Collapse of chain anadiplosis-structured DNA nanowires for highly sensitive colorimetric assay of nucleic acids.

PubMed

Xu, Jianguo; Wu, Zai-Sheng; Chen, Yanru; Zheng, Tingting; Le, Jingqing; Jia, Lee

2017-02-14

In this work, we have proposed a chain anadiplosis-structured DNA nanowire by using two well-defined assembly strands (AS1 and AS2). The presence of a target analyte would drive the single-stranded AS1 dissociate from the pre-formatted nanowire, converting into a fully double-stranded form responsible for extensive accumulation of G-rich cleavage fragment1 (GCF1) because of an autonomously performed polymerization/nicking/displacement process. In turn, the produced GCF1 is able to hybridize with the un-peeled AS2, allowing the replication over AS2 to occur and generate large amounts of G-rich cleavage fragment2 (GCF2) with the ability to hybridize with the un-peeled AS1, thereafter initiating new enzymatic reactions for further collection of GCF1. Because the reactions occur repeatedly, the assembled nanowires gradually dissociated and completely collapsed in the end, achieving the goal of substantial signal amplification for the colorimetric readout of the target analytes. The sensing feasibility is firstly verified by one trigger primer (TP), and then exemplified with the detection of the target, the kras oncogene, with high sensitivity and specificity. As a proof-of-concept strategy, the intelligent signal readout pathway and desired assay ability provide unique insights into the materials research and biological studies.

Improving colorimetric assays through protein enzyme-assisted gold nanoparticle amplification.

PubMed

Xie, Xiaoji; Xu, Wei; Liu, Xiaogang

2012-09-18

The discovery of the DNA-mediated assembly of gold nanoparticles was a great moment in the history of science; this understanding and chemical control enabled the rational design of functional nanomaterials as novel probes in biodetection. In contrast with conventional probes such as organic dyes, gold nanoparticles exhibit high photostability and unique size-dependent optical properties. Because of their high extinction coefficients and strong distance dependent optical properties, these nanoparticles have emerged over the past decade as a promising platform for rapid, highly sensitive colorimetric assays that allow for the visual detection of low concentrations of metal ions, small molecules, and biomacromolecules. These discoveries have deepened our knowledge of biological phenomena and facilitated the development of many new diagnostic and therapeutic tools. Despite these many advances and continued research efforts, current nanoparticle-based colorimetric detection systems still suffer from several drawbacks, such as limited sensitivity and selectivity. This Account describes the recent development of colorimetric assays based on protein enzyme-assisted gold nanoparticle amplification. The benefits of such detection systems include significantly improved detection sensitivity and selectivity. First, we discuss the general design of enzyme-modified nanoparticle systems in colorimetric assays. We show that a quantitative understanding of the unique properties of different enzymes is paramount for effective biological assays. We then examine the assays for nucleic acid detection based on different types of enzymes, including endonucleases, ligases, and polymerases. For each of these assays, we identify the underlying principles that contribute to the enhanced detection capability of nanoparticle systems and illustrate them with selected examples. Furthermore, we demonstrate that the combination of gold nanoparticles and specific enzymes can probe enzyme dynamics

Sensitive colorimetric visualization of dihydronicotinamide adenine dinucleotide based on anti-aggregation of gold nanoparticles via boronic acid-diol binding.

PubMed

Liu, Shufeng; Du, Zongfeng; Li, Peng; Li, Feng

2012-05-15

A facile, highly sensitive colorimetric strategy for dihydronicotinamide adenine dinucleotide (NADH) detection is proposed based on anti-aggregation of gold nanoparticles (AuNPs) via boronic acid-diol binding chemistry. The aggregation agent, 4-mercaptophenylboronic acid (MPBA), has specific affinity for AuNPs through Au-S interaction, leading to the aggregation of AuNPs by self-dehydration condensation at a certain concentration, which is responsible for a visible color change of AuNPs from wine red to blue. With the addition of NADH, MPBA would prefer reacting with NADH to form stable borate ester via boronic acid-diol binding dependent on the pH and solvent, revealing an obvious color change from blue to red with increasing the concentration of NADH. The anti-aggregation effect of NADH on AuNPs was seen by the naked eye and monitored by UV-vis extinction spectra. The linear range of the colorimetric sensor for NADH is from 8.0 × 10(-9)M to 8.0 × 10(-6)M, with a low detection limit of 2.0 nM. The as-established colorimetric strategy opened a new avenue for NADH determination. Copyright © 2012 Elsevier B.V. All rights reserved.

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

PubMed

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

2015-01-01

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

Highly selective fluorescent and colorimetric chemosensor for detection of Hg2 + ion in aqueous media

NASA Astrophysics Data System (ADS)

Zareh Jonaghani, Mohammad; Zali-Boeini, Hassan

2017-05-01

A highly efficient and selective fluorescent and colorimetric chemosensor based on naphthothiazole skeleton was synthesized and its colorimetric and fluorescent properties were investigated. The sensor displays a rapid and highly selective colorimetric and fluorescence response toward Hg2 + without interference with other metal ions in CH3CN/H2O mixture (50/50, v/v). The detection limit for the fluorescent chemosensor S1 toward Hg2 + was 3.42 × 10- 8 M.

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

NASA Astrophysics Data System (ADS)

He, Yi; Peng, Rufang

2014-11-01

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

Highly selective and sensitive macrocycle-based dinuclear foldamer for fluorometric and colorimetric sensing of citrate in water.

PubMed

Rhaman, Md Mhahabubur; Hasan, Mohammad H; Alamgir, Azmain; Xu, Lihua; Powell, Douglas R; Wong, Bryan M; Tandon, Ritesh; Hossain, Md Alamgir

2018-01-10

The selective detection of citrate anions is essential for various biological functions in living systems. A quantitative assessment of citrate is required for the diagnosis of various diseases in the human body; however, it is extremely challenging to develop efficient fluorescence and color-detecting molecular probes for sensing citrate in water. Herein, we report a macrocycle-based dinuclear foldamer (1) assembled with eosin Y (EY) that has been studied for anion binding by fluorescence and colorimetric techniques in water at neutral pH. Results from the fluorescence titrations reveal that the 1·EY ensemble strongly binds citrate anions, showing remarkable selectivity over a wide range of inorganic and carboxylate anions. The addition of citrate anions to the 1·EY adduct led to a large fluorescence enhancement, displaying a detectable color change under both visible and UV light in water up to 2 μmol. The biocompatibility of 1·EY as an intracellular carrier in a biological system was evaluated on primary human foreskin fibroblast (HF) cells, showing an excellent cell viability. The strong binding properties of the ensemble allow it to be used as a highly sensitive, detective probe for biologically relevant citrate anions in various applications.

Highly Sensitive and Selective Colorimetric and Off-On Fluorescent Reversible Chemosensors for Al3+ Based on the Rhodamine Fluorophore

PubMed Central

Mergu, Naveen; Singh, Ashok Kumar; Gupta, Vinod Kumar

2015-01-01

A series of rhodamine derivatives L1–L3 have been prepared and characterized by IR, 1H-NMR, 13C-NMR and ESI-MS. These compounds exhibited selective and sensitive “turn-on” fluorescent and colorimetric responses to Al3+ in methanol. Upon the addition of Al(III), the spiro ring was opened and a metal-probe complex was formed in a 1:1 stoichiometry, as was further confirmed by ESI-MS spectroscopy. The chemo-dosimeters L1–L3 exhibited good binding constants and low detection limits towards Al(III). We also successfully demonstrate the reversibility of the metal to ligand complexation (opened ring to spirolactam ring). PMID:25897498

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

PubMed

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

2016-08-01

High-risk human papillomavirus (HR-HPV) causes cervical cancer. HPV16 and HPV18 are the most prevalent strains of the virus reported in women worldwide. Loop-mediated isothermal amplification (LAMP) is an alternative method for DNA detection under isothermal conditions. However, it results in a turbid amplified product which is not easily detected by the naked eye. This study aimed to develop an improved technique by using gold nanoparticles (AuNPs) attached to a single-stranded DNA probe for the detection of HPV16 and HPV18. Detection of the LAMP product by AuNP color change was compared with detection by visual turbidity. The optimal conditions for this new LAMP-AuNP assay were an incubation time of 20min and a temperature of 65°C. After LAMP amplification was complete, its products were hybridized with the AuNP probe for 5min and then detected by the addition of magnesium salt. The color changed from red to blue as a result of aggregation of the AuNP probe under high ionic strength conditions produced by the addition of the salt. The sensitivity of the LAMP-AuNP assay was greater than the LAMP turbidity assay by up to 10-fold for both HPV genotypes. The LAMP-AuNP assay showed higher sensitivity and ease of visualization than did the LAMP turbidity for the detection of HPV16 and HPV18. Additionally, AuNP-HPV16 and AuNP-HPV18 probes were stable for over 1year. The combination of LAMP and the AuNP-probe colorimetric assay offers a simple, rapid and highly sensitive alternative diagnostic tool for the detection of HPV16 and HPV18 in district hospitals or field studies. Copyright © 2016 Elsevier B.V. All rights reserved.

Aspartic acid-promoted highly selective and sensitive colorimetric sensing of cysteine in rat brain.

PubMed

Qian, Qin; Deng, Jingjing; Wang, Dalei; Yang, Lifen; Yu, Ping; Mao, Lanqun

2012-11-06

Direct selective determination of cysteine in the cerebral system is of great importance because of the crucial roles of cysteine in physiological and pathological processes. In this study, we report a sensitive and selective colorimetric assay for cysteine in the rat brain with gold nanoparticles (Au-NPs) as the signal readout. Initially, Au-NPs synthesized with citrate as the stabilizer are red in color and exhibit absorption at 520 nm. The addition of an aqueous solution (20 μL) of cysteine or aspartic acid alone to a 200 μL Au-NP dispersion causes no aggregation, while the addition of an aqueous solution of cysteine into a Au-NP dispersion containing aspartic acid (1.8 mM) causes the aggregation of Au-NPs and thus results in the color change of the colloid from wine red to blue. These changes are ascribed to the ion pair interaction between aspartic acid and cysteine on the interface between Au-NPs and solution. The concentration of cysteine can be visualized with the naked eye and determined by UV-vis spectroscopy. The signal output shows a linear relationship for cysteine within the concentration range from 0.166 to 1.67 μM with a detection limit of 100 nM. The assay demonstrated here is highly selective and is free from the interference of other natural amino acids and other thiol-containing species as well as the species commonly existing in the brain such as lactate, ascorbic acid, and glucose. The basal dialysate level of cysteine in the microdialysate from the striatum of adult male Sprague-Dawley rats is determined to be around 9.6 ± 2.1 μM. The method demonstrated here is facile but reliable and durable and is envisaged to be applicable to understanding the chemical essence involved in physiological and pathological events associated with cysteine.

Highly Sensitive and Fast Response Colorimetric Humidity Sensors Based on Graphene Oxides Film.

PubMed

Chi, Hong; Liu, Yan Jun; Wang, FuKe; He, Chaobin

2015-09-16

Uniform graphene oxide (GO) film for optical humidity sensing was fabricated by dip-coating technique. The resulting GO thin film shows linear optical shifts in the visible range with increase of humidity in the whole relative humidity range (from dry state to 98%). Moreover, GO films exhibit ultrafast sensing to moisture within 250 ms because of the unique atomic thinness and superpermeability of GO sheets. The humidity sensing mechanism was investigated using XRD and computer simulation. The ultrasensitive humidity colorimetric properties of GOs film may enable many potential applications such as disposable humidity sensors for packaging, health, and environmental monitoring.

A highly efficient colorimetric immunoassay using a nanocomposite entrapping magnetic and platinum nanoparticles in ordered mesoporous carbon.

PubMed

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

2014-01-01

Nanocomposite to achieve ultrafast immunoassay: a new synergistically integrated nanocomposite consisting of magnetic and platinum nanoparticles, simultaneously entrapped in mesoporous carbon, is developed as a promising enzyme mimetic candidate to achieve ultrafast colorimetric immunoassays. Using new assay system, clinically important target molecules, such as human epidermal growth factor receptor 2 (HER2) and diarrhea-causing rotavirus, can be detected in only 3 min at room temperature with high specificity and sensitivity. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A novel, colorimetric method for biogenic amine detection based on arylalkylamine N-acetyltransferase.

PubMed

Leng, Pei-Qiang; Zhao, Feng-Lan; Yin, Bin-Cheng; Ye, Bang-Ce

2015-05-21

We developed a novel colorimetric method for rapid detection of biogenic amines based on arylalkylamine N-acetyltransferase (aaNAT). The proposed method offers distinct advantages including simple handling, high speed, low cost, good sensitivity and selectivity.

Reconsideration of the Zincke salt: An efficient colorimetric chemosensor for detection of ethylamines

NASA Astrophysics Data System (ADS)

Kim, Jong H.

2018-03-01

In this work, an efficient colorimetric chemosensor for the detection of ethylamines using a pyridinium salt (the Zincke salt) is reported. Highly sensitive and selective reactivity of the Zincke salt enables colorimetric response of the Zincke salt solution to the ethylamines by showing well-defined visible color changes from colorless to the deep red. Furthermore, the Zincke salt thin film exhibits discernable color changes in response to ethylamine gas as well, which allows fabrication of simple, fast and portable strip- and textile-type ethylamine sensors.

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

NASA Astrophysics Data System (ADS)

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

2016-04-01

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

Colorimetric and luminescent bifunctional iridium(III) complexes for the sensitive recognition of cyanide ions

NASA Astrophysics Data System (ADS)

Chen, Xiudan; Wang, Huili; Li, Jing; Hu, Wenqin; Li, Mei-Jin

2017-02-01

Two new cyclometalated iridium(III) complexes [(ppy)2Irppz]Cl (1) and [(ppy)2Irbppz]Cl (2) (where ppy = 2-phenylpyridine, ppz = 4,7-phenanthrolino-5,6:5,6-pyrazine, bppz = 2.3-di-2-pyridylpyrazine), were designed and synthesized. The structure of [(ppy)2Irppz]Cl was determined by single crystal X-ray diffraction. Their photophysical properties were also studied. This kind of complexes could coordinate with Cu2 +, the photoluminescence (PL) of the complex was quenched, and the color changed from orange-red to green. The forming M-Cu (M: complexes 1 and 2) ensemble could be further utilized as a colorimetric and emission ;turn-on; bifunctional detection for CN-, especially for complex 1-Cu2 + showed a high sensitivity toward CN- with a limit of diction is 97 nM. Importantly, this kind of iridium(III) complexes shows a unique recognition of cyanide ions over other anions which makes it an eligible sensing probe for cyanide ions.

Assessment of simple colorimetric procedures to determine smoking status of diabetic subjects.

PubMed

Smith, R F; Mather, H M; Ellard, G A

1998-02-01

The performance of a simple colorimetric assay for urinary nicotine metabolites to assess smoking status in diabetic subjects (n = 251) was investigated. Several variations of the colorimetric assay and a qualitative extraction procedure were evaluated in comparison with a cotinine immunoassay as the "gold standard." Among these, the best overall performance was achieved with the qualitative test (sensitivity 95%; specificity 100%). The quantitative measurement of total nicotine metabolites performed less well (sensitivity 92%; specificity 97%) but could be improved by incorporating a blank extraction (sensitivity 98%; specificity 98%). Allowance for diuresis appeared to offer no advantage over the other methods. These results support previous findings regarding the use of these colorimetric procedures in nondiabetic subjects and, contrary to other recent observations, their performance was not impaired in diabetic patients.

Highly selective colorimetric bacteria sensing based on protein-capped nanoparticles.

PubMed

Qiu, Suyan; Lin, Zhenyu; Zhou, Yaomin; Wang, Donggen; Yuan, Lijuan; Wei, Yihua; Dai, Tingcan; Luo, Linguang; Chen, Guonan

2015-02-21

A rapid and cost-effective colorimetric sensor has been developed for the detection of bacteria (Bacillus subtilis was selected as an example). The sensor was designed to rely on lysozyme-capped AuNPs with the advantages of effective amplification and high specificity. In the sensing system, lysozyme was able to bind strongly to Bacillus subtilis, which effectively induced a color change of the solution from light purple to purplish red. The lowest concentration of Bacillus subtilis detectable by the naked eye was 4.5 × 10(3) colony-forming units (CFU) mL(-1). Similar results were discernable from UV-Vis absorption measurements. A good specificity was observed through a statistical analysis method using the SPSS software (version 17.0). This simple colorimetric sensor may therefore be a rapid and specific method for a bacterial detection assay in complex samples.

A Sensitive Microplate Assay for Lipase Activity Measurement Using Olive Oil Emulsion Substrate: Modification of the Copper Soap Colorimetric Method.

PubMed

Mustafa, Ahmad; Karmali, Amin; Abdelmoez, Wael

2016-01-01

The present work involves a sensitive high-throughput microtiter plate based colorimetric assay for estimating lipase activity using cupric acetate pyridine reagent (CAPR). In the first approach, three factors two levels factorial design methodology was used to evaluate the interactive effect of different parameters on the sensitivity of the assay method. The optimization study revealed that the optimum CAPR concentration was 7.5% w/v, the optimum solvent was heptane and the optimum CAPR pH was 6. In the second approach, the optimized colorimetric microplate assay was used to measure lipase activity based on enzymatic hydrolysis of olive oil emulsion substrate at 37°C and 150 rpm. The emulsion substrates were formulated by using olive oil, triton X-100 (10% v/v in pH 8) and sodium phosphate buffer of pH 8 in ratio of 1:1:1 in the case of Candida sp. lipase. While in the case of immobilized lipozyme RMIM, The emulsion substrates were formulated by using olive oil, triton X-100 (1% v/v in pH 8) and sodium phosphate buffer of pH 8 in ratio of 2:1:1. Absorbance was measured at 655 nm. The stability of this assay (in terms of colored heptane phase absorbance readings) retained more than 92.5% after 24 h at 4°C compared to the absorbance readings measured at zero time. In comparison with other lipase assay methods, beside the developed sensitivity, the reproducibility and the lower limit of detection (LOD) of the proposed method, it permits analyzing of 96 samples at one time in a 96-well microplate. Furthermore, it consumes small quantities of chemicals and unit operations.

Plasmonic colorimetric sensors based on etching and growth of noble metal nanoparticles: Strategies and applications.

PubMed

Zhang, Zhiyang; Wang, Han; Chen, Zhaopeng; Wang, Xiaoyan; Choo, Jaebum; Chen, Lingxin

2018-08-30

Plasmonic colorimetric sensors have emerged as a powerful tool in chemical and biological sensing applications due to the localized surface plasmon resonance (LSPR) extinction in the visible range. Among the plasmonic sensors, the most famous sensing mode is the "aggregation" plasmonic colorimetric sensor which is based on plasmon coupling due to nanoparticle aggregation. Herein, this review focuses on the newly-developing plasmonic colorimetric sensing mode - the etching or the growth of metal nanoparticles induces plasmon changes, namely, "non-aggregation" plasmonic colorimetric sensor. This type of sensors has attracted increasing interest because of their exciting properties of high sensitivity, multi-color changes, and applicability to make a test strip. Of particular interest, the test strip by immobilization of nanoparticles on the substrate can avoid the influence of nanoparticle auto-aggregation and increase the simplicity in storage and use. Although there are many excellent reviews available that describe the advance of plasmonic sensors, limited attention has been paid to the plasmonic colorimetric sensors based on etching or growth of metal nanoparticles. This review highlights recent progress on strategies and application of "non-aggregation" plasmonic colorimetric sensors. We also provide some personal insights into current challenges associated with "non-aggregation" plasmonic colorimetric sensors and propose future research directions. Copyright © 2018 Elsevier B.V. All rights reserved.

Label-free colorimetric sensor for sensitive detection of choline based on DNAzyme-choline oxidase coupling.

PubMed

Nikzad, Nasrin; Karami, Zahra

2018-04-14

Changes in choline levels can be associated with diseases such as Alzheimer, Parkinson, Huntington, fatty liver, interstitial lung abnormalities, autism and so on. Therefore, quantitative determination of choline is important in the biological and clinical analysis. So far, several methods have been investigated for measuring choline in the body fluids, each of which has disadvantages such as the need for specialist ability, complexity, and high cost. For this purpose, a facile and sensitive colorimetric biosensor based on DNAzyme-choline oxidase coupling used for the determination of choline. In this method, the first, choline oxidase produces H 2 O 2 and betaine in the presence of choline and oxygen, then, the DNAzyme converts colorless ABTS into green ABTS + radicals. Compared to the previous methods, the linear range and the limit of detection of this talented biosensor were 0.1-25 μM and 22 nM. Choline measurement using this biosensor has shown satisfactory selectivity and repeatability. Its recovery was 96.9-103.7%, which shows the reliability of biosensor assay in biological samples. Simplicity, low cost, naked eye, high sensitivity, and precision are the benefits of this biosensor. Taken to gather, the proposed system can be considered as a great biosensor for measuring choline levels especially in point of care diagnostic. Copyright © 2018 Elsevier B.V. All rights reserved.

Colorimetric sensing of selenocystine using gold nanoparticles.

PubMed

Liu, Liyang; Wang, Xia; Yang, Juan; Bai, Yan

2017-10-15

We present a highly selective and sensitive colorimetric method for the detection of selenocystine (SeCys) coexisting with other amino acids, especially cysteine (Cys) using the gold nanoparticles (AuNPs). Firstly, Cys was oxidized to cystine (Cys-Cys) by dissolved oxygen under Cu 2+ catalysis in the pre-reaction, which eliminated the interference of Cys in the SeCys sensing process. Then SeCys induced the rapid aggregation of AuNPs through Au-Se bond and complex formation of Cu 2+ -SeCys in the colorimetric reaction, in which the color change of AuNPs from red to blue or purple with the naked eye detection or with a UV-vis spectrophotometric determination. The concentration of SeCys was quantified by the value at 670 nm from the second-derivative SPR absorbance spectrum. The linear range was from 2 μM to 14 μM with correlation coefficient of 0.999 and a detection limit (LOD) was 0.14 μM. Moreover, the colorimetric response of AuNPs exhibited remarkable specificity to SeCys coexisting with 18 amino acids in a simulation sample, in which the total concentration of Cys and Cys-Cys was less than 15 μM and the each concentration of other 16 common amino acids was 10 μM. Copyright © 2017 Elsevier Inc. All rights reserved.

Colorimetric detection for paper-based biosensing applications

NASA Astrophysics Data System (ADS)

Brink, C.; Joubert, T.-H.

2016-02-01

Research on affordable point-of-care health diagnostics is rapidly advancing1. Colorimetric biosensor applications are typically qualitative, but recently the focus has been shifted to quantitative measurements2,3. Although numerous qualitative point-of-care (POC) health diagnostic devices are available, the challenge exists of developing a quantitative colorimetric array reader system that complies with the ASSURED (Affordable, Sensitive, Specific, User-friendly, Rapid and Robust, Equipment-free, Deliverable to end-users) principles of the World Health Organization4. This paper presents a battery powered 8-bit tonal resolution colorimetric sensor circuit for paper microfluidic assays using low cost photo-detection circuitry and a low-power LED light source. A colorimetric 3×3-pixel array reader was developed for rural environments where resources and personnel are limited. The device sports an ultralow-power E-ink paper display. The colorimetric device includes integrated GPS functionality and EEPROM memory to log measurements with geo-tags for possible analysis of regional trends. The device competes with colour intensity measurement techniques using smartphone cameras, but proves to be a cheaper solution, compensating for the typical performance variations between cameras of different brands of smartphones. Inexpensive methods for quantifying bacterial assays have been shown using desktop scanners, which are not portable, and cameras, which suffer severely from changes in ambient light in different environments. Promising colorimetric detection results have been demonstrated using devices such as video cameras5, digital colour analysers6, flatbed scanners7 or custom portable readers8. The major drawback of most of these methods is the need for specialized instrumentation and for image analysis on a computer.

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

PubMed

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

2013-10-01

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

A high resolution Passive Flux Meter approach based on colorimetric responses

NASA Astrophysics Data System (ADS)

Chardi, K.; Dombrowski, K.; Cho, J.; Hatfield, K.; Newman, M.; Annable, M. D.

2016-12-01

Subsurface water and contaminant mass flux measurements are critical in determining risk, optimizing remediation strategies, and monitoring contaminant attenuation. The standard Passive Flux Meter, hereafter knows as a (PFM), is a well-developed device used for determining and monitoring rates of groundwater and contaminant mass flux in screened wells. The current PFM is a permeable device that contains granular activated carbon impregnated with alcohol tracers which is deployed in a flow field for a designated period of time. Once extracted, sampling requires laboratory analysis to quantify Darcy flux, which can be time consuming and have significant cost. To expedite test results, a modified PFM based on the image analysis of colorimetric responses, herein referred to as a colorimetric Passive Flux Meter (cPFM), was developed. Various dyes and sorbents were selected and evaluated to determine colorimetric response to water flow. Rhodamine, fluorescent yellow, fluorescent orange, and turmeric were the dye candidates while 100% wool and a 35% wool blend with 65% rayon were the sorbent candidates selected for use in the cPFM. Ultraviolet light image analysis was used to calculate average color intensity using ImageJ, a Java-based image processing program. These results were then used to quantify Darcy flux. Error ranges evaluated for Darcy flux using the cPFM are comparable to those with the standard, activated carbon based, PFM. The cPFM has the potential to accomplish the goal of obtaining high resolution Darcy flux data while eliminating high costs and analysis time. Implications of groundwater characteristics, such as PH and contaminant concentrations, on image analysis are to be tested through laboratory analysis followed by field testing of the cPFM.

Simple and Sensitive Colorimetric Assay for Pb2+ Based on Glutathione Protected Ag Nanoparticles by Salt Amplification.

PubMed

Chen, Zhang; Li, Huidong; Chu, Lin; Liu, Chenbin; Luo, Shenglian

2015-02-01

A simple and sensitive colorimetric assay for Pb2+ detection has been reported using glutathione protected silver nanoparticles (AgNPs) by salt amplification. The naked AgNPs aggregate under the influence of salt. Glutathione (GSH) can bind to AgNPs via Ag-S bond, helping AgNPs to against salt-induced aggregation. However, GSH binding to AgNPs can be compromised by the interaction between Pb2+ and GSH. As a result, Pb2+-mediated aggregation of AgNPs under the influence of salt is reflected by the UV-Visible spectrum, and the qualitative and quantitative detection for Pb2+ is accomplished, with the detection range 0.5-4 µM and a detection limit of 0.5 µM. At the same time, Pb2+ in real water sample is detected. Furthermore, the high selectivity and low cost of the assay means it is promising for enviromental applications.

Single-layer MnO2 nanosheets for sensitive and selective detection of glutathione by a colorimetric method

NASA Astrophysics Data System (ADS)

Di, Weihua; Zhang, Xiang; Qin, Weiping

2017-04-01

The rapid, sensitive and selective detection of glutathione (GSH) is of great importance in the biological systems. In this work, a template-free and one-step method was used to synthesize the single-layer MnO2 nanosheets via a redox reaction. The resulting product was characterized by XRD, TEM, FTIR, XPS and UV-vis absorption. The addition of GSH results in the change of solution color depth owing to the occurrence of a redox reaction between MnO2 and GSH, enabling colorimetric detection of GSH. At a pH of 3.6, the proposed sensor gives a linear calibration over a GSH concentration range of 10-100 μM, with a rapid response of less than 2 min and a low detection limit of 0.5 μM. The relative standard deviation for seven repeated determinations of GSH is lower than 5.6%. Furthermore, the chemical response of the synthesized MnO2 nanosheets toward GSH is selective. Owing to the advantages with good water solubility, rapid response, high sensitivity, good biocompatibility and operation simplicity, this two-dimensional MnO2-based sensing material might be potential for detecting GSH in biological applications.

Self-Referenced Smartphone-Based Nanoplasmonic Imaging Platform for Colorimetric Biochemical Sensing.

PubMed

Wang, Xinhao; Chang, Te-Wei; Lin, Guohong; Gartia, Manas Ranjan; Liu, Gang Logan

2017-01-03

Colorimetric sensors usually suffer due to errors from variation in light source intensity, the type of light source, the Bayer filter algorithm, and the sensitivity of the camera to incoming light. Here, we demonstrate a self-referenced portable smartphone-based plasmonic sensing platform integrated with an internal reference sample along with an image processing method to perform colorimetric sensing. Two sensing principles based on unique nanoplasmonics enabled phenomena from a nanostructured plasmonic sensor, named as nanoLCA (nano Lycurgus cup array), were demonstrated here for colorimetric biochemical sensing: liquid refractive index sensing and optical absorbance enhancement sensing. Refractive indices of colorless liquids were measured by simple smartphone imaging and color analysis. Optical absorbance enhancement in the colorimetric biochemical assay was achieved by matching the plasmon resonance wavelength with the chromophore's absorbance peak wavelength. Such a sensing mechanism improved the limit of detection (LoD) by 100 times in a microplate reader format. Compared with a traditional colorimetric assay such as urine testing strips, a smartphone plasmon enhanced colorimetric sensing system provided 30 times improvement in the LoD. The platform was applied for simulated urine testing to precisely identify the samples with higher protein concentration, which showed potential point-of-care and early detection of kidney disease with the smartphone plasmonic resonance sensing system.

Colorimetric detection of Cucumber green mottle mosaic virus using unmodified gold nanoparticles as colorimetric probes.

PubMed

Wang, Lin; Liu, Zhanmin; Xia, Xueying; Yang, Cuiyun; Huang, Junyi; Wan, Sibao

2017-05-01

Cucumber green mottle mosaic virus (CGMMV)causes a severe mosaic symptom of watermelon and cucumber, and can be transmitted via infected cucumber seeds, leaves and soil. It remains a challenge to detect this virus to prevent its introduction and infection and spread in fields. For this purpose, a simple and sensitive label-free colorimetric detection method for CGMMV has been developed with unmodified gold nanoparticles (AuNPs) as colorimetric probes. The method is based on the finding that the presence of RT-PCR target products of CGMMV and species-specific probes results in color change of AuNPs from red to blue after NaCl induction. Normally, species-specific probes attach to the surface of AuNPs and thereby increasing their resistance to NaCl-induced aggregation. The concentration of sodium, probes in the reaction system and evaluation of specificity and sensitivity of a novel assay, visual detection of Cucumber green mottle mosaic virus using unmodified AuNPs has been carried out with simple preparation of samples in our study. Through this assay, as low as 30pg/μL of CGMMV RNA was thus detected visually, by the naked eye, without the need for any sophisticated, expensive instrumentation and biochemical reagents. The specificity was 100% and exhibited good reproducibility in our assays. The results note that this assay is highly species-specific, simple, low-cost, and visual for easy detection of CGMMV in plant tissues. Therefore, visual assay is a potentially useful tool for middle or small-scales corporations and entry-exit inspection and quarantine bureau to detect CGMMV in cucumber seeds or plant tissues. Copyright © 2017 Elsevier B.V. All rights reserved.

Ultra-sensitive non-aggregation colorimetric sensor for detection of iron based on the signal amplification effect of Fe3+ catalyzing H2O2 oxidize gold nanorods.

PubMed

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

2013-11-15

Fe(3+) can catalyze H2O2 to oxidize along on the longitudinal axis of gold nanorods (AuNRs), which caused the aspect ratio of AuNRs to decrease, longitudinal plasmon absorption band (LPAB) of AuNRs to blueshift (Δλ) and the color of the solution to change obviously. Thus, a rapid response and highly sensitive non-aggregation colorimetric sensor for the determination of Fe(3+) has been developed based on the signal amplification effect of catalyzing H2O2 to oxidize AuNRs. This simple and selective sensor with a wide linear range of 0.20-30.00 μM has been utilized to detect Fe(3+) in blood samples, and the results consisted with those obtained by inductively coupled plasma-mass spectroscopy (ICP-MS). Simultaneously, the mechanism of colorimetric sensor for the detection of Fe(3+) was also discussed. Copyright © 2013 Elsevier B.V. All rights reserved.

A colorimetric sensor array for detection of triacetone triperoxide vapor.

PubMed

Lin, Hengwei; Suslick, Kenneth S

2010-11-10

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

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

NASA Astrophysics Data System (ADS)

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

2016-04-01

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

Colorimetric sensor array for determination and identification of toxic industrial chemicals.

PubMed

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

2010-11-15

A low-cost yet highly sensitive colorimetric sensor array for the detection and identification of toxic industrial chemicals (TICs) has been developed. The sensor consists of a disposable array of cross-responsive nanoporous pigments whose colors are changed by diverse chemical interactions with analytes. Clear differentiation among 20 different TICs has been easily achieved at both their IDLH (immediately dangerous to life or health) concentration within 2 min of exposure and PEL (permissible exposure limit) concentration within 5 min of exposure with no errors or misclassifications. Detection limits are generally well below the PEL (in most cases below 5% of PEL) and are typically in the low ppb range. The colorimetric sensor array is not responsive to changes in humidity or temperature over a substantial range. The printed arrays show excellent batch to batch reproducibility and long shelf life (greater than 3 months).

Copper-Based Metal-Organic Framework Nanoparticles with Peroxidase-Like Activity for Sensitive Colorimetric Detection of Staphylococcus aureus.

PubMed

Wang, Shuqin; Deng, Wenfang; Yang, Lu; Tan, Yueming; Xie, Qingji; Yao, Shouzhuo

2017-07-26

Cu-MOF nanoparticles with an average diameter of 550 nm were synthesized from 2-aminoterephthalic acid and Cu(NO 3 ) 2 by a mixed solvothermal method. The Cu-MOF nanoparticles can show peroxidase-like activity that can catalyze 3,3',5,5'-tetramethylbenzidine to produce a yellow chromogenic reaction in the presence of H 2 O 2 . The presence of abundant amine groups on the surfaces of Cu-MOF nanoparticles enables facile modification of Staphylococcus aureus (S. aureus) aptamer on Cu-MOF nanoparticles. By combining Cu-MOF-catalyzed chromogenic reaction with aptamer recognition and magnetic separation, a simple, sensitive, and selective colorimetric method for the detection of S. aureus was developed.

Colorimetric detection of trace copper ions based on catalytic leaching of silver-coated gold nanoparticles.

PubMed

Lou, Tingting; Chen, Lingxin; Chen, Zhaopeng; Wang, Yunqing; Chen, Ling; Li, Jinhua

2011-11-01

A colorimetric, label-free, and nonaggregation-based silver coated gold nanoparticles (Ag/Au NPs) probe has been developed for detection of trace Cu(2+) in aqueous solution, based on the fact that Cu(2+) can accelerate the leaching rate of Ag/Au NPs by thiosulfate (S(2)O(3)(2-)). The leaching of Ag/Au NPs would lead to dramatic decrease in the surface plasmon resonance (SPR) absorption as the size of Ag/Au NPs decreased. This colorimetric strategy based on size-dependence of nanoparticles during their leaching process provided a highly sensitive (1.0 nM) and selective detection toward Cu(2+), with a wide linear detection range (5-800 nM) over nearly 3 orders of magnitude. The cost-effective probe allows rapid and sensitive detection of trace Cu(2+) ions in water samples, indicating its potential applicability for the determination of copper in real samples.

New Fluorescent and Colorimetric Chemosensor for Detection of Cyanide with High Selectivity and Sensitivity in Aqueous Media.

PubMed

Zali-Boeini, Hassan; Zareh Jonaghani, Mohammad

2017-05-01

A fluorescent and colorimetric chemosensor for detection of cyanide ion based on a styryl quinoline derivative has been designed and synthesized. The chemosensor (E)-2-(4-mercaptostyryl)quinolin-8-ol L showed high selectivity for detection of cyanide over other anions such as F¯, Cl¯, Br¯, I¯, NO 3 ¯, SCN¯, N 3 ¯, ClO 4 ¯, H 2 PO 4 ¯, AcO¯, HCO 3 ¯, SO 4 2 ¯ and HSO 4 ¯in aqueous solution. The chemosensor L displayed an immediate visible and fluorescence changes from nearly colorless to orange and greenish-blue to brick-red upon addition of cyanide ion respectively. It is more likely, these distinct changes can be attributed to hydrogen bonding interaction between phenol group and cyanide anion leading to a 1:1 binding stoichiometry following with deprotonation of phenol group. The detection limit for chemosensor L toward CN¯ was 2.73× 10 -8  M. Thus, the chemosensor can be used efficiently and selectively for detection and monitoring of small amounts of cyanide ion in aqueous media.

Pre-oxidation for Colorimetric Sensor Array Detection of VOCs

PubMed Central

Lin, Hengwei; Jang, Minseok; Suslick, Kenneth S.

2011-01-01

A disposable pre-oxidation technique is reported that dramatically improves the detection and identification of volatile organic compounds (VOCs) by a colorimetric sensor array. By passing a vapor stream through a tube packed with chromic acid on silica immediately before the colorimetric sensor array, the sensitivity to less reactive VOCs is substantially increased and limits of detection (LODs) are improved ~300-fold, permitting the detection, identification, and discrimination of 20 commonly found indoor VOC pollutants at both their immediately dangerous to life or health (IDLH) and at permissible exposure limits (PEL) concentrations. LODs of these pollutants were on average 1.4% of their respective PELs. PMID:21967478

A High Affinity Red Fluorescence and Colorimetric Probe for Amyloid β Aggregates

NASA Astrophysics Data System (ADS)

Rajasekhar, K.; Narayanaswamy, Nagarjun; Murugan, N. Arul; Kuang, Guanglin; Ågren, Hans; Govindaraju, T.

2016-04-01

A major challenge in the Alzheimer’s disease (AD) is its timely diagnosis. Amyloid β (Aβ) aggregates have been proposed as the most viable biomarker for the diagnosis of AD. Here, we demonstrate hemicyanine-based benzothiazole-coumarin (TC) as a potential probe for the detection of highly toxic Aβ42 aggregates through switch-on, enhanced (~30 fold) red fluorescence (Emax = 654 nm) and characteristic colorimetric (light red to purple) optical outputs. Interestingly, TC exhibits selectivity towards Aβ42 fibrils compared to other abnormal protein aggregates. TC probe show nanomolar binding affinity (Ka = 1.72 × 107 M-1) towards Aβ42 aggregates and also displace ThT bound to Aβ42 fibrils due to its high binding affinity. The Aβ42 fibril-specific red-shift in the absorption spectra of TC responsible for the observed colorimetric optical output has been attributed to micro-environment change around the probe from hydrophilic-like to hydrophobic-like nature. The binding site, binding energy and changes in optical properties observed for TC upon interaction with Aβ42 fibrils have been further validated by molecular docking and time dependent density functional theory studies.

Wetting in color: colorimetric differentiation of organic liquids with high selectivity.

PubMed

Burgess, Ian B; Koay, Natalie; Raymond, Kevin P; Kolle, Mathias; Lončar, Marko; Aizenberg, Joanna

2012-02-28

Colorimetric litmus tests such as pH paper have enjoyed wide commercial success due to their inexpensive production and exceptional ease of use. Expansion of colorimetry to new sensing paradigms is challenging because macroscopic color changes are seldom coupled to arbitrary differences in the physical/chemical properties of a system. Here we present in detail the design of a "Wetting In Color Kit" (WICK), an inexpensive and highly selective colorimetric indicator for organic liquids that exploits chemically encoded inverse-opal photonic crystals to project minute differences in liquids' wettability to macroscopically distinct, easy-to-visualize structural color patterns. We show experimentally and corroborate with theoretical modeling using percolation theory that the highly symmetric structure of our large-area, defect-free SiO(2) inverse-opal films leads to sharply defined threshold wettability for liquid infiltration, occurring at intrinsic contact angles near 20° with an estimated resolution smaller than 5°. The regular structure also produces a bright iridescent color, which disappears when infiltrated with liquid, naturally coupling the optical and fluidic responses. To deterministically design a WICK that differentiates a broad range of liquids, we introduced a nondestructive quality control procedure to regulate the pore structure and developed two new surface modification protocols, both requiring only silanization and selective oxidation. The resulting tunable, built-in horizontal and vertical chemistry gradients let us tailor the wettability threshold to specific liquids across a continuous range. With patterned oxidation as a final step, we control the shape of the liquid-specific patterns displayed, making WICK easier to read. Using these techniques, we demonstrate the applicability of WICKs in several exemplary systems that colorimetrically distinguish (i) ethanol-water mixtures varying by only 2.5% in concentration; (ii) methanol, ethanol, and

A new ratiometric and colorimetric chemosensor for cyanide anion based on coumarin-hemicyanine hybrid.

PubMed

Yang, Zhenghao; Liu, Zhipeng; Chen, Yuncong; Wang, Xiaoqing; He, Weijiang; Lu, Yi

2012-07-14

A hybrid coumarin-hemicyanine dye, Cou-BT, was developed as a new ratiometric and colorimetric sensor for cyanide with a sensing mechanism via nucleophilic addition of cyanide anion to the benzothiolium group. Cou-BT shows high sensitivity and selectivity for cyanide detection over other common anion species in aqueous acetonitrile solution. The calculated pseudo-first-order rate constant for cyanide anion addition was (2.13 ± 0.08) × 10(-2) s(-1) at 298 K, and the detection limit was estimated to be 0.64 μM. The DFT and TDDFT calculation results suggest that the ratiometric and colorimetric sensing behavior of Cou-BT upon its reaction with cyanide was due to the interrupted π-conjugation and blocked ICT progress.

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

PubMed

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

2014-08-11

A colorimetric assay utilizing the formation of gold nanoparticles was developed to detect tetracycline antibiotics in fluidic samples. Tetracycline antibiotics showed the capability of directly reducing aurate salts into atomic gold which form gold nanoparticles spontaneously under proper conditions. The resulted gold nanoparticles showed characteristic plasmon absorbance at 526 nm, which can be visualized by naked eyes or with a spectrophotometer. UV-vis absorbance of the resulted gold nanoparticles is correlated directly with the concentrations of tetracycline antibiotics in the solution, allowing for quantitative colorimetric detection of tetracycline antibiotics. Reaction conditions, such as pH, temperature, reaction time, and ionic strength were optimized. Sensitivity of the colorimetric assay can be enhanced by the addition of gold nanoparticle seeds, a LOD as low as 20 ng mL(-1) can be achieved with the help of seed particles. The colorimetric assay showed minimum interference from ethanol, methanol, urea, glucose, and other antibiotics such as sulfonamides, amino glycosides etc. Validity of the method was also evaluated on urine samples spiked with tetracycline antibiotics. The method provides a broad spectrum detection method for rapid and sensitive detection of reductive substances such as tetracycline antibiotics in liquid and biological samples. Copyright © 2014 Elsevier B.V. All rights reserved.

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

PubMed

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

2016-05-17

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

Detection of proteins using a colorimetric bio-barcode assay.

PubMed

Nam, Jwa-Min; Jang, Kyung-Jin; Groves, Jay T

2007-01-01

The colorimetric bio-barcode assay is a red-to-blue color change-based protein detection method with ultrahigh sensitivity. This assay is based on both the bio-barcode amplification method that allows for detecting miniscule amount of targets with attomolar sensitivity and gold nanoparticle-based colorimetric DNA detection method that allows for a simple and straightforward detection of biomolecules of interest (here we detect interleukin-2, an important biomarker (cytokine) for many immunodeficiency-related diseases and cancers). The protocol is composed of the following steps: (i) conjugation of target capture molecules and barcode DNA strands onto silica microparticles, (ii) target capture with probes, (iii) separation and release of barcode DNA strands from the separated probes, (iv) detection of released barcode DNA using DNA-modified gold nanoparticle probes and (v) red-to-blue color change analysis with a graphic software. Actual target detection and quantification steps with premade probes take approximately 3 h (whole protocol including probe preparations takes approximately 3 days).

Dual-Modal Colorimetric/Fluorescence Molecular Probe for Ratiometric Sensing of pH and Its Application.

PubMed

Wu, Luling; Li, Xiaolin; Huang, Chusen; Jia, Nengqin

2016-08-16

As traditional pH meters cannot work well for minute regions (such as subcellular organelles) and in harsh media, molecular pH-sensitive devices for monitoring pH changes in diverse local heterogeneous environments are urgently needed. Here, we report a new dual-modal colorimetric/fluorescence merocyanine-based molecular probe (CPH) for ratiometric sensing of pH. Compared with previously reported pH probes, CPH bearing the benzyl group at the nitrogen position of the indolium group and the phenol, which is used as the acceptor for proton, could respond to pH changes immediately through both the ratiometric fluorescence signal readout and naked-eye colorimetric observation. The sensing process was highly stable and reversible. Most importantly, the suitable pKa value (6.44) allows CPH to presumably accumulate in lysosomes and become a lysosome-target fluorescent probe. By using CPH, the intralysosomal pH fluctuation stimulated by antimalaria drug chloroquine was successfully tracked in live cells through the ratiometric fluorescence images. Additionally, CPH could be immobilized on test papers, which exhibited a rapid and reversible colorimetric response to acid/base vapor through the naked-eye colorimetric analysis. This proof-of-concept study presents the potential application of CPH as a molecular tool for monitoring intralysosomal pH fluctuation in live cells, as well as paves the way for developing the economic, reusable, and fast-response optical pH meters for colorimetric sensing acid/base vapor with direct naked-eye observation.

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

NASA Astrophysics Data System (ADS)

Liu, Juewen; Lu, Yi

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

Colorimetric and fluorescent chemosensor for highly selective and sensitive relay detection of Cu2 + and H2PO4- in aqueous media

NASA Astrophysics Data System (ADS)

Su, Jun-Xia; Wang, Xiao-Ting; Chang, Jing; Wu, Gui-Yuan; Wang, Hai-Ming; Yao, Hong; Lin, Qi; Zhang, You-Ming; Wei, Tai-Bao

2017-07-01

In this manuscript, a new colorimetric and fluorescent chemosensor (T) was designed and synthesized, it could successively detect Cu2 + and H2PO4- in DMSO/H2O (v/v = 9:1, pH = 7.2) buffer solution with high selectivity and sensitivity. When added Cu2 + ions into the solution of T, it showed a color changes from yellow to colorless, meanwhile, the green fluorescence of sensor T quenched. This recognition behavior was not affected in the presence of other cations, including Hg2 +, Ag+, Ca2 +, Co2 +, Ni2 +, Cd2 +, Pb2 +, Zn2 +, Cr3 +, and Mg2 + ions. More interestingly, the Cu2 + ions contain sensor T solution could recover the color and fluorescence upon the addition of H2PO4- anions in the same medium. And other surveyed anions (including F-, Cl-, Br-, I-, AcO-, HSO4-, ClO4-, CN- and SCN-) had nearly no influence on the recognition behavior. The detection limits of T to Cu2 + and T-Cu2 + to H2PO4- were evaluated to be 1.609 × 10- 8 M and 0.994 × 10- 7 M, respectively. In addition, the sensor T also could be served as a recyclable component and the logic gate output was also defined in sensing materials. The test strips based on sensor T were fabricated, which acted as a convenient and efficient Cu2 + and H2PO4- test kits.

Click chemistry-mediated cyclic cleavage of metal ion-dependent DNAzymes for amplified and colorimetric detection of human serum copper (II).

PubMed

Li, Daxiu; Xie, Jiaqing; Zhou, Wenjiao; Jiang, Bingying; Yuan, Ruo; Xiang, Yun

2017-11-01

The determination of the level of Cu 2+ plays important roles in disease diagnosis and environmental monitoring. By coupling Cu + -catalyzed click chemistry and metal ion-dependent DNAzyme cyclic amplification, we have developed a convenient and sensitive colorimetric sensing method for the detection of Cu 2+ in human serums. The target Cu 2+ can be reduced by ascorbate to form Cu + , which catalyzes the azide-alkyne cycloaddition between the azide- and alkyne-modified DNAs to form Mg 2+ -dependent DNAzymes. Subsequently, the Mg 2+ ions catalyze the cleavage of the hairpin DNA substrate sequences of the DNAzymes and trigger cyclic generation of a large number of free G-quadruplex sequences, which bind hemin to form the G-quadruplex/hemin artificial peroxidase to cause significant color transition of the sensing solution for sensitive colorimetric detection of Cu 2+ . This method shows a dynamic range of 5 to 500 nM and a detection limit of 2 nM for Cu 2+ detection. Besides, the level of Cu 2+ in human serums can also be determined by using this sensing approach. With the advantages of simplicity and high sensitivity, such sensing method thus holds great potential for on-site determination of Cu 2+ in different samples. Graphical abstract Sensitive colorimetric detection of copper (II) by coupling click chemistry with metal ion-dependentDNAzymes.

Novel salicylic acid-oriented thiourea-type receptors as colorimetric chemosensor: Synthesis, characterizations and selective naked-eye recognition properties

NASA Astrophysics Data System (ADS)

Li, Shaowei; Cao, Xiufang; Chen, Changshui; Ke, Shaoyong

2012-10-01

Based on the salicylic acid backbone, three highly sensitive and selective colorimetric chemosensors with an acylthiourea binding unit have been designed, synthesized and characterized. These chemosensors have been utilized for selective recognition of fluoride anions in dry DMSO solution by typical spectroscopic titration techniques. Furthermore, the obtained chemosensors AR1-3 have shown naked-eye sensitivity for detection of biologically important fluoride ion over other anions in solution.

Colorimetric determination of sildenafil citrate (Viagra) through ion-associate complex formation.

PubMed

Amin, Alaa S; Moustafa, Moustafa E; El-Dosoky, Reham

2009-01-01

A simple, quick, accurate, and sensitive colorimetric method is described for the determination of sildenafil citrate (SLD). The method is based on the reaction of SLD with Congo Red, Sudan II, and Gentian Violet in buffered aqueous solutions at pH 2.5, 6.5, and 11.0, respectively, to give highly colored soluble ion-associate complex species; the colored products are quantitated colorimetrically at 523, 554, and 569 nm, respectively. The various experimental conditions were optimized. The stoichiometric ratio was found to be 1:1 for all ion associates; the calculated logarithmic stability constants were 8.51, 7.79, and 5.58, respectively. Beer's law was obeyed over the concentration range of 0.2-7.0 microg/mL, whereas the Ringbom optimum concentration range was 0.4-6.5 microg/mL. Values for molar absorptivity, Sandell sensitivity, and detection and quantification limits were also calculated. The proposed method was successfully applied to the determination of SLD in Viagra tablets and in serum samples by using the technique of standard additions with mean accuracy values of 100.06 +/- 1.14, 99.87 +/- 0.70, and 99.86 +/- 0.97% for Viagra tablets and 99.88 +/- 0.60, 99.90 +/- 0.90, and 100.24 +/- 0.80% for serum samples, respectively.

Palindromic Molecule Beacon-Based Cascade Amplification for Colorimetric Detection of Cancer Genes.

PubMed

Shen, Zhi-Fa; Li, Feng; Jiang, Yi-Fan; Chen, Chang; Xu, Huo; Li, Cong-Cong; Yang, Zhe; Wu, Zai-Sheng

2018-03-06

A highly sensitive and selective colorimetric assay based on a multifunctional molecular beacon with palindromic tail (PMB) was proposed for the detection of target p53 gene. The PMB probe can serve as recognition element, primer, and polymerization template and contains a nicking site and a C-rich region complementary to a DNAzyme. In the presence of target DNA, the hairpin of PMB is opened, and the released palindromic tails intermolecularly hybridize with each other, triggering the autonomous polymerization/nicking/displacement cycles. Although only one type of probe is involved, the system can execute triple and continuous polymerization strand displacement amplifications, generating large amounts of G-quadruplex fragments. These G-rich fragments can bind to hemin and form the DNAzymes that possess the catalytic activity similar to horseradish peroxidase, catalyzing the oxidation of ABTS by H 2 O 2 and producing the colorimetric signal. Utilizing the newly proposed sensing system, target DNA can be detected down to 10 pM with a linear response range from 10 pM to 200 nM, and mutant target DNAs are able to be distinguished even by the naked eye. The desirable detection sensitivity, high specificity, and operation convenience without any separation step and chemical modification demonstrate that the palindromic molecular beacon holds the potential for detecting and monitoring a variety of nucleic acid-related biomarkers.

Colorimetric values of esthetic stainless steel crowns.

PubMed

Hosoya, Yumiko; Omachi, Koichi; Staninec, Michal

2002-01-01

The colorimetric values of two different kinds of esthetic stainless steel crowns were measured and compared with the colorimetric values of primary anterior teeth in Japanese children. The colorimetric values of resin composite-faced stainless steel crowns (Kinder Krown) and epoxy-coated stainless steel crowns (White Steel Crown) were measured with a color difference meter. The Commission Internationale de Eclairage L*, a*, b*, and delta E*ab values and Munsell value, chroma, and hue were calculated. The data were compared with previously reported colorimetric values of Japanese primary anterior teeth measured with the same color difference meter used in this study. Compared to Japanese primary anterior teeth, Kinder Krown Pedo I and Pedo II showed much higher L* values and lower hue; on the other hand, White Steel Crown showed much higher L*, a*, b* values, much higher value and chroma, and much lower hue. Color analysis revealed that the colors of the White Steel Crown and Kinder Krown Pedo I were substantially different from the color of Japanese primary anterior teeth. The color difference between Pedo II crowns and Japanese primary anterior teeth was relatively high, but the color of Pedo II might be acceptable for clinical use.

Aggregation-based colorimetric sensor for determination of prothioconazole fungicide using colloidal silver nanoparticles (AgNPs)

NASA Astrophysics Data System (ADS)

Ivrigh, Zahra Jafar-Nezhad; Fahimi-Kashani, Nafiseh; Hormozi-Nezhad, M. Reza

2017-12-01

There is a growing interest in developing high-performance sensors monitoring fungicides, due to their broadly usage and their adverse effects on humans and wildlife. In the present study, a colorimetric probe has been proposed for detection of prothioconazole based on aggregation of unmodified silver nanoparticles (AgNPs). Under optimized condition, linear relationships between the concentration of prothioconazole and the absorbance ratio of A500/A395 were found over the range of 0.01 μg·mL- 1 to 0.4 μg·mL- 1 with quantification limit as low as 1.7 ng·mL- 1. Furthermore, AgNPs color change from yellow to pink-orange in presence of prothioconazole, indicates highly sensitive naked-eye colorimetric assay for quantifying prothioconazole in real applications. The proposed approach was successfully used for the determination of prothioconazole in wheat flour and paddy water sample.

Discrimination of complex mixtures by a colorimetric sensor array: coffee aromas.

PubMed

Suslick, Benjamin A; Feng, Liang; Suslick, Kenneth S

2010-03-01

The analysis of complex mixtures presents a difficult challenge even for modern analytical techniques, and the ability to discriminate among closely similar such mixtures often remains problematic. Coffee provides a readily available archetype of such highly multicomponent systems. The use of a low-cost, sensitive colorimetric sensor array for the detection and identification of coffee aromas is reported. The color changes of the sensor array were used as a digital representation of the array response and analyzed with standard statistical methods, including principal component analysis (PCA) and hierarchical clustering analysis (HCA). PCA revealed that the sensor array has exceptionally high dimensionality with 18 dimensions required to define 90% of the total variance. In quintuplicate runs of 10 commercial coffees and controls, no confusions or errors in classification by HCA were observed in 55 trials. In addition, the effects of temperature and time in the roasting of green coffee beans were readily observed and distinguishable with a resolution better than 10 degrees C and 5 min, respectively. Colorimetric sensor arrays demonstrate excellent potential for complex systems analysis in real-world applications and provide a novel method for discrimination among closely similar complex mixtures.

Discrimination of Complex Mixtures by a Colorimetric Sensor Array: Coffee Aromas

PubMed Central

Suslick, Benjamin A.; Feng, Liang; Suslick, Kenneth S.

2010-01-01

The analysis of complex mixtures presents a difficult challenge even for modern analytical techniques, and the ability to discriminate among closely similar such mixtures often remains problematic. Coffee provides a readily available archetype of such highly multicomponent systems. The use of a low-cost, sensitive colorimetric sensor array for the detection and identification of coffee aromas is reported. The color changes of the sensor array were used as a digital representation of the array response and analyzed with standard statistical methods, including principal component analysis (PCA) and hierarchical clustering analysis (HCA). PCA revealed that the sensor array has exceptionally high dimensionality with 18 dimensions required to define 90% of the total variance. In quintuplicate runs of 10 commercial coffees and controls, no confusions or errors in classification by HCA were observed in 55 trials. In addition, the effects of temperature and time in the roasting of green coffee beans were readily observed and distinguishable with a resolution better than 10 °C and 5 min, respectively. Colorimetric sensor arrays demonstrate excellent potential for complex systems analysis in real-world applications and provide a novel method for discrimination among closely similar complex mixtures. PMID:20143838

Colorimetric stack pad immunoassay for bacterial identification.

PubMed

Eltzov, Evgeni; Marks, Robert S

2017-01-15

A new colorimetric immunoassay concept, utilizing conventional lateral flow membranes (e.g., conjugation, sample, absorption and nitrocellulose), were placed in a different configuration in a stacking manner, where the liquid sample that may contain the analyte diffuses from the bottom to the upper-most layer. The key element of this proprietary technology is a capture layer, where a nitrocellulose membrane is modified with the target analyte of interest, namely in this study target Escherichia coli. During the immunoassay operation, samples contaminated with the target bacteria will conjugate to their corresponding HRP-antibodies laying in wait and the immune-target measurand complex flows by capillarity towards the upper-most layer to generate a colorimetric signal (positive answer) through an enzymatic reaction. In target-free samples, previously immobilized target bacteria on the capture layer will prevent the HRP-labeled anti-target antibodies from migrating to the upper-most layer, where the enzymatic substrate lays in wait. After optimization, the sensitivity of this approach was found to be 1,000 folds higher than ELISAs (10 2 cellsmL -1 ). The advantages of the stacked pad assay include: miniaturization, operational simplicity, fast response time (less than 5min), useful sensitivity. Copyright © 2016 Elsevier B.V. All rights reserved.

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

PubMed

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

2016-06-15

An enzyme-free and label-free colorimetric Pb(2+) sensor based on DNAzyme and molecular beacon (MB) has been developed and demonstrated by recycle using enzyme strand for signal amplification. The substrate strand DNA (S-DNA) of DNAzyme could be converted into MB structure with base pairs of stem part at the both ends. The MB could hybridize with enzyme strand DNA (E-DNA) to form DNAzyme, and be activated and cleaved in the presence of Pb(2+). The cleaved MB is much less stable, releasing from the DNAzyme as two product pieces. The product pieces of MB are flexible and could bind to unmodified AuNPs to effectively stabilize them against salt-induced aggregation. Then, the E-DNA is liberated to catalyze the next reaction and amplify the response signal. By taking advantage of repeated using of E-DNA, our proposed method exhibited high sensitive for Pb(2+) detection in a linear range from 0.05 to 5 nM with detection limit of 20 pM by UV-vis spectrometer. Moreover, this method was also used for determination of Pb(2+) in river water samples with satisfying results. Importantly, this strategy could reach high sensitivity without any modification and complex enzymatic or hairpins based amplification procedures. Copyright © 2016 Elsevier B.V. All rights reserved.

Naphthaldimine-based simple glucose derivative as a highly selective sensor for colorimetric detection of Cu2+ ion in aqueous media

NASA Astrophysics Data System (ADS)

Dolai, Bholanath; Bhaumik, Atanu; Pramanik, Nabakumar; Ghosh, Kalyan Sundar; Atta, Ananta Kumar

2018-07-01

Naphthaldimine-based glucose derivatives 1 and 3 have been designed, synthesized and characterized. In aqueous media, glucose derivative 1, exhibited high selectivity and sensitivity towards Cu2+ ion in comparison with various cations and anions. In presence of Cu2+, sensor 1 has provided significant naked-eye detectable color change. The formation of 1-Cu2+ complex has been analyzed by UV-vis spectroscopy, 1H NMR titration experiments, mass spectrometry and DFT (density functional theory) calculations. Limit of detection of 1 as a colorimetric sensor for Cu2+ ion is found to be 0.23 μM, much lower than recommended value of World Health Organization (WHO), which makes to Cu2+ sensor 1 more effective and useful.

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

PubMed

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

2015-02-15

As an essential element, copper ion (Cu(2+)) plays important roles in human beings for its participation in diverse metabolic processes as a cofactor and/or a structural component of enzymes. However, excessive uptake of Cu(2+) ion gives rise to the risk of certain diseases. So, it is important to develop simple ways to monitor and detect Cu(2+) ion. In this study, a simple, facile colorimetric sensor for the ultrasensitive determination of Cu(2+) ion was developed based on the following principle: L-cysteine and 1-chloro-2,4-dinitrobenzene (CDNB) could be conjugated to form the yellow product 2,4-dinitrophenylcysteine (DNPC), which was measurable at 355nm; however, upon addition of Cu(2+) ion, the absorbance of DNPC would be decreased owing to the Cu(2+) ion catalytic oxidation of L-cysteine to L-cystine in the presence of O2. Thus, the colorimetric detection of Cu(2+) ion could be achieved. The optimal pH, buffer, temperature and incubation time for the colorimetric sensor were obtained of pH 6.8 in 0.1M HEPES solution, 90 °C and 50 min, respectively. A good linearity within the range of 0.8-10 nM (r = 0.996) was attained, with a high detectability up to 0.5nM. Analyses of Cu(2+) ion in drinking water, lake water, seawater and biological samples were carried out and the method performances were found to agree well with that obtained by ICP-MS. The developed simple colorimetric sensor proved applicable for Cu(2+) ion determination in real samples with high sensitivity and selectivity. Copyright © 2014 Elsevier B.V. All rights reserved.

Passive Leak Detection Using Commercial Hydrogen Colorimetric Indicator

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

Hartmann, Kevin; Buttner, William; Burgess, Robert

Element One, Inc. (www.elem.com), a small business with in Boulder, CO, has been developing hydrogen detection technology based upon a highly selective colorimetric indicator. In its native state, the indicator pigment is a pale gray color, but becomes black upon exposure to hydrogen. The colorimetric change can be readily observed by the naked eye without the need for supplemental electronics or other hardware. Recently, the colorimetric indicator was integrated into a pliable, self-adhesive tape that can readily wrap around pneumatic fittings to serve as a hydrogen leak detector. A prototype version of the Element One indicator tape was tested withinmore » an NREL hydrogen system and successfully identified the unexpected presence of a small leak; a summary document for this case study is presented in Appendix 1. The tape was subsequently configured into 10-foot rolls as a product prototype that has just recently been commercialized and marketed under the tradename DetecTape(R). Figure 1 shows the commercial version of DetecTape along with an indicator sample in its native state and one that had been exposed to hydrogen. DetecTape is a self-adhesive silicone-based tape impregnated with a proprietary hydrogen-sensitive indicator based on transition metal oxides. A length of the tape can be cut from the roll and stretched by a factor of two or three times around a fitting. Due to the self-adhesive property of the tape, this provides a tight seal around the fitting. The seal is not hermetic, and is not intended to prevent the release of a leaking gas. However, a portion of the hydrogen leaking from a wrapped fitting will pass through the tape and react with the active indicator impregnated within the tape, thereby inducing blackening.« less

Silver nanoparticles-based colorimetric array for the detection of Thiophanate-methyl

NASA Astrophysics Data System (ADS)

Zheng, Mingda; Wang, Yingying; Wang, Chenge; Wei, Wei; Ma, Shuang; Sun, Xiaohan; He, Jiang

2018-06-01

A simple and selective colorimetric sensor based on citrate capped silver nanoparticles (Cit-AgNPs) is proposed for the detection of Thiophanate-methyl (TM) with high sensitivity and selectivity. The method based on the color change of Cit-AgNPs from yellow to cherry red with the addition of TM to Cit-AgNPs that caused a red-shift on the surface plasmon resonance (SPR) band from 394 nm to 525 nm due to the hydrogen-bonding and substitution. The density functional theory (DFT) method was also calculated the interactions between the TM and citrate ions. Under the optimized conditions, a linear relationship between the absorption ratio (A525nm/A394nm) and TM concentration was found in the range of 2-100 μM with correlation coefficient (R2) of 0.988. The detection limit of TM was 0.12 μM by UV-vis spectrometer. Moreover, the applicability of colorimetric sensor is successfully verified by the detection of TM in environmental samples with good recoveries.

The effect of carbonated beverages on colorimetric end-tidal CO(2) determination

PubMed

Qureshi; Park; Sturmann; Hsu

2000-10-01

Esophageal intubation is a significant complication of attempted airway control. Colorimetric end-tidal CO(2) monitors are highly sensitive and specific for detecting the presence of CO(2). There are reports of false-positive end-tidal CO(2) readings from esophageal intubations in patients who had ingested carbonated beverages. OBJECTIVE: To determine whether carbonated gastric contents can affect colorimetric end-tidal CO(2) readings. METHODS: End-tidal CO(2) was measured in sacrificed piglets at measured time intervals after instillation of 5-, 10-, 15-, and 20-mL aliquots of Diet Coke were placed into the stomach via a 28-French orogastric tube followed by esophageal intubation. The stomach was completely evacuated prior to each instillation and rechecked for baseline CO(2). RESULTS: Compiled data from three piglets (20-30 kg). Piglets were not ventilated or moved and determinations were measured at 20 degrees while supine. All data collected within 2 hours postmortem (table 24-1). CONCLUSIONS: The colorimetric end-tidal CO(2) turned "yellow" and did not change to blue with extended insufflations. The CO(2) of a small quantity of carbonated beverage in the stomach could be "blown off" by multiple insufflations. We conclude that esophageal intubation in the setting of recent ingestion of a carbonated beverage may result in a false-positive end-tidal CO(2) determination.

Sensitive detection of microRNAs based on the conversion of colorimetric assay into electrochemical analysis with duplex-specific nuclease-assisted signal amplification

PubMed Central

Xia, Ning; Liu, Ke; Zhou, Yingying; Li, Yuanyuan; Yi, Xinyao

2017-01-01

miRNAs have emerged as new biomarkers for the detection of a wide variety of cancers. By employing duplex-specific nuclease for signal amplification and gold nanoparticles (AuNPs) as the carriers of detection probes, a novel electrochemical assay of miRNAs was performed. The method is based on conversion of the well-known colorimetric assay into electrochemical analysis with enhanced sensitivity. DNA capture probes immobilized on the electrode surface and ferrocene (Fc)-labeled DNA detection probes (denoted “Fc-DNA-Fc”) presented in the solution induced the assembly of positively charged AuNPs on the electrode surface through the electrostatic interaction. As a result, a large number of Fc-DNA-Fc molecules were attached on the electrode surface, thus amplifying the electrochemical signal. When duplex-specific nuclease was added to recycle the process of miRNA-initiated digestion of the immobilized DNA probes, Fc-DNA-Fc-induced assembly of AuNPs on the electrode surface could not occur. This resulted in a significant fall in the oxidation current of Fc. The current was found to be inversely proportional to the concentration of miRNAs in the range of 0–25 fM, and a detection limit of 0.1 fM was achieved. Moreover, this work presents a new method for converting colorimetric assays into sensitive electrochemical analyses, and thus would be valuable for design of novel chemical/biosensors. PMID:28761341

Multiplexed Colorimetric Solid-Phase Extraction

NASA Technical Reports Server (NTRS)

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

2009-01-01

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

Use of a Smartphone as a Colorimetric Analyzer in Paper-based Devices for Sensitive and Selective Determination of Mercury in Water Samples.

