| 1. |
- Agnarsson, Björn, 1977, et al.
(author)
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Evanescent Light-Scattering Microscopy for Label-Free Interfacial Imaging: From Single Sub-100 nm Vesicles to Live Cells
- 2015
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In: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 9:12, s. 11849-11862
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Journal article (peer-reviewed)abstract
- Advancement in the understanding of biomolecular interactions has benefited greatly from the development of surface-sensitive bioanalytical sensors. To further increase their broad impact, significant efforts are presently being made to enable label-free and specific biomolecule detection with high sensitivity, allowing for quantitative interpretation and general applicability at low cost. In this work, we have addressed this challenge by developing a waveguide chip consisting of a flat silica core embedded in a symmetric organic cladding with a refractive index matching that of water. This is shown to reduce stray light (background) scattering and thereby allow for label-free detection of faint objects, such as individual sub-20 rim gold nanoparticles as well as sub-100 nm lipid vesicles. Measurements and theoretical analysis revealed that light-scattering signals originating from single surface-bound lipid vesicles enable characterization of their sizes without employing fluorescent lipids as labels. The concept is also demonstrated for label-free measurements of protein binding to and enzymatic (phospholipase A2) digestion of individual lipid vesicles, enabling an analysis of the influence on the measured kinetics of the dye-labeling of lipids required in previous assays. Further, diffraction-limited imaging of cells (platelets) binding to a silica surface showed that distinct subcellular features could be visualized and temporally resolved during attachment, activation, and spreading. Taken together, these results underscore the versatility and general applicability of the method, which due to its simplicity and compatibility with conventional microscopy setups may reach a widespread in life science and beyond.
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| 2. |
- Lundgren, Anders, 1978, et al.
(author)
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Affinity Purification and Single-Molecule Analysis of Integral Membrane Proteins from Crude Cell-Membrane Preparations
- 2018
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In: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 18:1, s. 381-385
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Journal article (peer-reviewed)abstract
- The function of integral membrane proteins is critically dependent on their naturally surrounding lipid membrane. Detergent-solubilized and purified membrane proteins are therefore often reconstituted into cell-membrane mimics and analyzed for their function with single-molecule microscopy. Expansion of this approach toward a broad range of pharmaceutically interesting drug targets and biomarkers however remains hampered by the fact that these proteins have low expression levels, and that detergent solubilization and reconstitution often cause protein conformational changes and loss of membrane-specific cofactors, which may impair protein function. To overcome this limitation, we here demonstrate how antibody-modified nanoparticles can be used to achieve affinity purification and enrichment of selected integral membrane proteins directly from cell membrane preparations. Nanoparticles were first bound to the ectodomain of β-secretase 1 (BACE1) contained in cell-derived membrane vesicles. In a subsequent step, these were merged into a continuous supported membrane in a microfluidic channel. Through the extended nanoparticle tag, a weak (∼fN) hydrodynamic force could be applied, inducing directed in-membrane movement of targeted BACE1 exclusively. This enabled selective thousand-fold enrichment of the targeted membrane protein while preserving a natural lipid environment. In addition, nanoparticle-targeting also enabled simultaneous tracking analysis of each individual manipulated protein, revealing how their mobility changed when moved from one lipid environment to another. We therefore believe this approach will be particularly useful for separation in-line with single-molecule analysis, eventually opening up for membrane-protein sorting devices analogous to fluorescence-activated cell sorting.
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| 3. |
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| 4. |
- Agnarsson, Björn, 1977, et al.
(author)
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Waveguide structure
- 2018
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Patent (other academic/artistic)abstract
- A waveguide structure for evanescent wave microscopy and/or spectroscopy, comprising an optically transparent core layer, a lower dielectric cladding layer and an upper dielectric cladding layer arranged on opposite sides of the core layer. The core layer has a refractive index higher than the refractive indices of the cladding layers. The upper cladding layer is made of an organic material. A sample well is arranged on an upper surface of the core layer formed by a cavity in the upper cladding layer, the sample well being adapted to contain a sample medium with one or more sample objects. The core layer is made of a first dielectric inorganic material, and the upper cladding layer has a refractive index which closely matches the refractive index of the sample medium. A method for manufacturing such waveguide structure, and a measurement system comprising the waveguide structure are also disclosed.
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| 5. |
- Block, Stephan, 1978, et al.
(author)
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Two-dimensional flow nanometry of biological nanoparticles for accurate determination of their size and emission intensity
- 2016
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 7, s. art no 12956 -
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Journal article (peer-reviewed)abstract
- Biological nanoparticles (BNPs) are of high interest due to their key role in various biological processes and use as biomarkers. BNP size and composition are decisive for their functions, but simultaneous determination of both properties with high accuracy remains challenging. Optical microscopy allows precise determination of fluorescence/scattering intensity, but not the size of individual BNPs. The latter is better determined by tracking their random motion in bulk, but the limited illumination volume for tracking this motion impedes reliable intensity determination. Here, we show that by attaching BNPs to a supported lipid bilayer, subjecting them to hydrodynamic flows and tracking their motion via surface-sensitive optical imaging enable determination of their diffusion coefficients and flow-induced drifts, from which accurate quantification of both BNP size and emission intensity can be made. For vesicles, the accuracy of this approach is demonstrated by resolving the expected radius-squared dependence of their fluorescence intensity for radii down to 15 nm.
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| 6. |
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| 7. |
- Hulander, Mats, et al.
