Anders Lundgren

Chalmers University of Technology, Goeteborg, Västra Götaland, Sweden

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Publications (10)50.83 Total impact


  • No preview · Article · Nov 2015
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    ABSTRACT: Advancement in the understanding of biomolecular interactions has benefited greatly from the development of surface-sensitive bionalaytical 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 allow for label-free detection of faint objects, such as individual 18 nm 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 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 sub-cellular 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 wide spread in life science and beyond.
    No preview · Article · Oct 2015 · ACS Nano
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    ABSTRACT: A simple and efficient principle for nanopatterning with wide applicability in the sub‐50 nanometer regime is chemisorption of nanoparticles; at homogeneous substrates, particles carrying surface charge may spontaneously self‐organize due to the electrostatic repulsion between adjacent particles. Guided by this principle, a method is presented to design, self‐assemble, and chemically functionalize gradient nanopatterns where the size of molecular domains can be tuned to match the level corresponding to single protein binding events. To modulate the binding of negatively charged gold nanoparticles both locally (100 μm) onto a single modified gold substrate, ion diffusion is used to achieve spatial control of the particles’ mutual electrostatic interactions. By subsequent tailoring of different molecules to surface‐immobilized particles and the void areas surrounding them, nanopatterns are obtained with variable chemical domains along the gradient surface. Fimbriated Escherichia coli bacteria are bound to gradient nanopatterns with similar molecular composition and macroscopic contact angle, but different sizes of nanoscopic presentation of adhesive (hydrophobic) and repellent poly(ethylene) glycol (PEG) domains. It is shown that small hydrophobic domains, similar in size to the diameter of the bacterial fimbriae, supported firmly attached bacteria resembling catch‐bond binding, whereas a high number of loosely adhered bacteria are observed on larger hydrophobic domains. Chemical gradients with the resolution needed to address complex biological binding events at the single protein level are prepared using surface‐deposited gold nanoparticles as a versatile template for orthogonal chemical modifications. The effect of hydrophobic domain arrangement on the sub‐50 nm scale is shown to influence binding of fimbriae carrying E. coli bacteria.
    No preview · Article · Feb 2014 · Particle and Particle Systems Characterization
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    Dataset: Figure S1
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    ABSTRACT: Positive secondary ion mass spectra from (A) cysteamine, nonwashed gold surface, (B) flat gold surface, (C) nanostructured gold surface, and (D) scratched area on nanostructured surface.
    Preview · Dataset · Oct 2011
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    ABSTRACT: The immune complement (IC) is a cell-free protein cascade system, and the first part of the innate immune system to recognize foreign objects that enter the body. Elevated activation of the system from, for example, biomaterials or medical devices can result in both local and systemic adverse effects and eventually loss of function or rejection of the biomaterial. Here, the researchers have studied the effect of surface nanotopography on the activation of the IC system. By a simple nonlithographic process, gold nanoparticles with an average size of 58 nm were immobilized on a smooth gold substrate, creating surfaces where a nanostructure is introduced without changing the surface chemistry. The activation of the IC on smooth and nanostructured surfaces was viewed with fluorescence microscopy and quantified with quartz crystal microbalance with dissipation monitoring in human serum. Additionally, the ability of pre-adsorbed human immunoglobulin G (IgG) (a potent activator of the IC) to activate the IC after a change in surface hydrophobicity was studied. It was found that the activation of the IC was significantly attenuated on nanostructured surfaces with nearly a 50% reduction, even after pre-adsorption with IgG. An increase in surface hydrophobicity blunted this effect. The possible role of the curvature of the nanoparticles for the orientation of adsorbed IgG molecules, and how this can affect the subsequent activation of the IC, are discussed. The present findings are important for further understanding of how surface nanotopography affects complex protein adsorption, and for the future development of biomaterials and blood-contacting devices.
    Full-text · Article · Oct 2011 · International Journal of Nanomedicine
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    Dataset: Figure S2
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    ABSTRACT: Negative secondary ion mass spectra from (A) cysteamine, nonwashed gold surface, (B) flat gold surface, (C) nanostructured gold surface, and (D) scratched area on nanostructured surface.
    Preview · Dataset · Oct 2011
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    Dataset: Figure S3
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    ABSTRACT: Representative QCM-D graph showing ΔF and ΔD for the adsorption of human IgG (100 μg/mL) for 20 minutes on hydrophilic and hydrophobic smooth and nanostructured gold surfaces. After 5 minutes of baseline with carrier buffer, IgG was introduced. After 20 minutes of adsorption of the protein, a 5-minute rinse with carrier buffer was performed. Note the ΔD when both nanostructured and smooth surfaces are hydrophobized, interpreted here as a higher degree of denaturation of the adsorbed protein. Abbreviations: ΔF, change in resonance frequency; ΔD, change in dissipation; IgG, immunoglobulin G; NP, nanoparticle; QCM-D, quartz crystal microbalance with dissipation monitoring.
    Preview · Dataset · Oct 2011
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    ABSTRACT: A single-chip electrochemical method based on impedance measurements in resonance mode has been employed to study lipid monolayer and bilayer formation on hydrophobic alkanethiolate and SiO(2) substrates, respectively. The processes were monitored by temporally resolving changes in interfacial capacitance and resistance, revealing information about the rate of formation, coverage, and defect density (quality) of the layers at saturation. The resonance-based impedance measurements were shown to reveal significant differences in the layer formation process of bilayers made from (i) positively charged lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-ethylphosphocholine (POEPC), (ii) neutral lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) on SiO(2), and (iii) monolayers made from POEPC on hydrophobic alkanethiolate substrates. The observed responses were represented with an equivalent circuit, suggesting that the differences primarily originate from the presence of a conductive aqueous layer between the lipid bilayers and the SiO(2). In addition, by adding the ion channel gramicidin D to bilayers supported on SiO(2), channel-mediated charge transport could be measured with high sensitivity (resolution around 1 pA).
    No preview · Article · Aug 2011 · Analytical Chemistry
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    ABSTRACT: Dendrimer-controlled cell growth: A dendrimer-gold-nanoparticle hybrid array (see picture; PEG=polyethylene glycol), which can control the apparent dendrimer surface density, was used to investigate cell adhesion. The effect of the macromolecular architecture on the attachment and the morphological development of endothelial cells was studied. The dendrimer outperformed a linear counterpart, most likely modulated by the different interactions between the dendrimer and the proteins in the cell media.
    Full-text · Article · Apr 2011 · Angewandte Chemie International Edition
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    ABSTRACT: Gold surfaces and structures modified with octanedithiol were reacted with dithiothreitol prior to immersion in buffered solutions of charge stabilized gold nanoparticles. The procedure gives a dithiol layer with adequate properties for a homogeneous octanedithiol monolayer and uniform and reproducible gold nanoparticle binding. The distance between the adsorbing particles is controlled by the particle electrostatic interactions and can be carefully tuned by variation of ionic strength. To some extent, long-range ordering occurs among the adsorbed particles. This behavior is facilitated by the particles' small size compared to the Debye screening but also by the homogeneity of the surface modification. The simple character of the system makes it attractive for fabrication of controlled nanoparticle arrays where further chemical and biological modifications are required.
    No preview · Article · Nov 2008 · Nano Letters

Publication Stats

78 Citations
50.83 Total Impact Points

Institutions

  • 2015
    • Chalmers University of Technology
      • Division of Biological Physics
      Goeteborg, Västra Götaland, Sweden
  • 2008-2014
    • University of Gothenburg
      • • Department of Chemistry & Molecular Biology
      • • Department of Cell- and Molecular Biology
      Goeteborg, Västra Götaland, Sweden