oa Polymer Nanofiber Materials Matching the Mechanic Properties of Native Aortic Valve

Porous electrospun nanofiber materials are very promising as matrices for heart valve tissue engineering. Not only biocompatibility is important for this material but also the mechanical features – it has to be strong enough to withhold the pressure after implantation as well as deformable enough for better distribution of shear stress along its surface. Deformability is also crucial for stimulation of fibre production by fibroblasts on these matrices. Altogether 8 differing density variants of electrospun nanofiber materials from gelatine, polyurethane (PUR), polylactic acid (PLA) and polycaprolactone (PCL) were analysed using uniaxial tensile tests. Data were compared to mechanical properties of porcine aortic valve (AV) leaflets in radial and circumferential directions. Data are presented as means ± standard deviation. In circumferential direction modulus of elasticity (E) of native porcine AV is 9.7±1.3MPa and - 1.0±0.2MPa in radial. Ultimate stress and strain is 44.8±5.9% and 2.3±0.6 MPa in circumferential and 95.6±31.4% and 0.5±0.2MPa in radial direction for native leaflets. Closest of the materials to match the mechanical properties of porcine AV in circumferential direction was PUR with density 6.2 g/sqm showing E of 3.9±0.5 MPa, ultimate stress and strain - 5.3±1.68MPa and 141.8±43.9MPa respectively. Closest to match radial direction was gelatine with density 5.7 g/sqm showing E of 0.64±0.14 MPa, ultimate stress and strain - 0.38±0.05MPa and 82.53±10.20MPa respectively. Native AV leaflets have a non-linear and anisotropic response to stress in uniaxial tensile tests. Hence to model as precisely as possible their mechanical properties we suggest to use a combined material made in a sandwich fashion with layers of gelatine on the outside and PUR in the middle with their fibbers predominantly orientated in perpendicular directions. The other tested materials PLA and PCL either lacked strength to mimic leaflets in circumferential direction or deformability required for the radial direction.