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David W. Schmidtke - One of the best experts on this subject based on the ideXlab platform.
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incorporation of single walled carbon nanotubes into ferrocene modified linear polyethylenimine Redox Polymer films
Langmuir, 2011Co-Authors: Tu O Tran, Stephen A. Merchant, Emily G Lammert, Jie Chen, Daniel B Brunski, J C Keay, M B Johnson, Daniel T Glatzhofer, David W. SchmidtkeAbstract:In this study, we describe the effects of incorporating single-walled carbon nanotubes (SWNTs) into Redox Polymer-enzyme hydrogels. The hydrogels were constructed by combining the enzyme glucose oxidase with a Redox Polymer (Fc-C(6)-LPEI) in which ferrocene was attached to linear poly(ethylenimine) by a six-carbon spacer. Incorporation of SWNTs into these films changed their morphology and resulted in a significant increase in the enzymatic response at saturating glucose concentrations (3 mA/cm(2)) as compared to films without SWNTs (0.6 mA/cm(2)). Likewise, the sensitivity at 5 mM glucose was significantly increased in the presence of SWNTs (74 μA/cm(2)·mM) as compared to control films (26 μA/cm(2)·mM). We demonstrate that the increase in the electrochemical and enzymatic response of these films depends on the amount of SWNTs incorporated and the method of SWNT incorporation. Furthermore, we report that the presence of SWNTs in thick films allows for more of the ferrocene Redox centers to become accessible. The high current densities of the hydrogels should allow for the construction of miniature biosensors and enzymatic biofuel cells.
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adsorption of glucose oxidase onto single walled carbon nanotubes and its application in layer by layer biosensors
Analytical Chemistry, 2009Co-Authors: Ta Wei Tsai, Gustavo Heckert, Luis F F Neves, Roger G Harrison, Daniel E Resasco, David W. SchmidtkeAbstract:In this study, we describe the use of a sodium cholate suspension-dialysis method to adsorb the Redox enzyme glucose oxidase (GOX) onto single-walled carbon nanotubes (SWNT). By this method, solutions of dispersed and debundled SWNTs were prepared that remained stable for 30 days and which retained 75% of the native enzymatic activity. We also demonstrate that GOX-SWNT conjugates can be assembled into amperometric biosensors with a poly[(vinylpyridine)Os(bipyridyl)2Cl2+/3+] Redox Polymer (PVP-Os) through a layer-by-layer (LBL) self-assembly process. Incorporation of SWNT-enzyme conjugates into the LBL films resulted in current densities as high as 440 μA/cm2, which were a 2-fold increase over the response of films without SWNTs. We also demonstrate that the adsorption pH of the Redox Polymer solution and the dispersion quality of SWNTs were important parameters in controlling the electrochemical and enzymatic properties of the LBL films.
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Amperometric Biosensors Based on Redox Polymer -- Carbon Nanotube -- Enzyme Composites
Analytical chemistry, 2005Co-Authors: Pratixa P. Joshi, Stephen A. Merchant, Youdan Wang, David W. SchmidtkeAbstract:Based on their size and unique electrical properties, carbon nanotubes offer the exciting possibility of developing ultrasensitive, electrochemical biosensors. In this study, we describe the construction of amperometric biosensors based on the incorporation of single-walled carbon nanotubes modified with enzyme into Redox Polymer hydrogels. The composite films were constructed by first incubating an enzyme in a single-walled carbon nanotube (SWNTs) solution and then cross-linking within a poly[(vinylpyridine)Os(bipyridyl)2Cl2+/3+] Polymer film. Incorporation of SWNTs, modified with glucose oxidase, into the Redox Polymer films resulted in a 2−10-fold increase in the oxidation and reduction peak currents during cyclic voltammetry, while the glucose electrooxidation current was increased 3-fold to ∼1 mA/cm2 for glucose sensors. Similar effects were also observed when SWNTs were modified with horseradish peroxidase prior to incorporation into Redox hydrogels.
Michael V. Pishko - One of the best experts on this subject based on the ideXlab platform.
