| 1. |
- Lindström, Sara, et al.
(författare)
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Nanoporous titania coating of microwell chips for stem cell culture and analysis
- 2010
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Ingår i: Journal of Biomechanical Science and Engineering. - : Japan Society of Mechanical Engineers. - 1880-9863. ; 5:3, s. 272-279
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Tidskriftsartikel (refereegranskat)abstract
- Stem cell research is today an active and promising field of research. To learn more about the biology of stem cells, technical improvements are needed such as tools to study stem cells in order to characterize them further and to gain insights to the molecular regulations of their maintenance, differentiation and identification. Common procedure when studying stem cells is to coat the surface where the stem cells are to be cultured with organic materials like matri-gel, poly-L-lysine and fibronectin. The resulting coating is usually relatively fragile and it is difficult to know if the coating is evenly distributed. In addition, these forms of coatings cannot be sterilized and re-used, but must be added as an initial, time-consuming step in the daily protocol. A microwell chip with hundreds of 500 nl wells has recently been shown to be a useful tool for stem cell culturing. This platform is here modified to facilitate and improve the coating conditions for adherent cell culture. A robust and highly porous film of TiO2 is deposited in the wells prior cell seeding. TiO2 is known to be biocompatible and provides a surface that is even and well characterized, simple to produce and re-usable. Furthermore it enables the microwell chips to be stored pre-coated for longer periods of time before use. We investigated the growth of rat mesenchymal stem cells on nanoporous titania films and found that they proliferated much faster than on conventional coatings. The combination of the robust TiO2 coating of the microwell chip enables thousands of individually separated single, or clones of, stem cells to be studied simultaneously and opens up the possibility for more user-friendly cell culturing.
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| 2. |
- Friedman, Mikaela, et al.
(författare)
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Engineering and characterization of a bispecific HER2 x EGFR-binding affibody molecule
- 2009
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Ingår i: Biotechnology and applied biochemistry. - 0885-4513 .- 1470-8744. ; 54, s. 121-131
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Tidskriftsartikel (refereegranskat)abstract
- HER2 (human epidermal-growth-factor receptor-2; ErbB2) and EGFR (epidermal-growth-factor receptor) are overexpressed in various forms of cancer, and the co-expression of both HER2 and EGFR has been reported in a number of studies. The simultaneous targeting of HER2 and EGFR has been discussed as a strategy with which to potentially increase efficiency and selectivity in molecular imaging and therapy of certain cancers. In an effort to generate a molecule capable of bispecifically targeting HER2 and EGFR, a gene fragment encoding a bivalent HER2-binding affibody molecule was genetically fused in-frame with a bivalent EGFR-binding affibody molecule via a (G(4)S)(3) [(Gly(4)-Ser)(3)]-encoding gene fragment. The encoded 30 kDa affibody construct (Z(HER2))(2)-(G(4)S)(3)-(Z(EGFR))(2), with potential for bs (bispecific) binding to HER2 and EGFR, was expressed in Escherichia coli and characterized in terms of its binding capabilities. The retained ability to bind HER2 and EGFR separately was demonstrated using both biosensor technology and flow-cytometric analysis, the latter using HER2- and EGFR-overexpressing cells. Furthermore, simultaneous binding to HER2 and EGFR was demonstrated in: (i) a sandwich format employing real-time biospecific interaction analysis where the bs affibody molecule bound immobilized EGFR and soluble HER2; (ii) immunofluorescence microscopy, where the bs affibody molecule bound EGFR-overexpressing cells and soluble HER2; and (iii) a cell-cell interaction analysis where the bs affibody molecule bound HER2-overexpressing SKBR-3 cells and EGFR-overexpressing A-431 cells. This is, to our knowledge, the first reported bs affinity protein with potential ability for the simultaneous targeting of HER2 and EGFR. The potential future use of this and similar constructs, capable of bs targeting of receptors to increase the efficacy and selectivity in imaging and therapy, is discussed.
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| 3. |
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| 4. |
- Grönwall, Caroline, et al.
