EMULSION TEMPLATING - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 668

bone formation. 19 , 20 The construct may be matured in vitro prior to
implantation or implanted directly.
Tissue engineering scaffolds typically consist of biodegradable
materials that will integrate fully with the host tissue. 19 In addition
tothechoiceofasuitablebiomaterial,thesuccessoftissueengineer-
ing constructs depends on the three-dimensional (3D) architecture
of the scaffold. An interconnected porous structure enables cellu-
lar migration and proliferation, vascularization, and the transport
of nutrients and metabolic waste. 10 , 13 , 20 , 21 The mechanical proper-
ties of the scaffold are especially important in orthopedic applica-
tions. Adequate support similar to native bone is necessary to allow
for continued loading and prevent stress-shielding effects. 10 , 11 , 17 , 22
Thus, the advancement of bone tissue engineering strategies is
strongly dependent on the development of high-porosity scaffolds
that meet these key requirements.
33.3 Scaffold Fabrication
Tissue engineers have developed numerous strategies to
create 3D bone scaffolds using a wide range of fabrication
techniques. 1 , 4 , 10 , 17 , 20 , 23 − 27 The fabrication process dictates scaffold
properties such as architecture, surface chemistry, biodegradation,
and strength. One of the primary challenges is to generate a scaffold
with high porosity that retains su cient mechanical strength for
orthopedic applications. High porosity is necessary for the proper
influx of nutrients and removal of waste products during tissue
regeneration.Themostcommontechniquestoproduceporousscaf-
folds include particulate leaching, gas foaming, and fiber bonding
(Fig. 33.2). 1 , 21 , 26 , 27
Many of these strategies provide exceptional architecture con-
trol; however, irregular defect sites require fabrication of complex
polymer molds to replicate the contours of the defect. In situ-
forming scaffolds can fill irregular-shaped defects, improve contact
between the scaffold and the surrounding tissue, and eliminate the
need for costly molding techniques. 28 , 29 Poly(methyl methacrylate)
(PMMA) bone cements are perhaps the most widely used injectable
material in orthopedics; however, PMMA is nondegradable, which