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characterization of oxidoreductase Redox Polymer electrostatic film assembly on gold by surface plasmon resonance spectroscopy and fourier transform infrared external reflection spectroscopy
Analytica Chimica Acta, 2002Co-Authors: Aleksandr Simonian, Jerry Elkind, And Alexander Revzin, James R Wild, Michael V. PishkoAbstract:The electrostatic assembly of nanocomposite thin films consisting of alternating layers of an organometallic Redox Polymer (RP) and oxidoreductase enzymes, glucose oxidase (GOX), lactate oxidase (LOX) and pyruvate oxidase (PYX), was investigated. Multilayer nanostructures were fabricated on gold surfaces by the deposition of an anionic self-assembled monolayer of 11-mercaptoundecanoic acid, followed by the electrostatic attachment of a cationic RP, poly(vinylpyridine Os(bis-bipyridine)2Cl-co-allylamine) (PVP-Os-AA), and anionic oxidoreductase enzymes. Surface plasmon resonance (SPR) spectroscopy, Fourier transform infrared external reflection spectroscopy (FT-IR–ERS) and electrochemistry were employed to characterize the assembly of these nanocomposite films. The surface concentration of GOX was found to be 2.4 ng/mm 2 for the first enzyme layer and 1.96 ng/mm 2 for the second enzyme layer, while values of 10.7 and 1.3 ng/mm 2 were obtained for PYX and LOX, respectively. The apparent affinity constant for GOX adsorption was found to be 8 × 10 7 M −1 . FT-IR–ERS was used to verify the incorporation of GOX and its conformational stability inside of these nanocomposite thin films. An SPR instrument with a flow-through cell was modified by additions of Ag/AgCl reference and Pt counter electrodes, with the gold-coated SPR surface film serving as the working electrode. This enabled real-time observation of the assembly of sensing components and immediate, in situ electrochemical verification of substrate-dependent current upon the addition of enzyme to the multilayer structure. A glucose-dependant amperometric response with sensitivity of 0.197 A/cm 2 /mM for a linear range of 1–10 mM of glucose was obtained. The SPR and FT-IR–ERS studies also showed no desorption of Polymer or enzyme from the nanocomposite RP–GOX structure when stored in aqueous environment occurred over the period of 3 weeks, suggesting that decreasing substrate sensitivity with time was due to loss of enzymatic activity rather than loss of film compounds from the nanostructure. © 2002 Elsevier Science B.V. All rights reserved.
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glucose lactate and pyruvate biosensor arrays based on Redox Polymer oxidoreductase nanocomposite thin films deposited on photolithographically patterned gold microelectrodes
Sensors and Actuators B-chemical, 2002Co-Authors: And Alexander Revzin, Aleksandr Simonian, Kaushik Sirkar, Michael V. PishkoAbstract:Abstract Glucose, lactate, and pyruvate sensor arrays were fabricated by depositing electrostatically complexed monolayers on lithographically patterned, individually addressable, gold microelectrodes. Standard photolithographic techniques combined with metal deposition were used to fabricate gold arrays on both SiO2/Si and flexible Mylar substrates. These gold arrays were then functionalized with a negative surface charge through chemisorption of 11-mercaptoundecanoic acid (MUA) followed by the electrostatic assembly of a nanocomposite thin-film of a cationic osmium Redox Polymer and anionic oxidoreductases, either glucose oxidase, lactate oxidase, or pyruvate oxidase. When tested electrochemically, glucose, lactate and pyruvate sensors exhibited analyte sensitivities of 0.26, 0.24 and 0.133 μA/(cm2 mM) respectively. Responses to analytes proved to be linear in the physiologically relevant concentration ranges for glucose (0–20 mM), lactate (0–10 mM), and pyruvate (0–2 mM). Standard deviations between individual electrodes of ∼18% (glucose) and 20% (lactate) were determined for the enzyme electrode arrays with five array members. Furthermore, the potential problem of sensor cross-talk was investigated by subsequently testing one array member and then array members adjacent to that sensor. The response from a pair of electrodes was approximately twice than that of a single electrode, demonstrating that the individual sensors are free of cross-talk.
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glucose and lactate biosensors based on Redox Polymer oxidoreductase nanocomposite thin films
Analytical Chemistry, 2000Co-Authors: Kaushik Sirkar, And Alexander Revzin, Michael V. PishkoAbstract:Glucose and lactate enzyme electrodes have been fabricated through the deposition of an anionic self-assembled monolayer and subsequent Redox Polymer/enzyme electrostatic complexation on gold substrates. These surfaces were functionalized with a negative charge using 11-mercaptoundecanoic acid (MUA), followed by alternating immersions in cationic Redox Polymer solutions and anionic glucose oxidase (GOX) or lactate oxidase (LAX) solutions to build the nanocomposite structure. The presence of the multilayer structure was verified by ellipsometry and sensor function characterized electrochemically. Reproducible analyte response curves from 2 to 20 mM (GOX) and 2−10 mM (LAX) were generated with the standard deviation between multiple sensors between 12 and 17%, a direct result of the reproducibility of the fabrication technique. In the case of glucose enzyme electrodes, the multilayer structure was further stabilized through the introduction of covalent bonds within and between the layers. Chemical cross-link...
