| 1. |
- Christakou, Athanasia. E., et al.
(författare)
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Aggregation and long-term positioning of cells by ultrasound in a multi-well microchip for high-resolution imaging of the natural killer cell immune synapse
- 2011
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Ingår i: 15th International Conference on Miniaturized Systems for Chemistry and Life Sciences 2011, MicroTAS 2011. - 9781618395955 ; , s. 329-331
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Konferensbidrag (refereegranskat)abstract
- In this study we investigate the ability of Natural Killer (NK) cells to form ultrasound-mediated intercellular contacts with target cells in a multi-well microdevice by high-resolution confocal-microscopy imaging of inhibitory immune synapses. Furthermore, we compare the NK-Target cell cluster migration with and without ultrasound actuation. Experiments indicate that clusters of cells are positioned and maintained centered in the wells for 17 hours when they are exposed continuously to ultrasound. Our system can be used for both screening high numbers of events in low resolution and also for high resolution imaging of long term cell-cell interactions.
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| 2. |
- Christakou, Athanasia E., et al.
(författare)
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Characterization of natural killer cells' cytotoxic heterogeneity using an array of sono-cages
- 2012
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Ingår i: Proceedings of the 16th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2012. - : Chemical and Biological Microsystems Society. - 9780979806452 ; , s. 1555-1557
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Konferensbidrag (refereegranskat)abstract
- Using a multi-well device as an array of sono-cages for single cell analysis, we quantify for the first time the heterogeneity of natural killer (NK) cells' cytotoxic response against cancer cells. We report a fraction of inactive NK cells within the tested population (36%), as well as the existence of few 'serial killers' that eliminate up to six targets during 4 hours. We also characterize the multi-well acoustic device in terms of trapping efficiency at different actuation voltages, using adherent and non-adherent cell lines. We show that the acoustic forces applied on the cells can be compared to forces of biological processes (i.e. cell adherence).
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| 3. |
- Christakou, Athanasia E., et al.
(författare)
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Live cell imaging in a micro-array of acoustic traps facilitates quantification of natural killer cell heterogeneity
- 2013
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Ingår i: Integrative Biology. - : Oxford University Press (OUP). - 1757-9694 .- 1757-9708. ; 5:4, s. 712-719
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Tidskriftsartikel (refereegranskat)abstract
- Natural killer (NK) cells kill virus-infected or cancer cells through the release of cytotoxic granules into a tight intercellular contact. NK cell populations comprise individual cells with varying sensitivity to distinct input signals, leading to disparate responses. To resolve this NK cell heterogeneity, we have designed a novel assay based on ultrasound-assisted cell-cell aggregation in a multiwell chip allowing high-resolution time-lapse imaging of one hundred NK-target cell interactions in parallel. Studying human NK cells' ability to kill MHC class I deficient tumor cells, we show that approximately two thirds of the NK cells display cytotoxicity, with some NK cells being particularly active, killing up to six target cells during the assay. We also report that simultaneous interaction with several susceptible target cells increases the cytotoxic responsiveness of NK cells, which could be coupled to a previously unknown regulatory mechanism with implications for NK-mediated tumor elimination.
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| 4. |
- Christakou, Athanasia E., et al.
(författare)
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Solid tumor spheroid formation by temperature-controlled high voltage ultrasound in a multi-well microdevice
- 2014
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Ingår i: 18th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2014. - : Chemical and Biological Microsystems SocietyChemical and Biological Microsystems Society. - 9780979806476 ; , s. 573-575
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Konferensbidrag (refereegranskat)abstract
- In the present work we demonstrate effective 3D growth of human hepatocellular carcinoma (HCC) HepG2 cell spheroids in parallel in a multi-well microdevice actuated with high voltage ultrasound in a temperature-controlled system. We compare the spheroid formation during continuous ultrasound exposure for one week where we formed spheroids in 59% of the wells, with the spheroid formation without ultrasound actuation, where we obtained 0% spheroids. Furthermore, we present an application of the tumor spheroids for investigating natural killer (NK) cells behavior against solid tumors.
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| 5. |
- Ohlin, Mathias, et al.
(författare)
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Analysis of trapping and streaming in an ultrasoundactuated multi-well microplate for single-cell studies
- 2012
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Ingår i: Proceedings of the 16th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2012. - : Chemical and Biological Microsystems Society. - 9780979806452 ; , s. 497-499
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Konferensbidrag (refereegranskat)abstract
- The dynamics of the acoustic streaming and the acoustic positioning performance in an ultrasound-actuated multiwell microplate are investigated by two different ultrasonic frequency actuation schemes: Frequency-modulation and single- frequency actuation. Our results show a significant decrease in size of the field of view when using frequencymodulation compared to single-frequency actuation, which can be used for improving the scanning time for 3D highresolution confocal microscopy by almost one order of magnitude. Furthermore, in the ultrasound-actuated multi-well microplate the high-voltage acoustic streaming show a complex time and temperature dependence and could gain stability by the use of temperature control.
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| 6. |
- Ohlin, Mathias, et al.
