Synthetic Polymers with Dithiolane Functional Groups for Biomedical Materials

 描述（由申请人提供）：天然大分子的多种生物学作用已经进化了数千年，并激发了合成类似物的开发，这些合成类似物可以模拟其天然同源物的结构、功能或生物学作用。该计划的目标是开发一类新的响应性生物相容性大分子轴承二硫杂环。三亚甲基碳酸酯单体的有机催化开环聚合是用于产生具有模拟天然聚合物的功能的不同官能团的合成的、可生物降解的聚合物的通用策略。斯坦福大学的Waymouth小组最近发现了一种有机催化合成策略，用于生成含有侧基二硫戊环杂环的水溶性聚合物。二硫杂环戊烷是具有二硫键的五元环，类似于硫辛酸辅因子中的二硫键。Dithiolanes交换容易与硫醇和可逆地减少到二硫醇与过量的硫醇，如glutathione.I建议，可逆和快速交换的dithiolanes与硫醇可以提供一个响应控制元件，可以促进释放的药物或探针在还原环境中的细胞，以及提供新的动态共价网络作为自适应矩阵细胞培养和组织工程。该项目的第一个目标是开发一种可靠的方法，用于快速，可控合成聚合物和水凝胶纳入二硫戊环功能。其它官能团，例如用于药物转运穿过细胞膜和脂质（“L”）以诱导胶束形成的胍鎓基团（“GD”），将与二硫戊环基团（“DT”）一起并入嵌段聚合物中。二硫戊环聚合物的合成将被调整和改进，以控制物理性能，如分子量，聚合物电荷和水溶性。下一个目标是产生靶向mRNA递送的嵌段聚合物结构阵列，包括诸如GD-DT-PEG-DT-GD、PEG-GD-DT和DT-GD-PEG-L的序列。将评价这些响应材料在细胞中结合、运输和释放信使RNA（mRNA）的能力。可以通过将荧光标记物连接到mRNA上来监测细胞中的三亚甲基碳酸酯低聚物/聚合物摄取，并评价基因表达以确定mRNA释放的程度。本提案中描述的最后一个目标是评估水凝胶作为组织工程的共价适应性网络。将通过向DT-PED-DT聚合物结构中添加二硫醇交联剂（HS-X-SH）来研究水凝胶的形成。可以通过改变二硫戊环聚合的程度、二硫醇交联剂与二硫戊环聚合物的比率以及通过添加能够形成永久共价交联的PEG-丙烯酸酯交联剂来控制水凝胶性质，例如胶凝时间、模量和应力松弛。这些特性将针对水凝胶注射进行优化。将与Fan Yang教授（斯坦福大学骨科和生物工程）合作在体外评价细胞活力和增殖。其他生物医学应用将由这些适应性和响应性高分子的物理和动态特性的新结果和见解指导。

 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.