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| 412(1-2) (2000), 29-35
A novel method based on plasma-polymerized films (PPFs) is proposed for immobilizing antibodies (antigens) through a polyelectrolyte-mediated layer. The immobilization of goat-anti- IgG antibody, as an example, is investigated. The n-butyl amine PPFs are deposited on the surfaces of quartz crystal microbalance (QCM) with a radio frequency plasma method using n- butyl amine as the precursor, the IR spectrum indicating the existence of amino-groups in the film. After self-assembling a polystyrenesulfonate (PSS) layer on the PPF, the goat-anti-IgG antibody is immobilized in a 0.2 mg ml(-1) of antibody immobilizing solution at pH 5.0. The QCM immunosensor can quantitatively determine NH IgG in the range of 0.7-126 mu g ml(-1). Moreover, the PSS and protein layers can easily be removed simply by shifting the pH, making the immunosensor regenerable. (C) 2000 Elsevier Science B.V. All rights reserved. [16] Layer-by-Layer Assembly of Multilayer Films Consisting of Silicotungstate and a Cationic Redox Polymer on 4-Aminobenzoic Acid Modified Glassy-Carbon Electrode and Their Electrocatalytic Effects L. Cheng, J. Y. Liu and S. J. Dong Anal. Chim. Acta. 417(2) (2000), 133-142 A novel 4-aminobenzoic acid (4-ABA) monolayer film is formed on glassy carbon electrode (GCE) by amino cation radical method. Silicotungstic heteropolyanion (SiW12O404-, denoted as SiW12)- containing multilayer films have been fabricated on the 4-ABA modified GCE surface by alternate deposition with a quaternized poly(4-vinylpyridine) partially complexed with [Os(bpy)(2)Cl](2+/+) (denoted as QPVP-Os). Cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS) and X-ray reflectivity (XR) have been used to characterise the as- prepared multilayer films. It is proved that the multilayer films are uniform and stable. The average thickness for a bilayer of QPVP-Os/SiW12 in the multilayer film is 30.2 Angstrom. The electrocatalytic activities of the multilayer films have been investigated on the reduction of three substrates of important analytical interests, HNO2, BrO3- and H2O2. Especially, the influence of layer number of the multilayer films on the electrocatalytic reduction of HNO2 has been investigated in detail. (C) 2000 Elsevier Science B.V. All rights reserved. [17] Fabrication of Multilayer Films Containing Horseradish- Peroxidase and Polycation-Bearing Os Complex by Means of Electrostatic Layer-by-Layer Adsorption and Its Application as a Hydrogen-Peroxide Sensor W. J. Li, Z. Wang, C. Q. Sun, M. Xian and M. Y. Zhao Anal. Chim. Acta. 418(2) (2000), 225-232 Layer-by-layer (LBL) assembled multilayer films were obtained on the surface of quartz slides and gold electrode by alternating deposition of negatively charged horseradish peroxidase (HRP) and quaternized poly(4-vinylpyridine) complexed of (Os(bpy)(2)Cl)(+/2+) (PVP-Os). The assembly process was monitored by UV-VIS spectroscopy. The electrochemical behavior of the enzyme electrode showed that multilayer films containing the enzyme and the redox polymer were highly stable. Mediator PVP-Os in the multilayer films as electron shuttle was able to transfer electrons successfully between the active center of the immobilized HRP and the electrode surface. The enzyme electrode of multilayer films was sensitive for the electrocatalytic reduction of hydrogen peroxide and can be used as amperometric sensors for hydrogen peroxide. (C) 2000 Elsevier Science B.V. All rights reserved. [18] Polyelectrolyte Multilayer Film-Coated Electrodes for Amperometric Determination of Hydrogen-Peroxide in the Presence of Ascorbic-Acid, Uric-Acid and Acetaminophen T. Hoshi, H. Saiki, S. Kuwazawa, Y. Kobayashi and J. Anzai Anal. Sci. 16(10) (2000), 1009-1010 [19] Probing Protein-Peptide-Protein Molecular Architecture by Atomic-Force Microscopy and Surface-Plasmon Resonance M. M. Stevens, S. Allen, W. C. Chan, M. C. Davies, C. J. Roberts, S. J. B. Tendler and P. M. Williams Analyst 125(2) (2000), 245-250
