Mechanical properties and biocompatibility of melt processed,self-reinforced ultrahigh molecular weight polyethylene

The low efficiency of fabrication of ultrahigh molecular weight polyethylene (UHMWPE)-based artificial knee joint implants is a bottleneck problem because of its extremely high melt viscosity. We prepared melt processable UHMWPE (MP-UHMWPE) by addition of 9.8 wt% ultralow molecular weight polyethylene (ULMWPE) as a flow accelerator. More importantly, an intense shear flow was applied during injection molding of MP-UHMWPE, which on one hand, promoted the self-diffusion of UHMWPE chains, thus effectively reducing the structural defects; on the other hand, increased the overall crystallinity and induced the formation of self-reinforcing superstructure, i.e., interlocked shish-kebabs and oriented lamellae. Aside from the good biocompatibility, and the superior fatigue and wear resistance to the compression-molded UHMWPE, the injection-molded MP-UHMWPE exhibits a noteworthy enhancement in tensile properties and impact strength, where the yield strength increases to 46.3 ± 4.4 MPa with an increment of 128.0%, the ultimate tensile strength and Young's modulus rise remarkably up to 65.5 ± 5.0 MPa and 1248.7 ± 45.3 MPa, respectively, and the impact strength reaches 90.6 kJ/m². These results suggested such melt processed and self-reinforced UHMWPE parts hold a great application promise for use of knee joint implants, particularly for younger and more active patients. Our work sets up a new method to fabricate high-performance UHMWPE implants by tailoring the superstructure during thermoplastic processing.     

基于自增强型互穿聚合物网络凝胶的中药缓释体系的构建与表征

目的 构建并表征用于中药缓释的自增强互穿聚合物网络水凝胶(SR-IPNH)体系。方法 基于洛沙姆网络和甘草酸(GA)网络,构建SR-IPNH体系。得益于GA自组装纤维网络与泊洛沙姆网络的相互渗透交联,水凝胶的机械强度得到显著提高。在本体系中,GA既是OA的治疗成分又是水凝胶的强化剂,使体系的机械强度不需借助化学交联剂就能得到强化。本工作考察了所制备凝胶的流变性、成胶性、体外可注射性、载药性能、体外释放行为及初步稳定性。结果 所制备的SR-IPNH在室温下具有良好的流动性,在35.1 ℃下能2.5 min内快速凝胶,证明本体系具有良好的热敏成胶性能。胶凝实验表明体系具有良好的可注射性和成胶性能,这为关节腔内原位注射治疗提供了必要条件。含量分析结果表明,体系中芍药苷和甘草酸的含量分别为1.88 %和0.86 %。流变学考察结果显示,甘草酸能使凝胶的储能模量G′显著上升,且损耗因子tan δ显著降低,这说明体系的弹性性能得到加强,机械强度得到提升。药物体外释放研究结果显示本体系具备显著的缓释性能,揭示GA的释放受到自扩散和凝胶溶解的双重影响。此外,稳定性实验结果显示室温、密闭和黑暗环境更适合SR-IPNH的贮藏。结论 本研究成功制备了SR-IPNH体系,表征结果展示出良好的机械强度和缓释性能。本工作为中医药治疗OA提供新的思路和技术支持。