Radiosynthesis of 3-indolyl[1-11C]acetic acid for phyto-PET-imaging: An improved production procedure and formulation method

• Streamlined [11C]IAA production process with improved radiochemical yield.
• A special formulation method for [11C]IAA was developed for in vivo phyto-PET-imaging.

An improved production procedure and formulation method for the carbon-11 radiolabeled phytohormone, 3-indolyl-[l-11C]acetic acid ([11C]IAA), was developed by modifying selected original reaction parameters. This updated procedure both doubled the yield (from 25.9±6.7% (n=12) to 61.0±0.3% (n=10)) and increased the concentration (0.2–0.4 GBq/0.15–0.3 mL), enabling us to provide the radiotracer [11C]IAA suitable for in vivo phyto-PET-imaging studies. The specific activity was improved by more than a factor of three (26.7±5.6 GBq/µmol to 82.5±36.1 GBq/µmol). The total synthesis time for both production and formulation was 81.8±3.0 min (n=10). In addition, a streamlined semi-remote controlled production system, containing five processing modules, was designed and built for routine [11C]IAA production. This integrated system facilitated routine high radiation level production of [11C]IAA while minimizing radiation exposure to the production chemists.