Electrochemical formation of hydrogel films for bioanalytics [Elektronische Ressource] / submitted by Johanna Bünsow

Johanna Spyri

Informations

• Publié par: technische_universitat_clausthal
• Publié le: 01 janvier 2008
• Nombre de lectures: 57
• Langue: English
• Poids de l'ouvrage: 8 Mo

Extrait

Electrochemical Formation
of Hydrogel Films for Bioanalytics
Doctoral Thesis
(Dissertation)
to be awarded the degree of
Doctor rerum naturalium (Dr. rer. nat.)
submitted by
Johanna Bünsow
from Kassel
approved by the Faculty of Natural and Materials Sciences,
Clausthal University of Technology

Date of oral examination
October 31, 2008




Chairperson of the Board of Examiners: Prof. Dr. Dieter Kaufmann
Chief Reviewer: Prof. Dr. Diethelm Johannsmann
Reviewer: Prof. Dr. Wilhelm Oppermann















This thesis was written at the Institute of Physical Chemistry at Clausthal University of
Technology, Clausthal-Zellerfeld, Germany, in the period from November 2005 to
October 2008. Parts of this work have been published previously. The following
publications have been finalized:
• “Patterned Hydrogel Layers Produced by Electrochemically Triggered
Polymerization”
Bünsow, J., Johannsmann, D. Macromolecular Rapid Communications, submitted.
• “Electrodeposition of Amino-Functionalized Particles in a pH Gradient:
Quantitative Investigations Employing an Electrochemical Quartz Crystal
Microbalance”
Bünsow, J., Grabs, I.-M., Schmidt-Naake, G., Johannsmann, D. Macromolecular
Symposia, accepted.
• “Preparation of Hydrogel-Silica Composite Films by Electrochemically Triggered
Deposition”
Bünsow, J., Petri, J., Johannsmann, D. Macromolecular Symposia, accepted.
• “Influence of Added Salt on the Thickness and Morphology of Electrochemically
Produced Responsive Hydrogel Films”
Bünsow, J., Johannsmann, D. Journal of Colloid and Interface Science 2008, 326,
61–65.
• “Production of Polyacrylic Acid Homo- and Copolymer Films by
Electrochemically Induced Free-Radical Polymerization: Preparation and
Swelling Behavior“
Bünsow, J., Johannsmann, D. Macromolecular Symposia 2007, 248, 207–212.
• “Formation of Surface-Attached Responsive Gel Layers via Electrochemically
Induced Free-Radical Polymerization”
Reuber, J., Reinhardt, H., Johannsmann, D. Langmuir 2006, 22, 3362–3367.
• “Simultaneous Determination of Density and Viscosity of Liquids Based on
Quartz-Crystal Resonators Covered with Nanoporous Alumina”
Goubaidoulline, I., Reuber, J., Merz, F., Johannsmann, D. Journal of Applied
Physics 2005, 98, 014305.

















