connect

    Chardin, G.

    2009-12-16

    The identification of Dark Matter is an outstanding question of contemporary physics. I summarize the main experimental strategies developed to answer this question, focusing on cryogenic detectors and comparing these detectors to their double-phase xenon and argon competitors. I discuss in particular the main developments in charge-phonon (CDMS, EDELWEISS) and light-phonon detectors (CRESST, ROSEBUD). Finally, I discuss the prospects of WIMP detection within the next few years by the CDMS, CRESST, EDELWEISS and XENON experiments, and their successors EURECA, GEODM and XENON-1 ton.

  4. Direct-Photon-Detection Communications

    NASA Technical Reports Server (NTRS)

    Lesh, J. R.; Katz, J.

    1985-01-01

    Optical communications system based on direct detection of photons rather than heterodyning of carrier with local oscillator. Direct-detection system uses single laser source, pulse-position modulation, and Reed-Solomon coding to protect against burst errors. Conventional photomultiplier tube is receiver. Technology applicable to terrestrial communications.

  5. Comparison of colorimetric and chemiluminescent enzyme-linked immunosorbent assay for the detection of endosulfan in food samples.

    PubMed

    Deepak, T S; Rashmi, Shenoy; Manonmani, Haravey K

    2015-12-01

    Pesticides have become part of food protection since their inception. Endosulfan, an organochlorine insecticide, has been used against insect pests such as whiteflies, aphids, red spiders and mites. Methods of immunochemical assays have been devised for the determination and analysis of pesticides and commonly used for the analysis of contaminants in food, water, soil and body fluids. Chicken IgY antibodies raised against endosulfan haptens were used for the detection of endosulfan. We have compared colorimetric (CO) and chemiluminescence (CL) enzyme-linked immunosorbent assay (ELISA) techniques for the detection of endosulfan isomers in a food matrix. CL ELISA assay was found to be more sensitive than CO assay. The mean recovery was 81.2-95.6% for α- and β-endosulfan-spiked food samples with 2.8-4.6% relative standard deviation. The detection of the endosulfan isomers was linear in the range 100 µg/mL-5 fg/mL, with a limit of detection at 100 µg/mL and 5 fg/mL for the CL ELISA method and 100 µg/mL and 1 ng/mL for the CO ELISA method respectively. These methods can be used for the rapid and reliable detection of organochlorine pesticide endosulfan. Copyright © 2015 John Wiley & Sons, Ltd. PMID:25808457

  6. Iodine-Mediated Etching of Gold Nanorods for Plasmonic ELISA Based on Colorimetric Detection of Alkaline Phosphatase.

    PubMed

    Zhang, Zhiyang; Chen, Zhaopeng; Wang, Shasha; Cheng, Fangbin; Chen, Lingxin

    2015-12-23

    Here, we propose a plasmonic enzyme-linked immunosorbent assay (ELISA) based on highly sensitive colorimetric detection of alkaline phosphatase (ALP), which is achieved by iodine-mediated etching of gold nanorods (AuNRs). Once the sandwich-type immunocomplex is formed, the ALP bound on the polystyrene microwells will hydrolyze ascorbic acid 2-phosphate into ascorbic acid. Subsequently, iodate is reduced to iodine, a moderate oxidant, which etches AuNRs from rod to sphere in shape. The shape change of AuNRs leads to a blue-shift of longitudinal localized surface plasmon resonance. As a result, the solution of AuNRs changes from blue to red. Benefiting from the highly sensitive detection of ALP, the proposed plasmonic ELISA has achieved an ultralow detection limit (100 pg/mL) for human immunoglobulin G (IgG). Importantly, the visual detection limit (3.0 ng/mL) allows the rapid differential diagnosis with the naked eye. The further detection of human IgG in fetal bovine serum indicates its applicability to the determination of low abundance protein in complex biological samples. PMID:26619266

  7. A new colorimetric platform for ultrasensitive detection of protein and cancer cells based on the assembly of nucleic acids and proteins.

    PubMed

    Chen, Chaohui; Liu, Yufei; Zheng, Zhenhua; Zhou, Guohua; Ji, Xinghu; Wang, Hanzhong; He, Zhike

    2015-06-23

    An amplified colorimetric method has been developed for the detection of protein and cancer cells based on the assembly of nucleic acids and proteins for the first time. In this process, the assembly of nucleic acids was triggered by a biotinylated DNA strand after a sandwich immunoreaction. The biotinylated DNA strand and sandwich immunocomplex were connected by streptavidin. Then, the assembly of biotinylated bovine serum albumin (Biotin-BSA) and streptavidin-horseradish peroxidase (SA-HRP) occurred at a node of the assembled products of nucleic acids through the biotin-streptavidin reaction. Under the catalysis of horseradish peroxidase, 3,3',5,5'-tetramethylbenzidine (TMB) was oxidized by H2O2 and the oxidized product was analyzed by its UV-vis absorbance signal and sensitive colorimetric detection. This colorimetric sensor could not only achieve the quantitative determination of protein by UV-vis absorbance but could also be applied for semiquantitative determination by digital visualization. Using alpha-fetoprotein (AFP) as the model target, this proposed colorimetric method showed a wide linear range from 5 pg/mL to 1 ng/mL with a detection limit of 1.95 pg/mL by the instrument, and even 5 pg/mL target protein could be distinguished simply by the naked eye. This approach was then expanded to detect cancer cells based on the recognition of folic acid receptors that were over-expressed on the cancer cells by folic acid-tethered DNA. More importantly, this strategy can be further used as a universal colorimetric method for the determination of viruses or other proteins by changing the corresponding antibodies. PMID:26092332

  8. Detection of measles, mumps and rubella viruses by immuno-colorimetric assay and its application in focus reduction neutralization tests.

    PubMed

    Vaidya, Sunil R; Kumbhar, Neelakshi S; Bhide, Vandana S

    2014-12-01

    Measles, mumps and rubella are vaccine-preventable diseases; however limited epidemiological data are available from low-income or developing countries. Thus, it is important to investigate the transmission of these viruses in different geographical regions. In this context, a cell culture-based rapid and reliable immuno-colorimetric assay (ICA) was established and its utility studied. Twenty-three measles, six mumps and six rubella virus isolates and three vaccine strains were studied. Detection by ICA was compared with plaque and RT-PCR assays. In addition, ICA was used to detect viruses in throat swabs (n?=?24) collected from patients with suspected measles or mumps. Similarly, ICA was used in a focus reduction neutralization test (FRNT) and the results compared with those obtained by a commercial IgG enzyme immuno assay. Measles and mumps virus were detected 2 days post-infection in Vero or Vero-human signaling lymphocytic activation molecule cells, whereas rubella virus was detected 3 days post-infection in Vero cells. The blue stained viral foci were visible by the naked eye or through a magnifying glass. In conclusion, ICA was successfully used on 35 virus isolates, three vaccine strains and clinical specimens collected from suspected cases of measles and mumps. Furthermore, an application of ICA in a neutralization test (i.e., FRNT) was documented; this may be useful for sero-epidemiological, cross-neutralization and pre/post-vaccine studies. PMID:25244651

  9. Colorimetric method for rapid detection of Oxacillin resistance in Staphylococcus aureus and its comparison with PCR for mec A gene.

    PubMed

    Ghanwate, Niraj; Thakare, Prashant; Bhise, P R; Gawande, Sonali

    2016-01-01

    Rapid and accurate detection of Methicillin Resistant Staphylococcus aureus (MRSA) is an important role of clinical microbiology laboratories to avoid treatment failure. The detection of MRSA is based on phenotypic assays which require at least 24 h to perform. Detection of the mecA gene or of PBP 2a is the "gold standard", but not always available. The aim of this study was to evaluate a rapid method for detection of MRSA by using 3 (4, 5 dimethyl thiazole -2-yl) -2, 5 diphenyl tetrazolium bromide (MTT). Total 126 isolates of MRSA were collected from tertiary healthcare center and were confirmed by oxacillin screening agar test as per CLSI guidelines. Amplification of mecA gene was performed by using PCR. MTT assay was carried out for all the isolates in 96 well Microtitre plate and compared with standard methods of CLSI. Out of 126 isolates, 98 were found to be mecA positive. MTT method was found to be 98.98% sensitive and 96.43% specific. The MTT based colorimetric method is rapid and simple test for screening of oxacillin resistance in Staphylococcus aureus. It significantly shortens the time to just 7 h required to obtained a drug susceptibility test and could be useful to screen MRSA. PMID:26960268

  10. Colorimetric method for rapid detection of Oxacillin resistance in Staphylococcus aureus and its comparison with PCR for mec A gene

    PubMed Central

    Ghanwate, Niraj; Thakare, Prashant; Bhise, P. R.; Gawande, Sonali

    2016-01-01

    Rapid and accurate detection of Methicillin Resistant Staphylococcus aureus (MRSA) is an important role of clinical microbiology laboratories to avoid treatment failure. The detection of MRSA is based on phenotypic assays which require at least 24 h to perform. Detection of the mecA gene or of PBP 2a is the “gold standard”, but not always available. The aim of this study was to evaluate a rapid method for detection of MRSA by using 3 (4, 5 dimethyl thiazole -2-yl) -2, 5 diphenyl tetrazolium bromide (MTT). Total 126 isolates of MRSA were collected from tertiary healthcare center and were confirmed by oxacillin screening agar test as per CLSI guidelines. Amplification of mecA gene was performed by using PCR. MTT assay was carried out for all the isolates in 96 well Microtitre plate and compared with standard methods of CLSI. Out of 126 isolates, 98 were found to be mecA positive. MTT method was found to be 98.98% sensitive and 96.43% specific. The MTT based colorimetric method is rapid and simple test for screening of oxacillin resistance in Staphylococcus aureus. It significantly shortens the time to just 7 h required to obtained a drug susceptibility test and could be useful to screen MRSA. PMID:26960268

  11. A colorimetric nitrite detection system with excellent selectivity and high sensitivity based on Ag@Au nanoparticles.

    PubMed

    Li, Tianhua; Li, Yonglong; Zhang, Yujie; Dong, Chen; Shen, Zheyu; Wu, Aiguo

    2015-02-21

    Excessive uptake of NO2(-) is detrimental to human health, but the currently available methods used to sensitively detect this ion in the environment are cumbersome and expensive. In this study, we developed an improved NO2(-) detection system based on a redox etching strategy of CTAB-stabilized Ag-Au core-shell nanoparticles (Ag@AuNPs). The detection mechanism was verified by UV-Vis spectroscopy, TEM and XPS. The detection system produces a color change from purple to colorless in response to an increase of NO2(-) concentration. The selectivity of detection of NO2(-), both with the unaided eye and by measurement of UV-Vis spectra, is excellent in relation to other ions, including Cu(2+), Co(2+), Ni(2+), Cr(3+), Al(3+), Pb(2+), Cd(2+), Ca(2+), Ba(2+), Zn(2+), Mn(2+), Mg(2+), Fe(3+), Hg(2+), Ag(+), K(+), F(-), PO4(3-), C2O4(2-), SO3(2-), CO3(2-), SO4(2-), NO3(-) and CH3-COO(-) (Ac(-)). The limit of detection (LOD) for NO2(-) is 1.0 ?M by eye and 0.1 ?M by UV-Vis spectroscopy. The LOD by eye is lower than the lowest previously reported value (4.0 ?M). There is a good linear relationship between A/A0 and the concentration of NO2(-) from 1.0 to 20.0 ?M NO2(-), which permits a quantitative assay. The applicability of our detection system was also verified by analysis of NO2(-) in tap water and lake water. The results demonstrate that our Ag@AuNP-based detection system can be used for the rapid colorimetric detection of NO2(-) in complex environmental samples, with excellent selectivity and high sensitivity. PMID:25564225

  12. Colorimetric detection of in situ metal acetates and fluorides by a bipyridyl-linked Schiff base.

    PubMed

    Suganya, Sivalingam; Zo, Hye Jin; Park, Jong S; Velmathi, Sivan

    2014-12-01

    Here, we present a new bipyridyl moiety linked Schiff base (bipy-1) that is well characterized using spectroscopic techniques. Colorimetric and UV-vis titrations were used to study the photophysical properties of bipy-1 in the presence of various tetrabutyl ammonium salt of anions and metal salts containing different counter cations. bipy-1 showed selective recognition of dimethyl sulphoxide solution of tetrabutyl ammonium salt of F(-) ion accompanied with a UV-vis band at 529?nm and interesting binding of aqueous Co, Ni, and Cu acetates/fluorides, as confirmed by distinct color changes from fluorescent green to pink or orange and a strong band around 480-510?nm in the UV-vis spectrum. However, in the presence of Co, Ni, and Cu countercations, any form of metal acetate/fluorides was found to be able to respond to similar color changes from fluorescent green to pink or orange, showing a band around 480-510?nm. This type of output clearly indicates that the in situ formation of Co, Ni, and Cu acetates/fluorides also coordinates with bipyridyl nitrogen atoms. PMID:25319616

  13. Highly efficient colorimetric detection of target cancer cells utilizing superior catalytic activity of graphene oxide-magnetic-platinum nanohybrids

    NASA Astrophysics Data System (ADS)

    Kim, Moon Il; Kim, Min Su; Woo, Min-Ah; Ye, Youngjin; Kang, Kyoung Suk; Lee, Jinwoo; Park, Hyun Gyu

    2014-01-01

    Enzyme-linked immunosorbent assays (ELISAs) have most widely been applied in immunoassays for several decades. However, several unavoidable limitations (e.g., instability caused by structural unfolding) of natural enzymes have hindered their widespread applications. Here, we describe a new nanohybrid consisting of Fe3O4 magnetic nanoparticles (MNPs) and platinum nanoparticles (Pt NPs), simultaneously immobilized on the surface of graphene oxide (GO). By synergistically integrating highly catalytically active Pt NPs and MNPs on GO whose frameworks possess high substrate affinity, the nanohybrid is able to achieve up to a 30-fold higher maximal reaction velocity (Vmax) compared to that of free GO for the colorimetric reaction of the peroxidase substrate, 3,3',5,5'-tetramethylbenzidine (TMB), and enable rapid detection of target cancer cells. Specifically, using this new assay system, clinically important breast cancer cells are detected in a 5 min time period at room temperature with high specificity and sensitivity. The remarkably high capability to catalyze oxidation reactions could allow the nanohybrid to replace conventional peroxidase-based immunoassay systems as part of new, rapid, robust and convenient assay systems which can be widely utilized for the identification of important target molecules.Enzyme-linked immunosorbent assays (ELISAs) have most widely been applied in immunoassays for several decades. However, several unavoidable limitations (e.g., instability caused by structural unfolding) of natural enzymes have hindered their widespread applications. Here, we describe a new nanohybrid consisting of Fe3O4 magnetic nanoparticles (MNPs) and platinum nanoparticles (Pt NPs), simultaneously immobilized on the surface of graphene oxide (GO). By synergistically integrating highly catalytically active Pt NPs and MNPs on GO whose frameworks possess high substrate affinity, the nanohybrid is able to achieve up to a 30-fold higher maximal reaction velocity (Vmax) compared to that of free GO for the colorimetric reaction of the peroxidase substrate, 3,3',5,5'-tetramethylbenzidine (TMB), and enable rapid detection of target cancer cells. Specifically, using this new assay system, clinically important breast cancer cells are detected in a 5 min time period at room temperature with high specificity and sensitivity. The remarkably high capability to catalyze oxidation reactions could allow the nanohybrid to replace conventional peroxidase-based immunoassay systems as part of new, rapid, robust and convenient assay systems which can be widely utilized for the identification of important target molecules. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr05539f

  14. Colorimetric and electrochemical phosphodiesterase inhibition assays for yessotoxin detection: development and comparison with LC-MS/MS.

    PubMed

    Campàs, Mònica; de la Iglesia, Pablo; Fernández-Tejedor, Margarita; Diogène, Jorge

    2010-03-01

    This work describes the development and applicability of two functional assays for the detection of yessotoxin (YTX), a polycyclic ether marine toxin produced by dinoflagellates. The assays are based on the interaction between this toxin and the phosphodiesterase (PDE) enzyme and the subsequent measurement of the enzyme activity by colorimetric and electrochemical methods. Firstly, several enzyme substrates were tested in order to select those able to be detected by colorimetry or electrochemistry after enzymatic hydrolysis. The substrates that provided the highest absorbance values and density currents were p-nitrophenyl phenylphosphonate and alpha-naphthyl phosphate, respectively. After optimisation of the experimental parameters, limits of detection of 0.8 and 0.6 microM were attained by colorimetry and electrochemistry, respectively. An inhibitory effect of YTX on the PDE activity was observed. The assays have been applied to the analysis of YTX production by Protoceratium reticulatum cultures, and results were compared with liquid chromatography-tandem mass spectrometry analysis. PMID:20140666

  15. A universal probe design for colorimetric detection of single-nucleotide variation with visible readout and high specificity

    PubMed Central

    Chen, Xueping; Zhou, Dandan; Shen, Huawei; Chen, Hui; Feng, Wenli; Xie, Guoming

    2016-01-01

    Single-nucleotide variation (SNV) is a crucial biomarker for drug resistance-related detection in cancer and bacterial infection. However, the unintended binding of DNA probes limits the specificity of SNV detection, and the need for redesigned sequences compromise the universality of SNV assay. Herein, we demonstrated a universal and low-cost assay for the colorimetric discrimination of drug-resistance related point mutation. By the use of a universal DNA probe and a split G-quadruplex, the signal could be recognized by naked eye at room temperature. The DNA probe was used as a signal reporter which not only improved the universality, but also enabled high specificity of probe hybridization. This assay was successfully applied in the detection of cancer-related SNV in the epidermal growth factor receptor (EGFR) gene, kirsten rat sarcoma viral oncogene homologue (KRAS), and tuberculosis drug-resistance related point mutation in RNA polymerase beta subunit gene (rpoB) with high specificity and visible readout. This method was simple, rapid, high-throughput and effective, which was suitable for point-of-care applications. PMID:26830326

  16. A universal probe design for colorimetric detection of single-nucleotide variation with visible readout and high specificity.

    PubMed

    Chen, Xueping; Zhou, Dandan; Shen, Huawei; Chen, Hui; Feng, Wenli; Xie, Guoming

    2016-01-01

    Single-nucleotide variation (SNV) is a crucial biomarker for drug resistance-related detection in cancer and bacterial infection. However, the unintended binding of DNA probes limits the specificity of SNV detection, and the need for redesigned sequences compromise the universality of SNV assay. Herein, we demonstrated a universal and low-cost assay for the colorimetric discrimination of drug-resistance related point mutation. By the use of a universal DNA probe and a split G-quadruplex, the signal could be recognized by naked eye at room temperature. The DNA probe was used as a signal reporter which not only improved the universality, but also enabled high specificity of probe hybridization. This assay was successfully applied in the detection of cancer-related SNV in the epidermal growth factor receptor (EGFR) gene, kirsten rat sarcoma viral oncogene homologue (KRAS), and tuberculosis drug-resistance related point mutation in RNA polymerase beta subunit gene (rpoB) with high specificity and visible readout. This method was simple, rapid, high-throughput and effective, which was suitable for point-of-care applications. PMID:26830326

  17. Colorimetric sensor array with unmodified noble metal nanoparticles for naked-eye detection of proteins and bacteria.

    PubMed

    Li, Dongyang; Dong, Yanhua; Li, Bingyu; Wu, Yayan; Wang, Kai; Zhang, Sichun

    2015-11-21

    Herein we report a novel strategy for the detection and identification of proteins using unmodified noble metal nanoparticles. Five gold nanoparticles (AuNPs) and two silver nanoparticles (AgNPs) with different sizes were utilized as sensing elements to create a colorimetric sensor array. In the presence of proteins, the UV-vis absorbance of the noble metal nanoparticles changed due to the interactions between the protein and nanoparticles, producing distinct absorbance response patterns which can be visually detected by the naked eye. The color pattern of the array is a unique "fingerprints" for each protein sample, which can be differentiated by linear discriminant analysis (LDA). Ten different proteins at concentrations of 0.5, 5 and 50 ?M have be successfully discriminated. Moreover, the array was also able to discriminate different bacteria at a concentration of 0.05 OD in 200 ?L, as well as cancer cells at the level of 5000 cells in 200 ?L. This work demonstrates that an unmodified noble metal nanoparticle-based protein detection array has potential for applications in medical diagnostics. PMID:26446513

  18. A sensitive and selective colorimetric method for detection of copper ions based on anti-aggregation of unmodified gold nanoparticles.

    PubMed

    Hormozi-Nezhad, M Reza; Abbasi-Moayed, Samira

    2014-11-01

    A highly sensitive and selective colorimetric method for detection of copper ions, based on anti-aggregation of D-penicillamine (D-PC) induced aggregated gold nanoparticles (AuNPs) was developed. Copper ions can hinder the aggregation of AuNPs induced by D-PC, through formation of mixed-valence complex with D-PC that is a selective copper chelator. In the presence of a fixed amount of D-PC, the aggregation of AuNPs decreases with increasing concentrations of Cu(2+) along with a color change from blue to red in AuNPs solution and an increase in the absorption ratio (A520/A650). Under the optimum experimental conditions (pH 7, [AuNPs] =3.0 nmol L(-1) and [NaCl]=25 mmol L(-1)), a linear calibration curve for Cu(2+) was obtained within the range of 0.05-1.85 µmol L(-1) with a limit of detection (3Sb) of 30 nmol L(-1). Excellent selectivity toward Cu(2+) was observed among various metal ions due to a specific complex formation between Cu(2+) and D-PC. The proposed method has been successfully applied for the detection of Cu(2+) in various real samples. PMID:25127588

  19. Rapid and simple colorimetric detection of Escherichia coli O157:H7 in apple juice using a novel recombinant bacteriophage-based Method.

    PubMed

    Hoang, Hoang A; Dien, Le T

    2015-01-01

    In this study, a bacteriophage-based method for the colorimetric detection of E. coli O157:H7 in apple juice was investigated. Firstly, a gene encoding Cytochrome c Peroxidase (CCP) chromogenic enzyme was inserted into a wild type PP01 phage genome to construct the recombinant PP01ccp phage that was used in the production of the chromogenic enzyme through specific infection into E. coli O157:H7. The method was then examined in the colorimetric detection of E. coli O157:H7 in broth, and the appearance of E. coli O157:H7 in broth was confirmed by the color change after a few minutes of the enzyme assay. Secondly, the method was investigated in the colorimetric detection of E. coli O157:H7 in apple juice. A low E. coli O157:H7 concentration as 1 CFU mL(-1) was detected in 15 h that was in a shorter time than in previous bioluminescence phage-based methods. Moreover, the method is much simpler compared to other previous phage-based methods since it enables detection without the need for expensive apparatus. PMID:26133507

  20. Visual and highly sensitive detection of cancer cells by a colorimetric aptasensor based on cell-triggered cyclic enzymatic signal amplification.

    PubMed

    Zhang, Xianxia; Xiao, Kunyi; Cheng, Liwei; Chen, Hui; Liu, Baohong; Zhang, Song; Kong, Jilie

    2014-06-01

    Rapid and efficient detection of cancer cells at their earliest stages is one of the central challenges in cancer diagnostics. We developed a simple, cost-effective, and highly sensitive colorimetric method for visually detecting rare cancer cells based on cell-triggered cyclic enzymatic signal amplification (CTCESA). In the absence of target cells, hairpin aptamer probes (HAPs) and linker DNAs stably coexist in solution, and the linker DNA assembles DNA-AuNPs, producing a purple solution. In the presence of target cells, the specific binding of HAPs to the target cells triggers a conformational switch that results in linker DNA hybridization and cleavage by nicking endonuclease-strand scission cycles. Consequently, the cleaved fragments of linker DNA can no longer assemble into DNA-AuNPs, resulting in a red color. UV-vis spectrometry and photograph analyses demonstrated that this CTCESA-based method exhibited selective and sensitive colorimetric responses to the presence of target CCRF-CEM cells, which could be detected by the naked eye. The linear response for CCRF-CEM cells in a concentration range from 10(2) to 10(4) cells was obtained with a detection limit of 40 cells, which is approximately 20 times lower than the detection limit of normal AuNP-based methods without amplification. Given the high specificity and sensitivity of CTCESA, this colorimetric method provides a sensitive, label-free, and cost-effective approach for early cancer diagnosis and point-to-care applications. PMID:24819867

  1. Non-aggregation based label free colorimetric sensor for the detection of Cu2+ based on catalyzing etching of gold nanorods by dissolve oxygen.

    PubMed

    Liu, Jia-Ming; Jiao, Li; Lin, Li-Ping; Cui, Ma-Lin; Wang, Xin-Xing; Zhang, Li-Hong; Zheng, Zhi-Yong; Jiang, Shu-Lian

    2013-12-15

    A label-free non-aggregation colorimetric sensor has been designed for the detection of Cu(2+), based on Cu(2+) catalyzing etching of gold nanorods (AuNRs) along longitudinal axis induced by dissolve oxygen in the presence of S2O3(2-), which caused the aspect ratio (length/width) of AuNRs to decrease and the color of the solution to distinctly change. The linear range and the detection limit (LD, calculated by 10 Sb/k, n=11) of this sensor were 0.080-4.8 M Cu(2+) and 0.22 M Cu(2+), respectively. This sensor has been utilized to detect Cu(2+) in tap water and human serum samples with the results agreeing well with those of inductively coupled plasma-mass spectroscopy (ICP-MS), showing its remarkable practicality. In order to prove the possibility of catalyzing AuNRs non-aggregation colorimetric sensor for the detection of Cu(2+), the morphological structures of AuNRs were characterized by high resolution transmission electron microscopy (HRTEM) and the sensing mechanism of colorimetric sensor for the detection of Cu(2+) was also discussed. PMID:24209363

  2. Colorimetric detection of Bi (III) in water and drug samples using pyridine-2,6-dicarboxylic acid modified silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Mohammadi, Somayeh; Khayatian, Gholamreza

    2015-09-01

    A new selective, simple, fast and sensitive method is developed for sensing assay of Bi (III) using pyridine-2,6-dicarboxylic acid or dipicolinic acid (DPA) modified silver nanoparticles (DPA-AgNPs). Silver nanoparticles (AgNPs) were synthesized by reducing silver nitrate (AgNO3) with sodium borohydride (NaBH4) in the presence of DPA. Bismuth detection is based on color change of nanoparticle solution from yellow to red that is induced in the presence of Bi (III). Aggregation of DPA-AgNPs has been confirmed with UV-vis absorption spectra and transmission electron microscopy (TEM) images. Under the optimized conditions, a good linear relationship (correlation coefficient r = 0.995) is obtained between the absorbance ratio (A525/A390) and the concentration of Bi (III) in the 0.40-8.00 μM range. This colorimetric probe allows Bi (III) to be rapidly quantified with a 0.01 μM limit of detection. The present method successfully applied to determine bismuth in real water and drug samples. Recoveries of water samples were in the range of 91.2-99.6%.

  3. Colorimetric detection of Bi (III) in water and drug samples using pyridine-2,6-dicarboxylic acid modified silver nanoparticles.

    PubMed

    Mohammadi, Somayeh; Khayatian, Gholamreza

    2015-09-01

    A new selective, simple, fast and sensitive method is developed for sensing assay of Bi (III) using pyridine-2,6-dicarboxylic acid or dipicolinic acid (DPA) modified silver nanoparticles (DPA-AgNPs). Silver nanoparticles (AgNPs) were synthesized by reducing silver nitrate (AgNO3) with sodium borohydride (NaBH4) in the presence of DPA. Bismuth detection is based on color change of nanoparticle solution from yellow to red that is induced in the presence of Bi (III). Aggregation of DPA-AgNPs has been confirmed with UV-vis absorption spectra and transmission electron microscopy (TEM) images. Under the optimized conditions, a good linear relationship (correlation coefficient r=0.995) is obtained between the absorbance ratio (A525/A390) and the concentration of Bi (III) in the 0.40-8.00 μM range. This colorimetric probe allows Bi (III) to be rapidly quantified with a 0.01 μM limit of detection. The present method successfully applied to determine bismuth in real water and drug samples. Recoveries of water samples were in the range of 91.2-99.6%. PMID:25919329

  4. Colorimetric microtiter plate receptor-binding assay for the detection of freshwater and marine neurotoxins targeting the nicotinic acetylcholine receptors.

    PubMed

    Rubio, Fernando; Kamp, Lisa; Carpino, Justin; Faltin, Erin; Loftin, Keith; Molg, Jordi; Aroz, Rmulo

    2014-12-01

    Anatoxin-a and homoanatoxin-a, produced by cyanobacteria, are agonists of nicotinic acetylcholine receptors (nAChRs). Pinnatoxins, spirolides, and gymnodimines, produced by dinoflagellates, are antagonists of nAChRs. In this study we describe the development and validation of a competitive colorimetric, high throughput functional assay based on the mechanism of action of freshwater and marine toxins against nAChRs. Torpedo electrocyte membranes (rich in muscle-type nAChR) were immobilized and stabilized on the surface of 96-well microtiter plates. Biotinylated ?-bungarotoxin (the tracer) and streptavidin-horseradish peroxidase (the detector) enabled the detection and quantitation of anatoxin-a in surface waters and cyclic imine toxins in shellfish extracts that were obtained from different locations across the US. The method compares favorably to LC/MS/MS and provides accurate results for anatoxin-a and cyclic imine toxins monitoring. Study of common constituents at the concentrations normally found in drinking and environmental waters, as well as the tolerance to pH, salt, solvents, organic and inorganic compounds did not significantly affect toxin detection. The assay allowed the simultaneous analysis of up to 25 samples within 3.5h and it is well suited for on-site or laboratory monitoring of low levels of toxins in drinking, surface, and ground water as well as in shellfish extracts. PMID:25260255

  5. Colorimetric microtiter plate receptor-binding assay for the detection of freshwater and marine neurotoxins targeting the nicotinic acetylcholine receptors

    USGS Publications Warehouse

    Rubio, Fernando; Kamp, Lisa; Carpino, Justin; Faltin, Erin; Loftin, Keith A.; Molgó, Jordi; Aráoz, Rómulo

    2014-01-01

    Anatoxin-a and homoanatoxin-a, produced by cyanobacteria, are agonists of nicotinic acetylcholine receptors (nAChRs). Pinnatoxins, spirolides, and gymnodimines, produced by dinoflagellates, are antagonists of nAChRs. In this study we describe the development and validation of a competitive colorimetric, high throughput functional assay based on the mechanism of action of freshwater and marine toxins against nAChRs. Torpedo electrocyte membranes (rich in muscle-type nAChR) were immobilized and stabilized on the surface of 96-well microtiter plates. Biotinylated α-bungarotoxin (the tracer) and streptavidin-horseradish peroxidase (the detector) enabled the detection and quantitation of anatoxin-a in surface waters and cyclic imine toxins in shellfish extracts that were obtained from different locations across the US. The method compares favorably to LC/MS/MS and provides accurate results for anatoxin-a and cyclic imine toxins monitoring. Study of common constituents at the concentrations normally found in drinking and environmental waters, as well as the tolerance to pH, salt, solvents, organic and inorganic compounds did not significantly affect toxin detection. The assay allowed the simultaneous analysis of up to 25 samples within 3.5 h and it is well suited for on-site or laboratory monitoring of low levels of toxins in drinking, surface, and ground water as well as in shellfish extracts.

  6. Loop-mediated isothermal amplification combined with colorimetric nanogold for detection of the microsporidian Enterocytozoon hepatopenaei in penaeid shrimp.

    TOXLINE Toxicology Bibliographic Information

    Suebsing R; Prombun P; Srisala J; Kiatpathomchai W

    2013-05-01

    AIMS: Enterocytozoon hepatopenaei is an emerging microsporidian parasite that has been linked to recent losses caused by white faeces syndrome (WFS) in cultivated giant or black tiger shrimp Penaeus (Penaeus) monodon and whiteleg shrimp Penaeus (Litopenaeus) vannamei in Asia. To more accurately assess its impact on shrimp production and to determine reservoir carriers for control measures, our objective was to establish a loop-mediated isothermal amplification (LAMP) assay combined with colorimetric nanogold (AuNP) for rapid, sensitive and inexpensive detection of this parasite.METHODS AND RESULTS: A set of six specific primers was designed to successfully detect the SSU rRNA gene of E. hepatopenaei by a LAMP reaction of 45 in at 65C combined with visual detection of the amplification product via hybridization at 65C for 5 min with a ssDNA-labelled nanogold probe, followed by salt-induced AuNP aggregation (total assay time, approximately 50 min). This method gave similar results to LAMP followed by electrophoresis or spectrophotometric detection, and it was more sensitive (002 fg total DNA) than a conventional nested PCR (02 fg total DNA). The new method gave negative results with shrimp DNA templates extracted from diseased shrimp containing other pathogens, indicating that the LAMP-AuNP assay was specific for E. hepatopenaei.CONCLUSIONS: Without sacrificing sensitivity or specificity, the new LAMP-AuNP assay significantly reduced the time, ease and cost for molecular detection of E. hepatopenaei in shrimp.SIGNIFICANCE AND IMPACT OF THE STUDY: The new method employs simple, inexpensive equipment and involves simple steps making it applicable for small field laboratories. Wider application of the method to screen broodstock before use in a hatchery, to screen postlarvae before stocking shrimp ponds, to test for natural carriers and to monitor shrimp in rearing ponds would help to assess and reduce the negative impact of this parasite in shrimp farming.

  7. Colorimetric detection of sequence-specific microRNA based on duplex-specific nuclease-assisted nanoparticle amplification.

    PubMed

    Wang, Qian; Li, Ru-Dong; Yin, Bin-Cheng; Ye, Bang-Ce

    2015-09-21

    Developing simple and rapid methods for sequence-specific microRNA (miRNA) analysis is imperative to the miRNA study and use in clinical diagnosis. We have developed a colorimetric method for miRNA detection based on duplex-specific nuclease (DSN)-assisted signal amplification coupled to the aggregation of gold nanoparticles (AuNPs). The proposed method involves two processes: target-mediated probe digestion by a DSN enzyme and probe-triggered AuNP aggregation as a switch for signal output. The reaction system consists of a rationally designed probe complex formed by two partly complementary DNA probes, and two sets of different oligonucleotide-modified AuNPs with sequences complementary to a DNA probe in the probe complex. In the presence of target miRNA, the probe complex is invaded, resulting in the formation of a miRNA-probe heteroduplex as the substrate of the DSN enzyme, and releasing the other probe to link to the AuNPs. The proposed method allows quantitative detection of miR-122 in the range of 20 pM to 1 nM with a detection limit of ?16 pM, and shows an excellent ability to discriminate single-base differences. Moreover, the detection assay can be applied to accurately quantify miR-122 in cancerous cell lysates which is in excellent agreement with the results from a commercial miRNA detection kit. This method is simple, cost-effective, highly selective, and free of dye label and separation procedures. PMID:26258182

  8. Binding-induced and label-free colorimetric method for protein detection based on autonomous assembly of hemin/G-quadruplex DNAzyme amplification strategy.

    PubMed

    Wu, Hao; Zhang, Kai; Liu, Yaling; Wang, Hongyong; Wu, Jun; Zhu, Feifan; Zou, Pei

    2015-02-15

    In this work, a new binding-induced and label-free colorimetric method for protein detection has been developed on the basis of an autonomous assembly of hemin/G-quadruplex DNAzyme amplification strategy. The system consists of two proximity probes carrying two aptamer sequences as recognition elements for target, and two hairpin structures include three-fourths and one-fourth of the G-quadruplex sequences in inactive configuration as functional elements. In the presence of target protein, two proximity probes bind to the protein simultaneously, forming a stable DNA-protein complex. Then the complex triggers an autonomous cross-opening of the two functional hairpin structures, leading to the formation of numerous hemin/G-quadruplex DNAzymes. The resulting DNAzymes catalyze the oxidation of colorless 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(2-)) to the green-colored ABTS(-) with the presence of H2O2, thus providing the amplified colorimetric detection of target. Using human ?-thrombin as the protein target, this binding-induced DNAzyme amplification colorimetric method affords high sensitivity with a detection limit of 1.9 pM. Furthermore, this method might be further extended to sensitive detection of other proteins by simply replacing recognition elements of proximity probes. PMID:25310491

  9. Tuning Toehold Length and Temperature to Achieve Rapid, Colorimetric Detection of DNA from the Disassembly of DNA-Gold Nanoparticle Aggregates.

    PubMed

    Lam, Michael K; Gadzikwa, Tendai; Nguyen, Trang; Kausar, Abu; Alladin-Mustan, B Safeenaz; Sikder, Md Delwar; Gibbs-Davis, Julianne M

    2016-02-16

    Gold nanoparticles have been widely utilized to achieve colorimetric detection for various diagnostic applications. One of the most frequently used methods for DNA detection involves the aggregation of DNA-modified gold nanoparticles driven by target DNA hybridization. This process, however, is intrinsically slow, limiting its use in rapid diagnostics. Here we take advantage of the reverse process: the disassembly of preformed aggregates triggered by the addition of target DNA via a strand displacement mechanism. A systematic study of the dependence of the disassembly rate on temperature, with and without toeholds, has delivered a system that produces an extremely rapid colorimetric response. Furthermore, using an optimal toehold length of 5 nucleotides, target triggered disassembly is rapid over a wide range of ambient temperatures. Using this overhang system, simple visualization of low picomole amounts of target DNA is possible within 10 min at room temperature. PMID:26707736

  10. Highly sensitive colorimetric detection of glucose in a serum based on DNA-embeded Au@Ag core-shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Kang, Fei; Hou, Xiangshu; Xu, Kun

    2015-10-01

    Glucose is a key energy substance in diverse biology and closely related to the life activities of the organism. To develop a simple and sensitive method for glucose detection is extremely urgent but still remains a key challenge. Herein, we report a colorimetric glucose sensor in a homogeneous system based on DNA-embedded core-shell Au@Ag nanoparticles. In this assay, a glucose substrate was first catalytically oxidized by glucose oxidase to produce H2O2 which would further oxidize and gradually etch the outer silver shell of Au@Ag nanoparticles. Afterwards, the solution color changed from yellow to red and the surface plasmon resonance (SPR) band of Au@Ag nanoparticles declined and red-shifted from 430 to 516 nm. Compared with previous silver-based glucose colorimetric detection strategies, the distinctive SPR band change is superior to the color variation, which is critical to the high sensitivity of this assay. Benefiting from the outstanding optical property, robust stability and well-dispersion of the core-shell Au@AgNPs hybrid, this colorimetric assay obtained a detection limit of glucose as low as 10 nM, which is at least a 10-fold improvement over other AgNPs-based procedures. Moreover, this optical biosensor was successfully employed to the determination of glucose in fetal bovine serum.

  11. Highly sensitive colorimetric detection of glucose in a serum based on DNA-embeded Au@Ag core-shell nanoparticles.

    PubMed

    Kang, Fei; Hou, Xiangshu; Xu, Kun

    2015-10-01

    Glucose is a key energy substance in diverse biology and closely related to the life activities of the organism. To develop a simple and sensitive method for glucose detection is extremely urgent but still remains a key challenge. Herein, we report a colorimetric glucose sensor in a homogeneous system based on DNA-embedded core-shell Au@Ag nanoparticles. In this assay, a glucose substrate was first catalytically oxidized by glucose oxidase to produce H2O2 which would further oxidize and gradually etch the outer silver shell of Au@Ag nanoparticles. Afterwards, the solution color changed from yellow to red and the surface plasmon resonance (SPR) band of Au@Ag nanoparticles declined and red-shifted from 430 to 516 nm. Compared with previous silver-based glucose colorimetric detection strategies, the distinctive SPR band change is superior to the color variation, which is critical to the high sensitivity of this assay. Benefiting from the outstanding optical property, robust stability and well-dispersion of the core-shell Au@AgNPs hybrid, this colorimetric assay obtained a detection limit of glucose as low as 10 nM, which is at least a 10-fold improvement over other AgNPs-based procedures. Moreover, this optical biosensor was successfully employed to the determination of glucose in fetal bovine serum. PMID:26376788

  12. BSA-stabilized Pt nanozyme for peroxidase mimetics and its application on colorimetric detection of mercury(II) ions.

    PubMed

    Li, Wei; Chen, Bin; Zhang, Haixiang; Sun, Yanhua; Wang, Jun; Zhang, Jinli; Fu, Yan

    2015-04-15

    Bovine serum albumin (BSA) is chosen as the nucleation templates to synthesize Pt-based peroxidase nanomimetics with the average diameter of 2.0nm. The efficient Pt nanozymes consist of 57% Pt(0) and 43% Pt(2+), which possess highly peroxidase-like activity with the Km values of 0.119mM and 41.8mM toward 3,3',5,5'-tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2), respectively. Interestingly, Hg(2+) is able to down-regulate the enzymatic activity of Pt nanoparticles, mainly through the interactions between Hg(2+) and Pt(0). It is the first report to explore a colorimetric Hg(2+) sensing system on the basis of peroxidase mimicking activities of Pt nanoparticles. One of our most intriguing results is that BSA-stabilized Pt nanozymes demonstrate the ability to sense Hg(2+) ions in aqueous solution without significant interference from other metal ions. The Hg(2+) detection limit of 7.2nM is achieved with a linear response range of 0-120nM, and the developed sensing system is potentially applicable for quantitative determination of Hg(2+) in drinking water. PMID:25437360

  13. Sensitive colorimetric detection of cyromazine in cucumber samples by using label-free gold nanoparticles and polythymine.

    PubMed

    Liu, Jinchuan; Bai, Wenhui; Zhu, Chao; Yan, Mengmeng; Yang, Shuming; Chen, Ailiang

    2015-05-01

    Cyromazine (CYR) can cause serious damage to the organs of animals or human beings, and it was found to bind to polythymine (polyT10) via multiple hydrogen bonding interactions. Based on this novel finding, a highly sensitive and simple colorimetric method was developed for CYR detection by using label-free gold nanoparticles (AuNPs) and polyT10. Under the optimized conditions, excellent linearity was acquired for CYR within the range of 1-500 ng mL(-1). In addition, the spectra and color changes of the AuNP solution were measured by spectrophotometry and observed by the naked eye, and the results showed that as low as 1 and 5 ng mL(-1) of CYR could be detected, depending upon the measurement methods. Afterwards, cucumber was selected to investigate the sample matrix effect and a sample pretreatment procedure was developed with simple homogenization and filtration. Even after 200 times dilution, the limit of detection (LOD) and limit of quantitation (LOQ) reached 252 ng g(-1) and 500 ng g(-1), respectively. The LOD and LOQ satisfied the Chinese requirement for the maximum residue limit (MRL), which is 0.5-1 ?g g(-1) of CYR in most vegetables. The assay also showed a good average recovery of 83.7-104.8% with the RSD of less than 7% and good selectivity for cyromazine over other pesticides that may exist in vegetable samples. The method proposed in this study was simple, fast, and highly sensitive and accurate, and the test result with this method was visible to the naked eye. Therefore, it could be used for routine determination of CYR residues in cucumber samples. PMID:25741673

  14. Immunosorbent analysis of ricin contamination in milk using colorimetric, chemiluminescence, and electrochemiluminescence detection

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Analytical methodology to detect ricin in food matrices is important because of the potential use of foodborne ricin as a terrorist weapon. Monoclonal antibodies (mAbs) that bind ricin were used for both capture and detection in sandwich enzyme-linked immunosorbent assay (ELISA) and electrochemilumi...

  15. Catalytic formation of silver nanoparticles by bovine serum albumin protected-silver nanoclusters and its application for colorimetric detection of ascorbic acid

    NASA Astrophysics Data System (ADS)

    Yang, Xiu-Hua; Ling, Jian; Peng, Jun; Cao, Qiu-E.; Wang, Lei; Ding, Zhong-Tao; Xiong, Jie

    2013-04-01

    We established a simple spectrophotometric and colorimetric method for detection of ascorbic acid based on the growth of silver nanoparticles in bovine serum albumin protected-silver nanoclusters (BSA-AgNCs) and Ag+ mixture. Due to the catalysis of BSA-AgNCs, ascorbic acid could reduce Ag+ to silver nanoparticles (NPs) at room temperature. The color of the mixture changed from colorless to yellow and a strong absorption band near 420 nm could be found in their absorption spectra owing to localized surface plasmon resonance (LSPR) of produced silver NPs. The absorbance changes at 420 nm had a good relationship with ascorbic acid concentration. Thus, we proposed a spectrophotometric and colorimetric method to determine ascorbic acid in concentration range from 2.0 to 50.0 ?M, with the corresponding limits of determination (3?) of 0.16 ?M.

  16. Visual and colorimetric detection of p-aminophenol in environmental water and human urine samples based on anisotropic growth of Ag nanoshells on Au nanorods.

    PubMed

    Lin, Tianran; Li, Zhihong; Song, Zhiping; Chen, Huan; Guo, Liangqia; Fu, Fengfu; Wu, Zujian

    2016-02-01

    A simple, sensitive, selective and high-resolution colorimetric method has been developed for the detection of p-aminophenol in environmental water and human urine samples. In the presence of p-aminophenol, silver ions are reduced to silver atoms and subsequently Ag nanoshells anisotropically grow on the surface of Au nanorods to generate orange slice-like Au@Ag core-shell nanocrystals, thereby resulting in the blue-shift of longitudinal surface plasmon resonance band of Au nanorods accompanying a sharp-contrast multicolor change. Using Au@Ag core-shell nanocrystals as the transducer, sub-micromolar p-aminophenol can be detected by the colorimetric method and 10?molL(-1) p-aminophenol can be visual readout by the naked eyes. Furthermore, a simple, cheap, portable test kit is constructed for the visual assay of urinary p-aminophenol without complicated sample pretreatment and sophisticated instruments. The proposed colorimetric method has the potential for the rapid and on-site analyses of p-aminophenol in environmental water and human urine samples. PMID:26653424

  17. Direct Detection of Cosmological Dust

    NASA Astrophysics Data System (ADS)

    Paerels, Frederik

    2000-09-01

    Detection of an X-ray scattering halo may be the only direct and unambiguous way to reveal dust in the intergalactic medium. Somewhat surprisingly, detecting cosmologically interesting amounts of dust should not be difficult with Chandra. We propose to search for a halo in the image of the soft X-ray bright, distant QSO 1508+5714 (z = 4.30). We can easily detect the amount of dust that could mimic the effect of a non-zero cosmological constant on the Hubble diagram of SNe Ia. Non-detection should settle this issue definitively. As a byproduct, we will obtain constraints on the history of dust from global star formation (or the other way around).

  18. A SIMPLE COLORIMETRIC METHOD TO DETECT BIOLOGICAL EVIDENCE OF HUMAN EXPOSURE TO MICROCYSTINS

    EPA Science Inventory

    Toxic cyanobacteria are contaminants of surface waters worldwide. Microcystins are some of the most commonly detected toxins. Biological evidence of human exposure may be difficult to obtain due to limitations associated with cost, laboratory capacity, analytic support, and exp...

  19. Multiplexed colorimetric detection of Kaposi's sarcoma associated herpesvirus and Bartonella DNA using gold and silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Mancuso, Matthew; Jiang, Li; Cesarman, Ethel; Erickson, David

    2013-01-01

    Kaposi's sarcoma (KS) is an infectious cancer occurring most commonly in human immunodeficiency virus (HIV) positive patients and in endemic regions, such as Sub-Saharan Africa, where KS is among the top four most prevalent cancers. The cause of KS is the Kaposi's sarcoma-associated herpesvirus (KSHV, also called HHV-8), an oncogenic herpesvirus that while routinely diagnosed in developed nations, provides challenges to developing world medical providers and point-of-care detection. A major challenge in the diagnosis of KS is the existence of a number of other diseases with similar clinical presentation and histopathological features, requiring the detection of KSHV in a biopsy sample. In this work we develop an answer to this challenge by creating a multiplexed one-pot detection system for KSHV DNA and DNA from a frequently confounding disease, bacillary angiomatosis. Gold and silver nanoparticle aggregation reactions are tuned for each target and a multi-color change system is developed capable of detecting both targets down to levels between 1 nM and 2 nM. The system developed here could later be integrated with microfluidic sample processing to create a final device capable of solving the two major challenges in point-of-care KS detection.

  20. A colorimetric and fluorescent turn on chemodosimeter for Pd2+ detection

    NASA Astrophysics Data System (ADS)

    Li, Lianqing; Liu, Zhihong

    2015-03-01

    A novel rhodamine derivative L had been successfully developed and well characterized by NMR, and Mass spectroscopy. Chemodosimeter L is a naked-eye fluorescent chemodosimeter for Pd2+ in aqueous solution. More over the detection limit of Chemodosimeter L is in 10-7 M level. The Ligand to L ratio was determined to be 1:2 according to the job's plot.

  1. DETECTION OF ESCHERICHIA COLI IN WATER USING A COLORIMETRIC GENE PROBE ASSAY

    EPA Science Inventory

    A commercially available DNA hydribization assay (Gene-trak , Framingham, MA. USA) was compared with the EC-MUG procedure for the detection of Escherichia coli in water. The gene probe gave positive responses for pure cultures of E. coli 0157:H7, E. fergusonii, Shigella sonnei, S...

