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  • 1.
    Lee, Hung-Hsun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Gavutis, Martynas
    Department of Nanoengineering, Center for Physical Sciences and Technology, Vilnius, Lithuania.
    Ruželė, Živilė
    Department of Nanoengineering, Center for Physical Sciences and Technology, Vilnius, Lithuania.
    Valiokas, Ramu̅nas
    Department of Nanoengineering, Center for Physical Sciences and Technology, Vilnius, Lithuania.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering. Center for Biomimetic Sensor Science, School of Materials Science and Engineering, Nanyang Technological University, Singapore.
    Mixed Self-Assembled Monolayers with Terminal Deuterated Anchors: Characterization and Probing of Model Lipid Membrane Formation2018In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 122, no 34, p. 8201-8210Article in journal (Refereed)
    Abstract [en]

    We describe herein a series of self-assembled monolayers (SAMs) on gold designed for adjustable tethering of model lipid membrane phases. The SAMs consist of deuterated aliphatic anchors, HS(CH2)(15)CONH-(CH2CH2O)(6)CH2CONH-X, where X is either -(CD2)(7)CD3 or -(CD2)(15)CD3, dispersed in a stable matrix of( )protein-repellent molecules, HS(CH2)(15)CONHCH2CH2OH. The mixed SAMs with variable surface densities of the anchors are thoroughly characterized before and after adsorption of phospholipids by means of ellipsometry, contact angle goniometry, and infrared reflection-absorption spectroscopy (IRRAS). In all cases, the bottom portions of the mixed SAMs (i.e., the h-alkyl thiol segments of the molecules) are arranged in a highly ordered all-trans conformation stabilized by a network of lateral hydrogen bonds. The terminal portions of the anchors (the oligo(ethylene glycol) spacer and deuterated alkyl segments, respectively), however, possess less ordered conformations in the mixed composition regime. For the SAMs containing the longer anchors (-(CD2)(15)CD3), the contact angle and infrared data point toward partial phase segregation. These findings are in excellent agreement with molecular dynamics simulations by Schulze and Stein. Upon analysis in air, the IRRAS data also indicate strong interaction between the adsorbed phospholipid molecules and the d-alkyl tails of the mixed SAM constituents. In such assemblies are the alkyl tails of the phospholipids aligned perpendicularly with respect to the supporting substrate, regardless of the anchor length. We also probed the in situ formation of a tethered bilayer lipid membrane (tBLM) via fusion of small unilamellar vesicles (SUVs) on the characterized SAMs using a quartz crystal microbalance with dissipation monitoring. Our experiments show that SUVs fuse efficiently of the two mixed SAMs with and without a pre-adsorbed lipid layer. Owing to the defined molecular composition and phase behavior, our SAM platform is attractive for detailed studies of tBLM formation and cell mimetic applications.

  • 2.
    Yandi, Wetra
    et al.
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics.
    Mieszkin, Sophie
    University of Birmingham, England; Newcastle University, England.
    Callow, Maureen E.
    University of Birmingham, England.
    Callow, James A.
    University of Birmingham, England.
    Finlay, John A.
    University of Birmingham, England; Newcastle University, England.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering. Nanyang Technology University, Singapore.
    Ederth, Thomas
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Antialgal activity of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes against the marine alga Ulva2017In: Biofouling (Print), ISSN 0892-7014, E-ISSN 1029-2454, Vol. 33, no 2, p. 169-183Article in journal (Refereed)
    Abstract [en]

    Marine biofouling has detrimental effects on the environment and economy, and current antifouling coatings research is aimed at environmentally benign, non-toxic materials. The possibility of using contact-active coatings is explored, by considering the antialgal activity of cationic poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes. The antialgal activity was investigated via zoospore settlement and sporeling growth assays of the marine algae Ulva linza and U. lactuca. The assay results for PDMAEMA brushes were compared to those for anionic and neutral surfaces. It was found that only PDMAEMA could disrupt zoospores that come into contact with it, and that it also inhibits the subsequent growth of normally settled spores. Based on the spore membrane properties, and characterization of the PDMAEMA brushes over a wide pH range, it is hypothesized that the algicidal mechanisms are similar to the bactericidal mechanisms of cationic polymers, and that further development could lead to successful contact-active antialgal coatings.

  • 3.
    Maleshlijski, S.
    et al.
    Ruhr University of Bochum, Germany; Karlsruhe Institute Technology, Germany; Heidelberg University, Germany.
    Sendra, G. H.
    Ruhr University of Bochum, Germany; Karlsruhe Institute Technology, Germany; Heidelberg University, Germany.
    Aldred, N.
    Newcastle University, England.
    Clare, A. S.
    Newcastle University, England.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering. Nanyang Technology University, Singapore.
    Grunze, M.
    Karlsruhe Institute Technology, Germany; Heidelberg University, Germany.
    Ederth, Thomas
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Rosenhahn, A.
    Ruhr University of Bochum, Germany; Karlsruhe Institute Technology, Germany; Heidelberg University, Germany.
    Imaging SPR combined with stereoscopic 3D tracking to study barnacle cyprid-surface interactions2016In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 643, p. 172-177Article in journal (Refereed)
    Abstract [en]

    Barnacle larvae (cyprids) explore surfaces to identify suitable settlement sites. This process is selective, and cyprids respond to numerous surface cues. To better understand the settlement process, it is desirable to simultaneously monitor both the surface exploration behavior and any close interactions with the surface. Stereoscopic 3D tracking of the cyprids provides quantitative access to surface exploration and pre-settlement rituals. Imaging surface plasmon resonance (SPR) reveals any interactions with the surfaces, such as surface inspection during bipedal walking and deposition of temporary adhesives. We report on a combination of both techniques to bring together information on swimming behavior in the vicinity of the interface and physical interactions of the cyprid with the surface. The technical requirements are described, and we applied the setup to cyprids of Balanus amphitrite. Initial data shows the applicability of the combined instrument to correlate exploration and touchdown events on surfaces with different chemical termination. (C) 2015 Published by Elsevier B.V.

  • 4.
    Koon Lim, Seng
    et al.
    Nanyang Technology University, Singapore.
    Sandén, Camilla
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Selegård, Robert
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Liedberg, Bo
    Nanyang Technology University, Singapore.
    Aili, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Tuning Liposome Membrane Permeability by Competitive Peptide Dimerization and Partitioning-Folding Interactions Regulated by Proteolytic Activity2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, no 21123, p. 1-9Article in journal (Refereed)
    Abstract [en]

    Membrane active peptides are of large interest for development of drug delivery vehicles and therapeutics for treatment of multiple drug resistant infections. Lack of specificity can be detrimental and finding routes to tune specificity and activity of membrane active peptides is vital for improving their therapeutic efficacy and minimize harmful side effects. We describe a de novo designed membrane active peptide that partition into lipid membranes only when specifically and covalently anchored to the membrane, resulting in pore-formation. Dimerization with a complementary peptide efficiently inhibits formation of pores. The effect can be regulated by proteolytic digestion of the inhibitory peptide by the matrix metalloproteinase MMP-7, an enzyme upregulated in many malignant tumors. This system thus provides a precise and specific route for tuning the permeability of lipid membranes and a novel strategy for development of recognition based membrane active peptides and indirect enzymatically controlled release of liposomal cargo.

  • 5.
    Vater, Svenja M.
    et al.
    Heidelberg University, Germany; Karlsruhe Institute Technology, Germany.
    Finlay, John
    University of Birmingham, England.
    Callow, Maureen E.
    University of Birmingham, England.
    Callow, James A.
    University of Birmingham, England.
    Ederth, Thomas
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering. Nanyang Technology University, Singapore.
    Grunze, Michael
    Karlsruhe Institute Technology, Germany.
    Rosenhahn, Axel
    Heidelberg University, Germany; Karlsruhe Institute Technology, Germany; Ruhr University of Bochum, Germany.
    Holographic microscopy provides new insights into the settlement of zoospores of the green alga Ulva linza on cationic oligopeptide surfaces2015In: Biofouling (Print), ISSN 0892-7014, E-ISSN 1029-2454, Vol. 31, no 2, p. 229-239Article in journal (Refereed)
    Abstract [en]

    Interaction of zoospores of Ulva linza with cationic, arginine-rich oligopeptide self-assembled monolayers (SAMs) is characterized by rapid settlement. Some spores settle (ie permanently attach) in a normal manner involving the secretion of a permanent adhesive, retraction of the flagella and cell wall formation, whilst others undergo pseudosettlement whereby motile spores are trapped (attached) on the SAM surface without undergoing the normal metamorphosis into a settled spore. Holographic microscopy was used to record videos of swimming zoospores in the vicinity of surfaces with different cationic oligopeptide concentrations to provide time-resolved insights into processes associated with attachment of spores. The data reveal that spore attachment rate increases with increasing cationic peptide content. Accordingly, the decrease in swimming activity in the volume of seawater above the surface accelerated with increasing surface charge. Three-dimensional trajectories of individual swimming spores showed a hit and stick motion pattern, exclusively observed for the arginine-rich peptide SAMs, whereby spores were immediately trapped upon contact with the surface.

  • 6.
    Yandi, Wetra
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, The Institute of Technology.
    Mieszkin, Sophie
    School of Biosciences, University of Birmingham, Birmingham, United Kingdom.
    Martin-Tanchereau, Pierre
    International Paint Ltd, Newcastle, United Kingdom; Department of Applied Sciences, Northumbria University, Newcastle upon Tyne, United Kingdom.
    Callow, Maureen E.
    School of Biosciences, University of Birmingham, Birmingham, United Kingdom.
    Callow, James A.
    School of Biosciences, University of Birmingham, Birmingham, United Kingdom.
    Tyson, Lyndsey
    International Paint Ltd, Newcastle, United Kingdom.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Ederth, Thomas
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Hydration and chain entanglement determines the optimum thickness of poly(HEMA-co-PEG10MA) brushes for effective antifouling properties2015Conference paper (Other academic)
  • 7.
    Liu, Xiaohu
    et al.
    Nanyang Technology University, Singapore .
    Wang, Yi
    Nanyang Technology University, Singapore .
    Chen, Peng
    Nanyang Technology University, Singapore .
    Wang, Yusong
    Nanyang Technology University, Singapore .
    Mang, Jinling
    Nanyang Technology University, Singapore .
    Aili, Daniel
    Nanyang Technology University, Singapore .
    Liedberg, Bo
    Nanyang Technology University, Singapore .
    Biofunctionalized Gold Nanoparticles for Colorimetric Sensing of Botulinum Neurotoxin A Light Chain2014In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 86, no 5, p. 2345-2352Article in journal (Refereed)
    Abstract [en]

    Botulinum neurotoxin is considered as one of the most toxic food-borne substances and is a potential bioweapon accessible to terrorists. The development of an accurate, convenient, and rapid assay for botulinum neurotoxins is therefore highly desirable for addressing biosafety concerns. Herein, novel biotinylated peptide substrates designed to mimic synaptosomal-associated protein 25 (SNAP-25) are utilized in gold nanoparticle-based assays for colorimetric detection of botulinum neurotoxin serotype A light chain (BoLcA). In these proteolytic assays, biotinylated peptides serve as triggers for the aggregation of gold nanoparticles, while the cleavage of these peptides by BoLcA prevents nanoparticle aggregation. Two different assay strategies are described, demonstrating limits of detection ranging from 5 to 0.1 nM of BoLcA with an overall assay time of 4 h. These hybrid enzyme-responsive nanomaterials provide rapid and sensitive detection for one of the most toxic substances known to man.

