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脂肪酸是心肌能量的主要来源,其摄取与血流量和浓度成正比[1]。脂肪酸从血液中清除的半衰期少于2 min,并以50%~60%的第一次提取分数浓缩在心肌细胞中。在心肌缺血或损伤时脂肪酸摄取和氧化量减少,因此脂肪酸摄取量的改变被认为是缺血和心肌损伤的敏感标志。
14(R, S)-[18F]氟-6-硫杂十七烷酸(14(R, S)-[18F]fluoro-6-thia-heptadecanoic acid,18F-FTHA)是脂肪酸代谢的长链脂肪酸底物,是一种假的长链脂肪酸,被组织吸收进入线粒体或掺入复合脂质,心肌中18F-FTHA摄取的累积量和摄取速率反映了长链脂肪酸的β-氧化速率[2]。18F-FTHA近年来被用于研究人类脂肪酸代谢,确定骨骼肌和心肌脂肪酸摄取率。在线粒体中,18F-FTHA经历了β-氧化的初始步骤[3],之后因硫杂原子的存在使得进一步的β-氧化被阻断,并被心肌组织捕获。这一特性使18F-FTHA在心肌细胞内富集,为PET显像提供了最佳信号。本研究着力实现18F-FTHA的自动化合成,并对其物理、化学和生物学性能进行鉴定。通过正常昆明小鼠体内的生物学分布实验确定其在心肌中的特异性摄取。
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在Tracerlab Fx-FN自动化合成器上完成了18F-FTHA的自动化合成,总合成时间约为50 min,其中前30 min为反应过程、后20 min为半制备型高效液相色谱仪分离过程。如图 3所示,收集16.2~17.8 min的放射性组分为18F-FTHA,未经衰减校正的放射化学产率为(10.0±1.7)%。
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18F-FTHA注射液为含10%乙醇的无色澄清透明溶液,pH值为6~7,比活度为65 GBq/mmol,18F半衰期为(109.8±5.0)min,放射性核纯度≥99%。
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分析测定结果显示,18F-FTHA的放射化学纯度>98%(图 4)。18F-FTHA在分析性高效液相色谱仪上的保留时间为16.8 min。18F-FTHA室温放置1、2、3、6 h后的放射化学纯度均>95%。证明其辐射自分解量极微,室温环境中较为稳定。
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小鼠尾部注射18F-FTHA后观察48 h,小鼠活动正常,无任何不良反应及死亡现象发生。18F-FTHA注射液常规培养细菌72 h,未见细菌生长。内毒素检测为阴性,内毒素含量小于1 EU/mL。
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18F-FTHA在正常小鼠体内不同时间点的生物学分布结果见表 1。由表 1可知,18F-FTHA显像剂在血液中清除快,心肌摄取高,非靶器官摄取较低。在注射显像剂后的各个时间点心肌摄取均高于肺部摄取,60 min时心肌/肺的摄取比值为6/1(t=0.27,P=0.01),90 min时心肌/肺的摄取比值为10/1(t=2.21,P=0.03),差异有统计学意义。肝脏摄取呈先高后低的趋势,在15 min和30 min时肝脏摄取均高于心肌,而60 min和90 min时心肌摄取均高于肝脏,而且有较高的心肌与肝脏放射性摄取比值,60 min时心肌/肝脏的摄取比值为3/1(t=0.75,P=0.02),90 min时心肌/肝脏的摄取比值为4/1(t=1.15,P=0.03),差异有统计学意义。
组织 放射性摄取率(%ID/g) 15 min 30 min 60 min 90 min 心肌 30.78±8.88 22.36±6.25 19.04±4.87 13.72±2.74 肝 38.27±7.42 26.39±3.75 5.99±2.96 3.34±1.34 肺 9.08±0.97 4.28±0.19 3.05±0.52 1.45±0.32 脾 1.62±0.47 1.06±0.14 0.47±0.12 0.40±0.11 肾 23.97±7.55 17.25±2.87 3.64±0.52 2.83±0.99 肌肉 3.79±0.53 2.37±0.21 1.75±0.20 1.19±0.18 骨 3.01±0.68 1.52±0.15 1.15±0.14 0.56±0.11 血 1.03±0.13 1.26±0.79 0.30±0.13 0.26±0.06 表 1 14(R, S)-[18F]氟-6-硫杂十七烷酸(18F-FTHA)在昆明小鼠体内的生物学分布(x+s,n=5)
Table 1. The biodistribution of 18F-FTHA in Kunming mice
心肌脂肪酸代谢显像剂18F-FTHA的自动化合成与生物学分布研究
Automated synthesis and biodistribution study of cardiac fatty acid metabolism imaging agent 18F-FTHA
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摘要:
目的实现心肌脂肪酸代谢显像剂14(R,S)-[18F]-氟-6-硫杂十七烷酸(18F-FTHA)的全自动化合成,并评价其在正常昆明小鼠体内的生物学分布特征。 方法采用自动化合成模块以苄基-14-(R,S)-对甲苯磺酰基-6-硫代十七烷酸脂为前体合成18F-FTHA。并对其物理(性状、放射性活度、比活度、半衰期和放射性核纯度)、化学(化学纯度、放射化学纯度和室温稳定性)和生物学(毒性、无菌和细菌内毒素)性能进行鉴定。昆明小鼠20只,采用随机数字表法分为4组(每组5只),经小鼠尾部静脉分别注射18F-FTHA显像剂7.4 MBq(体积 < 0.2 mL),注射后15、30、60、90 min时各处死1组,分别取心脏、肝脏、脾、肺、肾脏、肌肉和骨等主要器官和血液,称重并测定放射性计数,计算每克组织百分注射剂量率(%ID/g)。组间数据比较采用配对t检验。 结果合成时间约50 min,合成产率为(10.0±1.7)%。18F-FTHA注射液为含10%乙醇的无菌、无内毒素、无色澄清透明溶液,pH值为6~7,比活度为65 GBq/mmol,放射性核纯度≥99%,放化纯度>98%。正常昆明小鼠体内生物学分布实验结果显示,18F-FTHA在血液中清除快,心肌摄取高,非靶器官摄取较低。在注射显像剂后60 min时,心肌、肺和肝脏的放射性摄取分别为(19.04±4.87)%ID/g、(3.05±0.52)%ID/g和(5.99±2.96)%ID/g,心肌与肺的摄取比值为6/1(t=0.27,P=0.01),心肌与肝脏的摄取比值为3/1(t=0.75,P=0.02),差异均有统计学意义;肝脏摄取呈先高后低的趋势,在15 min和30 min时肝脏摄取略高于心肌摄取。 结论实现了18F-FTHA的自动化合成,其放化纯度高,稳定性好。物理、化学和生物学鉴定结果证实其安全可靠,小鼠体内生物学分布实验证实其心肌摄取高于非靶器官,可用于实验研究。 -
关键词:
- 心肌代谢 /
- 脂肪酸 /
- 正电子发射断层显像术 /
