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9 Bioinspired Hierarchically Structured Polymer Interfaces …
disease diagnosis, detection of fungi, bacteria, or virus. For instance, many of the
recently established technologies for detection of circulating tumor cells (CTCs,
they are detached cancer cells from solid primary tumors in the bloodstream, which
have been regarded as potentially accessible source for diagnosis and monitoring
of cancer progression and treatment) exploit nanostructures, including nanodots [1],
nanotubes [2, 3], nanopillars [4, 5], nanofibers [6, 7], nanowires [5, 8], nanorods
[9], and some other irregular nanostructures [10, 11]. These nanoscaled topographies allow for enhanced local topographic interactions between the substrate and
nanoscale components of the cellular surface (e.g., filopodia and microvilli) and result
in vastly improved cell-capture affinity compared to unstructured flat substrates [12].
Besides, at these nanostructured biointerfaces, cell activities such as recognition,
adhesion, nutrient uptake, and impulse conduction take place along with molecular interactions [13, 14]. These facts indicate the importance of combining nanostructures with surface chemistry to design functional cell biointerfaces that achieve
effective cell–materials interactions [15].
Except for nanostructures, microstructures have been recently utilized for
enhanced cell capture [16, 17]. Compared to plain surfaces, microstructured topographies provide a larger surface area for the immobilization of antibody (e.g., the
epithelial cell adhesion molecule anti-body (anti-EpCAM)), thereby increasing the
binding odds between membrane receptors and antibodies and thus enhancing the
CTC-capture efficiency. Moreover, the dimensions of CTCs themselves are on the
micron length scale, hence rough substrates possessing a microscale topographic
structures could afford better contact with the targeted cells and facilitate cell
capture [16]. Therefore, intricately hierarchically structured substrates exhibiting
both microstructures that accommodate cells (via maximized contact between cell
and the microstructure capture surrounding) and nanostructures fitting the cellular
pseudopods hold great promise to further enhance the capture of CTCs.
Numerous tools and processes are available to fabricate hierarchical surfaces,
such as chemical etching [18], chemical vapor deposition [19, 20], electrospinning
[21], hot embossing [22], and lithography [23], but specialized setups and optimized
conditions are required for most of these techniques. Noteworthy, multilevel structural hierarchy can often be observed in natural biological systems, such as rose
petals, butterfly wings, gecko feet, shells, etc. These natural hierarchical structures
can be directly utilized as templates to replicate the micro/nanostructures onto a
suitable substrate, which represents a low-cost strategy that is devoid of special
setup.
Here, natural red rose petal is a good potential template because the size of their
microstructures (diameters of the hemispherical micropapillae are 20–30 μm), which
is similar to that of a CTC, may facilitate cell attachment (Fig. 9.1). In addition,
there are many nanoscale wrinkles superimposed on these microstructures, being
conducive for cellular pseudopods to grasp on the surface [24]. For replication polydimethylsiloxane (PDMS) was chosen because it has been reported to replicate even
individual carbon nanotubes and the stiffness of soft polymeric material is close to
extracellular matrix [25]. This may lead to enhanced cell adhesion compared to stiff
inorganic materials [26]. The preparation of hierarchical rose petal-derived PDMS
9 Bioinspired Hierarchically Structured Polymer Interfaces …
disease diagnosis, detection of fungi, bacteria, or virus. For instance, many of the
recently established technologies for detection of circulating tumor cells (CTCs,
they are detached cancer cells from solid primary tumors in the bloodstream, which
have been regarded as potentially accessible source for diagnosis and monitoring
of cancer progression and treatment) exploit nanostructures, including nanodots [1],
nanotubes [2, 3], nanopillars [4, 5], nanofibers [6, 7], nanowires [5, 8], nanorods
[9], and some other irregular nanostructures [10, 11]. These nanoscaled topographies allow for enhanced local topographic interactions between the substrate and
nanoscale components of the cellular surface (e.g., filopodia and microvilli) and result
in vastly improved cell-capture affinity compared to unstructured flat substrates [12].
Besides, at these nanostructured biointerfaces, cell activities such as recognition,
adhesion, nutrient uptake, and impulse conduction take place along with molecular interactions [13, 14]. These facts indicate the importance of combining nanostructures with surface chemistry to design functional cell biointerfaces that achieve
effective cell–materials interactions [15].
Except for nanostructures, microstructures have been recently utilized for
enhanced cell capture [16, 17]. Compared to plain surfaces, microstructured topographies provide a larger surface area for the immobilization of antibody (e.g., the
epithelial cell adhesion molecule anti-body (anti-EpCAM)), thereby increasing the
binding odds between membrane receptors and antibodies and thus enhancing the
CTC-capture efficiency. Moreover, the dimensions of CTCs themselves are on the
micron length scale, hence rough substrates possessing a microscale topographic
structures could afford better contact with the targeted cells and facilitate cell
capture [16]. Therefore, intricately hierarchically structured substrates exhibiting
both microstructures that accommodate cells (via maximized contact between cell
and the microstructure capture surrounding) and nanostructures fitting the cellular
pseudopods hold great promise to further enhance the capture of CTCs.
Numerous tools and processes are available to fabricate hierarchical surfaces,
such as chemical etching [18], chemical vapor deposition [19, 20], electrospinning
[21], hot embossing [22], and lithography [23], but specialized setups and optimized
conditions are required for most of these techniques. Noteworthy, multilevel structural hierarchy can often be observed in natural biological systems, such as rose
petals, butterfly wings, gecko feet, shells, etc. These natural hierarchical structures
can be directly utilized as templates to replicate the micro/nanostructures onto a
suitable substrate, which represents a low-cost strategy that is devoid of special
setup.
Here, natural red rose petal is a good potential template because the size of their
microstructures (diameters of the hemispherical micropapillae are 20–30 μm), which
is similar to that of a CTC, may facilitate cell attachment (Fig. 9.1). In addition,
there are many nanoscale wrinkles superimposed on these microstructures, being
conducive for cellular pseudopods to grasp on the surface [24]. For replication polydimethylsiloxane (PDMS) was chosen because it has been reported to replicate even
individual carbon nanotubes and the stiffness of soft polymeric material is close to
extracellular matrix [25]. This may lead to enhanced cell adhesion compared to stiff
inorganic materials [26]. The preparation of hierarchical rose petal-derived PDMS