| 61. |
- Persson, Henrik, et al.
(författare)
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From immobilized cells to motile cells on a bed-of-nails: effects of vertical nanowire array density on cell behaviour.
- 2015
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- The field of vertical nanowire array-based applications in cell biology is growing rapidly and an increasing number of applications are being explored. These applications almost invariably rely on the physical properties of the nanowire arrays, creating a need for a better understanding of how their physical properties affect cell behaviour. Here, we investigate the effects of nanowire density on cell migration, division and morphology for murine fibroblasts. Our results show that few nanowires are sufficient to immobilize cells, while a high nanowire spatial density enables a "bed-of-nails" regime, where cells reside on top of the nanowires and are fully motile. The presence of nanowires decreases the cell proliferation rate, even in the "bed-of-nails" regime. We show that the cell morphology strongly depends on the nanowire density. Cells cultured on low (0.1 μm(-2)) and medium (1 μm(-2)) density substrates exhibit an increased number of multi-nucleated cells and micronuclei. These were not observed in cells cultured on high nanowire density substrates (4 μm(-2)). The results offer important guidelines to minimize cell-function perturbations on nanowire arrays. Moreover, these findings offer the possibility to tune cell proliferation and migration independently by adjusting the nanowire density, which may have applications in drug testing.
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| 62. |
- Persson, Henrik, et al.
(författare)
-
Vertical nanotubes connected by a subsurface nanochannel
- 2010
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Ingår i: 14th International Conference on Miniaturized Systems for Chemistry and Life Sciences 2010, MicroTAS 2010. - 9781618390622 ; 3, s. 1862-1864
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Konferensbidrag (refereegranskat)abstract
- We have built an array of vertical nanotubes connected by a subsurface nanofluidic channel. The nanotube system is to be used for cell injections. By culturing cells on top of the nanotubes the cells will be pierced and molecules can enter the cells via the subsurface channel. Several channels can be made on the same sample and different molecules can be injected into different subpopulations of cells. The advantages of our system over similar injection devices include spatial and temporal resolution as well as an increased choice of injected molecules.
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| 63. |
- Porro, Gloria, et al.
(författare)
-
Deterministic lateral displacement systems with arrayed three-dimensional electrodes for tunable particle sorting
- 2020
-
Ingår i: MicroTAS 2020 - 24th International Conference on Miniaturized Systems for Chemistry and Life Sciences. - 9781733419017 ; , s. 655-656
-
Konferensbidrag (refereegranskat)abstract
- Deterministic Lateral Displacement (DLD) is a passive technique employed for particles sorting. We recently introduced a DLD device composed of arrayed three-dimensional metal-covered pillars that can be used to locally apply an electric field. With our system we can exploit the dielectrophoretic (DEP) effect to exert forces on the bioparticles to be sorted, thus dynamically tuning the critical size of the passive sorting device.
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| 64. |
- Reisner, Walter W., et al.
(författare)
-
Melting mapping in nanochannels
- 2008
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Ingår i: ; , s. 1516-1518
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Konferensbidrag (refereegranskat)abstract
- We demonstrate direct visualization of melting mapping of DNA stretched in nanoscale channels[1] using standard staining methods and epifluorescence microscopy to gain information on the local AT/GC ratio along large DNA molecules. Our development opens up a novel route to mapping of large-scale genomic variations.
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| 65. |
- Salieb-Beugelaar, Georgette, et al.
(författare)
-
DNA movement in sub-20 nm nanoslits
- 2007
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Ingår i: Proceedings of the 11th International Conference on Miniaturized Systems for Chemistry and Life Sciences, uTAS 2007. - 9780979806407 ; , s. 1201-1203
-
Konferensbidrag (refereegranskat)abstract
- The movement of XbaI digested O-DNA in 20 nanometer and O-DNA in 12 nanometer high slits was investigated. We found that DNA moved intermittently and following preferential pathways, indicating an important influence of surface roughness. From these intermittent movements two different mobilities were calculated, the total averaged mobilities and averaged mobilities between the intermittent sticking events. The friction coefficient per unit length was calculated from the latter mobilities. A three order of magnitude increase was found for the 12 nm slits compared to the theoretical value. The mobility furthermore differs less than one order of magnitude between 20 nm and 12 nm slits, and the influence of varying the ionic strength of the buffer was not significant. This work is the first time DNA movement in such shallow constrictions is investigated.
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| 66. |
- Sköld, Niklas, et al.
(författare)
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Nanofluidics in hollow nanowires
- 2010
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Ingår i: NANOTECHNOLOGY. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 21:15
-
Tidskriftsartikel (refereegranskat)abstract
- We present a novel scheme for producing nanotube membranes using free-standing hollow nanowires, with easily controllable dimensions. GaAs–AlInP core–shell nanowires were grown by metal–organic vapor phase epitaxy and were partially embedded in a polymer film. The GaAs core and substrate were etched selectively, leaving tubes with open access to both sides of the membrane. Electrophoretic transport of T4-phage DNA through the hollow nanowires was demonstrated using epifluorescence microscopy.
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| 67. |
- Stollenwerk, Maria, et al.
