Versatile gold based SERS substrates fabricated by ultrafast laser ablation for sensing picric acid and ammonium nitrate

NASA Astrophysics Data System (ADS)

Byram, Chandu; Moram, Sree Sathya Bharathi; Shaik, Abdul Kalam; Soma, Venugopal Rao

2017-10-01

We demonstrate the detection of picric acid (PA) and ammonium nitrate (AN) at μM concentrations by utilizing gold (Au) nanostructures (NSs) as surface enhanced Raman scattering (SERS) substrates fabricated using the technique of ultrafast laser ablation in liquids. Au NPs and NSs were also utilized for detecting Rhodamine 6G (Rh6G) and methylene blue (MB). Detection of all the molecules using the same substrates (NPs and NSs) demonstrated their versatility. Detection limits of 10-5, 10-6, 10-7, 10-8 M were achieved for AN, PA, Rh6G and MB, respectively. Reproducibility of the SERS intensity using NSs and NPs as substrates demonstrate their efficacy.

A Nanocoaxial-Based Electrochemical Sensor for the Detection of Cholera Toxin

NASA Astrophysics Data System (ADS)

Archibald, Michelle M.; Rizal, Binod; Connolly, Timothy; Burns, Michael J.; Naughton, Michael J.; Chiles, Thomas C.

2015-03-01

Sensitive, real-time detection of biomarkers is of critical importance for rapid and accurate diagnosis of disease for point of care (POC) technologies. Current methods do not allow for POC applications due to several limitations, including sophisticated instrumentation, high reagent consumption, limited multiplexing capability, and cost. Here, we report a nanocoaxial-based electrochemical sensor for the detection of bacterial toxins using an electrochemical enzyme-linked immunosorbent assay (ELISA) and differential pulse voltammetry (DPV). Proof-of-concept was demonstrated for the detection of cholera toxin (CT). The linear dynamic range of detection was 10 ng/ml - 1 μg/ml, and the limit of detection (LOD) was found to be 2 ng/ml. This level of sensitivity is comparable to the standard optical ELISA used widely in clinical applications. In addition to matching the detection profile of the standard ELISA, the nanocoaxial array provides a simple electrochemical readout and a miniaturized platform with multiplexing capabilities for the simultaneous detection of multiple biomarkers, giving the nanocoax a desirable advantage over the standard method towards POC applications. Sensitive, real-time detection of biomarkers is of critical importance for rapid and accurate diagnosis of disease for point of care (POC) technologies. Current methods do not allow for POC applications due to several limitations, including sophisticated instrumentation, high reagent consumption, limited multiplexing capability, and cost. Here, we report a nanocoaxial-based electrochemical sensor for the detection of bacterial toxins using an electrochemical enzyme-linked immunosorbent assay (ELISA) and differential pulse voltammetry (DPV). Proof-of-concept was demonstrated for the detection of cholera toxin (CT). The linear dynamic range of detection was 10 ng/ml - 1 μg/ml, and the limit of detection (LOD) was found to be 2 ng/ml. This level of sensitivity is comparable to the standard optical ELISA used widely in clinical applications. In addition to matching the detection profile of the standard ELISA, the nanocoaxial array provides a simple electrochemical readout and a miniaturized platform with multiplexing capabilities for the simultaneous detection of multiple biomarkers, giving the nanocoax a desirable advantage over the standard method towards POC applications. This work was supported by the National Institutes of Health (National Cancer Institute award No. CA137681 and National Institute of Allergy and Infectious Diseases Award No. AI100216).

Multichannel waveguides for the simultaneous detection of disease biomarkers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukundan, Harshini; Price, Dominique Z; Grace, Wynne K

2009-01-01

The sensor team at the Los Alamos National Laboratory has developed a waveguide-based optical biosensor that has previously been used for the detection of biomarkers associated with diseases such as tuberculosis, breast cancer, anthrax and influenza in complex biological samples (e.g., serum and urine). However, no single biomarker can accurately predict disease. To address this issue, we developed a multiplex assay for the detection of components of the Bacillus anthracis lethal toxin on single mode planar optical waveguides with tunable quantum dots as the fluorescence reporter. This limited ability to multiplex is still insufficient for accurate detection of disease ormore » for monitoring prognosis. In this manuscript, we demonstrate for the first time, the design, fabrication and successful evaluation of a multichannel planar optical waveguide for the simultaneous detection of at least three unknown samples in quadruplicate. We demonstrate the simultaneous, rapid (30 min), quantitative (with internal standard) and sensitive (limit of detection of 1 pM) detection of protective antigen and lethal factor of Bacillus anthracis in complex biological samples (serum) using specific monoclonal antibodies labeled with quantum dots as the fluorescence reporter.« less

Can Blindsight Be Superior to "Sighted-Sight"?

ERIC Educational Resources Information Center

Trevethan, Ceri T.; Sahraie, Arash; Weiskrantz, Larry

2007-01-01

DB, the first blindsight case to be tested extensively (Weiskrantz, 1986) has demonstrated the ability to detect and discriminate a range of visual stimuli presented within his perimetrically blind visual field defect. In a temporal two alternative forced choice (2AFC) detection experiment we have investigated the limits of DB's detection ability…

Organic electrochemical transistor based immunosensor for prostate specific antigen (PSA) detection using gold nanoparticles for signal amplification.

PubMed

Kim, Duck-Jin; Lee, Nae-Eung; Park, Joon-Shik; Park, In-Jun; Kim, Jung-Gu; Cho, Hyoung J

2010-07-15

We demonstrated a highly sensitive organic electrochemical transistor (OECT) based immunosensor with a low detection limit for prostate specific antigen/alpha1-antichymotrypsin (PSA-ACT) complex. The poly(styrenesulfonate) doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) based OECT with secondary antibody conjugated gold nanoparticles (AuNPs) provided a detection limit of the PSA-ACT complex as low as 1pg/ml, as well as improved sensitivity and a dynamic range, due to the role of AuNPs in the signal amplification. The sensor performances were particularly improved in the lower concentration range where the detection is clinically important for the preoperative diagnosis and screening of prostate cancer. This result shows that the OECT-based immunosensor can be used as a transducer platform acceptable to the point-of-care (POC) diagnostic systems and demonstrates adaptability of organic electronics to clinical applications. Copyright (c) 2010 Elsevier B.V. All rights reserved.

An Optoelectronic Nose for Detection of Toxic Gases

PubMed Central

Lim, Sung H.; Feng, Liang; Kemling, Jonathan W.; Musto, Christopher J.; Suslick, Kenneth S.

2009-01-01

We have developed a simple colorimetric sensor array (CSA) for the detection of a wide range of volatile analytes and applied it to the detection of toxic gases. The sensor consists of a disposable array of cross-responsive nanoporous pigments whose colors are changed by diverse chemical interactions with analytes. Although no single chemically responsive pigment is specific for any one analyte, the pattern of color change for the array is a unique molecular fingerprint. Clear differentiation among 19 different toxic industrial chemicals (TICs) within two minutes of exposure at IDLH (immediately dangerous to life or health) concentration has been demonstrated. Quantification of each analyte is easily accomplished based on the color change of the array, and excellent detection limits have been demonstrated, generally below the PELs (permissible exposure limits). Identification of the TICs was readily achieved using a standard chemometric approach, i.e., hierarchical clustering analysis (HCA), with no misclassifications over 140 trials. PMID:20160982

Chemical detection demonstrated using an evanescent wave graphene optical sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maliakal, Ashok; Reith, Leslie; Cabot, Steve

Graphene devices have been constructed on silicon mirrors, and the graphene is optically probed through an evanescent wave interaction in an attenuated total reflectance configuration using an infrared spectrometer. The graphene is electrically biased in order to tune its optical properties. Exposure of the device to the chemicals iodine and ammonia causes observable and reversible changes to graphene's optical absorption spectra in the mid to near infrared range which can be utilized for the purpose of sensing. Electrical current measurements through the graphene are made simultaneously with optical measurements allowing for simultaneous sensing using two separate detection modalities. Our currentmore » results reveal sub-ppm detection limits for iodine and approximately 100 ppm detection limits for ammonia. We have also demonstrated that this approach will work at 1.55 μm, which opens up the possibility for graphene optical sensors that leverage commercial telecom light sources.« less

Failure Detecting Method of Fault Current Limiter System with Rectifier

NASA Astrophysics Data System (ADS)

Tokuda, Noriaki; Matsubara, Yoshio; Asano, Masakuni; Ohkuma, Takeshi; Sato, Yoshibumi; Takahashi, Yoshihisa

A fault current limiter (FCL) is extensively needed to suppress fault current, particularly required for trunk power systems connecting high-voltage transmission lines, such as 500kV class power system which constitutes the nucleus of the electric power system. We proposed a new type FCL system (rectifier type FCL), consisting of solid-state diodes, DC reactor and bypass AC reactor, and demonstrated the excellent performances of this FCL by developing the small 6.6kV and 66kV model. It is important to detect the failure of power devices used in the rectifier under the normal operating condition, for keeping the excellent reliability of the power system. In this paper, we have proposed a new failure detecting method of power devices most suitable for the rectifier type FCL. This failure detecting system is simple and compact. We have adapted the proposed system to the 66kV prototype single-phase model and successfully demonstrated to detect the failure of power devices.

Photonic crystal enhanced fluorescence using a quartz substrate to reduce limits of detection

PubMed Central

Pokhriyal, Anusha; Lu, Meng; Chaudhery, Vikram; Huang, Cheng-Sheng; Schulz, Stephen; Cunningham, Brian T.

2010-01-01

A Photonic Crystal (PC) surface fabricated upon a quartz substrate using nanoimprint lithography has been demonstrated to enhance light emission from fluorescent molecules in close proximity to the PC surface. Quartz was selected for its low autofluorescence characteristics compared to polymer-based PCs, improving the detection sensitivity and signal-to-noise ratio (SNR) of PC Enhanced Fluorescence (PCEF). Nanoimprint lithography enables economical fabrication of the subwavelength PCEF surface structure over entire 1x3 in2 quartz slides. The demonstrated PCEF surface supports a transverse magnetic (TM) resonant mode at a wavelength of λ = 632.8 nm and an incident angle of θ = 11°, which amplifies the electric field magnitude experienced by surface-bound fluorophores. Meanwhile, another TM mode at a wavelength of λ = 690 nm and incident angle of θ = 0° efficiently directs the fluorescent emission toward the detection optics. An enhancement factor as high as 7500 × was achieved for the detection of LD-700 dye spin-coated upon the PC, compared to detecting the same material on an unpatterned glass surface. The detection of spotted Alexa-647 labeled polypeptide on the PC exhibits a 330 × SNR improvement. Using dose-response characterization of deposited fluorophore-tagged protein spots, the PCEF surface demonstrated a 140 × lower limit of detection compared to a conventional glass substrate. PMID:21164826

Using personal glucose meters and functional DNA sensors to quantify a variety of analytical targets

PubMed Central

Xiang, Yu; Lu, Yi

2012-01-01

Portable, low-cost and quantitative detection of a broad range of targets at home and in the field has the potential to revolutionize medical diagnostics and environmental monitoring. Despite many years of research, very few such devices are commercially available. Taking advantage of the wide availability and low cost of the pocket-sized personal glucose meter—used worldwide by diabetes sufferers—we demonstrate a method to use such meters to quantify non-glucose targets, ranging from a recreational drug (cocaine, 3.4 μM detection limit) to an important biological cofactor (adenosine, 18 μM detection limit), to a disease marker (interferon-gamma of tuberculosis, 2.6 nM detection limit) and a toxic metal ion (uranium, 9.1 nM detection limit). The method is based on the target-induced release of invertase from a functional-DNA–invertase conjugate. The released invertase converts sucrose into glucose, which is detectable using the meter. The approach should be easily applicable to the detection of many other targets through the use of suitable functional-DNA partners (aptamers DNAzymes or aptazymes). PMID:21860458

Using personal glucose meters and functional DNA sensors to quantify a variety of analytical targets

NASA Astrophysics Data System (ADS)

Xiang, Yu; Lu, Yi

2011-09-01

Portable, low-cost and quantitative detection of a broad range of targets at home and in the field has the potential to revolutionize medical diagnostics and environmental monitoring. Despite many years of research, very few such devices are commercially available. Taking advantage of the wide availability and low cost of the pocket-sized personal glucose meter—used worldwide by diabetes sufferers—we demonstrate a method to use such meters to quantify non-glucose targets, ranging from a recreational drug (cocaine, 3.4 µM detection limit) to an important biological cofactor (adenosine, 18 µM detection limit), to a disease marker (interferon-gamma of tuberculosis, 2.6 nM detection limit) and a toxic metal ion (uranium, 9.1 nM detection limit). The method is based on the target-induced release of invertase from a functional-DNA-invertase conjugate. The released invertase converts sucrose into glucose, which is detectable using the meter. The approach should be easily applicable to the detection of many other targets through the use of suitable functional-DNA partners (aptamers, DNAzymes or aptazymes).

A Matched Filter Technique for Slow Radio Transient Detection and First Demonstration with the Murchison Widefield Array

NASA Astrophysics Data System (ADS)

Feng, L.; Vaulin, R.; Hewitt, J. N.; Remillard, R.; Kaplan, D. L.; Murphy, Tara; Kudryavtseva, N.; Hancock, P.; Bernardi, G.; Bowman, J. D.; Briggs, F.; Cappallo, R. J.; Deshpande, A. A.; Gaensler, B. M.; Greenhill, L. J.; Hazelton, B. J.; Johnston-Hollitt, M.; Lonsdale, C. J.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Oberoi, D.; Ord, S. M.; Prabu, T.; Udaya Shankar, N.; Srivani, K. S.; Subrahmanyan, R.; Tingay, S. J.; Wayth, R. B.; Webster, R. L.; Williams, A.; Williams, C. L.

2017-03-01

Many astronomical sources produce transient phenomena at radio frequencies, but the transient sky at low frequencies (<300 MHz) remains relatively unexplored. Blind surveys with new wide-field radio instruments are setting increasingly stringent limits on the transient surface density on various timescales. Although many of these instruments are limited by classical confusion noise from an ensemble of faint, unresolved sources, one can in principle detect transients below the classical confusion limit to the extent that the classical confusion noise is independent of time. We develop a technique for detecting radio transients that is based on temporal matched filters applied directly to time series of images, rather than relying on source-finding algorithms applied to individual images. This technique has well-defined statistical properties and is applicable to variable and transient searches for both confusion-limited and non-confusion-limited instruments. Using the Murchison Widefield Array as an example, we demonstrate that the technique works well on real data despite the presence of classical confusion noise, sidelobe confusion noise, and other systematic errors. We searched for transients lasting between 2 minutes and 3 months. We found no transients and set improved upper limits on the transient surface density at 182 MHz for flux densities between ˜20 and 200 mJy, providing the best limits to date for hour- and month-long transients.

Label-free optical biosensing with slot-waveguides.

PubMed

Barrios, Carlos A; Bañuls, María José; González-Pedro, Victoria; Gylfason, Kristinn B; Sánchez, Benito; Griol, Amadeu; Maquieira, A; Sohlström, H; Holgado, M; Casquel, R

2008-04-01

We demonstrate label-free molecule detection by using an integrated biosensor based on a Si(3)N(4)/SiO(2) slot-waveguide microring resonator. Bovine serum albumin (BSA) and anti-BSA molecular binding events on the sensor surface are monitored through the measurement of resonant wavelength shifts with varying biomolecule concentrations. The biosensor exhibited sensitivities of 1.8 and 3.2 nm/(ng/mm(2)) for the detection of anti-BSA and BSA, respectively. The estimated detection limits are 28 and 16 pg/mm(2) for anti-BSA and BSA, respectively, limited by wavelength resolution.

Sensitive DNA detection and SNP discrimination using ultrabright SERS nanorattles and magnetic beads for malaria diagnostics.

PubMed

Ngo, Hoan T; Gandra, Naveen; Fales, Andrew M; Taylor, Steve M; Vo-Dinh, Tuan

2016-07-15

One of the major obstacles to implement nucleic acid-based molecular diagnostics at the point-of-care (POC) and in resource-limited settings is the lack of sensitive and practical DNA detection methods that can be seamlessly integrated into portable platforms. Herein we present a sensitive yet simple DNA detection method using a surface-enhanced Raman scattering (SERS) nanoplatform: the ultrabright SERS nanorattle. The method, referred to as the nanorattle-based method, involves sandwich hybridization of magnetic beads that are loaded with capture probes, target sequences, and ultrabright SERS nanorattles that are loaded with reporter probes. Upon hybridization, a magnet was applied to concentrate the hybridization sandwiches at a detection spot for SERS measurements. The ultrabright SERS nanorattles, composed of a core and a shell with resonance Raman reporters loaded in the gap space between the core and the shell, serve as SERS tags for signal detection. Using this method, a specific DNA sequence of the malaria parasite Plasmodium falciparum could be detected with a detection limit of approximately 100 attomoles. Single nucleotide polymorphism (SNP) discrimination of wild type malaria DNA and mutant malaria DNA, which confers resistance to artemisinin drugs, was also demonstrated. These test models demonstrate the molecular diagnostic potential of the nanorattle-based method to both detect and genotype infectious pathogens. Furthermore, the method's simplicity makes it a suitable candidate for integration into portable platforms for POC and in resource-limited settings applications. Copyright © 2016. Published by Elsevier B.V.

Highly sensitive and specific on-site detection of serum cocaine by a low cost aptasensor.

PubMed

Oueslati, Rania; Cheng, Cheng; Wu, Jayne; Chen, Jiangang

2018-06-15

Cocaine is one of the most used illegal recreational drugs. Developing an on-site test for cocaine use detection has been a focus of research effort, since it is essential to the control and legal action against drug abuse. Currently most of cocaine detection methods are time-consuming and require special or expensive equipment, and the detection often suffers from high cross-reactivity with cocaine metabolites and relative low sensitivity with the best limit of detection reported at sub nanomolar (nM) level. In this work, an aptasensor has been developed using capacitive monitoring of sensor surface incorporating alternating current electrokinetics effects to speed up molecular transport and minimize matrix effects. The aptasensor is rapid, low cost, highly sensitive and specific as well as simple-to-use for the detection of cocaine from serum. The assay has a sample-to-result time of 30 s, a limit of detection of 7.8 fM, and a linear response for cocaine ranging from 14.5fM to 14.5pM in standard buffer, which are great improvements from other reported cocaine sensors. Special buffer is used for serum cocaine detection, and a limit of detection of 13.4 fM is experimentally demonstrated for cocaine spiked in human serum (equivalent to 1.34pM cocaine in neat serum). The specificity of the biosensor is also demonstrated with structurally similar chemicals, ecgonine ethyl ester and methylecgonidine. This biosensor shows high promise in detection of low levels of cocaine from complex matrices. Copyright © 2018 Elsevier B.V. All rights reserved.

Graphene nanosheet mediated MALDI-MS (GN-MALDI-MS) for rapid, in situ detection of intact incipient biofilm on material surfaces.

PubMed

Wu, Bo Sgum; Gopal, Judy; Hua, Pei-Yang; Wu, Hui-Fen

2016-09-01

Detection is the first step to efficient treatment, therefore early detection of biofilm gains paramount importance for the initiation of mitigation protocols. A systematic study was conducted to detect the biofilm formation (1h to 2month period) on aluminium, titanium surfaces and their corresponding oxide film surfaces. The limit of detection (LOD) in case of traditional MALDI-MS was limited to a 6h old biofilm. Whereas, in case of the Graphene nanosheet mediated MALDI-MS (GN-MALDI-MS) approach, early detection of the biofilm was demonstrated to be 1h on titanium surfaces and 3h for Al surfaces. Copyright © 2016 Elsevier B.V. All rights reserved.

Surface plasmon-enhanced fluorescence on Au nanohole array for prostate-specific antigen detection

PubMed Central

Zhang, Qingwen; Wu, Lin; Wong, Ten It; Zhang, Jinling; Liu, Xiaohu; Zhou, Xiaodong; Bai, Ping; Liedberg, Bo; Wang, Yi

2017-01-01

Localized surface plasmon (LSP) has been widely applied for the enhancement of fluorescence emission for biosensing owing to its potential for strong field enhancement. However, due to its small penetration depth, LSP offers limited fluorescence enhancement over a whole sensor chip and, therefore, insufficient sensitivity for the detection of biomolecules, especially large molecules. We demonstrate the simultaneous excitation of LSP and propagating surface plasmon (PSP) on an Au nanohole array under Kretschmann configuration for the detection of prostate-specific antigen with a sandwich immunoassay. The proposed method combines the advantages of high field enhancement by LSP and large surface area probed by PSP field. The simulated results indicated that a maximum enhancement of electric field intensity up to 1,600 times can be achieved under the simultaneous excitation of LSP and PSP modes. The sandwich assay of PSA carried out on gold nanohole array substrate showed a limit of detection of 140 fM supporting coexcitation of LSP and PSP modes. The limit of detection was approximately sevenfold lower than that when only LSP was resonantly excited on the same substrate. The results of this study demonstrate high fluorescence enhancement through the coexcitation of LSP and PSP modes and pave a way for its implementation as a highly sensitive bioassay. PMID:28392689

Plasmonics Enhanced Smartphone Fluorescence Microscopy.

PubMed

Wei, Qingshan; Acuna, Guillermo; Kim, Seungkyeum; Vietz, Carolin; Tseng, Derek; Chae, Jongjae; Shir, Daniel; Luo, Wei; Tinnefeld, Philip; Ozcan, Aydogan

2017-05-18

Smartphone fluorescence microscopy has various applications in point-of-care (POC) testing and diagnostics, ranging from e.g., quantification of immunoassays, detection of microorganisms, to sensing of viruses. An important need in smartphone-based microscopy and sensing techniques is to improve the detection sensitivity to enable quantification of extremely low concentrations of target molecules. Here, we demonstrate a general strategy to enhance the detection sensitivity of a smartphone-based fluorescence microscope by using surface-enhanced fluorescence (SEF) created by a thin metal-film. In this plasmonic design, the samples are placed on a silver-coated glass slide with a thin spacer, and excited by a laser-diode from the backside through a glass hemisphere, generating surface plasmon polaritons. We optimized this mobile SEF system by tuning the metal-film thickness, spacer distance, excitation angle and polarization, and achieved ~10-fold enhancement in fluorescence intensity compared to a bare glass substrate, which enabled us to image single fluorescent particles as small as 50 nm in diameter and single quantum-dots. Furthermore, we quantified the detection limit of this platform by using DNA origami-based brightness standards, demonstrating that ~80 fluorophores per diffraction-limited spot can be readily detected by our mobile microscope, which opens up new opportunities for POC diagnostics and sensing applications in resource-limited-settings.

Anomaly detection in reconstructed quantum states using a machine-learning technique

NASA Astrophysics Data System (ADS)

Hara, Satoshi; Ono, Takafumi; Okamoto, Ryo; Washio, Takashi; Takeuchi, Shigeki

2014-02-01

The accurate detection of small deviations in given density matrices is important for quantum information processing. Here we propose a method based on the concept of data mining. We demonstrate that the proposed method can more accurately detect small erroneous deviations in reconstructed density matrices, which contain intrinsic fluctuations due to the limited number of samples, than a naive method of checking the trace distance from the average of the given density matrices. This method has the potential to be a key tool in broad areas of physics where the detection of small deviations of quantum states reconstructed using a limited number of samples is essential.

Spinal arteriovenous shunts: accuracy of shunt detection, localization, and subtype discrimination using spinal magnetic resonance angiography and manual contrast injection using a syringe.

PubMed

Unsrisong, Kittisak; Taphey, Siriporn; Oranratanachai, Kanokporn

2016-04-01

The object of this study was to evaluate the accuracy of fast 3D contrast-enhanced spinal MR angiography (MRA) using a manual syringe contrast injection technique for detecting and evaluating spinal arteriovenous shunts (AVSs). This was a retrospective study of 15 patients and 20 spinal MRA and catheter angiography studies. The accuracy of using spinal MRA to detect spinal AVS, localize shunts, and discriminate the subtype and dominant arterial feeder of the AVS were studied. There were 14 pretherapeutic and 6 posttherapeutic follow-up spinal MRA and catheter spinal angiography studies. The spinal AVS was demonstrated in 17 of 20 studies. Spinal MRA demonstrated 100% sensitivity for detecting spinal AVS with no false-negative results. A 97% accuracy rate for AVS subtype discrimination and shunt level localization was achieved using this study's diagnostic criteria. The detection of the dominant arterial feeder was limited to 9 of these 17 cases (53%). The fast 3D contrast-enhanced MRA technique performed using manual syringe contrast injection can detect the presence of a spinal AVS, locate the shunt level, and discriminate AVS subtype in most cases, but is limited when detecting small arterial feeders.

A Supercompressible, Elastic, and Bendable Carbon Aerogel with Ultrasensitive Detection Limits for Compression Strain, Pressure, and Bending Angle.

PubMed

Zhuo, Hao; Hu, Yijie; Tong, Xing; Chen, Zehong; Zhong, Linxin; Lai, Haihong; Liu, Linxiang; Jing, Shuangshuang; Liu, Qingzhong; Liu, Chuanfu; Peng, Xinwen; Sun, Runcang

2018-05-01

Ultralight and compressible carbon materials have promising applications in strain and pressure detection. However, it is still difficult to prepare carbon materials with supercompressibility, elasticity, stable strain-electrical signal response, and ultrasensitive detection limits, due to the challenge in structural regulation. Herein, a new strategy to prepare a reduced graphene oxide (rGO)-based lamellar carbon aerogels with unexpected and integrated performances by designing wave-shape rGO layers and enhancing the interaction among the rGO layers is demonstrated. Addition of cellulose nanocrystalline and low-molecular-weight carbon precursors enhances the interaction among rGO layers and thus produces an ultralight, flexible, and superstable structure. The as-prepared carbon aerogel displays a supercompressibility (undergoing an extreme strain of 99%) and elasticity (100% height retention after 10 000 cycles at a strain of 30%), as well as stable strain-current response (at least 10 000 cycles). Particularly, the carbon aerogel is ultrasensitive for detecting tiny change in strain (0.012%) and pressure (0.25 Pa), which are the lowest detection limits for compressible carbon materials reported in the literature. Moreover, the carbon aerogel exhibits excellent bendable performance and can detect an ultralow bending angle of 0.052°. Additionally, the carbon aerogel also demonstrates its promising application as wearable devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

True detection limits in an experimental linearly heteroscedastic system.. Part 2

NASA Astrophysics Data System (ADS)

Voigtman, Edward; Abraham, Kevin T.

2011-11-01

Despite much different processing of the experimental fluorescence detection data presented in Part 1, essentially the same estimates were obtained for the true theoretical Currie decision levels ( YC and XC) and true Currie detection limits ( YD and XD). The obtained experimental values, for 5% probability of false positives and 5% probability of false negatives, were YC = 56.0 mV, YD = 125. mV, XC = 0.132 μg/mL and XD = 0.293 μg/mL. For 5% probability of false positives and 1% probability of false negatives, the obtained detection limits were YD = 158 . mV and XD = 0.371 μg/mL. Furthermore, by using bootstrapping methodology on the experimental data for the standards and the analytical blank, it was possible to validate previously published experimental domain expressions for the decision levels ( yC and xC) and detection limits ( yD and xD). This was demonstrated by testing the generated decision levels and detection limits for their performance in regard to false positives and false negatives. In every case, the obtained numbers of false negatives and false positives were as specified a priori.

Interferometric biosensing platform for multiplexed digital detection of viral pathogens and biomarkers

NASA Astrophysics Data System (ADS)

Daaboul, George

Label-free optical biosensors have been established as proven tools for monitoring specific biomolecular interactions. However, compact and robust embodiments of such instruments have yet to be introduced in order to provide sensitive, quantitative, and high-throughput biosensing for low-cost research and clinical applications. Here we present the interferometric reflectance-imaging sensor (IRIS). IRIS allows sensitive label free analysis using an inexpensive and durable multi-color LED illumination source on a silicon based surface. IRIS monitors biomolecular interaction through measurement of biomass addition to the sensor's surface. We demonstrate the capability of this system to dynamically monitor antigen---antibody interactions with a noise floor of 5.2 pg/mm 2 and DNA single mismatch detection under isothermal melting conditions in an array format. Ensemble detection of binding events using IRIS did not provide the sensitivity needed for detection of infectious disease and biomarkers at clinically relevant concentrations. Therefore, a new approach was adapted to the IRIS platform that allowed the detection and identification of individual nanoparticles on the sensor's surface. The new detection method was termed single-particle IRIS (SP-IRIS). We developed two detection modalities for SP-IRIS. The first modality is when the target is a nanoparticle such as a virus. We verified that SP-IRIS can accurately detect and size individual viral particles. Then we demonstrated that single nanoparticle counting and sizing methodology on SP-IRIS leads to a specific and sensitive virus sensor that can be multiplexed. Finally, we developed an assay for the detection of Ebola and Marburg. A detection limit of 3 x 103 PFU/ml was demonstrated for vesicular stomatitis virus (VSV) pseudotyped with Ebola or Marburg virus glycoprotein. We have demonstrated that virus detection can be done in human whole blood directly without the need for sample preparation. The second modality of SP-IRIS we developed was single molecule counting of biomarkers utilizing a sandwich assay with detection probes labeled with gold nanoparticles. We demonstrated the use of single molecule counting in a nucleic acid assay for melanoma biomarker detection. We showed that a single molecule counting assay can lead to detection limits in the attomolar range. The improved sensitivity of IRIS utilizing single nanoparticle detection holds promise for a simple and low-cost technology for rapid virus detection and multiplexed molecular screening for clinical applications.

Cost-effective flow-through nanohole array-based biosensing platform for the label-free detection of uropathogenic E. coli in real time.

PubMed

Gomez-Cruz, Juan; Nair, Srijit; Manjarrez-Hernandez, Angel; Gavilanes-Parra, Sandra; Ascanio, Gabriel; Escobedo, Carlos

2018-05-30

Rapid, inexpensive and sensitive detection of uropathogenic Escherichia coli (UPEC), a common cause of ascending urinary tract infections (UTIs) including cystitis and pyelonephritis, is critical given the increasing number of cases and its recurrence worldwide. In this paper, we present a label-free nanoplasmonic sensing platform, built with off-the-shelf optical and electronic components, which can detect intact UPEC at concentrations lower than the physiological limit for UTI diagnosis, in real time. The sensing platform consists of a red LED light source, lens assembly, CMOS detector, Raspberry Pi interface in conjugation with a metallic flow-through nanohole array-based sensor. Detection is achieved exploiting nanoplasmonic phenomena from the nanohole arrays through surface plasmon resonance imaging (SPRi) technique. The platform has a bulk sensitivity of 212 pixel intensity unit (PIU)/refractive index unit (RIU), and a resolution in the order of 10 -6 RIU. We demonstrate capture and detection of UPEC with a detection limit of ~100 CFU/ml - a concentration well below the threshold limit for UTI diagnosis in clinical samples. We also demonstrate detection of UPEC in spiked human urine samples for two different concentrations of bacteria. This work is particularly relevant for point-of-care applications, especially for regions around the world where accessibility to medical facilities is heavily dependent upon economy, and availability. Copyright © 2018 Elsevier B.V. All rights reserved.

Long range surface plasmon resonance with ultra-high penetration depth for self-referenced sensing and ultra-low detection limit using diverging beam approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Isaacs, Sivan, E-mail: sivan.isaacs@gmail.com; Abdulhalim, Ibrahim; NEW CREATE Programme, School of Materials Science and Engineering, 1 CREATE Way, Research Wing, #02-06/08, Singapore 138602

2015-05-11

Using an insulator-metal-insulator structure with dielectric having refractive index (RI) larger than the analyte, long range surface plasmon (SP) resonance exhibiting ultra-high penetration depth is demonstrated for sensing applications of large bioentities at wavelengths in the visible range. Based on the diverging beam approach in Kretschmann-Raether configuration, one of the SP resonances is shown to shift in response to changes in the analyte RI while the other is fixed; thus, it can be used as a built in reference. The combination of the high sensitivity, high penetration depth and self-reference using the diverging beam approach in which a dark linemore » is detected of the high sensitivity, high penetration depth, self-reference, and the diverging beam approach in which a dark line is detected using large number of camera pixels with a smart algorithm for sub-pixel resolution, a sensor with ultra-low detection limit is demonstrated suitable for large bioentities.« less

Censoring approach to the detection limits in X-ray fluorescence analysis

NASA Astrophysics Data System (ADS)

Pajek, M.; Kubala-Kukuś, A.

2004-10-01

We demonstrate that the effect of detection limits in the X-ray fluorescence analysis (XRF), which limits the determination of very low concentrations of trace elements and results in appearance of the so-called "nondetects", can be accounted for using the statistical concept of censoring. More precisely, the results of such measurements can be viewed as the left random censored data, which can further be analyzed using the Kaplan-Meier method correcting the data for the presence of nondetects. Using this approach, the results of measured, detection limit censored concentrations can be interpreted in a nonparametric manner including the correction for the nondetects, i.e. the measurements in which the concentrations were found to be below the actual detection limits. Moreover, using the Monte Carlo simulation technique we show that by using the Kaplan-Meier approach the corrected mean concentrations for a population of the samples can be estimated within a few percent uncertainties with respect of the simulated, uncensored data. This practically means that the final uncertainties of estimated mean values are limited in fact by the number of studied samples and not by the correction procedure itself. The discussed random-left censoring approach was applied to analyze the XRF detection-limit-censored concentration measurements of trace elements in biomedical samples.

Procedures for determination of detection limits: application to high-performance liquid chromatography analysis of fat-soluble vitamins in human serum.

PubMed

Browne, Richard W; Whitcomb, Brian W

2010-07-01

Problems in the analysis of laboratory data commonly arise in epidemiologic studies in which biomarkers subject to lower detection thresholds are used. Various thresholds exist including limit of detection (LOD), limit of quantification (LOQ), and limit of blank (LOB). Choosing appropriate strategies for dealing with data affected by such limits relies on proper understanding of the nature of the detection limit and its determination. In this paper, we demonstrate experimental and statistical procedures generally used for estimating different detection limits according to standard procedures in the context of analysis of fat-soluble vitamins and micronutrients in human serum. Fat-soluble vitamins and micronutrients were analyzed by high-performance liquid chromatography with diode array detection. A simulated serum matrix blank was repeatedly analyzed for determination of LOB parametrically by using the observed blank distribution as well as nonparametrically by using ranks. The LOD was determined by combining information regarding the LOB with data from repeated analysis of standard reference materials (SRMs), diluted to low levels; from LOB to 2-3 times LOB. The LOQ was determined experimentally by plotting the observed relative standard deviation (RSD) of SRM replicates compared with the concentration, where the LOQ is the concentration at an RSD of 20%. Experimental approaches and example statistical procedures are given for determination of LOB, LOD, and LOQ. These quantities are reported for each measured analyte. For many analyses, there is considerable information available below the LOQ. Epidemiologic studies must understand the nature of these detection limits and how they have been estimated for appropriate treatment of affected data.

Direct, rapid, and label-free detection of enzyme-substrate interactions in physiological buffers using CMOS-compatible nanoribbon sensors.

PubMed

Mu, Luye; Droujinine, Ilia A; Rajan, Nitin K; Sawtelle, Sonya D; Reed, Mark A

2014-09-10

We demonstrate the versatility of Al2O3-passivated Si nanowire devices ("nanoribbons") in the analysis of enzyme-substrate interactions via the monitoring of pH change. Our approach is shown to be effective through the detection of urea in phosphate buffered saline (PBS), and penicillinase in PBS and urine, at limits of detection of <200 μM and 0.02 units/mL, respectively. The ability to extract accurate enzyme kinetics and the Michaelis-Menten constant (Km) from the acetylcholine-acetylcholinesterase reaction is also demonstrated.

Rapid and sensitive detection of canine parvovirus type 2 by recombinase polymerase amplification.

PubMed

Wang, Jianchang; Liu, Libing; Li, Ruiwen; Wang, Jinfeng; Fu, Qi; Yuan, Wanzhe

2016-04-01

A novel recombinase polymerase amplification (RPA)-based method for detection of canine parvovirus type 2 (CPV-2) was developed. Sensitivity analysis showed that the detection limit of RPA was 10 copies of CPV-2 genomic DNA. RPA amplified both CPV-2a and -2b DNA but did not amplify the template of other important dog viruses (CCoV, PRV or CDV), demonstrating high specificity. The method was further validated with 57 canine fecal samples. An outstanding advantage of RPA is that it is an isothermal reaction and can be performed in a water bath, making RPA a potential alternative method for CPV-2 detection in resource-limited settings.

Rapid Detection of Ebola Virus with a Reagent-Free, Point-of-Care Biosensor

PubMed Central

Baca, Justin T.; Severns, Virginia; Lovato, Debbie; Branch, Darren W.; Larson, Richard S.

2015-01-01

Surface acoustic wave (SAW) sensors can rapidly detect Ebola antigens at the point-of-care without the need for added reagents, sample processing, or specialized personnel. This preliminary study demonstrates SAW biosensor detection of the Ebola virus in a concentration-dependent manner. The detection limit with this methodology is below the average level of viremia detected on the first day of symptoms by PCR. We observe a log-linear sensor response for highly fragmented Ebola viral particles, with a detection limit corresponding to 1.9 × 104 PFU/mL prior to virus inactivation. We predict greatly improved sensitivity for intact, infectious Ebola virus. This point-of-care methodology has the potential to detect Ebola viremia prior to symptom onset, greatly enabling infection control and rapid treatment. This biosensor platform is powered by disposable AA batteries and can be rapidly adapted to detect other emerging diseases in austere conditions. PMID:25875186

Electrochemistry and Spectroelectrochemistry of Luminescent Europium Complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lines, Amanda M.; Wang, Zheming; Clark, Sue B.

Fast, cost effective, and robust means of detecting and quantifying lanthanides are needed for supporting more efficient tracking within the nuclear, medicinal, and industrial fields. Spectroelectrochemistry (SEC) is a powerful technique combining electrochemistry and spectroscopy that can meet those needs. The primary limitation of SEC as a detection method for lanthanides is their low molar absorptivity in absorbance based measurements and low emission intensities in fluorescence based measurements; both lead to high limits of detection. These limitations can be circumvented by complexing the lanthanides with sensitizing ligands that enhance fluorescence, thereby dropping the limits of detection. Complexation may also stabilizemore » the metal ions in solution and improve the electrochemical reversibility, or Nernstian behavior, of the redox couples. To demonstrate this concept, studies were completed using europium in complexes with four different sensitizing ligands. Initial work indicates Eu in the four complexes studied does display the necessary characteristics for SEC analysis, which was successfully and reproducibly applied to all Eu complexes.« less

LITE microscopy: Tilted light-sheet excitation of model organisms offers high resolution and low photobleaching

PubMed Central

Gerbich, Therese M.; Rana, Kishan; Suzuki, Aussie; Schaefer, Kristina N.; Heppert, Jennifer K.; Boothby, Thomas C.; Allbritton, Nancy L.; Gladfelter, Amy S.; Maddox, Amy S.

2018-01-01

Fluorescence microscopy is a powerful approach for studying subcellular dynamics at high spatiotemporal resolution; however, conventional fluorescence microscopy techniques are light-intensive and introduce unnecessary photodamage. Light-sheet fluorescence microscopy (LSFM) mitigates these problems by selectively illuminating the focal plane of the detection objective by using orthogonal excitation. Orthogonal excitation requires geometries that physically limit the detection objective numerical aperture (NA), thereby limiting both light-gathering efficiency (brightness) and native spatial resolution. We present a novel live-cell LSFM method, lateral interference tilted excitation (LITE), in which a tilted light sheet illuminates the detection objective focal plane without a sterically limiting illumination scheme. LITE is thus compatible with any detection objective, including oil immersion, without an upper NA limit. LITE combines the low photodamage of LSFM with high resolution, high brightness, and coverslip-based objectives. We demonstrate the utility of LITE for imaging animal, fungal, and plant model organisms over many hours at high spatiotemporal resolution. PMID:29490939

Demonstration of Regenerable, Large-scale Ion Exchange System Using WBA Resin in Rialto, CA

DTIC Science & Technology

2008-03-01

Saturation Index MCL – Maximum Contaminant Level NaOH – Sodium hydroxide NDBA – N-nitrosodi-n-butylamine NDEA – N-nitrosodiethylamine NDMA ...analyzed using EPA Method 521. NDMA was 2.6 ppt with a detection limit of 2 ppt. All other nitrosamines analyzed (including NDEA, NDBA, NDPA, NMEA...using IC/MS/MS. Nitrosamines were analyzed using EPA Method 521. NDMA was 2.6 ppt with a detection limit of 2 ppt. All other nitrosamines

Demonstration of Regenerable, Large-Scale Ion Exchange System Using WBA Resin in Rialto, CA

DTIC Science & Technology

2008-03-05

NDMA – N-nitrosodimethylamine NDPA – N-nitrosodi-n-propylamine NMEA – N-nitrosomethylethylamine NMOR – N-nitrosomorpholine NPDES – National Pollutant...were analyzed using EPA Method 521. NDMA was 2.6 ppt with a detection limit of 2 ppt. All other nitrosamines analyzed (including NDEA, NDBA, NDPA...ppb) using IC/MS/MS. Nitrosamines were analyzed using EPA Method 521. NDMA was 2.6 ppt with a detection limit of 2 ppt. All other nitrosamines

Quartz-Seq2: a high-throughput single-cell RNA-sequencing method that effectively uses limited sequence reads.

PubMed

Sasagawa, Yohei; Danno, Hiroki; Takada, Hitomi; Ebisawa, Masashi; Tanaka, Kaori; Hayashi, Tetsutaro; Kurisaki, Akira; Nikaido, Itoshi

2018-03-09

High-throughput single-cell RNA-seq methods assign limited unique molecular identifier (UMI) counts as gene expression values to single cells from shallow sequence reads and detect limited gene counts. We thus developed a high-throughput single-cell RNA-seq method, Quartz-Seq2, to overcome these issues. Our improvements in the reaction steps make it possible to effectively convert initial reads to UMI counts, at a rate of 30-50%, and detect more genes. To demonstrate the power of Quartz-Seq2, we analyzed approximately 10,000 transcriptomes from in vitro embryonic stem cells and an in vivo stromal vascular fraction with a limited number of reads.

Nonparametric rank regression for analyzing water quality concentration data with multiple detection limits.

PubMed

Fu, Liya; Wang, You-Gan

2011-02-15

Environmental data usually include measurements, such as water quality data, which fall below detection limits, because of limitations of the instruments or of certain analytical methods used. The fact that some responses are not detected needs to be properly taken into account in statistical analysis of such data. However, it is well-known that it is challenging to analyze a data set with detection limits, and we often have to rely on the traditional parametric methods or simple imputation methods. Distributional assumptions can lead to biased inference and justification of distributions is often not possible when the data are correlated and there is a large proportion of data below detection limits. The extent of bias is usually unknown. To draw valid conclusions and hence provide useful advice for environmental management authorities, it is essential to develop and apply an appropriate statistical methodology. This paper proposes rank-based procedures for analyzing non-normally distributed data collected at different sites over a period of time in the presence of multiple detection limits. To take account of temporal correlations within each site, we propose an optimal linear combination of estimating functions and apply the induced smoothing method to reduce the computational burden. Finally, we apply the proposed method to the water quality data collected at Susquehanna River Basin in United States of America, which clearly demonstrates the advantages of the rank regression models.

Multiplexed Paper Analytical Device for Quantification of Metals using Distance-Based Detection

PubMed Central

Cate, David M.; Noblitt, Scott D.; Volckens, John; Henry, Charles S.

2015-01-01

Exposure to metal-containing aerosols has been linked with adverse health outcomes for almost every organ in the human body. Commercially available techniques for quantifying particulate metals are time-intensive, laborious, and expensive; often sample analysis exceeds $100. We report a simple technique, based upon a distance-based detection motif, for quantifying metal concentrations of Ni, Cu, and Fe in airborne particulate matter using microfluidic paper-based analytical devices. Paper substrates are used to create sensors that are self-contained, self-timing, and require only a drop of sample for operation. Unlike other colorimetric approaches in paper microfluidics that rely on optical instrumentation for analysis, with distance-based detection, analyte is quantified visually based on the distance of a colorimetric reaction, similar to reading temperature on a thermometer. To demonstrate the effectiveness of this approach, Ni, Cu, and Fe were measured individually in single-channel devices; detection limits as low as 0.1, 0.1, and 0.05 µg were reported for Ni, Cu, and Fe. Multiplexed analysis of all three metals was achieved with detection limits of 1, 5, and 1 µg for Ni, Cu, and Fe. We also extended the dynamic range for multi-analyte detection by printing concentration gradients of colorimetric reagents using an off the shelf inkjet printer. Analyte selectivity was demonstrated for common interferences. To demonstrate utility of the method, Ni, Cu, and Fe were measured from samples of certified welding fume; levels measured with paper sensors matched known values determined gravimetrically. PMID:26009988

Wide-field airborne laser diode array illuminator: demonstration results

NASA Astrophysics Data System (ADS)

Suiter, H. R.; Holloway, J. H., Jr.; Tinsley, K. R.; Pham, C. N.; Kloess, E. C., III; Witherspoon, N. H.; Stetson, S.; Crosby, F.; Nevis, A.; McCarley, K. A.; Seales, T. C.

2005-06-01

The Airborne Littoral Reconnaissance Technology (ALRT) program has successfully demonstrated the Wide-Field Airborne Laser Diode Array Illuminator (ALDAI-W). This illuminator is designed to illuminate a large area from the air with limited power, weight, and volume. A detection system, of which the ALDAI-W is a central portion, is capable of detecting surface-laid minefields in absolute darkness, extending the allowed mission times to night operations. This will be an overview report, giving processing results and suggested paths for additional development.

Point-of-care detection and real-time monitoring of intravenously delivered drugs via tubing with an integrated SERS sensor

NASA Astrophysics Data System (ADS)

Wu, Hsin-Yu; Cunningham, Brian T.

2014-04-01

We demonstrate an approach for detection, identification, and kinetic monitoring of drugs flowing within tubing, through the use of a plasmonic nanodome array (PNA) surface. The PNA structures are fabricated using a low-cost nanoreplica molding process upon a flexible plastic substrate that is subsequently integrated with a flow cell that connects in series with ordinary intravenous (IV) drug delivery tubing. To investigate the potential clinical applications for point-of-care detection and real-time monitoring, we perform SERS detection of ten pharmaceutical compounds (hydrocodone, levorphanol, morphine, oxycodone, methadone, phenobarbital, dopamine, diltiazem, promethazine, and mitoxantrone). We demonstrate dose-dependent SERS signal magnitude, resulting in detection limits (ng ml-1) well below typical administered dosages (mg ml-1). Further, we show that the detected drugs are not permanently attached to the PNA surface, and thus our approach is capable of performing continuous monitoring of drug delivery as materials flow through IV tubing that is connected in series with the sensor. Finally, we demonstrate the potential co-detection of multiple drugs when they are mixed together, and show excellent reproducibility and stability of SERS measurements for periods extending at least five days. The capabilities reported here demonstrate the potential to use PNA SERS surfaces for enhancing the safety of IV drug delivery.We demonstrate an approach for detection, identification, and kinetic monitoring of drugs flowing within tubing, through the use of a plasmonic nanodome array (PNA) surface. The PNA structures are fabricated using a low-cost nanoreplica molding process upon a flexible plastic substrate that is subsequently integrated with a flow cell that connects in series with ordinary intravenous (IV) drug delivery tubing. To investigate the potential clinical applications for point-of-care detection and real-time monitoring, we perform SERS detection of ten pharmaceutical compounds (hydrocodone, levorphanol, morphine, oxycodone, methadone, phenobarbital, dopamine, diltiazem, promethazine, and mitoxantrone). We demonstrate dose-dependent SERS signal magnitude, resulting in detection limits (ng ml-1) well below typical administered dosages (mg ml-1). Further, we show that the detected drugs are not permanently attached to the PNA surface, and thus our approach is capable of performing continuous monitoring of drug delivery as materials flow through IV tubing that is connected in series with the sensor. Finally, we demonstrate the potential co-detection of multiple drugs when they are mixed together, and show excellent reproducibility and stability of SERS measurements for periods extending at least five days. The capabilities reported here demonstrate the potential to use PNA SERS surfaces for enhancing the safety of IV drug delivery. Electronic supplementary information (ESI) available: Fabrication of PNA substrates, fabrication details of the flow cell, details of FDTD simulation, characterization of the scattering volume, and detection of diltiazem diluted in DI water and PBS. See DOI: 10.1039/c4nr00027g

Censoring: a new approach for detection limits in total-reflection X-ray fluorescence

NASA Astrophysics Data System (ADS)

Pajek, M.; Kubala-Kukuś, A.; Braziewicz, J.

2004-08-01

It is shown that the detection limits in the total-reflection X-ray fluorescence (TXRF), which restrict quantification of very low concentrations of trace elements in the samples, can be accounted for using the statistical concept of censoring. We demonstrate that the incomplete TXRF measurements containing the so-called "nondetects", i.e. the non-measured concentrations falling below the detection limits and represented by the estimated detection limit values, can be viewed as the left random-censored data, which can be further analyzed using the Kaplan-Meier (KM) method correcting for nondetects. Within this approach, which uses the Kaplan-Meier product-limit estimator to obtain the cumulative distribution function corrected for the nondetects, the mean value and median of the detection limit censored concentrations can be estimated in a non-parametric way. The Monte Carlo simulations performed show that the Kaplan-Meier approach yields highly accurate estimates for the mean and median concentrations, being within a few percent with respect to the simulated, uncensored data. This means that the uncertainties of KM estimated mean value and median are limited in fact only by the number of studied samples and not by the applied correction procedure for nondetects itself. On the other hand, it is observed that, in case when the concentration of a given element is not measured in all the samples, simple approaches to estimate a mean concentration value from the data yield erroneous, systematically biased results. The discussed random-left censoring approach was applied to analyze the TXRF detection-limit-censored concentration measurements of trace elements in biomedical samples. We emphasize that the Kaplan-Meier approach allows one to estimate the mean concentrations being substantially below the mean level of detection limits. Consequently, this approach gives a new access to lower the effective detection limits for TXRF method, which is of prime interest for investigation of metallic impurities on the silicon wafers.

Non-volatile analysis in fruits by laser resonant ionization spectrometry: application to resveratrol (3,5,4'-trihydroxystilbene) in grapes

NASA Astrophysics Data System (ADS)

Montero, C.; Orea, J. M.; Soledad Muñoz, M.; Lobo, R. F. M.; González Ureña, A.

A laser desorption (LD) coupled with resonance-enhanced multiphoton ionisation (REMPI) and time-of-flight mass spectrometry (TOFMS) technique for non-volatile trace analysis compounds is presented. Essential features are: (a) an enhanced desorption yield due to the mixing of metal powder with the analyte in the sample preparation, (b) a high resolution, great sensitivity and low detection limit due to laser resonant ionisation and mass spectrometry detection. Application to resveratrol content in grapes demonstrated the capability of the analytical method with a sensitivity of 0.2 pg per single laser shot and a detection limit of 5 ppb.

Swept-source based, single-shot, multi-detectable velocity range Doppler optical coherence tomography

PubMed Central

Meemon, Panomsak; Rolland, Jannick P.

2010-01-01

Phase-Resolved Doppler Optical Coherence Tomography (PR-DOCT) allows visualization and characterization of the location, direction, velocity, and profile of flow activity embedded in a static sample structure. The detectable Velocity Dynamic Range (VDR) of each particular PR-DOCT system is governed by a detectable Doppler phase shift, a flow angle, and an acquisition time interval used to determine the Doppler phase shift. In general, the lower boundary of the detectable Doppler phase shift is limited by the phase stability of the system, while the upper boundary is limited by the π phase ambiguity. For a given range of detectable Doppler phase shift, shortening the acquisition duration will increase not only the maximum detectable velocity but unfortunately also the minimum detectable velocity, which may lead to the invisibility of a slow flow. In this paper, we present an alternative acquisition scheme for PR-DOCT that extends the lower limit of the velocity dynamic range, while maintaining the maximum detectable velocity, hence increasing the overall VDR of PR-DOCT system. The essence of the approach is to implement a technique of multi-scale measurement to simultaneously acquire multiple VDRs in a single measurement. We demonstrate an example of implementation of the technique in a dual VDR DOCT, where two Doppler maps having different detectable VDRs were simultaneously detected, processed, and displayed in real time. One was a fixed VDR DOCT capable of measuring axial velocity of up to 10.9 mm/s without phase unwrapping. The other was a variable VDR DOCT capable of adjusting its detectable VDR to reveal slow flow information down to 11.3 μm/s. The technique is shown to effectively extend the overall detectable VDR of the PR-DOCT system. Examples of real time Doppler imaging of an African frog tadpole are demonstrated using the dual-VDR DOCT system. PMID:21258521

Nanoparticle-Functionalized Porous Polymer Monolith Detection Elements for Surface-Enhanced Raman Scattering

PubMed Central

Liu, Jikun; White, Ian; DeVoe, Don L.

2011-01-01

The use of porous polymer monoliths functionalized with silver nanoparticles is introduced in this work for high-sensitivity surface-enhanced Raman scattering (SERS) detection. Preparation of the SERS detection elements is a simple process comprising the synthesis of a discrete polymer monolith section within a silica capillary, followed by physically trapping silver nanoparticle aggregates within the monolith matrix. A SERS detection limit of 220 fmol for Rhodamine 6G (R6G) is demonstrated, with excellent signal stability over a 24 h period. The capability of the SERS-active monolith for label-free detection of biomolecules was demonstrated by measurements of bradykinin and cyctochrome c. The SERS-active monoliths can be readily integrated into miniaturized micro-total-analysis systems for on-line and label-free detection for a variety of biosensing, bioanalytical, and biomedical applications. PMID:21322579

An accurate and inexpensive color-based assay for detecting severe anemia in a limited-resource setting

PubMed Central

McGann, Patrick T.; Tyburski, Erika A.; de Oliveira, Vysolela; Santos, Brigida; Ware, Russell E.; Lam, Wilbur A.

2016-01-01

Severe anemia is an important cause of morbidity and mortality among children in resource-poor settings, but laboratory diagnostics are often limited in these locations. To address this need, we developed a simple, inexpensive, and color-based point-of-care (POC) assay to detect severe anemia. The purpose of this study was to evaluate the accuracy of this novel POC assay to detect moderate and severe anemia in a limited-resource setting. The study was a cross-sectional study conducted on children with sickle cell anemia in Luanda, Angola. The hemoglobin concentrations obtained by the POC assay were compared to reference values measured by a calibrated automated hematology analyzer. A total of 86 samples were analyzed (mean hemoglobin concentration 6.6 g/dL). There was a strong correlation between the hemoglobin concentrations obtained by the POC assay and reference values obtained from an automated hematology analyzer (r=0.88, P<0.0001). The POC assay demonstrated excellent reproducibility (r=0.93, P<0.0001) and the reagents appeared to be durable in a tropical setting (r=0.93, P<0.0001). For the detection of severe anemia that may require blood transfusion (hemoglobin <5 g/dL), the POC assay had sensitivity of 88.9% and specificity of 98.7%. These data demonstrate that an inexpensive (<$0.25 USD) POC assay accurately estimates low hemoglobin concentrations and has the potential to become a transformational diagnostic tool for severe anemia in limited-resource settings. PMID:26317494

Some final conclusions and supporting experiments related to the search for organic compounds on the surface of Mars

NASA Technical Reports Server (NTRS)

Biemann, K.; Lavoie, J. M., Jr.

1979-01-01

The Viking molecular analysis experiment has demonstrated the absence (within the detection limits which range from levels of parts per million to below parts per billion) of organic substances in the Martian surface soil at the two Viking landing sites. Laboratory experiments with sterile and nonsterile antarctic samples further demonstrate the capability and reliability of the instrument. The circumstances under which organic components could have escaped detection, such as inaccessibility or extreme thermal stability of organic polymers, are discussed but are found to be unlikely. The inability of the instrument to detect free oxygen evolved from soil samples is pointed out.

Theoretical limitations of quantification for noncompetitive sandwich immunoassays.

PubMed

Woolley, Christine F; Hayes, Mark A; Mahanti, Prasun; Douglass Gilman, S; Taylor, Tom

2015-11-01

Immunoassays exploit the highly selective interaction between antibodies and antigens to provide a vital method for biomolecule detection at low concentrations. Developers and practitioners of immunoassays have long known that non-specific binding often restricts immunoassay limits of quantification (LOQs). Aside from non-specific binding, most efforts by analytical chemists to reduce the LOQ for these techniques have focused on improving the signal amplification methods and minimizing the limitations of the detection system. However, with detection technology now capable of sensing single-fluorescence molecules, this approach is unlikely to lead to dramatic improvements in the future. Here, fundamental interactions based on the law of mass action are analytically connected to signal generation, replacing the four- and five-parameter fittings commercially used to approximate sigmoidal immunoassay curves and allowing quantitative consideration of non-specific binding and statistical limitations in order to understand the ultimate detection capabilities of immunoassays. The restrictions imposed on limits of quantification by instrumental noise, non-specific binding, and counting statistics are discussed based on equilibrium relations for a sandwich immunoassay. Understanding the maximal capabilities of immunoassays for each of these regimes can greatly assist in the development and evaluation of immunoassay platforms. While many studies suggest that single molecule detection is possible through immunoassay techniques, here, it is demonstrated that the fundamental limit of quantification (precision of 10 % or better) for an immunoassay is approximately 131 molecules and this limit is based on fundamental and unavoidable statistical limitations.

Comparison of detection limits in environmental analysis--is it possible? An approach on quality assurance in the lower working range by verification.

PubMed

Geiss, S; Einax, J W

2001-07-01

Detection limit, reporting limit and limit of quantitation are analytical parameters which describe the power of analytical methods. These parameters are used for internal quality assurance and externally for competing, especially in the case of trace analysis in environmental compartments. The wide variety of possibilities for computing or obtaining these measures in literature and in legislative rules makes any comparison difficult. Additionally, a host of terms have been used within the analytical community to describe detection and quantitation capabilities. Without trying to create an order for the variety of terms, this paper is aimed at providing a practical proposal for answering the main questions for the analysts concerning quality measures above. These main questions and related parameters were explained and graphically demonstrated. Estimation and verification of these parameters are the two steps to get real measures. A rule for a practical verification is given in a table, where the analyst can read out what to measure, what to estimate and which criteria have to be fulfilled. In this manner verified parameters detection limit, reporting limit and limit of quantitation now are comparable and the analyst himself is responsible to the unambiguity and reliability of these measures.

Minimum Detectable Dose as a Measure of Bioassay Programme Capability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carbaugh, Eugene H.

2003-01-01

This paper suggests that minimum detectable dose (MDD) be used to describe the capability of bioassay programs for which intakes are expected to be rare. This allows expression of the capability in units that correspond directly to primary dose limits. The concept uses the well-established analytical statistic minimum detectable amount (MDA) as the starting point and assumes MDA detection at a prescribed time post intake. The resulting dose can then be used as an indication of the adequacy or capability of the program for demonstrating compliance with the performance criteria. MDDs can be readily tabulated or plotted to demonstrate themore » effectiveness of different types of monitoring programs. The inclusion of cost factors for bioassay measurements can allow optimisation.« less

Minimum detectable dose as a measure of bioassay programme capability.

PubMed

Carbaugh, E H

2003-01-01

This paper suggests that minimum detectable dose (MDD) be used to describe the capability of bioassay programmes for which intakes are expected to be rare. This allows expression of the capability in units that correspond directly to primary dose limits. The concept uses the well established analytical statistic minimum detectable amount (MDA) as the starting point, and assumes MDA detection at a prescribed time post-intake. The resulting dose can then be used as an indication of the adequacy or capability of the programme for demonstrating compliance with the performance criteria. MDDs can be readily tabulated or plotted to demonstrate the effectiveness of different types of monitoring programmes. The inclusion of cost factors for bioassay measurements can allow optimisation.

A label-free aptamer-fluorophore assembly for rapid and specific detection of cocaine in biofluids.

PubMed

Roncancio, Daniel; Yu, Haixiang; Xu, Xiaowen; Wu, Shuo; Liu, Ran; Debord, Joshua; Lou, Xinhui; Xiao, Yi

2014-11-18

We report a rapid and specific aptamer-based method for one-step cocaine detection with minimal reagent requirements. The feasibility of aptamer-based detection has been demonstrated with sensors that operate via target-induced conformational change mechanisms, but these have generally exhibited limited target sensitivity. We have discovered that the cocaine-binding aptamer MNS-4.1 can also bind the fluorescent molecule 2-amino-5,6,7-trimethyl-1,8-naphthyridine (ATMND) and thereby quench its fluorescence. We subsequently introduced sequence changes into MNS-4.1 to engineer a new cocaine-binding aptamer (38-GC) that exhibits higher affinity to both ligands, with reduced background signal and increased signal gain. Using this aptamer, we have developed a new sensor platform that relies on the cocaine-mediated displacement of ATMND from 38-GC as a result of competitive binding. We demonstrate that our sensor can detect cocaine within seconds at concentrations as low as 200 nM, which is 50-fold lower than existing assays based on target-induced conformational change. More importantly, our assay achieves successful cocaine detection in body fluids, with a limit of detection of 10.4, 18.4, and 36 μM in undiluted saliva, urine, and serum samples, respectively.

Point-of-care detection and real-time monitoring of intravenously delivered drugs via tubing with an integrated SERS sensor.

PubMed

Wu, Hsin-Yu; Cunningham, Brian T

2014-05-21

We demonstrate an approach for detection, identification, and kinetic monitoring of drugs flowing within tubing, through the use of a plasmonic nanodome array (PNA) surface. The PNA structures are fabricated using a low-cost nanoreplica molding process upon a flexible plastic substrate that is subsequently integrated with a flow cell that connects in series with ordinary intravenous (IV) drug delivery tubing. To investigate the potential clinical applications for point-of-care detection and real-time monitoring, we perform SERS detection of ten pharmaceutical compounds (hydrocodone, levorphanol, morphine, oxycodone, methadone, phenobarbital, dopamine, diltiazem, promethazine, and mitoxantrone). We demonstrate dose-dependent SERS signal magnitude, resulting in detection limits (ng ml(-1)) well below typical administered dosages (mg ml(-1)). Further, we show that the detected drugs are not permanently attached to the PNA surface, and thus our approach is capable of performing continuous monitoring of drug delivery as materials flow through IV tubing that is connected in series with the sensor. Finally, we demonstrate the potential co-detection of multiple drugs when they are mixed together, and show excellent reproducibility and stability of SERS measurements for periods extending at least five days. The capabilities reported here demonstrate the potential to use PNA SERS surfaces for enhancing the safety of IV drug delivery.

An Enzyme-Free Signal Amplification Technique for Ultrasensitive Colorimetric Assay of Disease Biomarkers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ye, Haihang; Yang, Kuikun; Tao, Jing

Enzyme-based colorimetric assays have been widely used in research labs and clinical diagnosis for decades. Nevertheless, as constrained by the performance of enzymes, their detection sensitivity has not been substantially improved in recent years, which inhibits many critical applications such as early detection of cancers. In this work, we demonstrate an enzyme-free signal amplification technique, based on gold vesicles encapsulated with Pd-Ir nanoparticles as peroxidase mimics, for colorimetric assay of disease biomarkers with significantly enhanced sensitivity. This technique overcomes the intrinsic limitations of enzymes, thanks to the superior catalytic efficiency of peroxidase mimics and the efficient loading and release ofmore » these mimics. Using human prostate surface antigen as a model biomarker, we demonstrated that the enzyme-free assay could reach a limit of detection at the femtogram/mL level, which is over 10 3-fold lower than that of conventional enzyme-based assay when the same antibodies and similar procedure were used.« less

Refractive index sensor based on a polymer fiber directional coupler for low index sensing.

PubMed

Lee, Kwang Jo; Liu, Xiaoqi; Vuillemin, Nelly; Lwin, Richard; Leon-Saval, Sergio G; Argyros, Alexander; Kuhlmey, Boris T

2014-07-14

We propose, numerically analyze and experimentally demonstrate a novel refractive index sensor specialized for low index sensing. The device is based on a directional coupler architecture implemented in a single microstructured polymer optical fiber incorporating two waveguides within it: a single-mode core and a satellite waveguide consisting of a hollow high-index ring. This hollow channel is filled with fluid and the refractive index of the fluid is detected through changes to the wavelength at which resonant coupling occurs between the two waveguides. The sensor design was optimized for both higher sensitivity and lower detection limit, with simulations and experiments demonstrating a sensitivity exceeding 1.4 × 10(3) nm per refractive index unit. Simulations indicate a detection limit of ~2 × 10(-6) refractive index units is achievable. We also numerically investigate the performance for refractive index changes localized at the surface of the holes, a case of particular importance for biosensing.

An Enzyme-Free Signal Amplification Technique for Ultrasensitive Colorimetric Assay of Disease Biomarkers

DOE PAGES

Ye, Haihang; Yang, Kuikun; Tao, Jing; ...

2017-01-30

Enzyme-based colorimetric assays have been widely used in research labs and clinical diagnosis for decades. Nevertheless, as constrained by the performance of enzymes, their detection sensitivity has not been substantially improved in recent years, which inhibits many critical applications such as early detection of cancers. In this work, we demonstrate an enzyme-free signal amplification technique, based on gold vesicles encapsulated with Pd-Ir nanoparticles as peroxidase mimics, for colorimetric assay of disease biomarkers with significantly enhanced sensitivity. This technique overcomes the intrinsic limitations of enzymes, thanks to the superior catalytic efficiency of peroxidase mimics and the efficient loading and release ofmore » these mimics. Using human prostate surface antigen as a model biomarker, we demonstrated that the enzyme-free assay could reach a limit of detection at the femtogram/mL level, which is over 10 3-fold lower than that of conventional enzyme-based assay when the same antibodies and similar procedure were used.« less

Peptide Functionalized Gold Nanorods for the Sensitive Detection of a Cardiac Biomarker Using Plasmonic Paper Devices.

PubMed

Tadepalli, Sirimuvva; Kuang, Zhifeng; Jiang, Qisheng; Liu, Keng-Ku; Fisher, Marilee A; Morrissey, Jeremiah J; Kharasch, Evan D; Slocik, Joseph M; Naik, Rajesh R; Singamaneni, Srikanth

2015-11-10

The sensitivity of localized surface plasmon resonance (LSPR) of metal nanostructures to adsorbates lends itself to a powerful class of label-free biosensors. Optical properties of plasmonic nanostructures are dependent on the geometrical features and the local dielectric environment. The exponential decay of the sensitivity from the surface of the plasmonic nanotransducer calls for the careful consideration in its design with particular attention to the size of the recognition and analyte layers. In this study, we demonstrate that short peptides as biorecognition elements (BRE) compared to larger antibodies as target capture agents offer several advantages. Using a bioplasmonic paper device (BPD), we demonstrate the selective and sensitive detection of the cardiac biomarker troponin I (cTnI). The smaller sized peptide provides higher sensitivity and a lower detection limit using a BPD. Furthermore, the excellent shelf-life and thermal stability of peptide-based LSPR sensors, which precludes the need for special storage conditions, makes it ideal for use in resource-limited settings.

A megahertz-frequency tunable piecewise-linear electromechanical resonator realized via nonlinear feedback

NASA Astrophysics Data System (ADS)

Bajaj, Nikhil; Chiu, George T.-C.; Rhoads, Jeffrey F.

2018-07-01

Vibration-based sensing modalities traditionally have relied upon monitoring small shifts in natural frequency in order to detect structural changes (such as those in mass or stiffness). In contrast, bifurcation-based sensing schemes rely on the detection of a qualitative change in the behavior of a system as a parameter is varied. This can produce easy-to-detect changes in response amplitude with high sensitivity to structural change, but requires resonant devices with specific dynamic behavior which is not always easily reproduced. Desirable behavior for such devices can be produced reliably via nonlinear feedback circuitry, but has in past efforts been largely limited to sub-MHz operation, partially due to the time delay limitations present in certain nonlinear feedback circuits, such as multipliers. This work demonstrates the design and implementation of a piecewise-linear resonator realized via diode- and integrated circuit-based feedback electronics and a quartz crystal resonator. The proposed system is fabricated and characterized, and the creation and selective placement of the bifurcation points of the overall electromechanical system is demonstrated by tuning the circuit gains. The demonstrated circuit operates at 16 MHz. Preliminary modeling and analysis is presented that qualitatively agrees with the experimentally-observed behavior.

Stripping analysis of nanomolar perchlorate in drinking water with a voltammetric ion-selective electrode based on thin-layer liquid membrane.

PubMed

Kim, Yushin; Amemiya, Shigeru

2008-08-01

A highly sensitive analytical method is required for the assessment of nanomolar perchlorate contamination in drinking water as an emerging environmental problem. We developed the novel approach based on a voltammetric ion-selective electrode to enable the electrochemical detection of "redox-inactive" perchlorate at a nanomolar level without its electrolysis. The perchlorate-selective electrode is based on the submicrometer-thick plasticized poly(vinyl chloride) membrane spin-coated on the poly(3-octylthiophene)-modified gold electrode. The liquid membrane serves as the first thin-layer cell for ion-transfer stripping voltammetry to give low detection limits of 0.2-0.5 nM perchlorate in deionized water, commercial bottled water, and tap water under a rotating electrode configuration. The detection limits are not only much lower than the action limit (approximately 246 nM) set by the U.S. Environmental Protection Agency but also are comparable to the detection limits of the most sensitive analytical methods for detecting perchlorate, that is, ion chromatography coupled with a suppressed conductivity detector (0.55 nM) or electrospray ionization mass spectrometry (0.20-0.25 nM). The mass transfer of perchlorate in the thin-layer liquid membrane and aqueous sample as well as its transfer at the interface between the two phases were studied experimentally and theoretically to achieve the low detection limits. The advantages of ion-transfer stripping voltammetry with a thin-layer liquid membrane against traditional ion-selective potentiometry are demonstrated in terms of a detection limit, a response time, and selectivity.

Less-simplified models of dark matter for direct detection and the LHC

NASA Astrophysics Data System (ADS)

Choudhury, Arghya; Kowalska, Kamila; Roszkowski, Leszek; Sessolo, Enrico Maria; Williams, Andrew J.

2016-04-01

We construct models of dark matter with suppressed spin-independent scattering cross section utilizing the existing simplified model framework. Even simple combinations of simplified models can exhibit interference effects that cause the tree level contribution to the scattering cross section to vanish, thus demonstrating that direct detection limits on simplified models are not robust when embedded in a more complicated and realistic framework. In general for fermionic WIMP masses ≳ 10 GeV direct detection limits on the spin-independent scattering cross section are much stronger than those coming from the LHC. However these model combinations, which we call less-simplified models, represent situations where LHC searches become more competitive than direct detection experiments even for moderate dark matter mass. We show that a complementary use of several searches at the LHC can strongly constrain the direct detection blind spots by setting limits on the coupling constants and mediators' mass. We derive the strongest limits for combinations of vector + scalar, vector + "squark", and "squark" + scalar mediator, and present the corresponding projections for the LHC 14 TeV for a number of searches: mono-jet, jets + missing energy, and searches for heavy vector resonances.

Amplification-free point of care immunosensor for detecting type V collagen at a concentration level of ng/ml

NASA Astrophysics Data System (ADS)

Chung, Pei-Yu; Bracho-Sanchez, Evelyn R.; Jiang, Peng; Seagrave, JeanClare; Duncan, Matthew R.; Grotendorst, Gary R.; Schultz, Gregory; Batich, Christopher

2011-06-01

Point-of-care testing (POCT) is applicable in the immediate vicinity of the patient, where timely diagnosis or prognostic information could help doctors decide the following treatment. Among types of developed POCT, gold nanoparticle based lateral flow strip technology provides advantages such as simple operation, cost-effectiveness, and a user-friendly platform. Therefore, this type of POCT is most likely to be used in battlefields and developing countries. However, conventional lateral flow strips suffer from low detection limits. Although enzyme-linked amplification was demonstrated to improve the detection limit and sensitivity by stronger visible lines or by permitting electrochemical analytical instrumentation, the enzyme labels have potential to cause interference with other enzymes in our body fluids. To eliminate this limitation, we developed an amplification-free gold nanoparticle-based immunosensor applied for detecting collagen type V, which is produced or released abnormally during rejection of lung transplants and sulfur mustard exposure. By using suitable blocking protein to stabilize gold nanoparticles as the reporter probe, a low detection limit of ng/ml was achieved. This strategy is a promising platform for clinical POCT, with potential applications in military or disaster response.