  2. Colorimetric Detection of Ehrlichia Canis via Nucleic Acid Hybridization in Gold Nano-Colloids

    PubMed Central

    Muangchuen, Ajima; Chaumpluk, Piyasak; Suriyasomboon, Annop; Ekgasit, Sanong

    2014-01-01

    Canine monocytic ehrlichiosis (CME) is a major thick-bone disease of dog caused by Ehrlichia canis. Detection of this causal agent outside the laboratory using conventional methods is not effective enough. Thus an assay for E. canis detection based on the p30 outer membrane protein gene was developed. It was based on the p30 gene amplification using loop-mediated isothermal DNA amplification (LAMP). The primer set specific to six areas within the target gene were designed and tested for their sensitivity and specificity. Detection of DNA signals was based on modulation of gold nanoparticles' surface properties and performing DNA/DNA hybridization using an oligonucleotide probe. Presence of target DNA affected the gold colloid nanoparticles in terms of particle aggregation with a plasmonic color change of the gold colloids from ruby red to purple, visible by the naked eye. All the assay steps were completed within 90 min including DNA extraction without relying on standard laboratory facilities. This method was very specific to target bacteria. Its sensitivity with probe hybridization was sufficient to detect 50 copies of target DNA. This method should provide an alternative choice for point of care control and management of the disease. PMID:25111239

  3. Colorimetric detection of Ehrlichia canis via nucleic acid hybridization in gold nano-colloids.

    PubMed

    Muangchuen, Ajima; Chaumpluk, Piyasak; Suriyasomboon, Annop; Ekgasit, Sanong

    2014-01-01

    Canine monocytic ehrlichiosis (CME) is a major thick-bone disease of dog caused by Ehrlichia canis. Detection of this causal agent outside the laboratory using conventional methods is not effective enough. Thus an assay for E. canis detection based on the p30 outer membrane protein gene was developed. It was based on the p30 gene amplification using loop-mediated isothermal DNA amplification (LAMP). The primer set specific to six areas within the target gene were designed and tested for their sensitivity and specificity. Detection of DNA signals was based on modulation of gold nanoparticles' surface properties and performing DNA/DNA hybridization using an oligonucleotide probe. Presence of target DNA affected the gold colloid nanoparticles in terms of particle aggregation with a plasmonic color change of the gold colloids from ruby red to purple, visible by the naked eye. All the assay steps were completed within 90 min including DNA extraction without relying on standard laboratory facilities. This method was very specific to target bacteria. Its sensitivity with probe hybridization was sufficient to detect 50 copies of target DNA. This method should provide an alternative choice for point of care control and management of the disease. PMID:25111239

  4. A Novel Porphyrin-Containing Polyimide Nanofibrous Membrane for Colorimetric and Fluorometric Detection of Pyridine Vapor

    PubMed Central

    Lv, Yuanyuan; Zhang, Yani; Du, Yanglong; Xu, Jiayao; Wang, Junbo

    2013-01-01

    A novel zinc porphyrin-containing polyimide (ZPCPI) nanofibrous membrane for rapid and reversible detection of trace amounts of pyridine vapor is described. The membrane displays a distinct color change, as well as dramatic variations in absorption and fluorescent emission spectra, upon exposure to pyridine vapor. This condition allows the detection of the analyte at concentrations as low as 0.041 ppm. The vapochromic and spectrophotometric responses of the membrane are attributed to the formation of the ZPCPI-pyridine complex upon axial coordination. From surface plasmon resonance analysis, the affinity constant of ZPCPI-pyridine complex was calculated to be (3.98 0.25) 104 Lmol?1. The ZPCPI nanofibrous membrane also showed excellent selectivity for pyridine vapor over other common amines, confirming its applicability in the manufacture of pyridine-sensitive gas sensors. PMID:24256976

  5. BODIPY based colorimetric fluorescent probe for selective thiophenol detection: theoretical and experimental studies.

    PubMed

    Kand, Dnyaneshwar; Mishra, Pratyush Kumar; Saha, Tanmoy; Lahiri, Mayurika; Talukdar, Pinaki

    2012-09-01

    A BODIPY-based selective thiophenol probe capable of discriminating aliphatic thiols is reported. The fluorescence off-on effect upon reaction with thiol is elucidated with theoretical calculations. The sensing of thiophenol is associated with a color change from red to yellow and 63-fold enhancement in green fluorescence. Application of the probe for selective thiophenol detection is demonstrated by live cell imaging. PMID:22751002

  6. Colorimetric detection of hydrogen peroxide and glucose using the magnetic mesoporous silica nanoparticles.

    PubMed

    Wang, Yonghong; Zhou, Bo; Wu, Shun; Wang, Kemin; He, Xiaoxiao

    2015-03-01

    In this work, we synthesized a type of magnetic mesoporous silica nanoparticle (denoted as Fe3O4@MSN) with Fe3O4 as the core and mesoporous silica the shell. The superparamagnetic Fe3O4-core provides high peroxidase-mimic activity and makes the artificial enzymatic system easily recyclable. Furthermore, Fe3O4 nanoparticles are encapsulated in MSN shells to hinder the aggregation and keep them stable even under harsh conditions. Meanwhile, small active molecules are allowed to diffuse in and out of the MSN shells. Based on these functional units, the Fe3O4@MSN as robust nanoreactors can catalyze a self-organized cascade reaction, which includes oxidation of glucose by oxygen to yield gluconic acid and H2O2, and the latter further oxidizes 3,3,5,5-tetramethylbenzidine (TMB) to produce a color change. The Fe3O4@MSN, whose catalytic efficiency was not strongly dependent on pH and temperature, was successfully used for the detection of glucose and showed excellent sensitivity with a detection limit of 0.4×10(-5) mol/L. Nevertheless, the assay is also highly selective toward the glucose detection. PMID:25618726

  7. Development and evaluation of a colorimetric PCR system for the detection and typing of human papillomaviruses.

    PubMed

    Chouhy, Diego; Gil, Lisandro Bentez; Nocito, Ana L; Wojdyla, Daniel; Ornella, Leonardo; Cittadini, Jorge; Gardiol, Daniela; Giri, Adriana A

    2006-11-01

    In developing countries, the introduction of human papillomaviruses (HPV) DNA testing as an adjunct to cytological screening programs has been delayed due to the lack of high performance and cost effective diagnostic nucleic acid methods. In this study we report the development and evaluation of the L1HPVPCR, a PCR-based method for the detection and typing of five of the most prevalent high-risk HPV types. The L1HPVPCR assay combines amplification with the MY09/11 HPV consensus primer system, liquid hybridization of the PCR products with no radioactive probes and enzyme immunoassay analysis. The technique is a user-friendly system that allows accurate HPV DNA detection and typing with inexpensive instrumentation that could be performed with not sophisticated reagents in almost any laboratory. Different cutoff points for generic and specific HPV detection were determined using reproducibility analysis and receiver operating characteristic curves to ensure good analytical sensitivity and clinical effectiveness. We used the L1HPVPCR assay to estimate the prevalence of HPV infection in 127 women at risk of cervical cancer from the city of Rosario (Argentina), where no epidemiological data has been previously reported. Further, we explored the clinical utility of the L1HPVPCR assay respect the Pap smear using a combined diagnosis of cytology, histology and colposcopy as gold standard. In conclusion, our results indicate that the assay described here provides a tool for accurate HPV DNA testing and could be applied in regions where no commercial tests are available. PMID:17016633

  8. Gold nanoflowers based colorimetric detection of Hg2+ and Pb2+ ions

    NASA Astrophysics Data System (ADS)

    Nalawade, Pradnya; Kapoor, Sudhir

    2013-12-01

    An optical detection method based on the interaction of gold nanoflowers with Hg2+ and Pb2+ has been described. After interaction, gold nanoflowers change the color from violet to wine red. The nanoflowers are capable of determining Hg2+ and Pb2+ over a dynamic range of 1.0 10-6 and 1.0 10-5 M, respectively. The response time of nanoflowers depends on the concentration of ions. The presence of both Hg2+ and Pb2+ ions in the mixture having Au nanoflowers induced color changes of the solution within several seconds even at 1.0 10-6 M. Common metal ions were chosen to investigate their interference in Hg2+ and Pb2+ detection, and the concentration of each metal ion studied was 1.0 10-5 M. Other metallic ions could not induce color change even at 1.0 10-5 M. The feasibility of our method to detect Hg2+ and Pb2+ ions at high concentration in real water samples was verified. Water samples were from our own laboratory and no pretreatment was made. As the particles are stable they can be used for more than 3 months without observing any major deviation.

  9. Colorimetric Detection of Dengue by Single Tube Reverse-Transcription-Loop-Mediated Isothermal Amplification

    PubMed Central

    Teoh, Boon-Teong; Abd-Jamil, Juraina; Johari, Jefree; Sam, Sing-Sin; Tan, Kim-Kee; AbuBakar, Sazaly

    2015-01-01

    Dengue is usually diagnosed by isolation of the virus, serology or molecular diagnostic methods. Several commercial kits for the diagnosis of dengue are existing, but concerns have arisen regarding to the affordability and performance characteristics of these kits. Hence, the loop-mediated isothermal amplification (LAMP) is potentially ideal to be used especially in resource limited environments. Serum was collected from healthy donors and patients diagnosed with dengue infection. RNA extracted from the serum samples were tested by reverse-transcription-LAMP assay developed based on 3?-NCR gene sequences for DENV 14. Results were interpreted by a turbidity meter in real time or visually at the end of the assay. Sensitivity and specificity of RT-LAMP results were calculated and compared to qRT-PCR and ELISA. RT-LAMP is highly sensitive with the detection limit of 10 RNA copies for all serotypes. Dengue virus RNA was detected in all positive samples using RT-LAMP and none of the negative samples within 3045 minutes. With continuing efforts in the optimization of this assay, RT-LAMP may provide a simple and reliable test for detecting DENV in areas where dengue is prevalent. PMID:26384248

  10. A colorimetric chemosensor for Cu2+ ion detection based on an iridium(III) complex

    NASA Astrophysics Data System (ADS)

    Wang, Modi; Leung, Ka-Ho; Lin, Sheng; Chan, Daniel Shiu-Hin; Kwong, Daniel W. J.; Leung, Chung-Hang; Ma, Dik-Lung

    2014-10-01

    We report herein the synthesis and application of a series of novel cyclometalated iridium(III) complexes 1-3 bearing a rhodamine-linked NN ligand for the detection of Cu2+ ions. Under the optimised conditions, the complexes exhibited high sensitivity and selectivity for Cu2+ ions over a panel of other metal ions, and showed consistent performance in a pH value range of 6 to 8. Furthermore, the potential application of this system for the monitoring of Cu2+ ions in tap water or natural river water samples was demonstrated.

  11. A colorimetric chemosensor for Cu2+ ion detection based on an iridium(III) complex

    PubMed Central

    Wang, Modi; Leung, Ka-Ho; Lin, Sheng; Chan, Daniel Shiu-Hin; Kwong, Daniel W. J.; Leung, Chung-Hang; Ma, Dik-Lung

    2014-01-01

    We report herein the synthesis and application of a series of novel cyclometalated iridium(III) complexes 1?3 bearing a rhodamine-linked NN ligand for the detection of Cu2+ ions. Under the optimised conditions, the complexes exhibited high sensitivity and selectivity for Cu2+ ions over a panel of other metal ions, and showed consistent performance in a pH value range of 6 to 8. Furthermore, the potential application of this system for the monitoring of Cu2+ ions in tap water or natural river water samples was demonstrated. PMID:25348724

  12. Micromolar colorimetric detection of 2-hydroxy ketones with the water-soluble tetrazolium WST-1.

    PubMed

    Bommer, Martin; Ward, John M

    2016-01-15

    The archetypal triphenyl tetrazolium chloride (tetrazolium red) has been used in spectrophotometric microplate assays for 2-hydroxy ketones and, by extension, for the activity of enzymes including aminotransferase, transketolase, and pyruvate decarboxylase. Better sensitivity, dynamic range, and reproducibility of this method may be achieved by (i) in situ solubilization of the colored formazan with Cremophor EL and (ii) use of the newer-generation tetrazolium salts tetrazolium violet, iodonitrotetrazolium, or WST-1 (water-soluble tetrazolium). Two to 125?M hydroxy pyruvate, dihydroxy acetone, and indole pyruvate produced by serine:pyruvate, ?-alanine (?-amino acid):pyruvate, and aromatic amino acid aminotransferase, respectively, could be detected with WST-1. PMID:26408350

  13. Highly effective colorimetric and visual detection of ATP by a DNAzyme-aptamer sensor.

    PubMed

    Liu, Fang; Zhang, Juan; Chen, Rong; Chen, Lingli; Deng, Le

    2011-02-01

    A new and simple method was developed to detect adenosine triphosphate (ATP) by using a DNAzyme-aptamer sensor. The DNAzyme used was a single-stranded DNA that could combine with hemin. The aptamer, a single, short nucleic acid sequence that can specifically bind with many targets, was an anti-ATP aptamer. Two DNA sequences were designed: i) a functional chain (Chain A) consisting of two parts, i.e., the anti-ATP aptamer (recognition part) and the DNAzyme (signal transduction part) and ii) a blocker chain (Chain B), which could partially hybridize with Chain A. The hybridized chains A and B were unfolded by the addition of ATP and hemin, and the blocker chain and the complex of the functional chain with ATP and hemin were in solution. The DNAzyme in the functional chain formed a G-quadruplex with hemin and then catalyzed the oxidation by H(2) O(2) of 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS(2-) ) to the colored ABTS(.-) radical. The color change caused by this reaction could be clearly observed by naked eye, and the absorbance was recorded at 414?nm. The detection limit was 110(-6) ?M. PMID:21337503

  14. Biofunctionalized silver nanoparticles as a novel colorimetric probe for melamine detection in raw milk.

    PubMed

    Borase, Hemant P; Patil, Chandrashekhar D; Salunkhe, Rahul B; Suryawanshi, Rahul K; Salunke, Bipinchandra K; Patil, Satish V

    2015-01-01

    Nanoparticles have emerged as a promising analytical tool for monitoring food adulteration and safety. In the present study, silver nanoparticles (AgNPs) were synthesized using leaves' extract of Jatropha gossypifolia. AgNPs revealed a characteristic surface plasmon resonance (SPR) peak at 419nm and have spherical and grain shape with size range between 18 and 30nm. A selective and rapid method of melamine detection in raw milk was developed with the use of these biofunctionalized AgNPs. The color change, deviation in SPR spectra, and change in the absorption ratio (A500 /A419 ) of AgNPs occurred after an AgNPs-melamine interaction. The detection limit for melamine up to 2?M (252ppb) was attained with this method, which is quite lower than safety level recommendations of regulatory bodies demonstrating sensitivity of the method. Dynamicx light scattering and transmission electron microscopy analyses exhibited an increase in hydrodynamic diameter and size of AgNPs after melamine interaction. Melamine sensing by AgNPs was investigated by different physicochemical and thermal analyses. PMID:25322814

  15. A colorimetric sensor for the sequential detection of Cu(2+) and CN(-) in fully aqueous media: practical performance of Cu(2+).

    PubMed

    You, Ga Rim; Park, Gyeong Jin; Lee, Jae Jun; Kim, Cheal

    2015-05-21

    A new highly selective colorimetric chemosensor 1 (E)-9-(((5-mercapto-1,3,4-thiadiazol-2-yl)imino)methyl)-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-8-ol was designed and synthesized for the sequential detection of Cu(2+) and CN(-). This sensor 1 exhibited an obvious color change from yellow to orange in the presence of Cu(2+) in a fully aqueous solution. The detection limit (0.9 ?M) of 1 for Cu(2+) is far lower than the WHO limit (31.5 ?M) for drinking water. In addition, the resulting Cu(2+)-2 1 complex can be further used to detect toxic cyanide through a color change from orange to yellow, indicating the recovery of 1 from Cu(2+)-21. Importantly, chemosensor 1 could be used to detect and quantify Cu(2+) in water samples, and a colorimetric test strip of 1 for the detection of Cu(2+) could be useful for all practical purposes. PMID:25900000

  16. Cell damage detection using Escherichia coli reporter plasmids: fluorescent and colorimetric assays.

    PubMed

    Padilla-Martnez, Felipe; Carrizosa-Villegas, Luz Adriana; Rangel-Serrano, ngeles; Paramo-Prez, Itzel; Mondragn-Jaimes, Vernica; Anaya-Velzquez, Fernando; Padilla-Vaca, Felipe; Franco, Bernardo

    2015-08-01

    Bacterial reporter assays are powerful tools used to study the effect of different compounds that affect the physiology of cellular processes. Most bacterial reporters are luciferase based and can be monitored in real time. In the present study we designed and implemented two sets of Escherichia coli bacterial reporter assays, using a multicopy plasmid system. Each reporter strain was constructed using either green fluorescent protein or ?-galactosidase (LacZ) proteins. The designed reporter strains are capable of responding in a specific manner to molecules that either oxidative stress, or membrane, protein, or DNA damage. In order to respond to the desired stimulus, promoter sequences from E. coli were used. These sequences correspond to the promoter of the major catalase (KatG) activated with cellular oxidative damage, the promoter of the ?-hydroxydecanoyl-ACP dehydrase (FabA) which is activated with membrane perturbation, the promoter of DNA recombinase (RecA) which is activated by DNA lesions. For protein misfolding, the promoter of the heat-shock responsive chaperon (DnaK) was used. Our constructs displayed activation to damage from specific stimuli, and low response to nonspecific stimuli was detected. Our results suggest that these types of bacterial reporter strains can be used in semiquantitative (fluorometric) and qualitative (?-galactosidase activity) studies of different xenobiotic substances and pollutants. PMID:25983135

  17. Self-assembly of core-satellite gold nanoparticles for colorimetric detection of copper ions.

    PubMed

    Weng, Ziqing; Wang, Hongbin; Vongsvivut, Jitraporn; Li, Runqing; Glushenkov, Alexey M; He, Jin; Chen, Ying; Barrow, Colin J; Yang, Wenrong

    2013-11-25

    Molecule-coated nanoparticles are hybrid materials which can be engineered with novel properties. The molecular coating of metal nanoparticles can provide chemical functionality, enabling assembly of the nanoparticles that are important for applications, such as biosensing devices. Herein, we report a new self-assembly of core-satellite gold nanoparticles linked by a simple amino acid l-Cysteine for biosensing of Cu(2+). The plasmonic properties of core-satellite nano-assemblies were investigated, a new red shifted absorbance peak from about 600 to 800 nm was found, with specific wavelength depending on ratios with assembly of large and small gold nanoparticles. The spectral features obtained using surface-enhanced Raman spectroscopy (SERS) provided strong evidence for the assembly of the Cu(2+) ions to the L-Cysteine molecules leading to the successful formation of the core-satellite Cu(l-Cysteine) complex on the gold surfaces. In addition, a linear relationship between the concentration of mediating Cu(2+) and absorbance of self-assembled gold nanoparticles (GNPs) at 680 nm was obtained. These results strongly address the potential strategy for applying the functionalized GNPs as novel biosensing tools in trace detections of certain metal ions. PMID:24216206

  18. Label-free colorimetric detection of Hg? based on Hg?-triggered exonuclease III-assisted target recycling and DNAzyme amplification.

    PubMed

    Ren, Wang; Zhang, Ying; Huang, Wei Tao; Li, Nian Bing; Luo, Hong Qun

    2015-06-15

    This work reported a label-free colorimetric assay for sensitive detection of Hg(2+) based on Hg(2+)-triggered hairpin DNA probe (H-DNA) termini-binding and exonuclease ? (Exo ?)-assisted target recycling, as well as hemin/G-quadruplex (DNAzyme) signal amplification. The specific binding of free Hg(2+) with the thymine-thymine (T-T) mismatches termini of H-DNA could immediately trigger the Exo ? digestion, and then set free G-quadruplex segments and Hg(2+). The Exo ? impellent recycling of ultratrace Hg(2+) produced numerous G-quadruplexes. The corresponding DNAzymes catalyzed efficiently the H2O2-mediated oxidation of the ABTS(2-) to the colored product in the presence of hemin. Using the color change as the output signal, and the Exo ?-aided Hg(2+) recycling and DNAzyme as the signal amplifier, the ultrasensitive assay system successfully achieved visual detection of Hg(2+) as low as 1.0 nM by the naked eye, and was suitable for field monitoring. The calibration curve was linear in the range of 50.0 pM to 20.0 nM for Hg(2+) (R=0.9962) with a detection limit of 10.0 pM. Moreover, this proposed strategy showed excellent selectivity, portability and low-cost, and was successfully applied to colorimetric detection of Hg(2+) in laboratory tap water and Jialing river water samples. PMID:25590972

  19. Plasma dark matter direct detection

    NASA Astrophysics Data System (ADS)

    Clarke, J. D.; Foot, R.

    2016-01-01

    Dark matter in spiral galaxies like the Milky Way may take the form of a dark plasma. Hidden sector dark matter charged under an unbroken U(1)' gauge interaction provides a simple and well defined particle physics model realising this possibility. The assumed U(1)' neutrality of the Universe then implies (at least) two oppositely charged dark matter components with self-interactions mediated via a massless "dark photon" (the U(1)' gauge boson). In addition to nuclear recoils such dark matter can give rise to keV electron recoils in direct detection experiments. In this context, the detailed physical properties of the dark matter plasma interacting with the Earth is required. This is a complex system, which is here modelled as a fluid governed by the magnetohydrodynamic equations. These equations are numerically solved for some illustrative examples, and implications for direct detection experiments discussed. In particular, the analysis presented here leaves open the intriguing possibility that the DAMA annual modulation signal is due primarily to electron recoils (or even a combination of electron recoils and nuclear recoils). The importance of diurnal modulation (in addition to annual modulation) as a means of probing this kind of dark matter is also emphasised.

  20. Structural, morphological and optical studies of L-cysteine modified silver nanoparticles and its application as a probe for the selective colorimetric detection of Hg2+

    NASA Astrophysics Data System (ADS)

    Nidya, M.; Umadevi, M.; Rajkumar, Beulah J. M.

    2014-12-01

    We report an extensive study on the evolution of a highly facile, selective colorimetric probe for Hg2+ detection using cysteine modified silver nanoparticles. The nanoparticles are stable in a basic medium and the Surface Enhanced Raman Spectrum (SERS) reveal that the cysteine is bound to the Ag surface through the thiolate moiety with the charged carboxylate group pointing outwards in a morphology that lends itself to sensor applications. In the presence of Hg2+, the absorption peak is quenched resulting in a drastic colour change. The sensor displays high selectivity to Hg2+ over other metallic ions.

  1. Structural, morphological and optical studies of l-cysteine modified silver nanoparticles and its application as a probe for the selective colorimetric detection of Hg(2+).

    PubMed

    Nidya, M; Umadevi, M; Rajkumar, Beulah J M

    2014-12-10

    We report an extensive study on the evolution of a highly facile, selective colorimetric probe for Hg(2+) detection using cysteine modified silver nanoparticles. The nanoparticles are stable in a basic medium and the Surface Enhanced Raman Spectrum (SERS) reveal that the cysteine is bound to the Ag surface through the thiolate moiety with the charged carboxylate group pointing outwards in a morphology that lends itself to sensor applications. In the presence of Hg(2+), the absorption peak is quenched resulting in a drastic colour change. The sensor displays high selectivity to Hg(2+) over other metallic ions. PMID:24950383

  2. MicroRNA-triggered, cascaded and catalytic self-assembly of functional "DNAzyme ferris wheel" nanostructures for highly sensitive colorimetric detection of cancer cells.

    PubMed

    Zhou, Wenjiao; Liang, Wenbin; Li, Xin; Chai, Yaqin; Yuan, Ruo; Xiang, Yun

    2015-05-21

    The construction of DNA nanostructures with various sizes and shapes has significantly advanced during the past three decades, yet the application of these DNA nanostructures for solving real problems is still in the early stage. On the basis of microRNA-triggered, catalytic self-assembly formation of the functional "DNAzyme ferris wheel" nanostructures, we show here a new signal amplification platform for highly sensitive, label-free and non-enzyme colorimetric detection of a small number of human prostate cancer cells. The microRNA (miR-141), which is catalytically recycled and reused, triggers isothermal self-assembly of a pre-designed, G-quadruplex sequence containing hairpin DNAs into "DNAzyme ferris wheel"-like nanostructures (in association with hemin) with horseradish peroxidase mimicking activity. These DNAzyme nanostructures catalyze an intensified color transition of the probe solution for highly sensitive detection of miR-141 down to 0.5 pM with the naked eye, and the monitoring of as low as 283 human prostate cancer cells can also, theoretically, be achieved in a colorimetric approach. The work demonstrated here thus offers new opportunities for the construction of functional DNA nanostructures and for the application of these DNA nanostructures as an effective signal amplification means in the sensitive detection of nucleic acid biomarkers. PMID:25921227

  3. Colorimetric and fluorescence quenching aptasensors for detection of streptomycin in blood serum and milk based on double-stranded DNA and gold nanoparticles.

    PubMed

    Emrani, Ahmad Sarreshtehdar; Danesh, Noor Mohammad; Lavaee, Parirokh; Ramezani, Mohammad; Abnous, Khalil; Taghdisi, Seyed Mohammad

    2016-01-01

    Antibiotic residues in animal foodstuffs are of great concern to consumers. In this study, fluorescence quenching and colorimetric aptasensors were designed for detection of streptomycin based on aqueous gold nanoparticles (AuNPs) and double-stranded DNA (dsDNA). In the absence of streptomycin, aptamer/FAM-labeled complementary strand dsDNA is stable, resulting in the aggregation of AuNPs by salt and an obvious color change from red to blue and strong emission of fluorescence. In the presence of streptomycin, aptamer binds to its target and FAM-labeled complementary strand adsorbs on the surface of AuNPs. So the well-dispersed AuNPs remain stable against salt-induced aggregation with a wine-red color and the fluorescence of FAM-labeled complimentary strand is efficiently quenched by AuNPs. The colorimetric and fluorescence quenching aptasensors showed excellent selectivity toward streptomycin with limit of detections as low as 73.1 and 47.6 nM, respectively. The presented aptasensors were successfully used to detect streptomycin in milk and serum. PMID:26212949

  4. MicroRNA-triggered, cascaded and catalytic self-assembly of functional ``DNAzyme ferris wheel'' nanostructures for highly sensitive colorimetric detection of cancer cells

    NASA Astrophysics Data System (ADS)

    Zhou, Wenjiao; Liang, Wenbin; Li, Xin; Chai, Yaqin; Yuan, Ruo; Xiang, Yun

    2015-05-01

    The construction of DNA nanostructures with various sizes and shapes has significantly advanced during the past three decades, yet the application of these DNA nanostructures for solving real problems is still in the early stage. On the basis of microRNA-triggered, catalytic self-assembly formation of the functional ``DNAzyme ferris wheel'' nanostructures, we show here a new signal amplification platform for highly sensitive, label-free and non-enzyme colorimetric detection of a small number of human prostate cancer cells. The microRNA (miR-141), which is catalytically recycled and reused, triggers isothermal self-assembly of a pre-designed, G-quadruplex sequence containing hairpin DNAs into ``DNAzyme ferris wheel''-like nanostructures (in association with hemin) with horseradish peroxidase mimicking activity. These DNAzyme nanostructures catalyze an intensified color transition of the probe solution for highly sensitive detection of miR-141 down to 0.5 pM with the naked eye, and the monitoring of as low as 283 human prostate cancer cells can also, theoretically, be achieved in a colorimetric approach. The work demonstrated here thus offers new opportunities for the construction of functional DNA nanostructures and for the application of these DNA nanostructures as an effective signal amplification means in the sensitive detection of nucleic acid biomarkers.

  5. A nanosized metal-organic framework of Fe-MIL-88NH? as a novel peroxidase mimic used for colorimetric detection of glucose.

    PubMed

    Liu, Ya Li; Zhao, Xi Juan; Yang, Xiao Xi; Li, Yuan Fang

    2013-08-21

    In this paper, a nanosized porous metal-organic framework, Fe-MIL-88NH?, was facilely prepared with a uniform octahedral shape by the addition of acetic acid, and for the first time was demonstrated to possess intrinsic peroxidase-like activity. Kinetic analysis and electron spin resonance measurements indicated that the catalytic behavior was consistent with typical Michaelis-Menten kinetics and follows a ping-pong mechanism. As a novel peroxidase mimic material, Fe-MIL-88NH? shows the advantages of high catalytic efficiency, ultrahigh stability and high biocompatibility in aqueous medium compared with natural enzymes and other peroxidase nanomimetics. Here, Fe-MIL-88NH? was used to quickly catalyze oxidation of the peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H?O? to produce a colored product, which provided a simple, sensitive and selective method for the colorimetric detection of glucose. Glucose could be linearly detected in the range from 2.0 10?? to 3.0 10?? M with a detection limit of 4.8 10?? M, and the color variation for glucose response was also obvious by visual observation at concentrations as low as 2.0 10?? M. More importantly, the colorimetric method could be successfully applied to the determination of glucose in diluted serum samples. PMID:23775015

  6. Direct Detection Searches for WIMPs

    NASA Astrophysics Data System (ADS)

    Cabrera, Blas

    2014-03-01

    We have seen remarkable progress in direct detection searches for dark matter in the form of weakly interacting particles or WIMPs. Existing experiments using diverse technologies have set convincing limits for WIMPs under the spin independent interaction framework and have ruled out much of the phase space suggested by supersymmetric models. Liquid xenon experiments have provided the best limits for masses above 6 GeV/c2, with cryogenic detectors and bubble chambers setting the best limits for lighter mass WIMPs. In tension with the liquid xenon experiments are hints of signals and a claimed detection in the light WIMP mass sector. A number of theoretical ideas are consistent with light mass WIMPs, and a general approach, which probes all possible interactions between WIMPs and nucleons, stresses the need for a variety of target nuclei with the lowest possible thresholds to broadly cover the possibilities. As discussed extensively in P5 meetings, the down selection process for the second generation experiments (G2) will determine the progress over the next decade. As a community, we have asked the agencies for significant additional funds to be identified so that several G2 experiments can move forward and R&D on others continue. We need to continue this important search aggressively until we find WIMPs or reach the natural floor where the solar and atmospheric neutrinos become an irreducible background.

  7. Direct detection polarimetric radiometer (DDPR)

    NASA Astrophysics Data System (ADS)

    Koenig, G.; Koh, G.; Ryerson, C.

    2009-05-01

    Polarimetric signatures of terrain features and man-made objects have been measured using unique Direct Detection Polarimetric Radiometers (DDPR). The DDPRs are lightweight inexpensive systems operating at 35 and 94 GHz. Each system consists of a single antenna, amplifier, and a truncated cylindrical waveguide that directly measures Q, U, and V. The highly portable DDPRs are ideal for obtaining the Stokes vectors needed to study the physical characteristics of natural and man-made features. Field evaluations using the DDPR systems include measurements from an airborne platform over different terrain features and water, and ground based measurements of the polarimetric signature of grass, asphalt, buildings, and concealed munitions. The DDPR can function as a bistatic system by using an active source of polarization. Using this configuration and a soil chamber, we have investigated the effect of soil type and soil moisture on linear and circular polarization. This report will describe the DDPR and present the analysis of the airborne and ground based measurements, including the effects of soil type and soil moisture on sources of linear and circular polarization.

  8. Label-free colorimetric detection of mercury via Hg2+ ions-accelerated structural transformation of nanoscale metal-oxo clusters

    PubMed Central

    Chen, Kun; She, Shan; Zhang, Jiangwei; Bayaguud, Aruuhan; Wei, Yongge

    2015-01-01

    Mercury and its compounds are known to be extremely toxic but widely distributed in environment. Although many works have been reported to efficiently detect mercury, development of simple and convenient sensors is still longed for quick analyzing mercury in water. In this work, a nanoscale metal-oxo cluster, (n-Bu4N)2[Mo5NaO13(OCH3)4(NO)], (MLPOM), organically-derivatized from monolacunary Lindqvist-type polyoxomolybdate, is found to specifically react with Hg2+ in methanol/water via structural transformation. The MLPOM methanol solution displays a color change from purple to brown within seconds after being mixed with an aqueous solution containing Hg2+. By comparing the structure of polyoxomolybdate before and after reaction, the color change is revealed to be the essentially structural transformation of MLPOM accelerated by Hg2+. Based on this discovery, MLPOM could be utilized as a colorimetric sensor to sense the existence of Hg2+, and a simple and label-free method is developed to selectively detect aqueous Hg2+. Furthermore, the colorimetric sensor has been applied to indicating mercury contamination in industrial sewage. PMID:26559602

  9. Ratiometric and colorimetric "naked eye" selective detection of CN(-) ions by electron deficient Ni(II) porphyrins and their reversibility studies.

    PubMed

    Kumar, Ravi; Chaudhri, Nivedita; Sankar, Muniappan

    2015-05-21

    Highly electron deficient ?-substituted Ni(II) porphyrins (1-5) were synthesized and utilized as novel sensors for selective rapid visual detection of CN(-) ions. This article describes the single crystal X-ray structures, electronic spectral and electrochemical redox properties of these sensors. The ratiometric and colorimetric responses of these porphyrins were monitored by the change in optical absorption spectra. These sensors were found to be highly selective for cyanide ions with extremely high binding constants (10(16)-10(8) M(-2)) through axial ligation of CN(-) ions and are able to detect <0.11 ppm of CN(-) ions. 1-5 were recovered from 1-52CN(-) adducts by acid treatment and reused without loss of sensing ability. CN(-) binding strongly perturbs the redox properties of the parent porphyrin ?-system. The applicability of 1-5 as practical visible colorimetric test kits for CN(-) ions in aqueous and non-aqueous media has also been explored. The mode of binding was confirmed by single crystal X-ray, spectroscopic studies and DFT calculations. PMID:25901694

  10. Label-free colorimetric detection of mercury via Hg(2+) ions-accelerated structural transformation of nanoscale metal-oxo clusters.

    PubMed

    Chen, Kun; She, Shan; Zhang, Jiangwei; Bayaguud, Aruuhan; Wei, Yongge

    2015-01-01

    Mercury and its compounds are known to be extremely toxic but widely distributed in environment. Although many works have been reported to efficiently detect mercury, development of simple and convenient sensors is still longed for quick analyzing mercury in water. In this work, a nanoscale metal-oxo cluster, (n-Bu4N)2[Mo5NaO13(OCH3)4(NO)], (MLPOM), organically-derivatized from monolacunary Lindqvist-type polyoxomolybdate, is found to specifically react with Hg(2+) in methanol/water via structural transformation. The MLPOM methanol solution displays a color change from purple to brown within seconds after being mixed with an aqueous solution containing Hg(2+). By comparing the structure of polyoxomolybdate before and after reaction, the color change is revealed to be the essentially structural transformation of MLPOM accelerated by Hg(2+). Based on this discovery, MLPOM could be utilized as a colorimetric sensor to sense the existence of Hg(2+), and a simple and label-free method is developed to selectively detect aqueous Hg(2+). Furthermore, the colorimetric sensor has been applied to indicating mercury contamination in industrial sewage. PMID:26559602

  11. Label-free colorimetric detection of mercury via Hg2+ ions-accelerated structural transformation of nanoscale metal-oxo clusters

    NASA Astrophysics Data System (ADS)

    Chen, Kun; She, Shan; Zhang, Jiangwei; Bayaguud, Aruuhan; Wei, Yongge

    2015-11-01

    Mercury and its compounds are known to be extremely toxic but widely distributed in environment. Although many works have been reported to efficiently detect mercury, development of simple and convenient sensors is still longed for quick analyzing mercury in water. In this work, a nanoscale metal-oxo cluster, (n-Bu4N)2[Mo5NaO13(OCH3)4(NO)], (MLPOM), organically-derivatized from monolacunary Lindqvist-type polyoxomolybdate, is found to specifically react with Hg2+ in methanol/water via structural transformation. The MLPOM methanol solution displays a color change from purple to brown within seconds after being mixed with an aqueous solution containing Hg2+. By comparing the structure of polyoxomolybdate before and after reaction, the color change is revealed to be the essentially structural transformation of MLPOM accelerated by Hg2+. Based on this discovery, MLPOM could be utilized as a colorimetric sensor to sense the existence of Hg2+, and a simple and label-free method is developed to selectively detect aqueous Hg2+. Furthermore, the colorimetric sensor has been applied to indicating mercury contamination in industrial sewage.

  12. Microfluidic Integration of a Cloth-Based Hybridization Array System (CHAS) for Rapid, Colorimetric Detection of Enterohemorrhagic Escherichia coli (EHEC) Using an Articulated, Centrifugal Platform.

    PubMed

    Geissler, Matthias; Clime, Liviu; Hoa, Xuyen D; Morton, Keith J; Hbert, Harold; Poncelet, Lucas; Mounier, Maxence; Deschnes, Mylne; Gauthier, Martine E; Huszczynski, George; Corneau, Nathalie; Blais, Burton W; Veres, Teodor

    2015-10-20

    We describe the translation of a cloth-based hybridization array system (CHAS), a colorimetric DNA detection method that is used by food inspection laboratories for colony screening of pathogenic agents, onto a microfluidic chip format. We also introduce an articulated centrifugal platform with a novel fluid manipulation concept based on changes in the orientation of the chip with respect to the centrifugal force field to time the passage of multiple components required for the process. The platform features two movable and motorized carriers that can be reoriented on demand between 0 and 360 during stage rotation. Articulation of the chip can be used to trigger on-the-fly fluid dispensing through independently addressable siphon structures or to relocate solutions against the centrifugal force field, making them newly accessible for downstream transfer. With the microfluidic CHAS, we achieved significant reduction in the size of the cloth substrate as well as the volume of reagents and wash solutions. Both the chip design and the operational protocol were optimized to perform the entire process in a reliable, fully automated fashion. A demonstration with PCR-amplified genomic DNA confirms on-chip detection and identification of Escherichia coli O157:H7 from colony isolates in a colorimetric multiplex assay using rfbO157, fliCH7, vt1, and vt2 genes. PMID:26416260

  13. A rapid molecular diagnosis of cutaneous leishmaniasis by colorimetric malachite green-loop-mediated isothermal amplification (LAMP) combined with an FTA card as a direct sampling tool.

    PubMed

    Nzelu, Chukwunonso O; Cáceres, Abraham G; Guerrero-Quincho, Silvia; Tineo-Villafuerte, Edwin; Rodriquez-Delfin, Luis; Mimori, Tatsuyuki; Uezato, Hiroshi; Katakura, Ken; Gomez, Eduardo A; Guevara, Angel G; Hashiguchi, Yoshihisa; Kato, Hirotomo

    2016-01-01

    Leishmaniasis remains one of the world's most neglected diseases, and early detection of the infectious agent, especially in developing countries, will require a simple and rapid test. In this study, we established a quick, one-step, single-tube, highly sensitive loop-mediated isothermal amplification (LAMP) assay for rapid detection of Leishmania DNA from tissue materials spotted on an FTA card. An FTA-LAMP with pre-added malachite green was performed at 64°C for 60min using a heating block and/or water bath and DNA amplification was detected immediately after incubation. The LAMP assay had high detection sensitivity down to a level of 0.01 parasites per μl. The field- and clinic-applicability of the colorimetric FTA-LAMP assay was demonstrated with 122 clinical samples collected from patients suspected of having cutaneous leishmaniasis in Peru, from which 71 positives were detected. The LAMP assay in combination with an FTA card described here is rapid and sensitive, as well as simple to perform, and has great potential usefulness for diagnosis and surveillance of leishmaniasis in endemic areas. PMID:26516109

  14. Intrinsic peroxidase-like catalytic activity of nitrogen-doped graphene quantum dots and their application in the colorimetric detection of H2O2 and glucose.

    PubMed

    Lin, Liping; Song, Xinhong; Chen, Yiying; Rong, Mingcong; Zhao, Tingting; Wang, Yiru; Jiang, Yaqi; Chen, Xi

    2015-04-15

    In this paper, the highly intrinsic peroxidase-like catalytic activity of nitrogen-doped graphene quantum dots (N-GQDs) is revealed. This activity was greatly dependent on pH, temperature and H2O2 concentration. The experimental results showed that the stable N-GQDs could be used for the detection of H2O2 and glucose over a wide range of pH and temperature, offering a simple, highly selective and sensitive approach for their colorimetric sensing. The linearity between the analyte concentration and absorption ranged from 20 to 1170 ?M for H2O2 and 25 to 375 ?M for glucose with a detection limit of 5.3 ?M for H2O2 and 16 ?M for glucose. This assay was also successfully applied to the detection of glucose concentrations in diluted serum and fruit juice samples. PMID:25818144

  15. Colorimetric detection of anions in aqueous media using N-monosubstituted diaminomaleonitrile-based azo-azomethine receptors: real-life applications.

    PubMed

    Khanmohammadi, Hamid; Rezaeian, Khatereh; Abdollahi, Alieh

    2015-03-15

    New N-monosubstituted diaminomaleonitrile-based azo-azomethine dyes have been synthesized in order to develop colorimetric sensors for detection of biologically important anions in aqueous media. Importantly, the reported sensor decorated with strong electron-withdrawing group can detect inorganic fluoride in water even at 0.037 ppm level, which is lower than WHO permissible level (below 1 ppm). Successfully, the prepared dyes were used for qualitative and quantitative detection of inorganic fluoride in toothpaste and mouthwash. The anion recognition mechanism was also investigated by detailed UV-Vis and (1)H NMR experiments. The detailed (1)H NMR experiments corroborated that anion recognition is based on the deprotonation phenomenon. PMID:25576937

  16. Colorimetric detection of anions in aqueous media using N-monosubstituted diaminomaleonitrile-based azo-azomethine receptors: Real-life applications

    NASA Astrophysics Data System (ADS)

    Khanmohammadi, Hamid; Rezaeian, Khatereh; Abdollahi, Alieh

    2015-03-01

    New N-monosubstituted diaminomaleonitrile-based azo-azomethine dyes have been synthesized in order to develop colorimetric sensors for detection of biologically important anions in aqueous media. Importantly, the reported sensor decorated with strong electron-withdrawing group can detect inorganic fluoride in water even at 0.037 ppm level, which is lower than WHO permissible level (below 1 ppm). Successfully, the prepared dyes were used for qualitative and quantitative detection of inorganic fluoride in toothpaste and mouthwash. The anion recognition mechanism was also investigated by detailed UV-Vis and 1H NMR experiments. The detailed 1H NMR experiments corroborated that anion recognition is based on the deprotonation phenomenon.

  17. Colorimetric Detection of Sulfite in Foods by a TMB-O2-Co3O4 Nanoparticles Detection System.

    PubMed

    Qin, Wenjie; Su, Li; Yang, Chen; Ma, Yanhua; Zhang, Haijuan; Chen, Xingguo

    2014-06-25

    In this paper, we first discovered that Co3O4 nanoparticles (NPs) possess intrinsic oxidase-like activity and can catalytically oxidize peroxidase substrates, such as 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) and 3,3',5,5'-tetramethylbenzidine (TMB), to form colored products, in the absence of exogenously added H2O2. The presence of sulfite inhibited the TMB-O2-Co3O4 NPs reaction system and caused a change in color of the reaction system. On the basis of this phenomenon, a colormetric approach to detect sulfite was established with a good linear relationship ranging from 0.210(-6) to 1.610(-5) M and a detection limit of 5.310(-8) M. The method was used to detect sulfite in foods. Good recoveries ranging from 93.8% to 100.5% were obtained. Furthermore, the mechanism was studied and results showed that the oxidase-like activity of the Co3O4 NPs was not from OH or O2- radical generated. It may probably originate from their ability to transfer an electron between the peroxidase substrate and oxygen absorbed on the surface of the Co3O4 NPs. PMID:24885936

  18. An integrated slidable and valveless microdevice with solid phase extraction, polymerase chain reaction, and immunochromatographic strip parts for multiplex colorimetric pathogen detection.

    PubMed

    Kim, Yong Tae; Lee, Dohwan; Heo, Hyun Young; Kim, Do Hyun; Seo, Tae Seok

    2015-11-01

    A total integrated genetic analysis microsystem was developed, which consisted of solid phase extraction (SPE), polymerase chain reaction (PCR), and immunochromatographic strip (ICS) parts for multiplex colorimetric detection of pathogenic Staphylococcus aureus (S. aureus) and Escherichia coli O157:H7 (E. coli O157:H7) on a portable genetic analyzer. Utilizing a slidable chamber, which is a movable glass wafer, complex microvalves could be eliminated for fluidic control in the microchannel, which could simplify the chip design and chip operation. The integrated slidable microdevice was composed of 4 layers: a 4-point Pt/Ti resistance temperature detector (RTD) wafer, a micro-patterned channel wafer, a 2 ?L volume slidable chamber, and an ICS. The entire process from the DNA extraction in the SPE chamber to the detection of the target gene expression by the ICS was serially performed by simply sliding the slidable chamber from one part to another functional part. The total process for multiplex pathogenic S. aureus and E. coli O157:H7 detection on the integrated slidable microdevice was accomplished within 55 min with a detection limit of 5 cells. Furthermore, spiked bacteria samples in milk were also successfully analysed on the portable genetic analysis microsystem with sample-in-answer-out capability. The proposed total integrated microsystem is adequate for point-of-care DNA testing in that no microvalves and complex tubing systems are required due to the use of the slidable chamber and the bulky and expensive fluorescence or electrochemical detectors are not necessary due to the ICS based colorimetric detection. PMID:26394907

  19. Selective and sensitive detection of free bilirubin in blood serum using human serum albumin stabilized gold nanoclusters as fluorometric and colorimetric probe.

    PubMed

    Santhosh, Mallesh; Chinnadayyala, Somasekhar R; Kakoti, Ankana; Goswami, Pranab

    2014-09-15

    We report here a fluorescence quenching based non-enzymatic method for sensitive and reliable detection of free bilirubin in blood serum samples using human serum albumin (HSA) stabilized gold nanoclusters (HSA-AuNCs) as fluorescent probe. The fluorescence of the nanoclusters was strongly quenched by bilirubin in a concentration dependent manner by virtue of the inherent specific interaction between bilirubin and HSA. A strong binding constant of 0.55×10(6) L mole(-1) between the HSA-AuNC and bilirubin was discerned. The nano clusters each with size ~1.0 nm (in diameter) and a core of Au18 were homogeneously distributed in HSA molecules as revealed from the respective high resolution transmission electron microscopic and mass spectroscopic studies. The fluorescence quenching phenomena which obeyed a simple static quenching mechanism, was utilized for interference free detection of bilirubin with minimum detection limit (DL) of 248±12 nM (S/N=3). The fluorescence response of HSA-AuNCs against bilirubin was practically unaltered over a wide pH (6-9) and temperature (25-50 °C) range. Additionally, peroxidase-like catalytic activity of these nanoclusters was exploited for colorimetric detection of bilirubin in serum sample with a DL of 200±19 nM by following the decrease in absorbance (at λ440 nm) of the reaction and its rate constant (Kp) of 2.57±0.63 mL μg(-1) min(-1). Both these fluorometric and colorimetric methods have been successfully used for detection of free bilirubin in blood serum samples. PMID:24752148

  20. Silver nanoparticle based highly selective and sensitive solvatochromatic sensor for colorimetric detection of 1,4-dioxane in aqueous media.

    PubMed

    Kumar, Anshu; Vyas, Gaurav; Bhatt, Madhuri; Bhatt, Shreya; Paul, Parimal

    2015-11-14

    A citrate stabilised silver nanoparticle (Ci-AgNP) based solvatochromic sensor, which functions as a highly selective and sensitive colorimetric probe for 1,4-dioxane in aqueous media is reported. The surfaces of the AgNPs generate reactive oxygen species, which promote the degradation of 1,4-dioxane assembled in the vicinity of the nanoparticle surfaces through charge transfer interactions. During this process, Ag(0) is oxidised to Ag(+) and the yellow colour of the solution turns to colourless. The sensor was used for the estimation of 1,4-dioxane in ground water and also 1,4-dioxane vapour diffused in aqueous media. PMID:26377615

  1. Colorimetric and fluorimetric detection of fluoride and cyanide ions using tri and tetra coordinated boron containing chromophores.