PubMed

Jarujamrus, Purim; Meelapsom, Rattapol; Pencharee, Somkid; Obma, Apinya; Amatatongchai, Maliwan; Ditcharoen, Nadh; Chairam, Sanoe; Tamuang, Suparb

2018-01-01

A smartphone application, called CAnal, was developed as a colorimetric analyzer in paper-based devices for sensitive and selective determination of mercury(II) in water samples. Measurement on the double layer of a microfluidic paper-based analytical device (μPAD) fabricated by alkyl ketene dimer (AKD)-inkjet printing technique with special design doped with unmodified silver nanoparticles (AgNPs) onto the detection zones was performed by monitoring the gray intensity in the blue channel of AgNPs, which disintegrated when exposed to mercury(II) on μPAD. Under the optimized conditions, the developed approach showed high sensitivity, low limit of detection (0.003 mg L -1 , 3SD blank/slope of the calibration curve), small sample volume uptake (two times of 2 μL), and short analysis time. The linearity range of this technique ranged from 0.01 to 10 mg L -1 (r 2 = 0.993). Furthermore, practical analysis of various water samples was also demonstrated to have acceptable performance that was in agreement with the data from cold vapor atomic absorption spectrophotometry (CV-AAS), a conventional method. The proposed technique allows for a rapid, simple (instant report of the final mercury(II) concentration in water samples via smartphone display), sensitive, selective, and on-site analysis with high sample throughput (48 samples h -1 , n = 3) of trace mercury(II) in water samples, which is suitable for end users who are unskilled in analyzing mercury(II) in water samples.

Pyrrole based Schiff bases as colorimetric and fluorescent chemosensors for fluoride and hydroxide anions.

PubMed

Velmathi, Sivan; Reena, Vijayaraghavan; Suganya, Sivalingam; Anandan, Sambandam

2012-01-01

An efficient colorimetric sensor with pyrrole-NH moiety as binding site and nitro group as a signaling unit has been synthesized by a one step procedure and characterized by spectroscopic techniques, which displays excellent selectivity and sensitivity for fluoride and hydroxide ions. The hydrogen bonding with these anions provides remarkable colorimetric responses. (1)H NMR and FT IR studies has been carried out to confirm the hydrogen bonding. UV-vis and fluorescence spectral changes can be exploited for real time and on site application.

Improved colorimetric determination of serum zinc.

PubMed

Johnson, D J; Djuh, Y Y; Bruton, J; Williams, H L

1977-07-01

We show how zinc may easily be quantified in serum by first using an optimum concentration of guanidine hydrochloride to cause release of zinc from proteins, followed by complexation of released metals with cyanide. The cyanide complex of zinc is preferentially demasked with chloral hydrate, followed by a colorimetric reaction between zinc and 4-(2-pyridylazo)resorcinol. This is a sensitive water-soluble ligand; its complex with zinc has an absorption maximum at 497 nm. Values found by this technique compare favorably with those obtained by atomic absorption spectroscopy.

4-Aminothiophenol functionalized gold nanoparticle-based colorimetric sensor for the determination of nitramine energetic materials.

PubMed

Üzer, Ayşem; Can, Ziya; Akın, Ilknur; Erçağ, Erol; Apak, Reşat

2014-01-07

The heterocyclic nitramine compounds, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), are two most important military-purpose high explosives. Differentiation of RDX and HMX with colorimetric methods of determination has not yet been made because of their similar chemical structures. In this study, a sensitive colorimetric method for the determination of RDX and HMX was proposed on the basis of differential kinetics in the hydrolysis of the two compounds (yielding nitrite as a product) followed by their colorimetric determination using 4-aminothiophenol (4-ATP) modified gold nanoparticles (AuNPs) and naphthylethylene diamine (NED) as coupling agent for azo-dye formation, abbreviated as "4-ATP-AuNP+NED" colorimetric method. After alkaline hydrolysis in a 1 M Na2CO3 + 0.04 M NaOH mixture solution at room temperature, only RDX (but not HMX) was hydrolyzed to give a sufficient colorimetric response in neutralized solution, the molar absorptivity (ε) at 565 nm and the limit of detection (LOD) for RDX being (17.6 ± 1.3) × 10(3) L mol(-1) cm(-1) and 0.55 μg mL(-1), respectively. On the other hand, hot water bath (at 60 °C) hydrolysis enabled both nitramines, RDX and HMX, to give substantial colorimetric responses; i.e., ε and LOD for RDX were (32.8 ± 0.5) × 10(3) L mol(-1)cm(-1) and 0.20 μg mL(-1) and for HMX were (37.1 ± 2.8) × 10(3) L mol(-1)cm(-1) and 0.24 μg mL(-1), respectively. Unlike other AuNP-based nitrite sensors in the literature showing absorbance quenching within a relatively narrow concentration range, the developed sensor operated with an absorbance increase over a wide range of nitrite. Synthetic mixtures of (RDX + HMX) gave additive responses, and the proposed method was statistically validated against HPLC using nitramine mixtures.

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

PubMed

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

2016-11-15

Herein, a gold nanoparticles (AuNPs) based label-free colorimetric aptasensor for simple, sensitive and selective detection of Pt (II) was constructed for the first time. Four bases (G-G mismatch) mismatched streptavidin aptamer (MSAA) was used to protect AuNPs from salt-induced aggregation and recognize Pt (II) specifically. Only in the presence of Pt (II), coordination occurs between G-G bases and Pt (II), leading to the activation of streptavidin aptamer. Streptavidin coated magnetic beads (MBs) were used as separation agent to separate Pt (II)-coordinated MSAA. The residual less amount of MSAA could not efficiently protect AuNPs anymore and aggregation of AuNPs will produce a colorimetric product. With the addition of Pt (II), a pale purple-to-blue color variation could be observed by the naked eye. A detection limit of 150nM and a linear range from 0.6μM to 12.5μM for Pt (II) could be achieved without any amplification. Copyright © 2016 Elsevier B.V. All rights reserved.

Colorimetry and SERS dual-mode detection of telomerase activity: combining rapid screening with high sensitivity

NASA Astrophysics Data System (ADS)

Zong, Shenfei; Wang, Zhuyuan; Chen, Hui; Hu, Guohua; Liu, Min; Chen, Peng; Cui, Yiping

2014-01-01

As an important biomarker and therapeutic target, telomerase has attracted considerable attention concerning its detection and monitoring. Here, we present a colorimetry and surface enhanced Raman scattering (SERS) dual-mode telomerase activity detection method, which has several distinctive advantages. First, colorimetric functionality allows rapid preliminary discrimination of telomerase activity by the naked eye. Second, the employment of SERS technique results in greatly improved detection sensitivity. Third, the combination of colorimetry and SERS into one detection system can ensure highly efficacious and sensitive screening of numerous samples. Besides, the avoidance of polymerase chain reaction (PCR) procedures further guarantees fine reliability and simplicity. Generally, the presented method is realized by an ``elongate and capture'' procedure. To be specific, gold nanoparticles modified with Raman molecules and telomeric repeat complementary oligonucleotide are employed as the colorimetric-SERS bifunctional reporting nanotag, while magnetic nanoparticles functionalized with telomerase substrate oligonucleotide are used as the capturing substrate. Telomerase can synthesize and elongate telomeric repeats onto the capturing substrate. The elongated telomeric repeats subsequently facilitate capturing of the reporting nanotag via hybridization between telomeric repeat and its complementary strand. The captured nanotags can cause a significant difference in the color and SERS intensity of the magnetically separated sediments. Thus both the color and SERS can be used as indicators of the telomerase activity. With fast screening ability and outstanding sensitivity, we anticipate that this method would greatly promote practical application of telomerase-based early-stage cancer diagnosis.As an important biomarker and therapeutic target, telomerase has attracted considerable attention concerning its detection and monitoring. Here, we present a colorimetry and

Development of a novel colorimetric sensor based on alginate beads for monitoring rainbow trout spoilage.

PubMed

Majdinasab, Marjan; Hosseini, Seyed Mohammad Hashem; Sepidname, Marziyeh; Negahdarifar, Manizheh; Li, Peiwu

2018-05-01

Alginate is a non-toxic, renewable, and linear copolymer obtained from the brown algae Laminaria digitata that can be easily shaped into beads. Its good gel forming properties have made it useful for entrapping food and pharmaceutical ingredients. In this study, alginate beads were used in a novel application as a colorimetric sensor in food intelligent packaging. Colorimetric sensor was developed through entrapping red cabbage extract as a pH indicator in alginate beads. The pH indicator beads were used in rainbow trout packaging for monitoring fillets spoilage. Color change of beads during fish storage was measured using the CIELab method. The alginate bead colorimetric sensor is validated by measuring total volatile basic nitrogen (TVB-N) levels and microbial populations in fish samples. Moreover, peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) were evaluated during storage. Results indicated that increasing the bacterial population during storage and production of proteolytic enzymes resulted in protein degradation, accumulation of volatile amine compounds, increase in the pH and finally color change of alginate beads. The values of TVB-N, pH, PV and TBARS increased with time of storage. The results of TVB-N and microbial growth were in accordance with color change of beads and CIELab data. Therefore, the proposed system enjoys a high sensitivity to pH variations and is capable of monitoring the spoilage of fish or other protein-rich products through its wide range of color changes. The alginate beads containing the red cabbage extract can, thus, be used as a low-cost colorimetric sensor for intelligent packaging applications.

Novel colorimetric sensor for oral malodour.

PubMed

Alagirisamy, Nethaji; Hardas, Sarita S; Jayaraman, Sujatha

2010-02-19

Volatile sulphur compounds are the primary constituents of oral malodour. Quantitative tools for the detection of oral malodour are beneficial to evaluate the intensity of malodour, analyse its causes and monitor the effectiveness of customized treatments. We have developed an objective, cost effective, do-it-yourself colorimetric sensor for oral malodour quantification. The sensor consisted of a sensing solution, a gas sampling unit for collecting a known volume of mouth air and a photometric detector. The sensing solution was iodine and the depletion of iodine on reaction with hydrogen sulphide was detected colorimetrically using starch. The detection limit of the sensor is 0.05 microg L(-1) of hydrogen sulphide, which is fit-for-purpose for oral malodour detection in healthy subjects as well as halitosis patients. Volatile sulphur compounds in mouth air were quantified in healthy human volunteers using this portable sensor and the detected levels were in the range of 0.2-0.4 microg L(-1). There was a good correlation between the VSC levels detected by the colorimetric sensor and halimeter (R(2)=0.934). The developed sensor can be easily fabricated in the laboratory, and it shows high potential to be used as a clinical evaluation tool for oral malodour assessments. Copyright 2009 Elsevier B.V. All rights reserved.

Achromatic-chromatic colorimetric sensors for on-off type detection of analytes.

PubMed

Heo, Jun Hyuk; Cho, Hui Hun; Lee, Jin Woong; Lee, Jung Heon

2014-12-21

We report the development of achromatic colorimetric sensors; sensors changing their colors from achromatic black to other chromatic colors. An achromatic colorimetric sensor was prepared by mixing a general colorimetric indicator, whose color changes between chromatic colors, and a complementary colored dye with no reaction to the targeted analyte. As the color of an achromatic colorimetric sensor changes from black to a chromatic color, the color change could be much easily recognized than general colorimetric sensors with naked eyes. More importantly, the achromatic colorimetric sensors enable on-off type recognition of the presence of analytes, which have not been achieved from most colorimetric sensors. In addition, the color changes from some achromatic colorimetric sensors (achromatic Eriochrome Black T and achromatic Benedict's solution) could be recognized with naked eyes at much lower concentration ranges than normal chromatic colorimetric sensors. These results provide new opportunities in the use of colorimetric sensors for diverse applications, such as harsh industrial, environmental, and biological detection.

Self-templated fabrication of FeMnO3 nanoparticle-filled polypyrrole nanotubes for peroxidase mimicking with a synergistic effect and their sensitive colorimetric detection of glutathione.

PubMed

Chi, Maoqiang; Chen, Sihui; Zhong, Mengxiao; Wang, Ce; Lu, Xiaofeng

2018-06-05

A self-templated approach has been developed for the preparation of FeMnO3 nanoparticles filled in the hollow core of polypyrrole (PPy) nanotubes by an in situ polymerization process accompanied by the etching of FeMnO3 nanofibers. The prepared FeMnO3@PPy nanotubes exhibited a superior peroxidase-like activity. The catalytic reaction system has been used for the sensitive colorimetric detection of glutathione with a low detection limit and good selectivity.

Colorimetry and SERS dual-mode detection of telomerase activity: combining rapid screening with high sensitivity.

PubMed

Zong, Shenfei; Wang, Zhuyuan; Chen, Hui; Hu, Guohua; Liu, Min; Chen, Peng; Cui, Yiping

2014-01-01

As an important biomarker and therapeutic target, telomerase has attracted considerable attention concerning its detection and monitoring. Here, we present a colorimetry and surface enhanced Raman scattering (SERS) dual-mode telomerase activity detection method, which has several distinctive advantages. First, colorimetric functionality allows rapid preliminary discrimination of telomerase activity by the naked eye. Second, the employment of SERS technique results in greatly improved detection sensitivity. Third, the combination of colorimetry and SERS into one detection system can ensure highly efficacious and sensitive screening of numerous samples. Besides, the avoidance of polymerase chain reaction (PCR) procedures further guarantees fine reliability and simplicity. Generally, the presented method is realized by an "elongate and capture" procedure. To be specific, gold nanoparticles modified with Raman molecules and telomeric repeat complementary oligonucleotide are employed as the colorimetric-SERS bifunctional reporting nanotag, while magnetic nanoparticles functionalized with telomerase substrate oligonucleotide are used as the capturing substrate. Telomerase can synthesize and elongate telomeric repeats onto the capturing substrate. The elongated telomeric repeats subsequently facilitate capturing of the reporting nanotag via hybridization between telomeric repeat and its complementary strand. The captured nanotags can cause a significant difference in the color and SERS intensity of the magnetically separated sediments. Thus both the color and SERS can be used as indicators of the telomerase activity. With fast screening ability and outstanding sensitivity, we anticipate that this method would greatly promote practical application of telomerase-based early-stage cancer diagnosis.

CIE colorimetric system fails to calculate the chroma of a Nd:YAG crystal under the fluorescent illuminant F7

NASA Astrophysics Data System (ADS)

Liu, Yan; Chen, Qinghan; Bu, Xianhui; Feng, Pingyun

2002-06-01

The rare earth element neodymium doped yttrium aluminum garnet (Nd:YAG) is a laser crystal widely used for producing laser in the infrared range. Neodymium causes many characteristic absorption peaks in the transmittance spectrum of the Nd:YAG crystal in the visible range. The crystal appears pink under daylight and incandescent light, and colorless under fluorescent light. The colorimetric calculation results of chroma under the CIE standard fluorescent illuminant F7 do not agree with the color appearance under fluorescent light. The calculated chroma values should be near zero to agree with a colorless appearance, but it is actually 11.79 in the CIELAB color space. This failure of the colorimetric calculation is caused by the color matching functions of the CIE colorimetric observers. The color matching functions do not agree with the spectral sensitivity curves of the human eye, especially the x(λ) function does not matches the spectral sensitivity curve of the long wavelength cone photoreceptors.

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

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

A Schiff-based colorimetric fluorescent sensor with the potential for detection of fluoride ions.

PubMed

Huang, Cheng-Yin; Wan, Chin-Feng; Chir, Jiun-Ly; Wu, An-Tai

2013-11-01

A simple Schiff-based colorimetric fluorescent receptor 1 was prepared. It exhibits a "turn-on-type" mode with high sensitivity in the presence of F(-). The change in color is very easily observed by the naked eye in the presence of F(-), whereas other anions do not induce such a change. Job plot indicated a 1:2 complexation stoichiometry between receptor 1 and F(-). The association constant for 1-F(-) in CH3CN was determined as 1.32*10(5) M(-2) by a Hill plot.

Discovering the enzyme mimetic activity of metal-organic framework (MOF) for label-free and colorimetric sensing of biomolecules.

PubMed

Wang, Ying; Zhu, Yingjing; Binyam, Atsebeha; Liu, Misha; Wu, Yinan; Li, Fengting

2016-12-15

A label-free sensing strategy based on the enzyme-mimicking activity of MOF was demonstrated for colorimetric detection of biomolecules. Firstly obvious blue color was observed due to the high efficiency of peroxidase-like catalytic activity of Fe-MIL-88A (an ion-based MOF material) toward 3,3',5,5'-tetramethylbenzidine (TMB). Then in the presence of target biomolecule and corresponding aptamer, the mimetic activity of Fe-MIL-88A can be strongly inhibited and used directly to realize the colorimetric detection. On the basis of the interesting findings, we designed a straightforward, label-free and sensitive colorimetric method for biomolecule detection by using the enzyme mimetic property of MOF coupling with molecular recognition element. Compared with the existed publications, our work breaks the routine way by setting up an inorganic-organic MOF-aptamer hybrid platform for colorimetric determination of biomolecules, expanding the targets scope from H2O2 or glucose to biomolecules. As a proof of concept, thrombin and thrombin aptamer was used as a model analyte. The limit of detection of 10nM can be achieved with naked eyes and ultrahigh selectivity of thrombin toward numerous interfering substances with 10-fold concentration was demonstrated significantly. Of note, the method was further applied for the detection of thrombin in human serum samples, showing the results in agreement with those values obtained in an immobilization buffer by the colorimetric method. This inorganic-organic MOF-aptamer sensing strategy may in principle be universally applicable for the detection of a range of environmental or biomedical molecules of interests. Copyright © 2016 Elsevier B.V. All rights reserved.

Organic conjugated small molecule materials based optical probe for rapid, colorimetric and UV-vis spectral detection of phosphorylated protein in placental tissue

NASA Astrophysics Data System (ADS)

Wang, Yanfang; Yang, Na; Liu, Yi

2018-04-01

A novel organic small molecule with D-Pi-A structure was prepared, which was found to be a promising colorimetric and ratiometric UV-vis spetral probe for detection of phosphorylated proteins with the help of tetravalent zirconium ion. Such optical probe based on chromophore WYF-1 shows a rapid response (within 10 s) and high selectivity and sensitivity for phosphorylated proteins, giving distinct colorimetric and ratiometric UV-vis changes at 720 and 560 nm. The detection limit for phosphorylated proteins was estimated to be 100 nM. In addition, detection of phosphorylated proteins in placental tissue samples with this probe was successfully applied, which indicates that this probe holds great potential for phosphorylated proteins detection.

Highly selective and sensitive colorimetric determination of Cr3 + ion by 4-amino-5-methyl-4H-1,2,4-triazole-3-thiol functionalized Au nanoparticles

NASA Astrophysics Data System (ADS)

Shahrivari, Shima; Faridbod, Farnoush; Ganjali, Mohammad Reza

2018-02-01

In this work, a rapid, selective naked eyes colorimetric chemical probe for the detection of Cr3 + was developed based on functionalization of gold nanoparticles. For this purpose, surface of Au NPs was functionalized using 4-amino-5-methyl-4H-1,2,4-triazole-3-thiol (AMTT). Through colorimetric studies, it was found that in the presence of Cr3 + ions, AMTT-Au NPs instantly aggregated and resulted in a color change of the solution from red to blue. The color change of AMTT-Au NPs due to the aggregation induced by Cr3 + can be seen with even naked eyes and also by UV-Vis spectroscopy with a detection limit of 1.8 μM and 0.1 μM, respectively. AMTT-Au NPs showed excellent selectivity toward Cr3 + compared to other cations tested, including K+, Na+, Cs+, Fe3 +, Ni2 +, Cu2 +, Co2 +, Zn2 +, Ba2 +, Ca2 +, Mg2 +, Cd2 +, Pb2 +, Hg2 + ions and especially all trivalent lanthanide ions. The absorbance ratio (A650/A525) was linear toward Cr3 + concentrations in the range of 0.6-6.1 μM (R2 = 0.996). The best response was achieved over a pH range of 3-5. Furthermore, the proposed colorimetric method based on AMTT-Au NPs was successfully used for Cr3 + ion detection in plasma sample and some water samples.

A new azine derivative colorimetric and fluorescent dual-channel probe for cyanide detection

NASA Astrophysics Data System (ADS)

Yu, Bin; Li, Chun-Yu; Sun, Yin-Xia; Jia, Hao-Ran; Guo, Jian-Qiang; Li, Jing

2017-09-01

A novel azine derivative colorimetric and fluorescent dual-channel probe salicylaldehyde hydrazine-3,5-dibromosalicylaldehyde (1) has been designed, synthesized and characterized. The probe 1 is confirmed to have especial selectivity and good sensitivity on detecting CN- via UV-vis absorption and fluorescence spectrum in aqueous solution (H2O/DMSO, 1:4, v/v). This colorimetric and fluorescent dual-channel probe response to CN- owed to the deprotonation process and established the mechanism by using 1H NMR spectroscopy. Further researches showed that the detection limit of the probe 1 to CN- anions is 8.01 × 10- 9 M, significantly lower than the maximum level 1.9 × 10- 6 M in potable water from WHO guidelines.

Colorimetric characterization models based on colorimetric characteristics evaluation for active matrix organic light emitting diode panels.

PubMed

Gong, Rui; Xu, Haisong; Tong, Qingfen

2012-10-20

The colorimetric characterization of active matrix organic light emitting diode (AMOLED) panels suffers from their poor channel independence. Based on the colorimetric characteristics evaluation of channel independence and chromaticity constancy, an accurate colorimetric characterization method, namely, the polynomial compensation model (PC model) considering channel interactions was proposed for AMOLED panels. In this model, polynomial expressions are employed to calculate the relationship between the prediction errors of XYZ tristimulus values and the digital inputs to compensate the XYZ prediction errors of the conventional piecewise linear interpolation assuming the variable chromaticity coordinates (PLVC) model. The experimental results indicated that the proposed PC model outperformed other typical characterization models for the two tested AMOLED smart-phone displays and for the professional liquid crystal display monitor as well.

L-cysteine protected copper nanoparticles as colorimetric sensor for mercuric ions.

PubMed

Soomro, Razium A; Nafady, Ayman; Sirajuddin; Memon, Najma; Sherazi, Tufail H; Kalwar, Nazar H

2014-12-01

This report demonstrates a novel, simple and efficient protocol for the synthesis of copper nanoparticles in aqueous solution using L-cysteine as capping or protecting agent. UV-visible (UV-vis) spectroscopy was employed to monitor the LSPR band of L-cysteine functionalized copper nanoparticles (Cyst-Cu NPs) based on optimizing various reaction parameters. Fourier Transform Infrared (FTIR) spectroscopy provided information about the surface interaction between L-cysteine and Cu NPs. Transmission Electron Microscopy (TEM) confirmed the formation of fine spherical, uniformly distributed Cyst-Cu NPs with average size of 34 ± 2.1 nm. X-ray diffractometry (XRD) illustrated the formation of pure metallic phase crystalline Cyst-Cu NPs. As prepared Cyst-Cu NPs were tested as colorimetric sensor for determining mercuric (Hg(2+)) ions in an aqueous system. Cyst-Cu NPs demonstrated very sensitive and selective colorimetric detection of Hg(2+) ions in the range of 0.5 × 10(-6)-3.5 × 10(-6) mol L(-1) based on decrease in LSPR intensity as monitored by a UV-vis spectrophotometer. The developed sensor is simple, economic compared to those based on precious metal nanoparticles and sensitive to detect Hg(2+) ions with detection limit down to 4.3 × 10(-8) mol L(-1). The sensor developed in this work has a high potential for rapid and on-site detection of Hg(2+) ions. The sensor was successfully applied for assessment of Hg(2+) ions in real water samples collected from various locations of the Sindh River. Copyright © 2014 Elsevier B.V. All rights reserved.

Recyclable colorimetric sensor of Cr3 + and Pb2 + ions simultaneously using a zwitterionic amino acid modified gold nanoparticles

NASA Astrophysics Data System (ADS)

Sang, Fuming; Li, Xin; Zhang, Zhizhou; Liu, Jia; Chen, Guofu

2018-03-01

In this work, a rapid, simple and sensitive colorimetric sensor for simultaneous (or respective) detection of Cr3 + and Pb2 + using tyrosine functionalized gold nanoparticles (AuNPsTyr) has been developed. Tyrosine, a natural and zwitterionic amino acid, could be as a reducing and capping agent to synthesise AuNPs and allow for the simultaneous and selective detection of Cr3 + and Pb2 +. Upon the addition of Cr3 + or Pb2 + (a combination of them), the color of AuNPsTyr solution changes from red to blue grey and the characteristic surface plasmon resonance (SPR) band is red-shifted to 580 nm due to the aggregation of AuNPs. Interestingly, the aggregated AuNPsTyr can be regnerated and recycled by removing Pb2 + and Cr3 +. Even after 3 rounds, AuNPsTyr show almost the same A580 nm / A520 nm value for the assays of Pb2 + and Cr3 +, indicating the good recyclability of the colorimetric sensor. The responding time (within 1 min) and sensitivity of the colorimetric sensor are largely improved after the addition of 0.1 M NaCl. Moreover, the AuNPsTyr aggregated by Cr3 + or Pb2 + (a combination of them) show excellent selectivity compared to other metal ions (Cr3 +, Pb2 +, Fe2 +,Cu2 +,Zn2 +,Cr6 +,Ni2 +,Co2 +,Hg2 +,Mn2 +,Mg2 +,Ca2 +,Cd2 +). More importantly, the developed sensor manifests good stability at room temperature for 3 months, which has been successfully used to determine Cr3 + and Pb2 + in the real water samples with a high sensitivity.

Smartphone-Based VOC Sensor Using Colorimetric Polydiacetylenes.

PubMed

Park, Dong-Hoon; Heo, Jung-Moo; Jeong, Woomin; Yoo, Young Hyuk; Park, Bum Jun; Kim, Jong-Man

2018-02-07

Owing to a unique colorimetric (typically blue-to-red) feature upon environmental stimulation, polydiacetylenes (PDAs) have been actively employed in chemosensor systems. We developed a highly accurate and simple volatile organic compound (VOC) sensor system that can be operated using a conventional smartphone. The procedure begins with forming an array of four different PDAs on conventional paper using inkjet printing of four corresponding diacetylenes followed by photopolymerization. A database of color changes (i.e., red and hue values) is then constructed on the basis of different solvatochromic responses of the 4 PDAs to 11 organic solvents. Exposure of the PDA array to an unknown solvent promotes color changes, which are imaged using a smartphone camera and analyzed using the app. A comparison of the color changes to the database promoted by the 11 solvents enables the smartphone app to identify the unknown solvent with 100% accuracy. Additionally, it was demonstrated that the PDA array sensor was sufficiently sensitive to accurately detect the 11 VOC gases.

A colorimetric sensor array for identification of toxic gases below permissible exposure limits†

PubMed Central

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

2010-01-01

A colorimetric sensor array has been developed for the rapid and sensitive detection of 20 toxic industrial chemicals (TICs) at their PELs (permissible exposure limits). The color changes in an array of chemically responsive nanoporous pigments provide facile identification of the TICs with an error rate below 0.7%. PMID:20221484

Gold nanoparticles based colorimetric nanodiagnostics for cancer and infectious diseases

NASA Astrophysics Data System (ADS)

Valentini, Paola; Persano, Stefano; Cecere, Paola; Sabella, Stefania; Pompa, Pier Paolo

2014-03-01

Traditional in vitro diagnostics requires specialized laboratories and costly instrumentation, both for the amplification of nucleic acid targets (usually achieved by PCR) and for the assay readout, often based on fluorescence. We are developing hybrid nanomaterials-based sensors for the rapid and low-cost diagnosis of various disease biomarkers, for applications in portable platforms for diagnostics at the point-of-care. To this aim, we exploited the size and distancedependent optical properties of gold nanoparticles (AuNPs) to achieve colorimetric detection. Moreover, in order to avoid the complexity of thermal cycles associated to traditional PCR, the design of our systems includes signal amplification schemes, achieved by the use of enzymes (nucleases, helicase) or DNAzymes. Focused on instrument-free and sensitive detection, we carefully combined the intrinsic sensitivity by multivalency of functionalized AuNPs with isothermal and non-stringent enzyme-aided reaction conditions, controlled AuNPs aggregates, universal reporters and magnetic microparticles, the latter used both as a substrate and as a means for the colorimetric detection. We obtained simple and robust assays for the sensitive (pM range or better) naked-eye detection of cancer or infectious diseases (HPV, HCV) biomarkers, requiring no instrumentation except for a simple heating plate. Finally, we are also developing non-medical applications of these bio-nanosensors, such as in the development of on-field rapid tests for the detection of pollutants and other food and water contaminants.

Sensitive colorimetric assay for uric acid and glucose detection based on multilayer-modified paper with smartphone as signal readout.

PubMed

Wang, Xu; Li, Fang; Cai, Ziqi; Liu, Kaifan; Li, Jing; Zhang, Boyang; He, Jianbo

2018-04-01

In this work, a multilayer-modified paper-based colorimetric sensing platform with improved color uniformity and intensity was developed for the sensitive and selective determination of uric acid and glucose with smartphone as signal readout. In detail, chitosan, different kinds of chromogenic reagents, and horseradish peroxidase (HRP) combined with a specific oxidase, e.g., uricase or glucose oxidase (GOD), were immoblized onto the paper substrate to form a multilayer-modified test paper. Hydrogen peroxide produced by the oxidases (uricase or GOD) reacts with the substrates (uric acid or glucose), and could oxidize the co-immoblized chromogenic reagents to form colored products with HRP as catalyst. A simple strategy by placing the test paper on top of a light-emitting diode lamp was adopted to efficiently prevent influence from the external light. The color images were recorded by the smartphone camera, and then the gray values of the color images were calculated for quantitative analysis. The developed method provided a wide linear response from 0.01 to 1.0 mM for uric acid detection and from 0.02 to 4.0 mM for glucose detection, with a limit of detection (LOD) as low as 0.003 and 0.014 mM, respectively, which was much lower than for previously reported paper-based colorimetric assays. The proposed assays were successfully applied to uric acid and glucose detection in real serum samples. Furthermore, the enhanced analytical performance of the proposed method allowed the non-invasive detection of glucose levels in tear samples, which holds great potential for point-of-care analysis. Graphical abstract ᅟ.

Highly selective "turn-on" fluorescent and colorimetric sensing of fluoride ion using 2-(2-hydroxyphenyl)-2,3-dihydroquinolin-4(1H)-one based on excited-state proton transfer.

PubMed

Kanagaraj, Kuppusamy; Pitchumani, Kasi

2014-01-01

A simple, highly selective and sensitive colorimetric system for the detection of fluoride ion in an aqueous medium has been developed using 2-(2-hydroxyphenyl)-2,3-dihydroquinolin-4(1H)-one. This system allows selective "turn-on" fluorescence detection of fluoride ion, which is found to be dependent upon guest basicity. An excited-state proton transfer is proposed to be the signaling mechanism, which is rationalized by DFT and TD-DFT calculations. The present sensor can also be applied to detect fluoride levels in real water samples. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Colorimetric sensor for cysteine in human urine based on novel gold nanoparticles.

PubMed

Zhang, Yan; Jiang, Jingjing; Li, Min; Gao, Pengfei; Zhou, Ying; Zhang, Guomei; Shuang, Shaomin; Dong, Chuan

2016-12-01

Herein, a novel, high sensitive, and specific colorimetric sensor for cysteine (Cys) based on pectinase protected gold nanoparticles (P@AuNPs) has been demonstrated for the first time. The P@AuNPs were synthesized by "MW-assisted heat method" and were characterized by UV-vis, TEM, FT-IR and zeta potential techniques. Cys could cause the aggregation of P@AuNPs due to formation of the strong covalent Au-S bond and electrostatic binding. As the Cys concentration increased, the color of the solutions gradually changed from wine-red to blue as well as the large absorption band shifted from 523 to 650nm upon P@AuNPs aggregation. In addition, various experimental parameters such as pH, the amount of P@AuNPs and incubation time were investigated for the optimum sensing conditions. The concentration of Cys could be determined by monitoring with the naked eye or a UV-vis spectrometer. The proposed colorimetric sensor showed an extreme selectivity toward the determination of Cys in the presence of 20-fold all other different interferents. Under optimum conditions, this method exhibited two good linear ranges from 4.85×10 -9 to 3.02×10 -4 M (R 2 =0.996) and 3.25×10 -3 to 1.03×10 -2 M (R 2 =0.999), with a low detection limit of 4.6×10 -9 M. Moreover, this colorimetric sensor was successfully applied to the detection of Cys in human urine samples, demonstrating its great value for practical application in biological systems. Copyright © 2016 Elsevier B.V. All rights reserved.

Organic conjugated small molecule materials based optical probe for rapid, colorimetric and UV-vis spectral detection of phosphorylated protein in placental tissue.

PubMed

Wang, Yanfang; Yang, Na; Liu, Yi

2018-04-05

A novel organic small molecule with D-Pi-A structure was prepared, which was found to be a promising colorimetric and ratiometric UV-vis spetral probe for detection of phosphorylated proteins with the help of tetravalent zirconium ion. Such optical probe based on chromophore WYF-1 shows a rapid response (within 10s) and high selectivity and sensitivity for phosphorylated proteins, giving distinct colorimetric and ratiometric UV-vis changes at 720 and 560nm. The detection limit for phosphorylated proteins was estimated to be 100nM. In addition, detection of phosphorylated proteins in placental tissue samples with this probe was successfully applied, which indicates that this probe holds great potential for phosphorylated proteins detection. Copyright © 2018 Elsevier B.V. All rights reserved.

Colorimetric detection of mercury(II) in a high-salinity solution using gold nanoparticles capped with 3-mercaptopropionate acid and adenosine monophosphate.

PubMed

Yu, Cheng-Ju; Tseng, Wei-Lung

2008-11-04

A new colorimetric sensor for sensing Hg2+ in a high-salinity solution has been developed using gold nanoparticles (AuNPs) decorated with 3-mercaptopropionate acid (MPA) and adenosine monophosphate (AMP). Because of the high negative charge density of AMP on each AuNP surface, MPA/AMP-capped AuNPs are well dispersed in a high-salt solution. In contrast, the aggregation of MPA-capped AuNPs was induced by sodium ions, which shield the negative charges of the carboxylic groups of MPA. Through the coordination between the carboxylic group of MPA and Hg2+, the selectivity of MPA/AMP-capped AuNPs for Hg2+ in a high-salt solution is remarkably high over that of the other metals without the addition of a masking agent or a change in the temperature. We have carefully investigated the effect of the AMP concentration on the stability and sensitivity of MPA/AMP-capped AuNPs. Under optimum conditions, the lowest detectable concentration of Hg2+ using this probe was 500 nM on the basis of the measurement of the ratio of absorption at 620 nm to that at 520 nm. The sensitivity to Hg2+ can be further improved by modifying the MPA/AMP-capped AuNPs with highly fluorescent rhodamine 6G (R6G). By monitoring the fluorescence enhancement, the lowest detectable concentration of Hg2+ using R6G/MPA/AMP-capped AuNPs was 50 nM.

Colorimetric determination of Al(III) based on the aggregation of gold nanoparticles functionalized with novel 4-benzoyl pyrazolone derivative

NASA Astrophysics Data System (ADS)

Abubaker, Mariam; Ngah, Che Wan Zanariah Che Wan; Ahmad, Musa; Kuswandi, Bambang

2018-06-01

A sensitive and selective colorimetric method has been developed for detection of Al3+ ion using 4-benzoyl pyrazolone-functionalized gold nanoparticles (BMPBP-AuNPs) as novel colorimetric probes. The BMPBP-AuNPs were characterized by UV-visible spectrometry and transmission electron microscopy (TEM). It was found that the addition of the Al3+ ions led to a rapid aggregation of the BMPBP-AuNPs, which changed the color of the mixture from red to blue. Furthermore, there was a shift in the characteristic surface plasmon resonance (SPR) peak from 524 to 650 nm of BMPBP-AuNPs, which confirmed that a good linear relation (R2 = 0.9935) was present between the absorption ratio of 524 and 650 nm. Also, the assay detected the Al3+ ion concentrations in the linear range 0-12 ppm with the detection limit is 0.05 ppm. Finally, the synthesized BMPBP-AuNPs were successfully used as a colorimetric sensor for the selective and sensitive detection of the Al3+ ions in water samples.

A reversible fluorescent-colorimetric imino-pyridyl bis-Schiff base sensor for expeditious detection of Al(3+) and HSO3(-) in aqueous media.

PubMed

Ghorai, Anupam; Mondal, Jahangir; Chandra, Rukmani; Patra, Goutam K

2015-08-07

A reversible fluorescent-colorimetric imino-pyridyl bis-Schiff base receptor (N(1)E,N(4)E)-N(1),N(4)-bis(pyridine-4-ylmethylene)benzene-1,4-diamine for the detection of both Al(3+) and HSO3(-) in aqueous medium has been developed. Receptor exhibits an excellent selective fluorescent-colorimetric response toward Al(3+). The sensitivity of the fluorescent based assay (0.903 μM) for Al(3+) is far below the limit recommended in the World Health Organization (WHO) guidelines for drinking water (7.41 μM). From (1)H NMR data, the Job plot and the ESI-MS spectrum, 1 : 2 stoichiometric complexation between and Al(3+) has been established. Receptor shows remarkable detection ability in a wide pH range of 4-11 and was successfully utilised in the determination of Al(3+) in aqueous solution of bovine serum albumin protein, and of HSO3(-) in real food samples. Moreover, shows a highly selective colorimetric response to HSO3(-) by changing its colour from yellow to colorless immediately without any interference from other anions.

Colorimetric detection of endogenous hydrogen sulfide production in living cells

NASA Astrophysics Data System (ADS)

Ahn, Yong Jin; Lee, Young Ju; Lee, Jaemyeon; Lee, Doyeon; Park, Hun-Kuk; Lee, Gi-Ja

2017-04-01

Hydrogen sulfide (H2S) has received great attention as a third gaseous signal transmitter, following nitric oxide and carbon monoxide. In particular, H2S plays an important role in the regulation of cancer cell biology. Therefore, the detection of endogenous H2S concentrations within biological systems can be helpful to understand the role of gasotransmitters in pathophysiology. Although a simple and inexpensive method for the detection of H2S has been developed, its direct and precise measurement in living cells remains a challenge. In this study, we introduced a simple, facile, and inexpensive colorimetric system for selective H2S detection in living cells using a silver-embedded Nafion/polyvinylpyrrolidone (PVP) membrane. This membrane could be easily applied onto a polystyrene microplate cover. First, we optimized the composition of the coating membrane, such as the PVP/Nafion mixing ratio and AgNO3 concentration, as well as the pH of the Na2S (H2S donor) solution and the reaction time. Next, the in vitro performance of a colorimetric detection assay utilizing the silver/Nafion/PVP membrane was evaluated utilizing a known concentration of Na2S standard solution both at room temperature and at 37 °C in a 5% CO2 incubator. As a result, the sensitivity of the colorimetric assay for H2S at 37 °C in the incubator (0.0056 Abs./μM Na2S, R2 = 0.9948) was similar to that at room temperature (0.0055 Abs./μM Na2S, R2 = 0.9967). Moreover, these assays were less sensitive to interference from compounds such as glutathione, L-cysteine (Cys), and dithiothreitol than to the H2S from Na2S. This assay based on the silver/Nafion/PVP membrane also showed excellent reproducibility (2.8% RSD). Finally, we successfully measured the endogenous H2S concentrations in live C6 glioma cells by s-(5‧-adenosyl)-L-methionine stimulation with and without Cys and L-homocysteine, utilizing the silver/Nafion/PVP membrane. In summary, colorimetric assays using silver

Rapid determination of trace copper in animal feed based on micro-plate colorimetric reaction and statistical partitioning correction.

PubMed

Niu, Yiming; Wang, Jiayi; Zhang, Chi; Chen, Yiqiang

2017-04-15

The objective of this study was to develop a micro-plate based colorimetric assay for rapid and high-throughput detection of copper in animal feed. Copper ion in animal feed was extracted by trichloroacetic acid solution and reduced to cuprous ion by hydroxylamine. The cuprous ion can chelate with 2,2'-bicinchoninic acid to form a Cu-BCA complex which was detected with high sensitivity by micro-plate reader at 354nm. The whole assay procedure can be completed within 20min. To eliminate matrix interference, a statistical partitioning correction approach was proposed, which makes the detection of copper in complex samples possible. The limit of detection was 0.035μg/mL and the detection range was 0.1-10μg/mL of copper in buffer solution. Actual sample analysis indicated that this colorimetric assay produced results consistent with atomic absorption spectrometry analysis. These results demonstrated that the developed assay can be used for rapid determination of copper in animal feed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Fluorescent and colorimetric ion probes based on conjugated oligopyrroles.

PubMed

Ding, Yubin; Tang, Yunyu; Zhu, Weihong; Xie, Yongshu

2015-03-07

Metal ions and anions play important roles in many industrial and biochemical processes, and thus it is highly desired to detect them in the relevant systems. Small organic molecule based sensors for selective and sensitive detection of target ions show the advantages of low cost, high sensitivity and convenient implementation. In this area, pyrrole has incomparable advantages. It can be easily incorporated into linear and macrocyclic conjugated structures such as dipyrrins, porphyrins, and N-confused porphyrins, which may utilize the imino N and amino NH moieties for binding metal ions and anions, respectively. In this tutorial review, we focus on representative examples to describe the design, syntheses, sensing mechanisms, and applications of the conjugated oligopyrroles. These compounds could be used as colorimetric or fluorescent ion probes, with the advantages of vivid colour and fluorescence changes, easy structural modification and functionalization, and tunable emission wavelengths. Compared with normal porphyrins, simple di- and tripyrrins, as well as some porphyrinoids are more suitable for designing fluorescence "turn-on" metal probes, because they may exhibit flexible confirmations, and metal coordination will improve the rigidity, resulting in vivid fluorescence enhancement. It is noteworthy that the oligopyrrolic moieties may simultaneously act as the binding unit as well as the reporting moiety, which simplifies the design and syntheses of the probes.

Colorimetric detection of Cr (VI) based on the leaching of gold nanoparticles using a paper-based sensor.

PubMed

Guo, Jian-Feng; Huo, Dan-Qun; Yang, Mei; Hou, Chang-Jun; Li, Jun-Jie; Fa, Huan-Bao; Luo, Hui-Bo; Yang, Ping

2016-12-01

Herein, we have developed a simple, sensitive and paper-based colorimetric sensor for the selective detection of Chromium (Ⅵ) ions (Cr (VI)). Silanization-titanium dioxide modified filter paper (STCP) was used to trap bovine serum albumin capped gold nanoparticles (BSA-Au NPs), leading to the fabrication of BSA-Au NPs decorated membrane (BSA-Au NPs/STCP). The BSA-Au NPs/STCP operated on the principle that BSA-Au NPs anchored on the STCP were gradually etched by Cr (VI) as the leaching process of gold in the presence of hydrobromic acid (HBr) and hence induced a visible color change. Under optimum conditions, the paper-based colorimetric sensor showed clear color change after reaction with Cr (VI) as well as with favorable selectivity to a variety of possible interfering counterparts. The amount-dependent colorimetric response was linearly correlated with the Cr (VI) concentrations ranging from 0.5µM to 50.0µM with a detection limit down to 280nM. Moreover, the developed cost-effective colorimetric sensor has been successfully applied to real environmental samples which demonstrated the potential for field applications. Copyright © 2016 Elsevier B.V. All rights reserved.

A novel colorimetric assay for rapid detection of cysteine and Hg²⁺ based on gold clusters.

PubMed

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

2016-01-01

Inhibition and recovery of the catalytic activity of bovine serum albumin-capped gold nanoclusters (BSA-AuNCs) is observed for the first time by introduction of cysteine and Hg(2+). The prepared BSA-AuNCs possess highly intrinsic peroxidase-like activity. It can catalyze the oxidation of 3, 3, 5, 5-tetramethylbenzidine by H2O2 to produce a blue colored product. Based on this phenomenon, a new colorimetric assay for rapid, selective and sensitive detection of cysteine and Hg(2+) in aqueous solution has been demonstrated. The interaction process between target molecule and BSA-AuNCs is very fast, so that the whole test can be completed within ten minutes. Moreover, the fabricated colorimetric sensor is simple and cost-effective, without the need of nucleic acid based recognition element and complicated washing, separation and labeling process, thus holds great promise for routine analysis of cysteine and Hg(2+) in real samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Simple colorimetric detection of doxycycline and oxytetracycline using unmodified gold nanoparticles

NASA Astrophysics Data System (ADS)

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

2014-08-01

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

An improved colorimetric method for the determination of proline in the presence of other ninhydrin-positive compounds

PubMed Central

Wren, J. J.; Wiggall, P. H.

1965-01-01

1. The conditions required for sensitive and specific colorimetric determination of proline with acidified ninhydrin were investigated. 2. A method applicable to protein samples was developed. 3. The only compound found to interfere appreciably was a hydroxyproline. PMID:14342233

A Simple Assay for Ultrasensitive Colorimetric Detection of Ag⁺ at Picomolar Levels Using Platinum Nanoparticles.

PubMed

Wang, Yi-Wei; Wang, Meili; Wang, Lixing; Xu, Hui; Tang, Shurong; Yang, Huang-Hao; Zhang, Lan; Song, Hongbo

2017-11-02

In this work, uniformly-dispersed platinum nanoparticles (PtNPs) were synthesized by a simple chemical reduction method, in which citric acid and sodium borohydride acted as a stabilizer and reducer, respectively. An ultrasensitive colorimetric sensor for the facile and rapid detection of Ag⁺ ions was constructed based on the peroxidase mimetic activities of the obtained PtNPs, which can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H₂O₂ to produce colored products. The introduced Ag⁺ would be reduced to Ag⁰ by the capped citric acid, and the deposition of Ag⁰ on the PtNPs surface, can effectively inhibit the peroxidase-mimetic activity of PtNPs. Through measuring the maximum absorption signal of oxidized TMB at 652 nm, ultra-low detection limits (7.8 pM) of Ag⁺ can be reached. In addition to such high sensitivity, the colorimetric assay also displays excellent selectivity for other ions of interest and shows great potential for the detection of Ag⁺ in real water samples.

A sensitive gold nanoparticle-based colorimetric aptasensor for Staphylococcus aureus.

PubMed

Yuan, Jinglei; Wu, Shijia; Duan, Nuo; Ma, Xiaoyuan; Xia, Yu; Chen, Jie; Ding, Zhansheng; Wang, Zhouping

2014-09-01

In this study, a gold nanoparticle-based colorimetric aptasensor for Staphylococcus aureus (S. aureus) using tyramine signal amplification (TSA) technology has been developed. First, the biotinylated aptamer specific for S. aureus was immobilized on the surface of the wells of the microtiter plate via biotin-avidin binding. Then, the target bacteria (S. aureus), biotinylated-aptamer-streptavidin-HRP conjugates, biotinylated tyramine, hydrogen peroxide and avidin-catalase were successively introduced into the wells of the microtiter plate. After that, the existing catalase consumed the hydrogen peroxide. Finally, the freshly prepared gold (III) chloride trihydrate was added, the color of the reaction production would be changed and the absorbance at 550 nm could be measured with a plate reader. Under optimized conditions, there was a linear relationship between the absorbance at 550 nm and the concentration of S. aureus over the range from 10 to 10(6) cfu mL(-1) (with an R² of 0.9947). The limit of the developed method was determined to be 9 cfu mL(-1). Copyright © 2014 Elsevier B.V. All rights reserved.

Evaluation of a colorimetric reagent strip assay for urine specific gravity.

PubMed

Kirschbaum, B B

1983-06-01

N-Multistix SG provides a convenient colorimetric assay for the determination of the specific gravity (sp. gr.) of freshly voided urine. When compared with results obtained by standard hydrometry, the colorimetric assay sp. gr. was observed to decrease by as much as 0.010 units as urine pH increased from 5 to 7. Moderate levels of proteinuria that did not alter hydrometer readings effectively raised the colorimetric sp. gr. by 0.005-0.010 units. The colorimetric assay was almost completely insensitive to clinically encountered concentrations of glucose and urea but responded appropriately to monovalent salts. The magnitude of these observed discrepancies places serious limitations on the value of the colorimetric sp. gr. measurement.

Colorimetric Sensor Array for White Wine Tasting.

PubMed

Chung, Soo; Park, Tu San; Park, Soo Hyun; Kim, Joon Yong; Park, Seongmin; Son, Daesik; Bae, Young Min; Cho, Seong In

2015-07-24

A colorimetric sensor array was developed to characterize and quantify the taste of white wines. A charge-coupled device (CCD) camera captured images of the sensor array from 23 different white wine samples, and the change in the R, G, B color components from the control were analyzed by principal component analysis. Additionally, high performance liquid chromatography (HPLC) was used to analyze the chemical components of each wine sample responsible for its taste. A two-dimensional score plot was created with 23 data points. It revealed clusters created from the same type of grape, and trends of sweetness, sourness, and astringency were mapped. An artificial neural network model was developed to predict the degree of sweetness, sourness, and astringency of the white wines. The coefficients of determination (R2) for the HPLC results and the sweetness, sourness, and astringency were 0.96, 0.95, and 0.83, respectively. This research could provide a simple and low-cost but sensitive taste prediction system, and, by helping consumer selection, will be able to have a positive effect on the wine industry.

Colorimetric Sensor Array for White Wine Tasting

PubMed Central

Chung, Soo; Park, Tu San; Park, Soo Hyun; Kim, Joon Yong; Park, Seongmin; Son, Daesik; Bae, Young Min; Cho, Seong In

2015-01-01

A colorimetric sensor array was developed to characterize and quantify the taste of white wines. A charge-coupled device (CCD) camera captured images of the sensor array from 23 different white wine samples, and the change in the R, G, B color components from the control were analyzed by principal component analysis. Additionally, high performance liquid chromatography (HPLC) was used to analyze the chemical components of each wine sample responsible for its taste. A two-dimensional score plot was created with 23 data points. It revealed clusters created from the same type of grape, and trends of sweetness, sourness, and astringency were mapped. An artificial neural network model was developed to predict the degree of sweetness, sourness, and astringency of the white wines. The coefficients of determination (R2) for the HPLC results and the sweetness, sourness, and astringency were 0.96, 0.95, and 0.83, respectively. This research could provide a simple and low-cost but sensitive taste prediction system, and, by helping consumer selection, will be able to have a positive effect on the wine industry. PMID:26213946

The effects of colorimetric detection of heavy metal ions based on Au nanoparticles (NPs): size and shape—a case of Co2+

NASA Astrophysics Data System (ADS)

Leng, Yumin; He, Junbao; Li, Bo; Xing, Xiaojing; Guo, Yongming; Ye, Liqun; Lu, Zhiwen

2017-09-01

The different sized and shaped Au NPs have intrigued considerable attention, because they possess different surface plasma resonance (SPR) absorption bands and thus result in many colorimetric Au NP-based detection applications. In this article, four different sized and shaped Au NPs of nanodots/rods were prepared and characterized. The as-prepared Au NPs were modified by the negatively charged anions of [SCH2CO2]2- to investigate both the size and shape effects of modified Au NPs on colorimetric detection of Co2+ and the corresponding SPR absorption properties. The different-shaped Au NPs possess different SPR absorption properties. The Au nanorods appeared to be colorimetric sensitive for Co2+ sensing.

Integrating Deoxyribozymes into Colorimetric Sensing Platforms

PubMed Central

Chang, Dingran; Zakaria, Sandy; Deng, Mimi; Allen, Nicholas; Tram, Kha; Li, Yingfu

2016-01-01

Biosensors are analytical devices that have found a variety of applications in medical diagnostics, food quality control, environmental monitoring and biodefense. In recent years, functional nucleic acids, such as aptamers and nucleic acid enzymes, have shown great potential in biosensor development due to their excellent ability in target recognition and catalysis. Deoxyribozymes (or DNAzymes) are single-stranded DNA molecules with catalytic activity and can be isolated to recognize a wide range of analytes through the process of in vitro selection. By using various signal transduction mechanisms, DNAzymes can be engineered into fluorescent, colorimetric, electrochemical and chemiluminescent biosensors. Among them, colorimetric sensors represent an attractive option as the signal can be easily detected by the naked eye. This reduces reliance on complex and expensive equipment. In this review, we will discuss the recent progress in the development of colorimetric biosensors that make use of DNAzymes and the prospect of employing these sensors in a range of chemical and biological applications. PMID:27918487

Colorimetric consideration of transparencies for a typical LACIE scene

NASA Technical Reports Server (NTRS)

Juday, R. D. (Principal Investigator)

1979-01-01

The production film converter used to produce LACIE imagery is described as well as schemes designed to provide the analyst with operational film products. Two of these products are discussed from the standpoint of color theory. Colorimetric terminology is defined and the mathematical calculations are given. Topics covered include (1) history of product 1 and 3 algorithm development; (2) colorimetric assumptions for product 1 and 3 algorithms; (3) qualitative results from a colorimetric analysis of a typical LACIE scene; and (4) image-to-image color stability.

Multispectral Image Compression for Improvement of Colorimetric and Spectral Reproducibility by Nonlinear Spectral Transform

NASA Astrophysics Data System (ADS)

Yu, Shanshan; Murakami, Yuri; Obi, Takashi; Yamaguchi, Masahiro; Ohyama, Nagaaki

2006-09-01

The article proposes a multispectral image compression scheme using nonlinear spectral transform for better colorimetric and spectral reproducibility. In the method, we show the reduction of colorimetric error under a defined viewing illuminant and also that spectral accuracy can be improved simultaneously using a nonlinear spectral transform called Labplus, which takes into account the nonlinearity of human color vision. Moreover, we show that the addition of diagonal matrices to Labplus can further preserve the spectral accuracy and has a generalized effect of improving the colorimetric accuracy under other viewing illuminants than the defined one. Finally, we discuss the usage of the first-order Markov model to form the analysis vectors for the higher order channels in Labplus to reduce the computational complexity. We implement a multispectral image compression system that integrates Labplus with JPEG2000 for high colorimetric and spectral reproducibility. Experimental results for a 16-band multispectral image show the effectiveness of the proposed scheme.

The use of colorimetric sensor arrays to discriminate between pathogenic bacteria.

PubMed

Lonsdale, Claire L; Taba, Brian; Queralto, Nuria; Lukaszewski, Roman A; Martino, Raymond A; Rhodes, Paul A; Lim, Sung H

2013-01-01

A colorimetric sensor array is a high-dimensional chemical sensor that is cheap, compact, disposable, robust, and easy to operate, making it a good candidate technology to detect pathogenic bacteria, especially potential bioterrorism agents like Yersinia pestis and Bacillus anthracis which feature on the Center for Disease Control and Prevention's list of potential biothreats. Here, a colorimetric sensor array was used to continuously monitor the volatile metabolites released by bacteria in solid media culture in an Advisory Committee on Dangerous Pathogen Containment Level 3 laboratory. At inoculum concentrations as low as 8 colony-forming units per plate, 4 different bacterial species were identified with 100% accuracy using logistic regression to classify the kinetic profile of sensor responses to culture headspace gas. The sensor array was able to further discriminate between different strains of the same species, including 5 strains of Yersinia pestis and Bacillus anthracis. These preliminary results suggest that disposable colorimetric sensor arrays can be an effective, low-cost tool to identify pathogenic bacteria.

Needle Decompression of Tension Pneumothorax with Colorimetric Capnography.

PubMed

Naik, Nimesh D; Hernandez, Matthew C; Anderson, Jeff R; Ross, Erika K; Zielinski, Martin D; Aho, Johnathon M

2017-11-01

The success of needle decompression for tension pneumothorax is variable, and there are no objective measures assessing effective decompression. Colorimetric capnography, which detects carbon dioxide present within the pleural space, may serve as a simple test to assess effective needle decompression. Three swine underwent traumatically induced tension pneumothorax (standard of care, n = 15; standard of care with needle capnography, n = 15). Needle thoracostomy was performed with an 8-cm angiocatheter. Similarly, decompression was performed with the addition of colorimetric capnography. Subjective operator assessment of decompression was recorded and compared with true decompression, using thoracoscopic visualization for both techniques. Areas under receiver operating curves were calculated and pairwise comparison was performed to assess statistical significance (P < .05). The detection of decompression by needle colorimetric capnography was found to be 100% accurate (15 of 15 attempts), when compared with thoracoscopic assessment (true decompression). Furthermore, it accurately detected the lack of tension pneumothorax, that is, the absence of any pathologic/space-occupying lesion, in 100% of cases (10 of 10 attempts). Standard of care needle decompression was detected by operators in 9 of 15 attempts (60%) and was detected in 3 of 10 attempts when tension pneumothorax was not present (30%). True decompression, under direct visualization with thoracoscopy, occurred 15 of 15 times (100%) with capnography, and 12 of 15 times (80%) without capnography. Areas under receiver operating curves were 0.65 for standard of care and 1.0 for needle capnography (P = .002). Needle decompression with colorimetric capnography provides a rapid, effective, and highly accurate method for eliminating operator bias for tension pneumothorax decompression. This may be useful for the treatment of this life-threatening condition. Copyright © 2017 American College of Chest Physicians

Colorimetric carbon dioxide detector to determine accidental tracheal feeding tube placement.

PubMed

Howes, Daniel W; Shelley, Eric S; Pickett, William

2005-04-01

To determine the accuracy of colorimetric CO2 detection compared to the reference standard two-step radiological confirmation of feeding tube position. A prospective study was conducted with patients presenting to a 21-bed medical-surgical intensive care unit. An adapter was developed using an endotracheal tube adapter to connect a colorimetric CO2 detector to a feeding tube in an airtight manner. In part I of the study a feeding tube connected to the colorimeter was inserted into the endotracheal tubes of ten ventilated patients to test the device's ability to detect tracheal placement. In part II patients undergoing feeding tube insertion had tube position confirmed with the colorimeter as well as the reference standard two-step x-ray. In phase I the colorimeter correctly identified tracheal placement in all ten patients. In phase II 93/100 procedures ultimately were eligible; the colorimeter had a sensitivity of 0.88 (95% confidence interval: 0.65-1.00) and specificity of 0.99 (0.97-1.00). The device missed one of the eight tracheal placements. Agreement between the colorimeter and two-step x-ray interpretations was excellent (Kappa 0.86; standard error 0.10). We describe a novel, convenient method to confirm esophageal feeding tube placement. The device is easily assembled and inexpensive, but should not be reused. Colorimetric determination of tracheal feeding tube placement with this device has excellent agreement with the reference standard two-step radiological technique.

Plasmonic Metasurfaces Based on Nanopin-Cavity Resonator for Quantitative Colorimetric Ricin Sensing.

PubMed

Fan, Jiao-Rong; Zhu, Jia; Wu, Wen-Gang; Huang, Yun

2017-01-01

In view of the toxic potential of a bioweapon threat, rapid visual recognition and sensing of ricin has been of considerable interest while remaining a challenging task up to date. In this study, a gold nanopin-based colorimetric sensor is developed realizing a multicolor variation for ricin qualitative recognition and analysis. It is revealed that such plasmonic metasurfaces based on nanopin-cavity resonator exhibit reflective color appearance, due to the excitation of standing-wave resonances of narrow bandwidth in visible region. This clear color variation is a consequence of the reflective color mixing defined by different resonant wavelengths. In addition, the colored metasurfaces appear sharp color difference in a narrow refractive index range, which makes them especially well-suited for sensing applications. Therefore, this antibody-functionalized nanopin-cavity biosensor features high sensitivity and fast response, allowing for visual quantitative ricin detection within the range of 10-120 ng mL -1 (0.15 × 10 -9 -1.8 × 10 -9 m), a limit of detection of 10 ng mL -1 , and the typical measurement time of less than 10 min. The on-chip integration of such nanopin metasurfaces to portable colorimetric microfluidic device may be envisaged for the quantitative studies of a variety of biochemical molecules. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

PubMed

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

2015-08-15

Detection methods of antibiotic residues in blood serum and animal derived foods are of great interest. In this study a colorimetric aptasensor was designed for sensitive, selective and fast detection of tetracycline based on triple-helix molecular switch (THMS) and gold nanoparticles (AuNPs). As a biosensor, THMS shows distinct advantages including high stability, sensitivity and preserving the selectivity and affinity of the original aptamer. In the absence of tetracycline, THMS is stable, leading to the aggregation of AuNPs by salt and an obvious color change from red to blue. In the presence of tetracycline, aptamer binds to its target, signal transduction probe (STP) leaves the THMS and adsorbs on the surface of AuNPs. So the well-dispersed AuNPs remain stable against salt-induced aggregation with a red color. The presented aptasensor showed high selectivity toward tetracyclines with a limit of detection as low as 266 pM for tetracycline. The designed aptasensor was successfully applied to detect tetracycline in serum and milk. Copyright © 2015 Elsevier B.V. All rights reserved.

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

PubMed

Jung, Kwan Ho; Lee, Keun-Hyeung

2015-09-15

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

A highly selective colorimetric and ratiometric fluorescent probe for instantaneous sensing of Hg2+ in water, soil and seafood and its application on test strips.

PubMed

Lan, Linxin; Niu, Qingfen; Li, Tianduo

2018-09-06

A new simple and efficient oligothiophene-based colorimetric and ratiometric fluorescent probe has been developed for highly sensitive and fast detection of Hg 2+ in water, soil and seafood. The probe 5-(1,3-dithiolan-2-yl)-2,2':5',2″-terthiophene 3 TS can selectively detect Hg 2+ via the Hg 2+ -promoted deprotection reaction of thioacetals, which caused a remarkable color change from colorless to yellow and a strong fluorescence enhancement with emission color varying from blue to yellow, enabling naked-eye detection of Hg 2+ . The probe shows high sensitivity with the detection limit down to 1.03 × 10 -8  M. Visual color changes of 3 TS were observed on filter paper and TLC testing strips when they were impregnated on testing strips and immersed in Hg 2+ solution. Moreover, the probe 3 TS has been successfully used to rapidly detect trace amounts of hazardous Hg 2+ ions in tap, distilled, river and lake water, cropland soil, fish, shrimp and kelp samples with acceptable results and good recoveries. Copyright © 2018 Elsevier B.V. All rights reserved.

Zero- and two-dimensional hybrid carbon phosphors for high colorimetric purity white light-emission.

PubMed

Ding, Yamei; Chang, Qing; Xiu, Fei; Chen, Yingying; Liu, Zhengdong; Ban, Chaoyi; Cheng, Shuai; Liu, Juqing; Huang, Wei

2018-03-01

Carbon nanomaterials are promising phosphors for white light emission. A facile single-step synthesis method has been developed to prepare zero- and two-dimensional hybrid carbon phosphors for the first time. Zero-dimensional carbon dots (C-dots) emit bright blue luminescence under 365 nm UV light and two-dimensional nanoplates improve the dispersity and film forming ability of C-dots. As a proof-of-concept application, the as-prepared hybrid carbon phosphors emit bright white luminescence in the solid state, and the phosphor-coated blue LEDs exhibit high colorimetric purity white light-emission with a color coordinate of (0.3308, 0.3312), potentially enabling the successful application of white emitting phosphors in the LED field.

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

PubMed

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

2016-02-07

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

Adaptations of the Saker-Solomons test: simple, reliable colorimetric field assays for chloroquine and its metabolites in urine.

PubMed

Mount, D L; Nahlen, B L; Patchen, L C; Churchill, F C

1989-01-01

Two field-adapted colorimetric methods for measuring the antimalarial drug chloroquine in urine are described. Both are modifications of the method of Saker and Solomons for screening urine for phencyclidine and other drugs of abuse, using the colour reagent tetrabromophenolphthalein ethyl ester. One method is semiquantitative, detecting the presence of chloroquine (Cq) and its metabolites in urine with a 1 microgram/ml detection limit; it is more sensitive and reliable than the commonly used Dill-Glazko method and is as easy to apply in the field. The second method uses a hand-held, battery-operated filter photometer to quantify Cq and its metabolites with a 2 microgram/ml detection limit and a linear range up to 8 micrograms/ml. The first method was validated in the field using a published quantitative colorimetric method and samples from a malaria study in Nigeria. The second method was validated in the laboratory against high-performance liquid chromatographic results on paired samples from the Nigerian study. Both methods may be used in remote locations where malaria is endemic and no electricity is available.

A ditopic colorimetric sensor for fluoride ion based on thiourea mercury complex.

PubMed

Sun, Mei-Zhen; Wu, Fang-Ying; Wu, Yu-Mei; Liu, Wen-Ming

2008-12-01

A novel ditopic chromogenic receptor, N-5-(8-hydroxy)quinoline-N'-4'-nitro-phenyl thiourea (1), was synthesized. The metal complex 1-Hg(2+) showed sensitive and highly selective responses to F(-) over other anions such as CH(3)CO(2)(-), H(2)PO(4)(-), HSO(4)(-) and Cl(-). 1-Hg(2+)-F(-) complex formed, which promoted the intramolecular charge transfer and led to a dramatic spectral change. The color of 1-Hg(2+) solution changed from colorless to red upon addition of F(-). Thus, a colorimetric assay of F(-) was developed in acetonitrile by naked-eye detection. F(-) behaved linearly in the 8.0 x 10(-6) to 2.0 x 10(-5) mol L(-1) concentration range with LOD as 1.4 x 10(-6) mol L(-1).

A colorimetric probe based on desensitized ionene-stabilized gold nanoparticles for single-step test for sulfate ions.

