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  • 1.
    Agaton, Charlotta
    et al.
    KTH, Superseded Departments, Biotechnology.
    Uhlén, Mathias
    KTH, Superseded Departments, Biotechnology.
    Hober, Sophia
    KTH, Superseded Departments, Biotechnology.
    Genome-based proteomics2004In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 25, no 9, p. 1280-1288Article in journal (Refereed)
    Abstract [en]

    Protein-protein interactions play crucial roles in various biological pathways and functions. Therefore, the characterization of protein levels and also the network of interactions within an organism would contribute considerably to the understanding of life. The availability of the human genome sequence has created a range of new possibilities for biomedical research. A crucial challenge is to utilize the genetic information for better understanding of protein distribution and function in normal as well as in pathological biological processes. In this review, we have focused on different platforms used for systematic genome-based proteome analyses. These technologies are in many ways complementary and should be seen as various ways to elucidate different functions of the proteome.

  • 2.
    Aldaeus, Fredrik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
    Lin, Yuan
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Roeraade, Johan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
    Amberg, Gustav
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Superpositioned dielectrophoresis for enhanced trapping efficiency2005In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 26, no 22, p. 4252-4259Article in journal (Refereed)
    Abstract [en]

    One of the major applications for dielectrophoresis is selective trapping and fractionation of particles. If the surrounding medium is of low conductivity, the trapping force is high, but if the conductivity increases, the attraction decreases and may even become negative. However, high-conductivity media are essential when working with biological material such as living cells. In this paper, some basic calculations have been performed, and a model has been developed which employs both positive and negative dielectrophoresis in a channel with interdigitated electrodes. The finite element method was utilized to predict the trajectories of Escherichia coli bacteria in the superpositioned electrical fields. It is shown that a drastic improvement of trapping efficiency can be obtained in this way, when a high conductivity medium is employed.

  • 3.
    Andersson, Helene
    et al.
    KTH, Superseded Departments, Biotechnology.
    Jonsson, C.
    Moberg, Christina
    KTH, Superseded Departments, Chemistry.
    Stemme, Göran
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Patterned self-assembled beads in silicon channels2001In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 22, no 18, p. 3876-3882Article in journal (Refereed)
    Abstract [en]

    A novel technique enabling selective bead trapping in microfluidic devices without the use of physical barriers is presented in this paper. It is a fast, convenient and simple method, involving microcontact printing and self-assembly, that can be applied to silicon, quartz or plastic substrates. In the first step, channels are etched in the substrate. The surface chemistry of the internal walls of the channels is then modified by microcontact printing. The chip is submerged in a bead slurry where beads self-assemble based on surface chemistry and immobilize on the internal walls of the channels. Silicon channels (100 mum wide and 50 mum deep) have been covered with monolayers of streptavidin-, amino- and hydroxy-functionalized microspheres and resulted in good surface coverage of beads on the channel walls. A high-resolution pattern of lines of self-assembled streptavidin beads, as narrow as 5 mum, has also been generated on the bottom of a 500 mum wide and 50 mum deep channel. Flow tests were performed in sealed channels with the different immobilized beads to confirm that the immobilized beads could withstand the forces generated by water flowing in the channels. The presented results indicate that single beads can be precisely positioned within microfluidic devices based on self-assembly which is useful as screening and analysis tools within the field of biochemistry and organic chemistry.

  • 4.
    Andersson, Helene
    et al.
    KTH, Superseded Departments, Biotechnology.
    van der Wijngaart, Wouter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Stemme, Göran
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Micromachined filter-chamber array with passive valves for biochemical assays on beads2001In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 22, no 2, p. 249-257Article in journal (Refereed)
    Abstract [en]

    The filter-chamber array presented here enables a real-time parallel analysis of three different samples on beads in a volume of 3 nL, on a 1 cm(2) chip. The filter-chamber array is a system containing three filter-chambers, three passive valves at the inlet channels and a common outlet. The design enables parallel sample handling and time-controlled analysis. The device is microfabricated in silicon and sealed with a Pyrex lid to enable real-time analysis. Single nucleotide polymorphism analysis by using pyrose-quencing has successfully been performed in single filter-chamber devices. The passive valves consist of plasma-deposited octafluorocyclobutane and show a much higher resistance towards water and surface-active solutions than previous hydrophobic patches. The device is not sensitive to gas bubbles, clogging is rare and reversible, and the filter-chamber array is reusable. More complex (bio)chemical reactions on beads can be performed in the devices with passive valves than in the devices without valves.

  • 5. Curcio, M.
    et al.
    Stalhandske, P.
    Lindberg, P.
    Roeraade, Johan
    KTH, Superseded Departments, Chemistry.
    Multiplex high-throughput solid-phase minisequencing by capillary electrophoresis and liquid core waveguide fluorescence detection2002In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 23, no 10, p. 1467-1472Article in journal (Refereed)
    Abstract [en]

    Minisequencing, solid-phase single-nucleotide primer extension reaction, is a robust method for performing multiplex single-nucleotide polymorphism (SNP) analysis. We have combined this technology with capillary gel electrophoresis in a multicapillary format, using liquid core waveguide (LCW) fluorescence detection. Polymerase chain reaction (PCR) amplification of multiple DNA targets is performed with one primer for each target biotinylated. Separation of the complementary strands, minisequencing and washing steps are carried out using streptavidin-coated magnetic beads. Dideoxynucleotides analogues labelled with different fluorophores are used for the extension of the minisequencing primers. The extended oligonucleotides, the length of which defines the position on the target and the color the identity of the polymorphism, are then separated in a gel-filled array of capillaries, coated on the outside with a layer of a fluoropolymer to provide the liquid core waveguide characteristics. The technology has a potential for extremely high throughputs when a combination of multiplex PCR-minisequencing is used together with a large array of capillaries, four-color detection and high-speed separation.

