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:

Review

2.

Laser-induced breakdown spectroscopy for light elements detection in steel: State of the art   Review Article Pages 1-10 Mohamed A. Khater Highlights ► We review development of the LIBS technique for trace analysis of light elements. ► This includes recent advances in laser pulse structure and industrial LIBS systems. ► Detection of light elements by LIBS in the optical region is still difficult. ► LIBS combination with either DLIFS or DLAAS would represent a potential solution.

Regular Papers

3.

A dried urine spot test to simultaneously monitor Mo and Ti levels using solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry   Original Research Article Pages 11-19 L. Rello, A.C. Lapeña, M. Aramendía, M.A. Belarra, M. Resano Highlights ► Deposition of urine on clinical filters facilitates home-based collection schemes. ►SS HR CS GFAAS enables direct determination of Mo and Ti in urine dried spots. ► These elements may be used as biomarkers to detect prosthesis malfunctioning. ► The way in which the sample is deposited in the filter is a key to proper quantitation. ► The use of matrix-matched urine standards for calibration is recommended.

4.

Production of metastable 23S1 helium in a laser produced plasma at low pressures   Original Research Article Pages 20-25 M. Bišćan, S. Milošević Highlights ► Production and decay of 23S1metastable He upon laser ablation were studied. ► Various targets in the regime of low helium gas pressures were used. ► CRDS was employed for lineshape measurements of the He 388.8nm transition. ► At larger fluences highest yield of metastables was obtained for aluminum target.

5.

Spectroscopic characterization of atmospheric pressure argon plasmas sustained with the Torche à Injection Axiale sur Guide d'Ondes   Original Research Article Pages 26-35 R. Rincón, J. Muñoz, M. Sáez, M.D. Calzada Highlights ► Ar discharges generated with microwave TIAGO torch were studied by OES. ► Great influence of atmosphere surrounding the flame on discharge parameters ► Electron densities ranging from 1014cm−3to 1015cm−3depending on argon flow rate ► Gas temperatures ranging from 2500K to 6000K depending on gas flow rate ► Small impact of input power on electron density and gas temperature

6.

The influence of the sample introduction system on signals of different tin compounds in inductively coupled plasma-based techniques   Original Research Article Pages 36-42 Javier Montiel, Guillermo Grindlay, Luis Gras, Margaretha T.C. de Loos-Vollebregt, Juan Mora Highlights ► Tin ICP-based signals depend on the compound chemical form. ► Signal differences are related to the compound volatility. ► Signal differences are reduced using high efficient sample introduction systems.

7.

Laser ablation methods for analysis of urinary calculi: Comparison study based on calibration pellets   Original Research Article Pages 43-49 K. Štěpánková, K. Novotný, M. Vašinová Galiová, V. Kanický, J. Kaiser, D.W. Hahn Highlights ► In this study we compare several laser-ablation based analytical techniques. ► The aim is to prove the calibration capabilities and limitations of these methods. ► Calibration pellets were prepared from human urinary calculi. ► Simultaneous LIBS–LA-ICP-OES, LA-ICP-MS and LA-LIBS were utilized.

8.

Backscattered electron images, X-ray maps and Monte Carlo simulations applied to the study of plagioclase composition in volcanic rocks   Original Research Article Pages 50-58 V. Galván Josa, D. Fracchia, G. Castellano, E. Crespo, A. Kang, R. Bonetto Highlights ► High resolution maps of anorthite content in single plagioclase crystals were obtained. ► The procedure was tested on volcanic rocks and is suitable for more evolved plagioclases. ► The ultimate resolution of X-rays and BE signal were studied by Monte Carlo simulations. ► MC simulations allowed to explain the BE contrast enhancement due to interface crossing.

Technical Note

9.

Separate K-line contributions to fluorescence enhancement in electron probe microanalysis    Pages 59-63 L. Venosta, G. Castellano Highlights ► The fluorescence enhancement correction factor in EPMA is studied. ► Reed's correction formulae were modified to account for Kβ and Kα lines separately. ► The differences evidenced encourage the implementation of completeFcorrections. ► Trace elemental concentrations may demand complete assessment of fluorescence factor.

Analytical Note

10.

Application of multivariate curve resolution-alternating least squares for the determination of boron isotope ratios by inductively coupled plasma-optical emission spectrometry    Pages 64-68 Ehsan Zolfonoun, Seyed Javad Ahmadi Highlights ► A new method for the determination of boron isotope ratios by ICP-OES is proposed. ► It is based on the isotopic shift of10B and11B in the emission line of 208.957nm. ► MCR-ALS was used for the resolution of the atomic emission spectra of boron isotopes. ► The proposed method presents good statistical parameters.

