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  • 1.
    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.

  • 2.
    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.

  • 3.
    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: 2019-04-24
    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
  • 4.
    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)
  • 5.
    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.

  • 6.
    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.

  • 7.
    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)
  • 8.
    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)
  • 9.
    Andersson, Olof
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Nikkinen, Henrik
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Kanmert, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Enander, Karin
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    A multiple-ligand approach to extending the dynamic range of analyte quantification in protein microarrays2009In: Biosensors and bioelectronics, ISSN 0956-5663, Vol. 24, no 8, p. 2458-2464Article in journal (Refereed)
    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.

  • 10.
    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.

  • 11.
    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)
  • 12.
    Ekblad, Tobias
    et al.
    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.
    Tai, Feng-i
    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.
    Lateral Control of Protein Adsorption on Charged Polymer Gradients2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 6, p. 3755-3762Article in journal (Refereed)
    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.

  • 13.
    Ekblad, Tobias
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Faxälv, Lars
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Laboratory Medicine, Department of Clinical Chemistry.
    Andersson, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Wallmark, Nanny
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Larsson (Kaiser), Andréas
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Lindahl, Tomas L.
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Laboratory Medicine, Department of Clinical Chemistry.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Patterned Hydrogels for Controlled Platelet Adhesion from Whole Blood and Plasma2010In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 20, no 15, p. 2396-2403Article in journal (Refereed)
    Abstract [en]

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

  • 14.
    Larsson (Kaiser), Andréas
    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.
    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.
    Photografted poly(ethylene glycol) matrix for affinity interaction studies2007In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 8, no 1, p. 287-295Article in journal (Refereed)
    Abstract [en]

    A poly(ethylene glycol) (PEG)-based matrix for studies of affinity interactions is developed and demonstrated. The PEG matrix, less than 0.1 μm thick, is graft copolymerized onto a cycloolefin polymer from a mixture of PEG methacrylates using a free radical reaction initiated by UV light at 254 nm. The grafting process is monitored in real time, and characteristics such as thickness, homogeneity, relative composition, photostability, and performance in terms of protein resistance in complex biofluids and sensor qualities are investigated with null ellipsometry, infrared spectroscopy, and surface plasmon resonance. The matrix is subsequently modified to contain carboxyl groups, thereby making it possible to immobilize ligands in a controlled and functional manner. Human serum albumin and fibrinogen are immobilized and successfully detected by antibody recognition using surface plasmon resonance. The results are encouraging and suggest that the PEG matrix is suitable for biochip and biosensor applications in demanding biofluids.

  • 15.
    Liedberg, Bo
    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.
    Andersson, Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics.
    Photografted PEG matrix for biosensor applications2006In: Proceedings of the 9th Biosensors Congress,2006, Columbus: American Chemical Society , 2006Conference paper (Refereed)
  • 16.
    Lundgren, Anders
    et al.
    University of Gothenburg, Sweden .
    Hulander, Mats
    University of Gothenburg, Sweden .
    Brorsson, Joakim
    University of Gothenburg, Sweden .
    Hermansson, Malte
    University of Gothenburg, Sweden .
    Elwing, Hans
    University of Gothenburg, Sweden .
    Andersson, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Berglin, Mattias
    University of Gothenburg, Sweden SP Technical Research Institute Sweden, Sweden .
    Gold-Nanoparticle-Assisted Self-Assembly of Chemical Gradients with Tunable Sub-50 nm Molecular Domains2014In: Particle & particle systems characterization, ISSN 0934-0866, E-ISSN 1521-4117, Vol. 31, no 2, p. 209-218Article in journal (Refereed)
    Abstract [en]

    A simple and efficient principle for nanopatterning with wide applicability in the sub-50 nanometer regime is chemisorption of nanoparticles; at homogeneous substrates, particles carrying surface charge may spontaneously self-organize due to the electrostatic repulsion between adjacent particles. Guided by this principle, a method is presented to design, self-assemble, and chemically functionalize gradient nanopatterns where the size of molecular domains can be tuned to match the level corresponding to single protein binding events. To modulate the binding of negatively charged gold nanoparticles both locally (less than100 nm) and globally (greater than100 m) onto a single modified gold substrate, ion diffusion is used to achieve spatial control of the particles mutual electrostatic interactions. By subsequent tailoring of different molecules to surface-immobilized particles and the void areas surrounding them, nanopatterns are obtained with variable chemical domains along the gradient surface. Fimbriated Escherichia coli bacteria are bound to gradient nanopatterns with similar molecular composition and macroscopic contact angle, but different sizes of nanoscopic presentation of adhesive (hydrophobic) and repellent poly(ethylene) glycol (PEG) domains. It is shown that small hydrophobic domains, similar in size to the diameter of the bacterial fimbriae, supported firmly attached bacteria resembling catch-bond binding, whereas a high number of loosely adhered bacteria are observed on larger hydrophobic domains.

