| 1. |
- Albers, WM, et al.
(författare)
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Design of novel molecular wires for realizing long-distance electron transfer
- 1997
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Ingår i: Bioelectrochemistry and bioenergetics (Print). - : ELSEVIER SCIENCE SA LAUSANNE. - 0302-4598 .- 1872-8049. ; 42:1, s. 25-33
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Tidskriftsartikel (refereegranskat)abstract
- Novel heteroarene oligomers, consisting of two pyridinium groups, linked by thiophene units of variable length, thienoviologens, are described as promising candidates for molecular wires. Two representative thienoviologens were coated by adsorption from micromolar concentrations in ethanol onto octadecylmercaptan (ODM)-coated gold electrodes and induced a gradual restoration of the electrochemistry with hexacyanoferrate as a function of molecular wire concentration. Glucose oxidase and choline oxidase showed strong adsorption to these conductive layers, but showed striking differences in adsorption to the different thienoviologen layers. The measurements support the hypothesis that the molecules are incorporated in the ODM layer in a different fashion. Also the complex formation of an engineered azurin redox protein with water-soluble pyridyl ligands is presented in relation to a possible application of the thienoviologens as conductive spacers, in which the contact with the redox protein is achieved via complex formation with a free pyridine nitrogen. (C) 1997 Elsevier Science S.A.
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| 2. |
- CAGNINI, A, et al.
(författare)
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DISPOSABLE RUTHENIZED SCREEN-PRINTED BIOSENSORS FOR PESTICIDES MONITORING
- 1995
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier Science B.V., Amsterdam.. - 0925-4005 .- 1873-3077. ; 24:03-jan, s. 85-89
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Tidskriftsartikel (refereegranskat)abstract
- A disposable choline biosensor based on ruthenized carbon screen-printed electrodes has been prepared and its use for monitoring organophosphorus pesticides and carbamates is described. The presence of 0.5% ruthenium on activated carbon mixed to form a simple graphite-based ink for the working electrode surface increased the sensitivity towards hydrogen peroxide. The choline biosensor is based on such an electrode coupled with choline oxidase immobilized by adsorption. The inhibition effect of carbamates and organophosphorus pesticides on acetylcholinesterase was detected using this biosensor. With the optimized procedure described (pH, buffer composition, incubation time, substrate concentration) we are able to detect concentrations of pesticides (carbofuran) as low as 1 nM.
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| 3. |
- Cagnini, A, et al.
(författare)
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Ruthenized screen-printed choline oxidase-based biosensors for measurement of anticholinesterase activity
- 1995
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Ingår i: Microchimica Acta. - : Springer Science Business Media. - 0026-3672 .- 1436-5073. ; 121:04-jan, s. 155-166
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Tidskriftsartikel (refereegranskat)abstract
- Plastic disposable choline biosensors based on ruthenized-carbon screen-printed electrodes were prepared and their use for monitoring organophosphorus pesticides and carbamates is described. The presence of 0.5% ruthenium on activated carbon mixed to form a simple graphite-based ink for the working electrode surface increased the sensitivity towards hydrogen peroxide. The choline biosensor is based on such an electrode coupled with choline oxidase immobilized by adsorption and was used to detect the inhibition effect of carbamates and organophosphorus pesticides on acetylcholinesterase. With the optimized procedure described (pH, buffer composition, incubation time, substrate concentration), concentrations of pesticides (Carbofuran) as low as 1 nM could be detected.
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| 4. |
- Chen, B, et al.
(författare)
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The synthesis and screening of a combinatorial peptide library for affinity ligands for glycosylated haemoglobin
- 1998
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Ingår i: Biosensors & bioelectronics. - : Elsevier Science B.V., Amsterdam.. - 0956-5663 .- 1873-4235. ; 13:08-jul, s. 779-785
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports the synthesis and screening of a combinatorial peptide library for new affinity ligands for glycosylated haemoglobin (HbA(1c)), which is an important indicator of diabetes control. The new ligands are suitable for large-scale synthesis and overcome the disadvantages of antibodies (unstable and expensive to produce etc.), while remaining as efficient as antibodies in binding to the analyte. The library consisted of 262 144 hexapeptides synthesised using the one-bead-one-compound technique. The hexapeptides attached onto beads were screened with glycosylated haemoglobin HbA(1c). The structures of the peptides exhibiting high affinity were characterised by Edman microsequencing. Computer modelling simulation of one of the lead sequences has shown that this class of ligand has a high affinity and specificity for glycosylated haemoglobin. (C) 1998 Elsevier Science S.A. All rights reserved.
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| 5. |
- Dennison, MJ, et al.
(författare)
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Direct monitoring of formaldehyde vapour and detection of ethanol vapour using dehydrogenase-based biosensors
- 1996
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Ingår i: The Analyst. - : Royal Society of Chemistry. - 0003-2654 .- 1364-5528. ; 121:12, s. 1769-1773
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Tidskriftsartikel (refereegranskat)abstract
- Biosensors capable of directly detecting low levels of formaldehyde and ethanol vapour were constructed, Both biosensors are based on dehydrogenase enzymes which produce reduced nicotinamide adenine dinucleotide as part of the oxidation of formaldehyde and ethanol, The enzymes were immobilized in a reverse micelle medium which did not dehydrate significantly over time, and allowed direct gas-phase monitoring, A screen-printed electrode was used as transducer. Formaldehyde and ethanol vapour partitioned into the reverse micelle media, where it was acted upon by the relevant enzyme, Reduced nicotinamide adenine dinucleotide was oxidized at the working electrode at a potential of 800 mV versus an Ag/AgCl reference electrode, Formaldehyde could be measured over the concentration range 1 ppb-1.3 ppm and ethanol could be detected over the range 50-250 ppm.
