pH响应性多肽自组装纳米结构的组装规律及抗肿瘤作用机制研究

Deep understanding of new materials at the molecular level has become increasingly critical for a new generation of nanomaterials for nanotechnology, namely, the design, synthesis and fabrication of nanodevices at the molecular scale. Through molecular self-assembly, advances in the fields of nanotechnology and nanobiotechnology will be achieved with the help of materials that can be used to fabricate hierarchical structures and ever more sophisticated devices. Peptides represent attractive functional and structural building-blocks to create biomedical materials with high versatility. And supramolecular assemblies made from peptides have shown promising biomaterial features owing to ease of synthesis and functionalization, as well as their inherent biocompatibility. On the other hand, tumor microenvironment provides multiple cues that may be exploited to improve the efficacy of drug delivery systems. As development of cancer-targeted nanocarriers expands, peptides provide a level of molecular specificity that is naturally suited to the development of environmentally responsive drug carriers. In tumor microenvironment, cancer cell growth is dependent on neo-vascularisation to deliver oxygen and nutrients. The formation of new vessels relies on a complex series of orchestrated events with the activation of endothelial and peri-vascular cells (pericytes and smooth cells), and the modification of the surrounding basement membrane and extracellular matrix. Fibroblast growth factor (FGF) and vascular endothelial growth factor (VEGF) family members and their cognate receptors are key players in promoting tumor angiogenesis. This study will provide proof of principle that targeting FGF and VEGF receptors can inhibit tumor growth in breast cancer, indirectly through effects on vascularization and extracellular matrix remodeling. In this study, a novel environmentally responsive self-assembled peptide nanostructure as nanocarrier delivers a dual inhibitor of the FGF and VEGF receptors, E-3810. Controlled release of the inhibitor in the tumor microenvironment will inhibit tumor cell proliferation indirectly, reduced blood vessel density in tumors. This study will also explore the mechanisms of peptide self-assembly, potential microenvironmental physiology indicative of tumors and peptides that have demonstrated an ability to target and deliver to these signals. Thus, based on the mechanisms by which the specific stromal cell surface receptors promote tumorigenesis, this study will indicate that further exploring tumor stroma, in particular, FGFR and VEGFR as potential therapeutic targets in patients is warranted, providing a strong rationale for clinical evaluation. It is expected that these data will provide proof of principle that targeting stromal cell-mediated modifications of the tumor microenvironment may be an effective approach to treating epithelial-derived solid tumors.

本项目主要研究以调控肿瘤微环境的生物医学功能为导向的多肽纳米结构的设计及组装过程。通过合理设计多肽序列、并对氨基酸侧链进行改性和修饰的手段，构建新型pH响应性多肽自组装纳米结构。在中性条件下，功能多肽分子主要通过疏水作用和氢键的物理相互作用力，自组装形成形状和结构可控的纳米结构；在微酸性环境中，由于侧链之间存在正电荷的排斥力，自组装体解聚，从而构建对肿瘤微酸性环境快速响应的功能性纳米材料。利用它作为药物载体，实现能够同时抑制成纤维细胞生长因子受体（FGFR）和血管内皮生长因子受体（VEGFR）信号通路的双重特效抑制剂E-3810对肿瘤微环境的靶向输运、以及对肿瘤微酸性环境进行pH响应的药物可控释放。并将揭示多肽功能纳米结构的自组装原理；阐明自组装体的结构与其生物医学功能之间的构效关系。以期有效抑制肿瘤新生血管生成和肿瘤细胞的增殖，通过调控肿瘤微环境实现肿瘤治疗的科学目标。

肿瘤血管在肿瘤的发生发展中起着至关重要的作用，它为肿瘤组织提供充分的营养供给，也为肿瘤细胞随血液的转移提供了重要通道。肿瘤血管作为药物输运的主要媒介，是肿瘤微环境的一个重要治疗靶点。我们设计并构建了一系列具有肿瘤微环境响应性或靶向性的纳米药物，通过抑制肿瘤内部血管新生或诱导肿瘤局部血管栓塞，切断肿瘤生长的营养源；通过局部打破肿瘤血管的药物输运屏障效应，增加纳米药物在肿瘤组织中的灌注；以上策略都能有效抑制血管丰富的肿瘤的恶性生长和转移，对血管丰富的实体瘤治疗具有普适性，且以血管为靶标能够避免纳米药物因在肿瘤内部渗透率低而疗效差的难题。. 针对多肽药物半衰期短的问题，我们首次将抗血管多肽构建为肿瘤微环境响应性纳米结构，通过实现“分子—组装体—分子”的过程，提高多肽的稳定性和生物利用度，为多肽药物的应用提供新策略。针对诱导血栓形成和清除血小板在体内副作用高的难题，我们首次设计了具有肿瘤微环境靶向性或响应性的纳米药物，利用肿瘤微环境特异生物信号诱导的载体结构变化，实现凝血因子在肿瘤局部促发血栓以及肿瘤原位清除血小板，为凝血因子和血小板的抗肿瘤应用提供新思路。. 此外，多肽分子及其衍生物由于具有序列精确可控、稳定性高、生物相容性好、兼具生物功能性、良好的成药性、易大规模生产等特性，因此无需经过任何化学反应构建的多肽自组装纳米结构在靶向型药物递送系统和药物可控释放系统的生物医用方面的应用更是格外引人注目。我们在多肽纳米药物体系的设计、模块化可控构建、抗肿瘤治疗和调控肿瘤微环境（重点关注肿瘤基质微环境和肿瘤血管）的作用机制等领域开展了系统研究。其中，我们通过对多肽分子的巧妙设计，详尽的研究其自组装动力学过程及相关原理，实现对多肽组装体形貌转变的控制。首次实时观察到多肽自组装、多肽-药物共组装及自组装体重组的形貌变化过程，总结一系列组装规律，这也为精确调控多肽分子自组装过程的研究提供新的视角。