Page 113 - Tailoring Electrospinning Techniques for Regenerative Medicine - Marc Simonet

Next to controlling fiber alignment and diameter, it is also possible to structure the surface of the fiber itself. In general, electrospun fibers are smooth and have a circular cross section (Figure 5.5a). Flat (Figure 5.5b) or ribbon shapes are possible, in particular when working with high concentrated solutions.101 Inducing phase separations during the electrospinning process allows for adaptation of the fiber surface topography - from smooth to porous. Selecting specific solvents or solvent mixtures102 can create polymer-rich and poor regions, thereby forming pores within the fibers (Figure 5.5c). Other approaches with similar topographical e ects are electrospinning in a very humid environment,103 electrospinning into liquid nitrogen104 or by spinning immiscible polymers from the same solvent.105 Controlling the pores in the fibers might be of great interest as these pores could act as anchor points
and a ect cell behavior. Various studies showed that surface topography, smooth as well as rough, can play an imminent role in cell behavior.106–109
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ELECTROSPINNING FOR HEART VALVE TISSUE REGENERATION
Figure 5.5 SEM pictures of PLA fibers electrospun with di erent parameters resulting in: (a) round fibers with smooth surface, (b) flat fibers or (c) round fibers with porous surface.
5.6.4 Bioactive sca olds
The biomimetic properties of the electrospun sca olds can be improved by adding bioactive functions to the polymer. These functions can be chemically attached in a second labelling step of electrospun fibers110,111 or directly co-electrospun with the synthetic polymer.112 The latter approach is easiest, but requires special attention with respect to the stability and activity of the biomolecules.113 In addition, the majority of the biomolecules might be embedded within the fibers and not on the surface, allowing for their release over a prolonged period of time via di usion or fiber degradation. Other reported ways to incorporate and add biofunctionality are,
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