  • 6. Ehn, M.
    et al.
    Ahmadian, Afshin
    KTH, Superseded Departments, Biotechnology.
    Nilsson, Peter
    KTH, Superseded Departments, Biotechnology.
    Lundeberg, Joakim
    KTH, Superseded Departments, Biotechnology.
    Hober, Sophia
    KTH, Superseded Departments, Biotechnology.
    Escherichia coli single-stranded DNA-binding a molecular tool for improved sequence protein quality in pyrosequencing2002In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 23, no 19, p. 3289-3299Article in journal (Refereed)
    Abstract [en]

    Pyrosequencing is a four-enzyme bioluminometric DNA sequencing technique based on a DNA sequencing by synthesis principle. Currently, the technique is limited to analysis of short DNA sequences exemplified by single-nucleotide polymorphism analysis. In order to expand the field for pyrosequencing, the read length needs to be improved and efforts have been made to purify reaction components as well as add single-stranded DNA-binding protein (SSB) to the pyrosequencing reaction. In this study, we have performed a systematic effort to analyze the effects of SSB by comparing the pyrosequencing result of 103 independent complementary DNA (cDNA) clones. More detailed information about the cause of low quality sequences on templates with different characteristics was achieved by thorough analysis of the pyrograms. Also, real-time biosensor analysis was performed on individual cDNA clones for investigation of primer annealing and SSB binding on these templates. Results from these studies indicate that templates with high performance in pyrosequencing without SSB possess efficient primer annealing and low SSB affinity. Alternative strategies to improve the performance in pyrosequencing by increasing the primer-annealing efficiency have also been evaluated.

  • 7. Emmelkamp, J.
    et al.
    Wolbers, F.
    Andersson, Helene
    KTH, Superseded Departments, Biotechnology.
    DaCosta, R. S.
    Wilson, B. C.
    Vermes, I.
    van den Berg, A.
    The potential of autofluorescence for the detection of single living cells for label-free cell sorting in microfluidic systems2004In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 25, no 21-22, p. 3740-3745Article in journal (Refereed)
    Abstract [en]

    A novel method for studying unlabeled living mammalian cells based on their autofluorescence (AF) signal in a prototype microfluidic device is presented. When combined, cellular AF detection and microfluidic devices have the potential to facilitate high-throughput analysis of different cell populations. To demonstrate this, unlabeled cultured cells in microfluidic devices were excited with a 488 nm excitation light and the AF emission (> 505 nm) was detected using a confocal fluorescence microscope (CFM). For example, a simple microfluidic three-port glass microstructure was used together with conventional electroosmotic flow (EOF) to switch the direction of the fluid flow. As a means to test the potential of AF-based cell sorting in this microfluidic device, granulocytes were successfully differentiated from human red blood cells (RBCs) based on differences in AF This study demonstrated the use of a simple microfabricated device to perform high-throughput live cell detection and differentiation without the need for cell-specific fluorescent labeling dyes and thereby reducing the sample preparation time. Hence, the combined use of microfluidic devices and cell AF may have many applications in single-cell analysis.

  • 8.
    Emmer, Åsa
    et al.
    KTH, Superseded Departments, Chemistry.
    Roeraade, Johan
    KTH, Superseded Departments, Chemistry.
    Wall deactivation with fluorosurfactants for capillary electrophoretic analysis of biomolecules2001In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 22, no 4, p. 660-665Article in journal (Refereed)
    Abstract [en]

    This paper describes the use of fluorosurfactants as buffer additives for capillary electrophoretic separation of proteins and peptides. Due to fluorosurfactant bilayer formation at the capillary inner wall, the surface charge can be adjusted and even reversed. If the running buffer pH is kept at a level where the proteins have the same sign of charge as the wall, electrostatic repulsion will be obtained. The protein wall adsorption can therefore be reduced and the separation performance can be noticeably increased. The separation performance can also be further improved by including mixtures of different types of fluorosurfactants in the running buffer. The buffer system can accordingly be adapted for a certain separation problem. Mechanisms for the use of fluorosurfactants for wall deactivation in capillary electrophoretic protein separations is discussed in the present work and some examples of applications are also presented.

  • 9. Ericsson, O.
    et al.
    Sivertsson, A.
    Lundeberg, Joakim
    KTH, Superseded Departments, Biotechnology.
    Ahmadian, Afshin
    KTH, Superseded Departments, Biotechnology.
    Microarray-based resequencing by apyrase-mediated allele-specific extension2003In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 24, no 19-20, p. 3330-3338Article in journal (Refereed)
    Abstract [en]

    We have developed an array-based resequencing method to determine genetic alterations in putative cancer genes. The method relies on that the specificity of DNA polymerase in allele-specific extensions can be enhanced by terminating the extension reactions with apyrase and that a tiling set of primers are synthesized covering the investigated gene sequence. We report on such apyrase-mediated allele-specific primer extension (AMASE) assay as a method suitable for high-throughout resequencing and mutation detection in tumor suppressor genes and oncogenes. In the experimental setup, primers complementary to codons 12, 13 and codon 61 of the N-ras proto-oncogene were spotted onto glass slides. Overlapping sense and anti-sense primers were designed so that complementary primers for all possible mutations in each base position were investigated. The extension reactions were performed in a single step following hybridization of target DNA to the immobilized primers on the array surface. Mutation detection limits and the possibility of quantifying the mutations were investigated using synthetic oligonucleotides. In addition, 64 clinical samples were sequenced and 16 of these showed mutations in the N-ras gene.

