| 1. |
- Laiwattanapaisal, W., et al.
(författare)
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On-chip microfluidic systems for determination of L-glutamate based on enzymatic recycling of substrate
- 2009
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Ingår i: Biomicrofluidics. - : AIP Publishing. - 1932-1058. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Two microfluidic systems have been developed for specific analysis of L-glutamate in food based on substrate recycling fluorescence detection. L-glutamate dehydrogenase and a novel enzyme, D-phenylglycine aminotransferase, were covalently immobilized on (i) the surface of silicon microchips containing 32 porous flow channels of 235 mu m depth and 25 mu m width and (ii) polystyrene Poros (TM) beads with a particle size of 20 mu m. The immobilized enzymes recycle L-glutamate by oxidation to 2-oxoglutarate followed by the transfer of an amino group from D-4-hydroxyphenylglycine to 2-oxoglutarate. The reaction was accompanied by reduction of nicotinamide adenine dinucleotide (NAD(+)) to NADH, which was monitored by fluorescence detection (epsilon(ex)=340 nm, epsilon(em)=460 nm). First, the microchip-based system, L-glutamate was detected within a range of 3.1-50.0 mM. Second, to be automatically determined, sequential injection analysis (SIA) with the bead-based system was investigated. The bead-based system was evaluated by both flow injection analysis and SIA modes, where good reproducibility for L-glutamate calibrations was obtained (relative standard deviation of 3.3% and 6.6%, respectively). In the case of SIA, the beads were introduced and removed from the microchip automatically. The immobilized beads could be stored in a 20% glycerol and 0.5 mM ethylenediaminetetraacetic acid solution maintained at a pH of 7.0 using a phosphate buffer for at least 15 days with 72% of the activity remaining. The bead-based system demonstrated high selectivity, where L-glutamate recoveries were between 91% and 108% in the presence of six other L-amino acids tested.
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| 2. |
- Burestedt, E., et al.
(författare)
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Optimisation and validation of an automated solid phase extraction technique coupled on-line to enzyme-based biosensor detection for the determination of phenolic compounds in surface water samples
- 1995
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Ingår i: Chromatographia. - Heidelberg : Springer Berlin/Heidelberg. - 0009-5893 .- 1612-1112. ; 41:3-4, s. 207-215
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Tidskriftsartikel (refereegranskat)abstract
- A fully integrated screening system for phenolic compounds was developed incorporating on-line solid phase extraction, fractionation and biosensor detection. Two different types of biosensors, solid graphite and carbon paste electrodes incorporating the enzyme tyrosinase, were compared and used in the screening system. Interfacing of the solid phase extraction and fractionation with the biosensor detection was given special attention since the biosensors were not compatible with the organic modifier used for desorption of phenols from the solid phase extraction step. The system was validated with conventional analytical techniques. Surface water samples from the Ebro river were spiked with 1,10, and 25μg L−1 of catechol, phenol,p-cresol, respectively. Three out of seven samples were spiked and the correct samples were identified, containing phenols equivalent to the spiked concentrations. © 1995 Friedr. Vieweg & Sohn Verlagsgesellschaft mbH.
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| 3. |
- Dock, Eva, et al.
(författare)
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Multivariate data analysis of dynamic amperometric biosensor responses from binary analyte mixtures - application of sensitivity correction algorithms
- 2005
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Ingår i: Talanta. - : Elsevier BV. - 1873-3573 .- 0039-9140. ; 65:2, s. 298-305
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, it is demonstrated that a single-receptor biosensor can be used to quantitatively determine each analyte in binary Mixtures LIS in multivariate data analysis tools based on the dynamic responses received from flow injection peaks. Mixtures with different concentrations of two phenolic compounds, catechol and 4-chlorophenol, were measured with a graphite electrode modified with tyrosinase enzyme at an applied potential of -50 mV versus Ag/AgCl. A correction algorithm based on measurements of references in-between samples was applied to compensate for biosensor ageing as well as differences caused by deviations between biosensor preparations. After correction, the relative prediction errors with partial least squares regression (PLS-R) for catechol and 4-chlorophenol were 7.4 and 5.5%, respectively, using an analysis sequence measured on one biosensor. Additional validation mixtures of the two phenols were measured with a new biosensor, prepared with the same procedure but with a different batch of tyrosinase enzyme. Using the mixture responses for the first sensor as a calibration set in PLS-R. the relative prediction errors of the validation mixtures, after applying correction procedures. were 7.0% for catechol and 16.0% for 4-chlorophenol. These preliminary results indicate that by applying correction algorithms it could be possible to use less stable biosensors in continuous on-line measurements together with multivariate data analysis without time-consuming calibration procedures. (C) 2004 Elsevier B.V. All rights reserved.
