| 1. |
- Abrahamsson, D, et al.
(författare)
-
A preliminary study on DNA detection based on relative magnetic permeability measurements and histone HI conjugated superparamagnetic nanoparticles as magnetic tracers
- 2004
-
Ingår i: Biosensors & Bioelectronics. - : Elsevier BV. - 1873-4235 .- 0956-5663. ; 19:11, s. 1549-1557
-
Tidskriftsartikel (refereegranskat)abstract
- Histone H I conjugated superparamagnetic nanoparticles were assessed for their ability to work as magnetic tracers in conjunction with the relative magnetic permeability metre (MPM-100) for the detection and quantification of DNA (deoxyribonucleic acid). The method employed was based on the electrostatic adsorption of DNA (analyte) to amino group derivatised silica (carrier) and subsequent binding of histone HI conjugated superparamagnetic nanoparticles (magnetic tracer). The sandwich complexes formed were separated from the medium by sedimentation and the relative magnetic permeability of the sediments were measured with the MPM-100. Investigations were made with both calf thymus DNA and plasmid DNA in aqueous buffered solution as well as in a lysed cell culture with high protein content. For the quantification of calf thymus DNA, a linear relationship between the DNA concentration in the sample and the relative magnetic permeability of the pellet was found for DNA concentrations up to 67 mug/ml in buffered solutions as well as in a lysed cell culture. The limits of detection were determined to 12 and 31 mug/ml, respectively. For the quantification of plasmid DNA in buffered solution a linear range was established for concentrations in up to 150 VLg/ml and the limit of detection was determined to 52 mug/lnl.
|
|
| 2. |
- Bachinger, T., et al.
(författare)
-
Gas sensor arrays for early detection of infection in mammalian cell culture
- 2002
-
Ingår i: Biosensors & bioelectronics. - 0956-5663 .- 1873-4235. ; 17:5, s. 395-403
-
Tidskriftsartikel (refereegranskat)abstract
- The detection of bacterial infections in a mammalian cell culture process is realised using a gas sensor array. In production-scale and laboratory-scale cultivations of a perfused recombinant CHO-cell culture producing human blood coagulation Factor VIII, we show that the gas sensor array identifies bacterial contamination earlier than conventional methods. The sensitivity of the instrument is verified by inoculation of a blank cell culture medium with defined bacterial cell counts. © 2002 Elsevier Science B.V. All rights reserved.
|
|
| 3. |
- Bontidean, Ibolya, et al.
(författare)
-
Novel synthetic phytochelatin-based capacitive biosensor for heavy metal ion detection
- 2003
-
Ingår i: Biosensors & Bioelectronics. - 1873-4235. ; 18:5-6, s. 547-553
-
Tidskriftsartikel (refereegranskat)abstract
- A novel capacitance biosensor based on synthetic phytochelatins for sensitive detection of heavy metals is described. Synthetic phytochelatin (Glu-Cys)20Gly (EC20) fused to the maltose binding domain protein was expressed in Escherichia coli and purified for construction of the biosensor. The new biosensor was able to detect Hg2+, Cd2+, Pb2+, Cu2+ and Zn2+ ions in concentration range of 100 fM–10 mM, and the order of sensitivity was SZn>SCu>SHg>>SCdSPb. The biological sensing element of the sensor could be regenerated using EDTA and the storage stability of the biosensor was 15 days.
|
|
| 4. |
- Castillo Leon, Jaime, et al.
(författare)
-
Bienzyme biosensors for glucose, ethanol and putrescine built on oxidase and sweet potato peroxidase
- 2003
-
Ingår i: Biosensors & Bioelectronics. - 1873-4235. ; 18:5-6, s. 705-714
-
Tidskriftsartikel (refereegranskat)abstract
- Amperometric biosensors for glucose, ethanol, and biogenic amines (putrescine) were constructed using oxidase/peroxidase bienzyme systems. The H2O2 produced by the oxidase in reaction with its substrate is converted into a measurable signal via a novel peroxidase purified from sweet potato peels. All developed biosensors are based on redox hydrogels formed of oxidases (glucose oxidase, alcohol oxidase, or amine oxidase) and the newly purified sweet potato peroxidase (SPP) cross-linked to a redox polymer. The developed electrodes were characterized (sensitivity, stability, and performances in organic medium) and compared with similarly built ones using the 'classical' horseradish peroxidase (HRP). The SPP-based electrodes displayed higher sensitivity and better detection limit for putrescine than those using HRP and were also shown to retain their activity in organic phase much better than the HPR based ones. The importance of attractive or repulsive electrostatic interactions between the peroxidases and oxidases (determined by their isoelectric points) were found to play an important role in the sensitivity of the obtained sensors
|
|
| 5. |
- Chianella, I, et al.
(författare)
-
MIP-based solid phase extraction cartridges combined with MIP-based sensors for the detection of microcystin-LR
- 2003
-
Ingår i: Biosensors & bioelectronics. - : Elsevier Science B.V., Amsterdam.. - 0956-5663 .- 1873-4235. ; 18:03-feb, s. 119-127
-
Tidskriftsartikel (refereegranskat)abstract
- Microsystin-LR is one of the most widespread and dangerous toxins produced by the freshwater Cyanobacteria. The contamination of water supplies with microcystin-LR has been reported in several areas around the world and the development of an easy-to-use, rapid, robust and inexpensive sensor for this toxin is urgently required. In this work an artificial receptor for microcystin-LR was synthesised using the technique of molecular imprinting. The composition of the molecularly imprinted polymer (MIP) was optimised using computer modelling. The synthesised polymer was used both as a material for solid-phase extraction (SPE) and as a sensing element in a piezoelectric sensor. Using the combination of SPE followed by detection with a piezoelectric sensor the minimum detectable amount of toxin was 0.35 nM. The use of MIP-SPE provided up to 1000 fold preconcentration, which was more than sufficient for achieving the required detection limit for microcystin-LR in drinking water (I nM). This work is the first example where the same MIP receptor has been used successfully for both SPE and the corresponding sensor. (C) 2002 Elsevier Science B.V. All rights reserved.
|
|
| 6. |
- Christenson, Andreas, et al.
(författare)
-
Direct heterogeneous electron transfer of theophylline oxidase
- 2004
-
Ingår i: Biosensors & Bioelectronics. - : Elsevier BV. - 1873-4235 .- 0956-5663. ; 20:2, s. 176-183
-
Tidskriftsartikel (refereegranskat)abstract
- Direct electron transfer (DET) was shown between the heme containing enzyme theophylline oxidase (ThO) and the surface of both graphite and gold electrodes. As proof on graphite a steady state current for theophylline was recorded using the electrode modified with adsorbed ThO. The electrode showed a Michaelis–Menten-like response to theophylline with a detection limit of 0.2 mM and a Michaelis–Menten constant equal to 3.2 mM. These initial results open up a possibility for the development of reagentless third generation biosensor based on heterogeneous DET between ThO and an electrode. On gold DET between ThO and the surface of aldrithiol modified gold was studied with spectroelectrochemical measurements. DET was observed for soluble ThO as a change of its spectrum in a gold capillary responding to a change in the applied potential. It was shown that the redox conversion of the heme domain of the enzyme is directly (mediatorlessly) driven by the potential applied at the gold electrode. The measurements enabled an estimation of the formal potential (E°′) of the redox process equal to −275±50 mV versus Ag|AgClsat at pH 7.0. The experimentally determined number of the electrons involved in this heterogeneous electron transfer process was estimated to be equal to 0.53. The low precision in determination of the E°′ and the value of the number of electrons lower than one indicate that kinetic restrictions disturbed the evaluation of the true thermodynamic values from relatively fast spectroelectrochemical measurements. . . . This is the final, accepted and revised manuscript of this article. Use alternative location to go to the published article. Requires subscription.
|
|
| 7. |
- de Mattos, I L, et al.
(författare)
-
Sensor and biosensor based on Prussian Blue modified gold and platinum screen printed electrodes
- 2003
-
Ingår i: Biosensors & Bioelectronics. - 1873-4235. ; 18:2-3, s. 193-200
-
Tidskriftsartikel (refereegranskat)abstract
- Gold (Au) and platinum (Pt) screen-printed electrodes were modified with Prussian Blue (PB) for the development of amperometric sensors selective for hydrogen peroxide detection. The sensors exhibited sensitivities towards H2O2 equal to 2 A M−1 cm−2 for Au and 1 A M−1 cm−2 for Pt electrodes. The sensors were also employed as the basis for construction of glucose biosensors through further modification with crystallised glucose oxidase immobilised in a Nafion membrane. In order to improve the operational stability of the modified electrodes a buffer solution containing tetrabutylammonium toluene-4-sulfonate was used. The long-term performance of the sensors and biosensors were evaluated by continuous monitoring of hydrogen peroxide and glucose solutions (50 M and 1 mM, respectively) in the flow-injection mode for 10 h.
|
|
| 8. |
- Fall, C.J., et al.