  • 8.
    Di Fino, A.
    et al.
    Newcastle University, England .
    Petrone, Luigi
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Aldred, N.
    Newcastle University, England .
    Ederth, Thomas
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Clare, A. S.
    Newcastle University, England .
    Correlation between surface chemistry and settlement behaviour in barnacle cyprids (Balanus improvisus)2014In: Biofouling (Print), ISSN 0892-7014, E-ISSN 1029-2454, Vol. 30, no 2, p. 143-152Article in journal (Refereed)
    Abstract [en]

    In laboratory-based biofouling assays, the influence of physico-chemical surface characteristics on barnacle settlement has been tested most frequently using the model organism Balanus amphitrite (= Amphibalanus amphitrite). Very few studies have addressed the settlement preferences of other barnacle species, such as Balanus improvisus (= Amphibalanus improvisus). This study aimed to unravel the effects of surface physico-chemical cues, in particular surface-free energy (SFE) and surface charge, on the settlement of cyprids of B. improvisus. The use of well-defined surfaces under controlled conditions further facilitates comparison of the results with recent similar data for B. amphitrite. Zero-day-old cyprids of B. improvisus were exposed to a series of model surfaces, namely self-assembled monolayers (SAMs) of alkanethiols with varying end-groups, homogenously applied to gold-coated polystyrene (PS) Petri dishes. As with B. amphitrite, settlement of cyprids of B. improvisus was influenced by both SFE and charge, with higher settlement on low-energy (hydrophobic) surfaces and negatively charged SAMs. Positively charged SAMs resulted in low settlement, with intermediate settlement on neutral SAMs of similar SFE. In conclusion, it is demonstrated that despite previous suggestions to the contrary, these two species of barnacle show similar preferences in response to SFE; they also respond similarly to charge. These findings have positive implications for the development of novel antifouling (AF) coatings and support the importance of consistency in substratum choice for assays designed to compare surface preferences of fouling organisms.

  • 9.
    Lundgren, Anders
    et al.
    University of Gothenburg, Sweden .
    Hulander, Mats
    University of Gothenburg, Sweden .
    Brorsson, Joakim
    University of Gothenburg, Sweden .
    Hermansson, Malte
    University of Gothenburg, Sweden .
    Elwing, Hans
    University of Gothenburg, Sweden .
    Andersson, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Berglin, Mattias
    University of Gothenburg, Sweden SP Technical Research Institute Sweden, Sweden .
    Gold-Nanoparticle-Assisted Self-Assembly of Chemical Gradients with Tunable Sub-50 nm Molecular Domains2014In: Particle & particle systems characterization, ISSN 0934-0866, E-ISSN 1521-4117, Vol. 31, no 2, p. 209-218Article in journal (Refereed)
    Abstract [en]

    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 (less than100 nm) and globally (greater than100 m) 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.

  • 10.
    Yandi, Wetra
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, The Institute of Technology.
    Mieszkin, Sophie
    University of Birmingham, England .
    Martin-Tanchereau, Pierre
    Int Paint Ltd, England Northumbria University, England .
    Callow, Maureen E.
    University of Birmingham, England .
    Callow, James A.
    University of Birmingham, England .
    Tyson, Lyndsey
    Int Paint Ltd, England .
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, The Institute of Technology.
    Ederth, Thomas
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, The Institute of Technology.
    Hydration and Chain Entanglement Determines the Optimum Thickness of Poly(HEMA-co-PEG(10)MA) Brushes for Effective Resistance to Settlement and Adhesion of Marine Fouling Organisms2014In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, no 14, p. 11448-11458Article in journal (Refereed)
    Abstract [en]

    Understanding how surface physicochemical properties influence the settlement and adhesion of marine fouling organisms is important for the development of effective and environmentally benign marine antifouling coatings. We demonstrate that the thickness of random poly(HEMA-co-PEG(10)DMA) copolymer brushes affect antifouling behavior. Films of thicknesses ranging from 50 to 1000 angstrom were prepared via surface-initiated atom-transfer radical polymerization and characterized using infrared spectroscopy, ellipsometry, atomic force microscopy and contact angle measurements. The fouling resistance of these films was investigated by protein adsorption, attachment of the marine bacterium Cobetia marina, settlement and strength of attachment tests of zoospores of the marine alga Ulva linza and static immersion field tests. These assays show that the polymer film thickness influenced the antifouling performance, in that there is an optimum thickness range, 200-400 angstrom (dry thickness), where fouling of all types, as well as algal spore adhesion, was lower. Field test results also showed lower fouling within the same thickness range after 2 weeks of immersion. Studies by quartz crystal microbalance with dissipation and underwater captive bubble contact angle measurements show a strong correlation between lower fouling and higher hydration, viscosity and surface energy of the poly(HEMA-co-PEG(10)MA) brushes at thicknesses around 200-400 angstrom. We hypothesize that the reduced antifouling performance is caused by a lower hydration capacity of the polymer for thinner films, and that entanglement and crowding in the film reduces the conformational freedom, hydration capacity and fouling resistance for thicker films.

  • 11.
    Martinsson, Erik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, The Institute of Technology.
    Sepulveda, Borja
    ICN2 Institute Catala Nanociencia and Nanotecnol, Spain; CSIC Consejo Super Invest Cient, Spain.
    Chen, Peng
    Nanyang Technology University, Singapore.
    Elfwing, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, The Institute of Technology. Nanyang Technology University, Singapore.
    Aili, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, The Institute of Technology.
    Optimizing the Refractive Index Sensitivity of Plasmonically Coupled Gold Nanoparticles2014In: PLASMONICS, ISSN 1557-1955, Vol. 9, no 4, p. 773-780Article in journal (Refereed)
    Abstract [en]

    The possibility to enhance the local refractive index sensitivity using plasmonic coupling between spherical gold nanoparticles (Au-NPs) has been investigated. A strong and distinct optical coupling between Au-NPs of various sizes was achieved by controlling the interparticle separation using a layer-by-layer assembly of polyelectrolytes. The frequency of the coupled plasmon peak could be tuned by varying either the particle size or the interparticle separation, shown both experimentally and by theoretical simulations. The bulk refractive index (RI) sensitivity for the plasmonic coupling modes was investigated and compared to the RI sensitivity of monolayers of well-separated Au-NPs, and the results clearly demonstrates that the RI sensitivity can be significantly enhanced in plasmonically coupled Au-NPs. The proposed approach is simple and scalable and improves the rather modest RI sensitivity of spherical gold nanoparticles with a factor of 3, providing a new route for fabrication of inexpensive sensors based on plasmonic nanostructures.

  • 12.
    Wickham, Abeni M.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, The Institute of Technology.
    Islam, Mohammad Mirazul
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Health Sciences. Karolinska Institutet, Stockholm, Sweden.
    Mondal, Debasish
    Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences. Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Phopase, Jaywant
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, The Institute of Technology.
    Sadhu, Veera
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Tamás, Éva
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Thoracic and Vascular Surgery.
    Polisetti, Naresh
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Health Sciences.
    Richter-Dahlfors, Agneta
    Karolinska Institutet, Stockholm, Sweden.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, The Institute of Technology. Nanyang Technological University, Singapore.
    Griffith, May
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Health Sciences. Karolinska Institutet, Stockholm, Sweden.
    Polycaprolactone–thiophene-conjugated carbon nanotube meshes as scaffolds for cardiac progenitor cells2014In: Journal of Biomedical Materials Research. Part B - Applied biomaterials, ISSN 1552-4973, E-ISSN 1552-4981, Vol. 102, no 7, p. 1553-1561Article in journal (Refereed)
    Abstract [en]

    The myocardium is unable to regenerate itself after infarct, resulting in scarring and thinning of the heart wall. Our objective was to develop a patch to buttress and bypass the scarred area, while allowing regeneration by incorporated cardiac stem/progenitor cells (CPCs). Polycaprolactone (PCL) was fabricated as both sheets by solvent casting, and fibrous meshes by electrospinning, as potential patches, to determine the role of topology in proliferation and phenotypic changes to the CPCs. Thiophene-conjugated carbon nanotubes (T-CNTs) were incorporated to enhance the mechanical strength. We showed that freshly isolated CPCs from murine hearts neither attached nor spread on the PCL sheets, both with and without T-CNT. As electrospun meshes, however, both PCL and PCL/T-CNT supported CPC adhesion, proliferation, and differentiation. The incorporation of T-CNT into PCL resulted in a significant increase in mechanical strength but no morphological changes to the meshes. In turn, proliferation, but not differentiation, of CPCs into cardiomyocytes was enhanced in T-CNT containing meshes. We have shown that changing the topology of PCL, a known hydrophobic material, dramatically altered its properties, in this case, allowing CPCs to survive and differentiate. With further development, PCL/T-CNT meshes or similar patches may become a viable strategy to aid restoration of the postmyocardial infarction myocardium.

