Catli, Candan

Nanobiotechnology is an important branch of nanotechnology, which has been
dramatically developed for creating functional nanoscale materials for various
biomedical applications. The past few decades have witnessed significant advances in
the development of various functionalized surfaces for applications in a wide range of
fields such as chemistry, biology, pharmacy and physics. There has recently been
extensive research to modify gold surfaces, thereby opening up opportunities to
enhance breadth of their applicability. Recently developed methods have allowed the
modification of gold nanoparticles with suitable functionalizing agents, facilitate their
applications in different areas such as chemical and biological sensing, imaging
labelling, delivering, heating and biomedical applications such as cancer diagnostics
and therapy, drug delivery, gene delivery, DNA and RNA analysis, antibacterial agent,
vaccine preparation, brain implants, artificial skin and improving electrical signaling in
the heart. Apart from gold nanoparticle surfaces, there are various blood contacting
biomedical devices used for applications such as heart valves, vascular grafts, stents, in
vivo biosensors etc. The lack of hemo compatibility is main problem of cardiovascular
and other blood contacting medical devices. Congestion of small diameter vascular
grafts and failure of blood contacting biosensors due to thrombus formation on device
surface might be counted as some examples for this hemo compatibility problem. Non
specific protein adsorption can decrease device performance, such as in the case of in
vivo biosensor and stent surfaces. For this reason, improvement of anticoagulant
devices or drugs is required for long term applications.
Surface modification is an essential process in biotechnological fields such as tissue
engineering, biosensors, or implant manufacturing. Covalently bound polymer films
offer an efficient and convenient way of modifying physicochemical characteristics of
material surfaces used for various applications such as stabilization of colloidal
particles, non-fouling coatings, and responsive films for sensors. Sofar, several
strategies were developed for modification of device surfaces with an aim of reducing
non-specific protein adsorbtion. Synthetic polymers serve as excellent candidates for
surface modification because of their tunable mechanical properties, the variability of
film thickness, degree of functionality and because of the potential multifunctional
stimuli responsivity. Furthermore, synthetic polymers and their hybrids with biological
molecules have been widely used in biotechnology, biomedical, and pharmaceutical
technologies. In terms of the role of nanoscale properties in applications, it is important
to tailor the properties of polymers at molecular level to fulfill the performance criteria
better for any given application. The design requirements of polymers vary widely
according to the application. The key properties for various applications can be
counted as the molecular weight, molecular architecture, composition and chemical
functionality. The uniformity in these key properties is mandatory for most biological
applications of polymers (e.g. biomaterial surfaces), as it enables the performance to be
correlated with structure.
Among the variety of techniques that allow the formation of polymer thin films for
surface modification, polymer brushes have gained special attention along the past
decades due to their unique structures in combination with the possibility offered by
controlled / “living” radical polymerization techniques (CLRP) to generate polymeric
thin films with precisely controlled thickness, composition and architecture. Polymer
brushes can be defined as an assembly of polymer chains which are tethered by one
ends to a surface. Despite their interesting properties and the numerous reports
describing synthetic pathways of polymer brushes via different CLRP techniques,
polymer brush formation via Reversible Addition Fragmentation Chain Transfer
(RAFT) polymerization technique has received little attention so far. RAFT
polymerization is the most versatile platform for controlled synthesis of polymers for
biological applications, with respect to monomer types and reaction conditions. When
it comes to polymer brush formation on gold planar surfaces via RAFT technique,
there has been a few studies in literature. This thesis describes how RAFT
polymerization technique is successfully adapted onto gold surfaces with an aim of
construction of dense polymer brush layers.
So far, the privileged way to tune the desired features, functionalities of a surface has
been the growth of tethered polymer chains by the combination of a CRP technique
with “grafting from” approach. However, this approach is experimentally rather
complex as it involves multi-step synthetic procedures. With this background in mind,
the main objective of this thesis work was to develop novel Raft based synthetic
approaches for fabrication of polymer brushes with different architectures on gold
surface. The interest to develop new synthetic strategies, which are relatively easier
than multi-step procedures in literature used for synthesis of brushes, lies in the
possibility of utilization of these novel straightforward techniques for the design and
production of novel biomaterials used for advanced biomedical applications. The
originality of this thesis work stems from the fact that the chemisorption tendency of
raft agents toward gold and the specific mechanistic principles of RAFT, which allows
for various synthetic strategies of performing surface-confined RAFT
polymerizations, were successfully combined in order to develop novel straight
forward pathways for synthesis of polymer brushes with complex topologies on gold

Georg-August-University Göttingen

Novel synthetic approaches for fabrication of polymer brushes on gold surfaces via Raft polymerization: A new era for gold modification

https://ediss.uni-goettingen.de/bitstream/11858/00-1735-0000-002E-E353-2/1/ThesisCANDANCATLI.pdf

Novel synthetic approaches for fabrication of polymer brushes on gold surfaces via Raft polymerization: A new era for gold modification

Abstract

Similar works

Full text

Available Versions

Georg-August-University Göttingen