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Sample records for wafer-based platinum microelectrode

  1. Silicon Wafer-Based Platinum Microelectrode Array Biosensor for Near Real-Time Measurement of Glutamate in Vivo

    Directory of Open Access Journals (Sweden)

    Nigel T. Maidment

    2008-08-01

    Full Text Available Using Micro-Electro-Mechanical-Systems (MEMS technologies, we have developed silicon wafer-based platinum microelectrode arrays (MEAs modified with glutamate oxidase (GluOx for electroenzymatic detection of glutamate in vivo. These MEAs were designed to have optimal spatial resolution for in vivo recordings. Selective detection of glutamate in the presence of the electroactive interferents, dopamine and ascorbic acid, was attained by deposition of polypyrrole and Nafion. The sensors responded to glutamate with a limit of detection under 1μM and a sub-1-second response time in solution. In addition to extensive in vitro characterization, the utility of these MEA glutamate biosensors was also established in vivo. In the anesthetized rat, these MEA glutamate biosensors were used for detection of cortically-evoked glutamate release in the ventral striatum. The MEA biosensors also were applied to the detection of stress-induced glutamate release in the dorsal striatum of the freely-moving rat.

  2. Electrochemical Fabrication and Electrocatalytic Properties of Nanostructured Mesoporous Platinum Microelectrodes

    Institute of Scientific and Technical Information of China (English)

    Mengyan NIE; Joanne M. Elliott

    2005-01-01

    Electrodeposition from a lyotropic liquid crystal template medium was used to produce nanostructured platinum microelectrodes with high specific surface area and high mass transport efficiency. Compared to polished and conventional platinized microelectrodes, well-ordered nanostructured platinum microelectrodes exhibited enhanced electrocatalytic properties for oxygen and ascorbic acid, whilst well-ordered nanostructured platinum microelectrodes offered improved electrocatalytic properties for oxygen reduction compared to disordered nanostructured platinum microelectrodes.

  3. A Single Platinum Microelectrode for Identifying Soft Drink Samples

    OpenAIRE

    Lígia Bueno; Thiago R. L. C. Paixão

    2012-01-01

    Cyclic voltammograms recorded with a single platinum microelectrode were used along with a non-supervised pattern recognition, namely, Principal Component Analysis, to conduct a qualitative analysis of sixteen different brands of carbonated soft drinks (Kuat, Soda Antarctica, H2OH!, Sprite 2.0, Guarana Antarctica, Guarana Antarctica Zero, Coca-Cola, Coca-Cola Zero, Coca-Cola Plus, Pepsi, Pepsi Light, Pepsi Twist, Pepsi Twist Light, Pepsi Twist 3, Schin Cola, and Classic Dillar’s). In this ana...

  4. A Single Platinum Microelectrode for Identifying Soft Drink Samples

    Directory of Open Access Journals (Sweden)

    Lígia Bueno

    2012-01-01

    Full Text Available Cyclic voltammograms recorded with a single platinum microelectrode were used along with a non-supervised pattern recognition, namely, Principal Component Analysis, to conduct a qualitative analysis of sixteen different brands of carbonated soft drinks (Kuat, Soda Antarctica, H2OH!, Sprite 2.0, Guarana Antarctica, Guarana Antarctica Zero, Coca-Cola, Coca-Cola Zero, Coca-Cola Plus, Pepsi, Pepsi Light, Pepsi Twist, Pepsi Twist Light, Pepsi Twist 3, Schin Cola, and Classic Dillar’s. In this analysis, soft drink samples were not subjected to pre-treatment. Good differentiation among all the analysed soft drinks was achieved using the voltammetric data. An analysis of the loading plots shows that the potentials of −0.65 V, −0.4 V, 0.4 V, and 0.750 V facilitated the discrimination process. The electrochemical processes related to this potential are the reduction of hydrogen ions and inhibition of the platinum oxidation by the caffeine adsorption on the electrode surface. Additionally, the single platinum microelectrode was useful for the quality control of the soft drink samples, as it helped to identify the time at which the beverage was opened.

  5. Dynamics of Single Hydrogen Bubbles at a Platinum Microelectrode.

    Science.gov (United States)

    Yang, Xuegeng; Karnbach, Franziska; Uhlemann, Margitta; Odenbach, Stefan; Eckert, Kerstin

    2015-07-28

    Bubble dynamics, including the formation, growth, and detachment, of single H2 bubbles was studied at a platinum microelectrode during the electrolysis of 1 M H2SO4 electrolyte. The bubbles were visualized through a microscope by a high-speed camera. Electrochemical measurements were conducted in parallel to measure the transient current. The periodic current oscillations, resulting from the periodic formation and detachment of single bubbles, allow the bubble lifetime and size to be predicted from the transient current. A comparison of the bubble volume calculated from the current and from the recorded bubble image shows a gas evolution efficiency increasing continuously with the growth of the bubble until it reaches 100%. Two different substrates, glass and epoxy, were used to embed the Pt wire. While nearly no difference was found with respect to the growth law for the bubble radius, the contact angle differs strongly for the two types of cell. Data provided for the contact point evolution further complete the image of single hydrogen bubble growth. Finally, the velocity field driven by the detached bubble was measured by means of PIV, and the effects of the convection on the subsequent bubble were evaluated.

  6. Pulse Voltammetry in Single Cells Using Platinum Microelectrodes

    Science.gov (United States)

    1991-11-22

    ring electrodes [18) in a solution of 1.OxlO’ M H2PtCl6 and 0.5 M H2SO4 and reducing platinum at 0.0 V vs SSCE for a desired deposition time. Cyclic ...E. and the range for Ed in multiple pulse voltammetry can be chosen from examination of voltammograms obtained by cyclic voltammetry or lin-ir sweep... voltametry [3,13]. As pointed out by Sinru et al. [14) the potential and time of each pulse has a direct effect on the nature of the voltammetry

  7. Nanostructured silver and platinum modified carbon fiber microelectrodes coated with nafion for H2O2 determination

    Directory of Open Access Journals (Sweden)

    Vladimir Halouzka

    2010-12-01

    Full Text Available Carbon fiber microelectrodes equipped with nanostructured metals(platinum and silver and covered with a Nafion layer constitutesensitive H2O2 sensors. Metallic layers on carbon fibers wereprepared by surfactant assisted electrodeposition. In the case ofsilver, the procedure leads to coating which is composed of porous,partially aggregated and crystalline deposits containing silvernanoparticles. The electrodeposition of platinum leads to carbonfiber decorated with clusters of platinum nanoparticles. Aftercoating the electrodes with protective and antiinterference barriermade of Nafion, the sensing properties of the preparedmicroelectrodes towards hydrogen peroxide are investigated.

  8. Electrochemical layer-by-layer approach to fabricate mechanically stable platinum black microelectrodes using a mussel-inspired polydopamine adhesive

    Science.gov (United States)

    Kim, Raeyoung; Nam, Yoonkey

    2015-04-01

    Objective. Platinum black (PtBK) has long been used for microelectrode fabrication owing to its high recording performance of neural signals. The porous structure of PtBK enlarges the surface area and lowers the impedance, which results in background noise reduction. However, the brittleness of PtBK has been a problem in practice. In this work, we report mechanically stable PtBK microelectrodes using a bioinspired adhesive film, polydopamine (pDA), while maintaining the low impedance of PtBK. Approach. The pDA layer was incorporated into the PtBK structure through electrochemical layer-by-layer deposition. Varying the number of layers and the order of materials, multi-layered pDA-PtBK hybrids were fabricated and the electrical properties, both impedance and charge injection limit, were evaluated. Main results. Multilayered pDA-PtBK hybrids had electrical impedances as low as PtBK controls and charge injection limit twice larger than controls. For the 30 min-ultrasonication agitation test, impedance levels rarely changed for some of the pDA-PtBK hybrids indicating that the pDA improved the mechanical property of the PtBK structures. The pDA-PtBK hybrid microelectrodes readily recorded neural signals of cultured hippocampal neurons, where background noise levels and signal-to-noise were 2.43 ∼ 3.23 μVrms and 28.4 ∼ 69.1, respectively. Significance. The developed pDA-PtBK hybrid microelectrodes are expected to be applicable to neural sensors for neural prosthetic studies.

  9. Double Potential Pulse Chronocoulometry for Detection of Plasma Membrane Cholesterol Efflux at Disk Platinum Microelectrodes

    Science.gov (United States)

    West, Richard H.; Lu, Hui; Shaw, Kendrick; Chiel, Hillel J.; Kelley, Thomas J.; Burgess, James D.

    2016-01-01

    A double potential pulse scheme is reported for observation of cholesterol efflux from the plasma membrane of a single neuron cell. Capillary Pt disk microelectrodes having a thin glass insulator allow the 10 μm diameter electrode and cell to be viewed under optical magnification. The electrode, covalently functionalized with cholesterol oxidase, is positioned in contact with the cell surface resulting in enzyme catalyzed cholesterol oxidation and efflux of cholesterol from the plasma membrane at the electrode contact site. Enzymatically generated hydrogen peroxide accumulates at the electrode/cell interface during a 5 s hold-time and is oxidized during application of a potential pulse. A second, replicate potential pulse is applied 0.5 s after the first potential pulse to gauge background charge prior to significant accumulation of hydrogen peroxide. The difference in charge passed between the first and second potential pulse provides a measure of hydrogen peroxide generated by the enzyme and is an indication of the cholesterol efflux. Control experiments for bare Pt microelectrodes in contact with the cell plasma membrane show difference charge signals in the range of about 7–10 pC. Enzyme-modified electrodes in contact with the plasma membrane show signals in the range of 16–26 pC. PMID:27330196

  10. Novel platinum black electroplating technique improving mechanical stability.

    Science.gov (United States)

    Kim, Raeyoung; Nam, Yoonkey

    2013-01-01

    Platinum black microelectrodes are widely used as an effective neural signal recording sensor. The simple fabrication process, high quality signal recording and proper biocompatibility are the main advantages of platinum black microelectrodes. When microelectrodes are exposed to actual biological system, various physical stimuli are applied. However, the porous structure of platinum black is vulnerable to external stimuli and destroyed easily. The impedance level of the microelectrode increases when the microelectrodes are damaged resulting in decreased recording performance. In this study, we developed mechanically stable platinum black microelectrodes by adding polydopamine. The polydopamine layer was added between the platinum black structures by electrodeposition method. The initial impedance level of platinum black only microelectrodes and polydopamine added microelectrodes were similar but after applying ultrasonication the impedance value dramatically increased for platinum black only microelectrodes, whereas polydopamine added microelectrodes showed little increase which were nearly retained initial values. Polydopamine added platinum black microelectrodes are expected to extend the availability as neural sensors.

  11. The Electrochemiluminescent Behaviors of Luminol on the Platinum Heated Microelectrode%鲁米诺在铂热控微电极上的电致化学发光行为研究

    Institute of Scientific and Technical Information of China (English)

    罗芳; 高森; 林振宇

    2012-01-01

    The electrochemiluminescent(ECL) behavior of luminol on the platinum heated microelectrode (HME) has been studied. Two ECL peaks(ECL-l at 0. 45 V and ECL-2 at 0. 80 V) could be observed during the anodic scans when the temperature of the microelectrode was higher than 43 °C , while only one ECL peak(ECL-2) was found at the room temperature. It was found that both ECL-1 and ECL-2 intensities were independent to the scan rates of potential scanning when the electrode temperature was 43 ℃ but the ECL-2 intensities had a direct relationship with the square of the scan rates at room temperature. The reproducibilities of the ECL of luminol at 45 ℃ were better than those at room temperature,and the contaminant on platinum could be deleted easily due to heating. The mechanism of the ECL behavior of luminol on the HME has been discussed also.%研究了鲁米诺在铂热控微电极上的电致化学发光(ECL)行为.当电极表面温度为25℃时,在0.80 V有一个明显的ECL峰(ECL-2);当电极表面温度高于43℃时,鲁米诺在0.45 V和0.80V各出现一个ECL峰(ECL-1和ECL-2),而且这两个峰的强度随着电极表面温度的变化而变化.同时,对各ECL信号的发光机理进行了探讨.

  12. High Performance Wafer-Based Capillary Electrochromatography Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Los Gatos Research proposes to develop wafer-based capillary electrochromatography for lab-on-a-chip (LOC) applications. These microfluidic devices will be...

  13. Thermal modeling of wafer-based precision glass molding process

    Science.gov (United States)

    Hu, Yang; Shen, Lianguan; Zhou, Jian; Li, Mujun

    2016-10-01

    Wafer based precision glass optics manufacturing has been an innovative approach for combining high accuracy with mass production. However, due to the small ratio of thickness and diameter of the glass wafer, deformation and residual stress would be induced for the nonuniform temperature distribution in the glass wafer after molding. Therefore, thermal modelling of the heating system in the wafer based precision glass molding (PGM) process is of great importance in optimizing the heating system and the technique of the process. The current paper deals with a transient thermal modelling of a self-developed heating system for wafer based PGM process. First, in order to investigate the effect of radiation from the surface and interior of the glass wafer, the thermal modeling is simulated with a discrete ordinates radiation model in the CFD software FLUENT. Temperature distribution of the glass wafer obtained from the simulations is then used to evaluate the performance of heating system and investigate some importance parameters in the model, such as interior and surface radiation in glass wafer, thermal contact conductance between glass wafer and molds, thickness to diameter ratio of glass wafer. Finally, structure modification in the molding chamber is raised to decrease the temperature gradient in the glass wafer and the effect is significant.

  14. Underpotential deposition and anodic stripping voltammetry at mesoporous microelectrodes.

    Science.gov (United States)

    Sanchez, Pablo Lozano; Elliott, Joanne M

    2005-05-01

    Using the technique of liquid crystal templating a series of high surface area mesoporous platinum microelectrodes was fabricated. The underpotential deposition of metal ions at such electrodes was found to be similar to that at conventional platinum electrodes. The phenomena of underpotential deposition, in combination with the intrinsic properties of mesoporous microelectrodes (i.e. a high surface area and efficient mass transport) was exploited for the purpose of anodic stripping voltammetry. In particular the underpotential deposition of Ag(+), Pb(2+) and Cu(2+) ions was investigated and it was found that mesoporous microelectrodes were able to quantify the concentration of ions in solution down to the ppb range. The overall behaviour of the mesoporous electrodes was found to be superior to that of conventional microelectrodes and the effects of interference by surfactants were minimal.

  15. Silicon wafer-based tandem cells: The ultimate photovoltaic solution?

    Science.gov (United States)

    Green, Martin A.

    2014-03-01

    Recent large price reductions with wafer-based cells have increased the difficulty of dislodging silicon solar cell technology from its dominant market position. With market leaders expected to be manufacturing modules above 16% efficiency at 0.36/Watt by 2017, even the cost per unit area (60-70/m2) will be difficult for any thin-film photovoltaic technology to significantly undercut. This may make dislodgement likely only by appreciably higher energy conversion efficiency approaches. A silicon wafer-based cell able to capitalize on on-going cost reductions within the mainstream industry, but with an appreciably higher than present efficiency, might therefore provide the ultimate PV solution. With average selling prices of 156 mm quasi-square monocrystalline Si photovoltaic wafers recently approaching 1 (per wafer), wafers now provide clean, low cost templates for overgrowth of thin, wider bandgap high performance cells, nearly doubling silicon's ultimate efficiency potential. The range of possible Si-based tandem approaches is reviewed together with recent results and ultimate prospects.

  16. CMOS microelectrode array for the monitoring of electrogenic cells.

    Science.gov (United States)

    Heer, F; Franks, W; Blau, A; Taschini, S; Ziegler, C; Hierlemann, A; Baltes, H

    2004-09-15

    Signal degradation and an array size dictated by the number of available interconnects are the two main limitations inherent to standalone microelectrode arrays (MEAs). A new biochip consisting of an array of microelectrodes with fully-integrated analog and digital circuitry realized in an industrial CMOS process addresses these issues. The device is capable of on-chip signal filtering for improved signal-to-noise ratio (SNR), on-chip analog and digital conversion, and multiplexing, thereby facilitating simultaneous stimulation and recording of electrogenic cell activity. The designed electrode pitch of 250 microm significantly limits the space available for circuitry: a repeated unit of circuitry associated with each electrode comprises a stimulation buffer and a bandpass filter for readout. The bandpass filter has corner frequencies of 100 Hz and 50 kHz, and a gain of 1000. Stimulation voltages are generated from an 8-bit digital signal and converted to an analog signal at a frequency of 120 kHz. Functionality of the read-out circuitry is demonstrated by the measurement of cardiomyocyte activity. The microelectrode is realized in a shifted design for flexibility and biocompatibility. Several microelectrode materials (platinum, platinum black and titanium nitride) have been electrically characterized. An equivalent circuit model, where each parameter represents a macroscopic physical quantity contributing to the interface impedance, has been successfully fitted to experimental results.

  17. Experiments on pumping of liquids using arrays of microelectrodes subjected to travelling wave potentials

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Sanchez, P; Ramos, A [Dpto. de Electronica y Electromagnetismo, Universidad de Sevilla, 41012 Sevilla (Spain); Green, Nicolas G; Morgan, H [School of Electronics and Computer Science, University of Southampton, SO17 1BJ Southampton (United Kingdom)], E-mail: pablogarcia@us.es

    2008-12-01

    Net fluid flow of electrolytes driven on an array of microelectrodes subjected to a travelling-wave potential is presented. Two sizes of platinum microelectrodes have been studied. In both arrays, at low voltages the liquid flows according to the prediction given by ac electroosmotic theory. At voltages above a threshold the fluid flow is reversed. Measurements of the electrical current when the microelectrode array is pumping the liquid are also reported. Transient behaviours in both electrical current and fluid velocity have been observed.

  18. Evaluation of microelectrode materials for direct-current electrocorticography.

    Science.gov (United States)

    Li, Chunyan; Narayan, Raj K; Wu, Pei-Ming; Rajan, Neena; Wu, Zhizhen; Mehan, Neal; Golanov, Eugene V; Ahn, Chong H; Hartings, Jed A

    2016-02-01

    Direct-current electrocorticography (DC-ECoG) allows a more complete characterization of brain states and pathologies than traditional alternating-current recordings (AC-ECoG). However, reliable recording of DC signals is challenging because of electrode polarization-induced potential drift, particularly at low frequencies and for more conducting materials. Further challenges arise as electrode size decreases, since impedance is increased and the potential drift is augmented. While microelectrodes have been investigated for AC-ECoG recordings, little work has addressed microelectrode properties for DC-signal recording. In this paper, we investigated several common microelectrode materials used in biomedical application for DC-ECoG. Five of the most common materials including gold (Au), silver/silver chloride (Ag/AgCl), platinum (Pt), Iridium oxide (IrOx), and platinum-iridium oxide (Pt/IrOx) were investigated for electrode diameters of 300 μm. The critical characteristics such as polarization impedance, AC current-induced polarization, long-term stability and low-frequency noise were studied in vitro (0.9% saline). The two most promising materials, Pt and Pt/lrOx were further investigated in vivo by recording waves of spreading depolarization, one of the most important applications for DC-ECoG in clinical and basic science research. Our experimental results indicate that IrOx-based microelectrodes, particularly with composite layers of nanostructures, are excellent in all of the common evaluation characteristics both in vitro and in vivo and are most suitable for multimodal monitoring applications. Pt electrodes suffer high current-induced polarization, but have acceptable long-term stability suitable for DC-ECoG. Major significance. The results of this study provide quantitative data on the electrical properties of microelectrodes with commonly-used materials and will be valuable for development of neural recordings inclusive of low frequencies.

  19. Evaluation of microelectrode materials for direct-current electrocorticography

    Science.gov (United States)

    Li, Chunyan; Narayan, Raj K.; Wu, Pei-Ming; Rajan, Neena; Wu, Zhizhen; Mehan, Neal; Golanov, Eugene V.; Ahn, Chong H.; Hartings, Jed A.

    2016-02-01

    Objective. Direct-current electrocorticography (DC-ECoG) allows a more complete characterization of brain states and pathologies than traditional alternating-current recordings (AC-ECoG). However, reliable recording of DC signals is challenging because of electrode polarization-induced potential drift, particularly at low frequencies and for more conducting materials. Further challenges arise as electrode size decreases, since impedance is increased and the potential drift is augmented. While microelectrodes have been investigated for AC-ECoG recordings, little work has addressed microelectrode properties for DC-signal recording. In this paper, we investigated several common microelectrode materials used in biomedical application for DC-ECoG. Approach. Five of the most common materials including gold (Au), silver/silver chloride (Ag/AgCl), platinum (Pt), Iridium oxide (IrOx), and platinum-iridium oxide (Pt/IrOx) were investigated for electrode diameters of 300 μm. The critical characteristics such as polarization impedance, AC current-induced polarization, long-term stability and low-frequency noise were studied in vitro (0.9% saline). The two most promising materials, Pt and Pt/lrOx were further investigated in vivo by recording waves of spreading depolarization, one of the most important applications for DC-ECoG in clinical and basic science research. Main results. Our experimental results indicate that IrOx-based microelectrodes, particularly with composite layers of nanostructures, are excellent in all of the common evaluation characteristics both in vitro and in vivo and are most suitable for multimodal monitoring applications. Pt electrodes suffer high current-induced polarization, but have acceptable long-term stability suitable for DC-ECoG. Major significance. The results of this study provide quantitative data on the electrical properties of microelectrodes with commonly-used materials and will be valuable for development of neural recordings inclusive of

  20. Design optimization of thin-film/wafer-based tandem junction solar cells using analytical modeling

    Science.gov (United States)

    Davidson, Lauren; Toor, Fatima

    2016-03-01

    Several research groups are developing solar cells of varying designs and materials that are high efficiency as well as cost competitive with the single junction silicon (Si) solar cells commercially produced today. One of these solar cell designs is a tandem junction solar cell comprised of perovskite (CH3NH3PbI3) and silicon (Si). Loper et al.1 was able to create a 13.4% efficient tandem cell using a perovskite top cell and a Si bottom cell, and researchers are confident that the perovskite/Si tandem cell can be optimized in order to reach higher efficiencies without introducing expensive manufacturing processes. However, there are currently no commercially available software capable of modeling a tandem cell that is based on a thin-film based bottom cell and a wafer-based top cell. While PC1D2 and SCAPS3 are able to model tandem cells comprised solely of thin-film absorbers or solely of wafer-based absorbers, they result in convergence errors if a thin-film/wafer-based tandem cell, such as the perovskite/ Si cell, is modeled. The Matlab-based analytical model presented in this work is capable of modeling a thin-film/wafer-based tandem solar cell. The model allows a user to adjust the top and bottom cell parameters, such as reflectivity, material bandgaps, donor and acceptor densities, and material thicknesses, in order to optimize the short circuit current, open circuit voltage, and quantum efficiency of the tandem solar cell. Using the Matlab-based analytical model, we were able optimize a perovskite/Si tandem cell with an efficiency greater than 30%.

  1. Conducting polymer 3D microelectrodes

    DEFF Research Database (Denmark)

    Sasso, Luigi; Vazquez, Patricia; Vedarethinam, Indumathi

    2010-01-01

    Conducting polymer 3D microelectrodes have been fabricated for possible future neurological applications. A combination of micro-fabrication techniques and chemical polymerization methods has been used to create pillar electrodes in polyaniline and polypyrrole. The thin polymer films obtained...

  2. Biofunctionalization of diamond microelectrodes

    Energy Technology Data Exchange (ETDEWEB)

    Reitinger, Andreas Adam; Lud, Simon Quartus; Stutzmann, Martin; Garrido, Jose Antonio [Walter Schottky Institut, TU Muenchen (Germany); Hutter, Naima Aurelia; Richter, Gerhard; Jordan, Rainer [WACKER-Chair of Macromolecular Chemistry, TU Muenchen (Germany)

    2010-07-01

    In this work we present two main routes for the biofunctionalization of nanocrystalline diamond films, aiming at the application of diamond microelectrodes as amperometric biosensors. We report on direct covalent grafting of biomolecules on nanocrystalline diamond films via diazonium monophenyls and biphenyls as well as other linker molecules, forming self-assembled monolayers on the diamond surface. Monolayers with different functional head groups have been characterized. Patterning of the available functional groups using electron beam-induced chemical lithography allows the selective preparation of well-localized docking sites for the immobilization of biomolecules. Furthermore, polymer brushes are expected to enable novel paths for designing more advanced biosensing schemes, incorporating multifunctional groups and a higher loading capacity for biomolecules. Here, we focus on the preparation of polymer grafts by self-initiated photografting and photopolymerization. Further chemical modification of the grafted polymer brushes results in the introduction of additional functional molecules, paving the way for the incorporation of more complex molecular structures such as proteins. In a comparative study we investigate the advantages and disadvantages of both approaches.

  3. Soldering of Nanotubes onto Microelectrodes

    DEFF Research Database (Denmark)

    Madsen, Dorte Nørgaard; Mølhave, Kristian; Mateiu, Ramona Valentina

    2003-01-01

    Suspended bridges of individual multiwalled carbon nanotubes were fabricated inside a scanning electron microscope by soldering the nanotube onto microelectrodes with highly conducting gold-carbon material. By the decomposition of organometallic vapor with the electron beam, metal-containing solder...... bonds were formed at the intersection of the nanotube and the electrodes. Current-voltage curves indicated metallic conduction of the nanotubes, with resistances in the range of 9-29 kOmega. Bridges made entirely of the soldering material exhibited resistances on the order of 100 Omega, and the solder...... bonds were consistently found to be mechanically stronger than the carbon nanotubes....

  4. Platinum impact assessment

    OpenAIRE

    Yip, Joyce Pui Yan

    2007-01-01

    This paper presents a comprehensive strategic analysis of Company X's strategies to mitigate its risks from volatile platinum prices, since Platinum is a critical component of fuel cells. It is recommended that Company X consider leasing platinum to lower cash flow requirements to meet its platinum demand over the next 5 years. A shorter platinum leasing period will reduce Company X's platinum market risk. OEMs can set up metal accounts with catalyst suppliers to eliminate Company X from plat...

  5. Stretchable Micro-Electrode Array

    Energy Technology Data Exchange (ETDEWEB)

    Maghribi, M; Hamilton, J; Polla, D; Rose, K; Wilson, T; Krulevitch, P

    2002-03-08

    This paper focuses on the design consideration, fabrication processes and preliminary testing of the stretchable micro-electrode array. We are developing an implantable, stretchable micro-electrode array using polymer-based microfabrication techniques. The device will serve as the interface between an electronic imaging system and the human eye, directly stimulating retinal neurons via thin film conducting traces and electroplated electrodes. The metal features are embedded within a thin ({approx}50 micron) substrate fabricated using poly (dimethylsiloxane) (PDMS), a biocompatible elastomeric material that has very low water permeability. The conformable nature of PDMS is critical for ensuring uniform contact with the curved surface of the retina. To fabricate the device, we developed unique processes for metalizing PDMS to produce robust traces capable of maintaining conductivity when stretched (5%, SD 1.5), and for selectively passivating the conductive elements. An in situ measurement of residual strain in the PDMS during curing reveals a tensile strain of 10%, explaining the stretchable nature of the thin metalized devices.

  6. Conducting Polymer 3D Microelectrodes

    Directory of Open Access Journals (Sweden)

    Jenny Emnéus

    2010-12-01

    Full Text Available Conducting polymer 3D microelectrodes have been fabricated for possible future neurological applications. A combination of micro-fabrication techniques and chemical polymerization methods has been used to create pillar electrodes in polyaniline and polypyrrole. The thin polymer films obtained showed uniformity and good adhesion to both horizontal and vertical surfaces. Electrodes in combination with metal/conducting polymer materials have been characterized by cyclic voltammetry and the presence of the conducting polymer film has shown to increase the electrochemical activity when compared with electrodes coated with only metal. An electrochemical characterization of gold/polypyrrole electrodes showed exceptional electrochemical behavior and activity. PC12 cells were finally cultured on the investigated materials as a preliminary biocompatibility assessment. These results show that the described electrodes are possibly suitable for future in-vitro neurological measurements.

  7. Evaluation of the viscoelastic behaviour and glass/mould interface friction coefficient in the wafer based precision glass moulding

    DEFF Research Database (Denmark)

    Sarhadi, Ali; Hattel, Jesper Henri; Hansen, Hans Nørgaard

    2014-01-01

    Recent improvements in the manufacturing process of camera lenses have introduced the use of a newtechnology involving wafer based precision glass moulding. The utilization of this technology has someimportant advantages such as cost reduction, supply chain simplification and higher image quality......-placements, internal diameter and thickness of the rings are measured during the tests. Viscoelastic andstructural relaxation behaviour of the glass are implemented into the ABAQUS FEM software through aFORTRAN material subroutine (UMAT) and the FE model is validated with a sandwich seal test. Then, byFE simulation...

  8. Band-type microelectrodes for amperometric immunoassays

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ga-Yeon; Chang, Young Wook; Ko, Hyuk [Department of Materials Science and Engineering, Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul, 120-749 (Korea, Republic of); Kang, Min-Jung [Korea Institute of Science and Technology (KIST), Seoul (Korea, Republic of); Pyun, Jae-Chul, E-mail: jcpyun@yonsei.ac.kr [Department of Materials Science and Engineering, Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul, 120-749 (Korea, Republic of)

    2016-07-20

    A band-type microelectrode was made using a parylene-N film as a passivation layer. A circular-type, mm-scale electrode with the same diameter as the band-type microelectrode was also made with an electrode area that was 5000 times larger than the band-type microelectrode. By comparing the amperometric signals of 3,5,3′,5′-tetramethylbenzidine (TMB) samples at different optical density (OD) values, the band-type microelectrode was determined to be 9 times more sensitive than the circular-type electrode. The properties of the circular-type and the band-type electrodes (e.g., the shape of their cyclic voltammograms, the type of diffusion layer used, and the diffusion layer thickness per unit electrode area) were characterized according to their electrode area using the COMSOL Multiphysics software. From these simulations, the band-type electrode was estimated to have the conventional microelectrode properties, even when the electrode area was 100 times larger than a conventional circular-type electrode. These results show that both the geometry and the area of an electrode can influence the properties of the electrode. Finally, amperometric analysis based on a band-type electrode was applied to commercial ELISA kits to analyze human hepatitis B surface antigen (hHBsAg) and human immunodeficiency virus (HIV) antibodies. - Highlights: • A band-type microelectrode was made using a parylene-N film as a passivation layer. • The band-type microelectrode was 14-times more sensitive than circular-type electrode. • The influence of geometry on microelectrode properties was simulated using COMSOL. • The band-type electrode was applied to ELISA kits for hHBsAg and hHIV-antibodies.

  9. Failure Mechanisms of a Gold Microelectrode in Bioelectronics Applications

    Directory of Open Access Journals (Sweden)

    Jonghun Kim

    2015-01-01

    Full Text Available The generation, growth, and collapse of tiny bubbles are inevitable for a microelectrode working in aqueous environment, thus resulting in physical damages on the microelectrode. The failure mechanisms of a microelectrode induced by tiny bubble collapsing are investigated by generating tiny hydrogen bubbles on a gold microelectrode through deionized water electrolysis. The surface of the microelectrode is modified with a thiol-functionalized arginine-glycine-aspartic acid peptide to generate perfectly spherical bubbles in proximity of the surface. The failure of an Au microelectrode is governed by two damage mechanisms, depending on the thickness of the microelectrode: a water-hammer pressure due to the violent collapse of a single large bubble, formed through merging of small bubbles, for ultrathin Au microelectrodes of 40–60 nm in thickness, and an energy accumulation resulting from the repetitive collapse of tiny bubbles for thick Au microelectrodes of 100–120 nm.

  10. Robust Functionalization of Large Microelectrode Arrays by Using Pulsed Potentiostatic Deposition

    Science.gov (United States)

    Rothe, Joerg; Frey, Olivier; Madangopal, Rajtarun; Rickus, Jenna; Hierlemann, Andreas

    2016-01-01

    Surface modification of microelectrodes is a central step in the development of microsensors and microsensor arrays. Here, we present an electrodeposition scheme based on voltage pulses. Key features of this method are uniformity in the deposited electrode coatings, flexibility in the overall deposition area, i.e., the sizes and number of the electrodes to be coated, and precise control of the surface texture. Deposition and characterization of four different materials are demonstrated, including layers of high-surface-area platinum, gold, conducting polymer poly(ethylenedioxythiophene), also known as PEDOT, and the non-conducting polymer poly(phenylenediamine), also known as PPD. The depositions were conducted using a fully integrated complementary metal-oxide-semiconductor (CMOS) chip with an array of 1024 microelectrodes. The pulsed potentiostatic deposition scheme is particularly suitable for functionalization of individual electrodes or electrode subsets of large integrated microelectrode arrays: the required deposition waveforms are readily available in an integrated system, the same deposition parameters can be used to functionalize the surface of either single electrodes or large arrays of thousands of electrodes, and the deposition method proved to be robust and reproducible for all materials tested. PMID:28025569

  11. Microfabrication, characterization and in vivo MRI compatibility of diamond microelectrodes array for neural interfacing

    Energy Technology Data Exchange (ETDEWEB)

    Hébert, Clément, E-mail: clement.hebert@cea.fr [Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9 (France); Warnking, Jan; Depaulis, Antoine [INSERM, U836, Grenoble Institut des Neurosciences, Grenoble (France); Garçon, Laurie Amandine [Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9 (France); CEA/INAC/SPrAM/CREAB, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France); Mermoux, Michel [Université Grenoble Alpes, LEPMI, F-38000 Grenoble (France); CNRS, LEPMI, F-38000 Grenoble (France); Eon, David [Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9 (France); Mailley, Pascal [CEA-LETI-DTBS Minatec, 17 rue des Martyres, 38054 Grenoble (France); Omnès, Franck [Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9 (France)

    2015-01-01

    Neural interfacing still requires highly stable and biocompatible materials, in particular for in vivo applications. Indeed, most of the currently used materials are degraded and/or encapsulated by the proximal tissue leading to a loss of efficiency. Here, we considered boron doped diamond microelectrodes to address this issue and we evaluated the performances of a diamond microelectrode array. We described the microfabrication process of the device and discuss its functionalities. We characterized its electrochemical performances by cyclic voltammetry and impedance spectroscopy in saline buffer and observed the typical diamond electrode electrochemical properties, wide potential window and low background current, allowing efficient electrochemical detection. The charge storage capacitance and the modulus of the electrochemical impedance were found to remain in the same range as platinum electrodes used for standard commercial devices. Finally we observed a reduced Magnetic Resonance Imaging artifact when the device was implanted on a rat cortex, suggesting that boron doped-diamond is a very promising electrode material allowing functional imaging. - Highlights: • Microfabrication of all-diamond microelectrode array • Evaluation of as-grown nanocrystalline boron-doped diamond for electrical neural interfacing • MRI compatibility of nanocrystalline boron-doped diamond.

  12. Microscope in situ FTIRS studies of CO adsorption on an array of platinum micro electrodes

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    An array of platinum microelectrodes was de signed and fabricated. The adsorption of CO on such a Pt microelectrode (μ-Pt) was investigated by employing micro scope in situ FTIR spectroscopy. A nanostructured film is formed at the surface of μ-Pt (denoted as μ-Pt(R)) when ithas been subjected to a treatment of fast potential cycling.Abnormal infrared effects (AIREs) were observed in COadsorption on the surface of μ-Pt(R), consisting of the inver sion of the IR bipolar CO band and the extensively enhanced IR adsorption of COad species.``

  13. Suspended 3D pyrolytic carbon microelectrodes for electrochemistry

    DEFF Research Database (Denmark)

    Hemanth, Suhith; Caviglia, Claudia; Keller, Stephan Sylvest

    2017-01-01

    Carbon microelectrodes have a wide range of applications because of their unique material properties and biocompatibility. This work presents the fabrication and characterization of suspended pyrolytic carbon microstructures serving as three-dimensional (3D) carbon microelectrodes for electrochem...

  14. PLATINUM AND FUEL CELLS

    Science.gov (United States)

    Platinum requirements for fuel cell vehicles (FCVS) have been identified as a concern and possible problem with FCV market penetration. Platinum is a necessary component of the electrodes of fuel cell engines that power the vehicles. The platinum is deposited on porous electrodes...

  15. Batch fabrication of nanotubes suspended between microelectrodes

    DEFF Research Database (Denmark)

    Mateiu, Ramona Valentina; Stöckli, T.; Knapp, H. F.

    2007-01-01

    We report a fabrication method, which uses standard UV-lithography to pattern the catalyst for the chemical vapour deposition(CVD) of suspended double clamped single walled carbon nanotubes. By using an aqueous solution of Fe(NO3)3 the patterning of the catalyst material onto microelectrodes can ...

  16. LSM Microelectrodes: Kinetics and Surface Composition

    DEFF Research Database (Denmark)

    Hansen, Karin Vels; Norrman, Kion; Jacobsen, Torben;

    2015-01-01

    Lanthanum strontium manganite microelectrodes with the nominal composition of (La0.75Sr0.25)0.95MnO3 and a thickness of ca 500 nm was electrochemically characterized in situ at temperatures from 660 to 850◦C using a controlled atmosphere high temperature scanning probe microscope. Impedance...

  17. Pyrolytic 3D Carbon Microelectrodes for Electrochemistry

    DEFF Research Database (Denmark)

    Hemanth, Suhith; Caviglia, Claudia; Amato, Letizia

    2016-01-01

    This work presents the fabrication and characterization of suspended three-dimensional (3D) pyrolytic carbon microelectrodes for electrochemical applications. For this purpose, an optimized process with multiple steps of UV photolithography with the negative tone photoresist SU-8 followed by pyro...

  18. An Experimental Study on Electro Chemical Machining of Microelectrode

    Institute of Scientific and Technical Information of China (English)

    ZHANG Liao-yuan; LIU Yao

    2006-01-01

    Puts forward a new method in machining microelectrode by electro chemical machining (ECM) and plastic deformed theory. Theprocedure of this method is to machine the microelectrode according to the basic rule of ECM theory at first. Then, with the change of ECM machining parameters, one of the microelectrode ends is exerted by a load. As a result, the elastic and plastic deformation is produced at the machining section and the microelectrode diameter is reduced.It has been proved that the proposed method can determine the optimum machining parameters to machine the microelectrode of Cu.

  19. Efficient voltammetric discrimination of free bilirubin from uric acid and ascorbic acid by a CVD nanographite-based microelectrode.

    Science.gov (United States)

    Taurino, Irene; Van Hoof, Viviane; Magrez, Arnaud; Forró, László; De Micheli, Giovanni; Carrara, Sandro

    2014-12-01

    We report a novel electrochemical sensor based on nanographite grown on platinum microelectrodes for the determination of bilirubin in the presence of normal concentrations of albumin. The albumin is a protein with an intrinsic ability to bind the bilirubin therefore reducing the concentration of the free electroactive metabolite in human fluids. In addition, the proposed device permits the discrimination of free bilirubin from two interferents, uric acid and ascorbic acid, by the separation of their oxidation peaks in voltammetry. Preliminary measurements in human serum prove that the proposed nanostructured platform can be used to detect bilirubin.

  20. Platinum Migration at the Pt/YSZ Interface

    DEFF Research Database (Denmark)

    Nielsen, Jimmi; Jacobsen, Torben

    2006-01-01

    by potential sweep, step and impedance techniques. As expected, inductive behaviour and activation during step polarization is confirmed, but furthermore, a very accentuated noise pattern is seen during cathodic step polarization. Investigation of the YSZ and Pt surfaces afterwards reveals the growth......Electrode activation, inductive hysteresis and non-linearity are well known phenomena on Pt-YSZ electrodes, and recently also regular fluctuation patterns have been reported. The oxygen electrode on YSZ surfaces is studied at Pt micro-electrodes prepared by electrochemical etching of platinum wire...... of dendrite like Pt structures from the TPB. The formation of these may explain the observed noise and contribute to the explanation of the activation mechanism taking place at the platinum-YSZ interface....

  1. Graphene microelectrode arrays for neural activity detection

    OpenAIRE

    Du, Xiaowei; Wu,Lei; Cheng, Ji; Huang, Shanluo; Cai, Qi; Jin, Qinghui; Zhao, Jianlong

    2015-01-01

    We demonstrate a method to fabricate graphene microelectrode arrays (MEAs) using a simple and inexpensive method to solve the problem of opaque electrode positions in traditional MEAs, while keeping good biocompatibility. To study the interface differences between graphene–electrolyte and gold–electrolyte, graphene and gold electrodes with a large area were fabricated. According to the simulation results of electrochemical impedances, the gold–electrolyte interface can be described as a class...

  2. Behind platinum's sparkle.

    Science.gov (United States)

    Yam, Vivian W W

    2010-09-01

    As a rare and precious metal that is also resistant to wear and tarnish, platinum is known to be particularly well-suited to jewellery. Vivian Yam reflects on how, beyond its prestigious image, platinum has also found its way into a variety of fields ranging from the petrochemical to the pharmaceutical industry.

  3. Thermal modelling of the multi-stage heating system with variable boundary conditions in the wafer based precision glass moulding process

    DEFF Research Database (Denmark)

    Sarhadi, Ali; Hattel, Jesper Henri; Hansen, Hans Nørgaard;

    2012-01-01

    of the heating system in the glass moulding process considering detailed heating mechanisms therefore plays an important part in optimizing the heating system and the subsequent pressing stage in the lens manufacturing process.The current paper deals with three-dimensional transient thermal modelling...... of the multi-stage heating system in a wafer based glass moulding process. In order to investigate the importance of the radiation from the interior and surface of the glass, a simple finite volume code is developed to model one dimensional radiation–conduction heat transfer in the glass wafer for an extreme...... pressures. Finally, the three-dimensional modelling of the multi-stage heating system in the wafer based glass moulding process is simulated with the FEM software ABAQUS for a particular industrial application for mobile phone camera lenses to obtain the temperature distribution in the glass wafer...

  4. Wafer-based aberration metrology for lithographic systems using overlay measurements on targets imaged from phase-shift gratings.

    Science.gov (United States)

    van Haver, Sven; Coene, Wim M J; D'havé, Koen; Geypen, Niels; van Adrichem, Paul; de Winter, Laurens; Janssen, Augustus J E M; Cheng, Shaunee

    2014-04-20

    In this paper, a new methodology is presented to derive the aberration state of a lithographic projection system from wafer metrology data. For this purpose, new types of phase-shift gratings (PSGs) are introduced, with special features that give rise to a simple linear relation between the PSG image displacement and the phase aberration function of the imaging system. By using the PSGs as the top grating in a diffraction-based overlay stack, their displacement can be measured as an overlay error using a standard wafer metrology tool. In this way, the overlay error can be used as a measurand based on which the phase aberration function in the exit pupil of the lithographic system can be reconstructed. In practice, the overlay error is measured for a set of different PSG targets, after which this information serves as input to a least-squares optimization problem that, upon solving, provides estimates for the Zernike coefficients describing the aberration state of the lithographic system. In addition to a detailed method description, this paper also deals with the additional complications that arise when the method is implemented experimentally and this leads to a number of model refinements and a required calibration step. Finally, the overall performance of the method is assessed through a number of experiments in which the aberration state of the lithographic system is intentionally detuned and subsequently estimated by the new method. These experiments show a remarkably good agreement, with an error smaller than 5  mλ, among the requested aberrations, the aberrations measured by the on-tool aberration sensor, and the results of the new wafer-based method.

  5. LSM Microelectrodes: Kinetics and Surface Composition

    DEFF Research Database (Denmark)

    Hansen, Karin Vels; Norrman, Kion; Jacobsen, Torben

    2015-01-01

    Lanthanum strontium manganite microelectrodes with the nominal composition of (La0.75Sr0.25)0.95MnO3 and a thickness of ca 500 nm was electrochemically characterized in situ at temperatures from 660 to 850◦C using a controlled atmosphere high temperature scanning probe microscope. Impedance...... spectroscopy and cyclic voltammetry were performed on electrodes with diameters of 20–100 μm in oxygen, air and nitrogen both at open circuit voltage and at anodic and cathodic polarization. In situ conductance mapping, ex situ surface analysis by time-of-flight secondary ion mass spectrometry, and scanning...

  6. Platinum hypersensitivity and desensitization.

    Science.gov (United States)

    Miyamoto, Shingo; Okada, Rika; Ando, Kazumichi

    2015-09-01

    Platinum agents are drugs used for various types of cancer. With increased frequency of administration of platinum agents, hypersensitivity reactions appear more frequently, occurring in over 25% of cases from the seventh cycle or second line onward. It then becomes difficult to conduct treatment using these agents. Various approaches have been investigated to address hypersensitivity reactions to platinum agents. Desensitization, which gradually increases the concentration of the anticancer drug considered to be the antigen until the target dosage, has been reported as being particularly effective, with a success rate of 80-100%. The aims of this paper are to present the current findings regarding hypersensitivity reactions to platinum agents and to discuss attempts of using desensitization against hypersensitivity reactions worldwide. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  7. Screening metal nanoparticles using boron-doped diamond microelectrodes

    Energy Technology Data Exchange (ETDEWEB)

    Ivandini, Tribidasari A., E-mail: ivandini.tri@sci.ui.ac.id; Rangkuti, Prasmita K. [Department of Chemistry, FMIPA, Universitas Indonesia, Kampus UI Depok (Indonesia); Einaga, Yasuaki [Department of Chemistry, Faculty of Science and Technology, Keio University (Japan); JST ACCEL, 3-14-1 Hiyoshi, Yokohama 223-8522 (Japan)

    2016-04-19

    Boron-doped diamond (BDD) microelectrodes were used to observe the correlation between electrocatalytic currents caused by individual Pt nanoparticle (Pt-np) collisions at the electrode. The BDD microelectrodes, ∼20 µm diameter and ∼2 µm particle size, were fabricated at the surface of tungsten wires. Pt-np with a size of 1 to 5 nm with agglomerations up to 20 nm was used for observation. The electrolytic currents were observed via catalytic reaction of 15 mM hydrazine in 50 mM phosphate buffer solution at Pt-np at 0.4 V when it collides with the surface of the microelectrodes. The low current noise and wider potential window in the measurements using BDD microelectrode produced a better results, which represents a better correlation to the TEM result of the Pt-np, compared to when gold microelectrodes was used.

  8. Heterogeneous platinum-catalyzed hydrogenation of dialkyl(diolefin)platinum(II) complexes: A new route to platinum surface alkyls

    OpenAIRE

    McCarthy, Thomas J.; Shih, Yen-Shiang; Whitesides, George M.

    1981-01-01

    Platinum metal catalyzes the reduction of dialkyl(diolefin)platinum(II) complexes by dihydrogen to alkanes and platinum(0). The reaction involves adsorption of the platinum(II) complex on the platinum(0) catalyst surface with conversion of the alkyl moieties to platinum surface alkyls; these appear as alkane products. The platinum atom originally present in the soluble organoplatinum species becomes part of the platinum(0) surface.

  9. Penetrating microelectrode arrays with low-impedance sputtered iridium oxide electrode coatings.

    Science.gov (United States)

    Cogan, Stuart F; Ehrlich, Julia; Plante, Timothy D; Van Wagenen, Rick

    2009-01-01

    Sputtered iridium oxide (SIROF) is a candidate low-impedance coating for neural stimulation and recording electrodes. SIROF on planar substrates has exhibited a high charge-injection capacity and impedance suitable for indwelling cortical microelectrode applications. In the present work, the properties of SIROF electrode coatings deposited onto multi-shank penetrating arrays intended for intracortical and intraneural applications were examined. The charge-injection properties under constant current pulsing were evaluated for a range of pulsewidths and current densities using voltage transients to determine maximum potential excursions in an inorganic model of interstitial fluid at 37 degrees C. The charge-injection capacity of the SIROFs was significantly improved by the use of positive potential biasing in the interpulse period, but even without bias, the SIROFs reversibly inject higher charge than other iridium oxides or platinum. Typical deliverable charge levels of 25 to 160 nC/phase were obtained with 2000 mum(2) electrodes depending on pulsewidth and interpulse bias. Similar sized platinum electrodes could inject 3 to 8 nC/phase.

  10. Electric potential microelectrode for studies of electrobiogeophysics

    DEFF Research Database (Denmark)

    Damgaard, Lars Riis; Risgaard-Petersen, Nils; Nielsen, Lars Peter

    2014-01-01

    were needle-shaped, shielded Ag/AgCl half-cells that were rendered insensitive to redox-active species in the environment. Tip diameters of 40 to 100 μm and signal resolution of approximately 10 μV were achieved. A test in marine sediments with active cable bacteria showed an electric potential......Spatially separated electron donors and acceptors in sediment can be exploited by the so-called “cable bacteria.” Electric potential microelectrodes (EPMs) were constructed to measure the electric fields that should appear when cable bacteria conduct electrons over centimeter distances. The EPMs...... increase by approximately 2mV from the sediment-water interface to a depth of approximately 20mm, in accordance with the location and direction of the electric currents estimated from oxygen, pH, and H2S microprofiles. The EPM also captured emergence and decay of electric diffusion potentials...

  11. Pyrolytic 3D Carbon Microelectrodes for Electrochemistry

    DEFF Research Database (Denmark)

    Hemanth, Suhith; Caviglia, Claudia; Amato, Letizia

    2016-01-01

    electrochemical activity, chemical stability, and ease in surface functionalization [1]. The most common carbon microfabrication techniques (i.e. screen printing) produce two-dimensional (2D) electrodes, which limit the detection sensitivity. Hence several 3D microfabrication techniques have been explored......This work presents the fabrication and characterization of multi-layered three-dimensional (3D) pyrolysed carbon microelectrodes for electrochemical applications. For this purpose, an optimized UV photolithography and pyrolysis process with the negative tone photoresist SU-8 has been developed...... carbon [2]. This process enables fabrication of 2D and 3D electrodes with possibility for tailoring ad-hoc designs and unique sensitivities for specific applications. Due to this, pyrolysed carbon is becoming increasingly attractive for numerous applications, such as novel sensors and scaffolds for cell...

  12. Toxicity of platinum compounds.

    Science.gov (United States)

    Hartmann, Jörg Thomas; Lipp, Hans-Peter

    2003-06-01

    Since the introduction of platinum-based combination chemotherapy, particularly cisplatin, the outcome of the treatment of many solid tumours has changed. The leading platinum compounds in cancer chemotherapy are cisplatin, carboplatin and oxaliplatin. They share some structural similarities; however, there are marked differences between them in therapeutic use, pharmacokinetics and adverse effects profiles [1-4]. Compared to cisplatin, carboplatin has inferior efficacy in germ-cell tumour, head and neck cancer and bladder and oesophageal carcinoma, whereas both drugs seem to have comparable efficacy in advanced non-small cell and small cell lung cancer as well as ovarian cancer [5-7]. Oxaliplatin belongs to the group of diaminocyclohexane platinum compounds. It is the first platinum-based drug that has marked efficacy in colorectal cancer when given in combination with 5-fluorouracil and folinic acid [8,9]. Other platinum compounds such as oral JM216, ZD0473, BBR3464 and SPI-77, which is a pegylated liposomal formulation of cisplatin, are still under investigation [10-13], whereas nedaplatin has been approved in Japan for the treatment of non-small cell lung cancer and other solid tumours. This review focuses on cisplatin, carboplatin and oxaliplatin.

  13. Oxygen Reduction on Platinum

    DEFF Research Database (Denmark)

    Nesselberger, Markus

    This thesis investigates the electro reduction of oxygen on platinum nanoparticles, which serve as catalyst in low temperature fuel cells. Kinetic studies on model catalysts as well as commercially used systems are presented in order to investigate the particle size effect, the particle proximity...... carbon (HSAC) supported Pt nanoparticle (Pt/C) catalysts (of various size between 1 and 5 nm). The difference in SA between the individual Pt/C catalysts (1 to 5 nm) is very small and within the error of the measurements. The factor four of loss in SA when comparing platinum bulk and Pt/C can largely...

  14. Analytical possibilities of microelectrode use for stripping voltammetry

    Energy Technology Data Exchange (ETDEWEB)

    Matysik, F.M. (Leipzig Univ. (Germany). Dept. of Chemistry); Glaeser, P. (Leipzig Univ. (Germany). Dept. of Chemistry); Werner, G. (Leipzig Univ. (Germany). Dept. of Chemistry)

    1994-07-01

    The analytical utility of microelectrodes for stripping voltammetry is discussed from several points of view. The application of microelectrodes for microanalysis is demonstrated using a novel capillary flow injection system. Heavy metals at [mu]g l[sup -1] concentrations have been determined in [mu]l-samples. The influence of electrode size and convection during the deposition period of anodic stripping voltammetry on the reproducibility of trace metal determination was studied for various types of electrodes. In the case of mercury film microelectrodes, the precision can be improved if the accumulation of the analyte is performed under quiescent conditions. Practical examples of stripping voltammetry with microelectrodes such as copper determination in whisky and trace metal measurements in drinking water are given. (orig.)

  15. Biomineralization of platinum by microorganisms

    Science.gov (United States)

    Pavlova, L. M.; Radomskaya, V. I.; Shumilova, L. P.; Ionov, A. M.; Sorokin, P.

    2017-04-01

    The mechanism of platinum biomineralization by microscopic fungi is displayed based on data of electron microscopy, infrared and X-ray photoelectronic spectroscopy. It was suggested the platinum sorption process by microscopic fungi has some stages. The initial interaction is carried out by the mechanisms of physical and chemical sorption. Hereafter the reduction process of adsorbed platinum ions up to zero state is performed, probably, for account of organic compounds, which are produced by fungi biomass as metabolism result, and the process terminates by nulvalent particles aggregating up to nanosize forms. Obtained data on the platinum biomineralization extends the concept concerning the character of forming platinum nanoparticles in carbonous paleobasin.

  16. Platinum metals in the environment

    Energy Technology Data Exchange (ETDEWEB)

    Zereini, Fathi [Frankfurt Univ. (Germany). Dept. of Environmental Analytical Chemistry; Wiseman, Clare L.S. (ed.) [Toronto Univ. (Canada). School of the Environment

    2015-03-01

    This book contains the five chapters with the following topics: 1. SOURCES OF PGE EMISSIONS ELEMENTS: Sources of Platinum Group Elements (PGE) in the Environment; Impact of Platinum Group Element Emissions from Mining and Production Activities. 2. ANALYTICAL METHODS FOR THE DETERMINATION OF PGE IN BIOLOGICAL AND ENVIRONMENTAL MATRICES: Appraisal of Biosorption for Recovery, Separation and Determination of Platinum, Palladium and Rhodium in Environmental Samples; On the Underestimated Factors Influencing the Accuracy of Determination of Pt and Pd by Electrothermal Atomic Absorption Spectrometry in Road Dust Samples; Application of Solid Sorbents for Enrichment and Separation of Platinum Metal Ions; Voltammetric Analysis of Platinum in Environmental Matrices; Speciation Analysis of Chloroplatinates; Analysis of Platinum Group Elements in Environmental Samples: A Review. 3. OCCURRENCE, CHEMICAL BEHAVIOR AND FATE OF PGE IN THE ENVIRONMENT: Brazilian PGE Research Data Survey on Urban and Roadside Soils; Platinum, Palladium and Rhodium in a Bavarian Roadside Soil; Increase of Platinum Group Element Concentrations in Soils and Airborne Dust During the Period of Vehicular Exhaust Catalysts Introduction; Platinum-Group Elements in Urban Fluvial Bed Sediments-Hawaii; Long-Term Monitoring of Palladium and Platinum Contents in Road Dust of the City of Munich, Germany; Characterization of PGEs and Other Elements in Road Dusts and Airborne Particles in Houston, Texas; Accumulation and Distribution of Pt and Pd in Roadside Dust, Soil and Vegetation in Bulgaria; Increase of the Environmental Pt Concentration in the Metropolitan Area of Mexico City Associated to the Use of Automobile Catalytic Converters; Solubility of Emitted Platinum Group Elements (Pt, Pd and Rh) in Airborne Particulate Matter (PM10) in the Presence of Organic Complexing Agents; The Influence of Anionic Species (Cl{sup -}, NO{sub 3}{sup -}, SO{sub 4}{sup 2-}) on the Transformation and Solubility of Platinum in

  17. Modification of Microelectrode Arrays: New Microelectrochemical Devices for Sensor Applications.

    Science.gov (United States)

    1986-08-22

    oxides. W03 is known to be such a redox active material and has been widely studied in connection with electrochromic display devices (Dautremont... devices . Quinone- Viologen Connected Microelectrodes: Use of an Electroactive Molecular Material With An Intrinsic pH Dependence. W03 is an example of an...REPORT & PERIOD COVERED Modification of Microelectrode Arrays: New Interim Technical Report Microelectrochemical Devices for Sensor Applications 6

  18. Exercising Spatiotemporal Control of Cell Attachment with Optically Transparent Microelectrodes

    OpenAIRE

    Shah, Sunny S.; Lee, Ji Youn; Verkhoturov, Stanislav; Tuleuova, Nazgul; Schweikert, Emile A.; Ramanculov, Erlan; Revzin, Alexander

    2008-01-01

    This paper describes a novel approach of controlling cell-surface interactions through an electrochemical “switching” of biointerfacial properties of optically transparent microelectrodes. The indium tin oxide (ITO) microelectrodes, fabricated on glass substrates, were modified with poly(ethylene glycol) (PEG) silane to make glass and ITO regions resistant to protein and cell adhesion. Cyclic voltammetry, with potassium ferricyanide serving as a redox reporter molecule, was used to monitor el...

  19. Application of PEDOT-CNT Microelectrodes for Neurotransmitter Sensing

    OpenAIRE

    Samba, Ramona; Fuchsberber, Kai; Matiychyn, Ilona; Epple, Sebastian; Kiesel, Lydia; Stett, Alfred; Schuhmann, Wolfgang; Stelzle, Martin

    2016-01-01

    In this work, composite microelectrodes from poly(3,4-ethylenedioxythiophene) (PEDOT) and carbon nanotubes (CNT) are characterized as electrochemical sensing material for neurotransmitters. Dopamine can be detected using square wave voltammetry at these microelectrodes. The CNTs improve the sensitivity by a factor of two. In addition, the selectivity towards dopamine in the presence of ascorbic acid and uric acid was examined. While both electrodes, PEDOT and PEDOT-CNT are able to detect all ...

  20. Microelectrode array fabrication by electrical discharge machining and chemical etching.

    Science.gov (United States)

    Fofonoff, Timothy A; Martel, Sylvain M; Hatsopoulos, Nicholas G; Donoghue, John P; Hunter, Ian W

    2004-06-01

    Wire electrical discharge machining (EDM), with a complementary chemical etching process, is explored and assessed as a method for developing microelectrode array assemblies for intracortically recording brain activity. Assembly processes based on these methods are highlighted, and results showing neural activity successfully recorded from the brain of a mouse using an EDM-based device are presented. Several structures relevant to the fabrication of microelectrode arrays are also offered in order to demonstrate the capabilities of EDM.

  1. Graphene microelectrode arrays for neural activity detection.

    Science.gov (United States)

    Du, Xiaowei; Wu, Lei; Cheng, Ji; Huang, Shanluo; Cai, Qi; Jin, Qinghui; Zhao, Jianlong

    2015-09-01

    We demonstrate a method to fabricate graphene microelectrode arrays (MEAs) using a simple and inexpensive method to solve the problem of opaque electrode positions in traditional MEAs, while keeping good biocompatibility. To study the interface differences between graphene-electrolyte and gold-electrolyte, graphene and gold electrodes with a large area were fabricated. According to the simulation results of electrochemical impedances, the gold-electrolyte interface can be described as a classical double-layer structure, while the graphene-electrolyte interface can be explained by a modified double-layer theory. Furthermore, using graphene MEAs, we detected the neural activities of neurons dissociated from Wistar rats (embryonic day 18). The signal-to-noise ratio of the detected signal was 10.31 ± 1.2, which is comparable to those of MEAs made with other materials. The long-term stability of the MEAs is demonstrated by comparing differences in Bode diagrams taken before and after cell culturing.

  2. Fast batch injection analysis of H{sub 2}O{sub 2} using an array of Pt-modified gold microelectrodes obtained from split electronic chips

    Energy Technology Data Exchange (ETDEWEB)

    Pacheco, Bruno D.; Valerio, Jaqueline [Centro de Ciencias e Humanidades - Universidade Presbiteriana Mackenzie, Rua da Consolacao, 896, 01302-907 Sao Paulo, SP (Brazil); Angnes, Lucio [Departamento de Quimica Fundamental, Instituto de Quimica da USP, Av. Prof. Lineu Prestes, 748, 05508-000 Cidade Universitaria, Sao Paulo, SP (Brazil); Pedrotti, Jairo J., E-mail: jpedrotti@mackenzie.br [Centro de Ciencias e Humanidades - Universidade Presbiteriana Mackenzie, Rua da Consolacao, 896, 01302-907 Sao Paulo, SP (Brazil)

    2011-06-24

    Graphical abstract: Highlights: > An array of gold microelectrodes modified with Pt was used for batch injection analysis of H{sub 2}O{sub 2} in rainwater. > The microelectrode array (n = 14) was obtained from electronic chips developed for surface mounted device technology. > The analytical frequency of the method can attain 300 determinations per hour. > The volume-weighted mean concentration of H{sub 2}O{sub 2} in rainwater investigated (n = 25) was 14.2 {mu}mol L{sup -1}. - Abstract: A fast and robust analytical method for amperometric determination of hydrogen peroxide (H{sub 2}O{sub 2}) based on batch injection analysis (BIA) on an array of gold microelectrodes modified with platinum is proposed. The gold microelectrode array (n = 14) was obtained from electronic chips developed for surface mounted device technology (SMD), whose size offers advantages to adapt them in batch cells. The effect of the dispensing rate, volume injected, distance between the platinum microelectrodes and the pipette tip, as well as the volume of solution in the cell on the analytical response were evaluated. The method allows the H{sub 2}O{sub 2} amperometric determination in the concentration range from 0.8 {mu}mol L{sup -1} to 100 {mu}mol L{sup -1}. The analytical frequency can attain 300 determinations per hour and the detection limit was estimated in 0.34 {mu}mol L{sup -1} (3{sigma}). The anodic current peaks obtained after a series of 23 successive injections of 50 {mu}L of 25 {mu}mol L{sup -1} H{sub 2}O{sub 2} showed an RSD < 0.9%. To ensure the good selectivity to detect H{sub 2}O{sub 2}, its determination was performed in a differential mode, with selective destruction of the H{sub 2}O{sub 2} with catalase in 10 mmol L{sup -1} phosphate buffer solution. Practical application of the analytical procedure involved H{sub 2}O{sub 2} determination in rainwater of Sao Paulo City. A comparison of the results obtained by the proposed amperometric method with another one which

  3. A novel implantable multichannel silicon-based microelectrode

    Institute of Scientific and Technical Information of China (English)

    Sui Xiao-Hong; Zhang Ruo-Xin; Pei Wei-Hua; Chen Hong-Da

    2007-01-01

    Silicon-based microelectrodes have been confirmed to be helpful in neural prostheses. The fabricated 7-channel silicon-based microelectrode was feasible to be implanted into the brain cortex. The manufacturing process by microelectromechanical system (MEMS) technology was detailed with four photolithographic masks. The microscopic photographs and SEM images indicated that the probe shank was 3 mm long, 100μm wide and 20μm thick with the recording sites spaced 120μm apart for good signal isolation. To facilitate the insertion and minimize the trauma,the microelectrode is narrowed down gradually near the tip with the tip taper angle of 6 degrees. Curve of the single recording site impedance versus frequency was shown by test in vitro and the impedance declined from 150.5 kΩ to 6.0 kΩwith frequency changing from 10 k to 10 MHz.

  4. Microelectrode-guided Technique for Treatment of Parkinson's Diseases

    Institute of Scientific and Technical Information of China (English)

    陈坚; 杨正明; 郭东生; 牛洪泉

    2002-01-01

    From May, 2000 to June, 2001, 27 patients with Parkinson disease (PD), including 10cases of rigidity, 13 cases of tremor, 4 cases of rigidity and tremor, were treated by microelectrodeguided technique. Among them, phlebotomy was carried out in 17 cases and thalamotomy in 10 cases. All the targets of lesion were anatomically located by using MR and neurophysiological signals on microelectrode. Our results showed that the efficiency of microelectrode-guided technique for treatment of PD was 98 %. The postoperative unified parkinson disease rating scale were 12.3+ 9.1 and 13. 2± 8. 9 respectively, which significantly improved as compared with those before operation. It was concluded that by recognizing special electrical signals in neurons microelectrode-guided neuropsychological techniques can locate target at cellular level, which overcomes the individual difference in anatomy and function, and allow more accuracy, safety and efficiency of operation. This is especially true of PD patients who fail to respond to medical treatment.

  5. Modeling and Simulation of Microelectrode-Retina Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Beckerman, M

    2002-11-30

    The goal of the retinal prosthesis project is the development of an implantable microelectrode array that can be used to supply visually-driven electrical input to cells in the retina, bypassing nonfunctional rod and cone cells, thereby restoring vision to blind individuals. This goal will be achieved through the study of the fundamentals of electrical engineering, vision research, and biomedical engineering with the aim of acquiring the knowledge needed to engineer a high-density microelectrode-tissue hybrid sensor that will restore vision to millions of blind persons. The modeling and simulation task within this project is intended to address the question how best to stimulate, and communicate with, cells in the retina using implanted microelectrodes.

  6. Comparison of microelectrode sensing configurations for impedimetric cell monitoring

    DEFF Research Database (Denmark)

    Caviglia, Claudia; Heiskanen, Arto; Andresen, Thomas Lars

    2012-01-01

    A theoretical and experimental comparison between vertical and coplanar interdigitated sensing configurations for impedimetric cell growth tracking is presented. For the first time, these widely-adopted approaches are quantitatively compared on the same cell populations and on the same 10μm...... interdigitated microelectrodes using a versatile custom-made monitoring platform including a 24-channel miniaturized potentiostat. As expected, characterization of bare microelectrodes in buffer and tracking experiments with HeLa cells over 16 hours demonstrate that the coplanar configuration provides a higher...

  7. Combined Reactor and Microelectrode Measurements in Laboratory Grown Biofilms

    DEFF Research Database (Denmark)

    Larsen, Tove; Harremoës, Poul

    1994-01-01

    A combined biofilm reactor-/microelectrode experimental set-up has been constructed, allowing for simultaneous reactor mass balances and measurements of concentration profiles within the biofilm. The system consists of an annular biofilm reactor equipped with an oxygen microelectrode. Experiments...... were carried out with aerobic glucose and starch degrading biofilms. The well described aerobic glucose degradation biofilm system was used to test the combined reactor set-up. Results predicted from known biofilm kinetics were obtained. In the starch degrading biofilm, basic assumptions were tested...

