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NOTE: This Press Release has been sent electronically. If it has been sent to the wrong individual, or if you no longer wish to receive TandD Press Releases, please notify us at: PR@Beehive-Online.com

Just Published: Spectrochimica Acta Part B: Atomic Spectroscopy

A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:

Spectrochimica Acta Part B: Atomic Spectroscopy
http://rss.sciencedirect.com/publication/science/5287

Selected papers from the latest issue:

Micro- and nano-volume samples by electrothermal, near-torch vaporization sample introduction using removable, interchangeable and portable rhenium coiled-filament assemblies and axially-viewed inductively coupled plasma-atomic emission spectrometry

02 August 2012, 08:57:43

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Hamid R. Badiei, Bryant Lai, Vassili Karanassios
An electrothermal, near-torch vaporization (NTV) sample introduction for micro- or nano-volume samples is described. Samples were pipetted onto coiled-filament assemblies that were purposely developed to be removable and interchangeable and were dried and vaporized into a small-volume vaporization chamber that clips onto any ICP torch with a ball joint. Interchangeable assemblies were also constructed to be small-size (e.g., less than 3cm long with max diameter of 0.65cm) and light-weight (1.4g) so that they can be portable. Interchangeable assemblies with volume-capacities in three ranges (i.e., <1 μL, 1–10 μL and 10–100 μL) were fabricated and used. The horizontally-operated NTV sample introduction was interfaced to an axially-viewed ICP-AES (inductively coupled plasma-atomic emission spectrometry) system and NTV was optimized using ICP-AES and 8 elements (Pb, Cd, Zn, V, Ba, Mg, Be and Ca). Precision was 1.0-2.3% (peak height) and 1.1-2.4% (peak area). Detection limits (obtained using 5 μL volumes) expressed in absolute-amounts ranged between 4pg for Pb to 0.3fg (~5 million atoms) for Ca. Detection limits expressed in concentration units (obtained using 100 μL volumes of diluted, single-element standard solutions) were: 50pg/mL for Pb; 10pg/mL for Cd; 9pg/mL for Zn; 1pg/mL for V; 0.9pg/mL for Ba; 0.5pg/mL for Mg; 50fg/mL for Be; and 3fg/mL for Ca. Analytical capability and utility was demonstrated using the determination of Pb in pg/mL levels of diluted natural water Certified Reference Material (CRM) and the determination of Zn in 80nL volumes of the liquid extracted from an individual vesicle. It is shown that portable and interchangeable assemblies with dried sample residues on them can be transported without analyte loss (for the concentrations tested), thus opening up the possibility for “taking part of the lab to the sample” applications, such as testing for Cu concentration-compliance with the lead-copper rule of the Environmental Protection Agency. It is also shown that interchangeable assemblies with volume-capacities in the ranges mentioned above can be used interchangeably in the same calibration curve, thus in some cases and for on-site applications, volume-of-sample can be substituted for sample-dilution.

Highlights

► Absolute detection limits from 4pg (Pb) to 0.3fg (~5 million atoms) for Ca ► Relative detection limits (100 μL) from 50pg/mL for Pb to 3fg/mL for Ca ► Pb was determined in the 100's of pg/mL level using 100 μL of diluted CRM ► Zn in individual vesicles was determined using 80nL-volume samples ► Analytes pipetted on coils on-site and concentration determined in the lab

Focusing systems for the generation of X-ray micro beam: An overview

02 August 2012, 08:57:43

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
A. Guilherme, G. Buzanich, M.L. Carvalho
This manuscript reviews the most used optical systems for X-ray microprobes and summarizes the experiences in research with synchrotron radiation as well as with X-ray tube generators. The need for smaller beam spot sizes for various applications and the unique properties of X-rays have induced a remarkable and fast development in X-ray optical systems. These systems are divided into three main categories: diffractive, reflective and refractive. Examples of the three will be covered in this paper, highlighting the properties that allow having spot sizes down to sub-micrometer regime. However, the extraordinary capabilities of such systems are always relative. Therefore, an overview of the techniques that use such optical systems will be given, emphasizing their applicability on several case studies.

Highlights

► This work makes a revision on the most used focusing systems for X-ray microprobes ► This work summarizes the experiences with synchrotron radiation ► This work summarizes the experiences with X-ray tube generators. ► This work gives examples for diffractive, reflective and refractive systems

Testing a portable laser-induced breakdown spectroscopy system on geological samples

02 August 2012, 08:57:43

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Jozef Rakovský, Olivier Musset, JeanFrançois Buoncristiani, Vincent Bichet, Fabrice Monna, Pascal Neige, Pavel Veis
This paper illustrates the potentialities of a home-made portable LIBS (laser-induced breakdown spectroscopy) instrument in Earth sciences, more particularly in geochemically recognizing (i) tephra layers in lacustrine sediments and (ii) fossilization processes in ammonites. Abundances for selected lines of Al, Ca, Fe, Ti, Ba and Na were determined in lacustrine chalk sediments of the Jura, where the Laacher See Tephra (LST) layer is recorded. A statistical treatment of elemental maps produced from the section of a sedimentary column containing the LST event allows instrumental conditions to be optimized. Accumulating spectra from close shot positions gives better results than multiplying shots at the same location. A depth profile method was applied to study ammonite fossilization (pyritization, phosphatization) processes. Depth variations of Fe, Ca, Al intensities, and Fe/Ca and Al/Ca ratios provide indications about pyritization, but phosphatization processes cannot be determined with our device.

