新型自发泡骨粘合材料抗菌、促修复的作用和机制研究

Surgery is the ultimate treatment for spinal infection. The key principle for successful treatment of spinal infection is filling effective biomaterials and local antibiotic treatment on the basis of thorough debridement. Polymethylmethacrylate (PMMA) is the most common bone cement which has been used as graft substitutes in vertebral surgeries. However, its obvious deficiencies such as shrinkage during polymerization、lack of drug loading pore and antibiotic function lead to the recurrence of infection and long-term vertebral instability. Polymethyl methacrylate-polyacrylic acid-polystyrene (PMMA-PAA-PSt) is an novel self-expandable bone cement with independent intellectual property rights investigated by our research team. Previous results showed that the cement had good biocompatibility and the ability of swelling to form porous /coral structure, which gave us an new approach for manufacturing drug release bone cement. However, the compressive strength of new expandable bone cement is lower than that of the traditional PMMA. Therefore, this study aims to reinforce PMMA-PAA-PSt bone cement by aramid fiber, and make combined use of vancomycin and imipenem to synthesize a novel “expandable filling, slow releasing antibacterial ” multifunctional bone adhesive materials. We will evaluate the characterization、antibacterial and promoting osteogenesis properties of new cement by material analyzation、molecular biology methods and animal model. Then, the optimal expansion ratio for drug release of the cement was obtained. Finally, we will develop an novel expandable antibacterial cement, which is suitable for clinical usage and drug release. This study is of great theoretical and practical significance.

手术是脊柱感染的终极治疗手段，其关键是在彻底清除病灶基础上对骨缺损进行有效填充和局部抗菌治疗。然而椎体手术最常用的填充材料PMMA存在体积收缩、缺乏载药孔隙、无抗菌作用等缺陷，易致感染复发并影响椎体稳定的远期临床疗效。 “聚甲基丙烯酸甲酯-聚丙烯酸-聚苯乙烯（PMMA-PAA-PSt）”聚合物是本课题组研发的具有自主知识产权的新型吸水自膨胀骨粘合材料，其生物相容性好，吸水膨胀后可形成多孔/珊瑚样结构，为骨水泥载药释药提供了新的途径。由于膨胀骨水泥的抗压强度较PMMA降低，因此本研究拟通过芳酰胺纤维强化，联合万古霉素、亚胺培南负载，构建新型“膨胀填充、缓释抗菌”的多功能骨水泥，利用材料学、分子生物学和动物模型等方法分析新型骨水泥的表征、体内外抑菌及促成骨性能，得到最优膨胀倍率的释药骨水泥，最终获取一种满足手术要求、抑菌效果好的新型自发泡抗菌骨粘合材料。本研究具有极其重要的理论和现实意义。

本研究在前期课题组研发新型骨填充材料P(MMA-AA)与P(MMA-AA-St)优良的吸水膨胀性能基础上，结合严重感染创面局部pH5.5-6.5的特点，利用越橘提取物的PH响应机制，改性膨胀骨填充材料，实现抗生素的缓释作用和基于越橘提取物PH响应的感染清除作用，利用材料学和分子生物学等方法分析新型骨水泥的表征及体内外抑菌效果。扫描电镜提示P(MMA-AA)与P(MMA-AA-St)为可吸水膨胀的纳米微球，粒径分别为438.77±36.05nm、200.87±10.34nm；Zeta电位检测结果提示其携带负电荷，可与带正电荷的万古霉素（van）产生相互吸引，具备药物缓释基础；负载越橘提取物与万古霉素的P(MMA-AA)-van与P(MMA-AA-St)-van吸水率分别为100.44±2.86%、61.40±2.85%，膨胀率分别为105.76±2.51%、65.42±3.39%，具有较好的吸水膨胀性能；P(MMA-AA)-van和P(MMA-AA-St)-van的压缩强度分别为88.17±6.14 MPa与79.83±6.97MPa，均高于ISO5833标准所要求的70MPa，同时P(MMA-AA)-van和P(MMA-AA-St)-van的弹性模量也较PMMA-van显著下降；材料浸泡在pH5.4-pH9.4的梯度pH溶液中发现，P(MMA-AA)-van和P(MMA-AA-St)-van具有较好的pH响应特性，能够示意植入周围组织的炎症变化，提示感染清除的程度；体外释药结果提示，PMMA-van在1周内达到释放平衡，P(MMA-AA)-van缓释持续4周达到平衡，P(MMA-AA-St)-van可缓释持续约21周，两者总体释放率均显著高于PMMA-van；材料抗生素释放浸提液抑菌实验结果提示，P(MMA-AA)-van和P(MMA-AA-St)-van抑菌环大小随着释放时间增加而增大；体外细胞相容性实验提示，P(MMA-AA)-van与P(MMA-AA-St)-van均具有较好细胞相容性；SD大鼠感染模型，伤口分泌物细菌培养结果提示，植入P(MMA-AA)-van与P(MMA-AA-St)-van组相比PMMA-van组创面处菌落数量明显减少；综上所述，研发的新型自发泡抗菌骨粘合材料满足手术要求、抑菌效果好，在脊柱感染的手术治疗方面具有良好的应用前景。