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  • 1.
    Ahrén, Maria
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Olsson, Petter
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Söderlind, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Klasson, Anna
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Health Sciences, Radiology . Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Petoral, Rodrigo Jr
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Engström, Maria
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Käll, Per-Olov
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Uvdal, Kajsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Rare earth nanoparticles as contrast agent in MRI: Nanomaterial design and biofunctionalization2007In: IVC-17/ICSS-13 ICNT,2007, 2007Conference paper (Other academic)
  • 2. Aifa, Sami
    et al.
    Johansen, Knut
    Nilsson, Ulrica K
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Pharmacology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Svensson, Samuel
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Pharmacology.
    Interactions between the juxtamembrane domain of the EGFR and calmodulin measured by surface plasmon resonance2002In: Cellular Signalling, ISSN 0898-6568, E-ISSN 1873-3913, Vol. 14, no 12, p. 1005-1013Article in journal (Refereed)
    Abstract [en]

    One early response to epidermal growth factor receptor (EGFR) activation is an increase in intracellular calcium. We have used surface plasmon resonance (SPR) to study real-time interactions between the intracellular juxtamembrane (JM) region of EGFR and calmodulin. The EGFR-JM (Met644-Phe688) was expressed as a GST fusion protein and immobilised on a sensor chip surface. Calmodulin specifically interacts with EGFR-JM in a calcium-dependent manner with a high on and high off rate. Chemical modification of EGFR-JM by using arginine-selective phenylglyoxal or deletion of the basic segment Arg645-Arg657 inhibits the interaction. Phosphorylation of EGFR-JM by protein kinase C (PKC) or glutamate substitution of Thr654 inhibits the interaction, suggesting that PKC phosphorylation electrostatically interferes with calmodulin binding to basic arginine residues. Calmodulin binding was also inhibited by suramin. Our results suggest that EGFR-JM is essential for epidermal growth factor (EGF)-mediated calcium-calmodulin signalling and for signal integration between other signalling pathways.

  • 3.
    Aili, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Polypeptide-Based Nanoscale Materials2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Self-assembly has emerged as a promising technique for fabrication of novel hybrid materials and nanostructures. The work presented in this thesis has been focused on developing nanoscale materials based on synthetic de novo designed polypeptides. The polypeptides have been utilized for the assembly of gold nanoparticles, fibrous nanostructures, and for sensing applications.

    The 42-residue polypeptides are designed to fold into helix-loop-helix motifs and dimerize to form four-helix bundles. Folding is primarily driven by the formation of a hydrophobic core made up by the hydrophobic faces of the amphiphilic helices. The peptides have either a negative or positive net charge at neutral pH, depending on the relative abundance of Glu and Lys. Charge repulsion thus prevents homodimerization at pH 7 while promoting hetero-dimerization through the formation of stabilising salt bridges. A Cys incorporated in position 22, located in the loop region, allowed for directed, thiol-dependent, immobilization on planar gold surfaces and gold nanoparticles. The negatively charged (Glu-rich) peptide formed homodimers and folded in solution at pH < 6 or in the presence of certain metal ions, such as Zn2+. The folding properties of this peptide were retained when immobilized directly on gold, which enabled reversible assembly of gold nanoparticles resulting in aggregates with well-defined interparticle separations. Particle aggregation was found to induce folding of the immobilized peptides but folding could also be utilized to induce aggregation of the particles by exploiting the highly specific interactions involved in both homodimerization and hetero-association. The possibility to control the assembly of polypeptide-functionalized gold nanoparticles was utilized in a colorimetric protein assay. Analyte binding to immobilized ligands prevented the formation of dense particle aggregates when subjecting the particles to conditions normally causing extensive aggregation. Analyte binding could hence easily be distinguished by the naked eye. Moreover, the peptides were utilized to assemble gold nanoparticles on planar gold and silica substrates.

    Fibrous nanostructures were realized by linking monomers through a disulphide-bridge. The disulphide-linked peptides were found to spontaneously assemble into long and extremely thin peptide fibres as a result of a propagating association mediated by folding into four-helix bundles.

    List of papers
    1. Alpha-helix-inducing dimerization of synthetic polypeptide scaffolds on gold
    Open this publication in new window or tab >>Alpha-helix-inducing dimerization of synthetic polypeptide scaffolds on gold
    Show others...
    2005 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, no 6, p. 2480-2487Article in journal (Refereed) Published
    Abstract [en]

    Designed, synthetic polypeptides that assemble into four-helix bundles upon dimerization in solution were studied with respect to folding on planar gold surfaces. A model system with controllable dimerization properties was employed, consisting of negatively and positively charged peptides. Circular dichroism spectroscopy and surface plasmon resonance based measurements showed that at neutral pH, the peptides were able to form heterodimers in solution, but unfavorable electrostatic interactions prevented the formation of homodimers. The dimerization propensity was found to be both pH- and buffer-dependent. A series of infrared absorption−reflection spectroscopy experiments of the polypeptides attached to planar gold surfaces revealed that if the negatively charged peptide was immobilized from a loading solution where it was folded, its structure was retained on the surface provided it had a cysteine residue available for anchoring to gold. If it was immobilized as random coil, it remained unstructured on the surface but was able to fold through heterodimerization if subsequently exposed to a positively charged polypeptide. When the positively charged peptide was immobilized as random coil, heterodimerization could not be induced, probably because of high-affinity interactions between the charged primary amine groups and the gold surface. These observations are intended to pave the way for future engineering of functional surfaces based on polypeptide scaffolds where folding is known to be crucial for function.

    Place, publisher, year, edition, pages
    ACS Publications, 2005
    National Category
    Other Basic Medicine
    Identifiers
    urn:nbn:se:liu:diva-15115 (URN)10.1021/la048029u (DOI)
    Available from: 2008-10-16 Created: 2008-10-16 Last updated: 2018-01-12Bibliographically approved
    2. Aggregation-Induced Folding of a de novo Designed Polypeptide Immobilized on Gold Nanoparticles
    Open this publication in new window or tab >>Aggregation-Induced Folding of a de novo Designed Polypeptide Immobilized on Gold Nanoparticles
    Show others...
    2006 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 128, no 7, p. 2194 -2195Article in journal (Refereed) Published
    Abstract [en]

    This communication reports the first steps in the construction of a novel, nanoparticle-based hybrid material for biomimetic and biosensor applications. Gold nanoparticles were modified with synthetic polypeptides to enable control of the particle aggregation state in a switchable manner, and particle aggregation was, in turn, found to induce folding of the immobilized peptides.

    Place, publisher, year, edition, pages
    ACS Publications, 2006
    Keywords
    Not aviable
    National Category
    Other Basic Medicine
    Identifiers
    urn:nbn:se:liu:diva-14041 (URN)10.1021/ja057056j (DOI)
    Available from: 2006-09-28 Created: 2006-09-28 Last updated: 2018-01-13Bibliographically approved
    3. Folding Induced Assembly of Polypeptide Decorated Gold Nanoparticles
    Open this publication in new window or tab >>Folding Induced Assembly of Polypeptide Decorated Gold Nanoparticles
    Show others...
    2008 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 130, no 17, p. 5780-5788Article in journal (Refereed) Published
    Abstract [en]

    Reversible assembly of gold nanoparticles controlled by the homodimerization and folding of an immobilized de novo designed synthetic polypeptide is described. In solution at neutral pH, the polypeptide folds into a helix–loop–helix four-helix bundle in the presence of zinc ions. When immobilized on gold nanoparticles, the addition of zinc ions induces dimerization and folding between peptide monomers located on separate particles, resulting in rapid particle aggregation. The particles can be completely redispersed by removal of the zinc ions from the peptide upon addition of EDTA. Calcium ions, which do not induce folding in solution, have no effect on the stability of the peptide decorated particles. The contribution from folding on particle assembly was further determined utilizing a reference peptide with the same primary sequence but containing both D and L amino acids. Particles functionalized with the reference peptide do not aggregate, as the peptides are unable to fold. The two peptides, linked to the nanoparticle surface via a cysteine residue located in the loop region, form submonolayers on planar gold with comparable properties regarding surface density, orientation, and ability to interact with zinc ions. These results demonstrate that nanoparticle assembly can be induced, controlled, and to some extent tuned, by exploiting specific molecular interactions involved in polypeptide folding.

    Place, publisher, year, edition, pages
    ACS Publications, 2008
    National Category
    Other Basic Medicine
    Identifiers
    urn:nbn:se:liu:diva-15116 (URN)10.1021/ja711330f (DOI)
    Available from: 2008-10-16 Created: 2008-10-16 Last updated: 2018-01-12Bibliographically approved
    4. Controlled Assembly of Gold Nanoparticles using De Novo Designed Polypeptide Scaffolds
    Open this publication in new window or tab >>Controlled Assembly of Gold Nanoparticles using De Novo Designed Polypeptide Scaffolds
    Show others...
    2008 (English)In: Proceedings SPIE, Vol. 6885, Photonic Biosensing and Microoptics, 2008, p. 688506-1-688506-8Conference paper, Published paper (Refereed)
    Abstract [en]

    Heterodimerization between designed helix-loop-helix polypeptides was utilized in order to assemble gold nanoparticles on planar substrates. The peptides were designed to fold into four-helix bundles upon dimerization. A Cys-residue in the loop region was used to immobilize one of the complementary peptides on a maleimide containing SAM on planar gold substrates whereas the second peptide was immobilized directly on gold nanoparticles. Introducing the peptide decorated particles over a peptide functionalized surface resulted in particle assembly. Further, citrate stabilized particles were assembled on amino-silane modified glass and silicon substrates. By subsequently introducing peptides and gold nanoparticles, particle-peptide hybrid multi layers could be formed.