    PubMed

    Misra, Rajneesh; Jadhav, Thaksen; Dhokale, Bhausaheb; Mobin, Shaikh M

    2015-09-28

    Two organoboron based fluorophores pyrazabole and BODIPY have been designed and synthesized by the Pd-catalyzed Sonogashira cross-coupling reaction and successfully employed for fluoride and cyanide ion sensing. Pyrazabole acts as a fluorimetric sensor, whereas BODIPY acts as a fluorimetric as well as colorimetric sensor for fluoride and cyanide ions with ratiometric response. The photophysical properties of pyrazabole and BODIPY exhibit good electronic communication between triarylborane and pyrazabole/BODIPY. The single crystal X-ray structure of the pyrazabole shows a chair conformation for the pyrazabole core. The packing in pyrazabole and BODIPY shows interesting supramolecular structures. The computational studies show good agreement with the experimental results. PMID:26285867

  2. Simple, Fast and Selective Detection of Adenosine Triphosphate at Physiological pH Using Unmodified Gold Nanoparticles as Colorimetric Probes and Metal Ions as Cross-Linkers

    PubMed Central

    Deng, Dehua; Xia, Ning; Li, Sujuan; Xu, Chunying; Sun, Ting; Pang, Huan; Liu, Lin

    2012-01-01

    We report a simple, fast and selective colorimetric assay of adenosine triphosphate (ATP) using unmodified gold nanoparticles (AuNPs) as probes and metal ions as cross-linkers. ATP can be assembled onto the surface of AuNPs through interaction between the electron-rich nitrogen atoms and the electron-deficient surface of AuNPs. Accordingly, Cu2+ ions induce a change in the color and UV/Vis absorbance of AuNPs by coordinating to the triphosphate groups and a ring nitrogen of ATP. A detection limit of 50 nM was achieved, which is comparable to or lower than that achievable by the currently used electrochemical, spectroscopic or chromatographic methods. The theoretical simplicity and high selectivity reported herein demonstrated that AuNPs-based colorimetric assay could be applied in a wide variety of fields by rationally designing the surface chemistry of AuNPs. In addition, our results indicate that ATP-modified AuNPs are less stable in Cu2+, Cd2+ or Zn2+-containing solutions due to the formation of the corresponding dimeric metal-ATP complexes. PMID:23202201

  3. Multifunctional Oval Shape Gold Nanoparticle Based Selective Detection of Breast Cancer Cells Using Simple Colorimetric and Highly Sensitive Two-Photon Scattering Assay

    PubMed Central

    Lu, Wentong; Arumugam, Sri Ranjini; Senapati, Dulal; Singh, Anant K.; Arbneshi, Tahir; Yu, Sadia Afrin Khan Hongtao; Ray, Paresh Chandra

    2010-01-01

    Breast cancer is the most common cancer among women and it is the second leading cause of cancer deaths in women today. The key to the effective and ultimately successful treatment of diseases such as cancer is an early and accurate diagnosis. Driven by the need, in this article, we report for the first time a simple colorimetric and highly sensitive two-photon scattering assay for highly selective and sensitive detection of breast cancer SK-BR-3 cell lines in 100-cells/ml level using multifunctional (monoclonal anti-HER2/c-erb-2 antibody and S6 RNA aptamers conjugated) oval shape gold nanoparticle based nanoconjugate. When multifunctional oval shape gold nanoparticles were mixed with breast cancer SK-BR-3 cell line, a distinct color change occurs and two-photon scattering intensity increases by about 13 times. Experimental data with HaCaT non-cancerous cell line, as well as with MDA-MB-231 breast cancer cell line clearly demonstrated that our assay was highly sensitive to SK-BR-3 and it was able to distinguish from other breast cancer cell line which expresses low levels of HER-2. The mechanism of selectivity and assays response change, have been discussed. Our experimental results reported here open up a new possibility of rapid, easy and reliable diagnosis of cancer cell lines by monitoring the colorimetric change and measuring TPS intensity from multifunctional gold nanosystems. PMID:20155973

  4. Highly selective colorimetric detection and estimation of Hg2+ at nano-molar concentration by silver nanoparticles in the presence of glutathione.

    PubMed

    Alam, Ayesha; Ravindran, Aswathy; Chandran, Preethy; Sudheer Khan, S

    2015-02-25

    The present study investigated the colorimetric detection of mercury (Hg(2+)) ions by using silver nanoparticles (Ag NPs) in the presence of glutathione. The nanoparticles used in the study were synthesized biologically by using Polyalthia longifolia leaf extract. The synthesized nanoparticles were characterized by UV-visible spectrophotometer, transmission electron microscope, X-ray diffraction, particle size analyzer and zeta sizer. The particles were spherical in shape and it possesses the effective diameter of 5 nm. The zeta potential of the particles was determined to be -28.6 mV. Ag NPs-glutathione conjugates were able to detect Hg(2+) in nanomolar level. Ag NPs-glutathione conjugates upon interaction with Hg(2+) changes from yellowish brown to pale yellow and finally colorless. The study may be applied for the qualitative and quantitative estimation of mercury at very low concentration. PMID:25240142

  5. A new pyrene-based Schiff-base: A selective colorimetric and fluorescent chemosensor for detection of Cu(II) and Fe(III)

    NASA Astrophysics Data System (ADS)

    Bhorge, Yeshwant Ramchandra; Tsai, Haw-Tyng; Huang, Keh-Feng; Pape, Albert J.; Janaki, Sudhakar Narasimha; Yen, Yao-Pin

    2014-09-01

    A new receptor 1 was prepared, for the detection of Cu2+ and Fe3+ in solutions as a colorimetric and fluorescent sensor, respectively. Receptor 1 shows highly selective and sensitive recognition toward Cu2+ and Fe3+ by naked eye UV-Vis and fluorescent color changes in aqueous solution (DMSO/H2O = 8/2, v/v), respectively. The sensitivity toward Cu2+ or Fe3+ was not interfered with by the presence of other metal ions such as Mg2+, Cd2+, Ag+, Zn2+, Ni2+, Co2+, Mn2+, Cr3+, Ca2+, Na+, Pb2+, K+, Fe2+, Li+ and Hg2+ ions. Receptor 1 can be used for semi-quantitative recognition of Cu2+ ions at ppm level. The fluorescence microscopy experiments showed that the receptor is efficient for detection of Fe3+ in vitro, developing a good image of the biological organelles.

  6. Low-cost preparation of photoluminescent carbon nanodots and application as peroxidase mimetics in colorimetric detection of H2O2 and glucose.

    PubMed

    Wu, Di; Deng, Xiang; Huang, Xiaomei; Wang, Kun; Liu, Qingye

    2013-10-01

    A low-cost and facile preparation of water-soluble photoluminescent carbon nanodots (CDs) with a quantum yield of approximately 12.4% by hydrothermal method utilizing the leaves of Olea Europaea, a large number of planted trees in southwest of China, as a carbon source is developed for the first time. The prepared photoluminescent CDs not only show favorable photoluminescent properties, but also possess intrinsic peroxidase-like activity for colorimetric and UV-Vis absorption detection of hydrogen oxide (H2O2) and glucose. This sensing system exhibits excellent sensitivity toward H2O2 and glucose with the limit of detection as low as 0.6 microM and 5.2 microM. The practical use of this system for glucose determination in serum samples is also demonstrated successfully. The stability and low cost of photoluminescent CDs make them a powerful tool for a wide range of potential applications in biochemical analysis. PMID:24245121

  7. Direct colorimetric biosensing of mercury(II) ion based on aggregation of poly-(γ-glutamic acid)-functionalized gold nanoparticles.

    PubMed

    Guan, Huanan; Liu, Xiaofei; Wang, Wei; Liang, Jinzhong

    2014-01-01

    A simple and sensitive method for colorimetric detection of mercury ion (Hg(2+)) has been developed by using a poly (γ-glutamic acid) functionalized gold nanoparticles (PGA-AuNPs) system. Electrostatic self-assembly technique was used to assemble negatively charged PGA on the surface of positively charged CTAB-capped AuNPs. With the increase of Hg(2+) concentration, the color of the solution would progress from light red to purple blue. The results showed that the absorbance ratio (A750/A580) was linear with the Hg(2+) concentration in the range of 0.01-10 μM and from 50 to 300 μM, with the correlation coefficients of 0.998 and 0.991, respectively. The reported probe is suitable for real-time detection of Hg(2+) in water with the limit of detection (LOD) of 1.9 nM obtained by UV-vis spectrum, and exhibits selectivity toward one order of magnitude over other metal ions. This approach was applied successfully to the determination of Hg(2+) in tap water and mineral water, and the recoveries were from 90% to 103% and from 103.53% to 113%, respectively. The proposed method is rapid, low-cost and free of complex equipment, making it possible to analyze Hg(2+) in various water samples. PMID:24291429

  8. Direct colorimetric biosensing of mercury(II) ion based on aggregation of poly-(γ-glutamic acid)-functionalized gold nanoparticles.

    TOXLINE Toxicology Bibliographic Information

    Guan H; Liu X; Wang W; Liang J

    2014-01-01

    A simple and sensitive method for colorimetric detection of mercury ion (Hg(2+)) has been developed by using a poly (γ-glutamic acid) functionalized gold nanoparticles (PGA-AuNPs) system. Electrostatic self-assembly technique was used to assemble negatively charged PGA on the surface of positively charged CTAB-capped AuNPs. With the increase of Hg(2+) concentration, the color of the solution would progress from light red to purple blue. The results showed that the absorbance ratio (A750/A580) was linear with the Hg(2+) concentration in the range of 0.01-10 μM and from 50 to 300 μM, with the correlation coefficients of 0.998 and 0.991, respectively. The reported probe is suitable for real-time detection of Hg(2+) in water with the limit of detection (LOD) of 1.9 nM obtained by UV-vis spectrum, and exhibits selectivity toward one order of magnitude over other metal ions. This approach was applied successfully to the determination of Hg(2+) in tap water and mineral water, and the recoveries were from 90% to 103% and from 103.53% to 113%, respectively. The proposed method is rapid, low-cost and free of complex equipment, making it possible to analyze Hg(2+) in various water samples.

  9. A dual functional probe for "turn-on" fluorescence response of Pb(2+) and colorimetric detection of Cu(2+) based on a rhodamine derivative in aqueous media.

    PubMed

    Li, Min; Jiang, Xiu-Juan; Wu, Hui-Hui; Lu, Hong-Lin; Li, Hai-Yang; Xu, Hong; Zang, Shuang-Quan; Mak, Thomas C W

    2015-10-21

    A dual functional probe L based on rhodamine was devised and synthesized. Probe L can sense Pb(2+) and Cu(2+) in aqueous solution through two approaches: a significant fluorescence enhancement caused by Pb(2+) and a visible color change from colorless to orchid induced by Cu(2+). Competitive experiments showed that probe L had high fluorescence sensitivity for Pb(2+) and excellent colorimetric selectivity for Cu(2+) over many environmentally relevant ions. The mechanisms of L for sensing Pb(2+) and Cu(2+) have been well demonstrated by ESI-MS, (1)H NMR titration, IR, the crystal structure of L-Pb(2+) and density functional theory calculation of L-Cu(2+). In addition, fluorescence image detection of Pb(2+) in living cells displayed an enhanced fluorescence effect. PMID:26387873

  10. Molecular recognition and colorimetric detection of cholera toxin by poly(diacetylene) liposomes incorporating G{sub m1} ganglioside

    SciTech Connect

    Pan, J.J.; Charych, D.

    1997-03-19

    Molecular recognition sites on cell membranes serve as the main communication channels between the inside of a cell and its surroundings. Upon receptor binding, cellular messages such as ion channel opening or activation of enzymes are triggered. In this report, we demonstrate that artificial cell membranes made from conjugated lipid polymers (poly(diacetylene)) can, on a simple level, mimic membrane processes of molecular recognition and signal transduction. The ganglioside GM1 was incorporated into poly(diacetylene) liposomes. Molecular recognition of cholera toxin at the interface of the liposome resulted in a change of the membrane color due to conformational charges in the conjugated (ene-yne) polymer backbone. The `colored liposomes` might be used as simple colorimetric sensors for drug screening or as new tools to study membrane-membrane or membrane-receptor interactions. 21 refs., 3 figs.

  11. Colorimetric detection of iron ions (III) based on the highly sensitive plasmonic response of the N-acetyl-L-cysteine-stabilized silver nanoparticles.

    PubMed

    Gao, Xiaohui; Lu, Yizhong; He, Shuijian; Li, Xiaokun; Chen, Wei

    2015-06-16

    We report here a facile colorimetric sensor based on the N-acetyl-L-cysteine (NALC)-stabilized Ag nanoparticles (NALC-Ag NPs) for detection of Fe(3+) ions in aqueous solution. The Ag NPs with an average diameter of 6.55±1.0 nm are successfully synthesized through a simple method using sodium borohydride as reducing agent and N-acetyl-L-cysteine as protecting ligand. The synthesized silver nanoparticles show a strong surface plasmon resonance (SPR) around 400 nm and the SPR intensity decreases with the increasing of Fe(3+) concentration in aqueous solution. Based on the linear relationship between SPR intensity and concentration of Fe(3+) ions, the as-synthesized water-soluble silver nanoparticles can be used for the sensitive and selective detection of Fe(3+) ions in water with a linear range from 80 nM to 80 μM and a detection limit of 80 nM. On the basis of the experimental results, a new detection mechanism of oxidation-reduction reaction between Ag NPs and Fe(3+) ions is proposed, which is different from previously reported mechanisms. Moreover, the NALC-Ag NPs could be applied to the detection of Fe(3+) ions in real environmental water samples. PMID:26002486

  12. Colorimetric Method of Loop-Mediated Isothermal Amplification with the Pre-Addition of Calcein for Detecting Flavobacterium columnare and its Assessment in Tilapia Farms.

    PubMed

    Suebsing, Rungkarn; Kampeera, Jantana; Sirithammajak, Sarawut; Withyachumnarnkul, Boonsirm; Turner, Warren; Kiatpathomchai, Wansika

    2015-03-01

    Flavobacterium columnare, the causative agent of columnaris disease in fish, affects many economically important freshwater fish species. A colorimetric method of loop-mediated isothermal amplification with the pre-addition of calcein (LAMP-calcein) was developed and used to detect the presence of F. columnare in farmed tilapia (Nile Tilapia Oreochromis niloticus and red tilapia [Nile Tilapia × Mozambique Tilapia O. mossambicus]) and rearing water. The detection method, based on a change in color from orange to green, could be performed within 45 min at 63°C. The method was highly specific, as it had no cross-detections with 14 other bacterial species, including other fish pathogens and two Flavobacterium species. The method has a minimum detection limit of 2.2 × 10(2) F. columnare CFU; thus, it is about 10 times more sensitive than conventional PCR. With this method, F. columnare was detected in gonad, gill, and blood samples from apparently healthy tilapia broodstock as well as in samples of fertilized eggs, newly hatched fry, and rearing water. The bacteria isolated from the blood were further characterized biochemically and found to be phenotypically identical to F. columnare. The amplified products from the LAMP-calcein method had 97% homology with the DNA sequence of F. columnare. PMID:25584663

  13. Fano Resonant Aluminum Nanoclusters for Plasmonic Colorimetric Sensing.

    PubMed

    King, Nicholas S; Liu, Lifei; Yang, Xiao; Cerjan, Benjamin; Everitt, Henry O; Nordlander, Peter; Halas, Naomi J

    2015-11-24

    Aluminum is an abundant and high-quality material for plasmonics with potential for large-area, low-cost photonic technologies. Here we examine aluminum nanoclusters with plasmonic Fano resonances that can be tuned from the near-UV into the visible region of the spectrum. These nanoclusters can be designed with specific chromaticities in the blue-green region of the spectrum and exhibit a remarkable spectral sensitivity to changes in the local dielectric environment. We show that such structures can be used quite generally for colorimetric localized surface plasmon resonance (LSPR) sensing, where the presence of analytes is detected by directly observable color changes rather than through photodetectors and spectral analyzers. To quantify our results and provide a metric for optimization of such structures for colorimetric LSPR sensing, we introduce a figure of merit based on the color perception ability of the human eye. PMID:26426492

  14. Rapid colorimetric sensing of tetracycline antibiotics with in situ growth of gold nanoparticles.

    PubMed

    Shen, Li; Chen, Jing; Li, Na; He, Pingli; Li, Zhen

    2014-08-11

    A colorimetric assay utilizing the formation of gold nanoparticles was developed to detect tetracycline antibiotics in fluidic samples. Tetracycline antibiotics showed the capability of directly reducing aurate salts into atomic gold which form gold nanoparticles spontaneously under proper conditions. The resulted gold nanoparticles showed characteristic plasmon absorbance at 526 nm, which can be visualized by naked eyes or with a spectrophotometer. UV-vis absorbance of the resulted gold nanoparticles is correlated directly with the concentrations of tetracycline antibiotics in the solution, allowing for quantitative colorimetric detection of tetracycline antibiotics. Reaction conditions, such as pH, temperature, reaction time, and ionic strength were optimized. Sensitivity of the colorimetric assay can be enhanced by the addition of gold nanoparticle seeds, a LOD as low as 20 ng mL(-1) can be achieved with the help of seed particles. The colorimetric assay showed minimum interference from ethanol, methanol, urea, glucose, and other antibiotics such as sulfonamides, amino glycosides etc. Validity of the method was also evaluated on urine samples spiked with tetracycline antibiotics. The method provides a broad spectrum detection method for rapid and sensitive detection of reductive substances such as tetracycline antibiotics in liquid and biological samples. PMID:25066722

  15. Efficient ensemble system based on the copper binding motif for highly sensitive and selective detection of cyanide ions in 100% aqueous solutions by fluorescent and colorimetric changes.

    PubMed

    Jung, Kwan Ho; Lee, Keun-Hyeung

    2015-09-15

    A peptide-based ensemble for the detection of cyanide ions in 100% aqueous solutions was designed on the basis of the copper binding motif. 7-Nitro-2,1,3-benzoxadiazole-labeled tripeptide (NBD-SSH, NBD-SerSerHis) formed the ensemble with Cu(2+), leading to a change in the color of the solution from yellow to orange and a complete decrease of fluorescence emission. The ensemble (NBD-SSH-Cu(2+)) sensitively and selectively detected a low concentration of cyanide ions in 100% aqueous solutions by a colorimetric change as well as a fluorescent change. The addition of cyanide ions instantly removed Cu(2+) from the ensemble (NBD-SSH-Cu(2+)) in 100% aqueous solutions, resulting in a color change of the solution from orange to yellow and a "turn-on" fluorescent response. The detection limits for cyanide ions were lower than the maximum allowable level of cyanide ions in drinking water set by the World Health Organization. The peptide-based ensemble system is expected to be a potential and practical way for the detection of submicromolar concentrations of cyanide ions in 100% aqueous solutions. PMID:26320594

  16. Implementing a two-layer feed-forward catalytic DNA circuit for enzyme-free and colorimetric detection of nucleic acids.

    PubMed

    Ravan, Hadi

    2016-03-01

    In the present study, a highly sensitive and specific bio-sensing platform for enzyme-free and colorimetric detection of nucleic acids has been developed. The biosensor is composed of two DNA nanostructures and two fuel strands that construct the foundation of a feed-forward catalytic DNA circuit. Upon binding the target strand to a specific DNA nanostructure, the circuit is run in order that at the end a hemin-binding aptamer, with the ability to convert a colorless substrate into a colored substance is released. Based on this strategy, 4 pM of the target DNA can be easily detected in serum samples by naked eyes after only a two-hour incubation with the circuit; meanwhile, if the incubation time is extended to 3 h, the biosensor can detect 1 pM of the target DNA. Besides the elevated sensitivity, the circuit can truly discriminate a spurious target containing one nucleotide mismatch with high specificity. Overall, the enzyme-free catalytic DNA circuit can be used as a sensitive alternative method to enzyme-based biosensors for the specific and cost-effective detection of nucleic acids. PMID:26873470

  17. Highly sensitive colorimetric detection of Hg(II) and Cu(II) in aqueous solutions: from amino acids toward solid platforms.

    PubMed

    Park, Jooyoung; In, Byunggyu; Neupane, Lok Nath; Lee, Keun-Hyeung

    2015-02-01

    A chemosensor (NBD-H) based on an amino acid with 7-nitro-2,1,3-benzoxadiazole was used for selective detection of Hg(II) and Cu(II) among 15 metal ions in aqueous solutions by a colorimetric change. NBD-H sensitively differentiated Hg(II) and Cu(II) in aqueous solutions by a color change; a pink color for Hg(II) and an orange color for Cu(II). NBD-H showed nanomolar detection limits for Hg(II) (176 nM, R2 = 0.996) and Cu(II) (163 nM, R2 = 0.996). The detection limit for Cu(II) was much lower than the maximum allowable level of Cu(II) in drinking water recommended by the U.S. EPA. The binding mode study showed that deprotonation of the NH group of NBD-H played a critical role in the binding and sensing of metal ions. NBD-H immobilized on PEG-PS resin maintained the potent binding affinity and sensing ability for the metal ions. The resin with NBD-H was recyclable for the detection of metal ions in 100% aqueous solutions. PMID:25471472

  18. Colorimetric and dynamic light scattering detection of DNA sequences by using positively charged gold nanospheres: a comparative study with gold nanorods

    NASA Astrophysics Data System (ADS)

    Pylaev, T. E.; Khanadeev, V. A.; Khlebtsov, B. N.; Dykman, L. A.; Bogatyrev, V. A.; Khlebtsov, N. G.

    2011-07-01

    We introduce a new genosensing approach employing CTAB (cetyltrimethylammonium bromide)-coated positively charged colloidal gold nanoparticles (GNPs) to detect target DNA sequences by using absorption spectroscopy and dynamic light scattering. The approach is compared with a previously reported method employing unmodified CTAB-coated gold nanorods (GNRs). Both approaches are based on the observation that whereas the addition of probe and target ssDNA to CTAB-coated particles results in particle aggregation, no aggregation is observed after addition of probe and nontarget DNA sequences. Our goal was to compare the feasibility and sensitivity of both methods. A 21-mer ssDNA from the human immunodeficiency virus type 1 HIV-1 U5 long terminal repeat (LTR) sequence and a 23-mer ssDNA from the Bacillus anthracis cryptic protein and protective antigen precursor (pagA) genes were used as ssDNA models. In the case of GNRs, unexpectedly, the colorimetric test failed with perfect cigar-like particles but could be performed with dumbbell and dog-bone rods. By contrast, our approach with cationic CTAB-coated GNPs is easy to implement and possesses excellent feasibility with retention of comparable sensitivitya 0.1 nM concentration of target cDNA can be detected with the naked eye and 10 pM by dynamic light scattering (DLS) measurements. The specificity of our method is illustrated by successful DLS detection of one-three base mismatches in cDNA sequences for both DNA models. These results suggest that the cationic GNPs and DLS can be used for genosensing under optimal DNA hybridization conditions without any chemical modifications of the particle surface with ssDNA molecules and signal amplification. Finally, we discuss a more than two-three-order difference in the reported estimations of the detection sensitivity of colorimetric methods (0.1 to 10-100 pM) to show that the existing aggregation models are inconsistent with the detection limits of about 0.1-1 pM DNA and that other explanations should be developed.

  19. DNA probes for Bordetella species and a colorimetric reverse hybridization assay for the detection of Bordetella pertussis.

    PubMed

    Rossau, R; Michielsen, A; Jannes, G; Duhamel, M; Kersters, K; van Heuverswyn, H

    1992-08-01

    Three oligonucleotide probe sequences were inferred from the 16S ribosomal ribonucleic acid (rRNA) and the 16S-23S rRNA spacer sequences of Bordetella pertussis ATCC 10380. These probes were used in hybridization tests with deoxyribonucleic acid from Bordetella species and other relevant bacterial taxa. A probe from the spacer region hybridized exclusively to the B. pertussis strains tested and not to strains from other species. Using a combination of three probes, B. pertussis, B. parapertussis/B. bronchiseptica and B. avium could be specifically identified and differentiated from other taxa. Differentiation between B. parapertussis and B. bronchiseptica was not possible with the probes used. Using the spacer probe, a colorimetric hybridization assay specific for B. pertussis was developed based on enzymatic amplification of the 16S-23S rRNA spacer and reverse hybridization in microtitre wells. As compared with results using agarose gel electrophoresis, and Southern and dot-spot hybridization with a 32P-labelled probe, this assay proved to be faster and easier to perform and was found to be at least as sensitive and specific. PMID:1382221

  20. Directional recoil rate for direct detection of WIMPs

    NASA Astrophysics Data System (ADS)

    Alenazi, Moqbil; Gondolo, Paolo

    2007-10-01

    The problem of directional direct detection of weakly interacting massive particles (WIMPs) dark matter (DM) is investigated. We compute, analytically and numerically, the directional differential recoil rate dRd? of recoiled target nuclei hit by WIMPs in direct detection experiments in terms of the angle ?, which is the angle between the reference direction and the recoil direction. While the analytic method is for fixed reference direction and Gaussian distribution of WIMPs, the numeric method is a general method. The two methods give the same results. We apply the numeric method to various Maxwellian distributions including; a stream of WIMPs, the standard dark halo, streams of WIMPs from Sikivie's late-infall (SLI) halo model, and streams with anisotropic velocity distributions. We show the results as distributions of the nuclei's directional differential recoil rate dRd? as a function of ?. We introduce a `folded' directional differential recoil rate dRd|?| to overcome the difficulty of head-tail discrimination in some WIMP's direct detectors. We conclude that dRd|?| can be helpful in recognizing cases of anisotropic streams and isotropic standard dark halo but not in the case of SLI streams.

  1. Doped colorimetric assay liposomes

    DOEpatents

    Charych, Deborah; Stevens, Raymond C.

    2001-01-01

    The present invention provides compositions comprising colorimetric assay liposomes. The present invention also provides methods for producing colorimetric liposomes and calorimetric liposome assay systems. In preferred embodiments, these calorimetric liposome systems provide high levels of sensitivity through the use of dopant molecules. As these dopants allow the controlled destabilization of the liposome structure, upon exposure of the doped liposomes to analyte(s) of interest, the indicator color change is facilitated and more easily recognized.

  2. Label-free colorimetric detection of biological thiols based on target-triggered inhibition of photoinduced formation of AuNPs

    NASA Astrophysics Data System (ADS)

    Lim Jung, Ye; Park, Jung Hun; Kim, Moon Il; Park, Hyun Gyu

    2016-02-01

    A label-free colorimetric method for the detection of biological thiols (biothiols) was developed. This method is based on prevention of the photoinduced reduction of auric ions (Au(III)) in the presence of amino acids (acting as a reducing agent) by biothiols; the photoinduced reduction is inhibited due to the strong interaction of the biothiols with Au(III). In this method, the sample was first incubated in an assay solution containing Au(III) and threonine; the sample solution was then exposed to 254 nm UV light. For samples without biothiols, this process led to the photoreduction of Au(III) followed by growth of gold nanoparticles accompanied by the visually detectable development of a red coloration typified by an absorption peak at ca 530 nm. Conversely, in the presence of biothiols, reduction of Au(III) to Au(0) was prevented by entrapment of Au(III) within the biothiols via the thiol group. The solution thus remained colorless even after UV irradiation, which was used as an indicator of the presence of biothiols. Using this strategy, biothiols were very conveniently analyzed by monitoring color changes of the samples with the naked eye or a UV–vis spectrometer. The strategy based on this interesting phenomenon exhibited high selectivity toward biothiols over common amino acids and was successfully employed for reliable quantification of biothiols present in human plasma, demonstrating its great potential for clinical applications.

  3. Colorimetric detection of the flux of hydrogen peroxide released from living cells based on the high peroxidase-like catalytic performance of porous PtPd nanorods.

    PubMed

    Ge, Shenguang; Liu, Weiyan; Liu, Haiyun; Liu, Fang; Yu, Jinghua; Yan, Mei; Huang, Jiadong

    2015-09-15

    One-dimensional PtPd porous nanorods (PtPd PNRs) were successfully synthesized through a bromide-induced galvanic replacement reaction between Pd nanowires and K2PtCl6. The PtPd PNRs were porous and alloy-structured with Pt/Pd atomic ratio up to 1:1 which were demonstrated by spectroscopic methods. We had also proved that the nanorods could function as peroxidase mimetic for the detection of H2O2, with the detection limit of 8.6 nM and the linear range from 20 nM to 50 mM. The result demonstrated that PtPd PNRs exhibited much higher affinity to H2O2 over other peroxidase mimetics due to synergistically integrating highly catalytic activity of two metals. On the basis of the peroxidase-like activity, the PtPd PNRs were used as a signal transducer to develop a novel and simple colorimetric method for the study of the flux of H2O2 released from living cell. By using 3,3,5,5-tetramethylbenzidine as substrate, the H2O2 concentration could be distinguished by naked-eye observation without any instrumentation or complicated design. The method developed a new platform for a reliable collection of information on cellular reactive oxygen species release. And the nanomaterial could be used as a power tool for a wide range of potential applications in biotechnology and medicine. PMID:25982545

  4. Enzyme-free and label-free ultra-sensitive colorimetric detection of Pb(2+) using molecular beacon and DNAzyme based amplification strategy.

    PubMed

    Yun, Wen; Cai, Dingzhou; Jiang, JiaoLai; Zhao, Pengxiang; Huang, Yu; Sang, Ge

    2016-06-15

    An enzyme-free and label-free colorimetric Pb(2+) sensor based on DNAzyme and molecular beacon (MB) has been developed and demonstrated by recycle using enzyme strand for signal amplification. The substrate strand DNA (S-DNA) of DNAzyme could be converted into MB structure with base pairs of stem part at the both ends. The MB could hybridize with enzyme strand DNA (E-DNA) to form DNAzyme, and be activated and cleaved in the presence of Pb(2+). The cleaved MB is much less stable, releasing from the DNAzyme as two product pieces. The product pieces of MB are flexible and could bind to unmodified AuNPs to effectively stabilize them against salt-induced aggregation. Then, the E-DNA is liberated to catalyze the next reaction and amplify the response signal. By taking advantage of repeated using of E-DNA, our proposed method exhibited high sensitive for Pb(2+) detection in a linear range from 0.05 to 5nM with detection limit of 20pM by UV-vis spectrometer. Moreover, this method was also used for determination of Pb(2+) in river water samples with satisfying results. Importantly, this strategy could reach high sensitivity without any modification and complex enzymatic or hairpins based amplification procedures. PMID:26836648

  5. Label-free colorimetric detection of biological thiols based on target-triggered inhibition of photoinduced formation of AuNPs.

    PubMed

    Jung, Ye Lim; Park, Jung Hun; Kim, Moon Il; Park, Hyun Gyu

    2016-02-01

    A label-free colorimetric method for the detection of biological thiols (biothiols) was developed. This method is based on prevention of the photoinduced reduction of auric ions (Au(III)) in the presence of amino acids (acting as a reducing agent) by biothiols; the photoinduced reduction is inhibited due to the strong interaction of the biothiols with Au(III). In this method, the sample was first incubated in an assay solution containing Au(III) and threonine; the sample solution was then exposed to 254 nm UV light. For samples without biothiols, this process led to the photoreduction of Au(III) followed by growth of gold nanoparticles accompanied by the visually detectable development of a red coloration typified by an absorption peak at ca 530 nm. Conversely, in the presence of biothiols, reduction of Au(III) to Au(0) was prevented by entrapment of Au(III) within the biothiols via the thiol group. The solution thus remained colorless even after UV irradiation, which was used as an indicator of the presence of biothiols. Using this strategy, biothiols were very conveniently analyzed by monitoring color changes of the samples with the naked eye or a UV-vis spectrometer. The strategy based on this interesting phenomenon exhibited high selectivity toward biothiols over common amino acids and was successfully employed for reliable quantification of biothiols present in human plasma, demonstrating its great potential for clinical applications. PMID:26671249

  6. Median recoil direction as a WIMP directional detection signal

    SciTech Connect

    Green, Anne M.; Morgan, Ben

    2010-03-15

    Direct detection experiments have reached the sensitivity to detect dark matter weakly interacting massive particles (WIMPs). Demonstrating that a putative signal is due to WIMPs, and not backgrounds, is a major challenge, however. The direction dependence of the WIMP scattering rate provides a potential WIMP 'smoking gun'. If the WIMP distribution is predominantly smooth, the Galactic recoil distribution is peaked in the direction opposite to the direction of Solar motion. Previous studies have found that, for an ideal detector, of order 10 WIMP events would be sufficient to reject isotropy, and rule out an isotropic background. We examine how the median recoil direction could be used to confirm the WIMP origin of an anisotropic recoil signal. Specifically, we determine the number of events required to confirm the direction of solar motion as the median inverse recoil direction at 95% confidence. We find that for zero background 31 events are required, a factor of {approx}2 more than are required to simply reject isotropy. We also investigate the effect of a nonzero isotropic background. As the background rate is increased the number of events required increases, initially fairly gradually and then more rapidly, once the signal becomes subdominant. We also discuss the effect of features in the speed distribution at large speeds, as found in recent high resolution simulations, on the median recoil direction.

  7. Median recoil direction as a WIMP directional detection signal

    NASA Astrophysics Data System (ADS)

    Green, Anne M.; Morgan, Ben

    2010-03-01

    Direct detection experiments have reached the sensitivity to detect dark matter weakly interacting massive particles (WIMPs). Demonstrating that a putative signal is due to WIMPs, and not backgrounds, is a major challenge, however. The direction dependence of the WIMP scattering rate provides a potential WIMP smoking gun. If the WIMP distribution is predominantly smooth, the Galactic recoil distribution is peaked in the direction opposite to the direction of Solar motion. Previous studies have found that, for an ideal detector, of order 10 WIMP events would be sufficient to reject isotropy, and rule out an isotropic background. We examine how the median recoil direction could be used to confirm the WIMP origin of an anisotropic recoil signal. Specifically, we determine the number of events required to confirm the direction of solar motion as the median inverse recoil direction at 95% confidence. We find that for zero background 31 events are required, a factor of 2 more than are required to simply reject isotropy. We also investigate the effect of a nonzero isotropic background. As the background rate is increased the number of events required increases, initially fairly gradually and then more rapidly, once the signal becomes subdominant. We also discuss the effect of features in the speed distribution at large speeds, as found in recent high resolution simulations, on the median recoil direction.

  8. Ni(II)NTA AuNPs as a low-resource malarial diagnostic platform for the rapid colorimetric detection of Plasmodium falciparum Histidine-Rich Protein-2.

    PubMed

    Gulka, Christopher P; Swartz, Joshua D; Wright, David W

    2015-04-01

    Diagnosing infectious diseases remains a challenge in the developing world where there is a lack of dependable electricity, running water, and skilled technicians. Although rapid immunochromatographic tests (RDTs) have been deployed to diagnose diseases such as malaria, the extreme climate conditions encountered in these regions compounded with the discrepancies in test manufacturing have yielded varying results, so that more innovative and robust technologies are sought. Devoid of antibodies and thermally sensitive materials, we present a robust, colorimetric diagnostic platform for the detection of a malarial biomarker, Plasmodium falciparum Histidine-Rich Protein 2 (PfHRP-II). The assay exploits the optical properties of gold nanoparticles, covalently coupling them to a Ni(II)NTA recognition element specific for PfHRP-II. In the presence of the recombinant malarial biomarker (rcHRP-II), the Ni(II)NTA AuNPs begin to crosslink and aggregate in as little as one minute, triggering a red-to-purple color change in solution. To increase assay sensitivity and platform stability suitable for low-resource regions, the Ni(II)NTA AuNPs were assembled with varying spacer ligands in a mixed monolayer presentation. When assembled with a negatively charged Peg4-thiol ligand, the Ni(II)NTA AuNPs demonstrate low nanomolar limits of rcHRP-II detection in physiological concentrations of human serum albumin and maintain excellent stability at 37C when stored for four weeks. Detection of the malaria biomarker is also measured by capturing and processing images of aggregated gold nanoparticles with a smartphone camera. By utilizing a smartphone camera and image processing application, there is no significant difference in assay sensitivity and rcHRP-II limit of detection in comparison to a spectrophotometer, further making this diagnostic platform applicable for use in low-resource regions. PMID:25640131

  9. Enhancing sensitivity and selectivity in a label-free colorimetric sensor for detection of iron(II) ions with luminescent molybdenum disulfide nanosheet-based peroxidase mimetics.

    PubMed

    Wang, Yong; Hu, Jie; Zhuang, Qianfen; Ni, Yongnian

    2016-06-15

    In the present study, we demonstrated that the luminescent molybdenum disulfide (MoS2) nanosheets, which were prepared hydrothermally by using sodium molybdate and thiourea as precursors, possessed peroxidase-like activity, and could catalyze the oxidation of peroxidase substrate o-phenylenediamine (OPD) in the presence of hydrogen peroxide (H2O2) to produce a yellow color reaction. Further addition of Fe(2+) into the nanosheets led to peroxidase mimetics with greatly enhanced catalytic activity. The observation was exploited to develop a label-free colorimetric nanozyme sensor for detection of Fe(2+). The fabricated MoS2/OPD/H2O2 sensor showed a wide linear range of 0.01-0.8µM with a detection limit of 7nM. Moreover, it was found that the MoS2/OPD/H2O2 sensor displayed enhanced sensitivity and selectivity toward Fe(2+) compared with the OPD/H2O2 sensor, suggesting that the MoS2 nanosheets could improve the performance of the Fe(2+) sensor. An advanced chemometrics algorithm, multivariate curve resolution by alternating least squares (MCR-ALS), was further applied to interpret the origin of enhancing sensitivity and selectivity in the Fe(2+) sensor with the MoS2 nanosheets. The time-dependent UV-vis spectral data of the studied systems were collected, and submitted to the MCR-ALS. The results showed that the increased sensitivity and selectivity of the MoS2/OPD/H2O2 sensor for Fe(2+) detection likely arose from its large reaction rate constant. Finally, the proposed MoS2/OPD/H2O2 sensor was successfully applied for detection of Fe(2+) in water samples. PMID:26807525

  10. Biomarker detection technologies and future directions.

    PubMed

    Nimse, Satish Balasaheb; Sonawane, Mukesh Digambar; Song, Keum-Soo; Kim, Taisun

    2016-02-01

    Biomarkers play a vital role in disease detection and treatment follow-up. It is important to note that diseases in the early stage are typically treated with the greatest probability of success. However, due to various technical difficulties in current technologies for the detection of biomarkers, the potential of biomarkers is not explored completely. Therefore, the developments of technologies, which can enable the accurate detection of prostate cancer at an early stage with simple, experimental protocols are highly inevitable. This critical review evaluates the current methods and technologies used in the detection of biomarkers. The aim of this article is to provide a comprehensive review covering the advantages and disadvantages of the biomarker detection methods. Future directions for the development of technologies to achieve highly selective and sensitive detection of biomarkers for point-of-care applications are also commented on. PMID:26583164

  11. Disentangling dark matter dynamics with directional detection

    NASA Astrophysics Data System (ADS)

    Lisanti, Mariangela; Wacker, Jay G.

    2010-05-01

    Inelastic dark matter reconciles the DAMA anomaly with other null direct detection experiments and points to a nonminimal structure in the dark matter sector. In addition to the dominant inelastic interaction, dark matter scattering may have a subdominant elastic component. If these elastic interactions are suppressed at low momentum transfer, they will have similar nuclear recoil spectra to inelastic scattering events. While upcoming direct detection experiments will see strong signals from such models, they may not be able to unambiguously determine the presence of the subdominant elastic scattering from the recoil spectra alone. We show that directional detection experiments can separate elastic and inelastic scattering events and discover the underlying dynamics of dark matter models.

  12. Disentangling Dark Matter Dynamics with Directional Detection

    SciTech Connect

    Lisanti, Mariangela; Wacker, Jay G.; /SLAC

    2009-12-16

    Inelastic dark matter reconciles the DAMA anomaly with other null direct detection experiments and points to a non-minimal structure in the dark matter sector. In addition to the dominant inelastic interaction, dark matter scattering may have a subdominant elastic component. If these elastic interactions are suppressed at low momentum transfer, they will have similar nuclear recoil spectra to inelastic scattering events. While upcoming direct detection experiments will see strong signals from such models, they may not be able to unambiguously determine the presence of the subdominant elastic scattering from the recoil spectra alone. We show that directional detection experiments can separate elastic and inelastic scattering events and discover the underlying dynamics of dark matter models.

  13. A Colorimetric Bioassay for Perchlorate

    NASA Astrophysics Data System (ADS)

    Heinnickel, M. L.; Smith, S.; Coates, J. D.

    2007-12-01

    Recognition of perchlorate (ClO4-) as a widespread contaminant across the United States and its potential adverse affects towards human health has motivated the EPA to place ClO4- on its contaminant candidate list for drinking water supplies. While a federal MCL has not yet been set, a recommended public health goal of 1 ppb (?g.L-1) was established by the US EPA in 2002. To date, methods of detection require use of sensitive ion chromatographic equipment that are expensive, time consuming, and require highly trained personnel for use. Our studies are focused on the development of a highly sensitive, simple, and robust colorimetric bioassay based on the primary enzyme involved in microbial ClO4- reduction, the perchlorate reductase (Pcr). A previously published assay used reduced methyl viologen (MV, the dye is reduced with sodium hydrosulfite) as an electron donor to demonstrate Pcr activity. The assay directly correlates the amount of MV oxidized with the amount of ClO4- reduced by assuming a transfer of four electrons. To test this assumption, we compared actual concentrations of MV oxidized to ClO4- reduced in this assay. ClO4- concentrations were determined using a Dionex ICS-500 ion chromatography system, while MV concentrations were determined using a standard curve generated at 578 nm. Comparisons between the two revealed that twelve molecules of MV were oxidized for each molecule of ClO4- reduced. The oxidation of these additional eight MV molecules is explained by the interaction of the dye with chlorite (the product of the Pcr reaction) and other contaminants that could be present in the enzyme prep. This unsettling result indicated this assay would be problematic for the detection of ClO4- in soil, which has many chemicals that could react with MV. To improve upon this assay, we have tried to reduce ClO4- using less reactive dyes and reductants. The reductants ascorbic acid, NADH, and dithiothreitol drive Pcr catalyzed ClO4- reduction, however, they are not effective unless an accompanying dye is used as a shuttle. N-methylphenazinium methosulfate (PMS) was selected as the most suitable dye because of its interaction with NADH, an oxygen stable reductant. In addition, the positive redox potential of PMS (E' = +80 mV), makes it significantly less reactive than MV (E' = -450 mV). A comparison of actual concentrations of ClO4- reduced vs. NADH oxidized show exactly four molecules of NADH oxidized for each molecule of ClO4- that is reduced (8 electrons). These studies have resulted in the successful development of a method that can accurately determine ClO4- concentrations with a small error using the enzyme Pcr and indicate the great potential for the ultimate development of a simple, robust, and highly sensitive colorimetric bioassay for perchlorate that can be widely used to screen laboratory and environmental samples .

  14. A simple cassette as point-of-care diagnostic device for naked-eye colorimetric bacteria detection.

    PubMed

    Safavieh, Mohammadali; Ahmed, Minhaz Uddin; Sokullu, Esen; Ng, Andy; Braescu, Liliana; Zourob, Mohammed

    2014-01-21

    Effective pathogen detection is necessary for treatment of infectious diseases. Point of care (POC) devices have tremendously improved the global human heath. However, design criteria for sample processing POC devices for pathogen detection in limited infrastructure are challenging and can make a significant contribution to global health by providing rapid and sensitive detection of bacteria in food, water, and patient samples. In this paper, we demonstrate a novel portable POC diagnostic device that is simple to assemble for genetic detection of bacterial pathogens by isothermal DNA amplification. The device is fabricated with very low production cost, using simple methods and easy-to-access materials on a flexible ribbon polyethylene substrate. We showed that the device is capable of detection of 30 CFU mL(-1) of E. coli and 200 CFU mL(-1) of S. aureus in less than 1 hour. Through numerical simulations, we estimated that the device can be extended to high-throughput detection simultaneously performing a minimum of 36 analyses. This robust and sensitive detection device can be assembled and operated by non-specialist personnel, particularly for multiple bacterial pathogen detections in low-resource settings. PMID:24300967

  15. Microgels for multiplex and direct fluorescence detection

    NASA Astrophysics Data System (ADS)

    Causa, Filippo; Aliberti, Anna; Cusano, Angela M.; Battista, Edmondo; Netti, Paolo A.

    2015-05-01

    Blood borne oligonucleotides fragments contain useful clinical information whose detection and monitoring represent the new frontier in liquid biopsy as they can transform the current diagnosis procedure. For instance, recent studies have identified a new class of circulating biomarkers such as s miRNAs, and demonstrated that changes in their concentration are closely associated with the development of cancer and other pathologies. However, direct detection of miRNAs in body fluids is particularly challenging and demands high sensitivity -concentration range between atto to femtomolarspecificity, and multiplexing Here we report on engineered multifunctional microgels and innovative probe design for a direct and multiplex detection of relevant clinical miRNAs in fluorescence by single particle assay. Polyethyleneglycol-based microgels have a coreshell architecture with two spectrally encoded fluorescent dyes for multiplex analyses and are endowed with fluorescent probes for miRNA detection. Encoding and detection fluorescence signals are distinguishable by not overlapping emission spectra. Tuneable fluorescence probe conjugation and corresponding emission confinement on single microgel allows for enhanced target detection. Such suspension array has indeed high selectivity and sensitivity with a detection limit of 10-15 M and a dynamic range from 10-9 to 10-15 M. We believe that sensitivity in the fM concentration range, signal background minimization, multiplexed capability and direct measurement of such microgels will translate into diagnostic benefits opening up new roots toward liquid biopsy in the context of point-of-care testing through an easy and fast detection of sensitive diagnostic biomarkers directly in serum.

  16. Multicenter study of epidemiological cutoff values and detection of resistance in Candida spp. to anidulafungin, caspofungin, and micafungin using the Sensititre YeastOne colorimetric method.

    PubMed

    Espinel-Ingroff, A; Alvarez-Fernandez, M; Cantn, E; Carver, P L; Chen, S C-A; Eschenauer, G; Getsinger, D L; Gonzalez, G M; Govender, N P; Grancini, A; Hanson, K E; Kidd, S E; Klinker, K; Kubin, C J; Kus, J V; Lockhart, S R; Meletiadis, J; Morris, A J; Pelaez, T; Quinds, G; Rodriguez-Iglesias, M; Snchez-Reus, F; Shoham, S; Wengenack, N L; Borrell Sol, N; Echeverria, J; Esperalba, J; Gmez-G de la Pedrosa, E; Garca Garca, I; Linares, M J; Marco, F; Merino, P; Pemn, J; Prez Del Molino, L; Rosell Mayans, E; Rubio Calvo, C; Ruiz Prez de Pipaon, M; Yage, G; Garcia-Effron, G; Guinea, J; Perlin, D S; Sanguinetti, M; Shields, R; Turnidge, J

    2015-11-01

    Neither breakpoints (BPs) nor epidemiological cutoff values (ECVs) have been established for Candida spp. with anidulafungin, caspofungin, and micafungin when using the Sensititre YeastOne (SYO) broth dilution colorimetric method. In addition, reference caspofungin MICs have so far proven to be unreliable. Candida species wild-type (WT) MIC distributions (for microorganisms in a species/drug combination with no detectable phenotypic resistance) were established for 6,007 Candida albicans, 186 C. dubliniensis, 3,188 C. glabrata complex, 119 C. guilliermondii, 493 C. krusei, 205 C. lusitaniae, 3,136 C. parapsilosis complex, and 1,016 C. tropicalis isolates. SYO MIC data gathered from 38 laboratories in Australia, Canada, Europe, Mexico, New Zealand, South Africa, and the United States were pooled to statistically define SYO ECVs. ECVs for anidulafungin, caspofungin, and micafungin encompassing ?97.5% of the statistically modeled population were, respectively, 0.12, 0.25, and 0.06 ?g/ml for C. albicans, 0.12, 0.25, and 0.03 ?g/ml for C. glabrata complex, 4, 2, and 4 ?g/ml for C. parapsilosis complex, 0.5, 0.25, and 0.06 ?g/ml for C. tropicalis, 0.25, 1, and 0.25 ?g/ml for C. krusei, 0.25, 1, and 0.12 ?g/ml for C. lusitaniae, 4, 2, and 2 ?g/ml for C. guilliermondii, and 0.25, 0.25, and 0.12 ?g/ml for C. dubliniensis. Species-specific SYO ECVs for anidulafungin, caspofungin, and micafungin correctly classified 72 (88.9%), 74 (91.4%), 76 (93.8%), respectively, of 81 Candida isolates with identified fks mutations. SYO ECVs may aid in detecting non-WT isolates with reduced susceptibility to anidulafungin, micafungin, and especially caspofungin, since testing the susceptibilities of Candida spp. to caspofungin by reference methodologies is not recommended. PMID:26282428

  17. Simultaneous nucleophilic-substituted and electrostatic interactions for thermal switching of spiropyran: a new approach for rapid and selective colorimetric detection of thiol-containing amino acids.

    PubMed

    Li, Yinhui; Duan, Yu; Li, Jishan; Zheng, Jing; Yu, Huan; Yang, Ronghua

    2012-06-01

    Complementary electrostatic interaction between the zwitterionic merocyanine and dipolar molecules has emerged as a common strategy for reversibly structural conversion of spiropyrans. Herein, we report a concept-new approach for thermal switching of a spiropyran that is based on simultaneous nucleophilic-substitution reaction and electrostatic interaction. The nucleophilic-substitution at spiro-carbon atom of a spiropyran is promoted due to electron-deficient interaction induced by 6- and 8-nitro groups, which is responsible for the isomerization of the spiropyran by interacting with thiol-containing amino acids. Further, the electrostatic interaction between the zwitterionic merocyanine and the amino acids would accelerate the structural conversion. As proof-of-principle, we outline the route to glutathione (GSH)-induced ring-opening of 6,8-dinitro-1',3',3'-trimethylspiro [2H-1-benzopyran-2,2'-indoline] (1) and its application for rapid and sensitive colorimetric detection of GSH. In ethanol-water (1:99, v/v) solution at pH 8.0, the free 1 exhibited slight-yellow color, but the color changed clearly from slight-yellow to orange-yellow when GSH was introduced into the solution. Ring-opening rate of 1 upon accession of GSH in the dark is 0.45 s(-1), which is 4 orders of magnitude faster in comparison with the rate of the spontaneous thermal isomerization. The absorbance enhancement of 1 at 480 nm was in proportion to the GSH concentration of 2.5 × 10(-8)-5.0 × 10(-6) M with a detection limit of 1.0 × 10(-8) M. Furthermore, due to the specific chemical reaction between the probe and target, color change of 1 is highly selective for thiol-containing amino acids; interferences from other biologically active amino acids or anions are minimal. PMID:22545785

  18. A Method for the Highly Selective, Colorimetric and Ratiometric Detection of Hg(2+) in a 100% Aqueous Solution.

    PubMed

    Liu, Jingkai; Xu, Zhenghe; Xu, Lirong; Bian, Zhen; Sang, Guoqing; Zhu, Baocun

    2016-01-01

    Mercury (Hg) and its derivatives pose a serious threat to the environment and human health. Thus, the development of methods for the selective and sensitive determination of Hg(2+) is very important to understand its distribution, and to implement more detailed toxicological studies. Herein, we developed a new method for the detection of Hg(2+) based on the tricyanoethylene derivative and mercaptoethanol. This method could selectively detect Hg(2+) in a 100% aqueous solution by the naked-eye within the range of 1 - 60 ?M. Importantly, this method also could detect Hg(2+) quantitatively by ratiometic absorption spectroscopy in the range of 0.1 - 6 ?M with a detection limit of 55 nM. We anticipate that this proposed method will be used widely to monitor Hg(2+) in the environment. PMID:26960619

  19. A FRET-based ratiometric fluorescent and colorimetric probe for the facile detection of organophosphonate nerve agent mimic DCP.