(author)
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Gradients in surface nanotopography used to study platelet adhesion and activation
- 2013
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In: Colloids and Surfaces B-Biointerfaces. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 110, s. 261-269
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Journal article (peer-reviewed)abstract
- Gradients in surface nanotopography were prepared by adsorbing gold nanoparticles on smooth gold substrates using diffusion technique. Following a sintering procedure the particle binding chemistry was removed, and integration of the particles into the underlying gold substrate was achieved, leaving a nanostructured surface with uniform surface chemistry. After pre-adsorption of human fibrinogen, the effect of surface nanotopography on platelets was studied. The use of a gradient in nanotopography allowed for platelet adhesion and activation to be studied as a function of nanoparticle coverage on one single substrate. A peak in platelet adhesion was found at 23% nanoparticle surface coverage. The highest number of activated platelets was found on the smooth control part of the surface, and did not coincide with the number of adhered platelets. Activation correlated inversely with particle coverage, hence the lowest fraction of activated platelets was found at high particle coverage. Hydrophobization of the gradient surface lowered the total number of adhering cells, but not the ratio of activated cells. Little or no effect was seen on gradients with 36 nm particles, suggesting the existence of a lower limit for sensing of surface nano-roughness in platelets. These results demonstrate that parameters such as ratio between size and inter-particle distance can be more relevant for cell response than wettability on nanostructured surfaces. The minor effect of hydrophobicity, the generally reduced activation on nanostructured surfaces and the presence of a cut-off in activation of human platelets as a function of nanoparticle size could have implications for the design of future blood-contacting biomaterials.
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| 8. |
- Parveen, Nagma, 1988, et al.
(author)
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Membrane Deformation Induces Clustering of Norovirus Bound to Glycosphingolipids in a Supported Cell-Membrane Mimic
- 2018
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In: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 9:9, s. 2278-2284
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Journal article (peer-reviewed)abstract
- Quartz crystal microbalance with dissipation monitoring and total internal reflection fluorescence microscopy have been used to investigate binding of norovirus-like particles (noroVLPs) to a supported (phospho)lipid bilayer (SLB) containing a few percent of H or B type 1 glycosphingolipid (GSL) receptors. Although neither of these GSLs spontaneously form domains, noroVLPs were observed to form micron-sized clusters containing typically up to about 30 VLP copies, especially for B type 1, which is a higher-affinity receptor. This novel finding is explained by proposing a model implying that VLP-induced membrane deformation promotes VLP clustering, a hypothesis that was further supported by observing that functionalized gold nanoparticles were able to locally induce SLB deformation. Because similar effects are likely possible also at cellular membranes, our findings are interesting beyond a pure biophysicochemical perspective as they shed new light on what may happen during receptor-mediated uptake of viruses as well as nanocarriers in drug delivery. © Copyright 2018 American Chemical Society.
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| 9. |
- Armanious, Antonius, 1981, et al.
(author)
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Determination of Nanosized Adsorbate Mass in Solution Using Mechanical Resonators: Elimination of the So Far Inseparable Liquid Contribution
- 2021
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In: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 125:41, s. 22733-22746
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Journal article (peer-reviewed)abstract
- Assumption-free mass quantification of nanofilms, nanoparticles, and (supra)molecular adsorbates in a liquid environment remains a key challenge in many branches of science. Mechanical resonators can uniquely determine the mass of essentially any adsorbate; yet, when operating in a liquid environment, the liquid dynamically coupled to the adsorbate contributes significantly to the measured response, which complicates data interpretation and impairs quantitative adsorbate mass determination. Employing the Navier-Stokes equation for liquid velocity in contact with an oscillating surface, we show that the liquid contribution for rigid systems can be eliminated by measuring the response in solutions with identical kinematic viscosity but different densities. Guided by this insight, we used the quartz crystal microbalance (QCM), one of the most widely employed mechanical resonators, to experimentally demonstrate that the kinematic-viscosity matching can be utilized to quantify the dry mass of rigid and in many cases also nonrigid adsorbate systems, including, e.g., rigid nanoparticles, tethered biological nanoparticles (lipid vesicles), as well as highly hydrated polymeric films. For all the adsorbates, the dry mass determined using the kinematic-viscosity matching was within the uncertainty limits of the corresponding mass determined using complementary methods, i.e., QCM in air, scanning electron microscopy, surface plasmon resonance, and theoretical estimations. The same approach applied to the simultaneously measured energy dissipation made it possible to quantify the mechanical properties of the adsorbate and its attachment to the surface, as demonstrated by, for example, probing the hydrodynamic stabilization induced by nanoparticle crowding. In addition to a unique means to quantify the liquid contribution to the measured response of mechanical resonators, we also envision that the kinematic-viscosity-matching approach will open up applications beyond mass determination, including a new means to investigate orientation, spatial distribution, and binding strength of adsorbates without the need for complementary techniques.
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| 10. |
- Bengtsson, Stefan, 1961, et al.
(author)
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Carbon-based nanoelectromechanical devices
- 2011
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In: International Journal of High Speed Electronics and Systems. - 1793-6438. ; 20:1, s. 195-204
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Journal article (peer-reviewed)abstract
- Carbon-based nanoelectromechanical devices are approaching applications in electronics. Switches based on individual carbon nanotubes deliver record low off-state leakage currents. Arrays of vertically aligned carbon nanotubes or nanofibers can be fabricated to constitute varactors. Very porous, low density arrays of quasi-vertically aligned arrays of carbon nanotubes behave mechanically as a single unit with very unusual material properties.
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