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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

    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.

  2. 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.

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

    DOEpatents

    Charych, Deborah H.; Sasaki, Darryl; Yamanaka, Stacey

    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.

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

    DOEpatents

    Charych, Deborah H.; Sasaki, Darryl; Yamanaka, Stacey

    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.

  5. Direct Colorimetric Detection of a Receptor-Ligand Interaction by a Polymerized Bilayer Assembly

    NASA Astrophysics Data System (ADS)

    Charych, Deborah H.; Nagy, Jon O.; Spevak, Wayne; Bednarski, Mark D.

    1993-07-01

    Detection of receptor-ligand interactions is generally accomplished by indirect assays such as enzyme-linked immunosorbent assay. A direct colorimetric detection method based on a polydiacetylene bilayer assembled on glass microscope slides has been developed. The bilayer is composed of a self-assembled monolayer of octadecylsilane and a Langmuir-Blodgett monolayer of polydiacetylene. The polydiacetylene layer is functionalized with an analog of sialic acid, the receptor-specific ligand for the influenza virus hemagglutinin. The sialic acid ligand serves as a molecular recognition element and the conjugated polymer backbone signals binding at the surface by a chromatic transition. The color transition is readily visible to the naked eye as a blue to red color change and can be quantified by visible absorption spectroscopy. Direct colorimetric detection by polydiacetylene films offers new possibilities for diagnostic applications and screening for new drug candidates or binding ligands.

  6. Direct colorimetric detection of a receptor-ligand interaction by a polymerized bilayer assembly

    SciTech Connect

    Charych, D.H.; Nagy, J.O.; Bednarski, M.D. ); Spevak, W. )

    1993-07-30

    Detection of receptor-ligand interactions is generally accomplished by indirect assays such as enzyme-linked immunosorbent assay. A direct colorimetric detection method based on a polydiacetylene bilayer assembled on glass microscope slides has been developed. The bilayer is composed of a self-assembled monolayer of octadecylsilane and a Langmuir-Blodgett monolayer of polydiacetylene. The polydiacetylene layer is functionalized with an analog of sialic acid, the receptor-specific ligand for the influenza virus hemagglutinin. The sialic acid ligand serves as a molecular recognition element and the conjugated polymer backbone signals binding at the surface by a chromatic transition. The color transition is readily visible to the naked eye as a blue to red color change and can be quantified by visible absorption spectroscopy. Direct colorimetric detection by polydiacetylene films offers new possibilities for diagnostic applications and screening for new drug candidates or binding ligands.

  7. Direct visualization of lead corona and its nanomolar colorimetric detection using anisotropic gold nanoparticles.

    PubMed

    Dwivedi, Charu; Chaudhary, Abhishek; Gupta, Abhishek; Nandi, Chayan K

    2015-03-11

    The study presents dithiothreitol (DTT) functionalized anisotropic gold nanoparticles (GNP) based colorimetric sensor for detection of toxic lead ions in water. Our results demonstrate the selectivity and sensitivity of the developed sensor over various heavy metal ions with detection limit of ∼9 nM. The mechanism of sensing is explained on the basis of unique corona formation around the DTT functionalized anisotropic GNP. PMID:25719820

  8. 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 2.0×10(-9) to 6.3 ×10(-7) M with the detection limit of 9.4×10(-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

  9. Colorimetric Immunoassay for Detection of Tumor Markers

    PubMed Central

    Yin, Yongmei; Cao, Ya; Xu, Yuanyuan; Li, Genxi

    2010-01-01

    Tumor markers are substances, usually proteins, produced by the body in response to cancer growth, or by the cancer tissue itself. They can be detected in blood, urine, or tissue samples, and the discovery and detection of tumor markers may provide earlier diagnosis of cancer and improved therapeutic intervention. Colorimetric immunoassays for tumor marker detection have attracted considerable attention, due to their simplicity and high efficiency. The traditionally used colorimetric immunoassays for the detection of tumor markers are based on enzyme-linked immunosorbent assays, and the great achievement of nanotechnology has further opened opportunities for the development of such kind of immunoassays. This paper will summarize recent advances in the field of colorimetric immunoassays for detecting tumor markers, which is aimed to provide an overview in this field, as well as experimental guidance for the learner. PMID:21614193

  10. 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.

  11. A colorimetric sensor array for detection of triacetone triperoxide vapor.

    PubMed

    Lin, Hengwei; Suslick, Kenneth S

    2010-11-10

    Triacetone triperoxide (TATP), one of the most dangerous primary explosives, has emerged as an explosive of choice for terrorists in recent years. Owing to the lack of UV absorbance, fluorescence, or facile ionization, TATP is extremely difficult to detect directly. Techniques that are able to detect generally require expensive instrumentation, need extensive sample preparation, or cannot detect TATP in the gas phase. Here we report a simple and highly sensitive colorimetric sensor for the detection of TATP vapor with semiquantitative analysis from 50 ppb to 10 ppm. By using a solid acid catalyst to pretreat a gas stream, we have discovered that a colorimetric sensor array of redox sensitive dyes can detect even very low levels of TATP vapor from its acid decomposition products (e.g., H(2)O(2)) with limits of detection (LOD) below 2 ppb (i.e., <0.02% of its saturation vapor pressure). Common potential interferences (e.g., humidity, personal hygiene products, perfume, laundry supplies, volatile organic compounds, etc.) do not generate an array response, and the array can also differentiate TATP from other chemical oxidants (e.g., hydrogen peroxide, bleach, tert-butylhydroperoxide, peracetic acid). PMID:20949933

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

    NASA Astrophysics Data System (ADS)

    Schmitt, Katrin; Rist, Jonas; Peter, Carolin; Wöllenstein, Jürgen

    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 μm 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 λ = 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 100μW.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. BacT/Alert: an automated colorimetric microbial detection system.

    PubMed Central

    Thorpe, T C; Wilson, M L; Turner, J E; DiGuiseppi, J L; Willert, M; Mirrett, S; Reller, L B

    1990-01-01

    BacT/Alert (Organon Teknika Corp., Durham, N.C.) is an automated microbial detection system based on the colorimetric detection of CO2 produced by growing microorganisms. Results of an evaluation of the media, sensor, detection system, and detection algorithm indicate that the system reliably grows and detects a wide variety of bacteria and fungi. Results of a limited pilot clinical trial with a prototype research instrument indicate that the system is comparable to the radiometric BACTEC 460 system in its ability to grow and detect microorganisms in blood. On the basis of these initial findings, large-scale clinical trials comparing BacT/Alert with other commercial microbial detection systems appear warranted. PMID:2116451

  15. Colorimetric Detection and Identification of Natural and Artificial Sweeteners

    PubMed Central

    Musto, Christopher J.; Lim, Sung H.; Suslick, Kenneth S.

    2009-01-01

    A disposable, low-cost colorimetric sensor array has been created by pin-printing onto a hydrophilic membrane 16 chemically responsive nanoporous pigments made from indicators immobilized in an organically modified silane (ormosil). The array has been used to detect and identify 14 different natural and artificial sweeteners at millimolar concentrations as well as commonly used individual serving sweetener packets. The array has shown excellent reproducibility and long shelf-life and has been optimized to work in the biological pH regime. PMID:20337402

  16. Direct colorimetric method for determination of organophosphates in human urine.

    PubMed

    Namera, A; Utsumi, Y; Yashiki, M; Ohtani, M; Imamura, T; Kojima, T

    2000-01-20

    A simple and sensitive method for determination of organophosphorus pesticides in human urine was developed by detecting the color complexes which resulted from reactions of organophosphorus pesticides and 4-(4-nitrobenzyl)pyridine (NBP) in urine. Based on studies of reaction conditions, e.g. reaction temperature and time, and reagent concentration, a colorimetric method was established. A 0.1-ml volume of NBP (45% in acetone) was added to a 1.0-ml volume of a urine sample, and the mixture was heated at 100 degrees C for 20 min. After cooling, 0.1 ml of tetraethylenepentamine was added. The organophosphorus pesticides showed a characteristic purplish blue color and the coloring complexes which were produced were stable for several hours. Furthermore, these complexes could be determined spectrophotometrically. The detection limits were 0.10-10 microg/ml in urine. The required time for analysis was approximately 30 min for one sample. Comparing the result of the proposed method with those of the GC-MS method, the results were similar for the 12 poisoning cases studied. Thus, the proposed method is useful for detection of these pesticides in critical care practices. PMID:10612713

  17. Colorimetric paper bioassay for the detection of phenolic compounds.

    PubMed

    Alkasir, Ramiz S J; Ornatska, Maryna; Andreescu, Silvana

    2012-11-20

    A new type of paper based bioassay for the colorimetric detection of phenolic compounds including phenol, bisphenol A, catechol and cresols is reported. The sensor is based on a layer-by-layer (LbL) assembly approach formed by alternatively depositing layers of chitosan and alginate polyelectrolytes onto filter paper and physically entrapping the tyrosinase enzyme in between these layers. The sensor response is quantified as a color change resulting from the specific binding of the enzymatically generated quinone to the multilayers of immobilized chitosan on the paper. The color change can be quantified with the naked eye but a digitalized picture can also be used to provide more sensitive comparison to a calibrated color scheme. The sensor was optimized with respect to the number of layers, pH, enzyme, chitosan and alginate amounts. The colorimetric response was concentration dependent, with a detection limit of 0.86 (±0.1) μg/L for each of the phenolic compounds tested. The response time required for the sensor to reach steady-state color varied between 6 and 17 min depending on the phenolic substrate. The sensor showed excellent storage stability at room temperature for several months (92% residual activity after 260 days storage) and demonstrated good functionality in real environmental samples. A procedure to mass-produce the bioactive sensors by inkjet printing the LbL layers of polyelectrolyte and enzyme on paper is demonstrated. PMID:23113670

  18. Hybrid nanosensor for colorimetric and ultrasensitive detection of nuclease contaminations

    NASA Astrophysics Data System (ADS)

    Cecere, Paola; Valentini, Paola; Pompa, Pier Paolo

    2016-04-01

    Nucleases are ubiquitous enzymes that degrade DNA or RNA, thus they can prejudice the good outcome of molecular biology experiments involving nucleic acids. We propose a colorimetric test for the naked-eye detection of nuclease contaminations. The system uses an hybrid nanosensor, based on gold nanoparticles functionalized with DNA probes. Our assay is rapid, instrument-free, simple and low-cost. Moreover, it reaches sensitivity equal or better than those of commercial kits, and presents a lot of advantageous aspects. Therefore, it is very competitive, with a real market potential. This test will be relevant in routine process monitoring in scientific laboratories, and in quality control in clinical laboratories and industrial processes, allowing the simultaneous detection of nucleases with different substrate specificities and large-scale screening.

  19. 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

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

    PubMed

    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

  1. Colorimetric multiplexed immunoassay for sequential detection of tumor markers.

    PubMed

    Wang, Jing; Cao, Ya; Xu, Yuanyuan; Li, Genxi

    2009-10-15

    In this paper, a very simple and easily-operated colorimetric multiplexed immunoassay method for sequential detection of tumor markers has been presented. Magnetic microparticles which are conjugated with biotinylated antibodies are firstly added into the test solution. After fast magnetic collection, these complexes are separated from non-specific proteins. Through different enzymatic reactions of 3,3',5,5'-tetramethylbenzidine (TMB) and o-phenylenediamine (OPD) catalyzed by horseradish peroxidase molecules which are loaded on the surfaces of gold nanoparticles, two antigens carcinoembryonic antigen and alpha-fetoprotein can be detected even with naked eyes. The detection limit obtained from the spectrophotometric measurements is as low as 0.02 ng/mL. This proposed method also has high specificity and reproducibility, as well as excellent efficiency of 94 min for the detection of serum samples. So, this new multiplexed immunoassay method might be a promising approach for the diagnosis of cancer and some other diseases in clinical applications. PMID:19726177

  2. 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

  3. A gold nanoparticles-based colorimetric test to detect single nucleotide polymorphisms for improvement of personalized therapy of psoriasis

    NASA Astrophysics Data System (ADS)

    Marsella, Alessandra; Valentini, Paola; Tarantino, Paolo; Congedo, Maurizio; Pompa, Pier Paolo

    2016-04-01

    We report a simple, rapid and low-cost test, based on gold nanoparticles, for the naked-eye colorimetric detection of a signature of single nucleotide polymorphisms (SNPs) relevant for the personalized medicine of psoriasis patients. We validated the colorimetric assay on real-world DNA samples from a cohort of 30 psoriasis patients and we compared the results, in double-blind, with those obtained with two state-of-the-art instrumental techniques, namely reverse dot blotting and direct sequencing, finding 100% agreement. We demonstrated high accuracy, sensitivity and specificity of the colorimetric test that can be easily adapted for the genotypization of different SNPs, important for the pharmacogenomics of various diseases, and in other fields, such as food traceability and population structure analysis.

  4. 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

  5. Highly sensitive colorimetric detection of glucose and uric acid in biological fluids using chitosan-modified paper microfluidic devices.

    PubMed

    Gabriel, Ellen F M; Garcia, Paulo T; Cardoso, Thiago M G; Lopes, Flavio M; Martins, Felipe T; Coltro, Wendell K T

    2016-08-01

    This paper describes the modification of microfluidic paper-based analytical devices (μPADs) with chitosan to improve the analytical performance of colorimetric measurements associated with enzymatic bioassays. Chitosan is a natural biopolymer extensively used to modify biosensing surfaces due to its capability of providing a suitable microenvironment for the direct electron transfer between an enzyme and a reactive surface. This hypothesis was investigated using glucose and uric acid (UA) colorimetric assays as model systems. The best colorimetric sensitivity for glucose and UA was achieved using a chromogenic solution composed of 4-aminoantipyrine and sodium 3,5-dichloro-2-hydroxy-benzenesulfonate (4-AAP/DHBS), which provided a linear response for a concentration range between 0.1 and 1.0 mM. Glucose and UA were successfully determined in artificial serum samples with accuracies between 87 and 114%. The limits of detection (LODs) found for glucose and UA assays were 23 and 37 μM, respectively. The enhanced analytical performance of chitosan-modified μPADs allowed the colorimetric detection of glucose in tear samples from four nondiabetic patients. The achieved concentration levels ranged from 130 to 380 μM. The modified μPADs offered analytical reliability and accuracy as well as no statistical difference from the values achieved through a reference method. Based on the presented results, the proposed μPAD can be a powerful alternative tool for non-invasive glucose analysis. PMID:27272206

  6. 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

  7. 4-mercaptophenylboronic acid functionalized gold nanoparticles for colorimetric sialic acid detection.

    PubMed

    Sankoh, Supannee; Thammakhet, Chongdee; Numnuam, Apon; Limbut, Warakorn; Kanatharana, Proespichaya; Thavarungkul, Panote

    2016-11-15

    A simple and selective colorimetric sensor for sialic acid detection, based on the aggregation of 4-mercaptophenylboronic acid functionalized gold nanoparticles (4-MPBA-AuNPs) was developed. The color of the solution changed from wine-red to blue after binding with sialic acid. The colorimetric sensor provided good analytical performances with a linear dynamic range of 80µM to 2.00mM and a 68±2µM limit of detection without any effect from possible interferences and sample matrix. In addition, the quantitative results were obtained within only 10min. This developed sensor was used to detect sialic acid in blood serum samples and the results were in good agreement with those from the current periodate-resorcinol method (P>0.05) thus indicating that this developed colorimetric sensor can be used as an alternative method for sialic acid detection with a shorter analysis time and a high accuracy. PMID:27266659

  8. 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

  9. 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...

  10. Colorimetric Detection of Escherichia coli Based on the Enzyme-Induced Metallization of Gold Nanorods.

    PubMed

    Chen, Juhong; Jackson, Angelyca A; Rotello, Vincent M; Nugen, Sam R

    2016-05-01

    A novel enzyme-induced metallization colorimetric assay is developed to monitor and measure beta-galactosidase (β-gal) activity, and is further employed for colorimetric bacteriophage (phage)-enabled detection of Escherichia coli (E. coli). This assay relies on enzymatic reaction-induced silver deposition on the surface of gold nanorods (AuNRs). In the presence of β-gal, the substrate p-aminophenyl β-d-galactopyranoside is hydrolyzed to produce p-aminophenol (PAP). Reduction of silver ions by PAP generates a silver shell on the surface of AuNRs, resulting in the blue shift of the longitudinal localized surface plasmon resonance peak and multicolor changes of the detection solution from light green to orange-red. Under optimized conditions, the detection limit for β-gal is 128 pM, which is lower than the conventional colorimetric assay. Additionally, the assay has a broader dynamic range for β-gal detection. The specificity of this assay for the detection of β-gal is demonstrated against several protein competitors. Additionally, this technique is successfully applied to detect E. coli bacteria cells in combination with bacteriophage infection. Due to the simplicity and short incubation time of this enzyme-induced metallization colorimetric method, the assay is well suited for the detection of bacteria in low-resource settings. PMID:26997252

  11. 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

  12. Enzyme-free colorimetric detection systems based on the DNA strand displacement competition reaction

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Birkedal, V.; Gothelf, K. V.

    2016-05-01

    The strand displacement competition assay is based on the dynamic equilibrium of the competitive hybridization of two oligonucleotides (A and B) to a third oligonucleotide (S). In the presence of an analyte that binds to a specific affinity-moiety conjugated to strand B, the equilibrium shifts, which can be detected by a shift in the fluorescence resonance energy transfer signal between dyes attached to the DNA strands. In the present study we have integrated an ATP aptamer in the strand B and demonstrated the optical detection of ATP. Furthermore we explore a new readout method using a split G-quadruplex DNAzyme for colorimetric readout of the detection of streptavidin by the naked eye. Finally, we integrate the whole G-quadruplex DNAzyme system in a single DNA strand and show that it is applicable to colorimetric detection.

  13. 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

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

    PubMed

    Montes-Robles, Roberto; Moragues, María Esperanza; Vivancos, José-Luis; Ibáñez, Javier; Fraile, Rubén; Martínez-Máñez, Ramón; García-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

  15. 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.

  16. 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

  17. Label-free colorimetric aptasensor for sensitive detection of ochratoxin A utilizing hybridization chain reaction.

    PubMed

    Wang, Chengke; Dong, Xiaoya; Liu, Qian; Wang, Kun

    2015-02-20

    The combination of high selectivity of aptamer with the peroxidase-mimicking property of DNAzyme has presented considerable opportunities for designing colorimetric aptasensor for detection of ochratoxin A (OTA). The activities of both aptamer (as biorecognition element) and DNAzyme (as signal amplification element) are blocked via base pairing in the hairpin structure. Hybridization chain reaction (HCR) between two hairpin DNAs was employed to further improve the sensitivity of this method. The presence of OTA triggers the opening of the hairpin structure and the beginning of HCR, which results in the release of many DNAzyme, and generates enhanced colorimetric signals, which is correlated to the amounts of OTA with linear range between 0.01 to 0.32 nM, and the limit of detection is 0.01 nM under optimal conditions. OTA in yellow rice wine and wheat flour samples was also detected using this method. We demonstrate that a new colorimetric method for the detection of OTA has been established, which is simple, easy to conduct, label-free, sensitive, high throughput, and cost-saving. PMID:25682251

  18. A cellulose-based bioassay for the colorimetric detection of pathogen DNA.

    PubMed

    Saikrishnan, Deepika; Goyal, Madhu; Rossiter, Sharon; Kukol, Andreas

    2014-12-01

    Cellulose-paper-based colorimetric bioassays may be used at the point of sampling without sophisticated equipment. This study reports the development of a colorimetric bioassay based on cellulose that can detect pathogen DNA. The detection was based on covalently attached single-stranded DNA probes and visual analysis. A cellulose surface functionalized with tosyl groups was prepared by the N,N-dimethylacetamide-lithium chloride method. Tosylation of cellulose was confirmed by scanning electron microscopy, Fourier transform infrared spectroscopy and elemental analysis. Sulfhydryl-modified oligonucleotide probes complementary to a segment of the DNA sequence IS6110 of Mycobacterium tuberculosis were covalently immobilized on the tosylated cellulose. On hybridization of biotin-labelled DNA oligonucleotides with these probes, a colorimetric signal was obtained with streptavidin-conjugated horseradish peroxidase catalysing the oxidation of tetramethylbenzamidine by H2O2. The colour intensity was significantly reduced when the bioassay was subjected to DNA oligonucleotide of randomized base composition. Initial experiments have shown a sensitivity of 0.1 μM. A high probe immobilization efficiency (more than 90 %) was observed with a detection limit of 0.1 μM, corresponding to an absolute amount of 10 pmol. The detection of M. tuberculosis DNA was demonstrated using this technique coupled with PCR for biotinylation of the DNA. This work shows the potential use of tosylated cellulose as the basis for point-of-sampling bioassays. PMID:25354892

  19. Colorimetric and fluorometric detection of neomycin based on conjugated polydiacetylene supramolecules.

    PubMed

    Zhou, Guodong; Wang, Fang; Wang, Huilin; Kambam, Srinivasulu; Chen, Xiaoqiang

    2013-06-13

    Utilizing the colorimetric and fluorogenic changes, a system based on polydiacetylenes (PDAs) is developed for the detection of neomycin. The PDA supramolecules polymerized from the mixed liposome composed of N-(3-hydroxyphenyl)pentacosa-10,12-diynamide (PCDA-AP) and pentacosa-10,12-diynoic acid (PCDA) at an optimized ratio of 1:9 display a unique colorimetric change (blue to red) and fluorescent enhancement in the presence of neomycin. The detection limit for neomycin is estimated to be 2.55 × 10(-7) M by the fluorogenic method. The optical changes induced by neomycin can be attributed to the disruption of the hydrogen bonding between phenol and carboxylic acid from PCDA-AP and PCDA. PMID:23649672

  20. 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.

  1. 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.

  2. 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.

  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. 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

  5. ``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 μM, 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

  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 μM, 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. G-quadruplex-generating polymerase chain reaction for visual colorimetric detection of amplicons.

    PubMed

    Bhadra, Sanchita; Codrea, Vlad; Ellington, Andrew D

    2014-01-15

    We have developed a self-reporting polymerase chain reaction (PCR) system for visual colorimetric gene detection and distinction of single nucleotide polymorphisms (SNPs). Amplification is performed using target-specific primers modified with a 5'-end tail that is complementary to a G-quadruplex deoxyribozyme-forming sequence. At end-point, G-quadruplexes are forced to fold from PCR-generated duplex DNA and then are used to colorimetrically report the successful occurrence of PCR by assaying their peroxidase activity using a chromogenic substrate. Furthermore, primer design considerations for the G-quadruplex-generating PCR system have allowed us to visually distinguish SNPs associated with Mycobacterium tuberculosis drug resistance alleles. PMID:24135653

  8. [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

  9. Colorimetric peroxidase mimetic assay for uranyl detection in sea water.

    PubMed

    Zhang, Dingyuan; Chen, Zhuo; Omar, Haneen; Deng, Lin; Khashab, Niveen M

    2015-03-01

    Uranyl (UO2(2+)) is a form of uranium in aqueous solution that represents the greatest risk to human health because of its bioavailability. Different sensing techniques have been used with very sensitive detection limits especially the recently reported uranyl-specific DNAzymes systems. However, to the best of our knowledge, few efficient detection methods have been reported for uranyl sensing in seawater. Herein, gold nanoclusters (AuNCs) are employed in an efficient spectroscopic method to detect uranyl ion (UO2(2+)) with a detection limit of 1.86 μM. In the absence of UO2(2+), the BSA-stabilized AuNCs (BSA-AuNCs) showed an intrinsic peroxidase-like activity. In the presence of UO2(2+), this activity can be efficiently restrained. The preliminary quenching mechanism and selectivity of UO2(2+) was also investigated and compared with other ions. This design strategy could be useful in understanding the binding affinity of protein-stabilized AuNCs to UO2(2+) and consequently prompt the recycling of UO2(2+) from seawater. PMID:25658750

  10. 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.

  11. A Simple Colorimetric Assay for Specific Detection of Glutathione-S Transferase Activity Associated with DDT Resistance in Mosquitoes

    PubMed Central

    Rajatileka, Shavanti; Steven, Andrew; Hemingway, Janet; Ranson, Hilary; Paine, Mark; Vontas, John

    2010-01-01

    Background Insecticide-based methods represent the most effective means of blocking the transmission of vector borne diseases. However, insecticide resistance poses a serious threat and there is a need for tools, such as diagnostic tests for resistance detection, that will improve the sustainability of control interventions. The development of such tools for metabolism-based resistance in mosquito vectors lags behind those for target site resistance mutations. Methodology/Principal Findings We have developed and validated a simple colorimetric assay for the detection of Epsilon class Glutathione transferases (GST)-based DDT resistance in mosquito species, such as Aedes aegypti, the major vector of dengue and yellow fever worldwide. The colorimetric assay is based on the specific alkyl transferase activity of Epsilon GSTs for the haloalkene substrate iodoethane, which produces a dark blue colour highly correlated with AaGSTE2-2-overexpression in individual mosquitoes. The colour can be measured visually and spectrophotometrically. Conclusions/Significance The novel assay is substantially more sensitive compared to the gold standard CDNB assay and allows the discrimination of moderate resistance phenotypes. We anticipate that it will have direct application in routine vector monitoring as a resistance indicator and possibly an important impact on disease vector control. PMID:20824165

  12. Sensitive colorimetric detection of Listeria monocytogenes based on isothermal gene amplification and unmodified gold nanoparticles.

    PubMed

    Fu, Zhongyu; Zhou, Xiaoming; Xing, Da

    2013-12-15

    Listeria monocytogenes (L. monocytogenes), one of most problematic food-borne bacteria, is mainly transmitted through the food chain and may cause listeriosis. Therefore, the development of rapid and sensitive L. monocytogenes detection technique has become an urgent task. In this study, we proposed a method using hyperbranching rolling circle amplification (HRCA) combined with gold nanoparticle (GNP) based colorimetric strategy to offer an isothermal, highly sensitive and specific assay for the detection of L. monocytogenes. First, a linear padlock probe targeting a specific sequence in the hly gene was designed and followed with a ligation by Taq DNA ligase. After ligation, further amplification by HRCA with a thiolated primer and an unlabeled primer is performed. The resulting thiolated HRCA products were then captured onto GNP surface and made GNP more salt-tolerant. Detection of the bacteria can be achieved by a facilitated GNP based colorimetric testing using naked eyes. Through this approach, as low as 100 aM synthetic hly gene targets and about 75 copies of L. monocytogenes can be detected. The specificity is evaluated by distinguishing target L. monocytogenes from other bacteria. The artificial contaminated food samples were also detected for its potential applications in real food detection. This method described here is ideal for bacteria detection due to its simplicity and high sensitivity. PMID:23948710

  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. 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

  15. 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

    2016-02-01

    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

  16. Iodide-Responsive Cu-Au Nanoparticle-Based Colorimetric Platform for Ultrasensitive Detection of Target Cancer Cells.

    PubMed

    Ye, Xiaosheng; Shi, Hui; He, Xiaoxiao; Wang, Kemin; He, Dinggeng; Yan, Lv'an; Xu, Fengzhou; Lei, Yanli; Tang, Jinlu; Yu, Yanru

    2015-07-21

    Colorimetric analysis is promising in developing facile, fast, and point-of-care cancer diagnosis techniques, but the existing colorimetric cancer cell assays remain problematic because of dissatisfactory sensitivity as well as complex probe design or synthesis. To solve the problem, we here present a novel colorimetric analytical strategy based on iodide-responsive Cu-Au nanoparticles (Cu-Au NPs) combined with the iodide-catalyzed H2O2-TMB (3,3,5,5-tetramethylbenzidine) reaction system. In this strategy, bimetallic Cu-Au NPs prepared with an irregular shape and a diameter of ∼15 nm could chemically absorb iodide, thus indirectly inducing colorimetric signal variation of the H2O2-TMB system. By further utilizing its property of easy biomolecule modification, a versatile colorimetric platform was constructed for detection of any target that could cause the change of Cu-Au NPs concentration via molecular recognition. As proof of concept, an analysis of human leukemia CCRF-CEM cells was performed using aptamer Sgc8c-modified Cu-Au NPs as the colorimetric probe. Results showed that Sgc8c-modified Cu-Au NPs successfully achieved a simple, label-free, cost-effective, visualized, selective, and ultrasensitive detection of cancer cells with a linear range from 50 to 500 cells/mL and a detection limit of 5 cells in 100 μL of binding buffer. Moreover, feasibility was demonstrated for cancer cell analysis in diluted serum samples. The iodide-responsive Cu-Au NP-based colorimetric strategy might not only afford a new design pattern for developing cancer cell assays but also greatly extend the application of the iodide-catalyzed colorimetric system. PMID:26100583

  17. 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 μM H2O2, with a detection limit of 0.031 μM. 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 μM and the linear range was from 0.1 μM to 50.0 μM. 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

  18. A colorimetric and fluorescent probe for detecting intracellular biothiols.

    PubMed

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

    2016-11-15

    A new rapid and highly sensitive coumarin-based probe (probe 1) has been designed and synthesized for detecting intracellular thiols. Probe 1 was prepared by a 4-step procedure as a latent fluorescence probe to achieve high sensitivity and fluorescence turn-on response toward cysteine and homocysteine over GSH and other various natural amino acids under physiological conditions. Owing to specific cyclization between thiols and aldehyde group, probe 1 displayed a highly selectivity toward cysteine and homocysteine. Above all, probe 1 was successfully used for fluorescence imaging of biothiols in Hela cells, and quantitative determination had been achieved within a certain range. Then specific fluorescence imaging of mice organ tissues was obtained for proving the permeability of probe 1. Simultaneously, the viability was measured to be more than 80%, which shows probe 1 can be a rapid and biocompatible probe for biothiols in cells. Furthermore, the measurement of thiols detection in 5 kinds of animal serum showed that probe 1 can be used in determination of biothiols in blood. PMID:27155115

  19. A Rapid In Situ Colorimetric Assay for Cobalt Detection by the Naked Eye.

    PubMed

    Kang, Sung-Min; Jang, Sung-Chan; Kim, Gi Yong; Lee, Chang-Soo; Huh, Yun Suk; Roh, Changhyun

    2016-01-01

    A simple, rapid, and convenient colorimetric chemosensor of a specific target toward the end user is still required for on-site detection and real-time monitoring applications. In this study, we developed a rapid in situ colorimetric assay for cobalt detection using the naked eye. Interestingly, a yellow to light orange visual color transition was observed within 3 s when a Chrysoidine G (CG) chemosensor was exposed to cobalt. Surprisingly, the CG chemosensor had great selectivity toward cobalt without any interference of other metal ions. Under optimized conditions, a lower detection limit of 0.1 ppm via a spectrophotometer and a visual detection limit of 2 ppm with a linear range from 0.4 to 1 ppm (R² = 0.97) were determined. Moreover, the CG chemosensor is reversible and maintains its functionality after treatment with chelating agents. In conclusion, we show the superior capabilities of the CG chemosensor, which has the potential to provide extremely facile handling, high sensitivity, and a fast response time for applications of on-site detection to real-time cobalt monitoring for the general public. PMID:27144568

  20. 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] = 21.1 ± 0.4 parasites/μl). 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 45 min and detection limits similar to those of commercial enzyme-linked immunosorbent assay (ELISA) kits, which can take 4-6 h. 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

  1. 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

  2. A Rapid In Situ Colorimetric Assay for Cobalt Detection by the Naked Eye

    PubMed Central

    Kang, Sung-Min; Jang, Sung-Chan; Kim, Gi Yong; Lee, Chang-Soo; Huh, Yun Suk; Roh, Changhyun

    2016-01-01

    A simple, rapid, and convenient colorimetric chemosensor of a specific target toward the end user is still required for on-site detection and real-time monitoring applications. In this study, we developed a rapid in situ colorimetric assay for cobalt detection using the naked eye. Interestingly, a yellow to light orange visual color transition was observed within 3 s when a Chrysoidine G (CG) chemosensor was exposed to cobalt. Surprisingly, the CG chemosensor had great selectivity toward cobalt without any interference of other metal ions. Under optimized conditions, a lower detection limit of 0.1 ppm via a spectrophotometer and a visual detection limit of 2 ppm with a linear range from 0.4 to 1 ppm (R2 = 0.97) were determined. Moreover, the CG chemosensor is reversible and maintains its functionality after treatment with chelating agents. In conclusion, we show the superior capabilities of the CG chemosensor, which has the potential to provide extremely facile handling, high sensitivity, and a fast response time for applications of on-site detection to real-time cobalt monitoring for the general public. PMID:27144568

  3. Photonic nanosensor for colorimetric detection of metal ions.

    PubMed

    Yetisen, Ali K; Montelongo, Yunuen; Qasim, Malik M; Butt, Haider; Wilkinson, Timothy D; Monteiro, Michael J; Yun, Seok Hyun

    2015-01-01

    The real-time sensing of metal ions at point of care requires integrated sensors with low energy and sample consumption, reversibility, and rapid recovery. Here, we report a photonic nanosensor that reversibly and quantitatively reports on variation in the concentrations of Pb(2+) and Cu(2+) ions in aqueous solutions (<500 μL) in the visible region of the spectrum (λ(max) ≈ 400-700 nm). A single 6 ns laser pulse (λ = 532 nm) was used to pattern an ∼10 μm thick photosensitive recording medium. This formed periodic AgBr nanocrystal (ø ∼ 5-20 nm) concentrated regions, which produced Bragg diffraction upon illumination with a white light source. The sensor functionalized with 8-hydroxyquinoline allowed sensing through inducing Donnan osmotic pressure and tuning its lattice spacing. The sensor quantitatively measured Pb(2+) and Cu(2+) ion concentrations within the dynamic range of 0.1-10.0 mM with limits of detection of 11.4 and 18.6 μM in under 10 min. The sensor could be reset in 3 min and was reused at least 100 times without compromising its accuracy. The plasmonic nanosensor represents a simple and label-free analytical platform with potential scalability for applications in medical diagnostics and environmental monitoring. PMID:25710792

  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. 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.

