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排序方式: 共有1281条查询结果,搜索用时 31 毫秒
31.
The third generation amperometric biosensor for the determination of hydrogen peroxide (H2O2) has been described. For the fabrication of biosensor, o-aminobenzoic acid (oABA) was first electropolymerized on the surface of platinum (Pt) electrode as an electrostatic repulsion layer to reject interferences. Horseradish peroxidase (HRP) absorbed by nano-scaled particulate gold (nano-Au) was immobilized on the electrode modified with polymerized o-aminobenzoic acid (poABA) with L-cysteine as a linker to prepare a biosensor for the detection of H2O2. Amperometric detection of H2O2 was realized at a potential of +20 mV versus SCE. The resulting biosensor exhibited fast response, excellent reproducibility and sensibility, expanded linear range and low interferences. Temperature and pH dependence and stability of the sensor were investigated. The optimal sensor gave a linear response in the range of 2.99×10^-6 to 3.55×10^-3 mol·L^-1 to H2O2 with a sensibility of 0.0177 A·L^-1·mol^-1 and a detection limit (S/N = 3) of 4.3×10^-7 mol·L^-1. The biosensor demonstrated a 95% response within less than 10 s. 相似文献
32.
《Electroanalysis》2005,17(8):668-673
A self‐sampling‐and‐flow biosensor was fabricated by sandwiching a nitrocellulose strip on the working electrode side of the double‐sided microporous gold electrodes and a wicking pad on the counter electrode side. The double‐sided microporous electrodes were formed by plasma sputtering of gold on a porous nylon substrate. Sample was taken up to the enzyme‐immobilized working electrode by the capillary action of the front nitrocellulose strip dipped into the sample solution, analyzed electrochemically at the enzyme‐immobilized electrode, and diffuses out to the backside wicking pad through the micropores of the electrodes, constituting a complete flow cell device with no mechanical liquid‐transporting device. Biosensor was formed by co‐immobilizing the glucose oxidase and electron transfer mediator (ferrocene acetic acid) on the thioctic acid self‐assembled monolayer‐modified working electrode. A typical response time of the biosensor was about 5 min with the sensitivity of 2.98 nA/mM glucose, providing linear response up to 22.5 mM. To demonstrate the use of self‐sampling‐and‐flow biosensor, the consumption rate of glucose in the presence of yeast was monitored for five days. 相似文献
33.
This paper presents the construction of amperometric biosensors for the highly sensitive detection of carbamate insecticides based on the inhibition of acetylcholinesterase (AChE). This enzyme was immobilised by entrapment in an optimised sol-gel matrix on TCNQ-modified screen-printed electrodes. The enzyme activity was estimated by measuring the thiocholine produced by the enzymatic hydrolysis of the acetylthiocholine using TCNQ as mediator. Wild and genetically engineered AChEs from Drosophila melanogaster (Dm) were chosen for their high sensitivity towards insecticides, which substantially improves the LOD compared with cholinesterases from other sources. The wild type and three mutant enzymes were tested against three carbamate insecticides: carbaryl, carbofuran and pirimicard. The best LOD were obtained with the Y370A mutant for carbaryl (1 × 10−8 M), the E69W mutant for pirimicarb (2 × 10−8 M) and the I161V mutant for carbofuran (8 × 10−10 M). The biosensors were applied to the analysis of two potable water samples. 相似文献
34.
《Electroanalysis》2005,17(3):239-245
Oxygen dependence of a tyrosinase‐based electrochemical biosensor for determination of phenol in aqueous and organic media was systematically investigated. The result demonstrated that the enzymatic coupling reaction rate of tyrosinase (deoxy form) and O2 to regenerate tyrosinase (oxy form) is a kinetically fast reaction, and the significant change of O2 concentration in aqueous solution did not affect the coupling reaction. The further increase of O2 concentration did not increase the overall oxidation reaction rate of the substrate at low substrate concentration (e.g.,<10 μM phenol) when O2 concentration was greater than 8.9 ppm. The oxygen dependence was observed in the case of high substrate concentration due to insufficient amount of O2 available for the regeneration of tyrosinase. In other words, the upper linear range is oxygen dependent for tyrosinase biosensors. The phenol biosensors employing microelectrodes had wider upper linear ranges than macroelectrodes in both aqueous and organic phase, which can be explained by the oxygen dependence. 相似文献
35.
