Zhang Li, Hanif Muhammad, Li Jiacheng, Shah Abdul Hakim, Hussain Wajid, Zhang Guotao
Faculty of Mechanical Design and Vehicle Engineering, School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
Department of Physics, Khushal Khan Khattak University, Karak 27200, Pakistan.
Polymers (Basel). 2023 Jan 11;15(2):390. doi: 10.3390/polym15020390.
Shape memory polymers have received widespread attention from researchers because of their low density, shape variety, responsiveness to the environment, and transparency. This study deals with heat-shape memory polymers (SMPs) based on polylactic acid (PLA) for designing and fabricating a novel porous vascular scaffold to treat vascular restenosis. The solid isotropic material penalization method (SIMP) was applied to optimize the vascular scaffolds. Based on the torsional torque loading of Hyperworks Optistruct and the boundary conditions, the topological optimization model of a vascular scaffold unit was established. Forward and reverse hybrid modeling technology was applied to complete the final stent structure's assembly. The glass transition temperature for the present SMPs is 42.15 °C. With the increase in temperature, the ultimate tensile strength of the SMPs is reduced from 29.5 MPa to 11.6 MPa. The maximum modulus at room temperature was around 34 MPa. Stress relaxation curves show that the material classification is a "thermoset" polymer. The superb mechanical properties, the transition temperature of the SMPs, and the recovery ratio made it a feasible candidate for a vascular scaffold. A circular tube based on the shape memory polymers was presented as an example for analyzing the recovery ratio in an unfolding state. A higher recovery ratio was obtained at a temperature of 65 °C with a tube thickness of 2 mm. Finally, the proposed porous vascular scaffold was successfully fabricated, assessed, and compared with the original and previously developed vascular scaffolds. The proposed scaffold structure regains its initial shape with a recovery ratio of 98% (recovery temperature of 47 °C) in 16 s. The tensile strength, Young's modulus, and bending strength of the proposed scaffold were 29.5 MPa, 695.4 MPa, and 6.02 MPa, respectively. The results showed that the proposed scaffold could be regarded as a potential candidate for a vascular implantation.
形状记忆聚合物因其低密度、形状多样、对环境的响应性和透明性而受到研究人员的广泛关注。本研究涉及基于聚乳酸（PLA）的热形状记忆聚合物（SMP），用于设计和制造一种新型多孔血管支架以治疗血管再狭窄。采用固体各向同性材料惩罚方法（SIMP）对血管支架进行优化。基于Hyperworks Optistruct的扭转扭矩加载和边界条件，建立了血管支架单元的拓扑优化模型。应用正向和反向混合建模技术完成最终支架结构的组装。本SMP的玻璃化转变温度为42.15℃。随着温度升高，SMP的极限拉伸强度从29.5MPa降至11.6MPa。室温下的最大模量约为34MPa。应力松弛曲线表明该材料属于“热固性”聚合物。SMP优异的力学性能、转变温度和回复率使其成为血管支架的可行候选材料。以基于形状记忆聚合物的圆管为例分析其展开状态下的回复率。在65℃温度和2mm管厚度下获得了较高的回复率。最后，成功制造、评估了所提出的多孔血管支架，并与原始和先前开发的血管支架进行了比较。所提出的支架结构在16s内以98%的回复率（回复温度为47℃）恢复其初始形状。所提出支架的拉伸强度、杨氏模量和弯曲强度分别为29.5MPa、695.4MPa和6.02MPa。结果表明，所提出的支架可被视为血管植入的潜在候选材料。
