The endogenous amino acid, 5-aminolevulinic acid (5-ALA), has received significant attention as an imaging agent, including ongoing clinical trials for image-guided tumor resection due to its selective uptake and subsequent accumulation of the fluorescent protoporphyrin IX in tumor cells. Based on the widely reported selectivity of 5-ALA, a new positron emission tomography imaging probe was developed by reacting methyl 5-bromolevulinate with [¹³N] ammonia. The radiotracer, [¹³N] 5-ALA, was produced in high radiochemical yield (65%) in 10 min and could be purified using only solid phase cartridges. In vivo testing in rats bearing intracranial 9L glioblastoma showed peak tumor uptake occurred within 10 min of radiotracer administration. Immunohistochemical staining and fluorescent imaging was used to confirm the tumor location and accumulation of the tracer seen from the PET images. The quick synthesis and rapid tumor specific uptake of [¹³N] 5-ALA makes it a potential novel clinical applicable radiotracer for detecting and monitoring tumors noninvasively.

中文翻译：

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胶质瘤PET成像中¹³ N标记的5-氨基乙酰丙酸的放射化学合成与评价

内源性氨基酸5-氨基乙酰丙酸（5-ALA）作为显像剂已受到广泛关注，由于其在肿瘤细胞中的选择性摄取和随后荧光原卟啉IX的积累，因此正在进行以图像为指导的肿瘤切除的临床试验。基于广泛报道的5-ALA选择性，通过使5-溴乙酰丙酸甲酯与[ ¹³ N]氨反应开发了一种新的正电子发射断层显像成像探头。放射性示踪剂[ ¹³ N] 5-ALA在10分钟内以高放射化学产率（65％）产生，仅可使用固相小柱纯化。体内对患有颅内9L胶质母细胞瘤的大鼠进行的测试显示，在放射性示踪剂给药后10分钟内肿瘤吸收达到峰值。免疫组织化学染色和荧光成像用于确认从PET图像看到的肿瘤位置和示踪剂的积累。[ ¹³ N] 5-ALA的快速合成和快速的肿瘤特异性摄取使其成为潜在的新型临床适用放射性示踪剂，用于无创检测和监测肿瘤。