  • 10.
    Eriksson, Jonas
    et al.
    KTH, Superseded Departments, Biotechnology.
    Gharizadeh, Baback
    KTH, Superseded Departments, Biotechnology.
    Nordström, Tommy
    KTH, Superseded Departments, Biotechnology.
    Nyrén, Pål
    KTH, Superseded Departments, Biotechnology.
    Pyrosequencing (TM) technology at elevated temperature2004In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 25, no 1, p. 20-27Article in journal (Refereed)
    Abstract [en]

    To date, the Pyrosequencing(TM) technology has been performed at 28degreesC due to the low thermostability of the firefly luciferase. In this study, firefly luciferase was stabilized in the presence of glycine betaine, allowing DNA sequencing at 37degreesC. By increasing the temperature to 37degreesC, false signals due to primer-dimers and loop-structures were decreased significantly. In addition, a combination of (i) replacing the natural dGTP with 7'deaza-dGTP in the polymerase chain reaction (PCR), (ii) 1.6 m glycine betaine, and (iii) an increase of the temperature to 37degreesC enabled us to sequence a DNA template with the initial sequence 3'-ATGGCCCGGGGGGGAGCTCCA . . . 5'. Furthermore, we describe a method to analyze if a primer forms a primer-dimer with extendable 3'-ends.

  • 11.
    Frisk, Thomas
    et al.
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Rydholm, Susanna
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Andersson, Helene
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Stemme, Göran
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    A concept for miniaturized 3-D cell culture using an extracellular matrix gel2005In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 26, no 24, p. 4751-4758Article in journal (Refereed)
    Abstract [en]

    This paper presents a novel method to embed, anchor, and cultivate cells in a controlled 3-D flow-through microenvironment. This is realized using an etched silicon pillar flow chamber filled with extracellular matrix (ECM) gel mixed with cells. At 4 degrees C, while in liquid form, ECM gel is mixed with cells and injected into the chamber. Raising the temperature to 37 degrees C results in a gel, with cells embedded. The silicon pillars both stabilize and increase the surface to volume ratio of the gel. During polymerization the gel shrinks, thus creating channels, which enables perfusion through the chip. The pillars increase the mechanical stability of the gel permitting high surface flow rates without surface modifications. Within the structure cells were still viable and proliferating after 6 days of cultivation. Our method thus makes it possible to perform medium- to long-term cultivation of cells in a controlled 3-D environment. This concept opens possibilities to perform studies of cells in a more physiological environment compared to traditional 2-D cultures on flat substrates.

  • 12.
    Frisk, Thomas
    et al.
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Rydholm, Susanna
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Liebmann, Thomas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    Andersson-Svahn, Helene
    KTH, School of Biotechnology (BIO), Nano Biotechnology.
    Stemme, Göran
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics.
    A microfluidic device for parallel 3-D cell cultures in asymmetric environments2007In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 28, no 24, p. 4705-4712Article in journal (Refereed)
    Abstract [en]

    We demonstrate a concept for how a miniaturized 3-D cell culture in biological extracellular matrix (ECM) or synthetic gels bridges the gap between organ-tissue culture and traditional 2-D cultures. A microfluidic device for 3-D cell culture including microgradient environments has been designed, fabricated, and successfully evaluated. In the presented system stable diffusion gradients can be generated by application of two parallel fluid flows with different composition against opposite sides of a gel plug with embedded cello. Culture for up to two weeks was performed showing cells still viable and proliferating. The cell tracer dye calcein was used to verify gradient formation as the fluorescence intensity in exposed cells was proportional to the position in the chamber. Cellular response to an applied stimulus was demonstrated by use of an adenosine triphosphate gradient where the onset of a stimulated intracellular calcium release also depended on cell position.

  • 13. Gharizadeh, B.
    et al.
    Ghaderi, M.
    Donnelly, D.
    Amini, B.
    Wallin, K. L.
    Nyrén, Pål
    KTH, Superseded Departments, Biochemistry and Biotechnology.
    Multiple-primer DNA sequencing method2003In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 24, no 08-jul, p. 1145-1151Article in journal (Refereed)
    Abstract [en]

    A multiple-primer DNA sequencing approach suitable for genotyping, detection and identification of microorganisms and viruses has been developed. In this new method two or m ore sequencing primers, combined in a pool, are added to a DNA sample of interest. The oligonucleotide that hybridizes to the DNA sample will function as a primer during the subsequent DNA sequencing procedure. This strategy is suited for selective detection and genotyping of relevant microorganisms and samples harboring different DNA targets such as,multiple variant/infected samples as well as unspecific amplification products. This method is used here in a model system for detection and typing of high-risk oncogenic human papilloma viruses (HPVs) in samples containing multiple infections/variants or unspecific amplification products. Type-specific sequencing primers were designed for four of the most oncogenic (high-risk) HPV types (HPV-16, HPV-18, HPV-33, and HPV-45). The primers were combined and added to a sample containing a mixture of one high-risk (16, 18, 33, or 45) and one or two low-risk types. The DNA samples were sequenced by the Pyrosequencing(TM) technology and the Sanger dideoxy sequencing method. Correct genotyping was achieved in all tested combinations. This multiple-sequencing primer approach also improved the sequence data quality for samples containing unspecific amplification products. The new strategy is highly suitable for diagnostic typing of relevant species/genotypes of microorganisms.

