Synthetic Polymers with Dithiolane Functional Groups for Biomedical Materials

 描述(申请人提供)：天然大分子的各种生物学作用经过数千年的演变，激发了合成类似物的发展，这些合成类似物可以模仿其天然同类的结构、功能或生物学作用。该计划的目标是开发一类新型的具有响应性的生物相容的含二硫杂环的大分子。三亚甲基碳酸酯单体的有机催化开环聚合是合成具有模拟天然聚合物功能的不同官能团的生物可降解聚合物的一种通用策略。斯坦福大学的韦茅斯小组最近发现了一种有机催化合成策略，用于生成含有侧链二硫杂环的水溶性聚合物。二硫杂环是具有二硫键的五元环，类似于硫辛酸辅助因子中的二硫键。二硫杂环戊烷很容易与硫醇交换，与过量的硫醇可逆地还原为二硫醇，如谷胱甘肽。我认为，二硫杂环戊烷与硫醇的可逆快速交换可以提供一个响应的控制元件，促进药物或探针在细胞还原环境中的释放，并为细胞培养和组织工程提供新的动态共价网络作为自适应基质。该项目的第一个目标是开发一种可靠的方法，用于快速、可控地合成含有二硫杂环戊烷官能团的聚合物和水凝胶。在嵌段聚合物中，其他官能团，如用于药物跨细胞膜转运的胍基(“GD”)和用于诱导胶束形成的脂类(“L”)，将与二硫杂环戊烷(“DT”)一起并入。二硫杂环戊烷聚合物的合成将进行调整和精炼，以控制物理性质，如相对分子质量、聚合物电荷和水溶性。下一个目标是产生一系列针对信使核糖核酸传递的嵌段聚合物结构，包括序列，如Gd-DT-PEG-DT-Gd、PEG-Gd-DT和DT-Gd-PEG-L。这些反应材料将评估它们结合、运输和释放细胞内信使RNA(MRNA)的能力。细胞对碳酸三亚甲基齐聚物/聚合物的摄取可以通过在mRNA上贴上荧光标记来监测，并将评估基因表达以确定mRNA的释放程度。这项提案中描述的最后一个目标是评价水凝胶作为组织工程的共价适应性网络。通过在DT-PED-DT聚合物体系中添加二硫醇交联剂(HS-X-SH)来研究水凝胶的形成。通过改变二硫杂环戊烷的聚合度、二硫醇交联剂与二硫杂环戊烷聚合物的比例以及添加能够形成永久共价交联剂的聚乙二醇丙烯酸酯交联剂，可以控制水凝胶的性质，例如凝胶时间、模数和应力松弛。这些性能将针对水凝胶注射进行优化。细胞存活和增殖将在体外与范杨教授(斯坦福整形外科和生物工程)合作进行评估。其他生物医学应用将以对这些适应性和响应性大分子的物理和动态特性的新结果和洞察力为指导。

 DESCRIPTION (provided by applicant): The diverse biological roles of natural macromolecules have evolved over millennia and inspire the development of synthetic analogs that can mimic the structure, function or biological role of their natural congeners. The goal of this program is to develop a new class of responsive biocompatible macromolecules bearing dithiolane heterocycles. Organocatalytic ring-opening polymerization of trimethylene carbonate monomers is a versatile strategy for the generation of synthetic, biodegradable polymers with diverse functional groups that mimic the function of natural polymers. The Waymouth group at Stanford has recently discovered an organocatalytic synthetic strategy for generation of water-soluble polymers containing pendant dithiolane heterocycles. Dithiolanes are five-membered rings with disulfide bonds analogous to that in Lipoic acid cofactors. Dithiolanes exchange readily with thiols and are reversibly reduced to dithiols with excess thiols, such as glutathione.I propose that the reversible and rapid exchange of diothiolanes with thiols could provide a responsive control element that could facilitate release of drugs or probes in the reducing environment of the cell, as well as provide new dynamic covalent networks as adaptive matrices for cell culture and tissue engineering. The first goal of this project is to develop a reliable method for rapid, controlled synthesis of polymers and hydrogels incorporating dithiolane functionalities. Other functional groups, such as guanidinium groups ("GD") for drug transport across cell membranes and lipids ("L") to induce micelle formation, will be incorporated alongside dithiolane groups ("DT") in block polymers. The synthesis of dithiolane polymers will be tuned and refined to control physical properties such as molecular weight, polymer charge, and water solubility. The next goal is to generate an array of block polymer architectures targeted for mRNA delivery, including sequences such as GD-DT-PEG-DT-GD, PEG-GD-DT, and DT-GD-PEG-L. These responsive materials will be evaluated for their ability to bind, transport, and release messenger RNA (mRNA) in cells. Trimethylene carbonate oligomer/polymer uptake in cells can be monitored by attaching a fluorescent label to mRNA, and gene expression will be evaluated to determine the degree of mRNA release. The last goal described in this proposal is to evaluate hydrogels as covalent adaptable networks for tissue engineering. Hydrogel formation will be investigated by addition of dithiol cross linkers (HS-X-SH) to DT-PED-DT polymer architectures. Hydrogel properties such as gelation time, modulus, and stress relaxation can be controlled by varying the degree of dithiolane polymerization, the ratio of the dithiol cross-linker to the dithiolane polymer, and by adding a PEG- acrylate cross-linker capable of forming permanent covalent cross-links. These properties will be optimized for hydrogel injection. Cell viability and proliferation will be evaluated in vitro in collaboration wih Professor Fan Yang (Stanford Orthopaedic Surgery and Bioengineering). Other biomedical applications will be guided by new results and insights on the physical and dynamic properties of these adaptable and responsive macromolecules.