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Sökning: WFRF:(Fritzsche Joachim)

  • Resultat 1-10 av 46
  • [1]2345Nästa
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1.
  • Fritzsche, Michael, et al. (författare)
  • A Highly UV-transparent Fused Silica Biochip for Sensitive Hepatotoxicity Testing by Autofluorescence
  • 2014
  • Ingår i: Biochip Journal. - : Korean BioChip Society (KBCS). - 2092-7843 .- 1976-0280. ; 8:2, s. 115-121
  • Tidskriftsartikel (refereegranskat)abstract
    • Fabrication and application of a non-fluorescent and UV-transparent microfluidic biochip in fused silica that allows sensitive autofluorescence detection are described. The biochip is particularly useful in cell-based assays where the most informative autofluorescence signals from the cells reside in the ultraviolet spectral range and where plastic labware materials commonly used in cell culture work severely disturb such measurements. In this study the fused silica biochip was used for measuring intrinsic autofluorescence from liver cells in order to assess hepatotoxic effects of drugs. The assessment assay was carried out with the human liver cell line HepG2 under perfusion conditions in the microfluidics of the biochip. The autofluorescence from the.liver cells exposed to quinidine was readily recorded without background disturbance and correlated well with reference toxicity data.
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2.
  • Alizadehheidari, Mohammadreza, 1987, et al. (författare)
  • Nanoconfined circular DNA
  • 2014
  • Ingår i: 18th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2014. - : Chemical and Biological Microsystems Society. - 9780979806476 ; , s. 1353-1355
  • Konferensbidrag (refereegranskat)abstract
    • Studies of nanoconfined circular DNA are of interest both from a biological as well as a fundamental polymer physics perspective. We here present the use of nanofluidic channels as a tool for comparing statics and dynamics of the linear and circular configuration of the same DNA molecule.
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3.
  • Freitag, Camilla, et al. (författare)
  • Visualizing the entire DNA from a chromosome in a single frame
  • 2015
  • Ingår i: Biomicrofluidics. - : American Institute of Physics (AIP). - 1932-1058. ; 9:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The contiguity and phase of sequence information are intrinsic to obtain complete understanding of the genome and its relationship to phenotype. We report the fabrication and application of a novel nanochannel design that folds megabase lengths of genomic DNA into a systematic back-and-forth meandering path. Such meandering nanochannels enabled us to visualize the complete 5.7 Mbp (1mm) stained DNA length of a Schizosaccharomyces pombe chromosome in a single frame of a CCD. We were able to hold the DNA in situ while implementing partial denaturation to obtain a barcode pattern that we could match to a reference map using the Poland-Scheraga model for DNA melting. The facility to compose such long linear lengths of genomic DNA in one field of view enabled us to directly visualize a repeat motif, count the repeat unit number, and chart its location in the genome by reference to unique barcode motifs found at measurable distances from the repeat. Meandering nanochannel dimensions can easily be tailored to human chromosome scales, which would enable the whole genome to be visualized in seconds.
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4.
  • Fritzsche, Joachim, 1977, et al. (författare)
  • Single Particle Nanoplasmonic Sensing in Individual Nanofluidic Channels
  • 2016
  • Ingår i: Nano Letters. - 1530-6992 .- 1530-6984. ; 16:12, s. 7857-7864
  • Tidskriftsartikel (refereegranskat)abstract
    • Nanoplasmonics allows label-free optical sensing and spectroscopy at the single nanoparticle level by exploiting plasmonic excitations in metal nanoparticles. Nanofluidics offers exclusive possibilities for applying and controlling fluid flow and mass transport at the nanoscale and toward nanosized objects. Here, we combine these two concepts in a single device, by integrating single particle nanoplasmonic sensing with nanofluidics using advanced nanofabrication. The developed devices enable on-chip referenced parallel single particle nanoplasmonic sensing inside multiple individual nanofluidic channels with dimensions down to the 100 nm range. Beyond detailed discussion of the nanofabrication, general device characterization, and parallelized single particle plasmonic readout concepts, we demonstrate device function on two examples: (i) in situ measurements of local buffer concentrations inside a nanofluidic channel; (ii) real time binding kinetics of alkanethiol molecules to a single plasmonic nanonatenna sensor in a single nanochannel. Our concept thus provides a powerful solution for controlling mass transport to and from individual (plasmonic) nanoparticles, which in a long-term perspective offers unique opportunities for label-free detection of analyte molecules at low concentrations and for fundamental studies of fluids in extreme confinement.