PubMed

Arkhipova, Viktoriya V; Apyari, Vladimir V; Dmitrienko, Stanislava G

2015-03-15

Desensitized ionene-stabilized gold nanoparticles have been prepared and applied as a colorimetric probe for the single-step test for sulfate ions at the relatively high concentration level. The approach is based on aggregation of the nanoparticles leading to the change in absorption spectra and color of the solution. These nanoparticles are characterized by the decreased sensitivity due to both electrostatic and steric stabilization, which allows for simple, and rapid direct single-step determination of sulfate at the relatively high concentration level in real water samples without sample pretreatment or dilution. Influence of different factors (the time of interaction, pH, the concentrations of sulfate ions and the nanoparticles) on the aggregation and analytical performance of the procedure was investigated. The method allows for the determination of sulfate ions in the mass range of 0.2-0.4 mg with RSD of 5% from the sample volume of less than 2 mL. It has a sharp dependence of the colorimetric response on the concentration of sulfate, which makes it prospective for indicating deviations of the sulfate concentration regarding some declared value chosen within the above range. The time of the analysis is 2 min. The method was applied to the analysis of mineral water samples. Copyright © 2014 Elsevier B.V. All rights reserved.

The Use of Colorimetric Sensor Arrays to Discriminate between Pathogenic Bacteria

PubMed Central

Lonsdale, Claire L.; Taba, Brian; Queralto, Nuria; Lukaszewski, Roman A.; Martino, Raymond A.; Rhodes, Paul A.; Lim, Sung H.

2013-01-01

A colorimetric sensor array is a high-dimensional chemical sensor that is cheap, compact, disposable, robust, and easy to operate, making it a good candidate technology to detect pathogenic bacteria, especially potential bioterrorism agents like Yersinia pestis and Bacillus anthracis which feature on the Center for Disease Control and Prevention’s list of potential biothreats. Here, a colorimetric sensor array was used to continuously monitor the volatile metabolites released by bacteria in solid media culture in an Advisory Committee on Dangerous Pathogen Containment Level 3 laboratory. At inoculum concentrations as low as 8 colony-forming units per plate, 4 different bacterial species were identified with 100% accuracy using logistic regression to classify the kinetic profile of sensor responses to culture headspace gas. The sensor array was able to further discriminate between different strains of the same species, including 5 strains of Yersinia pestis and Bacillus anthracis. These preliminary results suggest that disposable colorimetric sensor arrays can be an effective, low-cost tool to identify pathogenic bacteria. PMID:23671629

G-Quadruplex-based DNAzyme for colorimetric detection of cocaine: using magnetic nanoparticles as the separation and amplification element.

PubMed

Du, Yan; Li, Bingling; Guo, Shaojun; Zhou, Zhixue; Zhou, Ming; Wang, Erkang; Dong, Shaojun

2011-02-07

The appearance of the aptamer provides good recognition elements for small molecules, especially for drugs. In this work, by combining the advantages of magnetic nanoparticles (MNPs) with colorimetric drug detection using hemin-G-quadruplex complex as the sensing element, we report a simple and sensitive DNAzyme-based colorimetric sensor for cocaine detection in a 3,3,5,5-tetramethylbenzidine sulfate (TMB)-H(2)O(2) reaction system. The whole experimental processes are simplified. Cocaine aptamer fragments, SH-C2, are covalently labeled onto the amine-functionalized MNPs. When the target cocaine and another cocaine aptamer fragments (C1) grafted with G-riched strand AG4 (i.e. C1-AG4) are present simultaneously, the C2 layer on MNPs hybridizes partly with C1-AG4 to bind the cocaine. The C1-AG4 can be combinded with hemin to form DNAzyme which can effectively catalyze the H(2)O(2)-mediated oxidation of TMB, giving rise to a change in solution color. Importantly, using MNPs as the separation and amplification elements could effectively reduce the background signal and the interference from the real samples. A linear response from 0.1 μM to 20 μM is obtained for cocaine and a detection limit of 50 nM is achieved, which provides high sensitivity and selectivity to detect cocaine.

Colorimetric chemosensor of symmetrical benzoylthiourea derivatives as for detection of Cu2+ in aqueous solution

NASA Astrophysics Data System (ADS)

Hamedan, N. A.; Hasan, S.; Zaki, H. M.; Alias, N. Z.

2017-02-01

A novel receptor, designed with a combination of oxygen (O), nitrogen (N) and sulfur (S) -binding sites for metal ions was synthesized. Ortho (A), meta (B) and para (C) bearing benzoyl thiourea were designed and synthesized with triamine group to apply as colorimetric chemosensors for detection of Cu2+. The structure was confirmed by characterized the compound using Elemental analysis, Fourier Infrared (FTIR) and proton Nuclear Magnetic Resonance (1H NMR) spectroscopy. Functional groups of C=O, N-H, C=N and C=S were found at 1677 cm-1, 3240 cm-1, 1591 cm-1, 1024 cm-1 respectively while 1H NMR shows peaks of alkane (CH2), benzene (Ar-H), CONH, CSNH at 3.68 - 4.14, 7.16 - 7.86, 8.74, and 9.2 respectively. Elemental analysis for A, B and C C20H21N5O2S2Br2 found was compatible with the expected theoretical calculation. For an application, all of these three sensors showed excellent colorimetric specific selectivity and high sensitivity for Cu2+ in acetonitrile/water binary solutions, so only A was selected for further studies towards sensitivity. When Cu2+ was added to the solution of A, a dramatic color change from yellow to green, while other cations Fe2+, Zn2+, Ni2+, Co2+, Cr3+ and Mn2+ did not interfere with the recognition process for Cu2+. The detection limit of the sensor C toward Cu2+ was 1.15 x 10-5 M, which is less sensitive that sensor A and B with a detection limit of 6.2 x 10-6 M and 1.5 x 10-6 M respectively. This indicated that the sensor A and B might be useful as an efficient chemical sensor.

Reverse phase protein microarrays: fluorometric and colorimetric detection.

PubMed

Gallagher, Rosa I; Silvestri, Alessandra; Petricoin, Emanuel F; Liotta, Lance A; Espina, Virginia

2011-01-01

The Reverse Phase Protein Microarray (RPMA) is an array platform used to quantitate proteins and their posttranslationally modified forms. RPMAs are applicable for profiling key cellular signaling pathways and protein networks, allowing direct comparison of the activation state of proteins from multiple samples within the same array. The RPMA format consists of proteins immobilized directly on a nitrocellulose substratum. The analyte is subsequently probed with a primary antibody and a series of reagents for signal amplification and detection. Due to the diversity, low concentration, and large dynamic range of protein analytes, RPMAs require stringent signal amplification methods, high quality image acquisition, and software capable of precisely analyzing spot intensities on an array. Microarray detection strategies can be either fluorescent or colorimetric. The choice of a detection system depends on (a) the expected analyte concentration, (b) type of microarray imaging system, and (c) type of sample. The focus of this chapter is to describe RPMA detection and imaging using fluorescent and colorimetric (diaminobenzidine (DAB)) methods.

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

NASA Astrophysics Data System (ADS)

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

2016-03-01

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

Emergency First Responders' Experience with Colorimetric Detection Methods

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

Sandra L. Fox; Keith A. Daum; Carla J. Miller

2007-10-01

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

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

PubMed

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

2014-01-24

Two new Hg(2+)-colorimetric and fluorescent sensors based on 2-[3-(2-aminoethylsulfanyl) propylsulfanyl]ethanamine covalently bound to one and two units of rhodamine-6G moieties, 1 and 2, were synthesised, and their sensing behaviors toward metal ions were investigated by UV/Vis and fluorescence spectroscopy. Upon the addition of Hg(2+), the sensors exhibited highly sensitive "turn-on" fluorescence enhancement as well as a color change from colorless to pink, which was readily noticeable for naked eye detection. Especially, 1 exhibited the reversible behavior and revealed a very high selectivity in the presence of competitive ions, particularly Cu(2+), Ag(+), Pb(2+), Ca(2+), Cd(2+), Co(2+), Fe(2+), Mn(2+), Na(+), Ni(2+), K(+), Ba(2+), Li(+) and Zn(2+), with a low detection limit of 1.7 ppb toward Hg(2+). Copyright © 2013 Elsevier B.V. All rights reserved.

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

PubMed

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

2016-04-15

Adenosine triphosphate (ATP) is the most direct source of energy in organisms. This study is the first to demonstrate that ATP-aptamer complexes provide greater protection for unmodified gold nanoparticles (AuNPs) against salt-induced aggregation than either aptamer or ATP alone. This protective effect was confirmed using transmission electron microscopy, dynamic light scattering, Zeta potential measurement, and fluorescence polarization techniques. Utilizing controlled particle aggregation/dispersion as a gauge, a sensitive and selective aptasensor for colorimetric detection of ATP was developed using ATP-binding aptamers as the identification element and unmodified AuNPs as the probe. This aptasensor exhibited a good linear relationship between the absorbance and the logarithm concentration of ATP within a 50-1000 nM range. ATP analogs such as guanosine triphosphate, uridine triphosphate and cytidine triphosphate resulted in little or no interference in the determination of ATP. Copyright © 2015 Elsevier B.V. All rights reserved.

Reverse Fluorescence Enhancement and Colorimetric Bimodal Signal Readout Immunochromatography Test Strip for Ultrasensitive Large-Scale Screening and Postoperative Monitoring.

PubMed

Yao, Yingyi; Guo, Weisheng; Zhang, Jian; Wu, Yudong; Fu, Weihua; Liu, Tingting; Wu, Xiaoli; Wang, Hanjie; Gong, Xiaoqun; Liang, Xing-Jie; Chang, Jin

2016-09-07

Ultrasensitive and quantitative fast screening of cancer biomarkers by immunochromatography test strip (ICTS) is still challenging in clinic. The gold nanoparticles (NPs) based ICTS with colorimetric readout enables a quick spectrum screening but suffers from nonquantitative performance; although ICTS with fluorescence readout (FICTS) allows quantitative detection, its sensitivity still deserves more efforts and attentions. In this work, by taking advantages of colorimetric ICTS and FICTS, we described a reverse fluorescence enhancement ICTS (rFICTS) with bimodal signal readout for ultrasensitive and quantitative fast screening of carcinoembryonic antigen (CEA). In the presence of target, gold NPs aggregation in T line induced colorimetric readout, allowing on-the-spot spectrum screening in 10 min by naked eye. Meanwhile, the reverse fluorescence enhancement signal enabled more accurately quantitative detection with better sensitivity (5.89 pg/mL for CEA), which is more than 2 orders of magnitude lower than that of the conventional FICTS. The accuracy and stability of the rFICTS were investigated with more than 100 clinical serum samples for large-scale screening. Furthermore, this rFICTS also realized postoperative monitoring by detecting CEA in a patient with colon cancer and comparing with CT imaging diagnosis. These results indicated this rFICTS is particularly suitable for point-of-care (POC) diagnostics in both resource-rich and resource-limited settings.

A colorimetric platform for sensitively differentiating telomere DNA with different lengths, monitoring G-quadruplex and dsDNA based on silver nanoclusters and unmodified gold nanoparticles

NASA Astrophysics Data System (ADS)

Qu, Fei; Chen, Zeqiu; You, Jinmao; Song, Cuihua

2018-05-01

Human telomere DNA plays a vital role in genome integrity control and carcinogenesis as an indication for extensive cell proliferation. Herein, silver nanoclusters (Ag NCs) templated by polymer and unmodified gold nanoparticles (Au NPs) are designed as a new colorimetric platform for sensitively differentiating telomere DNA with different lengths, monitoring G-quadruplex and dsDNA. Ag NCs can produce the aggregation of Au NPs, so the color of Au NPs changes to blue and the absorption peak moves to 700 nm. While the telomere DNA can protect Au NPs from aggregation, the color turns to red again and the absorption band blue shift. Benefiting from the obvious color change, we can differentiate the length of telomere DNA by naked eyes. As the length of telomere DNA is longer, the variation of color becomes more noticeable. The detection limits of telomere DNA containing 10, 22, 40, 64 bases are estimated to be 1.41, 1.21, 0.23 and 0.22 nM, respectively. On the other hand, when telomere DNA forms G-quadruplex in the presence of K+, or dsDNA with complementary sequence, both G-quadruplex and dsDNA can protect Au NPs better than the unfolded telomere DNA. Hence, a new colorimetric platform for monitoring structure conversion of DNA is established by Ag NCs-Au NPs system, and to prove this type of application, a selective K+ sensor is developed.

A new multifunctional Schiff base as a fluorescence sensor for Al³⁺ and a colorimetric sensor for CN⁻ in aqueous media: an application to bioimaging.

PubMed

Lee, Seul Ah; You, Ga Rim; Choi, Ye Won; Jo, Hyun Yong; Kim, Ah Ram; Noh, Insup; Kim, Sung-Jin; Kim, Youngmee; Kim, Cheal

2014-05-14

A multifunctional fluorescent and colorimetric receptor 1 ((E)-N'-((8-hydroxy-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-9-yl)methylene)benzohydrazide) for the detection of both Al(3+) and CN(-) in aqueous solution has been developed. Receptor 1 exhibited an excellent selective fluorescence response toward Al(3+). The sensitivity of the fluorescent based assay (0.193 μM) for Al(3+) is far below the limit in the World Health Organization (WHO) guidelines for drinking water (7.41 μM). In addition, receptor 1 showed an excellent detection ability in a wide pH range of 4-10 and also in living cells. Moreover, receptor 1 showed a highly selective colorimetric response to CN(-) by changing its color from colorless to yellow immediately without any interference from other anions.

Improved detection of chemical substances from colorimetric sensor data using probabilistic machine learning

NASA Astrophysics Data System (ADS)

Mølgaard, Lasse L.; Buus, Ole T.; Larsen, Jan; Babamoradi, Hamid; Thygesen, Ida L.; Laustsen, Milan; Munk, Jens Kristian; Dossi, Eleftheria; O'Keeffe, Caroline; Lässig, Lina; Tatlow, Sol; Sandström, Lars; Jakobsen, Mogens H.

2017-05-01

We present a data-driven machine learning approach to detect drug- and explosives-precursors using colorimetric sensor technology for air-sampling. The sensing technology has been developed in the context of the CRIM-TRACK project. At present a fully- integrated portable prototype for air sampling with disposable sensing chips and automated data acquisition has been developed. The prototype allows for fast, user-friendly sampling, which has made it possible to produce large datasets of colorimetric data for different target analytes in laboratory and simulated real-world application scenarios. To make use of the highly multi-variate data produced from the colorimetric chip a number of machine learning techniques are employed to provide reliable classification of target analytes from confounders found in the air streams. We demonstrate that a data-driven machine learning method using dimensionality reduction in combination with a probabilistic classifier makes it possible to produce informative features and a high detection rate of analytes. Furthermore, the probabilistic machine learning approach provides a means of automatically identifying unreliable measurements that could produce false predictions. The robustness of the colorimetric sensor has been evaluated in a series of experiments focusing on the amphetamine pre-cursor phenylacetone as well as the improvised explosives pre-cursor hydrogen peroxide. The analysis demonstrates that the system is able to detect analytes in clean air and mixed with substances that occur naturally in real-world sampling scenarios. The technology under development in CRIM-TRACK has the potential as an effective tool to control trafficking of illegal drugs, explosive detection, or in other law enforcement applications.

High-performance peroxidase mimics for rapid colorimetric detection of H2O2 and glucose derived from perylene diimides functionalized Co3O4 nanoparticles.

PubMed

Ding, Yanan; Chen, Miaomiao; Wu, Kaili; Chen, Mingxing; Sun, Lifang; Liu, Zhenxue; Shi, Zhiqiang; Liu, Qingyun

2017-11-01

N,N'-di-caboxy methyl perylene diimides (PDI), as one of the most promising functional materials in optional chemosensing, was first used to combine with Co 3 O 4 nanoparticles through a facile two-step hydrothermal method and obtain the PDI functionalized Co 3 O 4 nanocomposites (PDI-Co 3 O 4 NCs). PDI-Co 3 O 4 NCs were characterized by a series of technical analysis including transmission electron microscope (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR), respectively. The experimental results indicated that the as-prepared PDI-Co 3 O 4 NCs possessed the higher peroxidase-like activity than that of Co 3 O 4 nanoparticles without PDI, and could rapidly catalyze oxidation reaction of the chromogenic substrate TMB in the presence of H 2 O 2 to a blue product (oxTMB) observed by the naked eye. The improved catalytic activity of PDI-Co 3 O 4 NCs for colorimetric reactions could be attributed to the synergistic effects of PDI and Co 3 O 4 nanoparticles. On the basis of these experimental results, a convenient colorimetric system based on PDI-Co 3 O 4 as enzyme mimic that is highly sensitive and selective was developed for glucose detection. Meanwhile, the electron transfer between H 2 O 2 and TMB was responsible for the oxidation of TMB. The present work demonstrates a general strategy for the design of organic molecules functionalized oxide for different applications, such as nanocatalysts, biosensors and nanomedicine. Copyright © 2017 Elsevier B.V. All rights reserved.

Surface plasmon resonance based selective and sensitive colorimetric determination of azithromycin using unmodified silver nanoparticles in pharmaceuticals and human plasma

NASA Astrophysics Data System (ADS)

Chavada, Vijay D.; Bhatt, Nejal M.; Sanyal, Mallika; Shrivastav, Pranav S.

2017-01-01

In this article we report a novel method for colorimetric sensing and selective determination of a non-chromophoric drug-azithromycin, which lacks native absorbance in the UV-Visible region using unmodified silver nanoparticles (AgNPs). The citrate-capped AgNps dispersed in water afforded a bright yellow colour owing to the electrostatic repulsion between the particles due to the presence of negatively charged surface and showed surface plasmon resonance (SPR) band at 394 nm. Addition of positively charged azithromycin at a concentration as low as 0.2 μM induced rapid aggregation of AgNPs by neutralizing the negative charge on the particle surface. This phenomenon resulted in the colour change from bright yellow to purple which could be easily observed by the naked eye. This provided a simple platform for rapid determination of azithromycin based on colorimetric measurements. The factors affecting the colorimetric response like pH, volume of AgNPs suspension and incubation time were suitably optimized. The validated method was found to work efficiently in the established concentration range of 0.2-100.0 μM using two different calibration models. The selectivity of the method was also evaluated by analysis of nanoparticles-aggregation response upon addition of several anions, cations and some commonly prescribed antibiotics. The method was successfully applied for the analysis of azithromycin in pharmaceuticals and spiked human plasma samples with good accuracy and precision. The simplicity, efficiency and cost-effectiveness of the method hold tremendous potential for the analysis of such non-chromophoric pharmaceuticals.

Bio-functionalized silver nanoparticles for selective colorimetric sensing of toxic metal ions and antimicrobial studies

NASA Astrophysics Data System (ADS)

Vinod Kumar, V.; Anbarasan, S.; Christena, Lawrence Rene; SaiSubramanian, Nagarajan; Philip Anthony, Savarimuthu

2014-08-01

Hibiscus Sabdariffa (Gongura) plant extracts (leaves (HL) and stem (HS) were used for the first time in the green synthesis of bio-functionalized silver nanoparticles (AgNPs). The bio-functionality of AgNPs has been successfully utilized for selective colorimetric sensing of potentially health and environmentally hazardous Hg2+, Cd2+ and Pb2+ metal ions at ppm level in aqueous solution. Importantly, clearly distinguishable colour for all three metal ions was observed. The influence of extract preparation condition and pH were also explored on the formation of AgNPs. Both selectivity and sensitivity differed for AgNPs synthesized from different parts of the plant. Direct correlation between the stability of green synthesized AgNPs at different pH and its antibacterial effects has been established. The selective colorimetric sensing of toxic metal ions and antimicrobial effect of green synthesized AgNPs demonstrated the multifunctional applications of green nanotechnology.

A highly selective colorimetric and fluorescent chemosensor for Al(III) based-on simple naphthol in aqueous solution

NASA Astrophysics Data System (ADS)

Liu, Zhaodi; Xu, Huajie; Sheng, Liangquan; Chen, Shuisheng; Huang, Deqian; Liu, Jie

2016-03-01

A colorimetric and fluorescent chemosensor (L) for Al(III) was synthesized and fully characterized. L could be both used as a colorimetric and fluorescent chemosensor for the detection of Al3 + ions with low detection limit (8.87 × 10- 7 M) in CH3CN-H2O (1:1, v/v) solution. The binding ratio of L-Al3 + was determined from the Job plot (absorption and fluorescence spectra) and MALDI-TOF MS data to be 1:1. The binding constant (Ka) of Al3 + binding to L was calculated to be 4.8 × 105 M- 1 from a Benesi-Hildebrand plot. Moreover, the binding site of L with Al3 + was determined by 1H NMR titration experiment.

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

PubMed

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

2016-03-15

A new colorimetric probe 1 based on rhodamine B lactam was developed for naked-eye detection of Cu(2+). The optical feature of 1 for Cu(2+) was investigated by UV-vis absorption spectroscopy. Upon the addition of Cu(2+), the 1 displayed a distinct color change from colorless to pink, which can be directly detected by the naked eye. The stoichiometry of 1 to Cu(2+) complex was found to be 1:1 and the naked-eye detection limit was determined as low as 2 μM. The results suggest that the probe 1 may provide a convenient method for visual detection of Cu(2+) with high sensitivity. Copyright © 2015 Elsevier B.V. All rights reserved.

“Naked-eye” colorimetric and “turn-on” fluorometric chemosensors for reversible Hg2+ detection

NASA Astrophysics Data System (ADS)

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

2014-01-01

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

Novel colorimetric method overcoming phosphorus interference during trace arsenic analysis in soil solution.

PubMed

Makris, Konstantinos C; Punamiya, Pravin; Sarkar, Dibyendu; Datta, Rupali

2008-02-01

A sensitive (method detection limit, 2.0 microg As L(-1)) colorimetric determination of trace As(v) and As(iii) concentrations in the presence of soluble phosphorus (P) concentrations in soil/water extracts is presented. The proposed method modifies the malachite green method (MG) originally developed for P in soil and water. Our method relies upon the finding that As(iii) and As(v) do not develop the green color during P analysis using the MG method. When an optimum concentration of ascorbic acid (AA) is added to a sample containing up to 15 times P > As (microM) concentrations, the final sample absorbance due to P will be equal to that of As(v) molecules. The soluble As concentration can then be quantified by the concentration difference between the mixed oxyanion (As + P) absorbance (proposed method) and the MG method absorbance that measures only P. Our method is miniaturized using a 96-well microplate UV-VIS reader that utilizes minute reagent and sample volumes (120 and 200 microL sample(-1), respectively), thus, minimizing waste and offering flexibility in the field. Our method was tested in a suite of As-contaminated soils that successfully measured both As and P in soil water extracts and total digests. Mean% As recoveries ranged between 84 and 117%, corroborating data obtained with high-resolution inductively-coupled plasma mass-spectrometry. The performance of the proposed colorimetric As method was unaffected by the presence of Cu, Zn, Pb, Ni, Fe, Al, Si, and Cr in both neutral and highly-acidic (ca. pH 2) soil extracts. Data from this study provide the proof of concept towards creating a field-deployable, portable As kit.

A high throughput colorimetric assay of β-1,3-D-glucans by Congo red dye.

PubMed

Semedo, Magda C; Karmali, Amin; Fonseca, Luís

2015-02-01

Mushroom strains contain complex nutritional biomolecules with a wide spectrum of therapeutic and prophylactic properties. Among these compounds, β-d-glucans play an important role in immuno-modulating and anti-tumor activities. The present work involves a novel colorimetric assay method for β-1,3-d-glucans with a triple helix tertiary structure by using Congo red. The specific interaction that occurs between Congo red and β-1,3-d-glucan was detected by bathochromic shift from 488 to 516 nm (>20 nm) in UV-Vis spectrophotometer. A micro- and high throughput method based on a 96-well microtiter plate was devised which presents several advantages over the published methods since it requires only 1.51 μg of polysaccharides in samples, greater sensitivity, speed, assay of many samples and very cheap. β-D-Glucans of several mushrooms (i.e., Coriolus versicolor, Ganoderma lucidum, Pleurotus ostreatus, Ganoderma carnosum, Hericium erinaceus, Lentinula edodes, Inonotus obliquus, Auricularia auricular, Polyporus umbellatus, Cordyseps sinensis, Agaricus blazei, Poria cocos) were isolated by using a sequence of several extractions with cold and boiling water, acidic and alkaline conditions and quantified by this microtiter plate method. FTIR spectroscopy was used to study the structural features of β-1,3-D-glucans in these mushroom samples as well as the specific interaction of these polysaccharides with Congo red. The effect of NaOH on triple helix conformation of β-1,3-D-glucans was investigated in several mushroom species. Copyright © 2014 Elsevier B.V. All rights reserved.

Colorimetric Detection of Plasmodium vivax in Urine Using MSP10 Oligonucleotides and Gold Nanoparticles

PubMed Central

Alnasser, Yossef; Ferradas, Cusi; Clark, Taryn; Calderon, Maritza; Gurbillon, Alejandro; Gamboa, Dionicia; McKakpo, Uri S.; Quakyi, Isabella A.; Bosompem, Kwabena M.; Sullivan, David J.; Vinetz, Joseph M.; Gilman, Robert H.

2016-01-01

Plasmodium vivax is the most prevalent cause of human malaria in the world and can lead to severe disease with high potential for relapse. Its genetic and geographic diversities make it challenging to control. P. vivax is understudied and to achieve control of malaria in endemic areas, a rapid, accurate, and simple diagnostic tool is necessary. In this pilot study, we found that a colorimetric system using AuNPs and MSP10 DNA detection in urine can provide fast, easy, and inexpensive identification of P. vivax. The test exhibited promising sensitivity (84%), high specificity (97%), and only mild cross-reactivity with P. falciparum (21%). It is simple to use, with a visible color change that negates the need for a spectrometer, making it suitable for use in austere conditions. Using urine eliminates the need for finger-prick, increasing both the safety profile and patient acceptance of this model. PMID:27706158

Succinic acid functionalized silver nanoparticles (Suc-Ag NPs) for colorimetric sensing of melamine

NASA Astrophysics Data System (ADS)

Rajar, Kausar; Sirajuddin; Balouch, Aamna; Bhanger, M. I.; Shah, Muhammad Tariq; Shaikh, Tayyaba; Siddiqui, Samia

2018-03-01

In this study, a quantitative colorimetric sensing strategy is developed for the rapid, sensitive and selective determination of melamine. The sensing system relies on the application of succinic acid as a selective recognition probe functionalized over Ag NPs. The synthesized Ag NPs were modified with cysteamine to induce positively charged atmosphere which allowed easy and favorable functionalization of succinic acid. The di-carboxyl nature of succinic acid enabled its binding to both cysteamine and melamine. The strong and favorable linkage between succinic acids carbonyl and amine moieties of melamine triggered aggregation of silver NPs producing a significant shift in the measured absorption excitation. This change in the excitation along with the colorimetric response was found linearly proportional to the melamine concentration in the range of 0.1-1.2 μM. The developed sensor system is simple and unlike electrostatic attraction based sensor system utilize selective linkage for the recognition of melamine. In addition to this, the developed optical probe can efficiently be used for the determination of melamine in milk samples.

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

PubMed

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

2015-12-23

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

Polymeric assemblies for sensitive colorimetric assays

DOEpatents

Charych, Deborah

2000-01-01

The presently claimed invention relates to polymeric assemblies which visibly change color in the presence of analyte. In particular, the presently claimed invention relates to liposomes comprising a plurality of lipid monomers, which comprises a polymerizable group, a hydrophilic head group and a hydrophobic tail group, and one or more ligands. Overall carbon chain length, and polymerizable group positioning on the monomer influence color change sensitivity to analyte concentrations.

Poly(acrylic acid)-templated silver nanoclusters as a platform for dual fluorometric turn-on and colorimetric detection of mercury (II) ions.

PubMed

Tao, Yu; Lin, Youhui; Huang, Zhenzhen; Ren, Jinsong; Qu, Xiaogang

2012-01-15

An easy prepared fluorescence turn-on and colorimetric dual channel probe was developed for rapid assay of Hg(2+) ions with high sensitivity and selectivity by using poly(acrylic acid)-templated silver nanoclusters (PAA-AgNCs). The PAA-AgNCs exhibited weak fluorescence, while upon the addition of Hg(2+) ions, AgNCs gives a dramatic increase in fluorescence as a result of the changes of the AgNCs states. The detection limit was estimated to be 2 nM, which is much lower than the Hg(2+) detection requirement for drinking water of U.S. Environmental Protection Agency, and the turn-on sensing mode offers additional advantage to efficiently reduce background noise. Also, a colorimetric assay of Hg(2+) ions can be realized due to the observed absorbance changes of the AgNCs. More importantly, the method was successfully applied to the determination of Hg(2+) ions in real water samples, which suggests our proposed method has a great potential of application in environmental monitoring. Copyright © 2011 Elsevier B.V. All rights reserved.

Colorimetric determination of glutathione by using a nanohybrid composed of manganese dioxide and carbon dots.

PubMed

Wang, Qian; Pang, Hongchang; Dong, Yongqiang; Chi, Yuwu; Fu, Fengfu

2018-05-10

A kind of single-layer carbon based dots (CDs) with abundant carboxyl functional groups was hybridized with manganese dioxide (MnO 2 ). The resulting nanohybrid is stable and can be well dispersed in water. MnO 2 is capable of oxidizing the substrate 3,3'5,5'-tetramethylbenzidine (TMB) to form a blue product whose absorption (peaking at 655 nm) fades in the presence of glutathione (GSH). A sensitive and selective colorimetric GSH assay was worked out that has a linear response in the 10 to 0.1 µM GSH concentration range, with a 0.095 μM detection limit. The method was applied to the determination of GSH in spiked fetal calf serum where it gave excellent recoveries. Graphical abstract Schematic of the preparation of a nanohybrid composed of manganese dioxide and carbon based dots (MnO 2 /CDs). They can be used for the colorimetric detection of glutathione (GSH) based on the color change of 3,3'5,5'-tetramethylbenzidine (TMB).

Bio-functionalized silver nanoparticles for selective colorimetric sensing of toxic metal ions and antimicrobial studies.

PubMed

Vinod Kumar, V; Anbarasan, S; Christena, Lawrence Rene; SaiSubramanian, Nagarajan; Philip Anthony, Savarimuthu

2014-08-14

Hibiscus Sabdariffa (Gongura) plant extracts (leaves (HL) and stem (HS)) were used for the first time in the green synthesis of bio-functionalized silver nanoparticles (AgNPs). The bio-functionality of AgNPs has been successfully utilized for selective colorimetric sensing of potentially health and environmentally hazardous Hg(2+), Cd(2+) and Pb(2+) metal ions at ppm level in aqueous solution. Importantly, clearly distinguishable colour for all three metal ions was observed. The influence of extract preparation condition and pH were also explored on the formation of AgNPs. Both selectivity and sensitivity differed for AgNPs synthesized from different parts of the plant. Direct correlation between the stability of green synthesized AgNPs at different pH and its antibacterial effects has been established. The selective colorimetric sensing of toxic metal ions and antimicrobial effect of green synthesized AgNPs demonstrated the multifunctional applications of green nanotechnology. Copyright © 2014 Elsevier B.V. All rights reserved.

Ultrasensitive colorimetric immunoassay for hCG detection based on dual catalysis of Au@Pt core-shell nanoparticle functionalized by horseradish peroxidase

NASA Astrophysics Data System (ADS)

Wang, Weiguo; Zou, Yake; Yan, Jinwu; Liu, Jing; Chen, Huixiong; Li, Shan; Zhang, Lei

2018-03-01

In this paper, an ultrasensitive colorimetric biosensor for human chorionic gonadotrophin (hCG) detection was designed from bottom-up method based on the dual catalysis of the horseradish peroxidase (HRP) and Au@Pt nanoparticles (NPs) relative to H2O2-TEM system. HRP and monoclonal mouse anti-hCG antibody (β-submit, mAb1) were co-immobilized onto the Au@Pt NP surface to improve catalytic efficiency and specificity, which formed a dual functionalized Au@Pt-HRP probe with the mean size of 42.8 nm (D50). The colorimetric immunoassay was developed for the hCG detection, and the Au@Pt-HRP probe featured a higher sensitivity in the concentration range of 0.4-12.8 IU L- 1 with a low limit of detection (LOD) of 0.1 IU L- 1 compared with the LODs of 0.8 IU L- 1 for BA-ELISA and of 2.0 IU L- 1 for Au@Pt, which indicated that the Au@Pt-HRP probe possessed higher catalytic efficiency with 2.8-fold increase over Au@Pt and 33.8-fold increase over HRP. Also, the Au@Pt-HRP probe exhibited good precision and reproducibility, high specificity and acceptable accuracy with CV being less than 15%. The dual functionalized Au@Pt-HRP probe as a type of signal amplified method was firstly applied in the colorimetric immunoassay for the hCG detection.

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

PubMed

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

2015-08-15

In this work, we find that the peroxidase-like activity of MoS2 nanoparticles (NPs) is dependent on the surface charge. Negatively charged sodium dodecyl sulfate modified MoS2 nanoparticles (SDS-MoS2 NPs) possess highly-efficient peroxidase-like activity. MoS2 NPs with intrinsic peroxidase-like activity were synthesized through a simple one-pot hydrothermal route. The peroxidase-like activities of different surfactants modified MoS2 NPs were discussed. Compared with bare MoS2 NPs and positively charged cetyltrimethyl ammonium bromide modified MoS2 NPs, SDS-MoS2 NPs have the best peroxidase-like activity. SDS-MoS2 NPs can efficiently catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H2O2 to generate a blue product. On basis of this, we have successfully established a novel platform for colorimetric detection of H2O2, and the detection limit is 0.32μM. Furthermore, the SDS-MoS2 NPs based platform can also be used for high sensitivity and selectivity detection of glucose with a wide linear range of 5.0-500μM by controlling the generation of H2O2 in the presence of glucose oxidase. Copyright © 2015 Elsevier B.V. All rights reserved.

Highly selective and sensitive determination of dopamine in biological samples via tuning the particle size of label-free gold nanoparticles

NASA Astrophysics Data System (ADS)

Mohseni, Naimeh; Bahram, Morteza

2018-03-01

Herein, a rapid, sensitive and selective approach for the colorimetric detection of dopamine (DA) was developed utilizing unmodified gold nanoparticles (AuNPs). This assay relied upon the size-dependent aggregation behavior of DA and three other structurally similar catecholamines (CAs), offering highly specific and accurate detection of DA. By means of this study, we attempted to overcome the tedious procedures of surface premodifications and achieve selectivity through tuning the particle size of AuNPs. DA could induce the aggregation of the AuNPs via hydrogen-bonding interactions, resulting in a color change from pink to blue which can be monitored by spectrophotometry or even the naked-eye. The proposed colorimetric probe works over the 0.1 to 4 μM DA concentration range, with a lower detection limit (LOD) of 22 nM, which is much lower than the therapeutic lowest abnormal concentrations of DA in urine (0.57 μM) and blood (16 μM) samples. Furthermore, the selectivity and potential applicability of the developed method in spiked actual biological (human plasma and urine) specimens were investigated, suggesting that the present assay could satisfy the requirements for clinical diagnostics and biosensors.

A highly selective colorimetric and ratiometric fluorescent chemodosimeter for detection of fluoride ions based on 1,8-naphthalimide derivatives.

PubMed

Kai, Yumei; Hu, Yonghong; Wang, Kai; Zhi, Wenbiao; Liang, Mengmeng; Yang, Wenge

2014-01-24

A high selective colorimetric and ratiometric fluorescent probe based on 4-hydroxy-1, 8-naphthalimide was designed and synthesized to detect fluoride ions (F(-)). The sensing behavior of this probe was studied by UV-visible and fluorescence spectroscopy. The probe displays an 110 nm red-shift of fluorescence emission and the color changes from colorless to yellow by virtue of the strong affinity of F(-) toward silicon which can act as a new visual sensor for F(-). Copyright © 2013 Elsevier B.V. All rights reserved.

Synthesis of gold-cellobiose nanocomposites for colorimetric measurement of cellobiase activity.

PubMed

Lai, Cui; Zeng, Guang-Ming; Huang, Dan-Lian; Zhao, Mei-Hua; Wei, Zhen; Huang, Chao; Xu, Piao; Li, Ning-Jie; Zhang, Chen; Chen, Ming; Li, Xue; Lai, Mingyong; He, Yibin

2014-11-11

Gold-cellobiose nanocomposites (GCNCs) were synthesized by reducing gold salt with a polysaccharide, cellobiose. Here, cellobiose acted as a controller of nucleation or stabilizer in the formation of gold nanoparticles. The obtained GCNCs were characterized with UV-visible spectroscopy; Zetasizer and Fourier transform infrared (FT-IR) spectrophotometer. Moreover, 6-Mercapto-1-hexanol (MCH) was modified on GCNCs, and the MCH-GCNCs were used to determine the cellobiase activity in compost extracts based on the surface plasmon resonance (SPR) property of MCH-GCNCs. The degradation of cellobiose on MCH-GCNCs by cellobiase could induce the aggregation, and the SPR absorption wavelength of MCH-GCNCs correspondingly red shifted. Thus, the absorbance ratio of treated MCH-GCNCs (A650/A520) could be used to estimate the cellobiase activity, and the probe exhibited highly sensitive and selective detection of the cellobiase activity with a wide linear from 3.0 to 100.0U L(-1) within 20 min. Meanwhile, a good linear relationship with correlation coefficient of R2=0.9976 was obtained. This approach successfully showed the suitability of gold nanocomposites as a colorimetric sensor for the sensitive and specific enzyme activity detection. Copyright © 2014 Elsevier B.V. All rights reserved.

A sensitive, colorimetric immunosensor based on Cu-MOFs and HRP for detection of dibutyl phthalate in environmental and food samples.

PubMed

Zhu, Nuanfei; Zou, Yanmin; Huang, Menglu; Dong, Shuaibing; Wu, Xiangyang; Liang, Guoxi; Han, Zhixiang; Zhang, Zhen

2018-08-15

A sensitive and artful colorimetric immunosensor based on horseradish peroxidase (HRP) was designed by labelling metal-organic frameworks (Cu-MOFs) on the second antibody (Cu-MOFs@Ab 2 ) as signal amplification for the detection of trace dibutyl phthalate (DBP). In this system, when Cu-MOFs@Ab 2 was captured by antigen- primary antibody (Ab 1 ) complex, tremendous Cu(II) will be released from Cu-MOFs in the presence of nitric acid (HNO 3 ), and Cu(II) will be further reduced to Cu(I) after the addition of sodium ascorbate (SA), consequently, inhibiting the HRP to catalyse the colorless 3,3',5,5'-tetramethylbenzidine (TMB) into blue oxidized TMB (ox TMB). Under the optimized conditions, the limit of detection (LOD) was 1 μg L -1 , which was almost 60 times lower than that using a conventional ELISA with the same antibody. In addition, our method showed good accuracy and reproducibility (recoveries of 87.73-103.4%; CV values of 1.46-5.95%) through a spike-recovery analysis. The proposed immunosensor indicated great potential for trace DBP determination from environmental and food samples. Copyright © 2018. Published by Elsevier B.V.

Photonic Crystal Structures with Tunable Structure Color as Colorimetric Sensors

PubMed Central

Wang, Hui; Zhang, Ke-Qin

2013-01-01

Colorimetric sensing, which transduces environmental changes into visible color changes, provides a simple yet powerful detection mechanism that is well-suited to the development of low-cost and low-power sensors. A new approach in colorimetric sensing exploits the structural color of photonic crystals (PCs) to create environmentally-influenced color-changeable materials. PCs are composed of periodic dielectrics or metallo-dielectric nanostructures that affect the propagation of electromagnetic waves (EM) by defining the allowed and forbidden photonic bands. Simultaneously, an amazing variety of naturally occurring biological systems exhibit iridescent color due to the presence of PC structures throughout multi-dimensional space. In particular, some kinds of the structural colors in living organisms can be reversibly changed in reaction to external stimuli. Based on the lessons learned from natural photonic structures, some specific examples of PCs-based colorimetric sensors are presented in detail to demonstrate their unprecedented potential in practical applications, such as the detections of temperature, pH, ionic species, solvents, vapor, humidity, pressure and biomolecules. The combination of the nanofabrication technique, useful design methodologies inspired by biological systems and colorimetric sensing will lead to substantial developments in low-cost, miniaturized and widely deployable optical sensors. PMID:23539027

Infrared and colorimetric characterization of discolored kiln-dried hard maple lumber

Treesearch

Benjamin E. Dawson-Andoh; Michael Wiemann; Laurent Matuana; John Baumgras

2004-01-01

Discoloration of hard maple lumber commonly occurs during kiln-drying. In this study, discolored andnondiscolored kiln-dried hard maple lumber boards were characterized using a colorimetric method and Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR). Colorimetric measurements (L*, a*, b*) were found to be in good agreement with visual...

Rapid and selective lead (II) colorimetric sensor based on azacrown ether-functionalized gold nanoparticles

NASA Astrophysics Data System (ADS)

Alizadeh, A.; Khodaei, M. M.; Karami, Ch; Workentin, M. S.; Shamsipur, M.; Sadeghi, M.

2010-08-01

A gold nanoparticle (AuNPs)-based simple and fast colorimetric sensor for selective detecting of Pb(II) in aqueous solution has been developed. Monodisperse AuNPs (approx. 2.0 nm diameter) has been prepared facilely and further modified with an alkanethiol-bearing monoazacrown ether terminus. These AuNPs are shown to selectively sense Pb2 + through color change, which is visually discernible by an appearance of the surface plasmon band (SPB) at 520 nm. The recognition mechanism is attributed to the unique structure of the monoazacrown ether attached to AuNPs and metal sandwich coordination between two azacrown ether moieties that are attached to separate nanoparticles. This inter-particle cross-linking results in an aggregation and apparent color change from brown to purple. Additionally, TEM experiments support the optical absorption data proving the aggregation between azacrown ether-capped gold nanoparticles. This AuNP-based colorimetric assay is a facile and robust method and allows fast detection of Pb2 + at ambient temperatures. More importantly, the developed technique does not utilize enzymatic reactions, light-sensitive dye molecules, lengthy protocols or sophisticated instrumentation.

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

NASA Astrophysics Data System (ADS)

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

2015-02-01

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

A colorimetric and fluorogenic probe for bisulfite using benzopyrylium as the recognition unit.

PubMed

Zhang, Yun; Zhang, Xiangwen; Yang, Xiao-Feng; Zhang, Juan

2017-11-01

A coumarin-benzopyrylium (CB) platform has been developed for the colorimetric and fluorogenic detection of bisulfite. The proposed probe utilizes coumarin as the fluorophore and positively charged benzopyrylium as the reaction site. The method employs the nucleophilic addition of bisulfite to the benzopyrylium moiety of CB to inactivate the electron-deficient oxonium ion. The driving force for photo-induced electron transfer is considerably diminished, thereby promoting the emission intensity of the coumarin fluorophore. The fluorescence intensity at 510 nm is linear with bisulfite concentration over a range of 0.2-7.5 μM with a detection limit of 42 nM (3δ). CB shows a rapid response (within 30 s) and high selectivity and sensitivity for bisulfite. Preliminary studies show that CB has great potential for bisulfite detection in real samples and in living cells. Copyright © 2017 John Wiley & Sons, Ltd.

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

PubMed Central

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

2010-01-01

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

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

PubMed Central

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

2014-01-01

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

Absolute colorimetric characterization of a DSLR camera

NASA Astrophysics Data System (ADS)

Guarnera, Giuseppe Claudio; Bianco, Simone; Schettini, Raimondo

2014-03-01

A simple but effective technique for absolute colorimetric camera characterization is proposed. It offers a large dynamic range requiring just a single, off-the-shelf target and a commonly available controllable light source for the characterization. The characterization task is broken down in two modules, respectively devoted to absolute luminance estimation and to colorimetric characterization matrix estimation. The characterized camera can be effectively used as a tele-colorimeter, giving an absolute estimation of the XYZ data in cd=m2. The user is only required to vary the f - number of the camera lens or the exposure time t, to better exploit the sensor dynamic range. The estimated absolute tristimulus values closely match the values measured by a professional spectro-radiometer.

Simple Colorimetric Sensor for Trinitrotoluene Testing

NASA Astrophysics Data System (ADS)

Samanman, S.; Masoh, N.; Salah, Y.; Srisawat, S.; Wattanayon, R.; Wangsirikul, P.; Phumivanichakit, K.

2017-02-01

A simple operating colorimetric sensor for trinitrotoluene (TNT) determination using a commercial scanner as a captured image was designed. The sensor is based on the chemical reaction between TNT and sodium hydroxide reagent to produce the color change within 96 well plates, which observed finally, recorded using a commercial scanner. The intensity of the color change increased with increase in TNT concentration and could easily quantify the concentration of TNT by digital image analysis using the Image J free software. Under optimum conditions, the sensor provided a linear dynamic range between 0.20 and 1.00 mg mL-1(r = 0.9921) with a limit of detection of 0.10± 0.01 mg mL-1. The relative standard deviation for eight experiments for the sensitivity was 3.8%. When applied for the analysis of TNT in two soil extract samples, the concentrations were found to be non-detectable to 0.26±0.04 mg mL-1. The obtained recovery values (93-95%) were acceptable for soil samples tested.

Polyacrylic acid-coated cerium oxide nanoparticles: An oxidase mimic applied for colorimetric assay to organophosphorus pesticides.

PubMed

Zhang, Shi-Xiang; Xue, Shi-Fan; Deng, Jingjing; Zhang, Min; Shi, Guoyue; Zhou, Tianshu

2016-11-15

It is important and urgent to develop reliable and highly sensitive methods that can provide on-site and rapid detection of extensively used organophosphorus pesticides (OPs) for their neurotoxicity. In this study, we developed a novel colorimetric assay for the detection of OPs based on polyacrylic acid-coated cerium oxide nanoparticles (PAA-CeO2) as an oxidase mimic and OPs as inhibitors to suppress the activity of acetylcholinesterase (AChE). Firstly, highly dispersed PAA-CeO2 was prepared in aqueous solution, which could catalyze the oxidation of TMB to produce a color reaction from colorless to blue. And the enzyme of AChE was used to catalyze the substrate of acetylthiocholine (ATCh) to produce thiocholine (TCh). As a thiol-containing compound with reducibility, TCh can decrease the oxidation of TMB catalyzed by PAA-CeO2. Upon incubated with OPs, the enzymatic activity of AChE was inhibited to produce less TCh, resulting in more TMB catalytically oxidized by PAA-CeO2 to show an increasing blue color. The two representative OPs, dichlorvos and methyl-paraoxon, were tested using our proposed assay. The novel assay showed notable color change in a concentration-dependent manner, and as low as 8.62 ppb dichlorvos and 26.73 ppb methyl-paraoxon can be readily detected. Therefore, taking advantage of such oxidase-like activity of PAA-CeO2, our proposed colorimetric assay can potentially be a screening tool for the precise and rapid evaluation of the neurotoxicity of a wealth of OPs. Copyright © 2016 Elsevier B.V. All rights reserved.

8-Hydroxyquinoline based push-pull azo dye: Novel colorimetric chemosensor for anion detection

NASA Astrophysics Data System (ADS)

Arslan, Ömer; Aydıner, Burcu; Yalçın, Ergin; Babür, Banu; Seferoğlu, Nurgül; Seferoğlu, Zeynel

2017-12-01

A novel colorimetric chemosensor based on push-pull dye (8HQA) was synthesized and characterized by using IR, 1H/13C NMR and HRMS for the purpose of recognition of anions and cations in DMSO. The absorption maxima of the chemosensor were determined in different solvents. The selectivity and sensitivity of 8HQA to anions were determined with spectrophotometric and 1H NMR titration techniques. The selectivity of 8HQA for studied anions (CN-, F-, Cl-, I-, AcO-, HSO4- and H2PO4-) was determined in DMSO. There is no selectivity between competing anions such as CN-, F- AcO- and H2PO4- at the stoichiometric ratio of 1:1 in UV-vis titrations experiments however, it was observed different color changes upon addition of CN-, F-, AcO- and H2PO4- to the DMSO solution. In addition, the chemosensor showed no colorimetric response for the following anions; Cl-, I- and HSO4- in DMSO. The colorimetric sensing ability of 8HQA was studied in the presence of chloride salts of different cations such as Ca2+, Mg2+, Cu2+, Co2+, Sn2+, Ni2+, Cd2+ and Hg2+. Upon the addition of 4 equiv of each of the cations showed bathochromic shifts except for Ca2+and Cu2+. Interestingly, no selectivity was observed in interaction with metal cations. In addition, the molecular and electronic structures of 8HQA, as well as the molecular complexes of 8HQA, formed with the anions, were obtained theoretically and confirmed by DFT and TD-DFT calculations.

Colorimetric assay of copper ions based on the inhibition of peroxidase-like activity of MoS2 nanosheets

NASA Astrophysics Data System (ADS)

Chen, Huan; Li, Zhihong; Liu, Xueting; Zhong, Jianhai; Lin, Tianran; Guo, Liangqia; Fu, Fengfu

2017-10-01

The peroxidase-like catalytic activity of MoS2 nanomaterials has been utilized for colorimetric bioassays and medical diagnostics. However, the application of peroxidase-like catalytic activity of MoS2 nanomaterials in environmental analysis was seldom explored. Herein, copper ions were found to inhibit the peroxidase-like catalytic activity of MoS2 nanosheets, which can catalyze the oxidation of 3, 3‧, 5, 5‧-tetramethylbenzidine by H2O2 to produce a colorimetric product. Based on this finding, a simple sensitive colorimetric method for the detection of copper ions was developed. In the presence of copper ions, the absorbance and color of the solution decreased with the increasing concentration of copper ions. The color of the solution can be used to semi-quantitative on-site assay of copper ions by naked eyes. A linear relationship between the absorbance and the concentration of copper ions was observed in the range of 0.4-4.0 μmol L- 1 with a detection limit of 92 nmol L- 1, which was much lower than the maximum contaminant level of copper in drinking water legislated by the Environmental Protection Agency of USA and the World Health Organization. The method was applied to detect copper ions in environmental water samples with satisfactory results.

Re-evaluation of colorimetric Cl- data from natural waters with DOC

USGS Publications Warehouse

Norton, S.A.; Handlet, M.J.; Kahl, J.S.; Peters, N.E.

1996-01-01

Colorimetric Cl- data from natural solutions that contain dissolved organic carbon (DOC) may be biased high. We evaluated aquatic Cl- concentrations in ecosystem compartments at the Bear Brook Watershed, Maine, and from lakes in Maine, using ion chromatography and colorimetry. DOC imparts a positive interference on colorimetric Cl- results proportional to DOC concentrations at approximately 0.8 ??eq Cl-/L per mg DOC/L. The interference is not a function of Cl- concentration. The resulting bias in concentrations of Cl- may be 50% or more of typical environmental values for Cl- in areas remote from atmospheric deposition of marine aerosols. Such biased data in the literature appear to have led to spurious conclusions about recycling of Cl- by forests, the usefulness of Cl- as a conservative tracer in watershed studies, and calculations of elemental budgets, ion balance, charge density of DOC, and dry deposition factors.

Colorimetric determination of cyanide liberated from apricot kernels.

PubMed

Egli, K L

1977-07-01

A simple colorimetric method is described for determining the quantity of hydrogen cyanide produced by the spontaneous decomposition of amygdalin in apricot kernels. The evolved cyanide is collected in sodium hydroxide solution and assayed colorimetrically by reaction with picric acid. Results for duplicate assays, 3.02 and 3.06 mg CN-/g, compare well with those obtained by AOAC method 26.115 which specifies steam distillation and silver nitrate titration; results for triplicate assays were 3.02, 3.03, and 3.08 mg CN-/g by the latter. Recovery of cyanide from potassium cyanide at a level equivalent to 243 microgram CN-/g was 101.0%.

An Illumination-Adaptive Colorimetric Measurement Using Color Image Sensor

NASA Astrophysics Data System (ADS)

Lee, Sung-Hak; Lee, Jong-Hyub; Sohng, Kyu-Ik

An image sensor for a use of colorimeter is characterized based on the CIE standard colorimetric observer. We use the method of least squares to derive a colorimetric characterization matrix between RGB output signals and CIE XYZ tristimulus values. This paper proposes an adaptive measuring method to obtain the chromaticity of colored scenes and illumination through a 3×3 camera transfer matrix under a certain illuminant. Camera RGB outputs, sensor status values, and photoelectric characteristic are used to obtain the chromaticity. Experimental results show that the proposed method is valid in the measuring performance.

Gold nanoprobe functionalized with specific fusion protein selection from phage display and its application in rapid, selective and sensitive colorimetric biosensing of Staphylococcus aureus.

PubMed

Liu, Pei; Han, Lei; Wang, Fei; Petrenko, Valery A; Liu, Aihua

2016-08-15

Staphylococcus aureus (S. aureus) is one of the most ubiquitous pathogens in public healthcare worldwide. It holds great insterest in establishing robust analytical method for S. aureus. Herein, we report a S. aureus-specific recognition element, isolated from phage monoclone GQTTLTTS, which was selected from f8/8 landscape phage library against S. aureus in a high-throughput way. By functionalizing cysteamine (CS)-stabilized gold nanoparticles (CS-AuNPs) with S. aureus-specific pVIII fusion protein (fusion-pVIII), a bifunctional nanoprobe (CS-AuNPs@fusion-pVIII) for S. aureus was developed. In this strategy, the CS-AuNPs@fusion-pVIII could be induced to aggregate quickly in the presence of target S. aureus, resulting in a rapid colorimetric response of gold nanoparticles. More importantly, the as-designed probe exhibited excellent selectivity over other bacteria. Thus, the CS-AuNPs@fusion-pVIII could be used as the indicator of target S. aureus. This assay can detect as low as 19CFUmL(-1)S. aureus within 30min. Further, this approach can be applicable to detect S. aureus in real water samples. Due to its sensitivity, specificity and rapidness, this proposed method is promising for on-site testing of S. aureus without using any costly instruments. Copyright © 2016 Elsevier B.V. All rights reserved.

Intrinsic peroxidase-like activity of rhodium nanoparticles, and their application to the colorimetric determination of hydrogen peroxide and glucose.

PubMed

Choleva, Tatiana G; Gatselou, Vasiliki A; Tsogas, George Z; Giokas, Dimosthenis L

2017-12-05

The intrinsic peroxidase-like activity of rhodium nanoparticles (RhNPs) and their use as catalytic labels for sensitive colorimetric assays is presented. RhNPs catalyze the oxidation of the peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H 2 O 2 to produce a blue reaction product with a maximum absorbance at 652 nm. Kinetic studies show catalysis to follow Michaelis-Menten kinetics and a "ping-pong" mechanism. The calculated kinetic parameters indicate high affinity of RhNPs for both the substrate TMB and H 2 O 2 . In fact, they are better than other peroxidase mimicking nanomaterials and even the natural enzyme horseradish peroxidase. On the other hand, RhNPs exhibit no reactivity towards saccharides, thiols, amino acids and ascorbic acid. Based on these findings, a sensitive and selective colorimetric method was worked out for the determination of H 2 O 2 in real samples with a linear response in the 1-100 μM concentration range. By employing glucose oxidase, the glucose assay has a linear range that covers the 5 to 125 μM glucose concentration range. The detection limits are <0.75 μM for both species. The methods were applied to the determination of H 2 O 2 in spiked pharmaceutical formulations, and of glucose in soft drinks and blood plasma. Figures of merit include (a) good accuracy (with errors of <6%), (b) high recoveries (96.5-103.7%), and (c) satisfactory reproducibility (<6.3%). Graphical abstract Rhodium nanoparticles catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H 2 O 2 to produce a blue reaction product. The effect is exploited in photometric assays for hydrogen peroxide and glucose.

Hybrid nanosensor for colorimetric and ultrasensitive detection of nuclease contaminations

NASA Astrophysics Data System (ADS)

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

2016-04-01

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

Colorimetric detection of glucose based on ficin with peroxidase-like activity

NASA Astrophysics Data System (ADS)

Pang, Yanjiao; Huang, Zili; Yang, Yufang; Long, Yijuan; Zheng, Huzhi

2018-01-01

In this work, we developed a colorimetric biosensing system for glucose detection by coupling the peroxidase-like of ficin and the glucose oxidase (GOx). GOx can catalyze the oxidation of glucose to produce H2O2, then, ficin catalyzes the oxidation of peroxidase substrate 3,3‧,5,5‧-tetramethylbenzidine (TMB) by H2O2 to produce a blue color reaction. The present sensing system showed a linear response toward glucose detection over range of 2.0-100 μM with a detection limit of 0.5 μM. This system is simple, low cost, highly sensitive and selective for glucose detection, and was also applied to measuring glucose in human serum. Furthermore, in order to expand the application of ficin in biological sensing, we immobilized ficin onto the SiO2@Fe3O4 NPs, which exhibited the merits of recycling as well as allowing the repeated detection of glucose. Thus it may provide great potential applications in biomedicine, biotechnology and environmental chemistry.

Blue emitting copper nanoclusters as colorimetric and fluorescent probe for the selective detection of bilirubin

NASA Astrophysics Data System (ADS)

R. S., Aparna; J. S., Anjali Devi; John, Nebu; Abha, K.; S. S., Syamchand; George, Sony

2018-06-01

Hurdles to develop point of care diagnostic methods restrict the translation of progress in the health care sector from bench side to bedside. In this article a simple, cost effective fluorescent as well as colorimetric nanosensor was developed for the early and easy detection of hyperbilirubinemia. A stable, water soluble bovine serum albumin stabilised copper nanocluster (BSA CuNC) was used as the fluorescent probe which exhibited strong blue emission (404 nm) upon 330 nm excitation. The fluorescence of the BSA CuNC can be effectively quenched by the addition of bilirubin by the formation of copper-bilirubin complex. Meanwhile the copper-bilirubin complex resulted in an observable colour change from pale violet to green facilitating colorimetric detection. The prepared sensor displayed good selectivity and sensitivity over other co-existing molecules, and can be used for quantifying bilirubin with a detection limit down to 257 fM. Additionally, the as-prepared probe was coated on a paper strip to develop a portable paper strip sensor of bilirubin. Moreover, the method was successfully applied in real sample analysis and obtained promising result.

Sensitive method to monitor trace quantities of benzanthrone in workers of dyestuff industries

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

Joshi, A.; Khanna, S.K.; Singh, G.B.

1986-03-01

Dyestuff workers coming in contact with benzanthrone (an intermediate used for the synthesis of a variety of dyes) develop skin lesions, gastritis, liver malfunctions, and sexual disturbances. A highly sensitive fluorometric method to monitor trace quantities of benzanthrone in urine, serum, and biological tissues for experimental studies, has been developed. Coupled with simple extraction and resolution, optimum fluorescence is obtained in an equal mixture of chloroform:methanol, detecting as low as 2 ng benzanthrone. This method is approximately 250 times more sensitive than currently available colorimetric assay.

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.

Colorimetric detection of genetically modified organisms based on exonuclease III-assisted target recycling and hemin/G-quadruplex DNAzyme amplification.

PubMed

Zhang, Decai; Wang, Weijia; Dong, Qian; Huang, Yunxiu; Wen, Dongmei; Mu, Yuejing; Yuan, Yong

2017-12-21

An isothermal colorimetric method is described for amplified detection of the CaMV 35S promoter sequence in genetically modified organism (GMO). It is based on (a) target DNA-triggered unlabeled molecular beacon (UMB) termini binding, and (b) exonuclease III (Exo III)-assisted target recycling, and (c) hemin/G-quadruplex (DNAzyme) based signal amplification. The specific binding of target to the G-quadruplex sequence-locked UMB triggers the digestion of Exo III. This, in turn, releases an active G-quadruplex segment and target DNA for successive hybridization and cleavage. The Exo III impellent recycling of targets produces numerous G-quadruplex sequences. These further associate with hemin to form DNAzymes and hence will catalyze H 2 O 2 -mediated oxidation of the chromogenic enzyme substrate ABTS 2- causing the formation of a green colored product. This finding enables a sensitive colorimetric determination of GMO DNA (at an analytical wavelength of 420 nm) at concentrations as low as 0.23 nM. By taking advantage of isothermal incubation, this method does not require sophisticated equipment or complicated syntheses. Analyses can be performed within 90 min. The method also discriminates single base mismatches. In our perception, it has a wide scope in that it may be applied to the detection of many other GMOs. Graphical abstract An isothermal and sensitive colorimetric method is described for amplified detection of CaMV 35S promoter sequence in genetically modified organism (GMO). It is based on target DNA-triggered molecular beacon (UMB) termini-binding and exonuclease III assisted target recycling, and on hemin/G-quadruplex (DNAzyme) signal amplification.

Combined enzymatic and colorimetric method for determining the uronic acid and methylester content of pectin: Application to tomato products.

PubMed

Anthon, Gordon E; Barrett, Diane M

2008-09-01

A simple procedure for determining the galacturonic acid and methanol contents of soluble and insoluble pectins, relying on enzymatic pectin hydrolysis and colorimetric quantification, is described. Pectin samples are incubated with a commercial pectinase preparation, Viscozyme, then the galacturonic acid content of the hydrolyzed pectin is quantified colorimetrically using a modification of the Cu reduction procedure originally described by Avigad and Milner. This modification, substituting the commonly used Folin-Ciocalteau reagent for the arsenic containing Nelson reagent, gives a response that is linear, sensitive, and selective for uronic acids over neutral sugars. This method also avoids the use of concentrated acids needed for the commonly used m-phenylphenol method. Methanol, released by the action of the pectin methylesterase found in the Viscozyme, is quantified using alcohol oxidase and Purpald. This combined enzymatic and colorimetric procedure correctly determined the galacturonic acid and methanol content of purified, soluble citrus pectin. Application of the procedure to water insoluble pectins was evaluated with water insoluble material from apples and oranges. In both cases good agreement was obtained between this method and commonly used methods based on chemical pectin hydrolysis. Good agreement between these procedures was also found in the analysis of both soluble and insoluble pectins from several tomato products. Copyright © 2008 Elsevier Ltd. All rights reserved.

Label-free detection of specific DNA sequence-telomere using unmodified gold nanoparticles as colorimetric probes

NASA Astrophysics Data System (ADS)

Qi, Yingying; Li, Li; Li, Baoxin

2009-09-01

A simple and sensitive label-free colorimetric detection of telomere DNA has been developed. It was based on the color change of gold nanoparticles (AuNPs) due to DNA hybridization. UV-vis spectra and transmission electron microscopy (TEM) were used to investigate the change of AuNPs. Under the optimized conditions, the linear range for determination of telomere DNA was 5.7 × 10 -13 to 4.5 × 10 -6 mol/L. The detection limit (3 σ) of this method has decreased to pico-molar level.

A High-Throughput, Precipitating Colorimetric Sandwich ELISA Microarray for Shiga Toxins

PubMed Central

Gehring, Andrew; He, Xiaohua; Fratamico, Pina; Lee, Joseph; Bagi, Lori; Brewster, Jeffrey; Paoli, George; He, Yiping; Xie, Yanping; Skinner, Craig; Barnett, Charlie; Harris, Douglas

2014-01-01

Shiga toxins 1 and 2 (Stx1 and Stx2) from Shiga toxin-producing E. coli (STEC) bacteria were simultaneously detected with a newly developed, high-throughput antibody microarray platform. The proteinaceous toxins were immobilized and sandwiched between biorecognition elements (monoclonal antibodies) and pooled horseradish peroxidase (HRP)-conjugated monoclonal antibodies. Following the reaction of HRP with the precipitating chromogenic substrate (metal enhanced 3,3-diaminobenzidine tetrahydrochloride or DAB), the formation of a colored product was quantitatively measured with an inexpensive flatbed page scanner. The colorimetric ELISA microarray was demonstrated to detect Stx1 and Stx2 at levels as low as ~4.5 ng/mL within ~2 h of total assay time with a narrow linear dynamic range of ~1–2 orders of magnitude and saturation levels well above background. Stx1 and/or Stx2 produced by various strains of STEC were also detected following the treatment of cultured cells with mitomycin C (a toxin-inducing antibiotic) and/or B-PER (a cell-disrupting, protein extraction reagent). Semi-quantitative detection of Shiga toxins was demonstrated to be sporadic among various STEC strains following incubation with mitomycin C; however, further reaction with B-PER generally resulted in the detection of or increased detection of Stx1, relative to Stx2, produced by STECs inoculated into either axenic broth culture or culture broth containing ground beef. PMID:24921195

Colorimetric end-tidal CO2 detector for verification of endotracheal tube placement in out-of-hospital cardiac arrest.

PubMed

Hayden, S R; Sciammarella, J; Viccellio, P; Thode, H; Delagi, R

1995-06-01

To evaluate the ability of a disposable, colorimetric end-tidal CO2 detector to verify proper endotracheal (ET) tube placement in out-of-hospital cardiac arrest, and to correlate semiquantitative CO2 measurements with the rate of return of spontaneous circulation (ROSC). Prospective, observational study using a convenience sample of intubated out-of-hospital cardiac arrest patients. A disposable, colorimetric end-tidal CO2 detector was attached to the ET tube after intubation. In the absence of a colorimetric change, the paramedics reassessed the tube placement and could reintubate the patient. Tube placement was verified at the hospital. Paramedics were instructed to contact the base station and report the colorimetric change upon hospital arrival. ROSC was defined as restoration of a self-sustaining pulse until hospital arrival. Between December 1990 and May 1993, ET tubes were placed in 566 victims of out-of-hospital cardiac arrest. 541 of the 566 intubations (95.6%) were associated with a color change. In one case with a color change and out-of-hospital clinical evidence of proper tube placement, the tube was determined to be in the esophagus at the hospital. Correct placement of the remaining 565 of 566 (99.8%) tubes was verified. Of the 566 patients who had a colorimetric change, 91 (16%) had ROSC vs one of 25 (4%) patients who did not have a color change. In one subgroup (n = 179), the degree of color change was highly associated with ROSC (p = 0.004). A disposable, colorimetric end-tidal CO2 detector appears reliable in verifying proper ET tube placement in victims of out-of-hospital cardiac arrest. The degree of color change correlates with the probability of ROSC.

Comparative Chemometric Analysis for Classification of Acids and Bases via a Colorimetric Sensor Array.