Highlights

► Element cartography maps for sediment which contains tephra layer have been created. ► The maps have been used for on-site conditions determination by statistical treatment. ► Pyritization process on ammonite surface was identified successfully.

An investigation of Laser Induced Breakdown Spectroscopy for use as a control in the laser removal of rock from fossils found at the Malapa hominin site, South Africa

02 August 2012, 08:57:43

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
D.E. Roberts, A. du Plessis, J. Steyn, L.R. Botha, S. Pityana, L.R. Berger
Laser Induced Breakdown Spectroscopy (LIBS) was used to study the spectra from fossils and surrounding rock recovered from the Cradle of Mankind site at Malapa, South Africa. The objective was to find a suitable spectral line(s), specific to fossils, which could be used as a control signal to limit damage to fossils during high speed laser removal of the encasing rock. The calcified clastic matrix (rock) encasing the fossils was found to emit a variety of complex LIBS spectra. Nevertheless, it was found possible to distinguish fossils in a single LIBS pulse, and without significant damage to the fossil, using spectral lines of neutral phosphorus.

Highlights

► LIBS used to discriminate fossils from rock as potential processing control mechanism. ► 2million year old fossils from Malapa hominin site found to be high in phosphorus. ► Rock spectral lines from silicon, iron and manganese, but no phosphorus. ► Holds great promise for process control in laser preparation of fossils. ► Also promising for accurate identification of fossils at excavation sites.

Evaluation of quartz tubes as atomization cells for gold determination by thermospray flame furnace atomic absorption spectrometry

02 August 2012, 08:57:43

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Ezequiel Morzan, Ornela Piano, Jorge Stripeikis, Mabel Tudino
This work describes the development of a new analytical procedure able to determine gold by thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) using nickel tubes (NiT) and quartz tubes (QT) as atomization cells. Experiments involving changes in the flow injection operational parameters, reagents concentrations and sizes of the QT were performed in order to optimize sensitivity. Under the same operational conditions, it was observed that the employment of QT increases the sensitivity of gold determination when compared to the nickel tube. Since solutions of highly concentrated hydrochloric acid showed the best performance as carriers, quartz tubes were also preferred due to its greater tolerance to corrosion by mineral acids in comparison to NiT. In addition, changes in the internal diameter of the QT revealed an important improvement in sensitivity for smaller tubes. Under optimized conditions the main figures of merit showed values close to that of graphite furnace atomic absorption spectrometry with the addition of an excellent improvement of the sample throughput. They are: LOD (3s): 0.004μgmL^-1, sensitivity: 0.306 (μgmL^-1)^-1, RSD% (n=10, 1μgmL^-1): 2.5, linear range: 0.01 - 4μgmL^-1 and sample throughput: 72h^-1. This new method was employed for the determination of gold in homeopathic medicines with no need of sample digestion. Validation of the analytical results will be shown. A fully discussion of the most relevant findings regarding the role of the atomization cell as an strategic key for improving sensitivity will be also provided.

Highlights

► Quartz tubes as furnaces in TS-FFAAS ► Small tubes for controlling radial dispersion ► Improved figures of merit for gold determination ► Analysis of homeopathic medicines

Preface

02 August 2012, 08:57:43

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Şerife Yalcin, Roberta Fantoni

Calibration analysis of zeolites by laser induced breakdown spectroscopy

02 August 2012, 08:57:43

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
M. Horňáčková, Z. Grolmusová, M. Horňáček, J. Rakovský, P. Hudec, P. Veis
Laser induced breakdown spectroscopy was used for calibration analysis of different types of microporous crystalline aluminosilicates with exactly ordered structure — zeolites. The LIBS plasma was generated using a Q-switched Nd:YAG laser operating at the wavelength of 532nm and providing laser pulses of 4ns duration. Plasma emission was analysed by echelle type emission spectrometer, providing wide spectral range 200–950nm. The spectrometer was equipped with intensified CCD camera providing rapid spectral acquisition (gating time from 5ns). The optimum experimental conditions (time delay, gate width and laser pulse energy) have been determined for reliable use of LIBS for quantitative analysis. Samples of different molar ratios of Si/Al were used to create the calibration curves. Calibration curves for different types of zeolites (mordenite, type Y and ZSM-5) were constructed. Molar ratios of Si/Al for samples used for calibration were determined by classical wet chemical analysis and were in the range 5.3–51.8 for mordenite, 2.3–12.8 for type Y and 14–600 for ZSM-5. Zeolites with these molar ratios of Si/Al are usually used as catalysts in alkylation reactions. Laser induced breakdown spectroscopy is a suitable method for analysis of molar ratio Si/Al in zeolites, because it is simple, fast, and does not require sample preparation compared with classical wet chemical analysis which are time consuming, require difficult sample preparation and manipulation with strong acids and bases.

Highlights

► Determination of optimal experimental conditions for LIBS analysis of zeolites. ► Calibration curves for molar ratio of Si/Al determination in three zeolites types. ► Comparison of calibration curves obtained using peak area and peak amplitude.

