2
1 Reactive Platforms for Controllable Fabrication …
currently attracts a lot of attention for a number of reasons, originating, e.g., from
unsolved questions and problems in gene therapy [5].
In this context convenient and reproducible surface modification procedures that
yield robust, functional biointerfaces are highly desirable. The requirements for
obtaining such interfaces include, among others, the orientation-selective immobilization (conjugation) of biomolecules, such as receptors, antibodies and proteins,
the retention of the biological activity of these immobilized biomolecules, the control
(elimination) of non-specific biomolecule (e.g., protein) adsorption, high molecular
loading in bio-available configurations, the control of intermolecular distances in the
substrate normal direction, defined mechanical properties of underlying substrates,
as well as the control of roughness and topographical structures, patterns, etc.
Self-assembled monolayer (SAM) approaches [6], which can produce
monomolecular films, have been applied to immobilize biological molecules on a
variety of substrates. SAMs have also been successfully used for the development
of (in vitro) biosurfaces that can, for instance, mimic naturally occurring molecular
recognition processes due to the structural and compositional control in SAMs with
almost molecular precision [7]. However, a number of inherent characteristics, such
as environmental stability [8], and also the absence of independent control of chemical and topographical patterns together with variable substrate moduli, as deemed
crucial for cell–surface interaction studies [9], impose limitations for their application, e.g., in studies of cell–surface interactions. Similarly, the molecular loading of
these 2D systems is limited and thus impairs the development of new highly sensitive
biosensors.
As an alternative, the deposition of polymeric materials onto solid substrates
receives increasing attention [10]. Compared to SAMs, polymeric thin films have
been shown to possess a number of important advantages, such as robustness and
stability, and the unique possibility to introduce simultaneously topographic and
chemical (compositional) patterns that span the 100 µm to sub-100 nm regime, as
well as their defined mechanical modulus for various application areas [9]. Thin films
based on polymers that incorporate reactive functional groups also provide a quasi
3D geometry that can be further modified by chemical reactions with biomolecules
and thereby overcome the mentioned intrinsic limitations of SAMs [11].
1.2 Chemical and Topographical Pattern Fabrication
from Micrometer to Nanometer Length Scales
Truly functional biointerfaces call for advanced design and preparation in order to
match the sophisticated recognition ability of biological systems, which include the
control of chemical composition on length scales spanning the 100 µm to sub-100 nm
regime. Specifically, combined topographic and chemical patterns on surfaces are
required in order to match typical spacings of proteins on the nanometer scale and
entire cells at the 10–100 µm scale. For example, it was found that the distance
1 Reactive Platforms for Controllable Fabrication …
currently attracts a lot of attention for a number of reasons, originating, e.g., from
unsolved questions and problems in gene therapy [5].
In this context convenient and reproducible surface modification procedures that
yield robust, functional biointerfaces are highly desirable. The requirements for
obtaining such interfaces include, among others, the orientation-selective immobilization (conjugation) of biomolecules, such as receptors, antibodies and proteins,
the retention of the biological activity of these immobilized biomolecules, the control
(elimination) of non-specific biomolecule (e.g., protein) adsorption, high molecular
loading in bio-available configurations, the control of intermolecular distances in the
substrate normal direction, defined mechanical properties of underlying substrates,
as well as the control of roughness and topographical structures, patterns, etc.
Self-assembled monolayer (SAM) approaches [6], which can produce
monomolecular films, have been applied to immobilize biological molecules on a
variety of substrates. SAMs have also been successfully used for the development
of (in vitro) biosurfaces that can, for instance, mimic naturally occurring molecular
recognition processes due to the structural and compositional control in SAMs with
almost molecular precision [7]. However, a number of inherent characteristics, such
as environmental stability [8], and also the absence of independent control of chemical and topographical patterns together with variable substrate moduli, as deemed
crucial for cell–surface interaction studies [9], impose limitations for their application, e.g., in studies of cell–surface interactions. Similarly, the molecular loading of
these 2D systems is limited and thus impairs the development of new highly sensitive
biosensors.
As an alternative, the deposition of polymeric materials onto solid substrates
receives increasing attention [10]. Compared to SAMs, polymeric thin films have
been shown to possess a number of important advantages, such as robustness and
stability, and the unique possibility to introduce simultaneously topographic and
chemical (compositional) patterns that span the 100 µm to sub-100 nm regime, as
well as their defined mechanical modulus for various application areas [9]. Thin films
based on polymers that incorporate reactive functional groups also provide a quasi
3D geometry that can be further modified by chemical reactions with biomolecules
and thereby overcome the mentioned intrinsic limitations of SAMs [11].
1.2 Chemical and Topographical Pattern Fabrication
from Micrometer to Nanometer Length Scales
Truly functional biointerfaces call for advanced design and preparation in order to
match the sophisticated recognition ability of biological systems, which include the
control of chemical composition on length scales spanning the 100 µm to sub-100 nm
regime. Specifically, combined topographic and chemical patterns on surfaces are
required in order to match typical spacings of proteins on the nanometer scale and
entire cells at the 10–100 µm scale. For example, it was found that the distance