Theoretical detection limit of PIXE analysis using 20 MeV proton beams

NASA Astrophysics Data System (ADS)

Ishii, Keizo; Hitomi, Keitaro

2018-02-01

Particle-induced X-ray emission (PIXE) analysis is usually performed using proton beams with energies in the range 2∼3 MeV because at these energies, the detection limit is low. The detection limit of PIXE analysis depends on the X-ray production cross-section, the continuous background of the PIXE spectrum and the experimental parameters such as the beam currents and the solid angle and detector efficiency of X-ray detector. Though the continuous background increases as the projectile energy increases, the cross-section of the X-ray increases as well. Therefore, the detection limit of high energy proton PIXE is not expected to increase significantly. We calculated the cross sections of continuous X-rays produced in several bremsstrahlung processes and estimated the detection limit of a 20 MeV proton PIXE analysis by modelling the Compton tail of the γ-rays produced in the nuclear reactions, and the escape effect on the secondary electron bremsstrahlung. We found that the Compton tail does not affect the detection limit when a thin X-ray detector is used, but the secondary electron bremsstrahlung escape effect does have an impact. We also confirmed that the detection limit of the PIXE analysis, when used with 4 μm polyethylene backing film and an integrated beam current of 1 μC, is 0.4∼2.0 ppm for proton energies in the range 10∼30 MeV and elements with Z = 16-90. This result demonstrates the usefulness of several 10 MeV cyclotrons for performing PIXE analysis. Cyclotrons with these properties are currently installed in positron emission tomography (PET) centers.

Applications of Fault Detection in Vibrating Structures

NASA Technical Reports Server (NTRS)

Eure, Kenneth W.; Hogge, Edward; Quach, Cuong C.; Vazquez, Sixto L.; Russell, Andrew; Hill, Boyd L.

2012-01-01

Structural fault detection and identification remains an area of active research. Solutions to fault detection and identification may be based on subtle changes in the time series history of vibration signals originating from various sensor locations throughout the structure. The purpose of this paper is to document the application of vibration based fault detection methods applied to several structures. Overall, this paper demonstrates the utility of vibration based methods for fault detection in a controlled laboratory setting and limitations of applying the same methods to a similar structure during flight on an experimental subscale aircraft.

Rapid detection of Ebola virus with a reagent-free, point-of-care biosensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baca, Justin T.; Severns, Virginia; Lovato, Debbie

Surface acoustic wave (SAW) sensors can rapidly detect Ebola antigens at the point-of-care without the need for added reagents, sample processing, or specialized personnel. This preliminary study demonstrates SAW biosensor detection of the Ebola virus in a concentration-dependent manner. The detection limit with this methodology is below the average level of viremia detected on the first day of symptoms by PCR. We observe a log-linear sensor response for highly fragmented Ebola viral particles, with a detection limit corresponding to 1.9 × 10⁴ PFU/mL prior to virus inactivation. We predict greatly improved sensitivity for intact, infectious Ebola virus. This point-of-care methodologymore » has the potential to detect Ebola viremia prior to symptom onset, greatly enabling infection control and rapid treatment. This biosensor platform is powered by disposable AA batteries and can be rapidly adapted to detect other emerging diseases in austere conditions.« less

Rapid detection of Ebola virus with a reagent-free, point-of-care biosensor

DOE PAGES

Baca, Justin T.; Severns, Virginia; Lovato, Debbie; ...

2015-04-14

Surface acoustic wave (SAW) sensors can rapidly detect Ebola antigens at the point-of-care without the need for added reagents, sample processing, or specialized personnel. This preliminary study demonstrates SAW biosensor detection of the Ebola virus in a concentration-dependent manner. The detection limit with this methodology is below the average level of viremia detected on the first day of symptoms by PCR. We observe a log-linear sensor response for highly fragmented Ebola viral particles, with a detection limit corresponding to 1.9 × 10⁴ PFU/mL prior to virus inactivation. We predict greatly improved sensitivity for intact, infectious Ebola virus. This point-of-care methodologymore » has the potential to detect Ebola viremia prior to symptom onset, greatly enabling infection control and rapid treatment. This biosensor platform is powered by disposable AA batteries and can be rapidly adapted to detect other emerging diseases in austere conditions.« less

A novel turn-on fluorescent probe for Al3 + and Fe3 + in aqueous solution and its imaging in living cells

NASA Astrophysics Data System (ADS)

Dai, Yanpeng; Fu, Jiaxin; Yao, Kun; Song, Qianqian; Xu, Kuoxi; Pang, Xiaobin

2018-03-01

A quinoline-based fluorescence probe has been prepared and characterized. Probe 1 showed a selective sensing ability for Al3 + and Fe3 + ions through fluorescence enhancement response at 515 nm when it was excited at 360 nm. In the presence of Fe3 + ion, probe 1 exhibited a detection limit of 2.10 × 10- 6 M. As for Al3 +, its detection limit of 3.58 × 10- 7 M was significantly lower than the highest limit of Al3 + in drinking water recommended by the WHO (7.41 μM), representing a rare example in reported fluorescent probe for Al3 + ion. The fluorescence microscopy experiments have demonstrated that probe 1 could be used in live cells for the detection of Al3 + and Fe3 + ions.

High-field modulated ion-selective field-effect-transistor (FET) sensors with sensitivity higher than the ideal Nernst sensitivity.

PubMed

Chen, Yi-Ting; Sarangadharan, Indu; Sukesan, Revathi; Hseih, Ching-Yen; Lee, Geng-Yen; Chyi, Jen-Inn; Wang, Yu-Lin

2018-05-29

Lead ion selective membrane (Pb-ISM) coated AlGaN/GaN high electron mobility transistors (HEMT) was used to demonstrate a whole new methodology for ion-selective FET sensors, which can create ultra-high sensitivity (-36 mV/log [Pb 2+ ]) surpassing the limit of ideal sensitivity (-29.58 mV/log [Pb 2+ ]) in a typical Nernst equation for lead ion. The largely improved sensitivity has tremendously reduced the detection limit (10 -10  M) for several orders of magnitude of lead ion concentration compared to typical ion-selective electrode (ISE) (10 -7  M). The high sensitivity was obtained by creating a strong filed between the gate electrode and the HEMT channel. Systematical investigation was done by measuring different design of the sensor and gate bias, indicating ultra-high sensitivity and ultra-low detection limit obtained only in sufficiently strong field. Theoretical study in the sensitivity consistently agrees with the experimental finding and predicts the maximum and minimum sensitivity. The detection limit of our sensor is comparable to that of Inductively-Coupled-Plasma Mass Spectrum (ICP-MS), which also has detection limit near 10 -10  M.

Dual-wavelength quantum cascade laser for trace gas spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jágerská, J.; Tuzson, B.; Mangold, M.

2014-10-20

We demonstrate a sequentially operating dual-wavelength quantum cascade laser with electrically separated laser sections, emitting single-mode at 5.25 and 6.25 μm. Based on a single waveguide ridge, this laser represents a considerable asset to optical sensing and trace gas spectroscopy, as it allows probing multiple gas species with spectrally distant absorption features using conventional optical setups without any beam combining optics. The laser capability was demonstrated in simultaneous NO and NO{sub 2} detection, reaching sub-ppb detection limits and selectivity comparable to conventional high-end spectroscopic systems.

Oxygen measurements at high pressures with vertical cavity surface-emitting lasers

NASA Astrophysics Data System (ADS)

Wang, J.; Sanders, S. T.; Jeffries, J. B.; Hanson, R. K.

Measurements of oxygen concentration at high pressures (to 10.9 bar) were made using diode-laser absorption of oxygen A-band transitions near 760 nm. The wide current-tuning frequency range (>30 cm-1) of vertical cavity surface-emitting lasers (VCSELs) was exploited to enable the first scanned-wavelength demonstration of diode-laser absorption at high pressures; this strategy is more robust than fixed-wavelength strategies, particularly in hostile environments. The wide tuning range and rapid frequency response of the current tuning were further exploited to demonstrate wavelength-modulation absorption spectroscopy in a high-pressure environment. The minimum detectable absorbance demonstrated, 1×10-4, corresponds to 800 ppm-m oxygen detectivity at room temperature and is limited by etalon noise. The rapid- and wide-frequency tunability of VCSELs should significantly expand the application domain of absorption-based sensors limited in the past by the small current-tuning frequency range (typically <2 cm-1) of conventional edge-emitting diode lasers.

A sensitive and selective resonance Rayleigh scattering method for quick detection of avidin using affinity labeling Au nanoparticles

NASA Astrophysics Data System (ADS)

Wang, Qi; Huang, Xi; Fu, Xuan; Deng, Huan; Ma, Meihu; Cai, Zhaoxia

2016-06-01

Avidin is a glycoprotein with antinutritional property, which should be limited in daily food. We developed an affinity biosensor system based on resonance Rayleigh scattering (RRS) and using affinity biotin labeling Au nanoparticles (AuNPs). This method was selective and sensitive for quick avidin detection due to the avidin-biotin affinitive interaction. Under optimal conditions, RRS intensity of biotin-AuNPs increase linearly with an increasing concentration of avidin from 5 to 160 ng/mL. The lower limit of detection was 0.59 ng/mL. This rapid and selective avidin detection method was used in synthetic samples and egg products with recoveries of between 102.97 and 107.92%, thereby demonstrating the feasible and practical application of this assay.

Quantitative surface-enhanced resonance Raman scattering of phthalocyanine-labelled oligonucleotides

PubMed Central

Macaskill, A.; Chernonosov, A. A.; Koval, V. V.; Lukyanets, E. A.; Fedorova, O. S.; Smith, W. E.; Faulds, K.; Graham, D.

2007-01-01

The evaluation of phthalocyanine labels for the surface-enhanced resonance Raman scattering (SERRS) detection of oligonucleotides is reported. Three phthalocyanine-labelled oligonucleotides were assessed, each containing a different metal centre. Detection limits for each labelled oligonucleotide were determined using two excitation frequencies where possible. Limits of detection as low as 2.8 × 10−11 mol. dm−3 were obtained which are comparable to standard fluorescently labelled probes used in previous SERRS studies. The identification of two phthalocyanine-labelled oligonucleotides without separation was also demonstrated indicating their suitability for multiplexing. This study extends the range of labels suitable for quantitative surface-enhanced resonance Raman scattering with silver nanoparticles and offers more flexibility and choice when considering SERRS for quantitative DNA detection. PMID:17289751

Multiplex detection of pancreatic cancer biomarkers using a SERS-based immunoassay

NASA Astrophysics Data System (ADS)

Banaei, Nariman; Foley, Anne; Houghton, Jean Marie; Sun, Yubing; Kim, Byung

2017-11-01

Early diagnosis of pancreatic cancer (PC) is critical to reduce the mortality rate of this disease. Current biological analysis approaches cannot robustly detect several low abundance PC biomarkers in sera, limiting the clinical application of these biomarkers. Enzyme linked immunosorbent assay and radioimmunoassay are two common platforms for detection of biomarkers; however, they suffer from some limitation. This study demonstrates a novel system for multiplex detection of pancreatic biomarkers CA19-9, MMP7 and MUC4 in sera samples with high sensitivity using surface enhanced Raman spectroscopy. Measuring the levels of these biomarkers in PC patients, pancreatitis patients, and healthy individuals reveals the unique expression pattern of these markers in PC patients, suggesting the great potential of using this approach for early diagnostics of PCs.

Identifying and detecting facial expressions of emotion in peripheral vision.

PubMed

Smith, Fraser W; Rossit, Stephanie

2018-01-01

Facial expressions of emotion are signals of high biological value. Whilst recognition of facial expressions has been much studied in central vision, the ability to perceive these signals in peripheral vision has only seen limited research to date, despite the potential adaptive advantages of such perception. In the present experiment, we investigate facial expression recognition and detection performance for each of the basic emotions (plus neutral) at up to 30 degrees of eccentricity. We demonstrate, as expected, a decrease in recognition and detection performance with increasing eccentricity, with happiness and surprised being the best recognized expressions in peripheral vision. In detection however, while happiness and surprised are still well detected, fear is also a well detected expression. We show that fear is a better detected than recognized expression. Our results demonstrate that task constraints shape the perception of expression in peripheral vision and provide novel evidence that detection and recognition rely on partially separate underlying mechanisms, with the latter more dependent on the higher spatial frequency content of the face stimulus.

Identifying and detecting facial expressions of emotion in peripheral vision

PubMed Central

Rossit, Stephanie

2018-01-01

Facial expressions of emotion are signals of high biological value. Whilst recognition of facial expressions has been much studied in central vision, the ability to perceive these signals in peripheral vision has only seen limited research to date, despite the potential adaptive advantages of such perception. In the present experiment, we investigate facial expression recognition and detection performance for each of the basic emotions (plus neutral) at up to 30 degrees of eccentricity. We demonstrate, as expected, a decrease in recognition and detection performance with increasing eccentricity, with happiness and surprised being the best recognized expressions in peripheral vision. In detection however, while happiness and surprised are still well detected, fear is also a well detected expression. We show that fear is a better detected than recognized expression. Our results demonstrate that task constraints shape the perception of expression in peripheral vision and provide novel evidence that detection and recognition rely on partially separate underlying mechanisms, with the latter more dependent on the higher spatial frequency content of the face stimulus. PMID:29847562

A large-scale superhydrophobic surface-enhanced Raman scattering (SERS) platform fabricated via capillary force lithography and assembly of Ag nanocubes for ultratrace molecular sensing.

PubMed

Tan, Joel Ming Rui; Ruan, Justina Jiexin; Lee, Hiang Kwee; Phang, In Yee; Ling, Xing Yi

2014-12-28

An analytical platform with an ultratrace detection limit in the atto-molar (aM) concentration range is vital for forensic, industrial and environmental sectors that handle scarce/highly toxic samples. Superhydrophobic surface-enhanced Raman scattering (SERS) platforms serve as ideal platforms to enhance detection sensitivity by reducing the random spreading of aqueous solution. However, the fabrication of superhydrophobic SERS platforms is generally limited due to the use of sophisticated and expensive protocols and/or suffers structural and signal inconsistency. Herein, we demonstrate a high-throughput fabrication of a stable and uniform superhydrophobic SERS platform for ultratrace molecular sensing. Large-area box-like micropatterns of the polymeric surface are first fabricated using capillary force lithography (CFL). Subsequently, plasmonic properties are incorporated into the patterned surfaces by decorating with Ag nanocubes using the Langmuir-Schaefer technique. To create a stable superhydrophobic SERS platform, an additional 25 nm Ag film is coated over the Ag nanocube-decorated patterned template followed by chemical functionalization with perfluorodecanethiol. Our resulting superhydrophobic SERS platform demonstrates excellent water-repellency with a static contact angle of 165° ± 9° and a consequent analyte concentration factor of 59-fold, as compared to its hydrophilic counterpart. By combining the analyte concentration effect of superhydrophobic surfaces with the intense electromagnetic "hot spots" of Ag nanocubes, our superhydrophobic SERS platform achieves an ultra-low detection limit of 10(-17) M (10 aM) for rhodamine 6G using just 4 μL of analyte solutions, corresponding to an analytical SERS enhancement factor of 10(13). Our fabrication protocol demonstrates a simple, cost- and time-effective approach for the large-scale fabrication of a superhydrophobic SERS platform for ultratrace molecular detection.

Step-scan T cell-based differential Fourier transform infrared photoacoustic spectroscopy (DFTIR-PAS) for detection of ambient air contaminants

NASA Astrophysics Data System (ADS)

Liu, Lixian; Mandelis, Andreas; Huan, Huiting; Melnikov, Alexander

2016-10-01

A step-scan differential Fourier transform infrared photoacoustic spectroscopy (DFTIR-PAS) using a commercial FTIR spectrometer was developed theoretically and experimentally for air contaminant monitoring. The configuration comprises two identical, small-size and low-resonance-frequency T cells satisfying the conflicting requirements of low chopping frequency and limited space in the sample compartment. Carbon dioxide (CO2) IR absorption spectra were used to demonstrate the capability of the DFTIR-PAS method to detect ambient pollutants. A linear amplitude response to CO2 concentrations from 100 to 10,000 ppmv was observed, leading to a theoretical detection limit of 2 ppmv. The differential mode was able to suppress the coherent noise, thereby imparting the DFTIR-PAS method with a better signal-to-noise ratio and lower theoretical detection limit than the single mode. The results indicate that it is possible to use step-scan DFTIR-PAS with T cells as a quantitative method for high sensitivity analysis of ambient contaminants.

Microfluidic LC Device with Orthogonal Sample Extraction for On-Chip MALDI-MS Detection

PubMed Central

Lazar, Iulia M.; Kabulski, Jarod L.

2013-01-01

A microfluidic device that enables on-chip matrix assisted laser desorption ionization-mass spectrometry (MALDI-MS) detection for liquid chromatography (LC) separations is described. The device comprises an array of functional elements to carry out LC separations, integrates a novel microchip-MS interface to facilitate the orthogonal transposition of the microfluidic LC channel into an array of reservoirs, and enables sensitive MALDI-MS detection directly from the chip. Essentially, the device provides a snapshot MALDI-MS map of the content of the separation channel present on the chip. The detection of proteins with biomarker potential from MCF10A breast epithelial cell extracts, and detection limits in the low fmol range, are demonstrated. In addition, the design of the novel LC-MALDI-MS chip entices the promotion of a new concept for performing sample separations within the limited time-frame that accompanies the dead-volume of a separation channel. PMID:23592150

Linear segmentation algorithm for detecting layer boundary with lidar.

PubMed

Mao, Feiyue; Gong, Wei; Logan, Timothy

2013-11-04

The automatic detection of aerosol- and cloud-layer boundary (base and top) is important in atmospheric lidar data processing, because the boundary information is not only useful for environment and climate studies, but can also be used as input for further data processing. Previous methods have demonstrated limitations in defining the base and top, window-size setting, and have neglected the in-layer attenuation. To overcome these limitations, we present a new layer detection scheme for up-looking lidars based on linear segmentation with a reasonable threshold setting, boundary selecting, and false positive removing strategies. Preliminary results from both real and simulated data show that this algorithm cannot only detect the layer-base as accurate as the simple multi-scale method, but can also detect the layer-top more accurately than that of the simple multi-scale method. Our algorithm can be directly applied to uncalibrated data without requiring any additional measurements or window size selections.

Noise-immune cavity-enhanced analytical atomic spectrometry - NICE-AAS - A technique for detection of elements down to zeptogram amounts

NASA Astrophysics Data System (ADS)

Axner, Ove; Ehlers, Patrick; Hausmaninger, Thomas; Silander, Isak; Ma, Weiguang

2014-10-01

Noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) is a powerful technique for detection of molecular compounds in gas phase that is based on a combination of two important concepts: frequency modulation spectroscopy (FMS) for reduction of noise, and cavity enhancement, for prolongation of the interaction length between the light and the sample. Due to its unique properties, it has demonstrated unparalleled detection sensitivity when it comes to detection of molecular constituents in the gas phase. However, despite these, it has so far not been used for detection of atoms, i.e. for elemental analysis. The present work presents an assessment of the expected performance of Doppler-broadened (Db) NICE-OHMS for analytical atomic spectrometry, then referred to as noise-immune cavity-enhanced analytical atomic spectrometry (NICE-AAS). After a description of the basic principles of Db-NICE-OHMS, the modulation and detection conditions for optimum performance are identified. Based on a previous demonstrated detection sensitivity of Db-NICE-OHMS of 5 × 10- 12 cm- 1 Hz- 1/2 (corresponding to a single-pass absorbance of 7 × 10- 11 over 10 s), the expected limits of detection (LODs) of Hg and Na by NICE-AAS are estimated. Hg is assumed to be detected in gas phase directly while Na is considered to be atomized in a graphite furnace (GF) prior to detection. It is shown that in the absence of spectral interferences, contaminated sample compartments, and optical saturation, it should be feasible to detect Hg down to 10 zg/cm3 (10 fg/m3 or 10- 5 ng/m3), which corresponds to 25 atoms/cm3, and Na down to 0.5 zg (zg = zeptogram = 10- 21 g), representing 50 zg/mL (parts-per-sextillion, pps, 1:1021) in liquid solution (assuming a sample of 10 μL) or solely 15 atoms injected into the GF, respectively. These LODs are several orders of magnitude lower (better) than any previous laser-based absorption technique previously demonstrated under atmospheric pressure conditions. It is prophesied that NICE-AAS could provide such high detection sensitivity that the instrumentation should not, by itself, be the limiting factor of an assessment of elemental abundance; the accuracy of an assessment would then instead be limited by concomitant species, e.g. originating from the handling procedures of the sample or the environment.

A smartphone-based diagnostic platform for rapid detection of Zika, chikungunya, and dengue viruses

PubMed Central

Priye, Aashish; Bird, Sara W.; Light, Yooli K.; Ball, Cameron S.; Negrete, Oscar A.; Meagher, Robert J.

2017-01-01

Current multiplexed diagnostics for Zika, dengue, and chikungunya viruses are situated outside the intersection of affordability, high performance, and suitability for use at the point-of-care in resource-limited settings. Consequently, insufficient diagnostic capabilities are a key limitation facing current Zika outbreak management strategies. Here we demonstrate highly sensitive and specific detection of Zika, chikungunya, and dengue viruses by coupling reverse-transcription loop-mediated isothermal amplification (RT-LAMP) with our recently developed quenching of unincorporated amplification signal reporters (QUASR) technique. We conduct reactions in a simple, inexpensive and portable “LAMP box” supplemented with a consumer class smartphone. The entire assembly can be powered by a 5 V USB source such as a USB power bank or solar panel. Our smartphone employs a novel algorithm utilizing chromaticity to analyze fluorescence signals, which improves the discrimination of positive/negative signals by 5-fold when compared to detection with traditional RGB intensity sensors or the naked eye. The ability to detect ZIKV directly from crude human sample matrices (blood, urine, and saliva) demonstrates our device’s utility for widespread clinical deployment. Together, these advances enable our system to host the key components necessary to expand the use of nucleic acid amplification-based detection assays towards point-of-care settings where they are needed most. PMID:28317856

Flexible Ag-C60 nano-biosensors based on surface plasmon coupled emission for clinical and forensic applications.

PubMed

Mulpur, Pradyumna; Yadavilli, Sairam; Mulpur, Praharsha; Kondiparthi, Neeharika; Sengupta, Bishwambhar; Rao, Apparao M; Podila, Ramakrishna; Kamisetti, Venkataramaniah

2015-10-14

The relatively low sensitivity of fluorescence detection schemes, which are mainly limited by the isotropic nature of fluorophore emission, can be overcome by utilizing surface plasmon coupled emission (SPCE). In this study, we demonstrate directional emission from fluorophores on flexible Ag-C60 SPCE sensor platforms for point-of-care sensing, in healthcare and forensic sensing scenarios, with at least 10 times higher sensitivity than traditional fluorescence sensing schemes. Adopting the highly sensitive Ag-C60 SPCE platform based on glass and novel low-cost flexible substrates, we report the unambiguous detection of acid-fast Mycobacterium tuberculosis (Mtb) bacteria at densities as low as 20 Mtb mm(-2); from non-acid-fast bacteria (e.g., E. coli and S. aureus), and the specific on-site detection of acid-fast sperm cells in human semen samples. In combination with the directional emission and high-sensitivity of SPCE platforms, we also demonstrate the utility of smartphones that can replace expensive and cumbersome detectors to enable rapid hand-held detection of analytes in resource-limited settings; a much needed critical advance to biosensors, for developing countries.

Optimization of a sample processing protocol for recovery of Bacillus anthracis spores from soil

USGS Publications Warehouse

Silvestri, Erin E.; Feldhake, David; Griffin, Dale; Lisle, John T.; Nichols, Tonya L.; Shah, Sanjiv; Pemberton, A; Schaefer III, Frank W

2016-01-01

Following a release of Bacillus anthracis spores into the environment, there is a potential for lasting environmental contamination in soils. There is a need for detection protocols for B. anthracis in environmental matrices. However, identification of B. anthracis within a soil is a difficult task. Processing soil samples helps to remove debris, chemical components, and biological impurities that can interfere with microbiological detection. This study aimed to optimize a previously used indirect processing protocol, which included a series of washing and centrifugation steps. Optimization of the protocol included: identifying an ideal extraction diluent, variation in the number of wash steps, variation in the initial centrifugation speed, sonication and shaking mechanisms. The optimized protocol was demonstrated at two laboratories in order to evaluate the recovery of spores from loamy and sandy soils. The new protocol demonstrated an improved limit of detection for loamy and sandy soils over the non-optimized protocol with an approximate matrix limit of detection at 14 spores/g of soil. There were no significant differences overall between the two laboratories for either soil type, suggesting that the processing protocol will be robust enough to use at multiple laboratories while achieving comparable recoveries.

Detection of beryllium in digested autopsy tissues by inductively coupled plasma mass spectrometry using a high matrix interface configuration.

PubMed

Larivière, Dominic; Tremblay, Mélodie; Durand-Jézéquel, Myriam; Tolmachev, Sergei

2012-04-01

This article describes a robust methodology using the combination of instrumental design (high matrix interface-HMI), sample dilution and internal standardization for the quantification of beryllium (Be) in various digested autopsy tissues using inductively coupled plasma mass spectrometry. The applicability of rhodium as a proper internal standard for Be was demonstrated in three types of biological matrices (i.e., femur, hair, lung tissues). Using HMI, it was possible to achieve instrumental detection limits and sensitivity of 0.6 ng L(-1) and 157 cps L ng(-1), respectively. Resilience to high salt matrices of the HMI setup was also highlighted using bone mimicking solution ([Ca(2+)] = 26 to 1,400 mg L(-1)), providing a 14-fold increase in tolerance and a 2.7-fold decrease in method detection limit compared to optimized experimental conditions obtained without the HMI configuration. Precision of the methodology to detect low levels of Be in autopsy samples was demonstrated using hair and blood certified reference materials. Be concentration ranging from 0.015 to 255 μg kg(-1) in autopsy samples obtained from the U.S. Transuranium and Uranium Registries were measured using the methodology presented.

Experimental Study of the Detection Limit in Dual-Gate Biosensors Using Ultrathin Silicon Transistors.

PubMed

Wu, Ting; Alharbi, Abdullah; You, Kai-Dyi; Kisslinger, Kim; Stach, Eric A; Shahrjerdi, Davood

2017-07-25

Dual-gate field-effect biosensors (bioFETs) with asymmetric gate capacitances were shown to surpass the Nernst limit of 59 mV/pH. However, previous studies have conflicting findings on the effect of the capacitive amplification scheme on the sensor detection limit, which is inversely proportional to the signal-to-noise ratio (SNR). Here, we present a systematic experimental investigation of the SNR using ultrathin silicon transistors. Our sensors operate at low voltage and feature asymmetric front and back oxide capacitances with asymmetry factors of 1.4 and 2.3. We demonstrate that in the dual-gate configuration, the response of our bioFETs to the pH change increases proportional to the asymmetry factor and indeed exceeds the Nernst limit. Further, our results reveal that the noise amplitude also increases in proportion to the asymmetry factor. We establish that the commensurate increase of the noise amplitude originates from the intrinsic low-frequency characteristic of the sensor noise, dominated by number fluctuation. These findings suggest that this capacitive signal amplification scheme does not improve the intrinsic detection limit of the dual-gate biosensors.

A high performance three-phase enzyme electrode based on superhydrophobic mesoporous silicon nanowire arrays for glucose detection.

PubMed

Xu, Chenlong; Song, Zhiqian; Xiang, Qun; Jin, Jian; Feng, Xinjian

2016-04-14

We describe here a high performance oxygen-rich three-phase enzyme electrode based on superhydrophobic mesoporous silicon nanowire arrays for glucose detection. We demonstrate that its linear detection upper limit is 30 mM, more than 15 times higher than that can be obtained on the normal enzyme-electrode. Notably, the three-phase enzyme electrode output is insensitive to the significant oxygen level fluctuation in analyte solution.

Maximizing the Biochemical Resolving Power of Fluorescence Microscopy

PubMed Central

Esposito, Alessandro; Popleteeva, Marina; Venkitaraman, Ashok R.

2013-01-01

Most recent advances in fluorescence microscopy have focused on achieving spatial resolutions below the diffraction limit. However, the inherent capability of fluorescence microscopy to non-invasively resolve different biochemical or physical environments in biological samples has not yet been formally described, because an adequate and general theoretical framework is lacking. Here, we develop a mathematical characterization of the biochemical resolution in fluorescence detection with Fisher information analysis. To improve the precision and the resolution of quantitative imaging methods, we demonstrate strategies for the optimization of fluorescence lifetime, fluorescence anisotropy and hyperspectral detection, as well as different multi-dimensional techniques. We describe optimized imaging protocols, provide optimization algorithms and describe precision and resolving power in biochemical imaging thanks to the analysis of the general properties of Fisher information in fluorescence detection. These strategies enable the optimal use of the information content available within the limited photon-budget typically available in fluorescence microscopy. This theoretical foundation leads to a generalized strategy for the optimization of multi-dimensional optical detection, and demonstrates how the parallel detection of all properties of fluorescence can maximize the biochemical resolving power of fluorescence microscopy, an approach we term Hyper Dimensional Imaging Microscopy (HDIM). Our work provides a theoretical framework for the description of the biochemical resolution in fluorescence microscopy, irrespective of spatial resolution, and for the development of a new class of microscopes that exploit multi-parametric detection systems. PMID:24204821

Flexible Modeling of Survival Data with Covariates Subject to Detection Limits via Multiple Imputation.

PubMed

Bernhardt, Paul W; Wang, Huixia Judy; Zhang, Daowen

2014-01-01

Models for survival data generally assume that covariates are fully observed. However, in medical studies it is not uncommon for biomarkers to be censored at known detection limits. A computationally-efficient multiple imputation procedure for modeling survival data with covariates subject to detection limits is proposed. This procedure is developed in the context of an accelerated failure time model with a flexible seminonparametric error distribution. The consistency and asymptotic normality of the multiple imputation estimator are established and a consistent variance estimator is provided. An iterative version of the proposed multiple imputation algorithm that approximates the EM algorithm for maximum likelihood is also suggested. Simulation studies demonstrate that the proposed multiple imputation methods work well while alternative methods lead to estimates that are either biased or more variable. The proposed methods are applied to analyze the dataset from a recently-conducted GenIMS study.

Enhanced acoustic sensing through wave compression and pressure amplification in anisotropic metamaterials.

PubMed

Chen, Yongyao; Liu, Haijun; Reilly, Michael; Bae, Hyungdae; Yu, Miao

2014-10-15

Acoustic sensors play an important role in many areas, such as homeland security, navigation, communication, health care and industry. However, the fundamental pressure detection limit hinders the performance of current acoustic sensing technologies. Here, through analytical, numerical and experimental studies, we show that anisotropic acoustic metamaterials can be designed to have strong wave compression effect that renders direct amplification of pressure fields in metamaterials. This enables a sensing mechanism that can help overcome the detection limit of conventional acoustic sensing systems. We further demonstrate a metamaterial-enhanced acoustic sensing system that achieves more than 20 dB signal-to-noise enhancement (over an order of magnitude enhancement in detection limit). With this system, weak acoustic pulse signals overwhelmed by the noise are successfully recovered. This work opens up new vistas for the development of metamaterial-based acoustic sensors with improved performance and functionalities that are highly desirable for many applications.

Messenger RNA Detection in Leukemia Cell lines by Novel Metal-Tagged in situ Hybridization using Inductively Coupled Plasma Mass Spectrometry.

PubMed

Ornatsky, Olga I; Baranov, Vladimir I; Bandura, Dmitry R; Tanner, Scott D; Dick, John

2006-01-01

Conventional gene expression profiling relies on using fluorescent detection of hybridized probes. Physical characteristics of fluorophores impose limitations on achieving a highly multiplex gene analysis of single cells. Our work demonstrates the feasibility of using metal-tagged in situ hybridization for mRNA detection by inductively coupled plasma mass spectrometry (ICP-MS). ICP-MS as an analytical detector has a number of unique and relevant properties: 1) metals and their stable isotopes generate non-overlapping distinct signals that can be detected simultaneously; 2) these signals can be measured over a wide dynamic range; 3) ICP-MS is quantitative and very sensitive. We used commercial antibodies conjugated to europium (Eu) and gold together with biotinylated oligonucleotide probes reacted with terbium-labeled streptavidin to demonstrate simultaneous mRNA and protein detection by ICP-MS in leukemia cells.

Messenger RNA Detection in Leukemia Cell lines by Novel Metal-Tagged in situ Hybridization using Inductively Coupled Plasma Mass Spectrometry

PubMed Central

Ornatsky, Olga I.; Baranov, Vladimir I.; Bandura, Dmitry R.; Tanner, Scott D.; Dick, John

2006-01-01

Conventional gene expression profiling relies on using fluorescent detection of hybridized probes. Physical characteristics of fluorophores impose limitations on achieving a highly multiplex gene analysis of single cells. Our work demonstrates the feasibility of using metal-tagged in situ hybridization for mRNA detection by inductively coupled plasma mass spectrometry (ICP-MS). ICP-MS as an analytical detector has a number of unique and relevant properties: 1) metals and their stable isotopes generate non-overlapping distinct signals that can be detected simultaneously; 2) these signals can be measured over a wide dynamic range; 3) ICP-MS is quantitative and very sensitive. We used commercial antibodies conjugated to europium (Eu) and gold together with biotinylated oligonucleotide probes reacted with terbium-labeled streptavidin to demonstrate simultaneous mRNA and protein detection by ICP-MS in leukemia cells. PMID:23662035

Validation of APF as a Urinary Biomarker for Interstitial Cystitis

DTIC Science & Technology

2016-12-01

using a CKAP4127-360 biosensor with sufficient binding efficiency to detect as-APF in urine with detection limits in the high nM to uM range. Urine...specimens from 14 (47%) of 30 women diagnosed with IC/PBS demonstrated as-APF binding activity to the CKAP4127-360 biosensor compared with 22 (73%) of 30...CKAP4 immobilized biosensor to detect APF (1-24 months) 2) Determine the ability of the SPR-based assay to detect APF in urine from patients with IC (1

Two-channel highly sensitive sensors based on 4 × 4 multimode interference couplers

NASA Astrophysics Data System (ADS)

Le, Trung-Thanh

2017-12-01

We propose a new kind of microring resonators (MRR) based on 4 × 4 multimode interference (MMI) couplers for multichannel and highly sensitive chemical and biological sensors. The proposed sensor structure has advantages of compactness and high sensitivity compared with the reported sensing structures. By using the transfer matrix method (TMM) and numerical simulations, the designs of the sensor based on silicon waveguides are optimized and demonstrated in detail. We apply our structure to detect glucose and ethanol concentrations simultaneously. A high sensitivity of 9000 nm/RIU, detection limit of 2 × 10‒4 for glucose sensing and sensitivity of 6000 nm/RIU, detection limit of 1.3 × 10‒5 for ethanol sensing are achieved.

Resonant photoacoustic cell for pulsed laser analysis of gases at high temperature

NASA Astrophysics Data System (ADS)

Sorvajärvi, Tapio; Manninen, Albert; Toivonen, Juha; Saarela, Jaakko; Hernberg, Rolf

2009-12-01

A new approach to high temperature gas analysis by means of photoacoustic (PA) spectroscopy is presented. The transverse modes of the resonant PA cell were excited with a pulsed laser and detected with a microphone. Changes in the properties of the PA cell resulting from a varying temperature are discussed and considered when processing the PA signal. The feasibility of the proposed method was demonstrated by studying PA response from saturated vapor of potassium chloride (KCl) in the temperature range extending from 410 to 691 °C. The PA spectrum, the detection limit, and the signal saturation of KCl vapor are discussed. At 245 nm excitation wavelength and 300 μJ pulse energy, the achieved detection limit for KCl is 15 ppb.

Association of lipoarabinomannan with high density lipoprotein in blood: Implications for diagnostics

DOE PAGES

Sakamuri, Rama Murthy; Price, Dominique N.; Lee, Myungsun; ...

2013-02-14

Understanding the pathophysiology of tuberculosis, and the bio-distribution of pathogen-associated molecules in the host is essential for the development of efficient methods of intervention. One of the key virulence factors in the pathology of tuberculosis infection is Lipoarabinomannan (LAM). Previously, we have demonstrated the reliable detection of LAM in urine from tuberculosis patients in a sandwich immunoassay format. We also applied an ultra-sensitive detection strategy developed for amphiphilic biomarkers, membrane insertion, to the detection of LAM with a limit of detection of 10 fM. Herein, we evaluate the application of membrane insertion to the detection of LAM in patient serum,more » and demonstrate that the circulating concentrations of ‘monomeric’ LAM in serum are very low, despite significantly higher concentrations in the urine. Using spiked samples, we demonstrate that this discrepancy is due to the association of LAM with high-density lipoprotein (HDL) nanodiscs in human serum. Indeed, pull-down of HDL nanodiscs from human serum allows for the recovery of HDL-associated LAM. These studies suggest that LAM is likely associated with carrier molecules such as HDL in the blood of patients infected with tuberculosis. Furthermore, this phenomenon may not be limited to LAM in that many pathogen-associated molecular patterns like LAM are amphiphilic in nature and may also be associated with host lipid carriers. Such interactions are likely to affect host–pathogen interactions, pathogen bio-distribution and clearance in the host, and must be thoroughly understood for the effective design of vaccines and diagnostics.« less

Association of lipoarabinomannan with high density lipoprotein in blood: Implications for diagnostics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sakamuri, Rama Murthy; Price, Dominique N.; Lee, Myungsun

Understanding the pathophysiology of tuberculosis, and the bio-distribution of pathogen-associated molecules in the host is essential for the development of efficient methods of intervention. One of the key virulence factors in the pathology of tuberculosis infection is Lipoarabinomannan (LAM). Previously, we have demonstrated the reliable detection of LAM in urine from tuberculosis patients in a sandwich immunoassay format. We also applied an ultra-sensitive detection strategy developed for amphiphilic biomarkers, membrane insertion, to the detection of LAM with a limit of detection of 10 fM. Herein, we evaluate the application of membrane insertion to the detection of LAM in patient serum,more » and demonstrate that the circulating concentrations of ‘monomeric’ LAM in serum are very low, despite significantly higher concentrations in the urine. Using spiked samples, we demonstrate that this discrepancy is due to the association of LAM with high-density lipoprotein (HDL) nanodiscs in human serum. Indeed, pull-down of HDL nanodiscs from human serum allows for the recovery of HDL-associated LAM. These studies suggest that LAM is likely associated with carrier molecules such as HDL in the blood of patients infected with tuberculosis. Furthermore, this phenomenon may not be limited to LAM in that many pathogen-associated molecular patterns like LAM are amphiphilic in nature and may also be associated with host lipid carriers. Such interactions are likely to affect host–pathogen interactions, pathogen bio-distribution and clearance in the host, and must be thoroughly understood for the effective design of vaccines and diagnostics.« less

Detection of nanoplastics in food by asymmetric flow field-flow fractionation coupled to multi-angle light scattering: possibilities, challenges and analytical limitations.

PubMed

Correia, Manuel; Loeschner, Katrin

2018-02-06

We tested the suitability of asymmetric flow field-flow fractionation (AF4) coupled to multi-angle light scattering (MALS) for detection of nanoplastics in fish. A homogenized fish sample was spiked with 100 nm polystyrene nanoparticles (PSNPs) (1.3 mg/g fish). Two sample preparation strategies were tested: acid digestion and enzymatic digestion with proteinase K. Both procedures were found suitable for degradation of the organic matrix. However, acid digestion resulted in large PSNPs aggregates/agglomerates (> 1 μm). The presence of large particulates was not observed after enzymatic digestion, and consequently it was chosen as a sample preparation method. The results demonstrated that it was possible to use AF4 for separating the PSNPs from the digested fish and to determine their size by MALS. The PSNPs could be easily detected by following their light scattering (LS) signal with a limit of detection of 52 μg/g fish. The AF4-MALS method could also be exploited for another type of nanoplastics in solution, namely polyethylene (PE). However, it was not possible to detect the PE particles in fish, due to the presence of an elevated LS background. Our results demonstrate that an analytical method developed for a certain type of nanoplastics may not be directly applicable to other types of nanoplastics and may require further adjustment. This work describes for the first time the detection of nanoplastics in a food matrix by AF4-MALS. Despite the current limitations, this is a promising methodology for detecting nanoplastics in food and in experimental studies (e.g., toxicity tests, uptake studies). Graphical abstract Basic concept for the detection of nanoplastics in fish by asymmetric flow field-flow fractionation coupled to multi-angle light scattering.

Effects of capacity limits, memory loss, and sound type in change deafness.

PubMed

Gregg, Melissa K; Irsik, Vanessa C; Snyder, Joel S

2017-11-01

Change deafness, the inability to notice changes to auditory scenes, has the potential to provide insights about sound perception in busy situations typical of everyday life. We determined the extent to which change deafness to sounds is due to the capacity of processing multiple sounds and the loss of memory for sounds over time. We also determined whether these processing limitations work differently for varying types of sounds within a scene. Auditory scenes composed of naturalistic sounds, spectrally dynamic unrecognizable sounds, tones, and noise rhythms were presented in a change-detection task. On each trial, two scenes were presented that were same or different. We manipulated the number of sounds within each scene to measure memory capacity and the silent interval between scenes to measure memory loss. For all sounds, change detection was worse as scene size increased, demonstrating the importance of capacity limits. Change detection to the natural sounds did not deteriorate much as the interval between scenes increased up to 2,000 ms, but it did deteriorate substantially with longer intervals. For artificial sounds, in contrast, change-detection performance suffered even for very short intervals. The results suggest that change detection is generally limited by capacity, regardless of sound type, but that auditory memory is more enduring for sounds with naturalistic acoustic structures.

Modeling of a Single-Notch Microfiber Coupler for High-Sensitivity and Low Detection-Limit Refractive Index Sensing.

PubMed

Zhang, Jiali; Shi, Lei; Zhu, Song; Xu, Xinbiao; Zhang, Xinliang

2016-05-11

A highly sensitive refractive index sensor with low detection limit based on an asymmetric optical microfiber coupler is proposed. It is composed of a silica optical microfiber and an As₂Se₃ optical microfiber. Due to the asymmetry of the microfiber materials, a single-notch transmission spectrum is demonstrated by the large refractive index difference between the two optical microfibers. Compared with the symmetric coupler, the bandwidth of the asymmetric structure is over one order of magnitude narrower than that of the former. Therefore, the asymmetric optical microfiber coupler based sensor can reach over one order of magnitude smaller detection limit, which is defined as the minimal detectable refractive index change caused by the surrounding analyte. With the advantage of large evanescent field, the results also show that a sensitivity of up to 3212 nm per refractive index unit with a bandwidth of 12 nm is achieved with the asymmetric optical microfiber coupler. Furthermore, a maximum sensitivity of 4549 nm per refractive index unit can be reached while the radii of the silica optical microfiber and As₂Se₃ optical microfiber are 0.5 μm and a 0.128 μm, respectively. This sensor component may have important potential for low detection-limit physical and biochemical sensing applications.

Effectiveness of a flow-based device using riboflavin photochemistry in damaging blood-borne viral nucleic acids.

PubMed

Zhu, Liguo; Tong, Hongli; Wang, Shufang; Yu, Yang; Liu, Zhong; Li, Changqing; Wang, Deqing

2018-05-03

Effectiveness of a flow-based treatment device using riboflavin photochemistry was demonstrated by cytopathic effect method using indicator viruses. However, inactivation efficacy against real blood-borne viruses needs to be evaluated, especially at nucleic acid level. Special plasma samples with varying concentrations of blood-borne virus were selected using a strict blood selection procedure and were treated with device treatment (DT). Nucleic acid test (NAT) using polymerase chain reaction fluorescence method was used to detect virus copies. The NAT value of 4325 in plasma with high Hepatitis B Virus (HBV) concentrations decreased to 1330 with DT. After 100-fold dilution, the NAT value was below the NAT detection limits with DT compared with 23.0 that without DT. The NAT value of 61.9 in plasma with medium HBV concentrations decreased to 37.8 with DT, and after 10-fold dilution, the NAT value was below the NAT detection limits with DT compared with below 20 that without DT. The Ct values of plasma with low concentrations of blood-borne viruses were below the NAT detection limits with DT. There was a dose effect with DT which was effective in blood-borne viruses damaging nucleic acids to a level below the NAT detection limits. Copyright © 2018 Elsevier B.V. All rights reserved.

Aggregated silver nanoparticles based surface-enhanced Raman scattering enzyme-linked immunosorbent assay for ultrasensitive detection of protein biomarkers and small molecules.

PubMed

Liang, Jiajie; Liu, Hongwu; Huang, Caihong; Yao, Cuize; Fu, Qiangqiang; Li, Xiuqing; Cao, Donglin; Luo, Zhi; Tang, Yong

2015-06-02

Lowering the detection limit is critical to the design of bioassays required for medical diagnostics, environmental monitoring, and food safety regulations. The current sensitivity of standard color-based analyte detection limits the further use of enzyme-linked immunosorbent assays (ELISAs) in research and clinical diagnoses. Here, we demonstrate a novel method that uses the Raman signal as the signal-generating system of an ELISA and combines surface-enhanced Raman scattering (SERS) with silver nanoparticles aggregation for ultrasensitive analyte detection. The enzyme label of the ELISA controls the dissolution of Raman reporter-labeled silver nanoparticles through hydrogen peroxide and generates a strong Raman signal when the analyte is present. Using this assay, prostate-specific antigen (PSA) and the adrenal stimulant ractopamine (Rac) were detected in whole serum and urine at the ultralow concentrations of 10(-9) and 10(-6) ng/mL, respectively. The methodology proposed here could potentially be applied to other molecules detection as well as PSA and Rac.

Detecting position using ARKit II: generating position-time graphs in real-time and further information on limitations of ARKit

NASA Astrophysics Data System (ADS)

Dilek, Ufuk; Erol, Mustafa

2018-05-01

ARKit is a framework which allows developers to create augmented reality apps for the iPhone and iPad. In a previous study, we had shown that it could be used to detect position in educational physics experiments and emphasized that the ability to provide position data in real-time was one of the prominent features of this newly emerging technology. In this study, we demonstrate an example of how real-time data acquisition can be employed in educational settings, report some of the limitations of ARKit and how we have overcome these limitations. By means of ARKit or a similar framework, ordinary mobile devices can be adapted for use in microcomputer-based lab activities.

Direct Real-Time Detection of Vapors from Explosive Compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 ionsmore » (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.« less

Signal Detection Theory Applied to Helicopter Transmission Diagnostic Thresholds

NASA Technical Reports Server (NTRS)

Dempsey, Paula J.; Keller, Jonathan A.; Wade, Daniel R.

2008-01-01

Helicopter Health Usage Monitoring Systems (HUMS) have potential for providing data to support increasing the service life of a dynamic mechanical component in the transmission of a helicopter. Data collected can demonstrate the HUMS condition indicator responds to a specific component fault with appropriate alert limits and minimal false alarms. Defining thresholds for specific faults requires a tradeoff between the sensitivity of the condition indicator (CI) limit to indicate damage and the number of false alarms. A method using Receiver Operating Characteristic (ROC) curves to assess CI performance was demonstrated using CI data collected from accelerometers installed on several UH60 Black Hawk and AH64 Apache helicopters and an AH64 helicopter component test stand. Results of the analysis indicate ROC curves can be used to reliably assess the performance of commercial HUMS condition indicators to detect damaged gears and bearings in a helicopter transmission.

Signal Detection Theory Applied to Helicopter Transmission Diagnostic Thresholds

NASA Technical Reports Server (NTRS)

Dempsey, Paula J.; Keller, Jonathan A.; Wade, Daniel R.

2009-01-01

Helicopter Health Usage Monitoring Systems (HUMS) have potential for providing data to support increasing the service life of a dynamic mechanical component in the transmission of a helicopter. Data collected can demonstrate the HUMS condition indicator responds to a specific component fault with appropriate alert limits and minimal false alarms. Defining thresholds for specific faults requires a tradeoff between the sensitivity of the condition indicator (CI) limit to indicate damage and the number of false alarms. A method using Receiver Operating Characteristic (ROC) curves to assess CI performance was demonstrated using CI data collected from accelerometers installed on several UH60 Black Hawk and AH64 Apache helicopters and an AH64 helicopter component test stand. Results of the analysis indicate ROC curves can be used to reliably assess the performance of commercial HUMS condition indicators to detect damaged gears and bearings in a helicopter transmission.

Comparison of detection limit in fiber-based conventional, amplified, and gain-clamped cavity ring-down techniques

NASA Astrophysics Data System (ADS)

Sharma, K.; Abdul Khudus, M. I. M.; Alam, S. U.; Bhattacharya, S.; Venkitesh, D.; Brambilla, G.

2018-01-01

Relative performance and detection limit of conventional, amplified, and gain-clamped cavity ring-down techniques (CRDT) in all-fiber configurations are compared experimentally for the first time. Refractive index measurement using evanescent field in tapered fibers is used as a benchmark for the comparison. The systematic optimization of a nested-loop configuration in gain-clamped CRDT is also discussed, which is crucial for achieving a constant gain in a CRDT experiment. It is found that even though conventional CRDT has the lowest standard error in ring-down time (Δτ), the value of ring-down time (τ) is very small, thus leading to poor detection limit. Amplified CRDT provides an improvement in τ, albeit with two orders of magnitude higher Δτ due to amplifier noise. The nested-loop configuration in gain-clamped CRDT helps in reducing Δτ by an order of magnitude as compared to amplified CRDT whilst retaining the improvement in τ. A detection limit of 1 . 03 × 10-4 RIU at refractive index of 1.322 with a 3 mm long and 4.5 μm diameter tapered fiber is demonstrated with the gain-clamped CRDT.

Highly fluorescent carbon quantum dots as nanoprobes for sensitive and selective determination of mercury (II) in surface waters

NASA Astrophysics Data System (ADS)

Hua, Jianhao; Yang, Jian; Zhu, Yan; Zhao, Chunxi; Yang, Yaling

2017-12-01

A novel carbon quantum dots (CQDs) was successfully prepared through one-step green hydrothermal method using polyacrylamide as carbon source. The prepared CQDs were characterized using TEM, XRD, XPS, FT-IR, UV-Vis, and fluorescence spectroscopy. The CQDs was demonstrated as nanoprobes for mercury ion detection, moreover, it demonstrated excitation-dependent and superior stability in acidic and alkaline media. Besides, the probe exhibited a good linearity range (0.25-50 μM) and a low detection limit (13.48 nM). These attractive properties indicated that this novel CQDs can adapt to a variety of complex pH environment, which had extensive prospect and promising application for detection of mercury ions in complex water samples.

Peptide Functionalized Gold Nanorods for the Sensitive Detection of a Cardiac Biomarker Using Plasmonic Paper Devices (Postprint)

DTIC Science & Technology

2015-11-10

valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YY) 2. REPORT TYPE 3 . DATES COVERED (From...refractive index difference on the order of 3 × 10−4 refractive index units (RIU)), probe the conformational changes of individual biomacromolecules, detect...natural antibodies and short peptides, as BREs. We demonstrate that pep - tides provide a significantly higher sensitivity and lower limit of detection

Label-free impedimetric biosensor for Salmonella Typhimurium detection based on poly [pyrrole-co-3-carboxyl-pyrrole] copolymer supported aptamer.

PubMed

Sheikhzadeh, E; Chamsaz, M; Turner, A P F; Jager, E W H; Beni, V

2016-06-15

The Gram-negative bacterium, Salmonella Typhimurium (S. Typhimurium) is a food borne pathogen responsible for numerous hospitalisations and deaths all over the world. Conventional detection methods for pathogens are time consuming and labour-intensive. Hence, there is considerable interest in faster and simpler detection methods. Polypyrrole-based polymers, due to their intrinsic chemical and electrical properties, have been demonstrated to be valuable candidates for the fabrication of chemo/biosensors and functional surfaces. Similarly aptamers have been shown to be good alternatives to antibodies in the development of affinity biosensors. In this study, we report on the combination of poly [pyrrole-co-3-carboxyl-pyrrole] copolymer and aptamer for the development of a label-less electrochemical biosensor suitable for the detection of S. Typhimurium. Impedimetric measurements were facilitated by the effect of the aptamer/target interaction on the intrinsic conjugation of the poly [pyrrole-co-3-carboxyl-pyrrole] copolymer and subsequently on its electrical properties. The aptasensor detected S. Typhimurium in the concentration range 10(2)-10(8) CFU mL(-1) with high selectivity over other model pathogens and with a limit of quantification (LOQ) of 100 CFU mL(-1) and a limit of detection (LOD) of 3 CFU mL(-1). The suitability of the aptasensor for real sample detection was demonstrated via recovery studies performed in spiked apple juice samples. We envisage this to be a viable approach for the inexpensive and rapid detection of pathogens in food, and possibly in other environmental samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Natural gas pipeline leak detector based on NIR diode laser absorption spectroscopy.

PubMed

Gao, Xiaoming; Fan, Hong; Huang, Teng; Wang, Xia; Bao, Jian; Li, Xiaoyun; Huang, Wei; Zhang, Weijun

2006-09-01

The paper reports on the development of an integrated natural gas pipeline leak detector based on diode laser absorption spectroscopy. The detector transmits a 1.653 microm DFB diode laser with 10 mW and detects a fraction of the backscatter reflected from the topographic targets. To eliminate the effect of topographic scatter targets, a ratio detection technique was used. Wavelength modulation and harmonic detection were used to improve the detection sensitivity. The experimental detection limit is 50 ppmm, remote detection for a distance up to 20 m away topographic scatter target is demonstrated. Using a known simulative leak pipe, minimum detectable pipe leak flux is less than 10 ml/min.

Mid-infrared photoacoustic spectroscopy for atmospheric NO2 measurements

NASA Astrophysics Data System (ADS)

Lassen, Mikael; Lamard, Laurent; Balslev-Harder, David; Peremans, Andre; Petersen, Jan C.

2018-02-01

A photoacoustic (PA) sensor for spectroscopic measurements of NO2-N2 at ambient pressure and temperature is demonstrated. The PA sensor is pumped resonantly by a nanosecond pulsed single-mode mid-infrared (MIR) optical parametric oscillator (OPO). Spectroscopic measurements of NO2-N2 in the 3.25 μm to 3.55 μm wavelength region with a resolution bandwidth of 5 cm-1 and with a single shot detection limit of 1.6 ppmV (μmol/mol) is demonstrated. The measurements were conducted with a constant flow rate of 300 ml/min, thus demonstrating the suitability of the gas sensor for real time trace gas measurements. The acquired spectra is compared with data from the Hitran database and good agreement is found. An Allan deviation analysis shows that the detection limit at optimum integration time for the PAS sensor is 14 ppbV (nmol/mol) at 170 seconds of integration time, corresponding to a normalized noise equivalent absorption (NNEA) coefficient of 3.3×10-7 W cm-1 Hz-1/2.

Enhancement of laser-induced breakdown spectroscopy (LIBS) Detection limit using a low-pressure and short-pulse laser-induced plasma process.

PubMed

Wang, Zhen Zhen; Deguchi, Yoshihiro; Kuwahara, Masakazu; Yan, Jun Jie; Liu, Ji Ping

2013-11-01

Laser-induced breakdown spectroscopy (LIBS) technology is an appealing technique compared with many other types of elemental analysis because of the fast response, high sensitivity, real-time, and noncontact features. One of the challenging targets of LIBS is the enhancement of the detection limit. In this study, the detection limit of gas-phase LIBS analysis has been improved by controlling the pressure and laser pulse width. In order to verify this method, low-pressure gas plasma was induced using nanosecond and picosecond lasers. The method was applied to the detection of Hg. The emission intensity ratio of the Hg atom to NO (IHg/INO) was analyzed to evaluate the LIBS detection limit because the NO emission (interference signal) was formed during the plasma generation and cooling process of N2 and O2 in the air. It was demonstrated that the enhancement of IHg/INO arose by decreasing the pressure to a few kilopascals, and the IHg/INO of the picosecond breakdown was always much higher than that of the nanosecond breakdown at low buffer gas pressure. Enhancement of IHg/INO increased more than 10 times at 700 Pa using picosecond laser with 35 ps pulse width. The detection limit was enhanced to 0.03 ppm (parts per million). We also saw that the spectra from the center and edge parts of plasma showed different features. Comparing the central spectra with the edge spectra, IHg/INO of the edge spectra was higher than that of the central spectra using the picosecond laser breakdown process.

Simple Sample Processing Enhances Malaria Rapid Diagnostic Test Performance

PubMed Central

Davis, K. M.; Gibson, L. E.; Haselton, F. R.; Wright, D. W.

2016-01-01

Lateral flow immunochromatographic rapid diagnostic tests (RDTs) are the primary form of medical diagnostic used for malaria in underdeveloped nations. Unfortunately, many of these tests do not detect asymptomatic malaria carriers. In order for eradication of the disease to be achieved, this problem must be solved. In this study, we demonstrate enhancement in the performance of six RDT brands when a simple sample-processing step is added to the front of the diagnostic process. Greater than a 4-fold RDT signal enhancement was observed as a result of the sample processing step. This lowered the limit of detection for RDT brands to submicroscopic parasitemias. For the best performing RDTs the limits of detection were found to be as low as 3 parasites/μL. Finally, through individual donor samples, the correlations between donor source, WHO panel detection scores and RDT signal intensities were explored. PMID:24787948

Highly selectively monitoring heavy and transition metal ions by a fluorescent sensor based on dipeptide.

PubMed

Neupane, Lok Nath; Thirupathi, Ponnaboina; Jang, Sujung; Jang, Min Jung; Kim, Jung Hwa; Lee, Keun-Hyeung

2011-09-15

Fluorescent sensor (DMH) based on dipeptide was efficiently synthesized in solid phase synthesis. The dipeptide sensor shows sensitive response to Ag(I), Hg(II), and Cu(II) among 14 metal ions in 100% aqueous solution. The fluorescent sensor differentiates three heavy metal ions by response type; turn on response to Ag(I), ratiometric response to Hg(II), and turn off detection of Cu(II). The detection limits of the sensor for Ag(I) and Cu(II) were much lower than the EPA's drinking water maximum contaminant levels (MCL). Specially, DMH penetrated live cells and detected intracellular Ag(+) by turn on response. We described the fluorescent change, binding affinity, detection limit for the metal ions. The study of a heavy metal-responsive sensor based on dipeptide demonstrates its potential utility in the environment field. Copyright © 2011 Elsevier B.V. All rights reserved.

An optoelectronic nose for the detection of toxic gases.

PubMed

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

2009-10-01

We have developed a simple colorimetric sensor array that detects a wide range of volatile analytes and then applied it to the detection of toxic gases. The sensor consists of a disposable array of cross-responsive nanoporous pigments with colours that are changed by diverse chemical interactions with analytes. Although no single chemically responsive pigment is specific for any one analyte, the pattern of colour change for the array is a unique molecular fingerprint. Clear differentiation among 19 different toxic industrial chemicals (TICs) within two minutes of exposure at concentrations immediately dangerous to life or health were demonstrated. Based on the colour change of the array, quantification of each analyte was accomplished easily, and excellent detection limits were achieved, generally below the permissible exposure limits. Different TICs were identified readily using a standard chemometric approach (hierarchical clustering analysis), with no misclassifications over 140 trials.

SERS-based pesticide detection by using nanofinger sensors

NASA Astrophysics Data System (ADS)

Kim, Ansoon; Barcelo, Steven J.; Li, Zhiyong

2015-01-01

Simple, sensitive, and rapid detection of trace levels of extensively used and highly toxic pesticides are in urgent demand for public health. Surface-enhanced Raman scattering (SERS)-based sensor was designed to achieve ultrasensitive and simple pesticide sensing. We developed a portable sensor system composed of high performance and reliable gold nanofinger sensor strips and a custom-built portable Raman spectrometer. Compared to the general procedure and previously reported studies that are limited to laboratory settings, our analytical method is simple, sensitive, rapid, and cost-effective. Based on the SERS results, the chemical interaction of two pesticides, chlorpyrifos (CPF) and thiabendazole (TBZ), with gold nanofingers was studied to determine a fingerprint for each pesticide. The portable SERS-sensor system was successfully demonstrated to detect CPF and TBZ pesticides within 15 min with a detection limit of 35 ppt in drinking water and 7 ppb on apple skin, respectively.

Simple sample processing enhances malaria rapid diagnostic test performance.

PubMed

Davis, K M; Gibson, L E; Haselton, F R; Wright, D W

2014-06-21

Lateral flow immunochromatographic rapid diagnostic tests (RDTs) are the primary form of medical diagnostic used for malaria in underdeveloped nations. Unfortunately, many of these tests do not detect asymptomatic malaria carriers. In order for eradication of the disease to be achieved, this problem must be solved. In this study, we demonstrate enhancement in the performance of six RDT brands when a simple sample-processing step is added to the front of the diagnostic process. Greater than a 4-fold RDT signal enhancement was observed as a result of the sample processing step. This lowered the limit of detection for RDT brands to submicroscopic parasitemias. For the best performing RDTs the limits of detection were found to be as low as 3 parasites per μL. Finally, through individual donor samples, the correlations between donor source, WHO panel detection scores and RDT signal intensities were explored.

Label-free optical detection of single-base mismatches by the combination of nuclease and gold nanoparticles.

PubMed

Liu, Meiying; Yuan, Min; Lou, Xinhui; Mao, Hongju; Zheng, Dongmei; Zou, Ruxing; Zou, Nengli; Tang, Xiangrong; Zhao, Jianlong

2011-07-15

We report here an optical approach that enables highly selective and colorimetric single-base mismatch detection without the need of target modification, precise temperature control or stringent washes. The method is based on the finding that nucleoside monophosphates (dNMPs), which are digested elements of DNA, can better stabilize unmodified gold nanoparticles (AuNPs) than single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) with the same base-composition and concentration. The method combines the exceptional mismatch discrimination capability of the structure-selective nucleases with the attractive optical property of AuNPs. Taking S1 nuclease as one example, the perfectly matched 16-base synthetic DNA target was distinctively differentiated from those with single-base mutation located at any position of the 16-base synthetic target. Single-base mutations present in targets with varied length up to 80-base, located either in the middle or near to the end of the targets, were all effectively detected. In order to prove that the method can be potentially used for real clinic samples, the single-base mismatch detections with two HBV genomic DNA samples were conducted. To further prove the generality of this method and potentially overcome the limitation on the detectable lengths of the targets of the S1 nuclease-based method, we also demonstrated the use of a duplex-specific nuclease (DSN) for color reversed single-base mismatch detection. The main limitation of the demonstrated methods is that it is limited to detect mutations in purified ssDNA targets. However, the method coupled with various convenient ssDNA generation and purification techniques, has the potential to be used for the future development of detector-free testing kits in single nucleotide polymorphism screenings for disease diagnostics and treatments. Copyright © 2011 Elsevier B.V. All rights reserved.

Smartphone-Based Mobile Detection Platform for Molecular Diagnostics and Spatiotemporal Disease Mapping.

PubMed

Song, Jinzhao; Pandian, Vikram; Mauk, Michael G; Bau, Haim H; Cherry, Sara; Tisi, Laurence C; Liu, Changchun

2018-04-03

Rapid and quantitative molecular diagnostics in the field, at home, and at remote clinics is essential for evidence-based disease management, control, and prevention. Conventional molecular diagnostics requires extensive sample preparation, relatively sophisticated instruments, and trained personnel, restricting its use to centralized laboratories. To overcome these limitations, we designed a simple, inexpensive, hand-held, smartphone-based mobile detection platform, dubbed "smart-connected cup" (SCC), for rapid, connected, and quantitative molecular diagnostics. Our platform combines bioluminescent assay in real-time and loop-mediated isothermal amplification (BART-LAMP) technology with smartphone-based detection, eliminating the need for an excitation source and optical filters that are essential in fluorescent-based detection. The incubation heating for the isothermal amplification is provided, electricity-free, with an exothermic chemical reaction, and incubation temperature is regulated with a phase change material. A custom Android App was developed for bioluminescent signal monitoring and analysis, target quantification, data sharing, and spatiotemporal mapping of disease. SCC's utility is demonstrated by quantitative detection of Zika virus (ZIKV) in urine and saliva and HIV in blood within 45 min. We demonstrate SCC's connectivity for disease spatiotemporal mapping with a custom-designed website. Such a smart- and connected-diagnostic system does not require any lab facilities and is suitable for use at home, in the field, in the clinic, and particularly in resource-limited settings in the context of Internet of Medical Things (IoMT).

Multi-channeled single chain variable fragment (scFv) based microfluidic device for explosives detection.

PubMed

Charles, Paul T; Davis, Jasmine; Adams, André A; Anderson, George P; Liu, Jinny L; Deschamps, Jeffrey R; Kusterbeck, Anne W

2015-11-01

The development of explosives detection technologies has increased significantly over the years as environmental and national security agencies implement tighter pollution control measures and methods for improving homeland security. 2, 4, 6-Trinitrotoluene (TNT), known primarily as a component in munitions, has been targeted for both its toxicity and carcinogenic properties that if present at high concentrations can be a detriment to both humans, marine and plant ecosystems. Enabling end users with environmental detection and monitoring systems capable of providing real-time, qualitative and quantitative chemical analysis of these toxic compounds would be extremely beneficial. Reported herein is the development of a multi-channeled microfluidic device immobilized with single chain fragment variable (scFv) recombinant proteins specific for the explosive, TNT. Fluorescence displacement immunoassays performed under constant flow demonstrated trace level sensitivity and specificity for TNT. The utility of three multi-channeled devices immobilized with either (1) scFv recombinant protein, (2) biotinylated-scFv (bt-scFv) and (3) monoclonal anti-TNT (whole IgG molecule) were investigated and compared. Fluorescence dose response curves, crossreactivity measurements and limits of detection (LOD) for TNT were determined. Fluorescence displacement immunoassays for TNT in natural seawater demonstrated detection limits at sub-parts-per-billion levels (0.5 ppb) utilizing the microfluidic device with immobilized bt-scFv. Published by Elsevier B.V.

A smartphone-based diagnostic platform for rapid detection of Zika, chikungunya, and dengue viruses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Priye, Aashish; Bird, Sara W.; Light, Yooli K.

Current multiplexed diagnostics for Zika, dengue, and chikungunya viruses are situated outside the intersection of affordability, high performance, and suitability for use at the point-of-care in resource-limited settings. Consequently, insufficient diagnostic capabilities are a key limitation facing current Zika outbreak management strategies. We demonstrate highly sensitive and specific detection of Zika, chikungunya, and dengue viruses by coupling reverse-transcription loop-mediated isothermal amplification (RT-LAMP) with our recently developed quenching of unincorporated amplification signal reporters (QUASR) technique. We conduct reactions in a simple, inexpensive and portable “LAMP box” supplemented with a consumer class smartphone. The entire assembly can be powered by a 5more » V USB source such as a USB power bank or solar panel. The smartphone employs a novel algorithm utilizing chromaticity to analyze fluorescence signals, which improves the discrimination of positive/negative signals by 5-fold when compared to detection with traditional RGB intensity sensors or the naked eye. The ability to detect ZIKV directly from crude human sample matrices (blood, urine, and saliva) demonstrates our device’s utility for widespread clinical deployment. Altogether, these advances enable our system to host the key components necessary to expand the use of nucleic acid amplification-based detection assays towards point-of-care settings where they are needed most.« less

High-Performance Visible-Blind UV Phototransistors Based on n-Type Naphthalene Diimide Nanomaterials.

PubMed

Song, Inho; Lee, Seung-Chul; Shang, Xiaobo; Ahn, Jaeyong; Jung, Hoon-Joo; Jeong, Chan-Uk; Kim, Sang-Wook; Yoon, Woojin; Yun, Hoseop; Kwon, O-Pil; Oh, Joon Hak

2018-04-11

This study investigates the performance of single-crystalline nanomaterials of wide-band gap naphthalene diimide (NDI) derivatives with methylene-bridged aromatic side chains. Such materials are found to be easily used as high-performance, visible-blind near-UV light detectors. NDI single-crystalline nanoribbons are assembled using a simple solution-based process (without solvent-inclusion problems), which is then applied to organic phototransistors (OPTs). Such OPTs exhibit excellent n-channel transistor characteristics, including an average electron mobility of 1.7 cm 2 V -1 s -1 , sensitive UV detection properties with a detection limit of ∼1 μW cm -2 , millisecond-level responses, and detectivity as high as 10 15 Jones, demonstrating the highly sensitive organic visible-blind UV detectors. The high performance of our OPTs originates from the large face-to-face π-π stacking area between the NDI semiconducting cores, which is facilitated by methylene-bridged aromatic side chains. Interestingly, NDI-based nanoribbon OPTs exhibit a distinct visible-blind near-UV detection with an identical detection limit, even under intense visible light illumination (for example, 10 4 times higher intensity than UV light intensity). Our findings demonstrate that wide-band gap NDI-based nanomaterials are highly promising for developing high-performance visible-blind UV photodetectors. Such photodetectors could potentially be used for various applications including environmental and health-monitoring systems.

A smartphone-based diagnostic platform for rapid detection of Zika, chikungunya, and dengue viruses

DOE PAGES

Priye, Aashish; Bird, Sara W.; Light, Yooli K.; ...

2017-03-20

Current multiplexed diagnostics for Zika, dengue, and chikungunya viruses are situated outside the intersection of affordability, high performance, and suitability for use at the point-of-care in resource-limited settings. Consequently, insufficient diagnostic capabilities are a key limitation facing current Zika outbreak management strategies. We demonstrate highly sensitive and specific detection of Zika, chikungunya, and dengue viruses by coupling reverse-transcription loop-mediated isothermal amplification (RT-LAMP) with our recently developed quenching of unincorporated amplification signal reporters (QUASR) technique. We conduct reactions in a simple, inexpensive and portable “LAMP box” supplemented with a consumer class smartphone. The entire assembly can be powered by a 5more » V USB source such as a USB power bank or solar panel. The smartphone employs a novel algorithm utilizing chromaticity to analyze fluorescence signals, which improves the discrimination of positive/negative signals by 5-fold when compared to detection with traditional RGB intensity sensors or the naked eye. The ability to detect ZIKV directly from crude human sample matrices (blood, urine, and saliva) demonstrates our device’s utility for widespread clinical deployment. Altogether, these advances enable our system to host the key components necessary to expand the use of nucleic acid amplification-based detection assays towards point-of-care settings where they are needed most.« less

Determination of benazolin-ethyl residues in soil and rape seed by SPE clean-up and GC with electron capture detection.

PubMed

Liu, Xiaolu; Yang, Tao; Hu, Jiye

2013-01-01

A method has been developed and established for residue determination of benazolin-ethyl in soil and rape seed samples by gas chromatography with electron capture detection (GC-ECD). Limits of quantification of the method are 0.005 mg/kg for both soil and rape seed, which are sufficiently below the maximum residue limit, and the limit of detection is 0.0023 ng. The average recoveries of the analyte range from 85.89 to 105.84% with relative standard deviations (coefficient of variation) less than 5.53% at the three spike levels (0.005, 0.1 and 0.5 mg/kg). The half-life of benazolin-ethyl in soil from the experimental field is 4.62 days. The final residues of benazolin-ethyl in soil and rape seed samples are lower than 0.005 mg/kg at harvest time. Direct confirmation of the analyte in real samples is achieved by GC-mass spectrometry. It is demonstrated that the proposed method is simple, rapid and efficient, and reliable to detect benazolin-ethyl residues in soil and rape seed samples.

Electrochemical detection of p-ethylguaiacol, a fungi infected fruit volatile using metal oxide nanoparticles.

PubMed

Fang, Yi; Umasankar, Yogeswaran; Ramasamy, Ramaraja P

2014-08-07

Nanoparticles of TiO(2) or SnO(2) on screen-printed carbon (SP) electrodes have been developed for evaluating their potential application in the electrochemical sensing of volatiles in fruits and plants. These metal oxide nanoparticle-modified electrodes possess high sensitivity and low detection limit for the detection of p-ethylguaiacol, a fingerprint compound present in the volatile signature of fruits and plants infected with a pathogenic fungus Phytophthora cactorum. The electroanalytical data obtained using cyclic voltammetry and differential pulse voltammetry showed that both SnO(2) and TiO(2) exhibited high sensitivity (174-188 μA cm(-2) mM(-1)) and low detection limits (35-62 nM) for p-ethylguaiacol detection. The amperometric detection was highly repeatable with RSD values ranging from 2.48 to 4.85%. The interference studies show that other common plant volatiles do not interfere in the amperometric detection signal of p-ethylguaiacol. The results demonstrate that metal oxides are a reasonable alternative to expensive electrode materials such as gold or platinum for amperometric sensor applications.

A universal DNA-based protein detection system.

PubMed

Tran, Thua N N; Cui, Jinhui; Hartman, Mark R; Peng, Songming; Funabashi, Hisakage; Duan, Faping; Yang, Dayong; March, John C; Lis, John T; Cui, Haixin; Luo, Dan

2013-09-25

Protein immune detection requires secondary antibodies which must be carefully selected in order to avoid interspecies cross-reactivity, and is therefore restricted by the limited availability of primary/secondary antibody pairs. Here we present a versatile DNA-based protein detection system using a universal adapter to interface between IgG antibodies and DNA-modified reporter molecules. As a demonstration of this capability, we successfully used DNA nano-barcodes, quantum dots, and horseradish peroxidase enzyme to detect multiple proteins using our DNA-based labeling system. Our system not only eliminates secondary antibodies but also serves as a novel method platform for protein detection with modularity, high capacity, and multiplexed capability.