  6. Nucleic acid-coupled colorimetric analyte detectors

    DOEpatents

    Charych, Deborah H.; Jonas, Ulrich

    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.

  7. Fully automated and colorimetric foodborne pathogen detection on an integrated centrifugal microfluidic device.

    PubMed

    Oh, Seung Jun; Park, Byung Hyun; Choi, Goro; Seo, Ji Hyun; Jung, Jae Hwan; Choi, Jong Seob; Kim, Do Hyun; Seo, Tae Seok

    2016-05-21

    This work describes fully automated and colorimetric foodborne pathogen detection on an integrated centrifugal microfluidic device, which is called a lab-on-a-disc. All the processes for molecular diagnostics including DNA extraction and purification, DNA amplification and amplicon detection were integrated on a single disc. Silica microbeads incorporated in the disc enabled extraction and purification of bacterial genomic DNA from bacteria-contaminated milk samples. We targeted four kinds of foodborne pathogens (Escherichia coli O157:H7, Salmonella typhimurium, Vibrio parahaemolyticus and Listeria monocytogenes) and performed loop-mediated isothermal amplification (LAMP) to amplify the specific genes of the targets. Colorimetric detection mediated by a metal indicator confirmed the results of the LAMP reactions with the colour change of the LAMP mixtures from purple to sky blue. The whole process was conducted in an automated manner using the lab-on-a-disc and a miniaturized rotary instrument equipped with three heating blocks. We demonstrated that a milk sample contaminated with foodborne pathogens can be automatically analysed on the centrifugal disc even at the 10 bacterial cell level in 65 min. The simplicity and portability of the proposed microdevice would provide an advanced platform for point-of-care diagnostics of foodborne pathogens, where prompt confirmation of food quality is needed. PMID:27112702

  8. 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. 1 nM to 1 μM with a detection limit (LOD) of 0.06 nM 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

  9. 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

  10. 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 μg mL-1, respectively. The corresponding limit of detection for doxycycline and oxytetracycline was 0.0086 and 0.0838 μg mL-1, respectively. This assay was sensitive, selective, simple and readily used to detect tetracycline antibiotics in food products.

  11. Sensitive detection of transcription factors by isothermal exponential amplification-based colorimetric assay.

    PubMed

    Zhang, Yan; Hu, Juan; Zhang, Chun-Yang

    2012-11-01

    Transcription factors regulate gene expression by binding to specific DNA sequences within the regulatory regions of genes and have become potential targets in clinical diagnosis and drug development. However, traditional approaches for the detection of transcription factors are usually laborious and time-consuming with a low sensitivity. Here, we develop an isothermal exponential amplification reaction (EXPAR)-based colorimetric assay for simple and sensitive detection of transcription factor NF-κB p50. In this assay, the presence of NF-κB p50 is converted to the reporter oligonucleotides through protein-DNA interaction, exonuclease III digestion, and isothermal exponential amplification. The subsequent sandwich hybridization of the reporter oligonucleotides with the gold nanoparticle (AuNP)-labeled DNA probes generates a red-to-purple color change, allowing the visual detection of NF-κB p50 with the naked eye. Notably, this method converts the detection of transcription factors to the detection of DNA without the requirement of DNA marker-linked antibodies in the case of immuno-PCR and can sensitively measure NF-κB p50 with a detection limit of 3.8 pM, which has improved by as much as 4 orders of magnitude as compared with the conventional AuNP-based colorimetric assay and the label-free luminescence assay and up to 4 orders of magnitude as compared with fluorescence resonance energy transfer (FRET)-based assay as well. Importantly, this method can be used to measure TNF-α-induced endogenous NF-κB p50 in HeLa cell nuclear extracts and might be further applied for the detection of various DNA-binding proteins and aptamer-binding molecules. PMID:23050558

  12. 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

  13. Selective colorimetric detection of polynucleotides based on the distance-dependent optical properties of gold nanoparticles.

    PubMed

    Elghanian, R; Storhoff, J J; Mucic, R C; Letsinger, R L; Mirkin, C A

    1997-08-22

    A highly selective, colorimetric polynucleotide detection method based on mercaptoalkyloligonucleotide-modified gold nanoparticle probes is reported. Introduction of a single-stranded target oligonucleotide (30 bases) into a solution containing the appropriate probes resulted in the formation of a polymeric network of nanoparticles with a concomitant red-to-pinkish/purple color change. Hybridization was facilitated by freezing and thawing of the solutions, and the denaturation of these hybrid materials showed transition temperatures over a narrow range that allowed differentiation of a variety of imperfect targets. Transfer of the hybridization mixture to a reverse-phase silica plate resulted in a blue color upon drying that could be detected visually. The unoptimized system can detect about 10 femtomoles of an oligonucleotide. PMID:9262471

  14. Colorimetric Detection of Cadmium Ions Using DL-Mercaptosuccinic Acid-Modified Gold Nanoparticles.

    PubMed

    Chen, Na; Chen, Jun; Yang, Jing-Hua; Bai, Lian-Yang; Zhang, Yu-Ping

    2016-01-01

    A colorimetric assay has been developed for detection of Cd²⁺ utilizing DL-mercaptosuccinic acid-modified gold nanoparticles (MSA-AuNPs). The method showed good selectivity for Cd²⁺ over other metal ions. As a result, the linear relationships (r > 0.9606) between concentration 0.07 mM and 0.20 mM for cadmium ion were obtained. The detection limit was as low as 0.07 mM by the naked eye. The effect of pH on the aggregation was optimized. The MSA-AuNPs probe could be used to detect Cd²⁺ in an aqueous solution based on the aggregation-induced color change of MSA-AuNPs. PMID:27398533

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    A highly sensitive and selective pyridyl based colorimetric chemosensor (H2L) for the efficient detection of Ni2 + has been reported. The synthesized chemosensor H2L is highly efficient in detecting Ni2 + even in the presence of other metal ions that commonly co-exist with Ni2 +. H2L also shows distinct color change from green to deep red visible under naked eye due to specific binding with Ni2 +. This color change is due to formation of a new band at 510 nm upon gradual addition of Ni2 +. The association constant has been found to be 1.27 × 105 M- 1 with limit of detection (LOD) of 8.3 × 10- 7 M. Electronic structure of the H2L-Ni2 + complex and sensing mechanism have been interpreted theoretically by DFT and TDDFT calculations.

  16. 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.

  17. Colorimetric detection of urine glucose based ZnFe2O4 magnetic nanoparticles.

    PubMed

    Su, Li; Feng, Jie; Zhou, Ximin; Ren, Cuiling; Li, Honghong; Chen, Xingguo

    2012-07-01

    In this paper, we discovered that ZnFe(2)O(4) magnetic nanoparticles (MNPs) possess intrinsic peroxidase-like activity. ZnFe(2)O(4) MNPs exhibit several advantages such as high catalytic efficiency, good stability, monodispersion, and rapid separation over other peroxidase nanomimetics and horseradish peroxidase (HRP). ZnFe(2)O(4) MNPs were used as a colorimetric biosensor for the detection of urine glucose. This method is simple, inexpensive, highly sensitive, and selective for glucose detection using glucose oxidase (GOx) and ZnFe(2)O(4) MNPs with a linear range from 1.25 × 10(-6) to 1.875 × 10(-5) mol L(-1) with a detection limit of 3.0 × 10(-7) mol L(-1). The color change observable by the naked eyes based on the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) is the principle for the sensing of urine glucose level. PMID:22702236

  18. 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

  19. 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

  20. 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 µM 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

  1. A simple colorimetric DNA detection by target-induced hybridization chain reaction for isothermal signal amplification.

    PubMed

    Ma, Cuiping; Wang, Wenshuo; Mulchandani, Ashok; Shi, Chao

    2014-07-15

    A novel DNA detection method is presented based on a gold nanoparticle (AuNP) colorimetric assay and hybridization chain reaction (HCR). In this method, target DNA hybridized with probe DNA modified on AuNP, and triggered HCR. The resulting HCR products with a large number of negative charges significantly enhanced the stability of AuNPs, inhibiting aggregation of AuNPs at an elevated salt concentration. The approach was highly sensitive and selective. Using this enzyme-free and isothermal signal amplification method, we were able to detect target DNA at concentrations as low as 0.5 nM with the naked eye. Our method also has great potential for detecting other analytes, such as metal ions, proteins, and small molecules, if the target analytes could make HCR products attach to AuNPs. PMID:24780220

  2. Colorimetric TMPRSS2-ERG Gene Fusion Detection in Prostate Cancer Urinary Samples via Recombinase Polymerase Amplification

    PubMed Central

    Koo, Kevin M.; Wee, Eugene J.H.; Trau, Matt

    2016-01-01

    TMPRSS2 (Exon 1)-ERG (Exon 4) is the most frequent gene fusion event in prostate cancer (PC), and is highly PC-specific unlike the current serum prostate specific antigen (PSA) biomarker. However, TMPRSS2-ERG levels are currently measured with quantitative reverse-transcription PCR (RT-qPCR) which is time-consuming and requires costly equipment, thus limiting its use in clinical diagnostics. Herein, we report a novel rapid, cost-efficient and minimal-equipment assay named “FusBLU” for detecting TMPRSS2-ERG gene fusions from urine. TMPRSS2-ERG mRNA was amplified by isothermal reverse transcription-recombinase polymerase amplification (RT-RPA), magnetically-isolated, and detected through horseradish peroxidase (HRP)-catalyzed colorimetric reaction. FusBLU was specific for TMPRSS2-ERG mRNA with a low visual detection limit of 105 copies. We also demonstrated assay readout versatility on 3 potentially useful platforms. The colorimetric readout was detectable by naked eye for a quick yes/no evaluation of gene fusion presence. On the other hand, a more quantitative TMPRSS2-ERG detection was achievable by absorbance/electrochemical measurements. FusBLU was successfully applied to 12 urinary samples and results were validated by gold-standard RT-qPCR. We also showed that sediment RNA was likely the main source of TMPRSS2-ERG mRNA in urinary samples. We believe that our assay is a potential clinical screening tool for PC and could also have wide applications for other disease-related fusion genes. PMID:27375789

  3. Colorimetric TMPRSS2-ERG Gene Fusion Detection in Prostate Cancer Urinary Samples via Recombinase Polymerase Amplification.

    PubMed

    Koo, Kevin M; Wee, Eugene J H; Trau, Matt

    2016-01-01

    TMPRSS2 (Exon 1)-ERG (Exon 4) is the most frequent gene fusion event in prostate cancer (PC), and is highly PC-specific unlike the current serum prostate specific antigen (PSA) biomarker. However, TMPRSS2-ERG levels are currently measured with quantitative reverse-transcription PCR (RT-qPCR) which is time-consuming and requires costly equipment, thus limiting its use in clinical diagnostics. Herein, we report a novel rapid, cost-efficient and minimal-equipment assay named "FusBLU" for detecting TMPRSS2-ERG gene fusions from urine. TMPRSS2-ERG mRNA was amplified by isothermal reverse transcription-recombinase polymerase amplification (RT-RPA), magnetically-isolated, and detected through horseradish peroxidase (HRP)-catalyzed colorimetric reaction. FusBLU was specific for TMPRSS2-ERG mRNA with a low visual detection limit of 10(5) copies. We also demonstrated assay readout versatility on 3 potentially useful platforms. The colorimetric readout was detectable by naked eye for a quick yes/no evaluation of gene fusion presence. On the other hand, a more quantitative TMPRSS2-ERG detection was achievable by absorbance/electrochemical measurements. FusBLU was successfully applied to 12 urinary samples and results were validated by gold-standard RT-qPCR. We also showed that sediment RNA was likely the main source of TMPRSS2-ERG mRNA in urinary samples. We believe that our assay is a potential clinical screening tool for PC and could also have wide applications for other disease-related fusion genes. PMID:27375789

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

    PubMed

    Zhang, Li; Zhang, Xianhong

    2014-12-10

    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 Cu(2+). In the presence of Cu(2+) the BMSFH exhibits a rapid color change from colorless to yellow together with an obvious new band appeared at 502nm 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 Cu(2+) in a 1:1 stoichiometry and this binding to Cu(2+) is reversible, as indicated by the bleaching of the color when the Cu(2+) is extracted with EDTA. Experimental results indicate that the BMSFH can provide a rapid, selective and sensitive response to Cu(2+) with a linear dynamic range 3.0-330μmol/L and can be used as a potential Cu(2+) colorimetric probe in aqueous solution. PMID:24929315

  5. Beetroot-pigment-derived colorimetric sensor for detection of calcium dipicolinate in bacterial spores.

    PubMed

    Gonçalves, Letícia Christina Pires; Da Silva, Sandra Maria; DeRose, Paul C; Ando, Rômulo 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 1.4 × 10(5) L mol(-1). 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 2.0 × 10(-6) mol L(-1) and the LOD determined for both spores, B. cereus and B. anthracis, is (1.1 ± 0.3)× 10(6) spores mL(-1). 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

  6. A gold nanoparticle-based label free colorimetric aptasensor for adenosine deaminase detection and inhibition assay.

    PubMed

    Cheng, Fen; He, Yue; Xing, Xiao-Jing; Tan, Dai-Di; Lin, Yi; Pang, Dai-Wen; Tang, Hong-Wu

    2015-03-01

    A novel strategy for the fabrication of a colorimetric aptasensor using label free gold nanoparticles (AuNPs) is proposed in this work, and the strategy has been employed for the assay of adenosine deaminase (ADA) activity. The aptasensor consists of adenosine (AD) aptamer, AD and AuNPs. The design of the biosensor takes advantage of the special optical properties of AuNPs and the interaction between AuNPs and single-strand DNA. In the absence of ADA, the AuNPs are aggregated and are blue in color under appropriate salt concentration because of the grid structure of an AD aptamer when binding to AD, while in the presence of the analyte, AuNPs remain dispersed with red color under the same concentration of salt owing to ADA converting AD into inosine which has no affinity with the AD aptamer, thus allowing quantitative investigation of ADA activity. The present strategy is simple, cost-effective, selective and sensitive for ADA with a detection limit of 1.526 U L(-1), which is about one order of magnitude lower than that previously reported. In addition, a very low concentration of the inhibitor erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) could generate a distinguishable response. Therefore, the AuNP-based colorimetric biosensor has great potential in the diagnosis of ADA-relevant diseases and drug screening. PMID:25597304

  7. 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.

  8. Simple and Sensitive Paper-Based Device Coupling Electrochemical Sample Pretreatment and Colorimetric Detection.

    PubMed

    Silva, Thalita G; de Araujo, William R; Muñoz, Rodrigo A A; Richter, Eduardo M; Santana, Mário H P; Coltro, Wendell K T; Paixão, Thiago R L C

    2016-05-17

    We report the development of a simple, portable, low-cost, high-throughput visual colorimetric paper-based analytical device for the detection of procaine in seized cocaine samples. The interference of most common cutting agents found in cocaine samples was verified, and a novel electrochemical approach was used for sample pretreatment in order to increase the selectivity. Under the optimized experimental conditions, a linear analytical curve was obtained for procaine concentrations ranging from 5 to 60 μmol L(-1), with a detection limit of 0.9 μmol L(-1). The accuracy of the proposed method was evaluated using seized cocaine samples and an addition and recovery protocol. PMID:27103080

  9. Preparation of a novel colorimetric luminescence sensor strip for the detection of indole-3-acetic acid.

    PubMed

    Liu, Yan; Dong, Haitao; Zhang, Wenzhu; Ye, Zhiqiang; Wang, Guilan; Yuan, Jingli

    2010-06-15

    A novel colorimetric luminescence sensor strip for the detection of indole-3-acetic acid (IAA) has been fabricated by using green emissive quantum dots of cadmium telluride (CdTe QDs) as a background layer and a red emissive europium chelate, [4'-(9-anthryl)-2,2':6',2''-terpyridine-6,6''-diyl]bis(methylenenitrilo) tetrakis(acetate)-Eu(3+) (ATTA-Eu(3+)), as a specific sensing layer coated on the surface of glass slide, respectively. The luminescence response of the sensor strip is given by the dramatic changes in emission colors from green to red at different IAA concentrations. This approach provides a simple, rapid, sensitive and accurate method for the detection of IAA without using any special scientific instruments. PMID:20353890

  10. Colorimetric detection of biological hydrogen sulfide using fluorosurfactant functionalized gold nanorods.

    PubMed

    Zhang, Xuan; Zhou, Wenjuan; Yuan, Zhiqin; Lu, Chao

    2015-11-01

    As a well-known environmental pollutant but also an important gaseous transmitter, the specific detection of hydrogen sulfide (H2S) is significant in biological systems. In this study, fluorosurfactant functionalized gold nanorods (FSN-AuNRs) have been proposed to act as selective colorimetric nanoprobes for H2S. With the combination of strong gold-S interactions and small FSN bilayer interstices, FSN-AuNRs demonstrate favorable selectivity and sensitivity toward H2S over other anions and small biological molecules. The practical application of the present method in biological H2S detection was validated with human and mouse serum samples. Moreover, the proposed nanoprobe can also be used for evaluating the activity of H2S synthetase. PMID:26415625

  11. 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

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

    PubMed

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

    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

  13. In Situ Enzymatically Generated Photoswitchable Oxidase Mimetics and Their Application for Colorimetric Detection of Glucose Oxidase.

    PubMed

    Cao, Gen-Xia; Wu, Xiu-Ming; Dong, Yu-Ming; Li, Zai-Jun; Wang, Guang-Li

    2016-01-01

    In this study, a simple and amplified colorimetric assay is developed for the detection of the enzymatic activity of glucose oxidase (GOx) based on in situ formation of a photoswitchable oxidase mimetic of PO₄(3-)-capped CdS quantum dots (QDs). GOx catalyzes the oxidation of 1-thio-β-d-glucose to give 1-thio-β-d-gluconic acid which spontaneously hydrolyzes to β-d-gluconic acid and H₂S; the generated H₂S instantly reacts with Cd(2+) in the presence of Na₃PO₄ to give PO₄(3-)-stabilized CdS QDs in situ. Under visible-light (λ ≥ 400 nm) stimulation, the PO₄(3-)-capped CdS QDs are a new style of oxidase mimic derived by producing some active species, such as h⁺, (•)OH, O₂(•-) and a little H₂O₂, which can oxidize the typical substrate (3,3,5,5-tetramethylbenzydine (TMB)) with a color change. Based on the GOx-triggered growth of the oxidase mimetics of PO₄(3-)-capped CdS QDs in situ, we developed a simple and amplified colorimetric assay to probe the enzymatic activity of GOx. The proposed method allowed the detection of the enzymatic activity of GOx over the range from 25 μg/L to 50 mg/L with a low detection limit of 6.6 μg/L. We believe the PO₄(3-)-capped CdS QDs generated in situ with photo-stimulated enzyme-mimicking activity may find wide potential applications in biosensors. PMID:27409598

  14. 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 μU within 15 minutes of assay time. Similarly, cellulase activity can be detected in the range of 6 to 375 mU. 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 μM. 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

  15. One-pot synthesized DNA-templated Ag/Pt bimetallic nanoclusters as peroxidase mimics for colorimetric detection of thrombin.

    PubMed

    Zheng, Cheng; Zheng, Ai-Xian; Liu, Bo; Zhang, Xiao-Long; He, Yu; Li, Juan; Yang, Huang-Hao; Chen, Guonan

    2014-11-01

    We developed a facile one-step approach to synthesize DNA-templated Ag/Pt bimetallic nanoclusters (DNA-Ag/Pt NCs), which possess highly-efficient peroxidase-like catalytic activity. With this finding, an aptamer based sandwich-type strategy is employed to design a label-free colorimetric aptasensor for the protein detection with high sensitivity and selectivity. PMID:25223346

  16. Functional surface modification of natural cellulose substances for colorimetric detection and adsorption of Hg2+ in aqueous media.

    PubMed

    Zhang, Xuehai; Huang, Jianguo

    2010-09-01

    Immobilization of ruthenium dye or mercaptosilane monolayer onto metal oxide ultrathin film pre-coated cellulose nanofibres of natural cellulose substances yielded colorimetric sensing materials with high sensitivity and selectivity as well as good reversibility, and trapping materials with high efficiency for detection and adsorption of Hg(2+) ions in aqueous media. PMID:20514381

  17. 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

  18. A DNA-gold nanoparticle-based colorimetric competition assay for the detection of cysteine.

    PubMed

    Lee, Jae-Seung; Ulmann, Pirmin A; Han, Min Su; Mirkin, Chad A

    2008-02-01

    We report the development of a highly sensitive and selective colorimetric detection method for cysteine based upon oligonucleotide-functionalized gold nanoparticle probes that contain strategically placed thymidine-thymidine (T-T) mismatches complexed with Hg2+. This assay relies upon the distance-dependent optical properties of gold nanoparticles, the sharp melting transition of oligonucleotide-linked nanoparticle aggregates, and the very selective coordination of Hg2+ with cysteine. The concentration of cysteine can be determined by monitoring with the naked eye or a UV-vis spectrometer the temperature at which the purple-to-red color change associated with aggregate dissociation takes place. This assay does not utilize organic cosolvents, enzymatic reactions, light-sensitive dye molecules, lengthy protocols, or sophisticated instrumentation thereby overcoming some of the limitations of more conventional methods. PMID:18205426

  19. Smartphone based health accessory for colorimetric detection of biomarkers in sweat and saliva.

    PubMed

    Oncescu, Vlad; O'Dell, Dakota; Erickson, David

    2013-08-21

    The mobile health market is rapidly expanding and portable diagnostics tools offer an opportunity to decrease costs and increase the availability of healthcare. Here we present a smartphone based accessory and method for the rapid colorimetric detection of pH in sweat and saliva. Sweat pH can be correlated to sodium concentration and sweat rate in order to indicate to users the proper time to hydrate during physical exercise and avoid the risk of muscle cramps. Salivary pH below a critical threshold is correlated with enamel decalcification, an acidic breakdown of calcium in the teeth. We conduct a number of human trials with the device on a treadmill to demonstrate the ability to monitor changes in sweat pH due to exercise and electrolyte intake and predict optimal hydration. Additionally, we perform trials to measure salivary pH over time to monitor the effects of diet on oral health risks. PMID:23784453

  20. A smart phone-based robust correction algorithm for the colorimetric detection of Urinary Tract Infection.

    PubMed

    Karlsen, Haakon; Tao Dong

    2015-08-01

    This paper presents the preliminary work of developing a smart phone based application for colorimetric detection of Urinary Tract Infection. The purpose is to make a smart phone function as a practical point-of-care device for nurses or medical personnel without access to strip readers. The main challenge is the constancy of camera color perception across different illuminations and devices, which is the first step towards a practical solution without additional equipment. A reported black and white reference correction and a comprehensive color image normalization have been utilized in this work. Comprehensive color image normalization appears to be quite effective at correcting the difference in perceived color due to different illumination, and is therefore a candidate for inclusion in the further work. PMID:26736494

  1. Colorimetric Detection of an Airborne Remote Photocatalytic Reaction Using a Stratified Ag Nanoparticle Sheet.

    PubMed

    Degawa, Ryo; Wang, Pangpang; Tanaka, Daisuke; Park, Susie; Sakai, Nobuyuki; Tatsuma, Tetsu; Okamoto, Koichi; Tamada, Kaoru

    2016-08-16

    Photocatalysts are practically used for decomposition of harmful and fouling organic compounds. Among the photocatalytic reactions, remote oxidation via airborne species is a relatively slow process, so that a sensitive technique for its detection has been awaiting. Here, we investigated an airborne remote photocatalytic reaction of a TiO2 photocatalyst modified with Pt nanoparticles as co-catalysts via the color change caused by a decomposition of a multilayered silver nanoparticle sheet. The silver nanoparticle sheet fabricated by the Langmuir-Schaefer method on a gold substrate exhibits a unique multicolor depending upon the number of layers. The color originates from multiple light trapping in the stratified sheets that has a metamaterial characteristic along with an intra- and interlayer coupling of localized surface plasmon resonance (LSPR). The stepwise decomposition of the sheets was confirmed by the colorimetric data, which exhibited not only a monotonic decrease but also a maximized absorption of light when the film thickness reached the optimal thickness for light trapping or when the oxidation of the Ag core started. Scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and surface plasmon resonance (SPR) spectroscopy data provided a complete view of the decomposition process of this inorganic-organic nanocomposite film, and simulation by the transfer-matrix method explained a simultaneous plasmonic response rationally. The influence of the humidity and gas flow rate on the airborne remote photocatalytic reaction kinetics was examined by this colorimetric detection method, and it suggests that H2O in air plays an essential role in the reaction. PMID:27445001

  2. 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

  3. Homogeneous detection of unamplified genomic DNA sequences based on colorimetric scatter of gold nanoparticle probes

    PubMed Central

    Storhoff, James J; Lucas, Adam D; Garimella, Viswanadham; Bao, Y Paul; Müller, Uwe R

    2005-01-01

    Nucleic acid diagnostics is dominated by fluorescence-based assays that use complex and expensive enzyme-based target or signal-amplification procedures1–6. Many clinical diagnostic applications will require simpler, inexpensive assays that can be done in a screening mode. We have developed a ‘spot-and-read’ colorimetric detection method for identifying nucleic acid sequences based on the distance-dependent optical properties of gold nanoparticles. In this assay, nucleic acid targets are recognized by DNA-modified gold probes, which undergo a color change that is visually detectable when the solutions are spotted onto an illuminated glass waveguide. This scatter-based method enables detection of zeptomole quantities of nucleic acid targets without target or signal amplification when coupled to an improved hybridization method that facilitates probe-target binding in a homogeneous format. In comparison to a previously reported absorbance-based method7, this method increases detection sensitivity by over four orders of magnitude. We have applied this method to the rapid detection of mecA in methicillin-resistant Staphylococcus aureus genomic DNA samples. PMID:15170215

  4. 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

  5. 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 150 ng kg(-1) with a low detection limit (LOD) of 0.076 ng kg(-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

  6. 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

  7. 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

  8. 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. PMID:26637215

  9. 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

  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. 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

  12. Colorimetric paper-based detection of Escherichia coli, Salmonella spp., and Listeria monocytogenes from large volumes of agricultural water.

    PubMed

    Bisha, Bledar; Adkins, Jaclyn A; Jokerst, Jana C; Chandler, Jeffrey C; Pérez-Méndez, Alma; Coleman, Shannon M; Sbodio, Adrian O; Suslow, Trevor V; Danyluk, Michelle D; Henry, Charles S; Goodridge, Lawrence D

    2014-01-01

    This protocol describes rapid colorimetric detection of Escherichia coli, Salmonella spp., and Listeria monocytogenes from large volumes (10 L) of agricultural waters. Here, water is filtered through sterile Modified Moore Swabs (MMS), which consist of a simple gauze filter enclosed in a plastic cartridge, to concentrate bacteria. Following filtration, non-selective or selective enrichments for the target bacteria are performed in the MMS. For colorimetric detection of the target bacteria, the enrichments are then assayed using paper-based analytical devices (µPADs) embedded with bacteria-indicative substrates. Each substrate reacts with target-indicative bacterial enzymes, generating colored products that can be detected visually (qualitative detection) on the µPAD. Alternatively, digital images of the reacted µPADs can be generated with common scanning or photographic devices and analyzed using ImageJ software, allowing for more objective and standardized interpretation of results. Although the biochemical screening procedures are designed to identify the aforementioned bacterial pathogens, in some cases enzymes produced by background microbiota or the degradation of the colorimetric substrates may produce a false positive. Therefore, confirmation using a more discriminatory diagnostic is needed. Nonetheless, this bacterial concentration and detection platform is inexpensive, sensitive (0.1 CFU/ml detection limit), easy to perform, and rapid (concentration, enrichment, and detection are performed within approximately 24 hr), justifying its use as an initial screening method for the microbiological quality of agricultural water. PMID:24962090

  13. Colorimetric Paper-based Detection of Escherichia coli, Salmonella spp., and Listeria monocytogenes from Large Volumes of Agricultural Water

    PubMed Central

    Bisha, Bledar; Adkins, Jaclyn A.; Jokerst, Jana C.; Chandler, Jeffrey C.; Pérez-Méndez, Alma; Coleman, Shannon M.; Sbodio, Adrian O.; Suslow, Trevor V.; Danyluk, Michelle D.; Henry, Charles S.; Goodridge, Lawrence D.

    2014-01-01

    This protocol describes rapid colorimetric detection of Escherichia coli, Salmonella spp., and Listeria monocytogenes from large volumes (10 L) of agricultural waters. Here, water is filtered through sterile Modified Moore Swabs (MMS), which consist of a simple gauze filter enclosed in a plastic cartridge, to concentrate bacteria. Following filtration, non-selective or selective enrichments for the target bacteria are performed in the MMS. For colorimetric detection of the target bacteria, the enrichments are then assayed using paper-based analytical devices (µPADs) embedded with bacteria-indicative substrates. Each substrate reacts with target-indicative bacterial enzymes, generating colored products that can be detected visually (qualitative detection) on the µPAD. Alternatively, digital images of the reacted µPADs can be generated with common scanning or photographic devices and analyzed using ImageJ software, allowing for more objective and standardized interpretation of results. Although the biochemical screening procedures are designed to identify the aforementioned bacterial pathogens, in some cases enzymes produced by background microbiota or the degradation of the colorimetric substrates may produce a false positive. Therefore, confirmation using a more discriminatory diagnostic is needed. Nonetheless, this bacterial concentration and detection platform is inexpensive, sensitive (0.1 CFU/ml detection limit), easy to perform, and rapid (concentration, enrichment, and detection are performed within approximately 24 hr), justifying its use as an initial screening method for the microbiological quality of agricultural water. PMID:24962090

  14. 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

  15. Colorimetric detection of gene transcript by target-induced three-way junction formation.

    PubMed

    Wang, Xuchu; Liu, Weiwei; Yin, Binbin; Yu, Pan; Duan, Xiuzhi; Liao, Zhaoping; Liu, Chunhua; Sang, Yiwen; Zhang, Gong; Chen, Yuhua; Tao, Zhihua

    2016-09-01

    Gene transcript often varies by alternative splicing, which plays different biological role that results in diversity of gene expression. Therefore, a simple and accurate identification of targeted transcript variant is of prime importance to achieve a precise molecular diagnosis. In this work, we presented a three-way junction based system where two split G-quadruplex forming sequences were coupled into two probes. Only upon the introduction of target gene transcript that offering a specific recognizable splicing site did the two probes assembled into three way junction conformation in a devised process, thus providing a functional G-quadruplex conformation that greatly enhanced hemin peroxidation. A notable resolution for gene splicing site detection was achieved. The detection limitation by colorimetric assay was 0.063μM, and this system has been proved to discriminate even in a single base false level around splicing site (about 3 times of single mismatched analyte to gain an equal signal by perfect analyte ). Furthermore, recoveries of 78.1%, 88.1%, 104.6% were obtained with 0.75μM, 0.25μM, 0.083μM of target, respectively, showing a capacity to further exploit a simple equipped device for gene transcript detection. PMID:27343570

  16. Carbon dots for naked eye colorimetric ultrasensitive arsenic and glutathione detection.

    PubMed

    Gupta, Abhishek; Verma, Navneet Chandra; Khan, Syamantak; Nandi, Chayan Kanti

    2016-07-15

    A novel one-step method for the synthesis of bright, multicolor fluorescent sulphur doped carbon dots (CNDs) has been developed by using simple microwave assisted pyrolysis of citric acid and sodium thiosulphate. The synthesized CNDs showed dual mode naked eye colorimetric ultrasensitive sensing capability both for arsenic [As (III)] and glutathione (GSH) with high selectivity. Using fluorometric assay, the detection limit (DL) for As (III) was found to be as low as 32pM. The selectivity data show that the newly developed CNDs is very specific for As (III) even with interference by high concentrations of other metal ions. The CNDs were also able to detect GSH very selectively over other biothiols like cysteine (Cys) and homo-cysteine (H-cys) with a DL of 43nM, even in blood plasma. The fast kinetic data suggests that the present CNDs assay could be used onsite As (III) detection. The CNDs, further, showed its potential application in high resolution bioimaging of bacterial nucleoid segregation. PMID:27015150

  17. [Comparative research into sensitivity and specificity of immune-enzyme analysis with chemiluminescence and colorimetric detection for detecting antigens and antibodies to avian influenza viruses and newcastle disease].