  • 17.
    Tai, Feng-i
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering. Kagaku Analys AB, Göteborg, Sweden.
    Sterner, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering. Susos AG, Dübendorf, Switzerland.
    Andersson, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering. Insplorion AB, Göteborg, Sweden.
    Ekblad, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering. MariboHilleshög Research AB, Landskrona, Sweden.
    Ederth, Thomas
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Interaction Forces on Polyampholytic Hydrogel Gradient Surfaces2019In: ACS Omega, ISSN 2470-1343, Vol. 4, no 3, p. 5670-5681Article in journal (Refereed)
    Abstract [en]

    Rational design and informed development of nontoxic antifouling coatings requires a thorough understanding of the interactions between surfaces and fouling species. With more complex antifouling materials, such as composites or zwitterionic polymers, there follows also a need for better characterization of the materials as such. To further the understanding of the antifouling properties of charge-balanced polymers, we explore the properties of layered polyelectrolytes and their interactions with charged surfaces. These polymers were prepared via self-initiated photografting and photopolymerization (SIPGP); on top of a uniform bottom layer of anionic poly(methacrylic acid) (PMAA), a cationic poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) thickness gradient was formed. Infrared microscopy and imaging spectroscopic ellipsometry were used to characterize chemical composition and swelling of the combined layer. Direct force measurements by colloidal probe atomic force microscopy were performed to investigate the forces between the polymer gradients and charged probes. The swelling of PMAA and PDMAEMA are very different, with steric and electrostatic forces varying in a nontrivial manner along the gradient. The gradients can be tuned to form a protein-resistant charge-neutral region, and we demonstrate that this region, where both electrostatic and steric forces are small, is highly compressed and the origin of the protein resistance of this region is most likely an effect of strong hydration of charged residues at the surface, rather than swelling or bulk hydration of the polymer. In the highly swollen regions far from charge-neutrality, steric forces dominate the interactions between the probe and the polymer. In these regions, the SIPGP polymer has qualitative similarities with brushes, but we were unable to quantitatively describe the polymer as a brush, supporting previous data suggesting that these polymers are cross-linked.

  • 18.
    Tai, Feng-I
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics.
    Sterner, Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics.
    Andersson, Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics.
    Ekblad, Tobias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics.
    Ederth, Thomas
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics.
    pH-control of the protein resistance of hydrogel gradient films2015Conference paper (Other academic)
  • 19.
    Tai, Feng-i
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Sterner, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Andersson, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Ekblad, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Ederth, Thomas
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    pH-control of the protein resistance of thin hydrogel gradient films2014In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 10, no 32, p. 5955-5964Article in journal (Refereed)
    Abstract [en]

    We report on the preparation and characterization of thin polyampholytic hydrogel gradient films permitting pH-controlled protein resistance via the regulation of surface charges. The hydrogel gradients are composed of cationic poly(2-aminoethyl methacrylate hydrochloride) (PAEMA), and anionic poly(2-carboxyethyl acrylate) (PCEA) layers, which are fabricated by self-initiated photografting and photopolymerization (SIPGP). Using a two-step UV exposure procedure, a polymer thickness gradient of one component is formed on top of a uniform layer of the oppositely charged polymer. The swelling of the gradient films in water and buffers at different pH were characterized by imaging spectroscopic ellipsometry. The surface charge distribution and steric interactions with the hydrogel gradients were recorded by direct force measurement with colloidal-probe atomic force microscopy. We demonstrate that formation of a charged polymer thickness gradient on top of a uniform layer of opposite charge can result in a region of charge-neutrality. This charge-neutral region is highly resistant to non-specific adsorption of proteins, and its location along the gradient can be controlled via the pH of the surrounding buffer. The pH-controlled protein adsorption and desorption was monitored in real-time by imaging surface plasmon resonance, while the corresponding redistribution of surface charge was confirmed by direct force measurements.

  • 20.
    Ulrich, Christian
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Andersson, Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Leif, Nyholm
    Björefors, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Surface Gradients on Bipolar Electrodes2008In: ESEAC2008 European Society for ElectroAnalytical Chemistry,2008, 2008Conference paper (Other academic)
  • 21.
    Ulrich, Christian
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Andersson, Olof
    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 .
    Björefors, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    New Methods in Surface Science and Surface Analysis-Towards Biomimetic Sensing2007In: A Vinnova program conference: Multidisciplinary BIO,2007, 2007Conference paper (Refereed)
    Abstract [en]

            

  • 22.
    Ulrich, Christian
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied 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.
    Nyholm, Leif
    Uppsala University.
    Björefors , Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Potential and Current Density Distributions at Electrodes Intended for Bipolar Patterning2009In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 81, no 1, p. 453-459Article in journal (Refereed)
    Abstract [en]

