Biomedical Engineering Reference
In-Depth Information
cultured into a polyglycolic acid (PGA) non-woven scaffold
[CAO 06]. The tissue-engineered constructs were further placed in a
U-shape device for applying a constant deformation. This resulted in
the formation of ligament-like tissue 10 weeks post-seeding,
possessing a well organized and aligned collagen matrix. As the PGA
degraded within the time frame of the
in vitro
culture, the resulting
tissue became somehow “scaffold-free”. However, the rapid
degradation of the PGA could be detrimental to the mechanical
properties of the construct and to the cells due to the acidic
degradation products released in the media. Another approach
developed by Ignatius's group involved a fibrous highly porous PLLA
scaffold with a slower degradative pattern, suitable for cell attachment
and infiltration [HEC 06] as shown in Figure 7.2(c). This scaffold was
further utilized under uniaxial stretching in a bioreactor system for
advancing the maturation of the ligament-like tissue. This resulted in
an up-regulation of collagen type I and III and tenascin C, highly
relevant for ligament tissue engineering [KRE 12].
7.3.3.
Knitted/braided scaffolds
Ligament tissue engineering using a knitted scaffold was initially
developed by Goh's group in Singapore. The knitted scaffold is here
utilized for providing mechanical stability and strength but also for
delivering mesenchymal progenitor cells to the injured tissue, which
resulted in accelerated regeneration compared to the natural healing in
an Achilles tendon model in rabbits [OUY 03]. The scaffold was
further optimized and silk was utilized as the structural material for
providing enhanced mechanical support. However, the pore size
present in knitted structures does not allow an efficient cell seeding
and hence a poor cell delivery is attained. To circumvent this, several
strategies have been developed by incorporating a layer of materials
over the macroscopic pore of these structures. This was achieved by
immersing the silk scaffold into a silk solution and subsequently
freeze-drying the composite construct (Figure 7.2(d)) [FAN 09].
Hydrogels such as fibrin blue [OUY 03] or alginate [VAQ 10b] can
also be employed for encapsulating cells of interest as displayed in
Figure 7.2(e). This resulted in better regeneration of the treated tendon
in a rabbit model 12 weeks post-implantation. Another method