    PubMed

    Vitkova, O N; Kapustina, T P; Mikhailova, V V; Safonov, G A; Vlasova, N N; Belousova, R V

    2015-01-01

    The goal of this work was to demonstrate the results of the development of the enzyme-linked immunosorbent tests with chemiluminescence detection and colorimetric detection of specific viral antigens and antibodies for identifying the avian influenza and the Newcastle disease viruses: high sensitivity and specificity of the immuno- chemiluminescence assay, which are 10-50 times higher than those of the ELISA colorimetric method. The high effectiveness of the results and the automation of the process of laboratory testing (using a luminometer) allow these methods to be recommended for including in primary screening tests for these infectious diseases. PMID:27024917

  18. [Membrane transfer-based colorimetric DNA detection using enzyme modified gold nanoparticles].

    PubMed

    Li, Haiyan; Jing, Fengxiang; Gao, Qiuyue; Jia, Chunping; Chen, Jiwu; Jin, Qinghui; Zhao, Jianlong

    2010-08-01

    We report here a novel membrane transfer-based DNA detection method, in which alkaline phosphatase labeled gold nanoparticle (AuNP) probes were used as a means to amplify the detection signal. In this method, the capture probe P1, complimentary to the 3' end of target DNA, was immobilized on the chip. The multi-component AuNP probes were prepared by co-coating AuNPs with the detecting probe P2, complimentary to the 5' end of target DNA, and two biotin-labeled signal probes (T10 and T40) with different lengths. In the presence of target DNA, DNA hybridization led to the attachment of AuNPs on the chip surface where specific DNA sequences were located in a "sandwich" format. Alkaline phosphatase was then introduced to the surface via biotine-streptavidin interaction. By using BCIP/NBT alkaline phosphatase color development kit, a colorimetric DNA detection was achieved through membrane transfer. The signal on the membrane was then detected by the naked eye or an ordinary optical scanner. The method provided a detection of limit of 1 pmol/L for synthesized target DNA and 0.23 pmol/L for PCR products of Mycobacterium tuberculosis 16S rDNA when the ratio of probes used was 9:1:1 (T10:T40:P2). The method described here has many desirable advantages including high sensitivity, simple operation, and no need of sophisticated equipment. The method can be potentially used for reliable biosensings. PMID:21090120

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

    PubMed Central

    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 17β-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 17β-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

  20. 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

  1. Recyclable Colorimetric Detection of Trivalent Cations in Aqueous Media Using Zwitterionic Gold Nanoparticles.

    PubMed

    Zheng, Wenshu; Li, Huan; Chen, Wenwen; Ji, Jian; Jiang, Xingyu

    2016-04-01

    This report describes a colorimetric assay for trivalent metal cations (M(3+)) using gold nanoparticles (AuNPs)-modified with oppositely charged thiols that can form intermolecular zwitterionic surfaces. Zwitterionic AuNPs (Zw-AuNPs) are stable in high-salt solutions and well-dispersed in a wide range of pH values. M(3+) including Fe(3+), Al(3+), and Cr(3+) can effectively trigger the aggregation of Zw-AuNPs by interfering with their surface potential, and aggregated AuNPs can be regenerated and recycled by removing M(3+). In our approach, the output signal can be observed by the naked eye within a micromolar (μM) concentration range. Uniquely, our assay is capable of discriminating Fe(3+) from Fe(2+), which is challenging using traditional approaches. More importantly, Zw-AuNPs can be stored stably at room temperature for a long period (3 months) with constant detection performance. Both the cost-effectiveness and the long shelf life make Zw-AuNPs ideal for detecting M(3+) in resource-poor and remote areas. PMID:26958996

  2. 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 π-π 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.

  3. Low-ppm-Level colorimetric acid detection using gold nanoparticles with electro-steric stabilization.

    PubMed

    Bae, Doo Ri; Lee, You-Jin; Lee, Sung Woo; Han, Young-Kyu; Yoon, Jae-Sik; Lee, Ji-Hyun; Lee, Sang-Gil; Chang, Ki Soo; Yi, Gi-Ra; Lee, Gaehang

    2014-12-01

    Electro-sterically stabilized gold suspensions were employed in a colorimetric system for the detection of strong acid in water. Using oleyamine and oleic acid as steric stabilizer in 1,2-dichlorobenzene, hydrophobic gold nanoparticles were first synthesized by a reduction reaction of gold salts and were then transferred into water with a cationic surfactant. When the hydrochlo- ric acid solution higher than critical concentration was injected, particles were quickly aggregated and precipitated, creating a clear solution from the colored suspension. The particles were stable against chemical etching by corrosive ion such as chloride. Critical concentration was dependent of the size and concentration of the particles. The minimum concentration of dramatic color change was at 5 ppm level of hydrochloric acid, in which the largest colloidal gold nanoparticles (54 nm) were used. Furthermore, because of their steric repulsive soft layer on particles, particles could be reused for further detection experiments after regeneration by the simple pH-neutralization and washing process. PMID:25971086

  4. Colorimetric detection of pathogenic bacteria using platinum-coated magnetic nanoparticle clusters and magnetophoretic chromatography.

    PubMed

    Kwon, Donghoon; Lee, Sanghee; Ahn, Myung Mo; Kang, In Seok; Park, Ki-Hwan; Jeon, Sangmin

    2015-07-01

    A colorimetric method that uses platinum-coated magnetic nanoparticle clusters (Pt/MNCs) and magnetophoretic chromatography is developed to detect pathogenic bacteria. Half-fragments of monoclonal Escherichia coli O157:H7 (EC) antibodies were functionalized to Pt/MNCs and used to capture E. coli bacteria in milk. After magnetic separation of free Pt/MNCs and Pt/MNC-EC complexes from the milk, a precision pipette was used to imbibe the E. coli-containing solution, then a viscous polyethylene glycol solution. Due to difference in viscosities, the solutions separate into two liquid layers inside the pipette tip. The Pt/MNC-EC complexes were separated from the free Pt/MNCs by applying an external magnetic field, then added to a tetramethylbenzidine (TMB) solution. Catalytic oxidation of TMB by Pt produced color changes of the solution, which enabled identification of the presence of 10 cfu mL(-1) E. coli bacteria with the naked eye. The total assay time including separation, binding and detection was 30 min. PMID:26088777

  5. 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.

  6. Colorimetric detection of ractopamine and salbutamol using gold nanoparticles functionalized with melamine as a probe.

    PubMed

    Zhou, Ying; Wang, Peilong; Su, Xiaoou; Zhao, Hong; He, Yujian

    2013-08-15

    A highly selective and sensitive method is developed for colorimetric detection of ractopamine and salbutamol using gold nanoparticles (AuNPs) functionalized with melamine (MA), respectively. The presence of these β-agonists induces the aggregation of gold nanoparticles through hydrogen-bonding interaction that was accompanied by a distinct change in color and optical properties, which could be monitored by a UV-vis spectrophotometer or even naked eyes. This process caused a significant decrease in the absorbance ratio (A670 nm/A520 nm) of melamine-gold nanoparticles (MA-AuNPs), and the color changed from wine red to blue. The systems exhibited a wide liner range, from 1×10(-10)M to 5×10(-7)mol/L with a correlation coefficient of 0.995 for ractopamine, and 1×10(-10)M to 1×10(-5)mol/L with a correlation coefficient of 0.996 for salbutamol, with measuring the absorbance ratio (A670 nm/A520 nm). The detection limit of these β-agonists is as low as 1×10(-11)mol/L. Particularly, the developed method has been applied to the analysis of real swine feed samples and has achieved satisfactory results. PMID:23708531

  7. 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

  8. Screening and development of DNA aptamers as capture probes for colorimetric detection of patulin.

    PubMed

    Wu, Shijia; Duan, Nuo; Zhang, Weixiao; Zhao, Sen; Wang, Zhouping

    2016-09-01

    Patulin (PAT) is a kind of mycotoxin that has serious harmful impacts on both food quality and human health. A high-affinity ssDNA aptamer that specifically binds to patulin was generated using systemic evolution of ligands by exponential enrichment (SELEX) assisted by graphene oxide (GO). After 15 rounds of positive and negative selection, a highly enriched ssDNA pool was sequenced and the representative sequences were subjected to binding assays to evaluate their affinity and specificity. Of the eight aptamer candidates tested, the sequence PAT-11 bound to patulin with high affinity and excellent selectivity with a dissociation constant (Kd) of 21.83 ± 5.022 nM. The selected aptamer, PAT-11, was subsequently used as a recognition element to develop a detection method for patulin based on an enzyme-chromogenic substrate system. The colorimetric aptasensor exhibited a linear range from 50 to 2500 pg mL(-1), and the limit of detection was found to be 48 pg mL(-1). The results indicated that GO-SELEX technology was appropriate for the screening of aptamers against small-molecule toxins, offering a promising application for aptamer-based biosensors. PMID:27318239

  9. 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

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

    PubMed

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

    2014-09-01

    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 (Pb(2+)) and aluminum (Al(3+)) 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 Pb(2+) and 89 ppb for Al(3+), 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

  11. 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 451 pM. Moreover, the developed colorimetric aptasensor was successfully used to detect chloramphenicol in milk and serum with LODs of 697 and 601 pM, respectively. PMID:26599477

  12. 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

  13. Visual and colorimetric detection of Hg(2+) by cloud point extraction with functionalized gold nanoparticles as a probe.

    PubMed

    Tan, Zhi-qiang; Liu, Jing-fu; Liu, Rui; Yin, Yong-guang; Jiang, Gui-bin

    2009-12-01

    Association with Hg(2+) enhances the hydrophobicity and triggers the cloud point extraction of approximately 4 nm-diameter gold nanoparticle probes functionalized with mercaptopropionic acid and homocystine, which results in the color change of the TX-114-rich phase from colorless to red, and therefore provides a novel approach for visual and colorimetric detection of Hg(2+) with ultrahigh sensitivity and selectivity. PMID:19904384

  14. A label-free colorimetric sensor for Pb2+ detection based on the acceleration of gold leaching by graphene oxide.

    PubMed

    Shi, Xinhao; Gu, Wei; Zhang, Cuiling; Zhao, Longyun; Peng, Weidong; Xian, Yuezhong

    2015-03-14

    In this work, we developed a novel, label-free, colorimetric sensor for Pb(2+) detection based on the acceleration of gold leaching by graphene oxide (GO) at room temperature. Gold nanoparticles (AuNPs) can be dissolved in a thiosulfate (S2O3(2-)) aqueous environment in the presence of oxygen; however, the leaching rate is very slow due to the high activation energy (27.99 kJ mol(-1)). In order to enhance the reaction rate, some accelerators should be added. In comparison with the traditional accelerators (metal ions or middle ligands), we found that GO could efficiently accelerate the gold leaching reaction. Kinetic data demonstrate that the dissolution rate of gold in the Pb(2+)-S2O3(2-)-GO system is 5 times faster than that without GO at room temperature. In addition, the effects of surface modification and the nanoparticle size on the etching of AuNPs were investigated. Based on the GO-accelerated concentration-dependent colour changes of AuNPs, a colorimetric sensor for Pb(2+) detection was developed with a linear range from 0.1 to 20 μM and the limit of detection (LOD) was evaluated to be 0.05 μM. This colorimetric assay is simple, low-cost, label-free, and has numerous potential applications in the field of environmental chemistry. PMID:25656247

  15. 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.

  16. Gold nanoparticles mediated colorimetric assay for HIV-Tat protein detection

    NASA Astrophysics Data System (ADS)

    Hashwan, Saeed S. Ba; Ruslinda, A. Rahim; Fatin, M. F.; Gopinath, Subash C. B.; Thivina, V.; Tony, V. C. S.; Arshad, M. K. Md.; Hashim, U.

    2016-07-01

    Gold-nanoparticle (AuNP) based colorimetric assays have been formulated for different biomolecular interactions. With this assay the probe such as antibody immobilized on the Au surface and in the presence of appropriate binding partner (antigen), will interact with each other on the Au surface. By following this strategy, herein we formulated a detection system with two anti-HIV-Tat antibodies, Mono (McAb) - and polyclonal (PcAb) by immobilizing them independently with different AuNPs. Under this condition, these two antibodies are under dispersed condition, and in the presence of HIV-Tat antigen, these molecules will be connected and forms the aggregation of AuNPs. This strategy yield rapid results, can be monitored by the spectral changes in UV-Vis spectrophotometry. Experiments were performed with two different methods using two anti-HIV-Tats monoclonal and one Polyclonal antibody against the antigen HIV-Tat. Between these methods conjugation of HIV-Tat and McAb on the AuNP followed by addition of PcAb yielded better results.

  17. 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

  18. 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.

  19. 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 μM) of 1 for Cu2+ is much lower than that (30 μM) 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.

  20. 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.

  1. 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

  2. An engineered nano-plasmonic biosensing surface for colorimetric and SERS detection of DNA-hybridization events

    NASA Astrophysics Data System (ADS)

    Heydari, Esmaeil; Thompson, David; Graham, Duncan; Cooper, Jonathan M.; Clark, Alasdair W.

    2015-03-01

    We report a versatile nanophotonic biosensing platform that enables both colorimetric detection and enhanced Raman spectroscopy detection of molecular binding events. Through the integration of electron-beam lithography, dip-pennanolithography and molecular self-assembly, we demonstrate plasmonic nanostructures which change geometry and plasmonic properties in response to molecularly-mediated nanoparticle binding events. These biologically-active nanostructured surfaces hold considerable potential for use as multiplexed sensor platforms for point-of-care diagnostics, and as scaffolds for a new generation of molecularly dynamic metamaterials.

  3. 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 17β-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

  4. 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.

  5. 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...

  6. 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

  7. 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 10 cells. The proposed method could be extended to detect other cells and showed potential applications in cancer cell detection and early cancer diagnosis. PMID:26724767

  8. Optimizing Colorimetric Assay Based on V2O5 Nanozymes for Sensitive Detection of H2O2 and Glucose

    PubMed Central

    Sun, Jiaheng; Li, Chunyan; Qi, Yanfei; Guo, Shuanli; Liang, Xue

    2016-01-01

    Nanozyme-based chemical sensing is a rapidly emerging field of research. Herein, a simple colorimetric assay for the detection of hydrogen peroxide and glucose based on the peroxidase-like activity of V2O5 nanozymes has been established. In this assay, the effects of pH, substrate, nanozyme concentrations and buffer solution have been investigated. It was found that compared with 3,3′,5,5′-tetramethylbenzidine (TMB), the enzyme substrate o-phenylenediamine (OPD) seriously interfered with the H2O2 detection. Under the optimal reaction conditions, the resulting sensor displayed a good response to H2O2 with a linear range of 1 to 500 μM, and a detection limit of 1 μM at a signal-to-noise ratio of 3. A linear correlation was established between absorbance intensity and concentration of glucose from 10 to 2000 μM, with a detection limit of 10 μM. The current work presents a simple, cheap, more convenient, sensitive, and easy handling colorimetric assay. PMID:27110794

  9. Optimizing Colorimetric Assay Based on V₂O₅ Nanozymes for Sensitive Detection of H₂O₂ and Glucose.

    PubMed

    Sun, Jiaheng; Li, Chunyan; Qi, Yanfei; Guo, Shuanli; Liang, Xue

    2016-01-01

    Nanozyme-based chemical sensing is a rapidly emerging field of research. Herein, a simple colorimetric assay for the detection of hydrogen peroxide and glucose based on the peroxidase-like activity of V₂O₅ nanozymes has been established. In this assay, the effects of pH, substrate, nanozyme concentrations and buffer solution have been investigated. It was found that compared with 3,3',5,5'-tetramethylbenzidine (TMB), the enzyme substrate o-phenylenediamine (OPD) seriously interfered with the H₂O₂ detection. Under the optimal reaction conditions, the resulting sensor displayed a good response to H₂O₂ with a linear range of 1 to 500 μM, and a detection limit of 1 μM at a signal-to-noise ratio of 3. A linear correlation was established between absorbance intensity and concentration of glucose from 10 to 2000 μM, with a detection limit of 10 μM. The current work presents a simple, cheap, more convenient, sensitive, and easy handling colorimetric assay. PMID:27110794

  10. 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.

  11. 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).

  12. 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.

  13. 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.

  14. An enzyme-free catalytic DNA circuit for amplified detection of aflatoxin B1 using gold nanoparticles as colorimetric indicators.

    PubMed

    Chen, Junhua; Wen, Junlin; Zhuang, Li; Zhou, Shungui

    2016-05-14

    An enzyme-free biosensor for the amplified detection of aflatoxin B1 has been constructed based on a catalytic DNA circuit. Three biotinylated hairpin DNA probes (H1, H2, and H3) were designed as the assembly components to construct the sensing system (triplex H1-H2-H3 product). Cascaded signal amplification capability was obtained through toehold-mediated strand displacement reactions to open the hairpins and recycle the trigger DNA. By the use of streptavidin-functionalized gold nanoparticles as the signal indicators, the colorimetric readout can be observed by the naked eye. In the presence of a target, the individual nanoparticles (red) aggregate into a cross-linked network of nanoparticles (blue) via biotin-streptavidin coupling. The colorimetric assay is ultrasensitive, enabling the visual detection of trace levels of aflatoxin B1 (AFB1) as low as 10 pM without instrumentation. The calculated limit of detection (LOD) is 2 pM in terms of 3 times standard deviation over the blank response. The sensor is robust and works even when challenged with complex sample matrices such as rice samples. Our sensing platform is simple and convenient in operation, requiring only the mixing of several solutions at room temperature to achieve visible and intuitive results, and holds great promise for the point-of-use monitoring of AFB1 in environmental and food samples. PMID:27119550

  15. 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.

  16. 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

  17. A Sensitive, Colorimetric, High-Throughput Loop-Mediated Isothermal Amplification Assay for the Detection of Plasmodium knowlesi.

    PubMed

    Britton, Sumudu; Cheng, Qin; Grigg, Matthew J; William, Timothy; Anstey, Nicholas M; McCarthy, James S

    2016-07-01

    The simian parasite Plasmodium knowlesi is now the commonest cause of malaria in Malaysia and can rapidly cause severe and fatal malaria. However, microscopic misdiagnosis of Plasmodium species is common, rapid antigen detection tests remain insufficiently sensitive and confirmation of P. knowlesi requires polymerase chain reaction (PCR). Thus available point-of-care diagnostic tests are inadequate. This study reports the development of a simple, sensitive, colorimetric, high-throughput loop-mediated isothermal amplification assay (HtLAMP) diagnostic test using novel primers for the detection of P. knowlesi. This assay is able to detect 0.2 parasites/μL, and compared with PCR has a sensitivity of 96% for the detection of P. knowlesi, making it a potentially field-applicable point-of-care diagnostic tool. PMID:27162264

  18. 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 μM and 1.32 μM for I- ions via two different mechanistic routes. Also, the designed probe detects Br- with a detection limit down to 1.67 μM.

  19. 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

    2015-01-01

    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 μM and 1.32 μM for I(-) ions via two different mechanistic routes. Also, the designed probe detects Br(-) with a detection limit down to 1.67 μM. PMID:25950637

  20. Directional Antineutrino Detection

    NASA Astrophysics Data System (ADS)

    Safdi, B. R.; Suerfu, J.

    2014-12-01

    We propose the first truly directional antineutrino detector for antineutrinos near the threshold for the inverse beta decay (IBD) of hydrogen, with potential applications including the spatial mapping of geo-neutrinos, searches for stellar antineutrinos, and the monitoring of nuclear reactors. The detector consists of adjacent and separated target and neutron-capture layers. The IBD events, which result in a neutron and a positron, take place in the target layers. These layers are thin enough so that the neutrons escape without scattering elastically. The neutrons are detected in the thicker neutron-capture layers. The location of the IBD event is determined from the energy deposited by the positron as it slows in the medium and from the two gamma rays that come from the positron annihilation. Since the neutron recoils in the direction of the antineutrino's motion, a line may then be drawn between the IBD event location and the neutron-capture location to approximate the antineutrino's velocity. In some events, we may even measure the positron's velocity, which further increases our ability to reconstruct the antineutrino's direction of motion. Our method significantly improves upon previous methods by allowing the neutron to freely travel a long distance before diffusing and being captured. Moreover, our design is a straightforward modification of existing antineutrino detectors; a prototype could easily be built with existing technology. We verify our design through Monte Carlo simulations in Geant4, using commercially-available boron-loaded plastic scintillators for the target and neutron-capture layer materials. We are able to discriminate from background using multiple coincidence signatures within a short, ~microsecond time interval. We conclude that the detector could likely operate above ground with minimal shielding.

  1. Selective colorimetric detection of Cr(iii) and Cr(vi) using gallic acid capped gold nanoparticles.

    PubMed

    Dong, Chen; Wu, Genhua; Wang, Zhuqing; Ren, Wenzhi; Zhang, Yujie; Shen, Zheyu; Li, Tianhua; Wu, Aiguo

    2016-05-28

    A colorimetric assay is proposed for the selective detection of Cr(iii) and Cr(vi) via the aggregation-induced color change of gallic acid capped gold nanoparticles (GA-AuNPs). The AuNPs are characterized using UV-vis spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS) and Fourier-transform infrared spectrometry (FT-IR). To detect Cr(iii) and Cr(vi) coexisting in a sample, citrate and thiosulfate were applied to mask Cr(vi) for the detection of Cr(iii), and ethylenediaminetetraacetic acid disodium salt (EDTA) was applied to mask Cr(iii) for the detection of Cr(vi). At optimized experimental conditions, the selectivity of these AuNPs-based detection systems is excellent for Cr(iii) and/or Cr(vi) compared with other types of metal ions. The limit of detections (LODs) of a mixture of Cr(iii) and Cr(vi), Cr(iii) and Cr(vi) by eye vision are 1.5, 1.5 and 2 μM, respectively, and those by UV-vis spectroscopy are 0.05, 0.1 and 0.1 μM, respectively. The minimum detectable concentrations for Cr(iii) or Cr(vi) are all below the guideline value set by the US Environmental Protection Agency (EPA). The applicability of the AuNPs-based colorimetric sensor is also validated by the detection of Cr(iii) and Cr(vi) in electroplating wastewater and real water samples with high recoveries. PMID:26606324

  2. 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 50-1000 nM 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

  3. Sensitive and visual detection of sequence-specific DNA-binding protein via a gold nanoparticle-based colorimetric biosensor.

    PubMed

    Ou, Li-Juan; Jin, Pei-Yan; Chu, Xia; Jiang, Jian-Hui; Yu, Ru-Qin

    2010-07-15

    A novel exonuclease III (Exo III) protection-based colorimetric biosensing strategy was developed for rapid, sensitive, and visual detection of sequence-specific DNA-binding proteins. This strategy relied on the protection of DNA-cross-linked gold nanoparticle (AuNP) aggregates from Exo III-mediated digestion by specific interactions of target proteins with their binding sequences. Interestingly, we disclosed a new finding that binding of target proteins to their binding sequences in the aggregated AuNP network rendered a stable and long-period protection of DNA. Unlike conventional fluorescence assays merely based on temporal protection of DNA from Exo III digestion, the stable protection afforded a static color transition indicator for DNA-protein interactions with no time-dependent monitoring required in the assay. Therefore, it furnished the developed strategy with improved technical robustness and operational convenience. Furthermore, we introduced thioctic acid as a stable anchor for tethering DNA on AuNPs. This DNA-tethering protocol circumvented the interferences from thiol compounds in common enzymatic systems. The Exo III protection-based colorimetric biosensor was demonstrated using a model target of TATA binding protein, a key transcriptional factor involving in various transcriptional regulatory networks. The results revealed that the method allowed a specific, simple, and quantitative assay of the target protein with a linear response range from 0 to 120 nM and a detection limit of 10 nM. PMID:20565105

  4. 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

  5. Antibody-Free Colorimetric Detection of Total Aflatoxins in Rice Based on a Simple Two-Step Chromogenic Reaction.

    PubMed

    Du, Bibai; Su, Xiaoou; Yang, Kunhao; Pan, Long; Liu, Qingju; Gong, Lingling; Wang, Peilong; Yang, Jingkui; He, Yujian

    2016-04-01

    The prevalently used immunoassays for fast screening of aftatoxins (AFs) usually cannot meet the requirement for simultaneous determination of total AFs (aflatoxin B1 + aflatoxin B2 + aflatoxin G1 + aflatoxin G2) due to the deficiency of highly group-specific antibodies. This paper describes a two-step chromogenic reaction based method to quantitatively detect total AFs in rice using colorimetric measurement without antibody. In the method, colorless AFs transform into green-colored indophenol products through the reaction with sodium hydroxide and 2,6-dibromoquinone-4-chloroimide (DBQC) successively, allowing selectively determining total AFs up to 3.9 μg/kg over other competitive mycotoxins under optimal conditions by a UV-vis spectrophotometer. In addition, the colorimetric measurement results of the rice samples agree well with that of a standard HPLC method, demonstrating the good reliability and applicability of the method. Uniquely, the method has potential for on-site detection of total AFs in rice when using a nylon membrane-based device. PMID:26938207

  6. Colorimetric monitoring of rolling circle amplification for detection of H5N1 influenza virus using metal indicator.

    PubMed

    Hamidi, Seyed Vahid; Ghourchian, Hedayatollah

    2015-10-15

    A new colorimetric method for monitoring of rolling circle amplification was developed. At first H5N1 target hybrids with padlock probe (PLP) and then PLP is circularized upon the action of T4 ligase enzyme. Subsequently, the circular probe is served as a template for hyperbranched rolling circle amplification (HRCA) by utilizing Bst DNA polymerase enzyme. By improving the reaction, pyrophosphate is produced via DNA polymerization and chelates the Mg(2+) in the buffer solution. This causes change in solution color in the presence of hydroxy naphthol blue (HNB) as a metal indicator. By using pH shock instead of heat shock and isothermal RCA reaction not only the procedure becomes easier, but also application of HNB for colorimetric detection of RCA reaction further simplifies the assay. The responses of the biosensor toward H5N1 were linear in the concentration range from 0.16 to 1.20 pM with a detection limit of 28 fM. PMID:25974174

  7. Colorimetric detection of Mn2+ using silver nanoparticles cofunctionalized with 4-mercaptobenzoic acid and melamine as a probe.

    PubMed

    Zhou, Ying; Zhao, Hong; Li, Chang; He, Peng; Peng, Wenbo; Yuan, Longfei; Zeng, Lixi; He, Yujian

    2012-08-15

    A facile, selective and highly sensitive method is proposed for colorimetric detection of manganese ions using 4-mercaptobenzoic acid (4-MBA) and melamine (MA) modified silver nanoparticles (AgNPs). The presence of Mn(2+) induces the aggregation of AgNPs through cooperative metal-ligand interaction, resulting in a color change from bright yellow to purple. The cofunctionalized AgNPs showed obvious advantages over the ones functionalized only by 4-MBA or MA in terms of selectivity. Mn(2+) could be monitored by colorimetric response of AgNPs by a UV-vis spectrophotometer or even naked eyes. The absorbance ratio (A(550 nm)/A(408 nm)) is linear with the concentration of Mn(2+) ranging from 5×10(-7) mol/L to 1×10(-5) mol/L with a correlation coefficient of 0.993, and the detection limit is as low as 5×10(-8) mol/L. Particularly, this cost-effective process also allowed rapid and simple determination of the Mn(2+) in drinking water. PMID:22841088

  8. Fluorescence and colorimetric detection of ATP based on a strategy of self-promoting aggregation of a water-soluble polythiophene derivative.

    PubMed

    Cheng, Dandan; Li, Yandong; Wang, Jing; Sun, Yujiao; Jin, Lu; Li, Chenxi; Lu, Yan

    2015-05-18

    A sensitive fluorescent and colorimetric dual-modal probe for the detection of ATP has been developed based on a strategy of self-promoting aggregation of a cationic polythiophene derivative bearing anthracene groups in the side chain with a detection limit as low as 10(-9) M. PMID:25894335

  9. Development of a colorimetric inhibition assay for microcystin-LR detection: comparison of the sensitivity of different protein phosphatases.

    PubMed

    Sassolas, Audrey; Catanante, Gaëlle; Fournier, Didier; Marty, Jean Louis

    2011-10-15

    A colorimetric protein phosphatase (PP) inhibition test for the detection of microcystin-LR (MC-LR) has been developed. Three PP2As, one recombinant and two natural versions, as well as one PP1 produced by molecular engineering, were tested. First, assays were performed using the enzymes in solution to compare their sensitivity to MC-LR. The PP2A purchased from ZEU Immunotec and PP1 appeared more sensitive to the toxin than the other enzymes. With PP2A from ZEU Immunotec, the colorimetric test showed a detection limit of 0.0039 μg L(-1) and an IC(50) value of 0.21 μg L(-1). With PP1, the assay gave a detection limit of 0.05 μg L(-1) and an IC(50) value of 0.56 μg L(-1). Therefore, this assay allowed the detection of lower microcystin-LR (MC-LR) concentrations than the maximum level (1 μg L(-1)) recommended by the World Health Organisation (WHO). The main drawback of this PP-based approach in solution is poor enzyme stabilisation. To overcome this problem, enzymes were entrapped within either a photopolymer or an agarose gel. PP2A from ZEU Immunotec and PP1 were immobilised at the bottom of microwells. The agarose-based tests performed better than the photopolymer-based assay for all of the enzymes. Therefore, the agarose gel is a good candidate to replace the photopolymer, which is generally used in PP-immobilising membranes. The assays based on enzyme-entrapping agarose gels showed detection limits equal to 0.17 μg L(-1) and 0.29 μg L(-1) with immobilised PP2A from ZEU and PP1, respectively. In view of these performances, these tests can potentially be used for monitoring water quality. PMID:21962674

  10. Enhanced Colorimetric Immunoassay Accompanying with Enzyme Cascade Amplification Strategy for Ultrasensitive Detection of Low-Abundance Protein

    PubMed Central

    Gao, Zhuangqiang; Hou, Li; Xu, Mingdi; Tang, Dianping

    2014-01-01

    Methods based on enzyme labels have been developed for colorimetric immunoassays, but most involve poor sensitivity and are unsuitable for routine use. Herein, we design an enhanced colorimetric immunoassay for prostate-specific antigen (PSA) coupling with an enzyme-cascade-amplification strategy (ECAS-CIA). In the presence of target PSA, the labeled alkaline phosphatase on secondary antibody catalyzes the formation of palladium nanostructures, which catalyze 3,3′,5,5′-tetramethylbenzidine-H2O2 system to produce the colored products, thus resulting in the signal cascade amplification. Results indicated that the ECAS-CIA presents good responses toward PSA, and allows detection of PSA at a concentration as low as 0.05 ng mL−1. Intra- and inter-assay coefficients of variation are below 9.5% and 10.7%, respectively. Additionally, the methodology is validated for analysis of clinical serum specimens with consistent results obtained by PSA ELISA kit. Importantly, the ECAS-CIA opens a new horizon for protein diagnostics and biosecurity. PMID:24509941

  11. 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 10 aM to 1.0 nM, 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

  12. 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

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

    PubMed

    Sarkar, Amrita; Bhattacharyya, Sudipta; Mukherjee, Arindam

    2016-01-21

    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 (1-4). 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 (1) and thioimidazole bound anthraimidazoledione (4) were able to detect both F(-) and CN(-) in the presence of other anions Cl(-), Br(-), I(-), H2PO4(-), OAc(-), NO3(-)and ClO4(-). Both 1 and 4 could not differentiate F(-) from CN(-) and provided a similar response to both. The 1H NMR studies of 1 and 4 with F(-) showed the formation of [HF2](-) at 16.3 ppm and the 19F 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 3. 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 4 selective detection of F(-) was possible in the presence of 0.5 equivalent of Cu2+ 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 Cu2+ the F(-) detection limit was 0.038(5) ppm (below the WHO specified level) at a receptor concentration of 25 μM. PMID:26659520

  14. An enzyme-free catalytic DNA circuit for amplified detection of aflatoxin B1 using gold nanoparticles as colorimetric indicators

    NASA Astrophysics Data System (ADS)

    Chen, Junhua; Wen, Junlin; Zhuang, Li; Zhou, Shungui

    2016-05-01

    An enzyme-free biosensor for the amplified detection of aflatoxin B1 has been constructed based on a catalytic DNA circuit. Three biotinylated hairpin DNA probes (H1, H2, and H3) were designed as the assembly components to construct the sensing system (triplex H1-H2-H3 product). Cascaded signal amplification capability was obtained through toehold-mediated strand displacement reactions to open the hairpins and recycle the trigger DNA. By the use of streptavidin-functionalized gold nanoparticles as the signal indicators, the colorimetric readout can be observed by the naked eye. In the presence of a target, the individual nanoparticles (red) aggregate into a cross-linked network of nanoparticles (blue) via biotin-streptavidin coupling. The colorimetric assay is ultrasensitive, enabling the visual detection of trace levels of aflatoxin B1 (AFB1) as low as 10 pM without instrumentation. The calculated limit of detection (LOD) is 2 pM in terms of 3 times standard deviation over the blank response. The sensor is robust and works even when challenged with complex sample matrices such as rice samples. Our sensing platform is simple and convenient in operation, requiring only the mixing of several solutions at room temperature to achieve visible and intuitive results, and holds great promise for the point-of-use monitoring of AFB1 in environmental and food samples.An enzyme-free biosensor for the amplified detection of aflatoxin B1 has been constructed based on a catalytic DNA circuit. Three biotinylated hairpin DNA probes (H1, H2, and H3) were designed as the assembly components to construct the sensing system (triplex H1-H2-H3 product). Cascaded signal amplification capability was obtained through toehold-mediated strand displacement reactions to open the hairpins and recycle the trigger DNA. By the use of streptavidin-functionalized gold nanoparticles as the signal indicators, the colorimetric readout can be observed by the naked eye. In the presence of a target, the

  15. 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

  16. A plasmonic colorimetric strategy for visual miRNA detection based on hybridization chain reaction

    PubMed Central

    Miao, Jie; Wang, Jingsheng; Guo, Jinyang; Gao, Huiguang; Han, Kun; Jiang, Chengmin; Miao, Peng

    2016-01-01

    In this work, a novel colorimetric strategy for miRNA analysis is proposed based on hybridization chain reaction (HCR)-mediated localized surface plasmon resonance (LSPR) variation of silver nanoparticles (AgNPs). miRNA in the sample to be tested is able to release HCR initiator from a solid interface to AgNPs colloid system by toehold exchange-mediated strand displacement, which then triggers the consumption of fuel strands with single-stranded tails for HCR. The final produced long nicked double-stranded DNA loses the ability to protect AgNPs from salt-induced aggregation. The stability variation of the colloid system can then be monitored by recording corresponding UV-vis spectrum and initial miRNA level is thus determined. This sensing system involves only four DNA strands which is quite simple. The practical utility is confirmed to be excellent by employing different biological samples. PMID:27534372

  17. A plasmonic colorimetric strategy for visual miRNA detection based on hybridization chain reaction.

    PubMed

    Miao, Jie; Wang, Jingsheng; Guo, Jinyang; Gao, Huiguang; Han, Kun; Jiang, Chengmin; Miao, Peng

    2016-01-01

    In this work, a novel colorimetric strategy for miRNA analysis is proposed based on hybridization chain reaction (HCR)-mediated localized surface plasmon resonance (LSPR) variation of silver nanoparticles (AgNPs). miRNA in the sample to be tested is able to release HCR initiator from a solid interface to AgNPs colloid system by toehold exchange-mediated strand displacement, which then triggers the consumption of fuel strands with single-stranded tails for HCR. The final produced long nicked double-stranded DNA loses the ability to protect AgNPs from salt-induced aggregation. The stability variation of the colloid system can then be monitored by recording corresponding UV-vis spectrum and initial miRNA level is thus determined. This sensing system involves only four DNA strands which is quite simple. The practical utility is confirmed to be excellent by employing different biological samples. PMID:27534372

  18. 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

  19. The catalytic activity of Ag2S-montmorillonites as peroxidase mimetic toward colorimetric detection of H2O2.

    PubMed

    Liu, Qingyun; Jiang, Yanling; Zhang, Leyou; Zhou, Xinpei; Lv, Xintian; Ding, Yanyuan; Sun, Lifang; Chen, Pengpeng; Yin, Hailiang

    2016-08-01

    Nanocomposites based on silver sulfide (Ag2S) and Ca-montmorillonite (Ca(2+)-MMT) were synthesized by a simple hydrothermal method. The nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectra (FTIR). The as-prepared Ag2S-MMT nanocomposites were firstly demonstrated to possess intrinsic peroxidase-like activity and could rapidly catalytically oxidize the substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2 to produce a blue product which can be seen by the naked eye in only one minute. The experimental results revealed that the Ag2S-MMT nanocomposites exhibit higher thermal durance. Based on the TMB-H2O2 catalyzed color reaction, the Ag2S-MMT nanocomposites were exploited as a new type of biosensor for detection and estimation of H2O2 through a simple, cheap and selective colorimetric method. PMID:27157733

  20. Highly sensitive and selective colorimetric detection of glutathione based on Ag [I] ion-3,3',5,5'-tetramethylbenzidine (TMB).

