| 1. |
- Bergkvist, Jonas, et al.
(författare)
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Miniaturized flowthrough microdispenser with piezoceramic tripod actuation
- 2005
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Ingår i: Journal of Microelectromechanical Systems. - 1057-7157. ; 14:1, s. 134-140
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the further development of a silicon flowthrough microdispenser is described. Previously reported designs of the dispenser used bimorph, and later multilayered, piezoelectric actuator elements for the generation of droplets. The introduction of a multilayered actuator significantly reduced the voltage amplitude needed to dispense droplets. Dispenser properties relevant for chemical analysis systems, e.g., reduced sample volume, internal surface area, and dispersion, were improved by miniaturization of the device. In this paper, a new actuator design, the tripod, is presented to enable further dispenser miniaturization and to facilitate device assembly. Tripod actuators were manufactured using a prototyping process, based on micromilling, for multilayer piezoceramic components. A building technique for miniaturized electrical interconnects, based on microstructured flexible printed circuits, is also suggested in line with the prospect of future miniaturization. The microfluidic properties of the tripod- actuated dispenser were evaluated. Stable droplet generation in the frequency range from 0 to 3 kHz was demonstrated, providing a maximum dispensed flow rate of 7.8 muL/min.
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| 2. |
- Bjursten, Henrik, et al.
(författare)
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Particle separation using ultrasound can be used with human shed mediastinal blood.
- 2005
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Ingår i: Perfusion. - : SAGE Publications. - 1477-111X .- 0267-6591. ; 20:1, s. 39-43
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Tidskriftsartikel (refereegranskat)abstract
- Shed mediastinal blood collected by cardiotomy suction has been shown to be a large contributor to lipid microemboli ending up in different organs. The aim of this study was to test the separation efficiency on human shed blood of a new separation method developed to meet this demand. METHODS: Shed mediastinal blood collected from the pericardial cavity of 13 patients undergoing cardiac surgery with cardiopulmonary bypass was collected. The blood was processed in an eight-channel parallel PARSUS separator, and separation efficiency was determined. RESULTS: Erythrocyte recovery, in terms of a separation ratio, varied between 68% and 91%. Minor electrolyte changes took place, where levels of sodium increased and levels of potassium and calcium decreased. CONCLUSION: This study demonstrates that PARSUS technology can be used on human shed mediastinal blood with good separation efficiency. The technology is, thereby, suggested to have future clinical relevance.
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| 3. |
- Fehniger, Thomas E., et al.
(författare)
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Integrating disease knowledge and technology to deliver protein targets and biomarkers into drug discovery projects
- 2005
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Ingår i: Drug Discovery Today: Technologies. - : Elsevier BV. - 1740-6749. ; 2:4, s. 345-351
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Tidskriftsartikel (refereegranskat)abstract
- Biomarker discovery is dependent upon two disciplines: the field of clinical bioanalysis linked to disease aetiology and the application of high level technology platforms for identifying proteins/peptides in complex samples. However, diagnostic biomarker measurements require certain definitions of context that can only be achieved by combining protein science with clinical science. The evaluation of biomarkers requires careful attention to match (1) a specific biological question with (2) the appropriate clinical sample and (3) high resolution technology systems which link protein identities to clinical informatics.
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| 4. |
- Laurell, Thomas, et al.
(författare)
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The quest for high-speed and low-volume bioanalysis
- 2005
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 1520-6882 .- 0003-2700. ; 77:13, s. 264-272
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Tidskriftsartikel (refereegranskat)abstract
- Nanovials, microarrays, and microfluidics are brought together for the exploration of complex biological problems.
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| 5. |
- Lilliehorn, T, et al.
(författare)
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Dynamic arraying of microbeads for bioassays in microfluidic channels
- 2005
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Ingår i: Sensors and Actuators B: Chemical. - : Elsevier BV. - 0925-4005. ; 106:2, s. 851-858
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a new dynamic mode of generating bioanalytical arrays in microfluidic systems, based on ultrasonic trapping of microbeads using acoustic forces in standing waves. Trapping of microbead clusters in an array format within a flow-through device is demonstrated for the first time using a device with three integrated ultrasonic microtransducers. The lateral extension of each trapping site was essentially determined by the corresponding microtransducer dimensions, 0.8 mm x 0.8 mm. The flow-through volume was approximately 1 μ l and the trapping site volumes about 100 nl each. The strength of trapping was investigated, showing that 50% of the initially trapped beads were still trapped at a perfusion rate of 10 μ l/min. A fluorescence based avidin bioassay was successfully performed on biotin-coated microbeads trapped in the flow-through device, providing a first proof of principle of the proposed dynamic arraying concept. The dynamic arraying is believed to be expandable to two dimensions, thus, with a prospect of performing targeted and highly parallel protein analysis in microfluidic devices.
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| 6. |
- Lilliehorn, Tobias, et al.
(författare)
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Trapping of microparticles in the near field of an ultrasonic transducer
- 2005
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Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X. ; 43:5, s. 293-303
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Tidskriftsartikel (refereegranskat)abstract
- We are investigating means of handling microparticles in microfluidic systems, in particular localized acoustic trapping of microparticles in a flow-through device. Standing ultrasonic waves were generated across a microfluidic channel by ultrasonic microtransducers integrated in one of the channel walls. Particles in a fluid passing a transducer were drawn to pressure minima in the acoustic field, thereby being trapped and confined at the lateral position of the transducer. The spatial distribution of trapped particles was evaluated and compared with calculated acoustic intensity distributions. The particle trapping was found to be strongly affected by near field pressure variations due to diffraction effects associated with the finite sized transducer element. Since laterally confining radiation forces are proportional to gradients in the acoustic energy density, these near field pressure variations may be used to get strong trapping forces, thus increasing the lateral trapping efficiency of the device. In the experiments, particles were successfully trapped in linear fluid flow rates up to 1 mm/s. It is anticipated that acoustic trapping using integrated transducers can be exploited in miniaturised total chemical analysis systems (μTAS), where e.g. microbeads with immobilised antibodies can be trapped in arrays and subjected to minute amounts of sample followed by a reaction, detected using fluorescence.
