Ex vivo normothermic machine perfusion (NMP) is a new clinical strategy to assess and resuscitate organs likely to be declined for transplantation, thereby increasing the number of viable organs available. Short periods of NMP provide a window of opportunity to deliver therapeutics directly to the organ and, in particular, to the vascular endothelial cells (ECs) that constitute the first point of contact with the recipient’s immune system. ECs are the primary targets of both ischemia-reperfusion injury and damage from preformed antidonor antibodies, and reduction of perioperative EC injury could have long-term benefits by reducing the intensity of the host’s alloimmune response. Using NMP to administer therapeutics directly to the graft avoids many of the limitations associated with systemic drug delivery. We have previously shown that polymeric nanoparticles (NPs) can serve as depots for long-term drug release, but ensuring robust NP accumulation within a target cell type (graft ECs in this case) remains a fundamental challenge of nanomedicine. We show that surface conjugation of an anti-CD31 antibody enhances targeting of NPs to graft ECs of human kidneys undergoing NMP. Using a two-color quantitative microscopy approach, we demonstrate that targeting can enhance EC accumulation by about 5- to 10-fold or higher in discrete regions of the renal vasculature. In addition, our studies reveal that NPs can also nonspecifically accumulate within obstructed regions of the vasculature that are poorly perfused. These quantitative preclinical human studies demonstrate the therapeutic potential for targeted nanomedicines delivered during ex vivo NMP.

离体常温机器灌注（NMP）是一种新的临床策略，用于评估和复苏可能拒绝移植的器官，从而增加可用的存活器官的数量。短时间的 NMP 提供了一个机会之窗，将治疗药物直接递送至器官，特别是血管内皮细胞 (EC)，血管内皮细胞构成与受体免疫系统的第一个接触点。EC 是缺血再灌注损伤和预制抗供体抗体损伤的主要靶标，减少围手术期 EC 损伤可能会通过降低宿主同种免疫反应的强度而产生长期益处。使用 NMP 直接向移植物施用治疗剂可以避免与全身药物输送相关的许多限制。我们之前已经证明，聚合物纳米颗粒（NP）可以作为长期药物释放的储存库，但确保目标细胞类型（在本例中为移植物 EC）内的 NP 稳健积累仍然是纳米医学的基本挑战。我们表明，抗 CD31 抗体的表面缀合增强了 NP 的靶向性，以移植接受 NMP 的人肾 EC。使用双色定量显微镜方法，我们证明靶向可以将肾脉管系统离散区域中的 EC 积累增强约 5 至 10 倍或更高。此外，我们的研究表明，纳米粒子还可以非特异性地积聚在灌注不良的脉管系统阻塞区域内。这些定量的临床前人体研究证明了在离体 NMP 过程中递送靶向纳米药物的治疗潜力。