    Keywords
    Heterodimerization, polypeptides, gold nanoparticles, four-helix bundle, helix-loop-helix, self-assembly
    National Category
    Other Basic Medicine
    Identifiers
    urn:nbn:se:liu:diva-15118 (URN)10.1117/12.775806 (DOI)
    Available from: 2008-10-16 Created: 2008-10-16 Last updated: 2018-01-12Bibliographically approved
    5. Self-Assembly of Fibers and Nanorings from Disulfide-Linked Helix–Loop–Helix Polypeptides
    Open this publication in new window or tab >>Self-Assembly of Fibers and Nanorings from Disulfide-Linked Helix–Loop–Helix Polypeptides
    Show others...
    2008 (English)In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 47, no 30, p. 5554-5556Article in journal (Refereed) Published
    Place, publisher, year, edition, pages
    Wiley InterScience, 2008
    Keywords
    fibers, helical structures, nanostructures, polypeptides, self-assembly
    National Category
    Other Basic Medicine
    Identifiers
    urn:nbn:se:liu:diva-15120 (URN)10.1002/anie.200801155 (DOI)
    Available from: 2008-10-16 Created: 2008-10-16 Last updated: 2018-01-12Bibliographically approved
    6. Assembly of Polypeptide-Functionalized Gold Nanoparticles through a Heteroassociation- and Folding-Dependent Bridging
    Open this publication in new window or tab >>Assembly of Polypeptide-Functionalized Gold Nanoparticles through a Heteroassociation- and Folding-Dependent Bridging
    2008 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 8, no 8, p. 2473-2478Article in journal (Refereed) Published
    Abstract [en]

    Gold nanoparticles were functionalized with a synthetic polypeptide, de novo-designed to associate with a charge complementary linker polypeptide in a folding-dependent manner. A heterotrimeric complex that folds into two disulphide-linked four-helix bundles is formed when the linker polypeptide associates with two of the immobilized peptides. The heterotrimer forms in between separate particles and induces a rapid and extensive aggregation with a well-defined interparticle spacing. The aggregated particles are redispersed when the disulphide bridge in the linker polypeptide is reduced.

    Place, publisher, year, edition, pages
    ACS Publications, 2008
    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:liu:diva-15121 (URN)10.1021/nl8014796 (DOI)
    Note
    The original title of this article was "Assembly of Decorated Gold Nanoparticles through a Hetero-Association and Folding-Dependent Bridging".Available from: 2008-10-16 Created: 2008-10-16 Last updated: 2017-12-07
    7. Colorimetric Protein Sensing by Controlled Assembly of Gold Nanoparticles Functionalized with Synthetic Receptors
    Open this publication in new window or tab >>Colorimetric Protein Sensing by Controlled Assembly of Gold Nanoparticles Functionalized with Synthetic Receptors
    Show others...
    2009 (English)In: Small, ISSN 1613-6810, Vol. 5, no 21, p. 2445-2452Article in journal (Refereed) Published
    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.

    Keywords
    Not available.
    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:liu:diva-15122 (URN)10.1002/smll.200900530 (DOI)
    Available from: 2008-10-16 Created: 2008-10-16 Last updated: 2015-05-29Bibliographically approved
  • 4.
    Aili, Daniel
    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.
    Baltzer, Lars
    Division of Organic Chemistry, Department of Biochemistry and Organic Chemistry, BMC, Box 576, Uppsala UniVersity, SE-751 23 Uppsala, Sweden.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Assembly of Polypeptide-Functionalized Gold Nanoparticles through a Heteroassociation- and Folding-Dependent Bridging2008In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 8, no 8, p. 2473-2478Article in journal (Refereed)
    Abstract [en]

    Gold nanoparticles were functionalized with a synthetic polypeptide, de novo-designed to associate with a charge complementary linker polypeptide in a folding-dependent manner. A heterotrimeric complex that folds into two disulphide-linked four-helix bundles is formed when the linker polypeptide associates with two of the immobilized peptides. The heterotrimer forms in between separate particles and induces a rapid and extensive aggregation with a well-defined interparticle spacing. The aggregated particles are redispersed when the disulphide bridge in the linker polypeptide is reduced.

  • 5.
    Aili, Daniel
    et al.
    Linköping University, The Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Enander, Karin
    Linköping University, The Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Rydberg, Johan
    Linköping University, The Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Nesterenko, Irina
    Linköping University, The Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Björefors, Fredrik
    Linköping University, The Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Baltzer, Lars
    Division of Organic Chemistry, Department of Biochemistry and Organic Chemistry, BMC, Box 599, Uppsala University, SE-751 24 Uppsala, Sweden..
    Liedberg, Bo
    Linköping University, The Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Controlled Assembly of Gold Nanoparticles using De Novo Designed Polypeptide Scaffolds2008In: Proceedings SPIE, Vol. 6885, Photonic Biosensing and Microoptics, 2008, p. 688506-1-688506-8Conference paper (Refereed)
    Abstract [en]

    Heterodimerization between designed helix-loop-helix polypeptides was utilized in order to assemble gold nanoparticles on planar substrates. The peptides were designed to fold into four-helix bundles upon dimerization. A Cys-residue in the loop region was used to immobilize one of the complementary peptides on a maleimide containing SAM on planar gold substrates whereas the second peptide was immobilized directly on gold nanoparticles. Introducing the peptide decorated particles over a peptide functionalized surface resulted in particle assembly. Further, citrate stabilized particles were assembled on amino-silane modified glass and silicon substrates. By subsequently introducing peptides and gold nanoparticles, particle-peptide hybrid multi layers could be formed.

  • 6.
    Aili, Daniel
    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.
    Rydberg, Johan
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Nesterenko, Irina
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Björefors, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Baltzer, Lars
    Department of Biochemistry and Organic Chemistry, BMC, Box 599, Uppsala UniVersity, SE-751 24 Uppsala, Sweden.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Folding Induced Assembly of Polypeptide Decorated Gold Nanoparticles2008In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 130, no 17, p. 5780-5788Article in journal (Refereed)
    Abstract [en]

    Reversible assembly of gold nanoparticles controlled by the homodimerization and folding of an immobilized de novo designed synthetic polypeptide is described. In solution at neutral pH, the polypeptide folds into a helix–loop–helix four-helix bundle in the presence of zinc ions. When immobilized on gold nanoparticles, the addition of zinc ions induces dimerization and folding between peptide monomers located on separate particles, resulting in rapid particle aggregation. The particles can be completely redispersed by removal of the zinc ions from the peptide upon addition of EDTA. Calcium ions, which do not induce folding in solution, have no effect on the stability of the peptide decorated particles. The contribution from folding on particle assembly was further determined utilizing a reference peptide with the same primary sequence but containing both D and L amino acids. Particles functionalized with the reference peptide do not aggregate, as the peptides are unable to fold. The two peptides, linked to the nanoparticle surface via a cysteine residue located in the loop region, form submonolayers on planar gold with comparable properties regarding surface density, orientation, and ability to interact with zinc ions. These results demonstrate that nanoparticle assembly can be induced, controlled, and to some extent tuned, by exploiting specific molecular interactions involved in polypeptide folding.

  • 7.
    Aili, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Tai, Feng-I
    Linköping University, Department of Physics, Chemistry and Biology. 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.
    Baltzer, Lars
    Department of Biochemistry andOrganic Chemistry Uppsala University, BMC, Box 576, 75123 Uppsala, Sweden.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Self-Assembly of Fibers and Nanorings from Disulfide-Linked Helix–Loop–Helix Polypeptides2008In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 47, no 30, p. 5554-5556Article in journal (Refereed)
  • 8.
    Aili, Daniel
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Enander, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Baltzer, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Synthetic de novo designed polypeptides for control of nanoparticle assembly and biosensing2007In: Bionanotechnology; from self-assembly to cellbiology,2007, London: Biochemical Society Transactions , 2007, p. 532-Conference paper (Refereed)
    Abstract [en]

         

  • 9.
    Aili, Daniel
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Enander, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Baltzer, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Towards novel functional materials and sensors using de novo designed polypeptides on gold nanoparticles2006In: Europtrode VIII,2006, 2006Conference paper (Other academic)
    Abstract [en]

        

  • 10.
    Aili, Daniel
    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.
    Rydberg, Johan
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Baltzer, Lars
    Linköping University, Department of Physics, Chemistry and Biology. 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.
    Aggregation-Induced Folding of a de novo Designed Polypeptide Immobilized on Gold Nanoparticles2006In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 128, no 7, p. 2194 -2195Article in journal (Refereed)
    Abstract [en]

    This communication reports the first steps in the construction of a novel, nanoparticle-based hybrid material for biomimetic and biosensor applications. Gold nanoparticles were modified with synthetic polypeptides to enable control of the particle aggregation state in a switchable manner, and particle aggregation was, in turn, found to induce folding of the immobilized peptides.