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| 7. |
- Melander, Claes, et al.
(författare)
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Investigation of micro-immobilised enzyme reactors containing endoglucanases for efficient hydrolysis of cellodextrins and cellulose derivatives
- 2005
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 550:1-2, s. 182-190
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Tidskriftsartikel (refereegranskat)abstract
- Cellulases hydrolysing the interior parts of cellulose, also called endoglucanases, were immobilised in micro-immobilised enzyme reactors (RIMER) made of porous silicon with the purpose of investigating the use of such mu IMERs for hydrolysis of cellodextrins and soluble cellulose derivatives. The endoglucanases Trichoderma reesei Cel 12A (TrCel 12A) and Bacillus agaradhaerens Cel 5A (BaCel 5A) were covalently coupled to the surface of a silicon microchip through Schiff base formation. For characterisation cellohexaose was used as substrate for the immobilised enzymes. The characteristics of the RIMER were investigated by studying the product formation when varying the concentration, flow-rate, temperature and pH of the substrate solution. Hydrolysis was performed in the RIMER connected on-line to a chromatographic system, where the products were separated and detected using high-performance anion exchange chromatography (HPAEC) coupled to pulsed amperometric detection (PAD). A comparison of the hydrolytic pattern between BaCel 5A and TrCel 12A was carried out and the results show that the two investigated endoglucanases give specific hydrolytic patterns in the products formed that provide important information about the enzymes. The RIMERs are robust and can be employed continuously over a period of at least several days. Moreover, on appropriate storage, no activity loss is seen after 60 days. The ability of the BaCel 5A containing RIMER to perform hydrolysis of derivatised cellulose was also investigated using carboxymethyl cellulose (CMC) as substrate. Separation and detection were carried out using size exclusion chromatography (SEC) with refractive index detection (RI). The results show that the RIMERs are robust and can be employed for on-line hydrolysis of both cellodextrins and derivatised cellulose of high molecular weight. (c) 2005 Elsevier B.V. All rights reserved.
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| 8. |
- Melander, Claes, et al.
(författare)
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Microchip immobilized enzyme reactors for hydrolysis of methyl cellulose
- 2005
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 77:10, s. 3284-3291
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Tidskriftsartikel (refereegranskat)abstract
- Microchip immobilized enzyme reactors (mu IMERs) with immobilized endoglucanases were applied for the hydrolysis of methyl cellulose (MC). MCs of various molecular weights were hydrolyzed using two mu IMERs containing immobilized celloendoglucanase Cel 5A from Bacillus agaradhaerens (BaCel 5A) connected in series. Hydrolysis by the mu IMER could be confirmed from the average molar masses and molar mass distributions measured by size exclusion chromatography (SEC) with online multiangle light scattering and refractive index detection. Methylated cellooligosaccharides with degrees of polymerization (DP) between 1 and 6 formed during hydrolysis were analyzed by direct infusion electrospray ionization ion-trap mass spectrometry (ESI-ITMS). Mass spectra of mu IMER- and batch-hydrolyzed samples were compared and no significant differences were found, indicating that mu IMER hydrolysis was as efficient as conventional batch hydrolysis. A fast and automated hydrolysis with online MS detection was achieved by connecting the mu IMER to high-performance liquid chromatography and ESI-ITMS. This online separation reduced the relative intensities of interfering signals and increased the signal-to-noise ratios in MS. The mu IMER hydrolysates were also subjected to SEC interfaced with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. With this technique, oligomers with DP 3-30 could be detected. The hydrolysis by they mu-IMER was performed within 60 min, i.e. significantly faster compared with batch hydrolysis usually performed for at least 24 h. The mu IMER also allowed hydrolysis after 10 days of continuous use. The method presented in this work offers new approaches for the analysis of derivatized cellulose and provides the possibility of convenient online, fast, and more versatile analysis compared with the traditional batch method.
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| 9. |
- Petersson, Filip, et al.
(författare)
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Carrier medium exchange through ultrasonic particle switching in microfluidic channels
- 2005
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 1520-6882 .- 0003-2700. ; 77:5, s. 1216-1221
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a method, utilizing acoustic force manipulation of suspended particles, in which particles in a laminar flow microchannel are continuously translated from one medium to another with virtually no mixing of the two media. During the study, 5-mum polyamide spheres suspended in distilled water, spiked (contaminated) with Evans blue, were switched over to clean distilled water. More than 95% of the polyamide spheres could be collected in the clean medium while removing up to 95% of the contaminant. Preliminary experiments to use this method to wash blood were performed. Red blood cells were switched from blood, spiked with Evans blue, to clean blood plasma. At least 95% of the red blood cells (bovine blood) could be collected in clean blood plasma while up to 98% of the contaminant was removed. The obtained results indicate that the presented method can be used as a generic method for particle washing and, more specifically, be applied for both intraoperative and postoperative blood washing.
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| 10. |
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