  • 13.
    Wang, Yi
    et al.
    Nanyang Technological University, Singapore.
    Liu, Xiaohu
    Nanyang Technological University, Singapore.
    Zhang, Jinling
    Nanyang Technological University, Singapore.
    Aili, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, The Institute of Technology. Nanyang Technological University, Singapore.
    Liedberg, Bo
    Nanyang Technological University, Singapore.
    Time-resolved botulinum neurotoxin A activity monitored using peptide-functionalized Au nanoparticle energy transfer sensors2014In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 5, no 7, p. 2651-2656Article in journal (Refereed)
    Abstract [en]

    We report herein on the employment of synthetic peptide-functionalized gold nanoparticles (AuNPs) with various diameters as radiative quenchers for the time-resolved monitoring of botulinum A light chain (BoLcA) activity. The results demonstrate that larger AuNPs provide higher energy transfer efficiencies between the dye and the AuNPs, but poorer BoLcA activities for the proteolysis of peptides because of steric constraints. The initial turnover number for the BoLcA proteolysis of peptides on 18 nm AuNPs was retarded by a factor of 80 as compared with 1.4 nm AuNPs. A similar phenomenon has been observed for trypsin, however, with less hindrance on large AuNPs. Thus, the use of smaller 1.4 nm AuNPs in conjunction with robust synthetic peptides provides an attractive format for the time-resolved monitoring of protease activity and for BoLcA sensing at a highly competitive limit of detection (1 pM).

  • 14.
    Arslan Yildiz, Ahu
    et al.
    Max Planck Institute Polymer Research, Germany .
    Hakan Yildiz, Umit
    Nanyang Technology University, Singapore .
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Sinner, Eva-Kathrin
    Max Planck Institute Polymer Research, Germany .
    Biomimetic membrane platform: Fabrication, characterization and applications2013In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 103, p. 510-516Article in journal (Refereed)
    Abstract [en]

    A facile method for assembly of biomimetic membranes serving as a platform for expression and insertion of membrane proteins is described. The membrane architecture was constructed in three steps: (i) assembly/printing of alpha-laminin peptide (P19) spacer on gold to separate solid support from the membrane architecture; (ii) covalent coupling of different lipid anchors to the P19 layer to serve as stabilizers of the inner leaflet during bilayer formation; (iii) lipid vesicle spreading to form a complete bilayer. Two different lipid membrane systems were examined and two different P19 architectures prepared by either self-assembly or mu-contact printing were tested and characterized using contact angle (CA) goniometry, surface plasmon resonance (SPR) spectroscopy and imaging surface plasmon resonance (iSPR). It is shown that surface coverage of cushion layer is significantly improved by mu-contact printing thereby facilitating bilayer formation as compared to self-assembly. To validate applicability of proposed methodology, incorporation of Cytochrome bo(3) ubiquinol oxidase (Cyt-bo(3)) into biomimetic membrane was performed by in vitro expression technique which was further monitored by surface plasmon enhanced fluorescence spectroscopy (SPFS). The results showed that solid supported planar membranes, tethered by alpha-laminin peptide cushion layer, provide an attractive environment for membrane protein insertion and characterization.

  • 15.
    Aldred, Nick
    et al.
    Newcastle University, England .
    Gohad, Neeraj V.
    Clemson University, SC USA .
    Petrone, Luigi
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Orihuela, Beatriz
    Duke University, NC USA .
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Ederth, Thomas
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Mount, Andrew
    Clemson University, SC USA .
    Rittschof, Dan
    Duke University, NC USA .
    Clare, Anthony S.
    Newcastle University, England .
    Confocal microscopy-based goniometry of barnacle cyprid permanent adhesive2013In: Journal of Experimental Biology, ISSN 0022-0949, E-ISSN 1477-9145, Vol. 216, no 11, p. 1969-1972Article in journal (Refereed)
    Abstract [en]

    Biological adhesives are materials of particular interest in the fields of bio-inspired technology and antifouling research. The adhesive of adult barnacles has received much attention over the years; however, the permanent adhesive of the cyprid - the colonisation stage of barnacles - is a material about which very little is presently known. We applied confocal laser-scanning microscopy to the measurement of contact angles between the permanent adhesive of barnacle cyprid larvae and self-assembled monolayers of OH- and CH3-terminated thiols. Measurement of contact angles between actual bioadhesives and surfaces has never previously been achieved and the data may provide insight into the physicochemical properties and mechanism of action of these functional materials. The adhesive is a dual-phase system post-secretion, with the behaviour of the components governed separately by the surface chemistry. The findings imply that the cyprid permanent adhesion process is more complex than previously thought, necessitating broad re-evaluation of the system. Improved understanding will have significant implications for the production of barnacle-resistant coatings as well as development of bio-inspired glues for niche applications.

  • 16.
    Ericsson, Emma M
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Bui, Lan
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Konradsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, The Institute of Technology.
    Enander, Karin
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, The Institute of Technology.
    Controlled orientation and covalent attachment of proteins on biosensor surfaces by Chelation Assisted Photoimmobilization2013Conference paper (Other academic)
    Abstract [en]

    In the context of surface chemistry for affinity biosensor chips, it is widely accepted that uniform orientation of the immobilized recognition element (ligand) is preferred over random orientation. However, this assumption has often been based on studies where differences in ligand immobilization level have not been taken into account. In this contribution, we present a novel two-step method for homogenous orientation and covalent attachment of proteins to sensing surfaces, called Chelation Assisted Photoimmobilization (CAP). Careful quantification of the effect of ligand orientation on analyte responses was performed by comparing this strategy to immobilization by conventional amine coupling.

     In CAP, the chelation agent is nitrilotriacetic acid (NTA) which chelates Ni2+. A His-tagged ligand forms an oriented assembly when binding Ni2+-NTA and is then covalently bound to the surface via photolabile benzophenone (BP), which attacks C-H bonds upon UV light activation. We relied on a surface chemistry based on self-assembled monolayers (SAMs) of oligo(ethylene glycol) (OEG)-containing alkanethiolates on gold. Alkanethiols terminated with either NTA, BP or OEG were synthesized and mixed SAMs were characterized by infrared reflection absorption spectroscopy (IRAS), ellipsometry and contact angle goniometry. IRAS was also used to quantify ligand immobilization levels obtained either by CAP or by amine coupling via the carboxyl groups of an NTA-presenting surface. The model ligand was human IgG-Fc modified with a C-terminal 6xHis-tag and the analyte was Protein A. The ligand-analyte interaction was quantified by a surface plasmon resonance biosensor.

     Analyte responses were normalized with respect to the ligand amounts obtained by the two immobilization strategies. Interestingly, the normalized analyte response with randomly oriented ligand was >2 times higher than that with ligand immobilized by CAP. This shows that oriented ligand immobilization is not necessarily a means of increasing the sensitivity of a biosensor. Factors that may influence performance include the valency of the ligand and constraints related to the surface chemistry used for orientation.

  • 17.
    Ericsson, Emma
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Enander, Karin
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Bui, Lan
    Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Konradsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Controlled Orientation and Covalent Attachment of Proteins on Biosensor Surfaces by Chelation Assisted Photoimmobilization2013Manuscript (preprint) (Other academic)
    Abstract [en]

    This report presents a novel method for uniform orientation and covalent attachment of proteins to sensing surfaces, termed Chelation Assisted Photoimmobilization (CAP). Alkanethiols terminated with either nitrilotriacetic acid (NTA), benzophenone (BP) or oligo(ethylene glycol) were synthesized and mixed self-assembled monolayers (SAMs) were prepared on gold and thoroughly characterized by infrared reflection absorption spectroscopy (IRAS), ellipsometry and contact angle goniometry. In the process of CAP, NTA chelates Ni2+ and the complex coordinates a His-tagged ligand in an oriented assembly. The ligand is then photoimmobilized via BP, which forms covalent bonds upon UV light activation. The CAP concept was demonstrated using human IgG-Fc modified with C-terminal hexahistidine tags (His-IgGFc) as the ligand and protein A as the analyte.

    In the development of affinity biosensors, uniform orientation of ligand molecules where all analyte binding sites are accessible is often preferred to random orientation. In order to monitor the effect of ligand orientation on analyte response, the ligand-analyte interaction was quantified by surface plasmon resonance analysis, both in the case of CAP and when the ligand was attached by conventional amine coupling on surfaces presenting NTA. Responses were adjusted for differences in ligand immobilization level using IRAS. The normalized analyte response with randomly oriented ligand was 2.5 times higher than that with ligand immobilized by CAP, probably due to molecular crowding effects on the surface and the fact that His-IgGFc is bivalent for protein A. This is a reminder that many other factors than orientation alone may play a decisive role in analyte binding on biosensor surfaces.

  • 18.
    Koh, Li Buay
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Islam, Mohammad Mirazul
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Health Sciences. Swedish Nanoscience Center, Karolinska Institute, Stockholm , Sweden .
    Mitra, Debbie
    Ottawa Hospital Research Institute, University of Ottawa Eye Institute, ON, Canada.
    Noel, Christopher
    Ottawa Hospital Research Institute, University of Ottawa Eye Institute, ON, Canada.
    Merett, Kimberley
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Health Sciences. Ottawa Hospital Research Institute, University of Ottawa Eye Institute, ON, Canada.
    Odorcic, Silvia
    Ottawa Hospital Research Institute, University of Ottawa Eye Institute, ON, Canada.
    Fagerholm, Per
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuroscience. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Anaesthetics, Operations and Specialty Surgery Center, Department of Ophthalmology in Linköping.
    Jackson, William Bruce
    Ottawa Hospital Research Institute, University of Ottawa Eye Institute, ON, Canada.
    Liedberg, Bo
    Center for Biomimetic Sensor Science, Nanyang Technological University, Singapore.
    Phopase, Jaywant
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Griffith, May
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Health Sciences. Swedish Nanoscience Center, Karolinska Institute, Stockholm, Sweden.
    Epoxy Cross-Linked Collagen and Collagen-Laminin Peptide Hydrogels as Corneal Substitutes2013In: Journal of Functional Biomaterials, ISSN 2079-4983, E-ISSN 2079-4983, Vol. 4, no 3, p. 162-177Article in journal (Refereed)
    Abstract [en]

    A bi-functional epoxy-based cross-linker, 1,4-Butanediol diglycidyl ether (BDDGE), was investigated in the fabrication of collagen based corneal substitutes. Two synthetic strategies were explored in the preparation of the cross-linked collagen scaffolds. The lysine residues of Type 1 porcine collagen were directly cross-linked using l,4-Butanediol diglycidyl ether (BDDGE) under basic conditions at pH 11. Alternatively, under conventional methodology, using both BDDGE and 1-Ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC)/N-hydroxysuccinimide (NHS) as cross-linkers, hydrogels were fabricated under acidic conditions. In this latter strategy, Cu(BF4)2·XH2O was used to catalyze the formation of secondary amine bonds. To date, we have demonstrated that both methods of chemical cross-linking improved the elasticity and tensile strength of the collagen implants. Differential scanning calorimetry and biocompatibility studies indicate comparable, and in some cases, enhanced properties compared to that of the EDC/NHS controls. In vitro studies showed that human corneal epithelial cells and neuronal progenitor cell lines proliferated on these hydrogels. In addition, improvement of cell proliferation on the surfaces of the materials was observed when neurite promoting laminin epitope, IKVAV, and adhesion peptide, YIGSR, were incorporated. However, the elasticity decreased with peptide incorporation and will require further optimization. Nevertheless, we have shown that epoxy cross-linkers should be further explored in the fabrication of collagen-based hydrogels, as alternatives to or in conjunction with carbodiimide cross-linkers.