(författare)
-
Electronic and vibrational properties of Mg- and O-related complexes in GaN
- 2001
-
Ingår i: Materials Science & Engineering. - 0921-5107 .- 1873-4944. ; 82:1, s. 88-90
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate from first principles the energetic and vibrational properties of various candidate structures for the 3125 cm-1 local vibrational mode in GaN, known to be related to hydrogen passivated magnesium atoms. The orientation of the electric dipole of this mode has recently been measured with respect to the wurtzite c-axis, giving a result seemingly inconsistent with current atomic models for this defect. We study the possibility that complexes of magnesium, native impurities and hydrogen could give rise to the experimental observations. Furthermore, we consider a possible candidate giving rise to a 0.88-eV line in a variety of electron-irradiated GaN samples. We find evidence that a deep donor level including substitutional oxygen must result from a complex impurity.
|
|
| 9. |
- Ferapontova, Elena, et al.
(författare)
-
Effect of cysteine mutations on direct electron transfer of horseradish peroxidase on gold
- 2002
-
Ingår i: Biosensors & Bioelectronics. - 1873-4235. ; 17:11-12, s. 953-963
-
Tidskriftsartikel (refereegranskat)abstract
- Surface exposed cysteines were genetically engineered in the structure of recombinant horseradish peroxidase (rHRP). Recombinant forms of HRP with either a His-tag or a Strep-tag at the C-terminus were produced, which additionally had cysteines at positions 57, 189 or 309 (C-terminus) of the polypeptide chain. An E coli expression system was exploited. The effect of these mutations on the direct electron transfer (ET) between An and the enzyme was studied in the reaction of the bioelectrocatalytic reduction of H2O2, at -50 mV versus AgAgCl, on rHRP-modified Au electrodes placed in a wall-jet flow-through electrochemical cell. Adsorptive immobilisation of rHRPs on pre-oxidised Au from the protein solution at pH 6.0 provided a high and stable current response to H2O2 due to its bioelectrocatalytic reduction based on direct (mediatoriess) ET between Au and the active site of the rHRPs. Comparative analysis of the direct ET rate constants, estimated from the amperometric data on direct and mediated ET in the presence of catechol at pH 7.4 and 6.0, gave evidence that the introduction of the His-tag or cysteine in the C-terminal area of the enzyme resulted in an increased efficiency of direct ET due to a favourable coupled electron and proton transfer pathway. Due to the high efficiency of direct ET, the sensitivity was independent on the addition of the mediator or change of pH indicating that the response to H2O2 is determined solely by the mass transfer of the analyte to the active site of HRP. The sensitivities obtained for the Au electrodes modified with rHRPs (2.0 +/- 0.1 A M-1 cm(-2)) and the low detection limit for H2O2 (10 nM) paves the way to develop the P-chip (peroxidase chip) - a biosensors system of a microscopic size for a mediatorless detection of H2O2 based on direct ET between Au and the recombinant forms of HRP. (C) 2002 Elsevier Science B.V. All rights reserved.
|
|
| 10. |
- Filippini, Daniel, et al.
(författare)
-
Microplate based biosensing with a computer screen aided technique
- 2003
-
Ingår i: Biosensors & bioelectronics. - 0956-5663 .- 1873-4235. ; 19:1, s. 35-41
-
Tidskriftsartikel (refereegranskat)abstract
- Melanophores, dark pigment cells from the frog Xenopus laevis, have the ability to change light absorbance upon stimulation by different biological agents. Hormone exposure (e.g. melatonin or α-melanocyte stimulating hormone) has been used here as a reversible stimulus to test a new compact microplate reading platform. As an application, the detection of the asthma drug formoterol in blood plasma samples is demonstrated. The present system utilizes a computer screen as a (programmable) large area light source, and a standard web camera as recording media enabling even kinetic microplate reading with a versatile and broadly available platform, which suffices to evaluate numerous bioassays. Especially in the context of point of care testing or self testing applications these possibilities become advantageous compared with highly dedicated comparatively expensive commercial systems.
|
|
| 11. |
- Fällman, Erik, et al.
(författare)
-
Optical tweezers based force measurement system for quantitating binding interactions : system design and application for the study of bacterial adhesion
- 2004
-
Ingår i: Biosensors & bioelectronics. - : Elsevier. - 0956-5663 .- 1873-4235. ; 19:11, s. 1429-1437
-
Tidskriftsartikel (refereegranskat)abstract
- An optical force measurement system for quantitating forces in the pN range between micrometer-sized objects has been developed. The system was based upon optical tweezers in combination with a sensitive position detection system and constructed around an inverted microscope. A trapped particle in the focus of the high numerical aperture microscope-objective behaves like an omnidirectional mechanical spring in response to an external force. The particle’s displacement from the equilibrium position is therefore a direct measure of the exerted force. A weak probe laser beam, focused directly below the trapping focus, was used for position detection of the trapped particle (a polystyrene bead). The bead and the condenser focus the light to a distinct spot in the far field, monitored by a position sensitive detector. Various calibration procedures were implemented in order to provide absolute force measurements. The system has been used to measure the binding forces between Escherichia coli bacterial adhesins and galabiose-functionalized beads
|
|
| 12. |
- Gabig-Ciminska, Magdalena, et al.
(författare)
-
Electric chips for rapid detection and quantification of nucleic acids
- 2004
-
Ingår i: Biosensors & bioelectronics. - : Elsevier BV. - 0956-5663 .- 1873-4235. ; 19:6, s. 537-546
-
Tidskriftsartikel (refereegranskat)abstract
- A silicon chip-based electric detector coupled to bead-based sandwich hybridization (BBSH) is presented as an approach to perform rapid analysis of specific nucleic acids. A microfluidic platform incorporating paramagnetic beads with immobilized capture probes is used for the biorecognition steps. The protocol involves simultaneous sandwich hybridization of a single-stranded nucleic acid target with the capture probe on the beads and with a detection probe in the reaction solution, followed by enzyme labeling of the detection probe, enzymatic reaction, and finally, potentiometric measurement of the enzyme product at the chip surface. Anti-DIG-alkaline phosphatase conjugate was used for the enzyme labeling of the DIG-labeled detection probe. p-Aminophenol phosphate (pAPP) was used as a substrate. The enzyme reaction product, p-aminophenol (pAP), is oxidized at the anode of the chip to quinoneimine that is reduced back to pAP at the cathode. The cycling oxidation and reduction of these compounds result in a current producing a characteristic signal that can be related to the concentration of the analyte. The performance of the different steps in the assay was characterized using in vitro synthesized RNA oligonucleotides and then the instrument was used for analysis of 16S rRNA in Escherichia coli extract. The assay time depends on the sensitivity required. Artificial RNA target and 16S rRNA, in amounts ranging from 10(11) to 10(10) molecules, were assayed within 25 min and 4 h, respectively.
|
|
| 13. |
- Granéli, Annette, 1973, et al.
(författare)
-
Utilizing adsorbed proteoliposomes trapped in a non-ruptured state on SiO2 for amplified detection of membrane proteins
- 2004
-
Ingår i: Biosensors & bioelectronics. - : Elsevier BV. - 0956-5663 .- 1873-4235. ; 20:3, s. 498-504
-
Tidskriftsartikel (refereegranskat)abstract
- The quartz crystal microbalance with dissipation (QCM-D) technique was used to monitor the formation of supported phospholipid bilayers (SPBs) on SiO2 using proteoliposomes with reconstituted proton translocating nicotinamide nucleotide transhydrogenase (TH). Exposure of the surface to such proteoliposomes creates a lipid film composed of a mixture of proteolipid bilayers and adsorbed non-ruptured proteoliposomes, where the fraction of the latter is reduced if the TH-liposomes are pretreated with trypsin to remove the water soluble domains of TH [Langmuir 19 (2003) 842]. In the present work, the latter study is complemented by investigating the influence of trypsin treatment of the mixed adlayer (proteolipid bilayer + non-ruptured proteoliposomes) after adsorption on the surface. This demonstrates how trypsin-cleavage induced rupture of adsorbed TH-liposomes can be utilized to detect the presence of less than 0.04 pmol/cm2 of immobilized TH.
|
|
| 14. |
- Hansson, Kenny, 1972-, et al.