    PubMed

    Xuan, Weimin; Cao, Yanting; Zhou, Jiahong; Wang, Wei

    2013-11-18

    A FRET ratiometric fluorescent probe enabling a fast and highly sensitive response to OP nerve agent mimic DCP within 1 min and with as low as 0.17 ppm concentration detection limit has been developed. Moreover, the probe exhibits noticeable color changes under UV light and even with the naked eye. It is also demonstrated that it can detect both liquid and gas nerve agents. PMID:24080856

  20. Bio-inspired Maillard-Like reactions enable a simple and sensitive assay for colorimetric detection of methylglyoxal.

    PubMed

    Wang, Shih-Ting; Lin, Yiyang; Spicer, Christopher D; Stevens, Molly M

    2015-07-14

    A simple and selective assay for detecting methylglyoxal (MGO), a metabolite associated with diabetes, was developed by combining a bio-inspired chemical reaction with the anti-aggregation of gold nanoparticles. This assay could detect MGO at as low as 1 ?M by the naked eye and 0.05 ?M by UV/vis spectrometry, within the clinical range marking oxidative stress in diabetes, and demonstrated high selectivity over other physiologically relevant ketones and aldehydes. PMID:26073427

  1. Hydrophilic-Hydrophobic Patterned Molecularly Imprinted Photonic Crystal Sensors for High-Sensitive Colorimetric Detection of Tetracycline.

    PubMed

    Hou, Jue; Zhang, Huacheng; Yang, Qiang; Li, Mingzhu; Jiang, Lei; Song, Yanlin

    2015-06-01

    A hydrophilic-hydrophobic patterned molecularly imprinted (MIP) photonic crystal (PC) sensor is fabricated for highly sensitive tetracycline detection. The relationship between the tetracycline concentration, its corresponding color of the sensor, and the diameter of MIP-PC dot is found using a fan-shaped color card. This work provides a new strategy to design the sensors with tunable detection ranges for practical applications. PMID:25649896

  2. An unusual red-to-brown colorimetric sensing method for ultrasensitive silver(I) ion detection based on a non-aggregation of hyperbranched polyethylenimine derivative stabilized gold nanoparticles.

    PubMed

    Liu, Yi; Liu, Yang; Li, Zhongfa; Liu, Junshen; Xu, Li; Liu, Xunyong

    2015-08-01

    Here we have developed a facile and rapid colorimetric method for the sensitive and selective detection of Ag(+) based on the non-aggregation of gold nanoparticles (Au NPs) capped with hyperbranched polyethylenimine derivatives. In the detection process, an unusual colour change from red to brown was observed due to the formation of Au-Ag core-shell nanoparticles, which was more sensitive than that of the usual colorimetric assays (red to blue) based on the aggregation of Au NPs. After the colour changed, the non-aggregation-based Au-Ag core-shell nanomaterials did not aggregate further and could remain stable for a long time, which was convenient to record, detect and observe. The sensing probe exhibited a drastically long observing time for detecting Ag(+) owing to the stability of the Au-Ag core-shell non-aggregates, high sensitivity with a low detection limit of 8.76 nM by the naked eye and 1.09 nM by using a UV-vis spectrophotometer and a good linear relationship within the range from 1.09 to 109 nM. The colour change of the system is very fast, occurring within 1 to 2 minutes. Moreover, the proposed method also showed a remarkably high selectivity toward Ag(+) and was successfully used in tap water and drinking water samples. Therefore, this unusual colorimetric assay based on the non-aggregation of Au NPs has a great potential as a simple, rapid, sensitive and selective detection method for the detection of Ag(+). PMID:26079979

  3. A ratiometric colorimetric detection of the folate receptor based on terminal protection of small-molecule-linked DNA.

    PubMed

    Zhu, Yanhong; Wang, Guangfeng; Sha, Liang; Qiu, Yuwei; Jiang, Hong; Zhang, Xiaojun

    2015-02-21

    Development of strategies for the sensitive and selective detection of the folate receptor (FR) that are simple and low cost is of great importance for assessing cancer therapeutics due to its crucial role in physiological, pharmacological and pathological processes. In this paper, gold nanoparticle (AuNP)-based novel ratiometric colorimetry for the detection of the folate receptor (FR) is proposed based on terminal protection of small-molecule-linked DNA. The single-stranded DNA (ssDNA) terminally tethered to folic acid (FA) is protected from degradation by exonuclease I (Exo I) when the FA moiety is bound to FR. The hybridization between FR-protected DNA and DNA-functionalized Au NPs generated a red-to-purple colour change, allowing the visual detection of FR. The detection limit of FR can be as low as 0.33 ng mL(-1) with the naked eye. It provides a promising strategy for visual detection of the binding event of FA to its protein receptor-FR with advantages such as simplicity, high selectivity, and a wide linear range. PMID:25553613

  4. Multiplexed Colorimetric Detection of Kaposi’s Sarcoma Associated Herpesvirus and Bartonella DNA using Gold and Silver Nanoparticles

    PubMed Central

    Mancuso, Matthew; Jiang, Li; Cesarman, Ethel; Erickson, David

    2013-01-01

    Kaposi’s sarcoma (KS) is an infectious cancer occurring most commonly in human immunodeficiency virus (HIV) positive patients and in endemic regions, such as Sub-Saharan Africa, where KS is among the top four most prevalent cancers. The cause of KS is the Kaposi’s sarcoma-associated herpesvirus (KSHV, also called HHV-8), an oncogenic herpesvirus that while routinely diagnosed in developed nations, provides challenges to developing world medical providers and point-of-care detection. A major challenge in the diagnosis of KS is the existence of a number of other diseases with similar clinical presentation and histopathological features, requiring the detection of KSHV in a biopsy sample. In this work we develop an answer to this challenge by creating a multiplexed one-pot detection system for KSHV DNA and DNA from a frequently confounding disease, bacillary angiomatosis. Gold and silver nanoparticle aggregation reactions are tuned for each target and a multi-color change system is developed capable of detecting both targets down to levels between 1 nM and 2 nM. The system developed here could later be integrated with microfluidic sample processing to create a final device capable of solving the two major challenges in point-of-care KS detection. PMID:23340972

  5. Dark matter direct-detection experiments

    NASA Astrophysics Data System (ADS)

    Marrodán Undagoitia, Teresa; Rauch, Ludwig

    2016-01-01

    In recent decades, several detector technologies have been developed with the quest to directly detect dark matter interactions and to test one of the most important unsolved questions in modern physics. The sensitivity of these experiments has improved with a tremendous speed due to a constant development of the detectors and analysis methods, proving uniquely suited devices to solve the dark matter puzzle, as all other discovery strategies can only indirectly infer its existence. Despite the overwhelming evidence for dark matter from cosmological indications at small and large scales, clear evidence for a particle explaining these observations remains absent. This review summarises the status of direct dark matter searches, focusing on the detector technologies used to directly detect a dark matter particle producing recoil energies in the keV energy scale. The phenomenological signal expectations, main background sources, statistical treatment of data and calibration strategies are discussed.

  6. Colorimetric detection based on localised surface plasmon resonance of gold nanoparticles: Merits, inherent shortcomings and future prospects.

    PubMed

    Zhang, Yanlin; McKelvie, Ian D; Cattrall, Robert W; Kolev, Spas D

    2016-05-15

    Localised surface plasmon resonance (LSPR) of gold nanoparticles (AuNPs) has been exploited for two decades in analytical science and has proven to be a powerful tool for the detection of various kinds of substances including small molecules, ions, macro biomolecules and microbes. Detection can be performed by visual colour change observations, photometry or resonance light scattering. A wide range of applications have been studied in the areas of environmental, pharmaceutical and biological analysis and clinical diagnosis. In this article, some fundamental aspects and important applications involving LSPR of AuNPs are reviewed. Several inherent shortcomings of these techniques and possible strategies to circumvent them are discussed. PMID:26992537

  7. Onsite direct-read system for semi-quantitative detection of traces of beryllium on surfaces.

    PubMed

    Tekleab, T M; Mihaylov, G M; Kirollos, K S

    2006-06-01

    The present work describes a simple and reproducible direct-read system for onsite monitoring of beryllium on surfaces of work areas. It is based on the colorimetric reaction of beryllium with active ingredients deposited in a swab. A color comparator consisting of beryllium color chart was designed to enable the semi-quantitative determination of beryllium in surface samples. The system provides a minimum detection limit of 0.01 microg sample(-1). Metals tested for any interference effect include Al(3+), Ba(2+), Cd(2+), Cu(2+), Co(2+), Cr(3+), Cr(6+), Fe(3+), Hg(2+), Mg(2+), Ni(2+), Pb(2+), Ti(4+) and UO(2)(2+). Validation of the system showed no significant effect from metal interferences on the quantification of beryllium. PMID:16767229

  8. Water-dispersible silicon dots as a peroxidase mimetic for the highly-sensitive colorimetric detection of glucose.

    PubMed

    Chen, Qiong; Liu, Meiling; Zhao, Jiangna; Peng, Xue; Chen, Xiaojiao; Mi, Naxiu; Yin, Bangda; Li, Haitao; Zhang, Youyu; Yao, Shouzhuo

    2014-06-28

    We demonstrate that photoluminescent Si-dots exhibit intrinsic peroxidase-like activity, and can catalyze the oxidization of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2, and produce a color change. This strategy can be used to detect glucose with high sensitivity and selectivity. PMID:24834912

  9. Selective Colorimetric Detection of Hydrogen Sulfide Based on Primary Amine-Active Ester Cross-Linking of Gold Nanoparticles.

    PubMed

    Yuan, Zhiqin; Lu, Fengniu; Peng, Meihua; Wang, Chia-Wei; Tseng, Yu-Ting; Du, Yi; Cai, Na; Lien, Chia-Wen; Chang, Huan-Tsung; He, Yan; Yeung, Edward S

    2015-07-21

    Hydrogen sulfide (H2S) is a highly toxic environmental pollutant and also an important gaseous transmitter. Therefore, selective detection of H2S is very important, and visual detection of it with the naked eye is preferred in practical applications. In this study, thiolated azido derivates and active esters functionalized gold nanoparticles (AE-AuNPs)-based nanosensors have been successfully prepared for H2S perception. The sensing principle consists of two steps: first, H2S reduces the azide group to a primary amine; second, a cross-linking reaction between the primary amine and active ester induces the aggregation of AuNPs. The AE-AuNPs-based nanosensors show high selectivity toward H2S over other anions and thiols due to the specific azide-H2S chemistry. Under optimal conditions, 0.2 ?M H2S is detectable using a UV-vis spectrophotometer, and 4 ?M H2S can be easily detected by the naked eye. In addition, the practical application of the designed nanosensors was evaluated with lake water samples. PMID:26082264

  10. Pd/V.sub.2O.sub.5 device for colorimetric H.sub.2 detection

    SciTech Connect

    Liu, Ping; Tracy, C. Edwin; Pitts, J. Roland; Smith, II, R. Davis; Lee, Se-Hee

    2008-09-02

    A sensor structure for chemochromic optical detection of hydrogen gas over a wide response range, that exhibits stability during repeated coloring/bleaching cycles upon exposure and removal of hydrogen gas, comprising: a glass substrate (20); a vanadium oxide layer (21) coated on the glass substrate; and a palladium layer (22) coated on the vanadium oxide layer.

  11. Microfluidic paper-based analytical devices for colorimetric detection of urinary tract infection biomarkers on adult diapers.

    PubMed

    Chaohao Chen; Tao Dong

    2015-08-01

    Urinary tract infections (UTI) are common infection diseases in elderly patients. The conventional method of detecting UTI involves the collection of significant urine samples from the elderly patients. However, this is a very difficult and time-consuming procedure. This paper addresses the development of a microfluidic paper-based analytical device (?PAD) to detect UTI from urine collected from adult diapers. The design and fabrication for the ?PAD is shown. The fabrication process involves melting solid wax on top of filter paper using a hot plate, followed by pattern transfer using a mold with rubbed wax. To demonstrate the feasibility of the proposed method, the ?PAD with deposited nitrite reagent had detected different concentrations of nitrite solutions from 0.5 ppm to 100 ppm spiked in urine samples. A calibration curve was obtained by plotting the gray scale intensity values against the various nitrite concentrations. The results showed that the proposed paper-based device holds great potential as low-cost, disposable solution to sensitively detect UTI markers in urine sampled from diapers. PMID:26737632

  12. Colorimetric and fluorometric discrimination of geometrical isomers (maleic acid vs fumaric acid) with real-time detection of maleic acid in solution and food additives.

    PubMed

    Samanta, Soham; Kar, Chirantan; Das, Gopal

    2015-09-01

    Heterobis imine Schiff base probe L is able to discriminate geometrical isomers (maleic acid vs fumaric acid) through sharp colorimetric as well as fluorogenic responses even conspicuous with the naked eye. Colorimetric as well as fluorogenic sensing of maleic acid among various carboxylic acids was also demonstrated in ethanol-buffer medium. Sensing behavior of L was corroborated by (1)H NMR spectra, mass spectrometry, and theoretical calculations. Subsequently sensing behavior of L was used to probe maleic acid in starch rich food samples. PMID:26246182

  13. Detection of possible economically motivated adulterants in heparin sodium and low molecular weight heparins with a colorimetric microplate based assay.

    PubMed

    Sommers, Cynthia D; Keire, David A

    2011-09-15

    Recently, we described a 96-well plate format assay for visual detection of oversulfated chondroitin sulfate A (OSCS) contamination in heparin samples based on a water-soluble cationic polythiophene polymer (3-(2-(N-(N'-methylimidazole))ethoxy)-4-methylthiophene (LPTP)) and heparinase digestion of heparin. Here, we establish the specificity of the LPTP/heparinase test with a unique set of reagents that define the structural requirements for significant LPTP chemosensor color change. For example, we observed a biphasic behavior of larger shifts to the red in the UV absorbance spectra with decreasing average molecular weight of heparin chains with a break below 12-mer chain lengths. In addition, the oversulfation of chondroitin sulfate A (CSA) to a partially (PSCS) or fully (OSCS) sulfated form caused progressively less red shift of LPTP solutions. Furthermore, glycosaminoglycans (GAGs) containing glucuronic acid caused distinct spectral patterns compared to iduronic acid containing GAGs. We applied the LPTP/heparinase test to detection of OSCS (?0.03% (w/w) visually or 0.01% using a plate reader) in 10 ?g amounts of low molecular weight heparins (LMWHs; i.e. dalteparin, tinzaparin, or enoxaparin). Furthermore, because other oversulfated GAGs are possible economically motivated adulterants (EMAs) in heparin sodium, we tested the capacity of the LPTP/heparinase assay to detect oversulfated dermatan sulfate (OSDS), heparin (OSH), and heparan sulfate (OSHS). These potential EMAs were visually detectable at a level of ?0.1% when spiked into heparin sodium. We conclude that the LPTP/heparinase test visually detects oversulfated GAGs in heparin sodium and LMWHs in a format potentially amenable to high-throughput screening. PMID:21819047

  14. Novel antibody/gold nanoparticle/magnetic nanoparticle nanocomposites for immunomagnetic separation and rapid colorimetric detection of Staphylococcus aureus in milk.

    PubMed

    Sung, Yun Ju; Suk, Ho-Jun; Sung, Hwa Young; Li, Taihua; Poo, Haryoung; Kim, Min-Gon

    2013-05-15

    We demonstrated the new antibody/gold nanoparticle/magnetic nanoparticle nanocomposites (antibody/AuNP/MNPs) and their application in the detection of the foodborne pathogen, Staphylococcus aureus (S. aureus), in milk. The nanocomposites were synthesized by coating the MNPs with bovine serum albumin (BSA) then adsorbing the AuNPs and anti-S. aureus antibodies on their surface. Using the completed immunomagnetic nanostructures, S. aureus inoculated in the milk sample was captured and isolated from the medium using the permanent magnet. The nanoparticle-bound cells as well as the unbound cells in the supernatant were enumerated via surface plating to evaluate the target binding capacity of the nanocomposites. The capture efficiencies of the antibody/AuNP/MNPs were 96% and 78% for S. aureus in PBS and the milk sample respectively, which were significantly higher than those of the antibody-coupled MNPs without any AuNP. The captured cells were also applied to the selective filtration system to produce color signals that were used for the detection of the target pathogen. During the filtration, the cells bound to the antibody/AuNP/MNPs remained on the surface of the membrane filter while unbound nanoparticles passed through the uniform pores of the membrane. After the gold enhancement, the cells-particles complex resting on the membrane surface rendered a visible color, and the signal intensity became higher as the target cell concentration increased. The detection limits of this colorimetric sensor were 1.510(3) and 1.510(5)CFU for S. aureus in PBS and the milk sample respectively. This sensing mechanism also had the high specificity for S. aureus over the other pathogens such as Escherichia coli, Listeria monocytogenes, and Salmonella enterica. The assay required only 40min to obtain the results. With the use of the appropriate antibodies, our immunomagnetic nanocomposites-based detection strategy can provide an easy, convenient, and rapid sensing method for a wide range of pathogens. PMID:23370174

  15. Colorimetric and ratiometric fluorescent detection of sulfite in water via cationic surfactant-promoted addition of sulfite to ?,?-unsaturated ketone.

    PubMed

    Tian, Haiyu; Qian, Junhong; Sun, Qian; Bai, Hongyan; Zhang, Weibing

    2013-07-25

    Three fluorescent probes were constructed by incorporating an ?,?-unsaturated ketone to a coumarin fluorophore. The selective addition of sulfite to the alkene of TSP assisted by cetyltrimethyl ammonium bromide (CTAB) micelle can be visualized by dramatic color and ratiometric fluorescence changes. In CTAB-PBS system, the fluorescence intensity ratio at 465 nm and 592 nm (I465/I592) and the absorbance ratio at 390 nm and 470 nm (A390/A470) were linearly proportional to sulfite concentration in the range of 0.5-150 ?M, and the detection limit was 0.2 ?M. Good selectivity and competition of TSP1 towards sulfite over several anions and biological thiols were acquired. Probe TSP1 was used to detect sulfite in three realistic samples (mineral water, sugar and white wine) with good recovery. PMID:23845496

  16. Au nanoparticles and polyaniline coated resin beads for simultaneous catalytic oxidation of glucose and colorimetric detection of the product.

    PubMed

    Majumdar, Gitanjali; Goswami, Mausumi; Sarma, Tridib Kumar; Paul, Anumita; Chattopadhyay, Arun

    2005-03-01

    In this letter, we report the synthesis of Au nanoparticles (NPs) and polyaniline (PANI) on the same cation-exchange resin beads and demonstrate their use in catalyzing the oxidation of glucose to gluconic acid by Au NPs and simultaneously in detecting the formation of the acid by the color change of PANI. The synthesis was carried out by exchanging the cations of the resins with HAuCl4 and anilinuium chloride and then reducing the metal ions by NaBH4 to produce Au NPs followed by polymerization of aniline using H2O2. The green emeraldine salt form of PANI thus obtained was treated with NaOH to be converted to blue emeraldine base before use. The deposition of Au NPs was confirmed by a change in color of the bead, visible spectroscopy, X-ray diffraction, and scanning electron microscopic measurements. On the other hand, the presence of PANI was confirmed by Fourier transform infrared (FTIR) and ultraviolet-visible (UV-vis) spectroscopy. The formation of gluconic acid from glucose was confirmed by FTIR spectroscopy. We could detect the presence of glucose of a minimum 1.0 mM concentration in water, using the present method. Our experimental observations demonstrate the possibility of the incorporation of multifunctional components on the surfaces of resins for carrying out a chemical reaction as well as detection of the product. PMID:15723451

  17. Direct detection of dark matter axions with directional sensitivity

    SciTech Connect

    Irastorza, Igor G.; Garca, Juan A. E-mail: jagarpas@unizar.es

    2012-10-01

    We study the directional effect of the expected axion dark matter signal in a resonant cavity of an axion haloscope detector, for cavity geometries not satisfying the condition that the axion de Broglie wavelength ?{sub a} is sufficiently larger than the cavity dimensions L for a fully coherent conversion, i.e. ?{sub a}?>2?L. We focus on long thin cavities immersed in dipole magnets and find, for appropriately chosen cavity lengths, an O(1) modulation of the signal with the cavity orientation with respect the momentum distribution of the relic axion background predicted by the isothermal sphere model for the galactic dark matter halo. This effect can be exploited to design directional axion dark matter detectors, providing an unmistakable signature of the extraterrestrial origin of a possible positive detection. Moreover, the precise shape of the modulation may give information of the galactic halo distribution and, for specific halo models, give extra sensitivity for higher axion masses.

  18. Chitosan-capped silver nanoparticles as a highly selective colorimetric probe for visual detection of aromatic ortho-trihydroxy phenols.

    PubMed

    Chen, Zhaohui; Zhang, Xiaodan; Cao, Haiyan; Huang, Yuming

    2013-04-21

    We reported a new application of silver nanoparticles (NPs) for the visual sensing of aromatic polyphenols, such as gallic acid, pyrogallol and tannic acid, which is based on the intensified plasmon absorbance signals and visual changes from yellow to orange due to hydrogen-bonding recognition and subsequent catalytic oxidation of the target phenols by chitosan-capped AgNPs (Ch-AgNPs). The Ch-AgNPs are generated by the well-known reaction of AgNO3 with NaBH4 and stabilized with chitosan which is a polysaccharide biopolymer with excellent dispersive properties and stability in aqueous media. After optimizing some experimental conditions, a very simple and facile sensing system has been developed for the detection of gallic acid, pyrogallol and tannic acid in water samples. The proposed system promises high selectivity toward gallic acid, pyrogallol and tannic acid, and other phenolic compounds including p-aminobenzoic acid, pentachlorophenol, 2,4,6-trinitrophenol, 2,4-dinitrophenol, p-nitrophenol, 1-naphthol, ?-naphthol, p-aminophenol, catechol, hydroquinone, m-dihydroxybenzene, phloroglucin and phenol could not induce a color change even at 0.1 mM. The outstanding selectivity property of the proposed method for gallic acid, pyrogallol and tannic acid resulted from the Ch-AgNPs-mediated reduction of Ag(+) by the target phenols. Also, a wide linear response range was obtained for the three targets. The linear response ranges for gallic acid, pyrogallol, and tannic acid were from 1 10(-5) to 1 10(-3) M, 1 10(-5) to 1 10(-2) M and 1 10(-6) to 1 10(-4) M with a respective detection limit (DL) of 1 10(-5), 1 10(-5), and 1 10(-6) M. The proposed method was successfully applied to detect target phenols in environmental water samples. Furthermore, because the color change from yellow to orange is observable by the naked eye, it is easy to realize visual detection of the target phenols without any instrumentation or complicated design. The experimental results reported here open up an innovative application of the catalytic reactivity of AgNPs. PMID:23457709

  19. Specific and sensitive colorimetric detection of Al3+ using 5-mercaptomethyltetrazole capped gold nanoparticles in aqueous solution.

    PubMed

    Xue, Dingshuai; Wang, Hongyue; Zhang, Yanbin

    2014-02-01

    Contamination of food and drinking water by health-risk levels of Al(3+) calls for convenient assays. Here, we report a method to visibly detect Al(3+) at room temperature. Firstly, the chelating ligand of 5-mercaptomethyltetrazole (MMT) was synthesized and modified on the surface of AuNPs through the strong Au-S interaction to form a MMT-AuNP probe, which can remain well-dispersed and stable in an aqueous solution for a long time. Upon the addition of Al(3+), the interparticle crosslinking induced aggregation (color change from red to blue) of MMT-AuNPs was triggered through the Al(3+)-MMT interaction. Under optimal conditions, the absorbance ratio (A620/A520) of MMT-AuNPs is linear within the Al(3+) concentration range from 1.0 to 10.0 μM, and the detection limit (3σ) was as low as 0.53 μM. Moreover, an interference study showed that this MMT-AuNP probe discriminated Al(3+) from a wide range of environmentally dominant metal ions and anions. The practical utility of the new method was demonstrated by determining Al(3+) in several environmental water and human urine specimens, obtaining satisfactory results. Being a rapid, convenient and cost-effective method, it should become a powerful alternative to conventional methods for selective quantification of Al(3+) in routine laboratory practice or rapid on-site assay. PMID:24401419

  20. Continuous colorimetric screening assays for the detection of specific L- or D-α-amino acid transaminases in enzyme libraries.

    PubMed

    Heuson, Egon; Petit, Jean-Louis; Debard, Adrien; Job, Aurélie; Charmantray, Franck; de Berardinis, Véronique; Gefflaut, Thierry

    2016-01-01

    In the course of a project devoted to the stereoselective synthesis of non-proteinogenic α-amino acids using α-transaminases (α-TA), we report the design and optimization of generic high-throughput continuous assays for the screening of α-TA libraries. These assays are based on the use of L- or D-cysteine sulfinic acid (CSA) as irreversible amino donor and subsequent sulfite titration by colorimetry. The assays' quality was assessed under screening conditions. Hit selection thresholds were accurately determined for every couple of substrates and a library of 232 putative transaminases expressed in Escherichia coli host cells was screened. The reported high throughput screening assays proved very sensitive allowing the detection with high confidence of activities as low as 10 μU (i.e., 0.01 nmol substrate converted per min). The assays were also evidenced to be stereochemically discriminant since L-CSA and D-CSA allowed the exclusive detection of L-TA and D-TA, respectively. These generic assays thus allow testing the stereoselective conversion of a wide range of α-keto acids into α-amino acids of interest. As a proof of principle, the use of 2-oxo-4-phenylbutyric acid as acceptor substrate led to the identification of 54 new α-TA offering an access to valuable L- or D-homophenylalanine. PMID:26452497

  1. Atomic absorption spectroscopic, conductometric and colorimetric methods for determination of some fluoroquinolone antibacterials using ammonium reineckate

    NASA Astrophysics Data System (ADS)

    Al-Ghannam, Sheikha M.

    2008-04-01

    Three accurate, rapid and simple atomic absorption spectrometric (AAS), conductometric and colorimetric methods were developed for the determination of gatifloxacin (GTF), moxifloxacin (MXF) and sparfloxacin (SPF). The proposed methods depend upon the reaction of ammonium reineckate with the studied drugs to form stable precipitate of ion-pair complexes, which was dissolved in acetone. The pink coloured complexes were determined either by AAS or colorimetrically at ?max 525 nm directly using the dissolved complex. Using conductometric titration, the studied drugs could be evaluated in 50% (v/v) acetone. The optimizations of various experimental conditions were described. Optimum concentration ranges for the determination of GTF, MXF and SPF were 5.0-150, 40-440 ?g mL -1 and 0.10-1.5 mg mL -1 using atomic absorption (AAS), conductometric and colorimetric methods, respectively. Detection and quantification limits are ranges from 1.5 to 2.3 ?g mL -1 using AAS method or 30-45 ?g mL -1 using colorimetric method. The proposed procedures have been applied successfully to the analysis of these drugs in pharmaceutical formulations and the results are favourably comparable to the reference methods.

  2. Community detection in directed acyclic graphs

    NASA Astrophysics Data System (ADS)

    Speidel, Leo; Takaguchi, Taro; Masuda, Naoki

    2015-08-01

    Some temporal networks, most notably citation networks, are naturally represented as directed acyclic graphs (DAGs). To detect communities in DAGs, we propose a modularity for DAGs by defining an appropriate null model (i.e., randomized network) respecting the order of nodes. We implement a spectral method to approximately maximize the proposed modularity measure and test the method on citation networks and other DAGs. We find that the attained values of the modularity for DAGs are similar for partitions that we obtain by maximizing the proposed modularity (designed for DAGs), the modularity for undirected networks and that for general directed networks. In other words, if we neglect the order imposed on nodes (and the direction of links) in a given DAG and maximize the conventional modularity measure, the obtained partition is close to the optimal one in the sense of the modularity for DAGs. Contribution to the Topical Issue "Temporal Network Theory and Applications", edited by Petter Holme.

  3. Colorimetric detection of fluoride ion by 5-arylidenebarbituric acids: dual interaction mode for fluoride ion with single receptor.

    PubMed

    Saravanan, Chinnusamy; Easwaramoorthi, Shanmugam; Wang, Leeyih

    2014-04-01

    Two 5-arylidenebarbituric acid derivatives (IH and IM) have been synthesized by the Knoevenagel condensation of barbituric acid with 4-N,N-dimethylamino benzaldehyde and studied for anion sensing activities. Both receptors sense fluoride ion with high selectivity and sensitivity and the sensing action has been demonstrated by naked eye detection, UV-visible absorption, and fluorescence spectral changes in the presence of F(-). Indeed, the F(-) sensing mechanism for receptor IH depends on F(-) ion concentration. While at higher concentrations F(-) forms strong hydrogen bonding interaction with the N-H proton of the receptor, at lower concentrations sensing is influenced by the deprotonation of the methylene proton, followed by the chemical reaction, which is also confirmed by the (1)H-NMR technique. On the other hand, when replacing the N-H proton with a methyl group, IM does not show any concentration dependent behaviour with F(-). The F(-) concentration dependent sensing is attributed to the changes in the receptor-anion interaction equilibrium, where at higher F(-) concentrations, F(-) interacts with the receptor through hydrogen bonding and at lower concentrations it induces a chemical reaction. PMID:24500374

  4. Aberration features in directional dark matter detection

    SciTech Connect

    Bozorgnia, Nassim; Gelmini, Graciela B.; Gondolo, Paolo E-mail: gelmini@physics.ucla.edu

    2012-08-01

    The motion of the Earth around the Sun causes an annual change in the magnitude and direction of the arrival velocity of dark matter particles on Earth, in a way analogous to aberration of stellar light. In directional detectors, aberration of weakly interacting massive particles (WIMPs) modulates the pattern of nuclear recoil directions in a way that depends on the orbital velocity of the Earth and the local galactic distribution of WIMP velocities. Knowing the former, WIMP aberration can give information on the latter, besides being a curious way of confirming the revolution of the Earth and the extraterrestrial provenance of WIMPs. While observing the full aberration pattern requires extremely large exposures, we claim that the annual variation of the mean recoil direction or of the event counts over specific solid angles may be detectable with moderately large exposures. For example, integrated counts over Galactic hemispheres separated by planes perpendicular to Earth's orbit would modulate annually, resulting in Galactic Hemisphere Annual Modulations (GHAM) with amplitudes larger than the usual non-directional annual modulation.

  5. Direct detection of dark matter debris flows

    NASA Astrophysics Data System (ADS)

    Kuhlen, Michael; Lisanti, Mariangela; Spergel, David N.

    2012-09-01

    Tidal stripping of dark matter from subhalos falling into the Milky Way produces narrow, cold tidal streams as well as more spatially extended debris flows in the form of shells, sheets, and plumes. Here we focus on the debris flow in the Via Lactea II simulation, and show that this incompletely phase-mixed material exhibits distinctive high velocity behavior. Unlike tidal streams, which may not necessarily intersect the Earths location, debris flow is spatially uniform at 8 kpc and thus guaranteed to be present in the dark matter flux incident on direct detection experiments. At Earth-frame speeds greater than 450 km/s, debris flow comprises more than half of the dark matter at the Suns location, and up to 80% at even higher speeds. Therefore, debris flow is most important for experiments that are particularly sensitive to the high speed tail of the dark matter distribution, such as searches for light or inelastic dark matter or experiments with directional sensitivity. We show that debris flow yields a distinctive recoil energy spectrum and a broadening of the distribution of incidence direction.

  6. Directly detecting exozodiacal dust and disk variability

    NASA Astrophysics Data System (ADS)

    Scott, Nicholas J.

    2015-01-01

    Dust is common throughout stellar systems. The architecture of stellar systems may be typically comprised of a distant cold debris disk, a warm exozodiacal disk, and a hot inner disk. Dust in this exozodiacal region confounds exoplanet detections by scattering light or mimicking planetary emission. This environment must be well-modelled in order to find Earth-sized exoplanets. Interferometry at the Center for High Resolution Astronomy (CHARA) Array provides the angular resolution to directly detect near-infrared (NIR) excesses originating from warm and hot dust close to the host star. The recently upgraded Fiber-Linked Unit for Optical Recombination (JouFLU) is capable of measuring interferometric visibility contrasts to a precision of <0.1% and dust disk fluxes equal to 1% of the host star. There is likely a connection between these hot interferometrically detected dust disks and the harder-to-detect warm zodiacal dust analogues. In this way interferometric studies can observe the tip-of-the-iceberg of stellar system dust, providing details such as composition and grain size of dust, as well as statistics on the correlation of dust populations and stellar properties. These inner dust regions may exhibit a high degree of variability which should also be characterized and may give hint to the dust origin and replenishment mechanisms. JouFLU is currently involved in a large survey of exozodiacal dust stars of spectral types A through K with the aim to provide statistics about dust disk occurrence in relation to their host stars and the presence of cold dust reservoirs. Complementing this survey is a project of re-observing the earliest excess detections in order to determine their variability. In addition, NASA's InfraRed Telescope Facility (IRTF) provides a method for spectrophotometric detections of excess stellar flux corresponding to the presence of hot/warm exozodiacal dust. Multiple NIR interferometric instruments as well as medium resolution spectroscopy are a sensitive and affordable method of discovering inner disks and characterizing nearby habitable zone environments.

  7. The direct barbituric acid assay for nicotine metabolites in urine: a simple colorimetric test for the routine assessment of smoking status and cigarette smoke intake.

    PubMed

    Barlow, R D; Stone, R B; Wald, N J; Puhakainen, E V

    1987-05-29

    The qualitative direct barbituric acid (DBA) method of detecting urine nicotine metabolites was modified to make it quantitative. The performance of the quantitative DBA method was compared with the qualitative method and an established cotinine radio-immunoassay (RIA), using a panel of urines from 128 reported smokers and 383 reported non-smokers. The quantitative DBA method results were highly correlated with the cotinine RIA results, r = 0.85. The coefficients of variation for the two methods were 6% and 10%, respectively. Assuming that the reported smoking history was correct the qualitative DBA method gave a smoking detection rate of 91% and a false positive rate of 3%. At cut-off levels chosen to yield the same false positive rate the quantitative DBA method detected 93% of smokers, close to that of 98% detected with the cotinine RIA. The quantitative DBA method can be used to analyse over 170 samples per day compared to about 70 per day by RIA. It is therefore a fast and inexpensive alternative to cotinine assays for the assessment of smoking status and cigarette smoke intake. PMID:3608188

  8. The Earth's velocity for direct detection experiments

    SciTech Connect

    McCabe, Christopher

    2014-02-01

    The Earth's velocity relative to the Sun in galactic coordinates is required in the rate calculation for direct detection experiments. We provide a rigorous derivation of this quantity to first order in the eccentricity of the Earth's orbit. We also discuss the effect of the precession of the equinoxes, which has hitherto received little explicit discussion. Comparing with other expressions in the literature, we confirm that the expression of Lee, Lisanti and Safdi is correct, while the expression of Lewin and Smith, the de facto standard expression, contains an error. For calculations of the absolute event rate, the leading order expression is sufficient while for modulation searches, an expression with the eccentricity is required for accurate predictions of the modulation phase.

  9. Colorimetric elastase sensor with peptide conjugated cellulose nanocrystals is interfaced to dialysis membranes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Clinical detection of human neutrophil elastase (HNE) as point of care biomarker or in situ colorimetric adjuvant to chronic wound dressings presents potential advantages in the management of chronic wounds. A colorimetric approach to the detection of HNE using cotton cellulose nanocrystals (CCN) i...

  10. DIRECT DETECTION OF AN ULTRALUMINOUS ULTRAVIOLET SOURCE

    SciTech Connect

    Kaaret, Philip; Feng Hua; Wong, Diane S.; Tao Lian

    2010-05-01

    We present Hubble Space Telescope observations in the far UV of the ultraluminous X-ray source in NGC 6946 associated with the optical nebula MF 16. Both a point-like source coincident with the X-ray source and the surrounding nebula are detected in the FUV. The point source has a flux of 5 x 10{sup -16} erg s{sup -1} cm{sup -2} A{sup -1}, and the nebula has a flux of 1.6 x 10{sup -15} erg s{sup -1} cm{sup -2} A{sup -1}, quoted at 1533 A and assuming an extinction of A{sub V} = 1.54. Thus, MF 16 appears to host the first directly detected ultraluminous UV source. The flux of the point-like source is consistent with a blackbody with T{approx} 30,000 K, possibly from a massive companion star, but this spectrum does not create sufficient ionizing radiation to produce the nebular He II flux, and a second, hotter emission component would be required. A multicolor disk blackbody spectrum truncated with an outer disk temperature of {approx}16,000 K provides an adequate fit to the FUV, B, V, I, and He II fluxes and can produce the needed ionizing radiation. Additional observations are required to determine the physical nature of the source.

  11. A colorimetric proton sponge.

    PubMed

    Swor, Charles D; Zakharov, Lev N; Tyler, David R

    2010-10-15

    1,8-Bis(dimethylamino)naphthalene ("Proton Sponge") and bromomaleic anhydride react quickly at room temperature, generating 3-(4,5-bis(dimethylamino)napthalen-1-yl)furan-2,5-dione (4-maleicanhydridoproton sponge or "MAPS"). MAPS is a deep purple solid that exhibits positive solvatochromism in solution. It is a weaker base than Proton Sponge. When protonated in solution, MAPS loses its color, but the color change can be reversed by deprotonation with a stronger base. MAPS thus acts as a colorimetric version of a proton sponge. PMID:20857948

  12. EXTRAGALACTIC DARK MATTER AND DIRECT DETECTION EXPERIMENTS

    SciTech Connect

    Baushev, A. N.

    2013-07-10

    Recent astronomical data strongly suggest that a significant part of the dark matter content of the Local Group and Virgo Supercluster is not incorporated into the galaxy halos and forms diffuse components of these galaxy clusters. A portion of the particles from these components may penetrate the Milky Way and make an extragalactic contribution to the total dark matter containment of our Galaxy. We find that the particles of the diffuse component of the Local Group are apt to contribute {approx}12% to the total dark matter density near Earth. The particles of the extragalactic dark matter stand out because of their high speed ({approx}600 km s{sup -1}), i.e., they are much faster than the galactic dark matter. In addition, their speed distribution is very narrow ({approx}20 km s{sup -1}). The particles have an isotropic velocity distribution (perhaps, in contrast to the galactic dark matter). The extragalactic dark matter should provide a significant contribution to the direct detection signal. If the detector is sensitive only to the fast particles (v > 450 km s{sup -1}), then the signal may even dominate. The density of other possible types of the extragalactic dark matter (for instance, of the diffuse component of the Virgo Supercluster) should be relatively small and comparable with the average dark matter density of the universe. However, these particles can generate anomaly high-energy collisions in direct dark matter detectors.

  13. Direct Detection of Soil-Bound Prions

    PubMed Central

    Genovesi, Sacha; Leita, Liviana; Sequi, Paolo; Andrighetto, Igino; Sorgato, M. Catia; Bertoli, Alessandro

    2007-01-01

    Scrapie and chronic wasting disease are contagious prion diseases affecting sheep and cervids, respectively. Studies have indicated that horizontal transmission is important in sustaining these epidemics, and that environmental contamination plays an important role in this. In the perspective of detecting prions in soil samples from the field by more direct methods than animal-based bioassays, we have developed a novel immuno-based approach that visualises in situ the major component (PrPSc) of prions sorbed onto agricultural soil particles. Importantly, the protocol needs no extraction of the protein from soil. Using a cell-based assay of infectivity, we also report that samples of agricultural soil, or quartz sand, acquire prion infectivity after exposure to whole brain homogenates from prion-infected mice. Our data provide further support to the notion that prion-exposed soils retain infectivity, as recently determined in Syrian hamsters intracerebrally or orally challanged with contaminated soils. The cell approach of the potential infectivity of contaminated soil is faster and cheaper than classical animal-based bioassays. Although it suffers from limitations, e.g. it can currently test only a few mouse prion strains, the cell model can nevertheless be applied in its present form to understand how soil composition influences infectivity, and to test prion-inactivating procedures. PMID:17957252

  14. A Colorimetric Enzyme-Linked Immunosorbent Assay (ELISA) Detection Platform for a Point-of-Care Dengue Detection System on a Lab-on-Compact-Disc

    PubMed Central

    Thiha, Aung; Ibrahim, Fatimah

    2015-01-01

    The enzyme-linked Immunosorbent Assay (ELISA) is the gold standard clinical diagnostic tool for the detection and quantification of protein biomarkers. However, conventional ELISA tests have drawbacks in their requirement of time, expensive equipment and expertise for operation. Hence, for the purpose of rapid, high throughput screening and point-of-care diagnosis, researchers are miniaturizing sandwich ELISA procedures on Lab-on-a-Chip and Lab-on-Compact Disc (LOCD) platforms. This paper presents a novel integrated device to detect and interpret the ELISA test results on a LOCD platform. The system applies absorption spectrophotometry to measure the absorbance (optical density) of the sample using a monochromatic light source and optical sensor. The device performs automated analysis of the results and presents absorbance values and diagnostic test results via a graphical display or via Bluetooth to a smartphone platform which also acts as controller of the device. The efficacy of the device was evaluated by performing dengue antibody IgG ELISA on 64 hospitalized patients suspected of dengue. The results demonstrate high accuracy of the device, with 95% sensitivity and 100% specificity in detection when compared with gold standard commercial ELISA microplate readers. This sensor platform represents a significant step towards establishing ELISA as a rapid, inexpensive and automatic testing method for the purpose of point-of-care-testing (POCT) in resource-limited settings. PMID:25993517

  15. A Colorimetric Enzyme-Linked Immunosorbent Assay (ELISA) Detection Platform for a Point-of-Care Dengue Detection System on a Lab-on-Compact-Disc.

    PubMed

    Thiha, Aung; Ibrahim, Fatimah

    2015-01-01

    The enzyme-linked Immunosorbent Assay (ELISA) is the gold standard clinical diagnostic tool for the detection and quantification of protein biomarkers. However, conventional ELISA tests have drawbacks in their requirement of time, expensive equipment and expertise for operation. Hence, for the purpose of rapid, high throughput screening and point-of-care diagnosis, researchers are miniaturizing sandwich ELISA procedures on Lab-on-a-Chip and Lab-on-Compact Disc (LOCD) platforms. This paper presents a novel integrated device to detect and interpret the ELISA test results on a LOCD platform. The system applies absorption spectrophotometry to measure the absorbance (optical density) of the sample using a monochromatic light source and optical sensor. The device performs automated analysis of the results and presents absorbance values and diagnostic test results via a graphical display or via Bluetooth to a smartphone platform which also acts as controller of the device. The efficacy of the device was evaluated by performing dengue antibody IgG ELISA on 64 hospitalized patients suspected of dengue. The results demonstrate high accuracy of the device, with 95% sensitivity and 100% specificity in detection when compared with gold standard commercial ELISA microplate readers. This sensor platform represents a significant step towards establishing ELISA as a rapid, inexpensive and automatic testing method for the purpose of point-of-care-testing (POCT) in resource-limited settings. PMID:25993517

  16. Semi-automated direct colorimetric measurement of creatine kinase isoenzyme MB activity after extraction from serum by use of a CK-MB-specific monoclonal antibody.

    PubMed

    Landt, Y; Vaidya, H C; Porter, S E; Whalen, K; McClellan, A; Amyx, C; Parvin, C A; Kessler, G; Nahm, M H; Dietzler, D N

    1988-03-01

    This semi-automated colorimetric assay for the MB isoenzyme of creatine kinase (EC 2.7.3.2) is based on a monoclonal antibody ("Conan-MB") specific for this isoenzyme and is a modification of a previously published method (Vaidya et al., Clin Chem 1986;32:657-63). A 0.64-cm bead coated with 2 to 3 micrograms of antibody is incubated with 100 microL of serum and 10 microL of 0.2 mol/L beta-mercaptoethanol for 1 h at room temperature, to extract CK-MB. The beads are washed with de-ionized water and incubated with CK substrate for 45 min at 37 degrees C. A solution containing trans-1,2-diaminocyclohexane-N,N,N', N'-tetraacetic acid, p-iodonitrotetrazolium violet, and diaphorase is added and the resulting colored product is measured at 492 nm. The standard curve is linear to 200 U of CK-MB per liter, and analytical recovery is 97-113%. Total assay CV for low (9.7 U/L) and high (50.7 U/L) quality-control materials was 14.1% (n = 1878) and 11.6% (n = 1842), respectively. CK-MB activity correlated well (r = 0.978, n = 226) with CK-MB measured by a two-site mass immunoassay, and 99.4% of samples with CK-MB greater than or equal to 12 U/L (n = 347) were verified by electrophoresis on agarose. PMID:3349610

  17. Detecting Patterns of Aeolian Transport Direction

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The magnitude and direction of aeolian transport are of direct interest to those engaged in the study of aeolian processes. Although the magnitude of sediment transport has been studied extensively, the study of aeolian transport direction has garnered less attention. This paper describes the deve...

  18. Pt74Ag26 nanoparticle-decorated ultrathin MoS2 nanosheets as novel peroxidase mimics for highly selective colorimetric detection of H2O2 and glucose

    NASA Astrophysics Data System (ADS)

    Cai, Shuangfei; Han, Qiusen; Qi, Cui; Lian, Zheng; Jia, Xinghang; Yang, Rong; Wang, Chen

    2016-02-01

    To extend the functionalities of two-dimensional graphene-like layered compounds as versatile materials, the modification of transition metal dichalcogenide nanosheets such as MoS2 with metal nanoparticles is of great and widespread interest. However, few studies are available on the preparation of bimetallic nanoparticles supported on MoS2. Herein, a facile and efficient method to synthesize MoS2-PtAg nanohybrids by decorating ultrathin MoS2 nanosheets with octahedral Pt74Ag26 alloy nanoparticles has been reported. The as-prepared MoS2-Pt74Ag26 nanohybrids were investigated as novel peroxidase mimics to catalyze the oxidation of classical peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2, producing a blue colored reaction and exhibiting typical Michaelis-Menten kinetics. MoS2-Pt74Ag26 has a higher affinity for H2O2 than horseradish peroxidase (HRP) and a higher vmax value with TMB as the substrate than MoS2. The improved catalytic activity of hybrids for colorimetric reactions could be attributed to the synergistic effects of octahedral Pt74Ag26 nanoparticles and ultrathin MoS2 nanosheets as supports. Meanwhile, the generation of active oxygen species (&z.rad;OH) by H2O2 decomposition with MoS2-Pt74Ag26 was responsible for the oxidation of TMB. On the basis of these findings, a colorimetric method based on MoS2-Pt74Ag26 nanohybrids that is highly sensitive and selective was developed for glucose detection. Lower values of the limit of detection (LOD) were obtained, which is more sensitive than MoS2 nanosheets.To extend the functionalities of two-dimensional graphene-like layered compounds as versatile materials, the modification of transition metal dichalcogenide nanosheets such as MoS2 with metal nanoparticles is of great and widespread interest. However, few studies are available on the preparation of bimetallic nanoparticles supported on MoS2. Herein, a facile and efficient method to synthesize MoS2-PtAg nanohybrids by decorating ultrathin MoS2 nanosheets with octahedral Pt74Ag26 alloy nanoparticles has been reported. The as-prepared MoS2-Pt74Ag26 nanohybrids were investigated as novel peroxidase mimics to catalyze the oxidation of classical peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2, producing a blue colored reaction and exhibiting typical Michaelis-Menten kinetics. MoS2-Pt74Ag26 has a higher affinity for H2O2 than horseradish peroxidase (HRP) and a higher vmax value with TMB as the substrate than MoS2. The improved catalytic activity of hybrids for colorimetric reactions could be attributed to the synergistic effects of octahedral Pt74Ag26 nanoparticles and ultrathin MoS2 nanosheets as supports. Meanwhile, the generation of active oxygen species (&z.rad;OH) by H2O2 decomposition with MoS2-Pt74Ag26 was responsible for the oxidation of TMB. On the basis of these findings, a colorimetric method based on MoS2-Pt74Ag26 nanohybrids that is highly sensitive and selective was developed for glucose detection. Lower values of the limit of detection (LOD) were obtained, which is more sensitive than MoS2 nanosheets. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08038j

  19. Pt74Ag26 nanoparticle-decorated ultrathin MoS2 nanosheets as novel peroxidase mimics for highly selective colorimetric detection of H2O2 and glucose.