[20] Synthesis of Geometrically Well-Defined, Molecularly Thin Polymer-Films W. T. S. Huck, A. D. Stroock and G. M. Whitesides Angew. Chem., Int. Ed. Engl. 39(6) (2000), 1058 [21] Stepwise Assembled Photoactive Films Containing Donor-Linked Fullerenes C. P. Luo, D. M. Guldi, M. Maggini, E. Menna, S. Mondini, N. A. Kotov and M. Prato Angew. Chem., Int. Ed. Engl. 39(21) (2000), 3905 [22] Photovoltaic Heterostructure Devices Made of Sequentially Adsorbed Poly(Phenylene Vinylene) and Functionalized C-60 H. Mattoussi, M. F. Rubner, F. Zhou, J. Kumar, S. K. Tripathy and L. Y. Chiang Appl. Phys. Lett. 77(10) (2000), 1540-1542 We report on the preparation and characterization of rectifying photovoltaic heterostructure devices made of poly(phenylene vinylene), PPV, and C-60. The heterojunctions were built from solution using the technique of layer-by-layer sequential adsorption. This technique permits one to control the heterostructure at the molecular scale. Upon illumination with a laser beam, the devices showed large photoresponses (current and voltage) that resulted from a photoinduced electron transfer between the PPV (donor layer) and the C-60 (acceptor layer). The photocurrent was found to increase with the laser power and with the photon energy of the incident radiation. Also, a constant high photovoltage response of similar to 700- 800 mV was measured. Analysis of the time dependence of the photocurrent rise and decay, when the device was illuminated with a modulated square wave signal (chopped laser beam), permitted us to draw an analogy between the present heterojunction and a circuit made of a capacitor and a resistance in series. (C) 2000 American Institute of Physics. [S0003-6951(00)03236-8]. [23] Optical-Properties of Self-Assembled Thin-Film of Poly(P- Phenylene Vinylene)S and Its Application to Light-Emitting Devices with Microring Geometry T. Sonoda, T. Fujisawa, A. Fujii and K. Yoshino Appl. Phys. Lett. 76(22) (2000), 3227-3229 Periodic multilayer structures of poly(p-phenylene vinylene)s have been fabricated by a self-assembly method on flat surfaces and round surfaces of optical fibers. Alternating multilayers consisting of poly{1,4-[2-(5-carboxypentyloxy)-5- methoxyphenylene]vinylene} (CPMOPPV) and poly(p-phenylene vinylene) (PPV) were adsorbed onto the positively charged substrates. The optical properties of the periodic multilayer structures of CPMOPPV/PPV have been studied. Periodic multilayers with microring geometry have also been fabricated around the quartz fibers. Their optical properties have been studied, and yellow electroluminescence from a light-emitting device with microring geometry has been observed. (C) 2000 American Institute of Physics. [S0003-6951(00)03822-5]. [24] Surface-Relief Gratings from Electrostatically Layered Azo-Dye Films J. A. He, S. P. Bian, L. Li, J. Kumar, S. K. Tripathy and L. A. Samuelson Appl. Phys. Lett. 76(22) (2000), 3233-3235 Surface relief gratings (SRGs) were fabricated on composite films assembled by alternate electrostatic deposition of a polyelectrolyte, poly(dimethyldiallylammonium chloride), and an organic azo dye, congo red. The modulation of SRGs was found to increase with the thickness of the matrix films. Significant photochemical bleaching of the azo dye in the polymeric microenvironment as well as gradient-force-induced migration of the small azo dye contributes to the formation of the SRG structure. This finding demonstrates a facile method to fabricate SRGs for optical and information storage applications using commercially available azo dyes and polyelectrolytes. (C) 2000 American Institute of Physics. [S0003-6951(00)04922-6]. [25] Conformational State and Molecular Ionic Transformations of Polycytidyl Acid Immobilized in Multilayer Langmuir and Polyelectrolyte Films B. I. Sukhorukov, G. B. Sukhorukov, L. I. Shabarchina and M. M. Montrel Biofizika 45(1) (2000), 40-50 Multilayer films of complexes of polycytidylic acid with dioctadecyldimetylammonium were obtained by the Langmuir- Blodgett method (LB films), and complexes of poly(C) with polycations (poly-L-lysisne, polyethyleneimine, polyallylamine) were obtained by the method of alternate adsorption (polyionic assembly) from solutions of oppositely charged polyelectrolytes on the solid carrier (SA films). It was shown that poly(C) exists in SA films in a single-stranded state irrespective of whether in the starting solution it occurred in the single- stranded nonprotonated or double-stranded protonated