  • 14. Hanning, A.
    et al.
    Westberg, J.
    Roeraade, Johan
    KTH, Superseded Departments, Chemistry.
    A liquid core waveguide fluorescence detector for multicapillary electrophoresis applied to DNA sequencing in a 91-capillary array2000In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 21, no 15, p. 3290-3304Article in journal (Refereed)
    Abstract [en]

    A new laser-induced fluorescence (LIF) detector for multicapillary electrophoresis is presented. The detection principle is based on waveguiding of the emitted fluorescence from the point of illumination to the capillary ends by total internal reflection (TIR) and imaging of the capillary ends. The capillaries themselves thus act as liquid core waveguides (LCWs). At the illumination point, the capillaries are arranged in a planar array, which allows clean and efficient illumination with a line-focused laser beam. The capillary ends are rearranged into a small, densely packed two-dimensional array, which is imaged end-on with high light collection efficiency and excellent image quality. Wavelength dispersion is obtained with a single prism. Intercapillary optical crosstalk is less than 0.5%, and rejection of stray light is very efficient. The detector is applied to four-color DNA sequencing by gel electrophoresis in a 91-capillary array, with simple fluorescein and rhodamine dyes as fluorophores. Since the imaged two-dimensional array is so compact, the detector has a high potential for very large-scale multiplexing.

  • 15. Holmberg, A.
    et al.
    Blomstergren, A.
    Nord, O.
    Lukacs, M.
    Lundeberg, Joakim
    KTH, School of Biotechnology (BIO), Gene Technology.
    Uhlén, Mathias
    KTH, School of Biotechnology (BIO), Proteomics.
    The biotin-streptavidin interaction can be reversibly broken using water at elevated temperatures2005In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 26, no 3, p. 501-510Article in journal (Refereed)
    Abstract [en]

    The biotin-streptavidin system is the strongest noncovalent biological interaction known, having a dissociation constant, K-d, in the order of 4 x 10(-14) m. The strength and specificity of the interaction has led it to be one of the most widely used affinity pairs in molecular, immunological, and cellular assays. However, it has previously been impossible to re-use any streptavidin solid support, since the conditions needed to break the interaction with biotin has led to the denaturation of the streptavidin. Here, we show that a short incubation in nonionic aqueous solutions at temperatures above 70degreesC can efficiently break the interaction without denaturing the streptavidin tetramer. Both biotin and the streptavidin remain active after dissociation and both molecules can therefore be re-used. The efficiency of the regeneration allowed solid supports with streptavidin to be used many times, here exemplified with the multiple re-use of streptavidin beads used for sample preparation prior to automated DNA sequencing. The results suggest that streptavidin regeneration can be introduced as an improvement in existing methods and assays based on the streptavidin system as well as emerging solid phase applications in fields, such as microfluiclics and nanotechnology.

  • 16.
    Jacksén, Johan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
    Frisk, Thomas
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Redeby, Theres
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
    Parmar, Varun
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    van der Wijngaart, Wouter
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Stemme, Göran
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Emmer, Åsa
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
    Off-line integration of CE and MALDI-MS using a closed-open-closed microchannel system2007In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 28, no 14, p. 2458-2465Article in journal (Refereed)
    Abstract [en]

    In this work, a new technique for off-line hyphenation between CE and MALDI-MS is presented. Two closed fused-silica capillaries were connected via a silicon chip comprising an open microcanal. The EOF in the system was evaluated using mesityloxide or leucine-enkephalin as a sample and with a running buffer that rendered the analyte neutrally charged. Comparison was made between the EOF in a closed system (first capillary solely included in the electrical circuit) and in a closed-open system (first capillary and microcanal included in the electrical circuit). It was concluded that the experimental values of the EOF agreed with the theory. The influence of the capillary outer diameter on the peak dispersion was investigated using a closed-open-closed system (first capillary, microcanal and second capillary included in the electrical circuit). It was clearly seen that a capillary with 375 mu m od induced considerably higher peak dispersion than a 150 mu m od capillary, due to a larger liquid dead volume in the connection between the first capillary outlet and the microcanal. Mass spectrometric analysis has also been performed following CE separation runs in a closed-open-closed system with cytochrome c and lysozyme as model proteins. It was demonstrated that a signal distribution profile of the separated analytes could be recorded over a 30 mm long microcanal.

  • 17.
    Jönsson, Håkan
    et al.
    KTH, School of Biotechnology (BIO), Nano Biotechnology (closed 20130101).
    Zhang, Chi
    KTH, School of Biotechnology (BIO), Nano Biotechnology (closed 20130101).
    Uhlén, Mathias
    KTH, School of Biotechnology (BIO), Proteomics (closed 20130101).
    Andersson-Svahn, Helene
    KTH, School of Biotechnology (BIO), Nano Biotechnology (closed 20130101).
    A Homogeneous Assay for Protein Analysis in Droplets by Fluorescence Polarization2012In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 33, no 3, p. 436-439Article in journal (Refereed)
    Abstract [en]

    We present a novel homogeneous (mix-incubate-read) droplet microfluidic assay for specific protein detection in picoliter volumes by fluorescence polarization (FP), for the first time demonstrating the use of FP in a droplet microfluidic assay. Using an FP-based assay we detect streptavidin concentrations as low as 500?nM and demonstrate that an FP assay allows us to distinguish droplets containing 5?mu M rabbit IgG from droplets without IgG with an accuracy of 95%, levels relevant for hybridoma screening. This adds to the repertoire of droplet assay techniques a direct protein detection method which can be performed entirely inside droplets without the need for labeling of the analyte molecules.