    PubMed

    Ni, Pengjuan; Sun, Yujing; Dai, Haichao; Hu, Jingting; Jiang, Shu; Wang, Yilin; Li, Zhuang

    2015-01-15

    Glutathione (GSH) plays an important role in the biological system and serves many cellular functions. Since all of the biothiols possess similar functional groups, it is still challenging to selectively detect GSH over cysteine (Cys) and homocysteine (Hcy). In this work, a novel and simple colorimetric method for discriminative detection of glutathione (GSH) over Cys and Hcy is developed. The proposed method is based on the fact that Ag [I] ion could oxidize 3,3',5,5',-tetramethylbenzidine (TMB) to the oxidized TMB to induce a blue color and an absorption peak centered at 652 nm. However, the introduction of GSH could cause the reduction of oxidized TMB and it could also combine with Ag(+), both of which result in a blue color fading and a decrease of the absorbance at 652 nm. Based on this finding, we propose a method to qualitatively and quantitatively detect GSH by naked eyes and UV-vis spectroscopy, respectively. The proposed method shows a low detection limit of 0.1 µM by naked eyes and 0.05 µM with the help of UV-vis spectroscopy. In addition, this method has great potential in discriminatively detecting GSH over other amino acid and biothiols. More importantly, this method is simple and fast without the preparation of nanomaterials and has also been successfully applied to the detection of GSH in biological fluids. PMID:25058938

  1. 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

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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 μM by eye and 0.1 μM by UV-Vis spectroscopy. The LOD by eye is lower than the lowest previously reported value (4.0 μM). There is a good linear relationship between A/A0 and the concentration of NO2(-) from 1.0 to 20.0 μM 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

  7. Invader Assisted Enzyme-Linked Immunosorbent Assay for Colorimetric Detection of Disease Biomarkers Using Oligonucleotide Probe-Modified Gold Nanoparticles.

    PubMed

    Song, Qinxin; Qi, Xiemin; Jia, Huning; He, Liang; Kumar, Shalen; Pitman, Janet L; Zou, Bingjie; Zhou, Guohua

    2016-04-01

    We successfully developed an invader assisted ELISA assay (iaELISA) for sensitive detection of disease biomarkers. The method includes three key steps as follows; biotinylated detection antibody was at first used to capture targeted antigen by sandwich ELISA. The biotinylated oligonucleotide was then attached to detection antibody via streptavidin. Finally, the cascade invader reactions were employed to amplify the biotinylated oligonucleotide specific to the antigen so that detection of the antigen was transformed into signal amplification of the antigen-specific DNA. To achieve colorimetric detection, oligonucleotide probe and modified gold nanoparticles (AuNPs) were coupled with the invader assay. Utilization of the hairpin probes in the invader reaction brought about free AuNPs, resulting in the positive read-out (red color). On the other hand, aggregation of the AuNPs occurred when the hairpin probes were not utilized in the reaction. This method was successfully used to detect as low as 2.4 x 10(-11) g/mL of HBsAg by both naked eye and spectrophotometer. This sensitivity was about 100 times higher than that of conventional ELISA method. The method was also used to assay 16 serum specimens from HBV-infected patients and 8 serum specimens from HBV-negative donors and results were in good agreement with those obtained from the conventional ELISA. As the invader assay is sensitive to one base sequence, a good specificity was also obtained by detecting other antigens like hepatitis A virus (HAV) and BSA. The method has therefore much potential for ultrasensitive and cost-effective detection of targeted proteins that have clinical importance. PMID:27301208

  8. 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

  9. Hydrogen-bonding-induced colorimetric detection of melamine by nonaggregation-based Au-NPs as a probe.

    PubMed

    Cao, Qian; Zhao, Hong; He, Yujian; Li, Xiangjun; Zeng, Lixi; Ding, Nan; Wang, Jian; Yang, Jie; Wang, Guangwei

    2010-08-15

    A colorimetric, label-free, and nonaggregation-based gold nanoparticles probe has been developed for the detection of melamine. Gold nanoparticles were generated using 3,5-dihydroxybenzoic acid as a reducer without adding gold nanoparticle seeds at room temperature. Upon the addition of melamine, the reducer 3,5-dihydroxybenzoic acid can interact with melamine through strong hydrogen-bonding interaction. Consequently, the formation of gold nanoparticles was interrupted by melamine since there was not enough reducer for the reduction of Au(3+) ion. And the color change from purple to yellowgreen with increasing melamine concentration was observed. The plasmon absorbance of the formed Au-NPs allows the quantitative detection of melamine. A sensitive linear correlation existed between the absorbance and the logarithm of melamine concentration ranging from 1x10(-9) M to 1x10(-5) M with a linear coefficiency of 0.993. The system has a high selectivity to melamine with a low detection limit of 8x10(-10) M. PMID:20510598

  10. 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 µM Cu(2+) and 0.22 µM 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

  11. Intrinsic enzyme mimicking activity of gold nanoclusters upon visible light triggering and its application for colorimetric trypsin detection.

    PubMed

    Wang, Guang-Li; Jin, Lu-Yi; Dong, Yu-Ming; Wu, Xiu-Ming; Li, Zai-Jun

    2015-02-15

    In this research, a novel enzyme mimetics based on the photochemical property of gold nanoclusters was demonstrated. It was found that the bovine serum albumin (BSA) stabilized red or blue emitting gold nanoclusters (Au NCs) exhibited enzyme-like activity under visible light irradiation. The BSA-Au NCs had better stability against stringent conditions compared to natural enzyme. In addition, the photostimulated enzyme mimetics of BSA-Au NCs showed several unprecedented advantages over natural peroxidase or other existing alternatives based on nanomaterials, such as the independence of hydrogen peroxide on activity and the easily regulated activity by light irradiation. The mechanism of the photoresponsive enzyme-like activity of BSA-Au NCs was investigated. The photoactivated BSA-Au NCs was designed to develop a facile, cheap, and rapid colorimetric assay to detect trypsin through trypsin digestion of the protein template of BSA-stabilized Au NCs. The limit of detection for trypsin was 0.6 μg/mL, which was much lower than the average level of trypsin in patient's urine or serum. PMID:25310483

  12. 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.

  13. 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%.

  14. 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; Molgó, Jordi; Aráoz, Rómulo

    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 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. PMID:25260255

  15. 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

  16. New turn-on fluorescent and colorimetric probe for cyanide detection based on BODIPY-salicylaldehyde and its application in cell imaging.

    PubMed

    Sukato, Rangsarit; Sangpetch, Nuanphan; Palaga, Tanapat; Jantra, Suthikorn; Vchirawongkwin, Viwat; Jongwohan, Chanantida; Sukwattanasinitt, Mongkol; Wacharasindhu, Sumrit

    2016-08-15

    Development of cyanide sensor is important as the anion is harmful to human health and the environment. Herein, a new colorimetric and fluorescent probe GSB based on boron dipyrrole-methene (BODIPY) containing salicylaldehyde group for cyanide detection has been reported. GSB undergoes exclusive colorimetric change from orange to colorless and exhibits selective fluorescence turn-on at 504nm upon the addition of cyanide. Other 13 anions give almost no interference under physiological condition. Detection limit of the new cyanide-sensing GSB is 0.88μM, which is below World Health Organization (WHO) recommended level in drinking water. A calculation by density functional theory (DFT) shows suppression of photoinduced electron transfer (PET) mechanism along with the interruption of π-conjugation between salicylaldehyde and BODIPY core by cyanide anion. Cell imaging studies demonstrated that GSB is compatible and capable of sensing cyanide anion in living cells. PMID:27136733

  17. New two dimensional liquid-phase colorimetric assay based on old iodine-starch complexation for the naked-eye quantitative detection of analytes.

    PubMed

    Nie, Jinfang; Brown, Tom; Zhang, Yun

    2016-06-14

    A new type of quantitative point-of-care liquid-phase colorimetric assay (LPCA) termed as two dimensional (2D) LPCA is designed using old iodine-starch complexation reaction firstly discovered in 1814. The naked-eye 2D LPCA's utility is well demonstrated with the simple, low-cost, portable detection and quantification of model analytes in buffer and/or human serum samples without the use of external electronic readers. PMID:27074248

  18. Fe3O4 magnetic nanoparticle peroxidase mimetic-based colorimetric assay for the rapid detection of organophosphorus pesticide and nerve agent.

    PubMed

    Liang, Minmin; Fan, Kelong; Pan, Yong; Jiang, Hui; Wang, Fei; Yang, Dongling; Lu, Di; Feng, Jing; Zhao, Jianjun; Yang, Liu; Yan, Xiyun

    2013-01-01

    Rapid and sensitive detection methods are in urgent demand for the screening of extensively used organophosphorus pesticides and highly toxic nerve agents for their neurotoxicity. In this study, we developed a novel Fe(3)O(4) magnetic nanoparticle (MNP) peroxidase mimetic-based colorimetric method for the rapid detection of organophosphorus pesticides and nerve agents. The detection assay is composed of MNPs, acetylcholinesterase (AChE), and choline oxidase (CHO). The enzymes AChE and CHO catalyze the formation of H(2)O(2) in the presence of acetylcholine, which then activates MNPs to catalyze the oxidation of colorimetric substrates to produce a color reaction. After incubation with the organophosphorus neurotoxins, the enzymatic activity of AChE was inhibited and produced less H(2)O(2), resulting in a decreased catalytic oxidation of colorimetric substrates over MNP peroxidase mimetics, accompanied by a drop in color intensity. Three organophosphorus compounds were tested on the assay: acephate and methyl-paraoxon as representative organophosphorus pesticides and the nerve agent Sarin. The novel assay displayed substantial color change after incubation in organophosphorus neurotoxins in a concentration-dependent manner. As low as 1 nM Sarin, 10 nM methyl-paraoxon, and 5 μM acephate are easily detected by the novel assay. In conclusion, by employing the peroxidase-mimicking activity of MNPs, the developed colorimetric assay has the potential of becoming a screening tool for the rapid and sensitive assessment of the neurotoxicity of an overwhelming number of organophosphate compounds. PMID:23153113

  19. 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.

  20. 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

  1. Colorimetric Strategy for Highly Sensitive and Selective Simultaneous Detection of Histidine and Cysteine Based on G-Quadruplex-Cu(II) Metalloenzyme.

    PubMed

    Wu, Changtong; Fan, Daoqing; Zhou, Chunyang; Liu, Yaqing; Wang, Erkang

    2016-03-01

    In this present work, we proposed a colorimetric strategy for simultaneous detection of histidine and cysteine based on G-quadruplex-Cu(II) metalloenzyme for the first time. Because of the adding of histidine or cysteine, the formation of G-quadruplex-Cu(II) metalloenzyme will be disturbed, thus the catalytic activity to TMB-H2O2 reaction is inversely proportional to the concentration of histidine or cysteine. With this strategy, the limit of detection in experimental measurement for histidine and cysteine is 10 nM and 5 nM, respectively, which are both lower than previous colorimetric arrays. With the help of NEM, cysteine is alkylated and the reaction between Cu(2+) is inhibited, so the selectivity can also be guaranteed. The cost is quite low since the developed array is label free and enzyme free by using low-cost DNA and Cu(2+). More importantly, the colorimetric detection operation is very simple without any further modification process. PMID:26832965

  2. Detection of inhibition of 5-aminoimidazole-4-carboxamide ribotide transformylase by thioinosinic acid and azathioprine by a new colorimetric assay.

    PubMed Central

    Ha, T; Morgan, S L; Vaughn, W H; Eto, I; Baggott, J E

    1990-01-01

    The colorimetric assay for 5-aminoimidazole-4-carboxamide ribotide (AICAR) transformylase (phosphoribosylamino-imidazolecarboxamide formyltransferase; EC 2.1.2.3) has been extensively modified. The modified assay is based upon the short-term permanganate oxidation of the folate product, tetrahydrofolate (H4folate) to p-aminobenzoyl glutamate (pABG). The modified assay was used to detect the transformylase activity in crude extracts of peripheral-blood mononuclear cells (PBMCs). Azathioprine and its metabolite, thioinosinic acid (tIMP), are competitive inhibitors (with respect to AICAR) of the chicken liver transformylase and the transformylase from PBMCs of the MRL/lpr mouse, an animal model of systemic autoimmune disease. The Ki values of tIMP and azathioprine for the chicken liver enzyme are 39 +/- 4 microM and 120 +/- 10 microM, whereas the Ki values for the enzyme from PBMCs of the MRL/lpr mouse are 110 +/- 20 microM and 90 +/- 14 microM respectively. The anti-inflammatory drugs ibuprofen and naproxen are also inhibitors of the transformylase. PMID:2268263

  3. Genotoxic activity detected in soils from a hazardous waste site by the Ames test and an SOS colorimetric test

    SciTech Connect

    McDaniels, A.E.; Reyes, A.L.; Wymer, L.J.; Rankin, C.C.; Stelma, G.N. Jr. )

    1993-01-01

    Ten soil samples from a hazardous waste site were compared for their genotoxic activity by the Ames test (Salmonella reverse mutation assay) and a modified SOS colorimetric test. Polynuclear aromatic hydrocarbons known to produce frameshift mutations were found in high levels in the soils. Salmonella typhimurium TA98, sensitive to frameshift mutations, was selected as the Ames tester strain. Escherichia coli K12 PQ37 (sulA::lacZ) was the SOS tester strain. Organic extracts were prepared from the soil samples by Soxhlet extraction. One set of the soil samples was extracted with methylene chloride and a second set with cyclohexane. Two criteria from reproducible dose-related increases in response to the soil were used to compare the positive responses: 1. the concentrations required for doubling responses and 2. a minimum concentration required to produce statistically significant increases from background controls. Analysis of variance indicated that with S9 mix, Ames and SOS results were similar for the same soils and solvent extractions. However, without S9 mix, the SOS test was significantly more sensitive than the Ames test to the genotoxins extracted from the soils. Both the Ames and SOS tests detected lower concentrations of genotoxins in methylene chloride than in cyclohexane extracts. The simplicity of the method, reduction in expenses, and results within 1 working day all contribute to the advantages of the SOS test.

  4. 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

  5. Microfluidic toner-based analytical devices: disposable, lightweight, and portable platforms for point-of-care diagnostics with colorimetric detection.

    PubMed

    Oliveira, Karoliny Almeida; de Souza, Fabrício Ribeiro; de Oliveira, Cristina Rodrigues; da Silveira, Lucimeire Antonelli; Coltro, Wendell Karlos Tomazelli

    2015-01-01

    This chapter describes the development of microfluidic toner-based analytical devices (μTADs) to perform clinical diagnostics using a scanner or cell-phone camera. μTADs have been produced in a platform composed of polyester and toner by the direct-printing technology (DPT) in a matter of minutes. This technology offers simplicity and versatility, and it does not require any sophisticated instrumentation. Toner-based devices integrate the current generation of disposable analytical devices along paper-based chips. The cost of one μTAD has been estimated to be lower than $0.10. In addition, these platforms are lightweight and portable thus enabling their use for point-of-care applications. In the last 5 years, great efforts have been dedicated to spread out the use of μTADs in bioassays. The current chapter reports the fabrication of printed microplates and integrated microfluidic toner-based devices for dengue diagnostics and rapid colorimetric assays with clinically relevant analytes including cholesterol, triglycerides, total proteins, and glucose. The use of μTADs associated with cell-phone camera may contribute to the health care, in special, to people housed in developing regions or with limited access to clinics and hospitals. PMID:25626533

  6. 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 μg 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

  7. Label-free colorimetric sensor for ultrasensitive detection of heparin based on color quenching of gold nanorods by graphene oxide.

    PubMed

    Fu, Xiuli; Chen, Lingxin; Li, Jinhua; Lin, Meng; You, Huiyan; Wang, Wenhai

    2012-04-15

    A novel label-free colorimetric strategy was developed for ultrasensitive detection of heparin by using the super color quenching capacity of graphene oxide (GO). Hexadecyltrimethylammonium bromide (CTAB)-stabilized gold nanorods (AuNRs) could easily self-assembly onto the surface of GO through electrostatic interaction, resulting in decrease of the surface plasmon resonance (SPR) absorption and consequent color quenching change of the AuNRs from deep to light. Polycationic protamine was used as a medium for disturbing the electrostatic interaction between AuNRs and GO. The AuNRs were prevented from being adsorbed onto the surface of GO because of the stronger interaction between protamine and GO, showing a native color of the AuNRs. On the contrary, in the presence of heparin, which was more easily to combine with protamine, the AuNRs could self-assembly onto the surface of GO, resulting in the native color disappearing of AuNRs. As the concentration of heparin increased, the color of AuNRs would gradually fade until almost colorless. The amounts of self-assembly AuNRs were proportional to the concentration of heparin, and thereby the changes in the SPR absorption and color had been used to monitor heparin levels. Under optimized conditions, good linearity was obtained in a range of 0.02-0.28 μg/mL (R=0.9957), and a limit of detection was 5 ng/mL. The simultaneous possession of high sensitivity and selectivity, simplicity, rapidity, and visualization enabled this sensor to be potentially applicable for ultrasensitive and rapid on-site detection toward trace heparin. PMID:22387039

  8. 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...

  9. 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 μM, with the corresponding limits of determination (3σ) of 0.16 μM.

  10. 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...

  11. A label-free colorimetric detection of lead ions by controlling the ligand shells of gold nanoparticles.

    PubMed

    Hung, Yu-Lun; Hsiung, Tung-Ming; Chen, Yi-You; Huang, Chih-Ching

    2010-07-15

    We have developed a simple, colorimetric and label-free gold nanoparticle (Au NP)-based probe for the detection of Pb(2+) ions in aqueous solution, operating on the principle that Pb(2+) ions change the ligand shell of thiosulfate (S(2)O(3)(2-))-passivated Au NPs. Au NPs reacted with S(2)O(3)(2-) ions in solution to form Au(+).S(2)O(3)(2-) ligand shells on the Au NP surfaces, thereby inhibiting the access of 4-mercaptobutanol (4-MB). Surface-assisted laser desorption/ionization time-of-flight ionization mass spectrometry (SALDI-TOF MS) and inductively coupled plasma mass spectrometry (ICP-MS) measurements revealed that PbAu alloys formed on the surfaces of the Au NPs in the presence of Pb(2+) ions; these alloys weakened the stability of the Au(+).S(2)O(3)(2-) ligand shells, enhancing the access of 4-MB to the Au NP surfaces and, therefore, inducing their aggregation. As a result, the surface plasmon resonance (SPR) absorption of the Au NPs red-shifted and broadened, allowing quantitation of the Pb(2+) ions in the aqueous solution. This 4-MB/S(2)O(3)(2-)-Au NP probe is highly sensitive (linear detection range: 0.5-10 nM) and selective (by at least 100-fold over other metal ions) toward Pb(2+) ions. This cost-effective sensing system allows the rapid and simple determination of the concentrations of Pb(2+) ions in real samples (in this case, river water, Montana soil and urine samples). PMID:20602929

  12. RCA-Based Biosensor for Electrical and Colorimetric Detection of Pathogen DNA

    NASA Astrophysics Data System (ADS)

    Jeong, Jaepil; Kim, Hyejin; Lee, Dong Jun; Jung, Byung Jun; Lee, Jong Bum

    2016-05-01

    For the diagnosis and prevention of diseases, a range of strategies for the detection of pathogens have been developed. In this study, we synthesized the rolling circle amplification (RCA)-based biosensor that enables detection of pathogen DNA in two analytical modes. Only in the presence of the target DNA, the template DNA can be continuously polymerized by simply carrying out RCA, which gives rise to a change of surface structure of Au electrodes and the gap between the electrodes. Electrical signal was generated after introducing hydrogen tetrachloroaurate (HAuCl4) to the DNA-coated biosensor for the improvement of the conductivity of DNA, which indicates that the presence of the pathogen DNA can be detected in an electrical approach. Furthermore, the existence of the target DNA was readily detected by the naked eyes through change in colors of the electrodes from bright yellow to orange-red after RCA reaction. The RCA-based biosensor offers a new platform for monitoring of pathogenic DNA with two different detection modes in one system.

  13. RCA-Based Biosensor for Electrical and Colorimetric Detection of Pathogen DNA.

    PubMed

    Jeong, Jaepil; Kim, Hyejin; Lee, Dong Jun; Jung, Byung Jun; Lee, Jong Bum

    2016-12-01

    For the diagnosis and prevention of diseases, a range of strategies for the detection of pathogens have been developed. In this study, we synthesized the rolling circle amplification (RCA)-based biosensor that enables detection of pathogen DNA in two analytical modes. Only in the presence of the target DNA, the template DNA can be continuously polymerized by simply carrying out RCA, which gives rise to a change of surface structure of Au electrodes and the gap between the electrodes. Electrical signal was generated after introducing hydrogen tetrachloroaurate (HAuCl4) to the DNA-coated biosensor for the improvement of the conductivity of DNA, which indicates that the presence of the pathogen DNA can be detected in an electrical approach. Furthermore, the existence of the target DNA was readily detected by the naked eyes through change in colors of the electrodes from bright yellow to orange-red after RCA reaction. The RCA-based biosensor offers a new platform for monitoring of pathogenic DNA with two different detection modes in one system. PMID:27142880

  14. A Simple Colorimetric Chemosensor for Naked Eye Detection of Cyanide Ion.

    PubMed

    Gholamzadeh, Parisa; Mohammadi Ziarani, Ghodsi; Lashgari, Negar; Badiei, Alireza; Shayesteh, Alireza; Jafari, Maryam

    2016-09-01

    A simple cyanide chemosensor tetranitrile compound 1 was designed and synthesized via an efficient method in the presence of nanoporous SBA-Pr-NH2 as the catalyst. The chemosensor exhibited high selectivity and sensitivity for detecting CN¯ among different anions through a visual color change from light yellow to purple. The results confirmed that the chemosensor 1 causes the color of the solution to change depending on the concentration of CN¯. Linear changes of the optical properties of the sensor as a function of the concentrations of CN¯ was proved. The detection limit of 3.07 × 10(-7) M was calculated for CN¯. A simple paper test strip system for the rapid detection of CN¯ was developed. The TD-DFT calculations were carried out to understand the sensing mechanism. PMID:27448224

  15. 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...

  16. 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

  17. Development of an efficient protein phosphatase-based colorimetric test for okadaic acid detection.

    PubMed

    Sassolas, Audrey; Catanante, Gaëlle; Hayat, Akhtar; Marty, Jean-Louis

    2011-09-30

    Okadaic acid (OA), responsible for gastrointestinal problems, inhibits protein phosphatase 2A (PP2A). Therefore, the inhibition exerted by the toxin on PP2A could be used to detect the presence of OA in aqueous solution and in shellfish sample. In this work, two commercial PP2As (from ZEU Immunotec and Millipore) and one produced by molecular engineering (from GTP Technology) were tested. Enzymes were used in solution and also immobilized within a polymeric gel. In solution, best performances were obtained using PP2A purchased from ZEU Immunotec (Spain). OA was detected in aqueous solution in concentration as low as 0.0124 μg L(-1) using the enzyme from ZEU Immunotec whereas the detection limits were 0.47 μg L(-1) and 0.123 μg L(-1) with PP2As from Millipore and GTP Technology, respectively. Considering that the immobilization step contributes to stabilize the PP2A activity, enzymes were entrapped within a photopolymer and an agarose gel. These different polymeric matrices were optimized, tested and compared. Agarose gel seems to be a good alternative to the photopolymer largely used in our group. For instance, the IC(50) value obtained with the test based on PP2A from ZEU Immunotec immobilized within an agarose gel was 1.98 μg L(-1). This value was 1.8-fold lower than those obtained with the photopolymer test using the same enzyme. The proposed test is sensitive, fast and does not require expensive equipment. To evaluate the efficiency of the assay, PP inhibition tests based on PP2A from ZEU Immunotec in solution or immobilized within a gel were used for OA detection in contaminated shellfish. PMID:21839207

  18. 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

  19. 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

  20. 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.

  1. Polydiacetylene liposomes functionalized with sialic acid bind and colorimetrically detect influenza virus

    SciTech Connect

    Reichert, A.; Nagy, J.O.; Spevak, W.; Charych, D. )

    1995-01-18

    In this paper we have demonstrated that polymerized liposomes are biomolecular materials that provide a molecular recognition function (sialic acid) and a detection element (polydiacetylene backbone), all within a single supramolecular assembly. The binding event is transduced to a visible color change, readily seen with the naked eye and quantified by absorption spectroscopy. Specificity of the color change was demonstrated by competitive inhibition studies. In addition, nonspecific adsorption, if it occurs. does not appear to affect the color of the liposome solutions. 28 refs., 2 figs.

  2. 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 NˆN 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

  3. Simple and sensitive colorimetric sensors for the selective detection of Cu2+ in aqueous buffer.

    PubMed

    Huo, Jianzhong; Liu, Kai; Zhao, Xiaojun; Zhang, Xingxing; Wang, Ying

    2014-01-01

    Simple chromogenic sensor for the selective detection of Cu(2+) was described. With the addition of Cu(2+), a bathochromic shift about 82 nm was observed in the UV-VIS spectra, with the color change from colorless to bright yellow. This suggested that the coordination between receptor and Cu(2+) was formed, and the strong push-pull system occurred. The followed IR spectra indicated that Cu(2+) coordinated to the two phenolic oxygen atoms and one of two azomethines in the receptor. PMID:24161519

  4. Direct detection of Dark Matter

    NASA Astrophysics Data System (ADS)

    Belli, P.

    2016-07-01

    An overview of the latest results of Dark Matter direct detection will be summarized, with particular care to the DAMA/LIBRA-phase1 results and the evidence with high confidence level obtained by exploiting the model independent Dark Matter annual modulation signature for the presence of Dark Matter particles in the galactic halo. Results from other experiments using different procedures, different techniques and different target-materials will be shortly discussed. Results, implications and experimental perspectives will be addressed.

  5. 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 419 nm and have spherical and grain shape with size range between 18 and 30 nm. 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 μM (252 ppb) 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

  6. Direct Dark Matter Detection Phenomenology

    NASA Astrophysics Data System (ADS)

    Newstead, Jayden L.

    The identity and origin of dark matter is one of the more elusive mysteries in the fields of particle physics and cosmology. In the near future, direct dark matter detectors will offer a chance at observing dark matter non-gravitationally for the first time. In this thesis, formalisms are developed to analyze direct detection experiments and to quantify the extent to which properties of the dark matter can be determined. A range of non-standard assumptions about the dark matter are considered, including inelastic scattering, isospin violation and momentum dependent scattering. Bayesian inference is applied to realistic detector configurations to evaluate parameter estimation and model selection ability. A complete set of simplified models for spin-0, spin-1/2 and spin-1 dark matter candidates are formulated. The corresponding non-relativistic operators are found, and are used to derive observational signals for the simplified models. The ability to discern these simplified models with direct detection experiments is demonstrated. In the near future direct dark matter detectors will be sensitive to coherent neutrino scattering, which will limit the discovery potential of these experiments. It was found that eleven of the fourteen non-relativistic operators considered produce signals distinct from coherent scattering, and thus the neutrino background does not greatly affect the discovery potential in these cases.

  7. 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 μM) of 1 for Cu(2+) is far lower than the WHO limit (31.5 μM) 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+)-2·1. 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

  8. Blocked Enzymatic Etching of Gold Nanorods: Application to Colorimetric Detection of Acetylcholinesterase Activity and Its Inhibitors.

    PubMed

    Saa, Laura; Grinyte, Ruta; Sánchez-Iglesias, Ana; Liz-Marzán, Luis M; Pavlov, Valeri

    2016-05-01

    The anisotropic morphology of gold nanorods (AuNRs) has been shown to lead to nonuniform ligand distribution and preferential etching through their tips. We have recently demonstrated that this effect can be achieved by biocatalytic oxidation with hydrogen peroxide, catalyzed by the enzyme horseradish peroxidase (HRP). We report here that modification of AuNRs with thiol-containing organic molecules such as glutathione and thiocholine hinders enzymatic AuNR etching. Higher concentrations of thiol-containing molecules in the reaction mixture gradually decrease the rate of enzymatic etching, which can be monitored by UV-vis spectroscopy through changes in the AuNR longitudinal plasmon band. This effect can be applied to develop novel optical assays for acetylcholinesterase (AChE) activity. The biocatalytic hydrolysis of acetylthiocholine by AChE yields thiocholine, which prevents enzymatic AuNR etching in the presence of HRP. Additionally, the same bioassay can be used for the detection of nanomolar concentrations of AChE inhibitors such as paraoxon and galanthamine. PMID:27070402

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

    PubMed

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

    2010-04-19

    γ-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

  10. Smartphone spectrometer for colorimetric biosensing.

    PubMed

    Wang, Yi; Liu, Xiaohu; Chen, Peng; Tran, Nhung Thi; Zhang, Jinling; Chia, Wei Sheng; Boujday, Souhir; Liedberg, Bo

    2016-05-23

    We report on a smartphone spectrometer for colorimetric biosensing applications. The spectrometer relies on a sample cell with an integrated grating substrate, and the smartphone's built-in light-emitting diode flash and camera. The feasibility of the smartphone spectrometer is demonstrated for detection of glucose and human cardiac troponin I, the latter in conjunction with peptide-functionalized gold nanoparticles. PMID:27163736

  11. 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.

