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Bioassays on ultrasonically trapped microbead clusters in microfluidic systems

Lilliehorn, Tobias; Evander, Mikael LU ; Simu, Urban; Almqvist, Monica LU ; Johansson, Stefan; Laurell, Thomas LU and Nilsson, Johan LU (2004) Micro Total Analysis Systems 2004 In Micro Total Analysis Systems 2004 2. p.327-329
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... (More)
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. (Less)
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author
organization
publishing date
type
Chapter in Book/Report/Conference proceeding
publication status
published
subject
keywords
Ultrasound, Trapping, PZT, Microparticles, Microbeads
in
Micro Total Analysis Systems 2004
editor
Laurell, Thomas; Nilsson, Johan; Jensen, Klavs; Harrison, Jed and Kutter, Jörg
volume
2
pages
3 pages
publisher
The Royal Society of Chemistry
conference name
Micro Total Analysis Systems 2004
ISBN
0-85404-896-0
language
English
LU publication?
yes
id
7423042e-f7e3-4ee4-b4b8-e4b0103b1f33 (old id 789680)
date added to LUP
2007-12-21 13:22:31
date last changed
2016-04-16 07:21:24
@inproceedings{7423042e-f7e3-4ee4-b4b8-e4b0103b1f33,
  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.},
  author       = {Lilliehorn, Tobias and Evander, Mikael and Simu, Urban and Almqvist, Monica and Johansson, Stefan and Laurell, Thomas and Nilsson, Johan},
  booktitle    = {Micro Total Analysis Systems 2004},
  editor       = {Laurell, Thomas and Nilsson, Johan and Jensen, Klavs and Harrison, Jed and Kutter, Jörg},
  isbn         = {0-85404-896-0},
  keyword      = {Ultrasound,Trapping,PZT,Microparticles,Microbeads},
  language     = {eng},
  pages        = {327--329},
  publisher    = {The Royal Society of Chemistry},
  title        = {Bioassays on ultrasonically trapped microbead clusters in microfluidic systems},
  volume       = {2},
  year         = {2004},
}