Tokuji Miyashita - One of the best experts on this subject based on the ideXlab platform.
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Quasi-Solid-State Optical Logic Devices Based on Redox Polymer Nanosheet Assembly
Langmuir : the ACS journal of surfaces and colloids, 2009Co-Authors: Jun Matsui, Atsushi Aoki, Kenichi Abe, Masaya Mitsuishi, Tokuji MiyashitaAbstract:We report fabrication of a quasi-solid-state optical logic gate based on a Polymer nanosheet photodiode. Two amphiphilic coPolymers, p(DDA/Ru) and p(DDA/Fc), which respectively have a ruthenium dipyridyl complex and a ferrocene derivative as a Redox molecule, are synthesized to produce Redox Polymer nanosheets. To construct Polymer nanosheet photodiodes, two Redox Polymer nanosheets were assembled onto an indium-tinoxide (ITO) electrode in a tailor-made manner. The ITO electrode was connected with a counter electrode using an agarose gel electrolyte. The simple two-electrode system performs as a quasi-solid-state Polymer nanosheet photodiode (QS-PNP). The photocurrent flow direction of QS-PNP can be controlled to be anodic or be cathodic by changing the deposition order of the Redox Polymer nanosheets. The anodic and cathodic QS-PNPs were applied to construct optical OR and XOR logic gates. The OR logic gate was fabricated by connecting the anodic and cathodic QS-PNP in a series; XOR logic was fabricated by connecting two anodic QS-PNPs in series. In optical logic gates, excitations of p(DDA/Ru) were used as input signals, and photocurrent was used as an output signal. These optical logic gates operate in a quasi-solid-state in a simple two-electrode configuration, which facilitates integration of the logic elements.
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Impedance analysis of the electron transfer process in Redox Polymer Langmuir–Blodgett films
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2002Co-Authors: Atsushi Aoki, Tokuji MiyashitaAbstract:Abstract The electron transfer process in Redox Polymer Langmuir–Blodgett films containing tris(bipyridine)ruthenium complex has been investigated as a function of the number of monolayers by an impedance spectroscopy. The complex impedance and capacitance data show that the equivalent circuit model consists of the parallel circuit with the membrane capacitance of the LB films as a fast charging process and the faradaic capacitance controlled by the charge transfer resistance as a slow charging process. The charge transfer resistance and the faradaic capacitance increases with the number of the monolayers whereas the membrane capacitance decreases with increasing number of the monolayers.
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Photoinduced Electrochemical Properties of Organized Assembly of Amphiphilic Redox Polymers by Langmuir-Blodgett Technique
Journal of Japan Oil Chemists' Society, 2000Co-Authors: Atsushi Aoki, Tokuji MiyashitaAbstract:Spatial arrangement of the ruthenium dipyridyl complex and ferrocene derivative in hetero-deposited Redox Polymer Langmuir-Blodgett (LB) films was carried out for direction control of photocurrent flow produced by photoinduced electron transfer reaction and for high quantum efficiency. Two hetero-deposited structures were obtained by varying the deposition order of the Redox Polymer monolayers by the LB technique. Cyclic voltammograms of hetero-deposited Redox Polymer LB films exhibited current rectifying and charge storage properties. Light irradiation led to anodic photocurrent of hetero-deposited Redox Polymer LB films consisting of Ru coPolymer LB film as an inner layer and Fc coPolymer LB film as an outer layer on the ITO (Fc/Ru/ITO) electrodes. On the other hand, cathodic current was observed at the reverse layered structure (Ru/Fc/ITO) electrodes. The direction of photocurrent flow depended on the deposition order of Redox Polymer LB films on the ITO electrode. Photocurrent quantum efficiency of 5.9% of the hetero-deposited Redox Polymer LB film was achieved. High photocurrent conversion efficiency is explained by inhibition of recombination of photoinduced charge separation due to hetero-deposited LB film structures.