  • 18.
    Lin, Yuan
    et al.
    Department of Process Technology, SINTEF Materials and Chemistry.
    Shiomi, Junichiro
    Department of Mechanical Engineering, The University of Tokyo.
    Amberg, Gustav
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Numerical calculation of the dielectrophoretic force on a slender body2009In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 30, no 5, p. 831-838Article in journal (Refereed)
    Abstract [en]

    In this paper, a model is proposed to numerically calculate the dielectrophoretic (DEP) force acting on a straight slender body in a non-uniform electric field. The induced charges are assumed to be located along the centerline of the slender body. By enforcing the boundary conditions at the interfaces of the two dielectrics, an integral equations system is obtained with the induced charge densities as unknowns. Based on the calculated induced charge densities, expressions to calculate the DEP force and torque are obtained. The calculated induced charge density of a prolate ellipsoid under a uniform electric field is compared with the analytic solution and an excellent agreement is achieved. The smaller the slenderness (the ratio of maximum radius to length of the slender body), the smaller the error is. The DEP force that a prolate ellipsoid experiences in a general electric field is numerically calculated and compared with the results obtained by the commonly accepted effective dipole moment method. The current model is expected to possess higher accuracy than the effective dipole moment method and to demand less calculation work than the Maxwell stress tensor method.

  • 19.
    Lindström, Sara
    et al.
    KTH, School of Biotechnology (BIO), Nano Biotechnology.
    Andersson-Svahn, Helene
    KTH, School of Biotechnology (BIO), Nano Biotechnology.
    A microwell array device with integrated microfluidic components for enhanced single-cell analysis2009In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 30, no 24, p. 4166-4171Article in journal (Refereed)
    Abstract [en]

    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.

  • 20.
    Lindström, Sara
    et al.
    KTH, School of Biotechnology (BIO), Nano Biotechnology (closed 20130101).
    Larsson, Rolf
    Univ Uppsala Hosp, Dept Med Sci, Uppsala, Sweden.
    Andersson Svahn, Helene
    KTH, School of Biotechnology (BIO), Nano Biotechnology (closed 20130101).
    Towards high-throughput single cell/clone cultivation and analysis2008In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 29, p. 1219-1227Article in journal (Refereed)
    Abstract [en]

    In order to better understand cellular processes and behavior, a controlled way of studying high numbers of single cells and their clone formation is greatly needed. Numerous ways of ordering single cells into arrays have previously been described, but platforms in which each cell/clone can be addressed to an exact position in the microplate, cultivated for weeks and treated separately in a high-throughput manner have until now been missing. Here, a novel microplate developed for high-throughput single cell/clone cultivation and analysis is presented. Rapid single cell seeding into microwells, using conventional flow cytometry, allows several thousands of single cells to be cultivated, short-term (72 h) or long-term (10-14 days), and analyzed individually. By controlled sorting of individual cells to predefined locations in the microplate, analysis of single cell heterogeneity and clonogenic properties related to drug sensitivity can be accomplished. Additionally, the platform requires remarkably low number of cells, a major advantage when screening limited amounts of patient cell samples. By seeding single cells into the microplate it is possible to analyze the cells for over 14 generations, ending up with more than 10 000 cells in each well. Described here is a proof-of-concept on compartmentalization and cultivation of thousands of individual cells enabling heterogeneity analysis of various cells/clones and their response to different drugs.

  • 21. Litborn, E.
    et al.
    Emmer, Åsa
    KTH, Superseded Departments, Chemistry.
    Roeraade, Johan
    KTH, Superseded Departments, Chemistry.
    Parallel reactions in open chip-based nanovials with continuous compensation for solvent evaporation2000In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 21, no 1, p. 91-99Article in journal (Refereed)
    Abstract [en]

    In an earlier report (Litborn, E., Emmer,,Angstrom., Roeraade, J., Anal. Chim. Acta 1999, 401, 11-19, we described a technique for performing chemistry in chip-based vials. A major problem, solvent evaporation, was partially remedied by using a closed humidity chamber. in this paper we report an improved technique for performing parallel reactions in open, 15 nL volume, chip-based vials. The evaporation of solvent from the reaction fluid was continuously compensated by addition of solvent via an array of microcapillaries. The suitability of the method was demonstrated by performing eight separate peptide maps of myoglobin in parallel, using the three enzymes trypsin, alpha-chymotrypsin and endoproteinase Glu-C. The total amount of myoglobin utilized to perform the eight digests was less than 100 pmol. The corresponding amount of enzymes was ca. 0.1 pmol per reaction. In order to evaluate the operating limits of the technique, a study of the evaporation of solvents from a series of vials with proportionally smaller volumes operated at different temperatures was performed. The results showed that the concept for continuous compensation of solvent evaporation should be applicable to reaction volumes down to 30 pL.

  • 22.
    Mikkonen, Saara
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. Univ Bern, Inst Infect Dis, Clin Pharmacol Lab, Bern, Switzerland..
    Caslayskal, Jitka
    Univ Bern, Inst Infect Dis, Clin Pharmacol Lab, Bern, Switzerland..
    Gebauer, Petr
    Czech Acad Sci, Inst Analyt Chem, Brno, Czech Republic..
    Thormanni, Wolfgang
    Univ Bern, Inst Infect Dis, Clin Pharmacol Lab, Bern, Switzerland..
    Inverse cationic ITP for separation of methadone enantiomers with sulfated beta-cyclodextrin as chiral selector2019In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 40, no 5, p. 659-667Article in journal (Refereed)
    Abstract [en]