A Universal DNA-Based Protein Detection System

PubMed Central

Tran, Thua N. N.; Cui, Jinhui; Hartman, Mark R.; Peng, Songming; Funabashi, Hisakage; Duan, Faping; Yang, Dayong; March, John C.; Lis, John T.; Cui, Haixin; Luo, Dan

2014-01-01

Protein immune detection requires secondary antibodies which must be carefully selected in order to avoid interspecies cross-reactivity, and is therefore restricted by the limited availability of primary/secondary antibody pairs. Here we present a versatile DNA-based protein detection system using a universal adapter to interface between IgG antibodies and DNA-modified reporter molecules. As a demonstration of this capability, we successfully used DNA nano-barcodes, quantum dots, and horseradish peroxidase enzyme to detect multiple proteins using our DNA-based labeling system. Our system not only eliminates secondary antibodies but also serves as a novel method platform for protein detection with modularity, high capacity, and multiplexed capability. PMID:23978265

Dark matter effective field theory scattering in direct detection experiments

DOE PAGES

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

Dark matter effective field theory scattering in direct detection experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneck, K.; Cabrera, B.; Cerdeño, D. G.

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

Dark matter effective field theory scattering in direct detection experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneck, K.; Cabrera, B.; Cerdeño, D. G.

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. 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

Convenient, inexpensive quantification of elemental sulfur by simultaneous in situ reduction and colorimetric detection.

PubMed

Kwasniewski, Misha T; Allison, Rachel B; Wilcox, Wayne F; Sacks, Gavin L

2011-10-03

Rapid, inexpensive, and convenient methods for quantifying elemental sulfur (S(0)) with low or sub-μgg(-1) limits of detection would be useful for a range of applications where S(0) can act as a precursor for noxious off-aromas, e.g., S(0) in pesticide residues on winegrapes or as a contaminant in drywall. However, existing quantification methods rely on toxic reagents, expensive and cumbersome equipment, or demonstrate poor selectivity. We have developed and optimized an inexpensive, rapid method (∼15 min per sample) for quantifying S(0) in complex matrices. Following dispersion of the sample in PEG-400 and buffering, S(0) is quantitatively reduced to H(2)S in situ by dithiothreitol and simultaneously quantified by commercially available colorimetric H(2)S detection tubes. By employing multiple tubes, the method demonstrated linearity from 0.03 to 100 μg S(0) g(-1) for a 5 g sample (R(2)=0.994, mean CV=6.4%), and the methodological detection limit was 0.01 μg S(0) g(-1). Interferences from sulfite or sulfate were not observed. Mean recovery of an S(0) containing sulfur fungicide in grape macerate was 84.7% with a mean CV of 10.4%. Mean recovery of S(0) in a colloidal sulfur preparation from a drywall matrix was 106.6% with a mean CV of 6.9%. Comparable methodological detection limits, sensitivity, and recoveries were achieved in grape juice, grape macerate and with 1g drywall samples, indicating that the methodology should be robust across a range of complex matrices. Copyright © 2011 Elsevier B.V. All rights reserved.

Singular value decomposition metrics show limitations of detector design in diffuse fluorescence tomography

PubMed Central

Leblond, Frederic; Tichauer, Kenneth M.; Pogue, Brian W.

2010-01-01

The spatial resolution and recovered contrast of images reconstructed from diffuse fluorescence tomography data are limited by the high scattering properties of light propagation in biological tissue. As a result, the image reconstruction process can be exceedingly vulnerable to inaccurate prior knowledge of tissue optical properties and stochastic noise. In light of these limitations, the optimal source-detector geometry for a fluorescence tomography system is non-trivial, requiring analytical methods to guide design. Analysis of the singular value decomposition of the matrix to be inverted for image reconstruction is one potential approach, providing key quantitative metrics, such as singular image mode spatial resolution and singular data mode frequency as a function of singular mode. In the present study, these metrics are used to analyze the effects of different sources of noise and model errors as related to image quality in the form of spatial resolution and contrast recovery. The image quality is demonstrated to be inherently noise-limited even when detection geometries were increased in complexity to allow maximal tissue sampling, suggesting that detection noise characteristics outweigh detection geometry for achieving optimal reconstructions. PMID:21258566

A benzothiazole-based fluorescent probe for hypochlorous acid detection and imaging in living cells

NASA Astrophysics Data System (ADS)

Nguyen, Khac Hong; Hao, Yuanqiang; Zeng, Ke; Fan, Shengnan; Li, Fen; Yuan, Suke; Ding, Xuejing; Xu, Maotian; Liu, You-Nian

2018-06-01

A benzothiazole-based turn-on fluorescent probe with a large Stokes shift (190 nm) has been developed for hypochlorous acid detection. The probe displays prompt fluorescence response for HClO with excellent selectivity over other reactive oxygen species as well as a low detection limit of 0.08 μM. The sensing mechanism involves the HClO-induced specific oxidation of oxime moiety of the probe to nitrile oxide, which was confirmed by HPLC-MS technique. Furthermore, imaging studies demonstrated that the probe is cell permeable and can be applied to detect HClO in living cells.

Experimental Study of the Detection Limit in Dual-Gate Biosensors Using Ultrathin Silicon Transistors

DOE PAGES

Wu, Ting; Alharbi, Abdullah; You, Kai-Dyi; ...

2017-06-21

Dual-gate field-effect biosensors (bioFETs) with asymmetric gate capacitances were shown to surpass the Nernst limit of 59 mV/pH. However, previous studies have conflicting findings on the effect of the capacitive amplification scheme on the sensor detection limit, which is inversely proportional to the signal-to-noise ratio (SNR). In this paper, we present a systematic experimental investigation of the SNR using ultrathin silicon transistors. Our sensors operate at low voltage and feature asymmetric front and back oxide capacitances with asymmetry factors of 1.4 and 2.3. We demonstrate that in the dual-gate configuration, the response of our bioFETs to the pH change increasesmore » proportional to the asymmetry factor and indeed exceeds the Nernst limit. Further, our results reveal that the noise amplitude also increases in proportion to the asymmetry factor. We establish that the commensurate increase of the noise amplitude originates from the intrinsic low-frequency characteristic of the sensor noise, dominated by number fluctuation. Finally, these findings suggest that this capacitive signal amplification scheme does not improve the intrinsic detection limit of the dual-gate biosensors.« less

Experimental Study of the Detection Limit in Dual-Gate Biosensors Using Ultrathin Silicon Transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Ting; Alharbi, Abdullah; You, Kai-Dyi

Dual-gate field-effect biosensors (bioFETs) with asymmetric gate capacitances were shown to surpass the Nernst limit of 59 mV/pH. However, previous studies have conflicting findings on the effect of the capacitive amplification scheme on the sensor detection limit, which is inversely proportional to the signal-to-noise ratio (SNR). In this paper, we present a systematic experimental investigation of the SNR using ultrathin silicon transistors. Our sensors operate at low voltage and feature asymmetric front and back oxide capacitances with asymmetry factors of 1.4 and 2.3. We demonstrate that in the dual-gate configuration, the response of our bioFETs to the pH change increasesmore » proportional to the asymmetry factor and indeed exceeds the Nernst limit. Further, our results reveal that the noise amplitude also increases in proportion to the asymmetry factor. We establish that the commensurate increase of the noise amplitude originates from the intrinsic low-frequency characteristic of the sensor noise, dominated by number fluctuation. Finally, these findings suggest that this capacitive signal amplification scheme does not improve the intrinsic detection limit of the dual-gate biosensors.« less

Field Demonstration of Light Obscuration Particle Counting Technologies to Detect Fuel Contaminates

DTIC Science & Technology

2016-12-01

to detect fuel contamiation including particulates and free water 15. SUBJECT TERMS fuel, JP-8, aviation fuel, contamination, free water ...undissolved water , F24 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT none 18. NUMBER OF PAGES 12 19a. NAME OF RESPONSIBLE PERSON Joel...technical, interim, memorandum, master’s thesis, progress, quarterly, research , special, group study, etc. 3. DATES COVERED. Indicate the time during

A compact and portable optofluidic device for detection of liquid properties and label-free sensing

NASA Astrophysics Data System (ADS)

Lahoz, F.; Martín, I. R.; Walo, D.; Gil-Rostra, J.; Yubero, F.; Gonzalez-Elipe, A. R.

2017-06-01

Optofluidic lasers have been widely investigated over the last few years mainly because they can be easily integrated in sensor devices. However, high power pulse lasers are required as excitation sources, which, in practice, limit the portability of the system. Trying to overcome some of these limitations, in this paper we propose the combined use of a small CW laser with a Fabry-Perot optofluidic planar microcavity showing high sensitivity and versatility for detection of liquid properties and label-free sensing. Firstly, a fluorescein solution in ethanol is used to demonstrate the high performances of the FP microcavity as a temperature sensor both in the laser (high pump power above laser threshold) and in the fluorescence (low pump power) regimes. A shift in the wavelength of the resonant cavity modes is used to detect changes in the temperature and our results show that high sensitivities could be already obtained using cheap and portable CW diode lasers. In the second part of the paper, the demonstration of this portable device for label-free sensing is illustrated under low CW pumping. The wavelength positions of the optofluidic resonant modes are used to detect glucose concentrations in water solutions using a protein labelled with a fluorescent dye as the active medium.

Novel and remarkable enhanced-fluorescence system based on gold nanoclusters for detection of tetracycline.

PubMed

Yang, Xiaoming; Zhu, Shanshan; Dou, Yao; Zhuo, Yan; Luo, Yawen; Feng, Yuanjiao

2014-05-01

Tetracycline and Eu(3+), while coexisting, usually appear as a complex by chelating. This complex shows low fluorescence intensity, leading to its limitation of analytical goals. Gold nanoclusters (AuNCs), emerging as novel nano-material, are attracting increasing attentions in multiple fields. Herein, gold nanoclusters first function as a fluorescence-enhanced reagent rather than a conventional fluorescent-probe, and a dramatic enhanced-fluorescence system was built based on Eu(3+)-Tetracycline complex (EuTC) by introducing gold nanoclusters. Simultaneously, three types of gold nanoclusters were employed for exploring various conditions likely affecting the system, which demonstrate that no other gold nanoclusters than DNA-templated gold nanoclusters enormously caused fluorescence-enhancement of EuTC. Moreover, this enhanced-fluorescence system permitted available detection of tetracycline (TC) in a linear range of 0.01-5 μM, with a detection limit of 4 nM at a signal-to-noise ratio of 3. Significantly, the practicality of this method for detection of TC in human urine and milk samples was validated, demonstrating its advantages of simplicity, sensitivity and low cost. Interestingly, this system described here is probably promising for kinds of applications based on its dramatically enhanced-fluorescence. © 2013 Published by Elsevier B.V.

Limit of detection of 15{sub N} by gas-chromatography atomic emission detection: Optimization using an experimental design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deruaz, D.; Bannier, A.; Pionchon, C.

1995-08-01

This paper deals with the optimal conditions for the detection of {sup 15}N determined using a four-factor experimental design from [2{sup 13}C,-1,3 {sup 15}N] caffeine measured with an atomic emission detector (AED) coupled to gas chromatography (GC). Owing to the capability of a photodiodes array, AED can simultaneously detect several elements using their specific emission lines within a wavelength range of 50 nm. So, the emissions of {sup 15}N and {sup 14}N are simultaneously detected at 420.17 nm and 421.46 nm respectively. Four independent experimental factors were tested (1) helium flow rate (plasma gas); (2) methane pressure (reactant gas); (3)more » oxygen pressure; (4) hydrogen pressure. It has been shown that these four gases had a significant influence on the analytical response of {sup 15}N. The linearity of the detection was determined using {sup 15}N amounts ranging from 1.52 pg to 19 ng under the optimal conditions obtained from the experimental design. The limit of detection was studied using different methods. The limits of detection of {sup 15}N was 1.9 pg/s according to the IUPAC method (International-Union of Pure and Applied Chemistry). The method proposed by Quimby and Sullivan gave a value of 2.3 pg/s and that of Oppenheimer gave a limit of 29 pg/s. For each determination, and internal standard: 1-isobutyl-3.7 dimethylxanthine was used. The results clearly demonstrate that GC AED is sensitive and selective enough to detect and measure {sup 15}N-labelled molecules after gas chromatographic separation.« less

Thermodynamic framework to assess low abundance DNA mutation detection by hybridization.

PubMed

Willems, Hanny; Jacobs, An; Hadiwikarta, Wahyu Wijaya; Venken, Tom; Valkenborg, Dirk; Van Roy, Nadine; Vandesompele, Jo; Hooyberghs, Jef

2017-01-01

The knowledge of genomic DNA variations in patient samples has a high and increasing value for human diagnostics in its broadest sense. Although many methods and sensors to detect or quantify these variations are available or under development, the number of underlying physico-chemical detection principles is limited. One of these principles is the hybridization of sample target DNA versus nucleic acid probes. We introduce a novel thermodynamics approach and develop a framework to exploit the specific detection capabilities of nucleic acid hybridization, using generic principles applicable to any platform. As a case study, we detect point mutations in the KRAS oncogene on a microarray platform. For the given platform and hybridization conditions, we demonstrate the multiplex detection capability of hybridization and assess the detection limit using thermodynamic considerations; DNA containing point mutations in a background of wild type sequences can be identified down to at least 1% relative concentration. In order to show the clinical relevance, the detection capabilities are confirmed on challenging formalin-fixed paraffin-embedded clinical tumor samples. This enzyme-free detection framework contains the accuracy and efficiency to screen for hundreds of mutations in a single run with many potential applications in molecular diagnostics and the field of personalised medicine.

Probabilistic resident space object detection using archival THEMIS fluxgate magnetometer data

NASA Astrophysics Data System (ADS)

Brew, Julian; Holzinger, Marcus J.

2018-05-01

Recent progress in the detection of small space objects, at geosynchronous altitudes, through ground-based optical and radar measurements is demonstrated as a viable method. However, in general, these methods are limited to detection of objects greater than 10 cm. This paper examines the use of magnetometers to detect plausible flyby encounters with charged space objects using a matched filter signal existence binary hypothesis test approach. Relevant data-set processing and reduction of archival fluxgate magnetometer data from the NASA THEMIS mission is discussed in detail. Using the proposed methodology and a false alarm rate of 10%, 285 plausible detections with probability of detection greater than 80% are claimed and several are reviewed in detail.

Two New Fluorogenic Aptasensors Based on Capped Mesoporous Silica Nanoparticles to Detect Ochratoxin A

PubMed Central

Ribes, Àngela; Santiago‐Felipe, Sara; Bernardos, Andrea; Marcos, M. Dolores; Pardo, Teresa; Sancenón, Félix; Aznar, Elena

2017-01-01

Abstract Aptamers have been used as recognition elements for several molecules due to their great affinity and selectivity. Additionally, mesoporous nanomaterials have demonstrated great potential in sensing applications. Based on these concepts, we report herein the use of two aptamer‐capped mesoporous silica materials for the selective detection of ochratoxin A (OTA). A specific aptamer for OTA was used to block the pores of rhodamine B‐loaded mesoporous silica nanoparticles. Two solids were prepared in which the aptamer capped the porous scaffolds by using a covalent or electrostatic approach. Whereas the prepared materials remained capped in water, dye delivery was selectively observed in the presence of OTA. The protocol showed excellent analytical performance in terms of sensitivity (limit of detection: 0.5–0.05 nm), reproducibility, and selectivity. Moreover, the aptasensors were tested for OTA detection in commercial foodstuff matrices, which demonstrated their potential applicability in real samples. PMID:29046860

A rapid, naked-eye detection of hypochlorite and bisulfite using a robust and highly-photostable indicator dye Quinaldine Red in aqueous medium

NASA Astrophysics Data System (ADS)

Dutta, Tanoy; Chandra, Falguni; Koner, Apurba L.

2018-02-01

A ;naked-eye; detection of health hazardous bisulfite (HSO3-) and hypochlorite (ClO-) using an indicator dye (Quinaldine Red, QR) in a wide range of pH is demonstrated. The molecule contains a quinoline moiety linked to an N,N-dimethylaniline moiety with a conjugated double bond. Treatment of QR with HSO3- and ClO-, in aqueous solution at near-neutral pH, resulted in a colorless product with high selectivity and sensitivity. The detection limit was 47.8 μM and 0.2 μM for HSO3- and ClO- respectively. However, ClO- was 50 times more sensitive and with 2 times faster response compared to HSO3-. The detail characterization and related analysis demonstrate the potential of QR for a rapid, robust and highly efficient colorimetric sensor for the practical applications to detect hypochlorite in water samples.

Detection of alprazolam with a lab on paper economical device integrated with urchin like Ag@ Pd shell nano-hybrids.

PubMed

Narang, Jagriti; Malhotra, Nitesh; Singhal, Chaitali; Mathur, Ashish; Pn, Anoop Krishna; Pundir, C S

2017-11-01

We present results of the studies relating to fabrication of a microfluidic biosensor chip based on urchin like Ag@ Pd shell nano-hybrids that is capable of sensing alprazolam through electrochemical detection. Using this chip we demonstrate, with high reliability and in a time efficient manner, the detection of alprazolam present in buffer solutions at clinically relevant concentrations. Methylene blue (MB) was also doped as redox transition substance for sensing alprazolam. Nano-hybrids modified EμPAD showed wide linear range 1-300ng/ml and low detection limit of 0.025ng/l. Low detection limit can further enhance its suitability for forensic application. Nano-hybrids modified EμPAD was also employed for determination of drug in real samples such as human urine. Reported facile lab paper approach integrated with urchin like Ag@ Pd shell nano-hybrids could be well applied for the determination of serum metabolites. Copyright © 2016 Elsevier B.V. All rights reserved.

Detecting submerged bodies: controlled research using side-scan sonar to detect submerged proxy cadavers.

PubMed

Healy, Carrie A; Schultz, John J; Parker, Kenneth; Lowers, Bim

2015-05-01

Forensic investigators routinely deploy side-scan sonar for submerged body searches. This study adds to the limited body of literature by undertaking a controlled project to understand how variables affect detection of submerged bodies using side-scan sonar. Research consisted of two phases using small and medium-sized pig (Sus scrofa) carcasses as proxies for human bodies to investigate the effects of terrain, body size, frequency, swath width, and state of decomposition. Results demonstrated that a clear, flat, sandy pond floor terrain was optimal for detection of the target as irregular terrain and/or vegetation are major limitations that can obscure the target. A higher frequency towfish was preferred for small bodies, and a 20 m swath width allowed greater visibility and easier maneuverability of the boat in this environment. Also, the medium-sized carcasses were discernable throughout the 81-day study period, indicating that it is possible to detect bodies undergoing decomposition with side-scan sonar. © 2015 American Academy of Forensic Sciences.

Selective counting and sizing of single virus particles using fluorescent aptamer-based nanoparticle tracking analysis.

PubMed

Szakács, Zoltán; Mészáros, Tamás; de Jonge, Marien I; Gyurcsányi, Róbert E

2018-05-30

Detection and counting of single virus particles in liquid samples are largely limited to narrow size distribution of viruses and purified formulations. To address these limitations, here we propose a calibration-free method that enables concurrently the selective recognition, counting and sizing of virus particles as demonstrated through the detection of human respiratory syncytial virus (RSV), an enveloped virus with a broad size distribution, in throat swab samples. RSV viruses were selectively labeled through their attachment glycoproteins (G) with fluorescent aptamers, which further enabled their identification, sizing and counting at the single particle level by fluorescent nanoparticle tracking analysis. The proposed approach seems to be generally applicable to virus detection and quantification. Moreover, it could be successfully applied to detect single RSV particles in swab samples of diagnostic relevance. Since the selective recognition is associated with the sizing of each detected particle, this method enables to discriminate viral elements linked to the virus as well as various virus forms and associations.

Signal averaging limitations in heterodyne- and direct-detection laser remote sensing measurements

NASA Technical Reports Server (NTRS)

Menyuk, N.; Killinger, D. K.; Menyuk, C. R.

1983-01-01

The improvement in measurement uncertainty brought about by the averaging of increasing numbers of pulse return signals in both heterodyne- and direct-detection lidar systems is investigated. A theoretical analysis is presented which shows the standard deviation of the mean measurement to decrease as the inverse square root of the number of measurements, except in the presence of temporal correlation. Experimental measurements based on a dual-hybrid-TEA CO2 laser differential absorption lidar system are reported which demonstrate that the actual reduction in the standard deviation of the mean in both heterodyne- and direct-detection systems is much slower than the inverse square-root dependence predicted for uncorrelated signals, but is in agreement with predictions in the event of temporal correlation. Results thus favor the use of direct detection at relatively short range where the lower limit of the standard deviation of the mean is about 2 percent, but advantages of heterodyne detection at longer ranges are noted.

Cs2AgBiBr6 single-crystal X-ray detectors with a low detection limit

NASA Astrophysics Data System (ADS)

Pan, Weicheng; Wu, Haodi; Luo, Jiajun; Deng, Zhenzhou; Ge, Cong; Chen, Chao; Jiang, Xiaowei; Yin, Wan-Jian; Niu, Guangda; Zhu, Lujun; Yin, Lixiao; Zhou, Ying; Xie, Qingguo; Ke, Xiaoxing; Sui, Manling; Tang, Jiang

2017-11-01

Sensitive X-ray detection is crucial for medical diagnosis, industrial inspection and scientific research. The recently described hybrid lead halide perovskites have demonstrated low-cost fabrication and outstanding performance for direct X-ray detection, but they all contain toxic Pb in a soluble form. Here, we report sensitive X-ray detectors using solution-processed double perovskite Cs2AgBiBr6 single crystals. Through thermal annealing and surface treatment, we largely eliminate Ag+/Bi3+ disordering and improve the crystal resistivity, resulting in a detector with a minimum detectable dose rate as low as 59.7 nGyair s-1, comparable to the latest record of 0.036 μGyair s-1 using CH3NH3PbBr3 single crystals. Suppressed ion migration in Cs2AgBiBr6 permits relatively large external bias, guaranteeing efficient charge collection without a substantial increase in noise current and thus enabling the low detection limit.

Plasmonic trace sensing below the photon shot noise limit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pooser, Raphael C.; Lawrie, Benjamin J.

Plasmonic sensors are important detectors of biochemical trace compounds, but those that utilize optical readout are approaching their absolute limits of detection as defined by the Heisenberg uncertainty principle in both differential intensity and phase readout. However, the use of more general minimum uncertainty states in the form of squeezed light can push the noise floor in these sensors below the shot noise limit (SNL) in one analysis variable at the expense of another. Here, we demonstrate a quantum plasmonic sensor whose noise floor is reduced below the SNL in order to perform index of refraction measurements with sensitivities unobtainablemore » with classical plasmonic sensors. The increased signal-to-noise ratio can result in faster detection of analyte concentrations that were previously lost in the noise. As a result, these benefits are the hallmarks of a sensor exploiting quantum readout fields in order to manipulate the limits of the Heisenberg uncertainty principle.« less

Plasmonic trace sensing below the photon shot noise limit

DOE PAGES

Pooser, Raphael C.; Lawrie, Benjamin J.

2015-12-09

Plasmonic sensors are important detectors of biochemical trace compounds, but those that utilize optical readout are approaching their absolute limits of detection as defined by the Heisenberg uncertainty principle in both differential intensity and phase readout. However, the use of more general minimum uncertainty states in the form of squeezed light can push the noise floor in these sensors below the shot noise limit (SNL) in one analysis variable at the expense of another. Here, we demonstrate a quantum plasmonic sensor whose noise floor is reduced below the SNL in order to perform index of refraction measurements with sensitivities unobtainablemore » with classical plasmonic sensors. The increased signal-to-noise ratio can result in faster detection of analyte concentrations that were previously lost in the noise. As a result, these benefits are the hallmarks of a sensor exploiting quantum readout fields in order to manipulate the limits of the Heisenberg uncertainty principle.« less

A Game Theoretic Fault Detection Filter

NASA Technical Reports Server (NTRS)

Chung, Walter H.; Speyer, Jason L.

1995-01-01

The fault detection process is modelled as a disturbance attenuation problem. The solution to this problem is found via differential game theory, leading to an H(sub infinity) filter which bounds the transmission of all exogenous signals save the fault to be detected. For a general class of linear systems which includes some time-varying systems, it is shown that this transmission bound can be taken to zero by simultaneously bringing the sensor noise weighting to zero. Thus, in the limit, a complete transmission block can he achieved, making the game filter into a fault detection filter. When we specialize this result to time-invariant system, it is found that the detection filter attained in the limit is identical to the well known Beard-Jones Fault Detection Filter. That is, all fault inputs other than the one to be detected (the "nuisance faults") are restricted to an invariant subspace which is unobservable to a projection on the output. For time-invariant systems, it is also shown that in the limit, the order of the state-space and the game filter can be reduced by factoring out the invariant subspace. The result is a lower dimensional filter which can observe only the fault to be detected. A reduced-order filter can also he generated for time-varying systems, though the computational overhead may be intensive. An example given at the end of the paper demonstrates the effectiveness of the filter as a tool for fault detection and identification.

Limits on radio emission from meteors using the MWA

NASA Astrophysics Data System (ADS)

Zhang, Xiang; Hancock, Paul; Devillepoix, Hadrien A. R.; Wayth, Randall B.; Beardsley, A.; Crosse, B.; Emrich, D.; Franzen, T. M. O.; Gaensler, B. M.; Horsley, L.; Johnston-Hollitt, M.; Kaplan, D. L.; Kenney, D.; Morales, M. F.; Pallot, D.; Steele, K.; Tingay, S. J.; Trott, C. M.; Walker, M.; Williams, A.; Wu, C.; Ji, Jianghui; Ma, Yuehua

2018-04-01

Recently, low frequency, broadband radio emission has been observed accompanying bright meteors by the Long Wavelength Array (LWA). The broadband spectra between 20 and 60 MHz were captured for several events, while the spectral index (dependence of flux density on frequency, with Sν∝να) was estimated to be -4 ± 1 during the peak of meteor afterglows. Here we present a survey of meteor emission and other transient events using the Murchison Widefield Array (MWA) at 72-103 MHz. In our 322-hour survey, down to a 5σ detection threshold of 3.5 Jy/beam, no transient candidates were identified as intrinsic emission from meteors. We derived an upper limit of -3.7 (95% confidence limit) on the spectral index in our frequency range. We also report detections of other transient events, like reflected FM broadcast signals from small satellites, conclusively demonstrating the ability of the MWA to detect and track space debris on scales as small as 0.1 m in low Earth orbits.

A Control Allocation System for Automatic Detection and Compensation of Phase Shift Due to Actuator Rate Limiting

NASA Technical Reports Server (NTRS)

Yildiz, Yidiray; Kolmanovsky, Ilya V.; Acosta, Diana

2011-01-01

This paper proposes a control allocation system that can detect and compensate the phase shift between the desired and the actual total control effort due to rate limiting of the actuators. Phase shifting is an important problem in control system applications since it effectively introduces a time delay which may destabilize the closed loop dynamics. A relevant example comes from flight control where aggressive pilot commands, high gain of the flight control system or some anomaly in the system may cause actuator rate limiting and effective time delay introduction. This time delay can instigate Pilot Induced Oscillations (PIO), which is an abnormal coupling between the pilot and the aircraft resulting in unintentional and undesired oscillations. The proposed control allocation system reduces the effective time delay by first detecting the phase shift and then minimizing it using constrained optimization techniques. Flight control simulation results for an unstable aircraft with inertial cross coupling are reported, which demonstrate phase shift minimization and recovery from a PIO event.

Digital signal processing techniques for coherent optical communication

NASA Astrophysics Data System (ADS)

Goldfarb, Gilad

Coherent detection with subsequent digital signal processing (DSP) is developed, analyzed theoretically and numerically and experimentally demonstrated in various fiber-optic transmission scenarios. The use of DSP in conjunction with coherent detection unleashes the benefits of coherent detection which rely on the preservaton of full information of the incoming field. These benefits include high receiver sensitivity, the ability to achieve high spectral-efficiency and the use of advanced modulation formats. With the immense advancements in DSP speeds, many of the problems hindering the use of coherent detection in optical transmission systems have been eliminated. Most notably, DSP alleviates the need for hardware phase-locking and polarization tracking, which can now be achieved in the digital domain. The complexity previously associated with coherent detection is hence significantly diminished and coherent detection is once gain considered a feasible detection alternative. In this thesis, several aspects of coherent detection (with or without subsequent DSP) are addressed. Coherent detection is presented as a means to extend the dispersion limit of a duobinary signal using an analog decision-directed phase-lock loop. Analytical bit-error ratio estimation for quadrature phase-shift keying signals is derived. To validate the promise for high spectral efficiency, the orthogonal-wavelength-division multiplexing scheme is suggested. In this scheme the WDM channels are spaced at the symbol rate, thus achieving the spectral efficiency limit. Theory, simulation and experimental results demonstrate the feasibility of this approach. Infinite impulse response filtering is shown to be an efficient alternative to finite impulse response filtering for chromatic dispersion compensation. Theory, design considerations, simulation and experimental results relating to this topic are presented. Interaction between fiber dispersion and nonlinearity remains the last major challenge deterministic effects pose for long-haul optical data transmission. Experimental results which demonstrate the possibility to digitally mitigate both dispersion and nonlinearity are presented. Impairment compensation is achieved using backward propagation by implementing the split-step method. Efficient realizations of the dispersion compensation operator used in this implementation are considered. Infinite-impulse response and wavelet-based filtering are both investigated as a means to reduce the required computational load associated with signal backward-propagation. Possible future research directions conclude this dissertation.

Aptamer-based SERRS Sensor for Thrombin Detection

PubMed Central

Cho, Hansang; Baker, Brian R.; Wachsmann-Hogiu, Sebastian; Pagba, Cynthia V.; Laurence, Ted A.; Lane, Stephen M.; Lee, Luke P.; Tok, Jeffrey B.-H.

2012-01-01

We describe an aptamer-based Surface Enhanced Resonance Raman Scattering (SERRS) sensor with high sensitivity, specificity, and stability for the detection of a coagulation protein, human α-thrombin. The sensor achieves high sensitivity and a limit of detection of 100 pM by monitoring the SERRS signal change upon the single step of thrombin binding to immobilized thrombin binding aptamer. The selectivity of the sensor is demonstrated by the specific discrimination of thrombin from other protein analytes. The specific recognition and binding of thrombin by the thrombin binding aptamer is essential to the mechanism of the aptamer-based sensor, as shown through measurements using negative control oligonucleotides. In addition, the sensor can detect 1 nM thrombin in the presence of complex biofluids, such as 10% fetal calf serum, demonstrating that the immobilized, 5'-capped, 3'-capped aptamer is sufficiently robust for clinical diagnostic applications. Furthermore, the proposed sensor may be implemented for multiplexed detection using different aptamer-Raman probe complexes. PMID:19367849

MicroRNA Detection by DNA-Mediated Liposome Fusion.

PubMed

Jumeaux, Coline; Wahlsten, Olov; Block, Stephan; Kim, Eunjung; Chandrawati, Rona; Howes, Philip D; Höök, Fredrik; Stevens, Molly M

2018-03-02

Membrane fusion is a process of fundamental importance in biological systems that involves highly selective recognition mechanisms for the trafficking of molecular and ionic cargos. Mimicking natural membrane fusion mechanisms for the purpose of biosensor development holds great potential for amplified detection because relatively few highly discriminating targets lead to fusion and an accompanied engagement of a large payload of signal-generating molecules. In this work, sequence-specific DNA-mediated liposome fusion is used for the highly selective detection of microRNA. The detection of miR-29a, a known flu biomarker, is demonstrated down to 18 nm within 30 min with high specificity by using a standard laboratory microplate reader. Furthermore, one order of magnitude improvement in the limit of detection is demonstrated by using a novel imaging technique combined with an intensity fluctuation analysis, which is coined two-color fluorescence correlation microscopy. © 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

An Enhanced Platform to Analyse Low-Affinity Amyloid β Protein by Integration of Electrical Detection and Preconcentrator.

PubMed

Yoo, Yong Kyoung; Yoon, Dae Sung; Kim, Gangeun; Kim, Jinsik; Han, Sung Il; Lee, Junwoo; Chae, Myung-Sic; Lee, Sang-Myung; Lee, Kyu Hyoung; Hwang, Kyo Seon; Lee, Jeong Hoon

2017-10-30

Sensitivity and limit of detection (LOD) enhancement are essential criteria for the development of ultrasensitive molecular sensors. Although various sensor types have been investigated to enhance sensitivity and LOD, analyte detection and its quantification are still challenging, particularly for protein-protein interactions with low association constants. To solve this problem, here, we used ion concentration polarization (ICP)-based preconcentration to increase the local concentration of analytes in a microfluidic platform for LOD improvement. This was the first demonstration of a microfluidic device with an integrated ICP preconcentrator and interdigitated microelectrode (IME) sensor to detect small changes in surface binding between antigens and antibodies. We detected the amyloid beta (Aβ) protein, an Alzheimer's disease marker, with low binding affinity to its antibodies by adopting ICP preconcentration phenomena. We demonstrated that a combination of ICP preconcentrator and IME sensor increased the LOD by 13.8-fold to femtomolar level (8.15 fM), which corresponds to a significant advance for clinical applications.

Onboard Detection of Active Canadian Sulfur Springs: A Europa Analogue

NASA Technical Reports Server (NTRS)

Castano, Rebecca; Wagstaff, Kiri; Gleeson, Damhnait; Pappalardo, Robert; Chien, Steve; Tran, Daniel; Scharenbroich, Lucas; Moghaddam, Baback; Tang, Benyang; Bue, Brian;

Improvements in an in vivo neutron activation analysis (NAA) method for the measurement of fluorine in human bone.

PubMed

Mostafaei, F; McNeill, F E; Chettle, D R; Prestwich, W V

2013-10-01

We previously published a method for the in vivo measurement of bone fluoride using neutron activation analysis (NAA) and demonstrated the utility of the technique in a pilot study of environmentally exposed people. The method involved activation of the hand in an irradiation cavity at the McMaster University Accelerator Laboratory and acquisition of the resultant γ-ray signals in a '4π' NaI(Tl) detector array of nine detectors. In this paper we describe a series of improvements to the method. This was investigated via measurement of hand simulating phantoms doped with varying levels of fluorine and fixed amounts of sodium, chlorine and calcium. Four improvements to the technique were tested since our first publication. The previously published detection limit for phantom measurements using this system was 0.66 mg F/g Ca. The accelerator irradiation and detection facilities were relocated to a new section of the laboratory and one more detector was added to the detection system. This was found to reduce the detection limit (possibly because of better detection shielding and additional detector) to 0.59 mg F/g Ca, a factor of 1.12. A new set of phantoms was developed and in this work we show that they improved the minimum detectable limit for fluoride in phantoms irradiated using neutrons produced by 2.15 MeV protons on lithium by a factor of 1.55. We compared the detection limits previously obtained using a summed signal from the nine detectors with the detection limit obtained by acquiring the spectra in anticoincidence mode for reduction of the disturbing signal from chlorine in bone. This was found to improve the ratio of the detection of fluorine to chlorine (an interfering signal) by a factor of 2.8 and the resultant minimum detection limit was found to be reduced by a factor of 1.2. We studied the effects of changing the timing of γ-ray acquisition. Our previously published data used a series of three 10 s acquisitions followed by a 300 s count. Changing the acquisition to a series of six 5 s acquisitions was found to further improve the detection limit by a factor of 1.4. We also present data showing that if the neutron dose is delivered to the phantom in a shorter time period, i.e. the dose rate is increased and irradiation shortened then the detection limit can be reduced by a further factor of 1.35.The overall improvement in detection limit by employing all of these changes was found to be a factor of 3.9. The technique now has an in phantom detection limit of 0.17 mg F/g Ca compared to a previous detection limit of 0.66 mg F/g Ca. The system can now be tested on human volunteers to see if individuals with diagnosed fluorosis can be distinguished from the general Canadian population using this technique.

SU-D-BRD-07: Evaluation of the Effectiveness of Statistical Process Control Methods to Detect Systematic Errors For Routine Electron Energy Verification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parker, S

2015-06-15

Purpose: To evaluate the ability of statistical process control methods to detect systematic errors when using a two dimensional (2D) detector array for routine electron beam energy verification. Methods: Electron beam energy constancy was measured using an aluminum wedge and a 2D diode array on four linear accelerators. Process control limits were established. Measurements were recorded in control charts and compared with both calculated process control limits and TG-142 recommended specification limits. The data was tested for normality, process capability and process acceptability. Additional measurements were recorded while systematic errors were intentionally introduced. Systematic errors included shifts in the alignmentmore » of the wedge, incorrect orientation of the wedge, and incorrect array calibration. Results: Control limits calculated for each beam were smaller than the recommended specification limits. Process capability and process acceptability ratios were greater than one in all cases. All data was normally distributed. Shifts in the alignment of the wedge were most apparent for low energies. The smallest shift (0.5 mm) was detectable using process control limits in some cases, while the largest shift (2 mm) was detectable using specification limits in only one case. The wedge orientation tested did not affect the measurements as this did not affect the thickness of aluminum over the detectors of interest. Array calibration dependence varied with energy and selected array calibration. 6 MeV was the least sensitive to array calibration selection while 16 MeV was the most sensitive. Conclusion: Statistical process control methods demonstrated that the data distribution was normally distributed, the process was capable of meeting specifications, and that the process was centered within the specification limits. Though not all systematic errors were distinguishable from random errors, process control limits increased the ability to detect systematic errors using routine measurement of electron beam energy constancy.« less

External cavity diode laser-based detection of trace gases with NICE-OHMS using current modulation.

PubMed

Centeno, R; Mandon, J; Cristescu, S M; Axner, O; Harren, F J M

2015-03-09

We combine an external cavity diode laser with noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) using current modulation. With a finesse of 1600, we demonstrate noise equivalent absorption sensitivities of 4.1 x 10(-10) cm(-1) Hz(-1/2), resulting in sub-ppbv detection limits for Doppler-broadened transitions of CH(4) at 6132.3 cm(-1), C(2)H(2) at 6578.5 cm(-1) and HCN at 6541.7 cm(-1). The system is used for hydrogen cyanide detection from sweet almonds.

Microfluidic immunosensor with integrated liquid core waveguides for sensitive Mie scattering detection of avian influenza antigens in a real biological matrix.

PubMed

Heinze, Brian C; Gamboa, Jessica R; Kim, Keesung; Song, Jae-Young; Yoon, Jeong-Yeol

2010-11-01

This work presents the use of integrated, liquid core, optical waveguides for measuring immunoagglutination-induced light scattering in a microfluidic device, towards rapid and sensitive detection of avian influenza (AI) viral antigens in a real biological matrix (chicken feces). Mie scattering simulations were performed and tested to optimize the scattering efficiency of the device through proper scatter angle waveguide geometry. The detection limit is demonstrated to be 1 pg mL(-1) in both clean buffer and real biological matrix. This low detection limit is made possible through on-chip diffusional mixing of AI target antigens and high acid content microparticle assay reagents, coupled with real-time monitoring of immunoagglutination-induced forward Mie scattering via high refractive index liquid core optical waveguides in close proximity (100 μm) to the sample chamber. The detection time for the assay is <2 min. This device could easily be modified to detect trace levels of any biological molecules that antibodies are available for, moving towards a robust platform for point-of-care disease diagnostics.

Hybrid nanoporous silicon optical biosensor architectures for biological sample analysis

NASA Astrophysics Data System (ADS)

Bonanno, Lisa M.; Zheng, Hong; DeLouise, Lisa A.

2010-02-01

This work focuses on demonstrating proof-of-concept for a novel nanoparticle optical signal amplification scheme employing hybrid porous silicon (PSi) sensors. We are investigating the development of target responsive hydrogels integrated with PSi optical transducers. These hybrid-PSi sensors can be designed to provide a tunable material response to target concentration ranging from swelling to complete chain dissolution. The corresponding refractive index changes are significant and readily detected by the PSi transducer. However, to increase signal to noise, lower the limit of detection, and provide a visual read out capability, we are investigating the incorporation of high refractive index nanoparticles (NP) into the hydrogel for optical signal amplification. These NPs can be nonspecifically encapsulated, or functionalized with bioactive ligands to bind polymer chains or participate in cross linking. In this work, we demonstrate encapsulation of high refractive index QD nanoparticles into a 5wt% polyacrylamide hydrogel crosslinked with N,N'-methylenebisacrylamide (BIS) and N,N Bis-acryloyl cystamine (BAC). A QD loading (~0.29 wt%) produced a 2X larger optical shift compared to the control. Dissolution of disulphide crosslinks, using Tris[2-carboxyethyl] phosphine (TCEP) reducing agent, induced gel swelling and efficient QD release. We believe this hybrid sensor concept constitutes a versatile technology platform capable of detecting a wide range of bio/chemical targets provided target analogs can be linked to the polymer backbone and crosslinks can be achieved with target responsive multivalent receptors, such a antibodies. The optical signal amplification scheme will enable a lower limit of detection sensitivity not yet demonstrated with PSi technology and colorimetric readout visible to the naked eye.

Leapfrog diagnostics: Demonstration of a broad spectrum pathogen identification platform in a resource-limited setting

PubMed Central

2012-01-01

Background Resource-limited tropical countries are home to numerous infectious pathogens of both human and zoonotic origin. A capability for early detection to allow rapid outbreak containment and prevent spread to non-endemic regions is severely impaired by inadequate diagnostic laboratory capacity, the absence of a “cold chain” and the lack of highly trained personnel. Building up detection capacity in these countries by direct replication of the systems existing in developed countries is not a feasible approach and instead requires “leapfrogging” to the deployment of the newest diagnostic systems that do not have the infrastructure requirements of systems used in developed countries. Methods A laboratory for molecular diagnostics of infectious agents was established in Bo, Sierra Leone with a hybrid solar/diesel/battery system to ensure stable power supply and a satellite modem to enable efficient communication. An array of room temperature stabilization and refrigeration technologies for reliable transport and storage of reagents and biological samples were also tested to ensure sustainable laboratory supplies for diagnostic assays. Results The laboratory demonstrated its operational proficiency by conducting an investigation of a suspected avian influenza outbreak at a commercial poultry farm at Bo using broad range resequencing microarrays and real time RT-PCR. The results of the investigation excluded influenza viruses as a possible cause of the outbreak and indicated a link between the outbreak and the presence of Klebsiella pneumoniae. Conclusions This study demonstrated that by application of a carefully selected set of technologies and sufficient personnel training, it is feasible to deploy and effectively use a broad-range infectious pathogen detection technology in a severely resource-limited setting. PMID:22759725

Highly Sensitive Immunoassay Based on Controlled Rehydration of Patterned Reagents in a 2-Dimensional Paper Network

PubMed Central

2015-01-01

We have demonstrated a multistep 2-dimensional paper network immunoassay based on controlled rehydration of patterned, dried reagents. Previous work has shown that signal enhancement improves the limit of detection in 2-dimensional paper network assays, but until now, reagents have only been included as wet or dried in separate conjugate pads placed at the upstream end of the assay device. Wet reagents are not ideal for point-of-care because they must be refrigerated and typically limit automation and require more user steps. Conjugate pads allow drying but do not offer any control of the reagent distribution upon rehydration and can be a source of error when pads do not contact the assay membrane uniformly. Furthermore, each reagent is dried on a separate pad, increasing the fabrication complexity when implementing multistep assays that require several different reagents. Conversely, our novel method allows for consistent, controlled rehydration from patterned reagent storage depots directly within the paper membrane. In this assay demonstration, four separate reagents were patterned in different regions of the assay device: a gold-antibody conjugate used for antigen detection and three different signal enhancement components that must not be mixed until immediately before use. To show the viability of patterning and drying reagents directly onto a paper device for dry reagent storage and subsequent controlled release, we tested this device with the malaria antigen Plasmodium falciparum histidine-rich protein 2 (PfHRP2) as an example of target analyte. In this demonstration, the signal enhancement step increases the visible signal by roughly 3-fold and decreases the analytical limit of detection by 2.75-fold. PMID:24882058

Green preparation of carbon dots with papaya as carbon source for effective fluorescent sensing of Iron (III) and Escherichia coli.

PubMed

Wang, Ning; Wang, Yiting; Guo, Tingting; Yang, Ting; Chen, Mingli; Wang, Jianhua

2016-11-15

A simple one-step hydrothermal green approach was reported for the preparation of carbon dots (CDs) without any further decoration or modification with papaya powder as natural carbon source. In this economical and eco-friendly system, deionized water or 90% ethanol was used as solvent to produce water-soluble or ethanol-soluble CDs, respectively, termed as W-CDs and E-CDs. The quantum yield (QY) for W-CDs was 18.98%, while that for E-CDs was 18.39%. The potentials of the prepared carbon dots toward diverse applications were thoroughly investigated. W-CDs and E-CDs provide promising probes for fluorescence detection of Fe(3+), offering limits of detection of 0.48μmolL(-1) and 0.29μmolL(-1), respectively. W-CDs was further demonstrated to be a promising probe for fluorescence sensing of Escherichia coli O157: H7, along with a limit of detection of 9.5×10(4)cfumL(-1). Meanwhile, both W-CDs and E-CDs exhibit favorable biocompatibility, and demonstrated to be efficient for Hela cell imaging. Copyright © 2016 Elsevier B.V. All rights reserved.

Sandwiched gold/PNIPAm/gold microstructures for smart plasmonics application: towards the high detection limit and Raman quantitative measurements.

PubMed

Elashnikov, R; Mares, D; Podzimek, T; Švorčík, V; Lyutakov, O

2017-08-07

A smart plasmonic sensor, comprising a layer of a stimuli-responsive polymer sandwiched between two gold layers, is reported. As a stimuli-responsive material, a monolayer of poly(N-isopropylacrylamide) (PNIPAm) crosslinked globules is used. A quasi-periodic structure of the top gold layer facilitates efficient excitation and serves as a support for plasmon excitation and propagation. The intermediate layer of PNIPAm efficiently entraps targeted molecules from solutions. The sensor structure was optimized for efficient light focusing in the "active" PNIPAm layer. The optimization was based on the time-resolved finite-element simulations, which take into account the thickness of gold layers, size of PNIPAm globules and Raman excitation wavelength (780 nm). The prepared structures were characterized using SEM, AFM, UV-Vis refractometry and goniometry. Additional AFM scans were performed in water at two temperatures corresponding to the collapsed and swollen PNIPAm states. The Raman measurements demonstrate a high detection limit and perfect reproducibility of the Raman scattering signal for the prepared sensor. In addition, the use of created SERS structures for the detection of relevant molecules in the medical, biological and safety fields was demonstrated.

Electrochemical Study of Carbon Nanotubes/Nanohybrids for Determination of Metal Species Cu2+ and Pb2+ in Water Samples

PubMed Central

Oliveira Silva, Andréa Claudia; de Oliveira, Luis Carlos Ferreira; Vieira Delfino, Angladis; Meneghetti, Mario Roberto

2016-01-01

The use of nanomaterials, such as nanoparticles and nanotubes, for electrochemical detection of metal species has been investigated as a way of modifying electrodes by electrochemical stripping analysis. The present study develops a new methodology based on a comparative study of nanoparticles and nanotubes with differential pulse anodic stripping voltammetry (DPASV) and examines the simultaneous determination of copper and lead. The glassy carbon electrode modified by gold nanoparticles demonstrated increased sensitivity and decreased detection limits, among other improvements in analytical performance data. Under optimized conditions (deposition potential −0.8 V versus Ag/AgCl; deposition time, 300 s; resting time, 10 s; pulse amplitude, 50 mV; and voltage step height, 4 mV), the detection limits were 0.2279 and 0.3321 ppb, respectively, for determination of Pb2+ and Cu2+. The effects of cations and anions on the simultaneous determination of metal ions do not exhibit significant interference, thereby demonstrating the selectivity of the electrode for simultaneous determination of Pb2+ and Cu2+. The same method was also used to determine Cu2+ in water samples. PMID:27882263

Determination of mutagenic amines in water and food samples by high pressure liquid chromatography with amperometric detection using a multiwall carbon nanotubes-glassy carbon electrode.

PubMed

Bueno, Ana María; Marín, Miguel Ángel; Contento, Ana María; Ríos, Ángel

2016-02-01

A chromatographic method, using amperometric detection, for the sensitive determination of six representative mutagenic amines was developed. A glassy carbon electrode (GCE), modified with multiwall carbon nanotubes (GCE-CNTs), was prepared and its response compared to a conventional glassy carbon electrode. The chromatographic method (HPLC-GCE-CNTs) allowed the separation and the determination of heterocyclic aromatic amines (HAAs) classified as mutagenic amines by the International Agency for Research of Cancer. The new electrode was systematically studied in terms of stability, sensitivity, and reproducibility. Statistical analysis of the obtained data demonstrated that the modified electrode provided better sensitivity than the conventional unmodified ones. Detection limits were in the 3.0 and 7.5 ng/mL range, whereas quantification limits ranged between 9.5 and 25.0 ng/mL were obtained. The applicability of the method was demonstrated by the determination of the amines in several types of samples (water and food samples). Recoveries indicate very good agreement between amounts added and those found for all HAAs (recoveries in the 92% and 105% range). Copyright © 2015 Elsevier Ltd. All rights reserved.

Kernel-Phase Interferometry for Super-Resolution Detection of Faint Companions

NASA Astrophysics Data System (ADS)

Factor, Samuel M.; Kraus, Adam L.

2017-06-01

Direct detection of close in companions (exoplanets or binary systems) is notoriously difficult. While coronagraphs and point spread function (PSF) subtraction can be used to reduce contrast and dig out signals of companions under the PSF, there are still significant limitations in separation and contrast near λ/D. Non-redundant aperture masking (NRM) interferometry can be used to detect companions well inside the PSF of a diffraction limited image, though the mask discards ˜ 95% of the light gathered by the telescope and thus the technique is severely flux limited. Kernel-phase analysis applies interferometric techniques similar to NRM to a diffraction limited image utilizing the full aperture. Instead of non-redundant closure-phases, kernel-phases are constructed from a grid of points on the full aperture, simulating a redundant interferometer. I have developed a new, easy to use, faint companion detection pipeline which analyzes kernel-phases utilizing Bayesian model comparison. I demonstrate this pipeline on archival images from HST/NICMOS, searching for new companions in order to constrain binary formation models at separations inaccessible to previous techniques. Using this method, it is possible to detect a companion well within the classical λ/D Rayleigh diffraction limit using a fraction of the telescope time as NRM. Since the James Webb Space Telescope (JWST) will be able to perform NRM observations, further development and characterization of kernel-phase analysis will allow efficient use of highly competitive JWST telescope time. As no mask is needed, this technique can easily be applied to archival data and even target acquisition images (e.g. from JWST), making the detection of close in companions cheap and simple as no additional observations are needed.

Demonstration of the feasibility of an integrated x ray laboratory for planetary exploration

NASA Technical Reports Server (NTRS)

Franco, E. D.; Kerner, J. A.; Koppel, L. N.; Boyle, M. J.

1993-01-01

The identification of minerals and elemental compositions is an important component in the geological and exobiological exploration of the solar system. X ray diffraction and fluorescence are common techniques for obtaining these data. The feasibility of combining these analytical techniques in an integrated x ray laboratory compatible with the volume, mass, and power constraints imposed by many planetary missions was demonstrated. Breadboard level hardware was developed to cover the range of diffraction lines produced by minerals, clays, and amorphous; and to detect the x ray fluorescence emissions of elements from carbon through uranium. These breadboard modules were fabricated and used to demonstrate the ability to detect elements and minerals. Additional effort is required to establish the detection limits of the breadboard modules and to integrate diffraction and fluorescence techniques into a single unit. It was concluded that this integrated x ray laboratory capability will be a valuable tool in the geological and exobiological exploration of the solar system.

Fast contactless vibrating structure characterization using real time field programmable gate array-based digital signal processing: demonstrations with a passive wireless acoustic delay line probe and vision.

PubMed

Goavec-Mérou, G; Chrétien, N; Friedt, J-M; Sandoz, P; Martin, G; Lenczner, M; Ballandras, S

2014-01-01

Vibrating mechanical structure characterization is demonstrated using contactless techniques best suited for mobile and rotating equipments. Fast measurement rates are achieved using Field Programmable Gate Array (FPGA) devices as real-time digital signal processors. Two kinds of algorithms are implemented on FPGA and experimentally validated in the case of the vibrating tuning fork. A first application concerns in-plane displacement detection by vision with sampling rates above 10 kHz, thus reaching frequency ranges above the audio range. A second demonstration concerns pulsed-RADAR cooperative target phase detection and is applied to radiofrequency acoustic transducers used as passive wireless strain gauges. In this case, the 250 ksamples/s refresh rate achieved is only limited by the acoustic sensor design but not by the detection bandwidth. These realizations illustrate the efficiency, interest, and potentialities of FPGA-based real-time digital signal processing for the contactless interrogation of passive embedded probes with high refresh rates.

Demonstration of protein-fragment complementation assay using purified firefly luciferase fragments

PubMed Central

2013-01-01

Background Human interactome is predicted to contain 150,000 to 300,000 protein-protein interactions, (PPIs). Protein-fragment complementation assay (PCA) is one of the most widely used methods to detect PPI, as well as Förster resonance energy transfer (FRET). To date, successful applications of firefly luciferase (Fluc)-based PCA have been reported in vivo, in cultured cells and in cell-free lysate, owing to its high sensitivity, high signal-to-background (S/B) ratio, and reversible response. Here we show the assay also works with purified proteins with unexpectedly rapid kinetics. Results Split Fluc fragments both fused with a rapamycin-dependently interacting protein pair were made and expressed in E. coli system, and purified to homogeneity. When the proteins were used for PCA to detect rapamycin-dependent PPI, they enabled a rapid detection (~1 s) of PPI with high S/B ratio. When Fn7-8 domains (7 nm in length) that was shown to abrogate GFP mutant-based FRET was inserted between split Fluc and FKBP12 as a rigid linker, it still showed some response, suggesting less limitation in interacting partner’s size. Finally, the stability of the probe was investigated. Preincubation of the probes at 37 degreeC up to 1 h showed marked decrease of the luminescent signal to 1.5%, showing the limited stability of this system. Conclusion Fluc PCA using purified components will enable a rapid and handy detection of PPIs with high S/B ratio, avoiding the effects of concomitant components. Although the system might not be suitable for large-scale screening due to its limited stability, it can detect an interaction over larger distance than by FRET. This would be the first demonstration of Fluc PCA in vitro, which has a distinct advantage over other PPI assays. Our system enables detection of direct PPIs without risk of perturbation by PPI mediators in the complex cellular milieu. PMID:23536995

Rapid detection of mecA and spa by the loop-mediated isothermal amplification (LAMP) method.

PubMed

Koide, Y; Maeda, H; Yamabe, K; Naruishi, K; Yamamoto, T; Kokeguchi, S; Takashiba, S

2010-04-01

To develop a detection assay for staphylococcal mecA and spa by using loop-mediated isothermal amplification (LAMP) method. Staphylococcus aureus and other related species were subjected to the detection of mecA and spa by both PCR and LAMP methods. The LAMP successfully amplified the genes under isothermal conditions at 64 degrees C within 60 min, and demonstrated identical results with the conventional PCR methods. The detection limits of the LAMP for mecA and spa, by gel electrophoresis, were 10(2) and 10 cells per tube, respectively. The naked-eye inspections were possible with 10(3) and 10 cells for detection of mecA and spa, respectively. The LAMP method was then applied to sputum and dental plaque samples. The LAMP and PCR demonstrated identical results for the plaque samples, although frequency in detection of mecA and spa by the LAMP was relatively lower for the sputum samples when compared to the PCR methods. Application of the LAMP enabled a rapid detection assay for mecA and spa. The assay may be applicable to clinical plaque samples. The LAMP offers an alternative detection assay for mecA and spa with a great advantage of the rapidity.

Detection of chemical residues in food oil via surface-enhanced Raman spectroscopy

NASA Astrophysics Data System (ADS)

Sun, Kexi; Huang, Qing

2016-05-01

Highly ordered hexagonally patterned Ag-nanorod (Ag-NR) arrays for surface-enhanced Raman scattering (SERS) detection of unhealthy chemical residues in food oil was reported, which was obtained by sputtering Ag on the alumina nanotip arrays stuck out of conical-pore anodic aluminum oxide (AAO) templates. SERS measurements demonstrate that the as-fabricated large-scale Ag-nanostructures can serve as highly sensitive and reproducible SERS substrates for detection of trace amount of chemicals in oil with the lower detection limits of 2×10-6 M for thiram and 10-7 M for rhodamine B, showing the potential of application of SERS in rapid trace detection of pesticide residues and illegal additives in food oils.

Ultrasensitive and low-volume point-of-care diagnostics on flexible strips - a study with cardiac troponin biomarkers

NASA Astrophysics Data System (ADS)

Shanmugam, Nandhinee Radha; Muthukumar, Sriram; Prasad, Shalini

2016-09-01

We demonstrate a flexible, mechanically stable, and disposable electrochemical sensor platform for monitoring cardiac troponins through the detection and quantification of cardiac Troponin-T (cTnT). We designed and fabricated nanostructured zinc oxide (ZnO) sensing electrodes on flexible porous polyimide substrates. We demonstrate ultrasensitive detection is capable at very low sample volumes due to the confinement phenomenon of target species within the ZnO nanostructures leading to enhancement of biomolecular binding on the sensor electrode surface. The performance of the ZnO nanostructured sensor electrode was evaluated against gold and nanotextured ZnO electrodes. The electrochemical sensor functions on affinity based immunoassay principles whereby monoclonal antibodies for cTnT were immobilized on the sensor electrodes using thiol based chemistry. Detection of cTnT in phosphate buffered saline (PBS) and human serum (HS) buffers was achieved at low sample volumes of 20 μL using non-faradaic electrochemical impedance spectroscopy (EIS). Limit of detection (LOD) of 1E-4 ng/mL (i.e. 1 pg/mL) at 7% CV (coefficient of variation) for cTnT in HS was demonstrated on nanostructured ZnO electrodes. The mechanical integrity of the flexible biosensor platform was demonstrated with cyclic bending tests. The sensor performed within 12% CV after 100 bending cycles demonstrating the robustness of the nanostructured ZnO electrochemical sensor platform.

Trace analysis of muramic acid in indoor air using an automated derivatization instrument and GC-MS(2) or GC-MS(3).

PubMed

Harley, William M; Kozar, Michael P; Fox, Alvin

2002-09-01

An automated derivatization instrument has been developed for the preparation of alditol acetates from bacterial hydrolysates for analysis by gas chromatography-mass spectrometry (GC-MS). The current report demonstrates the utility of the automated instrument for the more demanding task of trace analysis of muramic acid (Mur) in airborne dust using gas chromatography-tandem mass spectrometry (GC-MS(2)). Conditions for efficient derivatization of Mur, vital for trace analysis, are rigorous including lactam and imido group formation under anhydrous conditions. Furthermore, as the detection limit is lowered, possible contamination or carry-over of samples becomes an increasingly greater consideration and must not occur. The instrument meets these criteria and was successfully used for assaying the levels of Mur in laboratory air, which were found to be much lower than in the previous studies of heavily occupied schools and agricultural environments. The potential for GC-MS(3) in further lowering the detection limit was also demonstrated.

Optical filter requirements in an EML-based single-sideband PAM4 intensity-modulation and direct-detection transmission system.

PubMed

Chen, Hsing-Yu; Kaneda, Noriaki; Lee, Jeffrey; Chen, Jyehong; Chen, Young-Kai

2017-03-20

The feasibility of a single sideband (SSB) PAM4 intensity-modulation and direct-detection (IM/DD) transmission based on a CMOS ADC and DAC is experimentally demonstrated in this work. To cost effectively build a >50 Gb/s system as well as to extend the transmission distance, a low cost EML and a passive optical filter are utilized to generate the SSB signal. However, the EML-induced chirp and dispersion-induced power fading limit the requirements of the SSB filter. To separate the effect of signal-signal beating interference, filters with different roll-off factors are employed to demonstrate the performance tolerance at different transmission distance. Moreover, a high resolution spectrum analysis is proposed to depict the system limitation. Experimental results show that a minimum roll-off factor of 7 dB/10GHz is required to achieve a 51.84Gb/s 40-km transmission with only linear feed-forward equalization.

Sensitivity enhancement for nitrophenols using cationic surfactant-modified activated carbon for solid-phase extraction surface-assisted laser desorption/ionization mass spectrometry.

PubMed

Chen, Y C; Tsai, M F

2000-01-01

Previous work has demonstrated that a combination of solid-phase extraction with surface-assisted laser desorption/ionization (SPE-SALDI) mass spectrometry can be applied to the determination of trace nitrophenols in water. An improved method to lower the detection limit of this hyphenated technique is described in this present study. Activated carbon powder is used as both the SPE adsorbent and the SALDI solid in the analysis by SPE-SALDI. The surface of the activated carbon is modified by passing an aqueous solution of a cationic surfactant through the SPE cartridge. The results demonstrate that the sensitivity for nitrophenols in the analysis by SPE-SALDI can be improved by using cationic surfactants to modify the surface of the activated carbon. The detection limit for nitrophenols is about 25 ppt based on a signal-to-noise ratio of 3 by sampling from 100 mL of solution. Copyright 2000 John Wiley & Sons, Ltd.

Lower limits of spin detection efficiency for two-parameter two-qubit (TPTQ) states with non-ideal ferromagnetic detectors

NASA Astrophysics Data System (ADS)

Majd, Nayereh; Ghasemi, Zahra

2016-10-01

We have investigated a TPTQ state as an input state of a non-ideal ferromagnetic detectors. Minimal spin polarization required to demonstrate spin entanglement according to entanglement witness and CHSH inequality with respect to (w.r.t.) their two free parameters have been found, and we have numerically shown that the entanglement witness is less stringent than the direct tests of Bell's inequality in the form of CHSH in the entangled limits of its free parameters. In addition, the lower limits of spin detection efficiency fulfilling secure cryptographic key against eavesdropping have been derived. Finally, we have considered TPTQ state as an output of spin decoherence channel and the region of ballistic transmission time w.r.t. spin relaxation time and spin dephasing time has been found.

Decision-feedback detection strategy for nonlinear frequency-division multiplexing

NASA Astrophysics Data System (ADS)

Civelli, Stella; Forestieri, Enrico; Secondini, Marco

2018-04-01

By exploiting a causality property of the nonlinear Fourier transform, a novel decision-feedback detection strategy for nonlinear frequency-division multiplexing (NFDM) systems is introduced. The performance of the proposed strategy is investigated both by simulations and by theoretical bounds and approximations, showing that it achieves a considerable performance improvement compared to previously adopted techniques in terms of Q-factor. The obtained improvement demonstrates that, by tailoring the detection strategy to the peculiar properties of the nonlinear Fourier transform, it is possible to boost the performance of NFDM systems and overcome current limitations imposed by the use of more conventional detection techniques suitable for the linear regime.

Sensitive and selective determination of methylenedioxylated amphetamines by high-performance liquid chromatography with fluorimetric detection.

PubMed

Sadeghipour, F; Veuthey, J L

1997-11-07

A rapid, sensitive and selective liquid chromatographic method with fluorimetric detection was developed for the separation and quantification of four methylenedioxylated amphetamines without interference of other drugs of abuse and common substances found in illicit tablets. The method was validated by examining linearity, precision and accuracy as well as detection and quantification limits. Methylenedioxylated amphetamines were quantified in eight tablets from illicit drug seizures and results were quantitatively compared to HPLC-UV analyses. To demonstrate the better sensitivity of the fluorimetric detection, methylenedioxylated amphetamines were analyzed in serum after a liquid-liquid extraction procedure and results were also compared to HPLC-UV analyses.

Amplification of interference color by using liquid crystal for protein detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Qingdi; Yang, Kun-Lin, E-mail: cheyk@nus.edu.sg

Micrometer-sized, periodic protein lines printed on a solid surface cause interference color which is invisible to the naked eye. However, the interference color can be amplified by using a thin layer of liquid crystal (LC) covered on the surface to form a phase diffraction grating. Strong interference color can thus be observed under ambient light. By using the LC-amplified interference color, we demonstrate naked-eye detection of a model protein—immunoglobulin G (IgG). Limit of detection can reach 20 μg/ml of IgG without using any instrumentation. This detection method is potentially useful for the development of low-cost and portable biosensors.

The analysis of tetracyclines, quinolones, macrolides, lincosamides, pleuromutilins, and sulfonamides in chicken feathers using UHPLC-MS/MS in order to monitor antibiotic use in the poultry sector.

PubMed

Jansen, Larissa J M; Bolck, Yvette J C; Rademaker, Janneau; Zuidema, Tina; Berendsen, Bjorn J A

2017-08-01

In The Netherlands, all antibiotic treatments should be registered at the farm and in a central database. To enforce correct antibiotic use and registration, and to enforce prudent use of antibiotics, there is a need for methods that are able to detect antibiotic treatments. Ideally, such a method is able to detect antibiotic applications during the entire lifespan of an animal, including treatments administered during the first days of the animals' lives. Monitoring tissue, as is common practice, only provides a limited window of opportunity, as residue levels in tissue soon drop below measurable quantities. The analysis of feathers proves to be a promising tool in this respect. Furthermore, a qualitative confirmatory method was developed for the analyses of six major groups of antibiotics in ground chicken feathers, aiming for a detection limit as low as reasonably possible. The method was validated according to Commission Decision 2002/657/EC. All compounds comply with the criteria and, as a matter of fact, 58% of the compounds could also be quantified according to regulations. Additionally, we demonstrated that a less laborious method, in which whole feathers were analyzed, proved successful in the detection of applied antibiotics. Most compounds could be detected at levels of 2 μg kg -1 or below with the exception of sulfachloropyridazine, tylosin, and tylvalosin. This demonstrates the effectiveness of feather analysis to detect antibiotic use to allow effective enforcement of antibiotic use and prevent the illegal, off-label, and nonregistered use of antibiotics.

DNA aptamer-based colorimetric detection platform for Salmonella Enteritidis.

PubMed

Bayraç, Ceren; Eyidoğan, Füsun; Avni Öktem, Hüseyin

2017-12-15

Food safety is a major issue to protect public health and a key challenge is to find detection methods for identification of hazards in food. Food borne infections affects millions of people each year and among pathogens, Salmonella Enteritidis is most widely found bacteria causing food borne diseases. Therefore, simple, rapid, and specific detection methods are needed for food safety. In this study, we demonstrated the selection of DNA aptamers with high affinity and specificity against S. Enteritidis via Cell Systematic Evolution of Ligands by Exponential Enrichment (Cell-SELEX) and development of sandwich type aptamer-based colorimetric platforms for its detection. Two highly specific aptamers, crn-1 and crn-2, were developed through 12 rounds of selection with K d of 0.971µM and 0.309µM, respectively. Both aptamers were used to construct sandwich type capillary detection platforms. With the detection limit of 10 3 CFU/mL, crn-1 and crn-2 based platforms detected target bacteria specifically based on color change. This platform is also suitable for detection of S. Enteritidis in complex food matrix. Thus, this is the first to demonstrate use of Salmonella aptamers for development of the colorimetric aptamer-based detection platform in its identification and detection with naked eye in point-of-care. Copyright © 2017 Elsevier B.V. All rights reserved.

Polarization-dependent optical reflection ultrasonic detection

NASA Astrophysics Data System (ADS)

Zhu, Xiaoyi; Huang, Zhiyu; Wang, Guohe; Li, Wenzhao; Li, Changhui

2017-03-01

Although ultrasound transducers based on commercial piezoelectric-material have been widely used, they generally have limited bandwidth centered at the resonant frequency. Currently, several pure-optical ultrasonic detection methods have gained increasing interest due to their wide bandwidth and high sensitivity. However, most of them require customized components (such as micro-ring, SPR, Fabry-Perot film, etc), which limit their broad implementations. In this study, we presented a simple pure-optical ultrasound detection method, called "Polarization-dependent Reflection Ultrasonic Detection" (PRUD). It detects the intensity difference between two polarization components of the probe beam that is modulated by ultrasound waves. PRUD detect the two components by using a balanced detector, which effectively suppressed much of the unwanted noise. We have achieved the sensitivity (noise equivalent pressure) to be 1.7kPa, and this can be further improved. In addition, like many other pure-optical ultrasonic detection methods, PRUD also has a flat and broad bandwidth from almost zero to over 100MHz. Besides theoretical analysis, we did a phantom study by imaging a tungsten filament to demonstrate the performance of PRUD. We believe this simple and economic method will attract both researchers and engineers in optical and ultrasound fields.

Early breast cancer screening using iron/iron oxide-based nanoplatforms with sub-femtomolar limits of detection.

PubMed

Udukala, Dinusha N; Wang, Hongwang; Wendel, Sebastian O; Malalasekera, Aruni P; Samarakoon, Thilani N; Yapa, Asanka S; Abayaweera, Gayani; Basel, Matthew T; Maynez, Pamela; Ortega, Raquel; Toledo, Yubisela; Bossmann, Leonie; Robinson, Colette; Janik, Katharine E; Koper, Olga B; Li, Ping; Motamedi, Massoud; Higgins, Daniel A; Gadbury, Gary; Zhu, Gaohong; Troyer, Deryl L; Bossmann, Stefan H

2016-01-01

Proteases, including matrix metalloproteinases (MMPs), tissue serine proteases, and cathepsins (CTS) exhibit numerous functions in tumor biology. Solid tumors are characterized by changes in protease expression levels by tumor and surrounding tissue. Therefore, monitoring protease levels in tissue samples and liquid biopsies is a vital strategy for early cancer detection. Water-dispersable Fe/Fe3O4-core/shell based nanoplatforms for protease detection are capable of detecting protease activity down to sub-femtomolar limits of detection. They feature one dye (tetrakis(carboxyphenyl)porphyrin (TCPP)) that is tethered to the central nanoparticle by means of a protease-cleavable consensus sequence and a second dye (Cy 5.5) that is directly linked. Based on the protease activities of urokinase plasminogen activator (uPA), MMPs 1, 2, 3, 7, 9, and 13, as well as CTS B and L, human breast cancer can be detected at stage I by means of a simple serum test. By monitoring CTS B and L stage 0 detection may be achieved. This initial study, comprised of 46 breast cancer patients and 20 apparently healthy human subjects, demonstrates the feasibility of protease-activity-based liquid biopsies for early cancer diagnosis.

A System for Multiplexed Direct Electrical Detection of DNA Synthesis.

PubMed

Anderson, Erik P; Daniels, Jonathan S; Yu, Heng; Karhanek, Miloslav; Lee, Thomas H; Davis, Ronald W; Pourmand, Nader

2008-01-29

An electronic system for the multiplexed detection of DNA polymerization is designed and characterized. DNA polymerization is detected by the measurement of small transient currents arising from ion diffusion during polymerization. A transimpedance amplifier is used to detect these small currents; we implemented a twenty-four channel recording system on a single printed circuit board. Various contributions to the input-referred current noise are analyzed and characterized, as it limits the minimum detectable current and thus the biological limit of detection. We obtained 8.5 pA RMS mean noise current (averaged over all 24 channels) over the recording bandwidth (DC to 2 kHz). With digital filtering, the input-referred current noise of the acquisition system is reduced to 2.4 pA, which is much lower than the biological noise. Electrical crosstalk between channels is measured, and a model for the crosstalk is presented. Minimizing the crosstalk is critical because it can lead to erroneous microarray data. With proper precautions, crosstalk is reduced to a negligible value (less than 1.4%). Using a micro-fabricated array of 24 gold electrodes, we demonstrated system functionality by detecting the presence of a target DNA oligonucleotide which hybridized onto its corresponding target.

Early breast cancer screening using iron/iron oxide-based nanoplatforms with sub-femtomolar limits of detection

PubMed Central

Samarakoon, Thilani N; Yapa, Asanka S; Abayaweera, Gayani; Basel, Matthew T; Maynez, Pamela; Ortega, Raquel; Toledo, Yubisela; Bossmann, Leonie; Robinson, Colette; Janik, Katharine E; Koper, Olga B; Li, Ping; Motamedi, Massoud; Higgins, Daniel A; Gadbury, Gary

2016-01-01

Summary Proteases, including matrix metalloproteinases (MMPs), tissue serine proteases, and cathepsins (CTS) exhibit numerous functions in tumor biology. Solid tumors are characterized by changes in protease expression levels by tumor and surrounding tissue. Therefore, monitoring protease levels in tissue samples and liquid biopsies is a vital strategy for early cancer detection. Water-dispersable Fe/Fe3O4-core/shell based nanoplatforms for protease detection are capable of detecting protease activity down to sub-femtomolar limits of detection. They feature one dye (tetrakis(carboxyphenyl)porphyrin (TCPP)) that is tethered to the central nanoparticle by means of a protease-cleavable consensus sequence and a second dye (Cy 5.5) that is directly linked. Based on the protease activities of urokinase plasminogen activator (uPA), MMPs 1, 2, 3, 7, 9, and 13, as well as CTS B and L, human breast cancer can be detected at stage I by means of a simple serum test. By monitoring CTS B and L stage 0 detection may be achieved. This initial study, comprised of 46 breast cancer patients and 20 apparently healthy human subjects, demonstrates the feasibility of protease-activity-based liquid biopsies for early cancer diagnosis. PMID:27335730

Plasmodium vivax molecular diagnostics in community surveys: pitfalls and solutions.

