Scaffolds for Tissue Engineering - Biodegradable Polymer-Based Scaffolds for Bone Tissue Engineering - page 6

tissues. The use of a scaffold can accelerate the wound healing process as the
adult mammal does not spontaneously regenerate tissues (other than noncritical-
sized bone defect) that have been lost or removed either due to accident or delib-
erate excision. The scaffolds, which are artificial matrix, can serve as a temporary
guide or template for cell adhesion, growth and function. Not only this, they also
synthesize extracellular matrix (ECM) and ultimately generate new tissue. It is
also expected that the scaffold should be degraded after the formation of natu-
ral tissues/organs in order to facilitate an entirely natural tissue replacement. It
was mentioned that the critical-sized bone defects might be healed with the aid
of scaffolds together with appropriate cell seeding densities and/or growth fac-
tors (Khan et al. 2008 ). Some attributes must be satisfied in order to regener-
ate new osseous tissue including (1) biocompatibility: the lack of immunogenic
response; (2) osteoconductivity: the porous interconnected structure permit-
ting new cells to attach, proliferate, and migrate through the structure and also
allows for the exchange of nutrient-waste as well as new blood vessel penetra-
tion; (3) osteoinductivity: having the quality for possessing the necessary proteins
and growth factors which can induce the progression of mesenchymal stem cells
and other osteoprogenitor cells toward the osteoblast lieage; (4) osteogenecity:
the osteoblasts which are present at the site of new bone formation that can pro-
duce minerals to calcify the collagen matrix to form the substrate for new bone;
(5) osteointegration: the newly formed mineralized tissue must be able to form
an intimate bonding with the implant material (Khan et al. 2008 ). Other design
considerations are discussed below.
1.3.1 Surface Properties
Scaffolds with appropriate surface chemistry facilitate cell attachment, prolifera-
tion and differentiation. Surface roughness is an important factor that can improve
osteoblast functions necessary for enhanced bone tissue engineering applications
and variations in cellular behavior have been reported to be based on whether a
surface was textured or not (Liu et al. 2006 ). Studies have shown that within the
scope of textured surfaces, variations in cellular behavior can only depend on the
size (Khan et al. 2008 ) of the texture or with certain cellular behaviors elicited by
nanoscale modifications on the surface of the material.
1.3.2 Physical Properties
Scaffolds should possess three dimensional, highly interconnected porous network
together with appropriate porosity, pore size and pore structure for cell growth and
transport of nutrients and metabolic waste (Hutmacher 2000 ). It was described
that together with osteoconductivity, a porous structure is critical to allow