DataApex announces a new control driver for the SEDERE ELSD 90LT

DataApex is pleased to announce the release of a new control driver for the Evaporative Light-Scattering Detector 90LT, manufactured by SEDERE Company. This is already the 3rd Sedere detector its control and digital data acquisition has been incorporated into Clarity Chromatography SW. The driver for ELSD 90LT has been officially released with Clarity Chromatography Software version 4.0.3.

SEDERE  is the leading manufacturer of Low-Temperature Evaporative Light-Scattering Detectors. SEDERE has more than 25 years of experience in the development of versatile detection systems for all chromatography Applications and their detectors are distributed worldwide.

Clarity Chromatography Software has a strong position in the chromatography data systems market. Clarity, the third generation of DataApex products, allows controlling more than 400 different instruments from the single environment and offers its users very high flexibility. Clarity is highly regarded for its intuitive approach, excellent performance, cost-effectiveness and proficient technical support.

DataApex is solely focused on chromatography software development. A strong emphasis is placed on technological innovation, visionary adoption of new laboratory standards, best practices and extensive customer support. DataApex products are sold in over 80 countries around the world. Ten chromatography instrument manufacturers privately resell labeled versions of DataApex’s software.  To obtain further information about DataApex Clarity products please contact us at clarity@dataapex.com or visit www.dataapex.com

Just Published: Analytica Chimica Acta

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:

Analytica Chimica Acta
http://rss.sciencedirect.com/publication/science/5216

Selected papers from the latest issue:

Review articles

2.

Quality assessment and authentication of virgin olive oil by NMR spectroscopy: A critical review   Review Article Pages 1-27 Photis Dais, Emmanuel Hatzakis Graphical abstract Highlights ► Overview of olive oil analysis by1H,13C, and31P NMR spectroscopy. ► Sample preparation. ► Experimental conditions and processing for metabonomic analysis. ► Multivariate statistical methods for NMR data analysis. ► Quality assessment and authentication of extra virgin olive oil.

3.

Multivariate curve resolution: A review of advanced and tailored applications and challenges   Review Article Pages 28-36 C. Ruckebusch, L. Blanchet Graphical abstract Highlights ► MCR is nowadays a well-established and widespread methodology for mixture analysis. ► The analytical issues requiring advanced applications of MCR are reviewed. ► Attention is paid to the literature published the years 2008–2012.

Chemometrics

4.

NIR imaging spectroscopy for quantification of constituents in polymers thin films loaded with paracetamol   Original Research Article Pages 37-44 Guilherme L. Alexandrino, Ronei J. Poppi Graphical abstract Highlights ► NIR chemical imaging and chemometrics were used for studying thin films based drug delivery systems. ► Thin films were polymers mixtures of HPMC, PVP and PEG-400 loaded with the drug paracetamol. ► MCR-ALS provided initial biased results on quantification of polymers and additional calibration step was required. ► Three different strategies were tested to suppress the bias on the quantification by MCR-ALS. ► Parcetamol distribution in the thin films has direct correlation with the PVP and PEG, but inverse correlation with HPMC.

5.

Effects of supervised Self Organising Maps parameters on classification performance   Original Research Article Pages 45-53 Davide Ballabio, Mahdi Vasighi, Peter Filzmoser Graphical abstract Highlights ► We evaluated effects of SOMs parameters on classification and computational time. ► The study was conducted on eighteen real datasets. ► Significant parameters and their interactions on classification were highlighted. ► Optimal architectures to reduce the computational time of SOMs was proposed.

Electrochemistry

6.

Glassy carbon electrodes modified with gold nanoparticles for the simultaneous determination of three food antioxidants   Original Research Article Pages 54-62 Xiaoyun Lin, Yongnian Ni, Serge Kokot Graphical abstract Highlights ► A gold nanoparticles modified glassy carbon electrode (AuNPs/GCE) was constructed. ► The electrochemical mechanism of BHA, BHT and TBHQ at the AuNPs/GCE was studied. ► The oxidation products of BHA and TBHQ were found to be the same. ► First-derivative method was used to resolve the overlapped voltammograms. ► Synthetic antioxidants in food samples were analyzed.

7.

Novel electrochemical biosensor based on functional composite nanofibers for sensitive detection of p53 tumor suppressor gene   Original Research Article Pages 63-69 Xiaoying Wang, Xiaobing Wang, Xiaoning Wang, Fentian Chen, Kehui Zhu, Qian Xu, Meng Tang Graphical abstract Highlights ► A novel electrochemical p53 biosensor based on functional composite nanofibers (MWNTs–PA6–PPy) was developed. ► The MWNTs–PA6–PPy electrode with large specific surface area and good biocompatibility can be used to enhance stability, speed and sensitivity. ► The biosensor can detect 50fM wild type p53 sequence. ► The strategy could be extended to develop various sensors for the detection of many kinds of analytes.

