Introduction - Microsurgery: Advances, Simulations, and Applications - page 31

tissue is lost, no ECM will be left around the tissue. This is why ECM
is required for in vitro creation of tissue substitutes.
Typically scaffolds should have porous structure to maximize
the function of cells and to supply enough oxygen and nutrients to
cells proliferated all over the scaffold. On the other hand, mechanical
strength with appropriate Young's modulus is required to maintain
its shape and to it the surrounding living tissue after implantation.
Therefore, the balance between porosity and mechanical strength
becomes important. Additionally, biodegradable materials are
preferred because scaffolds may disarrange the function of living
tissue after the complete regeneration of tissue. Some required
properties of biodegradable scaffolds are

1. Cell-adhesive substrate at differentiation and proliferation

2. Securement of regeneration space

3. Coniguration of restored tissue

4. Supply route of oxygen and nutrients to cells

5. Storage and slow release of cell growth factor (CGF)

6. Tissue substitute until regeneration (strength, compliance,
etc)

7. Bioabsorbability/biodegradability

8. Porous structure to accommodate cells

1.3.4 Production Methods of Biodegradable Scaffolds

The size of cells is around 20 μ m. Therefore, cells are surrounded by
microenvironments in our body. That is why microscale fabrication
technologies are necessary to fabricate biodegradable scaffolds.
Biodegradable polymers are fabricated into rope, sheet, tube, and
block-like 3D porous scaffolds depending on the shape of a targeted
part of tissue. Here, we introduce several representative methods to
fabricate biodegradable scaffolds.

1.3.4.1 Electrospinning
Electrospinning has been used as a iber-forming method since the
1930s. It can produce micro-nano-scale polymer ibers. Figure 1.24
shows a schematic of electrospinning. If high voltage (5-30 kV) is
applied between a needle and a collector, the ejection of polymer
solution from a syringe yields an electrically charged jet because
repulsive force becomes more dominant than surface tension. Jet