  • 19.
    Martinsson, Erik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Mehdi Shahjamali, Mohammad
    Nanyang Technology University, Singapore .
    Enander, Karin
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Boey, Freddy
    Nanyang Technology University, Singapore .
    Xue, Can
    Nanyang Technology University, Singapore .
    Aili, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Local Refractive Index Sensing Based on Edge Gold-Coated Silver Nanoprisms2013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 44, p. 23148-23154Article in journal (Refereed)
    Abstract [en]

    Bulk and surface refractive index sensitivity for localized surface plasmon resonance (LSPR) sensing based on edge gold-coated silver nanoprisms (GSNPs) and gold nanospheres was investigated and compared with conventional surface plasmon resonance (SPR) sensing based on propagating surface plasmons. The hybrid GSNPs benefit from an improved stability since the gold frame protecting the unstable silver facets located at the silver nanoprisms (SNPs) edges and tips prevents truncation or rounding of their sharp tips or edges, maintaining a high refractive index sensitivity even under harsh conditions. By using layer-by-layer deposition of polyelectrolytes and protein adsorption, we found that GSNPs exhibit 4-fold higher local refractive index sensitivity in close proximity (andlt;10 nm) to the surface compared to a flat gold film in the conventional SPR setup. Moreover, the sensitivity was 8-fold higher with GSNPs than with gold nanospheres. This shows that relatively simple plasmonic nanostructures for LSPR-based sensing can be engineered to outperform conventional SPR, which is particularly interesting in the context of detecting low molecular weight compounds where a small sensing volume, reducing bulk signals, is desired.

  • 20.
    Rafat, Mehrdad
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Health Sciences.
    Mondal, Debasish
    Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences.
    Islam, M.
    Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Griffith, May
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Health Sciences.
    Nanoparticles incorporated collagen hydrogels for sustained release of EGF2013In: Acta Ophthalmologica; Special Issue: Abstracts from the 2013 European Association for Vision and Eye Research Conference, Volume 91, Issue Supplement s252, page 0, August 2013, John Wiley & Sons, 2013Conference paper (Refereed)
    Abstract [en]

    Therapeutic biomolecules such as growth factors are essential for enhancing the regeneration of damaged tissues by inducing cell signaling activities such as cell migration, proliferation, and differentiation. Nevertheless, they have short half-lives in physiological conditions due to fast deactivation and degradation by enzymes and other physical and chemical reactions. Therefore, there is a great need for the suitable target delivery of nanoparticles to improve the release kinetics of growth factors as well as their therapeutic effectiveness. The main objective of this study was to develope and characterize a sustained delivery system consisting of an EGF-encapslated chitosan nanoparticles and collagen hydrogel carrier system to achieve a sustained release of EGF. In this study, we made EGF-loaded chitosan nanoparticles, which could be incorporated into an engineered collagen hydrogel scaffold. The particles were spherical in the size range of 60–100 nm. The release kinetics of EGF showed the release of growth factors in a sustained manner. Live-dead staining of human corneal epithelial (HCEC) cells was done to evaluate the cytotoxicity of the nanoparticles.

  • 21.
    Suriyanarayanan, Subrarnanian
    et al.
    Linnaeus University, Sweden .
    Lee, Hung-Hsun
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Aastrup, Teodor
    Attana AB, Sweden .
    Nicholls, Ian A
    Linnaeus University, Sweden .
    Protein-resistant hyperbranched polyethyleneimine brush surfaces2013In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 396, p. 307-315Article in journal (Refereed)
    Abstract [en]

    A novel hyperbranched polyethyleneimine (PEI) modified gold surface has been designed, fabricated, and investigated with respect to its ability to resist non-specific adsorption of proteins. The facile synthesis strategy, based on self-assembly, involves immobilization of polyethyleneimine to gold surfaces modified with 11-mercaptoundecanoic acid (MuDA) monolayers using traditional carbodiimide chemistry. The hyperbranched polymer brushes were characterized by X-ray photoelectron spectroscopy (XPS). Reflection absorption infrared spectroscopy (RAIRS) and ellipsometry measurements showed the thickness of the PEI brushes increases with adsorption solution ionic strength. Polymer brush surface concentrations can be improved from 2560 to 3880 chains/mu m(2) by changing the ionic strength of the adsorption solution (PBS) by varying NaCl concentration from 0 to 650 mM. Protein adsorption (pH 7.4) was evaluated under flow injection analysis (FIA) conditions using a quartz crystal microbalance (QCM). The PEI brushes suppress protein adsorption, for example, cytochrome C, bovine serum albumin (BSA), and ribonuclease A, to less than 0.08 mu g/cm(2) and the protein resistance increases with increasing ionic strength of the carrier solution, performance comparable to that achieved with comparable PEG-coated surfaces. The PEI brushes were exceptionally stable, with adsorption characteristics maintained after 6 months storage in aqueous conditions (pH 7.4, 25 degrees C, PBS). The potential of hyperbranched PEI structures as protein-resistant surfaces is discussed.

  • 22.
    Ericsson, Emma
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Enander, Karin
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Bui, Lan
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Konradsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Site-Specific and Covalent Attachment of His-Tagged Proteins by Chelation Assisted Photoimmobilization: A Strategy for Microarraying of Protein Ligands2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 37, p. 11687-11694Article in journal (Refereed)
    Abstract [en]

    A novel strategy for site-specific and covalent attachment of proteins has been developed, intended for robust and controllable immobilization of histidine (His)-tagged ligands in protein microarrays. The method is termed chelation assisted photoimmobilization (CAP) and was demonstrated using human IgG-Fc modified with C-terminal hexahistidines (His-IgGFc) as the ligand and protein A as the analyte. Alkanethiols terminated with either nitrilotriacetic acid (NTA), benzophenone (BP); or oligo(ethylene glycol) were synthesized and mixed self-assembled monolayers (SAMs) were prepared on gold and thoroughly characterized by infrared reflection absorption spectroscopy (IRAS), ellipsometry, and contact angle goniometry. In the process of CAP, NTA chelates Ni2+ and the complex coordinates the His-tagged ligand in an oriented assembly. The ligand is then photoimmobilized via BP, which forms covalent bonds upon UV light activation. In the development of affinity biosensors and protein microarrays, site-specific attachment of ligands in a fashion where analyte binding sites are available is often preferred to random coupling. Analyte binding performance of ligands immobilized either by CAP or by standard amine coupling was characterized by surface plasmon resonance in combination with IRAS. The relative analyte response with randomly coupled ligand was 2.5 times higher than when site-specific attachment was used. This is a reminder that also when immobilizing ligands via residues far from the binding site, there are many other factors influencing availability and activity. Still, CAP provides a valuable expansion of protein immobilization techniques since it offers attractive microarraying possibilities amenable to applications within proteomics.

  • 23.
    Mehdi Shahjamali, Mohammad
    et al.
    Nanyang Technology University.
    Bosman, Michel
    ASTAR.
    Cao, Shaowen
    Nanyang Technology University.
    Huang, Xiao
    Nanyang Technology University.
    Saadat, Somaye
    Nanyang Technology University.
    Martinsson, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Aili, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Yan Tay, Yee
    Nanyang Technology University.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Chye Joachim Loo, Say
    Nanyang Technology University.
    Zhang, Hua
    Nanyang Technology University.
    Boey, Freddy
    Nanyang Technology University.
    Xue, Can
    Nanyang Technology University.
    Gold Coating of Silver Nanoprisms2012In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 22, no 4, p. 849-854Article in journal (Refereed)
    Abstract [en]

    Coreshell Ag@Au nanoprisms are prepared through a surfactant-free seed-mediated approach by taking advantage of the anisotropic structure of silver nanoprisms as seeds. The gold coating on the silver nanoprism surface is achieved by using hydroxylamine as a mild reducing agent, and the final fully gold-coated prism structures are confirmed by microscopic and spectroscopic characterization. The resulting Ag@Au coreshell structure preserves the optical signatures of nanoprisms and offers versatile functionality and particularly better stability against oxidation than the bare silver nanoprism. The surface plasmon resonances of the coreshell Ag@Au nanoprisms can be tuned throughout the visible and near-IR range as a function of the Au shell thickness. Such tailorable optical features and surfactant-free gold shells have great potential applications in biosensing and bioimaging.

  • 24.
    Rafat, Mehrdad
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Health Sciences.
    Koh, Li Buay
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Islam, Mohammad Mirazul
    Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Griffith, May
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Health Sciences.
    Highly elastic epoxycross‐linked collagen hydrogels for corneal tissueengineering2012In: Acta Ophthalmologica; Special Issue: Abstracts from the 2012 European Association for Vision and Eye Research Conference, Volume 90, Issue Supplement s249, page 0, September 2012, John Wiley & Sons, 2012Conference paper (Refereed)
    Abstract [en]

    Purpose Our objective is to develop novel materials that support the regeneration of diseased or damaged corneas. Despite the promising clinical results that we previously reported on biosynthetic corneas, more robust and elastic materials are required to withstand the adverse host conditions faced for high risk transplantation in severely damaged or diseased corneas. This presentation will provide details on an epoxy cross-linked collagen-based scaffold with enhanced mechanical properties.

    Methods We have developed a range of collagen-based materials as mimics of the cell-free corneal stromal extracellular matrix. In this study, cross-linked polymer networks of collagen hydrogels were prepared using a hybrid of 1,4-butanediol diglycidyl ether (BDDGE) and carbodiimides (e.g. EDC-NHS) as cross-linkers. Briefly, 10w/w% porcine collagen type I was mixed in a T-piece system at various compositions and pH, e.g. pH 5, pH 11, and incorporated with laminin adhesive peptides (YIGSR, and IKVAV). Promising material formulations were tested for their physiochemical properties (e.g. mechanical, optical, water uptake, FTIR, and thermal degradation) and physiological properties (e.g. interactions with corneal cells, and biodegradation).