  8. Scanning electron microscopy of chronically implanted intracortical microelectrode arrays in non-human primates

    Science.gov (United States)

    Barrese, James C.; Aceros, Juan; Donoghue, John P.

    2016-04-01

    Objective. Signal attenuation is a major problem facing intracortical sensors for chronic neuroprosthetic applications. Many studies suggest that failure is due to gliosis around the electrode tips, however, mechanical and material causes of failure are often overlooked. The purpose of this study was to investigate the factors contributing to progressive signal decline by using scanning electron microscopy (SEM) to visualize structural changes in chronically implanted arrays and histology to examine the tissue response at corresponding implant sites. Approach. We examined eight chronically implanted intracortical microelectrode arrays (MEAs) explanted from non-human primates at times ranging from 37 to 1051 days post-implant. We used SEM, in vivo neural recordings, and histology (GFAP, Iba-1, NeuN). Three MEAs that were never implanted were also imaged as controls. Main results. SEM revealed progressive corrosion of the platinum electrode tips and changes to the underlying silicon. The parylene insulation was prone to cracking and delamination, and in some instances the silicone elastomer also delaminated from the edges of the MEA. Substantial tissue encapsulation was observed and was often seen growing into defects in the platinum and parylene. These material defects became more common as the time in vivo increased. Histology at 37 and 1051 days post-implant showed gliosis, disruption of normal cortical architecture with minimal neuronal loss, and high Iba-1 reactivity, especially within the arachnoid and dura. Electrode tracts were either absent or barely visible in the cortex at 1051 days, but were seen in the fibrotic encapsulation material suggesting that the MEAs were lifted out of the brain. Neural recordings showed a progressive drop in impedance, signal amplitude, and viable channels over time. Significance. These results provide evidence that signal loss in MEAs is truly multifactorial. Gliosis occurs in the first few months after implantation but does

  9. Platinum nitride with fluorite structure

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Rong; Zhang, Xiao-Feng

    2005-01-31

    The mechanical stability of platinum nitride has been studied using first-principles calculations. By calculating the single-crystal elastic constants, we show that platinum nitride can be stabilized in the fluorite structure, in which the nitrogen atoms occupy all the tetrahedral interstitial sites of the metal lattice. The stability is attributed to the pseudogap effect from analysis of the electronic structure.

  10. Characterizing Enzymatic Deposition for Microelectrode Neurotransmitter Detection

    Energy Technology Data Exchange (ETDEWEB)

    Hosein, W. K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Yorita, A. M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Tolosa, V. M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-08-12

    The enzyme immobilization process, one step in creating an enzymatic biosensor, was characterized and analyzed as a function of its physical properties. The neural glutamic biosensor is a flexible device, effectively minimizing trauma to the area of implantation. The Multielectrode Array (MEA) is composed primarily of a proprietary polymer which has been successfully implanted into human subjects in recent years. This polymer allows the device the pliability that other devices normally lack, though this poses some challenges to implantation. The electrodes are made of Platinum (Pt), and can range in number from eight to thirty two electrodes per device. These electrodes are electroplated with a semipermeable polymer layer to improve selectivity of the electrode to the neurotransmitter of interest, in this case glutamate. A signal is created from the interaction of glutamate in the brain with the glutamate oxidase (GluOx) which is immobilized on the surface of the electrode by using crosslinking chemistry in conjunction with glutaraldehyde and Bovine Serum Albumin (BSA). The glutamate is oxidized by glutamate oxidase, producing α-ketoglutarate and hydrogen peroxide (H2O2) as a by-product. The production of H2O2 is crucial for detection of the presence of the glutamate within the enzymatic coating, as it diffuses through the enzyme layer and oxidizes at the surface of the electrode. This oxidation is detectable by measurable change in the current using amperometry. Hence, the MEA allows for in vivo monitoring of neurotransmitter activity in real time. The sensitivity of the sensor to these neurotransmitters is dependent on the thickness of the layer, which is investigated in these experiments in order to optimize the efficacy of the device to detecting the substrate, once implanted.

  11. Electrochemical characterisation and anodic stripping voltammetry at mesoporous platinum rotating disc electrodes.

    Science.gov (United States)

    Lozano-Sanchez, Pablo; Elliott, Joanne M

    2008-02-01

    Using the technique of liquid crystal templating a rotating disc electrode (RDE) was modified with a high surface area mesoporous platinum film. The surface area of the electrode was characterised by acid voltammetry, and found to be very high (ca. 86 cm(2)). Acid characterisation of the electrode produced distorted voltammograms was interpreted as being due to the extremely large surface area which produced a combination of effects such as localised pH change within the pore environment and also ohmic drop effects. Acid voltammetry in the presence of two different types of surfactant, namely Tween 20 and Triton X-100, suggested antifouling properties associated with the mesoporous deposit. Further analysis of the modified electrode using a redox couple in solution showed typical RDE behaviour although extra capacitive currents were observed due to the large surface area of the electrode. The phenomenon of underpotential deposition was exploited for the purpose of anodic stripping voltammetry and results were compared with data collected for microelectrodes. Underpotential deposition of metal ions at the mesoporous RDE was found to be similar to that at conventional platinum electrodes and mesoporous microelectrodes although the rate of surface coverage was found to be slower at a mesoporous RDE. It was found that a mesoporous RDE forms a suitable system for quantification of silver ions in solution.

  12. A new O2-microelectrode and its application

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    A new oxygen microelectrode was introduced. An internalguard cathode was added besides its normal cathode sensor. It hasa low zero measuring current, high signal stability and its easy toconstruct. As it is small in size and high in stability, it may beused not only for routine environmental application, but for otherscientific research work as well.

  13. A Platform for Manufacturable Stretchable Micro-electrode Arrays

    NARCIS (Netherlands)

    Khoshfetrat Pakazad, S.; Savov, A.; Braam, S.R.; Dekker, R.

    2012-01-01

    A platform for the batch fabrication of pneumatically actuated Stretchable Micro-Electrode Arrays (SMEAs) by using state-of-the-art micro-fabrication techniques and materials is demonstrated. The proposed fabrication process avoids the problems normally associated with processing of thin film struct

  14. An Integrated DNA Modified Dual-microelectrode Sensor Probe

    Institute of Scientific and Technical Information of China (English)

    Xiang Qin LIN; Li Ping LU; Xiao Hua JIANG

    2005-01-01

    A unique method for preparing a coaxial dual-microelectrode sensor by vaporizing the nano-thickness Au layer on the DNA modified carbon fiber micro-column electrode was illustrated.The dual-electrode showed particular merit for determination in biological systems.

  15. Stripping chronopotentiometry for metal ion speciation analysis at a microelectrode

    NARCIS (Netherlands)

    Leeuwen, van H.P.; Town, R.

    2002-01-01

    The features of metal ion speciation determination by stripping chronopotentiometry (SCP) at a microelectrode are examined and compared with those of DP-SV. SCP measurements are essentially of a steady-state nature under experimentally achievable conditions and correspond to practically complete

  16. Stripping chronopotentiometry for metal ion speciation analysis at a microelectrode

    NARCIS (Netherlands)

    Leeuwen, van H.P.; Town, R.

    2002-01-01

    The features of metal ion speciation determination by stripping chronopotentiometry (SCP) at a microelectrode are examined and compared with those of DP-SV. SCP measurements are essentially of a steady-state nature under experimentally achievable conditions and correspond to practically complete dep

  17. Progress Towards Biocompatible Intracortical Microelectrodes for Neural Interfacing Applications

    Science.gov (United States)

    Jorfi, Mehdi; Skousen, John L.; Weder, Christoph; Capadona, Jeffrey R.

    2015-01-01

    To ensure long-term consistent neural recordings, next-generation intracortical microelectrodes are being developed with an increased emphasis on reducing the neuro-inflammatory response. The increased emphasis stems from the improved understanding of the multifaceted role that inflammation may play in disrupting both biologic and abiologic components of the overall neural interface circuit. To combat neuro-inflammation and improve recording quality, the field is actively progressing from traditional inorganic materials towards approaches that either minimizes the microelectrode footprint or that incorporate compliant materials, bioactive molecules, conducting polymers or nanomaterials. However, the immune-privileged cortical tissue introduces an added complexity compared to other biomedical applications that remains to be fully understood. This review provides a comprehensive reflection on the current understanding of the key failure modes that may impact intracortical microelectrode performance. In addition, a detailed overview of the current status of various materials-based approaches that have gained interest for neural interfacing applications is presented, and key challenges that remain to be overcome are discussed. Finally, we present our vision on the future directions of materials-based treatments to improve intracortical microelectrodes for neural interfacing. PMID:25460808

  18. AFM cantilever with in situ renewable mercury microelectrode

    NARCIS (Netherlands)

    Schön, Peter Manfred; Geerlings, J.; Tas, Niels Roelof; Sarajlic, Edin

    2013-01-01

    We report here first results obtained on a novel, in situ renewable mercury microelectrode integrated into an atomic force microscopy (AFM) cantilever. Our approach is based on a fountain pen probe with appropriate dimensions enabling reversible filling with(nonwetting) mercury under changing the

  19. Multi-microelectrode devices for intrafascicular use in peripheral nerve

    NARCIS (Netherlands)

    Rutten, W.L.C.

    1996-01-01

    This minisymposium paper gives an overview of experimental, modeling, design and microfabrication steps which lead towards the University of Twente three-dimensional 128-fold silicon microelectrode device. The device is meant for implantation in peripheral nerve for neuromuscular control purposes an

  20. AFM cantilever with in situ renewable mercury microelectrode

    NARCIS (Netherlands)

    Schön, Peter; Geerlings, Joël; Tas, Niels; Sarajlic, Edin

    2013-01-01

    We report here first results obtained on a novel, in situ renewable mercury microelectrode integrated into an atomic force microscopy (AFM) cantilever. Our approach is based on a fountain pen probe with appropriate dimensions enabling reversible filling with(nonwetting) mercury under changing the ap

  1. Progress towards biocompatible intracortical microelectrodes for neural interfacing applications

    Science.gov (United States)

    Jorfi, Mehdi; Skousen, John L.; Weder, Christoph; Capadona, Jeffrey R.

    2015-02-01

    To ensure long-term consistent neural recordings, next-generation intracortical microelectrodes are being developed with an increased emphasis on reducing the neuro-inflammatory response. The increased emphasis stems from the improved understanding of the multifaceted role that inflammation may play in disrupting both biologic and abiologic components of the overall neural interface circuit. To combat neuro-inflammation and improve recording quality, the field is actively progressing from traditional inorganic materials towards approaches that either minimizes the microelectrode footprint or that incorporate compliant materials, bioactive molecules, conducting polymers or nanomaterials. However, the immune-privileged cortical tissue introduces an added complexity compared to other biomedical applications that remains to be fully understood. This review provides a comprehensive reflection on the current understanding of the key failure modes that may impact intracortical microelectrode performance. In addition, a detailed overview of the current status of various materials-based approaches that have gained interest for neural interfacing applications is presented, and key challenges that remain to be overcome are discussed. Finally, we present our vision on the future directions of materials-based treatments to improve intracortical microelectrodes for neural interfacing.

  2. Highly trifluoromethylated platinum compounds.

    Science.gov (United States)

    Martínez-Salvador, Sonia; Forniés, Juan; Martín, Antonio; Menjón, Babil

    2011-07-11

    The homoleptic, square-planar organoplatinum(II) compound [NBu(4)](2) [Pt(CF(3))(4)] (1) undergoes oxidative addition of CF(3) I under mild conditions to give rise to the octahedral organoplatinum(IV) complex [NBu(4)](2) [Pt(CF(3))(5)I] (2). This highly trifluoromethylated species reacts with Ag(+) salts of weakly coordinating anions in Me(2)CO under a wet-air stream to afford the aquo derivative [NBu(4)][Pt(CF(3))(5) (OH(2))] (4) in around 75% yield. When the reaction of 2 with the same Ag(+) salts is carried out in MeCN, the solvento compound [NBu(4) ][Pt(CF(3))(5)(NCMe)] (5) is obtained in around 80% yield. The aquo ligand in 4 as well as the MeCN ligand in 5 are labile and can be cleanly replaced by neutral and anionic ligands to furnish a series of pentakis(trifluoromethyl)platinate(IV) compounds with formulae [NBu(4)][Pt(CF(3))(5) (L)] (L=CO (6), pyridine (py; 7), tetrahydrothiophene (tht; 8)) and [NBu(4)](2) [Pt(CF(3))(5)X] (X=Cl (9), Br (10)). The unusual carbonyl-platinum(IV) derivative [NBu(4)][Pt(CF(3))(5) (CO)] (6) is thermally stable and has a ν(CO) of 2194 cm(-1). The crystal structures of 2⋅CH(2)Cl(2), 5, [PPh(4) ][Pt(CF(3))(5)(CO)] (6'), and 7 have been established by X-ray diffraction methods. Compound 2 has shown itself to be a convenient entry to the chemistry of highly trifluoromethylated platinum compounds. To the best of our knowledge, compounds 2 and 4-10 are the organoelement compounds with the highest CF(3) content to have been isolated and adequately characterized to date.

  3. Understanding platinum-induced ototoxicity.

    Science.gov (United States)

    Langer, Thorsten; am Zehnhoff-Dinnesen, Antoinette; Radtke, Susanne; Meitert, Johannes; Zolk, Oliver

    2013-08-01

    Childhood cancer survival rates are now nearly 80% in more developed European countries because of improved therapies and better supportive care. Platinum chemotherapy drugs, such as cisplatin and carboplatin, are the cornerstone of many effective therapeutic protocols for childhood cancer. However, the antitumor efficacy of cisplatin and carboplatin comes at the cost of ototoxicity, which affects at least 60% of pediatric patients. Although ototoxicity is not life threatening, it can have debilitating effects on patients' quality of life. Recently, many initiatives have been launched with the ultimate goal of reducing cisplatin and high-dose carboplatin ototoxicity without compromising antitumor efficacy. This review addresses the incidence of platinum ototoxicity and its clinical presentation, time course, and early diagnostic evaluation. Genetic and non-genetic risk factors for platinum-associated ototoxicity, and their predictive value, are discussed. Recent developments in the prevention of platinum ototoxicity are also summarized. Copyright © 2013 Elsevier Ltd. All rights reserved.

  4. Inorganic nanocarriers for platinum drug delivery

    Directory of Open Access Journals (Sweden)

    Ping’an Ma

    2015-12-01

    Full Text Available Nowadays platinum drugs take up almost 50% of all the clinically used anticancer drugs. Besides cisplatin, novel platinum agents including sterically hindered platinum (II drugs, chemically reductive platinum (IV drugs, photosensitive platinum (IV drugs, and multinuclear platinum drugs have been developed recently, with a few entering clinic trials. Rapid development of nanobiotechnology makes targeted delivery of anticancer platinum agents to the tumor site possible, while simultaneously minimizing toxicity and maximizing the drug efficacy. Being versatile drug carriers to deliver platinum drugs, inorganic nanovehicles such as gold nanoparticles, iron oxide nanomaterials, carbon nanotubes, mesoporous nanosilica, metal-organic frameworks (MOFs, have been extensively studied over the past decades. In contrast to conventional polymeric and lipid nanoparticles, inorganic nanoparticles based drug carriers are peculiar as they have shown excellent theranostic effects, revealing themselves an indispensable part of future nanomedicine. Here, we will elaborate recent research advances on fabrication of inorganic nanoparticles for platinum drug delivery.

  5. Platinum availability for future automotive technologies.

    Science.gov (United States)

    Alonso, Elisa; Field, Frank R; Kirchain, Randolph E

    2012-12-04

    Platinum is an excellent catalyst, can be used at high temperatures, and is stable in many aggressive chemical environments. Consequently, platinum is used in many current industrial applications, notably automotive catalytic converters, and prospective vehicle fuel cells are expected to rely upon it. Between 2005 and 2010, the automotive industry used approximately 40% of mined platinum. Future automotive industry growth and automotive sales shifts toward new technologies could significantly alter platinum demand. The potential risks for decreased platinum availability are evaluated, using an analysis of platinum market characteristics that describes platinum's geophysical constraints, institutional efficiency, and dynamic responsiveness. Results show that platinum demand for an automotive fleet that meets 450 ppm greenhouse gas stabilization goals would require within 10% of historical growth rates of platinum supply before 2025. However, such a fleet, due largely to sales growth in fuel cell vehicles, will more strongly constrain platinum supply in the 2050 time period. While current platinum reserves are sufficient to satisfy this increased demand, decreasing platinum ore grade and continued concentration of platinum supply in a single geographic area are availability risk factors to platinum end-users.

  6. Chronic in vivo stability assessment of carbon fiber microelectrode arrays

    Science.gov (United States)

    Patel, Paras R.; Zhang, Huanan; Robbins, Matthew T.; Nofar, Justin B.; Marshall, Shaun P.; Kobylarek, Michael J.; Kozai, Takashi D. Y.; Kotov, Nicholas A.; Chestek, Cynthia A.

    2016-12-01

    Objective. Individual carbon fiber microelectrodes can record unit activity in both acute and semi-chronic (∼1 month) implants. Additionally, new methods have been developed to insert a 16 channel array of carbon fiber microelectrodes. Before assessing the in vivo long-term viability of these arrays, accelerated soak tests were carried out to determine the most stable site coating material. Next, a multi-animal, multi-month, chronic implantation study was carried out with carbon fiber microelectrode arrays and silicon electrodes. Approach. Carbon fibers were first functionalized with one of two different formulations of PEDOT and subjected to accelerated aging in a heated water bath. After determining the best PEDOT formula to use, carbon fiber arrays were chronically implanted in rat motor cortex. Some rodents were also implanted with a single silicon electrode, while others received both. At the end of the study a subset of animals were perfused and the brain tissue sliced. Tissue sections were stained for astrocytes, microglia, and neurons. The local reactive responses were assessed using qualitative and quantitative methods. Main results. Electrophysiology recordings showed the carbon fibers detecting unit activity for at least 3 months with average amplitudes of ∼200 μV. Histology analysis showed the carbon fiber arrays with a minimal to non-existent glial scarring response with no adverse effects on neuronal density. Silicon electrodes showed large glial scarring that impacted neuronal counts. Significance. This study has validated the use of carbon fiber microelectrode arrays as a chronic neural recording technology. These electrodes have demonstrated the ability to detect single units with high amplitude over 3 months, and show the potential to record for even longer periods. In addition, the minimal reactive response should hold stable indefinitely, as any response by the immune system may reach a steady state after 12 weeks.

  7. Cross-reactivity of Halogenated Platinum Salts

    Science.gov (United States)

    Halogenated platinum (Pt) salts are well-known respiratory sensitizers associated with the development of asthma. People may be exposed to a variety of platinum compounds in different contexts (e.g. occupationally, automobile exhaust). Published reports suggest that sensitizati...

  8. A microfluidic cell culture device with integrated microelectrodes for barrier studies

    DEFF Research Database (Denmark)

    Tan, Hsih-Yin; Dufva, Martin; Kutter, Jörg P.

    We present an eight cell culture microfluidic device fabricated using thiol-ene ‘click’ chemistry with embedded microelectrodes for evaluating barrier properties of human intestinal epithelial cells. The capability of the microelectrodes for trans-epithelial electrical resistance (TEER) measureme......We present an eight cell culture microfluidic device fabricated using thiol-ene ‘click’ chemistry with embedded microelectrodes for evaluating barrier properties of human intestinal epithelial cells. The capability of the microelectrodes for trans-epithelial electrical resistance (TEER......) measurements was demonstrated by using confluent human colorectal epithelial cells (Caco-2) and rat fibroblast (CT 26) cells cultured in the microfluidic device....

  9. Novel non-platinum metal catalyst material

    DEFF Research Database (Denmark)

    2014-01-01

    The present invention relates to a novel non-platinum metal catalyst material for use in low temperature fuel cells and electrolysers and to fuel cells and electrolysers comprising the novel non-platinum metal catalyst material. The present invention also relates to a novel method for synthesizing...... the novel non-platinum metal catalyst material....

  10. Coating Carbon Fibers With Platinum

    Science.gov (United States)

    Effinger, Michael R.; Duncan, Peter; Coupland, Duncan; Rigali, Mark J.

    2007-01-01

    A process for coating carbon fibers with platinum has been developed. The process may also be adaptable to coating carbon fibers with other noble and refractory metals, including rhenium and iridium. The coated carbon fibers would be used as ingredients of matrix/fiber composite materials that would resist oxidation at high temperatures. The metal coats would contribute to oxidation resistance by keeping atmospheric oxygen away from fibers when cracks form in the matrices. Other processes that have been used to coat carbon fibers with metals have significant disadvantages: Metal-vapor deposition processes yield coats that are nonuniform along both the lengths and the circumferences of the fibers. The electrical resistivities of carbon fibers are too high to be compatible with electrolytic processes. Metal/organic vapor deposition entails the use of expensive starting materials, it may be necessary to use a furnace, and the starting materials and/or materials generated in the process may be hazardous. The present process does not have these disadvantages. It yields uniform, nonporous coats and is relatively inexpensive. The process can be summarized as one of pretreatment followed by electroless deposition. The process consists of the following steps: The surfaces of the fiber are activated by deposition of palladium crystallites from a solution. The surface-activated fibers are immersed in a solution that contains platinum. A reducing agent is used to supply electrons to effect a chemical reduction in situ. The chemical reduction displaces the platinum from the solution. The displaced platinum becomes deposited on the fibers. Each platinum atom that has been deposited acts as a catalytic site for the deposition of another platinum atom. Hence, the deposition process can also be characterized as autocatalytic. The thickness of the deposited metal can be tailored via the duration of immersion and the chemical activity of the solution.

  11. Platinum Group Metals New Material

    Institute of Scientific and Technical Information of China (English)

    XIE Ming; ZHANG Jiankang; WANG Saibei; HU Jieqiong; LIU Manmen; CHEN Yongtai; ZHANG Jiming; YANG Youcai; YANG Yunfeng; ZHANG Guoquan

    2012-01-01

    Platinum group metals (PGM) include six elements,namely Pt,Pd,Rh,Ir,Os and Ru.PGM and their alloys are the important fundamental materials for modern industry and national defense construction,they have special physical and chemical properties,widely used in metallurgy,chemical,electric,electronic,information,energy,environmental protection,aviation,aerospace,navigation and other high technology industry.Platinum group metals and their alloys,which have good plasticity and processability,can be processed to electrical contact materials,resistance materials,solder,electronic paste,temperature-measurement materials,elastic materials,magnetic materials and high temperature structural materials.

  12. Spatial characterization of electric potentials generated by pulsed microelectrode arrays.

    Science.gov (United States)

    Kandagor, V; Cela, C J; Sanders, C A; Greenbaum, E; Lazzi, G; Humayun, M S; Zhou, D M; Castro, R; Gaikwad, S; Little, J

    2010-01-01

    This presentation is a report on the in situ characterization of stimulating microelectrodes in the context of multielectrode retinal prosthetic implants. The experimental system approximately replicates the geometric and electrical parameters of Second Sight Medical Products' Argus II Retinal Implant. Topographic maps of electric potentials have been prepared for a 60 electrode structure in which selected electrodes were stimulated with biphasic repetitively pulsed charge densities at 100 microC·cm(-2). Surface contour maps were prepared using a 10 microm diameter recording electrode.

  13. Modification of Carbon Nanotube Powder Microelectrode and Nitrite Reduction

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The properties of the carbon nanotube powder microelectrodes (denoted CNTPME) are remarkably altered by anodic pretreatment and preadsorption of mediators. It seems that anodic pretreatment leads the long and tangled carbon nanotubes to be partially cut shorter, resulting in more openings as shown by TEM. Besides, the anodic pretreatment may adjust the hydrophobicity of nanotubes to match with that of Os(bpy)32+. As a result, the real surface area and the ability of adsorbing mediator Os(bpy)32+ of the nanotubes are markedly increased so as to effectively catalyze NO2- reduction in acidic solution.

  14. A MULTIPLEXED ASSAY FOR DETERMINATION OF NEUROTOXICANT EFFECTS ON SPONTANEOUS NETWORK ACTIVITY AND CELL VIABILITY FROM MICROELECTRODE ARRAYS

    Science.gov (United States)

    AbstractTITLE: A MULTIPLEXED ASSAY FOR DETERMINATION OF NEUROTOXICANT EFFECTS ON SPONTANEOUS NETWORK ACTIVITY AND CELL VIABILITY FROM MICROELECTRODE ARRAYSABSTRACT BODY: Microelectrode array (MEA) recordings are increasingly being used as an in vitro method to detect and characte...

  15. Nanocarriers for delivery of platinum anticancer drugs☆

    Science.gov (United States)

    Oberoi, Hardeep S.; Nukolova, Natalia V.; Kabanov, Alexander V.; Bronich, Tatiana K.

    2014-01-01

    Platinum based anticancer drugs have revolutionized cancer chemotherapy, and continue to be in widespread clinical use especially for management of tumors of the ovary, testes, and the head and neck. However, several dose limiting toxicities associated with platinum drug use, partial anti-tumor response in most patients, development of drug resistance, tumor relapse, and many other challenges have severely limited the patient quality of life. These limitations have motivated an extensive research effort towards development of new strategies for improving platinum therapy. Nanocarrier-based delivery of platinum compounds is one such area of intense research effort beginning to provide encouraging preclinical and clinical results and may allow the development of the next generation of platinum chemotherapy. This review highlights current understanding on the pharmacology and limitations of platinum compounds in clinical use, and provides a comprehensive analysis of various platinum–polymer complexes, micelles, dendrimers, liposomes and other nanoparticles currently under investigation for delivery of platinum drugs. PMID:24113520

  16. Characterization of surface modification on microelectrode arrays for in vitro cell culture.

    Science.gov (United States)

    Lin, Shu-Ping; Chen, Jia-Jin J; Liao, Jiunn-Der; Tzeng, Shun-Fen

    2008-02-01

    This study aims to investigate surface-modified microelectrodes on the microelectrode arrays (MEAs) for neuronal interfaces with in vitro cell culture. The polyimide (PI) MEA was fabricated by using micro-electro-mechanical systems (MEMS) techniques. Self-assembled monolayers (SAMs) of 11-mercaptoundecanoic acid (MUA) were utilized to modify the microelectrode surface of the MEA. The SAMs' modified surface of microelectrodes offered a reliable interface to immobilize biological ligands through covalent bonding. To increase biocompatibility, the poly-D-lysine (PDL) was immobilized on the SAMs' modified microelectrodes. Several analytical techniques were used to define the physical structure and functional groups of surface-modified gold microelectrodes on the MEA. Spectra of the Fourier transform infrared reflection (FTIR) were applied to characterize the molecular structure of MUA-SAMs and PDL on the microelectrodes. The spectra, two peaks of amide I (at 1,613 cm(-1)) and amide II (at 1,548 cm(-1)), revealed that covalent amide bonding existed in PDL-MUA-SAMs modified surfaces. The thickness and formation of the MUA and PDL were also observed and quantified by using an atomic force microscope (AFM). The impedance measurement of PDL-MUA-SAMs modified MEA only increased slightly to an average of 524.6 +/- 55.8 kOmega from 352.9 +/- 34.4 kOmega of bare gold microelectrode (p stimulation/sensing schemes and for future implantation purposes.

  17. [Formylation of porphyrin platinum complexes].

    Science.gov (United States)

    Rumiantseva, V D; Konovalenko, L I; Nagaeva, E A; Mironov, A F

    2005-01-01

    The formylation reaction of platinum complexes of beta-unsubstituted porphyrins was studied. The interaction of deuteroporphyrin IX derivatives with the Vilsmeyer reagent led to the selective formylation of their macrocycles in the beta position. The resulting formyl derivatives of the porphyrins are of interest for fluorescent immunoassay.

  18. Impedance measurements on Au microelectrodes using controlled atmosphere high temperature scanning probe microscope

    DEFF Research Database (Denmark)

    Wu, Yuehua; Hansen, Karin Vels; Jacobsen, Torben

    2011-01-01

    High temperature impedance measurements on Au microelectrodes deposited on polished yttria stabilized zirconia (YSZ) pellets were demonstrated using a newly designed controlled atmosphere high temperature scanning probe microscope (CAHT-SPM). Probes based on Pt0.8Ir0.2 were fabricated and employed...... in all the investigations. The electrical properties of the Au microelectrodes were investigated using CAHT-SPM at various temperatures in air. The influences of the tip-sample force and of the size of the microelectrode on the electrical properties of the Au microelectrodes were also studied....... The impedance spectra of circular Au microelectrodes down to 8μm in diameter at different temperatures were successfully obtained. The CAHT-SPM presented in this paper is capable of obtaining topography images, conductivity images and impedance spectra in-situ in a temperature range from room temperature...

  19. Platinum-tin oxide core-shell catalysts for efficient electro-oxidation of ethanol.

    Science.gov (United States)

    Du, Wenxin; Yang, Guangxing; Wong, Emily; Deskins, N Aaron; Frenkel, Anatoly I; Su, Dong; Teng, Xiaowei

    2014-08-06

    Platinum-tin (Pt/Sn) binary nanoparticles are active electrocatalysts for the ethanol oxidation reaction (EOR), but inactive for splitting the C-C bond of ethanol to CO2. Here we studied detailed structure properties of Pt/Sn catalysts for the EOR, especially CO2 generation in situ using a CO2 microelectrode. We found that composition and crystalline structure of the tin element played important roles in the CO2 generation: non-alloyed Pt46-(SnO2)54 core-shell particles demonstrated a strong capability for C-C bond breaking of ethanol than pure Pt and intermetallic Pt/Sn, showing 4.1 times higher CO2 peak partial pressure generated from EOR than commercial Pt/C.

  20. Design of 3D Active Multichannel Silicon Neural Microelectrode

    Institute of Scientific and Technical Information of China (English)

    WANG Di; ZHANG Guoxiong; LI Xingfei

    2006-01-01

    To find a design method for 3D active multichannel silicon microelectrode,a microstructure of active neural recording system is presented,where two 2D probes,two integrated circuits and two spacers are microassembled on a 5 mm ×7 mm silicon platform,and 32 sites neural signals can be operated simultaneously.A theoretical model for measuring the neural signal by the silicon microelectrode is proposed based on the structure and fabrication process of a single-shank probe.The method of determining the dimensional parameters of the probe shank is discussed in the following three aspects,i.e.the structures of pallium and endocranium,coupled interconnecters noise,and strength characteristic of neural probe.The design criterion is to minimize the size of the neural probe as well as that the probe has enough stiffness to pierce the endocranium.The on-chip unity-gain bandpass amplifier has an overall gain of 42 dB over a bandwidth from 60 Hz to 10 kHz;and the DC-baseline stability circuit is of high input resistance above 30 MΩ to guarantee a cutoff frequency below 100 Hz.The circuit works in stimulating or recording modes.The conversion of the modes depends on the stimulating control signal.

  1. Coupled electrochemical reactions at bipolar microelectrodes and nanoelectrodes.

    Science.gov (United States)

    Guerrette, Joshua P; Oja, Stephen M; Zhang, Bo

    2012-02-07

    Here we report the voltammetric study of coupled electrochemical reactions on microelectrodes and nanoelectrodes in a closed bipolar cell. We use steady-state cyclic voltammetry to discuss the overall voltammetric response of closed bipolar electrodes (BPEs) and understand its dependence on the concentration of redox species and electrode size. Much of the previous work in bipolar electroanalytical chemistry has focused on the use of an "open" cell with the BPE located in an open microchannel. A closed BPE, on the other hand, has two poles placed in separate compartments and has remained relatively unexplored in this field. In this work, we demonstrated that carbon-fiber microelectrodes when backfilled with an electrolyte to establish conductivity are closed BPEs. The coupling between the oxidation reaction, e.g., dopamine oxidation, on the carbon disk/cylinder and the reduction of oxygen on the interior fiber is likely to be responsible for the conductivity. We also demonstrated the ability to quantitatively measure voltammetric properties of both the cathodic and anodic poles in a closed bipolar cell from a single cyclic voltammetry (CV) scan. It was found that "secondary" reactions such as oxygen reduction play an important role in this process. We also described the fabrication and use of Pt bipolar nanoelectrodes which may serve as a useful platform for future advances in nanoscale bipolar electrochemistry.

  2. Highly-compliant, conformal and stretchable microelectrode arrays

    Institute of Scientific and Technical Information of China (English)

    Zhang Hongzhi; Xie Lei; Yu Mei; Liu Zhiyuan; Li Yuchun; Yu Zhe

    2013-01-01

    Most biological tissues are supple and elastic,While current electronic devices fabricated by semiconductors and metals are usually stiff and brittle.As a result,implanted electronic devices can irritate and damage surrounding tissues,causing immune reaction and scarring.In this work,we develop stretchable microelectrode arrays,with the development of a novel soft lithography technology,which are designed and fabricated with a polymer/stretchable metal/polymer sandwich structure.With the great deformability of stretch,compression,bend and twisting,while preserving electrical property,this technology overcomes the fundamental mismatch of mechanical properties between biological tissues and electronic devices,and provides highly-compliant,conformal and stretchable bio-electronic interfaces.Here we also describe the following three applications of the stretchable electrode arrays:a.monitoring intracranial electroencephalography (EEG); b.stimulating peripheral nerves to drive muscles; c.monitoring epicardial electrocardiography (ECG).Stretchable microelectrode arrays create a promising field in biomedical applications for its better modulus match with biological tissues and robust mechanical and electrical properties.They allow for construction of electronic integrated circuits spread over on complex and dynamic curved surfaces,providing a much friendlier bio-electronic interface for diagnosis,treatment and intelligent bio-control.

  3. Long-term neural recordings using MEMS based moveable microelectrodes in the brain

    Directory of Open Access Journals (Sweden)

    Nathan Jackson

    2010-06-01

    Full Text Available One of the critical requirements of the emerging class of neural prosthetic devices is to maintain good quality neural recordings over long time periods. We report here a novel (Micro-ElectroMechanical Systems based technology that can move microelectrodes in the event of deterioration in neural signal to sample a new set of neurons. Microscale electro-thermal actuators are used to controllably move microelectrodes post-implantation in steps of approximately 9 µm. In this study, a total of 12 moveable microelectrode chips were individually implanted in adult rats. Two of the 12 moveable microelectrode chips were not moved over a period of 3 weeks and were treated as control experiments. During the first three weeks of implantation, moving the microelectrodes led to an improvement in the average SNR from 14.61 ± 5.21 dB before movement to 18.13 ± 4.99 dB after movement across all microelectrodes and all days. However, the average RMS values of noise amplitudes were similar at 2.98 ± 1.22 µV and 3.01 ± 1.16 µV before and after microelectrode movement. Beyond three weeks, the primary observed failure mode was biological rejection of the PMMA (dental cement based skull mount resulting in the device loosening and eventually falling from the skull. Additionally, the average SNR for functioning devices beyond three weeks was 11.88 ± 2.02 dB before microelectrode movement and was significantly different (p<0.01 from the average SNR of 13.34 ± 0.919 dB after movement. The results of this study demonstrate that MEMS based technologies can move microelectrodes in rodent brains in long-term experiments resulting in improvements in signal quality. Further improvements in packaging and surgical techniques will potentially enable movable microelectrodes to record cortical neuronal activity in chronic experiments.

  4. The platinum microelectrode/Nafion interface - An electrochemical impedance spectroscopic analysis of oxygen reduction kinetics and Nafion characteristics

    Science.gov (United States)

    Parthasarathy, Arvind; Dave, Bhasker; Srinivasan, Supramaniam; Appleby, John A.; Martin, Charles R.

    1992-01-01

    The objectives of this study were to use electrochemical impedance spectroscopy (EIS) to study the oxygen-reduction reaction under lower humidification conditions than previously studied. The EIS technique permits the discrimination of electrode kinetics of oxygen reduction, mass transport of O2 in the membrane, and the electrical characteristics of the membrane. Electrode-kinetic parameters for the oxygen-reduction reaction, corrosion current densities for Pt, and double-layer capacitances were calculated. The production of water due to electrochemical reduction of oxygen greatly influenced the EIS response and the electrode kinetics at the Pt/Nafion interface. From the finite-length Warburg behavior, a measure of the diffusion coefficient of oxygen in Nafion and diffusion-layer thickness was obtained. An analysis of the EIS data in the high-frequency domain yielded membrane and interfacial characteristics such as ionic conductivity of the membrane, membrane grain-boundary capacitance and resistance, and uncompensated resistance.

  5. Surface characterization of platinum electrodes.

    Science.gov (United States)

    Solla-Gullón, José; Rodríguez, Paramaconi; Herrero, Enrique; Aldaz, Antonio; Feliu, Juan M

    2008-03-14

    The quantitative analysis of the different surface sites on platinum samples is attempted from pure voltammetric data. This analysis requires independent knowledge of the fraction of two-dimensional (111) and (100) domains. Specific site-probe reactions are employed to achieve this goal. Irreversibly-adsorbed bismuth and tellurium have been revealed to be sensitive to the presence of (111) terrace domains of different width whereas almost all sites involved in (100) ordered domains have been characterized through germanium adatoms. The experimental protocol follows that used with well-defined single-crystal electrodes and, therefore, requires careful control of the surface cleanliness. Platinum basal planes and their vicinal stepped surfaces have been employed to obtain calibration plots between the charge density measured under the adatom redox peak, specific for the type of surface site, and the corresponding terrace size. The evaluation of the (100) bidimensional domains can also be achieved using the voltammetric profiles, once the fraction of (111) ordered domains present in the polyoriented platinum has been determined and their featureless contribution has been subtracted from the whole voltammetric response. Using that curve, it is possible to perform a deconvolution of the adsorption states of the polycrystalline sample different from those related to (111) domains. The fraction of (100)-related states in the deconvoluted voltammogram can then be compared to that expected from the independent estimation coming from the charge involved in the redox process undergone by the irreversibly-adsorbed germanium and thus check the result of the deconvolution. The information about the surface-site distribution can also be applied to analyze the voltammetric profile of nanocrystalline platinum electrodes.

  6. Request for Correction 11001 Toxicological Review of Halogenated Platinum Salts and Platinum Compounds

    Science.gov (United States)

    Request for Correction by the International Platinum Group Metals Association seeking the correction of information disseminated in the draft EPA document Toxicological Review of Halogenated Platinum Salts and Platinum Compounds: In Support of Summary Information on the Integrated Risk Information System (IRIS).

  7. Acetylcholinesterase biosensor for carbaryl detection based on interdigitated array microelectrodes.

    Science.gov (United States)

    Gong, Zhili; Guo, Yemin; Sun, Xia; Cao, Yaoyao; Wang, Xiangyou

    2014-10-01

    In this study, an acetylcholinesterase (AChE) biosensor with superior accuracy and sensitivity was successfully developed based on interdigitated array microelectrodes (IAMs). IAMs have a series of parallel microband electrodes with alternating microbands connected together. Chitosan was used as the enzyme immobilization material, and AChE was used as the model enzyme for carbaryl detection to fabricate AChE biosensor. Electrochemical impedance spectroscopy was used in conjunction with the fabricated biosensor to detect pesticide residues. Based on the inhibition of pesticides on the AChE activity, using carbaryl as model compounds, the biosensor exhibited a wide range, low detection limit, and high stability. Moreover, the biosensor can also be used as a new promising tool for pesticide residue analysis.

  8. Biocompatibility of intracortical microelectrodes: current status and future prospects

    Directory of Open Access Journals (Sweden)

    Cristina Marin

    2010-05-01

    Full Text Available Rehabilitation of sensory and/or motor functions in patients with neurological diseases is more and more dealing with artificial electrical stimulation and recording from populations of neurons using biocompatible chronic implants. As more and more patients have benefited from these approaches, the interest in neural interfaces has grown significantly. However an important problem reported with all available microelectrodes to date is long-term viability and biocompatibility. Therefore it is essential to understand the signals that lead to neuroglial activation and create a targeted intervention to control the response, reduce the adverse nature of the reactions and maintain an ideal environment for the brain-electrode interface. We discuss some of the exciting opportunities and challenges that lie in this intersection of neuroscience research, bioengineering, neurology and biomaterials.

  9. Phosphoric acid fuel cell platinum use study

    Science.gov (United States)

    Lundblad, H. L.

    1983-01-01

    The U.S. Department of Energy is promoting the private development of phosphoric acid fuel cell (PAFC) power plants for terrestrial applications. Current PAFC technology utilizes platinum as catalysts in the power electrodes. The possible repercussions that the platinum demand of PAFC power plant commercialization will have on the worldwide supply and price of platinum from the outset of commercialization to the year 2000 are investigated. The platinum demand of PAFC commercialization is estimated by developing forecasts of platinum use per unit of generating capacity and penetration of PAFC power plants into the electric generation market. The ability of the platinum supply market to meet future demands is gauged by assessing the size of platinum reserves and the capability of platinum producers to extract, refine and market sufficient quantities of these reserves. The size and timing of platinum price shifts induced by the added demand of PAFC commercialization are investigated by several analytical methods. Estimates of these price shifts are then used to calculate the subsequent effects on PAFC power plant capital costs.

  10. The robo-pigeon based on the multiple brain regions synchronization implanted microelectrodes.

    Science.gov (United States)

    Huai, Rui-Tuo; Yang, Jun-Qing; Wang, Hui

    2016-07-03

    Almost all multichannel microelectrodes are only applied to the same nucleus. The multiple brain regions synchronization implanted microelectrodes can be implanted in the several brain regions at the same time, when used in the robo-animal, which can reduce the operation process, shorten animals operation time. Due to electrode position relatively fixed, errors caused by each separately implanted electrode were reduced and the animal control effect was greatly increased compared to the original electrodes. The electrode fixed time was also extended. This microelectrode provided beneficial reference function for the study of the free state of small animals in different brain regions.

  11. Platinum microwire for subdural electrocorticography over human neocortex: millimeter-scale spatiotemporal dynamics.

    Science.gov (United States)

    Kellis, Spencer; Greger, Bradley; Hanrahan, Sara; House, Paul; Brown, Richard

    2011-01-01

    Platinum microwires, terminated at regular intervals to form a grid of contacts, were used to record electric potentials at the surface of the cerebral cortex in human subjects. The microwire grids were manufactured commercially with 75 μm platinum wire and 1 mm grid spacing, and are FDA approved. Because of their small size and spacing, these grids could be used to explore the scale of spatiotemporal dynamics in cortical surface potentials. Electrochemical impedance spectroscopy was used to characterize their recording properties and develop a frequency-dependent electrical model of the micro-electrodes. Data recorded from multiple sites in human cortex were analyzed to explore the relationship between linear correlation and separation distance. A model was developed to explore the impact of cerebrospinal fluid on signal spread among electrodes. Spatial variation in the per-electrode performance decoding articulated speech from face-motor and Wernicke's areas of cortex was explored to understand the scale of information processing at the cortex. We conclude that there are important dynamics at the millimeter scale in human subdural electrocorticography which may be important in maximizing the performance of neural prosthetic applications.

  12. Conductive Polymer Microelectrodes for on-chip measurement of transmitter release from living cells

    DEFF Research Database (Denmark)

    Larsen, Simon Tylsgaard; Matteucci, Marco; Taboryski, Rafael J.

    2012-01-01

    driven cell trapping inside closed chip devices. Conductive polymer microelectrodes were used to measure transmitter release using electrochemical methods such as cyclic voltammetry and constant potential amperometry. By measuring the oxidation current at a cyclic voltammogram, the concentration...

  13. Fabrication, calibration and evaluation of a phosphate ion-selective microelectrode

    Energy Technology Data Exchange (ETDEWEB)

    Wang, John J., E-mail: johnwang1974@gmail.co [University of Cincinnati, 12716 Ginger Wood Lane, Clarksburg, MD 20871 (United States); Bishop, Paul L. [Department of Civil and Environmental Engineering, PO Box 210071, University of Cincinnati, Cincinnati, OH 45221-0071 (United States)

    2010-12-15

    To conduct the micro-environment study of flocs in an enhanced biological phosphorus removal (EBPR) process, a phosphate ion-selective microelectrode was developed. The cobalt-based microelectrodes have tip diameters of 5-20 {mu}m and respond to all the three forms of phosphate ions, namely, H{sub 2}PO{sub 4}{sup -}, HPO{sub 4}{sup 2-}, and PO{sub 4}{sup 3-}. The calibration curve at pH 7.5 had a slope of 31.5 mV per decade change of concentration and a R{sup 2} value of 0.99. Other characteristics of this microelectrode, such as response time, interferences from pH, ion strength, DO and other anions were also evaluated. - This paper presents the first phosphate ion-selective microelectrode in the world used for micro-level phorphorus removal studies.

  14. Carbon Nanotubes Grown on Metal Microelectrodes for the Detection of Dopamine.

    Science.gov (United States)

    Yang, Cheng; Jacobs, Christopher B; Nguyen, Michael D; Ganesana, Mallikarjunarao; Zestos, Alexander G; Ivanov, Ilia N; Puretzky, Alexander A; Rouleau, Christopher M; Geohegan, David B; Venton, B Jill

    2016-01-05

    Microelectrodes modified with carbon nanotubes (CNTs) are useful for the detection of neurotransmitters because the CNTs enhance sensitivity and have electrocatalytic effects. CNTs can be grown on carbon fiber microelectrodes (CFMEs) but the intrinsic electrochemical activity of carbon fibers makes evaluating the effect of CNT enhancement difficult. Metal wires are highly conductive and many metals have no intrinsic electrochemical activity for dopamine, so we investigated CNTs grown on metal wires as microelectrodes for neurotransmitter detection. In this work, we successfully grew CNTs on niobium substrates for the first time. Instead of planar metal surfaces, metal wires with a diameter of only 25 μm were used as CNT substrates; these have potential in tissue applications due to their minimal tissue damage and high spatial resolution. Scanning electron microscopy shows that aligned CNTs are grown on metal wires after chemical vapor deposition. By use of fast-scan cyclic voltammetry, CNT-coated niobium (CNT-Nb) microelectrodes exhibit higher sensitivity and lower ΔEp value compared to CNTs grown on carbon fibers or other metal wires. The limit of detection for dopamine at CNT-Nb microelectrodes is 11 ± 1 nM, which is approximately 2-fold lower than that of bare CFMEs. Adsorption processes were modeled with a Langmuir isotherm, and detection of other neurochemicals was also characterized, including ascorbic acid, 3,4-dihydroxyphenylacetic acid, serotonin, adenosine, and histamine. CNT-Nb microelectrodes were used to monitor stimulated dopamine release in anesthetized rats with high sensitivity. This study demonstrates that CNT-grown metal microelectrodes, especially CNTs grown on Nb microelectrodes, are useful for monitoring neurotransmitters.

  15. Carbon Nanotubes Grown on Metal Microelectrodes for the Detection of Dopamine

    OpenAIRE

    Yang, Cheng; Jacobs, Christopher B.; Nguyen, Michael D.; Ganesana, Mallikarjunarao; Zestos, Alexander G.; Ivanov, Ilia N.; Puretzky, Alexander A.; Rouleau, Christopher M.; Geohegan, David B.; Venton, B. Jill

    2015-01-01

    Microelectrodes modified with carbon nanotubes (CNTs) are useful for the detection of neurotransmitters because the CNTs enhance sensitivity and have electrocatalytic effects. CNTs can be grown on carbon fiber microelectrodes (CFMEs) but the intrinsic electrochemical activity of carbon fibers makes evaluating the effect of CNT enhancement difficult. Metal wires are highly conductive and many metals have no intrinsic electrochemical activity for dopamine, so we investigated CNTs grown on metal...

  16. [Platinum compounds: metabolism, toxicity and supportive strategies].

    Science.gov (United States)

    Lipp, H P; Hartmann, J T

    2005-02-09

    Although the leading platinum compounds, cisplatin, carboplatin, and oxaliplatin, share some structural similarities, there are marked differences between them in therapeutic uses, pharmacokinetics, and adverse effects profiles. Compared with cisplatin, carboplatin has inferior efficacy in germ-cell tumors, head and neck cancers, and bladder and esophageal carcinomas, whereas the two drugs appear to have comparable efficacy in ovarian cancer, extensive small-cell lung cancers (SCLC), and advanced non-small-cell lung cancers (NSCLC). Oxaliplatin belongs to the group of diaminocyclohexane (DACH) platinum compounds. It is the first platinum-based drug that has marked efficacy in colorectal cancer when given in combination with 5-fluorouracil and folinic acid. Nedaplatin has been registered in Japan, whereas other derivatives, like JM216 (which is the only orally available platinum derivative), ZD0473, BBR3464, and SPI-77 (a liposomal formulation of cisplatin), are still under investigation. The adverse effects of platinum compounds are reviewed together with possible prevention strategies.

  17. Enhanced Flexible Tubular Microelectrode with Conducting Polymer for Multi-Functional Implantable Tissue-Machine Interface

    Science.gov (United States)

    Tian, Hong-Chang; Liu, Jing-Quan; Kang, Xiao-Yang; Tang, Long-Jun; Wang, Ming-Hao; Ji, Bo-Wen; Yang, Bin; Wang, Xiao-Lin; Chen, Xiang; Yang, Chun-Sheng

    2016-05-01

    Implantable biomedical microdevices enable the restoration of body function and improvement of health condition. As the interface between artificial machines and natural tissue, various kinds of microelectrodes with high density and tiny size were developed to undertake precise and complex medical tasks through electrical stimulation and electrophysiological recording. However, if only the electrical interaction existed between electrodes and muscle or nerve tissue without nutrition factor delivery, it would eventually lead to a significant symptom of denervation-induced skeletal muscle atrophy. In this paper, we developed a novel flexible tubular microelectrode integrated with fluidic drug delivery channel for dynamic tissue implant. First, the whole microelectrode was made of biocompatible polymers, which could avoid the drawbacks of the stiff microelectrodes that are easy to be broken and damage tissue. Moreover, the microelectrode sites were circumferentially distributed on the surface of polymer microtube in three dimensions, which would be beneficial to the spatial selectivity. Finally, the in vivo results confirmed that our implantable tubular microelectrodes were suitable for dynamic electrophysiological recording and simultaneous fluidic drug delivery, and the electrode performance was further enhanced by the conducting polymer modification.

  18. Direct-growth carbon nanotubes on 3D structural microelectrodes for electrophysiological recording.

    Science.gov (United States)

    Pan, Alice Ian; Lin, Min-Hsuan; Chung, Hui-Wen; Chen, Hsin; Yeh, Shih-Rung; Chuang, Yung-Jen; Chang, Yen-Chung; Yew, Tri-Rung

    2016-01-01

    A novel 3D carbon nanotube (CNT) microelectrode was developed through direct growth of CNTs on a gold pin-shaped 3D microelectrode at a low temperature (400 °C) for applications in neural and cardiac recording. With an electroplated Ni catalyst layer covering the entire surface of the pin-shaped structure, CNTs were synthesized on a 3D microelectrode by catalytic thermal chemical vapor deposition (CVD). According to the analyses by electrochemical impedance spectroscopy, the impedance of 3D microelectrodes after CNT growth and UV/O3 treatment decreased from 9.3 Ω mm(-2) to 1.2 Ω mm(-2) and the capacitance increased largely from 2.2 mF cm(-2) to 73.3 mF cm(-2). The existence of UVO3-treated CNT led to a large improvement of interfacial capacitance, contributing to the decrease of impedance. The electrophysiological detection capability of this 3D CNT microelectrode was demonstrated by the distinguished P waves, QRS complex and T waves in the electrocardiogram of the zebrafish heart and the action potential recorded from individual rat hippocampal neurons. The compatibility of integration with ICs, high resolution in space, electrophysiological signals, and non-invasive long-term recording suggest that the 3D CNT microelectrode exhibits promising potential for applications in electrophysiological research and clinical trials.

  19. Impedance biosensor for the rapid detection of Listeria spp. based on aptamer functionalized Pt-interdigitated microelectrodes array

    Science.gov (United States)

    Sidhu, R.; Rong, Y.; Vanegas, D. C.; Claussen, J.; McLamore, E. S.; Gomes, C.

    2016-05-01

    Listeria monocytogenes is one of the most common causes of food illness deaths worldwide, with multiple outbreaks in the United States alone. Current methods to detect foodborne pathogens are laborious and can take several hours to days to produce results. Thus, faster techniques are needed to detect bacteria within the same reliability level as traditional techniques. This study reports on a rapid, accurate, and sensitive aptamer biosensor device for Listeria spp. detection based on platinum interdigitated array microelectrodes (Pt-IDEs). Pt-IDEs with different geometric electrode gaps were fabricated by lithographic techniques and characterized by cyclic voltammetric (CV), electrochemical impedance spectroscopy (EIS), and potential amperometry (DCPA) measurements of reversible redox species. Based on these results, 50 μm Pt-IDE was chosen to further functionalize with a Listeria monocytogenes DNA aptamer selective to the cell surface protein internalin A, via metal-thiol self-assembly at the 5' end of the 47-mer's. EIS analysis was used to detect Listeria spp. without the need for label amplification and pre-concentration steps. The optimized aptamer concentration of 800 nM was selected to capture the bacteria through internalin A binding and the aptamer hairpin structure near the 3' end. The aptasensor was capable of detecting a wide range of bacteria concentration from 10 to 106 CFU/mL at lower detection limit of 5.39 +/- 0.21 CFU/mL with sensitivity of 268.1 +/- 25.40 (Ohms/log [CFU/mL]) in 17 min. The aptamer based biosensor offers a portable, rapid and sensitive alternative for food safety applications with one of the lowest detection limits reported to date.

  20. Polycrystalline-Diamond MEMS Biosensors Including Neural Microelectrode-Arrays

    Directory of Open Access Journals (Sweden)

    Donna H. Wang

    2011-08-01

    Full Text Available Diamond is a material of interest due to its unique combination of properties, including its chemical inertness and biocompatibility. Polycrystalline diamond (poly-C has been used in experimental biosensors that utilize electrochemical methods and antigen-antibody binding for the detection of biological molecules. Boron-doped poly-C electrodes have been found to be very advantageous for electrochemical applications due to their large potential window, low background current and noise, and low detection limits (as low as 500 fM. The biocompatibility of poly-C is found to be comparable, or superior to, other materials commonly used for implants, such as titanium and 316 stainless steel. We have developed a diamond-based, neural microelectrode-array (MEA, due to the desirability of poly-C as a biosensor. These diamond probes have been used for in vivo electrical recording and in vitro electrochemical detection. Poly-C electrodes have been used for electrical recording of neural activity. In vitro studies indicate that the diamond probe can detect norepinephrine at a 5 nM level. We propose a combination of diamond micro-machining and surface functionalization for manufacturing diamond pathogen-microsensors.

  1. Polycrystalline-Diamond MEMS Biosensors Including Neural Microelectrode-Arrays.

    Science.gov (United States)

    Varney, Michael W; Aslam, Dean M; Janoudi, Abed; Chan, Ho-Yin; Wang, Donna H

    2011-08-15

    Diamond is a material of interest due to its unique combination of properties, including its chemical inertness and biocompatibility. Polycrystalline diamond (poly-C) has been used in experimental biosensors that utilize electrochemical methods and antigen-antibody binding for the detection of biological molecules. Boron-doped poly-C electrodes have been found to be very advantageous for electrochemical applications due to their large potential window, low background current and noise, and low detection limits (as low as 500 fM). The biocompatibility of poly-C is found to be comparable, or superior to, other materials commonly used for implants, such as titanium and 316 stainless steel. We have developed a diamond-based, neural microelectrode-array (MEA), due to the desirability of poly-C as a biosensor. These diamond probes have been used for in vivo electrical recording and in vitro electrochemical detection. Poly-C electrodes have been used for electrical recording of neural activity. In vitro studies indicate that the diamond probe can detect norepinephrine at a 5 nM level. We propose a combination of diamond micro-machining and surface functionalization for manufacturing diamond pathogen-microsensors.

  2. Modelling small-patterned neuronal networks coupled to microelectrode arrays

    Science.gov (United States)

    Massobrio, Paolo; Martinoia, Sergio

    2008-09-01

    Cultured neurons coupled to planar substrates which exhibit 'well-defined' two-dimensional network architectures can provide valuable insights into cell-to-cell communication, network dynamics versus topology, and basic mechanisms of synaptic plasticity and learning. In the literature several approaches were presented to drive neuronal growth, such as surface modification by silane chemistry, photolithographic techniques, microcontact printing, microfluidic channel flow patterning, microdrop patterning, etc. This work presents a computational model fit for reproducing and explaining the dynamics exhibited by small-patterned neuronal networks coupled to microelectrode arrays (MEAs). The model is based on the concept of meta-neuron, i.e., a small spatially confined number of actual neurons which perform single macroscopic functions. Each meta-neuron is characterized by a detailed morphology, and the membrane channels are modelled by simple Hodgkin-Huxley and passive kinetics. The two main findings that emerge from the simulations can be summarized as follows: (i) the increasing complexity of meta-neuron morphology reflects the variations of the network dynamics as a function of network development; (ii) the dynamics displayed by the patterned neuronal networks considered can be explained by hypothesizing the presence of several short- and a few long-term distance interactions among small assemblies of neurons (i.e., meta-neurons).

  3. Microelectrode-based dielectric spectroscopy of glucose effect on erythrocytes.

    Science.gov (United States)

    Colella, L; Beyer, C; Fröhlich, J; Talary, M; Renaud, P

    2012-06-01

    The dielectric response of biconcave erythrocytes exposed to D-glucose and L-glucose has been investigated using a double array of planar interdigitated microelectrodes on a glass microchip. Erythrocytes are analyzed under physiological conditions suspended in hypo-osmolar balanced solutions containing different glucose concentrations (0-20 mM). The glucose effect on the cellular dielectric properties is evaluated by analyzing the spectra using two different approaches, the equivalent circuit model and a modified model for ellipsoidal particles. The results show that at elevated glucose concentration (15 mM) the membrane capacitance increases by 36%, whereas the cytosol conductivity slightly decreases with a variation of about 15%. On the contrary, no variation has been registered with L-glucose, a biologically inactive enantiomer of D-glucose. The paper discusses the possible mechanism controlling the membrane dielectric response. As the external D-glucose increases, the number of activated glucose transporter in the erythrocyte membrane raises and the transition from sugar-free state to sugar-bounded state induces a change in the dipole moments and in the membrane capacitance.

  4. On-chip electro-optic tuning of a lithium niobate microresonator with integrated in-plane microelectrodes

    CERN Document Server

    Wang, Min; Fang, Zhiwei; Liao, Yang; Wang, Peng; CHu, Wei; Qiao, Lingling; Lin, Jintian; Fang, Wei; Cheng, Ya

    2016-01-01

    We demonstrate electro-optic tuning of an on-chip lithium niobate microresonator with integrated in-plane microelectrodes. First two metallic microelectrodes on the substrate were formed via femtosecond laser process. Then a high-Q lithium niobate microresonator located between the microelectrodes was fabricated by femtosecond laser direct writing accompanied by focused ion beam milling. Due to the efficient structure designing, high electro-optical tuning coefficient of 3.41 pm/V was observed.

  5. Characterization of electrochemically modified polycrystalline platinum surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Krebs, L.C.; Ishida, Takanobu.

    1991-12-01

    The characterization of electrochemically modified polycrystalline platinum surfaces has been accomplished through the use of four major electrochemical techniques. These were chronoamperometry, chronopotentiommetry, cyclic voltammetry, and linear sweep voltammetry. A systematic study on the under-potential deposition of several transition metals has been performed. The most interesting of these were: Ag, Cu, Cd, and Pb. It was determined, by subjecting the platinum electrode surface to a single potential scan between {minus}0.24 and +1.25 V{sub SCE} while stirring the solution, that the electrocatalytic activity would be regenerated. As a consequence of this study, a much simpler method for producing ultra high purity water from acidic permanganate has been developed. This method results in water that surpasses the water produced by pyrocatalytic distillation. It has also been seen that the wettability of polycrystalline platinum surfaces is greatly dependent on the quantity of oxide present. Oxide-free platinum is hydrophobic and gives a contact angle in the range of 55 to 62 degrees. We have also modified polycrystalline platinum surface with the electrically conducting polymer poly-{rho}-phenylene. This polymer is very stable in dilute sulfuric acid solutions, even under applied oxidative potentials. It is also highly resistant to electrochemical hydrogenation. The wettability of the polymer modified platinum surface is severely dependent on the choice of supporting electrolyte chosen for the electrochemical polymerization. Tetraethylammonium tetrafluoroborate produces a film that is as hydrophobic as Teflon, whereas tetraethylammonium perchlorate produces a film that is more hydrophilic than oxide-free platinum.

  6. Room temperature synthesis of colloidal platinum nanoparticles

    Indian Academy of Sciences (India)

    G Sarala Devi; V J Rao

    2000-12-01

    Efficient preparation of stable dispersions of platinum nanoparticles from platinous chloride (K2PtCl4) was achieved by simultaneous addition of capping polymer material. The size of platinum nanoparticles was controlled by changing the ratio of concentration of capping polymer material to the concentration of platinum cation used. The morphology of colloidal particles were studied by means of UV-visible spectrophotometry and transmission electron microscopy (TEM). Particle size increased with low reagent concentration. The change in absorption spectra with the particle size was observed, i.e. blue shift attributed to decrease in particle size.

  7. Stabilizing platinum in phosphoric acid fuel cells

    Science.gov (United States)

    Remick, R. J.

    1981-10-01

    A carbon substrate for use in fabricating phosphoric acid fuel cell cathodes was modified by catalytic oxidation to stabilize the platinum catalyst by retarding the sintering of small platinum crystallites. Results of 100-hour operational tests confirmed that the rate of platinum surface area loss observed on catalytically oxidized supports was less than that observed with unmodified supports of the same starting material. Fuel cell electrodes fabricated from Vulcan XC-72R, which was modified by catalytic in a nitric oxide atmosphere, produced low platium sintering rates and high activity for the reduction of oxygen in the phosphoric acid environment.

  8. Antitumor effect of arabinogalactan and platinum complex.

    Science.gov (United States)

    Starkov, A K; Zamay, T N; Savchenko, A A; Ingevatkin, E V; Titova, N M; Kolovskaya, O S; Luzan, N A; Silkin, P P; Kuznetsova, S A

    2016-03-01

    The article presents the results of investigation of antitumor properties of platinum-arabinogalactan complex. We showed the ability of the complex to inhibit the growth of Ehrlich ascites tumor cells. It is found that the distribution of the platinum-arabinogalactan complex is not specific only for tumor cells in mice. The complex was found in all tissues and organs examined (ascites cells, embryonic cells, kidney, and liver). The mechanism of action of the arabinogalactan-platinum complex may be similar to cisplatin as the complex is able to accumulate in tumor cells.

  9. Mechanism of Platinum Derivatives Induced Kidney Injury

    Directory of Open Access Journals (Sweden)

    Feifei YAN

    2015-09-01

    Full Text Available Platinum derivatives are the most widely used chemotherapeutic agents to treat solid tumors including ovarian, head and neck, and testicular germ cell tumors, lung cancer, and colorectal cancer. Two major problems exist, however, in the clinic use of platinum derivatives. One is the development of tumor resistance to the drug during therapy, leading to treatment failure. The other is the drug’s toxicity such as the cisplatin’s nephrotoxicity, which limits the dose that can be administered. This paper describes the mechanism of platinum derivatives induced kidney injury.

  10. Hygroscopic particle behavior studied by interdigitated array microelectrode impedance sensors.

    Science.gov (United States)

    Schindelholz, Eric; Tsui, Lok-kun; Kelly, Robert G

    2014-01-09

    The hygroscopic behavior of soluble salts bears importance in many research fields including atmospheric sciences, corrosion, porous building materials, and pharmaceuticals. Several methods have been used to study deliquescence (solid to liquid) and efflorescence (liquid to solid) phase transitions of these salts. In this study, we measured the deliquescence and efflorescence RH values of single salt microparticles deposited on an interdigitated microelectrode sensor via electrical impedance. The salts examined were NaCl, LiCl, NaBr, KCl, and MgCl2. Measured values were in agreement with in situ optical microscopic observations and, with the exception of MgCl2, literature values. In the case of MgCl2, deliquescence occurred at 33% RH and 12-15% RH, with the latter range being previously unreported. The depressed deliquescence RH was hypothesized to be a result of the formation of a metastable MgCl2 hydrate. Incomplete efflorescence of MgCl2 was also observed after exposure to <1.5% RH for up to 22 h due to formation of solid shells which trapped fluid. The phenomena elucidated by these results provide an explanation for the anomalous water retention and uptake behavior of MgCl2 below 33% RH reported elsewhere in the literature. The results presented in this study validate the use of this method as an alternative or complementary method for study of bulk-phase transitions of substrate-deposited particles across a broad RH range. These findings also demonstrate the utility of this method for detection of fluid trapping which cannot be directly ascertained by gravimetric and line-of-sight techniques commonly used in the study of hygroscopic particles.

  11. Acute human brain responses to intracortical microelectrode arrays: Challenges and future prospects

    Directory of Open Access Journals (Sweden)

    Eduardo eFernandez

    2014-07-01

    Full Text Available The emerging field of neuroprosthetics is focused on the development of new therapeutic interventions that will be able to restore some lost neural function by selective electrical stimulation or by harnessing activity recorded from populations of neurons. As more and more patients benefit from these approaches, the interest in neural interfaces has grown significantly and a new generation of penetrating microelectrode arrays are providing unprecedented access to the neurons of the CNS. These microelectrodes have active tip dimensions that are similar in size to neurons and because they penetrate the nervous system, they provide selective access to these cells (within a few microns. However, the very long-term viability of chronically implanted microelectrodes and the capability of recording the same spiking activity over long time periods still remain to be established and confirmed in human studies. Here we review the main responses to acute implantation of microelectrode arrays, and emphasize that it will become essential to control the neural tissue damage induced by these intracortical microelectrodes in order to achieve the high clinical potentials accompanying this technology.

