| 1. |
- Aquilante, Laura, et al.
(författare)
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Determination of biogenic amines by using amperometric biosensors based on grass PEA amine oxidase and OAT polyamine oxidase
- 2020
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Ingår i: Studia Universitatis Babes-Bolyai Chemia. - : Babes-Bolyai University. - 1224-7154 .- 2065-9520. ; 65:3, s. 9-21
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Tidskriftsartikel (refereegranskat)abstract
- Grass pea amine oxidase (GPAO) and oat polyamine oxidase (OPAO) were immobilized along with horseradish peroxidase (HRP) and an Os-redox polymer (Os-RP) onto the surface of a graphite electrode by crosslinking with poly(ethylenglycol) diglycidyl ether. The resulted reagentless amperometric biosensors were inserted in a flow injection setup and used as electrochemical detectors for the biogenic amines (BA) detection. Both biosensors were operated at low applied potential (-50 mV vs. Ag/AgCl, KCl0.1M) where electrochemical interferences are minimal. The quantification of ten BA (tyramine, putrescine, cadaverine, histamine, cystamine, phenylethylamine, agmatine, tryptamine, spermine, and spermidine) either individual or in mixture (after a preliminary separation by using cation exchange chromatography) was reported. G/(Os-RP)-HRP-GPAO biosensor detected all ten BA, while G/(Os-RP)-HRP-OPAO biosensor detected only spermine and spermidine. Finally, a simple and low-cost method for free and acetylated polyamines determination in human urine samples, by using the highly selective G/(Os-RP)-HRP-OPAO biosensor, was proposed.
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| 2. |
- Badea, M, et al.
(författare)
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A flow immunoassay for alkylphenol ethoxylate surfactants and their metabolites - questions associated with cross-reactivity, matrix effects, and validation by chromatographic techniques
- 2003
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Ingår i: Analyst. - : Royal Society of Chemistry (RSC). - 1364-5528. ; 128:7, s. 849-856
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the application and evaluation of a competitive enzyme flow injection immunoassay (EFIIA) for screening of alkylphenol ethoxylate (APEO) surfactants in different water samples based on a generic immunoassay system previously developed ( see E. Burestedt, C Nistor, U. Schagerlof and J. Emneus, Anal. Chem., 2000, 72, 4171 - 4177). The detection limits for octylphenol ethoxylates (OPEOs), nonylphenol ethoxylates (NPEOs), and nonylphenol (NP) were 0.5 mug l(-1), between 2 and 3 mug l(-1), and 50 mug l(-1), respectively, with a sample throughput of 6 h(-1) (i.e., for triplicate analysis of each sample). Different OPEOs and NPEOs were highly cross-reactive within the assay, with sensitivities in the same order of magnitude for all the ethoxylates tested, thus the result obtained by the EFIIA method could be used as an "alkylphenol ethoxylate index". No or minor matrix effects with recoveries between 70 - 120% for the reference analyte NPEO10 in tap, and surface water, and acceptable for rainwater, were observed. Influent and effluent surfactant containing wastewater samples were analysed by EFIIA, LC-MS, LC-Fluoresence (LC-FL), and a commercial microplate ELISA. High recoveries for different concentrations of APEO(10) spiked into a 200 times diluted raw influent and effluent wastewater were achieved with the EFIIA method, however, the found APEO content of the same diluted wastewater samples, before spiking, could not be correlated directly to the chromatographic result by any of the immunoassays, and the possible reasons for this are discussed. The same trend of decreasing APEO content from influent to effluent wastewater could, however, be followed for all methods employed.
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| 3. |
- Cervin, Camilla, et al.
(författare)
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A combined in vitro and in vivo study on the interactions between somatostatin and lipid-based liquid crystalline drug carriers and bilayers
- 2009
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Ingår i: European Journal of Pharmaceutical Sciences. - : Elsevier BV. - 1879-0720 .- 0928-0987. ; 36:4-5, s. 377-385
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Tidskriftsartikel (refereegranskat)abstract
- Somatostatin (SST) is a peptide hormone active in the regulation of the endocrine system via different somatostatin receptors subtypes. It inhibits the release of multiple secondary peptide hormones, affecting neurotransmission and cell proliferation. SST has a high therapeutic potential in the treatment of disease, such as acromegali, acute pancreatitis and gastroenteropathic endocrine tumors. However, its practical use is hampered by a short in vivo half-life of only a few minutes in man. For this reason more long-lived SST analogues, including octreotide and lanreotide, have been developed. Here we have used native SST as a model compound for a different approach of extending plasma half-lives of in vivo labile biomolecules. Through association of the peptide hormone with lipid-based liquid crystalline nanoparticle (LCNP) carriers, the terminal half-life of SST injected intravenously in rats is shown to be significantly extended from less than 10 min to more than 1 h. The effect on the in vivo circulation behavior depends on the mode of peptide association to the lipid particles and related physicochemical properties are discussed on the basis of in vitro light scattering, z-potential and adsorption measurements. It is concluded that application of the LCNP delivery system represents an interesting alternative to chemical modifications of in vivo sensitive therapeutically interesting peptides. (c) 2008 Elsevier B.V All rights reserved.