Meinen Eltern


Acknowledgements
My thank goes to all the people who contributed to this work. I am particularly
thankful to Prof. Dr. Diethelm Johannsmann for giving me the opportunity to work on
this exciting project, for numerous interesting and helpful discussions, and for the
support on all stages and in all aspects of my PhD thesis.
I want to thank Prof. Dr. Wilhelm Oppermann for reviewing my thesis and many
stimulating discussions.
Special thanks go to PD Dr. Philipp Vana for fruitful discussions concerning the
combination of RAFT polymerization with EIP and for providing the RAFT agent
used in this work. For the synthetic work, I want to thank Johannes Kaschel and Kai
Kalz from the University of Göttingen. Without the participation in the European
Graduate School on Microstructural Control in Free-Radical Polymerization (EGS),
this collaboration would not have developed. Thus, I want to thank the EGS for help
in “networking” and for giving me the opportunity to meet many people with whom I
had numerous interesting discussions.
Another special thank goes to the group of Prof. Dr. Wolfgang Schuhmann at the Ruhr
University Bochum – particularly to Sebastian Neugebauer – for training me in
amperometric biosensing and electrochemical methods in general. Their introduction
helped a lot and enabled me to carry out the part of my work concerned with
amperometric glucose detection.
I am also very thankful to all people who contributed to this work (in no particular
order):
• Judith Petri always supported me with her work, especially in the field of
hybrid coatings and pOEGMA homopolymer films.
• Dr. Arne Langhoff helped me countless times with discussions, technical help,
and measurements with the confocal microscope.
• Dr. Ilya Reviakine introduced me to AFM imaging and helped me with many
stimulating discussions. In particular, his knowledge on biological systems was
very helpful.
• Mathis Düwel helped me a lot with his knowledge on electrochemistry.
• Markus Topp imaged spots with an optical microscope in the Institute of
Polymer Materials and Plastics Engineering, Clausthal University of
Technology.
• Uwe Cronjäger built quartz holders, the temperature controlled liquid cell, and
many more very helpful technical components.
• Roland Zain constructed the glass cell used for temperature controlled sensor
tests.
• Anne Finger acquired images of hydrogel spots with the confocal microscope.
• Robert Scherf investigated alternative electrochemical patterning techniques.
• Björn Kussmaul and Ralf Elze carried out preliminary studies on the effect of
salts on EIP of pNIPAm.
• Maria Krusche and Matthias Alhelm worked on the first steps towards a locally
induced pattern formation.
• Christian Kaldun, Maik Sievers, Katja Pohl, and Anne Enzenberg were
involved in experiments on the deposition of pOEGMA films and their
application in biosensing.
• Special thanks are addressed to Julia Gansel, Markus Susoff, Dr. Sebastian
Seiffert, and Dr. Arne Langhoff for the correction of this work and many
helpful discussions.
Of course I am also deeply grateful to all other people in the institute for numerous
discussions, for practical help whenever it was needed, and for the perfect working
atmosphere. My group as well as PD Dr. Jörg Adams and Dr. Andrey Turshatov
always gave me great input, especially in the group meetings. Many thanks are
dedicated to Kerstin and Sergiy for a funny time in our office. Michael and Astrid
never hesitated to support me when practical help, material, or reactants were needed.
Julia, Markus, Sebastian, Conny, and Arne always allowed me to join them for lunch
where we had countless discussions on science and beyond. Ralf is acknowledged for
his support with all electrical issues and all the unbelievable situations in the coffee
room.
The financial support to this work was provided by the German Research Foundation
(Deutsche Forschungsgemeinschaft, DFG) which is gratefully acknowledged. In
addition, I want to thank all the people from the priority program “Smart hydrogels”
for pleasant meetings and many stimulating discussions.
On the private side, I want to thank sincerely my husband Christian, my parents, and
Maximilian and Kamila for the support over all the years. I am also very thankful to
my family-in-law. Last but not least I thank all my friends, especially Tina, Julia, and
Friederike for being at my side.






Abstract
Thermoresponsive homo- and copolymer hydrogel films of N-isopropylacrylamide
(NIPAm) and oligo(ethylene glycol) methacrylate (OEGMA) were prepared by
electrochemically induced polymerization. The deposition was investigated with an
electrochemical quartz crystal microbalance (EQCM). The film thickness ranged from
5 to 100 nm. Factors of influence on the film thickness of pNIPAm were the
preparation temperature, the solution pH, and additives such as cross-linker, salt, and
chain transfer agents. The chain transfer agents used were sodium formate and a
reversible addition–fragmentation chain transfer (RAFT) agent. The pNIPAm films
showed a lower critical solution temperature (LCST) of 30 °C in water. Added salt
and copolymerization with the hydrophilic OEGMA shifted the LCST. In acidic
solutions, the surface roughness increased with the film thickness. Models for the
structure formation were proposed that take into account microgel formation and
hydrogen evolution underneath thick collapsed hydrogel films. Shifting the solution
pH to higher values hindered the polymerization. When chain transfer agents were
added to the basic reactant solution, both the film thickness and the lateral
homogeneity increased. Both chain transfer agents enhanced the rate of initiator
decomposition. Sodium formate additionally acted as an electrochemical initiator
itself. PNIPAm films produced in the presence of RAFT agent contained active RAFT
groups and could be electrochemically modified with polystyrene in a second
polymerization step.
Laterally heterogeneous films were produced by a new patterning technique where
oxygen bubbles induced the local deposition of the hydrogel. The hydrogel patterns
reproduced the size and the shape of the bubbles. The observed feature sizes were of a
few tens of microns. Structure formation could be actively controlled by
electrochemical production of an oxygen bubble in a small gap between the substrate
and an insulated counter electrode. The enzyme glucose oxidase could be
encapsulated into a hydrogel spot. The m