  • 11.
    Aili, Daniel
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Enander, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Rydberg, Johan
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Baltzer, Lars
    Uppsala University.
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Alpha helix-inducing dimerization of synthetic polypeptide scaffolds on gold - a model system for receptor mimicking and biosensing2004In: 8th World Congress on Biosensors,2004, 2004Conference paper (Other academic)
  • 12.
    Aili, Daniel
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Enander, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Rydberg, Johan
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Baltzer, Lars
    Uppsala University.
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Folding-induced aggregation of polypeptide-decorated gold nanoparticles - an nano-scale Lego for the construction of complex hybrid materials2004In: 5th International Conference on Biological Physics,2004, 2004Conference paper (Other academic)
  • 13.
    Aili, Daniel
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Enander, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Rydberg, Johan
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Baltzer, Lars
    Uppsala University.
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Immobilization and heterodimerisation of helix-loop-helix polypeptides on gold surfaces - a model system for peptide-surface interactions2003In: 1st World congress on Synthetic Receptors,2003, 2003Conference paper (Other academic)
  • 14.
    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.

  • 15.
    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.

  • 16.
    Ajalloueian, Fatemeh
    et al.
    Isfahan University of Technology, Iran / Uppsala University, Sweden .
    Tavanai, Hossein
    Isfahan University of Technology, Iran .
    Hilborn, Jons
    Uppsala University, Sweden .
    Donzel-Gargand, Olivier
    Uppsala University, Sweden .
    Leifer, Klaus
    Uppsala University, Sweden .
    Wickham, Abeni
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Arpanaei, Ayyoob
    National Institute of Genetic Engineering and Biotechnology, Tehran, Iran.
    Emulsion Electrospinning as an Approach to Fabricate PLGA/Chitosan Nanofibers for Biomedical Applications2014In: BioMed Research International, ISSN 2314-6133, no 475280Article in journal (Refereed)
    Abstract [en]

    Novel nanofibers from blends of polylactic-co-glycolic acid (PLGA) and chitosan have been produced through an emulsion electrospinning process. The spinning solution employed polyvinyl alcohol (PVA) as the emulsifier. PVA was extracted from the electrospun nanofibers, resulting in a final scaffold consisting of a blend of PLGA and chitosan. The fraction of chitosan in the final electrospun mat was adjusted from 0 to 33%. Analyses by scanning and transmission electron microscopy show uniform nanofibers with homogenous distribution of PLGA and chitosan in their cross section. Infrared spectroscopy verifies that electrospun mats contain both PLGA and chitosan. Moreover, contact angle measurements show that the electrospun PLGA/chitosanmats are more hydrophilic than electrospun mats of pure PLGA. Tensile strengths of 4.94 MPa and 4.21 MPa for PLGA/chitosan in dry and wet conditions, respectively, illustrate that the polyblend mats of PLGA/chitosan are strong enough for many biomedical applications. Cell culture studies suggest that PLGA/chitosan nanofibers promote fibroblast attachment and proliferation compared to PLGA membranes. It can be assumed that the nanofibrous composite scaffold of PLGA/chitosan could be potentially used for skin tissue reconstruction.

  • 17.
    Alarcon, Emilio I.
    et al.
    University of Ottawa, Canada; University of Ottawa, Canada; University of Ottawa, Canada.
    Udekwu, Klas I.
    Karolinska Institute, Sweden.
    Noel, Christopher W.
    University of Ottawa, Canada; .
    Gagnon, Luke B. -P.
    University of Ottawa, Canada.
    Taylor, Patrick K.
    University of Ottawa, Canada.
    Vulesevic, Branka
    University of Ottawa, Canada.
    Simpson, Madeline J.
    University of Ottawa, Canada.
    Gkotzis, Spyridon
    Karolinska Institute, Sweden.
    Islam, Mohammed Mirazul
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Medicine and Health Sciences. Karolinska Institute, Sweden.
    Lee, Chyan-Jang
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Richter-Dahlfors, Agneta
    Karolinska Institute, Sweden.
    Mah, Thien-Fah
    University of Ottawa, Canada.
    Suuronen, Erik J.
    University of Ottawa, Canada.
    Scaiano, Juan
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Medicine and Health Sciences. University of Ottawa, Canada.
    Griffith, May
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Medicine and Health Sciences. Karolinska Institute, Sweden.
    Safety and efficacy of composite collagen-silver nanoparticle hydrogels as tissue engineering scaffolds2015In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 7, no 44, p. 18789-18798Article in journal (Refereed)
    Abstract [en]

    The increasing number of multidrug resistant bacteria has revitalized interest in seeking alternative sources for controlling bacterial infection. Silver nanoparticles (AgNPs), are amongst the most promising candidates due to their wide microbial spectrum of action. In this work, we report on the safety and efficacy of the incorporation of collagen coated AgNPs into collagen hydrogels for tissue engineering. The resulting hybrid materials at [AgNPs] less than0.4 mu M retained the mechanical properties and biocompatibility for primary human skin fibroblasts and keratinocytes of collagen hydrogels; they also displayed remarkable anti-infective properties against S. aureus, S. epidermidis, E. coli and P. aeruginosa at considerably lower concentrations than silver nitrate. Further, subcutaneous implants of materials containing 0.2 mu M AgNPs in mice showed a reduction in the levels of IL-6 and other inflammation markers (CCL24, sTNFR-2, and TIMP1). Finally, an analysis of silver contents in implanted mice showed that silver accumulation primarily occurred within the tissue surrounding the implant.

  • 18.
    Alarcon, Emilio I
    et al.
    University of Ottawa.
    Udekwu, Klas
    Karolinska Institute.
    Skog, Mårten
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    Pacioni, NataliL
    University of Ottawa.
    Stamplecoskie, Kevin G
    University of Ottawa.
    Gonzalez-Bejar, Maria
    University of Ottawa.
    Polisetti, Naresh
    Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences.
    Wickham, Abeni
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Richter-Dahlfors, Agneta
    Karolinska Institute.
    Griffith, May
    Linköping University, Department of Clinical and Experimental Medicine, Ophthalmology. Linköping University, Faculty of Health Sciences.
    Scaiano, Juan C
    University of Ottawa.
    The biocompatibility and antibacterial properties of collagen-stabilized, photochemically prepared silver nanoparticles2012In: Biomaterials, ISSN 0142-9612, E-ISSN 1878-5905, Vol. 33, no 19, p. 4947-4956Article in journal (Refereed)
    Abstract [en]

    Spherical 3.5 nm diameter silver nanoparticles (AgNP) stabilized in type I collagen (AgNP@collagen) were prepared in minutes (5-15 min) at room temperature by a photochemical method initiated by UVA irradiation of a water-soluble non-toxic benzoin. This biocomposite was examined to evaluate its biocompatibility and its anti-bacterial properties and showed remarkable properties. Thus, while keratinocytes and fibroblasts were not affected by AgNP@collagen, it was bactericidal against Bacillus megaterium and E. coli but only bacteriostatic against S. epidermidis. In particular, the bactericidal properties displayed by AgNP@collagen were proven to be due to AgNP in AgNP@collagen, rather than to released silver ions, since equimolar concentrations of Ag are about four times less active than AgNP@collagen based on total Ag content. This new biocomposite was stable over a remarkable range of NaCl, phosphate, and 2-(N-morpholino)ethanesulfonic acid concentrations and for over one month at 4 degrees C. Circular dichroism studies show that the conformation of collagen in AgNP@collagen remains intact. Finally, we have compared the properties of AgNP@collagen with a similar biocomposite prepared using alpha-poly-L-Lysine and also with citrate stabilized AgNP; neither of these materials showed comparable biocompatibility, stability, or anti-bacterial activity.

  • 19.
    Aldred, Nick
    et al.
    1School of Marine Science and Technology, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK..
    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 C.
    1School of Marine Science and Technology, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK..
    In situ study of surface exploration by barnacle cyprids (Semibalanus balanoides) using imaging surface plasmon resonanceManuscript (preprint) (Other academic)
    Abstract [en]

    Imaging surface plasmon resonance (iSPR) was employed to investigate the interfacial adhesion phenomena that occur during the exploration of immersed surfaces by barnacle cyprids (Semibalanus balanoides). It was hypothesised that since the footprint material used by cyprids for temporary adhesion has previously been related to a large cuticular glycoprotein (SIPC), the passive deposition of cyprid footprints and the binding of SIPC to surfaces might correlate. Increased surface exploration (and footprint deposition) has also been related to increased likelihood of settlement in barnacle cyprids. If a correlation between footprint deposition and SIPC binding were to exist, therefore, there would be potential for the development of a high‐throughput assay to determine the efficacy of putative antifouling chemistries against cyprids prior to, or instead of, lengthy bio‐assays. Footprints were deposited in large numbers on carboxyl‐terminated self‐assembled monolayers (SAMs) and in very small numbers on ethylene glycol‐containing SAMs and hydrogel coatings. SIPC binding also followed the same trend. An exception to the correlation was an amineterminated SAM that accumulated few cyprid footprints, but bound SIPC strongly. It is concluded that there is great potential for the iSPR technique to be used in the evaluation of putatively non‐fouling surfaces as well as improving our understanding of the nature of the cyprid footprint material and its interactions with surfaces of different chemistry. However, the use of SIPC binding as a predictor of footprint accumulation/likelihood of settlement of cyprids to surfaces would be premature at this stage without first understanding the exceptions highlighted in this study.