(författare)
-
Comparative studies with surface plasmon resonance and free oscillation rheometry on the inhibition of platelets with cytochalasin E and monoclonal antibodies towards GPIIb/IIIa
- 2002
-
Ingår i: Biosensors & bioelectronics. - 0956-5663 .- 1873-4235. ; 17:9, s. 761-771
-
Tidskriftsartikel (refereegranskat)abstract
- In the haemostatic system a multitude of processes are intertwined in fine-tuned interactions that arrest bleeding, keep the circulatory system open, and the blood flowing. The occurrence of both surface and bulk interactions adds an additional dimension of complexity. These insights have led to the belief that global overall procedures can inform on the likely behaviour of the system in health and disease. Two sensing procedures: surface plasmon resonance (SPR), which senses surface interactions, and free oscillation rheometry (FOR), which senses interactions within the bulk, have been combined and evaluated. The contribution of blood cells, mainly platelets, to the SPR and FOR signals was explored by simultaneous SPR and FOR measurement during native whole blood coagulation, accelerated via the platelets through addition of SFLLRN peptide and inhibition of platelet aggregation with abciximab (ReoPro®) and of shape change with cytochalasin E. The SPR technique was found to be sensitive to inhibition of blood cell functions such as adhesion to and spreading on surfaces, as well as platelet aggregation. SPR seemed not to be directly sensitive to fibrin polymerisation in coagulating whole blood. The FOR technique detected the coagulation as a bulk phenomenon, i.e. the gelation of the blood due to fibrin formation was detected. The combination of SPR and FOR may therefore be suitable for studies on blood cell functions during coagulation.
|
|
| 15. |
- Hansson, Kenny, 1972-, et al.
(författare)
-
Surface plasmon resonance and free oscillation rheometry in combination : a useful approach for studies on haemostasis and interactions between whole blood and artificial surfaces
- 2002
-
Ingår i: Biosensors & bioelectronics. - 0956-5663 .- 1873-4235. ; 17:9, s. 747-759
-
Tidskriftsartikel (refereegranskat)abstract
- In haemostatic and biomaterial research biological processes at surfaces and in the bulk phase of the surface-contacting medium are important. The present work demonstrates the usefulness of the combination of surface plasmon resonance (SPR), sensitive to changes in refractive index at surfaces, and free oscillation rheometry (FOR), sensitive to rheological properties of the bulk, for simultaneous real-time measurements on coagulation and fibrinolysis of blood plasma and coagulation of whole blood. SFLLRN stimulated coagulation of native whole blood presented a higher SPR signal with different appearance than plasma coagulation, while the FOR signals corresponding to plasma and whole blood coagulation were similar. This indicated that the SPR technique was more sensitive to cell-surface interactions than to fibrin formation in whole blood during coagulation, while the FOR technique were equally sensitive to coagulation in whole blood and plasma. Spontaneous coagulation of native whole blood in contact with methyl- and hydroxyl-terminated self-assembled monolayers (SAM) on gold and gold surfaces regenerated after coagulation were also studied. The regenerated gold surfaces displayed the shortest coagulation times, although the contact-activation of blood coagulation for these surfaces was low. The methylated and hydroxylated surfaces were comparable in terms of coagulation activation, while the hydroxylated surfaces presented FOR signals that indicated detaching of the coagulum from the surface. The combination of SPR and FOR is well suited for studies of cell– and protein–surface interactions and simultaneous bulk processes. Possible applications are investigations of blood cell defects in patients and monitoring of native whole blood interactions with artificial surfaces.
|
|
| 16. |
- Hong, Feng, et al.
(författare)
-
Rapid and convenient determination of oxalic acid employing a novel oxalate biosensor based on oxalate oxidase and SIRE technology
- 2003
-
Ingår i: Biosensors & Bioelectronics. - 1873-4235. ; 18:9, s. 1173-1181
-
Tidskriftsartikel (refereegranskat)abstract
- A new method for rapid determination of oxalic acid was developed using oxalate oxidase and a biosensor based on SIRE (sensors based on injection of the recognition element) technology. The method was selective, simple, fast, and cheap compared with other present detection systems for oxalate. The total analysis time for each assay was 2-9 min. A linear range was observed between 0 and 5 mM when the reaction conditions were 30 degreesC and 60 s. The linear range and upper limit for concentration determination could be increased to 25 mM by shortening the reaction time. The lower limit of detection in standard solutions, 20 muM, could be achieved by means of modification of the reaction conditions, namely increasing the temperature and the reaction time. The biosensor method was compared with a conventional commercially available colorimetric method with respect to the determination of oxalic acid in urine samples. The urine oxalic acid concentrations determined with the biosensor method correlated well (R = 0.952) with the colorimetric method. (C) 2002 Elsevier Science B.V. All rights reserved.
|
|
| 17. |
- Håkansson, Kristina, et al.
(författare)
-
A biosensor for the analysis of acetonitrile
- 2004
-
Ingår i: Biosensors & Bioelectronics. - : Elsevier BV. - 1873-4235 .- 0956-5663. ; 19:7, s. 721-726
-
Tidskriftsartikel (refereegranskat)abstract
- A biosensor for monitoring acetonitrile was constructed. A mixed culture was taken from a degradation reactor and mounted on top of a Clark electrode. The amperometric biosensor was placed in a flow-through cell and integrated into a flow injection system. The metabolic response in terms of oxygen consumption was well correlated to the concentration of acetonitrile in standard solutions. However, when the reaction products, acetic acid and ammonia, were also present, the response was erratic, due to the additional metabolic reaction on acetate. By introducing a hydrophobic barrier it was possible to eliminate the negative influence of these charged products and thus to improve the operational selectivity of the sensor. The biosensor showed good stability for analysis during at least 6 days and future work will focus on using it for monitoring and control of degradation processes. (C) 2003 Elsevier B.V. All rights reserved.
|
|
| 18. |
- Jain, Seema Rani, et al.
(författare)
-
A chemiluminescence flow immunosensor based on a porous monolithic metacrylate and polyethylene composite disc modified with Protein G
- 2004
-
Ingår i: Biosensors & Bioelectronics. - : Elsevier BV. - 1873-4235 .- 0956-5663. ; 19:8, s. 795-803
-
Tidskriftsartikel (refereegranskat)abstract
- A generic, fast, sensitive and new type of flow immunosensor has been developed. The basis is a monolithic porous poly(glycidyl methacrylate-co-trimethylolpropane trimethacrylate) polymer disc modified with protein G, placed in a fountain type flow cell compartment, in close proximity to a photomultiplier tube (PMT). Analyte and HRP labelled analyte derivative (tracer) compete for anti-analyte antibody binding sites. The mixture is then injected into the flow immunosensor system where the formed analyte- and tracer-antibody complexes are trapped by the monolithic protein G disc. The amount of bound tracer, inversely related to the concentration of analyte in the sample, is determined in a second step by injection of luminol, p-iodophenol and H2O2, generating enhanced chemiluminescence (CL) with horseradish peroxidase (HRP). A third and final step is need for regeneration of the protein G disc so that a new analysis cycle can take place. The performance of the disc immunosensor system was compared with a one step continuous flow injection immunoassay (FIIA) system, using the same reagents and a protein G column, in terms of assay sensitivity and influence of matrix effects from various water samples (millipore-, tap- and surface water). The detection limit for the analyte atrazine in PBS and surface water (SW) was 0.208±0.004 g l−1 (PBS) and 0.59±0.120 g l−1 (SW) for the FIIA and 0.033±0.003 g l−1 (PBS) and 0.038±0.003 g l−1 (SW) for the disc immunosensor. Statistical comparison of the two systems shows that the disc immunosensor results were significantly less influenced by the sample matrix, which is explained by the fact that the sample in the FIIA arrives simultaneously with the matrix to the detector, whereas these are separated in time in the disc immunosensor system.
|
|
| 19. |
- Johansen, Knut, et al.
