Mechanically Stable Blood Substitutes

描述（由申请人提供）：为了改善创伤受害者和接受高失血手术的患者的预后，并避免输血的许多严重并发症，迫切需要一种携带氧气的血液替代品。本研究旨在工程化新型含血红蛋白（Hb）和肌动蛋白（Ac）的脂质体（LEAcHb）。通过这种新系统的两个关键特征，这些囊泡有望增加循环中的半衰期。首先，这些脂质体由与聚乙二醇（PEG）偶联的脂质组成。这一特征降低了网状内皮系统（RES）对这些脂质体的识别。其次，由于细胞骨架聚合物肌动蛋白在体循环中充当支架并稳定囊泡，这些囊泡既具有机械稳定性，又能在溶液中呈椭球状。因此，它们对血液剪切梯度具有高度的弹性。事实上，当暴露在血流中遇到的高剪切应力时，这些新型囊泡可以动态自愈。本应用的目的是了解如何设计LEAcHb囊泡结构和力学，以创建机械稳定和形状变化的囊泡分散体，用于人造血液替代品。我们假设脂质体的结构和力学控制可以通过改变脂质体的大小和包裹肌动蛋白的浓度来设计。我们计划通过追求三个具体目标来测试我们的假设并实现本应用的目标：1)确定单个肌动蛋白-血红蛋白脂质体的结构和力学，并将其与肌动蛋白-血红蛋白脂质体分散体的流变学和平均弯曲弹性联系起来。2)确定平衡态氧结合特性、O2和NO结合/释放动力学、Hb自氧化和血红蛋白释放动力学、H2O2和O2_介导的Hb氧化动力学、LEAcHb分散体的稳定性、补体激活、体内性能、循环半衰期和生物分布。3)利用LEAcHb分散体对不同血容量替代方案的血流动力学影响进行生理评估。这项提议的工作既具有创新性又意义重大，因为具有工程结构和机械特性的新型LEAcHb混合囊泡将被创造出来用作人工血液替代品。

DESCRIPTION (provided by applicant): To improve the outcome of trauma victims and of patients undergoing high-blood-loss surgical procedures and to avoid the many serious complications of blood transfusions, there is a critical need for an oxygen- carrying blood substitute. This study is aimed at engineering novel hemoglobin (Hb) and actin (Ac) containing liposomes (LEAcHb). These vesicles are expected to have increased half-lives in circulation via two key features of this novel system. First these liposomes are composed of lipid that is conjugated with poly(ethylene glycol) (PEG). This feature reduces recognition of these liposomes by the reticuloendothelial system (RES). Secondly, these vesicles are both mechanically stable and able to adopt an ellipsoidal shape in solution, since the cytoskeletal polymer actin acts as a scaffold and stabilizes the vesicles while in the systemic circulation. Hence, they are highly resilient to blood shear gradients. In fact these novel vesicles can dynamically self-heal themselves when exposed to high shear stresses encountered in the blood stream. The objective of this application is to understand how LEAcHb vesicle structure and mechanics can be engineered to create mechanically stable and shape changing vesicular dispersions for use as artificial blood substitutes. We postulate that control of liposome structure and mechanics can be engineered by varying liposome size and concentration of encapsulated actin. We plan to test our hypothesis and accomplish the objective of this application by pursuing three specific aims: 1) Determine the structure and mechanics of individual actin-hemoglobin containing liposomes, and relate this to the rheology and average bending elasticity of actin-hemoglobin containing liposome dispersions. 2) Determine the oxygen binding properties at equilibrium, kinetics of O2 and NO binding/release, kinetics of Hb autoxidation and hemin release, kinetics of H2O2 and O2_ mediated oxidation of Hb, stability, complement activation, in vivo performance, circulatory half-life, and biodistribution of LEAcHb dispersions. 3) Physiological assessment of the hemodynamic effects of various blood volume replacement regimens using LEAcHb dispersions. The proposed work is both innovative and significant, because novel LEAcHb hybrid vesicles with engineered structural and mechanical characteristics will be created for use as an artificial blood substitute.