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5.
  • Frykholm, K., et al. (författare)
  • Fast size-determination of intact bacterial plasmids using nanofluidic channels
  • 2015
  • Ingår i: Lab on a Chip. - : Royal Society of Chemistry. - 1473-0197 .- 1473-0189. ; 15:13, s. 2739-2743
  • Tidskriftsartikel (refereegranskat)abstract
    • We demonstrate how nanofluidic channels can be used as a tool to rapidly determine the number and sizes of plasmids in bacterial isolates. Each step can be automated at low cost, opening up opportunities for general use in microbiology labs.
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6.
  • Iarko, Vitalii, 1993, et al. (författare)
  • Extension of nanoconfined DNA: quantitative comparison between experiment and theory
  • 2015
  • Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - : American Physical Society. - 1539-3755 .- 1550-2376. ; 92:6, s. Art. Nr. 062701-
  • Tidskriftsartikel (refereegranskat)abstract
    • The extension of DNA confined to nanochannels has been studied intensively and in detail. Yet quantitative comparisons between experiments and model calculations are difficult because most theoretical predictions involve undetermined prefactors, and because the model parameters (contour length, Kuhn length, effective width) are difficult to compute reliably, leading to substantial uncertainties. Here we use a recent asymptotically exact theory for the DNA extension in the "extended de Gennes regime" that allows us to compare experimental results with theory. For this purpose we performed new experiments, measuring the mean DNA extension and its standard deviation while varying the channel geometry, dye intercalation ratio, and ionic buffer strength. The experimental results agree very well with theory at high ionic strengths, indicating that the model parameters are reliable. At low ionic strengths the agreement is less good. We discuss possible reasons. Our approach allows, in principle, to measure the Kuhn length and effective width of a single DNA molecule and more generally of semiflexible polymers in solution.
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7.
  • Werner, Erik, et al. (författare)
  • Hairpins in the conformations of a confined polymer
  • 2018
  • Ingår i: Biomicrofluidics. - 1932-1058. ; 12:2
  • Tidskriftsartikel (refereegranskat)abstract
    • If a semiflexible polymer confined to a narrow channel bends around by 180°, the polymer is said to exhibit a hairpin. The equilibrium extension statistics of the confined polymer are well understood when hairpins are vanishingly rare or when they are plentiful. Here, we analyze the extension statistics in the intermediate situation via experiments with DNA coated by the protein RecA, which enhances the stiffness of the DNA molecule by approximately one order of magnitude. We find that the extension distribution is highly non-Gaussian, in good agreement with Monte-Carlo simulations of confined discrete wormlike chains. We develop a simple model that qualitatively explains the form of the extension distribution. The model shows that the tail of the distribution at short extensions is determined by conformations with one hairpin. © 2018 Author(s).
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8.
  • Albinsson, David, 1990, et al. (författare)
  • Operando detection of single nanoparticle activity dynamics inside a model pore catalyst material
  • 2020
  • Ingår i: Science advances. - 2375-2548. ; 6:25
  • Tidskriftsartikel (refereegranskat)abstract
    • Nanoconfinement in porous catalysts may induce reactant concentration gradients inside the pores due to local conversion. This leads to inefficient active material use since parts of the catalyst may be trapped in an inactive state. Experimentally, these effects remain unstudied due to material complexity and required high spatial resolution. Here, we have nanofabricated quasi-two-dimensional mimics of porous catalysts, which combine the traits of nanofluidics with single particle plasmonics and online mass spectrometry readout. Enabled by single particle resolution at operando conditions during CO oxidation over a Cu model catalyst, we directly visualize reactant concentration gradient formation due to conversion on single Cu nanoparticles inside the “model pore” and how it dynamically controls oxidation state-and, thus, activity-of particles downstream. Our results provide a general framework for single particle catalysis in the gas phase and highlight the importance of single particle approaches for the understanding of complex catalyst materials.