PubMed

Kangas, Michael J; Burks, Raychelle M; Atwater, Jordyn; Lukowicz, Rachel M; Garver, Billy; Holmes, Andrea E

2018-02-01

With the increasing availability of digital imaging devices, colorimetric sensor arrays are rapidly becoming a simple, yet effective tool for the identification and quantification of various analytes. Colorimetric arrays utilize colorimetric data from many colorimetric sensors, with the multidimensional nature of the resulting data necessitating the use of chemometric analysis. Herein, an 8 sensor colorimetric array was used to analyze select acid and basic samples (0.5 - 10 M) to determine which chemometric methods are best suited for classification quantification of analytes within clusters. PCA, HCA, and LDA were used to visualize the data set. All three methods showed well-separated clusters for each of the acid or base analytes and moderate separation between analyte concentrations, indicating that the sensor array can be used to identify and quantify samples. Furthermore, PCA could be used to determine which sensors showed the most effective analyte identification. LDA, KNN, and HQI were used for identification of analyte and concentration. HQI and KNN could be used to correctly identify the analytes in all cases, while LDA correctly identified 95 of 96 analytes correctly. Additional studies demonstrated that controlling for solvent and image effects was unnecessary for all chemometric methods utilized in this study.

Fluoride-selective colorimetric sensor based on thiourea binding site and anthraquinone reporter.

PubMed

Wu, Fang-ying; Hu, Mei-hua; Wu, Yu-mei; Tan, Xiao-fang; Zhao, Yong-qiang; Ji, Zhao-jun

2006-11-01

A structurally simple colorimetric sensor, N-4-nitrobenzene-N'-1'-anthraquinone-thiourea (1), for anions was synthesized and characterized by (1)H NMR, ESI mass and IR methods. In acetonitrile, the addition of F(-) changed 1 solution from colorless to yellow. In the presence of other anions such as CH(3)CO(2)(-), H(2)PO(4)(-), HSO(4)(-) and Cl(-), however, the absorption spectrum of 1 was slightly red shifted with no obvious color changes observed. The association constants of anionic complexes followed the order of F(-)>CH(3)CO(2)(-)>H(2)PO(4)(-)>HSO(4)(-)>Cl(-)>Br(-), which was different from the order of anion basicity. AM1 calculation results indicated that the most stable configuration of 1 existed in the Z-E-conformation with a six-membered ring via intramolecular hydrogen bond. This made thiourea moiety of 1 in an unfavorable conformation to bond with oxygen-anionic substrates such as CH(3)CO(2)(-) and H(2)PO(4)(-), thus leading to a high selectivity and sensitivity for the detection of F(-).

Nucleic acid-coupled colorimetric analyte detectors

DOEpatents

Charych, Deborah H.; Jonas, Ulrich

2001-01-01

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

Reversible sol-to-gel transformation of uracil gelators: specific colorimetric and fluorimetric sensor for fluoride ions.

PubMed

Xing, Ling-Bao; Yang, Bing; Wang, Xiao-Jun; Wang, Jiu-Ju; Chen, Bin; Wu, Qianhong; Peng, Hui-Xing; Zhang, Li-Ping; Tung, Chen-Ho; Wu, Li-Zhu

2013-03-05

A new type of anthracene organogelator based on uracil was obtained using organic aromatic solvents, cyclohexane, DMSO, ethanol, and ethyl acetate. It was further characterized by field-emission scanning electron microscopy and transmission electron microscopy. Specifically, the resulting organogels were demonstrated to be promising colorimetric and fluorescent sensors toward fluoride ions with high sensitivity and selectivity, accompanying the disruption of the gelators. Spectroscopic study and (1)H NMR titration experiment revealed that the deprotonation of the hydrogen atom on the N position of uracil moiety by fluoride ions is responsible for the recognition events, evidenced by immediate transformation from the sol phase to the gel state upon adding a small amount of a proton solvent, methanol. The process is reversible, with zero loss in sensing activity and sol-to-gel transformation ability even after five runs.

Portable device for the detection of colorimetric assays

PubMed Central

Nowak, E.; Kawchuk, J.; Hoorfar, M.; Najjaran, H.

2017-01-01

In this work, a low-cost, portable device is developed to detect colorimetric assays for in-field and point-of-care (POC) analysis. The device can rapidly detect both pH values and nitrite concentrations of five different samples, simultaneously. After mixing samples with specific reagents, a high-resolution digital camera collects a picture of the sample, and a single-board computer processes the image in real time to identify the hue–saturation–value coordinates of the image. An internal light source reduces the effect of any ambient light so the device can accurately determine the corresponding pH values or nitrite concentrations. The device was purposefully designed to be low-cost, yet versatile, and the accuracy of the results have been compared to those from a conventional method. The results obtained for pH values have a mean standard deviation of 0.03 and a correlation coefficient R2 of 0.998. The detection of nitrites is between concentrations of 0.4–1.6 mg l−1, with a low detection limit of 0.2 mg l−1, and has a mean standard deviation of 0.073 and an R2 value of 0.999. The results represent great potential of the proposed portable device as an excellent analytical tool for POC colorimetric analysis and offer broad accessibility in resource-limited settings. PMID:29291093

Protein, enzyme and carbohydrate quantification using smartphone through colorimetric digitization technique.

PubMed

Dutta, Sibasish; Saikia, Gunjan Prasad; Sarma, Dhruva Jyoti; Gupta, Kuldeep; Das, Priyanka; Nath, Pabitra

2017-05-01

In this paper the utilization of smartphone as a detection platform for colorimetric quantification of biological macromolecules has been demonstrated. Using V-channel of HSV color space, the quantification of BSA protein, catalase enzyme and carbohydrate (using D-glucose) have been successfully investigated. A custom designed android application has been developed for estimating the total concentration of biological macromolecules. The results have been compared with that of a standard spectrophotometer which is generally used for colorimetric quantification in laboratory settings by measuring its absorbance at a specific wavelength. The results obtained with the designed sensor is found to be similar when compared with the spectrophotometer data. The designed sensor is low cost, robust and we envision that it could promote diverse fields of bio-analytical investigations. Schematic illustration of the smartphone sensing mechanism for colorimetric analysis of biomolecular samples. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Novel epoxy-silica nanoparticles to develop non-enzymatic colorimetric probe for analytical immuno/bioassays.

PubMed

Dixit, Chandra K; Bhakta, Snehasis; Macharia, John; Furtado, Jared; Suib, Steven L; Rusling, James F

2018-10-22

We have developed a novel method to develop epoxy silica nanoparticles (EfSiNP) in a single pot. High surface coverage of epoxy functional groups between 150 and 57000 molecules per particles (∼10 13 -10 16 molecules/mL of 200 nm EfSiNPs) was achieved for different preparation conditions. We then created a red colored probe by conjugating Fuchsin dye to the epoxy functionalities of EfSINPs. Anti-mouse IgG was co-immobilized with Fuchsin and their ratios were optimized for achieving optimum ratios by testing those in functional assays. Dye to antibody ratios were in good negative correlation with a coefficient of -1.00 measured at a confidence level of over 99%. We employed the developed non-enzymatic colorimetric immunonanoprobe for detecting mouse IgG in a direct immunoassay format. We achieved a sensitivity of 427 pg/mL with the assay. Copyright © 2018 Elsevier B.V. All rights reserved.

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

PubMed

Qian, Sihua; Lin, Hengwei

2014-03-01

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

Novel Colorimetric Aptasensor for Zearalenone Detection Based on Nontarget-Induced Aptamer Walker, Gold Nanoparticles, and Exonuclease-Assisted Recycling Amplification.

PubMed

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

2018-04-18

Zearalenone (ZEN) toxicity is a significant risk for human beings. Thus, it is of high importance to develop sensitive, precise, and inexpensive analytical methods for ZEN detection, especially in human serum. Here, a colorimetric aptasensor is presented for the determination of ZEN based on the nontarget-induced aptamer walker, catalytic reaction of gold nanoparticles (AuNPs), exonuclease III (Exo III) as a signal amplifier, and 4-nitrophenol as a colorimetric agent. Low amount of ZEN requirement and signal amplification are some of the distinct advantages of the proposed aptasensor. In the absence of ZEN, the aptamer (Apt) starts walking on the AuNP surface with the help of Exo III and binds to multiple complementary strands of aptamer, leading to the change of sample color from yellow to colorless. Upon the addition of ZEN, both the Apt and complementary strand exist as single-stranded DNAs on the surface of AuNPs, resulting in less access of 4-nitrophenol to the surface of AuNPs and less catalytic performance of AuNPs. In this situation, the color of the sample remains yellow (the color of 4-nitrophenol). The presented aptasensor was capable to detect ZEN in a wide linear dynamic range, 20-80 000 ng/L, with a detection limit of 10 ng/L. The prepared sensing strategy was successfully used for ZEN determination in the human serum sample.

A sensitive colorimetric method for the determination of nitrite in water supplies, meat and dairy products using ionic liquid-modified methyl red as a colour reagent.

PubMed

Zhang, Haijuan; Qi, Shengda; Dong, Yalei; Chen, Xiaojiao; Xu, Yinyin; Ma, Yanhua; Chen, Xingguo

2014-05-15

This paper describes a colorimetric approach to determine trace amounts of nitrite in water supplies, meat and dairy products using 1-butyl-3-methylimidazolium-modified methyl red ([BMIM]MR) as a colour reagent. The technique capitalises on the catalytic effect of nitrite on the oxidative degradation of [BMIM]MR by potassium bromate in acidic media. The absorbances were proportional to nitrite concentrations in the range of 8.70×10(-2) to 4.17 μM with a detection limit of 1.64×10(-2) μM. Compared with the method using methyl red as a colour reagent, 60 times improvement of sensitivity was obtained. Activation energy and the apparent rate constant for the catalytic reaction are 61.11 kJ mol(-1) and 1.18×10(4) s(-1), respectively. The proposed method was successfully applied for the analysis of nitrite in Yellow River water, chicken, and milk with recoveries ranging from 96% to 105%. Copyright © 2013 Elsevier Ltd. All rights reserved.

Highly Sensitive Naked-Eye Assay for Enterovirus 71 Detection Based on Catalytic Nanoparticle Aggregation and Immunomagnetic Amplification.

PubMed

Xiong, Ling-Hong; He, Xuewen; Xia, Junjie; Ma, Hanwu; Yang, Fan; Zhang, Qian; Huang, Dana; Chen, Long; Wu, Chunli; Zhang, Xiaomin; Zhao, Zheng; Wan, Chengsong; Zhang, Renli; Cheng, Jinquan

2017-05-03

Development of sensitive, convenient, and cost-effective virus detection product is of great significance to meet the growing demand of clinical diagnosis at the early stage of virus infection. Herein, a naked-eye readout of immunoassay by means of virion bridged catalase-mediated in situ reduction of gold ions and growth of nanoparticles, has been successfully proposed for rapid visual detection of Enterovirus 71 (EV71). Through tailoring the morphologies of the produced gold nanoparticles (GNPs) varying between dispersion and aggregation, a distinguishing color changing was ready for observation. This colorimetric detection assay, by further orchestrating the efficient magnetic enrichment and the high catalytic activity of enzyme, is managed to realize highly sensitive detection of EV71 virions with the limit of detection (LOD) down to 0.65 ng/mL. Our proposed method showed a much lower LOD value than the commercial ELISA for EV71 virion detection. Comparing to the current clinical gold standard polymerase chain reaction (PCR) method, our strategy provided the same diagnostic outcomes after testing real clinical samples. Besides, this strategy has no need of complicated sample pretreatment or expensive instruments. Our presented naked-eye immunoassay method holds a promising prospect for the early detection of virus-infectious disease especially in resource-constrained settings.

Hydrogen bonding recognition and colorimetric detection of isoprenaline using 2-amino-5-mercapto-1,3,4-thiadiazol functionalized gold nanoparticles

NASA Astrophysics Data System (ADS)

Khezri, Somayeh; Bahram, Morteza; Samadi, Naser

2018-01-01

In this paper, we describe a rapid, low-cost and highly sensitive colorimetric method for the detection of isoprenaline, based on 2-amino-5-mercapto-1,3,4-thiadiazol (AMTD) functionalized gold nanoparticles (AMTD-AuNPs) as a sensing element. Hydrogen bonding interaction between isoprenaline and AMTD resulted in the aggregation of AuNPs and a consequent color change of AuNPs from red to blue. The concentration of isoprenaline could be detected with the naked eye or a UV-visible spectrometer. Results showed that the absorbance ratio (A650/A524) was linear with isoprenaline concentrations in the range of 0.2 to 2.6 μM (R = 0.997). The detection limit of this method was 0.08 μM. The proposed method is simple, without using complicated instruments and adding salts for enhancing sensitivity. This probe could be successfully applied to the determination of isoprenaline in human serum samples and urine samples after deproteinization.

A Colorimetric Microplate Assay for DNA-Binding Activity of His-Tagged MutS Protein.

PubMed

Banasik, Michał; Sachadyn, Paweł

2016-09-01

A simple microplate method was designed for rapid testing DNA-binding activity of proteins. The principle of the assay involves binding of tested DNA by his-tagged protein immobilized on a nickel-coated ELISA plate, following colorimetric detection of biotinylated DNA with avidin conjugated to horseradish peroxidase. The method was used to compare DNA mismatch binding activities of MutS proteins from three bacterial species. The assay required relatively low amounts of tested protein (approximately 0.5-10 pmol) and DNA (0.1-10 pmol) and a relatively short time of analysis (up to 60 min). The method is very simple to apply and convenient to test different buffer conditions of DNA-protein binding. Sensitive colorimetric detection enables naked eye observations and quantitation with an ELISA reader. The performance of the assay, which we believe is a distinguishing trait of the method, is based on two strong and specific molecular interactions: binding of a his-tagged protein to a nickel-coated microplate and binding of biotinylated DNA to avidin. In the reported experiments, the solution was used to optimize the conditions for DNA mismatch binding by MutS protein; however, the approach could be implemented to test nucleic acids interactions with any protein of interest.

Two colorimetric and ratiometric fluorescence probes for hydrogen sulfide based on AIE strategy of α-cyanostilbenes

NASA Astrophysics Data System (ADS)

Zhao, Baoying; Yang, Binsheng; Hu, Xiangquan; Liu, Bin

2018-06-01

Aggregation-induced emission (AIE) active fluorescent probes have attracted great potential in biological sensors. In this paper two cyanostilbene based fluorescence chemoprobe Cya-NO2 (1) and Cya-N3 (2) were developed and evaluated for the selective and sensitive detection of hydrogen sulfide (H2S). Both of these probes behave aggression-induced emission (AIE) activity which fluoresces in the red region with a large Stokes shift. They exhibit rapid response to H2S with enormous colorimetric and ratiometric fluorescent changes. They are readily employed for assessing intracellular H2S levels.

Visualizing Capsaicinoids: Colorimetric Analysis of Chili Peppers

ERIC Educational Resources Information Center

Thompson, Robert Q.; Chu, Christopher; Gent, Robin; Gould, Alexandra P.; Rios, Laura; Vertigan, Theresa M.

2012-01-01

A colorimetric method for total capsaicinoids in chili pepper ("Capsicum") fruit is described. The placental material of the pepper, containing 90% of the capsaicinoids, was physically separated from the colored materials in the pericarp and extracted twice with methanol, capturing 85% of the remaining capsaicinoids. The extract, evaporated and…

Highly sensitive colorimetric and fluorescent sensor for cyanazine based on the inner filter effect of gold nanoparticles

NASA Astrophysics Data System (ADS)

Dong, Liang; Hou, Changjun; Yang, Mei; Fa, Huanbao; Wu, Huixiang; Shen, Caihong; Huo, Danqun

2016-06-01

Cyanazine residue poses a great threat to human health and its derivatives would remain in soils, natural waters, and other environmental domains for a long time. Herein, a simple, rapid, and ultra-sensitive analytical method for the determination of cyanazine (CZ) based on inner filter effect (IFE) of Au nanoparticles (AuNPs) on the fluorescence of CdTe quantum dots (QDs) is first described in this study. With the presence of citrate-stabilized AuNPs, the fluorescence of GSH-capped CdTe QDs was remarkably quenched by AuNPs via IFE. The fluorescence of the AuNP-CdTe QD system was recovered upon addition of CZ. CZ can adsorb on to the surface of AuNPs due to its cyano group that has good affinity with gold, which could induce the aggregation of AuNPs accompanying color change from red to blue. Thus, the IFE of AuNPs on CdTe QDs was weakened, and the fluorescence intensity of CdTe QDs was recovered accordingly. A good linear correlation for detection of CZ was exhibited from 0.05 to 9 μM, and the detection limit reached 0.1568 μM, which was much lower than the safety limit required by the USA, the UK, and China. In order to probe into the selectivity of AuNPs towards CZ over other pesticides, various frequently used pesticides were mixed with AuNPs. AuNP composite solution shows good selectivity towards CZ among other pesticides. This method was successfully carried out for the assessment of CZ in real samples with satisfactory results, which revealed many advantages such as high sensitivity, low cost, and non-time-consuming compared with traditional methods.

MATRIX DISCRIMINANT ANALYSIS WITH APPLICATION TO COLORIMETRIC SENSOR ARRAY DATA

PubMed Central

Suslick, Kenneth S.

2014-01-01

With the rapid development of nano-technology, a “colorimetric sensor array” (CSA) which is referred to as an optical electronic nose has been developed for the identification of toxicants. Unlike traditional sensors which rely on a single chemical interaction, CSA can measure multiple chemical interactions by using chemo-responsive dyes. The color changes of the chemo-responsive dyes are recorded before and after exposure to toxicants and serve as a template for classification. The color changes are digitalized in the form of a matrix with rows representing dye effects and columns representing the spectrum of colors. Thus, matrix-classification methods are highly desirable. In this article, we develop a novel classification method, matrix discriminant analysis (MDA), which is a generalization of linear discriminant analysis (LDA) for the data in matrix form. By incorporating the intrinsic matrix-structure of the data in discriminant analysis, the proposed method can improve CSA’s sensitivity and more importantly, specificity. A penalized MDA method, PMDA, is also introduced to further incorporate sparsity structure in discriminant function. Numerical studies suggest that the proposed MDA and PMDA methods outperform LDA and other competing discriminant methods for matrix predictors. The asymptotic consistency of MDA is also established. R code and data are available online as supplementary material. PMID:26783371

Influence of VO2 Nanoparticle Morphology on the Colorimetric Assay of H2O2 and Glucose

PubMed Central

Tian, Rui; Sun, Jiaheng; Qi, Yanfei; Zhang, Boyu; Guo, Shuanli; Zhao, Mingming

2017-01-01

Nanozyme-based colorimetric sensors have received considerable attention due to their unique properties. The size, shape, and surface chemistry of these nanozymes could dramatically influence their sensing behaviors. Herein, a comparative study of VO2 nanoparticles with different morphologies (nanofibers, nanosheets, and nanorods) was conducted and applied to the sensitive colorimetric detection of H2O2 and glucose. The peroxidase-like activities and mechanisms of VO2 nanoparticles were analyzed. Among the VO2 nanoparticles, VO2 nanofibers exhibited the best peroxidase-like activity. Finally, a comparative quantitative detections of H2O2 and glucose were done on fiber, sheet, and rod nanoparticles. Under the optimal reaction conditions, the lower limit of detection (LOD) of the VO2 nanofibers, nanosheets, and nanorods for H2O2 are found to be 0.018, 0.266, and 0.41 mM, respectively. The VO2 nanofibers, nanosheets, and nanorods show the linear response for H2O2 from 0.025–10, 0.488–62.5, and 0.488–15.625 mM, respectively. The lower limit of detection (LOD) of the VO2 nanofibers, nanosheets, and nanorods for glucose are found to be 0.009, 0.348, and 0.437 mM, respectively. The VO2 nanofibers, nanosheets, and nanorods show the linear response for glucose from 0.01–10, 0.625–15, and 0.625–10 mM, respectively. The proposed work will contribute to the nanozyme-based colorimetric assay. PMID:29068412

Mentha-Stabilized Silver Nanoparticles for High-Performance Colorimetric Detection of Al(III) in Aqueous Systems.

PubMed

Sharma, Rekha; Dhillon, Ankita; Kumar, Dinesh

2018-03-26

The present paper reports a facile and selective colorimetric method for the detection of potential environmental and health hazardous metal ions using green synthesized silver nanoparticles (AgNPs). Here the organic functional groups present in the plant extract (Mentha arvensis) are used as reductants and stabilizers in the synthesis of AgNPs. They also provide a suitable binding site to the (Al(III)) analyte in the detection mechanism. The leaf extract of Mentha arvensis was used to synthesize AgNPs at room-temperature and at 80 °C. The AgNPs synthesized at 80 °C exhibit excellent selective colorimetric detection of Al(III). The as-synthesized AgNPs have been characterized, and the synthesis, stabilization of NPs and detection mechanism has also been illustrated by using UV-vis, XPS, FTIR, TEM, EDX, SEM, AAS, and TGA analytical tools and techniques. The selectivity of detection probe was supported by the reaction between probe and metal ions followed first-order kinetics having the highest value of the regression coefficient (R 2  = 0.99) for Al(III) and the analysis of thermodynamic parameters. The prepared sensor showed a lower limit of detection (LOD) of 1 nM (S/N = 3.2) in real water samples. The proposed method can be successfully utilized for the detection of Al(III) from both drinking and real water samples at the nanomolar level.

Comparison of macro-gravimetric and micro-colorimetric lipid determination methods.

PubMed

Inouye, Laura S; Lotufo, Guiherme R

2006-10-15

In order to validate a method for lipid analysis of small tissue samples, the standard macro-gravimetric method of Bligh-Dyer (1959) [E.G. Bligh, W.J. Dyer, Can. J. Biochem. Physiol. 37 (1959) 911] and a modification of the micro-colorimetric assay developed by Van Handel (1985) [E. Van Handel, J. Am. Mosq. Control Assoc. 1 (1985) 302] were compared. No significant differences were observed for wet tissues of two species of fish. However, limited analysis of wet tissue of the amphipod, Leptocheirusplumulosus, indicated that the Bligh-Dyer gravimetric method generated higher lipid values, most likely due to the inclusion of non-lipid materials. Additionally, significant differences between the methods were observed with dry tissues, with the micro-colorimetric method consistently reporting calculated lipid values greater than as reported by the gravimetric method. This was most likely due to poor extraction of dry tissue in the standard Bligh-Dyer method, as no significant differences were found when analyzing a single composite extract. The data presented supports the conclusion that the micro-colorimetric method described in this paper is accurate, rapid, and minimizes time and solvent use.

A colorimetric assay for measuring iodide using Au@Ag core-shell nanoparticles coupled with Cu(2+).

PubMed

Zeng, Jingbin; Cao, Yingying; Lu, Chun-Hua; Wang, Xu-Dong; Wang, Qianru; Wen, Cong-Ying; Qu, Jian-Bo; Yuan, Cunguang; Yan, Zi-Feng; Chen, Xi

2015-09-03

Au@Ag core-shell nanoparticles (NPs) were synthesized and coupled with copper ion (Cu(2+)) for the colorimetric sensing of iodide ion (I(-)). This assay relies on the fact that the absorption spectra and the color of metallic core-shell NPs are sensitive to their chemical ingredient and dimensional core-to-shell ratio. When I(-) was added to the Au@Ag core-shell NPs-Cu(2+) system/solution, Cu(2+) can oxidize I(-) into iodine (I2), which can further oxidize silver shells to form silver iodide (AgI). The generated Au@AgI core-shell NPs led to color changes from yellow to purple, which was utilized for the colorimetric sensing of I(-). The assay only took 10 min with a lowest detectable concentration of 0.5 μM, and it exhibited excellent selectivity for I(-) over other common anions tested. Furthermore, Au@Ag core-shell NPs-Cu(2+) was embedded into agarose gels as inexpensive and portable "test strips", which were successfully used for the semi-quantitation of I(-) in dried kelps. Copyright © 2015 Elsevier B.V. All rights reserved.

Dual-responsive immunosensor that combines colorimetric recognition and electrochemical response for ultrasensitive detection of cancer biomarkers.

PubMed

Hong, Wooyoung; Lee, Sooyeon; Cho, Youngnam

2016-12-15

We developed a nanoroughened, biotin-doped polypyrrole immunosensor for the detection of tumor markers through dual-signal (electrochemical and colorimetric) channels, electrochemical and colorimetric, that demonstrates remarkable analytical performance. A rapid, one-step electric field-mediated method was employed to fabricate the immunosensor with nanoscale roughness by simply modulating the applied electrical potential. We demonstrated the successful detection of three tumor markers (CA125, CEA, and PSA) via the double enzymatic signal amplifications in the presence of a target antigen, ultimately leading to desired diagnostic accuracy and reliability. The addition of multiple horseradish peroxidase (HRP)- and antibody-labeled nanoparticles greatly amplified the signal and simplified the measurement of cancer biomarker proteins by sequentially magnifying electrochemical and colorimetric signals in a single platform. The two parallel assays performed using the proposed immunosensor have yielded highly consistent and reproducible results. Additionally, for the analysis of plasma samples in a clinical setting, the values obtained with our immunosensor were validated by correlating the results with those of a standard radioimmunoassay (RIA), which obtained very similar clinically valid responses. Copyright © 2016 Elsevier B.V. All rights reserved.

Highly sensitive DNA detection using cascade amplification strategy based on hybridization chain reaction and enzyme-induced metallization

PubMed Central

Yu, Xu; Zhang, Zhi-Ling; Zheng, Si-Yang

2014-01-01

A novel highly sensitive colorimetric assay for DNA detection using cascade amplification strategy based on hybridization chain reaction and enzyme-induced metallization was established. The DNA modified superparamagnetic beads were demonstrated to capture and enrich the target DNA in the hybridization buffer or human plasma. The hybridization chain reaction and enzyme-induced silver metallization on the gold nanoparticles were used as cascade signal amplification for the detection of target DNA. The metalization of silver on the gold nanoparticles induced a significant colour change from red to yellow until black depending on the concentration of the target DNA, which could be recognized by naked eyes. This method showed a good specificity for the target DNA detection, with the capabilty to discriminate single-base-pair mismatched DNA mutation (single nucleotide polymorphism). Meanwhile, this approach exhibited an excellent anti-interference capability with the convenience of the magentic seperation and washing, which enabled its usage in complex biological systems such as human blood plasma. As an added benefit, the utilization of hybridization chain reaction and enzyme-induced metallization improved detection sensitivity down to 10 pM, which is about 100-fold lower than that of traditional unamplified homogeneous assays. PMID:25500528

Colorimetric and Fluorescent Bimodal Ratiometric Probes for pH Sensing of Living Cells.

PubMed

Liu, Yuan-Yuan; Wu, Ming; Zhu, Li-Na; Feng, Xi-Zeng; Kong, De-Ming

2015-06-01

pH measurement is widely used in many fields. Ratiometric pH sensing is an important way to improve the detection accuracy. Herein, five water-soluble cationic porphyrin derivatives were synthesized and their optical property changes with pH value were investigated. Their pH-dependent assembly/disassembly behaviors caused significant changes in both absorption and fluorescence spectra, thus making them promising bimodal ratiometric probes for both colorimetric and fluorescent pH sensing. Different substituent identity and position confer these probes with different sensitive pH-sensing ranges, and the substituent position gives a larger effect. By selecting different porphyrins, different signal intensity ratios and different fluorescence excitation wavelengths, sensitive pH sensing can be achieved in the range of 2.1-8.0. Having demonstrated the excellent reversibility, good accuracy and low cytotoxicity of the probes, they were successfully applied in pH sensing inside living cells. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

NASA Astrophysics Data System (ADS)

Duy, Janice

The rapid identification of pathogenic organisms is necessary for recognizing and managing human and environmental health risks. Numerous detection schemes are available, but most are difficult to employ in non-laboratory settings due to their need for bulky, specialized equipment, multiple reagents, or highly trained personnel. To address this problem, a rapid, field-compatible biosensor system based on the colorimetric detection of nucleic acid hybrids was developed. Peptide nucleic acid (PNA) probes were used to capture ribosomal RNA sequences from environmental samples. Non-target nucleic acids, including single-base mismatches flanked by adenines and uracils, were removed with a micrococcal nuclease digestion step. Matched PNA-RNA hybrids remained intact and were indicated by the cyanine dye DiSC2(5). PNA-containing duplexes function as templates for the aggregation of DiSC2(5), visualized as a change in solution color from blue to purple. This transition can be measured as an increase in the solution absorbance at 540 nm (dye aggregate) at the expense of the dye monomer peak at 650 nm. These concomitant spectral changes were used to calculate a "hybridization signal" using the ratio A aggregate/Amonomer ≈ A540/A650. Testing with pathogenic environmental samples was accomplished using two model organisms: the harmful algal bloom-causing dinoflagellate Alexandrium species, and the potato wart disease-causing fungus Synchytrium endobioticum. In both cases, the colorimetric approach was able to distinguish the targets with sensitivities rivaling those of established techniques, but with the advantages of decreased hands-on time and cost. Assay fieldability was tested with a portable colorimeter designed to quantify the dye-indicated hybridization signal and assembled from commercially available components. Side-by-side testing revealed no difference in the sensing performance of the colorimeter compared to a laboratory spectrophotometer (Pearson's r=0

Colorimetric Characterization of Mobile Devices for Vision Applications.

PubMed

de Fez, Dolores; Luque, Maria José; García-Domene, Maria Carmen; Camps, Vicente; Piñero, David

2016-01-01

Available applications for vision testing in mobile devices usually do not include detailed setup instructions, sacrificing rigor to obtain portability and ease of use. In particular, colorimetric characterization processes are generally obviated. We show that different mobile devices differ also in colorimetric profile and that those differences limit the range of applications for which they are most adequate. The color reproduction characteristics of four mobile devices, two smartphones (Samsung Galaxy S4, iPhone 4s) and two tablets (Samsung Galaxy Tab 3, iPad 4), have been evaluated using two procedures: 3D LUT (Look Up Table) and a linear model assuming primary constancy and independence of the channels. The color reproduction errors have been computed with the CIEDE2000 color difference formula. There is good constancy of primaries but large deviations of additivity. The 3D LUT characterization yields smaller reproduction errors and dispersions for the Tab 3 and iPhone 4 devices, but for the iPad 4 and S4, both models are equally good. The smallest reproduction errors occur with both Apple devices, although the iPad 4 has the highest number of outliers of all devices with both colorimetric characterizations. Even though there is good constancy of primaries, the large deviations of additivity exhibited by the devices and the larger reproduction errors make any characterization based on channel independence not recommendable. The smartphone screens show, in average, the best color reproduction performance, particularly the iPhone 4, and therefore, they are more adequate for applications requiring precise color reproduction.

Selective spectrophotometric determination of TNT using a dicyclohexylamine-based colorimetric sensor.

PubMed

Erçağ, Erol; Uzer, Ayşem; Apak, Reşat

2009-05-15

Because of the extremely heterogeneous distribution of explosives in contaminated soils, on-site colorimetric methods are efficient tools to assess the nature and extent of contamination. To meet the need for rapid and low-cost chemical sensing of explosive traces or residues in soil and post-blast debris, a colorimetric absorption-based sensor for trinitrotoluene (TNT) determination has been developed. The charge-transfer (CT) reagent (dicyclohexylamine, DCHA) is entrapped in a polyvinylchloride (PVC) polymer matrix plasticised with dioctylphtalate (DOP), and moulded into a transparent sensor membrane sliced into test strips capable of sensing TNT showing an absorption maximum at 530 nm when placed in a 1-mm spectrophotometer cell. The sensor gave a linear absorption response to 5-50 mg L(-1) TNT solutions in 30% aqueous acetone with limit of detection (LOD): 3 mg L(-1). The sensor is only affected by tetryl, but not by RDX, pentaerythritoltetranitrate (PETN), dinitrotoluene (DNT), and picric acid. The proposed method was statistically validated for TNT assay against high performance liquid chromatography (HPLC) using a standard sample of Comp B. The developed sensor was relatively resistant to air and water, was of low-cost and high specificity, gave a rapid and reproducible response, and was suitable for field use of TNT determination in both dry and humid soil and groundwater with a portable colorimeter.

A smartphone colorimetric reader integrated with an ambient light sensor and a 3D printed attachment for on-site detection of zearalenone.

PubMed

Chen, Yuan; Fu, Qiangqiang; Li, Dagang; Xie, Jun; Ke, Dongxu; Song, Qifang; Tang, Yong; Wang, Hong

2017-11-01

Smartphone biosensors could be cost-effective, portable instruments to be used for the readout of liquid colorimetric assays. However, current reported smartphone colorimetric readers have relied on photos of liquid assays captured using a camera, and then analyzed using software programs. This approach results in a relatively low accuracy and low generality. In this work, we reported a novel smartphone colorimetric reader that has been integrated with an ambient light sensor and a 3D printed attachment for the readout of liquid colorimetric assays. The portable and low-cost ($0.15) reader utilized a simplified electronic and light path design. Furthermore, our reported smartphone colorimetric reader can be compatible with different smartphones. As a proof of principle, the utility of this device was demonstrated using it in conjunction with an enzyme-linked immunosorbent assay to detect zearalenone. Results were consistent with those obtained using a professional microplate reader. The developed smartphone colorimetric reader was capable of providing scalable, cost-effective, and accurate results for liquid colorimetric assays that related to clinical diagnoses, environment pollution, and food testing. Graphical abstract A novel smartphone colorimetric reader that has been integrated with an ambient light sensor and a 3D printed attachment for the readout of liquid colorimetric assays.

Evaluation of colorimetric loop-mediated isothermal amplification assay for visual detection of Streptococcus agalactiae and Streptococcus iniae in tilapia.

PubMed

Suebsing, R; Kampeera, J; Tookdee, B; Withyachumnarnkul, B; Turner, W; Kiatpathomchai, W

2013-10-01

Streptococcus agalactiae and Strep. iniae are bacterial pathogens that cause streptococcosis in many fish species. An accelerated colorimetric loop-mediated isothermal amplification (LAMP) assay with pre-addition of calcein was established, and the transmission and detection of Strep. agalactiae and Strep. iniae in tilapia under natural aquatic environment were investigated. A positive reaction was observed by a colour change from orange to green through the naked eyes after completion at 63°C for 30 min with 10 times higher sensitivity than that of nested PCR assays and without cross-amplification with other fish bacterial pathogens. All sample types of Nile and red tilapia (broodstock, fertilized egg, fry) were Strep. agalactiae- and Strep. iniae positive by this new method, implying that they could be vertically transmitted. With its application for screening broodstock and fry before stocking and for monitoring fish health in grow-out ponds, the method would become very useful in fish farming industry. The application of colorimetric LAMP with pre-addition of calcein offers simple, rapid and sensitive technique with applicability for small field laboratories. This technique explored the possible vertical transmission mode of Strep. agalactiae and Strep. iniae under natural aquatic environment. It could be such preliminary data provided for the screening broodstock before breeding and/or the specific-pathogen-free production. © 2013 The Society for Applied Microbiology.

Colorimetric Solid Phase Extraction (CSPE): Using Color to Monitor Spacecraft Water Quality

NASA Technical Reports Server (NTRS)

Gazda, Daniel B.; Nolan, Daniel J.; Rutz, Jeffrey A.; Schultz, John R.; Siperko, Lorraine M.; Porter, Marc D.; Lipert, Robert J.; Flint, Stephanie M.; McCoy, J. Torin

2010-01-01

In August 2009, an experimental water quality monitoring kit based on Colorimetric Solid Phase Extraction (CSPE) technology was delivered to the International Space Station (ISS). The kit, called the Colorimetric Water Quality Monitoring Kit (CWQMK), was launched as a Station Development Test Objective (SDTO) experiment to evaluate the suitability of CSPE technology for routine use monitoring water quality on the ISS. CSPE is a sorption-spectrophotometric technique that combines colorimetric reagents, solid-phase extraction, and diffuse reflectance spectroscopy to quantify trace analytes in water samples. In CSPE, a known volume of sample is metered through a membrane disk that has been impregnated with an analyte-specific colorimetric reagent and any additives required to optimize the formation of the analyte-reagent complex. As the sample flows through the membrane disk, the target analyte is selectively extracted, concentrated, and complexed. Formation of the analyte-reagent complex causes a detectable change in the color of the membrane disk that is proportional to the amount of analyte present in the sample. The analyte is then quantified by measuring the color of the membrane disk surface using a hand-held diffuse reflectance spectrophotometer (DRS). The CWQMK provides the capability to measure the ionic silver (Ag +) and molecular iodine (I2) in water samples on-orbit. These analytes were selected for the evaluation of CSPE technology because they are the biocides used in the potable water storage and distribution systems on the ISS. Biocides are added to the potable water systems on spacecraft to inhibit microbial growth. On the United States (US) segment of the ISS molecular iodine serves as the biocide, while the Russian space agency utilizes silver as a biocide in their systems. In both cases, the biocides must be maintained at a level sufficient to control bacterial growth, but low enough to avoid any negative effects on crew health. For example, the

Development, optimization and validation of a rapid colorimetric microplate bioassay for neomycin sulfate in pharmaceutical drug products.

PubMed

Francisco, Fabiane Lacerda; Saviano, Alessandro Morais; Pinto, Terezinha de Jesus Andreoli; Lourenço, Felipe Rebello

2014-08-01

Microbiological assays have been used to evaluate antimicrobial activity since the discovery of the first antibiotics. Despite their limitations, microbiological assays are widely employed to determine antibiotic potency of pharmaceutical dosage forms, since they provide a measure of biological activity. The aim of this work is to develop, optimize and validate a rapid colorimetric microplate bioassay for the potency of neomycin in pharmaceutical drug products. Factorial and response surface methodologies were used in the development and optimization of the choice of microorganism, culture medium composition, amount of inoculum, triphenyltetrazolium chloride (TTC) concentration and neomycin concentration. The optimized bioassay method was validated by the assessment of linearity (range 3.0 to 5.0μg/mL, r=0.998 and 0.994 for standard and sample curves, respectively), precision (relative standard deviation (RSD) of 2.8% and 4.0 for repeatability and intermediate precision, respectively), accuracy (mean recovery=100.2%) and robustness. Statistical analysis showed equivalency between agar diffusion microbiological assay and rapid colorimetric microplate bioassay. In addition, microplate bioassay had advantages concerning the sensitivity of response, time of incubation, and amount of culture medium and solutions required. Copyright © 2014 Elsevier B.V. All rights reserved.

Colorimetric Aptasensor Using Unmodified Gold Nanoparticles for Homogeneous Multiplex Detection

PubMed Central

Niu, Shucao; Lv, Zhenzhen; Liu, Jinchuan; Bai, Wenhui; Yang, Shuming; Chen, Ailiang

2014-01-01

Colorimetric aptasensors using unmodified gold nanoparticles (AuNPs) have attracted much attention because of their low cost, simplicity, and practicality, and they have been developed for various targets in the past several years. However, previous research has focused on developing single-target assays. Here, we report the development of a homogeneous multiplex aptasensor by using more than one class of aptamers to stabilize AuNPs. Using sulfadimethoxine (SDM), kanamycin (KAN) and adenosine (ADE) as example targets, a KAN aptamer (750 nM), an SDM aptamer (250 nM) and an ADE aptamer (500 nM) were mixed at a 1∶1∶1 volume ratio and adsorbed directly onto the surface of unmodified AuNPs by electrostatic interaction. Upon the addition of any of the three targets, the conformation of the corresponding aptamer changed from a random coil structure to a rigid folded structure, which could not adsorb and stabilize AuNPs. The AuNPs aggregated in a specific reaction buffer (20 mM Tris-HCl containing 20 mM NaCl and 5 mM KCl), which led to a color change from red to purple/blue. These results demonstrate that the multiplex colorimetric aptasensor detected three targets simultaneously while maintaining the same sensitivity as a single-target aptasensor for each individual target. The multiplex aptasensor could be extended to other aptamers for various molecular detection events. Due to its simple design, easy operation, fast response, cost effectiveness and lack of need for sophisticated instrumentation, the proposed strategy provides a powerful tool to examine large numbers of samples to screen for a small number of potentially positive samples containing more than one analyte, which can be further validated using sophisticated instruments. PMID:25279730

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

PubMed

Zhang, Jiangang; Zhang, Li; Wei, Yanli; Chao, Jianbing; Shuang, Shaomin; Cai, Zongwei; Dong, Chuan

2014-11-11

A novel rhodamine derivative 3-bromo-5-methylsalicylaldehyde rhodamine B hydrazone (BMSRH) has been synthesized by reacting rhodamine B hydrazide with 3-bromo-5-methylsalicylaldehyde and developed as a new colorimetric probe for the selective and sensitive detection of Cu2+. Addition of Cu2+ to the solution of BMSRH results in a rapid color change from colorless to red together with an obvious new band appeared at 552 nm in the UV-vis absorption spectra. This change is attributed to the spirocycle form of BMSRH opened via coordination with Cu2+ in a 1:1 stoichiometry and their association constant is determined as 3.2×10(4) L mol(-1). Experimental results indicate that the BMSRH can provide a rapid, selective and sensitive response to Cu2+ with a linear dynamic range 0.667-240 μmol/L. Common interferent ions do not show any interference on the Cu2+ determination. It is anticipated that BMSRH can be a good candidate probe and has potential application for Cu2+ determination. The proposed probe exhibits the following advantages: a quick, simple and facile synthesis. Copyright © 2014 Elsevier B.V. All rights reserved.

A Colorimetric Process to Visualize Erythrocyte Exovesicles Aggregates

ERIC Educational Resources Information Center

Saldanha, Carlota; Santos, Nuno C.; Martins-Silva, J.

2004-01-01

A biochemistry laboratory class protocol is described in order to create an opportunity for students to apply by doing the theoretical concepts underlying biomolecules and vesicles properties, together with the principles of centrifugation and colorimetric methodologies. Through simple procedures the students will i) observe the segregation of the…

Accelerated Colorimetric Micro-assay for Screening Mold Inhibitors

Treesearch

Carol A. Clausen; Vina W. Yang

2014-01-01

Rapid quantitative laboratory test methods are needed to screen potential antifungal agents. Existing laboratory test methods are relatively time consuming, may require specialized test equipment and rely on subjective visual ratings. A quantitative, colorimetric micro-assay has been developed that uses XTT tetrazolium salt to metabolically assess mold spore...

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

DOEpatents

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

2010-11-09

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

Design and development of a microfluidic platform for use with colorimetric gold nanoprobe assays

NASA Astrophysics Data System (ADS)

Bernacka-Wojcik, Iwona

Due to the importance and wide applications of the DNA analysis, there is a need to make genetic analysis more available and more affordable. As such, the aim of this PhD thesis is to optimize a colorimetric DNA biosensor based on gold nanoprobes developed in CEMOP by reducing its price and the needed volume of solution without compromising the device sensitivity and reliability, towards the point of care use. Firstly, the price of the biosensor was decreased by replacing the silicon photodetector by a low cost, solution processed TiO2 photodetector. To further reduce the photodetector price, a novel fabrication method was developed: a cost-effective inkjet printing technology that enabled to increase TiO2 surface area. Secondly, the DNA biosensor was optimized by means of microfluidics that offer advantages of miniaturization, much lower sample/reagents consumption, enhanced system performance and functionality by integrating different components. In the developed microfluidic platform, the optical path length was extended by detecting along the channel and the light was transmitted by optical fibres enabling to guide the light very close to the analysed solution. Microfluidic chip of high aspect ratio ( 13), smooth and nearly vertical sidewalls was fabricated in PDMS using a SU-8 mould for patterning. The platform coupled to the gold nanoprobe assay enabled detection of Mycobacterium tuberculosis using 3 mul on DNA solution, i.e. 20 times less than in the previous state-of-the-art. Subsequently, the bio-microfluidic platform was optimized in terms of cost, electrical signal processing and sensitivity to colour variation, yielding 160% improvement of colorimetric AuNPs analysis. Planar microlenses were incorporated to converge light into the sample and then to the output fibre core increasing 6 times the signal-to-losses ratio. The optimized platform enabled detection of single nucleotide polymorphism related with obesity risk (FTO) using target DNA concentration

Colorimetric detection of ammonia using smartphones based on localized surface plasmon resonance of silver nanoparticles.

PubMed

Amirjani, Amirmostafa; Fatmehsari, Davoud Haghshenas

2018-01-01

In this work, a rapid and straightforward method was developed for colorimetric determination of ammonia using smartphones. The mechanisms is based on the manipulation of the surface plasmon band of silver nanoparticles (AgNPs) via the formation of Ag (NH 3 ) 2 + complex. This complex decreases the amount of AgNPs in the solution and consequently, the color intensity of the colloidal system decreases. Not only the variation in color intensity of the solution can be tracked by a UV-vis spectrophotometer, but also a smartphone can be employed to monitor the color intensity variation by RGB analysis. Ammonia, in the concentration range of 10-1000mgL -1 , was successfully measured spectrophotometrically (UV-vis spectrophotometer) and colorimetrically (RGB measurement) with the detection limit of 180 and 200mgL -1 , respectively. Linear relationships were also developed for both methods. Also, the response time of the developed colorimetric sensor was around 20s. Both of the colorimetric and spectrophotometric methods showed a reliable performance for determination of ammonia in the real samples. Copyright © 2017 Elsevier B.V. All rights reserved.

A novel colorimetric probe derived from isonicotic acid hydrazide for copper (II) determination based on internal charge transfer (ICT).

PubMed

Liu, Qing; Fei, Qiang; Fei, Yanqun; Fan, Qian; Shan, Hongyan; Feng, Guodong; Huan, Yanfu

2015-12-05

A novel isonicotic acid hydrazide Schiff base derivative N'-(3,5-di-tert-butyl-2-hydroxy-benzylidene) isonicotinohydrazide (DHIH) has been synthesized and developed as a high selective and sensitive colorimetric probe for Cu(2+) determination. Addition of Cu(2+) to the solution of DHIH resulted in a rapid color change from colorless to yellow together with an obvious new absorption band appeared at the range of 400-440 nm by forming a 1:1 complex. Experimental results indicated that the DHIH could provide absorption response to Cu(2+) with a linear dynamic range from 1.0×10(-5) to 1.0×10(-4)mol/L. The detection limit of Cu(2+) was 5.24×10(-7)mol/L with good tolerance of other metal ions. Copyright © 2015 Elsevier B.V. All rights reserved.

Development of a high-throughput colorimetric Zika virus infection assay.

PubMed

Müller, Janis A; Harms, Mirja; Schubert, Axel; Mayer, Benjamin; Jansen, Stephanie; Herbeuval, Jean-Philippe; Michel, Detlef; Mertens, Thomas; Vapalahti, Olli; Schmidt-Chanasit, Jonas; Münch, Jan

2017-04-01

Zika virus (ZIKV) is an emerging pathogen that causes congenital infections which may result in birth defects, such as microcephaly. Currently, no approved treatment or vaccination is available. ZIKV can be readily detected in cell culture where virally infected cells are normally stained by specific antibodies. As ZIKV regularly causes a cytopathic effect, we were wondering whether this viral property can be used to quantitatively determine viral infectivity. We here describe the use of an 3-[4,5-dimethyl-2-thiazolyl]-2,5-diphenyl-2H-tetrazolium bromide-(MTT)-based cell viability assay that allows to determine ZIKV-induced cell death. We show that this colorimetric assay quantifies ZIKV infection over a broad range of viral dilutions in both monkey and human cells. It allows to determine inhibitory activities of antivirals that block ZIKV or to define the neutralizing antibody titers of ZIKV antisera. This MTT-based ZIKV detection assay can be evaluated by naked eye or computational tools, has a broad linear range, does not require large equipment or costly reagents, and thus represents a promising alternative to antibody-based assays, in particular in resource-poor settings. We propose to use this simple, fast, and cheap method for quantification of ZIKV neutralizing antibodies and testing of antiviral compounds.

Colorimetric biosensing of targeted gene sequence using dual nanoparticle platforms

PubMed Central

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

2015-01-01

We have developed a colorimetric biosensor using a dual platform of gold nanoparticles and graphene oxide sheets for the detection of Salmonella enterica. The presence of the invA gene in S. enterica causes a change in color of the biosensor from its original pinkish-red to a light purplish solution. This occurs through the aggregation of the primary gold nanoparticles–conjugated DNA probe onto the surface of the secondary graphene oxide–conjugated DNA probe through DNA hybridization with the targeted DNA sequence. Spectrophotometry analysis showed a shift in wavelength from 525 nm to 600 nm with 1 μM of DNA target. Specificity testing revealed that the biosensor was able to detect various serovars of the S. enterica while no color change was observed with the other bacterial species. Sensitivity testing revealed the limit of detection was at 1 nM of DNA target. This proves the effectiveness of the biosensor in the detection of S. enterica through DNA hybridization. PMID:25897217

Cost Effective Paper-Based Colorimetric Microfluidic Devices and Mobile Phone Camera Readers for the Classroom

ERIC Educational Resources Information Center

Koesdjojo, Myra T.; Pengpumkiat, Sumate; Wu, Yuanyuan; Boonloed, Anukul; Huynh, Daniel; Remcho, Thomas P.; Remcho, Vincent T.

2015-01-01

We have developed a simple and direct method to fabricate paper-based microfluidic devices that can be used for a wide range of colorimetric assay applications. With these devices, assays can be performed within minutes to allow for quantitative colorimetric analysis by use of a widely accessible iPhone camera and an RGB color reader application…

Photoacoustic and Colorimetric Visualization of Latent Fingerprints.

PubMed

Song, Kai; Huang, Peng; Yi, Chenglin; Ning, Bo; Hu, Song; Nie, Liming; Chen, Xiaoyuan; Nie, Zhihong

2015-12-22

There is a high demand on a simple, rapid, accurate, user-friendly, cost-effective, and nondestructive universal method for latent fingerprint (LFP) detection. Herein, we describe a combination imaging strategy for LFP visualization with high resolution using poly(styrene-alt-maleic anhydride)-b-polystyrene (PSMA-b-PS) functionalized gold nanoparticles (GNPs). This general approach integrates the merits of both colorimetric imaging and photoacoustic imaging. In comparison with the previous methods, our strategy is single-step and does not require the signal amplification by silver staining. The PSMA-b-PS functionalized GNPs have good stability, tunable color, and high affinity for universal secretions (proteins/polypeptides/amino acids), which makes our approach general and flexible for visualizing LFPs on different substrates (presumably with different colors) and from different people. Moreover, the unique optical property of GNPs enables the photoacoustic imaging of GNPs-deposited LFPs with high resolution. This allows observation of level 3 hyperfine features of LFPs such as the pores and ridge contours by photoacoustic imaging. This technique can potentially be used to identify chemicals within LFP residues. We believe that this dual-modality imaging of LFPs will find widespread use in forensic investigations and medical diagnostics.

Comparison of serum copper determination by colorimetric and atomic absorption spectrometric methods in seven different laboratories. The S.F.B.C. (Société Française de Biologie Clinique) Trace Element Group.

PubMed

Arnaud, J; Chappuis, P; Zawislak, R; Houot, O; Jaudon, M C; Bienvenu, F; Bureau, F

1993-02-01

An interlaboratory collaborative trial was conducted on the determination of serum copper using two different methods, based on colorimetry (test combination Copper, Boehringer Mannheim, Mannheim, Germany) and flame atomic absorption spectrometry (FAAS). The general performance of the colorimetric method was below that of FAAS, except for sensitivity and linear range, as assessed by detection limit (0.44 versus 1.32 mumol/L) and upper limit of linearity (150 versus 50 mumol/L). The range of the between-run CVs and the recovery of standard additions were, respectively, 2.3-11.9% and 92-127% for the colorimetric method and 1.1-6.0% and 93-101% for the FAAS method. Interferences were minimal with both methods. The two techniques correlated satisfactorily (the correlation coefficients ranged from 0.945-0.970 among laboratories) but the colorimetric assay exhibited slightly higher results than the FAAS method. Each method was transferable among laboratories.

A novel reaction-based colorimetric and ratiometric fluorescent sensor for cyanide anion with a large emission shift and high selectivity.

PubMed

Wang, Shaodan; Fei, Xiaoliang; Guo, Jing; Yang, Qingbiao; Li, Yaoxian; Song, Yan

2016-01-01

A hybrid carbazole-hemicyanine dye (Cac) has been developed as a novel colorimetric and ratiometric fluorescent sensor for cyanide detection. Upon treatment with cyanide, Cac displayed a remarkable fluorescence ratiometric response, with the emission wavelength displaying a very large emission shift (214 nm). The detection of cyanide was performed via the nucleophilic addition of cyanide anion to the indolium group of the sensor, which resulted in the blocking of the intramolecular charge transfer (ICT) process in the sensor, inducing a ratiometric fluorescence change and simultaneously an obvious color change. Furthermore, competitive anions did not showed any significant changes both in color and emission intensity ratio (I381/I595), indicating the high selectivity of the sensor to CN(-). Copyright © 2015 Elsevier B.V. All rights reserved.

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

NASA Astrophysics Data System (ADS)

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

2015-10-01

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

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

PubMed

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

2015-11-01

Herein, we present simple and rapid colorimetric and UV/VIS spectroscopic methods for detecting anionic arsenic (V) complexes in aqueous media. The methods exploit the aggregation of S-layer-functionalized spherical gold nanoparticles of sizes between 20 and 50 nm in the presence of arsenic species. The gold nanoparticles were functionalized with oligomers of the S-layer protein of Lysinibacillus sphaericus JG-A12. The aggregation of the nanoparticles results in a color change from burgundy-red for widely dispersed nanoparticles to blue for aggregated nanoparticles. A detailed signal analysis was achieved by measuring the shift of the particle plasmon resonance signal with UV/VIS spectroscopy. To further improve signal sensitivity, the influence of larger nanoparticles was tested. In the case of 50 nm gold nanoparticles, a concentration of the anionic arsenic (V) complex lower than 24 ppb was detectable. Copyright © 2015 Elsevier B.V. All rights reserved.

3D flower-like ferrous(II) phosphate nanostructures as peroxidase mimetics for sensitive colorimetric detection of hydrogen peroxide and glucose at nanomolar level.

PubMed

Guo, Jingjing; Wang, Yan; Zhao, Min

2018-05-15

Ferrous(II) phosphate nanoflowers (Fe 3 (PO 4 ) 2 ·8H 2 O NFs) were synthesized by a facial co-precipitation method. The structure, composition and morphology were characterized by XRD, EDX, element mapping and FESEM. The as-prepared Fe 3 (PO 4 ) 2 ·8H 2 O NFs exhibited excellent intrinsic peroxidase-like activity. Steady-state kinetic studies showed that Fe 3 (PO 4 ) 2 ·8H 2 O NFs exhibited stronger affinities with 3,3,5,5-tetramethylbenzidine (TMB) and H 2 O 2 as the substrates compared with the natural horseradish peroxidase (HRP) and the catalytic constant (k cat ) value was even higher than HRP and other reported nanomaterial based peroxidase mimics. The investigation of the catalytic mechanism by cyclic voltammetry, fluorescence spectroscopy and ESR displayed the catalytic activity of Fe 3 (PO 4 ) 2 ·8H 2 O NFs originated from the generation of •OH. The Fe 3 (PO 4 ) 2 ·8H 2 O NFs also exhibited higher robustness and better storage stability than HRP. Then, a Fe 3 (PO 4 ) 2 ·8H 2 O NFs-based colorimetric platform was developed to determine H 2 O 2 and glucose. The linear range of H 2 O 2 and glucose was as broad as 1 × 10 -5 -2.5 mM and 8 × 10 -4 -1.2 mM, and the detection limit (LOD) was as low as 5 nM and 35 nM, respectively. This simple assay offered a highly sensitive and specific strategy for H 2 O 2 and glucose determination, which had been successfully utilized for real sample analysis with good reproducibility and accuracy. Copyright © 2018 Elsevier B.V. All rights reserved.

Efficacy of a lead based paint XRF analyzer and a commercially available colorimetric lead test kit as qualitative field tools for determining presence of lead in religious powders.

PubMed

Shah, Manthan P; Shendell, Derek G; Meng, Qingyu; Ohman-Strickland, Pamela; Halperin, William

2018-04-23

The performances of a portable X-Ray Fluorescence (XRF) lead paint analyzer (RMD LPA-1, Protec Instrument Corp., Waltham, MA) and a commercially available colorimetric lead test kit (First Alert Lead Test Kit, eAccess Solutions, Inc., Palatine, IL) were evaluated for use by local or state health departments as potential cost-effective rapid analysis or "spot test" field techniques for tentative identification of lead content in sindoor powders. For both field-sampling methods, sensitivity, specificity and predictive values varied widely for samples containing <300,000 μg/g lead. For samples containing ≥300,000 μg/g lead, the aforementioned metrics were 100% (however, the CIs had a wide range). In addition, both field sampling methods showed clear, consistent positive readings only for samples containing ≥300,000 μg/g lead. Even samples with lead content as high as 5,110 μg/g were not positively identified by either field analysis technique. The results of this study suggest the XRF analyzer and colorimetric lead test kit cannot be used as a rapid field test for sindoor by health department inspectors.

Quercetin as colorimetric reagent for determination of zirconium

USGS Publications Warehouse

Grimaldi, F.S.; White, C.E.

1953-01-01

Methods described in the literature for the determination of zirconium are generally designed for relatively large amounts of this element. A good procedure using colorimetric reagent for the determination of trace amounts is desirable. Quercetin has been found to yield a sensitive color reaction with zirconium suitable for the determination of from 0.1 to 50?? of zirconium dioxide. The procedure developed involves the separation of zirconium from interfering elements by precipitation with p-dimethylaminoazophenylarsonic acid prior to its estimation with quercetin. The quercetin reaction is carried out in 0.5N hydrochloric acid solution. Under the operating conditions it is indicated that quercetin forms a 2 to 1 complex with zirconium; however, a 2 to 1 and a 1 to 1 complex can coexist under special conditions. Approximate values for the equilibrium constants of the complexes are K1 = 0.33 ?? 10-5 and K2 = 1.3 ?? 10-9. Seven Bureau of Standards samples of glass sands and refractories were analyzed with excellent results. The method described should find considerable application in the analysis of minerals and other materials for macro as well as micro amounts of zirconium.

Rapid colorimetric sensing of gadolinium by EGCG-derived AgNPs: the development of a nanohybrid bioimaging probe.

PubMed

Singh, Rohit Kumar; Mishra, Sourav; Jena, Satyapriya; Panigrahi, Bijayananda; Das, Bhaskar; Jayabalan, Rasu; Parhi, Pankaj Kumar; Mandal, Dindyal

2018-04-17

Polyphenol functionalized silver nanoparticles (AgNPs) have been developed and demonstrated as colorimetric sensors for the selective detection of gadolinium. The newly obtained AgNP-Gd3+ conjugates exhibit high aqueous dispersibility and excitation dependent fluorescence emission. The conjugates offer multicolor bioimaging potential owing to their excellent luminescence properties.

Azomethine H colorimetric method for determining dissolved boron in water

USGS Publications Warehouse

Spencer, R.R.; Erdmann, D.E.

1979-01-01

An automated colorimetric method for determining dissolved boron in water is described. The boron is complexed with azomethine H, which is readily available as the condensation product of H acid (8-amino-1-naphthol-3,6-disulfonic acid) and salicylaldehyde. The absorbance of the yellow complex formed is then measured colorimetrically at 410 nm. Interference effects from other dissolved species are minimized by the addition of diethylenetriaminepentaacetic acid (DTPA); however, iron, zinc, and bicarbonate interfere at concentrations above 400 ??g/L, 2000 ??g/L, and 200 mg/L, respectively. The bicarbonate interference can be eliminated by careful acidification of the sample with concentrated HCl to a pH between 5 and 6. Thirty samples per hour can be routinely analyzed over the range of from 10 to 400 ??g/L, boron.

Relationship between colorimetric (instrumental) evaluation and consumer-defined beef colour acceptability.

PubMed

Holman, Benjamin W B; Mao, Yanwei; Coombs, Cassius E O; van de Ven, Remy J; Hopkins, David L

2016-11-01

The relationship between instrumental colorimetric values (L*, a*, b*, the ratio of reflectance at 630nm and 580nm) and consumer perception of acceptable beef colour was evaluated using a web-based survey and standardised photographs of beef m. longissimus lumborum with known colorimetrics. Only L* and b* were found to relate to average consumer opinions of beef colour acceptability. Respondent nationality was also identified as a source of variation in beef colour acceptability score. Although this is a preliminary study with the findings necessitating additional investigation, these results suggest L* and b* as candidates for developing instrumental thresholds for consumer beef colour expectations. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

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

PubMed

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

2016-01-01

Leishmaniasis remains one of the world's most neglected diseases, and early detection of the infectious agent, especially in developing countries, will require a simple and rapid test. In this study, we established a quick, one-step, single-tube, highly sensitive loop-mediated isothermal amplification (LAMP) assay for rapid detection of Leishmania DNA from tissue materials spotted on an FTA card. An FTA-LAMP with pre-added malachite green was performed at 64°C for 60min using a heating block and/or water bath and DNA amplification was detected immediately after incubation. The LAMP assay had high detection sensitivity down to a level of 0.01 parasites per μl. The field- and clinic-applicability of the colorimetric FTA-LAMP assay was demonstrated with 122 clinical samples collected from patients suspected of having cutaneous leishmaniasis in Peru, from which 71 positives were detected. The LAMP assay in combination with an FTA card described here is rapid and sensitive, as well as simple to perform, and has great potential usefulness for diagnosis and surveillance of leishmaniasis in endemic areas. Copyright © 2015 Elsevier B.V. All rights reserved.

Colorimetric sensing of anions in water using ratiometric indicator-displacement assay.

PubMed

Feng, Liang; Li, Hui; Li, Xiao; Chen, Liang; Shen, Zheng; Guan, Yafeng

2012-09-19

The analysis of anions in water presents a difficult challenge due to their low charge-to-radius ratio, and the ability to discriminate among similar anions often remains problematic. The use of a 3×6 ratiometric indicator-displacement assay (RIDA) array for the colorimetric detection and identification of ten anions in water is reported. The sensor array consists of different combinations of colorimetric indicators and metal cations. The colorimetric indicators chelate with metal cations, forming the color changes. Upon the addition of anions, anions compete with the indicator ligands according to solubility product constants (K(sp)). The indicator-metal chelate compound changes color back dramatically when the competition of anions wins. The color changes of the RIDA array were used as a digital representation of the array response and analyzed with standard statistical methods, including principal component analysis and hierarchical clustering analysis. No confusion or errors in classification by hierarchical clustering analysis were observed in 44 trials. The limit of detection was calculated approximately, and most limits of detections of anions are well below μM level using our RIDA array. The pH effect, temperature influence, interfering anions were also investigated, and the RIDA array shows the feasibility of real sample testing. Copyright © 2012 Elsevier B.V. All rights reserved.

Colorimetric analysis of outdoor illumination across varieties of atmospheric conditions.

PubMed

Peyvandi, Shahram; Hernández-Andrés, Javier; Olmo, F J; Nieves, Juan Luis; Romero, Javier

2016-06-01

Solar illumination at ground level is subject to a good deal of change in spectral and colorimetric properties. With an aim of understanding the influence of atmospheric components and phases of daylight on colorimetric specifications of downward radiation, more than 5,600,000 spectral irradiance functions of daylight, sunlight, and skylight were simulated by the radiative transfer code, SBDART [Bull. Am. Meteorol. Soc.79, 2101 (1998)], under the atmospheric conditions of clear sky without aerosol particles, clear sky with aerosol particles, and overcast sky. The interquartile range of the correlated color temperatures (CCT) for daylight indicated values from 5712 to 7757 K among the three atmospheric conditions. A minimum CCT of ∼3600  K was found for daylight when aerosol particles are present in the atmosphere. Our analysis indicated that hemispheric daylight with CCT less than 3600 K may be observed in rare conditions in which the level of aerosol is high in the atmosphere. In an atmosphere with aerosol particles, we also found that the chromaticity of daylight may shift along the green-purple direction of the Planckian locus, with a magnitude depending on the spectral extinction by aerosol particles and the amount of water vapor in the atmosphere. The data analysis showed that an extremely high value of CCT, in an atmosphere without aerosol particles, for daylight and skylight at low sun, is mainly due to the effect of Chappuis absorption band of ozone at ∼600  nm. In this paper, we compare our data with well-known observations from previous research, including the ones used by the CIE to define natural daylight illuminants.

Design of a colorimetric sensing platform using reflection mode plasmonic colour filters

NASA Astrophysics Data System (ADS)

Mudachathi, Renilkumar; Tanaka, Takuo

2017-08-01

Plasmonic nano structures fabricated using inexpensive and abundant aluminum metal shows intense narrow reflection peaks with strong response to the external stimuli, provides a simple yet powerful detection mechanism that is well suited for the development of low cost and low power sensors, such as colorimetric sensors, which transduces external stimuli or environmental changes in to visible colour changes. Such low cost and disposable sensors have huge demands in the point-of-care and home health care diagnostic applications. We present the design of a colorimetric sensing platform based on reflection mode plasmonic colour filters on both silicon and glass substrate, which demonstrate a sharp colour change for varying ambient refractive index. The sensor is essentially a plasmonic metamaterial in which the aluminum square plate hovering on a PMMA nano pillar in the background of a perforated aluminum reflector forms the unit cell which is arranged periodically in a 2D square lattice. The meta-surface has two distinct absorption peaks in the visible region leaving a strong reflection band, which strongly responds to the ambient refractive index change, provides a means for the realization of low cost colorimetric sensing platform.

A Versatile Nanowire Platform for Highly Efficient Isolation and Direct PCR-free Colorimetric Detection of Human Papillomavirus DNA from Unprocessed Urine

PubMed Central

Lee, HyungJae; Choi, Mihye; Hwang, Sang-Hyun; Cho, Youngnam

2018-01-01

Purpose: As human papillomavirus (HPV) is primarily responsible for the development of cervical cancer, significant efforts have been devoted to develop novel strategies for detecting and identifying HPV DNA in urine. The analysis of target DNA sequences in urine offers a potential alternative to conventional methods as a non-invasive clinical screening and diagnostic assessment tool for the detection of HPV. However, the lack of efficient approaches to isolate and directly detect HPV DNA in urine has restricted its potential clinical use. In this study, we demonstrated a novel approach of using polyethylenimine-conjugated magnetic polypyrrole nanowires (PEI-mPpy NWs) for the extraction, identification, and PCR-free colorimetric detection of high-risk strains of HPV DNA sequences, particularly HPV-16 and HPV-18, in urine specimens of cervical cancer patients. Materials and Methods: We fabricated and characterized polyethylenimine-conjugated magnetic nanowires (PEI/mPpy NWs). PEI/mPpy NWs-based HPV DNA isolation and detection strategy appears to be a cost-effective and practical technology with greater sensitivity and accuracy than other urine-based methods. Results: The analytical and clinical performance of PEI-mPpy NWs was evaluated and compared with those of cervical swabs, demonstrating a superior type-specific concordance rate of 100% between urine and cervical swabs, even when using a small volume of urine (300 µL). Conclusion: We envision that PEI-mPpy NWs provide substantive evidence for clinical diagnosis and management of HPV-associated disease with their excellent performance in the recovery and detection of HPV DNA from minimal amounts of urine samples. PMID:29290816

Optical and Electrochemical Aptasensors for Sensitive Detection of Streptomycin in Blood Serum and Milk.

