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Lateral Control of Protein Adsorption on Charged Polymer Gradients
Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensorvetenskap och Molekylfysik. Linköpings universitet, Tekniska högskolan.
Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensorvetenskap och Molekylfysik. Linköpings universitet, Tekniska högskolan.
Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensorvetenskap och Molekylfysik. Linköpings universitet, Tekniska högskolan.
Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensorvetenskap och Molekylfysik. Linköpings universitet, Tekniska högskolan.ORCID-id: 0000-0002-1639-5735
Visa övriga samt affilieringar
2009 (Engelska)Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, nr 6, s. 3755-3762Artikel i tidskrift (Refereegranskat) 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.

Ort, förlag, år, upplaga, sidor
2009. Vol. 25, nr 6, s. 3755-3762
Nationell ämneskategori
Naturvetenskap
Identifikatorer
URN: urn:nbn:se:liu:diva-17501DOI: 10.1021/la803443dOAI: oai:DiVA.org:liu-17501DiVA, id: diva2:209880
Tillgänglig från: 2009-03-27 Skapad: 2009-03-27 Senast uppdaterad: 2019-04-24
Ingår i avhandling
1. Imaging surface plasmon resonance
Öppna denna publikation i ny flik eller fönster >>Imaging surface plasmon resonance
2008 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Linköping: Linköping University Electronic Press, 2008. s. 68
Serie
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1205
Nationell ämneskategori
Kemi
Identifikatorer
urn:nbn:se:liu:diva-14923 (URN)978-91-7393-820-4 (ISBN)
Disputation
2008-09-26, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2008-09-30 Skapad: 2008-09-30 Senast uppdaterad: 2017-01-11Bibliografiskt granskad
2. Hydrogel coatings for biomedical and biofouling applications
Öppna denna publikation i ny flik eller fönster >>Hydrogel coatings for biomedical and biofouling applications
2010 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Linköping: Linköping University Electronic Press, 2010. s. 74
Serie
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1302
Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:liu:diva-54304 (URN)978-91-7393-435-0 (ISBN)
Disputation
2010-03-19, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 00:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2010-03-08 Skapad: 2010-03-08 Senast uppdaterad: 2020-02-19Bibliografiskt granskad
3. Surface characterization and manipulation of polyampholytic hydrogel coatings
Öppna denna publikation i ny flik eller fönster >>Surface characterization and manipulation of polyampholytic hydrogel coatings
2019 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

This thesis is dedicated to building up fundamental knowledge about polyampholytic hydrogels, which are developed in our group for anti-fouling purposes. Charge-balanced polymers, where positive and negative charges balance each other, have emerged as interesting candidates for many applications in materials science. We have prepared charge-balanced materials by forming thickness gradients of oppositely charged polyelectrolytes, and use these as model systems for a systematic investigation of the materials and their responses to environmental changes. These hydrogel gradients were sequentially grafted from substrates via surface-initiated photografting and photopolymerization (SIPGP) of cationic and anionic polyelectrolytes. At some thickness ratios, these form a charge-balanced system where the net surface charge is zero, and with certain similarity to zwitterionic systems. The surface charge of the hydrogels is the principal parameter regulating non-specific protein adsorption, and among other things, we demonstrate that the position of the fouling-resistant charge-neutral region can be manipulated upon pH changes. The chemical compositions of the hydrogel gradients were characterized by microscopic infrared spectroscopy. Optical analysis by spectroscopic ellipsometry and imaging surface plasmon resonance were used to monitor the swelling of the hydrogel films, and protein adsorption onto these in real-time. Surface forces, i.e. the interactions with the hydrogels from an intermolecular perspective, which are related mainly to electrostatic and steric forces, were probed by direct force measurement using atomic force microscopy. Force curves were used to determine the surface charge distribution over the hydrogels, and to indicate the correlation between surface charge and protein adsorption. In the later work, hydrogel gradients were patterned as arrayed spots. Their thicknesses and surface roughness provide further information about the polymer structure and provides a basis for relating ellipsometric swelling profiles to thicknesses as obtained by atomic force microscopy. Finally, it is demonstrated how charged hydrogel films can be used as spacers to tune the optimum distance between silver nanoparticles and fluorophores for metal-enhanced fluorescence (MEF). The aim of this work is to understand polyampholytic hydrogels from various perspectives: surface charges and their distribution, the polymer structure, and surface interactions. The knowledge and experience obtained contribute to the general understanding of zwitterionic materials, and to the development of anti-fouling coatings, optical sensing platforms and other applications of charge-balanced hydrogels.

Ort, förlag, år, upplaga, sidor
Linköping: Linköping University Electronic Press, 2019. s. 74
Serie
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1987
Nyckelord
Hydrogels, antifouling, charge-balanced material, polyampholytes, force measurements, polymer swelling, protein adsorption, patterning, plasmonics
Nationell ämneskategori
Polymerkemi
Identifikatorer
urn:nbn:se:liu:diva-156496 (URN)10.3384/diss.diva-156496 (DOI)9789176850831 (ISBN)
Disputation
2019-05-17, Planck, Fysikhuset, Campus Valla, Linköping, 10:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2019-04-24 Skapad: 2019-04-24 Senast uppdaterad: 2019-04-29Bibliografiskt granskad

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