Reversible Gelation of Blood Using Self-Assembling Biopolymers: Understanding the Mechanism for Reversible Self-Assembly

使用自组装生物聚合物实现血液的可逆凝胶化：了解可逆自组装的机制

• 批准号: 1508155
• 负责人: Srinivasa Raghavan
• 金额: $ 36万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-15 至 2020-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1508155&HistoricalAwards=false
• 关键词: Reversible; Gelation; Blood; Using; Self

Non-Technical: This award by the Biomaterials program in the Division of Materials Research to University of Maryland at College Park is to study the interactions between two types of biopolymers and blood cells. Preliminary studies by this researcher have shown that these biopolymers convert blood into a gel. Such gelation of blood is reminiscent of the physical changes during blood clotting, which is used by the body to stop bleeding from an open wound. Accordingly, these blood-gelling polymers could be used as hemostatic agents, i.e., materials that can stop bleeding from serious wounds and injuries. The broader impacts of this project could include the use of these biopolymers as life-saving materials by emergency responders at accident sites or by soldiers in the battlefield. In addition, the discovery of a "clotting" mechanism that does not depend on the molecules present in normal blood of healthy people could prove to be significant for patients who suffer from clotting disorders such as hemophilia. With respect to teaching, training and outreach activities, the PI is active in training students (graduate and undergraduate) and outreach activities with active participation of underrepresented groups. YouTube videos to highlight the proposed studies are being developed.Technical: This project is based on the investigator's recent finding that a class of biopolymers are capable of converting blood into an elastic, self-supporting gel. These polymers are hydrophobically modified (hm) derivatives of chitosan (hmC) and alginate (hmA). This project is based on the hypothesis that the reversible gelation is due to: 1) binding of the hydrophobic group's interaction with red blood cell membranes during the gelation process; and 2) the degelation process is due to the interaction of the biopolymer hydrophobic groups with the inner hydrophobic pockets of cyclodextrins used in the degelation step. This proposal will study the mechanism to answer the question of why such gelation occurs, and how gelation is correlated to the structure of the polymers. This project will study the role of hydrophobic groups from hmC or hmA chains, their interactions with membranes of blood cells, and how these polymers interconnect the cells into a volume-filling network. A unique feature of this self-assembly-based mechanism is that blood gelling can be reversed by introduction of cyclodextrins, i.e., sugar-based supramolecules with an inner hydrophobic pocket. It is hypothesized that this reversal, i.e., ungelling, occurs because hydrophobic groups from hmC and hmA unbind from the cells and embed within the inner hydrphobic pockets of cyclodextrins. To test these mechanisms, studies will be carried out with a series of hmC and hmA derivatives varying in the length and fraction of hydrophobic units. These polymers will also be studied with heparinized or citrated bovine blood at various cell densities. Rheological techniques will be used to probe the viscoelasticity of the resulting gels; optical microscopy (bright field and confocal) will be used to study the structure of the resulting mixtures at the microscale; and scattering techniques will be used to understand the conformation of the polymer at the nanoscale. In addition, cyclodextrins of various types will be used to reverse the gelation process. Thus, the optimal compositions for both gelation and degelation of blood will be identified. Before the polymers could be used for such applications, a thorough fundamental understanding of the mechanism for this reversible gelation is necessary, which is the focus of this project. The broader impact activities included teaching and training of students (graduate and undergraduate) and outreach activities with active participation of underrepresented groups. In addition, YouTube videos to highlight of the proposed research are being developed.

非技术：该奖项由材料研究部的生物材料项目授予马里兰州大学帕克分校，旨在研究两种类型的生物聚合物和血细胞之间的相互作用。该研究人员的初步研究表明，这些生物聚合物将血液转化为凝胶。这种血液的凝胶化让人想起血液凝固过程中的物理变化，血液凝固被身体用来阻止开放性伤口的出血。因此，这些血液胶凝聚合物可用作止血剂，即，可以止血的材料，从严重的伤口和伤害。该项目的更广泛影响可能包括将这些生物聚合物用作事故现场应急人员或战场上士兵的救生材料。此外，发现一种不依赖于健康人正常血液中存在的分子的“凝血”机制，可能对血友病等凝血障碍患者具有重要意义。在教学、培训和外联活动方面，PI积极培训学生（研究生和本科生），并在代表性不足的群体的积极参与下开展外联活动。技术：该项目基于研究人员最近的发现，即一类生物聚合物能够将血液转化为弹性的自支撑凝胶。这些聚合物是壳聚糖（hmC）和藻酸盐（hmA）的疏水改性（hm）衍生物。该项目基于以下假设：可逆凝胶化是由于：1）在凝胶化过程中疏水基团与红细胞膜的相互作用的结合;以及2）去凝胶化过程是由于生物聚合物疏水基团与去凝胶化步骤中使用的环糊精的内部疏水口袋的相互作用。该建议将研究机理以回答为什么会发生这种凝胶化以及凝胶化如何与聚合物的结构相关的问题。该项目将研究来自hmC或hmA链的疏水基团的作用，它们与血细胞膜的相互作用，以及这些聚合物如何将细胞互连成体积填充网络。这种基于自组装的机制的独特特征是血液胶凝可以通过引入环糊精来逆转，即，具有内部疏水口袋的糖基超分子。假设这种逆转，即，由于hmC和hmA的疏水基团从细胞上脱离并嵌入环糊精的内部疏水口袋中，因此发生了非凝胶化。为了测试这些机制，将进行研究与一系列的hmC和hmA衍生物的疏水单元的长度和分数的变化。这些聚合物也将在不同细胞密度下用肝素化或柠檬酸化牛血进行研究。流变学技术将被用来探测所得凝胶的粘弹性;光学显微镜（明场和共聚焦）将被用来研究所得混合物的结构在微观尺度;和散射技术将被用来了解在纳米级的聚合物的构象。此外，各种类型的环糊精将用于逆转凝胶化过程。因此，将确定用于血液的凝胶化和去凝胶化的最佳组合物。在聚合物可用于此类应用之前，对这种可逆凝胶化的机制有一个彻底的基本理解是必要的，这是本项目的重点。影响范围更广的活动包括对学生（研究生和本科生）的教学和培训以及有代表性不足的群体积极参与的外联活动。此外，正在制作YouTube视频，突出介绍拟议的研究。