  12. Chitosan coated carbon fiber microelectrode for selective in vivo detection of neurotransmitters in live zebrafish embryos

    Energy Technology Data Exchange (ETDEWEB)

    Ozel, Rifat Emrah [Department of Chemistry and Biomolecular Science, 8 Clarkson Ave, Potsdam, NY 136995810 (United States); Wallace, Kenneth N. [Department of Biology, Clarkson University, Potsdam, NY 136995810 (United States); Andreescu, Silvana, E-mail: eandrees@clarkson.edu [Department of Chemistry and Biomolecular Science, 8 Clarkson Ave, Potsdam, NY 136995810 (United States)

    2011-06-10

    Graphical abstract: Chitosan coated fiber electrodes are sensitive to serotonin detection while rejecting physiological levels of ascorbic acid interferences. - Abstract: We report the development of a chitosan modified carbon fiber microelectrode for in vivo detection of serotonin. We find that chitosan has the ability to reject physiological levels of ascorbic acid interferences and facilitate selective and sensitive detection of in vivo levels of serotonin, a common catecholamine neurotransmitter. Presence of chitosan on the microelectrode surface was investigated using scanning electron microscopy (SEM) and cyclic voltammetry (CV). The electrode was characterized using differential pulse voltammetry (DPV). A detection limit of 1.6 nM serotonin with a sensitivity of 5.12 nA/{mu}M, a linear range from 2 to 100 nM and a reproducibility of 6.5% for n = 6 electrodes were obtained. Chitosan modified microelectrodes selectively measure serotonin in presence of physiological levels of ascorbic acid. In vivo measurements were performed to measure concentration of serotonin in the live embryonic zebrafish intestine. The sensor quantifies in vivo intestinal levels of serotonin while successfully rejecting ascorbic acid interferences. We demonstrate that chitosan can be used as an effective coating to reject ascorbic acid interferences at carbon fiber microelectrodes, as an alternative to Nafion, and that chitosan modified microelectrodes are reliable tools for in vivo monitoring of changes in neurotransmitter levels.

  13. Neural signal recording using microelectrode arrays fabricated on liquid crystal polymer material

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Choong Jae; Oh, Seung Jae; Song, Jong Keun; Kim, Sung June

    2004-01-05

    Microelectrode arrays have been developed for simultaneous multi-channel recordings from nervous systems, typically using silicon substrates. However, it has been known that it is difficult to meet the biocompatibility and durability requirements using silicon and other dielectric materials (SiO{sub 2}, Si{sub 3}N{sub 4}), due to environmental moisture and ions. Additional disadvantage of silicon being the rigid material makes it hard to apply these materials in chronic recording situations. Liquid Crystal Polymer (LCP) was recently introduced as a candidate material for electronic packaging purposes. The material acts as efficient barrier against ions and moisture, a desirable feature for a substrate material of microelectrode arrays. In this paper, we report on the neural recording performed using the LCP-based microelectrode arrays. The cell adhesion on the new material was compared very favorably with that using silicon, SiO{sub 2}, or polyimide material. The microelectrode arrays were patterned with Ti (500 Angst)/Au (3500 Angst) on the LCP film and were employed in both stimulation and recording from rat sciatic nerve. The electrical characteristic of the recorded signal was as good as those using other substrate materials, proving this material as an excellent candidate for next generation microelectrode arrays.

  14. Chitosan coated carbon fiber microelectrode for selective in vivo detection of neurotransmitters in live zebrafish embryos.

    Science.gov (United States)

    Ozel, Rıfat Emrah; Wallace, Kenneth N; Andreescu, Silvana

    2011-06-10

    We report the development of a chitosan modified carbon fiber microelectrode for in vivo detection of serotonin. We find that chitosan has the ability to reject physiological levels of ascorbic acid interferences and facilitate selective and sensitive detection of in vivo levels of serotonin, a common catecholamine neurotransmitter. Presence of chitosan on the microelectrode surface was investigated using scanning electron microscopy (SEM) and cyclic voltammetry (CV). The electrode was characterized using differential pulse voltammetry (DPV). A detection limit of 1.6 nM serotonin with a sensitivity of 5.12 nA/μM, a linear range from 2 to 100 nM and a reproducibility of 6.5% for n=6 electrodes were obtained. Chitosan modified microelectrodes selectively measure serotonin in presence of physiological levels of ascorbic acid. In vivo measurements were performed to measure concentration of serotonin in the live embryonic zebrafish intestine. The sensor quantifies in vivo intestinal levels of serotonin while successfully rejecting ascorbic acid interferences. We demonstrate that chitosan can be used as an effective coating to reject ascorbic acid interferences at carbon fiber microelectrodes, as an alternative to Nafion, and that chitosan modified microelectrodes are reliable tools for in vivo monitoring of changes in neurotransmitter levels.

  15. Silicon-substrate microelectrode arrays for parallel recording of neural activity in peripheral and cranial nerves.

    Science.gov (United States)

    Kovacs, G T; Storment, C W; Halks-Miller, M; Belczynski, C R; Della Santina, C C; Lewis, E R; Maluf, N I

    1994-06-01

    A new process for the fabrication of regeneration microelectrode arrays for peripheral and cranial nerve applications is presented. This type of array is implanted between the severed ends of nerves, the axons of which regenerate through via holes in the silicon and are thereafter held fixed with respect to the microelectrodes. The process described is designed for compatibility with industry-standard CMOS or BiCMOS processes (it does not involve high-temperature process steps nor heavily-doped etch-stop layers), and provides a thin membrane for the via holes, surrounded by a thick silicon supporting rim. Many basic questions remain regarding the optimum via hole and microelectrode geometries in terms of both biological and electrical performance of the implants, and therefore passive versions were fabricated as tools for addressing these issues in on-going work. Versions of the devices were implanted in the rat peroneal nerve and in the frog auditory nerve. In both cases, regeneration was verified histologically and it was observed that the regenerated nerves had reorganized into microfascicles containing both myelinated and unmyelinated axons and corresponding to the grid pattern of the via holes. These microelectrode arrays were shown to allow the recording of action potential signals in both the peripheral and cranial nerve setting, from several microelectrodes in parallel.

  16. Brain machine interfaces combining microelectrode arrays with nanostructured optical biochemical sensors

    Science.gov (United States)

    Hajj-Hassan, Mohamad; Gonzalez, Timothy; Ghafer-Zadeh, Ebrahim; Chodavarapu, Vamsy; Musallam, Sam; Andrews, Mark

    2009-02-01

    Neural microelectrodes are an important component of neural prosthetic systems which assist paralyzed patients by allowing them to operate computers or robots using their neural activity. These microelectrodes are also used in clinical settings to localize the locus of seizure initiation in epilepsy or to stimulate sub-cortical structures in patients with Parkinson's disease. In neural prosthetic systems, implanted microelectrodes record the electrical potential generated by specific thoughts and relay the signals to algorithms trained to interpret these thoughts. In this paper, we describe novel elongated multi-site neural electrodes that can record electrical signals and specific neural biomarkers and that can reach depths greater than 8mm in the sulcus of non-human primates (monkeys). We hypothesize that additional signals recorded by the multimodal probes will increase the information yield when compared to standard probes that record just electropotentials. We describe integration of optical biochemical sensors with neural microelectrodes. The sensors are made using sol-gel derived xerogel thin films that encapsulate specific biomarker responsive luminophores in their nanostructured pores. The desired neural biomarkers are O2, pH, K+, and Na+ ions. As a prototype, we demonstrate direct-write patterning to create oxygen-responsive xerogel waveguide structures on the neural microelectrodes. The recording of neural biomarkers along with electrical activity could help the development of intelligent and more userfriendly neural prosthesis/brain machine interfaces as well as aid in providing answers to complex brain diseases and disorders.

  17. Platinum-Resistor Differential Temperature Sensor

    Science.gov (United States)

    Kolbly, R. B.; Britcliffe, M. J.

    1985-01-01

    Platinum resistance elements used in bridge circuit for measuring temperature difference between two flowing liquids. Temperature errors with circuit are less than 0.01 degrees C over range of 100 degrees C.

  18. Fate of platinum metals in the environment.

    Science.gov (United States)

    Pawlak, Justyna; Łodyga-Chruścińska, Elżbieta; Chrustowicz, Jakub

    2014-07-01

    For many years now automotive exhaust catalysts have been used to reduce the significant amounts of harmful chemical substances generated by car engines, such as carbon monoxide, nitrogen oxides, and aromatic hydrocarbons. Although they considerably decrease environmental contamination with the above-mentioned compounds, it is known that catalysts contribute to the environmental load of platinum metals (essential components of catalysts), which are released with exhaust fumes. Contamination with platinum metals stems mainly from automotive exhaust converters, but other major sources also exist. Since platinum group elements (PGEs): platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru) and iridium (Ir) seem to spread in the environment and accumulate in living organisms, they may pose a threat to animals and humans. This paper discusses the modes and forms of PGE emission as well as their impact on the environment and living organisms.

  19. VB Platinum Tile & Carpet, Inc. Information Sheet

    Science.gov (United States)

    VB Platinum Tile & Carpet, Inc. (the Company) is located in Bristow, Virginia. The settlement involves renovation activities conducted at a property constructed prior to 1978, located in Washington, DC.

  20. Stabilizing platinum in phosphoric acid fuel cells

    Science.gov (United States)

    Remick, R. J.

    1982-01-01

    Platinum sintering on phosphoric acid fuel cell cathodes is discussed. The cathode of the phosphoric acid fuel cell uses a high surface area platinum catalyst dispersed on a conductive carbon support to minimize both cathode polarization and fabrication costs. During operation, however, the active surface area of these electrodes decreases, which in turn leads to decreased cell performance. This loss of active surface area is a major factor in the degradation of fuel cell performance over time.

  1. Preparation of metal nanoband microelectrode on poly(dimethylsiloxane) for chip-based amperometric detection

    Energy Technology Data Exchange (ETDEWEB)

    Chen Shaopeng; Wu Jian; Yu Xiaodong [Key Laboratory of Analytical Chemistry for Life Science, Ministry of Education of China, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China); Xu Jingjuan, E-mail: xujj@nju.edu.cn [Key Laboratory of Analytical Chemistry for Life Science, Ministry of Education of China, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China); Chen Hongyuan [Key Laboratory of Analytical Chemistry for Life Science, Ministry of Education of China, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China)

    2010-04-30

    We proposed herein a novel approach for fabricating nanoband microelectrodes for electrochemical detection on an electrophoresis microchip. The metal films were first obtained via region-selective electroless deposition of gold or copper films on PDMS substrates by selective region plasma oxidation through shadow masking. Both metal films show uniform surfaces with the thickness at the level of 100 nm. By casting another PDMS layer on the metal films, the cross section of the sandwich structures can be used as nanoband microelectrodes, which can be renewed just by cutting. These nanoband microelectrodes are successfully used as electrochemical detectors in microchip electrophoresis for the detection of amino acids, proteins and neurotransmitter molecules. Moreover, integrating an Au-Cu double-metal detector with a double-channel electrophoresis system, we can easily distinguish electroactive amino acids from that of non-electroactive amino acids.

  2. Simulation of an ac electro-osmotic pump with step microelectrodes

    Science.gov (United States)

    Kim, Byoung Jae; Lee, Seung-Hyun; Rezazadeh, Soghra; Sung, Hyung Jin

    2011-05-01

    Pumps with step microelectrodes subjected to an ac voltage are known to have faster pumping rates than those with planar asymmetric microelectrodes. The driving force for pumping in these systems is ac electro-osmosis. This paper aims to understand the flow behaviors of pumps with step microelectrodes by using a realistic model applicable to high external voltages. This model takes the steric effect due to the finite sizes of ions into account and copes with the exponential sensitivity of the counterion concentration to voltage. The effects on the pumping flow rate of varying the pump parameters were investigated. The geometrical parameters were optimized, and the effects of varying the ac frequency and amplitude were examined. The electrical potential of the fluid and the electrical charge at the electrode surface were solved simultaneously, and the Stokes equation was used to describe the fluid flow.

  3. Fabrication of graphene coated carbon fiber microelectrode for highly sensitive detection application.

    Science.gov (United States)

    Bai, Jie; Wang, Xiaojuan; Meng, Yuning; Zhang, Hui-Min; Qu, Liangti

    2014-01-01

    Graphene, as a novel carbon nanomaterial, exhibits superior performance in electrochemical sensors. Here, graphene was applied to the microelectrode system by a simple method. A novel graphene coating carbon fiber microelectrode (G-CFM) was fabricated by electrodepositing graphene on the surface of carbon fiber. The fabrication method is fast and simple. Scanning electron microscopy and Raman spectroscopy demonstrated that carbon fiber was successfully modified by graphene. The electrochemical behavior of G-CFM was characterized by potassium ferricyanide and dopamine (DA). The electrode exhibited much larger current response and less overpotential response, compared to CFM. The microsensor for DA showed good sensitivity and selectivity, and the electrode had good stability. It is believable that the unique characteristic of graphene holds promise for the advanced microelectrode system for highly sensitive detection of various targets.

  4. Microelectrode arrays with overlapped diffusion layers as electroanalytical detectors: theory and basic applications.

    Science.gov (United States)

    Tomčík, Peter

    2013-10-11

    This contribution contains a survey of basic literature dealing with arrays of microelectrodes with overlapping diffusion layers as prospective tools in contemporary electrochemistry. Photolithographic thin layer technology allows the fabrication of sensors of micrometric dimensions separated with a very small gap. This fact allows the diffusion layers of single microelectrodes to overlap as members of the array. Various basic types of microelectrode arrays with interacting diffusion layers are described and their analytical abilities are accented. Theoretical approaches to diffusion layer overlapping and the consequences of close constitution effects such as collection efficiency and redox cycling are discussed. Examples of basis applications in electroanalytical chemistry such as amperometric detectors in HPLC and substitutional stripping voltammetry are also given.

  5. Microelectrode Arrays with Overlapped Diffusion Layers as Electroanalytical Detectors: Theory and Basic Applications

    Directory of Open Access Journals (Sweden)

    Peter Tomčík

    2013-10-01

    Full Text Available This contribution contains a survey of basic literature dealing with arrays of microelectrodes with overlapping diffusion layers as prospective tools in contemporary electrochemistry. Photolithographic thin layer technology allows the fabrication of sensors of micrometric dimensions separated with a very small gap. This fact allows the diffusion layers of single microelectrodes to overlap as members of the array. Various basic types of microelectrode arrays with interacting diffusion layers are described and their analytical abilities are accented. Theoretical approaches to diffusion layer overlapping and the consequences of close constitution effects such as collection efficiency and redox cycling are discussed. Examples of basis applications in electroanalytical chemistry such as amperometric detectors in HPLC and substitutional stripping voltammetry are also given.

  6. Micro-electrode flux estimation confirms that the Solanum pimpinellifolium cu3 mutant still responds to systemin

    NARCIS (Netherlands)

    Lanfermeijer, Frank C.; Staal, Marten; Malinowski, Robert; Stratmann, Johannes W.; Elzenga, J. Theo M.

    2008-01-01

    In this study, we introduce the Micro-Electrode Ion Flux Estimation technique as a sensitive and accurate technique to study systemin-induced changes in ion fluxes from isolated nearly intact plant tissues. Our results demonstrate the effectiveness and value of the Micro-Electrode Ion Flux Estimatio

  7. The Effect of Residual Endotoxin Contamination on the Neuroinflammatory Response to Sterilized Intracortical Microelectrodes.

    Science.gov (United States)

    Ravikumar, Madhumitha; Hageman, Daniel J; Tomaszewski, William H; Chandra, Gabriella M; Skousen, John L; Capadona, Jeffrey R

    2014-05-01

    A major limitation to the use of microelectrode technologies in both research and clinical applications is our inability to consistently record high quality neural signals. There is increasing evidence that recording instability is linked, in part, to neuroinflammation. A number of factors including extravasated blood products and macrophage released soluble factors are believed to mediate neuroinflammation and the resulting recording instability. However, the roles of other inflammatory stimuli, such as residual endotoxin contamination, are poorly understood. Therefore, to determine the effect of endotoxin contamination we examined the brain tissue response of C57/BL6 mice to non-functional microelectrodes with a range of endotoxin levels. Endotoxin contamination on the sterilized microelectrodes was measured using a limulus amebocyte lysate test following FDA guidelines. Microelectrodes sterilized by autoclave, dry heat, or ethylene oxide gas, resulted in variable levels of residual endotoxins of 0.55 EU/mL, 0.22 EU/mL, and 0.11 EU/mL, respectively. Histological evaluation at two weeks showed a direct correlation between microglia/macrophage activation and endotoxin levels. Interestingly, astrogliosis, neuronal loss, and blood brain barrier dysfunction demonstrated a threshold-dependent response to bacterial endotoxins. However, at sixteen weeks, no histological differences were detected, regardless of initial endotoxin levels. Therefore, our results demonstrate that endotoxin contamination, within the range examined, contributes to initial but not chronic microelectrode associated neuroinflammation. Our results suggest that minimizing residual endotoxins may impact early recording quality. To this end, endotoxins should be considered as a potent stimulant to the neuroinflammatory response to implanted intracortical microelectrodes.

  8. In Vivo Monitoring of H2O2 with Polydopamine and Prussian Blue-coated Microelectrode.

    Science.gov (United States)

    Li, Ruixin; Liu, Xiaomeng; Qiu, Wanling; Zhang, Meining

    2016-08-02

    In vivo monitoring of hydrogen peroxide (H2O2) in the brain is of importance for understanding the function of both reactive oxygen species (ROS) and signal transmission. Producing a robust microelectrode for in vivo measurement of H2O2 is challenging due to the complex brain environment and the instability of electrocatalysts employed for the reduction of H2O2. Here, we develop a new kind of microelectrode for in vivo monitoring of H2O2, which is prepared by, first, electrodeposition of Prussian blue (PB) onto carbon nanotube (CNT) assembled carbon fiber microelectrodes (CFEs) and then overcoating of the CFEs with a thin membrane of polydopamine (PDA) through self-polymerization. Scanning electron microscopic and X-ray proton spectroscopic results confirm the formation of PDA/PB/CNT/CFEs. The PDA membrane enables PB-based electrodes to show high stability in both in vitro and in vivo studies and to stably catalyze the electrochemical reduction of H2O2. The microelectrode is selective for in vivo measurements of H2O2, interference-free from O2 and other electroactive species coexisting in the brain. These properties, along with good linearity, high biocompatibility, and stability toward H2O2, substantially enable the microelectrode to track H2O2 changes in vivo during electrical stimulation and microinfusion of H2O2 and drug, which demonstrates that the microelectrode could be well suited for in vivo monitoring of dynamic changes of H2O2 in rat brain.

  9. Correlations between histology and neuronal activity recorded by microelectrodes implanted chronically in the cerebral cortex

    Science.gov (United States)

    McCreery, Douglas; Cogan, Stuart; Kane, Sheryl; Pikov, Victor

    2016-06-01

    Objective. To quantify relations between the neuronal activity recorded with chronically-implanted intracortical microelectrodes and the histology of the surrounding tissue, using radial distance from the tip sites and time after array implantation as parameters. Approach. ‘Utah’-type intracortical microelectrode arrays were implanted into cats’ sensorimotor cortex for 275-364 days. The brain tissue around the implants was immuno-stained for the neuronal marker NeuN and for the astrocyte marker GFAP. Pearson’s product-moment correlations were used to quantify the relations between these markers and the amplitudes of the recorded neuronal action potentials (APs) and their signal-to-noise ratios (S/N). Main results. S/N was more stable over post-implant time than was AP amplitude, but its increased correlation with neuronal density after many months indicates ongoing loss of neurons around the microelectrodes. S/N was correlated with neuron density out to at least 140 μm from the microelectrodes, while AP amplitude was correlated with neuron density and GFAP density within ˜80 μm. Correlations between AP amplitude and histology markers (GFAP and NeuN density) were strongest immediately after implantation, while correlation between the neuron density and S/N was strongest near the time the animals were sacrificed. Unlike AP amplitude, there was no significant correlation between S/N and density of GFAP around the tip sites. Significance. Our findings indicate an evolving interaction between changes in the tissue surrounding the microelectrodes and the microelectrode’s electrical properties. Ongoing loss of neurons around recording microelectrodes, and the interactions between their delayed electrical deterioration and early tissue scarring around the tips appear to pose the greatest threats to the microelectrodes’ long-term functionality.

  10. Application of thin-shielded mercury microelectrodes in anodic stripping voltammetry.

    Science.gov (United States)

    Daniele, Salvatore; Bragato, Carlo; Baldo, M Antonietta; Ciani, Ilenia

    2008-10-19

    The performance in anodic stripping voltammetry (ASV) of hemispherical mercury microelectrodes, fabricated by electrodeposition of liquid mercury on the surface of Pt microdisks which were surrounded by a rather thick or thin insulating shield, was compared. The Pt microdisks were produced by sealing a wire of 25 microm diameter into a glass capillary, and by coating the cylindrical length of the Pt wire with a cathodic electrophoretic paint. The ratio of the overall tip radius b, to the basal radius of the electrode a, so-called RG=b/a, was equal to 110+/-10 and 1.52+/-0.01 for the thick- and thin-shielded microdisk, respectively. The mercury microelectrodes were characterized by cyclic voltammetry at 1 mVs(-1), in 1mM Ru(NH(3))(6)(3+) aqueous solution. The steady-state voltammogram recorded with the thin-shielded mercury microelectrode displayed less hysteresis, while the steady-state current was about 30% higher than that of the thicker one. This was a consequence of the additional flux due to diffusion from behind the plane of the electrode. The flux enhancement, which was operative at the thin-shielded mercury microelectrode during the deposition step in the ASV experiments, allowed recording stripping peaks for Cd and Pb, which resulted about 32% larger than those recorded at the thicker shielded mercury microelectrode, under same experimental conditions. The usefulness of the thin-shielded mercury microelectrode for ASV measurements in real samples was verified by determining the content of heavy metal ions released in the pore water (pH 4.5) of a soil slurry.

  11. In-Vivo Characterization of Glassy Carbon Micro-Electrode Arrays for Neural Applications and Histological Analysis of the Brain Tissue

    Science.gov (United States)

    Vomero, Maria

    The aim of this work is to fabricate and characterize glassy carbon Microelectrode Arrays (MEAs) for sensing and stimulating neural activity, and conduct histological analysis of the brain tissue after the implant to determine long-term performance. Neural applications often require robust electrical and electrochemical response over a long period of time, and for those applications we propose to replace the commonly used noble metals like platinum, gold and iridium with glassy carbon. We submit that such material has the potential to improve the performances of traditional neural prostheses, thanks to better charge transfer capabilities and higher electrochemical stability. Great interest and attention is given in this work, in particular, to the investigation of tissue response after several weeks of implants in rodents' brain motor cortex and the associated materials degradation. As part of this work, a new set of devices for Electrocorticography (ECoG) has been designed and fabricated to improve durability and quality of the previous generation of devices, designed and manufactured by the same research group in 2014. In-vivo long-term impedance measurements and brain activity recordings were performed to test the functionality of the neural devices. In-vitro electrical characterization of the carbon electrodes, as well as the study of the adhesion mechanisms between glassy carbon and different substrates is also part of the research described in this book.

  12. Direct Growth of Carbon Nanotubes on New High-Density 3D Pyramid-Shaped Microelectrode Arrays for Brain-Machine Interfaces

    Directory of Open Access Journals (Sweden)

    Bahareh Ghane Motlagh

    2016-09-01

    Full Text Available Silicon micromachined, high-density, pyramid-shaped neural microelectrode arrays (MEAs have been designed and fabricated for intracortical 3D recording and stimulation. The novel architecture of this MEA has made it unique among the currently available micromachined electrode arrays, as it has provided higher density contacts between the electrodes and targeted neural tissue facilitating recording from different depths of the brain. Our novel masking technique enhances uniform tip-exposure for variable-height electrodes and improves process time and cost significantly. The tips of the electrodes have been coated with platinum (Pt. We have reported for the first time a selective direct growth of carbon nanotubes (CNTs on the tips of 3D MEAs using the Pt coating as a catalyzer. The average impedance of the CNT-coated electrodes at 1 kHz is 14 kΩ. The CNT coating led to a 5-fold decrease of the impedance and a 600-fold increase in charge transfer compared with the Pt electrode.

  13. A PARYLENE-BASED MICROELECTRODE ARRAY IMPLANT FOR SPINAL CORD STIMULATION IN RATS.

    Science.gov (United States)

    Nandra, Mandheerej S; Lavrov, Igor A; Edgerton, V Reggie; Tai, Yu-Chong

    2011-01-23

    The design and fabrication of an epidural spinal cord implant using a parylene-based microelectrode array is presented. Rats with hindlimb paralysis from a complete spinal cord transection were implanted with the device and studied for up to eight weeks, where we have demonstrated recovery of hindlimb stepping functionality through pulsed stimulation. The microelectrode array allows for a high degree of freedom and specificity in selecting the site of stimulation compared to wire-based implants, and triggers varied biological responses that can lead to an increased understanding of the spinal cord and locomotion recovery for victims of spinal cord injury.

  14. Concept for E.coli detection using interdigitated microelectrode impedance sensor.

    Science.gov (United States)

    Settu, Kalpana; Liu, Jen-Tsai; Chen, Ching-Jung; Tsai, Jang-Zern; Chang, Shwu Jen

    2013-01-01

    This paper presents the concept to detect Escherichia coli O157:H7 based on electrochemical impedance spectroscopy at interdigitated microelectrode. Interdigitated microelectrode structures was designed and fabricated, with glass as substrate material and gold electrodes. The performance of the sensors was studied by measuring the capacitance in air and impedance spectra in DI water. The feasibility of the fabricated sensor for detecting different concentrations of Escherichia coli in water was demonstrated. Electrochemical impedance spectroscopy (EIS) was employed as the detection technique. The impedance based response significant change for different E.coli concentrations in the frequency range between 1 kHz to 100 kHz.

  15. Strain response of stretchable micro-electrodes: Controlling sensitivity with serpentine designs and encapsulation

    Energy Technology Data Exchange (ETDEWEB)

    Gutruf, Philipp; Walia, Sumeet; Nur Ali, Md; Sriram, Sharath, E-mail: sharath.sriram@gmail.com, E-mail: madhu.bhaskaran@gmail.com; Bhaskaran, Madhu, E-mail: sharath.sriram@gmail.com, E-mail: madhu.bhaskaran@gmail.com [Functional Materials and Microsystems Research Group, School of Electrical and Computer Engineering, RMIT University, GPO Box 2476, Melbourne, Victoria (Australia)

    2014-01-13

    The functionality of flexible electronics relies on stable performance of thin film micro-electrodes. This letter investigates the behavior of gold thin films on polyimide, a prevalent combination in flexible devices. The dynamic behavior of gold micro-electrodes has been studied by subjecting them to stress while monitoring their resistance in situ. The shape of the electrodes was systematically varied to examine resistive strain sensitivity, while an additional encapsulation was applied to characterize multilayer behavior. The realized designs show remarkable tolerance to repetitive strain, demonstrating that curvature and encapsulation are excellent approaches for minimizing resistive strain sensitivity to enable durable flexible electronics.

  16. Platinum in Earth surface environments

    Science.gov (United States)

    Reith, F.; Campbell, S. G.; Ball, A. S.; Pring, A.; Southam, G.

    2014-04-01

    Platinum (Pt) is a rare precious metal that is a strategic commodity for industries in many countries. The demand for Pt has more than doubled in the last 30 years due to its role in the catalytic conversion of CO, hydrocarbons and NOx in modern automobiles. To explore for new Pt deposits, process ores and deal with ecotoxicological effects of Pt mining and usage, the fundamental processes and pathways of Pt dispersion and re-concentration in surface environments need to be understood. Hence, the aim of this review is to develop a synergistic model for the cycling of Pt in Earth surface environments. This is achieved by integrating the geological/(biogeo)chemical literature, which focuses on naturally occurring Pt mobility around ore deposits, with the environmental/ecotoxicological literature dealing with anthropogenic Pt dispersion. In Pt deposits, Pt occurs as sulfide-, telluride- and arsenide, native metal and alloyed to other PGEs and iron (Fe). Increased mining and utilization of Pt combined with the burning of fossil fuels have led to the dispersion of Pt-containing nano- and micro-particles. Hence, soils and sediments in industrialized areas, urban environments and along major roads are now commonly Pt enriched. Platinum minerals, nuggets and anthropogenic particles are transformed by physical and (bio)geochemical processes. Complexation of Pt ions with chloride, thiosulfate, ammonium, cyanide, low- and high molecular weight organic acids (LMWOAs and HMWOAs) and siderophores can facilitate Pt mobilization. Iron-oxides, clays, organic matter and (micro)biota are known to sequester Pt-complexes and -particles. Microbes and plants are capable of bioaccumulating and reductively precipitating mobile Pt complexes. Bioaccumulation can lead to toxic effects on plants and animals, including humans. (Bio)mineralization in organic matter-rich sediments can lead to the formation of secondary Pt particles and -grains. Ultimately, Pt is enriched in oceanic sediments

  17. computer modeling ter modeling ter modeling of platinum reforming ...

    African Journals Online (AJOL)

    eobe

    naphtha to complex chemical reactions, at h temperature and ... at is leaving any stage of the platinum reforming reactors in terms of ... In this study, only platinum reforming .... IV. Hydrocracking of paraffinic hydrocarbons: +. →. ( +. +. +. +. ) (18).

  18. Platinum uptake from chloride solutions using biosorbents

    Directory of Open Access Journals (Sweden)

    Mehmet Hakan Morcali

    2013-04-01

    Full Text Available Present work investigates platinum uptake from synthetically prepared, dilute platinum-bearing solutions using biomass residues, i.e. pistachio nut shell and rice husk, which are abundant in Turkey, and provides a comparison between these two biosorbents. Effects of the different uptake parameters, sorbent dosage, contact time, temperature and pH of solution on platinum uptake (% were studied in detail on a batch sorption. Before the pistachio nut shell was activated, platinum uptake (% was poor compared to the rice husk. However, after the pistachio nut shell was activated at 1000 °C under an argon atmosphere, the platinum uptake (% increased two-fold. The pistachio nut shell (original and activated and rice husk were shown to be better than commercially available activated carbon in terms of adsorption capacity. These two sorbents have also been characterized by FTIR and SEM. Adsorption equilibrium data best complied with the Langmuir isotherm model. Maximum adsorption capacities, Qmax, at 25 °C were found to be 38.31 and 42.02 mg.g- 1for the activated pistachio nut shell and rice husk, respectively. Thermodynamic calculations using the measured ∆H°, ∆S° and ∆G° values indicate that the uptake process was spontaneous and endothermic. The experimental data were shown to be fit the pseudo-second-order kinetic model.

  19. Fast prototyping of conducting polymer microelectrodes using resistance-controlled high precision drilling

    DEFF Research Database (Denmark)

    Kafka, Jan Robert; Geschke, Oliver; Skaarup, Steen

    2011-01-01

    ) covering a PEDOT layer. The sudden drop in electrical resistance between the metal drill and the PEDOT layer upon physical contact was employed as stop criterion for the drilling process. Arrays of 3×3 microelectrodes of diameter 30μm or 100μm, respectively, and having center-to-center electrode spacings...

  20. Modeling of the cell-electrode interface noise for microelectrode arrays.

    Science.gov (United States)

    Guo, Jing; Yuan, Jie; Chan, Mansun

    2012-12-01

    Microelectrodes are widely used in the physiological recording of cell field potentials. As microelectrode signals are generally in the μV range, characteristics of the cell-electrode interface are important to the recording accuracy. Although the impedance of the microelectrode-solution interface has been well studied and modeled in the past, no effective model has been experimentally verified to estimate the noise of the cell-electrode interface. Also in existing interface models, spectral information is largely disregarded. In this work, we developed a model for estimating the noise of the cell-electrode interface from interface impedances. This model improves over existing noise models by including the cell membrane capacitor and frequency dependent impedances. With low-noise experiment setups, this model is verified by microelectrode array (MEA) experiments with mouse muscle myoblast cells. Experiments show that the noise estimated from this model has models. With this model, noise of the cell-electrode interface can be estimated by simply measuring interface impedances. This model also provides insights for micro- electrode design to achieve good recording signal-to-noise ratio.

  1. Development of a Microelectrode Array Sensing Platform for Combination Electrochemical and Spectrochemical Aqueous Ion Testing.

    Science.gov (United States)

    Gardner, Robert D; Zhou, Anhong; Zufelt, Nephi A

    2009-02-02

    A microelectrode array sensor platform was designed and fabricated to increase diversity, flexibility, and versatility of testing capabilities over that of traditionally reported sensor platforms. These new sensor platforms consist of 18 individual addressable microelectrodes, photolithography fabricated, that employ a glass base substrate and a resist polymer layer that acts as an insulating agent to protect the circuitry and wiring of the sensor from undesired solution interactions. Individually addressable microelectrodes increase diversity by allowing isolated electrochemical testing between electrodes, global array testing, or some combination of electrodes to perform electrochemical methods. Furthermore, because of the optical transparency of the glass base substrate and the resist mask layer, along with the small size of the electrode array, spectrochemical analysis is possible within the sample area that acts as electrochemical cell and cuvette, while the microelectrode array passively resides within the optical path length during spectrochemical testing. This unique arrangement offers improved testing possibilities for various applications, including simultaneous electrochemical and spectrochemical analysis in environmental testing, identification or quantification of possible species for bioavailability in the biotechnology field, and process control in industrial applications. Electrochemical characteristics and spectrochemcial use of the sensor platform are proven with potassium ferricyanide, an electrochemical standard analyte, and electrochemical measurements are compared against a commercially available working electrode of similar size. Additionally, the electrochemical method of differential pulse anodic stripping voltammetry is performed with the sensor platform to detect copper and lead heavy metal ions in aqueous solution, demonstrating the potential for use with environmental samples.

  2. Carbon nanotube fiber microelectrodes show a higher resistance to dopamine fouling.

    Science.gov (United States)

    Harreither, Wolfgang; Trouillon, Raphaël; Poulin, Philippe; Neri, Wilfrid; Ewing, Andrew G; Safina, Gulnara

    2013-08-06

    We have compared the properties and resistance to DA fouling of a carbon nanotube fiber (CNTF) microelectrode to a traditional carbon fiber (CF) microelectrode. These two materials show comparable electrochemical activities for outer-sphere and inner-sphere redox reactions. Although the CNTF might have a higher intrinsic RC constant, thus limiting its high-frequency behavior, the CNTF shows a significantly higher durability than the CF in terms of electrode stability. During constant oxidation of 100 μM DA, the signal measured by the CNTF microelectrode shows a 2-h window over which no decrease in current is observed. Under the same conditions, the current obtained at the CF microelectrode decreases by almost 50%. A model of the fouling process, assuming the formation of growing patches of insulator on the surface, has been compared to the data. This model is found to be in good agreement with our results and indicates a growth rate of the patches in the 0.1-2 nm s(-1) range.

  3. Novel estradiol sensors based on carbon nanotube multilayer modified gold hair microelectrodes

    Institute of Scientific and Technical Information of China (English)

    Jun Hui Xu; Cheng Guo Hu; Sheng Shui Hu

    2009-01-01

    Multi-walled carbon nanotube multilayers were modified onto a newly proposed gold hair microelectrode via a simple layer-by-layer assembling method. The resulting electrode showed a sensitive oxidation response to estradiol with detection limit as low as 1.0×10~(-8) mol/L, foreseeing a promising approach to the fabrication of high-sensitive microsensors.

  4. Characterization of Early Cortical Neural Network Development in Multiwell Microelectrode Array Plates

    Science.gov (United States)

    We examined the development of neural network activity using microelectrode array (MEA) recordings made in multi-well MEA plates (mwMEAs) over the first 12 days in vitro (DIV). In primary cortical cultures made from postnatal rats, action potential spiking activity was essentiall...

  5. Characterization of Early Cortical Neural Network Development in Multiwell Microelectrode Array Plates

    Science.gov (United States)

    We examined the development of neural network activity using microelectrode array (MEA) recordings made in multi-well MEA plates (mwMEAs) over the first 12 days in vitro (DIV). In primary cortical cultures made from postnatal rats, action potential spiking activity was essentiall...

  6. Performance Improvement by Layout Designs of Conductive Polymer Microelectrode Based Impedimetric Biosensors

    DEFF Research Database (Denmark)

    Rosati, Giulio; Daprà, Johannes; Cherré, Solène

    2014-01-01

    In this work we present a theoretical, computational, and experimental evaluation of the performance of an impedimetric biosensor based on interdigitated conductive polymer (PEDOT:TsO) microelectrodes in a microfluidic system. The influence of the geometry of the electrodes and microchannels...

  7. Electrochemical detection of single cancer and healthy cell collisions on a microelectrode.

    Science.gov (United States)

    Dick, Jeffrey E

    2016-09-18

    The electrochemical detection of single cancer cells and healthy cells is reported. Detection was achieved by monitoring the consumption of a single cell's contents upon its collisions with a microelectrode in the presence of surfactant. The electrochemical response between acute lymphoblastic lymphoma T-cells and healthy thymocytes differed by two orders of magnitude.

  8. Extensions of Callendar's equations for platinum resistance thermometry

    DEFF Research Database (Denmark)

    Diamond, Joseph M.

    1969-01-01

    measurements where the platinum thermometer and the measurement means may be less than ideal. To this end. Callendar's definition of platinum temperature is generalized to mean the temperature found by linear interpolation with a platinum thermometer between given fixed points and using a given measurement...

  9. Platinum Publications as of April 30, 2014 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 21 prestigious science journals. This list represents new publications generated from PubMed as of the date shown above. Articles designated as Platinum Highlights are noteworthy articles selected by Dr. Craig Reynolds, associate director, National Cancer Institute, from among the most recently published Platinum Publications.

  10. Platinum Publications, September 30–October 27, 2016 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 42 prestigious science journals. This list represents articles published during the time period shown above, as generated from PubMed. Articles designated as Platinum Highlights are noteworthy articles selected by Dr. Craig Reynolds, associate director, National Cancer Institute, from among the most recently published Platinum Publications.

  11. Platinum Publications as of June 25, 2014 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 21 prestigious science journals. This list represents new publications generated from PubMed as of the date shown above. Articles designated as Platinum Highlights are noteworthy articles selected by Dr. Craig Reynolds, associate director, National Cancer Institute, from among the most recently published Platinum Publications.

  12. Platinum Publications, July 1–July 28, 2016 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 42 prestigious science journals. This list represents articles published during the time period shown above, as generated from PubMed. Articles designated as Platinum Highlights are noteworthy articles selected by Dr. Craig Reynolds, associate director, National Cancer Institute, from among the most recently published Platinum Publications.

  13. Platinum Publications as of March 6, 2014 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 21 prestigious science journals. This list represents new publications generated from PubMed as of the date shown above. Articles designated as Platinum Highlights are noteworthy articles selected by Dr. Craig Reynolds, associate director, National Cancer Institute, from among the most recently published Platinum Publications.

  14. Platinum Publications, October 1–29, 2015 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 42 prestigious science journals. This list represents articles published during the time period shown above, as generated from PubMed. Articles designated as Platinum Highlights are noteworthy articles selected by Dr. Craig Reynolds, associate director, National Cancer Institute, from among the most recently published Platinum Publications.

  15. Platinum Publications, December 1–December 29, 2016 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 42 prestigious science journals. This list represents articles published during the time period shown above, as generated from PubMed. Articles designated as Platinum Highlights are noteworthy articles selected from among the most recently published Platinum Publications.

  16. Platinum Publications as of May 29, 2014 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 21 prestigious science journals. This list represents new publications generated from PubMed as of the date shown above. Articles designated as Platinum Highlights are noteworthy articles selected by Dr. Craig Reynolds, associate director, National Cancer Institute, from among the most recently published Platinum Publications.

  17. Platinum Publications as of September 25, 2014 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 21 prestigious science journals. This list represents new publications generated from PubMed as of the date shown above. Articles designated as Platinum Highlights are noteworthy articles selected by Dr. Craig Reynolds, associate director, National Cancer Institute, from among the most recently published Platinum Publications.

  18. Platinum Publications, January 26–February 28, 2017 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 42 prestigious science journals. This list represents articles published during the time period shown above, as generated from PubMed. Articles designated as Platinum Highlights are noteworthy articles selected from among the most recently published Platinum Publications.

  19. Platinum Publications as of December 3, 2013 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 21 prestigious science journals. This list represents new publications generated from PubMed as of the date shown above. Articles designated as Platinum Highlights are noteworthy articles selected by Dr. Craig Reynolds, associate director, National Cancer Institute, from among the most recently published Platinum Publications.

  20. Deposition of the platinum crystals on the carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A new technique and the affecting factors for depositing platinum on the carbon nanotubes were investigated. The results show that the deposited platinum crystals in the atmosphere of hydrogen or nitrogen have a small size and a homogeneous distribution on the surface of the carbon nanotubes. The pretreatment would decrease the platinum particles on the carbon nanotubes significantly.

  1. 76 FR 8627 - Revision of Class E Airspace; Platinum, AK

    Science.gov (United States)

    2011-02-15

    ... Federal Aviation Administration 14 CFR Part 71 Revision of Class E Airspace; Platinum, AK AGENCY: Federal... Platinum, AK, to accommodate the addition of a Standard Instrument Approach Procedure (SIAP), at the Platinum Airport. The FAA is taking this action to enhance safety and management of Instrument Flight...

  2. Surface decorated platinum carbonyl clusters

    Science.gov (United States)

    Ciabatti, Iacopo; Femoni, Cristina; Iapalucci, Maria Carmela; Longoni, Giuliano; Zacchini, Stefano; Zarra, Salvatore

    2012-06-01

    Four molecular Pt-carbonyl clusters decorated by Cd-Br fragments, i.e., [Pt13(CO)12{Cd5(μ-Br)5Br2(dmf)3}2]2- (1), [Pt19(CO)17{Cd5(μ-Br)5Br3(Me2CO)2}{Cd5(μ-Br)5Br(Me2CO)4}]2- (2), [H2Pt26(CO)20(CdBr)12]8- (3) and [H4Pt26(CO)20(CdBr)12(PtBr)x]6- (4) (x = 0-2), have been obtained from the reactions between [Pt3n(CO)6n]2- (n = 2-6) and CdBr2.H2O in dmf at 120 °C. The structures of these molecular clusters with diameters of 1.5-2 nm have been determined by X-ray crystallography. Both 1 and 2 are composed of icosahedral or bis-icosahedral Pt-CO cores decorated on the surface by Cd-Br motifs, whereas 3 and 4 display a cubic close packed Pt26Cd12 metal frame decorated by CO and Br ligands. An oversimplified and unifying approach to interpret the electron count of these surface decorated platinum carbonyl clusters is suggested, and extended to other low-valent organometallic clusters and Au-thiolate nanoclusters.Four molecular Pt-carbonyl clusters decorated by Cd-Br fragments, i.e., [Pt13(CO)12{Cd5(μ-Br)5Br2(dmf)3}2]2- (1), [Pt19(CO)17{Cd5(μ-Br)5Br3(Me2CO)2}{Cd5(μ-Br)5Br(Me2CO)4}]2- (2), [H2Pt26(CO)20(CdBr)12]8- (3) and [H4Pt26(CO)20(CdBr)12(PtBr)x]6- (4) (x = 0-2), have been obtained from the reactions between [Pt3n(CO)6n]2- (n = 2-6) and CdBr2.H2O in dmf at 120 °C. The structures of these molecular clusters with diameters of 1.5-2 nm have been determined by X-ray crystallography. Both 1 and 2 are composed of icosahedral or bis-icosahedral Pt-CO cores decorated on the surface by Cd-Br motifs, whereas 3 and 4 display a cubic close packed Pt26Cd12 metal frame decorated by CO and Br ligands. An oversimplified and unifying approach to interpret the electron count of these surface decorated platinum carbonyl clusters is suggested, and extended to other low-valent organometallic clusters and Au-thiolate nanoclusters. CCDC 867747 and 867748. For crystallographic data in CIF or other electronic format see DOI: 10.1039/c2nr30400g

  3. Autonomous movement of platinum-loaded stomatocytes.

    Science.gov (United States)

    Wilson, Daniela A; Nolte, Roeland J M; van Hest, Jan C M

    2012-02-26

    Polymer stomatocytes are bowl-shaped structures of nanosize dimensions formed by the controlled deformation of polymer vesicles. The stable nanocavity and strict control of the opening are ideal for the physical entrapment of nanoparticles which, when catalytically active, can turn the stomatocyte morphology into a nanoreactor. Herein we report an approach to generate autonomous movement of the polymer stomatocytes by selectively entrapping catalytically active platinum nanoparticles within their nanocavities and subsequently using catalysis as a driving force for movement. Hydrogen peroxide is free to access the inner stomatocyte cavity, where it is decomposed by the active catalyst (the entrapped platinum nanoparticles) into oxygen and water. This generates a rapid discharge, which induces thrust and directional movement. The design of the platinum-loaded stomatocytes resembles a miniature monopropellant rocket engine, in which the controlled opening of the stomatocytes directs the expulsion of the decomposition products away from the reaction chamber (inner stomatocyte cavity).

  4. 2-Methoxycycloocta-1,5-dienyl platinum complexes as precursors for platinum nanoparticles

    Indian Academy of Sciences (India)

    Ninad Ghavale; Sandip Dey; Vimal K Jain; R Tewari

    2009-02-01

    Thermolysis of [Pt2 (-OR)2 (C8H12OMe)2] (R = Me or Ac) in hexadecylamine (HDA) at 210°C under argon atmosphere gave platinum nanoparticles which were characterized by XRD, EDAX and TEM analysis. Both spherical (∼ 10 nm) and rod-like (∼ 19 nm length with aspect ratio of 2.3) face centred cubic (fcc) platinum metal nanoparticles could be isolated. The thermogravimetric analyses of these complexes revealed that they undergo a single step decomposition leading to the formation of platinum metal powder.

  5. The roles of blood-derived macrophages and resident microglia in the neuroinflammatory response to implanted Intracortical microelectrodes

    Science.gov (United States)

    Ravikumar, Madhumitha; Sunil, Smrithi; Black, James; Barkauskas, Deborah S.; Haung, Alex Y.; Miller, Robert H.; Selkirk, Stephen M.; Capadona, Jeffrey R.

    2014-01-01

    Resident microglia and blood-borne macrophages have both been implicated to play a dominant role in mediating the neuroinflammatory response affecting implanted intracortical microelectrodes. However, the distinction between each cell type has not been demonstrated due to a lack of discriminating cellular markers. Understanding the subtle differences of each cell population in mediating neuroinflammation can aid in determining the appropriate therapeutic approaches to improve microelectrode performance. Therefore, the goal of this study is to characterize the role of infiltrating blood-derived cells, specifically macrophages, in mediating neuroinflammation following intracortical microelectrode implantation. Interestingly, we found no correlation between microglia and neuron populations at the microelectrode-tissue interface. On the other hand, blood-borne macrophages consistently dominated the infiltrating cell population following microelectrode implantation. Most importantly, we found a correlation between increased populations of blood-derived cells (including the total macrophage population) and neuron loss at the microelectrode-tissue interface. Specifically, the total macrophage population was greatest at two and sixteen weeks post implantation, at the same time points when we observed the lowest densities of neuronal survival in closest proximity to the implant. Together, our results suggest a dominant role of infiltrating macrophages, and not resident microglia, in mediating neurodegeneration following microelectrode implantation. PMID:24973296

  6. Experimental and theoretical characterization of implantable neural microelectrodes modified with conducting polymer nanotubes.

    Science.gov (United States)

    Abidian, Mohammad Reza; Martin, David C

    2008-03-01

    Neural prostheses transduce bioelectric signals to electronic signals at the interface between neural tissue and neural microelectrodes. A low impedance electrode-tissue interface is important for the quality of signal during recording as well as quantity of applied charge density during stimulation. However, neural microelectrode sites exhibit high impedance because of their small geometric surface area. Here we analyze nanostructured-conducting polymers that can be used to significantly decrease the impedance of microelectrode typically by about two orders of magnitude and increase the charge transfer capacity of microelectrodes by three orders of magnitude. In this study poly(pyrrole) (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT) nanotubes were electrochemically polymerized on the surface of neural microelectrode sites (1250 microm(2)). An equivalent circuit model comprising a coating capacitance in parallel with a pore resistance and interface impedance in series was developed and fitted to experimental results to characterize the physical and electrical properties of the interface. To confirm that the fitting parameters correlate with physical quantities of interface, theoretical equations were used to calculate the parameter values thereby validating the proposed model. Finally, an apparent diffusion coefficient was calculated for PPy film (29.2+/-1.1 x 10(-6) cm(2)/s), PPy nanotubes (PPy NTs) (72.4+/-3.3 x 10(-6) cm(2)/s), PEDOT film (7.4+/-2.1 x 10(-6) cm(2)/s), and PEDOT nanotubes (PEDOT NTs) (13.0+/-1.8 x 10(-6) cm(2)/s). The apparent diffusion coefficient of conducting polymer nanotubes was larger than the corresponding conducting polymer films.

  7. Electrochemical Analysis of the Electrodeposition of Platinum Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hae-Min; Cho, Sung-Woon; Kim, Jun-Hyun; Kim, Chang-Koo [Ajou University, Suwon (Korea, Republic of)

    2015-10-15

    A bath for electrodeposition of platinum nanoparticles on low-cost graphite substrates was developed to attach nanoparticles directly onto a substrate, and electrochemical characteristics of the electrodeposition of platinum nanoparticles were investigated. The reaction mechanism was examined by the analysis of polarization behavior. Cyclic voltammetry measurements revealed that the electrodeposition of platinum nanoparticles was limited by mass transfer. The chronoamperometric study showed an instantaneous nucleation mechanism during the electrodeposition of platinum nanoparticles on graphite. Because graphite is much cheaper than other carbon-based substrates, the electrodeposition of platinum nanoparticles on the graphite is expected to have useful applications.

  8. Outpatient desensitization in selected patients with platinum hypersensitivity reactions.

    Science.gov (United States)

    O'Malley, David M; Vetter, Monica Hagan; Cohn, David E; Khan, Ambar; Hays, John L

    2017-06-01

    Platinum-based chemotherapies are a standard treatment for both initial and recurrent gynecologic cancers. Given this widespread use, it is important to be aware of the features of platinum hypersensitivity reactions and the subsequent treatment of these reactions. There is also increasing interest in the development of desensitization protocols to allow patients with a history of platinum hypersensitivity to receive further platinum based therapy. In this review, we describe the management of platinum hypersensitivity reactions and the desensitization protocols utilized at our institution. We also describe the clinical categorizations utilized to triage patients to appropriate desensitization protocols. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. Synthesis and characterization of new platinum(II) and platinum(IV) triphyrin complexes.

    Science.gov (United States)

    Xue, Zhaoli; Kuzuhara, Daiki; Ikeda, Shinya; Okujima, Tetsuo; Mori, Shigeki; Uno, Hidemitsu; Yamada, Hiroko

    2013-02-18

    Metalation of 6,13,20,21-tetrakis(4-methylphenyl)-22H-tribenzo[14]triphyrin(2.1.1) with PtCl(2) gave a platinum(II) complex having a square-planar coordination structure with two pyrrolic nitrogen atoms and two chloride ions, with a saddle-shaped macrocycle. This platinum(II) complex was easily oxidized by air to an octahedral platinum(IV) complex coordinated by three pyrrolic nitrogen atoms as a tridentate monoanionic cyclic ligand and three chloride ions. When platinum(II) triphyrin was crystallized in air, an oxygen atom was incorporated between two α-carbon atoms of the pyrroles as an oxygen bridge to intercept the 14π aromatic system.

  10. Anticancer platinum (IV) prodrugs with novel modes of activity.

    Science.gov (United States)

    Chin, Chee Fei; Wong, Daniel Yuan Qiang; Jothibasu, Ramasamy; Ang, Wee Han

    2011-01-01

    Over the past four decades, the search for improved platinum drugs based on the classical platinum (II)-diam(m)ine pharmacophore has yielded only a handful of successful candidates. New methodologies centred on platinum (IV) complexes, with better stability and expanded coordination spheres, offer the possibility of overcoming limitations inherent to platinum (II) drugs. In this review, novel strategies of targeting and killing cancer cells using platinum (IV) constructs are discussed. These approaches exploit the unique electrochemical characteristics and structural attributes of platinum (IV) complexes as a means of developing anticancer prodrugs that can target and selectively destroy cancer cells. Anticancer platinum (IV) prodrugs represent promising new strategies as targeted chemotherapeutic agents in the ongoing battle against cancer.

  11. The Dynamics of Platinum Precipitation in an Ion Exchange Membrane

    CERN Document Server

    Burlatsky, S F; Atrazhev, V V; Dmitriev, D V; Kuzminyh, N Y; Erikhman, N S

    2013-01-01

    Microscopy of polymer electrolyte membranes that have undergone operation under fuel cell conditions, have revealed a well defined band of platinum in the membrane. Here, we propose a physics based model that captures the mechanism of platinum precipitation in the polymer electrolyte membrane. While platinum is observed throughout the membrane, the preferential growth of platinum at the band of platinum is dependent on the electrochemical potential distribution in the membrane. In this paper, the location of the platinum band is calculated as a function of the gas concentration at the cathode and anode, gas diffusion coefficients and solubility constants of the gases in the membrane, which are functions of relative humidity. Under H2/N2 conditions the platinum band is located near the cathode-membrane interface, as the oxygen concentration in the cathode gas stream increases and/or the hydrogen concentration in the anode gas stream decreases, the band moves towards the anode. The model developed in this paper...

  12. Platinum compounds with anti-tumour activity

    NARCIS (Netherlands)

    Plooy, A.C.M.; Lohman, P.H.M.

    1980-01-01

    Ten platinum (Pt) coordination complexes with different ligands, comprising both Pt(II) and Pt(IV) complexes of which the cis-compounds all possessed at least some anti-tumour activity and the trans-compounds were inactive, were tested as to their effect on cell survival and the induction and repair

  13. On the enzymatic formation of platinum nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Govender, Y.; Riddin, T. L. [Rhodes University, Department of Biochemistry, Microbiology and Biotechnology (South Africa); Gericke, M. [MINTEK (South Africa); Whiteley, C. G., E-mail: C.Whiteley@ru.ac.z [Rhodes University, Department of Biochemistry, Microbiology and Biotechnology (South Africa)

    2010-01-15

    A dimeric hydrogenase enzyme (44.5 and 39.4 kDa sub units) was isolated in a 39.5% yield from the fungus Fusarium oxysporum and purified 4.64-fold by ion exchange chromatography on Sephacryl S-200. Characterisation of the enzyme afforded pH and temperature optima of 7.5 and 38 {sup o}C, respectively, a half-life stability of 36 min and a V{sub max} and K{sub m} of 3.57 nmol min{sup -1} mL{sup -1} and 2.25 mM, respectively. This enzyme was inhibited (non-competitively) by hydrogen hexachloroplatinic acid (H{sub 2}PtCl{sub 6}) at 1 or 2 mM with a K{sub i} value of 118 {mu}M. Incubation of the platinum salt with the pure enzyme under an atmosphere of hydrogen and optimum enzyme conditions (pH 7.5, 38 {sup o}C) afforded <10% bioreduction after 8 h while at conditions suitable for platinum nanoparticle formation (pH 9, 65 {sup o}C) over 90% reduction took place after the same length of time. Cell-free extract from the fungal isolates produced nearly 90% bioreduction of the platinum salt under both pH and temperature conditions. The bioreduction of the platinum salt by a hydrogenase enzyme takes place by a passive process and not an active one as previously understood.

  14. Platinum catalysed hydrolytic amidation of unactivated nitriles

    NARCIS (Netherlands)

    Cobley, Christopher J.; Heuvel, Marco van den; Abbadi, Abdelilah; Vries, Johannes G. de

    2000-01-01

    The platinum(II) complex, [(Me2PO··H··OPMe2)PtH(PMe2OH)], efficiently catalyses the direct conversion of unactivated nitriles to N-substituted amides with both primary and secondary amines. Possible mechanisms for this reaction are discussed and evidence for initial amidine formation is reported.

  15. Targeting Platinum Compounds: synthesis and biological activity

    OpenAIRE

    VAN ZUTPHEN, Steven

    2005-01-01

    Inspired by cisplatin, the inorganic drug discovered by Barnett Rosenberg in 1965, the research described in this thesis uses targeting ligands, or ligands varied in a combinatorial fashion, to find platinum complexes with more specific modes of action. These studies have lead to the development of novel (solid-phase) synthetic methods and to the discovery of several compounds with promising biological properties.

  16. Targeting Platinum Compounds : synthesis and biological activity

    NARCIS (Netherlands)

    Zutphen, Steven van

    2005-01-01

    Inspired by cisplatin, the inorganic drug discovered by Barnett Rosenberg in 1965, the research described in this thesis uses targeting ligands, or ligands varied in a combinatorial fashion, to find platinum complexes with more specific modes of action. These studies have lead to the development of

  17. Skin Sensitizing Potency of Halogenated Platinum Salts.

    Science.gov (United States)

    The relationship between occupational exposure to halogenated platinum (Pt) salts and Pt-specific allergic sensitization is well-established. Although human case reports and clinical studies demonstrate that Pt salts are potent skin sensitizers, no studies have been published tha...

  18. Platinum catalysed hydrolytic amidation of unactivated nitriles

    NARCIS (Netherlands)

    Cobley, Christopher J.; Heuvel, Marco van den; Abbadi, Abdelilah; Vries, Johannes G. de

    2000-01-01

    The platinum(II) complex, [(Me2PO··H··OPMe2)PtH(PMe2OH)], efficiently catalyses the direct conversion of unactivated nitriles to N-substituted amides with both primary and secondary amines. Possible mechanisms for this reaction are discussed and evidence for initial amidine formation is reported. Is

  19. In Situ Identification and Stratification of Monochloramine Inhibition Effects on Nitrifying Biofilms as Determined by the Use of Microelectrodes

    Science.gov (United States)

    The nitrifying biofilm grown in an annular biofilm reactor and the microbial deactivation achieved after monochloramine treatment were investigated using microelectrodes. The nitrifying biofilm ammonium microprofile was measured and the effect of monochloramine on nitrifying bio...

  20. Solid-contact potentiometric polymer membrane microelectrodes for the detection of silver ions at the femtomole level

    OpenAIRE

    2006-01-01

    In recent years, ion-selective electrodes based on polymer membranes have been shown to exhibit detection limits that are often in the nanomolar concentration range, and thus drastically lower than traditionally accepted. Since potentiometry is less dependent on scaling laws that other established analytical techniques, their performance in confined sample volumes is explored here. Solid-contact silver-selective microelectrodes, with a sodium-selective microelectrode as a reference, were inse...

  1. Theoretical and experimental comparison of microelectrode sensing configurations for impedimetric cell monitoring

    DEFF Research Database (Denmark)

    Carminati, M.; Caviglia, Claudia; Heiskanen, Arto

    2013-01-01

    A theoretical and experimental comparison between vertical and coplanar interdigitated sensing configurations for impedimetric cell growth tracking is presented. These widely-adopted approaches are quantitatively compared on the same cell populations and on the same 10 μm interdigitated microelec......A theoretical and experimental comparison between vertical and coplanar interdigitated sensing configurations for impedimetric cell growth tracking is presented. These widely-adopted approaches are quantitatively compared on the same cell populations and on the same 10 μm interdigitated...... microelectrodes using a versatile custom-made monitoring platform including a 24-channel miniaturized potentiostat. The characterization of bare microelectrodes in buffer and tracking experiments with HeLa cells over 16 hours demonstrate that the coplanar configuration provides a higher sensitivity to cell...

  2. Electrochemical Characterisation and Application of Multi Microelectrode Array Devices to Biological Electrochemistry

    Directory of Open Access Journals (Sweden)

    William S. McIntire

    2001-06-01

    Full Text Available A new design for microelectrode array (MEA devices fabricated by semiconductor-processing techniques is presented. The microelectrode surfaces consist of gold and are surrounded by an insulating silicon nitride layer. Each chip of these so-called Multi MEAs contains regular arrays with circular-shaped electrodes of eight different sizes: 1, 3, 5, 10, 50, 100, 500 and 1000μm. The Multi MEAs were electrochemically characterised by use of ferrocenecarboxylic acid. Well-defined cyclic voltammograms of the two small redox proteins, horse heart cytochrome c and amicyanin from Thiobacillus versutus, were obtained at variously surface-modified Multi MEAs. Furthermore, a very simple method to manufacture Multi MEAs with carbon surfaces is introduced.

  3. An electrochemical immunosensor based on interdigitated array microelectrode for the detection of chlorpyrifos.

    Science.gov (United States)

    Cao, Yaoyao; Sun, Xia; Guo, Yemin; Zhao, Wenping; Wang, Xiangyou

    2015-02-01

    An electrochemical immunosensor based on interdigitated array microelectrodes (IDAMs) was developed for sensitive, specific and rapid detection of chlorpyrifos. Anti-chlorpyrifos monoclonal antibodies were orientedly immobilized onto the gold microelectrode surface through protein A. Chlorpyrifos were then captured by the immobilized antibody, resulting in an impedance change in the IDAMs surface. Electrochemical impedance spectroscopy was used in conjunction with the fabricated sensor to detect chlorpyrifos. Under optimum conditions, the impedance value change of chlorpyrifos was proportional to its concentrations in the range of 10(0)-10(5) ng/mL. The detection limit was found to be 0.014 ng/mL for chlorpyrifos. The proposed chlorpyrifos immunosensor could be used as a screening method in pesticide determination for the analysis of environmental, agricultural and pharmaceutical samples due to its rapidity, sensitivity and low cost.

  4. Impedance Characterization of the Degradation of Insulating Layer Patterned on Interdigitated Microelectrode.

    Science.gov (United States)

    Lee, Gihyun; Kim, Sohee; Cho, Sungbo

    2015-10-01

    Life-time and functionality of planar microelectrode-based devices are determined by not only the corrosion-resistance of the electrode, but also the durability of the insulation layer coated on the transmission lines. Degradation of the insulating layer exposed to a humid environment or solution may cause leakage current or signal loss, and a decrease in measurement sensitivity. In this study, degradation of SU-8, an epoxy-based negative photoresist and insulating material, patterned on Au interdigitated microelectrode (IDE) for long-term (>30 days) immersion in an electrolyte at 37 °C was investigated by electrical impedance spectroscopy and theoretical equivalent circuit modeling. From the experiment and simulation results, it was found that the degradation level of the insulating layer of the IDE electrode can be characterized by monitoring the resistance of the insulating layer among the circuit parameters of the designed equivalent circuit modeling.

  5. Flexible complementary metal oxide semiconductor microelectrode arrays with applications in single cell characterization

    Science.gov (United States)

    Pajouhi, H.; Jou, A. Y.; Jain, R.; Ziabari, A.; Shakouri, A.; Savran, C. A.; Mohammadi, S.

    2015-11-01

    A highly flexible microelectrode array with an embedded complementary metal oxide semiconductor (CMOS) instrumentation amplifier suitable for sensing surfaces of biological entities is developed. The array is based on ultrathin CMOS islands that are thermally isolated from each other and are interconnected by meandered nano-scale wires that can adapt to cellular surfaces with micro-scale curvatures. CMOS temperature sensors are placed in the islands and are optimally biased to have high temperature sensitivity. While no live cell thermometry is conducted, a measured temperature sensitivity of 0.15 °C in the temperature range of 35 to 40 °C is achieved by utilizing a low noise CMOS lock-in amplifier implemented in the same technology. The monolithic nature of CMOS sensors and amplifier circuits and their versatile flexible interconnecting wires overcome the sensitivity and yield limitations of microelectrode arrays fabricated in competing technologies.

  6. Vertically aligned carbon nanotube-sheathed carbon fibers as pristine microelectrodes for selective monitoring of ascorbate in vivo.

    Science.gov (United States)

    Xiang, Ling; Yu, Ping; Hao, Jie; Zhang, Meining; Zhu, Lin; Dai, Liming; Mao, Lanqun

    2014-04-15

    Using as-synthesized vertically aligned carbon nanotube-sheathed carbon fibers (VACNT-CFs) as microelectrodes without any postsynthesis functionalization, we have developed in this study a new method for in vivo monitoring of ascorbate with high selectivity and reproducibility. The VACNT-CFs are formed via pyrolysis of iron phthalocyanine (FePc) on the carbon fiber support. After electrochemical pretreatment in 1.0 M NaOH solution, the pristine VACNT-CF microelectrodes exhibit typical microelectrode behavior with fast electron transfer kinetics for electrochemical oxidation of ascorbate and are useful for selective ascorbate monitoring even with other electroactive species (e.g., dopamine, uric acid, and 5-hydroxytryptamine) coexisting in rat brain. Pristine VACNT-CFs are further demonstrated to be a reliable and stable microelectrode for in vivo recording of the dynamic increase of ascorbate evoked by intracerebral infusion of glutamate. Use of a pristine VACNT-CF microelectrode can effectively avoid any manual electrode modification and is free from person-to-person and/or electrode-to-electrode deviations intrinsically associated with conventional CF electrode fabrication, which often involves electrode surface modification with randomly distributed CNTs or other pretreatments, and hence allows easy fabrication of highly selective, reproducible, and stable microelectrodes even by nonelectrochemists. Thus, this study offers a new and reliable platform for in vivo monitoring of neurochemicals (e.g., ascorbate) to largely facilitate future studies on the neurochemical processes involved in various physiological events.

  7. Concurrent chemoradiotherapy comparison of taxanes and platinum versus 5-fluorouracil and platinum in nasopharyngeal carcinoma treatment

    Institute of Scientific and Technical Information of China (English)

    Chen Xichuang; Hong Yuan; Feng Jinhua; Ye Jianlin; Zheng Panpan; Guan Xiyin; You Xiaohong

    2014-01-01

    Background Nasopharyngeal carcinoma (NPC) is a squamous-cell carcinoma especially prevailing among the natives of southern China.The regimen of concurrent chemoradiotherapy (CCRT) that include platinum and 5-fluorouracil (5-FU)is considered to be the standard treatment for NPC.However,its clinical use is limited by its toxicity.Our purpose was to evaluate the efficacy and safety of the regimen of CCRT with taxanes and platinum versus the regimen of CCRT with 5-FU and platinum in NPC treatment.Methods Medline,the Cochrane library,and the Chinese medical literature database were searched for eligible studies.Meta-analysis was performed using Review Manager (Version 5.2).Results Six random controlled trials (RCTs) including 514 patients met our criteria.Meta-analysis showed that the regimen of CCRT with taxanes and platinum had an improved significant difference in complete remission (CR) and less incidence rate in adverse reactions such as gastrointestinal impairment grades Ⅲll-Ⅳ,liver and kidney impairment grades Ⅰ-Ⅱ,and radiodermatitis grades Ⅲ-Ⅳ versus the conventional regimen of CCRT with 5-FU and platinum,while the long-term effectiveness rate of overall survival,Iocoregional failure-free survival,or distant metastasis failure-free survival between the two groups was therapeutic equivalence.Conclusions The regimen of CCRT with taxanes and platinum in NPC therapy may be more efficient and safe compared to the conventional modality of 5-FU and platinum in CCRT.However,we need more high-quality studies of multi-center and randomized double-blind clinical trials to further compare,analyze,and confirm the findings.

