Tracerlab fxc

The PET tracer, L-[methyl-¹¹C]-methionine, was synthesised in compliance with good manufacturing practice using a captive solvent in loop methylation method without preparative HPLC, adapted from methods published previously [45 (link)–47 (link)]. Briefly, [¹¹C]CO₂ was produced using a PETtrace cyclotron (GE Healthcare, Milwaukee, WI, USA) via the ¹⁴ N(p, $\alpha$ )¹¹C reaction before conversion to [¹¹C]MeI in the MeI MicroLab (GE Healthcare). This was then transferred to the HPLC loop of a modified TracerLabFXC (GE Healthcare) synthesiser containing an L-homocysteine precursor solution (0.5 M aqueous NaOH solution in ethanol). ¹¹C-methionine was produced in yields averaging 376 MBq with a radiochemical purity of > 96% and specific activity between 263 and 452.5 MBq.

[¹¹C]CO₂ was generated by bombarding N₂ gas (360 psi 99.9999% pure N₂ doped with 0.5% O₂) via the ¹⁴N(p,α)¹¹C nuclear reaction using a EBCO TR-19/9 cyclotron. General bombardment conditions for [¹¹C]CH₃I/ [¹¹C]CH₃OTf production: 5–40 min beam time with 25 µA current. After the bombardment, target gas containing radioactivity was released and delivered to a GE TRACERlab FXC automatic synthesizer to convert [¹¹C]CO₂ to [¹¹C]CH₃I or [¹¹C]CH₃OTf. It took 16–18 min from end of bombardment (EOB) to finish the collection of [¹¹C]CH₃I or [¹¹C]CH₃OTf radioactivity in the reaction vial.

The 6-OH-BTA-0 precursor was obtained from either ABX advanced biochemical compounds GTmbH (Radeberg, Germany) or Pharmasynth AS (Tartu, Estonia), standard reagents were obtained from Sigma-Aldrich/Merck, sterile solutions were obtained from either Sygehus Apotek Fyn (Odense, Denmark) or Region Hovedstadens Apotek (Herlev, Denmark), and sterile Cathivex-GV 0.22 µm filters (SLGV0250S) were obtained from Merck Millipore. [¹¹C]CO₂ was produced by the bombardment of the target gas, 99.5% N₂ + 0.5% O₂ (Strandmøllen A/S, Klampenborg, Denmark), using a GE PETtrace cyclotron (Table 3).
The automated [¹¹C]PiB production and product purification processes were performed on a Tracerlab FXc (GE HealthCare, Uppsala, Sweden) fitted with a S1021 HPLC pump (SYKAM, Eresing, Germany), Chromolith Performance RP-18e column (100 × 10 mm, Merck, Soeborg, Denmark), and K-2001 UV detector (Knauer, Berlin, Germany). The radiosynthesis process and semi-preparative HPLC are described further in Section S3 (Supplementary Materials) and Table 2.

¹¹C-CHDI-180R was synthesized using an automated module (TRACERlab FXC; GE Healthcare) by adapting a method we previously described (15 (link)). The CHDI-180R precursor was radiolabeled by mixing the precursor (0.5–1.2 mg) with dimethylsulfoxide (100 ± 50 μL) and 4–10 mg of cesium carbonate (Cs₂CO₃). Then, ¹¹C-CH₃I was synthesized using a TRACERlab FX2-MEI box and bubbled into the vented reaction vial. The reaction was heated at 60°C ± 5°C for 1 min, after which 0.9 mL of the preparative mobile phase (0.10 M ammonium formate:acetonitrile; 60:40 v/v) was added to the reaction and the reaction mixture was injected onto a semipreparative high-performance liquid chromatography (HPLC) column (BetaBasic C18 7.6-mm outer diameter × 250-mm length; Thermo Scientific) at a flow rate of 1–1.5 mL/min. The radioactive product was passed through a sterilizing 0.2-μm filter in a volume of 1–1.5 mL to an empty sterile vial. The product radioactivity was assayed and diluted with sterile, preservative-free 0.9% saline. The mass of ¹¹C-CHDI-180R in the product was analyzed using HPLC mass spectrometry with ultraviolet and radiation detection to determine product radiochemical purity, chemical purity, injected mass, and identity. ¹¹C-CHDI-180R was synthesized with a radiochemical purity of more than 99% and a molar activity of 1,412 ± 556 GBq/μmol (mean ± SEM) at the end of synthesis.