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| 4. |
- Ersboll, A. K., et al.
(författare)
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Desloratadine Exposure and Incidence of Seizure: A Nordic Post-authorization Safety Study Using a New-User Cohort Study Design, 2001-2015
- 2021
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Ingår i: Drug Safety. - : Springer Science and Business Media LLC. - 0114-5916 .- 1179-1942. ; 44, s. 1231-1242
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Tidskriftsartikel (refereegranskat)abstract
- Introduction A small number of adverse events of seizure in patients using desloratadine (DL) have been reported. The European Medicines Agency requested a post-authorization safety study to investigate whether there is an association between DL exposure and seizure. Objective The aim was to study the association between DL exposure and incidence of first seizure. Methods A new-user cohort study of individuals redeeming a first-ever prescription of DL in Denmark, Finland, Norway, and Sweden in 2001-2015 was conducted. DL exposure was defined as days' supply plus a 4-week grace period. DL unexposed periods were initiated 27 weeks after DL prescription redemption. Poisson regression was used to estimate the adjusted incidence rate and adjusted incidence rate ratio (aIRR) of incident seizure. Results A total of 1,807,347 first-ever DL users were included in the study, with 49.3% male and a mean age of 29.5 years at inclusion; 20.3% were children aged 0-5 years. The adjusted incidence rates of seizure were 21.7 and 31.6 per 100,000 person-years during DL unexposed and exposed periods, respectively. A 46% increased incidence rate of seizure was found during DL exposed periods (aIRR = 1.46, 95% confidence interval [CI] 1.34-1.59). The aIRR ranged from 1.85 (95% CI 1.65-2.08) in children aged 0-5 years to 1.01 in adults aged 20 years or more (95% CI 0.85-1.19). Conclusion This study found an increased incidence rate of seizure during DL exposed periods as compared to unexposed periods among individuals younger than 20 years. No difference in incidence rate of seizure was observed in adults between DL exposed and unexposed.
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| 5. |
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| 6. |
- Kjaerulff, T. M., et al.
(författare)
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Patterns of finasteride use in the male populations of four Nordic countries: A cross-national drug utilization study
- 2016
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Ingår i: Scandinavian Journal of Urology. - : Informa UK Limited. - 2168-1805 .- 2168-1813. ; 50:3, s. 220-227
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Tidskriftsartikel (refereegranskat)abstract
- Objective Finasteride 5 mg is a drug used to treat prostate hyperplasia. Little is known about its pattern of usage. This cross-national analysis of individual-level data from Denmark, Finland, Norway and Sweden was undertaken to appraise its usage and describe cross-national differences. Materials and methods Individual-level data from nationwide prescription registers in Denmark (1995-2009), Finland (1997-2010), Norway (2004-2009) and Sweden (July 2005-2011) were used to examine cross-national finasteride utilization patterns in the adult male population (>= 15 years). The study presents period prevalences, incidence rates, waiting time distributions and Lorenz curves. Results During the study period, 295,620 men had at least one prescription redemption of finasteride 5 mg, and there were approximately 3 million dispensing events of finasteride prescriptions in the four Nordic countries. Different patterns of finasteride use were observed among the four Nordic countries. The period prevalence was markedly higher in Finland and Sweden than in Denmark and Norway. In 2009, period prevalences were 18.2/1000 males in Finland and 12.0/1000 males in Sweden compared to 6.7/1000 males in Norway and 4.9/1000 males in Denmark. Incidence rates of finasteride use for Finland, Norway and Sweden were about three times that for Denmark in 2008-2009. Long-term use of finasteride was found in all four Nordic countries with a high ratio between prevalent and incident users. Conclusion Despite resemblances regarding political systems and healthcare services in the Nordic countries, differences in finasteride utilization were found across Denmark, Finland, Norway and Sweden. RAMS P, 1994, BRITISH MEDICAL JOURNAL, V308, P929
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| 7. |
- Kjellström, S, et al.