    Chiral ITP of the weak base methadone using inverse cationic configurations with H+ as leading component and multiple isomer sulfated beta-CD (S-beta-CD) as leading electrolyte (LE) additive, has been studied utilizing dynamic computer simulation, a calculation model based on steady-state values of the ITP zones, and capillary ITP. By varying the amount of acidic S-beta-CD in the LE composed of 3-morpholino-2-hydroxypropanesulfonic acid and the chiral selector, and employing glycylglycine as terminating electrolyte (TE), inverse cationic ITP provides systems in which either both enantiomers, only the enantiomer with weaker complexation, or none of the two enantiomers form cationic ITP zones. For the configuration studied, the data reveal that only S-methadone migrates isotachophoretically when the S-beta-CD concentration in the LE is between about 0.484 and 1.113 mM. Under these conditions, R-methadone migrates zone electrophoretically in the TE. An S-beta-CD concentration between about 0.070 and 0.484 mM results in both S- and R-methadone forming ITP zones. With >1.113 mM and < about 0.050 mM of S-beta-CD in the LE both enantiomers are migrating within the TE and LE, respectively. Chiral inverse cationic ITP with acidic S-beta-CD in the LE is demonstrated to permit selective ITP trapping and concentration of the less interacting enantiomer of a weak base.

  • 23.
    Mikkonen, Saara
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Rokhas, Maria Khihon
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Jacksén, Johan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Emmer, Åsa
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Sample preconcentration in open microchannels combined with MALDI-MS2012In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 33, no 22, p. 3343-3350Article in journal (Refereed)
    Abstract [en]

    In this work, a method for preconcentrating samples in 1 cm long, 50-150 μm wide open microchannels is presented. Platinum electrodes were positioned at the channel ends, voltage was applied, and charged analyte was preconcentrated at the oppositely charged side during continuous supply of sample. The preconcentration was initially studied in a closed system, where an influence on the analyte position from a pH gradient, generated by water electrolysis, was observed. In the open channel, the analyte distribution after preconcentration was evaluated using MALDI-MS with the channel as MALDI target. MALDI matrix was applied with an airbrush or by electrospray matrix deposition and by using the latter technique higher degrees of crystallization in the channels were obtained. After preconcentrating a 1 nM cytochrome c solution for 5 min, corresponding to a supplied amount of 1.25 fmol, a signal on the cathodic channel end could be detected. When a solution of cytochrome c trypsin digest was supplied, the peptides were preconcentrated at different positions along the channel depending on their charge.

  • 24.
    Mikkonen, Saara
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Thormann, Wolfgang
    Emmer, Åsa
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Computer simulations of sample preconcentration in carrier-free systems and isoelectric focusing in microchannels using simple ampholytes2015In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 36, no 19, p. 2386-2395Article in journal (Refereed)
    Abstract [en]

    In this work, electrophoretic preconcentration of protein and peptide samples in microchannels was studied theoretically using the 1D dynamic simulator GENTRANS, and experimentally combined with MS. In all configurations studied, the sample was uniformly distributed throughout the channel before power application, and driving electrodes were used as microchannel ends. In the first part, previously obtained experimental results from carrier-free systems are compared to simulation results, and the effects of atmospheric carbon dioxide and impurities in the sample solution are examined. Simulation provided insight into the dynamics of the transport of all components under the applied electric field and revealed the formation of a pure water zone in the channel center. In the second part, the use of an IEF procedure with simple well defined amphoteric carrier components, i.e. amino acids, for concentration and fractionation of peptides was investigated. By performing simulations a qualitative description of the analyte behavior in this system was obtained. Neurotensin and [Glu1]-Fibrinopeptide B were separated by IEF in microchannels featuring a liquid lid for simple sample handling and placement of the driving electrodes. Component distributions in the channel were detected using MALDI- and nano-ESI-MS and data were in agreement with those obtained by simulation. Dynamic simulations are demonstrated to represent an effective tool to investigate the electrophoretic behavior of all components in the microchannel.

  • 25. Nilsson, H.
    et al.
    Wiklund, Martin
    KTH, Superseded Departments, Physics.
    Johansson, T.
    Hertz, Hans M.
    KTH, Superseded Departments, Physics.
    Nilsson, S.
    Microparticles for selective protein determination in capillary electrophoresis2001In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 22, no 12, p. 2384-2390Article in journal (Refereed)
    Abstract [en]

    A system for detection of trace amounts of protein was developed. Two different monoclonal antibodies against human chorionic gonadotropin (hCG) were covalently bound to latex particles. When the latex particles were mixed with a sample containing hCG, a latex-protein-latex complex (immunocomplex) was formed. The complex was separated from the single latex particles using capillary electrophoresis and detected using UV-Vis detection. Limit of detection was 8 amol hCG. The separation was also monitored in real time using laser induced fluorescence - charge coupled device (LIF-CCD) imaging detection. However, a limitation of the method is the restriction to detection of proteins for which monoclonal antibodies are available.

  • 26. Nourizad, N.
    et al.
    Gharizadeh, B.
    Nyrén, Pål
    KTH, Superseded Departments, Biochemistry and Biotechnology.
    Method for clone checking2003In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 24, no 11, p. 1712-1715Article in journal (Refereed)
    Abstract [en]

    A new method for simple and fast clone checking is described. We combined the Pyrosequencing(TM) technology with a preprogrammed nucleoticle dispensation strategy for fast analysis of DNA constructs. To test this method, the N-terminus region of plasmids constructed for the production of recombinant apyrase was analyzed. Of the ten plasmids tested, seven constructs were correct, two constructs showed one base deletion, and one construct showed deletion of a 195 bp fragment. The preprogrammed nucleoticle dispensation strategy allowed the identification of the sequence downstream of the deletions. Thus, this method determines both the location and nature of possible artifacts.

