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

非技术性：这个奖项由材料研究部的生物材料项目授予位于学院公园的马里兰大学，目的是研究两种类型的生物聚合物与血细胞之间的相互作用。这位研究人员的初步研究表明，这些生物聚合物可以将血液转化为凝胶。这样的血液凝结让人想起凝血过程中的物理变化，凝血是身体用来止血的开放伤口。因此，这些凝血聚合物可以用作止血剂，即可以为严重创伤和伤害止血的材料。该项目的更广泛影响可能包括事故现场的应急人员或战场上的士兵将这些生物聚合物用作救生材料。此外，一种不依赖于健康人正常血液中存在的分子的“凝血”机制的发现，可能被证明对患有血友病等凝血障碍的患者具有重要意义。关于教学、培训和外联活动，和平协会积极参与培训学生(研究生和本科生)和外联活动，人数不足的群体积极参与。YouTube上的视频正在开发中，以突出拟议中的研究。技术：该项目是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有弹性的、自我支撑的凝胶。这些聚合物是壳聚糖(HMC)和海藻酸盐(HMA)的疏水改性(Hm)衍生物。该项目基于以下假设，即可逆凝胶是由于：1)在凝胶过程中疏水基团与红细胞膜的相互作用；以及2)脱胶过程是由于生物聚合物疏水基团与脱胶步骤中使用的环糊精的内部疏水口袋相互作用所致。这项提案将研究胶凝的机理，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。该项目将研究HMC或HMA链上的疏水基团的作用，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一个独特特征是，可以通过引入环糊精来逆转血液凝集，即具有内部疏水口袋的糖基超分子。据推测，这种反转现象的发生是因为HMC和HMA中的疏水基团从细胞中解离并嵌入到环糊精的内部疏水口袋中。为了测试这些机制，将用一系列HMC和HMA衍生物进行研究，这些衍生物的疏水单元的长度和比例都不同。这些聚合物还将在不同的细胞密度下用肝素化或柠檬化的牛血进行研究。流变学技术将被用来探测得到的凝胶的粘弹性；光学显微镜(亮场和共焦)将被用来在微观尺度上研究得到的混合物的结构；散射技术将被用来在纳米尺度上了解聚合物的构象。此外，还将使用各种类型的环糊精来逆转凝胶化过程。因此，血液的凝胶和脱胶的最佳成分将被确定。在聚合物可以用于此类应用之前，必须从根本上彻底了解这种可逆凝胶化的机理，这也是本项目的重点。更广泛的影响活动包括对学生(研究生和本科生)的教学和培训，以及由代表人数不足的群体积极参与的外联活动。此外，正在开发YouTube视频，以突出拟议的研究。

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.