  12. 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

  13. Modification-free and N-acetyl-L-cysteine-induced colorimetric response of AuNPs: A mechanistic study and sensitive Hg(2+) detection.

    PubMed

    Tang, Jie; Wu, Peng; Hou, Xiandeng; Xu, Kailai

    2016-10-01

    A facile yet sensitive and selective method was proposed for Hg(2+) detection based on N-acetyl-L-cysteine(NAC)-induced colorimetric response of AuNPs. The proposed method can be easily performed by introducing the premixing of NAC and Hg(2+) into as-prepared citrate-capped AuNPs solution. A combination of experimental and theoretical studies was applied to illustrate the mechanism of this AuNPs colorimetric system. The strong interaction of NAC and AuNPs through Au-S bond could lead to the aggregation of AuNPs, but the formation of NAC-Hg-NAC complex decreased the affinity between NAC and AuNPs and resulted in an anti-aggregation effect. Therefore, the color of the AuNPs solution would progress from purple to red with the increase of Hg(2+) concentration. The proposed method had a high sensitivity with a limit of detection of 9.9nM. Coexistent metal ions, including Cd(2+), Mn(2+), Al(3+), Ag(+), K(+), Mg(2+), Ca(2+), Cr(3+), Cu(2+), Fe(3+), Pb(2+), Ni(2+) and Zn(2+), did not interfere with the detection of Hg(2+). This method can be used to monitor Hg(2+) in tap water. PMID:27474283

  14. A simplified approach to the determination of N-nitroso glyphosate in technical glyphosate using HPLC with post-derivatization and colorimetric detection.

    PubMed

    Kim, Manuela; Stripeikis, Jorge; Iñón, Fernando; Tudino, Mabel

    2007-05-15

    A simple and sensitive HPLC post-derivatization method with colorimetric detection has been developed for the determination of N-nitroso glyphosate in samples of technical glyphosate. Separation of the analyte was accomplished using an anionic exchange resin (2.50mmx4.00mm i.d., 15mum particle size, functional group: quaternary ammonium salt) with Na(2)SO(4) 0.0075M (pH 11.5) (flow rate: 1.0mLmin(-1)) as mobile phase. After separation, the eluate was derivatized with a colorimetric reagent containing sulfanilamide 0.3% (w/v), [N-(1-naphtil)ethilendiamine] 0.03% (w/v) and HCl 4.5M in a thermostatized bath at 95 degrees C. Detection was performed at 546nm. All stages of the analytical procedure were optimized taking into account the concept of analytical minimalism: less operation times and costs; lower sample, reagents and energy consumption and minimal waste. The limit of detection (k=3) calculated for 10 blank replicates was 0.04mgL(-1) (0.8mgkg(-1)) in the solid sample which is lower than the maximum tolerable accepted by the Food and Agriculture Organization of the United Nations. PMID:19071724

  15. [Fe(CN)6]4- decorated mesoporous gelatin thin films for colorimetric detection and as sorbents of heavy metal ions.

    PubMed

    Shi, Li; Huang, Hubiao; Sun, Luwei; Lu, Yanping; Du, Binyang; Mao, Yiyin; Li, Junwei; Ye, Zhizhen; Peng, Xinsheng

    2013-09-28

    [Fe(CN)6](4-) decorated mesoporous gelatin films, acting as colorimetric sensors and sorbents for heavy metal ions, were prepared by incorporating [Fe(CN)6](4-) ions into the mesoporous gelatin films through electrostatic interaction. Gelatin-Prussian blue (PB) and gelatin-PB analogue composite films were successfully synthesized by immersing the [Fe(CN)6](4-) decorated gelatin films into aqueous solutions of metal ions, such as Fe(3+), Cu(2+), Co(2+), Pb(2+) and Cd(2+) (all as nitrates). The in situ formation process of PB or its analogues in the films was investigated using quartz crystal microbalance (QCM) measurements. According to the different colors of the PB nanoparticles and its analogues, the [Fe(CN)6](4-) decorated mesoporous gelatin films demonstrated colorimetric sensor abilities for detecting the corresponding metal ions by the naked eye with sufficient sensitivity at 1 ppm level and a quite short response time of 5 minutes. Moreover, due to the [Fe(CN)6](4-) functionality and other functional groups of gelatin itself, this [Fe(CN)6](4-) decorated mesoporous gelatin film shows a tens times higher adsorption ability for heavy metal ions in water than that of activated carbon. Due to both the efficient detection and high adsorption ability for heavy metal ions, this film has wide potential applications for the detection and purification of heavy metal ions from polluted water. PMID:23887280

  16. 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.

  17. Direct Fast-Neutron Detection

    SciTech Connect

    DC Stromswold; AJ Peurrung; RR Hansen; PL Reeder

    2000-01-18

    Direct fast-neutron detection is the detection of fast neutrons before they are moderated to thermal energy. We have investigated two approaches for using proton-recoil in plastic scintillators to detect fast neutrons and distinguish them from gamma-ray interactions. Both approaches use the difference in travel speed between neutrons and gamma rays as the basis for separating the types of events. In the first method, we examined the pulses generated during scattering in a plastic scintillator to see if they provide a means for distinguishing fast-neutron events from gamma-ray events. The slower speed of neutrons compared to gamma rays results in the production of broader pulses when neutrons scatter several times within a plastic scintillator. In contrast, gamma-ray interactions should produce narrow pulses, even if multiple scattering takes place, because the time between successive scattering is small. Experiments using a fast scintillator confirmed the presence of broader pulses from neutrons than from gamma rays. However, the difference in pulse widths between neutrons and gamma rays using the best commercially available scintillators was not sufficiently large to provide a practical means for distinguishing fast neutrons and gamma rays on a pulse-by-pulse basis. A faster scintillator is needed, and that scintillator might become available in the literature. Results of the pulse-width studies were presented in a previous report (peurrung et al. 1998), and they are only summarized here.

  18. A highly selective colorimetric and "turn-on" fluorimetric chemosensor for detecting CN(-) based on unsymmetrical azine derivatives in aqueous media.

    PubMed

    Sun, You; Hu, Jing-Han; Qi, Jing; Li, Jian-Bin

    2016-10-01

    A novel highly selective chemosensor S1 for cyanide based on unsymmetrical azine derivative was successfully designed and synthesized, which showed both colorimetric and fluorescence turn-on responses for cyanide ions in aqueous. This structurally simple chemosensor could detect CN(-) anion over other anions in aqueous solution DMSO/H2O (v/v=3:2) undergo deprotonation reaction. Results showed that the chemosensor S1 exhibited 50 fold enhancement in fluorescence at 530nm and showed an obvious change in color from colorless to yellow that could be detected by naked eye under the UV-lamp after the addition of CN(-) in aqueous solution. Moreover, the detection limit on fluorescence response of the sensor to CN(-) is down to 6.17×10(-8)M by titration method. Test strips based on S1 were obtain, which could be used as a convenient and efficient CN(-) test kit to detect CN(-) in aqueous solution. PMID:27261890

  19. Surface-plasmon-based colorimetric detection of Cu(II) ions using label-free gold nanoparticles in aqueous thiosulfate systems

    NASA Astrophysics Data System (ADS)

    Tripathy, Suraj Kumar; Woo, Ju Yeon; Han, Chang-Soo

    2012-08-01

    We report colorimetric, label-free and non-aggregation-based gold nanoparticle (AuNP) probes for the highly selective detection of Cu(II) ions in aqueous environments. This detection scheme relies on the ability of Cu(II) ions to catalyze the leaching of gold at room temperature in the presence of thiosulfate species and ammonia. This simple and cost-effective probe provides rapid detection of Cu(II) ions at concentrations as low as 10 ppm. A similar detection method using AuNPs in ammonia-free thiosulfate solution is also viable at moderate reaction temperature (50 °C). The ammonia-free method also leads to marked damping and red-shifting of the surface plasmon resonance signal of the AuNP dispersion. The two methods clearly differ in the nature of the surface plasmon damping phenomenon, and their working mechanisms are plausibly explained based on the experimental investigations.

  20. A label-free colorimetric aptasensor for simple, sensitive and selective detection of Pt (II) based on platinum (II)-oligonucleotide coordination induced gold nanoparticles aggregation.

    PubMed

    Fan, Daoqing; Zhai, Qingfeng; Zhou, Weijun; Zhu, Xiaoqing; Wang, Erkang; Dong, Shaojun

    2016-11-15

    Herein, a gold nanoparticles (AuNPs) based label-free colorimetric aptasensor for simple, sensitive and selective detection of Pt (II) was constructed for the first time. Four bases (G-G mismatch) mismatched streptavidin aptamer (MSAA) was used to protect AuNPs from salt-induced aggregation and recognize Pt (II) specifically. Only in the presence of Pt (II), coordination occurs between G-G bases and Pt (II), leading to the activation of streptavidin aptamer. Streptavidin coated magnetic beads (MBs) were used as separation agent to separate Pt (II)-coordinated MSAA. The residual less amount of MSAA could not efficiently protect AuNPs anymore and aggregation of AuNPs will produce a colorimetric product. With the addition of Pt (II), a pale purple-to-blue color variation could be observed by the naked eye. A detection limit of 150nM and a linear range from 0.6μM to 12.5μM for Pt (II) could be achieved without any amplification. PMID:27281107

  1. 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.

  2. 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; Hébert, Harold; Poncelet, Lucas; Mounier, Maxence; Deschênes, Mylène; 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

  3. 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

  4. 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

  5. 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 μM for H2O2 and 25 to 375 μM for glucose with a detection limit of 5.3 μM for H2O2 and 16 μM for glucose. This assay was also successfully applied to the detection of glucose concentrations in diluted serum and fruit juice samples. PMID:25818144

  6. 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 μL 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

  7. 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 assay’s 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

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    The present study investigated the colorimetric detection of mercury (Hg2+) 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 Hg2+ in nanomolar level. Ag NPs-glutathione conjugates upon interaction with Hg2+ 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.

  10. Unusual sequence length-dependent gold nanoparticles aggregation of the ssDNA sticky end and its application for enzyme-free and signal amplified colorimetric DNA detection

    PubMed Central

    He, Hongfei; Dai, Jianyuan; Duan, Zhijuan; Zheng, Baozhan; Meng, Yan; Guo, Yong; Dan Xiao

    2016-01-01

    It is known that the adsorption of short single-stranded DNA (ssDNA) on unmodified gold nanoparticles (AuNPs) is much faster than that for long ssDNA, and thus leads to length-dependent AuNPs aggregation after addition of salt, the color of the solutions sequentially changed from red to blue in accordance with the increase of ssDNA length. However, we found herein that the ssDNA sticky end of hairpin DNA exhibited a completely different adsorption behavior compared to ssDNA, an inverse blue-to-red color variation was observed in the colloid solution with the increase of sticky end length when the length is within a certain range. This unusual sequence length-dependent AuNPs aggregation might be ascribed to the effect of the stem of hairpin DNA. On the basis of this unique phenomenon and catalytic hairpin assembly (CHA) based signal amplification, a novel AuNPs-based colorimetric DNA assay with picomolar sensitivity and specificity was developed. This unusual sequence length-dependent AuNPs aggregation of the ssDNA sticky end introduces a new direction for the AuNPs-based colorimetric assays. PMID:27477392

  11. Unusual sequence length-dependent gold nanoparticles aggregation of the ssDNA sticky end and its application for enzyme-free and signal amplified colorimetric DNA detection

    NASA Astrophysics Data System (ADS)

    He, Hongfei; Dai, Jianyuan; Duan, Zhijuan; Zheng, Baozhan; Meng, Yan; Guo, Yong; Dan Xiao

    2016-08-01

    It is known that the adsorption of short single-stranded DNA (ssDNA) on unmodified gold nanoparticles (AuNPs) is much faster than that for long ssDNA, and thus leads to length-dependent AuNPs aggregation after addition of salt, the color of the solutions sequentially changed from red to blue in accordance with the increase of ssDNA length. However, we found herein that the ssDNA sticky end of hairpin DNA exhibited a completely different adsorption behavior compared to ssDNA, an inverse blue-to-red color variation was observed in the colloid solution with the increase of sticky end length when the length is within a certain range. This unusual sequence length-dependent AuNPs aggregation might be ascribed to the effect of the stem of hairpin DNA. On the basis of this unique phenomenon and catalytic hairpin assembly (CHA) based signal amplification, a novel AuNPs-based colorimetric DNA assay with picomolar sensitivity and specificity was developed. This unusual sequence length-dependent AuNPs aggregation of the ssDNA sticky end introduces a new direction for the AuNPs-based colorimetric assays.

  12. Sensitivity enhancement in the colorimetric detection of lead(II) ion using gallic acid-capped gold nanoparticles: improving size distribution and minimizing interparticle repulsion.

    PubMed

    Huang, Kuan-Wei; Yu, Cheng-Ju; Tseng, Wei-Lung

    2010-01-15

    We have developed a colorimetric assay for the highly sensitive and selective detection of Pb(2+) by narrowing the size distribution of gallic acid-capped gold nanoparticles (GA-AuNPs) and minimizing electrostatic repulsion between each GA-AuNP. We unveil that the particle size and size distribution of GA-AuNPs could be controlled by varying the pH of HAuCl(4) with fixed concentrations of HAuCl(4) and GA. When the pH of the precursor solution (i.e., HAuCl(4)) was adjusted from 2.2 to 11.1, the average diameter of GA-AuNPs was decreased from 75.1 nm to 9.3 nm and their size distribution was reduced from 56.6-93.6 nm to 9.0-9.6 nm. The colorimetric sensitivity of the Pb(2+)-induced aggregation of GA-AuNPs could be improved using narrow size distribution of GA-AuNPs. Moreover, further enhancement of the colorimetric sensitivity of GA-AuNPs toward Pb(2+) could be achieved by adding NaClO(4) to minimize electrostatic repulsion between GA-AuNPs, which provide a small energy barrier for Pb(2+) to overcome. Under the optimum conditions (1.0 mM NaClO(4) and 20 mM formic acid at pH 4.5), the selectivity of 9.3 nm GA-AuNPs for Pb(2+) over other metal ions in aqueous solutions is remarkably high, and its minimum detectable concentration for Pb(2+) is 10nM. We demonstrate the practicality of 9.3 nm GA-AuNPs for the determination of Pb(2+) in drinking water. This approach offers several advantages, including simplicity (without temperature control), low cost (no enzyme or DNA), high sensitivity, high selectivity, and a large linear range (10.0-1000.0 nM). PMID:19782557

  13. Aqueous sols of oligo(ethylene glycol) surface decorated polydiacetylene vesicles for colorimetric detection of Pb 2+.

    PubMed

    Narkwiboonwong, Pat; Tumcharern, Gamolwan; Potisatityuenyong, Anupat; Wacharasindhu, Sumrit; Sukwattanasinitt, Mongkol

    2011-01-15

    A series of ethylene glycol (EG), triethylene glycol (3EG) and pentaethylene glycol (5EG) esters of 10,12-pentacosadiynoic acid (PCDA) are synthesized. The glycol ester lipids can be hydrated and well dispersed in water but they cannot form polydiacetylenes upon UV irradiation. They however can be mixed with PCDA up to 30 mol% and polymerized to form blue sols. The mixed polydiacetylene sols show blue to red thermochromic transition with two-stepped transition temperatures. The first transition temperature decreases with the increase of the glycol ester content as well as the length of their chains indicating greater fluidity of the self-assembled structure due to less collaborative hydrogen bonding among the lipid head groups. These mixed polydiacetylene sol prepared from 30 mol% of the penta(ethylene glycol) ester show linear colorimetric response selectively to Pb(2+) in the range of 5-30 μM. PMID:21147331

  14. Recent progress in the development of fluorescent, luminescent and colorimetric probes for detection of reactive oxygen and nitrogen species.

    PubMed

    Chen, Xiaoqiang; Wang, Fang; Hyun, Ji Young; Wei, Tingwen; Qiang, Jian; Ren, Xintong; Shin, Injae; Yoon, Juyoung

    2016-05-21

    Reactive oxygen (ROS) and nitrogen (RNS) species cause oxidative and nitrosative stresses, respectively. These stresses are implicated not only in diverse physiological processes but also in various pathological processes, including cancer and neurodegenerative disorders. In addition, some ROS and RNS in the environment are pollutants that threaten human health. As a consequence of these effects, sensitive methods, which can be employed to selectively monitor ROS and RNS in live cells, tissues and organisms as well as in environmental samples, are needed so that their biological roles can be understood and their concentrations in environmental samples can be determined. In this review, fluorescent, luminescent and colorimetric ROS and RNS probes, which have been developed since 2011, are comprehensively discussed. PMID:27092436

  15. 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.

  16. Label-free and enzyme-free colorimetric detection of microRNA by catalyzed hairpin assembly coupled with hybridization chain reaction.

    PubMed

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

    2016-07-15

    In this study, a simple, label-free, and enzyme-free colorimetric biosensor has been developed for amplified detection of let-7a microRNA (miRNA) on the basis of dual signal amplification strategy. The sensing system mainly consists of four unlabeled hairpin probes termed H1, H2, H3, and H4. Upon sensing of the target miRNA, hairpin H1 is opened. Then hairpin H2 hybridizes with H1 forming H1-H2 duplex and frees the target miRNA that can be recycled to trigger another reaction cycle. In addition, the newly formed H1-H2 duplex hybridizes with hairpin H3, and this triggers the autonomous cross-opening of the two hairpins H3 and H4 through hybridization chain reaction. During this process, numerous split G-quadruplex structures are generated and further associate with cofactor hemin to form massive peroxidase-mimicking DNAzymes. The resulting DNAzymes catalyze the H2O2-mediated oxidation of colorless 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(2-)) to the green-colored ABTS(•-), inducing a remarkably amplified colorimetric signal. This newly developed sensing system exhibits high sensitivity toward miRNA with a detection limit of 7.4fM and a large dynamic range of 6 orders of magnitude from 10fM to 10nM. Furthermore, it exhibits a good performance to discriminate single-base difference among the miRNA family members and holds a great potential for early diagnosis in gene-related diseases. PMID:26985582

  17. 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

  18. 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

  19. 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

  20. 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

  1. 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 sensitivity—a 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

  2. 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

  3. Sequential injection analysis of lead using time-based colorimetric detection and preconcentration on an anionic-exchange resin.

    PubMed

    Aracama, Nestor Zárate; Araújo, Alberto N; Perez-Olmos, Ricardo

    2004-04-01

    The development of a sequential injection analysis manifold for the colorimetric determination of lead in water samples is described The concentration of lead was assessed from its catalytic effect on the reaction of resazurine reduction caused by sulfide in an alkali medium. To that effect, the reaction zone was stopped at the detector, and the time interval required for the attainment of an absorbance decrease of 0.800 at the wavelength of 610 nm was estimated. Interference of other transition metals of the samples was minimized by adding potassium iodide to the sample and retaining the iodocomplexes formed in an on-line anionic resin (AGI X8). Elution was made with a 2 mol/L sodium hydroxide solution. The relationship [SIA] microg/L = 0.99 (+/- 0.11) x [ETAAS] microg/L + 0 (+/- 4) was obtained upon comparing the results given by the proposed system and by electrothermal atomization atomic absorption spectrometry (ETAAS) after the analysis of ten water samples. PMID:15116968

  4. High sensitivity, loop-mediated isothermal amplification combined with colorimetric gold-nanoparticle probes for visual detection of high risk human papillomavirus genotypes 16 and 18.

    PubMed

    Kumvongpin, Ratchanida; Jearanaikool, Patcharee; Wilailuckana, Chotechana; Sae-Ung, Nattaya; Prasongdee, Prinya; Daduang, Sakda; Wongsena, Metee; Boonsiri, Patcharee; Kiatpathomchai, Wansika; Swangvaree, Sukumarn Sanersak; Sandee, Alisa; Daduang, Jureerut

    2016-08-01

    High-risk human papillomavirus (HR-HPV) causes cervical cancer. HPV16 and HPV18 are the most prevalent strains of the virus reported in women worldwide. Loop-mediated isothermal amplification (LAMP) is an alternative method for DNA detection under isothermal conditions. However, it results in a turbid amplified product which is not easily detected by the naked eye. This study aimed to develop an improved technique by using gold nanoparticles (AuNPs) attached to a single-stranded DNA probe for the detection of HPV16 and HPV18. Detection of the LAMP product by AuNP color change was compared with detection by visual turbidity. The optimal conditions for this new LAMP-AuNP assay were an incubation time of 20min and a temperature of 65°C. After LAMP amplification was complete, its products were hybridized with the AuNP probe for 5min and then detected by the addition of magnesium salt. The color changed from red to blue as a result of aggregation of the AuNP probe under high ionic strength conditions produced by the addition of the salt. The sensitivity of the LAMP-AuNP assay was greater than the LAMP turbidity assay by up to 10-fold for both HPV genotypes. The LAMP-AuNP assay showed higher sensitivity and ease of visualization than did the LAMP turbidity for the detection of HPV16 and HPV18. Additionally, AuNP-HPV16 and AuNP-HPV18 probes were stable for over 1year. The combination of LAMP and the AuNP-probe colorimetric assay offers a simple, rapid and highly sensitive alternative diagnostic tool for the detection of HPV16 and HPV18 in district hospitals or field studies. PMID:27086727

  5. SDS-MoS2 nanoparticles as highly-efficient peroxidase mimetics for colorimetric detection of H2O2 and glucose.

    PubMed

    Zhao, Kai; Gu, Wei; Zheng, Sisi; Zhang, Cuiling; Xian, Yuezhong

    2015-08-15

    In this work, we find that the peroxidase-like activity of MoS2 nanoparticles (NPs) is dependent on the surface charge. Negatively charged sodium dodecyl sulfate modified MoS2 nanoparticles (SDS-MoS2 NPs) possess highly-efficient peroxidase-like activity. MoS2 NPs with intrinsic peroxidase-like activity were synthesized through a simple one-pot hydrothermal route. The peroxidase-like activities of different surfactants modified MoS2 NPs were discussed. Compared with bare MoS2 NPs and positively charged cetyltrimethyl ammonium bromide modified MoS2 NPs, SDS-MoS2 NPs have the best peroxidase-like activity. SDS-MoS2 NPs can efficiently catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H2O2 to generate a blue product. On basis of this, we have successfully established a novel platform for colorimetric detection of H2O2, and the detection limit is 0.32μM. Furthermore, the SDS-MoS2 NPs based platform can also be used for high sensitivity and selectivity detection of glucose with a wide linear range of 5.0-500μM by controlling the generation of H2O2 in the presence of glucose oxidase. PMID:25966379

  6. 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.

  7. A facile strategy for the preparation of ZnS nanoparticles deposited on montmorillonite and their higher catalytic activity for rapidly colorimetric detection of H2O2.

    PubMed

    Ding, Yanyuan; Sun, Lifang; Jiang, Yanling; Liu, Shunxiang; Chen, Mingxing; Chen, Miaomiao; Ding, Yanan; Liu, Qingyun

    2016-10-01

    In this paper, ZnS nanoparticles deposited on montmorillonite (ZnS-MMT) were prepared by a facile method at room temperature and characterized by powder X-ray diffraction (XRD), Energy-dispersive X-ray Detector (EDX) and transmission electron microscope (TEM), respectively. Significantly, the as-prepared ZnS-MMT nanocomposites have been proven to possess intrinsic peroxidase-like activity that can rapidly catalyze the reaction of peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2 and produce a blue color product in less than 30 seconds, which provides a sensitive colorimetric sensor to detect H2O2. Due to the synergistic effects between montmorillonite and ZnS nanoparticles, the obtained ZnS-MMT nanocomposites exhibit higher catalytic activity than that of MMT or ZnS alone. The catalytic behaviors of the ZnS-MMT nanocomposites showed a typical Michaelis-Menten kinetics. The catalytic activity and the catalytic mechanism were investigated using the procedures of steady-state kinetics and hydroxyl radical detection. ESR data revealed that the peroxidase-like activity of ZnS-MMT originated from the generation of OH radicals. PMID:27287113

  8. 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.

  9. 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

  10. 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

  11. Synthesis, characterization and application of poly(acrylamide-co-methylenbisacrylamide) nanocomposite as a colorimetric chemosensor for visual detection of trace levels of Hg and Pb ions.

    PubMed

    Sedghi, Roya; Heidari, Bahareh; Behbahani, Mohammad

    2015-03-21

    In this study, a new colorimetric chemosensor based on TiO2/poly(acrylamide-co-methylenbisacrylamide) nanocomposites was designed for determination of mercury and lead ions at trace levels in environmental samples. The removal and preconcentration of lead and mercury ions on the sorbent was achieved due to sharing an electron pair of N and O groups of polymer chains with the mentioned heavy metal ions. The hydrogel sensor was designed by surface modification of a synthesized TiO2 nanoparticles using methacryloxypropyltrimethoxysilan (MAPTMS), which provided a reactive C=C bond that polymerized the acrylamide and methylenbisacrylamide. The sorbent was characterized using X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM), EDS analysis and Fourier transform in frared (FT-IR) spectrometer. This nanostructured composite with polymer shell was developed as a sensitive and selective sorbent for adsorption of mercury and lead ions from aqueous solution at optimized condition. This method involves two-steps: (1) preconcentration of mercury and lead ions by the synthesized sorbent and (2) its selective monitoring of the target ions by complexation with dithizone (DZ). The color of the sorbent in the absence and presence of mercury and lead ions shifts from white to violet and red, respectively. The detection limit of the synthesized nanochemosensor for mercury and lead ions was 1 and 10 μg L(-1), respectively. The method was successfully applied for trace detection of mercury and lead ions in tap, river, and sea water samples. PMID:25497023

  12. 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 5 nM with detection limit of 20 pM 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

  13. 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 37°C 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

  14. 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 0.01-0.8 µM with a detection limit of 7 nM. 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

  15. 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.

  16. 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.

  17. 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 (μg.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

  18. 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.

  19. Disentangling dark matter dynamics with directional detection

    SciTech Connect

    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.

  20. 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 μM. Importantly, this method also could detect Hg(2+) quantitatively by ratiometic absorption spectroscopy in the range of 0.1 - 6 μM 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

  1. 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

  2. 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

  3. Simple and fast colorimetric detection of inorganic arsenic selectively adsorbed onto ferrihydrite-coated silica gel using silver nanoplates.

    PubMed

    Siangproh, Weena; Chailapakul, Orawan; Songsrirote, Kriangsak

    2016-06-01

    The optical detection for inorganic arsenic (As) semi-quantitative determination is presented by using silver nanoplates (AgNPls). The color of AgNPs is immediately changed in the presence of As(III) and As(V) with the same sensitivity. To improve the selectivity of AgNPls for As detection, ferrihydrite-coated silica gel (SiO2-Fh) was specifically exploited as adsorbent for arsenic prior to As detection by AgNPls. The developed method provides the detection limit of 0.5ppm with the detection range between 0.5ppm and 30.0ppm for As determination observed with naked eye, and allows to determine total inorganic arsenic. This is the first report of As detection approach combining As removal technology together with nanotechnology. This combined technique provides a rapid, sensitive and selective method for monitoring As levels in aqueous samples, and can be employed as a testing field kit to screen arsenic contamination outside of a laboratory. PMID:27130109

  4. 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.

  5. Spectral efficiency of optical direct detection

    NASA Astrophysics Data System (ADS)

    Martinez, Alfonso

    2007-04-01

    The spectral efficiency (channel capacity) of the optical direct-detection channel is studied. The modeling of the optical direct-detection channel as a discrete-time Poisson channel is reviewed. Closed-form integral representations for the entropy of random variables with Poisson and negative binomial distributions are derived. The spectral efficiency achievable with an arbitrary input gamma density is expressed in closed integral form. Simple, nonasymptotic upper and lower bounds to the channel capacity are computed. Numerical results are presented and compared with previous bounds and approximations.

  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. 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 (μPAD) to detect UTI from urine collected from adult diapers. The design and fabrication for the μPAD 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 μPAD 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

  8. Pd/V.sub.2O.sub.5 device for colorimetric H.sub.2 detection

    DOEpatents

    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.

  9. 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.

  10. 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 1.5×10(3) and 1.5×10(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

  11. Dual colorimetric and fluorescent sensor based on semiconducting polymer dots for ratiometric detection of lead ions in living cells.

    PubMed

    Kuo, Shih-Yu; Li, Hsiang-Hau; Wu, Pei-Jing; Chen, Chuan-Pin; Huang, Ya-Chi; Chan, Yang-Hsiang

    2015-01-01

    Recently, semiconducting polymer dots (Pdots) have become a novel type of ultrabright fluorescent probes which hold great promise in biological imaging and analytical detection. Here we developed a visual sensor based on Pdots for Pb(2+) detection. We first embedded near-infrared (NIR) dyes into the matrix of poly[(9,9-dioctylfluorene)-co-2,1,3-benzothiadiazole-co-4,7-di(thiophen-2-yl)-2,1,3-benzothiadiazole] (PFBT-DBT) polymer and then capped the Pdots with polydiacetylenes (PDAs), in which parts of the PDAs were prefunctionalized with 15-crown-5 moieties to form Pdots. The high selectivity of these Pdots for lead ions is attributed to the formation of 2:1 15-crown-5-Pb(2+)-carboxylate sandwich complex on the Pdot surface. After Pb(2+) chelation, the conjugation system of the PDA was perturbed and strained, causing a chromatic change of the PDA from blue to red. At the same time, the encapsulated NIR dyes were liable to leach out that resulted in an emission variation of the Pdots. Accordingly, lead ions can be recognized by either color change or emission variation of the Pdots. We also loaded these nanoprobes into live HeLa cells through endocytosis, and then monitored changes in Pb(2+) levels within cells, demonstrating their utility for use in cellular and bioimaging applications. In addition, we fabricated easy-to-prepare test strips impregnated with Pdot-poly(vinyl alcohol) films to identify Pb(2+) in real samples, which proved their applicability for in situ on-site detection. Our results suggest that this Pdot-based visual sensor shows promising potential for advanced environmental and biological applications. PMID:25822074

  12. 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 Ag NPs (Ch-Ag NPs). The Ch-Ag NPs 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, β-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-Ag NPs-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

  13. 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

  14. Wind measurement via direct detection lidar

    NASA Astrophysics Data System (ADS)

    Afek, I.; Sela, N.; Narkiss, N.; Shamai, G.; Tsadka, S.

    2013-10-01

    Wind sensing Lidar is considered a promising technology for high quality wind measurements required for various applications such as hub height wind resource assessment, power curve measurements and advanced, real time, forward looking turbine control. Until recently, the only available Lidar technology was based on coherent Doppler shift detection, whose market acceptance has been slow primarily due to its exuberant price. Direct detection Lidar technology provides an alternative to remote sensing of wind by incorporating high precision measurement, a robust design and an affordable price tag.

  15. DIRECTIONAL DETECTION OF FISSION-SPECTRUM NEUTRONS.

    SciTech Connect

    VANIER,P.E.

    2007-05-04

    Conventional neutron detectors consisting of {sup 3}He tubes surrounded by a plastic moderator can be quite efficient in detecting fission spectrum neutrons, but do not indicate the direction of the incident radiation. We have developed a new directional detector based on double proton recoil in two separated planes of plastic scintillators. This method allows the spectrum of the neutrons to be measured by a combination of peak amplitude in the first plane and time of flight to the second plane. It also allows the determination of the angle of scattering in the first plane. If the planes are position-sensitive detectors, then the direction of the scattered neutron is known, and the direction of the incident neutron can be determined to lie on a cone of s fixed angle. The superposition of many such cones generates an image that indicates the presence of a localized source. Typical background neutron fluences from the interaction of cosmic rays with the atmosphere are low and fairly uniformly distributed in angle. Directional detection helps to locate a manmade source in the presence of natural background. Monte Carlo simulations are compared with experimental results.

  16. Scalar dark matter: direct vs. indirect detection

    NASA Astrophysics Data System (ADS)

    Duerr, Michael; Pérez, Pavel Fileviez; Smirnov, Juri

    2016-06-01

    We revisit the simplest model for dark matter. In this context the dark matter candidate is a real scalar field which interacts with the Standard Model particles through the Higgs portal. We discuss the relic density constraints as well as the predictions for direct and indirect detection. The final state radiation processes are investigated in order to understand the visibility of the gamma lines from dark matter annihilation. We find two regions where one could observe the gamma lines at gamma-ray telescopes. We point out that the region where the dark matter mass is between 92 and 300 GeV can be tested in the near future at direct and indirect detection experiments.

  17. [Determination of trace mercury in wastewater by a flow injection analysis composed of immobilized ionic liquid enrichment and colorimetric detection].