  8. Enhanced electroanalysis in lithium potassium eutectic (LKE) using microfabricated square microelectrodes.

    Science.gov (United States)

    Corrigan, Damion K; Blair, Ewen O; Terry, Jonathan G; Walton, Anthony J; Mount, Andrew R

    2014-11-18

    Molten salts (MSs) are an attractive medium for chemical and electrochemical processing and as a result there is demand for MS-compatible analysis technologies. However, MSs containing redox species present a challenging environment in which to perform analytical measurements because of their corrosive nature, significant thermal convection and the high temperatures involved. This paper outlines the fabrication and characterization of microfabricated square microelectrodes (MSMs) designed for electrochemical analysis in MS systems. Their design enables precise control over electrode dimension, the minimization of stress because of differential thermal expansion through design for high temperature operation, and the minimization of corrosive attack through effective insulation. The exemplar MS system used for characterization was lithium chloride/potassium chloride eutectic (LKE), which has potential applications in pyrochemical nuclear fuel reprocessing, metal refining, molten salt batteries and electric power cells. The observed responses for a range of redox ions between 400 and 500 °C (673 and 773 K) were quantitative and typical of microelectrodes. MSMs also showed the reduced iR drop, steady-state diffusion-limited response, and reduced sensitivity to convection seen for microelectrodes under ambient conditions and expected for these electrodes in comparison to macroelectrodes. Diffusion coefficients were obtained in close agreement with literature values, more readily and at greater precision and accuracy than both macroelectrode and previous microelectrode measurements. The feasibility of extracting individual physical parameters from mixtures of redox species (as required in reprocessing) and of the prolonged measurement required for online monitoring was also demonstrated. Together, this demonstrates that MSMs provide enhanced electrode devices widely applicable to the characterization of redox species in a range of MS systems.

  9. Nanowire-templated microelectrodes for high-sensitivity pH detection

    DEFF Research Database (Denmark)

    Antohe, V.A.; Radu, Adrian; Mátéfi-Tempfli, Mária

    2009-01-01

    A highly sensitive pH capacitive sensor has been designed by confined growth of vertically aligned nanowire arrays on interdigited microelectrodes. The active surface of the device has been functionalized with an electrochemical pH transducer (polyaniline). We easily tune the device features...... by combining lithographic techniques with electrochemical synthesis. The reported electrical LC resonance measurements show considerable sensitivity enhancement compared to conventional capacitive pH sensors realized with microfabricated interdigited electrodes. The sensitivity can be easily improved...

  10. Electrochemical Behavior of Mitoxantrone and Its Determination at a Pt/C Implanted Modified Microelectrode

    Institute of Scientific and Technical Information of China (English)

    QIAN Yong-gui; SUN Zi-jie; HU Jing-bo; LU Yi-qiang; LI Qi-long

    2004-01-01

    In a 0.02 mol/L Na2HPO4-KH2PO4(PBS) buffer solution(pH=6.82), the electrochemical behavior of mitoxantrone was studied by linear-sweep voltammetry and cyclic voltammetry at a Pt/C ion implantation modified microelectrode. A sensitive reduction peak was observed. The peak potential was -0.72 V(vs.SCE), the peak current was proportional to the concentration of mitoxantrone within the ranges of 7.0×10-8-9.0×10-7 mol/L and 1.0×10-6-2.4×10-5 mol/L, with a detection limit of 4.0×10-8 mol/L. The linear correlation coefficients were 0.9994 and 0.9992, respectively. This method has been applied to the direct determination of mitoxantrone in simulated urine. The recoveries were in the range from 96.2% to 105.9%. The reduction process was a quasi-reversible one with adsorptive characteristics at the Pt/C microelectrode. The electrode reaction rate constant ks and the electron transfer coefficient α of the system were determined to be 4.5 and 0.65 s-1, respectively. The experiments showed that Pt element had surely been implanted into the surface of the carbon fiber, and the atomic Pt improved the electrocatalytic activity. The Pt/C microelectrode had a good stability and reproducibility.

  11. Boron-doped diamond nano/microelectrodes for bio-sensing and in vitro measurements

    Science.gov (United States)

    Dong, Hua; Wang, Shihua; Galligan, James J.; Swain, Greg M.

    2015-01-01

    Since the fabrication of the first diamond electrode in the mid 1980s, repid progress has been made on the development and application of this new type of electrode material. Boron-doped diamond (BDD) electrodes exhibit outstanding properties compared to oxygen-containing sp2 carbon electrodes. These properties make BDD electrodes an ideal choice for use in complex samples. In recent years, BDD microelectrodes have been applied to in vitro and in vivo measurements of biological molecules in animals, tissues and cells. This review will summarize recent progress in the development and applications of BDD electrodes in bio-sensing and in vitro measurements of biomolecules. In the first section, the methods for BDD nanocrystalline diamond film deposition and BDD microelectrodes preparation are described. This is followed by a description and discussion of several approaches for characterization of the BDD electrode surface structure, morphology, and electrochemical activity. Further, application of BDD microelectrodes for use in the in vitro analysis of norepinephrine (NE), serotonin (5-HT), nitric oxide (NO), histamine, and adenosine from tissues are summarized and finally some of the remaining challenges are discussed. PMID:21196394

  12. A single carbon fiber microelectrode with branching carbon nanotubes for bioelectrochemical processes.

    Science.gov (United States)

    Zhao, Xueyan; Lu, Xin; Tze, William T Y; Wang, Ping

    2010-06-15

    Carbon fiber electrodes are greatly promising for microelectronic applications including high performance biosensors, miniaturized transmitters, and energy storage and generation devices. For biosensor applications, one drawback of using carbon fiber microelectrodes, especially single fiber electrodes, is the weak electronic signals, a consequence of low surface area of fibers, which ultimately limit the sensitivity of the sensors. In this paper, we report a novel single fiber microelectrode with branched carbon nanotubes for enhanced sensing performance. The fiber microelectrode was prepared from carbonization of cellulose fibers. Upon introduction of carbon nanotubes, the carbon fibers exhibited a significant increase in the specific surface area from carbon nanotubes enhanced the redox reactions on surfaces of the electrode by reducing the oxidation potential of NAD(H) from 0.8 to 0.55 V. The single carbon fiber with branched nanotubes was also examined for the detection of glycerol, and the results showed linear responding signals in a concentration range of 40-250 microM. These results are comparable to the properties of fossil-based carbon materials, and thus our cellulose-based carbon electrodes provide a potentially sustainable alternative in bioelectrochemical applications.

  13. Effects of adsorbed proteins, an antifouling agent and long-duration DC voltage pulses on the impedance of silicon-based neural microelectrodes.

    Science.gov (United States)

    Sommakia, Salah; Rickus, Jenna L; Otto, Kevin J

    2009-01-01

    The successful use of implantable neural microelectrodes as neuroprosthetic devices depends on the mitigation of the reactive tissue response of the brain. One of the factors affecting the ultimate severity of the reactive tissue response and the in vivo electrical properties of the microelectrodes is the initial adsorption of proteins onto the surface of the implanted microelectrodes. In this study we quantify the increase in microelectrode impedance magnitude at physiological frequencies following electrode immersion in a 10% bovine serum albumin (BSA) solution. We also demonstrate the efficacy of a common antifouling molecule, poly(ethylene glycol) (PEG), in preventing a significant increase in microelectrode impedance. In addition, we show the feasibility of using long-duration DC voltage pulses to remove adsorbed proteins from the microelectrode surface.

  14. Development of Microelectrode Arrays Using Electroless Plating for CMOS-Based Direct Counting of Bacterial and HeLa Cells.

    Science.gov (United States)

    Niitsu, Kiichi; Ota, Shoko; Gamo, Kohei; Kondo, Hiroki; Hori, Masaru; Nakazato, Kazuo

    2015-10-01

    The development of two new types of high-density, electroless plated microelectrode arrays for CMOS-based high-sensitivity direct bacteria and HeLa cell counting are presented. For emerging high-sensitivity direct pathogen counting, two technical challenges must be addressed. One is the formation of a bacteria-sized microelectrode, and the other is the development of a high-sensitivity and high-speed amperometry circuit. The requirement for microelectrode formation is that the gold microelectrodes are required to be as small as the target cell. By improving a self-aligned electroless plating technique, the dimensions of the microelectrodes on a CMOS sensor chip in this work were successfully reduced to 1.2 μm × 2.05 μm. This is 1/20th of the smallest size reported in the literature. Since a bacteria-sized microelectrode has a severe limitation on the current flow, the amperometry circuit has to have a high sensitivity and high speed with low noise. In this work, a current buffer was inserted to mitigate the potential fluctuation. Three test chips were fabricated using a 0.6- μm CMOS process: two with 1.2 μm × 2.05 μm (1024 × 1024 and 4 × 4) sensor arrays and one with 6- μm square (16 × 16) sensor arrays; and the microelectrodes were formed on them using electroless plating. The uniformity among the 1024 × 1024 electrodes arranged with a pitch of 3.6 μm × 4.45 μm was optically verified. For improving sensitivity, the trenches on each microelectrode were developed and verified optically and electrochemically for the first time. Higher sensitivity can be achieved by introducing a trench structure than by using a conventional microelectrode formed by contact photolithography. Cyclic voltammetry (CV) measurements obtained using the 1.2 μm × 2.05 μm 4 × 4 and 6- μm square 16 × 16 sensor array with electroless-plated microelectrodes successfully demonstrated direct counting of the bacteria-sized microbeads and HeLa cells.

  15. Remarkable NO oxidation on single supported platinum atoms.

    Science.gov (United States)

    Narula, Chaitanya K; Allard, Lawrence F; Stocks, G M; Moses-DeBusk, Melanie

    2014-11-28

    Our first-principles density functional theoretical modeling suggests that NO oxidation is feasible on fully oxidized single θ-Al2O3 supported platinum atoms via a modified Langmuir-Hinshelwood pathway. This is in contrast to the known decrease in NO oxidation activity of supported platinum with decreasing Pt particle size believed to be due to increased platinum oxidation. In order to validate our theoretical study, we evaluated single θ-Al2O3 supported platinum atoms and found them to exhibit remarkable NO oxidation activity. A comparison of turnover frequencies (TOF) of single supported Pt atoms with those of platinum particles for NO oxidation shows that single supported Pt atoms are as active as fully formed platinum particles. Thus, the overall picture of NO oxidation on supported Pt is that NO oxidation activity decreases with decreasing Pt particle size but accelerates when Pt is present only as single atoms.

  16. Synthesis of Bimetallic Platinum Nanoparticles for Biosensors

    Directory of Open Access Journals (Sweden)

    Gerard M. Leteba

    2013-08-01

    Full Text Available The use of magnetic nanomaterials in biosensing applications is growing as a consequence of their remarkable properties; but controlling the composition and shape of metallic nanoalloys is problematic when more than one precursor is required for wet chemistry synthesis. We have developed a successful simultaneous reduction method for preparation of near-spherical platinum-based nanoalloys containing magnetic solutes. We avoided particular difficulties in preparing platinum nanoalloys containing Ni, Co and Fe by the identification of appropriate synthesis temperatures and chemistry. We used transmission electron microscopy (TEM to show that our particles have a narrow size distribution, uniform size and morphology, and good crystallinity in the as-synthesized condition. Energy dispersive spectroscopy (EDS and X-ray diffraction (XRD confirms the coexistence of Pt with the magnetic solute in a face-centered cubic (FCC solid solution.

  17. Catalytic converters as a source of platinum

    Directory of Open Access Journals (Sweden)

    A. Fornalczyk

    2011-10-01

    Full Text Available The increase of Platinum Group Metals demand in automotive industry is connected with growing amount of cars equipped with the catalytic converters. The paper presents the review of available technologies during recycling process. The possibility of removing platinum from the used catalytic converters applying pyrometallurgical and hyrdometallurgical methods were also investigated. Metals such as Cu, Pb, Ca, Mg, Cd were used in the pyrometallurgical research (catalytic converter was melted with Cu, Pb and Ca or Mg and Cd vapours were blown through the whole carrier. In hydrometallurgical research catalytic converters was dissolved in aqua regia. Analysis of Pt contents in the carrier before and after the process was performed by means of atomic absorption spectroscopy. Obtained result were discussed.

  18. Examining the surfaces in used platinum catalysts

    Directory of Open Access Journals (Sweden)

    Trumić B.

    2009-01-01

    Full Text Available For the purpose of finding more advanced platinum catalyst manufacturing technologies and achieving a higher degree of ammonia oxidation, metallographic characterization has been done on the surface of catalyst gauzes and catalyst gripper gauzes made from platinum and palladium alloys. For the examined samples of gauzes as well as the cross section of the wires, a chemical analysis was provided. The purpose of this paper is the metallographic characterization of examined alloys carried out by way of electronic microscopic scanning, X-rays as well as chemical assays which contributed greatly to a better understanding of the surface deactivation, in other words a better consideration of structural changes occurring on the wire surface.

  19. Improving the accuracy of microelectrode recording in deep brain stimulation surgery with intraoperative CT.

    Science.gov (United States)

    Kochanski, Ryan B; Pal, Gian; Bus, Sander; Metman, Leo Verhagen; Sani, Sepehr

    2017-06-01

    Microelectrode recording (MER) is used to confirm electrophysiological signals within intended anatomic targets during deep brain stimulation (DBS) surgery. We describe a novel technique called intraoperative CT-guided extrapolation (iCTE) to predict the intended microelectrode trajectory and, if necessary, make corrections in real-time before dural opening. Prior to dural opening, a guide tube was inserted through the headstage and rested on dura. Intraoperative CT (iCT) was obtained, and a trajectory was extrapolated along the path of the guide tube to target depth using targeting software. The coordinates were recorded and compared to initial plan coordinates. If needed, adjustments were made using the headstage to correct for error. The guide tube was then inserted and MER ensued. At target, iCT was performed and microelectrode tip coordinates were compared with planned/adjusted track coordinates. Radial error between MER track and planned/adjusted track was calculated. For comparison, MER track error prior to the iCTE technique was assessed retrospectively in patients who underwent MER using iCT, whereby iCT was performed following completion of the first MER track. Forty-seven MER tracks were analyzed prior to iCTE (pre-iCTE), and 90 tracks were performed using the iCTE technique. There was no difference between radial error of pre-iCTE MER track and planned trajectory (2.1±0.12mm) compared to iCTE predicted trajectory and planned trajectory (1.76±0.13mm, p>0.05). iCTE was used to make trajectory adjustments which reduced radial error between the newly corrected and final microelectrode tip coordinates to 0.84±0.08mm (preliability was also tested using a second blinded measurement reviewer which showed no difference between predicted and planned MER track error (p=0.53). iCTE can predict and reduce trajectory error for microelectrode placement compared with the traditional use of iCT post MER. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Stability of Porous Platinum Nanoparticles: Combined In Situ TEM and Theoretical Study

    DEFF Research Database (Denmark)

    Chang, Shery L. Y.; Barnard, Amanda S.; Dwyer, Christian

    2012-01-01

    Porous platinum nanoparticles provide a route for the development of catalysts that use less platinum without sacrificing catalytic performance. Here, we examine porous platinum nanoparticles using a combination of in situ transmission electron microscopy and calculations based on a first...

  1. Platinum Acetylide Two-Photon Chromophores (Preprint)

    Science.gov (United States)

    2007-04-01

    the higher energy range that lead to its photodegradation . Secondly, because there is a quadratic dependence of two-photon absorption (2PA) on the...to either an electron donating amino- fluorenyl or electron withdrawing benzothiazolyl-fluorene that are themselves known as two-photon absorbing dyes ...groups in place of phenyl groups have shown a doubling of the intrinsic cr2value at 740 nm.40,41In this paper we describe novel platinum dyes that

  2. Redeposition of electrochemically dissolved platinum as nanoparticles on carbon

    DEFF Research Database (Denmark)

    Norgaard, C. F.; Stamatin, S. N.; Skou, E. M.

    2014-01-01

    Electrochemical dissolution of platinum has been proposed by several research groups as an environmentally friendly way to recover platinum from catalytic structures such as fuel cell electrodes. For the case of electrochemical dissolution of platinum in hydrochloric acid electrolyte, the present...... on carbon was then identified, quantified, and the particle size evaluated by powder X-ray diffraction, thermogravimetric analysis and cyclic voltammetry. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved....

  3. Platinum germanium ordering in UPtGe

    Science.gov (United States)

    Hoffmann, Rolf-Dieter; Pöttgen, Rainer; Lander, Gerry H.; Rebizant, Jean

    2001-09-01

    The non-centrosymmetric structure of UPtGe was investigated by X-ray diffraction on both powders and single crystals: EuAuGe type, Imm2, a=432.86(5), b=718.81(8), c=751.66(9) pm, wR2=0.0738 for 399 F2 values and 22 variables. The platinum and germanium atoms form two-dimensional layers of puckered Pt 3Ge 3 hexagons with short PtGe intralayer distances of 252 and 253 pm. These condensed two-dimensionally infinite nets are interconnected to each other via weak PtPt contacts with bond distances of 300 pm. The two crystallographically independent uranium atoms are situated above and below the six-membered platinum-germanium rings. The U1 atoms have six closer germanium neighbors while the U2 atoms have six closer platinum neighbors. The group-subgroup relation with the KHg 2 type structure is presented.

  4. Preparation and Electrochemical Properties of Porous Platinum Electrode

    Institute of Scientific and Technical Information of China (English)

    HE Xin; CHEN Boxun; CHEN Qiao

    2012-01-01

    Porous platinum electrodes were prepared by adding YSZ,as an active material,in platinum paste.Relationship between microstructure and electrochemical performance of O2(g),Pt/YSZ electrode have been characterized by SEM and cyclic voltammetry.Results showed that the microstructure of platinum electrode is a significant impact on the cyclic voltammetry.With the increase of platinum electrode's porosity,the area of three-phase boundary of O2(g)/Pt/YSZ was increased.The electrochemical reactivity was also enhanced.These were presented as the increase of current density and cathode voltage in cyclic voltammetry.

  5. Controlled synthesis of porous platinum nanostructures for catalytic applications.

    Science.gov (United States)

    Cao, Yanqin; Zhang, Junwei; Yang, Yong; Huang, Zhengren; Long, Nguyen Viet; Nogami, Masayuki

    2014-02-01

    Porous platinum, that has outstanding catalytic and electrical properties and superior resistant characteristics to corrosion, has been widely applied in chemical, petrochemical, pharmaceutical, electronic, and automotive industries. As the catalytic activity and selectivity depend on the size, shape and structure of nanomaterials, the strategies for controlling these factors of platinum nanomaterials to get excellent catalytic properties are discussed. Here, recent advances in the design and preparation of various porous platinum nanostructures are reviewed, including wet-chemical synthesis, electro-deposition, galvanic replacement reaction and de-alloying technology. The applications of various platinum nanostructures are also discussed, especially in fuel cells.

  6. Localized electron transfer rates and microelectrode-based enrichment of microbial communities within a phototrophic microbial mat

    Energy Technology Data Exchange (ETDEWEB)

    Babauta, Jerome T. [Washington State Univ., Pullman, WA (United States); Atci, Erhan [Washington State Univ., Pullman, WA (United States); Ha, Phuc T. [Washington State Univ., Pullman, WA (United States); Lindemann, Stephen R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Ewing, Timothy [Washington State Univ., Pullman, WA (United States); Call, Douglas R. [Washington State Univ., Pullman, WA (United States); Fredrickson, James K. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Beyenal, Haluk [Washington State Univ., Pullman, WA (United States)

    2014-01-01

    Phototrophic microbial mats frequently exhibit sharp, light-dependent redox gradients that regulate microbial respiration on specific electron acceptors as a function of depth. In this work, a benthic phototrophic microbial mat from Hot Lake, a hypersaline, epsomitic lake located near Oroville in north-central Washington, was used to develop a microscale electrochemical method to study local electron transfer processes within the mat. To characterize the physicochemical variables influencing electron transfer, we initially quantified redox potential, pH, and dissolved oxygen gradients by depth in the mat under photic and aphotic conditions. We further demonstrated that power output of a mat fuel cell was light-dependent. To study local electron transfer processes, we deployed a microscale electrode (microelectrode) with tip size ~20 μm. To enrich a subset of microorganisms capable of interacting with the microelectrode, we anodically polarized the microelectrode at depth in the mat. Subsequently, to characterize the microelectrode- associated community and compare it to the neighboring mat community, we performed amplicon sequencing of the V1-V3 region of the 16S gene. Differences in Bray-Curtis beta diversity, illustrated by large changes in relative abundance at the phylum level, suggested successful enrichment of specific mat community members on the microelectrode surface. The microelectrode-associated community exhibited substantially reduced alpha diversity and elevated relative abundances of Prosthecochloris, Loktanella, Catellibacterium, other unclassified members of Rhodobacteraceae, Thiomicrospira, and Limnobacter, compared with the community at an equivalent depth in the mat. Our results suggest that local electron transfer to an anodically polarized microelectrode selected for a specific microbial population, with substantially more abundance and diversity of sulfur-oxidizing phylotypes compared with the neighboring mat community.

  7. How much platinum passes the placental barrier? Analysis of platinum applications in 21 patients with cervical cancer during pregnancy.

    Science.gov (United States)

    Köhler, Christhardt; Oppelt, Peter; Favero, Giovanni; Morgenstern, Bernd; Runnebaum, Ingo; Tsunoda, Audrey; Schmittel, Alexander; Schneider, Achim; Mueller, Michael; Marnitz, Simone

    2015-08-01

    Cervical cancer is the most common solid cancer diagnosed in pregnancy. Platinum is an active drug in the treatment of patients with cervical cancer. In the second and third trimesters, platinum is used to prevent cancer progression until fetal maturity is reached. However, knowledge about the transplacental passage of platinum is very limited. Between May 2008 and June 2014, platinum-based neoadjuvant chemotherapy was applied to 21 consecutive patients with cervical cancer diagnosed in their second trimester. At the time of delivery by cesarean delivery, synchronous samples from maternal blood, umbilical cord blood, and amniotic fluid were taken and analyzed for platinum concentrations. The mean week of gestation at cancer diagnosis was 17 (13-23). On average 3 (range, 2-4) cycles of chemotherapy were applied. Cesarean deliveries were carried out between 30.4 and 36.5 weeks of gestation. Twenty-two healthy babies without renal, hepatic, auditory, or hematopoietic impairment were delivered. Platinum concentrations in umbilical cord blood and amniotic fluid were 23-65% and 11-42% of the maternal blood, respectively. This series on in vivo measurement of platinum concentrations in the fetomaternal compartment observed that because of consistently lower platinum values in the fetoplacental unit, a placental filtration mechanism of platinum may be assumed. Copyright © 2015 Elsevier Inc. All rights reserved.

  8. Electrochemical determination of vitamin C on platinum microelectrode%铂微电极快速检测食品中Vc

    Institute of Scientific and Technical Information of China (English)

    张俊霞; 何保山; 张长辉

    2016-01-01

    以铂微电极(PME)作为工作电极,简化三电极为两电极系统,利用多壁碳纳米管(MWCNTs)具有高比表面积、高催化活性、显著增强响应电流的特性,将分散于N,N-二甲基甲酰胺(DMF)的羧基化MWCNTs修饰于自制PME表面,建立一种新型检测Vc的生物传感器.与常见的宏观电极相比,羧基化MWCNTs修饰的铂丝微电极(DMF/carboxyl/MWCNTs/PME)检测Vc,降低了Vc的氧化电位,增大了氧化峰电流值,提高了电子转移速率,并展现出良好的灵敏度及稳定性.通过一系列检测条件及修饰材料的优化,将DMF/carboxyl/MWCNTs/PME应用于Vc标准液检测中,测得Vc浓度在(1.0×10-4~2.0×1O-1)mol/L内与氧化电流值呈线性关系,且线性方程为:I(A)=4.19711×10-8+1.27293×10-5C (mol/L),检测限为1.0×10-5 mol/L(S/N=3).DMF/carboxyl/MWCNTs/PME检测实际样品的回收率为97%~113%,验证了DMF/carboxyl/MWCNTs/PME快速检测食品中Vc的可行性.

  9. Modelling and sensitivity analysis of urinary platinum excretion in anticancer chemotherapy for the recovery of platinum

    DEFF Research Database (Denmark)

    Folens, Karel; Mortier, Séverine Thérèse F C; Baeten, Janis

    2016-01-01

    Platinum (Pt) based antineoplastics are important in cancer therapy. To date the Pt which is urinary excreted by the patients ends up in wastewater. This is disadvantageous from both an economic as from an ecological point of view because Pt is a valuable material and the excretion products are t...

  10. Substrate arrays of iridium oxide microelectrodes for in vitro neuronal interfacing

    Directory of Open Access Journals (Sweden)

    Shady Gawad

    2009-01-01

    Full Text Available The design of novel bidirectional interfaces for in vivo and in vitro nervous systems is an important step towards future functional neuroprosthetics. Small electrodes, structures and devices are necessary to achieve high-resolution and target-selectivity during stimulation and recording of neuronal networks, while significant charge transfer and large signal-to-noise ratio are required for accurate time resolution. In addition, the physical properties of the interface should remain stable across time, especially when chronic in vivo applications or in vitro long-term studies are considered, unless a procedure to actively compensate for degradation is provided. In this short report, we describe the use and fabrication of arrays of 120 planar microelectrodes (MEAs of sputtered Iridium Oxide (IrOx. The effective surface area of individual microelectrodes is significantly increased using electrochemical activation, a procedure that may also be employed to restore the properties of the electrodes as required. The electrode activation results in a very low interface impedance, especially in the lower frequency domain, which was characterized by impedance spectroscopy. The increase in the roughness of the microelectrodes surface was imaged using digital holographic microscopy and electron microscopy. Aging of the activated electrodes was also investigated, comparing storage in saline with storage in air. Demonstration of concept was achieved by recording multiple single-unit spike activity in acute brain slice preparations of rat neocortex. Data suggests that extracellular recording of action potentials can be achieved with planar IrOx MEAs with good signal-to-noise ratios.

  11. BioMEA: a versatile high-density 3D microelectrode array system using integrated electronics.

    Science.gov (United States)

    Charvet, Guillaume; Rousseau, Lionel; Billoint, Olivier; Gharbi, Sadok; Rostaing, Jean-Pierre; Joucla, Sébastien; Trevisiol, Michel; Bourgerette, Alain; Chauvet, Philippe; Moulin, Céline; Goy, François; Mercier, Bruno; Colin, Mikael; Spirkovitch, Serge; Fanet, Hervé; Meyrand, Pierre; Guillemaud, Régis; Yvert, Blaise

    2010-04-15

    Microelectrode arrays (MEAs) offer a powerful tool to both record activity and deliver electrical microstimulations to neural networks either in vitro or in vivo. Microelectronics microfabrication technologies now allow building high-density MEAs containing several hundreds of microelectrodes. However, dense arrays of 3D micro-needle electrodes, providing closer contact with the neural tissue than planar electrodes, are not achievable using conventional isotropic etching processes. Moreover, increasing the number of electrodes using conventional electronics is difficult to achieve into compact devices addressing all channels independently for simultaneous recording and stimulation. Here, we present a full modular and versatile 256-channel MEA system based on integrated electronics. First, transparent high-density arrays of 3D-shaped microelectrodes were realized by deep reactive ion etching techniques of a silicon substrate reported on glass. This approach allowed achieving high electrode aspect ratios, and different shapes of tip electrodes. Next, we developed a dedicated analog 64-channel Application Specific Integrated Circuit (ASIC) including one amplification stage and one current generator per channel, and analog output multiplexing. A full modular system, called BIOMEA, has been designed, allowing connecting different types of MEAs (64, 128, or 256 electrodes) to different numbers of ASICs for simultaneous recording and/or stimulation on all channels. Finally, this system has been validated experimentally by recording and electrically eliciting low-amplitude spontaneous rhythmic activity (both LFPs and spikes) in the developing mouse CNS. The availability of high-density MEA systems with integrated electronics will offer new possibilities for both in vitro and in vivo studies of large neural networks.

  12. Chronic tissue response to untethered microelectrode implants in the rat brain and spinal cord

    Science.gov (United States)

    Ersen, Ali; Elkabes, Stella; Freedman, David S.; Sahin, Mesut

    2015-02-01

    Objective. Microelectrodes implanted in the central nervous system (CNS) often fail in long term implants due to the immunological tissue response caused by tethering forces of the connecting wires. In addition to the tethering effect, there is a mechanical stress that occurs at the device-tissue interface simply because the microelectrode is a rigid body floating in soft tissue and it cannot reshape itself to comply with changes in the surrounding tissue. In the current study we evaluated the scar tissue formation to tetherless devices with two significantly different geometries in the rat brain and spinal cord in order to investigate the effects of device geometry. Approach. One of the implant geometries resembled the wireless, floating microstimulators that we are currently developing in our laboratory and the other was a (shank only) Michigan probe for comparison. Both electrodes were implanted into either the cervical spinal cord or the motor cortices, one on each side. Main results. The most pronounced astroglial and microglial reactions occurred within 20 μm from the device and decreased sharply at larger distances. Both cell types displayed the morphology of non-activated cells past the 100 μm perimeter. Even though the aspect ratios of the implants were different, the astroglial and microglial responses to both microelectrode types were very mild in the brain, stronger and yet limited in the spinal cord. Significance. These observations confirm previous reports and further suggest that tethering may be responsible for most of the tissue response in chronic implants and that the electrode size has a smaller contribution with floating electrodes. The electrode size may be playing primarily an amplifying role to the tethering forces in the brain whereas the size itself may induce chronic response in the spinal cord where the movement of surrounding tissues is more significant.

  13. Exhaust system having a gold-platinum group metal catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Ragle, Christie Susan [Havana, IL; Silver, Ronald G [Peoria, IL; Zemskova, Svetlana Mikhailovna [Edelstein, IL; Eckstein, Colleen J [Metamora, IL

    2011-12-06

    A method of providing an exhaust treatment device is disclosed. The method includes applying a catalyst including gold and a platinum group metal to a particulate filter. The concentration of the gold and the platinum group metal is sufficient to enable oxidation of carbon monoxide and nitric oxide.

  14. Corrosion Studies of Platinum Nano-Particles for Fuel Cells

    DEFF Research Database (Denmark)

    Shim, Signe Sarah

    The main focus of the present thesis is on corrosion and prevention of corrosion of platinum particles supported on carbon. This is important for instance in connection with start up and shutdown of fuel cells. The degradation mechanism of platinum particles supported on carbon has been...

  15. On-Chip Determination of Dopamine Exocytosis Using Mercaptopropionic Acid Modified Microelectrodes

    DEFF Research Database (Denmark)

    Spégel, C.; Heiskanen, Arto; Acklid, J.

    2007-01-01

    Gold and platinum, which often are used for thin film metallization, are not suitable for the measurement of dopamine (DA), since the oxidation product of DA forms a non-conducting polymer on the electrode surface. In this work several thiols were screened for their ability to prevent this polyme...

  16. Beta-functionalised polythiophenes as microelectrode modifiers in low conductive media.

    Science.gov (United States)

    Cocchi, Marina; Franchini, GianCarlo; Manfredini, Matteo; Marchetti, Andrea; Pigani, Laura; Seeber, Renato; Tassi, Lorenzo; Ulrici, Alessandro; Vignali, Moris; Zanardi, Chiara; Zannini, Paolo

    2002-03-01

    A study on polythiophene coated microelectrodes is reported, the goal being that of checking the capability of these electrochemical systems to work in low conductive media. The possibility of electrochemically p-doping the polymer in the presence of very low concentrations or even in the absence of supporting electrolyte in the solution is ascertained, opening the way to the use of similar systems in pure solvent media. This result is obtained in such conditions that the presence of residual charges--and corresponding counterions--trapped inside the film coating can be reasonably hypothesised.

  17. Pre-implantation electrochemical characterization of a Parylene C sheath microelectrode array probe.

    Science.gov (United States)

    Hara, Seth A; Kim, Brian J; Kuo, Jonathan T W; Lee, Curtis; Gutierrez, Christian A; Hoang, Tuan; Meng, Ellis

    2012-01-01

    We present the preliminary electrochemical characterization of 3D Parylene C sheath microelectrode array probes towards realizing reliable chronic neuroprosthetic recordings. Electrochemical techniques were used to verify electrode integrity after our novel post-fabrication thermoforming process was applied to flat surface micromachined structures to achieve a hollow sheath probe shape. Characterization of subsequent neurotrophic coatings was performed and accelerated life testing was used to simulate six months in vivo. Prior to probe implantation, crosstalk was measured and electrode surface properties were evaluated through the use of electrochemical impedance spectroscopy.

  18. Electrohydrodynamic actuation of co-flowing liquids by means of microelectrode arrays

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Sanchez, Pablo; Ferney, Mathieu; Ramos, Antonio, E-mail: pablogarcia@us.es [Depto. de Electronica y Electromagnetismo, University of Sevilla (Spain)

    2011-06-23

    Electric fields induce forces at the interface between liquids with different electrical properties (conductivity and/or permittivity). We explore how to use these forces for manipulating two coflowing streams of liquids in a microchannel. A microelectrode array is fabricated at the bottom of the channel and one of the two liquids is labelled with a fluorescent dye for observing the phenomenon. The diffuse interface between the two liquids is deflected depending on the ac signal and conductivity (or permittivity) ratio between the liquids. Only a few volts are needed for observing the interface destabilization, in contrast with other electrode configurations where hundreds of volts are applied.

  19. Platinum contamination issues in ferroelectric memories

    Science.gov (United States)

    Boubekeur, H.; Mikolajick, T.; Pamler, W.; Hopfner, J.; Frey, L.; Ryssel, H.

    2002-09-01

    The contamination risk of processing with platinum electrodes on device performance in ferroelectric memories is assessed in this work. Details of platinum diffusion to the active regions at annealing temperatures of 800 degC are investigated by secondary ion mass spectroscopy, deep level transient spectroscopy, and Rutherford backscattering spectrometry techniques. Cross sectional transmission electron microscopy and local elemental analysis by energy dispersive x-ray spectroscopy were used to examine the precipitation of Pt in defect free silicon as an eventual cause of gate oxide degradation. The impact of platinum contamination on device performance is evaluated under the typical ferroelectric memory processing conditions. Results from leakage current and charge to breakdown measurements of intentionally contaminated diode and metal-oxide-semiconductor (MOS) structures, respectively, are presented. The results show that the degradation depends strongly on device design and configuration. A phosphorus doped polysilicon plug, which has the function of connecting the select transistor to the capacitor module, provides effective gettering regions and prevents the diffusion of Pt atoms to the active regions. Under typical processing conditions, no evident Pt precipitates were observed and up to a concentration level of 4 x1014 atoms/cm2, the leakage current of intentionally contaminated diodes does not increase, if the contamination occurs after front-end phosphorus doped poly-Si processing. Results from constant current charge to breakdown show a small number of breakdown events due to redeposition of Pt at the periphery of the MOS structure. The risk of processing with Pt electrodes in ferroelectric memories requires great care. Precautions like sealing the back surface and incorporating phosphorus doped polysilicon as the plug material are necessary to avoid the detrimental effects of Pt.

  20. Platinum-induced neurotoxicity: A review of possible mechanisms.

    Science.gov (United States)

    Kanat, Ozkan; Ertas, Hulya; Caner, Burcu

    2017-08-10

    Patients treated with platinum-based chemotherapy frequently experience neurotoxic symptoms, which may lead to premature discontinuation of therapy. Despite discontinuation of platinum drugs, these symptoms can persist over a long period of time. Cisplatin and oxaliplatin, among all platinum drugs, have significant neurotoxic potential. A distal dose-dependent symmetrical sensory neuropathy is the most common presentation of platinum neurotoxicity. DNA damage-induced apoptosis of dorsal root ganglion (DRG) neurons seems to be the principal cause of neurological symptoms. However, DRG injury alone cannot explain some unique symptoms such as cold-aggravated burning pain affecting distal extremities that is observed with oxaliplatin administration. In this article, we briefly reviewed potential mechanisms for the development of platinum drugs-associated neurological manifestations.

  1. Under-Reported Aspects of Platinum Drug Pharmacology

    Directory of Open Access Journals (Sweden)

    Dirk Theile

    2017-02-01

    Full Text Available Platinum drugs remain the backbone of many antineoplastic regimens. Among the numerous chemical or pharmacological effects of platinum drugs, some aspects tend to be under-reported. Thus, this perspective paper intends to stress some neglected properties of platinum drugs: first, the physico-chemical characteristics (aquation reaction kinetics that determine site-specific toxicity; second, the impact on RNA molecules. Knowledge of the ‘RNA world’ has dramatically changed our understanding of cellular and molecular biology. The inherent RNA-crosslinking properties should make platinum-based drugs interact with coding and non-coding RNAs. Third, we will discuss the impact on the immune system, which is now recognized to substantially contribute to chemotherapy efficacy. Together, platinum drugs are in fact old drugs, but are worth re-focusing on. Many aspects are still mysterious but can pave the way to new drugs or an improved application of the already existing compounds.

  2. Extracellular recordings from locally dense microelectrode arrays coupled to dissociated cortical cultures.

    Science.gov (United States)

    Berdondini, L; Massobrio, P; Chiappalone, M; Tedesco, M; Imfeld, K; Maccione, A; Gandolfo, M; Koudelka-Hep, M; Martinoia, S

    2009-03-15

    High-density microelectrode arrays (MEAs) enabled by recent developments of microelectronic circuits (CMOS-MEA) and providing spatial resolutions down to the cellular level open the perspective to access simultaneously local and overall neuronal network activities expressed by in vitro preparations. The short inter-electrode separation results in a gain of information on the micro-circuit neuronal dynamics and signal propagation, but requires the careful evaluation of the time resolution as well as the assessment of possible cross-talk artifacts. In this respect, we have realized and tested Pt high-density (HD)-MEAs featuring four local areas with 10microm inter-electrode spacing and providing a suitable noise level for the assessment of the high-density approach. First, simulated results show how possible artifacts (duplicated spikes) can be theoretically observed on nearby microelectrodes only for very high-shunt resistance values (e.g. R(sh)=50 kOmega generates up to 60% of false positives). This limiting condition is not compatible with typical experimental conditions (i.e. dense but not confluent cultures). Experiments performed on spontaneously active cortical neuronal networks show that spike synchronicity decreases by increasing the time resolution and analysis results show that the detected synchronous spikes on nearby electrodes are likely to be unresolved (in time) fast local propagations. Finally, functional connectivity analysis results show stronger local connections than long connections spread homogeneously over the whole network demonstrating the expected gain in detail provided by the spatial resolution.

  3. Voltammetric studies on the electrochemical determination of methylmercury in chloride medium at carbon microelectrodes

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, F. [Centro de Electroquimica e Cinetica da Universidade de Lisboa, Departamento de Quimica e Bioquimica, Faculdade de Ciencias, Universidade de Lisboa, Campo Grande, Ed. C8, 1749-016 Lisbon (Portugal); Neto, M.M.M. [Centro de Electroquimica e Cinetica da Universidade de Lisboa, Departamento de Quimica e Bioquimica, Faculdade de Ciencias, Universidade de Lisboa, Campo Grande, Ed. C8, 1749-016 Lisbon (Portugal) and Departamento de Quimica Agricola e Ambiental, Instituto Superior de Agronomia, Tapada da Ajuda, 1349-017 Lisbon (Portugal)]. E-mail: mm.neto@netcabo.pt; Rocha, M.M. [Centro de Electroquimica e Cinetica da Universidade de Lisboa, Departamento de Quimica e Bioquimica, Faculdade de Ciencias, Universidade de Lisboa, Campo Grande, Ed. C8, 1749-016 Lisbon (Portugal); Fonseca, I.T.E. [Centro de Electroquimica e Cinetica da Universidade de Lisboa, Departamento de Quimica e Bioquimica, Faculdade de Ciencias, Universidade de Lisboa, Campo Grande, Ed. C8, 1749-016 Lisbon (Portugal)

    2006-10-10

    Electroanalytical techniques have been used to determine methylmercury at low levels in environmental matrices. The electrochemical behaviour of methylmercury at carbon microelectrodes in a hydrochloric acid medium using cyclic, square wave and fast-scan linear-sweep voltammetric techniques has been investigated. The analytical utility of the methylmercury reoxidation peak has been explored, but the recorded peak currents were found to be poorly reproducible. This is ascribed to two factors: the adsorption of insoluble chloromercury compounds on the electrode surface, which appears to be an important contribution to hinder the voltammetric signal of methylmercury; and the competition between the reoxidation of the methylmercury radical and its dimerization reaction, which limits the reproducibility of the methylmercury peak. These problems were successfully overcome by adopting the appropriate experimental conditions. Fast-scan rates were employed and an efficient electrochemical regeneration procedure of the electrode surface was achieved, under potentiostatic conditions in a mercury-free solution containing potassium thiocyanate-a strong complexing agent. The influence of chloride ion concentration was analysed. Interference by metals, such as lead and cadmium, was considered. Calibration plots were obtained in the micromolar and submicromolar concentration ranges, allowing the electrochemical determination of methylmercury in trace amounts. An estuarine water sample was analysed using the new method with a glassy carbon microelectrode.

  4. Nafion-CNT coated carbon-fiber microelectrodes for enhanced detection of adenosine.

    Science.gov (United States)

    Ross, Ashley E; Venton, B Jill

    2012-07-07

    Adenosine is a neuromodulator that regulates neurotransmission. Adenosine can be monitored using fast-scan cyclic voltammetry at carbon-fiber microelectrodes and ATP is a possible interferent in vivo because the electroactive moiety, adenine, is the same for both molecules. In this study, we investigated carbon-fiber microelectrodes coated with Nafion and carbon nanotubes (CNTs) to enhance the sensitivity of adenosine and decrease interference by ATP. Electrodes coated in 0.05 mg mL(-1) CNTs in Nafion had a 4.2 ± 0.2 fold increase in current for adenosine, twice as large as for Nafion alone. Nafion-CNT electrodes were 6 times more sensitive to adenosine than ATP. The Nafion-CNT coating did not slow the temporal response of the electrode. Comparing different purine bases shows that the presence of an amine group enhances sensitivity and that purines with carbonyl groups, such as guanine and hypoxanthine, do not have as great an enhancement after Nafion-CNT coating. The ribose group provides additional sensitivity enhancement for adenosine over adenine. The Nafion-CNT modified electrodes exhibited significantly more current for adenosine than ATP in brain slices. Therefore, Nafion-CNT modified electrodes are useful for sensitive, selective detection of adenosine in biological samples.

  5. Enabling long term monitoring of dopamine using dimensionally stable ultrananocrystalline diamond microelectrodes

    Science.gov (United States)

    Dutta, Gaurab; Tan, Chao; Siddiqui, Shabnam; Arumugam, Prabhu U.

    2016-09-01

    Chronic dopamine (DA) monitoring is a critical enabling technology to identify the neural basis of human behavior. Carbon fiber microelectrodes (CFM), the current gold standard electrode for in vivo fast scan cyclic voltammetry (FSCV), rapidly loses sensitivity due to surface fouling during chronic neural testing. Periodic voltage excursions at elevated anodic potentials regenerate fouled CFM surfaces but they also chemically degrade the CFM surfaces. Here, we compare the dimensional stability of 150 μm boron-doped ultrananocrystalline diamond (BDUNCD) microelectrodes in 1X PBS during ‘electrochemical cleaning’ with a similar-sized CFM. Scanning electron microscopy and Raman spectroscopy confirm the exceptional dimensional stability of BDUNCD after 40 h of FSCV cycling (∼8 million cycles). The fitting of electrochemical impedance spectroscopy data to an appropriate circuit model shows a 2x increase in charge transfer resistance and an additional RC element, which suggests oxidation of BDUNCD electrode surface. This could have likely increased the DA oxidation potential by ∼34% to +308 mV. A 2x increase in BDUNCD grain capacitance and a negligible change in grain boundary impedance suggests regeneration of grains and the exposure of new grain boundaries, respectively. Overall, DA voltammogram signals were reduced by only ∼20%. In contrast, the CFM is completely etched with a ∼90% reduction in the DA signal using the same cleaning conditions. Thus, BDUNCD provides a robust electrode surface that is amenable to repeated and aggressive cleaning which could be used for chronic DA sensing.

  6. Comparative analysis of system identification techniques for nonlinear modeling of the neuron-microelectrode junction.

    Science.gov (United States)

    Khan, Saad Ahmad; Thakore, Vaibhav; Behal, Aman; Bölöni, Ladislau; Hickman, James J

    2013-03-01

    Applications of non-invasive neuroelectronic interfacing in the fields of whole-cell biosensing, biological computation and neural prosthetic devices depend critically on an efficient decoding and processing of information retrieved from a neuron-electrode junction. This necessitates development of mathematical models of the neuron-electrode interface that realistically represent the extracellular signals recorded at the neuroelectronic junction without being computationally expensive. Extracellular signals recorded using planar microelectrode or field effect transistor arrays have, until now, primarily been represented using linear equivalent circuit models that fail to reproduce the correct amplitude and shape of the signals recorded at the neuron-microelectrode interface. In this paper, to explore viable alternatives for a computationally inexpensive and efficient modeling of the neuron-electrode junction, input-output data from the neuron-electrode junction is modeled using a parametric Wiener model and a Nonlinear Auto-Regressive network with eXogenous input trained using a dynamic Neural Network model (NARX-NN model). Results corresponding to a validation dataset from these models are then employed to compare and contrast the computational complexity and efficiency of the aforementioned modeling techniques with the Lee-Schetzen technique of cross-correlation for estimating a nonlinear dynamic model of the neuroelectronic junction.

  7. A simple implantation method for flexible, multisite microelectrodes into rat brains

    Directory of Open Access Journals (Sweden)

    Anja eRichter

    2013-07-01

    Full Text Available A long term functional and reliable coupling between neural tissue and implanted microelectrodes is the key issue in acquiring neural electrophysiological signals or therapeutically excite neural tissue. The currently often used rigid micro-electrodes are thought to cause a severe foreign body reaction resulting in a thick glial scar and consequently a poor tissue-electrode coupling in the chronic phase. We hypothesize, that this adverse effect might be remedied by probes compliant to the soft brain tissue, i.e. replacing rigid electrodes by flexible ones. Unfortunately, this flexibility comes at the price of a low stiffness, which makes targeted low trauma implantation very challenging. In this study, we demonstrate an adaptable and simple method to implant extremely flexible microprobes even to deep areas of rat’s brain. Implantation of flexible probes is achieved by rod supported stereotactic insertion fostered by a hydrogel (2% agarose in PBS cushion on the exposed skull. We were thus able to implant very flexible micro-probes in 70 rats as deep as the rodent's subthalamic nucleus. This work describes in detail the procedures and steps needed for minimal invasive, but reliable implantation of flexible probes.

  8. A simple implantation method for flexible, multisite microelectrodes into rat brains.

    Science.gov (United States)

    Richter, Anja; Xie, Yijing; Schumacher, Anett; Löffler, Susanne; Kirch, Robert D; Al-Hasani, Jaafar; Rapoport, Daniel H; Kruse, Charli; Moser, Andreas; Tronnier, Volker; Danner, Sandra; Hofmann, Ulrich G

    2013-01-01

    A long term functional and reliable coupling between neural tissue and implanted microelectrodes is the key issue in acquiring neural electrophysiological signals or therapeutically excite neural tissue. The currently often used rigid micro-electrodes are thought to cause a severe foreign body reaction resulting in a thick glial scar and consequently a poor tissue-electrode coupling in the chronic phase. We hypothesize, that this adverse effect might be remedied by probes compliant to the soft brain tissue, i.e., replacing rigid electrodes by flexible ones. Unfortunately, this flexibility comes at the price of a low stiffness, which makes targeted low trauma implantation very challenging. In this study, we demonstrate an adaptable and simple method to implant extremely flexible microprobes even to deep areas of rat's brain. Implantation of flexible probes is achieved by rod supported stereotactic insertion fostered by a hydrogel (2% agarose in PBS) cushion on the exposed skull. We were thus able to implant very flexible micro-probes in 70 rats as deep as the rodent's subthalamic nucleus. This work describes in detail the procedures and steps needed for minimal invasive, but reliable implantation of flexible probes.

  9. A novel electroporation system for efficient molecular delivery into Chlamydomonas reinhardtii with a 3-dimensional microelectrode

    Science.gov (United States)

    Kang, Seongsu; Kim, Kwon-Ho; Kim, Yeu-Chun

    2015-11-01

    Electroporation is one of the most widely used transfection methods because of its high efficiency and convenience among the various transfection methods. Previous micro-electroporation systems have some drawbacks such as limitations in height and design, time-consuming and an expensive fabrication process due to technical constraints. This study fabricates a three dimensional microelectrode using the 3D printing technique. The interdigitated microstructure consisting of poly lactic acid was injected by a 3D printer and coated with silver and aluminum with a series of dip-coatings. With the same strength of electric field (V cm-1), a higher efficiency for molecular delivery and a higher cellular viability are achieved with the microelectrode than with a standard cuvette. In addition, this study investigates chemicophysical changes such as Joule heating and dissolved metal during electroporation and showed the micro-electroporation system had less chemicophysical changes. It was concluded that the proposed micro-electroporation system will contribute to genetic engineering as a promising delivery tool, and this combination of 3D printing and electroporation has many potential applications for diverse designs or systems.

  10. Integrated microelectrode arrays for trace-metal analysis of aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Saban, S.B.; Darling, R.B. [Univ. of Washington, Seattle, WA (United States). Dept. of Electrical Engineering

    1995-12-31

    Stripping Voltammetry (SV) at microelectrodes has gained increased interest in the analysis of aqueous solutions due to its ability to analyze low concentrations (ppb) of electroactive metallic species in solution. Existing integrated circuit (IC) technology allows the inexpensive fabrication of microelectrodes with dimensions on the order of microns and with a high degree of uniformity and reproducibility. Additional circuitry, both multiplexing and signal conditioning, can be placed directly onto the sensor offering increased sensitivity and flexibility. Multi-element electrochemical sensors containing arrays of Pt, Au, and Ag electrodes and capable of individual measurement through built-in multiplexing or simultaneous measurement at the appropriate potential ranges for each individual electrode were fabricated using existing 2 micron IC technology. Results of simultaneous measurements of low concentrations of Cd, Pb, Cu, As, and Hg in solution indicate that interferences due to intermetallic compound formation at electrode surfaces can be isolated by the extra information provided by the differences in the formation of these compounds at different electrode surfaces.

  11. Dual-side and three-dimensional microelectrode arrays fabricated from ultra-thin silicon substrates

    Science.gov (United States)

    Du, Jiangang; Roukes, Michael L.; Masmanidis, Sotiris C.

    2009-07-01

    A method for fabricating planar implantable microelectrode arrays was demonstrated using a process that relied on ultra-thin silicon substrates, which ranged in thickness from 25 to 50 µm. The challenge of handling these fragile materials was met via a temporary substrate support mechanism. In order to compensate for putative electrical shielding of extracellular neuronal fields, separately addressable electrode arrays were defined on each side of the silicon device. Deep reactive ion etching was employed to create sharp implantable shafts with lengths of up to 5 mm. The devices were flip-chip bonded onto printed circuit boards (PCBs) by means of an anisotropic conductive adhesive film. This scalable assembly technique enabled three-dimensional (3D) integration through formation of stacks of multiple silicon and PCB layers. Simulations and measurements of microelectrode noise appear to suggest that low impedance surfaces, which could be formed by electrodeposition of gold or other materials, are required to ensure an optimal signal-to-noise ratio as well a low level of interchannel crosstalk.

  12. Characterization of poly(3,4-ethylenedioxythiophene):tosylate conductive polymer microelectrodes for transmitter detection.

    Science.gov (United States)

    Larsen, Simon T; Vreeland, Richard F; Heien, Michael L; Taboryski, Rafael

    2012-04-21

    In this paper we investigate the physical and electrochemical properties of micropatterned poly(3,4-ethylenedioxythiophene):tosylate (PEDOT:tosylate) microelectrodes for neurochemical detection. PEDOT:tosylate is a promising conductive polymer electrode material for chip-based bioanalytical applications such as capillary electrophoresis, high-performance liquid chromatography, and constant potential amperometry at living cells. Band electrodes with widths down to 3 μm were fabricated on polymer substrates using UV lithographic methods. The electrodes are electrochemically stable in a range between -200 mV and 700 mV vs. Ag/AgCl and show a relatively low resistance. A wide range of transmitters is shown to oxidize readily on the electrodes. Kinetic rate constants and half wave potentials are reported. The capacitance per area was found to be high (1670 ± 130 μF cm(-2)) compared to other thin film microelectrode materials. Finally, we use constant potential amperometry to measure the release of transmitters from a group of PC 12 cells. The results show how the current response decreases for a series of stimulations with high K(+) buffer.

  13. Design rule for optimization of microelectrodes used in electric cell-substrate impedance sensing (ECIS).

    Science.gov (United States)

    Price, Dorielle T; Rahman, Abdur Rub Abdur; Bhansali, Shekhar

    2009-03-15

    This paper presents an experimentally derived design rule for optimization of microelectrodes used in electric cell-substrate impedance sensing (ECIS) up to 10MHz. The effect of change in electrode design (through electrode sensor area, lead trace widths, and passivation coating thickness) on electrode characteristics was experimentally evaluated using electrochemical impedance spectroscopy (EIS) measurements and analyzed using equivalent circuit models. A parasitic passivation coating impedance was successfully minimized by designing electrodes with either a thicker passivation layer or a smaller lead trace area. It was observed that the passivated lead trace area to passivation coating thickness ratio has a critical value of 5.5, under which the impedance contribution of the coating is minimized. The optimized design of ECIS-based microelectrode devices reported in this work will make it possible to probe the entire beta dispersion region of adherent biological cell layers by reducing measurement artifacts and improving the quality of data across the beta-dispersion region. The new design will enable the use of the commonly used ECIS technique to measure real-time cellular properties in high frequency ranges (beta dispersion) that was not possible thus far.

  14. A novel electroporation system for efficient molecular delivery into Chlamydomonas reinhardtii with a 3-dimensional microelectrode.

    Science.gov (United States)

    Kang, Seongsu; Kim, Kwon-Ho; Kim, Yeu-Chun

    2015-11-02

    Electroporation is one of the most widely used transfection methods because of its high efficiency and convenience among the various transfection methods. Previous micro-electroporation systems have some drawbacks such as limitations in height and design, time-consuming and an expensive fabrication process due to technical constraints. This study fabricates a three dimensional microelectrode using the 3D printing technique. The interdigitated microstructure consisting of poly lactic acid was injected by a 3D printer and coated with silver and aluminum with a series of dip-coatings. With the same strength of electric field (V cm(-1)), a higher efficiency for molecular delivery and a higher cellular viability are achieved with the microelectrode than with a standard cuvette. In addition, this study investigates chemicophysical changes such as Joule heating and dissolved metal during electroporation and showed the micro-electroporation system had less chemicophysical changes. It was concluded that the proposed micro-electroporation system will contribute to genetic engineering as a promising delivery tool, and this combination of 3D printing and electroporation has many potential applications for diverse designs or systems.

  15. Monofunctional and Higher-Valent Platinum Anticancer Agents

    Science.gov (United States)

    Johnstone, Timothy C.; Wilson, Justin J.

    2013-01-01

    Platinum compounds represent one of the great success stories of metals in medicine. Following the serendipitous discovery of the anticancer activity of cisplatin by Rosenberg, a large number of cisplatin variants have been prepared and tested for their ability to kill cancer cells and inhibit tumor growth. These efforts continue today with increased realization that new strategies are needed to overcome issues of toxicity and resistance inherent to treatment by the approved platinum anticancer agents. One approach has been the use of so-called “non-traditional” platinum(II) and platinum(IV) compounds that violate the structure-activity relationships that governed platinum drug-development research for many years. Another is the use of specialized drug delivery strategies. Here we describe recent developments from our laboratory involving monofunctional platinum(II) complexes together with an historical account of the manner by which we came to investigate these compounds and their relationship to previously studied molecules. We also discuss work carried out using platinum(IV) prodrugs and the development of nanoconstructs designed to deliver them in vivo. PMID:23738524

  16. Surface Analysis of 4-Aminothiophenol Adsorption at Polycrystalline Platinum Electrodes

    Science.gov (United States)

    Rosario-Castro, Belinda I.; Fachini, Estevao R.; Contes, Enid J.; Perez-Davis, Marla E.; Cabrera, Carlos R.

    2008-01-01

    Formation of self-assembled monolayer (SAM) of 4-aminothiophenol (4-ATP) on polycrystalline platinum electrodes has been studied by surface analysis and electrochemistry techniques. The 4-ATP monolayer was characterized by cyclic voltammetry (CV), Raman spectroscopy, reflection absorption infrared (RAIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry (CV) experiments give an idea about the packing quality of the monolayer. RAIR and Raman spectra for 4-ATP modified platinum electrodes showed the characteristic adsorption bands for neat 4-ATP indicating the adsorption of 4-ATP molecules on platinum surface. The adsorption on platinum was also evidenced by the presence of sulfur and nitrogen peaks by XPS survey spectra of the modified platinum electrodes. High resolution XPS studies and RAIR spectrum for platinum electrodes modified with 4-ATP indicate that molecules are sulfur-bonded to the platinum surface. The formation of S-Pt bond suggests that ATP adsorption gives up an amino terminated SAM. Thickness of the monolayer was evaluated via angle-resolved XPS (AR-XPS) analyses. Derivatization of 4-ATP SAM was performed using 16-Br hexadecanoic acid.

  17. Cisplatin and platinum drugs at the molecular level. (Review).

    Science.gov (United States)

    Boulikas, Teni; Vougiouka, Maria

    2003-01-01

    Over twenty years of intensive work toward improvement of cisplatin, and with hundreds of platinum drugs tested, has resulted in the introduction of the widely used carboplatin and of oxaliplatin used only for a very narrow spectrum of cancers. A number of interesting platinum compounds including the orally administered platinum drug JM216, nedaplatin, the sterically hindered platinum(II) complex ZD0473, the trinuclear platinum complex BBR3464, and the liposomal forms Lipoplatin and SPI-77 are under clinical evaluation. This review summarizes the molecular mechanisms of platinum compounds for DNA damage, DNA repair and induction of apoptosis via activation or modulation of signaling pathways and explores the basis of platinum resistance. Cisplatin, carboplatin, oxaliplatin and most other platinum compounds induce damage to tumors via induction of apoptosis; this is mediated by activation of signal transduction leading to the death receptor mechanisms as well as mitochondrial pathways. Apoptosis is responsible for the characteristic nephrotoxicity, ototoxicity and most other toxicities of the drugs. The major limitation in the clinical applications of cisplatin has been the development of cisplatin resistance by tumors. Mechanisms explaining cisplatin resistance include the reduction in cisplatin accumulation inside cancer cells because of barriers across the cell membrane, the faster repair of cisplatin adducts, the modulation of apoptotic pathways in various cells, the upregulation in transcription factors, the loss of p53 and other protein functions and a higher concentration of glutathione and metallothioneins in some type of tumors. A number of experimental strategies to overcome cisplatin resistance are at the preclinical or clinical level such as introduction of the bax gene, inhibition of the JNK pathway, introduction of a functional p53 gene, treatment of tumors with aldose reductase inhibitors and others. Particularly important are combinations of platinum

  18. Bio-inspired routes for synthesizing efficient nanoscale platinum electrocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Jennifer N. [Univ. of California, San Diego, CA (United States); Wang, Joseph [Univ. of California, San Diego, CA (United States)

    2014-08-31

    The overall objective of the proposed research is to use fundamental advances in bionanotechnology to design powerful platinum nanocrystal electrocatalysts for fuel cell applications. The new economically-viable, environmentally-friendly, bottom-up biochemical synthetic strategy will produce platinum nanocrystals with tailored size, shape and crystal orientation, hence leading to a maximum electrochemical reactivity. There are five specific aims to the proposed bio-inspired strategy for synthesizing efficient electrocatalytic platinum nanocrystals: (1) isolate peptides that both selectively bind particular crystal faces of platinum and promote the nucleation and growth of particular nanocrystal morphologies, (2) pattern nanoscale 2-dimensional arrays of platinum nucleating peptides from DNA scaffolds, (3) investigate the combined use of substrate patterned peptides and soluble peptides on nanocrystal morphology and growth (4) synthesize platinum crystals on planar and large-area carbon electrode supports, and (5) perform detailed characterization of the electrocatalytic behavior as a function of catalyst size, shape and morphology. Project Description and Impact: This bio-inspired collaborative research effort will address key challenges in designing powerful electrocatalysts for fuel cell applications by employing nucleic acid scaffolds in combination with peptides to perform specific, environmentally-friendly, simultaneous bottom-up biochemical synthesis and patterned assembly of highly uniform and efficient platinum nanocrystal catalysts. Bulk synthesis of nanoparticles usually produces a range of sizes, accessible catalytic sites, crystal morphologies, and orientations, all of which lead to inconsistent catalytic activities. In contrast, biological systems routinely demonstrate exquisite control over inorganic syntheses at neutral pH and ambient temperature and pressures. Because the orientation and arrangement of the templating biomolecules can be precisely

  19. The RSC Faraday prize lecture of 1989 on platinum.

    Science.gov (United States)

    Thomas, John Meurig

    2017-08-25

    In 1861, Michael Faraday gave one of his last Friday Evening Discourses at the Royal Institution of Great Britain, London, on platinum, which he described as "this beautiful, magnificent and valuable metal". More than a hundred and twenty years later (in 1989), the author re-enacted, at the Royal Institution, many of the demonstrations that Faraday carried out in his memorable Discourse. This article outlines many of Faraday's views on, and experiments with, platinum. It also describes the continuing importance and utilization of platinum, both as perceived in 1989 and from present perspectives.

  20. New Perfluorophtalate Complexes of Platinum(II) With Chemotherapeutic Potential

    OpenAIRE

    de Oliveira, M. B.; J. Miller; Banks, R. E.; Kelland, L R; McAuliffe, C. A.; Mahmood, N; Rowland, I. J.

    1996-01-01

    Two new platinum(II) complexes have been synthesized and their anti-tumour and anti-HIV activities have been evaluated. The new complexes are: (i) cis-tetrafluorophthalate-ammine-morpholine-platinum(II) or MMF3 and (ii) cis-tetrafluorophthalate- ammine-piperidine-platinum(II) or MPF4. They were characterized by elemental analysis, IR spectra and 1H and 13C NMR spectra. They were tested against five human ovarian carcinoma cell lines, viz., CH1, CH1cisR, A2780, A2780cisR and SKOV-3. They were ...

  1. Study of supported platinum catalysts by anomalous scattering

    Energy Technology Data Exchange (ETDEWEB)

    Georgopoulos, P.; Cohen, J.B.

    1985-01-01

    Platinum metal catalysts supported on silica gel and alumina were examined by wide-angle anomalous x-ray scattering at the Cornell High Energy Synchrotron Source. Complete removal of the support background features is achieved by this method, eliminating errors due to inaccurate background estimation. Platinum diffraction patterns from very-high-percentage metal-exposed catalysts were obtained for the first time, as well as from platinum supported on alumina. This technique is suitable for examining catalysts under working conditions and is superior to EXAFS for determinations of particle morphology and size distribution. 10 references, 8 figures.

  2. Interaction of novel bis(platinum) complexes with DNA.

    OpenAIRE

    Roberts, J D; Van Houten, B; Qu, Y; Farrell, N P

    1989-01-01

    Bis(platinum) complexes [[cis-PtCl2(NH3)]2H2N(CH2)nNH2] are a novel series of potential anticancer agents in which two cis-diamine(platinum) groups are linked by an alkyldiamine of variable length. These complexes are potentially tetrafunctional, a unique feature in comparison with known anticancer agents. Studies of DNA interactions of bis(platinum) complexes in comparison with cisplatin demonstrate significant differences. Investigations of interstrand crosslink formation in which crosslink...

  3. Platinum(II) and platinum(IV) complexes stabilized by abnormal/mesoionic C4-bound dicarbenes.

    Science.gov (United States)

    Khlebnikov, Vsevolod; Heckenroth, Marion; Müller-Bunz, Helge; Albrecht, Martin

    2013-03-28

    Platinum(II) complexes comprising abnormal diimidazolylidene ligands were synthesized from cis-PtMe(2)(DMSO)(2) using microwave-assisted double C-H bond activation. NMR analysis revealed an unusual solvolysis process, induced by coordinating solvents such as DMSO and MeCN, which has not been observed in related normal dicarbene complexes. NMR and IR spectroscopy and crystallographic analysis of the mono-substituted DMSO complex indicate a sulfur-bonding of the DMSO ligand to the platinum(II) center. Analysis of the DMSO exchange kinetics provided for the first time a quantitative measure of the trans effect of abnormal carbene ligands. The kinetic exchange rate in these bidentate abnormal dicarbene complexes is 0.050(±2) s(-1) and thus similar to analogous platinum(II) complexes containing phenylpyridine, yet significantly slower than that induced by pyridylidene pyridine. Reaction of the dicarbene platinum(II) complexes with PhICl(2), Br(2) and I(2) afforded the corresponding platinum(IV) complexes. Linkage isomerism of the Pt(IV)-bound DMSO was observed when the bromination reaction was performed in DMSO solution. Moreover, solvolysis was less pronounced in the platinum(IV) complexes than in the corresponding platinum(II) analogues.

  4. Toward high-throughput screening of NAD(P)-dependent oxidoreductases using boron-doped diamond microelectrodes and microfluidic devices.

    Science.gov (United States)

    Oyobiki, Ryo; Kato, Taisuke; Katayama, Michinobu; Sugitani, Ai; Watanabe, Takeshi; Einaga, Yasuaki; Matsumoto, Yoshinori; Horisawa, Kenichi; Doi, Nobuhide

    2014-10-07

    Although oxidoreductases are widely used in many applications, such as biosensors and biofuel cells, improvements in the function of existing oxidoreductases or the discovery of novel oxidoreductases with greater activities is desired. To increase the activity of oxidoreductases by directed evolution, a powerful screening technique for oxidoreductases is required. In this study, we demonstrate the utility of boron-doped diamond (BDD) microelectrodes for quantitative and potentially high-throughput measurement of the activity of NAD(P)-dependent oxidoreductases. We first confirmed that BDD microelectrodes can quantify the activity of low concentrations (10-100 pM) of glucose-6-phosphate dehydrogenase and alcohol dehydrogenase with a measuring time of 1 ms per sample. In addition, we found that poisoning of BDD microelectrodes can be repressed by optimizing the pH and by adding l-arginine to the enzyme solution as an antiaggregation agent. Finally, we fabricated a microfluidic device containing a BDD electrode for the first time and observed the elevation of the oxidation current of NADH with increasing flow rate. These results imply that the combination of a BDD microelectrode and microfluidics can be used for high-throughput screening of an oxidoreductase library containing a large number (>10(6)) of samples, each with a small (nanoliter) sample volume.

  5. Intraneural stimulation using 2D wire-microelectrode arrays: II. Comparison with single-wire electrode results

    NARCIS (Netherlands)

    Smit, J.P.A.; Rutten, W.L.C.