8.

Sensitive voltammetric determination of paracetamol by poly (4-vinylpyridine)/multiwalled carbon nanotubes modified glassy carbon electrode   Original Research Article Pages 70-76 Hanieh Ghadimi, Ramin M.A.Tehrani, Abdussalam Salhin Mohamed Ali, Norita Mohamed, Sulaiman Ab Ghani Graphical abstract Highlights ► A P4VP/MWCNT modified glassy carbon electrode was fabricated and characterized. ► The electrode was useful for determination of paracetamol. ► At optimum conditions, ascorbic acid and uric acid did not interfere in the electrode activity. ► The electrode exhibited good sensitivity, reproducibility and stability. ► The electrode was used for the determination of paracetamol in formulation tablets and urine samples.

Mass Spectrometry

9.

Isotope pattern deconvolution-tandem mass spectrometry for the determination and confirmation of diclofenac in wastewaters   Original Research Article Pages 77-85 Ángel Castillo, Emma Gracia-Lor, Antoni Francesc Roig-Navarro, Juan Vicente Sancho, Pablo Rodríguez-González, J. Ignacio García Alonso Graphical abstract Highlights ► Isotope dilution with isotope pattern deconvolution (IPD) has been applied to LC–MS/MS. ► The procedure allows the determination of organic compounds without calibration graph. ► Diclofenac determination in wastewater showed the need of this methodology in LC–MS/MS. ► Confirmation was accomplished with routine transitions used in multiresidue analysis. ► IPD permits the minimal labeling of the analyte which minimizes isotopic effect.

NEW LC Column Line for Protein Separations

Protea Biosciences Group, Inc. a leading developer of new bioanalytical technologies, announced at the ASMS Sanibel Conference the introduction of Amplus^® wide-pore core shell HPLC columns, a new line of liquid chromatography columns specifically designed for intact proteins analysis.

This new family of HPLC silica-based columns employ core shell technology combined with a specific porosity designed to facilitate proteins separation, including those with high molecular weight.

"This year the ASMS Sanibel Conference is focused on Top Down proteomics applications and we thought it was a great opportunity to introduce a new technology designed for intact protein chromatographic analysis,” stated Alessandro Baldi, PhD, Vice President and General Manager of Protea Biosciences. ‘Amplus’ technology provides scientists with high chromatographic efficiency and facilitates Top Down proteomics approach to study intact proteins with or without mass spectrometry.”

Amplus, the new brand of analytical columns, has been developed in collaboration with the Japanese firm CromaNik Technologies and it is available in different chemistries and porosities to facilitate and resolve the most difficult separations in Top Down proteomics studies.

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:

Innovative biocompatible nanospheres as biomimetic platform for electrochemical glucose biosensor

24 February 2013, 14:33:06

15 June 2013
Publication year: 2013
Source:Biosensors and Bioelectronics, Volume 44

In this work, the silica– phytic acid (SiO2–PA) nanocomposites were synthesized by the method of reverse microemulsion and electrostatic binding. The newly designed materials were used to develop a novel glucose biosensor by immobilizing glucose oxidase (GOx) onto the SiO2–PA nanocomposites film on the surface of glassy carbon electrode (GCE). The characteristics of SiO2–PA nanocomposites and GOx were obtained by using transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and circular dichroism (CD) technique. All the results indicated that silica nanoparticales were modified with phosphate radicals successfully and the biomimetic surface was built. The entrapped GOx could preserve its bioactivity and exhibited an excellent electrochemical behavior with a formal potential of −0.548V in phosphate buffer solution (PBS) (pH=7). Response studies to glucose were carried out using differential pulse voltammetry (DPV). The results indicated that the modified electrode can be used to determine glucose without interference from l-ascorbic acid (AA) and uric acid (UA) with the low detection limit of 0.012mM. The comparison tests of DPVs of different electrodes in the absence and presence of glucose were also studied. The biosensor can also be used for quantification of the concentration of glucose in real samples.

Highlights

► Innovative SiO2–PA NPs were prepared by reverse microemulsion and electrostatic binding method. ► Biomimetic surface provided by SiO2–PA NPs could preserve bioactivity of GOx. ► The GOx biosensor modified by SiO2–PA NPs exhibited an excellent electrochemical behavior.