  • 20.
    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.

  • 21.
    Andersson, Henrik
    et al.
    Attana AB, Björnnäsvägen 21, SE-114 19 Stockholm, Sweden/The Ångström Laboratory, Solid State Electronics, Uppsala University, P.O. Box 534, SE-751 21 Uppsala, Sweden.
    Myrskog, Annika
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Ingemarsson, Björn
    Attana AB, Björnnäsvägen 21, SE-114 19 Stockholm, Sweden.
    Pei, Zhichao
    Attana AB, Björnnäsvägen 21, SE-114 19 Stockholm, Sweden.
    Optimizing immobilization conditions on a two dimensional carboxylbiosensor surface: pH dependence of antibody orientation andantigen binding capacity2009In: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309Article in journal (Other academic)
    Abstract [en]

    The performance of immunosensors is highly dependent on the amount of immobilized antibodies and their remaining antigen binding capacity. In this work, a method for immobilization of antibodies on a two dimensional carboxyl surface has been optimized using quartz crystal microbalance biosensors. We have shown that successful immobilization is highly dependent on surface pKa, antibody pI and pH of immobilization buffer. By use of EDC/sulfo-NHS activation reagents, the effect of the intrinsic surface pKa is avoided and immobilization also at very low pH has been made possible which is of importance for immobilization of acidic proteins. Generic immobilization conditions were demonstrated on a panel of antibodies which resulted in an average coefficient of variation of 4% for the immobilization of these antibodies.

    Antigen binding capacity as a function of immobilization pH was studied. In most cases the antigen binding capacity followed the immobilization response. However, the antigen to antibody binding ratio differed between the antibodies investigated, and for one of the antibodies, the antigen binding capacity was significantly lower than expected from immobilization in a certain pH range. Tests with anti-Fc and anti-Fab antibodies on different antibody surfaces showed that the orientation of the antibodies on the surface had a profound effect on the antigen binding capacity of the immobilized antibodies.

  • 22.
    Andersson, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Imaging surface plasmon resonance2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The central theme of this thesis is the use of imaging Surface Plasmon Resonance (iSPR) as a tool in the characterization of surfaces with laterally varying properties. Within the scope of this work, an instrument for iSPR analysis was designed and built. SPR is a very sensitive technique for monitoring changes in optical properties in the immediate vicinity of a sensor surface, which is very useful in biosensing and surface science research. We have employed SPR in the Kretschmann configuration, wherein surface plasmons are excited by means of an evanescent field arising from total internal reflection from the backside of the sensor surface. In iSPR, the signal is the reflectivity of TM-polarized light which is measured using an imaging detector, typically a CCD camera. Advantages of this technique include extreme surface sensitivity and, because detection is done from the backside, compatibility with complex samples. In addition, SPR is a non-labeling technique, and in imaging mode, a lateral resolution in the µm range can be attained.

    The imaging SPR instrument could be operated in either wavelength interrogation mode or in intensity mode. In the former case, the objective is to find the SPR wave-length, λSPR, which is the wavelength at which the reflected intensity is at a minimum. In intensity mode, a snapshot of the intensity reflectance is taken at a fixed wavelength hand incidence angle.

    In biosensor science, the use of an imaging technique offers a major advantage by enabling parallelization and thereby increasing throughput. We have, for example, used iSPR in biochemical interaction analysis to monitor immobilization and specific binding to protein and synthetic polypeptide micro arrays. The primary interest has been the study of soft matter surfaces that possess properties interesting in the field of biomimetics or for applications in biosensing. Specifically, the surfaces studied in this thesis include patterned self-assembled monolayers of thiolates on gold, a graft polymerized poly(ethylene glycol) (PEG) based hydrogel, a dextran hydrogel, and a polyelectrolyte charge gradient. Our results show that the PEG-based hydrogel is very well suited for use as a platform in protein immobilization in an array format, owing to the very low unspecific binding. In addition, well defined microarray templates were designed by patterning of hydrophobic barriers on dextran and monolayer surfaces. A polypeptide affinity microarray was further designed and immobilized on such a patterned monolayer substrate, in order to demonstrate the potential of analyte quantification with high sensitivity over a large dynamic range.

    Furthermore, iSPR was combined with electrochemistry to enable laterally resolved studies of electrochemical surface reactions. Using this combination, the electrochemical properties of surfaces patterned with self assembled monolayers can be studied in parallel, with a spatial resolution in the µm regime. We have also employed electrochemistry and iSPR for the investigation of potential and current density gradients on bipolar electrodes.

    The imaging SPR instrument could be operated in either wavelength interrogation mode or in intensity mode. In the former case, the objective is to find the SPR wave-length, λSPR, which is the wavelength at which the reflected intensity is at a minimum. In intensity mode, a snapshot of the intensity reflectance is taken at a fixed wavelength hand incidence angle.In biosensor science, the use of an imaging technique offers a major advantage by enabling parallelization and thereby increasing throughput. We have, for example, used iSPR in biochemical interaction analysis to monitor immobilization and specific binding to protein and synthetic polypeptide micro arrays. The primary interest has been the study of soft matter surfaces that possess properties interesting in the field of biomimetics or for applications in biosensing. Specifically, the surfaces studied in this thesis include patterned self-assembled monolayers of thiolates on gold, a graft polymerized poly(ethylene glycol) (PEG) based hydrogel, a dextran hydrogel, and a polyelectrolyte charge gradient. Our results show that the PEG-based hydrogel is very well suited for use as a platform in protein immobilization in an array format, owing to the very low unspecific binding. In addition, well defined microarray templates were designed by patterning of hydrophobic barriers on dextran and monolayer surfaces. A polypeptide affinity microarray was further designed and immobilized on such a patterned monolayer substrate, in order to demonstrate the potential of analyte quantification with high sensitivity over a large dynamic range.Furthermore, iSPR was combined with electrochemistry to enable laterally resolved studies of electrochemical surface reactions. Using this combination, the electrochemical properties of surfaces patterned with self assembled monolayers can be studied in parallel, with a spatial resolution in the µm regime. We have also employed electrochemistry and iSPR for the investigation of potential and current density gradients on bipolar electrodes.

    List of papers
    1. Protein Microarrays on Carboxymethylated Dextran Hydrogels: Immobilization, Characterization and Application
    Open this publication in new window or tab >>Protein Microarrays on Carboxymethylated Dextran Hydrogels: Immobilization, Characterization and Application
    2004 (English)In: Microchimica Acta, ISSN 0026-3672, E-ISSN 1436-5073, Vol. 147, no 1-2, p. 21-30Article in journal (Refereed) Published
    Abstract [en]

    Tetraoctadecylammonium bromide (TOAB, (CH3(CH2)17)4N+Br) has been used to print temporary hydrophobic barriers on carboxymethylated dextran (CMD) hydrogels to create a generic platform for protein microarray applications. The primary reason for printing temporary hydrophobic barriers is to prevent cross-contamination and overflow during microdrop dispensing. Equally important is to eliminate the risk for non-specific binding to the barriers during analyte exposure. This has been accomplished by introducing a regeneration step that removes the barriers after ligand immobilization. The overall fabrication process was characterized by microscopic wetting, atomic force microscopy, imaging ellipsometry, fluorescence microscopy, surface plasmon microscopy and biospecific interaction analysis. A series of model proteins including transferrin, Protein A, anti-myoglobin and bovine serum albumin was spotted into the TOAB-defined areas under different experimental conditions, e.g. at increased humidity and reduced substrate temperature or with glycerol as an additive in the protein solution. Much emphasis was devoted to studies aiming at exploring the homogeneity and activity of the immobilized proteins. The printed barriers were removed after protein immobilization using tert-n-butyl alcohol (TBA). TBA was found to be a very efficient agent as compared to previously used salt regeneration solutions, and the regeneration time could be reduced from 30 to 10 minutes. Finally, the potential of using the well established CMD hydrogel chemistry as a platform for protein microarrays was exploited using surface plasmon microscopy.

    Keywords
    Reversible hydrophobic barrier, microcontact printing, piezodispensing, protein microarrays, surface plasmon microscopy
    National Category
    Other Basic Medicine
    Identifiers
    urn:nbn:se:liu:diva-14919 (URN)10.1007/s00604-004-0223-5 (DOI)
    Available from: 2008-09-30 Created: 2008-09-30 Last updated: 2018-01-13
    2. Imaging SPR for detection of local electrochemical processes on patterned surfaces
    Open this publication in new window or tab >>Imaging SPR for detection of local electrochemical processes on patterned surfaces
    2008 (English)In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 134, no 2, p. 545-550Article in journal (Refereed) Published
    Abstract [en]

    Imaging surface plasmon resonance (iSPR) was used in conjunction with voltammetry to investigate the possibility of detecting local electrochemical processes in situ on chemically modified electrodes. More specifically, a pattern of self-assembled monolayers (SAMs) of thiocholesterol and 1-hexadecanethiol was microcontact printed on gold substrates, and the blocking characteristics on different parts of the pattern were investigated. The SPR images reflected the changes in the refractive index over the working electrode due to electrochemical processes, which in the present case showed the ability of the SAMs to impede faradaic reactions. The results show that differences in packing densities or porosity of SAMs in different regions of a patterned surface can be visualized as electrochemical images using iSPR. The strength of utilizing an optical detection method for electrochemical characterization lies in the ability to achieve lateral resolution in real-time. Electrochemical reactions can also be used to enhance the contrast in SPR images of thin layers of components with similar thicknesses and refractive indices.