Modelling the position of analyte emission maxima in low temperature direct current arc plasma using statistical procedures

02 August 2012, 08:57:43

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
J. Savović, M.S. Pavlović, M. Stoiljković, M. Kuzmanović, M. Momčilović, V. Vasić
In low temperature argon arc plasma, emission spectral lines of different analytes have characteristic radial distributions with emission maxima distributed over a wide plasma region, from the arc axis toward the arc periphery. It was assumed that the occurrence of emission maxima is a result of collective action of factors that control vaporization, dissociation, excitation, ionization and analyte transport. A statistical analysis was used to reveal a correlation between these various factors and a radial position of maximum emission. A regression analysis was used both for predictive and explanatory purposes: a model was built that successfully predicted analyte spatial emission characteristics, based on their physical properties and local plasma parameters, and a relative importance of proposed predictors was estimated.

Highlights

► PCR analysis was used to model radial emission profiles in DC arc plasma. ► The main factors governing the radial distribution of atomic emission were analyzed. ► A model was built based on local plasma parameters and analyte physical properties.

Investigation of materials of different crystal structure under various time delays using double pulse laser induced breakdown spectroscopy

02 August 2012, 08:57:43

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
E. Yurdanur-Tasel, H. Berberoglu, S. Bilikmen
The performance of a commercial, compact and portable laser induced breakdown spectroscopy (LIBS) system and a constructed laboratory LIBS system with different experimental approaches were investigated in order to make improvements in the qualitative results. One of the experimental studies pertained to the investigation of the different crystal surfaces of silicon. The second experimental study involved the polarization effects by which the polarization dependency was demonstrated. The third and final experimental study was an unconventional orthogonal double pulse configuration with a 45° angle of incidence for both lasers in opposite directions. By means of these experimental approaches reliable, reproducible results were obtained, relative intensities of the emission lines were enhanced and better signal to noise ratios were observed. Furthermore, the qualitative analysis performance of the commercial system software was compared with the code developed. The code yielded more accurate and precise analysis capability.

Highlights

► Double pulse LIBS with lasers at 45° angle to the sample is investigated. ► Si (100) emission intensities are higher than (111) due to dangling bond density. ► Plasma polarization behavior is strong at the peaks of the smaller wavelengths. ► A basic and more accurate code for the analysis of spectral lines is developed.

Correlation between native bonds in a polymeric material and molecular emissions from the laser-induced plasma observed with space and time resolved imaging

02 August 2012, 08:57:43

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
S. Grégoire, V. Motto-Ros, Q.L. Ma, W.Q. Lei, X.C. Wang, F. Pelascini, F. Surma, V. Detalle, J. Yu
Emissions from C2 molecules and CN radicals in laser-induced plasmas on polymeric materials were observed with time-resolved spectroscopic imaging. More precisely, differential imaging with a pair of narrowband filters (one centered on the emission line and another out of the line) was used to extract emission images of interested molecules or radicals. The correlation between the molecular emission image of the plasma and the molecular structure of the polymer to be analyzed was studied for four different types of materials: polyamide (PA) with native CN bonds, polyethylene (PE) with simple CC bonds, polystyrene (PS) with delocalized double CC bonds, and polyoxymethylene (POM) which neither contains CC nor CN bonds. A clear correlation is demonstrated between emission and molecular structure of the material, allowing the identification of several organic compounds by differential spectroscopic imaging.

Highlights

► Plasma Imaging method to discriminate different type of polymers ► Molecular emissions (CN and C2) are spatially and temporally correlated to native bonds ► Several formation processes of molecular fragments are observed

Experimental and theoretical investigations about the vaporization process of laser-produced aerosols and individual particles inside inductively-coupled plasma sources - Implications for the extraction efficiency of ions prior to mass spectrometry and accuracy of analyses

02 August 2012, 08:57:43

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
Luca Flamigni, Joachim Koch, Detlef Günther
Current quantification capabilities of laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) are known to be restricted by elemental fractionation as a result of LA-, transport-, and ICP-induced effects which, particularly, may provoke inaccuracies whenever calibration strategies on basis of non-matrix matched standard materials are applied. The present study is dealing with the role of the ICP in this complex scenario. Therefore, the vaporization process of laser-produced aerosols and subsequent diffusion losses occurring inside ICP sources were investigated using 2-D optical emission spectrometry (OES) and ICP-quadrupole (Q)MS of individual particles. For instance, Na- and Ca-specific OES of aerosols produced by LA of silicate glasses or metals revealed axial shifts in the onset and maximum position of atomic emission which were in a range of few millimeters. The occurrence of these shifts was found to arise from composition-dependent particle/aerosol penetration depths, i.e. the displacement of axial vaporization starting points controlling the ion extraction efficiency through the ICP-MS vacuum interface due to a delayed, diffusion-driven expansion of oxidic vs. metallic aerosols. Furthermore, ICP-QMS of individual particles resulted in 1/e half-value signal durations of approximately one hundred microseconds, which complies with modeled values if OES maxima are assumed to coincide with positions of instantaneous vaporization and starting points for atomic diffusion. To prove phenomena observed for their consistency, in addition, “ab-initio” as well as semi-empirical simulations of particle/aerosol penetration depths followed by diffusion-driven expansion was accomplished indicating differences of up to 15% in the relative ion extraction efficiency depending on whether analytes are supplied as metals or oxides. Implications of these findings on the accuracy achievable by state-of-the-art LA-ICP-MS systems are outlined.

