多肽导向分子内嵌且能主动隐形的脑靶向脂质体递药系统研究

Peptide ligand modified long-circulating liposome is currently one of the most widely used systems for targeted drug delivery and the extracellular domain of certain membrane proteins normally served as the target. However, the possible ectodomain shielding or mutation may greatly interrupt the specific recognition between target protein and peptide ligand while the endogenous ligand or antibody may act as competitive inhibitors. And the peptide ligand conjugated on the liposomal surface often suffer from poor in vivo stability. Moreover, the typical polyethylene glycol decoration may have the challenge of accelerated blood clearance phenomenon and potential steric hindrance for peptide ligand recognizing target protein. The proposal aims to develop a novel brain targeting liposome capturing insulin receptor of the blood brain barrier (BBB) for efficient anti-Alzheimer's disease drug delivery. The conserved and structurally stable transmembrane domain served as the target sequence and the corresponding peptide ligand can insert into the lipid bilayer due to its natural physico-chemical property, and recognize the target protein and cells. Furthermore, the ‘self-marker’ peptide which can mimic CD47 protein was anchored onto the liposome surface, producing a liposomal nanocarrier differentiated by macrophage as endogenous matter with active stealth effect and then effectively penetrated BBB for intracerebral drug delivery. In this study, the possible influencing.factors and relative mechanisms will be systematically investigated for this new form of peptide-modified liposome and a comparison among different peptide ligands of the same receptor will be performed. The easy preparation with potential druggability of this brain targeting liposome will provide new ideas for efficient targeted diagnosis and treatment of brain diseases and other human diseases.

多肽类导向分子修饰的长循环脂质体是靶向递药系统的重要代表，但仍面临挑战：以目标细胞膜蛋白胞外区为靶点，胞外序列可能脱落或突变导致“失靶”，内源性配体/抗体也可能竞争性干扰；某些多肽经化学偶联于载体表面可能面临稳定性问题，或不易偶联；聚乙二醇修饰法具有潜在空间位阻及ABC现象等问题。项目拟针对血脑屏障胰岛素受体探索一种新的靶向脂质体构建模式：以该膜蛋白保守且稳定的跨膜区为靶，所得多肽配体能自然嵌入磷脂层形成导向分子内嵌的脂质体，高效识别靶蛋白与靶细胞；进一步将“自我标签”锚定于脂质体表面，脂质体能被巨噬细胞视作内源性物质而血中循环时间显著延长、高效跨越血脑屏障并有效介导药物脑内递释。项目将系统探讨该脂质体实现“主动隐形”和脑靶向递药的各类要素、机制并与针对相同受体、按不同方式构建的多肽修饰脂质体进行比较。项目注重递药系统的潜在成药性，有望为针对脑部疾病及其他重大疾病的递药研究提供有益的思路

多肽类导向分子修饰的长循环脂质体是靶向递药系统的重要代表，但仍面临挑战：以目标细胞膜蛋白胞外区为靶点，胞外序列可能脱落或突变导致“失靶”，内源性配体/抗体也可能竞争性干扰；某些多肽经化学偶联于载体表面可能面临稳定性问题，或不易偶联；聚乙二醇修饰法具有潜在空间位阻及ABC现象等问题。项目以血脑屏障胰岛素受体为靶探索一种新的靶向脂质体构建模式与递药策略。项目首先基于内源性细胞普遍存在的CD47- SIRPα信号通路设计了一种CD47衍生的、耐酶解的D型Self肽（D-Self, DS），并将其修饰在空白脂质体表面（DSL）。DSL进入体内后会快速与巨噬细胞作用，而DS与SIRPα的互作激活“don’t- eat-me”信号通路使少量的DSL即能够长期抑制巨噬细胞的吞噬能力，使后续注射的靶向制剂可以有效规避被巨噬细胞快速清除。项目接下来以胰岛素受体保守且稳定的跨膜区为靶，所设计得到的多肽配体能有效作用于跨膜区，具有高度的亲合力和特异性，也正是由于该种多肽配体的理化性质，其能自然嵌入磷脂层形成导向分子内嵌的脂质体。多肽配体内嵌后，在复杂生理环境下能保持高度稳定性，该多肽内嵌型脂质体能够高效识别靶蛋白与靶细胞且不受内源性配体的干扰，并在长循环递药策略辅助下能够高效跨越血脑屏障和实现药物脑内递释。这种多肽导向分子内嵌于脂质体的策略也在整合素、PDGF等多个重要疾病膜蛋白上得到了验证，说明该策略具有较好的普适性。我们还尝试进一步丰富和提升本项目的研究内涵：除开展经静脉注射进行靶向递药的研究之外，在研究中发现多肽内嵌型脂质体的独特理化性质，因此也同步开展了经口服实现靶向递药的相关研究；开展了表面富含CD47蛋白的红细胞膜定向包裹脂质体递药系统的策略研究；还尝试构建了基于表面糖基修饰的长循环脂质体递药研究。代表性论文发表在ACS Nano(2篇)和Nano Letters等期刊上，分别被F1000推荐、被国际学术媒体C.E.N.（化学与工程新闻）药学专栏报道和被遴选为ACS Nano封面论文；项目主持人入选教育部青年长江学者，并牵头获批重庆市高校创新研究群体1项。