Development of bioactive surface for pediatric hemodialysis catheters to prevent thrombogenic, inflammatory and biofilm complications

 描述(申请人提供)：最常见的血液透析导管并发症是血栓形成、炎症和生物膜。血栓沉积和炎症已被证明会导致不充分的透析，导致更高的并发症发生率和更高的死亡率，并可以采取许多不同的形式，包括孤立的血栓，导管尖端附近血管的血栓形成，或导管管腔内形成的纤维蛋白鞘。儿童透析的情况更加糟糕，因为儿童导管的口径较小，血流速度较低，因此特别容易发生血栓形成和导管并发症。引发导管相关并发症的基本机制是人体对接触异物的固有非特异性免疫反应。当异物如导管插入患者的循环时，异物的直接反应是循环中的蛋白质吸附到导管表面(包括凝血酶、组织因子和补体C3a/C5a)。吸附将构象变化引导到暴露正常隐藏的表位的蛋白质上，激活炎症细胞，如单核细胞和血小板，从而导致血栓形成。此外，透析患者的免疫系统会受到损害，因为有丝分裂原的额外储存会导致对异物表面的过敏反应。因此，重要的是有一个导管表面， 减轻异物反应，防止慢性炎症和血栓形成。这项建议的目的是开发和评估一种新型表面的功效，该表面的灵感来自于自然产生的内皮糖基化。建议的生物活性表面将最大限度地减少最常用的儿科血液透析导管(Split cathTM，Medcomp)的血栓形成和炎症潜力，从而防止慢性炎症和最大限度地减少血栓形成。表面改性(特定Aim1)包括四个步骤：1)清洁聚碳酸酯/聚氨酯导管表面，为后续的改进提供一致、稳定的表面。2)等离子体增强气相沉积活化，生成可接枝水凝胶的活性部位。3)通过自由基聚合将水凝胶接枝到活化表面。4)生物活性肝素的偶联。每一步都将 单独进行评估，在满足验收标准之前不会尝试后续步骤。血液灌流研究(特定目标2)将用于评估符合特定目标1验收标准的表面。测试表面将对循环血液中的蛋白质/细胞黏附和细胞激活进行评估。符合特定目标2中规定的体外接受标准的表面将在30天的大鼠模型(特定目标3)中进行评估。9个对照导管和9(9)个表面处理导管将使用放置在上腔静脉的~1 cm节段导管(表面处理或对照)进行评估。植入导管表面的有效性将通过：(1)导管周围组织的免疫组织化学分析来评估。(2)细胞层/导管生物膜的扫描电子显微镜(SEM)；(3)血样流式细胞仪检测白细胞和血小板的活化及血栓形成情况。

 DESCRIPTION (provided by applicant): The most common hemodialysis catheter complications are thrombosis, inflammation, and biofilms. Thrombotic deposition and inflammation have been shown to result in inadequate dialysis and lead to higher complication rates and increased mortality and can take many different forms including isolated clots, thrombosis in vessels adjacent to the catheter tip, or fibrin sheaths formed within the catheter lumen. The situation in pediatric dialysis is even more woeful because pediatric catheters are a smaller caliber with lower blood flow rates making them particularly prone to thrombosis and catheter complications. The fundamental mechanism initiating the catheter--‐related complications is the body's inherent non--‐specific immune response to contact with foreign materials. When a foreign object such as a catheter is inserted into the patient's circulation the immediate foreign body response is the adsorption of circulating proteins onto the catheter's surface (including thrombin, tissue factor and complement C3a/C5a). Adsorption directs conformational changes to the proteins that expose normally hidden epitopes activating inflammatory cells such as monocytes and platelets that leads to thrombosis. In addition, dialysis patients have compromised immune systems with additional stores of mitogens that induce a hyper reaction to foreign surfaces. Therefore, it is vital to have a catheter surface that mitigates the foreign body response and prevents chronic inflammation and thrombosis. This objective of this proposal is to develop and evaluate the efficacy of a novel surface inspired by the naturally occurring endothelial glycocalyx. The proposed bioactive surface will minimize the thrombogenic and inflammatory potential of the most commonly used pediatric hemodialysis catheter (Split CathTM, MedComp) thus preventing chronic inflammation and minimizing thrombosis. The surface modification (Specific Aim1) consists of four steps: 1) Cleaning of the polycarbonate/polyurethane catheter surface to provide a consistent, stable surface for subsequent modifications. 2) Activation by plasma enhanced vapor deposition to generate active sites to which the hydrogel can be grafted. 3) Grafting of a hydrogel via free radical polymerization to the activated surface. 4) Coupling of bioactive heparin. Each of the steps will be individually evaluated and subsequent steps will not be attempted until acceptance criteria are met. Blood perfusion studies (Specific Aim 2) will be used to evaluate surfaces that meet Specific Aim 1 acceptance criteria. Tested surfaces will be evaluated for protein/cell adherence and cellular activation in the circulating blood. Surfaces meeting in vitro acceptance criteria specified in Specific Aim 2 will be evaluated in a 30 day rat model (Specific Aim 3). Nine (9) control and nine (9) surface treated catheters will be evaluated using a ~1 cm segment catheter (surface treated or control) placed in the superior vena cava. The efficacy of the surface on the implanted catheters will be assessed by: (1) Immunohistochemical analysis of the tissue surrounding the catheter. (2) Scanning electron microscopy (SEM) on the cellular layer / biofilm on the catheter (3) Flow cytometry of blood samples to quantify white cell and platelet activation and thrombogenesis.