PubMed

Ramezani, Mohammad; Abnous, Khalil; Taghdisi, Seyed Mohammad

2017-01-01

Detection and quantitation of antibiotic residues in blood serum and foodstuffs are in great demand. We have developed aptasensors for detection of streptomycin using electrochemical and optical methods. In the first method, an electrochemical aptasensor was developed for sensitive and selective detection of streptomycin, based on combination of exonuclease I (Exo I), complementary strand of aptamer (CS), arch shaped structure of aptamer (Apt)-CS conjugate, and gold electrode. The designed electrochemical aptasensor exhibited high selectivity toward streptomycin with a limit of detection (LOD) as low as 11.4 nM. Moreover, the developed electrochemical aptasensor was successfully used to detect streptomycin in milk and serum with LODs of 14.1 and 15.3 nM, respectively. In the second method, fluorescence quenching and colorimetric aptasensors were designed for detection of streptomycin based on aqueous gold nanoparticles (AuNPs) and double-stranded DNA (dsDNA). In the absence of streptomycin, aptamer/FAM-labeled complementary strand dsDNA is stable, resulting in the aggregation of AuNPs by salt bridge and an obvious color change from red to blue and strong emission of fluorescence. The colorimetric and fluorescence quenching aptasensors showed excellent selectivity toward streptomycin with limit of detections as low as 73.1 and 47.6 nM, respectively. The presented aptasensors were successfully used to detect streptomycin in milk and serum. For serum, LODs were determined to be 58.2 and 102.4 nM for fluorescence quenching and colorimetric aptasensors, respectively. For milk, LODs were calculated to be 56.2 and 108.7 nM for fluorescence quenching and colorimetric aptasensors, respectively.

Highly sensitive and robust peroxidase-like activity of Au-Pt core/shell nanorod-antigen conjugates for measles virus diagnosis.

PubMed

Long, Lin; Liu, Jianbo; Lu, Kaishun; Zhang, Tao; Xie, Yunqing; Ji, Yinglu; Wu, Xiaochun

2018-05-02

As a promising candidate for artificial enzymes, catalytically active nanomaterials show several advantages over natural enzymes, such as controlled synthesis at low cost, tunability of catalytic activities, and high stability under stringent conditions. Rod-shaped Au-Pt core/shell nanoparticles (Au@Pt NRs), prepared by Au nanorod-mediated growth, exhibit peroxidase-like activities and could serve as an inexpensive replacement for horseradish peroxidase, with potential applications in various bio-detections. The determination of measles virus is accomplished by a capture-enzyme-linked immunosorbent assay (ELISA) using Au@Pt NR-antigen conjugates. Based on the enhanced catalytic properties of this nanozyme probe, a linear response was observed up to 10 ng/mL measles IgM antibodies in human serum, which is 1000 times more sensitive than commercial ELISA. Hence, these findings provide positive proof of concept for the potential of Au@Pt NR-antigen conjugates in the development of colorimetric biosensors that are simple, robust, and cost-effective.

Colorimetric characterization of digital cameras with unrestricted capture settings applicable for different illumination circumstances

NASA Astrophysics Data System (ADS)

Fang, Jingyu; Xu, Haisong; Wang, Zhehong; Wu, Xiaomin

2016-05-01

With colorimetric characterization, digital cameras can be used as image-based tristimulus colorimeters for color communication. In order to overcome the restriction of fixed capture settings adopted in the conventional colorimetric characterization procedures, a novel method was proposed considering capture settings. The method calculating colorimetric value of the measured image contains five main steps, including conversion from RGB values to equivalent ones of training settings through factors based on imaging system model so as to build the bridge between different settings, scaling factors involved in preparation steps for transformation mapping to avoid errors resulted from nonlinearity of polynomial mapping for different ranges of illumination levels. The experiment results indicate that the prediction error of the proposed method, which was measured by CIELAB color difference formula, reaches less than 2 CIELAB units under different illumination levels and different correlated color temperatures. This prediction accuracy for different capture settings remains the same level as the conventional method for particular lighting condition.

A colorimetric aptasensor for sulfadimethoxine detection based on peroxidase-like activity of graphene/nickel@palladium hybrids.

PubMed

Wang, Aicheng; Zhao, Huimin; Chen, Xiaochi; Tan, Bing; Zhang, Yaobin; Quan, Xie

2017-05-15

A sensitive, rapid and label-free colorimetric aptasensor for sulfadimethoxine (SDM) detection was developed based on the tunable peroxidase-like activity of graphene/nickel@palladium nanoparticle (Gr/Ni@Pd) hybrids. The addition of the SDM aptamer could inhibit the peroxidase-like catalytic activity of the hybrids. However, the target SDM and aptamer could be triggered tightly and recover the catalytic activity of the Gr/Ni@Pd hybrids. Due to the peroxidase-like catalytic activity, Gr/Ni@Pd could catalyze the decomposition of H 2 O 2 with releasing hydroxyl radicals which further oxidized reagent 3, 3', 5, 5'-Tetramethylbenzidine (TMB) to oxTMB accompanied with a colorless-to-blue color change. The original color change could be applied to obtain quantitative detection of SDM, due to the relationship between the concentration of the target and the color difference. As a result, this approach performed a linear response for SDM from 1 to 500 ng/mL with a limit detection of 0.7 ng/mL (S/N = 3) under the optimized conditions and realized the detection of SDM in spiked lake water samples. Therefore, this colorimetric aptasensor was an alternative assay for SDM detection in real water. Moreover, with its design principle, this work might be applied to detecting other small molecule by employing appropriate aptamer. Copyright © 2017 Elsevier Inc. All rights reserved.

A novel cerium oxide nanoparticles-based colorimetric sensor using tetramethyl benzidine reagent for antioxidant activity assay.

PubMed

Ozdemir Olgun, F Ayca; Üzer, Ayşem; Ozturk, Birsen Demirata; Apak, Reşat

2018-05-15

Antioxidant activity (AOA) assays using nanotechnology are recently developed utilizing nanoparticles of transition metal oxides, especially nanoceria that can switch between trivalent and tetravalent oxidation states of cerium. Cerium oxide nanoparticles (CeO-NPs) may act as both an oxidant and an antioxidant, depending on the preparation method and particle size. A novel colorimetric sensor for AOA assay is proposed with the use of poly(acrylic acid) sodium salt (PAANa)-coated CeO-NPs. PAANa-coated CeO-NPs oxidized tetramethyl benzidine (TMB), a peroxidase substrate, in a slightly acidic solution at pH 4.0 to a blue charge-transfer complex. Antioxidants decreased the color intensity of the nanoceria suspension, and were indirectly determined by absorbance difference. Detection limits, linearity, additivity and precision were calculated, e.g., quercetin quantification with the proposed assay showed a detection limit of 8.25 × 10 -9 mol L -1 . The trolox equivalent antioxidant capacities of hydrophilic and lipophilic antioxidants were compatible with those of conventional antioxidant assays. Potential interferents such as glucose, citric acid, mannitol, sorbitol and benzoic acid did not adversely affect AOA determination. The developed sensor is more sensitive and selective than similar colorimetric sensors relying on the intrinsic color change of nanoceria. The measurement wavelength is sufficiently red-shifted, preventing possible interferences from plant pigments. Copyright © 2018 Elsevier B.V. All rights reserved.

Evaluation of a Colorimetric Personal Dosimeter for Nitrogen Oxide.

ERIC Educational Resources Information Center

Diamond, Philip

A personal colorimetric dosimeter for nitrogen dioxide was developed. Tests were performed to determine the response of these strips to various concentrations of NO2. The dosimeter strips were satisfactory for approximate determinations of total exposure (concentration + time) of nitrogen dioxide. The total exposure was calculated in terms of time…

Highly sensitive on-site detection of glucose in human urine with naked eye based on enzymatic-like reaction mediated etching of gold nanorods.

PubMed

Zhang, Zhiyang; Chen, Zhaopeng; Cheng, Fangbin; Zhang, Yaowen; Chen, Lingxin

2017-03-15

Based on enzymatic-like reaction mediated etching of gold nanorods (GNRs), an ultrasensitive visual method was developed for on-site detection of urine glucose. With the catalysis of MoO 4 2 - , GNRs were efficiently etched by H 2 O 2 which was generated by glucose-glucose oxidase enzymatic reaction. The etching of GNRs lead to a blue-shift of logitudinal localized surface plasmon resonance of GNRs, accompanied by an obvious color change from blue to red. The peak-shift and the color change can be used for detection of glucose by the spectrophotometer and the naked eyes. Under optimal condition, an excellent sensitivity toward glucose is obtained with a detection limit of 0.1μM and a visual detection limit of 3μM in buffer solution. Benefiting from the high sensitivity, the successful colorimetric detection of glucose in original urine samples was achieved, which indicates the practical applicability to the on-site determination of urine glucose. Copyright © 2016 Elsevier B.V. All rights reserved.

A colorimetric and ratiometric fluorescent chemosensor for fluoride based on proton transfer.

PubMed

Jia, Chuandong; Wu, Biao; Liang, Jianjun; Huang, Xiaojuan; Yang, Xiao-Juan

2010-01-01

N-Phenyl-N'-(3-quinolinyl)urea (1) has been developed as a highly selective colorimetric and ratiometric fluorescent chemosensor for fluoride ion based on a proton transfer mechanism. Evidences for the mechanism were provided by UV-vis and fluorescence titration and especially (1)H and (19)F NMR experiments. The sensor gave the largest ratiometric fluorescent response reported so far (R(max)/R(min) = 2620) to fluoride. Taking H(+) as the "recovering reagent", the sensor can be reversibly "used" and "recovered" for several cycles with only a slight decay of the response ability.

A novel fluoride ion colorimetric chemosensor based on coumarin.

PubMed

Zhuang, Xiaoqing; Liu, Weimin; Wu, Jiasheng; Zhang, Hongyan; Wang, Pengfei

2011-09-01

A novel visible colorimetric sensor (L1) with high selectivity for fluoride ion based on coumarin has been synthesized by a simple modification of our earlier report. The chemosensor L1 shows an obvious color change from yellow to blue upon addition of fluoride ion with a large red shift of 145 nm in acetonitrile, and without interference of other anions such as Cl-, Br-, I-, NO3-, H2PO4-, HSO4-, and AcO-. The investigation of 1H NMR spectrum titration indicates the proposed mechanism is that F- first establishes a hydrogen bonding interaction with L1, and then the formation of [F-H-F]- induces deprotonation. Copyright © 2011 Elsevier B.V. All rights reserved.

Nano-textured high sensitivity ion sensitive field effect transistors

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

Hajmirzaheydarali, M.; Sadeghipari, M.; Akbari, M.

2016-02-07

Nano-textured gate engineered ion sensitive field effect transistors (ISFETs), suitable for high sensitivity pH sensors, have been realized. Utilizing a mask-less deep reactive ion etching results in ultra-fine poly-Si features on the gate of ISFET devices where spacing of the order of 10 nm and less is achieved. Incorporation of these nano-sized features on the gate is responsible for high sensitivities up to 400 mV/pH in contrast to conventional planar structures. The fabrication process for this transistor is inexpensive, and it is fully compatible with standard complementary metal oxide semiconductor fabrication procedure. A theoretical modeling has also been presented to predict themore » extension of the diffuse layer into the electrolyte solution for highly featured structures and to correlate this extension with the high sensitivity of the device. The observed ultra-fine features by means of scanning electron microscopy and transmission electron microscopy tools corroborate the theoretical prediction.« less

Developing and Demonstrating an Augmented Reality Colorimetric Titration Tool

ERIC Educational Resources Information Center

Tee, Nicholas Yee Kwang; Gan, Hong Seng; Li, Jonathan; Cheong, Brandon Huey-Ping; Tan, Han Yen; Liew, Oi Wah; Ng, Tuck Wah

2018-01-01

The handling of chemicals in the laboratory presents a challenge in instructing large class sizes and when students are relatively new to the laboratory environment. In this work, we describe and demonstrate an augmented reality colorimetric titration tool that operates out of the smartphone or tablet of students. It allows multiple students to…

Highly sensitive, colorimetric detection of mercury(II) in aqueous media by quaternary ammonium group-capped gold nanoparticles at room temperature.

PubMed

Liu, Dingbin; Qu, Weisi; Chen, Wenwen; Zhang, Wei; Wang, Zhuo; Jiang, Xingyu

2010-12-01

We provide a highly sensitive and selective assay to detect Hg(2+) in aqueous solutions using gold nanoparticles modified with quaternary ammonium group-terminated thiols at room temperature. The mechanism is the abstraction of thiols by Hg(2+) that led to the aggregation of nanoparticles. With the assistance of solar light irradiation, the detection limit can be as low as 30 nM, which satisfies the guideline concentration of Hg(2+) in drinking water set by the WHO. In addition, the dynamic range of detection is wide (3 × 10(-8)-1 × 10(-2) M). This range, to our best knowledge, is the widest one that has been reported so far in gold nanoparticle (AuNP)-based assays for Hg(2+).

Effect of black point on accuracy of LCD displays colorimetric characterization

NASA Astrophysics Data System (ADS)

Li, Tong; Xie, Kai; He, Nannan; Ye, Yushan

2018-03-01

Black point is the point at which RGB's single channel digital drive value is 0. Due to the problem of light leakage of liquid-crystal displays (LCDs), black point's luminance value is not 0, this phenomenon bring some errors to colorimetric characterization of LCDs, especially low luminance value driving greater sampling effect. This paper describes the characteristic accuracy of polynomial model method and the effect of black point on accuracy, the color difference accuracy is given. When considering the black point in the characteristics equation, the maximum color difference is 3.246, the maximum color difference than without considering the black points reduced by 2.36. The experimental results show that the accuracy of LCDs colorimetric characterization can be improved, if the effect of black point is eliminated properly.

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

PubMed

Růzicka, F; Holá, V

2008-02-01

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

Modeling colorimetric characteristics of ON-OFF behavior of photochromic dyes based on bis-azospiropyrans

NASA Astrophysics Data System (ADS)

Kandi, Saeideh Gorji; Nourmohammadian, Farahnaz

2013-10-01

In the present study, colorimetric characteristics of six photochromic bis-azospiropyrans based dyes are investigated. The colorimetric axes of these dyes in terms of hue, chroma and lightness are considered via UV exposure time. Results showed that, the hue angle of these dyes changes rapidly at the first times of UV irradiation, and then remains almost constant. However, chroma and lightness continuously change till about 80-240 s for different dyes. In addition, it is shown that variations of lightness and chroma by UV exposure time have an exponential trend, which can be modeled mathematically.

Rapid and Sensitive Colorimetric ELISA using Silver Nanoparticles, Microwaves and Split Ring Resonator Structures

PubMed Central

Addae, Sarah A.; Pinard, Melissa A.; Caglayan, Humeyra; Cakmakyapan, Semih; Caliskan, Deniz; Ozbay, Ekmel; Aslan, Kadir

2010-01-01

We report a new approach to colorimetric Enzyme-Linked Immunosorbent Assay (ELISA) that reduces the total assay time to < 2 min and the lower-detection-limit by 100-fold based on absorbance readout. The new approach combines the use of silver nanoparticles, microwaves and split ring resonators (SRR). The SRR structure is comprised of a square frame of copper thin film (30 µm thick, 1 mm wide, overall length of ~9.4 mm on each side) with a single split on one side, which was deposited onto a circuit board (2×2 cm2). A single micro-cuvette (10 µl volume capacity) was placed in the split of the SRR structures. Theoretical simulations predict that electric fields are focused in and above the micro-cuvette without the accumulation of electrical charge that breaks down the copper film. Subsequently, the walls and the bottom of the micro-cuvette were coated with silver nanoparticles using a modified Tollen’s reaction scheme. The silver nanoparticles served as a mediator for the creation of thermal gradient between the bioassay medium and the silver surface, where the bioassay is constructed. Upon exposure to low power microwave heating, the bioassay medium in the micro-cuvette was rapidly and uniformly heated by the focused electric fields. In addition, the creation of thermal gradient resulted in the rapid assembly of the proteins on the surface of silver nanoparticles without denaturing the proteins. The proof-of-principle of the new approach to ELISA was demonstrated for the detection of a model protein (biotinylated-bovine serum albumin, b-BSA). In this regard, the detection of b-BSA with bulk concentrations (1 µM to 1 pM) was carried out on commercially available 96-well high throughput screening (HTS) plates and silver nanoparticle-deposited SRR structures at room temperature and with microwave heating, respectively. While the room temperature bioassay (without microwave heating) took 70 min to complete, the identical bioassay took < 2 min to complete using

Microfluidic immunosensor for rapid and highly-sensitive salivary cortisol quantification.

PubMed

Pinto, V; Sousa, P; Catarino, S O; Correia-Neves, M; Minas, G

2017-04-15

This paper presents a novel poly(dimethylsiloxane) (PDMS) microfluidic immunosensor that integrates a complementary metal-oxide-semiconductor (CMOS) optical detection system for a rapid and highly-sensitive quantification of salivary cortisol. The simple and non-invasive method of saliva sampling provides an interesting alternative to the blood, allowing a fast sampling at short intervals, relevant for many clinical diagnostic applications. The developed approach is based on the covalent immobilization of a coating antibody (Ab), a polyclonal anti-IgG, onto a treated PDMS surface. The coating Ab binds the capture Ab, an IgG specific for cortisol, allowing its correct orientation. Horseradish peroxidase (HRP)-labelled cortisol is added to compete with the cortisol in the sample, for the capture Ab binding sites. The HRP-labelled cortisol, bonded to the capture Ab, is measured through the HRP enzyme and the tetramethylbenzidine (TMB) substrate reaction. The cortisol quantification is performed by colorimetric detection of HRP-labelled cortisol, through optical absorption at 450nm, using a CMOS silicon photodiode as the photodetector. Under the developed optimized conditions presented here, e.g., microfluidic channels geometry, immobilization method and immunoassay conditions, the immunosensor shows a linear range of detection between 0.01-20ng/mL, a limit of detection (LOD) of 18pg/mL and an analysis time of 35min, featuring a great potential for point-of-care applications requiring continuous monitoring of the salivary cortisol levels during a circadian cycle. Copyright © 2016 Elsevier B.V. All rights reserved.

Colorimetric micro-assay for accelerated screening of mould inhibitors

Treesearch

Carol A. Clausen; Vina W. Yang

2013-01-01

Since current standard laboratory methods are time-consuming macro-assays that rely on subjective visual ratings of mould growth, rapid and quantitative laboratory methods are needed to screen potential mould inhibitors for use in and on cellulose-based products. A colorimetric micro-assay has been developed that uses XTT tetrazolium salt to enzymatically assess...

Method for estimating effects of unknown correlations in spectral irradiance data on uncertainties of spectrally integrated colorimetric quantities

NASA Astrophysics Data System (ADS)

Kärhä, Petri; Vaskuri, Anna; Mäntynen, Henrik; Mikkonen, Nikke; Ikonen, Erkki

2017-08-01

Spectral irradiance data are often used to calculate colorimetric properties, such as color coordinates and color temperatures of light sources by integration. The spectral data may contain unknown correlations that should be accounted for in the uncertainty estimation. We propose a new method for estimating uncertainties in such cases. The method goes through all possible scenarios of deviations using Monte Carlo analysis. Varying spectral error functions are produced by combining spectral base functions, and the distorted spectra are used to calculate the colorimetric quantities. Standard deviations of the colorimetric quantities at different scenarios give uncertainties assuming no correlations, uncertainties assuming full correlation, and uncertainties for an unfavorable case of unknown correlations, which turn out to be a significant source of uncertainty. With 1% standard uncertainty in spectral irradiance, the expanded uncertainty of the correlated color temperature of a source corresponding to the CIE Standard Illuminant A may reach as high as 37.2 K in unfavorable conditions, when calculations assuming full correlation give zero uncertainty, and calculations assuming no correlations yield the expanded uncertainties of 5.6 K and 12.1 K, with wavelength steps of 1 nm and 5 nm used in spectral integrations, respectively. We also show that there is an absolute limit of 60.2 K in the error of the correlated color temperature for Standard Illuminant A when assuming 1% standard uncertainty in the spectral irradiance. A comparison of our uncorrelated uncertainties with those obtained using analytical methods by other research groups shows good agreement. We re-estimated the uncertainties for the colorimetric properties of our 1 kW photometric standard lamps using the new method. The revised uncertainty of color temperature is a factor of 2.5 higher than the uncertainty assuming no correlations.

Visual detection of organophosphorus pesticides represented by mathamidophos using Au nanoparticles as colorimetric probe.

PubMed

Li, Hongkun; Guo, Jiajia; Ping, Hong; Liu, Lurui; Zhang, Minwei; Guan, Fengrui; Sun, Chunyan; Zhang, Qian

2011-12-15

With citrate-coated Au nanoparticles as colorimetric probe, a novel visual method for rapid assay of organophosphorus pesticides has been developed. The assay principle is based on catalytic hydrolysis of acetylthiocholine into thiocholine by acetylcholinesterase, which induces the aggregation of Au nanoparticles and the color change from claret-red to purple or even grey. The original plasmon absorption of Au nanoparticles at 522 nm decreases, and simultaneously, a new absorption band appears at 675 nm. The irreversible inhibition of organophosphorus pesticides on acetylcholinesterase prevents aggregation of Au nanoparticles. Under optimum conditions, the absorbance at 522 nm of Au nanoparticles is related linearly to the concentration of mathamidophos in the range of 0.02-1.42 μg/mL with a detection limit of 1.40 ng/mL. This colorimetric method has been successfully utilized to detect mathamidophos in vegetables with satisfactory results. The proposed colorimetric assay exhibits good reproducibility and accuracy, providing a simple and rapid method for the analysis of organophosphorus pesticides. Copyright © 2011 Elsevier B.V. All rights reserved.

Colorimetric Assay for Determination of Lead (II) Based on Its Incorporation into Gold Nanoparticles during Their Synthesis

PubMed Central

Ding, Nan; Cao, Qian; Zhao, Hong; Yang, Yimin; Zeng, Lixi; He, Yujian; Xiang, Kaixiang; Wang, Guangwei

2010-01-01

In this report, we present a new method for visual detection of Pb2+. Gold nanoparticles (Au-NPs) were synthesized in one step at room temperature, using gallic acid (GA) as reducer and stabilizer. Pb2+ is added during the gold nanoparticle formation. Analysis of Pb2+ is conducted by a dual strategy, namely, colorimetry and spectrometry. During Au-NPs synthesis, addition of Pb2+ would lead to formation of Pb-GA complex, which can induce the aggregation of newly-formed small unstable gold nanoclusters. Consequently, colorimetric detection of trace Pb2+ can be realized. As the Pb2+ concentration increases, the color turns from red-wine to purple, and finally blue. This method offers a sensitive linear correlation between the shift of the absorption band (Δλ) and logarithm of Pb2+ concentration ranging from 5.0 × 10−8 to 1.0 × 10−6 M with a linear fit coefficient of 0.998, and a high selectivity for Pb2+ detection with a low detection limit down to 2.5 × 10−8 M. PMID:22163517

[Colorimetric characterization of LCD based on wavelength partition spectral model].

PubMed

Liu, Hao-Xue; Cui, Gui-Hua; Huang, Min; Wu, Bing; Xu, Yan-Fang; Luo, Ming

2013-10-01

To establish a colorimetrical characterization model of LCDs, an experiment with EIZO CG19, IBM 19, DELL 19 and HP 19 LCDs was designed and carried out to test the interaction between RGB channels, and then to test the spectral additive property of LCDs. The RGB digital values of single channel and two channels were given and the corresponding tristimulus values were measured, then a chart was plotted and calculations were made to test the independency of RGB channels. The results showed that the interaction between channels was reasonably weak and spectral additivity property was held well. We also found that the relations between radiations and digital values at different wavelengths varied, that is, they were the functions of wavelength. A new calculation method based on piecewise spectral model, in which the relation between radiations and digital values was fitted by a cubic polynomial in each piece of wavelength with measured spectral radiation curves, was proposed and tested. The spectral radiation curves of RGB primaries with any digital values can be found out with only a few measurements and fitted cubic polynomial in this way and then any displayed color can be turned out by the spectral additivity property of primaries at given digital values. The algorithm of this method was discussed in detail in this paper. The computations showed that the proposed method was simple and the number of measurements needed was reduced greatly while keeping a very high computation precision. This method can be used as a colorimetrical characterization model.

Silicon micro sensors as integrated readout platform for colorimetric and fluorescence based opto-chemical transducers

NASA Astrophysics Data System (ADS)

Will, Matthias; Martan, Tomas; Brodersen, Olaf

2011-09-01

Opto-chemical transducer almost offers unlimited possibilities for detection of physical quantities. New technologies and research show a steady increasing of publications in the area of sensoric principles. For transfer to real world applications the optical response has to be converted into an electrical signal. An exceptional opto chemical transducer loses the attraction if complex and expensive instruments for analysis are requires. Therefore, the readout system must be very compact and producible for low cost. In this presentation, the technology platform as a solution for these problems will be presented. We combine micro structuring of silicon, photodiode fabrication, chip in chip mounting and novel assembly technologies for creation of a flexible sensor platform. This flexible combination of technologies allows fabricating a family of planar optical remission sensors. With variation of design and modifications, we are able to detect colorimetric, fluorescent properties of an sensitive layer attached on the sensor surface. In our sensor with typical size of 6mm x 6mm x 1mm different emitting sources based on LED's or laser diodes, multiple detection cannels for the remitted light and also measurement of temperature are included. Based on these sensors we proof the concept by demonstrating sensors for oxygen, carbon dioxide and ammonia based on colorimetric and fluorescent changes in the transducer layer. In both configurations, LED's irradiated the sensitive polymer layer through a transparent substrate. The absorption or fluorescence properties of dyed polymer are changed by the chemical reaction and light response is detected by PIN diodes. The signal shift is analyzed by using a computer controlled evaluation board of own construction. Accuracy and reliability of the remission sensor system were verified and the whole sensor system was experimentally tested in the range of concentrations from 50 ppm up to 100 000 ppm for CO2 and O2 Furthermore, we develop

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

PubMed

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

2007-05-15

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

Paper-Plastic Hybrid Microfluidic Device for Smartphone-Based Colorimetric Analysis of Urine.

PubMed

Jalal, Uddin M; Jin, Gyeong Jun; Shim, Joon S

2017-12-19

In this work, a disposable paper-plastic hybrid microfluidic lab-on-a-chip (LOC) has been developed and successfully applied for the colorimetric measurement of urine by the smartphone-based optical platform using a "UrineAnalysis" Android app. The developed device was cost-effectively implemented as a stand-alone hybrid LOC by incorporating the paper-based conventional reagent test strip inside the plastic-based LOC microchannel. The LOC device quantitatively investigated the small volume (40 μL) of urine analytes for the colorimetric reaction of glucose, protein, pH, and red blood cell (RBC) in integration with the finger-actuating micropump. On the basis of our experiments, the conventional urine strip showed large deviation as the reaction time goes by, because dipping the strip sensor in a bottle of urine could not control the reaction volume. By integrating the strip sensor in the LOC device for urine analysis, our device significantly improves the time-dependent inconstancy of the conventional dipstick-based urine strip, and the smartphone app used for image analysis enhances the visual assessment of the test strip, which is a major user concern for the colorimetric analysis in point-of-care (POC) applications. As a result, the user-friendly LOC, which is successfully implemented in a disposable format with the smartphone-based optical platform, may be applicable as an effective tool for rapid and qualitative POC urinalysis.

A Colorimetric Sensor for Qualitative Discrimination and Quantitative Detection of Volatile Amines

PubMed Central

Tang, Zhonglin; Yang, Jianhua; Yu, Junyun; Cui, Bo

2010-01-01

We have developed a novel colorimetric sensor based on a digital camera and white LED illumination. Colorimetric sensor arrays (CSAs) were made from a set of six chemically responsive dyes impregnated on an inert substrate plate by solution casting. Six common amine aqueous solutions, including dimethylamine, triethylamine, diisopropylamine, aniline, cyclohexylamine, and pyridine vaporized at 25 °C and six health-related trimethylamine (TMA) concentrations including 170 ppm, 51 ppm, 8 ppm, 2 ppm, 125 ppb and 50 ppb were analyzed by the sensor to test its ability for the qualitative discrimination and quantitative detection of volatile amines. We extracted the feature vectors of the CSA's response to the analytes from a fusional color space, which was obtained by conducting a joint search algorithm of sequential forward selection and sequential backward selection (SFS&SBS) based on the linear discriminant criteria (LDC) in a mixed color space composed of six common color spaces. The principle component analysis (PCA) followed by the hierarchical cluser analysis (HCA) were utilized to discriminate 12 analytes. Results showed that the colorimetric sensor grouped the six amine vapors and five TMA concentrations correctly, while TMA concentrations of 125 ppb and 50 ppb were indiscriminable from each other. The limitation of detection (LOD) of the sensor for TMA was found to be lower than 50 ppb. The CSAs were reusable for TMA concentrations below 8 ppm. PMID:22163560

Colorimetric detection of melamine based on p-chlorobenzenesulfonic acid-modified AuNPs

NASA Astrophysics Data System (ADS)

Li, Jianfang; Huang, Pengcheng; Wu, Fangying

2016-06-01

A highly selective and sensitive method is developed for colorimetric detection of melamine using gold nanoparticles (AuNPs) functionalized with p-chlorobenzenesulfonic acid. The addition of melamine induced the aggregation of AuNPs, as evidenced from the morphological characterizations and the color changed from red wine to blue, which could also be monitored by the UV-visible spectrometer and even naked eyes. This process caused a significant increase in the absorbance ratio (A650nm/A520nm) of p-chlorobenzenesulfonic acid-AuNPs. Under optimized conditions, the system exhibited a linear response to melamine in the range of 6.0 × 10-7-1.5 × 10-6 mol L-1 with a correlation coefficient of 0.997, and the limit of detection can even be 2.3 nM, which was much lower than some other methods and the safe limits (20 μM in both the USA and EU, 8.0 μM for infant formula in China, 1.2 μM in the CAC (Codex Alimentarius Commission) review for melamine in liquid infant formula). More importantly, the developed method presented excellent tolerance to coexisting common metal ions such as Ca2+, Zn2+, whose concentration is 1000 times of melamine, so that it had been applied to the analysis of melamine in liquid milk and milk powder with the recovery of 97.0-101 % and 100-103 %, respectively, indicating that the proposed method is quite a highly effective means to determine melamine in milk products.

High-sensitivity ESCA instrument

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

Davies, R.D.; Herglotz, H.K.; Lee, J.D.

1973-01-01

A new electron spectroscopy for chemical analysis (ESCA) instrument has been developed to provide high sensitivity and efficient operation for laboratory analysis of composition and chemical bonding in very thin surface layers of solid samples. High sensitivity is achieved by means of the high-intensity, efficient x-ray source described by Davies and Herglotz at the 1968 Denver X-Ray Conference, in combination with the new electron energy analyzer described by Lee at the 1972 Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy. A sample chamber designed to provide for rapid introduction and replacement of samples has adequate facilities for various sample treatmentsmore » and conditiouing followed immediately by ESCA analysis of the sample. Examples of application are presented, demonstrating the sensitivity and resolution achievable with this instrument. Its usefulness in trace surface analysis is shown and some chemical shifts'' measured by the instrument are compared with those obtained by x-ray spectroscopy. (auth)« less

Design, Certification, and Deployment of the Colorimetric Water Quality Monitoring Kit (CWQMK)

NASA Technical Reports Server (NTRS)

Gazda, Daniel B.; Nolan, Daniel J.; Rutz, Jeff A.; Schultz, John R.; Siperko, Lorraine M.; Porter, Marc D.; Lipert, Robert J.; Flint, Stephanie M.; McCoy, J. Torin

2010-01-01

In August 2009, an experimental water quality monitoring kit based on Colorimetric Solid Phase Extraction (CSPE) technology was delivered to the International Space Station (ISS) aboard STS-128/17A. The kit, called the Colorimetric Water Quality Monitoring Kit (CWQMK), was flown and deployed as a Station Development Test Objective (SDTO) experiment on the ISS. The goal of the SDTO experiment is to evaluate the acceptability of CSPE technology for routine water quality monitoring on the ISS. This paper provides an overview of the SDTO experiment, as well as a detailed description of the CWQMK hardware and a summary of the testing and analysis conducted to certify the CWQMK for use on the ISS. The initial results obtained from the SDTO experiment are also reported and discussed in detail

Measurement of Chlorine Dioxide in Water by DPD Colorimetric Method

NASA Astrophysics Data System (ADS)

Song, Min; Yan, Panping; Yao, Jun

2018-01-01

In order to solve the problems of chlorine dioxide in water by DPD colorimetric method, this paper discusses the effects of the formulation, temperature, color development time and amount of color reagent on the measurement process, improving the on-line instrument for domestic and drinking water in chlorine dioxide measurement precision and accuracy.

Polyhedral Oligomeric Silsesquioxane Polymer-Caged Silver Nanoparticle as a Smart Colorimetric Probe for the Detection of Hydrogen Sulfide.

PubMed

Zhang, Yue; Shen, Hui-Yan; Hai, Xin; Chen, Xu-Wei; Wang, Jian-Hua

2017-01-17

The rapid and accurate detection of hydrogen sulfide is of great concern due to its unique role on environmental pollution and signal transmission in physiological systems. Herein, we report a smart colorimetric probe for the selective detection of H 2 S. The probe is prepared via a surfactant-free route with cross-linked polyhedral oligomeric silsesquioxane (POSS) polymer cage as capping ligand and reducing agent under microwave irradiation, called poly-POSS-formaldehyde polymer (PPF) cage-AgNPs or PPF-AgNPs for short. The caged silver nanoparticles are well-dispersed with narrow size distribution within 6.0-8.4 nm. Chloride ions and aldehyde groups in PPF make the nucleation and growth of Ag nanoparticles accomplished within a very short time of 1 min. The positively charged PPF-AgNPs exhibit excellent selectivity to H 2 S against other anionic species and thiols due to the specific Ag-H 2 S interaction, where the favorable protection effect of PPF polymer cage from the nanoparticle aggregation is demonstrated. The colorimetric probe presents a quick response to H 2 S (<3 min) and favorable sensitivity within a linear range of 0.7-10 μM along with a detection limit of 0.2 μM. The probe is well demonstrated by analysis of H 2 S in various water and biological samples.

Enhancing the peroxidase-like activity of ficin via heme binding and colorimetric detection for uric acid.

PubMed

Pan, Yadi; Yang, Yufang; Pang, Yanjiao; Shi, Ying; Long, Yijuan; Zheng, Huzhi

2018-08-01

Ficin, a classical sulfhydryl protease, was found to possess intrinsic peroxidase-like activity. In this paper, we have put forward a novel strategy to improving the peroxidase-like activity of ficin through binding heme. Heme-ficin complexes were successfully obtained by simple one-step syntheticism. The results demonstrated that the catalytic activity and efficiency of heme-ficin complexes were about 1.7 times and 3 times higher than those of native ficin, respectively. Taking advantages of the high peroxidase-like activity, the heme-ficin complexes were used for colorimetric determination of uric acid with a low detection limit of 0.25 μM. Based on the excellent selectivity and sensitivity, we detected the concentration of uric acid in human serum successfully. On the basis of these findings, the heme-ficin complexes are promising for wide applications in various fields. Thus we not only optimized the peroxidase-like activity of the ficin, but also established a new strategy for development of artificial enzyme mimics by mimicking the architecture of the active site in horseradish peroxidase. Copyright © 2018 Elsevier B.V. All rights reserved.

Design of a dual-function peptide probe as a binder of angiotensin II and an inducer of silver nanoparticle aggregation for use in label-free colorimetric assays.

PubMed

Okochi, Mina; Kuboyama, Masashi; Tanaka, Masayoshi; Honda, Hiroyuki

2015-09-01

Label-free colorimetric assays using metallic nanoparticles have received much recent attention, for their application in simple and sensitive methods for detection of biomolecules. Short peptide probes that can bind to analyte biomolecules are attractive ligands in molecular nanotechnology; however, identification of biological recognition motifs is usually based on trial-and-error experiments. Herein, a peptide probe was screened for colorimetric detection of angiotensin II (Ang II) using a mechanism for non-crosslinking aggregation of silver nanoparticles (AgNPs). The dual-function peptides, which bind to the analyte and induce AgNP aggregation, were identified using a two-step strategy: (1) screening of an Ang II-binding peptide from an Ang II receptor sequence library, using SPOT technology, which enable peptides synthesis on cellulose membranes via an Fmoc method and (2) selection of peptide probes that effectively induce aggregation of AgNPs using a photolinker modified peptide array. Using the identified peptide probe, KGKNKRRR, aggregation of AgNPs was detected by observation of a pink color in the absence of Ang II, whereas AgNPs remained dispersed in the presence of Ang II (yellow). The color changes were not observed in the presence of other hormone molecules. Ang II could be detected within 15 min, with a detection limit of 10 µM, by measuring the ratio of absorbance at 400 nm and 568 nm; the signal could also be observed with the naked eye. These data suggest that the peptide identified here could be used as a probe for simple and rapid colorimetric detection of Ang II. This strategy for the identification of functional peptides shows promise for the development of colorimetric detection of various diagnostically important biomolecules. Copyright © 2015 Elsevier B.V. All rights reserved.

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

PubMed

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

2015-03-14

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

Oligothiophene-based colorimetric and ratiometric fluorescence dual-channel cyanide chemosensor: Sensing ability, TD-DFT calculations and its application as an efficient solid state sensor

NASA Astrophysics Data System (ADS)

Lan, Linxin; Li, Tianduo; Wei, Tao; Pang, He; Sun, Tao; Wang, Enhua; Liu, Haixia; Niu, Qingfen

2018-03-01

An oligothiophene-based colorimetric and ratiometric fluorescence dual-channel cyanide chemosensor 3 T-2CN was reported. Sensor 3 T-2CN showed both naked-eye recognition and ratiometric fluorescence response for CN- with an excellent selectivity and high sensitivity. The sensing mechanism based on the nucleophilic attack of CN- on the vinyl Cdbnd C bond has been successfully confirmed by the optical measurements, 1H NMR titration, FT-IR spectra as well as the DFT/TD-DFT calculations. Moreover, the detection limit was calculated to be 0.19 μM, which is much lower than the maximum permission concentration in drinking water (1.9 μM). Importantly, test strips (filter paper and TLC plates) containing 3 T-2CN were fabricated, which could act as a practical and efficient solid state optical sensor for CN- in field measurements.

Colorimetric assay for urinary track infection disease diagnostic on flexible substrate

NASA Astrophysics Data System (ADS)

Safavieh, Mohammadali; Ahmed, Minhaz Uddin; Zourob, Mohammed

2012-10-01

We are presenting cassette as a novel point of care diagnostic device. This device is easy to use, low cost to prepare, high throughput and can analyze several samples at the same time. We first, demonstrate the preparation method of the device. Then, fabrication of the flexible substrate has been presented. The device has been used for detection of the real sample of E.coli bacteria following by colorimetric detection. We have shown that we could detect 30 cfu/ml bacteria and 100 fg/μl of Staphylococous aureus DNA in 1 hr using LAMP amplification technique. This device will be helpful in hospitals and doctor's office for analysis of several patients' samples at the same time.

A colorimetric sensor array of porous pigments.

PubMed

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

2009-12-01

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

A colorimetric sensor array of porous pigments

PubMed Central

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

2010-01-01

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

Highly selective and sensitive coumarin-triazole-based fluorometric 'turn-off' sensor for detection of Pb2+ ions.

PubMed

Shaily; Kumar, Ajay; Parveen, Iram; Ahmed, Naseem

2018-06-01

Exposure to even very low concentrations of Pb 2+ is known to cause cardiovascular, neurological, developmental, and reproductive disorders, and affects children in particular more severely. Consequently, much effort has been dedicated to the development of colorimetric and fluorescent sensors that can selectively detect Pb 2+ ions. Here, we describe the development of a triazole-based fluorescent sensor L5 for Pb 2+ ion detection. The fluorescence intensity of chemosensor L5 was selectively quenched by Pb 2+ ions and a clear color change from colorless to yellow could be observed by the naked eye. Chemosensor L5 exhibited high sensitivity and selectivity towards Pb 2+ ions in phosphate-buffered solution [20 mM, 1:9 DMSO/H 2 O (v/v), pH 8.0] with a 1:1 binding stoichiometry, a detection limit of 1.9 nM and a 6.76 × 10 6  M -1 binding constant. Additionally, low-cost and easy-to-prepare test strips impregnated with chemosensor L5 were also produced for efficient of Pb 2+ detection and proved the practical use of this test. Copyright © 2018 John Wiley & Sons, Ltd.

Identification of human flavin-containing monooxygenase 3 substrates by a colorimetric screening assay.

PubMed

Catucci, Gianluca; Polignano, Isabelle; Cusumano, Debora; Medana, Claudio; Gilardi, Gianfranco; Sadeghi, Sheila J

2017-04-01

Human hepatic flavin-containing monooxygenase 3 is a phase I drug-metabolizing enzyme that is responsible for the oxidation of a variety of drugs and xenobiotics. This work reports on a high throughput rapid colorimetric assay for the screening of substrates or inhibitors of this enzyme. The method is based on the competition of two substrates for access to the active site of hFMO3 whereby the enzymatic product of the first drug converts nitro-5-thiobenzoate (TNB, yellow) to 5,5'-dithiobis (2-nitrobenzoate) (DTNB, colourless). Upon addition of a competing substrate, the amount of detected DNTB is decreased. The assay is validated testing three known substrates of hFMO3, namely benzydamine, tozasertib and tamoxifen. The latter drugs resulted in 41%-55% inhibition. In addition, two other drugs also classified as doping drugs, selegiline and clomiphene, were selected based on their chemical structure similarity to known substrates of hFMO3. These drugs showed 21% and 60% inhibition in the colorimetric assay and therefore were proven to be hFMO3 substrates. LC-MS was used to confirm their N-oxide products. Further characterisation of these newly identified hFMO3 substrates was performed determining their K m and k cat values that resulted to be 314 μM and 1.4 min -1 for selegiline and, 18 μM and 0.1 min -1 for clomiphene. This method paves the way for a rapid automated high throughput screening of nitrogen-containing compounds as substrates/inhibitors of hFMO3. Copyright © 2017 Elsevier Inc. All rights reserved.

Gold nanorods for in-drop colorimetric determination of thiomersal after photochemical decomposition.

PubMed

Martín-Alonso, Manuel; Pena-Pereira, Francisco; Lavilla, Isela; Bendicho, Carlos

2018-03-13

This work reports on the implementation of gold nanorods (AuNRs) in headspace solvent microextraction for colorimetric determination of volatile analyte derivatives in a single drop. The exposure of AuNRs to both H 2 Se and elemental mercury (Hg 0 ) results in a shift of the longitudinal plasmonic band, unlike a number of volatiles. Accordingly, a method is reported for the determination of Hg 0 with potential applicability to the determination of thiomersal (sodium ethylmercurithiosalicylate). It is based on the photochemical decomposition of thiomersal into Hg(II) and subsequent exposure of AuNRs-containing microdrop to in situ generated Hg 0 . Colorimetric analysis of the enriched drop was carried out without dilution by means of a cuvetteless microvolume UV-vis spectrometer. Under optimal conditions, the limit of detection was 0.5 ng mL -1 (as Hg). The repeatability, expressed as relative standard deviation, was 8.4% (for n = 10). AuNRs exposed to increasing concentrations of the analyte were characterized by means of transmission electron microscopy and UV-vis spectrophotometry to ascertain the mechanism of detection. The method was finally applied to the determination of thiomersal in various pharmaceutical samples and showed quantitative recoveries. Graphical abstract Schematic illustration of a miniaturized colorimetric method based on the use of a microdrop of gold nanorods (AuNRs) for thiomersal determination in pharmaceuticals. It is based on the photochemical decomposition of thiomersal and subsequent Hg 0 generation with in-drop amalgamation.

Easy design of colorimetric logic gates based on nonnatural base pairing and controlled assembly of gold nanoparticles.

PubMed

Zhang, Li; Wang, Zhong-Xia; Liang, Ru-Ping; Qiu, Jian-Ding

2013-07-16

Utilizing the principles of metal-ion-mediated base pairs (C-Ag-C and T-Hg-T), the pH-sensitive conformational transition of C-rich DNA strand, and the ligand-exchange process triggered by DL-dithiothreitol (DTT), a system of colorimetric logic gates (YES, AND, INHIBIT, and XOR) can be rationally constructed based on the aggregation of the DNA-modified Au NPs. The proposed logic operation system is simple, which consists of only T-/C-rich DNA-modified Au NPs, and it is unnecessary to exquisitely design and alter the DNA sequence for different multiple molecular logic operations. The nonnatural base pairing combined with unique optical properties of Au NPs promises great potential in multiplexed ion sensing, molecular-scale computers, and other computational logic devices.

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

PubMed Central

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

2012-01-01

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

Chemiluminescent optical fiber immunosensor for the detection of anti-West Nile virus IgG.

PubMed

Herrmann, Sebastien; Leshem, Boaz; Landes, Shimi; Rager-Zisman, Bracha; Marks, Robert S

2005-03-31

An ELISA-based optical fiber methodology developed for the detection of anti-West Nile virus IgG antibodies in serum was compared to standard colorimetric and chemiluminescent ELISA based on microtiter plates. Colorimetric ELISA was the least sensitive, especially at high titer dilutions. The fiber-optic immunosensor based on the same ELISA immunological rationale was the most sensitive technique.

G-quadruplex based Exo III-assisted signal amplification aptasensor for the colorimetric detection of adenosine.

PubMed

Xu, Lei; Shen, Xin; Li, Bingzhi; Zhu, Chunhong; Zhou, Xuemin

2017-08-08

Adenosine is an endogenous nucleotide pivotally involved in nucleic acid and energy metabolism. Its excessive existence may indicate tumorigenesis, typically lung cancer. Encouraged by its significance as the clinical biomarker, sensitive assay methods towards adenosine have been popularized, with high cost and tedious procedures as the inevitable defects. Herein, we report a label-free aptamer-based exonuclease III (Exo III) amplification colorimetric aptasensor for the highly sensitive and cost-effective detection of adenosine. The strategy employed two unlabeled hairpin DNA oligonucleotides (HP1 and HP2), where HP1 contained the aptamer towards adenosine and HP2 embedded the guanine-rich sequence (GRS). In the presence of adenosine, hairpin HP1 could form specific binding with adenosine and trigger the unfolding of HP1's hairpin structure. The resulting adenosine-HP1 complex could hybridize with HP2, generating the Exo III recognition site. After Exo III-assisted degradation, the GRS was released from HP2, and the adenosine-HP1 was released back to the solution to combine another HP2, inducing the cycling amplification. After multiple circulations, the released ample GRSs were induced to form G-quadruplex, further catalyzing the oxidation of TMB, yielding a color change which was finally mirrored in the absorbance change. On the contrary, the absence of adenosine failed to unfold HP1, remaining color unchanged eventually. Thanks to the amplification strategy, the limit of detection was lowered to 17 nM with a broad linear range from 50 nM to 6 μM. The proposed method was successfully applied to the detection of adenosine in biological samples and satisfying recoveries were acquired. Copyright © 2017 Elsevier B.V. All rights reserved.

A Colorimetric and Fluorescent Chemosensor of Fe3+ Based on an Asymmetrical Squarylium Dye

NASA Astrophysics Data System (ADS)

Lu, Min; Wang, Yue; Li, Ying; Li, Zhongyu; Xu, Song; Yao, Chao

2018-05-01

A novel asymmetrical squarylium-dye-based dual signaling probe was synthesized and found to exhibit colorimetric and fluorescent properties on selective binding towards Fe3+ in ethanol/water (4:1, v/v) solution. The binding constant was determined to be 7.69 × 102 M-1, and the detection limit of SQ was 9.158 × 10-6 M. Most importantly, the 1:2 stoichiometry of the host-guest complexation was confirmed by Job's method. Moreover, the high sensing ability of the receptor towards Fe3+ was also investigated by the electrochemical technique.

Colorimetric microdetermination of captopril in pure form and in pharmaceutical formulations

NASA Astrophysics Data System (ADS)

Shama, Sayed Ahmed; El-Sayed Amin, Alla; Omara, Hany

2006-11-01

A simple, rapid, accurate, precise and sensitive colorimetric method for the determination of captopril (CAP) in bulk sample and in dosage forms is described. The method is based on oxidation of the drug by potassium permanganate in acidic medium and determination of the unreacted oxidant by measuring the decrease in absorbance for five different dyes; methylene blue (MB); acid blue 74 (AB), acid red 73 (AR), amaranth dye (AM) and acid orange 7 (AO) at a suitable λmax (660, 610, 510, 520, and 485 nm), respectively. Regression analysis of Beer's plots showed good correlation in the concentration ranges (0.4 12.5, 0.3 10, 0.5 11, 0.4 8.3 and 0.5 9.3 μg ml-1), respectively. The apparent molar absorbtivity, Sandell sensitivity, detection and quantitation limits were calculated. For more accurate results, Ringbom optimum concentration ranges were 0.5 12, 0.5 9.6, 0.6 10.5, 0.5 8.0 and 0.7 9.0 μg ml-1, respectively. The validity of the proposed method was tested by analyzing in pure and dosage forms containing CAP whether alone or in combination with hydrochlorothiazide. Statistical analysis of the results reflects that the proposed procedures are precise, accurate and easily applicable for the determination of CAP in pure form and in pharmaceutical preparations. Also, the stability constant was determined and the free energy change was calculated potentiometrically.

Colorimetric assay for lead ions based on the leaching of gold nanoparticles.

PubMed

Chen, Yi-You; Chang, Huan-Tsung; Shiang, Yen-Chun; Hung, Yu-Lun; Chiang, Cheng-Kang; Huang, Chih-Ching

2009-11-15

A colorimetric, label-free, and nonaggregation-based gold nanoparticles (Au NPs) probe has been developed for the detection of Pb(2+) in aqueous solution, based on the fact that Pb(2+) ions accelerate the leaching rate of Au NPs by thiosulfate (S(2)O(3)(2-)) and 2-mercaptoethanol (2-ME). Au NPs reacted with S(2)O(3)(2-) ions in solution to form Au(S(2)O(3))(2)(3-) complexes on the Au NP surfaces, leading to slight decreases in their surface plasmon resonance (SPR) absorption. Surface-assisted laser desorption/ionization time-of-flight ionization mass spectrometry (SALDI-TOF MS) data reveals the formation of Pb-Au alloys on the surfaces of the Au NPs in the presence of Pb(2+) ions and 2-ME. The formation of Pb-Au alloys accelerated the Au NPs rapidly dissolved into solution, leading to dramatic decreases in the SPR absorption. The 2-ME/S(2)O(3)(2-)-Au NP probe is highly sensitive (LOD = 0.5 nM) and selective (by at least 1000-fold over other metal ions) toward Pb(2+) ions, with a linear detection range (2.5 nM-10 muM) over nearly 4 orders of magnitude. The cost-effective probe allows rapid and simple determination of the concentrations of Pb(2+) ions in environmental samples (Montana soil and river), with results showing its great practicality for the detection of lead in real samples.

96-Well Plate Colorimetric Assay for K(sub i) Determination of (plusmn)-2-Benzylsuccinic Acid, an Inhibitor of Carboxypeptidase A

ERIC Educational Resources Information Center

Wentland, Mark P.; Raza, Shaan; Yingtong Gao

2004-01-01

An appropriate assay to determine the inhibition potency of carboxypeptidase A (CPA) in 96-well format to illustrate how high throughput screening is used in modern drug discovery to identify bioactive molecules is developed. Efforts in developing a colorimetric 96-well plate assay for determination of the K(sub i) for inhibition of CPA by…

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

PubMed

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

2013-12-15

A label-free non-aggregation colorimetric sensor has been designed for the detection of Cu(2+), based on Cu(2+) catalyzing etching of gold nanorods (AuNRs) along longitudinal axis induced by dissolve oxygen in the presence of S2O3(2-), which caused the aspect ratio (length/width) of AuNRs to decrease and the color of the solution to distinctly change. The linear range and the detection limit (LD, calculated by 10 Sb/k, n=11) of this sensor were 0.080-4.8 µM Cu(2+) and 0.22 µM Cu(2+), respectively. This sensor has been utilized to detect Cu(2+) in tap water and human serum samples with the results agreeing well with those of inductively coupled plasma-mass spectroscopy (ICP-MS), showing its remarkable practicality. In order to prove the possibility of catalyzing AuNRs non-aggregation colorimetric sensor for the detection of Cu(2+), the morphological structures of AuNRs were characterized by high resolution transmission electron microscopy (HRTEM) and the sensing mechanism of colorimetric sensor for the detection of Cu(2+) was also discussed. © 2013 Elsevier B.V. All rights reserved.

Colorimetric fluoride ion sensing by polyborylated ferrocenes: structural influences on thermodynamics and kinetics.

PubMed

Day, Joanna K; Bresner, Christopher; Coombs, Natalie D; Fallis, Ian A; Ooi, Li-Ling; Aldridge, Simon

2008-02-04

The thermodynamic factors underlying the use of ferroceneboronic esters as electrochemical or colorimetric fluoride ion sensors have been investigated through the synthesis of a range of systematically related derivatives differing in the number/nature of the boronic ester substituents and in the nature of ancillary ligands. Thus, if the shift in electrochemical potential associated with the conversion of one (or more) boronic ester group(s) to anionic boronate(s) on fluoride binding is sufficient to allow oxidation of the resulting host/guest complex by dioxygen, colorimetric sensing is possible. In practice, while monofunctional systems of the type CpFe[eta(5)-C(5)H(4)B(OR)(2)] offer selectivity in fluoride binding, electrochemical shifts in chloroform solution are insufficient to allow for a colorimetric response. Two chemical modification strategies have been shown to be successful in realizing a colorimetric sensor: (i) the use of the more strongly electron-donating Cp(*) ancillary ligand (which shifts the oxidation potential of both the free receptor and the resulting fluoride adduct cathodically by ca. -400 mV) and (ii) receptors featuring two or more binding sites and consequently a larger fluoride-induced electrochemical shift. Thus, in the case of [eta(5)-C(5)H(4)B(OR)(2)](2)Fe [(OR)(2) = OC(H)PhC(H)PhO, 2(s)], the binding of 2 equiv of fluoride gives an electrochemical shift (in chloroform) of -960 mV (cf. -530 mV for the corresponding monofunctional analogue, 1(s)). Related tris- and tetrakis-functionalized systems are also shown to be oxidized as the bis(fluoride) adducts, presumably because of fast oxidation kinetics, relative to the rate of the (electrostatically unfavorable) binding of a third equivalent of fluoride. Furthermore, the rate of sensor response (as measured by UV/vis spectroscopy) is found to be strongly enhanced by the presence of pendant (uncomplexed) three-coordinate boronic ester functions (e.g., a rate enhancement of 1-2 orders of

High-Sensitivity GaN Microchemical Sensors

NASA Technical Reports Server (NTRS)

Son, Kyung-ah; Yang, Baohua; Liao, Anna; Moon, Jeongsun; Prokopuk, Nicholas

2009-01-01

Systematic studies have been performed on the sensitivity of GaN HEMT (high electron mobility transistor) sensors using various gate electrode designs and operational parameters. The results here show that a higher sensitivity can be achieved with a larger W/L ratio (W = gate width, L = gate length) at a given D (D = source-drain distance), and multi-finger gate electrodes offer a higher sensitivity than a one-finger gate electrode. In terms of operating conditions, sensor sensitivity is strongly dependent on transconductance of the sensor. The highest sensitivity can be achieved at the gate voltage where the slope of the transconductance curve is the largest. This work provides critical information about how the gate electrode of a GaN HEMT, which has been identified as the most sensitive among GaN microsensors, needs to be designed, and what operation parameters should be used for high sensitivity detection.

Colorimetric and fluorimetric detection of Hg2 + and Cr3 + by boronic acid conjugated rhodamine derivatives: Mechanistic aspects and their bio-imaging application in bacterial cells

NASA Astrophysics Data System (ADS)

Vallu, Rama Krishna; Velugula, Krishna; Doshi, Sejal; Chinta, Jugun Prakash

2018-01-01

Colorimetric and fluorimetric detection of toxic metal ions such as Hg2 + and Cr3 + has gained tremendous popularity over the conventional methods due to their operational simplicity, high selectivity, and speediness. Although numerous colorimetric and fluorescent receptors for Hg2 + or Cr3 + were reported in the literature, boronic acid-based receptors for these metal ions are rather scarce in the literature. Hence, in the present study dual function boronic acid conjugated rhodamine derivatives were developed, and their toxic metal ion detection abilities were studied by absorption, emission and visual detection methods. Absorption and emission spectral studies revealed that these derivatives displayed selectivity towards Hg2 +, Cr3 + and Fe3 + among the other metal ions studied by forming new absorption band. Both the derivatives exhibited colorimetric response towards Hg2 + and Cr3 + by the change in color of the solution to pink and reddish pink with Fe3 +. The detailed mechanism involved in the detection of Hg2 + was deduced by 1H NMR and ESI-MS studies. Further, these derivatives were used for fluorescence imaging of Hg2 + and Cr3 + in S. aureus bacterial cells. Thus the present manuscript demonstrated the use of boronic acid conjugated rhodamine derivatives as a dual function (colorimetric and fluorescent) probes and as imaging agents for Hg2 + and Cr3 +, which are known for their toxic influence on bacterial cells.

Efficient colorimetric pH sensor based on responsive polymer-quantum dot integrated graphene oxide.

PubMed

Paek, Kwanyeol; Yang, Hyunseung; Lee, Junhyuk; Park, Junwoo; Kim, Bumjoon J

2014-03-25

In this paper, we report the development of a versatile platform for a highly efficient and stable graphene oxide (GO)-based optical sensor that exhibits distinctive ratiometric color responses. To demonstrate the applicability of the platform, we fabricated a colorimetric, GO-based pH sensor that responds to a wide range of pH changes. Our sensing system is based on responsive polymer and quantum dot (QD) hybrids integrated on a single GO sheet (MQD-GO), with the GO providing an excellent signal-to-noise ratio and high dispersion stability in water. The photoluminescence emissions of the blue and orange color-emitting QDs (BQDs and OQDs) in MQD-GO can be controlled independently by different pH-responsive linkers of poly(acrylic acid) (PAA) (pKa=4.5) and poly(2-vinylpyridine) (P2VP) (pKa=3.0) that can tune the efficiencies of Förster resonance energy transfer from the BQDs to the GO and from the OQDs to the GO, respectively. As a result, the color of MQD-GO changes from orange to near-white to blue over a wide range of pH values. The detailed mechanism of the pH-dependent response of the MQD-GO sensor was elucidated by measurements of time-resolved fluorescence and dynamic light scattering. Furthermore, the MQD-GO sensor showed excellent reversibility and high dispersion stability in pure water, indicating that our system is an ideal platform for biological and environmental applications. Our colorimetric GO-based optical sensor can be expanded easily to various other multifunctional, GO-based sensors by using alternate stimuli-responsive polymers.

Localized surface plasmon resonance of gold nanoparticles as colorimetric probes for determination of Isoniazid in pharmacological formulation.

PubMed

Zargar, Behrooz; Hatamie, Amir

2013-04-01

Isoniazid is an important antibiotic, which is widely used to treat tuberculosis. This study presents a colorimetric method for the determination of Isoniazid based on localized surface plasmon resonance (LSPR) property of gold nanoparticles. An LSPR band is produced by reducing gold ions in solution using Isoniazid as the reducing agent. Influences of the following relevant variables were examined and optimized in the experiment, formation time of gold nanoparticles, pH, buffer and stabilizer. These tests demonstrated that under optimum conditions the absorbance of Au nanoparticles at 530 nm related linearly to the concentration of Isoniazid in the range of 1.0-8.0 μg mL(-1) with a detection limit of 0.98 μg mL(-1). This colorimetric method has been successfully applied to the determine Isoniazid in tablets and spiked serum samples. The proposed colorimetric assay exhibits good reproducibility and accuracy, providing a simple and rapid method for analysis of Isoniazid. Copyright © 2013 Elsevier B.V. All rights reserved.

Localized surface plasmon resonance of gold nanoparticles as colorimetric probes for determination of Isoniazid in pharmacological formulation

NASA Astrophysics Data System (ADS)

Zargar, Behrooz; Hatamie, Amir

2013-04-01

Isoniazid is an important antibiotic, which is widely used to treat tuberculosis. This study presents a colorimetric method for the determination of Isoniazid based on localized surface plasmon resonance (LSPR) property of gold nanoparticles. An LSPR band is produced by reducing gold ions in solution using Isoniazid as the reducing agent. Influences of the following relevant variables were examined and optimized in the experiment, formation time of gold nanoparticles, pH, buffer and stabilizer. These tests demonstrated that under optimum conditions the absorbance of Au nanoparticles at 530 nm related linearly to the concentration of Isoniazid in the range of 1.0-8.0 μg mL-1 with a detection limit of 0.98 μg mL-1. This colorimetric method has been successfully applied to the determine Isoniazid in tablets and spiked serum samples. The proposed colorimetric assay exhibits good reproducibility and accuracy, providing a simple and rapid method for analysis of Isoniazid.

Covalent immobilisation of antibodies in Teflon-FEP microfluidic devices for the sensitive quantification of clinically relevant protein biomarkers.

PubMed

Pivetal, Jeremy; Pereira, Filipa M; Barbosa, Ana I; Castanheira, Ana P; Reis, Nuno M; Edwards, Alexander D

2017-03-13

This study reports for the first time the sensitive colorimetric and fluorescence detection of clinically relevant protein biomarkers by sandwich immunoassays using the covalent immobilisation of antibodies onto the fluoropolymer surface inside Teflon®-FEP microfluidic devices. Teflon®-FEP has outstanding optical transparency ideal for high-sensitivity colorimetric and fluorescence bioassays, however this thermoplastic is regarded as chemically inert and very hydrophobic. Covalent immobilisation can offer benefits over passive adsorption to plastic surfaces by allowing better control over antibody density, orientation and analyte binding capacity, and so we tested a range of different and novel covalent immobilisation strategies. We first functionalised the inner surface of a 10-bore, 200 μm internal diameter FEP microcapillary film with high-molecular weight polyvinyl alcohol (PVOH) without changing the outstanding optical transparency of the device delivered by the matched refractive index of FEP and water. Glutaraldehyde immobilisation was compared with the use of photoactivated linkers and NHS-ester crosslinkers for covalently immobilising capture antibodies onto PVOH. Three clinically relevant sandwich ELISAs were tested against the cytokine IL-1β, the myocardial infarct marker cardiac troponin I (cTnI), and the chronic heart failure marker brain natriuretic peptide (BNP). Overall, glutaraldehyde immobilisation was effective for BNP assays, but yielded unacceptable background for IL-1β and cTnI assays caused by direct binding of the biotinylated detection antibody to the modified PVOH surface. We found NHS-ester groups reacted with APTES-treated PVOH coated fluoropolymers. This facilitated a novel method for capture antibody immobilisation onto fluoropolymer devices using a bifunctional NHS-maleimide crosslinker. The density of covalently immobilised capture antibodies achieved using PVOH/APTES/NHS/maleimide approached levels seen with passive adsorption

High-Sensitivity Spectrophotometry.

ERIC Educational Resources Information Center

Harris, T. D.

1982-01-01

Selected high-sensitivity spectrophotometric methods are examined, and comparisons are made of their relative strengths and weaknesses and the circumstances for which each can best be applied. Methods include long path cells, noise reduction, laser intracavity absorption, thermocouple calorimetry, photoacoustic methods, and thermo-optical methods.…

Giant Gold Nanowire Vesicle-Based Colorimetric and SERS Dual-Mode Immunosensor for Ultrasensitive Detection of Vibrio parahemolyticus.

PubMed

Guo, Zhiyong; Jia, Yaru; Song, Xinxin; Lu, Jing; Lu, Xuefei; Liu, Baoqing; Han, Jiaojiao; Huang, Youju; Zhang, Jiawei; Chen, Tao

2018-05-15

Conventional methods for the detection of Vibrio parahemolyticus (VP) usually need tedious, labor-intensive processes, and have low sensitivity, which further limits their practical applications. Herein, we developed a simple and efficient colorimetry and surface-enhanced Raman scattering (SERS) dual-mode immunosensor for sensitive detection of VP, by employing giant Au vesicles with anchored tiny gold nanowires (AuNW) as a smart probe. Due to the larger specific surface and special hollow structure of giant Au vesicles, silver staining would easily lead to vivid color change for colorimetric analysis and further amplify SERS signals. The t-test was further used to determine if two sets of data from colorimetry and SERS were significantly different from each other. The result shows that there was no significant difference between data from the two methods. Two sets of data can mutually validate each other and avoid false positive and negative detection. The designed colorimetry-SERS dual-mode sensor would be very promising in various applications such as food safety inspection, personal healthcare, and on-site environmental monitoring.

Oligothiophene-based colorimetric and ratiometric fluorescence dual-channel cyanide chemosensor: Sensing ability, TD-DFT calculations and its application as an efficient solid state sensor.

PubMed

Lan, Linxin; Li, Tianduo; Wei, Tao; Pang, He; Sun, Tao; Wang, Enhua; Liu, Haixia; Niu, Qingfen

2018-03-15

An oligothiophene-based colorimetric and ratiometric fluorescence dual-channel cyanide chemosensor 3 T-2CN was reported. Sensor 3 T-2CN showed both naked-eye recognition and ratiometric fluorescence response for CN - with an excellent selectivity and high sensitivity. The sensing mechanism based on the nucleophilic attack of CN - on the vinyl CC bond has been successfully confirmed by the optical measurements, 1 H NMR titration, FT-IR spectra as well as the DFT/TD-DFT calculations. Moreover, the detection limit was calculated to be 0.19μM, which is much lower than the maximum permission concentration in drinking water (1.9μM). Importantly, test strips (filter paper and TLC plates) containing 3 T-2CN were fabricated, which could act as a practical and efficient solid state optical sensor for CN - in field measurements. Copyright © 2017 Elsevier B.V. All rights reserved.

