Radiosynthesis of 18F-Labeled RGD Peptides

¹⁸F-NFP was synthesized as previously reported with HPLC purification [30 (link), 33 (link)]. As a typical procedure for all the ¹⁸F-FP-RGD peptides, ¹⁸F-FP-SRGD2 was synthesized as follows: the HPLC-purified ¹⁸F-NFP was rotary-evaporated to dryness, redis solved in DMSO (200 μL), and added to a solution of SRGD2 (1.0 μmol) and DIPEA (20 μL). The reaction mixture was allowed to incubate at 60°C for 30 min. After dilution with 2 mL of water and 0.1% TFA, the mixture was injected into the semipreparative HPLC. The collected fractions containing ¹⁸F-FP-SRGD2 were combined and rotary-evaporated to remove MeCN and TFA (the radiochemical yields and radio-HPLC retention time were shown in the “Electronic Supplementary Materials”). The activity was then reconstituted in normal saline and passed through a 0.22-μm Millipore filter into a sterile multidose vial for in vivo experiments.
¹⁸F-SFB was synthesized by an automated protocol developed in our research lab using a commercially available synthesis module (GE TRACERlab FX_FN; GE Healthcare; detailed procedure to be published elsewhere). The purified ¹⁸F-SFB were rotary-evaporated to dryness, redissolved in DMSO (200 μL), and added to a solution of SRGD2 (1.0 μmol) and DIPEA (20 μL). The reaction mixture was allowed to incubate at 60°C for 30 min. After dilution with 2 mL of 0.1% TFA water, the mixture was injected into the semipreparative HPLC. The collected fractions containing ¹⁸F-FB-SRGD2 were combined and rotary-evaporated to remove MeCN and TFA (the radiochemical yields and radio-HPLC retention time were shown in the “Electronic Supplementary Materials”). The activity was then reconstituted in normal saline and passed through a 0.22-μm Millipore filter into a sterile multidose vial for in vivo experiments.