(författare)
-
Quantitation of bacterial adhesion to polymer surfaces by bioluminescence
- 1998
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Ingår i: Zentralblatt fur Bakteriologie. - 0934-8840. ; 287:1-2, s. 7-18
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Tidskriftsartikel (refereegranskat)abstract
- Quantitation of microbes adhering to a surface is commonly used in studies of microbial adhesion to different surfaces. We have quantified different staphylococcal strains adhering to polymer surfaces by measuring bacterial ATP (adenosine triphosphate) by bioluminescence. The method is sensitive, having a detection limit of 104 bacterial cells. Viable counting of bacterial cells may yield falsely low results due to the presence of 'dormant' and adherent bacteria. By using bioluminescence, this can be avoided. Cells of different bacterial species and cells of strains of the same species were shown to differ significantly in their basal ATP content (8.7 x 10-13 - 5.2 x 10-22 MATP). The size of adherent and planktonic bacteria decreased with time (0.7 μm → 0.3 μm, 20 days). During incubation in nutrient-poor buffer ('starvation'), the ATP content of adherent bacteria decreased after 24-96 h whereas that of planktonic bacteria was stable over 20 days. The presence of human serum or plasma did not interfere significantly with the test results. Since the ATP concentration of bacterial strains of different species varies and is also influenced by the growth conditions of bacteria (solid or liquid culture medium), a species-specific standard curve has to be established for bacteria grown under the same culture conditions. We conclude that the method is a sensitive tool to quantify adherent bacteria during experiments lasting for less than 6 h and constitutes a valuable method to be used in conjunction with different microscopical techniques.
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| 68. |
- Ström, Oskar E., et al.
(författare)
-
DNA concentration wave formation in pillar arrays
- 2020
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Ingår i: MicroTAS 2020 - 24th International Conference on Miniaturized Systems for Chemistry and Life Sciences. - 9781733419017 ; , s. 240-241
-
Konferensbidrag (refereegranskat)abstract
- High throughput in particle and molecular sorting schemes is an important performance indicator and can be realized through increased volumetric processing rates or increased concentrations. Here we investigate the effect of increased concentration of high-molecular weight DNA in micropillar arrays for deterministic lateral displacement (DLD). We find that the array imposes regular fluctuations in the concentration of the DNA if the sample concentration and flow rates exceed respective threshold values. We characterize the resulting concentration waves and study their influence on microsphere trajectories in the device. We expect our results to be relevant e.g. for sample preparation of cell lysates which can often be complicated by the release of chromosomal DNA.
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| 69. |
- Ström, Oskar E., et al.
(författare)
-
Geometry-Dependent Elastic Flow Dynamics in Micropillar Arrays
- 2024
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Ingår i: Micromachines. - 2072-666X. ; 15:2
-
Tidskriftsartikel (refereegranskat)abstract
- Regular device-scale DNA waves for high DNA concentrations and flow velocities have been shown to emerge in quadratic micropillar arrays with potentially strong relevance for a wide range of microfluidic applications. Hexagonal arrays constitute another geometry that is especially relevant for the microfluidic pulsed-field separation of DNA. Here, we report on the differences at the micro and macroscopic scales between the resulting wave patterns for these two regular array geometries and one disordered array geometry. In contrast to the large-scale regular waves visible in the quadratic array, in the hexagonal arrays, waves occur in a device-scale disordered zig-zag pattern with fluctuations on a much smaller scale. We connect the large-scale pattern to the microscopic flow and observe flow synchronization that switches between two directions for both the quadratic and hexagonal arrays. We show the importance of order using the disordered array, where steady-state stationary and highly fluctuating flow states persist in seemingly random locations across the array. We compare the flow dynamics of the arrays to that in a device with sparsely distributed pillars. Here, we observe similar vortex shedding, which is clearly observable in the quadratic and disordered arrays. However, the shedding of these vortices couples only in the flow direction and not laterally as in the dense, ordered arrays. We believe that our findings will contribute to the understanding of elastic flow dynamics in pillar arrays, helping us elucidate the fundamental principles of non-Newtonian fluid flow in complex environments as well as supporting applications in engineering involving e.g., transport, sorting, and mixing of complex fluids.
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| 70. |
- Ström, Oskar E., et al.
(författare)
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High-Throughput Separation of Long DNA in Deterministic Lateral Displacement Arrays
- 2022
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Ingår i: Micromachines. - : MDPI AG. - 2072-666X. ; 13:10
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Tidskriftsartikel (refereegranskat)abstract
- Length-based separation of DNA remains as relevant today as when gel electrophoresis was introduced almost 100 years ago. While new, long-read genomics technologies have revolutionised accessibility to powerful genomic data, the preparation of samples has not proceeded at the same pace, with sample preparation often constituting a considerable bottleneck, both in time and difficulty. Microfluidics holds great potential for automated, sample-to-answer analysis via the integration of preparatory and analytical steps, but for this to be fully realised, more versatile, powerful and integrable unit operations, such as separation, are essential. We demonstrate the displacement and separation of DNA with a throughput that is one to five orders of magnitude greater than other microfluidic techniques. Using a device with a small footprint (23 mm × 0.5 mm), and with feature sizes in the micrometre range, it is considerably easier to fabricate than parallelized nano-array-based approaches. We show the separation of 48.5 kbp and 166 kbp DNA strands achieving a significantly improved throughput of 760 ng/h, compared to previous work and the separation of low concentrations of 48.5 kbp DNA molecules from a massive background of sub 10 kbp fragments. We show that the extension of DNA molecules at high flow velocities, generally believed to make the length-based separation of long DNA difficult, does not place the ultimate limitation on our method. Instead, we explore the effects of polymer rotations and intermolecular interactions at extremely high DNA concentrations and postulate that these may have both negative and positive influences on the separation depending on the detailed experimental conditions.
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