基于短肽修饰的嵌段共聚物构筑生物分子响应性的仿生组装体

In this project, we will construct biomimetic polymeric assemblies responsive to biological molecules from amphiphilic block copolymers with pendant short peptides. We will prepare di- and tri-peptides containing a reductive-responsive p-nitrophenyl methoxycarbonyl (NPmoc) group or an oxidative-responsive p-boronophenylmethoxycarbonyl (BPmoc) at their N-terminal. Peptide-functionalized methacrylates will be synthesized by coupling BPmoc-peptides and NPmoc-peptides to 2-aminoethylmethacrylate. Using a PEG-based chain transfer agent, a series of amphiphilic block copolymers with different pendant short peptides will be obtained by reversible addition-fragmentation chain transfer (RAFT) polymerization of the peptide-functionalized methacrylates. We will investigate the self-assembly behaviors of these block copolymers in the aqueous solution, and explore the influences of the fraction of hydrophobic block and the secondary structure of peptides on the morphology of the assemblies. Block copolymers that can self-assemble to form vesicles will be selected to construct biologically responsive-vesicles by co-assembling with various enzymes. The enzyme-loaded vesicles are capable of sensing a variety of disease-related biomarkers such as sarcosine, glucose, lactic acid and uric acid. The vesicles that encapsulates multiple enzymes can be endowed with a capacity for “OR” or “AND” logic-type sensing towards multiple biomolecules as stimuli. We will study the disassembly process of vesicles response to biological stimuli, and explore the factors that affect the properties of vesicles. The biomolecule-responsive vesicles will be used to detect sarcosine, glucose, uric acid and lactic acid in serum to establish a rapid and sensitive bioassay method. By the combination of block copolymers containing pendant short peptides and various enzymes, we can construct intelligent assemblies responsive to a variety of biological stimuli using the block copolymers with the same structures as building blocks. In this strategy, we do not need to synthesize different polymers responsive to each stimulus. The biomolecule-responsive assemblies have promising applications in the areas of bioassays, controlled drug delivery and artificial organelles. These researches will provide a highly versatile approach for the design and construction of intelligent biomimetic materials.

本项目中我们拟合成短肽修饰的响应性嵌段共聚物，通过嵌段共聚物与多种酶进行共组装，构筑一系列对内源性生物分子具有响应性的仿生组装体。我们将主要进行三方面的研究工作：1）基于还原响应性基团对硝基苯基甲氧羰基、氧化响应性基团苯硼酸基甲氧羰基合成一系列短肽修饰的双亲性嵌段共聚物，响应性单元通过短肽链与聚合物主链相连，对这些嵌段共聚物在水中的自组装行为及机理进行详细的研究。调节短肽中氨基酸的结构及序列，在分子水平上实现对组装体的形态结构进行调控，筛选能够形成囊泡的嵌段共聚物。2）嵌段共聚物与多种酶进行共组装，构筑对肌氨酸，葡萄糖，尿酸，辅酶、乳酸等生物分子具有灵敏响应性的仿生囊泡。3）将生物分子响应性的囊泡用于对肌氨酸、乳酸、葡萄糖、辅酶等分子的检测，建立一种快速灵敏的检测方法。采用短肽修饰的嵌段共聚物与多种酶构筑生物分子响应性的仿生组装体，可以丰富组装体的功能并且简化聚合物的合成，为设计制备智能性仿生高分子材料提供新的途径。

对外界环境刺激能够产生反应，改变结构与性质，显示功能变化的响应性高分子及其形成的组装体，在纳米技术，微电子技术，生物技术及医药等领域具有巨大的应用前景。以内源性生物信号作为响应性高分子的刺激源，则可以模仿细胞的刺激-应答功能构建更加适宜于生物技术和生物医药领域的智能系统。通过本项目的研究我们合成了一系列具有多重刺激响应性的双亲性嵌段共聚物，对共聚合的溶液自组装行为以及共组装行为进行了研究，构筑了对内源性刺激具有响应性的高分子组装体，取得以下成果，包括：（1）合成了4-硝基苯基氨基甲酸酯（NBC）修饰的双亲性嵌段共聚物，通过调节NBC基团与聚合物主链之间氨基酸间隔臂的结构以及憎水链段的长度，分别构筑了具有还原和pH双重响应性以及具有酶、pH和光三重响应性的胶束和囊泡；（2）基于酶催化的酪氨酸偶联反应和巯基氧化反应，制备了对温度，pH和GSH具有响应性的蛋白质纳米凝胶。在类似癌细胞内的弱酸性和还原环境中，载药蛋白质纳米凝胶可以实现药物的控制释放。另外，基于巯基-二硫交换反应制备了具有还原响应性的蛋白质杂化水凝胶并将其用于治疗心肌梗塞的支架材料。3）合成了蛋氨酸修饰的具有pH和H2O2双重响应性的嵌段共聚物，通过与蛋白质的共组装构筑了具有葡萄糖响应性的蛋白质杂化纳米凝胶，该纳米凝胶具有良好的生物相容性并能有效杀死癌细胞；（4）利用硫醚的烷基化反应制备了含有锍鎓阳离子和苯硼酸的聚电解质，通过与蛋白质的共组装构筑了对H2O2, ATP和pH具有响应性的蛋白质杂化胶束，可应用于蛋白质的控制释放；通过与四苯基乙烯衍生物的共组装构建了具有H2O2响应性的荧光聚离子复合胶束，应用于对葡萄糖，肌氨酸等生物分子的荧光检测；（5）研究了苯硼酸和硫醚共同修饰的双亲性嵌段聚合物与铜离子的共组装，构筑了金属离子复合纳米囊泡，对其响应性能以及类芬顿反应的活性进行了研究。本项目中构筑的多重响应性高分子组装体，是一类结构新颖的智能性仿生材料，在生物技术、药物缓释以及仿生化学等领域具有广泛的应用。