A “turn-off” SERS-based detection platform for ultrasensitive detection of thrombin based on enzymatic assays

24 February 2013, 14:33:06

15 June 2013
Publication year: 2013
Source:Biosensors and Bioelectronics, Volume 44

Herein we describe a novel “turn-off” biosensing strategy for thrombin detection based on Surface Enhanced Raman scattering (SERS) and the mediation of spacing between 4-mercaptobenzoic acid (4-MBA) labeled gold nanoparticles (AuNPs). The multiple arginine peptides that initiated gold nano-aggregates incorporating Raman reporter molecules due to the formation of “Hot Spots”, are induced to disband by the addition of thrombin in which the peptides are catalytically cleaved into fragments and thus SERS signals of 4-MBA are sharply declined because of the weakened ability of fragments to induce aggregation. Through this strategy, a novel “turn-off” SERS biosensor for thrombin based on enzymatic amplification is established with sensitivity, selectivity and simplicity as AuNPs and peptides are easily accessible. Compared with non-enzymatic amplification based methods, this newly proposed method has improved sensitivity. The limit of detection was 160fM (at the ratio of signal to noise, S/N=3:1). Further, controlled experiments showed that the method exhibited good selectivity over other proteases. The method demonstrated the capability and the potential for application in complex matrix and future biomarker development. The results also presented the potential and superiority of SERS biosensor based on signal amplification.

Highlights

► “Turn-off” SERS-based enzymatic assay is newly proposed. ► The method works on catalytic property of thrombin to cleave multi-arginine peptides. ► Ultrasensitive detection of target was achieved together with potential of use in complex matrix.

Immobilization of bovine serum albumin-protected gold nanoclusters by using polyelectrolytes of opposite charges for the development of the reusable fluorescent Cu2+-sensor

24 February 2013, 14:33:06

15 June 2013
Publication year: 2013
Source:Biosensors and Bioelectronics, Volume 44

In this paper, we reported a facile method of fabricating a reusable fluorescent Cu²⁺-sensor. To fabricate the reusable sensor, the bovine serum albumin-protected gold nanoclusters (BSAGNCs) were complexed with polyelectrolytes, i.e., positively charged polydiallyldimethylammonium (PDDA) and negatively charged polystyrenesulfonate (PSS), and were coated on a glass slide. The prepared film-modified glass slides exhibited the recyclability of fluorescent signal “off–on” behaviors: the fluorescence could be switched “off” by immersing the film sensors in Cu²⁺ solution and “on” by washing with ethylene diamine tetraacetic acid (EDTA) solution. The prepared film-modified glass slides exhibited high selectivity towards Cu²⁺ the fluorescence quenching behavior in the form of the Stern–Volmer equation. In addition, the spiked tap water samples were analyzed with satisfactory results. These demonstrations provide a new convenient approach to develop the BSAGNCs-based, reusable fluorescence sensors.

Highlights

► The BSA-protected GNCs were modified with polyelectrolytes of opposite charges. ► Bare glass slides were modified with the prepared complexes of protein–polyelectrolytes. ► A reusable fluorescence sensor for copper ion was proposed.

Interaction of anticancer drug methotrexate with DNA analyzed by electrochemical and spectroscopic methods

24 February 2013, 14:33:06

15 June 2013
Publication year: 2013
Source:Biosensors and Bioelectronics, Volume 44

Electrochemical DNA biosensor was used to study the interaction of methotrexate (MTX) with DNA immobilized on the bare surface of glassy carbon electrode (GCE). The binding mechanism of MTX with DNA was elucidated by using constant current potentiometric technique further supported by UV–Visible and FT-IR studies. The decrease in guanine peak area was used as an analytical signal for the interaction of drug with DNA in acetate buffer solution at pH 4.2 (20% ethanol). The binding constant (K) value calculated for MTX was 3.821×10⁵ M⁻¹. UV–Visible studies indicated hyperchromic and hypsochromic shifts in the maximum absorption bands of MTX after interaction with DNA. FT-IR investigations of MTX–DNA interaction revealed significant changes in the characteristic IR absorption bands of all the bases and phosphate groups of DNA. Furthermore, the shift of characteristics bands of CO, NH, CH and OH groups of MTX endow evidence for the interaction of MTX with DNA supporting the intercalative binding between them.

Highlights

► An electrochemical DNA biosensor was constructed by immobilizing the DNA to the surface of glassy carbon electrode (GCE). ► This electrode was used to determine the binding of methotraxate drug with DNA. ► Determination of bonding was done by using constant current potentiometric technique, UV–Visible and FTIR spectroscopy. ► Results demonstrated the intercalative binding between DNA and methotraxate.

