Faculty of Energy Engineering and Physics, Amirkabir University of Technology, Tehran, Iran.
Radiation Applications Research School, Nuclear Science and Technology Research Institute, Tehran, Iran.
Bioorg Chem. 2023 Jan;130:106237. doi: 10.1016/j.bioorg.2022.106237. Epub 2022 Nov 5.
Amino acid metabolism is recognized as a target for medical imaging due to its increase in malignant cells. Several radiotracers with primary achievement and possible subsequent chances have been designed and tested to image amino acid metabolism. Here, we report a new amino acid conjugate, with the purpose of extending [Tc][Tc-HYNIC/EDDA]-Met(O) for single photon emission tomography (SPECT) imaging. The S-oxo-l-methionine (Met(O)) amino acid hydrazinonicotinamide (HYNIC) chelator conjugate (HYNIC-Met(O)) was prepared, using Fmoc solid-phase synthesis, and was radiolabeled with [Tc]technetium pertechnetate, using tricine and ethylenediamine-N,N-diacetic acid (EDDA) as co-ligands. In vitro cellular uptake profile and saturation binding of radiotracer were determined on C6 glioma cells. Biodistribution and imaging studies were carried out on rat bearing C6 tumor tissue grafts. [Tc][Tc-HYNIC/EDDA]-Met(O) was prepared in high yield and radiochemical purity (>98 %). The partition coefficient result showed that radioconjugate was very hydrophilic. The radioconjugate indicated both high cell uptake and in vitro internalization. Low nanomolar dissociation constant (66.02 nM) in C6 glioma cells was obtained for it as well. [Tc][Tc-HYNIC/EDDA]-Met(O) revealed magnificent tumor uptake at early time points, with 1.98 ± 0.33 % injected activity per gram tumor (% IA/g) at 30 min post injection. The tumor uptake continued for 1 and 2 h and was 0.45 ± 0.33 % IA/g at 4 h. The uptake in other organs decreased much more rapidly causing high tumor to normal organ ratios so that the highest ratio of 13.25 of tumor-to-muscle at 60 min after injection was obtained with high contrast in gamma imaging. These results point out a very favorable [Tc]Tc-labeled amino acid for targeting amino acid metabolism through target system L amino acid transporter (LAT1) in malignant cells especially C6 glioma cells. [Tc][Tc-HYNIC/EDDA]-Met(O) manifests extremely good distribution, excretion and imaging attributes. So it seems to be an appropriate nominate for clinical imaging.
氨基酸代谢因其在恶性细胞中的增加而被认为是医学成像的目标。已经设计并测试了几种具有初步成果和可能后续机会的放射性示踪剂来成像氨基酸代谢。在这里,我们报告了一种新的氨基酸缀合物,目的是将 [Tc][Tc-HYNIC/EDDA]-Met(O) 扩展用于单光子发射断层扫描 (SPECT) 成像。S-氧代-L-蛋氨酸 (Met(O)) 氨基酸肼基烟酸 (HYNIC) 螯合剂缀合物 (HYNIC-Met(O)) 是使用 Fmoc 固相合成制备的,并使用 tricine 和乙二胺-N,N-二乙酸 (EDDA) 作为共配体用 [Tc]锝高锝酸盐进行放射性标记。在 C6 神经胶质瘤细胞上测定放射性示踪剂的细胞摄取曲线和饱和结合。在携带 C6 肿瘤组织移植物的大鼠上进行了生物分布和成像研究。[Tc][Tc-HYNIC/EDDA]-Met(O) 以高产率和放射化学纯度 (>98%) 制备。分配系数结果表明放射性缀合物具有非常亲水性。放射性缀合物也表现出高细胞摄取和体外内化。在 C6 神经胶质瘤细胞中,也获得了 66.02 nM 的低纳米摩尔解离常数。[Tc][Tc-HYNIC/EDDA]-Met(O) 在早期时间点显示出巨大的肿瘤摄取,在注射后 30 分钟时肿瘤每克 1.98±0.33% 注入活性 (%IA/g)。肿瘤摄取持续 1 至 2 小时,在 4 小时时为 0.45±0.33%IA/g。其他器官的摄取减少得更快,导致肿瘤与正常器官的比值很高,因此在注射后 60 分钟时获得了 13.25 的最高肿瘤-肌肉比值,γ成像具有高对比度。这些结果表明,[Tc]Tc 标记的氨基酸通过恶性细胞(特别是 C6 神经胶质瘤细胞)中的靶系统 L 氨基酸转运体 (LAT1) 对氨基酸代谢具有非常有利的靶向性。[Tc][Tc-HYNIC/EDDA]-Met(O) 表现出极好的分布、排泄和成像特性。因此,它似乎是临床成像的合适候选者。