| 1. |
- Akbari, Elham, et al.
(författare)
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SEPARATION OF CLUSTERS OF GROUP A STREPTOCOCCI USING DETERMINISTIC LATERAL DISPLACEMENT
- 2021
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Ingår i: MicroTAS 2021 - 25th International Conference on Miniaturized Systems for Chemistry and Life Sciences. - 9781733419031 ; , s. 1201-1202
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Konferensbidrag (refereegranskat)abstract
- Differences in morphologies of bacteria and bacteria clusters are known to influence their pathogenicity. However, it is difficult to separate cells and cell clusters based on morphology using standard cell biological methods, making studies of the underlying mechanisms difficult. Here we report a simple label-free method for the continuous separation of clusters of group A streptococci, based on cluster size and morphology, using Deterministic Lateral Displacement (DLD). In general, this opens up for the generation of cell populations with heterogenicity in cluster size and physical properties.
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| 2. |
- Akbari, Elham, et al.
(författare)
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SEPARATION OF SINGLETS AND CLUSTERS OF GROUP A STREPTOCOCCI USING DETERMINISTIC LATERAL DISPLACEMENT AND FILTER SONICATION
- 2022
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Ingår i: MicroTAS 2022 - 26th International Conference on Miniaturized Systems for Chemistry and Life Sciences. - 9781733419048 ; , s. 306-307
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Konferensbidrag (refereegranskat)abstract
- Differences in morphologies of bacteria and bacteria clusters are thought to contribute to their virulence and colonization. However, the conventional standard cell biological methods cannot separate bacteria and bacteria clusters based on their morphologies and sizes, making studies of the underlying mechanisms difficult. Here we report a simple label-free method for the continuous separation of singlets and clusters, of group A streptococci, based on their size and morphology, using Deterministic Lateral Displacement and filter-sonication. In general, this opens up for the generation of cell populations with heterogenicity in cluster size and physical properties.
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| 3. |
- Al-Fandi, M, et al.
(författare)
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Nano-engineered living bacterial motors for active microfluidic mixing.
- 2010
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Ingår i: IET Nanobiotechnology. - : Institution of Engineering and Technology (IET). - 1751-875X .- 1751-8741. ; 4:3, s. 61-71
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Tidskriftsartikel (refereegranskat)abstract
- Active micromixers with rotating elements are attractive microfluidic actuators in many applications because of their mixing ability at a short distance. However, miniaturising the impeller design poses technical challenges including the fabrication and driving means. As a possible solution inspired by macro magnetic bar-stirrers, this study proposes the use of tethered, rotating bacteria as mixing elements. A tethered cell is a genetically engineered, harmless Escherichia coli (E. coli) attached to a surface by a single, shortened flagellum. The tethered flagellum acts as a pivot around which the entire cell body smoothly rotates. Videomicroscopy, image analysis and computational fluid dynamics (CFD) are utilised to demonstrate a proof-of-concept for the micro mixing process. Flow visualisation experiments show that a approximately 3 [micro sign]m long tethered E. coli rotating at approximately 240 rpm can circulate a 1 [micro sign]m polystyrene bead in the adjacent area at an average speed of nearly 4 [micro sign]m/s. The Peclet (Pe(b)) number for the stirred bead is evaluated to approximately 4. CFD simulations show that the rotary motion of a tethered E. coli rotating at 240 rpm can generate fluid velocities, up to 37 [micro sign]m/s bordering the cell envelop. Based on these simulations, the Strouhal number (St) is calculated to about 2. This hybrid bio-inorganic micromxer could be used as a local, disposable mixer.
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| 4. |
- Arellano-Caicedo, Carlos, et al.
(författare)
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Habitat complexity affects microbial growth in fractal maze
- 2023
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Ingår i: Current biology : CB. - : Elsevier BV. - 1879-0445 .- 0960-9822. ; 33:8, s. 4-1458
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Tidskriftsartikel (refereegranskat)abstract
- The great variety of earth's microorganisms and their functions are attributed to the heterogeneity of their habitats, but our understanding of the impact of this heterogeneity on microbes is limited at the microscale. In this study, we tested how a gradient of spatial habitat complexity in the form of fractal mazes influenced the growth, substrate degradation, and interactions of the bacterial strain Pseudomonas putida and the fungal strain Coprinopsis cinerea. These strains responded in opposite ways: complex habitats strongly reduced fungal growth but, in contrast, increased the abundance of bacteria. Fungal hyphae did not reach far into the mazes and forced bacteria to grow in deeper regions. Bacterial substrate degradation strongly increased with habitat complexity, even more than bacterial biomass, up to an optimal depth, while the most remote parts of the mazes showed both decreased biomass and substrate degradation. These results suggest an increase in enzymatic activity in confined spaces, where areas may experience enhanced microbial activity and resource use efficiency. Very remote spaces showing a slower turnover of substrates illustrate a mechanism which may contribute to the long-term storage of organic matter in soils. We demonstrate here that the sole effect of spatial microstructures affects microbial growth and substrate degradation, leading to differences in local microscale spatial availability. These differences might add up to considerable changes in nutrient cycling at the macroscale, such as contributing to soil organic carbon storage.
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| 5. |
- Arellano-Caicedo, Carlos, et al.
