| 1. |
- Barkefors, Irmeli, et al.
(författare)
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A fluidic device to study directional angiogenesis in complex tissue and organ culture models
- 2009
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Ingår i: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0197 .- 1473-0189. ; 9:4, s. 529-535
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Tidskriftsartikel (refereegranskat)abstract
- Many signals that induce angiogenesis have been identified; however, it is still not clear how these signals interact to shape the vascular system. We have developed a fluidic device for generation of molecular gradients in 3-dimensional cultures of complex tissues and organs in order to create an assay for precise induction and guidance of growing blood vessels. The device features a centrally placed culture chamber, flanked by channels attached to a perfusion system used to generate gradients. A separate network of vacuum channels permits reversible attachment of the device to a flat surface. We show that the fluidic device can be used to create growth factor gradients that induce directional angiogenesis in embryonic mouse kidneys and in clusters of differentiating stem cells. These results demonstrate that the device can be used to accurately manipulate complex morphogenetic processes with a high degree of experimental control.
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| 2. |
- Beech, Jason, et al.
(författare)
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Tipping the balance of deterministic lateral displacement devices using dielectrophoresis.
- 2009
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Ingår i: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0189 .- 1473-0197. ; 9:18, s. 2698-2706
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Tidskriftsartikel (refereegranskat)abstract
- We report the use of dielectrophoresis (DEP) to achieve tunability, improve dynamic range and open up for the separation of particles with regard to parameters other than hydrodynamic size in deterministic lateral displacement (DLD) devices. DLD devices have been shown capable of rapidly and continuously separating micrometer sized plastic spheres by size with a resolution of 20 nm in diameter and of being able to handle the separation of biological samples as wide ranging as bacterial artificial chromosomes and blood cells. DEP, while not exhibiting the same resolution in size separation as DLD, has the benefit of being easy to tune and can, by choosing the frequency, be used to probe a variety of particle properties. By combining DLD and DEP we open up for the advantages, while avoiding the drawbacks, of the two techniques. We present a proof of principle in which the critical size for separation of polystyrene beads is tuned in the range 2-6 microm in a single device by the application of moderate (100 V cm(-1)), low frequency (100 Hz) AC electric fields. The behaviour of the device was further investigated by performing simulations of particle trajectories, the results of which were in good qualitative agreement with experiments, indicating the potential of the method for tunable, high-resolution separations with respect to both size and polarisability.
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| 3. |
- Gamby, Jean, et al.
(författare)
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Polycarbonate microchannel network with carpet of Gold NanoWires as SERS-active device
- 2009
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Ingår i: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0197 .- 1473-0189. ; 9:12, s. 1806-1808
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Tidskriftsartikel (refereegranskat)abstract
- A polycarbonate (PC) microchannel network supporting gold nanowires was developed to be a SERS-active microchip. Observations of large increases in a Raman cross-section, allowed us to collect vibrational signatures which are not easily detectable by Raman techniques due to the high fluorescence level of bare PC. Compared to other SERS experiments, this study relies on the use of dielectric polymer/metal surfaces which are well defined at microscale and nanoscale levels. This device seems a promising tool for sensing the adsorption of biomolecules.
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| 4. |
- Johansson, Linda, et al.
(författare)
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Effective mixing of laminar flows at a density interface by an integrated ultrasonic transducer
- 2009
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Ingår i: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0197 .- 1473-0189. ; 9:2, s. 297-304
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Tidskriftsartikel (refereegranskat)abstract
- An acoustic mixer for glass channel microfluidic systems is presented. An acoustic standing wave, perpendicular to the fluid flow, is generated by the excitation of a miniaturized piezoelectric transducer operated around 10 MHz. The transducer is fabricated into a planar printed circuit board structure, constituting the bottom channel wall, which makes the mixer simple to integrate with a wide selection of microfluidic channel designs. The mixing occurs at a fluid-fluid density interface due to the acoustic radiation force; an analytical expression is derived to qualitatively describe this phenomenon. Only a small density difference in the range of 2–5% is required to achieve 150–270% peak broadening of a fluorescent sample between sheath flows, which we use as a measure of the mixing efficiency. The mixing efficiency is measured with regard to its sensitivity to the density difference, the fluid velocity and the transducer driving frequency. Transducers at different positions along the microchannel make it possible to compare the mixing of straight versus diagonal flows across the transducer surface. We finally demonstrate enhanced chemical lysis of E. coli K12 cells in the device due to active fluid mixing.
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| 5. |
- Lindström, Sara, et al.