    1995-01-01

    A two-dimensional wire-microelectrode array was inserted into the peroneal nerve of the rat through an incision. For each of the electrodes in the array the corresponding twitch-force recruitment curve was recorded from the extensor digitorum longus muscle (EDL). The mean value and standard deviatio

  6. On-Line Monitoring the Growth of E. coli or HeLa Cells Using an Annular Microelectrode Piezoelectric Biosensor

    Science.gov (United States)

    Tong, Feifei; Lian, Yan; Han, Junliang

    2016-01-01

    Biological information is obtained from the interaction between the series detection electrode and the organism or the physical field of biological cultures in the non-mass responsive piezoelectric biosensor. Therefore, electric parameter of the electrode will affect the biosensor signal. The electric field distribution of the microelectrode used in this study was simulated using the COMSOL Multiphysics analytical tool. This process showed that the electric field spatial distribution is affected by the width of the electrode finger or the space between the electrodes. In addition, the characteristic response of the piezoelectric sensor constructed serially with an annular microelectrode was tested and applied for the continuous detection of Escherichia coli culture or HeLa cell culture. Results indicated that the piezoelectric biosensor with an annular microelectrode meets the requirements for the real-time detection of E. coli or HeLa cells in culture. Moreover, this kind of piezoelectric biosensor is more sensitive than the sensor with an interdigital microelectrode. Thus, the piezoelectric biosensor acts as an effective analysis tool for acquiring online cell or microbial culture information. PMID:27999343

  7. Further Evaluation of DNT Hazard Screening using Neural Networks from Rat Cortical Neurons on Multi-well Microelectrode Arrays

    Science.gov (United States)

    Thousands of chemicals have not been characterized for their DNT potential. Due to the need for DNT hazard identification, efforts to develop screening assays for DNT potential is a high priority. Multi-well microelectrode arrays (MEA) measure the spontaneous activity of electr...

  8. Evaluation of the Neuroactivity of ToxCast Compounds Using Multi-well Microelectrode Array Recordings in Primary Cortical Neurons

    Science.gov (United States)

    Evaluation of the Neuroactivity of ToxCast Compounds Using Multi-well Microelectrode Array Recordings in Primary Cortical Neurons P Valdivia1, M Martin2, WR LeFew3, D Hall3, J Ross1, K Houck2 and TJ Shafer3 1Axion Biosystems, Atlanta GA and 2NCCT, 3ISTD, NHEERL, ORD, US EPA, RT...

  9. Further Evaluation of DNT Hazard Screening using Neural Networks from Rat Cortical Neurons on Multi-well Microelectrode Arrays

    Science.gov (United States)

    Thousands of chemicals have not been characterized for their DNT potential. Due to the need for DNT hazard identification, efforts to develop screening assays for DNT potential is a high priority. Multi-well microelectrode arrays (MEA) measure the spontaneous activity of electr...

  10. E platinum, a newly synthesized platinum compound, induces apoptosis through ROS-triggered ER stress in gastric carcinoma cells.

    Science.gov (United States)

    Wang, Xiaoping; Guo, Qinglong; Tao, Lei; Zhao, Li; Chen, Yan; An, Teng; Chen, Zhen; Fu, Rong

    2017-01-01

    Gastric cancer (GC) is still one of the leading causes of death in cancer-related diseases. In this study, we aimed to investigate the antitumor effect of E Platinum, a newly platinum-based chemotherapeutic agent bearing the basic structure of Oxaliplatin, in a variety of gastric carcinoma cells and the underlying mechanisms. We demonstrated that E Platinum significantly induced apoptosis in gastric cancer cells via mitochondrial apoptotic pathway as a result of increased reactive oxygen species (ROS). We also found that E Platinum enhanced Ca(2+) flux out from the endoplasmic reticulum by increasing the protein expression of IP3R type 1 (IP3R1) and decreasing the expression of ERp44. Dysfunction of Ca(2+) homeostasis in endoplasmic reticulum (ER) leads to accumulation of unfolded proteins and ER stress. Mechanically, E Platinum increased ER stress associated protein expression such as GRP78, p-PERK, p-eIF2α, ATF4, and CHOP. However, knocking down CHOP reversed E Platinum-induced apoptosis by blocking mitochondrial apoptotic pathway. Furthermore, 10 mg/kg of E Platinum significantly suppressed BGC-823 tumor growth in vivo without toxicity, which correlated with induction of apoptosis and expression of ER stress related proteins in tumor tissues. Taken together, E Platinum inhibited tumor growth and induced apoptosis by ROS-mediated ER stress activation both in vitro and in vivo. Our study indicated that E Platinum may be a potential and effective treatment for gastric cancer in clinical. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  11. Optimisation of a microfluidic analysis chamber for the placement of microelectrodes.

    Science.gov (United States)

    Rogers, Michelle; Leong, Chi; Niu, Xize; de Mello, Andrew; Parker, Kim H; Boutelle, Martyn G

    2011-03-28

    The behaviour of droplets entering a microfluidic chamber designed to house microelectrode detectors for real time analysis of clinical microdialysate is described. We have designed an analysis chamber to collect the droplets produced by multiphase flows of oil and artificial cerebral spinal fluid. The coalescence chamber creates a constant aqueous environment ideal for the placement of microelectrodes avoiding the contamination of the microelectrode surface by oil. A stream of alternating light and dark coloured droplets were filmed as they passed through the chamber using a high speed camera. Image analysis of these videos shows the colour change evolution at each point along the chamber length. The flow in the chamber was simulated using the general solution for Poiseuille flow in a rectangular chamber. It is shown that on the centre line the velocity profile is very close to parabolic, and an expression is presented for the ratio between this centre line velocity and the mean flow velocity as a function of channel aspect ratio. If this aspect ratio of width/height is 2, the ratio of flow velocities closely matches that of Poiseuille flow in a circular tube, with implications for connections between microfluidic channels and connection tubing. The droplets are well mixed as the surface tension at the interface with the oil dominates the viscous forces. However once the droplet coalesces with the solution held in the chamber, the no-slip condition at the walls allows Poiseuille flow to take over. The meniscus at the back of the droplet continues to mix the droplet and acts as a piston until the meniscus stops moving. We have found that the no-slip conditions at the walls of the chamber, create a banding effect which records the history of previous drops. The optimal position for sensors is to be placed at the plane of droplet coalescence ideally at the centre of the channel, where there is an abrupt concentration change leading to a response time ≪16 ms, the

  12. Electrooxidation of saccharides at platinum electrode

    Science.gov (United States)

    Han, Ji-Hyung; Chung, Taek Dong

    2012-10-01

    Saccharides have been emerging as promising fuels for future energy industry because they possess high energy density and tremendous amount of them can be obtained from abundant biomass. Direct electrochemical oxidation of saccharides to generate electricity is a potentially competitive approach in terms of the demand for small, handy, and cost-effective electric power sources. To develop efficient sugar fuel cell, it is necessary to understand mechanism of electrooxidation of saccharide at electrode surface. Although glucose oxidation at platinum surface has been well known, fundamental mechanism study on electrooxidation of other sugars is still in its infancy. Based on research of glucose oxidation, we will predict the electrooxidation of other saccharides such as fructose.

  13. Thermodynamic ground states of platinum metal nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Aberg, D; Sadigh, B; Crowhurst, J; Goncharov, A

    2007-10-09

    We have systematically studied the thermodynamic stabilities of various phases of the nitrides of the platinum metal elements using density functional theory. We show that for the nitrides of Rh, Pd, Ir and Pt two new crystal structures, in which the metal ions occupy simple tetragonal lattice sites, have lower formation enthalpies at ambient conditions than any previously proposed structures. The region of stability can extend up to 17 GPa for PtN{sub 2}. Furthermore, we show that according to calculations using the local density approximation, these new compounds are also thermodynamically stable at ambient pressure and thus may be the ground state phases for these materials. We further discuss the fact that the local density and generalized gradient approximations predict different values of the absolute formation enthalpies as well different relative stabilities between simple tetragonal and the pyrite or marcasite structures.

  14. Fabrication of iron-platinum ferromagnetic nanoparticles

    Science.gov (United States)

    Elkins, Kevin Eugene

    Fabrication of chemically disordered FePt particles ranging from 2--9 nm with a precision of 1 nm has been achieved through modification of key process variables including surfactant concentration, heating rates and the type of iron precursor. In addition, the shape evolution of the FePt nanoparticles during particle growth can be manipulated to give cubic or rod geometries through changes to the surfactant injection sequence and solvent system. The primary method for synthesis of the disordered FePt nanoparticles is the polyol reduction reported by Fievet et al., which has been modified and used extensively for synthesis of differing nanoparticle systems. Our procedures use platinum acetylacetonate, iron pentacarbonyl or ferric acetylacetonate as precursors for the FePt alloy, oleic acid and oleyl amine for the surfactants, 1,2-hexadecanediol to assist with the reduction of the precursors and either dioctyl ether or phenyl ether for the solvent system. For iron pentacarbonyl based reactions, adjustment of heating rates to reflux temperatures from 1--15°C per minute allows control of FePt particle diameters from 3--8 nm. Substitution of iron pentacarbonyl with ferric acetylacetonate as the iron source results in 2 nm particles. A high platinum to surfactant ratio of 10 to 1 will yield 9 nm FePt particles when iron pentacarbonyl is used as the precursor. For use of these particles in advanced applications, the synthesized particles must be transformed to the L1o phase through annealing at temperatures above 500°C. Inhibition of particle sintering can be avoided through dispersion in a NaCl matrix at a weight ratio of 400 to 1 salt to fcc FePt particles. Production of L1o FePt nanoparticles with high magnetic anisotropy with this process has been successful, allowing the original size and size distribution of the particles.

  15. Quantitative Analysis of Rat Dorsal Root Ganglion Neurons Cultured on Microelectrode Arrays Based on Fluorescence Microscopy Image Processing.

    Science.gov (United States)

    Mari, João Fernando; Saito, José Hiroki; Neves, Amanda Ferreira; Lotufo, Celina Monteiro da Cruz; Destro-Filho, João-Batista; Nicoletti, Maria do Carmo

    2015-12-01

    Microelectrode Arrays (MEA) are devices for long term electrophysiological recording of extracellular spontaneous or evocated activities on in vitro neuron culture. This work proposes and develops a framework for quantitative and morphological analysis of neuron cultures on MEAs, by processing their corresponding images, acquired by fluorescence microscopy. The neurons are segmented from the fluorescence channel images using a combination of segmentation by thresholding, watershed transform, and object classification. The positioning of microelectrodes is obtained from the transmitted light channel images using the circular Hough transform. The proposed method was applied to images of dissociated culture of rat dorsal root ganglion (DRG) neuronal cells. The morphological and topological quantitative analysis carried out produced information regarding the state of culture, such as population count, neuron-to-neuron and neuron-to-microelectrode distances, soma morphologies, neuron sizes, neuron and microelectrode spatial distributions. Most of the analysis of microscopy images taken from neuronal cultures on MEA only consider simple qualitative analysis. Also, the proposed framework aims to standardize the image processing and to compute quantitative useful measures for integrated image-signal studies and further computational simulations. As results show, the implemented microelectrode identification method is robust and so are the implemented neuron segmentation and classification one (with a correct segmentation rate up to 84%). The quantitative information retrieved by the method is highly relevant to assist the integrated signal-image study of recorded electrophysiological signals as well as the physical aspects of the neuron culture on MEA. Although the experiments deal with DRG cell images, cortical and hippocampal cell images could also be processed with small adjustments in the image processing parameter estimation.

  16. Platinum-Catalyzed Selective Tin-Carbon Bond Formation

    NARCIS (Netherlands)

    Thoonen, Sander Hendrikus Lambertus

    2003-01-01

    In conclusion, two improved methods for the selective synthesis of monoorganotin trihalides were developed. The platinum-catalyzed Kocheshkov redistribution reaction of dialkyltin dichlorides with tin tetrachloride is the most interesting. Contrary to the other two methods described (the direct

  17. Wireless gas sensing in South African underground platinum mines

    CSIR Research Space (South Africa)

    Abu-Mahfouz, Adnan M

    2014-04-01

    Full Text Available Approximately 70% of South African mines are classified as fiery, where methane gas potentially could cause explosions. The number of flammable gas reports and accidents are increasing steadily for both gold and platinum mines. However...

  18. Safety profile of Colgate Platinum Professional Toothwhitening System.

    Science.gov (United States)

    Adam-Rodwell, G; Kong, B M; Bagley, D M; Tonucci, D; Christina, L M

    1994-01-01

    Colgate Platinum, a professional tooth-whitening paste containing 10% urea peroxide as the active ingredient, was evaluated for potential acute oral toxicity, genotoxicity, and irritation to oral mucosa. Oral administration to rats of a single dose of 5 g/kg of Colgate Platinum did not induce any adverse effects. Colgate Platinum was not mutagenic in Ames/Salmonella Plate Incorporation assay and did not induce primary DNA damage in the bone marrow hematopoietic cells of rats that were given oral doses of up to 1 g/kg for 5 consecutive days. Results of the oral mucosa irritation study in rats indicated that Colgate Platinum did not induce damage to soft and hard tissues of oral cavity after repeated applications for 28 days. Collectively, the data from these studies document the safety of the product for the intended use.

  19. Resolving the Structure of Active Sites on Platinum Catalytic Nanoparticles

    DEFF Research Database (Denmark)

    Chang, Lan Yun; Barnard, Amanda S.; Gontard, Lionel Cervera

    2010-01-01

    Accurate understanding of the structure of active sites is fundamentally important in predicting catalytic properties of heterogeneous nanocatalysts. We present an accurate determination of both experimental and theoretical atomic structures of surface monatomic steps on industrial platinum nanop...

  20. Defining Therapy for Recurrent Platinum-sensitive Ovarian Cancer

    Science.gov (United States)

    In this phase III clinical trial, women with platinum-sensitive, recurrent ovarian epithelial, fallopian tube, or primary peritoneal cancer will be randomly assigned to undergo secondary cytoreductive surgery, if they are candidates for such surgery, and

  1. Platinum single crystal electrodes for the electrocatalysis of methane oxidation

    Directory of Open Access Journals (Sweden)

    Mayara Munaretto

    2011-03-01

    Full Text Available The main objective of this paper is to characterize the voltammetric profiles of platinum single crystals of low Miller indexes Pt(100 and Pt(110 and study their catalytic activities on the oxidation of methane. In this way, it was developed a metallic surface modified by presence of other metal oxide, which presents catalytic activity for this reaction. It is well known that the electrooxidation of methane (CH4 leads mainly to the formation of CO2 and H2O, however, the oxidation can also lead to the formation of CO, a reaction intermediate that has strong interaction with metal surfaces, such as platinum. This molecule tends to accumulate on the platinum surface and to passive it, due to the self-poisoning, decreasing its catalytic activity. Therefore, the main aim of this work was the development of a platinum electrode modified by deposition of titanium oxide, which presented electrocatalytic properties for the oxidation of methane.

  2. Platinum blue staining of cells grown in electrospun scaffolds.

    Science.gov (United States)

    Yusuf, Mohammed; Millas, Ana Luiza G; Estandarte, Ana Katrina C; Bhella, Gurdeep K; McKean, Robert; Bittencourt, Edison; Robinson, Ian K

    2014-01-01

    Fibroblast cells grown in electrospun polymer scaffolds were stained with platinum blue, a heavy metal stain, and imaged using scanning electron microscopy. Good contrast on the cells was achieved compared with samples that were gold sputter coated. The cell morphology could be clearly observed, and the cells could be distinguished from the scaffold fibers. Here we optimized the required concentration of platinum blue for imaging cells grown in scaffolds and show that a higher concentration causes platinum aggregation. Overall, platinum blue is a useful stain for imaging cells because of its enhanced contrast using scanning electron microscopy (SEM). In the future it would be useful to investigate cell growth and morphology using three-dimensional imaging methods.

  3. Internalization of Ineffective Platinum Complex in Nanocapsules Renders It Cytotoxic.

    Science.gov (United States)

    Vrana, Oldrich; Novohradsky, Vojtech; Medrikova, Zdenka; Burdikova, Jana; Stuchlikova, Olga; Kasparkova, Jana; Brabec, Viktor

    2016-02-18

    Anticancer therapy by platinum complexes, based on nanocarrier-based delivery, may offer a new approach to improve the efficacy and tolerability of the platinum family of anticancer drugs. The original rules for the design of new anticancer platinum drugs were affected by the fact that, although cisplatin (cis-[PtCl2 (NH3)2) was an anticancer drug, its isomer transplatin was not cytotoxic. For the first time, it is demonstrated that simple encapsulation of an inactive platinum compound in phospholipid bilayers transforms it into an efficient cytotoxic agent. Notably, the encapsulation of transplatin makes it possible to overcome the resistance mechanisms operating in cancer cells treated with cisplatin and prevents inactivation of transplatin in the extracellular environment. It is also shown that transplatin delivered to the cells in nanocapsules, in contrast to free (nonencapsulated) complex, forms cytotoxic cross-links on DNA.

  4. Platinum electrodeposition from a dinitrosulfatoplatinate(II) electrolyte

    Science.gov (United States)

    Weiser, Mathias; Schulze, Claudia; Schneider, Michael; Michaelis, Alexander

    2016-12-01

    In this work a halogen-free electrolyte to deposit platinum nanoparticle is studied. The investigated [Pt(NO2)2SO4]2--complex is suitable for electrochemical deposition on halogen sensitive substrates. The mechanism and kinetic of particle deposition is investigated using a glassy carbon rotating disk electrode. Nano sized platinum particles are deposited by using pulse plating technique. The size of the smallest platinum nanoparticle is 5 nm. The shape of the particle distribution strictly depends on the plating time. The platinum deposition is usually superimposed with hydrogen evolution. A diffusion coefficient of the [Pt(NO2)2SO4]2--complex is determined to 5.4 × 10-6 cm2s-1. The current efficiency depends on the deposition parameters and amounts to 37% under the chosen pulse plating conditions.

  5. Interfacial electronic effects control the reaction selectivity of platinum catalysts

    Science.gov (United States)

    Chen, Guangxu; Xu, Chaofa; Huang, Xiaoqing; Ye, Jinyu; Gu, Lin; Li, Gang; Tang, Zichao; Wu, Binghui; Yang, Huayan; Zhao, Zipeng; Zhou, Zhiyou; Fu, Gang; Zheng, Nanfeng

    2016-05-01

    Tuning the electronic structure of heterogeneous metal catalysts has emerged as an effective strategy to optimize their catalytic activities. By preparing ethylenediamine-coated ultrathin platinum nanowires as a model catalyst, here we demonstrate an interfacial electronic effect induced by simple organic modifications to control the selectivity of metal nanocatalysts during catalytic hydrogenation. This we apply to produce thermodynamically unfavourable but industrially important compounds, with ultrathin platinum nanowires exhibiting an unexpectedly high selectivity for the production of N-hydroxylanilines, through the partial hydrogenation of nitroaromatics. Mechanistic studies reveal that the electron donation from ethylenediamine makes the surface of platinum nanowires highly electron rich. During catalysis, such an interfacial electronic effect makes the catalytic surface favour the adsorption of electron-deficient reactants over electron-rich substrates (that is, N-hydroxylanilines), thus preventing full hydrogenation. More importantly, this interfacial electronic effect, achieved through simple organic modifications, may now be used for the optimization of commercial platinum catalysts.

  6. Co-deposition of carbon dots and reduced graphene oxide nanosheets on carbon-fiber microelectrode surface for selective detection of dopamine

    Science.gov (United States)

    Fang, Jian; Xie, Zhigang; Wallace, Gordon; Wang, Xungai

    2017-08-01

    In this work, carbon dots (CD) decorated graphene oxide (GO) nanosheets were electrochemically reduced and deposited onto carbon fiber (CF) to fabricate microelectrodes for highly sensitive and selective dopamine (DA) detection, in the presence of ascorbic acid (AA) and uric acid (UA). The results have shown that surface modification considerably increases the electrocatalytic activity of the carbon fiber microelectrode. Due to possible aggregation of the rGO sheets during deposition, modifying the microelectrode surface with rGO sheets alone cannot achieve the selectivity required for simultaneous detection of DA, AA and UA. Through attaching CD onto GO sheets, the rGO + CD/CF microelectrode performance was significantly improved. The existence of CD on GO sheets can effectively avoid inter-layer stacking of the rGO sheets and provide increased surface area for neurotransmitter-electrode interaction enhancement. The CD can also increase the charge storage capacity of GO sheets. This is the first report on applying both CD and rGO for surface modification of carbon fiber microelectrode. The rGO + CD/CF microelectrode has achieved a linear DA detection concentration range of 0.1-100 μM, with a detection limit of 0.02 μM. The sensitivity of the microelectrode towards DA was as high as 6.5 nA/μM, which is significantly higher than previously reported carbon fiber microelectrodes. The highly sensitive all-carbon based microelectrodes should find use in a number of biomedical applications, such as neurotransmitter detection, neural signal recording and cell physiology studies.

  7. Addressing of LnCaP Cell Using Magnetic Particles Assisted Impedimetric Microelectrode.

    Science.gov (United States)

    Nguyen, Dung Thi Xuan; Tran, Trong Binh; Nguyen, Phuong-Diem; Min, Junhong

    2016-03-01

    In this study, we provide a facile, effective technique for a simple isolation and enrichment of low metastatic prostate tumor cell LNCaP using biocompatible, magnetic particles asissted impedimetric sensing system. Hydrophobic cell membrane anchors (BAM) were generated onto magnetic particles which diameters vary from 50 nm to 5 μm and were used to capture LNCaP cells from the suspension. Finally, magnetic particle-LNCaP complex were addressed onto the surface of the interdigitated microelectrode (IDM). Cell viability was monitored by our laboratory developed-technique Electrical Cell Substrate Impedance Sensing (ECIS). The results reavealed that 50 nm-magnetic particles showed best performance in terms of cell separation and cell viability. This technique provides a simple and efficient method for the direct addressing of LNCaP cell on the surface and enhances better understanding of cell behavior for cancer management in the near future.

  8. Research on Electric Impedance Spectroscopy of Living Cell Suspensions by a Chip with Microelectrodes

    Institute of Scientific and Technical Information of China (English)

    Xing Yang; Zhaoying Zhou; Mingfei Xiao; Ying Wu; Shangfeng Liu

    2006-01-01

    A microfabricated electrical impedance spectroscopy (EIS) chip with microelectrodes was developed. The substrate and the electrodes of the chip were made of glass and gold, respectively. The experimental results demonstrated that the EIS-chip could distinguish different solutions (physiological saline, culture medium, living cell suspension etc.) by scanning from 10Hz to 45kHz. A 6-element circuit model was used for fitting the real part and the imaginary part admittance curves of the living cell suspension. An actual circuit was also built and tested to verify the 6-element circuit model proposed. The micro-EIS chip has several advantages including the use of small sample volumes, high resolution and ease of operation. It shows good application prospects in the areas of cellular electrophysiology, drug screening and bio-sensors etc.

  9. The potential of microelectrode arrays and microelectronics for biomedical research and diagnostics.

    Science.gov (United States)

    Jones, Ian L; Livi, Paolo; Lewandowska, Marta K; Fiscella, Michele; Roscic, Branka; Hierlemann, Andreas

    2011-03-01

    Planar microelectrode arrays (MEAs) are devices that can be used in biomedical and basic in vitro research to provide extracellular electrophysiological information about biological systems at high spatial and temporal resolution. Complementary metal oxide semiconductor (CMOS) is a technology with which MEAs can be produced on a microscale featuring high spatial resolution and excellent signal-to-noise characteristics. CMOS MEAs are specialized for the analysis of complete electrogenic cellular networks at the cellular or subcellular level in dissociated cultures, organotypic cultures, and acute tissue slices; they can also function as biosensors to detect biochemical events. Models of disease or the response of cellular networks to pharmacological compounds can be studied in vitro, allowing one to investigate pathologies, such as cardiac arrhythmias, memory impairment due to Alzheimer's disease, or vision impairment caused by ganglion cell degeneration in the retina.

  10. Communication—Microelectrode Detection of Cholesterol Efflux from the Human Buccel Mucosa

    Science.gov (United States)

    Yu, Xiaochun; Kelley, Thomas J.; Chiel, Hillel J.; Burgess, James D.

    2016-01-01

    It has previously demonstrated that cholesterol efflux from the cell plasma membrane is increased in a mouse model of cystic fibrosis (CF) compared to a wild-type control. A noninvasive means of characterizing plasma membrane cholesterol efflux at the surface of airway tissue of CF patients is needed to extend the trends found in animal models of CF to the human disease state. Microelectrode-induced cholesterol efflux from the plasma membrane of cells at the surface of tissue is proposed as a strategy to demonstrate increased cholesterol efflux for CF in human subjects. Data demonstrating detection of cholesterol efflux from the human buccal mucosa is reported as proof-of-concept for an in vivo diagnostic assay. PMID:27546897

  11. Stimulation of human embryonic stem cell-derived cardiomyocytes on thin-film microelectrodes.

    Science.gov (United States)

    Viitanen, Jouko; Heimala, Päivi; Hokkanen, Ari; Iljin, Kristiina; Kerkelä, Erja; Kolari, Kai; Kattelus, Hannu

    2011-05-01

    We describe successful long-term stimulation of human embryonic stem cell-derived cardiomyocyte clusters on thin-film microelectrode structures in vitro. Interdigitated electrode structures were constructed using plain titanium on glass as the electrode material. Titanium rapidly oxidizes in atmospheric conditions to produce an insulating TiO(χ) layer with high relative permittivity. Capacitive coupling to the incubation medium and to the cells adherent to the electrodes was still efficient, and the dielectric layer prevented electrolysis, allowing a wider window of possible stimulation amplitudes to be used, relative to conducting surfaces. A common hypothesis suggests that to achieve proper differentiation of electroactive cells from the stem cells electrical stimuli are also needed. Spontaneously beating cardiomyocyte clusters were seeded on the glass-electrode surfaces, and we successfully altered and resynchronized a clearly different beat interval. The new pace was reliably maintained for extended periods of several tens of minutes.

  12. Characterization of the chemical architecture of carbon-fiber microelectrodes. 1. Carboxylates.

    Science.gov (United States)

    Pantano, P; Kuhr, W G

    1991-07-15

    A new method to characterize the chemical architecture of a carbon-fiber microelectrode surface is described. Derivatization of carboxyl groups on the carbon surface with a poly(oxyalkalene)diamine (Jeffamine ED-600), followed by biotinylation of the free amine, allowed the attachment of a fluorescein isothiocyanate (FITC) conjugate of ExtrAvidin. The fluorescence observed after excitation at 488 nm was imaged with a fluorescence microscope equipped with a CCD camera, yielding a spatial map of the distribution of modified carboxyl groups on the surface of the carbon fiber with 0.5-micron resolution. Colloidal gold particles (15 nm diameter) coated with ExtrAvidin were used in place of the FITC-ExtrAvidin, and the carbon-fiber surface was imaged with scanning electron microscopy on a submicron scale. This selective information regarding surface-bound functional groups (i.e. carboxylates) has proven invaluable toward the rational design of novel sensors based on surface-modified ultramicroelectrodes.

  13. PEDOT-CNT composite microelectrodes for recording and electrostimulation applications: fabrication, morphology and electrical properties

    Directory of Open Access Journals (Sweden)

    Ramona eGerwig

    2012-05-01

    Full Text Available Composites of carbon nanotubes and poly(3,4-ethylenedioxythiophene (PEDOT and layers of PEDOT are deposited onto microelectrodes by electropolymerization of ethylenedioxythiophene in the presence of a suspension of carbon nanotubes and polystyrenesulfonate. Analysis by FIB and SEM demonstrate that CNT-PEDOT composites exhibit a porous morphology whereas PEDOT layers are more compact. Accordingly, capacitance and charge injection capacity of the composite material exceed those of pure PEDOT layers. In vitro cell culture experiments reveal excellent biocompatibility and mechanical stability of both PEDOT and PEDOT-CNT electrodes. Signals recorded from heart muscle cells demonstrate the high S/N ratio achievable with these electrodes. Long-term pulsing experiments confirm stability of charge injection capacity. In conclusion, a robust fabrication procedure for composite PEDOT-CNT electrodes is demonstrated and results show that these electrodes are well suited for stimulation and recording in cardiac and neurophysiological research.

  14. A Research on Sour Sensation Mechanism of Fungiform Taste Receptor Cells Based on Microelectrode Array

    Science.gov (United States)

    Zhang, Wei; Chen, Peihua; Xiao, Lidan; Liu, Qingjun; Wang, Ping

    2009-05-01

    Taste receptor cells as the fundamental units of taste sensation are not only passive receivers to outside stimulus, but some primary process for the signals and information. In this paper, an innovation on acquisition of taste receptor cells was introduced and larger amount of cells could be obtained. A multichannel microelectrode array (MEA) system was applied in signal recording, which is used in non-invasive, multiple and simultaneous extracellular recording of taste receptor cells. The cells were treated with sour solutions of different pHs, and the relations between concentration of hydrogen and firing rate were observed. Firing rates on pH 7, pH 4 and pH 2 were approximately 1.38±0.01 (MEAN±SE)/s, 1.61±0.07/s and 2.75+0.15/s.

  15. Characterization of poly(3,4-ethylenedioxythiophene):tosylate conductive polymer microelectrodes for transmitter detection

    DEFF Research Database (Denmark)

    Larsen, Simon T.; Vreeland, Richard F.; Heien, Michael L.

    2012-01-01

    applications such as capillary electrophoresis, high-performance liquid chromatography, and constant potential amperometry at living cells. Band electrodes with widths down to 3 μm were fabricated on polymer substrates using UV lithographic methods. The electrodes are electrochemically stable in a range......In this paper we investigate the physical and electrochemical properties of micropatterned poly(3,4-ethylenedioxythiophene):tosylate (PEDOT:tosylate) microelectrodes for neurochemical detection. PEDOT:tosylate is a promising conductive polymer electrode material for chip-based bioanalytical...... between −200 mV and 700 mV vs. Ag/AgCl and show a relatively low resistance. A wide range of transmitters is shown to oxidize readily on the electrodes. Kinetic rate constants and half wave potentials are reported. The capacitance per area was found to be high (1670 ± 130 μF cm−2) compared to other thin...

  16. Purification of carbon nanotubes through an electric field near the arranged microelectrodes

    Science.gov (United States)

    Shim, Hyung Cheoul; Lee, Hyung Woo; Yeom, Sujin; Kwak, Yoon Keun; Lee, Seung S.; Kim, Soo Hyun

    2007-03-01

    In this work, we attempt to purify multi-walled carbon nanotubes (MWNTs) using electrophoresis induced by the application of an AC electric field to a set of microelectrodes in a microliquid channel. This purifying method is different from conventional methods based on chemical processes. It was observed that most of the MWNTs could pass along the microliquid channel without attaching to the electrode under specific conditions of 1 kHz, at 0.2 Vrms μm-1. On the other hand, the majority of the carbon impurities attached to the electrodes under identical conditions. Field emission scanning electron microscopy (FESEM) images and Raman spectra confirm that this condition is beneficial for removing carbon impurities. The proposed approach has potential applicability in the development of microdevices that can simultaneously perform the purification and fabrication of MWNTs.

  17. Purification of carbon nanotubes through an electric field near the arranged microelectrodes

    Energy Technology Data Exchange (ETDEWEB)

    Shim, Hyung Cheoul [School of Mechanical, Aerospace and Systems Engineering, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Lee, Hyung Woo [Massachusetts Institute of Technology (MIT), Micro and Nano Systems Laboratory, 77 Massachusetts Avenue, Room 5-008, Cambridge, MA 02139 (United States); Yeom, Sujin [School of Mechanical, Aerospace and Systems Engineering, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Kwak, Yoon Keun [School of Mechanical, Aerospace and Systems Engineering, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Lee, Seung S [School of Mechanical, Aerospace and Systems Engineering, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Kim, Soo Hyun [School of Mechanical, Aerospace and Systems Engineering, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

    2007-03-21

    In this work, we attempt to purify multi-walled carbon nanotubes (MWNTs) using electrophoresis induced by the application of an AC electric field to a set of microelectrodes in a microliquid channel. This purifying method is different from conventional methods based on chemical processes. It was observed that most of the MWNTs could pass along the microliquid channel without attaching to the electrode under specific conditions of 1 kHz, at 0.2 V{sub rms} {mu}m{sup -1}. On the other hand, the majority of the carbon impurities attached to the electrodes under identical conditions. Field emission scanning electron microscopy (FESEM) images and Raman spectra confirm that this condition is beneficial for removing carbon impurities. The proposed approach has potential applicability in the development of microdevices that can simultaneously perform the purification and fabrication of MWNTs.

  18. Doped Overoxidized Polypyrrole Microelectrodes as Sensors for the Detection of Dopamine Released from Cell Populations

    DEFF Research Database (Denmark)

    Sasso, Luigi; Heiskanen, Arto; Diazzi, Francesco

    2013-01-01

    A surface modification of interdigitated gold microelectrodes (IDEs) with a doped polypyrrole (PPy) film for detection of dopamine released from populations of differentiated PC12 cells is presented. A thin PPy layer was potentiostatically electropolymerized from an 10 aqueous pyrrole solution onto...... in dopamine detection. Overoxidation of the PPy films was shown to contribute to a significant enhancement in sensitivity to dopamine. The changes caused by overoxidation in the electrochemical behavior and electrode morphology were investigated using cyclic voltammetry and SEM as well as AFM, respectively....... The optimal dopant for dopamine detection was found to be polystyrenesulfonate anion (PSS-15 ). Rat pheochromocytoma (PC12) cells, a suitable model to study exocytotic dopamine release, were differentiated on IDEs functionalized with an overoxidized PSS--doped PPy film. The modified electrodes were used...

  19. Investigation of parameters controlling the dielectrophoretic assembly of carbon nanotubes on microelectrodes

    DEFF Research Database (Denmark)

    Dimaki, Maria; Bøggild, Peter

    2008-01-01

    Networks of single-walled carbon nanotubes were assembled onto microelectrodes by dielectrophoresis. The dependence of the obtained networks on several assembly parameters such as bias voltage, field application time, frequency, electrode geometry and the nanotube solvent were investigated both...... structurally and electrically. Reproducible differences in morphological and electrical properties were observed for the parameters investigated. Application of a bias voltage above 10 V for more than 30 seconds with nanotubes in an SDS solution, resulted in dense networks with a relatively low resistance...... in the 10 k Omega regime. On the other hand, individual nanotubes and bundles were assembled with lower voltages applied for less than 10 seconds and with other nanotubes solutions. The experimental results were combined with theoretical calculations in order to find a geometry and voltage independent...

  20. Microelectrode Arrays and the Use of PEG-Functionalized Diblock Copolymer Coatings

    Directory of Open Access Journals (Sweden)

    Sakshi Uppal

    2014-09-01

    Full Text Available PEG-modified diblock copolymer surfaces have been examined for their compatibility with microelectrode array based analytical methods. The use of PEG-modified polymer surfaces on the arrays was initially problematic because the redox couples used in the experiments were adsorbed by the polymer. This led the current measured by cyclic voltammetry for the redox couple to be unstable and increase with time. However, two key findings allow the experiments to be successful. First, after multiple cyclic voltammograms the current associated with the redox couple does stabilize so that a good baseline current can be established. Second, the rate at which the current stabilizes is consistent every time a particular coated array is used. Hence, multiple analytical experiments can be conducted on an array coated with a PEG-modified diblock copolymer and the data obtained is comparable as long as the data for each experiment is collected at a consistent time point.

  1. Surface modified microelectrodes for selective electroanalysis of metal ions in environmental components.

    Science.gov (United States)

    Barancok, D; Cirák, J; Tomcík, P; Gmucová, K

    2002-01-01

    The surface modification of electrodes was achieved by the Langmuir-Blodgett technique. The monolayers of laponite clay and polythiophene were formed at the air-water interface and these films were then transferred onto carbon microelectrodes. The behaviour of both untreated and coated electrodes was tested by originally developed double-step voltcoulometry (DSVCM). The dependence of charge response on the concentration of Cu(2+) species was investigated. Straight calibration curves were obtained and enhanced sensitivity of coated electrodes was documented. It is shown that the accumulation of Cu ions into laponite clay was maintained even after transferring the electrode into a pure water. The characteristic features of the "memory effect" are discussed.

  2. Mechanical Flexibility Reduces the Foreign Body Response to Long-Term Implanted Microelectrodes in Rabbit Cortex

    Science.gov (United States)

    Sohal, Harbaljit S.; Clowry, Gavin J.

    2016-01-01

    Micromotion between the brain and implanted electrodes is a major contributor to the failure of invasive microelectrodes. Movements of the electrode tip cause recording instabilities while spike amplitudes decline over the weeks/months post-implantation due to glial cell activation caused by sustained mechanical trauma. We compared the glial response over a 26–96 week period following implantation in the rabbit cortex of microwires and a novel flexible electrode. Horizontal sections were used to obtain a depth profile of the radial distribution of microglia, astrocytes and neurofilament. We found that the flexible electrode was associated with decreased gliosis compared to the microwires over these long indwelling periods. This was in part due to a decrease in overall microgliosis and enhanced neuronal density around the flexible probe, especially at longer periods of implantation. PMID:27788240

  3. Platinum group metal nitrides and carbides: synthesis, properties and simulation

    Energy Technology Data Exchange (ETDEWEB)

    Ivanovskii, Alexander L [Institute of Solid State Chemistry, Urals Branch of the Russian Academy of Sciences, Ekaterinburg (Russian Federation)

    2009-04-30

    Experimental and theoretical data on new compounds, nitrides and carbides of the platinum group 4d and 5d metals (ruthenium, rhodium, palladium, osmium, iridium, platinum), published over the past five years are summarized. The extreme mechanical properties of platinoid nitrides and carbides, i.e., their high strength and low compressibility, are noted. The prospects of further studies and the scope of application of these compounds are discussed.

  4. Problems and Characteristics of Russian Platinum Metals Exporters

    Institute of Scientific and Technical Information of China (English)

    ANDREEV A. M.; KELCHEVSKAYA N. R.

    2012-01-01

    The paper revealed the place and role of Russia in the global market of platinum metals,highlighted features of pricing in the export of Russian platinum group metals,the main problems of pricing in the export contracts related to the instability of markets and imperfect currency and customs legislation of the Russian Federation,proposed innovative ways to solutions to existing problems in the preparation and conclusion of export contracts.

  5. CROWN FUNCTIONALIZED LINEAR POLYSILOXANE PLATINUM COMPLEX AS HYDROSILYLATION CATALYST

    Institute of Scientific and Technical Information of China (English)

    CHEN Yuanyin; LU Xueran; GONG Shuling; ZHANG Baolian

    1994-01-01

    A modified method of preparing crown functionalized linear polysiloxane has been described.4'-allylbenzo-15-crown-5 was subjected to hydrosilylation with methyldichlorosilane,followed by polycondensation with silanol-terminated polydimethylsiloxane to give the title crown functionalized linear polysiloxane. It was found that the polysiloxane could be coordinated with platinum salt to form platinum complex, which could catalyze the hydrosilylation of olefins with triethoxysilane efficiently.

  6. Mineral resource of the month: platinum group metals

    Science.gov (United States)

    Loferski, Patricia J.

    2010-01-01

    The article focuses on platinum group metals (PGMs) and their properties. According to the author, PGMs, which include iridium, osmium, palladium, platinum, rhodium, and ruthenium, are among the rarest mineral commodities in the Earth's crust. PGMs are primarily used as catalytic converters that clean harmful exhaust from vehicle engines. They are also used in the chemical industry as catalysts in the production of nitric acid and in the petroleum refining industry.

  7. Iridium oxide microelectrode arrays for in vitro stimulation of individual rat neurons from dissociated cultures.

    Science.gov (United States)

    Eick, Stefan; Wallys, Jens; Hofmann, Boris; van Ooyen, André; Schnakenberg, Uwe; Ingebrandt, Sven; Offenhäusser, Andreas

    2009-01-01

    We present the first in vitro extracellular stimulation of individual neurons from dissociated cultures with iridium oxide (IrO(x)) electrodes. Microelectrode arrays with sputtered IrO(x) films (SIROF) were developed for electrophysiological investigations with electrogenic cells. The microelectrodes were characterized with scanning electron and atomic force microscopy, revealing rough and porous electrodes with enlarged surface areas. As shown by cyclic voltammetry and electrochemical impedance spectroscopy, the large surface area in combination with the good electrochemical properties of SIROF resulted in high charge storage capacity and low electrode impedance. Thus, we could transfer the good properties of IrO(x) as material for in vivo stimulation electrodes to multi-electrode arrays with electrode diameters as small as 10 mum for in vitro applications. Single rat cortical neurons from dissociated cultures were successfully stimulated to fire action potentials using single or trains of biphasic rectangular voltage-controlled stimulation pulses. The stimulated cell's membrane potential was simultaneously monitored using whole-cell current-clamp recordings. This experimental configuration allowed direct evaluation of the influence of pulse phase sequence, amplitude, and number on the stimulation success ratio and action potential latency. Negative phase first pulses were more effective for extracellular stimulation and caused reduced latency in comparison to positive phase first pulses. Increasing the pulse amplitude also improved stimulation reliability. However, in order to prevent cell or electrode damage, the pulse amplitude is limited to voltages below the threshold for irreversible electrochemical reactions at the electrode. As an alternative to increasing the amplitude, a higher number of stimulation pulses was also shown to increase stimulation success.

  8. Iridium oxide microelectrode arrays for in vitro stimulation of individual rat neurons from dissociated cultures

    Directory of Open Access Journals (Sweden)

    Stefan Eick

    2009-11-01

    Full Text Available We present the first in-vitro extracellular stimulation of individual neurons from dissociated cultures with iridium oxide (IrOx electrodes. Microelectrode arrays with sputtered IrOx films (SIROF were developed for electrophysiological investigations with electrogenic cells. The microelectrodes were characterized with scanning electron and atomic force microscopy, revealing rough and porous electrodes with enlarged surface areas. As shown by cyclic voltammetry and electrochemical impedance spectroscopy, the large surface area in combination with the good electrochemical properties of SIROF resulted in high charge storage capacity and low electrode impedance. Thus, we could transfer the good properties of IrOx as material for in-vivo stimulation electrodes to MEAs with electrode diameters as small as 10 µm for in-vitro applications. Single rat cortical neurons from dissociated cultures were successfully stimulated to fire action potentials using single or trains of biphasic rectangular voltage-controlled stimulation pulses. The stimulated cell’s membrane potential was simultaneously monitored using whole-cell current-clamp recordings. This experimental configuration allowed direct evaluation of the influence of pulse phase sequence, amplitude, and number on the stimulation success ratio and action potential latency. Negative phase first pulses were more effective for extracellular stimulation and caused reduced latency in comparison to positive phase first pulses. Increasing the pulse amplitude also improved stimulation reliability. However, in order to prevent cell or electrode damage, the pulse amplitude is limited to voltages below the threshold for irreversible electrochemical reactions at the electrode. As an alternative to increasing the amplitude, a higher number of stimulation pulses was also shown to increase stimulation success.

  9. High temporal resolution measurements of dopamine with carbon nanotube yarn microelectrodes.

    Science.gov (United States)

    Jacobs, Christopher B; Ivanov, Ilia N; Nguyen, Michael D; Zestos, Alexander G; Venton, B Jill

    2014-06-17

    Fast-scan cyclic voltammetry (FSCV) can detect small changes in dopamine concentration; however, measurements are typically limited to scan repetition frequencies of 10 Hz. Dopamine oxidation at carbon-fiber microelectrodes (CFMEs) is dependent on dopamine adsorption, and increasing the frequency of FSCV scan repetitions decreases the oxidation current, because the time for adsorption is decreased. Using a commercially available carbon nanotube yarn, we characterized carbon nanotube yarn microelectrodes (CNTYMEs) for high-speed measurements with FSCV. For dopamine, CNTYMEs have a significantly lower ΔEp than CFMEs, a limit of detection of 10 ± 0.8 nM, and a linear response to 25 μM. Unlike CFMEs, the oxidation current of dopamine at CNTYMEs is independent of scan repetition frequency. At a scan rate of 2000 V/s, dopamine can be detected, without any loss in sensitivity, with scan frequencies up to 500 Hz, resulting in a temporal response that is four times faster than CFMEs. While the oxidation current is adsorption-controlled at both CFMEs and CNTYMEs, the adsorption and desorption kinetics differ. The desorption coefficient of dopamine-o-quinone (DOQ), the oxidation product of dopamine, is an order of magnitude larger than that of dopamine at CFMEs; thus, DOQ desorbs from the electrode and can diffuse away. At CNTYMEs, the rates of desorption for dopamine and dopamine-o-quinone are about equal, resulting in current that is independent of scan repetition frequency. Thus, there is no compromise with CNTYMEs: high sensitivity, high sampling frequency, and high temporal resolution can be achieved simultaneously. Therefore, CNTYMEs are attractive for high-speed applications.

  10. [Finite element analysis of temperature field of retina by electrical stimulation with microelectrode array].

    Science.gov (United States)

    Wang, Wei; Qiao, Qingli; Gao, Weiping; Wu, Jun

    2014-12-01

    We studied the influence of electrode array parameters on temperature distribution to the retina during the use of retinal prosthesis in order to avoid thermal damage to retina caused by long-term electrical stimulation. Based on real epiretinal prosthesis, a three-dimensional model of electrical stimulation for retina with 4 X 4 microelectrode array had been established using the finite element software (COMSOL Multiphysics). The steady-state temperature field of electrical stimulation of the retina was calculated, and the effects of the electrode parameters such as the distance between the electrode contacts, the materials and area of the electrode contact on temperature field were considered. The maximum increase in the retina steady temperature was about 0. 004 degrees C with practical stimulation current. When the distance between the electrode contacts was changed from 130 microm to 520 microm, the temperature was reduced by about 0.006 microC. When the contact radius was doubled from 130 microm to 260 microm, the temperature decrease was about 0.005 degrees C. It was shown that there were little temperature changes in the retina with a 4 x 4 epiretinal microelectrode array, reflecting the safety of electrical stimulation. It was also shown that the maximum temperature in the retina decreased with increasing the distance between the electrode contacts, as well as increasing the area of electrode contact. However, the change of the maximum temperature was very small when the distance became larger than the diameter of electrode contact. There was no significant difference in the effects of temperature increase among the different electrode materials. Rational selection of the distance between the electrode contacts and their area in electrode design can reduce the temperature rise induced by electrical stimulation.

  11. Synthesis of nanosized platinum based catalyst using sol-gel process

    Science.gov (United States)

    Ingale, S. V.; Wagh, P. B.; Bandyopadhyay, D.; Singh, I. K.; Tewari, R.; Gupta, S. C.

    2015-02-01

    The nano-sized platinum based catalysts using high surface area silica support have been prepared by sol-gel method. Tetramethoxysilane (TMOS) diluted in methanol was hydrolyzed to form a porous silica gel. Platinum (2%) was loaded at sol state using platinum chloride solution. After gelation, the solvent from the gel pores was extracted at ambient temperature which resulted in porous silica matrix incorporated with nanosized platinum. X-ray diffraction studies indicated the presence of elemental platinum in the silica-platinum composites. Transmission electron microscopy of the platinum -silica composites revealed that nanosized platinum particles of about 5-10 nm are homogeneously dispersed in silica matrix. Chemisorptions studies showed high dispersion (more than 50%) of platinum on silica support with specific surface area of 400 m2/g which puts them as promising candidates as catalyst in heterogeneous reactions.

  12. Platinum drugs and DNA repair mechanisms in lung cancer.

    Science.gov (United States)

    Bonanno, Laura; Favaretto, Adolfo; Rosell, Rafael

    2014-01-01

    The standard first-line treatment for around 80% of newly-diagnosed advanced non-small cell lung cancer (NSCLC) is chemotherapy. Currently, patients are allocated to chemotherapy on the basis of clinical conditions, comorbidities and histology. If feasible, platinum-based chemotherapy is considered as the most efficacious option. Due to the heterogeneity in terms of platinum-sensitivity among patients with NSCLC, great efforts have been made in order to identify molecular predictive markers of platinum resistance. Based on the mechanism of action of platinum, several components of DNA repair pathways have been investigated as potential predictive markers. The main DNA repair pathways involved in the repair of platinum-induced DNA damage are nucleotide excision repair and homologous recombination. The most studied potential predictive markers of platinum-sensitivity are Excision Repair Cross Complementing-1 (ERCC1) and Brest Cancer Type-I Susceptibility protein (BRCA1); however, increasing biological knowledge about DNA repair pathways suggests the potential clinical usefulness of integrated analysis of multiple DNA repair components.

  13. Liposomes, a promising strategy for clinical application of platinum derivatives.

    Science.gov (United States)

    Zalba, Sara; Garrido, María J

    2013-06-01

    Liposomes represent a versatile system for drug delivery in various pathologies. Platinum derivatives have been demonstrated to have therapeutic efficacy against several solid tumors. But their use is limited due to their side effects. Since liposomal formulations are known to reduce the toxicity of some conventional chemotherapeutic drugs, the encapsulation of platinum derivatives in these systems may be useful in reducing toxicity and maintaining an adequate therapeutic response. This review describes the strategies applied to platinum derivatives in order to improve their therapeutic activity, while reducing the incidence of side effects. It also reviews the results found in the literature for the different platinum-drugs liposomal formulations and their current status. The design of liposomes to achieve effectiveness in antitumor treatment is a goal for platinum derivatives. Liposomes can change the pharmacokinetic parameters of these encapsulated drugs, reducing their side effects. However, few liposomal formulations have demonstrated a significant advantage in therapeutic terms. Lipoplatin, a cisplatin formulation in Phase III, combines a reduction in the toxicity associated with an antitumor activity similar to the free drug. Thermosensitive or targeted liposomes for tumor therapy are also included in this review. Few articles about this strategy applied to platinum drugs can be found in the literature.

  14. In vitro permeation of platinum and rhodium through Caucasian skin.

    Science.gov (United States)

    Franken, A; Eloff, F C; Du Plessis, J; Badenhorst, C J; Jordaan, A; Du Plessis, J L

    2014-12-01

    During platinum group metals (PGMs) refining the possibility exists for dermal exposure to PGM salts. The dermal route has been questioned as an alternative route of exposure that could contribute to employee sensitisation, even though literature has been focused on respiratory exposure. This study aimed to investigate the in vitro permeation of platinum and rhodium through intact Caucasian skin. A donor solution of 0.3mg/ml of metal, K2PtCl4 and RhCl3 respectively, was applied to the vertical Franz diffusion cells with full thickness abdominal skin. The receptor solution was removed at various intervals during the 24h experiment, and analysed with high resolution ICP-MS. Skin was digested and analysed by ICP-OES. Results indicated cumulative permeation with prolonged exposure, with a significantly higher mass of platinum permeating after 24h when compared to rhodium. The mass of platinum retained inside the skin and the flux of platinum across the skin was significantly higher than that of rhodium. Permeated and skin retained platinum and rhodium may therefore contribute to sensitisation and indicates a health risk associated with dermal exposure in the workplace.

  15. The electrochemical reduction of the purines guanine and adenine at platinum electrodes in several room temperature ionic liquids

    Energy Technology Data Exchange (ETDEWEB)

    Zanoni, Maria Valnice Boldrin, E-mail: boldrinv@iq.unesp.br [Department of Analytical Chemistry, Institute of Chemistry, University of Sao Paulo State, Araraquara, R. Prof. Francisco Degni, CP 355, 14801-970, SP (Brazil); Rogers, Emma I. [Department of Chemistry, Physical and Theoretical Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ (United Kingdom); Hardacre, Christopher, E-mail: c.hardacre@qub.ac.uk [School of Chemistry and Chemical Engineering/QUILL, Queen' s University Belfast, Belfast, Northern Ireland BT9 5AG (United Kingdom); Compton, Richard G., E-mail: richard.compton@chem.ox.ac.uk [Department of Chemistry, Physical and Theoretical Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ (United Kingdom)

    2010-02-05

    The reduction of guanine was studied by microelectrode voltammetry in the room temperature ionic liquids (RTILs) N-hexyltriethylammonium bis (trifluoromethanesulfonyl) imide [N{sub 6,2,2,2}][N(Tf){sub 2}], 1-butyl-3-methylimidazolium hexafluorosphosphate [C{sub 4}mim][PF{sub 6}], N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide [C{sub 4}mpyrr][N(Tf){sub 2}], 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [C{sub 4}mim][N(Tf){sub 2}], N-butyl-N-methyl-pyrrolidinium dicyanamide [C{sub 4}mpyrr][N(NC){sub 2}] and tris(P-hexyl)-tetradecylphosphonium trifluorotris(pentafluoroethyl)phosphate [P{sub 14,6,6,6}][FAP] on a platinum microelectrode. In [N{sub 6,2,2,2}][NTf{sub 2}] and [P{sub 14,6,6,6}][FAP], but not in the other ionic liquids studied, guanine reduction involves a one-electron, diffusion-controlled process at very negative potential to produce an unstable radical anion, which is thought to undergo a dimerization reaction, probably after proton abstraction from the cation of the ionic liquid. The rate of this subsequent reaction depends on the nature of the ionic liquid, and it is faster in the ionic liquid [P{sub 14,6,6,6}][FAP], in which the formation of the resulting dimer can be voltammetrically monitored at less negative potentials than required for the reduction of the parent molecule. Adenine showed similar behaviour to guanine but the pyrimidines thymine and cytosine did not; thymine was not reduced at potentials less negative than required for solvent (RTIL) decomposition while only a poorly defined wave was seen for cytosine. The possibility for proton abstraction from the cation in [N{sub 6,2,2,2}][NTf{sub 2}] and [P{sub 14,6,6,6}][FAP] is noted and this is thought to aid the electrochemical dimerization process. The resulting rapid reaction is thought to shift the reduction potentials for guanine and adenine to lower values than observed in RTILs where the scope for proton abstraction is not present. Such shifts are

  16. Platinum- and platinum alloy-coated palladium and palladium alloy particles and uses thereof

    Science.gov (United States)

    Adzic, Radoslav; Zhang, Junliang; Mo, Yibo; Vukmirovic, Miomir Branko

    2010-04-06

    The present invention relates to particle and nanoparticle composites useful as oxygen-reduction electrocatalysts. The particle composites are composed of a palladium or palladium-alloy particle or nanoparticle substrate coated with an atomic submonolayer, monolayer, bilayer, or trilayer of zerovalent platinum atoms. The invention also relates to a catalyst and a fuel cell containing the particle or nanoparticle composites of the invention. The invention additionally includes methods for oxygen reduction and production of electrical energy by using the particle and nanoparticle composites of the invention.

  17. Clinical pharmacology and pharmacokinetics of cis-platinum and analogs.

    Science.gov (United States)

    Ribaud, P; Gouveia, J; Bonnay, M; Mathe, G

    1981-01-01

    cis-Platinum (DDP), the first metal coordination complex introduced into clinical trials, is remarkable for its therapeutic index. A short review of the numerator of this index, ie, the clinical activities of DDP given as a single agent or in combination therapy is presented. Toxicity of DDP, the denominator of the index, is given more attention, particularly nephrotoxicity, whose cumulative character and molecular mechanism are still in question and which can most often be prevented by following certain safety rules that are detailed in this paper. Pharmacokinetics data of free and filterable platinum are reviewed and discussed according to the different modalities of administration of DDP, and to what is known about its toxicity and its mechanism of cell kill. The rationale for using DDP in combination treatment is presented and the question of possible long-term toxicities is raised. cis-platinum analogs are sought for the purpose of enlarging the spectrum of activity, increasing selectivity and diminishing toxicity. Malonato-platinum has been shown not to be cross-resistant with DDP and to be clinically effective in adult acute leukemia. In a phase I study, malonato-platinum, which is poorly soluble, was administered in 6-24-hour infusions to 49 patients in doses ranging from 3 to 32 mg/kg. GI toxicity was universal. Hematological toxicity appeared to be mild and not clearly dose-related (the 3-32 mg/kg patients were not yet evaluable). Platinum pharmacokinetics in urine and plasma were performed using flameless absorption spectrophotometry. Preliminary results have suggested that malonato-platinum presented several pharmacokinetic features in common with DDP. Minor responses were seen in four solid tumor patients, three of whom were refractory to DDP. Other analogs soon to be introduced into clinical trials are listed.

  18. In Vivo Neural Recording and Electrochemical Performance of Microelectrode Arrays Modified by Rough-Surfaced AuPt Alloy Nanoparticles with Nanoporosity

    Directory of Open Access Journals (Sweden)

    Zongya Zhao

    2016-11-01

    Full Text Available In order to reduce the impedance and improve in vivo neural recording performance of our developed Michigan type silicon electrodes, rough-surfaced AuPt alloy nanoparticles with nanoporosity were deposited on gold microelectrode sites through electro-co-deposition of Au-Pt-Cu alloy nanoparticles, followed by chemical dealloying Cu. The AuPt alloy nanoparticles modified gold microelectrode sites were characterized by scanning electron microscopy (SEM, electrochemical impedance spectroscopy (EIS, cyclic voltammetry (CV and in vivo neural recording experiment. The SEM images showed that the prepared AuPt alloy nanoparticles exhibited cauliflower-like shapes and possessed very rough surfaces with many different sizes of pores. Average impedance of rough-surfaced AuPt alloy nanoparticles modified sites was 0.23 MΩ at 1 kHz, which was only 4.7% of that of bare gold microelectrode sites (4.9 MΩ, and corresponding in vitro background noise in the range of 1 Hz to 7500 Hz decreased to 7.5 μ V rms from 34.1 μ V rms at bare gold microelectrode sites. Spontaneous spike signal recording was used to evaluate in vivo neural recording performance of modified microelectrode sites, and results showed that rough-surfaced AuPt alloy nanoparticles modified microelectrode sites exhibited higher average spike signal-to-noise ratio (SNR of 4.8 in lateral globus pallidus (GPe due to lower background noise compared to control microelectrodes. Electro-co-deposition of Au-Pt-Cu alloy nanoparticles combined with chemical dealloying Cu was a convenient way for increasing the effective surface area of microelectrode sites, which could reduce electrode impedance and improve the quality of in vivo spike signal recording.

  19. Effects of recording media composition on the responses of Nafion-coated carbon fiber microelectrodes measured using high-speed chronoamperometry.

    Science.gov (United States)

    Gerhardt, G A; Hoffman, A F

    2001-08-15

    The present study concerns methodological issues of electrochemical recordings using Nafion-coated 30 microm diameter single carbon fiber microelectrodes for high-speed chronoamperometric measurements of biogenic amines. First, the single carbon fiber microelectrodes were coated with Nafion and dried at 85 vs. 200 degrees C and their recording properties were determined. Second, the effects of shifts in solution pH, ionic strength, changes in recording solution levels of Ca(2+) or Mg(2+) and temperature on the recording characteristics and sensitivity of Nafion-coated high temperature dried (200 degrees C) single carbon fiber microelectrodes for measures of dopamine were studied. These studies showed that the high temperature drying of the Nafion produced a microelectrode with better recording properties: higher selectivity for cations versus anions, increased differences between the reduction and oxidation current ratios for the identification of dopamine versus serotonin, and more rapid response times. In addition, these studies demonstrated that the chronoamperometric recordings were insensitive to small changes in pH and divalent cations such as Ca(2+) or Mg(2+). However, increases in ionic strength decreased the sensitivity of the microelectrodes, while increases in temperature produced increases in the sensitivity of the microelectrodes for biogenic amines. These data support that Nafion-coated high temperature (200 degrees C) dried microelectrodes have enhanced recording properties as compared to microelectrodes, which are coated with Nafion and dried at 85 degrees C. In addition, high-speed chronoamperometric recordings of biogenic amines are not affected by solution changes in divalent cations (Ca(2+) or Mg(2+)).

  20. Platinum metals in magmatic sulfide ores

    Science.gov (United States)

    Naldrett, A.J.; Duke, J.M.

    1980-01-01

    Platinum-group elements (PGE) are mined predominantly from deposits that have formed by the segregation of molten iron-nickel-copper sulfides from silicate magmas. The absolute concentrations of PGE in sulfides from different deposits vary over a range of five orders of magnitude, whereas those of other chalcophile elements vary by factors of only 2 to 100. However, the relative proportions of the different PGE in a given deposit are systematically related to the nature of the parent magma. The absolute and relative concentrations of PGE in magmatic sulfides are explained in terms of the degree of partial melting of mantle peridotite required to produce the parent magma and the processes of batch equilibration and fractional segregation of sulfides. The Republic of South Africa and the U.S.S.R. together possess more than 97 percent of the world PGE reserves, but significant undeveloped resources occur in North America. The Stillwater complex in Montana is perhaps the most important example. Copyright ?? 1980 AAAS.

  1. Platinum states in citrate sols by EXAFS.

    Science.gov (United States)

    Lin, Chia-Shiang; Khan, Maksudur R; Lin, Shawn D

    2005-07-01

    Platinum sols have been prepared by citrate reduction in the temperature range of 343-363 K. The Pt state in the solution was examined by EXAFS (extended X-ray absorption fine-structure spectroscopy). It did not show any PtPt bonding, a characteristic for reduced Pt sols. EXAFS model fitting further proved the presence of PtO with 4 oxygen neighbors, which suggests a tetraplanar coordination configuration. The possibility of neighboring Pt sharing oxygen ligand or the formation of PtO(x) is rejected by EXAFS model fitting. Citrate was found to be the most likely ligand to orient its oxygen end toward a charged Pt center. Thus we have revealed that the citrate treatment at this temperature range was clearly insufficient to reduce H2PtCl(6(aq)). Neither an extended period of reaction time nor an excess citrate reduced the Pt precursor. It is therefore highly recommended that the citrate sols should be carefully prepared and used.

  2. Development of radioactive platinum group metal catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H.S.; Kim, Y.S.; Kim, Y.E. [and others

    1999-03-01

    The fission product nuclides generated during the irradiation of reactor fuel include many useful elements, among them platinum group metals such as ruthenium, rhodium and palladium which are of great industrial importance, occur rarely in nature and are highly valuable. In this research, the authors reviewed various PGM recovery methods. Recovery of palladium from seven-component simulated waste solutions was conducted by selective precipitation method. The recovery yield was more than 99.5% and the purity of the product was more than 99%. Wet-proof catalyst was prepared with the recovered palladium. The specific surface area of the catalyst support was more than 400m{sup 2}/g.The content of palladium impregnated on the support was 1 to 10 wt. %. Hydrogen isotope exchange efficiency of more than 93% to equilibrium with small amount of the catalyst was obtained. It was turned out possible to consider using such palladium or other very low active PGM materials in applications where its activity is unimportant as in nuclear industries. (author). 86 refs., 44 tabs., 88 figs.

  3. Development of radioactive platinum group metal catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H.S.; Kim, Y.S.; Kim, Y.E. [and others

    1999-03-01

    The fission product nuclides generated during the irradiation of reactor fuel include many useful elements, among them platinum group metals such as ruthenium, rhodium and palladium which are of great industrial importance, occur rarely in nature and are highly valuable. In this research, the authors reviewed various PGM recovery methods. Recovery of palladium from seven-component simulated waste solutions was conducted by selective precipitation method. The recovery yield was more than 99.5% and the purity of the product was more than 99%. Wet-proof catalyst was prepared with the recovered palladium. The specific surface area of the catalyst support was more than 400m{sup 2}/g.The content of palladium impregnated on the support was 1 to 10 wt. %. Hydrogen isotope exchange efficiency of more than 93% to equilibrium with small amount of the catalyst was obtained. It was turned out possible to consider using such palladium or other very low active PGM materials in applications where its activity is unimportant as in nuclear industries. (author). 86 refs., 44 tabs., 88 figs.

  4. Rapid Voltammetric Measurements at Conducting Polymer Microelectrodes Using Ultralow-Capacitance Poly(3,4-ethylenedioxythiophene):Tosylate

    DEFF Research Database (Denmark)

    Meier, Adam R.; Matteucci, Marco; Vreeland, Richard F.

    2016-01-01

    :tOsylate microelectrodes and were used to perform fast-scan cyclic voltammetry (FSCV) measurements. Using a scan rate of 100 V/s, we measured ferrocene carboxylic acid and dopamine by FSCV. In contrast to carbon-fiber microelectrodes, the reduction peak showed higher sensitivity when compared to the oxidation peak......We use a vapor-phase synthesis to generate conducting polymer films with low apparent capacitance and high conductance enabling rapid electrochemical measurements. Specifically, oxidative chemical vapor deposition was used to create thin films of poly(3,4-ethylenedioxythiophene):tosylate (PEDOT......:tosylate). These films had a conductance of 17.1 ± 1.7 S/cm. Furthermore, they had an apparent capacitance of 197 ± 14 μF/cm2, which is an order of magnitude lower than current commercially available and previously reported PEDOT. Using a multistage photolithography process, these films were patterned into PEDOT...

  5. A direct in situ fingerprinting method for acid rock drainage using voltammetric techniques with a single renewable gold microelectrode.

    Science.gov (United States)

    Nuzzio, Donald B; Zettler, Erik R; Aguilera, Angeles; Amaral-Zettler, Linda A

    2011-04-15

    Electrochemistry allows for rapid identification of multiple metals and other chemical complexes common in acid rock drainage (ARD) systems. Voltammetric scans using a single gold microelectrode of water samples from geochemically distinct areas of the Río Tinto (RT) in southwestern Spain were clearly recognizable in the field and in samples stored at room temperature for over 6 months. Major voltammetric peaks of iron(III) and copper(II) were identified on a single constantly renewable gold microelectrode. Confirmation of these peaks was performed by spiking with standard metal solutions in the laboratory. This voltammetric technique is a rapid, direct and inexpensive in situ method for identification of water sources and their chemical characteristics, as well as an economical way to monitor environmental changes and remediation efforts.

  6. A cyclo olefin polymer microfluidic chip with integrated gold microelectrodes for aqueous ans non-aqueous electrochemistry

    DEFF Research Database (Denmark)

    Illa, Xavi; Sala, Olga Ordeig; Snakenborg, Detlef

    2010-01-01

    This paper presents an entirely polymeric microfluidic system, made of cyclo olefin polymer (COP), with integrated gold microband electrodes for electrochemical applications in organic media. In the present work, we take advantage of the COP's high chemical stability to polar organic solvents...... in two different ways: (i) to fabricate gold microelectrodes using COP as a substrate by standard lithographic and lift-off techniques; and (ii) to perform electrochemical experiments in organic media. In particular, fourteen parallel gold microelectrodes with a width of 14 m and separated from...... and 24 m deep channel was fabricated via hot embossing. Cyclic voltammetric measurements were carried out in aqueous and organic media, using a solution consisting of 5 mM ferrocyanide/ferricyanide in 0.5 M KNO3 and 5 mM ferrocene in 0.1 M TBAP/acetonitrile, respectively. Experimental currents obtained...

