Theranostic system for targeted, sustained-delivery with quantitative "hot spot" MPI of magnetic extracellular vesicles

治疗性细胞移植在治愈或缓解各种疾病方面具有巨大的潜力。在……里面 在临床上，细胞移植物通常在移植后的短时间内死亡或停止功能。一种新兴的 策略是使用来自间充质干细胞(MSCs)的细胞外小泡(EV)作为佐剂 为了细胞疗法。然而，在向目标地点有效交付电动汽车并在目标地点保留电动汽车方面仍然存在挑战， 以及无法使用临床相关的药物来阐明EVS的生物分布和药代动力学特征 工具。此外，一些新的研究表明，多次注射电动汽车对治疗结果至关重要， 这些都是目前的临床给药途径很难实现的。我们计划开发治疗鼻音， 可注射微球EV递送系统(EVDS)，用于EV的局部、靶向和持续递送，同时 通过磁粉成像(MPI)实现体内EV跟踪。我们的EVDS设计是模块化的， 该系统的每个主要组件都可以独立修改以适应不同的目的。我们的利益在于 用于治疗1型和晚期2型糖尿病的胰岛移植。EVDS-LipoCap的两种设计 和MiCap-被提出。LipoCaps(500μm)可通过门静脉(临床测试)注入肝脏 胰岛移植方案)，用于与胰岛共植入，或用于移植后的后续剂量。麦克风 (900微米)适合于体积较大的植入部位，如腹膜腔。这两种设计 目的是获得电动汽车在当地的持续运送到小岛。LipoCaps和MICap将由超纯的 海藻酸盐，FDA批准的食品、化妆品和医药产品的辅料。为了最大限度地减少 周围脂肪和组织的特定摄取从藻酸盐基质释放后，EVS将被加载到胰岛内- 在海藻酸盐包埋前靶向脂质体。这将通过将脂质体偶联到 Exendin-4，胰岛表面大量表达的胰升糖素样肽-1受体的配体 β细胞。此外，电动汽车将被贴上临床级超顺磁性氧化铁的标签。 纳米粒子(USPIO)，以便于MPI成像。MPI是一种新兴的模式，它提供了“热点” 可视化以及EV量化，非常类似于不使用放射性试剂的PET和SPECT。 与1H MRI不同，血液池中的背景伪影和运动效果不是MPI的问题。MPI是 据报道，比19F MRI和CT更敏感，因此可能会减少引入的标签数量 对病人的影响。MPI可以告知医生电动汽车的时间和空间行为，这反过来又可以 负担得起定制的电动汽车治疗。为了系统地研究该项目的可行性，有三个具体目标 1)合成和表征携带MSC-EVS的LipoCaps和MICap，并检测其 对体外培养的人胰岛存活和功能的影响；2)建立一种USPIO标记方法 EV特性，同时最大化MPI检测灵敏度；3)测试所提出的EVDS是否可以改善胰岛 MPI追踪免疫缺陷NU/J小鼠的存活和功能。

Transplantation of therapeutic cells holds great potential to cure or provide relief to various ailments. In the clinic, cell grafts often perish or cease to function within a short period post-transplantation. An emerging strategy is the use of extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) as an adjuvant to cell therapy. However, there remain challenges for effective EV delivery to and retention at the target sites, and the inability to elucidate the biodistribution and pharmacokinetic profiles of EVs using a clinically relevant tool. Moreover, a few new studies indicated that multiple deliveries of EVs are essential for therapeutic outcomes, which are hard to accomplish using the current clinical administration routes. We propose to develop theranostic, injectable microspheroid EV-delivery systems (EVDS) for local, targeted, and sustained-delivery of EVs while enabling EV tracking in vivo with magnetic particle imaging (MPI). The design of our EVDS is modular where each main component of the system can be independently modified to suit different purposes. Our interest lies in pancreatic islet transplantation to treat type 1 and advanced type 2 diabetes. Two designs of EVDS – LipoCap and MICap – are proposed. LipoCaps (500 μm) can be infused into the liver via the portal vein (a clinically tested islet transplantation protocol) for co-implantation with islets, or for follow-up doses post-transplantation. MICaps (900 µm) are appropriate for implant site with larger volumes, such as the intraperitoneal cavity. Both designs aim to obtain a local, sustained delivery of EVs to islets. LipoCaps and MICaps will be composed of ultrapurified alginate, an FDA-approved excipient of food, cosmetic and pharmaceutical products. In order to minimize non- specific uptake by nearby fat and tissues after the release from alginate matrix, EVs will be loaded inside islet- targeting liposomes prior to alginate encapsulation. This will be achieved by conjugating the liposomes to exendin-4, a ligand of glucagon-like peptide-1 receptors which are abundantly expressed on the surface of islet beta cells. In addition, EVs will be labeled with clinical-grade ultrasmall superparamagnetic iron oxide nanoparticles (USPIO) to facilitate imaging by MPI. MPI is an emerging modality that provides “hot spot” visualization as well as EV quantification, much alike to PET and SPECT without the use of radioactive agents. Unlike 1H MRI, background artifacts from blood pools and motion effects are not an issue with MPI. MPI is reported to be more sensitive than 19F MRI and CT, and therefore may reduce the quantity of labels introduced into the patients. MPI may inform physicians on the temporal and spatial behavior of EVs which, in turns, may afford EV therapy to be customized. To systemically investigate the feasibility of the project, three specific aims are proposed: 1) To synthesize and characterize LipoCaps and MICaps carrying MSC-EVs, and to test their effects on human islets’ survival and function in vitro; 2) To develop a USPIO-labeling method that will preserve EV properties while maximizing MPI detection sensitivity; 3) To test if the proposed EVDS can improve islet survival and function in immunodeficient NU/J mice while being tracked by MPI.