PubMed

Gruenberg, Maria; Moniz, Clara Antunes; Hofmann, Natalie Ellen; Wampfler, Rahel; Koepfli, Cristian; Mueller, Ivo; Monteiro, Wuelton Marcelo; Lacerda, Marcus; de Melo, Gisely Cardoso; Kuehn, Andrea; Siqueira, Andre M; Felger, Ingrid

2018-01-30

A distinctive feature of Plasmodium vivax infections is the overall low parasite density in peripheral blood. Thus, identifying asymptomatic infected individuals in endemic communities requires diagnostic tests with high sensitivity. The detection limits of molecular diagnostic tests are primarily defined by the volume of blood analysed and by the copy number of the amplified molecular marker serving as the template for amplification. By using mitochondrial DNA as the multi-copy template, the detection limit can be improved more than tenfold, compared to standard 18S rRNA targets, thereby allowing detection of lower parasite densities. In a very low transmission area in Brazil, application of a mitochondrial DNA-based assay increased prevalence from 4.9 to 6.5%. The usefulness of molecular tests in malaria epidemiological studies is widely recognized, especially when precise prevalence rates are desired. Of concern, however, is the challenge of demonstrating test accuracy and quality control for samples with very low parasite densities. In this case, chance effects in template distribution around the detection limit constrain reproducibility. Rigorous assessment of false positive and false negative test results is, therefore, required to prevent over- or under-estimation of parasite prevalence in epidemiological studies or when monitoring interventions.

Assessing carotid atherosclerosis by fiber-optic multispectral photoacoustic tomography

NASA Astrophysics Data System (ADS)

Hui, Jie; Li, Rui; Wang, Pu; Phillips, Evan; Bruning, Rebecca; Liao, Chien-Sheng; Sturek, Michael; Goergen, Craig J.; Cheng, Ji-Xin

2015-03-01

Atherosclerotic plaque at the carotid bifurcation is the underlying cause of the majority of ischemic strokes. Noninvasive imaging and quantification of the compositional changes preceding gross anatomic changes within the arterial wall is essential for diagnosis of disease. Current imaging modalities such as duplex ultrasound, computed tomography, positron emission tomography are limited by the lack of compositional contrast and the detection of flow-limiting lesions. Although high-resolution magnetic resonance imaging has been developed to characterize atherosclerotic plaque composition, its accessibility for wide clinical use is limited. Here, we demonstrate a fiber-based multispectral photoacoustic tomography system for excitation of lipids and external acoustic detection of the generated ultrasound. Using sequential ultrasound imaging of ex vivo preparations we achieved ~2 cm imaging depth and chemical selectivity for assessment of human arterial plaques. A multivariate curve resolution alternating least squares analysis method was applied to resolve the major chemical components, including intravascular lipid, intramuscular fat, and blood. These results show the promise of detecting carotid plaque in vivo through esophageal fiber-optic excitation of lipids and external acoustic detection of the generated ultrasound. This imaging system has great potential for serving as a point-ofcare device for early diagnosis of carotid artery disease in the clinic.

Simple, Sensitive and Accurate Multiplex Detection of Clinically Important Melanoma DNA Mutations in Circulating Tumour DNA with SERS Nanotags

PubMed Central

Wee, Eugene J.H.; Wang, Yuling; Tsao, Simon Chang-Hao; Trau, Matt

2016-01-01

Sensitive and accurate identification of specific DNA mutations can influence clinical decisions. However accurate diagnosis from limiting samples such as circulating tumour DNA (ctDNA) is challenging. Current approaches based on fluorescence such as quantitative PCR (qPCR) and more recently, droplet digital PCR (ddPCR) have limitations in multiplex detection, sensitivity and the need for expensive specialized equipment. Herein we describe an assay capitalizing on the multiplexing and sensitivity benefits of surface-enhanced Raman spectroscopy (SERS) with the simplicity of standard PCR to address the limitations of current approaches. This proof-of-concept method could reproducibly detect as few as 0.1% (10 copies, CV < 9%) of target sequences thus demonstrating the high sensitivity of the method. The method was then applied to specifically detect three important melanoma mutations in multiplex. Finally, the PCR/SERS assay was used to genotype cell lines and ctDNA from serum samples where results subsequently validated with ddPCR. With ddPCR-like sensitivity and accuracy yet at the convenience of standard PCR, we believe this multiplex PCR/SERS method could find wide applications in both diagnostics and research. PMID:27446486

Simple, Sensitive and Accurate Multiplex Detection of Clinically Important Melanoma DNA Mutations in Circulating Tumour DNA with SERS Nanotags.

PubMed

Wee, Eugene J H; Wang, Yuling; Tsao, Simon Chang-Hao; Trau, Matt

2016-01-01

Sensitive and accurate identification of specific DNA mutations can influence clinical decisions. However accurate diagnosis from limiting samples such as circulating tumour DNA (ctDNA) is challenging. Current approaches based on fluorescence such as quantitative PCR (qPCR) and more recently, droplet digital PCR (ddPCR) have limitations in multiplex detection, sensitivity and the need for expensive specialized equipment. Herein we describe an assay capitalizing on the multiplexing and sensitivity benefits of surface-enhanced Raman spectroscopy (SERS) with the simplicity of standard PCR to address the limitations of current approaches. This proof-of-concept method could reproducibly detect as few as 0.1% (10 copies, CV < 9%) of target sequences thus demonstrating the high sensitivity of the method. The method was then applied to specifically detect three important melanoma mutations in multiplex. Finally, the PCR/SERS assay was used to genotype cell lines and ctDNA from serum samples where results subsequently validated with ddPCR. With ddPCR-like sensitivity and accuracy yet at the convenience of standard PCR, we believe this multiplex PCR/SERS method could find wide applications in both diagnostics and research.

Perils of categorical thinking: "Oxic/anoxic" conceptual model in environmental remediation

USGS Publications Warehouse

Bradley, Paul M.

2012-01-01

Given ambient atmospheric oxygen concentrations of about 21 percent (by volume), the lower limit for reliable quantitation of dissolved oxygen concentrations in groundwater samples is in the range of 0.1–0.5 mg/L. Frameworks for assessing in situ redox condition are often applied using a simple two-category (oxic/anoxic) model of oxygen condition. The "oxic" category defines the environmental range in which dissolved oxygen concentrations are clearly expected to impact contaminant biodegradation, either by supporting aerobic biodegradation of electron-donor contaminants like petroleum hydrocarbons or by inhibiting anaerobic biodegradation of electron-acceptor contaminants like chloroethenes. The tendency to label the second category "anoxic" leads to an invalid assumption that oxygen is insignificant when, in fact, the dissolved oxygen concentration is less than detection but otherwise unknown. Expressing dissolved oxygen concentrations as numbers of molecules per volume, dissolved oxygen concentrations that fall below the 0.1 mg/L field detection limit range from 1 to 1017 molecules/L. In light of recent demonstrations of substantial oxygen-linked biodegradation of chloroethene contaminants at dissolved oxygen concentrations well below the 0.1–0.5 mg/L field detection limit, characterizing "less than detection" oxygen concentrations as "insignificant" is invalid.

On-chip integrated optofluidic complex refractive index sensing using silicon photonic crystal nanobeam cavities.

PubMed

Zhang, Xingwang; Zhou, Guangya; Shi, Peng; Du, Han; Lin, Tong; Teng, Jinghua; Chau, Fook Siong

2016-03-15

Complex refractive index sensing is proposed and experimentally demonstrated in optofluidic sensors based on silicon photonic crystal nanobeam cavities. The sensitivities are 58 and 139 nm/RIU, respectively, for the real part (n) and the imaginary part (κ) of the complex refractive index, and the corresponding detection limits are 1.8×10(-5) RIU for n and 4.1×10(-6) RIU for κ. Moreover, the capability of the complex refractive index sensing method to detect the concentration composition of the ternary mixture is demonstrated without the surface immobilization of functional groups, which is impossible to realize with the conventional refractive index sensing scheme.

Optical hydrogen sensors based on metal-hydrides

NASA Astrophysics Data System (ADS)

Slaman, M.; Westerwaal, R.; Schreuders, H.; Dam, B.

2012-06-01

For many hydrogen related applications it is preferred to use optical hydrogen sensors above electrical systems. Optical sensors reduce the risk of ignition by spark formation and are less sensitive to electrical interference. Currently palladium and palladium alloys are used for most hydrogen sensors since they are well known for their hydrogen dissociation and absorption properties at relatively low temperatures. The disadvantages of palladium in sensors are the low optical response upon hydrogen loading, the cross sensitivity for oxygen and carbon, the limited detection range and the formation of micro-cracks after some hydrogen absorption/desorption cycles. In contrast to Pd, we find that the use of magnesium or rear earth bases metal-hydrides in optical hydrogen sensors allow tuning of the detection levels over a broad pressure range, while maintaining a high optical response. We demonstrate a stable detection layer for detecting hydrogen below 10% of the lower explosion limit in an oxygen rich environment. This detection layer is deposited at the bare end of a glass fiber as a micro-mirror and is covered with a thin layer of palladium. The palladium layer promotes the hydrogen uptake at room temperature and acts as a hydrogen selective membrane. To protect the sensor for a long time in air a final layer of a hydrophobic fluorine based coating is applied. Such a sensor can be used for example as safety detector in automotive applications. We find that this type of fiber optic hydrogen sensor is also suitable for hydrogen detection in liquids. As example we demonstrate a sensor for detecting a broad range of concentrations in transformer oil. Such a sensor can signal a warning when sparks inside a high voltage power transformer decompose the transformer oil over a long period.

Flower-like ZnO decorated polyaniline/reduced graphene oxide nanocomposites for simultaneous determination of dopamine and uric acid.

PubMed

Ghanbari, Kh; Moloudi, M

2016-11-01

A novel sensor was fabricated by electrochemical deposition of ZnO flower-like/polyaniline nanofiber/reduced graphene oxide nanocomposite (ZnO/PANI/RGO) on glassy carbon electrode (GCE) for direct detection of dopamine (DA) and uric acid (UA) in the presence of fixed concentration of ascorbic acid (AA). Surface morphology and characterization of the modified electrodes were confirmed by field emission scanning microscopy (FE-SEM), X-ray diffraction (XRD), Raman and FT-IR spectroscopies. For individual detection, the linear responses were in the two concentration ranges of 0.001-1 μM and 1-1000 μM with detection limit 0.8 nM (S/N = 3) for DA, and also 0.1-100 μM and 100-1000 μM with detection limit 0.042 μM (S/N = 3) for UA. Simultaneous determination of these species in their mixture solution showed the linear responses in the two concentration ranges of 0.1-90 μM and 90-1000 μM with detection limit 0.017 μM (S/N = 3) for DA and also showed two linear range of 0.5-90 μM and 100-1000 μM with detection limit 0.12 μM (S/N = 3) for UA, with coexistence of 1000 μM AA. The applicability of sensor for the analysis of DA, and UA in dopamine injection solution, human serum and human urine samples was successfully demonstrated. Copyright © 2016 Elsevier Inc. All rights reserved.

Thermodynamic framework to assess low abundance DNA mutation detection by hybridization

PubMed Central

Willems, Hanny; Jacobs, An; Hadiwikarta, Wahyu Wijaya; Venken, Tom; Valkenborg, Dirk; Van Roy, Nadine; Vandesompele, Jo; Hooyberghs, Jef

2017-01-01

The knowledge of genomic DNA variations in patient samples has a high and increasing value for human diagnostics in its broadest sense. Although many methods and sensors to detect or quantify these variations are available or under development, the number of underlying physico-chemical detection principles is limited. One of these principles is the hybridization of sample target DNA versus nucleic acid probes. We introduce a novel thermodynamics approach and develop a framework to exploit the specific detection capabilities of nucleic acid hybridization, using generic principles applicable to any platform. As a case study, we detect point mutations in the KRAS oncogene on a microarray platform. For the given platform and hybridization conditions, we demonstrate the multiplex detection capability of hybridization and assess the detection limit using thermodynamic considerations; DNA containing point mutations in a background of wild type sequences can be identified down to at least 1% relative concentration. In order to show the clinical relevance, the detection capabilities are confirmed on challenging formalin-fixed paraffin-embedded clinical tumor samples. This enzyme-free detection framework contains the accuracy and efficiency to screen for hundreds of mutations in a single run with many potential applications in molecular diagnostics and the field of personalised medicine. PMID:28542229

Network hydraulics inclusion in water quality event detection using multiple sensor stations data.

PubMed

Oliker, Nurit; Ostfeld, Avi

2015-09-01

Event detection is one of the current most challenging topics in water distribution systems analysis: how regular on-line hydraulic (e.g., pressure, flow) and water quality (e.g., pH, residual chlorine, turbidity) measurements at different network locations can be efficiently utilized to detect water quality contamination events. This study describes an integrated event detection model which combines multiple sensor stations data with network hydraulics. To date event detection modelling is likely limited to single sensor station location and dataset. Single sensor station models are detached from network hydraulics insights and as a result might be significantly exposed to false positive alarms. This work is aimed at decreasing this limitation through integrating local and spatial hydraulic data understanding into an event detection model. The spatial analysis complements the local event detection effort through discovering events with lower signatures by exploring the sensors mutual hydraulic influences. The unique contribution of this study is in incorporating hydraulic simulation information into the overall event detection process of spatially distributed sensors. The methodology is demonstrated on two example applications using base runs and sensitivity analyses. Results show a clear advantage of the suggested model over single-sensor event detection schemes. Copyright © 2015 Elsevier Ltd. All rights reserved.

Optimization and validation of moving average quality control procedures using bias detection curves and moving average validation charts.

PubMed

van Rossum, Huub H; Kemperman, Hans

2017-02-01

To date, no practical tools are available to obtain optimal settings for moving average (MA) as a continuous analytical quality control instrument. Also, there is no knowledge of the true bias detection properties of applied MA. We describe the use of bias detection curves for MA optimization and MA validation charts for validation of MA. MA optimization was performed on a data set of previously obtained consecutive assay results. Bias introduction and MA bias detection were simulated for multiple MA procedures (combination of truncation limits, calculation algorithms and control limits) and performed for various biases. Bias detection curves were generated by plotting the median number of test results needed for bias detection against the simulated introduced bias. In MA validation charts the minimum, median, and maximum numbers of assay results required for MA bias detection are shown for various bias. Their use was demonstrated for sodium, potassium, and albumin. Bias detection curves allowed optimization of MA settings by graphical comparison of bias detection properties of multiple MA. The optimal MA was selected based on the bias detection characteristics obtained. MA validation charts were generated for selected optimal MA and provided insight into the range of results required for MA bias detection. Bias detection curves and MA validation charts are useful tools for optimization and validation of MA procedures.

Demonstration and Evaluation of Solid Phase Microextraction for the Assessment of Bioavailability and Contaminant Mobility. ESTCP Cost and Performance Report

DTIC Science & Technology

2012-08-01

subsequent chemical analysis (into acetonitrile for high-performance liquid chromatography [ HPLC ] analysis or hexane for gas chromatography [GC... analysis ) is rapid and complete. In this work, PAHs were analyzed by Waters 2795 HPLC with fluorescent detection (USEPA Method 8310) and PCBs were...detection limits by direct water injection versus SPME with PDMS and coefficient of variation and correlation coefficient for SPME. Analysis by HPLC

Innovative qPCR using interfacial effects to enable low threshold cycle detection and inhibition relief

PubMed Central

Harshman, Dustin K.; Rao, Brianna M.; McLain, Jean E.; Watts, George S.; Yoon, Jeong-Yeol

2015-01-01

Molecular diagnostics offers quick access to information but fails to operate at a speed required for clinical decision-making. Our novel methodology, droplet-on-thermocouple silhouette real-time polymerase chain reaction (DOTS qPCR), uses interfacial effects for droplet actuation, inhibition relief, and amplification sensing. DOTS qPCR has sample-to-answer times as short as 3 min 30 s. In infective endocarditis diagnosis, DOTS qPCR demonstrates reproducibility, differentiation of antibiotic susceptibility, subpicogram limit of detection, and thermocycling speeds of up to 28 s/cycle in the presence of tissue contaminants. Langmuir and Gibbs adsorption isotherms are used to describe the decreasing interfacial tension upon amplification. Moreover, a log-linear relationship with low threshold cycles is presented for real-time quantification by imaging the droplet-on-thermocouple silhouette with a smartphone. DOTS qPCR resolves several limitations of commercially available real-time PCR systems, which rely on fluorescence detection, have substantially higher threshold cycles, and require expensive optical components and extensive sample preparation. Due to the advantages of low threshold cycle detection, we anticipate extending this technology to biological research applications such as single cell, single nucleus, and single DNA molecule analyses. Our work is the first demonstrated use of interfacial effects for sensing reaction progress, and it will enable point-of-care molecular diagnosis of infections. PMID:26601245

Active sampling technique to enhance chemical signature of buried explosives

NASA Astrophysics Data System (ADS)

Lovell, John S.; French, Patrick D.

2004-09-01

Deminers and dismounted countermine engineers commonly use metal detectors, ground penetrating radar and probes to locate mines. Many modern landmines have a very low metal content, which severely limits the effectiveness of metal detectors. Canines have also been used for landmine detection for decades. Experiments have shown that canines smell the explosives which are known to leak from most types of landmines. The fact that dogs can detect landmines indicates that vapor sensing is a viable approach to landmine detection. Several groups are currently developing systems to detect landmines by "sniffing" for the ultra-trace explosive vapors above the soil. The amount of material that is available to passive vapor sensing systems is limited to no more than the vapor in equilibrium with the explosive related chemicals (ERCs) distributed in the surface soils over and near the landmine. The low equilibrium vapor pressure of TNT in the soil/atmosphere boundary layer and the limited volume of the boundary layer air imply that passive chemical vapor sensing systems require sensitivities in the picogram range, or lower. ADA is working to overcome many of the limitations of passive sampling methods, by the use of an active sampling method that employs a high-powered (1,200+ joules) strobe lamp to create a highly amplified plume of vapor and/or ERC-bearing fine particulates. Initial investigations have demonstrated that this approach can amplify the detectability of TNT by two or three orders of magnitude. This new active sampling technique could be used with any suitable explosive sensor.

A liquid-phase microextraction method, combining a dual gauge microsyringe with a hollow fiber membrane, for the determination of organochlorine pesticides in aqueous solution by gas chromatography/ion trap mass spectrometry.

PubMed

Yan, Chih-Hao; Wu, Hui-Fen

2004-01-01

A liquid-phase microextraction (LPME) method has been demonstrated for the extraction and determination of organochlorine pesticides (OCPs) in aqueous solution. The method combines a dual gauge microsyringe with a hollow fiber membrane (LPME/DGM-HF) followed by detection by gas chromatography/ion trap mass spectrometry (GC/ITMS). The advantages include speed, low solvent and sample consumption, simplicity and ease of use. The extraction time, solvent selection, salt concentration and sample stirring rate have been investigated in order to optimize extraction efficiency. The viability is evaluated by measuring the linearity and detection limit of the five OCPs in aqueous solution. Detection linearity for the OCPs has been achieved over a range of concentrations between 1 and 500 microg/L (r2 > 0.930), with a detection limit of 0.1 microg/L for each OCP. Copyright 2004 John Wiley & Sons, Ltd.

A chromogenic and fluorogenic rhodol-based chemosensor for hydrazine detection and its application in live cell bioimaging

NASA Astrophysics Data System (ADS)

Tiensomjitr, Khomsan; Noorat, Rattha; Chomngam, Sinchai; Wechakorn, Kanokorn; Prabpai, Samran; Kanjanasirirat, Phongthon; Pewkliang, Yongyut; Borwornpinyo, Suparerk; Kongsaeree, Palangpon

2018-04-01

A rhodol-based fluorescent probe has been developed as a selective hydrazine chemosensor using levulinate as a recognition site. The rhodol levulinate probe (RL) demonstrated high selectivity and sensitivity toward hydrazine among other molecules. The chromogenic response of RL solution to hydrazine from colorless to pink could be readily observed by the naked eye, while strong fluorescence emission could be monitored upon excitation at 525 nm. The detection process occurred via a ring-opening process of the spirolactone initiated by hydrazinolysis, triggering the fluorescence emission with a 53-fold enhancement. The probe rapidly reacted with hydrazine in aqueous medium with the detection limit of 26 nM (0.83 ppb), lower than the threshold limit value (TLV) of 10 ppb suggested by the U.S. Environmental Protection Agency. Furthermore, RL-impregnated paper strips could detect hydrazine vapor. For biological applicability of RL, its membrane-permeable property led to bioimaging of hydrazine in live HepG2 cells by confocal fluorescence microscopy.

Plasmonic nanosensors with inverse sensitivity by means of enzyme-guided crystal growth

NASA Astrophysics Data System (ADS)

Rodríguez-Lorenzo, Laura; de La Rica, Roberto; Álvarez-Puebla, Ramón A.; Liz-Marzán, Luis M.; Stevens, Molly M.

2012-07-01

Lowering the limit of detection is key to the design of sensors needed for food safety regulations, environmental policies and the diagnosis of severe diseases. However, because conventional transducers generate a signal that is directly proportional to the concentration of the target molecule, ultralow concentrations of the molecule result in variations in the physical properties of the sensor that are tiny, and therefore difficult to detect with confidence. Here we present a signal-generation mechanism that redefines the limit of detection of nanoparticle sensors by inducing a signal that is larger when the target molecule is less concentrated. The key step to achieve this inverse sensitivity is to use an enzyme that controls the rate of nucleation of silver nanocrystals on plasmonic transducers. We demonstrate the outstanding sensitivity and robustness of this approach by detecting the cancer biomarker prostate-specific antigen down to 10-18 g ml-1 (4 × 10-20 M) in whole serum.

Remote monitoring of fish in small streams: A unified approach using PIT tags

USGS Publications Warehouse

Zydlewski, G.B.; Horton, G.; Dubreuil, T.; Letcher, B.; Casey, S.; Zydlewski, Joseph D.

2006-01-01

Accurate assessments of fish populations are often limited by re-observation or recapture events. Since the early 1990s, passive integrated transponders (PIT tags) have been used to understand the biology of many fish species. Until recently, PIT applications in small streams have been limited to physical recapture events. To maximize recapture probability, we constructed PIT antenna arrays in small streams to remotely detect individual fish. Experiences from two different laboratories (three case studies) allowed us to develop a unified approach to applying PIT technology for enhancing data assessments. Information on equipment, its installation, tag considerations, and array construction is provided. Theoretical and practical definitions are introduced to standardize metrics for assessing detection efficiency. We demonstrate how certain conditions (stream discharge, vibration, and ambient radio frequency noise) affect the detection efficiency and suggest that by monitoring these conditions, expectations of efficiency can be modified. We emphasize the importance of consistently estimating detection efficiency for fisheries applications.

Trace detection of oxygen--ionic liquids in gas sensor design.

PubMed

Baltes, N; Beyle, F; Freiner, S; Geier, F; Joos, M; Pinkwart, K; Rabenecker, P

2013-11-15

This paper presents a novel electrochemical membrane sensor on basis of ionic liquids for trace analysis of oxygen in gaseous atmospheres. The faradaic response currents for the reduction of oxygen which were obtained by multiple-potential-step-chronoamperometry could be used for real time detection of oxygen down to concentrations of 30 ppm. The theoretical limit of detection was 5 ppm. The simple, non-expensive sensors varied in electrolyte composition and demonstrated a high sensitivity, a rapid response time and an excellent reproducibility at room temperature. Some of them were continuously used for at least one week and first results promise good long term stability. Voltammetric, impedance and oxygen detection studies at temperatures up to 200 °C (in the presence and absence of humidity and CO2) revealed also the limitations of certain ionic liquids for some electrochemical high temperature applications. Application areas of the developed sensors are control and analysis processes of non oxidative and oxygen free atmospheres. Copyright © 2013 Elsevier B.V. All rights reserved.

Detection of BCG bacteria using a magnetoresistive biosensor: A step towards a fully electronic platform for tuberculosis point-of-care detection.

PubMed

Barroso, Teresa G; Martins, Rui C; Fernandes, Elisabete; Cardoso, Susana; Rivas, José; Freitas, Paulo P

2018-02-15

Tuberculosis is one of the major public health concerns. This highly contagious disease affects more than 10.4 million people, being a leading cause of morbidity by infection. Tuberculosis is diagnosed at the point-of-care by the Ziehl-Neelsen sputum smear microscopy test. Ziehl-Neelsen is laborious, prone to human error and infection risk, with a limit of detection of 10 4 cells/mL. In resource-poor nations, a more practical test, with lower detection limit, is paramount. This work uses a magnetoresistive biosensor to detect BCG bacteria for tuberculosis diagnosis. Herein we report: i) nanoparticle assembly method and specificity for tuberculosis detection; ii) demonstration of proportionality between BCG cell concentration and magnetoresistive voltage signal; iii) application of multiplicative signal correction for systematic effects removal; iv) investigation of calibration effectiveness using chemometrics methods; and v) comparison with state-of-the-art point-of-care tuberculosis biosensors. Results present a clear correspondence between voltage signal and cell concentration. Multiplicative signal correction removes baseline shifts within and between biochip sensors, allowing accurate and precise voltage signal between different biochips. The corrected signal was used for multivariate regression models, which significantly decreased the calibration standard error from 0.50 to 0.03log 10 (cells/mL). Results show that Ziehl-Neelsen detection limits and below are achievable with the magnetoresistive biochip, when pre-processing and chemometrics are used. Copyright © 2017 Elsevier B.V. All rights reserved.

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

2015-08-04

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.

Assembling substrate-less plasmonic metacrystals at the oil/water interface for multiplex ultratrace analyte detection.

PubMed

Lee, Yih Hong; Lee, Hiang Kwee; Ho, Jonathan Yong Chew; Yang, Yijie; Ling, Xing Yi

2016-08-15

Current substrate-less SERS platforms are limited to uncontrolled aggregation of plasmonic nanoparticles or quasi-crystalline arrays of spherical nanoparticles, with no study on how the lattice structures formed by nanoparticle self-assembly affect their detection capabilities. Here, we organize Ag octahedral building blocks into two large-area plasmonic metacrystals at the oil/water interface, and investigate their in situ SERS sensing capabilities. Amphiphilic octahedra assemble into a hexagonal close-packed metacrystal, while hydrophobic octahedra assemble into an open square metacrystal. The lower packing density square metacrystal gives rise to much stronger SERS enhancement than the denser packing hexagonal metacrystal, arising from the larger areas of plasmonic hotspots within the square metacrystal at the excitation wavelength. We further demonstrate the ability of the square metacrystal to achieve quantitative ultratrace detection of analytes from both the aqueous and organic phases. Detection limits are at the nano-molar levels, with analytical enhancement factors reaching 10(8). In addition, multiplex detection across both phases can be achieved in situ without any loss of signal quantitation.

Suspended Microchannel Resonators for Ultralow Volume Universal Detection

PubMed Central

Son, Sungmin; Grover, William H.; Burg, Thomas P.; Manalis, Scott R.

2008-01-01

Universal detectors that maintain high sensitivity as the detection volume is reduced to the subnanoliter scale can enhance the utility of miniaturized total analysis systems (μ-TAS). Here the unique scaling properties of the suspended microchannel resonator (SMR) are exploited to show universal detection in a 10 pL analysis volume with a density detection limit of ∼1 μg/cm3 (10 Hz bandwidth) and a dynamic range of 6 decades. Analytes with low UV extinction coefficients such as polyethylene glycol (PEG) 8 kDa, glucose, and glycine are measured with molar detection limits of 0.66, 13.5, and 31.6 μM, respectively. To demonstrate the potential for real-time monitoring, gel filtration chromatography was used to separate different molecular weights of PEG as the SMR acquired a chromatogram by measuring the eluate density. This work suggests that the SMR could offer a simple and sensitive universal detector for various separation systems from liquid chromatography to capillary electrophoresis. Moreover, since the SMR is itself a microfluidic channel, it can be directly integrated into μ-TAS without compromising overall performance. PMID:18489125

Impedimetric Zika and Dengue Biosensor based on Functionalized Graphene Oxide Wrapped Silica Particles

NASA Astrophysics Data System (ADS)

Jin, Seon-Ah; Marinero, Ernesto E.; Stanciu, Lia A. Stanciu; Poudyal, Shishir; Kuhn, Richard J.

A composite of 3-Aminopropyltriethoxysilane (APTES) functionalized graphene oxide (APTES-GO) wrapped on SiO2 particles (SiO2@APTES-GO) was prepared via self-assembly. Transmission electron microscopy (TEM) and ATR-Fourier Transform Infrared spectroscopy (ATR-FTIR) confirmed wrapping of the SiO2 particles by the APTES-GO sheets. An impedimetric biosensor was constructed and used to sensitively detect Zika and dengue DNA and RNA via primer hybridization using different oligonucleotide sequences. The results demonstrate that the SiO2@APTES-GO electrode materials provide enhanced RNA detection sensitivity with selectivity and detection limit (1 femto-Molar), compared to both APTES-GO and APTES-SiO2. The three-dimensional structure, higher contact area, electrical properties and the ability for rapid hybridization offered by the SiO2@APTES-GO resulted in a successful design of a Zika and dengue biosensor with the lowest detection limit reported to date. We are in the process of developing a platform for multiple viral detection for point-of-care diagnostics for arthropode borne viral infectious diseases.

Free-space optical communications research and demonstrations at the U.S. Naval Research Laboratory.

PubMed

Rabinovich, W S; Moore, C I; Mahon, R; Goetz, P G; Burris, H R; Ferraro, M S; Murphy, J L; Thomas, L M; Gilbreath, G C; Vilcheck, M; Suite, M R

2015-11-01

Free-space optical communication can allow high-bandwidth data links that are hard to detect, intercept, or jam. This makes them attractive for many applications. However, these links also require very accurate pointing, and their availability is affected by weather. These challenges have limited the deployment of free-space optical systems. The U.S. Naval Research Laboratory has, for the last 15 years, engaged in research into atmospheric propagation and photonic components with a goal of characterizing and overcoming these limitations. In addition several demonstrations of free-space optical links in real-world Navy applications have been conducted. This paper reviews this work and the principles guiding it.

Digital image profilers for detecting faint sources which have bright companions, phase 2

NASA Technical Reports Server (NTRS)

Morris, Elena; Flint, Graham

1991-01-01

A breadboard image profiling system developed for the first phase of this project demonstrated the potential for detecting extremely faint optical sources in the presence of light companions. Experimental data derived from laboratory testing of the device supports the theory that image profilers of this type may approach the theoretical limit imposed by photon statistics. The objective of Phase 2 of this program is the development of a ground-based multichannel image profiling system capable of detecting faint stellar objects slightly displaced from brighter stars. We have finalized the multichannel image profiling system and attempted three field tests.

Detection of low-level PTFE contamination: An application of solid-state NMR to structure elucidation in the pharmaceutical industry.

PubMed

Pham, Tran N; Day, Caroline J; Edwards, Andrew J; Wood, Helen R; Lynch, Ian R; Watson, Simon A; Bretonnet, Anne-Sophie Z; Vogt, Frederick G

2011-01-25

We report a novel use of solid-state ¹⁹F nuclear magnetic resonance to detect and quantify polytetrafluoroethylene contamination from laboratory equipment, which due to low quantity (up to 1% w/w) and insolubility remained undetected by standard analytical techniques. Solid-state ¹⁹F NMR is shown to be highly sensitive to such fluoropolymers (detection limit 0.02% w/w), and is demonstrated as a useful analytical tool for structure elucidation of unknown solid materials. Copyright © 2010 Elsevier B.V. All rights reserved.

Atom-atom entanglement by single-photon detection.

PubMed

Slodička, L; Hétet, G; Röck, N; Schindler, P; Hennrich, M; Blatt, R

2013-02-22

A scheme for entangling distant atoms is realized, as proposed in the seminal paper by [C. Cabrillo et al., Phys. Rev. A 59, 1025 (1999)]. The protocol is based on quantum interference and detection of a single photon scattered from two effectively one meter distant laser cooled and trapped atomic ions. The detection of a single photon heralds entanglement of two internal states of the trapped ions with high rate and with a fidelity limited mostly by atomic motion. Control of the entangled state phase is demonstrated by changing the path length of the single-photon interferometer.

Fiber optofluidic biosensor for the label-free detection of DNA hybridization and methylation based on an in-line tunable mode coupler.

PubMed

Gao, Ran; Lu, Dan-Feng; Cheng, Jin; Jiang, Yi; Jiang, Lan; Xu, Jian-Dong; Qi, Zhi-Mei

2016-12-15

An optical fiber optofluidic biosensor for the detection of DNA hybridization and methylation has been proposed and experimentally demonstrated. An in-line fiber Michelson interferometer was formed in the photonic crystal fiber. A micrhole in the collapsed region, which combined the tunable mode coupler and optofluidic channel, was fabricated by using femtosecond laser micromachining. The mode field diameter of the guided light is changed with the refractive index in the optofluidic channel, which results in the tunable coupling ratio. Label-free detections of the DNA hybridization and methylation have been experimentally demonstrated. The probe single stranded DNA (ssDNA) was bound with the surface of the optofluidic channel through the Poly-l-lysine layer, and the hybridization between a short 22-mer probe ssDNA and a complementary target ssDNA was carried out and detected by interrogating the fringe visibility of the reflection spectrum. Then, the DNA methylation was also detected through the binding between the methylated DNA and the 5-methylcytosine (5-mC) monoclonal antibody. The experiments results demonstrate that the limit of detection of 5nM is achieved, establishing the tunable mode coupler as a sensitive and versatile biosensor. The sensitive optical fiber optofluidic biosensor possesses high specificity and low temperature cross-sensitivity. Copyright © 2016 Elsevier B.V. All rights reserved.

Direct detection of Mycobacterium avium in environmental water and scale samples by loop-mediated isothermal amplification.

PubMed

Nishiuchi, Yukiko; Tamaru, Aki; Suzuki, Yasuhiko; Kitada, Seigo; Maekura, Ryoji; Tateishi, Yoshitaka; Niki, Mamiko; Ogura, Hisashi; Matsumoto, Sohkichi

2014-06-01

We previously demonstrated the colonization of Mycobacterium avium complex in bathrooms by the conventional culture method. In the present study, we aimed to directly detect M. avium organisms in the environment using loop-mediated isothermal amplification (LAMP), and to demonstrate the efficacy of LAMP by comparing the results with those obtained by culture. Our data showed that LAMP analysis has detection limits of 100 fg DNA/reaction for M. avium. Using an FTA(®) elute card, DNA templates were extracted from environmental samples from bathrooms in the residences of 29 patients with pulmonary M. avium disease. Of the 162 environmental samples examined, 143 (88%) showed identical results by both methods; 20 (12%) and 123 (76%) samples were positive and negative, respectively, for M. avium. Of the remaining 19 samples (12%), seven (5%) and 12 (7%) samples were positive by the LAMP and culture methods, respectively. All samples that contained over 20 colony forming units/primary isolation plate, as measured by the culture method, were also positive by the LAMP method. Our data demonstrate that the combination of the FTA elute card and LAMP can facilitate prompt detection of M. avium in the environment.

Single-ion adsorption and switching in carbon nanotubes

DOE PAGES

Bushmaker, Adam W.; Oklejas, Vanessa; Walker, Don; ...

2016-01-25

Single-ion detection has, for many years, been the domain of large devices such as the Geiger counter, and studies on interactions of ionized gasses with materials have been limited to large systems. To date, there have been no reports on single gaseous ion interaction with microelectronic devices, and single neutral atom detection techniques have shown only small, barely detectable responses. Here we report the observation of single gaseous ion adsorption on individual carbon nanotubes (CNTs), which, because of the severely restricted one-dimensional current path, experience discrete, quantized resistance increases of over two orders of magnitude. Only positive ions cause changes,more » by the mechanism of ion potentialinduced carrier depletion, which is supported by density functional and Landauer transport theory. Lastly, our observations reveal a new single-ion/CNT heterostructure with novel electronic properties, and demonstrate that as electronics are ultimately scaled towards the one-dimensional limit, atomic-scale effects become increasingly important.« less

Nanopore sensing at ultra-low concentrations using single-molecule dielectrophoretic trapping

NASA Astrophysics Data System (ADS)

Freedman, Kevin J.; Otto, Lauren M.; Ivanov, Aleksandar P.; Barik, Avijit; Oh, Sang-Hyun; Edel, Joshua B.

2016-01-01

Single-molecule techniques are being developed with the exciting prospect of revolutionizing the healthcare industry by generating vast amounts of genetic and proteomic data. One exceptionally promising route is in the use of nanopore sensors. However, a well-known complexity is that detection and capture is predominantly diffusion limited. This problem is compounded when taking into account the capture volume of a nanopore, typically 108-1010 times smaller than the sample volume. To rectify this disproportionate ratio, we demonstrate a simple, yet powerful, method based on coupling single-molecule dielectrophoretic trapping to nanopore sensing. We show that DNA can be captured from a controllable, but typically much larger, volume and concentrated at the tip of a metallic nanopore. This enables the detection of single molecules at concentrations as low as 5 fM, which is approximately a 103 reduction in the limit of detection compared with existing methods, while still maintaining efficient throughput.

High-sensitivity silicon ultraviolet p+-i-n avalanche photodiode using ultra-shallow boron gradient doping

DOE PAGES

Xia, Zhenyang; Zang, Kai; Liu, Dong; ...

2017-08-21

Photo detection of ultraviolet (UV) light remains a challenge since the penetration depth of UV light is limited to the nanometer scale. Therefore, the doping profile and electric field in the top nanometer range of the photo detection devices become critical. Traditional UV photodetectors usually use a constant doping profile near the semiconductor surface, resulting in a negligible electric field, which limits the photo-generated carrier collection efficiency of the photodetector. Here, we demonstrate, via the use of an optimized gradient boron doping technique, that the carrier collection efficiency and photo responsivity under the UV wavelength region have been enhanced. Moreover,more » the ultrathin p+-i-n junction shows an avalanche gain of 2800 and an ultra-low junction capacitance (sub pico-farad), indicating potential applications in the low timing jitter single photon detection area.« less

High-sensitivity silicon ultraviolet p+-i-n avalanche photodiode using ultra-shallow boron gradient doping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xia, Zhenyang; Zang, Kai; Liu, Dong

Photo detection of ultraviolet (UV) light remains a challenge since the penetration depth of UV light is limited to the nanometer scale. Therefore, the doping profile and electric field in the top nanometer range of the photo detection devices become critical. Traditional UV photodetectors usually use a constant doping profile near the semiconductor surface, resulting in a negligible electric field, which limits the photo-generated carrier collection efficiency of the photodetector. Here, we demonstrate, via the use of an optimized gradient boron doping technique, that the carrier collection efficiency and photo responsivity under the UV wavelength region have been enhanced. Moreover,more » the ultrathin p+-i-n junction shows an avalanche gain of 2800 and an ultra-low junction capacitance (sub pico-farad), indicating potential applications in the low timing jitter single photon detection area.« less

Self-Biased 215MHz Magnetoelectric NEMS Resonator for Ultra-Sensitive DC Magnetic Field Detection

NASA Astrophysics Data System (ADS)

Nan, Tianxiang; Hui, Yu; Rinaldi, Matteo; Sun, Nian X.

2013-06-01

High sensitivity magnetoelectric sensors with their electromechanical resonance frequencies < 200 kHz have been recently demonstrated using magnetostrictive/piezoelectric magnetoelectric heterostructures. In this work, we demonstrate a novel magnetoelectric nano-electromechanical systems (NEMS) resonator with an electromechanical resonance frequency of 215 MHz based on an AlN/(FeGaB/Al2O3) × 10 magnetoelectric heterostructure for detecting DC magnetic fields. This magnetoelectric NEMS resonator showed a high quality factor of 735, and strong magnetoelectric coupling with a large voltage tunable sensitivity. The admittance of the magnetoelectric NEMS resonator was very sensitive to DC magnetic fields at its electromechanical resonance, which led to a new detection mechanism for ultra-sensitive self-biased RF NEMS magnetoelectric sensor with a low limit of detection of DC magnetic fields of ~300 picoTelsa. The magnetic/piezoelectric heterostructure based RF NEMS magnetoelectric sensor is compact, power efficient and readily integrated with CMOS technology, which represents a new class of ultra-sensitive magnetometers for DC and low frequency AC magnetic fields.

Application of flat panel OLED display technology for the point-of-care detection of circulating cancer biomarkers

PubMed Central

Katchman, Benjamin A.; Smith, Joseph T.; Obahiagbon, Uwadiae; Kesiraju, Sailaja; Lee, Yong-Kyun; O’Brien, Barry; Kaftanoglu, Korhan; Blain Christen, Jennifer; Anderson, Karen S.

2016-01-01

Point-of-care molecular diagnostics can provide efficient and cost-effective medical care, and they have the potential to fundamentally change our approach to global health. However, most existing approaches are not scalable to include multiple biomarkers. As a solution, we have combined commercial flat panel OLED display technology with protein microarray technology to enable high-density fluorescent, programmable, multiplexed biorecognition in a compact and disposable configuration with clinical-level sensitivity. Our approach leverages advances in commercial display technology to reduce pre-functionalized biosensor substrate costs to pennies per cm2. Here, we demonstrate quantitative detection of IgG antibodies to multiple viral antigens in patient serum samples with detection limits for human IgG in the 10 pg/mL range. We also demonstrate multiplexed detection of antibodies to the HPV16 proteins E2, E6, and E7, which are circulating biomarkers for cervical as well as head and neck cancers. PMID:27374875

Application of flat panel OLED display technology for the point-of-care detection of circulating cancer biomarkers.

PubMed

Katchman, Benjamin A; Smith, Joseph T; Obahiagbon, Uwadiae; Kesiraju, Sailaja; Lee, Yong-Kyun; O'Brien, Barry; Kaftanoglu, Korhan; Blain Christen, Jennifer; Anderson, Karen S

2016-07-04

Point-of-care molecular diagnostics can provide efficient and cost-effective medical care, and they have the potential to fundamentally change our approach to global health. However, most existing approaches are not scalable to include multiple biomarkers. As a solution, we have combined commercial flat panel OLED display technology with protein microarray technology to enable high-density fluorescent, programmable, multiplexed biorecognition in a compact and disposable configuration with clinical-level sensitivity. Our approach leverages advances in commercial display technology to reduce pre-functionalized biosensor substrate costs to pennies per cm(2). Here, we demonstrate quantitative detection of IgG antibodies to multiple viral antigens in patient serum samples with detection limits for human IgG in the 10 pg/mL range. We also demonstrate multiplexed detection of antibodies to the HPV16 proteins E2, E6, and E7, which are circulating biomarkers for cervical as well as head and neck cancers.

Electrically contacted enzyme based on dual hairpin DNA structure and its application for amplified detection of Hg2+.

PubMed

Wang, Guangfeng; Huang, Hao; Zhang, Xiaojun; Wang, Lun

2012-05-15

In the present study, based on a dual hairpin DNA structure, a novel system of electrically contacted enzyme and its signal amplification for ultrasensitive detection of Hg(2+) was demonstrated. In the presence of Hg(2+), with the interaction of thymine-Hg(2+)-thymine (T-Hg(2+)-T), DNA sequence dully labeled with ferrocene (Fc) at 5' end and horseradish peroxidase (HRP) at 3' end, hybridized to the capture probe and formed the dual hairpin structure on the electrode. Fc unit acts as a relay that electrically contacts HRP with the electrode and activates the bioelectrocatalyzed reduction of H(2)O(2). And based on the bioelectrocatalyzed signal amplification of the presented system, Hg(2+) could be quantitatively detected in the range of 10(-10)-10(-6)M with a low detection limit of 52 pM. And it also demonstrated excellent selectivity against other interferential metal ions. Copyright © 2012 Elsevier B.V. All rights reserved.

NO2 trace measurements by optical-feedback cavity-enhanced absorption spectroscopy

NASA Astrophysics Data System (ADS)

Ventrillard-Courtillot, I.; Foldes, T.; Romanini, D.

2009-04-01

In order to reach the sub-ppb NO2 detection level required for environmental applications in remote areas, we are developing a spectrometer that exploits a technique that we introduced several years ago, named Optical-Feedback Cavity-Enhanced Absorption Spectroscopy (OF-CEAS) [1]. It allows very sensitive and selective measurements, together with the realization of compact and robust set-ups as was subsequently demonstrated during measurements campaigns in harsh environments [2,3]. OF-CEAS benefits from the optical feedback (OF) to efficiently inject a cw-laser in a high finesse cavity (typically F >10 000). Absorption spectra are acquired on a small spectral region (~1 cm-1) that enables selective and quantitative measurements at a fast acquisition rate (~10 Hz) with a detection limit of several 10-10 cm-1 as reported in this paper. Spectra are obtained with high spectral resolution (~150 MHz) and are self calibrated by cavity rind-down measurements regularly performed (typically every second). Therefore, OF-CEAS appears very attractive for NO2 trace detection. This work is performed in the blue spectral region where NO2 has intense electronic transitions. Our setup involves a commercial extended cavity diode laser (ECDL) working at room temperature around 411nm. A first setup was developed [4] to demonstrate that OF sensitivity of ECDL is fully consistent with this technique, initially introduced with distributed feedback diode lasers in the near infrared region. In this paper we will report on a new set-up developed for in-situ measurements with proper mechanical, acoustic and thermal insulation. Additionally, new data processing was implemented allowing real time concentration measurements. It is based on a reference spectra recorded under controlled conditions by OF-CEAS and used later to fit the observed spectra. We will present measurements performed with calibrated NO2 reference samples demonstrating a good linearity of the apparatus. The minimum detectable absorption loss is estimated by considering the standard deviation of the spectra. We achieved better than 2x10-10 cm-1 for a single spectrum recorded in less than 100ms at 100mbar. This limit constitutes an improved of more than one order of magnitude as compare to the previous measurements reported in [4]. It leads to a detection limit of 3x108 molecules/cm3, corresponding to about 150pptv at 100mbar. At atmospheric pressure the same measurement would yield a detection limit of 15pptv assuming we can maintain the same level of sensitivity. But currently, works are under development to transfer the low minimum detectable absorption limit, already obtained for one spectrum, to a set of real time measurements. These are now limited by amplitude fluctuations of a few ppb from one spectrum to another one. [1] J. Morville, S. Kassi, M. Chenevier, and D. Romanini, Appl. Phys. B, 80, 1027 (2005). [2] D. Romanini, M. Chenevrier, S. Kassi, M. Schmidt, C. Valant, M. Ramonet, J. Lopez, and H.-J. Jost, Appl. Phys. B, 83, 659 (2006). [2] E.R.T. Kerstel, R.Q. Iannone, M. Chenevrier, S. Kassi, H.-J. Jost and D. Romanini, Appl. Phys. B, 84, 343 (2006). [4] I. Courtillot, J. Morville, V. Motto-Ros, and D. Romanini, Appl. Phys. B, 85, 407 (2006).

40 CFR 141.719 - Additional filtration toolbox components.

Code of Federal Regulations, 2011 CFR

2011-07-01

... establish a quality control release value (QCRV) for a non-destructive performance test that demonstrates... Detection Limit) (5) Challenge testing must be conducted at the maximum design flow rate for the filter as... representative hydraulic conditions at the maximum design flux and maximum design process recovery specified by...

40 CFR 141.719 - Additional filtration toolbox components.

Code of Federal Regulations, 2010 CFR

2010-07-01

... establish a quality control release value (QCRV) for a non-destructive performance test that demonstrates... Detection Limit) (5) Challenge testing must be conducted at the maximum design flow rate for the filter as... representative hydraulic conditions at the maximum design flux and maximum design process recovery specified by...

Differential Language Influence on Math Achievement

ERIC Educational Resources Information Center

Chen, Fang

2010-01-01

New models are commonly designed to solve certain limitations of other ones. Quantile regression is introduced in this paper because it can provide information that a regular mean regression misses. This research aims to demonstrate its utility in the educational research and measurement field for questions that may not be detected otherwise.…

LIQUID CHROMATOGRAPHY/MASS SPECTROMETRY LIBRARY AND STRATEGY FOR IDENTIFYING HARMFUL ORGANICS IN DRINKING WATER

EPA Science Inventory

This project will demonstrate ways to detect contaminants by LC/MS technologies in order to protect water systems and environments. Contaminants can affect drinking water usage and limit acceptable sources of ground and reservoir supplies. The analytical method to enhance the s...

Hydroacoustic basis for detection and characterization of eelgrass (Zostera marina)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sabol, B.; McCarthy, E.; Rocha, K.

1997-06-01

Understanding the distribution and density of seagrasses is important for a variety of environmental applications. Physical techniques for detection and characterization are labor and cost intensive and provide little insight into spatial distribution. optical-based techniques are limited by water clarity - frequently resulting in systematic underestimation of the extent of seagrasses. Active hydroacoustic techniques have shown the ability to detect seagrasses but the phenomenology behind detection is poorly understood. Laboratory and in-situ hydroacoustic measurements are presented for eelgrass (Zostera marina), a common seagrass in the United States. Based on these data, hydroacoustic approaches for wide area detection and mapping aremore » discussed and several are demonstrated within areas of established eelgrass beds in Narragansett Bay, Rhode Island.« less

Nucleic acid in-situ hybridization detection of infectious agents

NASA Astrophysics Data System (ADS)

Thompson, Curtis T.

2000-04-01

Limitations of traditional culture methods and newer polymerase chain reaction (PCR)-based methods for detection and speciation of infectious agents demonstrate the need for more rapid and better diagnostics. Nucleic acid hybridization is a detection technology that has gained wide acceptance in cancer and prenatal cytogenetics. Using a modification of the nucleic acid hybridization technique known as fluorescence in-situ hybridization, infectious agents can be detected in a variety of specimens with high sensitivity and specificity. The specimens derive from all types of human and animal sources including body fluids, tissue aspirates and biopsy material. Nucleic acid hybridization can be performed in less than one hour. The result can be interpreted either using traditional fluorescence microscopy or automated platforms such as micro arrays. This paper demonstrates proof of concept for nucleic acid hybridization detection of different infectious agents. Interpretation within a cytologic and histologic context is possible with fluorescence microscopic analysis, thereby providing confirmatory evidence of hybridization. With careful probe selection, nucleic acid hybridization promises to be a highly sensitive and specific practical diagnostic alternative to culture, traditional staining methods, immunohistochemistry and complicated nucleic acid amplification tests.

Detecting Thermal Cloaks via Transient Effects

PubMed Central

Sklan, Sophia R.; Bai, Xue; Li, Baowen; Zhang, Xiang

2016-01-01

Recent research on the development of a thermal cloak has concentrated on engineering an inhomogeneous thermal conductivity and an approximate, homogeneous volumetric heat capacity. While the perfect cloak of inhomogeneous κ and inhomogeneous ρcp is known to be exact (no signals scattering and only mean values penetrating to the cloak’s interior), the sensitivity of diffusive cloaks to defects and approximations has not been analyzed. We analytically demonstrate that these approximate cloaks are detectable. Although they work as perfect cloaks in the steady-state, their transient (time-dependent) response is imperfect and a small amount of heat is scattered. This is sufficient to determine the presence of a cloak and any heat source it contains, but the material composition hidden within the cloak is not detectable in practice. To demonstrate the feasibility of this technique, we constructed a cloak with similar approximation and directly detected its presence using these transient temperature deviations outside the cloak. Due to limitations in the range of experimentally accessible volumetric specific heats, our detection scheme should allow us to find any realizable cloak, assuming a sufficiently large temperature difference. PMID:27605153

Radio Detection of Cosmic Rays-Achievements and Future Potential

NASA Astrophysics Data System (ADS)

Huege, Tim

When modern efforts for radio detection of cosmic rays started about a decade ago, hopes were high but the true potential was unknown. Since then, we have achieved a detailed understanding of the radio emission physics and have consequently succeeded in developing sophisticated detection schemes and analysis approaches. In particular, we have demonstrated that the important air-shower parameters arrival direction, particle energy and depth of shower maximum can be reconstructed reliably from radio measurements, with a precision that is comparable with that of other detection techniques. At the same time, limitations inherent to the radio-emission mechanisms have become apparent. In this article, I shortly review the capabilities of radio detection in the very high-frequency band, and discuss the potential for future application in existing and new experiments for cosmic-ray detection.

Dangerous gas detection based on infrared video

NASA Astrophysics Data System (ADS)

Ding, Kang; Hong, Hanyu; Huang, Likun

2018-03-01

As the gas leak infrared imaging detection technology has significant advantages of high efficiency and remote imaging detection, in order to enhance the detail perception of observers and equivalently improve the detection limit, we propose a new type of gas leak infrared image detection method, which combines background difference methods and multi-frame interval difference method. Compared to the traditional frame methods, the multi-frame interval difference method we proposed can extract a more complete target image. By fusing the background difference image and the multi-frame interval difference image, we can accumulate the information of infrared target image of the gas leak in many aspect. The experiment demonstrate that the completeness of the gas leakage trace information is enhanced significantly, and the real-time detection effect can be achieved.

Combining hyperspectral imaging and Raman spectroscopy for remote chemical sensing

NASA Astrophysics Data System (ADS)

Ingram, John M.; Lo, Edsanter

2008-04-01

The Photonics Research Center at the United States Military Academy is conducting research to demonstrate the feasibility of combining hyperspectral imaging and Raman spectroscopy for remote chemical detection over a broad area of interest. One limitation of future trace detection systems is their ability to analyze large areas of view. Hyperspectral imaging provides a balance between fast spectral analysis and scanning area. Integration of a hyperspectral system capable of remote chemical detection will greatly enhance our soldiers' ability to see the battlefield to make threat related decisions. It can also queue the trace detection systems onto the correct interrogation area saving time and reconnaissance/surveillance resources. This research develops both the sensor design and the detection/discrimination algorithms. The one meter remote detection without background radiation is a simple proof of concept.

Multispecies breath analysis faster than a single respiratory cycle by optical-feedback cavity-enhanced absorption spectroscopy

NASA Astrophysics Data System (ADS)

Ventrillard-Courtillot, Irene; Gonthiez, Thierry; Clerici, Christine; Romanini, Daniel

2009-11-01

We demonstrate a first application, of optical-feedback cavity-enhanced absorption spectroscopy (OF-CEAS) to breath analysis in a medical environment. Noninvasive monitoring of trace species in exhaled air was performed simultaneous to spirometric measurements on patients at Bichat Hospital (Paris). The high selectivity of the OF-CEAS spectrometer and a time response of 0.3 s (limited by sample flow rate) allowed following the evolution of carbon monoxide and methane concentrations during individual respiratory cycles, and resolving variations among different ventilatory patterns. The minimum detectable absorption on this time scale is about 3×10-10 cm-1. At the working wavelength of the instrument (2.326 μm), this translates to concentration detection limits of ~1 ppbv (45 picomolar, or ~1.25 μg/m3) for CO and 25 ppbv for CH4, well below concentration values found in exhaled air. This same instrument is also able to provide measurement of NH3 concentrations with a detection limit of ~10 ppbv however, at present, memory effects do not allow its measurement on fast time scales.

Limits on radio emission from meteors using the MWA

NASA Astrophysics Data System (ADS)

Zhang, X.; Hancock, P.; Devillepoix, H. A. R.; Wayth, R. B.; Beardsley, A.; Crosse, B.; Emrich, D.; Franzen, T. M. O.; Gaensler, B. M.; Horsley, L.; Johnston-Hollitt, M.; Kaplan, D. L.; Kenney, D.; Morales, M. F.; Pallot, D.; Steele, K.; Tingay, S. J.; Trott, C. M.; Walker, M.; Williams, A.; Wu, C.; Ji, Jianghui; Ma, Yuehua

2018-07-01

Recently, low-frequency, broad-band radio emission has been observed accompanying bright meteors by the Long Wavelength Array (LWA). The broad-band spectra between 20 and 60 MHz were captured for several events, while the spectral index (dependence of flux density on frequency, with Sν ∝ να) was estimated to be -4 ± 1 during the peak of meteor afterglows. Here we present a survey of meteor emission and other transient events using the Murchison Wide Field Array (MWA) at 72-103 MHz. In our 322 h survey, down to a 5σ detection threshold of 3.5 Jy beam-1, no transient candidates were identified as intrinsic emission from meteors. We derived an upper limit of -3.7 (95 per cent confidence limit) on the spectral index in our frequency range. We also report detections of other transient events, such as reflected FM broadcast signals from small satellites, conclusively demonstrating the ability of the MWA to detect and track space debris on scales as small as 0.1 m in low Earth orbits.

Determination of benzothiazole and benzotriazole derivates in tire and clothing textile samples by high performance liquid chromatography-electrospray ionization tandem mass spectrometry.

PubMed

Avagyan, Rozanna; Sadiktsis, Ioannis; Thorsén, Gunnar; Östman, Conny; Westerholm, Roger

2013-09-13

A high performance liquid chromatography-tandem mass spectrometry method utilizing electrospray ionization in positive and negative mode has been developed for the separation and detection of benzothiazole and benzotriazole derivates. Ultra-sonication assisted solvent extraction of these compounds has also been developed and the overall method demonstrated on a selected clothing textile and an automobile tire sample. Matrix effects and extraction recoveries, as well as linearity and limits of detection have been evaluated. The calibration curves spanned over more than two orders of magnitude with coefficients of correlation R(2)>0.99 and the limits of detection and the limits of quantification were in the range 1.7-58pg injected and 18-140pg/g, respectively. The extraction recoveries ranged between 69% and 102% and the matrix effects between 75% and 101%. Benzothiazole and benzotriazole derivates were determined in the textile sample and benzothiazole derivatives determined in the tire sample with good analytical performance. Copyright © 2013 Elsevier B.V. All rights reserved.

Detection limit of intragenic deletions with targeted array comparative genomic hybridization

PubMed Central

2013-01-01

Background Pathogenic mutations range from single nucleotide changes to deletions or duplications that encompass a single exon to several genes. The use of gene-centric high-density array comparative genomic hybridization (aCGH) has revolutionized the detection of intragenic copy number variations. We implemented an exon-centric design of high-resolution aCGH to detect single- and multi-exon deletions and duplications in a large set of genes using the OGT 60 K and 180 K arrays. Here we describe the molecular characterization and breakpoint mapping of deletions at the smaller end of the detectable range in several genes using aCGH. Results The method initially implemented to detect single to multiple exon deletions, was able to detect deletions much smaller than anticipated. The selected deletions we describe vary in size, ranging from over 2 kb to as small as 12 base pairs. The smallest of these deletions are only detectable after careful manual review during data analysis. Suspected deletions smaller than the detection size for which the method was optimized, were rigorously followed up and confirmed with PCR-based investigations to uncover the true detection size limit of intragenic deletions with this technology. False-positive deletion calls often demonstrated single nucleotide changes or an insertion causing lower hybridization of probes demonstrating the sensitivity of aCGH. Conclusions With optimizing aCGH design and careful review process, aCGH can uncover intragenic deletions as small as dozen bases. These data provide insight that will help optimize probe coverage in array design and illustrate the true assay sensitivity. Mapping of the breakpoints confirms smaller deletions and contributes to the understanding of the mechanism behind these events. Our knowledge of the mutation spectra of several genes can be expected to change as previously unrecognized intragenic deletions are uncovered. PMID:24304607

Resolution Limits of Nanoimprinted Patterns by Fluorescence Microscopy

NASA Astrophysics Data System (ADS)

Kubo, Shoichi; Tomioka, Tatsuya; Nakagawa, Masaru

2013-06-01

The authors investigated optical resolution limits to identify minimum distances between convex lines of fluorescent dye-doped nanoimprinted resist patterns by fluorescence microscopy. Fluorescent ultraviolet (UV)-curable resin and thermoplastic resin films were transformed into line-and-space patterns by UV nanoimprinting and thermal nanoimprinting, respectively. Fluorescence immersion observation needed an immersion medium immiscible to the resist films, and an ionic liquid of triisobutyl methylphosphonium tosylate was appropriate for soluble thermoplastic polystyrene patterns. Observation with various numerical aperture (NA) values and two detection wavelength ranges showed that the resolution limits were smaller than the values estimated by the Sparrow criterion. The space width to identify line patterns became narrower as the line width increased. The space width of 100 nm was demonstrated to be sufficient to resolve 300-nm-wide lines in the detection wavelength range of 575-625 nm using an objective lens of NA= 1.40.

Ultra-sensitive suspended atomically thin-layered black phosphorus mercury sensors.

PubMed

Li, Peng; Zhang, Dongzhi; Jiang, Chuanxing; Zong, Xiaoqi; Cao, Yuhua

2017-12-15

The extraordinary properties of black phosphorus (BP) make it a promising candidate for next-generation transistor chemical sensors. However, BP films reported so far are supported on substrate, and substrate scattering drastically deteriorates its electrical properties. Consequentially, the potential sensing capability of intrinsic BP is highly underestimated and its sensing mechanism is masked. Additionally, the optimum sensing regime of BP remains unexplored. This article is the first demonstration of suspended BP sensor operated in subthreshold regime. BP exhibited significant enhancement of sensitivity for ultra-low-concentration mercury detection in the absence of substrate, and the sensitivity reached maximum in subthreshold regime. Without substrate scattering, the suspended BP device demonstrated 10 times lower 1/f noise which contributed to better signal-to-noise ratio. Therefore, rapid label-free trace detection of Hg 2+ was achieved with detection limit of 0.01 ppb, lower than the world health organization (WHO) tolerance level (1 ppb). The time constant for ion detection extracted was 3s. Additionally, experimental results revealed that good stability, repeatability, and selectivity were achieved. BP sensors also demonstrated the ability of detecting mercury ions in environment water samples. The underling sensing mechanism of intrinsic BP was ascribed to the carrier density variation resulted from surface charge gating effect, so suspended BP in subthreshold regime with optimum gating effect demonstrated the best sensitivity. Our results show the prominent advantages of intrinsic BP as a sensing material. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

A novel approach to eliminate detection of contaminating Staphylococcal species introduced during clinical testing

PubMed Central

Ao, Wanyuan; Clifford, Adrianne; Corpuz, Maylene; Jenison, Robert

2017-01-01

We describe here a strategy that can distinguish between Staphylococcus species truly present in a clinical sample from contaminating Staphylococcus species introduced during the testing process. Contaminating Staphylococcus species are present at low levels in PCR reagents and colonize lab personnel. To eliminate detection of contaminants, we describe an approach that utilizes addition of sufficient quantities of either non-target Staphylococcal cells (Staphylococcus succinus or Staphylococcus muscae) or synthetic oligonucleotide templates to helicase dependent isothermal amplification reactions to consume Staphylococcus-specific tuf and mecA gene primers such that contaminating Staphylococcus amplification is suppressed to below assay limits of detection. The suppressor template DNA is designed with perfect homology to the primers used in the assay but an internal sequence that is unrelated to the Staphylococcal species targeted for detection. Input amount of the suppressor is determined by a mathematical model described herein and is demonstrated to completely suppress contaminating levels of Staphylococcus while not negatively impacting the appropriate clinical assay limit of detection. We have applied this approach to improve the specificity of detection of Staphylococcus species present in positive blood cultures using a chip-based array that produces results visible to the unaided eye. PMID:28225823

Solar-thermal complex sample processing for nucleic acid based diagnostics in limited resource settings

PubMed Central

Gumus, Abdurrahman; Ahsan, Syed; Dogan, Belgin; Jiang, Li; Snodgrass, Ryan; Gardner, Andrea; Lu, Zhengda; Simpson, Kenneth; Erickson, David

2016-01-01

The use of point-of-care (POC) devices in limited resource settings where access to commonly used infrastructure, such as water and electricity, can be restricted represents simultaneously one of the best application fits for POC systems as well as one of the most challenging places to deploy them. Of the many challenges involved in these systems, the preparation and processing of complex samples like stool, vomit, and biopsies are particularly difficult due to the high number and varied nature of mechanical and chemical interferents present in the sample. Previously we have demonstrated the ability to use solar-thermal energy to perform PCR based nucleic acid amplifications. In this work demonstrate how the technique, using similar infrastructure, can also be used to perform solar-thermal based sample processing system for extracting and isolating Vibrio Cholerae nucleic acids from fecal samples. The use of opto-thermal energy enables the use of sunlight to drive thermal lysing reactions in large volumes without the need for external electrical power. Using the system demonstrate the ability to reach a 95°C threshold in less than 5 minutes and maintain a stable sample temperature of +/− 2°C following the ramp up. The system is demonstrated to provide linear results between 104 and 108 CFU/mL when the released nucleic acids were quantified via traditional means. Additionally, we couple the sample processing unit with our previously demonstrated solar-thermal PCR and tablet based detection system to demonstrate very low power sample-in-answer-out detection. PMID:27231636

An optical system for detecting 3D high-speed oscillation of a single ultrasound microbubble

PubMed Central

Liu, Yuan; Yuan, Baohong

2013-01-01

As contrast agents, microbubbles have been playing significant roles in ultrasound imaging. Investigation of microbubble oscillation is crucial for microbubble characterization and detection. Unfortunately, 3-dimensional (3D) observation of microbubble oscillation is challenging and costly because of the bubble size—a few microns in diameter—and the high-speed dynamics under MHz ultrasound pressure waves. In this study, a cost-efficient optical confocal microscopic system combined with a gated and intensified charge-coupled device (ICCD) camera were developed to detect 3D microbubble oscillation. The capability of imaging microbubble high-speed oscillation with much lower costs than with an ultra-fast framing or streak camera system was demonstrated. In addition, microbubble oscillations along both lateral (x and y) and axial (z) directions were demonstrated. Accordingly, this system is an excellent alternative for 3D investigation of microbubble high-speed oscillation, especially when budgets are limited. PMID:24049677

Aligned Silver Nanorod Array as SERS Substrates for Viral Sensing

NASA Astrophysics Data System (ADS)

Zhao, Yiping; Shanmukh, Saratchandra; Chaney, Stephen B.; Jones, Les; Dluhy, Richard A.; Tripp, Ralph A.

2006-03-01

The aligned silver nanorod array substrates prepared by the oblique angle deposition method are capable of providing extremely high enhancement factors (˜10^9) at near-infrared wavelengths (785 nm) for a standard reporter molecule 1,2 trans-(bis)pyridyl-ethene (BPE). The enhancement factor depends strongly on the length of the Ag nanorods, the substrate coating, as well as the polarization of the excitation laser beam. With the current optimum structure, we demonstrate that the detection limit for BPE can be lower than 0.1 fM. The applicability of this substrate to the detection of bioagents has been investigated by looking several viruses, such as Adenovirus, HIV, Rhinovirus and Respiratory Syncytial Virus (RSV), at low quantities (˜0.5uL). Different viruses have different fingerprint Raman spectrum. The detection of virus presented in infected cells has also been demonstrated.

High-speed and high-efficiency travelling wave single-photon detectors embedded in nanophotonic circuits

PubMed Central

Pernice, W.H.P.; Schuck, C.; Minaeva, O.; Li, M.; Goltsman, G.N.; Sergienko, A.V.; Tang, H.X.

2012-01-01

Ultrafast, high-efficiency single-photon detectors are among the most sought-after elements in modern quantum optics and quantum communication. However, imperfect modal matching and finite photon absorption rates have usually limited their maximum attainable detection efficiency. Here we demonstrate superconducting nanowire detectors atop nanophotonic waveguides, which enable a drastic increase of the absorption length for incoming photons. This allows us to achieve high on-chip single-photon detection efficiency up to 91% at telecom wavelengths, repeatable across several fabricated chips. We also observe remarkably low dark count rates without significant compromise of the on-chip detection efficiency. The detectors are fully embedded in scalable silicon photonic circuits and provide ultrashort timing jitter of 18 ps. Exploiting this high temporal resolution, we demonstrate ballistic photon transport in silicon ring resonators. Our direct implementation of a high-performance single-photon detector on chip overcomes a major barrier in integrated quantum photonics. PMID:23271658

Automated Detection of Diabetic Retinopathy using Deep Learning.

PubMed

Lam, Carson; Yi, Darvin; Guo, Margaret; Lindsey, Tony

2018-01-01

Diabetic retinopathy is a leading cause of blindness among working-age adults. Early detection of this condition is critical for good prognosis. In this paper, we demonstrate the use of convolutional neural networks (CNNs) on color fundus images for the recognition task of diabetic retinopathy staging. Our network models achieved test metric performance comparable to baseline literature results, with validation sensitivity of 95%. We additionally explored multinomial classification models, and demonstrate that errors primarily occur in the misclassification of mild disease as normal due to the CNNs inability to detect subtle disease features. We discovered that preprocessing with contrast limited adaptive histogram equalization and ensuring dataset fidelity by expert verification of class labels improves recognition of subtle features. Transfer learning on pretrained GoogLeNet and AlexNet models from ImageNet improved peak test set accuracies to 74.5%, 68.8%, and 57.2% on 2-ary, 3-ary, and 4-ary classification models, respectively.

High Sensitivity Terahertz Detection through Large-Area Plasmonic Nano-Antenna Arrays.

PubMed

Yardimci, Nezih Tolga; Jarrahi, Mona

2017-02-16

Plasmonic photoconductive antennas have great promise for increasing responsivity and detection sensitivity of conventional photoconductive detectors in time-domain terahertz imaging and spectroscopy systems. However, operation bandwidth of previously demonstrated plasmonic photoconductive antennas has been limited by bandwidth constraints of their antennas and photoconductor parasitics. Here, we present a powerful technique for realizing broadband terahertz detectors through large-area plasmonic photoconductive nano-antenna arrays. A key novelty that makes the presented terahertz detector superior to the state-of-the art is a specific large-area device geometry that offers a strong interaction between the incident terahertz beam and optical pump at the nanoscale, while maintaining a broad operation bandwidth. The large device active area allows robust operation against optical and terahertz beam misalignments. We demonstrate broadband terahertz detection with signal-to-noise ratio levels as high as 107 dB.

High Sensitivity Terahertz Detection through Large-Area Plasmonic Nano-Antenna Arrays

PubMed Central

Yardimci, Nezih Tolga; Jarrahi, Mona

2017-01-01

Plasmonic photoconductive antennas have great promise for increasing responsivity and detection sensitivity of conventional photoconductive detectors in time-domain terahertz imaging and spectroscopy systems. However, operation bandwidth of previously demonstrated plasmonic photoconductive antennas has been limited by bandwidth constraints of their antennas and photoconductor parasitics. Here, we present a powerful technique for realizing broadband terahertz detectors through large-area plasmonic photoconductive nano-antenna arrays. A key novelty that makes the presented terahertz detector superior to the state-of-the art is a specific large-area device geometry that offers a strong interaction between the incident terahertz beam and optical pump at the nanoscale, while maintaining a broad operation bandwidth. The large device active area allows robust operation against optical and terahertz beam misalignments. We demonstrate broadband terahertz detection with signal-to-noise ratio levels as high as 107 dB. PMID:28205615

Silk-molded flexible, ultrasensitive, and highly stable electronic skin for monitoring human physiological signals.

PubMed

Wang, Xuewen; Gu, Yang; Xiong, Zuoping; Cui, Zheng; Zhang, Ting

2014-03-05

Flexible and transparent E-skin devices are achieved by combining silk-molded micro-patterned polydimethylsiloxane (PDMS) with single-walled carbon nanotube (SWNT) ultrathin films. The E-skin sensing device demonstrates superior sensitivity, a very low detectable pressure limit, a fast response time, and a high stability for the detection of superslight pressures, which may broaden their potential use as cost-effective wearable electronics for healthcare applications. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Peptide Functionalized Gold Nanorods for the Sensitive Detection of a Cardiac Biomarker Using Plasmonic Paper Devices (Postprint)

DTIC Science & Technology

2015-11-10

currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YY) 2. REPORT TYPE 3 . DATES COVERED...refractive index difference on the order of 3 × 10−4 refractive index units (RIU)), probe the conformational changes of individual biomacromolecules...natural antibodies and short peptides, as BREs. We demonstrate that pep - tides provide a significantly higher sensitivity and lower limit of detection

Novel fluorescent probe for highly sensitive bioassay using sequential enzyme-linked immunosorbent assay-capillary isoelectric focusing (ELISA-cIEF).

PubMed

Henares, Terence G; Uenoyama, Yuta; Nogawa, Yuto; Ikegami, Ken; Citterio, Daniel; Suzuki, Koji; Funano, Shun-ichi; Sueyoshi, Kenji; Endo, Tatsuro; Hisamoto, Hideaki

2013-06-07

This paper presents a novel rhodamine diphosphate molecule that allows highly sensitive detection of proteins by employing sequential enzyme-linked immunosorbent assay and capillary isoelectric focusing (ELISA-cIEF). Seven-fold improvement in the immunoassay sensitivity and a 1-2 order of magnitude lower detection limit has been demonstrated by taking advantage of the combination of the enzyme-based signal amplification of ELISA and the concentration of enzyme reaction products by cIEF.