  7. Synthesis and characterization of potential iron–platinum drugs and supplements by laser liquid photolysis

    CSIR Research Space (South Africa)

    Nkosi, SS

    2013-06-01

    Full Text Available , and structure was systematically investigated. Different nanostructures of iron–platinum alloy and chemically disordered iron–platinum L10 phase were obtained without annealing. The prepared precursor solution underwent deep photolysis to polycrystalline iron...

  8. A dual-emissive ionic liquid based on an anionic platinum(II) complex

    OpenAIRE

    Ogawa, Tomohiro; Yoshida, Masaki; Ohara, Hiroki; Kobayashia, Atsushi; Kato, Masako

    2015-01-01

    An ionic liquid fabricated froman anionic cyclometalated platinum(II) complex and an imidazolium cation exhibits dual emission from the monomeric and aggregated forms of the platinum complex anions, leading to temperature-dependent color changes of luminescence.

  9. A dual-emissive ionic liquid based on an anionic platinum(ii) complex.

    Science.gov (United States)

    Ogawa, Tomohiro; Yoshida, Masaki; Ohara, Hiroki; Kobayashi, Atsushi; Kato, Masako

    2015-09-07

    An ionic liquid fabricated from an anionic cyclometalated platinum(ii) complex and an imidazolium cation exhibits dual emission from the monomeric and aggregated forms of the platinum complex anions, leading to temperature-dependent color changes of luminescence.

  10. A Microelectrochemical Diode with Submicron Contact Spacing Based on the Connection of Two Microelectrodes Using Dissimilar Redox Polymers.

    Science.gov (United States)

    2014-09-26

    of substantially less than one micron * involving a combination of conventional microfabrication techniques and electrochemistry . We recently reported...Southwestern * Analytical ) was dried at 70° under vacuum for >24 hours. LiCIO 4 (Alfa) and [Ru(NH 3 )6]C] 3 (Strem) were used as received, as was...0.3 Pm. The ability to generate redox products at one microelectrode and detect them at the others has some possible analytical utility which will be

  11. Pharmacokinetics of Malonato (1,2 diaminocyclohexane) platinum.

    Science.gov (United States)

    Kelsen, D P; Ribaud, P; Alcock, N; Burchenal, J H; Young, C W; Mathe, G

    1981-01-01

    Malonato-(1,2 diaminocyclohexane) platinum (MP) is a new platinum analog currently undergoing phase I clinical trials. Using flameless atomic absorption spectrophotometry, the pharmacokinetics of MP were studied at five dosage levels. The drug was given as a prolonged intravenous infusion, lasting from 6 to 24 hours. Peak plasma platinum concentrations (Pt) were seen at the end of the infusion, and ranged from 1.1 microgram/ml when 3 mg/kg was given to 14-20.5 micrograms/ml at the 24-mg/kg level. Following completion of the infusion, a prolonged T1/2 beta (mean 63.5 hours) was noted. The percentage of free:total platinum was high (90-95%) at the beginning of the infusion but fell rapidly, to only 15-21% at the end of the 24-hour infusions. Urinary excretion accounted for 16-37.5% of the total administered dose. MP appears to have several pharmacokinetic features in common with cisplatin: rapid binding to protein, a prolonged terminal phase half-life involving primarily bound platinum, and incomplete excretion by the kidney.

  12. Neurotoxicity Caused by the Treatment with Platinum Analogues

    Directory of Open Access Journals (Sweden)

    Sousana Amptoulach

    2011-01-01

    Full Text Available Platinum agents (cisplatin, carboplatin, and oxaliplatin are a class of chemotherapy agents that have a broad spectrum of activity against several solid tumors. Toxicity to the peripheral nervous system is the major dose-limiting toxicity of at least some of the platinum drugs of clinical interest. Among the platinum compounds in clinical use, cisplatin is the most neurotoxic, inducing mainly sensory neuropathy of the upper and lower extremities. Carboplatin is generally considered to be less neurotoxic than cisplatin, but it is associated with a higher risk of neurological dysfunction if administered at high dose or in combination with agents considered to be neurotoxic. Oxaliplatin induces two types of peripheral neuropathy, acute and chronic. The incidence of oxaliplatin-induced neuropathy is related to various risk factors such as treatment schedule, cumulative dose, and time of infusion. To date, several neuroprotective agents including thiol compounds, vitamin E, various anticonvulsants, calcium-magnesium infusions, and other nonpharmacological strategies have been tested for their ability to prevent platinum-induced neurotoxicity with controversial results. Further studies on the prevention and treatment of neurotoxicity of platinum analogues are warranted.

  13. Presentation and Diagnosis of Hypersensitivity to Platinum Drugs.

    Science.gov (United States)

    Caiado, Joana; Castells, Mariana

    2015-04-01

    Hypersensitivity reactions (HSRs) to platinum drugs are increasing due to their extensive use in a wide variety of malignancies and the repeated exposures in patients with increased life expectancy. Understanding the incidence of HSR to platinum drugs and associated risk factors can help with the diagnosis and may provide protection against severe HSRs. A thorough clinical history with identification of the typical and atypical symptoms, the relationship with the platin administration, and the number of previous exposures are the key to the diagnosis. An elevated serum tryptase at the time of the HSR indicates that IgE and/or mast cells/basophils were involved in the HSR. Skin testing to platinum drugs is a highly sensitive and specific diagnostic tool, which helps provide risk stratification and management recommendations. Platinum specific IgE measurement and basophil activation test (BAT) are emerging as new diagnostic tools and in combination with skin testing can help support the diagnosis and the cross-reactivity between the three most commonly used platinum drugs, namely carboplatin, cisplatin, and oxaliplatin.

  14. Structures of 38-atom gold-platinum nanoalloy clusters

    Energy Technology Data Exchange (ETDEWEB)

    Ong, Yee Pin; Yoon, Tiem Leong [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Lim, Thong Leng [Faculty of Engineering and Technology, Multimedia University, Melaka Campus, 75450 Melaka (Malaysia)

    2015-04-24

    Bimetallic nanoclusters, such as gold-platinum nanoclusters, are nanomaterials promising wide range of applications. We perform a numerical study of 38-atom gold-platinum nanoalloy clusters, Au{sub n}Pt{sub 38−n} (0 ≤ n ≤ 38), to elucidate the geometrical structures of these clusters. The lowest-energy structures of these bimetallic nanoclusters at the semi-empirical level are obtained via a global-minimum search algorithm known as parallel tempering multi-canonical basin hopping plus genetic algorithm (PTMBHGA), in which empirical Gupta many-body potential is used to describe the inter-atomic interactions among the constituent atoms. The structures of gold-platinum nanoalloy clusters are predicted to be core-shell segregated nanoclusters. Gold atoms are observed to preferentially occupy the surface of the clusters, while platinum atoms tend to occupy the core due to the slightly smaller atomic radius of platinum as compared to gold’s. The evolution of the geometrical structure of 38-atom Au-Pt clusters displays striking similarity with that of 38-atom Au-Cu nanoalloy clusters as reported in the literature.

  15. Microfabrication of an Implantable silicone Microelectrode array for an epiretinal prosthesis

    Energy Technology Data Exchange (ETDEWEB)

    Maghribi, M

    2003-06-10

    Millions of people suffering from diseases such as retinitis pigmentosa and macular degeneration are legally blind due to the loss of photoreceptor function. Fortunately a large percentage of the neural cells connected to the photoreceptors remain viable, and electrical stimulation of these cells has been shown to result in visual perception. These findings have generated worldwide efforts to develop a retinal prosthesis device, with the hope of restoring vision. Advances in microfabrication, integrated circuits, and wireless technologies provide the means to reach this challenging goal. This dissertation describes the development of innovative silicone-based microfabrication techniques for producing an implantable microelectrode array. The microelectrode array is a component of an epiretinal prosthesis being developed by a multi-laboratory consortium. This array will serve as the interface between an electronic imaging system and the human eye, directly stimulating retinal neurons via thin film conducting traces. Because the array is intended as a long-term implant, vital biological and physical design requirements must be met. A retinal implant poses difficult engineering challenges due to the size of the intraocular cavity and the delicate retina. Not only does it have to be biocompatible in terms of cytotoxicity and degradation, but it also has to be structurally biocompatible, with regard to smooth edges and high conformability; basically mimicking the biological tissue. This is vital to minimize stress and prevent physical damage to the retina. Also, the device must be robust to withstand the forces imposed on it during fabrication and implantation. In order to meet these biocompatibility needs, the use of non-conventional microfabrication materials such as silicone is required. This mandates the enhancement of currently available polymer-based fabrication techniques and the development of new microfabrication methods. Through an iterative process, devices

  16. Needle-type environmental microsensors: design, construction and uses of microelectrodes and multi-analyte MEMS sensor arrays

    Science.gov (United States)

    Lee, Woo Hyoung; Lee, Jin-Hwan; Choi, Woo-Hyuck; Hosni, Ahmed A.; Papautsky, Ian; Bishop, Paul L.

    2011-04-01

    The development of environmental microsensor techniques is a revolutionary advance in the measurement of both absolute levels and changes in chemical species in the field of environmental engineered and natural systems. The tiny tip (5-15 µm diameter) of microsensors makes them very attractive experimental tools for direct measurements of the chemical species of interest inside biological samples (e.g., biofilm, flocs). Microelectrodes fabricated from pulled micropipettes (e.g., dissolved oxygen, oxidation-reduction potential, ion-selective microelectrode) have contributed to greater understanding of biological mechanisms for decades using microscopic monitoring, and currently microelectromechanical system (MEMS) microfabrication technologies are being successfully applied to fabricate multi-analyte sensor systems for in situ monitoring. This review focuses on needle-type environmental microsensor technology, including microelectrodes and multi-analyte MEMS sensor arrays. Design, construction and applications to biofilm research of these sensors are described. Practical methods for biofilm microprofile measurements are presented and several in situ applications for a biofilm study are highlighted. Ultimately, the developed needle-type microsensors combined with molecular biotechnology (such as microscopic observation with fluorescent probes) show the tremendous promise of micro-environmental sensor technology.

  17. The Polypyrrole/Multiwalled Carbon Nanotube Modified Au Microelectrode for Sensitive Electrochemical Detection of Trace Levels of Pb2+

    Directory of Open Access Journals (Sweden)

    Xuxing Zhu

    2017-03-01

    Full Text Available The sensitive detection of trace levels of heavy metal ions such as Pb2+ is of significant importance due to the health hazard they pose. In this paper, we present a polypyrrole (PPy/multiwalled carbon nanotube (MWCNT-modified Au microelectrode. The PPy/MWCNT composite film was electrochemically deposited on the microelectrode by cyclic voltammetry (CV. The composite film was investigated by scanning electron microscope (SEM, CV, and electrochemical impedance spectroscopy (EIS, and the results show that this film presents a uniformly distributed and web-like entangled structure and good conductivity. Differential pulse stripping voltammetry (DPSV was applied to determine trace levels of Pb2+. Experimental conditions including accumulation time and deposition potential were optimized. In optimal conditions, the PPy/MWCNT-modified microelectrode performed sensitive detection of Pb2+ within a concentration range from 1 to 100 μg·L−1, and the limit of detection was 0.65 μg·L−1 at the signal-to-noise ratio of three.

  18. O2 Plasma Etching and Antistatic Gun Surface Modifications for CNT Yarn Microelectrode Improve Sensitivity and Antifouling Properties.

    Science.gov (United States)

    Yang, Cheng; Wang, Ying; Jacobs, Christopher B; Ivanov, Ilia N; Venton, B Jill

    2017-05-16

    Carbon nanotube (CNT) based microelectrodes exhibit rapid and selective detection of neurotransmitters. While different fabrication strategies and geometries of CNT microelectrodes have been characterized, relatively little research has investigated ways to selectively enhance their electrochemical properties. In this work, we introduce two simple, reproducible, low-cost, and efficient surface modification methods for carbon nanotube yarn microelectrodes (CNTYMEs): O2 plasma etching and antistatic gun treatment. O2 plasma etching was performed by a microwave plasma system with oxygen gas flow and the optimized time for treatment was 1 min. The antistatic gun treatment flows ions by the electrode surface; two triggers of the antistatic gun was the optimized number on the CNTYME surface. Current for dopamine at CNTYMEs increased 3-fold after O2 plasma etching and 4-fold after antistatic gun treatment. When the two treatments were combined, the current increased 12-fold, showing the two effects are due to independent mechanisms that tune the surface properties. O2 plasma etching increased the sensitivity due to increased surface oxygen content but did not affect surface roughness while the antistatic gun treatment increased surface roughness but not oxygen content. The effect of tissue fouling on CNT yarns was studied for the first time, and the relatively hydrophilic surface after O2 plasma etching provided better resistance to fouling than unmodified or antistatic gun treated CNTYMEs. Overall, O2 plasma etching and antistatic gun treatment improve the sensitivity of CNTYMEs by different mechanisms, providing the possibility to tune the CNTYME surface and enhance sensitivity.

  19. Determination of Sediment Oxygen Demand in the Ziya River Watershed, China: Based on Laboratory Core Incubation and Microelectrode Measurements.

    Science.gov (United States)

    Rong, Nan; Shan, Baoqing; Wang, Chao

    2016-02-19

    A study coupling sedimentcore incubation and microelectrode measurement was performed to explore the sediment oxygen demand (SOD) at 16 stations in the Ziya River Watershed, a severely polluted and anoxic river system in the north of China. Total oxygen flux values in the range 0.19-1.41 g/(m²·d) with an average of 0.62 g/(m²·d) were obtained by core incubations, and diffusive oxygen flux values in the range 0.15-1.38 g/(m²·d) with an average of 0.51 g/(m²·d) were determined by microelectrodes. Total oxygen flux obviously correlated with diffusive oxygen flux (R² = 0.842). The microelectrode method produced smaller results than the incubation method in 15 of 16 sites, and the diffusive oxygen flux was smaller than the total oxygen flux. Although the two sets of SOD values had significant difference accepted by the two methods via the Wilcoxon signed-rank test (p Watershed when the dissolved oxygen (DO) recovered in the overlying water.

  20. Spatial and temporal characteristics of V1 microstimulation during chronic implantation of a microelectrode array in a behaving macaque

    Science.gov (United States)

    Davis, T. S.; Parker, R. A.; House, P. A.; Bagley, E.; Wendelken, S.; Normann, R. A.; Greger, B.

    2012-12-01

    Objective. It has been hypothesized that a vision prosthesis capable of evoking useful visual percepts can be based upon electrically stimulating the primary visual cortex (V1) of a blind human subject via penetrating microelectrode arrays. As a continuation of earlier work, we examined several spatial and temporal characteristics of V1 microstimulation. Approach. An array of 100 penetrating microelectrodes was chronically implanted in V1 of a behaving macaque monkey. Microstimulation thresholds were measured using a two-alternative forced choice detection task. Relative locations of electrically-evoked percepts were measured using a memory saccade-to-target task. Main results. The principal finding was that two years after implantation we were able to evoke behavioural responses to electric stimulation across the spatial extent of the array using groups of contiguous electrodes. Consistent responses to stimulation were evoked at an average threshold current per electrode of 204 ± 49 µA (mean ± std) for groups of four electrodes and 91 ± 25 µA for groups of nine electrodes. Saccades to electrically-evoked percepts using groups of nine electrodes showed that the animal could discriminate spatially distinct percepts with groups having an average separation of 1.6 ± 0.3 mm (mean ± std) in cortex and 1.0° ± 0.2° in visual space. Significance. These results demonstrate chronic perceptual functionality and provide evidence for the feasibility of a cortically-based vision prosthesis for the blind using penetrating microelectrodes.

  1. Influence of droplet coverage on the electrochemical response of planar microelectrodes and potential solving strategies based on nesting concept

    Directory of Open Access Journals (Sweden)

    Yue Yu

    2016-08-01

    Full Text Available Recently, biosensors have been widely used for the detection of bacteria, viruses and other toxins. Electrodes, as commonly used transducers, are a vital part of electrochemical biosensors. The coverage of the droplets can change significantly based on the hydrophobicity of the microelectrode surface materials. In the present research, screen-printed interdigitated microelectrodes (SPIMs, as one type of planar microelectrode, were applied to investigate the influence of droplet coverage on electrochemical response. Furthermore, three dimensional (3D printing technology was employed to print smart devices with different diameters based on the nesting concept. Theoretical explanations were proposed to elucidate the influence of the droplet coverage on the electrochemical response. 3D-printed ring devices were used to incubate the SPIMs and the analytical performances of the SPIMs were tested. According to the results obtained, our device successfully improved the stability of the signal responses and eliminated irregular signal changes to a large extent. Our proposed method based on the nesting concept provides a promising method for the fabrication of stable electrochemical biosensors. We also introduced two types of electrode bases to improve the signal stability.

  2. Influence of droplet coverage on the electrochemical response of planar microelectrodes and potential solving strategies based on nesting concept

    Science.gov (United States)

    Yu, Yue

    2016-01-01

    Recently, biosensors have been widely used for the detection of bacteria, viruses and other toxins. Electrodes, as commonly used transducers, are a vital part of electrochemical biosensors. The coverage of the droplets can change significantly based on the hydrophobicity of the microelectrode surface materials. In the present research, screen-printed interdigitated microelectrodes (SPIMs), as one type of planar microelectrode, were applied to investigate the influence of droplet coverage on electrochemical response. Furthermore, three dimensional (3D) printing technology was employed to print smart devices with different diameters based on the nesting concept. Theoretical explanations were proposed to elucidate the influence of the droplet coverage on the electrochemical response. 3D-printed ring devices were used to incubate the SPIMs and the analytical performances of the SPIMs were tested. According to the results obtained, our device successfully improved the stability of the signal responses and eliminated irregular signal changes to a large extent. Our proposed method based on the nesting concept provides a promising method for the fabrication of stable electrochemical biosensors. We also introduced two types of electrode bases to improve the signal stability. PMID:27635356

  3. The Researches on Performance and Technology of Strengthened Pure Platinum Wire

    Institute of Scientific and Technical Information of China (English)

    ZHAI Buying; WU Baoan; PAN Xiong; YANG Hao; WANG Yunchun; CHEN Xiaojun; WANG Jianshen; LI Guogang; XUE Liqian

    2012-01-01

    This paper discusses about the purity of strengthened pure platinum wire and the development method of platinum micro wire,in order to solve the difficulties of low tensile strength,easy to break,and low rate of micro wire.And it contrasts some performance of strengthened pure platinum wire and sponge Pt wire.The researches draw a conclusion that the thermoelectric properties of strengthened pure platinum micro wire was in accordance with national standards and satisfied users' requirements.

  4. The effects of platinum on nickel electrodes in the nickel hydrogen cell

    Science.gov (United States)

    Zimmerman, Albert H.

    1991-01-01

    Interactions of platinum and platinum compounds with the nickel electrode that are possible in the nickel hydrogen cell, where both the nickel electrode and a platinum catalyst hydrogen electrode are in intimate contact with the alkaline electrolyte, are examined. Additionally, a mechanism of nickel cobalt oxyhydroxide formation in NiH2 cells is presented.

  5. Preparation and Characterization of Atactic Poly(vinyl alcohol)/Platinum Nanocomposites by Electrospinning

    Science.gov (United States)

    Seok Lyoo, Won; Jae Lee, Young; Wook Cha, Jin; Jae Kim, Min; Woo Joo, Sang; Soon Gal, Yeong; Hwan Oh, Tae; Soo Han, Sung

    2010-06-01

    Poly(vinyl alcohol) (PVA)/platinum composite nanofibers were successfully prepared by the electrospinning method. Water-based colloidal platinum in a PVA solution was directly mixed without any chemical or structural modifications into PVA polymer fibers to form organic-inorganic composite nanofibers. The PVA/platinum composite nanofibers were characterized by field emission scanning electron microscopy (SEM).

  6. Platinum Publications, December 30, 2016–January 25, 2017 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 42 prestigious science journals. This list represents articles published during the time period shown above, as generated from PubMed. Articles designated as Platinum Highlights are noteworthy articles selected from among the most recently published Platinum Publications.

  7. POLYMER-PLATINUM COMPLEX CATALYSTS FOR OXIDATION OF METHANOL TO FORMALDEHYDE

    Institute of Scientific and Technical Information of China (English)

    HUANG Meiyu; HUANG Li; ZHENG Qingyao; WANG Dianxun; JIANG Yingyan

    1984-01-01

    Two kinds of polymer-platinum complexes: silica-supported poly-γ-diphenylphosphinopropyl-siloxane-platinum complex and silica-supported polyphenylsilazane-platinum complex, have been found very active and selective in catalyzation of oxidation of methanol to formaldehyde at room temperature and under an atmospheric oxygen pressure. Their catalytic activities are greatly affected by P or N/Pt gram atomic ratio.

  8. 75 FR 77572 - Proposed Revision of Class E Airspace; Platinum AK

    Science.gov (United States)

    2010-12-13

    ... Federal Aviation Administration 14 CFR Part 71 Proposed Revision of Class E Airspace; Platinum AK AGENCY... action proposes to revise Class E airspace at Platinum AK. The creation of a new Standard Instrument Approach Procedure (SIAP) at the Platinum Airport has made this action necessary to enhance safety...

  9. 76 FR 67793 - Notification of Expanded Pricing Grid for Precious Metals Products Containing Platinum and Gold...

    Science.gov (United States)

    2011-11-02

    ... United States Mint Notification of Expanded Pricing Grid for Precious Metals Products Containing Platinum..., 2009, outlining the new pricing methodology for numismatic products containing platinum and gold. Since that time, the price of platinum and gold has increased considerably, and is approaching the...

  10. 40 CFR 440.110 - Applicability; description of the platinum ore subcategory.

    Science.gov (United States)

    2010-07-01

    ... platinum ore subcategory. 440.110 Section 440.110 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS ORE MINING AND DRESSING POINT SOURCE CATEGORY Platinum Ores Subcategory § 440.110 Applicability; description of the platinum ore subcategory. The provisions of...

  11. Flow Injection Analysis with Electrochemical Detection for Rapid Identification of Platinum-Based Cytostatics and Platinum Chlorides in Water

    Directory of Open Access Journals (Sweden)

    Marketa Kominkova

    2014-02-01

    Full Text Available Platinum-based cytostatics, such as cisplatin, carboplatin or oxaliplatin are widely used agents in the treatment of various types of tumors. Large amounts of these drugs are excreted through the urine of patients into wastewaters in unmetabolised forms. This phenomenon leads to increased amounts of platinum ions in the water environment. The impacts of these pollutants on the water ecosystem are not sufficiently investigated as well as their content in water sources. In order to facilitate the detection of various types of platinum, we have developed a new, rapid, screening flow injection analysis method with electrochemical detection (FIA-ED. Our method, based on monitoring of the changes in electrochemical behavior of analytes, maintained by various pH buffers (Britton-Robinson and phosphate buffer and potential changes (1,000, 1,100 and 1,200 mV offers rapid and cheap selective determination of platinum-based cytostatics and platinum chlorides, which can also be present as contaminants in water environments.

  12. Flow injection analysis with electrochemical detection for rapid identification of platinum-based cytostatics and platinum chlorides in water.

    Science.gov (United States)

    Kominkova, Marketa; Heger, Zbynek; Zitka, Ondrej; Kynicky, Jindrich; Pohanka, Miroslav; Beklova, Miroslava; Adam, Vojtech; Kizek, Rene

    2014-02-04

    Platinum-based cytostatics, such as cisplatin, carboplatin or oxaliplatin are widely used agents in the treatment of various types of tumors. Large amounts of these drugs are excreted through the urine of patients into wastewaters in unmetabolised forms. This phenomenon leads to increased amounts of platinum ions in the water environment. The impacts of these pollutants on the water ecosystem are not sufficiently investigated as well as their content in water sources. In order to facilitate the detection of various types of platinum, we have developed a new, rapid, screening flow injection analysis method with electrochemical detection (FIA-ED). Our method, based on monitoring of the changes in electrochemical behavior of analytes, maintained by various pH buffers (Britton-Robinson and phosphate buffer) and potential changes (1,000, 1,100 and 1,200 mV) offers rapid and cheap selective determination of platinum-based cytostatics and platinum chlorides, which can also be present as contaminants in water environments.

  13. Oscillatory instabilities in the electrooxidation of borohydride on platinum

    Energy Technology Data Exchange (ETDEWEB)

    Machado, Eduardo G.; Varela, Hamilton, E-mail: varela@iqsc.usp.br [Universidade de Sao Paulo (USP), Sao Carlos, SP (Brazil). Instituto de Quimica

    2014-03-15

    The borohydride ion has been pointed as a promising alternative fuel. Most of the investigation on its electrochemistry is devoted to the electrocatalytic aspects of its electrooxidation on platinum and gold surfaces. Besides the known kinetic limitations and intricate mechanism, our Group has recently found the occurrence of two regions of bi-stability and autocatalysis in the electrode potential during the open circuit interaction of borohydride and oxidized platinum surfaces. Following this previous contribution, the occurrence of more complicated phenomena is here presented: namely the presence of electrochemical oscillations during the electrooxidation of borohydride on platinum in alkaline media. Current oscillations were found to be associated to two distinct instability windows and characterized in the resistance-potential parameter plane. The dynamic features of such oscillations suggest the existence of distinct mechanisms according to the potential region. Previously published results obtained under non-oscillatory regime were used to give some hints on the surface chemistry behind the observed dynamics. (author)

  14. Current View in Platinum Drug Mechanisms of Peripheral Neurotoxicity

    Directory of Open Access Journals (Sweden)

    Alessia Chiorazzi

    2015-08-01

    Full Text Available Peripheral neurotoxicity is the dose-limiting factor for clinical use of platinum derivatives, a class of anticancer drugs which includes cisplatin, carboplatin, and oxaliplatin. In particular cisplatin and oxaliplatin induce a severe peripheral neurotoxicity while carboplatin is less neurotoxic. The mechanisms proposed to explain these drugs’ neurotoxicity are dorsal root ganglia alteration, oxidative stress involvement, and mitochondrial dysfunction. Oxaliplatin also causes an acute and reversible neuropathy, supposed to be due by transient dysfunction of the voltage-gated sodium channels of sensory neurons. Recent studies suggest that individual genetic variation may play a role in the pathogenesis of platinum drug neurotoxicity. Even though all these mechanisms have been investigated, the pathogenesis is far from clearly defined. In this review we will summarize the current knowledge and the most up-to-date hypotheses on the mechanisms of platinum drug-induced peripheral neurotoxicity.

  15. Preparation of platinum/iridium scanning probe microscopy tips

    DEFF Research Database (Denmark)

    Sørensen, Alexis Hammer; Hvid, U.; Mortensen, M.W.

    1999-01-01

    for the production of sharp tips. After being etched the tips are ready for use in scanning tunneling microscopes, or they may be bent to form integrated tip/cantilever systems in ordinary commercial atomic force microscopes, being applicable as tapping mode tips and as electrostatic force microscopy tips. ©1999......We report on the development of an etching setup for use in the preparation of platinum/iridium tips for atomic force microscopy and scanning electrostatic force microscopy as well as scanning tunneling microscopy. The etching process is based on a two step electrochemical procedure. The first step....... This mechanism is based on the formation of oxygen and hydrogen at the platinum/iridium electrode when the potential is above the dissociation potential of water (~ 1.23 V) and storage of these products interstitially in the outer layers of the platinum wire. This leads to "microexplosions" that detach fragments...

  16. Platinum-Iridium Alloy Films Prepared by MOCVD

    Institute of Scientific and Technical Information of China (English)

    WEI Yan; CHEN Li; CAI Hongzhong; ZHENG Xu; YANG Xiya; HU Changyi

    2012-01-01

    Platinum-Iridium alloy films were prepared by MOCVD on Mo substrate using metal-acetylacetonate precursors.Effects of deposition conditions on composition,microstructure and mechanical properties were determined.In these experimental conditions,the purities of films are high and more than 99.0%.The films are homogeneous and monophase solid solution of Pt and Ir.Weight percentage of platinum are much higher than iridium in the alloy.Lattice constant of the alloy changes with the platinum composition.Iridium composition showing an up-down-up trend at the precursor temperature of 190~230℃ and the deposition temperature at 400~550℃.The hardness of Pt-Ir alloys prepared by MOCVD is three times more than the alloys prepared by casting.

  17. Interaction of DNA with Bis(diiminosuccinonitrilo)platinum(Ⅱ)

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhi-Gang; SUN Yuan-Yuan; JIANG Xiao-Ming

    2008-01-01

    Interaction of DNA with bis(diiminosuccinonitrilo)platinum(Ⅱ) has been studied by UV-visible absorbance spectra, fluorescence spectra and viscosity measurements. The UV-visible absorption spectra of the metal complex exhibit hypochromism with a small blue shift on interaction with DNA. Scatchard plot analyses indicate that the binding sites of the metal complex on DNA are different from those of ethidium bromide. Viscosity experiments reveal that the binding of the metal complex decreases the relative viscosity of DNA. These results suggest that the platinum diimine complex interact with DNA by surface binding. These studies are helpful for us to understand the action mechanism of bis(diiminosuccinonitrilo)platinum(Ⅱ) as a potential photodynamic therapeutic agent, and further to develop it.

  18. Synthesis and Electrocatalytic Performance of BDD-Supported Platinum Nanoparticles

    Science.gov (United States)

    Lyu, Xiao; Hu, Jingping; Foord, John S.; Lou, Changsheng; Zhang, Weiqiang

    2015-02-01

    Platinum nanoparticles were deposited on boron-doped diamond substrate by electroless method without pre-activation. The mechanism of this deposition is a galvanic process along with a chemical process. Platinum particles are in nanoscale with diameter around 30-50 nm and height of around 3 nm observed from AFM and SEM images. The electrochemical activity of Pt nanoparticles was evaluated by cyclic voltammograms of hydrogen desorption process in 0.5 M H2SO4. The deposited platinum shows great stability in subsequent cycling in sulfuric acid and exhibits a high selectivity toward H2O2 detection in the range of 1 to 400 μM compared with those produced by electrochemical deposition.

  19. Decitabine reactivated pathways in platinum resistant ovarian cancer.

    Science.gov (United States)

    Fang, Fang; Zuo, Qingyao; Pilrose, Jay; Wang, Yinu; Shen, Changyu; Li, Meng; Wulfridge, Phillip; Matei, Daniela; Nephew, Kenneth P

    2014-06-15

    Combination therapy with decitabine, a DNMTi and carboplatin resensitized chemoresistant ovarian cancer (OC) to platinum inducing promising clinical activity. We investigated gene-expression profiles in tumor biopsies to identify decitabine-reactivated pathways associated with clinical response. Gene-expression profiling was performed using RNA from paired tumor biopsies before and 8 days after decitabine from 17 patients with platinum resistant OC. Bioinformatic analysis included unsupervised hierarchical-clustering, pathway and GSEA distinguishing profiles of "responders" (progression-free survival, PFS>6 months) and "non-responders" (PFSdecitabine (TGF-β and Hh). Gene-expression profiling identified specific pathways altered by decitabine and associated with platinum-resensitization and clinical benefit in OC. Our data could influence patient stratification for future studies using epigenetic therapies.

  20. Brain computer interface learning for systems based on electrocorticography and intracortical microelectrode arrays.

    Science.gov (United States)

    Hiremath, Shivayogi V; Chen, Weidong; Wang, Wei; Foldes, Stephen; Yang, Ying; Tyler-Kabara, Elizabeth C; Collinger, Jennifer L; Boninger, Michael L

    2015-01-01

    A brain-computer interface (BCI) system transforms neural activity into control signals for external devices in real time. A BCI user needs to learn to generate specific cortical activity patterns to control external devices effectively. We call this process BCI learning, and it often requires significant effort and time. Therefore, it is important to study this process and develop novel and efficient approaches to accelerate BCI learning. This article reviews major approaches that have been used for BCI learning, including computer-assisted learning, co-adaptive learning, operant conditioning, and sensory feedback. We focus on BCIs based on electrocorticography and intracortical microelectrode arrays for restoring motor function. This article also explores the possibility of brain modulation techniques in promoting BCI learning, such as electrical cortical stimulation, transcranial magnetic stimulation, and optogenetics. Furthermore, as proposed by recent BCI studies, we suggest that BCI learning is in many ways analogous to motor and cognitive skill learning, and therefore skill learning should be a useful metaphor to model BCI learning.

  1. Ferrocene pixels by laser-induced forward transfer: towards flexible microelectrode printing

    Science.gov (United States)

    Mitu, B.; Matei, A.; Filipescu, M.; Palla Papavlu, A.; Bercea, A.; Lippert, T.; Dinescu, M.

    2017-03-01

    The aim of this work is to demonstrate the potential of laser-induced forward transfer (LIFT) as a printing technology, alternative to standard microfabrication techniques, in the area of flexible micro-electrode fabrication. First, ferrocene thin films are deposited onto fused silica and fused silica substrates previously coated with a photodegradable polymer film (triazene polymer) by matrix assisted pulsed laser evaporation (MAPLE). The morphology and chemical structure of the ferrocene thin films deposited by MAPLE has been investigated by atomic force microscopy and Fourier transformed infrared spectroscopy, and no structural damage occurs as a result of the laser deposition. Second, LIFT is applied to print for the first time ferrocene pixels and lines onto flexible polydimethylsiloxane (PDMS) substrates. The ferrocene pixels and lines are flawlessly transferred onto the PDMS substrates in air at room temperature, without the need of additional conventional photolithography processes. We believe that these results are very promising for a variety of applications ranging from flexible electronics to lab-on-a-chip devices, MEMS, and medical implants.

  2. Alternative Post-Processing on a CMOS Chip to Fabricate a Planar Microelectrode Array

    Science.gov (United States)

    López-Huerta, Francisco; Herrera-May, Agustín L.; Estrada-López, Johan J.; Zuñiga-Islas, Carlos; Cervantes-Sanchez, Blanca; Soto, Enrique; Soto-Cruz, Blanca S.

    2011-01-01

    We present an alternative post-processing on a CMOS chip to release a planar microelectrode array (pMEA) integrated with its signal readout circuit, which can be used for monitoring the neuronal activity of vestibular ganglion neurons in newborn Wistar strain rats. This chip is fabricated through a 0.6 μm CMOS standard process and it has 12 pMEA through a 4 × 3 electrodes matrix. The alternative CMOS post-process includes the development of masks to protect the readout circuit and the power supply pads. A wet etching process eliminates the aluminum located on the surface of the p+-type silicon. This silicon is used as transducer for recording the neuronal activity and as interface between the readout circuit and neurons. The readout circuit is composed of an amplifier and tunable bandpass filter, which is placed on a 0.015 mm2 silicon area. The tunable bandpass filter has a bandwidth of 98 kHz and a common mode rejection ratio (CMRR) of 87 dB. These characteristics of the readout circuit are appropriate for neuronal recording applications. PMID:22346681

  3. Electrochemical Examination of the Structure of Thin Hydrogel Layers Anchored to Regular and Microelectrode Surfaces.

    Science.gov (United States)

    Kaniewska, Klaudia; Karbarz, Marcin; Ziach, Krzysztof; Siennicka, Alicja; Stojek, Zbigniew; Hyk, Wojciech

    2016-09-01

    For the examination of hydrogel structure, thin layers of thermoresponsive gels based on poly(N-isopropylacrylamide) (pNIPA) and copolymer poly(N-isopropylacrylamide-co-sodium acrylate) (p(NIPA-co-AS)) were successfully anchored to microelectrode and regular electrode surfaces using the electrochemically induced free radical polymerization. The obtained layers were stable and covered the entire surface of the electrodes. Electroactive probes 1,1'-ferrocenedimethanol (Fc(CH2OH)2) and synthesized derivatives of ferrocene modified with polyethylene glycol units (Fc-PEGn) of various length (n = 4, 9, 75, and 135) were employed for studying the volume phase transition of the thin hydrogel layers and for the determination of their structural parameters. The quantitative information on the structural parameters of the hydrogel layers was derived from the obstruction model for diffusion using the voltammetrically determined diffusion coefficients for the model redox probe Fc(CH2OH)2. An approach to the determination of the effective radii of the gel openings (channels) for pNIPA and p(NIPA-co-AS) microlayers was developed. The obtained results were matched with the experimental results and allowed derivation of quantitative conclusions. The voltammograms obtained with modified electrodes in solutions containing Fc-PEG4, Fc-PEG9, and Fc-PEG75 were well defined and of appropriate height. However, the voltammograms recorded for Fc-PEG135, the hydrodynamic radius of which exceeded the size of the gel channels, were at the baseline level.

  4. Urease-gelatin interdigitated microelectrodes for the conductometric determination of protease activity.

    Science.gov (United States)

    Ionescu, Rodica E; Fillit, Chrystelle; Jaffrezic-Renault, Nicole; Cosnier, Serge

    2008-11-15

    Conductometric microbiosensors for the determination of trypsin were elaborated via the modification of microfabricated interdigitated gold electrodes by a cross-linked urease/BSA coating covered by a gelatin film. The resulting microelectrodes were exposed to different trypsin concentrations ranging from 100 pg/mL to 1mg/mL (1 mU/mL to 10,000 U/mL) for selective proteolytic degradation of the gelatin film. Then, the conductometric response of the microbiosensors to urea (33 microM) was recorded as a function of the trypsin concentration, the gelatin amount (8-80 ng) and the incubation time (40s, 100 min). The optimum incubation time for each trypsin concentration was determined leading to a detection limit of 100 pg/mL (1 mU/mL). In these optimized conditions, the proof of concept of this sensitive, disposable, low-cost and label-free trypsin biosensors based on a conductometric transducer was demonstrated for the first time.

  5. A comparison of microelectrodes for a visual cortical prosthesis using finite element analysis

    Directory of Open Access Journals (Sweden)

    Emma Kate Brunton

    2012-09-01

    Full Text Available Altering the geometry of microelectrodes for use in a cortical neural prosthesis modifies the electric field generated in tissue, thereby affecting electrode efficacy and tissue damage. Commonly, electrodes with an active region located at the tip (conical electrodes are used for stimulation of cortex but there is argument to believe this geometry may not be the best. Here we use finite element analysis to compare the electric fields generated by three types of electrodes, a conical electrode with exposed active tip, an annular electrode with active area located up away from the tip, and a striped annular electrode where the active annular region has bands of insulation interrupting the full active region. The results indicate that current density on the surface of the conical electrodes can be up to ten times greater than current density on annular electrodes of the same height, which may increase the propensity for tissue damage. However choosing the most efficient electrode geometry in order to reduce power consumption is dependent on the distance of the electrode to the target neurons. If neurons are located within 10 micrometers of the electrode, then a small conical electrode would be more power efficient. On the other hand if the target neuron is greater than 500 micrometers away – as happens normally when insertion of an array of electrodes into cortex results in a kill zone around each electrode due to insertion damage and inflammatory responses - then a large annular electrode would be more efficient.

  6. A Facile Approach for Constructing Conductive Polymer Patterns for Application in Electrochromic Devices and Flexible Microelectrodes.

    Science.gov (United States)

    Kim, Dabum; Kim, Jeonghun; Ko, Youngsang; Shim, Kyubin; Kim, Jung Ho; You, Jungmok

    2016-12-07

    We developed a novel strategy for fabricating poly(3,4-ethylenedioxythiophene) (PEDOT) patterns on various substrates, including hydrogels, via sequential solution procedure without multistep chemical etching or lift-off processes. First, PEDOT nanothin films were prepared on a glass substrate by solution phase monomer casting and oxidative polymerization. As a second step, after UV-induced poly(ethylene glycol) (PEG) photolithography at the PEDOT/PEG interface through a photomask, the hydrogel was peeled away from the PEDOT-coated glass substrate to detach the UV-exposed PEDOT region, which left the UV nonexposed PEDOT region intact on the glass substrate, resulting in PEDOT patterns. In a final step, the PEDOT patterns were cleanly transferred from the glass to a flexible hydrogel substrate by a direct-transfer process based on a second round of gelation process. Using this strategy, PEDOT patterns on ITO glass or ITO film were used to successfully fabricate an electrochromic (EC) device that exhibited stable electrochromic switching as a function of applied potential. Furthermore, PEDOT patterns on hydrogel were used to fabricate all organic, flexible microelectrodes with good electrical properties and excellent mechanical flexibility. Importantly, the conductivity of PEDOT patterns on hydrogel (ca. 235 S cm(-1)) described here is significantly higher than that previously reported (ca. 20-70 S cm(-1)). This approach can be easily integrated into various technological fabrication steps for the development of next-generation bioelectronics systems.

  7. Interdigitated microelectrode based impedance biosensor for detection of salmonella enteritidis in food samples

    Energy Technology Data Exchange (ETDEWEB)

    Kim, G [National Institute of Agricultural Engineering, 249 Seodun-dong, Suwon, Republic of Korea, 441-100 (Korea, Republic of); Morgan, M; Hahm, B K; Bhunia, A [Department of Food Science, Purdue University, West Lafayette, IN 47907 (United States); Mun, J H; Om, A S [Department of Food and Nutrient, Hanyang University, 17 Haengdang-dong, Seoul, Republic of Korea, 133-791 (Korea, Republic of)], E-mail: giyoungkim@rda.go.kr

    2008-03-15

    Salmonella enteritidis outbreaks continue to occur, and S. enteritidis-related outbreaks from various food sources have increased public awareness of this pathogen. Conventional methods for pathogens detection and identification are labor-intensive and take days to complete. Some immunological rapid assays are developed, but these assays still require prolonged enrichment steps. Recently developed biosensors have shown great potential for the rapid detection of foodborne pathogens. To develop the biosensor, an interdigitated microelectrode (IME) was fabricated by using semiconductor fabrication process. Anti-Salmonella antibodies were immobilized based on avidin-biotin binding on the surface of the IME to form an active sensing layer. To increase the sensitivity of the sensor, three types of sensors that have different electrode gap sizes (2 {mu}m, 5 {mu}m, 10 {mu}m) were fabricated and tested. The impedimetric biosensor could detect 10{sup 3} CFU/mL of Salmonella in pork meat extract with an incubation time of 5 minutes. This method may provide a simple, rapid and sensitive method to detect foodborne pathogens.

  8. Interdigitated microelectrode based impedance biosensor for detection of salmonella enteritidis in food samples

    Science.gov (United States)

    Kim, G.; Morgan, M.; Hahm, B. K.; Bhunia, A.; Mun, J. H.; Om, A. S.

    2008-03-01

    Salmonella enteritidis outbreaks continue to occur, and S. enteritidis-related outbreaks from various food sources have increased public awareness of this pathogen. Conventional methods for pathogens detection and identification are labor-intensive and take days to complete. Some immunological rapid assays are developed, but these assays still require prolonged enrichment steps. Recently developed biosensors have shown great potential for the rapid detection of foodborne pathogens. To develop the biosensor, an interdigitated microelectrode (IME) was fabricated by using semiconductor fabrication process. Anti-Salmonella antibodies were immobilized based on avidin-biotin binding on the surface of the IME to form an active sensing layer. To increase the sensitivity of the sensor, three types of sensors that have different electrode gap sizes (2 μm, 5 μm, 10 μm) were fabricated and tested. The impedimetric biosensor could detect 103 CFU/mL of Salmonella in pork meat extract with an incubation time of 5 minutes. This method may provide a simple, rapid and sensitive method to detect foodborne pathogens.

  9. Brain Computer Interface Learning for Systems Based on Electrocorticography and Intracortical Microelectrode Arrays

    Directory of Open Access Journals (Sweden)

    Shivayogi V Hiremath

    2015-06-01

    Full Text Available A brain-computer interface (BCI system transforms neural activity into control signals for external devices in real time. A BCI user needs to learn to generate specific cortical activity patterns to control external devices effectively. We call this process BCI learning, and it often requires significant effort and time. Therefore, it is important to study this process and develop novel and efficient approaches to accelerate BCI learning. This article reviews major approaches that have been used for BCI learning, including computer-assisted learning, co-adaptive learning, operant conditioning, and sensory feedback. We focus on BCIs based on electrocorticography and intracortical microelectrode arrays for restoring motor function. This article also explores the possibility of brain modulation techniques in promoting BCI learning, such as electrical cortical stimulation, transcranial magnetic stimulation, and optogenetics. Furthermore, as proposed by recent BCI studies, we suggest that BCI learning is in many ways analogous to motor and cognitive skill learning, and therefore skill learning should be a useful metaphor to model BCI learning.

  10. Assessment of mitochondrial membrane potential using an on-chip microelectrode in a microfluidic device.

    Science.gov (United States)

    Lim, Tae-Sun; Dávila, Antonio; Wallace, Douglas C; Burke, Peter

    2010-07-07

    The mitochondrial membrane potential is used to generate and regulate energy in living systems, driving the conversion of ADP to ATP, regulating ion homeostasis, and controlling apoptosis, all central to human health and disease. Therefore, there is a need for tools to study its regulation in a controlled environment for potential clinical and scientific applications. For this aim, an on-chip tetraphenylphosphonium (TPP(+)) selective microelectrode sensor was constructed in a microfluidic environment. The concentration of isolated mitochondria (Heb7A) used in a membrane potential measurement was 0.3 ng microL(-1), four orders of magnitude smaller than the concentration used in conventional assays (3 microg microL(-1)). In addition, the volume of the chamber (85 microL) is 2 orders of magnitude smaller than traditional experiments. As a demonstration, changes in the membrane potential are clearly measured in response to a barrage of well-known substrates and inhibitors of the electron transport chain. This general approach, which to date has not been demonstrated for study of mitochondrial function and bio-energetics in generally, can be instrumental in advancing the field of mitochondrial research and clinical applications by allowing high throughput studies of the regulation, dynamics, and statistical properties of the mitochondrial membrane potential in response to inhibitors and inducers of apoptosis in a controlled (microfluidic) chemical environment.

  11. Diamond microelectrodes and CMOS microelectronics for wireless transmission of fast-scan cyclic voltammetry.

    Science.gov (United States)

    Roham, Masoud; Halpern, Jeffrey M; Martin, Heidi B; Chiel, Hillel J; Mohseni, Pedram

    2007-01-01

    This paper reports on technology development at the sensor and circuit levels for wireless transmission of fast-scan cyclic voltammetry (FSCV) in neurochemical detection. Heavily conductive, boron-doped diamond is selectively deposited onto the polished tip of a tungsten microelectrode to fabricate versatile, implantable, micro-needle microprobes capable of neurochemical sensing in the brain. In addition, an integrated circuit is fabricated in a 0.5-microm CMOS technology for processing and wireless transmission of the electrochemical signals corresponding to extracellular concentration changes of various neurotransmitters. The chip consists of a current-based, second-order, front-end SigmaDelta ADC and an on-chip, RF-FSK transmitter at the back-end. The ADC core and the transmitter consume 22microA and 400microA, respectively, from a 2.6-V power supply. Major electroactive neurotransmitters such as serotonin and dopamine in micromolar concentration have been wirelessly recorded at 433MHz using 300-V/s FSCV in flow injection analysis experiments.

  12. Intra-operative micro-electrode recording in functional neurosurgery: Past, present, future.

    Science.gov (United States)

    Maiti, Tanmoy K; Konar, Subhas; Bir, Shyamal; Kalakoti, Piyush; Nanda, Anil

    2016-10-01

    The field of functional neurosurgery has experienced a rise, fall and lastly a renaissance over the past 75years. Micro-electrode recording (MER) played a key role during this eventful journey. However, as the intra-operative MRI continues to evolve, a pertinent question about the utility of MER has been raised in recent years. In this article, we critically review these current controversies. The English literature is reviewed and the complex technique of MER is discussed in a simplified manner. The improvement of neuroimaging and its application in functional neurosurgery, especially in deep brain stimulation, is discussed. Finally, the current controversies and technical advances which can direct the future are reviewed. The results of existing meta-analyses addressing the controversies are summarized. Wide variations of pre-operative and intra-operative targeting methods have been described in the literature. Though functional neurosurgery is generally safe, complications do occur and multiple passes during MER can certainly add to the risk of inadvertent hemorrhage and infection. Additionally, the recent introduction of newer MRI modalities has ensured better delineation of the target. However, MER is still useful to address brain shift, for mapping of newer targets, for ablative surgeries and in centers without an intra-operative imaging facility. In the current scenario, it is nearly impossible to conduct a prospective study to decide the utility of MER. The importance of MER may further diminish in the future as a routine procedure, but its role as a gold standard procedure may still persist.

  13. In vivo voltammetric detection of rat brain lactate with carbon fiber microelectrodes coated with lactate oxidase.

    Science.gov (United States)

    Shram, N F; Netchiporouk, L I; Martelet, C; Jaffrezic-Renault, N; Bonnet, C; Cespuglio, R

    1998-07-01

    To allow rat brain lactate measurement in vivo, a specific sensor based on a carbon fiber (phi = 30 microns) microelectrode coated with lactate oxidase was prepared. Combined with the differential normal pulse voltammetry measurement method, such a sensor, with a sensitivity of 9.15 +/- 0.91 mA.M-1.cm-2, provided a lactate linear response in concentrations ranging from 0.1 to 2.0 mM. The measurements performed appeared to be essentially insensitive to usual interference caused by the electroactive compounds present in the brain (ascorbic acid and peptides). In vivo detection performed in the cortex of the anesthetized rat led to the determination of a lactate concentration of 0.41 +/- 0.02 mM. Moreover, to validate the results obtained in vivo, an ex vivo determination of the lactate level was also performed in samples of brain tissue, plasma, and cerebrospinal fluid, using both voltammetry and a clinical analyzer with colorimetric-based detection. A good correlation was observed between the sets of data established by both methods.

  14. Overoxidized polypyrrole-coated carbon fiber microelectrodes for dopamine measurements with fast-scan cyclic voltammetry.

    Science.gov (United States)

    Pihel, K; Walker, Q D; Wightman, R M

    1996-07-01

    Thin films of overoxidized polypyrrole have been electro-chemically coated onto carbon fiber microelectrodes and used for dopamine measurements with background-substracted, fast-scan cyclic voltammetry at a scan rate of 300 V/s. The films were stable on the electrode surface only when the electrodes were scanned to high potentials (1400 mV vs SSCE) in pH 7.4 aqueous buffer. Dopamine sensitivity and ascorbate and dihydroxyphenylacetic acid (DOPAC) rejection at the overoxidized polypyrrole-coated electrode were compared to those at carbon fiber electrodes coated with Nafion, a perfluorinated ion-exchange material. At 300 V/s, the overoxidized polypyrrole-coated electrode was almost 3 times more sensitive to dopamine than an uncoated disk electrode. Furthermore, the films were as effective as Nafion in the attenuation of the response to ascorbate and DOPAC, common interferences of dopamine in vivo. Overoxidized polypyrrole-coated electrodes maintained a stable response to dopamine for several hours when implanted in the rat brain. The electrochemical deposition procedure was effective at both elliptical and cylindrical electrodes. This is in contrast to the dip-coating procedures employed with Nafion films that lead to nonuniform coatings at cylindrical electrodes.

  15. A digital microfluidic device with integrated nanostructured microelectrodes for electrochemical immunoassays.

    Science.gov (United States)

    Rackus, Darius G; Dryden, Michael D M; Lamanna, Julian; Zaragoza, Alexandre; Lam, Brian; Kelley, Shana O; Wheeler, Aaron R

    2015-01-01

    Nanostructured microelectrodes (NMEs) are three-dimensional electrodes that have superb sensitivity for electroanalysis. Here we report the integration of NMEs with the versatile fluid-handling system digital microfluidics (DMF), for eventual application to distributed diagnostics outside of the laboratory. In the new methods reported here, indium tin oxide DMF top plates were modified to include Au NMEs as well as counter and pseudoreference electrodes. The new system was observed to outperform planar sensing electrodes of the type that are typically integrated with DMF. A rubella virus (RV) IgG immunoassay was developed to evaluate the diagnostic potential for the new system, relying on magnetic microparticles coated with RV particles and analysis by differential pulse voltammetry. The limit of detection of the assay (0.07 IU mL(-1)) was >100× below the World Health Organization defined cut-off for rubella immunity. The sensitivity of the integrated device and its small size suggest future utility for distributed diagnostics.

  16. Alternative post-processing on a CMOS chip to fabricate a planar microelectrode array.

    Science.gov (United States)

    López-Huerta, Francisco; Herrera-May, Agustín L; Estrada-López, Johan J; Zuñiga-Islas, Carlos; Cervantes-Sanchez, Blanca; Soto, Enrique; Soto-Cruz, Blanca S

    2011-01-01

    We present an alternative post-processing on a CMOS chip to release a planar microelectrode array (pMEA) integrated with its signal readout circuit, which can be used for monitoring the neuronal activity of vestibular ganglion neurons in newborn Wistar strain rats. This chip is fabricated through a 0.6 μm CMOS standard process and it has 12 pMEA through a 4 × 3 electrodes matrix. The alternative CMOS post-process includes the development of masks to protect the readout circuit and the power supply pads. A wet etching process eliminates the aluminum located on the surface of the p+ -type silicon. This silicon is used as transducer for recording the neuronal activity and as interface between the readout circuit and neurons. The readout circuit is composed of an amplifier and tunable bandpass filter, which is placed on a 0.015 mm2 silicon area. The tunable bandpass filter has a bandwidth of 98 kHz and a common mode rejection ratio (CMRR) of 87 dB. These characteristics of the readout circuit are appropriate for neuronal recording applications.

  17. A novel stretchable micro-electrode array (SMEA) design for directional stretching of cells

    Science.gov (United States)

    Khoshfetrat Pakazad, S.; Savov, A.; van de Stolpe, A.; Dekker, R.

    2014-03-01

    Stretchable micro-electrode arrays (SMEAs) are useful tools to study the electrophysiology of living cells seeded on the devices under mechanical stimulation. For such applications, the SMEAs are used as cell culture substrates; therefore, the surface topography and mechanical properties of the devices should be minimally affected by the embedded stretchable electrical interconnects. In this paper, a novel design and micro-fabrication technology for a pneumatically actuated SMEA are presented to achieve stretchability with minimal surface area dedicated to the electrical interconnects and a well-defined surface strain distribution combined with integrated diverse micro-patterns to enable alignment and directional stretching of cells. The special mechanical design also enables the SMEA to have a prolonged electro-mechanical fatigue life time required for long-term cyclic stretching of the cell cultures (stable resistance of electrical interconnects for more than 160 thousand cycles of 20% stretching and relaxing). The proposed fabrication method is based on the state of the art micro-fabrication techniques and materials and circumvents the processing problems associated with using unconventional methods and materials to fabricate stretchable electrode arrays. The electrochemical impedance spectroscopy characterization of the SMEA shows 4.5 MΩ impedance magnitude at 1 kHz for a TiN electrode 12 um in diameter. Cell culture experiments demonstrate the robustness of the SMEAs for long-term culturing experiments and compatibility with inverted fluorescent microscopy.

  18. Recording nerve signals in canine sciatic nerves with a flexible penetrating microelectrode array

    Science.gov (United States)

    Byun, Donghak; Cho, Sung-Joon; Lee, Byeong Han; Min, Joongkee; Lee, Jong-Hyun; Kim, Sohee

    2017-08-01

    Objective. Previously, we presented the fabrication and characterization of a flexible penetrating microelectrode array (FPMA) as a neural interface device. In the present study, we aim to prove the feasibility of the developed FPMA as a chronic intrafascicular recording tool for peripheral applications. Approach. For recording from the peripheral nerves of medium-sized animals, the FPMA was integrated with an interconnection cable and other parts that were designed to fit canine sciatic nerves. The uniformity of tip exposure and in vitro electrochemical properties of the electrodes were characterized. The capability of the device to acquire in vivo electrophysiological signals was evaluated by implanting the FPMA assembly in canine sciatic nerves acutely as well as chronically for 4 weeks. We also examined the histology of implanted tissues to evaluate the damage caused by the device. Main results. Throughout recording sessions, we observed successful multi-channel recordings (up to 73% of viable electrode channels) of evoked afferent and spontaneous nerve unit spikes with high signal quality (SNR  >  4.9). Also, minor influences of the device implantation on the morphology of nerve tissues were found. Significance. The presented results demonstrate the viability of the developed FPMA device in the peripheral nerves of medium-sized animals, thereby bringing us a step closer to human applications. Furthermore, the obtained data provide a driving force toward a further study for device improvements to be used as a bidirectional neural interface in humans.

  19. Purification of Carbon Nanotubes through an Electric Field near a Microelectrode

    Energy Technology Data Exchange (ETDEWEB)

    Shim, H C [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology(KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon, 305-701 (Korea, Republic of); Lee, H W [Massachusetts Institute of Technology(MIT), Micro and Nano Systems Laboratory, 77 Massachusetts Ave. Room 5-008, Cambridge, MA 02139 (United States); Yeom, S J [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology(KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon, 305-701 (Korea, Republic of); Kwak, Y K [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology(KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon, 305-701 (Korea, Republic of); Lee, S S [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology(KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon, 305-701 (Korea, Republic of); Kim, S H [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology(KAIST), 373-1, Guseong-dong, Yuseong-gu, Daejeon, 305-701 (Korea, Republic of)

    2007-04-15

    In this work, we attempt to purify multi-walled carbon nanotubes (MWNTs) using electrophoresis induced by application of an ac electric field to a set of microelectrodes in a microliquid channel. This purifying method is different from conventional methods based on chemical processes. We observed that the most of the MWNTs could pass along the microliquid channel without attaching to the electrode under specific conditions of 1 kHz, 0.2 V{sub rms}/{mu}m. On the other hand, the majority of the carbon impurities attached to the electrodes under same condition. Field emission scanning electron microscopy (FESEM) images confirm that this condition is beneficial for removing the carbon impurities. We aligned and attached this purified MWNTs and raw materials to extra electrodes with 5 MHz, 0.8 V{sub rms}/{mu}m. This experimental FESEM images show a clear difference between before and after purification. The proposed approach has potential applicability to the development of microdevices that can simultaneously perform purification and fabrication of MWNTs.

  20. Purification of Carbon Nanotubes through an Electric Field near a Microelectrode

    Science.gov (United States)

    Shim, H. C.; Lee, H. W.; Yeom, S. J.; Kwak, Y. K.; Lee, S. S.; Kim, S. H.

    2007-04-01

    In this work, we attempt to purify multi-walled carbon nanotubes (MWNTs) using electrophoresis induced by application of an ac electric field to a set of microelectrodes in a microliquid channel. This purifying method is different from conventional methods based on chemical processes. We observed that the most of the MWNTs could pass along the microliquid channel without attaching to the electrode under specific conditions of 1 kHz, 0.2 Vrms/μm. On the other hand, the majority of the carbon impurities attached to the electrodes under same condition. Field emission scanning electron microscopy (FESEM) images confirm that this condition is beneficial for removing the carbon impurities. We aligned and attached this purified MWNTs and raw materials to extra electrodes with 5 MHz, 0.8 Vrms/μm. This experimental FESEM images show a clear difference between before and after purification. The proposed approach has potential applicability to the development of microdevices that can simultaneously perform purification and fabrication of MWNTs.

  1. The electrochemical redox processes in methacrylate-based polymer electrolytes II. - Study on microelectrodes

    Energy Technology Data Exchange (ETDEWEB)

    Nadherna, Martina [Institute of Inorganic Chemistry of the AS CR, v.v.i., 250 68 Husinec-Rez (Czech Republic)] [Department of Analytical Chemistry, Faculty of Science, Charles University in Prague, Albertov 2030, 128 40 Prague 2 (Czech Republic); Reiter, Jakub, E-mail: reiter@iic.cas.c [Institute of Inorganic Chemistry of the AS CR, v.v.i., 250 68 Husinec-Rez (Czech Republic)

    2010-08-01

    The electrochemical behaviour of ferrocene was studied in different gel polymer electrolytes based on methyl, ethyl and 2-ethoxyethyl methacrylate and compared to the liquid aprotic solution (propylene carbonate). Voltammetric and chronoamperometric measurements on microelectrodes were conducted in order to describe the qualitative as well as quantitative behaviour of ferrocene in different conditions. Heterogeneous electron-transfer rate constants and diffusion coefficients of ferrocene in polymer electrolytes were estimated to be 1.1-7.8 x 10{sup -3} cm s{sup -1} and 4-13 x 10{sup -8} cm{sup 2} s{sup -1} depending on the electrolyte composition. The influence of the polymer polarity, ferrocene concentration and level of polymer cross-linkage on the kinetics of ferrocene oxidation and its transport was discussed. The electrolytes with poly(2-ethoxyethyl methacrylate) exhibit the highest ionic conductivity (2-4 x 10{sup -4} S cm{sup -1}) as well as diffusion coefficient of ferrocene (1.3 x 10{sup -7} cm{sup 2} s{sup -1}) in their structure.

  2. Label-free interdigitated microelectrode based biosensors for bacterial biofilm growth monitoring using Petri dishes.

    Science.gov (United States)

    Paredes, Jacobo; Becerro, Sheila; Arana, Sergio

    2014-05-01

    Impedance microbiology (IM) is a known technique that has been applied during the last decades to detect the presence of microorganisms in real samples in different fields: food industry, healthcare, environment, etc. Bacterial biofilms however have not been so far studied despite the fact that they are the most common microbiological formation and that they present resistance to antimicrobial agents. In situ early detection of bacterial biofilm is still a challenge nowadays that causes huge impact in many different scenarios. The ability to detect biofilm generation early will allow better and more efficient treatments preventing high costs and important problems. In this work a new performance of this technique with interdigitated microelectrode sensors (IDE) is proposed. A specific culturing setup where the sensors have been integrated in Petri Dishes has been developed. From the results it can be highlighted that low frequencies are more sensitive for detection than higher ones. The results achieved record variations of approximately 40% in the equivalent serial resistance after 10h of culture. Electrical models have been successfully simulated to find the electrical behavior of the development of biofilms. Variations in both the capacitance and resistance were recorded during the growth of the microbes.

  3. Reusable conductimetric array of interdigitated microelectrodes for the readout of low-density microarrays.

    Science.gov (United States)

    Mallén, Maria; Díaz-González, María; Bonilla, Diana; Salvador, Juan P; Marco, María P; Baldi, Antoni; Fernández-Sánchez, César

    2014-06-17

    Low-density protein microarrays are emerging tools in diagnostics whose deployment could be primarily limited by the cost of fluorescence detection schemes. This paper describes an electrical readout system of microarrays comprising an array of gold interdigitated microelectrodes and an array of polydimethylsiloxane microwells, which enabled multiplexed detection of up to thirty six biological events on the same substrate. Similarly to fluorescent readout counterparts, the microarray can be developed on disposable glass slide substrates. However, unlike them, the presented approach is compact and requires a simple and inexpensive instrumentation. The system makes use of urease labeled affinity reagents for developing the microarrays and is based on detection of conductivity changes taking place when ionic species are generated in solution due to the catalytic hydrolysis of urea. The use of a polydimethylsiloxane microwell array facilitates the positioning of the measurement solution on every spot of the microarray. Also, it ensures the liquid tightness and isolation from the surrounding ones during the microarray readout process, thereby avoiding evaporation and chemical cross-talk effects that were shown to affect the sensitivity and reliability of the system. The performance of the system is demonstrated by carrying out the readout of a microarray for boldenone anabolic androgenic steroid hormone. Analytical results are comparable to those obtained by fluorescent scanner detection approaches. The estimated detection limit is 4.0 ng mL(-1), this being below the threshold value set by the World Anti-Doping Agency and the European Community.

  4. Redox-filled Carbon-Fiber Microelectrodes for Single-Cell Exocytosis

    Science.gov (United States)

    Cox, Jonathan T.; Gunderson, Christopher G.; Zhang, Bo

    2014-01-01

    Carbon-fiber microelectrodes (CFEs) are the primary electroanalytical tool in single-cell exocytosis and in-vivo studies. Here we report a new study on the kinetic properties of electrolyte-filled CFEs in single-cell measurements and demonstrate that the addition of outer sphere redox species, such as Fe(CN)63− and Ru(NH3)63+, in the backfill electrolyte solution can greatly enhance the kinetic response of CFEs. We show that at 750 mV, a voltage normally applied for detection of dopamine, the presence of fast outer sphere redox species in the backfilling solution significantly enhances the kinetic response of CFEs toward fast dopamine detection at single PC12 cells. Moreover, we also demonstrate that the use of Fe(CN)63− in the backfilling solution has enabled direct measurement of dopamine at applied voltages as low as 200 mV. This kinetic enhancement is believed to be due to faster electron-transfer kinetics on the coupling pole as compared to the sluggish reduction of oxygen. We anticipate that such redox-filled CFE ultramicroelectrodes will find many useful applications in single cell exocytosis and in-vivo sensing. PMID:24833889

  5. Doped overoxidized polypyrrole microelectrodes as sensors for the detection of dopamine released from cell populations.

    Science.gov (United States)

    Sasso, Luigi; Heiskanen, Arto; Diazzi, Francesco; Dimaki, Maria; Castillo-León, Jaime; Vergani, Marco; Landini, Ettore; Raiteri, Roberto; Ferrari, Giorgio; Carminati, Marco; Sampietro, Marco; Svendsen, Winnie E; Emnéus, Jenny

    2013-07-07

    A surface modification of interdigitated gold microelectrodes (IDEs) with a doped polypyrrole (PPy) film for detection of dopamine released from populations of differentiated PC12 cells is presented. A thin PPy layer was potentiostatically electropolymerized from an aqueous pyrrole solution onto electrode surfaces. The conducting polymer film was doped during electropolymerization by introducing counter-ions in the monomer solution. Several counter-ions were tested and the resulting electrode modifications were characterized electrochemically to find the optimal dopant that increases sensitivity in dopamine detection. Overoxidation of the PPy films was shown to contribute to a significant enhancement in sensitivity to dopamine. The changes caused by overoxidation in the electrochemical behavior and electrode morphology were investigated using cyclic voltammetry and SEM as well as AFM, respectively. The optimal dopant for dopamine detection was found to be polystyrene sulfonate anion (PSS(-)). Rat pheochromocytoma (PC12) cells, a suitable model to study exocytotic dopamine release, were differentiated on IDEs functionalized with an overoxidized PSS(-)-doped PPy film. The modified electrodes were used to amperometrically detect dopamine released by populations of cells upon triggering cellular exocytosis with an elevated K(+) concentration. A comparison between the generated current on bare gold electrodes and gold electrodes modified with overoxidized doped PPy illustrates the clear advantage of the modification, yielding 2.6-fold signal amplification. The results also illustrate how to use cell population based dopamine exocytosis measurements to obtain biologically significant information that can be relevant in, for instance, the study of neural stem cell differentiation into dopaminergic neurons.