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A structural effect on electrochemical behavior of hetero-deposited Redox Polymer Langmuir–Blodgett films containing ferrocene and tris(bipyridine)ruthenium derivatives ☆
Journal of Electroanalytical Chemistry, 1999Co-Authors: Atsushi Aoki, Tokuji MiyashitaAbstract:Abstract A structural effect on the electrochemical behavior of hetero-deposited Redox Polymer Langmuir–Blodgett (LB) films containing ferrocene (Fc coPolymer) and tris(bipyridine)ruthenium derivatives (Ru coPolymer) on electrodes was investigated by cyclic voltammetry. The hetero-deposited LB film structure consists of Ru coPolymer LB film (three layers) as an inner layer and Fc coPolymer LB film (two layers) as an outer layer on ITO electrodes. The hetero-deposited Redox Polymer LB films which are prepared by the deposition at a surface pressure higher than 28 mN m−1 show that the Redox behavior of the ferrocene moiety in the outer Fc coPolymer LB film is controlled by the Redox condition of the ruthenium complex in the inner Ru coPolymer LB film and not directly influenced by the electrode potential. On the other hand, in the LB films prepared at a pressure less than 25 mN m−1, such behavior was not observed because the inner Ru coPolymer LB films cannot work as an insulator between the outer Fc coPolymer LB films and the ITO electrode. The voltammetric shapes of the Ru coPolymer LB films were distorted with increasing deposition surface pressure. These results indicate that the insulating property of the inner layer is improved whereas the electron transfer rate in the interlayer becomes slower with increasing deposition surface pressure because of the formation of the high packing density of alkyl side chains of the LB films.
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Effective photoinduced electron transfer in hetero-deposited Redox Polymer LB films
Langmuir, 1999Co-Authors: Atsushi Aoki, Yumiko Abe, Tokuji MiyashitaAbstract:The spatial arrangement of the ruthenium dipyridyl complex and ferrocene derivative in heterodeposited Redox Polymer Langmuir−Blodgett (LB) films is used for the direction control of the photocurre...
Kuo-chuan Ho - One of the best experts on this subject based on the ideXlab platform.
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synthesis of Redox Polymer nanobeads and nanocomposites for glucose biosensors
ACS Applied Materials & Interfaces, 2013Co-Authors: Jen Yuan Wang, Lin-chi Chen, Kuo-chuan HoAbstract:Redox Polymer nanobeads of branched polyethylenimine binding with ferrocene (BPEI-Fc) were synthesized using a simple chemical process. The functionality and morphology of the Redox Polymer nanobeads were investigated by Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). This hydrophilic Redox nanomaterial could be mixed with glucose oxidase (GOx) for drop-coating on a screen-printed carbon electrode (SPCE) for glucose sensing application. Electrochemical properties of the BPEI-Fc/GOx/SPCE prepared under different conditions were studied by cyclic voltammetry (CV). On the basis of these CV results, the synthetic condition of the BPEI-Fc/GOx/SPCE could be optimized. By incorporating conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), the performance of a Redox Polymer nanobead–based enzyme electrode could be further improved. The influence of PEDOT:PSS on the nanocomposite enzyme electrode was discussed from the aspects of the apparent ele...
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Synthesis of Redox Polymer nanobeads and nanocomposites for glucose biosensors
ACS Applied Materials and Interfaces, 2013Co-Authors: Jen Yuan Wang, Lin-chi Chen, Kuo-chuan HoAbstract:Redox Polymer nanobeads of branched polyethylenimine binding with ferrocene (BPEI-Fc) were synthesized using a simple chemical process. The functionality and morphology of the Redox Polymer nanobeads were investigated by Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). This hydrophilic Redox nanomaterial could be mixed with glucose oxidase (GOx) for drop-coating on a screen-printed carbon electrode (SPCE) for glucose sensing application. Electrochemical properties of the BPEI-Fc/GOx/SPCE prepared under different conditions were studied by cyclic voltammetry (CV). On the basis of these CV results, the synthetic condition of the BPEI-Fc/GOx/SPCE could be optimized. By incorporating conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), the performance of a Redox Polymer nanobead–based enzyme electrode could be further improved. The influence of PEDOT:PSS on the nanocomposite enzyme electrode was discussed from the aspects of the apparent electron diffusion coefficient (D(app)) and the charge transfer resistance (R(ct)). The glucose-sensing sensitivity of the BPEI-Fc/PEDOT:PSS/GOx/SPCE is calculated to be 66 μA mM(–1) cm(–2), which is 2.5 times higher than that without PEDOT:PSS. The apparent Michaelis constant (K(M)(app)) of the BPEI-Fc/PEDOT:PSS/GOx/SPCE estimated by the Lineweaver–Burk plot is 2.4 mM, which is much lower than that of BPEI-Fc/GOx/SPCE (11.2 mM). This implies that the BPEI-Fc/PEDOT:PSS/GOx/SPCE can catalytically oxidize glucose in a more efficient way. The interference test was carried out by injection of glucose and three common interferences: ascorbic acid (AA), dopamine (DA), and uric acid (UA) at physiological levels. The interferences of DA (4.2%) and AA (7.8%) are acceptable and the current response to UA (1.6%) is negligible, compared to the current response to glucose.
