Biomedical Engineering Reference
In-Depth Information
5.2.4 Electrostatic Spinning
Electrospinning is an interesting method which enables the production
of fi brous scaffolds with fi ber diameters within the range of submicron to
nanometer (Figure 5.2b). In this process, a continuous fi lament is drawn
from polymer-composite solution or melts by high electrostatic forces and is
deposited on a grounded conductive collector [21]. This method is increas-
ingly being used to produce fi bers for tissue engineering scaffolds, which
exhibit two important advantages. First, the interconnectivity of voids avail-
able for tissue in growth is suitable, and secondly, ultrathin fi bers, produced
by this method, offer high surface-to-volume ratio within the tissue scaffolds.
5.2.5 Microsphere Sintering
In this method, microspheres of polymer nanocomposites are synthesized
using emulsion and solvent technique. Followed by sintering 3D porous
microsphere scaffolds were achieved [22] (Figure 5.2c). It has been dem-
onstrated that PLGA-nano-HA composites microspheres [21] exhibited
osteoblastic phenotype expression and differentiation of mesenchymal
stem cells (MSCs) toward the osteogenic linage.
5.2.6 Rapid Prototyping
This is a group of technologies involving computer-aided design, materi-
als science and engineering, which can build physical 3D biomimetic scaf-
folds using layer-by-layer deposition and laser sintering [23]. This offers
new opportunities for 3D complex structure of materials at fi ner length
scales, which rely on the quality of the fi lament of the ink material which
is continuously extruded from a nozzle and deposited onto a substrate to
yield complex structures in a layer-by-layer build sequence (Figure 5.2d).
The process requires the optimization of viscosity and viscoelasticity
of the ink and the hardening of the ink after extrusion from the nozzle.
High resolution of complex 3D scaffold structures is achievable with fea-
ture sizes from a few hundred microns to submicron scale. By controlling
ink rheology, a complex 3D scaffold consisting of continuous solid, high
porosity and high pores interconnectivity has been constructed [23].
5.3
Nonbiodegradable Polymer and Nanocomposites
Nondegradable polymers have good mechanical properties and chemi-
cal stability and therefore are widely used in bone tissue engineering. The
representative examples of nonbiodegradable polymers utilized as poly-
mer matrices for nanocomposites preparation for bone tissue engineering
are presented in Table 5.1. The most important synthetic nondegradable
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