    Keywords
    Imaging surface plasmon resonance, Microcontact printing, Local electrochemical analysis, Surface analysis
    National Category
    Inorganic Chemistry
    Identifiers
    urn:nbn:se:liu:diva-14884 (URN)10.1016/j.snb.2008.05.042 (DOI)
    Available from: 2008-09-29 Created: 2008-09-29 Last updated: 2017-12-13
    3. Formation of Molecular Gradients on Bipolar Electrodes
    Open this publication in new window or tab >>Formation of Molecular Gradients on Bipolar Electrodes
    2008 (English)In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 47, no 16, p. 3034-3036Article in journal (Refereed) Published
    Keywords
    Bipolar electrodes, electrochemistry, imaging, molecular gradients, surface chemistry
    National Category
    Inorganic Chemistry
    Identifiers
    urn:nbn:se:liu:diva-14881 (URN)10.1002/anie.200705824 (DOI)
    Available from: 2008-09-29 Created: 2008-09-29 Last updated: 2017-12-13Bibliographically approved
    4. Gradient Hydrogel Matrix for Microarray and Biosensor Applications: An Imaging SPR Study
    Open this publication in new window or tab >>Gradient Hydrogel Matrix for Microarray and Biosensor Applications: An Imaging SPR Study
    2009 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 10, no 1, p. 142-148Article in journal (Refereed) Published
    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.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-16523 (URN)10.1021/bm801029b (DOI)
    Available from: 2009-01-30 Created: 2009-01-30 Last updated: 2017-12-14
    5. Lateral Control of Protein Adsorption on Charged Polymer Gradients
    Open this publication in new window or tab >>Lateral Control of Protein Adsorption on Charged Polymer Gradients
    Show others...
    2009 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 6, p. 3755-3762Article in journal (Refereed) Published
    Abstract [en]

    This work describes the fabrication, characterization, and protein adsorption behavior of charged polymer gradients. The thin gradient films were fabricated by a two-step technique using UV-initiated free-radical polymerization in a reactor with a moving shutter. A homogeneous layer of cationic poly(2-aminoethyl methacrylate hydrochloride) was first formed, followed by a layer of oppositely charged poly(2-carboxyethyl acrylate) with a continuously increasing thickness. Adsorption from protein solutions as well as human blood plasma was investigated by imaging surface plasmon resonance and infrared microscopy. The results showed excessive protein adsorption in the areas where one of the polymers dominated the composition, while there was a clear minimum at an intermediate position of the gradient. The charge of the surface was estimated by direct force measurements and found to correlate well with the protein adsorption, showing the lowest net charge in the same area as the protein adsorption minimum. We therefore hypothesize that a combination of the charged polymers, in the right proportions, can result in a protein-resistant surface due to balanced charges.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-17501 (URN)10.1021/la803443d (DOI)
    Available from: 2009-03-27 Created: 2009-03-27 Last updated: 2017-12-13
    6. A multiple-ligand approach to extending the dynamic range of analyte quantification in protein microarrays
    Open this publication in new window or tab >>A multiple-ligand approach to extending the dynamic range of analyte quantification in protein microarrays
    2009 (English)In: Biosensors and bioelectronics, ISSN 0956-5663, Vol. 24, no 8, p. 2458-2464Article in journal (Refereed) Published
    Abstract [en]

    This work describes a concept for extending the dynamic range of quantification in an affinity biosensor assay by using a set of ligands with different affinities toward a common analyte. For a demonstration of the principle, three synthetic, biotinylated polypeptides capable of binding a model protein analyte with different affinities (10-9 M ≤ Kd ≤ 10-7 M) were immobilized in a microarray format on a gold slide covered with an oligo(ethylene glycol)-containing alkane thiolate self-assembled monolayer. For controllable immobilization, coupling was mediated by the biotinneutravidin interaction. A five-element affinity array, comprising single-peptide spots as well as spots where peptides were immobilized in mixtures, was realized by means of piezodispensation. Imaging surface plasmon resonance was used to study binding of the analyte to the different spots. The lower limit of quantification was ~3 nM and the corresponding upper limit was increased by more than an order of magnitude compared to if only the highest-affinity ligand would have been used. Affinity array sensors with multiple ligands for each analyte are particularly interesting for omitting dilution steps and providing highly accurate data in assays where several analytes such as disease biomarkers with extremely variable concentrations are quantified in parallel.

    Keywords
    Imaging surface plasmon resonance, Biosensor, Affinity microarray, Analyte quantification, Synthetic polypeptide
    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:liu:diva-14922 (URN)10.1016/j.bios.2008.12.030 (DOI)
    Available from: 2008-09-30 Created: 2008-09-30 Last updated: 2015-05-29
  • 23.
    Andersson, Olof
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Björefors, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Ulrich, Christian
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Ederth, Thomas
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Characterization of Surface Modifications using Voltammetry and Imaging SPR2006In: Europtrode VIII, 2006Conference paper (Other academic)
  • 24.
    Andersson, Olof
    et al.
    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.
    Aldred, Nick
    Newcastle University.
    Clare, Anthony S
    Newcastle University.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Novel application of imaging surface plasmon resonance for in situ studies of the surface exploration of marine organisms2009In: BIOINTERPHASES, ISSN 1559-4106, Vol. 4, no 4, p. 65-68Article in journal (Refereed)
    Abstract [en]

    The surface interactions of exploring cyprids of the barnacle Semibalanus balanoides were studied in situ using imaging surface plasmon resonance. It was demonstrated how the deposition of a proteinaceous adhesive could be followed in real time as the cyprids explored and temporarily attached to a surface. Furthermore, the amount of protein left on the surface when the cyprids moved on could be quantified. Clear differences were demonstrated between an oligo(ethyleneglycol) coated surface and a bare gold substrate. It is anticipated that this technique will be a valuable tool in the development of novel surface chemistries that can prevent biofouling.

  • 25.
    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.

  • 26.
    Andersson, Olof
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Larsson (Kaiser), Andréas
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Ekblad, Tobias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Imaging surface plasmon resonance studies of hydrogel and gradient surfaces for biosensor and array applications2008In: Europtrode IX,2008, 2008Conference paper (Other academic)
  • 27.
    Andersson, Olof
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Nikkinen, Henrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Enander, Karin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Towards affinity arrays for the detection of protein analytes2008In: Europtrode IX,2008, 2008Conference paper (Other academic)
  • 28.
    Andersson, Olof
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Ulrich, Christian
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Björefors, Fredrik
    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.
    Imaging SPR for detection of local electrochemical processes on patterned surfaces2008In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 134, no 2, p. 545-550Article in journal (Refereed)
    Abstract [en]

    Imaging surface plasmon resonance (iSPR) was used in conjunction with voltammetry to investigate the possibility of detecting local electrochemical processes in situ on chemically modified electrodes. More specifically, a pattern of self-assembled monolayers (SAMs) of thiocholesterol and 1-hexadecanethiol was microcontact printed on gold substrates, and the blocking characteristics on different parts of the pattern were investigated. The SPR images reflected the changes in the refractive index over the working electrode due to electrochemical processes, which in the present case showed the ability of the SAMs to impede faradaic reactions. The results show that differences in packing densities or porosity of SAMs in different regions of a patterned surface can be visualized as electrochemical images using iSPR. The strength of utilizing an optical detection method for electrochemical characterization lies in the ability to achieve lateral resolution in real-time. Electrochemical reactions can also be used to enhance the contrast in SPR images of thin layers of components with similar thicknesses and refractive indices.

  • 29.
    Andersson, Olof
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Ulrich, Christian
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Björefors, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Characterization Of Surface Modifications Using Voltammetry Combined With Imaging SPR2006Conference paper (Other academic)
  • 30.
    Andersson, Theresa
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Lundqvist, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Biotechnology . Linköping University, The Institute of Technology.
    Dolphin, Gunnar T.
    Linköping University, Department of Physics, Chemistry and Biology. 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.
    Jonsson, Bengt-Harald
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Biotechnology . Linköping University, The Institute of Technology.
    Nilsson, Jonas W.
    Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry . Linköping University, The Institute of Technology.
    Baltzer, Lars
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    The binding of human Carbonic Anhydrase II by functionalized folded polypeptide receptors2005In: Chemistry and Biology, ISSN 1074-5521, E-ISSN 1879-1301, Vol. 12, no 11, p. 1245-1252Article in journal (Refereed)
    Abstract [en]

    Several receptors for human carbonic anhydrase II (HCAII) have been prepared by covalently attaching benzenesulfonamide carboxylates via aliphatic aminocarboxylic acid spacers of variable length to the side chain of a lysine residue in a designed 42 residue helix-loop-helix motif. The sulfonamide group binds to the active site zinc ion of human carbonic anhydrase II located in a 15 Å deep cleft. The dissociation constants of the receptor-HCAII complexes were found to be in the range from low micromolar to better than 20 nM, with the lowest affinities found for spacers with less than five methylene groups and the highest affinity found for the spacer with seven methylene groups. The results suggest that the binding is a cooperative event in which both the sulfonamide residue and the helix-loop-helix motif contribute to the overall affinity.