    This paper deals with the use of reaction gradients on bipolar electrodes for the patterning of electrode surfaces. More specifically, the potential and current density distributions in two setups containing bipolar electrodes were investigated to optimize and design specific gradient geometries. Comparisons with simulations based on simple conductivity models showed a good qualitative agreement, demonstrating that these models could be used to predict bipolar behavior in more complex setups. In conjunction with imaging surface plasmon resonance (iSPR) experiments, the reaction gradients on bipolar electrodes could further be visualized. It was, for example, found that the gradient in potential difference was approximately linearly distributed in the center of the bipolar electrode and that these potential differences could be determined using an ordinary Ag/AgCl reference electrode. The present results thus provide a better understanding of the processes relevant for bipolar patterning. This approach was finally used to generate a circular gradient region in a self-assembled monolayer, thereby showing the possibilities to create interesting substrates for biosensors and microarray applications.

  • 23.
    Ulrich, Christian
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Andersson, Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Nyholm, Leif
    Björefors, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Formation and Imaging of Gradients in Electrochemical Reactions and Molecular Films2008In: ESEAC2008 European Society for ElectroAnalytical Chemistry,2008, 2008Conference paper (Other academic)
  • 24.
    Ulrich, Christian
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied 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.
    Nyholm, Leif
    Department of Materials Chemistry, Uppsala University, P.O. Box 538, 75121 Uppsala, Sweden.
    Björefors, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Formation of Molecular Gradients on Bipolar Electrodes2008In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 47, no 16, p. 3034-3036Article in journal (Refereed)
  • 25.
    Wigenius, Jens
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Magnusson, Karin
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Björk, Per
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. 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.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    DNA Chips with Conjugated Polyelectrolytes in Resonance Energy Transfer Mode2010In: LANGMUIR, ISSN 0743-7463, Vol. 26, no 5, p. 3753-3759Article in journal (Refereed)
    Abstract [en]

    We show how to use well-defined conjugated polyelectrolytes (CPEs) combined With Surface energy patterning to Fabricate DNA Chips utilizing A fluorescence signal amplification. Cholesterol-modified DNA strands in complex with it CPE are adsorbed to a surface energy pattern, formed by printing with soft elastomer stamps. Hybridization of the surface bound DNA strands with it short complementary strand from Solution is monitored using both fluorescence microscopy and imaging surface plasmon resonance. The CPEs act as antennas, enhancing resonance energy transfer to the dye-labeled DNA when complementary hybridization of the double strand occurs.

  • 26.
    Zhou, Ye
    et al.
    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.
    Lindberg, Peter
    Biacore AB, Rapsgatan 7, S-754 50, Uppsala, Sweden.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Protein Microarrays on Carboxymethylated Dextran Hydrogels: Immobilization, Characterization and Application2004In: Microchimica Acta, ISSN 0026-3672, E-ISSN 1436-5073, Vol. 147, no 1-2, p. 21-30Article in journal (Refereed)
    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.

  • 27.
    Zhou, Ye
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Andersson, Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Lindberg, P.
    Biacore AB, Rapsgatan 7, S-754 50 Uppsala, Sweden.
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Reversible hydrophobic barriers introduced by microcontact printing: Application to protein microarrays2004In: Mikrochimica Acta, ISSN 0026-3672, E-ISSN 1436-5073, Vol. 146, no 3-4, p. 193-205Article in journal (Refereed)
    Abstract [en]

    Microcontact printing (µCP) has been used to introduce temporary hydrophobic barriers on carboxymethylated dextran (CMD) hydrogels on gold. Among the investigated types of inks, tetraoctadecylammonium bromide (TOAB), electrostatically bound to the CMD layer, provided the most well-defined features both with respect to pattern-definition and reversibility upon exposure to a regeneration solution. The printed patterns were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), microscopic wetting and imaging null ellipsometry to explore the influence of concentration of ink solution and contact time on the appearance of the printed layer. AFM revealed that the printed TOAB molecules aggregated into clusters rather than into a homogeneous mono- or multilayer on the CMD hydrogel. It was also observed that printed areas of TOAB that are larger than 25?µm are inhomogeneous most likely because of an edge transfer lithography (ETL) mechanism. A protein model system based on Protein A-rabbit antimouse Fc ? was used to evaluate the potential of the patterned surface as a protein microarray chip by means of surface plasmon microscopy (SPM). Moreover, non-specific adsorption of several proteins onto TOAB barriers was also studied using surface plasmon resonance (SPR), and it is evident that undesired adsorption can be eliminated by removing barriers after ligand immobilization, but prior to analyte exposure, by treating the patterned surface with a simple salt regeneration solution. © Springer-Verlag/Wien 2004.

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