40
2 Surface Reactions and Fabrication of Bioreactive Platforms …
copolymer. Microdomain patterns can also be obtained from epitaxy. In crystalline
materials, control of the solidification process is central to many technologies that
rely on the features of the resultant microstructure for achieving optimum properties.
A vertically oriented lamellar structure has been achieved by utilizing crystallization
from the microphase-separated state of a low molecular mass diblock copolymer
adjacent to boundaries formed by dewetting from the substrate. Self-organization of
hollow spherical micelles from a rod-coil diblock copolymer system in a selective
solvent for the flexible coil block and their long range, close packed self-ordering
into iridescent, ordered microporous solids is another method to get ordered patterns.
Biomaterials based on block copolymers: Block copolymers have a tendency to
self-assemble at surfaces and into micelles in a selective solvent. At an aqueous
interface, the amphiphilic property of block copolymers composed of hydrophilic
and hydrophobic segments can cause the distal end of the hydrophilic chain to extend
into the bulk aqueous solution, anchoring the hydrophilic block to the substrate
surface through hydrophobic segments. In an aqueous solution, micelles with core–
shell structure and formed through the segregation of insoluble blocks into the core,
which is surrounded by a hydrophilic shell composed of hydrophilic blocks. This
interfacial activity of amphiphilic block copolymers provides their high utility in the
biomedical field as colloidal dispersants, surface modifiers and drug carriers, and
characterization of micelle properties.
Otsuka et al. have described the recent progress in the field of block copolymer
assembly on the surface and in the solution, focusing on the biological and biomedical
application of poly(ethylene glycol) (PEG)-based block copolymers. Otsuka et al.
designed block copolymer (PEG-b-PLA) having an end-functionalized PEG (acetalPEG) segment. Reactive block copolymers of acetal-PEG-PLA can be utilized as
surface modifiers of biodegradable PLA to provide the reactive sites on the PEGylated
surface. PEG chains tethered on a surface or forming the corona of nanometer scaled
micelle exhibit the ability to sterically exclude other macromolecules and particles,
which is related to high flexibility and the large exclusion volume of PEG strands in
water. This property is particularly useful for preventing the adsorption of proteins
and adhesion of cells. In this regard, these supramolecular structures involving PEGbased block copolymers should be of substantial importance for the development of
blood contraction biomaterials, which are expected to play a key role in such fields
as cell and tissue engineering, bio-sensing, and drug delivery systems.
Biomolecules patterning on block copolymer films: By using self-assembly of
diblock copolymer, the function behind molecular arrangement of single integrins
in cell adhesion has been studied. A separation of ≥73 nm between the adhesive
dots resulted in limited cell attachment and spreading and dramatically reduces the
formation of focal adhesion and actin stress fibers. These cellular responses have been
attributed to restricted integrin clustering rather than insufficient number of ligand
molecules in cell–matrix interface since micro-nanopatterned substrates consisting
of alternating fields with dense and no nano-dots support cell adhesion.
2 Surface Reactions and Fabrication of Bioreactive Platforms …
copolymer. Microdomain patterns can also be obtained from epitaxy. In crystalline
materials, control of the solidification process is central to many technologies that
rely on the features of the resultant microstructure for achieving optimum properties.
A vertically oriented lamellar structure has been achieved by utilizing crystallization
from the microphase-separated state of a low molecular mass diblock copolymer
adjacent to boundaries formed by dewetting from the substrate. Self-organization of
hollow spherical micelles from a rod-coil diblock copolymer system in a selective
solvent for the flexible coil block and their long range, close packed self-ordering
into iridescent, ordered microporous solids is another method to get ordered patterns.
Biomaterials based on block copolymers: Block copolymers have a tendency to
self-assemble at surfaces and into micelles in a selective solvent. At an aqueous
interface, the amphiphilic property of block copolymers composed of hydrophilic
and hydrophobic segments can cause the distal end of the hydrophilic chain to extend
into the bulk aqueous solution, anchoring the hydrophilic block to the substrate
surface through hydrophobic segments. In an aqueous solution, micelles with core–
shell structure and formed through the segregation of insoluble blocks into the core,
which is surrounded by a hydrophilic shell composed of hydrophilic blocks. This
interfacial activity of amphiphilic block copolymers provides their high utility in the
biomedical field as colloidal dispersants, surface modifiers and drug carriers, and
characterization of micelle properties.
Otsuka et al. have described the recent progress in the field of block copolymer
assembly on the surface and in the solution, focusing on the biological and biomedical
application of poly(ethylene glycol) (PEG)-based block copolymers. Otsuka et al.
designed block copolymer (PEG-b-PLA) having an end-functionalized PEG (acetalPEG) segment. Reactive block copolymers of acetal-PEG-PLA can be utilized as
surface modifiers of biodegradable PLA to provide the reactive sites on the PEGylated
surface. PEG chains tethered on a surface or forming the corona of nanometer scaled
micelle exhibit the ability to sterically exclude other macromolecules and particles,
which is related to high flexibility and the large exclusion volume of PEG strands in
water. This property is particularly useful for preventing the adsorption of proteins
and adhesion of cells. In this regard, these supramolecular structures involving PEGbased block copolymers should be of substantial importance for the development of
blood contraction biomaterials, which are expected to play a key role in such fields
as cell and tissue engineering, bio-sensing, and drug delivery systems.
Biomolecules patterning on block copolymer films: By using self-assembly of
diblock copolymer, the function behind molecular arrangement of single integrins
in cell adhesion has been studied. A separation of ≥73 nm between the adhesive
dots resulted in limited cell attachment and spreading and dramatically reduces the
formation of focal adhesion and actin stress fibers. These cellular responses have been
attributed to restricted integrin clustering rather than insufficient number of ligand
molecules in cell–matrix interface since micro-nanopatterned substrates consisting
of alternating fields with dense and no nano-dots support cell adhesion.