Local detection of mechanically induced ATP release from bone cells with ATP microbiosensors

24 February 2013, 14:33:06

15 June 2013
Publication year: 2013
Source:Biosensors and Bioelectronics, Volume 44

The mechanically induced release of adenosine-5′-triphosphate (ATP) from osteoblastic cells (MC3T3-E1) was measured in real time. A stretching device integrated into scanning electrochemical microscopy was developed to apply controlled mechanical strain to MC3T3-E1 cells. For ATP secretion, a stepwise yet uniform mechanical stress was imposed onto MC3T3-E1 cells. The ATP biosensors were positioned at a distance of approximately 30–40μm above the cell surface. Calibration functions were recorded prior to the cell measurements and revealed a linear response up to 40μM with a sensitivity of 1–5pA/μM ATP. Stretching MC3T3-E1 cells up to 21% resulted in a concentration of 30.57±4.82μM of extracellular ATP (N=12) detected above the cell surface. As a control experiment, nifedipine, a L-type voltage sensitive calcium channel (L-VSCC) inhibitor was applied, which blocks Ca²⁺entry from the outer medium into the cell. Inhibition resulted in a significantly smaller amount of released ATP, i.e., 7.08±1.93μM ATP (N=10). Further control experiments with glucose microbiosensors did not yield significant changes of the baseline current (N=8).

Highlights

► Miniaturized ATP biosensors. ► Scanning electrochemical microscopy combined with a cell stretching device. ► Mechanically induced ATP release at MC3T3-E1 osteoblastic cells.

Fabrication of a new electrochemical sensor based on a new nano-molecularly imprinted polymer for highly selective and sensitive determination of tramadol in human urine samples

24 February 2013, 14:33:06

15 June 2013
Publication year: 2013
Source:Biosensors and Bioelectronics, Volume 44

A new nano-molecularly imprinted polymer bead was synthesized and applied to the fabrication of a chemically modified carbon paste electrode. Nano-molecularly imprinted polymer with molecular recognition capacity was made-up by using SiO2@Fe3O4 as the core and the supporting material. The electrode was applied to the simple, rapid, highly selective and sensitive determination of tramadol using square wave voltammetry. The molecularly imprinted polymer and multi-walled carbon nanotubes modified carbon paste electrode was prepared by incorporating the synthesized nano-MIP and multi-walled carbon nanotubes in carbon paste electrode. The limit of detection and the linear range were found to be 0.004 and 0.01 to 20μmolL⁻¹ of tramadol, respectively. The effects of potentially interfering substances on the determination of this compound were investigated. And it was found that the electrode is highly selective. The proposed chemically modified carbon paste electrode was used for the determination of tramadol in infected and healthy human urine and pharmaceutical samples.

Highlights

► A new nano-molecularly imprinted polymer bead was synthesized. ► The prepared nano-polymer bead was characterized by different methods. ► The bead was used to the fabrication of a chemically modified CPE. ► The electrode was used to the rapid and selective determination of tramadol.

Horseradish peroxidase-catalyzed synthesis of poly(thiophene-3-boronic acid) biocomposites for mono-/bi-enzyme immobilization and amperometric biosensing

24 February 2013, 14:33:06

15 June 2013
Publication year: 2013
Source:Biosensors and Bioelectronics, Volume 44

We report here on a facile enzymatic polymerization protocol to prepare enzyme—poly(thiophene-3-boronic acid) (PTBA) polymeric biocomposites (PBCs) for high-performance mono-/bi-enzyme amperometric biosensing. Horseradish peroxidase (HRP)-catalyzed polymerization of thiophene-3-boronic acid (TBA) monomer was conducted in aqueous solution containing HRP (or plus glucose oxidase (GOx)) by either directly added or GOx-glucose generated oxidant H2O2. The mono-/bi-enzyme amperometric biosensors were prepared simply by casting the dialysis-isolated PBCs on Au-plated Au electrode (Auplate/Au), followed by coating with an outer-layer chitosan (CS) film. The boronic acid residues are capable of covalent bonding with enzyme at the glycosyl sites (boronic acid-diols interaction), which should less affect the enzymatic activity as compared with the common cases of covalent bonding at the peptide chains, and UV–vis spectrophotometric tests confirmed that the encapsulated HRP almost possesses its pristine enzymatic specific activity. The enzyme electrodes were studied by cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry in the presence of Fe(CN)6 ⁴⁻ mediator. The CS/HRP–PTBA/Auplate/Au electrode responded linearly to H2O2 concentration from 1 to 300μM with a sensitivity of 390μAmM⁻¹ cm⁻² and a limit of detection (LOD) of 0.1μM. The bienzyme CS/GOx−HRP−PTBA(H2O2)/Auplate/Au electrode responded linearly to glucose concentration from 5μM to 0.83mM with a sensitivity of 75.1μAmM⁻¹ cm⁻² and a LOD of 1μM, and it is found here that the use of Fe(CN)6 ⁴⁻ that can only efficiently mediate HRP favorably avoids the “unusual amperometric responses” observed when other mediators that can efficiently turn over both HRP and GOx are used.