  • 31.
    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.

  • 32.
    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.

  • 33.
    Arvidsson, A.
    et al.
    Dept. of Biomaterials/Handicap Res., Institute for Surgical Sciences, Göteborg University, 405 30 Göteborg, Sweden.
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Moller, K.
    Möller, K., Dept. of Chem. and Mat. Technology, Swed. Natl. Test. and Res. Institute, Borås, Sweden.
    Lyven, B.
    Lyvén, B., Dept. of Chem. and Mat. Technology, Swed. Natl. Test. and Res. Institute, Borås, Sweden.
    Sellen, A.
    Sellén, A., MediTeam Dental AB, Sävedalen, Sweden.
    Wennerberg, A.
    Prosthet. Dent. and Dent. Mat. Sci., Faculty of Odontology, Göteborg University, Göteborg, Sweden.
    Chemical and topographical analyses of dentine surfaces after Carisolv™ treatment2002In: Journal of Dentistry, ISSN 0300-5712, E-ISSN 1879-176X, Vol. 30, no 2-3, p. 67-75Article in journal (Refereed)
    Abstract [en]

    Objectives. The aim of this study was to characterise the surface chemistry of cavities after chemomechanical caries excavation, and also to measure the surface topography after caries removal with Carisolv™ or burs, followed by acid etching. Methods. Fourier transform (FT)-Raman spectroscopy was used to study the relative amounts of organic material and minerals of sound enamel, dentine, and cavities, after caries excavation. Fourier transform infrared spectroscopy (FTIR) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) were used for detection of Carisolv™ substances (i.e. mainly sodium hypochlorite, amino acids, and the gelling agent carboxymethyl cellulose). In total, 19 carious and 11 sound extracted teeth were used for the chemical analyses. Topographic examination of 30 carious extracted teeth was performed with a contact profilometer. Results. The relative amounts of organic material and minerals did not significantly differ between sound dentine and the cavities after caries removal with burs or Carisolv™. The FTIR analyses indicated extremely small amounts of Carisolv™ substances at the cavity surface, but the LA-ICP-MS analyses did not confirm those findings. Furthermore, the topographical parameters did not significantly differ between etched cavities after caries removal using burs or Carisolv™. Conclusions. The chemical and topographical analyses in the present study imply that any differences between the cavities after caries excavation with burs or with Carisolv™ are insignificant. © 2002 Elsevier Science Ltd. All rights reserved.

  • 34. Augulis, R
    et al.
    Valiokas, Ramunas
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Rotomskis, R
    Atomic force microscopy of self-assembled nanostructures of TPPS4 on SAM substrates2004In: Solid State Phenomena, ISSN 1012-0394, E-ISSN 1662-9779, Vol. 97-98, p. 195-200Article in journal (Refereed)
    Abstract [en]

    The adsorption of organic molecules on solid surfaces is one of the fundamental processes for the development of molecular-based nanodevices. Here we focus on the adsorption and ordering of the TPPS4-based J-aggregates on silicon and gold as well as on self-assembled monolayer (SAM) surfaces. The SAMs used for the experiments were based on the chemisorption of thiol containing compounds onto gold. Long omega-substituted alkanethiols are spontaneously assembled on gold to form highly ordered and densely packed layers with controllable chemical and physical properties. TPPS4 J-aggregates were dispersed on SAM surfaces, and on plain gold and silicon substrates for comparison. The dimensions of aggregates, measured by means of atomic force microscopy, varied depending on the type of substrate. Long stripe-like aggregates were flattened on the substrate surface, and the height and width of aggregates highly correlated with the polarity of surface groups. For example, the J-aggregates were narrower on hydrophobic substrates (with non-polar groups) and wider on hydrophilic substrates (with polar groups). These observations support the hypothesis, that TPPS4 forms,soft" cylindrical aggregates, that appear flattened on the substrate.

  • 35.
    Benesch, Johan
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Svedhem, S.
    Svensson, Stefan
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry .
    Valiokas, Ramunas
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Tengvall, Pentti
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Protein adsorption to oligo(ethylene glycol) self-assembled monolayers: Experiments with fibrinogen, heparinized plasma, and serum2001In: Journal of Biomaterials Science. Polymer Edition, ISSN 0920-5063, E-ISSN 1568-5624, Vol. 12, no 6, p. 581-597Article in journal (Refereed)
    Abstract [en]

    Low protein adsorption is believed advantageous for blood-contacting materials and ethylene glycols (EG)-based polymeric compounds are often attached to surfaces for this purpose. In the present study, the adsorption of fibrinogen, serum, and plasma were studied by ellipsometry on a series of well-defined oligo(EG) terminated alkane-thiols self-assembled on gold. The layers were prepared with compounds of the general structure HS-(CH2)15-CONH-EGn, where n = 2, 4, and 6. Methoxy-terminated tri(EG) undecanethiol and hydroxyl-terminated hexadecanethiol self-assembled monolayers (SAMs) were used as references. The results clearly demonstrate that the adsorption depends on the experimental conditions with small amounts of fibrinogen adsorbing from a single protein solution, but larger amounts of proteins from serum and plasma. The adsorption of fibrinogen and blood plasma decreased with an increasing number of EG repeats and was temperature-dependent. Significantly less serum adsorbed to methoxy tri(EG) than to hexa(EG) and more proteins remained on the latter surface after incubation in a sodium dodecyl sulfate (SDS) solution, indicating a looser protein binding to the methoxy-terminated surface. All surfaces adsorbed complement factor 3(C3) from serum and plasma, although no surface-mediated complement activation was observed. The present study points to the importance of a careful choice of the protein model system before general statements regarding the protein repellant properties of potential surfaces can be made.

  • 36.
    Bertilsson, L
    et al.
    Universität der Bundeswehr München.
    Potje-Kamloth, K
    Universität der Bundeswehr München.
    Liess, HD
    Universität der Bundeswehr München.
    Engquist, Isak
    Linköping University, Department of Science and Technology. 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.
    Adsorption of dimethyl methylphosphonate on self-assembled alkanethiolate monolayers1998In: JOURNAL OF PHYSICAL CHEMISTRY B, ISSN 1089-5647, Vol. 102, no 7, p. 1260-1269Article in journal (Refereed)
    Abstract [en]

    The adsorption of dimethyl methylphosphonate (DMMP), a model molecule for sarin, on three different organic interfaces, prepared by solution self-assembly of alkanethiols on gold, was followed by a surface acoustic wave mass sensor and infrared reflection-absorption spectroscopy at room temperature. The surfaces, characterized by the following tail groups (-OH, -CH3, -COOH), show both quantitative and qualitative differences concerning the interaction with DMMP, the acid surface giving rise to the strongest adsorption. Results obtained in UHV, at low temperatures using infrared spectroscopy and temperature-programmed desorption, support this observation and give complementary information about the nature of the interaction. The hydrogen-bond-accepting properties of the P=O part of DMMP and its impact on the design of sensing interfaces based on hydrogen bonding, as well as the use of self-assembled monolayers to study molecular interactions, are discussed.

  • 37.
    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.

  • 38.
    Björefors, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Daniels, Tad
    Allara, David
    Molecular Electronics - Assembly and Contacting of Single Molecular Wires2003In: Analysdagarna,2003, 2003Conference paper (Refereed)
    Abstract [en]

      

  • 39.
    Björefors, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Ekeroth, Johan
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Borgh, Annika
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Konradsson, Peter
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry .
    Electrochemical Analysis of Self-Assembled Monolayers2001In: Analysdagarna,2001, 2001Conference paper (Refereed)
  • 40.
    Björefors, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Characterization of the capacitance and quality of thiol based self-assembled monolayers by impedance spectroscopy and cyclic voltammetry2000In: ESEAC2000 European Society for ElectroAnalytical Chemistry,2000, 2000Conference paper (Other academic)
  • 41.
    Björefors, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Petoral Jr, Rodrigo M.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Electrochemical impedance spectroscopy for investigations on ion permeation in ?-functionalized self-assembled monolayers2007In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 79, no 21, p. 8391-8398Article in journal (Refereed)
    Abstract [en]

    Electrochemical impedance spectroscopy was employed to explore the possibility of relating the permeation of electrolyte ions in ?-functionalized self-assembled monolayers to structural or polarity changes induced by interaction with metal ions. The monolayers were based on alkanethiols modified with a phosphorylated tyrosine analogue, which from previous work are known to drastically change their organization on gold surfaces upon interaction with aluminum and magnesium ions. The ion permeation was evaluated by using relatively low excitation frequencies, 1000 to 2 Hz, and quantified by an extra resistive component in the equivalent circuit (R SAM). The extent of ion permeation influenced by the dc potential, the electrolyte concentration, the functional group, and the thiol length were also investigated. It was, for example, found that RSAM decreased ~20% when the thiol organization collapsed and that RSAM increased ~4-5 times when the electrolyte concentration was decreased by 1 order of magnitude. Interesting observations were also made regarding the potential dependence of RSAM and the double layer capacitance. The evaluation of the ion permeation can be used to indirectly detect whether the organization of a SAM is influenced by, for example, electric fields or chemical and biological interactions. This analysis can be performed without addition of redox species, but is on the other hand complicated by the fact that other factors also influence the presence of ions within the monolayer. In addition, a second parallel RC process was obtained in some of the impedance spectra when using even lower frequencies, and its resistive component revealed different results compared to RSAM. Such data may be useful for the understanding of complex double layer phenomena at modified electrodes. © 2007 American Chemical Society.

