Implant surface modification strategies against periprosthetic infections

 描述（由申请人提供）：金属植入物的假体周围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容易发生，更难以根除。目前改善植入物表面防污性能或局部递送抗生素的方法已显示出一些短期益处，但这些方法的长期结果并不令人满意。拟定研究的目的是通过协同提供具有稳定防污和足够杀菌性能的金属植入物表面，同时不影响骨整合，解决假体周围感染的挑战。这将通过接枝功能聚合物刷含有两性离子和万古霉素轴承图案与模块化可调的化学组成，分子量，和空间排列的功能图案从金属合金表面使用表面引发的“活”原子转移自由基聚合（SI-ATRP）和生物正交叠氮化物/炔环加成“点击”化学实现。两性离子基序的选择是 这是由于它们稳定的防污性能以及我们最近发现它们作为生物矿化的有效介质的新作用。在目标1中，我们将使用强大的SI-ATRP和“点击”化学从商业Ti6 Al 4V基材表面接枝具有模块化呈现的防污和杀菌功能基序的均聚物、无规和嵌段共聚物的库。通过X射线光电子能谱、水接触角、热重分析/凝胶渗透色谱以及表面划痕试验对涂层的性能和坚固性进行了表征和验证。在目标2中，我们将通过定量金黄色葡萄球菌（S.金黄色葡萄球菌）培养物、非特异性蛋白吸附、以及粘附的骨髓基质细胞在修饰表面上的存活/增殖。在目标3中，将选自目标2的顶部官能均聚物、嵌段和无规共聚物表面刷组合物施加到Ti6 Al 4V髓内（IM）杆。将表面改性的IM棒、沿着未改性的对照和用万古霉素单层改性的IM棒植入接种有S.金黄色葡萄球菌或盐水（未感染的对照）。通过定量S.金黄色葡萄球菌粘附在取出的IM棒上，死骨形成和股骨增宽/皮质变薄（通过microCT），以及固定股骨的失效扭矩。对这些结果进行评分，以指导表面刷组合物的选择，该表面刷组合物对假体周围感染具有最持久的抑制作用，对正常股骨形态和机械完整性的干扰最小。表面刷组合物的生物相容性还通过接受没有细菌接种物的植入物的大鼠的重要/清道夫器官和股骨的病理学（骨质溶解、急性/慢性炎症反应和对涂层的过敏反应的迹象）来检查。本研究的成功完成预计将确定生物相容性表面聚合物刷组合物，其提供持续的保护以防止/抑制假体周围感染，其可以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.