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| 4. |
- Muresan, Laura, et al.
(författare)
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Amine oxidase amperometric biosensor coupled to liquid chromatography for biogenic amines determination
- 2008
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Ingår i: MICROCHIMICA ACTA. - : Springer Science and Business Media LLC. - 0026-3672 .- 1436-5073. ; 163:3-4, s. 219-225
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Konferensbidrag (refereegranskat)abstract
- A selective and sensitive method is presented for biogenic amines (BA) determination. The novelty consists in coupling a highly selective electrochemical biosensor to a weak acid cation-exchange column for online detection of amines. A bienzyme design, based on a recently isolated amine oxidase from grass pea and commercial horseradish peroxidase, was used for the biosensor construction. The enzymes were co-immobilized on the surface of a graphite electrode together with the electrochemical mediator (Os-redox polymer). The electrochemical detection was performed at a low applied potential (-50 mV vs. Ag/AgCl, KCl0.1 M), where biases from interferences are minimal. The separation and determination of six BA, with relevance in food analysis (tyramine, putrescine, cadaverine, histamine, agmatine and spermidine), were investigated. Irrespective of the BA nature, the amine oxidase-based biosensor showed a linear response up to 5 mM, and its sensitivity decreases in the following order: cadaverine, putrescine, spermidine, agmatine, histamine and tyramine. The approach was used to estimate the BA content in fish samples, after their extraction with methanesulfonic acid.
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| 5. |
- Muresan, Laura, et al.
(författare)
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AMPEROMETRIC BIOSENSORS FOR GLUCOSE AND ETHANOL DETERMINATION IN WINE USING FLOW INJECTION ANALYSIS
- 2008
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Ingår i: Studia Universitatis Babes-Bolyai, Chemia. - 2065-9520. ; 53:1, s. 71-79
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Tidskriftsartikel (refereegranskat)abstract
- Reagentless amperometric biosensors for glucose and ethanol were developed and successfully applied for monitoring glucose and ethanol concentrations in wine during the fermentation process. The glucose biosensor was based on commercially available glucose oxidase and horseradish peroxidase co-immobilized on solid graphite using Os(II)-redox hydrogel (RH) [1]. In the case of ethanol biosensor, the quinohemoprotein dependent alcohol dehydrogenase was immobilized on the graphite electrode surface using the same RH [2]. Both biosensors were operated at low applied potentials (-50 mV vs. Ag/AgCl, KCl0.1M for glucose biosensor, and +250 mV vs. Ag/AgCl, KCl0.1M for ethanol biosensor), where biases from interferences are minimal. The bioelectroanalytical parameters, estimated from flow injection analysis measurements, were found as follows: sensitivity, 0.73 +/- 0.01 mu A mM(-1) for glucose and 0.45 +/- 0.01 mu A mM(-1) for ethanol; linear range up to 1 mM in both cases; detection limit, 7.0 mu M for glucose and 8.9 mu M for ethanol. The results for real samples were found in good agreement with those reported by Barsan et al. [3].
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| 6. |
- Muresan, Laura, et al.
(författare)
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Monitoring of glucose and glutamate using enzyme microstructures and scanning electrochemical microscopy.
- 2009
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Ingår i: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 76, s. 81-86
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Tidskriftsartikel (refereegranskat)abstract
- Glucose oxidase and glutamate oxidase lines, with typical width of 100 microm, were patterned on gold surfaces using a micro-dispensing system, by shooting 100 pl droplets of the corresponding enzyme solutions. The probe of a scanning electrochemical microscope (SECM) was then carefully positioned in the close proximity of the enzyme microstructure and poised to +600 mV vs. Ag/AgCl, KCl 0.1 M. The H(2)O(2), generated by the enzyme lines at different concentrations of glucose and glutamate in the surrounding solution, was sequentially monitored. Reproducible calibration curves for glucose and glutamate were obtained in one single experiment, proving that the combination of enzyme microstructures with SECM can provide a new way of achieving multianalyte detection.