Adam Heller - One of the best experts on this subject based on the ideXlab platform.
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enzyme amplified amperometric detection of hybridization and of a single base pair mutation in an 18 base oligonucleotide on a 7 mu m diameter microelectrode
In: Liron Z and Bromberg A and Fisher M (eds.) NOVEL APPROACHES IN BIOSENSORS AND RAPID DIAGNOSTIC ASSAYS. (pp. 79 - 100). KLUWER ACADEMIC PLENUM PUBL, 2001Co-Authors: Daren J Caruana, T De Lumleywoodyear, Adam HellerAbstract:A single base pair mismatch in an 18 base oligonucleotide was detected with a 7 mum diameter carbon microelectrode. The hybridization was followed directly and in real time by steady state amperometry. The microelectrode was coated with a hybridization-sensing layer in a two-step electrophoretic process, which yielded microelectrodes with reproducible dimensions. In the first step, a thin film of an electron-conducting Redox Polymer was deposited electrophoretically at constant potential in a low ionic strength solution. In the second step a carbodiimide activated single stranded probe was reactively electrophoretically deposited and covalently attached to the Redox Polymer film. The labeling enzyme, thermostable soybean peroxidase (SBP), was covalently bound to the 5'-end of the target single stranded oligonucleotide. When the Redox Polymer and the enzyme were brought to close proximity by hybridization of the target and probe oligonucleotides, the film on the electrode switched from being a non-catalyst to a catalyst for H2O2 electroreduction at -0.06 V vs. Ag/AgCl. The current observed corresponded to that generated by approximately 40,000 surface bound and electrically connected SBP molecules.
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enzyme amplified amperometric detection of hybridization and of a single base pair mutation in an 18 base oligonucleotide on a 7 µm diameter microelectrode
Journal of the American Chemical Society, 1999Co-Authors: Daren J Caruana, Adam HellerAbstract:A single base pair mismatch in an 18 base oligonucleotide was detected with a 7 µm diameter carbon microelectrode. The hybridization was followed directly and in real time by steady state amperometry. The microelectrode was coated with a hybridization-sensing layer in a two-step electrophoretic process, which yielded microelectrodes with reproducible dimensions. In the first step, a thin film of an electron-conducting Redox Polymer was deposited electrophoretically at constant potential in a low ionic strength solution. In the second step a carbodiimide activated single stranded probe was reactively electrophoretically deposited and covalently attached to the Redox Polymer film. The labeling enzyme, thermostable soybean peroxidase (SBP), was covalently bound to the 5’-end of the target single stranded oligonucleotide. When the Redox Polymer and the enzyme were brought to close proximity by hybridization of the target and probe oligonucleotides, the film on the electrode switched from being a non-catalyst to a catalyst for H2O2 electroreduction at -0.06 V vs. Ag/AgC1. The current observed corresponded to that generated by approximately 40,000 surface bound and electrically connected SBP molecules.
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polyacrylamide based Redox Polymer for connecting Redox centers of enzymes to electrodes
Analytical Chemistry, 1995Co-Authors: Thierry De Lumleywoodyear, Patrick Rocca, Jamie Lindsay, Yael Dror, Amihay Freeman, Adam HellerAbstract:Enzyme electrodes based on complexing a water-soluble coPolymer of acrylamide and vinylimidazole with [Os(dmebpy)2C1]+/2+ (dmebpy = 4,4'-dimethyl-2,2'-bipyridine) and cross-linking with oxidases by water-soluble cross-linkers are described. The potential of the polyacrylamide-based Redox Polymer is +55 mV (SCE), a typical electron diffusion coefficient (De) in the Redox hydrogel that results from its cross-linking is (1.3 +/- 0.1) x 10(-9) cm2/s. The properties of the enzyme electrodes formed when this Redox hydrogel "wired" horseradish peroxidase (HRP), lactate oxidase (LOx) or glucose oxidase (GOx) depended on the thickness of the hydrogel film, the chemistry of their cross-linking, and their enzyme content. At the wired HRP electrodes, H2O2 was electrocatalytically reduced to water at 0.0 V (SCE). Lactate and glucose were electrocatalytically oxidized at 0.16 V (SCE). The GOx electrodes, when made with 140 micrograms/cm2 thick Polymer films, were selective for glucose in the presence of physiological concentrations of urate and ascorbate.
