活性氧介导二级构象驱动的聚氨基酸多级自组装结构和功能调控

Inspired by nature, the self-assembly of poly (amino acid) has attracted wide attention due to its unique protein-mimetic structures and promising biomedical applications. However, the effective control over the secondary conformation and hierarchical assembly of poly (amino acid) still remains a great challenge. In this study, we aim to design and synthesize a series of poly (L-cysteine)-based diblock copolymers bearing side groups with different steric hindrance, rigidity, arm lengths and hydrophobicity. The oxidation of thioether groups in side chains in response to reactive oxygen species (ROS) is expected to change both the packing characteristics of hydrophobic side moieties and the secondary conformations of polypeptide backbone, thus driving the transformation of assembled architectures and allowing for the construction of functional switches. By combining computational simulation and experimental techniques, we systematically investigate the influence of chemical structures and stimuli-responsiveness on the secondary conformations and hierarchical self-assembly behaviors of the copolymers, and reveal the general rules of conformation and assembly control. Furthermore, we assess the roles of hierarchically assembled structures and functional switches in determining the biological effect and in vivo fate of polymeric assemblies, taking tumor cells and animals as models. This work provides a new strategy for the construction and control of hierarchical biomimetic structures and functions of poly (amino acid). In addition, the study is of theoretical significance to understand the folding and biological functions of proteins, and also potentially valuable for using in biosensing, disease treatment and diagnostic applications.

受自然界启发，聚氨基酸的自组装由于其独特的仿蛋白结构及其在纳米科技和生物医学领域的应用前景受到广泛关注。然而，如何对聚氨基酸的构象和高级组装结构进行有效调控仍然是个难题。本项目设计并合成一系列含有不同位阻、刚性、臂长和疏水性侧基的聚半胱氨酸衍生嵌段共聚物，利用侧链硫醚对活性氧的响应性来调节聚氨基酸疏水侧基的排列参数和主链的二级构象，并进一步驱动聚合物自组装结构的转变，同时赋予其构象功能开关。本课题拟采用计算机模拟技术和实验相结合的手段系统研究聚氨基酸的化学结构和刺激响应性与其二级构象和多级自组装行为之间的科学关系，揭示聚氨基酸构象和自组装调控的基本规律，并以肿瘤细胞和小动物为模型评价聚氨基酸多级自组装行为和功能开关对其生物学效应和体内命运的影响。本研究为聚氨基酸多级仿生结构和功能的调控提供一种新思路，对于理解蛋白质折叠和功能具有理论价值，并在生物传感、疾病诊断和治疗方面有巨大的应用潜力。

受自然界启发，聚氨基酸的自组装由于其独特的仿蛋白结构及其在纳米科技和生物医学领域的应用前景受到广泛关注。然而，如何对聚氨基酸的有序二级构象进行有效调控仍然是个难题。此外，目前对于高分子二级构象与其自组装结构之间的科学关系还缺乏认识。本项目建立了“氧化门控”有序调控聚氨基酸二级构象的新方法。使用氨基甲酸酯键连接的疏水胆固醇“锁”住聚半胱氨酸的有序构象，利用内源性或外源性活性氧作为“门控”触发高分子疏水嵌段由β折叠转变为α螺旋构象，进而降低膜的厚度，并重构氢键和相行为，从而在保留囊泡完整性的同时增强其膜通透性，实现了小分子和大分子物质的特异性跨膜转运。该囊泡能够作为活体纳米反应器进行特异性的催化反应，并在体内显现出优异的糖尿病治疗效果。为了克服内源性刺激所带来的时空障碍以及能量壁垒，利用外源性光敏分子构建光控变构囊泡，通过组装限域催化实现聚氨基酸超快光控变构行为，在近红外光照5min内实现高分子构象从β折叠到α螺旋的转变，比活性氧触发的构象转变快200倍。光控变构行为不仅提高了纳米粒子的入胞和溶酶体逃逸能力，而且能够实现疏水索拉菲尼和亲水蜂毒肽的按需释放，从而诱发溶膜、氧化应激和免疫原性细胞死亡，并在体内完全消除肿瘤，产生优异的免疫记忆，避免肿瘤的转移和复发。进一步，为了监控构象转变过程，将四苯基乙烯引入聚半胱氨酸侧链，利用其聚集诱导发光性质对β折叠-无规卷曲构象转变进行实时监控和定量，同时能够可视化跟踪药物释放和细胞摄取性能。为了系统探究构象转变机理，设计和合成系列含有不同疏水侧链的聚半胱氨酸，结合分子动力学模拟发现侧链疏水和氢键相互作用是实现构象有序转变的关键因素。本项目研究为聚氨基酸多级自组装结构和功能调控提供了新思路，对于理解蛋白质折叠和功能具有理论意义，所设计的具有构象功能开关的仿生纳米材料在生物传感、药物传递、疾病诊断和治疗等领域具有广阔的应用前景。

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