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ABSTRACT: An amperometric choline biosensor was developed by immobilizing choline oxidase (ChOx) in a layer-by-layer (LBL) multilayer film on a platinum (Pt) electrode modified with Prussian blue (PB). 6-O-Ethoxytrimethylammoniochitosan chloride (EACC) was used to prepare the ChOx LBL films. The choline biosensor was used at 0.0V versus Ag/AgCl to detect choline and exhibited good characteristics such as relative low detection limit (5x10(-7)M), short response time (within 10s), high sensitivity (88.6muAmM(-1)cm(-2)) and a good selectivity. The results were explained based on the ultrathin nature of the LBL films and the low operating potential that could be due to the efficient catalytic reduction of H(2)O(2) by PB. In addition, the effects of pH, temperature and applied potential on the amperometric response of choline biosensor were evaluated. The apparent Michaelis-Menten constant was found to be (0.083+/-0.001)x10(-3)M. The biosensor showed excellent long-term storage stability, which originates from a strong adsorption of ChOx in the EACC multilayer film. When the present choline biosensor was applied to the analysis of phosphatidylcholine in serum samples, the measurement values agreed satisfactorily with those by a hospital method.
Talanta 12/2006; 70(4):852-8. · 3.79 Impact Factor
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ABSTRACT: An acetylcholine (ACh) biosensor has been fabricated with bienzymes/poly(diallyldimethylammonium chloride) (PDDA) multilayer film-modified platinum (Pt) electrodes by a layer-by-layer technique (LBL). The ACh biosensor was optimized and the properties are described. This ACh biosensor was used for the detection of organophosphate pesticide trichlorfon. The detection limits (found 0.001 μg/mL for trichlorfon) make it possible to detect the pollutants. This simple protocol of biosensor preparation, high sensitivity and stability are very promising for the determination of environmental pollutants in field conditions.
Electroanalysis 05/2005; 17(14):1285 - 1290. · 2.87 Impact Factor
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ABSTRACT: Platinum nanoparticles (Ptnano) were used in combination with multi-walled carbon nanotubes (MWCNTs) for fabricating sensitivity-enhanced electrochemical l-lactate biosensor. The composite film of MWCNTs and Ptnano was dispersed on the surface of the glassy carbon electrode (GCE). l-lactate oxidase (LOD) was immobilized on MWCNTs/Ptnano/GCE surface by adsorption. The resulting LOD/MWCNTs/Ptnano electrode was covered by a thin layer of sol–gel to avoid the loss of LOD in determination and to improve the anti-interferent ability. Moreover, the sol–gel microenviroment contributes to both intensified stability and permselectivity. The cyclic voltammetry results indicated that MWCNTs/Ptnano catalyst displayed a higher performance than MWCNTs. Under the optimized conditions of applied potential 0.5 V, pH 6.4, room temperature, the proposed biosensor showed a large determination range (0.2–2.0 mM), a short response time (within 5 s), a high sensitivity (6.36 μA mM− 1) and good stability (90% remains after 4 weeks). The fabricated biosensor had practically good selectivity against interferences. The results for whole blood samples measured by the present biosensor showed a good agreement with those measured by spectrophotometric method.
Materials Science and Engineering: C. 28(7):1070-1075.
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ABSTRACT: A layer-by-layer deposition technique was employed for fabricating choline biosensors using chloline oxidase (ChOx) and polycations such as poly(ethyleneimine) (PEI) and poly(diallyldimethylammonium chloride) (PDDA). A platinum electrode was coated with ChOx/PEI or ChOx/PDDA thin film to prepare amperometric choline sensors. The amperometric response of the sensors depended significantly on the type of the polycations. The ChOx/PDDA film suppressed the permeation of choline, resulting in a lower response than that of the ChOx/PEI film-based sensors. The results were rationalized based on the different chemical structures of the polycationic materials.
Materials Science and Engineering: C. 25(4):433-435.
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ABSTRACT: The loading of multi-walled carbon nanotubes (MWNTs) and glucose oxidase (GOx) in the alternate layers of a glucose biosensor was first optimized based on a layer-by-layer construction on the surface of a graphite disk electrode. With the increasing of MWNTs/GOx layers, the response current to glucose was changed regularly and the response current reached a maximum value when the number of MWNTs/GOx layers was 6. Owing to a good electrical conductivity, strong adsorption and excellent bioconsistency of MWNTs, the (MWNTs/GOx)6 films-coated glucose biosensor had an excellent electrochemical properties. The response current of the (MWNTs/GOx)6 films-coated biosensor to 3 × 10− 2 M glucose was 1.63 μA while the response time was only 6.7 s. The linear range and the lowest detectable concentration of this biosensor was 5 × 10− 4∼1.5 × 10− 2 M and 0.9 × 10− 4 M, respectively.
Materials Science and Engineering: C.
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ABSTRACT: A new type of amperometric l-lactate biosensor based on silica sol-gel and multi-walled carbon nanotubes (MWCNTs) organic–inorganic hybrid composite material was developed. The sol-gel film was used to immobilize l-lactate oxidase on the surface of glassy carbon electrode (GCE). MWCNTs were used to increase the current response and improve the performance of biosensor. The sol-gel film fabrication process parameters such as H2O : TEOS and pH were optimized, Effects of some experimental variables such as applied potential, temperature, and pH on the current response of the biosensor were investigated. Analytical characteristics and dynamic parameters of the biosensors with and without MWCNTs in the hybrid film were compared, and the results showed that analytical performance of the biosensor could be improved greatly after introduction of the MWCNTs. Sensitivity, linear range, limit of detection (S / N = 3) were 2.097 μA mM− 1, 0.3 to 1.5 mM, 0.8 × 10− 3 mM for the biosensor without MWCNTs and 6.031 μA mM− 1, 0.2 to 2.0 mM, 0.3 × 10− 3 mM for the biosensor with MWCNTs, respectively. This method has been used to determine the l-lactate concentration in real human blood samples.
Materials Science and Engineering: C.
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ABSTRACT: A layer-by-layer deposition technique was employed for fabricating choline sensors with different polycations. We used two kinds of choline oxidase (ChOx)/polycation thin films to modify platinum (Pt) electrodes, each having the same enzyme (ChOx) but with different polycations, poly(ethyleneimine) (PEI) and poly(diallyldimethylammonium chloride) (PDDA). The Pt electrodes coated with a ChOx/PEI or ChOx/PDDA thin film were used successfully as choline sensors. The ChOx/PEI film-modified sensor showed a higher response, wider dynamic range and shorter response time than those of the ChOx/PDDA film-based sensor. The results were rationalized based on the different permeability of the thin films due to the different structure of the polycationic materials. The assembly processes of the thin films were monitored by quartz crystal microbalance (QCM) measurements.
Sensors and Actuators B: Chemical.