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

PubMed

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

2015-09-09

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

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

PubMed

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

2014-07-15

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

High sensitivity optical molecular imaging system

NASA Astrophysics Data System (ADS)

An, Yu; Yuan, Gao; Huang, Chao; Jiang, Shixin; Zhang, Peng; Wang, Kun; Tian, Jie

2018-02-01

Optical Molecular Imaging (OMI) has the advantages of high sensitivity, low cost and ease of use. By labeling the regions of interest with fluorescent or bioluminescence probes, OMI can noninvasively obtain the distribution of the probes in vivo, which play the key role in cancer research, pharmacokinetics and other biological studies. In preclinical and clinical application, the image depth, resolution and sensitivity are the key factors for researchers to use OMI. In this paper, we report a high sensitivity optical molecular imaging system developed by our group, which can improve the imaging depth in phantom to nearly 5cm, high resolution at 2cm depth, and high image sensitivity. To validate the performance of the system, special designed phantom experiments and weak light detection experiment were implemented. The results shows that cooperated with high performance electron-multiplying charge coupled device (EMCCD) camera, precision design of light path system and high efficient image techniques, our OMI system can simultaneously collect the light-emitted signals generated by fluorescence molecular imaging, bioluminescence imaging, Cherenkov luminance and other optical imaging modality, and observe the internal distribution of light-emitting agents fast and accurately.

Colorimetric detection of catalytic reactivity of nanoparticles in complex matrices.

PubMed

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

2015-03-17

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

Individual Colorimetric Observer Model

PubMed Central

Asano, Yuta; Fairchild, Mark D.; Blondé, Laurent

2016-01-01

This study proposes a vision model for individual colorimetric observers. The proposed model can be beneficial in many color-critical applications such as color grading and soft proofing to assess ranges of color matches instead of a single average match. We extended the CIE 2006 physiological observer by adding eight additional physiological parameters to model individual color-normal observers. These eight parameters control lens pigment density, macular pigment density, optical densities of L-, M-, and S-cone photopigments, and λmax shifts of L-, M-, and S-cone photopigments. By identifying the variability of each physiological parameter, the model can simulate color matching functions among color-normal populations using Monte Carlo simulation. The variabilities of the eight parameters were identified through two steps. In the first step, extensive reviews of past studies were performed for each of the eight physiological parameters. In the second step, the obtained variabilities were scaled to fit a color matching dataset. The model was validated using three different datasets: traditional color matching, applied color matching, and Rayleigh matches. PMID:26862905

Colorimetric determination of glutathione in human serum and cell lines by exploiting the peroxidase-like activity of CuS-polydopamine-Au composite.

PubMed

Wang, Yanying; Liu, Yaqin; Ding, Fang; Zhu, Xiaoyan; Yang, Li; Zou, Ping; Rao, Hanbing; Zhao, Qingbiao; Wang, Xianxiang

2018-06-07

In this study, we developed a simple colorimetric approach to detect glutathione (GSH). The proposed approach is based on the ability of CuS-PDA-Au composite material to catalytically oxidize 3,3',5,5'-tetramethylbenzidine (TMB) to ox-TMB to induce a blue color with an absorption peak centered at 652 nm. However, the introduction of GSH can result in a decrease in oxidized TMB; similarly, it can combine with Au nanoparticles (Au NPs) on the surface of CuS-PDA-Au composite material. Both approaches can result in a fading blue color and a reduction of the absorbance at 652 nm. Based on this above, we proposed a technique to detect GSH quantitatively and qualitatively through UV-Vis spectroscopy and naked eye, respectively. This approach demonstrates a low detection limit of 0.42 μM with a broad detection range of 5 × 10 -7 -1 × 10 -4  M with the assistance of UV-Vis spectroscopy. More importantly, this approach is convenient and rapid. This method was successfully applied to GSH detection in human serum and cell lines. Graphical abstract A colorimetric approach has been developed by exploiting the peroxidase-like activity of CuS-polydopamine-Au composite for sensitive glutathione detection.

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

NASA Astrophysics Data System (ADS)

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

2016-05-01

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

Selection of DNA aptamers against Human Cardiac Troponin I for colorimetric sensor based dot blot application.

PubMed

Dorraj, Ghamar Soltan; Rassaee, Mohammad Javad; Latifi, Ali Mohammad; Pishgoo, Bahram; Tavallaei, Mahmood

2015-08-20

Troponin T and I are ideal markers which are highly sensitive and specific for myocardial injury and have shown better efficacy than earlier markers. Since aptamers are ssDNA or RNA that bind to a wide variety of target molecules, the purpose of this research was to select an aptamer from a 79bp single-stranded DNA (ssDNA) random library that was used to bind the Human Cardiac Troponin I from a synthetic nucleic acids library by systematic evolution of ligands exponential enrichment (Selex) based on several selection and amplification steps. Human Cardiac Troponin I protein was coated onto the surface of streptavidin magnetic beads to extract specific aptamer from a large and diverse random ssDNA initial oligonucleotide library. As a result, several aptamers were selected and further examined for binding affinity and specificity. Finally TnIApt 23 showed beast affinity in nanomolar range (2.69nM) toward the target protein. A simple and rapid colorimetric detection assay for Human Cardiac Troponin I using the novel and specific aptamer-AuNPs conjugates based on dot blot assay was developed. The detection limit for this protein using aptamer-AuNPs-based assay was found to be 5ng/ml. Copyright © 2015 Elsevier B.V. All rights reserved.

Development of a novel tridentate ligand for colorimetric detection of Mn2+ based on AgNPs.

PubMed

Wei, Jianyu; Chen, Jinfan; Yue, Guozong; Hu, Liangsheng; Zhao, Danqing; Zhu, Jing; Yang, Luming; Huang, Deshun; Zhao, Pengxiang

2018-05-09

A novel tridentate ligand nitrilotris(methylene)tris(1,2,3-triazole)triacetate (NTTTA) has been synthesized by click reaction and followed with ester hydrolysis reaction. The silver nanoparticles (AgNPs) were then modified and stabilized by this ligand, and subsequently been employed for the highly selective and sensitive colorimetric detection of Mn 2+ in aqueous solution. The presence of Mn 2+ can cause the aggregation of AgNPs, which leads to the color change of the dispersion from yellow to brown, as well as the decrease and red-shift of the surface plasmon resonance absorption. The detection limit of Mn 2+ was as approximately 0.5 μM by the naked eyes. UV-vis spectroscopy analysis showed a good linear relationship between the logarithm of the ratios (A 550 /A 395 ) and the concentration of Mn 2+ over the range of 0.05 μM-10 μM, and the LOD was calculated to be 12.6 nM (S/N = 3). The present assay showed good simplicity without the need of adjusting the pH value. The feasibility of this technique was evaluated for successful detection of Mn 2+ in tap water and lake water samples, with good recoveries. Copyright © 2018 Elsevier B.V. All rights reserved.

One-step, room temperature, colorimetric melamine sensing using an in-situ formation of silver nanoparticles through modified Tollens process

NASA Astrophysics Data System (ADS)

Wang, Huiying; Chen, Dinglong; Yu, Longquan; Chang, Ming; Ci, Lijie

2015-02-01

We have developed a rapid, sensitive, one-step, and selective colorimetric detection method for melamine (MEL) in milk powder based upon an in-situ formation of silver nanoparticles (AgNPs) through modified Tollens process at room temperature. The triazine ring N atoms of MEL molecule were strategically designed to complex the Ag+ through electron donor-acceptor interaction. During the AgNPs formation procedure, the MEL molecule, which has been covalently bonded with the Ag+ ions, was adsorbed to the surface of as-prepared AgNPs, resulting in the aggregation of the adjacent AgNPs with detectable decreases of absorption signal. The concentration of MEL can be determined with the naked eye or a UV-vis spectrometer at which the yellow-to-brown color change associated with aggregate enhancement takes place. This method enables rapid (less than 30 min) and sensitive (limit of detection, LOD, 10 nM) detection, and it was also able to discriminate MEL from sixteen other milk relevant coexisting compounds. This assay does not utilize organic cosolvents, enzymatic reactions, light-sensitive dye molecules, lengthy protocols, or sophisticated instrumentation thereby overcoming some of the limitations of conventional methods.

Proposed Ultra-High Sensitivity High-Frequency Gravitational Wave Detector

NASA Astrophysics Data System (ADS)

Baker, Robert M. L.; Stephenson, Gary V.; Li, Fangyu

2008-01-01

The paper discusses the proposed improvement of a High-Frequency Relic Gravitational Wave (HFRGW) detector designed by Li, Baker, Fang, Stephenson and Chen in order to greatly improve its sensitivity. The improved detector is inspired by the Laser Interferometer Gravitational Observatory or LIGO, but is sensitive to the high-frequency end of the gravitational-wave spectrum. As described in prior papers it utilizes the Gertsenshtein effect, which introduces the conversion of gravitational waves to electromagnetic (EM) waves in the presence of a static magnetic field. Such a conversion, if it leads to photons moving in a direction perpendicular to the plane of the EM waves and the magnetic field, will allow for ultra-high sensitivity HFRGW detection. The use of sensitive microwave, single photon detectors such as a circuit QED and/or the Rydberg Atom Cavity Detector, or off-the-shelf detectors, could lead to such detection. When the EM-detection photons are focused at the microwave detectors by fractal-membrane reflectors sensitivity is also improved. Noise sources external to the HFRGW detector will be eliminated by placing a tight mosaic of superconducting tiles (e.g., YBCO) and/or fractal membranes on the interior surface of the detector's cryogenic containment vessel in order to provide a perfect Faraday cage. Internal thermal noise will be eliminated by means of a microwave absorbing (or reflecting) interior enclosure shaped to conform to a high-intensity continuous microwave Gaussian beam (GB), will reduce any background photon flux (BPF) noise radiated normal to the GB's axis. Such BPF will be further attenuated by a series of microwave absorbing baffles forming tunnels to the sensitive microwave detectors on each side of the GB and at right angles to the static magnetic field. A HFGW detector of bandwidth of 1 KHz to 10 KHz or less in the GHz band has been selected. It is concluded that the utilization of the new ultra-high-sensitivity microwave detectors

A dual-responsive colorimetric and fluorescent chemosensor based on diketopyrrolopyrrole derivative for naked-eye detection of Fe3 + and its practical application

NASA Astrophysics Data System (ADS)

Zhang, Shanshan; Sun, Tao; Xiao, Dejun; Yuan, Fang; Li, Tianduo; Wang, Enhua; Liu, Haixia; Niu, Qingfen

2018-01-01

A novel dual-responsive colorimetric and fluorescent chemosensor L based on diketopyrrolopyrrole derivative for Fe3 + detection was designed and synthesized. In presence of Fe3 +, sensor L displayed strong colorimetric response as amaranth to rose pink and significant fluorescence enhancement and chromogenic change, which served as a naked-eye indicator by an obvious color change from purple to red. The binding constant for L-Fe3 + complex was found as 2.4 × 104 with the lower detection limit of 14.3 nM. The sensing mechanism was investigated in detail by fluorescence measurements, IR and 1H NMR spectra. Sensor L for Fe3 + detection also exhibited high anti-interference performance, good reversibility, wide pH response range and instantaneous response time. Furthermore, the sensor L has been used to quantify Fe3 + ions in practical water samples with good recovery.

Ultrasensitive colorimetric detection of heparin based on self-assembly of gold nanoparticles on graphene oxide.

PubMed

Fu, Xiuli; Chen, Lingxin; Li, Jinhua

2012-08-21

A novel colorimetric method was developed for ultrasensitive detection of heparin based on self-assembly of gold nanoparticles (AuNPs) onto the surface of graphene oxide (GO). Polycationic protamine was used as a medium for inducing the self-assembly of citrate-capped AuNPs on GO through electrostatic interaction, resulting in a shift in the surface plasmon resonance (SPR) absorption of AuNPs and exhibiting a blue color. Addition of polyanionic heparin disturbed the self-assemble of AuNPs due to its strong affinity to protamine. With the increase of heparin concentration, the amounts of self-assembly AuNPs decreased and the color changed from blue to red in solution. Therefore, a "blue-to-red" colorimetric sensing strategy based on self-assembly of AuNPs could be established for heparin detection. Compared with the commonly reported aggregation-based methods ("red-to-blue"), the color change from blue to red was more eye-sensitive, especially in low concentration of target. Moreover, stronger interaction between protamine and heparin led to distinguish heparin from its analogues as well as various potentially coexistent physiological species. The strategy was simply achieved by the self-assembly nature of AuNPs and the application of two types of polyionic media, showing it to be label-free, simple, rapid and visual. This method could selectively detect heparin with a detection limit of 3.0 ng mL(-1) in standard aqueous solution and good linearity was obtained over the range 0.06-0.36 μg mL(-1) (R = 0.9936). It was successfully applied to determination of heparin in fetal bovine serum samples as low as 1.7 ng mL(-1) with a linear range of 0-0.8 μg mL(-1).

Confined stimuli-responsive polymer gel in inverse opal polymer membrane for colorimetric glucose sensor.

PubMed

Honda, Masaki; Kataoka, Kazunori; Seki, Takahiro; Takeoka, Yukikazu

2009-07-21

We developed a totally synthetic colorimetric glucose-sensing system that is composed of glucose-responsive hydrogel particles confined in an inverse opal polymer membrane. This system exhibits structural color on the basis of Bragg diffraction arising from the 3-D ordered structure with periodicity on the order of the wavelength of visible light. The volume of the hydrogel particles reversibly changes as the glucose concentration varies in the separated pores of the inverse opal polymer membrane; this system reveals a reversible change in the color appearance and the peak intensity of the reflection spectra with the variation in the glucose concentration. By careful design of the system, we can detect the important range of glucose concentration around the threshold value for diagnosing diabetes mellitus by using the colorimetric glucose-sensing system.

Colorimetric chemosensors based on diketopyrrolopyrrole for selective and reversible recognition of fluoride ions

NASA Astrophysics Data System (ADS)

Zhang, Yan; Yang, Xiaofeng; Sun, Guoxin; Zhang, Hao; Liu, Xiaolei; Zhu, Fengqiao; Qin, Shuchun; Zhao, Ziqi; Cui, Yu

2018-06-01

A series of colorimetric and reversible receptors for fluoride anions based on diketopyrrolopyrrole (DPP) were designed and synthesized successfully. The position of nitro substituent on the phenylhydrazide affected the alteration of photophysical properties to varying degrees. While the photoluminescence intensity of receptor 1 was weaker than that of receptor 2 and receptor 3 on account of the formation of intramolecular hydrogen bond deriving from oxygen atom of nitro substituent and hydrogen atom of hydrazide. The receptor 2 was a preferable chemosensor for responding fluoride anions. The fluorescence was quenched in the presence of fluoride anion resulted from the photo-induced electron transfer (PET) effect from the amide. The formation of deprotonation species, which produced by hydrazide Nsbnd H moiety and F- was answerable for the spectral changes. Especially, the spectral and color responses of receptors could be switched back and forth successively by adding F- and HSO4- anions in DMSO solution. These receptors could response fluoride anion sensitively, visually and selectively in a manner of reversible with a low determination.

Colorimetric Detection and Identification of Natural and Artificial Sweeteners

PubMed Central

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

2009-01-01

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

Colorimetric detection and identification of natural and artificial sweeteners.

PubMed

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

2009-08-01

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

The mode of sensitization and its influence on allograft outcomes in highly sensitized kidney transplant recipients.

PubMed

Redfield, Robert R; Scalea, Joseph R; Zens, Tiffany J; Mandelbrot, Didier A; Leverson, Glen; Kaufman, Dixon B; Djamali, Arjang

2016-10-01

We sought to determine whether the mode of sensitization in highly sensitized patients contributed to kidney allograft survival. An analysis of the United Network for Organ Sharing dataset involving all kidney transplants between 1997 and 2014 was undertaken. Highly sensitized adult kidney transplant recipients [panel reactive antibody (PRA) ≥98%] were compared with adult, primary non-sensitized and re-transplant recipients. Kaplan-Meier survival analyses were used to determine allograft survival rates. Cox proportional hazards regression analyses were conducted to determine the association of graft loss with key predictors. Fifty-three percent of highly sensitized patients transplanted were re-transplants. Pregnancy and transfusion were the only sensitizing event in 20 and 5%, respectively. The 10-year actuarial graft survival for highly sensitized recipients was 43.9% compared with 52.4% for non-sensitized patients, P < 0.001. The combination of being highly sensitized by either pregnancy or blood transfusion increased the risk of graft loss by 23% [hazard ratio (HR) 1.230, confidence interval (CI) 1.150-1.315, P < 0.001], and the combination of being highly sensitized from a prior transplant increased the risk of graft loss by 58.1% (HR 1.581, CI 1.473-1.698, P < 0.001). The mode of sensitization predicts graft survival in highly sensitized kidney transplant recipients (PRA ≥98%). Patients who are highly sensitized from re-transplants have inferior graft survival compared with patients who are highly sensitized from other modes of sensitization. © The Author 2016. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved.

A rapid colorimetric assay for mold spore germination using XTT tetrazolium salt

Treesearch

Carol A. Clausen; Vina W. Yang

2011-01-01

Current laboratory test methods to measure efficacy of new mold inhibitors are time consuming, some require specialized test equipment and ratings are subjective. Rapid, simple quantitative assays to measure the efficacy of mold inhibitors are needed. A quantitative, colorimetric microassay was developed using XTT tetrazolium salt to metabolically assess mold spore...

Operator-Friendly Technique and Quality Control Considerations for Indigo Colorimetric Measurement of Ozone Residual

EPA Science Inventory

Drinking water ozone disinfection systems measure ozone residual concentration, C, for regulatory compliance reporting of concentration-times-time (CT), and the resultant log-inactivation of virus, Giardia and Cryptosporidium. The indigotrisulfonate (ITS) colorimetric procedure i...

Colorimetric Recognition of Aldehydes and Ketones.

PubMed

Li, Zheng; Fang, Ming; LaGasse, Maria K; Askim, Jon R; Suslick, Kenneth S

2017-08-07

A colorimetric sensor array has been designed for the identification of and discrimination among aldehydes and ketones in vapor phase. Due to rapid chemical reactions between the solid-state sensor elements and gaseous analytes, distinct color difference patterns were produced and digitally imaged for chemometric analysis. The sensor array was developed from classical spot tests using aniline and phenylhydrazine dyes that enable molecular recognition of a wide variety of aliphatic or aromatic aldehydes and ketones, as demonstrated by hierarchical cluster, principal component, and support vector machine analyses. The aldehyde/ketone-specific sensors were further employed for differentiation among and identification of ten liquor samples (whiskies, brandy, vodka) and ethanol controls, showing its potential applications in the beverage industry. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bio-inspired colorimetric film based on hygroscopic coloration of longhorn beetles (Tmesisternus isabellae)

PubMed Central

Seo, Han-bok; Lee, Seung-Yop

2017-01-01

Structure-dependent colour is caused by the interaction of light with photonic crystal structures rather than pigments. The elytra of longhorn beetles Tmesisternus isabellae appear to be iridescent green in a dry state and turn to red when exposed to humidity. Based on the hygroscopic colouration of the longhorn beetle, we have developed centimeter-scale colorimetric opal films using a novel self-assembly method. The micro-channel assisted assembly technique adopts both natural evaporation and rotational forced drying, enhancing the surface binding of silica particles and the packing density by reducing the lattice constant and structural defects. The fabricated large-scale photonic film changes its structural colour from green to red when exposed to water vapour, similarly to the colorimetric feature of the longhorn beetle. The humidity-dependent colour change of the opal film is shown to be reversible and durable over five-hundred cycles of wetting and drying. PMID:28322307

Bio-inspired colorimetric film based on hygroscopic coloration of longhorn beetles (Tmesisternus isabellae)

NASA Astrophysics Data System (ADS)

Seo, Han-Bok; Lee, Seung-Yop

2017-03-01

Structure-dependent colour is caused by the interaction of light with photonic crystal structures rather than pigments. The elytra of longhorn beetles Tmesisternus isabellae appear to be iridescent green in a dry state and turn to red when exposed to humidity. Based on the hygroscopic colouration of the longhorn beetle, we have developed centimeter-scale colorimetric opal films using a novel self-assembly method. The micro-channel assisted assembly technique adopts both natural evaporation and rotational forced drying, enhancing the surface binding of silica particles and the packing density by reducing the lattice constant and structural defects. The fabricated large-scale photonic film changes its structural colour from green to red when exposed to water vapour, similarly to the colorimetric feature of the longhorn beetle. The humidity-dependent colour change of the opal film is shown to be reversible and durable over five-hundred cycles of wetting and drying.

Discrimination of honeys using colorimetric sensor arrays, sensory analysis and gas chromatography techniques.

PubMed

Tahir, Haroon Elrasheid; Xiaobo, Zou; Xiaowei, Huang; Jiyong, Shi; Mariod, Abdalbasit Adam

2016-09-01

Aroma profiles of six honey varieties of different botanical origins were investigated using colorimetric sensor array, gas chromatography-mass spectrometry (GC-MS) and descriptive sensory analysis. Fifty-eight aroma compounds were identified, including 2 norisoprenoids, 5 hydrocarbons, 4 terpenes, 6 phenols, 7 ketones, 9 acids, 12 aldehydes and 13 alcohols. Twenty abundant or active compounds were chosen as key compounds to characterize honey aroma. Discrimination of the honeys was subsequently implemented using multivariate analysis, including hierarchical clustering analysis (HCA) and principal component analysis (PCA). Honeys of the same botanical origin were grouped together in the PCA score plot and HCA dendrogram. SPME-GC/MS and colorimetric sensor array were able to discriminate the honeys effectively with the advantages of being rapid, simple and low-cost. Moreover, partial least squares regression (PLSR) was applied to indicate the relationship between sensory descriptors and aroma compounds. Copyright © 2016 Elsevier Ltd. All rights reserved.

Interfacial Polymerization for Colorimetric Labeling of Protein Expression in Cells

PubMed Central

Lilly, Jacob L.; Sheldon, Phillip R.; Hoversten, Liv J.; Romero, Gabriela; Balasubramaniam, Vivek; Berron, Brad J.

2014-01-01

Determining the location of rare proteins in cells typically requires the use of on-sample amplification. Antibody based recognition and enzymatic amplification is used to produce large amounts of visible label at the site of protein expression, but these techniques suffer from the presence of nonspecific reactivity in the biological sample and from poor spatial control over the label. Polymerization based amplification is a recently developed alternative means of creating an on-sample amplification for fluorescence applications, while not suffering from endogenous labels or loss of signal localization. This manuscript builds upon polymerization based amplification by developing a stable, archivable, and colorimetric mode of amplification termed Polymer Dye Labeling. The basic concept involves an interfacial polymer grown at the site of protein expression and subsequent staining of this polymer with an appropriate dye. The dyes Evans Blue and eosin were initially investigated for colorimetric response in a microarray setting, where both specifically stained polymer films on glass. The process was translated to the staining of protein expression in human dermal fibroblast cells, and Polymer Dye Labeling was specific to regions consistent with desired protein expression. The labeling is stable for over 200 days in ambient conditions and is also compatible with modern mounting medium. PMID:25536421

Interfacial polymerization for colorimetric labeling of protein expression in cells.

PubMed

Lilly, Jacob L; Sheldon, Phillip R; Hoversten, Liv J; Romero, Gabriela; Balasubramaniam, Vivek; Berron, Brad J

2014-01-01

Determining the location of rare proteins in cells typically requires the use of on-sample amplification. Antibody based recognition and enzymatic amplification is used to produce large amounts of visible label at the site of protein expression, but these techniques suffer from the presence of nonspecific reactivity in the biological sample and from poor spatial control over the label. Polymerization based amplification is a recently developed alternative means of creating an on-sample amplification for fluorescence applications, while not suffering from endogenous labels or loss of signal localization. This manuscript builds upon polymerization based amplification by developing a stable, archivable, and colorimetric mode of amplification termed Polymer Dye Labeling. The basic concept involves an interfacial polymer grown at the site of protein expression and subsequent staining of this polymer with an appropriate dye. The dyes Evans Blue and eosin were initially investigated for colorimetric response in a microarray setting, where both specifically stained polymer films on glass. The process was translated to the staining of protein expression in human dermal fibroblast cells, and Polymer Dye Labeling was specific to regions consistent with desired protein expression. The labeling is stable for over 200 days in ambient conditions and is also compatible with modern mounting medium.

Extractive colorimetric method for the determination of dothiepin hydrochloride and risperidone in pure and in dosage forms.

PubMed

Hassan, Wafaa El-Sayed

2008-08-01

Three rapid, simple, reproducible and sensitive extractive colorimetric methods (A--C) for assaying dothiepin hydrochloride (I) and risperidone (II) in bulk sample and in dosage forms were investigated. Methods A and B are based on the formation of an ion pair complexes with methyl orange (A) and orange G (B), whereas method C depends on ternary complex formation between cobalt thiocyanate and the studied drug I or II. The optimum reaction conditions were investigated and it was observed the calibration curves resulting from the measurements of absorbance concentration relations of the extracted complexes were linear over the concentration range 0.1--12 microg ml(-1) for method A, 0.5--11 mug ml(-1) for method B, and 3.2--80 microg ml(-1) for method C with a relative standard deviation (RSD) of 1.17 and 1.28 for drug I and II, respectively. The molar absorptivity, Sandell sensitivity, Ringbom optimum concentration ranges, and detection and quantification limits for all complexes were calculated and evaluated at maximum wavelengths of 423, 498, and 625 nm, using methods A, B, and C, respectively. The interference from excipients commonly present in dosage forms and common degradation products was studied. The proposed methods are highly specific for the determination of drugs I and II, in their dosage forms applying the standard additions technique without any interference from common excipients. The proposed methods have been compared statistically to the reference methods and found to be simple, accurate (t-test) and reproducible (F-value).

Colorimetric detection of melamine in milk by using gold nanoparticles-based LSPR via optical fibers

PubMed Central

Chang, Keke; Wang, Shun; Zhang, Hao; Guo, Qingqian; Hu, Xinran; Lin, Zhili; Sun, Haifeng; Jiang, Min

2017-01-01

A biosensing system with optical fibers is proposed for the colorimetric detection of melamine in liquid milk samples by using the localized surface plasmon resonance (LSPR) of unmodified gold nanoparticles (AuNPs). The biosensing system consists of a broadband light source that covers the spectral range from 200 nm to 1700 nm, an optical attenuator, three types of 600 μm premium optical fibers with SMA905 connectors and a miniature spectrometer with a linear charge coupled device (CCD) array. The biosensing system with optical fibers is low-cost, simple and is well-proven for the detection of melamine. Its working principle is based on the color changes of AuNPs solution from wine-red to blue due to the inter-particle coupling effect that causes the shifts of wavelength and absorbance in LSPR band after the to-be-measured melamine samples were added. Under the optimized conditions, the detection response of the LSPR biosensing system was found to be linear in melamine detection in the concentration range from 0μM to 0.9 μM with a correlation coefficient (R2) 0.99 and a detection limit 33 nM. The experimental results obtained from the established LSPR biosensing system in the actual detection of melamine concentration in liquid milk samples show that this technique is highly specific and sensitive and would have a huge application prospects. PMID:28475597

Screening the sequence selectivity of DNA-binding molecules using a gold nanoparticle-based colorimetric approach.

PubMed

Hurst, Sarah J; Han, Min Su; Lytton-Jean, Abigail K R; Mirkin, Chad A

2007-09-15

We have developed a novel competition assay that uses a gold nanoparticle (Au NP)-based, high-throughput colorimetric approach to screen the sequence selectivity of DNA-binding molecules. This assay hinges on the observation that the melting behavior of DNA-functionalized Au NP aggregates is sensitive to the concentration of the DNA-binding molecule in solution. When short, oligomeric hairpin DNA sequences were added to a reaction solution consisting of DNA-functionalized Au NP aggregates and DNA-binding molecules, these molecules may either bind to the Au NP aggregate interconnects or the hairpin stems based on their relative affinity for each. This relative affinity can be measured as a change in the melting temperature (Tm) of the DNA-modified Au NP aggregates in solution. As a proof of concept, we evaluated the selectivity of 4',6-diamidino-2-phenylindone (an AT-specific binder), ethidium bromide (a nonspecific binder), and chromomycin A (a GC-specific binder) for six sequences of hairpin DNA having different numbers of AT pairs in a five-base pair variable stem region. Our assay accurately and easily confirmed the known trends in selectivity for the DNA binders in question without the use of complicated instrumentation. This novel assay will be useful in assessing large libraries of potential drug candidates that work by binding DNA to form a drug/DNA complex.

Headspace-Sampling Paper-Based Analytical Device for Colorimetric/Surface-Enhanced Raman Scattering Dual Sensing of Sulfur Dioxide in Wine.

PubMed

Li, Dan; Duan, Huazhen; Ma, Yadan; Deng, Wei

2018-05-01

This study demonstrates a novel strategy for colorimetric/surface-enhanced Raman scattering (SERS) dual-mode sensing of sulfur dioxide (SO 2 ) by coupling headspace sampling (HS) with paper-based analytical device (PAD). The smart and multifunctional PAD is fabricated with a vacuum filtration method in which 4-mercaptopyridine (Mpy)-modified gold nanorods (GNRs)-reduced graphene oxide (rGO) hybrids (rGO/MPy-GNRs), anhydrous methanol, and starch-iodine complex are immobilized into cellulose-based filter papers. The resultant PAD exhibits a deep-blue color with a strong absorption peak at 600 nm due to the formation of an intermolecular charge-transfer complex between starch and iodine. However, the addition of SO 2 induces the Karl Fischer reaction, resulting in the decrease of color and increase of SERS signals. Therefore, the PAD can be used not only as a naked-eye indicator of SO 2 changed from blue to colorless but also as a highly sensitive SERS substrates because of the SO 2 -triggered conversion of Mpy to pyridine methyl sulfate on the GNRs. A distinguishable change in the color was observed at a SO 2 concentration of 5 μM by the naked eye, and a detection limit as low as 1.45 μM was obtained by virtue of UV-vis spectroscopy. The PAD-based SERS method is effective over a wide range of concentrations (1 μM to 2000 μM) for SO 2 , and the detection limit for SO 2 is found to be 1 μM. The HS-PAD based colorimetric/SERS method is applied for the determination of SO 2 in wine, and the detection results match well with those obtained from the traditional Monier-Williams method. This study not only offers a new method for on-site monitoring of SO 2 but also provides a new strategy for designing of paper-based sensing platform for a wide range of field-test applications.

Biothiols induced colour change of silver nanoparticles: A colorimetric sensing strategy

NASA Astrophysics Data System (ADS)

Thomas, Ambily; Sivasankaran, Unni; Kumar, Krishnapillai Girish

2018-01-01

A sensor for the detection and determination of bio-thiols (glutathione (GSH) and cysteamine (Cyste)) has been developed by integrating the distinguished distance related optical characteristics of silver nanoparticles with the simplicity of colorimetric technique. In presence of these analytes, shift in surface plasmon resonance (SPR) absorption of silver nanoparticles (AgNPs) with change in its colour was observed. Yellow coloured AgNPs solution becomes colourless in presence of GSH and changes to red in presence of Cyste. FTIR, TEM and DLS studies were used to confirm the mechanism. The difference in absorption of AgNPs in the absence and presence of GSH was found to vary linearly in the range 1.00 × 10- 5 M to 5.00 × 10- 7 M concentration range with limit of detection at 3.68 × 10- 7 M. The method can also be applied to quantify Cyste in the range 1.10 × 10- 6 M to 5.00 × 10- 8 M with limit of detection at 1.80 × 10- 8 M. The utility of the proposed colorimetric assay is validated by determination of GSH and Cyste in artificial blood serum.

A label-free colorimetric isothermal cascade amplification for the detection of disease-related nucleic acids based on double-hairpin molecular beacon.

PubMed

Wu, Dong; Xu, Huo; Shi, Haimei; Li, Weihong; Sun, Mengze; Wu, Zai-Sheng

2017-03-08

K-Ras mutations at codon 12 play an important role in an early step of carcinogenesis. Here, a label-free colorimetric isothermal cascade amplification for ultrasensitive and specific detection of K-Ras point mutation is developed based on a double-hairpin molecular beacon (DHMB). The biosensor consists of DHMB probe and a primer-incorporated polymerization template (PPT) designed partly complementary to DHMB. In the presence of polymerase, target DNA is designed to trigger strand displacement amplification (SDA) via promote the hybridization of PPT with DHMB and subsequently initiates cascade amplification process with the help of the nicking endonuclease. During the hybridization and enzymatic reaction, G-quadruplex/hemin DNAzymes are generated, catalyzing the oxidation of ABTS 2- by H 2 O 2 in the presence of hemin. Utilizing the proposed facile colorimetric scheme, the target DNA can be quantified down to 4 pM with the dynamic response range of 5 orders of magnitude, indicating the substantially improved detection capability. Even more strikingly, point mutation in K-ras gene can be readily observed by the naked eye without the need for the labeling or expensive equipment. Given the high-performance for K-Ras analysis, the enhanced signal transduction capability associated with double-hairpin structure of DHMB provides a novel rout to screen biomarkers, and the descripted colorimetric biosensor seems to hold great promise for diagnostic applications of genetic diseases. Copyright © 2016 Elsevier B.V. All rights reserved.

Ultrasensitive and highly selective detection of Cu2 + ions based on a new carbazole-Schiff

NASA Astrophysics Data System (ADS)

Yin, Jun; Bing, Qijing; Wang, Lin; Wang, Guang

2018-01-01

A new chemosensor for Cu2 + based on Schiff base with high sensitivity and selectivity was designed and synthesized. The fluorescence intensity of the chemosensor in CH3CN solution was enhanced 160-fold after the addition of 10 equiv. Cu2 + over other metal ions. In addition, it also facilitates colorimetric detection for Cu2 + in CH3CN solution. The chemosensor displayed low detection limit and fast response time to Cu2 +.

Design, Certification, and Deployment of the Colorimetric Water Quality Monitoring Kit (CWQMK)

NASA Technical Reports Server (NTRS)

Gazda, Daniel B.; Nolan, Daniel J.; Rutz, Jeff A.; Schultz, John R.; Siperko, Lorraine M.; Porter, Marc D.; Lipert, Robert J.; Carrizales, Stephanie M.; McCoy, J. Torin

2009-01-01

In August 2009, an experimental water quality monitoring kit based on Colorimetric Solid Phase Extraction (CSPE) technology was delivered to the International Space Station (ISS) aboard STS-128/17A. The kit, called the Colorimetric Water Quality Monitoring Kit (CWQMK), was developed by a team of scientists and engineers from NASA s Habitability and Environmental Factors Division in the Space Life Sciences Directorate at Johnson Space Center, the Wyle Integrated Science and Engineering Group in Houston, Texas, the University of Utah, and Iowa State University. The CWQMK was flown and deployed as a Station Development Test Objective (SDTO) experiment on ISS. The goal of the SDTO experiment was to evaluate the acceptability of CSPE technology for routine water quality monitoring on ISS. This paper provides an overview of the SDTO experiment, as well as a detailed description of the CWQMK hardware and a summary of the testing and analysis conducted to certify the CWQMK for use on ISS. The results obtained from the SDTO experiment are also reported and discussed in detail.

An imaging-based photometric and colorimetric measurement method for characterizing OLED panels for lighting applications

NASA Astrophysics Data System (ADS)

Zhu, Yiting; Narendran, Nadarajah; Tan, Jianchuan; Mou, Xi

2014-09-01

The organic light-emitting diode (OLED) has demonstrated its novelty in displays and certain lighting applications. Similar to white light-emitting diode (LED) technology, it also holds the promise of saving energy. Even though the luminous efficacy values of OLED products have been steadily growing, their longevity is still not well understood. Furthermore, currently there is no industry standard for photometric and colorimetric testing, short and long term, of OLEDs. Each OLED manufacturer tests its OLED panels under different electrical and thermal conditions using different measurement methods. In this study, an imaging-based photometric and colorimetric measurement method for OLED panels was investigated. Unlike an LED that can be considered as a point source, the OLED is a large form area source. Therefore, for an area source to satisfy lighting application needs, it is important that it maintains uniform light level and color properties across the emitting surface of the panel over a long period. This study intended to develop a measurement procedure that can be used to test long-term photometric and colorimetric properties of OLED panels. The objective was to better understand how test parameters such as drive current or luminance and temperature affect the degradation rate. In addition, this study investigated whether data interpolation could allow for determination of degradation and lifetime, L70, at application conditions based on the degradation rates measured at different operating conditions.

High sensitivity knitted fabric strain sensors

NASA Astrophysics Data System (ADS)

Xie, Juan; Long, Hairu; Miao, Menghe

2016-10-01

Wearable sensors are increasingly used in smart garments for detecting and transferring vital signals and body posture, movement and respiration. Existing fabric strain sensors made from metallized yarns have low sensitivity, poor comfort and low durability to washing. Here we report a knitted fabric strain sensor made from a cotton/stainless steel (SS) fibre blended yarn which shows much higher sensitivity than sensors knitted from metallized yarns. The fabric feels softer than pure cotton textiles owing to the ultrafine stainless steel fibres and does not lose its electrical property after washing. The reason for the high sensitivity of the cotton/SS knitted fabric sensor was explored by comparing its sensing mechanism with the knitted fabric sensor made from metallized yarns. The results show that the cotton/SS yarn-to-yarn contact resistance is highly sensitive to strain applied to hooked yarn loops.

Super-Absorbent Polymer Valves and Colorimetric Chemistries for Time-Sequenced Discrete Sampling and Chloride Analysis of Sweat via Skin-Mounted Soft Microfluidics.

PubMed

Kim, Sung Bong; Zhang, Yi; Won, Sang Min; Bandodkar, Amay J; Sekine, Yurina; Xue, Yeguang; Koo, Jahyun; Harshman, Sean W; Martin, Jennifer A; Park, Jeong Min; Ray, Tyler R; Crawford, Kaitlyn E; Lee, Kyu-Tae; Choi, Jungil; Pitsch, Rhonda L; Grigsby, Claude C; Strang, Adam J; Chen, Yu-Yu; Xu, Shuai; Kim, Jeonghyun; Koh, Ahyeon; Ha, Jeong Sook; Huang, Yonggang; Kim, Seung Wook; Rogers, John A

2018-03-01

This paper introduces super absorbent polymer valves and colorimetric sensing reagents as enabling components of soft, skin-mounted microfluidic devices designed to capture, store, and chemically analyze sweat released from eccrine glands. The valving technology enables robust means for guiding the flow of sweat from an inlet location into a collection of isolated reservoirs, in a well-defined sequence. Analysis in these reservoirs involves a color responsive indicator of chloride concentration with a formulation tailored to offer stable operation with sensitivity optimized for the relevant physiological range. Evaluations on human subjects with comparisons against ex situ analysis illustrate the practical utility of these advances. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dandelions, tulips and orchids: evidence for the existence of low-sensitive, medium-sensitive and high-sensitive individuals.

PubMed

Lionetti, Francesca; Aron, Arthur; Aron, Elaine N; Burns, G Leonard; Jagiellowicz, Jadzia; Pluess, Michael

2018-01-22

According to empirical studies and recent theories, people differ substantially in their reactivity or sensitivity to environmental influences with some being generally more affected than others. More sensitive individuals have been described as orchids and less-sensitive ones as dandelions. Applying a data-driven approach, we explored the existence of sensitivity groups in a sample of 906 adults who completed the highly sensitive person (HSP) scale. According to factor analyses, the HSP scale reflects a bifactor model with a general sensitivity factor. In contrast to prevailing theories, latent class analyses consistently suggested the existence of three rather than two groups. While we were able to identify a highly sensitive (orchids, 31%) and a low-sensitive group (dandelions, 29%), we also detected a third group (40%) characterised by medium sensitivity, which we refer to as tulips in keeping with the flower metaphor. Preliminary cut-off scores for all three groups are provided. In order to characterise the different sensitivity groups, we investigated group differences regarding the Big Five personality traits, as well as experimentally assessed emotional reactivity in an additional independent sample. According to these follow-up analyses, the three groups differed in neuroticism, extraversion and emotional reactivity to positive mood induction with orchids scoring significantly higher in neuroticism and emotional reactivity and lower in extraversion than the other two groups (dandelions also differed significantly from tulips). Findings suggest that environmental sensitivity is a continuous and normally distributed trait but that people fall into three distinct sensitive groups along a sensitivity continuum.

Colorimetric polymer-metal nanocomposite sensor of ammonia for the agricultural industry of confined animal feeding operations

NASA Astrophysics Data System (ADS)

Sarkisov, Sergey S.; Czarick, Michael; Fairchild, Brian D.; Liang, Yi; Kukhtareva, Tatiana; Curley, Michael J.

2014-02-01

The proposed colorimetric sensor of ammonia for the confined animal feeding industry uses the method of optoelectronic spectroscopic measurement of the reversible change of the color of a nanocomposite reagent film in response to ammonia. The film is made of a gold nanocolloid in a polymer matrix with an ammonia-sensitive indicator dye additive. The response of the indicator dye (increase of the optical absorption between 550 and 650 nm) is enhanced by the nanoparticles (˜8 nm in size) in two ways: (a) concentration of the optical field near the nanoparticle due to the plasmon resonance and (b) catalytic acceleration of the chemical reaction of deprotonization of the indicator dye in the presence of ammonia and water vapor. This enhancement helps to miniaturize the sensing element without compromising its sensitivity of <1 parts per million (ppm) for the range 0 to 100 ppm. The sensor underwent field tests in commercial poultry farms in Georgia and Arkansas and was compared against a scientific-grade photoacoustic gas analyzer. The coefficient of correlation between the sensor and the photoacoustic data for several weeks of continuous side-by-side operation in a commercial poultry house was ˜0.9 and the linear regression slope was 1.0. The conclusions on the necessary improvements were made.

A Comparison of Optical, Electrochemical, Magnetic, and Colorimetric Point-of-Care Biosensors for Infectious Disease Diagnosis.

PubMed

Pashchenko, Oleksandra; Shelby, Tyler; Banerjee, Tuhina; Santra, Santimukul

2018-06-18

Each year, infectious diseases are responsible for millions of deaths, most of which occur in the rural areas of developing countries. Many of the infectious disease diagnostic tools used today require a great deal of time, a laboratory setting, and trained personnel. Due to this, the need for effective point-of-care (POC) diagnostic tools is greatly increasing with an emphasis on affordability, portability, sensitivity, specificity, timeliness, and ease of use. In this Review, we discuss the various diagnostic modalities that have been utilized toward this end and are being further developed to create POC diagnostic technologies, and we focus on potential effectiveness in resource-limited settings. The main modalities discussed herein are optical-, electrochemical-, magnetic-, and colorimetric-based modalities utilized in diagnostic technologies for infectious diseases. Each of these modalities feature pros and cons when considering application in POC settings but, overall, reveal a promising outlook for the future of this field of technological development.

Developing on-site paper colorimetric monitoring technique for quick evaluating copper ion concentration in mineral wastewater

NASA Astrophysics Data System (ADS)

Liu, Guokun; Peng, Jingji; Zheng, Hong; Yuan, Dongxing

2018-05-01

With the reinforce of the copper mining, the on-site monitoring of the accompanied effluent discharge is highly demanded for the emergency response to minimize the negative effect of the effluent on the surrounding ecosystem. On the basis of the specific interaction between Cu2+ and L-Cysteine (L-Cys), which was modified on gold nanoparticles (Au NPs), and the aggregation dependent surface plasmon resonance (SPR) of Au NPs, we developed an easy-on-going paper colorimetric method for the quick evaluating the copper ion concentration in the waste water excreted from the copper mine. The color change of L-Cys modified Au NPs (L-Cys-Au NPs)immobilized on a filter paper was very sensitive to the Cu2+ concentration and free of interference from other metal ions typically in waste water. The proposed paper colorimetry has the LOD of 0.09 mg/L and the linear range of 0.1-10 mg/L, respectively, with the RSD (n = 5) was 6.6% for 1 mg/L Cu2+ and 3.5% for 5 mg/L Cu2+. The quantitative analysis results for the mineral wastewater is in good agreement the China National Environmental Protection Standards HJ485-2009, which indicates the current method could be developed to the on-site detection technique for the emergency response in monitoring Cu2+ in industrial wastewater or polluted water.

A quinoline-based fluorometric and colorimetric dual-modal pH probe and its application in bioimaging

NASA Astrophysics Data System (ADS)

Zhu, Qin; Li, Zhao; Mu, Lan; Zeng, Xi; Redshaw, Carl; Wei, Gang

2018-01-01

The compound (E)-8-hydroxyl-2-[(E)-2-(2, 4-dihydroxyphenyl)vinyl]-quinoline (1) has been developed as a fluorometric and colorimetric dual-modal probe for pH detection in solution and in vivo. Remarkable changes in the fluorescence intensity with large Stokes shifts and colorimetric responses were observed as a function of pH. The sensing mechanisms involving protonation and deprotonation processes over the acidic and alkaline pH ranges were confirmed by 1H NMR and IR spectroscopic analysis. Furthermore, the application of probe 1 for the imaging of live PC3 cells was successfully achieved. Test strips based on probe 1 were fabricated, and were found to act as a convenient and efficient pH test kits.

A novel fluorescent probe for rapid and sensitive detection of hydrogen sulfide in living cells

NASA Astrophysics Data System (ADS)

Pan, Jian; Xu, Junchao; Zhang, Youlai; Wang, Liang; Qin, Caiqin; Zeng, Lintao; Zhang, Yue

2016-11-01

A novel fluorescent probe for H2S was developed based on a far-red emitting indole-BODIPY, which was decorated with morpholine and 2,4-dinitrobenzenesulfonyl (DNBS) group. This probe showed rapid response (t1/2 = 3 min), high selectivity and sensitivity for H2S with significant colorimetric and fluorescence OFF-ON signals, which was triggered by cleavage of 2,4-dinitrobenzenesulfonyl group. This probe could quantitatively detect the concentrations of H2S ranging from 0 to 60 μM, and the detection of limit was found to be as low as 26 nM. Cell imaging results indicated that the probe could detect and visualize H2S in the living cells.

A novel cyanide-selective colorimetric and fluorescent chemosensor: first molecular security keypad lock based on phosphotungstic acid and CN- inputs.

PubMed

Tavallali, Hossein; Deilamy-Rad, Gohar; Parhami, Abolfath; Hasanli, Nahid

2014-02-15

Rhodamine B (RhB) an available dye has been developed as novel and efficient colorimetric and fluorometric chemosensor for cyanide ions in an absolutely aqueous media. The UV-vis absorption and fluorescent emission titrations experiments have been employed to study the sensing process. RhB could act as an efficient "ON-OFF" fluorescent response for phosphotungstic acid (H3PW12O40 or PTA) based on an ion associate process. Also (RhB(+))3 · PTA(3-) could operate as an "OFF-ON" fluorescent sensor for cyanide anions based on a ligand substitution process. It has been identified as highly sensitive probe for CN(-) which responds at 0.3 and 0.04 μmol L(-1) concentration levels by absorption and fluorescent method respectively. Depending upon the sequence of addition of PTA and CN(-) ions into the solution, RhB could be as a molecular security keypad lock with PTA and CN(-) inputs. The ionic inputs to new fluorophore have been mimicked as a superimposed electronic molecular keypad lock. The results were compared successfully (>96%) with the data of a spectrophotometry approved method (EPA 9014-1) for cyanide ions. Copyright © 2013 Elsevier B.V. All rights reserved.

A dual-responsive colorimetric and fluorescent chemosensor based on diketopyrrolopyrrole derivative for naked-eye detection of Fe3+ and its practical application.

PubMed

Zhang, Shanshan; Sun, Tao; Xiao, Dejun; Yuan, Fang; Li, Tianduo; Wang, Enhua; Liu, Haixia; Niu, Qingfen

2018-01-15

A novel dual-responsive colorimetric and fluorescent chemosensor L based on diketopyrrolopyrrole derivative for Fe 3+ detection was designed and synthesized. In presence of Fe 3+ , sensor L displayed strong colorimetric response as amaranth to rose pink and significant fluorescence enhancement and chromogenic change, which served as a naked-eye indicator by an obvious color change from purple to red. The binding constant for L-Fe 3+ complex was found as 2.4×10 4 with the lower detection limit of 14.3nM. The sensing mechanism was investigated in detail by fluorescence measurements, IR and 1 H NMR spectra. Sensor L for Fe 3+ detection also exhibited high anti-interference performance, good reversibility, wide pH response range and instantaneous response time. Furthermore, the sensor L has been used to quantify Fe 3+ ions in practical water samples with good recovery. Copyright © 2017 Elsevier B.V. All rights reserved.

A colorimetric sensor for the selective detection of fluoride ions.

PubMed

Wan, Chin-Feng; Chir, Jiun-Ly; Wu, An-Tai

2017-05-01

A colorimetric receptor L was prepared. Receptor L can selectively sense F - based on distinct color changes among a series of ions. It can selectively sense F - through an intramolecular hydrogen bond interaction. A Job plot indicated a 1:1 complexation stoichiometry between receptor L and F - . The association constant for L-F - in CH 3 CN was determined as 9.70 × 10 4  M -1 using a Stern-Volmer plot. Copyright © 2016 John Wiley & Sons, Ltd.

A small molecule sensor for fluoride based on an autoinductive, colorimetric signal amplification reaction.

PubMed

Baker, Matthew S; Phillips, Scott T

2012-05-14

This article describes a small molecule reagent that is capable of detecting fluoride down to 0.12 mM (2.3 ppm) in water. The reagent reveals this level of fluoride through a novel autoinductive signal amplification reaction that produces an unambiguous colorimetric readout.

Colorimetric detection of UV light-induced single-strand DNA breaks using gold nanoparticles.

PubMed

Kim, Joong Hyun; Chung, Chan Ho; Chung, Bong Hyun

2013-02-21

We developed a colorimetric method to specifically detect single-strand DNA breaks using gold nanoparticles. In our assay, broken DNA cannot stabilize gold nanoparticles to prevent salt-induced aggregation as good as intact DNA can, and this effect can be easily observed with the naked eye as a red-to-purple color change.

A novel polydentate ligand chromophore for simultaneously colorimetric detection of trace Ag + and Fe3 +

NASA Astrophysics Data System (ADS)

Yan, Zhengquan; Zhao, Qi; Wen, Meijun; Hu, Lei; Zhang, Xuezhong; You, Jinmao

2017-11-01

A novel polydentate ligand chromophore, 3,6-di-(N-ethyl-N-ethoxyl phenylazo) acridine (EEPA), was identified and synthesized. After its structure was characterized by FTIR, 1H NMR, mass spectra and element analyses, it was noted to find that there was a simultaneously colorimetric response to Ag+ and Fe3 + accompanying with different color changes, i.e., from brown to light purple for Ag+ and further to purple-red for Fe3 +, respectively. Their different action mechanisms, a 1:2 complex mode for EEPA-Ag+ and 1:1 for EEPA-Fe3 +, were investigated and confirmed by means of Job's plot and theoretical calculation. EEPA would be a potential colorimetric chemo-dosimeter for simultaneous detection of Ag+ and Fe3 + with the detection limits of 1.6 nmol·L- 1 and 69 nmol·L- 1, respectively.

Colorimetric evaluation of iPhone apps for colour vision tests based on the Ishihara test.

PubMed

Dain, Stephen J; AlMerdef, Ali

2016-05-01

Given the versatility of smart phone displays, it was inevitable that applications (apps) providing colour vision testing would appear as an option. In this study, the colorimetric characteristics of five available iPhone apps for colour vision testing are assessed as a prequel to possible clinical evaluation. The colours of the displays produced by the apps are assessed with reference to the colours of a printed Ishihara test. The visual task is assessed on the basis of the colour differences and the alignment to the dichromatic confusion lines. The apps vary in quality and while some are colorimetrically acceptable, there are also some problems with their construction in making them a clinically useful app rather than curiosity driven self-testing. There is no reason why, in principle, a suitable test cannot be designed for smart phones. © 2016 Optometry Australia.

Approach to the Highly Sensitized Kidney Transplant Candidate

PubMed Central

Vranic, Gayle M.

2016-01-01

For patients with ESRD, kidney transplant offers significant survival and quality-of-life advantages compared with dialysis. But for patients seeking transplant who are highly sensitized, wait times have traditionally been long and options limited. The approach to the highly sensitized candidate for kidney transplant has changed substantially over time owing to new advances in desensitization, options for paired donor exchange (PDE), and changes to the deceased-donor allocation system. Initial evaluation should focus on determining living-donor availability because a compatible living donor is always the best option. However, for most highly sensitized candidates this scenario is unlikely. For candidates with an incompatible donor, PDE can improve the prospects of finding a compatible living donor but for many highly sensitized patients the probability of finding a match in the relatively small pools of donors in PDE programs is limited. Desensitization of a living donor/recipient pair with low levels of incompatibility is another reasonable approach. But for pairs with high levels of pathologic HLA antibodies, outcomes after desensitization for the patient and allograft are less optimal. Determining the degree of sensitization by calculated panel-reactive antibody (cPRA) is critical in counseling the highly sensitized patient on expected wait times to deceased-donor transplant. For candidates with a high likelihood of finding a compatible deceased donor in a reasonable time frame, waiting for a kidney is a good strategy. For the candidate without a living donor and with a low probability of finding a deceased-donor match, desensitization on the waiting list can be considered. The approach to the highly sensitized kidney transplant candidate must be individualized and requires careful discussion among the transplant center, patient, and referring nephrologist. PMID:26915916

Improving reflectance reconstruction from tristimulus values by adaptively combining colorimetric and reflectance similarities

NASA Astrophysics Data System (ADS)

Cao, Bin; Liao, Ningfang; Li, Yasheng; Cheng, Haobo

2017-05-01

The use of spectral reflectance as fundamental color information finds application in diverse fields related to imaging. Many approaches use training sets to train the algorithm used for color classification. In this context, we note that the modification of training sets obviously impacts the accuracy of reflectance reconstruction based on classical reflectance reconstruction methods. Different modifying criteria are not always consistent with each other, since they have different emphases; spectral reflectance similarity focuses on the deviation of reconstructed reflectance, whereas colorimetric similarity emphasizes human perception. We present a method to improve the accuracy of the reconstructed spectral reflectance by adaptively combining colorimetric and spectral reflectance similarities. The different exponential factors of the weighting coefficients were investigated. The spectral reflectance reconstructed by the proposed method exhibits considerable improvements in terms of the root-mean-square error and goodness-of-fit coefficient of the spectral reflectance errors as well as color differences under different illuminants. Our method is applicable to diverse areas such as textiles, printing, art, and other industries.

High-Sensitivity Microwave Optics.

ERIC Educational Resources Information Center

Nunn, W. M., Jr.

1981-01-01

Describes a 3.33-cm wavelength (9 GHz) microwave system that achieves a high overall signal sensitivity and a well-collimated beam with moderate-size equipment. The system has been used to develop microwave versions of the Michelson interferometer, Bragg reflector, Brewster's law and total internal reflection, and Young's interference experiment.…

High refractive index and temperature sensitivity LPGs for high temperature operation

NASA Astrophysics Data System (ADS)

Nascimento, I. M.; Gouveia, C.; Jana, Surnimal; Bera, Susanta; Baptista, J. M.; Moreira, Paulo; Biwas, Palas; Bandyopadhyay, Somnath; Jorge, Pedro A. S.

2013-11-01

A fiber optic sensor for high sensitivity refractive index and temperature measurement able to withstand temperature up to 450 °C is reported. Two identical LPG gratings were fabricated, whereas one was coated with a high refractive index (~1.78) sol-gel thin film in order to increase its sensitivity to the external refractive index. The two sensors were characterized and compared in refractive index and temperature. Sensitivities of 1063 nm/RIU (1.338 - 1.348) and 260 pm/°C were achieved for refractive index and temperature, respectively.

Colorimetric qualification of shear sensitive liquid crystal coatings

NASA Technical Reports Server (NTRS)

Muratore, Joseph J., Jr.

1993-01-01

The work that has been done to date on the Shear Sensitive Liquid Crystal Project demonstrated that cholesteric liquid crystal coatings respond to both the direction and magnitude of a shearing force. The response of the coating is to selectively scatter incident white light into a spectrum of colors. Discernible color changes at a fixed angle of observation and illumination are the result of an applied shear stress. The intention was to be able to convert these observable color patterns from a flow visualization technique into a quantitative tool. One of the earlier intentions was to be able to use liquid crystals in dynamic flow fields. This was assumed possible because liquid crystals had made it possible to visualize transients in surface shear forces. Although the transients were visualized by color changes to an order one micro second, the time response of a coating to align to a shearing force is dependent on the magnitude of the change between its initial and final states. Unfortunately, the response is not instantaneous. It is for this reason any future attempt at quantifying the magnitude and directions of a shearing force are limited to surface shear stress vector fields in three dimensional steady state flows. This limitation does not significantly detract from the utility of liquid crystal coatings. The measurement of skin friction in the study of transition on wings, prediction of drag forces, performance assessment, and the investigation of boundary layer behavior is of great importance in aerodynamics. There exist numerous examples of techniques for the measurement of surface shear stress. Most techniques require arduous calibrations and necessitate extensive preparation of the receiving surfaces. However, the main draw back of instruments such as Preston tubes, hot films, buried wire gages, and floating element balances is that they only provide a point measurement. The advantages of capturing global shear data would be appreciable when compared

A signal-amplified electrochemical DNA biosensor incorporated with a colorimetric internal control for Vibrio cholerae detection using shelf-ready reagents.

PubMed

Low, Kim-Fatt; Zain, Zainiharyati Mohd; Yean, Chan Yean

2017-01-15

A novel enzyme/nanoparticle-based DNA biosensing platform with dual colorimetric/electrochemical approach has been developed for the sequence-specific detection of the bacterium Vibrio cholerae, the causative agent of acute diarrheal disease in cholera. This assay platform exploits the use of shelf-stable and ready-to-use (shelf-ready) reagents to greatly simplify the bioanalysis procedures, allowing the assay platform to be more amenable to point-of-care applications. To assure maximum diagnosis reliability, an internal control (IC) capable of providing instant validation of results was incorporated into the assay. The microbial target, single-stranded DNA amplified with asymmetric PCR, was quantitatively detected via electrochemical stripping analysis of gold nanoparticle-loaded latex microspheres as a signal-amplified hybridization tag, while the incorporated IC was analyzed using a simplified horseradish peroxidase enzyme-based colorimetric scheme by simple visual observation of enzymatic color development. The platform showed excellent diagnostic sensitivity and specificity (100%) when challenged with 145 clinical isolate-spiked fecal specimens. The limits of detection were 0.5ng/ml of genomic DNA and 10 colony-forming units (CFU)/ml of bacterial cells with dynamic ranges of 0-100ng/ml (R 2 =0.992) and log 10 (1-10 4 CFU/ml) (R 2 =0.9918), respectively. An accelerated stability test revealed that the assay reagents were stable at temperatures of 4-37°C, with an estimated ambient shelf life of 200 days. The versatility of the biosensing platform makes it easily adaptable for quantitative detection of other microbial pathogens. Copyright © 2016 Elsevier B.V. All rights reserved.

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

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

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

2011-12-15

Simple and low cost colorimetric sensors for explosives detection were explored and developed. Anodized aluminum oxide (AAO) with large surface area through its porous structure and light background color was utilized as the substrate for colorimetric sensors. Fabricated thin AAO films with thickness less than {approx} 500 nm allowed us to observe interference colors which were used as the background color for colorimetric detection. AAO thin films with various thickness and pore-to-pore distance were prepared through anodizing aluminum foils at different voltages and times in dilute sulfuric acid. Various interference colors were observed on these samples due to their differencemore » in structures. Accordingly, suitable anodization conditions that produce AAO samples with desired light background colors for optical applications were obtained. Thin film interference model was applied to analyze the UV-vis reflectance spectra and to estimate the thickness of the AAO membranes. We found that the thickness of produced AAO films increased linearly with anodization time in sulfuric acid. In addition, the growth rate was higher for AAO anodized using higher voltages. The thin film interference formulism was further validated with a well established layer by layer deposition technique. Coating poly(styrene sulfonate) sodium salt (PSS) and poly(allylamine hydrochloride) (PAH) layer by layer on AAO thin film consistently shifted its surface color toward red due to the increase in thickness. The red shift of UV-vis reflectance was correlated quantitatively to the number of layers been assembled. This sensitive red shift due to molecular attachment (increase in thickness) on AAO substrate was applied toward nitroaromatics detection. Aminopropyltrimethoxysilane (APTS) which can be attached onto AAO nanowells covalently through silanization and attract TNT molecules was coated and applied for TNT detection. UV-vis spectra of AAO with APTS shifted to the longer wavelength

Evidence in obese children: contribution of hyperlipidemia, obesity-inflammation, and insulin sensitivity.

PubMed

Chang, Chi-Jen; Jian, Deng-Yuan; Lin, Ming-Wei; Zhao, Jun-Zhi; Ho, Low-Tone; Juan, Chi-Chang

2015-01-01

Evidence shows a high incidence of insulin resistance, inflammation and dyslipidemia in adult obesity. The aim of this study was to assess the relevance of inflammatory markers, circulating lipids, and insulin sensitivity in overweight/obese children. We enrolled 45 male children (aged 6 to 13 years, lean control = 16, obese = 19, overweight = 10) in this study. The plasma total cholesterol, HDL cholesterol, triglyceride, glucose and insulin levels, the circulating levels of inflammatory factors, such as TNF-α, IL-6, and MCP-1, and the high-sensitive CRP level were determined using quantitative colorimetric sandwich ELISA kits. Compared with the lean control subjects, the obese subjects had obvious insulin resistance, abnormal lipid profiles, and low-grade inflammation. The overweight subjects only exhibited significant insulin resistance and low-grade inflammation. Both TNF-α and leptin levels were higher in the overweight/obese subjects. A concurrent correlation analysis showed that body mass index (BMI) percentile and fasting insulin were positively correlated with insulin resistance, lipid profiles, and inflammatory markers but negatively correlated with adiponectin. A factor analysis identified three domains that explained 74.08% of the total variance among the obese children (factor 1: lipid, 46.05%; factor 2: obesity-inflammation, 15.38%; factor 3: insulin sensitivity domains, 12.65%). Our findings suggest that lipid, obesity-inflammation, and insulin sensitivity domains predominantly exist among obese children. These factors might be applied to predict the outcomes of cardiovascular diseases in the future.

Disulfide-induced self-assembled targets: A novel strategy for the label free colorimetric detection of DNAs/RNAs via unmodified gold nanoparticles

NASA Astrophysics Data System (ADS)

Shokri, Ehsan; Hosseini, Morteza; Davari, Mehdi D.; Ganjali, Mohammad R.; Peppelenbosch, Maikel P.; Rezaee, Farhad

2017-04-01

A modified non-cross-linking gold-nanoparticles (Au-NPs) aggregation strategy has been developed for the label free colorimetric detection of DNAs/RNAs based on self-assembling target species in the presence of thiolated probes. Two complementary thiol- modified probes, each of which specifically binds at one half of the target introduced SH groups at both ends of dsDNA. Continuous disulfide bond formation at 3‧ and 5‧ terminals of targets leads to the self-assembly of dsDNAs into the sulfur- rich and flexible products with different lengths. These products have a high affinity for the surface of Au-NPs and efficiently protect the surface from salt induced aggregation. To evaluate the assay efficacy, a small part of the citrus tristeza virus (CTV) genome was targeted, leading to a detection limit of about 5 × 10-9 mol.L-1 over a linear ranged from 20 × 10-9 to 10 × 10-7 mol.L-1. This approach also exhibits good reproducibility and recovery levels in the presence of plant total RNA or human plasma total circulating RNA extracts. Self-assembled targets can be then sensitively distinguished from non-assembled or mismatched targets after gel electrophoresis. The disulfide reaction method and integrating self-assembled DNAs/RNAs targets with bare AuNPs as a sensitive indicator provide us a powerful and simple visual detection tool for a wide range of applications.

High selectivity of colorimetric detection of p-nitrophenol based on Ag nanoclusters

NASA Astrophysics Data System (ADS)

Qu, Fei; Chen, Ping; Zhu, Shuyun; You, Jinmao

2017-01-01

Ag nanoclusters (Ag NCs) templated by hyperbranched polyethyleneimine (PEI) with different terminal groups and molecular weights had been developed as a special optical sensor for detecting p-nitrophenol (p-NP). When adding p-NP into Ag NCs, an obvious color change from pale yellow to deep yellow could be observed by naked eyes, accompanying with an apparent red-shift of absorption peak, and the reason was attributed to the formation of oxygen anion of p-NP based on the transfer of H+ from p-NP to amine groups of PEI. The molecular weights of template would greatly affect the sensitivity of p-NP. Ag NCs capped by PEI terminated ethylenediamine (EDA) possessed better sensitivity than other Ag NCs, showing good linear range from 5 to 140 μM with the limit of detection as low as 1.28 μM. Most importantly, this present system displayed high selectivity toward p-NP even in the presence of other nitrophenols and nitrotoluenes. This reliable method had been successfully applied for the detection of p-NP in real water and soil samples.

Colorimetric-Based Detection of TNT Explosives Using Functionalized Silica Nanoparticles

PubMed Central

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

2015-01-01

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

Colorimetric and atomic absorption spectrometric determination of mucolytic drug ambroxol through ion-pair formation with iron and thiocyanate.

PubMed

Levent, Abdulkadir; Sentürk, Zühre

2010-09-01

Colorimetric and atomic absorption spectrometric methods have been developed for the determination of mucolytic drug Ambroxol. These procedures depend upon the reaction of iron(III) metal ion with the drug in the presence of thiocyanate ion to form stable ion-pair complex which extractable chloroform. The red-coloured complex was determined either colorimetrically at 510 nm or by indirect atomic absorption spectrometry (AAS) via the determination of the iron content in the formed complex. The optimum experimental conditions for pH, concentrations of Fe(3+) and SCN(-), shaking time, phase ratio, and the number of extractions were determined. Under the proposed conditions, linearity was obeyed in the concentration ranges 4.1x10(-6) - 5.7x10(-5) M (1.7-23.6 µg mL(-1)) using both methods, with detection limits of 4.6x10(-7) M (0.19 µg mL(-1)) for colorimetry and 1.1x10(-6) M (0.46 µg mL(-1)) for AAS. The proposed methods were applied for the determination of Ambroxol in tablet dosage forms. The results obtained were statistically analyzed and compared with those obtained by applying the high-performance liquid chromatographic method with diode-array detection.