    Results The hybrid BDDGE hydrogels demonstrated improved mechanical properties and degree of cross-linking while maintaining their optical clarity and biocompatibility compared to controls (e.g. EDC/NHS-crosslinked hydrogels). Incorporation of laminin-derived cell-adhesive peptide (IKVAV) demonstrated significant increase in corneal cells (HCECs) proliferation compared to controls.

    Conclusion The hybrid BDDGE-crosslinked collagen-based hydrogels have the potential for use as tissue-engineered corneal substitutes.

  • 25.
    Wang, Yusong
    et al.
    Nanyang Technology University, Singapore Nanyang Technology University, Singapore .
    Aili, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Selegård, Robert
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Tay, Yeeyan
    Nanyang Technology University, Singapore .
    Baltzer, Lars
    Uppsala University, Sweden .
    Zhang, Hua
    Nanyang Technology University, Singapore Nanyang Technology University, Singapore .
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Specific functionalization of CTAB stabilized anisotropic gold nanoparticles with polypeptides for folding-mediated self-assembly2012In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 22, no 38, p. 20368-20373Article in journal (Refereed)
    Abstract [en]

    Anisotropic nanoparticles stabilized by cetyltrimethylammonium bromide (CTAB) are notoriously difficult to homogenously functionalize using conventional gold-thiol chemistry. Using surface assisted laser desorption time of flight mass spectroscopy and scanning transmission electron microscopy-energy dispersive X-ray spectroscopy, we demonstrate that silver species adsorbed on the particle surface prevent effective surface functionalization. When covered by a thin gold film, particle functionalization was drastically improved. A thiol-containing polypeptide was immobilized on arrowhead gold nanorods (NRs) and was subsequently able to selectively heteroassociate with a complementary polypeptide resulting in a folding-mediated bridging aggregation of the NRs. Despite using arrowhead NRs with a pronounced difference in surface arrangement on the {111} facets on the arrowheads compared to the {100} facets at the particle sides, the polypeptides were efficiently and homogeneously immobilized on the particles after gold film overgrowth.

  • 26.
    Malysheva, Lyuba
    et al.
    Bogolyubov Institute for Theoretical Physics, 03680, Kiev, Ukraine.
    Onipko, Alexander
    Bogolyubov Institute for Theoretical Physics, 03680, Kiev, Ukraine.
    Fyrner, Timmy
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Lee, Hung-Hsun
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Valiokas, Ramūnas
    Department of Nanoengineering, Center for Physical Sciences and Engineering, Savanoriu 231, LT-02300 Vilnius, Lithuania.
    Konradsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Spectroscopic Characterization and Modeling of Methyl- and Hydrogen-Terminated Oligo (ethylene glycol) Self-Assembled Monolayers2012In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 22, p. 12008-12016Article in journal (Refereed)
    Abstract [en]

    Two series of oligo (ethylene glycol) (OEG) thiol compounds HS-(CH2CH2O)nR with R = CH3, H and n = 5, 6, 7, have been synthesized and used to form self-assembled monolayers (SAMs) on gold. The data from null ellipsometry, infrared reflection-absorption spectroscopy and ab initio calculations of this type of OH- and CH3-terminated OEG SAMs are used to examine the rarely addressed in-SAM orientation of oligo (ethylene glycols) and to provide detailed assignments of infrared bands in the fingerprint and CH-stretching regions. Based on these results, a new spectral band has been observed at 2947 cm-1 and identified by the firstprinciple calculations as localized vibrations that are specific for hydrogen-terminated OEG thiolate SAMs. This band can be used as an indicator of a high crystalline like ordering. It is further more stressed that theory agrees with the experimentally obtained CH-stretching spectra remarkably well if, and only if, the OEG helix axis within studied SAMs is tilted by about 20o with respect to the surface normal.

  • 27.
    Chen, Peng
    et al.
    Nanyang Technology University.
    Yin, Zongyou
    Nanyang Technology University.
    Huang, Xiao
    Nanyang Technology University.
    Wu, Shixin
    Nanyang Technology University.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Zhang, Hua
    Nanyang Technology University.
    Assembly of Graphene Oxide and Au(0.7)Ag(0.3) Alloy Nanoparticles on SiO(2): A New Raman Substrate with Ultrahigh Signal-to-Background Ratio2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 49, p. 24080-24084Article in journal (Refereed)
    Abstract [en]

    Resonance Raman spectroscopy (RRS) often suffers from the large fluorescence background which obscures the much weaker Raman scattering. To address this fundamental problem, a novel Raman substrate has been fabricated by adsorption of Au(0.7)Ag(0.3) alloy nanoparticles (NPs) on a graphene oxide (GO) coated SiO(2) surface, which offers both excellent Raman enhancement and fluorescence quenching. Our experimental data reveal that a Raman to fluorescence background intensity ratio of 1.6 can be obtained for a highly fluorescent dye like Alexa fluor 488. Moreover, we demonstrate that the Raman enhancement mainly originates from the Au(0.7)Ag(0.3) alloy NPs and that the fluorescence quenching mainly arises from the underlying functionalized GO (FGO) substrate.

  • 28.
    Petrone, Luigi
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Di Fino, Alessio
    Newcastle University.
    Aldred, Nick
    Newcastle University.
    Sukkaew, Pitsiri
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Ederth, Thomas
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Clare, Anthony S
    Newcastle University.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Effects of surface charge and Gibbs surface energy on the settlement behaviour of barnacle cyprids (Balanus amphitrite)2011In: Biofouling (Print), ISSN 0892-7014, E-ISSN 1029-2454, Vol. 27, no 9, p. 1043-1055Article in journal (Refereed)
    Abstract [en]

    Gibbs surface energy has long been considered to be an important parameter in the design of fouling-resistant surfaces for marine applications. Rigorous testing of the hypothesis that settlement is related to Gibbs surface energy however has never been accomplished, due mainly to practical limitations imposed by the necessary combination of surface engineering and biological evaluation methods. In this article, the effects of surface charge and Gibbs surface energy on the settlement of cyprids of an important fouling barnacle, Balanus amphitrite, were evaluated. Settlement assays were conducted on a range of self-assembled monolayers (SAMs) (CH(3)-, OH-, COOH-, N(CH(3))(3)(+)-, NH(2)-terminated), presented in gold-coated polystyrene well plates, varying in terms of their surface charge and Gibbs surface energy. Contrary to contemporary theory, settlement was not increased by high-energy surfaces, rather the opposite was found to be the case with cyprids settling in greater numbers on a low-energy CH(3)- SAM compared to a high-energy OH- SAM. Settlement was also greater on negatively-charged SAMs, compared to neutral and positively-charged SAMs. These findings are discussed in the context of data drawn from surfaces that varied in multiple characteristics simultaneously, as have been used previously for such experiments. The finding that surface charge, rather than total surface energy, may be responsible for surface selection by cyprids, will have significant implications for the design of future fouling-resistant materials.

  • 29.
    Stuppy, S.M.
    et al.
    Applied Physical Chemistry, Ruprecht-Karls-University Heidelberg, Heidelberg, Germany; Institute for Functional Interfaces, IFG, Karlsruhe Institute of Technology, Karlsruhe, Germany.
    Arpa Sancet, M. P.
    Applied Physical Chemistry, Ruprecht-Karls-University Heidelberg, Heidelberg, Germany; Institute for Functional Interfaces, IFG, Karlsruhe Institute of Technology, Karlsruhe, Germany.
    Heydt, M.
    Ocean Engineering and Oceanography, Florida Institute of Technology, Melbourne Florida, USA.
    Schilp, S.
    Ocean Engineering and Oceanography, Florida Institute of Technology, Melbourne Florida, USA.
    Zargiel, K.
    Ocean Engineering and Oceanography, Florida Institute of Technology, Melbourne Florida, USA.
    Ederth, Thomas
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Swain, G. W.
    Ocean Engineering and Oceanography, Florida Institute of Technology, Melbourne Florida, USA.
    Callow, J. A.
    School of Bioscience, University of Birmingham, Birmingham, UK.
    Callow, M. E.
    School of Bioscience, University of Birmingham, Birmingham, UK.
    Rosenhahn, A.
    Institute for Functional Interfaces, IFG, Karlsruhe Institute of Technology, Karlsruhe, Germany.
    Grunze, M.
    Applied Physical Chemistry, Ruprecht-Karls-University Heidelberg, Heidelberg, Germany; Institute for Toxicology and Genetics, ITG, Karlsruhe Institute of Technology, Karlsruhe, Germany.
    From lab to field - chemistry depending surface colonization and 3D tracking2011Conference paper (Other academic)
  • 30.
    Rakickas, Tomas
    et al.
    Centre for Physics Science and Technology, Vilnius.
    Ericsson, Emma
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Ruzele, Zivile
    Centre for Physics Science and Technology, Vilnius.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Valiokas, Ramunas
    Centre for Physics Science and Technology, Vilnius.
    Functional Hydrogel Density Patterns Fabricated by Dip-Pen Nanolithography and Photografting2011In: SMALL, ISSN 1613-6810, Vol. 7, no 15, p. 2153-2157Article in journal (Refereed)
    Abstract [en]

    n/a

  • 31.
    Aili, Daniel
    et al.
    University of London Imperial College of Science Technology and Medicine.
    Gryko, Piotr
    University of London Imperial College of Science Technology and Medicine.
    Sepulveda, Borja
    Research Centre Nanosci and Nanotechnol CIN2 CSIC.
    Dick, John A. G.
    University of London Imperial College of Science Technology and Medicine.
    Kirby, Nigel
    Australian Synchrotron.
    Heenan, Richard
    Rutherford Appleton Lab.
    Baltzer, Lars
    Uppsala University.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Ryan, Mary P.
    University of London Imperial College of Science Technology and Medicine.
    Stevens, Molly M.
    University of London Imperial College of Science Technology and Medicine.
    Polypeptide Folding-Mediated Tuning of the Optical and Structural Properties of Gold Nanoparticle Assemblies2011In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 11, no 12, p. 5564-5573Article in journal (Refereed)
    Abstract [en]

    Responsive hybrid nanomaterials with well-defined properties are of significant interest for the development of biosensors with additional applications in tissue engineering and drug delivery. Here, we present a detailed characterization using UV-vis spectroscopy and small angle X-ray scattering of a hybrid material comprised of polypeptide-decorated gold nanoparticles with highly controllable assembly properties. The assembly is triggered by a folding-dependent bridging of the particles mediated by the heteroassociation of immobilized helix-loop-helix polypeptides and a complementary nonlinear polypeptide present in solution. The polypeptides are de novo designed to associate and fold into a heterotrimeric complex comprised of two disulfide-linked four-helix bundles. The particles form structured assemblies with a highly defined interparticle gap (4.8 +/- 0.4 nm) that correlates to the size of the folded polypeptides. Transitions in particle aggregation dynamics, mass-fractal dimensions and ordering, as a function of particle size and the concentration of the bridging polypeptide, are observed; these have significant effects on the optical properties of the assemblies. The assembly and ordering of the particles are highly complex processes that are affected by a large number of variables including the number of polypeptides bridging the particles and the particle mobility within the aggregates. A fundamental understanding of these processes is of paramount interest for the development of novel hybrid nanomaterials with tunable structural and optical properties and for the optimization of nanoparticle-based colorimetric biodetection strategies.

