Ultralow Protein Adsorption Hemocompatible Biomaterials

体外表面的血液凝结仍然是许多设备临床应用的主要限制，包括心血管搭桥、支架、导管和葡萄糖传感器。在许多情况下，血小板是生物材料表面血液凝固的发起者。我们实验室最近的研究已经确定了消除血小板粘附的定量设计标准，即需要将纤维蛋白原吸附降低到非常低的水平（小于5 ng/cm2），远远低于大多数材料的吸附水平。我们制造的射频等离子体沉积的四肽材料通常可以满足这一标准，但这是否会产生我们所寻求的完全与血液相容的生物材料仍有待证明。我们还必须确定，超低纤维蛋白原摄取可以持续实现，并且材料在这方面是稳定的。因此，提出了一系列完善glyme技术和评价其血液相容性的研究。提案的具体目的如下：将优化四甲酰胺等离子体处理条件，以实现涂层均匀性、耐久性和超低蛋白质摄取，并将制造一种新的反应器来处理更长的管的内表面。一个关于紧密结合的水在使涂层不结垢中的作用的假设将被检验。将评估两种用于生产等离子体沉积的聚乙二醇样表面的新单体。2. 将血浆中纤维蛋白原的吸附与ESCA和TOF-SIMS的一系列四烯酶表面化学数据进行比较，以确定导致超低纤维蛋白原摄取的条件。四烯酰胺系列将在不同的反应器条件下生产，这将导致表面化学的变化，从而使我们能够测试这样一个假设，即实现超低污染必须满足的标准是高的，相对于非醚碳优化的醚碳含量和防止分层。对纤维连接蛋白、玻璃体连接蛋白、血管性血友病因子和IgG的抗污染能力也将被测量。对血浆中所有蛋白质的吸收阻力将通过表面等离子体共振和二维凝胶电泳来表征。3. 血液相互作用将采用体外和体内两种方法进行表征。在体外血小板粘附和促凝剂激活的一系列glyme包被材料将测量其预暴露于血浆或纤维蛋白原后。非血小板介导的凝血事件的作用将通过测量凝血时间和凝血酶活性的再钙化血浆接触的四烯酶进行评估。非粘性接触对血小板活化和聚集的影响将通过激光栓塞检测来表征。通过测量急性期和稳定状态的凝血指标，将对采用管状四甲素体外分流术的狗评估具有超低纤维蛋白原和血小板摄取的材料的体内血液相容性。

Blood clotting on foreign surfaces remains a major limitation in the clinical application of many devices, including cardiovascular bypass, stents, catheters, and glucose sensors. In many situations, platelets are the initiator of blood clotting on the biomaterial surface. Recent studies in our lab have identified a quantitative design criterion to eliminate platelet adhesion, namely the need to reduce fibrinogen adsorption to very low levels (less than 5 ng/cm2), far below that which occurs on most materials. Radio frequency plasma deposited tetraglyme materials we have made can often meet this criteria, but it remains to be shown whether this results in the perfectly blood compatible biomaterial that we seek. We also must establish that ultra-low fibrinogen uptake can be achieved consistently and that the materials are stable in this regard. Therefore, a series of studies to perfect the glyme technology and evaluate its blood compatibility is proposed. The specific aims of the proposal are as follows: 1. Tetraglyme plasma treatment conditions will be optimized to achieve coating uniformity, durability and ultra low protein uptake and a new reactor to treat the inside surfaces of longer tubes will be made. A hypothesis about the role of tightly bound water in causing non-fouling of glyme coatings will be tested. Two new monomers for producing plasma deposited PEG- like surfaces will be evaluated. 2. Fibrinogen adsorption from plasma will be compared to ESCA and TOF-SIMS surface chemical data for a series of tetraglymes to establish the conditions that result in ultra-low fibrinogen uptake. The tetraglyme series will be made under varying reactor conditions which will cause variations in surface chemistry, and thus allow us to test the hypothesis that the criteria that must be met to achieve ultra- low fouling are high, optimized ether carbon content relative to non-ether carbon and prevention of delamination. Resistance to fouling by fibronectin, vitronectin, von Willebrand factor, and IgG will also be measured. Resistance to uptake of all proteins from plasma will be characterized with surface plasmon resonance and by two dimensional gel electrophoresis. 3. Blood interactions will be characterized using both in vitro and in vivo methodology. In vitro platelet adhesion and procoagulant activation on a series of glyme coated materials will be measured after their pre-exposure to blood plasma or fibrinogen. The role of non-platelet mediated clotting events will be assessed by measuring clotting times and clotting enzyme activity in recalcified plasma in contact with the tetraglymes. The effect of non-adhesive encounters on platelet activation and aggregation will be characterized using laser emboli detection. In vivo blood compatibility of materials exhibiting ultralow fibrinogen and platelet uptake will be assessed in dogs with tubular tetraglyme ex vivo shunts by measuring both acute phase and steady state indicators of clotting.