| 1. |
- Palleschi, G., et al.
(author)
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Amperometric tetrathiafulvalene-mediated lactate electrode using lactate oxidase absorbed on carbon foil
- 1990
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In: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 234:2, s. 459-463
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Journal article (other academic/artistic)abstract
- The features of a new sensor for determining l-lactate are reported. The enzyme lactate oxidase and the mediator, tetrathiafulvalene (TTF), are absorbed on carbon foil disks previously bonded onto the ends of glass tubes. Linear calibration graphs were obtained in the range 10−4−10−3 M with physiological phosphate buffer (pH 7.35) and at 30°C with a response time of a few seconds. Calibration graphs in the range 10−3−10−2 M were also obtained and the difference in response times between these two ranges were investigated. The results are promising for assembling disposable lactate sensors for in vitro or for in or ex vivo measurements.
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| 2. |
- Sandberg Hiltunen, Maria, 1966-
(author)
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DNA and peptide sequences and chemical processes multivariately modelled by principal component analysis and partial least-squares projections to latent structures
- 1993
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In: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 277, s. 239-253
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Journal article (peer-reviewed)abstract
- Biopolymer sequences (e.g., DNA, RNA, proteins and polysaccharides) and chemical processes (e.g., a batch or continuous polymer synthesis run in a chemical plant) have close similarities from the modelling point of view. When a set of sequences or processes is characterized by multivariate data, a three-way data matrix is obtained. With sequences the position and with processes the time is one direction in this matrix. The multivariate modelling of this matrix by principal component analysis (PCA) or partial least-squares (PLS) methods for the following purposes is discussed: classification of sequences; quantitative relationships between sequence and biological activity or chemical properties; optimizing a sequence with respect to selected properties; process diagnostics; and quantitative relationships between process variables and product quality variables. To obtain good models, a number of problems have to be adequately dealt with: appropriate characterization of the sequence or process; experimental design (selecting sequences or process settings); transforming the three-way into a two-way matrix; and appropriate modelling and validation (modelling interactions, periodicities, “time series” structures and “neighbour effects”). A multivariate approach to sequence and process modelling using PCA and PLS projections to latent structures is discussed and illustrated with several sets of peptide and DNA promoter data.
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| 3. |
- ERASIN, BR, et al.
(author)
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A FIXED-FILM BIOASSAY FOR THE DETECTION OF MICROPOLLUTANTS TOXIC TO ANAEROBIC SLUDGES
- 1994
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In: Analytica Chimica Acta. - : Elsevier Science B.V., Amsterdam.. - 0003-2670 .- 1873-4324. ; 298:1
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Journal article (peer-reviewed)abstract
- Micropollutants in waste water streams can be a serious problem for the anaerobic digestion process. A short-term acute bioassay system is described for testing the effects of new and potentially toxic compounds on anaerobic digestion processes. Change in methanogenic activity was used as the monitored process parameter and the performance of intoxicated inocula was compared to activity prior to adding test compounds and to the activity of a parallel control assay. The performance of the bioassay was tested with chlorinated solvents and heavy metals. Trichloroethane caused a 50% reduction in methanogenic activity at 7 mg/l assay. The performance of suspended and fixed biomass assays were compared; the suspended growth was found to be five times more sensitive to trichloroethane. There was no clear inhibition with the heavy metals even at the highest concentration used (up to 750 mg Cu/l). The duration of assay was found to be an important parameter in the evaluation of anaerobic toxicity.
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| 4. |
- HENDRY, SP, et al.
(author)
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POLYFERROCENES AS MEDIATORS IN AMPEROMETRIC BIOSENSORS FOR GLUCOSE
- 1993
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In: Analytica Chimica Acta. - : Elsevier Science B.V., Amsterdam.. - 0003-2670 .- 1873-4324. ; 281:3, s. 453-459
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Journal article (peer-reviewed)abstract
- This paper describes the first successful application of polymeric ferrocenes as mediators in amperometric biosensors. The results have implications for the design of stable biosensors and bioelectronic devices involving electron transfer from oxidoreductases to electrode surfaces. The behaviour of two ferrocene polymers in enzyme electrodes was explored and a distinctive pH profile was noted. It is suggested that changes in either the enzyme conformation or the polymer in response to hydrogen ion concentration may explain the difference in behaviour between monomeric and polymeric ferrocenes.
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| 5. |
- NEWMAN, JD, et al.