Ferritin-mediated biomimetic synthesis of bimetallic Au-Ag nanoparticles on graphene nanosheets for electrochemical detection of hydrogen peroxide

NASA Astrophysics Data System (ADS)

Wang, Li; Wang, Jiku; Ni, Pengjuan; Li, Zhuang

2015-03-01

We demonstrated a biomimetic green synthesis of bimetallic Au-Ag nanoparticles (NPs) on graphene nanosheets (GNs). The spherical protein, ferritin (Fr), was bound onto GNs and served as the template for the synthesis of GN/Au-Ag nanohybrids. The created GN/Au-Ag nanohybrids were further utilized to fabricate a non-enzymatic amperometric biosensor for the sensitive detection of hydrogen peroxide (H2O2), and this biosensor displayed high performances to determine H2O2 with a detection limit of 20.0 × 10-6 M and a linear detection range from 2.0 μM to 7.0 mM.

Spatially-Aware Temporal Anomaly Mapping of Gamma Spectra

NASA Astrophysics Data System (ADS)

Reinhart, Alex; Athey, Alex; Biegalski, Steven

2014-06-01

For security, environmental, and regulatory purposes it is useful to continuously monitor wide areas for unexpected changes in radioactivity. We report on a temporal anomaly detection algorithm which uses mobile detectors to build a spatial map of background spectra, allowing sensitive detection of any anomalies through many days or months of monitoring. We adapt previously-developed anomaly detection methods, which compare spectral shape rather than count rate, to function with limited background data, allowing sensitive detection of small changes in spectral shape from day to day. To demonstrate this technique we collected daily observations over the period of six weeks on a 0.33 square mile research campus and performed source injection simulations.

Chirped Laser Dispersion Spectroscopy for Remote Open-Path Trace-Gas Sensing

PubMed Central

Nikodem, Michal; Wysocki, Gerard

2012-01-01

In this paper we present a prototype instrument for remote open-path detection of nitrous oxide. The sensor is based on a 4.53 μm quantum cascade laser and uses the chirped laser dispersion spectroscopy (CLaDS) technique for molecular concentration measurements. To the best of our knowledge this is the first demonstration of open-path laser-based trace-gas detection using a molecular dispersion measurement. The prototype sensor achieves a detection limit down to the single-ppbv level and exhibits excellent stability and robustness. The instrument characterization, field deployment performance, and the advantages of applying dispersion sensing to sensitive trace-gas detection in a remote open-path configuration are presented. PMID:23443389

Chirped laser dispersion spectroscopy for remote open-path trace-gas sensing.

PubMed

Nikodem, Michal; Wysocki, Gerard

2012-11-28

In this paper we present a prototype instrument for remote open-path detection of nitrous oxide. The sensor is based on a 4.53 μm quantum cascade laser and uses the chirped laser dispersion spectroscopy (CLaDS) technique for molecular concentration measurements. To the best of our knowledge this is the first demonstration of open-path laser-based trace-gas detection using a molecular dispersion measurement. The prototype sensor achieves a detection limit down to the single-ppbv level and exhibits excellent stability and robustness. The instrument characterization, field deployment performance, and the advantages of applying dispersion sensing to sensitive trace-gas detection in a remote open-path configuration are presented.

Improvement of charge-pumping electrically detected magnetic resonance and its application to silicon metal-oxide-semiconductor field-effect transistor

NASA Astrophysics Data System (ADS)

Hori, Masahiro; Tsuchiya, Toshiaki; Ono, Yukinori

2017-01-01

Charge-pumping electrically detected magnetic resonance (CP EDMR), or EDMR in the CP mode, is improved and applied to a silicon metal-oxide-semiconductor field-effect transistor (MOSFET). Real-time monitoring of the CP process reveals that high-frequency transient currents are an obstacle to signal amplification for EDMR. Therefore, we introduce cutoff circuitry, leading to a detection limit for the number of spins as low as 103 for Si MOS interface defects. With this improved method, we demonstrate that CP EDMR inherits one of the most important features of the CP method: the gate control of the energy window of the detectable interface defects for spectroscopy.

Rapid Waterborne Pathogen Detection with Mobile Electronics.

PubMed

Wu, Tsung-Feng; Chen, Yu-Chen; Wang, Wei-Chung; Kucknoor, Ashwini S; Lin, Che-Jen; Lo, Yu-Hwa; Yao, Chun-Wei; Lian, Ian

2017-06-09

Pathogen detection in water samples, without complex and time consuming procedures such as fluorescent-labeling or culture-based incubation, is essential to public safety. We propose an immunoagglutination-based protocol together with the microfluidic device to quantify pathogen levels directly from water samples. Utilizing ubiquitous complementary metal-oxide-semiconductor (CMOS) imagers from mobile electronics, a low-cost and one-step reaction detection protocol is developed to enable field detection for waterborne pathogens. 10 mL of pathogen-containing water samples was processed using the developed protocol including filtration enrichment, immune-reaction detection and imaging processing. The limit of detection of 10 E. coli O157:H7 cells/10 mL has been demonstrated within 10 min of turnaround time. The protocol can readily be integrated into a mobile electronics such as smartphones for rapid and reproducible field detection of waterborne pathogens.

Hybrid Monte Carlo/Deterministic Methods for Accelerating Active Interrogation Modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peplow, Douglas E.; Miller, Thomas Martin; Patton, Bruce W

2013-01-01

The potential for smuggling special nuclear material (SNM) into the United States is a major concern to homeland security, so federal agencies are investigating a variety of preventive measures, including detection and interdiction of SNM during transport. One approach for SNM detection, called active interrogation, uses a radiation source, such as a beam of neutrons or photons, to scan cargo containers and detect the products of induced fissions. In realistic cargo transport scenarios, the process of inducing and detecting fissions in SNM is difficult due to the presence of various and potentially thick materials between the radiation source and themore » SNM, and the practical limitations on radiation source strength and detection capabilities. Therefore, computer simulations are being used, along with experimental measurements, in efforts to design effective active interrogation detection systems. The computer simulations mostly consist of simulating radiation transport from the source to the detector region(s). Although the Monte Carlo method is predominantly used for these simulations, difficulties persist related to calculating statistically meaningful detector responses in practical computing times, thereby limiting their usefulness for design and evaluation of practical active interrogation systems. In previous work, the benefits of hybrid methods that use the results of approximate deterministic transport calculations to accelerate high-fidelity Monte Carlo simulations have been demonstrated for source-detector type problems. In this work, the hybrid methods are applied and evaluated for three example active interrogation problems. Additionally, a new approach is presented that uses multiple goal-based importance functions depending on a particle s relevance to the ultimate goal of the simulation. Results from the examples demonstrate that the application of hybrid methods to active interrogation problems dramatically increases their calculational efficiency.« less

Femtogram-level detection of Clostridium botulinum neurotoxin type A by sandwich immunoassay using nanoporous substrate and ultra-bright fluorescent suprananoparticles.

PubMed

Bok, Sangho; Korampally, Venumadhav; Darr, Charles M; Folk, William R; Polo-Parada, Luis; Gangopadhyay, Keshab; Gangopadhyay, Shubhra

2013-03-15

We report a simple, robust fluorescence biosensor for the ultra-sensitive detection of Clostridium botulinum Neurotoxin Type A (BoNT/A) in complex, real-world media. High intrinsic signal amplification was achieved through the combined use of ultra-bright, photostable dye-doped nanoparticle (DOSNP) tags and high surface area nanoporous organosilicate (NPO) thin films. DOSNP with 22 nm diameter were synthesized with more than 200 times equivalent free dye fluorescence and conjugated to antibodies with average degree of substitution of 90 dyes per antibody, representing an order of magnitude increase compared with conventional dye-labeled antibodies. The NPO films were engineered to form constructive interference at the surface where fluorophores were located. In addition, DOSNP-labeled antibodies with NPO films increased surface roughness causing diffuse scattering resulting in 24% more scattering intensity than dye-labeled antibody with NPO films. These substrates were used for immobilization of capture antibodies against BoNT/A, which was further quantified by DOSNP-labeled signal antibodies. The combination of optical effects enhanced the fluorescence and, therefore, the signal-to-noise ratio significantly. BoNT/A was detected in PBS buffer down to 21.3 fg mL(-1) in 4 h. The assay was then extended to several complex media and the four-hour detection limit was found to be 145.8 fg mL(-1) in orange juice and 164.2 fg mL(-1) in tap water, respectively, demonstrating at least two orders of magnitude improvement comparing to the reported detection limit of other enzyme-linked immunosorbent assays (ELISA). This assay, therefore, demonstrates a novel method for rapid, ultra-low level detection of not only BoNT/A, but other analytes as well. Copyright © 2012 Elsevier B.V. All rights reserved.

Discrimination Report: ESTCP UXO Discrimination Study, ESTCPProject #MM-0437

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gasperikova, Erika; Smith, J. Torquil; Morrison, H. Frank

2007-12-21

The FY06 Defense Appropriation contains funding for the 'Development of Advanced, Sophisticated, Discrimination Technologies for UXO Cleanup' in the Environmental Security Technology Certification Program. In 2003, the Defense Science Board observed: 'The problem is that instruments that can detect the buried UXOs also detect numerous scrap metal objects and other artifacts, which leads to an enormous amount of expensive digging. Typically 100 holes may be dug before a real UXO is unearthed! The Task Force assessment is that much of this wasteful digging can be eliminated by the use of more advanced technology instruments that exploit modern digital processing andmore » advanced multi-mode sensors to achieve an improved level of discrimination of scrap from UXOs.' Significant progress has been made in discrimination technology. To date, testing of these approaches has been primarily limited to test sites with only limited application at live sites. Acceptance of discrimination technologies requires demonstration of system capabilities at real UXO sites under real world conditions. Any attempt to declare detected anomalies to be harmless and requiring no further investigation require demonstration to regulators of not only individual technologies, but of an entire decision making process. This discrimination study was be the first phase in what is expected to be a continuing effort that will span several years.« less

Ultrahigh polarimetric image contrast enhancement for skin cancer diagnosis using InN plasmonic nanoparticles in the terahertz range

NASA Astrophysics Data System (ADS)

Ney, Michael; Abdulhalim, Ibrahim

2015-12-01

Mueller matrix imaging sensitivity, to delicate water content changes in tissue associated with early stages of skin cancer, is demonstrated by numerical modeling to be enhanced by localized surface plasmon resonance (LSPR) effects at the terahertz (THz) range when InN nanoparticles (NPs) coated with Parylene-C are introduced into the skin. A skin tissue model tailored for THz wavelengths is established for a Monte Carlo simulation of polarized light propagation and scattering, and a comparative study based on simulated Mueller matrices is presented considering different NPs' parameters and insertion into the skin methods. The insertion of NPs presenting LSPR in the THz is demonstrated to enable the application of polarization-based sample characterization techniques adopted from the scattering dominated visible wavelengths domain for the, otherwise, relatively low scattering THz domain, where such approach is irrelevant without the NPs. Through these Mueller polarimetry techniques, the detection of water content variations in the tissue is made possible and with high sensitivity. This study yields a limit of detection down to 0.0018% for relative changes in the water content based on linear degree of polarization-an improvement of an order of magnitude relative to the limit of detection without NPs calculated in a previous ellipsometric study.

Ultrahigh polarimetric image contrast enhancement for skin cancer diagnosis using InN plasmonic nanoparticles in the terahertz range.

PubMed

Ney, Michael; Abdulhalim, Ibrahim

2015-01-01

Mueller matrix imaging sensitivity, to delicate water content changes in tissue associated with early stages of skin cancer, is demonstrated by numerical modeling to be enhanced by localized surface plasmon resonance (LSPR) effects at the terahertz (THz) range when InN nanoparticles (NPs) coated with Parylene-C are introduced into the skin. A skin tissue model tailored for THz wavelengths is established for a Monte Carlo simulation of polarized light propagation and scattering, and a comparative study based on simulated Mueller matrices is presented considering different NPs’ parameters and insertion into the skin methods. The insertion of NPs presenting LSPR in the THz is demonstrated to enable the application of polarization-based sample characterization techniques adopted from the scattering dominated visible wavelengths domain for the, otherwise, relatively low scattering THz domain, where such approach is irrelevant without the NPs. Through these Mueller polarimetry techniques, the detection of water content variations in the tissue is made possible and with high sensitivity. This study yields a limit of detection down to 0.0018% for relative changes in the water content based on linear degree of polarization--an improvement of an order of magnitude relative to the limit of detection without NPs calculated in a previous ellipsometric study.

Molecular beacon anchored onto a graphene oxide substrate

NASA Astrophysics Data System (ADS)

Darbandi, Arash; Datta, Debopam; Patel, Krunal; Lin, Gary; Stroscio, Michael A.; Dutta, Mitra

2017-09-01

In this article, we report a graphene oxide-based nanosensor incorporating semiconductor quantum dots linked to DNA-aptamers that functions as a ‘turn-off’ fluorescent nanosensor for detection of low concentrations of analytes. A specific demonstration of this turn-off aptasensor is presented for the case of the detection of mercury (II) ions. In this system, ensembles of aptamer-based quantum-dot sensors are anchored onto graphene oxide (GO) flakes which provide a platform for analyte detection in the vicinity of GO. Herein, the operation of this ensemble-based nanosensor is demonstrated for mercury ions, which upon addition of mercury, quenching of the emission intensity from the quantum dots is observed due to resonance energy transfer between quantum dots and the gold nanoparticle connected via a mercury target aptamer. A key result is that the usually dominant effect of quenching of the quantum dot due to close proximity to the GO can be reduced to negligible levels by using a linker molecule in conjunctions with the aptamer-based nanosensor. The effect of ionic concentration of the background matrix on the emission intensity was also investigated. The sensor system is found to be highly selective towards mercury and exhibits a linear behavior (r 2 > 0.99) in the nanomolar concentration range. The detection limit of the sensor towards mercury with no GO present was found to be 16.5 nM. With GO attached to molecular beacon via 14 base, 35 base, and 51 base long linker DNA, the detection limit was found to be 38.4 nM, 9.45 nM, and 11.38 nM; respectively.

Fast fMRI can detect oscillatory neural activity in humans.

PubMed

Lewis, Laura D; Setsompop, Kawin; Rosen, Bruce R; Polimeni, Jonathan R

2016-10-25

Oscillatory neural dynamics play an important role in the coordination of large-scale brain networks. High-level cognitive processes depend on dynamics evolving over hundreds of milliseconds, so measuring neural activity in this frequency range is important for cognitive neuroscience. However, current noninvasive neuroimaging methods are not able to precisely localize oscillatory neural activity above 0.2 Hz. Electroencephalography and magnetoencephalography have limited spatial resolution, whereas fMRI has limited temporal resolution because it measures vascular responses rather than directly recording neural activity. We hypothesized that the recent development of fast fMRI techniques, combined with the extra sensitivity afforded by ultra-high-field systems, could enable precise localization of neural oscillations. We tested whether fMRI can detect neural oscillations using human visual cortex as a model system. We detected small oscillatory fMRI signals in response to stimuli oscillating at up to 0.75 Hz within single scan sessions, and these responses were an order of magnitude larger than predicted by canonical linear models. Simultaneous EEG-fMRI and simulations based on a biophysical model of the hemodynamic response to neuronal activity suggested that the blood oxygen level-dependent response becomes faster for rapidly varying stimuli, enabling the detection of higher frequencies than expected. Accounting for phase delays across voxels further improved detection, demonstrating that identifying vascular delays will be of increasing importance with higher-frequency activity. These results challenge the assumption that the hemodynamic response is slow, and demonstrate that fMRI has the potential to map neural oscillations directly throughout the brain.

Superhydrophobic Analyte Concentration Utilizing Colloid-Pillar Array SERS Substrates

DOE PAGES

Wallace, Ryan A.; Charlton, Jennifer J.; Kirchner, Teresa B.; ...

2014-11-04

In order to detect a few molecules present in a large sample it is important to know the trace components in the medicinal and environmental sample. Surface enhanced Raman spectroscopy (SERS) is a technique that can be utilized to detect molecules at very low absolute numbers. However, detection at trace concentration levels in real samples requires properly designed delivery and detection systems. Moreover, the following work involves superhydrophobic surfaces that includes silicon pillar arrays formed by lithographic and dewetting protocols. In order to generate the necessary plasmonic substrate for SERS detection, simple and flow stable Ag colloid was added tomore » the functionalized pillar array system via soaking. The pillars are used native and with hydrophobic modification. The pillars provide a means to concentrate analyte via superhydrophobic droplet evaporation effects. A 100-fold concentration of analyte was estimated, with a limit of detection of 2.9 10-12 M for mitoxantrone dihydrochloride. Additionally, analytes were delivered to the surface via a multiplex approach in order to demonstrate an ability to control droplet size and placement for scaled-up applications in real world applications. Finally, a concentration process involving transport and sequestration based on surface treatment selective wicking is demonstrated.« less

Superhydrophobic Analyte Concentration Utilizing Colloid-Pillar Array SERS Substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wallace, Ryan A.; Charlton, Jennifer J.; Kirchner, Teresa B.

In order to detect a few molecules present in a large sample it is important to know the trace components in the medicinal and environmental sample. Surface enhanced Raman spectroscopy (SERS) is a technique that can be utilized to detect molecules at very low absolute numbers. However, detection at trace concentration levels in real samples requires properly designed delivery and detection systems. Moreover, the following work involves superhydrophobic surfaces that includes silicon pillar arrays formed by lithographic and dewetting protocols. In order to generate the necessary plasmonic substrate for SERS detection, simple and flow stable Ag colloid was added tomore » the functionalized pillar array system via soaking. The pillars are used native and with hydrophobic modification. The pillars provide a means to concentrate analyte via superhydrophobic droplet evaporation effects. A 100-fold concentration of analyte was estimated, with a limit of detection of 2.9 10-12 M for mitoxantrone dihydrochloride. Additionally, analytes were delivered to the surface via a multiplex approach in order to demonstrate an ability to control droplet size and placement for scaled-up applications in real world applications. Finally, a concentration process involving transport and sequestration based on surface treatment selective wicking is demonstrated.« less

Residual Agar Determination in Bacterial Spores by Electrospray Ionization Mass Spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wahl, Karen L.; Colburn, Heather A.; Wunschel, David S.

2010-02-15

Presented here is an analytical method to detect residual agar from a bacterial spore sample as an indication of culturing on an agar plate. This method is based on the resolubilization of agar polysaccharide from a bacterial spore sample, enzymatic digestion, followed by electrospray ionization tandem mass spectrometry (ESI-MSn) analysis for detection of a specific agar fragment ion. A range of Bacillus species and strains were selected to demonstrate the effectiveness of this approach. The characteristic agar fragment ion was detected in the spores grown on agar that were washed from 1 to 5 times, irradiated or non-irradiated and notmore » in the spores grown in broth. A sample containing approximately 108 spores is currently needed for confident detection of residual agar from culture on agar plates in the presence of bacterial spores with a limit of detection of approximately 1 ppm agar spiked into a broth-grown spore sample. The results of a proficiency test with 42 blinded samples are presented demonstrating the utility of this method with no false positives and only 3 false negatives for samples that were below the detection level of the method as documented.« less

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.

ATP-mediated intrinsic peroxidase-like activity of Fe3O4-based nanozyme: One step detection of blood glucose at physiological pH.

PubMed

Vallabani, N V Srikanth; Karakoti, Ajay S; Singh, Sanjay

2017-05-01

Fe 3 O 4 nanoparticles (Fe 3 O 4 NPs), demonstrating peroxidase-like activity has garnered attention in the detection of several biomolecules, therefore, emerged as an excellent nano-biosensing agent. The intrinsic peroxidase-like activity of Fe 3 O 4 NPs at acidic pH is the fundamental action driving the oxidation of substrates like TMB, resulting in a colorimetric product formation used in the detection of biomolecules. Hence, the detection sensitivity essentially depends on the ability of oxidation by Fe 3 O 4 NPs in presence of H 2 O 2 . However, the limited sensitivity and pH condition constraint have been identified as the major drawbacks in the detection of biomolecules at physiological pH. Herein, we report overwhelming of the fundamental limitation of acidic pH and tuning the peroxidase-like activity of Fe 3 O 4 NPs at physiological pH by using ATP. In presence of ATP, Fe 3 O 4 NPs exhibited enhanced peroxidase-like activity over a wide range of pH and temperatures. Mechanistically, it was found that the ability of ATP to participate in single electron transfer reaction, through complexation with Fe 3 O 4 NPs, results in the generation of hydroxyl radicals which are responsible for enhanced peroxidase activity at physiological pH. We utilized this ATP-mediated enhanced peroxidase-like activity of Fe 3 O 4 NPs for single step detection of glucose with a colorimetric detection limit of 50μM. Further, we extended this single step detection method to monitor glucose level in human blood serum and detected in a time span of <5min at pH 7.4. Copyright © 2017 Elsevier B.V. All rights reserved.

Aptamer Based Microsphere Biosensor for Thrombin Detection

PubMed Central

Zhu, Hongying; Suter, Jonathan D.; White, Ian M.; Fan, Xudong

2006-01-01

We have developed an optical microsphere resonator biosensor using aptamer as receptor for the measurement of the important biomolecule thrombin. The sphere surface is modified with anti-thrombin aptamer, which has excellent binding affinity and selectivity for thrombin. Binding of the thrombin at the sphere surface is monitored by the spectral position of the microsphere's whispering gallery mode resonances. A detection limit on the order of 1 NIH Unit/mL is demonstrated. Control experiments with non-aptamer oligonucleotide and BSA are also carried out to confirm the specific binding between aptamer and thrombin. We expect that this demonstration will lead to the development of highly sensitive biomarker sensors based on aptamer with lower cost and higher throughput than current technology.

Development of the fast and efficient gamma detector using Cherenkov light for TOF-PET

NASA Astrophysics Data System (ADS)

Canot, C.; Alokhina, M.; Abbon, P.; Bard, J. P.; Tauzin, G.; Yvon, D.; Sharyy, V.

2017-12-01

In this paper we present two configurations of innovative gamma detectors using Cherenkov light for time-of-flight—Positron Emission Tomography (PET). The first uses heavy crystals as a Cherenkov radiator to develop a demonstrator for a whole body PET scanner with high detection efficiency. We demonstrated a 30% detection efficiency and a 180 ps (FWHM) time resolution, mainly limited by the time transit spread of the photomultiplier. The second configuration uses an innovative liquid, the TriMethyl Bismuth, to develop a high precision brain-scanning PET device with time-of-flight capability. According to Geant4 simulation, we expect to reach a precision of 150 ps (FWHM) and an efficiency of about 25%.

New Possibilities of Substance Identification Based on THz Time Domain Spectroscopy Using a Cascade Mechanism of High Energy Level Excitation

PubMed Central

Trofimov, Vyacheslav A.; Varentsova, Svetlana A.; Zakharova, Irina G.; Zagursky, Dmitry Yu.

2017-01-01

Using an experiment with thin paper layers and computer simulation, we demonstrate the principal limitations of standard Time Domain Spectroscopy (TDS) based on using a broadband THz pulse for the detection and identification of a substance placed inside a disordered structure. We demonstrate the spectrum broadening of both transmitted and reflected pulses due to the cascade mechanism of the high energy level excitation considering, for example, a three-energy level medium. The pulse spectrum in the range of high frequencies remains undisturbed in the presence of a disordered structure. To avoid false absorption frequencies detection, we apply the spectral dynamics analysis method (SDA-method) together with certain integral correlation criteria (ICC). PMID:29186849

False Detection of Dangerous and Netural Substances in Commonly Used Materials by Means of the Standard THz Time Domain Spectroscopy

NASA Astrophysics Data System (ADS)

Trofimov, V. A.; Varentsova, S. A.

2016-04-01

Essential limitations of the standard THz Time Domain Spectroscopy (TDS), which lead to false detection of dangerous and neutral substances in commonly used materials, are demonstrated using the physical experiment with chocolate under real conditions as well as with semiconductors under laboratory conditions. To overcome this disadvantage, we propose using the time-dependent spectrum of the THz pulse, transmitted through or reflected from a substance. For quality assessment of the standard substance absorption frequency presence in the signal under analysis, we use time-dependent integral correlation criteria. The influence of aperture placed in front of the sample on spectral properties of silicon wafers with different resistivity is demonstrated as well.

Towards non-contact photo-acoustic endoscopy using speckle pattern analysis

NASA Astrophysics Data System (ADS)

Lengenfelder, Benjamin; Mehari, Fanuel; Tang, Yuqi; Klämpfl, Florian; Zalevsky, Zeev; Schmidt, Michael

2017-03-01

Photoacoustic Tomography combines the advantages of optical and acoustic imaging as it makes use of the high optical contrast of tissue and the high resolution of ultrasound. Furthermore, high penetration depths in tissue in the order of several centimeters can be achieved by the combination of these modalities. Extensive research is being done in the field of miniaturization of photoacoustic devices, as photoacoustic imaging could be of significant benefits for the physician during endoscopic interventions. All the existing miniature systems are based on contact transducers for signal detection that are placed at the distal end of an endoscopic device. This makes the manufacturing process difficult and impedance matching to the inspected surface a requirement. The requirement for contact limits the view of the physician during the intervention. Consequently, a fiber based non-contact optical sensing technique would be highly beneficial for the development of miniaturized photoacoustic endoscopic devices. This work demonstrates the feasibility of surface displacement detection using remote speckle-sensing using a high speed camera and an imaging fiber bundle that is used in commercially available video endoscopes. The feasibility of displacement sensing is demonstrated by analysis of phantom vibrations which are induced by loudspeaker membrane oscillations. Since the usability of the remote speckle-sensing for photo-acoustic signal detection was already demonstrated, the fiber bundle approach demonstrates the potential for non-contact photoacoustic detections during endoscopy.

Enhanced dopamine detection sensitivity by PEDOT/graphene oxide coating on in vivo carbon fiber electrodes.

PubMed

Taylor, I Mitch; Robbins, Elaine M; Catt, Kasey A; Cody, Patrick A; Happe, Cassandra L; Cui, Xinyan Tracy

2017-03-15

Dopamine (DA) is a monoamine neurotransmitter responsible for regulating a variety of vital life functions. In vivo detection of DA poses a challenge due to the low concentration and high speed of physiological signaling. Fast scan cyclic voltammetry at carbon fiber microelectrodes (CFEs) is an effective method to monitor real-time in vivo DA signaling, however the sensitivity is somewhat limited. Electrodeposition of poly(3,4-ethylene dioxythiophene) (PEDOT)/graphene oxide (GO) onto the CFE surface is shown to increase the sensitivity and lower the limit of detection for DA compared to bare CFEs. Thicker PEDOT/GO coatings demonstrate higher sensitivities for DA, but display the negative drawback of slow adsorption and electron transfer kinetics. The moderate thickness resulting from 25 s electrodeposition of PEDOT/GO produces the optimal electrode, exhibiting an 880% increase in sensitivity, a 50% decrease in limit of detection and minimally altered electrode kinetics. PEDOT/GO coated electrodes rapidly and robustly detect DA, both in solution and in the rat dorsal striatum. This increase in DA sensitivity is likely due to increasing the electrode surface area with a PEDOT/GO coating and improved adsorption of DA's oxidation product (DA-o-quinone). Increasing DA sensitivity without compromising electrode kinetics is expected to significantly improve our understanding of the DA function in vivo. Copyright © 2016 Elsevier B.V. All rights reserved.

Enhanced Dopamine Detection Sensitivity by PEDOT/Graphene Oxide Coating on in vivo Carbon Fiber Electrodes

PubMed Central

Taylor, I. Mitch; Robbins, Elaine M.; Catt, Kasey A.; Cody, Patrick A.; Weaver, Cassandra L.; Cui, Xinyan Tracy

2016-01-01

Dopamine (DA) is a monoamine neurotransmitter responsible for regulating a variety of vital life functions. In vivo detection of DA poses a challenge due to the low concentration and high speed of physiological signaling. Fast scan cyclic voltammetry at carbon fiber microelectrodes (CFEs) is an effective method to monitor real-time in vivo DA signaling, however the sensitivity is somewhat limited. Electrodeposition of poly(3,4-ethylene dioxythiophene) (PEDOT)/graphene oxide (GO) onto the CFE surface is shown to increase the sensitivity and lower the limit of detection for DA compared to bare CFEs. Thicker PEDOT/GO coatings demonstrate higher sensitivities for DA, but display the negative drawback of slow adsorption and electron transfer kinetics. The moderate thickness resulting from 25 s electrodeposition of PEDOT/GO produces the optimal electrode, exhibiting an 880% increase in sensitivity, a 50% decrease in limit of detection and minimally altered electrode kinetics. PEDOT/GO coated electrodes rapidly and robustly detect DA, both in solution and in the rat dorsal striatum. This increase in DA sensitivity is likely due to increasing the electrode surface area with a PEDOT/GO coating and improved adsorption of DA’s oxidation product (DA-o-quinone). Increasing DA sensitivity without compromising electrode kinetics is expected to significantly improve our understanding of the DA function in vivo. PMID:27268013

A statistical assessment of pesticide pollution in surface waters using environmental monitoring data: Chlorpyrifos in Central Valley, California.

PubMed

Wang, Dan; Singhasemanon, Nan; Goh, Kean S

2016-11-15

Pesticides are routinely monitored in surface waters and resultant data are analyzed to assess whether their uses will damage aquatic eco-systems. However, the utility of the monitoring data is limited because of the insufficiency in the temporal and spatial sampling coverage and the inability to detect and quantify trace concentrations. This study developed a novel assessment procedure that addresses those limitations by combining 1) statistical methods capable of extracting information from concentrations below changing detection limits, 2) statistical resampling techniques that account for uncertainties rooted in the non-detects and insufficient/irregular sampling coverage, and 3) multiple lines of evidence that improve confidence in the final conclusion. This procedure was demonstrated by an assessment on chlorpyrifos monitoring data in surface waters of California's Central Valley (2005-2013). We detected a significant downward trend in the concentrations, which cannot be observed by commonly-used statistical approaches. We assessed that the aquatic risk was low using a probabilistic method that works with non-detects and has the ability to differentiate indicator groups with varying sensitivity. In addition, we showed that the frequency of exceedance over ambient aquatic life water quality criteria was affected by pesticide use, precipitation and irrigation demand in certain periods anteceding the water sampling events. Copyright © 2016 Elsevier B.V. All rights reserved.

Ligand replacement-induced fluorescence switch of quantum dots for ultrasensitive detection of organophosphorothioate pesticides.

PubMed

Zhang, Kui; Mei, Qingsong; Guan, Guijian; Liu, Bianhua; Wang, Suhua; Zhang, Zhongping

2010-11-15

The development of a simple and on-site assay for the detection of organophosphorus pesticed residues is very important for food safety and exosystem protection. This paper reports the surface coordination-originated fluorescence resonance energy transfer (FRET) of CdTe quantum dots (QDs) and a simple ligand-replacement turn-on mechanism for the highly sensitive and selective detection of organophosphorothioate pesticides. It has been demonstrated that coordination of dithizone at the surface of CdTe QDs in basic media can strongly quench the green emission of CdTe QDs by a FRET mechanism. Upon the addition of organophosphorothioate pesticides, the dithizone ligands at the CdTe QD surface are replaced by the hydrolyzate of the organophosphorothioate, and hence the fluorescence is turned on. The fluorescence turn on is immediate, and the limit of detection for chlorpyrifos is as low as ∼0.1 nM. Two consecutive linear ranges allow a wide determination of chlorpyrifos concentrations from 0.1 nM to 10 μM. Importantly, the fluorescence turn-on chemosensor can directly detect chlorpyrifos residues in apples at a limit of 5.5 ppb, which is under the maximum residue limit allowed by the U.S. Environmental Protection Agency. The very simple strategy reported here should facilitate the development of fluorescence turn-on chemosensors for chemo/biodetection.

Challenges in paper-based fluorogenic optical sensing with smartphones

NASA Astrophysics Data System (ADS)

Ulep, Tiffany-Heather; Yoon, Jeong-Yeol

2018-05-01

Application of optically superior, tunable fluorescent nanotechnologies have long been demonstrated throughout many chemical and biological sensing applications. Combined with microfluidics technologies, i.e. on lab-on-a-chip platforms, such fluorescent nanotechnologies have often enabled extreme sensitivity, sometimes down to single molecule level. Within recent years there has been a peak interest in translating fluorescent nanotechnology onto paper-based platforms for chemical and biological sensing, as a simple, low-cost, disposable alternative to conventional silicone-based microfluidic substrates. On the other hand, smartphone integration as an optical detection system as well as user interface and data processing component has been widely attempted, serving as a gateway to on-board quantitative processing, enhanced mobility, and interconnectivity with informational networks. Smartphone sensing can be integrated to these paper-based fluorogenic assays towards demonstrating extreme sensitivity as well as ease-of-use and low-cost. However, with these emerging technologies there are always technical limitations that must be addressed; for example, paper's autofluorescence that perturbs fluorogenic sensing; smartphone flash's limitations in fluorescent excitation; smartphone camera's limitations in detecting narrow-band fluorescent emission, etc. In this review, physical optical setups, digital enhancement algorithms, and various fluorescent measurement techniques are discussed and pinpointed as areas of opportunities to further improve paper-based fluorogenic optical sensing with smartphones.

Evaluation of a gas chromatography method for azelaic acid determination in selected biological samples

PubMed Central

Garelnabi, Mahdi; Litvinov, Dmitry; Parthasarathy, Sampath

2010-01-01

Background: Azelaic acid (AzA) is the best known dicarboxilic acid to have pharmaceutical benefits and clinical applications and also to be associated with some diseases pathophysiology. Materials and Methods: We extracted and methylesterified AzA and determined its concentration in human plasma obtained from healthy individuals and also in mice fed AzA containing diet for three months. Results: AzA was detected in Gas Chromatography (GC) and confirmed by Liquid chromatography mass spectrometry (LCMS), and gas chromatography mass spectrometry (GCMC). Our results have shown that AzA can be determined efficiently in selected biological samples by GC method with 1nM limit of detection (LoD) and the limit of quantification (LoQ); was established at 50nM. Analytical Sensitivity as assayed by hexane demonstrated an analytical sensitivity at 0.050nM. The method has demonstrated 8-10% CV batch repeatability across the sample types and 13-18.9% CV for the Within-Lab Precision analysis. The method has shown that AzA can efficiently be recovered from various sample preparation including liver tissue homogenate (95%) and human plasma (97%). Conclusions: Because of its simplicity and lower limit of quantification, the present method provides a useful tool for determining AzA in various biological sample preparations. PMID:22558586

Evaluation of a gas chromatography method for azelaic acid determination in selected biological samples.

PubMed

Garelnabi, Mahdi; Litvinov, Dmitry; Parthasarathy, Sampath

2010-09-01

Azelaic acid (AzA) is the best known dicarboxilic acid to have pharmaceutical benefits and clinical applications and also to be associated with some diseases pathophysiology. We extracted and methylesterified AzA and determined its concentration in human plasma obtained from healthy individuals and also in mice fed AzA containing diet for three months. AzA was detected in Gas Chromatography (GC) and confirmed by Liquid chromatography mass spectrometry (LCMS), and gas chromatography mass spectrometry (GCMC). Our results have shown that AzA can be determined efficiently in selected biological samples by GC method with 1nM limit of detection (LoD) and the limit of quantification (LoQ); was established at 50nM. Analytical Sensitivity as assayed by hexane demonstrated an analytical sensitivity at 0.050nM. The method has demonstrated 8-10% CV batch repeatability across the sample types and 13-18.9% CV for the Within-Lab Precision analysis. The method has shown that AzA can efficiently be recovered from various sample preparation including liver tissue homogenate (95%) and human plasma (97%). Because of its simplicity and lower limit of quantification, the present method provides a useful tool for determining AzA in various biological sample preparations.

Detection of semi-volatile organic compounds in permeable ...

EPA Pesticide Factsheets

Abstract The Edison Environmental Center (EEC) has a research and demonstration permeable parking lot comprised of three different permeable systems: permeable asphalt, porous concrete and interlocking concrete permeable pavers. Water quality and quantity analysis has been ongoing since January, 2010. This paper describes a subset of the water quality analysis, analysis of semivolatile organic compounds (SVOCs) to determine if hydrocarbons were in water infiltrated through the permeable surfaces. SVOCs were analyzed in samples collected from 11 dates over a 3 year period, from 2/8/2010 to 4/1/2013.Results are broadly divided into three categories: 42 chemicals were never detected; 12 chemicals (11 chemical test) were detected at a rate of less than 10% or less; and 22 chemicals were detected at a frequency of 10% or greater (ranging from 10% to 66.5% detections). Fundamental and exploratory statistical analyses were performed on these latter analyses results by grouping results by surface type. The statistical analyses were limited due to low frequency of detections and dilutions of samples which impacted detection limits. The infiltrate data through three permeable surfaces were analyzed as non-parametric data by the Kaplan-Meier estimation method for fundamental statistics; there were some statistically observable difference in concentration between pavement types when using Tarone-Ware Comparison Hypothesis Test. Additionally Spearman Rank order non-parame

Detection and Quantification of 8-Hydroxy-2′-Deoxyguanosine in Alzheimer’s Transgenic Mouse Urine using Capillary Electrophoresis

PubMed Central

Zhang, Cheng; Nestorova, Gergana; Rissman, Robert A.; Feng, June

2013-01-01

8-Hydroxy-2′-deoxyguanosine (8-OHdG) is one of the major forms of oxidative deoxyribonucleic acid (DNA) damage, and is commonly analyzed as an excellent marker of DNA lesions. The purpose of this study was to develop a sensitive method to accurately and rapidly quantify the 8-OHdG by using capillary electrophoresis with laser-induced fluorescence detection (CE-LIF). The method involved the use of specific antibody to detect DNA lesions (8-OHdG) and consecutive fluorescence labeling. Next, the urine sample with 8-OHdG fluorescently labeled along with other constituents was resolved by capillary electrophoretic system and the lesion of interest was detected using fluorescence detector. The limit of detection was 0.18 fmol, which is sufficient sensitivity for detection and quantification of 8-OHdG in untreated urine samples. The relative standard deviation (RSD) was found to be 11.32 % for migration time, and 5.52 % for peak area. To demonstrate the utility of this method, the urinary concentration of 8-OHdG in an Alzheimer’s transgenic mouse model was determined. Collectively, our results indicate that this methodology offers great advantages such as high separation efficiency, good selectivity, low limit of detection (LOD), simplicity and low cost of analysis. PMID:23712533

Label-free virus detection using silicon photonic microring resonators

PubMed Central

McClellan, Melinda S.; Domier, Leslie L; Bailey, Ryan C.

2013-01-01

Viruses represent a continual threat to humans through a number of mechanisms, which include disease, bioterrorism, and destruction of both plant and animal food resources. Many contemporary techniques used for the detection of viruses and viral infections suffer from limitations such as the need for extensive sample preparation or the lengthy window between infection and measurable immune response, for serological methods. In order to develop a method that is fast, cost-effective, and features reduced sample preparation compared to many other virus detection methods, we report the application of silicon photonic microring resonators for the direct, label-free detection of intact viruses in both purified samples as well as in a complex, real-world analytical matrix. As a model system, we demonstrate the quantitative detection of Bean pod mottle virus, a pathogen of great agricultural importance, with a limit of detection of 10 ng/mL. By simply grinding a small amount of leaf sample in buffer with a mortar and pestle, infected leaves can be identified over a healthy control with a total analysis time of less than 45 min. Given the inherent scalability and multiplexing capability of the semiconductor-based technology, we feel that silicon photonic microring resonators are well-positioned as a promising analytical tool for a number of viral detection applications. PMID:22138465

Fault detection and identification in missile system guidance and control: a filtering approach

NASA Astrophysics Data System (ADS)

Padgett, Mary Lou; Evers, Johnny; Karplus, Walter J.

1996-03-01

Real-world applications of computational intelligence can enhance the fault detection and identification capabilities of a missile guidance and control system. A simulation of a bank-to- turn missile demonstrates that actuator failure may cause the missile to roll and miss the target. Failure of one fin actuator can be detected using a filter and depicting the filter output as fuzzy numbers. The properties and limitations of artificial neural networks fed by these fuzzy numbers are explored. A suite of networks is constructed to (1) detect a fault and (2) determine which fin (if any) failed. Both the zero order moment term and the fin rate term show changes during actuator failure. Simulations address the following questions: (1) How bad does the actuator failure have to be for detection to occur, (2) How bad does the actuator failure have to be for fault detection and isolation to occur, (3) are both zero order moment and fine rate terms needed. A suite of target trajectories are simulated, and properties and limitations of the approach reported. In some cases, detection of the failed actuator occurs within 0.1 second, and isolation of the failure occurs 0.1 after that. Suggestions for further research are offered.

Competition-Mediated Pyrene-Switching Aptasensor: Probing Lysozyme in Human Serum with a Monomer-Excimer Fluorescence Switch

PubMed Central

Huang, Jin; Zhu, Zhi; Bamrungsap, Suwussa; Zhu, Guizhi; You, Mingxu; He, Xiaoxiao; Wang, Kemin; Tan, Weihong

2010-01-01

Lysozyme (Lys) plays crucial roles in the innate immune system, and the detection of Lys in urine and serum has considerable clinical importance. Traditionally, the presence of Lys has been detected by immunoassays; however, these assays are limited by the availability of commercial antibodies and tedious protein modification, and prior sample purification. To address these limitations, we report here the design, synthesis and application of a competition-mediated pyrene-switching aptasensor for selective detection of Lys in buffer and human serum. The detection strategy is based on the attachment of pyrene molecules to both ends of a hairpin DNA strand, which becomes the partially complementary competitor to an anti-Lys aptamer. In the presence of target Lys, the aptamer hybridizes with part of the competitor, which opens the hairpin such that both pyrene molecules are spatially separated. In the presence of target Lys, however, the competitor is displaced from the aptamer by the target, subsequently forming an initial hairpin structure. This brings the two pyrene moieties into close proximity to generate an excimer, which, in turn, results in a shift of fluorescence emission from ca. 400 nm (pyrene monomer) to 495 nm (pyrene excimer). The proposed method for Lys detection showed sensitivity as low as 200 pM and high selectivity in buffer. When measured by steady-state fluorescence spectrum, the detection of Lys in human serum showed a strong fluorescent background, which obscured detection of the excimer signal. However, time-resolved emission measurement (TREM) supported the potential of the method in complex environments with background fluorescence by demonstrating the temporal separation of probe fluorescence emission decay from the intense background signal. We have also demonstrated that the same strategy can be applied to the detection of small biomolecules such as adenosine triphosphate (ATP), sowing the generality of our approach. Therefore, the competition-mediated pyrene-switching aptasensor is promising to have potential for clinical and forensic applications. PMID:21080638

Feasibility of Detecting Bioorganic Compounds in Enceladus Plumes with the Enceladus Organic Analyzer

PubMed Central

Razu, Md Enayet; Kim, Jungkyu; Stockton, Amanda M.; Turin, Paul; Butterworth, Anna

2017-01-01

Abstract Enceladus presents an excellent opportunity to detect organic molecules that are relevant for habitability as well as bioorganic molecules that provide evidence for extraterrestrial life because Enceladus' plume is composed of material from the subsurface ocean that has a high habitability potential and significant organic content. A primary challenge is to send instruments to Enceladus that can efficiently sample organic molecules in the plume and analyze for the most relevant molecules with the necessary detection limits. To this end, we present the scientific feasibility and engineering design of the Enceladus Organic Analyzer (EOA) that uses a microfluidic capillary electrophoresis system to provide sensitive detection of a wide range of relevant organic molecules, including amines, amino acids, and carboxylic acids, with ppm plume-detection limits (100 pM limits of detection). Importantly, the design of a capture plate that effectively gathers plume ice particles at encounter velocities from 200 m/s to 5 km/s is described, and the ice particle impact is modeled to demonstrate that material will be efficiently captured without organic decomposition. While the EOA can also operate on a landed mission, the relative technical ease of a fly-by mission to Enceladus, the possibility to nondestructively capture pristine samples from deep within the Enceladus ocean, plus the high sensitivity of the EOA instrument for molecules of bioorganic relevance for life detection argue for the inclusion of EOA on Enceladus missions. Key Words: Lab-on-a-chip—Organic biomarkers—Life detection—Planetary exploration. Astrobiology 17, 902–912. PMID:28915087

Assisted inhibition effect of acetylcholinesterase with n-octylphosphonic acid and application in high sensitive detection of organophosphorous pesticides by matrix-assisted laser desorption/ionization Fourier transform mass spectrometry.

PubMed

Cai, Tingting; Zhang, Li; Wang, Haoyang; Zhang, Jing; Guo, Yinlong

2011-11-14

A simple and practical approach to improve the sensitivity of acetylcholinesterase (AChE)-inhibited method has been developed for monitoring organophosphorous (OP) pesticide residues. In this work, matrix-assisted laser desorption/ionization Fourier transform mass spectrometry (MALDI-FTMS) was used to detect AChE activity. Due to its good salt-tolerance and low sample consumption, MALDI-FTMS facilitates rapid and high-throughput screening of OP pesticides. Here we describe a new method to obtain low detection limits via employing external reagents. Among candidate compounds, n-octylphosphonic acid (n-Octyl-PA) displays assistant effect to enhance AChE inhibition by OP pesticides. In presence of n-Octyl-PA, the percentages of AChE inhibition still kept correlation with OP pesticide concentrations. The detection limits were improved significantly even by 10(2)-10(3) folds in comparison with conventional enzyme-inhibited methods. Different detection limits of OP pesticides with different toxicities were as low as 0.005 μg L(-1) for high toxic pesticides and 0.05 μg L(-1) for low toxic pesticides. Besides, the reliability of results from this method to analyze cowpea samples had been demonstrated by liquid-chromatography tandem mass spectrometry (LC-MS/MS). The application of this commercial available assistant agent shows great promise to detect OP compounds in complicated biological matrix and broadens the mind for high sensitivity detection of OP pesticide residues in agricultural products. Copyright © 2011 Elsevier B.V. All rights reserved.

Diffusion of Antimicrobials Across Silicone Hydrogel Contact Lenses.

PubMed

Zambelli, Alison M; Brothers, Kimberly M; Hunt, Kristin M; Romanowski, Eric G; Nau, Amy C; Dhaliwal, Deepinder K; Shanks, Robert M Q

2015-09-01

To measure the diffusion of topical preparations of moxifloxacin, amphotericin B (AmB), and polyhexamethylene biguanide (PHMB) through silicone hydrogel (SH) contact lenses (CLs) in vitro. Using an in vitro model, the diffusion of three antimicrobials through SH CLs was measured. Diffused compounds were measured using a spectrophotometer at set time points over a period of 4 hr. The amount of each diffused antimicrobial was determined by comparing the experimental value with a standard curve. A biological assay was performed to validate the CL diffusion assay by testing antimicrobial activity of diffused material against lawns of susceptible bacteria (Staphylococcus epidermidis) and yeast (Saccharomyces cerevisiae). Experiments were repeated at least two times with a total of at least four independent replicates. Our data show detectable moxifloxacin and PHMB diffusion through SH CLs at 30 min, whereas AmB diffusion remained below the limit of detection within the 4-hr experimental period. In the biological assay, diffused moxifloxacin demonstrated microbial killing starting at 20 min on bacterial lawns, whereas PHMB and AmB failed to demonstrate killing on microbial lawns over the course of the 60-min experiment. In vitro diffusion assays demonstrate limited penetration of certain anti-infective agents through SH CLs. Further studies regarding the clinical benefit of using these agents along with bandage CL for corneal pathologic condition are warranted.

Immuno-analysis of microparticles: probing at the limits of detection

PubMed Central

Latham, Sharissa L.; Tiberti, Natalia; Gokoolparsadh, Naveena; Holdaway, Karen; Olivier Couraud, Pierre; Grau, Georges E. R.; Combes, Valery

2015-01-01

Microparticle (MP) research is clouded by debate regarding the accuracy and validity of flow cytometry (FCM) as an analytical methodology, as it is influenced by many variables including the pre-analytical conditions, instruments physical capabilities and detection parameters. This study utilises a simplistic in vitro system for generating MP, and through comparative analysis with immuno-electron microscopy (Immuno-EM) assesses the strengths and limitations of probe selection and high-sensitivity FCM. Of the markers examined, MP were most specifically labelled with phosphatidylserine ligands, annexin V and lactadherin, although only ~60% MP are PS positive. Whilst these two ligands detect comparable absolute MP numbers, they interact with the same population in distinct manners; annexin V binding is enhanced on TNF induced MP. CD105 and CD54 expression were, as expected, consistent and enhanced following TNF activation respectively. Their labelling however accounted for as few as 30–40% of MP. The greatest discrepancies between FCM and I-EM were observed in the population solely labelled for the surface antigen. These findings demonstrate that despite significant improvements in resolution, high-sensitivity FCM remains limited in detecting small-size MP expressing low antigen levels. This study highlights factors to consider when selecting endothelial MP probes, as well as interpreting and representing data. PMID:26553743

Rapid detection of serum antibody by dual-path platform VetTB assay in white-tailed deer infected with Mycobacterium bovis

USDA-ARS?s Scientific Manuscript database

Bovine tuberculosis (TB) in various cervid species remains a significant problem affecting both farmed herds and free-ranging populations. Traditional skin testing was demonstrated to have serious limitations in certain deer species, whereas emerging serological assays showed promising diagnostic pe...

Laser-Induced Breakdown Spectroscopy of Trace Metals

NASA Technical Reports Server (NTRS)

Simons, Stephen (Technical Monitor); VanderWal, Randall L.; Ticich, Thomas M.; West, Joseph R., Jr.

2004-01-01

An alternative approach for laser-induced breakdown spectroscopy (LIBS) determination of trace metal determination in liquids is demonstrated. The limits of detection (LOD) for the technique ranged from 10 ppb to 10 ppm for 15 metals metals (Mg, Al, Si, Ca, Ti, Cr, Fe, Co, Ni, Cu, Zn, As, Cd, Hg, Pb) tested.

Demonstration and Validation of a Regenerated Cellulose Dialysis Membrane Diffusion Sampler for Monitoring Ground Water Quality and Remediation Progress at DoD Sites

DTIC Science & Technology

2007-08-30

ITRC Interstate Technology Regulatory Council LRL Laboratory reporting level LDPE Low-density polyethylene MDL Minimum detection limit MNA...diameter of the well. Another diffusion membrane sampler design consists of a tubular-shaped bag made of flexible low-density polyethylene ( LDPE ...

Is There Life on Exoplanet Maja? A Demonstration for Schools

ERIC Educational Resources Information Center

Planinsic, Gorazd; Marshall, Rick

2012-01-01

Astronomy and astrophysics are very popular with pupils, but the experimental work they can do tends to be rather limited. The search for life elsewhere in the Universe ("exobiology") has received an enormous boost since the detection of a rapidly increasing number of planets ("exoplanets") orbiting other stars in our galaxy. Recently (March…

Flexible shrink-induced high surface area electrodes for electrochemiluminescent sensing.

PubMed

Pegan, Jonathan D; Ho, Adrienne Y; Bachman, Mark; Khine, Michelle

2013-11-07

Photolithographically defined metallic thin film on commodity shrink-wrap is leveraged to create robust electrodes. By thermally shrinking the film, electrodes are reduced by 20× in footprint for improved resolution and conductivity with >600% enhancements in electrochemically active surface area; as electrochemiluminescent sensors, they demonstrate improved limits of detection.

Experimental photonic generation of chirped pulses using nonlinear dispersion-based incoherent processing.

PubMed

Rius, Manuel; Bolea, Mario; Mora, José; Ortega, Beatriz; Capmany, José

2015-05-18

We experimentally demonstrate, for the first time, a chirped microwave pulses generator based on the processing of an incoherent optical signal by means of a nonlinear dispersive element. Different capabilities have been demonstrated such as the control of the time-bandwidth product and the frequency tuning increasing the flexibility of the generated waveform compared to coherent techniques. Moreover, the use of differential detection improves considerably the limitation over the signal-to-noise ratio related to incoherent processing.

In-vivo digital wavefront sensing using swept source OCT

PubMed Central

Kumar, Abhishek; Wurster, Lara M.; Salas, Matthias; Ginner, Laurin; Drexler, Wolfgang; Leitgeb, Rainer A.

2017-01-01

Sub-aperture based digital adaptive optics is demonstrated in a fiber based point scanning optical coherence tomography system using a 1060 nm swept source laser. To detect optical aberrations in-vivo, a small lateral field of view of ~150×150 μm2 is scanned on the sample at a high volume rate of 17 Hz (~1.3 kHz B-scan rate) to avoid any significant lateral and axial motion of the sample, and is used as a “guide star” for the sub-aperture based DAO. The proof of principle is demonstrated using a micro-beads phantom sample, wherein a significant root mean square wavefront error (RMS WFE) of 1.48 waves (> 1μm) is detected. In-vivo aberration measurement with a RMS WFE of 0.33 waves, which is ~5 times higher than the Marechal’s criterion of 1/14 waves for the diffraction limited performance, is shown for a human retinal OCT. Attempt has been made to validate the experimental results with the conventional Shack-Hartmann wavefront sensor within reasonable limitations. PMID:28717573

Isotachophoresis-Based Surface Immunoassay.

PubMed

Paratore, Federico; Zeidman Kalman, Tal; Rosenfeld, Tally; Kaigala, Govind V; Bercovici, Moran

2017-07-18

In the absence of amplification methods for proteins, the immune-detection of low-abundance proteins using antibodies is fundamentally limited by binding kinetic rates. Here, we present a new class of surface-based immunoassays in which protein-antibody reaction is accelerated by isotachophoresis (ITP). We demonstrate the use of ITP to preconcentrate and deliver target proteins to a surface decorated with specific antibodies, where effective utilization of the focused sample is achieved by modulating the driving electric field (stop-and-diffuse ITP mode) or applying a counter flow that opposes the ITP motion (counterflow ITP mode). Using enhanced green fluorescent protein (EGFP) as a model protein, we carry out an experimental optimization of the ITP-based immunoassay and demonstrate a 1300-fold improvement in limit of detection compared to a standard immunoassay, in a 6 min protein-antibody reaction. We discuss the design of buffer chemistries for other protein systems and, in concert with experiments, provide full analytical solutions for the two operation modes, elucidating the interplay between reaction, diffusion, and accumulation time scales and enabling the prediction and design of future immunoassays.

Rapid Diagnostic Assay for Intact Influenza Virus Using a High Affinity Hemagglutinin Binding Protein.

PubMed

Anderson, Caitlin E; Holstein, Carly A; Strauch, Eva-Maria; Bennett, Steven; Chevalier, Aaron; Nelson, Jorgen; Fu, Elain; Baker, David; Yager, Paul

2017-06-20

Influenza is a ubiquitous and recurring infection that results in approximately 500 000 deaths globally each year. Commercially available rapid diagnostic tests are based upon detection of the influenza nucleoprotein, which are limited in that they are unable to differentiate by species and require an additional viral lysis step. Sample preprocessing can be minimized or eliminated by targeting the intact influenza virus, thereby reducing assay complexity and leveraging the large number of hemagglutinin proteins on the surface of each virus. Here, we report the development of a paper-based influenza assay that targets the hemagglutinin protein; the assay employs a combination of antibodies and novel computationally designed, recombinant affinity proteins as the capture and detection agents. This system leverages the customizability of recombinant protein design to target the conserved receptor-binding pocket of the hemagglutinin protein and to match the trimeric nature of hemagglutinin for improved avidity. Using this assay, we demonstrate the first instance of intact influenza virus detection using a combination of antibody and affinity proteins within a porous network. The recombinant head region binder based assays yield superior analytical sensitivity as compared to the antibody based assay, with lower limits of detection of 3.54 × 10 7 and 1.34 × 10 7 CEID 50 /mL for the mixed and all binder stacks, respectively. Not only does this work describe the development of a novel influenza assay, it also demonstrates the power of recombinant affinity proteins for use in rapid diagnostic assays.

Cardiovascular disease testing on the Dimension Vista system: biomarkers of acute coronary syndromes.

PubMed

Kelley, Walter E; Lockwood, Christina M; Cervelli, Denise R; Sterner, Jamie; Scott, Mitchell G; Duh, Show-Hong; Christenson, Robert H

2009-09-01

Performance characteristics of the LOCI cTnI, CK-MB, MYO, NTproBNP and hsCRP methods on the Dimension Vista System were evaluated. Imprecision (following CLSI EP05-A2 guidelines), limit of quantitation (cTnI), limit of blank, linearity on dilution, serum versus plasma matrix studies (cTnI), and method comparison studies were conducted. Method imprecision of 1.8 to 9.7% (cTnI), 1.8 to 5.7% (CK-MB), 2.1 to 2.2% (MYO), 1.6 to 3.3% (NTproBNP), and 3.5 to 4.2% (hsCRP) were demonstrated. The manufacturer's claimed imprecision, detection limits and upper measurement limits were met. Limit of Quantitation was 0.040 ng/mL for the cTnI assay. Agreement of serum and plasma values for cTnI (r=0.99) was shown. Method comparison study results were acceptable. The Dimension Vista cTnI, CK-MB, MYO, NTproBNP, and hsCRP methods demonstrate acceptable performance characteristics for use as an aid in the diagnosis and risk assessment of patients presenting with suspected acute coronary syndromes.

Operation bandwidth optimization of photonic differentiators.

PubMed

Yan, Siqi; Zhang, Yong; Dong, Jianji; Zheng, Aoling; Liao, Shasha; Zhou, Hailong; Wu, Zhao; Xia, Jinsong; Zhang, Xinliang

2015-07-27

We theoretically investigate the operation bandwidth limitation of the photonic differentiator including the upper limitation, which is restrained by the device operation bandwidth and the lower limitation, which is restrained by the energy efficiency (EE) and detecting noise level. Taking the silicon photonic crystal L3 nano-cavity (PCN) as an example, for the first time, we experimentally demonstrate that the lower limitation of the operation bandwidth does exist and differentiators with different bandwidths have significantly different acceptable pulse width range of input signals, which are consistent to the theoretical prediction. Furthermore, we put forward a novel photonic differentiator scheme employing cascaded PCNs with different Q factors, which is likely to expand the operation bandwidth range of photonic differentiator dramatically.

Prospects and fundamental limitations of room temperature, non-avalanche, semiconductor photon-counting sensors (Conference Presentation)

NASA Astrophysics Data System (ADS)

Ma, Jiaju; Zhang, Yang; Wang, Xiaoxin; Ying, Lei; Masoodian, Saleh; Wang, Zhiyuan; Starkey, Dakota A.; Deng, Wei; Kumar, Rahul; Wu, Yang; Ghetmiri, Seyed Amir; Yu, Zongfu; Yu, Shui-Qing; Salamo, Gregory J.; Fossum, Eric R.; Liu, Jifeng

2017-05-01

This research investigates the fundamental limits and trade-space of quantum semiconductor photodetectors using the Schrödinger equation and the laws of thermodynamics.We envision that, to optimize the metrics of single photon detection, it is critical to maximize the optical absorption in the minimal volume and minimize the carrier transit process simultaneously. Integration of photon management with quantum charge transport/redistribution upon optical excitation can be engineered to maximize the quantum efficiency (QE) and data rate and minimize timing jitter at the same time. Due to the ultra-low capacitance of these quantum devices, even a single photoelectron transfer can induce a notable change in the voltage, enabling non-avalanche single photon detection at room temperature as has been recently demonstrated in Si quanta image sensors (QIS). In this research, uniform III-V quantum dots (QDs) and Si QIS are used as model systems to test the theory experimentally. Based on the fundamental understanding, we also propose proof-of-concept, photon-managed quantum capacitance photodetectors. Built upon the concepts of QIS and single electron transistor (SET), this novel device structure provides a model system to synergistically test the fundamental limits and tradespace predicted by the theory for semiconductor detectors. This project is sponsored under DARPA/ARO's DETECT Program: Fundamental Limits of Quantum Semiconductor Photodetectors.

Anti-Hermitian photodetector facilitating efficient subwavelength photon sorting.

PubMed

Kim, Soo Jin; Kang, Ju-Hyung; Mutlu, Mehmet; Park, Joonsuk; Park, Woosung; Goodson, Kenneth E; Sinclair, Robert; Fan, Shanhui; Kik, Pieter G; Brongersma, Mark L

2018-01-22

The ability to split an incident light beam into separate wavelength bands is central to a diverse set of optical applications, including imaging, biosensing, communication, photocatalysis, and photovoltaics. Entirely new opportunities are currently emerging with the recently demonstrated possibility to spectrally split light at a subwavelength scale with optical antennas. Unfortunately, such small structures offer limited spectral control and are hard to exploit in optoelectronic devices. Here, we overcome both challenges and demonstrate how within a single-layer metafilm one can laterally sort photons of different wavelengths below the free-space diffraction limit and extract a useful photocurrent. This chipscale demonstration of anti-Hermitian coupling between resonant photodetector elements also facilitates near-unity photon-sorting efficiencies, near-unity absorption, and a narrow spectral response (∼ 30 nm) for the different wavelength channels. This work opens up entirely new design paradigms for image sensors and energy harvesting systems in which the active elements both sort and detect photons.

[Detection of recombinant-DNA in foods from stacked genetically modified plants].

PubMed

Sorokina, E Iu; Chernyshova, O N

2012-01-01

A quantitative real-time multiplex polymerase chain reaction method was applied to the detection and quantification of MON863 and MON810 in stacked genetically modified maize MON 810xMON 863. The limit of detection was approximately 0,1%. The accuracy of the quantification, measured as bias from the accepted value and the relative repeatability standard deviation, which measures the intra-laboratory variability, were within 25% at each GM-level. A method verification has demonstrated that the MON 863 and the MON810 methods can be equally applied in quantification of the respective events in stacked MON810xMON 863.

Probabilistic double guarantee kidnapping detection in SLAM.

PubMed

Tian, Yang; Ma, Shugen

2016-01-01

For determining whether kidnapping has happened and which type of kidnapping it is while a robot performs autonomous tasks in an unknown environment, a double guarantee kidnapping detection (DGKD) method has been proposed. The good performance of DGKD in a relative small environment is shown. However, a limitation of DGKD is found in a large-scale environment by our recent work. In order to increase the adaptability of DGKD in a large-scale environment, an improved method called probabilistic double guarantee kidnapping detection is proposed in this paper to combine probability of features' positions and the robot's posture. Simulation results demonstrate the validity and accuracy of the proposed method.

Inspection applications with higher electron beam energies

NASA Astrophysics Data System (ADS)

Norman, D. R.; Jones, J. L.; Yoon, W. Y.; Haskell, K. J.; Sterbentz, J. W.; Zabriskie, J. M.; Hunt, A. W.; Harmon, F.; Kinlaw, M. T.

2005-12-01

The Idaho National Laboratory has developed prototype shielded nuclear material detection systems based on pulsed photonuclear assessment (PPA) techniques for the inspection of cargo containers. During this work, increased nuclear material detection capabilities have been demonstrated at higher electron beam energies than those allowed by federal regulations for cargo inspection. This paper gives a general overview of a nuclear material detection system, the PPA technique and discusses the benefits of using these higher energies. This paper also includes a summary of the numerical and test results from LINAC operations up to 24 MeV and discusses some of the federal energy limitations associated with cargo inspection.

Noninvasive photoacoustic detecting intraocular foreign bodies with an annular transducer array.

PubMed

Yang, Diwu; Zeng, Lvming; Pan, Changning; Zhao, Xuehui; Ji, Xuanrong

2013-01-14

We present a fast photoacoustic imaging system based on an annular transducer array for detection of intraocular foreign bodies. An eight-channel data acquisition system is applied to capture the photoacoustic signals using multiplexing and the total time of data acquisition and transferring is within 3 s. A limited-view filtered back projection algorithm is used to reconstruct the photoacoustic images. Experimental models of intraocular metal and glass foreign bodies were constructed on ex vivo pig's eyes and clear photoacoustic images of intraocular foreign bodies were obtained. Experimental results demonstrate the photoacoustic imaging system holds the potential for in clinic detecting the intraocular foreign bodies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Seong-Wook; Tian, Chao; Martini, Rainer, E-mail: rmartini@stevens.edu

We demonstrated highly sensitive detection of explosive dissolved in solvent with a portable spectroscopy system (Q-MACS) by tracing the explosive byproduct, N{sub 2}O, in combination with a pulsed electric discharge system for safe explosive decomposition. Using Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), the gas was monitored and analyzed by Q-MACS and the presence of the dissolved explosive clearly detected. While HMX presence could be identified directly in the air above the solutions even without plasma, much better results were achieved under the decomposition. The experiment results give an estimated detection limit of 10 ppb, which corresponds to a 15 pg of HMX.

An uncertainty-based distributed fault detection mechanism for wireless sensor networks.

PubMed

Yang, Yang; Gao, Zhipeng; Zhou, Hang; Qiu, Xuesong

2014-04-25

Exchanging too many messages for fault detection will cause not only a degradation of the network quality of service, but also represents a huge burden on the limited energy of sensors. Therefore, we propose an uncertainty-based distributed fault detection through aided judgment of neighbors for wireless sensor networks. The algorithm considers the serious influence of sensing measurement loss and therefore uses Markov decision processes for filling in missing data. Most important of all, fault misjudgments caused by uncertainty conditions are the main drawbacks of traditional distributed fault detection mechanisms. We draw on the experience of evidence fusion rules based on information entropy theory and the degree of disagreement function to increase the accuracy of fault detection. Simulation results demonstrate our algorithm can effectively reduce communication energy overhead due to message exchanges and provide a higher detection accuracy ratio.

Evaluation of a Portable Microchip Electrophoresis Fluorescence Detection System for the Analysis of Amino Acid Neurotransmitters in Brain Dialysis Samples

PubMed Central

OBORNY, Nathan J.; COSTA, Elton E. Melo; SUNTORNSUK, Leena; ABREU, Fabiane C.; LUNTE, Susan M.

2016-01-01

A portable fluorescence detection system for use with microchip electrophoresis was developed and compared to a benchtop system. Using this system, six neuroactive amines commonly found in brain dialysate—arginine, citrulline, taurine, histamine, glutamate, and aspartate—were derivatized offline with naphthalene-2,3-dicarboxaldehyde/cyanide, separated electrophoretically, and detected by fluorescence. Limits of detection for the analytes of interest were 50nM – 250nM for the benchtop system and 250 nM – 1.3 μM for the portable system, both of which were adequate for analyte determination in brain microdialysis samples. The portable system was then demonstrated for the detection of the same six amines in a rat brain microdialysis sample. PMID:26753703

Detection of admittivity anomaly on high-contrast heterogeneous backgrounds using frequency difference EIT.

PubMed

Jang, J; Seo, J K

2015-06-01

This paper describes a multiple background subtraction method in frequency difference electrical impedance tomography (fdEIT) to detect an admittivity anomaly from a high-contrast background conductivity distribution. The proposed method expands the use of the conventional weighted frequency difference EIT method, which has been used limitedly to detect admittivity anomalies in a roughly homogeneous background. The proposed method can be viewed as multiple weighted difference imaging in fdEIT. Although the spatial resolutions of the output images by fdEIT are very low due to the inherent ill-posedness, numerical simulations and phantom experiments of the proposed method demonstrate its feasibility to detect anomalies. It has potential application in stroke detection in a head model, which is highly heterogeneous due to the skull.

Enhancing Community Detection By Affinity-based Edge Weighting Scheme

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoo, Andy; Sanders, Geoffrey; Henson, Van

Community detection refers to an important graph analytics problem of finding a set of densely-connected subgraphs in a graph and has gained a great deal of interest recently. The performance of current community detection algorithms is limited by an inherent constraint of unweighted graphs that offer very little information on their internal community structures. In this paper, we propose a new scheme to address this issue that weights the edges in a given graph based on recently proposed vertex affinity. The vertex affinity quantifies the proximity between two vertices in terms of their clustering strength, and therefore, it is idealmore » for graph analytics applications such as community detection. We also demonstrate that the affinity-based edge weighting scheme can improve the performance of community detection algorithms significantly.« less

A controlled comparison of the BacT/ALERT® 3D and VIRTUO™ microbial detection systems.

PubMed

Totty, H; Ullery, M; Spontak, J; Viray, J; Adamik, M; Katzin, B; Dunne, W M; Deol, P

2017-10-01

The performance of the next-generation BacT/ALERT® VIRTUO™ Microbial Detection System (VIRTUO™, bioMérieux Inc., Hazelwood, MO) was compared to the BacT/ALERT® 3D Microbial Detection System (3D, bioMérieux Inc., Durham, NC) using BacT/ALERT® FA Plus (FA Plus), BacT/ALERT® PF Plus (PF Plus), BacT/ALERT® FN Plus (FN Plus), BacT/ALERT® Standard Aerobic (SA), and BacT/ALERT® Standard Anaerobic (SN) blood culture bottles (bioMérieux Inc., Durham, NC). A seeded limit of detection (LoD) study was performed for each bottle type in both systems. The LoD studies demonstrated that both systems were capable of detecting organisms at nearly identical levels [<10 colony-forming units (CFU) per bottle], with no significant difference. Following LoD determination, a seeded study was performed to compare the time to detection (TTD) between the systems using a panel of clinically relevant microorganisms inoculated at or near the LoD with 0, 4, or 10 mL of healthy human blood. VIRTUO™ exhibited a faster TTD by an average of 3.5 h, as well as demonstrated a significantly improved detection rate of 99.9% compared to 98.8% with 3D (p-value <0.05).

Superhydrophobic analyte concentration utilizing colloid-pillar array SERS substrates.

PubMed

Wallace, Ryan A; Charlton, Jennifer J; Kirchner, Teresa B; Lavrik, Nickolay V; Datskos, Panos G; Sepaniak, Michael J

2014-12-02

The ability to detect a few molecules present in a large sample is of great interest for the detection of trace components in both medicinal and environmental samples. Surface enhanced Raman spectroscopy (SERS) is a technique that can be utilized to detect molecules at very low absolute numbers. However, detection at trace concentration levels in real samples requires properly designed delivery and detection systems. The following work involves superhydrophobic surfaces that have as a framework deterministic or stochastic silicon pillar arrays formed by lithographic or metal dewetting protocols, respectively. In order to generate the necessary plasmonic substrate for SERS detection, simple and flow stable Ag colloid was added to the functionalized pillar array system via soaking. Native pillars and pillars with hydrophobic modification are used. The pillars provide a means to concentrate analyte via superhydrophobic droplet evaporation effects. A ≥ 100-fold concentration of analyte was estimated, with a limit of detection of 2.9 × 10(-12) M for mitoxantrone dihydrochloride. Additionally, analytes were delivered to the surface via a multiplex approach in order to demonstrate an ability to control droplet size and placement for scaled-up uses in real world applications. Finally, a concentration process involving transport and sequestration based on surface treatment selective wicking is demonstrated.

Integration of an optical CMOS sensor with a microfluidic channel allows a sensitive readout for biological assays in point-of-care tests.

PubMed

Van Dorst, Bieke; Brivio, Monica; Van Der Sar, Elfried; Blom, Marko; Reuvekamp, Simon; Tanzi, Simone; Groenhuis, Roelf; Adojutelegan, Adewole; Lous, Erik-Jan; Frederix, Filip; Stuyver, Lieven J

2016-04-15

In this manuscript, a microfluidic detection module, which allows a sensitive readout of biological assays in point-of-care (POC) tests, is presented. The proposed detection module consists of a microfluidic flow cell with an integrated Complementary Metal-Oxide-Semiconductor (CMOS)-based single photon counting optical sensor. Due to the integrated sensor-based readout, the detection module could be implemented as the core technology in stand-alone POC tests, for use in mobile or rural settings. The performance of the detection module was demonstrated in three assays: a peptide, a protein and an antibody detection assay. The antibody detection assay with readout in the detection module proved to be 7-fold more sensitive that the traditional colorimetric plate-based ELISA. The protein and peptide assay showed a lower limit of detection (LLOD) of 200 fM and 460 fM respectively. Results demonstrate that the sensitivity of the immunoassays is comparable with lab-based immunoassays and at least equal or better than current mainstream POC devices. This sensitive readout holds the potential to develop POC tests, which are able to detect low concentrations of biomarkers. This will broaden the diagnostic capabilities at the clinician's office and at patient's home, where currently only the less sensitive lateral flow and dipstick POC tests are implemented. Copyright © 2015 Elsevier B.V. All rights reserved.

Surface scattering plasmon resonance fibre sensors: demonstration of rapid influenza A virus detection

NASA Astrophysics Data System (ADS)

Franςois, A.; Boehm, J.; Oh, S. Y.; Kok, T.; Monro, T. M.