(författare)
-
Sensitivity deviation : Instrumental linearity errors that influence concentration analyses and kinetic evaluation of biomolecular interactions
- 2000
-
Ingår i: Biosensors & bioelectronics. - 0956-5663 .- 1873-4235. ; 15:9-10, s. 503-509
-
Tidskriftsartikel (refereegranskat)abstract
- Many scientific instruments utilise multiple element detectors, e.g. CCD's or photodiode arrays, to monitor the change in a position of an optical pattern. For example, instruments for affinity biosensing based on surface plasmon resonance (SPR) or resonant mirror are equipped with such detectors. An important and desired property of these bioanalytical instruments is that the calculation of the movement or change in shape follows the true change. This is often not the case and it may lead to linearity errors, and to sensitivity errors. The sensitivity is normally defined as the slope of the calibration curve. A new parameter is introduced to account for the linearity errors, the sensitivity deviation, defined as the deviation from the undistorted slope of the calibration curve. The linearity error and the sensitivity deviation are intimately related and the sensitivity deviation may lead to misinterpretation of kinetic data, mass transport limitations and concentration analyses. Because the linearity errors are small (e.g. 10 pg/mm2 of biomolecules on the sensor surface) with regard to the dynamic range (e.g. 30 000 pg/mm2), they can be difficult to discover. However, the linearity errors are often not negligible with regard to a typical response (e.g. 0-100 pg/mm2), and may therefore cause serious problems. A method for detecting linearity errors is outlined. Further on, this paper demonstrates how integral linearity errors of less than 1% can result in a sensitivity deviation of 10%, a value that in our opinion cannot be ignored in biospecific interaction analysis (BIA). It should also be stressed out that this phenomenon also occurs in other instruments using array detectors. (C) 2000 Elsevier Science S.A.Many scientific instruments utilize multiple element detectors, e.g. CCD's or photodiode arrays, to monitor the change in a position of an optical pattern. For example, instruments for affinity biosensing based on surface plasmon resonance (SPR) or resonant mirror are equipped with such detectors. An important and desired property of these bioanalytical instruments is that the calculation of the movement or change in shape follows the true change. This is often not the case and it may lead to linearity errors, and to sensitivity errors. The sensitivity is normally defined as the slope of the calibration curve. A new parameter is introduced to account for the linearity errors, the sensitivity deviation, defined as the deviation from the undistorted slope of the calibration curve. The linearity error and the sensitivity deviation are intimately related and the sensitivity deviation may lead to misinterpretation of kinetic data, mass transport limitations and concentration analyses. Because the linearity errors are small (e.g. 10 pg/mm2 of biomolecules on the sensor surface) with regard to the dynamic range (e.g. 30 000 pg/mm2), they can be difficult to discover. However, the linearity errors are often not negligible with regard to a typical response (e.g. 0-100 pg/mm2), and may therefore cause serious problems. A method for detecting linearity errors is outlined. Further on, this paper demonstrates how integral linearity errors of less than 1% can result in a sensitivity deviation of 10%, a value that in our opinion cannot be ignored in biospecific interaction analysis (BIA). It should also be stressed out that this phenomenon also occurs in other instruments using array detectors.
|
|
| 20. |
- Liang, Z P, et al.
(författare)
-
Electrochemical study of the XNA on Gold (TM) microarray
- 2004
-
Ingår i: Biosensors & Bioelectronics. - : Elsevier BV. - 1873-4235 .- 0956-5663. ; 20:2, s. 211-216
-
Tidskriftsartikel (refereegranskat)abstract
- A novel electrode array was developed based on the XNA on Gold(TM) microarray platform. The platform combines self-assembling monolayers, thick film patterning and streptavidin based immobilization to provide a robust, versatile platform capable of analysing virtually any biomolecule including nucleic acids, proteins, carbohydrates and lipids. Electrochemical analysis of the self-assembling monolayer/streptavidin (SAMS) XNA on Gold(TM) coating revealed that the ferrocene redox current for the SAMS modified electrode was greater than that with a bare Gold(TM) electrode. The electrochemical reaction of K4Fe(CN)(6) was inhibited by the SAMS coating, but was reactivated upon addition of ferrocene. These results indicate that ferrocene is involved as a mediator in the electron transfer of K4Fe(CN)(6) to the SAMS modified electrode. Addition of DNA to the SAMS resulted in only a minor change in the electrochemical signal, indicating that XNA on Gold(TM) can be used for electrochemical based bioanalysis. After cycling a SAMS electrode 50 times, no signs of deterioration were detected showing that coating has excellent stability. In addition to the biosensing applications, the scheme provides a non-invasive method for accessing the quality of the SAMS coatings which is of industrial interest. These studies show that the XNA on Gold(TM) microarray platform can be used for electrochemical studies, thus providing an additional alternative for developing multianalyte biosensors as well as expanding the range of detection methods available for microarray analysis. (C) 2004 Elsevier B.V. All rights reserved.
|
|
| 21. |
- Liljeblad, Mathias, et al.
(författare)
-
Analysis of glycoproteins in cell culture supernatants using a lectin immunosensor technique
- 2002
-
Ingår i: Biosensors & bioelectronics. - 0956-5663 .- 1873-4235. ; 17:10, s. 883-891
-
Tidskriftsartikel (refereegranskat)abstract
- A method based on a surface plasmon resonance technique for detection of changes in concentration and glycosylation of proteins in cell culture supernatant is described. The method was used to analyze α1-acid glycoprotein (AGP) produced by a human hepatoma cell line (HepG2). Cell culture supernatant was injected to a BIACORE 2000 instrument and AGP was captured on the sensor chip by immobilized antibodies. The captured glycoprotein was then analyzed for content of carbohydrate epitopes using three different lectins, Aleuria aurantia lectin (AAL), Sambucus nigra agglutinin (SNA), and Triticum vulgaris agglutinin (wheat germ agglutinin, WGA). The method was used to analyze changes in concentration and glycosylation of AGP produced by HepG2 cells grown with or without three different cytokines, interleukin-1β (IL-1β), interleukin-6 (IL-6), and transforming growth factor β-1 (TGFβ1). Using the described method it was shown that when HepG2 cells were grown in the presence of IL-6 both AGP concentration and fucosylation increased. When HepG2 cells instead were grown in the presence of TGFβ1 AGP fucosylation increased whereas AGP concentration decreased.
|
|
| 22. |
- Liu, Jing, et al.
(författare)
-
Immobilised activated sludge based biosensor for biochemical oxygen demand measurement
- 2000
-
Ingår i: Biosensors & Bioelectronics. - 1873-4235. ; 14:12, s. 883-893
-
Tidskriftsartikel (refereegranskat)abstract
- A biochemical oxygen demand (BOD) sensor, based on an immobilised mixed culture of microorganisms in combination with a dissolved oxygen electrode, has been developed for the purpose of on-line monitoring of the biological treatment process for waste and wastewater. The sensor was designed for easy replacement of the biomembrane, thereby making it suitable for short-term use. The drawbacks of activated sludge based sensor, such as short sensor lifetime, were thereby circumvented. The sensor BOD measurements were carried out in the kinetic mode using a flow injection system, resulting in 25 s for one measurement followed by 4-8 min recovery time. Based on the results of normalised sensor responses, the OECD synthetic wastewater was considered to be a more suitable calibration solution in comparison with the GGA solution. Good agreement was achieved between the results of the sensor BOD measurement and those obtained from BOD5 analysis of a wastewater sample from a food-processing factory. Reproducibility of responses using one sensor was below +/-5.6% standard deviation. Reproducibility of responses using different sensors was within acceptable bias limits, viz. +/-15% standard deviation.
|
|
| 23. |
- Liu, Jing, et al.
(författare)
-
Short-term BOD (BODst) as a parameter for on-line monitoring of biological treatment process Part 1. A novel design of BOD biosensor for easy renewal of bio-receptor
- 2004
-
Ingår i: Biosensors & Bioelectronics. - : Elsevier BV. - 1873-4235 .- 0956-5663. ; 20:3, s. 562-570
-
Tidskriftsartikel (refereegranskat)abstract
- A novel design of a biochemical oxygen demand (BOD) biosensor has been developed for on-line monitoring of easily biodegradable organic compounds in aqueous samples. The biological recognition element of the sensor could be easily renewed by injecting new bacterial paste without disassembling the sensor system. The sensor measurements were carried out in the initial-rate mode using a flow injection (FI) system, resulting in 60s for one sample analysis followed by a recovery time less than 10 min. The sensor performance achieved showed a wide detection linearity over the range of 5-700 mg BOD5.1(-1) and a generally good agreement between the BOD values estimated by the biosensor and the conventional 5-day test. Furthermore, the precision test was in the control range (i.e. repeatability less than or equal to+/-7.5%, reproducibility less than or equal to+/-7.3%). The sensor could be used over 1 week in continuous test, however, the best performance was found within the first 24 h where standard deviation of the sensor response was +/-2.4%. The design of the sensor allows easy and fast renewal of the cells used as sensing elements. Replacement of biological recognition element and calibration of the sensor responses can be performed in a rather simple procedure on a daily regular basis. By using a mixed culture as the bio-receptor, one gets a sensor that reacts to a wide range of substrates. The new sensor construction will thus allow fast and convenient replacement of the bio-receptor and on-line assay of a broad range of substrates. This makes the sensor being an interesting and promising candidate for on-line monitoring of biological treatment process. (C) 2004 Elsevier B.V. All rights reserved.
|
|
| 24. |
- Liu, Jing, et al.