Highlights

► Specification of particle/aerosol penetration depths inside ICP sources by 2-D OES ► Application of a theory describing particle vaporization and analyte diffusion ► Modeling of ICP-MS ion extraction efficiencies ► Discussion about 2-D OES as a complementary tuning strategy for LA-ICP-MS

Hβ Stark broadening in cold plasmas with low electron densities calibrated with Thomson scattering

02 August 2012, 08:57:43

Publication year: 2012
Source:Spectrochimica Acta Part B: Atomic Spectroscopy
J.M. Palomares, S. Hübner, E.A.D. Carbone, N. de Vries, E.M. van Veldhuizen, A. Sola, A. Gamero, J.J.A.M. v d Mullen
In the present work Stark broadening measurements have been carried out on low electron density (n e <5·10¹⁹ m⁻³) and (relatively) low gas temperature (T g <1100K) argon–hydrogen plasma, under low-intermediate pressure conditions (3mbar–40mbar). A line fitting procedure is used to separate the effects of the different broadening mechanisms (e.g. Doppler and instrumental broadening) from the Stark broadening. A Stark broadening theory is extrapolated to lower electron density values, below its theoretical validity regime. Thomson scattering measurements are used to calibrate and validate the procedure. The results show an agreement within 20%, what validates the use of this Stark broadening method under such low density conditions. It is also found that Stark broadened profiles cannot be assumed to be purely Lorentzian. Such an assumption would lead to an underestimation of the electron density. This implies that independent information on the gas temperature is needed to find the correct values of n e .

Highlights

► Stark broadening measurements at low density and temperature conditions ► Calibration with Thomson scattering ► Indications of the non-Lorentzian shape of the Stark broadening ► Impossibility of simultaneous diagnostic of gas temperature and electron density

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Just Published: Biosensors & Bioelectronics

A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:

Biosensors & Bioelectronics
http://rss.sciencedirect.com/publication/science/5223

Selected papers from the latest issue:

Nanopore sensors: From hybrid to abiotic systems

01 August 2012, 10:42:44

Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 38, Issue 1
Armagan Kocer, Lara Tauk, Philippe Déjardin
The use of nanopores of well controlled geometry for sensing molecules in solution is reviewed. Focus is concentrated especially on synthetic track-etch pores in polymer foils and on biological nanopores, i.e. ion channels. After a brief section about multipore sensors, specific attention is provided to works relative to a single nanopore sensor. The different strategies to combine the robustness of supports with the high selectivity of the biological channels are reviewed. The scope ranges from keeping the membrane natural environment of biological channels in supported and suspended bilayer membranes, to considering completely abiotic designed nanopores created through synthetic materials. The α-hemolysine channel and the mechanosensitive channel of large conductance with their modifications are especially considered in the first strategy, the conical functionalized nanopores created in polymer foils in the second one. The different attempts of reading macromolecules are also discussed. A third hybrid strategy, which was not extensively explored, consists in the inclusion of a biological structure into a well-designed nanopore through the support, as recently with gramicidin.

Highlights

► Different strategies used in producing pores of controlled geometry are described. ► Ways to include biological or bioinspired channels in bilayer membranes are recalled. ► Focus on single pore devices and on robust supports like track-etch polymer foils.

CuO thin film based uric acid biosensor with enhanced response characteristics

01 August 2012, 10:42:44

Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 38, Issue 1
Kajal Jindal, Monika Tomar, Vinay Gupta
An efficient reagentless uric acid biosensor has been realized using a copper oxide (CuO) thin film matrix grown onto platinum (Pt) coated corning glass substrates by pulsed laser deposition (PLD) technique. The p-type CuO matrix successfully introduces redox property in the electrode and provides enhanced electron communication features. Sensing response obtained by the bioelectrocatalytic oxidation of uric acid by uricase/CuO/Pt/glass electrode was studied without any external mediator using cyclic voltammetry (CV) and photometric assay. The studies reveal that the uricase/CuO/Pt/glass bio-electrode exhibits good linearity over a wide range of 0.05mM to 1.0mM uric acid concentration with enhanced response of 2.7mA/mM and high shelf life (>14 weeks). A low Michaelis–Menten constant (K m ) of 0.12mM, indicate that the immobilized enzyme (uricase) has enhanced affinity towards its analyte (uric acid). The results confirm promising application of the p-type CuO thin film matrix for the realization of a reagentless integrated implantable biosensor.

Highlights

► Article is focused on the development of a reagentless uric acid biosensor. ► Biosensing is based on the bioelectrocatalytic oxidation of uric acid by uricase. ► CuO matrix introduces redox property for charge transfer eliminating need for external mediator. ► Uricase/CuO/Pt/glass bio-electrode shows a fast and good linear response. ► A low K m of 0.12mM is observed with enhanced sensing response (sensitivity-2.7mA/mM).