    PubMed

    Cai, Shuangfei; Han, Qiusen; Qi, Cui; Lian, Zheng; Jia, Xinghang; Yang, Rong; Wang, Chen

    2016-02-14

    To extend the functionalities of two-dimensional graphene-like layered compounds as versatile materials, the modification of transition metal dichalcogenide nanosheets such as MoS2 with metal nanoparticles is of great and widespread interest. However, few studies are available on the preparation of bimetallic nanoparticles supported on MoS2. Herein, a facile and efficient method to synthesize MoS2-PtAg nanohybrids by decorating ultrathin MoS2 nanosheets with octahedral Pt74Ag26 alloy nanoparticles has been reported. The as-prepared MoS2-Pt74Ag26 nanohybrids were investigated as novel peroxidase mimics to catalyze the oxidation of classical peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2, producing a blue colored reaction and exhibiting typical Michaelis-Menten kinetics. MoS2-Pt74Ag26 has a higher affinity for H2O2 than horseradish peroxidase (HRP) and a higher vmax value with TMB as the substrate than MoS2. The improved catalytic activity of hybrids for colorimetric reactions could be attributed to the synergistic effects of octahedral Pt74Ag26 nanoparticles and ultrathin MoS2 nanosheets as supports. Meanwhile, the generation of active oxygen species (?OH) by H2O2 decomposition with MoS2-Pt74Ag26 was responsible for the oxidation of TMB. On the basis of these findings, a colorimetric method based on MoS2-Pt74Ag26 nanohybrids that is highly sensitive and selective was developed for glucose detection. Lower values of the limit of detection (LOD) were obtained, which is more sensitive than MoS2 nanosheets. PMID:26811962

  20. Cost Effective Paper-Based Colorimetric Microfluidic Devices and Mobile Phone Camera Readers for the Classroom

    ERIC Educational Resources Information Center

    Koesdjojo, Myra T.; Pengpumkiat, Sumate; Wu, Yuanyuan; Boonloed, Anukul; Huynh, Daniel; Remcho, Thomas P.; Remcho, Vincent T.

    2015-01-01

    We have developed a simple and direct method to fabricate paper-based microfluidic devices that can be used for a wide range of colorimetric assay applications. With these devices, assays can be performed within minutes to allow for quantitative colorimetric analysis by use of a widely accessible iPhone camera and an RGB color reader application

  1. Cost Effective Paper-Based Colorimetric Microfluidic Devices and Mobile Phone Camera Readers for the Classroom

    ERIC Educational Resources Information Center

    Koesdjojo, Myra T.; Pengpumkiat, Sumate; Wu, Yuanyuan; Boonloed, Anukul; Huynh, Daniel; Remcho, Thomas P.; Remcho, Vincent T.

    2015-01-01

    We have developed a simple and direct method to fabricate paper-based microfluidic devices that can be used for a wide range of colorimetric assay applications. With these devices, assays can be performed within minutes to allow for quantitative colorimetric analysis by use of a widely accessible iPhone camera and an RGB color reader application…

  2. Measurement of microbial activity in soil by colorimetric observation of in situ dye reduction: an approach to detection of extraterrestrial life

    PubMed Central

    Crawford, Ronald L; Paszczynski, Andrzej; Lang, Qingyong; Erwin, Daniel P; Allenbach, Lisa; Corti, Giancarlo; Anderson, Tony J; Cheng, I Francis; Wai, Chien; Barnes, Bruce; Wells, Richard; Assefi, Touraj; Mojarradi, Mohammad

    2002-01-01

    Background Detecting microbial life in extraterrestrial locations is a goal of space exploration because of ecological and health concerns about possible contamination of other planets with earthly organisms, and vice versa. Previously we suggested a method for life detection based on the fact that living entities require a continual input of energy accessed through coupled oxidations and reductions (an electron transport chain). We demonstrated using earthly soils that the identification of extracted components of electron transport chains is useful for remote detection of a chemical signature of life. The instrument package developed used supercritical carbon dioxide for soil extraction, followed by chromatography or electrophoresis to separate extracted compounds, with final detection by voltammetry and tandem mass-spectrometry. Results Here we used Earth-derived soils to develop a related life detection system based on direct observation of a biological redox signature. We measured the ability of soil microbial communities to reduce artificial electron acceptors. Living organisms in pure culture and those naturally found in soil were shown to reduce 2,3-dichlorophenol indophenol (DCIP) and the tetrazolium dye 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide inner salt (XTT). Uninoculated or sterilized controls did not reduce the dyes. A soil from Antarctica that was determined by chemical signature and DNA analysis to be sterile also did not reduce the dyes. Conclusion Observation of dye reduction, supplemented with extraction and identification of only a few specific signature redox-active biochemicals such as porphyrins or quinones, provides a simplified means to detect a signature of life in the soils of other planets or their moons. PMID:12150716

  3. Individual Colorimetric Observer Model

    PubMed Central

    Asano, Yuta; Fairchild, Mark D.; Blondé, Laurent

    2016-01-01

    This study proposes a vision model for individual colorimetric observers. The proposed model can be beneficial in many color-critical applications such as color grading and soft proofing to assess ranges of color matches instead of a single average match. We extended the CIE 2006 physiological observer by adding eight additional physiological parameters to model individual color-normal observers. These eight parameters control lens pigment density, macular pigment density, optical densities of L-, M-, and S-cone photopigments, and λmax shifts of L-, M-, and S-cone photopigments. By identifying the variability of each physiological parameter, the model can simulate color matching functions among color-normal populations using Monte Carlo simulation. The variabilities of the eight parameters were identified through two steps. In the first step, extensive reviews of past studies were performed for each of the eight physiological parameters. In the second step, the obtained variabilities were scaled to fit a color matching dataset. The model was validated using three different datasets: traditional color matching, applied color matching, and Rayleigh matches. PMID:26862905

  4. Directional detection of a neutron source

    SciTech Connect

    Vanier, P. E.; Forman, L.

    2006-07-01

    Advantages afforded by the development of new directional neutron detectors and imagers are discussed. Thermal neutrons have mean free paths in air of about 20 meters, and can be effectively imaged using coded apertures. Fission spectrum neutrons have ranges greater than 100 meters, and carry enough energy to scatter at least twice in multilayer detectors which can yield both directional and spectral information. Such strategies allow better discrimination between a localized spontaneous fission source and the low, but fluctuating, level of background neutrons generated by cosmic rays. A coded aperture thermal neutron imager will be discussed as well as a proton-recoil double-scatter fast-neutron directional detector with time-of-flight energy discrimination. (authors)

  5. DIRECTIONAL DETECTION OF A NEUTRON SOURCE.

    SciTech Connect

    VANIER, P.E.; FORMAN, L.

    2006-10-23

    Advantages afforded by the development of new directional neutron detectors and imagers are discussed. Thermal neutrons have mean free paths in air of about 20 meters, and can be effectively imaged using coded apertures. Fission spectrum neutrons have ranges greater than 100 meters, and carry enough energy to scatter at least twice in multilayer detectors which can yield both directional and spectral information. Such strategies allow better discrimination between a localized spontaneous fission source and the low, but fluctuating, level of background neutrons generated by cosmic rays. A coded aperture thermal neutron imager will be discussed as well as a proton-recoil double-scatter fast-neutron directional detector with time-of-flight energy discrimination.

  6. A colorimetric and smartphone readable method for uracil-DNA glycosylase detection based on the target-triggered formation of G-quadruplex.

    PubMed

    Nie, Huaijun; Wang, Wei; Li, Wang; Nie, Zhou; Yao, Shouzhuo

    2015-04-21

    A simple, visible and smartphone readable strategy for the sensitive detection of uracil-DNA glycosylase (UDG) activity has been developed. This is based on the UDG-catalyzed removal of uracil bases, which induces the formation of a G-quadruplex-cofactor complex. The guanine-rich DNA probe can form a special G-quadruplex structure with hemin to display peroxidase activity and catalyze the H2O2-mediated oxidation of ABTS(2-) to the colored ABTS?(-), providing a visible signal for UDG detection. The proposed sensing platform exhibits a good linear response to UDG concentrations ranging from 0.008 to 0.2 U mL(-1), with a low detection limit of 0.008 U mL(-1). Based on the theory of chromatics, we can directly read out the color value using a smartphone app to reflect the content of UDG with high resolution, providing a new vision for the portable assay strategy. Furthermore, the utility of this method for screening potential UDG inhibitors has also been demonstrated. PMID:25713817

  7. A sensitive colorimetric method for the determination of imipramine hydrochloride and desipramine hydrochloride.

    PubMed

    el-Yazbi, F A; Korany, M A; Bedair, M

    1985-12-01

    A simple and rapid colorimetric method for the determination of imipramine hydrochloride and desipramine hydrochloride in their tablet formulations and in biological fluids is presented. The method is based on the reaction of these drugs with 3-methyl-2-benzothiazolone hydrazone in the presence of ferric chloride, with direct measurement at 635 nm. Cyclohexane was used to extract these drugs from serum and urine, at basic pH, by a single manual extraction. The method can detect 0.5 microgram/ml of each drug. The main advantages of this method are its simplicity and high sensitivity. PMID:4093508

  8. Colorimetric disposable paper coated with ZnO@ZnS core-shell nanoparticles for detection of copper ions in aqueous solutions.

    PubMed

    Sadollahkhani, Azar; Hatamie, Amir; Nur, Omer; Willander, Magnus; Zargar, Behrooz; Kazeminezhad, Iraj

    2014-10-22

    In this study, we have proposed a new nanoparticle-containing test paper sensor that could be used as an inexpensive, easy-to-use, portable, and highly selective sensor to detect Cu(2+) ions in aqueous solutions. This disposable paper sensor is based on ZnO@ZnS core-shell nanoparticles. The core-shell nanoparticles were synthesized using a chemical method and then they were used for coating the paper. The synthesis of the ZnO@ZnS core-shell nanoparticles was performed at a temperature as low as 60 °C, and so far this is the lowest temperature for the synthesis of such core-shell nanoparticles. The sensitivity of the paper sensor was investigated for different Cu(2+) ion concentrations in aqueous solutions and the results show a direct linear relation between the Cu(2+) ions concentration and the color intensity of the paper sensor with a visual detection limit as low as 15 μM (∼0.96 ppm). Testing the present paper sensor on real river turbulent water shows a maximum 5% relative error for determining the Cu(2+) ions concentration, which confirms that the presented paper sensor can successfully be used efficiently for detection in complex solutions with high selectivity. Photographs of the paper sensor taken using a regular digital camera were transferred to a computer and analyzed by ImageJ Photoshop software. This finding demonstrates the potential of the present disposable paper sensor for the development of a portable, accurate, and selective heavy metal detection technology. PMID:25275616

  9. Indirect detection of radiation sources through direct detection of radiolysis products

    DOEpatents

    Farmer, Joseph C. (Tracy, CA); Fischer, Larry E. (Los Gatos, CA); Felter, Thomas E. (Livermore, CA)

    2010-04-20

    A system for indirectly detecting a radiation source by directly detecting radiolytic products. The radiation source emits radiation and the radiation produces the radiolytic products. A fluid is positioned to receive the radiation from the radiation source. When the fluid is irradiated, radiolytic products are produced. By directly detecting the radiolytic products, the radiation source is detected.

  10. Direct WIMP detection with cryogenic detectors.

    PubMed

    Kraus, Hans

    2003-11-15

    Cryogenic detectors have been developed since the mid 1980s and have been applied successfully to dark-matter searches since the mid 1990s. Among the advantages of cryogenic detectors are their high sensitivity to nuclear recoil, their low detection thresholds, the wide choice of target materials and the possibility of implementing event type recognition on an event-by-event basis. I explain the basics of cryogenic detectors, review various implementations, discuss advantages and drawbacks and give an overview of current dark-matter-search experiments based upon cryogenic detectors. PMID:14667319

  11. A direct detection of Escherichia coli genomic DNA using gold nanoprobes

    PubMed Central

    2012-01-01

    Background In situation like diagnosis of clinical and forensic samples there exists a need for highly sensitive, rapid and specific DNA detection methods. Though conventional DNA amplification using PCR can provide fast results, it is not widely practised in diagnostic laboratories partially because it requires skilled personnel and expensive equipment. To overcome these limitations nanoparticles have been explored as signalling probes for ultrasensitive DNA detection that can be used in field applications. Among the nanomaterials, gold nanoparticles (AuNPs) have been extensively used mainly because of its optical property and ability to get functionalized with a variety of biomolecules. Results We report a protocol for the use of gold nanoparticles functionalized with single stranded oligonucleotide (AuNP- oligo probe) as visual detection probes for rapid and specific detection of Escherichia coli. The AuNP- oligo probe on hybridization with target DNA containing complementary sequences remains red whereas test samples without complementary DNA sequences to the probe turns purple due to acid induced aggregation of AuNP- oligo probes. The color change of the solution is observed visually by naked eye demonstrating direct and rapid detection of the pathogenic Escherichia coli from its genomic DNA without the need for PCR amplification. The limit of detection was ~54 ng for unamplified genomic DNA. The method requires less than 30 minutes to complete after genomic DNA extraction. However, by using unamplified enzymatic digested genomic DNA, the detection limit of 11.4 ng was attained. Results of UV-Vis spectroscopic measurement and AFM imaging further support the hypothesis of aggregation based visual discrimination. To elucidate its utility in medical diagnostic, the assay was validated on clinical strains of pathogenic Escherichia coli obtained from local hospitals and spiked urine samples. It was found to be 100% sensitive and proves to be highly specific without any cross reaction with non-Escherichia coli strains. Conclusion This work gives entry into a new class of DNA/gold nanoparticles hybrid materials which might have optical property that can be controlled for application in diagnostics. We note that it should be possible to extend this strategy easily for developing new types of DNA biosensor for point of care detection. The salient feature of this approach includes low-cost, robust reagents and simple colorimetric detection of pathogen. PMID:22309695

  12. Colorimetric biosensing of pathogens using gold nanoparticles.

    PubMed

    Verma, Mohit S; Rogowski, Jacob L; Jones, Lyndon; Gu, Frank X

    2015-11-01

    Rapid detection of pathogens is crucial to minimize adverse health impacts of nosocomial, foodborne, and waterborne diseases. Gold nanoparticles are extremely successful at detecting pathogens due to their ability to provide a simple and rapid color change when their environment is altered. Here, we review general strategies of implementing gold nanoparticles in colorimetric biosensors. First, we highlight how gold nanoparticles have improved conventional genomic analysis methods by lowering detection limits while reducing assay times. Then, we focus on emerging point-of-care technologies that aim at pathogen detection using simpler assays. These advances will facilitate the implementation of gold nanoparticle-based biosensors in diverse environments throughout the world and help prevent the spread of infectious diseases. PMID:25792228

  13. Direct detection optical relay satellite for deep-space communication

    NASA Astrophysics Data System (ADS)

    Mecherle, G. Stephen; Akle, Wade; Starkus, Charles J.; Klein, James E.

    1994-08-01

    This paper describes an earth orbiting Deep Space Relay Satellite System (DSRSS) based on optical direct detection communication for the user spacecraft to DSRS link. The optical direct detection DSRSS is considered as a possible augmentation to the Deep Space Network (DSN), after the 70 meter antennas are upgraded to Ka Band near the turn of the century. While development is required, the extrapolation from current technology appears relatively straightforward, and the direct detection system appears capable of exceeding an order of magnitude improvement over the upgraded Ka Band DSN. For example, with a 75 cm aperture on the user spacecraft, the optical direct detection system provides a capability of 1.23 Mbps at Pluto, a 13 dB advantage over the upgraded DSN. The direct detection system can also provide 0.83 Mbps with a 60 cm user aperture, an 11 dB improvement.

  14. Colorimetric barbiturate sensing with hybrid spin crossover assemblies.

    PubMed

    Young, Michael C; Liew, Erica; Hooley, Richard J

    2014-05-21

    Spin crossover complexes based on either iron(II) or iron(III) give a colorimetric response upon self-assembly with barbituric acids. They can be used as visible sensors for these narcotics, selectively detecting barbiturates in the presence of other biologically-relevant hydrogen bonding species. PMID:24715100

  15. Ink-jet printed colorimetric gas sensors on plastic foil

    NASA Astrophysics Data System (ADS)

    Courbat, Jerome; Briand, Danick; de Rooij, Nico F.

    2010-08-01

    An all polymeric colorimetric gas sensor with its associated electronics for ammonia (NH3) detection targeting low-cost and low-power applications is presented. The gas sensitive layer was inkjet printed on a plastic foil. The use of the foil directly as optical waveguide simplified the fabrication, made the device more cost effective and compatible with large scale fabrication techniques, such as roll to roll processes. Concentrations of 500 ppb of NH3 in nitrogen with 50% of RH were measured with a power consumption of about 868 ?W in an optical pulsed mode of operation. Such sensors foresee applications in the field of wireless systems, for environmental and safety monitoring. The fabrication of the planar sensor was based on low temperature processing. The waveguide was made of PEN or PET foil and covered with an ammonia sensitive layer deposited by inkjet printing, which offered a proper and localized deposition of the film. The influence of the substrate temperature and its surface pretreatment were investigated to achieve the optimum deposition parameters for the printed fluid. To improve the light coupling from the light source (LED) to the detectors (photodiodes), polymeric micro-mirrors were patterned in an epoxy resin. With the printing of the colorimetric film and additive patterning of polymeric micro-mirrors on plastic foil, a major step was achieved towards the implementation of full plastic selective gas sensors. The combination with printed OLED and PPD would further lead to an integrated all polymeric optical transducer on plastic foil fully compatible with printed electronics processes.

  16. Magnetic colorimetric immunoassay for human interleukin-6 based on the oxidase activity of ceria spheres.

    PubMed

    Peng, Juan; Guan, Jufang; Yao, Huiqin; Jin, Xiaoyong

    2016-01-01

    A novel magnetic colorimetric immunoassay strategy was designed for sensitive detection of human interleukin-6 (IL-6) using ceria spheres as labels. Ceria spheres showed excellent oxidase activity, which can directly catalyze the oxidation of substrate o-phenylenediamine (OPD) to a stable yellow product, 2,3-diaminophenazine (oxOPD). The absorbance of oxOPD was recorded to reflect the level of IL-6. The relatively mild conditions made the immunoassay strategy more robust, reliable, and easy. A linear relationship between absorbance intensity and the logarithm of IL-6 concentrations was obtained in the range of 0.0001-10ngmL(-1) with a detection limit of 0.04pgmL(-1) (S/N=3). The colorimetric immunoassay exhibited high sensitivity and specificity for the detection of IL-6. This immunoassay has been successfully applied in the detection of IL-6 in serum samples and can be readily extended toward the on-site monitoring of cancer biomarkers in serum samples. PMID:26416691

  17. A smartphone-based colorimetric reader for bioanalytical applications using the screen-based bottom illumination provided by gadgets.

    PubMed

    Vashist, Sandeep Kumar; van Oordt, Thomas; Schneider, E Marion; Zengerle, Roland; von Stetten, Felix; Luong, John H T

    2015-05-15

    A smartphone-based colorimetric reader (SBCR) was developed using a Samsung Galaxy SIII mini, a gadget (iPAD mini, iPAD4 or iPhone 5s), integrated with a custom-made dark hood and base holder assembly. The smartphone equipped with a back camera (5 megapixels resolution) was used for colorimetric imaging via the hood and base-holder assembly. A 96- or 24-well microtiter plate (MTP) was positioned on the gadget's screensaver that provides white light-based bottom illumination only in the specific regions corresponding to the bottom of MTP's wells. The pixel intensity of the captured images was determined by an image processing algorithm. The developed SBCR was evaluated and compared with a commercial MTP reader (MTPR) for three model assays: our recently developed human C-reactive protein sandwich enzyme-linked immunosorbent assay (ELISA), horseradish peroxidase direct ELISA, and bicinchoninic acid protein estimation assay. SBCR had the same precision, dynamic range, detection limit and sensitivity as MTPR for all three assays. With advanced microfabrication and data processing, SBCR will become more compact, lighter, inexpensive and enriched with more features. Therefore, SBCR with a remarkable computing power could be an ideal point-of-care (POC) colorimetric detection device for the next-generation of cost-effective POC diagnostics, immunoassays and diversified bioanalytical applications. PMID:25168283

  18. Simultaneous direct detection of Shiga-toxin producing Escherichia coli (STEC) strains by optical biosensing with oligonucleotide-functionalized gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Quintela, Irwin A.; de Los Reyes, Benildo G.; Lin, Chih-Sheng; Wu, Vivian C. H.

    2015-01-01

    A simultaneous direct detection of Shiga-toxin producing strains of E. coli (STEC; ``Big Six'' - O26, O45, O103, O111, O121, and O145) as well as O157 strains by optical biosensing with oligonucleotide-functionalized gold nanoparticles (AuNPs) was developed. Initially, conserved regions of stx genes were amplified by asymmetric polymerase chain reaction (asPCR). Pairs of single stranded thiol-modified oligonucleotides (30-mer) were immobilized onto AuNPs and used as probes to capture regions of stx1 (119-bp) and/or stx2 (104-bp) genes from STEC strains. DNA samples from pure cultures and food samples were sandwich hybridized with AuNP-oligo probes at optimal conditions (50 °C, 30 min). A complex was formed from the hybridization of AuNP-probes and target DNA fragments that retained the initial red color of the reaction solutions. For non-target DNA, a color change from red to purplish-blue was observed following an increase in salt concentration, thus providing the basis of simultaneous direct colorimetric detection of target DNA in the samples. Enrichment and pooling systems were incorporated to efficiently process a large number of food samples (ground beef and blueberries) and detection of live targets. The detection limit was <1 log CFU g-1, requiring less than 1 h to complete after DNA sample preparation with 100% specificity. Gel electrophoresis verified AuNP-DNA hybridization while spectrophotometric data and transmission electron microscope (TEM) images supported color discrimination based on the occurrence of molecular aggregation. In conclusion, the significant features of this approach took advantage of the unique colorimetric properties of AuNPs as a low-cost and simple approach yet with high specificity for simultaneous detection of STEC strains.A simultaneous direct detection of Shiga-toxin producing strains of E. coli (STEC; ``Big Six'' - O26, O45, O103, O111, O121, and O145) as well as O157 strains by optical biosensing with oligonucleotide-functionalized gold nanoparticles (AuNPs) was developed. Initially, conserved regions of stx genes were amplified by asymmetric polymerase chain reaction (asPCR). Pairs of single stranded thiol-modified oligonucleotides (30-mer) were immobilized onto AuNPs and used as probes to capture regions of stx1 (119-bp) and/or stx2 (104-bp) genes from STEC strains. DNA samples from pure cultures and food samples were sandwich hybridized with AuNP-oligo probes at optimal conditions (50 °C, 30 min). A complex was formed from the hybridization of AuNP-probes and target DNA fragments that retained the initial red color of the reaction solutions. For non-target DNA, a color change from red to purplish-blue was observed following an increase in salt concentration, thus providing the basis of simultaneous direct colorimetric detection of target DNA in the samples. Enrichment and pooling systems were incorporated to efficiently process a large number of food samples (ground beef and blueberries) and detection of live targets. The detection limit was <1 log CFU g-1, requiring less than 1 h to complete after DNA sample preparation with 100% specificity. Gel electrophoresis verified AuNP-DNA hybridization while spectrophotometric data and transmission electron microscope (TEM) images supported color discrimination based on the occurrence of molecular aggregation. In conclusion, the significant features of this approach took advantage of the unique colorimetric properties of AuNPs as a low-cost and simple approach yet with high specificity for simultaneous detection of STEC strains. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05869k

  19. Photonic crystal structures with tunable structure color as colorimetric sensors.

    PubMed

    Wang, Hui; Zhang, Ke-Qin

    2013-01-01

    Colorimetric sensing, which transduces environmental changes into visible color changes, provides a simple yet powerful detection mechanism that is well-suited to the development of low-cost and low-power sensors. A new approach in colorimetric sensing exploits the structural color of photonic crystals (PCs) to create environmentally-influenced color-changeable materials. PCs are composed of periodic dielectrics or metallo-dielectric nanostructures that affect the propagation of electromagnetic waves (EM) by defining the allowed and forbidden photonic bands. Simultaneously, an amazing variety of naturally occurring biological systems exhibit iridescent color due to the presence of PC structures throughout multi-dimensional space. In particular, some kinds of the structural colors in living organisms can be reversibly changed in reaction to external stimuli. Based on the lessons learned from natural photonic structures, some specific examples of PCs-based colorimetric sensors are presented in detail to demonstrate their unprecedented potential in practical applications, such as the detections of temperature, pH, ionic species, solvents, vapor, humidity, pressure and biomolecules. The combination of the nanofabrication technique, useful design methodologies inspired by biological systems and colorimetric sensing will lead to substantial developments in low-cost, miniaturized and widely deployable optical sensors. PMID:23539027

  20. Photonic Crystal Structures with Tunable Structure Color as Colorimetric Sensors

    PubMed Central

    Wang, Hui; Zhang, Ke-Qin

    2013-01-01

    Colorimetric sensing, which transduces environmental changes into visible color changes, provides a simple yet powerful detection mechanism that is well-suited to the development of low-cost and low-power sensors. A new approach in colorimetric sensing exploits the structural color of photonic crystals (PCs) to create environmentally-influenced color-changeable materials. PCs are composed of periodic dielectrics or metallo-dielectric nanostructures that affect the propagation of electromagnetic waves (EM) by defining the allowed and forbidden photonic bands. Simultaneously, an amazing variety of naturally occurring biological systems exhibit iridescent color due to the presence of PC structures throughout multi-dimensional space. In particular, some kinds of the structural colors in living organisms can be reversibly changed in reaction to external stimuli. Based on the lessons learned from natural photonic structures, some specific examples of PCs-based colorimetric sensors are presented in detail to demonstrate their unprecedented potential in practical applications, such as the detections of temperature, pH, ionic species, solvents, vapor, humidity, pressure and biomolecules. The combination of the nanofabrication technique, useful design methodologies inspired by biological systems and colorimetric sensing will lead to substantial developments in low-cost, miniaturized and widely deployable optical sensors. PMID:23539027

  1. Simultaneous direct detection of Shiga-toxin producing Escherichia coli (STEC) strains by optical biosensing with oligonucleotide-functionalized gold nanoparticles.

    PubMed

    Quintela, Irwin A; de los Reyes, Benildo G; Lin, Chih-Sheng; Wu, Vivian C H

    2015-02-14

    A simultaneous direct detection of Shiga-toxin producing strains of E. coli (STEC; "Big Six" - O26, O45, O103, O111, O121, and O145) as well as O157 strains by optical biosensing with oligonucleotide-functionalized gold nanoparticles (AuNPs) was developed. Initially, conserved regions of stx genes were amplified by asymmetric polymerase chain reaction (asPCR). Pairs of single stranded thiol-modified oligonucleotides (30-mer) were immobilized onto AuNPs and used as probes to capture regions of stx1 (119-bp) and/or stx2 (104-bp) genes from STEC strains. DNA samples from pure cultures and food samples were sandwich hybridized with AuNP-oligo probes at optimal conditions (50 °C, 30 min). A complex was formed from the hybridization of AuNP-probes and target DNA fragments that retained the initial red color of the reaction solutions. For non-target DNA, a color change from red to purplish-blue was observed following an increase in salt concentration, thus providing the basis of simultaneous direct colorimetric detection of target DNA in the samples. Enrichment and pooling systems were incorporated to efficiently process a large number of food samples (ground beef and blueberries) and detection of live targets. The detection limit was <1 log CFU g(-1), requiring less than 1 h to complete after DNA sample preparation with 100% specificity. Gel electrophoresis verified AuNP-DNA hybridization while spectrophotometric data and transmission electron microscope (TEM) images supported color discrimination based on the occurrence of molecular aggregation. In conclusion, the significant features of this approach took advantage of the unique colorimetric properties of AuNPs as a low-cost and simple approach yet with high specificity for simultaneous detection of STEC strains. PMID:25563863

  2. Simple and specific colorimetric detection of Staphylococcus using its volatile 2-[3-acetoxy-4,4,14-trimethylandrost-8-en-17-yl] propanoic acid in the liquid phase and head space of cultures.

    PubMed

    Saranya, Raju; Aarthi, Raju; Sankaran, Krishnan

    2015-05-01

    Spread of drug-resistant Staphylococcus spp. into communities pose danger demanding effective non-invasive and non-destructive tools for its early detection and surveillance. Characteristic volatile organic compounds (VOCs) produced by bacteria offer new diagnostic targets and novel approaches not exploited so far in infectious disease diagnostics. Our search for such characteristic VOC for Staphylococcus spp. led to the depiction of 2-[3-acetoxy-4,4,14-trimethylandrost-8-en-17-yl] propanoic acid (ATMAP), a moderately volatile compound detected both in the culture and headspace when the organism was grown in tryptone soya broth (TSB) medium. A simple and inexpensive colorimetric method (colour change from yellow to orange) using methyl red as the pH indicator provided an absolutely specific way for identifying Staphylococcus spp., The assay performed in liquid cultures (7-h growth in TSB) as well as in the headspace of plate cultures (grown for 10 h on TSA) was optimised in a 96-well plate and 12-well plate formats, respectively, employing a set of positive and negative strains. Only Staphylococcus spp. showed the distinct colour change from yellow to orange due to the production of the above VOC while in the case of other organisms, the reagent remained yellow. The method validated using known clinical and environmental strains (56 including Staphylococcus, Proteus, Pseudomonas, Klebsiella, Bacillus, Shigella and Escherichia coli) was found to be highly efficient showing 100% specificity and sensitivity. Such simple methods of bacterial pathogen identification are expected to form the next generation tools for the control of infectious diseases through early detection and surveillance of causative agents. PMID:25900191

  3. An integrated direct loop-mediated isothermal amplification microdevice incorporated with an immunochromatographic strip for bacteria detection in human whole blood and milk without a sample preparation step.

    PubMed

    Lee, Dohwan; Kim, Yong Tae; Lee, Jee Won; Kim, Do Hyun; Seo, Tae Seok

    2016-05-15

    We have developed an integrated direct loop-mediated isothermal amplification (Direct LAMP) microdevice incorporated with an immunochromatographic strip (ICS) to identify bacteria contaminated in real samples. The Direct LAMP is a novel isothermal DNA amplification technique which does not require thermal cycling steps as well as any sample preparation steps such as cell lysis and DNA extraction for amplifying specific target genes. In addition, the resultant amplicons were colorimetrically detected on the ICS, thereby enabling the entire genetic analysis process to be simplified. The two functional units (Direct LAMP and ICS) were integrated on a single device without use of the tedious and complicated microvalve and tubing systems. The utilization of a slidable plate allows us to manipulate the fluidic control in the microchannels manually and the sequential operation of the Direct LAMP and ICS detection could be performed by switching the slidable plate to each functional unit. Thus, the combination of the direct isothermal amplification without any sample preparation and thermal cycling steps, the ICS based amplicon detection by naked eyes, and the slidable plate to eliminate the microvalves in the integrated microdevice would be an ideal platform for point-of-care DNA diaganotics. On the integrated Direct LAMP-ICS microdevice, we could analyze Staphylococcus aureus (S. aureus) and Escherichia coli O157:H7 (E. coli O157:H7) contaminated in human whole blood or milk at a single-cell level within 1h. PMID:26710344

  4. Comparing readout strategies to directly detect dark matter

    NASA Astrophysics Data System (ADS)

    Billard, J.

    2015-01-01

    Over the past decades, several ideas and technologies have been developed to directly detect weakly interacting massive particles (WIMP) from the galactic halo. All these detection strategies share the common goal of discriminating a WIMP signal from the residual backgrounds. By directly detecting WIMPs, one can measure some or all of the observables associated to each nuclear recoil candidates, such as their energy and direction. In this study, we compare and examine the discovery potentials of each readout strategies from counting only (bubble chambers) to directional detectors (Time Projection Chambers) with 1d-, 2d-, and 3d-sensitivity. Using a profile likelihood analysis, we show that, in the case of a large and irreducible background contamination characterized by an energy distribution similar to the expected WIMP signal, directional information can improve the sensitivity of the experiment by several orders of magnitude. We also found that 1d directional detection is only less effective than a full 3d directional sensitivity by about a factor of 3, or 10 if we assume no sense recognition, still improving by a factor of 2 or more if only the energy of the events is being measured.

  5. Colorimetric determination of melamine in milk using unmodified silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Kumar, Naveen; Kumar, Harish; Mann, Bimlesh; Seth, Raman

    2016-03-01

    Melamine is nitrogen rich chemical compound used as an adulterant in dairy products by unscrupulous people to increase the apparent protein content. This incident prompted the researchers to develop simple methods for easy detection of melamine in food samples. In the present paper, we report a simple and sensitive colorimetric method for detection of melamine in milk based on silver nanoparticles. This method relies upon the principle that melamine causes the aggregation of silver nanoparticles, resulting in abrupt color change from yellow to red under optimized conditions. The concentration of melamine in adulterated sample can be quantitated by monitoring the absorption spectra of silver nanoparticles using ultraviolet-visible (UV-Vis) spectrometer. The present colorimetric method which utilizes silver nanoparticles of 35 nm can reliably detect melamine down to a concentration of 0.04 mg l- 1.

  6. Colorimetric determination of melamine in milk using unmodified silver nanoparticles.

    PubMed

    Kumar, Naveen; Kumar, Harish; Mann, Bimlesh; Seth, Raman

    2016-03-01

    Melamine is nitrogen rich chemical compound used as an adulterant in dairy products by unscrupulous people to increase the apparent protein content. This incident prompted the researchers to develop simple methods for easy detection of melamine in food samples. In the present paper, we report a simple and sensitive colorimetric method for detection of melamine in milk based on silver nanoparticles. This method relies upon the principle that melamine causes the aggregation of silver nanoparticles, resulting in abrupt color change from yellow to red under optimized conditions. The concentration of melamine in adulterated sample can be quantitated by monitoring the absorption spectra of silver nanoparticles using ultraviolet-visible (UV-Vis) spectrometer. The present colorimetric method which utilizes silver nanoparticles of 35nm can reliably detect melamine down to a concentration of 0.04mgl(-1). PMID:26654965

  7. Colorimetric characterization of LED luminaires

    NASA Astrophysics Data System (ADS)

    Costa, C. L. M.; Vieira, R. R.; Pereira, R. C.; Silva, P. V. M.; Oliveira, I. A. A.; Sardinha, A. S.; Viana, D. D.; Barbosa, A. H.; Souza, L. P.; Alvarenga, A. D.

    2015-01-01

    The Optical Metrology Division of Inmetro - National Institute of Metrology, Quality and Technology has recently started the colorimetric characterization of lamps by implementing Correlated Color Temperature (CCT) and Color Rendering Index (CRI) measurements of incandescent lamps, followed by the CFL, and LED lamps and luminaires. Here we present the results for the verification of the color characterization of samples of SSL luminaires for public as well as indoor illumination that are sold in Brazil.

  8. Ratiometric and colorimetric near-infrared sensors for multi-channel detection of cyanide ion and their application to measure β-glucosidase.

    PubMed

    Xing, Panfei; Xu, Yongqian; Li, Hongjuan; Liu, Shuhui; Lu, Aiping; Sun, Shiguo

    2015-01-01

    A near-infrared sensor for cyanide ion (CN(-)) was developed via internal charge transfer (ICT). This sensor can selectively detect CN(-) either through dual-ratiometric fluorescence (logarithm of I414/I564 and I803/I564) or under various absorption (356 and 440 nm) and emission (414, 564 and 803 nm) channels. Especially, the proposed method can be employed to measure β-glucosidase by detecting CN(-) traces in commercial amygdalin samples. PMID:26549546

  9. Ratiometric and colorimetric near-infrared sensors for multi-channel detection of cyanide ion and their application to measure β-glucosidase

    PubMed Central

    Xing, Panfei; Xu, Yongqian; Li, Hongjuan; Liu, Shuhui; Lu, Aiping; Sun, Shiguo

    2015-01-01

    A near-infrared sensor for cyanide ion (CN−) was developed via internal charge transfer (ICT). This sensor can selectively detect CN− either through dual-ratiometric fluorescence (logarithm of I414/I564 and I803/I564) or under various absorption (356 and 440 nm) and emission (414, 564 and 803 nm) channels. Especially, the proposed method can be employed to measure β-glucosidase by detecting CN− traces in commercial amygdalin samples. PMID:26549546

  10. Ratiometric and colorimetric near-infrared sensors for multi-channel detection of cyanide ion and their application to measure β-glucosidase

    NASA Astrophysics Data System (ADS)

    Xing, Panfei; Xu, Yongqian; Li, Hongjuan; Liu, Shuhui; Lu, Aiping; Sun, Shiguo

    2015-11-01

    A near-infrared sensor for cyanide ion (CN‑) was developed via internal charge transfer (ICT). This sensor can selectively detect CN‑ either through dual-ratiometric fluorescence (logarithm of I414/I564 and I803/I564) or under various absorption (356 and 440 nm) and emission (414, 564 and 803 nm) channels. Especially, the proposed method can be employed to measure β-glucosidase by detecting CN‑ traces in commercial amygdalin samples.

  11. Directional detection as a strategy to discover Galactic Dark Matter

    NASA Astrophysics Data System (ADS)

    Billard, J.; Mayet, F.; Macas-Prez, J. F.; Santos, D.

    2010-07-01

    Directional detection of Galactic Dark Matter is a promising search strategy for discriminating WIMP events from background. Technical progress on gaseous detectors and read-outs has permitted the design and construction of competitive experiments. However, to take full advantage of this powerful detection method, one need to be able to extract information from an observed recoil map to identify a WIMP signal. We present a comprehensive formalism, using a map-based likelihood method allowing to recover the main incoming direction of the signal and its significance, thus proving its Galactic origin. This is a blind analysis intended to be used on any directional data. Constraints are deduced in the (?,m) plane and systematic studies are presented in order to show that, using this analysis tool, unambiguous Dark Matter detection can be achieved on a large range of exposures and background levels.

  12. Global limits and interference patterns in dark matter direct detection

    SciTech Connect

    Catena, Riccardo; Gondolo, Paolo

    2015-08-13

    We compare the general effective theory of one-body dark matter nucleon interactions to current direct detection experiments in a global multidimensional statistical analysis. We derive exclusion limits on the 28 isoscalar and isovector coupling constants of the theory, and show that current data place interesting constraints on dark matter-nucleon interaction operators usually neglected in this context. We characterize the interference patterns that can arise in dark matter direct detection from pairs of dark matter-nucleon interaction operators, or from isoscalar and isovector components of the same operator. We find that commonly neglected destructive interference effects weaken standard direct detection exclusion limits by up to one order of magnitude in the coupling constants.

  13. Can the Existence of Dark Energy be Directly Detected?

    SciTech Connect

    Perl, Martin L.; /SLAC /KIPAC, Menlo Park

    2011-11-23

    The majority of astronomers and physicists accept the reality of dark energy and also believe that it can only be studied indirectly through observation of the motions of stars and galaxies. In this paper I open the experimental question of whether it is possible to directly detect dark energy through the presence of dark energy density. Two thirds of this paper outlines the major aspects of dark energy density as now comprehended by the astronomical and physics community. The final third summarizes various proposals for direct detection of dark energy density or its possible effects. At this time I do not have a fruitful answer to the question: Can the Existence of Dark Energy Be Directly Detected?

  14. Closing supersymmetric resonance regions with direct detection experiments

    SciTech Connect

    Kelso, Chris

    2014-01-01

    One of the few remaining ways that neutralinos could potentially evade constraints from direct detection experiments is if they annihilate through a resonance, as can occur if 2m{sub ??} falls within about ~10% of either m{sub A/H}, m{sub h}, or m{sub Z}. Assuming a future rate of progress among direct detection experiments that is similar to that obtained over the past decade, we project that within 7 years the light Higgs and Z pole regions will be entirely closed, while the remaining parameter space near the A/H resonance will require that 2m{sub ??} be matched to the central value (near m{sub A}) to within less than 4%. At this rate of progress, it will be a little over a decade before multi-ton direct detection experiments will be able to close the remaining, highly-tuned, regions of the A/H resonance parameter space.

  15. Direct detection of classically undetectable dark matter through quantum decoherence

    NASA Astrophysics Data System (ADS)

    Riedel, C. Jess

    2013-12-01

    Although various pieces of indirect evidence about the nature of dark matter have been collected, its direct detection has eluded experimental searches despite extensive effort. If the mass of dark matter is below 1 MeV, it is essentially imperceptible to conventional detection methods because negligible energy is transferred to nuclei during collisions. Here I propose directly detecting dark matter through the quantum decoherence it causes rather than its classical effects, such as recoil or ionization. I show that quantum spatial superpositions are sensitive to low-mass dark matter that is inaccessible to classical techniques. This provides new independent motivation for matter interferometry with large masses, especially on spaceborne platforms. The apparent dark matter wind we experience as the Sun travels through the Milky Way ensures interferometers and related devices are directional detectors, and so are able to provide unmistakable evidence that decoherence has Galactic origins.

  16. Plasmonic Enzyme-Linked Immunosorbent Assay Using Nanospherical Brushes as a Catalase Container for Colorimetric Detection of Ultralow Concentrations of Listeria monocytogenes.

    PubMed

    Chen, Rui; Huang, Xiaolin; Xu, Hengyi; Xiong, Yonghua; Li, Yanbin

    2015-12-30

    Plasmonic enzyme-linked immunosorbent assay (pELISA) based on catalase (CAT)-mediated gold nanoparticle growth exhibits ultrahigh sensitivity for detecting disease-related biomarkers using sandwich formats. However, the limit of detection (LOD) of this strategy for Listeria monocytogenes is only around 10(3) CFU/mL, which considerably exceeds the amount of L. monocytogenes commonly present in food products (<100 CFU/g). Herein, we report an improved pELISA method for detection of L. monocytogenes at ultralow concentrations with the sandwich formats using silica nanoparticles carrying poly(acrylic acid) brushes as a "CAT container" to increase enzyme loading for enhancing the detection signal. Under optimal conditions, the proposed pELISA exhibits good specificity and excellent sensitivity for L. monocytogenes with a LOD of 8 10(1) CFU/mL in 0.01 M phosphate-buffered saline, via a reaction that can be discriminated by the naked eye. The LOD obtained by this method was 2 and 5 orders of magnitude lower than that of conventional CAT-based pELISA and horseradish peroxidase (HRP)-based conventional ELISA, respectively. Coupled with large-volume immunomagnetic separation, the LOD for L. monocytogenes-spiked lettuce samples reached 8 10(1) CFU/g. The improved pELISA also exhibited a great potential in detecting a single cell of L. monocytogenes in 100 ?L of solution. PMID:26646325

  17. Direct detection of PCR products for HLA class II typing.

    PubMed

    Chia, D; Terasaki, P; Chan, H; Tonai, R; Siauw, P A

    1993-09-01

    Direct detection of the PCR, or DD-PCR is proposed as an efficient method for performing PCR assays. Following the PCR reaction, ethidium homodimer dye is added to the reaction mixture and read by fluorescence. The dye step circumvents the necessity of running reactions on agarose gel electrophoresis, which is the current standard. This simple modification should find wide application for assays utilizing the PCR reaction. Here we show the ready detection of HLA class II polymorphism. PMID:8284789

  18. Field-stepped direct detection electron paramagnetic resonance

    NASA Astrophysics Data System (ADS)

    Yu, Zhelin; Liu, Tengzhi; Elajaili, Hanan; Rinard, George A.; Eaton, Sandra S.; Eaton, Gareth R.

    2015-09-01

    The widest scan that had been demonstrated previously for rapid scan EPR was a 155 G sinusoidal scan. As the scan width increases, the voltage requirement across the resonating capacitor and scan coils increases dramatically and the background signal induced by the rapidly changing field increases. An alternate approach is needed to achieve wider scans. A field-stepped direct detection EPR method that is based on rapid-scan technology is now reported, and scan widths up to 6200 G have been demonstrated. A linear scan frequency of 5.12 kHz was generated with the scan driver described previously. The field was stepped at intervals of 0.01 to 1 G, depending on the linewidths in the spectra. At each field data for triangular scans with widths up to 11.5 G were acquired. Data from the triangular scans were combined by matching DC offsets for overlapping regions of successive scans. This approach has the following advantages relative to CW, several of which are similar to the advantages of rapid scan. (i) In CW if the modulation amplitude is too large, the signal is broadened. In direct detection field modulation is not used. (ii) In CW the small modulation amplitude detects only a small fraction of the signal amplitude. In direct detection each scan detects a larger fraction of the signal, which improves the signal-to-noise ratio. (iii) If the scan rate is fast enough to cause rapid scan oscillations, the slow scan spectrum can be recovered by deconvolution after the combination of segments. (iv) The data are acquired with quadrature detection, which permits phase correction in the post processing. (v) In the direct detection method the signal typically is oversampled in the field direction. The number of points to be averaged, thereby improving the signal-to-noise ratio, is determined in post processing based on the desired field resolution. A degased lithium phthalocyanine sample was used to demonstrate that the linear deconvolution procedure can be employed with field-stepped direct detection EPR signals. Field-stepped direct detection EPR spectra were obtained for Cu2+ doped in Ni(diethyldithiocarbamate)2, Cu2+ doped in Zn tetratolylporphyrin, perdeuterated tempone in sucrose octaacetate, vanadyl ion doped in a parasubstituted Zn tetratolylporphyrin, Mn2+ impurity in CaO, and an oriented crystal of Mn2+ doped in Mg(acetylacetonate)2(H2O)2.

  19. Field-stepped direct detection electron paramagnetic resonance.

    PubMed

    Yu, Zhelin; Liu, Tengzhi; Elajaili, Hanan; Rinard, George A; Eaton, Sandra S; Eaton, Gareth R

    2015-09-01

    The widest scan that had been demonstrated previously for rapid scan EPR was a 155G sinusoidal scan. As the scan width increases, the voltage requirement across the resonating capacitor and scan coils increases dramatically and the background signal induced by the rapidly changing field increases. An alternate approach is needed to achieve wider scans. A field-stepped direct detection EPR method that is based on rapid-scan technology is now reported, and scan widths up to 6200G have been demonstrated. A linear scan frequency of 5.12kHz was generated with the scan driver described previously. The field was stepped at intervals of 0.01 to 1G, depending on the linewidths in the spectra. At each field data for triangular scans with widths up to 11.5G were acquired. Data from the triangular scans were combined by matching DC offsets for overlapping regions of successive scans. This approach has the following advantages relative to CW, several of which are similar to the advantages of rapid scan. (i) In CW if the modulation amplitude is too large, the signal is broadened. In direct detection field modulation is not used. (ii) In CW the small modulation amplitude detects only a small fraction of the signal amplitude. In direct detection each scan detects a larger fraction of the signal, which improves the signal-to-noise ratio. (iii) If the scan rate is fast enough to cause rapid scan oscillations, the slow scan spectrum can be recovered by deconvolution after the combination of segments. (iv) The data are acquired with quadrature detection, which permits phase correction in the post processing. (v) In the direct detection method the signal typically is oversampled in the field direction. The number of points to be averaged, thereby improving the signal-to-noise ratio, is determined in post processing based on the desired field resolution. A degased lithium phthalocyanine sample was used to demonstrate that the linear deconvolution procedure can be employed with field-stepped direct detection EPR signals. Field-stepped direct detection EPR spectra were obtained for Cu(2+) doped in Ni(diethyldithiocarbamate)2, Cu(2+) doped in Zn tetratolylporphyrin, perdeuterated tempone in sucrose octaacetate, vanadyl ion doped in a parasubstituted Zn tetratolylporphyrin, Mn(2+) impurity in CaO, and an oriented crystal of Mn(2+) doped in Mg(acetylacetonate)2(H2O)2. PMID:26232363

  20. A PET-based fluorometric chemosensor for the determination of mercury(ii) and pH, and hydrolysis reaction-based colorimetric detection of hydrogen sulfide.

    PubMed

    Lee, Jae Jun; Kim, Yong Sung; Nam, Eunju; Lee, Sun Young; Lim, Mi Hee; Kim, Cheal

    2016-04-01

    A simple fluorescent chemosensor 1 for the detection of Hg(2+) and pH was developed by a combination of 2-aminoethyl piperazine and 4-chloro-7-nitrobenz-2-oxa-1,3-diazole. The sensor 1 showed OFF-ON behavior for different colors of fluorescence in the presence of Hg(2+) and under acidic conditions, respectively, in a near-perfect aqueous solution. The turn-on fluorescence caused by inhibition of photoinduced electron transfer was explained by theoretical calculations. 1 could be used to quantify Hg(2+) in water samples, and its in vitro studies with HeLa cells showed fluorescence in the presence of Hg(2+). In addition, 1 could selectively detect S(2-) by changing its color from orange to pink in a near-perfect aqueous solution. Moreover, 1 could be used as a practical, visible test kit for S(2-). PMID:26928649

  1. Analysis of the theoretical bias in dark matter direct detection

    SciTech Connect

    Catena, Riccardo

    2014-09-01

    Fitting the model ''A'' to dark matter direct detection data, when the model that underlies the data is ''B'', introduces a theoretical bias in the fit. We perform a quantitative study of the theoretical bias in dark matter direct detection, with a focus on assumptions regarding the dark matter interactions, and velocity distribution. We address this problem within the effective theory of isoscalar dark matter-nucleon interactions mediated by a heavy spin-1 or spin-0 particle. We analyze 24 benchmark points in the parameter space of the theory, using frequentist and Bayesian statistical methods. First, we simulate the data of future direct detection experiments assuming a momentum/velocity dependent dark matter-nucleon interaction, and an anisotropic dark matter velocity distribution. Then, we fit a constant scattering cross section, and an isotropic Maxwell-Boltzmann velocity distribution to the simulated data, thereby introducing a bias in the analysis. The best fit values of the dark matter particle mass differ from their benchmark values up to 2 standard deviations. The best fit values of the dark matter-nucleon coupling constant differ from their benchmark values up to several standard deviations. We conclude that common assumptions in dark matter direct detection are a source of potentially significant bias.