(författare)
-
Short-term BOD (BODst) as a parameter for on-line monitoring of biological treatment process. Part II: Instrumentation of integrated flow injection analysis (FIA) system for BODst estimation
- 2004
-
Ingår i: Biosensors & Bioelectronics. - : Elsevier BV. - 1873-4235 .- 0956-5663. ; 20:3, s. 571-578
-
Tidskriftsartikel (refereegranskat)abstract
- An instrument with integrated flow injection analysis (FIA) system has been developed for on-line monitoring a process for conversion of biomass under field condition. The instrument consists of a newly designed biosensor for easy renewal of the bio-receptor without disassembling the sensor, a FIA controller for controlling the analysis operations, and a computer-based data acquisition system for data recording and processing. The instrument performed a sequence operations automatically including preparation of sample in the desired concentration, sample loading, sample injection, signal recording, data processing, and self-cleaning of the system. This makes the instrument being an interesting and promising device for on-line process monitonng. (C) 2004 Elsevier B.V. All rights reserved.
|
|
| 25. |
- Lotierzo, M, et al.
(författare)
-
Surface plasmon resonance sensor for domoic acid based on grafted imprinted polymer
- 2004
-
Ingår i: Biosensors & bioelectronics. - : Elsevier Science B.V., Amsterdam.. - 0956-5663 .- 1873-4235. ; 20:2, s. 145-152
-
Tidskriftsartikel (refereegranskat)abstract
- A molecularly imprinted polymer (MIP) film for domoic acid (DA) was synthesised by direct photo-grafting onto a gold chip suitable for a surface plasmon resonance (SPR) based bioanalytical instrument system, the BlAcore 3000(TM). The gold surface was first functionalised with a self-assembled monolayer of 2-mercaptoethylamine and subsequent carbodiimide chemistry was performed for covalent attachment of the photoinitiator, 4,4-azobis(cyanovaleric acid). This ensured that the formation of the MIP thin film, comprising 2-(diethyl amino) ethyl methacrylate as functional monomer and ethylene glycol dimethacrylate as cross-linker, occurred only at the surface level. Optimisation and control over the grafting procedure were achieved using contact angle measurements and atomic force microscope (AFM) imaging. The surface grafting resulted in the formation of thin and homogeneous MIP film with thickness of 40 nm. A competitive binding assay was performed with free DA and its conjugate with horseradish peroxidase, which was used as a refractive label. The sensor was evaluated for its sensitivity, cross-reactivity, and robustness by using a BlAcore 3000(TM). Likewise, monoclonal antibodies acting as natural receptors for the toxin were studied with the same BlAcore system. Results of a comparison between the artificial and natural receptors are reported. In contrast to monoclonal antibodies, the regeneration of MIP chip did not affect its recognition properties and continuous measurement was possible over a period of at least 2 months. (C) 2004 Elsevier B.V. All rights reserved.
|
|
| 26. |
- Lucarelli, F, et al.
(författare)
-
Carbon and gold electrodes as electrochemical transducers for DNA hybridisation sensors
- 2004
-
Ingår i: Biosensors & bioelectronics. - : Elsevier Science B.V., Amsterdam.. - 0956-5663 .- 1873-4235. ; 19:6, s. 515-530
-
Forskningsöversikt (refereegranskat)abstract
- Genosensor technology relying on the use of carbon and gold electrodes is reviewed. The key steps of each analytical procedure, namely DNA-probe immobilisation, hybridisation, labelling and electrochemical investigation of the surface, are discussed in detail with separate sections devoted to label-free and newly emerging magnetic assays. Special emphasis has been given to protocols that have been used with real DNA samples. (C) 2003 Elsevier B.V. All fights reserved.
|
|
| 27. |
- Mak, Wing Cheung, et al.
(författare)
-
Biosensor for rapid phosphate monitoring in sequencing batch reactor (SBR) system
- 2003
-
Ingår i: Biosensors & bioelectronics. - : Elsevier. - 0956-5663 .- 1873-4235. ; 19:3, s. 233-237
-
Tidskriftsartikel (refereegranskat)abstract
- A thick-film phosphate biosensor based on hydrogel immobilized pyruvate oxidase (POD) has been developed for rapid phosphate process control monitoring in an experimental sequencing batch reactor (SBR) system. We have employed a phosphate biosensor in an off-line monitoring of phosphate concentrations in a bench scale SBR. Measurements with biosensor show a good correlation (r2=0.98) with those of commercial colorimetric phosphate testing kits. The signal response time was 1 min with a detection limit of 5 microM. The biosensor method showed a good operational stability, needed less experimental procedures and a small sample size (approximately 20 microl). This allows its practical application for rapid phosphate measurements to obtain real time process data in a SBR system.
|
|
| 28. |
- Mak, Wing Cheung, et al.
(författare)
-
Novel biosensors for quantitative phytic acid and phytase measurement
- 2004
-
Ingår i: Biosensors & bioelectronics. - : Elsevier. - 0956-5663 .- 1873-4235. ; 19:9, s. 1029-1035
-
Tidskriftsartikel (refereegranskat)abstract
- Phytase (EC 3.1.3.26) and phytic acid (myo-inositol hexaphosphate) play an important environmental role in poultry industry and have a health aspect in food industry. Novel biosensors have been developed for simple, one step quantitative phytic acid and phytase detection. A system based on the sequentially acting enzyme phytase and pyruvate oxidase (POD) was employed for the development of phytase and phytic acid biosensors. Poly(carbamoylsulphonate) (PCS) hydrogel immobilized POD electrode was applied for the detection of phytase. It was based on the indication of phosphate ions produced by the hydrolysis of phytic acid. The phytase biosensor showed a linear response ranging from 0.5 to 6.0 units/ml. A bi-enzyme sensor based on co-immobilization of phytase and POD was developed for the detection of phytic acid on the basis of amperometric detection of the enzymatically-generated hydrogen peroxide at 0.6 V versus Ag/AgCl. It showed a linear response ranging from 0.2 to 2.0 mM with a detection limit of 0.002 mM.
|
|
| 29. |
|
|
| 30. |
- Mosbach, M., et al.
(författare)
-
A miniaturised electrochemical affinity assay based on a wall-free sample droplet and micro-dispensing of the redox-labelled binding partner
- 2001
-
Ingår i: Biosensors & Bioelectronics. - : Elsevier BV. - 1873-4235 .- 0956-5663. ; 16:9-12, s. 611-620
-
Tidskriftsartikel (refereegranskat)abstract
- An affinity-assay was developed that is based on the modulation of the diffusion coefficient of a redox-labelled hapten upon complementary recognition of the analyte leading to an increase of molecular weight and hence to a decrease of the diffusion coefficient. The slower diffusion is monitored by means of cyclic voltammetry. In order to demonstrate the feasibility of this assay format, recognition of biotin by streptavidin has been chosen as a model system. Labelling of biotin was achieved by covalent binding of a ferrocene derivative to the biotin unit. To reduce the consumption of expensive compounds and to allow automatisation of the assay a novel miniaturised set-up was developed based on a wall-free sample droplet which forms the electrochemical cell with typical volumes of up to 10 mul. This droplet is dispensed by means of a step-motor driven syringe pump through a specially designed electrode holder spanning the gap between a micro-working electrode and a macroscopic counter electrode. By means of a piezo-driven micro-dispenser a predefined number of nano-droplets (100 pl volume each) containing the redox-labelled hapten are shot into the sample droplet. By this, any physical contact and hence any cross-contamination between the sample and the reagent solution could be avoided. Signal amplification can be achieved by redox recycling between the micro-electrode and the perpendicular positioned macroscopic counter electrode. (C) 2001 Elsevier Science B.V. All rights reserved.
|
|
| 31. |
- Mosbach, M, et al.