  • 27.
    Periyannan Rajeswari, Prem Kumar
    et al.
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology.
    Jönsson, Håkan N
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology.
    Andersson Svahn, Helene
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology.
    Droplet size influences division of mammalian cell factories in droplet microfluidic cultivation2016In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683Article in journal (Refereed)
    Abstract [en]

    The potential of using droplet microfluidics for screening mammalian cell factories has been limited by the difficulty in achieving continuous cell division during cultivation in droplets. Here, we report the influence of droplet size on mammalian cell division and viability during cultivation in droplets. Chinese Hamster Ovary (CHO) cells, the most widely used mammalian host cells for biopharmaceuticals production were encapsulated and cultivated in 33, 180 and 320 pL droplets for 3 days. Periodic monitoring of the droplets during incubation showed that the cell divisions in 33 pL droplets stopped after 24 h, whereas continuous cell division was observed in 180 and 320 pL droplets for 72 h. The viability of the cells cultivated in the 33 pL droplets also dropped to about 50% in 72 h. In contrast, the viability of the cells in the larger droplets was above 90% even after 72 h of cultivation, making them a more suitable droplet size for 72-h cultivation. This study shows a direct correlation of microfluidic droplet size to the division and viability of mammalian cells. This highlights the importance of selecting suitable droplet size for mammalian cell factory screening assays.

  • 28.
    Pettersson, Erik
    et al.
    KTH, School of Biotechnology (BIO), Gene Technology.
    Ståhl, Patrik L.
    KTH, School of Biotechnology (BIO), Gene Technology.
    Mahdessian, Hovsep
    KTH, School of Biotechnology (BIO), Gene Technology.
    Käller, Max
    KTH, School of Biotechnology (BIO), Gene Technology.
    Lundeberg, Joakim
    KTH, School of Biotechnology (BIO), Gene Technology.
    Ahmadian, Afshin
    KTH, School of Biotechnology (BIO), Gene Technology.
    Visual DNA as a diagnostic tool2009In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 30, no 21, p. 3691-3695Article in journal (Refereed)
    Abstract [en]

    We report on the incorporation of the Visual DNA concept in a genotyping assay as a simple and straightforward detection tool. The principle of trapping streptavidin-coated superparamagnetic beads of micrometer size for visualization of genetic variances is used for PrASE-based detection of a panel of mutations in the severe and common genetic disorder of cystic fibrosis. The method allows a final investigation of genotypes by the naked eye and the output is easily documented using a regular hand-held device with an integrated digital camera. A number of samples were run through the assay, showing rapid and accurate detection using superparamagnetic beads and an off-the-shelf neodymium magnet. The assay emphasizes the power of Visual DNA and demonstrates the potential value of the method in future point-of-care tests.

  • 29.
    Rokhas, Maria Khihon
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Mikkonen, Saara
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Beyer, J.
    Jacksén, Johan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Emmer, Åsa
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    CE analysis of single wood cells performing hydrolysis and preconcentration in open microchannels2014In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 35, no 2-3, p. 450-457Article in journal (Refereed)
    Abstract [en]

    In the present work, monosaccharides from pulp samples and single wood fibers were analyzed with CE, using indirect detection due to the lack of chromophores on the monosaccharides. The hydrolysis degradation of cellulose and hemicellulose into monosaccharides was performed using TFA, either in bulk scale or in microscale. In the microscale, one single wood fiber was hydrolyzed in an open microchannel manufactured on a silicon microchip with the dimensions 50 μm × 50 μm (length 1 or 3 cm). The low monosaccharide amounts derived from a single fiber implied that a preconcentration step was necessary to increase the detectability. Thus, an electromigration preconcentration of the hydrolyzed samples was performed within the microchannel, which resulted in a significantly enhanced signal intensity of the monosaccharides. In addition to the experimental study, computer simulations were performed regarding the preconcentration step of monosaccharides. The results from these simulations correlated well with the experimental results.

  • 30.
    Russom, Aman
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Ahmadian, Afshin
    KTH, Superseded Departments, Biotechnology.
    Andersson, Helene
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Nilsson, Peter
    KTH, Superseded Departments, Biotechnology.
    Stemme, Göran
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Single-nucleotide polymorphism analysis by allele-specific extension of fluorescently labeled nucleotides in a microfluidic flow-through device2003In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 24, no 1-2, p. 158-161Article in journal (Refereed)
    Abstract [en]

    We describe a microfluidic approach for allele-specific extension of fluorescently labeled nucleotides for scoring of single-nucleotide polymorphism (SNP). The method takes advantage of the fact that the reaction kinetics differs between matched and mismatched configurations of allele-specific primers hybridized to DNA template. A microfluidic flow-through device for biochemical reactions on beads was used to take advantage of the reaction kinetics to increase the sequence specificity of the DNA polymerase, discriminating mismatched configurations from matched. The volume of the reaction chamber was 12.5 nL. All three possible variants of an SNP site at codon 72 of the p53 gene were scored using our approach. This work demonstrates the possibility of scoring SNP by allele-specific extension of fluorescently labeled nucleotides in a microfluidic flow-through device, The sensitive detection system and easy microfabrication of the microfluidic device enable further miniaturization and production of an array format of microfluidic devices for high-throughput SNP analysis.

