Page 125 - Tailoring Electrospinning Techniques for Regenerative Medicine - Marc Simonet

The molecular weight of both materials was analyzed before and a er gamma sterilization by gel permeation chromatography (GPC) in tetrahydrofurane on a Shimadzu LC-10ADVP system with a Shimadzu RID-10A refractive index detector, a Shimadzu SPD-M10AVP UV-Vis detector at 270 nm, and a combination of a PLgel 5-μm mixed-C and a PLgel 5-μm mixed-D column in series. All reported molecular weights are relative to polystyrene standards.
Mechanical and fatigue properties of the valve sca olds
The mechanical properties of the electrospun PCL and PCL2kU4Un sca olds were measured before and a er sterilization on 5 strips each (5*25 mm) at room temperature on a Zwick tensile tester (Model Z010, Germany) at a crosshead speed of 100%/min and a sample gauge length of 10 mm. The Young’s-modulus was measured between 0 and 5% elongation from the obtained stress-strain curve. Yield strength was determined at the end of the linear stress-strain response and the ultimate tensile strength (UTS) was defined as the peak stress value.
Fatigue properties were measured on a Bose LM1 Test Bench system (Friedrichsdorf, Germany) in water at 37 °C. All samples were conditioned for 24 h in 37°C water prior to the test. Elongation was set to 10% with a sample gauge length of 10 mm and a frequency of 2 respectively 10 Hz up to 3 million
cycles. Fatigue failure was defined at the cycle where the stress response dropped below 10% of the original stress response at the beginning of the test. PCL sca olds were tested prior and a er sterilization at 2 and 10Hz, on 5 strips (5*25 mm) each. PCL2kU4Un sca olds were tested at 10 Hz on 3 strips (5*25 mm) prior to sterilization and 5 strips (5*25 mm) a er γ-sterilization.
6.3.2 In-vitro valve performance
The hemodynamic performance and functionality of
the sterilized electrospun PCL and PCL2kU4Un valves
were assessed in a custom build pulse duplicator22
for 20 h at a simulated cardiac output of 5 l/min
and heart rate of 70 bpm (LifeTec, Eindhoven, The Netherlands) under pulmonary and aortic pressures
in 0.9% saline at 37°C. To compensate for a systematic
leakage along the stent and to add an additional
safety margin for in-vivo use, valves were tested at
elevated pulmonary pressures (50/25 mmHg rather 6 than the normal 35/15 mmHg). For these tests, the
pressure regime in the pulse duplicator was tuned with a polyurethane valve dummy to meet elevated pulmonary conditions. To reach the 120/80 mmHg for the aortic conditions, tuning was performed on the PCL2kU4Un valve. Performance of the tested valves was visualized with a high-speed video camera (Motion-Scope M-5, IDT, Lommel Belgium) a er 20 min and 20 h, and by measuring occurring flows and pressures every 2 hours. Recorded mean pressure,
FROM A POLYMER TOWARDS AN IN-SITU TISSUE ENGINEERED HEART VALVE
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