Conductimetric immunosensor for atrazine detection based on antibodies labelled with gold nanoparticles

A novel conductimetric immunosensor for atrazine detection has been designed and developed. This immunosensor is mainly based on antibodies labelled with gold nanoparticles. Additionally, the immunosensor consists of an array of two coplanar non-passivated interdigitated metallic μ-electrodes (IDμE) and immunoreagents specifically developed to detect this pesticide. The chemical recognition layer was covalent immobilized on the interdigital space. Immunochemical detection of the concentration of atrazine is achieved by a competitive reaction that occurs before the inclusion of the labelled antibodies. It is shown that the gold nanoparticles provide an amplification of the conductive signal and hence makes possible to detect atrazine by means of simple DC measurements.The conductimetric immunosensor and its biofunctionalization steps have been characterized by chemical affinity methods and impedance spectroscopy.This work describes the immunosensor structure, fabrication, physico-chemical and analytical characterization, and the immunosensor response using conductivity measurements. The immunosensor developed detects atrazine with limits of detection in the order of 0.1–1 μg L⁻¹, far below the maximum residue level (MRL) (100 μg L⁻¹) established by European Union (EU) for residues of this herbicide in the wine.Although in this paper the competitive reaction occurs in buffer, an initial study of the wine matrix effect is also described.     

Consolidated biocomposite membrane technology for production of potentiometric biosensors

Consolidated membrane technology, consisting of a simple compression of dry components, is proposed for production of potentiometric biosensor membranes. In order to present this concept, two different kinds of conventional potentiometric biosensors have been designed both based on this novel biocomposite membrane technology. In the first case, a -amygdalin biosensor based on β-glucosidase incorporated in an iodide-selective membrane has been prepared. In the second case, two enzymes, glucose oxidase (GOD) and peroxidase (POD) are incorporated in the iodide-selective membrane to form a biocomposite for glucose sensing. Some of the main characteristics of the developed potentiometric biosensors are discussed. This involves both the manufacturing technology and the analytical evaluation of biosensors. Results obtained, indicate that this pressing technology is suitable for mass production of potentiometric biosensing devices. For the biosensor based on β-glucosidase, the recommended pressure was 2.3·10⁴ kg/cm². At this pressure, it was observed that the immobilisation of enzymes in the bulk of the electroactive salts was efficient. The -amygdalin biosensor had a linear response in the range of 3.9·10⁻³ to 10⁻² M and a practical lower detection limit of 2.5·10⁻³ M. For the biosensor based on GOD and POD the optimal consolidation pressure was 2.0·10⁴ kg/cm². In batch measurements, this biosensor has a response time of approximately 2 min. The linear range was between 0.3 and 1.1 mM glucose.     

Simultaneous measurement of Pb, Cd and Zn using differential pulse anodic stripping voltammetry at a bismuth/poly(p-aminobenzene sulfonic acid) film electrode

A novel sensor was developed for simultaneous detection of Pb, Cd and Zn, based on the differential pulse anodic stripping response at a bismuth/poly(p-aminobenzene sulfonic acid) (Bi/poly(p-ABSA)) film electrode. This electrode was generated in situ by depositing simultaneously bismuth and the metals by reduction at −1.40 V on the poly(p-ABSA) modified electrode. Compared with the bismuth film electrode, the Bi/poly(p-ABSA) film electrode can yield a larger stripping signal for Pb, Cd and Zn. Under the optimum conditions, a linear response was observed for Cd and Zn in the range from 1.00 to 110.00 μg L⁻¹ and for Pb in the range from 1.00 to 130.00 μg L⁻¹. The detection limits of Pb(II), Cd(II) and Zn(II) were 0.80, 0.63 and 0.62 μg L⁻¹, respectively. Finally this sensor had been applied to the simultaneous determination of Pb(II), Cd(II) and Zn(II) in river water samples and the results were quite corresponding to the value obtained by atomic absorption spectrometry.     