A 3D localized surface plasmon resonance biosensor for the study of trivalent arsenic binding to the ArsA ATPase

01 August 2012, 10:42:44

Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 38, Issue 1
Chang Liu, Vittoria Balsamo, Dali Sun, Melodie Naja, Xuemei Wang, Barry Rosen, Chen-Zhong Li
A self-assembled 3D hydrogel–nanoparticle composite integrated surface plasmon resonance (SPR) sensor is reported here. The novel assembled substrate was developed by means of a surface mediated radical co-polymerization process to obtain a highly sensitive hydrogel-based thin film that possesses specific binding sites for target analytes. Initially, amino group modified gold nanoparticles (AuNPs) were covalently linked to acrylic acid monomer. Following this, N-isopropylacrylamide (NIPAAm) and AuNPs linked acrylic acid (AAc) monomers were randomly co-polymerized by the “grafting from” method in the presence of initiator and crosslinker onto the sensing surface. Surface charecterization techniques were utilized to evaluate the thickness and composition of the hydrogel-nanoparticle film. The sensing platform was employed to study the binding kinetics and conformational changes of the ArsA ATPase as a consequence of binding trivalent arsenicals under a variety of conditions. ArsA, the catalytic subunit of the ArsAB arsenite (As(III)) translocating ATPase, is one of the five proteins encoded by the arsenical resistance (ars) operon of plasmid R773 in cells of Escherichia coli, that confers resistance to trivalent and pentavalent salts of the metalloid arsenic. SPR measurements indicate that the 3D hydrogel-nanoparticle coated sensors exhibited a higher sensitivity than that of the 2D AuNPs decorated sensors. Binding of As(III) to ArsA is greatly facilitated by the presence of magnesium ion and ATP.

Highlights:

► We developed a 3D hydrogel-nanoparticle sensing platform for Localized Surface Plasmon Resonance. ► We demonstrated the enhanced sensitivity for protein binding study using the 3D structured sensor. ► The binding kinetics of the arsenic detoxifying systems is quantitatively investigated. ► We investigated pathway of As(III) binding to ArsA protein using the LSPR sensing system. ► We demonstrated a direct channeling of As(III) transfer from ArsD to ArsA.

A novel sensor based on electrochemical polymerization of diglycolic acid for determination of acetaminophen

01 August 2012, 10:42:44

Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 38, Issue 1
Fen Xu, Hui-Ying Ru, Li-Xian Sun, Yong-Jin Zou, Cheng-Li Jiao, Tao-Yi Wang, Jia-Ming Zhang, Qian Zheng, Huai-Ying Zhou
Diglycolic acid (DA) polymer was coated on glassy carbon (GC) electrode by cyclic voltammetry (CV) technique for the first time. The electrochemical performances of the modified electrode were investigated by CV and electrochemical impedance (EIS). The obtained electrode showed an excellent electrocatalytic activity for the oxidation of acetaminophen (ACOP). A couple of well-defined reversible electrochemical redox peaks were observed on the ploy(DA)/GC electrode in ACOP solution. Compared with bare GC electrode, the oxidation peak potential of ACOP on ploy(DA)/GC electrode moved from 0.289V to 0.220V. Meanwhile, the oxidation peak current was much higher on the modified electrode than that on the bare GC electrode, indicating DA polymer modified electrode possessed excellent performance for the oxidation of ACOP. This kind of capability of the modified electrode can be enlisted for the highly sensitive and selective determination of ACOP. Under the optimized conditions, a wide linear range from 2×10⁻⁸ to 5.0×10⁻⁴ M with a correlation coefficient 0.9995 was obtained. The detection limit was 6.7×10⁻⁹ M (at the ratio of signal to noise, S/N=3:1). The modified electrode also exhibited very good stability and reproducibility for the detection of ACOP. The established method was applied to the determination of ACOP in samples. An average recovery of 100.1% was achieved. These results indicated that this method was reliable for determining ACOP.

Highlights

► Diglycolic acid polymer coated on glassy carbon electrode by cyclic voltammetry. ► Modified electrode has an excellent electrocatalytic activity for acetaminophen. ► A wide linear range is from 2×10⁻⁸ to 5.0×10⁻⁴ M. ► The detection limit is 6.7×10⁻⁹ M.

A graphene oxide based biosensor for microcystins detection by fluorescence resonance energy transfer

01 August 2012, 10:42:44

Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 38, Issue 1
Yan Shi, Jiazhen Wu, Yujing Sun, Yue Zhang, Zhiwei Wen, Haichao Dai, Hongda Wang, Zhuang Li
Water safety is one of the most pervasive problems afflicting people throughout the world. Microcystin, a hepatotoxin produced by cyanobacteria, poses a growing and serious threat of water safety. According to World Health Organization (WHO), the limit of content of microcystin-LR (MC-LR) in drinking water is as low as 1μg/L; it is thus necessary to explore a sensitive method for the trace detection of microcystins (MCs). Based on the observation of gold nanoparticles (Au NPs) induced graphene oxide (GO) fluorescence quenching, a reliable biosensor was developed here for microcystins detection. MCs could be attached on Au NPs through the interaction with single strand-DNA (ss-DNA) modified on Au NPs, which formed Au–DNA–MCs complexes. These MCs in the complexes could be immunologically recognized by the antibodies adsorbed on GO sheets, as a result, Au NPs were close enough to quench the photoluminescence of GO by the fluorescence resonance energy transfer (FRET). The fluorescence intensity decreased with the increase of MCs as more Au NPs linked onto GO surface. The limit of detection was 0.5 and 0.3μg/L for microcystin-LR and microcystin-RR (MC-RR), respectively, which satisfies the strictest standard of WHO. Well defined results were also obtained in natural lake water and the specificity experiment. The antibody used here could recognize Adda group, the conservative part of MCs, which allowed the biosensor to detect both single toxin and the total content of MCs existing in the water sample.