  2. Comparison of direct and heterodyne detection optical intersatellite communication links

    NASA Technical Reports Server (NTRS)

    Chen, C. C.; Gardner, C. S.

    1987-01-01

    The performance of direct and heterodyne detection optical intersatellite communication links are evaluated and compared. It is shown that the performance of optical links is very sensitive to the pointing and tracking errors at the transmitter and receiver. In the presence of random pointing and tracking errors, optimal antenna gains exist that will minimize the required transmitter power. In addition to limiting the antenna gains, random pointing and tracking errors also impose a power penalty in the link budget. This power penalty is between 1.6 to 3 dB for a direct detection QPPM link, and 3 to 5 dB for a heterodyne QFSK system. For the heterodyne systems, the carrier phase noise presents another major factor of performance degradation that must be considered. In contrast, the loss due to synchronization error is small. The link budgets for direct and heterodyne detection systems are evaluated. It is shown that, for systems with large pointing and tracking errors, the link budget is dominated by the spatial tracking error, and the direct detection system shows a superior performance because it is less sensitive to the spatial tracking error. On the other hand, for systems with small pointing and tracking jitters, the antenna gains are in general limited by the launch cost, and suboptimal antenna gains are often used in practice. In which case, the heterodyne system has a slightly higher power margin because of higher receiver sensitivity.

  3. Non-relativistic effective theory of dark matter direct detection

    SciTech Connect

    Fan, JiJi; Wang, Lian-Tao; Reece, Matthew E-mail: mreece@princeton.edu

    2010-11-01

    Dark matter direct detection searches for signals coming from dark matter scattering against nuclei at a very low recoil energy scale ? 10 keV. In this paper, a simple non-relativistic effective theory is constructed to describe interactions between dark matter and nuclei without referring to any underlying high energy models. It contains the minimal set of operators that will be tested by direct detection. The effective theory approach highlights the set of distinguishable recoil spectra that could arise from different theoretical models. If dark matter is discovered in the near future in direct detection experiments, a measurement of the shape of the recoil spectrum will provide valuable information on the underlying dynamics. We bound the coefficients of the operators in our non-relativistic effective theory by the null results of current dark matter direct detection experiments. We also discuss the mapping between the non-relativistic effective theory and field theory models or operators, including aspects of the matching of quark and gluon operators to nuclear form factors.

  4. Channel simulation for direct-detection optical communication systems

    NASA Technical Reports Server (NTRS)

    Tycz, M.; Fitzmaurice, M. W.

    1974-01-01

    A technique is described for simulating the random modulation imposed by atmospheric scintillation and transmitter pointing jitter on a direct-detection optical communication system. The system is capable of providing signal fading statistics which obey log-normal, beta, Rayleigh, Ricean, or chi-square density functions. Experimental tests of the performance of the channel simulator are presented.

  5. Channel simulation for direct detection optical communication systems

    NASA Technical Reports Server (NTRS)

    Tycz, M.; Fitzmaurice, M. W.

    1974-01-01

    A technique is described for simulating the random modulation imposed by atmospheric scintillation and transmitter pointing jitter on a direct detection optical communication system. The system is capable of providing signal fading statistics which obey log normal, beta, Rayleigh, Ricean or chi-squared density functions. Experimental tests of the performance of the Channel Simulator are presented.

  6. Direct detection of the inflationary gravitational-wave background

    SciTech Connect

    Smith, Tristan L.; Kamionkowski, Marc; Cooray, Asantha

    2006-01-15

    Inflation generically predicts a stochastic background of gravitational waves over a broad range of frequencies, from those accessible with cosmic microwave background (CMB) measurements, to those accessible directly with gravitational-wave detectors, like NASA's Big-Bang Observer (BBO) or Japan's Deci-Hertz Interferometer Gravitational-wave Observer (DECIGO), both currently under study. Here we investigate the detectability of the inflationary gravitational-wave background at BBO/DECIGO frequencies. To do so, we survey a range of slow-roll inflationary models consistent with constraints from the CMB and large-scale structure (LSS). We go beyond the usual assumption of power-law power spectra, which may break down given the 16 orders of magnitude in frequency between the CMB and direct detection, and solve instead the inflationary dynamics for four classes of inflaton potentials. Direct detection is possible in a variety of inflationary models, although probably not in any in which the gravitational-wave signal does not appear in the CMB polarization. However, direct detection by BBO/DECIGO can help discriminate between inflationary models that have the same slow-roll parameters at CMB/LSS scales.

  7. Copper-incorporated SBA-15 with peroxidase-like activity and its application for colorimetric detection of glucose in human serum.

    PubMed

    Mu, Jianshuai; He, Yun; Wang, Yan

    2016-02-01

    The copper incorporated SBA-15 (Cu-SBA-15) materials with different amount of Cu in framework were synthesized, and the products were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM) and N2 adsorption/desorption. The Cu contents incorporated into the framework of SBA-15 were measured by inductively coupling plasma atomic emission spectrometer (ICP-AES). Cu-SBA-15 samples were found to exhibit the peroxidase-like activity, similar to the natural peroxidase. The effect of various parameters such as the content of Cu incorporated, pH and temperature on the peroxidase-like activity was studied. Based on the peroxidase-like activity, the Cu-SBA-15 was applied to the determination of H2O2. The linear range for detecting H2O2 was from 0.8 to 60mM with a detection limit of 3.7M. Coupled with glucose oxidase, the Cu-SBA-15 was successfully used for the determination of glucose with the linear range of 2-80mM and a detection limit of 5.4M. The determination of glucose in human serum showed high accuracy, good reproducibility, as well as high selectivity against uric acid, ascorbic acid, dopamine and glucose analogs including fructose, maltose and lactose. PMID:26653419

  8. Rapid onsite detection of bacterial spores of biothreat importance by paper-based colorimetric method using erbium-pyrocatechol violet complex.

    PubMed

    Shivakiran, M S; Venkataramana, M; Lakshmana Rao, P V

    2016-01-01

    Dipicolinic acid (DPA) is an important chemical marker for the detection of bacterial spores. In this study, complexes of lanthanide series elements such as erbium, europium, neodymium, and terbium were prepared with pyrocatechol violet and effectively immobilized the pyrocatechol violet (PV)-metal complex on a filter paper using polyvinyl alcohol. These filter paper strips were employed for the onsite detection of bacterial spores. The test filter papers were evaluated quantitatively with different concentrations of DPA and spores of various bacteria. Among the four lanthanide ions, erbium displayed better sensitivity than the other ions. The limit of detection of this test for DPA was 60 μM and 5 × 10(6) spores. The effect of other non-spore-forming bacteria and interfering chemicals on the test strips was also evaluated. The non-spore-forming bacteria did not have considerable effect on the test strip whereas chemicals such as EDTA had significant effects on the test results. The present test is rapid and robust, capable of providing timely results for better judgement to save resources on unnecessary decontamination procedures during false alarms. PMID:26603759

  9. Directed energy active illumination for near-Earth object detection

    NASA Astrophysics Data System (ADS)

    Riley, Jordan; Lubin, Philip; Hughes, Gary B.; O'Neill, Hugh; Meinhold, Peter; Suen, Jonathan; Bible, Johanna; Johansson, Isabella E.; Griswold, Janelle; Cook, Brianna

    2014-09-01

    On 15 February 2013, a previously unknown ~20 m asteroid struck Earth near Chelyabinsk, Russia, releasing kinetic energy equivalent to ~570 kt TNT. Detecting objects like the Chelyabinsk impactor that are orbiting near Earth is a difficult task, in part because such objects spend much of their own orbits in the direction of the Sun when viewed from Earth. Efforts aimed at protecting Earth from future impacts will rely heavily on continued discovery. Ground-based optical observatory networks and Earth-orbiting spacecraft with infrared sensors have dramatically increased the pace of discovery. Still, less than 5% of near-Earth objects (NEOs) >=100 m/~100 Mt TNT have been identified, and the proportion of known objects decreases rapidly for smaller sizes. Low emissivity of some objects also makes detection by passive sensors difficult. A proposed orbiting laser phased array directed energy system could be used for active illumination of NEOs, enhancing discovery particularly for smaller and lower emissivity objects. Laser fiber amplifiers emit very narrow-band energy, simplifying detection. Results of simulated illumination scenarios are presented based on an orbiting emitter array with specified characteristics. Simulations indicate that return signals from small and low emissivity objects is strong enough to detect. The possibility for both directed and full sky blind surveys is discussed, and the resulting diameter and mass limits for objects in different observational scenarios. The ability to determine both position and speed of detected objects is also discussed.

  10. Directional statistics for realistic weakly interacting massive particle direct detection experiments. II. 2D readout

    NASA Astrophysics Data System (ADS)

    Morgan, Ben; Green, Anne M.

    2005-12-01

    The direction dependence of the WIMP direct detection rate provides a powerful tool for distinguishing a WIMP signal from possible backgrounds. We study the number of events required to discriminate a WIMP signal from an isotropic background for a detector with 2-d readout using nonparametric circular statistics. We also examine the number of events needed to (i) detect a deviation from rotational symmetry, due to flattening of the Milky Way halo and (ii) detect a deviation in the mean direction due to a tidal stream. If the senses of the recoils are measured then of order 20--70 events (depending on the plane of the 2-d readout and the detector location) will be sufficient to reject isotropy of the raw recoil angles at 90% confidence. If the senses can not be measured these number increase by roughly 2 orders of magnitude (compared with an increase of 1 order of magnitude for the case of full 3-d readout). The distributions of the reduced angles, with the (time-dependent) direction of solar motion subtracted, are far more anisotropic, however, and if the isotropy tests are applied to these angles then the numbers of events required are similar to the case of 3-d readout. A deviation from rotational symmetry will only be detectable if the Milky Way halo is significantly flattened. The deviation in the mean direction due to a tidal stream is potentially detectable, however, depending on the density and direction of the stream. The meridian plane (which contains the Earth’s spin axis) is, for all detector locations, the optimum readout plane for rejecting isotropy. However readout in this plane can not be used for detecting flattening of the Milky Way halo or a stream with direction perpendicular to the galactic plane. In these cases the optimum readout plane depends on the detector location.

  11. Detection of Laser Optic Defects Using Gradient Direction Matching

    SciTech Connect

    Chen, B Y; Kegelmeyer, L M; Liebman, J A; Salmon, J T; Tzeng, J; Paglieroni, D W

    2005-12-14

    That National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) will be the world's largest and most energetic laser. It has thousands of optics and depends heavily on the quality and performance of these optics. Over the past several years, we have developed the NIF Optics Inspection Analysis System that automatically finds defects in a specific optic by analyzing images taken of that optic. This paper describes a new and complementary approach for the automatic detection of defects based on detecting the diffraction ring patterns in downstream optic images caused by defects in upstream optics. Our approach applies a robust pattern matching algorithm for images called Gradient Direction Matching (GDM). GDM compares the gradient directions (the direction of flow from dark to light) of pixels in a test image to those of a specified model and identifies regions in the test image whose gradient directions are most in line with those of the specified model. For finding rings, we use luminance disk models whose pixels have gradient directions all pointing toward the center of the disk. After GDM identifies potential rings locations, we rank these rings by how well they fit the theoretical diffraction ring pattern equation. We perform false alarm mitigation by throwing out rings of low fit. A byproduct of this fitting procedure is an estimate of the size of the defect and its distance from the image plane. We demonstrate the potential effectiveness of this approach by showing examples of rings detected in real images of NIF optics.

  12. Detection of laser optic defects using gradient direction matching

    NASA Astrophysics Data System (ADS)

    Chen, Barry Y.; Kegelmeyer, Laura M.; Liebman, Judith A.; Salmon, J. Thaddeus; Tzeng, Jack; Paglieroni, David W.

    2006-02-01

    That National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) will be the world's largest and most energetic laser. It has thousands of optics and depends heavily on the quality and performance of these optics. Over the past several years, we have developed the NIF Optics Inspection Analysis System that automatically finds defects in a specific optic by analyzing images taken of that optic. This paper describes a new and complementary approach for the automatic detection of defects based on detecting the diffraction ring patterns in downstream optic images caused by defects in upstream optics. Our approach applies a robust pattern matching algorithm for images called Gradient Direction Matching (GDM). GDM compares the gradient directions (the direction of flow from dark to light) of pixels in a test image to those of a specified model and identifies regions in the test image whose gradient directions are most in line with those of the specified model. For finding rings, we use luminance disk models whose pixels have gradient directions all pointing toward the center of the disk. After GDM identifies potential rings locations, we rank these rings by how well they fit the theoretical diffraction ring pattern equation. We perform false alarm mitigation by throwing out rings of low fit. A byproduct of this fitting procedure is an estimate of the size of the defect and its distance from the image plane. We demonstrate the potential effectiveness of this approach by showing examples of rings detected in real images of NIF optics.

  13. Direct Detection of Sub-GeV Dark Matter

    SciTech Connect

    Essig, Rouven; Mardon, Jeremy; Volansky, Tomer

    2012-03-20

    Direct detection strategies are proposed for dark matter particles with MeV to GeV mass. In this largely unexplored mass range, dark matter scattering with electrons can cause single-electron ionization signals, which are detectable with current technology. Ultraviolet photons, individual ions, and heat are interesting alternative signals. Focusing on ionization, we calculate the expected dark matter scattering rates and estimate the sensitivity of possible experiments. Backgrounds that may be relevant are discussed. Theoretically interesting models can be probed with existing technologies, and may even be within reach using ongoing direct detection experiments. Significant improvements in sensitivity should be possible with dedicated experiments, opening up a window to new regions in dark matter parameter space.

  14. Dark matter directional detection in non-relativistic effective theories

    SciTech Connect

    Catena, Riccardo

    2015-07-20

    We extend the formalism of dark matter directional detection to arbitrary one-body dark matter-nucleon interactions. The new theoretical framework generalizes the one currently used, which is based on 2 types of dark matter-nucleon interaction only. It includes 14 dark matter-nucleon interaction operators, 8 isotope-dependent nuclear response functions, and the Radon transform of the first 2 moments of the dark matter velocity distribution. We calculate the recoil energy spectra at dark matter directional detectors made of CF{sub 4}, CS{sub 2} and {sup 3}He for the 14 dark matter-nucleon interactions, using nuclear response functions recently obtained through numerical nuclear structure calculations. We highlight the new features of the proposed theoretical framework, and present our results for a spherical dark matter halo and for a stream of dark matter particles. This study lays the foundations for model independent analyses of dark matter directional detection experiments.

  15. An antenna for directional detection of WISPy dark matter

    SciTech Connect

    Jaeckel, Joerg; Redondo, Javier E-mail: redondo@mpp.mpg.de

    2013-11-01

    It is an intriguing possibility that the cold dark matter of the Universe may consist of very light and very weakly interacting particles such as axion(-like particles) and hidden photons. This opens up (but also requires) new techniques for direct detection. One possibility is to use reflecting surfaces to facilitate the conversion of dark matter into photons, which can be concentrated in a detector with a suitable geometry. In this note we show that this technique also allows for directional detection and inference of the full vectorial velocity spectrum of the dark matter particles. We also note that the non-vanishing velocity of dark matter particles is relevant for the conception of (non-directional) discovery experiments and outline relevant features.

  16. Dark matter directional detection in non-relativistic effective theories

    NASA Astrophysics Data System (ADS)

    Catena, Riccardo

    2015-07-01

    We extend the formalism of dark matter directional detection to arbitrary one-body dark matter-nucleon interactions. The new theoretical framework generalizes the one currently used, which is based on 2 types of dark matter-nucleon interaction only. It includes 14 dark matter-nucleon interaction operators, 8 isotope-dependent nuclear response functions, and the Radon transform of the first 2 moments of the dark matter velocity distribution. We calculate the recoil energy spectra at dark matter directional detectors made of CF4, CS2 and 3He for the 14 dark matter-nucleon interactions, using nuclear response functions recently obtained through numerical nuclear structure calculations. We highlight the new features of the proposed theoretical framework, and present our results for a spherical dark matter halo and for a stream of dark matter particles. This study lays the foundations for model independent analyses of dark matter directional detection experiments.

  17. Selective turn-off phosphorescent and colorimetric detection of mercury(II) in water by half-lantern platinum(II) complexes.

    PubMed

    Sicilia, Violeta; Borja, Pilar; Baya, Miguel; Casas, Jos M

    2015-04-21

    The platinum(ii) half-lantern dinuclear complexes [{Pt(bzq)(?-C7H4NS2-?N,S)}2] () and [{Pt(bzq)(?-C7H4NOS-?N,S)}2] () [bzq = benzo[h]quinolinate, C7H4NS2 = 2-mercaptobenzothiazolate, C7H4NOS = 2-mercaptobenzoxazolate] in solution of DMSO-H2O undergo a dramatic color change from yellowish-orange to purple and turn-off phosphorescence in the presence of a small amount of Hg(2+), being discernible by the naked-eye and by spectroscopic methods. Other metal ions as Ag(+), Li(+), Na(+), K(+), Ca(2+), Mg(2+), Ba(2+), Pb(2+), Cd(2+), Zn(2+) and Tl(+) were tested and, even in a big excess, showed no interference in the selective detection of Hg(2+) in water. Job's plot analysis indicated a 1?:?1 stoichiometry in the complexation mode of Hg(2+) by /. The phosphorescence quenching attributed to the formation of [/?:?Hg(2+)] complexes showed binding constants of K = 1.13 10(5) M(-1) () and K = 1.99 10(4) M(-1) (). The limit of detection has been also evaluated. In addition, dried paper test strips impregnated in DMSO solutions of and can detect concentration of Hg(2+) in water as low as 1 10(-5) M for and 5 10(-5) M for , making these complexes good candidates to be used as real-time Hg(2+) detectors. The nature of the interaction of the Pt2 half-lantern complex with the Hg(2+) cation, has been investigated by theoretical calculations. PMID:25781389

  18. Simple colorimetric method determines uranium in tissue

    NASA Technical Reports Server (NTRS)

    Doran, D.; Frigerio, N. A.

    1967-01-01

    Simple colorimetric micromethod determines concentrations of uranium in tissue. The method involves dry ashing organic extraction, and colorimetric determination of uranyl ferrocyanide. This uranium determination technique could be used in agricultural research, tracer studies, testing of food products, or medical research.

  19. Colorimetric phosphorescence measurements with a color camera for oxygen determination

    NASA Astrophysics Data System (ADS)

    Bhagwat, Prajakta; Achanta, Gowthami Satya; Henthorn, David; Kim, Chang-Soo

    2011-05-01

    We developed a simple oxygen imaging platform with phosphorescent oxygen sensor films to demonstrate a quantitative oxygen determination method utilizing a color CCD camera. Phosphorescence quenching of a luminophore Pt(II) meso-tetrakis (pentafluorophenyl) porphyrin complex (PtTFPP) immobilized in poly (dimethylsiloxane) (PDMS) matrix, is the principal detection mechanism. This sensor material was cast to form a film on the bottom surface of a transparent Petri dish. As levels of dissolved oxygen increased, phosphorescence of the complex decreased, allowing for measurement of oxygen levels which developed in the sensor film. A camera with a charge-coupled device (CCD) was used in conjunction with processing software to quantify oxygen levels colorimetrically. Microscopic images were collected using a CCD camera and stored as a set of red/green/blue (RGB) images. Phosphorescence excitation (390 nm peak) is limited to the blue (B) pixels of the CCD chip, and these values were discarded; while retaining the oxygen-responsive phosphorescence emission (645 nm peak) almost identical with the response range of the red (R) pixels. Red pixel intensity analysis effectively extracts color intensity information, which can be in turn directly related to oxygen contents. Color CCD cameras allow simultaneous acquisition of many types of chemical information by combining the merits of digital imaging with the attributes of spectroscopic measurement. Therefore, use of color CCD cameras is considered as an inexpensive alternative to time-resolved imaging for relatively short-term monitoring.

  20. Three-dimensional track reconstruction for directional Dark Matter detection

    SciTech Connect

    Billard, J.; Mayet, F.; Santos, D. E-mail: mayet@lpsc.in2p3.fr

    2012-04-01

    Directional detection of Dark Matter is a promising search strategy. However, to perform such detection, a given set of parameters has to be retrieved from the recoiling tracks: direction, sense and position in the detector volume. In order to optimize the track reconstruction and to fully exploit the data of forthcoming directional detectors, we present a likelihood method dedicated to 3D track reconstruction. This new analysis method is applied to the MIMAC detector. It requires a full simulation of track measurements in order to compare real tracks to simulated ones. We conclude that a good spatial resolution can be achieved, i.e. sub-mm in the anode plane and cm along the drift axis. This opens the possibility to perform a fiducialization of directional detectors. The angular resolution is shown to range between 20 to 80, depending on the recoil energy, which is however enough to achieve a high significance discovery of Dark Matter. On the contrary, we show that sense recognition capability of directional detectors depends strongly on the recoil energy and the drift distance, with small efficiency values (50%70%). We suggest not to consider this information either for exclusion or discovery of Dark Matter for recoils below 100 keV and then to focus on axial directional data.

  1. Performance evaluation of a colorimetric hydrazine dosimeter

    NASA Astrophysics Data System (ADS)

    Brenner, Karen P.; Rose-Pehrsson, Susan L.

    1994-06-01

    A dosimeter for real-time, colorimetric detection of hydrazine in air has been developed. The passive badge consists of a dosimeter card containing a vanillin solution coated on a thin paper substrate. The active patch consists of a thick cellulose substrate coated with a vanillin solution. When placed in a plastic sample holder attached to a personnel pump, up to 5 L/min can be drawn through the active badge substrate. Through a condensation reaction, vanillin reacts with hydrazine to form a colored product that absorbs in the visible region. The hydrazone formed in the reaction is yellow; its intensity is proportional to the dose. When exposed passively to hydrazine, the experimental detection limit is less than 20 ppb-hrs. Extrapolated results indicate a detection limit of less than 5 ppb-hrs for long sampling periods. Actively sampling of hydrazine vapors gives an experimental detection limit of less than 100 ppb-L at a sample rate of 5 L/min. Relative humidity effects on badge response were minor. High humidity enhanced the color development on the vanillin badge; while low humidity had no effect on badge response. Interference testing of the dosimeters revealed a tobacco smoke interference. Preliminary shelf life tests indicated no decrease in sensitivity to hydrazine when stored at room temperature for 6 months.

  2. Highly selective colorimetric detection and preconcentration of Bi(III) ions by dithizone complexes anchored onto mesoporous TiO2

    NASA Astrophysics Data System (ADS)

    Faisal, Mohd; Ismail, Adel A.; Harraz, Farid A.; Bouzid, Houcine; Al-Sayari, Saleh A.; Al-Hajry, Ali

    2014-02-01

    We successfully developed a single-step detection and removal unit for Bi(III) ions based on dithizone (DZ) anchored on mesoporous TiO2 with rapid colorometric response and high selectivity for the first time. [(DZ)3-Bi] complex is easily separated and collected by mesoporous TiO2 as adsorbent and preconcentrator without any color change of the produced complex onto the surface of mesoporous TiO2 (TiO2-[(DZ)3-Bi]) at different Bi(III) concentrations. This is because highly potent mesoporous TiO2 architecture provides proficient channeling or movement of Bi(III) ions for efficient binding of metal ion, and the simultaneous excellent adsorbing nature of mesoporous TiO2 provides an extra plane for the removal of metal ions.

  3. Highly selective colorimetric detection and preconcentration of Bi(III) ions by dithizone complexes anchored onto mesoporous TiO2

    PubMed Central

    2014-01-01

    We successfully developed a single-step detection and removal unit for Bi(III) ions based on dithizone (DZ) anchored on mesoporous TiO2 with rapid colorometric response and high selectivity for the first time. [(DZ)3-Bi] complex is easily separated and collected by mesoporous TiO2 as adsorbent and preconcentrator without any color change of the produced complex onto the surface of mesoporous TiO2 (TiO2-[(DZ)3-Bi]) at different Bi(III) concentrations. This is because highly potent mesoporous TiO2 architecture provides proficient channeling or movement of Bi(III) ions for efficient binding of metal ion, and the simultaneous excellent adsorbing nature of mesoporous TiO2 provides an extra plane for the removal of metal ions. PMID:24502680

  4. Indicator approach to develop a chemosensor for the colorimetric sensing of thiol-containing water and its application for the thiol detection in plasma.

    PubMed

    Huo, Fang-Jun; Yang, Yu-Tao; Su, Jing; Sun, Yuan-Qiang; Yin, Cai-Xia; Yan, Xu-Xiu

    2011-05-01

    A strategy for the determination of the presence of thiol-containing amino acids was successfully established by simply assembling copper chloride and xylenol orange (3,3'-bis[N,N-bis(carboxymethyl)aminomethyl]-o-cresolsulfonephthalein trisodium salt; XO) in a 1 : 1 molar ratio in quasi-physiological water solution (pH 6.0). The copper(II)-XO ensemble was highly selective for thiol species such as cysteine, homocysteine, and glutathione without interference from other amino acids and could quantitatively detect thiol in the range from 10 to 200 μM with a linear relationship having an average molar absorbance constant of 6530 L mol(-1) cm(-1) in pure water. The whole recognition process for thiol gave rise to a rapid visual color change from purple-red to yellow which can be observed simultaneously with the naked-eye. PMID:21373697

  5. Direct detection of expanded trinucleotide repeats using DNA hybridization techniques

    SciTech Connect

    Petronis, A.; Tatuch, Y.; Kennedy, J.L.

    1994-09-01

    Recently, unstable trinucleotide repeats have been shown to be the etiologic factor in several neuropsychiatric diseases, and they may play a similar role in other disorders. To our knowledge, a method that detects expanded trinucleotide sequences with the opportunity for direct localization and cloning has not been achieved. We have developed a set of hybridization-based methods for direct detection of unstable DNA expansion. Our analysis of myotonic dystrophy patients that possess different degrees of (CTG){sub n} expansion, versus unaffected controls, has demonstrated the identification of the trinucleotide instability site without any prior information regarding genetic map location. High stringency modified Southern blot hybridization with a PCR-generated trinucleotide repeat probe allowed us to detect the DNA fragment containing the expansion in myotonic dystrophy patients. The same probe was used for fluorescent in situ hybridization and several regions of (CTG){sub n}/(CAG){sub n} repeats in the human genome were detected, including the myotonic dystrophy locus on chromosome 19q. These strategies can be applied to directly clone genes involved in disorders caused by unstable DNA.

  6. Rapid directivity detection by azimuthal amplitude spectra inversion

    NASA Astrophysics Data System (ADS)

    Cesca, Simone; Heimann, Sebastian; Dahm, Torsten

    2011-01-01

    An early detection of the presence of rupture directivity plays a major role in the correct estimation of ground motions and risks associated to the earthquake occurrence. We present here a simple method for a fast detection of rupture directivity, which may be additionally used to discriminate fault and auxiliary planes and have first estimations of important kinematic source parameters, such as rupture length and rupture time. Our method is based on the inversion of amplitude spectra from P-wave seismograms to derive the apparent duration at each station and on the successive modelling of its azimuthal behaviour. Synthetic waveforms are built assuming a spatial point source approximation, and the finite apparent duration of the spatial point source is interpreted in terms of rupture directivity. Since synthetic seismograms for a point source are calculated very quickly, the presence of directivity may be detected within few seconds, once a focal mechanism has been derived. The method is here first tested using synthetic datasets, both for linear and planar sources, and then successfully applied to recent Mw 6.2-6.8 shallow earthquakes in Peloponnese, Greece. The method is suitable for automated application and may be used to improve kinematic waveform modelling approaches.

  7. Spaceborne Simulations of Two Direct-Detection Doppler Lidar Techniques

    NASA Technical Reports Server (NTRS)

    McGill, Matthew J.; Li, Steve X.

    1998-01-01

    Direct-detection (or incoherent) lidar is now a proven technique for measuring winds in the atmosphere. Over the last few years, several types of direct-detection lidar have evolved. These methods rely on Fabry-Perot interferometers(also termed etalons) or other narrow-passband filters to provide the required spectral resolution. One method, now called the edge (EDG) technique, uses a sharply-sloping filter and measures changes in the filter transmission caused by Doppler shifting of the laser wavelength. A variation of the EDG method, called the double-edge (DEDG) technique, uses two filters. The molecular DEDG method was first demonstrated by Chanin et al. for stratospheric measurements and more recently Korb et al. successfully demonstrated the aerosol DEDG through the troposphere. A second method, here termed the multi-channel (MC) technique, measures Doppler shifts by observing angular displacement of a Fabry-Perot fringe in a spatially resolving detector. The EDG technique thus employs the Fabry-Perot to convert the frequency shift into an amplitude signal, while the MC technique uses the Fabry-Perot to resolve the spectral signature which is then fitted to determine the centroid. The focus of this presentation is on the DEDG and MC methods because these are viewed as the current state of the art in direct-detection lidar. Successful ground-based demonstrations of direct-detection wind measurements have resulted in proposals for spaceborne systems. With this new emphasis on spaceborne systems comes the need for accurate prediction of spaceborne direct-detection Doppler lidar performance. Previously, the EDG and MC methods have been compared although only for aerosol Doppler systems. A recent paper by McGill and Spinhirne compares the DEDG and MC methods in a non-system specific manner for both the aerosol and molecular Doppler systems. The purpose of this presentation is to extend the previous work of McGill and Spinhirne to examine the performance of spaceborne profiling systems. Particular emphasis will be placed on the molecular systems, as these are viewed as the strength of direct-detection Doppler lidar.

  8. Principal direction-based Hough transform for line detection

    NASA Astrophysics Data System (ADS)

    Zhao, Yao; Pan, Haibin; Du, Changping; Zheng, Yao

    2015-04-01

    A robust and fast line detection method based on Hough transform (HT) is proposed in this paper. Edge pixels are extracted based on the summation and ratio of principal curvatures. Probabilistic sampling on the edge pixels is applied to reduce the count of voting. Then a one-to-one voting strategy is applied by taking advantages of the information of principal direction. The principal direction is also conducive for the successive accurate line segment extraction. The experiments demonstrate that the proposed method shows better locating accuracy and computation efficiency compared with several significant variations of HT.

  9. Future directions for H sub x O sub y detection

    NASA Technical Reports Server (NTRS)

    Crosley, David R. (Editor); Hoell, James M. (Editor)

    1986-01-01

    The activities and recommendations of the NASA workshop on the Future Directions for H sub x O sub y detection are given. The objective of this workshop was to access future directions for the measurement of the OH radical as well as other H sub x O sub y species. The workshop discussions were focused by two broad questions: (1) What are the capabilities of potential measurement methods? and (2) Will the results from the most promising method be useful in furthering understanding of tropospheric chemistry?

  10. A colorimetric assay for sulfiredoxin activity using inorganic phosphate measurement.

    PubMed

    Kim, Hojin; Kim, Hyeryeon; Hong, Sohyun; Rhee, Sue Goo; Jeong, Woojin

    2009-10-01

    2-Cys peroxiredoxin (Prx) is the major subgroup of a family of Prx enzymes that reduce peroxide molecules such as hydrogen peroxide (H(2)O(2)). 2-Cys Prxs are inactivated when their active site cysteine residue is hyperoxidized to sulfinic acid. Sulfiredoxin (Srx) is an enzyme that catalyzes reduction of hyperoxidized 2-Cys Prxs in the presence of ATP, Mg(2+), and thiol equivalent. Therefore, Srx activity is crucial for cellular function of 2-Cys Prxs. The method currently available for the determination of Srx activity relies on immunoblot detection using antibodies to hyperoxidized enzymes. Here we introduce a simple quantitative assay for Srx activity based on the colorimetric determination of inorganic phosphate released in Srx-dependent reduction of hyperoxidized Prx using the malachite green. The colorimetric assay was used for high-throughput screening of 25,000 chemicals to find Srx inhibitors. PMID:19563768

  11. An Automated Directed Spectral Search Methodology for Small Target Detection

    NASA Astrophysics Data System (ADS)

    Grossman, Stanley I.

    Much of the current efforts in remote sensing tackle macro-level problems such as determining the extent of wheat in a field, the general health of vegetation or the extent of mineral deposits in an area. However, for many of the remaining remote sensing challenges being studied currently, such as border protection, drug smuggling, treaty verification, and the war on terror, most targets are very small in nature - a vehicle or even a person. While in typical macro-level problems the objective vegetation is in the scene, for small target detection problems it is not usually known if the desired small target even exists in the scene, never mind finding it in abundance. The ability to find specific small targets, such as vehicles, typifies this problem. Complicating the analyst's life, the growing number of available sensors is generating mountains of imagery outstripping the analysts' ability to visually peruse them. This work presents the important factors influencing spectral exploitation using multispectral data and suggests a different approach to small target detection. The methodology of directed search is presented, including the use of scene-modeled spectral libraries, various search algorithms, and traditional statistical and ROC curve analysis. The work suggests a new metric to calibrate analysis labeled the analytic sweet spot as well as an estimation method for identifying the sweet spot threshold for an image. It also suggests a new visualization aid for highlighting the target in its entirety called nearest neighbor inflation (NNI). It brings these all together to propose that these additions to the target detection arena allow for the construction of a fully automated target detection scheme. This dissertation next details experiments to support the hypothesis that the optimum detection threshold is the analytic sweet spot and that the estimation method adequately predicts it. Experimental results and analysis are presented for the proposed directed search techniques of spectral image based small target detection. It offers evidence of the functionality of the NNI visualization and also provides evidence that the increased spectral dimensionality of the 8-band Worldview-2 datasets provides noteworthy improvement in results over traditional 4-band multispectral datasets. The final experiment presents the results from a prototype fully automated target detection scheme in support of the overarching premise. This work establishes the analytic sweet spot as the optimum threshold defined as the point where error detection rate curves -- false detections vs. missing detections -- cross. At this point the errors are minimized while the detection rate is maximized. It then demonstrates that taking the first moment statistic of the histogram of calculated target detection values from a detection search with test threshold set arbitrarily high will estimate the analytic sweet spot for that image. It also demonstrates that directed search techniques -- when utilized with appropriate scene-specific modeled signatures and atmospheric compensations -- perform at least as well as in-scene search techniques 88% of the time and grossly under-performing only 11% of the time; the in-scene only performs as well or better 50% of the time. It further demonstrates the clear advantage increased multispectral dimensionality brings to detection searches improving performance in 50% of the cases while performing at least as well 72% of the time. Lastly, it presents evidence that a fully automated prototype performs as anticipated laying the groundwork for further research into fully automated processes for small target detection.

  12. Scalar split WIMPs in future direct detection experiments

    NASA Astrophysics Data System (ADS)

    Ghorbani, Karim; Ghorbani, Hossein

    2016-03-01

    We consider a simple renormalizable dark matter model consisting of two real scalars with a mass splitting δ , interacting with the SM particles through the Higgs portal. We find a viable parameter space respecting all the bounds imposed by invisible Higgs decay experiments at the LHC, the direct detection experiments by XENON100 and LUX, and the dark matter relic abundance provided by WMAP and Planck. Despite the singlet scalar dark matter model that is fragile against the future direct detection experiments, the scalar split model introduced here survives such forthcoming bounds. We emphasize the role of the coannihilation processes and the mixing effects in this feature. For mDM˜63 GeV in this model we can explain as well the observed gamma-ray excess in the analyses of the Fermi-LAT data at Galactic latitudes 2 ° ≤|b |≤2 0 ° and Galactic longitudes |l |<2 0 ° .

  13. Dark matter effective field theory scattering in direct detection experiments

    NASA Astrophysics Data System (ADS)

    Schneck, K.; Cabrera, B.; Cerdeño, D. G.; Mandic, V.; Rogers, H. E.; Agnese, R.; Anderson, A. J.; Asai, M.; Balakishiyeva, D.; Barker, D.; Basu Thakur, R.; Bauer, D. A.; Billard, J.; Borgland, A.; Brandt, D.; Brink, P. L.; Bunker, R.; Caldwell, D. O.; Calkins, R.; Chagani, H.; Chen, Y.; Cooley, J.; Cornell, B.; Crewdson, C. H.; Cushman, P.; Daal, M.; Di Stefano, P. C. F.; Doughty, T.; Esteban, L.; Fallows, S.; Figueroa-Feliciano, E.; Godfrey, G. L.; Golwala, S. R.; Hall, J.; Harris, H. R.; Hofer, T.; Holmgren, D.; Hsu, L.; Huber, M. E.; Jardin, D. M.; Jastram, A.; Kamaev, O.; Kara, B.; Kelsey, M. H.; Kennedy, A.; Leder, A.; Loer, B.; Lopez Asamar, E.; Lukens, P.; Mahapatra, R.; McCarthy, K. A.; Mirabolfathi, N.; Moffatt, R. A.; Morales Mendoza, J. D.; Oser, S. M.; Page, K.; Page, W. A.; Partridge, R.; Pepin, M.; Phipps, A.; Prasad, K.; Pyle, M.; Qiu, H.; Rau, W.; Redl, P.; Reisetter, A.; Ricci, Y.; Roberts, A.; Saab, T.; Sadoulet, B.; Sander, J.; Schnee, R. W.; Scorza, S.; Serfass, B.; Shank, B.; Speller, D.; Toback, D.; Upadhyayula, S.; Villano, A. N.; Welliver, B.; Wilson, J. S.; Wright, D. H.; Yang, X.; Yellin, S.; Yen, J. J.; Young, B. A.; Zhang, J.; SuperCDMS Collaboration

    2015-05-01

    We examine the consequences of the effective field theory (EFT) of dark matter-nucleon scattering for current and proposed direct detection experiments. Exclusion limits on EFT coupling constants computed using the optimum interval method are presented for SuperCDMS Soudan, CDMS II, and LUX, and the necessity of combining results from multiple experiments in order to determine dark matter parameters is discussed. We demonstrate that spectral differences between the standard dark matter model and a general EFT interaction can produce a bias when calculating exclusion limits and when developing signal models for likelihood and machine learning techniques. We also discuss the implications of the EFT for the next-generation (G2) direct detection experiments and point out regions of complementarity in the EFT parameter space.

  14. Dark matter effective field theory scattering in direct detection experiments

    SciTech Connect

    Schneck, K.; Cabrera, B.; Cerdeno, D. G.; Mandic, V.; Rogers, H. E.; Agnese, R.; Anderson, A. J.; Asai, M.; Balakishiyeva, D.; Barker, D.; Basu Thakur, R.; Bauer, D. A.; Billard, J.; Borgland, A.; Brandt, D.; Brink, P. L.; Bunker, R.; Caldwell, D. O.; Calkins, R.; Chagani, H.; Chen, Y.; Cooley, J.; Cornell, B.; Crewdson, C. H.; Cushman, Priscilla B.; Daal, M.; Di Stefano, P. C.; Doughty, T.; Esteban, L.; Fallows, S.; Figueroa-Feliciano, E.; Godfrey, G. L.; Golwala, S. R.; Hall, Jeter C.; Harris, H. R.; Hofer, T.; Holmgren, D.; Hsu, L.; Huber, M. E.; Jardin, D. M.; Jastram, A.; Kamaev, O.; Kara, B.; Kelsey, M. H.; Kennedy, A.; Leder, A.; Loer, B.; Lopez Asamar, E.; Lukens, W.; Mahapatra, R.; McCarthy, K. A.; Mirabolfathi, N.; Moffatt, R. A.; Morales Mendoza, J. D.; Oser, S. M.; Page, K.; Page, W. A.; Partridge, R.; Pepin, M.; Phipps, A.; Prasad, K.; Pyle, M.; Qiu, H.; Rau, W.; Redl, P.; Reisetter, A.; Ricci, Y.; Roberts, A.; Saab, T.; Sadoulet, B.; Sander, J.; Schnee, R. W.; Scorza, S.; Serfass, B.; Shank, B.; Speller, D.; Toback, D.; Upadhyayula, S.; Villano, A. N.; Welliver, B.; Wilson, J. S.; Wright, D. H.; Yang, X.; Yellin, S.; Yen, J. J.; Young, B. A.; Zhang, J.

    2015-05-01

    We examine the consequences of the effective eld theory (EFT) of dark matter-nucleon scattering or current and proposed direct detection experiments. Exclusion limits on EFT coupling constants computed using the optimum interval method are presented for SuperCDMS Soudan, CDMS II, and LUX, and the necessity of combining results from multiple experiments in order to determine dark matter parameters is discussed. We demonstrate that spectral di*erences between the standard dark matter model and a general EFT interaction can produce a bias when calculating exclusion limits and when developing signal models for likelihood and machine learning techniques. We also discuss the implications of the EFT for the next-generation (G2) direct detection experiments and point out regions of complementarity in the EFT parameter space.

  15. Future Directions for the Early Detection of Recurrent Breast Cancer

    PubMed Central

    Schneble, Erika J.; Graham, Lindsey J.; Shupe, Matthew P.; Flynt, Frederick L.; Banks, Kevin P.; Kirkpatrick, Aaron D.; Nissan, Aviram; Henry, Leonard; Stojadinovic, Alexander; Shumway, Nathan M.; Avital, Itzhak; Peoples, George E.; Setlik, Robert F.

    2014-01-01

    The main goal of follow-up care after breast cancer treatment is the early detection of disease recurrence. In this review, we emphasize the multidisciplinary approach to this continuity of care from surgery, medical oncology, and radiology. Challenges within each setting are briefly addressed as a means of discussion for the future directions of an effective and efficient surveillance plan of post-treatment breast cancer care. PMID:24790657

  16. Review of Dark Matter Direct Detection Using Cryogenic Detectors

    SciTech Connect

    Brink, P.L.; /SLAC

    2012-06-13

    The direct detection of the Universe's Dark Matter is one of the key questions in particle astrophysics. Cryogenic based detectors offer advantages in low radioactive backgrounds, target mass, sensitivity to the small energy depositions and rejection of possible background sources. I will summarize the main experimental approaches, including both cryogenic crystal and liquid targets and the options pursued for their signal readout. Recent advances from around the world and prospects for future proposed experiments will be discussed.

  17. Assessing Astrophysical Uncertainties in Direct Detection Experiments Using Galaxy Simulations

    NASA Astrophysics Data System (ADS)

    Brooks, Alyson; Sloane, Jonathan; Buckley, Matthew

    2016-01-01

    Experiments that will directly detect dark matter are strongly dependent on the velocity of the dark matter particle. These experiments are composed of various elements; the heavier the element, the higher the velocity of dark matter must be to register a visible impact. The velocity of the dark matter is set by astrophysics. To date, all direct detection experiments assume that the dark matter in the Milky Way follows a Maxwellian velocity distribution. N-Body simulations that include only dark matter have long shown that this assumption is incorrect. In this work, we use high resolution cosmological simulations of Milky Way-mass galaxies that include dark matter, gas, and stellar physics, in order to explore the additional effect of baryons on the velocity distribution of dark matter in the solar neighborhood. We show that the baryons have a significant impact, altering the predictions from the dark matter-only case, leading to a distribution that is closer to Maxwellian. However, in all of our galaxies, the high velocity tail drops off more steeply than in the standard Maxwellian. We discuss how the inclusion of baryons change the interpretation of current direct detection experiments.

  18. Direct detection of classically undetectable dark matter through quantum decoherence

    NASA Astrophysics Data System (ADS)

    Riedel, C. Jess

    2014-03-01

    Although various pieces of indirect evidence about the nature of dark matter have been collected, its direct detection has eluded experimental searches despite extensive effort. If the mass of dark matter is below 1 MeV, it is essentially imperceptible to conventional detection methods because negligible energy is transferred to nuclei during collisions. Here I propose directly detecting dark matter through the quantum decoherence it causes rather than its classical effects such as recoil or ionization. I show that quantum spatial superpositions are sensitive to low-mass dark matter which is inaccessible to classical techniques. This provides new independent motivation for matter interferometry with large masses, especially on spaceborne platforms. The apparent dark matter wind we experience as the Sun travels through the Milky Way ensures interferometers and related devices are directional detectors, and so are able to provide unmistakable evidence that decoherence has galactic origins. This research was partially supported by the U.S. Department of Energy through the LANL/LDRD program, and by the John Templeton Foundation through grant number 21484.

  19. WIMP dark matter direct-detection searches in noble gases

    NASA Astrophysics Data System (ADS)

    Baudis, Laura

    2014-09-01

    Cosmological observations and the dynamics of the Milky Way provide ample evidence for an invisible and dominant mass component. This so-called dark matter could be made of new, colour and charge neutral particles, which were non-relativistic when they decoupled from ordinary matter in the early universe. Such weakly interacting massive particles (WIMPs) are predicted to have a non-zero coupling to baryons and could be detected via their collisions with atomic nuclei in ultra-low background, deep underground detectors. Among these, detectors based on liquefied noble gases have demonstrated tremendous discovery potential over the last decade. After briefly introducing the phenomenology of direct dark matter detection, I will review the main properties of liquefied argon and xenon as WIMP targets and discuss sources of background. I will then describe existing and planned argon and xenon detectors that employ the so-called single- and dual-phase detection techniques, addressing their complementarity and science reach.

  20. (In)direct detection of boosted dark matter

    SciTech Connect

    Agashe, Kaustubh; Cui, Yanou; Necib, Lina; Thaler, Jesse E-mail: cuiyo@umd.edu E-mail: jthaler@mit.edu

    2014-10-01

    We initiate the study of novel thermal dark matter (DM) scenarios where present-day annihilation of DM in the galactic center produces boosted stable particles in the dark sector. These stable particles are typically a subdominant DM component, but because they are produced with a large Lorentz boost in this process, they can be detected in large volume terrestrial experiments via neutral-current-like interactions with electrons or nuclei. This novel DM signal thus combines the production mechanism associated with indirect detection experiments (i.e. galactic DM annihilation) with the detection mechanism associated with direct detection experiments (i.e. DM scattering off terrestrial targets). Such processes are generically present in multi-component DM scenarios or those with non-minimal DM stabilization symmetries. As a proof of concept, we present a model of two-component thermal relic DM, where the dominant heavy DM species has no tree-level interactions with the standard model and thus largely evades direct and indirect DM bounds. Instead, its thermal relic abundance is set by annihilation into a subdominant lighter DM species, and the latter can be detected in the boosted channel via the same annihilation process occurring today. Especially for dark sector masses in the 10 MeV10 GeV range, the most promising signals are electron scattering events pointing toward the galactic center. These can be detected in experiments designed for neutrino physics or proton decay, in particular Super-K and its upgrade Hyper-K, as well as the PINGU/MICA extensions of IceCube. This boosted DM phenomenon highlights the distinctive signatures possible from non-minimal dark sectors.

  1. Detecting modulated lasers in the battlefield and determining their direction

    NASA Astrophysics Data System (ADS)

    McAulay, Alastair D.

    2009-05-01

    Many different lasers are deployed in the battlefield for range finding, target designation, communications, dazzle, location of targets, munitions guidance, and destruction. Laser warning devices on military systems detect and identify lasers striking them in order to assess their threat level and plan avoidance or retaliation. Types of lasers and their characteristics are discussed: power, frequency, coherence, bandwidth, direction, pulse length and modulation. We describe three approaches for laser warning devices from which specific cases may be tailored: simultaneous estimation of direction and wavelength with a grating, wavefront direction only estimation for low light levels with lenses, absolute simultaneous wavelength only estimation with a Fizeau interferometer. We investigate the feasibility and compare the suitability of these approaches for different applications.

  2. Direct Real-Time Detection of Vapors from Explosive Compounds

    SciTech Connect

    Ewing, Robert G.; Clowers, Brian H.; Atkinson, David A.

    2013-10-03

    The real-time detection of vapors from low volatility explosives including PETN, tetryl, RDX and nitroglycerine along with various compositions containing these substances is demonstrated. This was accomplished with an atmospheric flow tube (AFT) using a non-radioactive ionization source and coupled to a mass spectrometer. Direct vapor detection was demonstrated in less than 5 seconds at ambient temperature without sample pre-concentration. The several seconds of residence time of analytes in the AFT provides a significant opportunity for reactant ions to interact with analyte vapors to achieve ionization. This extended reaction time, combined with the selective ionization using the nitrate reactant ions (NO3- and NO3-•HNO3), enables highly sensitive explosives detection. Observed signals from diluted explosive vapors indicate detection limits below 10 ppqv using selected ion monitoring (SIM) of the explosive-nitrate adduct at m/z 349, 378, 284 and 289 for tetryl, PETN, RDX and NG respectively. Also provided is a demonstration of the vapor detection from 10 different energetic formulations, including double base propellants, plastic explosives and commercial blasting explosives using SIM for the NG, PETN and RDX product ions.