(författare)
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Flow immunochemical bio-recognition detection for the determination of interleukin-10 in cell samples
- 2000
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Ingår i: Journal of Immunological Methods. - 0022-1759. ; 246:1-2, s. 30-119
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Tidskriftsartikel (refereegranskat)abstract
- On- and off-line heterogeneous non-competitive flow immunoassays for the determination of Interleukin-10 are described. The sample containing IL-10 is mixed, either on-line in a reaction coil or off-line in a test tube, with fluorescent labelled anti-IL-10 antibodies to form an antibody-antigen complex. The labelled unbound antibodies are trapped on an immobilized IL-10 column whereas the IL-10-antibody complexes are eluted and detected downstream by a fluorescence detector. The optimization of the systems was performed with respect to choice of affinity support, flow rate, carrier buffer additives, pH and antibody-antigen association. Both bio recognition assays were tested with a spiked cell medium and the IL-10 detection limits in this matrix was found to be 8 fmol using the off-line incubation mode and 40 fmol using the on-line incubation mode. The sample through-put was 26 and 40 samples per hour in the on-line and off-line incubation modes, respectively. IL-10 identification in the sample fractions was achieved using MALDI-TOF MS.
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| 8. |
- Kjellström, S, et al.
(författare)
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On-line coupling of microdialysis sampling with liquid chromatography for the determination of peptide and non-peptide leukotrienes
- 1998
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Ingår i: Journal of chromatography. A. - 0021-9673. ; 823:1-2, s. 489-496
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Tidskriftsartikel (refereegranskat)abstract
- An automated on-line sampling method was developed using microdialysis as the simultaneous sampling and sample pre-treatment technique. The extraction fraction values of microdialysis probes sampling different eicosanoids were investigated. The impact of cyclodextrins in the perfusion liquid used for sampling hydrophobic eicosanoids in biological systems was also studied. The total time for one analysis was 7.6 min allowing seven measurements per hour for monitoring kinetic changes in biological systems.
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| 9. |
- Nistor, Catalin, et al.
(författare)
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Multivariate analysis to separate the signal given by cross-reactants in immunoassay with sample matrix dilution
- 2004
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 380:7-8, s. 898-907
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a new approach to achieve selectivity in an immunoassay by separating the signals given by two cross-reactive compounds present simultaneously in a complex sample matrix. The method is based on the sequential dilution of the sample containing a mixture of the two analytes, spiking each diluted sample with a reference compound, and the detection by enzyme-linked immunosorbent assay (ELISA). The obtained multivariate response was used for the individual calibrations of the assay for each. of the two cross-reactants simultaneously by using principal component analysis (PCA) and partial least squares regression (PLSR) data modeling. The calibration models showed. that the signal separation due the analytes 2,4-dinitro-phenol (2,4-DNP) and 4-nitrophenol (4-NP) was possible with a prediction concentration error of 1.4 muM and 72 muM, respectively.
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| 10. |
- Tonning, E, et al.
(författare)
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Chemometric exploration of an amperometric biosensor array for fast determination of wastewater quality
- 2005
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Ingår i: Biosensors & Bioelectronics. - : Elsevier BV. - 1873-4235 .- 0956-5663. ; 21:4, s. 608-617
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Tidskriftsartikel (refereegranskat)abstract
- Four wastewater samples of different treatment qualities; untreated, alarm, alert and normal, from a Swedish chen-ti-thermo-mechanical pulp mill and pure water were investigated using an amperometric bioelectronic tongue in a batch cell. The aim was to explore enzymatically modified screen-printed amperometric sensors for the discrimination of wastewater quality and to counteract the inherent drift. Seven out of eight platinum electrodes on the array were modified with four different enzymes; tyrosinase, horseradish peroxidase, acetyl cholinesterase and butyryl cholinesterase. At a constant potential the current intensity on each sensor was measured for 200s, 100s before injection and 100s after injection of the sample. The dynamic biosensor response curves from the eight sensors were used for principal component analysis (PCA). A simple baseline and sensitivity correction equivalent to multiplicative drift correction (MDC), using steady state intensities of reference sample (catechol) recordings, was employed. A clear pattern emerged in perfect agreement with prior knowledge of the samples explaining 97% of the variation in the data by two principal components (PCs). The first PC described the treatment quality of the samples and the second PC described the difference between treated and untreated samples. Horseradish peroxidase and pure platinum sensors were found to be the determinant sensors, while the rest did not contribute much to the discrimination. The wastewater samples were characterized by the chemical oxygen demand (COD), biological oxygen demand (BOD), total organic carbon (TOC), inhibition of nitrification, inhibition of respiration and toxicity towards Vibrio fischeri using Microtox (R), the freshwater alga Pseudokirchneriella subcapita and the freshwater crustacean Daphnia magna. (c) 2005 Elsevier B.V. All rights reserved.
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