  • 32.
    Aldred, Nick
    et al.
    Newcastle University.
    Ekblad, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Andersson, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Clare, Anthony S.
    Newcastle University.
    Real-Time Quantification of Microscale Bioadhesion Events In situ Using Imaging Surface Plasmon Resonance (iSPR)2011In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 3, no 6, p. 2085-2091Article in journal (Refereed)
    Abstract [en]

    From macro- to nanoscales, adhesion phenomena are all-pervasive in nature yet remain poorly understood. In recent years, studies of biological adhesion mechanisms, terrestrial and marine, have provided inspiration for "biomimetic" adhesion strategies and important insights for the development of fouling-resistant materials. Although the focus of most contemporary bioadhesion research is on large organisms such as marine mussels, insects and geckos, adhesion events on the micro/nanoscale are critical to our understanding of important underlying mechanisms. Observing and quantifying adhesion at this scale is particularly relevant for the development of biomedical implants and in the prevention of marine biofouling. However, such characterization has so far been restricted by insufficient quantities of material for biochemical analysis and the limitations of contemporary imaging techniques. Here, we introduce a recently developed optical method that allows precise determination of adhesive deposition by microscale organisms in situ and in real time; a capability not before demonstrated. In this extended study we used the cypris larvae of barnacles and a combination of conventional and imaging surface plasmon resonance techniques to observe and quantify adhesive deposition onto a range of model surfaces (CH(3)-, COOH-, NH(3)-, and mPEG-terminated SAMs and a PEGMA/HEMA hydrogel). We then correlated this deposition to passive adsorption of a putatively adhesive protein from barnacles. In this way, we were able to rank surfaces in order of effectiveness for preventing barnacle cyprid exploration and demonstrate the importance of observing the natural process of adhesion, rather than predicting surface effects from a model system. As well as contributing fundamentally to the knowledge on the adhesion and adhesives of barnacle larvae, a potential target for future biomimetic glues, this method also provides a versatile technique for laboratory testing of fouling-resistant chemistries.

  • 33.
    Roder, Friedrich
    et al.
    University of Osnabruck.
    Waichman, Sharon
    University of Osnabruck.
    Paterok, Dirk
    University of Osnabruck.
    Schubert, Robin
    University of Osnabruck.
    Richter, Christian
    University of Osnabruck.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Piehler, Jacob
    University of Osnabruck.
    Reconstitution of Membrane Proteins into Polymer-Supported Membranes for Probing Diffusion and Interactions by Single Molecule Techniques2011In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 83, no 17, p. 6792-6799Article in journal (Refereed)
    Abstract [en]

    We have established a robust and versatile analytical platform for probing membrane protein function in a defined lipid environment on solid supports. This approach is based on vesicle capturing onto an ultrathin poly(ethylene glycol) (PEG) polymer brush functionalized with fatty acid moieties and subsequent vesicle fusion into a contiguous membrane. In order to ensure efficient formation of these tethered polymer-supported membranes (PSM), very small unilamellar vesicles (VSUV) containing fluorescent lipids or model transmembrane proteins were generated by detergent depletion with cyclodextrin. Thus, very rapid reconstitution of membrane proteins into PSM was possible in a format compatible with microfluidics. Moreover, surfaces could be regenerated with detergent solution and reused multiple times. Lipid and protein diffusion in these membranes was investigated by fluorescence recovery after photobleaching, single molecule tracking, and fluorescence correlation spectroscopy. Full mobility of lipids and a high degree of protein mobility as well as homogeneous diffusion of both were observed. Quantitative ligand binding studies by solid phase detection techniques confirmed functional integrity of a transmembrane receptor reconstituted into these PSM. Colocomotion of individual ligand-receptor complexes was detected, demonstrating the applicability for single molecule fluorescence techniques.

  • 34.
    Ederth, Thomas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Ekblad, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Pettitt, Michala E
    University of Birmingham.
    Conlan, Sheelagh L
    Newcastle University.
    Du, Chun-Xia
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Callow, Maureen E
    University of Birmingham.
    Callow, James A
    University of Birmingham.
    Mutton, Robert
    Newcastle University.
    Clare, Anthony S
    Newcastle University.
    D`Souza, Fraddry
    TNO Science and Industry.
    Donnelly, Glen
    TNO Science and Industry.
    Bruin, Anouk
    TNO Science and Industry.
    Willemsen, Peter R
    TNO Science and Industry.
    Su, Xueju J
    University of Dundee.
    Wang, Su
    University of Dundee.
    Zhao, Qi
    University of Dundee.
    Hederos, Markus
    Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry. Linköping University, The Institute of Technology.
    Konradsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Resistance of Galactoside-Terminated Alkanethiol Self-Assembled Monolayers to Marine Fouling Organisms2011In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 3, no 10, p. 3890-3901Article in journal (Refereed)
    Abstract [en]

    Self-assembled monolayers (SAMs) of galactoside-terminated alkanethiols have protein-resistance properties which can be tuned via the degree of methylation [Langmuir 2005, 21, 2971-2980]. Specifically, a partially methylated compound was more resistant to nonspecific protein adsorption than the hydroxylated or fully methylated counterparts. We investigate whether this also holds true for resistance to the attachment and adhesion of a range of marine species, in order to clarify to what extent resistance to protein adsorption correlates with the more complex adhesion of fouling organisms. The partially methylated galactoside-terminated SAM was further compared to a mixed monolayer of omega-substituted methyl- and hydroxyl-terminated alkanethiols with wetting properties and surface ratio of hydroxyl to methyl groups matching that of the galactoside. The settlement (initial attachment) and adhesion strength of four model marine fouling organisms were investigated, representing both micro- and macrofoulers; two bacteria (Cobetia marina and Marinobacter hydrocarbonoclasticus), barnacle cypris larvae (Balanus amphitrite), and algal zoospores (Ulva linza). The minimum in protein adsorption onto the partially methylated galactoside surface was partly reproduced in the marine fouling assays, providing some support for a relationship between protein resistance and adhesion of marine fouling organisms. The mixed alkanethiol SAM, which was matched in wettability to the partially methylated galactoside SAM, consistently showed higher settlement (initial attachment) of test organisms than the galactoside, implying that both wettability and surface chemistry are insufficient to explain differences in fouling resistance. We suggest that differences in the structure of interfacial water may explain the variation in adhesion to these SAMs.

  • 35.
    Fyrner, Timmy
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Lee, Hung-Hsun
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Mangone, Alberto
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Ekblad, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Pettitt, Michala E
    University of Birmingham, UK.
    Callow, Maureen E
    University of Birmingham, UK.
    Callow, James A
    University of Birmingham, UK.
    Conlan, Sheelagh L
    Newcastle University, UK.
    Mutton, Robert
    Newcastle University, UK.
    Clare, Anthony S
    Newcastle Universitym, UK.
    Konradsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Ederth, Thomas
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Saccharide-Functionalized Alkanethiols for Fouling-Resistant Self-Assembled Monolayers: Synthesis, Monolayer Properties, and Antifouling Behavior2011In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 24, p. 15034-15047Article in journal (Refereed)
    Abstract [en]

    We describe the synthesis of a series of mono-, di-, and trisaccharide-functionalized alkanethiols as well as the formation of fouling-resistant self-assembled monolayers (SAMs) from these. The SAls,,Is were characterized using ellipsometry, wetting measurements, and infrared reflection absorption spectroscopy (WAS). We show that the structure of the carbohydrate moiety affects the packing density and that this also alters the alkane chain organization. Upon increasing the size of the sugar moieties (from mono- to di- and trisaccharides), the structural qualities of the monolayers deteriorated with increasing disorder, and for the trisaccharide, slow reorganization dynamics in response to changes in the environmental polarity were observed. The antifouling properties of these SAMs were investigated through protein adsorption experiments from buffer solutions as well as settlement (attachment) tests using two common marine fouling species, zoospores of the green macroalga Ulva linza and cypris larvae of the barnacle Balanus amphitrite. The SAMs showed overall good resistance to fouling by both the proteins and the tested marine organisms. To improve the packing density of the SAMs with bulky headgroups, we employed mixed SAMs where the saccharide-thiols are diluted with a filler molecule having a small 2-hydroxyethyl headgroup. This method also provides a means by which the steric availability of sugar moieties can be varied, which is of interest for specific interaction studies with surface-bound sugars. The results of the surface dilution study and the low nonspecific adsorption onto the SAMs both indicate the feasibility of this approach.

