Page 128 - Tailoring Electrospinning Techniques for Regenerative Medicine - Marc Simonet

CHAPTER 6
6.4 Results
6.4.1 Sca old production and characterization
Sca old production and sterilization
All electrospun sca olds had a thickness of 0.45 to 0.6 mm. The thickness of the implanted PCL2kU4Un valves was 0.55 to 0.60 mm. For practical reasons, the valves tested in the pulse duplicator had an inner diameter of 29 mm and were sutured into a stent (Figure 6.1a). For the in-vivo studies, the valve dimensions were adapted to an inner diameter of 21 mm (Figure 6.1b). The stainless steel reinforcement ring (Figure 6.1c) was scaled accordingly and no stent was used.
Structural and intrinsic properties
The SEM pictures in (Figure 6.1d and e) showed that electrospinning with the selected parameters resulted in sca olds with a random fiber distribution. The average fiber diameters prior to sterilization
were: 5.2±0.5 μm for PCL2kU4Un and 11.0±0.9 μm for PCL sca olds. γ-Sterilization did not change the fiber diameter (5.1±0.5 μm for PCL2kU4Un and 10.5±0.8 μm for PCL).
For the PCL the average molecular weight dropped from 103 kDa to 79 kDa due to γ-sterilization. PCL2kU4Un showed a similar change in average molecular weight due to γ-radiation from 76 to 60 kDa (Table 6.1).
Mechanical and fatigue properties
The spun meshes were mechanically characterized before and a er γ-sterilization (Table 6.1). Non- sterile PCL and PCL2kU4Un sca olds have distinct di erent mechanical properties. PCL2kU4Un has an approximate 13 times lower Young’s-Modulus compared to PCL. Additionally, with a yield point of nearly 20% vs. 3% for PCL, PCL2kU4Un is also
Figure 6.1 The valve sca old from a macroscopic and microscopic view. (a) Photograph of a PCL2kU4Un valve for in-vitro testing with an inner diameter of 29 mm (b) photograph of a PCL2kU4Un valve for in-vivo testing with an inner diameter of 21 mm (c) schematic of the stainless steel reinforcement structure, (d & e) scanning electron microscope pictures of non-sterile electrospun sca olds (d) PCL and( e) PCL2kU4Un.
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