(author)
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INK-JET PRINTING FOR THE FABRICATION OF AMPEROMETRIC GLUCOSE BIOSENSORS
- 1992
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In: Analytica Chimica Acta. - : Elsevier Science B.V., Amsterdam.. - 0003-2670 .- 1873-4324. ; 262:1, s. 13-17
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Journal article (peer-reviewed)abstract
- Ink-jet printing has been demonstrated as a manufacturing technique that facilitates the rapid, reproducible and economical production of amperometric glucose biosensors. Glucose was chosen as the analyte for demonstrating the process. For eight electrodes produced, the relative standard deviation of the response was less than 5%. The technique is extremely versatile, and will enable a wide variety of reagents to be placed on virtually any sensor design. This technique will be of particular benefit for the mass manufacture of intricate devices, where existing production techniques, such as screen-printing, may not be suitable.
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| 6. |
- SAINI, S, et al.
(author)
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ORGANIC-PHASE ENZYME ELECTRODES
- 1991
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In: Analytica Chimica Acta. - : Elsevier Science B.V., Amsterdam.. - 0003-2670 .- 1873-4324. ; 249:1
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Journal article (peer-reviewed)abstract
- Organic phase enzyme electrodes (OPEEs) offer new possibilities both for the design of biosensors for use in organic solvents and in the construction of devices incorporating an organic phase for use with aqueous samples. The advantages that accrue from performing biocatalytic and electrochemical reactions in non-aqueous systems are discussed in relation to possible applications in medicine. pharmaceuticals, petrochemicals, the food industry, environmental monitoring and defence. This critical but speculative review considers the detailed implications of operating enzyme electrodes in organic solvents and briefly examines the broader issues of optical, calorimetric and piezoelectric transduction coupled with both catalytic and affinity systems, such as nucleic acid probes and antibodies.
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| 7. |
- SCHUBERT, F, et al.
(author)
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MEDIATED AMPEROMETRIC ENZYME ELECTRODE INCORPORATING PEROXIDASE FOR THE DETERMINATION OF HYDROGEN-PEROXIDE IN ORGANIC-SOLVENTS
- 1991
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In: Analytica Chimica Acta. - : Elsevier Science B.V., Amsterdam.. - 0003-2670 .- 1873-4324. ; 245:2, s. 133-138
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Journal article (peer-reviewed)abstract
- An amperometric enzyme electrode incorporating horseradish peroxidase is described for the determination of hydrogen peroxide in organic solvents. The enzyme was co-adsorbed with an electron mediator, potassium hexacyanoferrate(II), on the surface of a graphite foil electrode, making reagentless measurement possible. The electrochemical reduction of the enzymatically oxidized mediator was utilized as the analytical signal. Studies in different solvent systems revealed that the electrode could be operated in dioxane, chloroform and chlorobenzene, the last two providing approximately double the sensitivity of the former. The presence of a small amount of aqueous buffer was essential for sensor activity. During 2 weeks of intermittent use, the sensitivity of the electrode decreased to 40% of its initial value. At least 50 assays could be performed with a single sensor.
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| 8. |
- WHITE, SF, et al.
(author)
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LACTATE, GLUTAMATE AND GLUTAMINE BIOSENSORS BASED ON RHODINISED CARBON ELECTRODES
- 1994
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In: Analytica Chimica Acta. - : Elsevier Science B.V., Amsterdam.. - 0003-2670 .- 1873-4324. ; 295:3, s. 243-251
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Journal article (peer-reviewed)abstract
- Amperometric enzyme sensors for lactate, glutamate and glutamine were constructed using rhodinised carbon electrodes. All three sensors operated at a potential of +400 mV (Ag/AgCl). Lactate sensors were constructed using lactate oxidase immobilized in hydroxyethylcellulose, overlaid with a cellulose acetate membrane. Using a flow-injection system, the sensors had a linear range of 0.1 to 1.5 mM. Measurements of lactate concentrations from a mammalian cell culture were compared with results obtained from a commercial instrument. A correlation coefficient of r=0.982 (n = 15) was obtained. Glutamate and glutamine sensors were fabricated based on glutaraldehyde immobilization; the former by incorporating glutamate oxidase and the latter based on glutamate oxidase and glutaminase (both had a linear range of 0.1 to 1.5 mM). The feasibility of using these sensors, in conjunction with a previously described glucose sensor, for mammalian cell culture monitoring is discussed
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| 9. |
- Xie, Bin, et al.
(author)
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Microbiosensor based on an integrated thermopile
- 1994
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In: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670. ; 299:2, s. 165-170
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Journal article (peer-reviewed)abstract
- A microbiosensor based on an integrated thermopile was designed and fabricated on a quartz chip. The thermopile, which was manufactured by doping boron in polysilicon together with aluminium, provided a potential output of ca. 2 mV K. A silicone rubber membrane was used to form and seal the microchannel. The total column volume was 20 μl. Glucose oxidase and catalase were co-immobilized on spherical CPG beads (controlled pore glass) and in turn charged into the microchannel. Using 1 μl sample volumes, a linear range of 2 to 25 mM glucose was obtained using a flow rate of 105 μl min. The relative standard deviation for 100 glucose samples (10 mM) was 5%.
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