One of the major problems facing the treatment of neurological disorders is the poor delivery of therapeutic agents into the brain. Our goal is to develop a multifunctional and biodegradable nanodrug delivery system that crosses the blood–brain barrier (BBB) to access brain tissues affected by neurological disease. In this study, we synthesized a biodegradable nontoxic β-poly(l-malic acid) (PMLA or P) as a scaffold to chemically bind the BBB crossing peptides Angiopep-2 (AP2), MiniAp-4 (M4), and the transferrin receptor ligands cTfRL and B6. In addition, a trileucine endosome escape unit (LLL) and a fluorescent marker (rhodamine or rh) were attached to the PMLA backbone. The pharmacokinetics, BBB penetration, and biodistribution of nanoconjugates were studied in different brain regions and at multiple time points via optical imaging. The optimal nanoconjugate, P/LLL/AP2/rh, produced significant fluorescence in the parenchyma of cortical layers II/III, the midbrain colliculi, and the hippocampal CA1-3 cellular layers 30 min after a single intravenous injection; clearance was observed after 4 h. The nanoconjugate variant P/LLL/rh lacking AP2, or the variant P/AP2/rh lacking LLL, showed significantly less BBB penetration. The LLL moiety appeared to stabilize the nanoconjugate, while AP2 enhanced BBB penetration. Finally, nanoconjugates containing the peptides M4, cTfRL, and B6 displayed comparably little and/or inconsistent infiltration of brain parenchyma, likely due to reduced trans-BBB movement. P/LLL/AP2/rh can now be functionalized with intra-brain targeting and drug treatment moieties that are aimed at molecular pathways implicated in neurological disorders.

中文翻译：

---

三亮氨酸和Angiopep-2的组合驱动跨血脑屏障的聚阴离子聚苹果酸纳米药物平台。

神经系统疾病的治疗面临的主要问题之一是治疗药物向大脑的输送不畅。我们的目标是开发一种多功能且可生物降解的纳米药物输送系统，该系统可以穿越血脑屏障（BBB）进入受神经疾病影响的脑组织。在这项研究中，我们合成了一种可生物降解的无毒β-聚（l-苹果酸（PMLA或P）作为支架，可化学结合BBB穿越肽Angiopep-2（AP2），MiniAp-4（M4）和运铁蛋白受体配体cTfRL和B6。此外，三亮氨酸内体逃逸单元（LLL）和荧光标记（若丹明或rh）连接到PMLA骨架。药代动力学，BBB渗透，纳米缀合物的生物分布在不同脑区，并在多个时间点进行了研究通过光学成像。最佳的纳米偶联物P / LLL / AP2 / rh，在单次静脉内注射后30分钟，在皮层II / III，中脑胶体和海马CA1-3细胞层的薄壁组织中产生了明显的荧光。4小时后观察到清除率。缺少AP2的纳米共轭物变体P / LLL / rh，或缺少LLL的变体P / AP2 / rh，表现出明显更少的BBB渗透。LLL部分似乎稳定了纳米共轭物，而AP2增强了BBB的渗透。最后，含有肽M4，cTfRL和B6的纳米共轭物表现出相对较少的脑实质和/或不一致的脑实质浸润，这可能是由于反式BBB运动减少所致。