Zinc Biosorption by Seaweed Illustrated by the Zincon Colorimetric Method and the Langmuir Isotherm

ERIC Educational Resources Information Center

Areco, Maria Mar; dos Santos Afonso, Maria; Valdman, Erika

2007-01-01

An experiment is conducted to promote biotechnology knowledge that is an emerging technology on cleaning treatment, showing the potential of seaweed to remove heavy-metal ions from solution. The rapid and accurate determination of zinc in aqueous solution by the zincon colorimetric method gives an interesting and simple experiment for any…

Structure-activity relationships and colorimetric properties of specific probes for the putative cancer biomarker human arylamine N-acetyltransferase 1.

PubMed

Egleton, James E; Thinnes, Cyrille C; Seden, Peter T; Laurieri, Nicola; Lee, Siu Po; Hadavizadeh, Kate S; Measures, Angelina R; Jones, Alan M; Thompson, Sam; Varney, Amy; Wynne, Graham M; Ryan, Ali; Sim, Edith; Russell, Angela J

2014-06-01

A naphthoquinone inhibitor of human arylamine N-acetyltransferase 1 (hNAT1), a potential cancer biomarker and therapeutic target, has been reported which undergoes a distinctive concomitant color change from red to blue upon binding to the enzyme. Here we describe the use of in silico modeling alongside structure-activity relationship studies to advance the hit compound towards a potential probe to quantify hNAT1 levels in tissues. Derivatives with both a fifty-fold higher potency against hNAT1 and a two-fold greater absorption coefficient compared to the initial hit have been synthesized; these compounds retain specificity for hNAT1 and its murine homologue mNat2 over the isoenzyme hNAT2. A relationship between pKa, inhibitor potency and colorimetric properties has also been uncovered. The high potency of representative examples against hNAT1 in ZR-75-1 cell extracts also paves the way for the development of inhibitors with improved intrinsic sensitivity which could enable detection of hNAT1 in tissue samples and potentially act as tools for elucidating the unknown role hNAT1 plays in ER+ breast cancer; this could in turn lead to a therapeutic use for such inhibitors. Copyright © 2014. Published by Elsevier Ltd.

High-sensitivity temperature sensor based on highly-birefringent microfiber

NASA Astrophysics Data System (ADS)

Sun, Li-Peng; Li, Jie; Jin, Long; Gao, Shuai; Tian, Zhuang; Ran, Yang; Guan, Bai-Ou

2013-09-01

We demonstrate an ultrasensitive temperature sensor by sealing a highly-birefringent microfiber into an alcoholinfiltrated copper capillary. With a Sagnac loop configuration, the interferometric spectrum is strongly dependent on the external refractive index (RI) with sensitivity of 36800nm/RIU around RI=1.356. As mainly derived from the ultrahigh RI sensitivity, the temperature response can reach as high as -14.72 nm/°C in the range of 30.9-36.9 °C. The measured response time is ~8s, as determined by the heat-conducting characteristic of the device and the diameter of the copper capillary. Our sensor is featured with low cost, easy fabrication and robustness.

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

NASA Astrophysics Data System (ADS)

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

2011-07-01

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

Determination of water-soluble vitamins using a colorimetric microbial viability assay based on the reduction of water-soluble tetrazolium salts.

PubMed

Tsukatani, Tadayuki; Suenaga, Hikaru; Ishiyama, Munetaka; Ezoe, Takatoshi; Matsumoto, Kiyoshi

2011-07-15

A method for the determination of water-soluble vitamins using a colorimetric microbial viability assay based on the reduction of the tetrazolium salt {2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt (WST-8)} via 2-methyl-1,4-napthoquinone (NQ) was developed. Measurement conditions were optimized for the microbiological determination of water-soluble vitamins, such as vitamin B(6), biotin, folic acid, niacin, and pantothenic acid, using microorganisms that have a water-soluble vitamin requirement. A linear relationship between absorbance and water-soluble vitamin concentration was obtained. The proposed method was applied to determine the concentration of vitamin B(6) in various foodstuffs. There was good agreement between vitamin B(6) concentrations determined after 24h using the WST-8 colorimetric method and those obtained after 48h using a conventional method. The results suggest that the WST-8 colorimetric assay is a useful method for the rapid determination of water-soluble vitamins in a 96-well microtiter plate. Copyright © 2011 Elsevier Ltd. All rights reserved.

Colorimetric detection of copper in water using a Schiff base derivative

NASA Astrophysics Data System (ADS)

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

2013-09-01

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

A comparison of two colorimetric assays, based upon Lowry and Bradford techniques, to estimate total protein in soil extracts.

PubMed

Redmile-Gordon, M A; Armenise, E; White, R P; Hirsch, P R; Goulding, K W T

2013-12-01

Soil extracts usually contain large quantities of dissolved humified organic material, typically reflected by high polyphenolic content. Since polyphenols seriously confound quantification of extracted protein, minimising this interference is important to ensure measurements are representative. Although the Bradford colorimetric assay is used routinely in soil science for rapid quantification protein in soil-extracts, it has several limitations. We therefore investigated an alternative colorimetric technique based on the Lowry assay (frequently used to measure protein and humic substances as distinct pools in microbial biofilms). The accuracies of both the Bradford assay and a modified Lowry microplate method were compared in factorial combination. Protein was quantified in soil-extracts (extracted with citrate), including standard additions of model protein (BSA) and polyphenol (Sigma H1675-2). Using the Lowry microplate assay described, no interfering effects of citrate were detected even with concentrations up to 5 times greater than are typically used to extract soil protein. Moreover, the Bradford assay was found to be highly susceptible to two simultaneous and confounding artefacts: 1) the colour development due to added protein was greatly inhibited by polyphenol concentration, and 2) substantial colour development was caused directly by the polyphenol addition. In contrast, the Lowry method enabled distinction between colour development from protein and non-protein origin, providing a more accurate quantitative analysis. These results suggest that the modified-Lowry method is a more suitable measure of extract protein (defined by standard equivalents) because it is less confounded by the high polyphenolic content which is so typical of soil extracts.

Application of Colorimetric Solid Phase Extraction (C-SPE) to Monitoring Nickel(II) and Lead(II) in Spacecraft Water Supplies

NASA Technical Reports Server (NTRS)

Diaz, Neil C.; Gazda, Daniel B.; Fritz, James S.; Porter, Marc D.; Rutz, Jeff; Mudgett, Paul; Schultz, John

2004-01-01

Archived water samples collected on the International Space Station (ISS) and returned to Earth for analysis have, in a few instances, contained trace levels of heavy metals. Building on our previous advances using Colorimetric Solid Phase Extraction (C-SPE) as a biocide monitoring technique, we are devising methods for the low level monitoring of nickel(II), lead(II) and other heavy metals. C-SPE is a sorption-spectrophotometric platform based on the extraction of analytes onto a membrane impregnated with a colorimetric reagent that are then quantified on the surface of the membrane using a diffuse reflectance spectrophotometer. Along these lines, we have determined nickel(II) via complexation with dimethylglyoxime (DMG) and begun to examine the analysis of lead(II) by its reaction with 2,5- dimercapto-1,3,4-thiadiazole (DMTD) and 4-(2- pyridylazo)-resorcinol (PAR). These developments are also extending a new variant of C-SPE in which immobilized reagents are being incorporated into this methodology in order to optimize sample reaction conditions and to introduce the colorimetric reagent. This paper describes the status of our development of these two new methods.

A novel biphenolic ligand for selective Mg2+ and Zn2+ ions sensing followed by colorimetric, spectroscopic and cell imaging methods.

PubMed

Maheswari, Palanisamy Uma; Renuga, Duraisamy; Henry, Linda Jeeva Kumari; Ruckmani, Kandasamy

2018-04-30

The (E)-2-((2-hydrohy-5-methylphenylimino) methyl) phenol ligand was synthesized. The receptor was characterized by IR, 1 H and 13 C NMR and CHN analysis. The ligand exhibits colorimetric and fluorometric sensing of Zn 2+ and Mg 2+ ions in semi-aqueous medium (DMSO-H2O). The receptor was tested with series of transition metal ions (Cr 2+ , Fe 2+ , Ni 2+ , Co 2+ , Cu 2+ , Zn 2+ ) and heavy metal ions (Sn 2+ , Pd 2+ , Ce 2+ , Hg 2+ , Cd 2+ ) and the essential human body elements like Ca 2+ , Mg 2+ , Na + and K + ions. The naked eye colorimetric sensing was absorbed only for Zn 2+ and Mg 2+ . Both ions (ZnCl 2 and MgCl 2 in H 2 O), when added to the colorless solutions of the receptor of about 1 equivalence in incremental additions turn the solution into bright turmeric yellow. All other ions remain inactive, in colorimetric sensing. Further the Zn 2+ and Mg 2+ ions were probed by absorption and emission spectroscopy through incremental addition of respective metal ions. The in-situ deprotonation of the ligand on both Mg 2+ and Zn 2+ ions binding was confirmed by 1 H NMR titration studies. The imino nitrogen of the receptor is not coordinated to the metal ions. The Job's plot studies reveal the 1:2 binding ratio of metal ions to the receptor. The high fold fluorescence output on metal ions binding was positively used to sense the Zn 2+ and Mg 2+ ions, separately and together in HeLa cancer cells through cell imaging. Copyright © 2018 Elsevier B.V. All rights reserved.

Highly sensitive long-period fiber-grating strain sensor with low temperature sensitivity

NASA Astrophysics Data System (ADS)

Wang, Yi-Ping; Xiao, Limin; Wang, D. N.; Jin, Wei

2006-12-01

A long-period fiber-grating sensor with a high strain sensitivity of -7.6 pm/μɛ and a low temperature sensitivity of 3.91 pm/°C is fabricated by use of focused CO2 laser beam to carve periodic grooves on a large- mode-area photonic crystal fiber. Such a strain sensor can effectively reduce the cross-sensitivity between strain and temperature, and the temperature-induced strain error obtained is only 0.5 μɛ/°C without using temperature compensation.

Visual colorimetric detection of tin(II) and nitrite using a molybdenum oxide nanomaterial-based three-input logic gate.

PubMed

Du, Jiayan; Zhao, Mengxin; Huang, Wei; Deng, Yuequan; He, Yi

2018-05-09

We report a molybdenum oxide (MoO 3 ) nanomaterial-based three-input logic gate that uses Sn 2+ , NO 2 - , and H + ions as inputs. Under acidic conditions, Sn 2+ is able to reduce MoO 3 nanosheets, generating oxygen-vacancy-rich MoO 3-x nanomaterials along with strong localized surface plasmon resonance (LSPR) and an intense blue solution as the output signal. When NO 2 - is introduced, the redox reaction between the MoO 3 nanosheets and Sn 2+ is strongly inhibited because the NO 2 - consumes both H + and Sn 2+ . The three-input logic gate was employed for the visual colorimetric detection of Sn 2+ and NO 2 - under different input states. The colorimetric assay's limit of detection for Sn 2+ and the lowest concentration of NO 2 - detectable by the assay were found to be 27.5 nM and 0.1 μM, respectively. The assay permits the visual detection of Sn 2+ and NO 2 - down to concentrations as low as 2 μM and 25 μM, respectively. The applicability of the logic-gate-based colorimetric assay was demonstrated by using it to detect Sn 2+ and NO 2 - in several water sources.

Methylation-Sensitive High Resolution Melting (MS-HRM).

PubMed

Hussmann, Dianna; Hansen, Lise Lotte

2018-01-01

Methylation-Sensitive High Resolution Melting (MS-HRM) is an in-tube, PCR-based method to detect methylation levels at specific loci of interest. A unique primer design facilitates a high sensitivity of the assays enabling detection of down to 0.1-1% methylated alleles in an unmethylated background.Primers for MS-HRM assays are designed to be complementary to the methylated allele, and a specific annealing temperature enables these primers to anneal both to the methylated and the unmethylated alleles thereby increasing the sensitivity of the assays. Bisulfite treatment of the DNA prior to performing MS-HRM ensures a different base composition between methylated and unmethylated DNA, which is used to separate the resulting amplicons by high resolution melting.The high sensitivity of MS-HRM has proven useful for detecting cancer biomarkers in a noninvasive manner in urine from bladder cancer patients, in stool from colorectal cancer patients, and in buccal mucosa from breast cancer patients. MS-HRM is a fast method to diagnose imprinted diseases and to clinically validate results from whole-epigenome studies. The ability to detect few copies of methylated DNA makes MS-HRM a key player in the quest for establishing links between environmental exposure, epigenetic changes, and disease.

UV-vis spectroscopy and colorimetric models for detecting anthocyanin-metal complexes in plants: An overview of in vitro and in vivo techniques.

PubMed

Fedenko, Volodymyr S; Shemet, Sergiy A; Landi, Marco

2017-05-01

Although anthocyanin (ACN) biosynthesis is one of the best studied pathways of secondary metabolism in plants, the possible physiological and ecological role(s) of these pigments continue to intrigue scientists. Like other dihydroxy B-ring substituted flavonoids, ACNs have an ability to bind metal and metalloid ions, a property that has been exploited for a variety of purposes. For example, the metal binding ability may be used to stabilize ACNs from plant food sources, or to modify their colors for using them as food colorants. The complexation of metals with cyanidin derivatives can also be used as a simple, sensitive, cheap, and rapid method for determination concentrations of several metals in biological and environmental samples using UV-vis spectroscopy. Far less information is available on the ecological significance of ACN-metal complexes in plant-environment interactions. Metalloanthocyanins (protocyanin, nemophilin, commelinin, protodelphin, cyanosalvianin) are involved in the copigmentation phenomenon that leads to blue-pigmented petals, which may facilitate specific plant-pollinator interactions. ACN-metal formation and compartmentation into the vacuole has also been proposed to be part of an orchestrated detoxification mechanism in plants which experience metal/metalloid excess. However, investigations into ACN-metal interactions in plant biology may be limited because of the complexity of the analytical techniques required. To address this concern, here we describe simple methods for the detection of ACN-metal both in vitro and in vivo using UV-vis spectroscopy and colorimetric models. In particular, the use of UV-vis spectra, difference absorption spectra, and colorimetry techniques will be described for in vitro determination of ACN-metal features, whereas reflectance spectroscopy and colorimetric parameters related to CIE L * a * b * and CIE XYZ systems will be detailed for in vivo analyses. In this way, we hope to make this high-informative tool

Colorimetric method for the detection of melamine using in-situ formed silver nanoparticles via tannic acid

NASA Astrophysics Data System (ADS)

Alam, Md. Fazle; Laskar, Amaj Ahmed; Ahmed, Shahbaz; Shaida, Mohd. Azfar; Younus, Hina

2017-08-01

Melamine toxicity has recently attracted worldwide attention as it causes renal failure and the death of humans and animals. Therefore, developing a simple, fast and sensitive method for the routine detection of melamine is the need of the hour. Herein, we have developed a selective colorimetric method for the detection of melamine in milk samples based upon in-situ formation of silver nanoparticles (AgNPs) via tannic acid. The AgNPs thus formed were characterized by UV-Visible spectrophotometer, transmission electron microscope (TEM), zetasizer and dynamic light scattering (DLS). The AgNPs were used to detect melamine under in vitro condition and in raw milk spiked with melamine. Under optimal conditions, melamine could be selectively detected in vitro within the concentration range of 0.05-1.4 μM with a limit of detection (LOD) of 0.01 μM, which is lower than the strictest melamine safety requirement of 1 ppm. In spiked raw milk, the recovery percentage range was 99.5-106.5% for liquid milk and 98.5-105.5% for powdered milk. The present method shows extreme selectivity with no significant interference with other substances like urea, glucose, glycine, ascorbic acid etc. This assay method does not utilize organic cosolvents, enzymatic reactions, light sensitive dye molecules and sophisticated instrumentation, thereby overcoming some of the limitations of the other conventional methods.

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

PubMed Central

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

2011-01-01

Abstract Shiga toxin–producing Escherichia coli O157 is a leading cause of foodborne illness worldwide. To evaluate better methods to rapidly detect and genotype E. coli O157 strains, the present study evaluated the use of ampliPHOX, a novel colorimetric detection method based on photopolymerization, for pathogen identification with DNA microarrays. A low-density DNA oligonucleotide microarray was designed to target stx1 and stx2 genes encoding Shiga toxin production, the eae gene coding for adherence membrane protein, and the per gene encoding the O157-antigen perosamine synthetase. Results from the validation experiments demonstrated that the use of ampliPHOX allowed the accurate genotyping of the tested E. coli strains, and positive hybridization signals were observed for only probes targeting virulence genes present in the reference strains. Quantification showed that the average signal-to-noise ratio values ranged from 47.73 ± 7.12 to 76.71 ± 8.33, whereas average signal-to-noise ratio values below 2.5 were determined for probes where no polymer was formed due to lack of specific hybridization. Sensitivity tests demonstrated that the sensitivity threshold for E. coli O157 detection was 100–1000 CFU/mL. Thus, the use of DNA microarrays in combination with photopolymerization allowed the rapid and accurate genotyping of E. coli O157 strains. PMID:21288130

An improved method for LCD displays colorimetric characterization

NASA Astrophysics Data System (ADS)

Li, Tong; Xie, Kai; Wang, Qiaojie; He, Nannan; Ye, Yushan

2018-03-01

The colorimetric characterization of the display can achieve the purpose of precisely controlling the color of the monitor. This paper describes an improved method for estimating the gamma value of liquid-crystal displays (LCDs) without using a measurement device was described by Xiao et al. It relies on observer's luminance matching by presenting eight half-tone patterns with luminance from 1/9 to 8/9 of the maximum value of each color channel. Since the previous method lacked partial low frequency information, we partially replaced the half-tone patterns. A large number of experiments show that the color difference is reduced from 3.726 to 2.835, and our half-tone pattern can better estimate the visual gamma value of LCDs.

Spectrophotometric, colorimetric and visually detection of Pseudomonas aeruginosa ETA gene based gold nanoparticles DNA probe and endonuclease enzyme

NASA Astrophysics Data System (ADS)

Amini, Bahram; Kamali, Mehdi; Salouti, Mojtaba; Yaghmaei, Parichehreh

2018-06-01

Colorimetric DNA detection is preferred over other methods for clinical molecular diagnosis because it does not require expensive equipment. In the present study, the colorimetric method based on gold nanoparticles (GNPs) and endonuclease enzyme was used for the detection of P. aeruginosa ETA gene. Firstly, the primers and probe for P. aeruginosa exotoxin A (ETA) gene were designed and checked for specificity by the PCR method. Then, GNPs were synthesized using the citrate reduction method and conjugated with the prepared probe to develop the new nano-biosensor. Next, the extracted target DNA of the bacteria was added to GNP-probe complex to check its efficacy for P. aeruginosa ETA gene diagnosis. A decrease in absorbance was seen when GNP-probe-target DNA cleaved into the small fragments of BamHI endonuclease due to the weakened electrostatic interaction between GNPs and the shortened DNA. The right shift of the absorbance peak from 530 to 562 nm occurred after adding the endonuclease. It was measured using a UV-VIS absorption spectroscopy that indicates the existence of the P. aeruginosa ETA gene. Sensitivity was determined in the presence of different concentrations of target DNA of P. aeruginosa. The results obtained from the optimized conditions showed that the absorbance value has linear correlation with concentration of target DNA (R: 0.9850) in the range of 10-50 ng mL-1 with the limit detection of 9.899 ng mL-1. Thus, the specificity of the new method for detection of P. aeruginosa was established in comparison with other bacteria. Additionally, the designed assay was quantitatively applied to detect the P. aeruginosa ETA gene from 103 to 108 CFU mL-1 in real samples with a detection limit of 320 CFU mL-1.

Spectrophotometric, colorimetric and visually detection of Pseudomonas aeruginosa ETA gene based gold nanoparticles DNA probe and endonuclease enzyme.

PubMed

Amini, Bahram; Kamali, Mehdi; Salouti, Mojtaba; Yaghmaei, Parichehreh

2018-06-15

Colorimetric DNA detection is preferred over other methods for clinical molecular diagnosis because it does not require expensive equipment. In the present study, the colorimetric method based on gold nanoparticles (GNPs) and endonuclease enzyme was used for the detection of P. aeruginosa ETA gene. Firstly, the primers and probe for P. aeruginosa exotoxin A (ETA) gene were designed and checked for specificity by the PCR method. Then, GNPs were synthesized using the citrate reduction method and conjugated with the prepared probe to develop the new nano-biosensor. Next, the extracted target DNA of the bacteria was added to GNP-probe complex to check its efficacy for P. aeruginosa ETA gene diagnosis. A decrease in absorbance was seen when GNP-probe-target DNA cleaved into the small fragments of BamHI endonuclease due to the weakened electrostatic interaction between GNPs and the shortened DNA. The right shift of the absorbance peak from 530 to 562nm occurred after adding the endonuclease. It was measured using a UV-VIS absorption spectroscopy that indicates the existence of the P. aeruginosa ETA gene. Sensitivity was determined in the presence of different concentrations of target DNA of P. aeruginosa. The results obtained from the optimized conditions showed that the absorbance value has linear correlation with concentration of target DNA (R: 0.9850) in the range of 10-50ngmL -1 with the limit detection of 9.899ngmL -1 . Thus, the specificity of the new method for detection of P. aeruginosa was established in comparison with other bacteria. Additionally, the designed assay was quantitatively applied to detect the P. aeruginosa ETA gene from 10 3 to 10 8 CFUmL -1 in real samples with a detection limit of 320CFUmL -1 . Copyright © 2018 Elsevier B.V. All rights reserved.

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

PubMed

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

2015-09-01

Gold nanoparticles (AuNPs) were synthesized at room temperature following a simple, rapid, and green route using fresh-squeezed apple juice as a reducing reagent. The optimal AuNPs, based on the particle color, stability, and color change suitable for colorimetric detection of cysteine (Cys), are synthesized using 5 mL of 10% apple juice, 1 mL of 10 mM gold precursor solution, and 1 mL of 0.1 M NaOH. Under this set of parameters, the AuNPs are synthesized within 30 min at room temperature. The average size (11.1 ± 3.2 nm) and ζ potential (-36.5 mV) of the AuNPs synthesized were similar to those of AuNPs prepared via the conventional citrate-reduction method. In the presence of Cys, unlike with any other amino acid, the AuNPs aggregated, possibly due to the gold-sulfur covalent interaction, yielding red-to-purple color change of the sample solution. The red-shift of the localized surface plasmon resonance peak of the AuNPs responsible for the color change was recorded by UV-vis spectrometer. The effect of other potential interferents such as glucose, ascorbic acid, K(+) , Na(+) , Ca(2+) , Zn(2+) , Ag(+) , Ni(2+) , Cu(2+) , Co(2+) , and Hg(2+) were also examined. The results show that AuNPs can be used to selectively detect and measure Cys with a linear dependency in the range of 2 to 100 μM and a limit of detection (signal-to-noise ratio > 3) of 50 nM. The results suggest that the green-synthesized AuNPs are useful for simple, rapid, and sensitive colorimetric detection of Cys, which is an essential amino acid in food and biological systems. © 2015 Institute of Food Technologists®

A spectrally tunable solid-state source for radiometric, photometric, and colorimetric applications

NASA Astrophysics Data System (ADS)

Fryc, Irena; Brown, Steven W.; Eppeldauer, George P.; Ohno, Yoshihiro

2004-10-01

A spectrally tunable light source using a large number of LEDs and an integrating sphere has been designed and being developed at NIST. The source is designed to have a capability of producing any spectral distributions mimicking various light sources in the visible region by feedback control of individual LEDs. The output spectral irradiance or radiance of the source will be calibrated by a reference instrument, and the source will be used as a spectroradiometric as well as photometric and colorimetric standard. The use of the tunable source mimicking spectra of display colors, for example, rather than a traditional incandescent standard lamp for calibration of colorimeters, can reduce the spectral mismatch errors of the colorimeter measuring displays significantly. A series of simulations have been conducted to predict the performance of the designed tunable source when used for calibration of colorimeters. The results indicate that the errors can be reduced by an order of magnitude compared with those when the colorimeters are calibrated against Illuminant A. Stray light errors of a spectroradiometer can also be effectively reduced by using the tunable source producing a blackbody spectrum at higher temperature (e.g., 9000 K). The source can also approximate various CIE daylight illuminants and common lamp spectral distributions for other photometric and colorimetric applications.

Indigo Carmine-Cu complex probe exhibiting dual colorimetric/fluorimetric sensing for selective determination of mono hydrogen phosphate ion and its logic behavior

NASA Astrophysics Data System (ADS)

Tavallali, Hossein; Deilamy-Rad, Gohar; Moaddeli, Ali; Asghari, Khadijeh

2017-08-01

A new selective probe based on copper complex of Indigo Carmine (IC-Cu2) for colorimetric, naked-eye, and fluorimetric recognition of mono hydrogen phosphate (MHP) ion in H2O/DMSO (4:1 v/v, 1.0 mmol L- 1 HEPES buffer solution pH 7.5) was developed. Detection limit of HPO42 - determination, achieved by fluorimetric and 3lorimetric method, are 0.071 and 1.46 μmol L- 1, respectively. Potential, therefore is clearly available in IC-Cu2 complex to detect HPO42 - in micromolar range via dual visible color change and fluorescence response. Present method shows high selectivity toward HPO42 - over other phosphate species and other anions and was successfully utilized for analysis of P2O5 content of a fertilizer sample. The results obtained by proposed chemosensor presented good agreement with those obtained the colorimetric reference method. INHIBIT and IMPLICATION logic gates operating at molecular level have been achieved using Cu2 + and HPO42 - as chemical inputs and UV-Vis absorbance signal as output.

Label-free and pH-sensitive colorimetric materials for the sensing of urea

NASA Astrophysics Data System (ADS)

Li, Lu; Long, Yue; Gao, Jin-Ming; Song, Kai; Yang, Guoqiang

2016-02-01

This communication demonstrates a facile method for naked-eye detection of urea based on the structure color change of pH-sensitive photonic crystals. The insertion of urease provides excellent selectivity over other molecules. The detection of urea in different concentration ranges could be realized by changing the molar ratio between the functional monomer and cross-linker.This communication demonstrates a facile method for naked-eye detection of urea based on the structure color change of pH-sensitive photonic crystals. The insertion of urease provides excellent selectivity over other molecules. The detection of urea in different concentration ranges could be realized by changing the molar ratio between the functional monomer and cross-linker. Electronic supplementary information (ESI) available: Materials and chemicals, characterization, experimental details, and SEM images. See DOI: 10.1039/c5nr07690k

A Rapid Colorimetric Method Reveals Fraudulent Substitutions in Sea Urchin Roe Marketed in Sardinia (Italy).

PubMed

Meloni, Domenico; Spina, Antonio; Satta, Gianluca; Chessa, Vittorio

2016-06-25

In recent years, besides the consumption of fresh sea urchin specimens, the demand of minimally-processed roe has grown considerably. This product has made frequent consumption in restaurants possible and frauds are becoming widespread with the partial replacement of sea urchin roe with surrogates that are similar in colour. One of the main factors that determines the quality of the roe is its colour and small differences in colour scale cannot be easily discerned by the consumers. In this study we have applied a rapid colorimetric method for reveal the fraudulent partial substitution of semi-solid sea urchin roe with liquid egg yolk. Objective assessment of whiteness (L*), redness (a*), yellowness (b*), hue (h*), and chroma (C*) was carried out with a digital spectrophotometer using the CIE L*a*b* colour measurement system. The colorimetric method highlighted statistically significant differences among sea urchin roe and liquid egg yolk that could be easily discerned quantitatively.

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

PubMed

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

2016-01-01

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

High-sensitivity density fluctuation detector

NASA Technical Reports Server (NTRS)

Azzazy, M.; Modarress, D.; Hoeft, T.

1987-01-01

A high-sensitivity differential interferometer has been developed to detect small density fluctuations over an optical path length of the order of the boundary layer thickness near transition. Two experimental configurations have been used to evaluate the performance of the interferometer: an open shear-layer configuration and a wind-tunnel turbulent spot configuration. In each experiment small temperature fluctuations were introduced as the signal source. Simultaneous cold-wire measurements have been compared with the interferometer data. The comparison shows that the interferometer is sensitive to very weak phase variations of the order of 0.001 of the laser wavelength.

A novel reflectance-based aptasensor using gold nanoparticles for the detection of oxytetracycline.

PubMed

Seo, Ho Bin; Kwon, Young Seop; Lee, Ji-eun; Cullen, David; Noh, Hongseok Moses; Gu, Man Bock

2015-10-07

We present a novel reflectance-based colorimetric aptasensor using gold nanoparticles for the detection of oxytetracycline for the first time. It was found that the reflectance-based measurement at two wavelengths (650 and 520 nm) can generate more stable and sensitive signals than absorbance-based sensors to determine the aggregation of AuNPs, even at high AuNP concentrations. One of the most common antibacterial agents, oxytetracycline (OTC), was detected at concentrations as low as 1 nM in both buffer solution and tap water, which was 25-fold more sensitive, compared to the previous absorbance-based colorimetric aptasensors. This reflectance-based colorimetric aptasensor using gold nanoparticles is considered to be a better platform for portable sensing of small molecules using aptamers.

Exploration of Nanoparticle-Mediated Photothermal Effect of TMB-H2O2 Colorimetric System and Its Application in a Visual Quantitative Photothermal Immunoassay.

PubMed

Fu, Guanglei; Sanjay, Sharma T; Zhou, Wan; Brekken, Rolf A; Kirken, Robert A; Li, XiuJun

2018-05-01

The exploration of new physical and chemical properties of materials and their innovative application in different fields are of great importance to advance analytical chemistry, material science, and other important fields. Herein, we, for the first time, discovered the photothermal effect of an iron oxide nanoparticles (NPs)-mediated TMB (3,3',5,5'-tetramethylbenzidine)-H 2 O 2 colorimetric system, and applied it toward the development of a new NP-mediated photothermal immunoassay platform for visual quantitative biomolecule detection using a thermometer as the signal reader. Using a sandwich-type proof-of-concept immunoassay, we found that the charge transfer complex of the iron oxide NPs-mediated one-electron oxidation product of TMB (oxidized TMB) exhibited not only color changes, but also a strong near-infrared (NIR) laser-driven photothermal effect. Hence, oxidized TMB was explored as a new sensitive photothermal probe to convert the immunoassay signal into heat through the near-infrared laser-driven photothermal effect, enabling simple photothermal immunoassay using a thermometer. Based on the new iron oxide NPs-mediated TMB-H 2 O 2 photothermal immunoassay platform, prostate-specific antigen (PSA) as a model biomarker can be detected at a concentration as low as 1.0 ng·mL -1 in normal human serum. The discovered photothermal effect of the colorimetric system and the developed new photothermal immunoassay platform open up a new horizon for affordable detection of disease biomarkers and have great potential for other important material and biomedical applications of interest.

Colorimetric determination of Timolol concentration based on localized surface plasmon resonance of silver nanoparticles

NASA Astrophysics Data System (ADS)

Amirjani, Amirmostafa; Bagheri, Mozhgan; Heydari, Mojgan; Hesaraki, Saeed

2016-09-01

In this work, a rapid and simple colorimetric method based on the surface plasmon resonance of silver nanoparticles (AgNPs) was developed for the detection of the drug Timolol. The method used is based on the interaction of Timolol with the surface of the as-synthesized AgNPs, which promotes aggregation of the nanoparticles. This aggregation exploits the surface plasmon resonance through the electric dipole-dipole interaction and coupling among the agglomerated particles, hence bringing forth distinctive changes in the spectra as well as the color of colloidal silver. UV-vis spectrophotometery was used to monitor the changes of the localized surface plasmon resonance of AgNPs at wavelengths of 400 and 550 nm. The developed colorimetric sensor has a wide dynamic range of 1.0 × 10-7 M-1.0 × 10-3 M for detection of Timolol with a low detection limit of 1.2 × 10-6 M. The proposed method was successfully applied for the determination of Timolol concentration in ophthalmic eye-drop solution with a response time lower than 40 s.

Universal, colorimetric microRNA detection strategy based on target-catalyzed toehold-mediated strand displacement reaction

NASA Astrophysics Data System (ADS)

Park, Yeonkyung; Lee, Chang Yeol; Kang, Shinyoung; Kim, Hansol; Park, Ki Soo; Park, Hyun Gyu

2018-02-01

In this work, we developed a novel, label-free, and enzyme-free strategy for the colorimetric detection of microRNA (miRNA), which relies on a target-catalyzed toehold-mediated strand displacement (TMSD) reaction. The system employs a detection probe that specifically binds to the target miRNA and sequentially releases a catalyst strand (CS) intended to trigger the subsequent TMSD reaction. Thus, the presence of target miRNA releases the CS that mediates the formation of an active G-quadruplex DNAzyme which is initially caged and inactivated by a blocker strand. In addition, a fuel strand that is supplemented for the recycling of the CS promotes another TMSD reaction, consequently generating a large number of active G-quadruplex DNAzymes. As a result, a distinct colorimetric signal is produced by the ABTS oxidation promoted by the peroxidase mimicking activity of the released G-quadruplex DNAzymes. Based on this novel strategy, we successfully detected miR-141, a promising biomarker for human prostate cancer, with high selectivity. The diagnostic capability of this system was also demonstrated by reliably determining target miR-141 in human serum, showing its great potential towards real clinical applications. Importantly, the proposed approach is composed of separate target recognition and signal transduction modules. Thus, it could be extended to analyze different target miRNAs by simply redesigning the detection probe while keeping the same signal transduction module as a universal signal amplification unit, which was successfully demonstrated by analyzing another target miRNA, let-7d.

Universal, colorimetric microRNA detection strategy based on target-catalyzed toehold-mediated strand displacement reaction.

PubMed

Park, Yeonkyung; Lee, Chang Yeol; Kang, Shinyoung; Kim, Hansol; Park, Ki Soo; Park, Hyun Gyu

2018-02-23

In this work, we developed a novel, label-free, and enzyme-free strategy for the colorimetric detection of microRNA (miRNA), which relies on a target-catalyzed toehold-mediated strand displacement (TMSD) reaction. The system employs a detection probe that specifically binds to the target miRNA and sequentially releases a catalyst strand (CS) intended to trigger the subsequent TMSD reaction. Thus, the presence of target miRNA releases the CS that mediates the formation of an active G-quadruplex DNAzyme which is initially caged and inactivated by a blocker strand. In addition, a fuel strand that is supplemented for the recycling of the CS promotes another TMSD reaction, consequently generating a large number of active G-quadruplex DNAzymes. As a result, a distinct colorimetric signal is produced by the ABTS oxidation promoted by the peroxidase mimicking activity of the released G-quadruplex DNAzymes. Based on this novel strategy, we successfully detected miR-141, a promising biomarker for human prostate cancer, with high selectivity. The diagnostic capability of this system was also demonstrated by reliably determining target miR-141 in human serum, showing its great potential towards real clinical applications. Importantly, the proposed approach is composed of separate target recognition and signal transduction modules. Thus, it could be extended to analyze different target miRNAs by simply redesigning the detection probe while keeping the same signal transduction module as a universal signal amplification unit, which was successfully demonstrated by analyzing another target miRNA, let-7d.

High blood pressure and visual sensitivity

NASA Astrophysics Data System (ADS)

Eisner, Alvin; Samples, John R.

2003-09-01

The study had two main purposes: (1) to determine whether the foveal visual sensitivities of people treated for high blood pressure (vascular hypertension) differ from the sensitivities of people who have not been diagnosed with high blood pressure and (2) to understand how visual adaptation is related to standard measures of systemic cardiovascular function. Two groups of middle-aged subjects-hypertensive and normotensive-were examined with a series of test/background stimulus combinations. All subjects met rigorous inclusion criteria for excellent ocular health. Although the visual sensitivities of the two subject groups overlapped extensively, the age-related rate of sensitivity loss was, for some measures, greater for the hypertensive subjects, possibly because of adaptation differences between the two groups. Overall, the degree of steady-state sensitivity loss resulting from an increase of background illuminance (for 580-nm backgrounds) was slightly less for the hypertensive subjects. Among normotensive subjects, the ability of a bright (3.8-log-td), long-wavelength (640-nm) adapting background to selectively suppress the flicker response of long-wavelength-sensitive (LWS) cones was related inversely to the ratio of mean arterial blood pressure to heart rate. The degree of selective suppression was also related to heart rate alone, and there was evidence that short-term changes of cardiovascular response were important. The results suggest that (1) vascular hypertension, or possibly its treatment, subtly affects visual function even in the absence of eye disease and (2) changes in blood flow affect retinal light-adaptation processes involved in the selective suppression of the flicker response from LWS cones caused by bright, long-wavelength backgrounds.

The Alpha-Defensin Immunoassay and Leukocyte Esterase Colorimetric Strip Test for the Diagnosis of Periprosthetic Infection

PubMed Central

Wyatt, M.C.; Beswick, A.D.; Kunutsor, S.K.; Wilson, M.J.; Whitehouse, M.R.; Blom, A.W.

2016-01-01

Background: Synovial biomarkers have recently been adopted as diagnostic tools for periprosthetic joint infection (PJI), but their utility is uncertain. The purpose of this systematic review and meta-analysis was to synthesize the evidence on the accuracy of the alpha-defensin immunoassay and leukocyte esterase colorimetric strip test for the diagnosis of PJI compared with the Musculoskeletal Infection Society diagnostic criteria. Methods: We performed a systematic review to identify diagnostic technique studies evaluating the accuracy of alpha-defensin or leukocyte esterase in the diagnosis of PJI. MEDLINE and Embase on Ovid, ACM, ADS, arXiv, CERN DS (Conseil Européen pour la Recherche Nucléaire Document Server), CrossRef DOI (Digital Object Identifier), DBLP (Digital Bibliography & Library Project), Espacenet, Google Scholar, Gutenberg, HighWire, IEEE Xplore (Institute of Electrical and Electronics Engineers digital library), INSPIRE, JSTOR (Journal Storage), OAlster (Open Archives Initiative Protocol for Metadata Harvesting), Open Content, Pubget, PubMed, and Web of Science were searched for appropriate studies indexed from inception until May 30, 2015, along with unpublished or gray literature. The classification of studies and data extraction were performed independently by 2 reviewers. Data extraction permitted meta-analysis of sensitivity and specificity with construction of receiver operating characteristic curves for each test. Results: We included 11 eligible studies. The pooled diagnostic sensitivity and specificity of alpha-defensin (6 studies) for PJI were 1.00 (95% confidence interval [CI], 0.82 to 1.00) and 0.96 (95% CI, 0.89 to 0.99), respectively. The area under the curve (AUC) for alpha-defensin and PJI was 0.99 (95% CI, 0.98 to 1.00). The pooled diagnostic sensitivity and specificity of leukocyte esterase (5 studies) for PJI were 0.81 (95% CI, 0.49 to 0.95) and 0.97 (95% CI, 0.82 to 0.99), respectively. The AUC for leukocyte esterase and PJI

Microstructure-Sensitive Modeling of High Cycle Fatigue (Preprint)

DTIC Science & Technology

2009-03-01

SUBJECT TERMS microplasticity , microstructure-sensitive modeling, high cycle fatigue, fatigue variability 16. SECURITY CLASSIFICATION OF: 17...3Air Force Research Laboratory Wright Patterson Air Force Base, Ohio 45433 Keywords: Microplasticity , microstructure-sensitive modeling, high cycle...cyclic microplasticity ) plays a key role in modeling fatigue resistance. Unlike effective properties such as elastic stiffness, fatigue is

Highly selective potentiometric and colorimetric determinations of cobalt (II) ion using thiazole based ligands.

PubMed

Singhal, Divya; Singh, Ashok Kumar; Upadhyay, Anjali

2014-12-01

New PVC-membrane electrodes were prepared by using 2-((thiazol-2-ylimino)methyl)phenol (L1) and 2-((thiazol-2-ylamino)methyl)phenol (L2) and explored as Co(II) selective electrodes. The effect of various plasticizers and anion excluder was studied in detail and improved performance was observed. It was found that the electrode based on L1 shows better response characteristics in comparison to L2. Optimum performance was observed for the membrane electrode having a composition of L1:NaTPB:DBP:PVC≡2:8:78:62 (w/w, mg). The performance of PME based on L1 was compared with that of CGE. The electrodes exhibit Nernstian slope for Co(II) ions with a limit of detection of 6.91×10(-7) mol L(-1) for PME and 7.94×10(-8) mol L(-1) for CGE. The response time for PME and CGE was found to be 15s and 12 s respectively. The potentiometric responses are independent in the pH range 3.0-9.0 for CGE. The CGE could be used for a period of 90 days. The CGE was used as an indicator electrode in potentiometric titration of EDTA with Co(2+) ion. Further the selectivity of the L1 and L2 was also confirmed by the UV-vis and colorimetric studies and found that L1 is more selective for Co(II) ion. Copyright © 2014 Elsevier B.V. All rights reserved.

Retinal sensitivity and choroidal thickness in high myopia.

PubMed

Zaben, Ahmad; Zapata, Miguel Á; Garcia-Arumi, Jose

2015-03-01

To estimate the association between choroidal thickness in the macular area and retinal sensitivity in eyes with high myopia. This investigation was a transversal study of patients with high myopia, all of whom had their retinal sensitivity measured with macular integrity assessment microperimetry. The choroidal thicknesses in the macular area were then measured by optical coherence tomography, and statistical correlations between their functionality and the anatomical structuralism, as assessed by both types of measurements, were analyzed. Ninety-six eyes from 77 patients with high myopia were studied. The patients had a mean age ± standard deviation of 38.9 ± 13.2 years, with spherical equivalent values ranging from -6.00 diopter to -20.00 diopter (8.74 ± 2.73 diopter). The mean central choroidal thickness was 159.00 ± 50.57. The mean choroidal thickness was directly correlated with sensitivity (r = 0.306; P = 0.004) and visual acuity but indirectly correlated with the spherical equivalent values and patient age. The mean sensitivity was not significantly correlated with the macular foveal thickness (r = -0.174; P = 0.101) or with the overall macular thickness (r = 0.103; P = 0.334); furthermore, the mean sensitivity was significantly correlated with visual acuity (r = 0.431; P < 0.001) and the spherical equivalent values (r = -0.306; P = 0.003). Retinal sensitivity in highly myopic eyes is directly correlated with choroidal thickness and does not seem to be associated with retinal thickness. Thus, in patients with high myopia, accurate measurements of choroidal thickness may provide more accurate information about this pathologic condition because choroidal thickness correlates to a greater degree with the functional parameters, patient age, and spherical equivalent values.

Augmented Reality for Real-Time Detection and Interpretation of Colorimetric Signals Generated by Paper-Based Biosensors.

PubMed

Russell, Steven M; Doménech-Sánchez, Antonio; de la Rica, Roberto

2017-06-23

Colorimetric tests are becoming increasingly popular in point-of-need analyses due to the possibility of detecting the signal with the naked eye, which eliminates the utilization of bulky and costly instruments only available in laboratories. However, colorimetric tests may be interpreted incorrectly by nonspecialists due to disparities in color perception or a lack of training. Here we solve this issue with a method that not only detects colorimetric signals but also interprets them so that the test outcome is understandable for anyone. It consists of an augmented reality (AR) app that uses a camera to detect the colored signals generated by a nanoparticle-based immunoassay, and that yields a warning symbol or message when the concentration of analyte is higher than a certain threshold. The proposed method detected the model analyte mouse IgG with a limit of detection of 0.3 μg mL -1 , which was comparable to the limit of detection afforded by classical densitometry performed with a nonportable device. When adapted to the detection of E. coli, the app always yielded a "hazard" warning symbol when the concentration of E. coli in the sample was above the infective dose (10 6 cfu mL -1 or higher). The proposed method could help nonspecialists make a decision about drinking from a potentially contaminated water source by yielding an unambiguous message that is easily understood by anyone. The widespread availability of smartphones along with the inexpensive paper test that requires no enzymes to generate the signal makes the proposed assay promising for analyses in remote locations and developing countries.

Colorimetric assay for on-the-spot alcoholic strength sensing in spirit samples based on dual-responsive lanthanide coordination polymer particles with ratiometric fluorescence.

PubMed

Deng, Jingjing; Shi, Guoyue; Zhou, Tianshu

2016-10-26

This study demonstrates a new strategy for colorimetric detection of alcoholic strength (AS) in spirit samples based on dual-responsive lanthanide infinite coordination polymer (Ln-ICP) particles with ratiometric fluorescence. The ICP used in this study are composed of two components: one is the supramolecular Ln-ICP network formed by the coordination between the ligand 2,2'-thiodiacetic acid (TDA) and central metal ion Eu 3+ ; and the other is a fluorescent dye, i.e., coumarin 343 (C343), both as the cofactor ligand and as the sensitizer, doped into the Ln-ICP network through self-adaptive chemistry. Upon being excited at 300 nm, the red fluorescence of Ln-ICP network itself at 617 nm is highly enhanced due to the concomitant energy transfer from C343 to Eu 3+ , while the fluorescence of C343 at 495 nm is supressed. In pure ethanol solvent, the as-formed C343@Eu-TDA is well dispersed and quite stable. However, the addition of water into ethanolic dispersion of C343@Eu-TDA destructs Eu-TDA network structure, resulting in the release of C343 from ICP network into the solvent. Consequently, the fluorescence of Eu-TDA turns off and the fluorescence of C343 turns on, leading to the fluorescent color change of the dispersion from red to blue, which constitutes a new mechanism for colorimetric sensing of AS in commercial spirit samples. With the method developed here, we could clearly distinguish the AS of different spirit samples within a wide linear range from 10% vol to 100% vol directly by "naked eye" with the help of UV-lamp (365 nm). This study not only offers a new method for on-the-spot visible detection of AS, but also provides a strategy for dual-responsive sensing mode by rational designing the optical properties of the Ln-ICP network and the guest, respectively. Copyright © 2016 Elsevier B.V. All rights reserved.

Facial skin color measurement based on camera colorimetric characterization

NASA Astrophysics Data System (ADS)

Yang, Boquan; Zhou, Changhe; Wang, Shaoqing; Fan, Xin; Li, Chao

2016-10-01

The objective measurement of facial skin color and its variance is of great significance as much information can be obtained from it. In this paper, we developed a new skin color measurement procedure which includes following parts: first, a new skin tone color checker made of pantone Skin Tone Color Checker was designed for camera colorimetric characterization; second, the chromaticity of light source was estimated via a new scene illumination estimation method considering several previous algorithms; third, chromatic adaption was used to convert the input facial image into output facial image which appears taken under canonical light; finally the validity and accuracy of our method was verified by comparing the results obtained by our procedure with these by spectrophotometer.

Paper-based tuberculosis diagnostic devices with colorimetric gold nanoparticles

NASA Astrophysics Data System (ADS)

Tsai, Tsung-Ting; Shen, Shu-Wei; Cheng, Chao-Min; Chen, Chien-Fu

2013-08-01

A colorimetric sensing strategy employing gold nanoparticles and a paper assay platform has been developed for tuberculosis diagnosis. Unmodified gold nanoparticles and single-stranded detection oligonucleotides are used to achieve rapid diagnosis without complicated and time-consuming thiolated or other surface-modified probe preparation processes. To eliminate the use of sophisticated equipment for data analysis, the color variance for multiple detection results was simultaneously collected and concentrated on cellulose paper with the data readout transmitted for cloud computing via a smartphone. The results show that the 2.6 nM tuberculosis mycobacterium target sequences extracted from patients can easily be detected, and the turnaround time after the human DNA is extracted from clinical samples was approximately 1 h.

A simple, reversible, colorimetric and water-soluble fluorescent chemosensor for the naked-eye detection of Cu2 + in 100% aqueous media and application to real samples

NASA Astrophysics Data System (ADS)

Sun, Tao; Niu, Qingfen; Li, Tianduo; Guo, Zongrang; Liu, Haixia

2018-01-01

A simple, reversible, colorimetric and water-soluble fluorescent chemosensor ADA for the naked-eye detection of Cu2 + was developed. Sensor ADA showed high selectivity and sensitivity toward Cu2 + in 100% aqueous media over wide pH range. Sensor ADA exhibited a red-shift in the absorption spectra from 466 to 480 nm that is accompanied by significant color change from light yellow to yellowish brown instantaneously. The Cu2 + recognition is based on the chelation-enhanced fluorescence quenching (CHEQ) effect of the paramagnetic nature. The lowest detection limit is determined to be 15.8 nM, which is much lower than the allowable level of Cu2 + in drinking water set by U.S. Environmental Protection Agency ( 20 μM) and the World Health Organization ( 30 μM). The 1:1 binding process was confirmed by fluorescence measurements, IR analysis and DFT studies. Moreover, sensor ADA was successfully applied for determination of trace level of Cu2 + with 4 reuse cycles in various water samples, which affords promising potential in ion-detection field.

Mimicking an Enzyme-Based Colorimetric Aptasensor for Antibiotic Residue Detection in Milk Combining Magnetic Loop-DNA Probes and CHA-Assisted Target Recycling Amplification.

PubMed

Luan, Qian; Gan, Ning; Cao, Yuting; Li, Tianhua

2017-07-19

A mimicking-enzyme-based colorimetric aptasensor was developed for the detection of kanamycin (KANA) in milk using magnetic loop-DNA-NMOF-Pt (m-L-DNA) probes and catalytic hairpin assembly (CHA)-assisted target recycling for signal amplification. The m-L-DNA probes were constructed via hybridization of hairpin DNA H1 (containing aptamer sequence) immobilized magnetic beads (m-H1) and signal DNA (sDNA, partial hybridization with H1) labeled nano Fe-MIL-88NH 2 -Pt (NMOF-Pt-sDNA). In the presence of KANA and complementary hairpin DNA H2, the m-L-DNA probes decomposed and formed an m-H1/KANA intermediate, which triggered the CHA reaction to form a stable duplex strand (m-H1-H2) while releasing KANA again for recycling. Consequently, numerous NMOF-Pt-sDNA as mimicking enzymes can synergistically catalyze 3,3',5,5'-tetramethylbenzidine (TMB) for color development. The aptasensor exhibited high selectivity and sensitivity for KANA in milk with a detection limit of 0.2 pg mL -1 within 30 min. The assay can be conveniently extended for on-site screening of other antibiotics in foods by simply changing the base sequence of the probes.

Base-driven sunlight oxidation of silver nanoprisms for label-free visual colorimetric detection of hexahydro-1,3,5-trinitro-1,3,5-triazine explosive.

PubMed

He, Yi; Wang, Li

2017-05-05

Here we report a label-free method for visual colorimetric detection of hexahydro-1,3,5-trinitro-1,3,5-triazine (HTT) explosive based on base-driven sunlight oxidation of silver nanoprisms (AgNPRs). Under natural sunlight illumination, the surface plasmon of AgNPRs is excited, which populates O 2 antibonding orbitals to generate negative-ion state (O 2 - ). The resultant O 2 - with a strong oxidation activity can etch AgNPRs to smaller nanodisks with the aid of NaOH aqueous solution, leading to a blue shift of the absorption peak and color change from blue to pink. However, when HTT is introduced, the resultant O 2 - will be consumed by the nitrite and formaldehyde that are produced from the alkaline hydrolysis of HTT. Under this condition, the etching of AgNPRs does not occur, and the detection solution remains blue. This assay can sensitively detect as low as 1nM HTT, a level which is three orders of magnitude lower than that of gold nanoparticle-based colorimetric assays (2.6μM), and shows linearity in the range of 0.003-3.3μM. The lowest detectable concentration with the naked eye is 0.1μM. Additionally, the present assay exhibits good selectivity, and can be applied in the detection of HTT in natural water and soil samples with recoveries ranging from 90% to 100%. Copyright © 2017 Elsevier B.V. All rights reserved.

High Sensitivity Optically Pumped Quantum Magnetometer

PubMed Central

Tiporlini, Valentina; Alameh, Kamal

2013-01-01

Quantum magnetometers based on optical pumping can achieve sensitivity as high as what SQUID-based devices can attain. In this paper, we discuss the principle of operation and the optimal design of an optically pumped quantum magnetometer. The ultimate intrinsic sensitivity is calculated showing that optimal performance of the magnetometer is attained with an optical pump power of 20 μW and an operation temperature of 48°C. Results show that the ultimate intrinsic sensitivity of the quantum magnetometer that can be achieved is 327 fT/Hz1/2 over a bandwidth of 26 Hz and that this sensitivity drops to 130 pT/Hz1/2 in the presence of environmental noise. The quantum magnetometer is shown to be capable of detecting a sinusoidal magnetic field of amplitude as low as 15 pT oscillating at 25 Hz. PMID:23766716

Optimization of the cydex blue assay: A one-step colorimetric protein assay using cyclodextrins and compatible with detergents and reducers

PubMed Central

2018-01-01

Sodium dodecyl sulfate electrophoresis (SDS) is a protein separation technique widely used, for example, prior to immunoblotting. Samples are usually prepared in a buffer containing both high concentrations of reducers and high concentrations of SDS. This conjunction renders the samples incompatible with common protein assays. By chelating the SDS, cyclodextrins make the use of simple, dye-based colorimetric assays possible. In this paper, we describe the optimization of the assay, focussing on the cyclodextrin/SDS ratio and the use of commercial assay reagents. The adaptation of the assay to a microplate format and using other detergent-containing conventional extraction buffers is also described. PMID:29641569

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.

Magnetic bead-based enzyme-chromogenic substrate system for ultrasensitive colorimetric immunoassay accompanying cascade reaction for enzymatic formation of squaric acid-iron(III) chelate.

PubMed

Lai, Wenqiang; Tang, Dianping; Zhuang, Junyang; Chen, Guonan; Yang, Huanghao

2014-05-20

This work reports on a simple and feasible colorimetric immunoassay with signal amplification for sensitive determination of prostate-specific antigen (PSA, used as a model) at an ultralow concentration by using a new enzyme-chromogenic substrate system. We discovered that glucose oxidase (GOx), the enzyme broadly used in enzyme-linked immunosorbent assay (ELISA), has the ability to stimulate in situ formation of squaric acid (SQA)-iron(III) chelate. GOx-catalyzed oxidization of glucose leads to the formation of gluconic acid and hydrogen peroxide (H2O2). The latter can catalytically oxidize iron(II) to iron(III), which can rapidly (<1 min) coordinate with the SQA. Formation of the iron-squarate complex causes the color of the solution to change from bluish purple to bluish red accompanying the increasing absorbance with the increment of iron(III) concentration. On the basis of the SQA-iron(III) system, a new immunoassay protocol with GOx-labeled anti-PSA detection antibody can be designed for the detection of target PSA on capture antibody-functionalized magnetic immunosensing probe, monitored by recording the color or absorbance (λ = 468 nm) of the generated SQA-iron(III) chelate. The absorbance intensity shows to be dependent on the concentration of target PSA. A linear dependence between the absorbance and target PSA concentration is obtained under optimal conditions in the range from 1.0 pg mL(-1) to 30 ng mL(-1) with a detection limit (LOD) of 0.5 pg mL(-1) (0.5 ppt) estimated at the 3Sblank level. The sensitivity displays to be 3-5 orders of magnitude better than those of most commercialized human PSA ELISA kits. In addition, the developed colorimetric immunoassay was validated by assaying 12 human serum samples, receiving in good accordance with those obtained by the commercialized PSA ELISA kit. Importantly, the SQA-based immunosensing system can be further extended for the detection of other low-abundance proteins or biomarkers by controlling the target

Modified nondestructive colorimetric method to evaluate the variability of oxygen diffusion rate through wine bottle closures.

PubMed

Brotto, Laura; Battistutta, Franco; Tat, Lara; Comuzzo, Piergiorgio; Zironi, Roberto

2010-03-24

Some modifications to a previous nondestructive colorimetric method that permits evaluation of the oxygen diffusion rate through wine closures were proposed. The method is based on the reaction of indigo carmine solution with oxygen and the tristimulus measurement of the consequent color change. Simplified preparation and measurement procedures were set up, allowing the analysis of a large number of samples simultaneously. The method was applied to the evaluation of the variability within the lot of 20 different types of stoppers (synthetic, produced by molding, and natural cork). The closures were tested at a storage temperature of 26 degrees C. With regard to oxygen permeability, the natural cork stopper showed a low homogeneity within the lot, especially during the first month after bottling, whereas the synthetic closure showed a greater steadiness in the performance. The limits of the colorimetric method were also analyzed, and three possible causes of degradation of the indigo carmine solution were identified: oxygen, light, and heat.

Highly sensitive detection using microring resonator and nanopores

NASA Astrophysics Data System (ADS)

Bougot-Robin, K.; Hoste, J. W.; Le Thomas, N.; Bienstman, P.; Edel, J. B.

2016-04-01

One of the most significant challenges facing physical and biological scientists is the accurate detection and identification of single molecules in free-solution environments. The ability to perform such sensitive and selective measurements opens new avenues for a large number of applications in biological, medical and chemical analysis, where small sample volumes and low analyte concentrations are the norm. Access to information at the single or few molecules scale is rendered possible by a fine combination of recent advances in technologies. We propose a novel detection method that combines highly sensitive label-free resonant sensing obtained with high-Q microcavities and position control in nanoscale pores (nanopores). In addition to be label-free and highly sensitive, our technique is immobilization free and does not rely on surface biochemistry to bind probes on a chip. This is a significant advantage, both in term of biology uncertainties and fewer biological preparation steps. Through combination of high-Q photonic structures with translocation through nanopore at the end of a pipette, or through a solid-state membrane, we believe significant advances can be achieved in the field of biosensing. Silicon microrings are highly advantageous in term of sensitivity, multiplexing, and microfabrication and are chosen for this study. In term of nanopores, we both consider nanopore at the end of a nanopipette, with the pore being approach from the pipette with nanoprecise mechanical control. Alternatively, solid state nanopores can be fabricated through a membrane, supporting the ring. Both configuration are discussed in this paper, in term of implementation and sensitivity.

Novel colorimetric sensors for cyanide based on azo-hydrazone tautomeric skeletons.

PubMed

Adegoke, Olajire A; Adesuji, Temitope E; Thomas, Olusegun E

2014-07-15

The monoazo dyes, 4-carboxyl-2, 6-dinitrophenylazohydroxynaphthalenes dyes (AZ-01, AZ-03 and AZ-04), were evaluated as a highly selective colorimetric chemosensor for cyanide ion. The recognition of cyanide ion gave an obvious colour change from light yellow to brownish red and upon dilution with acetone produced a purple to lilac colour. Optimum conditions for the reaction between the azo dyes and cyanide ion were established at 30°C for 5 min, and different variables affecting the reaction were carefully studied and optimised. Under the optimum conditions, linear relationships between the CN(-) concentrations and light absorption were established. Using these azo-hydrazone molecular switch entities, excellent selectivity towards the detection of CN(-) in aqueous solution over miscellaneous competitive anions was observed. Such selectivity mainly results from the possibility of nucleophilic attack on the azo-hydrazone chemosensors by cyanide anions in aqueous system, which is not afforded by other competing anions. The cyanide chemosensor method described here should have potential application as a new family probes for detecting cyanide in aqueous solution. Copyright © 2014 Elsevier B.V. All rights reserved.

Tuning Sensory Properties of Triazole-Conjugated Spiropyrans: Metal-Ion Selectivity and Paper-Based Colorimetric Detection of Cyanide

PubMed Central

Lee, Juhyen; Choi, Eun Jung; Kim, Inwon; Lee, Minhe; Satheeshkumar, Chinnadurai; Song, Changsik

2017-01-01

Tuning the sensing properties of spiropyrans (SPs), which are one of the photochromic molecules useful for colorimetric sensing, is important for efficient analysis, but their synthetic modification is not always simple. Herein, we introduce an alkyne-functionalized SP, the modification of which would be easily achieved via Cu-catalyzed azide-alkyne cycloaddition (“click reaction”). The alkyne-SP was conjugated with a bis(triethylene glycol)-benzyl group (EG-BtSP) or a simple benzyl group (BtSP), forming a triazole linkage from the click reaction. The effects of auxiliary groups to SP were tested on metal-ion sensing and cyanide detection. We found that EG-BtSP was more Ca2+-sensitive than BtSP in acetonitrile, which were thoroughly examined by a continuous variation method (Job plot) and UV-VIS titrations, followed by non-linear regression analysis. Although both SPs showed similar, selective responses to cyanide in a water/acetonitrile co-solvent, only EG-BtSP showed a dramatic color change when fabricated on paper, highlighting the important contributions of the auxiliary groups. PMID:28783127

Dual Colorimetric and Fluorescent Authentication Based on Semiconducting Polymer Dots for Anticounterfeiting Applications.

PubMed

Tsai, Wei-Kai; Lai, Yung-Sheng; Tseng, Po-Jung; Liao, Chia-Hsien; Chan, Yang-Hsiang

2017-09-13

Semiconducting polymer dots (Pdots) have recently emerged as a novel type of ultrabright fluorescent probes that can be widely used in analytical sensing and material science. Here, we developed a dual visual reagent based on Pdots for anticounterfeiting applications. We first designed and synthesized two types of photoswitchable Pdots by incorporating photochromic dyes with multicolor semiconducting polymers to modulate their emission intensities and wavelengths. The resulting full-color Pdot assays showed that the colorimetric and fluorescent dual-readout abilities enabled the Pdots to serve as an anticounterfeiting reagent with low background interference. We also doped these Pdots into flexible substrates and prepared these Pdots as inks for pen handwriting as well as inkjet printing. We further applied this reagent in printing paper and checks for high-security anticounterfeiting purposes. We believe that this dual-readout method based on Pdots will create a new avenue for developing new generations of anticounterfeiting technologies.

Smartphone-based colorimetric analysis for detection of saliva alcohol concentration.

PubMed

Jung, Youngkee; Kim, Jinhee; Awofeso, Olumide; Kim, Huisung; Regnier, Fred; Bae, Euiwon

2015-11-01

A simple device and associated analytical methods are reported. We provide objective and accurate determination of saliva alcohol concentrations using smartphone-based colorimetric imaging. The device utilizes any smartphone with a miniature attachment that positions the sample and provides constant illumination for sample imaging. Analyses of histograms based on channel imaging of red-green-blue (RGB) and hue-saturation-value (HSV) color space provide unambiguous determination of blood alcohol concentration from color changes on sample pads. A smartphone-based sample analysis by colorimetry was developed and tested with blind samples that matched with the training sets. This technology can be adapted to any smartphone and used to conduct color change assays.

Evaluation of micro-colorimetric lipid determination method with samples prepared using sonication and accelerated solvent extraction methods

EPA Science Inventory

Two common laboratory extraction techniques were evaluated for routine use with the micro-colorimetric lipid determination method developed by Van Handel (1985) [E. Van Handel, J. Am. Mosq. Control Assoc. 1(1985) 302] and recently validated for small samples by Inouye and Lotufo ...

Microstructured graphene arrays for highly sensitive flexible tactile sensors.

PubMed

Zhu, Bowen; Niu, Zhiqiang; Wang, Hong; Leow, Wan Ru; Wang, Hua; Li, Yuangang; Zheng, Liyan; Wei, Jun; Huo, Fengwei; Chen, Xiaodong

2014-09-24

A highly sensitive tactile sensor is devised by applying microstructured graphene arrays as sensitive layers. The combination of graphene and anisotropic microstructures endows this sensor with an ultra-high sensitivity of -5.53 kPa(-1) , an ultra-fast response time of only 0.2 ms, as well as good reliability, rendering it promising for the application of tactile sensing in artificial skin and human-machine interface. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Highly linear, sensitive analog-to-digital converter

NASA Technical Reports Server (NTRS)

Cox, J.; Finley, W. R.

1969-01-01

Analog-to-digital converter converts 10 volt full scale input signal into 13 bit digital output. Advantages include high sensitivity, linearity, low quantitizing error, high resistance to mechanical shock and vibration loads, and temporary data storage capabilities.

Design of mitochondria-targeted colorimetric and ratiometric fluorescent probes for rapid detection of SO2 derivatives in living cells

NASA Astrophysics Data System (ADS)

Yang, Yutao; Zhou, Tingting; Bai, Bozan; Yin, Caixia; Xu, Wenzhi; Li, Wei

2018-05-01

Two mitochondria-targeted colorimetric and ratiometric fluorescent probes for SO2 derivatives were constructed based on the SO2 derivatives-triggered Michael addition reaction. The probes exhibit high specificity toward HSO3-/SO32- by interrupting their conjugation system resulting in a large ratiometric blue shift of 46-121 nm in their emission spectrum. The two well-resolved emission bands can ensure accurate detection of HSO3-. The detection limits were calculated to be 1.09 and 1.35 μM. Importantly, probe 1 and probe 2 were successfully used to fluorescence ratiometric imaging of endogenous HSO3- in BT-474 cells.

Color digital halftoning taking colorimetric color reproduction into account

NASA Astrophysics Data System (ADS)

Haneishi, Hideaki; Suzuki, Toshiaki; Shimoyama, Nobukatsu; Miyake, Yoichi

1996-01-01

Taking colorimetric color reproduction into account, the conventional error diffusion method is modified for color digital half-toning. Assuming that the input to a bilevel color printer is given in CIE-XYZ tristimulus values or CIE-LAB values instead of the more conventional RGB or YMC values, two modified versions based on vector operation in (1) the XYZ color space and (2) the LAB color space were tested. Experimental results show that the modified methods, especially the method using the LAB color space, resulted in better color reproduction performance than the conventional methods. Spatial artifacts that appear in the modified methods are presented and analyzed. It is also shown that the modified method (2) with a thresholding technique achieves a good spatial image quality.

Development of high-sensitivity SWIR APD receivers

NASA Astrophysics Data System (ADS)

Bai, Xiaogang; Yuan, Ping; Chang, James; Sudharsanan, Rengarajan; Krainak, Michael; Yang, Guangning; Sun, Xiaoli; Lu, Wei

2013-06-01

Emerging short wavelength infrared (SWIR) LIght Detection And Ranging (LIDAR) and long range laser rangefinder systems, require large optical aperture avalanche photodiodes (APDs) receivers with high sensitivity and high bandwidth. A large optical aperture is critical to increase the optical coupling efficiency and extend the LIDAR sensing range of the above systems. Both APD excess noise and transimpedance amplifier (TIA) noise need to be reduced in order to achieve high receiver sensitivity. The dark current and capacitance of large area APDs increase with APD aperture and thus limit the sensitivity and bandwidth of receivers. Spectrolab has been developing low excess noise InAlAs/InGaAs APDs with impact ionization engineering (I2E) designs for many years and has demonstrated APDs with optical gain over 100 utilizing multiple period I2E structures in the APD multiplier. These high gain I2E APDs have an excess noise factor less than 0.15. With an optical aperture of 200 μm, low excess noise multiple periods I2E APDs have capacitances about 1.7 pF. In addition, optical gains of InAlAs based APDs show very little temperature dependence and will enable APD photoreceivers without thermal electric cooling.

