McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University , Montreal, QC, Canada.
Bioconjug Chem. 2012 Jan 18;23(1):106-14. doi: 10.1021/bc200525x. Epub 2012 Jan 5.
N-Succinimidyl 3-(di-tert-butyl[(18)F]fluorosilyl)benzoate ([(18)F]SiFB), a novel synthon for one-step labeling of proteins, was synthesized via a simple (18)F-(19)F isotopic exchange. A new labeling technique that circumvents the cleavage of the highly reactive active ester moiety under regular basic (18)F-labeling conditions was established. In order to synthesize high radioactivity amounts of [(18)F]SiFB, it was crucial to partially neutralize the potassium oxalate/hydroxide that was used to elute (18)F(-) from the QMA cartridge with oxalic acid to prevent decomposition of the active ester moiety. Purification of [(18)F]SiFB was performed by simple solid-phase extraction, which avoided time-consuming HPLC and yielded high specific activities of at least 525 Ci/mmol and radiochemical yields of 40-56%. In addition to conventional azeotropic drying of (18)F(-) in the presence of [K(+)⊂2.2.2.]C(2)O(4), a strong anion-exchange (SAX) cartridge was used to prepare anhydrous (18)F(-) for nucleophilic radio-fluorination omitting the vacuum assisted drying of (18)F(-). Using a lyophilized mixture of [K(+)⊂2.2.2.]OH resolubilized in acetonitrile, the (18)F(-) was eluted from the SAX cartridge and used directly for the [(18)F]SiFB synthesis. [(18)F]SiFB was applied to the labeling of various proteins in likeness to the most commonly used labeling synthon in protein labeling, N-succinimidyl-4-[(18)F]fluorobenzoate ([(18)F]SFB). Rat serum albumin (RSA), apo-transferrin, a β-cell-specific single chain antibody, and erythropoietin were successfully labeled with [(18)F]SiFB in good radiochemical yields between 19% and 36%. [(18)F]SiFB- and [(18)F]SFB-derivatized RSA were directly compared as blood pool imaging agents in healthy rats using small animal positron emission tomography. Both compounds demonstrated identical biodistributions in healthy rats, accurately visualizing the blood pool with PET.
N-琥珀酰亚胺基 3-(二叔丁基[(18)F]氟硅基)苯甲酸酯([(18)F]SiFB)，一种用于一步标记蛋白质的新型合成子，通过简单的(18)F-(19)F 同位素交换合成。建立了一种新的标记技术，该技术避免了在常规碱性(18)F 标记条件下切割高反应性活性酯部分。为了合成[(18)F]SiFB 的高放射性活度，用草酸部分中和用于从 QMA 柱中洗脱(18)F(-)的草酸钾/氢氧化物至关重要，以防止活性酯部分分解。[(18)F]SiFB 的纯化通过简单的固相萃取进行，避免了耗时的 HPLC，并产生了至少 525 Ci/mmol 的高比活度和 40-56%的放射化学产率。除了在[K(+)⊂2.2.2.]C(2)O(4)存在下常规共沸干燥(18)F(-)之外，还使用强阴离子交换(SAX)柱来制备无水(18)F(-)，从而省略了(18)F(-)的真空辅助干燥。使用在乙腈中重新溶解的冻干[K(+)⊂2.2.2.]OH 混合物，从 SAX 柱中洗脱(18)F(-)并直接用于[(18)F]SiFB 合成。[(18)F]SiFB 被应用于各种蛋白质的标记，类似于蛋白质标记中最常用的标记合成子 N-琥珀酰亚胺基-4-[(18)F]氟苯甲酸酯([(18)F]SFB)。成功地以 19%-36%的放射化学产率标记了牛血清白蛋白(RSA)、脱铁转铁蛋白、β 细胞特异性单链抗体和促红细胞生成素。[(18)F]SiFB 和[(18)F]SFB 衍生的 RSA 在健康大鼠中直接比较作为血池成像剂，使用小动物正电子发射断层扫描。两种化合物在健康大鼠中的分布相同，准确地用 PET 可视化血池。
