仿生各向异性高分子人工瓣膜制备及性能研究（英文）

Bio-inspired anisotropic polymeric heart valves exhibiting valve-like mechanical and hemodynamic behavior

人体心脏瓣膜具有力学各向异性特征,使其能够承受长期的开合循环负荷.本文采用静电纺丝法分别制备了具有各向异性(anisotropic silk fibroin,ASF)和各向同性(isotropic silk fibroin,ISF)的丝素蛋白纤维膜,并进一步与聚乙二醇二丙烯酸酯(poly(ethylene glycol)diacrylate,PEGDA)水凝胶结合,作为人工高分子瓣膜材料(PEGDA-ASF和PEGDA-ISF).有限元分析结果表明PEGDA-ASF瓣膜在心脏舒张期的最大主应力值(2.20 MPa)低于PEGDA-ISF瓣膜(2.37 MPa).与人体瓣膜相似,收缩期时PEGDA-ASF瓣膜在瓣叶根部附近会产生一个弯折区域,而PEGDA-ISF瓣膜的弯折区却接近瓣叶的自由边缘.此外,PEGDA-ASF瓣膜在打开过程中,能够通过动态调整弯折区域获得较为平滑的表面形貌.因此,人工高分子瓣膜的各向异性特征对于实现其与人体瓣膜相似的力学和流体动力学行为起着至关重要的作用.

Native heart valve leaflets with layered fibrous structures show anisotropic characteristics,allowing them to withstand complex mechanical loading for long-term cardiac cycles.Herein,two types of silk fibroin(SF)fiber membranes with anisotropic(ASF)and isotropic(ISF)properties were prepared by electrospinning,and were further combined with poly(ethylene glycol)diacrylate(PEGDA)hydrogels to serve as polymeric heart valve(PHV)substitutes(PEGDA-ASF and PEGDA-ISF).The uniaxial tensile tests showed obvious anisotropy of PEGDA-ASF with elastic moduli of 10.95±1.09 and3.55±0.32 MPa,respectively,along the directions parallel and perpendicular to the fiber alignment,while PEGDA-ISF possessed isotropic property with elastic moduli of 4.54±0.43 MPa.The PHVs from both PEGDA-ASF and PEGDA-ISF presented appropriate hydrodynamic properties from pulse duplicator tests according to the ISO 5840-3 standard.However,finite element analysis(FEA)revealed the anisotropic PEGDA-ASF valve showed a lower maximum principle stress value(2.20 MPa)in commissures during diastole compared with that from the isotropic PEGDA-ISF valve(2.37 MPa).In the fully open state,the bending area of the PEGDA-ASF valve appeared in the belly portion and near the attachment line like native valves,however,which was close to free edges for the PEGDA-ISF valve.The Gauss curvature analysis also indicated that the anisotropic PEGDA-ASF valve can produce appropriate surface morphology by dynamically adjusting the movement of bending area during the opening process.Hence,anisotropy of PHVs with bio-inspired layered fibrous struc-tures played important roles in mechanical and hydrodynamic behavior mimicking native heart valves.