  3. Direct real-time detection of vapors from explosive compounds.

    PubMed

    Ewing, Robert G; Clowers, Brian H; Atkinson, David A

    2013-11-19

    The real-time detection of vapors from low volatility explosives including PETN, tetryl, RDX, and nitroglycerine along with various compositions containing these substances was demonstrated. This was accomplished with an atmospheric flow tube (AFT) using a nonradioactive ionization source coupled to a mass spectrometer. Direct vapor detection was accomplished in less than 5 s at ambient temperature without sample preconcentration. The several seconds of residence time of analytes in the AFT provided a significant opportunity for reactant ions to interact with analyte vapors to achieve ionization. This extended reaction time, combined with the selective ionization using the nitrate reactant ions (NO3(-) and NO3(-)HNO3), enabled highly sensitive explosives detection from explosive vapors present in ambient laboratory air. Observed signals from diluted explosive vapors indicated detection limits below 10 ppqv using selected ion monitoring (SIM) of the explosive-nitrate adduct at m/z 349, 378, 284, and 289 for tetryl, PETN, RDX, and NG, respectively. Also provided is a demonstration of the vapor detection from 10 different energetic formulations sampled in ambient laboratory air, including double base propellants, plastic explosives, and commercial blasting explosives using SIM for the NG, PETN, and RDX product ions. PMID:24090362

  4. Direct mass spectrometric detection of trace explosives in soil samples.

    PubMed

    Ma, Lipo; Xin, Bin; Chen, Yi

    2012-04-01

    The detection of explosives in soil is of great significance in public security programmes and environmental science. In the present work, a ppb-level method was established to directly detect the semi-volatile explosives, RDX and TNT, present in complex soil samples. The method used thermal sampling technique and a direct current atmospheric pressure glow discharge source mounted with a brass cylinder electrode (9 mm × 4.6 mm i.d./5.6 mm o.d.) to face the samples, requiring no sample pretreatment steps such as soil extraction (about ten hours). It was characterized by the merits of easy operation, high sensitivity and fast speed, and has been validated by real soil samples from various locations around a factory or firecracker releasing fields. It took only 5 min per sample, with the limit of detection down to 0.5 ppb (S/N = 3) trinitrohexahydro-1,3,5-triazine in soils heated at 170 °C. It is also extendable to the analysis of other volatile analytes. PMID:22363928

  5. Monthly modulation in dark matter direct-detection experiments

    NASA Astrophysics Data System (ADS)

    Britto, Vivian; Meyers, Joel

    2015-11-01

    The signals in dark matter direct-detection experiments should exhibit modulation signatures due to the Earth's motion with respect to the Galactic dark matter halo. The annual and daily modulations, due to the Earth's revolution about the Sun and rotation about its own axis, have been explored previously. Monthly modulation is another such feature present in direct detection signals, and provides a nearly model-independent method of distinguishing dark matter signal events from background. We study here monthly modulations in detail for both WIMP and WISP dark matter searches, examining both the effect of the motion of the Earth about the Earth-Moon barycenter and the gravitational focusing due to the Moon. For WIMP searches, we calculate the monthly modulation of the count rate and show the effects are too small to be observed in the foreseeable future. For WISP dark matter experiments, we show that the photons generated by WISP to photon conversion have frequencies which undergo a monthly modulating shift which is detectable with current technology and which cannot in general be neglected in high resolution WISP searches.

  6. Direct and indirect detection of dissipative dark matter

    SciTech Connect

    Fan, JiJi; Katz, Andrey; Shelton, Jessie E-mail: katz.andrey@gmail.com

    2014-06-01

    We study the constraints from direct detection and solar capture on dark matter scenarios with a subdominant dissipative component. This dissipative dark matter component in general has both a symmetric and asymmetric relic abundance. Dissipative dynamics allow this subdominant dark matter component to cool, resulting in its partial or total collapse into a smaller volume inside the halo (e.g., a dark disk) as well as a reduced thermal velocity dispersion compared to that of normal cold dark matter. We first show that these features considerably relax the limits from direct detection experiments on the couplings between standard model (SM) particles and dissipative dark matter. On the other hand, indirect detection of the annihilation of the symmetric dissipative dark matter component inside the Sun sets stringent and robust constraints on the properties of the dissipative dark matter. In particular, IceCube observations force dissipative dark matter particles with mass above 50 GeV to either have a small coupling to the SM or a low local density in the solar system, or to have a nearly asymmetric relic abundance. Possible helioseismology signals associated with purely asymmetric dissipative dark matter are discussed, with no present constraints.

  7. Clustering and community detection in directed networks: A survey

    NASA Astrophysics Data System (ADS)

    Malliaros, Fragkiskos D.; Vazirgiannis, Michalis

    2013-12-01

    Networks (or graphs) appear as dominant structures in diverse domains, including sociology, biology, neuroscience and computer science. In most of the aforementioned cases graphs are directed - in the sense that there is directionality on the edges, making the semantics of the edges nonsymmetric as the source node transmits some property to the target one but not vice versa. An interesting feature that real networks present is the clustering or community structure property, under which the graph topology is organized into modules commonly called communities or clusters. The essence here is that nodes of the same community are highly similar while on the contrary, nodes across communities present low similarity. Revealing the underlying community structure of directed complex networks has become a crucial and interdisciplinary topic with a plethora of relevant application domains. Therefore, naturally there is a recent wealth of research production in the area of mining directed graphs - with clustering being the primary method sought and the primary tool for community detection and evaluation. The goal of this paper is to offer an in-depth comparative review of the methods presented so far for clustering directed networks along with the relevant necessary methodological background and also related applications. The survey commences by offering a concise review of the fundamental concepts and methodological base on which graph clustering algorithms capitalize on. Then we present the relevant work along two orthogonal classifications. The first one is mostly concerned with the methodological principles of the clustering algorithms, while the second one approaches the methods from the viewpoint regarding the properties of a good cluster in a directed network. Further, we present methods and metrics for evaluating graph clustering results, demonstrate interesting application domains and provide promising future research directions.

  8. Functional self-assembling bolaamphiphilic polydiacetylenes as colorimetric sensor scaffolds

    SciTech Connect

    Song, Jie; Cisar, Justin S.; Bertozzi, Carolyn R.

    2004-05-28

    Conjugated polymers capable of responding to external stimuli by changes in optical, electrical or electrochemical properties can be used for the construction of direct sensing devices. Polydiacetylene-based systems are attractive for sensing applications due to their colorimetric response to changes in the local environment. Here we present the design, preparation and characterization of self-assembling functional bolaamphiphilic polydiacetylenes (BPDAs) inspired by Nature's strategy for membrane stabilization. We show that by placing polar headgroups on both ends of the diacetylene lipids in a transmembranic fashion, and altering the chemical nature of the polar surface residues, the conjugated polymers can be engineered to display a range of radiation-, thermal- and pH-induced colorimetric responses. We observed dramatic nanoscopic morphological transformations accompanying charge-induced chromatic transitions, suggesting that both side chain disordering and main chain rearrangement play important roles in altering the effective conjugation lengths of the poly(ene-yne). These results establish the foundation for further development of BPDA-based colorimetric sensors.

  9. Ultrabroadband direct detection of nonclassical photon statistics at telecom wavelength

    PubMed Central

    Wakui, Kentaro; Eto, Yujiro; Benichi, Hugo; Izumi, Shuro; Yanagida, Tetsufumi; Ema, Kazuhiro; Numata, Takayuki; Fukuda, Daiji; Takeoka, Masahiro; Sasaki, Masahide

    2014-01-01

    Broadband light sources play essential roles in diverse fields, such as high-capacity optical communications, optical coherence tomography, optical spectroscopy, and spectrograph calibration. Although a nonclassical state from spontaneous parametric down-conversion may serve as a quantum counterpart, its detection and characterization have been a challenging task. Here we demonstrate the direct detection of photon numbers of an ultrabroadband (110 nm FWHM) squeezed state in the telecom band centred at 1535 nm wavelength, using a superconducting transition-edge sensor. The observed photon-number distributions violate Klyshko's criterion for the nonclassicality. From the observed photon-number distribution, we evaluate the second- and third-order correlation functions, and characterize a multimode structure, which implies that several tens of orthonormal modes of squeezing exist in the single optical pulse. Our results and techniques open up a new possibility to generate and characterize frequency-multiplexed nonclassical light sources for quantum info-communications technology. PMID:24694515

  10. Direct electrochemical sensor for fast reagent-free DNA detection.

    PubMed

    Komarova, Elena; Aldissi, Matt; Bogomolova, Anastasia

    2005-07-15

    A novel reagentless direct electrochemical DNA sensor has been developed using ultrathin films of the conducting polymer polypyrrole doped with an oligonucleotide probe. Our goal was to develop a prototype electrochemical DNA sensor for detection of a biowarfare pathogen, variola major virus. The sensor has been optimized for higher specificity and sensitivity. It was possible to detect 1.6 fmol of complementary oligonucleotide target in 0.1 ml in seconds by using chronoamperometry. The sensitivity of the developed sensor is comparable to indirect electrochemical DNA sensors, which use electrochemical labels and reagent-intensive amplification. The developed sensing electrode is reusable, highly stable and suitable for storage in solution or in dry state. PMID:15967367

  11. Theoretical antineutrino detection, direction and ranging at long distances

    NASA Astrophysics Data System (ADS)

    Jocher, Glenn R.; Bondy, Daniel A.; Dobbs, Brian M.; Dye, Stephen T.; Georges, James A.; Learned, John G.; Mulliss, Christopher L.; Usman, Shawn

    2013-06-01

    In this paper we introduce the concept of what we call NUDAR (NeUtrino Direction and Ranging), making the point that measurements of the observed energy and direction vectors can be employed to passively deduce the exact three-dimensional location and thermal power of geophysical and anthropogenic neutrino sources from even a single detector. Earlier studies have presented the challenges of long-range detection, dominated by the unavoidable inverse-square falloff in neutrinos, which force the use of kiloton scale detectors beyond a few kilometers. Earlier work has also presented the case for multiple detectors, and has reviewed the background challenges. We present the most precise background estimates to date, all handled in full three dimensions, as functions of depth and geographical location. For the present calculations, we consider a hypothetical 138 kiloton detector which can be transported to an ocean site and deployed to an operational depth. We present a Bayesian estimation framework to incorporate any a priori knowledge of the reactor that we are trying to detect, as well as the estimated uncertainty in the background and the oscillation parameters. Most importantly, we fully employ the knowledge of the reactor spectrum and the distance-dependent effects of neutrino oscillations on such spectra. The latter, in particular, makes possible determination of range from one location, given adequate signal statistics. Further, we explore the rich potential of improving detection with even modest improvements in individual neutrino direction determination. We conclude that a 300 MWth reactor can indeed be geolocated, and its operating power estimated with one or two detectors in the hundred kiloton class at ranges out to a few hundred kilometers. We note that such detectors would have natural and non-interfering utility for scientific studies of geo-neutrinos, neutrino oscillations, and astrophysical neutrinos. This motivates the development of cost effective methods of constructing and deploying such next generation detectors.

  12. Direct detection of Vibrio cholerae in stool samples.

    PubMed Central

    Varela, P; Pollevick, G D; Rivas, M; Chinen, I; Binsztein, N; Frasch, A C; Ugalde, R A

    1994-01-01

    A direct method to detect Vibrio cholerae in stool samples was developed by using a PCR procedure that did not require a DNA purification step. Dilution (1/100) of stool samples prevented inhibition of the reaction by contaminants, and two consecutive PCRs, the second one with a nested primer, achieved the desired sensitivity. Comparison of the results obtained from stool swab samples processed by the two-step PCR and by an enzyme-linked immunosorbent assay using GM1 as the capture molecule showed that the former is more sensitive and gave positive results even when V. cholerae was not culturable or dead. Images PMID:8051251

  13. Direct/indirect detection signatures of nonthermally produced dark matter

    SciTech Connect

    Nagai, Minoru; Nakayama, Kazunori

    2008-09-15

    We study direct and indirect detection possibilities of neutralino dark matter produced nonthermally by, e.g., the decay of long-lived particles, as is easily implemented in the case of anomaly or mirage-mediation models. In this scenario, large self-annihilation cross sections are required to account for the present dark matter abundance, and it leads to significant enhancement of the gamma-ray signature from the galactic center and the positron flux from the dark matter annihilation. It is found that GLAST and PAMELA will find the signal or give tight constraints on such nonthermal production scenarios of neutralino dark matter.

  14. Passive, Direct-Read Monitoring System for Selective Detection and Quantification of Hydrogen Chloride

    NASA Technical Reports Server (NTRS)

    Chapman, K. B.; Mihaylov, G. M.; Kirollos, K. S.

    2000-01-01

    Monitoring the exposure of an employee to hydrogen chloride or hydrochloric acid in the presence of other acids has been a challenge to the industrial hygiene community. The capability of a device to differentiate the levels of acid vapors would allow for more accurate determinations of exposure and therefore improved occupational health. In this work, a selective direct-read colorimetric badge system was validated for Short Term Exposure Limit (STEL) monitoring of hydrogen chloride. The passive colorimetric badge system consists of a direct reading badge and a color scale. The badge has a coated indicator layer with a diffusive resistance in the shape of an exclamation mark. An exclamation mark will appear if hydrogen chloride is present in the atmosphere at concentrations at or above 2.0 ppm. By using the color scale, the intensity of the color formed on the badge can be further quantified up to 25 ppm. The system was validated according to a protocol based on the NIOSH Protocol for the Evaluation of Passive Monitors. The badge was exposed to relative humidities ranging from 11% to 92%, temperatures ranging from 7 C to 400 C and air velocities ranging from 5 cm/sec to 170 cm/sec. All experiments were conducted in a laboratory vapor generation system. Hydrofluoric acid, nitric acid, sulfuric acid, chlorine, hydrogen sulfide and organic acids showed no effect on the performance of the hydrogen chloride monitoring system. The passive badge and color scale system exceeded the accuracy requirements as defined by NIOSH. At ambient conditions, the mean coefficient of variation was 10.86 and the mean bias was 1.3%. This data was presented previously at the American Industrial Hygiene Conference and Exposition in Toronto, Canada in June 1999.

  15. Active THz medical imaging using broadband direct detection

    NASA Astrophysics Data System (ADS)

    Taylor, Zachary D.; Garritano, James; Tewari, Priyamvada; Diebold, Eric; Sung, Shijun; Bajwa, Neha; Nowroozi, Bryan; Stojadinovic, Alexander; Llombart, Nuria; Brown, Elliott R.; Grundfest, Warren S.

    2013-03-01

    Research in THz imaging is generally focused on three primary application areas: medical, security, and nondestructive evaluation (NDE). While work in THz security imaging and personnel screening is populated by a number of different active and passive system architectures, research in medical imaging in is generally performed with THz time-domain systems. These systems typically employ photoconductive or electro-optic source/detector pairs and can acquire depth resolved data or spectrally resolved pixels by synchronously sampling the electric field of the transmitted/reflected waveform. While time-domain is a very powerful scientific technique, results reported in the literature suggest that desired THz contrast in medical imaging may not require the volume of data accessible from time-resolved measurements and that a simpler direct detection, active technique may be sufficient for specific applications. In this talk we discuss an active direct detection reflectometer system architecture operating at a center frequency of ~ 525 GHz that uses a photoconductive source and schottky diode detector. This design takes advantage or radar-like pulse rectification and novel reflective optical design to achieve high target imaging contrast with significant potential for high speed acquisition time. Results in spatially resolved hydration mapping of burn wounds are presented and future outlooks discussed.

  16. Directional detection of dark matter in universal bound states

    NASA Astrophysics Data System (ADS)

    Laha, Ranjan

    2015-10-01

    It has been suggested that several small-scale structure anomalies in ? CDM cosmology can be solved by strong self-interaction between dark matter particles. It was shown by Braaten and Hammer [Phys. Rev. D 88, 063511 (2013), 10.1103/PhysRevD.88.063511] that the presence of a near threshold S-wave resonance can make the scattering cross section at nonrelativistic speeds come close to saturating the unitarity bound. This can result in the formation of a stable bound state of two asymmetric dark matter particles (which we call darkonium). The work of Laha and Braaten [Phys. Rev. D, 89, 103510 (2014), 10.1103/PhysRevD.89.103510] studied the nuclear recoil energy spectrum in dark matter direct detection experiments due to this incident bound state. Here we study the angular recoil spectrum and show that it is uniquely determined up to normalization by the S-wave scattering length. Observing this angular recoil spectrum in a dark matter directional detection experiment will uniquely determine many of the low-energy properties of dark matter independent of the underlying dark matter microphysics.

  17. The Direct Detectability of Giant Exoplanets in the Optical

    NASA Astrophysics Data System (ADS)

    Greco, Johnny P.; Burrows, Adam

    2015-08-01

    Motivated by the possibility that a coronagraph will be put on the Wide-field Infrared Survey Telescope (WFIRST)/Astrophysics Focused Telescope Assets (AFTA), we explore the direct detectability of extrasolar giant planets (EGPs) in the optical. We quantify a planet's detectability by the fraction of its orbit for which it is in an observable configuration ({f}{obs}). Using a suite of Monte Carlo experiments, we study the dependence of {f}{obs} upon the inner working angle (IWA) and minimum achievable contrast ({C}{min}) of the direct-imaging observatory; the planet's phase function, geometric albedo, single-scattering albedo, radius, and distance from Earth; and the semimajor axis distribution of EGPs. We calculate phase functions for a given geometric or single-scattering albedo, assuming various scattering mechanisms. We find that the Lambertian phase function can predict significantly larger {f}{obs}s with respect to the more realistic Rayleigh phase function. For observations made with WFIRST/AFTA's baseline capabilities ({C}{min} {10}-9, {IWA} 0\\buildrel{\\prime\\prime}\\over{.} 2), Jupiter-like planets orbiting stars within 10, 30, and 50 pc of Earth have volume-averaged observability fractions of 12%, 3%, and 0.5%, respectively. At 10 pc, such observations yield {f}{obs}\\gt 1% for low- to modest-eccentricity planets with semimajor axes in the range 2-10 AU. If {C}{min}={10}-10, this range extends to 35 AU. We find that, in all but the most optimistic configurations, the probability for detection in a blind search is low (< 5%). However, with orbital parameter constraints from long-term radial-velocity campaigns and Gaia astrometry, the tools we develop in this work can be used to determine both the most promising systems to target and when to observe them.

  18. Understanding WIMP-baryon interactions with direct detection: a roadmap

    SciTech Connect

    Gluscevic, Vera; Peter, Annika H.G. E-mail: apeter@physics.osu.edu

    2014-09-01

    We study prospects of dark-matter direct-detection searches for probing non-relativistic effective theory for WIMP-baryon scattering. We simulate a large set of noisy recoil-energy spectra for different scattering scenarios (beyond the standard momentum-independent contact interaction), for Generation 2 and futuristic experiments. We analyze these simulations and quantify the probability of successfully identifying the operator governing the scattering, if a WIMP signal is observed. We find that the success rate depends on a combination of factors: the WIMP mass, the mediator mass, the type of interaction, and the experimental energy window. For example, for a 20 GeV WIMP, Generation 2 is only likely to identify the right operator if the interaction is Coulomb-like, and is unlikely to do so in any other case. For a WIMP with a mass of 200 GeV or higher, success is almost guaranteed. We also find that, regardless of the scattering model and the WIMP parameters, a single Generation 2 experiment is unlikely to successfully discern the momentum dependence of the underlying operator on its own, but prospects improve drastically when experiments with different target materials and energy windows are analyzed jointly. Furthermore, we examine the quality of parameter estimation and degeneracies in the multi-dimensional parameter space of the effective theory. We find in particular that the resulting WIMP mass estimates can be severely biased if data are analyzed assuming the standard (momentum-independent) operator while the actual operator has momentum-dependence. Finally, we evaluate the ultimate reach of direct detection, finding that the prospects for successful operator selection prior to reaching the irreducible backgrounds are excellent, if the signal is just below the current limits, but slim if Generation 2 does not report WIMP detection.

  19. Development of a novel gamma probe for detecting radiation direction

    NASA Astrophysics Data System (ADS)

    Pani, R.; Pellegrini, R.; Cinti, M. N.; Longo, M.; Donnarumma, R.; D'Alessio, A.; Borrazzo, C.; Pergola, A.; Ridolfi, S.; De Vincentis, G.

    2016-01-01

    Spatial localization of radioactive sources is currently a main issue interesting different fields, including nuclear industry, homeland security as well as medical imaging. It is currently achieved using different systems, but the development of technologies for detecting and characterizing radiation is becoming important especially in medical imaging. In this latter field, radiation detection probes have long been used to guide surgery, thanks to their ability to localize and quantify radiopharmaceutical uptake even deep in tissue. Radiolabelled colloid is injected into, or near to, the tumor and the surgeon uses a hand-held radiation detector, the gamma probe, to identify lymph nodes with radiopharmaceutical uptkake. The present work refers to a novel scintigraphic goniometric probe to identify gamma radiation and its direction. The probe incorporates several scintillation crystals joined together in a particular configuration to provide data related to the position of a gamma source. The main technical characteristics of the gamma locator prototype, i.e. sensitivity, spatial resolution and detection efficiency, are investigated. Moreover, the development of a specific procedure applied to the images permits to retrieve the source position with high precision with respect to the currently used gamma probes. The presented device shows a high sensitivity and efficiency to identify gamma radiation taking a short time (from 30 to 60 s). Even though it was designed for applications in radio-guided surgery, it could be used for other purposes, as for example homeland security.

  20. Isothermal Detection of Mycoplasma pneumoniae Directly from Respiratory Clinical Specimens.

    PubMed

    Petrone, Brianna L; Wolff, Bernard J; DeLaney, Alexandra A; Diaz, Maureen H; Winchell, Jonas M

    2015-09-01

    Mycoplasma pneumoniae is a leading cause of community-acquired pneumonia (CAP) across patient populations of all ages. We have developed a loop-mediated isothermal amplification (LAMP) assay that enables rapid, low-cost detection of M. pneumoniae from nucleic acid extracts and directly from various respiratory specimen types. The assay implements calcein to facilitate simple visual readout of positive results in approximately 1 h, making it ideal for use in primary care facilities and resource-poor settings. The analytical sensitivity of the assay was determined to be 100 fg by testing serial dilutions of target DNA ranging from 1 ng to 1 fg per reaction, and no cross-reactivity was observed against 17 other Mycoplasma species, 27 common respiratory agents, or human DNA. We demonstrated the utility of this assay by testing nucleic acid extracts (n = 252) and unextracted respiratory specimens (n = 72) collected during M. pneumoniae outbreaks and sporadic cases occurring in the United States from February 2010 to January 2014. The sensitivity of the LAMP assay was 88.5% tested on extracted nucleic acid and 82.1% evaluated on unextracted clinical specimens compared to a validated real-time PCR test. Further optimization and improvements to this method may lead to the availability of a rapid, cost-efficient laboratory test for M. pneumoniae detection that is more widely available to primary care facilities, ultimately facilitating prompt detection and appropriate responses to potential M. pneumoniae outbreaks and clusters within the community. PMID:26179304

  1. Halo-independent direct detection analyses without mass assumptions

    SciTech Connect

    Anderson, Adam J.; Fox, Patrick J.; Kahn, Yonatan; McCullough, Matthew

    2015-10-06

    Results from direct detection experiments are typically interpreted by employing an assumption about the dark matter velocity distribution, with results presented in the mχ – σn plane. Recently methods which are independent of the DM halo velocity distribution have been developed which present results in the vmin – g~ plane, but these in turn require an assumption on the dark matter mass. Here we present an extension of these halo-independent methods for dark matter direct detection which does not require a fiducial choice of the dark matter mass. With a change of variables from vmin to nuclear recoil momentum (pR), the full halo-independent content of an experimental result for any dark matter mass can be condensed into a single plot as a function of a new halo integral variable, which we call tilde h(pR). The entire family of conventional halo-independent tilde g~(vmin) plots for all DM masses are directly found from the single tilde h~(pR) plot through a simple rescaling of axes. By considering results in tildeh~(pR) space, one can determine if two experiments are inconsistent for all masses and all physically possible halos, or for what range of dark matter masses the results are inconsistent for all halos, without the necessity of multiple tilde g~(vmin) plots for different DM masses. As a result, we conduct a sample analysis comparing the CDMS II Si events to the null results from LUX, XENON10, and SuperCDMS using our method and discuss how the results can be strengthened by imposing the physically reasonable requirement of a finite halo escape velocity.

  2. Halo-independent direct detection analyses without mass assumptions

    NASA Astrophysics Data System (ADS)

    Anderson, Adam J.; Fox, Patrick J.; Kahn, Yonatan; McCullough, Matthew

    2015-10-01

    Results from direct detection experiments are typically interpreted by employing an assumption about the dark matter velocity distribution, with results presented in the m?-?n plane. Recently methods which are independent of the DM halo velocity distribution have been developed which present results in the vmin-tilde g plane, but these in turn require an assumption on the dark matter mass. Here we present an extension of these halo-independent methods for dark matter direct detection which does not require a fiducial choice of the dark matter mass. With a change of variables from vmin to nuclear recoil momentum (pR), the full halo-independent content of an experimental result for any dark matter mass can be condensed into a single plot as a function of a new halo integral variable, which we call tilde h(pR). The entire family of conventional halo-independent tilde g(vmin) plots for all DM masses are directly found from the single tilde h(pR) plot through a simple rescaling of axes. By considering results in tilde h(pR) space, one can determine if two experiments are inconsistent for all masses and all physically possible halos, or for what range of dark matter masses the results are inconsistent for all halos, without the necessity of multiple tilde g(vmin) plots for different DM masses. We conduct a sample analysis comparing the CDMS II Si events to the null results from LUX, XENON10, and SuperCDMS using our method and discuss how the results can be strengthened by imposing the physically reasonable requirement of a finite halo escape velocity.

  3. Halo-independent direct detection analyses without mass assumptions

    DOE PAGESBeta

    Anderson, Adam J.; Fox, Patrick J.; Kahn, Yonatan; McCullough, Matthew

    2015-10-06

    Results from direct detection experiments are typically interpreted by employing an assumption about the dark matter velocity distribution, with results presented in the mχ – σn plane. Recently methods which are independent of the DM halo velocity distribution have been developed which present results in the vmin – g~ plane, but these in turn require an assumption on the dark matter mass. Here we present an extension of these halo-independent methods for dark matter direct detection which does not require a fiducial choice of the dark matter mass. With a change of variables from vmin to nuclear recoil momentum (pR),more » the full halo-independent content of an experimental result for any dark matter mass can be condensed into a single plot as a function of a new halo integral variable, which we call tilde h(pR). The entire family of conventional halo-independent tilde g~(vmin) plots for all DM masses are directly found from the single tilde h~(pR) plot through a simple rescaling of axes. By considering results in tildeh~(pR) space, one can determine if two experiments are inconsistent for all masses and all physically possible halos, or for what range of dark matter masses the results are inconsistent for all halos, without the necessity of multiple tilde g~(vmin) plots for different DM masses. As a result, we conduct a sample analysis comparing the CDMS II Si events to the null results from LUX, XENON10, and SuperCDMS using our method and discuss how the results can be strengthened by imposing the physically reasonable requirement of a finite halo escape velocity.« less

  4. Halo-independent direct detection analyses without mass assumptions

    SciTech Connect

    Anderson, Adam J.; Fox, Patrick J.; Kahn, Yonatan; McCullough, Matthew

    2015-10-06

    Results from direct detection experiments are typically interpreted by employing an assumption about the dark matter velocity distribution, with results presented in the m{sub χ}−σ{sub n} plane. Recently methods which are independent of the DM halo velocity distribution have been developed which present results in the v{sub min}−g-tilde plane, but these in turn require an assumption on the dark matter mass. Here we present an extension of these halo-independent methods for dark matter direct detection which does not require a fiducial choice of the dark matter mass. With a change of variables from v{sub min} to nuclear recoil momentum (p{sub R}), the full halo-independent content of an experimental result for any dark matter mass can be condensed into a single plot as a function of a new halo integral variable, which we call h-til-tilde(p{sub R}). The entire family of conventional halo-independent g-tilde(v{sub min}) plots for all DM masses are directly found from the single h-tilde(p{sub R}) plot through a simple rescaling of axes. By considering results in h-tilde(p{sub R}) space, one can determine if two experiments are inconsistent for all masses and all physically possible halos, or for what range of dark matter masses the results are inconsistent for all halos, without the necessity of multiple g-tilde(v{sub min}) plots for different DM masses. We conduct a sample analysis comparing the CDMS II Si events to the null results from LUX, XENON10, and SuperCDMS using our method and discuss how the results can be strengthened by imposing the physically reasonable requirement of a finite halo escape velocity.

  5. Gold nanoparticles based colorimetric nanodiagnostics for cancer and infectious diseases

    NASA Astrophysics Data System (ADS)

    Valentini, Paola; Persano, Stefano; Cecere, Paola; Sabella, Stefania; Pompa, Pier Paolo

    2014-03-01

    Traditional in vitro diagnostics requires specialized laboratories and costly instrumentation, both for the amplification of nucleic acid targets (usually achieved by PCR) and for the assay readout, often based on fluorescence. We are developing hybrid nanomaterials-based sensors for the rapid and low-cost diagnosis of various disease biomarkers, for applications in portable platforms for diagnostics at the point-of-care. To this aim, we exploited the size and distancedependent optical properties of gold nanoparticles (AuNPs) to achieve colorimetric detection. Moreover, in order to avoid the complexity of thermal cycles associated to traditional PCR, the design of our systems includes signal amplification schemes, achieved by the use of enzymes (nucleases, helicase) or DNAzymes. Focused on instrument-free and sensitive detection, we carefully combined the intrinsic sensitivity by multivalency of functionalized AuNPs with isothermal and non-stringent enzyme-aided reaction conditions, controlled AuNPs aggregates, universal reporters and magnetic microparticles, the latter used both as a substrate and as a means for the colorimetric detection. We obtained simple and robust assays for the sensitive (pM range or better) naked-eye detection of cancer or infectious diseases (HPV, HCV) biomarkers, requiring no instrumentation except for a simple heating plate. Finally, we are also developing non-medical applications of these bio-nanosensors, such as in the development of on-field rapid tests for the detection of pollutants and other food and water contaminants.

  6. Photoacoustic and Colorimetric Visualization of Latent Fingerprints.

    PubMed

    Song, Kai; Huang, Peng; Yi, Chenglin; Ning, Bo; Hu, Song; Nie, Liming; Chen, Xiaoyuan; Nie, Zhihong

    2015-12-22

    There is a high demand on a simple, rapid, accurate, user-friendly, cost-effective, and nondestructive universal method for latent fingerprint (LFP) detection. Herein, we describe a combination imaging strategy for LFP visualization with high resolution using poly(styrene-alt-maleic anhydride)-b-polystyrene (PSMA-b-PS) functionalized gold nanoparticles (GNPs). This general approach integrates the merits of both colorimetric imaging and photoacoustic imaging. In comparison with the previous methods, our strategy is single-step and does not require the signal amplification by silver staining. The PSMA-b-PS functionalized GNPs have good stability, tunable color, and high affinity for universal secretions (proteins/polypeptides/amino acids), which makes our approach general and flexible for visualizing LFPs on different substrates (presumably with different colors) and from different people. Moreover, the unique optical property of GNPs enables the photoacoustic imaging of GNPs-deposited LFPs with high resolution. This allows observation of level 3 hyperfine features of LFPs such as the pores and ridge contours by photoacoustic imaging. This technique can potentially be used to identify chemicals within LFP residues. We believe that this dual-modality imaging of LFPs will find widespread use in forensic investigations and medical diagnostics. PMID:26528550

  7. Direct Spectral Detection: An Efficient Method to Detect and Characterize Binary Systems

    NASA Astrophysics Data System (ADS)

    Gullikson, Kevin; Kraus, Adam; Dodson-Robinson, Sarah; Jaffe, Daniel; Lee, Jeong-Eun; Mace, Gregory N.; MacQueen, Phillip; Park, Sunkyung; Riddle, Andrew

    2016-01-01

    Young, intermediate-mass stars are experiencing renewed interest as targets for direct-imaging planet searches. However, these types of stars are part of multiple systems more often than not. Close stellar companions affect the formation and orbital architecture of planetary systems, and the properties of the companions can help constrain the binary formation mechanism. Unfortunately, close companions are difficult and expensive to detect with imaging techniques. In this paper, we describe the direct spectral detection method wherein a high-resolution spectrum of the primary is cross-correlated against a template for a companion star. Variants of this method have previously been used to search for stellar, brown dwarf, and even planetary companions. We show that the direct spectral detection method can detect companions as late as M-type orbiting A0 or earlier primary stars in a single epoch on small-aperture telescopes. In addition to estimating the detection limits, we determine the sources of uncertainty in characterizing the companion temperature, and find that large systematic biases can exist. After calibrating the systematic biases with synthetic binary star observations, we apply the method to a sample of 34 known binary systems with an A- or B-type primary star. We detect nine total companions, including four of the five known companions with literature temperatures between 4000 K \\lt T\\lt 6000 {{K}}, the temperature range for which our method is optimized. We additionally characterize the companion for the first time in two previously single-lined binary systems and one binary identified with speckle interferometry. This method provides an inexpensive way to use small-aperture telescopes to detect binary companions with moderate mass ratios, and is competitive with high-resolution imaging techniques inside 100-200 mas.

  8. Detections and confirmations of electromagnetic pulses directly excited by earthquakes

    NASA Astrophysics Data System (ADS)

    Tsutsui, M.

    2013-12-01

    In order to detect and confirm electromagnetic (EM) pulses directly excited by earthquakes, we have been observing EM noise in boreholes of 100 m in depth at various places such as on mountain sides and seashores, inserting EM sensor systems into the boreholes. In the observations, we detected tremendous number of EM pulses of a few kHz with duration of a few millisecond. From detailed analysis of these EM pulses, we found that almost all of these EM pulses were lightning and artificial ones, and we could not confirm any earthquake-related EM pulse at all. The reason why earthquake-related EM pulses could not be detected in the earth was considered that the amplitude of the EM pulses would be strongly decayed during their propagations in the earth due to high electrical conductivity of the earth's medium. The decay rate is generally given by a specific distance so-called 'Skin depth ' through which the amplitude decays to 1/e (e = 2.718), and the skin depth is inversely proportional to square root of EM frequency. This means that high frequency EM waves decay and fade out in a short distance but lower frequency ones can survive for a long distance. Therefore EM waves of a few kHz had been severe to propagate for long distance in the earth. So we shifted down the monitoring frequency to the range of a few tens of Hz. As the result, we have finally detected earthquake-excited EM pulses in the earth and above the ground. By simultaneous capturing of waveforms of detected EM pulses and of seismic accelerations measured at the same observation site, we have confirmed close relationship between earthquakes and EM pulses, in which the waveform of magnetic component clearly shows primary tremor corresponding to seismic P-wave although it can't be seen in the waveform of seismic acceleration. Furthermore, by a laboratory experiment on giving stress impact to a granite pillar, excitation mechanism of EM pulses from granite has been confirmed as the Piezo-electric effect. These results have proved that seismic P-wave could be easily generated even by extremely weak stress impact to earth's crusts compared to that for causing earthquakes, and that EM waves could be excited by small seismic vibrations. Furthermore, we found an analogy of situations in EM pulse excitations between in the laboratory experiment and in active faults, which means that EM pulses can be excited by the fractures of small stones in active faults before earthquakes. So we here propose a method for detecting EM pulses as a precursor of earthquakes.

  9. Tropospheric Wind Profile Measurements with a Direct Detection Doppler Lidar

    NASA Technical Reports Server (NTRS)

    Gentry, Bruce M.; Li, Steven X.; Korb, C. Laurence; Chen, Huailin; Mathur, Savyasachee

    1998-01-01

    Research has established the importance of global tropospheric wind measurements for large scale improvements in numerical weather prediction. In addition, global wind measurements provide data that are fundamental to the understanding and prediction of global climate change. These tasks are closely linked with the goals of the NASA Earth Science Enterprise and Global Climate Change programs. NASA Goddard has been actively involved in the development of direct detection Doppler lidar methods and technologies to meet the wind observing needs of the atmospheric science community. In this paper we describe a recently developed prototype wind lidar system using a direct detection Doppler technique for measuring wind profiles from the surface through the troposphere. This system uses a pulsed ND:YAG laser operating at 1064 nm as the transmitter. The laser pulse is directed to the atmosphere using a 40 cm diameter scan mirror. The portion of the laser energy backscattered from aerosols and molecules is collected by a 40 cm diameter telescope and coupled via fiber optics into the Doppler receiver. Single photon counting APD's are used to detect the atmospheric backscattered signal. The principle element of the receiver is a dual bandpass tunable Fabry Perot etalon which analyzes the Doppler shift of the incoming laser signal using the double edge technique. The double edge technique uses two high resolution optical filters having bandpasses offset relative to one another such that the 'edge' of the first filter's transmission function crosses that of the second at the half power point. The outgoing laser frequency is located approximately at the crossover point. Due to the opposite going slopes of the edges, a Doppler shift in the atmospheric backscattered laser frequency produces a positive change in signal for one filter and a negative change in the second filter. Taking the ratio of the two edge channel signals yields a result which is directly proportional to the component of the wind along the line-of-sight of the laser. Measuring the radial wind in several directions provides sufficient information to determine the true wind speed and direction. The lidar has operated from our laboratory at Goddard since June, 1997. Wind profiles have been obtained to altitudes of 12 km with a vertical resolution of 330 in. Vector wind data are obtained by rotating the scan mirror to measure line-of-sight wind profiles for at least two azimuth angles at an elevation angle of 45 degrees. The precision of the data as determined from the standard deviation of multiple independent lidar profiles is in the range of 1 to 3 m/sec up to 10 km. Good agreement is obtained when the lidar data are compared with the upper air rawinsonde soundings taken at Dulles airport. Examples of the wind lidar data will be presented along with a description of the instrument and future developments.

  10. Detectability of Tidally Heated Exomoons Using Direct Imaging Techniques

    NASA Astrophysics Data System (ADS)

    Peters, Mary Anne; Turner, E. L.

    2013-01-01

    We determine the capability of ground and space-based observatories, both existing and planned, to directly image tidally heated exomoons orbiting exoplanets. Tidally heated exomoons, or THEMs, can conceivably be much more luminous than their host exoplanet and as little as 1000 times dimmer than the system's primary star. Tidal forces can heat THEMs at arbitrarily large angular separations from the host star, in both young and old star systems, to temperatures of hundreds or even thousands of degrees Kelvin. THEMs may thus be far easier targets for direct imaging studies than giant exoplanets which must be both young and at a large projected angular separation from their host star to be imaged with existing high contrast instrumentation. Current instruments are capable of detecting nearby THEMs with Teff ? 600K and R ? Rearth in K-band. Future mid-infrared space telescopes, such as JWST and SPICA, will be capable of directly imaging THEMs around ~25 nearby stars with Teff ? 300K and R?Rearth orbiting at angular separations ? 12AU at a 5? confidence level in a 10,000 second integration. It is feasible that previously imaged exoplanets are actually THEMs or blends of such objects with hot young planets; we speculate that Fomalhaut b could be such a case. If THEMs exist and are common (i.e., nearby), it may be far easier to directly image a THEM with surface conditions that allow for liquid water than it will be to image an Earth-like planet in the classical Habitable Zone of its primary star.

  11. Magnetic Bead-Based Colorimetric Immunoassay for Aflatoxin B1 Using Gold Nanoparticles

    PubMed Central

    Wang, Xu; Niessner, Reinhard; Knopp, Dietmar

    2014-01-01

    A competitive colorimetric immunoassay for the detection of aflatoxin B1 (AFB) has been established using biofunctionalized magnetic beads (MBs) and gold nanoparticles (GNPs). Aflatoxin B1-bovine serum albumin conjugates (AFB-BSA) modified MBs were employed as capture probe, which could specifically bind with GNP-labeled anti-AFB antibodies through immunoreaction, while such specific binding was competitively inhibited by the addition of AFB. After magnetic separation, the supernatant solution containing unbound GNPs was directly tested by UV-Vis spectroscopy. The absorption intensity was directly proportional to the AFB concentration. The influence of GNP size, incubation time and pH was investigated in detail. After optimization, the developed method could detect AFB in a linear range from 20 to 800 ng/L, with the limit of detection at 12 ng/L. The recoveries for spiked maize samples ranged from 92.8% to 122.0%. The proposed immunoassay provides a promising approach for simple, rapid, specific and cost-effective detection of toxins in the field of food safety. PMID:25405511

  12. Direct detection of dark matter in universal bound states

    NASA Astrophysics Data System (ADS)

    Laha, Ranjan; Braaten, Eric

    2014-05-01

    We study the signatures for internal structure of dark matter in direct detection experiments in the context of asymmetric self-interacting dark matter. The self-interaction cross section of two dark matter particles at low energies is assumed to come close to saturating the S-wave unitarity bound, which requires the presence of a resonance near their scattering threshold. The universality of S-wave near-threshold resonances then implies that the low-energy scattering properties of a two-body bound state of dark matter particles are completely determined by its binding energy, irrespective of the underlying microphysics. The form factor for elastic scattering of the bound state from a nucleus and the possibility of break up of the bound state produce new signatures in the nuclear recoil energy spectrum. If these features are observed in experiments, it will give a smoking-gun signature for the internal structure of dark matter.

  13. Direct-detection wind lidar operating with a multimode laser.

    PubMed

    Bruneau, Didier; Blouzon, Frdric; Spatazza, Joseph; Montmessin, Franck; Pelon, Jacques; Faure, Benot

    2013-07-10

    A direct-detection wind lidar that operates with a multimode laser has been developed and tested. The instrument exploits the light backscattered by particles using a Mach-Zehnder interferometer with an optical path difference matched to the free spectral range of the laser longitudinal modes. In addition to requiring no monomodal emission, the system requires no frequency locking between the interferometer and the laser. We report laboratory and atmospheric measurements that show that the lidar is capable of measuring the radial wind velocity with a systematic error lower than 1 ms(-1) and a random error lower than 2 ms(-1) for a signal-to-noise ratio of 100. The development is motivated by the possibility to probe wind with a compact system in planetary atmospheres. PMID:23852210

  14. Halo independent comparison of direct dark matter detection data

    SciTech Connect

    Gondolo, Paolo; Gelmini, Graciela B. E-mail: gelmini@physics.ucla.edu

    2012-12-01

    We extend the halo-independent method of Fox, Liu, and Weiner to include energy resolution and efficiency with arbitrary energy dependence, making it more suitable for experiments to use in presenting their results. Then we compare measurements and upper limits on the direct detection of low mass ( ? 10 GeV) weakly interacting massive particles with spin-independent interactions, including the upper limit on the annual modulation amplitude from the CDMS collaboration. We find that isospin-symmetric couplings are severely constrained both by XENON100 and CDMS bounds, and that isospin-violating couplings are still possible at the lowest energies, while the tension of the higher energy CoGeNT bins with the CDMS modulation constraint remains. We find the CRESST-II signal is not compatible with the modulation signals of DAMA and CoGeNT.

  15. Light magnetic dark matter in direct detection searches

    NASA Astrophysics Data System (ADS)

    Del Nobile, Eugenio; Kouvaris, Chris; Panci, Paolo; Sannino, Francesco; Virkajrvi, Jussi

    2012-08-01

    We study a fermionic Dark Matter particle carrying magnetic dipole moment and analyze its impact on direct detection experiments. In particular we show that it can accommodate the DAMA, CoGeNT and CRESST experimental results. Assuming conservative bounds, this candidate is shown not to be ruled out by the CDMS, XENON and PICASSO experiments. We offer an analytic understanding of how the long-range interaction modifies the experimental allowed regions, in the cross section versus Dark Matter mass parameter space, with respect to the typically assumed contact interaction. Finally, in the context of a symmetric Dark Matter sector, we determine the associated thermal relic density, and further provide relevant constraints imposed by indirect searches and colliders.

  16. DNA transducer-triggered signal switch for visual colorimetric bioanalysis.

    PubMed

    Chen, Wenhong; Yan, Yurong; Zhang, Ye; Zhang, Xuemei; Yin, Yibing; Ding, Shijia

    2015-01-01

    A simple and versatile colorimetric biosensor has been developed for sensitive and specific detection of a wide range of biomolecules, such as oligonucleotides and aptamer-recognized targets. Combining the signal transducer and catalyzed hairpin assembly (CHA)-based signal amplification, the target DNA binds with the hairpin DNA to form a new nucleic acid sequence and creates a toehold in the transducer for initiating the recycle amplification reaction of CHA. The catalyzed assembly process produces a large amount of G-rich DNA. In the presence of hemin, the G-rich DNA forms G-quadruplex/hemin complex and mimic horseradish peroxidase activity, which catalyzes a colorimetric reaction. Under optimal conditions, the calibration curve of synthetic target DNA has good linearity from 50 pM to 200 nM with a detection limit of 32 pM. This strategy has been successfully applied to detect S. pneumoniae as low as 156 CFU mL(-1), and shows a good specificity against closely related streptococci and major pathogenic bacteria. In addition, the developed method enables successful visual analysis of S. pneumoniae in clinical samples by the naked eye. Importantly, this method demonstrates excellent assay versatility for sensitively detecting oligonucleotides or aptamer-recognized targets. PMID:26060886

  17. DNA transducer-triggered signal switch for visual colorimetric bioanalysis

    PubMed Central

    Chen, Wenhong; Yan, Yurong; Zhang, Ye; Zhang, Xuemei; Yin, Yibing; Ding, Shijia

    2015-01-01

    A simple and versatile colorimetric biosensor has been developed for sensitive and specific detection of a wide range of biomolecules, such as oligonucleotides and aptamer-recognized targets. Combining the signal transducer and catalyzed hairpin assembly (CHA)-based signal amplification, the target DNA binds with the hairpin DNA to form a new nucleic acid sequence and creates a toehold in the transducer for initiating the recycle amplification reaction of CHA. The catalyzed assembly process produces a large amount of G-rich DNA. In the presence of hemin, the G-rich DNA forms G-quadruplex/hemin complex and mimic horseradish peroxidase activity, which catalyzes a colorimetric reaction. Under optimal conditions, the calibration curve of synthetic target DNA has good linearity from 50?pM to 200?nM with a detection limit of 32?pM. This strategy has been successfully applied to detect S. pneumoniae as low as 156?CFU mL?1, and shows a good specificity against closely related streptococci and major pathogenic bacteria. In addition, the developed method enables successful visual analysis of S. pneumoniae in clinical samples by the naked eye. Importantly, this method demonstrates excellent assay versatility for sensitively detecting oligonucleotides or aptamer-recognized targets. PMID:26060886

  18. Subcarrier multiplexing with dispersion reduction and direct detection

    DOEpatents

    Sargis, Paul D. (Modesto, CA); Haigh, Ronald E. (Tracy, CA); McCammon, Kent G. (Livermore, CA)

    1997-01-01

    An SCM system for simultaneously reducing the concomitant problems of receiver complexity and dispersion penalty and without requiring the use of an expensive, high-bandwidth optical detector. The system provides both a dispersion reduction and a direct detection to the receiver, with microwave mixers and lithium niobate external modulators that produce sidebands that are only separated by a few gigahertz from a principal laser optical carrier. Digital data streams are independently impressed upon these sidebands for transmission over an ordinary single-mode fiber. Independent high-speed data streams are upconverted to microwave frequencies. These subcarriers are then combined with a microwave power combiner and amplified with a microwave amplifier. A solid-state 1550-nm laser carrier is modulated by the microwave subcarriers. An erbium-doped fiber amplifier (EDFA) is used just prior to long-distance transmission over ordinary single-mode fiber. The transmitted optical signal may then traverse multiple EDFAs to compensate for long-haul optical fiber losses prior to detection. At a receiving end, the optical signal is split into multiple paths. The subcarrier channels are optically pre-selected using a narrowband optical filter, such as a fiber Fabry-Perot (FFP) filter. An optical detector converts the selected optical signal into a baseband electrical data stream.

  19. Subcarrier multiplexing with dispersion reduction and direct detection

    DOEpatents

    Sargis, P.D.; Haigh, R.E.; McCammon, K.G.

    1997-01-21

    An SCM system is disclosed for simultaneously reducing the concomitant problems of receiver complexity and dispersion penalty and without requiring the use of an expensive, high-bandwidth optical detector. The system provides both a dispersion reduction and a direct detection to the receiver, with microwave mixers and lithium niobate external modulators that produce sidebands that are only separated by a few gigahertz from a principal laser optical carrier. Digital data streams are independently impressed upon these sidebands for transmission over an ordinary single-mode fiber. Independent high-speed data streams are upconverted to microwave frequencies. These subcarriers are then combined with a microwave power combiner and amplified with a microwave amplifier. A solid-state 1550-nm laser carrier is modulated by the microwave subcarriers. An erbium-doped fiber amplifier (EDFA) is used just prior to long-distance transmission over ordinary single-mode fiber. The transmitted optical signal may then traverse multiple EDFAs to compensate for long-haul optical fiber losses prior to detection. At a receiving end, the optical signal is split into multiple paths. The subcarrier channels are optically pre-selected using a narrowband optical filter, such as a fiber Fabry-Perot (FFP) filter. An optical detector converts the selected optical signal into a baseband electrical data stream. 2 figs.

  20. Direct MRI detection of impending plaque development in multiple sclerosis

    PubMed Central

    Absinta, Martina; Nair, Govind; Sati, Pascal; Cortese, Irene C.M.; Filippi, Massimo

    2015-01-01

    Objectives: To detect and localize MRI signal changes prior to the parenchymal contrast enhancement that classically defines the radiologic onset of the developing white matter lesion in multiple sclerosis (MS). Methods: We reviewed 308 high-resolution (≤1 mm3 voxels) MRI scans at 3T and 7T in 29 patients with active MS. The presence of pre-parenchymal enhancement abnormalities before the appearance of parenchymal enhancement was evaluated in all available scans. Results: Pre-enhancement signal changes were noted in 26 of 162 enhancing lesions (16%) as linear enhancement of the central vein and/or perivenular hyperintense signal on T2 fluid-attenuated inversion recovery or T2* images. They occur up to 2 months before focal enhancement within the parenchyma in 10% of cases. Conclusions: In some lesions, the abrupt opening of the blood-brain barrier, detected by contrast enhancement on MRI, can have directly visible antecedent MRI changes centered on the central vein. We propose that these findings might be the basis for prior reports of subtle pre-parenchymal enhancement changes in quantitative MRI indices. In line with the venulocentric model of lesion development, our findings are consistent with the centrality of early perivenular events in lesion formation in vivo. PMID:26401516

  1. Direct x-ray detection with conjugated polymer devices

    NASA Astrophysics Data System (ADS)

    Boroumand, F. A.; Zhu, M.; Dalton, A. B.; Keddie, J. L.; Sellin, P. J.; Gutierrez, J. J.

