An improved loop method for [11C]DASB synthesis using DMSO as a solvent

Objectives [11C]DASB has been widely used for serotonin transporter imaging. Conventional [11C]DASB synthesis method was time consuming and complicated. In the present study, we tried to apply a HPLC loop method for [11C]DASB synthesis and compared the production yield using DMF or DMSO as a solvent.

Methods The [11C]CH3I was synthesized by the reported gas phase method and then captured in the HPLC loop, which contained 1 mg of MASB as a precursor in each solvent, DMF or DMSO. After 1 min at room temperature, the reaction mixture was purified by HPLC system. Radiolabeling yield in each solvent (DMF or DMSO) was calculated from the radioactivity of [11C]CH3I trap in the automatic synthesizer.

Results Total synthesis time including HPLC purification was about 30 min. The decay corrected yield of [11C]DASB syntheses in DMSO and DMF were 42.8±6.9% (n=24) and 15.0±2.6% (n=19), respectively. According to this procedure using DMSO as a solvent, the mean radioactivity and specific activity obtained were 2.9±0.7 GBq (n=9) and 26.7±15.2 GBq/μmol.

Conclusions We established a simple loop method for [11C]DASB synthesis which is easier and faster than a tube method. In addition, DMSO was found to be the optimal solvent for [11C]DASB synthesis.