Institute for Drug Research, The Hebrew University of Jerusalem, Jerusalem, Israel.
Casali Institute for Applied Chemistry, The Hebrew University of Jerusalem, Jerusalem, Israel.
Surg Endosc. 2018 Feb;32(2):963-970. doi: 10.1007/s00464-017-5773-9. Epub 2017 Aug 4.
Iatrogenic ureteral injury is an increasing concern in the laparoscopic era, affecting both patient morbidity and costs. Current techniques enabling intraoperative ureteral identification require invasive procedures or radiations. Our aim was to develop a real-time, non-invasive, radiation-free method to visualize ureters, based on near-infrared (NIR) imaging. For this purpose, we interfered with the biliary excretion pathway of the indocyanine green (ICG) fluorophore by loading it into liposomes, enabling renal excretion. In this work, we studied various parameters influencing ureteral imaging.
Fluorescence intensity (FI) of various liposomal ICG sizes and doses were characterized in vitro and subsequently tested in vivo in mice and pigs. Quantification was performed by measuring FI in multiple points and applying the ureteral/retroperitoneum ratio (U/R).
The optimal liposomal ICG loading dose was 20%, for the different liposomes' sizes tested (30, 60, 100 nm). Higher concentration of ICG decreased FI. In vivo, the optimal liposome size for ureteral imaging was 60 nm, which yielded a U/R of 5.2 ± 1.7 (p < 0.001 vs. free ICG). The optimal ICG dose was 8 mg/kg (U/R = 2.1 ± 0.4, p < 0.05 vs. 4 mg/kg). Only urine after liposomal ICG injection had a measurable FI, and not after free ICG injection. Using a NIR-optimized laparoscopic camera, ureters could be effectively imaged in pigs, from 10 min after injection and persisting for at least 90 min. Ureteral peristaltic waves could be clearly identified only after liposomal ICG injection.
Optimization of liposomal ICG allowed to visualize enhanced ureters in animal models and seems a promising fluorophore engineering, which calls for further developments.
医源性输尿管损伤是腹腔镜时代日益关注的问题，会影响患者的发病率和成本。目前，实现术中输尿管识别的技术需要有创操作或放射。我们的目标是开发一种实时、无创、无辐射的方法来可视化输尿管，基于近红外（NIR）成像。为此，我们通过将吲哚菁绿（ICG）荧光团载入脂质体来干扰其胆汁排泄途径，从而实现肾脏排泄。在这项工作中，我们研究了影响输尿管成像的各种参数。
在体外对各种脂质体 ICG 大小和剂量的荧光强度（FI）进行了表征，然后在小鼠和猪体内进行了测试。通过测量多个点的 FI 并应用输尿管/腹膜后比值（U/R）进行定量。
对于测试的不同脂质体大小（30、60、100nm），最佳脂质体 ICG 加载剂量为 20%。更高浓度的 ICG 会降低 FI。在体内，用于输尿管成像的最佳脂质体大小为 60nm，其 U/R 为 5.2±1.7（p<0.001 对比游离 ICG）。最佳 ICG 剂量为 8mg/kg（U/R=2.1±0.4，p<0.05 对比 4mg/kg）。只有在注射脂质体 ICG 后尿液才有可测量的 FI，而在注射游离 ICG 后则没有。使用 NIR 优化的腹腔镜相机，可在猪体内有效成像输尿管，在注射后 10 分钟开始，至少持续 90 分钟。只有在注射脂质体 ICG 后才能清楚地识别输尿管蠕动波。
脂质体 ICG 的优化允许在动物模型中可视化增强的输尿管，并且似乎是一种很有前途的荧光团工程，需要进一步发展。
