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pH-control of the protein resistance of thin hydrogel gradient films
Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
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2014 (English)In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 10, no 32, p. 5955-5964Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Royal Society of Chemistry , 2014. Vol. 10, no 32, p. 5955-5964
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:liu:diva-110502DOI: 10.1039/c4sm00833bISI: 000340474400011PubMedID: 24987939OAI: oai:DiVA.org:liu-110502DiVA, id: diva2:746404
Note

Funding Agencies|European Commission [NMP-CT-2005-011827]; European Community [237997]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]

Available from: 2014-09-12 Created: 2014-09-12 Last updated: 2019-04-24
In thesis
1. Surface characterization and manipulation of polyampholytic hydrogel coatings
Open this publication in new window or tab >>Surface characterization and manipulation of polyampholytic hydrogel coatings
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
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.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2019. p. 74
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1987
Keywords
Hydrogels, antifouling, charge-balanced material, polyampholytes, force measurements, polymer swelling, protein adsorption, patterning, plasmonics
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:liu:diva-156496 (URN)10.3384/diss.diva-156496 (DOI)9789176850831 (ISBN)
Public defence
2019-05-17, Planck, Fysikhuset, Campus Valla, Linköping, 10:00 (English)
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Supervisors
Available from: 2019-04-24 Created: 2019-04-24 Last updated: 2019-04-29Bibliographically approved

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Tai, Feng-iAndersson, OlofEkblad, TobiasEderth, Thomas

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