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| 6. |
- DENNISON, MJ, et al.
(författare)
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GAS-PHASE MICROBIOSENSOR FOR MONITORING PHENOL VAPOR AT PPB LEVELS
- 1995
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Ingår i: Analytical Chemistry. - : ACS American Chemical Society. - 0003-2700 .- 1520-6882. ; 67:21, s. 3922-3927
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Tidskriftsartikel (refereegranskat)abstract
- A microbiosensor capable of measuring very low levels of phenol vapor directly in the gas phase has been constructed. The microbiosensor is based on the enzyme polyphenol oxidase, which catalyzes the oxidation of phenols to catechols and then to quinones, Polyphenol oxidase was immobilized in a glycerol-based gel which did not dehydrate significantly over time. An interdigitated microelectrode array was used as transducer. Phenol vapor partitioned into the glycerol gel, where it was enzymatically oxidized to quinone. Signal amplification was achieved by redox recycling of the quinone/catechol couple, This redox recycling produced a biosensor capable of measuring phenol vapor concentrations of 30 ppb. The biosensor produced a constant signal after 5 days of continuous use at room temperature and has potential application in the held of health and safety monitoring, where its ease of use, selectivity, and realtime monitoring would provide personnel with accurate data.
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| 7. |
- Hart, AL, et al.
(författare)
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On the use of screen- and ink-jet printing to produce amperometric enzyme electrodes for lactate
- 1996
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Ingår i: Biosensors & bioelectronics. - : Elsevier Science B.V., Amsterdam.. - 0956-5663 .- 1873-4235. ; 11:3, s. 263-270
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Tidskriftsartikel (refereegranskat)abstract
- Prototype electrochemical lactate electrodes based on lactate oxidase were produced by screen-printing and application of membranes by dip-coating or ink-jet printing. The link between enzyme and electrode was made by electro-deposition of platinum onto graphite pads. The linear range of the sensors was small; up to 2 mM lactate. Electrodes retained their activity when stored dry; activity remained high for 244 days. The properties of the electrodes indicate that screen- and ink-jet printing are feasible techniques for the machine production of lactate sensors.
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| 8. |
- Hobson, NS, et al.
(författare)
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Microbial detection
- 1996
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Ingår i: Biosensors & bioelectronics. - : Elsevier Science B.V., Amsterdam.. - 0956-5663 .- 1873-4235. ; 11:5, s. 455-477
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Forskningsöversikt (refereegranskat)abstract
- There is a widespread need for commercial instrumentation for the rapid and inexpensive detection of microbial contamination of food, industrial waste water and clinical samples. A large number of detection methods have been developed utilizing the optical, electrochemical, biochemical and physical properties of microorganisms. The need for a device which can produce a rapid, accurate, sensitive, real-time analysis for clinical, industrial and environmental applications has led to considerable progress being achieved in recent years in the development of biosensors for microbial detection. This intense research has resulted in the commercialization of several instruments. Techniques used for the quantification of microorganisms are reviewed under the general categories of non-bioelectrochemical and bioelectrochemical methods.
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| 9. |
- Jaffari, SA, et al.
(författare)
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Novel hexacyanoferrate(III) modified graphite disc electrodes and their application in enzyme electrodes .1.
- 1997
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Ingår i: Biosensors & bioelectronics. - : Elsevier Science B.V., Amsterdam.. - 0956-5663 .- 1873-4235. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- We report a novel procedure for the electrochemical modification of graphite disc electrodes with potassium hexacyanoferrate(III) using cyclic voltammetry. Cyclic voltammograms of the modified electrodes in 0.1 M potassium chloride showed two redox couples, at 0.22 and 0.148V and at 0.923 and 0.798 V. These redox potentials correspond to those cited for Prussian blue type films. These modified electrodes exhibited excellent stability during repeated potential cycling in 0.1 M potassium chloride with no difference in peak heights between the second and thirtieth scans. We used glucose oxidase as the model enzyme to investigate application of these novel modified graphite disc electrodes in the development of biosensors. The resulting glucose sensors exhibited a response to glucose at potentials as low as 450 mV vs. saturated calomel electrode with a linear range up to 1.5 mM glucose and sensitivity of 50 +/- 10 nA mM(-1) cm(-2) (geometric area). The modified graphite disc electrodes displayed an electrocatalytic effect on hydrogen peroxide with sensitivity of 0.70 mu A mM(-1) cm(-2) (geometric area). The effect of ascorbic acid, 4-acetamidophenol and uric acid, common interferents found in blood, is also reported. (C) 1996 Published by Elsevier Science Limited
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| 10. |
- JAFFARI, SA, et al.
(författare)
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RECENT ADVANCES IN AMPEROMETRIC GLUCOSE BIOSENSORS FOR IN-VIVO MONITORING
- 1995
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Ingår i: Physiological Measurement. - : Iop Publishing. - 0967-3334 .- 1361-6579. ; 16:1
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Forskningsöversikt (refereegranskat)abstract
- Electrochemical biosensors for glucose, based on the specific glucose oxidizing enzyme glucose oxidase, have generated considerable interest. Several commercial devices based on this principle have been developed and are widely used for in vitro monitoring of glucose e.g. in hospitals, doctors surgeries and for home monitoring by patients themselves. A significant advance in the application of biosensor technology would be the development of portable, implantable sensors which could continuously indicate the blood glucose concentration, enabling swift corrective action to be taken by the patient. This review highlights recent developments in amperometric glucose biosensors for in vivo monitoring and also considers the remaining barriers which need to be overcome to enable successful introduction of an implantable sensor.
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