Highlights

► Preparation of mono-/bi-enzyme biocomposites by enzymatic polymerization. ► Boronic acid polymer as a biocompatible matrix for enzyme immobilization. ► High-performance biosensing of H2O2 and glucose.

A novel enzyme-free and label-free fluorescence aptasensor for amplified detection of adenosine

24 February 2013, 14:33:06

15 June 2013
Publication year: 2013
Source:Biosensors and Bioelectronics, Volume 44

A novel enzyme-free and label-free fluorescence aptasensor based on target-catalyzed hairpin self-assembly is developed for amplified detection of adenosine. This aptasensor contains four DNA strands termed as aptamer-catalysis strand, inhibit strand, hairpin structures H1 and H2 which are partially complementary. Meanwhile, a sequence that can form DNA G-quadruplex is partly hidden in the stem of H2. In the absence of adenosine, aptamer-catalysis strand is inhibited, and cannot trigger the self-assembly between H1 and H2. Upon the addition of adenosine, the binding event of aptamer and adenosine triggers the self-assembly between H1 and H2, resulting in the formation of G-quadruplex at the end of H1–H2 complex. The addition of N-methyl mesoporphyrin IX, which has a pronounced structural selectivity for G-quadruplex, generates label-free fluorescence signal. In the optimum conditions, we could detect adenosine as low as 6μM by monitoring the change in fluorescence intensity. Furthermore, this amplified aptasensor shows high selectivity toward adenosine against its analogs due to the specific recognition ability of the aptamer for the target. Thus, the proposed aptasensor could be used as a simple and selective platform for target detection.

Highlights

► A novel fluorescence amplified aptasensor was developed. ► The aptasensor was based on target-catalyzed self-hairpin assembly. ► The aptasensor was enzyme-free and label-free, making it simple and inexpensive. ► The limit of detection of the aptasensor for adenosine was 6μM. ► This strategy provided a simple, rapid and high selective versatile platform.

A highly sensitive label-free electrochemical aptasensor for interferon-gamma detection based on graphene controlled assembly and nuclease cleavage-assisted target recycling amplification

24 February 2013, 14:33:06

15 June 2013
Publication year: 2013
Source:Biosensors and Bioelectronics, Volume 44

We report here a highly sensitive and label-free electrochemical aptasensing technology for detection of interferon-gamma (IFN-γ) based on graphene controlled assembly and enzyme cleavage-assisted target recycling amplification strategy. In this work, in the absence of IFN-γ, the graphene could not be assembled onto the 16-mercaptohexadecanoic acid (MHA) modified gold electrode because the IFN-γ binding aptamer was strongly adsorbed on the graphene due to the strong π–π interaction. Thus the electronic transmission was blocked (eT OFF). However, the presence of target IFN-γ and DNase I led to desorption of aptamer from the graphene surface and further cleavage of the aptamer, thereby releasing the IFN-γ. The released IFN-γ could then re-attack other aptamers on the graphene, resulting in the successive release of the aptamers from the graphene. At the same time, the “naked” graphene could be assembled onto the MHA modified gold electrode with hydrophobic interaction and π-conjunction, mediating the electron transfer between the electrode and the electroactive indicator. Then, measurable electrochemical signals were generated (eT ON), which was related to the concentration of the IFN-γ. By taking advantages of graphene and enzyme cleavage-assisted target recycling amplification, the developed label-free electrochemical aptasensing technology showed a linear response to concentration of IFN-γ range from 0.1 to 0.7pM. The detection limit of IFN-γ was determined to be 0.065pM. Moreover, this aptasensor shows good selectivity toward the target in the presence of other relevant proteins. Our strategy thus opens new opportunities for label-free and amplified detection of other kinds of proteins.

Highlights

► We develop an electrochemical aptasensor for IFN-γ detection. ► The detection method is based on graphene and nuclease cleavage amplification. ► Signal transduction and amplification of graphene on the MHA/SAM electrode. ► It is a label-free, highly sensitive strategy for the detection of IFN-γ. ► The assay has good response in complicated cell media.