    PubMed

    Zhang, Jun; Mao, Li-li; Yang, Gui-peng; Gao, Xian-chi; Tang, Xu-li

    2010-07-01

    Amberlite XAD-7 resin was modified by room temperature ionic liquid (1-hexyl-3-methylimidazolium hexafluorophosphate, [C6 mim]PF6) coating through a maceration method, gaining a new sort of hydrophobic adsorbent for the solid phase extraction mini-column. Trace inorganic mercury in wastewater samples was preconcentrated and determined by flow injection online mini-column sampling coupled with spectrophotometric determination. In acid medium, dithizone was employed as chelator with cetyltrimethylammonium bromide (CTMAB) to form a red neutral mercury-dithizone complex, which could be extracted quantificationally by solid phase extraction technique on the mini-column. Under the optimized conditions, the linearity and the detection limit of the proposed method were found to be 0.35 to 50.0 microg x L(-1) Hg2+ and 0.067 microg x L(-1) Hg2+, respectively. The enrichment factor of 25 times could be achieved with a 50 mL sampling volume and the developed procedure was successfully applied for the determination of mercury in the certified reference material (GSBZ50016-90) and the spiked dock wastewater samples with the recovery of 99%-103%. PMID:20828014

  18. 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 λmax 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 μg 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 μg mL -1 using AAS method or 30-45 μg 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.

  19. 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 Central

    Alvarez-Fernandez, M.; Cantón, 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.; Quindós, G.; Rodriguez-Iglesias, M.; Sánchez-Reus, F.; Shoham, S.; Wengenack, N. L.; Borrell Solé, N.; Echeverria, J.; Esperalba, J.; Gómez-G. de la Pedrosa, E.; García García, I.; Linares, M. J.; Marco, F.; Merino, P.; Pemán, J.; Pérez del Molino, L.; Roselló Mayans, E.; Rubio Calvo, C.; Ruiz Pérez de Pipaon, M.; Yagüe, G.; Garcia-Effron, G.; Guinea, J.; Perlin, D. S.; Sanguinetti, M.; Shields, R.; Turnidge, J.

    2015-01-01

    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 μg/ml for C. albicans, 0.12, 0.25, and 0.03 μg/ml for C. glabrata complex, 4, 2, and 4 μg/ml for C. parapsilosis complex, 0.5, 0.25, and 0.06 μg/ml for C. tropicalis, 0.25, 1, and 0.25 μg/ml for C. krusei, 0.25, 1, and 0.12 μg/ml for C. lusitaniae, 4, 2, and 2 μg/ml for C. guilliermondii, and 0.25, 0.25, and 0.12 μg/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

  20. 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; Cantón, 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; Quindós, G; Rodriguez-Iglesias, M; Sánchez-Reus, F; Shoham, S; Wengenack, N L; Borrell Solé, N; Echeverria, J; Esperalba, J; Gómez-G de la Pedrosa, E; García García, I; Linares, M J; Marco, F; Merino, P; Pemán, J; Pérez Del Molino, L; Roselló Mayans, E; Rubio Calvo, C; Ruiz Pérez de Pipaon, M; Yagüe, 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 μg/ml for C. albicans, 0.12, 0.25, and 0.03 μg/ml for C. glabrata complex, 4, 2, and 4 μg/ml for C. parapsilosis complex, 0.5, 0.25, and 0.06 μg/ml for C. tropicalis, 0.25, 1, and 0.25 μg/ml for C. krusei, 0.25, 1, and 0.12 μg/ml for C. lusitaniae, 4, 2, and 2 μg/ml for C. guilliermondii, and 0.25, 0.25, and 0.12 μg/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

  1. 'PET' vs. 'push-pull' induced ICT: a remarkable coumarinyl-appended pyrimidine based naked eye colorimetric and fluorimetric sensor for the detection of Hg2+ ions in aqueous media with test trips.

    PubMed

    Goswami, Shyamaprosad; Das, Avijit Kumar; Maity, Sibaprasad

    2013-12-14

    A novel colorimetric and fluorescent chemosensor based on 7-(diethylamino)-3-(pyrimidin-4-yl)-2H-chromen-2-one (PYC) has been designed and synthesized for the detection of Hg(2+) in the presence of other competing metals in mixed aqueous media. The PYC exhibits naked eye color change from green to red, and the fluorescence color changes from yellowish green to light orange with Hg(2+). It also shows a red shift in wavelength of about 80 nm in absorption spectra. Test strips based on PYC were fabricated, which could act as convenient and efficient Hg(2+) test kits. PMID:24096453

  2. 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.

  3. Direct detection of dark matter axions with directional sensitivity

    SciTech Connect

    Irastorza, Igor G.; García, 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 λ{sub a} is sufficiently larger than the cavity dimensions L for a fully coherent conversion, i.e. λ{sub a}∼>2πL. 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.

  4. Miniature laser direct-detection radar

    NASA Astrophysics Data System (ADS)

    Acharekar, Madhu; Lebeau, Robert

    1992-06-01

    A miniature laser with a total volume less than 15 cu cm and weight less than 100 g has been designed, fabricated, and assembled. The laser uses a composite rod consisting of Nd:Cr:GSGG material rod cladded with an Er:Cr:YSGG tube. The laser provides output at 1 and 3 micron wavelengths. The size and weight reduction is obtained by chemical pumping which eliminates the prime power and the power supply. The laser is used as an illuminator in a direct detection radar.

  5. NASA direct detection laser diode driver

    NASA Technical Reports Server (NTRS)

    Seery, B. D.; Hornbuckle, C. A.

    1989-01-01

    TRW has developed a prototype driver circuit for GaAs laser diodes as part of the NASA/Goddard Space Flight Center's Direct Detection Laser Transceiver (DDLT) program. The circuit is designed to drive the laser diode over a range of user-selectable data rates from 1.7 to 220 Mbps, Manchester-encoded, while ensuring compatibility with 8-bit and quaternary pulse position modulation (QPPM) formats for simulating deep space communications. The resulting hybrid circuit has demonstrated 10 to 90 percent rise and fall times of less than 300 ps at peak currents exceeding 100 mA.

  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

  7. 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...

  8. The Earth's velocity for direct detection experiments

    NASA Astrophysics Data System (ADS)

    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. Dark matter direct detection with accelerometers

    NASA Astrophysics Data System (ADS)

    Graham, Peter W.; Kaplan, David E.; Mardon, Jeremy; Rajendran, Surjeet; Terrano, William A.

    2016-04-01

    The mass of the dark matter particle is unknown, and may be as low as ˜1 0-22 eV . The lighter part of this range, below ˜eV , is relatively unexplored both theoretically and experimentally but contains an array of natural dark matter candidates. An example is the relaxion, a light boson predicted by cosmological solutions to the hierarchy problem. One of the few generic signals such light dark matter can produce is a time-oscillating, equivalence-principle-violating force. We propose searches for this using accelerometers, and consider in detail the examples of torsion balances, atom interferometry, and pulsar timing. These approaches have the potential to probe large parts of unexplored parameter space in the next several years. Thus such accelerometers provide radically new avenues for the direct detection of dark matter.

  10. Direct detection constraints on superheavy dark matter.

    PubMed

    Albuquerque, Ivone F M; Baudis, Laura

    2003-06-01

    The dark matter in the Universe might be composed of superheavy particles (mass greater, similar 10(10) GeV). These particles can be detected via nuclear recoils produced in elastic scatterings from nuclei. We estimate the observable rate of strongly interacting supermassive particles (simpzillas) in direct dark matter search experiments. The simpzilla energy loss in Earth and in the experimental shields is taken into account. The most natural scenarios for simpzillas are ruled out based on recent EDELWEISS and CDMS results. The dark matter can be composed of superheavy particles only if these interact weakly with normal matter or if their mass is above 10(15) GeV. PMID:12857302

  11. 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.

  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 Exoplanet Detection with Binary Differential Imaging

    NASA Astrophysics Data System (ADS)

    Rodigas, Timothy J.; Weinberger, Alycia; Mamajek, Eric E.; Males, Jared R.; Close, Laird M.; Morzinski, Katie; Hinz, Philip M.; Kaib, Nathan

    2015-10-01

    Binaries are typically excluded from direct imaging exoplanet surveys. However, the recent findings of Kepler and radial velocity programs show that planets can and do form in binary systems. Here, we suggest that visual binaries offer unique advantages for direct imaging. We show that Binary Differential Imaging (BDI), whereby two stars are imaged simultaneously at the same wavelength within the isoplanatic patch at a high Strehl ratio, offers improved point spread function (PSF) subtraction that can result in increased sensitivity to planets close to each star. We demonstrate this by observing a young visual binary separated by 4″ with MagAO/Clio-2 at 3.9 μm, where the Strehl ratio is high, the isoplanatic patch is large, and giant planets are bright. Comparing BDI to angular differential imaging (ADI), we find that BDI’s 5σ contrast is ˜0.5 mag better than ADI’s within ˜1″ for the particular binary we observed. Because planets typically reside close to their host stars, BDI is a promising technique for discovering exoplanets in stellar systems that are often ignored. BDI is also 2-4× more efficient than ADI and classical reference PSF subtraction, since planets can be detected around both the target and PSF reference simultaneously. We are currently exploiting this technique in a new MagAO survey for giant planets in 140 young nearby visual binaries. BDI on a space-based telescope would not be limited by isoplanatism effects and would therefore be an even more powerful tool for imaging and discovering planets. This paper includes data obtained at the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  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. 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

  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. 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…

  19. 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

  20. 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

  1. Systematic aspects of direct extrasolar planet detection

    NASA Technical Reports Server (NTRS)

    Brown, Robert A.

    1988-01-01

    Using the first optical observatory in space, the Hubble Space Telescope, images of possible extrasolar planets will have poor contrast against the background of diffracted and scattered starlight. The very long exposure time required to achieve an adequate signal-to-noise ratio will make their detection infeasible. For a future telescope, a 16-fold increase in either the smoothness of the collecting area of the optics would reduce the exposure time to a tolerable value, but the contrast would remain low and the required photometric precision high. In this situation, the feasibility of detection would be contingent on the careful identification and control of systematic errors.

  2. 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

  3. 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.

  4. Indirect detection of radiation sources through direct detection of radiolysis products

    DOEpatents

    Farmer, Joseph C.; Fischer, Larry E.; Felter, Thomas E.

    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.

  5. Colorimetric filtrations of metal chelate precipitations for the quantitative determination of nickel(II) and lead(II).

    PubMed

    Feng, Liang; Zhang, Yue; Wen, Liying; Chen, Liang; Shen, Zheng; Guan, Yafeng

    2011-10-21

    A colorimetric filtration method has been developed for the highly selective and sensitive determination of Ni(2+) and Pb(2+) ions. Determinations of Ni(2+) and Pb(2+) follow the filtration using nioxime (1,2-cyclohexanedione dioxime) and rhodizonic acid disodium salt, respectively, as colorimetric reagents. Different from regular instrumentation techniques, the metal chelate precipitations are continuously pumped into a home-made flow cell at a constant flow rate, and filtered by a cellulose acetate/nitrate membrane. The color changes of the membrane are imaged using a conventional flatbed scanner, and digitized. The special selection of individual channels in the red, green, and blue channels of the images filters the influences of coexisting ions and provides a highly selective detection of Ni(2+) and Pb(2+) cations. The linear relationship between the colorimetric response of the chosen channel and Ni(2+) or Pb(2+) concentrations indicates a quantitative detection. The detection limit for Pb(2+) is 3 μM (almost half of the Chinese wastewater discharge standard concentration), and is well below the nM level (94 nM) for Ni(2+) (a quarter of the WHO drinking water safe-exposure standard for Ni(2+)). The determinations take five to ten minutes. No shelf life issue exists because the chelating indicators react with metal directly without any pre-immobilizations. PMID:21860847

  6. 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

  7. Reversible colorimetric probes for mercury sensing.

    PubMed

    Coronado, Eugenio; Galán-Mascarós, José R; Martí-Gastaldo, Carlos; Palomares, Emilio; Durrant, James R; Vilar, Ramón; Gratzel, M; Nazeeruddin, Md K

    2005-09-01

    The selectivity and sensitivity of two colorimetric sensors based on the ruthenium complexes N719 [bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II) bis(tetrabutylammonium) bis(thiocyanate)] and N749 [(2,2':6',2' '-terpyridine-4,4',4' '-tricarboxylate)ruthenium(II) tris(tetrabutylammonium) tris(isothiocyanate)] are described. It was found that mercury ions coordinate reversibly to the sulfur atom of the dyes' NCS groups. This interaction induces a color change in the dyes at submicromolar concentrations of mercury. Furthermore, the color change of these dyes is selective for mercury(II) when compared with other ions such as lead(II), cadmium(II), zinc(II), or iron(II). The detection limit for mercury(II) ions--using UV-vis spectroscopy--in homogeneous aqueous solutions is estimated to be approximately 20 ppb for N719 and approximately 150 ppb for N749. Moreover, the sensor molecules can be adsorbed onto high-surface-area mesoporous metal oxide films, allowing reversible heterogeneous sensing of mercury ions in aqueous solution. The results shown herein have important implications in the development of new reversible colorimetric sensors for the fast, easy, and selective detection and monitoring of mercuric ions in aqueous solutions. PMID:16131215

  8. 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 μW 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.

  9. A novel development of dithizone as a dual-analyte colorimetric chemosensor: detection and determination of cyanide and cobalt (II) ions in dimethyl sulfoxide/water media with biological applications.

    PubMed

    Tavallali, Hossein; Deilamy-Rad, Gohar; Parhami, Abolfath; Mousavi, Seyede Zahra

    2013-08-01

    The behavior of dithizone (DTZ), an easily available dye has been studied for the first time in chromogenic sensing of CN(-) as an anionic species and for Co(2+) as a cationic species in DMSO/H2O media. So employing DTZ an efficient colorimetric chemosensor was afforded with a chromogenic selectivity for Co(2+) over other cations with detection limit of 0.04 μmol L(-1). The complex of Co(2+) with DTZ also displayed ability to detect up to 0.43 μmol L(-1) CN(-) (K(+) salts) among other competing anions through a fast response time of less than 30s which is much lower than most recently reported chromogenic probes. The linear dynamic ranges for the determination of Co(2+) and CN(-) were 0.3-4.4 and 3.3-58.6 μmol L(-1) respectively. This method could have potential application in a variety of cases requiring rapid and accurate analysis of Co(2+) and CN(-) for human serum and water samples. PMID:23811160

  10. 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 0.0001-10 ng mL(-1) with a detection limit of 0.04 pg mL(-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

  11. 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

  12. 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

  13. 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

  14. Paper-based colorimetric immunosensor for visual detection of carcinoembryonic antigen based on the high peroxidase-like catalytic performance of ZnFe2O4-multiwalled carbon nanotubes.

    PubMed

    Liu, Weiyan; Yang, Hongmei; Ding, Yanan; Ge, Shenguang; Yu, Jinghua; Yan, Mei; Song, Xianrang

    2014-01-01

    A new paper-based colorimetric immunosensor for the detection of carcinoembryonic antigen (CEA) was developed based on the intrinsic peroxidase activity of ZnFe2O4-multiwalled carbon nanotubes (ZnFe2O4@MWNTs). The immunosensor platform was prepared by depositing chitosan and porous gold onto filter paper and entrapping the primary antibodies (Ab1) onto the layers. Secondary antibodies (Ab2) were assembled on the surface of the functionalized ZnFe2O4@MWNTs. The immunosensor response was quantified as a color change resulting from ZnFe2O4@MWNTs catalyzing the oxidation of 3,3',5,5'-tetramethylbenzidine in the presence of H2O2. The catalytic performance of ZnFe2O4@MWNTs was higher than ZnFe2O4 due to the high electrical conductance of MWNTs, moreover, the electron communications between ZnFe2O4@MWNTs and substrates are electrically "wired". Detection was achieved by measuring the color change when the concentrations of CEA were different. The color change can be quantified with the naked eye but a digitalized picture can also be used to provide more sensitive comparison to a calibrated color scheme. This method was simple for CEA detection with a linear range from 0.005 to 30 ng mL(-1) and a detection limit of 2.6 pg mL(-1). Such an equipment-free immunoassay has great potential in resource-limited environments. PMID:24205509

  15. 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

  16. 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

  17. 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

  18. Directional complex-valued coherence attributes for discontinuous edge detection

    NASA Astrophysics Data System (ADS)

    Wang, Shangxu; Yuan, Sanyi; Yan, Binpeng; He, Yanxiao; Sun, Wenju

    2016-06-01

    We propose directional complex-valued coherence attributes through a simple calculation of the cross-correlation between neighboring complex seismic traces normalized by their corresponding envelope within a local time window along a certain spatial direction. For 3D seismic data with varying directional geological edges, the complex-valued coherence attributes along different spatial directions are distinct, and the coherence along a certain direction can highlight discontinuities at (or near) the perpendicular direction. These separate directional coherence attributes can assist in interpreting the dominant direction(s) of fault development, which is vital in determining sweet spots and locating hydrocarbon wells, and can facilitate the detection of weak or hidden geological edges. In addition, we obtain the minimum complex-valued coherence attribute by comparing all directional coherence volumes to describe the entire lineament and spatial extension direction of geological abnormalities (e.g., channels). In essence, the minimum coherence attribute can be regarded as the result of implementing multi-trace complex-valued coherence calculation along the direction perpendicular to the structural trend. An example of 3D synthetic data with a fault system and channel complex is employed to demonstrate the effectiveness of the directional and minimum complex-valued coherence attributes. The application on a real 3D seismic data of tight sandstone reservoir with faults, flexures and fractures, illustrates that the directional and minimum complex-valued coherence attributes can highlight subtle structures and the directional details of geological abnormalities, which are favorably consistent with the manually interpreted results.

  19. Ring-like features in directional dark matter detection

    SciTech Connect

    Bozorgnia, Nassim; Gelmini, Graciela B.; Gondolo, Paolo E-mail: gelmini@physics.ucla.edu

    2012-06-01

    We discuss a novel dark matter signature relevant for directional detection of Weakly Interacting Massive Particles (WIMPs). For heavy enough WIMPs and low enough recoil energies, the maximum of the recoil rate is not in the direction of the average WIMP arrival direction but in a ring around it at an angular radius that increases with the WIMP mass and can approach 90° at very low energies. The ring is easier to detect for smaller WIMP velocity dispersion and larger average WIMP velocities relative to the detector. In principle the ring could be used as an additional indication of the WIMP mass range.

  20. 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.

  1. 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

  2. Predictions of hydrodynamic simulations for direct dark matter detection

    NASA Astrophysics Data System (ADS)

    Bozorgnia, Nassim; Calore, Francesca; Schaller, Matthieu; Lovell, Mark; Bertone, Gianfranco; Frenk, Carlos S.; Crain, Robert A.; Navarro, Julio F.; Schaye, Joop; Theuns, Tom

    2016-05-01

    We study the effects of galaxy formation on dark matter direct detection using hydrodynamic simulations obtained from the “Evolution and Assembly of GaLaxies and their Environments” (EAGLE) and APOSTLE projects. We extract the local dark matter density and velocity distribution of the simulated Milky Way analogues, and use them directly to perform an analysis of current direct detection data. The local dark matter density of the Milky Way-like galaxies is 0.41–0.73 GeV/cm3, and a Maxwellian distribution (with best fit peak speed of 223–289 km/s) describes well the local dark matter speed distribution. We find that the consistency between the result of different direct detection experiments cannot be improved by using the dark matter distribution of the simulated haloes.

  3. 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.

  4. 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 35 nm can reliably detect melamine down to a concentration of 0.04 mg l(-1). PMID:26654965

  5. 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.

  6. 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.

  7. 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

  8. A novel highly selective colorimetric sensor for aluminum (III) ion using Schiff base derivative.

    PubMed

    Wang, Dong-Fang; Ke, Ying-Chang; Guo, Hong-Xu; Chen, Jianhua; Weng, Wen

    2014-03-25

    A novel colorimetric sensor, 2-hydroxy naphthaldehyde isonicotinoyl hydrazone (HINH), was easily synthesized by the condensation of isoniazid and 2-hydroxy-1-naphthaldehyde. The as-prepared compound showed effective colorimetric single selectivity and high sensitivity for aluminum cation in CH3CN/H2O (1:3) binary solutions. The detection limit is 1.0×10(-8) M Al(3+) based on UV-vis changes. PMID:24316541

  9. 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?

  10. 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.

  11. 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.

  12. Monolayer g-C3N4 Fluorescent Sensor for Sensitive and Selective Colorimetric Detection of Silver ion from Aqueous Samples.

    PubMed

    Cao, Yujuan; Wu, Wei; Wang, Song; Peng, Hong; Hu, Xiaogang; Yu, Ying

    2016-03-01

    Rapid and sensitive detection of heavy-metal ions in natural water environments worldwide is urgently needed because of their severe threats to human health. In the present work, monolayer graphite-like flake C3N4 (g-C3N4) materials were applied as a new fluorescent sensor for the detection of trace silver ion in aqueous solution. The thickness of synthesized g-C3N4 was 0.45 nm and obtained by exfoliating twice with ultrasonic. With the presence of ethylene diamine tetraacetic acid as a screening agent, the highly sensitive sensor reached a low detection limit of 52.3 nmol/L for silver (I) ion and there was no disturbance when silver (I) ion coexisted with other metal ions in water samples. Under the optimal conditions, the monolayer g-C3N4 was successfully used to detect trace silver (I) ion in different environmental water and drinking water samples. PMID:26753758

  13. Maximum patch method for directional dark matter detection

    SciTech Connect

    Henderson, Shawn; Monroe, Jocelyn; Fisher, Peter

    2008-07-01

    Present and planned dark matter detection experiments search for WIMP-induced nuclear recoils in poorly known background conditions. In this environment, the maximum gap statistical method provides a way of setting more sensitive cross section upper limits by incorporating known signal information. We give a recipe for the numerical calculation of upper limits for planned directional dark matter detection experiments, that will measure both recoil energy and angle, based on the gaps between events in two-dimensional phase space.

  14. Direct Detection of Biotinylated Proteins by Mass Spectrometry

    PubMed Central

    2015-01-01

    Mass spectrometric strategies to identify protein subpopulations involved in specific biological functions rely on covalently tagging biotin to proteins using various chemical modification methods. The biotin tag is primarily used for enrichment of the targeted subpopulation for subsequent mass spectrometry (MS) analysis. A limitation of these strategies is that MS analysis does not easily discriminate unlabeled contaminants from the labeled protein subpopulation under study. To solve this problem, we developed a flexible method that only relies on direct MS detection of biotin-tagged proteins called “Direct Detection of Biotin-containing Tags” (DiDBiT). Compared with conventional targeted proteomic strategies, DiDBiT improves direct detection of biotinylated proteins ∼200 fold. We show that DiDBiT is applicable to several protein labeling protocols in cell culture and in vivo using cell permeable NHS-biotin and incorporation of the noncanonical amino acid, azidohomoalanine (AHA), into newly synthesized proteins, followed by click chemistry tagging with biotin. We demonstrate that DiDBiT improves the direct detection of biotin-tagged newly synthesized peptides more than 20-fold compared to conventional methods. With the increased sensitivity afforded by DiDBiT, we demonstrate the MS detection of newly synthesized proteins labeled in vivo in the rodent nervous system with unprecedented temporal resolution as short as 3 h. PMID:25117199

  15. 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

  16. Directed dynamical influence is more detectable with noise.

    PubMed

    Jiang, Jun-Jie; Huang, Zi-Gang; Huang, Liang; Liu, Huan; Lai, Ying-Cheng

    2016-01-01

    Successful identification of directed dynamical influence in complex systems is relevant to significant problems of current interest. Traditional methods based on Granger causality and transfer entropy have issues such as difficulty with nonlinearity and large data requirement. Recently a framework based on nonlinear dynamical analysis was proposed to overcome these difficulties. We find, surprisingly, that noise can counterintuitively enhance the detectability of directed dynamical influence. In fact, intentionally injecting a proper amount of asymmetric noise into the available time series has the unexpected benefit of dramatically increasing confidence in ascertaining the directed dynamical influence in the underlying system. This result is established based on both real data and model time series from nonlinear ecosystems. We develop a physical understanding of the beneficial role of noise in enhancing detection of directed dynamical influence. PMID:27066763

  17. Directed dynamical influence is more detectable with noise

    PubMed Central

    Jiang, Jun-Jie; Huang, Zi-Gang; Huang, Liang; Liu, Huan; Lai, Ying-Cheng

    2016-01-01

    Successful identification of directed dynamical influence in complex systems is relevant to significant problems of current interest. Traditional methods based on Granger causality and transfer entropy have issues such as difficulty with nonlinearity and large data requirement. Recently a framework based on nonlinear dynamical analysis was proposed to overcome these difficulties. We find, surprisingly, that noise can counterintuitively enhance the detectability of directed dynamical influence. In fact, intentionally injecting a proper amount of asymmetric noise into the available time series has the unexpected benefit of dramatically increasing confidence in ascertaining the directed dynamical influence in the underlying system. This result is established based on both real data and model time series from nonlinear ecosystems. We develop a physical understanding of the beneficial role of noise in enhancing detection of directed dynamical influence. PMID:27066763

  18. Directed dynamical influence is more detectable with noise

    NASA Astrophysics Data System (ADS)

    Jiang, Jun-Jie; Huang, Zi-Gang; Huang, Liang; Liu, Huan; Lai, Ying-Cheng

    2016-04-01

    Successful identification of directed dynamical influence in complex systems is relevant to significant problems of current interest. Traditional methods based on Granger causality and transfer entropy have issues such as difficulty with nonlinearity and large data requirement. Recently a framework based on nonlinear dynamical analysis was proposed to overcome these difficulties. We find, surprisingly, that noise can counterintuitively enhance the detectability of directed dynamical influence. In fact, intentionally injecting a proper amount of asymmetric noise into the available time series has the unexpected benefit of dramatically increasing confidence in ascertaining the directed dynamical influence in the underlying system. This result is established based on both real data and model time series from nonlinear ecosystems. We develop a physical understanding of the beneficial role of noise in enhancing detection of directed dynamical influence.

  19. 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

  20. Colorimetric and ratiometric fluorescent detection of sulfite in water via cationic surfactant-promoted addition of sulfite to α,β-unsaturated ketone.

    PubMed

    Tian, Haiyu; Qian, Junhong; Sun, Qian; Bai, Hongyan; Zhang, Weibing

    2013-07-25

    Three fluorescent probes were constructed by incorporating an α,β-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 μM, and the detection limit was 0.2 μM. 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

  1. 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 3.7 µM. Coupled with glucose oxidase, the Cu-SBA-15 was successfully used for the determination of glucose with the linear range of 2-80 mM and a detection limit of 5.4 µM. 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

  2. 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

  3. A selective colorimetric and ratiometric fluorescent probe for hydrogen sulfide.

    PubMed

    Wu, Ming-Yu; Li, Kun; Hou, Ji-Ting; Huang, Zheng; Yu, Xiao-Qi

    2012-10-01

    A reaction-based colorimetric and ratiometric fluorescent probe based on an ICT-strategy for selective detection of H(2)S that exploited the H(2)S-mediated reduction of nitrocompound to amines was explored. And it displayed high selectivity for H(2)S over other relevant reactive sulfur, oxygen, nitrogen species and other anions with more than 120 nm blue shift and the change of emission intensity ratio inducted by H(2)S was over 4750. PMID:22965805

  4. 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, José M

    2015-04-21

    The platinum(ii) half-lantern dinuclear complexes [{Pt(bzq)(μ-C7H4NS2-κN,S)}2] () and [{Pt(bzq)(μ-C7H4NOS-κN,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

  5. Colorimetric Solid-Phase Extractor

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The heart of a colorimetric solid phase extractor (CSPE) test kit quickly measures the concentration of the biocides silver or iodine in astronauts' drinking water to determine whether concentrations are safe. When 10 milliliters (ml) of water is drawn through the disk, the disk will turn color (yellow in this picture for iodine) indicating the presence of the biocides. The device could someday be used to test water safety at reservoirs and water treatment plants on Earth. (photo credit: Microanalytical Instrumentation Center, Iowa State University).

  6. Portable paper-based device for quantitative colorimetric assays relying on light reflectance principle.

    PubMed

    Li, Bowei; Fu, Longwen; Zhang, Wei; Feng, Weiwei; Chen, Lingxin

    2014-04-01

    This paper presents a novel paper-based analytical device based on the colorimetric paper assays through its light reflectance. The device is portable, low cost (<20 dollars), and lightweight (only 176 g) that is available to assess the cost-effectiveness and appropriateness of the original health care or on-site detection information. Based on the light reflectance principle, the signal can be obtained directly, stably and user-friendly in our device. We demonstrated the utility and broad applicability of this technique with measurements of different biological and pollution target samples (BSA, glucose, Fe, and nitrite). Moreover, the real samples of Fe (II) and nitrite in the local tap water were successfully analyzed, and compared with the standard UV absorption method, the quantitative results showed good performance, reproducibility, and reliability. This device could provide quantitative information very conveniently and show great potential to broad fields of resource-limited analysis, medical diagnostics, and on-site environmental detection. PMID:24375226

  7. Colorimetric recognition of the coralyne-poly(dA) interaction using unmodified gold nanoparticle probes, and further detection of coralyne based upon this recognition system.

    PubMed

    Lv, Zhaozi; Wei, Hui; Li, Bingling; Wang, Erkang

    2009-08-01

    Among the functional nucleic acids studied, adenine-rich nucleic acids have attracted attention due to their critical roles in many biological processes and self-assembly-based nanomaterials, especially deoxyribonucleic acids (abbreviated as poly(dA)). Therefore the ligands binding to poly(dA) might serve as potential therapeutic agents. Coralyne, a kind of planar alkaloid, has been firstly found that it could bind strongly to poly(dA). This work herein reports an approach for visual sensing of the coralyne-poly(dA) interaction. This method was based on the coralyne inducing poly(dA) into the homo-adenine DNA duplex and the difference in electrostatic affinity between single-stranded DNA and double-stranded DNA with gold nanoparticles (GNPs). Furthermore, we applied the recognition process of the interaction between coralyne and poly(dA) into specific coralyne detection with the assistance of certain software (such as Photoshop). A linear response from 0 to 728 nM was obtained for coralyne, and a detection limit of 91 nM was achieved. PMID:20448933

  8. 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.

  9. 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.

  10. 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.

  11. Generalized halo independent comparison of direct dark matter detection data

    SciTech Connect

    Nobile, Eugenio Del; Gelmini, Graciela; Huh, Ji-Haeng; Gondolo, Paolo E-mail: gelmini@physics.ucla.edu E-mail: jhhuh@physics.ucla.edu

    2013-10-01

    We extend the halo-independent method to compare direct dark matter detection data, so far used only for spin-independent WIMP-nucleon interactions, to any type of interaction. As an example we apply the method to magnetic moment interactions.

  12. Halo-Independent Comparison of Direct Dark Matter Detection Data

    DOE PAGESBeta

    Del Nobile, Eugenio

    2014-01-01

    We review the halo-independent formalism that allows comparing data from different direct dark matter detection experiments without making assumptions on the properties of the dark matter halo. We apply this method to spin-independent WIMP-nuclei interactions, for both isospin-conserving and isospin-violating couplings, and to WIMPs interacting through an anomalous magnetic moment.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. A novel colorimetric and turn-on fluorescent chemosensor for iron(III) ion detection and its application to cellular imaging.

    PubMed

    Luo, Aoheng; Wang, Hongqing; Wang, Yuyuan; Huang, Qiao; Zhang, Qin

    2016-11-01

    A novel rhodamine-based dual probe Rh-2 for trivalent ferric ions (Fe(3+)) was successfully designed and synthesized, which exhibited a highly sensitive and selective recognition towards Fe(3+) with an enhanced fluorescence emission in methanol-water media (v/v=7/3, pH=7.2). The probe Rh-2 could be applied to the determination of Fe(3+) with a linear range covering from 3.0×10(-7) to 1.4×10(-5)M and a detection limit of 1.24×10(-8)M. Meanwhile, the binding ratio of Rh-2 and Fe(3+) was found to be 1:1. Most importantly, the fluorescence and color signal changes of the Rh-2 solution were specific to Fe(3+) over other commonly coexistent metal ions. Moreover, the probe Rh-2 has been used to image Fe(3+) in living cells with satisfying results. PMID:27267282

  18. 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

  19. 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.

  20. 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.

  1. Direct Fast-Neutron Detection: A Progress Report

    SciTech Connect

    AJ Peurrung; DC Stromswold; PL Reeder; RR Hansen

    1998-10-18

    It is widely acknowledged that Mure neutron-detection technologies will need to offer increased performance at lower cost. One clear route toward these goals is rapid and direct detection of fast neutrons prior to moderation. This report describes progress to date in an effort to achieve such neutron detection via proton recoil within plastic scintillator. Since recording proton-recoil events is of little practical use without a means to discriminate effectively against gamma-ray interactions, the present effort is concentrated on demonstrating a method that distinguishes between pulse types. The proposed method exploits the substantial difference in the speed of fission neutrons and gamma-ray photons. Should this effort ultimately prove successful, the resulting. technology would make a valuable contribution toward meeting the neutron-detection needs of the next century. This report describes the detailed investigations that have been part of Pacific Northwest National Laborato@s efforts to demonstrate direct fast-neutron detection in the laboratory. Our initial approach used a single, solid piece of scintillator along with the electronics needed for pulse-type differentiation. Work to date has led to the conclusion that faster scintillator and/or faster electronics will be necessary before satisfactory gamma-ray discrimination is achieved with this approach. Acquisition and testing of both faster scintillator and faster electronics are currently in progress. The "advanced" approach to direct fast-neutron detection uses a scintillating assembly with an overall density that is lower than that of ordinary plastic scintillator. The lower average density leads to longer interaction times for both neutrons and gamma rays, allowing easier discrimination. The modeling, optimization, and design of detection systems using this approach are described in detail.