  • 42.
    Björefors, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Stålhandske, Per
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Characterization of the Capacitance and Quality of Thiol Based Self-Assembled Monolayers by Impedance Spectroscopy and Cyclic Voltammetry2000In: ISE 2000 International Society of Electrochemistry,2000, 2000Conference paper (Other academic)
  • 43. Blomberg, Eva
    et al.
    Claesson, Per M.
    Konradsson, Peter
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry .
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Globotriose- and oligo(ethylene glycol)-terminated self-assembled monolayers: Surface forces, wetting, and surfactant adsorption2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 24, p. 10038-10046Article in journal (Refereed)
    Abstract [en]

    A set of oligo( ethylene glycol)-terminated and globotriose-terminated self-assembled monolayers (SAMs) has been prepared on gold substrates. Such model surfaces are well defined and have good stability due to the strong binding of thiols and disulfides to the gold substrate. They are thus very suitable for addressing questions related to effects of surface composition on wetting properties, surface interactions, and surfactant adsorption. These issues are addressed in this report. Accurate wetting tension measurements have been performed as a function of temperature using the Wilhelmy plate technique. The results show that the nonpolar character of oligo( ethylene glycol)-terminated SAMs increases slightly but significantly with temperature in the range 20-55 degrees C. On the other hand, globotriose-terminated SAMs are fully wetted by water at room temperature. Surface forces measurements have been performed and demonstrated that the interactions between oligo( ethylene glycol)-terminated SAMs are purely repulsive and similar to those determined between adsorbed surfactant layers with the same terminal headgroup. On the other hand, the interactions between globotriose-terminated SAMs include a short-range attractive force component that is strongly affected by the packing density in the layer. In some cases it is found that the attractive force component increases with contact time. Both these observations are rationalized by an orientation- and conformation-dependent interaction between globotriose headgroups, and it is suggested that hydrogen-bond formation, directly or via bridging water molecules, is the molecular origin of these effects.

  • 44.
    Borgh, Annika
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Biomimetic surfaces: Preparation, characterization and application2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes the preparation, characterization and application of a few biomimetic surfaces. Biomimetics is a modern development of the ancient Greek concept of mimesis, i.e. man-made imitation of nature. The emphasis has been on the preparation and characterization of two types of model systems with properties inspired by nature with future applications in bioanalysis, biosensors and antifreeze materials. One type of model system involves phosphorylated surfaces; the other consists of surfaces mimicking antifreeze (glyco)proteins. The surfaces were made by chemisorbing organosulfur substances to a gold surface into monomolecular layers, so called self-assembled monolayers (SAMs). The physicochemical properties of the SAMs were thoroughly characterized with null ellipsometry, contact angle goniometry, x-ray photoelectron spectroscopy and infrared spectroscopy prior to application.

    The work on antifreeze surfaces was inspired by the structural properties of antifreeze (glyco)proteins, which can be found in polar fish. Two model systems were developed and studied with respect to ice nucleation of condensed water layers. One was designed to mimic the active domain of antifreeze glycoproteins (AFGP) and the other mimicked type I antifreeze proteins (AFP I). Subsequent ice nucleation studies showed a significant difference between the AFGP model and a (OH/CH3) reference system displaying identical wetting properties, whereas the AFP I model was indistinguishable from the reference system.

    The model systems with phosphorylated surfaces were inspired from phosphorylations and biomineralization. Two systems were developed, short- and long-chained amino acid analogues, with and without a phosphate group. A novel approach with protected groups before attachment to gold were developed for the long-chained analogues. The protective groups could be removed successfully after assembly. The long-chained SAMs were evaluated with electrochemical methods and significantly higher capacitance values were observed for the phosphorylated SAMs compared to the non-phosphorylated.

    List of papers
    1. A new route to the formation of biomimetic phosphate assemblies on gold: Synthesis and characterization
    Open this publication in new window or tab >>A new route to the formation of biomimetic phosphate assemblies on gold: Synthesis and characterization
    Show others...
    2006 (English)In: Journal of Colloid and Interface Science, ISSN 1095-7103, Vol. 295, no 1, p. 41-49Article in journal (Refereed) Published
    Abstract [en]

    A biomimetic model system based on long-chain alkanethiols tailored with serine, threonine and tyrosine side-chain groups is created as a platform for the study of phosphorylated amino acids. The phosphorylated analogues are synthesized with protective tert-butyl groups that after assembly on thin polycrystalline gold films are removed in an acidic deprotection solution to form the corresponding phosphate self-assembled monolayers (SAMs). The SAMs are thoroughly characterized with null ellipsometry, contact angle goniometry, infrared reflection–absorption spectroscopy and X-ray photoelectron spectroscopy. The assembly and the subsequent deprotection process are optimized with respect to molecular orientation and chain conformation by varying the incubation time and the exposure time to the deprotection solution. The high quality of the generated SAMs suggests that the present assembly/deprotection approach is an attractive alternative when traditional synthetic routes become demanding because of solubility problems.

    Keywords
    SAM; Thiols; Gold; Phosphorylated amino acids; Surface deprotection scheme
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-14334 (URN)10.1016/j.jcis.2005.08.026 (DOI)
    Available from: 2007-03-16 Created: 2007-03-16 Last updated: 2010-09-06
    2. Electrochemical Evaluation of the Interfacial Capacitance upon Phosphorylation of Amino Acid Analogue Molecular Films
    Open this publication in new window or tab >>Electrochemical Evaluation of the Interfacial Capacitance upon Phosphorylation of Amino Acid Analogue Molecular Films
    Show others...
    2001 (English)In: Analytical Chemistry, ISSN 0003-2700, Vol. 73, no 18, p. 4463-4468Article in journal (Refereed) Published
    Abstract [en]

    An approach based on electrochemistry to differentiate between phosphorylated and nonphosphorylated amino acid analogues adsorbed on gold is presented. Analogues of serine, threonine, and tyrosine, containing thiohexadecyl headgroups, were synthesized and assembled on gold, and the surface capacitance was evaluated using electrochemical impedance spectroscopy. A procedure for deprotection of tert-butyl phosphate protecting groups, on the monolayer, is also described. Characterizations of the assembled analogues by cyclic voltammetry, infrared spectroscopy, and ellipsometry are used to confirm the insulating properties of the monolayers and the outcome of surface modifications. The results from cyclic voltammetry show good insulating properties for the monolayers even after phosphate deprotection. The infrared measurements reveal well-ordered monolayers, and the thickness from ellipsometry is in good agreement with expectations from molecular modeling. The impedance experiments show a capacitance increase up to 0.6 μF/cm2 as phosphate groups are introduced. The results in this study indicate the possibility of using a surface chemical and impedance spectroscopy approach to detect the kinase/phosphatase activity and kinetics involved in phosphorylation reactions.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-14335 (URN)10.1021/ac010487+ (DOI)
    Available from: 2007-03-16 Created: 2007-03-16 Last updated: 2009-05-11
    3. Synthesis and Monolayer Characterization of Phosphorylated Amino Acid Analogs
    Open this publication in new window or tab >>Synthesis and Monolayer Characterization of Phosphorylated Amino Acid Analogs
    2002 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 254, no 2, p. 322-330Article in journal (Refereed) Published
    Abstract [en]

    The synthesis of a series of thiols containing phosphorylated and non-phosphorylated serine, threonine, and tyrosine amino acid residues is described. The synthesized molecules, based on 3-mercaptopropionic acid, were assembled onto gold and subsequently characterized using infrared reflection-absorption spectroscopy, ellipsometry, X-ray photoelectron spectroscopy, and contact angle goniometry. The ellipsometric analysis indicates that they form densely packed and well-oriented monolayers on gold, with thicknesses that are in good agreement with estimated values from space-filling models. The bulky and space-demanding phosphorylated threonine analog was, however, found to be an exception. The increase in layer thickness when adding a phosphate group to the threonine is only 35% of that observed for the two other analogs. A detailed infrared examination of the influence of cation coordination to the phosphorylated serine analog using calcium and magnesium reveals structural similarities to those of the inorganic phosphate compound calcium hydroxy apatite. We furthermore discuss the application of these monolayers as soft templates for biomineralization.

