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Hydrogels from a water-soluble Zwitterionic polythiophene: dynamics under pH change and biomolecular interactions observed using quartz crystal microbalance with dissipation monitoring
Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
Solid State Physics, Lund University, Lund, Sweden .
Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
2005 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, no 16, 7292-7298 p.Article in journal (Refereed) Published
Abstract [en]

The water-soluble zwitterionic polythiophene, poly(3-((S)-5-amino-5- carboxyl-3-oxapentyl)-2,5-thiophene) hydrochloride (POWT), is a conjugated polyelectrolyte (CPE) with properties well suited for biochip applications. CPEs readily form hydrogels when exposed to water-based buffer solutions or biomolecule solutions. In this work, we used in situ quartz crystal microbalance with dissipation (QCM-D) monitoring to collect information on the interaction between POWT films exposed to buffers with different pH and POWT/DNA chains. Our data show that POWT swells significantly when exposed to low-pH buffers, such as pH 4 acetate, this is seen as an increase in thickness and decrease in viscosity obtained via a Voight-based modeling of combined f and D QCM-D measurements. The magnitude of thickness and viscosity change upon changing from a pH 10 carbonate buffer to pH 4 acetate is 100% increase in thickness and 50% decrease in viscosity. The response of the hydrogel under pH change is well correlated with fluorescence data from POWT films on glass. The state of the hydrogel is important during interaction with biomolecules; illustrated by the observation that a swollen CPE hydrogel adsorbs a higher amount of DNA than a compacted one. In agreement with previous results, the QCM-D data confirmed that the POWT/DNA hydrogel sense complementary DNA specifically and with negligible binding of noncomplementary DNA. These results are important for efficient constructions of biochips in water environments using this class of materials.

Place, publisher, year, edition, pages
2005. Vol. 21, no 16, 7292-7298 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-12726DOI: 10.1021/la050479eOAI: oai:DiVA.org:liu-12726DiVA: diva2:16928
Available from: 2007-12-07 Created: 2007-12-07 Last updated: 2017-12-14
In thesis
1. Biological Sensing and DNA Templated Electronics Using Conjugated Polymers
Open this publication in new window or tab >>Biological Sensing and DNA Templated Electronics Using Conjugated Polymers
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Conjugated polymers have been found useful in a wide range of applications such as solar cells, sensor elements and printed electronics, due to their optical and electronic properties. Functionalization with charged side chains has enabled water solubility, resulting in an enhanced interaction with biomolecules. This thesis focus on the emerging research fields, where these conjugated polyelectrolytes (CPEs) are combined with biomolecules for biological sensing and DNA nanowire assembling.

CPEs have shown large potential in biomolecular detection where the optical read out is due to the geometrical alternation in the backbone and aggregation state. This thesis focused on transferring the biomolecular detection to a surface of CPEs. The characterization of the CPE layer show that a hydrogel can be formed, and how the layer can undergo geometrical changes upon external stimulus such as pH change. A selective sensor surface can be created by imprinting ssDNA or an antibody in the CPE layer. The discrimination for complementary DNA hybridization and specific antibody interaction can be monitored by surface plasmon resonance or quartz crystal microbalance. We have also taken the step out from the controlled test tube experiments to the complex environment of the cell showing the potential for staining of compartments and structures in live and fixed cell. Depending on the conditions and CPE used, cell nuclei, acidic vesicles and cytoskeleton structure can be visualized. Furthermore, the live staining shows no sign of toxic effect on cultured fibroblasts.

CPEs can also be a valuable element when assembling electronics in the true nano regime. I have used DNA as building template due to its attractive size features, with a width of around 2 nm and a length scale in the µm regime, and the inbuilt base-paring recognition elements. This thesis shows how DNA can be decorated with CPEs and stretched on surfaces into a model for aligned semiconducting nanowire geometries. Not only making the template structures is of importance, but also how to place them on the correct surface position, i.e. on electrodes. Strategies for positioning DNA nanowires using transfer printing and surface energy patterning methods have therefore been developed in the thesis. The stretched DNA decorated with CPE also offers a way to further study the molecular binding interaction between the two molecules. Single molecular spectroscopy in combination with polarization has given information of the variation of the CPE binding along a DNA chain.