  2. A Simple Paper-Based Colorimetric Device for Rapid Mercury(II) Assay.

    PubMed

    Chen, Weiwei; Fang, Xueen; Li, Hua; Cao, Hongmei; Kong, Jilie

    2016-01-01

    Contamination of the environment by mercury(II) ions (Hg(2+)) poses a serious threat to human health and ecosystems. Up to now, many reported Hg(2+) sensors require complex procedures, long measurement times and sophisticated instrumentation. We have developed a simple, rapid, low cost and naked-eye quantitative method for Hg(2+) environmental analysis using a paper-based colorimetric device (PCD). The sample solution to which platinum nanoparticles (PtNPs) have been added is dispensed to the detection zone on the PCD, where the 3,3,5,5-tetramethylbenzidine (TMB) substrate has been pre-loaded. The PtNPs effect a rapid oxidization of TMB, inducing blue colorization on the PCD. However, Hg(2+) in the solution rapidly interact with the PtNPs, suppressing the oxidation capacity and hence causing a decrease in blue intensity, which can be observed directly by the naked eye. Moreover, Hg(2+) at concentrations as low as 0.01 uM, can be successfully monitored using a fiber optic device, which gives a digital readout proportional to the intensity of the blue color change. This paper-based colorimetric device (PCD) shows great potential for field measurement of Hg(2+). PMID:27554633

  3. A Simple Paper-Based Colorimetric Device for Rapid Mercury(II) Assay

    PubMed Central

    Chen, Weiwei; Fang, Xueen; Li, Hua; Cao, Hongmei; Kong, Jilie

    2016-01-01

    Contamination of the environment by mercury(II) ions (Hg2+) poses a serious threat to human health and ecosystems. Up to now, many reported Hg2+ sensors require complex procedures, long measurement times and sophisticated instrumentation. We have developed a simple, rapid, low cost and naked-eye quantitative method for Hg2+ environmental analysis using a paper-based colorimetric device (PCD). The sample solution to which platinum nanoparticles (PtNPs) have been added is dispensed to the detection zone on the PCD, where the 3,3,5,5-tetramethylbenzidine (TMB) substrate has been pre-loaded. The PtNPs effect a rapid oxidization of TMB, inducing blue colorization on the PCD. However, Hg2+ in the solution rapidly interact with the PtNPs, suppressing the oxidation capacity and hence causing a decrease in blue intensity, which can be observed directly by the naked eye. Moreover, Hg2+ at concentrations as low as 0.01 uM, can be successfully monitored using a fiber optic device, which gives a digital readout proportional to the intensity of the blue color change. This paper-based colorimetric device (PCD) shows great potential for field measurement of Hg2+. PMID:27554633

  4. Directional Detection of Fast Neutrons Using a Time Projection Chamber

    SciTech Connect

    Bowden, N; Heffner, M; Carosi, G; Carter, D; Foxe, M; Jovanovic, I

    2009-06-03

    Spontaneous fission in Special Nuclear Material (SNM) such as plutonium and highly enriched uranium (HEU) results in the emission of neutrons with energies in the MeV range (hereafter 'fast neutrons'). These fast neutrons are largely unaffected by the few centimeters of intervening high-Z material that would suffice for attenuating most emitted gamma rays, while tens of centimeters of hydrogenous materials are required to achieve substantial attenuation of neutron fluxes from SNM. Neutron detectors are therefore an important complement to gamma-ray detectors in SNM search and monitoring applications. The rate at which SNM emits fast neutrons varies from about 2 per kilogram per second for typical HEU to some 60,000 per kilogram per second for metallic weapons grade plutonium. These rates can be compared with typical sea-level (cosmogenic) neutron backgrounds of roughly 5 per second per square meter per steradian in the relevant energy range [1]. The fact that the backgrounds are largely isotropic makes directional neutron detection especially attractive for SNM detection. The ability to detect, localize, and ultimately identify fast neutron sources at standoff will ultimately be limited by this background rate. Fast neutrons are particularly well suited to standoff detection and localization of SNM or other fast neutrons sources. Fast neutrons have attenuation lengths of about 60 meters in air, and retain considerable information about their source direction even after one or two scatters. Knowledge of the incoming direction of a fast neutron, from SNM or otherwise, has the potential to significantly improve signal to background in a variety of applications, since the background arriving from any one direction is a small fraction of the total background. Imaging or directional information therefore allows for source detection at a larger standoff distance or with shorter dwell times compared to nondirectional detectors, provided high detection efficiency can be

  5. Dual channel sensor for detection and discrimination of heavy metal ions based on colorimetric and fluorescence response of the AuNPs-DNA conjugates.

    PubMed

    Tan, Lulu; Chen, Zhengbo; Zhao, Yan; Wei, Xiangcong; Li, Yonghui; Zhang, Chi; Wei, Xinling; Hu, Xiaochen

    2016-11-15

    We have presented an extensible, facile and sensitive multidimensional sensor based on DNA-gold nanoparticle (DNA-AuNP) conjugates for heavy metal ions (Ag(+), Hg(2+), Cr(3+), Sn(4+), Cd(2+), Cu(2+), Pb(2+), Zn(2+), and Mn(2+)) discrimination. In the presence of metal ions, the excluded effect of DNA and AuNPs with the same negative charges is disrupted, and the amount of FAM-labeled DNA adsorbed on AuNP surfaces increases, resulting in a more obvious fluorescence quenching effect. With the addition of NH2OH and HAuCl4, AuNPs grow into morphologically varied nanostructures (spherical to branched) depending on the resulting aptamer coverage, which gives rise to different colored solutions (reddish blush, purple and blue) observed by naked eyes. By simply changing the DNA sequences, three sensing elements can be easily obtained and added into this dual-channel multidimensional sensor. 9 heavy metal ions are distinguished by linear discriminant analysis (LDA) and primary component analysis (PCA). A highly sensitive discrimination of metal ion targets with the detection limit as low as 50nM with 100% identification accuracy is obtained. Remarkably, Cu(2+) and Hg(2+) ions with similar catalytic performance at various concentrations (300nM, 400nM, 500nM, respectively) and the mixture of the two metal ions with different volume ratios (total metal ion concentration: 500nM) can be successfully discriminated. In addition, nine heavy metal ions are also well-distinguished in river samples, and the accuracy of discrimination of these metal ions samples reaches 100%. Therefore, it will broaden the application field of DNA-AuNP conjugates-based multidimensional sensors. PMID:27208473

  6. Detecting groundwater flow direction from infrared thermal images

    NASA Astrophysics Data System (ADS)

    Ahmad, Akhundzadah Noor; Saito, Hirotaka; Asada, Kei; Kato, Makoto

    In this study we propose an approach to directly measure temperature changes around the heat source placed in a borehole using an infrared camera for determining groundwater flow direction. A plastic box filled with sands with a cylindrical perforated column placed in middle of the box was used in lab experiments. A heater was inserted in the center of the borehole. To detect the flow direction from the temperature distribution, an infrared camera that was placed face-down at the top of the cylinder (i.e., borehole) was used. COMSOL was used to numerically simulate coupled water flow and heat transfer to evaluate experimental results. Results show that when the flux is in the order of 10-2 to 10-4cm s-1, we can determine the groundwater flow direction because of a skewed temperature distribution due to convective transport of heat.

  7. 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.

  8. 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?

  9. 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

  10. Dark matter effective field theory scattering in direct detection experiments

    DOE PAGESBeta

    Schneck, K.; Cabrera, B.; Cerdeño, D. G.; Mandic, V.; Rogers, H. E.; Agnese, R.; Anderson, A. J.; Asai, M.; Balakishiyeva, D.; Barker, D.; et al

    2015-05-18

    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. Here. 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. In conclusion, we discussmore » the implications of the EFT for the next-generation (G2) direct detection experiments and point out regions of complementarity in the EFT parameter space.« less

  11. Dark matter effective field theory scattering in direct detection experiments

    DOE PAGESBeta

    Schneck, K.

    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 implicationsmore » of the EFT for the next-generation (G2) direct detection experiments and point out regions of complementarity in the EFT parameter space.« less

  12. (In)Direct detection of boosted dark matter

    NASA Astrophysics Data System (ADS)

    Agashe, Kaustubh; Cui, Yanou; Necib, Lina; Thaler, Jesse

    2016-05-01

    We present a new multi-component dark matter model with a novel experimental signature that mimics neutral current interactions at neutrino detectors. In our model, the dark matter is composed of two particles, a heavier dominant component that annihilates to produce a boosted lighter component that we refer to as boosted dark matter. The lighter component is relativistic and scatters off electrons in neutrino experiments to produce Cherenkov light. This model combines the indirect detection of the dominant component with the direct detection of the boosted dark matter. Directionality can be used to distinguish the dark matter signal from the atmospheric neutrino background. We discuss the viable region of parameter space in current and future experiments.

  13. 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.

  14. Dark matter effective field theory scattering in direct detection experiments

    SciTech Connect

    Schneck, K.

    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.

  15. Dark matter effective field theory scattering in direct detection experiments

    SciTech Connect

    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.

    2015-05-18

    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. Here. 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. In conclusion, we 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.

  16. Directional detection of dark matter in universal bound states

    SciTech Connect

    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 in Ref. [1] 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). Ref. [2] 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. Directional detection of dark matter in universal bound states

    SciTech Connect

    Laha, Ranjan

    2015-10-06

    It has been suggested that several small-scale structure anomalies in Λ CDM cosmology can be solved by strong self-interaction between dark matter particles. It was shown in Ref. [1] 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). Ref. [2] 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. Furthermore, 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.

  18. Direct detection of martian microorganisms based on fluorescence microscopy

    NASA Astrophysics Data System (ADS)

    Kawasaki, Y.

    1999-01-01

    The direct detection of microorganisms and their traces using optical microscopes is one of the most promising techniques to obtain the decisive evidences for extraterrestrial life. The most significant points of this technique are high sensitivity and spatial information with a resolution of 0.2mm. Besides, information on local environments and microscopic ecology can also be obtained. Many difficulties, however, must be solved to get reliable results. We have started to develop a noble technique based on the fluorescence microscopy with special interest to the detection of microorganisms in extreme environments including Mars. The principle is to detect molecules/subcellular organs which are responsible for the three basic characteristics of life; genetic information, metabolism, and discrimination of self from non-self. We have screened fluorescence probes and found several are applicable. We could detect almost all the microorganisms already identified. Discrimination of viable from dead cells was possible. The terrestrial microfossils, some of the artificial primitive microorganism-like-objects, dried bacteria and polycyclic aromatic hydrocarbons mixed with simulated Martian sand could be detected. We are now designing a compact detection hardware.

  19. 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.

  20. 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 χ⁰} 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 χ₀} 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.

  1. 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.

  2. Physics from solar neutrinos in dark matter direct detection experiments

    NASA Astrophysics Data System (ADS)

    Cerdeño, David G.; Fairbairn, Malcolm; Jubb, Thomas; Machado, Pedro A. N.; Vincent, Aaron C.; Bœhm, Céline

    2016-05-01

    The next generation of dark matter direct detection experiments will be sensitive to both coherent neutrino-nucleus and neutrino-electron scattering. This will enable them to explore aspects of solar physics, perform the lowest energy measurement of the weak angle sin2 θ W to date, and probe contributions from new theories with light mediators. In this article, we compute the projected nuclear and electron recoil rates expected in several dark matter direct detection experiments due to solar neutrinos, and use these estimates to quantify errors on future measurements of the neutrino fluxes, weak mixing angle and solar observables, as well as to constrain new physics in the neutrino sector. Our analysis shows that the combined rates of solar neutrino events in second generation experiments (SuperCDMS and LZ) can yield a measurement of the pp flux to 2.5% accuracy via electron recoil, and slightly improve the 8B flux determination. Assuming a low-mass argon phase, projected tonne-scale experiments like DARWIN can reduce the uncertainty on both the pp and boron-8 neutrino fluxes to below 1%. Finally, we use current results from LUX, SuperCDMS and CDMSlite to set bounds on new interactions between neutrinos and electrons or nuclei, and show that future direct detection experiments can be used to set complementary constraints on the parameter space associated with light mediators.

  3. New method for analyzing dark matter direct detection data

    NASA Astrophysics Data System (ADS)

    Davis, Jonathan H.; Enßlin, Torsten; BÅ`hm, Céline

    2014-02-01

    The experimental situation of dark matter direct detection has reached an exciting crossroads, with potential hints of a discovery of dark matter (DM) from the CDMS, CoGeNT, CRESST-II and DAMA experiments in tension with null results from xenon-based experiments such as XENON100 and LUX. Given the present controversial experimental status, it is important that the analytical method used to search for DM in direct detection experiments is both robust and flexible enough to deal with data for which the distinction between signal and background points is difficult, and hence where the choice between setting a limit or defining a discovery region is debatable. In this article we propose a novel (Bayesian) analytical method, which can be applied to all direct detection experiments and which extracts the maximum amount of information from the data. We apply our method to the XENON100 experiment data as a worked example, and show that firstly our exclusion limit at 90% confidence is in agreement with their own for the 225 live days data, but is several times stronger for the 100 live days data. Secondly we find that, due to the two points at low values of S1 and S2 in the 225 days data set, our analysis points to either weak consistency with low-mass dark matter or the possible presence of an unknown background. Given the null result from LUX, the latter scenario seems the more plausible.

  4. Dark matter direct detection with non-Maxwellian velocity structure

    SciTech Connect

    Kuhlen, Michael; Weiner, Neal; Diemand, Jürg; Moore, Ben; Potter, Doug; Stadel, Joachim; Madau, Piero; Zemp, Marcel E-mail: neal.weiner@nyu.edu E-mail: pmadau@ucolick.org E-mail: dpotter@physik.uzh.ch E-mail: mzemp@umich.edu

    2010-02-01

    The velocity distribution function of dark matter particles is expected to show significant departures from a Maxwell-Boltzmann distribution. This can have profound effects on the predicted dark matter - nucleon scattering rates in direct detection experiments, especially for dark matter models in which the scattering is sensitive to the high velocity tail of the distribution, such as inelastic dark matter (iDM) or light (few GeV) dark matter (LDM), and for experiments that require high energy recoil events, such as many directionally sensitive experiments. Here we determine the velocity distribution functions from two of the highest resolution numerical simulations of Galactic dark matter structure (Via Lactea II and GHALO), and study the effects for these scenarios. For directional detection, we find that the observed departures from Maxwell-Boltzmann increase the contrast of the signal and change the typical direction of incoming DM particles. For iDM, the expected signals at direct detection experiments are changed dramatically: the annual modulation can be enhanced by more than a factor two, and the relative rates of DAMA compared to CDMS can change by an order of magnitude, while those compared to CRESST can change by a factor of two. The spectrum of the signal can also change dramatically, with many features arising due to substructure. For LDM the spectral effects are smaller, but changes do arise that improve the compatibility with existing experiments. We find that the phase of the modulation can depend upon energy, which would help discriminate against background should it be found.

  5. Spectrally efficient optical transmission based on Stokes vector direct detection.

    PubMed

    Li, An; Che, Di; Chen, Vivian; Shieh, William

    2014-06-30

    We propose a novel detection scheme called Stokes vector direct detection (SV-DD) to realize high electrical spectral efficiency and cost-effective optical communication for short and medium reach. With SV-DD, the signal is modulated in only one polarization and combined with the carrier in the orthogonal polarization for fiber transmission. At reception, the combined signal is detected in Stokes space by three or four photo-detectors. Compared with conventional DD technique, SV-DD is resilient to both chromatic dispersion and signal-to-signal beat noise. Furthermore, SV-DD does not require polarization tracking or narrow band optical filtering for carrier extraction. In this paper, we present for the first time the numerical analysis and experimental demonstration of single-carrier SV-DD. We report 62.5-Gb/s data rate single-carrier SV-DD transmission over 160-km SSMF using 12.5-Gbaud 32-QAM modulation. PMID:24977825

  6. (In)direct detection of boosted dark matter

    NASA Astrophysics Data System (ADS)

    Agashe, Kaustubh; Cui, Yanou; Necib, Lina; Thaler, Jesse

    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 MeV-10 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.

  7. (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 MeV–10 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.

  8. Superconducting Nuclear Recoil Sensor for Directional Dark Matter Detection

    NASA Astrophysics Data System (ADS)

    Junghans, Ann; Baldwin, Kevin; Hehlen, Markus; Lafler, Randy; Loomba, Dinesh; Phan, Nguyen; Weisse-Bernstein, Nina

    The Universe consists of 72% dark energy, 23% dark matter and only 5% of ordinary matter. One of the greatest challenges of the scientific community is to understand the nature of dark matter. Current models suggest that dark matter is made up of slowly moving, weakly interacting massive particles (WIMPs). But detecting WIMPs is challenging, as their expected signals are small and rare compared to the large background that can mimic the signal. The largest and most robust unique signature that sets them apart from other particles is the day-night variation of the directionality of dark matter on Earth. This modulation could be observed with a direction-sensitive detector and hence, would provide an unambiguous signature for the galactic origin of WIMPs. There are many studies underway to attempt to detect WIMPs both directly and indirectly, but solid-state WIMP detectors are widely unexplored although they would present many advantages to prevalent detectors that use large volumes of low pressure gas. We present first results of a novel multi-layered architecture, in which WIMPs would interact primarily with solid layers to produce nuclear recoils that then induce measureable voltage pulses in adjacent superconductor layers. This work was supported by the U.S. Department of Energy through the LANL Laboratory Directed Research and Development Program.

  9. 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.

  10. 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

  11. Discrimination of Dental Caries Using Colorimetric Characteristics of Fluorescence Spectrum.

    PubMed

    Chen, Qingguang; Zhu, Haihua; Xu, Ying; Lin, Bin; Chen, Hui

    2015-01-01

    The feasibility of colorimetric parameters for the discrimination of the stages of dental caries based on a light-induced autofluorescence spectrum at a 405-nm excitation wavelength was investigated. The fluorescence spectra of 4 groups of tooth samples (10 sound, 10 early-stage decay, 14 established decay, and 10 severe decay), which were classified by the International Caries Detection and Assessment System, were experimentally measured in vitro. The carious lesion samples had an additional fluorescence peak at around 627 nm. The mathematical relation of the fluorescence spectrum and human color perception was established and computed. With increasing severity, the fluorescence color changed from green to yellow according to the colorimetric parameters of the CIE 1931 (x, y) chromaticity coordinates and dominant wavelengths. The results from a one-way ANOVA of the dominant wavelength showed a statistically significant difference among the 4 classified groups. The colorimetric parameters of the light-induced fluorescence spectrum can potentially be applied to evaluate the various carious levels. PMID:26112288

  12. 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.

  13. 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.

  14. 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.

  15. Ultrabroadband direct detection of nonclassical photon statistics at telecom wavelength.

    PubMed

    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

  16. 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

  17. Direct Detection and Sequencing of Damaged DNA Bases

    PubMed Central

    2011-01-01

    Products of various forms of DNA damage have been implicated in a variety of important biological processes, such as aging, neurodegenerative diseases, and cancer. Therefore, there exists great interest to develop methods for interrogating damaged DNA in the context of sequencing. Here, we demonstrate that single-molecule, real-time (SMRT®) DNA sequencing can directly detect damaged DNA bases in the DNA template - as a by-product of the sequencing method - through an analysis of the DNA polymerase kinetics that are altered by the presence of a modified base. We demonstrate the sequencing of several DNA templates containing products of DNA damage, including 8-oxoguanine, 8-oxoadenine, O6-methylguanine, 1-methyladenine, O4-methylthymine, 5-hydroxycytosine, 5-hydroxyuracil, 5-hydroxymethyluracil, or thymine dimers, and show that these base modifications can be readily detected with single-modification resolution and DNA strand specificity. We characterize the distinct kinetic signatures generated by these DNA base modifications. PMID:22185597

  18. Direct Hydrocarbon Detection Using Multi-channel Transient Electromagnetics

    NASA Astrophysics Data System (ADS)

    Hobbs, B. A.; Ziolkowski, A. M.; Wright, D. A.

    We present a transient electromagnetic method for the detection of hydrocarbons and for monitoring their movement within a reservoir. Replacement of brine by gas or oil can cause a change in electrical resistivity of a porous rock of as much as 4 orders of magnitude. Seismic methods on the other hand are generally poor at detecting fluid content because the fluid content of a media has only a slight effect on its acoustic impedance. The data presented in this paper were collected as part of two Multi-channel Transient ElectroMagnetic (MTEM) surveys carried out in 1994 and 1996 over an underground gas storage reservoir at St. Illiers la Ville in France. The reservoir is a 30% porosity sandstone anticline about 30m thick at a depth of around 700m. In the summer gas is pumped in and the gas-water contact falls; in the winter gas is extracted and the gas- water contact rises. The position of the contact is known from constant monitoring at over 40 wells. The surveys had two objectives: first, to attempt to detect the reservoir directly from the data; second, to detect the movement of the gas water contact be- tween the 2 survey times. A recent breakthrough in the understanding of the system has allowed both these objectives to be achieved.

  19. 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

  20. WIMP physics with ensembles of direct-detection experiments

    NASA Astrophysics Data System (ADS)

    Peter, Annika H. G.; Gluscevic, Vera; Green, Anne M.; Kavanagh, Bradley J.; Lee, Samuel K.

    2014-12-01

    The search for weakly-interacting massive particle (WIMP) dark matter is multi-pronged. Ultimately, the WIMP-dark-matter picture will only be confirmed if different classes of experiments see consistent signals and infer the same WIMP properties. In this work, we review the ideas, methods, and status of direct-detection searches. We focus in particular on extracting WIMP physics (WIMP interactions and phase-space distribution) from direct-detection data in the early discovery days when multiple experiments see of order dozens to hundreds of events. To demonstrate the essential complementarity of different direct-detection experiments in this context, we create mock data intended to represent the data from the near-future Generation 2 experiments. We consider both conventional supersymmetry-inspired benchmark points (with spin-independent and -dependent elastic cross sections just below current limits), as well as benchmark points for other classes of models (inelastic and effective-operator paradigms). We also investigate the effect on parameter estimation of loosening or dropping the assumptions about the local WIMP phase-space distribution. We arrive at two main conclusions. Firstly, teasing out WIMP physics with experiments depends critically on having a wide set of detector target materials, spanning a large range of target nuclear masses and spin-dependent sensitivity. It is also highly desirable to obtain data from low-threshold experiments. Secondly, a general reconstruction of the local WIMP velocity distribution, which will only be achieved if there are multiple experiments using different target materials, is critical to obtaining a robust and unbiased estimate of the WIMP mass.

  1. Sensitive colorimetric visualization of perfluorinated compounds using poly(ethylene glycol) and perfluorinated thiols modified gold nanoparticles.

    PubMed

    Niu, Hongyun; Wang, Saihua; Zhou, Zhen; Ma, Yurong; Ma, Xunfeng; Cai, Yaqi

    2014-05-01

    In this work, we have developed a novel sensing strategy employing mixed poly(ethylene glycol)-terminated (PEG-thiols) and perfluoroalkyl-terminated (F-thiols) alkanethiols modified gold nanoparticles (Au@PEG-F NPs) as a probe to detect perfluorinated compounds (PFCs) from water samples. PEG-thiols with high density and long carbon chains make the Au NPs probe well-dispersed in solution and stable even in high concentration of salt solution; F-thiols provide specific fluorous-fluorous interactions to PFCs, which results in adsorption of PFCs on Au@PEG-F NPs. The adsorbed PFCs cause the aggregation of Au@PEG-F NPs probes and thus induce the insolubility of probes and precipitation directly from reaction solution due to the superhydrophobicity of perfluorocarbon monolayers, leading to color and absorbance response of the assay to PFCs. The preparation of the Au@PEG-F NPs probe is very simple, and the colorimetric assay based on this mechanism for the detection of PFCs is selective and convenient. Combined with UV-vis spectrophotometry, the assay demonstrates good sensitivities to PFCs with wide linear range. In the designed concentration range, the response of the colorimetric assay to long-chain PFCs (perfluoroalkyl chain ≥7) is discerned even as the concentration of these PFCs is as low as 10 μg L(-1). This low-cost and sensitive assay shows great potential to measure total PFCs in water samples. To the best of our knowledge, this is the first application of the specific fluorous-fluorous interactions and Au NPs based probes for colorimetric recognition for PFCs. PMID:24684731

  2. 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.

  3. Nanoparticle-catalyzed reductive bleaching for fabricating turn-off and enzyme-free amplified colorimetric bioassays.

    PubMed

    Li, Wei; Qiang, Weibing; Li, Jie; Li, Hui; Dong, Yifan; Zhao, Yaju; Xu, Danke

    2014-01-15

    Nanoparticle-catalyzed reductive bleaching reactions of colored substrates are emerging as a class of novel indicator reactions for fabricating enzyme-free amplified colorimetric biosensing (turn-off mode), which are exactly opposite to the commonly used oxidative coloring processes of colorless substrates in traditional enzyme-catalyzed amplified colorimetric bioassays (turn-on mode). In this work, a simple theoretical analysis shows that the sensitivity of this colorimetric bioassay can be improved by increasing the amplification factor (kcatΔt), or enhancing the binding affinity between analyte and receptor (Kd), or selecting the colored substrates with high extinction coefficients (ε). Based on this novel strategy, we have developed a turn-off and cost-effective amplified colorimetric thrombin aptasensor. This aptasensor made full use of sandwich binding of two affinity aptamers for increased specificity, magnetic particles for easy separation and enrichment, and gold nanoparticle (AuNP)-catalyzed reductive bleaching reaction to generate the amplified colorimetric signal. With 4-nitrophenol (4-NP) as the non-dye colored substrate, colorimetric bioassay of thrombin was achieved by the endpoint method with a detection limit of 91pM. In particular, when using methylene blue (MB) as the substrate, for the first time, a more convenient and efficient kinetic-based colorimetric thrombin bioassay was achieved without the steps of acidification termination and magnetic removal of particles, with a low detection limit of 10pM, which was superior to the majority of the existing colorimetric thrombin aptasensors. The proposed colorimetric protocol is expected to hold great promise in field analysis and point-of-care applications. PMID:23962710

  4. A colorimetric sensor array of porous pigments.

    PubMed

    Lim, Sung H; Kemling, Jonathan W; Feng, Liang; Suslick, Kenneth S

    2009-12-01

    The development of a low-cost, simple colorimetric sensor array capable of the detection and identification of toxic gases is reported. This technology uses a disposable printed array of porous pigments in which metalloporphyrins and chemically-responsive dyes are immobilized in a porous matrix of organically modified siloxanes (ormosils) and printed on a porous membrane. The printing of the ormosil into the membrane is highly uniform and does not lessen the porosity of the membrane, as shown by scanning electron microscopy. When exposed to an analyte, these pigments undergo reactions that result in well-defined color changes due to strong chemical interactions: ligation to metal ions, Lewis or Brønsted acid-base interactions, hydrogen bonding, etc. Striking visual identification of 3 toxic gases has been shown at the IDLH (immediately dangerous to life and health) concentration, at the PEL (permissible exposure level), and at a level well below the PEL. Identification and quantification of analytes were achieved using the color change profiles, which were readily distinguishable in a hierarchical clustering analysis (HCA) dendrogram, with no misclassifications in 50 trials. PMID:19918616

  5. A colorimetric sensor array of porous pigments

    PubMed Central

    Lim, Sung H.; Kemling, Jonathan W.; Feng, Liang

    2010-01-01

    The development of a low-cost, simple colorimetric sensor array capable of detection and identification of toxic gases is reported. This technology uses a disposable printed array of porous pigments in which metalloporphyrins and chemically responsive dyes are immobilized in a porous matrix of organically modified siloxanes (ormosils) and printed on a porous membrane. The printing of the ormosil into the membrane is highly uniform and does not lessen the porosity of the membrane, as shown by scanning electron microscopy. When exposed to an analyte, these pigments undergo reactions that result in well-defined color changes due to strong chemical interactions: ligation to metal ions, Lewis or Bronsted acid-base interactions, hydrogen bonding, etc. Striking visual identification of 3 toxic gases has been shown at the IDLH (immediately dangerous to life and health), at the PEL (permissible exposure level), and at a level well below the PEL. Identification and quantification of analytes were achieved using the color change profiles, which were readily distinguishable in a hierarchical clustering analysis (HCA) dendrogram, with no misclassifications in 50 trials. PMID:19918616

  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. 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.

  8. 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.

  9. Directional detection of dark matter in universal bound states

    DOE PAGESBeta

    Laha, Ranjan

    2015-10-06

    It has been suggested that several small-scale structure anomalies in Λ CDM cosmology can be solved by strong self-interaction between dark matter particles. It was shown in Ref. [1] 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). Ref. [2] studied the nuclear recoil energy spectrum in dark matter direct detection experiments due to this incident bound state. Here we study the angularmore » recoil spectrum, and show that it is uniquely determined up to normalization by the S-wave scattering length. Furthermore, 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.« less

  10. Direct detection of the 229Th nuclear clock transition

    NASA Astrophysics Data System (ADS)

    von der Wense, Lars; Seiferle, Benedict; Laatiaoui, Mustapha; Neumayr, Jürgen B.; Maier, Hans-Jörg; Wirth, Hans-Friedrich; Mokry, Christoph; Runke, Jörg; Eberhardt, Klaus; Düllmann, Christoph E.; Trautmann, Norbert G.; Thirolf, Peter G.

    2016-05-01

    Today’s most precise time and frequency measurements are performed with optical atomic clocks. However, it has been proposed that they could potentially be outperformed by a nuclear clock, which employs a nuclear transition instead of an atomic shell transition. There is only one known nuclear state that could serve as a nuclear clock using currently available technology, namely, the isomeric first excited state of 229Th (denoted 229mTh). Here we report the direct detection of this nuclear state, which is further confirmation of the existence of the isomer and lays the foundation for precise studies of its decay parameters. On the basis of this direct detection, the isomeric energy is constrained to between 6.3 and 18.3 electronvolts, and the half-life is found to be longer than 60 seconds for 229mTh2+. More precise determinations appear to be within reach, and would pave the way to the development of a nuclear frequency standard.

  11. Direct detection of the (229)Th nuclear clock transition.

    PubMed

    von der Wense, Lars; Seiferle, Benedict; Laatiaoui, Mustapha; Neumayr, Jürgen B; Maier, Hans-Jörg; Wirth, Hans-Friedrich; Mokry, Christoph; Runke, Jörg; Eberhardt, Klaus; Düllmann, Christoph E; Trautmann, Norbert G; Thirolf, Peter G

    2016-05-01

    Today's most precise time and frequency measurements are performed with optical atomic clocks. However, it has been proposed that they could potentially be outperformed by a nuclear clock, which employs a nuclear transition instead of an atomic shell transition. There is only one known nuclear state that could serve as a nuclear clock using currently available technology, namely, the isomeric first excited state of (229)Th (denoted (229m)Th). Here we report the direct detection of this nuclear state, which is further confirmation of the existence of the isomer and lays the foundation for precise studies of its decay parameters. On the basis of this direct detection, the isomeric energy is constrained to between 6.3 and 18.3 electronvolts, and the half-life is found to be longer than 60 seconds for (229m)Th(2+). More precise determinations appear to be within reach, and would pave the way to the development of a nuclear frequency standard. PMID:27147026

  12. Recent results in dark matter direct detection experiments

    NASA Astrophysics Data System (ADS)

    Kelso, Christopher Michael

    Three dark matter direct detection experiments (DAMA/LIBRA, CoGeNT, and CRESST-II) have each reported signals which resemble that predicted for a dark matter particle with a mass of roughly 10 GeV. We review the theoretical background for direct detection experiments as well as these particular detectors and their reported signals over the last few years. We also compare the signals of these experiments and discuss whether they can be explained by a single species of dark matter particle, without conflicting with the constraints of other experiments. We show that the spectrum of events reported by CoGeNT and CRESST-II are consistent with each other and with the constraints from CDMS-II, although some tension with xenon- based experiments remains. Similarly, the modulation signals reported by DAMA/LIBRA and CoGeNT appear to be compatible, although the corresponding amplitude of the observed modulations are a factor of at least a few higher than would be naively expected, based on the event spectra reported by CoGeNT and CRESST-II. We also discuss some ways that this apparent discrepancy could potentially be resolved.