Ultra-sensitive polysilicon wire glucose sensor using a 3-aminopropyltriethoxysilane and polydimethylsiloxane-treated hydrophobic fumed silica nanoparticle mixture as the sensing membrane

In this paper a highly sensitive glucose biosensor is proposed based on a polysilicon (poly-Si) wire structure coated with 3-aminopropyltriethoxysilane (γ-APTES) mixed with polydimethylsiloxane-treated hydrophobic fumed silica nanoparticles (NPs) as the sensing membrane. The γ-APTES and fumed silica NPs mixture was directly transferred to and coated onto the poly-Si wire region with the help of a focus-ion-beam (FIB) processed capillary atomic-force-microscope (C-AFM) tip. After the necessary curing and UV illumination processes, the resultant sensor showed an extremely wide linear detection range from 0.1 μM to 10 mM with a channel current sensitivity as high as 5.33 A mM⁻¹ cm⁻² (or a channel conductance sensitivity of 70 μS mM⁻¹), and a detection limit as low as 10 nM can be achieved. Our experimental results showed that the poly-Si wire sensor has good selective analysis and operational stability on glucose detection under a 10:1 concentration ratio of glucose and uric acid. Its linear range and lowest detection limit remain virtually unimpaired in the presence of uric acid.     

电磁流量计三值方波励磁信号的控制

电磁流量计是一种根据法拉第电磁感应定律来测量管内导电介质体积流量的感应式仪表。本文在分析电磁流量计的励磁信号种类和特点的基础上,选择了低频三值矩形方波作为电磁流量计的励磁信号,设计了电磁流量计的励磁线圈,并分析了线圈的物理和几何参数,在此基础上设计励磁系统硬件电路,包括电源、固态继电器、控制器Labjack的选型和控制方法等。最后设计了低频三值方波的控制程序,为电磁流量计提供了一种性能良好的励磁控制方案。     

The Synergy™ HT - A Unique Multi-Detection Microplate Reader for HTS and Drug Discovery

Pharmaceutical and biotechnology research requires instrumentation to be both functional and versatile. In the HTS and Drug Discovery environments, microplate based assays are developed to make determinations on large numbers of samples. Regardless of the assay protocol, the end result is the measurement by some sort of detection device. Towards that end, Bio-Tek has developed the Synergy™ HT Multi-Detection microplate reader. Microplate Reader. Synergy HT utilizes two independent sets of optics to provide uncompromised performance. For absorbance measurements, there is a xenon-flash lamp with a monochromator for wavelength selection and photodiode detection. This allows the selection of any wavelength for endpoint or kinetic measures from 200 nm to 999 nm in 1 nm increments, as well as spectral scans. Traditional visible wavelength fluorescence measurements are made using a tungsten-halogen lamp with interference filters (excitation and emission) for wavelength selection and photomultiplier (PMT) detection. Glow luminescence measurements are also easily accomplished in Synergy HT. If time-resolved or UV excitation fluorescence measurements are required, Synergy HT automatically integrates the xenon-flashmonochromator excitation with the interference emission filter and PMT detection. Typical applications include antibody-antigen binding, receptor-liquid binding, ELISA, nucleic acid quantitation using fluorescent dyes or direct UV analysis. Synergy HT is capable of reading any plate format up to 384-well plates and provides temperature control up to 50° C and shaking as standard features. It is compact (16″ W × 15″ D × 10″ H) and robotics-compatible through the OLE functionality of the KC4™ data reduction software that is bundled with the instrument. An upgrade to CFR 21 Part 11 compliant software is also available.     

An amperometric ethanol sensor based on a Pd–Ni/SiNWs electrode

A new amperometric ethanol sensor has been developed. The sensor uses the silicon nanowires covered with co-deposited palladium–nickel (Pd–Ni/SiNWs) as the working electrode. The detection of ethanol concentration is based on the response currents resulted from the electro-catalytic oxidation of ethanol. The performance of the sensor was characterized by cyclic voltammetry and fixed potential amperometry techniques. In 1 M KOH solution containing different ethanol concentrations, the sensor shows a good sensitivity of 7.48 mA mM⁻¹ cm⁻² and the corresponding detection limit (signal-to-noise ratio = 3) of 6 μM for cyclic voltammetry. Meanwhile, it also displays a sensitivity of 0.76 mA mM⁻¹ cm⁻² and the corresponding detection limit of 10 μM for fixed potential amperometry. The results demonstrate that the Pd–Ni/SiNWs electrodes are potential as the electrochemical integrated sensors for ethanol detection.     