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9.
  • Albinsson, David, 1990, et al. (författare)
  • Shedding light on CO oxidation surface chemistry on single Pt catalyst nanoparticles inside a nanofluidic model pore
  • 2021
  • Ingår i: ACS Catalysis. - 2155-5435. ; 11:4, s. 2021-2033
  • Tidskriftsartikel (refereegranskat)abstract
    • Investigating a catalyst under relevant application conditions is experimentally challenging and parameters like reaction conditions in terms of temperature, pressure, and reactant mixing ratios, as well as catalyst design, may significantly impact the obtained experimental results. For Pt catalysts widely used for the oxidation of carbon monoxide, there is keen debate on the oxidation state of the surface at high temperatures and at/above atmospheric pressure, as well as on the most active surface state under these conditions. Here, we employ a nanoreactor in combination with single-particle plasmonic nanospectroscopy to investigate individual Pt catalyst nanoparticles localized inside a nanofluidic model pore during carbon monoxide oxidation at 2 bar in the 450-550 K temperature range. As a main finding, we demonstrate that our single-particle measurements effectively resolve a kinetic phase transition during the reaction and that each individual particle has a unique response. Based on spatially resolved measurements, we furthermore observe how reactant concentration gradients formed due to conversion inside the model pore give rise to position-dependent kinetic phase transitions of the individual particles. Finally, employing extensive electrodynamics simulations, we unravel the surface chemistry of the individual Pt nanoparticles as a function of reactant composition and find strongly temperature-dependent Pt-oxide formation and oxygen spillover to the SiO2 support as the main processes. These results therefore support the existence of a Pt surface oxide in the regime of high catalyst activity and demonstrate the possibility to use plasmonic nanospectroscopy in combination with nanofluidics as a tool for in situ studies of individual catalyst particles.
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10.
  • Albinsson, David, 1990, et al. (författare)
  • Single Particle Nanoplasmonic Sensing in Individual Nanofluidic Channels
  • 2017
  • Ingår i: The 8th International Conference on Surface Plasmon Photonics (SPP8).
  • Konferensbidrag (refereegranskat)abstract
    • By combining the precise mass transport control of nanofluidics with the single particle sensing abilities of nanoplasmonics we demonstrate real time single particle parallel readout of multiple nanofluidic channels from the same chip using plasmonic nanospectroscopy.The exceptional label-free sensitivity of individual plasmonic nanoparticles combined with dark-field scattering spectroscopy has proven to be a powerful tool in catalysis[1], materials science[2], and gas sensing[3], as well as to detect single molecular binding events[4]. However, despite the proven sensitivity of single particle plasmonic nanosensors, the detection of ultralow concentrations of specific analyte molecules is limited by the fact that they usually are free to diffuse away from the sensing surface, which gives rise to unpractical detection times on the order of days.As a first step to alleviate this limitation, we present an integrated nanoplasmonic-nanofluidic platform comprised of nanochannels integrated with a single plasmonic nanoantenna sensor, schematically presented in Fig 1. The dimensions of the nanofluidic system are chosen such that the entire volume of analyte solution is forced to pass the plasmonic sensor within the decay length of the near field, in order to significantly enhance the probability of direct interaction of the sensor surface with analyte in the channel. The developed devices enable on-chip referenced parallel single particle nanoplasmonic sensing inside multiple individual nanofluidic channels with dimensions down to the 100 nm range. Beyond detailed discussion of the nanofabrication, general device characterization, and parallelized single particle plasmonic readout concepts, we present the device function on two examples: (i) in situ measurements of local buffer concentrations inside a nanofluidic channel; (ii) real time binding kinetics of alkanethiol molecules to a single plasmonic nanoantenna sensor in a single nanochannel.
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