18F-fluciclovine radiosynthesis

As previously described⁴⁰, ¹⁸F-fluciclovine was produced on a FAST-lab synthesizer using single use cassette kits provided by Blue Earth Diagnostics. The ¹⁸F-fluciclovine (¹⁸F-FACBC) was produced with a radioactivity yield of 49.1 ± 3.8% (n = 4) with an end of synthesis activity concentration of 1,481 ± 190 MBq ml⁻¹. At the end of synthesis, the radiochemical purity was 99.18 ± 0.13% (n = 4) and the molar activity was 1,044.45 ± 638.14 GBq μmol⁻¹ (n = 3). The final ¹⁸F-fluciclovine product was formulated in citrate buffer and was terminally filtered through a 0.2-μm filter. The tracer was then shipped to DFCI’s Molecular Cancer Imaging facility, where citrate was removed by passing the tracer through a prefilled AG 1-X8 column (Bio-Rad, cat. no. 7316211). The first 1-ml fraction was discarded and the subsequent 1.1-ml fraction was passed through a sterile filter (Fisher, cat. no. 09–720-3) and collected in a butyl septum-sealed sterile glass vial. Radiochemical purity of the citrate-free product was measured using thin-layer chromatography. Thin-layer chromatography silica gel 60 aluminum strips were eluted over 8.0 cm using a mobile phase consisting of acetonitrile:methanol:water:acetic acid at 20:5:5:1 v/v. Radiochemical purity was 99.03% (n = 5).