Synergistic anti-fouling coating and minimal systemic antibiotic injections for combating periprosthetic infections

项目总结/摘要 假体周围感染（PPI）发生在1-4%的初次全关节置换术和高达30%的翻修术中 关节成形术和难以预防或治疗的倾向，由于细菌，特别是葡萄球菌 金黄色葡萄球菌（S.金黄色葡萄球菌），以在植入物表面上定殖和形成生物膜并侵入周围的骨 矩阵传统的抗生素预防和治疗不能充分应对这一挑战。我们 最近表明，当从Ti6 Al 4V髓内（IM）植入物接枝防污两性离子聚合物时， 联合单次全身注射万古霉素可有效抑制S.种植体上的金黄色葡萄球菌定植 表面和PPI在小鼠股骨管，显着优于单独治疗。在这里，我们的目标是 通过设计一种强有力的抗- 污垢嵌段共聚物浸涂作为金属植入物的现成产品， 用于在初次植入物插入和植入期间持续保护协同抗生素预防方案 修订，分别针对甲氧西林敏感和耐甲氧西林（MRSA）S。金黄色葡萄球菌PPI。在目标1中， 具有防污两性离子侧链和金属的高分子量聚甲基丙烯酸酯嵌段共聚物 表面结合侧链通过顺序反向加成断裂链转移（RAFT）制备， 聚合和铜催化的叠氮化物-炔环加成（CuAAC）。利用优秀的 通过RAFT控制聚合度和侧链的高保真CuAAC修饰， 金属合金表面结合残基各自的嵌段长度和化学性质以及空间密度， 模块化地改变以确定最佳的共聚物组成和浸涂方案，以实现一致的 在Ti6 Al 4V上有稳定的防污涂层，可以承受流动清洗、灭菌和货架储存。 涂层表面的特征在于水接触角，X射线光电子能谱，和电阻 到体外非特异性蛋白质吸附和细菌定殖。在目标2和3中，顶部防污浸- 将目标1中选择的涂层应用于Ti6 Al 4 V IM销，并与协同抗生素一起沿着进行检查 预防性治疗，以实现PPI长期抑制和PPI复发的有效性和安全性， 对甲氧西林敏感的S.金黄色葡萄球菌或MRSA在大鼠中插入初次和翻修植入物后， 分别PPI或复发性PPI的程度作为针涂层的函数，以及 通过全血细胞计数和µCT定量纵向监测协同抗生素预防 皮质骨增厚，并通过回收针上细菌的终点定量、扭转试验和 组织学/电子显微镜表征6个月的过程中骨折股骨。长期 涂层的安全性通过股骨组织学和全身器官病理学检查， 控制这项研究的成功将确定最佳的浸涂组合物和协同抗生素 预防方案，以有效地打击PPI和PPI复发，从而建立他们的 临床相关性作为一种新的抗PPI策略，并将其推进到临床转化的下一阶段。

PROJECT SUMMARY/ABSTRACT Periprosthetic infections (PPIs) occur in 1-4% of primary total joint replacement and up to 30% of revision arthroplasty and are difficult to prevent or treat due to the tendency of bacteria, especially Staphylococcus aureus (S. aureus), to colonize and form biofilms on implant surfaces and to invade the surrounding bone matrices. Conventional antibiotic prophylaxis and treatments do not adequately address this challenge. We recently showed that anti-fouling zwitterionic polymers grafted from Ti6Al4V intramedullary (IM) implants, when combined with a single systemic injection of vancomycin, effectively inhibited S. aureus colonization on implant surfaces and PPI in murine femoral canals, significantly outperforming either treatment alone. Here, we aim to facilitate the clinical translation of this promising synergistic anti-PPI strategy by engineering a robust anti- fouling block copolymer dip-coating as an off-the-shelf product for metallic implants, and an effective and safe synergistic antibiotic prophylaxis regimen for sustained protection during primary implant insertion and implant revision, respectively, against methicillin-sensitive and methicillin-resistant (MRSA) S. aureus PPIs. In Aim 1, high-molecular weight polymethacrylate block copolymers with anti-fouling zwitterionic sidechains and metal surface-binding sidechains are prepared by sequential Reverse Addition Fragmentation Chain Transfer (RAFT) polymerization and copper-catalyzed azide-alkyne cycloaddition (CuAAC). Taking advantage of the excellent control over the degree of polymerization by RAFT and the high-fidelity CuAAC modification of sidechains, the respective block lengths and chemical nature and spatial density of metal alloy surface-binding residues are modularly altered to identify an optimal copolymer composition and dip-coating protocol to achieve consistent and stable anti-fouling coating on Ti6Al4V that can sustain flow wash, sterilization and over-the-shelf storage. Coated surfaces are characterized by water contact angels, x-ray photoelectron spectroscopy, and resistance to non-specific protein adsorption and bacterial colonizations in vitro. In Aims 2 and 3, the top anti-fouling dip- coating chosen in Aim 1 is applied to Ti6Al4V IM pins and examined, along with synergistic antibiotic prophylaxis, for the efficacy and safety in achieving long-term inhibition of PPI and recurrent PPI caused by methicillin-sensitive S. aureus or MRSA following the insertion of primary and revision implants in rats, respectively. The degree of PPI or recurrent PPI as a function of pin coating and the timing/frequency of synergistic antibiotic prophylaxis are longitudinally monitored by complete blood counts and µCT quantification of cortical bone thickening, and by endpoint quantification of bacteria on the retrieved pin, torsion test and histology/electron microscopy characterizations of explanted femurs over the course of 6 months. Long-term safety of the coating is examined by both femoral histology and systemic organ pathology in the uninfected control. Success of this study will identify an optimal dip-coating composition and synergistic antibiotic prophylaxis regimens to effectively combat PPI and recurring PPI, respectively, thereby establishing their clinical relevance as a new anti-PPI strategy and advancing them to the next stage of their clinical translations.