conformation. Conversely, in the LB film poly(C) preferred to be in a double protonated conformation. UV-spectra of water- insoluble LB and SA films at different pH values of surrounding water medium were investigated. Proton titration curves of poly(C) immobilized in LB films were obtained. The analysis of the shape of titration curves showed that the molecular-ionic transformation of poly(C) in LB films is accompanied by both the conformational transition of the polynucleotide and the molecular rearrangement in the whole film. Poly(C) was found to transform from the double- to single-stranded state and vice versa in the < > in SA films occurred without conformational transitions of the polynucleotide. As opposed to poly(C) in solution a rather big hysteresis of forward and back titration curves was found for both types of multilayer films, indicating molecular rearrangements in films. The reason for the structural transformations of poly(C) upon fabrication of LB or SA films and the mechanism of molecular ionic transformations of poly(C) in films art: discussed ill terms of a simple model of ion exchange. An assumption about the nature of structural transformations of LB and SA films during their protonation- deprotonation is put forward. [26] Effect of Media Composition on Long-Term in-Vitro Stability of Barium Alginate and Polyacrylic-Acid Multilayer Microcapsules A. Gaumann, M. Laudes, B. Jacob, R. Pommersheim, C. Laue, W. Vogt and J. Schrezenmeir Biomaterials 21(18) (2000), 1911-1917 For a number of applications stability of microcapsules is a critical factor. Since the maintenance of polyelectrolyte complexes depends considerably on the ion composition we tested the physical properties of barium alginate capsules and searched for conditions to improve stability by a multilayer coating with polyethylenimine (PEI) and polyacrylic acid (PAA). Mechanical stability and diameters were determined in barium alginate capsules and compared with multilayer capsules. Multilayer coating resulted in smaller capsules than barium complexing alone. The difference was more pronounced when CaCl2 was used instead of NaCl during coating. Barium alginate capsules and application of CaCl2 during coating led to continuous pressure profiles, whereas NaCl resulted in bursting at a defined pressure, indicating the additional contribution to mechanical stability by the outer layers. After 7 d culture: mechanical stability of coated capsules decreased in RPMI and NaCl but was most pronounced in sodium citrate. The capsule diameter increased in sodium citrate, less pronounced in NaCl and was significantly different to RPMI and double distilled water. During long-term culture in RPMI, the diameter increased and mechanical stability decreased significantly, Multilayer coating improved mechanical stability which was impeded most in sodium citrate, to a lesser extent by NaCl and RPMI even after long-term exposure. (C) 2000 Elsevier Science Ltd, All rights reserved. [27] Reagentless Biosensors Based on Self-Deposited Redox Polyelectrolyte-Oxidoreductases Architectures A. Narvaez, G. Suarez, I. C. Popescu, I. Katakis and E. Dominguez Biosensors and Bioelectronics 15(1-2) (2000), 43-52 Reagentless fructose and alcohol biosensors have been produced with a versatile enzyme immobilisation technique which mimics natural interactions and flexibility of living systems. The electrode architecture is built up on electrostatic interactions by the sequential adsorption of redox polyelectrolytes and redox enzymes giving rise to the efficient transformation of substrate fluxes into electrocatalytic currents. All investigated multilayer structures were self- deposited on 3-mercapto-1-propanesulfonic acid monolayers self- assembled on gold electrodes. Fructose dehydrogenase, horseradish peroxidase (HRP) and the couple HRP-alcohol oxidase were electrochemically connected with a cationic poly[(vinylpyridine)Os(bpy)(2)Cl] redox polymer (RP) interface in a layer-by-layer self-deposited architecture. The dependence of the distance on the electrochemical response of this interface was also studied showing a clear decrease in the Faradaic current when the distance to the electrode surface was increased. The sensitivities obtained for each biosensor were 19.3, 