《Electroanalysis》2006,18(3):259-266
In this paper, a new strategy for constructing a mediator‐type amperometric hydrogen peroxide (H2O2) microbiosensor was described. An electropolymerized thionine film (PTH) was deposited directly onto a gold electrode surface. The resulting redox film was extremely thin, adhered well onto a substrate (electrode), and had a highly cross‐linked network structure. Consequently, horseradish peroxidase (HRP) was successfully immobilized on nanometer‐sized Au colloids, which were supported by thiol‐tailed groups of 11‐mercaptoundecanoic acid (11‐MUA) monolayer covalently bound onto PTH film. With the aid of the PTH mediator, HRP‐labeled Au colloids microbiosensor displayed excellent electrocatalytical response to the reduction of H2O2. This matrix showed a biocompatible microenvironment for retaining the native activity of the covalent HRP and a very low mass transport barrier to the substrate, which provided a fast amperometric response to H2O2. The proposed H2O2 microbiosensor exhibited linear range of 3.5 μM–0.7 mM with a detection limit of 0.05 μM (S/N=3). The response showed a Michaelis‐Menten behavior at larger H2O2 concentrations. The KMapp value for the biosensors based on 24 nm Au colloids was found to be 47 μM, which demonstrated that HRP immobilized on Au colloids exhibited a high affinity to H2O2 with no loss of enzymatic activity. This microbiosensor possessed good analytical performance and storage stability. 相似文献
36.
Fausto LucarelliGiovanna Marrazza Ilaria PalchettiS Cesaretti Marco Mascini 《Analytica chimica acta》2002,469(1):93-99
This paper describes a disposable indicator-free electrochemical DNA biosensor applied to the detection of apolipoprotein E (apoE) sequences in PCR samples. In the indicator-free assays, the duplex formation was detected by measuring the electrochemical signal of the guanine base of nucleic acids. The biosensor format involved the immobilisation of an inosine-modified (guanine-free) probe onto a screen-printed electrode (SPE) transducer and the detection of the duplex formation in connection with the square-wave voltammetric measurement of the oxidation peak of the guanine of the target sequence.The indicator-free scheme has been characterised using 23-mer oligonucleotides as model: parameters affecting the hybridisation assay such as probe immobilisation conditions, hybridisation time, use of hybridisation accelerators were examined and optimised.The analysis of PCR samples (244 bp DNA fragments, obtained by amplification of DNA extracted from human blood) required a further optimisation of the experimental procedure. In particular, a lower steric hyndrance of the probe modified surface was essential to allow an efficient hybridisation of the target DNA fragment. Negative controls have been performed using the PCR blank and amplicons unrelated to the immobilised probe. A 10 min hybridisation time allowed a full characterisation of each sample. 相似文献
37.
QinZHAO RuoYUAN ChangLiMO YaQinCHAI XiaZHONG 《中国化学快报》2004,15(2):208-211
Naphthol green B was used, for the first time, as a new mediator in an amperometric glucose biosensor. It is a good mediator, promoting electron transfer from glucose oxidase to graphite electrode. The biosensor shows high sensitivity to glucose at low potential with response time of 30 seconds. The linear range is from 1.5 to 18μmol/L glucose with detection limit of 0.5μmol/L glucose. 相似文献
38.
An electrochemical biosensor for the specific detection of short DNA sequences from the E. coli pathogen is described. This hybridization device relies on the immobilization of a 25-mer oligonucleotide probe, from the E. coli lacZ gene, onto a screen-printed carbon electrode. Chronopotentiometric detection of the Co(bpy)3+3 indicator is used for monitoring the hybridization event. Numerous variables of the assay protocol, including those of the probe immobilization step, the hybridization event, and the indicator association/detection, are characterized and optimized. Hybridization times of 2- and 30-min are sufficient for detecting 300- and 50 ng/mL, respectively, of the E. coli DNA target. Applicability to analysis of untreated environmental water samples is illustrated. Such single-use electrochemical sensors hold great promise for decentralized environmental and food testing for the E. coli pathogen. 相似文献
39.
Kagan Kerman Yasutaka Morita Yuzuru Takamura Mehmet Ozsoz Eiichi Tamiya 《Analytica chimica acta》2004,510(2):169-174
The unique binding event between Escherichia coli single-stranded DNA binding protein (SSB) and single-stranded oligonucleotides conjugated to gold (Au) nanoparticles is utilized for the electrochemical detection of DNA hybridization. SSB was attached onto a self-assembled monolayer (SAM) of single-stranded oligonucleotide modified Au nanoparticle, and the resulting Au-tagged SSB was used as the hybridization label. Changes in the Au oxidation signal was monitored upon binding of Au tagged SSB to probe and hybrid on the electrode surface. The amplified oxidation signal of Au nanoparticles provided a detection limit of 2.17 pM target DNA, which can be applied to genetic diagnosis applications. This work presented here has important implications with regard to combining a biological binding event between a protein and DNA with a solid transducer and metal nanoparticles. 相似文献
40.
IntroductionAmperometricbiosensorofhydrogenperoxideisofpracticalimportancebecauseofitswideapplicationsinchemical,biological,clinical,environmentalandmanyotherfields.Forimprovementofsensor抯quality,vari-ouskindsofchemicalmodificationmethodshavebeendevelopedforreducingredoxoverpotentialsofH2O2atelectrodesurfaces,increasingthedetectionsensitivity,linearrange,stabilityandlivetime.Ithasbeenshownthattheuseofsub-micrometersizedmetalparticlessuchasPt-blackcansignificantlyimprovethequalityofthebiosens… 相似文献