LONG TERM BIODEGRADATION OF ELASTOMERIC MATERIALS

具有优异的物理和化学性能的组合 聚氨酯(PU)及其生物相容性导致了他们的 在广泛的生物医学应用中使用。在过去的十年里， 当一些PU被提出时，人们对PU的生物稳定性提出了担忧 起搏器导线被显示经历了环境应力破裂 人类。这个实验室目前的研究方向是一个基本的 对PU弹性体的生物相容性和生物稳定性的了解 提出了体内细胞/聚合物反馈控制的假说。 生物降解。为了确认和/或修改该假设， 实验程序将在已知组成的PU上进行 添加和不添加可增强生物稳定性的特定添加剂。这个 拟议研究的具体目标是： 1)阐明细胞降解的化学机制 试剂(自由基、高氯酸、酸)--导致水解链和/或氧化链 非聚醚软体对聚醚聚氨酯及其他脓液的裂解 生物降解机制(S)可能不同的部分。 相关研究将在体外加速条件下进行 模拟体内的环境。 2)体内和体外处理后的表面降解特性 暴露，并将结果与对性能的影响相关联 属性。材料表征的方法将包括衰减 全反射红外光谱、光声红外 光谱、ESCA、接触角、凝胶渗透色谱、 扫描电子显微镜和扫描声学显微镜。 3)确定应力应变状态对PU速率的影响 生物降解。单轴和双轴应变的影响将是 在体内和体外进行检查，结果将与 在体外氧化和高温下测定的蠕变和疲劳行为 水解条件。 4)确定了PU表面化学的作用效果和 添加剂对中性粒细胞和中性粒细胞黏附的影响 静态和动态条件下的单核/巨噬细胞，以及 没有补语的存在。这些研究将是相互关联的 通过体内实验来检验抗氧化剂和 巨噬细胞抑制剂对生物降解的影响。

The combination of outstanding physical and chemical properties of polyurethanes (PUs) coupled with their biocompatibility have led to their use in a wide range of biomedical applications. In the last decade, concerns regarding the biostability of PUs were raised when some PU pacemaker leads were shown to undergo environmental stress-cracking in humans. Current studies in this laboratory directed toward a fundamental understanding of biocompatibility and biostability of PU elastomers have led to a hypothesis for the cell/polymer feedback control of in vivo biodegradation. In order to confirm and/or modify the hypothesis, experimental procedures will be carried out on PUs of known composition with and without specific additives that enhance biostability. The specific aims of the proposed research are: 1) To elucidate the chemical mechanisms by which cellular degrading agents (radicals, HOCl, acid)- cause hydrolytic and/or oxidative chain cleavage of polyetherurethanes, and other PUs with non-polyether soft segments where the mechanism(s) of biodegradation may be different. Correlative studies will be made with accelerated in Vitro conditions that mimic the in Vivo environment. 2) To characterize the surface degradation after in Vivo and in Vitro exposure, and correlate the results with the effect on performance properties. Methods of material characterization will include attenuated total reflectance infrared spectroscopy, photoacoustic infrared spectroscopy, ESCA, contact angle, gel permeation chromatography, scanning electron microscopy and scanning acoustic microscopy. 3) To ascertain the effect of stress and strain state on the rate of PU biodegradation. The effects of uniaxial and biaxial strain will be examined in vivo and in vitro, and the results will be correlated with creep and fatigue behavior as determined in vitro under oxidative and hydrolytic conditions. 4) To determine the effect of PU surface chemistry and the effect of additives on the adhesion of polymorphonuclear leukocytes and monocytes/macrophages under static and dynamic conditions, with and without the presence of complement. These studies will be correlated with in vivo experiments to examine the effects of antioxidants and macrophage inhibitors on biodegradation.