    2007-07-01

    The authors report the first direct detection of x-ray induced photocurrents in thick films (up to 20?m) of conjugated polymers. Schottky-based "sandwich" structures were fabricated from layers of either poly[1-methoxy-4-(2-ethylhexyloxy)-phenylenevinylene] (MEH-PPV) or poly(9,9-dioctylfluorene) (PFO) on indium tin oxide substrates using a top contact of aluminum. Good rectification was achieved from the Al-polymer contact, with a reverse bias leakage current density as low as 4nA/cm2 at an electric field strength of 25kV/cm. Irradiation with x-rays from a 50kV x-ray tube produced a linear increase in photocurrent over a dose rate range from 4to18mGy/s. The observed x-ray sensitivities of 240nC/mGy/cm3 for MEH-PPV and 480nC/mGy/cm3 for PFO structures are comparable to that reported for Si devices. A response time of <150ms to pulsed x-ray irradiation was measured with no evidence of long-lived current transients. Conjugated polymers offer the advantage of easy coatability over large areas and on curved surfaces. Their low average atomic number provides tissue-equivalent dosimetric response, with many potential applications including medical x-ray and synchrotron photon detection.

  2. DIRECT DETECTIONS OF YOUNG STARS IN NEARBY ELLIPTICAL GALAXIES

    SciTech Connect

    Ford, H. Alyson; Bregman, Joel N.

    2013-06-20

    Small amounts of star formation in elliptical galaxies are suggested by several results: surprisingly young ages from optical line indices, cooling X-ray gas, and mid-infrared dust emission. Such star formation has previously been difficult to directly detect, but using ultraviolet Hubble Space Telescope Wide Field Camera 3 imaging, we have identified individual young stars and star clusters in four nearby ellipticals. Ongoing star formation is detected in all galaxies, including three ellipticals that have previously exhibited potential signposts of star-forming conditions (NGC 4636, NGC 4697, and NGC 4374), as well as the typical ''red and dead'' NGC 3379. The current star formation in our closest targets, where we are most complete, is between 2.0 and 9.8 Multiplication-Sign 10{sup -5} M{sub Sun} yr{sup -1}. The star formation history was roughly constant from 0.5 to 1.5 Gyr (at (3-5) Multiplication-Sign 10{sup -4} M{sub Sun} yr{sup -1}), but decreased by a factor of several in the past 0.3 Gyr. Most star clusters have a mass between 10{sup 2} and 10{sup 4} M{sub Sun }. The specific star formation rates of {approx}10{sup -16} yr{sup -1} (at the present day) or {approx}10{sup -14} yr{sup -1} (when averaging over the past Gyr) imply that a fraction 10{sup -8} of the stellar mass is younger than 100 Myr and 10{sup -5} is younger than 1 Gyr, quantifying the level of frosting of recent star formation over the otherwise passive stellar population. There is no obvious correlation between either the presence or spatial distribution of postulated star formation indicators and the star formation we detect.

  3. Direct Detections of Young Stars in Nearby Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    Ford, H. Alyson; Bregman, Joel N.

    2013-06-01

    Small amounts of star formation in elliptical galaxies are suggested by several results: surprisingly young ages from optical line indices, cooling X-ray gas, and mid-infrared dust emission. Such star formation has previously been difficult to directly detect, but using ultraviolet Hubble Space Telescope Wide Field Camera 3 imaging, we have identified individual young stars and star clusters in four nearby ellipticals. Ongoing star formation is detected in all galaxies, including three ellipticals that have previously exhibited potential signposts of star-forming conditions (NGC 4636, NGC 4697, and NGC 4374), as well as the typical "red and dead" NGC 3379. The current star formation in our closest targets, where we are most complete, is between 2.0 and 9.8 × 10-5 M ⊙ yr-1. The star formation history was roughly constant from 0.5 to 1.5 Gyr (at (3-5) × 10-4 M ⊙ yr-1), but decreased by a factor of several in the past 0.3 Gyr. Most star clusters have a mass between 102 and 104 M ⊙. The specific star formation rates of ~10-16 yr-1 (at the present day) or ~10-14 yr-1 (when averaging over the past Gyr) imply that a fraction 10-8 of the stellar mass is younger than 100 Myr and 10-5 is younger than 1 Gyr, quantifying the level of frosting of recent star formation over the otherwise passive stellar population. There is no obvious correlation between either the presence or spatial distribution of postulated star formation indicators and the star formation we detect. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program 11583.

  4. Highly selective colorimetric sensing of Cu(II) ions in aqueous solution via modulation of intramolecular charge transfer transition of aminonaphthoquinone chemosensor

    NASA Astrophysics Data System (ADS)

    Madhupriya, Selvaraj; Elango, Kuppanagounder P.

    2012-11-01

    An aminonaphthoquinone based colorimetric chemosensor has been developed and demonstrated for the highly selective detection of Cu(II) ions in aqueous solution. The intramolecular charge transfer (ICT) transition exits in amine moiety directly attached to the quinone ring is modulated by the d-d transition of a square planar Cu(II)-receptor complex resulting in a change of color from yellow to blue. No significant color change was observed upon addition of other selected metal ions. The sensing property has been investigated using various spectral techniques (UV-Vis, fluorescence) and product analysis (Elemental analysis, magnetic moment, UV-Vis, FT-IR, EPR).

  5. Direct Detection of Polarized, Scattered Light from Exoplanets

    NASA Astrophysics Data System (ADS)

    Laughlin, Gregory

    We propose to radically advance the state of exoplanet characterization, which lags dramatically behind exoplanet discovery. We propose to directly detect scattered light from the atmospheres of close-in, highly eccentric, and extended/non-spherical exoplanets and thereby determine the following: orbital inclination (and therefore masses free of the M sin i mass ambiguity), geometric albedo, presence or lack of hazes and cloud layers, and scattering particle size and composition. Such measurements are crucial to the understanding of exoplanet atmospheres, because observations with NASA s Hubble, Spitzer, and Kepler space telescopes present the following questions: 1) Do exoplanets have highly reflective haze layers? 2) How does the upper atmospheric composition differ between exoplanets with and without thermal inversions? 3) What are the optical manifestations of the extreme heating of highly eccentric exoplanets? 4) Are the atmospheres of certain exoplanets truly escaping their Roche lobes? Using the POLISH2 polarimeter developed by the Postdoctoral Associate (Wiktorowicz) for the Lick 3-m telescope, we propose to monitor the linear polarization state of exoplanet host stars at the part per million level. POLISH2 consistently delivers nearly photon shot noise limited measurements with this precision. In addition, the simultaneous full-Stokes measurements of POLISH2 and the equatorial mount of the Lick 3-m telescope ensure that systematic effects are mitigated to the part per million level. Indeed, we find the accuracy of the POLISH2 polarimeter to be 0.1 parts per million. This instrument and telescope represent the highest precision polarimeter in the world for exoplanet research. We present potential detection of polarized, scattered light from the HD 189733b, Tau Boo b, and WASP-12b exoplanets. We propose to observe hot Jupiters on circular orbits, highly eccentric exoplanets, exoplanets with extended or non-spherical scattering surfaces, and 55 Cnc e, the super-Earth with the highest expected polarimetric signal-to- noise ratio. These exoplanets should all produce detectable polarization, and they present unique opportunities to study the atmospheres of wildly different exoplanets. Extending the PI s (Laughlin) Monte Carlo ray-tracing code, and utilizing the Co-I s (Fortney) experience in modeling exoplanet atmospheres, we propose to fund a graduate student to model the polarization data obtained from POLISH2 and invert the above variables. This is because they affect the amplitude and shape of the periodic variability in the polarization state of light from the system. Indeed, the discovery of spherical, sulfuric acid droplets suspended in the Venusian atmosphere was made forty years ago with Mie scattering models to fit polarimetric measurements. The PI s ray-tracing code, which has been used to model the rapid heating of the eccentric HD 80606b exoplanet, currently includes Rayleigh scattering and alkali metal absorption in a self-consistent manner. The direct detection of exoplanets as well as characterization of their atmospheric compositions and structure is directly related to the goals of the Origins program and to the NASA 2010 Science Plan, which emphasizes exploration of exoplanets and exoplanetary systems.

  6. Direct Detection Doppler Lidar for Spaceborne Wind Measurement

    NASA Technical Reports Server (NTRS)

    Korb, C. Laurence; Flesia, Cristina

    1999-01-01

    Aerosol and molecular based versions of the double-edge technique can be used for direct detection Doppler lidar spaceborne wind measurement. The edge technique utilizes the edge of a high spectral resolution filter for high accuracy wind measurement using direct detection lidar. The signal is split between an edge filter channel and a broadband energy monitor channel. The energy monitor channel is used for signal normalization. The edge measurement is made as a differential frequency measurement between the outgoing laser signal and the atmospheric backscattered return for each pulse. As a result the measurement is insensitive to laser and edge filter frequency jitter and drift at a level less than a few parts in 10(exp 10). We have developed double edge versions of the edge technique for aerosol and molecular-based lidar measurement of the wind. Aerosol-based wind measurements have been made at Goddard Space Flight Center and molecular-based wind measurements at the University of Geneva. We have demonstrated atmospheric measurements using these techniques for altitudes from 1 to more than 10 km. Measurement accuracies of better than 1.25 m/s have been obtained with integration times from 5 to 30 seconds. The measurements can be scaled to space and agree, within a factor of two, with satellite-based simulations of performance based on Poisson statistics. The theory of the double edge aerosol technique is described by a generalized formulation which substantially extends the capabilities of the edge technique. It uses two edges with opposite slopes located about the laser frequency at approximately the half-width of each edge filter. This doubles the signal change for a given Doppler shift and yields a factor of 1.6 improvement in the measurement accuracy compared to the single edge technique. The use of two high resolution edge filters substantially reduces the effects of Rayleigh scattering on the measurement, as much as order of magnitude, and allows the signal to noise ratio to be substantially improved in areas of low aerosol backscatter. We describe a method that allows the Rayleigh and aerosol components of the signal to be independently determined using the two edge channels and an energy monitor channel. The effects of Rayleigh scattering may then subtracted from the measurement and we show that the correction process does not significantly increase the measurement noise for Rayleigh to aerosol ratios up to 10. We show that for small Doppler shifts a measurement accuracy of 0.4 m/s can be obtained for 5000 detected photon, 1.2 m/s for 1000 detected photons, and 3.7 m/s for 50 detected photons for a Rayleigh to aerosol ratio of 5. Methods for increasing the dynamic range of the aerosol-based system to more than +/- 100 m/s are given.

  7. Detecting Stealth Dark Matter Directly through Electromagnetic Polarizability

    DOE PAGESBeta

    Appelquist, T.; Berkowitz, E.; Brower, R. C.; Buchoff, M. I.; Fleming, G. T.; Jin, X. Y.; Kiskis, J.; Kribs, G. D.; Neil, E. T.; Osborn, J. C.; et al

    2015-10-23

    We calculate the spin-independent scattering cross section for direct detection that results from the electromagnetic polarizability of a composite scalar “stealth baryon” dark matter candidate, arising from a dark SU(4) confining gauge theory—“stealth dark matter.” In the nonrelativistic limit, electromagnetic polarizability proceeds through a dimension-7 interaction leading to a very small scattering cross section for dark matter with weak-scale masses. This represents a lower bound on the scattering cross section for composite dark matter theories with electromagnetically charged constituents. We carry out lattice calculations of the polarizability for the lightest “baryon” states in SU(3) and SU(4) gauge theories using themore » background field method on quenched configurations. We find the polarizabilities of SU(3) and SU(4) to be comparable (within about 50%) normalized to the stealth baryon mass, which is suggestive for extensions to larger SU(N) groups. The resulting scattering cross sections with a xenon target are shown to be possibly detectable in the dark matter mass range of about 200–700 GeV, where the lower bound is from the existing LUX constraint while the upper bound is the coherent neutrino background. Significant uncertainties in the cross section remain due to the more complicated interaction of the polarizablity operator with nuclear structure; however, the steep dependence on the dark matter mass, 1/m6B, suggests the observable dark matter mass range is not appreciably modified. We highlight collider searches for the mesons in the theory as well as the indirect astrophysical effects that may also provide excellent probes of stealth dark matter.« less

  8. Detecting Stealth Dark Matter Directly through Electromagnetic Polarizability

    SciTech Connect

    Appelquist, T.; Berkowitz, E.; Brower, R. C.; Buchoff, M. I.; Fleming, G. T.; Jin, X. Y.; Kiskis, J.; Kribs, G. D.; Neil, E. T.; Osborn, J. C.; Rebbi, C.; Rinaldi, E.; Schaich, D.; Schroeder, C.; Syritsyn, S.; Vranas, P.; Weinberg, E.; Witzel, O.

    2015-10-23

    We calculate the spin-independent scattering cross section for direct detection that results from the electromagnetic polarizability of a composite scalar “stealth baryon” dark matter candidate, arising from a dark SU(4) confining gauge theory—“stealth dark matter.” In the nonrelativistic limit, electromagnetic polarizability proceeds through a dimension-7 interaction leading to a very small scattering cross section for dark matter with weak-scale masses. This represents a lower bound on the scattering cross section for composite dark matter theories with electromagnetically charged constituents. We carry out lattice calculations of the polarizability for the lightest “baryon” states in SU(3) and SU(4) gauge theories using the background field method on quenched configurations. We find the polarizabilities of SU(3) and SU(4) to be comparable (within about 50%) normalized to the stealth baryon mass, which is suggestive for extensions to larger SU(N) groups. The resulting scattering cross sections with a xenon target are shown to be possibly detectable in the dark matter mass range of about 200–700 GeV, where the lower bound is from the existing LUX constraint while the upper bound is the coherent neutrino background. Significant uncertainties in the cross section remain due to the more complicated interaction of the polarizablity operator with nuclear structure; however, the steep dependence on the dark matter mass, 1/m6B, suggests the observable dark matter mass range is not appreciably modified. We highlight collider searches for the mesons in the theory as well as the indirect astrophysical effects that may also provide excellent probes of stealth dark matter.

  9. Detecting Stealth Dark Matter Directly through Electromagnetic Polarizability.

    PubMed

    Appelquist, T; Berkowitz, E; Brower, R C; Buchoff, M I; Fleming, G T; Jin, X-Y; Kiskis, J; Kribs, G D; Neil, E T; Osborn, J C; Rebbi, C; Rinaldi, E; Schaich, D; Schroeder, C; Syritsyn, S; Vranas, P; Weinberg, E; Witzel, O

    2015-10-23

    We calculate the spin-independent scattering cross section for direct detection that results from the electromagnetic polarizability of a composite scalar "stealth baryon" dark matter candidate, arising from a dark SU(4) confining gauge theory-"stealth dark matter." In the nonrelativistic limit, electromagnetic polarizability proceeds through a dimension-7 interaction leading to a very small scattering cross section for dark matter with weak-scale masses. This represents a lower bound on the scattering cross section for composite dark matter theories with electromagnetically charged constituents. We carry out lattice calculations of the polarizability for the lightest "baryon" states in SU(3) and SU(4) gauge theories using the background field method on quenched configurations. We find the polarizabilities of SU(3) and SU(4) to be comparable (within about 50%) normalized to the stealth baryon mass, which is suggestive for extensions to larger SU(N) groups. The resulting scattering cross sections with a xenon target are shown to be potentially detectable in the dark matter mass range of about 200-700 GeV, where the lower bound is from the existing LUX constraint while the upper bound is the coherent neutrino background. Significant uncertainties in the cross section remain due to the more complicated interaction of the polarizablity operator with nuclear structure; however, the steep dependence on the dark matter mass, 1/m(B)(6), suggests the observable dark matter mass range is not appreciably modified. We briefly highlight collider searches for the mesons in the theory as well as the indirect astrophysical effects that may also provide excellent probes of stealth dark matter. PMID:26551103

  10. Detecting Stealth Dark Matter Directly through Electromagnetic Polarizability

    NASA Astrophysics Data System (ADS)

    Appelquist, T.; Berkowitz, E.; Brower, R. C.; Buchoff, M. I.; Fleming, G. T.; Jin, X.-Y.; Kiskis, J.; Kribs, G. D.; Neil, E. T.; Osborn, J. C.; Rebbi, C.; Rinaldi, E.; Schaich, D.; Schroeder, C.; Syritsyn, S.; Vranas, P.; Weinberg, E.; Witzel, O.; Lattice Strong Dynamics LSD Collaboration

    2015-10-01

    We calculate the spin-independent scattering cross section for direct detection that results from the electromagnetic polarizability of a composite scalar "stealth baryon" dark matter candidate, arising from a dark SU(4) confining gauge theory—"stealth dark matter." In the nonrelativistic limit, electromagnetic polarizability proceeds through a dimension-7 interaction leading to a very small scattering cross section for dark matter with weak-scale masses. This represents a lower bound on the scattering cross section for composite dark matter theories with electromagnetically charged constituents. We carry out lattice calculations of the polarizability for the lightest "baryon" states in SU(3) and SU(4) gauge theories using the background field method on quenched configurations. We find the polarizabilities of SU(3) and SU(4) to be comparable (within about 50%) normalized to the stealth baryon mass, which is suggestive for extensions to larger SU(N ) groups. The resulting scattering cross sections with a xenon target are shown to be potentially detectable in the dark matter mass range of about 200-700 GeV, where the lower bound is from the existing LUX constraint while the upper bound is the coherent neutrino background. Significant uncertainties in the cross section remain due to the more complicated interaction of the polarizablity operator with nuclear structure; however, the steep dependence on the dark matter mass, 1 /mB6 , suggests the observable dark matter mass range is not appreciably modified. We briefly highlight collider searches for the mesons in the theory as well as the indirect astrophysical effects that may also provide excellent probes of stealth dark matter.

  11. A novel colorimetric sensor for Hg(2+) based on hybridization chain reaction and silver nanowire amplification.

    PubMed

    Tang, Shurong; Tong, Ping; Wang, Meili; Chen, Jinghua; Li, Guangwen; Zhang, Lan

    2015-10-18

    Through the silver ion catalysis to form colored KMnO4, and combined with the DNA hybridization chain reaction and silver nanowire for signal amplification, a highly sensitive and selective colorimetric sensor has been developed for the detection of Hg(2+). PMID:26313655

  12. Au@Ag core/shell nanoparticles as colorimetric probes for cyanide sensing.

    PubMed

    Zeng, Jing-bin; Cao, Ying-ying; Chen, Jing-jing; Wang, Xu-dong; Yu, Jian-feng; Yu, Bin-bin; Yan, Zi-feng; Chen, Xi

    2014-09-01

    We synthesize Au@Ag core/shell nanoparticles (NPs) using a Au NP assisted Tollens reaction. The as-synthesized NPs are used for the colorimetric cyanide sensing with a detection limit of 0.4 ?M. The bimetallic NPs are immobilized into agarose gels as portable "test strips". PMID:25054637

  13. A highly sensitive colorimetric metalloimmunoassay based on copper-mediated etching of gold nanorods.

    PubMed

    Cheng, Fangbin; Chen, Zhaopeng; Zhang, Zhiyang; Chen, Lingxin

    2016-03-01

    A highly sensitive colorimetric metalloimmunoassay with a detection limit of 0.15 ng ml(-1) for human IgG based on copper-mediated etching of gold nanorods was proposed. The assay is more sensitive than traditional ELISA, electrochemical metalloimmunoassay and HRP mimic nanomaterial tag-based immunoassay. PMID:26911421

  14. New Completeness Methods for Estimating Exoplanet Discoveries by Direct Detection

    NASA Astrophysics Data System (ADS)

    Brown, Robert A.; Soummer, Rémi

    2010-05-01

    We report on new methods for evaluating realistic observing programs that search stars for planets by direct imaging, where observations are selected from an optimized star list and stars can be observed multiple times. We show how these methods bring critical insight into the design of the mission and its instruments. These methods provide an estimate of the outcome of the observing program: the probability distribution of discoveries (detection and/or characterization) and an estimate of the occurrence rate of planets (η). We show that these parameters can be accurately estimated from a single mission simulation, without the need for a complete Monte Carlo mission simulation, and we prove the accuracy of this new approach. Our methods provide tools to define a mission for a particular science goal; for example, a mission can be defined by the expected number of discoveries and its confidence level. We detail how an optimized star list can be built and how successive observations can be selected. Our approach also provides other critical mission attributes, such as the number of stars expected to be searched and the probability of zero discoveries. Because these attributes depend strongly on the mission scale (telescope diameter, observing capabilities and constraints, mission lifetime, etc.), our methods are directly applicable to the design of such future missions and provide guidance to the mission and instrument design based on scientific performance. We illustrate our new methods with practical calculations and exploratory design reference missions for the James Webb Space Telescope (JWST) operating with a distant starshade to reduce scattered and diffracted starlight on the focal plane. We estimate that five habitable Earth-mass planets would be discovered and characterized with spectroscopy, with a probability of zero discoveries of 0.004, assuming a small fraction of JWST observing time (7%), η = 0.3, and 70 observing visits, limited by starshade fuel.

  15. NEW COMPLETENESS METHODS FOR ESTIMATING EXOPLANET DISCOVERIES BY DIRECT DETECTION

    SciTech Connect

    Brown, Robert A.; Soummer, Remi

    2010-05-20

    We report on new methods for evaluating realistic observing programs that search stars for planets by direct imaging, where observations are selected from an optimized star list and stars can be observed multiple times. We show how these methods bring critical insight into the design of the mission and its instruments. These methods provide an estimate of the outcome of the observing program: the probability distribution of discoveries (detection and/or characterization) and an estimate of the occurrence rate of planets ({eta}). We show that these parameters can be accurately estimated from a single mission simulation, without the need for a complete Monte Carlo mission simulation, and we prove the accuracy of this new approach. Our methods provide tools to define a mission for a particular science goal; for example, a mission can be defined by the expected number of discoveries and its confidence level. We detail how an optimized star list can be built and how successive observations can be selected. Our approach also provides other critical mission attributes, such as the number of stars expected to be searched and the probability of zero discoveries. Because these attributes depend strongly on the mission scale (telescope diameter, observing capabilities and constraints, mission lifetime, etc.), our methods are directly applicable to the design of such future missions and provide guidance to the mission and instrument design based on scientific performance. We illustrate our new methods with practical calculations and exploratory design reference missions for the James Webb Space Telescope (JWST) operating with a distant starshade to reduce scattered and diffracted starlight on the focal plane. We estimate that five habitable Earth-mass planets would be discovered and characterized with spectroscopy, with a probability of zero discoveries of 0.004, assuming a small fraction of JWST observing time (7%), {eta} = 0.3, and 70 observing visits, limited by starshade fuel.

  16. A direction detective asymmetrical twin-core fiber curving sensor

    NASA Astrophysics Data System (ADS)

    An, Maowei; Geng, Tao; Yang, Wenlei; Zeng, Hongyi; Li, Jian

    2015-10-01

    Long period fiber gratings (LPFGs), which can couple the core mode to the forward propagating cladding modes of a fiber and have the advantage of small additional loss, no backward reflection, small size, which is widely used in optical fiber sensors and optical communication systems. LPFG has different fabricating methods, in order to write gratings on the twin-core at the same time effectively, we specially choose electric heating fused taper system to fabricate asymmetric dual-core long period fiber grating, because this kind of method can guarantee the similarity of gratings on the twin cores and obtain good geometric parameters of LPFG, such as cycle, cone waist. Then we use bending test platform to conduct bending test for each of the core of twin-core asymmetric long period fiber grating. Experiments show that: the sensitivity of asymmetrical twin-core long period fiber grating's central core under bending is -5.47nm·m, while the sensitivity of asymmetric twin-core long period fiber grating partial core changed with the relative position of screw micrometer. The sensitivity at 0°, 30°, 90° direction is -4.22nm·m, -9.84nm·m, -11.44nm·m respectively. The experiment results strongly demonstrate the properties of rim sensing of asymmetrical twin-core fiber gratings which provides the possibility of simultaneously measuring the bending magnitude and direction and solving the problem of cross sensing when multi-parameter measuring. In other words, we can detect temperature and bend at the same time by this sensor. As our knowledge, it is the first time simultaneously measuring bend and temperature using this structure of fiber sensors.

  17. Colorimetric determination of o-phenylenediamine in water samples based on the formation of silver nanoparticles as a colorimetric probe

    NASA Astrophysics Data System (ADS)

    Li, Nan; Gu, Yu; Gao, Mengmeng; Wang, Zilu; Xiao, Deli; Li, Yun; Lin, Rui; He, Hua

    2015-04-01

    A simple, rapid and cost-effective method for visual colorimetric detection of o-phenylenediamine (OPD) based on the formation of silver nanoparticles (AgNPs) has been developed in this paper. Silver ions can be reduced to AgNPs by OPD in a few minutes, causing changes in absorption spectra and color of the reaction system. Therefore, colorimetric detection of OPD could be realized by a UV-vis spectrophotometer or even the naked eye. Results showed that the absorption intensity of AgNPs at 416 nm exhibited a good linear correlation (R2 = 0.998) with OPD concentration in the range from 10-6 to 8 × 10-5 mol L-1 and the detection limit (3 σ/S) was calculated to be 1.61 × 10-7 mol L-1. Furthermore, as low as 4 × 10-6 mol L-1 OPD can be visualized by the naked eye without the requirement of any complicated or expensive instruments. This proposed method has been successfully applied to determine OPD in water samples, and may provide an innovative platform in the development of sensors for guiding environmental monitoring in the future.

  18. Sensitiveness of the colorimetric estimation of titanium

    USGS Publications Warehouse

    Wells, R.C.

    1911-01-01

    The accuracy of the colorimetric estimation of titanium is practically constant over concentrations ranging from the strongest down to those containing about 1.5 mg. TiO2 in 100 cc. The change in concentration required to produce a perceptible difference in intensity between two solutions, at favorable concentrations, was found to be about 6.5 per cent, which does not differ much from the results of others with chromium and copper solutions. With suitable precautions, such as comparing by substitution and taking the mean of several settings or of the two perceptibly different extremes, the accuracy of the colorimetric comparisons appears to be about 2 per cent.

  19. Direct detection of light ''Ge-phobic'' exothermic dark matter

    SciTech Connect

    Gelmini, Graciela B.; Georgescu, Andreea; Huh, Ji-Haeng E-mail: a.georgescu@physics.ucla.edu

    2014-07-01

    We present comparisons of direct dark matter (DM) detection data for light WIMPs with exothermic scattering with nuclei (exoDM), both assuming the Standard Halo Model (SHM) and in a halo model–independent manner. Exothermic interactions favor light targets, thus reducing the importance of upper limits derived from xenon targets, the most restrictive of which is at present the LUX limit. In our SHM analysis the CDMS-II-Si and CoGeNT regions become allowed by these bounds, however the recent SuperCDMS limit rejects both regions for exoDM with isospin-conserving couplings. An isospin-violating coupling of the exoDM, in particular one with a neutron to proton coupling ratio of -0.8 (which we call ''Ge-phobic''), maximally reduces the DM coupling to germanium and allows the CDMS-II-Si region to become compatible with all bounds. This is also clearly shown in our halo-independent analysis.

  20. Direct detection of light anapole and magnetic dipole DM

    SciTech Connect

    Nobile, Eugenio Del; Gelmini, Graciela B.; Huh, Ji-Haeng; Gondolo, Paolo E-mail: gelmini@physics.ucla.edu E-mail: jhhuh@physics.ucla.edu

    2014-06-01

    We present comparisons of direct detection data for ''light WIMPs'' with an anapole moment interaction (ADM) and a magnetic dipole moment interaction (MDM), both assuming the Standard Halo Model (SHM) for the dark halo of our galaxy and in a halo-independent manner. In the SHM analysis we find that a combination of the 90% CL LUX and CDMSlite limits or the new 90% CL SuperCDMS limit by itself exclude the parameter space regions allowed by DAMA, CoGeNT and CDMS-II-Si data for both ADM and MDM. In our halo-independent analysis the new LUX bound excludes the same potential signal regions as the previous XENON100 bound. Much of the remaining signal regions is now excluded by SuperCDMS, while the CDMSlite limit is much above them. The situation is of strong tension between the positive and negative search results both for ADM and MDM. We also clarify the confusion in the literature about the ADM scattering cross section.

  1. Detection of biological threats. A challenge for directed molecular evolution.

    PubMed

    Petrenko, Valery A; Sorokulova, Iryna B

    2004-08-01

    The probe technique originated from early attempts of Anton van Leeuwenhoek to contrast microorganisms under the microscope using plant juices, successful staining of tubercle bacilli with synthetic dyes by Paul Ehrlich and discovery of a stain for differentiation of gram-positive and gram-negative bacteria by Hans Christian Gram. The technique relies on the principle that pathogens have unique structural features, which can be recognized by specifically labeled organic molecules. A hundred years of extensive screening efforts led to discovery of a limited assortment of organic probes that are used for identification and differentiation of bacteria. A new challenge--continuous monitoring of biological threats--requires long lasting molecular probes capable of tight specific binding of pathogens in unfavorable conditions. To respond to the challenge, probe technology is being revolutionized by utilizing methods of combinatorial chemistry, phage display and directed molecular evolution. This review describes how molecular evolution methods are applied for development of peptide, antibody and phage probes, and summarizes the author's own data on development of landscape phage probes against Salmonella typhimurium. The performance of the probes in detection of Salmonella is illustrated by a precipitation test, enzyme-linked immunosorbent assay (ELISA), fluorescence-activated cell sorting (FACS) and fluorescent, optical and electron microscopy. PMID:15234514

  2. Direct detection constraints on dark photon dark matter

    NASA Astrophysics Data System (ADS)

    An, Haipeng; Pospelov, Maxim; Pradler, Josef; Ritz, Adam

    2015-07-01

    Dark matter detectors built primarily to probe elastic scattering of WIMPs on nuclei are also precise probes of light, weakly coupled, particles that may be absorbed by the detector material. In this paper, we derive constraints on the minimal model of dark matter comprised of long-lived vector states V (dark photons) in the 0.01- 100 keV mass range. The absence of an ionization signal in direct detection experiments such as XENON10 and XENON100 places a very strong constraint on the dark photon mixing angle, down to O (10-15), assuming that dark photons comprise the dominant fraction of dark matter. This sensitivity to dark photon dark matter exceeds the indirect bounds derived from stellar energy loss considerations over a significant fraction of the available mass range. We also revisit indirect constraints from V ? 3 ? decay and show that limits from modifications to the cosmological ionization history are comparable to the updated limits from the diffuse ?-ray flux.

  3. Directional dark matter by polar angle direct detection and application of columnar recombination

    NASA Astrophysics Data System (ADS)

    Li, Jin

    2015-08-01

    We report a systematic study on the directional sensitivity of a direct dark matter detector that detects the polar angle of a recoiling nucleus. A weakly interacting massive particle (WIMP)-mass independent method is used to obtain the sensitivity of a general detector in an isothermal galactic dark matter halo. By using two-dimensional distributions of energy and polar angle, a detector without head-tail information with 6.3 times the statistics is found to achieve the same performance level as a full three-dimensional tracking dark matter detector. Optimum operation orientations are obtained for various experimental configurations, with detectors that are space- or Earth-fixed, have head-tail capability or not, and use energy information or not. Earth-fixed detectors are found to have best sensitivity when the polar axis is oriented at a 45 degree angle from the Earth's pole. With background contamination that mimics the WIMP signal's energy distribution, the performance is found to decrease at a rate less than the decrease of signal purity. The WIMP-mass dependence of the performance of a detector with various energy thresholds that uses gaseous xenon as target material is reported. We find that with a 5 10-46 cm2 spin-independent WIMP-nucleon cross-section and a 30 GeV WIMP, a 770 kg .year 's exposure with a polar detector of 10 keV threshold can make a three sigma discovery of directional WIMPs in the isothermal galactic dark matter halo. For a columnar recombination detector, experimental considerations are discussed.

  4. Bed bug detection: Current technologies and future directions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study evaluates current technologies used to detect bed bug infestations, and presents new information regarding the underlying chemical basis of canines scent detection. The manuscript also reports new and future devices that may play a part in bed bug detection in the future....

  5. Paper-based tuberculosis diagnostic devices with colorimetric gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Tsai, Tsung-Ting; Shen, Shu-Wei; Cheng, Chao-Min; Chen, Chien-Fu

    2013-08-01

    A colorimetric sensing strategy employing gold nanoparticles and a paper assay platform has been developed for tuberculosis diagnosis. Unmodified gold nanoparticles and single-stranded detection oligonucleotides are used to achieve rapid diagnosis without complicated and time-consuming thiolated or other surface-modified probe preparation processes. To eliminate the use of sophisticated equipment for data analysis, the color variance for multiple detection results was simultaneously collected and concentrated on cellulose paper with the data readout transmitted for cloud computing via a smartphone. The results show that the 2.6 nM tuberculosis mycobacterium target sequences extracted from patients can easily be detected, and the turnaround time after the human DNA is extracted from clinical samples was approximately 1 h.

  6. Identifying the theory of dark matter with direct detection

    SciTech Connect

    Gluscevic, Vera; Gresham, Moira I.; McDermott, Samuel D.; Peter, Annika H.G.; Zurek, Kathryn M.

    2015-12-29

    Identifying the true theory of dark matter depends crucially on accurately characterizing interactions of dark matter (DM) with other species. In the context of DM direct detection, we present a study of the prospects for correctly identifying the low-energy effective DM-nucleus scattering operators connected to UV-complete models of DM-quark interactions. We take a census of plausible UV-complete interaction models with different low-energy leading-order DM-nuclear responses. For each model (corresponding to different spin–, momentum–, and velocity-dependent responses), we create a large number of realizations of recoil-energy spectra, and use Bayesian methods to investigate the probability that experiments will be able to select the correct scattering model within a broad set of competing scattering hypotheses. We conclude that agnostic analysis of a strong signal (such as Generation-2 would see if cross sections are just below the current limits) seen on xenon and germanium experiments is likely to correctly identify momentum dependence of the dominant response, ruling out models with either “heavy” or “light” mediators, and enabling downselection of allowed models. However, a unique determination of the correct UV completion will critically depend on the availability of measurements from a wider variety of nuclear targets, including iodine or fluorine. We investigate how model-selection prospects depend on the energy window available for the analysis. In addition, we discuss accuracy of the DM particle mass determination under a wide variety of scattering models, and investigate impact of the specific types of particle-physics uncertainties on prospects for model selection.

  7. Direct Detection of Dark Matter with Resonant Annihilation

    NASA Astrophysics Data System (ADS)

    Li, Bo; Zhou, Yu-Feng

    2015-07-01

    In the scenario where the dark matter (DM) particles χbar chi pair annihilate through a resonance particle R, the constraint from DM relic density makes the corresponding cross section for DM-nuclei elastic scattering extremely small, and can be below the neutrino background induced by the coherent neutrino-nuclei scattering, which makes the DM particle beyond the reach of the conventional DM direct detection experiments. We present an improved analytical calculation of the DM relic density in the case of resonant DM annihilation for s- and p-wave cases and invesitgate the condition for the DM-nuclei scattering cross section to be above the neutrino background. We show that in Higgs-portal type models, for DM particles with s-wave annihilation, the spin-independent DM-nucleus scattering cross section is proportional to ΓR/mR, the ratio of the decay width and the mass of R. For a typical DM particle mass ˜ 50 GeV, the condition leads to ΓR/mR gtrsim Script O(10-4). In p-wave annihilation case, the spin-independent scattering cross section is insensitive to ΓR/mR, and is always above the neutrino background, as long as the DM particle is lighter than the top quark. The real singlet DM model is discussed as a concrete example. Supported by the National Basic Research Program of China (973 Program) under Grant No. 2010CB833000; the National Nature Science Foundation of China (NSFC) under Grant Nos. 10975170, 10821504, 10905084, and 11335012; and the Project of Knowledge Innovation Program (PKIP) of the Chinese Academy of Science

  8. Identifying the theory of dark matter with direct detection

    NASA Astrophysics Data System (ADS)

    Gluscevic, Vera; Gresham, Moira I.; McDermott, Samuel D.; Peter, Annika H. G.; Zurek, Kathryn M.

    2015-12-01

    Identifying the true theory of dark matter depends crucially on accurately characterizing interactions of dark matter (DM) with other species. In the context of DM direct detection, we present a study of the prospects for correctly identifying the low-energy effective DM-nucleus scattering operators connected to UV-complete models of DM-quark interactions. We take a census of plausible UV-complete interaction models with different low-energy leading-order DM-nuclear responses. For each model (corresponding to different spin-, momentum-, and velocity-dependent responses), we create a large number of realizations of recoil-energy spectra, and use Bayesian methods to investigate the probability that experiments will be able to select the correct scattering model within a broad set of competing scattering hypotheses. We conclude that agnostic analysis of a strong signal (such as Generation-2 would see if cross sections are just below the current limits) seen on xenon and germanium experiments is likely to correctly identify momentum dependence of the dominant response, ruling out models with either "heavy" or "light" mediators, and enabling downselection of allowed models. However, a unique determination of the correct UV completion will critically depend on the availability of measurements from a wider variety of nuclear targets, including iodine or fluorine. We investigate how model-selection prospects depend on the energy window available for the analysis. In addition, we discuss accuracy of the DM particle mass determination under a wide variety of scattering models, and investigate impact of the specific types of particle-physics uncertainties on prospects for model selection.

  9. Visualizing Capsaicinoids: Colorimetric Analysis of Chili Peppers

    ERIC Educational Resources Information Center

    Thompson, Robert Q.; Chu, Christopher; Gent, Robin; Gould, Alexandra P.; Rios, Laura; Vertigan, Theresa M.

    2012-01-01

    A colorimetric method for total capsaicinoids in chili pepper ("Capsicum") fruit is described. The placental material of the pepper, containing 90% of the capsaicinoids, was physically separated from the colored materials in the pericarp and extracted twice with methanol, capturing 85% of the remaining capsaicinoids. The extract, evaporated and

  10. Visualizing Capsaicinoids: Colorimetric Analysis of Chili Peppers

    ERIC Educational Resources Information Center

    Thompson, Robert Q.; Chu, Christopher; Gent, Robin; Gould, Alexandra P.; Rios, Laura; Vertigan, Theresa M.

    2012-01-01

    A colorimetric method for total capsaicinoids in chili pepper ("Capsicum") fruit is described. The placental material of the pepper, containing 90% of the capsaicinoids, was physically separated from the colored materials in the pericarp and extracted twice with methanol, capturing 85% of the remaining capsaicinoids. The extract, evaporated and…

  11. Direct detection of hyaluronidase in urine using cationic gold nanoparticles: a potential diagnostic test for bladder cancer.

    PubMed

    Nossier, Ahmed Ibrahim; Eissa, Sanaa; Ismail, Manal Fouad; Hamdy, Mohamed Ahmed; Azzazy, Hassan Mohamed El-Said

    2014-04-15

    Hyaluronidase (HAase) was reported as a urinary marker of bladder cancer. In this study, a simple colorimetric gold nanoparticle (AuNP) assay was developed for rapid and sensitive detection of urinary HAase activity. Charge interaction between polyanionic hyaluronic acid (HA) and cationic AuNPs stabilized with cetyl trimethyl ammonium bromide (CTAB) led to formation of gold aggregates and a red to blue color shift. HAase digests HA into small fragments preventing the aggregation of cationic AuNPs. The nonspecific aggregation of AuNPs in urine samples was overcome by pre-treatment of samples with the polycationic chitosan that was able to agglomerate all negatively charged interfering moieties before performing the assay. The developed AuNP assay was compared with zymography for qualitative detection of urinary HAase activity in 40 bladder carcinoma patients, 11 benign bladder lesions patients and 15 normal individuals, the assay sensitivity was 82.5% vs. 65% for zymography, while the specificity for both assays was 96.1%. The absorption ratio, A530/A620 of the reacted AuNP solution was used to quantify the HAase activity. The best cut off value was 93.5 ?U/ng protein, at which the sensitivity was 90% and the specificity was 80.8%.The developed colorimetric AuNP HAase assay is simple, inexpensive, and can aid noninvasive diagnosis of bladder cancer. PMID:24240162

  12. A line detection algorithm based on direction filter and regional growth

    NASA Astrophysics Data System (ADS)

    Zhang, Cheng; Zhang, Jun; Tian, Jinwen

    2015-12-01

    In this paper, a line detection algorithm, which is based on direction filter and regional growth, is proposed for line detection problem in a specific angle. Our algorithm is better than the state-of-the-art algorithm in the detection of the specific direction of the line, which have a higher detection rate, less error and missing detection, lower computational complexity, higher efficiency of the algorithm and better anti-interference ability.

  13. A Novel Colorimetric Immunoassay Utilizing the Peroxidase Mimicking Activity of Magnetic Nanoparticles

    PubMed Central

    Woo, Min-Ah; Kim, Moon Il; Jung, Jae Hwan; Park, Ki Soo; Seo, Tae Seok; Park, Hyun Gyu

    2013-01-01

    A simple colorimetric immunoassay system, based on the peroxidase mimicking activity of Fe3O4 magnetic nanoparticles (MNPs), has been developed to detect clinically important antigenic molecules. MNPs with ca. 10 nm in diameter were synthesized and conjugated with specific antibodies against target molecules, such as rotaviruses and breast cancer cells. Conjugation of the MNPs with antibodies (MNP-Abs) enabled specific recognition of the corresponding target antigenic molecules through the generation of color signals arising from the colorimetric reaction between the selected peroxidase substrate, 3,3?,5,5?-tetramethylbenzidine (TMB) and H2O2. Based on the MNP-promoted colorimetric reaction, the target molecules were detected and quantified by measuring absorbance intensities corresponding to the oxidized form of TMB. Owing to the higher stabilities and economic feasibilities of MNPs as compared to horseradish peroxidase (HRP), the new colorimetric system employing MNP-Abs has the potential of serving as a potent immunoassay that should substitute for conventional HRP-based immunoassays. The strategy employed to develop the new methodology has the potential of being extended to the construction of simple diagnostic systems for a variety of biomolecules related to human cancers and infectious diseases, particularly in the realm of point-of-care applications. PMID:23665902

  14. Comparison of IPDA lidar receiver sensitivity for coherent detection and for direct detection using sine-wave and pulsed modulation.

    PubMed

    Sun, Xiaoli; Abshire, James B

    2012-09-10

    We use theoretical models to compare the receiver signal to noise ratio (SNR) vs. average rate of detected signal photons for an integrated path differential absorption (IPDA) lidar using coherent detection with continuous wave (CW) lasers and direct detection with sine-wave and pulse modulations. The results show the coherent IPDA lidar has high receiver gain and narrow bandwidth to overcome the effects of detector circuit noise and background light, but the actual receiver performance can be limited by the coherent mixing efficiency, speckle and other factors. For direct detection, using sine-wave modulation allows the use of a low peak power laser transmitter and synchronous detection. The pulse modulation technique requires higher laser peak powers but is more efficient than sine-wave modulation in terms of average detected signal photon rate required to achieve a given receiver SNR. We also conducted experiments for the direct detection cases and the results agreed well with theory. PMID:23037252

  15. Colorimetric plasmon sensors with multilayered metallic nanoparticle sheets.

    PubMed

    Shinohara, Shuhei; Tanaka, Daisuke; Okamoto, Koichi; Tamada, Kaoru

    2015-07-28

    Colorimetric plasmon sensors for naked-eye detection of molecular recognition events have been proposed. Here, 3-layered Ag nanoparticle (NP) sheets on a Au substrate fabricated using the Langmuir-Schaefer method were utilized as the detection substrates. A drastic color change was observed following the binding of Au NPs via avidin-biotin interactions at less than 30% surface coverage. The color change was attributed not only to the localized surface plasmon resonance (LSPR) of the adsorbed Au NPs but also to the multiple light trapping effect derived from the stratified Au and Ag NPs, as predicted by a finite-difference time-domain (FDTD) simulation. This plasmonic multi-color has great potential in the development of simple and highly sensitive diagnostic systems. PMID:26113242

  16. A Wash-Free Homogeneous Colorimetric Immunoassay Method.

    PubMed

    Liu, Huiqiao; Rong, Pengfei; Jia, Hongwei; Yang, Jie; Dong, Bo; Dong, Qiong; Yang, Cejun; Hu, Pengzhi; Wang, Wei; Liu, Haitao; Liu, Dingbin

    2016-01-01

    Rapid and convenient biosensing platforms could be beneficial to timely diagnosis and treatment of diseases in virtually any care settings. Sandwich immunoassays, the most commonly used methods for protein detection, often rely on expensive tags such as enzyme and tedious wash and incubation procedures operated by skilled labor. In this report, we revolutionized traditional sandwich immunoassays by providing a wash-free homogeneous colorimetric immunoassay method without requirement of any separation steps. The proposed strategy was realized by controlling the growth of gold nanoparticles (AuNPs) to mediate the interparticle spacing in the protein-AuNP oligomers. We have demonstrated the successful in vitro detection of cancer biomarker in serum samples from patients with high clinical sensitivity and specificity. PMID:26722373

  17. A Wash-Free Homogeneous Colorimetric Immunoassay Method

    PubMed Central

    Liu, Huiqiao; Rong, Pengfei; Jia, Hongwei; Yang, Jie; Dong, Bo; Dong, Qiong; Yang, Cejun; Hu, Pengzhi; Wang, Wei; Liu, Haitao; Liu, Dingbin

    2016-01-01

    Rapid and convenient biosensing platforms could be beneficial to timely diagnosis and treatment of diseases in virtually any care settings. Sandwich immunoassays, the most commonly used methods for protein detection, often rely on expensive tags such as enzyme and tedious wash and incubation procedures operated by skilled labor. In this report, we revolutionized traditional sandwich immunoassays by providing a wash-free homogeneous colorimetric immunoassay method without requirement of any separation steps. The proposed strategy was realized by controlling the growth of gold nanoparticles (AuNPs) to mediate the interparticle spacing in the protein-AuNP oligomers. We have demonstrated the successful in vitro detection of cancer biomarker in serum samples from patients with high clinical sensitivity and specificity. PMID:26722373

  18. Bed bug detection: current technologies and future directions.

    PubMed

    Vaidyanathan, Rajeev; Feldlaufer, Mark F

    2013-04-01

    Technologies to detect bed bugs have not kept pace with their global resurgence. Early detection is critical to prevent infestations from spreading. Detection based exclusively on bites is inadequate, because reactions to insect bites are non-specific and often misdiagnosed. Visual inspections are commonly used and depend on identifying live bugs, exuviae, or fecal droplets. Visual inspections are inexpensive, but they are time-consuming and unreliable when only a few bugs are present. Use of a dog to detect bed bugs is gaining in popularity, but it can be expensive, may unintentionally advertise a bed bug problem, and is not foolproof. Passive monitors mimic natural harborages; they are discreet and typically use an adhesive to trap bugs. Active monitors generate carbon dioxide, heat, a pheromone, or a combination to attract bed bugs to a trap. New technologies using DNA analysis, mass spectrometry, and electronic noses are innovative but impractical and expensive for widespread use. PMID:23553226

  19. Bed Bug Detection: Current Technologies and Future Directions

    PubMed Central

    Vaidyanathan, Rajeev; Feldlaufer, Mark F.

    2013-01-01

    Technologies to detect bed bugs have not kept pace with their global resurgence. Early detection is critical to prevent infestations from spreading. Detection based exclusively on bites is inadequate, because reactions to insect bites are non-specific and often misdiagnosed. Visual inspections are commonly used and depend on identifying live bugs, exuviae, or fecal droplets. Visual inspections are inexpensive, but they are time-consuming and unreliable when only a few bugs are present. Use of a dog to detect bed bugs is gaining in popularity, but it can be expensive, may unintentionally advertise a bed bug problem, and is not foolproof. Passive monitors mimic natural harborages; they are discreet and typically use an adhesive to trap bugs. Active monitors generate carbon dioxide, heat, a pheromone, or a combination to attract bed bugs to a trap. New technologies using DNA analysis, mass spectrometry, and electronic noses are innovative but impractical and expensive for widespread use. PMID:23553226

  20. A System for Multiplexed Direct Electrical Detection of DNA Synthesis

    PubMed Central

    Anderson, Erik P.; Daniels, Jonathan S.; Yu, Heng; Karhanek, Miloslav; Lee, Thomas H.; Davis, Ronald W.; Pourmand, Nader

    2008-01-01

    An electronic system for the multiplexed detection of DNA polymerization is designed and characterized. DNA polymerization is detected by the measurement of small transient currents arising from ion diffusion during polymerization. A transimpedance amplifier is used to detect these small currents; we implemented a twenty-four channel recording system on a single printed circuit board. Various contributions to the input-referred current noise are analyzed and characterized, as it limits the minimum detectable current and thus the biological limit of detection. We obtained 8.5 pA RMS mean noise current (averaged over all 24 channels) over the recording bandwidth (DC to 2 kHz). With digital filtering, the input-referred current noise of the acquisition system is reduced to 2.4 pA, which is much lower than the biological noise. Electrical crosstalk between channels is measured, and a model for the crosstalk is presented. Minimizing the crosstalk is critical because it can lead to erroneous microarray data. With proper precautions, crosstalk is reduced to a negligible value (less than 1.4%). Using a micro-fabricated array of 24 gold electrodes, we demonstrated system functionality by detecting the presence of a target DNA oligonucleotide which hybridized onto its corresponding target. PMID:19183700