2011-06-01

The management of threats such as pandemics and explosives, and of health and the environment requires the rapid deployment of highly sensitive detection tools. Sensors based on Surface Plasmon Resonance (SPR) allow rapid, labelfree, highly sensitive detection, and indeed this phenomenon underpins the only label-free optical biosensing technology that is available commercially. In these sensors, the existence of surface plasmons is inferred indirectly from absorption features that correspond to the coupling of light to the surface plasmon. Although SPR is not intrinsically a radiative process, under certain conditions the surface plasmon can itself couple to the local photon states, and emit light as first described byKretschmann. Here we show that by collecting and characterising this re-emitted light, it is possible to realise new SPR sensing architectures that are more compact, versatile and robust than existing approaches. This approach addresses existing practical limitations associated with current SPR technologies, including bulk, cost and calibration. It is applicable to a range of SPR geometries, including optical fibres, planar waveguides and prism configurations, and is in principle capable of detecting multiple analytes simultaneously. Moreover, this technique allows to combine SPR sensing and fluorescence sensing into a single platform which has never been demonstrated before and consequently use these two methods for a more reliable diagnostic. As an example, this approach has been used to demonstrate the rapid detection of the seasonal influenza virus.

Duplex recombinase polymerase amplification assays incorporating competitive internal controls for bacterial meningitis detection.

PubMed

Higgins, Owen; Clancy, Eoin; Forrest, Matthew S; Piepenburg, Olaf; Cormican, Martin; Boo, Teck Wee; O'Sullivan, Nicola; McGuinness, Claire; Cafferty, Deirdre; Cunney, Robert; Smith, Terry J

2018-04-01

Recombinase polymerase amplification (RPA) is an isothermal nucleic acid amplification technology that provides rapid and robust infectious disease pathogen detection, ideal for point-of-care (POC) diagnostics in disease-prevalent low-resource countries. We have developed and evaluated three duplex RPA assays incorporating competitive internal controls for the detection of leading bacterial meningitis pathogens. Streptococcus pneumoniae, Neisseria meningitidis and Haemophilus influenzae singleplex RPA assays were initially developed and evaluated, demonstrating 100% specificity with limits of detection of 4.1, 8.5 and 3.9 genome copies per reaction, respectively. Each assay was further developed into internally controlled duplex RPA assays via the incorporation of internal amplification control templates. Clinical performance of each internally controlled duplex RPA assay was evaluated by testing 64 archived PCR-positive clinical samples. Compared to real-time PCR, all duplex RPA assays demonstrated 100% diagnostic specificity, with diagnostic sensitivities of 100%, 86.3% and 100% for the S. pneumoniae, N. meningitidis and H. influenzae assays, respectively. This study details the first report of internally controlled duplex RPA assays for the detection of bacterial meningitis pathogens: S. pneumoniae, N. meningitidis and H. influenzae. We have successfully demonstrated the clinical diagnostic utility of each duplex RPA assay, introducing effective diagnostic technology for POC bacterial meningitis identification in disease-prevalent developing countries. Copyright © 2018 Elsevier Inc. All rights reserved.

Methodological Guidelines for Accurate Detection of Viruses in Wild Plant Species

PubMed Central

Renner, Kurra; Cole, Ellen; Seabloom, Eric W.; Borer, Elizabeth T.; Malmstrom, Carolyn M.

2016-01-01

Ecological understanding of disease risk, emergence, and dynamics and of the efficacy of control strategies relies heavily on efficient tools for microorganism identification and characterization. Misdetection, such as the misclassification of infected hosts as healthy, can strongly bias estimates of disease prevalence and lead to inaccurate conclusions. In natural plant ecosystems, interest in assessing microbial dynamics is increasing exponentially, but guidelines for detection of microorganisms in wild plants remain limited, particularly so for plant viruses. To address this gap, we explored issues and solutions associated with virus detection by serological and molecular methods in noncrop plant species as applied to the globally important Barley yellow dwarf virus PAV (Luteoviridae), which infects wild native plants as well as crops. With enzyme-linked immunosorbent assays (ELISA), we demonstrate how virus detection in a perennial wild plant species may be much greater in stems than in leaves, although leaves are most commonly sampled, and may also vary among tillers within an individual, thereby highlighting the importance of designing effective sampling strategies. With reverse transcription-PCR (RT-PCR), we demonstrate how inhibitors in tissues of perennial wild hosts can suppress virus detection but can be overcome with methods and products that improve isolation and amplification of nucleic acids. These examples demonstrate the paramount importance of testing and validating survey designs and virus detection methods for noncrop plant communities to ensure accurate ecological surveys and reliable assumptions about virus dynamics in wild hosts. PMID:26773088

A matched filter method for ground-based sub-noise detection of terrestrial extrasolar planets in eclipsing binaries: application to CM Draconis.

PubMed

Jenkins, J M; Doyle, L R; Cullers, D K

1996-02-01

The photometric detection of extrasolar planets by transits in eclipsing binary systems can be significantly improved by cross-correlating the observational light curves with synthetic models of possible planetary transit features, essentially a matched filter approach. We demonstrate the utility and application of this transit detection algorithm for ground-based detections of terrestrial-sized (Earth-to-Neptune radii) extrasolar planets in the dwarf M-star eclipsing binary system CM Draconis. Preliminary photometric observational data of this system demonstrate that the observational noise is well characterized as white and Gaussian at the observational time steps required for precision photometric measurements. Depending on planet formation scenarios, terrestrial-sized planets may form quite close to this low-luminosity system. We demonstrate, for example, that planets as small as 1.4 Earth radii with periods on the order of a few months in the CM Draconis system could be detected at the 99.9% confidence level in less than a year using 1-m class telescopes from the ground. This result contradicts commonly held assumptions limiting present ground-based efforts to, at best, detections of gas giant planets after several years of observation. This method can be readily extended to a number of other larger star systems with the utilization of larger telescopes and longer observing times. Its extension to spacecraft observations should also allow the determination of the presence of terrestrial-sized planets in nearly 100 other known eclipsing binary systems.

A matched filter method for ground-based sub-noise detection of terrestrial extrasolar planets in eclipsing binaries: application to CM Draconis

NASA Technical Reports Server (NTRS)

Jenkins, J. M.; Doyle, L. R.; Cullers, D. K.

1996-01-01

The photometric detection of extrasolar planets by transits in eclipsing binary systems can be significantly improved by cross-correlating the observational light curves with synthetic models of possible planetary transit features, essentially a matched filter approach. We demonstrate the utility and application of this transit detection algorithm for ground-based detections of terrestrial-sized (Earth-to-Neptune radii) extrasolar planets in the dwarf M-star eclipsing binary system CM Draconis. Preliminary photometric observational data of this system demonstrate that the observational noise is well characterized as white and Gaussian at the observational time steps required for precision photometric measurements. Depending on planet formation scenarios, terrestrial-sized planets may form quite close to this low-luminosity system. We demonstrate, for example, that planets as small as 1.4 Earth radii with periods on the order of a few months in the CM Draconis system could be detected at the 99.9% confidence level in less than a year using 1-m class telescopes from the ground. This result contradicts commonly held assumptions limiting present ground-based efforts to, at best, detections of gas giant planets after several years of observation. This method can be readily extended to a number of other larger star systems with the utilization of larger telescopes and longer observing times. Its extension to spacecraft observations should also allow the determination of the presence of terrestrial-sized planets in nearly 100 other known eclipsing binary systems.

Methodological Guidelines for Accurate Detection of Viruses in Wild Plant Species.

PubMed

Lacroix, Christelle; Renner, Kurra; Cole, Ellen; Seabloom, Eric W; Borer, Elizabeth T; Malmstrom, Carolyn M

2016-01-15

Ecological understanding of disease risk, emergence, and dynamics and of the efficacy of control strategies relies heavily on efficient tools for microorganism identification and characterization. Misdetection, such as the misclassification of infected hosts as healthy, can strongly bias estimates of disease prevalence and lead to inaccurate conclusions. In natural plant ecosystems, interest in assessing microbial dynamics is increasing exponentially, but guidelines for detection of microorganisms in wild plants remain limited, particularly so for plant viruses. To address this gap, we explored issues and solutions associated with virus detection by serological and molecular methods in noncrop plant species as applied to the globally important Barley yellow dwarf virus PAV (Luteoviridae), which infects wild native plants as well as crops. With enzyme-linked immunosorbent assays (ELISA), we demonstrate how virus detection in a perennial wild plant species may be much greater in stems than in leaves, although leaves are most commonly sampled, and may also vary among tillers within an individual, thereby highlighting the importance of designing effective sampling strategies. With reverse transcription-PCR (RT-PCR), we demonstrate how inhibitors in tissues of perennial wild hosts can suppress virus detection but can be overcome with methods and products that improve isolation and amplification of nucleic acids. These examples demonstrate the paramount importance of testing and validating survey designs and virus detection methods for noncrop plant communities to ensure accurate ecological surveys and reliable assumptions about virus dynamics in wild hosts. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Evaluation of lophine derivatives as L-012 (luminol analog)-dependent chemiluminescence enhancers for measuring horseradish peroxidase and H2O2.

PubMed

Ichibangase, T; Ohba, Y; Kishikawa, N; Nakashima, K; Kuroda, N

2014-03-01

8-Amino-5-chloro-7-phenylpyrido[3,4-d]pyridazine-1,4(2H,3H)dione (L-012) was recently synthesized as a new chemiluminescence (CL) probe; the light intensity and the sensitivity of L-012 are higher than those of other CL probes such as luminol. Previously, our group developed four lophine-based CL enhancers of the horseradish peroxidase (HRP)-catalyzed CL oxidation of luminol, namely 2-(4-hydroxyphenyl)-4,5-diphenylimidazole (HDI), 2-(4-hydroxyphenyl)-4,5-di(2-pyridyl)imidazole (HPI), 4-(4,5-diphenyl-1H-imidazol-2-yl)phenylboronic acid (DPA), and 4-[4,5-di(2-pyridyl)-1H-imidazol-2-yl]phenylboronic acid (DPPA), and showed that DPPA was suitable for the photographic detection of HRP. In this study, we replaced luminol with L-012 and evaluated these as L-012-dependent CL enhancers. In addition, to detect HRP and/or H2O2 with higher sensitivity, each detection condition for the L-012-HRP-H2O2 enhanced CL was optimized. All the derivatives enhanced the L-012-dependent CL as well as luminol CL; HPI generated the highest enhanced luminescence. Under optimized conditions for HRP detection, the detection limit of HRP was 0.08 fmol. By contrast, the detection limit of HRP with the enhanced L-012-dependent CL using 4-iodophenol, which is a common enhancer of luminol CL, was 1.1 fmol. With regard to H2O2 detection, the detection limits for enhanced CL with HPI and 4-iodophenol were 0.29 and 1.5 pmol, respectively. Therefore, it is demonstrated that HPI is the most superior L-012-dependent CL enhancer. Copyright © 2013 John Wiley & Sons, Ltd.

Quantum dot enabled detection of Escherichia coli using a cell-phone†

PubMed Central

Zhu, Hongying; Sikora, Uzair; Ozcan, Aydogan

2013-01-01

We report a cell-phone based Escherichia coli (E. coli) detection platform for screening of liquid samples. In this compact and cost-effective design attached to a cell-phone, we utilize anti-E. coli O157:H7 antibody functionalized glass capillaries as solid substrates to perform a quantum dot based sandwich assay for specific detection of E. coli O157:H7 in liquid samples. Using battery-powered inexpensive light-emitting-diodes (LEDs) we excite/pump these labelled E. coli particles captured on the capillary surface, where the emission from the quantum dots is then imaged using the cell-phone camera unit through an additional lens that is inserted between the capillary and the cell-phone. By quantifying the fluorescent light emission from each capillary tube, the concentration of E. coli in the sample is determined. We experimentally confirmed the detection limit of this cell-phone based fluorescent imaging and sensing platform as ~5 to 10 cfu mL−1 in buffer solution. We also tested the specificity of this E. coli detection platform by spiking samples with different species (e.g., Salmonella) to confirm that non-specific binding/detection is negligible. We further demonstrated the proof-of-concept of our approach in a complex food matrix, e.g., fat-free milk, where a similar detection limit of ~5 to 10 cfu mL−1 was achieved despite challenges associated with the density of proteins that exist in milk. Our results reveal the promising potential of this cell-phone enabled field-portable and cost-effective E. coli detection platform for e.g., screening of water and food samples even in resource limited environments. The presented platform can also be applicable to other pathogens of interest through the use of different antibodies. PMID:22396952

Quantum dot enabled detection of Escherichia coli using a cell-phone.

PubMed

Zhu, Hongying; Sikora, Uzair; Ozcan, Aydogan

2012-06-07

We report a cell-phone based Escherichia coli (E. coli) detection platform for screening of liquid samples. In this compact and cost-effective design attached to a cell-phone, we utilize anti-E. coli O157:H7 antibody functionalized glass capillaries as solid substrates to perform a quantum dot based sandwich assay for specific detection of E. coli O157:H7 in liquid samples. Using battery-powered inexpensive light-emitting-diodes (LEDs) we excite/pump these labelled E. coli particles captured on the capillary surface, where the emission from the quantum dots is then imaged using the cell-phone camera unit through an additional lens that is inserted between the capillary and the cell-phone. By quantifying the fluorescent light emission from each capillary tube, the concentration of E. coli in the sample is determined. We experimentally confirmed the detection limit of this cell-phone based fluorescent imaging and sensing platform as ∼5 to 10 cfu mL(-1) in buffer solution. We also tested the specificity of this E. coli detection platform by spiking samples with different species (e.g., Salmonella) to confirm that non-specific binding/detection is negligible. We further demonstrated the proof-of-concept of our approach in a complex food matrix, e.g., fat-free milk, where a similar detection limit of ∼5 to 10 cfu mL(-1) was achieved despite challenges associated with the density of proteins that exist in milk. Our results reveal the promising potential of this cell-phone enabled field-portable and cost-effective E. coli detection platform for e.g., screening of water and food samples even in resource limited environments. The presented platform can also be applicable to other pathogens of interest through the use of different antibodies.

Rapid and sensitive detection of Zika virus by reverse transcription loop-mediated isothermal amplification.

PubMed

Wang, Xuan; Yin, Fenggui; Bi, Yuhai; Cheng, Gong; Li, Jing; Hou, Lidan; Li, Yunlong; Yang, Baozhi; Liu, Wenjun; Yang, Limin

2016-12-01

Zika virus (ZIKV) is an arbovirus that recently emerged and has expanded worldwide, causing a global threat and raising international concerns. Current molecular diagnostics, e.g., real-time PCR and reverse transcription PCR (RT-PCR), are time consuming, expensive, and can only be deployed in a laboratory instead of for field diagnostics. This study aimed to develop a one-step reverse transcription loop-mediated isothermal amplification (RT-LAMP) platform showing sensitivity, specificity, and more convenience than previous methods, being easily distributed and implemented. Specific primers were designed and screened to target the entire ZIKV genome. The analytical sensitivity and specificity of the assay were evaluated and compared with traditional PCR and quantitative real-time PCR. Three different simulated clinical sample quick preparation protocols were evaluated to establish a rapid and straightforward treatment procedure for clinical specimens in open field detection. The RT-LAMP assay for detection of ZIKV demonstrated superior specificity and sensitivity compared to traditional PCR at the optimum reaction temperature. For the ZIKV RNA standard, the limit of detection was 20 copies/test. For the simulated ZIKV clinical samples, the limit of detection was 0.02 pfu/test, which was one order of magnitude higher than RT-PCR and similar to real-time PCR. The detection limit of simulated ZIKV specimens prepared using a protease quick processing method was consistent with that of samples prepared using commercial nucleic acid extraction kits, indicating that our ZIKV detection method could be used in point-of-care testing. The RT-LAMP assay had excellent sensitivity and specificity for detecting ZIKV and can be deployed together with a rapid specimen processing method, offering the possibility for ZIKV diagnosis outside of the laboratory. Copyright © 2016 Elsevier B.V. All rights reserved.

Thermal noise limit for ultra-high vacuum noncontact atomic force microscopy

PubMed Central

Lübbe, Jannis; Temmen, Matthias; Rode, Sebastian; Rahe, Philipp; Kühnle, Angelika

2013-01-01

Summary The noise of the frequency-shift signal Δf in noncontact atomic force microscopy (NC-AFM) consists of cantilever thermal noise, tip–surface-interaction noise and instrumental noise from the detection and signal processing systems. We investigate how the displacement-noise spectral density d z at the input of the frequency demodulator propagates to the frequency-shift-noise spectral density d Δ f at the demodulator output in dependence of cantilever properties and settings of the signal processing electronics in the limit of a negligible tip–surface interaction and a measurement under ultrahigh-vacuum conditions. For a quantification of the noise figures, we calibrate the cantilever displacement signal and determine the transfer function of the signal-processing electronics. From the transfer function and the measured d z, we predict d Δ f for specific filter settings, a given level of detection-system noise spectral density d z ds and the cantilever-thermal-noise spectral density d z th. We find an excellent agreement between the calculated and measured values for d Δ f. Furthermore, we demonstrate that thermal noise in d Δ f, defining the ultimate limit in NC-AFM signal detection, can be kept low by a proper choice of the cantilever whereby its Q-factor should be given most attention. A system with a low-noise signal detection and a suitable cantilever, operated with appropriate filter and feedback-loop settings allows room temperature NC-AFM measurements at a low thermal-noise limit with a significant bandwidth. PMID:23400758

Thermal noise limit for ultra-high vacuum noncontact atomic force microscopy.

PubMed

Lübbe, Jannis; Temmen, Matthias; Rode, Sebastian; Rahe, Philipp; Kühnle, Angelika; Reichling, Michael

2013-01-01

The noise of the frequency-shift signal Δf in noncontact atomic force microscopy (NC-AFM) consists of cantilever thermal noise, tip-surface-interaction noise and instrumental noise from the detection and signal processing systems. We investigate how the displacement-noise spectral density d(z) at the input of the frequency demodulator propagates to the frequency-shift-noise spectral density d(Δ) (f) at the demodulator output in dependence of cantilever properties and settings of the signal processing electronics in the limit of a negligible tip-surface interaction and a measurement under ultrahigh-vacuum conditions. For a quantification of the noise figures, we calibrate the cantilever displacement signal and determine the transfer function of the signal-processing electronics. From the transfer function and the measured d(z), we predict d(Δ) (f) for specific filter settings, a given level of detection-system noise spectral density d(z) (ds) and the cantilever-thermal-noise spectral density d(z) (th). We find an excellent agreement between the calculated and measured values for d(Δ) (f). Furthermore, we demonstrate that thermal noise in d(Δ) (f), defining the ultimate limit in NC-AFM signal detection, can be kept low by a proper choice of the cantilever whereby its Q-factor should be given most attention. A system with a low-noise signal detection and a suitable cantilever, operated with appropriate filter and feedback-loop settings allows room temperature NC-AFM measurements at a low thermal-noise limit with a significant bandwidth.

Comprehensive Laboratory Evaluation of a Highly Specific Lateral Flow Assay for the Presumptive Identification of Bacillus anthracis Spores in Suspicious White Powders and Environmental Samples

PubMed Central

Ramage, Jason G.; Prentice, Kristin W.; DePalma, Lindsay; Venkateswaran, Kodumudi S.; Chivukula, Sruti; Chapman, Carol; Bell, Melissa; Datta, Shomik; Singh, Ajay; Hoffmaster, Alex; Sarwar, Jawad; Parameswaran, Nishanth; Joshi, Mrinmayi; Thirunavkkarasu, Nagarajan; Krishnan, Viswanathan; Morse, Stephen; Avila, Julie R.; Sharma, Shashi; Estacio, Peter L.; Stanker, Larry; Hodge, David R.

2016-01-01

We conducted a comprehensive, multiphase laboratory evaluation of the Anthrax BioThreat Alert® test strip, a lateral flow immunoassay (LFA) for the rapid detection of Bacillus anthracis spores. The study, conducted at 2 sites, evaluated this assay for the detection of spores from the Ames and Sterne strains of B. anthracis, as well as those from an additional 22 strains. Phylogenetic near neighbors, environmental background organisms, white powders, and environmental samples were also tested. The Anthrax LFA demonstrated a limit of detection of about 106 spores/mL (ca. 1.5 × 105 spores/assay). In this study, overall sensitivity of the LFA was 99.3%, and the specificity was 98.6%. The results indicated that the specificity, sensitivity, limit of detection, dynamic range, and repeatability of the assay support its use in the field for the purpose of qualitatively evaluating suspicious white powders and environmental samples for the presumptive presence of B. anthracis spores. PMID:27661796

Wavelength modulation spectroscopy coupled with an external-cavity quantum cascade laser operating between 7.5 and 8 µm

NASA Astrophysics Data System (ADS)

Maity, Abhijit; Pal, Mithun; Maithani, Sanchi; Dutta Banik, Gourab; Pradhan, Manik

2018-04-01

We demonstrate a mid-infrared detection strategy with 1f-normalized 2f-wavelength modulation spectroscopy (WMS-2f/1f) using a continuous wave (CW) external-cavity quantum cascade laser (EC-QCL) operating between 7.5 and 8 µm. The detailed performance of the WMS-2f/1f detection method was evaluated by making rotationally resolved measurements in the (ν 4  +  ν 5) combination band of acetylene (C2H2) at 1311.7600 cm-1. A noise-limited detection limit of three parts per billion (ppb) with an integration time of 110 s was achieved for C2H2 detection. The present high-resolution CW-EC-QCL system coupled with the WMS-2f/1f strategy was further validated with an extended range of C2H2 concentration of 0.1-1000 ppm, which shows excellent promise for real-life practical sensing applications. Finally, we utilized the WMS-2f/1f technique to measure the C2H2 concentration in the exhaled breath of smokers.

Detection of bacteria from a cecal anaerobic competitive exclusion culture with an immunoassay electrochemiluminescence sensor

NASA Astrophysics Data System (ADS)

Beier, Ross C.; Young, Colin R.; Stanker, Larry H.

1999-01-01

A competitive exclusion (CE) culture of chicken cecal anaerobes has been developed and used in this laboratory for control of Salmonella typhimurium in chickens. The CE culture consists of 29 different species of micro-organisms, and is known as CF3. Detection of one of the CF3 bacteria, Eubacteria, and S. typhimurium were demonstrated using a commercial immunomagnetic (IM) electrochemiluminescence (ECL) sensor, the ORIGENR Analyzer. Analysis was achieved using a sandwich immunoassay. Bacteria were captured on antibody- conjugated 280 micron sized magnetic beads followed by binding of reporter antibodies labelled with ruthenium (II) tris(dipyridyl) chelate [Ru(bpy)32+]. The magnetic beads were then trapped on an electrode in the reaction cell of the ORIGENR Analyzer by a magnet, and the ECL was evoked from Ru(bpy)32+ on the tagged reporter antibodies by an electrical potential at the electrode. Preliminary IM-ECL assays with Eubacteria yielded a detection limit of 105 cfu/mL. Preliminary IM-ECL assays with S. typhimurium yielded a similar detection limit of 105 cfu/mL.

Detection of the Spermicide Nonoxynol-9 Via GC-MS

NASA Astrophysics Data System (ADS)

Musah, Rabi A.; Vuong, Angela L.; Henck, Colin; Shepard, Jason R. E.

2012-05-01

The spermicide nonoxynol-9 is actually a complex mixture of dozens of closely related amphiphilic compounds, and the chemical properties of this assortment significantly hamper its characterization by GC-MS. The inability to perform routine GC-MS testing on nonoxynol-9 has limited its evidentiary value in forensic casework, which relies heavily on this technique for analysis. A disturbing trend in sexual assault is the use of condoms by assailants, to avoid leaving behind DNA evidence that can connect a perpetrator to a victim. This observation necessitates the development of alternative methods for the analysis of trace evidence that can show causal links between a victim and a suspect. Detection of lubricants associated with sexual assault is one such way to establish this connection. The development of GC-MS methods that permit facile detection of both nonoxynol-9 alone and nonoxynol-9 extracted from other complex matrices that have potential as trace evidence in sexual assault is reported. A detection limit of 2.14 μg of nonoxynol-9 is demonstrated, and a detailed mass spectral profile that elaborates on what is known of its structure is provided.

A chromogenic and fluorogenic rhodol-based chemosensor for hydrazine detection and its application in live cell bioimaging.

PubMed

Tiensomjitr, Khomsan; Noorat, Rattha; Chomngam, Sinchai; Wechakorn, Kanokorn; Prabpai, Samran; Kanjanasirirat, Phongthon; Pewkliang, Yongyut; Borwornpinyo, Suparerk; Kongsaeree, Palangpon

2018-04-15

A rhodol-based fluorescent probe has been developed as a selective hydrazine chemosensor using levulinate as a recognition site. The rhodol levulinate probe (RL) demonstrated high selectivity and sensitivity toward hydrazine among other molecules. The chromogenic response of RL solution to hydrazine from colorless to pink could be readily observed by the naked eye, while strong fluorescence emission could be monitored upon excitation at 525 nm. The detection process occurred via a ring-opening process of the spirolactone initiated by hydrazinolysis, triggering the fluorescence emission with a 53-fold enhancement. The probe rapidly reacted with hydrazine in aqueous medium with the detection limit of 26 nM (0.83 ppb), lower than the threshold limit value (TLV) of 10 ppb suggested by the U.S. Environmental Protection Agency. Furthermore, RL-impregnated paper strips could detect hydrazine vapor. For biological applicability of RL, its membrane-permeable property led to bioimaging of hydrazine in live HepG2 cells by confocal fluorescence microscopy. Copyright © 2018 Elsevier B.V. All rights reserved.

Using rapid-scan EPR to improve the detection limit of quantitative EPR by more than one order of magnitude.

PubMed

Möser, J; Lips, K; Tseytlin, M; Eaton, G R; Eaton, S S; Schnegg, A

2017-08-01

X-band rapid-scan EPR was implemented on a commercially available Bruker ELEXSYS E580 spectrometer. Room temperature rapid-scan and continuous-wave EPR spectra were recorded for amorphous silicon powder samples. By comparing the resulting signal intensities the feasibility of performing quantitative rapid-scan EPR is demonstrated. For different hydrogenated amorphous silicon samples, rapid-scan EPR results in signal-to-noise improvements by factors between 10 and 50. Rapid-scan EPR is thus capable of improving the detection limit of quantitative EPR by at least one order of magnitude. In addition, we provide a recipe for setting up and calibrating a conventional pulsed and continuous-wave EPR spectrometer for rapid-scan EPR. Copyright © 2017 Elsevier Inc. All rights reserved.

A microcantilever-based silver ion sensor using DNA-functionalized gold nanoparticles as a mass amplifier

NASA Astrophysics Data System (ADS)

You, Juneseok; Song, Yeongjin; Park, Chanho; Jang, Kuewhan; Na, Sungsoo

2017-06-01

Silver ions have been used to sterilize many products, however, it has recently been demonstrated that silver ions can be toxic. This toxicity has been studied over many years with the lethal concentration at 10 μM. Silver ions can accumulate through the food chain, causing serious health problems in many species. Hence, there is a need for a commercially available silver ion sensor, with high detection sensitivity. In this work, we develop an ultra-sensitive silver ion sensor platform, using cytosine based DNA and gold nanoparticles as the mass amplifier. We achieve a lower detection limit for silver ions of 10 pM; this detection limit is one million times lower than the toxic concentration. Using our sensor platform we examine highly selective characteristics of other typical ions in water from natural sources. Furthermore, our sensor platform is able to detect silver ions in a real practical sample of commercially available drinking water. Our sensor platform, which we have termed a ‘MAIS’ (mass amplifier ion sensor), with a simple detection procedure, high sensitivity, selectivity and real practical applicability has shown potential as an early toxicity assessment of silver ions in the environment.

Non-invasive detection of cocaine dissolved in beverages using displaced Raman spectroscopy.

PubMed

Eliasson, C; Macleod, N A; Matousek, P

2008-01-21

We demonstrate the potential of Raman spectroscopy to detect cocaine concealed inside transparent glass bottles containing alcoholic beverages. A clear Raman signature of cocaine with good signal-to-noise was obtained from a approximately 300 g solution of adulterated cocaine (purity 75%) in a 0.7 L authentic brown bottle of rum with 1 s acquisition time. The detection limit was estimated to be of the order of 9 g of pure cocaine per 0.7 L (approximately 0.04 moles L(-1)) with 1 s acquisition time. The technique holds great promise for the fast, non-invasive, detection of concealed illicit compounds inside beverages using portable Raman instruments, thus permitting drug trafficking to be combated more effectively.

End-to-end commissioning demonstration of the James Webb Space Telescope

NASA Astrophysics Data System (ADS)

Acton, D. Scott; Towell, Timothy; Schwenker, John; Shields, Duncan; Sabatke, Erin; Contos, Adam R.; Hansen, Karl; Shi, Fang; Dean, Bruce; Smith, Scott

2007-09-01

The one-meter Testbed Telescope (TBT) has been developed at Ball Aerospace to facilitate the design and implementation of the wavefront sensing and control (WFSC) capabilities of the James Webb Space Telescope (JWST). We have recently conducted an "end-to-end" demonstration of the flight commissioning process on the TBT. This demonstration started with the Primary Mirror (PM) segments and the Secondary Mirror (SM) in random positions, traceable to the worst-case flight deployment conditions. The commissioning process detected and corrected the deployment errors, resulting in diffraction-limited performance across the entire science FOV. This paper will describe the commissioning demonstration and the WFSC algorithms used at each step in the process.

How noise affects quantum detector tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Q., E-mail: wang@physics.leidenuniv.nl; Renema, J. J.; Exter, M. P.van

2015-10-07

We determine the full photon number response of a NbN superconducting nanowire single photon detector via quantum detector tomography, and the results show the separation of linear, effective absorption efficiency from the internal detection efficiencies. In addition, we demonstrate an error budget for the complete quantum characterization of the detector. We find that for short times, the dominant noise source is shot noise, while laser power fluctuations limit the accuracy for longer timescales. The combined standard uncertainty of the internal detection efficiency derived from our measurements is about 2%.

Superconducting Detectors for Superlight Dark Matter.

PubMed

Hochberg, Yonit; Zhao, Yue; Zurek, Kathryn M

2016-01-08

We propose and study a new class of superconducting detectors that are sensitive to O(meV) electron recoils from dark matter-electron scattering. Such devices could detect dark matter as light as the warm dark-matter limit, m(X)≳1  keV. We compute the rate of dark-matter scattering off of free electrons in a (superconducting) metal, including the relevant Pauli blocking factors. We demonstrate that classes of dark matter consistent with terrestrial and cosmological or astrophysical constraints could be detected by such detectors with a moderate size exposure.

Superconducting Detectors for Superlight Dark Matter

NASA Astrophysics Data System (ADS)

Hochberg, Yonit; Zhao, Yue; Zurek, Kathryn M.

2016-01-01

We propose and study a new class of superconducting detectors that are sensitive to O (meV ) electron recoils from dark matter-electron scattering. Such devices could detect dark matter as light as the warm dark-matter limit, mX≳1 keV . We compute the rate of dark-matter scattering off of free electrons in a (superconducting) metal, including the relevant Pauli blocking factors. We demonstrate that classes of dark matter consistent with terrestrial and cosmological or astrophysical constraints could be detected by such detectors with a moderate size exposure.

Beyond detection: nuclear physics with a webcam in an educational setting

NASA Astrophysics Data System (ADS)

Pallone, Arthur

2015-03-01

Nuclear physics affects our daily lives in such diverse fields from medicine to art. I believe three obstacles - limited time, lack of subject familiarity and thus comfort on the part of educators, and equipment expense - must be overcome to produce a nuclear-educated populace. Educators regularly use webcams to actively engage students in scientific discovery as evidenced by a literature search for the term webcam paired with topics such as astronomy, biology, and physics. Inspired by YouTube videos that demonstrate alpha particle detection by modified webcams, I searched for examples that go beyond simple detection with only one education-oriented result - the determination of the in-air range of alphas using a modified CCD camera. Custom-built, radiation-hardened CMOS detectors exist in high energy physics and for soft x-ray detection. Commercial CMOS cameras are used for direct imaging in electron microscopy. I demonstrate charged-particle spectrometry with a slightly modified CMOS-based webcam. When used with inexpensive sources of radiation and free software, the webcam charged-particle spectrometer presents educators with a simple, low-cost technique to include nuclear physics in science education.

Photoinitiator Nucleotide for Quantifying Nucleic Acid Hybridization

PubMed Central

Johnson, Leah M.; Hansen, Ryan R.; Urban, Milan; Kuchta, Robert D.; Bowman, Christopher N.

2010-01-01

This first report of a photoinitiator-nucleotide conjugate demonstrates a novel approach for sensitive, rapid and visual detection of DNA hybridization events. This approach holds potential for various DNA labeling schemes and for applications benefiting from selective DNA-based polymerization initiators. Here, we demonstrate covalent, enzymatic incorporation of an eosin-photoinitiator 2′-deoxyuridine-5′-triphosphate (EITC-dUTP) conjugate into surface-immobilized DNA hybrids. Subsequent radical chain photoinitiation from these sites using an acrylamide/bis-acrylamide formulation yields a dynamic detection range between 500pM and 50nM of DNA target. Increasing EITC-nucleotide surface densities leads to an increase in surface-based polymer film heights until achieving a film height plateau of 280nm ±20nm at 610 ±70 EITC-nucleotides/μm2. Film heights of 10–20 nm were obtained from eosin surface densities of approximately 20 EITC-nucleotides/μm2 while below the detection limit of ~10 EITC-nucleotides/μm2, no detectable films were formed. This unique threshold behavior is utilized for instrument-free, visual quantification of target DNA concentration ranges. PMID:20337438

Quantifiable long-term monitoring on parks and nature preserves

USGS Publications Warehouse

Beck, Scott; Moorman, Christopher; DePerno, Christopher S.; Simons, Theodore R.

2013-01-01

Herpetofauna have declined globally, and monitoring is a useful approach to document local and long-term changes. However, monitoring efforts often fail to account for detectability or follow standardized protocols. We performed a case study at Hemlock Bluffs Nature Preserve in Cary, NC to model occupancy of focal species and demonstrate a replicable long-term protocol useful to parks and nature preserves. From March 2010 to 2011, we documented occupancy of Ambystoma opacum(Marbled Salamander), Plethodon cinereus (Red-backed Salamander), Carphophis amoenus (Eastern Worm Snake), and Diadophis punctatus (Ringneck Snake) at coverboard sites and estimated breeding female Ambystoma maculatum (Spotted Salamander) abundance via dependent double-observer egg-mass counts in ephemeral pools. Temperature influenced detection of both Marbled and Red-backed Salamanders. Based on egg-mass data, we estimated Spotted Salamander abundance to be between 21 and 44 breeding females. We detected 43 of 53 previously documented herpetofauna species. Our approach demonstrates a monitoring protocol that accounts for factors that influence species detection and is replicable by parks or nature preserves with limited resources.

Reaction-Based Off-On Near-infrared Fluorescent Probe for Imaging Alkaline Phosphatase Activity in Living Cells and Mice.

PubMed

Tan, Yi; Zhang, Ling; Man, Ka Ho; Peltier, Raoul; Chen, Ganchao; Zhang, Huatang; Zhou, Liyi; Wang, Feng; Ho, Derek; Yao, Shao Q; Hu, Yi; Sun, Hongyan

2017-03-01

Alkaline phosphatases are a group of enzymes that play important roles in regulating diverse cellular functions and disease pathogenesis. Hence, developing fluorescent probes for in vivo detection of alkaline phosphatase activity is highly desirable for studying the dynamic phosphorylation in living organisms. Here, we developed the very first reaction-based near-infrared (NIR) probe (DHXP) for sensitive detection of alkaline phosphatase activity both in vitro and in vivo. Our studies demonstrated that the probe displayed an up to 66-fold fluorescence increment upon incubation with alkaline phosphatases, and the detection limit of our probe was determined to be 0.07 U/L, which is lower than that of most of alkaline phosphatase probes reported in literature. Furthermore, we demonstrated that the probe can be applied to detecting alkaline phosphatase activity in cells and mice. In addition, our probe possesses excellent biocompatibility and rapid cell-internalization ability. In light of these prominent properties, we envision that DHXP will add useful tools for investigating alkaline phosphatase activity in biomedical research.

Application of gas-coupled laser acoustic detection to gelatins and underwater sensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Caron, James N.; Kunapareddy, Pratima

2014-02-18

Gas-coupled Laser Acoustic Detection (GCLAD) has been used as a method to sense ultrasound waves in materials without contact of the material surface. To sense the waveform, a laser beam is directed parallel to the material surface and displaced or deflected when the radiated waveform traverses the beam. We present recent tests that demonstrate the potential of using this technique for detecting ultrasound in gelatin phantoms and in water. As opposed to interferometric detection, GCLAD operates independently of the optical surface properties of the material. This allows the technique to be used in cases where the material is transparent ormore » semi-transparent. We present results on sensing ultrasound in gelatin phantoms that are used to mimic biological materials. As with air-coupled transducers, the frequency response of GCLAD at high frequencies is limited by the high attenuation of ultrasound in air. In contrast, water has a much lower attenuation. Here we demonstrate the use of a GCLAD-like system in water, measuring the directivity response at 1 MHz and sensing waveforms with higher frequency content.« less

Automated processing integrated with a microflow cytometer for pathogen detection in clinical matrices

PubMed Central

Golden, J.P.; Verbarg, J.; Howell, P.B.; Shriver-Lake, L.C.; Ligler, F.S.

2012-01-01

A spinning magnetic trap (MagTrap) for automated sample processing was integrated with a microflow cytometer capable of simultaneously detecting multiple targets to provide an automated sample-to-answer diagnosis in 40 min. After target capture on fluorescently coded magnetic microspheres, the magnetic trap automatically concentrated the fluorescently coded microspheres, separated the captured target from the sample matrix, and exposed the bound target sequentially to biotinylated tracer molecules and streptavidin-labeled phycoerythrin. The concentrated microspheres were then hydrodynamically focused in a microflow cytometer capable of 4-color analysis (two wavelengths for microsphere identification, one for light scatter to discriminate single microspheres and one for phycoerythrin bound to the target). A three-fold decrease in sample preparation time and an improved detection limit, independent of target preconcentration, was demonstrated for detection of Escherichia coli 0157:H7 using the MagTrap as compared to manual processing. Simultaneous analysis of positive and negative controls, along with the assay reagents specific for the target, was used to obtain dose–response curves, demonstrating the potential for quantification of pathogen load in buffer and serum. PMID:22960010

Automated processing integrated with a microflow cytometer for pathogen detection in clinical matrices.

PubMed

Golden, J P; Verbarg, J; Howell, P B; Shriver-Lake, L C; Ligler, F S

2013-02-15

A spinning magnetic trap (MagTrap) for automated sample processing was integrated with a microflow cytometer capable of simultaneously detecting multiple targets to provide an automated sample-to-answer diagnosis in 40 min. After target capture on fluorescently coded magnetic microspheres, the magnetic trap automatically concentrated the fluorescently coded microspheres, separated the captured target from the sample matrix, and exposed the bound target sequentially to biotinylated tracer molecules and streptavidin-labeled phycoerythrin. The concentrated microspheres were then hydrodynamically focused in a microflow cytometer capable of 4-color analysis (two wavelengths for microsphere identification, one for light scatter to discriminate single microspheres and one for phycoerythrin bound to the target). A three-fold decrease in sample preparation time and an improved detection limit, independent of target preconcentration, was demonstrated for detection of Escherichia coli 0157:H7 using the MagTrap as compared to manual processing. Simultaneous analysis of positive and negative controls, along with the assay reagents specific for the target, was used to obtain dose-response curves, demonstrating the potential for quantification of pathogen load in buffer and serum. Published by Elsevier B.V.

Visual detection of Brucella in bovine biological samples using DNA-activated gold nanoparticles

PubMed Central

Kumar, Satish; Kaur, Gurpreet; Ali, Syed Atif; Shrivastava, Sameer; Gupta, Praveen K.; Cooper, Jonathan M.; Chaudhuri, Pallab

2017-01-01

Brucellosis is a bacterial disease, which, although affecting cattle primarily, has been associated with human infections, making its detection an important challenge. The existing gold standard diagnosis relies on the culture of bacteria which is a lengthy and costly process, taking up to 45 days. New technologies based on molecular diagnosis have been proposed, either through dip-stick, immunological assays, which have limited specificity, or using nucleic acid tests, which enable to identify the pathogen, but are impractical for use in the field, where most of the reservoir cases are located. Here we demonstrate a new test based on hybridization assays with metal nanoparticles, which, upon detection of a specific pathogen-derived DNA sequence, yield a visual colour change. We characterise the components used in the assay with a range of analytical techniques and show sensitivities down to 1000 cfu/ml for the detection of Brucella. Finally, we demonstrate that the assay works in a range of bovine samples including semen, milk and urine, opening up the potential for its use in the field, in low-resource settings. PMID:28719613

Tandem mass spectrometry for the detection of plant pathogenic fungi and the effects of database composition on protein inferences.

PubMed

Padliya, Neerav D; Garrett, Wesley M; Campbell, Kimberly B; Tabb, David L; Cooper, Bret

2007-11-01

LC-MS/MS has demonstrated potential for detecting plant pathogens. Unlike PCR or ELISA, LC-MS/MS does not require pathogen-specific reagents for the detection of pathogen-specific proteins and peptides. However, the MS/MS approach we and others have explored does require a protein sequence reference database and database-search software to interpret tandem mass spectra. To evaluate the limitations of database composition on pathogen identification, we analyzed proteins from cultured Ustilago maydis, Phytophthora sojae, Fusarium graminearum, and Rhizoctonia solani by LC-MS/MS. When the search database did not contain sequences for a target pathogen, or contained sequences to related pathogens, target pathogen spectra were reliably matched to protein sequences from nontarget organisms, giving an illusion that proteins from nontarget organisms were identified. Our analysis demonstrates that when database-search software is used as part of the identification process, a paradox exists whereby additional sequences needed to detect a wide variety of possible organisms may lead to more cross-species protein matches and misidentification of pathogens.

Light emitting diode, photodiode-based fluorescence detection system for DNA analysis with microchip electrophoresis.

PubMed

Hall, Gordon H; Glerum, D Moira; Backhouse, Christopher J

2016-02-01

Electrophoretic separation of fluorescently end-labeled DNA after a PCR serves as a gold standard in genetic diagnostics. Because of their size and cost, instruments for this type of analysis have had limited market uptake, particularly for point-of-care applications. This might be changed through a higher level of system integration and lower instrument costs that can be realized through the use of LEDs for excitation and photodiodes for detection--if they provide sufficient sensitivity. Here, we demonstrate an optimized microchip electrophoresis instrument using polymeric fluidic chips with fluorescence detection of end-labeled DNA with a LOD of 0.15 nM of Alexa Fluor 532. This represents orders of magnitude improvement over previously reported instruments of this type. We demonstrate the system with an electrophoretic separation of two PCR products and their respective primers. We believe that this is the first LED-induced fluorescence microchip electrophoresis system with photodiode-based detection that could be used for standard applications of PCR and electrophoresis. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

On Integral Upper Limits Assuming Power-law Spectra and the Sensitivity in High-energy Astronomy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahnen, Max L., E-mail: m.knoetig@gmail.com

The high-energy non-thermal universe is dominated by power-law-like spectra. Therefore, results in high-energy astronomy are often reported as parameters of power-law fits, or, in the case of a non-detection, as an upper limit assuming the underlying unseen spectrum behaves as a power law. In this paper, I demonstrate a simple and powerful one-to-one relation of the integral upper limit in the two-dimensional power-law parameter space into the spectrum parameter space and use this method to unravel the so-far convoluted question of the sensitivity of astroparticle telescopes.

Gas Sensor Based on Photonic Crystal Fibres in the 2ν3 and ν2 + 2ν3 Vibrational Bands of Methane

PubMed Central

Cubillas, Ana M.; Lazaro, Jose M.; Conde, Olga M.; Petrovich, Marco N.; Lopez-Higuera, Jose M.

2009-01-01

In this work, methane detection is performed on the 2ν3 and ν2 + 2ν3 absorption bands in the Near-Infrared (NIR) wavelength region using an all-fibre optical sensor. Hollow-core photonic bandgap fibres (HC-PBFs) are employed as gas cells due to their compactness, good integrability in optical systems and feasibility of long interaction lengths with gases. Sensing in the 2ν3 band of methane is demonstrated to achieve a detection limit one order of magnitude better than that of the ν2 + 2ν3 band. Finally, the filling time of a HC-PBF is demonstrated to be dependent on the fibre length and geometry. PMID:22454584

Gold nanoparticle-based optical microfluidic sensors for analysis of environmental pollutants.

PubMed

Lafleur, Josiane P; Senkbeil, Silja; Jensen, Thomas G; Kutter, Jörg P

2012-11-21

Conventional methods of environmental analysis can be significantly improved by the development of portable microscale technologies for direct in-field sensing at remote locations. This report demonstrates the vast potential of gold nanoparticle-based microfluidic sensors for the rapid, in-field, detection of two important classes of environmental contaminants - heavy metals and pesticides. Using gold nanoparticle-based microfluidic sensors linked to a simple digital camera as the detector, detection limits as low as 0.6 μg L(-1) and 16 μg L(-1) could be obtained for the heavy metal mercury and the dithiocarbamate pesticide ziram, respectively. These results demonstrate that the attractive optical properties of gold nanoparticle probes combine synergistically with the inherent qualities of microfluidic platforms to offer simple, portable and sensitive sensors for environmental contaminants.

ELISA for sulfonamides and its application for screening in water contamination.

PubMed

Shelver, Weilin L; Shappell, Nancy W; Franek, Milan; Rubio, Fernando R

2008-08-13

Two enzyme-linked immunosorbent assays (ELISAs) were tested for their suitability for detecting sulfonamides in wastewater from various stages in wastewater treatment plants (WWTPs), the river into which the wastewater is discharged, and two swine-rearing facilities. The sulfamethoxazole ELISA cross-reacts with several compounds, achieving detection limits of <0.04 microg/L for sulfamethoxazole (SMX), sulfamethoxypyridine, sulfachloropyridine, and sulfamethoxine, whereas the sulfamethazine (SMZ) ELISA is more compound specific, with a detection limit of <0.03 microg/L. Samples from various stages of wastewater purifications gave 0.6-3.1 microg/L by SMX-ELISA, whereas river samples were approximately 10-fold lower, ranging from below detection to 0.09 microg/L. Swine wastewater samples analyzed by the SMX-ELISA were either at or near detectable limits from one facility, whereas the other facility had concentrations of approximately 0.5 microg/L, although LC-MS/MS did not confirm the presence of SMX. Sulfamethazine ELISA detected no SMZ in either WWTP or river samples. In contrast, wastewater samples from swine facilities analyzed by SMZ-ELISA were found to contain approximately 30 microg/L [piglet (50-100 lb) wastewater] and approximately 7 microg/L (market-weight hog wastewater). Sulfamethazine ELISA analyses of wastewater from another swine facility found concentrations to be near or below detection limits. A solid phase extraction method was used to isolate and concentrate sulfonamides from water samples prior to LC-MS/MS multiresidue confirmatory analysis. The recoveries at 1 microg/L fortification ranged from 42 +/- 4% for SMZ to 88 +/- 4% for SMX ( n = 6). The ELISA results in the WWTPs were confirmed by LC-MS/MS, as sulfonamide multiresidue confirmatory analysis identified SMX, sulfapyridine, and sulfasalazine to be present in the wastewater. Sulfamethazine presence at one swine-rearing facility was also confirmed by LC-MS/MS, demonstrating the usefulness of the ELISA technique as a rapid and high-throughput screening method.

Ultratrace level determination and quantitative analysis of kidney injury biomarkers in patient samples attained by zinc oxide nanorods

NASA Astrophysics Data System (ADS)

Singh, Manpreet; Alabanza, Anginelle; Gonzalez, Lorelis E.; Wang, Weiwei; Reeves, W. Brian; Hahm, Jong-In

2016-02-01

Determining ultratrace amounts of protein biomarkers in patient samples in a straightforward and quantitative manner is extremely important for early disease diagnosis and treatment. Here, we successfully demonstrate the novel use of zinc oxide nanorods (ZnO NRs) in the ultrasensitive and quantitative detection of two acute kidney injury (AKI)-related protein biomarkers, tumor necrosis factor (TNF)-α and interleukin (IL)-8, directly from patient samples. We first validate the ZnO NRs-based IL-8 results via comparison with those obtained from using a conventional enzyme-linked immunosorbent method in samples from 38 individuals. We further assess the full detection capability of the ZnO NRs-based technique by quantifying TNF-α, whose levels in human urine are often below the detection limits of conventional methods. Using the ZnO NR platforms, we determine the TNF-α concentrations of all 46 patient samples tested, down to the fg per mL level. Subsequently, we screen for TNF-α levels in approximately 50 additional samples collected from different patient groups in order to demonstrate a potential use of the ZnO NRs-based assay in assessing cytokine levels useful for further clinical monitoring. Our research efforts demonstrate that ZnO NRs can be straightforwardly employed in the rapid, ultrasensitive, quantitative, and simultaneous detection of multiple AKI-related biomarkers directly in patient urine samples, providing an unparalleled detection capability beyond those of conventional analysis methods. Additional key advantages of the ZnO NRs-based approach include a fast detection speed, low-volume assay condition, multiplexing ability, and easy automation/integration capability to existing fluorescence instrumentation. Therefore, we anticipate that our ZnO NRs-based detection method will be highly beneficial for overcoming the frequent challenges in early biomarker development and treatment assessment, pertaining to the facile and ultrasensitive quantification of hard-to-trace biomolecules.Determining ultratrace amounts of protein biomarkers in patient samples in a straightforward and quantitative manner is extremely important for early disease diagnosis and treatment. Here, we successfully demonstrate the novel use of zinc oxide nanorods (ZnO NRs) in the ultrasensitive and quantitative detection of two acute kidney injury (AKI)-related protein biomarkers, tumor necrosis factor (TNF)-α and interleukin (IL)-8, directly from patient samples. We first validate the ZnO NRs-based IL-8 results via comparison with those obtained from using a conventional enzyme-linked immunosorbent method in samples from 38 individuals. We further assess the full detection capability of the ZnO NRs-based technique by quantifying TNF-α, whose levels in human urine are often below the detection limits of conventional methods. Using the ZnO NR platforms, we determine the TNF-α concentrations of all 46 patient samples tested, down to the fg per mL level. Subsequently, we screen for TNF-α levels in approximately 50 additional samples collected from different patient groups in order to demonstrate a potential use of the ZnO NRs-based assay in assessing cytokine levels useful for further clinical monitoring. Our research efforts demonstrate that ZnO NRs can be straightforwardly employed in the rapid, ultrasensitive, quantitative, and simultaneous detection of multiple AKI-related biomarkers directly in patient urine samples, providing an unparalleled detection capability beyond those of conventional analysis methods. Additional key advantages of the ZnO NRs-based approach include a fast detection speed, low-volume assay condition, multiplexing ability, and easy automation/integration capability to existing fluorescence instrumentation. Therefore, we anticipate that our ZnO NRs-based detection method will be highly beneficial for overcoming the frequent challenges in early biomarker development and treatment assessment, pertaining to the facile and ultrasensitive quantification of hard-to-trace biomolecules. Electronic supplementary information (ESI) available: Typical SEM images of the ZnO NRs used in the biomarker assays are provided in Fig. S1. See DOI: 10.1039/c5nr08706f

Detection of Ammonia-Oxidizing Bacteria (AOB) Using a Porous Silicon Optical Biosensor Based on a Multilayered Double Bragg Mirror Structure.

PubMed

Zhang, Hongyan; Lv, Jie; Jia, Zhenhong

2018-01-01

We successfully demonstrate a porous silicon (PS) double Bragg mirror by electrochemical etching at room temperature as a deoxyribonucleic acid (DNA) label-free biosensor for detecting ammonia-oxidizing bacteria (AOB). Compared to various other one-dimension photonic crystal configurations of PS, the double Bragg mirror structure is quite easy to prepare and exhibits interesting optical properties. The width of high reflectivity stop band of the PS double Bragg mirror is about 761 nm with a sharp and deep resonance peak at 1328 nm in the reflectance spectrum, which gives a high sensitivity and distinguishability for sensing performance. The detection sensitivity of such a double Bragg mirror structure is illustrated through the investigation of AOB DNA hybridization in the PS pores. The redshifts of the reflectance spectra show a good linear relationship with both complete complementary and partial complementary DNA. The lowest detection limit for complete complementary DNA is 27.1 nM and the detection limit of the biosensor for partial complementary DNA is 35.0 nM, which provides the feasibility and effectiveness for the detection of AOB in a real environment. The PS double Bragg mirror structure is attractive for widespread biosensing applications and provides great potential for the development of optical applications.

Single-molecule detection of protein efflux from microorganisms using fluorescent single-walled carbon nanotube sensor arrays

NASA Astrophysics Data System (ADS)

Landry, Markita Patricia; Ando, Hiroki; Chen, Allen Y.; Cao, Jicong; Kottadiel, Vishal Isaac; Chio, Linda; Yang, Darwin; Dong, Juyao; Lu, Timothy K.; Strano, Michael S.

2017-05-01

A distinct advantage of nanosensor arrays is their ability to achieve ultralow detection limits in solution by proximity placement to an analyte. Here, we demonstrate label-free detection of individual proteins from Escherichia coli (bacteria) and Pichia pastoris (yeast) immobilized in a microfluidic chamber, measuring protein efflux from single organisms in real time. The array is fabricated using non-covalent conjugation of an aptamer-anchor polynucleotide sequence to near-infrared emissive single-walled carbon nanotubes, using a variable chemical spacer shown to optimize sensor response. Unlabelled RAP1 GTPase and HIV integrase proteins were selectively detected from various cell lines, via large near-infrared fluorescent turn-on responses. We show that the process of E. coli induction, protein synthesis and protein export is highly stochastic, yielding variability in protein secretion, with E. coli cells undergoing division under starved conditions producing 66% fewer secreted protein products than their non-dividing counterparts. We further demonstrate the detection of a unique protein product resulting from T7 bacteriophage infection of E. coli, illustrating that nanosensor arrays can enable real-time, single-cell analysis of a broad range of protein products from various cell types.

Surface enhanced Raman scattering (SERS) spectra of trinitrotoluene in silver colloids prepared by microwave heating method.

PubMed

Zhang, Chunling; Wang, Kaijun; Han, Dejun; Pang, Qing

2014-03-25

Surface enhanced Raman spectroscopy (SERS) has been demonstrated for the detection of trace levels of explosives due to its high sensitivity, speed of detection and fingerprint feature. 2,4,6-Trinitrotoluene (TNT), a leading example of nitroaromatic explosives, is causing wide concern. In this study, SERS spectra of TNT solution in silver colloids have been successfully measured and a comparison was drawn with the normal Raman spectra of bulk TNT. The silver colloids were prepared by the microwave heating method and characterized by UV-Vis spectra and the scanning electron microscopy (SEM). NaCl and pH value have a great impact on SERS intensity of TNT, the corresponding experimental research results and theoretical interpretations were further illustrated to a certain extent. Moreover, the detection limit of TNT in aqueous solution was achieved as low as 10(-10) mol L(-1) and some preliminary experiments of detecting TNT vapor (about 10 μg/L) using SERS have been carried out. Our results demonstrated the potential of SERS for probing TNT with high sensitivity, and suggest SERS as a powerful method for detection of TNT and similar species at trace levels. Copyright © 2013 Elsevier B.V. All rights reserved.

Enzymatic glucose detection using ZnO nanorods on the gate region of AlGaN /GaN high electron mobility transistors

NASA Astrophysics Data System (ADS)

Kang, B. S.; Wang, H. T.; Ren, F.; Pearton, S. J.; Morey, T. E.; Dennis, D. M.; Johnson, J. W.; Rajagopal, P.; Roberts, J. C.; Piner, E. L.; Linthicum, K. J.

2007-12-01

ZnO nanorod-gated AlGaN /GaN high electron mobility transistors (HEMTs) are demonstrated for the detection of glucose. A ZnO nanorod array was selectively grown on the gate area using low temperature hydrothermal decomposition to immobilize glucose oxidase (GOx). The one-dimensional ZnO nanorods provide a large effective surface area with high surface-to-volume ratio and provide a favorable environment for the immobilization of GOx. The AlGaN /GaN HEMT drain-source current showed a rapid response of less than 5s when target glucose in a buffer with a pH value of 7.4 was added to the GOx immobilized on the ZnO nanorod surface. We could detect a wide range of concentrations from 0.5nMto125μM. The sensor exhibited a linear range from 0.5nMto14.5μM and an experiment limit of detection of 0.5nM. This demonstrates the possibility of using AlGaN /GaN HEMTs for noninvasive exhaled breath condensate based glucose detection of diabetic application.

The Hidden Snake in the Grass: Superior Detection of Snakes in Challenging Attentional Conditions

PubMed Central

Soares, Sandra C.; Lindström, Björn; Esteves, Francisco; Öhman, Arne

2014-01-01

Snakes have provided a serious threat to primates throughout evolution. Furthermore, bites by venomous snakes still cause significant morbidity and mortality in tropical regions of the world. According to the Snake Detection Theory (SDT Isbell, 2006; 2009), the vital need to detect camouflaged snakes provided strong evolutionary pressure to develop astute perceptual capacity in animals that were potential targets for snake attacks. We performed a series of behavioral tests that assessed snake detection under conditions that may have been critical for survival. We used spiders as the control stimulus because they are also a common object of phobias and rated negatively by the general population, thus commonly lumped together with snakes as “evolutionary fear-relevant”. Across four experiments (N = 205) we demonstrate an advantage in snake detection, which was particularly obvious under visual conditions known to impede detection of a wide array of common stimuli, for example brief stimulus exposures, stimuli presentation in the visual periphery, and stimuli camouflaged in a cluttered environment. Our results demonstrate a striking independence of snake detection from ecological factors that impede the detection of other stimuli, which suggests that, consistent with the SDT, they reflect a specific biological adaptation. Nonetheless, the empirical tests we report are limited to only one aspect of this rich theory, which integrates findings across a wide array of scientific disciplines. PMID:25493937

The Hidden Snake in the Grass: Superior Detection of Snakes in Challenging Attentional Conditions.

PubMed

Soares, Sandra C; Lindström, Björn; Esteves, Francisco; Ohman, Arne

2014-01-01

Snakes have provided a serious threat to primates throughout evolution. Furthermore, bites by venomous snakes still cause significant morbidity and mortality in tropical regions of the world. According to the Snake Detection Theory (SDT Isbell, 2006; 2009), the vital need to detect camouflaged snakes provided strong evolutionary pressure to develop astute perceptual capacity in animals that were potential targets for snake attacks. We performed a series of behavioral tests that assessed snake detection under conditions that may have been critical for survival. We used spiders as the control stimulus because they are also a common object of phobias and rated negatively by the general population, thus commonly lumped together with snakes as "evolutionary fear-relevant". Across four experiments (N = 205) we demonstrate an advantage in snake detection, which was particularly obvious under visual conditions known to impede detection of a wide array of common stimuli, for example brief stimulus exposures, stimuli presentation in the visual periphery, and stimuli camouflaged in a cluttered environment. Our results demonstrate a striking independence of snake detection from ecological factors that impede the detection of other stimuli, which suggests that, consistent with the SDT, they reflect a specific biological adaptation. Nonetheless, the empirical tests we report are limited to only one aspect of this rich theory, which integrates findings across a wide array of scientific disciplines.

Demonstration of Uncued Optical Surveillance of LEO

NASA Astrophysics Data System (ADS)

Zimmer, P.; Ackermann, M.; McGraw, J.

2014-09-01

J.T. McGraw and Associates, LLC, in collaboration with the University of New Mexico (UNM), has built and is operating two proof-of-concept wide-field imaging systems to test novel techniques for uncued surveillance of LEO. The imaging systems are built from off-the-shelf optics and detectors resulting in a 350mm aperture and a 6 square degree field of view. For streak detection, field of view is of critical importance because the maximum exposure time on the object is limited by its crossing time and measurements of apparent angular motion are better constrained with longer streaks. The current match of the detector to the optical system is optimized for detection of objects at altitudes above 450km, which for a circular orbit, corresponds to apparent motions of approximately 1 deg./sec. Using our GPU-accelerated detection scheme, the proof-of-concept systems have detected objects fainter than V=12.3, which approximately corresponds to a 24 cm object at 1000 km altitude at better than 6 sigma significance, from sites near and within Albuquerque, NM. This work demonstrates scalable optical systems designed for near real time detection of fast moving objects, which can be then handed off to other instruments capable of tracking and characterizing them. The two proof-of-concept systems, separated by ~30km, work together by taking simultaneous images of the same orbital volume to constrain the orbits of detected objects using parallax measurements. These detections are followed-up by photometric observations taken at UNM to independently assess the objects and the quality of the derived orbits. We believe this demonstrates the potential of small telescope arrays for detecting and cataloguing heretofore unknown LEO objects.

On developing thermal cave detection techniques for earth, the moon and mars

USGS Publications Warehouse

Wynne, J. Judson; Titus, Timothy N.; Chong Diaz, Guillermo

2008-01-01

The purpose of this study is to (1) demonstrate the viability of detecting terrestrial caves at thermal-infrared wavelengths, (2) improve our understanding of terrestrial cave thermal behavior, (3) identify times of day when cave openings have the maximum thermal contrast with the surrounding surface regolith, and (4) further our understanding of how to detect caves on Earth, the Moon and Mars. We monitored the thermal behavior of two caves in the Atacama Desert of northern Chile. Through this work, we identified times when temperature contrasts between entrance and surface were greatest, thus enabling us to suggest optimal overflight times. The largest thermal contrast for both caves occurred during mid-day. One cave demonstrated thermal behavior at the entrance suggestive of cold-trapping, while the second cave demonstrated temperature shifts suggestive of airflow. We also collected thermograms without knowing optimal detection times; these images suggest both caves may also be detectable during off-peak times. We suggest cave detection using thermal remote sensing on Earth and other planetary objects will be limited by (1) capturing imagery in the appropriate thermal wavelength, (2) the size of cave entrance vs. the sensor's spatial resolution, (3) the viewing angle of the platform in relation to the slope trajectory of the cave entrance, (4) the strength of the thermal signal associated with the cave entrance, and (5) the time of day and season of thermal image capture. Through this and other studies, we will begin to identify the range of conditions under which caves are detectable in the thermal infrared and thus improve our detection capabilities of these features on Earth, the Moon and Mars. ?? 2008 Elsevier B.V.

Complexation-Based Detection of Nickel(II) at a Graphene-Chelate Probe in the Presence of Cobalt and Zinc by Adsorptive Stripping Voltammetry

PubMed Central

Pokpas, Keagan; Jahed, Nazeem; Baker, Priscilla G.

2017-01-01

The adsorptive stripping voltammetric detection of nickel and cobalt in water samples at metal film electrodes has been extensively studied. In this work, a novel, environmentally friendly, metal-free electrochemical probe was constructed for the ultra-trace determination of Ni2+ in water samples by Adsorptive Cathodic Stripping Voltammetry (AdCSV). The electrochemical platform is based on the adsorptive accumulation of Ni2+ ions directly onto a glassy carbon electrode (GCE) modified with dimethylglyoxime (DMG) as chelating agent and a Nafion-graphene (NGr) nanocomposite to enhance electrode sensitivity. The nafion-graphene dimethylglyoxime modified glassy carbon electrode (NGr-DMG-GCE) shows superior detection capabilities as a result of the improved surface-area-to-volume ratio and enhanced electron transfer kinetics following the incorporation of single layer graphene, while limiting the toxic effects of the sensor by removal of the more common mercury, bismuth and lead films. Furthermore, for the first time the NGr-DMG-GCE, in the presence of common interfering metal ions of Co2+ and Zn2+ demonstrates good selectivity and preferential binding towards the detection of Ni2+ in water samples. Structural and morphological characterisation of the synthesised single layer graphene sheets was conducted by Raman spectrometry, HRTEM and HRSEM analysis. The instrumental parameters associated with the electrochemical response, including accumulation potential and accumulation time were investigated and optimised in addition to the influence of DMG and graphene concentrations. The NGr-DMG-GCE demonstrated well resolved, reproducible peaks, with RSD (%) below 5% and a detection limit of 1.5 µg L−1 for Ni2+ reduction at an accumulation time of 120 s. The prepared electrochemical sensor exhibited good detection and quantitation towards Ni2+ detection in tap water samples, well below 0.1 mg L−1 set by the WHO and EPA standards. This is comparable to the South African drinking water guidelines of 0.15 mg L−1. PMID:28757588

A paper-based resonance energy transfer nucleic acid hybridization assay using upconversion nanoparticles as donors and quantum dots as acceptors.

PubMed

Doughan, Samer; Uddayasankar, Uvaraj; Krull, Ulrich J

2015-06-09

Monodisperse aqueous upconverting nanoparticles (UCNPs) were covalently immobilized on aldehyde modified cellulose paper via reduction amination to develop a luminescence resonance energy transfer (LRET)-based nucleic acid hybridization assay. This first account of covalent immobilization of UCNPs on paper for a bioassay reports an optically responsive method that is sensitive, reproducible and robust. The immobilized UCNPs were decorated with oligonucleotide probes to capture HPRT1 housekeeping gene fragments, which in turn brought reporter conjugated quantum dots (QDs) in close proximity to the UCNPs for LRET. This sandwich assay could detect unlabeled oligonucleotide target, and had a limit of detection of 13 fmol and a dynamic range spanning nearly 3 orders of magnitude. The use of QDs, which are excellent LRET acceptors, demonstrated improved sensitivity, limit of detection, dynamic range and selectivity compared to similar assays that have used molecular fluorophores as acceptors. The selectivity of the assay was attributed to the decoration of the QDs with polyethylene glycol to eliminate non-specific adsorption. The kinetics of hybridization were determined to be diffusion limited and full signal development occurred within 3 min. Copyright © 2015 Elsevier B.V. All rights reserved.

Cryogen-free heterodyne-enhanced mid-infrared Faraday rotation spectrometer

PubMed Central

Wang, Yin; Nikodem, Michal; Wysocki, Gerard

2013-01-01

A new detection method for Faraday rotation spectra of paramagnetic molecular species is presented. Near shot-noise limited performance in the mid-infrared is demonstrated using a heterodyne enhanced Faraday rotation spectroscopy (H-FRS) system without any cryogenic cooling. Theoretical analysis is performed to estimate the ultimate sensitivity to polarization rotation for both heterodyne and conventional FRS. Sensing of nitric oxide (NO) has been performed with an H-FRS system based on thermoelectrically cooled 5.24 μm quantum cascade laser (QCL) and a mercury-cadmium-telluride photodetector. The QCL relative intensity noise that dominates at low frequencies is largely avoided by performing the heterodyne detection in radio frequency range. H-FRS exhibits a total noise level of only 3.7 times the fundamental shot noise. The achieved sensitivity to polarization rotation of 1.8 × 10−8 rad/Hz1/2 is only 5.6 times higher than the ultimate theoretical sensitivity limit estimated for this system. The path- and bandwidth-normalized NO detection limit of 3.1 ppbv-m/Hz1/2 was achieved using the R(17/2) transition of NO at 1906.73 cm−1. PMID:23388967

Evaluating quality of adhesive joints in glass-fiber plastic piping by using active thermal NDT

NASA Astrophysics Data System (ADS)

Grosso, M.; Marinho, C. A.; Nesteruk, D. A.; Rebello, J. M.; Soares, S. D.; Vavilov, V. P.

2013-05-01

GRP-type composites (Glass-fibre Reinforced Plastics) have been continuously employed in the oil industry in recent years, often on platforms, especially in pipes for water or oil under moderate temperatures. In this case, the pipes are usually connected through adhesive joints and, consequently, the detection of defects in these joints, as areas without adhesive or adhesive failure (disbonding), gains great importance. One-sided inspection on the joint surface (front side) is a challenging task because the material thickness easily exceeds 10 mm that is far beyond the limits of the capacity of thermography applied to GRP inspection, as confirmed by the experience. Detection limits have been evaluated both theoretically and experimentally as a function of outer wall thickness and defect lateral size. The 3D modeling was accomplished by using the ThermoCalc-6L software. The experimental unit consisted of a FLIR SC640 and NEC TH- 9100 IR imagers and some home-made heaters with the power from 1,5 to 30 kW. The results obtained by applying pulsed heating have demonstrated that the inspection efficiency is strongly dependent on the outer wall thickness with a value of about 8 mm being a detection limit.

Discriminating Malingered from Genuine Civilian Posttraumatic Stress Disorder: A Validation of Three MMPI-2 Infrequency Scales (F, Fp, and Fptsd)

ERIC Educational Resources Information Center

Elhai, Jon D.; Naifeh, James A.; Zucker, Irene S.; Gold, Steven N.; Deitsch, Sarah E.; Frueh, B. Christopher

2004-01-01

The Infrequency-Posttraumatic Stress Disorder scale (Fptsd), recently created for the Minnesota Multiphasic Personality Inventory-2 (MMPI-2), has demonstrated incremental validity over other MMPI-2 scales in malingered posttraumatic stress disorder (PTSD) detection. Fptsd was developed with combat-exposed PTSD patients, potentially limiting its…

Measuring Adult Literacy in Health Care: Performance of the Newest Vital Sign

ERIC Educational Resources Information Center

Osborn, Chandra Y.; Weiss, Barry D.; Davis, Terry C.; Skripkauskas, Silvia; Rodrigue, Christopher; Bass, Pat F., III; Wolf, Michael S.

2007-01-01

Objective: To compare performance of the newest vital sign (NVS) with existing literacy measures. Methods: We administered the NVS and REALM to 129 patients, and NVS and S-TOFHLA to 119 patients all in public clinics. Results: The NVS demonstrated high sensitivity for detecting limited literacy and moderate specificity (area under the receiver…

A nucleic acid strand displacement system for the multiplexed detection of tuberculosis-specific mRNA using quantum dots

NASA Astrophysics Data System (ADS)

Gliddon, H. D.; Howes, P. D.; Kaforou, M.; Levin, M.; Stevens, M. M.

2016-05-01

The development of rapid, robust and high performance point-of-care diagnostics relies on the advancement and combination of various areas of research. We have developed an assay for the detection of multiple mRNA molecules that combines DNA nanotechnology with fluorescent nanomaterials. The core switching mechanism is toehold-mediated strand displacement. We have used fluorescent quantum dots (QDs) as signal transducers in this assay, as they bring many benefits including bright fluorescence and multiplexing abilities. The resulting assay is capable of multiplexed detection of long RNA targets against a high concentration of background non-target RNA, with high sensitivity and specificity and limits of detection in the nanomolar range using only a standard laboratory plate reader. We demonstrate the utility of our QD-based system for the detection of two genes selected from a microarray-derived tuberculosis-specific gene expression signature. Levels of up- and downregulated gene transcripts comprising this signature can be combined to give a disease risk score, making the signature more amenable for use as a diagnostic marker. Our QD-based approach to detect these transcripts could pave the way for novel diagnostic assays for tuberculosis.The development of rapid, robust and high performance point-of-care diagnostics relies on the advancement and combination of various areas of research. We have developed an assay for the detection of multiple mRNA molecules that combines DNA nanotechnology with fluorescent nanomaterials. The core switching mechanism is toehold-mediated strand displacement. We have used fluorescent quantum dots (QDs) as signal transducers in this assay, as they bring many benefits including bright fluorescence and multiplexing abilities. The resulting assay is capable of multiplexed detection of long RNA targets against a high concentration of background non-target RNA, with high sensitivity and specificity and limits of detection in the nanomolar range using only a standard laboratory plate reader. We demonstrate the utility of our QD-based system for the detection of two genes selected from a microarray-derived tuberculosis-specific gene expression signature. Levels of up- and downregulated gene transcripts comprising this signature can be combined to give a disease risk score, making the signature more amenable for use as a diagnostic marker. Our QD-based approach to detect these transcripts could pave the way for novel diagnostic assays for tuberculosis. Electronic supplementary information (ESI) available: Base pair mismatch tuning of CProbes. Binding capacity of the QDs. Theoretical limit of detection (LOD) for the monoplex systems. Kinetics of strand displacement. Kinetics of QProbe-CProbe binding. LOD and saturation point calculations. See DOI: 10.1039/c6nr00484a

Copper sulfide nanodisk as photoacoustic contrast agent for ovarian tumor detection

NASA Astrophysics Data System (ADS)

Wang, Junxin; Hsu, Su-Wen; Tao, Andrea R.; Jokerst, Jesse V.

2017-03-01

Ultrasound is broadly used in the clinics yet is limited in early cancer detection because of its poor contrast between healthy and diseased tissues. Photoacoustic imaging can improve this limitation and has been extensively studied in pre-clinical models. Contrast agents can help improve the accuracy of diagnosis. We recently reported a novel copper sulfide (CuS) nanodisk with strong directionally-localized surface plasmon resonance in the near infrared region. This plasmonic resonance of nanodisks is tunable by changing the size and aspect ratio of CuS nanodisk. Here, we demonstrate this CuS nanodisk is a strong photoacoustic contrast agent. We prepared CuS nanodisks via a solvent-based synthesis followed by surface modification of poly(ethylene glycol) methyl ether thiol for in vivo applications. These CuS nanodisks can be detected at a concentration as low as 26 pM at 920 nm. Their nanosize and strong photoacoustic response make this novel CuS nanodisk a strong candidate for photoacoustic cancer imaging.