Spectral stability based event localizing temporal decomposition

In this paper a new approach to Temporal Decomposition (TD) of speech, called Spectral Stability Based Event Localizing Temporal Decomposition (S²BEL-TD), is presented. The original method of TD proposed by Atal (1983, Proceedings of the International Conference on Acoustics, Speech, and Signal Processing, 81–84) is known to have the drawbacks of high computational cost, and the high parameter sensitivity of the number and locations of events. In S²BEL-TD, the event localization is performed based on a maximum spectral stability criterion. This overcomes the high parameter sensitivity of events of Atal’s method. Also, S²BEL-TD avoids the use of the computationally costly singular value decomposition routine used in Atal’s method, thus resulting in a computationally simpler algorithm for TD. Simulation results show that an average spectral distortion of about 1.5 dB can be achieved with line spectral frequencies as the spectral parameter. It is shown that the temporal pattern of the speech excitation parameters can also be well described using the S²BEL-TD technique.     

Synthesis, characteristics and luminescent properties of a new europium(III) organic complex applied in near UV LED

A novel indane based β-diketone with trifluorobutane in the contraposition, 5-acetylindane-4,4,4-trifluorobutane-1,3-dione (HAITFBD) and its europium(III) ternary complex, Eu(AITFBD)₃phen, were designed and synthesized, where phen was 1,10-phenanthroline. The complex was characterized by IR, UV-visible, thermogravimetric analysis (TGA) and photoluminescence (PL) spectroscopy in details. The results show that the Eu(III) complex exhibits high thermal stability, wide and strong excitation bands from 300 nm to 425 nm when monitored at 611 nm, which matches well with the 380 nm-emitting InGaN chips. The complex exhibits intense red emission under excitation of near UV light due to the f-f transitions of the central Eu³⁺ ion. Based on the emission spectrum, the CIE chromaticity coordinates of the LED are calculated as x = 0.63 and y = 0.34, which is suitable to be used as an efficient red phosphor in fabrication of white LEDs. The fluorescence lifetime and the luminescence quantum yield were also measured. The lowest triplet state energy of the primary ligand AITFBD was measured to be 17,730 cm⁻¹, higher than that of the lowest excitation state energy level of the central Eu³⁺ ion, ⁵D₀, and this suggests that the photoluminescence of the complex is a ligand-sensitized luminescence process (antenna effect). Finally, a bright red light-emitting diode was fabricated by coating the Eu(AITFBD)₃phen complex onto a 380 nm-emitting InGaN chip. All the results indicate that Eu(AITFBD)₃phen can be applied as a red component for fabrication of near ultraviolet-based white light-emitting diodes.     

Model diagnostic plots for repeated measures data using the generalized estimating equations approach

The generalized estimating equations (GEE) approach has been widely used to analyze repeated measures data. However, in the absence of likelihood ratio tests, model diagnostic checking tools are not well established for the GEE approach, whereas they are for other likelihood-based approaches. Diagnostic checking tools are essential for determining a model’s goodness of fit, especially for non-normal data. In this paper, we propose simple residual plots to investigate the goodness of fit of the model based on the GEE approach for discrete data. The proposed residual plots are based on the quantile–quantile (Q–Q) plots of a χ²-distribution, and are particularly useful for comparing several models simultaneously.     

Characterization and failure analysis of MEMS: high resolution optical investigation of small out-of-plane movements and fast vibrations

