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Lateral Control of Protein Adsorption on Charged Polymer Gradients
Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.ORCID iD: 0000-0002-1639-5735
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2009 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 6, 3755-3762 p.Article 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.

Place, publisher, year, edition, pages
2009. Vol. 25, no 6, 3755-3762 p.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-17501DOI: 10.1021/la803443dOAI: oai:DiVA.org:liu-17501DiVA: diva2:209880
Available from: 2009-03-27 Created: 2009-03-27 Last updated: 2017-12-13
In thesis
1. Imaging surface plasmon resonance
Open this publication in new window or tab >>Imaging surface plasmon resonance
2008 (English)Doctoral 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.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2008. 68 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1205
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-14923 (URN)978-91-7393-820-4 (ISBN)
Public defence
2008-09-26, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2008-09-30 Created: 2008-09-30 Last updated: 2017-01-11Bibliographically approved
2. Hydrogel coatings for biomedical and biofouling applications
Open this publication in new window or tab >>Hydrogel coatings for biomedical and biofouling applications
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Many applications share a substantial and yet unmet need for prediction and control of interactions between surfaces and proteins or living cells. Examples are blood-contacting biomaterials, biosensors, and non-toxic anti-biofouling coatings for ship hulls. The main focus of this thesis work has been the synthesis, characterization and properties of a group of coatings, designed for such applications. Many types of substrates, particularly plastics, were coated directly with ultrathin, hydrophilic polymer coatings, using a newly developed polymerization method initiated by short-wavelength ultraviolet light.

The thesis contains eight papers and an introduction aimed to provide a context for the research work. The common theme, discussed and analyzed throughout the work, has been the minimization of non-specific binding of proteins to surfaces, thereby limiting the risk of uncontrolled attachment of cells and higher organisms. This has mainly been accomplished through the incorporation of monomer units bearing poly(ethylene glycol) (PEG) side chains in the coatings. Such PEG-containing “protein resistant” coatings have been used in this work as matrices for biosensor applications, as blood-contacting inert surfaces and as antibiofouling coatings for marine applications, with excellent results. The properties of the coatings, and their interactions with proteins and cells, have been thoroughly characterized using an array of techniques such as infrared spectroscopy, ellipsometry, atomic force microscopy, surface plasmon resonance and neutron reflectometry. In addition, other routes to fabricate coatings with high protein resistance have also been utilized. For instance, the versatility of the fabrication method has enabled the design of gradients with varying electrostatic charge, affecting the protein adsorption and leading to protein resistance in areas where the charges are balanced.

This thesis also describes a novel application of imaging surface plasmon resonance for the investigation of the surface exploration behavior of marine biofouling organisms, in particular barnacle larvae. This technique allows for real-time assessment of the rate of surface exploration and the deposition of protein-based adhesives onto surfaces, a process which was previously very difficult to investigate experimentally. In this thesis, the method was applied to several model surface chemistries, including the hydrogels described above. The new method promises to provide insights into the interactions between biofouling organisms and a surface during the critical stages prior to permanent settlement, hopefully facilitating the development of antibiofouling coatings for marine applications.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2010. 74 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1302
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-54304 (URN)978-91-7393-435-0 (ISBN)
Public defence
2010-03-19, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 00:00 (English)
Opponent
Supervisors
Available from: 2010-03-08 Created: 2010-03-08 Last updated: 2017-01-11Bibliographically approved

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Ekblad, TobiasAndersson, OlofTai, Feng-iEderth, ThomasLiedberg , Bo

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