Construction of an amperometric bilirubin biosensor based on covalent immobilization of bilirubin oxidase onto zirconia coated silica nanoparticles/chitosan hybrid film

24 February 2013, 14:33:06

15 June 2013
Publication year: 2013
Source:Biosensors and Bioelectronics, Volume 44

A method is described for the construction of a highly sensitive electrochemical biosensor for the detection of bilirubin. The sensor is based on covalent immobilization of bilirubin oxidase (BOx) onto zirconia coated silica nanoparticles (SiO2@ZrONPs)/chitosan (CHIT) composite electrodeposited onto Au electrode. The enzyme electrode was characterized by scanning electron microscopy (SEM), Fourier transform infra-red spectroscopy (FTIR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The biosensor showed optimum response within 2s at pH 8.5 (0.1M Tris–HCl) and 35°C, when operated at 20mVs⁻¹. The biosensor exhibited excellent sensitivity (detection limit as 0.1nM), fast response time and wider linear range (from 0.02 to 250μM). Analytical recovery of added bilirubin was 95.56–97.0%. Within batch and between batch coefficients of variation were 3.2% and 3.35% respectively. The enzyme electrode was used 150 times over a period of 120 days, when stored at 4°C. The biosensor measured bilirubin levels in sera of apparently healthy and persons suffering from jaundice, which correlated well with a standard colorimetric method (r=0.99).

Highlights

► Constructed a BOx/SiO2@ZrONPs/CHIT/Au hybrid film. ► Fabricated an improved amperometric bilirubin biosensor based on this film. ► Biosensor had a detection limit of 0.1nM and linear range of 0.02–250μM. ► Employed for bilirubin determination in different serum samples.

Electrochemical sensor using neomycin-imprinted film as recognition element based on chitosan-silver nanoparticles/graphene-multiwalled carbon nanotubes composites modified electrode

24 February 2013, 14:33:06

15 June 2013
Publication year: 2013
Source:Biosensors and Bioelectronics, Volume 44

A novel imprinted electrochemical sensor for neomycin recognition was developed based on chitosan-silver nanoparticles (CS-SNP)/graphene-multiwalled carbon nanotubes (GR-MWCNTs) composites decorated gold electrode. Molecularly imprinted polymers (MIPs) were synthesized by electropolymerization using neomycin as the template, and pyrrole as the monomer. The mechanism of the fabrication process and a number of factors affecting the activity of the imprinted sensor have been discussed and optimized. The characterization of imprinted sensor has been carried out by scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). The performance of the proposed imprinted sensor has been investigated using cyclic voltammetry (CV) and amperometry. Under the optimized conditions, the linear range of the sensor was from 9×10⁻⁹ mol/L to 7×10⁻⁶ mol/L, with the limit of detection (LOD) of 7.63×10⁻⁹ mol/L (S/N=3). The film exhibited high binding affinity and selectivity towards the template neomycin, as well as good reproducibility and stability. Furthermore, the proposed sensor was applied to determine the neomycin in milk and honey samples based on its good reproducibility and stability, and the acceptable recovery implied its feasibility for practical application.

Highlights

► A selective electrochemical molecularly imprinted sensor for the detection of neomycin was developed. ► CS-SNP and GR-MWCNTs nanocomposites were used to improve the sensitivity of the sensor. ► MIPs were synthesized by electropolymerization using neomycin as the template, and pyrrole as the monomer. ► The sensor showed high selectivity, excellent stability and good reproducibility for the determination of neomycin. ► The developed sensor was successfully used for neomycin determination in real spiked samples.

Integration of gold nanoparticles in PDMS microfluidics for lab-on-a-chip plasmonic biosensing of growth hormones

24 February 2013, 14:33:06

15 June 2013
Publication year: 2013
Source:Biosensors and Bioelectronics, Volume 44

Gold nanoparticles were synthesized in a poly(dimethylsiloxane) (PDMS) microfluidic chip by using an in-situ method, on the basis of reductive properties of the cross-linking agent of PDMS. The proposed integrated device was further used as a sensitive and low-cost LSPR-based biosensor for the detection of polypeptides. Synthesis of nanoparticles in the microfluidic environment resulted in improvement of size distribution with only 8% variation, compared with the macro-environment that yields about 67% variation in size. The chemical kinetics of the in-situ reaction in the microfluidic environment was studied in detail and compared with the reaction carried out at the macro-scale. The effect of temperature and gold precursor concentration on the kinetics of the reaction was investigated and the apparent activation energy was estimated to be E a ⁎ = 30 kJ / mol . The sensitivity test revealed that the proposed sensor has a high sensitivity of 74nm/RIU to the surrounding medium. The sensing of bovine growth hormone also known as bovine somatotropin (bST) shows that the proposed biosensor can reach a detection limit of as low as 3.7ng/ml (185pM). The results demonstrate the successful integration of microfluidics and nanoparticles which provides a potential alternative for protein detection in clinical diagnostics.

Highlights

► An in-situ method for integration of gold NP in a PDMS microfluidic chip is proposed. ► The kinetics is fully studied and the activation energy is estimated to be 30kJ/mol. ► The reaction in microchannel is found to be slower than at the macro-scale. ► The size uniformity of GNPs is found to be considerably improved in the micro-environment. ► A detection limit of 4ng/mL for bovine GH is obtained for the proposed biosensor.