A high resolution optical tool is required to investigate the mechanical behavior and failure modes of micro-electromechanical systems (MEMS). We report on the possibilities of a newly developed optical characterization tool for MEMS devices. Both slow movements and fast mechanical vibrations up to 15 MHz can be monitored. The instrument can perform an imaging operation for a complete image at once by employing laser TV holography, which is a large advantage over scanning laser Doppler vibrometers. For vibration measurements, this new, interference based instrument uses a beat frequency between object excitation and reference beam excitation. A normal CCD camera is used to obtain 3D images and movies of periodic mechanical motions of MEMS devices. Excitation can be by means of a PZT, or by using electronic excitation. We show that the instrument is a very useful tool for the characterization and failure analysis of MEMS devices.The whole MEMS team at IMEC and their coworkers in projects are thanked for providing many of the samples shown in this paper. In particular, we would like to thank the following people. Melexis is thanked for providing the membrane sample of Fig. 4–6 and 14. Figs. 7–9 were measured in the frame of the MISTRA project (IWT contract 000167). Theo Rijks (Philips Natlab) provided the sample of Figs. 10 and 11. Chris Muhlstein sent the sample of Fig. 12 to us. Hans de Vries (Philips Centre for Industrial Technology/EP&A) is thanked for providing the sample of Fig. 13. The switch of Fig. 15 was made in the MIRS project (5012352345). Laurent Francis (IMEC) is thanked for providing the sample of Fig. 16. Sjoerd van de Geijn of Océ-Technologies B.V. provided the sample of Fig. 17.     

Differential pulse voltammetric determination of N-acetylcysteine by the electrocatalytic oxidation at the surface of carbon nanotube-paste electrode modified with cobalt salophen complexes

The preparation and electrochemical performance of the carbon nanotube-paste electrode modified with salophen complexes of cobalt(III) perchlorate, with various substituents on the salophen ligand, as well as their electrocatalytic activity toward the oxidation of N-acetylcysteine (NAC) is investigated. Several Schiff base complexes containing various nucleophilic and electrophilic functional groups were prepared, and their electrochemical characteristics for the electro-oxidation of NAC were evaluated using cyclic and differential pulse voltammetry (CV and DPV). The results revealed, the modified electrodes show an efficient and selective electrocatalytic activity toward the anodic oxidation of NAC among biologically important compounds in buffered solutions at pH of 7.0. The best voltammetric responses were obtained for a carbon-paste electrode (CPE) modified with a salophen complex containing para-methoxy groups on its salicylaldehyde ring. The analytical response of the modified electrode for response to other sulfhydryl compounds (e.g., cysteine, penicillamine, captopril and mercaptopropionyl glycine) in comparison to NAC was investigated by CV and DPV methods. The DPV method was applied as a sensitive method for the quantitative detection of the trace amounts of NAC. A linear dynamic range from 1 × 10⁻⁷ to 1 × 10⁻⁴ M with calibration sensitivity of 0.0646 μA/μM is resulted for NAC in DPV measurements. The detection limit was 5 × 10⁻⁸ M, which is remarkably lower than those reported previously for NAC using other modified electrodes. The results of voltammetric determinations show a very good reproducibility, and the R.S.D. for the slope of the calibration curve, based on 10 measurements in a period of two months, was <3.9%. The detection system provides very stable electrochemical responses toward NAC, makes it very suitable for using in pharmaceutical and clinical measurements.     

Gold nanowire array electrode for non-enzymatic voltammetric and amperometric glucose detection

The non-enzymatic voltammetric and amperometric detection of glucose using a gold nanowire array electrode is described. The voltammetric detection of glucose was performed by cyclic and differential-pulse voltammetry. The detection of glucose by partial and direct oxidation of glucose during the anodic and cathodic potential sweeps was shown in cyclic voltammetry. An unusual decrease in overpotential for partial oxidation of glucose on a Au NW array electrode was observed. A linear differential-pulse voltammetric response for partial oxidation of glucose was observed up to a glucose concentration of at least 20 mM with a sensitivity of 41.9 μA mM⁻¹ cm⁻² and detection limit below 30 μM (signal-to-noise ratio of 3) for glucose oxidation at low potentials, where the influence of possible intermediates can be avoided. The amperometric response was also linear up to a glucose concentration of 10 mM with a sensitivity of 309.0 μA mM⁻¹ cm⁻². The wide dynamic range and high sensitivity, selectivity and stability, as well as good biocompatibility of the Au NW electrode make it promising for the fabrication of non-enzymatic glucose sensors.     