58.1 and 10.6 mA M-1 cm(-1) for fructose, H2O2 and methanol, respectively. The sensitivity values can be easily controlled by a rational deposition and manipulation of the charge in the catalytic layers. The electrostatic assembly of the electrochemical interface and the catalytic layers resulted in integrated biochemical systems in which mass transfer diffusion and heterogeneous catalytic and electron transfer steps are efficiently coupled and can be easily manipulated. (C) 2000 Elsevier Science S.A. All rights reserved. [28] Construction of Multicomponent Catalytic Films Based on Avidin- Biotin Technology for the Electroenzymatic Oxidation of Molecular-Hydrogen A. L. Delacey, M. Detcheverry, J. Moiroux and C. Bourdillon Biotechn. Bioeng. 68(1) (2000), 1-10 Two methods based on the avidin-biotin technology were developed for the multimonolayer immobilization of Desulfovibrio gigas hydrogenase on glassy carbon or gold electrodes. In both methods the molecular structure of the modified interface was the result of a step-by-step process. The first method alternates monolayers of avidin and biotinylated hydrogenase, the mediator (methyl viologen) being free to diffuse in the structure. In the second method, the avidin monolayers were used to immobilize both the biotinylated enzyme and a long-chain biotinylated viologen derivative. The viologen head of this hydrophilic arm shuttles the electrons between the electrode and the enzyme. The modified electrodes were evaluated for the electroenzymatic oxidation of molecular hydrogen, which has interest for the development of enzymatic fuel cells. The parameters that affect the current density of mediated oxidation of H-2 at the modified electrodes was studied. The second structure, which has given typical catalytic currents of 25 mu A per cm(2) for 10 monolayers, was found clearly less efficient than the first structure (500 mu A per cm(2) for 10 monolayers). In both methods the catalytic currents increased linearly with the number of monolayers of hydrogenase immobilized, which indicates that the multilayer structures are spatially ordered. (C) 2000 John Wiley & Sons, Inc. [29] Polyelectrolyte Adsorption D. Andelman and J. F. Joanny C. R. Acad. Sci. Ser. IV, Phys. Astr. 1(9) (2000), 1153-1162 The problem of charged polymer chains (polyelectrolytes) as they adsorb on a planar surface is addressed theoretically. We review the basic mechanisms and theory underlying polyelectrolyte adsorption on a single surface in two situations: adsorption of a single charged chain, and adsorption from a bulk solution in theta solvent conditions. The behavior of flexible and semi-rigid chains is discussed separately and is expressed as function of the polymer and surface charges, ionic strength of the solution and polymer bulk concentration. We mainly review mean-field results and briefly comment about fluctuation effects. The phenomenon of polyelectrolyte adsorption on a planar surface as presented here is of relevance to the stabilization of colloidal suspensions. In this respect we also mention calculations of the inter-plate force between two planar surfaces in presence of polyelectrolyte. Finally, we comment on the problem of charge overcompensation and its implication to multi-layers formation of alternating positive and negative polyelectrolytes on planar surfaces and colloidal particles. (C) 2000 Academie des sciences/Editions scientifiques et medicales Elsevier SAS. [30] Oxidation-Induced Variation in Polyelectrolyte Multilayers Prepared from Sulfonated Self-Dopable Poly(Alkoxythiophene) J. Lukkari, A. Viinikanoja, J. Paukkunen, M. Salomaki, M. Janhonen, T. Aaritalo and J. Kankare J. Chem. Soc., Chem. Commun. Iss 7 (2000), 571-572 Polyelectrolyte multilayers have been prepared using both the neutral and oxidised forms of a poly(alkoxythiophene) derivative with pendant sulfonate groups and it is shown that the oxidation state of the polymer affects multilayer formation. [31] Self-Assembly of Freebase-Tetrapyridylporphyrins and Metalated- Tetrapyridylporphyrins to Modified Gold Surfaces C. V. K. Sharma, G. A. Broker, G. J. Szulczewski and R. D. Rogers J. Chem. Soc., Chem. Commun. Yüklə 0,52 Mb. Dostları ilə paylaş:
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