Place, publisher, year, edition, pages
Institutionen för fysik, kemi och biologi, 2007
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1154
Keyword
conjugated polymer, conjugated polyelectrolyte, DNA, sensor, nanowire
National Category
Industrial Biotechnology
Identifiers
urn:nbn:se:liu:diva-10180 (URN)978-91-85895-17-5 (ISBN)
Public defence
2007-12-14, Planck, Fysikhuset, Campus Valla, Linköpings Universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2007-12-07 Created: 2007-12-07 Last updated: 2009-04-23
2. Hydrogels of conjugated polyelectrolytes for biosensor and biochip applications
Open this publication in new window or tab >>Hydrogels of conjugated polyelectrolytes for biosensor and biochip applications
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis describes the use of conjugated polyelectrolytes (CPEs) in biosensor devices. The method is based on non-covalent assembly of the biomolecule of interest and the CPE functioning as the reporter, in one case as a transducer, of biomolecular events. Devices of these assemblies on solid supports that can operate in liquid solutions have been the focus. Polythiophenes, both semiconducting and conducting, is the class of materials that has been used in this work. The semiconducting polythiophenes have ionic side chains which makes them water soluble. This ionic side chain is capable of both forming electrostatic and hydrogen bonds, and when paired with the hydrophobic backbone of the polymer a great number of interactions with biomolecules are possible. The highly conducting polythiophene derivative PEDOT -PSS, (PEDOT) doped with ionic and water soluble PSS polyelectrolyte, was used as the conducting material in 3D-electrode. Both the semiconducting and conducting polymers described above forms hydrogels on solid supports if crosslinked with the appropriate ion, biomolecule or polymer. Evaluation of the CPEs, both with and without biomolecules, was performed in liquid, solid and hydrogel state using a number of techniques. This was done to understand how the CPEs behave when exposed to different buffer systems and various biomolecules.

Hydrogels of conjugated polyelectrolytes combined with biomolecules are attractive as biosensors. The advantage with the hydrogel format is the high water content, the porous structure and the large capacity of binding molecules. High water content is important to preserve the biomolecules by providing the correct buffered environment. In this thesis we demonstrated a hydrogel of the highly conducting PEDOT -PSS polymer that was crosslinked on a solid support together with horseradish peroxidase (HRP) enzyme, forming an enzyme-enhanced electrode. Further studies of hydrogels were done using in situ quartz crystal microbalance with dissipation (QCM-D). POWT is a CPE withproperties well suited for biochip applications and readily forms hydrogels when exposed to water-based buffer solutions or biomolecule solutions. Detection ofcomplementary DNA and rejection of non-complementary DNA in a POWT hydrogel was demonstrated. The interaction between POWT and DNAoligonucleotides was also evaluated using fluorescence resonance energy transfer (FRET) in solution. Labeled DNA oligonucleotides with energy accepting or donating fluorophores allowed us to determine distance and binding stoichiometry in the non-covalent POWT-DNA complex.

Patterning and anchoring of biomolecules and non-covalent assembled CPE-biomolecule complexes to a chip surface was studied; in the adsorbed state these complexes are hydrogels. Our novel method is based on the modification of the surface energy of a hydrophilic substrate surface using hydrophobic poly(dimethylsiloxane) (PDMS) elastomer stamp containing a relief pattern. Different conformations in biomolecules could be detected using fluorescence microscopy, where the CPEs acts as reporters and the PDMS modified substrates as discriminator. Also, excellent enzyme activity in patterned CPE/Horseradish peroxidase (HRP) enzyme was shown.

Distances between the individual molecules in solid state devices of conjugated polymers can be small. In luminescence devices, such as light emitting diodes or fluorescence biosensors, there is a chance of interaction between conjugated molecules especially if more than one type of molecule is present. Quenching of the light and fluorescence energy transfer can occur and a simple approach to study this was developed.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2005. 78 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 982
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-30215 (URN)15710 (Local ID)91-85457-58-2 (ISBN)15710 (Archive number)15710 (OAI)
Public defence
2005-12-09, Hörsal Planck, Campus Valla, Linköping, 10:15 (Swedish)
Opponent
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2012-12-03

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Åsberg, PeterBjörk, PerInganäs, Olle

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