Department of Chemistry, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada.
The Ottawa Hospital, 501 Smyth Road, Ottawa, ON K1H 8L6, Canada.
Bioconjug Chem. 2020 Dec 16;31(12):2737-2749. doi: 10.1021/acs.bioconjchem.0c00525. Epub 2020 Nov 24.
Random formation of thrombi is classified as a pathological process that may result in partial or complete obstruction of blood flow and limited perfusion. Further complications include pulmonary embolism, thrombosis-induced myocardial infraction, ischemic stroke, and others. Location and full delineation of the blood clot are considered to be two clinically relevant aspects that could streamline proper diagnosis and treatment follow-up. In this work, we prepared two types of X-ray attenuating contrast formulations, using fibrinogen aptamer as the clot-seeking moiety. Two novel aptamer-targeted formulations were designed. Iodine-modified bases were directly incorporated into a fibrinogen aptamer (iodo-FA). Isothermal titration calorimetry was used to confirm that these modifications did not negatively impact target binding. Iodo-FA was tested for its ability to produce concentration-dependent contrast enhancement in a phantom CT. It was subsequently tested with clotted human and swine blood. This allowed for translation into testing, using fluoroscopy. FA was also used to functionalize gold nanoparticles (FA-AuNPs), and contrast capabilities were confirmed. This formulation was tested using clotted human blood in a CT scan. Unmodified FA and iodo-FA demonstrated a nearly identical affinity toward fibrin, confirming that base modifications did not impact target binding. Iodo-FA and FA-AuNPs both demonstrated excellent concentration-dependent contrast enhancement capabilities (40.5 HU mM and 563.6 HU μM, respectively), which were superior to the clinically available agent, iopamidol. CT testing revealed that iodo-FA is able to penetrate into the blood clots, producing contrast enhancement throughout, while FA-AuNPs only accumulated on the surface of the clot. Iodo-FA was thereby translated to testing, confirming target-binding associated accumulation of the contrast material at the location of the clot within the dilation of the external carotid artery. This resulted in a 34% enhancement of the clot. Both iodo-FA and FA-AuNPs were confirmed to be effective contrast formulations in CT. Targeting of fibrin, a major structural constituent of thrombi, with these novel contrast agents would allow for higher contrast enhancement and better clot delineation in CT and fluoroscopy.
血栓的随机形成被归类为一种病理过程，可能导致部分或完全阻塞血流和有限的灌注。进一步的并发症包括肺栓塞、血栓引起的心肌梗死、缺血性中风等。血栓的位置和完全描绘被认为是两个与临床相关的方面，可以简化适当的诊断和治疗随访。在这项工作中，我们制备了两种类型的 X 射线衰减对比制剂，使用纤维蛋白原适体作为寻找血栓的部分。设计了两种新型的适体靶向制剂。碘修饰的碱基直接掺入纤维蛋白原适体（碘-FA）中。等温滴定量热法用于确认这些修饰不会对靶结合产生负面影响。碘-FA 用于测试其在幻影 CT 中产生浓度依赖性对比增强的能力。随后在凝固的人和猪血液中进行了测试。这允许使用透视术进行翻译测试。FA 还用于功能化金纳米粒子（FA-AuNPs），并确认了对比能力。在 CT 扫描中使用凝固的人血测试了该制剂。未修饰的 FA 和碘-FA 对纤维蛋白表现出几乎相同的亲和力，证实碱基修饰不影响靶结合。碘-FA 和 FA-AuNPs 均表现出出色的浓度依赖性对比增强能力（分别为 40.5 HU mM 和 563.6 HU μM），优于临床可用的试剂碘帕醇。CT 测试表明，碘-FA 能够穿透到血栓中，在整个过程中产生对比增强，而 FA-AuNPs 仅在血栓表面积聚。因此，碘-FA 被转化为透视测试，确认在颈外动脉扩张处的血栓位置处存在与靶标结合的对比材料的积累。这导致了 34%的血栓增强。碘-FA 和 FA-AuNPs 均被确认为 CT 中的有效对比制剂。用这些新型对比剂靶向血栓的主要结构成分纤维蛋白，将允许在 CT 和透视术中实现更高的对比增强和更好的血栓描绘。