Highlights

► Based on the observation of gold nanoparticles (Au NPs) induced graphene oxide (GO) fluorescence quenching, a reliable MCs biosensor was developed here for microcystins detection. ► Limit of detection was 0.5 and 0.3μg/L for MC-LR and MC-RR, respectively, which satisfies the strictest standard of WHO. ► Well defined results were also obtained in natural lake water and the specificity experiment.

Signal amplification architecture for electrochemical aptasensor based on network-like thiocyanuric acid/gold nanoparticle/ssDNA

01 August 2012, 10:42:44

Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 38, Issue 1
Zhengbo Chen, Lidong Li, Yu Tian, Xiaojiao Mu, Lin Guo
In this work, we described signal amplification architecture for electronic aptamer-based sensor (E-AB), which is applicable to a wide range of aptamers. Herein, we only take lysozyme as the representative sensing target. The amplification method was based on the network of thiocyanuric acid (TCA)/gold nanoparticles (AuNPs) modified with ssDNA. The binding event can be detected by a decrease in the integrated charge of the surface-bound [Ru(NH3)6]³⁺ which electrostatically absorbed onto the negatively charged phosphate backbones of DNA. In the presence of target molecules, a large amount of TCA/AuNP/ssDNA network associated with [Ru(NH3)6]³⁺ would be removed from the electrode surface, leading to a significant decrease of redox current. Cyclic voltammetry (CV) signals of [Ru(NH3)6]³⁺ provides quantitative measures of the concentrations of lysozyme, with a linear calibration ranging from 5pM to 1nM and a detection limit is 0.1pM. The detection limit of the proposed sensor is one order of magnitude and three orders of magnitude more sensitive than the detection limits in the absence of TCA (5pM) and in the absence of TCA/AuNP/ssDNA network (0.5nM). This amplification method is promising for broad potential application in clinic assay and various protein analysis.

Highlights

► This paper presents a signal amplification method for any electrochemical aptasensors. ► The amplification approach is based on thiocyanuric acid-gold nanoparticles network. ► Such an aptasensor opens a rapid, selective and sensitive route for clinical assay.

Highly sensitive visible light activated photoelectrochemical biosensing of organophosphate pesticide using biofunctional crossed bismuth oxyiodide flake arrays

01 August 2012, 10:42:44

Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 38, Issue 1
Jingming Gong, Xiaoqing Wang, Xue Li, Kewei Wang
A new, highly sensitive and selective biosensor for the photoelectrochemical (PEC) detection of organophosphate pesticides (OPs) has been developed, whereby newly synthesized crossed bismuth oxyiodide (BiOI) nanoflake arrays (BiOINFs) are fabricated as a photoactive electrode via a successive ionic layer adsorption and reaction (SILAR) approach. The smart integration of BiOINFs with biomolecules acetylcholinesterase (AChE) yields a novel AChE–BiOINFs hybrid, constructing a three-dimensional (3D) porous network biosensing platform. The composition and surface structure of the sensor were carefully characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and various electrochemical techniques. Such interlaced network architectures, providing better mass transport and allowing more AChE loading per unit area, as well as the intrinsically strong visible light-harvesting effect from BiOI, greatly facilitate the PEC responses. On the basis of the effect of OPs on the photocurrent of AChE–BiOINFs/ITO, a highly sensitive visible light-activated photoelectrochemical biosensor was developed for biosensing OPs. The conditions for OPs detection were optimized by using methyl parathion (MP) as a model OP compound. Under the optimized experimental conditions, our results show that such a newly designed AChE–BiOINFs/ITO photoactive electrode provides remarkably improved sensitivity and selectivity for the biosensing of OPs. The detection limit was found to be as low as about 0.04ngmL⁻¹ (S/N=3). Toward the goal for practical applications, the resulting sensor was further evaluated by monitoring MP in spiked vegetable samples, showing fine applicability for the detection of MP in real samples.

Highlights

► Newly synthesized crossed BiOI nanoflake arrays fabricated as a photoactive electrode. ► The first smart integration of BiOINFs with acetylcholinesterase. ► A highly sensitive and selective biosensor for PEC detection of OPs developed.

