Biomedical Engineering Reference
In-Depth Information
Table 2 Nanofabrication methods for 3D cell environment engineering
Structure size
Phase separation
Synthetic biodegrafable
polymers (poly
L -lactic acid)
50 nm fi ber diamater
Zhang and Ma ( 2000 )
Polyethylene oxide,
polylactic acid, and
5-100 nm fi ber
Zhou et al. ( 2003 ) ,
Sun et al. ( 2003 ) ,
and Zussman et al.
( 2003 )
Self-assembly of
Synthetic peptide-
5-8 nm fi ber diameter Hartgerink et al.
( 2002, 2001 ) and
Silva et al. ( 2004 )
Thermal assembly
100 nm-thick fi brils
Pederson et al. ( 2003 )
Carbon nanotubes
Down to 3-5 nm
Michalet et al. ( 2005 ) ,
Berry and Curtis
( 2003 ) , and Gillies
and Frechet
( 2005 )
beads (iron oxide)
20-500 nm diameter
10 nm
recently to produce synthetic scaffolds with nanofeatures for tissue engineering. For
example, a phase separation technique is proposed to generate synthetic nanofi -
brous ECM, which mimics the fi ne fi brillar architecture of collagen (Zhang and Ma
2000 ). Three-dimensional negative replicas are produced from a porogen material.
Polymeric materials, like PLA, are cast over porogen and thermally phase-separated
to form nanofi brous matrices. The porogen material is then leached out with water
to fi nally form the synthetic nanofi brous ECM with predesigned macroporous archi-
tectures. The diameter of the fi bers ranges from 50 to 500 nm, which is similar to
collagen matrix. These scaffolds can induce cells to assemble in a 3D fashion that
resembles the natural cell organization in natural tissue.
Electrospinning of nanofi bers is a relatively novel process that allows the con-
tinuous production of polymer fi bers (polyethylene oxide, PLA, and polycaprolac-
tone) ranging from less than 5 nm to over 1 mm in diameter (Zhou et al. 2003 ; Sun
et al. 2003 ). The reduction of the diameter into the nanometer range gives rise to a
set of favorable properties, including increase of the surface-to-volume ratio, varia-
tions in wetting behavior, and modifi cations of the release rate. The electrospinning
technique relies on a high electric fi eld-assisted assembly of nanofi bers into well-
ordered 3D structures (Zussman et al. 2003 ) . The fi bers from biodegradable poly-
mers that can be aligned to create 3D matrix of parallel or periodic arrays may be
useful for tissue engineering. A recent study from our laboratory demonstrates that
human MSC adhesion and stretching are preferred along the direction of electro-
spun polycaprolactone (PCL) polymers of ~100 nm diameter (Fig. 5 ), revealing that
the preferred orientation and alignment of the cells on the patterned substrate coin-
cide with the fi ber orientation. A cell viability test shows that nanofi ber-directed cell
orientation and alignment do not cause adverse cellular damage. This capability
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