(författare)
-
Picodroplet-deposition of enzymes on functionalized self-assembled monolayers as a basis for miniaturized multi-sensor structures
- 2001
-
Ingår i: Biosensors & Bioelectronics. - : Elsevier BV. - 1873-4235 .- 0956-5663. ; 16:9-12, s. 827-837
-
Tidskriftsartikel (refereegranskat)abstract
- We are reporting on a novel approach for structured immobilisation of enzymes on gold surfaces modified with monolayers of functionalised alkylthiols. The formation of enzyme spots is achieved by shooting very small volumes of an appropriate enzyme solution (down to 100 pl) onto a thiol-monolayer modified gold surface using a micro-dispenser. Formation of enzyme patterns is obtained by moving the micro-dispenser relative to the modified gold surface using a micro-positioning device. Enzyme spots with typical lateral dimensions of 100 ml are obtained, but also, more complex structures, e.g. lines or meander structures, can be achieved by multiple droplets dispensed during the concomitant movement of the micro-dispenser. The first enzyme layer on top of the functionalised thiol-monolayer is subsequently covalently immobilised using either carbodiimide activation of carboxilic headgroups at the enzyme or via already introduced activated ester functions at the monolayer. Immobilised enzyme activities of glucose oxidase and lactate oxidase patterns have been characterised by means of scanning electrochemical microscopy. The product of the enzyme-catalysed reaction, H2O2, is detected with an micro-electrode in the presence of either or both substrates, glucose and lactate, leading to a visualisation of the corresponding enzyme pattern and the lateral enzymatic activity. (C) 2001 Elsevier Science B.V. All rights reserved.
|
|
| 32. |
- Niculescu, Mihaela, et al.
(författare)
-
Visualization of micropatterned complex biosensor sensing chemistries by means of scanning electrochemical microscopy
- 2004
-
Ingår i: Biosensors & Bioelectronics. - : Elsevier BV. - 1873-4235 .- 0956-5663. ; 19:10, s. 1175-1184
-
Tidskriftsartikel (refereegranskat)abstract
- Redox hydrogel-based micropatterned complex biosensor architectures, used as sensing chemistries in amperometric ethanol or glucose biosensors, were deposited on gold, graphite or glass. Well-localized immobilization of active hydrogels with variable compositions was achieved by dispensing 100 pl droplets of cocktails containing alcohol or glucose dehydrogenase, redox polymer (PVI(13)dmeOs) and crosslinker (PEGDGE) while moving the target surface relative to the position of the nozzle of a piezo-actuated microdispenser. The resulting structures were microscopic patterns of enzyme-containing lines of a redox hydrogel with a line width of about 100 mum. Scanning electrochemical microscopy (SECM) in the amperometric feedback mode was used to visualize the immobilized enzyme microstructures and their localized biochemical activity was observed with high lateral resolution by detecting the enzymatically consumed substrate using K-4[Fe(CN)(6)] as a free-diffusing electron-transfer mediator. (C) 2003 Elsevier B.V. All rights reserved.
|
|
| 33. |
- Pavlou, AK, et al.
(författare)
-
An intelligent rapid odour recognition model in discrimination of Helicobacter pylori and other gastroesophageal isolates in vitro
- 2000
-
Ingår i: Biosensors & bioelectronics. - : Elsevier Science B.V., Amsterdam.. - 0956-5663 .- 1873-4235. ; 15:08-jul, s. 333-342
-
Tidskriftsartikel (refereegranskat)abstract
- Two series of experiments are reported which result in the discrimination between Helicobacter pylori and other bacterial gastroesophageal isolates using a newly developed odour generating system, an electronic nose and a hybrid intelligent odour recognition system. In the first series of experiments, after 5 h of growth (37 degreesC), 53 volatile sniffs were collected over the headspace of complex broth cultures of the following clinical isolates: Staphylococcus aureus, Klebsiella sp., H. pylori, Enterococcus faecalis (10(7) ml(-1)), Mixed infection (Proteus mirabilis, Escherichia coli, and E. faecalis 3 x 10(6) mi each) and sterile cultures. Fifty-six normalised variables were extracted from 14 conductive polymer sensor responses and analysed by a 3-layer back propagation neural network (NN). The NN prediction rate achieved was 98% and the test data (37.7% of all data) was recognised correctly. Successful clustering of bacterial classes was also achieved by discriminant analysis (DA) of a normalised subset of sensor data. Cross-validation identified correctly seven unknown samples. In the second series of experiments after 150 min of microaerobic growth at 37 degreesC, 24 volatile samples were collected over the headspace of H. pylori cultures in enriched (HPP) and normal (HP) media and 11 samples over sterile (N) cultures. Forty-eight sensor parameters were extracted from 12 sensor responses and analysed by a 3-layer NN previously optimised by a genetic algorithm (GA). GA-NN analysis achieved a 94% prediction rate or unknown data. Additionally the genetically selected 16 input neurones were used to perform DA-cross validation that showed a clear clustering of three groups and reclassified correctly nine sniffs. It is concluded that the most important factors that govern the performance of an intelligent bacterial odour detection system are: (a) an odour generation mechanism, (b) a rapid odour delivery system similar to the mammalian olfactory system, (c) a gas sensor array of high reproducibility and (d) a hybrid intelligent model (expert system) which will enable the parallel use of GA-NNs and multivariate techniques. (C) 1999 Elsevier Science S.A. All rights reserved.
|
|
| 34. |
- Pavlou, Alexandros K., et al.
(författare)
-
Detection of Mycobacterium tuberculosis (TB) in vitro and in situ using an electronic nose in combination with a neural network system
- 2004
-
Ingår i: Biosensors & bioelectronics. - : Elsevier. - 0956-5663 .- 1873-4235. ; 20:3, s. 538-544
-
Tidskriftsartikel (refereegranskat)abstract
- The use of volatile production patterns produced by Mycobacterium tuberculosis and associated bacterial infections from sputum samples were examined in vitro and in situ using an electronic nose based on a 14 sensor conducting polymer array. In vitro, it was possible to successfully discriminate between M. tuberculosis (TB) and control media, and between M. tuberculosis and M. avium, M. scrofulaceum and Pseudomonas aeruginosa cultures in the stationary phase after 5-6 h incubation at 37degreesC based on 35 samples. Using neural network (NN) analysis and cross-validation it was possible to successfully identify 100% of the TB cultures from others. A second in vitro study with 61 samples all four groups were successfully discriminated with 14 of 15 unknowns within each of the four groups successfully identified using cross-validation and discriminant function analysis. Subsequently, lipase enzymes were added to 46 sputum samples directly obtained from patients and the head space analysed. Parallel measurements of bacterial contamination were also carried out for confirmation using agar media. NN analysis was carried out using some of the samples as a training set. Based on the NN and genetic algorithms of up to 10 generations it was possible to successfully cross-validate 9 of 10 unknown samples. PCA was able to discriminate between TB infection alone, the controls, M. avium, P. aeruginosa and a mixed infection. These findings will have significant implications for the development of rapid qualitative systems for screening of patient samples and clinical diagnosis of tuberculosis.
|
|
| 35. |
- Pavlou, AK, et al.
(författare)
-
Use of an electronic nose system for diagnoses of urinary tract infections
- 2002
-
Ingår i: Biosensors & bioelectronics. - : Elsevier Science B.V., Amsterdam.. - 0956-5663 .- 1873-4235. ; 17:10, s. 893-899
-
Tidskriftsartikel (refereegranskat)abstract
- The use of volatile production patterns produced by bacterial contaminants in urine samples were examined using electronic nose technology. In two experiments 25 and 45 samples from patients were analysed for specific bacterial contaminants using agar culture techniques and the major UTI bacterial species identified. These samples were also analysed by incubation in a volatile generation test tube system for 4-5 h. The volatile production patterns were then analysed using an electronic nose system with 14 conducting polymer sensors. In the first experiment analysis of the data using a neural network (NN) enabled identification of all but one of the samples correctly when compared to the culture information. Four groups could be distinguished, i.e. normal urine, Escherichia coli infected, Proteus spp. and Staphylococcus spp. In the second experiment it was again possible to use NN systems to examine the volatile production patterns and identify 18 of 19 unknown UTI cases. Only one normal patient sample was mis-identified as an E coli infected sample. Discriminant function analysis also differentiated between normal urine samples, that infected with E coli and with Staphylococcus spp. This study has shown the potential for early detection of microbial contaminants in urine samples using electronic nose technology for the first time. These findings will have implications for the development of rapid systems for use in clinical practice. (C) 2002 Elsevier Science B.V. All rights reserved.
|
|
| 36. |
- Pfeiffer, Dorothea, et al.
(författare)
-
Professor Frieder Scheller turns 60
- 2002
-
Ingår i: Biosensors & bioelectronics. - : Elsevier. - 0956-5663 .- 1873-4235. ; 17:11-12, s. 911-912
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 37. |
- Piehler, J., et al.
