植物环蛋白的组装：一种新型天然超分子材料及其作为药物载体的研究

A lot of superparticles have been synthesized or discovered as carriers of medicinal molecules in recent years, such as cyclodextrins and caspids of virus. Although these nanomaterials show some good characters, the disadvatages are also obvious. For example, cyclodextrins prefer to load hydrophobic molecules; and caspids show potential risk to the human health, which blocks the way to use them in clinic..Cyclotide is a fantastic family of natural peptide, which presents a stable and special structure. The head-to-tail cyclic backbone and cyclic cystine knot make the structure as rigid as small molecules,and also make cyclotide resistant to acid, organic solvent, heat and enzymatic hydrolysis. Some long loops make cyclotide as flexible as macromolecules also. Hydrophobic and hydrophobic residues present in different areas of the structure, which indicates that cyclotide could assemble to be superparticle..This project is going to study the self-assembly of cyclotide and the characters of the superparticle. The research on relationships between concentration of cyclotide and surrounding enviroment (such as ions, pH, and temperature) to the assembling process of cyclotide superparticle would be helpful to build up a novel carrier for pharmaceutic compounds.

目前药物输送载体主要为人工合成的超分子材料，虽然有其自身优势，但疏水内腔限制了对亲水分子的输送。近年报道的病毒衣壳蛋白虽可以输送几乎所有的药物分子，但单体分子量过大，代谢过程复杂，毒性不明等问题同样制约其应用。.植物环蛋白是一类具有特殊结构且非常稳定的天然多肽分子。其首尾环合的骨架及半胱氨酸结使分子具有类似小分子的刚性，且对水解酶、酸、有机溶剂和高温均具有较高抗性。部分较长的环结构又使分子具有类似大分子的柔性。根据疏水性残基与亲水性残基分别集中分布于分子不同部位的特征，申请者推测环蛋白分子具有良好的自组装潜力，并得到前期研究结果的支持。.本项目旨在研究植物环蛋白的自组装行为及其超分子自组装体的性质。通过系统地研究环蛋白浓度、组装环境和组装条件对组装过程及超分子结构的影响，寻找合适的条件组合使植物环蛋白超分子自组装体具有药物输送的功能。

本项目以MCTI-I为模型分子，建立了囊泡型环蛋白超分子制备方法，确定了影响环蛋白超分子稳定性的主要因素，并在此基础上进行了初步进行了小分子跨膜输送实验。经过系统地研究，我们发现提高环蛋白溶液的pH值或降低环蛋白在溶液中的浓度均可提高环蛋白分子的表面电势。但是，我们发现环蛋白分子的表面电势不是决定其所形成的水包油乳液稳定性的关键因素。通过跟踪乳液透光率的动态变化，我们发现利用pH 7.8下1.0 mg/mL的环蛋白溶液可以制备相对稳定的乳液。进一步地，我们确认了环蛋白以单分子层形式吸附于油/水界面，而且所形成的囊泡可以有效地将药物分子从细胞外转运至细胞内，并显著降低药物分子对活细胞的毒害。本项目完成了所有计划的研究内容，证实环蛋白分子确实为一种新型超分子药物载体材料，具有良好的生物医学材料开发前景。