Implant surface modification strategies against periprosthetic infections

 描述(申请人提供)：假体周围金属植入物感染是骨科手术中最严重的并发症之一，尽管采取了严格的预防和手术方法，但其发病率最近在全国范围内呈上升趋势。植入物周围的生物膜形成是一种常见的威胁，使这些严重的局部感染更有可能发生，也更难根除。目前在改善植入物表面的抗污染性能或局部注射抗生素方面的方法已经显示出一些短期的好处，但这些方法的长期结果并不令人满意。本研究的目标是在不影响骨整合的情况下，协同提供具有稳定的抗污垢和足够的杀菌性能的金属种植体表面，以应对假体周围感染的挑战。这将通过使用表面引发的活性原子转移自由基聚合(SI-ATRP)和生物正交叠氮化物/炔环加成的生物正交叠氮/炔环加成化学方法从金属合金表面接枝含有两性离子和万古霉素基序的功能性聚合物刷子，这些基序的化学成分、相对分子质量和功能基序的空间排列可通过表面引发的活性原子转移自由基聚合(SI-ATRP)和生物正交叠氮/炔环加成反应实现。两性离子主题的选择是 其动机是它们稳定的防污性能和我们最近发现的它们作为生物矿化的有效介体的新作用。在目标1中，我们将使用强大的SI-ATRP和“点击”化学技术，从商业Ti6Al4V衬底表面嫁接具有模块呈现的防污和杀菌功能基元的均聚物、随机共聚物和嵌段共聚物库。通过X射线光电子能谱、水接触角测量、热重分析/凝胶渗透色谱和表面划痕试验对涂层的性能和耐磨性进行了表征和验证。在目标2中，我们将通过量化修饰表面上贴壁的骨髓基质细胞在体外对金黄色葡萄球菌(S.aureus)培养的抑制、非特异性蛋白吸收以及存活/增殖来筛选最有效的杀菌和防污染且与细胞兼容的表面刷剂组合物。在目标3中，将选自目标2的顶端功能均聚物、嵌段和随机共聚物表面刷组合物应用于Ti6Al4V髓内(IM)棒。将表面修饰的IM棒与未修饰的对照组和单层万古霉素修饰的IM棒一起植入接种金黄色葡萄球菌或生理盐水的大鼠股骨髓管内(未感染对照组)。评价表面聚合物刷涂涂层在减少短期(3周)和长期(最长6个月)假体周围感染方面的效果，方法是通过量化回收的IM杆上附着的金黄色葡萄球菌、死骨形成和股骨增宽/皮质变薄(通过MicroCT)以及移植股骨的失效扭矩。对这些结果进行评分，以指导表面刷剂组合物的选择，该组合物对假体周围感染提供最持久的抑制，对正常股骨形态和机械完整性的干扰最小。表面刷子组合物的生物相容性还通过接受未接种细菌的植入物的大鼠的重要/清道夫器官和股骨的病理(骨溶解、急性/慢性炎症反应和对涂层的过敏反应)进行检查。这项研究的成功完成有望确定一种生物相容的表面聚合物刷组合物，提供持续的预防/抑制假体周围感染的能力，可广泛应用于各种金属外科植入物。

 DESCRIPTION (provided by applicant): Periprosthetic infection of metallic implants is one of the most serious complications in orthopedic surgeries and its incidence has seen a recent nationwide upward trend despite rigorous prophylaxis and surgical approaches. Biofilm formation surrounding the implant is a common threat that makes these serious local infections both more likely to occur and more difficult to eradicate. Current approaches in improving the anti-fouling property of implant surfaces or locally delivering antibiotics have shown some short-term benefits, but the long-term outcomes of these approaches are not satisfactory. The goal of the proposed study is to address the challenge of periprosthetic infections by synergistically affording metallic implant surfaces with stable anti- fouling and sufficient bactericidal propertie without compromising osteointegration. This will be realized by grafting functional polymer brushes containing zwitterionic and vancomycin-bearing motifs with modularly tunable chemical compositions, molecular weights, and spatial arrangements of the functional motifs from metallic alloy surfaces using surface initiated "living" atom-transfer radical polymerization (SI-ATRP) and bioorthogonal azide/alkyne cycloaddition "click" chemistry. The choice of the zwitterionic motif is motivated by their stable anti-fouling properties and our recent discovery of their novel role as potent mediators of biomineralization. In Aim 1, we will surface-graft a library of homopolymers, random and block copolymers with modularly presented anti-fouling and bactericidal functional motifs from commercial Ti6Al4V substrates using the robust SI-ATRP and "click" chemistry. The properties and robustness of the coatings are characterized and validated by X-ray photoelectron spectroscopy, water contact angle measurements, thermo-gravimetric analysis/gel permeation chromatography as well as surface scratch test. In Aim 2, we will screen for the most effective bactericidal and anti-fouling yet cytocompatible surface brush compositions by quantification of in vitro inhibition of Staphylococcus aureus (S. aureus) cultures by, non-specific protein absorptions on, and viability/proliferation of adherent bone marrow stromal cells on the modified surfaces. In Aim 3, the top functional homopolymer, block and random copolymer surface brush compositions chosen from Aim 2 are applied to Ti6Al4V intramedullary (IM) rods. The surface modified IM rods, along with unmodified control and that modified with a monolayer of vancomycin, are implanted in rat femoral medullary canals inoculated with either S. aureus or saline (uninfected control). The efficacy of the surface polymer brush coatings in reducing short-term (3 weeks) and longer-term (up to 6 months) periprosthetic infections are evaluated by quantification of S. aureus adhered on the retrieved IM rod, sequestrum formation and femur widening/cortex thinning (by microCT), and the failure torque of explanted femurs. These outcomes are scored to guide the selection of the surface brush composition affording the most sustained inhibition to periprosthetic infections and minimal perturbation to normal femoral morphology and mechanical integrity. Biocompatibility of the surface brush compositions are also examined by the pathology of vital/scavenger organs and femurs (for signs of osteolysis, acute/chronic inflammatory responses and allergic reactions to the coating) of the rats receiving implants without bacterial inoculum. Successful completion of this study is expected to identify a biocompatible surface polymer brush composition affording sustained protection against / inhibition of periprosthetic infections that can be broadly applied o a wide range of metallic surgical implants.