  6. Monitoring of Saccharomyces cerevisiae cell proliferation on thiol-modified planar gold microelectrodes using impedance spectroscopy.

    Science.gov (United States)

    Heiskanen, Arto R; Spégel, Christer F; Kostesha, Natalie; Ruzgas, Tautgirdas; Emnéus, Jenny

    2008-08-19

    An impedance spectroscopic study of the interaction between thiol-modified Au electrodes and Saccharomyces cerevisiae of strain EBY44 revealed that the cells formed an integral part of the interface, modulating the capacitive properties until a complete monolayer was obtained, whereas the charge transfer resistance ( R ct) to the redox process of [Fe(CN)6] 3-/4- showed a linear relationship to the number of cells even beyond the monolayer coverage. R ct showed strong pH dependence upon increasing the pH of the utilized buffer to 7.2. Upon addition of S. cerevisiae cells at pH 7.2, the obtained value of R ct showed over 560% increase with respect to the value obtained on the same thiol-modified electrode without cells. It was demonstrated that real-time monitoring of S. cerevisiae proliferation, with frequency-normalized imaginary admittance (real capacitance) as the indicator, was possible using a miniaturized culture system, ECIS Cultureware, with integrated planar cysteamine-modified Au microelectrodes. A monolayer coverage was reached after 20-28 h of cultivation, observed as an approximately 15% decrease in the real capacitance of the system.

  7. Te/Pt nanonetwork modified carbon fiber microelectrodes for methanol oxidation

    Science.gov (United States)

    Tsai, Hsiang-Yu; Shih, Zih-Yu; Lin, Zong-Hong; Chang, Huan-Tsung

    2013-05-01

    Te/Pt nanonetwork-decorated carbon fiber microelectrodes (CFMEs) have been fabricated and employed as anodic catalysts in a direct methanol fuel cell (DMFC). Te nanowires were prepared from tellurite ions (TeO32-) through a seed-mediated growth process and were deposited onto CFMEs to form three-dimensional Te nanonetworks. The Te nanonetworks then acted as a framework and reducing agent to reduce PtCl62- ions to form Te/Pt through a galvanic replacement reaction, leading to the formation of Te/PtCFMEs. By controlling the reaction time, the amount of Pt and morphology of Te/Pt nanonetworks were controlled, leading to various degrees of electrocatalytic activity. The Te/PtCFMEs provide a high electrochemical active surface area (129.2 m2 g-1), good catalytic activity (1.2 A mg-1), high current density (20.0 mA cm-2), long durability, and tolerance toward the poisoning species for methanol oxidation in 0.5 M sulfuric acid containing 1 M methanol. We have further demonstrated an enhanced current density by separately using 3 and 5 Te/PtCFMEs. Our results show that the low-cost, stable, and effective Te/PtCFMEs have great potential in the fabrication of cost-effective fuel cells.

  8. Engineering Customized TALENs Using the Platinum Gate TALEN Kit.

    Science.gov (United States)

    Sakuma, Tetsushi; Yamamoto, Takashi

    2016-01-01

    Among various strategies for constructing customized transcription activator-like effector nucleases (TALENs), the Golden Gate assembly is the most widely used and most characterized method. The principle of Golden Gate assembly involves cycling reactions of digestion and ligation of multiple plasmids in a single tube, resulting in PCR-, fragmentation-, and purification-free concatemerization of DNA-binding repeats. Here, we describe the protocols for Golden Gate assembly-based TALEN construction using the Platinum Gate TALEN Kit, which allows generation of highly active Platinum TALENs.

  9. Distribution of platinum and cobalt atoms in a bimetallic nanoparticle

    Science.gov (United States)

    Chui, Yu Hang; Chan, Kwong-Yu

    2005-06-01

    Molecular dynamics simulations are performed to investigate the atomic distribution and the structure of platinum-cobalt nanoparticles. Heating and cooling techniques are applied before getting equilibrated structures at 298 K. Both crystalline (fcc) and amorphous structures are partly observed depending on cooling rates. The atomic distributions in different regions of a bimetallic nanoparticle are analyzed. Although platinum tends to occupy surface and near-surface sites of the bimetallic nanoparticle, a complete segregation to form a core-shell structure is not observed.

  10. Addition of platinum and silver nanoparticles to toughen dental porcelain.

    Science.gov (United States)

    Fujieda, Tokushi; Uno, Mitsunori; Ishigami, Hajime; Kurachi, Masakazu; Wakamatsu, Nobukazu; Doi, Yutaka

    2012-01-01

    Several studies have investigated toughening porcelain that is layered over a frame or a core. The introduction of residual compressive stress to the surface of porcelain has been shown to be effective to strengthen it. In the present study, nanoparticles of precious metals of silver and platinum (rather than non-precious metals) were used to evaluate if they could increase the fracture resistance of porcelain. The addition of silver and platinum nanoparticles was found to improve the mechanical properties of porcelain since it increased both the Young's modulus and the fracture toughness of commercial porcelain.

  11. Diffuse X-Ray Scattering from Several Platinum Chain Compounds

    DEFF Research Database (Denmark)

    Braude, A.; Lindegaard-Andersen, Asger; Carneiro, K.

    1980-01-01

    Values of the Fermi wavevector for several platinum based one-dimensional conductors were determined from diffuse X-ray scattering measurements. The values were compared with those expected from the chemical compositions. The importance of conclusive values of this parameter is stressed and the c......Values of the Fermi wavevector for several platinum based one-dimensional conductors were determined from diffuse X-ray scattering measurements. The values were compared with those expected from the chemical compositions. The importance of conclusive values of this parameter is stressed...

  12. Synthesis of platinum nanoparticle electrocatalysts by atomic layer deposition

    Science.gov (United States)

    Lubers, Alia Marie

    Demand for energy continues to increase, and without alternatives to fossil fuel combustion the effects on our environment will become increasingly severe. Fuel cells offer a promising improvement on current methods of energy generation; they are able to convert hydrogen fuel into electricity with a theoretical efficiency of up to 83% and interface smoothly with renewable hydrogen production. Fuel cells can replace internal combustion engines in vehicles and are used in stationary applications to power homes and businesses. The efficiency of a fuel cell is maximized by its catalyst, which is often composed of platinum nanoparticles supported on carbon. Economical production of fuel cell catalysts will promote adoption of this technology. Atomic layer deposition (ALD) is a possible method for producing catalysts at a large scale when employed in a fluidized bed. ALD relies on sequential dosing of gas-phase precursors to grow a material layer by layer. We have synthesized platinum nanoparticles on a carbon particle support (Pt/C) by ALD for use in proton exchange membrane fuel cells (PEMFCs) and electrochemical hydrogen pumps. Platinum nanoparticles with different characteristics were deposited by changing two chemistries: the carbon substrate through functionalization; and the deposition process by use of either oxygen or hydrogen as ligand removing reactants. The metal depositing reactant was trimethyl(methylcyclopentadienyl)platinum(IV). Functionalizing the carbon substrate increased nucleation during deposition resulting in smaller and more dispersed nanoparticles. Use of hydrogen produced smaller nanoparticles than oxygen, due to a gentler hydrogenation reaction compared to using oxygen's destructive combustion reaction. Synthesized Pt/C materials were used as catalysts in an electrochemical hydrogen pump, a device used to separate hydrogen fuel from contaminants. Catalysts deposited by ALD on functionalized carbon using a hydrogen chemistry were the most

  13. Effects of Cluster Size on Platinum-Oxygen Bonds Formation in Small Platinum Clusters

    Science.gov (United States)

    Oemry, Ferensa; Padama, Allan Abraham B.; Kishi, Hirofumi; Kunikata, Shinichi; Nakanishi, Hiroshi; Kasai, Hideaki; Maekawa, Hiroyoshi; Osumi, Kazuo; Sato, Kaoru

    2012-03-01

    We present the results of density functional theory calculation in oxygen dissociative adsorption process on two types of isolated platinum (Pt) clusters: Pt4 and Pt10, by taking into account the effect of cluster reconstruction. The strength of Pt-Pt bonds in the clusters is mainly defined by d-d hybridization and interstitial bonding orbitals (IBO). Oxygen that adsorbed on the clusters is weakening the IBO and thus inducing geometry reconstruction as occurred in Pt10 cluster. However, cluster that could undergo structural deformation is found to promote oxygen dissociation with no energy barrier. The details show that maintaining well-balanced of attractive and repulsive (Hellmann-Feynman) forces between atoms is considered to be the main key to avoid any considerable rise of energy barrier. Furthermore, a modest energy barrier that gained in Pt4 cluster is presumed to be originate from inequality of intramolecular forces between atoms.

  14. Preparation of MgO supported platinum nanoparticle catalyst using toluene dispersed platinum sol

    Science.gov (United States)

    Seth, Jhumur; Nepak, Devadutta; Chaudhari, Vijay R.; Prasad, Bhagavatula L. V.

    2017-10-01

    An effective way of anchoring Pt nanoparticles on MgO using toluene dispersed platinum nanoparticles (Pt-NPs) as one of the ingredient is demonstrated. The usage of particles dispersed in toluene allows the retention of size and size distribution of preformed Pt-NPs even after deposition on MgO support with high active surface area, which is crucial for heterogeneous catalysis. The catalyst thus prepared, displayed selective hydrogenation of cinnamaldehyde to cinnamyl alcohol with high turn on frequency (TOF - 105 h-1) with respect to the total Pt content. We attribute this efficient catalytic performance to the uniform distribution and deposition of Pt on the active MgO support and its better accessible surface as evidenced by the cyclic-voltammetry results.

  15. Effect of Rotation Rate on the Formation of Platinum-modified Polyaniline Film and Electrocatalytic Oxidation of Methanol

    Institute of Scientific and Technical Information of China (English)

    Qiu Hong LI; Lin NIU; Chang Qiao ZHANG; Feng Hua WEI; Hu ZHANG

    2004-01-01

    The oxidation of methanol was investigated on platinum-modified polyaniline electrode. Changes in the electrode rotation rates (Ω) during platinum electrodeposition remarkably affect the formation and distribution of platinum in the polymer matrix and consequently lead to different currents of methanol oxidation. The results show that platinum loading is proportional to rotation ratesΩ1/2.

  16. Physical and electrochemical study of platinum thin films deposited by sputtering and electrochemical methods

    Energy Technology Data Exchange (ETDEWEB)

    Quinones, C. [Universidad de Cartagena, Cartagena de Indias (Colombia); Departamento de Quimica, Universidad Nacional de Colombia, Cra. 30 No 45-03, Bogota (Colombia); Vallejo, W., E-mail: wavallejol@unal.edu.co [Departamento de Quimica, Universidad Nacional de Colombia, Cra. 30 No 45-03, Bogota (Colombia); Mesa, F. [Departamento de Ciencias Basicas, Universidad Libre, Carrera 70 No 53-40, Bogota (Colombia)

    2011-06-15

    In this work platinum thin films deposited by sputtering and electrochemical methods were characterized through physical and electrochemical analysis. The as-grown platinum thin films were characterized through X-ray diffraction (XRD), atomic force microscopy (AFM); scanning electronic microscopy (SEM) and through electrochemical impedance spectroscopy (EIS) measurements. Structural studies indicated that platinum thin films were polycrystalline. Morphological characteristics were significantly affected by the substrate type and synthesis method. Finally the EIS analysis indicated that platinum films were electrochemically stable and present both low resistance of charge transfer and low series resistance; the equivalent circuit of platinum interface has been proposed.

  17. Recent strikes in South Africa’s platinum-group metal mines: effects upon world platinum-group metal supplies

    Science.gov (United States)

    Yager, Thomas R.; Soto-Viruet, Yadira; Barry, James J.

    2012-01-01

    The recent labor disputes over wages and working conditions that have affected South Africa’s three leading platinum-group metal (PGM) producers have affected an industry already plagued by market pressures and labor unrest and raised the specter of constraints in the world’s supply of these metals. Although low demand for these metals in 2011 and 2012 helped to offset production losses of recent years, and particularly those losses caused by the strikes in 2012, a prolonged resumption of strikes could cause severe shortages of iridium, platinum, rhodium, ruthenium, and, to a lesser extent, palladium.

  18. [Comparison of the effectiveness of platinum-based chemotherapy versus non-platinum-based chemotherapy for triple-negative breast cancer with metastases confined to the lungs].

    Science.gov (United States)

    Hong, Ruoxi; Ma, Fei; Shi, Xiuqing; Li, Qing; Zhang, Pin; Yuan, Peng; Wang, Jiayu; Fan, Ying; Cai, Ruigang; Li, Qiao; Xu, Binghe

    2014-10-01

    To compare the effect of first-line treatment with platinum-based chemotherapy and non-platinum-based chemotherapy in patients with lung metastases from triple negative breast cancer (TNBC). Sixty-five eligible patients were divided into platinum-treated group and non-platinum-treated group according to the first-line therapy. Factors predicting the chemotherapeutic efficacy included overall survival (OS), progression-free survival (PFS) and objective response (OR). In the platinum-treated group of 32 patients, 2 cases (6.3%) achieved CR, 16 cases (50.0%) achieved PR, 11 (34.4%) cases achieved SD, and 3 patients (9.4%) achieved PD. In the non-platinum-treated group of 33 patients, 2 cases (6.1%) achieved CR, 6 cases (18.2%) achieved PR, 16 cases (48.5%) achieved SD, and 9 cases (27.3%) achieved PD. Median PFS was significantly longer in the platinum-treated group than in the non-platinum-treated group (10 months vs. 6.0 months, P = 0.012), and OS was also improved (32 months vs. 22 months, P = 0.006). Multivariate analysis of several factors including local-regional lymph node involvement, lung metastasis-related symptoms, first-line platinum-based chemotherapy, disease-free interval, size and number of lung lesions, showed that first-line platinum-based chemotherapy was an independent prognostic factor for TNBC patients with lung metastases. Compared with non-platinum-based chemotherapy, the first-line platinum-based chemotherapy can improve PFS and OS in TNBC patients with metastases confined to the lungs.

  19. Single-Atom Catalyst of Platinum Supported on Titanium Nitride for Selective Electrochemical Reactions.

    Science.gov (United States)

    Yang, Sungeun; Kim, Jiwhan; Tak, Young Joo; Soon, Aloysius; Lee, Hyunjoo

    2016-02-05

    As a catalyst, single-atom platinum may provide an ideal structure for platinum minimization. Herein, a single-atom catalyst of platinum supported on titanium nitride nanoparticles were successfully prepared with the aid of chlorine ligands. Unlike platinum nanoparticles, the single-atom active sites predominantly produced hydrogen peroxide in the electrochemical oxygen reduction with the highest mass activity reported so far. The electrocatalytic oxidation of small organic molecules, such as formic acid and methanol, also exhibited unique selectivity on the single-atom platinum catalyst. A lack of platinum ensemble sites changed the reaction pathway for the oxygen-reduction reaction toward a two-electron pathway and formic acid oxidation toward direct dehydrogenation, and also induced no activity for the methanol oxidation. This work demonstrates that single-atom platinum can be an efficient electrocatalyst with high mass activity and unique selectivity.

  20. A Density Functional Study of Bare and Hydrogenated Platinum Clusters

    CERN Document Server

    Sebetci, A

    2006-01-01

    We perform density functional theory calculations using Gaussian atomic-orbital methods within the generalized gradient approximation for the exchange and correlation to study the interactions in the bare and hydrogenated platinum clusters. The minimum-energy structures, binding energies, relative stabilities, vibrational frequencies and the highest occupied and lowest unoccupied molecular-orbital gaps of Pt_nH_m (n=1-5, m=0-2) clusters are calculated and compared with previously studied pure platinum and hydrogenated platinum clusters. We investigate any magic behavior in hydrogenated platinum clusters and find that Pt_4H_2 is more stable than its neighboring sizes. Our results do not agree with a previous conclusion that 3D geometries of Pt tetramer and pentamer are unfavored. On the contrary, the lowest energy structure of Pt_4 is found to be a distorted tetrahedron and that of Pt_5 is found to be a bridge site capped tetrahedron which is a new global minimum for Pt_5 cluster. The successive addition of H ...

  1. In situ measurements of Merensky pillar behaviour at Impala Platinum

    CSIR Research Space (South Africa)

    Watson, BP

    2009-12-01

    Full Text Available to stabilize the stoping excavations. This paper describes the in situ measurement, of stress within a Merensky pillar from Impala Platinum. These measurements were used to derive a stress-strain curve that includes pre and post failure behaviour. 2D FLAC...

  2. EGFR-targeting peptide-coupled platinum(IV) complexes.

    Science.gov (United States)

    Mayr, Josef; Hager, Sonja; Koblmüller, Bettina; Klose, Matthias H M; Holste, Katharina; Fischer, Britta; Pelivan, Karla; Berger, Walter; Heffeter, Petra; Kowol, Christian R; Keppler, Bernhard K

    2017-06-01

    The high mortality rate of lung cancer patients and the frequent occurrence of side effects during cancer therapy demonstrate the need for more selective and targeted drugs. An important and well-established target for lung cancer treatment is the occasionally mutated epidermal growth factor receptor (EGFR). As platinum(II) drugs are still the most important therapeutics against lung cancer, we synthesized in this study the first platinum(IV) complexes coupled to the EGFR-targeting peptide LARLLT (and the shuffled RTALLL as reference). Notably, HPLC-MS measurements revealed two different peaks with the same molecular mass, which turned out to be a transcyclization reaction in the linker between maleimide and the coupled cysteine moiety. With regard to the EGFR specificity, subsequent biological investigations (3-day viability, 14-day clonogenic assays and platinum uptake) on four different cell lines with different verified EGFR expression levels were performed. Unexpectedly, the results showed neither an enhanced activity nor an EGFR expression-dependent uptake of our new compounds. Consequently, fluorophore-coupled peptides were synthesized to re-evaluate the targeting ability of LARLLT itself. However, also with these molecules, flow cytometry measurements showed no correlation of drug uptake with the EGFR expression levels. Taken together, we successfully synthesized the first platinum(IV) complexes coupled to an EGFR-targeting peptide; however, the biological investigations revealed that LARLLT is not an appropriate peptide for enhancing the specific uptake of small-molecule drugs into EGFR-overexpressing cancer cells.

  3. Electroreduction of cefetamet on mercury platinum and gold electrodes

    Directory of Open Access Journals (Sweden)

    P. ZUMAN

    2000-01-01

    Full Text Available The electroreduction of cefetamet (CEF using gold and platinum electrodes has been investigated in slightly alkaline medium (pH 8.40 where adsorption, previously observed at mercury electrode, was pronounced. This investigation was performed in order to determine whether the adsorption interfers with the reduction process even at solid electrodes and to compare with a mercury electrode.

  4. Platinum on Carbon Nanofibers as Catalyst for Cinnamaldehyde Hydrogenation

    NARCIS (Netherlands)

    Plomp, A.J.

    2009-01-01

    The aim of the work described in this thesis was to investigate the role and nature of nanostructured carbon materials, oxygen surface groups and promoters on platinum-based catalysts for the selective hydrogenation of cinnamaldehyde. The selective hydrogenation of cinnamaldehyde to cinnamyl alcohol

  5. Platinum redispersion on metal oxides in low temperature fuel cells

    DEFF Research Database (Denmark)

    Tripkovic, Vladimir; Cerri, Isotta; Nagami, Tetsuo

    2013-01-01

    in detail; however, due to different operating conditions it is not straightforward to link the chemical and the electrochemical environment. The largest differences reflect in (1) the oxidation state of the surface (the oxygen species coverage), (2) temperature and (3) the possibility of platinum...

  6. Preparation of low-platinum-content platinum-nickel, platinum-cobalt binary alloy and platinum-nickel-cobalt ternary alloy catalysts for oxygen reduction reaction in polymer electrolyte fuel cells

    Science.gov (United States)

    Li, Mu; Lei, Yanhua; Sheng, Nan; Ohtsuka, Toshiaki

    2015-10-01

    A series of low-platinum-content platinum-nickel (Pt-Ni), platinum-cobalt (Pt-Co) binary alloys and platinum-nickel-cobalt (Pt-Ni-Co) ternary alloys electrocatalysts were successfully prepared by a three-step process based on electrodeposition technique and studied as electrocatalysts for oxygen reduction reaction (ORR) in polymer-electrolyte fuel cells. Kinetics of ORR was studied in 0.5 M H2SO4 solution on the Pt-Ni, Pt-Co and Pt-Ni-Co alloys catalysts using rotating disk electrode technique. Both the series of Pt-Ni, Pt-Co binary alloys and the Pt-Ni-Co ternary alloys catalysts exhibited an obvious enhancement of ORR activity in comparison with pure Pt. The significant promotion of ORR activities of Pt-Ni and Pt-Co binary alloys was attributed to the enhancement of the first electron-transfer step, whereas, Pt-Ni-Co ternary alloys presented a more complicated mechanism during the electrocatalysis process but a much more efficient ORR activities than the binary alloys.

  7. Polyamide platinum anticancer complexes designed to target specific DNA sequences.

    Science.gov (United States)

    Jaramillo, David; Wheate, Nial J; Ralph, Stephen F; Howard, Warren A; Tor, Yitzhak; Aldrich-Wright, Janice R

    2006-07-24

    Two new platinum complexes, trans-chlorodiammine[N-(2-aminoethyl)-4-[4-(N-methylimidazole-2-carboxamido)-N-methylpyrrole-2-carboxamido]-N-methylpyrrole-2-carboxamide]platinum(II) chloride (DJ1953-2) and trans-chlorodiammine[N-(6-aminohexyl)-4-[4-(N-methylimidazole-2-carboxamido)-N-methylpyrrole-2-carboxamido]-N-methylpyrrole-2-carboxamide]platinum(II) chloride (DJ1953-6) have been synthesized as proof-of-concept molecules in the design of agents that can specifically target genes in DNA. Coordinate covalent binding to DNA was demonstrated with electrospray ionization mass spectrometry. Using circular dichroism, these complexes were found to show greater DNA binding affinity to the target sequence: d(CATTGTCAGAC)(2), than toward either d(GTCTGTCAATG)(2,) which contains different flanking sequences, or d(CATTGAGAGAC)(2), which contains a double base pair mismatch sequence. DJ1953-2 unwinds the DNA helix by around 13 degrees , but neither metal complex significantly affects the DNA melting temperature. Unlike simple DNA minor groove binders, DJ1953-2 is able to inhibit, in vitro, RNA synthesis. The cytotoxicity of both metal complexes in the L1210 murine leukaemia cell line was also determined, with DJ1953-6 (34 microM) more active than DJ1953-2 (>50 microM). These results demonstrate the potential of polyamide platinum complexes and provide the structural basis for designer agents that are able to recognize biologically relevant sequences and prevent DNA transcription and replication.

  8. Molecular pathways: the immunogenic effects of platinum-based chemotherapeutics

    NARCIS (Netherlands)

    Hato, S.V.; Khong, A.; Vries, I.J.M. de; Lesterhuis, W.J.

    2014-01-01

    The platinum-based drugs cisplatin, carboplatin, and oxaliplatin belong to the most widely used chemotherapeutics in oncology, showing clinical efficacy against many solid tumors. Their main mechanism of action is believed to be the induction of cancer cell apoptosis as a response to their covalent

  9. Effect of heat leaks in platinum resistance thermometry.

    Science.gov (United States)

    Goldratt, E; Yeshurun, Y; Greenfield, A J

    1980-03-01

    The effect of heat leaks in platinum resistance thermometry is analyzed. An experimental method is proposed for estimating the magnitude of this effect. Results are reported for the measurement of the temperature of a hot, solid body under different heat-leak configurations. Design criteria for thermometers are presented which minimize the effect of such heat leaks.

  10. Production of platinum radioisotopes at Brookhaven Linac Isotope Producer (BLIP

    Directory of Open Access Journals (Sweden)

    Smith Suzanne V.

    2017-01-01

    Full Text Available The accelerator production of platinum isotopes was investigated at the Brookhaven Linac Isotope Producer (BLIP. In this study high purity natural platinum foils were irradiated at 53.2, 65.7, 105.2, 151.9, 162.9 and 173.3.MeV. The irradiated foils were digested in aqua regia and then converted to their hydrochloride salt with concentrated hydrochloric acid before analyzing by gamma spectrometry periodically for at least 10 days post end of bombardment. A wide range of platinum (Pt, gold (Au and iridium (Ir isotopes were identified. Effective cross sections at BLIP for Pt-188, Pt-189, Pt-191 and Pt-195m were compared to literature and theoretical cross sections determined using Empire-3.2. The majority of the effective cross sections (<70 MeV confirm those reported in the literature. While the absolute values of the theoretical cross sections were up to a factor of 3 lower, Empire 3.2 modeled thresholds and maxima correlated well with experimental values. Preliminary evaluation into a rapid separation of Pt isotopes from high levels of Ir and Au isotopes proved to be a promising approach for large scale production. In conclusion, this study demonstrated that with the use of isotopically enriched target material accelerator production of selected platinum isotopes is feasible over a wide proton energy range.

  11. A Multimethod Approach for Investigating Algal Toxicity of Platinum Nanoparticles

    DEFF Research Database (Denmark)

    Sørensen, Sara Nørgaard; Engelbrekt, Christian; Lützhøft, Hans-Christian Holten

    2016-01-01

    The ecotoxicity of platinum nanoparticles (PtNPs) widely used in for example automotive catalytic converters, is largely unknown. This study employs various characterization techniques and toxicity end points to investigate PtNP toxicity toward the green microalgae Pseudokirchneriella subcapitata...

  12. Responses of fibroblasts and glial cells to nanostructured platinum surfaces

    Science.gov (United States)

    Pennisi, C. P.; Sevcencu, C.; Dolatshahi-Pirouz, A.; Foss, M.; Lundsgaard Hansen, J.; Nylandsted Larsen, A.; Zachar, V.; Besenbacher, F.; Yoshida, K.

    2009-09-01

    The chronic performance of implantable neural prostheses is affected by the growth of encapsulation tissue onto the stimulation electrodes. Encapsulation is associated with activation of connective tissue cells at the electrode's metallic contacts, usually made of platinum. Since surface nanotopography can modulate the cellular responses to materials, the aim of the present work was to evaluate the 'in vitro' responses of connective tissue cells to platinum strictly by modulating its surface nanoroughness. Using molecular beam epitaxy combined with sputtering, we produced platinum nanostructured substrates consisting of irregularly distributed nanopyramids and investigated their effect on the proliferation, cytoskeletal organization and cellular morphology of primary fibroblasts and transformed glial cells. Cells were cultured on these substrates and their responses to surface roughness were studied. After one day in culture, the fibroblasts were more elongated and their cytoskeleton less mature when cultured on rough substrates. This effect increased as the roughness of the surface increased and was associated with reduced cell proliferation throughout the observation period (4 days). Morphological changes also occurred in glial cells, but they were triggered by a different roughness scale and did not affect cellular proliferation. In conclusion, surface nanotopography modulates the responses of fibroblasts and glial cells to platinum, which may be an important factor in optimizing the tissue response to implanted neural electrodes.

  13. Enhancement of Platinum Cathode Catalysis by Addition of Transition Metals

    Science.gov (United States)

    Duong, Hung Tuan

    2009-01-01

    The sluggish kinetics of oxygen reduction reaction (ORR) contributes significantly to the loss of cathode overpotential in fuel cells, thus requiring high loadings of platinum (Pt), which is an expensive metal with limited supply. However, Pt and Pt-based alloys are still the best available electrocatalysts for ORR thus far. The research presented…

  14. Platinum on Carbon Nanofibers as Catalyst for Cinnamaldehyde Hydrogenation

    NARCIS (Netherlands)

    Plomp, A.J.

    2009-01-01

    The aim of the work described in this thesis was to investigate the role and nature of nanostructured carbon materials, oxygen surface groups and promoters on platinum-based catalysts for the selective hydrogenation of cinnamaldehyde. The selective hydrogenation of cinnamaldehyde to cinnamyl alcohol

  15. SILICA-BOUND CROWN ETHERS PLATINUM COMPLEX AS HYDROSILYLATION CATALYST

    Institute of Scientific and Technical Information of China (English)

    CHEN Yuanyin; MENG Lingzhi; LI Liping; LUO Jieqi; HU Jinchang

    1993-01-01

    Silica-bound 15-Crown-5, 18-Crown-6 with a spacer of propyloxymethyl and their platinum complexes have been synthesized. It was found that they were efficient catalysts for the hydrosilylation of olefins with triethoxysilane in the temperature range of 60 to 130 ℃ .

  16. Niraparib Maintenance Therapy in Platinum-Sensitive, Recurrent Ovarian Cancer

    DEFF Research Database (Denmark)

    Mirza, Mansoor R; Monk, Bradley J; Herrstedt, Jørn

    2016-01-01

    Background Niraparib is an oral poly(adenosine diphosphate [ADP]-ribose) polymerase (PARP) 1/2 inhibitor that has shown clinical activity in patients with ovarian cancer. We sought to evaluate the efficacy of niraparib versus placebo as maintenance treatment for patients with platinum-sensitive, ...

  17. Microelectrode and Impedance Analysis of Anion Secretion in Calu-3 Cells

    Directory of Open Access Journals (Sweden)

    Tamada T

    2001-07-01

    Full Text Available Calu-3 cells secrete HCO(3(- in response to cAMP agonists but can be stimulated to secrete Cl(- with K(+ channel activating agonists. Microelectrode and impedance analysis experiments were performed to obtain a better understanding of the conductances and driving forces involved in these different modes of anion secretion in Calu-3 cells. Microelectrode studies revealed apical and basolateral membrane depolarizations upon the addition of forskolin (V(ap -52 mV vs. -21 mV; V(bl -60 mV vs. -44 mV that paralleled the hyperpolarization of the mucosal negative transepithelial voltage (V(T -8 mV vs. -23 mV. These changes were accompanied by a decrease in the apical membrane fractional resistance (F(Rap from approximately 0.50 to 0.08, consistent with the activation of an apical membrane conductance. The subsequent addition of 1-ethyl-2-benzimidazolinone (1-EBIO, a K(+ channel activator, hyperpolarized V(ap to -27 mV, V(bl to -60 mV and V(T to -33 mV. Impedance analysis revealed the apical membrane resistance (R(ap of the forskolin-stimulated cells was less than 20 ohm cm(2, indeed in most monolayers R(ap fell to less than 5 ohm cm(2. The impedance derived estimate of the basolateral membrane resistance (R(bl was approximately 170 ohm cm(2 in forskolin treated cells and fell to 50 ohm cm(2 with the addition of 1-EBIO. Using these values for the R(bl and the F(Rap value of 0.08 yields a R(ap of approximately 14 ohm cm(2 in the presence of forskolin and 4 ohm cm(2 in the presence of forskolin plus 1-EBIO. Thus, by two independent methods, forskolin-stimulated Calu-3 cells are seen to have a very high apical membrane conductance of 50 to 200 mS/cm(2. Therefore, we would assert that even at one-tenth the anion selectivity for Cl(-, this high conductance could support the conductive exit of HCO(3(- across the apical membrane. We further propose that this high apical membrane conductance serves to clamp the apical membrane potential near the equilibrium

  18. Tissue Platinum Concentration and Tumor Response in Non–Small-Cell Lung Cancer

    Science.gov (United States)

    Kim, Eric S.; Lee, J. Jack; He, Guangan; Chow, Chi-Wan; Fujimoto, Junya; Kalhor, Neda; Swisher, Stephen G.; Wistuba, Ignacio I.; Stewart, David J.; Siddik, Zahid H.

    2012-01-01

    Purpose Platinum resistance is a major limitation in the treatment of advanced non–small-cell lung cancer (NSCLC). Reduced intracellular drug accumulation is one of the most consistently identified features of platinum-resistant cell lines, but clinical data are limited. We assessed the effects of tissue platinum concentrations on response and survival in NSCLC. Patients and Methods We measured total platinum concentrations by flameless atomic absorption spectrophotometry in 44 archived fresh-frozen NSCLC specimens from patients who underwent surgical resection after neoadjuvant platinum-based chemotherapy. Tissue platinum concentration was correlated with percent reduction in tumor size on post- versus prechemotherapy computed tomography scans. The relationship between tissue platinum concentration and survival was assessed by univariate and multicovariate Cox proportional hazards regression model analysis and Kaplan-Meier analysis. Results Tissue platinum concentration correlated significantly with percent reduction in tumor size (P < .001). The same correlations were seen with cisplatin, carboplatin, and all histology subgroups. Furthermore, there was no significant impact of potential variables such as number of cycles and time lapse from last chemotherapy on platinum concentration. Patients with higher platinum concentration had longer time to recurrence (P = .034), progression-free survival (P = .018), and overall survival (P = .005) in the multicovariate Cox model analysis after adjusting for number of cycles. Conclusion This clinical study established a relationship between tissue platinum concentration and response in NSCLC. It suggests that reduced platinum accumulation might be an important mechanism of platinum resistance in the clinical setting. Further studies investigating factors that modulate intracellular platinum concentration are warranted. PMID:22891266

  19. Modelling and Analysis of Electrical Potentials Recorded in Microelectrode Arrays (MEAs).

    Science.gov (United States)

    Ness, Torbjørn V; Chintaluri, Chaitanya; Potworowski, Jan; Łęski, Szymon; Głąbska, Helena; Wójcik, Daniel K; Einevoll, Gaute T

    2015-10-01

    Microelectrode arrays (MEAs), substrate-integrated planar arrays of up to thousands of closely spaced metal electrode contacts, have long been used to record neuronal activity in in vitro brain slices with high spatial and temporal resolution. However, the analysis of the MEA potentials has generally been mainly qualitative. Here we use a biophysical forward-modelling formalism based on the finite element method (FEM) to establish quantitatively accurate links between neural activity in the slice and potentials recorded in the MEA set-up. Then we develop a simpler approach based on the method of images (MoI) from electrostatics, which allows for computation of MEA potentials by simple formulas similar to what is used for homogeneous volume conductors. As we find MoI to give accurate results in most situations of practical interest, including anisotropic slices covered with highly conductive saline and MEA-electrode contacts of sizable physical extensions, a Python software package (ViMEAPy) has been developed to facilitate forward-modelling of MEA potentials generated by biophysically detailed multicompartmental neurons. We apply our scheme to investigate the influence of the MEA set-up on single-neuron spikes as well as on potentials generated by a cortical network comprising more than 3000 model neurons. The generated MEA potentials are substantially affected by both the saline bath covering the brain slice and a (putative) inadvertent saline layer at the interface between the MEA chip and the brain slice. We further explore methods for estimation of current-source density (CSD) from MEA potentials, and find the results to be much less sensitive to the experimental set-up.

  20. Electroanalytical method for determination of the pesticide dichlorvos using gold-disk microelectrodes.

    Science.gov (United States)

    De Souza, Djenaine; Machado, Sergio A S

    2005-08-01

    This paper reports the use of laboratory-prepared gold microelectrodes and square-wave voltammetry for analytical determination of low concentrations of the pesticide dichlorvos in pure and natural water samples. After optimization of the experimental and voltammetric conditions, the best voltammetric responses-current intensity and voltammetric profile-were obtained in 0.1 mol L(-1) NaClO4 with f=100 s(-1), a=50 mV, and DeltaE(s)=2 mV. The observed detection and quantification limits in pure water were 7.8 and 26.0 microg L(-1), respectively. The reproducibility and repeatability of the method were also determined; the results were 1.4% (n=5) and 1.2% (n=10), respectively. Possible interfering effects were evaluated in natural water samples collected at different points with different levels of contamination from agricultural, domestic, or industrial waste from an urban stream. Results showed that the detection and quantification limits increased as a function of the quantity of organic matter present in the samples. Nonetheless, the values observed for these method characteristics were below the maximum value allowed by the Brazilian code for organophosphorus pesticides in water samples. Recovery curves constructed using the standard addition method were shown to be satisfactory compared with those obtained from high-performance liquid chromatography, confirming the suitability of the method for analysis of natural water samples. Finally, when the method was used to determine dichlorvos in spiked cows' milk samples, satisfactory recovery and relative standard deviations were obtained.

  1. Multivariate regression methods for estimating velocity of ictal discharges from human microelectrode recordings

    Science.gov (United States)

    Liou, Jyun-you; Smith, Elliot H.; Bateman, Lisa M.; McKhann, Guy M., II; Goodman, Robert R.; Greger, Bradley; Davis, Tyler S.; Kellis, Spencer S.; House, Paul A.; Schevon, Catherine A.

    2017-08-01

    Objective. Epileptiform discharges, an electrophysiological hallmark of seizures, can propagate across cortical tissue in a manner similar to traveling waves. Recent work has focused attention on the origination and propagation patterns of these discharges, yielding important clues to their source location and mechanism of travel. However, systematic studies of methods for measuring propagation are lacking. Approach. We analyzed epileptiform discharges in microelectrode array recordings of human seizures. The array records multiunit activity and local field potentials at 400 micron spatial resolution, from a small cortical site free of obstructions. We evaluated several computationally efficient statistical methods for calculating traveling wave velocity, benchmarking them to analyses of associated neuronal burst firing. Main results. Over 90% of discharges met statistical criteria for propagation across the sampled cortical territory. Detection rate, direction and speed estimates derived from a multiunit estimator were compared to four field potential-based estimators: negative peak, maximum descent, high gamma power, and cross-correlation. Interestingly, the methods that were computationally simplest and most efficient (negative peak and maximal descent) offer non-inferior results in predicting neuronal traveling wave velocities compared to the other two, more complex methods. Moreover, the negative peak and maximal descent methods proved to be more robust against reduced spatial sampling challenges. Using least absolute deviation in place of least squares error minimized the impact of outliers, and reduced the discrepancies between local field potential-based and multiunit estimators. Significance. Our findings suggest that ictal epileptiform discharges typically take the form of exceptionally strong, rapidly traveling waves, with propagation detectable across millimeter distances. The sequential activation of neurons in space can be inferred from clinically

  2. Stimulus induced high frequency oscillations are present in neuronal networks on microelectrode arrays.

    Directory of Open Access Journals (Sweden)

    Chadwick M Hales

    2012-05-01

    Full Text Available Pathological high frequency oscillations (250-600Hz are present in the brains of epileptic animals and humans. The etiology of these oscillations and how they contribute to the diseased state remains unclear. This work identifies the presence of microstimulation-evoked high frequency oscillations (250-400Hz in dissociated neuronal networks cultured on microelectrode arrays (MEAs. Oscillations are more apparent with higher stimulus voltages. As with in vivo studies, activity is isolated to a single electrode, however the MEA provides improved spatial resolution with no spread of the oscillation to adjacent electrodes 200µm away. Oscillations develop across 4 weeks in vitro. Oscillations still occur in the presence of tetrodotoxin and synaptic blockers, and they cause no apparent disruption in the ability of oscillation-presenting electrodes to elicit directly evoked action potentials (dAPs or promote the spread of synaptic activity throughout the culture. Chelating calcium with ethylene glycol tetraacetic acid (EGTA causes a temporal prolongation of the oscillation. Finally, carbenoxolone significantly reduces or eliminates the high frequency oscillations. Gap junctions may play a significant role in maintaining the oscillation given the inhibitory effect of carbenoxolone, the propagating effect of reduced calcium conditions and the isolated nature of the activity as demonstrated in previous studies. This is the first demonstration of stimulus evoked high frequency oscillations in dissociated cultures. Unlike current models that rely on complex in vivo recording conditions, this work presents a simple controllable model in neuronal cultures on MEAs to further investigate how the oscillations occur at the molecular level and how they may contribute to the pathophysiology of disease.

  3. Improved focalization of electrical microstimulation using microelectrode arrays: a modeling study.

    Directory of Open Access Journals (Sweden)

    Sébastien Joucla

    Full Text Available Extracellular electrical stimulation (EES of the central nervous system (CNS has been used empirically for decades, with both fundamental and clinical goals. Currently, microelectrode arrays (MEAs offer new possibilities for CNS microstimulation. However, although focal CNS activation is of critical importance to achieve efficient stimulation strategies, the precise spatial extent of EES remains poorly understood. The aim of the present work is twofold. First, we validate a finite element model to compute accurately the electrical potential field generated throughout the extracellular medium by an EES delivered with MEAs. This model uses Robin boundary conditions that take into account the surface conductance of electrode/medium interfaces. Using this model, we determine how the potential field is influenced by the stimulation and ground electrode impedances, and by the electrical conductivity of the neural tissue. We confirm that current-controlled stimulations should be preferred to voltage-controlled stimulations in order to control the amplitude of the potential field. Second, we evaluate the focality of the potential field and threshold-distance curves for different electrode configurations. We propose a new configuration to improve the focality, using a ground surface surrounding all the electrodes of the array. We show that the lower the impedance of this surface, the more focal the stimulation. In conclusion, this study proposes new boundary conditions for the design of precise computational models of extracellular stimulation, and a new electrode configuration that can be easily incorporated into future MEA devices, either in vitro or in vivo, for a better spatial control of CNS microstimulation.

  4. Production and consumption of tropical seagrass fields in Eastern Indonesia measured with bell jars and microelectrodes

    Science.gov (United States)

    Lindeboom, H. J.; Sandee, A. J. J.

    During the Indonesian-Dutch Snellius-II Expedition the production and consumption of tropical seagrass species were measured with bell jars at four sampling stations in eastern Indonesia. Applying a conversion factor of 0.29, the amount of carbon fixed and mineralized was calculated from the recorded oxygen evolution. The gross production of the different seagrass communities was found to be between 1230 and 4700 mg C·m -2·d -1. The consumption lay between 860 and 3860 mg C·m -2·d -1. From these data a relatively low net production of 60 to 1060 mg C·m -2· -1 could be calculated. At one sampling station incubations were carried out at different depths in a sloping Halodule uninervis (Forssk.) Aschers meadow, which indicated that seagrasses above a depth of about 2 m may become subject to photoinhibition. A linear correlation between biomass and measured production was found for Thalassia hemprichii (Ehrenb.) Aschers. Above a biomass of 100 g DW·m -2 the production per unit of biomass decreased due to self shading. Using microelectrodes the oxygen production of epiphytes was found to be 230 mg C·m -2 leaf surface·d -1. at 1900 μE·m -2·s -1 assuming an epiphyte coverage of 40%. This indicated that up to 36% of the primary production in a seagrass community may be attributed to epiphytes. The seagrass fields in Indonesia were found to be healthy ecosystems with a high primary production, but organisms within the communities use the abundance of organic matter very efficiently, creating net production rates of 100 to 300 mg C·m -2·d -1 which are similar to barren areas.

  5. Microelectrode chip based real time monitoring of vital MCF-7 mamma carcinoma cells by impedance spectroscopy.

    Science.gov (United States)

    Wolf, Peter; Rothermel, Andrée; Beck-Sickinger, Annette G; Robitzki, Andrea A

    2008-10-15

    Sensorchip based impedance spectroscopy can detect inhibitory effects of human neuropeptide Y (hNPY) on living cells in a non-invasive labelling free way in real time without the need of supporting reagents. Since the discovery that neoplasmatic transformations in breast cancer are correlated with a change of the receptor subtype expression of hNPY in the affected tissue, the hNPY receptor-ligand system has come to the fore of cancer research. Today there are different methods detecting hNPY receptor interactions like fluorescent and radioactive labelling or detecting hNPY-pathway activation like cyclic adenosine monophosphate (cAMP) and G protein-coupled receptor (GPCR)-assays. For all these assays it is necessary to either label related proteins with additional substances, which can affect the nature state of the cell, or the need of producing cell lysate which allows only a snapshot of the investigated cells. To overcome these problems we established a new method to detect hNPY-receptor interactions. Therefore, we monitor the complex electric resistance (impedance) of cells attached to a microelectrode over a wide frequency range. Cell alterations are detected as changes in the impedance spectra. After application of the adenylyl cyclase-stimulating reagent forskolin, impedance is decreased at 5 kHz frequency within minutes. This effect can be inhibited by preincubating the cells with hNPY for a time range of 20 min. The inhibitory effect of hNPY can be washed out and the same cells can be stimulated by forskolin again.

  6. Interdigitated microelectrode (IME) impedance sensor for the detection of viable Salmonella typhimurium.

    Science.gov (United States)

    Yang, Liju; Li, Yanbin; Griffis, Carl L; Johnson, Michael G

    2004-05-15

    Interdigitated microelectrodes (IMEs) were used as impedance sensors for rapid detection of viable Salmonella typhimurium in a selective medium and milk samples. The impedance growth curves, impedance against bacterial growth time, were recorded at four frequencies (10Hz, 100Hz, 1kHz, and 10kHz) during the growth of S. typhimurium. The impedance did not change until the cell number reached 10(5)-10(6) CFUml(-1). The greatest change in impedance was observed at 10Hz. To better understand the mechanism of the IME impedance sensor, an equivalent electrical circuit, consisting of double layer capacitors, a dielectric capacitor, and a medium resistor, was introduced and used for interpreting the change in impedance during bacterial growth. Bacterial attachment to the electrode surface was observed with scanning electron microscopy, and it had effect on the impedance measurement. The detection time, t(D), defined as the time for the impedance to start change, was obtained from the impedance growth curve at 10Hz and had a linear relationship with the logarithmic value of the initial cell number of S. typhimurium in the medium and milk samples. The regression equations for the cell numbers between 4.8 and 5.4 x 10(5) CFUml(-1) were t(D) = -1.38 log N + 10.18 with R(2) = 0.99 in the pure medium and t(D) = -1.54 log N + 11.33 with R(2) = 0.98 in milk samples, respectively. The detection times for 4.8 and 5.4 x 10(5) CFUml(-1) initial cell numbers were 9.3 and 2.2 h, respectively, and the detection limit could be as low as 1 cell in a sample.

  7. Nanoscale surface morphology and monomer concentration dependence on impedance of electrocoated 2,2-dimethyl-3,4-propylene-dioxythiophene on carbon fiber microelectrode.

    Science.gov (United States)

    Sarac, A Sezai; Gencturk, Ash; Schulz, Burkhard; Gilsing, Hans-Detlev; Serantoni, Marina

    2007-10-01

    Poly(2,2-Dimethyl-3,4-propylenedioxythiophene) (PProDOT-Me2) thin films have been cyclovoltametrically coated onto carbon fiber microelectrode (CFME) as an active functionalized microelectrode. An electrochemical impedance spectroscopic study on the prepared electrodes is reported in this paper which electropolymerization performed under different initial monomer concentrations. The electrochemical impedance data fitted to equivalent circuit model, used to find out numerical values of the proposed components. Effect of the parameters on the capacitive behavior of the (PProDOT-Me2) coated carbon fiber microelectrode and morphology of films obtained by AFM and SEM was discussed. Highly porous coating was obtained at 100 mV/s scan rate and 10 cycles. EDX and ATR-FTIR results indicated the doping of anion of electrolyte due to formation of polaronic and bipolaronic sites. The presence of surface functional groups were determined by ATR-FTIR. Nanoscale conjugated polymer modified carbon fiber microelectrodes exhibited high capacitance of approximately 90 degrees phase angle, and vertical line in Nyquist plot. The capacitive behavior of CFME was increased by this very thin film coating of PProDOT-Me2. The electroactivity of Poly 2,2-Dimethyl-3,4-propylenedioxythiophene on the carbon fiber microelectrode open the possibility of using these coated electrodes for electrochemical microsupercapacitors and biosensor electrodes.

  8. The physical state of potassium in frog skeletal muscle studied by ion-sensitive microelectrodes and by electron microscopy: interpretation of seemingly incompatible results.

    Science.gov (United States)

    Edelmann, L

    2014-01-01

    According to the commonly accepted membrane pump theory most of cellular K+ ions are freely dissolved in free cellular water; the alternative association-induction hypothesis postulates that the bulk of cellular K+ is adsorbed (weakly bound) to cellular proteins that are maintained in a specific labile state in the cytoplasm of a living cell. K+ activities measured with ion-sensitive microelectrodes in the cytoplasm of frog skeletal muscle seem to confirm the claim that most of cellular K+ ions are free in cellular water. On the other hand, it is evident from electron microscopic ion binding studies that in frog skeletal muscle most of cellular K+ ions are adsorbed to cellular proteins. The conflicting results can be explained with the assumption that a damage of the cytoplasm caused by the impaling microelectrode leads to a liberation of adsorbed ions. Using the light microscope tests the possibility that microelectrodes damage the muscle cytoplasm. It is found that microelectrodes produce visible traumas that increase with time. Electron microscopic ion binding studies with damaged muscle support the view that monovalent cations are liberated in the disturbed area of a muscle fiber. It is concluded that a K(+)-sensitive microelectrode is not suited to determine the concentration of free K+ ions in intact frog skeletal muscle.

  9. Electrochemiluminescence Behavior of Ru(bpy)3^2+/ Carbofuran System on an Electrically Heated Microelectrode Chip%Electrochemiluminescence Behavior of Ru(bpy)3^2+/ Carbofuran System on an Electrically Heated Microelectrode Chip

    Institute of Scientific and Technical Information of China (English)

    叶瑞洪; 陈晓萍; 邱彬; 林振宇

    2011-01-01

    An electrically heated microelectrode chip (HMEC) was designed and the Ru(bpy)3^2+/carbofuran electro- chemiluminescence (ECL) systems were applied to characterize the performance of the HMEC. The ECL intensities increase at elevated electrode temperature, and the detection limit at 60℃ (electrode surface temperature) was about 10 times lower than that at 30℃. The results indicate that new heated electrode can be handled easily and can be mass produced, the difference between the electrodes was little. The stability of the HMEC was good since the electrode surface can hardly be destroyed during detection and storage.

  10. Study of gold-platinum and platinum-gold surface modification and its influence on hydrogen evolution and oxygen reduction

    Directory of Open Access Journals (Sweden)

    BRANIMIR N. GRGUR

    2005-02-01

    Full Text Available Surface modification of the electrodes was conducted from sulfuric acid solutions containing the corresponding metal–chloride complexes using cyclic voltammetry. Comparing the charges of the hydrogen underpotential deposition region, and the corresponding oxide reduction regions, it is concluded that a platinum overlayer on gold forms 3D islands, while gold on platinum forms 2D islands. Foreign metals present in an amount of up to one monolayer exert an influence on the change in reaction rate with respect to both hydrogen evolution (HER and oxygen reduction (ORR reactions. Aplatinum overlayer on a gold substrate increases the activity forHER and for ORR, compared with pure gold. These results can be understood in terms of a simple model, in which the change in the H and OH binding energies are directly proportional to the shift of the d-bond center of the overlayer. On the contrary, a gold layer on platinum slightly decreases the activity for both reactions compared with pure platinum.

  11. Facile development of Au-ring microelectrode for in vivo analysis using non-toxic polydopamine as multifunctional material.

    Science.gov (United States)

    Lin, Yuqing; Wang, Keqing; Xu, Yanan; Li, Linbo; Luo, Jingxuan; Wang, Chao

    2016-04-15

    In this study, we describe a facile and fast wet deposition technique to bottom-up fabricate Au-ring microelectrodes (Au-RMEs) using non-toxic polydopamine as multifunctional grafting material instead of commonly used (3-aminopropyl)-trimethoxysilane (APTMS). The Au-RMEs are fabricated by growing Au film uniformly inside of a pulled glass capillary. Au-RMEs with tip apex diameter ranging from 15 to 50 μm were fabricated involving four consequent steps, i.e. hydroxylating the inside wall of a pulled glass capillaries, grafting adhesive polydopamine (PDA) film to hydroxyl group surface, seeding gold nanoparticles (AuNPs) onto PDA surface and finally growing thickness-tunable gold layer on top of gold nanoparticles. After 3-mercaptopropionic acid (MPA) self-assembled monolayers (SAMs) modification, the Au-RMEs obtain improved specificity and sensitivity for monitoring of dopamine (DA) with respect to alleviating ascorbic acid (AA) interference. The current response is in wide linearity to DA concentration in the range of 0.2-100.0 μM with a correlation coefficient of 0.998 and the detection limit as low as 50.0 nM (S/N=3). In addition, the designed glass substrates of Au-RMEs were mechanically stronger and their tips can be further sharped by adjusting the pulling program. In order to demonstrate the utility of these fabricated microelectrodes in neurochemistry, Au-RMEs were used for electrochemical monitoring of DA release stimulated by K(+) in the striatum of rats. Thus, this study offers a novel and reliable strategy for preparing Au microelectrodes and maybe an attractive alternative to the traditional options for continuous and in vivo electrochemical monitoring of DA in various physiological processes.

  12. Optimizing treatment of the partially platinum-sensitive ovarian cancer patient.

    Science.gov (United States)

    Colombo, Nicoletta

    2013-12-01

    Ovarian cancer is the leading cause of gynecological cancer deaths worldwide. Despite primary treatment with platinum-containing regimens, the majority of women will experience recurrent disease and subsequent death. Recurrent ovarian cancer remains a challenge for successful management, and the choice of second-line chemotherapy is complex due to the range of different factors that need to be considered. One of the main considerations is the platinum-free interval and, specifically, the optimal treatment for patients who are partially platinum-sensitive (platinum-free interval: 6-12 months). Data from the large, multicenter, randomized OVA-301 study have shown that combined trabectedin-pegylated liposomal doxorubicin (PLD) significantly prolonged median overall survival compared with PLD alone (p = 0.0027) in 214 patients with partially platinum-sensitive advanced relapsed ovarian cancer. Furthermore, in OVA-301 patients with partially platinum-sensitive disease who received platinum therapy immediately after disease progression (n = 94), final median overall survival was improved by 9 months (p = 0.0153) in trabectedin-PLD patients compared with PLD alone. In addition to demonstrating a survival advantage, trabectedin-PLD may also allow the treatment of patients having not yet recovered from previous platinum toxicity. In summary, the data suggest the use of combined trabectedin-PLD as a second-line treatment option in patients with partially platinum-sensitive recurrent ovarian cancer, followed by a third-line platinum-containing regimen.

  13. Application of liposomal technologies for delivery of platinum analogs in oncology

    Directory of Open Access Journals (Sweden)

    Liu D

    2013-08-01

    Full Text Available Demin Liu1, Chunbai He1, Andrew Z Wang2, Wenbin Lin1 1Department of Chemistry, University of Chicago, Chicago, IL, USA; 2Laboratory of Nano- and Translational Medicine, Department of Radiation Oncology, and Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC, USA Abstract: Platinum-based chemotherapy, such as cisplatin, oxaliplatin, and carboplatin, is one of the most widely utilized classes of cancer therapeutics. While highly effective, the clinical applications of platinum-based drugs are limited by their toxicity profiles as well as suboptimal pharmacokinetic properties. Therefore, one of the key research areas in oncology has been to develop novel platinum analog drugs and engineer new platinum drug formulations to improve the therapeutic ratio further. Such efforts have led to the development of platinum analogs including nedaplatin, heptaplatin, and lobaplatin. Moreover, reformulating platinum drugs using liposomes has resulted in the development of L-NDPP (Aroplatin™, SPI-77, Lipoplatin™, Lipoxal™, and LiPlaCis®. Liposomes possess several attractive biological activities, including biocompatibility, high drug loading, and improved pharmacokinetics, that are well suited for platinum drug delivery. In this review, we discuss the various platinum drugs and their delivery using liposome-based drug delivery vehicles. We compare and contrast the different liposome platforms as well as speculate on the future of platinum drug delivery research. Keywords: liposome, platinum analog, drug delivery, cancer

  14. PHASE Ⅱ STUDY OF GEMCITABINE COMBINED WITH PLATINUM CHEMOTHERAPY FOR RECURRENT EPITHELIAL OVARIAN CANCER

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Objective To evaluate the anti-tumor effect and toxicity of gemcitabine combined with platinum chemotherapy on recurrent epithelial ovarian cancer.Methods Phase Ⅱ study of gemcitabine combined with platinum chemotherapy was carried out in 22 patients with recurrent epithelial ovarian cancer. Median age of patients was 50. 5 years old. Seven patients were platinum-sensitive and 15 patients were platinum-resistant or -refractor. All patients received gemcitabine combined with carboplatin or oxaliplatin chemotherapy. Patients' response rate (RR) and toxicity of gemcitabine combined with platinum chemotherapy were evaluated.Results A total of 98 gemcitabine-based chemotherapy cycles were performed. Total RR was 36.4%, RR of platinum-sensitive patients was 4/7 and platinum-resistant and -refractory patients was 4/15. The estimated median survival time was 10. 0 months (95% CI: 7.0-13.0) after initiation of gemcitabine combined with platinum chemotherapy.There was no significant difference in survival time between platinum-resistant/refractory group and platinum-sensitive group (P = 0. 061 ). Side effects of gemcitabine combined with platinum chemotherapy were observed in 81.8 % of patients. Grade Ⅱ/Ⅲ anemia (54.5%) and grade Ⅲ/Ⅳ neutropenia (54.5%) were most common toxicities. Ten (45.5%) patients had to delay their chemotherapy cycles or reduce the dose of chemotherapeutic drugs because of the severe side effects. Fourteen (63.6%) patients received granulocyte colony-stimulating factor to relieve neutropenia,and 8 (36. 4% ) patients received component blood transfusion to treat anemia or thrombocytopenia. There was no treatment-associated death.Conclusion Gemcitabine combined with platinum chemotherapy appears to be an effective and well-tolerant treatment for recurrent epithelial ovarian cancer, including platinum-resistant or -refractory diseases.

  15. STABILITY OF THE NEW ANTICANCER PLATINUM ANALOG 1,2-DIAMINOMETHYL-CYCLOBUTANE-PLATINUM(II)-LACTATE (LOBAPLATIN-D19466) IN INTRAVENOUS SOLUTIONS

    NARCIS (Netherlands)

    GUCHELAAR, HJ; UGES, DRA; AULENBACHER, P; DEVRIES, EGE; MULDER, NH

    The chemical stability of the new anticancer platinum analogue 1,2-diaminomethyl-cyclobutane-platinum(II)-lactate (D19466) in infusion media was studied in an accelerated stability testing experiment with a selective HPLC-UV method. Variables were time, temperature, light, concentration, and

  16. Comparison of Intracellular Stress Response of NCI-H526 Small Cell Lung Cancer (SCLC) Cells to Platinum(II) Cisplatin and Platinum(IV) Oxoplatin

    Energy Technology Data Exchange (ETDEWEB)

    Hamilton, Gerhard [Ludwig Boltzmann Cluster of Translational Oncology, A-1090 Vienna (Austria)

    2014-07-08

    In attempts to develop an orally applicable platinum-based drug, platinum(IV) drugs which exhibit higher in vivo stability compared to the platinum(II) drug cisplatin were formulated. The first such chemotherapeutic agent, namely satraplatin, failed to receive approval. In the present work, we checked the initial cellular stress response of the chemosensitive NCI-H526 small cell lung cancer (SCLC) cells by determination of the relative phosphorylation of 46 specific phosphorylation sites of 38 selected proteins in a six hours response to cisplatin (platinum(II)) or oxoplatin (platinum(IV)), respectively. Oxoplatin is considered as prodrug of cisplatin, although several findings point to differences in intracellular effects. Cisplatin induced hyperphosphorylation of p38α MAPK and AMPKα1, whereas oxoplatin treatment resulted in increased phosphorylation of a large number of signaling proteins involved in stress response/drug resistance, including JNK, GSK-3α, AMPKα1, src kinases, STATs, CHK-2 and especially focal adhesion kinase (FAK). Cisplatin exerts markedly higher cytotoxicity upon four hours short-term exposure in comparison to oxoplatin and, correspondingly, the extended initial stress response to the platinum(IV) drug oxoplatin thus is expected to increase clinical drug resistance. Induction of a substantial stress response to any prodrug of a platinum-based compound may likewise limit the effectivity of its active metabolite(s), such contributing to the failure of selected derivatized platinum complexes.

  17. Comparison of Intracellular Stress Response of NCI-H526 Small Cell Lung Cancer (SCLC Cells to Platinum(II Cisplatin and Platinum(IV Oxoplatin

    Directory of Open Access Journals (Sweden)

    Gerhard Hamilton

    2014-07-01

    Full Text Available In attempts to develop an orally applicable platinum-based drug, platinum(IV drugs which exhibit higher in vivo stability compared to the platinum(II drug cisplatin were formulated. The first such chemotherapeutic agent, namely satraplatin, failed to receive approval. In the present work, we checked the initial cellular stress response of the chemosensitive NCI-H526 small cell lung cancer (SCLC cells by determination of the relative phosphorylation of 46 specific phosphorylation sites of 38 selected proteins in a six hours response to cisplatin (platinum(II or oxoplatin (platinum(IV, respectively. Oxoplatin is considered as prodrug of cisplatin, although several findings point to differences in intracellular effects. Cisplatin induced hyperphosphorylation of p38α MAPK and AMPKα1, whereas oxoplatin treatment resulted in increased phosphorylation of a large number of signaling proteins involved in stress response/drug resistance, including JNK, GSK-3α, AMPKα1, src kinases, STATs, CHK-2 and especially focal adhesion kinase (FAK. Cisplatin exerts markedly higher cytotoxicity upon four hours short-term exposure in comparison to oxoplatin and, correspondingly, the extended initial stress response to the platinum(IV drug oxoplatin thus is expected to increase clinical drug resistance. Induction of a substantial stress response to any prodrug of a platinum-based compound may likewise limit the effectivity of its active metabolite(s, such contributing to the failure of selected derivatized platinum complexes.

  18. Platinum thickness dependence of the inverse spin-Hall voltage from spin pumping in a hybrid yttrium iron garnet/platinum system

    NARCIS (Netherlands)

    Castel, V.; Vlietstra, N.; Ben Youssef, J.; van Wees, B. J.

    2012-01-01

    We show the experimental observation of the platinum thickness dependence in a hybrid yttrium iron garnet/platinum system of the inverse spin-Hall effect from spin pumping, over a large frequency range and for different radio-frequency powers. From the measurement of the voltage at the resonant cond

  19. Recent Advances in Platinum (IV) Complex-Based Delivery Systems to Improve Platinum (II) Anticancer Therapy.

    Science.gov (United States)

    Han, Xiaopeng; Sun, Jin; Wang, Yongjun; He, Zhonggui

    2015-11-01

    Cisplatin and its platinum (Pt) (II) derivatives play a key role in the fight against various human cancers such as testicular, ovarian, head and neck, lung tumors. However, their application in clinic is limited due to dose- dependent toxicities and acquired drug resistances, which have prompted extensive research effort toward the development of more effective Pt (II) delivery strategies. The synthesis of Pt (IV) complex is one such an area of intense research fields, which involves their in vivo conversion into active Pt (II) molecules under the reducing intracellular environment, and has demonstrated encouraging preclinical and clinical outcomes. Compared with Pt (II) complexes, Pt (IV) complexes not only exhibit an increased stability and reduced side effects, but also facilitate the intravenous-to-oral switch in cancer chemotherapy. The overview briefly analyzes statuses of Pt (II) complex that are in clinical use, and then focuses on the development of Pt (IV) complexes. Finally, recent advances in Pt (IV) complexes in combination with nanocarriers are highlighted, addressing the shortcomings of Pt (IV) complexes, such as their instability in blood and irreversibly binding to plasma proteins and nonspecific distribution, and taking advantage of passive and active targeting effect to improve Pt (II) anticancer therapy. © 2015 Wiley Periodicals, Inc.

  20. TP53 status and taxane-platinum versus platinum-based therapy in ovarian cancer patients: A non-randomized retrospective study

    Directory of Open Access Journals (Sweden)

    Markowska Janina

    2008-01-01

    Full Text Available Abstract Background Taxane-platinum therapy (TP has replaced platinum-based therapy (PC or PAC, DNA damaging chemotherapy in the postoperative treatment of ovarian cancer patients; however, it is not always effective. TP53 protein plays a differential role in response to DNA-damaging agents and taxanes. We sought to define profiles of patients who benefit the most from TP and also of those who can be treated with PC. Methods We compared the effectiveness of PC/PAC (n = 253 and TP (n = 199 with respect to tumor TP53 accumulation in ovarian cancer patients with FIGO stage IIB-IV disease; this was a non-randomized retrospective study. Immunohistochemical analysis was performed on 452 archival tumors; univariate and multivariate analysis by the Cox's and logistic regression models was performed in all patients and in subgroups with [TP53(+] and without TP53 accumulation [TP53(-]. Results The advantage of taxane-platinum therapy over platinum-based therapy was seen in the TP53(+, and not in the TP53(- group. In the TP53(+ group taxane-platinum therapy enhanced the probability of complete remission (p = .018, platinum sensitivity (p = .014, platinum highly sensitive response (p = .038 and longer survival (OS, p = .008. Poor tumor differentiation diminished the advantage from taxane-platinum therapy in the TP53(+ group. In the TP53(- group PC/PAC was at least equally efficient as taxane-platinum therapy and it enhanced the chance of platinum highly sensitive response (p = .010. However, in the TP53(- group taxane-platinum therapy possibly diminished the risk of death in patients over 53 yrs (p = .077. Among factors that positively interacted with taxane-platinum therapy in some analyses were endometrioid and clear cell type, FIGO III stage, bulky residual tumor, more advanced age of patient and moderate tumor differentiation. Conclusion Our results suggest that taxane-platinum therapy is particularly justified in patients with TP53(+ tumors or older

  1. Failure mode analysis of silicon-based intracortical microelectrode arrays in non-human primates

    Science.gov (United States)

    Barrese, James C.; Rao, Naveen; Paroo, Kaivon; Triebwasser, Corey; Vargas-Irwin, Carlos; Franquemont, Lachlan; Donoghue, John P.