High sensitivity boundary layer transition detector

NASA Technical Reports Server (NTRS)

Azzazy, M.; Modarress, D.; Hoeft, T.

1985-01-01

A high sensitivity differential interferometer has been developed to locate the region where the boundary layer flow changes from laminar to turbulent. Two experimental configurations have been used to evaluate the performance of the interferometer, open shear layer configuration and wind tunnel turbulent spot configuration. In each experiment small temperature fluctuations were introduced as the signal source. Simultaneous cold wire measurements have been compared with the interferometer data. The comparison shows that the interferometer is sensitive to very weak phase variations in the order of .001 the laser wavelength.

Ultra-long high-sensitivity Φ-OTDR for high spatial resolution intrusion detection of pipelines.

PubMed

Peng, Fei; Wu, Han; Jia, Xin-Hong; Rao, Yun-Jiang; Wang, Zi-Nan; Peng, Zheng-Pu

2014-06-02

An ultra-long phase-sensitive optical time domain reflectometry (Φ-OTDR) that can achieve high-sensitivity intrusion detection over 131.5km fiber with high spatial resolution of 8m is presented, which is the longest Φ-OTDR reported to date, to the best of our knowledge. It is found that the combination of distributed Raman amplification with heterodyne detection can extend the sensing distance and enhances the sensitivity substantially, leading to the realization of ultra-long Φ-OTDR with high sensitivity and spatial resolution. Furthermore, the feasibility of applying such an ultra-long Φ-OTDR to pipeline security monitoring is demonstrated and the features of intrusion signal can be extracted with improved SNR by using the wavelet detrending/denoising method proposed.

Reaction-based Indicator displacement Assay (RIA) for the selective colorimetric and fluorometric detection of peroxynitrite.

PubMed

Sun, Xiaolong; Lacina, Karel; Ramsamy, Elena C; Flower, Stephen E; Fossey, John S; Qian, Xuhong; Anslyn, Eric V; Bull, Steven D; James, Tony D

2015-05-01

Using the self-assembly of aromatic boronic acids with Alizarin Red S (ARS), we developed a new chemosensor for the selective detection of peroxynitrite. Phenylboronic acid (PBA), benzoboroxole (BBA) and 2-( N , N -dimethylaminomethyl)phenylboronic acid (NBA) were employed to bind with ARS to form the complex probes. In particular, the ARS-NBA system with a high binding affinity can preferably react with peroxynitrite over hydrogen peroxide and other ROS/RNS due to the protection of the boron via the solvent-insertion B-N interaction. Our simple system produces a visible colorimetric change and on-off fluorescence response towards peroxynitrite. By coupling a chemical reaction that leads to an indicator displacement, we have developed a new sensing strategy, referred to herein as RIA (Reaction-based Indicator displacement Assay).

Naked-eye fingerprinting of single nucleotide polymorphisms on psoriasis patients

NASA Astrophysics Data System (ADS)

Valentini, Paola; Marsella, Alessandra; Tarantino, Paolo; Mauro, Salvatore; Baglietto, Silvia; Congedo, Maurizio; Paolo Pompa, Pier

2016-05-01

We report a low-cost test, based on gold nanoparticles, for the colorimetric (naked-eye) fingerprinting of a panel of single nucleotide polymorphisms (SNPs), relevant for the personalized therapy of psoriasis. Such pharmacogenomic tests are not routinely performed on psoriasis patients, due to the high cost of standard technologies. We demonstrated high sensitivity and specificity of our colorimetric test by validating it on a cohort of 30 patients, through a double-blind comparison with two state-of-the-art instrumental techniques, namely reverse dot blotting and sequencing, finding 100% agreement. This test offers high parallelization capabilities and can be easily generalized to other SNPs of clinical relevance, finding broad utility in diagnostics and pharmacogenomics.We report a low-cost test, based on gold nanoparticles, for the colorimetric (naked-eye) fingerprinting of a panel of single nucleotide polymorphisms (SNPs), relevant for the personalized therapy of psoriasis. Such pharmacogenomic tests are not routinely performed on psoriasis patients, due to the high cost of standard technologies. We demonstrated high sensitivity and specificity of our colorimetric test by validating it on a cohort of 30 patients, through a double-blind comparison with two state-of-the-art instrumental techniques, namely reverse dot blotting and sequencing, finding 100% agreement. This test offers high parallelization capabilities and can be easily generalized to other SNPs of clinical relevance, finding broad utility in diagnostics and pharmacogenomics. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr02200f

A new automated colorimetric method for measuring total oxidant status.

PubMed

Erel, Ozcan

2005-12-01

To develop a new, colorimetric and automated method for measuring total oxidation status (TOS). The assay is based on the oxidation of ferrous ion to ferric ion in the presence of various oxidant species in acidic medium and the measurement of the ferric ion by xylenol orange. The oxidation reaction of the assay was enhanced and precipitation of proteins was prevented. In addition, autoxidation of ferrous ion present in the reagent was prevented during storage. The method was applied to an automated analyzer, which was calibrated with hydrogen peroxide and the analytical performance characteristics of the assay were determined. There were important correlations with hydrogen peroxide, tert-butyl hydroperoxide and cumene hydroperoxide solutions (r=0.99, P<0.001 for all). In addition, the new assay presented a typical sigmoidal reaction pattern in copper-induced lipoprotein autoxidation. The novel assay is linear up to 200 micromol H2O2 Equiv./L and its precision value is lower than 3%. The lower detection limit is 1.13 micromol H2O2 Equiv./L. The reagents are stable for at least 6 months on the automated analyzer. Serum TOS level was significantly higher in patients with osteoarthritis (21.23+/-3.11 micromol H2O2 Equiv./L) than in healthy subjects (14.19+/-3.16 micromol H2O2 Equiv./L, P<0.001) and the results showed a significant negative correlation with total antioxidant capacity (TAC) (r=-0.66 P<0.01). This easy, stable, reliable, sensitive, inexpensive and fully automated method that is described can be used to measure total oxidant status.

High-sensitivity strain visualization using electroluminescence technologies

NASA Astrophysics Data System (ADS)

Xu, Jian; Jo, Hongki

2016-04-01

Visualizing mechanical strain/stress changes is an emerging area in structural health monitoring. Several ways are available for strain change visualization through the color/brightness change of the materials subjected to the mechanical stresses, for example, using mechanoluminescence (ML) materials and mechanoresponsive polymers (MRP). However, these approaches were not effectively applicable for civil engineering system yet, due to insufficient sensitivity to low-level strain of typical civil structures and limitation in measuring both static and dynamic strain. In this study, design and validation for high-sensitivity strain visualization using electroluminescence technologies are presented. A high-sensitivity Wheatstone bridge, of which bridge balance is precisely controllable circuits, is used with a gain-adjustable amplifier. The monochrome electroluminescence (EL) technology is employed to convert both static and dynamic strain change into brightness/color change of the EL materials, through either brightness change mode (BCM) or color alternation mode (CAM). A prototype has been made and calibrated in lab, the linearity between strain and brightness change has been investigated.

Sunlight Induced Preparation of Functionalized Gold Nanoparticles as Recyclable Colorimetric Dual Sensor for Aluminum and Fluoride in Water.

PubMed

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

2017-05-24

A sunlight induced simple green route has been developed for the synthesis of polyacrylate functionalized gold nanoparticles (PAA-AuNPs), in which poly(acrylic acid) functions as a reducing as well as stabilizing agent. This material has been characterized on the basis of spectroscopic and microscopic studies; it exhibited selective colorimetric detection of Al 3+ in aqueous media, and the Al 3+ induced aggregated PAA-AuNPs exhibited detection of F - with sharp color change and high selectivity and sensitivity out of a large number of metal ions and anions tested. The mechanistic study revealed that, for Al 3+ , the color change is due to a shift of the SPR band because of the Al 3+ induced aggregation of PAA-AuNPs, whereas for F - , the reverse color change (blue to red) with return of the SPR band to its original position is due to dispersion of aggregated PAA-AuNPs, as F - removes Al 3+ from the aggregated species by complex formation. Only concentration-dependent fluoride ion can prevent Al 3+ from aggregating PAA-AuNPs. The method is successfully used for the detection of F - in water collected from various sources by the spiking method, in toothpastes of different brands by the direct method. The solid Al 3+ -PAA-AuNPs were isolated, adsorbed on ZIF@8 (zeolitic imidazolate framework) and on a cotton strip, and applied as solid sensing material for detection of F - in aqueous media.

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.

Phase sensitive diffraction sensor for high sensitivity refractive index measurement

NASA Astrophysics Data System (ADS)

Kumawat, Nityanand; Varma, Manoj; Kumar, Sunil

2018-02-01

In this study a diffraction based sensor has been developed for bio molecular sensing applications and performing assays in real time. A diffraction grating fabricated on a glass substrate produced diffraction patterns both in transmission and reflection when illuminated by a laser diode. We used zeroth order I(0,0) as reference and first order I(0,1) as signal channel and conducted ratiometric measurements that reduced noise by more than 50 times. The ratiometric approach resulted in a very simple instrumentation with very high sensitivity. In the past, we have shown refractive index measurements both for bulk and surface adsorption using the diffractive self-referencing approach. In the current work we extend the same concept to higher diffraction orders. We have considered order I(0,1) and I(1,1) and performed ratiometric measurements I(0,1)/I(1,1) to eliminate the common mode fluctuations. Since orders I(0,1) and I(1,1) behaved opposite to each other, the resulting ratio signal amplitude increased more than twice compared to our previous results. As a proof of concept we used different salt concentrations in DI water. Increased signal amplitude and improved fluid injection system resulted in more than 4 times improvement in detection limit, giving limit of detection 1.3×10-7 refractive index unit (RIU) compared to our previous results. The improved refractive index sensitivity will help significantly for high sensitivity label free bio sensing application in a very cost-effective and simple experimental set-up.

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

PubMed

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

2013-04-03

An easy-to-use colorimetric test-system for the efficient detection of creatinine in aqueous samples was developed. The test-system is based on composite molecularly imprinted polymer (MIP) membranes with artificial receptor sites capable of creatinine recognition. A thin MIP layer was created on the surface of microfiltration polyvinylidene fluoride (PVDF) membranes using method of photo-initiated grafting polymerization. The MIP layer was obtained by co-polymerization of a functional monomer (e.g. 2-acrylamido-2-methyl-1-propanesulfonic acid, itaconic acid or methacrylic acid) with N, N'-methylenebisacrylamide as a cross-linker. The choice of the functional monomer was based on the results of computational modeling. The creatinine-selective composite MIP membranes were used for measuring creatinine in aqueous samples. Creatinine molecules were selectively adsorbed by the MIP membranes and quantified using color reaction with picrates. The intensity of MIP membranes staining was proportional to creatinine concentration in an analyzed sample. The colorimetric test-system based on the composite MIP membranes was characterized with 0.25 mM detection limit and 0.25-2.5mM linear dynamic range. Storage stability of the MIP membranes was estimated as at least 1 year at room temperature. As compared to the traditional methods of creatinine detection the developed test-system is characterized by simplicity of operation, small size and low cost. Copyright © 2013 Elsevier B.V. All rights reserved.

Naked eye screening of 11 phenolic compounds and colorimetric determination using polydiacetylene vesicles with α-cyclodextrin

NASA Astrophysics Data System (ADS)

Anekthirakun, Pimpimon; Sukwattanasinitt, Mongkol; Tuntulani, Thawatchai; Imyim, Apichat

2013-07-01

The colorimetric response (CR) of poly(10,12-pentacosadiynoic acid) vesicles (PPCDA) induced by α-cyclodextrin (α-CD) in an aqueous solution has been studied. Various parameters affecting the CR, such as response time and concentration were investigated. The blue color of 0.01 mM PPCDA solution became pinkish red with the addition of α-CD at the concentration higher than 3 mM. The inhibition of the color transition from blue to red was investigated using 11 phenolic compounds. The color transition could be inhibited and observed by naked eye in the presence of 4 phenolic compounds, i.e. 4-nitrophenol (4-NP) and 4-bromophenol (4-BP) and 4-chlorophenol (4-CP) and 3-nitrophenol (3-NP). A colorimetric method for the determination of these compounds was validated and applied for surface water analysis. The linear range from the plot of CR against phenolic compounds concentration was in the order of 0.5-2.0 mM with R2 more than 0.99. The recoveries were 90-95% with good precision (1-4%RSD, n = 10).

Freely suspended nanocomposite membranes as highly sensitive sensors

NASA Astrophysics Data System (ADS)

Jiang, Chaoyang; Markutsya, Sergiy; Pikus, Yuri; Tsukruk, Vladimir V.

2004-10-01

Highly sensitive sensor arrays are in high demand for prospective applications in remote sensing and imaging. Measuring microscopic deflections of compliant micromembranes and cantilevers is developing into one of the most versatile approaches for thermal, acoustic and chemical sensing. Here, we report on an innovative fabrication of compliant nanocomposite membranes with nanoscale thickness showing extraordinary sensitivity and dynamic range, which makes them candidates for a new generation of membrane-based sensor arrays. These nanomembranes with a thickness of 25-70 nm, which can be freely suspended over large (hundred micrometres) openings are fabricated with molecular precision by time-efficient, spin-assisted layer-by-layer assembly. They are designed as multilayered molecular composites made of a combination of polymeric monolayers and a metal nanoparticle intralayer. We demonstrate that these nanocomposite membranes possess unparalleled sensitivity and a unique autorecovering ability. The membrane nanostructure that is responsible for these outstanding properties combines multilayered polymer/nanoparticle organization, high polymer-chain orientation, and a pre-stretched state.

Rituximab in highly sensitized kidney transplant recipients.

PubMed

Munoz, A S; Rioveros, A A; Cabanayan-Casasola, C B; Danguilan, R A; Ona, E T

2008-09-01

Rituximab, an anti-CD20 monoclonal antibody therapy, depletes B cells and suppresses antibody production. This study sought to describe the efficacy and safety of rituximab among seven highly sensitized kidney transplant patients. A highly sensitized patient was defined as panel-reactive antibody (PRA) >30%, more than three pregnancies, or history of positive tissue crossmatch. Demographics, immunological risk profile, and immunosuppression were collected on all highly sensitized patients transplanted from March to July 2007 and given rituximab. We noted graft function as well as clinical events posttransplantation. The seven patients included in the study showed a mean age of 39 years (range = 17-60) and a mean follow-up of 3 months (range = 1.5-5). Their average PRA was 62% with mean HLA mismatches of three. Five patients (71%) were retransplantations; one had a history of a positive crossmatch, and two had multiple pregnancies. Two had donor-specific antibody, but negative tissue crossmatches. All had living donors. Six patients received a single dose of rituximab (375 mg/m2) 1 day prior to transplantation and one received two doses after 19 sessions of plasmapheresis. All were given tacrolimus, mycophenolate, and steroids combined with induction therapy using 30 mg alemtuzumab in 33%; two doses of 20 mg basiliximab in 33%; and seven doses of 1 mg/kg/dose of daclizumab in 14%. Mean shown creatinine levels were 1.1 and 1.2 mg/dL at 1 and 6 months posttransplantation. Two recipients experienced acute humoral rejections within 1 month after transplantation. Both were given steroid pulsing, one of whom was steroid-resistant necessitating alemtuzumab therapy and plasmapheresis. Graft function of both improved with creatinine values of 1.3 mg/dL on discharge. No episodes of infection were noted. Rituximab can be safely administered and may be effective to improve outcomes among highly sensitized kidney transplant patients.

Comparative analysis for strength serum sodium and potassium in three different methods: Flame photometry, ion-selective electrode (ISE) and colorimetric enzymatic.

PubMed

Garcia, Rafaela Alvim; Vanelli, Chislene Pereira; Pereira Junior, Olavo Dos Santos; Corrêa, José Otávio do Amaral

2018-06-19

Hydroelectrolytic disorders are common in clinical situations and may be harmful to the patient, especially those involving plasma sodium and potassium dosages. Among the possible methods for the dosages are flame photometry, ion-selective electrode (ISE) and colorimetric enzymatic method. We analyzed 175 samples in the three different methods cited from patients attending the laboratory of the University Hospital of the Federal University of Juiz de Fora. The values obtained were statistically treated using SPSS 19.0 software. The present study aims to evaluate the impact of the use of these different methods in the determination of plasma sodium and potassium. The averages obtained for sodium and potassium measurements by flame photometry were similar (P > .05) to the means obtained for the two electrolytes by ISE. The averages obtained by the colorimetric enzymatic method presented statistical difference in relation to ISE, both for sodium and potassium. In the correlation analysis, both flame photometry and colorimetric enzymatic showed a strong correlation with the ISE method for both dosages. At the first time in the same work sodium and potassium were analyzed by three different methods and the results allowed us to conclude that the methods showed a positive and strong correlation, and can be applied in the clinical routine. © 2018 Wiley Periodicals, Inc.

The strain-rate sensitivity of high-strength high-toughness steels.

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

Dilmore, M.F.; Crenshaw, Thomas B.; Boyce, Brad Lee

2006-01-01

The present study examines the strain-rate sensitivity of four high strength, high-toughness alloys at strain rates ranging from 0.0002 s-1 to 200 s-1: Aermet 100, a modified 4340, modified HP9-4-20, and a recently developed Eglin AFB steel alloy, ES-1c. A refined dynamic servohydraulic method was used to perform tensile tests over this entire range. Each of these alloys exhibit only modest strain-rate sensitivity. Specifically, the strain-rate sensitivity exponent m, is found to be in the range of 0.004-0.007 depending on the alloy. This corresponds to a {approx}10% increase in the yield strength over the 7-orders of magnitude change in strain-rate.more » Interestingly, while three of the alloys showed a concominant {approx}3-10% drop in their ductility with increasing strain-rate, the ES1-c alloy actually exhibited a 25% increase in ductility with increasing strain-rate. Fractography suggests the possibility that at higher strain-rates ES-1c evolves towards a more ductile dimple fracture mode associated with microvoid coalescence.« less

Colorimetric DNAzyme Biosensor for Convenience Detection of Enterotoxin B Harboring Staphylococcus aureus from Food Samples.

PubMed

Mondal, Bhairab; N, Bhavanashri; Ramlal, Shylaja; Kingston, Joseph

2018-02-14

In the present study, a colorimetric DNAzymes biosensor strategy was devised in combination with immunomagnetic separation for rapid and easy detection of enterotoxin B harboring Staphylococcus aureus from food and clinical samples. The method employs immunocapture of S. aureus and amplification of seb gene by DNAzyme complementary sequence integrated forward primer and with specific reverse primer. The DNAzyme sequence integrated dsDNA PCR products when treated with hemin and TMB (3,3',5,5'-tetramethylbenzidine) in the presence of H 2 O 2 produce colorimetric signal. A linear relationship of optical signal with the initial template of seb was obtained which could be monitored by visually or spectrophotrometrically for qualitative and quantitative detection. The limit of detection for the assay was approximately 10 2 CFU/mL of seb gene harboring target. This method is convenient compared to gel based and ELISA systems. Further, spiking studies and analysis on natural samples emphasized the robustness and applicability of developed method. Altogether, the established assay could be a reliable alternative, low-cost, viable detection tool for the routine investigation of seb from food and clinical sources.

Colorimetric Humidity Sensor Using Inverse Opal Photonic Gel in Hydrophilic Ionic Liquid.

PubMed

Kim, Seulki; Han, Sung Gu; Koh, Young Gook; Lee, Hyunjung; Lee, Wonmok

2018-04-27

We demonstrate a fast response colorimetric humidity sensor using a crosslinked poly(2-hydroxyethyl methacrylate) (PHEMA) in the form of inverse opal photonic gel (IOPG) soaked in 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM⁺][BF₄ − ]), a non-volatile hydrophilic room temperature ionic liquid (IL). An evaporative colloidal assembly enabled the fabrication of highly crystalline opal template, and a subsequent photopolymerization of PHEMA followed by solvent-etching and final soaking in IL produced a humidity-responsive IOPG showing highly reflective structural color by Bragg diffraction. Three IOPG sensors with different crosslinking density were fabricated on a single chip, where a lightly crosslinked IOPG exhibited the color change response over entire visible spectrum with respect to the humidity changes from 0 to 80% RH. As the water content increased in IL, thermodynamic interactions between PHEMA and [BMIM⁺][BF₄ − ] became more favorable, to show a red-shifted structural color owing to a longitudinal swelling of IOPG. Highly porous IO structure enabled fast humidity-sensing kinetics with the response times of ~1 min for both swelling and deswelling. Temperature-dependent swelling of PHEMA in [BMIM⁺][BF₄ − ] revealed that the current system follows an upper critical solution temperature (UCST) behavior with the diffraction wavelength change as small as 1% at the temperature changes from 10 °C to 30 °C.

Highly selective and reversible chemosensor for Pd(2+) detected by fluorescence, colorimetry, and test paper.

PubMed

Wang, Mian; Liu, Xiaomei; Lu, Huizhe; Wang, Hongmei; Qin, Zhaohai

2015-01-21

A "turn-on" fluorescent and colorimetric chemosensor (RBS) for Pd(2+) has been designed and synthesized through introduction of sulfur as a ligand atom to Rhodamine B. RBS exhibits high selectivity (freedom from the interference of Hg(2+ )in particular) and sensitivity toward Pd(2+) with a detection limit as low as 2.4 nM. RBS is also a reversible sensor, and it can be made into test paper to detect Pd(2+) in pure water. Compared to the chemosensors that introduced phosphorus to Rhodamine to detect Pd(2+), RBS can be synthesized more simply and economically.

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

PubMed

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

2015-03-01

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

A label-free DNA hairpin biosensor for colorimetric detection of target with suitable functional DNA partners.

PubMed

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

2013-11-15

The combination of aptamer and peroxidase-mimicking DNAzyme within a hairpin structure can form a functional DNA probe. The activities of both aptamer (as biorecognition element) and DNAzyme (as signal amplification element) are blocked via base pairing in the hairpin structure. The presence of target triggers the opening of the hairpin to form target/aptamer complex and releases G-quadruplex sequence which can generate amplified colorimetric signals. In this work, we elaborated a universal and simple procedure to design an efficient and sensitive hairpin probe with suitable functional DNA partners. A fill-in-the-blank process was developed for sequence design, and two key points including the pretreatment of the hairpin probe and the selection of suitable signal transducer sequence were proved to enhance the detection sensitivity. Cocaine was chosen as a model target for a proof of concept. A series of hairpins with different numbers of base pairs in the stem region were prepared. Hairpin-C10 with ten base pairs was screened out and a lowest detectable cocaine concentration of 5 μM by colorimetry was obtained. The proposed functional DNA hairpin showed good selectivity and satisfactory analysis in spiked biologic fluid. The whole "mix-and-measure" detection based on DNA hairpin without the need of immobilization and labeling was indicated to be time and labor saving. The strategy has potential to be transplanted into more smart hairpins toward other targets for general application in bioanalytical chemistry. Copyright © 2013 Elsevier B.V. All rights reserved.

Highly sensitive beam steering with plasmonic antenna

PubMed Central

Rui, Guanghao; Zhan, Qiwen

2014-01-01

In this work, we design and study a highly sensitive beam steering device that integrates a spiral plasmonic antenna with a subwavelength metallic waveguide. The short effective wavelength of the surface plasmon polaritons (SPPs) mode supported by the metallic waveguide is exploited to dramatically miniaturize the device and improve the sensitivity of the beam steering. Through introducing a tiny displacement of feed point with respect to the geometrical center of the spiral plasmonic antenna, the direction of the radiation can be steered at considerably high angles. Simulation results show that steering angles of 8°, 17° and 34° are obtainable for a displacement of 50 nm, 100 nm and 200 nm, respectively. Benefiting from the reduced device size and the shorter SPP wavelength, the beam steering sensitivity of the beam steering is improved by 10-fold compared with the case reported previously. This miniature plasmonic beam steering device may find many potential applications in quantum optical information processing and integrated photonic circuits. PMID:25091405

Target-induced proximity ligation triggers recombinase polymerase amplification and transcription-mediated amplification to detect tumor-derived exosomes in nasopharyngeal carcinoma with high sensitivity.

PubMed

Liu, Wanli; Li, Jianpei; Wu, Yixian; Xing, Shan; Lai, Yanzhen; Zhang, Ge

2018-04-15

Tumor-derived exosomes (TEXs) are extracellular vesicles that are continuously released into the blood by tumor cells and carry specific surface markers of the original tumor cells. Substantial evidence has implicated TEXs as attractive diagnostic markers for cancer. However, the detection of TEXs in blood at an early tumor stage is challenging due to their very low concentration. Here, we established a method called PLA-RPA-TMA assay that allows TEXs to be detected with high sensitivity and specificity. Based on two proximity ligation assay (PLA) probes that recognize a biomarker on a TEX, we generated a unique surrogate DNA signal for the specific biomarker, which was synchronously amplified twice by recombinase polymerase amplification (RPA) coupled with transcription-mediated amplification (TMA), and then the products of the RPA-TMA reaction were quantitatively detected using a gold nanoparticle-based colorimetric assay. We established proof-of-concept evidence for this approach using TEXs from nasopharyngeal carcinoma (NPC) cells, with a detection limit of 10 2 particles/mL, and reported the measurement of plasma Epstein-Barr virus latent membrane protein 1 (LPM1)-positive (LMP1 + , accuracy: 0.956) and epidermal growth factor receptor (EGFR)-positive (EGFR + , accuracy: 0.906) TEXs as potent early diagnostic biomarkers for NPC. Copyright © 2017 Elsevier B.V. All rights reserved.

Construction of mathematical model for measuring material concentration by colorimetric method

NASA Astrophysics Data System (ADS)

Liu, Bing; Gao, Lingceng; Yu, Kairong; Tan, Xianghua

2018-06-01

This paper use the method of multiple linear regression to discuss the data of C problem of mathematical modeling in 2017. First, we have established a regression model for the concentration of 5 substances. But only the regression model of the substance concentration of urea in milk can pass through the significance test. The regression model established by the second sets of data can pass the significance test. But this model exists serious multicollinearity. We have improved the model by principal component analysis. The improved model is used to control the system so that it is possible to measure the concentration of material by direct colorimetric method.

A simple, reversible, colorimetric and water-soluble fluorescent chemosensor for the naked-eye detection of Cu2+ in ~100% aqueous media and application to real samples.

PubMed

Sun, Tao; Niu, Qingfen; Li, Tianduo; Guo, Zongrang; Liu, Haixia

2018-01-05

A simple, reversible, colorimetric and water-soluble fluorescent chemosensor ADA for the naked-eye detection of Cu 2+ was developed. Sensor ADA showed high selectivity and sensitivity toward Cu 2+ in ~100% aqueous media over wide pH range. Sensor ADA exhibited a red-shift in the absorption spectra from 466 to 480nm that is accompanied by significant color change from light yellow to yellowish brown instantaneously. The Cu 2+ recognition is based on the chelation-enhanced fluorescence quenching (CHEQ) effect of the paramagnetic nature. The lowest detection limit is determined to be 15.8nM, which is much lower than the allowable level of Cu 2+ in drinking water set by U.S. Environmental Protection Agency (~20μM) and the World Health Organization (~30μM). The 1:1 binding process was confirmed by fluorescence measurements, IR analysis and DFT studies. Moreover, sensor ADA was successfully applied for determination of trace level of Cu 2+ with 4 reuse cycles in various water samples, which affords promising potential in ion-detection field. Copyright © 2017 Elsevier B.V. All rights reserved.

Nanofiber-net-binary structured membranes for highly sensitive detection of trace HCl gas

NASA Astrophysics Data System (ADS)

Wang, Xianfeng; Wang, Jialin; Si, Yang; Ding, Bin; Yu, Jianyong; Sun, Gang; Luo, Wenjing; Zheng, Gang

2012-11-01

This work describes the detection of trace hydrogen chloride (HCl) gas through analyses of the resonance frequency signal from quartz crystal microbalance (QCM) sensors coated with polyaniline (PANI) functionalized polyamide 6 (PA 6) (PANI-PA 6) nanofiber-net-binary (NNB) structured membranes. The PA 6 NNB substrate comprising nanofibers and spider-web-like nano-nets fabricated by a versatile electro-spinning/netting (ESN) process offered an ideal interface for the uniform PANI functionalization and enhanced sensing performance. Benefiting from the large specific surface area, high porosity, and strong adhesive force to the QCM electrode of the PANI-PA 6 NNB membranes, the developed HCl-selective sensors exhibited a rapid response, good reproducibility and stability, and low detection limit (7 ppb) at room temperature. Additionally, the PANI-PA 6 NNB sensing membranes presented visible color changes upon cycled exposure to HCl and ammonia, suggesting their potential application in the development of colorimetric sensors. The PANI-PA 6 NNB coated QCM sensors are considered to be a promising candidate for trace HCl gas detection in practical applications.

High-sensitivity sucrose erbium-doped fiber ring laser sensor

NASA Astrophysics Data System (ADS)

Khaleel, Wurood Abdulkhaleq; Al-Janabi, Abdul Hadi M.

2017-02-01

We investigate a high-sensitivity sucrose sensor based on a standard erbium-doped fiber ring laser incorporating a coreless fiber (CF). A single-mode-coreless-single mode (SCS) structure with a very low insertion loss has been constructed. The SCS fiber structure performed dual function as an intracavity fiber filter and/or a sensing element. The gain medium (erbium-doped fiber) is pumped by a 975-nm wavelength fiber coupled diode laser. Laser emission around 1537 nm with -2 dBm peak output power is obtained when a CF in SCS structure has a diameter of 125 μm. The 3-dB line-width of the laser is <0.14 nm, which is beneficial to high precision sensing. The sucrose concentration varied from 0% to 60%, and the relationship between the lasing wavelength and the sucrose concentration exhibited linear behavior (R2=0.996), with sensitivity of 0.16 nm/% was obtained. To improve the measurement sensitivity, the CF is etched by hydrofluoric acid. The splice joint of etched CF with SMF is a taper, which improves its sensitivity to sucrose changes. An average sensitivity of 0.57 nm/% and a high signal-to-noise ratio of 50 dB make the proposed sensor suitable for potential applications.

A novel colorimetric and "turn-on" fluorimetric chemosensor for selective recognition of CN- ions based on asymmetric azine derivatives in aqueous media

NASA Astrophysics Data System (ADS)

Pei, Peng-Xiang; Hu, Jing-Han; Long, Chen; Ni, Peng-Wei

2018-06-01

A novel chemosensor 2-((Z)-(((E)-quinolin-2-ylmethylene)hydrazono)methyl)phenol PX has been successfully designed and synthesized, which showed both colorimetric and "turn-on" fluorescence responses for CN- in DMSO/H2O (3:2, v/v; pH = 7.20) solution. The sensor could respond effectively to the stimulation of CN- ions via deprotonation and sensing mechanism of intramolecular charge transfer (ICT). Moreover, the sensor PX was successfully utilized to detect CN- in bitter almond, and the detection limit on fluorescence response of PX towards CN- was down to 4.5 × 10-7 M. Test strips containing PX were also prepared, which could act as a practical colorimetric tool to detect CN- in aqueous media.

Efficient colorimetric and fluorescent detection of fluoride in DMSO-water mixtures with arylaldoximes.

PubMed

Rosen, Christian B; Hansen, Dennis J; Gothelf, Kurt V

2013-12-07

Fluoride detection through hydrogen bonding or deprotonation is most commonly achieved using amide, urea or pyrrole derivatives. The sensor molecules are often complex constructs and several synthetic steps are required for their preparation. Here we report the discovery that simple arylaldoximes have remarkable properties as fluoride anion sensors, providing distinct colorimetric or fluorescent readouts, depending on the structure of the arylaldoxime. The oximes showed exceptional selectivity towards fluoride over other typical anions, and low detection limits for fluoride in both DMSO and DMSO-water mixtures were obtained.

Real-time monitoring of enzyme-free strand displacement cascades by colorimetric assays

NASA Astrophysics Data System (ADS)

Duan, Ruixue; Wang, Boya; Hong, Fan; Zhang, Tianchi; Jia, Yongmei; Huang, Jiayu; Hakeem, Abdul; Liu, Nannan; Lou, Xiaoding; Xia, Fan

2015-03-01

The enzyme-free toehold-mediated strand displacement reaction has shown potential for building programmable DNA circuits, biosensors, molecular machines and chemical reaction networks. Here we report a simple colorimetric method using gold nanoparticles as signal generators for the real-time detection of the product of the strand displacement cascade. During the process the assembled gold nanoparticles can be separated, resulting in a color change of the solution. This assay can also be applied in complex mixtures, fetal bovine serum, and to detect single-base mismatches. These results suggest that this method could be of general utility to monitor more complex enzyme-free strand displacement reaction-based programmable systems or for further low-cost diagnostic applications.The enzyme-free toehold-mediated strand displacement reaction has shown potential for building programmable DNA circuits, biosensors, molecular machines and chemical reaction networks. Here we report a simple colorimetric method using gold nanoparticles as signal generators for the real-time detection of the product of the strand displacement cascade. During the process the assembled gold nanoparticles can be separated, resulting in a color change of the solution. This assay can also be applied in complex mixtures, fetal bovine serum, and to detect single-base mismatches. These results suggest that this method could be of general utility to monitor more complex enzyme-free strand displacement reaction-based programmable systems or for further low-cost diagnostic applications. Electronic supplementary information (ESI) available: Experimental procedures and analytical data are provided. See DOI: 10.1039/c5nr00697j

Non-crosslinking gold nanoprobe-LAMP for simple, colorimetric, and specific detection of Salmonella typhi

NASA Astrophysics Data System (ADS)

Bozorgmehr, Ali; Yazdanparast, Razieh; Mollasalehi, Hamidreza

2016-12-01

In this study, we developed a non-crosslinking gold nanoprobe loop-mediated isothermal amplification (LAMP) method for nanodiagnosis of bacterial typhoid fever source, Salmonella typhi. Therefore, a unique region in the S. typhi genomic DNA was targeted for LAMP amplification using a specific set of four precisely designed primers. Also, for specific colorimetric visualization of the amplicons, a thiolated oligonucleotide probe, complementary to the single-stranded loop region of the amplicons between F2 and F1C segments, was designed. The probe was bound to the surface of gold nanoparticles via covalent bonds. Increasing the salt concentration in the detection reaction medium led to aggregation of nanoprobes in the blank and the negative vessels in a time-dependent form. That was followed by a change in the surface plasmon resonance (SPR) leading to blue/black color that was observable by the naked eyes after about 5 min. Meanwhile, the original pink/red color was retained in the positive sample due to the large interparticle spaces and the stability against the ionic strength elevation which persisted for about 30 min. The whole process of DNA extraction, amplification, and detection took less than 2 h with a sensitivity of 20 CFU/ml. The developed gold nanoprobe-LAMP could serve as a simple, rapid, and cost-effective method for nanodiagnosis of S. typhi in point-of-need applications.

Novel colorimetric assay for paraquat detection on-silica bead using negatively charged silver nanoparticles.

PubMed

Siangproh, Weena; Somboonsuk, Thachkorn; Chailapakul, Orawan; Songsrirote, Kriangsak

2017-11-01

A simple, rapid, sensitive, and economical method based on colorimetry for the determination of paraquat, a widely used herbicide, was developed. Citrate-coated silver nanoparticles (AgNPs) were synthesized as the colorimetric probe. The mechanism of the assay is related to the aggregation of negatively charged AgNPs as induced by positively-charged paraquat resulting from coulombic attraction which causes the color to change from a deep greenish yellow to pale yellow in accordance with the concentrations of paraquat. Silica gel was exploited as the paraquat adsorbent for purification and pre-concentration prior to the direct determination with negatively charged AgNPs without the requirement of the elution step. The validity of the proposed approach was evaluated by spiking standard paraquat in water and plant samples. Recoveries of paraquat in water samples were 93.6% and 95.4% for groundwater and canal water, respectively, while those in plant samples were 89.5% and 86.6% for Chinese cabbage and green apple, respectively,after using the optimized extraction procedure. The absorbance of AgNPs at 400nm was linearly related to the concentration of paraquat over the range of 0.05-50mgL -1 , with detection limits of 0.05mgL -1 for water samples, and 0.10mgL -1 for plant samples by naked eye determination. Copyright © 2017 Elsevier B.V. All rights reserved.

Comparison of tetrazolium colorimetric and [3H]-uridine assays for in vitro chemosensitivity testing.

PubMed

Ford, C H; Richardson, V J; Tsaltas, G

1989-01-01

We have routinely used a [3H]-uridine microplate assay for assessing chemosensitivity. A colorimetric assay with the advantages of safety, cost and simplicity has previously been described and relies on the ability of living cells to reduce a soluble tetrazolium salt, 3-4,5-dimethylthiazol-2,5-diphenyl-tetrazolium bromide (MMT), into an insoluble formazan precipitate. We compared the chemosensitivity of 14 human tumour cell lines of colonic, lung and cervical carcinoma origin to doxorubicin, vindesine or vindesine immunoconjugates in both the [3H]-uridine assay and a modified MTT assay to evaluate whether we could change to the non-radiolabelled method. Correlation between the concentration of drug causing 50% inhibition of cell growth (IC50) for these agents between the two assays was very poor. However, taking account of recent reports in the literature, we modified the MTT assay by removing serum-containing medium and using dimethyl sulphoxide to solubilise the formazan precipitate. This considerably improved the correlation between the assays for doxorubicin (r = 0.871; P = 0.001) and vindesine (r = 0.981; P less than 0.001). Our data indicates that the MTT assay can be used to replace the [3H]-uridine assay for chemosensitivity screening, but further modifications are necessary to improve the sensitivity and decrease the problem of cell loss after washing, which was noted with some adherent cell lines.

Genotype-based dosage of acenocoumarol in highly-sensitive geriatric patients.

PubMed

Lozano, Roberto; Franco, María-Esther; López, Luis; Moneva, Juan-José; Carrasco, Vicente; Pérez-Layo, Maria-Angeles

2015-03-01

Our aim was to determinate the acenocoumarol dose requirement in highly sensitive geriatric patients, based on a minimum of genotype (VKORC1 and CYP2C9) data. We used a Gaussian kernel density estimation test to identify patients highly sensitive to the drug and PHARMACHIP®-Cuma test (Progenika Biopharma, SA, Grifols, Spain) to determine the CYP2C9 and VKORC1 genotype. All highly sensitive geriatric patients were taking ≤5.6 mg/week of acenocoumarol (AC), and 86% of these patients presented the following genotypes: CYP2C9*1/*3 or CYP2C9*1/*2 plus VKORC1 A/G, CYP2C9*3/*3, or VKORC1 A/A. VKORC1 A and CYP2C9*2 and/or *3 allelic variants extremely influence on AC dose requirement of highly sensitive geriatric patients. These patients display acenocoumarol dose requirement of ≤5.6 mg/week.

The combined rapid detection and species-level identification of yeasts in simulated blood culture using a colorimetric sensor array.

PubMed

Shrestha, Nabin K; Lim, Sung H; Wilson, Deborah A; SalasVargas, Ana Victoria; Churi, Yair S; Rhodes, Paul A; Mazzone, Peter J; Procop, Gary W

2017-01-01

A colorimetric sensor array (CSA) has been demonstrated to rapidly detect and identify bacteria growing in blood cultures by obtaining a species-specific "fingerprint" of the volatile organic compounds (VOCs) produced during growth. This capability has been demonstrated in prokaryotes, but has not been reported for eukaryotic cells growing in culture. The purpose of this study was to explore if a disposable CSA could differentially identify 7 species of pathogenic yeasts growing in blood culture. Culture trials of whole blood inoculated with a panel of clinically important pathogenic yeasts at four different microorganism loads were performed. Cultures were done in both standard BacT/Alert and CSA-embedded bottles, after adding 10 mL of spiked blood to each bottle. Color changes in the CSA were captured as images by an optical scanner at defined time intervals. The captured images were analyzed to identify the yeast species. Time to detection by the CSA was compared to that in the BacT/Alert system. One hundred sixty-two yeast culture trials were performed, including strains of several species of Candida (Ca. albicans, Ca. glabrata, Ca. parapsilosis, and Ca. tropicalis), Clavispora (synonym Candida) lusitaniae, Pichia kudriavzevii (synonym Candida krusei) and Cryptococcus neoformans, at loads of 8.2 × 105, 8.3 × 103, 8.5 × 101, and 1.7 CFU/mL. In addition, 8 negative trials (no yeast) were conducted. All negative trials were correctly identified as negative, and all positive trials were detected. Colorimetric responses were species-specific and did not vary by inoculum load over the 500000-fold range of loads tested, allowing for accurate species-level identification. The mean sensitivity for species-level identification by CSA was 74% at detection, and increased with time, reaching almost 95% at 4 hours after detection. At an inoculum load of 1.7 CFU/mL, mean time to detection with the CSA was 6.8 hours (17%) less than with the BacT/Alert platform. The CSA

Tuning the chromaticity of the emission color of the copolymers containing Eu(III), Tb(III), Be(II) ions based on colorimetric principle

NASA Astrophysics Data System (ADS)

Zhang, Aiqin; Yang, Yamin; Zhai, Guangmei; Jia, Husheng; Xu, Bingshe

2016-02-01

In this work, a method of tuning the chromaticity of the emission color of the copolymers containing Eu(III), Tb(III), Be(II) ions based on colorimetric principle was proposed. The technological route from coordination to copolymerization was employed to obtain the white light macromolecular phosphor. The three primary color monomers have been synthesized and their Commission Internationale de L'Eclairage (CIE) coordinates are respectively (0.540, 0.314), (0.231, 0.463), and (0.161, 0.054). The molar feed ratios of the three primary color monomers were calculated from the CIE coordinates based on colorimetric principle. Serial copolymers have been synthesized by free radical copolymerization of the three primary color monomers and methyl methacrylate. The quantum efficiency of the copolymers was higher than that of the complex monomers. The complexes were directly boned to the polymer chain, in which the energy transfer was reduced significantly compared to the doped-polymers. The experimental values of copolymers' CIE coordinates were located in the white light region in good agreement with theoretical values. The results indicate that the chromaticity of the emission color of the copolymers containing Eu(III), Tb(III), Be(II) ions could be tuned by theoretical calculation based on colorimetric principle.

High-sensitivity DPSK receiver for high-bandwidth free-space optical communication links.

PubMed

Juarez, Juan C; Young, David W; Sluz, Joseph E; Stotts, Larry B

2011-05-23

A high-sensitivity modem and high-dynamic range optical automatic gain controller (OAGC) have been developed to provide maximum link margin and to overcome the dynamic nature of free-space optical links. A sensitivity of -48.9 dBm (10 photons per bit) at 10 Gbps was achieved employing a return-to-zero differential phase shift keying based modem and a commercial Reed-Solomon forward error correction system. Low-noise optical gain was provided by an OAGC with a noise figure of 4.1 dB (including system required input loses) and a dynamic range of greater than 60 dB.

A novel coumarin Schiff-base as a Ni(II) ion colorimetric sensor

NASA Astrophysics Data System (ADS)

Wang, Lingyun; Ye, Decheng; Cao, Derong

2012-05-01

A novel coumarin Schiff base compound (L) prepared from 7-diethylaminocoumarin-3-aldehyde and 3-amino-7-hydroxycoumarin was synthesized and evaluated as a chemoselective Ni2+ sensor. Addition of Ni2+ to CH3CN solution of L resulted in a rapid color change from yellow to red together with a large red shift from 465 to 516 nm. Moreover, other common alkali-, alkaline earth-, transition- and rare earth metal ions induced no or minimal spectral changes. Experimental results indicated that L could be used as a potential Ni2+ colorimetric and naked-eye chemosensor in CH3CN solution.

Fiber specklegram sensors sensitivities at high temperatures

NASA Astrophysics Data System (ADS)

Rodriguez-Cobo, L.; Lomer, M.; Lopez-Higuera, J. M.

2015-09-01

In this work, the sensitivity of Fiber Specklegram Sensors to high temperatures (up to 800ºC) have been studied. Two multimode silica fibers have been introduced into a tubular furnace while a HeNe laser source was launched into a fiber edge, projecting speckle patterns to a commercial webcam. A computer generated different heating and cooling sweeps while the specklegram evolution was recorded. The achieved results exhibit a remarkably linearity in FSS's sensitivity for temperatures under 800ºC, following the thermal expansion of fused silica.

Sensitive detection of respiratory syncytial virus based on a dual signal amplified plasmonic enzyme-linked immunosorbent assay.

PubMed

Zhan, Lei; Wu, Wen Bi; Yang, Lin; Huang, Cheng Zhi

2017-04-15

The timely detection of infectious pathogen is critical in clinical early diagnosis and treatment of infectious diseases. Plasmonic enzyme-linked immunosorbent assay (ELISA), by means of enzyme-mediated growth or aggregation of AuNPs, has received considerable attention because it allows a naked-eye detection of target in very low numbers. In this work, a dual-signal amplified plasmonic ELISA combined the high loading capacity of magnetic beads with the establishing stimulation effect of zinc ion has been developed to detect RSV as a model pathogen based on alkaline phosphatase-triggered dispersion of aggregated AuNPs. In ideal conditions, the proposed immunoassay can conveniently distinguish the concentration of RSV in a range of 0.1-30 pg/mL. In addition, the limit of detection of RSV of this immunoassay exceeds that of conventional ELISA by about 50 times. The high sensitivity makes this approach a good alternative to existing colorimetric immunoassays for pathogen detection. Copyright © 2017 Elsevier B.V. All rights reserved.

Enhanced DNA Sensing via Catalytic Aggregation of Gold Nanoparticles

PubMed Central

Huttanus, Herbert M.; Graugnard, Elton; Yurke, Bernard; Knowlton, William B.; Kuang, Wan; Hughes, William L.; Lee, Jeunghoon

2014-01-01

A catalytic colorimetric detection scheme that incorporates a DNA-based hybridization chain reaction into gold nanoparticles was designed and tested. While direct aggregation forms an inter-particle linkage from only ones target DNA strand, the catalytic aggregation forms multiple linkages from a single target DNA strand. Gold nanoparticles were functionalized with thiol-modified DNA strands capable of undergoing hybridization chain reactions. The changes in their absorption spectra were measured at different times and target concentrations and compared against direct aggregation. Catalytic aggregation showed a multifold increase in sensitivity at low target concentrations when compared to direct aggregation. Gel electrophoresis was performed to compare DNA hybridization reactions in catalytic and direct aggregation schemes, and the product formation was confirmed in the catalytic aggregation scheme at low levels of target concentrations. The catalytic aggregation scheme also showed high target specificity. This application of a DNA reaction network to gold nanoparticle-based colorimetric detection enables highly-sensitive, field-deployable, colorimetric readout systems capable of detecting a variety of biomolecules. PMID:23891867

A biodegradable colorimetric film for rapid low-cost field determination of formaldehyde contamination by digital image colorimetry.

PubMed

Wongniramaikul, Worawit; Limsakul, Wadcharawadee; Choodum, Aree

2018-05-30

A biodegradable colorimetric film was fabricated on the lid of portable tube for in-tube formaldehyde detection. Based on the entrapment of colorimetric reagents within a thin film of tapioca starch, the yellow reaction product was observed with formaldehyde. Intensity of the blue channel from the digital image of yellow product showed a linear relationship in the range of 0-25 mg L -1 with low detection limit of 0.7 ± 0.1 mg L -1 . Inter-day precision of 0.61-3.10%RSD were obtained with less than 4.2% relative error from control samples. The developed method was applied for various food samples in Phuket and formaldehyde concentration range was non-detectable to 1.413 mg kg -1 . The quantified concentrations of formaldehyde in fish and squid samples provided relative errors of -7.7% and +10.8% compared to spectrophotometry. This low cost sensor (∼0.04 USD/test) with digital image colorimetry was thus an effective alternative for formaldehyde detection in food sample. Copyright © 2018 Elsevier Ltd. All rights reserved.

Coumarin based colorimetric and fluorescence on-off chemosensor for F-, CN- and Cu2 + ions

NASA Astrophysics Data System (ADS)

Roy, Debashis; Chakraborty, Arijit; Ghosh, Rina

2018-02-01

(E)-4-Chloro-3-[{2-(4-nitrophenyl)hydrazono}methyl]-2H-chromen-2-one (C), a coumarin derivative has been studied toward its ion sensing properties for F-, CN- and Cu2 +. A proton-transfer mechanism for F- sensing has been deduced with the help of 1H NMR titration alongwith from the changes in the absorption and emission spectra of C in the presence of F-. C formed 1:1 stoichiometric complex with each of these analytes. Sensing of C toward Cu2 + is poor, but interestingly in the presence of F- or CN- the sensing ability of Cu2 + gets enhanced many folds, and C can act as F- or CN- mediated off-on sensor for Cu2 +. Moreover, colorimetric strip (pre-coated with the coumarin derived compound) tests for F- and CN- from their DMSO solution at high temperature ( 100 °C) opens up the door for easiest naked eye recognition and distinction of these ions, and also for naked-eye detection of F- and CN- from its aqueous solution at high temperature ( 100 °C).

Highly Sensitive Ratiometric Fluorescent Sensor for Trinitrotoluene Based on the Inner Filter Effect between Gold Nanoparticles and Fluorescent Nanoparticles.

PubMed

Lu, Hongzhi; Quan, Shuai; Xu, Shoufang

2017-11-08

In this work, we developed a simple and sensitive ratiometric fluorescent assay for sensing trinitrotoluene (TNT) based on the inner filter effect (IFE) between gold nanoparticles (AuNPs) and ratiometric fluorescent nanoparticles (RFNs), which was designed by hybridizing green emissive carbon dots (CDs) and red emissive quantum dots (QDs) into a silica sphere as a fluorophore pair. AuNPs in their dispersion state can be a powerful absorber to quench CDs, while the aggregated AuNPs can quench QDs in the IFE-based fluorescent assays as a result of complementary overlap between the absorption spectrum of AuNPs and emission spectrum of RFNs. As a result of the fact that TNT can induce the aggregation of AuNPs, with the addition of TNT, the fluorescent of QDs can be quenched, while the fluorescent of CDs would be recovered. Then, ratiometric fluorescent detection of TNT is feasible. The present IFE-based ratiometric fluorescent sensor can detect TNT ranging from 0.1 to 270 nM, with a detection limit of 0.029 nM. In addition, the developed method was successfully applied to investigate TNT in water and soil samples with satisfactory recoveries ranging from 95 to 103%, with precision below 4.5%. The simple sensing approach proposed here could improve the sensitivity of colorimetric analysis by changing the ultraviolet analysis to ratiometric fluorescent analysis and promote the development of a dual-mode detection system.

Rapid recognition of volatile organic compounds with colorimetric sensor arrays for lung cancer screening.

PubMed

Zhong, Xianhua; Li, Dan; Du, Wei; Yan, Mengqiu; Wang, You; Huo, Danqun; Hou, Changjun

2018-06-01

Volatile organic compounds (VOCs) in breath can be used as biomarkers to identify early stages of lung cancer. Herein, we report a disposable colorimetric array that has been constructed from diverse chemo-responsive colorants. Distinguishable difference maps were plotted within 4 min for specifically targeted VOCs. Through the consideration of various chemical interactions with VOCs, the arrays successfully discriminate between 20 different volatile organic compounds in breath that are related to lung cancer. VOCs were identified either with the visualized difference maps or through pattern recognition with an accuracy of at least 90%. No uncertainties or errors were observed in the hierarchical cluster analysis (HCA). Finally, good reproducibility and stability of the array was achieved against changes in humidity. Generally, this work provides fundamental support for construction of simple and rapid VOC sensors. More importantly, this approach provides a hypothesis-free array method for breath testing via VOC profiling. Therefore, this small, rapid, non-invasive, inexpensive, and visualized sensor array is a powerful and promising tool for early screening of lung cancer. Graphical abstract A disposable colorimetric array has been developed with broadly chemo-responsive dyes to incorporate various chemical interactions, through which the arrays successfully discriminate 20 VOCs that are related to lung cancer via difference maps alone or chemometrics within 4 min. The hydrophobic porous matrix provides good stability against changes in humidity.

Colorimetric molecular diagnosis of the HIV gag gene using DNAzyme and a complementary DNA-extended primer.

PubMed

Kim, Seong U; Batule, Bhagwan S; Mun, Hyoyoung; Byun, Ju-Young; Shim, Won-Bo; Kim, Min-Gon

2018-02-07

We have developed a novel strategy for the colorimetric detection of PCR products by utilizing a target-specific primer modified at the 5'-end with an anti-DNAzyme sequence. A single-stranded DNAzyme sequence folds into a G-quadruplex structure with hemin and shows strong peroxidase activity. When the complementary strand binds to the DNAzyme sequence, it blocks the formation of the G-quadraduplex structure and loses its peroxidase activity. In the presence of the target gene, PCR amplification proceeds, and anti-DNAzyme sequence modified primers present in the reaction mixture form a double strand through primer extension. Therefore, it does not block the DNAzyme sequence. Further, a colorimetric signal is generated by the addition of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) and H 2 O 2 at the end of the reaction. We have successfully detected a single copy of the HIV type 1 gag gene in buffer and 10 copies in human serum. The strategy developed could be used to detect DNA and RNA in complex biological samples by simple primer designing that includes DNAzyme and a DNA extended primer.

A high-sensitivity current sensor utilizing CrNi wire and microfiber coils.

PubMed

Xie, Xiaodong; Li, Jie; Sun, Li-Peng; Shen, Xiang; Jin, Long; Guan, Bai-ou

2014-05-12

We obtain an extremely high current sensitivity by wrapping a section of microfiber on a thin-diameter chromium-nickel wire. Our detected current sensitivity is as high as 220.65 nm/A2 for a structure length of only 35 μm. Such sensitivity is two orders of magnitude higher than the counterparts reported in the literature. Analysis shows that a higher resistivity or/and a thinner diameter of the metal wire may produce higher sensitivity. The effects of varying the structure parameters on sensitivity are discussed. The presented structure has potential for low-current sensing or highly electrically-tunable filtering applications.

Single photon detector with high polarization sensitivity.

PubMed

Guo, Qi; Li, Hao; You, LiXing; Zhang, WeiJun; Zhang, Lu; Wang, Zhen; Xie, XiaoMing; Qi, Ming

2015-04-15

Polarization is one of the key parameters of light. Most optical detectors are intensity detectors that are insensitive to the polarization of light. A superconducting nanowire single photon detector (SNSPD) is naturally sensitive to polarization due to its nanowire structure. Previous studies focused on producing a polarization-insensitive SNSPD. In this study, by adjusting the width and pitch of the nanowire, we systematically investigate the preparation of an SNSPD with high polarization sensitivity. Subsequently, an SNSPD with a system detection efficiency of 12% and a polarization extinction ratio of 22 was successfully prepared.

Color dependence with horizontal-viewing angle and colorimetric characterization of two displays using different backlighting

NASA Astrophysics Data System (ADS)

Castro, José J.; Pozo, Antonio M.; Rubiño, Manuel

2013-11-01

In this work we studied the color dependence with a horizontal-viewing angle and colorimetric characterization of two liquid-crystal displays (LCD) using two different backlighting: Cold Cathode Fluorescent Lamps (CCFLs) and light-emitting diodes (LEDs). The LCDs studied had identical resolution, size, and technology (TFT - thin film transistor). The colorimetric measurements were made with the spectroradiometer SpectraScan PR-650 following the procedure recommended in the European guideline EN 61747-6. For each display, we measured at the centre of the screen the chromaticity coordinates at horizontal viewing angles of 0, 20, 40, 60 and 80 degrees for the achromatic (A), red (R), green (G) and blue (B) channels. Results showed a greater color-gamut area for the display with LED backlight, compared with the CCFL backlight, showing a greater range of colors perceptible by human vision. This color-gamut area diminished with viewing angle for both displays. Higher differences between trends for viewing angles were observed in the LED-backlight, especially for the R- and G-channels, demonstrating a higher variability of the chromaticity coordinates with viewing angle. The best additivity was reached by the LED-backlight display (a lower error percentage). LED-backlight display provided better color performance of visualization.

NK sensitivity of neuroblastoma cells determined by a highly sensitive coupled luminescent method

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

Ogbomo, Henry; Hahn, Anke; Geiler, Janina

2006-01-06

The measurement of natural killer (NK) cells toxicity against tumor or virus-infected cells especially in cases with small blood samples requires highly sensitive methods. Here, a coupled luminescent method (CLM) based on glyceraldehyde-3-phosphate dehydrogenase release from injured target cells was used to evaluate the cytotoxicity of interleukin-2 activated NK cells against neuroblastoma cell lines. In contrast to most other methods, CLM does not require the pretreatment of target cells with labeling substances which could be toxic or radioactive. The effective killing of tumor cells was achieved by low effector/target ratios ranging from 0.5:1 to 4:1. CLM provides highly sensitive, safe,more » and fast procedure for measurement of NK cell activity with small blood samples such as those obtained from pediatric patients.« less

Sensitivity of high-frequency Rayleigh-wave data revisited

USGS Publications Warehouse

Xia, J.; Miller, R.D.; Ivanov, J.

2007-01-01

Rayleigh-wave phase velocity of a layered earth model is a function of frequency and four groups of earth properties: P-wave velocity, S-wave velocity (Vs), density, and thickness of layers. Analysis of the Jacobian matrix (or the difference method) provides a measure of dispersion curve sensitivity to earth properties. Vs is the dominant influence for the fundamental mode (Xia et al., 1999) and higher modes (Xia et al., 2003) of dispersion curves in a high frequency range (>2 Hz) followed by layer thickness. These characteristics are the foundation of determining S-wave velocities by inversion of Rayleigh-wave data. More applications of surface-wave techniques show an anomalous velocity layer such as a high-velocity layer (HVL) or a low-velocity layer (LVL) commonly exists in near-surface materials. Spatial location (depth) of an anomalous layer is usually the most important information that surface-wave techniques are asked to provide. Understanding and correctly defining the sensitivity of high-frequency Rayleigh-wave data due to depth of an anomalous velocity layer are crucial in applying surface-wave techniques to obtain a Vs profile and/or determine the depth of an anomalous layer. Because depth is not a direct earth property of a layered model, changes in depth will result in changes in other properties. Modeling results show that sensitivity at a given depth calculated by the difference method is dependent on the Vs difference (contrast) between an anomalous layer and surrounding layers. The larger the contrast is, the higher the sensitivity due to depth of the layer. Therefore, the Vs contrast is a dominant contributor to sensitivity of Rayleigh-wave data due to depth of an anomalous layer. Modeling results also suggest that the most sensitive depth for an HVL is at about the middle of the depth to the half-space, but for an LVL it is near the ground surface. ?? 2007 Society of Exploration Geophysicists.

An SPR based immunoassay for the sensitive detection of the soluble epithelial marker E-cadherin.

PubMed

Vergara, Daniele; Bianco, Monica; Pagano, Rosanna; Priore, Paola; Lunetti, Paola; Guerra, Flora; Bettini, Simona; Carallo, Sonia; Zizzari, Alessandra; Pitotti, Elena; Giotta, Livia; Capobianco, Loredana; Bucci, Cecilia; Valli, Ludovico; Maffia, Michele; Arima, Valentina; Gaballo, Antonio

2018-06-11

Protein biomarkers are important diagnostic tools for cancer and several other diseases. To be validated in a clinical context, a biomarker should satisfy some requirements including the ability to provide reliable information on a pathological state by measuring its expression levels. In parallel, the development of an approach capable of detecting biomarkers with high sensitivity and specificity would be ideally suited for clinical applications. Here, we performed an immune-based label free assay using Surface Plasmon Resonance (SPR)-based detection of the soluble form of E-cadherin, a cell-cell contact protein that is involved in the maintaining of tissue integrity. With this approach, we obtained a specific and quantitative detection of E-cadherin from a few hundred μl of serum of breast cancer patients by obtaining a 10-fold enhancement in the detection limit over a traditional colorimetric ELISA. Copyright © 2018 Elsevier Inc. All rights reserved.

Interoceptive threat leads to defensive mobilization in highly anxiety sensitive persons.

PubMed

Melzig, Christiane A; Holtz, Katharina; Michalowski, Jaroslaw M; Hamm, Alfons O

2011-06-01

To study defensive mobilization elicited by the exposure to interoceptive arousal sensations, we exposed highly anxiety sensitive students to a symptom provocation task. Symptom reports, autonomic arousal, and the startle eyeblink response were monitored during guided hyperventilation and a recovery period in 26 highly anxiety sensitive persons and 22 controls. Normoventilation was used as a non-provocative comparison condition. Hyperventilation led to autonomic arousal and a marked increase in somatic symptoms. While high and low anxiety sensitive persons did not differ in their defensive activation during hyperventilation, group differences were detected during early recovery. Highly anxiety sensitive students exhibited a potentiation of startle response magnitudes and increased autonomic arousal after hyper- as compared to after normoventilation, indicating defensive mobilization evoked by the prolonged presence of feared somatic sensations. Copyright © 2010 Society for Psychophysiological Research.

A colorimetric chiral sensor based on chiral crown ether for the recognition of the two enantiomers of primary amino alcohols and amines.

PubMed

Cho, Eun Na Rae; Li, Yinan; Kim, Hee Jin; Hyun, Myung Ho

2011-04-01

A new colorimetric chiral sensor material consisting of three different functional sites such as chromophore (2,4-dinitrophenylazophenol dye), binding site (crown ether), and chiral barrier (3,3'-diphenyl-1,1'-binaphthyl group) was prepared and applied to the recognition of the two enantiomers of primary amino alcohols and amines. Among five primary amino alcohols and two primary amines tested, the two enantiomers of phenylalaninol show the highest difference in the absorption maximum wavelength (Δλ(max)=43.5 nm) and in the association constants (K(S)/K(R)=2.51) upon complexation with the colorimetric chiral sensor material and, consequently, the two enantiomers of phenylalaninol were clearly distinguished from each other by the color difference. Copyright © 2010 Wiley-Liss, Inc.

Highly sensitive, self-powered and wearable electronic skin based on pressure-sensitive nanofiber woven fabric sensor.

PubMed

Zhou, Yuman; He, Jianxin; Wang, Hongbo; Qi, Kun; Nan, Nan; You, Xiaolu; Shao, Weili; Wang, Lidan; Ding, Bin; Cui, Shizhong

2017-10-11

The wearable electronic skin with high sensitivity and self-power has shown increasing prospects for applications such as human health monitoring, robotic skin, and intelligent electronic products. In this work, we introduced and demonstrated a design of highly sensitive, self-powered, and wearable electronic skin based on a pressure-sensitive nanofiber woven fabric sensor fabricated by weaving PVDF electrospun yarns of nanofibers coated with PEDOT. Particularly, the nanofiber woven fabric sensor with multi-leveled hierarchical structure, which significantly induced the change in contact area under ultra-low load, showed combined superiority of high sensitivity (18.376 kPa -1 , at ~100 Pa), wide pressure range (0.002-10 kPa), fast response time (15 ms) and better durability (7500 cycles). More importantly, an open-circuit voltage signal of the PPNWF pressure sensor was obtained through applying periodic pressure of 10 kPa, and the output open-circuit voltage exhibited a distinct switching behavior to the applied pressure, indicating the wearable nanofiber woven fabric sensor could be self-powered under an applied pressure. Furthermore, we demonstrated the potential application of this wearable nanofiber woven fabric sensor in electronic skin for health monitoring, human motion detection, and muscle tremor detection.

Highly sensitive catalytic spectrophotometric determination of ruthenium

NASA Astrophysics Data System (ADS)

Naik, Radhey M.; Srivastava, Abhishek; Prasad, Surendra

2008-01-01

A new and highly sensitive catalytic kinetic method (CKM) for the determination of ruthenium(III) has been established based on its catalytic effect on the oxidation of L-phenylalanine ( L-Pheala) by KMnO 4 in highly alkaline medium. The reaction has been followed spectrophotometrically by measuring the decrease in the absorbance at 526 nm. The proposed CKM is based on the fixed time procedure under optimum reaction conditions. It relies on the linear relationship where the change in the absorbance (Δ At) versus added Ru(III) amounts in the range of 0.101-2.526 ng ml -1 is plotted. Under the optimum conditions, the sensitivity of the proposed method, i.e. the limit of detection corresponding to 5 min is 0.08 ng ml -1, and decreases with increased time of analysis. The method is featured with good accuracy and reproducibility for ruthenium(III) determination. The ruthenium(III) has also been determined in presence of several interfering and non-interfering cations, anions and polyaminocarboxylates. No foreign ions interfered in the determination ruthenium(III) up to 20-fold higher concentration of foreign ions. In addition to standard solutions analysis, this method was successfully applied for the quantitative determination of ruthenium(III) in drinking water samples. The method is highly sensitive, selective and very stable. A review of recently published catalytic spectrophotometric methods for the determination of ruthenium(III) has also been presented for comparison.

Performance of terahertz metamaterials as high-sensitivity sensor

NASA Astrophysics Data System (ADS)

He, Yanan; Zhang, Bo; Shen, Jingling

2017-09-01

A high-sensitivity sensor based on the resonant transmission characteristics of terahertz (THz) metamaterials was investigated, with the proposal and fabrication of rectangular bar arrays of THz metamaterials exhibiting a period of 180 μm on a 25 μm thick flexible polyimide. Varying the size of the metamaterial structure revealed that the length of the rectangular unit modulated the resonant frequency, which was verified by both experiment and simulation. The sensing characteristics upon varying the surrounding media in the sample were tested by simulation and experiment. Changing the surrounding medium from that of air to that of alcohol or oil produced resonant frequency redshifts of 80 GHz or 150 GHz, respectively, which indicates that the sensor possessed a high sensitivity of 667 GHz per unit of refractive index. Finally, the influence of the sample substrate thickness on the sensor sensitivity was investigated by simulation. It may be a reference for future sensor design.

Colorimetric detection of copper ions in sub-micromolar concentrations using a triarylamine-linked resin bead.

PubMed

Thomas, Tony George; Sreenath, Kesavapillai; Gopidas, Karical R

2012-11-21

The triarylamine derivative ETPA reacts with Cu(2+) to give deeply colored, stable radical cations in acetonitrile solution. ETPA was immobilized on to a tentagel resin bead which was then used for the fabrication of a simple device capable of the colorimetric detection of submicromolar concentrations of Cu(2+) ions in water. The naked eye detection limit reported here for Cu(2+) is one of the lowest ever reported for small molecule sensors.