(författare)
-
A high-density poly(ethylene glycol) polymer brush for immobilization on glass-type surfaces
- 2000
-
Ingår i: Biosensors & bioelectronics. - 0956-5663 .- 1873-4235. ; 15:9-10, s. 473-481
-
Tidskriftsartikel (refereegranskat)abstract
- Label-free heterogeneous phase detection critically depends on the properties of the interfacial layer. We have obtained high-density monomolecular poly(ethylene glycol) (PEG) layers by solvent-free coupling of homo-bifunctional PEGs (2000 g/mol) at 75°C to silica surfaces silanized with glycidyloxipropyltrimethoxysilane (GOPTS). Characterization by ellipsometry and contact angles revealed that PEG layers up to 3.4 ng/mm2 with low roughness and flexibility were obtained. Specific and non-specific binding at these PEG surfaces was monitored by reflectometric interference spectroscopy (RIfS). No significant non-specific adsorption upon incubation of 1 mg/ml ovalbumin was detectable ( < 10 pg/mm2), and 150 pg/mm2 upon incubation of 10% calf serum, less than 10% of the amount adsorbed to the solely silanized surfaces. The terminal functional groups of the PEG layers were utilized to couple ligands and a protein. Specific protein interaction with these immobilized compounds was detected with saturation loadings in the range of protein monolayers (2-4 ng/mm2). The excellent functional properties, the high stability of the layers, the generic and practical coupling procedure and the versatility for immobilizing compounds of very different functionality make these PEG layers very attractive for application in label-free detection with silica or metal-oxide based transducers. (C) 2000 Elsevier Science S.A.Label-free heterogeneous phase detection critically depends on the properties of the interfacial layer. We have obtained high-density monomolecular poly(ethylene glycol) (PEG) layers by solvent-free coupling of homo-bifunctional PEGs (2000 g/mol) at 75 °C to silica surfaces silanized with glycidyloxipropyltrimethoxysilane (GOPTS). Characterization by ellipsometry and contact angles revealed that PEG layers up to 3.4 ng/mm2 with low roughness and flexibility were obtained. Specific and non-specific binding at these PEG surfaces was monitored by reflectometric interference spectroscopy (RIfS). No significant non-specific adsorption upon incubation of 1 mg/ml ovalbumin was detectable (<10 pg/mm2), and 150 pg/mm2 upon incubation of 10% calf serum, less than 10% of the amount adsorbed to the solely silanized surfaces. The terminal functional groups of the PEG layers were utilized to couple ligands and a protein. Specific protein interaction with these immobilized compounds was detected with saturation loadings in the range of protein monolayers (2-4 ng/mm2). The excellent functional properties, the high stability of the layers, the generic and practical coupling procedure and the versatility for immobilizing compounds of very different functionality make these PEG layers very attractive for application in label-free detection with silica or metal-oxide based transducers.
|
|
| 38. |
- Piletsky, SA, et al.
(författare)
-
Substitution of antibodies and receptors with molecularly imprinted polymers in enzyme-linked and fluorescent assays
- 2001
-
Ingår i: Biosensors & bioelectronics. - : Elsevier Science B.V., Amsterdam.. - 0956-5663 .- 1873-4235. ; 16:12-sep, s. 701-707
-
Tidskriftsartikel (refereegranskat)abstract
- A new technique for coating microtitre plates with molecularly imprinted polymers (MIP), specific for low-molecular weight analytes (epinephrine, atrazine) and proteins is presented. Oxidative polymerization was performed in the presence of template; monomers: 3-aminophenylboronic acid (APBA), 3-thiopheneboronic acid (TBA) and aniline were polymerized in water and the polymers were grafted onto the polystyrene surface of the microplates. It was found that this process results in the creation of synthetic materials with antibody-like binding properties. It was shown that the MIP-coated microplates are particularly useful for assay development. The high stability of the polymers and good reproducibility of the measurements make MIP coating an attractive alternative to conventional antibodies or receptors used in enzyme linked immunosorbent assay (ELISA). (C) 2001 Elsevier Science B.V. All rights reserved.
|
|
| 39. |
- Rose, A, et al.
(författare)
-
GDH biosensor based off-line capillary immunoassay for alkylphenols and their ethoxylates
- 2002
-
Ingår i: Biosensors & Bioelectronics. - 1873-4235. ; 17:11-12, s. 1033-1043
-
Tidskriftsartikel (refereegranskat)abstract
- The application of a quinoprotein glucose dehydrogenase modified thick-film sensor as label detector in a capillary immunoassay (CIA) for xenoestrogens is presented. The detection of the alkylphenols and their ethoxylates is based on the competition between the analyte and tracer molecules for the binding sites of anti-alkylphenol ethoxylate antibodies. This assay is performed off-line in small disposable PVC capillaries coated with immobilized antibodies. This format allows the combination of the assay with a small portable device potentially useful for on-site environmental monitoring. Beside high amplification the utilization of beta-galactosidase as enzyme label allows the direct combination with a GDH biosensor at optimal pH conditions. The bioelectrocatalytic properties of this biosensor offer an additional amplification and thus allow a very sensitive quantification of 4-aminophenol, generated by the beta-galactosidase. Detection limits of the analytes in the mug/l range were obtained, while other phenolics and surfactants showed no or very little cross reactivity.
|
|
| 40. |
- Siegel, G, et al.
(författare)
-
A receptor-based biosensor for lipoprotein docking at the endothelial surface and vascular matrix
- 2001
-
Ingår i: Biosensors & bioelectronics. - 0956-5663 .- 1873-4235. ; 16, s. 895-904
-
Tidskriftsartikel (refereegranskat)abstract
- Proteoheparan sulfate can be adsorbed to a methylated silica surface in a monomolecular layer via its transmembrane hydrophobic protein core domain. Due to electrostatic repulsion, its anionic glycosaminoglycan side chains are stretched out into the blood substitute solution, representing a receptor site for specific lipoprotein binding through basic amino acid-rich residues within their apolipoproteins. The binding process was studied by ellipsometric techniques showing that HDL has a high binding affinity to the receptor and a protective effect on interfacial heparan sulfate proteoglycan layers, with respect to LDL and Ca2+ complexation. LDL was found to deposit strongly at the proteoheparan sulfate, particularly in the presence of Ca2+, thus creating the complex formation `proteoglycan¯low density lipoprotein¯calcium'. This ternary complex build-up may be interpreted as arteriosclerotic nanoplaque formation on the molecular level responsible for the arteriosclerotic primary lesion. On the other hand, HDL bound to heparan sulfate proteoglycan protected against LDL docking and completely suppressed calcification of the proteoglycan¯lipoprotein complex. In addition, HDL and aqueous garlic extract were able to reduce the ternary complex deposition and to disintegrate HS-PG/LDL/Ca2+ aggregates. Although much remains unclear regarding the mechanism of lipoprotein depositions at proteoglycan-coated surfaces, it seems clear that the use of such systems offers possibilities for investigating lipoprotein deposition at a `nanoscopic' level under close to physiological conditions. In particular, Ca2+-promoted LDL deposition and the protective effect of HDL, even at high Ca2+ and LDL concentrations, agree well with previous clinical observations regarding risk and beneficial factors for early stages of atherosclerosis. Therefore, we believe that the system can be of some use in investigations, e.g. of the interplay between different lipoproteins in arteriosclerotic plaque formation, as well as in high throughput screening of candidate drugs to atherosclerosis in a biosensor application
|
|
| 41. |
- Subrahmanyam, S, et al.
(författare)
-
Bite-and-Switch approach using computationally designed molecularly imprinted polymers for sensing of creatinine
- 2001
-
Ingår i: Biosensors & bioelectronics. - : Elsevier Science B.V., Amsterdam.. - 0956-5663 .- 1873-4235. ; 16:12-sep, s. 631-637
-
Tidskriftsartikel (refereegranskat)abstract
- A method for the selective detection of creatinine is reported, which is based on the reaction between polymerised hemithioacetal formed by allyl mercaptan, o-phthalic aldehyde, and primary amine leading to the formation Of fluorescent isoindole complex. This method has been demonstrated previously for the detection of creatine using creatine-imprinted molecularly imprinted polymers (MlPs) Since MlPs created using traditional methods were unable to differentiate between creatine and creatinine, a new approach to the rational design of a molecularly imprinted polymer (MIP) selective for creatinine was developed using computer simulation. A virtual library of functional monomers was assigned and screened against the target molecule, creatinine, using molecular modelling software. The monomers giving the highest binding score were further tested using simulated annealing in order to mimic the complexation of the functional monomers with template in the monomer mixture. The result of this simulation gave an optimised MIP composition. The computationally designed polymer demonstrated superior selectivity in comparison to the polymer prepared using traditional approach, a detection limit of 25 muM and good stability. The Bite-and-Switch approach combined with molecular imprinting can be used for the design of assays and sensors, selective for amino containing substances. (C) 2001 Elsevier Science B.V. All rights reserved.
|
|
| 42. |
- Testorf, Martin, 1972-, et al.