Thin-film organic photodiodes for integrated on-chip chemiluminescence detection – application to antioxidant capacity screening

We demonstrate that solution processed thin-film organic photodiodes (OPDs) can be used as compact and sensitive integrated detectors for antioxidant capacity screening. The OPDs were fabricated with blends of regioregular poly(3-hexylthiophene) (P3HT) and (6,6)-phenyl C₆₁ butyric-acid methyl-ester (PCBM). The devices had a broadband photoresponse from 350 nm to 650 nm with a peak responsivity of 0.25 A/W at 550 nm and a dark current density of 0.59 μA/cm² under 10 mV bias for a device area of 1 mm². The signal rise and fall times of the detectors were 0.51 μs and 0.66 μs, respectively. The detectors were applied to an on-chip peroxyoxalate chemiluminescence (PO-CL) assay for antioxidant capacity determination. Antioxidant standards were injected into a stream of PO-CL reagents, resulting in a CL emission decrease that correlated with the antioxidant capacity. For the encountered CL signals the OPDs provided a comparable response to photomultiplier tubes (PMTs) commonly used in analytical applications. Antioxidant capacity screening results showed excellent consistency between the two detection methods. The compact and portable detection system is suited not only to low-cost in-the-field antioxidant capacity screening, but could have wider applications for chemiluminescence based diagnostic tests at the point-of-care.     

Voltammetric sensor for amoxicillin determination in human urine using polyglutamic acid/glutaraldehyde film

A voltammetric sensor for determination of amoxicillin (AMX) was developed based on a glutaraldehyde cross-linked polyglutamic acid modified glassy carbon electrode. The proposed method is based on pre-concentration of AMX by cathodic accumulation as its oxidative product before being determined indirectly at potential as low as +0.23 V by square wave voltammetry. Linear response range, sensitivity and limit of detection were 2.0–25.0, 1.06 and 0.9.2 μmol L⁻¹, respectively, for AMX in 0.1 mol L⁻¹ acetate buffer pH 5.2, pre-accumulation time of 60 s and accumulation potential of +1.0 V. It was demonstrated that the glassy carbon electrode modified with PGA/GLU could be used for AMX determination in human urine without any separation step.     

水环境重金属铜离子光学检测仪器的设计

针对水质污染中的重金属污染设计了一种自动化检测仪器,能够特异性检测水环境中重金属铜离子.仪器采用光学方法进行检测,具有检测速度快,操作简单,重复性好等优点.仪器能够自动控制水路实现了溶液进样自动化,同时设计了水路闭环检测模块,实现了精确进样以及故障检测.仪器能够自动调节激光器光强适应于不同浓度样品的检测.实际检测结果表明本仪器检出限达到0.006 mg/L,在0.1 mg/L到2.00 mg/L具有良好的线性度,检测准确度小于6.4%,精密度小于4.52%.     

3D reconstruction of buildings from LiDAR data considering various types of roof structures

In this article, a different approach has been proposed to detect and reconstruct buildings in 3D space. In this regard, some potentially primary features were produced and a genetic algorithm (GA) was employed in order to select the optimum features. The selected features were utilized to detect the building by using k-nearest neighbour (k-NN) algorithm. The detection results were used as inputs of reconstruction procedure. The proposed approach for 3D reconstruction consists of three main steps: roof planes were separated in the first step. Then, the corners of each plane boundary were extracted in order to provide the roof reconstruction possibility. Finally, the walls were reconstructed and merged to roofs and the final 3D model was obtained. Results evaluation indicated that the average value of buildings detection in the test areas was 87.84% in Quality. Moreover, the average value of buildings reconstruction in the test areas was 76.95% in object based Quality, and 95.66% in Quality of building planes that were greater than 25 m², respectively. Also, the average of altimetric and planimetric RMS of the test areas were 0.3 m and 0.75 m, respectively.     