  13. Corner detection and classification using anisotropic directional derivative representations.

    PubMed

    Shui, Peng-Lang; Zhang, Wei-Chuan

    2013-08-01

    This paper proposes a corner detector and classifier using anisotropic directional derivative (ANDD) representations. The ANDD representation at a pixel is a function of the oriented angle and characterizes the local directional grayscale variation around the pixel. The proposed corner detector fuses the ideas of the contour- and intensity-based detection. It consists of three cascaded blocks. First, the edge map of an image is obtained by the Canny detector and from which contours are extracted and patched. Next, the ANDD representation at each pixel on contours is calculated and normalized by its maximal magnitude. The area surrounded by the normalized ANDD representation forms a new corner measure. Finally, the nonmaximum suppression and thresholding are operated on each contour to find corners in terms of the corner measure. Moreover, a corner classifier based on the peak number of the ANDD representation is given. Experiments are made to evaluate the proposed detector and classifier. The proposed detector is competitive with the two recent state-of-the-art corner detectors, the He & Yung detector and CPDA detector, in detection capability and attains higher repeatability under affine transforms. The proposed classifier can discriminate effectively simple corners, Y-type corners, and higher order corners. PMID:23743776

  14. 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 Λ 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.

  15. Optical beamforming networks employing phase modulation and direct detection

    NASA Astrophysics Data System (ADS)

    Xue, Xiaoxiao; Zheng, Xiaoping; Zhang, Hanyi; Zhou, Bingkun

    2011-06-01

    We propose a novel dispersion-based optical beamforming network scheme employing phase modulation and direct detection. Optical phase modulators have the advantages of simple-structure, low loss and absence of bias. Dispersion-induced phase-to-intensity conversion is utilized to facilitate direct detection. A structure of wideband dispersive device (WDD) cascaded with periodic dispersive device (PDD) is introduced to enhance the system flexibility, so that the delay adjustability and RF response can be properly designed respectively by choosing appropriate dispersions of the WDD and PDD. A concept-proof system with a wideband chirped fiber grating (CFG) as the WDD and two multiband CFGs (MCFG1 and MCFG2) as the PDD separately is built to demonstrate the basic idea. The delay tuning range is 0-1.8 ns with increment of 164.2 ps. The passband center is 30 GHz for MCFG1 and 20 GHz for MCFG2, and the fractional bandwidth is 51.8%. The shot-noise-limited spurious-free dynamic range is also analyzed and measured to be 105.7 dB ṡ Hz2/3 when the average photocurrent is 2.7 mA.

  16. 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.

  17. Understanding WIMP-baryon interactions with direct detection: a roadmap

    NASA Astrophysics Data System (ADS)

    Gluscevic, Vera; Peter, Annika H. G.

    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.

  18. Isothermal Detection of Mycoplasma pneumoniae Directly from Respiratory Clinical Specimens

    PubMed Central

    Petrone, Brianna L.; Wolff, Bernard J.; DeLaney, Alexandra A.; Diaz, Maureen H.

    2015-01-01

    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

  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. 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 mχ-σn 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.

  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 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.

  2. 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.

  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. Neutralino Dark Matter: Update on Direct and Indirect Detection

    SciTech Connect

    Scopel, S.

    2005-12-02

    Neutralinos represent a viable solution to the Dark Matter problem. In particular, while I discuss here a wide range for their masses, I will deserve a special attention to light neutralinos, which arise in supersymmetric models without unifications conditions of gaugino masses at the GUT scale. They have sizeable direct and indirect detection signals, which are bounded from below by the cosmological constraint on their relic abundance, but are not yet excluded by present direct and indirect searches, including limits coming from the BR(Bs {yields} {mu}+ + {mu}-) decay rate. They represent so an interesting experimental challenge. An intriguing aspect of light neutralinos is also that they could explain the DAMA modulation effect in a still existing compatibility window with other direct search experiments. I also discuss the gamma-ray signal from dark matter annihilation in our Galaxy and give some examples of external objects, namely the Andromeda Galaxy (M31) and M87. Predictions for the fluxes turn out to be below the level required to explain the possible indications of a {gamma}-ray excess shown by EGRET, CANGAROO-II and HESS (toward the Galactic Center) and HEGRA (from M87). As far as future experiments are concerned, only the signal from the galactic center could be accessible to both satellite-borne experiments and to ACTs, even though this requires very steep dark matter density profiles.

  5. Detecting Tsunami Genesis and Scales Directly from Coastal GPS Stations

    NASA Astrophysics Data System (ADS)

    Song, Y. Tony

    2013-04-01

    Different from the conventional approach to tsunami warnings that rely on earthquake magnitude estimates, we have found that coastal GPS stations are able to detect continental slope displacements of faulting due to big earthquakes, and that the detected seafloor displacements are able to determine tsunami source energy and scales instantaneously. This method has successfully replicated several historical tsunamis caused by the 2004 Sumatra earthquake, the 2005 Nias earthquake, the 2010 Chilean earthquake, and the 2011 Tohoku-Oki earthquake, respectively, and has been compared favorably with the conventional seismic solutions that usually take hours or days to get through inverting seismographs (reference listed). Because many coastal GPS stations are already in operation for measuring ground motions in real time as often as once every few seconds, this study suggests a practical way of identifying tsunamigenic earthquakes for early warnings and reducing false alarms. Reference Song, Y. T., 2007: Detecting tsunami genesis and scales directly from coastal GPS stations, Geophys. Res. Lett., 34, L19602, doi:10.1029/2007GL031681. Song, Y. T., L.-L. Fu, V. Zlotnicki, C. Ji, V. Hjorleifsdottir, C.K. Shum, and Y. Yi, 2008: The role of horizontal impulses of the faulting continental slope in generating the 26 December 2004 Tsunami, Ocean Modelling, doi:10.1016/j.ocemod.2007.10.007. Song, Y. T. and S.C. Han, 2011: Satellite observations defying the long-held tsunami genesis theory, D.L. Tang (ed.), Remote Sensing of the Changing Oceans, DOI 10.1007/978-3-642-16541-2, Springer-Verlag Berlin Heidelberg. Song, Y. T., I. Fukumori, C. K. Shum, and Y. Yi, 2012: Merging tsunamis of the 2011 Tohoku-Oki earthquake detected over the open ocean, Geophys. Res. Lett., doi:10.1029/2011GL050767 (Nature Highlights, March 8, 2012).

  6. Spectroscopic direct detection of reflected light from extrasolar planets

    NASA Astrophysics Data System (ADS)

    Martins, J. H. C.; Figueira, P.; Santos, N. C.; Lovis, C.

    2013-12-01

    At optical wavelengths, an exoplanet's signature is essentially reflected light from the host star - several orders of magnitude fainter. Since it is superimposed on the star spectrum its detection has been a difficult observational challenge. However, the development of a new generation of instruments like Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) and next-generation telescopes like the European Extremely Large Telescope (E-ELT) put us in a privileged position to detect these planets' reflected light as we will have access to extremely high signal-to-noise ratio spectra. With this work, we propose an alternative approach for the direct detection of the reflected light of an exoplanet. We simulated observations with ESPRESSO at Very Large Telescope (VLT) and high-resolution spectrograph (HIRES) at E-ELT of several star+planet systems, encompassing 10 h of the most favourable orbital phases. To the simulated spectra we applied the cross-correlation function to operate in a much higher signal-to-noise ratio domain than when compared with the spectra. The use of the cross-correlation function permitted us to recover the simulated planet signals at a level above 3σnoise significance on several prototypical (e.g. Neptune-type planet with a 2 d orbit with the VLT at 4.4σnoise significance) and real planetary systems (e.g. 55 Cnc e with the E-ELT at 4.9σnoise significance). Even by using a more pessimistic approach to the noise level estimation, where systematics in the spectra increase the noise 2-3 times, the detection of the reflected light from large close-orbit planets is possible. We have also shown that this kind of study is currently within reach of current instruments and telescopes (e.g. 51 Peg b with the VLT at 5.2σnoise significance), although at the limit of their capabilities.

  7. 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

  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

  9. 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

  10. 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

  11. 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 5σ 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.

  12. Light magnetic dark matter in direct detection searches

    NASA Astrophysics Data System (ADS)

    Del Nobile, Eugenio; Kouvaris, Chris; Panci, Paolo; Sannino, Francesco; Virkajärvi, 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.

  13. 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.

  14. Highly selective colorimetric sensing of Cu(II) ions in aqueous solution via modulation of intramolecular charge transfer transition of aminonaphthoquinone chemosensor.

    PubMed

    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). PMID:22750343

  15. 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.

  16. Subcarrier multiplexing with dispersion reduction and direct detection

    DOEpatents

    Sargis, Paul D.; Haigh, Ronald E.; McCammon, Kent G.

    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.

  17. 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.

  18. 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.

  19. Direct and Indirect Dark Matter Detection in Gauge Theories

    SciTech Connect

    Queiroz, Farinaldo

    2013-01-01

    The Dark matter (DM) problem constitutes a key question at the interface among Particle Physics, Astrophysics and Cosmology. The observational data which have been accumulated in the last years point to an existence of non baryonic amount of DM. Since the Standard Model (SM) does not provide any candidate for such non-baryonic DM, the evidence of DM is a major indication for new physics beyond the SM. We will study in this work one of the most popular DM candidates, the so called WIMPs (Weakly Interacting Massive Particles) from a direct and indirect detection perspective. In order to approach the direct and indirect dection of DM in the context of Particle Physics in a more pedagogic way, we will begin our discussion talking about a minimal extension of the SM. Later we will work on the subject in a 3-3-1 model. Next, we will study the role of WIMPs in the Big Bang Nucleosynthesis. Lastly, we will look for indirect DM signals in the center of our galaxy using the NASA Satellite, called Fermi-LAT. Through a comprehensive analysis of the data events observed by Fermi-LAT and some background models, we will constrain the dark matter annihilation cross section for several annihilation channels and dark matter halo profiles.

  20. Reactive Arrays of Colorimetric Sensors for Metabolite and Steroid Identification.

    PubMed

    Batres, Gary; Jones, Talia; Johnke, Hannah; Wilson, Mark; Holmes, Andrea E; Sikich, Sharmin

    2014-12-31

    The work described herein examines a rapid mix-and-measure method called DETECHIP suitable for screening of steroids and metabolites. The addition of steroids and metabolites to reactive arrays of colorimetric sensors generated characteristic color "fingerprints" that were used to identify the analyte. A color analysis tool was used to identify the analyte pool that now includes biologically relevant analytes. The mix-and-measure arrays allowed the detection of disease metabolites, orotic acid and argininosuccinic acid; and the steroids androsterone, 1,4-androstadiene, testosterone, stanozolol, and estrone. The steroid 1,4-androstadiene was also detected by this method while dissolved in synthetic urine. Some of the steroids, such as androstadiene, stanozolol, and androsterone were co-dissolved with (2-hydroxypropyl)-β-cyclodextrin in order to increase solubility in aqueous buffered solutions. The colorimetric arrays do not intend to eliminate ELISA or mass spectroscopy based screening, but to possibly provide an alternative analytical detection method for steroids and metabolites. PMID:25019034

  1. 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

  2. Colorimetric and fluorometric dual-readout sensor for lysozyme.

    PubMed

    Zheng, Hanye; Qiu, Suyan; Xu, Kefeng; Luo, Linguang; Song, Yibiao; Lin, Zhenyu; Guo, Longhua; Qiu, Bin; Chen, Guonan

    2013-11-01

    A novel, highly sensitive and selective dual-readout sensor (colorimetric and fluorometric) for the detection of lysozyme was proposed. The fluorescence of triazolylcoumarin molecules was quenched by Au nanoparticles (AuNPs) initially through the fluorescence resonance energy transfer (FRET), after the addition of lysozyme, the stronger binding of lysozyme onto the surfaces of AuNPs made triazolylcoumarin molecules remove from the AuNPs surface and led to the recovery of the fluorescence of triazolylcoumarin molecules, and accompanied by the discernable color change of the solution from red to purple. The lowest detectable concentration for lysozyme was 50 ng mL(-1) by the naked eye, and the limit of detection (LOD) was 23 ng mL(-1) by fluorescence measurements. In addition, satisfactory results for lysozyme detection in hen egg white were confirmed in the study. Moreover, the presented sensor provides a reliable option to determine lysozyme with high sensitivity and selectivity. PMID:23978821

  3. Evaluation of the Spectral Response of Functionalized Silk Inverse Opals as Colorimetric Immunosensors.

    PubMed

    Burke, Kelly A; Brenckle, Mark A; Kaplan, David L; Omenetto, Fiorenzo G

    2016-06-29

    Regenerated silk fibroin is a high molecular weight protein obtained by purifying the cocoons of the domesticated silkworm, Bombyx mori. This report exploits the aqueous processing and tunable β sheet secondary structure of regenerated silk to produce nanostructures (i.e., inverse opals) that can be used as colorimetric immunosensors. Such sensors would enable direct detection of antigens by changes in reflectance spectra induced by binding events within the nanostructure. Silk inverse opals were prepared by solution casting and annealing in a humidified atmosphere to render the silk insoluble. Next, antigen sensing capabilities were imparted to silk through a three step synthesis: coupling of avidin to silk surfaces, coupling of biotin to antibodies, and lastly antibody attachment to silk through avidin-biotin interactions. Varying the antibody enables detection of different antigens, as demonstrated using different protein antigens: antibodies, red fluorescent protein, and the beta subunit of cholera toxin. Antigen binding to sensors induces a red shift in the opal reflectance spectra, while sensors not exposed to antigen showed either no shift or a slight blue shift. This work constitutes a first step for the design of biopolymer-based optical systems that could directly detect antigens using commercially available reagents and environmentally friendly chemistries. PMID:27322909

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  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

    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

  11. 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.

  12. 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

  13. Visual Screening and Colorimetric Determination of Clenbuterol and Ractopamine Using Unmodified Gold Nanoparticles as Probe.

    PubMed

    Luo, Yeli; Liu, Xin; Guo, Jiajia; Gao, Hanting; Li, Ying; Xu, Jingyue; Shen, Fei; Sun, Chunyan

    2016-01-01

    In this paper, a sensitive method for the colorimetric detection of clenbuterol and ractopamine using citrate-stabilized gold nanoparticles (AuNPs) as probe was developed. The concentration of clenbuterol and ractopamine could be determined with naked eyes or a UV-vis spectrometer. By optimizing the influence of NaHSO₄ and incubation time, clenbuterol could be detected in the linear range of 0.1-4 µg/mL with the detection limit of 0.0158 µg/mL, and ractopamine could be detected in the linear range of 1-9 µg/mL with the detection limit of 0.0229 µg/mL. The proposed method could be successfully applied to detect clenbuterol and ractopamine in pig urines by a simple pre-treatment with excellent recoveries. The proposed colorimetric assay exhibits good reproducibility and accuracy, providing a simple and rapid method for the analysis of clenbuterol and ractopamine. PMID:27398486

  14. Paper bioassay based on ceria nanoparticles as colorimetric probes.

    PubMed

    Ornatska, Maryna; Sharpe, Erica; Andreescu, Daniel; Andreescu, Silvana

    2011-06-01

    We report the first use of redox nanoparticles of cerium oxide as colorimetric probes in bioanalysis. The method is based on changes in the physicochemical properties of ceria nanoparticles, used here as chromogenic indicators, in response to the analyte. We show that these particles can be fully integrated in a paper-based bioassay. To construct the sensor, ceria nanoparticles and glucose oxidase were coimmobilized onto filter paper using a silanization procedure. In the presence of glucose, the enzymatically generated hydrogen peroxide induces a visual color change of the ceria nanoparticles immobilized onto the bioactive sensing paper, from white-yellowish to dark orange, in a concentration-dependent manner. A detection limit of 0.5 mM glucose with a linear range up to 100 mM and a reproducibility of 4.3% for n = 11 ceria paper strips were obtained. The assay is fully reversible and can be reused for at least 10 consecutive measurement cycles, without significant loss of activity. Another unique feature is that it does not require external reagents, as all the sensing components are fixed onto the paper platform. The bioassay can be stored for at least 79 days at room temperature while maintaining the same analytical performance. An example of analytical application was demonstrated for the detection of glucose in human serum. The results demonstrate the potential of this type of nanoparticles as novel components in the development of robust colorimetric bioassays. PMID:21524141

  15. 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.

  16. 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.

  17. Direct detection of exothermic dark matter with light mediator

    NASA Astrophysics Data System (ADS)

    Geng, Chao-Qiang; Huang, Da; Lee, Chun-Hao; Wang, Qing

    2016-08-01

    We study the dark matter (DM) direct detection for the models with the effects of the isospin-violating couplings, exothermic scatterings, and/or the lightness of the mediator, proposed to relax the tension between the CDMS-Si signals and null experiments. In the light of the new updates of the LUX and CDMSlite data, we find that many of the previous proposals are now ruled out, including the Ge-phobic exothermic DM model and the Xe-phobic DM one with a light mediator. We also examine the exothermic DM models with a light mediator but without the isospin violation, and we are unable to identify any available parameter space that could simultaneously satisfy all the experiments. The only models that can partially relax the inconsistencies are the Xe-phobic exothermic DM models with or without a light mediator. But even in this case, a large portion of the CDMS-Si regions of interest has been constrained by the LUX and SuperCDMS data.

  18. Applications of Direct Detection Device in Transmission Electron Microscopy

    PubMed Central

    Jin, Liang; Milazzo, Anna-Clare; Kleinfelder, Stuart; Li, Shengdong; Leblanc, Philippe; Duttweiler, Fred; Bouwer, James C.; Peltier, Steven T.; Ellisman, Mark H.; Xuong, Nguyen-Huu

    2008-01-01

    A prototype Direct Detection Device (DDD) camera system has shown great promise in improving both the spatial resolution and the signal to noise ratio for electron microscopy at 120–400 keV beam energies (Xuong, et al., 2007. Methods in Cell Biology, 79, 721–739). Without the need for a resolution-limiting scintillation screen as in the charge coupled device (CCD), the DDD camera can outperform CCD based systems in terms of spatial resolution, due to its small pixel size (5 μm). In this paper, the modulation transfer function (MTF) of the DDD prototype is measured and compared with the specifications of commercial scientific CCD camera systems. Combining the fast speed of the DDD with image mosaic techniques, fast wide-area imaging is now possible. In this paper, the first large area mosaic image and the first tomography dataset from the DDD camera are presented, along with an image processing algorithm to correct the specimen drift utilizing the fast readout of the DDD system. PMID:18054249

  19. 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.

  20. 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…

  1. Colorimetric determination of tobramycin in parenteral solutions.

    PubMed

    Das Gupta, V

    1988-06-01

    A colorimetric method based on a reaction between tobramycin and alkaline copper sulphate solution has been proposed to quantify tobramycin in injections. The excipients present and normal saline did not interfere with the assay procedure. A tobramycin sample which was decomposed using either sulphuric acid or sodium hydroxide solution indicated fairly good stability on both sides of the pH scale. PMID:3209627

  2. 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....

  3. Enhancement of Colorimetric Response of Enzymatic Reactions by Thermally Evaporated Plasmonic Thin Films: Application to Glial Fibrillary Acidic Protein

    PubMed Central

    Abel, Biebele; Kabir, Tabassum S.; Odukoya, Babatunde; Mohammed, Muzaffer; Aslan, Kadir

    2015-01-01

    We report the enhancement of the colorimetric response of horseradish peroxidase (HRP) and alkaline phosphatase (AP) in bioassays by thermally evaporated silver, gold, copper and nickel thin films. In this regard, a model bioassay based on biotin-avidin interactions was employed. Biotin groups and enzymes were introduced to all surfaces using a biotinylated linker molecule and avidin, respectively. The colorimetric response of HRP in the model bioassay carried out on the plasmonic thin films were up to 4.4-fold larger as compared to control samples (i.e., no plasmonic thin films), where the largest enhancement of colorimetric response was observed on silver thin films. The colorimetric response of AP on plasmonic thin films was found to be similar to those observed on control samples, which was attributed to the loss of enzymes from the surface during the bioassay steps. The extent of enzymes immobilized on to plasmonic thin films was found to affect the colorimetric response of the model bioassay. These findings allowed us to demonstrate the use of silver thin films for the detection of glial fibrillary acidic protein (GFAP), where the colorimetric response of the standard bioassays for GFAP was enhanced up to 67% as compared to bioassays on glass slides. PMID:25663850

  4. 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.

  5. 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

  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. Automatic colorimetric calibration of human wounds

    PubMed Central

    2010-01-01

    Background Recently, digital photography in medicine is considered an acceptable tool in many clinical domains, e.g. wound care. Although ever higher resolutions are available, reproducibility is still poor and visual comparison of images remains difficult. This is even more the case for measurements performed on such images (colour, area, etc.). This problem is often neglected and images are freely compared and exchanged without further thought. Methods The first experiment checked whether camera settings or lighting conditions could negatively affect the quality of colorimetric calibration. Digital images plus a calibration chart were exposed to a variety of conditions. Precision and accuracy of colours after calibration were quantitatively assessed with a probability distribution for perceptual colour differences (dE_ab). The second experiment was designed to assess the impact of the automatic calibration procedure (i.e. chart detection) on real-world measurements. 40 Different images of real wounds were acquired and a region of interest was selected in each image. 3 Rotated versions of each image were automatically calibrated and colour differences were calculated. Results 1st Experiment: Colour differences between the measurements and real spectrophotometric measurements reveal median dE_ab values respectively 6.40 for the proper patches of calibrated normal images and 17.75 for uncalibrated images demonstrating an important improvement in accuracy after calibration. The reproducibility, visualized by the probability distribution of the dE_ab errors between 2 measurements of the patches of the images has a median of 3.43 dE* for all calibrated images, 23.26 dE_ab for all uncalibrated images. If we restrict ourselves to the proper patches of normal calibrated images the median is only 2.58 dE_ab! Wilcoxon sum-rank testing (p < 0.05) between uncalibrated normal images and calibrated normal images with proper squares were equal to 0 demonstrating a highly

  8. PDM-16QAM vector signal generation and detection based on intensity modulation and direct detection

    NASA Astrophysics Data System (ADS)

    Chen, Long; Yu, Jianjun; Li, Xinying

    2016-07-01

    We experimentally demonstrate a novel and simple method to generate and detect high speed polarization-division-multiplexing 16-ary quadrature-amplitude-modulation (PDM-16QAM) vector signal enabled by Mach-Zehnder modulator-based (MZM-based) optical-carrier-suppression (OCS) intensity modulation and direct detection. Due to the adoption of OCS intensity modulation, carrier beating can be avoided at the receiver, and thus polarization de-multiplexing can be implemented by digital-signal-processing-based (DSP-based) cascaded multi-modulus algorithm (CMMA) equalization instead of a polarization tracking system. The change of both amplitude and phase information due to the adoption of OCS modulation can be equalized by DSP-based amplitude and phase precoding at the transmitter. Up to 64-Gb/s PDM-16QAM vector signal is generated and detected after 2-km single-mode fiber-28 (SMF-28) or 20-km large-effective-area fiber (LEAF) transmission with a bit-error-ratio (BER) less than the hard-decision forward-error-correction (HD-FEC) threshold of 3.8×10-3.

  9. Interface engineering catalytic graphene for smart colorimetric biosensing.

    PubMed

    Liu, Meng; Zhao, Huimin; Chen, Shuo; Yu, Hongtao; Quan, Xie

    2012-04-24

    Herein a hybrid catalyst consisting of "naked" Au-NPs in situ grown on graphene sheets is engineered, which exhibits a synergetic effect in mimicking peroxidase at its interface, although free Au-NPs or graphene alone has very little activity. What is more, one of the unique features of our synergetic catalyst is that its interface can be reversibly switched from "inactive" to "active" upon treatment with different ssDNA species in solution, thus providing a powerful and versatile basis for designing graphene/DNA-based label-free colorimetric biosensors. Compared with other signal transduction modes in traditional graphene/aptamer-based systems, our novel signaling strategy not only avoids any labeling or modification procedures but also reduces the background signal due to the "off-on" switching mode during the sensing. Furthermore, this facile and general approach can be applicable to the other extended graphene/aptamer-based systems for colorimetric detection of a wide range of analytes. We envision that the tunable graphene-based smart interface could find potential applications in the development of biocatalysis, bioassays, and smart material devices in the future. PMID:22443302

  10. 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

  11. Colorimetric high-throughput assay for alkene epoxidation catalyzed by cytochrome P450 BM-3 variant 139-3.

    PubMed

    Alcalde, Miguel; Farinas, Edgardo T; Arnold, Frances H

    2004-03-01

    Cytochrome P450 BM-3 variant 139-3 is highly active in the hydroxylation of alkanes and fatty acids (AGlieder, ET Farinas, and FH Arnold, Nature Biotech 2002;20:1135-1139); it also epoxidizes various alkenes, including styrene. Here the authors describe a colorimetric, high-throughput assay suitable for optimizing this latter activity by directed evolution. The product of styrene oxidation by 139-3, styrene oxide, reacts with the nucleophile gamma-(4-nitrobenzyl)pyridine (NBP) to form a purple-colored precursor dye, which can be monitored spectrophotometrically in cell lysates. The sensitivity limit of this assay is 50-100 microM of product, and the detection limit for P450 BM-3 139-3 is ~0.2 microM of enzyme. To validate the assay, activities in a small library of random mutants were compared to those determined using an NADPH depletion assay for initial turnover rates. PMID:15006137

  12. Cost-effective and sensitive colorimetric immunosensing using an iron oxide-to-Prussian blue nanoparticle conversion strategy.

    PubMed

    Fu, Guanglei; Sanjay, Sharma T; Li, XiuJun

    2016-06-21

    The development of new sensitive, cost-effective and user-friendly colorimetric bioassays is in increasing demand to meet the requirement of modern clinical diagnostics and field detection. Herein, a novel iron oxide-to-Prussian blue (PB) nanoparticle (NP) conversion strategy was developed and applied to sensitive colorimetric immunosensing of cancer biomarkers. In a typical sandwich-type immunosensing system, the captured spherical antibody-conjugated iron oxide NPs were transformed into cubic PB NPs, which exhibited a highly visible blue color with high molar extinction coefficients. Hence, a new colorimetric immunosensing strategy was developed as a result of this low cost and simple transformation process. Without the aid of any complex nanoparticle stabilizing ligands and signal amplification processes, prostate-specific antigen as a model analyte can be detected at a concentration as low as 1.0 ng mL(-1) by the naked eye with good reliability for detection of real human serum samples. This is the first attempt to develop and apply the iron oxide-to-PB NP colorimetric conversion strategy for immunosensing, and shows great promise for the development of new sensitive, cost-effective and user-friendly colorimetric bioassays in various bioanalytical applications, especially in low-resource settings. PMID:27140740

  13. 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

  14. 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

  15. Directional dark matter detection with the DMTPC m3 experiment

    NASA Astrophysics Data System (ADS)

    Leyton, Michael; DMTPC Collaboration

    2016-05-01

    Directional reconstruction provides a unique way to positively identify signal interactions induced by dark matter particles, owing to the motion of the Earth through the galactic dark matter halo. Directional information can additionally serve as a powerful discriminant against neutron (and neutrino-induced) backgrounds that have the same final-state signature as a signal interaction. The Dark Matter Time Projection Chamber (DMTPC) collaboration uses gas-based TPC technology, with both optical and charge readout, to measure the directional anisotropy of nuclear recoils induced by particles traversing the detector volume. Here, we present preliminary results from recent calibration runs of the DMTPC m3 detector in a surface laboratory, as well as a study of its projected directional sensitivity.

  16. Technique for detecting a direct signal pulse from an underwater explosive source in a waveguide

    NASA Astrophysics Data System (ADS)

    Kostenko, K. V.; Kryukov, Yu. S.

    2016-01-01

    A technique for detecting direct signal pulses based on steep rising edges of acoustic pressure is developed. The technique consists in calculating the mirror derivative of the received signal and normalizing it in a specific manner. This makes it possible to amplify weak direct signals and suppress strong reflected ones. A key feature of this technique is that it ensures a high probability of detection of direct signal pulses while keeping the number of false detections at a minimum.

  17. Development of a nanobody-alkaline phosphatase fusion protein and its application in a highly sensitive direct competitive fluorescence enzyme immunoassay for detection of ochratoxin A in cereal

    PubMed Central

    Liu, Xing; Xu, Yang; Wan, De-bin; Xiong, Yong-hua; He, Zhen-yun; Wang, Xian-xian; Gee, Shirley J.; Ryu, Dojin; Hammock, Bruce D.

    2015-01-01

    A rapid and sensitive direct competitive fluorescence enzyme immunoassay (dc-FEIA) for ochratoxin A (OTA) based on a nanobody (Nb)-alkaline phosphatase (AP) fusion protein was developed. The VHH gene of Nb28 was subcloned into the expression vector pecan45 containing the AP double mutant gene. The Nb28-AP construct was transformed into E. coli BL21(DE3)plysS and soluble expression in bacteria was confirmed by SDS-PAGE and Western blot. Both the Nb properties and AP enzymatic activity were validated by colorimetric and fluorometric analysis. The 50% inhibitory concentration and the detection limit of the dc-FEIA were 0.13 ng/mL and 0.04 ng/mL, respectively, with a linear range of 0.06–0.43 ng/mL. This assay was compared with LC-MS/MS, and the results indicated the reliability of Nb-AP fusion protein-based dc-FEIA for monitoring OTA contamination in cereal. PMID:25531426

  18. A Nonstationary Markov Model Detects Directional Evolution in Hymenopteran Morphology

    PubMed Central

    Klopfstein, Seraina; Vilhelmsen, Lars; Ronquist, Fredrik

    2015-01-01

    Directional evolution has played an important role in shaping the morphological, ecological, and molecular diversity of life. However, standard substitution models assume stationarity of the evolutionary process over the time scale examined, thus impeding the study of directionality. Here we explore a simple, nonstationary model of evolution for discrete data, which assumes that the state frequencies at the root differ from the equilibrium frequencies of the homogeneous evolutionary process along the rest of the tree (i.e., the process is nonstationary, nonreversible, but homogeneous). Within this framework, we develop a Bayesian approach for testing directional versus stationary evolution using a reversible-jump algorithm. Simulations show that when only data from extant taxa are available, the success in inferring directionality is strongly dependent on the evolutionary rate, the shape of the tree, the relative branch lengths, and the number of taxa. Given suitable evolutionary rates (0.1–0.5 expected substitutions between root and tips), accounting for directionality improves tree inference and often allows correct rooting of the tree without the use of an outgroup. As an empirical test, we apply our method to study directional evolution in hymenopteran morphology. We focus on three character systems: wing veins, muscles, and sclerites. We find strong support for a trend toward loss of wing veins and muscles, while stationarity cannot be ruled out for sclerites. Adding fossil and time information in a total-evidence dating approach, we show that accounting for directionality results in more precise estimates not only of the ancestral state at the root of the tree, but also of the divergence times. Our model relaxes the assumption of stationarity and reversibility by adding a minimum of additional parameters, and is thus well suited to studying the nature of the evolutionary process in data sets of limited size, such as morphology and ecology. PMID:26272507

  19. A Nonstationary Markov Model Detects Directional Evolution in Hymenopteran Morphology.

    PubMed

    Klopfstein, Seraina; Vilhelmsen, Lars; Ronquist, Fredrik

    2015-11-01

    Directional evolution has played an important role in shaping the morphological, ecological, and molecular diversity of life. However, standard substitution models assume stationarity of the evolutionary process over the time scale examined, thus impeding the study of directionality. Here we explore a simple, nonstationary model of evolution for discrete data, which assumes that the state frequencies at the root differ from the equilibrium frequencies of the homogeneous evolutionary process along the rest of the tree (i.e., the process is nonstationary, nonreversible, but homogeneous). Within this framework, we develop a Bayesian approach for testing directional versus stationary evolution using a reversible-jump algorithm. Simulations show that when only data from extant taxa are available, the success in inferring directionality is strongly dependent on the evolutionary rate, the shape of the tree, the relative branch lengths, and the number of taxa. Given suitable evolutionary rates (0.1-0.5 expected substitutions between root and tips), accounting for directionality improves tree inference and often allows correct rooting of the tree without the use of an outgroup. As an empirical test, we apply our method to study directional evolution in hymenopteran morphology. We focus on three character systems: wing veins, muscles, and sclerites. We find strong support for a trend toward loss of wing veins and muscles, while stationarity cannot be ruled out for sclerites. Adding fossil and time information in a total-evidence dating approach, we show that accounting for directionality results in more precise estimates not only of the ancestral state at the root of the tree, but also of the divergence times. Our model relaxes the assumption of stationarity and reversibility by adding a minimum of additional parameters, and is thus well suited to studying the nature of the evolutionary process in data sets of limited size, such as morphology and ecology. PMID:26272507

  20. Calculations of rates for direct detection of neutralino dark matter

    NASA Technical Reports Server (NTRS)

    Griest, Kim

    1988-01-01

    The detection rates in cryogenic detectors of neutralinos, the most well motivated supersymmetric dark-matter candidate, are calculated. These rates can differ greatly from the special case of pure photinos and pure Higgsinos which are usually considered. In addition, a new term is found in the elastic-scattering cross section proportional to the Z-ino component which is 'spin independent', even for these Majorana particles. As a result, substantial detection rates exist for previously disfavored, mostly spinless materials such as germanium and mercury.