(författare)
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Habitat geometry in artificial microstructure affects bacterial and fungal growth, interactions, and substrate degradation
- 2021
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- Microhabitat conditions determine the magnitude and speed of microbial processes but have been challenging to investigate. In this study we used microfluidic devices to determine the effect of the spatial distortion of a pore space on fungal and bacterial growth, interactions, and substrate degradation. The devices contained channels differing in bending angles and order. Sharper angles reduced fungal and bacterial biomass, especially when angles were repeated in the same direction. Substrate degradation was only decreased by sharper angles when fungi and bacteria were grown together. Investigation at the cellular scale suggests that this was caused by fungal habitat modification, since hyphae branched in sharp and repeated turns, blocking the dispersal of bacteria and the substrate. Our results demonstrate how the geometry of microstructures can influence microbial activity. This can be transferable to soil pore spaces, where spatial occlusion and microbial feedback on microstructures is thought to explain organic matter stabilization.
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| 6. |
- Arellano-Caicedo, Carlos, et al.
(författare)
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Quantification of growth and nutrient consumption of bacterial and fungal cultures in microfluidic microhabitat models
- 2024
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Ingår i: STAR Protocols. - 2666-1667. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- Understanding microbes in nature requires consideration of their microenvironment. Here, we present a protocol for quantifying biomass and nutrient degradation of bacterial and fungal cultures (Pseudomonas putida and Coprinopsis cinerea, respectively) in microfluidics. We describe steps for mask design and fabrication, master printing, polydimethylsiloxane chip fabrication, and chip inoculation and imaging using fluorescence microscopy. We include procedures for image analysis, plotting, and statistics. For complete details on the use and execution of this protocol, please refer to Arellano-Caicedo et al. (2023).1
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| 7. |
- Barrett, Michael P., et al.
(författare)
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Microfluidics-based approaches to the isolation of African trypanosomes
- 2017
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Ingår i: Pathogens. - : MDPI AG. - 2076-0817. ; 6:4
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Forskningsöversikt (refereegranskat)abstract
- African trypanosomes are responsible for significant levels of disease in both humans and animals. The protozoan parasites are free-living flagellates, usually transmitted by arthropod vectors, including the tsetse fly. In the mammalian host they live in the bloodstream and, in the case of human-infectious species, later invade the central nervous system. Diagnosis of the disease requires the positive identification of parasites in the bloodstream. This can be particularly challenging where parasite numbers are low, as is often the case in peripheral blood. Enriching parasites from body fluids is an important part of the diagnostic pathway. As more is learned about the physicochemical properties of trypanosomes, this information can be exploited through use of different microfluidic-based approaches to isolate the parasites from blood or other fluids. Here, we discuss recent advances in the use of microfluidics to separate trypanosomes from blood and to isolate single trypanosomes for analyses including drug screening.
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| 8. |
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| 9. |
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| 10. |
- Beech, Jason
(författare)
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Microfluidics Separation and Analysis of Biological Particles
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the last decade, powerful communication and information technology in the form of the mobile phone has been put into the hands of more than 50% of the global population. In stark contrast, a lack of access to medical diagnostic technology with which to diagnose both communicable and non-communicable diseases will mean that many of these people will die of easily treatable conditions. Small, portable, effective and affordable devices able to give relevant information about the health of an individual, even in resource poor environments, could potentially help to change this. And the developing world is not the only resource poor environment; areas struck by natural disaster or by outbreaks of infectious disease or on the battlefield or even at the frontiers of exploration we find environments in which a mobile phone-sized laboratory would have a profound impact, not only on medical, but environmental diagnostics. There are also less dramatic examples. Compared to a well-equipped hospital most environments are resource poor, including the home. Blood sugar measuring devices for example put important information immediately into the hands of the diabetes sufferer in their own home, allowing them to make informed, life-saving decisions about food intake and medication without recourse to medical doctors. These diagnostic devices will be based on technologies that go under the collective names of micro-total-analysis systems, µTAS, or Lab-on-a-Chip. One of the uniting, integral features of all these technologies is the need to manipulate small volumes of fluids, often containing cells or other particles, from which the diagnostic information is to be wrung. The manipulation of such small volumes of fluids is known as microfluidics. This doctoral thesis is concerned with particle separation science. More specifically it is concerned with the development of tools for the separation of biologically relevant particles, an important step in almost any analysis, using techniques that have been made possible through the advent of microfluidics. A technique based on the flow of fluid through arrays of micrometre-sized obstacles, Deterministic Lateral Displacement (DLD), is promising because of its exceptional resolution, its suitability for biological separations, the wide range of sizes across which it works and not least because of the promise it holds as a candidate for integration within a lab-on-a-chip. The first devices utilizing the principle were limited to use in the separation of particles by size only. However, there are many physical properties other than size holding a wealth of information about particles, for example cancer and infection with malaria or HIV have been shown to change the deformability of cells and so measuring deformability could provide a means of diagnosing these conditions. The central tenet of this work is that DLD can be used to separate particles by highly relevant physical properties other than size, for example shape, deformability or electrical properties and that devices that can do this in a cheap and simple way will constitute powerful particle separation tools, useful for diagnostic applications and well suited for integration in a Lab-on-a-Chip. The aim of this thesis is to present four research papers, documenting the development of new methods that improve the existing DLD technique. Paper I describes how the elastomeric properties of polydimethylsiloxane can be utilized to achieve tuneable separation in DLD devices, making it easier to take advantage of the high resolution inherent in the method. Paper II presents the use of dielectrophoresis to achieve tuneability, improve dynamic range and open up for the separation of particles with regard to factors other than size. Paper III describes how control of particle orientation can be used to separate particles based on their shape and how this can be used to separate blood-borne parasites from blood. Finally Paper IV deals with the size, shape and deformability of cells and how DLD devices can be used, both to measure these properties, and to perform separations based on them. The hope is that these methods might ultimately play a small part in helping diagnostics technology to become as ubiquitous as information technology has become in the last ten years and that this will have a profound impact on global health.
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