Porous silicon optical microcavity biosensor on silicon-on-insulator wafer for sensitive DNA detection

24 February 2013, 14:33:06

15 June 2013
Publication year: 2013
Source:Biosensors and Bioelectronics, Volume 44

Silicon-on-insulator (SOI) wafer is one of the most appealing platforms for optical integrated circuit with the potential to realize high performance Ultra Large Scale Integration (ULSI) and device miniaturization. In this work, based on simulations to obtain appropriate optical properties of a porous silicon microcavity (PSM), we successfully fabricated a highly efficient PSM on SOI wafer by electrochemical etching for DNA detection at optical wavelength 1555.0nm. The narrow resonance peak with a full width at half maximum about 26.0nm in the reflectance spectrum gives a high Q factor which causes high sensitivity for sensing performance. The sensitivity of this sensor is investigated through 19-base pair DNA hybridization in the PSM by surface modification using a standard cross link chemistry method. The red shift of the reflectance spectra shows a good linear relationship with complementary DNA concentration, ranging from 0.625 to 12.500μM, and the detection limit is 43.9nM. This optical PSM on SOI is highly sensitive, fast responsive, easy to fabricate and low-costly, that will broadly benefit to develop a new optical label-free biosensor on SOI wafer and has a great potential for biochips based on integrated optical devices.

Highlights

► A sensitive label-free PSM biosensor on SOI wafer was fabricated by electrochemical etching. ► By simulations and experiments, we optimized PSM biosensor with a high Q value and a high sensitivity. ► This biosensor was used for DNA detection and red shift shows a good linear relationship with DNA. ► This optical PSM on SOI could be a great potential for biochips based on integrated optical devices.

In situ amplification signaling-based autonomous aptameric machine for the sensitive fluorescence detection ofcocaine

24 February 2013, 14:33:06

15 June 2013
Publication year: 2013
Source:Biosensors and Bioelectronics, Volume 44

The development of autonomous DNA machines and their use for specific sensing purpose have recently attracted considerable research attention. In existing autonomous machines, the target recognition process and signal transduction are separated from each other. This results in misunderstanding of the operation behavior, and the assay capability is compromised when serving as a sensing tool. In this communication, the integrated signal transduction-based autonomous aptameric machine, in which the recognition element and signal reporters are integrated into a DNA strand, is developed. This new machine can execute the in situ amplification of target binding-induced signal. The authentic operation behavior of autonomous DNA machine is discovered: the machine's products directly hybridize to the “track” rather than to the signaling probes. Along this line, the machine is employed to detect the cocaine in a more straightforward fashion, and improved assay characteristics (for example, the dynamic response range is widened by more than 500-fold) are achieved. Our efforts not only clarify the concept described in traditional autonomous DNA machines but also have made technological advancements that are expected to be especially valuable in designing nucleic acid-based machines employed in basic research and medical diagnosis.

Highlights

► In situ amplification signaling-based aptameric machine has been developed. ► Discovering operation behavior of scission/replication-based autonomous machine. ► The developed aptameric machine exhibits substantially improved assay characteristics.

Multiplex electrochemiluminescence immunoassay of two tumor markers using multicolor quantum dots as labels and graphene asconductingbridge

24 February 2013, 14:33:06

15 June 2013
Publication year: 2013
Source:Biosensors and Bioelectronics, Volume 44

A multiplex electrochemiluminescence (ECL) immunoassay for simultaneous determination of two different tumor markers, alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA), using multicolor quantum dots as labels and graphene as conducting bridge was developed. Herein, a typical sandwich immune complex was constructed on the glass carbon electrode, with QDs525 and QDs625 labeled on secondary anti-AFP and anti-CEA antibodies, respectively, thus to obtain distinguishable ECL signals. Because most of those QDs labeled on secondary antibodies were beyond the space domain of the ECL reaction, graphene was used as a conducting bridge to promote the electron transfer between QDs and the electrode, leading to about 30-fold enhancement of the ECL intensity. Experimental results revealed that the multiplex electrochemiluminescence immunoassay enabled the simultaneous monitoring of AFP and CEA in a single run with a working range of 0.001–0.1pg/mL. The detection limit (LOD) for both analytes at 0.4fg/mL was very low. No obvious cross-reactivity was found. Precision, recovery and stability were satisfactory. This novel multiplex ECL immunoassay provided a simple, sensitive, specific and reliable alternative for the simultaneous detection of tumor markers in clinical laboratory.

Highlights

► A multiplex ECL immunoassay of two tumor markers was proposed. ► Multicolor QDs were labeled to obtain distinguishable ECL signals. ► G was used as a conducting bridge, improving the ECL intensity about 30-folds. ► LOD for AFP and CEA was about 0.4fg/mL.