Page 30 - Tailoring Electrospinning Techniques for Regenerative Medicine - Marc Simonet

CHAPTER 1
Figure 1.5 Electrospinning setups inducing fiber alignment with (a) guiding electrodes and (b) stirring electrodes; both schematics adapted from www.electospintech.com, licensed under CC BY 2.0
Mechanical properties, like moduli, strength, fatigue, creep resistance etc. can be changed by the selected material and spinning parameters. All mechanical characteristics of the chosen material(s) will be reflected in the electrospun sca old. One has to be aware though, that the inherent high porosities of electrospun sca olds, 80 to 90% porosity is very common, limits the overall mechanical strength. Fiber diameter, the amount of fiber fusion and fiber orientation will influence the overall mechanics of the sca olds.83,100,112–114 The design of the sca old, and the rigidity of the entangled or fused fiber connections enables a further refinement of the mechanical characteristics, for example improving fatigue and creep resistance.115
A 3D sca old can only be functional if it allows cell ingrowth, tissue formation and nutrition exchange. Electrospinning is typically a layer by layer
deposition method, so each fibrous layer lies on top of the previously deposited one. This results in densely packed sca olds, since the void size between fibers scales with the fiber diameter.116 Several studies showed that the resulting void spaces of sca olds with fiber diameters of a few micrometers or less hinder or even prevent cell infiltration.9,117–119 This has led to the development of several methods to increase the void sizes to improve cell ingrowth into 3D sca olds. These include, spinning bimodal fibers,91,92 using void templates such as fibers, salt or ice crystals93,94,120,121 and spinning in air or liquids.122–125 One can also use specifically designed grid-like targets or porous targets where air gets constantly pushed through these pores.126–128 Voids can also be induced post spinning, using lasers or similar to cut holes into the sca old.125
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