In situ enzymatic silver enhancement based on functionalized graphene oxide and layer-by-layer assembled gold nanoparticles for ultrasensitive detection of thrombin

01 August 2012, 10:42:44

Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 38, Issue 1
Yan Wang, Ruo Yuan, Yaqin Chai, Yali Yuan, Lijuan Bai
A highly specific in situ amplification strategy was designed for ultrasensitive detection of thrombin by combining the layer-by-layer (LBL) assembled amplification with alkaline phosphatase (ALP) and gold nanoparticles (Au) mediated silver deposition. High-density carboxyl functionalized graphene oxide (FGO) was introduced as a nanocarrier for LBL assembling of alkaline phosphatase decorated gold nanoparticles (ALP-Au), which was further adopted to label thrombin aptamer II. After sandwich-type reaction, numerous ALP were captured onto the aptasensor surface and catalyzed the hydrolysis of ascorbic acid 2-phosphate (AAP), which in situ generated ascorbic acid (AA), reducing Ag⁺ to Ag nanoparticles (AgNPs) for electrochemical readout. Inspiringly, the in situ amplification strategy with ethanolamine as an effective blocking agent showed remarkable amplification efficiency, very little nonspecific adsorption, and low background signal, which was favorable to enhance the sensitivity of aptasensor. Our novel dramatic signal amplification strategy, with a detection limit of 2.7fM, showed about 2–3 orders of magnitude improvement in the sensitivity for thrombin detection compared to other universal enzyme-based electrochemical assay.

Highlights

► A highly specific one-step in situ silver signal-transduction label was designed for ultrasensitive electrochemical detection of thrombin by combining the layer-by-layer (LBL) assembled amplification with in situ enzyme-induced silver deposition. ► The selected KCl detection solution provided a well-defined symmetrically sharp silver stripping peak, which potentially paved sensitive way for electrochemical readout. ► With ethanolamine as an effective blocking agent, the aptasensor gave a low background signal, assisting to push down the detection limit.

Efficient one-pot synthesis of molecularly imprinted silica nanospheres embedded carbon dots for fluorescent dopamine optosensing

01 August 2012, 10:42:44

Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 38, Issue 1
Yan Mao, Yu Bao, Dongxue Han, Fenghua Li, Li Niu
A new type of eco-friendly molecularly imprinted polymer (MIP) was synthesized through an efficient one-pot room-temperature sol–gel polymerization and applied as a molecular recognition element to construct dopamine (DA) fluorescence (FL) optosensor. Highly luminescent carbon dots (CDs) were firstly synthesized via a one-step reaction in organosilane, and their surface were anchored with MIP matrix (CDs@MIP). The resulting composite of a synergetic combination of CDs with MIP showed high photostability and template selectivity. Moreover, the composite allowed a highly sensitive determination of DA via FL intensity decreasing when removal of the original templates. The new MIP-based DA sensing protocol was applied to detect DA concentration in aqueous solution, the relative FL intensity of CDs@MIP decreased linearly with the increasing DA in the concentration range of 25–500nM with a detection limit (3σ) of 1.7nM. Furthermore, the proposed method was successfully intended for the determination of trace DA in human urine samples without the interference of other molecules and ions.

Highlights

► An eco-friendly CDs@MIP composite was synthesized. ► The synthesis process was a one-pot room-temperature sol–gel polymerization. ► CDs@MIP was the molecular recognition element of fluorescence optosensor. ► The optosensor exhibited high sensitive and selective towards dopamine.

Electrochemical DNA biosensor for bovine papillomavirus detection using polymeric film on screen-printed electrode

01 August 2012, 10:42:44

Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 38, Issue 1
Gustavo A. Nascimento, Elaine V.M. Souza, Danielly S. Campos-Ferreira, Mariana S. Arruda, Carlos H.M. Castelletti, Marcela S.O. Wanderley, Marek H.F. Ekert, Danyelly Bruneska, José L. Lima-Filho
A new electrochemical DNA biosensor for bovine papillomavirus (BPV) detection that was based on screen-printed electrodes was comprehensively studied by electrochemical methods of cyclic voltammetry (CV) and differential pulse voltammetry (DPV). A BPV probe was immobilised on a working electrode (gold) modified with a polymeric film of poly-L-lysine (PLL) and chitosan. The experimental design was carried out to evaluate the influence of polymers, probe concentration (BPV probe) and immobilisation time on the electrochemical reduction of methylene blue (MB). The polymer poly-L-lysine (PLL), a probe concentration of 1μM and an immobilisation time of 60min showed the best result for the BPV probe immobilisation. With the hybridisation of a complementary target sequence (BPV target), the electrochemical signal decreased compared to a BPV probe immobilised on the modified PLL-gold electrode. Viral DNA that was extracted from cattle with papillomatosis also showed a decrease in the MB electrochemical reduction, which suggested that the decreased electrochemical signal corresponded to a bovine papillomavirus infection. The hybridisation specificity experiments further indicated that the biosensor could discriminate the complementary sequence from the non-complementary sequence. Thus, the results showed that the development of analytical devices, such as a biosensor, could assist in the rapid and efficient detection of bovine papillomavirus DNA and help in the prevention and treatment of papillomatosis in cattle.

Highlights

► Electrochemical DNA sensor used to detect bovine papillomavirus. ► Polymeric film from poly-L-lysine (PLL) and chitosan was formed on gold electrode. ► Methylene blue (MB) electrochemical reduction decreased when the hybridisation occurred. ► The extracted Viral DNA from cattle with papillomatosis also decreased electrochemical signal. ► The detection limit was 4.35nM in the range from 5nM to 100nM.