(författare)
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Selection and characterization of Affibody ligands binding to Alzheimer amyloid beta peptides
- 2007
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Ingår i: Journal of Biotechnology. - : Elsevier BV. - 0168-1656 .- 1873-4863. ; 128:1, s. 162-183
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Tidskriftsartikel (refereegranskat)abstract
- Affibody (Affibody) ligands specific for human amyloid beta (Abeta) peptides (40 or 42 amino acid residues in size), involved in the progress of Alzheimer's disease, were selected by phage display technology from a combinatorial protein library based on the 58-amino acid residue staphylococcal protein A-derived Z domain. Post-selection screening of 384 randomly picked clones, out of which 192 clones were subjected to DNA sequencing and clustering, resulted in the identification of 16 Affibody variants that were produced and affinity purified for ranking of their binding properties. The two most promising Affibody variants were shown to selectively and efficiently bind to Abeta peptides, but not to the control proteins. These two Affibody ligands were in dimeric form (to gain avidity effects) coupled to affinity resins for evaluation as affinity devices for capture of Abeta peptides from human plasma and serum. It was found that both ligands could efficiently capture Abeta that were spiked (100 microgml(-1)) to plasma and serum samples. A ligand multimerization problem that would yield suboptimal affinity resins, caused by a cysteine residue present at the binding surface of the Affibody ligands, could be circumvented by the generation of second-generation Affibody ligands (having cysteine to serine substitutions). In an epitope mapping effort, the preferred binding site of selected Affibody ligands was mapped to amino acids 30-36 of Abeta, which fortunately would indicate that the Affibody molecules should not bind the amyloid precursor protein (APP). In addition, a significant effort was made to analyze which form of Abeta (monomer, dimer or higher aggregates) that was most efficiently captured by the selected Affibody ligand. By using Western blotting and a dot blot assay in combination with size exclusion chromatography, it could be concluded that selected Affibody ligands predominantly bound a non-aggregated form of analyzed Abeta peptide, which we speculate to be dimeric Abeta. In conclusion, we have successfully selected Affibody ligands that efficiently capture Abeta peptides from human plasma and serum. The potential therapeutic use of these optimized ligands for extracorporeal capture of Abeta peptides in order to slow down or reduce amyloid plaque formation, is discussed.
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| 5. |
- Guldevall, Karolin, et al.
(författare)
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Imaging Immune Surveillance of Individual Natural Killer Cells Confined in Microwell Arrays
- 2010
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 5:11, s. e15453-
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Tidskriftsartikel (refereegranskat)abstract
- New markers are constantly emerging that identify smaller and smaller subpopulations of immune cells. However, there is a growing awareness that even within very small populations, there is a marked functional heterogeneity and that measurements at the population level only gives an average estimate of the behaviour of that pool of cells. New techniques to analyze single immune cells over time are needed to overcome this limitation. For that purpose, we have designed and evaluated microwell array systems made from two materials, polydimethylsiloxane (PDMS) and silicon, for high-resolution imaging of individual natural killer (NK) cell responses. Both materials were suitable for short-term studies (<4 hours) but only silicon wells allowed long-term studies (several days). Time-lapse imaging of NK cell cytotoxicity in these microwell arrays revealed that roughly 30% of the target cells died much more rapidly than the rest upon NK cell encounter. This unexpected heterogeneity may reflect either separate mechanisms of killing or different killing efficiency by individual NK cells. Furthermore, we show that high-resolution imaging of inhibitory synapse formation, defined by clustering of MHC class I at the interface between NK and target cells, is possible in these microwells. We conclude that live cell imaging of NK-target cell interactions in multi-well microstructures are possible. The technique enables novel types of assays and allow data collection at a level of resolution not previously obtained. Furthermore, due to the large number of wells that can be simultaneously imaged, new statistical information is obtained that will lead to a better understanding of the function and regulation of the immune system at the single cell level.
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| 6. |
- Khorshidi, Mohammad Ali, et al.
(författare)
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Analysis of transient migration behavior of natural killer cells imaged in situ and in vitro
- 2011
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Ingår i: Integrative Biology. - : Oxford University Press (OUP). - 1757-9694 .- 1757-9708. ; 3:7, s. 770-778
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Tidskriftsartikel (refereegranskat)abstract
- We present a simple method for rapid and automatic characterization of lymphocyte migration from time-lapse fluorescence microscopy data. Time-lapse imaging of natural killer (NK) cells in vitro and in situ, both showed that individual cells transiently alter their migration behavior. Typically, NK cells showed periods of high motility, interrupted by transient periods of slow migration or almost complete arrests. Analysis of in vitro data showed that these periods frequently coincided with contacts with target cells, sometimes leading to target cell lysis. However, NK cells were also commonly observed to stop independently of contact with other cells. In order to objectively characterize the migration of NK cells, we implemented a simple method to discriminate when NK cells stop or have low motilities, have periods of directed migration or undergo random movement. This was achieved using a sliding window approach and evaluating the mean squared displacement (MSD) to assess the migration coefficient and MSD curvature along trajectories from individual NK cells over time. The method presented here can be used to quickly and quantitatively assess the dynamics of individual cells as well as heterogeneity within ensembles. Furthermore, it may also be used as a tool to automatically detect transient stops due to the formation of immune synapses, cell division or cell death. We show that this could be particularly useful for analysis of in situ time-lapse fluorescence imaging data where most cells, as well as the extracellular matrix, are usually unlabelled and thus invisible.
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| 7. |
- Lindström, Sara, et al.
