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Passivating Proteins in Implantable Glucose Sensors

钝化植入式血糖传感器中的蛋白质

基本信息

批准号：
6792087
负责人：
WILLIAM KENNETH WARD
金额：
$ 30.54万
依托单位：
LEGACY EMANUEL HOSPITAL AND HEALTH CENTER
依托单位国家：
美国
项目类别：
财政年份：
2002
资助国家：
美国
起止时间：
2002-09-30 至 2006-11-30
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): Inadequate control of blood glucose contributes to the complications of diabetes (renal, retinal, neural). A glucose sensor implanted subcutaneously could provide continuous glucose data, help prevent these complications, and give early warning for hypoglycemia, but the useful life of current devices is limited by foreign body encapsulation. The goal of this work is to develop coatings that will reduce the foreign body reaction to implanted glucose sensors, thereby extending their useful life. Specifically, studies of protein coatings that will reduce monocyte/macrophage adhesion are proposed. The role of fibrinogen and its macrophage-binding region will also be explored. The effect of these coatings will be addressed during chronic studies of glucose sensors implanted subcutaneously in rats. 1. Passivating protein coatings will be created and characterized as follows: a. The degree to which four proteins in buffered solutions will adsorb to polyurethane-coated surfaces will be measured using Iodine-125 radiolabeled proteins. The proteins will include von Willebrand factor, high molecular weight kininogen, albumin, and hemoglobin. Protein concentration will be varied to determine the isotherms for each protein, in order to establish concentrations needed to attain saturation or monolayer adsorption. b. For each protein, the resistance to displacement by blood plasma will be measured. Methods to reduce displacement will be evaluated, including variations in adsorption time and postadsorptive residence time. c. Adsorption conditions found to give coatings that are substantially resistant to displacement will be evaluated in regard to their ability to inhibit macrophage adhesion and foreign body giant cell formation in vitro. d. Glucose sensors preadsorbed with protein under conditions resulting in the least displacement by plasma and the greatest inhibition of monocyte adhesion and foreign body giant cell [FBGC] formation will be sent to Legacy where they will be evaluated to assess useful in vivo lifetime. 2. Passivating antibody coatings will be created and characterized as follows: a. The surface polyurethane will be preadsorbed with flbrinogen and treated with a monoclonal antibody that binds to fibrinogen's macrophage binding region. b. The ability of glutaraldehyde to further stabilize the fibrinogen/antibody-treated surfaces will be assessed. c. The resistance to displacement of the antibody by exposure to plasma will be evaluated. d. The efficacy of antibody blockade to reduce monocyte adhesion and FBGC formation will be evaluated. e. Glucose sensors preadsorbed with fibrinogen and antibody, with or without glutaraldehyde, will be prepared for chronic in vivo evaluation of sensor function. 3. The role of fibrinogen adsorption in the foreign body reaction will be studied as follows: a. A series of gas plasma-deposited polyethylene oxide-like coatings on the sensor will be created under conditions that cause variations in their fibrinogen adsorption. b. The variation of in vitro phagocyte uptake on these surfaces and will be measured. c. Sensor surfaces with high and with low amounts of fibrinogen, including some passivated with antibodies and glutaraldehyde, will be prepared for evaluation in the Legacy animal laboratory. 4. Glucose sensor function will be evaluated after protein adsorption in vitro to assess any coating-induced change. 5. Sensors will be serially evaluated in vivo during normoglycemia and hyperglycemia in order to assess the effect of passivating proteins and antibody-blocked fibrinogen coatings on lag time, sensitivity, stability, and useful sensor life. 6. Because future users with diabetes will wish to minimize capillary blood calibrations, there will be an assessment in coated sensors as to whether calibrations performed only once per week will lead to sufficient sensor accuracy. 7. After explantation, percent of remaining radiolabeled protein will be measured and correlated with in vivo function in order to better understand the effects of displacement of passivating proteins or antibody-blocked fibrinogen. 8. A histologic evaluation will be performed to assess the effect of passivating proteins and antibody blocked fibrinogen on the nature of the foreign body capsule.

描述（由申请方提供）：血糖控制不充分会导致糖尿病并发症（肾脏、视网膜、神经）。皮下植入的葡萄糖传感器可以提供连续的葡萄糖数据，帮助预防这些并发症，并提供低血糖的早期预警，但目前器械的使用寿命受到异物包裹的限制。这项工作的目标是开发涂层，减少异物对植入葡萄糖传感器的反应，从而延长其使用寿命。具体而言，提出了减少单核细胞/巨噬细胞粘附的蛋白质涂层的研究。纤维蛋白原及其巨噬细胞结合区的作用也将探讨。这些涂层的影响将在大鼠皮下植入葡萄糖传感器的长期研究中得到解决。 1.钝化蛋白涂层的制备和表征如下： a.将使用碘-125放射性标记的蛋白质测量缓冲溶液中的四种蛋白质吸附到聚乙烯包被表面的程度。蛋白质包括血管性血友病因子、高分子量激肽原、白蛋白和血红蛋白。将改变蛋白质浓度以确定每种蛋白质的等温线，以确定达到饱和或单层吸附所需的浓度。 B.对于每种蛋白质，将测量对血浆置换的抵抗力。将评估减少置换的方法，包括吸附时间和吸附后停留时间的变化。 C.将评价发现产生基本上抗置换的涂层的吸附条件在体外抑制巨噬细胞粘附和异物巨细胞形成的能力。 D.在血浆置换最少、单核细胞粘附和异物巨细胞[FBGC]形成抑制最大的条件下，用蛋白质预吸附的葡萄糖探头将被发送至Legacy，在那里对其进行评价，以评估其体内使用寿命。 2.将制备钝化抗体包被并表征如下： a.表面聚氨酯将被纤维蛋白原预吸附，并用与纤维蛋白原的巨噬细胞结合区结合的单克隆抗体处理。 B.将评估戊二醛进一步稳定纤维蛋白原/抗体处理表面的能力。 C.将评价暴露于血浆时抗体的抗置换性。 D.将评价抗体阻断降低单核细胞粘附和FBGC形成的功效。 e.将准备用纤维蛋白原和抗体（含或不含戊二醛）预吸附的葡萄糖探头，用于探头功能的长期体内评价。 3.纤维蛋白原吸附在异物反应中的作用将研究如下： a.传感器上的一系列气体等离子体沉积的聚氧化乙烯类涂层将在引起纤维蛋白原吸附变化的条件下形成。 B.将测量这些表面上的体外吞噬细胞摄取的变化。 C.将准备具有高和低纤维蛋白原量的传感器表面（包括一些用抗体和戊二醛钝化的表面），以便在Legacy动物实验室进行评价。 4.将在体外蛋白质吸附后评价葡萄糖探头功能，以评估任何涂层诱导的变化。 5.将在血糖正常和高血糖期间对传感器进行连续体内评价，以评估钝化蛋白和抗体封闭的纤维蛋白原涂层对滞后时间、灵敏度、稳定性和有用传感器寿命的影响。 6.由于未来的糖尿病用户希望尽量减少毛细血管血液校准，因此将对涂层传感器进行评估，以确定每周仅进行一次校准是否会导致足够的传感器准确度。 7.纯化后，将测量剩余放射性标记蛋白的百分比，并将其与体内功能相关联，以更好地了解钝化蛋白或抗体阻断的纤维蛋白原置换的影响。 8.将进行组织学评价，以评估钝化蛋白和抗体阻断的纤维蛋白原对异物包膜性质的影响。