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- Lilliehorn, Tobias, et al.
(författare)
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Bioassays on ultrasonically trapped microbead clusters in microfluidic systems
- 2004
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Ingår i: Micro Total Analysis Systems 2004. - 0854048960 ; 2, s. 327-329
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Konferensbidrag (refereegranskat)abstract
- The handling of biochemically functionalised beads or particles is becoming increasingly important in µTAS. Bead-based analysis of e.g. proteins can be made sensitive due to the large active surface area and flexible by chemical design of the bead surface. We have developed a microfluidic device utilising an array of integrated and individually controlled ultrasonic microtransducers for particle trapping [1]. Particles inserted in the device are subjected to acoustic radiation forces [2] confining them at localised trapping sites. We would now, for the first time at an international conference, like to present a technique for performing bioassays on such ultrasonically trapped beads in microfluidic systems. The microfluidic device is shown in Fig. 1, where the piezoceramic ultrasonic transducers can be seen in the channel crossings in the insert. The device is designed as an acoustic resonator, to obtain localised standing acoustic waves at each transducer with essentially one pressure node in the middle of the 72 µm deep channel when operated near 10 MHz. This configuration is chosen to keep trapped particles away from the interior surfaces of the device, thus enabling fast switching of beads with a minimum in carry-over between assays. The fluidic chip, shown in Fig. 2, is designed to allow injection of microbeads, washing fluid and sample to the three trapping sites. It has been shown that the microbead clusters, as shown in Fig. 3, can be trapped at considerably high perfusion rates, up to 10 µl/min, Fig 4. As a model bioassay, 6.7 µm biotin-covered beads (PC-B-6.0, Gerlinde Kisker, Germany) were injected and transported to one tapping site using washing fluid (water). Activating the transducer trapped the beads. A solution of FITC-tagged avidin was perfused over the bead bed at 3 µl/min, using the corresponding orthogonal sample channel. After 100 s the sample flow was turned off and the bead trap was washed by perfusing water at 3 µl/min. The fluorescence response from the trapped bead clusters was monitored during the assay, and the result is shown in Fig. 5. After excess avidin was washed from the bead trap, a measured step response . indicated that avidin had bound to the beads. Finally the possibility of moving trapped microbeads between the individually controlled trapping sites in the device is shown in Fig. 6, where the transducers are activated sequentially while keeping the bead carrying washing fluid at 3 µl/min during the experiment. Work in the near future will be focused on optimising the device with respect to the bioassay performance, and in a longer perspective on expanding the concept to two dimensions to enable a new dynamic mode of generating bioanalytical arrays.
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| 4. |
- Bengtsson, Martin, et al.
(författare)
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Influence of Nonuniform Channel Width Distribution in Porous Silicon High Aspect Ratio Parallel Channel Micro Reactors
- 2005
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Ingår i: [Host publication title missing]. - 0854046437 ; 1, s. 629-631
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Konferensbidrag (refereegranskat)abstract
- The paper focuses on the fact that, since the flow rate in parallel channels relies strongly on the channel width, the combination may lead to inaccurate results if errors in the fabrication process lead to an uneven distribution of channel widths. Parallel channel enzyme reactors were designed with channel widths distributed normally with different degrees of standard deviation. The reactors were then evaluated with regard to dispersion and to catalytic effect of the immobilised enzyme. It was shown that for lower concentrations the catalytic efficiency decreased significantly even for small variations in the distribution of channel widths and reactors with poor homogeneity in channel widths also diluted the sample more than the others.
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| 5. |
- 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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| 8. |
- Ekström, Simon, et al.
(författare)
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Integrated selective enrichment target (ISET) - A generic microfabricated sample preparation device
- 2005
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Ingår i: Micro Total Analysis Systems 2004, Vol 2. - 0260-6291. - 9780854048960 ; :297, s. 548-550
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Konferensbidrag (refereegranskat)abstract
- A combined sample preparation and sample presentation device, Integrated Selective Enrichment Target (ISET), consisting of an array with 96 perforated nanovials is described. Each perforated nanovial can be filled with soild-phase extraction media for purification and concentration of biomolecules prior to mass spectrometry. The ISET platform provides an efficient, economic and generic sample treatment process, allowing for rapid in-parallel handling of minute sample volumes, with a minimum of sample transfers.
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| 9. |
- Ekström, Simon, et al.
(författare)
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Polymeric integrated selective enrichment target (ISET) for solid-phase-based sample preparation in MALDI-TOF MS
- 2007
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Ingår i: Journal of Mass Spectrometry. - : Wiley. - 1076-5174 .- 1096-9888. ; 42:11, s. 1445-1452
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Tidskriftsartikel (refereegranskat)abstract
- d A polymer microfabricated proteomic sample preparation and MALDI MS sample presentation device, the integrated selective enrichment target (ISET), comprising an array of perforated nanovials is reported. Each perforated nanovial can be filled with selective extraction media (microbeads) for purification and concentration of protein/peptides prior to matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). The main areas covered are the influence of the molding-process-induced surface roughness and how to address the lack of inherent conductivity in the polyetheretherketone (PEEK) material for optimal MALDI MS readout. Application of the disposable polymeric ISET devices for solid-phase extraction and phosphopeptide capture is also demonstrated.
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| 10. |
- Evander, Mikael, et al.
(författare)
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Acoustic Differential Extraction - ultrasonic DNA-extraction from sexual assault evidence
- 2007
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Ingår i: International Congress on Ultrasonics. ; 1, s. 151-151
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Konferensbidrag (refereegranskat)abstract
- Isolation of the male and female DNA is one of the most important steps in obtaining the DNA profile of the perpetrator in sexual assault cases. The sample is obtained by taking a vaginal swab containing both epithelial cells from the female and sperm cells from the male from the victim. The purity of the extracted male fraction decides whether or not a single-source DNA profile of the suspect will be obtained or not. The existing techniques are have poor separation efficiency, time-consuming, labour-intensive and are neither easily automated nor integrated with further analysis steps. A novel method of DNA extraction based on ultrasonic trapping, Acoustic Differential Extraction, has been developed. A microfluidic device using laminar flow valving and miniature PZT transducers retains the sperm cells while mobilizing the female fraction into a separate outlet. The device was evaluated using a mock sexual assault sample and the separated fractions were analyzed using quantitative PCR and STR-profiling. A 16-fold enrichment of the male fraction, making an originally hard-to-detect-male DNA profile readily profiled, has been demonstrated. The STR-profiling of the male and female fractions showed a male fraction purity of up to 99 % making it possible to obtain a single-source DNA-profile of the suspect. The microfluidic format of the device makes it possible to downscale the sample time from 4-8 hours to 10 minutes. It is also possible to integrate this method with further downstream analysis steps necessarey for the full forensic DNA analysis.
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