    Place, publisher, year, edition, pages
    Maryland Heights, MO, United States: Academic Press, 2002
    Keywords
    SAM; phosphorylated amino acid; phosphate layer; alkanethiols; gold; counterion influence
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-14336 (URN)10.1006/jcis.2002.8576 (DOI)000178935400016 ()
    Available from: 2007-03-16 Created: 2007-03-16 Last updated: 2017-12-13Bibliographically approved
    4. Mimicking the properties of antifreeze glycoproteins: synthesis and characterization of a model system for ice nucleation and antifreeze studies
    Open this publication in new window or tab >>Mimicking the properties of antifreeze glycoproteins: synthesis and characterization of a model system for ice nucleation and antifreeze studies
    2005 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, no 33, p. 15849-15859Article in journal (Refereed) Published
    Abstract [en]

    Synthesis of β-D-Gal-(1 → 3)-β-D-GalNAc coupled to HOC2H4NHCOC15H30SH is described. This compound was coadsorbed at various proportions with C2H5OC2H4NHCOC15H30SH to form statistically mixed self-assembled monolayers (SAMs) on gold in an attempt to mimic the properties of the active domain in antifreeze glycoproteins (AFGPs). The monolayers were characterized by null ellipsometry, contact angle goniometry, X-ray photoelectron spectroscopy, and infrared reflection−absorption spectroscopy. The disaccharide compound adsorbed preferentially, and SAMs prepared at a solution molar ratio >0.3 displayed total wetting. The mixed SAMs showed well-organized alkyl chains up to a disaccharide surface fraction of 0.8. The amount of gauche conformers in the alkyls increased rapidly above this point, and the monolayers became disordered and less densely packed. Furthermore, the generated mixed SAMs were subjected to water vapor at constant relative humidity and the subsequent ice crystallization on a cooled substrate was monitored via an optical microscope. Interestingly, rapid crystallization occurred within a narrow range of temperatures on mixed SAMs with a high disaccharide content, surface fraction >0.3. The reported crystallization temperatures and the ice layer topography were compared with results obtained for a much simpler reference system composed of −OH/−CH3 terminated n-alkanethiols in order to account for changes in topography of the water/ice layer with surface energy. Although preliminary, the obtained results can be useful in the search for the molecular mechanism behind the antifreeze activity of AFGPs.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-14337 (URN)10.1021/jp050752l (DOI)
    Available from: 2007-03-16 Created: 2007-03-16 Last updated: 2017-12-13
    5. Biomimetic Surfaces for Ice Interaction Studies
    Open this publication in new window or tab >>Biomimetic Surfaces for Ice Interaction Studies
    Manuscript (Other academic)
    Identifiers
    urn:nbn:se:liu:diva-14338 (URN)
    Available from: 2007-03-16 Created: 2007-03-16 Last updated: 2010-01-13
  • 45.
    Borgh, Annika
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Ekeroth, Johan
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Petoral Jr., Rodrigo M.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular 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.
    A new route to the formation of biomimetic phosphate assemblies on gold: Synthesis and characterization2006In: Journal of Colloid and Interface Science, ISSN 1095-7103, Vol. 295, no 1, p. 41-49Article in journal (Refereed)
    Abstract [en]

    A biomimetic model system based on long-chain alkanethiols tailored with serine, threonine and tyrosine side-chain groups is created as a platform for the study of phosphorylated amino acids. The phosphorylated analogues are synthesized with protective tert-butyl groups that after assembly on thin polycrystalline gold films are removed in an acidic deprotection solution to form the corresponding phosphate self-assembled monolayers (SAMs). The SAMs are thoroughly characterized with null ellipsometry, contact angle goniometry, infrared reflection–absorption spectroscopy and X-ray photoelectron spectroscopy. The assembly and the subsequent deprotection process are optimized with respect to molecular orientation and chain conformation by varying the incubation time and the exposure time to the deprotection solution. The high quality of the generated SAMs suggests that the present assembly/deprotection approach is an attractive alternative when traditional synthetic routes become demanding because of solubility problems.

  • 46.
    Carlsson, Jenny
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Gullstrand, Camilla
    Linköping University, Department of Clinical and Experimental Medicine, Pediatrics . Linköping University, Faculty of Health Sciences.
    Westermark, Gunilla
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    Ludvigsson, Johnny
    Linköping University, Department of Clinical and Experimental Medicine, Pediatrics . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Paediatrics and Gynecology and Obstetrics, Department of Paediatrics in Linköping.
    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.
    An indirect competitive immunoassay for insulin autoantibodies based on surface plasmon resonance2008In: Biosensors and Bioelectronics, ISSN 0956-5663, Vol. 24, no 4, p. 876-881Article in journal (Refereed)
    Abstract [en]

    We have developed a sensitive and specific method based on surface plasmon resonance (SPR) for detection of insulin autoantibodies (IAA) in serum samples from individuals at high risk of developing type 1 diabetes (T1D). When measuring trace molecules in undiluted sera with label-free techniques like SPR, non-specific adsorption of matrix proteins to the sensor surface is often a problem, since it causes a signal that masks the analyte response. The developed method is an indirect competitive immunoassay designed to overcome these problems. Today, IAA is mainly measured in radio immunoassays (RIAs), which are time consuming and require radioactively labeled antigen. With our SPR-based immunoassay the overall assay time is reduced by a factor of >100 (4 days to 50 min), while sensitivity is maintained at a level comparable to that offered by RIA.

  • 47.
    Carlsson, Jenny
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Gullstrand, Camilla
    Linköping University, Department of Clinical and Experimental Medicine, Pediatrics. Linköping University, Faculty of Health Sciences.
    Westermark, Gunilla
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    Ludvigsson, Johnny
    Linköping University, Department of Clinical and Experimental Medicine, Pediatrics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center of Paediatrics and Gynaecology and Obstetrics, Department of Paediatrics in Linköping.
    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.
    Determination of insulin autoantibodies using surface plasmon resonance: A screening study of newly diagnosed type 1 diabetes patients2008Manuscript (preprint) (Other academic)
    Abstract [en]

    We have investigated the screening potential of a surface plasmon resonance (SPR)-based indirectcompetitive immunoassay for quantification of insulin autoantibodies (IAA) in sera from childrennewly diagnosed with type 1 diabetes (T1D), using a radioimmunoassay (RIA) as reference technique.The two methods agreed well with respect to sample classification of 54 sera from newly diagnosedT1D children and 32 reference sera from non-diabetic children. Interestingly, five samples from newlydiagnosed T1D patients classified as IAA-negative according to RIA were IAA-positive with the SPRbasedassay, suggesting that the SPR-based assay might provide a higher sensitivity than the referenceRIA. However, 14 percent of the analyzed samples (five samples from non-diabetics and seven fromnewly diagnosed T1D patients) gave rise to anomalously high and easily distinguishable responses withthe SPR-based method, precluding IAA-quantification. A considerable part of the paper is devoted to adiscussion of possible causes of these anomalous responses. They were not due to temporary changesin the status of the patients, such as infections at the time of sampling, and also not related tocomplement activation. It is speculated whether a plausible explanation should instead be sought in theexistence of anti-idiotypic antibodies to IAA.

  • 48.
    Chen, Peng
    et al.
    Nanyang Technology University, Singapore.
    Selegård, Robert
    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.
    Liedberg, Bo
    Nanyang Technology University, Singapore.
    Peptide functionalized gold nanoparticles for colorimetric detection of matrilysin (MMP-7) activity2013In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 5, no 19, p. 8973-8976Article in journal (Refereed)
    Abstract [en]

    A peptide with two cleavage sites for MMP-7 has been synthesized and immobilized on gold nanoparticles (AuNPs) through a cysteine residue. Digestion of the peptide by MMP-7 decreases its size and net charge, which leads to the aggregation of the AuNPs. The color shift caused by aggregation enables a direct and quantitative measurement of the concentration and activity of MMP-7 with an estimated limit of detection of 5 nM (0.1 μg mL−1).

  • 49.
    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.

  • 50.
    Cheung Mak, Wing
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Kwan Yee, Cheung
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Medicine and Health Sciences.
    Orban, Jenny
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics.
    Lee, Chyan-Jang
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Turner, Anthony
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Griffith, May
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Medicine and Health Sciences.
    Surface-Engineered Contact Lens as an Advanced Theranostic Platform for Modulation and Detection of Viral Infection2015In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 7, no 45, p. 25487-25494Article in journal (Refereed)
    Abstract [en]

    We have demonstrated an entirely new concept of a wearable theranostic device in the form of a contact lens (theranostic lens) with a dual-functional hybrid surface to modulate and detect a pathogenic attack, using a the corneal HSV serotype-1 (HSV-1) model. The theranostic lenses were constructed using a facile layer-by-layer surface engineering technique, keeping the theranostic lenses with good surface wettability, optically transparency, and nontoxic toward human corneal epithelial cells. The theranostic lenses were used to capture and concentrate inflammatory cytokines such as interleukin-1 alpha (IL-1 alpha), which is upregulated during HSV-1 reactivation, for sensitive, noninvasive diagnostics. The theranostic lens also incorporated an antiviral coating to serve as a first line of defense to protect patients against disease. Our strategy tackles major problems in tear diagnostics that are mainly associated with the sampling of a relatively small volume of fluid and the low concentration of biomarkers. The theranostic lenses show effective anti-HSV-1 activity and good analytical performance for the detection of IL-1a, with a limit of detection of 1.43 pg mL(-1) and a wide linear range covering the clinically relevant region. This work offers a new paradigm for wearable noninvasive healthcare devices combining diagnosis and protection against disease, while supporting patient compliance. We believe that this approach holds immense promise as a next-generation point-of-care and decentralized diagnostic/theranostic platform for a range of biomarkers.

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