(författare)
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Controlling acoustic streaming in a multi-well microplate for improving live cell assays
- 2011
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Ingår i: 15th International Conference on Miniaturized Systems for Chemistry and Life Sciences 2011, MicroTAS 2011. - 9781618395955 ; , s. 1612-1614
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Konferensbidrag (refereegranskat)abstract
- Acoustic streaming in a multi-well microplate is investigated using two different ultrasonic actuation frequency-schemes: Single-frequency and frequency-modulation. The streaming is tracked by the use of 1 μm fluorescent polymer beads and micro-particle image velocimetry. The suspension also contained human B cells for studying the acoustic trapping and aggregation performance simultaneously with the acoustic streaming. Our results show a significant difference in the acoustic streaming between the two ultrasonic actuation schemes. A rotational fluid flow speed decreased a factor of 30 when frequency-modulation was applied compared to single-frequency actuation without apparently interfering with the acoustic cell trapping function.
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| 7. |
- Ohlin, Mathias, et al.
(författare)
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Influence of acoustic streaming on ultrasonic particle manipulation in a 100-well ring-transducer microplate
- 2013
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 23:3, s. 035008-
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Tidskriftsartikel (refereegranskat)abstract
- We characterize and quantify the performance of ultrasonic particle aggregation and positioning in a 100-well microplate. We analyze the result when operating a planar ultrasonic ring transducer at different single actuation frequencies in the range 2.20-2.40 MHz, and compare with the result obtained from different schemes of frequency-modulated actuation. Compared to our previously used wedge transducer design, the ring transducer has a larger contact area facing the microplate, resulting in lower temperature increase for a given actuation voltage. Furthermore, we analyze the dynamics of acoustic streaming occurring simultaneously with the particle trapping in the wells of the microplate, and we define an adaptive ultrasonic actuation scheme for optimizing both efficiency and robustness of the method. The device is designed as a tool for ultrasound-mediated cell aggregation and positioning. This is a method for high-resolution optical characterization of time-dependent cellular processes at the level of single cells. In this paper, we demonstrate how to operate our device in order to optimize the scanning time of 3D confocal microscopy with the aim to perform high-resolution time-lapse imaging of cells or cell-cell interactions in a highly parallel manner.
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| 8. |
- Vanherberghen, Bruno, et al.
(författare)
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Ultrasound-controlled cell aggregation in a multi-well chip
- 2010
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Ingår i: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0197 .- 1473-0189. ; 10:20, s. 2727-2732
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a microplate platform for parallelized manipulation of particles or cells by frequency-modulated ultrasound. The device, consisting of a silicon-glass microchip and a single ultrasonic transducer, enables aggregation, positioning and high-resolution microscopy of cells distributed in an array of 100 microwells centered on the microchip. We characterize the system in terms of temperature control, aggregation and positioning efficiency, and cell viability. We use time-lapse imaging to show that cells continuously exposed to ultrasound are able to divide and remain viable for at least 12 hours inside the device. Thus, the device can be used to induce and maintain aggregation in a parallelized fashion, facilitating long-term microscopy studies of, e.g., cell-cell interactions.
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| 9. |
- Wiklund, Martin, et al.
(författare)
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Acoustofluidics 14 : Applications of acoustic streaming in microfluidic devices
- 2012
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Ingår i: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0197 .- 1473-0189. ; 12:14, s. 2438-2451
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In part 14 of the tutorial series "Acoustofluidics - exploiting ultrasonic standing wave forces and acoustic streaming in microfluidic systems for cell and particle manipulation", we provide a qualitative description of acoustic streaming and review its applications in lab-on-a-chip devices. The paper covers boundary layer driven streaming, including Schlichting and Rayleigh streaming, Eckart streaming in the bulk fluid, cavitation microstreaming and surface-acoustic-wave-driven streaming.
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| 10. |
- Wiklund, Martin, et al.
(författare)
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On-chip acoustic sample preparation for cell studies and diagnostics
- 2013
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Ingår i: Proceedings of Meetings on Acoustics. - : Acoustical Society of America (ASA). ; , s. 1-3
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Konferensbidrag (refereegranskat)abstract
- We describe a novel platform for acoustic sample preparation in microchannels and microplates. The utilized method is based on generating a multitude of acoustic resonances at a set of different frequencies in microstructures, in order to accurately control the migration and positioning of particles and cells suspended in fluid channels and chambers. The actuation frequencies range from 30 kHz to 7 MHz, which are applied simultaneously and/or in sweeps. We present two devices: A closed microfluidic chip designed for pre-alignment, size-based separation, isolation, up-concentration and lysis of cells, and an open multi-well microplate designed for parallel aggregation and positioning of cells. Both devices in the platform are compatible with high-resolution live-cell microscopy, which is used for fluorescence-based optical characterization. Two bioapplications are demonstrated for each of the devices: The first device is used for size-selective cell isolation and lysis for DNA-based diagnostics, and the second device is used for quantifying the heterogeneity in cytotoxic response of natural killer cells interacting with cancer cells.
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