  • 36.
    Nygren, Patrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Lundqvist, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Biotechnology. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Broo, Klas
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Biotechnology. Linköping University, The Institute of Technology.
    Jonsson, Bengt-Harald
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Biotechnology. Linköping University, The Institute of Technology.
    Ederth, Thomas
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Secondary structure in de novo designed peptides induced by electrostatic interaction with particles and membranes.2011Conference paper (Other academic)
  • 37.
    Palaniappan, AL
    et al.
    School of Materials Science and Engineering. Nanyang Technological University, Singapore 639798, Singapore.
    Goh, W.H
    School of Materials Science and Engineering. Nanyang Technological University, Singapore 639798, Singapore.
    Tey, J.N.
    School of Materials Science and Engineering. Nanyang Technological University, Singapore 639798, Singapore.
    Wijaya, I.P.M.
    School of Materials Science and Engineering. Nanyang Technological University, Singapore 639798, Singapore.
    Moochhala, S.M.
    School of Materials Science and Engineering. Nanyang Technological University, Singapore 639798, Singapore, DSO National Laboratories, 27 Meidical Drive, Singapore 117510, Singapore; Centre for Biomimetic Sensor Science, 50 Nanyang Drive, Singapore 637553, Singapore.
    Liedberg, Bo
    School of Materials Science and Engineering. Nanyang Technological University, Singapore 639798, Singapore, DSO National Laboratories, 27 Meidical Drive, Singapore 117510, Singapore; Centre for Biomimetic Sensor Science, 50 Nanyang Drive, Singapore 637553, Singapore.
    Mhaisalkar, S.G.
    School of Materials Science and Engineering. Nanyang Technological University, Singapore 639798, Singapore, DSO National Laboratories, 27 Meidical Drive, Singapore 117510, Singapore; Centre for Biomimetic Sensor Science, 50 Nanyang Drive, Singapore 637553, Singapore.
    Aligned carbon nanotubes on quartz substrate for liquid gated biosensing2010In: Biosensors and Bioelectronics, Vol. 25, p. 1989-1993Article in journal (Refereed)
    Abstract [en]

    A facile and high performance biosensing platform using aligned carbon nanotubes on quaratz substrate is reported in this communication. Single walled carbon nanotubes are grown on quartz substrates by a chemical vapor despotition process and are characterized with field emission scanning electron microscopy and atomic force microscopy in order to verify the quality of the material. The quartz substrate is then directly used as a biosensor in a field effect transistor configuration. In order to demonstrate the sensing capabilities of the fabricated sensor devices, electronic detection of prostate specific antigen, a potential cancer biomarker, is carried out by adopting liquid gated configuration. A conductivity change due to the specific binding of target antigen with the immobilized receptor andtibody demonstrates the sensing capabilities of the fabricated device. Sub-nM detection sensitivities have been obtained using the adopted direct immunoassay approach, which shows that the device responds to clinically relevant concentration regimes

  • 38.
    Faxälv, Lars
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Laboratory Medicine, Department of Clinical Chemistry.
    Ekblad, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Lindahl, Tomas L.
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Laboratory Medicine, Department of Clinical Chemistry.
    Blood compatibility of photografted hydrogel coatings2010In: ACTA BIOMATERIALIA, ISSN 1742-7061, Vol. 6, no 7, p. 2599-2608Article in journal (Other academic)
    Abstract [en]

    In this work we have evaluated the haemocompatibility of different surface modifications, intended for biomaterials and biosensor applications. Polystyrene slides were coated with thin hydrogel films by self-initiated photografting of four different monomers. The hydrogel surface modifications were thoroughly characterized and tested for their protein resistance and ability to facilitate platelet adhesion and activation of the coagulation system. There was very little protein adsorption from human plasma on the hydrogels formed from poly(ethylene glycol) methacrylate (PEGMA) and 2-hydroxyethyl methacrylate (HEMA). Platelet adhesion tests performed under both static and flow conditions showed that these coatings also demonstrated very high resistance towards platelet adhesion. A small amount of platelets were found to adhere to hydrogels formed from ethylene glycol methyl ether methacrylate (EGMEMA) and 2-carboxyethyl methacrylate (CEA). The polystyrene substrates themselves facilitated large amounts of platelet adhesion under both static and flow conditions. Utilizing a novel setup for imaging of coagulation, it was shown that none of the hydrogel surfaces activated the coagulation system to any great extent. We suggest that this simple fabrication method can be used to produce hydrogel coatings with unusually high blood compatibility, suitable for demanding biomaterials applications.

  • 39.
    Andrésen, Cecilia
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Biotechnology . Linköping University, The Institute of Technology.
    Jalal, Shah
    Karolinska University Hospital.
    Aili, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Wang, Yi
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Islam, Sohidul
    Karolinska University Hospital.
    Jarl, Anngelica
    Linköping University, Department of Physics, Chemistry and Biology, Molecular genetics . Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Wretlind, Bengt
    Karolinska University Hospital.
    Mårtensson, Lars-Göran
    Linköping University, Department of Physics, Chemistry and Biology, Biochemistry. Linköping University, The Institute of Technology.
    Sunnerhagen, Maria
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Biotechnology . Linköping University, The Institute of Technology.
    Critical biophysical properties in the Pseudomonas aeruginosa efflux gene regulator MexR are targeted by mutations conferring multidrug resistance2010In: Protein Science, ISSN 0961-8368, E-ISSN 1469-896X, Vol. 19, no 4, p. 680-692Article in journal (Refereed)
    Abstract [en]

    The self-assembling MexA-MexB-OprM efflux pump system, encoded by the mexO operon, contributes to facile resistance of Pseudomonas aeruginosa by actively extruding multiple antimicrobials. MexR negatively regulates the mexO operon, comprising two adjacent MexR binding sites, and is as such highly targeted by mutations that confer multidrug resistance (MDR). To understand how MDR mutations impair MexR function, we studied MexR-wt as well as a selected set of MDR single mutants distant from the proposed DNA-binding helix. Although DNA affinity and MexA-MexB-OprM repression were both drastically impaired in the selected MexR-MDR mutants, MexR-wt bound its two binding sites in the mexO with high affinity as a dimer. In the MexR-MDR mutants, secondary structure content and oligomerization properties were very similar to MexR-wt despite their lack of DNA binding. Despite this, the MexR-MDR mutants showed highly varying stabilities compared with MexR-wt, suggesting disturbed critical interdomain contacts, because mutations in the DNA-binding domains affected the stability of the dimer region and vice versa. Furthermore, significant ANS binding to MexR-wt in both free and DNA-bound states, together with increased ANS binding in all studied mutants, suggest that a hydrophobic cavity in the dimer region already shown to be involved in regulatory binding is enlarged by MDR mutations. Taken together, we propose that the biophysical MexR properties that are targeted by MDR mutations stability, domain interactions, and internal hydrophobic surfaces are also critical for the regulation of MexR DNA binding.

  • 40.
    Becker, Richard
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Inorganic Chemistry . Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Inorganic Chemistry . Linköping University, The Institute of Technology.
    CTAB promoted synthesis of Au nanorods - Temperature effects and stability consideration2010In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 343, no 1, p. 25-30Article in journal (Refereed)
    Abstract [en]

    A systematic study is performed of the influence of surfactant and temperature on the aspect ratio and monodispersity of Au nanorods, synthesized by a seed-mediated growth technique in water using cetyltrimethylammonium bromide (CTAB) as surfactant. The changes in aspect ratio with temperature show an "anomalous" behaviour, where the aspect ratio first decreases with increasing temperature, reaching a minimum at about 55oC, and after that increases again reaching a maximum at about 80oC. A physical explanation of the observed behaviour is proposed. It has also been studied how the CTAB concentration in the cleansing water used in the post-synthesis treatment of the samples affected the stability of the gold suspension. It was found that without the presence of a surfactant such as CTAB in the washing medium, only very few centrifugations can be carried out without considerable loss of product. Characterization of prepared samples was performed with UV-Vis and TEM.

  • 41.
    Myrskog, Annica
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Anderson, Henrik
    Attana AB, Björnnäsvägen 21, SE-114 19 Stockholm, Sweden/Uppsala University, Ångström Laboratory, Solid State Electronics, P.O. Box 534, SE-751 21 Uppsala, Sweden.
    Ingemarsson, Björn
    Attana AB, Björnnäsvägen 21, SE-114 19 Stockholm, Sweden.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Esterification of self-assembled carboxylic acid-terminated thiolmonolayers in acid environment: A time dependent study2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 2, p. 821-829Article in journal (Refereed)
    Abstract [en]

    This contribution reports on the influence of acids on the quality of carboxylic acid terminated self-assembled monolayers (SAMs) on gold prepared from ethanolic solution of HS-(CH2)15-COOH and HS-(CH2)11CONH–(EG)6CH2-COOH. Null ellipsometry, contact angle goniometry and infrared reflection-absorption spectroscopy are used to monitor the physical and chemical changes occurring within the SAMs upon acid post treatment; after incubation with acids present in the solution; and after incubation in aged acid containing solutions. The presence of acid has a positive effect on the crystallinity, packing and orientation of the supporting alkyl and ethylene glycol subunits of the SAM. Our studies also confirm previous findings stating that the carboxylic groups are rapidly converted into ethyl ester groups in the presence of hydrochloric acid in the incubation solution. It is also evident that the conversion occurs in the presence of the weaker acid, acetic acid, although at a much slower rate than for hydrochloric acid. This is a new observation that has not been reported on before. The physical and chemical characterization is also complemented with a functional bioaffinity study. The functional evaluation revealed that the present model system was surprisingly insensitive to the degree of esterification of the carboxylic acid SAMs, but that 4 weeks of storage of the two investigated thiols in hydrochloric acid containing ethanol resulted in SAMs that were completely inactive with respect to immobilization and subsequent binding of the antigen. It was encouraging to note that the non-specific binding of both antigen and antibody was extremely low on the two SAMs, regardless of the relative amount of ethyl esters on the surface.

  • 42.
    Ekblad, Tobias
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Faxälv, Lars
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Laboratory Medicine, Department of Clinical Chemistry.
    Andersson, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Wallmark, Nanny
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Larsson (Kaiser), Andréas
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Lindahl, Tomas L.
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Laboratory Medicine, Department of Clinical Chemistry.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Patterned Hydrogels for Controlled Platelet Adhesion from Whole Blood and Plasma2010In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 20, no 15, p. 2396-2403Article in journal (Refereed)
    Abstract [en]

    This work describes the preparation and properties of hydrogel surface chemistries enabling controlled and well-defined cell adhesion. The hydrogels may be prepared directly on plastic substrates, such as polystyrene slides or dishes, using a quick and experimentally simple photopolymerization process, compatible with photolithographic and microfluidic patterning methods. The intended application for these materials is as substrates for diagnostic cell adhesion assays, particularly for the analysis of human platelet function. The adsorption of fibrinogen and other platelet promoting molecules is shown to be completely inhibited by the hydrogel, provided that the film thickness is sufficient (>5 nm). This allows the hydrogel to be used as a matrix for presenting selected bioactive ligands without risking interference from nonspecifically adsorbed platelet adhesion factors, even in undiluted whole blood and blood plasma. This concept is demonstrated by preparing patterns of proteins on hydrogel surfaces, resulting in highly controlled platelet adhesion. Further insights into the protein immobilization and platelet adhesion processes are provided by studies using imaging surface plasmon resonance. The hydrogel surfaces used in this work appear to provide an ideal platform for cell adhesion studies of platelets, and potentially also for other cell types.