  • 31.
    Russom, Aman
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Haasl, Sjoerd
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Ohlander, Anna
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Andersson, Helene
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Stemme, Göran
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Genotyping by dynamic heating of monolayered beads on a microheated surface2004In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 25, no 21-22, p. 3712-3719Article in journal (Refereed)
    Abstract [en]

     A miniaturized bead-based dynamic allele-specific hybridization (DASH) approach for sing le-nucleotide polymorphism analysis is presented. Chips with integrated heater and temperature sensors for open-surface DNA analysis were microfabricated. Microcontact printing using a poly(dimethylsiloxane) (PDMS) stamp was employed to create monolayers of immobilized beads on the surface of the chip. This chip allows fast, well-controllable temperature ramping. The temperature distribution was homogeneous over the entire heater area. All three possible variants of an SNP site of a synthesized oligonucleotide were accurately scored using the bead-based DASH approach. Our assay has a nonoptimized temperature ramping rate of 4degreesC-6degreesC/min compared to earlier reported values of 2degreesC-3degreesC/min, thereby reducing the total analysis time by a factor of 2. Reliable DASH measurement data from areas as small as 12 x 13 mum was achieved. Our bead-based DASH approach has enabled a dramatic volume reduction and is a step towards developing a cost-effective high-throughput DASH method on arrays of single beads.

  • 32.
    Russom, Aman
    et al.
    Center for Engineering in Medicine, Massachusetts General Hospital, Harvard Medical School, Boston.
    Irimia, Daniel
    Toner, Mehmet
    Chemical gradient-mediated melting curve analysis for genotyping of SNPs2009In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 30, no 14, p. 2536-2543Article in journal (Refereed)
    Abstract [en]

    This report describes a microfluidic solid-phase chemical gradient-mediated melting curve analysis method for SNP analysis. The method is based on allele-specific denaturation to discriminate mismatched (MM) from perfectly matched (PM) DNA duplexes upon exposure to linear chemical gradient. PM and MM DNA duplexes conjugated on beads are captured in a microfluidic gradient generator device designed with dams, keeping the beads trapped perpendicular to a gradient generating channel. Two denaturants, formamide and urea, were tested for their ability to destabilize the DNA duplex by competing with Watson-Crick pairing. Upon exposure to the chemical gradient, rapid denaturing profile was monitored in real time using fluorescence microscopy. The results show that the two duplexes exhibit different kinetics of denaturation profiles, enabling discrimination of MM from PM DNA duplexes to score SNP.

  • 33. Shirai, Kentaro
    et al.
    Renberg, Björn
    KTH, School of Biotechnology (BIO), Nano Biotechnology.
    Sato, Kae
    Mawatari, Kazuma
    Konno, Tomohiro
    Ishihara, Kazuhiko
    Kitamori, Takehiko
    Graft linker immobilization for spatial control of protein immobilization inside fused microchips2009In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 30, no 24, p. 4251-4255Article in journal (Refereed)
    Abstract [en]

    Fused silica glass microchips have several attractive features for lab-on-a-chip applications; they can be machined with excellent precision down to nanospace; are stable; transparent and can be modified with a range of silanization agents to change channel surface properties. For immobilization, however, ligands must be added after bonding, since the harsh bonding conditions using heat or hydrofluoric acid would remove all prior immobilized ligands. For spatial control over immobilization, UV-mediated immobilization offers several advantages; spots can be created in parallel, the feature size can be made small, and spatial control over patterns and positions is excellent. However, UV sensitive groups are often based on hydrophobic chemical moieties, which unfortunately result in greater non-specific binding of biomolecules, especially proteins. Here, we present techniques in which any -CHx (x = 1,2,3) containing surface coating can be used as foundation for grafting a hydrophilic linker with a chemical anchor, a carboxyl group, to which proteins and amine containing molecules can be covalently coupled. Hence, the attractive features of many well-known protein and biomolecule repelling polymer coatings can be utilized while achieving site-specific immobilization only to pre-determined areas within the bonded microchips.

  • 34. Viefhues, Martina
    et al.
    Eichhorn, Ralf
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, Sweden.
    DNA dielectrophoresis: Theory and applications a review2017In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 38, no 11, p. 1483-1506Article, review/survey (Refereed)
    Abstract [en]

    Dielectrophoresis is the migration of an electrically polarizable particle in an inhomogeneous electric field. This migration can be exploited for several applications with (bio)molecules or cells. Dielectrophoresis is a noninvasive technique; therefore, it is very convenient for (selective) manipulation of (bio)molecules or cells. In this review, we will focus on DNA dielectrophoresis as this technique offers several advantages in trapping and immobilization, separation and purification, and analysis of DNA molecules. We present and discuss the underlying theory of the most important forces that have to be considered for applications with dielectrophoresis. Moreover, a review of DNA dielectrophoresis applications is provided to present the state-of-the-art and to offer the reader a perspective of the advances and current limitations of DNA dielectrophoresis.

  • 35.
    Woldegiorgis, Andreas
    et al.
    KTH, Superseded Departments, Chemistry.
    Jansson, K.
    Curcio, Mario
    KTH, Superseded Departments, Chemistry.
    Roeraade, Johan
    KTH, Superseded Departments, Chemistry.
    Nanowires for surface enlargement of narrow-bore fused-silica tubing2004In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 25, no 21-22, p. 3660-3668Article in journal (Refereed)
    Abstract [en]

    A method for preparation of silica nanowires with dimensions of d = 10-100 nm, 5-500 nm, is described. The nanostructured material is an integral part of the inner surface of narrow bore fused-silica capillary tubing. The wire preparation method is based on a decomposition of 2-chloro-1,1,2-trifluoroethyl methyl ether at elevated temperature and pressure. The silica bulk material is rearranged via a sustained silica-hydrogen fluoride chemistry, and reaction mechanisms for this process are proposed. The method is suitable for preparing long lengths of tubing with the modified surface. It is our belief that the texture of the capillary wall with its increased surface area is useful for applications such as microreactions, catalysis, and high-resolution pressure and/or electrodriven open-tubular liquid chromatography.

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