    2013-12-01

    Objective. Brain-computer interfaces (BCIs) using chronically implanted intracortical microelectrode arrays (MEAs) have the potential to restore lost function to people with disabilities if they work reliably for years. Current sensors fail to provide reliably useful signals over extended periods of time for reasons that are not clear. This study reports a comprehensive retrospective analysis from a large set of implants of a single type of intracortical MEA in a single species, with a common set of measures in order to evaluate failure modes. Approach. Since 1996, 78 silicon MEAs were implanted in 27 monkeys (Macaca mulatta). We used two approaches to find reasons for sensor failure. First, we classified the time course leading up to complete recording failure as acute (abrupt) or chronic (progressive). Second, we evaluated the quality of electrode recordings over time based on signal features and electrode impedance. Failure modes were divided into four categories: biological, material, mechanical, and unknown. Main results. Recording duration ranged from 0 to 2104 days (5.75 years), with a mean of 387 days and a median of 182 days (n = 78). Sixty-two arrays failed completely with a mean time to failure of 332 days (median = 133 days) while nine array experiments were electively terminated for experimental reasons (mean = 486 days). Seven remained active at the close of this study (mean = 753 days). Most failures (56%) occurred within a year of implantation, with acute mechanical failures the most common class (48%), largely because of connector issues (83%). Among grossly observable biological failures (24%), a progressive meningeal reaction that separated the array from the parenchyma was most prevalent (14.5%). In the absence of acute interruptions, electrode recordings showed a slow progressive decline in spike amplitude, noise amplitude, and number of viable channels that predicts complete signal loss by about eight years. Impedance measurements showed

  2. Characterizing the Material Properties of Polymer-Based Microelectrode Arrays for Retinal Prosthesis

    Energy Technology Data Exchange (ETDEWEB)

    Park, C S; Maghribi, M

    2003-05-10

    The Retinal Prosthesis project is a three year project conducted in part at the Lawrence Livermore National Laboratory and funded by the Department of Energy to create an epiretinal microelectrode array for stimulating retinal cells. The implant must be flexible to conform to the retina, robust to sustain handling during fabrication and implantation, and biocompatible to withstand physiological conditions within the eye. Using poly(dimethyl siloxane) (PDMS), LLNL aims to use microfabrication techniques to increase the number of electrodes and integrate electronics. After the initial designs were fabricated and tested in acute implantation, it became obvious that there was a need to characterize and understand the mechanical and electrical properties of these new structures. This knowledge would be imperative in gaining credibility for polymer microfabrication and optimizing the designs. Thin composite microfabricated devices are challenging to characterize because they are difficult to handle, and exhibit non-linear, viscoelastic, and anisotropic properties. The objective of this research is to device experiments and protocols, develop an analytical model to represent the composite behavior, design and fabricate test structures, and conduct experimental testing to determine the mechanical and electrical properties of PDMS-metal composites. Previous uniaxial stretch tests show an average of 7% strain before failure on resistive heaters of similar dimensions deposited on PDMS. Lack of background information and questionable human accuracy demands a more sophisticated and thorough testing method. An Instron tensile testing machine was set up to interface with a digital multiplexor and computer interface to simultaneously record and graph position, load, and resistance across devices. With a compliant load cell for testing polymers and electrical interconnect grips designed and fabricated to interface the sample to the electronics, real-time resistance measurements

  3. Creation of defined single cell resolution neuronal circuits on microelectrode arrays

    Science.gov (United States)

    Pirlo, Russell Kirk

    2009-12-01

    The way cell-cell organization of neuronal networks influences activity and facilitates function is not well understood. Microelectrode arrays (MEAs) and advancing cell patterning technologies have enabled access to and control of in vitro neuronal networks spawning much new research in neuroscience and neuroengineering. We propose that small, simple networks of neurons with defined circuitry may serve as valuable research models where every connection can be analyzed, controlled and manipulated. Towards the goal of creating such neuronal networks we have applied microfabricated elastomeric membranes, surface modification and our unique laser cell patterning system to create defined neuronal circuits with single-cell precision on MEAs. Definition of synaptic connectivity was imposed by the 3D physical constraints of polydimethylsiloxane elastomeric membranes. The membranes had 20mum clear-through holes and 2-3mum deep channels which when applied to the surface of the MEA formed microwells to confine neurons to electrodes connected via shallow tunnels to direct neurite outgrowth. Tapering and turning of channels was used to influence neurite polarity. Biocompatibility of the membranes was increased by vacuum baking, oligomer extraction, and autoclaving. Membranes were bound to the MEA by oxygen plasma treatment and heated pressure. The MEA/membrane surface was treated with oxygen plasma, poly-D-lysine and laminin to improve neuron attachment, survival and neurite outgrowth. Prior to cell patterning the outer edge of culture area was seeded with 5x10 5 cells per cm and incubated for 2 days. Single embryonic day 7 chick forebrain neurons were then patterned into the microwells and onto the electrodes using our laser cell patterning system. Patterned neurons successfully attached to and were confined to the electrodes. Neurites extended through the interconnecting channels and connected with adjacent neurons. These results demonstrate that neuronal circuits can be

  4. A feasibility study of multi-site,intracellular recordings from mammalian neurons by extracellular gold mushroom-shaped microelectrodes

    Science.gov (United States)

    Ojovan, Silviya M.; Rabieh, Noha; Shmoel, Nava; Erez, Hadas; Maydan, Eilon; Cohen, Ariel; Spira, Micha E.

    2015-01-01

    The development of multi-electrode array platforms for large scale recording of neurons is at the forefront of neuro-engineering research efforts. Recently we demonstrated, at the proof-of-concept level, a breakthrough neuron-microelectrode interface in which cultured Aplysia neurons tightly engulf gold mushroom-shaped microelectrodes (gMμEs). While maintaining their extracellular position, the gMμEs record synaptic- and action-potentials with characteristic features of intracellular recordings. Here we examined the feasibility of using gMμEs for intracellular recordings from mammalian neurons. To that end we experimentally examined the innate size limits of cultured rat hippocampal neurons to engulf gMμEs and measured the width of the “extracellular” cleft formed between the neurons and the gold surface. Using the experimental results we next analyzed the expected range of gMμEs-neuron electrical coupling coefficients. We estimated that sufficient electrical coupling levels to record attenuated synaptic- and action-potentials can be reached using the gMμE-neuron configuration. The definition of the engulfment limits of the gMμEs caps diameter at ≤2–2.5 μm and the estimated electrical coupling coefficients from the simulations pave the way for rational development and application of the gMμE based concept for in-cell recordings from mammalian neurons. PMID:26365404

  5. A carbon needle microelectrode decorated with TiO₂ nanosheets dominated by reactive facets as a highly electrocatalytic sensing element.

    Science.gov (United States)

    Bai, Xue; Huang, Xin; Zhang, Qi; Hua, Zulin; Qin, Caidie; Qin, Qin

    2015-10-01

    We demonstrate a highly efficient electrocatalytic activity of TiO2 nanosheets with reactive (001) facets grown on a carbon needle microelectrode (TiO2-CNE). This microelectrode is prepared by a simple hydrothermal process. Scanning electron microscopy, high-resolution transmission electron microscopy, and electrochemical impedance spectroscopy were used to characterize as-prepared TiO2-CNE. These methods confirm that the surface area-to-volume ratio and electron transfer rate of TiO2-CNE are considerably greater than those of the bare electrode. In addition, the amperometric response for acetaminophen (AP) oxidation is remarkably facilitated by 13.9 times at the TiO2-CNE by the enlarged surface area-to-volume ratio, as well as the exposure of high-energy (001) facets. Furthermore, the constructed electrochemical sensor displays excellent analytical performance for AP detection over a range of 0.002-100.0 μM, with a detection limit of 0.83 nM (S/N=3). The electrode was applied for the in vitro determination of AP in fish blood 30 min after injection in the abdominal cavity. Consequently, the present approach shows feasibility and great potential in constructing highly sensitive and low-consumption miniaturized electrochemical sensors in the field of biological applications.

  6. A comparative study of carbon fiber-based microelectrodes for the measurement of nitric oxide in brain tissue.

    Science.gov (United States)

    Santos, Ricardo M; Lourenço, Cátia F; Piedade, Ana P; Andrews, Rodney; Pomerleau, François; Huettl, Peter; Gerhardt, Greg A; Laranjinha, João; Barbosa, Rui M

    2008-12-01

    The measurement of Nitric oxide (NO) in real-time has been a major concern due to the involvement of this ubiquitous free radical modulator in several physiological and pathological pathways in tissues. Here we performed a study aiming at evaluating different types of carbon fibers, namely Textron, Amoco, Courtaulds and carbon nanotubes (University of Kentucky) covered with Nafion/o-phenylenediamine (o-PD) for NO measurement in terms of sensitivity, LOD, response time and selectivity against major potential interferents in the brain (ascorbate, nitrite and dopamine). The results indicate that, as compared with the other carbon fibers and nanotubes, Textron carbon fiber microelectrodes coated with two layers of Nafion and o-PD exhibited better characteristics for NO measurement as they are highly selective against ascorbate (>30,000:1), nitrite (>2000:1) and dopamine (>80:1). These coated Textron microelectrodes showed an average sensitivity of 341+/-120pA/microM and a detection limit of 16+/-11nM. The better performance of the Textron fibers is likely related to a stronger adhesion or more uniform coating of the Nafion and o-PD polymers to the fiber surface. In addition, the background current of the Textron carbon fibers is low, contributing to the excellent signal-to-noise for detection of NO.

  7. Effect of cocaine, nomifensine, GBR 12909 and WIN 35428 on carbon fiber microelectrode sensitivity for voltammetric recording of dopamine.

    Science.gov (United States)

    Davidson, C; Ellinwood, E H; Douglas, S B; Lee, T H

    2000-08-15

    Electrochemical measurements using voltammetry or amperometry at carbon-fiber microelectrodes have been used in vitro and in vivo to examine regulatory mechanisms for the central dopamine system. In many of these experiments, dopamine efflux concentrations under control conditions are determined followed by their alterations in response to a drug treatment. The present study demonstrates that some drugs can affect dopamine measurements, not only by their expected pharmacological action but also by directly altering the microelectrode responsivity. The commonly used reuptake inhibitors GBR 12909 (10 microM) and nomifensine (5 microM) drastically reduce electrode sensitivity and, in the case of nomifensine, increase the time to reach a plateau in response to dopamine boluses (i.e. reduced 'frequency response'). Cocaine (10 microM) and WIN 35428 (2 microM) have negligible effect on these indices. This decrease in sensitivity was found in both nafion and non-nafion coated electrodes. Further, the reduction in sensitivity seen in non-nafion coated electrodes was not prevented by increasing the reversal potential (from +1.0 to +1.3 V) and voltage scan rate (from 350 to 450 V/s). These data suggest that care must be taken when interpreting data from voltammetric or amporometric experiments using carbon electrodes where GBR 12909 or nomifensine are used, especially at high concentrations. Furthermore, wherever possible, direct effects of a drug on electrode sensitivity and frequency response should be determined.

  8. In situ 2D maps of pH shifts across brass-lead galvanic joints using microelectrodes

    Science.gov (United States)

    Ma, Xiangmeng; Lee, Woo Hyoung; Lytle, Darren A.

    2017-02-01

    Galvanic corrosion in drinking water distribution systems, such as conditions following partial lead service line replacement, can be a significant source of lead in tap water. The objective of this work was to measure the pH directly near metal surfaces using a novel experimental tool in order to understand the water chemistry at a lead-containing galvanic couple in drinking water. Specifically, pH microprofiles in the proximity of corroding metal surfaces were measured using a microelectrode to construct detailed in situ 2D spatial maps of the pH across a galvanic couple at 100 µm above the metal’s surface under flowing and stagnation conditions. The opposite pH trend was directly observed across the galvanic couple under flow and stagnation conditions. Water stagnation resulted in a pH at the anode (leaded solder) of 1.5 pH units lower than the bulk water pH (9.0) and as much as 2.5 pH units lower than the cathode (brass). These conditions can enhance lead release at the anode, which reflects different anodic-cathodic relationships of coupled metals primarily controlled by water flow. Most importantly, this work has demonstrated the ability to make real pH measurement at the surface of corroding metals using a novel microelectrode approach.

  9. Electrical control of deep NV centers in diamond by means of sub-superficial graphitic micro-electrodes

    CERN Document Server

    Forneris, J; Tengattini, A; Enrico, E; Grilj, V; Skukan, N; Amato, G; Boarino, L; Jakšić, M; Olivero, P

    2016-01-01

    The control of the charge state of nitrogen-vacancy (NV) centers in diamond is of primary importance for the stabilization of their quantum-optical properties, in applications ranging from quantum sensing to quantum computing. To this purpose, in this work current-injecting micro-electrodes were fabricated in bulk diamond for NV charge state control. Buried (i.e. 3 {\\mu}m in depth) graphitic micro-electrodes with spacing of 9 {\\mu}m were created in single-crystal diamond substrates by means of a 6 MeV C scanning micro-beam. The high breakdown field of diamond was exploited to electrically control the variation in the relative population of the negative (NV-) and neutral (NV0) charge states of sub-superficial NV centers located in the inter- electrode gap regions, without incurring into current discharges. Photoluminescence spectra acquired from the biased electrodes exhibited an electrically induced increase up to 40% in the NV- population at the expense of the NV0 charge state. The variation in the relative ...

  10. Determination of glutathione in single HepG2 cells by capillary electrophoresis with reduced graphene oxide modified microelectrode.

    Science.gov (United States)

    Wang, Xiaolei; Wang, Jun; Fu, Hongyan; Liu, Dongju; Chen, Zhenzhen

    2014-12-01

    Determination of intracellular bioactive species will afford beneficial information related to cell metabolism, signal transduction, cell function, and disease treatment. In this study, the electrochemically reduced graphene oxide modified carbon fiber microdisk electrode (ER-GOME) was used as a detector of CZE-electrochemical detection and developed to detect glutathione (GSH). The electrocatalytic activity of the modified microelectrode was characterized by cyclic voltammetry. Under optimized experimental conditions, the concentration linear range of GSH was from 1 to 60 μM. When the S/N ratio was 3, the concentration detection limit was 1 μM. Compared with the unmodified carbon fiber microdisk electrode, the sensitivity was enhanced more than five times. With the use of this method, the average contents of GSH in single HepG2 cells were found to be 7.13 ± 1.11 fmol (n = 10). Compared with gold/mercury amalgam microelectrode, which was usually used in determining GSH, the electrochemically reduced graphene oxide modified carbon fiber microdisk electrode was friendly to environment for free mercury. Furthermore, there were several merits of the novel electrochemical detector coupled with CE, such as comparative repeatability, easy fabrication, and high sensitivity, hold great potential for the single-cell assay.

  11. Delivery of molecules into cells using localized single cell electroporation on ITO micro-electrode based transparent chip.

    Science.gov (United States)

    Chen, Sheng-Chiech; Santra, Tuhin Subhra; Chang, Chia-Jung; Chen, Tsung-Ju; Wang, Pen-Cheng; Tseng, Fan-Gang

    2012-10-01

    Single cell electroporation is one of the nonviral method which successfully allows transfection of exogenous macromolecules into individual living cell. We present localized cell membrane electroporation at single-cell level by using indium tin oxide (ITO) based transparent micro-electrodes chip with inverted microscope. A focused ion beam (FIB) technique has been successfully deployed to fabricate transparent ITO micro-electrodes with submicron gaps, which can generate more intense electric field to produce very localized cell membrane electroporation. In our approach, we have successfully achieved 0.93 μm or smaller electroporation region on the cell surface to inject PI (Propidium Iodide) dye into the cell with 60 % cell viability. This experiments successfully demonstrate the cell self-recover process from the injected PI dye intensity variation. Our localized cell membrane electroporation technique (LSCMEP) not only generates reversible electroporation process but also it provides a clear optical path for potentially monitoring/tracking of drugs to deliver in single cell level.

  12. HPLC-ED of low-molecular weight brominated phenols and tetrabromobisphenol A using pretreated carbon fiber microelectrode.

    Science.gov (United States)

    Bartosova, Zdenka; Jirovsky, David; Riman, Daniel; Halouzka, Vladimir; Svidrnoch, Martin; Hrbac, Jan

    2014-05-01

    Electrochemically pretreated carbon fiber microelectrode was used to develop a simple, fast and sensitive HPLC-ECD method for the determination of brominated phenols. In addition to simple mono-, di- and tri-bromophenols (4-bromophenol, 2,4-dibromophenol, 2,6-dibromophenol, 2,4,6-tri-bromophenol) the possibility of electrochemical detection of 3,3',5,5'-tetrabromobisphenol A in oxidation mode is reported for the first time. The isocratic separation was achieved within 14 min using ternary mobile phase consisting of 50mM-phosphate buffer (pH 3.5), acetonitrile and methanol (35/15/50, v/v), and detection potential of E=+1450 mV (vs. Ag/AgCl). The carbon fiber microelectrode permitted to use high anodic potentials (up to +1800 mV vs. Ag/AgCl), the optimum analytical response was achieved at +1450 mV vs. Ag/AgCl. The limits of detection (LOD) for the studied analytes were within the range of 1.8-56.6 ng mL(-1). The developed method was applied to determination of brominated phenols in spiked water samples. Furthermore, after simple extraction with methyl tert-butyl ether, it was possible to quantify tetrabromobisphenol A (TBBA) in a piece of CRT monitor plastic casing. The found amount of TBBA was 10.22 mg kg(-1) (±0.43).

  13. Platinum recycling going green via induced surface potential alteration enabling fast and efficient dissolution

    Science.gov (United States)

    Hodnik, Nejc; Baldizzone, Claudio; Polymeros, George; Geiger, Simon; Grote, Jan-Philipp; Cherevko, Serhiy; Mingers, Andrea; Zeradjanin, Aleksandar; Mayrhofer, Karl J. J.

    2016-01-01

    The recycling of precious metals, for example, platinum, is an essential aspect of sustainability for the modern industry and energy sectors. However, due to its resistance to corrosion, platinum-leaching techniques rely on high reagent consumption and hazardous processes, for example, boiling aqua regia; a mixture of concentrated nitric and hydrochloric acid. Here we demonstrate that complete dissolution of metallic platinum can be achieved by induced surface potential alteration, an ‘electrode-less' process utilizing alternatively oxidative and reductive gases. This concept for platinum recycling exploits the so-called transient dissolution mechanism, triggered by a repetitive change in platinum surface oxidation state, without using any external electric current or electrodes. The effective performance in non-toxic low-concentrated acid and at room temperature is a strong benefit of this approach, potentially rendering recycling of industrial catalysts, including but not limited to platinum-based systems, more sustainable. PMID:27767178

  14. Platinum recycling going green via induced surface potential alteration enabling fast and efficient dissolution

    Science.gov (United States)

    Hodnik, Nejc; Baldizzone, Claudio; Polymeros, George; Geiger, Simon; Grote, Jan-Philipp; Cherevko, Serhiy; Mingers, Andrea; Zeradjanin, Aleksandar; Mayrhofer, Karl J. J.

    2016-10-01

    The recycling of precious metals, for example, platinum, is an essential aspect of sustainability for the modern industry and energy sectors. However, due to its resistance to corrosion, platinum-leaching techniques rely on high reagent consumption and hazardous processes, for example, boiling aqua regia; a mixture of concentrated nitric and hydrochloric acid. Here we demonstrate that complete dissolution of metallic platinum can be achieved by induced surface potential alteration, an `electrode-less' process utilizing alternatively oxidative and reductive gases. This concept for platinum recycling exploits the so-called transient dissolution mechanism, triggered by a repetitive change in platinum surface oxidation state, without using any external electric current or electrodes. The effective performance in non-toxic low-concentrated acid and at room temperature is a strong benefit of this approach, potentially rendering recycling of industrial catalysts, including but not limited to platinum-based systems, more sustainable.

  15. Tuning the activity of platinum(IV) anticancer complexes through asymmetric acylation.

    Science.gov (United States)

    Chin, Chee Fei; Tian, Quan; Setyawati, Magdiel Inggrid; Fang, Wanru; Tan, Emelyn Sue Qing; Leong, David Tai; Ang, Wee Han

    2012-09-13

    Platinum(II) anticancer drug cisplatin is one of the most important chemotherapeutic agents in clinical use but is limited by its high toxicity and severe side effects. Platinum(IV) anticancer prodrugs can overcome these limitations by resisting premature aquation and binding to essential plasma proteins. Structure-activity relationship studies revealed a link between the efficacy of platinum(IV) complexes with the nature of their axial ligands, which can be modified to enhance the properties of the prodrug. The existing paradigm of employing platinum(IV) complexes with symmetrical axial carboxylate ligands does not fully exploit their vast potential. A new approach was conceived to control properties of platinum(IV) prodrugs using contrasting axial ligands via sequential acylation. We report a novel class of asymmetric platinum(IV) carboxylates based on the cisplatin template containing both hydrophilic and lipophilic ligands on the same scaffold designed to improve their aqueous properties and enhance their efficacy against cancer cells in vitro.

  16. Platinum overlayers on Co(0001) and Ni(111): numerical simulation of surface alloying

    Science.gov (United States)

    Légaré, P.; Cabeza, G. F.; Castellani, N. J.

    1999-11-01

    The surface alloying of one and two monolayers (ML) of platinum deposited on Ni(111) and Co(0001) were studied by means of the ECT-BFS method. The 1 ML deposit appears to be very stable on both substrates. Platinum can diffuse at high temperature only, the large activation barrier being represented by the first substrate layer. On the contrary, the stability of the 2 ML deposit is poor so that alloying is easily obtained. In both cases, the platinum diffusion produces metastable states. The lowest-energy states exhibit a propensity for platinum dilution in a limited region below the surface. The initial platinum thickness determines not only the features of the alloyed region, but also the surface concentration. The surface alloys have features qualitatively similar to those reported for the (111) surface of bulk Pt-Ni and Pt-Co alloys: a platinum-rich surface and oscillating concentration profiles.

  17. Morphology of Platinum Nanowire Array Electrodeposited Within Anodic Aluminium Oxide Template Characterized by Atomic Force Microscopy

    Institute of Scientific and Technical Information of China (English)

    孔令斌; 陆梅; 李梦轲; 郭新勇; 力虎林

    2003-01-01

    Uniform platinum nanowires were synthesized by electrodepositing the platinum under a very low altering current frequency (20Hz) and increasing voltage (5-15 V) in the pores of anodic aluminium oxide (AAO) template.Atomic force microscopy observation indicates that the template membranes we obtained have hexagonally closepacked nanochannels. The platinum nanowires have highly ordered arrays after partially dissolving the aluminium oxide membrane. With the increasing dissolving time, the platinum nanowire array collapsed. A concave topography of the aluminium substrate was observed after the aluminium oxide membrane was dissolved completely and the platinum nanowires were released from the template. Platinum nanowires were also characterized by transmission electron microscopy and the phase structure of the Al/AAO/Pt composite was proven by x-ray diffraction.

  18. Nanostructured gold and platinum electrodes on silicon structures for biosensing

    Science.gov (United States)

    Ogurtsov, V. I.; Sheehan, M. M.

    2005-01-01

    Gold and platinum metal electrodes on Si/SiO2 having undergone anisotropic potassium hydroxide (KOH) etch treatment are considered. This treatment etches at different rates and directions in the material resulting in creation of numerous pyramid shaped holes in the silicon substrate. This surface is used to make metal electrodes with increased electrode efficiency. The electrodes can serve as the sensors or as the sensor substrates (for surface polymer modification) and because both gold and platinum are inert they have applications for food safety biosensing. Wine, an economically significant food product, was chosen as a matrix, and impedance spectroscopy (EIS) was selected as a method of investigation of electrode behaviour. Based on results of EIS, different complexity equivalent circuits were determined by applying fitting mean square root optimisation of sensor complex impedance measurements.

  19. Hollow platinum alloy tailored counter electrodes for photovoltaic applications

    Science.gov (United States)

    Li, Pinjiang; Zhang, Yange; Fa, Wenjun; Yang, Xiaogang; Wang, Liang

    2017-08-01

    Without sacrifice of photovoltaic performances, low-platinum alloy counter electrodes (CEs) are promising in bringing down the fabrication cost of dye-sensitized solar cells (DSSCs). We present here the realization of ZnO nanostructure assisted hollow platinum-nickel (PtNi) alloy microstructure CEs with a simple hydrothermal methods and maximization of electrocatalytic behaviors by tuning Zn precursors. The maximal power conversion efficiency is up to 8.74% for the liquid-junction dye-sensitized solar cells with alloyed PtNi0.41 electrode, yielding a 37.6% cell efficiency enhancement in comparison with pristine solar cell from planar Pt electrode. Moreover, the dissolution-resistant and charge-transfer abilities toward I-/I3- redox electrolyte have also been markedly enhanced due to competitive dissolution reactions and alloying effects.

  20. The extractive metallurgy of south africa's platinum ores

    Science.gov (United States)

    Cramer, Larry A.

    2001-10-01

    The extraction technology for platinum-group metals (PGMs) has changed dramatically in the last 80 years, and the changes are likely to continue for years to come. This article will review advances in PGM extraction, including developments in semi-autogenous and fully autogenous milling; flotation equipment applications for treating high-chrome ores; increases in power densities for future smelting furnaces, and new methods for meeting rising environmental standards.

  1. Phase I trials of WR-2721 and cis-platinum

    Energy Technology Data Exchange (ETDEWEB)

    Glover, D.; Glick, J.H.; Weiler, C.; Yuhas, J.; Kligerman, M.M.

    1984-09-01

    WR-2721 is a sulfhydryl compound which in the animal model improves renal tolerance to cis-platinum (DDP) by factors of 1.3 to 1.7. Phase I trials were initiated to establish the toxicity and dose modification factor when WR-2721 was given prior to escalating doses of DDP. Nineteen patients received 27 courses of WR-2721 (450-910 mg/m/sup 2/) 20 minutes prior to DDP (50-120 mg/m/sup 2/). Mild, transient nephrotoxicity was observed in only 2 of 15 courses of DDP 80-100 mg/m/sup 2/ when WR-2721 was given prior to DDP. Although 5 of 9 patients treated with WR-2721 prior to 120 mg/m/sup 2/ of DDP developed transient nephrotoxicity, their serum creatinines returned to normal baseline values within 1 to 2 weeks. Thirty-four courses of WR-2721 (740 mg/m/sup 2/) prior to DDP 120-150 mg/m/sup 2/ with mannitol diuresis were administered. Biweekly serum creatinine and monthly creatinine clearances have remained normal in all patients treated with 120 mg/m/sup 2/ of platinum and WR-2721. Four of 10 patients treated with 150 mg/m/sup 2/ of cis-platinum experienced transient nephrotoxicity 5-7 days after treatment. Mild ototoxicity was noted in 4 patients following 150 mg/m/sup 2/ of DDP. WR-2721 does not appear to protect against the antitumor efficacy of DDP. Compared to retrospective series, our data suggest that WR-2721 may provide some protection against platinum-induced nephrotoxicity, but the dose modification factors remain to be established.

  2. Experimental Studies on Thermal and Electrical Properties of Platinum Nanofilms

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xing; ZHANG Qing-Guang; CAO Bing-Yang; FUJII Motoo; TAKAHASHI Koji; IKUTA Tatsuya

    2006-01-01

    @@ We experimentally studied the in-plane thermal and electrical properties of a suspended platinum nanofilm in thickness of 15 nm. The measured results show that the in-plane thermal conductivity, the electrical conductivity and the resistance-temperature coefficient of the studied nanofilm are much less than those of the bulk material,while the Lorenz number is greater than the bulk value.

  3. Stabilization of 200-atom platinum nanoparticles by organosilane fragments

    KAUST Repository

    Pelzer, Katrin

    2011-04-19

    Three\\'s a charm: Platinum nanoparticles of 2 nm diameter and containing approximately 200 atoms covered with n-octylsilyl groups (see picture, right; Pt blue, Si red, C gray, H turquoise) form when [Pt(dba)2] (dba=dibenzylideneacetone) decomposes in the presence of n-octylsilane. The particles adopt a cuboctahedral structure with an edge length of three atoms. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Treatment of pulmonary arteriovenous malformation using platinum coils: case report

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Man Deuk; Kim, Jeung Sook; Lim, Chang Young [College of Medicine, Pochon CHA University, Pochon (China)

    2005-07-15

    Pulmonary arteriovenous malformation (PAVM) is an abnormal direct communication between the pulmonary arteries and veins without any capillary network. The patients may be completely asymptomatic or may they develop serious complications including hemoptysis and brain abscess. We present here a case of incidentally found PAVM in a 33-year-old male who underwent embolization using platinum coils. Coil embolization is a safe, highly effective procedure that should be considered more often for the treatment of PAVM.

  5. Platinum(II) complexes as spectroscopic probes for biomolecules

    Energy Technology Data Exchange (ETDEWEB)

    Ratilla, E.

    1990-09-21

    The use of platinum(II) complexes as tags and probes for biomolecules is indeed advantageous for their reactivities can be selective for certain purposes through an interplay of mild reaction conditions and of the ligands bound to the platinum. The use of {sup 195}Pt NMR as a method of detecting platinum and its interactions with biomolecules was carried out with the simplest model of platinum(II) tagging to proteins. Variable-temperature {sup 195}Pt NMR spectroscopy proved useful in studying the stereodynamics of complex thioethers like methionine. The complex, Pt(trpy)Cl{sup +}, with its chromophore has a greater potential for probing proteins. It is a noninvasive and selective tag for histidine and cysteine residues on the surface of cytochrome c at pH 5. The protein derivatives obtained are separable, and the tags are easily quantitated and differentiated through the metal-to-ligand charge transfer bands which are sensitive to the environment of the tag. Increasing the pH to 7.0 led to the modification by Pt(trpy)Cl{sup +}of Arg 91 in cytochrome c. Further studies with guanidine-containing ligands as models for arginine modification by Pt(trpy)Cl{sup +} showed that guanidine can act as a terminal ligand and as a bridging ligand. Owing to the potential utility of Pt(trpy)L{sup n+} as electron dense probes of nucleic acid structure, interactions of this bis-Pt(trpy){sup 2+} complex with nucleic acids was evaluated. Indeed, the complex interacts non-covalently with nucleic acids. Its interactions with DNA are not exactly the same as those of its precedents. Most striking is its ability to form highly immobile bands of DNA upon gel electrophoresis. 232 refs.

  6. Modification of platinum surfaces by spontaneous deposition: Methanol oxidation electrocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    MacDonald, J.P.; Gualtieri, B.; Runga, N.; Teliz, E.; Zinola, C.F. [Fundamental Electrochemistry Laboratory, School of Sciences, Universidad de la Republica, Igua Street No. 4225, CP 11400, Montevideo (Uruguay)

    2008-12-15

    The presence of a second metal on platinum surfaces affects the performance of methanol oxidation. However, most of the electrocatalytic reactions are studied by using electrochemically deposited platinum alloys, but in the case of spontaneous deposition the situation is not so clear since the surface distribution, stability and morphology are usually not well documented. The formation of surface decorated samples on mono- and poly-crystalline platinum is followed by electrochemical and spectroscopic techniques and analysis of their performance towards methanol adsorption and oxidation compared with that on pure platinum. Pt/Sn and Pt/Ru are of special interest because of their well-known performance in methanol fuel cells. Methanol oxidation on Pt(111)/Ru, Pt(111)/Sn and Pt(111) shows that ruthenium is the only one able to promote the reaction since the simultaneous dissolution of tin occurs and competes with the process of interest. The in situ infrared spectroscopy is used to compare methanol oxidation on Pt(111)/Ru and Pt(111) in acid media using p-polarized light. The formation of bridge bound carbon monoxide is inhibited in the presence of ruthenium ad-species, whereas on Pt(111) the three adsorption configurations are observed. Linear sweep polarization curves and Tafel slopes (calculated from steady state potentiostatic plots) for methanol oxidation are compared on polycrystalline surfaces modified by tin or ruthenium at different coverages. There is almost no change in the Tafel slopes due to the presence of the foreign metal except for Pt/Ru, where a 0.09 V decade{sup -1} slope was calculated below 0.55 V due to hydroxyl adsorbates on ruthenium islands. The anodic stripping of methanol residues on the three surfaces indicates a lower amount of carbon monoxide-type adsorbates on Pt/Ru, and the simultaneous tin dissolution process leading to residues oxidation on Pt/Sn electrodes. (author)

  7. Mechanistic basis for overcoming platinum resistance using copper chelating agents.

    Science.gov (United States)

    Liang, Zheng D; Long, Yan; Tsai, Wen-Bin; Fu, Siqing; Kurzrock, Razelle; Gagea-Iurascu, Mihai; Zhang, Fan; Chen, Helen H W; Hennessy, Bryan T; Mills, Gordon B; Savaraj, Niramol; Kuo, Macus Tien

    2012-11-01

    Platinum-based antitumor agents are widely used in cancer chemotherapy. Drug resistance is a major obstacle to the successful use of these agents because once drug resistance develops, other effective treatment options are limited. Recently, we conducted a clinical trial using a copper-lowering agent to overcome platinum drug resistance in ovarian cancer patients and the preliminary results are encouraging. In supporting this clinical study, using three pairs of cisplatin (cDDP)-resistant cell lines and two ovarian cancer cell lines derived from patients who had failed in platinum-based chemotherapy, we showed that cDDP resistance associated with reduced expression of the high-affinity copper transporter (hCtr1), which is also a cDDP transporter, can be preferentially resensitized by copper-lowering agents because of enhanced hCtr1 expression, as compared with their drug-sensitive counterparts. Such a preferential induction of hCtr1 expression in cDDP-resistant variants by copper chelation can be explained by the mammalian copper homeostasis regulatory mechanism. Enhanced cell-killing efficacy by a copper-lowering agent was also observed in animal xenografts bearing cDDP-resistant cells. Finally, by analyzing a public gene expression dataset, we found that ovarian cancer patients with elevated levels of hCtr1 in their tumors, but not ATP7A and ATP7B, had more favorable outcomes after platinum drug treatment than those expressing low hCtr1 levels. This study reveals the mechanistic basis for using copper chelation to overcome cDDP resistance in clinical investigations.

  8. Characterisation of carbon nanotubes decorated with platinum nanoparticles

    OpenAIRE

    M. Pawlyta; D. Łukowiec; A.D. Dobrzańska-Danikiewicz

    2012-01-01

    Purpose: In presented work results of synthesis of carbon nanotubes decorated with platinum nanoparticles by organic colloidal process as an example of direct formation of nanoparticles onto CNTs are reported.Design/methodology/approach: Powder XRD and transmission electron microscopy were used for characterisation of the morphology of composite as well as the distribution of nanocrystals on the CNTs surfaces.Findings: TEM results confirm that CNT were homogeneous and clean, without any admix...

  9. Determination of Platinum Metals in Carbonaceous Mineral Raw Materials by Stripping Voltammetry

    OpenAIRE

    Kolpakova, Nina Alexandrovna; Oskina, Yuliya Aleksandrovna; Dyachenko, Elena Nikolaevna; Pshenichkin, Anatoliy Yakovlevich

    2015-01-01

    The paper considers the possibility of determining platinum metals in mineral raw materials by stripping voltammetry on a graphite electrode modified by metals. Stripping voltammetry method is characterized by low determination limit, wide intervals of determined content and high sensitivity. As a result of the research the conditions for the determination of gold, platinum and palladium by stripping voltammetry have been selected. The comparison of the results of gold, palladium and platinum...

  10. Lowering the resistivity of polyacrylate ion-selective membranes by platinum nanoparticles addition.

    Science.gov (United States)

    Jaworska, Ewa; Kisiel, Anna; Maksymiuk, Krzysztof; Michalska, Agata

    2011-01-01

    The effect of platinum nanoparticles introduction into polyacrylate membranes was examined. Platinum nanoparticles were added to the membrane cocktail before photopolymerization of the poly(n-butyl acrylate) based ion-selective membranes. Thus obtained sensors were characterized with significantly lowered electrical resistance and increased stability of potential readings compared to classical poly(n-butyl acrylate) membranes. The analytical parameters of platinum nanoparticle containing membranes were well comparable with those of classical membranes.

  11. Elaboration and Properties of Nanocomposite Structures Based on Crown Modified Platinum Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    H.Perez; S.Cavaliere-jaricot; P-A.Albouy; A.Etcheberry

    2007-01-01

    1 Results This paper presents the development of platinum nanocomposites structures based on organically modified c.a.2 nm core platinum nanoparticles.The chemical modification of the 4-mercaptoaniline functionalized particles by various in coming molecules is evidenced and precisely quantified.The particles can be dissolved like molecules in various solvents depending on the features of the new crown and X-rays shows that the interparticle distance is affected by the crown modification.These platinum n...

  12. High Performance Wafer-Based Capillary Electrochromatography Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Phase II research comprises designing, constructing, and testing a chip-based capillary electrochromatography (CEC) prototype for separation and analysis of...

  13. Platinum-induced structural collapse in layered oxide polycrystalline films

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jianlin; Liu, Changhui [CAS Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026 (China); Huang, Haoliang [CAS Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026 (China); Fu, Zhengping; Peng, Ranran, E-mail: pengrr@ustc.edu.cn, E-mail: yllu@ustc.edu.cn [CAS Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026 (China); Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026 (China); Zhai, Xiaofang [Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026 (China); Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026 (China); Lu, Yalin, E-mail: pengrr@ustc.edu.cn, E-mail: yllu@ustc.edu.cn [CAS Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026 (China); Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026 (China); Laser and Optics Research Center, Department of Physics, United States Air Force Academy, Colorado 80840 (United States)

    2015-03-30

    Effect of a platinum bottom electrode on the SrBi{sub 5}Fe{sub 1−x}Co{sub x}Ti{sub 4}O{sub 18} layered oxide polycrystalline films was systematically studied. The doped cobalt ions react with the platinum to form a secondary phase of PtCoO{sub 2}, which has a typical Delafossite structure with a weak antiferromagnetism and an exceptionally high in-plane electrical conductivity. Formation of PtCoO{sub 2} at the interface partially consumes the cobalt dopant and leads to the structural collapsing from 5 to 4 layers, which was confirmed by X-ray diffraction and high resolution transmission electron microscopy measurements. Considering the weak magnetic contribution from PtCoO{sub 2}, the observed ferromagnetism should be intrinsic of the Aurivillius compounds. Ferroelectric properties were also indicated by the piezoresponse force microscopy. In this work, the platinum induced secondary phase at the interface was observed, which has a strong impact on Aurivillius structural configuration and thus the ferromagnetic and ferroelectric properties.

  14. Organo-platinum complexes as antitumor agents (review).

    Science.gov (United States)

    Hill, J M; Speer, R J

    1982-01-01

    Rosenberg et al discovered in the coordination complexes of platinum a new, novel type of potential antitumor agent. Cisplatin [cis-dichlorodiammine platinum (II)4 proved active against a variety of rodent tumors and acted synergistically when combined with other chemotherapeutic agents. Initial clinical tests by Hill et al in 1971, showed cisplatin to be active against malignant lymphoma, Hodgkin's disease, and certain other malignancies. Significant nephrotoxicity, nausea, and vomiting were noted. Since then, cisplatin has been tested alone and in combination chemotherapy and has proven an efficacious anticancer agent in squamous cell carcinoma of head and neck, ovarian carcinoma, disseminated testicular cancer, and others. Its therapeutic value was acknowledged when approved in 1978 by the U.S. FDA for treatment of the latter cancer. The current clinical literature indicates clearly that the full potential of this drug has not yet been realized. Hydration and diuresis have served to mitigate much of the nephrotoxicity, while significant strides toward amelioration of the nausea and vomiting have also been achieved. Literally, thousands of chemically-related congeners have been synthesized, and many have shown marked potency against rodent tumors. Very few, however, have been evaluated clinically, vis-a-vis malonato trans(-)-1,2-diaminocyclohexane platinum(II); this appears a most promising and fertile area of future investigation.

  15. Upper eyelid platinum chain placement for treating paralytic lagophthalmos.

    Science.gov (United States)

    Bianchi, B; Ferri, A; Leporati, M; Ferrari, S; Lanfranco, D; Ferri, T; Sesenna, E

    2014-12-01

    For the definitive treatment of lagophthalmos and satisfactory rehabilitation of the affected eye, different surgical strategies have been proposed, including static or dynamic procedures. Although some of these can have good results, lid loading is now the most common technique for treating paralytic long-term lagophthalmos. Among the different types of loading, the use of a platinum chain is preferred to the use of a standard gold weight because platinum has a higher density than gold and is also more biocompatible. In this paper authors retrospectively analyzed 43 patients with regards to functional and cosmetic results. Questionnaires were also employed to assess changes and improvements in the patients' quality of life. Analysis of the excellent results achieved confirmed that platinum chain lid loading should be considered as a first-line treatment for paralytic lagophthalmos rehabilitation. It is a simple, reliable, and effective technique that significantly improves the health-related quality of life of patients. Copyright © 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

  16. First platinum moderated positron beam based on neutron capture

    CERN Document Server

    Hugenschmidt, C; Repper, R; Schreckenbach, K; Sperr, P; Triftshaeuser, W

    2002-01-01

    A positron beam based on absorption of high energy prompt gamma-rays from thermal neutron capture in sup 1 sup 1 sup 3 Cd was installed at a neutron guide of the high flux reactor at the ILL in Grenoble. Measurements were performed for various source geometries, dependent on converter mass, moderator surface and extraction voltages. The results lead to an optimised design of the in-pile positron source which will be implemented at the Munich research reactor FRM-II. The positron source consists of platinum foils acting as gamma-e sup + e sup - -converter and positron moderator. Due to the negative positron work function moderation in heated platinum leads to emission of monoenergetic positrons. The positron work function of polycrystalline platinum was determined to 1.95(5) eV. After acceleration to several keV by four electrical lenses the beam was magnetically guided in a solenoid field of 7.5 mT leading to a NaI-detector in order to detect the 511 keV gamma-radiation of the annihilating positrons. The posi...

  17. Optoelectronic method for determining platinum in biological products

    Science.gov (United States)

    Radu, Simona; Ionicǎ, Mihai; Macovei, Radu Alexandru; Caragea, Genica; Forje, Mǎrgǎrita; Grecu, Iulia; Vlǎdescu, Marian; Viscol, Oana

    2016-12-01

    Of all platinum metals, platinum has the most uses and it's the most abundant and most easily to be processed. Its use in auto catalysts results in environmental contamination of crowded cities and high-traffic roads. In medicine, Pt is used as a cytostatic drug. In order to study the degree of contamination of the population with Pt or the correctness of treatment with Pt, it has been developed a method for its determination from urine or blood samples with a system Graphite Furnance - Atomic Absorption Spectrometer, (GF-AAS) Varian. There are presented the methods of sampling processing for blood or urine that followed the digest of the organic matrix. In the determination of the operating parameters for the system GF-AAS, was aimed the reducing of the nonanatomic absorbance by optimizing the drying temperatures, the calcination and atomization temperatures and the removal of the nonanatomic absorbance with D2 lamp. As a result of the use of the method are presented the concentrations of Pt in the blood or urine of a group of patients in Bucharest, a city with heavy traffic of vehicles. GF-AAS method presented is sensitive, reproducible, and relatively easy to apply with an acceptable cost. With this method, the concentration of Pt can be determined from blood and urine, both in order to establish the degree of contamination with Pt and for monitoring cancer therapy with platinum compounds.

  18. Porous platinum-based catalysts for oxygen reduction

    Science.gov (United States)

    Erlebacher, Jonah D; Snyder, Joshua D

    2014-11-25

    A porous metal that comprises platinum and has a specific surface area that is greater than 5 m.sup.2/g and less than 75 m.sup.2/g. A fuel cell includes a first electrode, a second electrode spaced apart from the first electrode, and an electrolyte arranged between the first and the second electrodes. At least one of the first and second electrodes is coated with a porous metal catalyst for oxygen reduction, and the porous metal catalyst comprises platinum and has a specific surface area that is greater than 5 m.sup.2/g and less than 75 m.sup.2/g. A method of producing a porous metal according to an embodiment of the current invention includes producing an alloy consisting essentially of platinum and nickel according to the formula Pt.sub.xNi.sub.1-x, where x is at least 0.01 and less than 0.3; and dealloying the alloy in a substantially pH neutral solution to reduce an amount of nickel in the alloy to produce the porous metal.

  19. In vitro permeation of platinum through African and Caucasian skin.

    Science.gov (United States)

    Franken, A; Eloff, F C; du Plessis, J; Badenhorst, C J; Du Plessis, J L

    2015-02-03

    The majority of the South African workforce are Africans, therefore potential racial differences should be considered in risk and exposure assessments in the workplace. Literature suggests African skin to be a superior barrier against permeation and irritants. Previous in vitro studies on metals only included skin from Caucasian donors, whereas this study compared the permeation of platinum through African and Caucasian skin. A donor solution of 0.3 mg/ml of potassium tetrachloroplatinate (K₂PtCl₄) dissolved in synthetic sweat was applied to the vertical Franz diffusion cells with full thickness abdominal skin. Skin from three female African and three female Caucasian donors were included (n=21). The receptor solution was removed at various intervals during the 24 h experiment, and analysed with high resolution inductively coupled plasma-mass spectrometry (ICP-MS). Skin was digested and analysed by inductively coupled plasma-optical emission spectrometry (ICP-OES). Significantly higher permeation of platinum through intact African skin (p=0.044), as well as a significantly higher mass of platinum retention in African skin in comparison with Caucasian skin (p=0.002) occurred. Significant inter-donor variation was found in both racial groups (pplatinum salts. These results are contradictory to limited literature suggesting a superior barrier in African skin and further investigation is necessary to explain the higher permeation through African skin.

  20. Application of liposomal technologies for delivery of platinum analogs in oncology.

    Science.gov (United States)

    Liu, Demin; He, Chunbai; Wang, Andrew Z; Lin, Wenbin

    2013-01-01

    Platinum-based chemotherapy, such as cisplatin, oxaliplatin, and carboplatin, is one of the most widely utilized classes of cancer therapeutics. While highly effective, the clinical applications of platinum-based drugs are limited by their toxicity profiles as well as suboptimal pharmacokinetic properties. Therefore, one of the key research areas in oncology has been to develop novel platinum analog drugs and engineer new platinum drug formulations to improve the therapeutic ratio further. Such efforts have led to the development of platinum analogs including nedaplatin, heptaplatin, and lobaplatin. Moreover, reformulating platinum drugs using liposomes has resulted in the development of L-NDPP (Aroplatin™), SPI-77, Lipoplatin™, Lipoxal™, and LiPlaCis®. Liposomes possess several attractive biological activities, including biocompatibility, high drug loading, and improved pharmacokinetics, that are well suited for platinum drug delivery. In this review, we discuss the various platinum drugs and their delivery using liposome-based drug delivery vehicles. We compare and contrast the different liposome platforms as well as speculate on the future of platinum drug delivery research.

  1. Effect of the Platinum Electroplated Layer Thickness on the Coatings' Microstructure

    Science.gov (United States)

    Zagula-Yavorska, Maryana; Gancarczyk, Kamil; Sieniawski, Jan

    2017-03-01

    CMSX 4 and Inconel 625 superalloys were coated by platinum layers (3 and 7 μm thick) in the electroplating process. The heat treatment of platinum layers (at 1,050 ˚C for 2 h) was performed to increase platinum adherence to the superalloys substrate. The diffusion zone obtained on CMSX 4 superalloy (3 and 7 μm platinum thick before heat treatment) consisted of two phases: γ-Ni(Al, Cr) and (Al0.25Pt0.75)Ni3. The diffusion zone obtained on Inconel 625 superalloy (3 μm platinum thick before heat treatment) consisted of the α-Pt(Ni, Cr, Al) phase. Moreover, γ-Ni(Cr, Al) phase was identified. The X-ray diffraction (XRD) results revealed the presence of platinum in the diffusion zone of the heat-treated coating (7 μm platinum thick) on Inconel 625 superalloy. The surface roughness parameter Ra of heat-treated coatings increased with the increase of platinum layers thickness. This was due to the unequal mass flow of platinum and nickel.

  2. Influence of Surface Structure of Platinum Electrodes on Electrooxidation of CO

    Institute of Scientific and Technical Information of China (English)

    XIA Xing-hua; ZHANG Dai; SONG Yan-yan

    2003-01-01

    The oxidation of CO on platinum electrodes in an acid solution was studied with the conventional electrochemical methods and the on-line electrochemical mass spectroscopy. It was found that this reaction is strongly determined by the surface morphology of platinum. The pretreatment of platinum electrodes can change the surface properties dramatically, in consequence it can improve the electrocatalytic activity towards the electrooxidation of CO. The existence of surface active sites on the roughened platinum electrodes can be used to explain its high electrocatalysis towards the oxidation of CO.

  3. Dialkyl bisphosphonate platinum(II) complex as a potential drug for metastatic bone tumor.

    Science.gov (United States)

    Nakatake, Hidetoshi; Ekimoto, Hisao; Aso, Mariko; Ogawa, Atsushi; Yamaguchi, Asami; Suemune, Hiroshi

    2011-01-01

    Bisphosphonates have high affinity for hydroxyapatite (HA), which is abundantly present in bone. Also, platinum complexes are known that have a wide spectrum of antitumor activities. The conjugate of bisphosphonate and a platinum complex might have HA affinity and antitumor activity, and become a drug for metastatic bone tumor. In this study, the authors synthesized platinum complexes that had dialkyl bisphosphonic acid as a ligand, and evaluated the possibility of the synthesized complexes as a drug for metastatic bone tumor. The synthesized dialkyl bisphosphonate platinum(II) complex was characterized, and its stability in an aqueous solution was also confirmed. The synthesized platinum complex showed higher HA affinity than other platinum complexes such as cisplatin and carboplatin in an experiment of adsorption to HA. In vitro, the platinum complex showed tumor growth inhibitory effect stronger than or equal to cisplatin, which is the most commonly used antitumor agent. Moreover, the platinum complex showed a bone absorption inhibitory effect on the osteoclast. These results suggest potential of dialkyl bisphosphonate platinum(II) complexes as a drug for metastatic bone tumor.

  4. Application of liposomal technologies for delivery of platinum analogs in oncology

    Science.gov (United States)

    Liu, Demin; He, Chunbai; Wang, Andrew Z; Lin, Wenbin

    2013-01-01

    Platinum-based chemotherapy, such as cisplatin, oxaliplatin, and carboplatin, is one of the most widely utilized classes of cancer therapeutics. While highly effective, the clinical applications of platinum-based drugs are limited by their toxicity profiles as well as suboptimal pharmacokinetic properties. Therefore, one of the key research areas in oncology has been to develop novel platinum analog drugs and engineer new platinum drug formulations to improve the therapeutic ratio further. Such efforts have led to the development of platinum analogs including nedaplatin, heptaplatin, and lobaplatin. Moreover, reformulating platinum drugs using liposomes has resulted in the development of L-NDPP (Aroplatin™), SPI-77, Lipoplatin™, Lipoxal™, and LiPlaCis®. Liposomes possess several attractive biological activities, including biocompatibility, high drug loading, and improved pharmacokinetics, that are well suited for platinum drug delivery. In this review, we discuss the various platinum drugs and their delivery using liposome-based drug delivery vehicles. We compare and contrast the different liposome platforms as well as speculate on the future of platinum drug delivery research. PMID:24023517

  5. Fabrication of platinum coated nanoporous gold film electrode: A nanostructured ultra low-platinum loading electrocatalyst for hydrogen evolution reaction

    Energy Technology Data Exchange (ETDEWEB)

    Kiani, Abolfazl; Hatami, Somayeh [Department of Chemistry, Faculty of Science, University of Isfahan, Isfahan (Iran)

    2010-06-15

    The electrolytic hydrogen evolution reaction (HER) on platinum coated nanoporous gold film (PtNPGF) electrode is demonstrated. The deposition of platinum occurred as a spontaneous redox process in which a copper layer, obtained by underpotential deposition, was oxidized by platinum ions, which were reduced and simultaneously deposited. The present method could provide a very low Pt-loading electrode and the results demonstrated that ultra thin Pt coating effected efficiently and behaved as the nanostructured Pt for electrocatalytic hydrogen evolution reaction. The loading of Pt was calculated as 4.2 x 10{sup -3} {mu}g cm{sup -2} for PtNPGF electrode. The current density at -0.4 V and -0.8 V vs. Ag/AgCl was as high as 0.66 A {mu}g{sup -1} Pt and 3 A {mu}g{sup -1} Pt, respectively and the j{sub 0} was evaluated as 0.03 mA cm{sup -2} or 8 mA {mu}g{sup -1} Pt. The results indicated that increasing electrode area had no catalytic effect, but the nanostructure nature of as-fabricated electrode and submonolayer deposition of copper resulted in electrocatalytic activity for PtNPGF electrode. (author)

  6. Characterization of ToxCast Phase II compounds disruption of spontaneous network activity in cortical networks grown on multi-well microelectrode array (mwMEA) plates.

    Science.gov (United States)

    The development of multi-well microelectrode array (mwMEA) systems has increased in vitro screening throughput making them an effective method to screen and prioritize large sets of compounds for potential neurotoxicity. In the present experiments, a multiplexed approach was used...

  7. K+ transport in the mesonephric collecting duct system of the toad Bufo bufo : microelectrode recordings from isolated and perfused tubules

    DEFF Research Database (Denmark)

    Møbjerg, Nadja; Larsen, Erik Hviid; Novak, Ivana

    2002-01-01

    We studied the mechanisms of K(+) transport in cells from isolated and perfused collecting tubules and ducts from the mesonephric kidney of the toad Bufo bufo. Cells were impaled with microelectrodes across the basal cell membrane. The basolateral membrane potential (V(bl)) depolarized upon chang...

  8. Distribution of Sulfate-Reducing Bacteria, O2, and H2s in Photosynthetic Biofilms Determined by Oligonucleotide Probes and Microelectrodes Rid A-1977-2009

    DEFF Research Database (Denmark)

    RAMSING, NB; KUHL, M.; JØRGENSEN, BB

    1993-01-01

    penetration, we incubated two 4-mm-thick biofilm samples in darkness or exposed to light at natural intensity. Gradients of O2, H2S, and pH were examined with microelectrodes during incubation. The samples were subsequently frozen with liquid nitrogen and sliced on a cryomicrotome in 20-mum vertical slices...

  9. Fabrication of a gold microelectrode for amperometric detection on a polycarbonate electrophoresis chip by photodirected electroless plating.

    Science.gov (United States)

    Kong, Yong; Chen, Hengwu; Wang, Yurong; Soper, Steven A

    2006-07-01

    A novel method of photoresist-free micropatterning coupled with electroless gold plating is described for the fabrication of an integrated gold electrode for electrochemical detection (ED) on a polycarbonate (PC) electrophoresis microchip. The microelectrode layout was photochemically patterned onto the surface of a PC plate by selective exposure of the surface coated without photoresist to 254 nm UV light through a chromium/quartz photomask. Thus, the PC plate was selectively sensitized by formation of reactive chemical moieties in the exposed areas. After a series of wet chemistry reactions, the UV-exposed area was activated with a layer of gold nanoparticles that served as a seed to catalyze the electroless plating. The gold microelectrode was then selectively plated onto the activated area by using an electroless gold plating bath. Nonselective gold deposition on the unwanted areas was eliminated by sonication of the activated PC plate in a KSCN solution before electroless plating, and the adhesion of the plated electrodes to the PC surface was strengthened with thermal annealing. Compared with the previously reported electroless plating technique for fabrication of microelectrodes on a microchip, the present method avoided the use of a membrane stencil with an electrode pattern to restrict the area to be wet-chemically sensitized. The CE with integrated ED (CE-ED) microchip was assembled by thermal bonding an electrode-plated PC cover plate to a microchannel-embossed PC substrate. The novel method allows one to fabricate low-cost, electrode-integrated, complete PC CE-ED chips with no need of a clean room. The fabricated CE-ED microchip was demonstrated for separation and detection of model analytes, including dopamine (DA) and catechol (CA). Detection limits of 0.65 and 1.03 microM were achieved for DA and CA, respectively, and theoretical plate number of 1.4 x 10(4) was obtained for DA. The plated gold electrode can be used for about 4 h, bearing usually more

  10. Elution of platinum from carboplatin-impregnated calcium sulfate hemihydrate beads in vitro.

    Science.gov (United States)

    Tulipan, Rachel J; Phillips, Heidi; Garrett, Laura D; Dirikolu, Levent; Mitchell, Mark A

    2016-11-01

    OBJECTIVE To characterize the elution of platinum from carboplatin-impregnated calcium sulfate hemihydrate (CSH) beads in vitro. SAMPLE 60 carboplatin-impregnated CSH beads and 9 CSH beads without added carboplatin (controls). PROCEDURES Carboplatin-impregnated CSH beads (each containing 4.6 mg of carboplatin [2.4 mg of platinum]) were placed into separate 10-mL plastic tubes containing 5 mL of PBSS in groups of 1, 3, 6, or 10; 3 control beads were placed into a single tube of PBSS at the same volume. Experiments were conducted in triplicate at 37°C and a pH of 7.4 with constant agitation. Eluent samples were collected at 1, 2, 3, 6, 12, 24, and 72 hours. Samples were analyzed for platinum content by inductively coupled plasma-mass spectrometry. RESULTS The mean concentration of platinum released per carboplatin-impregnated bead over 72 hours was 445.3 mg/L. Cumulative concentrations of platinum eluted increased as the number of beads per tube increased. There was a significant difference in platinum concentrations over time, with values increasing over the first 12 hours and then declining for all tubes. There was also a significant difference in percentage of total incorporated platinum released into tubes with different numbers of beads: the percentage of eluted platinum was higher in tubes containing 1 or 3 beads than in those containing 6 or 10 beads. CONCLUSIONS AND CLINICAL RELEVANCE Carboplatin-impregnated CSH beads eluted platinum over 72 hours. Further studies are needed to determine whether implantation of carboplatin-impregnated CSH beads results in detectable levels of platinum systemically and whether the platinum concentrations eluted locally are toxic to tumor cells.

  11. Determinants of ototoxicity in 451 platinum-treated Dutch survivors of childhood cancer : A DCOG late-effects study

    NARCIS (Netherlands)

    Clemens, Eva; de Vries, Andrica C.; Pluijm, Saskia F.; Zehnhoff-Dinnesen, Antoinette Am; Tissing, Wim J.; Loonen, Jacqueline J.; van Dulmen-den Broeder, Eline; Bresters, Dorine; Versluys, Birgitta; Kremer, Leontien C.; van der Pal, Heleen J.; van Grotel, Martine; van den Heuvel-Eibrink, Marry M.

    2016-01-01

    Platinum-containing chemotherapeutics are efficacious for a variety of pediatric malignancies, nevertheless these drugs can induce ototoxicity. However, ototoxicity data on large cohorts of childhood cancer survivors (CCSs) who received platinum agents, but not cranial irradiation are scarce.

  12. Structure and reactivity of a unique Y-shaped tricoordinate bis(silyl)platinum(II)-NHC complex

    NARCIS (Netherlands)

    Berthon-Gelloz, G.; de Bruin, B.; Tinant, B.; Markó, I.E.

    2009-01-01

    A unique, three-coordinate Y-shaped bis(silyl)platinum(II) complex was isolated and characterized. DFT studies on a model system shed light on the nature of this unusual coordination mode for platinum(II).

  13. H2O2在具有纳米结构的Rh微电极上的电催化氧化%The Oxidation of Hydrogen Peroxide on Nanostructured Rhodium Microelectrodes

    Institute of Scientific and Technical Information of China (English)

    Philip N.Bartlett; Thomas F.Esterle

    2012-01-01

    在含有C12EO8(Octaethyleneglycol Monododecyl Ether)的H1溶致液晶相中Pt微电极上电沉积Rh介孔膜.该电极在中性、低浓度(CH2O2〈10 mmol.L-1)条件下,对H2O2有较好的氧化还原响应及稳定性.由于电流磁滞效应,H2O2在Rh介孔膜微电极上的氧化与电位相关,且遵循与Rh(OH)3有关的CEE(Chemical reaction step by two sequential electrochemical steps)反应机制.H2O2浓度较大时,由于孔电极表面其结合点位趋于饱和或孔内溶液酸化的反应限制,电流呈现一平台.Rh介孔膜厚度小于200 nm的电极,H2O2浓度校正曲线符合膜孔反应一维扩散模型.%Mesoporous Rh films were deposited onto platinum microelectrodes from the H 1 lyotropic liquid crystalline phase of C 12 EO 8 (octaethyleneglycol monododecyl ether).The electrodes show well defined voltammetry for the oxidation and the reduction of hydrogen peroxide at low concentrations (10 mmol.L -1 ) with excellent stability for operation at neutral pH.Based on the hysteresis in the current and the potential dependence the oxidation of hydrogen peroxide occurs through a CEE mechanism involving Rh(OH) 3 on the mesoporous Rh electrode surface.At higher hydrogen peroxide concentrations the current reaches a plateau that is due to either saturation of the binding sites for hydrogen peroxide or limitation of the reaction due to acidification of the solution within the pores.For the thin films (below 200 nm) the hydrogen peroxide calibration curves we fitted to a one dimensional model for diffusion and reaction within the pores.

  14. A novel bio-mimicking, planar nano-edge microelectrode enables enhanced long-term neural recording

    Science.gov (United States)

    Wijdenes, Pierre; Ali, Hasan; Armstrong, Ryden; Zaidi, Wali; Dalton, Colin; Syed, Naweed I.

    2016-01-01

    Our inability to accurately monitor individual neurons and their synaptic activity precludes fundamental understanding of brain function under normal and various pathological conditions. However, recent breakthroughs in micro- and nano-scale fabrication processes have advanced the development of neuro-electronic hybrid technology. Among such devices are three-dimensional and planar electrodes, offering the advantages of either high fidelity or longer-term recordings respectively. Here, we present the next generation of planar microelectrode arrays with “nano-edges” that enable long-term (≥1 month) and high fidelity recordings at a resolution 15 times higher than traditional planar electrodes. This novel technology enables better understanding of brain function and offers a tremendous opportunity towards the development of future bionic hybrids and drug discovery devices. PMID:27731326

  15. Application of voltammetric techniques at microelectrodes to the study of the chemical stability of highly reactive species.

    Science.gov (United States)

    Laborda, Eduardo; Olmos, José-Manuel; Torralba, Encarnación; Molina, Angela

    2015-02-03

    The application of voltammetric techniques to the study of chemical speciation and stability is addressed both theoretically and experimentally in this work. In such systems, electrode reactions are coupled to homogeneous chemical equilibria (complexations, protonations, ion associations, ...) that can be studied in a simple, economical, and accurate way by means of electrochemical methods. These are of particular interest when some of the participating species are unstable given that the generation and characterization of the species are performed in situ and on a short time scale. With the above aim, simple explicit solutions are presented in this article for quantitative characterization with any voltammetric technique and with the most common electrode geometries. From the theoretical results obtained, it is pointed out that the use of square-wave voltammetry in combination with microelectrodes is very suitable. Finally, the theory is applied to the investigation of the ion association between the anthraquinone radical monoanion and the tetrabutylammonium cation in acetonitrile medium.

  16. In vivo pH monitoring using boron doped diamond microelectrode and silver needles: application to stomach disorder diagnosis.

    Science.gov (United States)

    Fierro, Stéphane; Seishima, Ryo; Nagano, Osamu; Saya, Hideyuki; Einaga, Yasuaki

    2013-11-19

    This study presents the in vivo electrochemical monitoring of pH using boron doped diamond (BDD) microelectrode and silver needles for potential application in medical diagnosis. Accurate calibration curve for pH determination were obtained through in vitro electrochemical measurements. The increase induced in stomach pH by treatment with pantoprazole was used to demonstrate that it is possible to monitor the pH in vivo using the simple and noninvasive system proposed herein. Using the results of the in vivo and in vitro experiments, a quantitative analysis of the increase in stomach pH is also presented. It is proposed that the catheter-free pH monitoring system presented in this study could be potentially employed in any biological environment.

  17. Noninvasive microelectrode ion flux estimation technique (MIFE) for the study of the regulation of root membrane transport by cyclic nucleotides

    KAUST Repository

    Ordoñez, Natalia Maria

    2013-09-03

    Changes in ion permeability and subsequently intracellular ion concentrations play a crucial role in intracellular and intercellular communication and, as such, confer a broad array of developmental and adaptive responses in plants. These changes are mediated by the activity of plasma-membrane based transport proteins many of which are controlled by cyclic nucleotides and/or other signaling molecules. The MIFE technique for noninvasive microelectrode ion flux measuring allows concurrent quantification of net fluxes of several ions with high spatial (μm range) and temporal (ca. 5 s) resolution, making it a powerful tool to study various aspects of downstream signaling events in plant cells. This chapter details basic protocols enabling the application of the MIFE technique to study regulation of root membrane transport in general and cyclic nucleotide mediated transport in particular. © Springer Science+Business Media New York 2013.

  18. Application of double pulse theory for hemispherical microelectrodes to the experimental study of slow charge transfer processes

    Energy Technology Data Exchange (ETDEWEB)

    Laborda, Eduardo [Departamento de Quimica Fisica, Universidad de Murcia, Espinardo 30100, Murcia (Spain); Rogers, Emma I. [Department of Chemistry, Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ (United Kingdom); Martinez-Ortiz, Francisco [Departamento de Quimica Fisica, Universidad de Murcia, Espinardo 30100, Murcia (Spain); Molina, Angela, E-mail: amolina@um.e [Departamento de Quimica Fisica, Universidad de Murcia, Espinardo 30100, Murcia (Spain); Compton, Richard G., E-mail: richard.compton@chem.ox.ac.u [Department of Chemistry, Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ (United Kingdom)

    2010-09-01

    Differential Pulse Voltammetry and Reverse Pulse Voltammetry are applied to the study of the electrode kinetics of slow charge transfer processes at hemispherical microelectrodes of ca. 25 {mu}m radius. The electrochemical reversibility of three redox systems: 3-nitrophenolate{sup -/2-{center_dot}}, 3-nitrophthalate{sup 2-/3-{center_dot}} and europium{sup 3+/2+}, are evaluated with both techniques by determining the heterogeneous rate constant, the electron transfer coefficient as well as the formal potential for each. The experimental results show the value of these techniques for the characterization of the electrode kinetics by means of simple diagnostic criteria and single-point fit to general working curves. Further, theory developed for double potential pulse under radial diffusion conditions is validated.

  19. A novel bio-mimicking, planar nano-edge microelectrode enables enhanced long-term neural recording

    Science.gov (United States)

    Wijdenes, Pierre; Ali, Hasan; Armstrong, Ryden; Zaidi, Wali; Dalton, Colin; Syed, Naweed I.

    2016-10-01

    Our inability to accurately monitor individual neurons and their synaptic activity precludes fundamental understanding of brain function under normal and various pathological conditions. However, recent breakthroughs in micro- and nano-scale fabrication processes have advanced the development of neuro-electronic hybrid technology. Among such devices are three-dimensional and planar electrodes, offering the advantages of either high fidelity or longer-term recordings respectively. Here, we present the next generation of planar microelectrode arrays with “nano-edges” that enable long-term (≥1 month) and high fidelity recordings at a resolution 15 times higher than traditional planar electrodes. This novel technology enables better understanding of brain function and offers a tremendous opportunity towards the development of future bionic hybrids and drug discovery devices.

  20. Dynamic and static calcium gradients inside large snail (Helix aspersa) neurones detected with calcium-sensitive microelectrodes

    OpenAIRE

    Thomas, Roger C.; Postma, Marten

    2007-01-01

    We have used quartz Ca2+-sensitive microelectrodes (CASMs) in large voltage-clamped snail neurones to investigate the inward spread of Ca2+ after a brief depolarisation. Both steady state and [Ca2+] i transients changed with depth of penetration. When the CASM tip was within 20 μm of the far side of the cell the [Ca2+] i transient time to peak was 4.4 ± 0.5 s, rising to 14.7 ± 0.7 s at a distance of 80 μm. We estimate that the Ca2+ transients travelled centripetally at an average speed of 6 μ...