(författare)
-
The electric charge of pigment granules in pigment cells
- 2001
-
Ingår i: Biosensors & bioelectronics. - 0956-5663 .- 1873-4235. ; 16:1-2, s. 31-36
-
Tidskriftsartikel (refereegranskat)abstract
- Black pigment cells called melanophores change colour in response to environmental changes and have lately been studied as promising biosensors. To further elucidate the intracellular processes involved in the colour changes of these cells, and to find optimal biosensing principles, the electric charge of intracellular pigment granules, melanosomes, has been determined in vitro by electrophoresis. Melanosomes from the two extreme states in the cell colour change (aggregated and dispersed melanosomes) were measured. The charge was found to be −1.5·10−16 and −1.7·10−16 C, aggregated and dispersed melanosomes, respectively, without significant difference between the two conditions. This charge is of the same order of magnitude as the one of 1000 electrons. The origin of the melanosome charge, and the use of these findings in new biosensor principles, is discussed.
|
|
| 43. |
- Tkac, Jan, et al.
(författare)
-
Improved selectivity of microbial biosensor using membrane coating. Application to the analysis of ethanol during fermentation
- 2003
-
Ingår i: Biosensors & bioelectronics. - 0956-5663 .- 1873-4235. ; 18:9, s. 1125-1134
-
Tidskriftsartikel (refereegranskat)abstract
- A ferricyanide mediated microbial biosensor for ethanol detection was prepared by surface modification of a glassy carbon electrode. The selectivity of the whole Gluconobacter oxydans cell biosensor for ethanol determination was greatly enhanced by the size exclusion effect of a cellulose acetate (CA) membrane. The use of a CA membrane increased the ethanol to glucose sensitivity ratio by a factor of 58.2 and even the ethanol to glycerol sensitivity ratio by a factor of 7.5 compared with the use of a dialysis membrane. The biosensor provides rapid and sensitive detection of ethanol with a limit of detection of 0.85 µM (S/N=3). The selectivity of the biosensor toward alcohols was better compared to previously published enzyme biosensors based on alcohol oxidase or alcohol dehydrogenases. The biosensor was successfully used in an off-line monitoring of ethanol during batch fermentation by immobilized Saccharomyces cerevisiae cells with an initial glucose concentration of 200 g l-1. © 2002 Elsevier Science B.V. All rights reserved.
|
|
| 44. |
- Tombelli, S, et al.
(författare)
-
Coupling of a DNA piezoelectric biosensor and polymerase chain reaction to detect apolipoprotein E polymorphisms
- 2000
-
Ingår i: Biosensors & bioelectronics. - : Elsevier Science B.V., Amsterdam.. - 0956-5663 .- 1873-4235. ; 15:08-jul, s. 363-370
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we report the coupling of the Polymerase Chain Reaction (PCR) with a piezoelectric biosensor to detect a point mutation in a human gene. Biotinylated 23-mer probes were immobilised on the streptavidin coated gold surface of a quartz crystal; streptavidin was covalently bound to the thiol/dextran modified gold surface. The hybridisation of the immobilised probes with a short sequence (23 mer) complementary, non-complementary and mismatched DNA was investigated: the device was able to distinguish the different synthetic oligonucleotides. Many cycles of measurements can be performed on the same crystal surface regenerating the single strand of DNA with 1 mM of HCl. The same hybridisation reaction was then performed using real samples of human DNA extracted from blood and amplified by PCR, following a standard procedure for genetic detection of the polymorphism of the apolipoprotein E (apoE) gene. The procedure was able to distinguish the sequences present in the different samples, which differ only in one base: in this way it was possible distinguish between different groups of genotypes with apoE typing. Experiments with blank samples confirmed the absence of adsorption or non-specific effects on the quartz crystal treated with the reported procedure. (C) 2000 Elsevier Science S.A. All rights reserved.
|
|
| 45. |
- Tombelli, S, et al.
(författare)
-
Improved procedures for immobilisation of oligonucleotides on gold-coated piezoelectric quartz crystals
- 2002
-
Ingår i: Biosensors & bioelectronics. - : Elsevier Science B.V., Amsterdam.. - 0956-5663 .- 1873-4235. ; 17:12-nov, s. 929-936
-
Tidskriftsartikel (refereegranskat)abstract
- The high sensitivity and specificity of DNA hybridisation techniques makes them powerful tools for environmental or clinical analysis. This work describes the development of a DNA piezoelectric biosensor for the detection of the hybridisation reaction. Attention was focused on the choice of the coating chemistry that could be used for the immobilisation of oligonucleotides onto the gold surface of the quartz crystal. Four immobilisation procedures were tested and compared considering the amount of immobilised probe, the extent of the hybridisation reaction, the possibility of regeneration and the absence of non-specific adsorption. All the experiments were performed with oligonucleotides of 25 bases (probe, target and non-complementary oligonucleotide). The four coating methods were all based on the use of self-assembled monolayers (SAM). Three of them employed the interaction between streptavidin and biotin for the immobilisation of a biotinylated probe. Results indicated that immobilisation of a biotinylated probe on streptavidin linked to a layer of carboxylated dextran provides higher sensitivity for the detection of the hybridisation reaction, absence of non-specific adsorption and a higher stability with respect to the regeneration step. (C) 2002 Elsevier Science B.V. All rights reserved.
|
|
| 46. |
|
|
| 47. |
|
|
| 48. |
- Turner, Anthony, 1950-
(författare)
-
Prof G G Guilbault
- 2003
-
Ingår i: Biosensors & bioelectronics. - : Elsevier. - 0956-5663 .- 1873-4235. ; 18, s. 109-110
-
Tidskriftsartikel (refereegranskat)
|
|
| 49. |
- van Noort, D., et al.
(författare)
-
Porous gold surfaces for biosensor applications
- 2000
-
Ingår i: Biosensors & bioelectronics. - 0956-5663 .- 1873-4235. ; 15:3-4, s. 203-209
-
Tidskriftsartikel (refereegranskat)abstract
- The sensitivity of optical biosensors where the detection takes place on a planar gold surface can be improved by making the surface porous. The porosity allows a larger number of ligands per surface area resulting in larger optical shifts when interacting with specifically binding analyte molecules. The porous gold was deposited as a thin layer on a planar gold surface by electrochemical deposition in a solution of tetrachloroaurate and lead acetate. A protein, streptavidin, was adsorbed into the formed porous layer and the time course of the adsorption was monitored by in-situ ellipsometry. When the porous layer was 500 nm in thickness a six-fold increase of the ellipsometric response was obtained compared with a planar gold surface. The dependency of porosity and layer thickness was explained with a mathematical model of the gold/porous gold/protein/solution system. Copyright (C) 2000 Elsevier Science S.A.The sensitivity of optical biosensors where the detection takes place on a planar gold surface can be improved by making the surface porous. The porosity allows a larger number of ligands per surface area resulting in larger optical shifts when interacting with specifically binding analyte molecules. The porous gold was deposited as a thin layer on a planar gold surface by electrochemical deposition in a solution of tetrachloroaurate and lead acetate. A protein, streptavidin, was adsorbed into the formed porous layer and the time course of the adsorption was monitored by in-situ ellipsometry. When the porous layer was 500 nm in thickness a six-fold increase of the ellipsometric response was obtained compared with a planar gold surface. The dependency of porosity and layer thickness was explained with a mathematical model of the gold/porous gold/protein/solution system.
|
|
| 50. |
- Vikinge, Trine P., et al.
(författare)
-
Comparison of surface plasmon resonance and quartz crystal microbalance in the study of whole blood and plasma coagulation
- 2000
-
Ingår i: Biosensors & bioelectronics. - 0956-5663 .- 1873-4235. ; 15:11-12, s. 605-613
-
Tidskriftsartikel (refereegranskat)abstract
- The coagulation of blood plasma and whole blood was studied with a surface plasmon resonance (SPR) based device and a quartz crystal microbalance instrument with energy dissipation detection (QCM-D). The SPR and QCM-D response signals were similar in shape but differing in time scales, reflecting differences in detection mechanisms. The QCM-D response time was longer than SPR, as a physical coupling of the sample to the substrate is required for molecules to be detected by the QCM-method. Change of sample properties within the evanescent field is sufficient for detection with SPR. Both the SPR signals and the QCM-D frequency and dissipation shifts showed dependency on concentrations of coagulation activator and sensitivity to heparin additions. The ratio of dissipation to frequency shifts, commonly considered to reflect viscoelastic properties of the sample, varied with the concentration of activator in blood plasma but not in whole blood. Additions of heparin to the thromboplastin activated whole blood sample, however, made the ratio variation reoccur. Implications of these observations for the understanding of the blood coagulation processes as well as the potential of the two methods in the clinic and in research are discussed.
|
|
