| 1. |
- Danielsson, Bengt, et al.
(author)
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Heat Sensitive Biosensors
- 1993
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In: Uses of Immobilized Biological Compounds. - Dordrecht : Springer Netherlands. - 0168-132X. - 9780792325291 - 9789401048545 - 9789401119320 ; 252, s. 541-548
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Book chapter (peer-reviewed)abstract
- The unsurpassed versatility of heat sensitive biosensors is illustrated by various new applications of the flow-calorimetric biosensor system, the enzyme thermistor (ET) developed in our laboratory. The ET measures the reaction heat in a small column containing immobilized biocatalyst. Since most biological reactions are exothermic, the ET has a very broad applicability and numerous assays of clinical as well as biotechnological interest have been studied. The procedure is well suited for monitoring and control of biotechnological processes due to its high operational stability. New results from this area are presented as well as developments on an automated thermometric immunoassay (TELISA). Miniaturized ET-devices are suitable for portable monitoring of, for instance, blood glucose. Other recent work include determinations in organic solvents, direct characterization of immobilized biocatalysts, and monitoring of bioactivities in solution.
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| 2. |
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| 3. |
- Harborn, Ulrika, et al.
(author)
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Determination of glucose in diluted blood with a thermal flow injection analysis biosensor
- 1994
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In: Analytical Letters. - : Informa UK Limited. - 0003-2719 .- 1532-236X. ; 27:14, s. 2639-2645
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Journal article (peer-reviewed)abstract
- The glucose concentration in diluted whole blood has been measured, using a miniaturized thermal biosensor based on the enzyme thermistor principle. The biosensor is a small flow injection system. A sample volume of 20μl is injected into a flow of 50μ1/min. The heat produced when the sample passes the enzyme column is measured with a thermistor connected to a Wheatstone bridge. The enzyme column contains glucose oxidase and catalase co-immobilized on a solid support material. Samples of whole blood usually cause problems in flow-systems. The blood cells tend to block the enzyme column and the back pressure increases. We have tested a supeiporous agarose material as enzyme support material using tenfold diluted samples of whole human blood. The blood was collected from the finger-tip and diluted with buffer containing an anticoagulant and sodium fluoride. The number of samples possible to inject and the accuracy compared to the Boehringer Mannheim Reflolux have been determined. At least 100 ten-fold diluted blood samples could be injected on a micro-column of superporous agarose. The obtained glucose concentration correlated well with the one obtained with the reference instrument.
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| 4. |
- Xie, Bin, et al.
(author)
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Development of a thermal micro-biosensor fabricated on a silicon chip
- 1992
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In: Sensors and Actuators B: Chemical. - 0925-4005. ; 6:1-3, s. 127-130
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Journal article (peer-reviewed)abstract
- In order to develop a sensitive, versatile and inexpensive portable instrument, a calorimetric micro-biosensor was designed and fabricated by etching part of the flow system into a silicon wafer. The utility of the device was tested using the enzymes, catalase and penicillinase. This sensor showed good reproducibility and linearity up to 100 mM. The system also showed higher sensitivity than the conventional enzyme thermistor (ET) when identical sample volumes (20 μl) were applied. Finally, future prospects in this field are discussed.
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| 5. |
- Xie, Bin, et al.
(author)
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Electrochemically Assisted Biosensors
- 1994
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In: ; , s. 246-246
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Conference paper (peer-reviewed)abstract
- This chapter describes a study focusing on electrochemically assisted biosensors. Electrochemical regeneration of electron-transfer mediators or cofactors, such as NAD+ has been extensively applied in redox reactions catalyzed by oxidoreductases. This electrochemical regeneration shows many advantages in use of amperometric biosensors, such as extended linear range. To demonstrate the feasibility of constructing such a biosensor, a ferrocene-mediated thermal glucose sensor was fabricated. In this study, the heat production (Δq) accompanying the glucose oxidation catalyzed by glucose oxidase was detected, as opposed to the electrical signal (current or potential change) that is normally measured in electrochemical analysis. Ferrocene was used as electron-transfer mediator to extend the linear range up to 20 mM glucose. Fiber optic biosensors for fluorescence measurement, such as NADH-based biosensors, could be modified in a similar way, if the electrochemical regeneration of NAD+ in the dehydrogenase-catalyzed reaction can be accomplished in the fiberoptic measurement system. Therefore, the sensitivity and the linear range of the sensors could be improved because recycling of NAD+/NADH can be electrochemically sustained.
