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| 2. |
- Hansson, Kenny, 1972-, et al.
(författare)
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Surface plasmon resonance (SPR) analysis of coagulation in whole blood with application in prothrombin time assay
- 1999
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Ingår i: Biosensors & bioelectronics. - 0956-5663 .- 1873-4235. ; 14:8-9, s. 671-682
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Tidskriftsartikel (refereegranskat)abstract
- It is previously shown that surface plasmon resonance (SPR) can be used to study blood plasma coagulation. This work explores the use of this technique for the analysis of tissue factor induced coagulation, i.e. prothrombin time (PT) analysis, of whole blood and plasma. The reference method was nephelometry. The prothrombin time analysis by SPR was performed by mixing two volumes of blood/plasma, one volume of thromboplastin, and one volume of CaCl2 solution directly on a sensor surface. The measurements show good agreement between nephelometry and SPR plasma analysis and also between SPR plasma and whole blood analysis. The effect of anticoagulant treatment on the clotting times was significant both quantitatively and qualitatively. The impact on the SPR signal of different physiological events in the coagulation process is discussed, and tentative interpretations of the sensorgram features are given. The major advantage of the SPR method compared to nephelometry is the possibility to perform analysis on whole blood instead of plasma. In conclusion, SPR is a promising method for whole blood coagulation analysis.
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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- 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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| 7. |
- LOUGHRAN, MG, et al.
(författare)
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AMPEROMETRIC DETECTION OF HISTAMINE AT A QUINOPROTEIN DEHYDROGENASE ENZYME ELECTRODE
- 1995
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Ingår i: Biosensors & bioelectronics. - : Elsevier Science B.V., Amsterdam.. - 0956-5663 .- 1873-4235. ; 10:07-jun, s. 569-576
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Tidskriftsartikel (refereegranskat)abstract
- Methylamine dehydrogenase, a tryptophan tryptophyl quinone (TTQ) containing quinoprotein, catalyzes the oxidation of a variety of primary aliphatic monoamines and diamines to their respective aldehydes and ammonia. This paper reports the construction and characterization of an enzyme electrode capable of detecting histamine and methylamine at +200 mV versus a saturated calomel reference electrode. The methylamine dehydrogenase isolated from Paracoccus denitrificans was used in conjunction with the insoluble mediator tetracyanoquinodimethane (TCNQ) to construct enzyme electrodes which will potentially provide simple rapid analysis of histamine without the need for the extensive sample pretreatments currently required in HPLC and GLC analysis. The linear response of this amperometric sensor, between 0 and 200 mu M, correlates well with elevated histamine levels predominant in patients with chronic myelogenous leukaemia, whilst the observed limit of detection, 4.8 mu M, compares favourably with the lower limits of detection reported for a potentiometric histamine sensitive enzyme electrode.
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| 8. |
- SAINI, S, et al.
(författare)
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PRELIMINARY INVESTIGATION OF A BIOELECTROCHEMICAL SENSOR FOR THE DETECTION OF PHENOL VAPORS
- 1995
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Ingår i: Biosensors & bioelectronics. - : Elsevier Science B.V., Amsterdam.. - 0956-5663 .- 1873-4235. ; 10:10-sep, s. 945-957
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Tidskriftsartikel (refereegranskat)abstract
- This work investigates the feasibility of constructing a bioelectrochemical sensor that can operate directly in gases. A series of experiments are described, resulting in a sensor that is responsive to phenol vapours. The sensor was based on ionically conducting films that incorporate a biological redox catalyst at the surface of an array of interdigitated microband electrodes. Exposure to phenol vapour drives the bioelectrochemical reaction, providing a basis for a current signal under constant potential conditions. Ionic materials included Nafion and films based on tetrabutylammonium toluene-4-sulphonate (TEATS). The quasi-reversible electrode reaction of potassium hexacyanoferrate (II) within TEATS was investigated as a function of drying time. E(0) and k(0) were determined at a TEATS modified microdisc electrode under steady-state conditions. Drying time (water loss) from the TEATS film had the effect of increasing the film ionic strength. It was shown that as the film ionic strength increased, E(0) for potassium hexacyanoferrate (II) shifts toward positive potentials (because of ion pairing) and there was a corresponding increase in the heterogeneous rate constant, k(0). The latter effect was attributed to increasing ion-ion (cation-ferrocyanide ion) interactions as the film dried and the enhancing effect this had on the prevention of surface poisoning reactions at the electrode. These factors are discussed in relation to sensor design.
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| 9. |
- Siegel, G, et al.
(författare)
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Anionic biopolymers as blood flow sensors
- 1996
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Ingår i: Biosensors & bioelectronics. - 0956-5663 .- 1873-4235. ; 11, s. 281-294
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Tidskriftsartikel (refereegranskat)abstract
- The finding of flow-dependent vasodilatation rests on the basic observation that with an increase in blood flow the vessels become wider, with a decrease the vascular smooth muscle cells contract. Proteoheparan sulphate could be the sensor macromolecule at the endothelial cell membrane-blood interface, that reacts on the shear stress generated by the flowing blood, and that informs and regulates the vascular smooth muscle cells via a signal transduction chain. This anionic biopolyelectrolyte possesses viscoelastic and specific ion binding properties which allow a change of its configuration in dependence on shear stress and electrostatic charge density. The blood flow sensor undergoes a conformational transition from a random coil to an extended filamentous state with increasing flow, whereby Na+ ions from the blood are bound. Owing to the intramolecular elastic recoil forces of proteoheparan sulphate the slowing of a flow rate causes an entropic coiling the expulsion of Na+ ions and thus an interruption of the signal chain. Under physiological conditions, the conformation and Na+ binding proved to be extremely Ca2+-sensitive while K+ and Mg2+ ions play a minor role for the susceptibility of the sensor. Via counterion migration of the bound Na+ ions along the sensor glycosaminoglycan side chains and following Na+ passage through an unspecific ion channel in the endothelial cell membrane, the signal transduction chain leads to a membrane depolarization with Ca2+ influx into the cells. This stimulates the EDRF/NO production and release from the endothelial cells. The consequence is vasodilatation.
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| 10. |
- Skuridin, SG, et al.
(författare)
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A new approach for creating double-stranded DNA biosensors
- 1996
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Ingår i: Biosensors & bioelectronics. - : Elsevier Science B.V., Amsterdam.. - 0956-5663 .- 1873-4235. ; 11:9, s. 903-911
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Tidskriftsartikel (refereegranskat)abstract
- The principle of sandwich-type biosensors based on liquid-crystalline dispersions formed from [DNA-polycation] complexes is outlined. These biosensors will find application in the determination of a range of compounds and physical factors that affect the ability of a given polycationic molecule to maintain intermolecular crosslinks between neighbouring DNA molecules. In the case of liquid-crystalline dispersions formed from [DNA-protamine] complexes the lowest concentration of hydrolytic enzyme (trypsin) detectable was approximate to-10(-14) M. (C) 1996 Elsevier Science Limited.
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