  • 43.
    Ekblad, Tobias
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Protein adsorption and surface patterning2010In: CURRENT OPINION IN COLLOID and INTERFACE SCIENCE, ISSN 1359-0294, Vol. 15, no 6, p. 499-509Article, review/survey (Refereed)
    Abstract [en]

    Surface patterning has become an important discipline of biologically oriented surface science over the past decades Many methods have been developed that allow the formation of patterns on the micro- and nanoscalle This Opinion discusses the role of protein adsorption in patterning technologies highlighting how it can be used as an integrated part of the patterning process how it can be controlled by patterns with appropriate properties and how it may lead to disruption of formed patterns if not properly accounted for Recent examples from literature are used to emphasize some of the most interesting developments in the field such as novel surface chemistries only allowing specific protein adsorption directed self-sorting adsorption of proteins on patterned surfaces and control of protein adsorption through nanopatterning

  • 44.
    Nygren, Patrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Lundqvist, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Biotechnology. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Jonsson, Bengt-Harald
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Biotechnology. Linköping University, The Institute of Technology.
    Ederth, Thomas
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Secondary Structure in de Novo Designed Peptides Induced by Electrostatic Interaction with a Lipid Bilayer Membrane2010In: LANGMUIR, ISSN 0743-7463, Vol. 26, no 9, p. 6437-6448Article in journal (Refereed)
    Abstract [en]

    We show that it is possible to induce a defined secondary structure in de nova designed peptides upon electrostatic attachment to negatively charged lipid bilayer vesicles without partitioning of the peptides into the membrane, and that the secondary structure can be varied via small changes in the primary amino acid sequence of the peptides. The peptides have a random-coil conformation in solution, and results from far-UV circular dichroism spectroscopy demonstrate that the structure induced by the interaction with silica nanoparticles is solely alpha-helical and also strongly pH-dependent. The present study shows that negatively charged vesicles, to which the peptides are electrostatically adsorbed via cationic amino acid residues, induce either alpha-helices or beta-sheets and that the conformation is dependent on both lipid composition and variations in peptide primary structure. The pH-dependence of the vesicle-induced peptide secondary structure is weak, which correlates well with small differences in the vesicles electrophoretic mobility, and thus the surface charge, as the pH is varied.

  • 45.
    Becker, Richard
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Söderlind, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Synthesis of silver nanowires in aqueous solutions2010In: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 64, no 8, p. 956-958Article in journal (Refereed)
    Abstract [en]

    Silver nanowires with a diameter of 30 nm and typical lengths of 5–10 μm have been synthesized in an aqueous medium. To initiate the reaction, citrate ions were used, and during the reaction the aromatic organicmolecules polymerize forming “straight” chain surfactants which support the formation of nanowires. Characterization by TEM and HRETM revealed the nanowires to be highly crystalline with a growth along the [110] direction.

  • 46.
    Aili, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Selegård, Robert
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Baltzer, Lars
    Division of Organic Chemistry, Department of Biochemistry and Organic Chemistry, BMC, Box 576, Uppsala University, SE-751 23 Uppsala, Sweden.
    Enander, Karin
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Colorimetric Protein Sensing by Controlled Assembly of Gold Nanoparticles Functionalized with Synthetic Receptors2009In: Small, ISSN 1613-6810, Vol. 5, no 21, p. 2445-2452Article in journal (Refereed)
    Abstract [en]

    A strategy for colorimetric sensing of proteins, based on the induced assembly of polypeptide-functionalized gold nanoparticles, is described. Recognition was accomplished using a polypeptide sensor scaffold designed to specifically bind the model analyte, human carbonic anhydrase II (HCAII). The extent of particle aggregation, induced by the Zn2+-triggered dimerization and folding of a second polypeptide also present on the surface of the gold nanoparticle, gave a readily detectable colorimetric shift that was dependent on the concentration of the target protein. In the absence of HCAII, particle aggregation resulted in a major redshift of the plasmon peak whereas analyte binding prevented formation of dense aggregates, significantly reducing the magnitude of the redshift. The limit of detection of HCAII was estimated to be around 15 nM. The versatility of the technique was demonstrated using a second model system based on the recognition of a peptide sequence from the tobacco mosaic virus coat protein (TMVP by a recombinant antibody fragment. This strategy is proposed as a generic platform for robust and specific protein analysis that can be further developed for monitoring a wide range of target proteins.

  • 47.
    Aili, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Selegård, Robert
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Baltzer, Lars
    Uppsala University .
    Enander, Karin
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Colorimetric sensing: Small 21/20092009In: Small, ISSN 1613-6810, E-ISSN 1613-6829, Vol. 5, no 21Article in journal (Other academic)
    Abstract [en]

    The cover picture illustrates a novel concept for colorimetric protein sensing based on the controllable assembly of polypeptide-functionalized gold nanoparticles. Recognition of the analyte is accomplished by polypeptide-based synthetic receptors immobilized on gold nanoparticles. Also present on the particle surface is a de novo-designed helix-loop-helix polypeptide that homodimerizes and folds into four-helix bundles in the presence of Zn2+, resulting in particle aggregation. Analyte binding interferes with the folding-induced aggregation, giving rise to a clearly detectable colorimetric response.

  • 48.
    Bittoun, Eyal
    et al.
    Technion Israel Institute Technology.
    Marmur, Abraham
    Technion Israel Institute Technology.
    Östblom, Mattias
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Ederth, Thomas
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Filled Nanoporous Surfaces: Controlled Formation and Wettability2009In: LANGMUIR, ISSN 0743-7463, Vol. 25, no 20, p. 12374-12379Article in journal (Refereed)
    Abstract [en]

    The controlled filling of hydrophobic nanoporous surfaces with hydrophilic molecules and their wetting properties are described and demonstrated by using thiocholesterol (TC) self-assembled monolayers (SAMs) on gold and mercaptoundecanoic acid (MUA) as the filling agent. A novel procedure was developed for filling the nanopores in the TC SAMs by immersing them into a "cocktail" solution of TC and MUA, with TC in huge excess. This procedure results in an increasing coverage of MUA with increasing immersion time up to an area fraction of similar to 23%, while the amount of TC remains almost constant. Our findings strongly support earlier observations where linear omega-substituted alkanethiols selectively fill defects (nanopores) in the TC SAM (Yang et al. Langmuir 1997, 12, 1704-1707). They also support the formation of a homogeneously mixed SAM, given by the distribution of TC on the gold surface, rather than of a phase-segregated overlayer structure with domains of varying size, shape, and composition. The wetting properties of the Filled SAMs were investigated by measuring the most stable contact angle as well as contact angle hysteresis. It is shown that the most stable contact angle is very well described by the Cassie equation, since the drops arc much larger than the scale of chemical heterogeneity of the SAM surfaces. In addition, it is demonstrated that contact angle hysteresis is sensitive to the chemical heterogeneity of the surface, even at the nanometric scale.

  • 49.
    Andersson, Olof
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Larsson (Kaiser), Andréas
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Ekblad, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Gradient Hydrogel Matrix for Microarray and Biosensor Applications: An Imaging SPR Study2009In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 10, no 1, p. 142-148Article in journal (Refereed)
    Abstract [en]

    A biosensor matrix based on UV-initiated graft copolymerized poly(ethylene glycol) methacrylate and 2-hydroxyethyl methacrylate has been studied using imaging surface plasmon resonance (iSPR). By using a photo mask and a programmable shutter to vary the exposure time laterally, a gradient of matrix spots with physical thicknesses ranging from a few to tens of nanometers was generated. To maximize the dynamic range, imaging SPR was employed in wavelength interrogation mode. By finding the minimum in the reflectance spectra from each pixel of an image, SPR wavelength maps were constructed. The shift in SPR wavelength upon biospecific interaction was then measured both as a function of matrix thickness and composition. The performance of the matrix was evaluated in terms of immobilization of human serum albumin, biomolecular interaction with its antibody, and nonspecific binding of human fibrinogen. In addition, a low molecular weight interaction pair based on a synthetic polypeptide and calmodulin was also studied to explore the size selectivity of the hydrogel matrix. Our results show that the gradient matrix exhibits excellent properties for quick evaluation and screening of optimal hydrogel performance. The mixed hydrogel matrices display very low levels of nonspecific binding. It is also evident that the low molecular weight calmodulin is capable of freely diffusing and interacting throughout the entire hydrogel matrix, whereas the much larger albumin and its corresponding antibody, in particular, are partly/completely hindered from penetrating the interior of the matrix. This size-selectivity is attributed to a significant UV-initiated cross-linking or branching of the matrix during fabrication and/or protein mediated multipoint attachment during immobilization.

  • 50.
    Ederth, Thomas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Pettitt, M E
    University of Birmingham.
    Nygren, Patrik
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Du, Chun-Xia
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Ekblad, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Zhou, Ye
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Falk, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Callow, M E
    University of Birmingham.
    Callow, J A
    University of Birmingham.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Interactions of Zoospores of Ulva linza with Arginine-Rich Oligopeptide Monolayers2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 16, p. 9375-9383Article in journal (Refereed)
    Abstract [en]

    We recently reported oil the strong interactions of zoospores of the green alga, Ulva linza with all arginine-rich oligopeptide self-assembled monolayer (SAM) [Biofouling 2008, 24, 303-312], where the arginine-rich peptide induced not only high spore settlement, but also a form of abnormal settlement, or "pseudo-settlement", whereby it proportion of spores do not go through the normal process of surface exploration, adhesive exocytosis, and loss of flagella. Further. it was demonstrated that both the total number of settled spores and the fraction of pseudosettled spores were related to the surface density of the arginine-rich peptide. Here we present a further investigation of the interactions of zoospores of ulva with a set of oligomeric, de nom designed, arginine-rich peptides, specifically aimed to test the effect of peptide primary structure on the interaction. Via variations in the peptide length and by permutations in the amino acid sequences, we gain further insight into the spore-surface interactions. The interpretation of the biological assays is supported by physicochemical characterization of the SAMs using infrared spectroscopy, ellipsometry, and contact angle measurement. Results confirm the importance of arginine residues for the anomalous pseudosettlement, and we found that settlement is modulated by variations in both the total length and peptide primary structure. To elucidate the Causes of the anomalous settlement and the possible relation to peptide-membrane interactions, we also compared the settlement of the "naked" zoospores of Ulva(which present it lipoprotein membrane to the exterior without a discrete polysaccharide cell wall), with the settlement of diatoms (unicellular algae that are surrounded by it silica cell wall), onto the peptide SAMs. Cationic SAMs do not notably affect settlement (attachment), adhesion strength, or viability of diatom cells, Suggesting that the effect of the peptides on zoospores of Ulva is mediated via specific peptide-membrane interactions.

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