CELL - BASED NANOCOMPOSITES AND BIOMOLECULES FOR BONE TISSUE ENGINEERING - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 559

distinct and well-defi ned cytoskeleton with actin stress fi bers was present on
coated surfaces, whereas on uncoated Ti surfaces, the actin fi laments were not
present in the cytoskeleton structure. Rapid bone mineralization was seen in
those coatings with a high Si content (4.9 wt% Si) by Day 16 of culture. The draw-
back of high Si content was that rapid dissolution of the coating was apparent
because of the small HA crystal size; thus, the attachment of cells at very early
stages may not be ideal. As such, it was found that 2.2 wt% Si was an ideal content
for HA coatings 108 .
16.3.6 Peptide-Based Materials
In tissue engineering, material design is of utmost importance. Attempts have
been made to fabricate scaffolds to mimic the chemical composition and struc-
tural properties of ECM because one would think that a tissue-engineered
scaffold with these characteristics will have a better chance at enhancing tissue
regeneration in the body. Structural proteins for example, collagen, are in the
nanometer range and this nanotopography is said to affect cellular responses
such as adhesion, proliferation, growth and differentiation. Since the native
ECM is of a nanofi brous structure, several methods have been developed to
make nanofi bers or nanofi brous scaffolds, such as drawing, template synthesis,
phase separation, self-assembly and electrospinning. Briefl y, drawing involves
a micropipette that is submersed in a droplet of solution and withdrawn to
draw a fi ber. In template synthesis, polymer is extruded through a porous mem-
brane into a solidifi cation solution for nanofi ber formation. Phase separation
is one method whereby separation of at least two different phases takes place,
by the incorporation of polymer into a particular solvent; subsequently the
freezing and freeze-drying processes give rise to a gel-like structure. For self-
assembly method, smaller molecules act as building blocks to self-assemble fi bers
using specifi c bonds. Lastly, electrospinning uses a high voltage electric fi eld
to draw fi bers out of a needle tip where the syringe is loaded with polymer
solution 109 - 112 .
In order to “coax” native cells to adhere to the biomaterials, so that the cells
would not view the material as a “foreign” object, peptides design and develop-
ment have been gaining much attention, because these peptides contain adhesion
domains of the ECM, thereby they may have an impact on cell attachment, pro-
liferation, and so on, and even inducing tissue formation.
Specifi cally, amphiphilic peptides with a carbon alkyl tail and other func-
tional peptide motifs could be synthesized to form nanofi bers via the self-assem-
bly process 113,114 . Hosseinkhani et al. demonstrated that the incorporating MSC
isolated from the femurs of rats into collagen sponge self-assembled peptide-
amphiphile (PA) nanofi ber hybrid scaffold in a bioreactor perfusion culture
system had an impact on in vitro and in vivo osteogenic differentiation of
the MSCs. The hybrid material that consists of a hydrogel (PA) and a sponge
(collagen sponge reinforced with PGA fi ber), when subjected in a perfusion
culture or static culture, induced bone formation throughout the constructs, with