Rapid detection of avian influenza H5N1 virus using impedance measurement of immuno-reaction coupled with RBC amplification

01 August 2012, 10:42:44

Publication year: 2012
Source:Biosensors and Bioelectronics, Volume 38, Issue 1
Jacob Lum, Ronghui Wang, Kentu Lassiter, Balaji Srinivasan, Daad Abi-Ghanem, Luc Berghman, Billy Hargis, Steve Tung, Huaguang Lu, Yanbin Li
Avian influenza virus (AIV) subtype H5N1 was first discovered in the 1990s and since then its emergence has become a likely source of a global pandemic and economic loss. Currently accepted gold standard methods of influenza detection, viral culture and rRT-PCR, are time consuming, expensive and require special training and laboratory facilities. A rapid, sensitive, and specific screening method is needed for in-field or bedside testing of AI virus to effectively implement quarantines and medications. Therefore, the objective of this study was to improve the specificity and sensitivity of an impedance biosensor that has been developed for the screening of AIV H5. Three major components of the developed biosensor are immunomagnetic nanoparticles for the separation of AI virus, a microfluidic chip for sample control and an interdigitated microelectrode for impedance measurement. In this study polyclonal antibody against N1 subtype was immobilized on the surface of the microelectrode to specifically bind AIV H5N1 to generate more specific impedance signal and chicken red blood cells (RBC) were used as biolabels to attach to AIV H5N1 captured on the microelectrode to amplify impedance signal. RBC amplification was shown to increase the impedance signal change by more than 100% compared to the protocol without RBC biolabels, and was necessary for forming a linear calibration curve for the biosensor. The use of a second antibody against N1 offered much greater specificity and reliability than the previous biosensor protocol. The biosensor was able to detect AIV H5N1 at concentrations down to 10³ EID50 ml⁻¹ in less than 2h.

Highlights

► A biosensor was developed for rapid screening of avian influenza virus H5 subtype. ► Immunomagnetic nanoparticles were used for separation of avian influenza virus. ► A microfluidic chip was developed for sample control and delivery. ► An interdigitated microelectrode was designed and fabricated for impedance measurement. ► Chicken red blood cells were used as biolabels to amplify impedance signal.

On-demand webinar discusses latest advances in 3D Cell Culture technology

AMSBIO, a supplier of advanced 3D tools to the life science community, recently participated in a '3D Cell Culture in Drug Discovery and Disease Modeling' webinar. Due to huge demand, the webinar which aired on 22nd May, has been reproduced in an on-demand version*.

Driven by the limitations of 2D cell cultures - scientists search for alternative solutions that mirror the environment experienced by normal cells in the body and replicate complex tissue structures and in vivo-like morphology. The '3D Cell Culture in Drug Discovery and Disease Modeling' webinar focuses on discussing the latest advances in 3D technology and its contribution to conducting more realistic research.

Dr Erik Miljan, founding director of Simply Cells Ltd assesses the impact on the physiological relevance of in vitro cell based models using traditional ECM proteins, recombinant biomimetics hydrogels and other matrices like polystyrene scaffolds in drug discovery and disease modeling applications. Highlighting real examples including spheroid and neuronal stem cell culture, Dr Miljan demonstrates how different 3D technologies can be applied to specific needs of researchers.

"This webinar offers a fantastic opportunity to learn about the many benefits of growing cells in 3D", said Dr Alex Sim, Managing Director of AMSBIO. "The scientific team at AMSBIO is very excited about the applications that 3D culture opens up for life science researchers and the fact that we offer the most comprehensive range of reagents for all its uses".

The on-demand version of the 3D Cell Culture webinar, as well as downloadable white papers and articles on the subject are available from the AMSBIO website*.

Founded in 1987, AMS Biotechnology (AMSBIO) is recognised as a leading international provider of unique, innovative products & custom services for life sciences research. The AMSBIO range includes over 23,000 polyclonal & monoclonal antibodies, peptides, recombinant proteins, extracellular matrix, molecular detection reagents, & tissue DNA, RNA, protein & microarray products. Key research areas include: apoptosis, cell invasion & migration, cell signaling, DNA damage, 3D culture, electrophoresis, glycobiology, post-translational modification & stem cell biology.

JEOL Puts New Spin on NeoScope Benchtop SEM

Since its initial introduction in 2008, the JEOL NeoScope benchtop Scanning Electron Microscope (SEM), represented by Nikon Instruments, has been used for inspection of electronic parts, forensics analysis, pharmaceutical inspection, and imaging insects for student projects. It is also used in conjunction with both optical microscopes and traditional SEMs in the lab.

Now JEOL introduces the NeoScope with higher magnification, multi-touch screen control, and a sleek new design.

As simple to use as a digital camera, the NeoScope is a high resolution SEM that produces images with a large depth of field at magnifications ranging from 10X - 60,000X. It features both high and low vacuum operation, three selectable accelerating voltages, and secondary electron and backscattered electron imaging. The NeoScope accommodates samples up to 70mm in diameter and 50mm in thickness. Both conductive and non-conductive samples can be examined. Optional EDS is available for elemental analysis.

An additional new feature of the NeoScope SEM is touch screen interface with the familiar look and feel of today's smart phones and touch pads. Automatic functions as well as pre-stored recipe files make it easy to use for a multitude of sample types. Any skill level of user will appreciate the simplicity and fast operation, from sample loading to imaging in vacuum in less than three minutes.

Visit www.nikoninstruments.com or www.jeolusa.com for more information about the NeoScope from JEOL.