(författare)
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A microwell array device with integrated microfluidic components for enhanced single-cell analysis
- 2009
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Ingår i: Electrophoresis. - : Wiley. - 0173-0835 .- 1522-2683. ; 30:24, s. 4166-4171
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Tidskriftsartikel (refereegranskat)abstract
- Increasing awareness of the importance of cell heterogeneity in many biological and medical contexts is prompting increasing interest in systems that allow single-cell analysis rather than conventional bulk analysis (which provides average values for variables of interest from large numbers of cells). Recently, we presented a microwell chip for long-term, high-throughput single-cell analysis. The chip has proved to be useful for purposes such as screening individual cancer and stem cells for protein/gene markers. However, liquids in the wells can only be added or changed by manually rinsing the chip, or parts of it. This procedure has several well-known drawbacks - including risks of cross-contamination, large dead volumes and laboriousness - but there have been few previous attempts to integrate liquid rinsing/switching channels in "ready-to-use" systems for single-cell analysis. Here we present a microwell system designed (using flow simulations) for single-cell analysis with integrated microfluidic components (microchannels, magnetically driven micropumps and reservoirs) for supplying the cell culture wells with reagents, or rinsing, thus facilitating controlled, directed liquid handling. It can be used totally independently, since tubing is not essential. The practical utility of the integrated system has been demonstrated by culturing endothelial cells in the microwells, and successfully applying live-cell Calcein AM staining. Systems such as this combining high-density microwell chips with microfluidic components have great potential in numerous screening applications, such as exploring the important, but frequently undetected, heterogeneity in drug responses among individual cells.
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| 8. |
- Lindström, Sara, et al.
(författare)
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A microwell chip for parallel culture and analysis of stem cells
- 2009
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Ingår i: Proceedings of Conference, MicroTAS 2009 - The 13th International Conference on Miniaturized Systems for Chemistry and Life Sciences. - : Chemical and Biological Microsystems Society. - 9780979806421 ; , s. 1309-1311
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Konferensbidrag (refereegranskat)abstract
- With recent findings on the role of reprogramming factors on stem cells, in vitro screening assays for studying (de)-differentiation is of great interest. We developed a miniaturized stem cell screening chip that is easily accessible and provides means of rapidly studying thousands of individual stem/progenitor cell samples, using low reagent volumes. Results presented here include weeklong culturing and differentiation assays of mouse embryonic stem cells, mouse adult neural stem cells, and human embryonic stem cells. The possibility to maintain the cells as stem/progenitor cells over time was shown, as was isolation and clonal analysis.
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| 9. |
- Lindström, Sara, et al.
(författare)
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High-Density Microwell Chip for Culture and Analysis of Stem Cells
- 2009
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Ingår i: PLos ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 4:9, s. e6997-
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Tidskriftsartikel (refereegranskat)abstract
- With recent findings on the role of reprogramming factors on stem cells, in vitro screening assays for studying (de)differentiation is of great interest. We developed a miniaturized stem cell screening chip that is easily accessible and provides means of rapidly studying thousands of individual stem/progenitor cell samples, using low reagent volumes. For example, screening of 700,000 substances would take less than two days, using this platform combined with a conventional bio-imaging system. The microwell chip has standard slide format and consists of 672 wells in total. Each well holds 500 nl, a volume small enough to drastically decrease reagent costs but large enough to allow utilization of standard laboratory equipment. Results presented here include weeklong culturing and differentiation assays of mouse embryonic stem cells, mouse adult neural stem cells, and human embryonic stem cells. The possibility to either maintain the cells as stem/progenitor cells or to study cell differentiation of stem/progenitor cells over time is demonstrated. Clonality is critical for stem cell research, and was accomplished in the microwell chips by isolation and clonal analysis of single mouse embryonic stem cells using flow cytometric cell-sorting. Protocols for practical handling of the microwell chips are presented, describing a rapid and user-friendly method for the simultaneous study of thousands of stem cell cultures in small microwells. This microwell chip has high potential for a wide range of applications, for example directed differentiation assays and screening of reprogramming factors, opening up considerable opportunities in the stem cell field.
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| 10. |
- Lindström, Sara, et al.
(författare)
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High throughput single cell clone analysis
- 2006
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Ingår i: Micro Total Analysis Systems - Proceedings of MicroTAS 2006 Conference. - : Japan Academic Association Inc. ; , s. 410-412
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Konferensbidrag (refereegranskat)abstract
- A novel microplate has been developed for high throughput single cell/clone analysis. Rapid single cell seeding using a conventional FACS into micro wells allows several thousands of single cells to be cultivated, short-term (72 h) or long-term (10-14 days), and analyzed individually. The platform requires a remarkably low number of cells, a major advantage when screening limited amounts of patient cell samples. Analysis of single cell heterogeneity and colony formation related to drug sensitivity can be accomplished in a high throughput manner.
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