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| 6. |
- Xie, Bin, et al.
(author)
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Fast determination of whole blood glucose with a calorimetric micro-biosensor
- 1993
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In: Sensors and Actuators B: Chemical. - 0925-4005. ; 15:1-3, s. 141-144
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Journal article (peer-reviewed)abstract
- Fast determination of whole blood glucose without any pretreatment was achieved using a calorimetric FIA micro-biosensor. Glucose oxidase was covalently immobilized, together with catalase, onto controlled pore glass beads and packed into a micro-column. By reducing the sample volume down to 1 μ1, a measurement period of about 40 s and an enlarged linear range of 0.5-20 mM glucose were obtained. The correlation coefficient was 0.98 when the micro-biosensor was compared to the Reflolux-S blood glucose analyser. The relative standard deviation for 100 blood samples was 3.7%.
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| 7. |
- Xie, Bin, et al.
(author)
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Ferrocene-mediated thermal biosensor
- 1993
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In: The Analyst. - 0003-2654. ; 118:7, s. 845-848
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Journal article (peer-reviewed)abstract
- A biosensor that combines electrochemistry and calorimetry was investigated. Using this sensor, glucose measurements were performed by employing glucose oxidase together with ferrocene as electron-transfer mediator. The electrochemical reaction was accomplished by applying a voltage between a platinum column (working electrode), in contact with a crushed reticulated vitreous carbon (RVC) matrix onto which glucose oxidase was immobilized, and platinum wires (counter electrodes) located at the inlet and outlet of the column. For detection, the thermal signal generated by the redox reaction was measured as opposed to measuring the electrochemical signal. By using this method, a linear range of glucose concentration up to 20 mmol l-1 was achieved.
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| 8. |
- 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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| 9. |
- Xie, Bin, et al.
(author)
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Miniaturized thermal biosensors
- 1993
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In: Sensors and Actuators B: Chemical. - 0925-4005. ; 16:1-3, s. 443-447
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Journal article (peer-reviewed)abstract
- Miniaturized thermal biosensors based on three different designs have been constructed. Properties relevant to decentralized bioanalysis have been investigated. A short measurement period (30 s per sample) and a broad linear range (0.5 mM to 100 mM for glucose and penicillin-V), using 1 μl sample volume, have been achieved.
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| 10. |
- Xie, Bin, et al.
(author)
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Urea and lactate determined in 1-μL whole-blood samples with a miniaturized thermal biosensor
- 1994
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In: Clinical Chemistry. - : Oxford University Press (OUP). - 0009-9147 .- 1530-8561. ; 40:12, s. 2282-2287
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Journal article (peer-reviewed)abstract
- A miniaturized flow-injected thermal biosensor was developed for the determination of urea and L-lactate in undiluted blood in 1-μL samples. The sensor employed a small enzyme column constructed of stainless steel tubing and microbead thermistors. Urease and lactate oxidase/catalase were separately immobilized onto controlled-pore glass beads, which, in turn, were charged into the enzyme column. With a flow rate of 70 μL/min, linear analytical ranges from 0.2 to at least 50 mmol/L and 0.2 to 14 mmol/L were obtained for urea and lactate, respectively. The relative standard deviations (CVs) for measurements of analyte in buffer were 0.91% for urea and 1.84% for lactate. For urea in whole blood, the CV for 50 determinations was 4.1%. Contrived samples containing various concentrations of urea and L-lactate in whole blood were determined with this sensor and with a spectrophotometric method. Comparisons of the results gave correlation coefficients of 0.989 and 0.984 for 30 blood urea and 30 blood lactate assays in concentrations ranging from 4 to 20.9 mmol/L and from 1.7 to 12.7 mmol/L, respectively.
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