- 14(R, S)-[18F]-氟-6-硫杂十七烷酸 /
- 生物学分布
Abstract:ObjectiveTo achieve the fully automated synthesis of myocardial fatty acid metabolism imaging agent 14(R, S)-[18F]fluoro-6-thia-heptadecanoic acid (18F-FTHA), its biological distribution characteristics in normal Kunming mice were evaluated. MethodsAn automated synthesis module benzyl-14-tosyloxy-6-thia-heptadecanoate was used as precursor. The synthesis process was completed in four steps:nucleophilic substitution, alkaline hydrolysis, semi-preparative high-performance liquid chromatography, and solid-phase extraction. The physical(traits, activity, specific activity, half-life, and radionuclide purity), chemical (chemical purity, radiochemical purity, and room temperature stability), and biological properties (toxicity, sterility, and bacterial endotoxin) of the compound were identified. Twenty Kunming mice were randomly divided into four groups, with five mice in each group. The imaging agent 18F-FTHA 7.4 MBq(volume < 0.2 mL) was injected through the tail vein. A group of mice was sacrificed at 15, 30, 60, and 90 min after injection, and the blood and main organs, such as heart, liver, spleen, lung, kidney, muscle, and bone, were obtained and weighed. The radioactivity count was measured by a gamma counter. The radioactive uptake(%ID/g) was calculated. ResultsThe total synthesis time was about 50 min. The synthetic yield was(10.0±1.7)%. The 18F-FTHA is an injection containing 10% ethanol. The compound is a sterile, endotoxin-free, colorless clear solution. Its pH value is 6-7, specific activity is 65 GBq/mmol, radioactive nuclear purity is ≥ 99%, and radiochemical purity is > 98%, which remained at > 95% after 6 h at room temperature. Biodistribution experiments in normal Kunming mice showed that 18F-FTHA rapidly cleared in the blood, and a high myocardial uptake and low non-target organ uptake were observed. At 60 min after injection, the radioactivity uptake of myocardium, lungs, and liver reached(19.04±4.87)%ID/g, (3.05±0.52)%ID/g and(5.99±2.96)%ID/g, respectively. The heart-to-lung and heart-to-liver uptake ratios totaled 6/1 and 3/1, respectively. The liver uptake at 15 and 30 min was slightly higher than the myocardial uptake. ConclusionsThe synthesis of 18F-FTHA, which features high radiochemical purity and good stability, has been automatically completed. Physical, chemical, and biological property identification results confirmed that the compound is safe and reliable. The biological distribution experiments on mice confirmed that myocardial uptake was higher than that of non-target organs. Thus, 18F-FTHA is suitable for experimental research. -
表 1 14(R, S)-[18F]氟-6-硫杂十七烷酸(18F-FTHA)在昆明小鼠体内的生物学分布(x+s,n=5)
Table 1. The biodistribution of 18F-FTHA in Kunming mice
组织 放射性摄取率(%ID/g) 15 min 30 min 60 min 90 min 心肌 30.78±8.88 22.36±6.25 19.04±4.87 13.72±2.74 肝 38.27±7.42 26.39±3.75 5.99±2.96 3.34±1.34 肺 9.08±0.97 4.28±0.19 3.05±0.52 1.45±0.32 脾 1.62±0.47 1.06±0.14 0.47±0.12 0.40±0.11 肾 23.97±7.55 17.25±2.87 3.64±0.52 2.83±0.99 肌肉 3.79±0.53 2.37±0.21 1.75±0.20 1.19±0.18 骨 3.01±0.68 1.52±0.15 1.15±0.14 0.56±0.11 血 1.03±0.13 1.26±0.79 0.30±0.13 0.26±0.06 -
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