New Strategy for Controlled Release of Liposomal Contents

ID：MPS/DMR/BMAT（7623）1005515 主要研究者：赵燕ORG：爱荷华州州立大学脂质体内容物控制释放的新策略智力优势：本提案的目的是设计和合成能够在脂质双层中形成纳米尺寸亲水孔的低聚物。中心假设是，最近在PI的实验室开发的两亲性低聚物具有几个关键特征作为成孔材料。 这一假设是基于天然成孔蛋白和初步研究中发现的结构特征。 为了检验中心假设并实现本提案的总体目标，PI建议追求以下两个具体目标：（1）控制脂质双层中成孔低聚物的构象。 在初步研究中，PI制备了具有纳米尺寸内部亲水通道的寡胆酸盐折叠体。 当掺入到脂质双层中时，发现折叠体的链长和膜的厚度之间的适当匹配对折叠至关重要。 四个独立的策略（即，亲水锚定、疏水匹配、π-π相互作用和离子配对）来控制脂质双层中低聚物的折叠。 这些分子的构象将通过荧光共振能量转移（FRET）、荧光猝灭、UV-vis和固态NMR光谱来表征。 (2)通过成孔低聚物控制脂质双层的渗透性。 所讨论的折叠体形成具有亲水孔和胆固醇样外观的螺旋结构。 在初步研究中发现十二聚体和环状三聚体允许羧基荧光素（CF）穿过脂质双层。通过控制寡胆酸盐的构象、较短折叠体链的可逆连接和环状低聚物的可逆聚集，PI期望通过温度、金属离子和分子或氧化还原信号来调节通过孔的交通。更广泛的影响：拟议的研究预计将在化学和制药行业产生广泛的影响。 脂质体已经在临床上用于递送药物（例如，阿霉素）;成孔材料可以通过控制释放的时间和位置来提高药物的功效。 亲水性分子穿过疏水性膜屏障的递送不仅对于药物递送而且对于临床研究、分子生物学和传感器开发都是重要的。 易于合成的成孔材料将在这些应用中开辟许多途径。 这两个PI为拟议的研究带来了互补的专业知识。 Zhao团队在构象可控材料的设计和合成方面经验丰富，Hong团队在膜结合肽和蛋白质的生物物理表征方面经验丰富。 合作不仅可以帮助PI探索任何一个单独难以探索的研究领域，还可以挑战学生更具创造性地思考。 与不同背景的同事一起工作，学生将接触到非常不同的思维和解决问题的风格。 这种合作将使他们在未来的职业生涯中能够在团队环境中有效地工作，并解决需要多个学科协调努力的问题。 这两个PI已经有本科生在实验室工作。 在过去的夏天，代表性不足的本科生通过ISU招募？科学和工程领域的妇女计划（PWSE）参与了这项研究。 PI将继续这一努力，利用仿生化学的吸引力吸引学生学习科学。

ID: MPS/DMR/BMAT(7623) 1005515 PI: Zhao, Yan ORG: Iowa State UniversityTitle: New Strategy for Controlled Release of Liposomal ContentsINTELLECTUAL MERIT: The objective of this proposal is to design and synthesize oligomers capable of forming nanometer-sized hydrophilic pores in lipid bilayers. The central hypothesis is that facially amphiphilic oligomers developed recently in the PI's laboratory have several critical features as pore-forming materials. This hypothesis is based on structural features found in natural pore-forming proteins and in preliminary studies. To test the central hypothesis and accomplish the overall objective of this proposal, the PI proposes to pursue the following two specific objectives: (1) Control the conformation of pore-forming oligomers in lipid bilayers. In the preliminary study, the PI has prepared oligocholate foldamers with nanometer-sized internal hydrophilic channels. When incorporated into lipid bilayers, the proper matching between the chain length of the foldamer and the thickness of the membrane was found critical to the folding. Four independent strategies (i.e., hydrophilic anchoring, hydrophobic matching, pi-pi interactions, and ion-pairing) are proposed to control the folding of the oligomers in lipid bilayers. The conformations of these molecules will be characterized by fluorescence resonance energy transfer (FRET), fluorescence quenching, UV-vis, and solid-state NMR spectroscopy. (2) Control the permeability of lipid bilayers by pore-forming oligomers. The foldamers in question form helical structures with a hydrophilic pore and a cholesterol-like exterior. A dodecamer and a cyclic trimer were found to allow the passage of carboxyfluorescein (CF) across lipid bilayers in the preliminary study. By controlling the conformation of the oligocholates, reversible ligation of shorter foldamer strands, and reversible aggregation of cyclic oligomers, the PI expects to regulate the traffic through the pore by temperature, metal ions, and molecular or redox signals. BROADER IMPACTS: The proposed research is expected to have several broad impacts in the chemical and pharmaceutical industries. Liposomes are already used clinically to deliver drugs (e.g., doxorubicin); pore-forming materials may improve the efficacy of the drugs by controlling the timing and location of release. Delivery of hydrophilic molecules across a hydrophobic membrane barrier is not only important to drug delivery but also to clinical research, molecular biology, and sensor development. Pore-forming materials that can be easily synthesized will open up many avenues in these applications. The two PIs bring complementary expertise to the proposed research. The Zhao group is experienced with design and synthesis of conformationally controllable materials and the Hong group with biophysical characterization of membrane-bound peptides and proteins. Collaboration will not only help the PIs explore research areas difficult for either one alone but also challenge the students to think more creatively. Working together with co-workers with dissimilar backgrounds, students will be exposed to very different thinking and problem-solving styles. This kind of collaboration will prepare them to work effectively in a team environment in their future careers and tackle problems that require coordinated efforts from multiple disciplines. Both PIs already have undergraduate students working in the lab. In the past summers, underrepresented undergraduate students recruited through ISU?s Program for Women in Science and Engineering (PWSE) have participated in the research. The PIs will continue this effort, taking advantage of the attractiveness of biomimetic chemistry to attract students to science.