Mechanically Stable Blood Substitutes

描述(申请人提供)：为了改善创伤受害者和接受高失血外科手术的患者的预后，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。本研究旨在设计新型的含血红蛋白(Hb)和肌动蛋白(Ac)的脂质体(LEAcHb)。这些囊泡有望通过这一新系统的两个关键特征增加循环中的半衰期。首先，这些脂质体是由聚乙二醇偶联脂类物质组成的。这一特征减少了网状内皮系统(RES)对这些脂质体的识别。其次，这些囊泡在机械上是稳定的，并且能够在溶液中呈椭圆形，因为细胞骨架聚合物肌动蛋白充当支架，在体循环中稳定囊泡。因此，它们对血液剪切梯度具有很强的弹性。事实上，当这些新奇的囊泡暴露在血流中遇到的高剪应力时，它们可以动态地自我修复。这项应用的目的是了解如何设计LEAcHb囊泡结构和力学，以创造机械稳定和形状变化的囊泡分散体，用作人造血液替代品。我们推测，通过改变脂质体的大小和包裹的肌动蛋白浓度，可以控制脂质体的结构和力学。我们计划通过三个具体目标来验证我们的假设并实现这一应用的目标：1)确定含有肌动蛋白-血红蛋白的脂质体的结构和力学，并将其与含有肌动蛋白-血红蛋白的脂质体分散体的流变学和平均弯曲弹性相关联。2)测定LEAcHb分散体在平衡状态下的氧结合性质、O2和NO结合/释放动力学、Hb自氧化和氯化血红素释放动力学、H_2O_2和O_2介导的Hb氧化动力学、稳定性、补体活化、体内性能、循环半衰期和生物分布。3)对使用LEAcHb分散体的不同血容量替代方案的血流动力学效应进行生理学评估。这项拟议的工作既是创新的，也是有意义的，因为将创造出具有工程结构和机械特性的新型LEAcHb杂交囊泡，用作人造血液替代品。

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.