Immobilization of horseradish peroxidase and nile blue into the ormosil nanocomposite for the fabrication of hydrogen peroxide biosensor based on MWCNT modified glassy carbon electrode

A novel approach to construct a second-generation amperometric biosensor is described. The classical redox dye nile blue (NB) as mediator and horseradish peroxidase as a base enzyme were coimmobilized into the multiwalled carbon nanotubes (MWCNTs) modified ormosil matrix. Nafion was dispersed into the matrix to enhance the rate of the electron transfer and prevent the cracking of the ormosil film. The surface morphology of MWCNT/NB/NAF/HRP nanocomposite was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS). Cyclic voltammetry and amperometry measurements were used to study and optimize the performance of the resulting peroxide biosensor. The apparent Michaelis–Menten constant was determined to be 1.1 mM. The effect of pH, applied potential and amount of the HRP enzyme on the electrochemical biosensor has been systematically studied. The fabricated biosensor demonstrated significant electrocatalytic activity for the reduction of hydrogen peroxide with wide linear range from 2 × 10⁻⁷ to 3.8 × 10⁻⁴ M, and low detection limit 1 × 10⁻⁷ M (S/N = 3) with fast response time <3 s. The facile procedure of immobilizing HRP and MWCNTs into the ormosil used in the present work can promote the development of electrochemical research for enzymes, proteins, biosensors, biofuel cells and other bioelectrochemical devices.     

Electrochemical sensor for hydroperoxides determination based on Prussian blue film modified electrode

An electrochemical sensor for hydroperoxides determination was investigated. The sensor was based on the electrocatalytic reduction of hydroperoxides on Prussian blue (PB)-modified glassy carbon electrode. The modified electrode possesses a high electrocatalytic effect towards all studied peroxides with the highest effect obtained with H₂O₂ followed by tert-butyl hydroperoxide (TBH), cumene hydroperoxide (CH) and linoleic acid hydroperoxide (LAH). In addition, the modified electrode showed a good stability and a fast response time (<20 s). The lower detection limits of H₂O₂, TBH, CH and LAH were found to be 10⁻⁷ mol L⁻¹, 2 × 10⁻⁷ mol L⁻¹, 3.5 × 10⁻⁷ mol L⁻¹ and 4 × 10⁻⁷ mol L⁻¹, respectively. The electrochemical sensor was then applied for amperometric determination of peroxide value (PV) in edible oil at an applied potential of 50 mV (vs. Ag/AgCl (1 M KCl)). A good linearity has been found in the range 0.02–1.0 mequiv. O₂/kg, with a detection limit (S/N = 3) of 0.001 mequiv. O₂/kg. The precision of the method (R.S.D., n = 9) for within and between-days is better than 1.9% and 2.7%, respectively at 0.1 mequiv. O₂/kg. The method was successfully applied to the determination of PV in real edible oil samples with an excellent agreement with results obtained with the official standard procedure. The proposed method is accurate, simple, cheap and could be used to control edible oil rancidity with a high sample throughputs (more than 120 samples/h).     

Electrochemical DNA biosensor for the detection of interaction between di[azino-di(5,6-azafluorene)-κ-NN′]dichlormanganous and DNA

A new Mn(II) complex of MnL₂Cl₂ (L = azino-di(5,6-azafluorene)-κ²-NN′) was synthesized and utilized as an electrochemical indicator for the determination of hepatitis B virus (HBV) based on its interaction with MnL₂Cl₂. The electrochemical behavior of interaction of MnL₂Cl₂ with salmon sperm DNA was investigated on glassy carbon electrode (GCE). In the presence of salmon sperm DNA, the peak current of [MnL₂]²⁺ was decreased and the peak potential was shifted positively without appearance of new peaks. The binding ratio between [MnL₂]²⁺ and salmon sperm DNA was calculated to be 2:1 and the binding constant was 3.72 × 10⁸ mol² L⁻². The extent of hybridization was evaluated on the basis of the difference between signals of [MnL₂]²⁺ with probe DNA before and after hybridization with complementary sequence. Control experiments performed with non-complementary and mismatch sequence demonstrated the good selectivity of the biosensor. With this approach, a sequence of the HBV could be quantified over the range from 1.76 × 10⁻⁸ to 1.07 × 10⁻⁶ mol L⁻¹, with a linear correlation of r = 0.9904 and a detection limit of 6.80 × 10⁻⁹ mol L⁻¹. Additionally, the binding mechanism was preliminarily discussed. The mode of interaction between MnL₂Cl₂ and DNA was found to be primary intercalation binding.