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| 7. |
- Muresan, Laura, et al.
(författare)
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Reagentless Amperometric Biosensor For Nadh Detection
- 2009
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Ingår i: Revue Roumaine de Chimie. - 0035-3930. ; 54:9, s. 755-760
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Tidskriftsartikel (refereegranskat)abstract
- A sensitive and selective amperometric biosensor, based on NADH-oxidase (NADOx) working in tandem with horseradish peroxidase (HRP), which is electrically connected to graphite electrode via Os-redox polymer (RP), was developed. Two designs were considered for the biosensor optimization: (i) the first one, [G/HRP-NADOx], exploited the direct electron transfer between HRP and the graphite electrode (G); (ii) the second one, [G/RP-HR-P-NADOx], used R-P as mediator. In both cases the enzyme matrix was cross-linked using poly(ethylenglycol) diglycidyl ether. The biosensors sensitivities, estimated as the slopes of linear ranges from the calibration curves, recorded in a single line flow injection setup, showed that G/RP-HRP-NADOx electrode (1.62 +/- 0.05 mA M-1) presents a higher efficiency than G/HRP-NADOx electrode (0.30 +/- 0.03 mA M-1).
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| 8. |
- Nistor, Catalin, et al.
(författare)
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A capillary-based amperometric flow immunoassay for 2,4,6-trichlorophenol
- 2003
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642. ; 375:1, s. 125-132
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the development of two different capillary-based heterogeneous competitive flow immunoassay formats (capillary flow injection immunoassay (CFIIA) and capillary sequential injection immunoassay (CSIIA)) for the determination of 2,4,6-trichlorophenol (2,4,6-TCP). The assays are based on the competition between the analyte and an analyte derivative labelled with the enzyme #-galactosidase, for an anti-TCP antibody, followed by the injection of the mixture at equilibrium into a flow stream, where separation between the fractions bound and unbound to the antibody is performed in a glass capillary containing immobilised protein A. The antibody-tracer fraction retained inside the protein A capillary was measured by injection of 4-aminophenyl-#-D-galactoside (4-APG), followed by amperometric detection of the enzymatically generated 4-aminophenol (4-AP), leading to a negative correlation between the signal and the analyte concentration.
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| 9. |
- Nistor, Catalin, et al.
(författare)
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A glucose dehydrogenase biosensor as an additional signal amplification step in an enzyme-flow immunoassay.
- 2002
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Ingår i: Analyst. - : Royal Society of Chemistry (RSC). - 1364-5528. ; 127:8, s. 1076-1081
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Tidskriftsartikel (refereegranskat)abstract
- Both the antibody affinity and the detectability of the label are essential in deciding the final characteristics of a heterogeneous immunoassay. This paper describes an approach to obtain a supplementary enhancement of the signal generated by using an enzyme label, e.g., by including the product of the enzymatic reaction in an additional amplification cycle during the detection step performed with an amperometric biosensor based on glucose dehydrogenase (GDH). An immunoassay format with a labelled analyte derivative that competes with the analyte present in the sample for a limited amount of antibody binding sites was employed. The beta-galactosidase label hydrolyses the substrate aminophenyl-beta-galactopyranoside, and the generated aminophenol enters then into a bioelectrocatalytic amplification cycle at the GDH biosensor. The principle was applied for determination of 4-nitrophenol, with the best minimal concentration of 1.5 microM and a midpoint of the calibration of 24 microM. The potentials and limitations of such a system are discussed.
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| 10. |
- Nistor, Catalin, et al.
(författare)
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Detection of Escherichia coli in water by culture-based amperometric and luminometric methods.
- 2002
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Ingår i: Water Science and Technology. - 0273-1223. ; 45:4-5, s. 191-199
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Tidskriftsartikel (refereegranskat)abstract
- The application of amperometric biosensor- and chemiluminiscence based methods for rapid detection of viable E. coli in water has been investigated. An amplification of the amperometric signal by a factor of 4 was obtained when the cellobiose dehydrogenase (CDH) biosensor was used instead of a plain graphite electrode for detection of b-galactosidase (b-GAL) activity at 22.5 degrees C. A linear correlation was demonstrated for detection time (DT) vs. initial concentrations (logarithmic units) of E. coli IT1 and E. coli in environmental samples, respectively, by use of the CDH biosensor or a chemiluminometric technique. The study has shown that an E. coli concentration > or = 10(4) cfu/100 mL in environmental samples was determined by the CDH biosensor within one working day. However, further reduction of the DT can be obtained, e.g. by increasing the signal amplification factor using other biosensors.
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