(författare)
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PCR amplification and genetic analysis in a microwell cell culturing chip
- 2009
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Ingår i: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0197 .- 1473-0189. ; , s. 3465-3471
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Tidskriftsartikel (refereegranskat)abstract
- We have previously described a microwell chip designed for high throughput, long-term single-cell culturing and clonal analysis in individual wells providing a controlled way of studying high numbers of individual adherent or non-adherent cells. Here we present a method for the genetic analysis of cells cultured on-chip by PCR and minisequencing, demonstrated using two human adherent cell lines: one wild type and one with a single-base mutation in the p53 gene. Five wild type or mutated cells were seeded per well (in a defined set of wells, each holding 500 nL of culture medium) in a 672-microwell chip. The cell chip was incubated overnight, or cultured for up to five days, depending on the desired colony size, after which the cells were lysed and subjected to PCR directly in the wells. PCR products were detected, in the wells, using a biotinylated primer and a fluorescently labelled primer, allowing the products to be captured on streptavidin-coated magnetic beads and detected by a fluorescence microscope. In addition, to enable genetic analysis by minisequencing, the double-stranded PCR products were denatured and the immobilized strands were kept in the wells by applying a magnetic field from the bottom of the wells while the wells were washed, a minisequencing reaction mixture was added, and after incubation in appropriate conditions the expected genotypes were detected in the investigated microwells, simultaneously, by an array scanner. We anticipate that the technique could be used in mutation frequency screening, providing the ability to correlate cells' proliferative heterogeneity to their genetic heterogeneity, in hundreds of samples simultaneously. The presented method of single-cell culture and DNA amplification thus offers a potentially powerful alternative to single-cell PCR, with advantageous robustness and sensitivity
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| 6. |
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| 7. |
- Manneberg, Otto, et al.
(författare)
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Flow-free transport of cells in microchannels by frequency-modulated ultrasound
- 2009
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Ingår i: Lab on a Chip. - 1473-0197 .- 1473-0189. ; 9, s. 833-837
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate flow-free transport of cells and particles by the use of frequency-modulated ultrasonic actuation of a microfluidic chip. Two different modulation schemes are combined: A rapid (1 kHz) linear frequency sweep around similar to 6.9 MHz is used for two-dimensional spatial stabilization of the force field over a 5 mm long inlet channel of constant cross section, and a slow (0.2-0.7 Hz) linear frequency sweep around similar to 2.6 MHz is used for flow-free ultrasonic transport and positioning of cells or particles. The method is used for controlling the motion and position of cells monitored with high-resolution optical microscopy, but can also be used more generally for improving the robustness and performance of ultrasonic manipulation micro-devices.
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| 8. |
- Santillo, Michael F, et al.
(författare)
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Temporal analysis of protozoan lysis in a microfluidic device.
- 2009
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Ingår i: Lab on a chip. - : Royal Society of Chemistry (RSC). - 1473-0197 .- 1473-0189. ; 9:19, s. 2796-802
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Tidskriftsartikel (refereegranskat)abstract
- A microfluidic device was fabricated and characterized for studying cell lysis of Arcella vulgaris, a nonpathogenic amoeba, over time. The device contains a series of chambers which capture cells allowing them to be subsequently exposed to a constant flow of biocidal agent. With this microfluidic system, individual cells are observed as they undergo lysis. This allows high-throughput measurements of individual lysis events, which are not possible with conventional techniques. Differences in lysis and decay times for Arcella were seen at different flow rates and concentrations of benzalkonium chloride, a biocidal detergent. The efficacy of benzalkonium chloride, chlorhexidine digluconate, phenol, sodium dodecyl sulfate, and Triton X-100 were compared, revealing information on their mechanisms of action. The presented device allows cell capture, controlled exposure to chemical biocides, and observation of lysis with single-cell resolution. Observations at the single cell level give insight into the mechanistic details of the lysis of individual Arcella cells vs. the population; decay times for individual Arcella cells were much shorter when compared to a population of 15 cells.
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| 9. |
- Schaller, Vincent, 1979, et al.
(författare)
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Towards an electrowetting-based digital microfluidic platform for magnetic immunoassays
- 2009
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Ingår i: Lab on a Chip - Miniaturisation for Chemistry and Biology. - : Royal Society of Chemistry (RSC). - 1473-0189 .- 1473-0197. ; 9:23, s. 3433-3436
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate ElectroWetting-On-Dielectric (EWOD) transport and SQUID gradiometer detection of magnetic nanoparticles (MNPs) suspended in a 2 mu l de-ionized water droplet. This proof-of-concept methodology constitutes the first development step towards a highly sensitive magnetic immunoassay platform with SQUID readout and droplet-based sample handling. Magnetic AC-susceptibility measurements were performed on MNPs with a hydrodynamic diameter of 100 nm using a high-Tc dc Superconducting Quantum Interference Device (SQUID) gradiometer as detector. We observed that the signal amplitude per unit volume is 2.5 times higher for a 2 ml sample droplet compared to a 30 ml sample volume.
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| 10. |
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