Biochip-Based Detection of KRAS Mutation in Non-Small Cell Lung Cancer

PubMed Central

Kriegshäuser, Gernot; Fabjani, Gerhild; Ziegler, Barbara; Zöchbauer-Müller, Sabine; End, Adelheid; Zeillinger, Robert

2011-01-01

This study is aimed at evaluating the potential of a biochip assay to sensitively detect KRAS mutation in DNA from non-small cell lung cancer (NSCLC) tissue samples. The assay covers 10 mutations in codons 12 and 13 of the KRAS gene, and is based on mutant-enriched PCR followed by reverse-hybridization of biotinylated amplification products to an array of sequence-specific probes immobilized on the tip of a rectangular plastic stick (biochip). Biochip hybridization identified 17 (21%) samples to carry a KRAS mutation of which 16 (33%) were adenocarcinomas and 1 (3%) was a squamous cell carcinoma. All mutations were confirmed by DNA sequencing. Using 10 ng of starting DNA, the biochip assay demonstrated a detection limit of 1% mutant sequence in a background of wild-type DNA. Our results suggest that the biochip assay is a sensitive alternative to protocols currently in use for KRAS mutation testing on limited quantity samples. PMID:22272089

Nanopore sensing at ultra-low concentrations using single-molecule dielectrophoretic trapping

PubMed Central

Freedman, Kevin J.; Otto, Lauren M.; Ivanov, Aleksandar P.; Barik, Avijit; Oh, Sang-Hyun; Edel, Joshua B.

2016-01-01

Single-molecule techniques are being developed with the exciting prospect of revolutionizing the healthcare industry by generating vast amounts of genetic and proteomic data. One exceptionally promising route is in the use of nanopore sensors. However, a well-known complexity is that detection and capture is predominantly diffusion limited. This problem is compounded when taking into account the capture volume of a nanopore, typically 108–1010 times smaller than the sample volume. To rectify this disproportionate ratio, we demonstrate a simple, yet powerful, method based on coupling single-molecule dielectrophoretic trapping to nanopore sensing. We show that DNA can be captured from a controllable, but typically much larger, volume and concentrated at the tip of a metallic nanopore. This enables the detection of single molecules at concentrations as low as 5 fM, which is approximately a 103 reduction in the limit of detection compared with existing methods, while still maintaining efficient throughput. PMID:26732171

Apricot DNA as an indicator for persipan: detection and quantitation in marzipan using ligation-dependent probe amplification.

PubMed

Luber, Florian; Demmel, Anja; Hosken, Anne; Busch, Ulrich; Engel, Karl-Heinz

2012-06-13

The confectionery ingredient marzipan is exclusively prepared from almond kernels and sugar. The potential use of apricot kernels, so-called persipan, is an important issue for the quality assessment of marzipan. Therefore, a ligation-dependent probe amplification (LPA) assay was developed that enables a specific and sensitive detection of apricot DNA, as an indicator for the presence of persipan. The limit of detection was determined to be 0.1% persipan in marzipan. The suitability of the method was confirmed by the analysis of 20 commercially available food samples. The integration of a Prunus -specific probe in the LPA assay as a reference allowed for the relative quantitation of persipan in marzipan. The limit of quantitation was determined to be 0.5% persipan in marzipan. The analysis of two self-prepared mixtures of marzipan and persipan demonstrated the applicability of the quantitation method at concentration levels of practical relevance for quality control.

Evaluation of Total Nitrite Pattern Visualization as an Improved Method for Gunshot Residue Detection and its Application to Casework Samples.

PubMed

Berger, Jason; Upton, Colin; Springer, Elyah

2018-04-23

Visualization of nitrite residues is essential in gunshot distance determination. Current protocols for the detection of nitrites include, among other tests, the Modified Griess Test (MGT). This method is limited as nitrite residues are unstable in the environment and limited to partially burned gunpowder. Previous research demonstrated the ability of alkaline hydrolysis to convert nitrates to nitrites, allowing visualization of unburned gunpowder particles using the MGT. This is referred to as Total Nitrite Pattern Visualization (TNV). TNV techniques were modified and a study conducted to streamline the procedure outlined in the literature to maximize the efficacy of the TNV in casework, while reducing the required time from 1 h to 5 min, and enhancing effectiveness on blood-soiled samples. The TNV method was found to provide significant improvement in the ability to detect significant nitrite residues, without sacrificing efficiency, that would allow for the determination of the muzzle-to-target distance. © 2018 American Academy of Forensic Sciences.

Mass Spectrometry Based Ultrasensitive DNA Methylation Profiling Using Target Fragmentation Assay.

PubMed

Lin, Xiang-Cheng; Zhang, Ting; Liu, Lan; Tang, Hao; Yu, Ru-Qin; Jiang, Jian-Hui

2016-01-19

Efficient tools for profiling DNA methylation in specific genes are essential for epigenetics and clinical diagnostics. Current DNA methylation profiling techniques have been limited by inconvenient implementation, requirements of specific reagents, and inferior accuracy in quantifying methylation degree. We develop a novel mass spectrometry method, target fragmentation assay (TFA), which enable to profile methylation in specific sequences. This method combines selective capture of DNA target from restricted cleavage of genomic DNA using magnetic separation with MS detection of the nonenzymatic hydrolysates of target DNA. This method is shown to be highly sensitive with a detection limit as low as 0.056 amol, allowing direct profiling of methylation using genome DNA without preamplification. Moreover, this method offers a unique advantage in accurately determining DNA methylation level. The clinical applicability was demonstrated by DNA methylation analysis using prostate tissue samples, implying the potential of this method as a useful tool for DNA methylation profiling in early detection of related diseases.

Measuring xenon in human plasma and blood by gas chromatography/mass spectrometry.

PubMed

Thevis, Mario; Piper, Thomas; Geyer, Hans; Thomas, Andreas; Schaefer, Maximilian S; Kienbaum, Peter; Schänzer, Wilhelm

2014-07-15

Due to the favorable pharmacokinetic properties and minimal side effects of xenon, its use in modern anesthesia has been well accepted, and recent studies further demonstrated the intra- and postoperative neuro-, cardio-, and reno-protective action of the noble gas. Since the production of the hypoxia-inducible factor 1α (HIF-1α) and its downstream effector erythropoietin as well as noradrenalin reuptake inhibition have been found to play key roles in this context, the question arose as to whether the use of xenon is a matter for doping controls and preventive doping research. The aim of the present study was hence to evaluate whether the (ab)use of xenon can be detected from doping control samples with the instrumentation commonly available in sports drug testing laboratories. Plasma was saturated with xenon according to reported protocols, and the target analyte was measured by means of gas chromatography/time-of-flight and triple quadrupole mass spectrometry with headspace injection. Recording the accurate mass of three major xenon isotopes at m/z 128.9048, 130.9045 and 131.9042 allowed for the unequivocal identification of the analyte and the detection assay was characterized concerning limit of detection (LOD), intraday precision, and specificity as well as analyte recovery under different storage conditions. Xenon was detected in fortified plasma samples with detection limits of approximately 0.5 nmol/mL to 50 nmol/mL, depending on the type of mass spectrometer used. The method characteristics of intraday precision (coefficient of variation <20%) and specificity demonstrated the fitness-for-purpose of the analytical approach to unambiguously detect xenon at non-physiological concentrations in human plasma and blood. Eventually, authentic plasma and blood samples collected pre-, intra-, and post-operative (4, 8, and 24 h) were positively analyzed after storage for up to 30 h, and provided proof-of-concept for the developed assay. If relevant to doping controls, xenon can be determined from plasma and blood samples, i.e. common specimens of routine sports drug testing in the context of Athlete Biological Passport (ABP) analyses. Optimization of sampling and analytical procedures will allow the detection limit to be further improved and potentially enable accurate quantification of the anesthetic agent. Copyright © 2014 John Wiley & Sons, Ltd.

Detecting changes in student teachers' conceptions of teaching science to adolescent English language learners

NASA Astrophysics Data System (ADS)

Pomeroy, Jonathon Richard

2000-10-01

This research study investigated the changes that occurred in six student teachers' conceptions of teaching science to adolescent English language learners over the duration of their participation in a one-year, graduate level, science teacher education program. Cases were created for each of the student teachers based on their concept maps, writing samples, interviews, lesson plans, informal interviews with cooperating teachers, and observation notes collected on biweekly visitations. The cases were divided into three dyads each consisting of two student teachers with similar preprogram and student teaching experiences. Cross case analysis revealed the existence of seven themes related to teaching science to adolescent English language learners. Further analysis suggested that student teachers that worked with experienced cooperating teachers and who had achieved a sense of autonomy over their student teaching demonstrated broad and sophisticated growth across all seven themes. Student teachers who had not achieved a sense of autonomy, demonstrated growth in two to three themes. Student teachers who demonstrated broad and sophisticated growth were able to clearly articulate their conceptions of teaching science to English language learners where as those who demonstrated limited growth were not. This research establishes the use of concept maps as a tool for detecting changes in student teachers' conceptions of teaching science to adolescent English language learners as well as the sensitivity of concept maps to detect the types of changes historically detected by writing samples and interviews. Recommendations based on the implications from are included.

Determination of methyl mercury by aqueous phase Eehylation, followed by gas chromatographic separation with cold vapor atomic fluorescence detection

USGS Publications Warehouse

De Wild, John F.; Olsen, Mark L.; Olund, Shane D.

2002-01-01

A recent national sampling of streams in the United States revealed low methyl mercury concentrations in surface waters. The resulting median and mean concentrations, calculated from 104 samples, were 0.06 nanograms per liter (ng/L) and 0.15 ng/L, respectively. This level of methyl mercury in surface water in the United States has created a need for analytical techniques capable of detecting sub-nanogram per liter concentrations. In an attempt to create a U.S. Geological Survey approved method, the Wisconsin District Mercury Laboratory has adapted a distillation/ethylation/ gas-phase separation method with cold vapor atomic fluorescence spectroscopy detection for the determination of methyl mercury in filtered and unfiltered waters. This method is described in this report. Based on multiple analyses of surface water and ground-water samples, a method detection limit of 0.04 ng/L was established. Precision and accuracy were evaluated for the method using both spiked and unspiked ground-water and surface-water samples. The percent relative standard deviations ranged from 10.2 to 15.6 for all analyses at all concentrations. Average recoveries obtained for the spiked matrices ranged from 88.8 to 117 percent. The precision and accuracy ranges are within the acceptable method-performance limits. Considering the demonstrated detection limit, precision, and accuracy, the method is an effective means to quantify methyl mercury in waters at or below environmentally relevant concentrations

Quantification of susceptibility change at high-concentrated SPIO-labeled target by characteristic phase gradient recognition.

PubMed

Zhu, Haitao; Nie, Binbin; Liu, Hua; Guo, Hua; Demachi, Kazuyuki; Sekino, Masaki; Shan, Baoci

2016-05-01

Phase map cross-correlation detection and quantification may produce highlighted signal at superparamagnetic iron oxide nanoparticles, and distinguish them from other hypointensities. The method may quantify susceptibility change by performing least squares analysis between a theoretically generated magnetic field template and an experimentally scanned phase image. Because characteristic phase recognition requires the removal of phase wrap and phase background, additional steps of phase unwrapping and filtering may increase the chance of computing error and enlarge the inconsistence among algorithms. To solve problem, phase gradient cross-correlation and quantification method is developed by recognizing characteristic phase gradient pattern instead of phase image because phase gradient operation inherently includes unwrapping and filtering functions. However, few studies have mentioned the detectable limit of currently used phase gradient calculation algorithms. The limit may lead to an underestimation of large magnetic susceptibility change caused by high-concentrated iron accumulation. In this study, mathematical derivation points out the value of maximum detectable phase gradient calculated by differential chain algorithm in both spatial and Fourier domain. To break through the limit, a modified quantification method is proposed by using unwrapped forward differentiation for phase gradient generation. The method enlarges the detectable range of phase gradient measurement and avoids the underestimation of magnetic susceptibility. Simulation and phantom experiments were used to quantitatively compare different methods. In vivo application performs MRI scanning on nude mice implanted by iron-labeled human cancer cells. Results validate the limit of detectable phase gradient and the consequent susceptibility underestimation. Results also demonstrate the advantage of unwrapped forward differentiation compared with differential chain algorithms for susceptibility quantification at high-concentrated iron accumulation. Copyright © 2015 Elsevier Inc. All rights reserved.

Small target pre-detection with an attention mechanism

NASA Astrophysics Data System (ADS)

Wang, Yuehuan; Zhang, Tianxu; Wang, Guoyou

2002-04-01

We introduce the concept of predetection based on an attention mechanism to improve the efficiency of small-target detection by limiting the image region of detection. According to the characteristics of small-target detection, local contrast is taken as the only feature in predetection and a nonlinear sampling model is adopted to make the predetection adaptive to detect small targets with different area sizes. To simplify the predetection itself and decrease the false alarm probability, neighboring nodes in the sampling grid are used to generate a saliency map, and a short-term memory is adopted to accelerate the `pop-out' of targets. We discuss the fact that the proposed approach is simple enough in computational complexity. In addition, even in a cluttered background, attention can be led to targets in a satisfying few iterations, which ensures that the detection efficiency will not be decreased due to false alarms. Experimental results are presented to demonstrate the applicability of the approach.

Highly Sensitive, Label-Free Detection of 2,4-Dichlorophenoxyacetic Acid Using an Optofluidic Chip.

PubMed

Feng, Xueling; Zhang, Gong; Chin, Lip Ket; Liu, Ai Qun; Liedberg, Bo

2017-07-28

A highly sensitive approach for rapid and label-free detection of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) using an optofluidic chip is demonstrated. The optofluidic chip is prepared by covalent immobilization of 2,4-D-bovine serum albumin (2,4-D-BSA) conjugate to an integrated microring resonator. Subsequent detection of 2,4-D carried out in a competitive immunoreaction format enables selective detection of 2,4-D in different types of water samples, including bottled, tap, and lake water, at a limit of detection (LOD) of 4.5 pg/mL and in a quantitative range of 15-10 5 pg/mL. The microring resonator-based optofluidic chip is reusable with ultrahigh sensitivity that offers real-time and on-site detection of low-molecular-weight targets for potential applications in food safety and environmental monitoring.

Detection of argan oil adulteration with vegetable oils by high-performance liquid chromatography-evaporative light scattering detection.

PubMed

Salghi, Rachid; Armbruster, Wolfgang; Schwack, Wolfgang

2014-06-15

Triacylglycerol profiles were selected as indicator of adulteration of argan oils to carry out a rapid screening of samples for the evaluation of authenticity. Triacylglycerols were separated by high-performance liquid chromatography-evaporative light scattering detection. Different peak area ratios were defined to sensitively detect adulteration of argan oil with vegetable oils such as sunflower, soy bean, and olive oil up to the level of 5%. Based on four reference argan oils, mean limits of detection and quantitation were calculated to approximately 0.4% and 1.3%, respectively. Additionally, 19 more argan oil reference samples were analysed by high-performance liquid chromatography-refractive index detection, resulting in highly comparative results. The overall strategy demonstrated a good applicability in practise, and hence a high potential to be transferred to routine laboratories. Copyright © 2013 Elsevier Ltd. All rights reserved.

Acoustic thermometry for detecting quenches in superconducting coils and conductor stacks

NASA Astrophysics Data System (ADS)

Marchevsky, M.; Gourlay, S. A.

2017-01-01

Quench detection capability is essential for reliable operation and protection of superconducting magnets, coils, cables, and machinery. We propose a quench detection technique based on sensing local temperature variations in the bulk of a superconducting winding by monitoring its transient acoustic response. Our approach is primarily aimed at coils and devices built with high-temperature superconductor materials where quench detection using standard voltage-based techniques may be inefficient due to the slow velocity of quench propagation. The acoustic sensing technique is non-invasive, fast, and capable of detecting temperature variations of less than 1 K in the interior of the superconductor cable stack in a 77 K cryogenic environment. We show results of finite element modeling and experiments conducted on a model superconductor stack demonstrating viability of the technique for practical quench detection, discuss sensitivity limits of the technique, and its various applications.

An Uncertainty-Based Distributed Fault Detection Mechanism for Wireless Sensor Networks

PubMed Central

Yang, Yang; Gao, Zhipeng; Zhou, Hang; Qiu, Xuesong

2014-01-01

Exchanging too many messages for fault detection will cause not only a degradation of the network quality of service, but also represents a huge burden on the limited energy of sensors. Therefore, we propose an uncertainty-based distributed fault detection through aided judgment of neighbors for wireless sensor networks. The algorithm considers the serious influence of sensing measurement loss and therefore uses Markov decision processes for filling in missing data. Most important of all, fault misjudgments caused by uncertainty conditions are the main drawbacks of traditional distributed fault detection mechanisms. We draw on the experience of evidence fusion rules based on information entropy theory and the degree of disagreement function to increase the accuracy of fault detection. Simulation results demonstrate our algorithm can effectively reduce communication energy overhead due to message exchanges and provide a higher detection accuracy ratio. PMID:24776937

The Use of Spontaneous Raman Scattering for Hydrogen Leak Detection

NASA Technical Reports Server (NTRS)

Degroot, Wim A.

1994-01-01

A fiber optic probe has been built and demonstrated that utilizes back scattered spontaneous Raman spectroscopy to detect and identify gaseous species. The small probe, coupled to the laser and data acquisition equipment with optical fibers, has applications in gaseous leak detection and process monitoring. The probe design and data acquisition system are described. Raman scattering theory has been reviewed and the results of intensity calculations of hydrogen and nitrogen Raman scattering are given. Because the device is in its developmental stage, only preliminary experimental results are presented here. Intensity scans across the rotational-vibrational Raman lines of nitrogen and hydrogen are presented. Nitrogen at a partial pressure of 0.077 MPa was detected. Hydrogen at a partial pressure of 2 kPa approached the lower limit of detectability with the present apparatus. Potential instrument improvements that would allow more sensitive and rapid hydrogen detection are identified.

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

FDVIBSPC16: Sheath Flow SERS for Chemical Profiling in Urine

PubMed Central

Riordan, Colleen M.; Jacobs, Kevin T.; Negri, Pierre; Schultz, Zachary D.

2016-01-01

The molecular specificity and sensitivity of surface enhanced Raman scattering (SERS) makes it an attractive method for biomedical diagnostics. Here we present results demonstrating the utility and complications for SERS characterization in urine. The chemical fingerprint characteristic of Raman spectra suggests use as a label free diagnostic; however, the complex composition of biological fluids presents a tremendous challenge. In particular, the limited number of surface sites and competing absorption tend to mask the presence of analytes in solution, particularly when the solution contains multiple analytes. To address these problems and characterize biological fluids we have demonstrated a sheath-flow interface for SERS detection. This sheath-flow SERS interface uses hydrodynamic focusing to confine analyte molecules eluting out of a column onto a planar SERS substrate where the molecules are detected by their intrinsic SERS signal. In this report we compare direct detection of benzoylecgonine in urine using DSERS with chemical profiling by capillary zone electrophoresis and sheath-flow SERS detection. The SERS spectrum from the observed migration peaks can identify benzoylecgonine and other distinct spectra are also observed, suggesting improved chemical diagnostics in urine. With over 2000 reported compounds in urine, identification of each of the detected species is an enormous task. Nonetheless, these samples provide a benchmark to establish the potential clinical utility of sheath-flow SERS detection. PMID:27034996

A rapid, highly sensitive and culture-free detection of pathogens from blood by positive enrichment.

PubMed

Vutukuru, Manjula Ramya; Sharma, Divya Khandige; Ragavendar, M S; Schmolke, Susanne; Huang, Yiwei; Gumbrecht, Walter; Mitra, Nivedita

2016-12-01

Molecular diagnostics is a promising alternative to culture based methods for the detection of bloodstream infections, notably due to its overall lower turnaround time when starting directly from patient samples. Whole blood is usually the starting diagnostic sample in suspected bloodstream infections. The detection of low concentrations of pathogens in blood using a molecular assay necessitates a fairly high starting volume of blood sample in the range of 5-10mL. This large volume of blood sample has a substantial accompanying human genomic content that interferes with pathogen detection. In this study, we have established a workflow using magnetic beads coated with Apolipoprotein H that makes it possible to concentrate pathogens from a 5.0mL whole blood sample, thereby enriching pathogens from whole blood background and also reducing the sample volume to ~200μL or less. We have also demonstrated that this method of enrichment allows detection of 1CFU/mL of Escherichia coli, Enterococcus gallinarum and Candida tropicalis from 5mL blood using quantitative PCR; a detection limit that is not possible in unenriched samples. The enrichment method demonstrated here took 30min to complete and can be easily integrated with various downstream molecular and microbiological techniques. Copyright © 2016 Elsevier B.V. All rights reserved.

Rapid and Sensitive Detection of Protein Biomarker Using a Portable Fluorescence Biosensor based on Quantum Dots and a Lateral Flow Test Strip

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Zhaohui; Wang, Ying; Wang, Jun

2010-08-15

A portable fluorescence biosensor with rapid and ultrasensitive response for trace protein has been built up with quantum dots and lateral flow test strip. The superior signal brightness and high photostability of quantum dots are combined with the promising advantages of lateral flow test strip and resulted in high sensitivity, selectivity and speedy for protein detection. Nitrated ceruloplasmin, a significant biomarker for cardiovascular disease, lung cancer and stress response to smoking, was used as model protein to demonstrate the good performances of this proposed Qdot-based lateral flow test strip. Quantitative detection of nitrated ceruloplasmin was realized by recording the fluorescencemore » intensity of quantum dots captured on the test line. Under optimal conditions, this portable fluorescence biosensor displays rapid responses for nitrated ceruloplasmin in wide dynamic range with a detection limit of 0.1ng/mL (S/N=3). Furthermore, the biosensor was successfully utilized for spiked human plasma sample detection with the concentration as low as 1ng/mL. The results demonstrate that the quantum dot-based lateral flow test strip is capable for rapid, sensitive, and quantitative detection of nitrated ceruloplasmin and hold a great promise for point-of-care and in field analysis of other protein biomarkers.« less

Ultra-sensitive and selective Hg{sup 2+} detection based on fluorescent carbon dots

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Ruihua; Li, Haitao; Kong, Weiqian

2013-07-15

Graphical abstract: Fluorescent carbon dots were efficiently synthesized by one-step sodium hydroxide-assisted reflux method from PEG and demonstrated to show high selectivity toward Hg2+ ions detection. - Highlights: • FCDs were synthesized by one-step sodium hydroxide-assisted reflux method from PEG. • The FCDs emit blue photoluminescence and have upconversion fluorescent property. • The FCDs show ultra-sensitive detective ability for Hg{sup 2+} ions. - Abstract: Fluorescent carbon dots (FCDs) were efficiently synthesized by one-step sodium hydroxide-assisted reflux method from poly(ethylene glycol) (PEG). The obtained FCDs exhibit excellent water-solubility and high stability. Under the UV irradiation, the FCDs could emit bright bluemore » photoluminescence, and also they were found to show excellent up-conversion fluorescence. It was further demonstrated that such FCDs can serve as effective fluorescent sensing platform for Hg{sup 2+} ions detection with ultra-sensitivity and selectivity. The sensing system achieved a limit of detection as low as 1 fM, which is much lower than all the previous reported sensing systems for Hg{sup 2+} ions detection. This FCDs sensing system has been successfully applied for the analysis of Hg{sup 2+} ions in water samples from river, lake, and tap water, showing good practical feasibility.« less

Luminol-based electrochemiluminescent biosensors for highly sensitive medical diagnosis and rapid antioxidant detection

NASA Astrophysics Data System (ADS)

Tamiya, Eiichi; Inoue, Yuki; Saito, Masato

2018-03-01

We present a review of luminol-based electrochemiluminescence (ECL) biosensors that perform enzymatic reactions and bioanalysis using antioxidant molecules by controlling the spatiotemporal production of a luminescent substrate, catalase activity, and glycated albumin (GA). The ECL intensity depends on the antioxidant capacity because radicals are neutralized by the antioxidants, which suppresses the luminescence. The antioxidant capacities of 22 types beverages were evaluated by comparison with a standard curve of Trolox. The time necessary for the ECL measurement of the antioxidant capacity is only 2 min with screen-printed electrodes and a portable ECL measurement system. Our system was also used to monitor reactive oxygen species released from neutrophils, which play an important role in the immune system, defending against viral and bacterial infections. The quenching of ECL imaging by catalase reaction localized in the multichamber electrode using the electrogenerated substrate was examined as a potential candidate for a sensitive reporting system. The substrate was successfully generated at applied potentials between -1 and -0.4 V in multichamber electrodes and the substrate confinement within the chamber was observed within 60 s of generation. The microchamber electrode system demonstrated a detection limit of 90 fM catalase. We also demonstrated a detection limit of 0.1 µM GA in human serum albumin, which is an improvement of about 70 times over colorimetric methods.

Single-Plex Quantitative Assays for the Detection and Quantification of Most Pneumococcal Serotypes

PubMed Central

Chochua, Sopio; Satzke, Catherine; Dunne, Eileen M.; Mulholland, Kim; Klugman, Keith P.

2015-01-01

Streptococcus pneumoniae globally kills more children than any other infectious disease every year. A prerequisite for pneumococcal disease and transmission is colonization of the nasopharynx. While the introduction of pneumococcal conjugate vaccines has reduced the burden of pneumococcal disease, understanding the impact of vaccination on nasopharyngeal colonization has been hampered by the lack of sensitive quantitative methods for the detection of >90 known S. pneumoniae serotypes. In this work, we developed 27 new quantitative (q)PCR reactions and optimized 26 for a total of 53 qPCR reactions targeting pneumococcal serotypes or serogroups, including all vaccine types. Reactions proved to be target-specific with a limit of detection of 2 genome equivalents per reaction. Given the number of probes required for these assays and their unknown shelf-life, the stability of cryopreserved reagents was evaluated. Our studies demonstrate that two-year cryopreserved probes had similar limit of detection as freshly-diluted probes. Moreover, efficiency and limit of detection of 1-month cryopreserved, ready-to-use, qPCR reaction mixtures were similar to those of freshly prepared mixtures. Using these reactions, our proof-of-concept studies utilizing nasopharyngeal samples (N=30) collected from young children detected samples containing ≥2 serotypes/serogroups. Samples colonized by multiple serotypes/serogroups always had a serotype that contributes at least 50% of the pneumococcal load. In addition, a molecular approach called S6-q(PCR)2 was developed and proven to individually detect and quantify epidemiologically-important serogroup 6 strains including 6A, 6B, 6C and 6D. This technology will be useful for epidemiological studies, diagnostic platforms and to study the pneumobiome. PMID:25798884

Resolution enhancement in digital holography by self-extrapolation of holograms.

PubMed

Latychevskaia, Tatiana; Fink, Hans-Werner

2013-03-25

It is generally believed that the resolution in digital holography is limited by the size of the captured holographic record. Here, we present a method to circumvent this limit by self-extrapolating experimental holograms beyond the area that is actually captured. This is done by first padding the surroundings of the hologram and then conducting an iterative reconstruction procedure. The wavefront beyond the experimentally detected area is thus retrieved and the hologram reconstruction shows enhanced resolution. To demonstrate the power of this concept, we apply it to simulated as well as experimental holograms.

Plasmonic gold mushroom arrays with refractive index sensing figures of merit approaching the theoretical limit

NASA Astrophysics Data System (ADS)

Shen, Yang; Zhou, Jianhua; Liu, Tianran; Tao, Yuting; Jiang, Ruibin; Liu, Mingxuan; Xiao, Guohui; Zhu, Jinhao; Zhou, Zhang-Kai; Wang, Xuehua; Jin, Chongjun; Wang, Jianfang

2013-08-01

Localized surface plasmon resonance (LSPR)-based sensing has found wide applications in medical diagnosis, food safety regulation and environmental monitoring. Compared with commercial propagating surface plasmon resonance (PSPR)-based sensors, LSPR ones are simple, cost-effective and suitable for measuring local refractive index changes. However, the figure of merit (FOM) values of LSPR sensors are generally 1-2 orders of magnitude smaller than those of PSPR ones, preventing the widespread use of LSPR sensors. Here we describe an array of submicrometer gold mushrooms with a FOM reaching ~108, which is comparable to the theoretically predicted upper limit for standard PSPR sensors. Such a high FOM arises from the interference between Wood’s anomaly and the LSPRs. We further demonstrate the array as a biosensor for detecting cytochrome c and alpha-fetoprotein, with their detection limits down to 200 pM and 15 ng ml-1, respectively, suggesting that the array is a promising candidate for label-free biomedical sensing.

Turn-on fluorescence sensor based on single-walled-carbon-nanohorn-peptide complex for the detection of thrombin.

PubMed

Zhu, Shuyun; Liu, Zhongyuan; Hu, Lianzhe; Yuan, Yali; Xu, Guobao

2012-12-14

Proteases play a central role in several widespread diseases. Thus, there is a great need for the fast and sensitive detection of various proteolytic enzymes. Herein, we have developed a carbon nanotube (CNT)-based protease biosensing platform that uses peptides as a fluorescence probe for the first time. Single-walled carbon nanohorns (SWCNHs) and thrombin were used to demonstrate this detection strategy. SWCNHs can adsorb a fluorescein-based dye (FAM)-labeled peptide (FAM-pep) and quench the fluorescence of FAM. In contrast, thrombin can cleave FAM-pep on SWCNHs and recover the fluorescence of FAM, which allows the sensitive detection of thrombin. This biosensor has a high sensitivity and selectivity toward thrombin, with a detection limit of 100 pM. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Detection of feline coronavirus using microcantilever sensors

NASA Astrophysics Data System (ADS)

Velanki, Sreepriya; Ji, Hai-Feng

2006-11-01

This work demonstrated the feasibility of detecting severe acute respiratory syndrome associated coronavirus (SARS-CoV) using microcantilever technology by showing that the feline coronavirus (FIP) type I virus can be detected by a microcantilever modified by feline coronavirus (FIP) type I anti-viral antiserum. A microcantilever modified by FIP type I anti-viral antiserum was developed for the detection of FIP type I virus. When the FIP type I virus positive sample is injected into the fluid cell where the microcantilever is held, the microcantilever bends upon the recognition of the FIP type I virus by the antiserum on the surface of the microcantilever. A negative control sample that does not contain FIP type I virus did not cause any bending of the microcantilever. The detection limit of the sensor was 0.1 µg ml-1 when the assay time was <1 h.

Strategically functionalized carbon nanotubes as the ultrasensitive electrochemical probe for picomolar detection of sildenafil citrate (Viagra).

PubMed

Gopalan, Anantha Iyengar; Lee, Kwang Pill; Komathi, Shanmugasundaram

2011-02-15

The present work demonstrates the utility of the functionalized carbon nanotubes, poly(4-aminobenzene sulfonic acid) (PABS) grafted multiwalled carbon nanotubes, MWNT-g-PABS, as an electrode modifier towards achieving ultrasensitive detection of a model drug, sildenafil citrate (SC). PABS units in MWNT-g-PABS interact with SC, pre-concentrate and accumulate at the surface. The electron transduction from SC to electrode is augmented via MWNT-g-PABS. As a result, the MWNT-g-PABS modified electrode exhibited ultrasensitive (57.7 μA/nM) and selective detection of SC with a detection limit of 4.7 pM. The present work provides scope towards targeting ultrasensitivity for the detection of biomolecules/drug through rational design and incorporation of appropriate chemical components to carbon nanotubes. Copyright © 2010 Elsevier B.V. All rights reserved.

Low-Complexity Noncoherent Signal Detection for Nanoscale Molecular Communications.

PubMed

Li, Bin; Sun, Mengwei; Wang, Siyi; Guo, Weisi; Zhao, Chenglin

2016-01-01

Nanoscale molecular communication is a viable way of exchanging information between nanomachines. In this investigation, a low-complexity and noncoherent signal detection technique is proposed to mitigate the inter-symbol-interference (ISI) and additive noise. In contrast to existing coherent detection methods of high complexity, the proposed noncoherent signal detector is more practical when the channel conditions are hard to acquire accurately or hidden from the receiver. The proposed scheme employs the molecular concentration difference to detect the ISI corrupted signals and we demonstrate that it can suppress the ISI effectively. The difference in molecular concentration is a stable characteristic, irrespective of the diffusion channel conditions. In terms of complexity, by excluding matrix operations or likelihood calculations, the new detection scheme is particularly suitable for nanoscale molecular communication systems with a small energy budget or limited computation resource.

Evanescent Properties of Optical Diffraction from 2-Dimensional Hexagonal Photonic Crystals and Their Sensor Applications.

PubMed

Liao, Yu-Yang; Chen, Yung-Tsan; Chen, Chien-Chun; Huang, Jian-Jang

2018-04-03

The sensitivity of traditional diffraction grating sensors is limited by the spatial resolution of the measurement setup. Thus, a large space is required to improve sensor performance. Here, we demonstrate a compact hexagonal photonic crystal (PhC) optical sensor with high sensitivity. PhCs are able to diffract optical beams to various angles in azimuthal space. The critical wavelength that satisfies the phase matching or becomes evanescent was used to benchmark the refractive index of a target analyte applied on a PhC sensor. Using a glucose solution as an example, our sensor demonstrated very high sensitivity and a low limit of detection. This shows that the diffraction mechanism of hexagonal photonic crystals can be used for sensors when compact size is a concern.

Synergistic electron transfer effect-based signal amplification strategy for the ultrasensitive detection of dopamine.

PubMed

Lu, Qiujun; Chen, Xiaogen; Liu, Dan; Wu, Cuiyan; Liu, Meiling; Li, Haitao; Zhang, Youyu; Yao, Shouzhuo

2018-05-15

The selective and sensitive detection of dopamine (DA) is of great significance for the identification of schizophrenia, Huntington's disease, and Parkinson's disease from the perspective of molecular diagnostics. So far, most of DA fluorescence sensors are based on the electron transfer from the fluorescence nanomaterials to DA-quinone. However, the limited electron transfer ability of the DA-quinone affects the level of detection sensitivity of these sensors. In this work, based on the DA can reduce Ag + into AgNPs followed by oxidized to DA-quinone, we developed a novel silicon nanoparticles-based electron transfer fluorescent sensor for the detection of DA. As electron transfer acceptor, the AgNPs and DA-quinone can quench the fluorescence of silicon nanoparticles effectively through the synergistic electron transfer effect. Compared with traditional fluorescence DA sensors, the proposed synergistic electron transfer-based sensor improves the detection sensitivity to a great extent (at least 10-fold improvement). The proposed sensor shows a low detection limit of DA, which is as low as 0.1 nM under the optimal conditions. This sensor has potential applicability for the detection of DA in practical sample. This work has been demonstrated to contribute to a substantial improvement in the sensitivity of the sensors. It also gives new insight into design electron transfer-based sensors. Copyright © 2018. Published by Elsevier B.V.

Mass-tag enhanced immuno-laser desorption/ionization mass spectrometry for sensitive detection of intact protein antigens.

PubMed

Lorey, Martina; Adler, Belinda; Yan, Hong; Soliymani, Rabah; Ekström, Simon; Yli-Kauhaluoma, Jari; Laurell, Thomas; Baumann, Marc

2015-05-19

A new read-out method for antibody arrays using laser desorption/ionization-mass spectrometry (LDI-MS) is presented. Small, photocleavable reporter molecules with a defined mass called "mass-tags" are used for detection of immunocaptured proteins from human plasma. Using prostate specific antigen (PSA), a biomarker for prostate cancer, as a model antigen, a high sensitivity generic detection methodology based immunocapture with a primary antibody and with a biotin labeled secondary antibody coupled to mass-tagged avidin is demonstrated. As each secondary antibody can bind several avidin molecules, each having a large number of mass-tags, signal amplification can be achieved. The developed PSA sandwich mass-tag analysis method provided a limit of detection below 200 pg/mL (6 pM) for a 10 μL plasma sample, well below the clinically relevant cutoff value of 3-4 ng/mL. This brings the limit of detection (LOD) for detection of intact antigens with matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) down to levels comparable to capture by anti-peptide antibodies selected reaction monitoring (SISCAPA SRM) and enzyme linked immunosorbent assay (ELISA), as 6 pM corresponds to a maximal amount of 60 amol PSA captured on-spot. We propose the potential use of LDI (laser desorption/ionization) with mass-tag read-out implemented in a sandwich assay format for low abundant and/or early disease biomarker detection.

Simultaneous Detection of Dopamine and Uric Acid Using a Poly(l-lysine)/Graphene Oxide Modified Electrode

PubMed Central

Zhang, Yuehua; Lei, Wu; Xu, Yujuan; Xia, Xifeng; Hao, Qingli

2016-01-01

A novel, simple and selective electrochemical method was investigated for the simultaneous detection of dopamine (DA) and uric acid (UA) on a poly(l-lysine)/graphene oxide (GO) modified glassy carbon electrode (PLL/GO/GCE) by differential pulse voltammetry (DPV). The electrochemically prepared PLL/GO sensory platform toward the oxidation of UA and DA exhibited several advantages, including high effective surface area, more active sites and enhanced electrochemical activity. Compared to the PLL-modified GCE (PLL/GCE), GO-modified GCE and bare GCE, the PLL/GO/GCE exhibited an increase in the anodic potential difference and a remarkable enhancement in the current responses for both UA and DA. For the simultaneous detection of DA and UA, the detection limits of 0.021 and 0.074 μM were obtained, while 0.031 and 0.018 μM were obtained as the detection limits for the selective detection of UA and DA, using DPV in the linear concentration ranges of 0.5 to 20.0 and 0.5 to 35 μM, respectively. In addition, the PLL/GO/GCE demonstrated good reproducibility, long-term stability, excellent selectivity and negligible interference of ascorbic acid (AA). The proposed modified electrode was successfully implemented in the simultaneous detection of DA and UA in human blood serum, urine and dopamine hydrochloride injection with satisfactory results. PMID:28335305

Label-free virus detection using silicon photonic microring resonators.

PubMed

McClellan, Melinda S; Domier, Leslie L; Bailey, Ryan C

2012-01-15

Viruses represent a continual threat to humans through a number of mechanisms, which include disease, bioterrorism, and destruction of both plant and animal food resources. Many contemporary techniques used for the detection of viruses and viral infections suffer from limitations such as the need for extensive sample preparation or the lengthy window between infection and measurable immune response, for serological methods. In order to develop a method that is fast, cost-effective, and features reduced sample preparation compared to many other virus detection methods, we report the application of silicon photonic microring resonators for the direct, label-free detection of intact viruses in both purified samples as well as in a complex, real-world analytical matrix. As a model system, we demonstrate the quantitative detection of Bean pod mottle virus, a pathogen of great agricultural importance, with a limit of detection of 10 ng/mL. By simply grinding a small amount of leaf sample in buffer with a mortar and pestle, infected leaves can be identified over a healthy control with a total analysis time of less than 45 min. Given the inherent scalability and multiplexing capability of the semiconductor-based technology, we feel that silicon photonic microring resonators are well-positioned as a promising analytical tool for a number of viral detection applications. Copyright © 2011 Elsevier B.V. All rights reserved.

Development of a quantitative fluorescence single primer isothermal amplification-based method for the detection of Salmonella.

PubMed

Wang, Jianchang; Li, Rui; Hu, Lianxia; Sun, Xiaoxia; Wang, Jinfeng; Li, Jing

2016-02-16

Food-borne disease caused by Salmonella has long been, and continues to be, an important global public health problem, necessitating rapid and accurate detection of Salmonella in food. Real time PCR is the most recently developed approach for Salmonella detection. Single primer isothermal amplification (SPIA), a novel gene amplification technique, has emerged as an attractive microbiological testing method. SPIA is performed under a constant temperature, eliminating the need for an expensive thermo-cycler. In addition, SPIA reactions can be accomplished in 30 min, faster than real time PCR that usually takes over 2h. We developed a quantitative fluorescence SPIA-based method for the detection of Salmonella. Using Salmonella Typhimurium genomic DNA as template and a primer targeting Salmonella invA gene, we showed the detection limit of SPIA was 2.0 × 10(1)fg DNA. Its successful amplification of different serotypic Salmonella genomic DNA but not non-Salmonella bacterial DNA demonstrated the specificity of SPIA. Furthermore, this method was validated with artificially contaminated beef. In conclusion, we showed high sensitivity and specificity of SPIA in the detection of Salmonella, comparable to real time PCR. In addition, SPIA is faster and more cost-effective (non-use of expensive cyclers), making it a potential alternative for field detection of Salmonella in resource-limited settings that are commonly encountered in developing countries. Copyright © 2015 Elsevier B.V. All rights reserved.

Novel Carbon Dioxide Microsensor Based on Tin Oxide Nanomaterial Doped With Copper Oxide

NASA Technical Reports Server (NTRS)

Xu, Jennifer C.; Hunter, Gary W.; Lukco, Dorothy; Liu, Chung-Chiun; Ward, Benjamin J.

2008-01-01

Carbon dioxide (CO2) is one of the major indicators of fire and therefore its measurement is very important for low-false-alarm fire detection and emissions monitoring. However, only a limited number of CO2 sensing materials exist due to the high chemical stability of CO2. In this work, a novel CO2 microsensor based on nanocrystalline tin oxide (SnO2) doped with copper oxide (CuO) has been successfully demonstrated. The CuO-SnO2 based CO2 microsensors are fabricated by means of microelectromechanical systems (MEMS) technology and sol-gel nanomaterial-synthesis processes. At a doping level of CuO: SnO2 = 1:8 (molar ratio), the resistance of the sensor has a linear response to CO2 concentrations for the range of 1 to 4 percent CO2 in air at 450 C. This approach has demonstrated the use of SnO2, typically used for the detection of reducing gases, in the detection of an oxidizing gas.

Polymeric Flexible Immunosensor Based on Piezoresistive Micro-Cantilever with PEDOT/PSS Conductive Layer.

PubMed

Zhao, Rui; Sun, Ying

2018-02-03

In this paper, a fully polymeric micro-cantilever with the surface passivation layer of parylene-C and the strain resistor of poly(3,4-ethylenedioxythiophene)/poly (styrene sulfonate) (PEDOT/PSS) was proposed and demonstrated for immunoassays. By optimizing the design and fabrication of the polymeric micro-cantilever, a square resistance of 220 Ω/□ for PEDOT/PSS conductive layer have been obtained. The experimental spring constant and the deflection sensitivity were measured to be 0.017 N/m and 8.59 × 10 -7 nm -1 , respectively. The biological sensing performances of polymeric micro-cantilever were investigated by the immunoassay for human immunoglobulin G (IgG). The immunosensor was experimentally demonstrated to have a linear behavior for the detection of IgG within the concentrations of 10~100 ng/mL with a limit of detection (LOD) of 10 ng/mL. The experimental results indicate that the proposed polymeric flexible conductive layer-based sensors are capable of detecting trace biological substances.

Fast two-photon imaging of subcellular voltage dynamics in neuronal tissue with genetically encoded indicators.

PubMed

Chamberland, Simon; Yang, Helen H; Pan, Michael M; Evans, Stephen W; Guan, Sihui; Chavarha, Mariya; Yang, Ying; Salesse, Charleen; Wu, Haodi; Wu, Joseph C; Clandinin, Thomas R; Toth, Katalin; Lin, Michael Z; St-Pierre, François

2017-07-27

Monitoring voltage dynamics in defined neurons deep in the brain is critical for unraveling the function of neuronal circuits but is challenging due to the limited performance of existing tools. In particular, while genetically encoded voltage indicators have shown promise for optical detection of voltage transients, many indicators exhibit low sensitivity when imaged under two-photon illumination. Previous studies thus fell short of visualizing voltage dynamics in individual neurons in single trials. Here, we report ASAP2s, a novel voltage indicator with improved sensitivity. By imaging ASAP2s using random-access multi-photon microscopy, we demonstrate robust single-trial detection of action potentials in organotypic slice cultures. We also show that ASAP2s enables two-photon imaging of graded potentials in organotypic slice cultures and in Drosophila . These results demonstrate that the combination of ASAP2s and fast two-photon imaging methods enables detection of neural electrical activity with subcellular spatial resolution and millisecond-timescale precision.

Polymeric Flexible Immunosensor Based on Piezoresistive Micro-Cantilever with PEDOT/PSS Conductive Layer

PubMed Central

Sun, Ying

2018-01-01

In this paper, a fully polymeric micro-cantilever with the surface passivation layer of parylene-C and the strain resistor of poly(3,4-ethylenedioxythiophene)/poly (styrene sulfonate) (PEDOT/PSS) was proposed and demonstrated for immunoassays. By optimizing the design and fabrication of the polymeric micro-cantilever, a square resistance of 220 Ω/□ for PEDOT/PSS conductive layer have been obtained. The experimental spring constant and the deflection sensitivity were measured to be 0.017 N/m and 8.59 × 10−7 nm−1, respectively. The biological sensing performances of polymeric micro-cantilever were investigated by the immunoassay for human immunoglobulin G (IgG). The immunosensor was experimentally demonstrated to have a linear behavior for the detection of IgG within the concentrations of 10~100 ng/mL with a limit of detection (LOD) of 10 ng/mL. The experimental results indicate that the proposed polymeric flexible conductive layer-based sensors are capable of detecting trace biological substances. PMID:29401669

Analysis of the penetration of a caffeine containing shampoo into the hair follicles by in vivo laser scanning microscopy

NASA Astrophysics Data System (ADS)

Lademann, J.; Richter, H.; Schanzer, S.; Klenk, A.; Sterry, W.; Patzelt, A.

2010-02-01

In previous in vitro investigations, it was demonstrated that caffeine is able to stimulate the hair growth. Therefore, a penetration of caffeine into the hair follicle is necessary. In the present study, in vivo laser scanning microscopy (LSM) was used to investigate the penetration and storage of a caffeine containing shampoo into the hair follicles. It was shown that a 2-min contact time of the shampoo with the skin was enough to accumulate significant parts of the shampoo in the hair follicles. A penetration of the shampoo up to a depth of approx. 200 μm could be detected, which represents the detection limit of the LSM. At this depth, the close network of the blood capillaries surrounding the hair follicles commences. Even after 24 h, the substance was still detectable in the hair follicles. This demonstrates the long-term reservoir function of the hair follicles for topically applied substances such as caffeine.

Metal-organic gel enhanced fluorescence anisotropy for sensitive detection of prostate specific antigen

NASA Astrophysics Data System (ADS)

Zhao, Ting Ting; Peng, Zhe Wei; Yuan, Dan; Zhen, Shu Jun; Huang, Cheng Zhi; Li, Yuan Fang

2018-03-01

In this contribution, we demonstrated that Cu-based metal-organic gel (Cu-MOG) was able to serve as a novel amplification platform for fluorescence anisotropy (FA) assay for the first time, which was confirmed by the sensitive detection of a common cancer biomarker, prostate specific antigen (PSA). The dye-labeled probe aptamer (PA) product was adsorbed onto the benzimidazole derivative-containing Cu-MOG via electrostatic incorporation and strong π-π stacking interactions, which significantly increased the FA value due to the enlargement of the molecular volume of the PA/Cu-MOG complex. With the introduction of target PSA, the FA value was obviously decreased on account of the specific recognition between PSA and PA which resulted in the detachment of PA from the surface of MOG. The linear range was from 0.5-8 ng/mL, with a detection limit of 0.33 ng/mL. Our work has thus helped to demonstrate promising application of MOG material in the fields of biomolecules analysis and disease diagnosis.

Detection of foreign body using fast thermoacoustic tomography with a multielement linear transducer array

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nie Liming; Xing Da; Yang Diwu

2007-04-23

Current imaging modalities face challenges in clinical applications due to limitations in resolution or contrast. Microwave-induced thermoacoustic imaging may provide a complementary modality for medical imaging, particularly for detecting foreign objects due to their different absorption of electromagnetic radiation at specific frequencies. A thermoacoustic tomography system with a multielement linear transducer array was developed and used to detect foreign objects in tissue. Radiography and thermoacoustic images of objects with different electromagnetic properties, including glass, sand, and iron, were compared. The authors' results demonstrate that thermoacoustic imaging has the potential to become a fast method for surgical localization of occult foreignmore » objects.« less

UV plasmonic device for sensing ethanol and acetone

NASA Astrophysics Data System (ADS)

Honda, Mitsuhiro; Ichikawa, Yo; Rozhin, Alex G.; Kulinich, Sergei A.

2018-01-01

In the present study, we demonstrate efficient detection of volatile organic vapors with improved sensitivity, exploiting the localized surface plasmon resonance of indium nanograins in the UV range (UV-LSPR). The sensitivity of deep-UV-LSPR measurements toward ethanol was observed to be 0.004 nm/ppm, which is 10 times higher than that of a previously reported visible-LSPR device based on Ag nanoprisms [Sensors 11, 8643 (2011)]. Although practical issues such as improving detection limits are still remaining, the results of the present study suggest that the new approach based on UV-LSPR may open new avenues to the detection of organic molecules in solid, liquid, and gas phases using plasmonic sensors.

Rapid synthesis of N, S co-doped carbon dots and their application for Fe3+ ion detection

NASA Astrophysics Data System (ADS)

Zhang, Jian; Wang, Junbin; Fu, Jinping; Fu, Xucheng; Gan, Wei; Hao, Hequn

2018-02-01

In this study, nitrogen and sulfur co-doped carbon dots (NSCDs) were fabricated by microwave-assisted one-pot synthesis using vitamin C and thiourea as precursors. The as-prepared NSCDs demonstrated excellent properties, including aqueous dispensability, strong fluorescence emission, excellent environmental stability, high selectivity, and sensitivity toward Fe3+ ions. The NSCD-based material can be used as a "turn off" fluorescent probe for detecting Fe3+ ions at a low detection limit (4.2 nM). In addition, the "turn off" and "turn on" of NSCD fluorescent probe could be modulated by adding Fe3+ and EDTA, indicating weak interaction between the Fe3+ ions and NSCDs.

Stand-off detection of trace explosives by infrared photothermal imaging

NASA Astrophysics Data System (ADS)

Papantonakis, Michael R.; Kendziora, Chris; Furstenberg, Robert; Stepnowski, Stanley V.; Rake, Matthew; Stepnowski, Jennifer; McGill, R. Andrew

2009-05-01

We have developed a technique for the stand-off detection of trace explosives using infrared photothermal imaging. In this approach, infrared quantum cascade lasers tuned to strong vibrational absorption bands of the explosive particles illuminate a surface of interest, preferentially heating the explosives material. An infrared focal plane array is used to image the surface and detect a small increase in the thermal intensity upon laser illumination. We have demonstrated the technique using TNT and RDX residues at several meters of stand-off distance under laboratory conditions, while operating the lasers below the eye-safe intensity limit. Sensitivity to explosives traces as small as a single grain (~100 ng) of TNT has been demonstrated using an uncooled bolometer array. We show the viability of this approach on a variety of surfaces which transmit, reflect or absorb the infrared laser light and have a range of thermal conductivities. By varying the incident wavelength slightly, we demonstrate selectivity between TNT and RDX. Using a sequence of lasers at different wavelengths, we increase both sensitivity and selectivity while reducing the false alarm rate. At higher energy levels we also show it is possible to generate vapor from solid materials with inherently low vapor pressures.

Proposed biomimetic molecular sensor array for astrobiology applications

NASA Astrophysics Data System (ADS)

Cullen, D. C.; Grant, W. D.; Piletsky, S.; Sims, M. R.

2001-08-01

A key objective of future astrobiology lander missions, e.g. to Mars and Europa, is the detection of biomarkers - molecules whose presence indicates the existence of either current or extinct life. To address limitations of current analytical methods for biomarker detection, we describe the methodology of a new project for demonstration of a robust molecular-recognition sensor array for astrobiology biomarkers. The sensor array will be realised by assembling components that have been demonstrated individually in previous or current research projects. The major components are (1) robust artificial molecular receptors comprised of molecular imprinted polymer (MIP) recognition systems and (2) a sensor array comprised of both optical and electrochemical sensor elements. These components will be integrated together using ink-jet printing technology coupled with in situ photo-polymerisation of MIPs. For demonstration, four model biomarkers are chosen as targets and represent various classes of potential biomarkers. Objectives of the proposed work include (1) demonstration of practical proof-of-concept, (2) identify areas for further development and (3) provide performance and design data for follow-up projects leading to astrobiology missions.

"Paper Machine" for Molecular Diagnostics.

PubMed

Connelly, John T; Rolland, Jason P; Whitesides, George M

2015-08-04

Clinical tests based on primer-initiated amplification of specific nucleic acid sequences achieve high levels of sensitivity and specificity. Despite these desirable characteristics, these tests have not reached their full potential because their complexity and expense limit their usefulness to centralized laboratories. This paper describes a device that integrates sample preparation and loop-mediated isothermal amplification (LAMP) with end point detection using a hand-held UV source and camera phone. The prototype device integrates paper microfluidics (to enable fluid handling) and a multilayer structure, or a "paper machine", that allows a central patterned paper strip to slide in and out of fluidic path and thus allows introduction of sample, wash buffers, amplification master mix, and detection reagents with minimal pipetting, in a hand-held, disposable device intended for point-of-care use in resource-limited environments. This device creates a dynamic seal that prevents evaporation during incubation at 65 °C for 1 h. This interval is sufficient to allow a LAMP reaction for the Escherichia coli malB gene to proceed with an analytical sensitivity of 1 double-stranded DNA target copy. Starting with human plasma spiked with whole, live E. coli cells, this paper demonstrates full integration of sample preparation with LAMP amplification and end point detection with a limit of detection of 5 cells. Further, it shows that the method used to prepare sample enables concentration of DNA from sample volumes commonly available from fingerstick blood draw.

Detecting Ionising Radiation with Polarised Light

NASA Astrophysics Data System (ADS)

Parsons, Steven

Several groups have demonstrated the potential of the Pockels effect in Cadmium Zinc Telluride (CZT) as a means to detect ionizing radiation. Migrating charge carriers are believed to generate the signal detected via the Pockels effect due to the distortions they create within the electric field, however trapped space charge beneath the cathode has been regularly observed which suggests that the signal amplitude is potentially dominated by a large dose element. In this work, the effects of electric field collapse at the location of charge carrier generation, rather than where space charge builds up, is demonstrated. This confirms the potential to apply the technique for imaging dose rate distributions. Charged coupled device (CCD) images representing the changes in electric field within the crystal were taken and the response to illumination from a collimated 1550 nm 4.5 mW IR laser and irradiation from 150 kVp X-rays measured. The data demonstrates that the signal acquired is a combination of both the local change in the electric field at the location where the carriers are being released/generated and an element caused by them becoming trapped, leading to space charge near the cathode. Whilst the presence of both components has been demonstrated, their time response to an IR pulse measured via a photo-diode is the same (within the 6 ms time limitation of the system). This means that when using a Pockels detection system the average change in field can be considered proportional only to the incident dose rate when working in the millisecond regime. In addition to finding the origins of the detected signal an investigation into the effects of doping a Cadmium Manganese Telluride crystal with vanadium was carried out to see whether the large increases in Pockels constant found in the literature when using doped CZT could be replicated. However, it was found that whilst there is a slight improvement in the constant and hence the sensitivity of the crystals it was not as significant as hoped. A fibre optic Mach-Zehnder interferometer has also been designed and built with the aim of developing further the results from a previous free-space concept demonstrator. In its present condition the effects of environment have been minimised but the detector system struggles with large attenuation losses due to repeated coupling into fibres and is currently not usable, however, increasing the power of the laser and trying to limit even further the free-space elements in the future should remedy this.

Field-Effect Transistor-Integration with TiO2 Nanoparticles for Sensing of Cardiac Troponin I Biomarker.

PubMed

Arshad, M K Md; Adzhri, R; Fathil, M F M; Gopinath, Subash C B; N M, Nuzaihan M

2018-08-01

The development of electrical biosensor towards device miniaturization in order to achieve better sensitivity with enhanced electrical signal has certain limitations especially complexity in fabrication process and costs. In this paper, an alternative technique with minor modification in the device structure is presented for signal amplification by implementing ambipolar conduction in the biosensor itself. We demonstrated the field-effect transistor (FET)-based biosensor coupled back-gate for attaining a higher sensitivity with the detection of lower target abundance. To utilize the coupled back-gate as a pre-amplifier, silicon-on-insulator wafer with thicknesses of top-silicon and buried oxide (BOX) layers of 70 nm and 145 nm, respectively were desired. Titanium dioxide (TiO2) nanomaterial was deposited using sol-gel method on the channel which acts as a transducer. Surface functionalization on TiO2 thin film allowed an effective immobilization of anti-cardiac troponin I antibody to interact cardiac troponin I (cTnI). Binding events at each step was validated by X-ray photoelectron spectroscopy (XPS) analysis. Further, electrical characterization (Id-Vd) confirms the potentiality of FET-based biosensor to detect cTnI (represents acute myocardial infarction disease) with the concentration ranges from 10 μg/ml down to 1 fg/ml. The sensitivity of 459.2 nA (g/ml)-1 and lower detection limit of 1 fg/ml were achieved at Vbg = -5 V and Vd = 5 V. The designed device demonstrates its ability to detect lower level of cTnI with pre-amplified electrical signal by back-gate biasing.

The CHARIS High-Contrast Integral-Field Spectrograph

NASA Technical Reports Server (NTRS)

Groff, Tyler D.; Chilcote, Jeffrey; Brandt, Timothy; Kasdin, N. Jeremy; Galvin, Michael; Loomis, Craig; Rizzo, Maxime; Knapp, Gillian; Guyon, Olivier; Jovanovic, Nemanja;

Detecting Unknown Artificial Urban Surface Materials Based on Spectral Dissimilarity Analysis.

PubMed

Jilge, Marianne; Heiden, Uta; Habermeyer, Martin; Mende, André; Juergens, Carsten

2017-08-08

High resolution imaging spectroscopy data have been recognised as a valuable data resource for augmenting detailed material inventories that serve as input for various urban applications. Image-specific urban spectral libraries are successfully used in urban imaging spectroscopy studies. However, the regional- and sensor-specific transferability of such libraries is limited due to the wide range of different surface materials. With the developed methodology, incomplete urban spectral libraries can be utilised by assuming that unknown surface material spectra are dissimilar to the known spectra in a basic spectral library (BSL). The similarity measure SID-SCA (Spectral Information Divergence-Spectral Correlation Angle) is applied to detect image-specific unknown urban surfaces while avoiding spectral mixtures. These detected unknown materials are categorised into distinct and identifiable material classes based on their spectral and spatial metrics. Experimental results demonstrate a successful redetection of material classes that had been previously erased in order to simulate an incomplete BSL. Additionally, completely new materials e.g., solar panels were identified in the data. It is further shown that the level of incompleteness of the BSL and the defined dissimilarity threshold are decisive for the detection of unknown material classes and the degree of spectral intra-class variability. A detailed accuracy assessment of the pre-classification results, aiming to separate natural and artificial materials, demonstrates spectral confusions between spectrally similar materials utilizing SID-SCA. However, most spectral confusions occur between natural or artificial materials which are not affecting the overall aim. The dissimilarity analysis overcomes the limitations of working with incomplete urban spectral libraries and enables the generation of image-specific training databases.

Rayleigh-wave diffractions due to a void in the layered half space

USGS Publications Warehouse

Xia, J.; Xu, Y.; Miller, R.D.; Nyquist, Jonathan E.

2006-01-01

Void detection is challenging due to the complexity of near-surface materials and the limited resolution of geophysical methods. Although multichannel, high-frequency, surface-wave techniques can provide reliable shear (S)-wave velocities in different geological settings, they are not suitable for detecting voids directly based on anomalies of the S-wave velocity because of limitations on the resolution of S-wave velocity profiles inverted from surface-wave phase velocities. Xia et al. (2006a) derived a Rayleigh-wave diffraction traveltime equation due to a void in the homogeneous half space. Encouraging results of directly detecting a void from Rayleigh-wave diffractions were presented (Xia et al., 2006a). In this paper we used four two-dimensional square voids in the layered half space to demonstrate the feasibility of detecting a void with Rayleigh-wave diffractions. Rayleigh-wave diffractions were recognizable for all these models after removing direct surface waves by F-K filtering. We evaluate the feasibility of applying the Rayleigh-wave diffraction traveltime equation to a void in the layered earth model. The phase velocity of diffracted Rayleigh waves is predominately determined by surrounding materials of a void. The modeling results demonstrate that the Rayleigh-wave diffraction traveltime equation due to a void in the homogeneous half space can be applied to the case of a void in the layered half space. In practice, only two diffraction times are necessary to define the depth to the top of a void and the average velocity of diffracted Rayleigh waves. ?? 2005 Society of Exploration Geophysicists.

Detecting Unknown Artificial Urban Surface Materials Based on Spectral Dissimilarity Analysis

PubMed Central

Jilge, Marianne; Heiden, Uta; Habermeyer, Martin; Mende, André; Juergens, Carsten

2017-01-01

High resolution imaging spectroscopy data have been recognised as a valuable data resource for augmenting detailed material inventories that serve as input for various urban applications. Image-specific urban spectral libraries are successfully used in urban imaging spectroscopy studies. However, the regional- and sensor-specific transferability of such libraries is limited due to the wide range of different surface materials. With the developed methodology, incomplete urban spectral libraries can be utilised by assuming that unknown surface material spectra are dissimilar to the known spectra in a basic spectral library (BSL). The similarity measure SID-SCA (Spectral Information Divergence-Spectral Correlation Angle) is applied to detect image-specific unknown urban surfaces while avoiding spectral mixtures. These detected unknown materials are categorised into distinct and identifiable material classes based on their spectral and spatial metrics. Experimental results demonstrate a successful redetection of material classes that had been previously erased in order to simulate an incomplete BSL. Additionally, completely new materials e.g., solar panels were identified in the data. It is further shown that the level of incompleteness of the BSL and the defined dissimilarity threshold are decisive for the detection of unknown material classes and the degree of spectral intra-class variability. A detailed accuracy assessment of the pre-classification results, aiming to separate natural and artificial materials, demonstrates spectral confusions between spectrally similar materials utilizing SID-SCA. However, most spectral confusions occur between natural or artificial materials which are not affecting the overall aim. The dissimilarity analysis overcomes the limitations of working with incomplete urban spectral libraries and enables the generation of image-specific training databases. PMID:28786947

A new paper-based analytical device for detection of Glucose-6-phosphate dehydrogenase deficiency.

PubMed

Kaewarsa, Phuritat; Laiwattanapaisal, Wanida; Palasuwan, Attakorn; Palasuwan, Duangdao

2017-03-01

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a genetic haemolytic disorder. Most persons with G6PD deficiency are asymptomatic, but exposure to oxidant drugs, such as the anti-malarial drug primaquine, may induce haemolysis, which is commonly found in Asian countries. A reliable test is necessary for diagnosing the deficiency to prevent an acute haemolytic crisis. This study proposes a novel quantitative method to detect G6PD deficiency using paper-based analytical devices (G6PDD-PAD). Wax printing was utilized for fabricating circular reaction zone patterns in paper. The colorimetric assay is based on the formation of formazan via a reduction of tetra-nitro blue tetrazolium (TNBT) by the G6PD enzyme on G6PDD-PAD. Detection was achieved by capturing the colour using a desktop scanner and the colour intensity was analysed with Adobe Photoshop C56. The results showed that the G6PD activity analysed by G6PDD-PAD was highly correlated with the standard biochemical assay (SBA) (r 2 =0.87, p<0.01). Moreover, good agreement by Bland-Altman bias plot was demonstrated between G6PDD-PAD and the SBA (mean bias 1.4 IU/gHb). The detection limit was 0 IU/gHb of G6PD activity. This study demonstrates the feasibility of using G6PDD-PAD. This simple, low-cost test ($0.1/test) should be useful for diagnosing G6PD deficiency in resource-limited settings. Copyright © 2016 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Faidy, C.

Practical applications of the leak-before break concept are presently limited in French Pressurized Water Reactors (PWR) compared to Fast Breeder Reactors. Neithertheless, different fracture mechanic demonstrations have been done on different primary, auxiliary and secondary PWR piping systems based on similar requirements that the American NUREG 1061 specifications. The consequences of the success in different demonstrations are still in discussion to be included in the global safety assessment of the plants, such as the consequences on in-service inspections, leak detection systems, support optimization,.... A large research and development program, realized in different co-operative agreements, completes the general approach.

Pseudo-Random Modulation of a Laser Diode for Generating Ultrasonic Longitudinal Waves

NASA Technical Reports Server (NTRS)

Madaras, Eric I.; Anatasi, Robert F.

2004-01-01

Laser generated ultrasound systems have historically been more complicated and expensive than conventional piezoelectric based systems, and this fact has relegated the acceptance of laser based systems to niche applications for which piezoelectric based systems are less suitable. Lowering system costs, while improving throughput, increasing ultrasound signal levels, and improving signal-to-noise are goals which will help increase the general acceptance of laser based ultrasound. One current limitation with conventional laser generated ultrasound is a material s damage threshold limit. Increasing the optical power to generate more signal eventually damages the material being tested due to rapid, high heating. Generation limitations for laser based ultrasound suggests the use of pulse modulation techniques as an alternate generation method. Pulse modulation techniques can spread the laser energy over time or space, thus reducing laser power densities and minimizing damage. Previous experiments by various organizations using spatial or temporal pulse modulation have been shown to generate detectable surface, plate, and bulk ultrasonic waves with narrow frequency bandwidths . Using narrow frequency bandwidths improved signal detectability, but required the use of expensive and powerful lasers and opto-electronic systems. The use of a laser diode to generate ultrasound is attractive because of its low cost, small size, light weight, simple optics and modulation capability. The use of pulse compression techniques should allow certain types of laser diodes to produce usable ultrasonic signals. The method also does not need to be limited to narrow frequency bandwidths. The method demonstrated here uses a low power laser diode (approximately 150 mW) that is modulated by controlling the diode s drive current and the resulting signal is recovered by cross correlation. A potential application for this system which is briefly demonstrated is in detecting signals in thick composite materials where attenuation is high and signal amplitude and bandwidth are at a premium.

Graphene quantum dots for ultrasensitive detection of acetylcholinesterase and its inhibitors

NASA Astrophysics Data System (ADS)

Li, Nan; Wang, Xuewan; Chen, Jie; Sun, Lei; Chen, Peng

2015-09-01

Graphene quantum dots (GQDs) are emerging zero-dimensional materials promising a wide spectrum of novel applications including development of optical sensors. Herein, a GQD-based fluorometric sensor is devised to detect acetylcholinesterase (AChE, a critical enzyme in central nervous system and neuromuscular junctions) with an ultralow detection limit (0.58 pM with S/N of 5.0), using a photoluminescence ‘turn-off’ mechanism. This simple ‘mix-and-detect’ platform can also be employed to sense a variety of compounds that can directly or indirectly inhibit the enzymatic activities of AChE, such as nerve gases, pesticides, and therapeutic drugs. As the proof-of-concept demonstrations, we show the sensitive detection of paraoxon (a pesticide), tacrine (a drug to treat Alzheimer’s disease), and dopamine (an important neurotransmitter).

Sequence-specific label-free nucleic acid biosensor for the detection of the hepatitis C virus genotype 1a using a disposable pencil graphite electrode.

PubMed

Donmez, Soner; Arslan, Fatma; Arslan, Halit

2016-05-01

In this paper, we demonstrate a simple, sensitive, inexpensive, disposable and label-free electrochemical nucleic acid biosensor for the detection of the hepatitis C virus genotype 1a (HCV1a). The nucleic acid biosensor was designed with the amino-linked inosine-substituted 20-mer probes, which were immobilized onto a disposable pencil graphite electrode (PGE) by covalent linking. The proposed nucleic acid biosensor was linear in the range of 0.05 and 0.75 μM, exhibiting a limit of detection of 54.9 nM. The single-stranded synthetic PCR product analogs of HCV1a were also detected with satisfactory results under optimal conditions, showing the potential application of this biosensor.

A novel assay method for the trace determination of Th and U in copper and lead using inductively coupled plasma mass spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

LaFerriere, Brian D.; Maiti, Tapas C.; Arnquist, Isaac J.

2015-03-01

This study describes a novel sample preparation and assay method developed in support of the MAJORANA DEMONSTRATOR experiment for the determination of thorium and uranium levels in copper and lead shielding components. Meticulously clean sample preparation methods combined with novel anion exchange separations for analyte pre-concentration and matrix removal were developed. Quantification was performed by inductively coupled plasma mass spectrometry. Detection limits of 0.0084 pg 232Th/g and 0.0106 pg 238U/g were determined for copper, while detection limits of 0.23 pg 232Th/g and 0.46 pg 238U/g were achieved for lead. These methods allow the Majorana Collaboration to accurately assay detector componentsmore » and ensure that the experiment’s stringent radiopurity requirements are met.« less

Undoing measurement-induced dephasing in circuit QED

NASA Astrophysics Data System (ADS)

Frisk Kockum, A.; Tornberg, L.; Johansson, G.

2012-05-01

We analyze the backaction of homodyne detection and photodetection on superconducting qubits in circuit quantum electrodynamics. Although both measurement schemes give rise to backaction in the form of stochastic phase rotations, which leads to dephasing, we show that this can be perfectly undone provided that the measurement signal is fully accounted for. This result improves on an earlier one [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.82.012329 82, 012329 (2010)], showing that the method suggested can be made to realize a perfect two-qubit parity measurement. We propose a benchmarking experiment on a single qubit to demonstrate the method using homodyne detection. By analyzing the limited measurement efficiency of the detector and bandwidth of the amplifier, we show that the parameter values necessary to see the effect are within the limits of existing technology.

Double-Paddle Oscillators as Probes of Quantum Turbulence in the Zero Temperature Limit

NASA Astrophysics Data System (ADS)

Schmoranzer, David; Jackson, Martin; Zemma, Elisa; Luzuriaga, Javier

2017-06-01

We present a technical report on our tests of a double-paddle oscillator as a detector of quantum turbulence in superfluid 4He at low temperatures ranging from 20 to 1100 mK. The device, known to operate well in the two-fluid regime (Zemma and Luzuriaga in J Low Temp Phys 166:171-181, 2012), is also capable of detecting quantum turbulence in the zero temperature limit. The oscillator demonstrated Lorentzian responses with quality factors of order 10^5 in vacuum, and displayed negative-Duffing resonances in liquid, even at moderate drives. In superfluid He-II at low temperatures, its sensitivity was adversely affected by acoustic damping at higher harmonics. While it successfully created and detected the quantum turbulence, its overall performance does not compare favourably with other oscillators such as tuning forks.

Analytical and clinical performance characteristics of the Abbott RealTime MTB RIF/INH Resistance, an assay for the detection of rifampicin and isoniazid resistant Mycobacterium tuberculosis in pulmonary specimens.

PubMed

Kostera, Joshua; Leckie, Gregor; Tang, Ning; Lampinen, John; Szostak, Magdalena; Abravaya, Klara; Wang, Hong

2016-12-01

Clinical management of drug-resistant tuberculosis patients continues to present significant challenges to global health. To tackle these challenges, the Abbott RealTime MTB RIF/INH Resistance assay was developed to accelerate the diagnosis of rifampicin and/or isoniazid resistant tuberculosis to within a day. This article summarizes the performance of the Abbott RealTime MTB RIF/INH Resistance assay; including reliability, analytical sensitivity, and clinical sensitivity/specificity as compared to Cepheid GeneXpert MTB/RIF version 1.0 and Hain MTBDRplus version 2.0. The limit of detection (LOD) of the Abbott RealTime MTB RIF/INH Resistance assay was determined to be 32 colony forming units/milliliter (cfu/mL) using the Mycobacterium tuberculosis (MTB) strain H37Rv cell line. For rifampicin resistance detection, the Abbott RealTime MTB RIF/INH Resistance assay demonstrated statistically equivalent clinical sensitivity and specificity as compared to Cepheid GeneXpert MTB/RIF. For isoniazid resistance detection, the assay demonstrated statistically equivalent clinical sensitivity and specificity as compared to Hain MTBDRplus. The performance data presented herein demonstrate that the Abbott RealTime MTB RIF/INH Resistance assay is a sensitive, robust, and reliable test for realtime simultaneous detection of first line anti-tuberculosis antibiotics rifampicin and isoniazid in patient specimens. Copyright © 2016 The Author. Published by Elsevier Ltd.. All rights reserved.

Diffusion of Antimicrobials Across Silicone Hydrogel Contact Lenses

PubMed Central

Zambelli, Alison M.; Brothers, Kimberly M.; Hunt, Kristin M.; Romanowski, Eric G.; Nau, Amy C.; Dhaliwal, Deepinder K.; Shanks, Robert M. Q.

2014-01-01

Objectives To measure the diffusion of topical preparations of moxifloxacin, amphotericin B (AmB), and polyhexamethylene biguanide (PHMB) through silicone hydrogel (SH) contact lenses in vitro. Methods Using an in vitro model, the diffusion of three antimicrobials through SH contact lenses was measured. Diffused compounds were measured using a spectrophotometer at set time points over a period of four hours. The amount of each diffused antimicrobial was determined by comparing the experimental value to a standard curve. A biological assay was performed to validate the contact lens diffusion assay by testing antimicrobial activity of diffused material against lawns of susceptible bacteria (Staphylococcus epidermidis) and yeast (Saccharomyces cerevisiae). Experiments were repeated at least two times with a total of at least 4 independent replicates. Results Our data show detectable moxifloxacin and PHMB diffusion through SH contact lenses at 30 minutes, while amphotericin B diffusion remained below the limit of detection within the 4 hour experimental period. In the biological assay, diffused moxifloxacin demonstrated microbial killing starting at 20 minutes on bacterial lawns, whereas PHMB and amphotericin B failed to demonstrate killing on microbial lawns over the course of the 60 minute experiment. Conclusions In vitro diffusion assays demonstrate limited penetration of certain anti-infective agents through silicone hydrogel contact lenses. Further studies regarding the clinical benefit of using these agents along with bandage contact lens use for corneal pathology are warranted. PMID:25806673

Design and operation of a portable scanner for high performance microchip capillary array electrophoresis.

PubMed

Scherer, James R; Liu, Peng; Mathies, Richard A

2010-11-01

We have developed a compact, laser-induced fluorescence detection scanner, the multichannel capillary array electrophoresis portable scanner (McCAEPs) as a platform for electrophoretic detection and control of high-throughput, integrated microfluidic devices for genetic and other analyses. The instrument contains a confocal optical system with a rotary objective for detecting four different fluorescence signals, a pneumatic system consisting of two pressure/vacuum pumps and 28 individual addressable solenoid valves for control of on-chip microvalves and micropumps, four Polymerase Chain Reaction (PCR) temperature control systems, and four high voltage power supplies for electrophoresis. The detection limit of the instrument is ~20 pM for on-chip capillary electrophoresis of fluorescein dyes. To demonstrate the system performance for forensic short tandem repeat (STR) analysis, two experiments were conducted: (i) electrophoretic separation and detection of STR samples on a 96-lane microfabricated capillary array electrophoresis microchip. Fully resolved PowerPlex(®) 16 STR profiles amplified from 1 ng of 9947A female standard DNA were successfully obtained; (ii) nine-plex STR amplification, sample injection, separation, and fluorescence detection of 100-copy 9948 male standard DNA in a single integrated PCR- capillary electrophoresis microchip. These results demonstrate that the McCAEPs can be used as a versatile control and detection instrument that operates integrated microfluidic devices for high-performance forensic human identification.

Design and operation of a portable scanner for high performance microchip capillary array electrophoresis

NASA Astrophysics Data System (ADS)

Scherer, James R.; Liu, Peng; Mathies, Richard A.

2010-11-01

We have developed a compact, laser-induced fluorescence detection scanner, the multichannel capillary array electrophoresis portable scanner (McCAEPs) as a platform for electrophoretic detection and control of high-throughput, integrated microfluidic devices for genetic and other analyses. The instrument contains a confocal optical system with a rotary objective for detecting four different fluorescence signals, a pneumatic system consisting of two pressure/vacuum pumps and 28 individual addressable solenoid valves for control of on-chip microvalves and micropumps, four Polymerase Chain Reaction (PCR) temperature control systems, and four high voltage power supplies for electrophoresis. The detection limit of the instrument is ˜20 pM for on-chip capillary electrophoresis of fluorescein dyes. To demonstrate the system performance for forensic short tandem repeat (STR) analysis, two experiments were conducted: (i) electrophoretic separation and detection of STR samples on a 96-lane microfabricated capillary array electrophoresis microchip. Fully resolved PowerPlex® 16 STR profiles amplified from 1 ng of 9947A female standard DNA were successfully obtained; (ii) nine-plex STR amplification, sample injection, separation, and fluorescence detection of 100-copy 9948 male standard DNA in a single integrated PCR- capillary electrophoresis microchip. These results demonstrate that the McCAEPs can be used as a versatile control and detection instrument that operates integrated microfluidic devices for high-performance forensic human identification.

Demonstration of a portable near-infrared CH4 detection sensor based on tunable diode laser absorption spectroscopy

NASA Astrophysics Data System (ADS)

Zheng, Chuan-Tao; Huang, Jian-Qiang; Ye, Wei-Lin; Lv, Mo; Dang, Jing-Min; Cao, Tian-Shu; Chen, Chen; Wang, Yi-Ding

2013-11-01

A portable near-infrared (NIR) CH4 detection sensor based on a distributed feedback (DFB) laser modulated at 1.654 μm is experimentally demonstrated. Intelligent temperature controller with an accuracy of -0.07 to +0.09 °C as well as a scan and modulation module generating saw-wave and cosine-wave signals are developed to drive the DFB laser, and a cost effective lock-in amplifier used to extract the second harmonic signal is integrated. Thorough experiments are carried out to obtain detection performances, including detection range, accuracy, stability and the minimum detection limit (MDL). Measurement results show that the absolute detection error relative to the standard value is less than 7% within the range of 0-100%, and the MDL is estimated to be about 11 ppm under an absorption length of 0.2 m and a noise level of 2 mVpp. Twenty-four hours monitoring on two gas samples (0.1% and 20%) indicates that the absolute errors are less than 7% and 2.5%, respectively, suggesting good long term stability. The sensor reveals competitive characteristics compared with other reported portable or handheld sensors. The developed sensor can also be used for the detection of other gases by adopting other DFB lasers with different center-wavelength using the same hardware and slightly modified software.

An optimized microfabricated platform for the optical generation and detection of hyperpolarized 129Xe

PubMed Central

Kennedy, Daniel J.; Seltzer, Scott J.; Jiménez-Martínez, Ricardo; Ring, Hattie L.; Malecek, Nicolas S.; Knappe, Svenja; Donley, Elizabeth A.; Kitching, John; Bajaj, Vikram S.; Pines, Alexander

2017-01-01

Low thermal-equilibrium nuclear spin polarizations and the need for sophisticated instrumentation render conventional nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) incompatible with small-scale microfluidic devices. Hyperpolarized 129Xe gas has found use in the study of many materials but has required very large and expensive instrumentation. Recently a microfabricated device with modest instrumentation demonstrated all-optical hyperpolarization and detection of 129Xe gas. This device was limited by 129Xe polarizations less than 1%, 129Xe NMR signals smaller than 20 nT, and transport of hyperpolarized 129Xe over millimeter lengths. Higher polarizations, versatile detection schemes, and flow of 129Xe over larger distances are desirable for wider applications. Here we demonstrate an ultra-sensitive microfabricated platform that achieves 129Xe polarizations reaching 7%, NMR signals exceeding 1 μT, lifetimes up to 6 s, and simultaneous two-mode detection, consisting of a high-sensitivity in situ channel with signal-to-noise of 105 and a lower-sensitivity ex situ detection channel which may be useful in a wider variety of conditions. 129Xe is hyperpolarized and detected in locations more than 1 cm apart. Our versatile device is an optimal platform for microfluidic magnetic resonance in particular, but equally attractive for wider nuclear spin applications benefitting from ultra-sensitive detection, long coherences, and simple instrumentation. PMID:28266629

An optimized microfabricated platform for the optical generation and detection of hyperpolarized 129Xe

DOE PAGES

Kennedy, Daniel J.; Seltzer, Scott J.; Jiménez-Martínez, Ricardo; ...

2017-03-07

Low thermal-equilibrium nuclear spin polarizations and the need for sophisticated instrumentation render conventional nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) incompatible with small-scale microfluidic devices. Hyperpolarized 129Xe gas has found use in the study of many materials but has required very large and expensive instrumentation. Recently a microfabricated device with modest instrumentation demonstrated all-optical hyperpolarization and detection of 129Xe gas. This device was limited by 129Xe polarizations less than 1%, 129Xe NMR signals smaller than 20 nT, and transport of hyperpolarized 129Xe over millimeter lengths. Higher polarizations, versatile detection schemes, and flow of 129Xe over larger distances are desirablemore » for wider applications. Here we demonstrate an ultra-sensitive microfabricated platform that achieves 129Xe polarizations reaching 7%, NMR signals exceeding 1 μT, lifetimes up to 6 s, and simultaneous two-mode detection, consisting of a high-sensitivity in situ channel with signal-to-noise of 10 5 and a lower-sensitivity ex situ detection channel which may be useful in a wider variety of conditions. 129Xe is hyperpolarized and detected in locations more than 1 cm apart. Our versatile device is an optimal platform for microfluidic magnetic resonance in particular, but equally attractive for wider nuclear spin applications benefitting from ultra-sensitive detection, long coherences, and simple instrumentation.« less

Demonstration Report: ESTCP UXO Discrimination Study ESTCP PROJECT # MM-0838

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gasperikova, Erika

2010-02-15

In 2003, the Defense Science Board observed: 'The problem is that instruments that can detect the buried UXOs also detect numerous scrap metal objects and other artifacts, which leads to an enormous amount of expensive digging. Typically 100 holes may be dug before a real UXO is unearthed! The Task Force assessment is that much of this wasteful digging can be eliminated by the use of more advanced technology instruments that exploit modern digital processing and advanced multi-mode sensors to achieve an improved level of discrimination of scrap from UXOs.' Significant progress has been made in discrimination technology. To date,more » testing of these approaches has been primarily limited to test sites with only limited application at live sites. Acceptance of discrimination technologies requires demonstration of system capabilities at real UXO sites under real world conditions. Any attempt to declare detected anomalies to be harmless and requiring no further investigation will require demonstration to regulators of not only individual technologies, but of an entire decision making process. This characterization study was be the second phase in what is expected to be a continuing effort that will span several years. The FY06 Defense Appropriation contained funding for the 'Development of Advanced, Sophisticated, Discrimination Technologies for UXO Cleanup' in the Environmental Security Technology Certification Program (ESTCP). ESTCP responded by conducting a UXO Discrimination Study at the former Camp Sibert, AL. The results of this first demonstration were very encouraging. Although conditions were favorable at this site, a single target of interest (4.2-in mortar) and benign topography and geology, all of the classification approaches demonstrated were able to correctly identify a sizable fraction of the anomalies as arising from non-hazardous items that could be safely left in the ground. To build upon the success of the first phase of this study, ESTCP sponsored a second study in 2009 at the former Camp San Luis Obispo, CA, a site with more challenging topography and a wider mix of targets-of-interest (TOI). There were two primary objectives of this study: (1) Test and validate detection and discrimination capabilities of currently available and emerging technologies on real sites under operational conditions; and (2) Investigate in cooperation with regulators and program managers how discrimination technologies can be implemented in cleanup operations.« less

Multi-site assessment of the precision and reproducibility of multiple reaction monitoring–based measurements of proteins in plasma

PubMed Central

Addona, Terri A; Abbatiello, Susan E; Schilling, Birgit; Skates, Steven J; Mani, D R; Bunk, David M; Spiegelman, Clifford H; Zimmerman, Lisa J; Ham, Amy-Joan L; Keshishian, Hasmik; Hall, Steven C; Allen, Simon; Blackman, Ronald K; Borchers, Christoph H; Buck, Charles; Cardasis, Helene L; Cusack, Michael P; Dodder, Nathan G; Gibson, Bradford W; Held, Jason M; Hiltke, Tara; Jackson, Angela; Johansen, Eric B; Kinsinger, Christopher R; Li, Jing; Mesri, Mehdi; Neubert, Thomas A; Niles, Richard K; Pulsipher, Trenton C; Ransohoff, David; Rodriguez, Henry; Rudnick, Paul A; Smith, Derek; Tabb, David L; Tegeler, Tony J; Variyath, Asokan M; Vega-Montoto, Lorenzo J; Wahlander, Åsa; Waldemarson, Sofia; Wang, Mu; Whiteaker, Jeffrey R; Zhao, Lei; Anderson, N Leigh; Fisher, Susan J; Liebler, Daniel C; Paulovich, Amanda G; Regnier, Fred E; Tempst, Paul; Carr, Steven A

2010-01-01

Verification of candidate biomarkers relies upon specific, quantitative assays optimized for selective detection of target proteins, and is increasingly viewed as a critical step in the discovery pipeline that bridges unbiased biomarker discovery to preclinical validation. Although individual laboratories have demonstrated that multiple reaction monitoring (MRM) coupled with isotope dilution mass spectrometry can quantify candidate protein biomarkers in plasma, reproducibility and transferability of these assays between laboratories have not been demonstrated. We describe a multilaboratory study to assess reproducibility, recovery, linear dynamic range and limits of detection and quantification of multiplexed, MRM-based assays, conducted by NCI-CPTAC. Using common materials and standardized protocols, we demonstrate that these assays can be highly reproducible within and across laboratories and instrument platforms, and are sensitive to low µg/ml protein concentrations in unfractionated plasma. We provide data and benchmarks against which individual laboratories can compare their performance and evaluate new technologies for biomarker verification in plasma. PMID:19561596

Multiplexed detection of DNA sequences using a competitive displacement assay in a microfluidic SERRS-based device.

PubMed

Yazdi, Soroush H; Giles, Kristen L; White, Ian M

2013-11-05

We demonstrate sensitive and multiplexed detection of DNA sequences through a surface enhanced resonance Raman spectroscopy (SERRS)-based competitive displacement assay in an integrated microsystem. The use of the competitive displacement scheme, in which the target DNA sequence displaces a Raman-labeled reporter sequence that has lower affinity for the immobilized probe, enables detection of unlabeled target DNA sequences with a simple single-step procedure. In our implementation, the displacement reaction occurs in a microporous packed column of silica beads prefunctionalized with probe-reporter pairs. The use of a functionalized packed-bead column in a microfluidic channel provides two major advantages: (i) immobilization surface chemistry can be performed as a batch process instead of on a chip-by-chip basis, and (ii) the microporous network eliminates the diffusion limitations of a typical biological assay, which increases the sensitivity. Packed silica beads are also leveraged to improve the SERRS detection of the Raman-labeled reporter. Following displacement, the reporter adsorbs onto aggregated silver nanoparticles in a microfluidic mixer; the nanoparticle-reporter conjugates are then trapped and concentrated in the silica bead matrix, which leads to a significant increase in plasmonic nanoparticles and adsorbed Raman reporters within the detection volume as compared to an open microfluidic channel. The experimental results reported here demonstrate detection down to 100 pM of the target DNA sequence, and the experiments are shown to be specific, repeatable, and quantitative. Furthermore, we illustrate the advantage of using SERRS by demonstrating multiplexed detection. The sensitivity of the assay, combined with the advantages of multiplexed detection and single-step operation with unlabeled target sequences makes this method attractive for practical applications. Importantly, while we illustrate DNA sequence detection, the SERRS-based competitive displacement assay is applicable to detection of a variety of biological macromolecules, including proteins and proteolytic enzymes.

In Vivo and Ex Vivo Transcutaneous Glucose Detection Using Surface-Enhanced Raman Spectroscopy

NASA Astrophysics Data System (ADS)

Ma, Ke

Diabetes mellitus is widely acknowledged as a large and growing health concern. The lack of practical methods for continuously monitoring glucose levels causes significant difficulties in successful diabetes management. Extensive validation work has been carried out using surface-enhanced Raman spectroscopy (SERS) for in vivo glucose sensing. This dissertation details progress made towards a Raman-based glucose sensor for in vivo, transcutaneous glucose detection. The first presented study combines spatially offset Raman spectroscopy (SORS) with SERS (SESORS) to explore the possibility of in vivo, transcutaneous glucose sensing. A SERS-based glucose sensor was implanted subcutaneously in Sprague-Dawley rats. SERS spectra were acquired transcutaneously and analyzed using partial least-squares (PLS). Highly accurate and consistent results were obtained, especially in the hypoglycemic range. Additionally, the sensor demonstrated functionality at least17 days after implantation. A subsequent study further extends the application of SESORS to the possibility of in vivo detection of glucose in brain through skull. Specifically, SERS nanoantennas were buried in an ovine tissue behind a bone with 8 mm thickness and detected by using SESORS. In addition, quantitative detection through bones by using SESORS was also demonstrated. A device that could measure glucose continuously as well as noninvasively would be of great use to patients with diabetes. The inherent limitation of the SESORS approach may prevent this technique from becoming a noninvasive method. Therefore, the prospect of using normal Raman spectroscopy for glucose detection was re-examined. Quantitative detection of glucose and lactate in the clinically relevant range was demonstrated by using normal Raman spectroscopy with low power and short acquisition time. Finally, a nonlinear calibration method called least-squares support vector machine regression (LS-SVR) was investigated for analyzing spectroscopic data sets of glucose detection. Comparison studies were demonstrated between LS-SVR and PLS. LS-SVR demonstrated significant improvements in accuracy over PLS for glucose detection, especially when a global calibration model was required. The improvements imparted by LS-SVR open up the possibility of developing an accurate prediction algorithm for Raman-based glucose sensing applicable to a large human population. Overall, these studies show the high promise held by the Raman-based sensor for the challenge of optimal glycemic control.

Unique capabilities of AC frequency scanning and its implementation on a Mars Organic Molecule Analyzer linear ion trap.

PubMed

Snyder, Dalton T; Kaplan, Desmond A; Danell, Ryan M; van Amerom, Friso H W; Pinnick, Veronica T; Brinckerhoff, William B; Mahaffy, Paul R; Cooks, R Graham

2017-06-21

A limitation of conventional quadrupole ion trap scan modes which use rf amplitude control for mass scanning is that, in order to detect a subset of an ion population, the rest of the ion population must also be interrogated. That is, ions cannot be detected out of order; they must be detected in order of either increasing or decreasing mass-to-charge (m/z). However, an ion trap operated in the ac frequency scan mode, where the rf amplitude is kept constant and instead the ac frequency is used for mass-selective operations, has no such limitation because any variation in the ac frequency affects only the subset of ions whose secular frequencies match the perturbation frequency. Hence, an ion trap operated in the ac frequency scan mode can perform any arbitrary mass scan, as well as a sequence of scans, using a single ion injection; we demonstrate both capabilities here. Combining these two capabilities, we demonstrate the acquisition of a full mass spectrum, a product ion spectrum, and a second generation product ion spectrum using a single ion injection event. We further demonstrate a "segmented scan" in which different mass ranges are interrogated at different rf amplitudes in order to improve resolution over a portion of the mass range, and a "periodic scan" in which ions are continuously introduced into the ion trap to achieve a nearly 100% duty cycle. These unique scan modes, along with other characteristics of ac frequency scanning, are particularly appropriate for miniature ion trap mass spectrometers. Hence, implementation of ac frequency scanning on a prototype of the Mars Organic Molecule Analyzer mass spectrometer is also described.

Validation of shortened 2-day sterility testing of mesenchymal stem cell-based therapeutic preparation on an automated culture system.

PubMed

Lysák, Daniel; Holubová, Monika; Bergerová, Tamara; Vávrová, Monika; Cangemi, Giuseppina Cristina; Ciccocioppo, Rachele; Kruzliak, Peter; Jindra, Pavel

2016-03-01

Cell therapy products represent a new trend of treatment in the field of immunotherapy and regenerative medicine. Their biological nature and multistep preparation procedure require the application of complex release criteria and quality control. Microbial contamination of cell therapy products is a potential source of morbidity in recipients. The automated blood culture systems are widely used for the detection of microorganisms in cell therapy products. However the standard 2-week cultivation period is too long for some cell-based treatments and alternative methods have to be devised. We tried to verify whether a shortened cultivation of the supernatant from the mesenchymal stem cell (MSC) culture obtained 2 days before the cell harvest could sufficiently detect microbial growth and allow the release of MSC for clinical application. We compared the standard Ph. Eur. cultivation method and the automated blood culture system BACTEC (Becton Dickinson). The time to detection (TTD) and the detection limit were analyzed for three bacterial and two fungal strains. The Staphylococcus aureus and Pseudomonas aeruginosa were recognized within 24 h with both methods (detection limit ~10 CFU). The time required for the detection of Bacillus subtilis was shorter with the automated method (TTD 10.3 vs. 60 h for 10-100 CFU). The BACTEC system reached significantly shorter times to the detection of Candida albicans and Aspergillus brasiliensis growth compared to the classical method (15.5 vs. 48 and 31.5 vs. 48 h, respectively; 10-100 CFU). The positivity was demonstrated within 48 h in all bottles, regardless of the size of the inoculum. This study validated the automated cultivation system as a method able to detect all tested microorganisms within a 48-h period with a detection limit of ~10 CFU. Only in case of B. subtilis, the lowest inoculum (~10 CFU) was not recognized. The 2-day cultivation technique is then capable of confirming the microbiological safety of MSC and allows their timely release for clinical application.

Role of CD81 and CD58 in minimal residual disease detection in pediatric B lymphoblastic leukemia.

PubMed

Tsitsikov, E; Harris, M H; Silverman, L B; Sallan, S E; Weinberg, O K

2018-06-01

Minimal residual disease (MRD) in B lymphoblastic leukemia has been demonstrated to be a powerful predictor of clinical outcome in numerous studies in both children and adults. In this study, we evaluated 86 pediatric patients with both diagnostic and remission flow cytometry studies and compared expression of CD81, CD58, CD19, CD34, CD20, and CD38 in the detection of MRD. We evaluated 86 patients with B lymphoblastic leukemia who had both diagnostic studies and remission studies for the presence of MRD using multicolor flow cytometry. We established our detection limit for identifying abnormal lymphoblasts using serial dilutions. We also compared flow cytometry findings with molecular MRD detection in a subset of patients. We found that we can resolve differences between hematogones and lymphoblasts in 85 of 86 cases using a combination of CD45, CD19, CD34, CD10, CD20, CD38, CD58, and CD81. Our detection limit using flow cytometry is 0.002% for detecting a population of abnormal B lymphoblasts. Comparison with MRD assessment by molecular methods showed a high concordance rate with flow cytometry findings. Our study highlights importance of using multiple markers to detect MRD in B lymphoblastic leukemia. Our findings indicate that including both CD58 and CD81 markers in addition to CD19, CD34, CD20, CD38, and CD10 are helpful in MRD detection by flow cytometry. © 2018 John Wiley & Sons Ltd.

Cytology specimens offer an effective alternative to formalin-fixed tissue as demonstrated by novel automated detection for ALK break-apart FISH testing and immunohistochemistry in lung adenocarcinoma.

PubMed

Rosenblum, Frida; Hutchinson, Lloyd M; Garver, Joann; Woda, Bruce; Cosar, Ediz; Kurian, Elizabeth M

2014-11-01

Minimally invasive sampling by cytology or core needle biopsy often provides an initial diagnosis for treatment in patients with lung nodules. From these limited specimens, multiple molecular studies are frequently requested. Current guidelines from the US Food and Drug Administration recommend using formalin-fixed paraffin-embedded tissue sections for the detection of anaplastic lymphoma kinase (ALK) gene rearrangement by fluorescence in situ hybridization (FISH). The authors compared alcohol-fixed and formalin-fixed cytology specimens using a novel automated detection for ALK rearrangements by FISH and immunohistochemistry (IHC). ALK FISH testing was performed on 129 lung adenocarcinomas from 71 cytology cases and 58 biopsy/resection specimens using Papanicolaou staining with integrated cytomorphology. IHC with the ALK D5F3 antibody was performed on cases with residual material (88 of 129 cases). The mean age of the patients was 66 years; there were 62 women and 67 men. ALK gene rearrangement was present in 4% of cytology specimens (3 of 71 specimens) and 7% of surgical specimens (4 of 58 specimens). FISH in 13 cases was technically unsuccessful. Of the 7 FISH-positive cases, only 2 cytology cases (4%) and 2 surgical cases (6%) were found to be positive with the ALK antibody, demonstrating 80% concordance. The one case found to be negative for ALK by IHC demonstrated a variant rearrangement of the ALK 2p23 gene locus by FISH. The results of the current study validate the usefulness of alcohol-fixed and/or formalin-fixed cytology specimens for ALK rearrangement by a novel automated FISH method. IHC using the D5F3 antibody for ALK is specific in this limited cohort. The authors also demonstrated that alcohol-fixed cytology specimens can be used for ALK rearrangement by automated FISH, alone or in conjunction with IHC. © 2014 American Cancer Society.

Optimization and characterization of condensation nucleation light scattering detection coupled with supercritical fluid chromatography

NASA Astrophysics Data System (ADS)

Yang, Shaoping

This dissertation is an investigation of two aspects of coupling condensation nucleation light scattering detection (CNLSD) with supercritical fluid chromatography (SFC). In the first part, it was demonstrated that CNLSD was compatible with packed column SFC using either pure CO2 or organic solvent modified CO2 as mobile phases. Factors which were expected to affect the interface between SFC and CNLSD were optimized for the detector to reach low detection limits. With SFC using pure CO2 as mobile phase, the detection limit of CNLSD with SFC was observed to be at low nanogram levels, which was at the same level of flame ionization detection (FID) coupled with SFC. For SFC using modified CO2 as mobile phase, detection limits at the picogram level were observed for CNLSD at optimal conditions, which were at least ten times lower than those reached by evaporative light scattering detection. In the second part, particle size distributions of aerosols produced from rapid expansion of supercritical solutions were measured with a scanning mobility particle sizer. The effect of the factors, which were investigated in the first part for their effects on signal intensities and signal to noise ratios (S/N), on particle size distributions (PSDs) of both analyte and background were investigated. Whenever possible, both particle sizes and particle number obtained from PSDs were used to explain the optimization results. In general, PSD data support the observations made in the first part. The detection limits of CNLSD obtained were much higher than predicted. PSDs did not provide direct explanation of this problem. The amount of analyte deposited in the transport tubing, evaporated to gas phase, and condensed to form particles was determined experimentally. Almost no analyte was found in the gas phase. Less than 3% was found in the particle forms. The vast majority of analyte was lost in the transport tubing, especially in the short distance after supercritical fluid expansion. A mechanism was proposed to explain the loss of analyte in the transport tubing.

Ultimate detectability of volatile organic compounds: how much further can we reduce their ambient air sample volumes for analysis?

PubMed

Kim, Yong-Hyun; Kim, Ki-Hyun

2012-10-02

To understand the ultimately lowest detection range of volatile organic compounds (VOCs) in air, application of a high sensitivity analytical system was investigated by coupling thermal desorption (TD) technique with gas chromatography (GC) and time-of-flight (TOF) mass spectrometry (MS). The performance of the TD-GC/TOF MS system was evaluated using liquid standards of 19 target VOCs prepared in the range of 35 pg to 2.79 ng per μL. Studies were carried out using both total ion chromatogram (TIC) and extracted ion chromatogram (EIC) mode. EIC mode was used for calibration to reduce background and to improve signal-to-noise. The detectability of 19 target VOCs, if assessed in terms of method detection limit (MDL, per US EPA definition) and limit of detection (LOD), averaged 5.90 pg and 0.122 pg, respectively, with the mean coefficient of correlation (R(2)) of 0.9975. The minimum quantifiable mass of target analytes, when determined using real air samples by the TD-GC/TOF MS, is highly comparable to the detection limits determined experimentally by standard. In fact, volumes for the actual detection of the major aromatic VOCs like benzene, toluene, and xylene (BTX) in ambient air samples were as low as 1.0 mL in the 0.11-2.25 ppb range. It was thus possible to demonstrate that most target compounds including those in low abundance could be reliably quantified at concentrations down to 0.1 ppb at sample volumes of less than 10 mL. The unique sensitivity of this advanced analytical system can ultimately lead to a shift in field sampling strategy with smaller air sample volumes facilitating faster, simpler air sampling (e.g., use of gas syringes rather than the relative complexity of pumps or bags/canisters), with greatly reduced risk of analyte breakthrough and minimal interference, e.g., from atmospheric humidity. The improved detection limits offered by this system can also enhance accuracy and measurement precision.

Accumulation of polycyclic aromatic hydrocarbons by Neocalanus copepods in Port Valdez, Alaska.

PubMed

Carls, Mark G; Short, Jeffrey W; Payne, James

2006-11-01

Sampling zooplankton is a useful strategy for observing trace hydrocarbon concentrations in water because samples represent an integrated average over a considerable effective sampling volume and are more representative of the sampled environment than discretely collected water samples. We demonstrate this method in Port Valdez, Alaska, an approximately 100 km(2) basin that receives about 0.5-2.4 kg of polynuclear aromatic hydrocarbons (PAH) per day. Total PAH (TPAH) concentrations (0.61-1.31 microg/g dry weight), composition, and spatial distributions in a lipid-rich copepod, Neocalanus were consistent with the discharge as the source of contamination. Although Neocalanus acquire PAH from water or suspended particulate matter, total PAH concentrations in these compartments were at or below method detection limits, demonstrating plankton can amplify trace concentrations to detectable levels useful for study.

Smartphone spectroscopy: three unique modalities for point-of-care testing

NASA Astrophysics Data System (ADS)

Long, Kenneth D.; Yu, Hojeong; Cunningham, Brian T.

2015-06-01

Here we demonstrate three principle modalities for a smartphone-based spectrometer: absorption, fluorescence, and photonic crystal (PC)-based label-free detection. When combined with some simple optical components, the rear-facing CMOS camera in a mobile device can provide spectrometric data that rivals that of laboratory instruments, but at a fraction of the cost. The use of a smartphone-based platform poses significant advantages based upon the rise of smartphone apps, which allow for user-interface and data-processing algorithms to be packaged and distributed within environments that are externally maintained with potential for integration with services such as cloud storage, GIS-tagging, and remote expert analysis. We demonstrate the absorption modality of our device by performing an enzyme-linked immunosorbent assay (ELISA) on both a cancer biomarker and a peanut allergen, demonstrating clinically relevant limits of detection (LOD). Second, we demonstrate the success of a molecular beacon (MB)-based assay on the smartphone platform, achieving an LOD of 1.3 pM for a specific RNA sequence, less than that of a commercial benchtop instrument. Finally, we use a PC biosensor to perform label-free detection of a representative biological interaction: Protein A and human immunoglobulin G (IgG) in the nanomolar regime. Our work represents the first demonstration of smartphone-based spectroscopy for biological assays, and the first mobile-device-enabled detection instrument that serves to measure three distinct sensing modalities (label-free biosensing, absorption spectroscopy, and fluorescence spectroscopy). The smartphone platform has the potential to expand the use of spectrometric analysis to environments assay from the laboratory, which may include rural or remote locations, low-resource settings, and consumer markets.

Conservation in a cup of water: estimating biodiversity and population abundance from environmental DNA.

PubMed

Lodge, David M; Turner, Cameron R; Jerde, Christopher L; Barnes, Matthew A; Chadderton, Lindsay; Egan, Scott P; Feder, Jeffrey L; Mahon, Andrew R; Pfrender, Michael E

2012-06-01

Three mantras often guide species and ecosystem management: (i) for preventing invasions by harmful species, 'early detection and rapid response'; (ii) for conserving imperilled native species, 'protection of biodiversity hotspots'; and (iii) for assessing biosecurity risk, 'an ounce of prevention equals a pound of cure.' However, these and other management goals are elusive when traditional sampling tools (e.g. netting, traps, electrofishing, visual surveys) have poor detection limits, are too slow or are not feasible. One visionary solution is to use an organism's DNA in the environment (eDNA), rather than the organism itself, as the target of detection. In this issue of Molecular Ecology, Thomsen et al. (2012) provide new evidence demonstrating the feasibility of this approach, showing that eDNA is an accurate indicator of the presence of an impressively diverse set of six aquatic or amphibious taxa including invertebrates, amphibians, a fish and a mammal in a wide range of freshwater habitats. They are also the first to demonstrate that the abundance of eDNA, as measured by qPCR, correlates positively with population abundance estimated with traditional tools. Finally, Thomsen et al. (2012) demonstrate that next-generation sequencing of eDNA can quantify species richness. Overall, Thomsen et al. (2012) provide a revolutionary roadmap for using eDNA for detection of species, estimates of relative abundance and quantification of biodiversity. © 2012 Blackwell Publishing Ltd.

E-DNA sensor of Mycobacterium tuberculosis based on electrochemical assembly of nanomaterials (MWCNTs/PPy/PAMAM).

PubMed

Miodek, Anna; Mejri, Nawel; Gomgnimbou, Michel; Sola, Christophe; Korri-Youssoufi, Hafsa

2015-09-15

Two-step electrochemical patterning methods have been employed to elaborate composite nanomaterials formed with multiwalled carbon nanotubes (MWCNTs) coated with polypyrrole (PPy) and redox PAMAM dendrimers. The nanomaterial has been demonstrated as a molecular transducer for electrochemical DNA detection. The nanocomposite MWCNTs-PPy has been formed by wrapping the PPy film on MWCNTs during electrochemical polymerization of pyrrole on the gold electrode. The MWCNTs-PPy layer was modified with PAMAM dendrimers of fourth generation (PAMAM G4) with covalent bonding by electro-oxidation method. Ferrocenyl groups were then attached to the surface as a redox marker. The electrochemical properties of the nanomaterial (MWCNTs-PPy-PAMAM-Fc) were studied using both square wave voltammetry and cyclic voltammetry to demonstrate efficient electron transfer. The nanomaterial shows high performance in the electrochemical detection of DNA hybridization leading to a variation in the electrochemical signal of ferrocene with a detection limit of 0.3 fM. Furthermore, the biosensor demonstrates ability for sensing DNA of rpoB gene of Mycobacterium tuberculosis in real PCR samples. Developed biosensor was suitable for detection of sequences with a single nucleotide polymorphism (SNP) T (TCG/TTG), responsible for resistance of M. tuberculosis to rifampicin drug, and discriminating them from wild-type samples without such mutation. This shows potential of such systems for further application in pathogens diagnostic and therapeutic purpose.

Detecting trihalomethanes using nanoporous-carbon coated surface-acoustic-wave sensors

DOE PAGES

Siegal, Michael P.; Mowry, Curtis D.; Pfeifer, Kent B.; ...

2015-03-07

We study nanoporous-carbon (NPC) grown via pulsed laser deposition (PLD) as a sorbent coating on 96.5-MHz surface-acoustic-wave (SAW) devices to detect trihalomethanes (THMs), regulated byproducts from the chemical treatment of drinking water. Using both insertion-loss and isothermal-response measurements from known quantities of chloroform, the highest vapor pressure THM, we optimize the NPC mass-density at 1.05 ± 0.08 g/cm3 by controlling the background argon pressure during PLD. Precise THM quantities in a chlorobenzene solvent are directly injected into a separation column and detected as the phase-angle shift of the SAW device output compared to the drive signal. Using optimized NPC-coated SAWs,more » we study the chloroform response as a function of operating temperatures ranging from 10–50°C. Finally, we demonstrate individual responses from complex mixtures of all four THMs, with masses ranging from 10–2000 ng, after gas chromatography separation. As a result, estimates for each THM detection limit using a simple peak-height response evaluation are 4.4 ng for chloroform and 1 ng for bromoform; using an integrated-peak area response analysis improves the detection limits to 0.73 ng for chloroform and 0.003 ng bromoform.« less

Hybridization chain reaction amplification for highly sensitive fluorescence detection of DNA with dextran coated microarrays.

PubMed

Chao, Jie; Li, Zhenhua; Li, Jing; Peng, Hongzhen; Su, Shao; Li, Qian; Zhu, Changfeng; Zuo, Xiaolei; Song, Shiping; Wang, Lianhui; Wang, Lihua

2016-07-15

Microarrays of biomolecules hold great promise in the fields of genomics, proteomics, and clinical assays on account of their remarkably parallel and high-throughput assay capability. However, the fluorescence detection used in most conventional DNA microarrays is still limited by sensitivity. In this study, we have demonstrated a novel universal and highly sensitive platform for fluorescent detection of sequence specific DNA at the femtomolar level by combining dextran-coated microarrays with hybridization chain reaction (HCR) signal amplification. Three-dimensional dextran matrix was covalently coated on glass surface as the scaffold to immobilize DNA recognition probes to increase the surface binding capacity and accessibility. DNA nanowire tentacles were formed on the matrix surface for efficient signal amplification by capturing multiple fluorescent molecules in a highly ordered way. By quantifying microscopic fluorescent signals, the synergetic effects of dextran and HCR greatly improved sensitivity of DNA microarrays, with a detection limit of 10fM (1×10(5) molecules). This detection assay could recognize one-base mismatch with fluorescence signals dropped down to ~20%. This cost-effective microarray platform also worked well with samples in serum and thus shows great potential for clinical diagnosis. Copyright © 2016 Elsevier B.V. All rights reserved.

Multiplexed detection of anthrax-related toxin genes.

PubMed

Moser, Michael J; Christensen, Deanna R; Norwood, David; Prudent, James R

2006-02-01

Simultaneous analysis of three targets in three colors on any real-time polymerase chain reaction (PCR) instrument would increase the flexibility of real-time PCR. For the detection of Bacillus strains that can cause inhalation anthrax-related illness, this ability would be valuable because two plasmids confer virulence, and internal positive controls are needed to monitor the testing in cases lacking target-specific signals. Using a real-time PCR platform called MultiCode-RTx, multiple assays were developed that specifically monitor the presence of Bacillus anthracis-specific virulence plasmid-associated genes. In particular for use on LightCycler-1, two triplex RTx systems demonstrated high sensitivity with limits of detection nearing single-copy levels for both plasmids. Specificity was established using a combination of Ct values and correct amplicon melting temperatures. All reactions were further verified by detection of an internal positive control. For these two triplex RTx assays, the analytical detection limit was one to nine plasmid copy equivalents, 100% analytical specificity with a 95% confidence interval (CI) of 9%, and 100% analytical sensitivity with a CI of 2%. Although further testing using clinical or environmental samples will be required to assess diagnostic sensitivity and specificity, the RTx platform achieves similar results to those of probe-based real-time systems.

Polythiophene nanofilms for sensitive fluorescence detection of viruses in drinking water.

PubMed

Wankar, Shashwati; Turner, Nicholas W; Krupadam, Reddithota J

2016-08-15

Molecular imprints of the tobacco necrosis virus (TNV) have been formed within polythiophene nanofilms with an approximate thickness of 200nm. These films have been electrochemically deposited onto conducting Au surfaces. Upon rebinding, the TNV-polythiophene complex changes the fluorescence intensity of the nanofilm. The fluorescence intensity at 410nm was observed to be proportional to the concentration of viruses in the range of 0.1-10ngL(-1) (0.15-15pg) with the lower calculated detection limit of 2.29ngL(-1) (3.4pg). The intensity of the fluorescence emission is not affected by the thickness of the polythiophene film and the nature of TNV specific binding sites. Kinetic data analyses showed that the nanofilm responds to TNV within 2min; and cross-selectivity studies with tobacco mosaic virus (TMV) showed an excellent specificity for the targeted TNV. These binding experiments demonstrate the potential of fluorescence emission for the specific, label free and rapid detection of viruses using nanofilm sensors. Taking into account the lower limit of detection, the fluorescence sensing reported here is reliable, simple to perform, rapid, cost-effective and offers a sensitive analytical method for virus detection in water resources. Copyright © 2016 Elsevier B.V. All rights reserved.

Novel nanoarchitectures for electrochemical biosensing

NASA Astrophysics Data System (ADS)

Archibald, Michelle M.

Sensitive, real-time detection of biomarkers is of critical importance for rapid and accurate diagnosis of disease for point-of-care (POC) technologies. Current methods, while sensitive, do not adequately allow for POC applications due to several limitations, including complex instrumentation, high reagent consumption, and cost. We have investigated two novel nanoarchitectures, the nanocoax and the nanodendrite, as electrochemical biosensors towards the POC detection of infectious disease biomarkers to overcome these limitations. The nanocoax architecture is composed of vertically-oriented, nanoscale coaxial electrodes, with coax cores and shields serving as integrated working and counter electrodes, respectively. The dendritic structure consists of metallic nanocrystals extending from the working electrode, increasing sensor surface area. Nanocoaxial- and nanodendritic-based electrochemical sensors were fabricated and developed for the detection of bacterial toxins using an electrochemical enzyme-linked immunosorbent assay (ELISA) and differential pulse voltammetry (DPV). Proof-of-concept was demonstrated for the detection of cholera toxin (CT). Both nanoarchitectures exhibited levels of sensitivity that are comparable to the standard optical ELISA used widely in clinical applications. In addition to matching the detection profile of the standard ELISA, these electrochemical nanosensors provide a simple electrochemical readout and a miniaturized platform with multiplexing capabilities toward POC implementation. Further development as suggested in this thesis may lead to increases in sensitivity, enhancing the attractiveness of the architectures for future POC devices.

The effect of hybridization-induced secondary structure alterations on RNA detection using backscattering interferometry

PubMed Central

Adams, Nicholas M.; Olmsted, Ian R.; Haselton, Frederick R.; Bornhop, Darryl J.; Wright, David W.

2013-01-01

Backscattering interferometry (BSI) has been used to successfully monitor molecular interactions without labeling and with high sensitivity. These properties suggest that this approach might be useful for detecting biomarkers of infection. In this report, we identify interactions and characteristics of nucleic acid probes that maximize BSI signal upon binding the respiratory syncytial virus nucleocapsid gene RNA biomarker. The number of base pairs formed upon the addition of oligonucleotide probes to a solution containing the viral RNA target correlated with the BSI signal magnitude. Using RNA folding software mfold, we found that the predicted number of unpaired nucleotides in the targeted regions of the RNA sequence generally correlated with BSI sensitivity. We also demonstrated that locked nucleic acid (LNA) probes improved sensitivity approximately 4-fold compared to DNA probes of the same sequence. We attribute this enhancement in BSI performance to the increased A-form character of the LNA:RNA hybrid. A limit of detection of 624 pM, corresponding to ∼105 target molecules, was achieved using nine distinct ∼23-mer DNA probes complementary to regions distributed along the RNA target. Our results indicate that BSI has promise as an effective tool for sensitive RNA detection and provides a road map for further improving detection limits. PMID:23519610

Establishment and application of a novel isothermal amplification assay for rapid detection of chloroquine resistance (K76T) in Plasmodium falciparum

PubMed Central

Chahar, Madhvi; Mishra, Neelima; Anvikar, Anup; Dixit, Rajnikant; Valecha, Neena

2017-01-01

Chloroquine (CQ) resistance in Plasmodium falciparum is determined by the mutations in the chloroquine resistance transporter (Pfcrt) gene. The point mutation at codon 76 (K76T), which has been observed in more than 91% of P. falciparum isolates in India, is the major determinant of CQ resistance. To overcome the limitations and challenges of traditional methods, in this investigation we developed an easy to use loop mediated isothermal amplification (LAMP) protocol for rapid detection of the K76T mutation associated with CQ resistance in P. falciparum with naked eye visualization. In- house designed primers were synthesized and optimized to specifically distinguish the CQ resistant mutants of P. falciparum. The LAMP reaction was optimal at 61 °C for 60 min and calcein dye was added prior to amplification to enable visual detection. We demonstrate the detection limit of <2 ng/μl respectively, supporting the high sensitivity of this calcein based LAMP method. To the best of our knowledge this is the first report on the establishment of an easy, reliable and cost effective LAMP assay for rapid and specific detection of highly CQ resistance in P. falciparum malaria. PMID:28134241

An Integrated Quantum Dot Barcode Smartphone Optical Device for Wireless Multiplexed Diagnosis of Infected Patients

NASA Astrophysics Data System (ADS)

Ming, Kevin

Integrating mobile-cellular devices with multiplex molecular diagnostics can potentially provide the most powerful platform for tracking, managing and preventing the transmission of infectious diseases. With over 6.9 billion subscriptions globally, handheld mobile-cellular devices can be programmed to spatially map, temporally track, and transmit information on infections over wide geographical space and boundaries. Current cell phone diagnostic technologies have poor limit of detection, dynamic range, and cannot detect multiple pathogen targets simultaneously, limiting their utility to single infections with high load. Here we combined recent advances in quantum dot barcode technology for molecular detection with smartphones to engineer a simple and low-cost chip-based wireless multiplex diagnostic device. We validated our device using a variety of synthetic genomic targets for the respiratory virus and blood-borne pathogens, and demonstrated that it could detect clinical samples after simple amplification. More importantly, we confirmed that the device is capable of detecting patients infected with a single or multiple infectious pathogens (e.g., HIV and hepatitis B) in a single test. This device advances the capacity for global surveillance of infectious diseases and has the potential to accelerate knowledge exchange-transfer of emerging or exigent disease threats with healthcare and military organizations in real-time.

SISGR: Room Temperature Single-Molecule Detection and Imaging by Stimulated Emission Microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Xiaoliang Sunney

Single-molecule spectroscopy has made considerable impact on many disciplines including chemistry, physics, and biology. To date, most single-molecule spectroscopy work is accomplished by detecting fluorescence. On the other hand, many naturally occurring chromophores, such as retinal, hemoglobin and cytochromes, do not have detectable fluorescence. There is an emerging need for single-molecule spectroscopy techniques that do not require fluorescence. In the last proposal period, we have successfully demonstrated stimulated emission microscopy, single molecule absorption, and stimulated Raman microscopy based on a high-frequency modulation transfer technique. These first-of-a- kind new spectroscopy/microscopy methods tremendously improved our ability to observe molecules that fluorescence weakly,more » even to the limit of single molecule detection for absorption measurement. All of these methods employ two laser beams: one (pump beam) excites a single molecule to a real or virtual excited state, and the other (probe beam) monitors the absorption/emission property of the single. We extract the intensity change of the probe beam with high sensitivity by implementing a high-frequency phase-sensitive detection scheme, which offers orders of magnitude improvement in detection sensitivity over direct absorption/emission measurement. However, single molecule detection based on fluorescence or absorption is fundamentally limited due to their broad spectral response. It is important to explore other avenues in single molecule detection and imaging which provides higher molecular specificity for studying a wide variety of heterogeneous chemical and biological systems. This proposal aimed to achieve single-molecule detection sensitivity with near resonance stimulated Raman scattering (SRS) microscopy. SRS microscopy was developed in our lab as a powerful technique for imaging heterogeneous samples based on their intrinsic vibrational contrasts, which provides much higher molecular specificity than absorption and fluorescence. Current sensitivity limit of SRS microscopy has not yet reached single molecule detection. We proposed to capitalize on our state-of-the-art SRS microscopy and develop near-resonance enhanced SRS for single molecule detection of carotenoids and heme proteins. The specific aims we pursued are: (1) building the next SRS generation microscope that utilizes near resonance enhancement to allow detection and imaging of single molecules with undetectable fluorescence, such as -carotene. (2) using near-resonance SRS as a contrast mechanism to study dye-sensitize semiconductor interface, elucidating the heterogeneous electron ejection kinetics with high spatial and temporal resolution. (3) studying the binding and unbinding of oxygen in single hemoglobin molecules in order to gain molecular level understanding of the long-standing issue of cooperativity. The new methods developed in the fund period of this grant have advanced the detection sensitivity in many aspects. Near-resonance SRS improved the signal by using shorter wavelengths for SRS microscopy. Frequency modulation and multi-color SRS target the reduction of background to improve the chemical specificity of SRS while maintaining the high imaging speed. Time-domain coherent Raman scattering microscopy targets to reduce the noise floor of coherent Raman microscopy. These methods have already demonstrated first-of-a-kind new applications in biology and medical research. However, we are still one order of magnitude away from single molecule limit. It is important to continue to improve the laser specification and develop new imaging methods to finally achieve label-free single molecule microscopy.« less

Limits to magnetic resonance microscopy

NASA Astrophysics Data System (ADS)

Glover, Paul; Mansfield, Peter, Sir

2002-10-01

The last quarter of the twentieth century saw the development of magnetic resonance imaging (MRI) grow from a laboratory demonstration to a multi-billion dollar worldwide industry. There is a clinical body scanner in almost every hospital of the developed nations. The field of magnetic resonance microscopy (MRM), after mostly being abandoned by researchers in the first decade of MRI, has become an established branch of the science. This paper reviews the development of MRM over the last decade with an emphasis on the current state of the art. The fundamental principles of imaging and signal detection are examined to determine the physical principles which limit the available resolution. The limits are discussed with reference to liquid, solid and gas phase microscopy. In each area, the novel approaches employed by researchers to push back the limits of resolution are discussed. Although the limits to resolution are well known, the developments and applications of MRM have not reached their limit.

Detection and quantification of new psychoactive substances (NPSs) within the evolved "legal high" product, NRG-2, using high performance liquid chromatography-amperometric detection (HPLC-AD).

PubMed

Zuway, Khaled Y; Smith, Jamie P; Foster, Christopher W; Kapur, Nikil; Banks, Craig E; Sutcliffe, Oliver B

2015-09-21

The global increase in the production and abuse of cathinone-derived New Psychoactive Substances (NPSs) has developed the requirement for rapid, selective and sensitive protocols for their separation and detection. Electrochemical sensing of these compounds has been demonstrated to be an effective method for the in-field detection of these substances, either in their pure form or in the presence of common adulterants, however, the technique is limited in its ability to discriminate between structurally related cathinone-derivatives (for example: (±)-4′-methylmethcathinone (4-MMC, 2a) and (±)-4′-methyl-N-ethylmethcathinone (4-MEC, 2b) when they are both present in a mixture. In this paper we demonstrate, for the first time, the combination of HPLC-UV with amperometric detection (HPLC-AD) for the qualitative and quantitative analysis of 4-MMC and 4-MEC using either a commercially available impinging jet (LC-FC-A) or custom-made iCell channel (LC-FC-B) flow-cell system incorporating embedded graphite screen-printed macroelectrodes. The protocol offers a cost-effective, reproducible and reliable sensor platform for the simultaneous HPLC-UV and amperometric detection of the target analytes. The two systems have similar limits of detection, in terms of amperometric detection [LC-FC-A: 14.66 μg mL(-1) (2a) and 9.35 μg mL(-1) (2b); LC-FC-B: 57.92 μg mL(-1) (2a) and 26.91 μg mL(-1) (2b)], to the previously reported oxidative electrochemical protocol [39.8 μg mL(-1) (2a) and 84.2 μg mL(-1) (2b)], for two synthetic cathinones, prevalent on the recreational drugs market. Though not as sensitive as standard HPLC-UV detection, both flow cells show a good agreement, between the quantitative electroanalytical data, thereby making them suitable for the detection and quantification of 4-MMC and 4-MEC, either in their pure form or within complex mixtures. Additionally, the simultaneous HPLC-UV and amperometric detection protocol detailed herein shows a marked improvement and advantage over previously reported electroanalytical methods, which were either unable to selectively discriminate between structurally related synthetic cathinones (e.g. 4-MMC and 4-MEC) or utilised harmful and restrictive materials in their design.

Molecularly imprinted fluorescent hollow nanoparticles as sensors for rapid and efficient detection λ-cyhalothrin in environmental water.

PubMed

Wang, Jixiang; Qiu, Hao; Shen, Hongqiang; Pan, Jianming; Dai, Xiaohui; Yan, Yongsheng; Pan, Guoqing; Sellergren, Börje

2016-11-15

Molecularly imprinted fluorescent polymers have shown great promise in biological or chemical separations and detections, due to their high stability, selectivity and sensitivity. In this work, molecularly imprinted fluorescent hollow nanoparticles, which could rapidly and efficiently detect λ-cyhalothrin (a toxic insecticide) in water samples, was reported. The molecularly imprinted fluorescent sensor showed excellent sensitivity (the limit of detection low to 10.26nM), rapid detection rate (quantitative detection of λ-cyhalothrin within 8min), regeneration ability (maintaining good fluorescence properties after 8 cycling operation) and appreciable selectivity over several structural analogs. Moreover, the fluorescent sensor was further used to detect λ-cyhalothrin in real samples form the Beijing-Hangzhou Grand Canal Water. Despite the relatively complex components of the environmental water, the molecularly imprinted fluorescent hollow nanosensor still showed good recovery, clearly demonstrating the potential value of this smart sensor nanomaterial in environmental monitoring. Copyright © 2016 Elsevier B.V. All rights reserved.

Design and analysis of a spectro-angular surface plasmon resonance biosensor operating in the visible spectrum

NASA Astrophysics Data System (ADS)

Filion-Côté, Sandrine; Roche, Philip J. R.; Foudeh, Amir M.; Tabrizian, Maryam; Kirk, Andrew G.

2014-09-01

Surface plasmon resonance (SPR) sensing is one of the most widely used methods to implement biosensing due to its sensitivity and capacity for label-free detection. Whilst most commercial SPR sensors operate in the angular regime, it has recently been shown that an increase in sensitivity and a greater robustness against noise can be achieved by measuring the reflectivity when varying both the angle and wavelength simultaneously, in a so-called spectro-angular SPR biosensor. A single value decomposition method is used to project the two-dimensional spectro-angular reflection signal onto a basis set and allow the image obtained from an unknown refractive index sample to be compared very accurately with a pre-calculated reference set. Herein we demonstrate that a previously reported system operated in the near infra-red has a lower detection limit when operating in the visible spectrum due to the improved spatial resolution and numerical precision of the image sensor. The SPR biosensor presented here has an experimental detection limit of 9.8 × 10-7 refractive index unit. To validate the system as a biosensor, we also performed the detection of synthetic RNA from pathogenic Legionella pneumophila with the developed biosensing platform.

VCSEL based Faraday rotation spectroscopy at 762nm for battery powered trace molecular oxygen detection

NASA Astrophysics Data System (ADS)

So, Stephen; Wysocki, Gerard

2010-02-01

Faraday Rotation Spectroscopy (FRS) is a polarization based spectroscopic technique which can provide higher sensitivity concentration measurements of paramagnetic gases and free radicals than direct absorption spectroscopic techniques. We have developed sensor systems which require only 0.2W to perform TDLAS (tunable diode laser absorption spectroscopy), and can additionally be quickly duty cycled, enabling operation in wireless sensor networks of laser-based trace gas sensors We adapted our integrated TDLAS electronics to perform FRS in a compact and more sensitive system for quantification of molecular oxygen (O2) using a 762.3nm VCSEL in the A band. Using an AC magnetic field, we demonstrate detector noise dominated performance, achieving 2.1×10-6/Hz1/2 equivalent detectable fractional absorption and a minimum detection limit of 462 ppmv O2 in 1 second in a 15cm path. At longer paths and integration times, such a sensor will enable oxygen measurements at biotic respiration levels (<1ppmv) to measure CO2 - O2 exchange for mapping natural exchange of greenhouse gases. Potential improvement of detection limits by increasing various system performance parameters is described.

Photoacoustic and photothermal detection of circulating tumor cells, bacteria and nanoparticles in cerebrospinal fluid in vivo and ex vivo.

PubMed

Nedosekin, Dmitry A; Juratli, Mazen A; Sarimollaoglu, Mustafa; Moore, Christopher L; Rusch, Nancy J; Smeltzer, Mark S; Zharov, Vladimir P; Galanzha, Ekaterina I

2013-06-01

Circulating cells, bacteria, proteins, microparticles, and DNA in cerebrospinal fluid (CSF) are excellent biomarkers of many diseases, including cancer and infections. However, the sensitivity of existing methods is limited in their ability to detect rare CSF biomarkers at the treatable, early-stage of diseases. Here, we introduce novel CSF tests based on in vivo photoacoustic flow cytometry (PAFC) and ex vivo photothermal scanning cytometry. In the CSF of tumor-bearing mice, we molecularly detected in vivo circulating tumor cells (CTCs) before the development of breast cancer brain metastasis with 20-times higher sensitivity than with current assays. For the first time, we demonstrated assessing three pathways (i.e., blood, lymphatic, and CSF) of CTC dissemination, tracking nanoparticles in CSF in vivo and their imaging ex vivo. In label-free CSF samples, we counted leukocytes, erythrocytes, melanoma cells, and bacteria and imaged intracellular cytochromes, hemoglobin, melanin, and carotenoids, respectively. Taking into account the safety of PAFC, its translation for use in humans is expected to improve disease diagnosis beyond conventional detection limits. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Detecting ionizing radiation with optical fibers down to biomedical doses

NASA Astrophysics Data System (ADS)

Avino, S.; D'Avino, V.; Giorgini, A.; Pacelli, R.; Liuzzi, R.; Cella, L.; De Natale, P.; Gagliardi, G.

2013-10-01

We report on a passive ionizing radiation sensor based on a fiber-optic resonant cavity interrogated by a high resolution interferometric technique. After irradiation in clinical linear accelerators, we observe significant variations of the fiber thermo-optic coefficient. Exploiting this effect, we demonstrate an ultimate detection limit of 160 mGy with an interaction volume of only 6 × 10-4 mm3. Thanks to its reliability, compactness, and sensitivity at biomedical dose levels, our system lends itself to real applications in radiation therapy procedures as well as in radiation monitoring and protection in medicine, aerospace, and nuclear power plants.

Impedance Biosensing to detect food allergens, endocrine disrupting chemicals, and food pathogens

NASA Astrophysics Data System (ADS)

Radhakrishnan, Rajeswaran

Electrochemical impedance biosensors can be viewed as an AC electroanalytical method for the analyte detection in the fields of biomedicine, environmental monitoring, and food and agriculture, amongst others. The most common format for AC impedance biosensing involves surface immobilization of an antibody, receptor protein, DNA strand, or other species capable of bio-recognition, and AC impedance detection of the binding event. Technological application of AC impedance biosensors has been hindered by several obstacles, including the more complex circuitry required for AC relative to DC electrochemistry, chemical and physical interference arising from non-specific adsorption, and the stability and reproducibility of protein immobilization. One focus of these PhD studies is on methods to reduce or compensate for non-specific adsorption, including sample dilution, site blocking with BSA, and the use of control electrodes onto which reference antibodies are immobilized. Examples that will be presented include impedance detection of food pathogens, such as Listeria monocytogenes, using a mouse monoclonal antibody immobilized onto an Au electrode. This yields detection limits of 5 CFU/ml and 4 CFU/ml for ideal solutions and filtered tomato extract, respectively. Control experiments with an Au electrode onto which a mouse monoclonal antibody to GAPDH is immobilized demonstrate that non-specific adsorption is insignificant for the system and methodology studied here. Control experiments with Salmonella enterica demonstrate no cross-reactivity to this food pathogen. In addition, Detection of two endocrine-disrupting chemicals (EDC), norfluoxetine and BDE-47, is reported here by impedance biosensing, with a detection limit of 8.5 and 1.3 ng/ml for norfluoxetine and BDE-47, respectively. Additional research has focused on alternative substrates and linker chemistries for protein immobilization, including the use of degenerate (highly doped) Si and bidendate thiol monolayer onto Au. Advantages of degenerate Si include a simpler equivalent circuit, simple and reproducible surface preparation, easy incorporation into ULSI devices, and the greater strength of Si-C bonds (~520 kJ/mole) relative to Au-S bonds (125-150 kJ/mole). New results demonstrating antibody regeneration atop degenerate (highly doped) Si are also reported. Using 0.2 M KSCN and 10 mM HF for antibody regeneration, peanut protein Ara h 1 is detected daily during a thirty-day trial. An impedance biosensor is reported that employs the bidentate thiol 16-[3,5-bis(mercaptomethyl)phenoxy]-hexadecanoic acid (BMPHA) to immobilize the mouse monoclonal antibody to peanut protein Ara h 1. The detection limit for Ara h 1 is approximately 0.71 ng/mL (0.01 nM), which is about one order of magnitude lower than that obtained for antibody immobilization atop the monodendate thiol, 16-mercaptohexadecanoic acid (16 MHA). Antibody regeneration was studied daily using a gentle denaturing agent, 0.2 M KSCN at pH 7.3. The antibody-coated on Au electrodes retained activity towards Ara h1 for 10 and 20 days of regeneration of the monodendate- and BMPHA-coated Au electrodes, respectively. This prolonged activity illustrates the superior stability of protein films atop the BMPHA bidentate thiol- coated Au electrode relative to the 16-MHA monodendate thiol-coated Au electrode.

Non-Enzymatic Detection of Bacterial Genomic DNA Using the Bio-Barcode Assay

PubMed Central

Hill, Haley D.; Vega, Rafael A.; Mirkin, Chad A.

2011-01-01

The detection of bacterial genomic DNA through a non-enzymatic nanomaterials based amplification method, the bio-barcode assay, is reported. The assay utilizes oligonucleotide functionalized magnetic microparticles to capture the target of interest from the sample. A critical step in the new assay involves the use of blocking oligonucleotides during heat denaturation of the double stranded DNA. These blockers bind to specific regions of the target DNA upon cooling, and prevent the duplex DNA from re-hybridizing, which allows the particle probes to bind. Following target isolation using the magnetic particles, oligonucleotide functionalized gold nanoparticles act as target recognition agents. The oligonucleotides on the nanoparticle (barcodes) act as amplification surrogates. The barcodes are then detected using the Scanometric method. The limit of detection for this assay was determined to be 2.5 femtomolar, and this is the first demonstration of a barcode type assay for the detection of double stranded, genomic DNA. PMID:17927207

A triphenylamine-functionalized luminescent sensor for efficient p-nitroaniline detection.

PubMed

Ji, Ning-Ning; Shi, Zhi-Qiang; Hu, Hai-Liang; Zheng, He-Gen

2018-05-14

The combination of π-conjugated fluorophores within a hybrid system gives rise to a triphenylamine-functionalized material [Zn(bpba)(NO3)] (1) (Hbpba = 4-(bis(4-(pyridin-4-yl)phenyl)amino)benzoic acid). Compound 1 features a 2D + 2D → 2D parallel polycatenation structure with 63-hcb net. Photophysical studies revealed that the title phase showed superior sensitivity towards p-nitroaniline (p-NA) with a low detection limit (down to ∼0.10 ppm). Specifically, following a new detection route, vapor-sensing experiments using a saturated ethanol solution of nitroaromatic isomers have been established for the first time. Highly sensitive and selective detection of p-NA by the proposed material with a rapid response time (t = 30 s, QE > 90.0%) as compared to that via the control isomers (t = 60s, QE < 6.0%) demonstrates an attractive feasible route and a promising luminescent sensor for nitroaromatic detection.

Antibody-Mediated Small Molecule Detection Using Programmable DNA-Switches.

PubMed

Rossetti, Marianna; Ippodrino, Rudy; Marini, Bruna; Palleschi, Giuseppe; Porchetta, Alessandro

2018-06-13

The development of rapid, cost-effective, and single-step methods for the detection of small molecules is crucial for improving the quality and efficiency of many applications ranging from life science to environmental analysis. Unfortunately, current methodologies still require multiple complex, time-consuming washing and incubation steps, which limit their applicability. In this work we present a competitive DNA-based platform that makes use of both programmable DNA-switches and antibodies to detect small target molecules. The strategy exploits both the advantages of proximity-based methods and structure-switching DNA-probes. The platform is modular and versatile and it can potentially be applied for the detection of any small target molecule that can be conjugated to a nucleic acid sequence. Here the rational design of programmable DNA-switches is discussed, and the sensitive, rapid, and single-step detection of different environmentally relevant small target molecules is demonstrated.

A Novel Sensitive Luminescence Probe Microspheres for Rapid and Efficient Detection of τ-Fluvalinate in Taihu Lake

PubMed Central

Wang, Jixiang; Wang, Yunyun; Qiu, Hao; Sun, Lin; Dai, Xiaohui; Pan, Jianming; Yan, Yongsheng

2017-01-01

Fluorescent molecularly imprinted polymers have shown great promise in biological or chemical separations and detection, due to their high stability, selectivity and sensitivity. In this work, fluorescent molecularly imprinted microsphere was synthesized via precipitation polymerization, which could separate efficiently and rapidly detect τ-fluvalinate (a toxic insecticide) in water samples, was reported. The fluorescent imprinted sensor showed excellent stability, outstanding selectivity and the limit of detection low to 12.14 nM, good regeneration ability which still kept good sensitivity after 8 cycling experiments and fluorescence quenching mechanism was illustrated in details. In addition, the fluorescent sensor was further used to detect τ-fluvalinate in real samples from Taihu Lake. Despite the relatively complex components of the environment water, the fluorescent imprinted microspheres sitll showed good recovery, clearly demonstrating the potental value of this smart sensor nanomaterial in environment monitoring. PMID:28485402

Leveraging zinc interstitials and oxygen vacancies for sensitive biomolecule detection through selective surface functionalization

NASA Astrophysics Data System (ADS)

Radha Shanmugam, Nandhinee; Muthukumar, Sriram; Chaudhry, Shajee; Prasad, Shalini

2015-03-01

In this study, functionally engineered EIS technique was implemented to investigate the influence of surface functionalization on sensitivity of biomolecule detection using nanostructured ZnO platform. Organic molecules with thiol and carboxylic functional groups were chosen to control biomolecule immobilization on zinc and oxygen-terminated 2D planar and 1D nanostructured ZnO surfaces. The amount of functionalization and its influence on charge perturbations at the ZnO-electrolyte interface were studied using fluorescence and EIS measurements. We observed the dependence of charge transfer on both the polarity of platform and concentration of cross-linker molecules. Such selectively modified surfaces were used for detection of cortisol, a major stress indicator. Results demonstrated preferential binding of thiol groups to Zn terminations and thus leveraging ZnO interstitials increases the sensitivity of detection over larger dynamic range with detection limit at 10fg/mL.

Urine sample used for detection of toxoplasma gondii infection by loop-mediated isothermal amplification (LAMP).

PubMed

Hu, Xin; Pan, Chang-Wang; Li, Ya-Fei; Wang, Han; Tan, Feng

2012-02-01

In this study, a loop-mediated isothermal amplification (LAMP) assay was established to detect Toxoplasma gondii DNA in mice infected with T. gondii PRU strain. This LAMP assay was based on the sequence of highly repetitive B1 gene. The detection limit of T. gondii LAMP assay was 1 pg of T. gondii DNA, which was evaluated using 10-fold serially diluted DNA of cultured parasites. The LAMP assay was also highly specific for T. gondii and able to detect T. gondii DNA in urine of mice treated with dexamethasone at 90 day post infection (p.i.), although this assay could not detect the DNA in mice urine 2-6 days p.i. These results demonstrated that LAMP is effective for evaluation of therapy effectiveness for T. gondii infection. The established LAMP assay may represent a useful and practical tool for the routine diagnosis and therapeutic evaluation of human toxoplasmosis.

Development of Engineered Bacteriophages for Escherichia coli Detection and High-Throughput Antibiotic Resistance Determination.

PubMed

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

2017-04-28

T7 bacteriophages (phages) have been genetically engineered to carry the lacZ operon, enabling the overexpression of beta-galactosidase (β-gal) during phage infection and allowing for the enhanced colorimetric detection of Escherichia coli (E. coli). Following the phage infection of E. coli, the enzymatic activity of the released β-gal was monitored using a colorimetric substrate. Compared with a control T7 phage, our T7 lacZ phage generated significantly higher levels of β-gal expression following phage infection, enabling a lower limit of detection for E. coli cells. Using this engineered T7 lacZ phage, we were able to detect E. coli cells at 10 CFU·mL -1 within 7 h. Furthermore, we demonstrated the potential for phage-based sensing of bacteria antibiotic resistance profiling using our T7 lacZ phage, and subsequent β-gal expression to detect antibiotic resistant profile of E. coli strains.

;Turn-on; fluorescent probe detection of Ca2 + ions and applications to bioimaging

NASA Astrophysics Data System (ADS)

Zhang, Huifang; Yin, Caixia; Liu, Tao; Zhang, Yongbin; Huo, Fangjun

2017-06-01

Ca2 + is intracellular divalent cation with the largest concentration variations and involved in many biological phenomena and often acted as a second messenger in signaling pathway. Therefore, the development of probes for specific Ca2 + detection is of great importance. Herein, a novel turn-on fluorescent probe for the detection of Ca2 + in MeCN-aqueous medium was designed and synthesized. The probe displayed responses to Ca2 + with a fluorescence enhancement at 525 nm, accompanying with a distinct fluorescence change from nearly colorless to bright yellow-green. Besides, the probe exhibited a rapid signal response time (within 25 s), a good linearity range and a lower detection limit (2.70 × 10- 7 M). In addition, the ability of the probe to detect Ca2 + in living cells (HeLa cells) via an enhancement of the fluorescence has also been demonstrated.

Progress in proton-detected solid-state NMR (SSNMR): Super-fast 2D SSNMR collection for nano-mole-scale proteins

NASA Astrophysics Data System (ADS)

Ishii, Yoshitaka; Wickramasinghe, Ayesha; Matsuda, Isamu; Endo, Yuki; Ishii, Yuji; Nishiyama, Yusuke; Nemoto, Takahiro; Kamihara, Takayuki

2018-01-01

Proton-detected solid-state NMR (SSNMR) spectroscopy has attracted much attention due to its excellent sensitivity and effectiveness in the analysis of trace amounts of amyloid proteins and other important biological systems. In this perspective article, we present the recent sensitivity limit of 1H-detected SSNMR using "ultra-fast" magic-angle spinning (MAS) at a spinning rate (νR) of 80-100 kHz. It was demonstrated that the high sensitivity of 1H-detected SSNMR at νR of 100 kHz and fast recycling using the paramagnetic-assisted condensed data collection (PACC) approach permitted "super-fast" collection of 1H-detected 2D protein SSNMR. A 1H-detected 2D 1H-15N correlation SSNMR spectrum for ∼27 nmol of a uniformly 13C- and 15N-labeled GB1 protein sample in microcrystalline form was acquired in only 9 s with 50% non-uniform sampling and short recycle delays of 100 ms. Additional data suggests that it is now feasible to detect as little as 1 nmol of the protein in 5.9 h by 1H-detected 2D 1H-15N SSNMR at a nominal signal-to-noise ratio of five. The demonstrated sensitivity is comparable to that of modern solution protein NMR. Moreover, this article summarizes the influence of ultra-fast MAS and 1H-detection on the spectral resolution and sensitivity of protein SSNMR. Recent progress in signal assignment and structural elucidation by 1H-detected protein SSNMR is outlined with both theoretical and experimental aspects.

Limits of Spatial Attention in Three-Dimensional Space and Dual-task Driving Performance

PubMed Central

Andersen, George J.; Ni, Rui; Bian, Zheng; Kang, Julie

2010-01-01

The present study examined the limits of spatial attention while performing two driving relevant tasks that varied in depth. The first task was to maintain a fixed headway distance behind a lead vehicle that varied speed. The second task was to detect a light-change target in an array of lights located above the roadway. In Experiment 1 the light detection task required drivers to encode color and location. The results indicated that reaction time to detect a light-change target increased and accuracy decreased as a function of the horizontal location of the light-change target and as a function of the distance from the driver. In a second experiment the light change task was changed to a singleton search (detect the onset of a yellow light) and the workload of the car following task was systematically varied. The results of Experiment 2 indicated that RT increased as a function of task workload, the 2D position of the light-change target and the distance of the light-change target. A multiple regression analysis indicated that the effect of distance on light detection performance was not due to changes in the projected size of the light target. In Experiment 3 we found that the distance effect in detecting a light change could not be explained by the location of eye fixations. The results demonstrate that when drivers attend to a roadway scene attention is limited in three-dimensional space. These results have important implications for developing tests for assessing crash risk among drivers as well as the design of in vehicle technologies such as head-up displays. PMID:21094336

Evaluation of a manual DNA extraction protocol and an isothermal amplification assay for detecting HIV-1 DNA from dried blood spots for use in resource-limited settings.

PubMed

Jordan, Jeanne A; Ibe, Christine O; Moore, Miranda S; Host, Christel; Simon, Gary L

2012-05-01

In resource-limited settings (RLS) dried blood spots (DBS) are collected on infants and transported through provincial laboratories to a central facility where HIV-1 DNA PCR testing is performed using specialized equipment. Implementing a simpler approach not requiring such equipment or skilled personnel could allow the more numerous provincial laboratories to offer testing, improving turn-around-time to identify and treat infected infants sooner. Assess performances of a manual DNA extraction method and helicase-dependent amplification (HDA) assay for detecting HIV-1 DNA from DBS. 60 HIV-1 infected adults were enrolled, blood samples taken and DBS made. DBS extracts were assessed for DNA concentration and beta globin amplification using PCR and melt-curve analysis. These same extracts were then tested for HIV-1 DNA using HDA and compared to results generated by PCR and pyrosequencing. Finally, HDA limit of detection (LOD) studies were performed using DBS extracts prepared with known numbers of 8E5 cells. The manual extraction protocol consistently yielded high concentrations of amplifiable DNA from DBS. LOD assessment demonstrated HDA detected ∼470 copies/ml of HIV-1 DNA extracts in 4/4 replicates. No statistical difference was found using the McNemar's test when comparing HDA to PCR for detecting HIV-1 DNA from DBS. Using just a magnet, heat block and pipettes, the manual extraction protocol and HDA assay detected HIV-1 DNA from DBS at levels that would be useful for early infant diagnosis. Next steps will include assessing HDA for non-B HIV-1 subtypes recognition and comparison to Roche HIV-1 DNA v1.5 PCR assay. Copyright © 2012 Elsevier B.V. All rights reserved.